U.S. patent application number 14/246460 was filed with the patent office on 2014-12-18 for methods and devices for transmitting/obtaining identification information and positioning by visible light signal.
This patent application is currently assigned to Zhuhai Hengqin Great Aim Visible Light Communication Technology Co. Ltd.. The applicant listed for this patent is Zhuhai Hengqin Great Aim Visible Light Communication Technology Co. Ltd.. Invention is credited to Cheng Guo, Hong Hu.
Application Number | 20140372072 14/246460 |
Document ID | / |
Family ID | 49491285 |
Filed Date | 2014-12-18 |
United States Patent
Application |
20140372072 |
Kind Code |
A1 |
Guo; Cheng ; et al. |
December 18, 2014 |
Methods and Devices for Transmitting/Obtaining Identification
Information and Positioning by Visible Light Signal
Abstract
The present invention discloses methods and devices for
transmitting/obtaining identification information and positioning
by visible light signal. The method for transmitting identification
information of a light source by visible light signal, the method
comprising: modulating, on the basis of the identification
information to be transmitted, a driving signal of the light source
to obtain a modulated driving signal for driving the light source
to emit visible light signal having its level changed between a
peak level and a bottom level with varied frequencies at different
time points; and emitting the visible light signal having its level
changed between a peak level and a bottom level with varied
frequencies at different time points on the basis of the modulated
driving signal, so as to transmit identification information
corresponding to the varied numbers of bright or dark stripes shown
in one or more images obtained from the visible light signal at one
or more time points, which numbers are corresponding to the varied
frequencies.
Inventors: |
Guo; Cheng; (Beijing,
CN) ; Hu; Hong; (Beijing, CN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Zhuhai Hengqin Great Aim Visible Light Communication Technology Co.
Ltd. |
Zhuhai City |
|
CN |
|
|
Assignee: |
Zhuhai Hengqin Great Aim Visible
Light Communication Technology Co. Ltd.
Zhuhai City
CN
|
Family ID: |
49491285 |
Appl. No.: |
14/246460 |
Filed: |
April 7, 2014 |
Current U.S.
Class: |
702/150 ;
315/291; 315/307 |
Current CPC
Class: |
H05B 47/19 20200101;
G01C 15/002 20130101; H05B 47/10 20200101; H05B 47/105 20200101;
H05B 47/125 20200101; H04B 10/116 20130101 |
Class at
Publication: |
702/150 ;
315/291; 315/307 |
International
Class: |
G01C 15/00 20060101
G01C015/00; H05B 37/02 20060101 H05B037/02 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 9, 2013 |
CN |
201310121480.2 |
Claims
1. A method for transmitting identification information of a light
source by visible light signal, the method comprising: modulating,
on the basis of the identification information to be transmitted, a
driving signal of the light source to obtain a modulated driving
signal for driving the light source to emit visible light signal
having its level changed between a peak level and a bottom level
with varied frequencies at different time points; and emitting the
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time points
on the basis of the modulated driving signal, so as to transmit
identification information corresponding to the varied numbers of
bright or dark stripes shown in one or more images obtained from
the visible light signal at one or more time points, which numbers
are corresponding to the varied frequencies.
2. The method according to claim 1, wherein modulating on the basis
of the identification information to be transmitted a driving
signal of the light source to obtain a modulated driving signal
comprises: modulating on the basis of the identification
information to be transmitted a driving voltage or a driving
current of the light source to obtain a first modulated driving
voltage or a first modulated driving current.
3. The method according to claim 2, wherein the first modulated
driving current is greater than an un-modulated driving current, so
that luminous flux of the light source driven by the first
modulated driving current is equal to luminous flux of the light
source driven by the un-modulated driving current.
4. The method according to claim 2, further comprising: emitting
the visible light signal on the basis of a second modulated driving
current which is greater than an un-modulated driving current
together with a high frequency carrier wave signal, so that
luminous flux of the light source driven by the second modulated
driving current is constant among periods comprising peak levels
and bottom levels.
5. The method according to claim 2, wherein the first modulated
driving voltage or the first modulated driving current is used for
driving the light source to emit a visible light signal with a
frequency from 100 Hz to 1.37 MHz, and duration of each bottom
level of the visible light signal is fixed, or duration of each
peak level of the light pulse signal is fixed.
6. The method according to claim 1, further comprising: detecting
the presence of a human being within a illumination scope of the
light source; and emitting a visible light signal on the basis of
un-modulated driving signal in the absence of a human being.
7. The method according to claim 1, wherein the identification
information corresponding to the varied numbers of bright or dark
stripes comprises data bits, which comprise data corresponding to
the varied frequencies, and each data bit corresponds to a number
among the varied numbers of bright or dark stripes.
8. The method according to claim 7, wherein the identification
information corresponding to the varied numbers of bright or dark
stripes further comprises one or more start bits and/or one or more
error correction bits, the one or more start bits being used to
identify a start position of a set of data bits, and the one or
more error correction bits being used to check error in the data
bits.
9. A method for positioning by visible light signals, the method
comprising: obtaining at a position one or more images at one or
more time points from a visible light signal having its level
changed between a peak level and a bottom level with varied
frequencies at different time points emitted by a light source;
measuring varied numbers of bright or dark stripes in the one or
more images, the varied numbers of bright or dark stripes being
corresponding to the varied frequencies; obtaining identification
information of the light source corresponding to the varied number
of the bright or dark stripes; and determining the position by
checking the identification information in a predetermined map
database.
10. The method according to claim 9, further comprising: before
determining the position by checking the identification information
in a predetermined map database, determining an area of the
position by means of one or more wireless positioning schemes; and
determining the position by checking the identification information
in a predetermined map database comprises: determining the position
by checking the identification information with data of the area in
the predetermined map database.
11. The method according to claim 9, wherein obtaining at a
position one or more images at one or more time points from a
visible light signal comprises capturing at the position on an
image sensor with a rolling shutter the one or more images in which
different portions of the image sensor are exposed at different
time points.
12. The method according to claim 9, wherein the visible light
signal is emitted by the light source on the basis of a modulated
driving signal, which drives the light source to emit the visible
light signal having its level changed between a peak level and a
bottom level with varied frequencies at different time points.
13. The method according to claim 9, wherein the light source is
one or more light sources, and obtaining one or more images at one
or more time points from visible light signal having its level
changed between a peak level and a bottom level with varied
frequencies at different time points emitted by a light source
comprises: obtaining one or more images at one or more time points
from visible light signal having their level changed between peak
levels and bottom levels with varied frequencies at different time
points emitted by the one or more light sources, wherein one or
more exposed regions in each image correspond to the one or more
light sources, measuring the varied numbers of bright or dark
stripes in the one or more images comprises: measuring the varied
numbers of the bright or dark stripes of the one or more exposed
regions in each image, and obtaining identification information
corresponding to the varied numbers of the bright or dark stripes
comprises: obtaining identification information corresponding to
the varied numbers of the bright or dark stripes of the one or more
exposed regions in each image.
14. The method according to claim 9, wherein the identification
information corresponding to the varied numbers of bright or dark
stripes comprises data bits which comprise data corresponding to
the varied frequencies, and each data bit corresponds to a number
among the varied numbers of bright or dark stripes.
15. The method according to claim 9, wherein the identification
information corresponding to the varied numbers of bright or dark
stripes further comprises one or more start bits and/or one or more
error correction bits, the one or more start bits being used to
identify a start position of a set of data bits, and the one or
more error correction bits being used to check error in the data
bits.
16. A light source for transmitting identification information by
visible light signal, comprising: a modulator configured to
modulate, on the basis of the identification information to be
transmitted, a driving signal of the light source to obtain a
modulated driving signal for driving the light source to emit
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time
points; and an emitter configured to emit the visible light signal
having its level changed between a peak level and a bottom level
with varied frequencies at different time points on the basis of
the modulated driving signal, so as to transmit identification
information corresponding to the varied numbers of bright or dark
stripes shown in one or more images obtained from the visible light
signal at one or more time points, which numbers are corresponding
to the varied frequencies.
17. The light source according to claim 16, wherein the modulator
is configured to modulate on the basis of the identification
information to be transmitted a driving voltage or a driving
current of the light source to obtain a first modulated driving
voltage or a first modulated driving current.
18. The light source according to claim 17, wherein the first
modulated driving current is greater than an un-modulated driving
current, so that luminous flux of the light source driven by the
first modulated driving current is equal to luminous flux of the
light source driven by the un-modulated driving current.
19. The light source according to claim 17, wherein the emitter is
configured to emit the visible light signal on the basis of a
second modulated driving current which is greater than an
un-modulated driving current together with a high frequency carrier
wave signal, so that luminous flux of the light source driven by
the second modulated driving current is constant among periods
comprising peak levels and bottom levels.
20. The light source according to claim 17, wherein the first
modulated driving voltage or the first modulated driving current is
used for driving the light source to emit a visible light signal
with a frequency from 100 Hz to 1.37 MHz, and duration of each
bottom level of the visible light signal is fixed, or duration of
each peak level of the light pulse signal is fixed.
21. The light source according to claim 16, further comprising: a
detector configured to detect the presence of a human being within
a illumination scope of the light source; and wherein the emitter
is configured to emit a visible light signal on the basis of
un-modulated driving signal in the absence of a human being.
22. The light source according to claim 16, wherein the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits, which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
23. The light source according to claim 22, wherein the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more start bits
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits.
24. A device for positioning by visible light signal, comprising:
an image sensor configured to obtain at a position one or more
images at one or more time points from a visible light signal
having its level changed between a peak level and a bottom level
with varied frequencies at different time points emitted by a light
source; a memory configured to store the one or more images
obtained by the image sensor at one or more time points; and a
processor configured to measure varied numbers of bright or dark
stripes in the one or more images stored in the memory, obtain
identification information of the light source corresponding to the
varied number of the bright and dark stripes, and determine the
position by checking the identification information in a
predetermined map database, the varied numbers of bright or dark
stripes being corresponding to the varied frequencies.
25. The device according to claim 24, wherein the processor is
configured to before determining the position by checking the
identification information in a predetermined map database,
determine an area of the position by means of one or more wireless
positioning schemes; and the processor is configured to determine
the position by checking the identification information with data
of the area in the predetermined map database.
26. The device according to claim 24, wherein the image sensor is
an image sensor with a rolling shutter and is configured to obtain
the one or more images in which different portions of the image
sensor are exposed at different time points.
27. The device according to claim 24, wherein the visible light
signal is emitted by the light source on the basis of a modulated
driving signal, which drives the light source to emit the visible
light signal having its level changed between a peak level and a
bottom level with varied frequencies at different time points.
28. The device according to claim 24, wherein the light source is
one or more light sources, and the image sensor is configured to
obtain one or more images at one or more time points from visible
light signal having their level changed between peak levels and
bottom levels with varied frequencies at different time points
emitted by the one or more light sources, wherein one or more
exposed regions in each image correspond to the one or more light
sources, the memory is configured to store the one or more images
obtained by the image sensor at one or more time points; and the
processor is configured to measure the varied numbers of the bright
or dark stripes of the one or more exposed regions in each image,
obtain identification information corresponding to the varied
numbers of the bright or dark stripes of the one or more exposed
regions in each image.
29. The device according to claim 24, wherein the identification
information corresponding to the varied numbers of bright or dark
stripes comprises data bits which comprise data corresponding to
the varied frequencies, and each data bit corresponds to a number
among the varied numbers of bright or dark stripes.
30. The device according to claim 24, wherein the identification
information corresponding to the varied numbers of bright or dark
stripes further comprises one or more start bits and/or one or more
error correction bits, the one or more start bits being used to
identify a start position of a set of data bits, and the one or
more error correction bits being used to check error in the data
bits.
Description
TECHNICAL FIELD
[0001] The present invention generally relates to the field of
visible light communication, and particularly relates to methods
and devices for transmitting/obtaining identification information
and positioning by visible light signal.
BACKGROUND
[0002] Currently, global positioning system (GPS) is the most
widely used positioning system. However, GPS is difficult to
achieve a good positioning accuracy in an indoor environment and
practically cannot be used for indoor positioning applications,
since the signal of GPS is blocked by the roof and walls of
buildings and thus is very weak or disappeared in the indoor
environment.
[0003] Visible light communication is also developed to transmit
identification information for positioning by using the variation
of visible light (color, intensity, or position). Such
communication technology for transmitting identification
information is based on high-frequency blinking visible lights. In
details, the identification information to be transmitted is
firstly compiled into a digital signal; this digital signal is then
applied to modulate the duration time or frequencies of the driving
current or driving voltage of the light source, so that the light
source blinks in high frequencies.
[0004] This high-frequency blinking signal can be detected by a
photosensitive device, for example, an image sensor. The image
sensor may be based on the "rolling shutter" mechanism, which means
that different parts of the sensor, each row or each column, are
exposed at different time. Based on this feature, when taking
pictures of a light source with rapidly changing brightness, the
image sensor with a rolling shutter can deliver an image which
contains bright or dark stripes. By measuring the width of the
stripes, the frequencies of the driving current or driving voltage
of the light source may be calculated and the transmitted
identification information may thus be restored.
[0005] However, this method has following drawbacks: the width of
the stripes can be affected by local over-exposure of the image
sensor, for instance, the bright stripes may become broader and the
dark stripes may become narrower or even disappear within the
over-exposed area, causing failure of the image analysis and
decoding and different background lighting conditions may induce
uncertainties for measuring the width of stripes.
[0006] Additionally, the photosensitive devices used in such
visible light communication technology require to be specially
designed to detect the visible light signal, and thus, only can be
applied in limited scenarios. Additionally, although the
commercially available mobile devices (such as, smartphones,
tablets, PDAs) have photosensitive components, for example, the
image sensor, they are not suitable for sensing such high-frequency
blinking signal.
SUMMARY
[0007] Objects of the present invention are to provide technical
solutions for transmitting identification information, obtaining
identification information, or positioning by visible light
signals, which obviate at least one of the above-mentioned
disadvantages.
[0008] According to a first aspect of the present invention, there
is provided a method transmitting identification information of a
light source by visible light signal, the method comprising:
modulating, on the basis of the identification information to be
transmitted, a driving signal of the light source to obtain a
modulated driving signal for driving the light source to emit
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time
points; and emitting the visible light signal having its level
changed between a peak level and a bottom level with varied
frequencies at different time points on the basis of the modulated
driving signal, so as to transmit identification information
corresponding to the varied numbers of bright or dark stripes shown
in one or more images obtained from the visible light signal at one
or more time points, which numbers are corresponding to the varied
frequencies.
[0009] According to some embodiments of the present invention,
modulating on the basis of the identification information to be
transmitted a driving signal of the light source to obtain a
modulated driving signal comprises: modulating on the basis of the
identification information to be transmitted a driving voltage or a
driving current of the light source to obtain a first modulated
driving voltage or a first modulated driving current.
[0010] According to some embodiments of the present invention, the
first modulated driving current is greater than an un-modulated
driving current, so that luminous flux of the light source driven
by the first modulated driving current is equal to luminous flux of
the light source driven by the un-modulated driving current.
[0011] According to some embodiments of the present invention, the
method further comprising: emitting the visible light signal on the
basis of a second modulated driving current which is greater than
an un-modulated driving current together with a high frequency
carrier wave signal, so that luminous flux of the light source
driven by the second modulated driving current is constant among
periods comprising peak levels and bottom levels.
[0012] According to some embodiments of the present invention, the
first modulated driving voltage or the first modulated driving
current is used for driving the light source to emit a visible
light signal with a frequency from 100 Hz to 1.37 MHz, and duration
of each bottom level of the visible light signal is fixed, or
duration of each peak level of the light pulse signal is fixed.
[0013] According to some embodiments of the present invention, the
method further comprising: detecting the presence of a human being
within a illumination scope of the light source; and emitting a
visible light signal on the basis of un-modulated driving signal in
the absence of a human being.
[0014] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits, which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0015] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more start bits
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits.
[0016] According to a second aspect of the present invention, there
is provided a method for obtaining identification information of a
light source from visible light signals, the method comprising:
obtaining one or more images at one or more time points from a
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time points
emitted by a light source; measuring the varied numbers of bright
or dark stripes in the one or more images, the varied numbers of
bright or dark stripes being corresponding to the varied
frequencies; and obtaining identification information corresponding
to the varied numbers of the bright or dark stripes.
[0017] According to a third aspect of the present invention, there
is provided a method for positioning by visible light signals, the
method comprising: obtaining at a position one or more images at
one or more time points from a visible light signal having its
level changed between a peak level and a bottom level with varied
frequencies at different time points emitted by a light source;
measuring varied numbers of bright or dark stripes in the one or
more images, the varied numbers of bright or dark stripes being
corresponding to the varied frequencies; obtaining identification
information of the light source corresponding to the varied number
of the bright or dark stripes; and determining the position by
checking the identification information in a predetermined map
database.
[0018] According to some embodiments of the present invention, the
method further comprising: before determining the position by
checking the identification information in a predetermined map
database, determining an area of the position by means of one or
more wireless positioning schemes; and determining the position by
checking the identification information in a predetermined map
database comprises: determining the position by checking the
identification information with data of the area in the
predetermined map database.
[0019] According to some embodiments of the present invention, the
wireless positioning scheme comprises positioning by means of GPS,
GPRS, GSM, CDMA, WIFI, Zigbee, Bluetooth, and RFID.
[0020] According to some embodiments of the present invention,
identification information of a light source is unique for an area
at which the light source is located.
[0021] According to some embodiments of the present invention,
obtaining at a position one or more images at one or more time
points from a visible light signal comprises: obtaining at the
position the one or more images at one or more time points by an
image capturing device comprising an image sensor whose exposure
mode is rolling shutter mode, and a sampling rate of the rolling
shutter is higher than the frame rate of the image sensor.
[0022] According to some embodiments of the present invention,
obtaining at a position one or more images at one or more time
points from a visible light signal comprises capturing at the
position on an image sensor with a rolling shutter the one or more
images in which different portions of the image sensor are exposed
at different time points.
[0023] According to some embodiments of the present invention, the
visible light signal is emitted by the light source on the basis of
a modulated driving signal, which drives the light source to emit
the visible light signal having its level changed between a peak
level and a bottom level with varied frequencies at different time
points.
[0024] According to some embodiments of the present invention, the
light source is one or more light sources, and obtaining one or
more images at one or more time points from visible light signal
having its level changed between a peak level and a bottom level
with varied frequencies at different time points emitted by a light
source comprises: obtaining one or more images at one or more time
points from visible light signal having their level changed between
peak levels and bottom levels with varied frequencies at different
time points emitted by the one or more light sources, wherein one
or more exposed regions in each image correspond to the one or more
light sources, measuring the varied numbers of bright or dark
stripes in the one or more images comprises: measuring the varied
numbers of the bright or dark stripes of the one or more exposed
regions in each image, and obtaining identification information
corresponding to the varied numbers of the bright or dark stripes
comprises: obtaining identification information corresponding to
the varied numbers of the bright or dark stripes of the one or more
exposed regions in each image.
[0025] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0026] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more start bits
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits.
[0027] According to a fourth aspect of the present invention, there
is provided light source for transmitting identification
information by visible light signal, comprising: a modulator
configured to modulate, on the basis of the identification
information to be transmitted, a driving signal of the light source
to obtain a modulated driving signal for driving the light source
to emit visible light signal having its level changed between a
peak level and a bottom level with varied frequencies at different
time points; and an emitter configured to emit the visible light
signal having its level changed between a peak level and a bottom
level with varied frequencies at different time points on the basis
of the modulated driving signal, so as to transmit identification
information corresponding to the varied numbers of bright or dark
stripes shown in one or more images obtained from the visible light
signal at one or more time points, which numbers are corresponding
to the varied frequencies.
[0028] According to some embodiments of the present invention, the
modulator is configured to modulate on the basis of the
identification information to be transmitted a driving voltage or a
driving current of the light source to obtain a first modulated
driving voltage or a first modulated driving current.
[0029] According to some embodiments of the present invention, the
first modulated driving current is greater than an un-modulated
driving current, so that luminous flux of the light source driven
by the first modulated driving current is equal to luminous flux of
the light source driven by the un-modulated driving current.
[0030] According to some embodiments of the present invention, the
emitter is configured to emit the visible light signal on the basis
of a second modulated driving current which is greater than an
un-modulated driving current together with a high frequency carrier
wave signal, so that luminous flux of the light source driven by
the second modulated driving current is constant among periods
comprising peak levels and bottom levels.
[0031] According to some embodiments of the present invention, the
first modulated driving voltage or the first modulated driving
current is used for driving the light source to emit a visible
light signal with a frequency from 100 Hz to 1.37 MHz, and duration
of each bottom level of the visible light signal is fixed, or
duration of each peak level of the light pulse signal is fixed.
[0032] According to some embodiments of the present invention, the
light source further comprising: a detector configured to detect
the presence of a human being within an illumination scope of the
light source; and the emitter is configured to emit a visible light
signal on the basis of un-modulated driving signal in the absence
of a human being.
[0033] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits, which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0034] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more start bits
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits.
[0035] According to a fifth aspect of the present invention, there
is provided a device for obtaining identification information of a
light source from visible light signal, comprising: an image sensor
configured to obtain one or more images at one or more time points
from a visible light signal having its level changed between a peak
level and a bottom level with varied frequencies at different time
points emitted by a light source; a memory configured to store the
one or more images obtained by the image sensor at one or more time
points; and a processor configured to measure varied numbers of
bright or dark stripes in the one or more images stored in the
memory and obtain identification information corresponding to the
varied numbers of the bright or dark stripes, the varied numbers of
bright or dark stripes being corresponding to the varied
frequencies.
[0036] According to a sixth aspect of the present invention, there
is provided a device for positioning by visible light signal,
comprising: an image sensor configured to obtain at a position one
or more images at one or more time points from a visible light
signal having its level changed between a peak level and a bottom
level with varied frequencies at different time points emitted by a
light source; a memory configured to store the one or more images
obtained by the image sensor at one or more time points; and a
processor configured to measure varied numbers of bright or dark
stripes in the one or more images stored in the memory, obtain
identification information of the light source corresponding to the
varied number of the bright and dark stripes, and determine the
position by checking the identification information in a
predetermined map database, the varied numbers of bright or dark
stripes being corresponding to the varied frequencies.
[0037] According to some embodiments of the present invention, the
processor is configured to before determining the position by
checking the identification information in a predetermined map
database, determine an area of the position by means of one or more
wireless positioning schemes; and the processor is configured to
determine the position by checking the identification information
with data of the area in the predetermined map database.
[0038] According to some embodiments of the present invention, the
wireless positioning scheme comprises positioning by means of GPS,
GPRS, GSM, CDMA, WIFI, Zigbee, Bluetooth, and RFID.
[0039] According to some embodiments of the present invention,
identification information of a light source is unique for an area
at which the light source is located.
[0040] According to some embodiments of the present invention,
exposure mode of the image sensor is rolling shutter mode, and a
sampling rate of the rolling shutter is higher than the frame rate
of the image sensor.
[0041] According to some embodiments of the present invention, the
image sensor is an image sensor with a rolling shutter and is
configured to obtain the one or more images in which different
portions of the image sensor are exposed at different time
points.
[0042] According to some embodiments of the present invention, the
visible light signal is emitted by the light source on the basis of
a modulated driving signal, which drives the light source to emit
the visible light signal having its level changed between a peak
level and a bottom level with varied frequencies at different time
points.
[0043] According to some embodiments of the present invention, the
light source is one or more light sources, and the image sensor is
configured to obtain one or more images at one or more time points
from visible light signal having their level changed between peak
levels and bottom levels with varied frequencies at different time
points emitted by the one or more light sources, wherein one or
more exposed regions in each image correspond to the one or more
light sources, the memory is configured to store the one or more
images obtained by the image sensor at one or more time points; and
the processor is configured to measure the varied numbers of the
bright or dark stripes of the one or more exposed regions in each
image, obtain identification information corresponding to the
varied numbers of the bright or dark stripes of the one or more
exposed regions in each image.
[0044] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0045] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more start bits
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits.
[0046] In conclusion, the embodiments of the present invention
provide an efficient and effective approach for positioning,
transmitting and obtaining information, which can achieve indoor
positioning, transmit and obtain information much faster and more
accurate, and the information transmitted and obtained may contain
more data bits. The present invention has advantages of high
confidentiality, no occupancy of wireless channel resources, low
cost, and easy integration with various light sources. Further, the
present invention effectively avoids the undesirable blinking of
the light source detectable by human eyes.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] The accompanying drawings are included to provide a further
understanding of embodiments and constitute a part of this
description. The drawings illustrate embodiments and together with
the description serve to explain principles of embodiments. The
elements of the drawings are not necessarily to scale relative to
each other. Similar reference numerals designate corresponding
similar parts. It should be expressly understood that the drawings
are included for illustrative purposes and do not in any manner
limit the scope of the present invention.
[0048] FIG. 1 is a flow chart illustrating a method 100 for
transmitting information by visible light signal from a light
source according to an embodiment of the present invention;
[0049] FIGS. 2a-2c are the schematic diagrams of the driving
signals for driving the light source according to embodiments of
the present invention;
[0050] FIGS. 3a, 3c and 3e are the schematic diagrams of the
driving signals for driving the light source according to
embodiments of the present invention;
[0051] FIGS. 3b, 3d and 3f are the images obtained from the driving
signals of FIGS. 3a, 3c and 3e respectively according to
embodiments of the present invention;
[0052] FIG. 3g shows visible light signal with varied frequencies
at different time points emitted by a light source driven by a
first modulated driving current according to another embodiment of
the present invention;
[0053] FIG. 4a is the schematic diagram of a modulated driving
current of a light source equal to the un-modulated driving current
according to an embodiment of the present invention.
[0054] FIG. 4b is the schematic diagram of a modulated driving
current greater than the un-modulated driving current according to
an embodiment of the present invention.
[0055] FIG. 4c is the schematic diagram of a modulated driving
current greater than the un-modulated driving current without high
frequency carrier wave signal according to an embodiment of the
present invention;
[0056] FIG. 4d is the schematic diagram of a modulated driving
current greater than the un-modulated driving current together with
a high frequency carrier wave signal according to an embodiment of
the present invention;
[0057] FIG. 5a is the schematic diagram of the information
corresponding to the varied numbers of bright or dark stripes
comprising a start bit according to an embodiment of the present
invention;
[0058] FIG. 5b is the schematic diagram of the information
corresponding to the varied numbers of bright or dark stripes
comprising a start bit and an error correction bit according to an
embodiment of the present invention;
[0059] FIG. 6 shows a light source emitting visible light signal
for transmitting information in response to the presence of a human
being according to an embodiment of the present invention;
[0060] FIG. 7 is a flow chart illustrating a method for obtaining
information from visible light signal according to an embodiment of
the present invention;
[0061] FIG. 8 is a flow chart illustrating a method for positioning
by visible light signals according to an embodiment of the present
invention;
[0062] FIG. 9 is a schematic diagram of an image containing one or
more exposed regions corresponding to one or more light sources
according to an embodiment of the present invention;
[0063] FIG. 10 is a schematic diagram of a light source and a
device for transmitting information by visible light signal
according to an embodiment of the present invention;
[0064] FIG. 11 is a flowchart of a process that a mobile device
accesses the indoor map;
[0065] FIG. 12 is the schematic diagram of a mobile device
integrated with a positioning software;
[0066] FIG. 13 is the schematic diagram of the relation between the
map database and the identification information of light
sources;
[0067] FIG. 14 is the schematic diagram of a light source with a
mobile modification device comprising a receiver and a
transmitter;
[0068] FIG. 15 is the schematic diagram of a mobile modification
device that can update the information stored in the light
source;
[0069] FIG. 16 is the schematic diagram of a mobile modification
device updating the identification information of the light
source;
[0070] FIG. 17 is the flow chart of updating the identification
information of a light source;
[0071] FIG. 18 is the flow chart of searching the identification
information of a light source;
[0072] FIG. 19a shows that the image sensor is placed horizontally
for capturing image;
[0073] FIG. 19b shows the captured image under when the image
sensor is placed horizontally;
[0074] FIG. 20a shows that the image sensor for capturing image is
tilted from the horizontal plane;
[0075] FIG. 20b shows the image captured by the image sensor when
the image sensor is tilted from the horizontal plane;
[0076] FIG. 21 shows the diagram on how to calculate the midpoint
of the image;
[0077] FIG. 22a shows the schematic diagram of a gyroscope;
[0078] FIG. 22b is a schematic diagram of the coordinate system an
accelerometer of the mobile device;
[0079] FIG. 23 shows the schematic diagram on how to calculate the
midpoint of the captured image;
[0080] FIG. 24 is the schematic diagram of the format of the data
stored in the databases;
[0081] FIG. 25 is the schematic diagram of information related to
the identification information of the light source;
[0082] FIG. 26 is the schematic diagram of recording a route;
[0083] FIG. 27 is the schematic diagram of the captured image of
two light sources;
[0084] FIG. 28 is the schematic diagram of the captured image of
two light sources which is calibrated;
[0085] FIG. 29 is a schematic diagram of a light source comprising
an AC/DC converter, a micro-controller and a memory according to an
embodiment of the present invention;
[0086] FIG. 30a is a flowchart of a process that the exposure time
of the image sensor is adjusted before capturing an image according
to an embodiment of the present invention;
[0087] FIGS. 30b and 30c are schematic diagrams of the sampling
duration rate of the image sensor and the duration of the peak
level or bottom level of the visible light signal emitted by the
light source according to an embodiment of the present
invention;
[0088] FIG. 30d is a schematic diagram of an image obtained from
the visible light signal having the duration of the peak level of
as shown in FIG. 30c according to an embodiment of the present
invention;
[0089] FIGS. 31a and 31b are schematic diagrams of the exposed
region in the image detected according to an embodiment of the
present invention;
[0090] FIGS. 32a-32c are schematic diagrams of strategy for
detecting the exposed region in the image according to an
embodiment of the present invention;
[0091] FIG. 33 is a flowchart of a process that the exposure time
of the image sensor is adjusted before capturing an image according
to an embodiment of the present invention;
[0092] FIG. 34a is a schematic diagram of the image captured by the
image sensor according to embodiments of the present invention;
[0093] FIG. 34b is a schematic diagram of the exposed region within
the image being searched from the center of the image outwards
along a spiral route according to embodiments of the present
invention;
[0094] FIG. 34c is a schematic diagram of the determined
rectangular exposed region in the image according to an embodiment
of the present invention;
[0095] FIG. 34d is a schematic diagram of determining the
coordinates of the rectangular exposed region in the image
according to an embodiment of the present invention;
[0096] FIG. 34e is a schematic diagram of optimized exposed region
in the image according to an embodiment of the present
invention;
[0097] FIG. 34f is a schematic diagram of measuring the number of
the bright or dark strips according to an embodiment of the present
invention;
[0098] FIG. 34g is a schematic diagram of measuring the number of
the bright or dark strips according to another embodiment of the
present invention;
[0099] FIG. 35 is a schematic diagram of a device containing
multiple image sensors according to an embodiment of the present
invention;
[0100] FIG. 36A is a schematic diagram of an interface with the
real-time image and the information obtained therefrom displayed in
full screen according to an embodiment of the present
invention;
[0101] FIG. 36B is a schematic diagram of an interface with the
information obtained from the image displayed according to an
embodiment of the present invention;
[0102] FIG. 37 is a schematic diagram showing an embodiment of the
present invention with a device for obtaining information from
visible light signals comprising an image sensor activated by an
activation signal sent by the transmitter;
[0103] FIG. 38 is a schematic diagram showing an embodiment of the
present invention with a hardware-based switch installed on the
transmitter for activating the image sensor in the device for
obtaining information from visible light signals;
[0104] FIG. 39 is a schematic diagram showing an embodiment of the
present invention with a sensor integrated in the emitter;
[0105] FIG. 40 is a schematic diagram showing an embodiment of the
present invention with a transmitter for transmitting multiple
types of information;
[0106] FIG. 41 is a schematic diagram showing an embodiment of the
present invention with a transmitter comprising a light source, a
processor, a battery, and a charging circuit;
[0107] FIG. 42 is a schematic diagram showing an embodiment of the
present invention with a transmitter comprising a light source, a
processor, a battery, a charging circuit, and a sensor;
[0108] FIG. 43 is a schematic diagram showing an embodiment of the
present invention with a transmitter comprising a light source, a
processor, a battery, a charging circuit, a sensor, and a
memory;
[0109] FIG. 44 is a schematic diagram of the device for obtaining
information according to an embodiment of the present
invention;
[0110] FIG. 45 is a schematic diagram showing an embodiment of the
present invention with an image sensor integrated in a ring;
[0111] FIG. 46 is a schematic diagram showing an embodiment of the
present invention with a transmitter integrated in a wearable
electronic device powered by a power supply;
[0112] FIG. 47 is a schematic diagram of a transmitter comprising
two or more light sources and a microprocessor according to an
embodiment of the present invention;
[0113] FIG. 48 is a schematic diagram of a transmitter comprising
two or more light sources, a microprocessor, and a driver according
to an embodiment of the present invention;
[0114] FIG. 49 is a schematic diagram of a transmitter comprising a
microprocessor and a battery charging circuit according to an
embodiment of the present invention;
[0115] FIG. 50 is a schematic diagram of a transmitter comprising a
microprocessor, a battery charging circuit, and a memory according
to an embodiment of the present invention;
[0116] FIG. 51 is a schematic diagram of a transmitter comprising a
microprocessor, a battery charging circuit, a memory, and a sensor
according to an embodiment of the present invention;
[0117] FIG. 52 is a schematic diagram of a transmitter comprising a
microprocessor, a battery charging circuit, a memory, a sensor, and
a network adaptor according to an embodiment of the present
invention;
[0118] FIG. 53 is a schematic diagram illustrating communication
between a transmitter and a device for obtaining information from
visible light signals comprising an image sensor according to an
embodiment of the present invention;
[0119] FIG. 54 is a flowchart of a process that a transmitter sends
visible light signals according to an embodiment of the present
invention;
[0120] FIG. 55 is a flowchart of a process that an image sensor
receives the visible light signals according to an embodiment of
the present invention; and
[0121] FIG. 56 is a schematic diagram of a positioning system based
on the visible light signals according to an embodiment of the
present invention.
DETAILED DESCRIPTION
[0122] In the following description, for purposes of explanation
rather than limitation, specific details, such as the particular
architecture, structure, techniques, etc., are set forth for
illustration. However, it will be apparent to those of ordinary
skill in the art that other embodiments that depart from these
specific details would still be understood to be within the scope
of the present invention. Moreover, for the purpose of clarity,
detailed descriptions of well-known devices, circuits, and methods
are omitted so as not to obscure the description of the present
invention. It is to be understood that the features of the various
exemplary embodiments described herein may be combined with each
other, unless specifically noted otherwise.
[0123] According to a first aspect of the present invention, there
is provided a method for transmitting identification information of
a light source by visible light signal. FIG. 1 is a flow chart
illustrating the method 100 for transmitting identification
information of a light source by visible light signal according to
an embodiment of the present invention.
[0124] As shown in FIG. 1, the method 100 begins with a step 110 of
modulating, on the basis of the identification information to be
transmitted, a driving signal of the light source to obtain a
modulated driving signal for driving the light source to emit
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time
points.
[0125] According to some embodiments of the present invention, the
light source may be any type of light source emitting visible light
signal, for example, LED, fluorescent, or incandescent lamp.
[0126] According to some embodiments of the present invention, the
identification information transmitted by visible light signal may
be any type of identification information, for example, the
identifier (ID) of the light source, and other identification
information.
[0127] According to some embodiments of the present invention, the
driving signal of the light source may be in the forms of square
wave, sine wave, triangle wave, wave on a higher-frequency carrier,
the aforesaid waves containing DC component, or in other forms of
wave.
[0128] According to some embodiments of the present invention, the
driving signal of the light source may be modulated by the Pulse
Width Modulation (PWM). Generally, the pulse duration is fixed, and
the duty of the signal can be modulated, wherein the duty in a
pulse cycle (such as square wave) is the ratio of the positive
pulse duration (i.e., duration of the positive part) to the total
duration.
[0129] According to some embodiments of the present invention, the
step 110 may comprise: modulating on the basis of the
identification information to be transmitted a driving voltage or a
driving current of the light source to obtain a first modulated
driving voltage or a first modulated driving current. And the first
modulated driving voltage or the first modulated driving current
may be used to drive the light source to emit the visible light
signal having its level changed between a peak level and a bottom
level with varied frequencies at different time points.
[0130] FIGS. 2a-2c are the schematic diagrams of the driving
signals for driving the light source according to embodiments of
the present invention. In FIG. 2a, the driving signal, optionally
the driving current, of a light source is in the form of sine wave
with a frequency of f.sub.2a. In FIG. 2b, the driving signal,
optionally the driving current, of the light source is in the form
of sine wave with a frequency of f.sub.2b, and
f.sub.2a>f.sub.2b.
[0131] According to some embodiments of the present invention, the
driving signal, optionally the driving current, of the light source
may be modulated on the basis of the identification information to
be transmitted to obtain a first modulated driving current, as
shown in FIG. 2c, which has a frequency of f.sub.2b at time points
within a time interval .DELTA.T1, a frequency of f.sub.2a at time
points within a time interval 2 .DELTA.T2, a frequency of f.sub.2b
at time points within a time interval 3 .DELTA.T3, a frequency of
f.sub.2a at time points within a time interval 4 .DELTA.T4, and a
frequency of f.sub.2b at time points within a time interval 5
.DELTA.T5. The first modulated driving current may be used to drive
the light source to emit the visible light signal having its level
changed between a peak level and a bottom level with varied
frequencies at different time points, for example, with varied
frequencies f.sub.2a and f.sub.2b at different time points within
.DELTA.T1, .DELTA.T2, .DELTA.T3, .DELTA.T4 and .DELTA.T5.
Alternatively, the driving voltage of the light source may also be
modulated on the basis of the identification information to be
transmitted. Alternatively, the driving current or the driving
voltage of the light source may have other wave forms.
Alternatively, the driving current or the driving voltage of the
light source may be modulated to emit visible light signal with
three or more kinds of varied frequencies at different time
points.
[0132] As shown in FIG. 1, after the step 110 described
hereinbefore, a step 120 of the method 100 is performed, that is,
emitting the visible light signal having its level changed between
a peak level and a bottom level with varied frequencies at
different time points on the basis of the modulated driving signal,
so as to transmit identification information corresponding to the
varied numbers of bright or dark stripes shown in one or more
images obtained from the visible light signal at one or more time
points, which numbers are corresponding to the varied
frequencies.
[0133] Optionally, the dark stripe corresponds to the bottom level
of the visible light signal, and the bright stripe corresponds to
the peak level of the visible light signal. The varied number of
the bright stripes and dark stripes corresponds to different
identification information transmitted.
[0134] FIGS. 3a, 3c and 3e are the schematic diagrams of the
driving signals for driving the light source, and FIGS. 3b, 3d and
3f are the images obtained respectively according to embodiments of
the present invention.
[0135] In FIG. 3a, the driving signal, optionally the driving
current, of a light source is in the form of square wave with a
frequency of f.sub.3a and the starting time for capturing an image
is at the time point when one of the peal levels of the visible
light signal is emitted. Optionally, from the driving signal shown
in FIG. 3a, an image with 10 dark stripes and 11 bright stripes as
shown in FIG. 3b may be obtained, where the number of the bright or
dark stripes is corresponding to the frequency f.sub.3a.
Alternatively, where the starting time for capturing an image is at
the time point when one of the bottom levels of the visible light
signal is emitted, an image having 11 dark stripes and 10 bright
stripes may be obtained (not shown).
[0136] In FIG. 3c, the driving signal, optionally the driving
current, of a light source is in the form of square wave with a
frequency of f.sub.3c with f.sub.3a>f.sub.3c and the starting
time for capturing an image is at the time point when one of the
peal levels of the visible light signal is emitted. Optionally,
from the driving signal shown in FIG. 3c, an image with 5 dark
stripes and 6 bright stripes as shown in FIG. 3d may be obtained,
where the number of the bright or dark stripes is corresponding to
the frequency f.sub.3c. Alternatively, where the starting time for
capturing an image is at the time point when one of the bottom
levels of the visible light signal is emitted, an image having 6
dark stripes and 5 bright stripes may be obtained (not shown).
[0137] In FIG. 3e, the driving signal, optionally the driving
current, of a light source is in the form of square wave with a
frequency of f.sub.3e with f.sub.3c>f.sub.3e, and the starting
time for capturing an image is at the time point when one of the
peal levels of the visible light signal is emitted. Optionally,
from the driving signal shown in FIG. 3c, an image with 3 dark
stripes and 4 bright stripes as shown in FIG. 3f may be obtained,
where the number of the bright or dark stripes is corresponding to
the frequency f.sub.3e. Alternatively, where the starting time for
capturing an image is at the time point when one of the bottom
levels of the visible light signal is emitted, an image having 4
dark stripes and 3 bright stripes may be obtained (not shown).
[0138] FIG. 3g shows a visible light signal with varied frequencies
at different time points emitted by a light source driven by a
first modulated driving current. The first modulated driving
current may be used to drive the light source to emit the visible
light signal having its level changed between a peak level and a
bottom level with varied frequencies at different time points, for
example, with varied frequencies f.sub.3a, f.sub.3c and f.sub.3e at
different time points within time intervals .DELTA.T1, .DELTA.T2
and .DELTA.T3. Optionally, within each time interval with a
different frequency, a code is transmitted, for example, within
.DELTA.T1 a code "1" is transmitted, within .DELTA.T2 a code "2" is
transmitted, and within .DELTA.T3 a code "3" is transmitted.
[0139] After emitting the visible light signal on the basis of the
first modulated driving current, as shown in FIG. 3g, an image with
10 dark stripes and 11 bright stripes as shown in FIG. 3b,
corresponding to f.sub.3a, may be obtained at different time points
within .DELTA.T1; an image with 5 dark stripes and 6 bright stripes
as shown in FIG. 3d, corresponding to f.sub.3c, may be obtained at
different time points within .DELTA.T2; and an image with 3 dark
stripes and 4 bright stripes as shown in FIG. 3f, corresponding to
f.sub.3e, may be obtained at different time points within
.DELTA.T3. The identification information corresponding to the
varied numbers of bright or dark stripes shown in the images in
FIG. 3b, 3d, 3f obtained from the visible light signal in FIG. 3g
is transmitted, and the numbers of bright or dark stripes are
corresponding to frequencies f.sub.3a, f.sub.3c, f.sub.3e.
Alternatively, the driving voltage of the light source may also be
modulated on the basis of the identification information to be
transmitted.
[0140] Alternatively, the driving current or the driving voltage of
the light source may have other wave forms. Alternatively, the
driving current or the driving voltage of the light source may be
modulated to emit visible light signal with four or more kinds of
varied frequencies at different time points.
[0141] According to an embodiment of the present invention, the
first modulated driving current is greater than the un-modulated
driving current, so that luminous flux of the light source driven
by the first modulated driving current is equal to luminous flux of
the light source driven by the un-modulated driving current.
[0142] The luminous flux is the measure of the power of light
emitted by the light source during unit time, and is proportional
to the area below the wave of the driving signal, the variation of
which is sensitive to human eye. The driving signal may be
modulated with the first modulated driving currents greater than
un-modulated driving currents, so that luminous flux of the light
source is constant throughout the transmission of identification
information to avoid blinking.
[0143] FIG. 4a is the schematic diagram of a modulated driving
current of a light source equal to the un-modulated driving current
according to an embodiment of the present invention. It can be
assumed that the luminous flux of the light source driven by the
un-modulated driving currents is 100%. Assuming that the width of
the peak levels and bottom levels of the modulated driving current
may be 0.1 ms respectively and the modulated driving current is
equal to the un-modulated driving current, the luminous flux of the
light source driven by the modulated driving current shown in FIG.
4a can be calculated to be (0.1*0+0.1*1)*100%/(0.1+0.1)=50%. The
luminous flux 50% of the light source driven by the modulated
driving current is lower than that of the light source driven by
the un-modulated driving current (100%), causing undesirable
blinking of the light source detectable by human eye.
[0144] FIG. 4b is the schematic diagram of a modulated driving
current greater than the un-modulated driving current according to
an embodiment of the present invention. Still, assuming that the
width of the peak levels and bottom levels of the modulated driving
current is 0.1 ms, respectively, and the modulated driving current
is twice of the un-modulated driving current, the luminous flux of
the light source driven by the modulated driving current shown in
FIG. 4b can be calculated to be (0.1*0+0.1*2)*100%/(0.1+0.1)=100%.
The luminous flux 100% of the light source driven by the modulated
driving current is equal to the luminous flux 100% of light source
driven by the un-modulated driving current, avoiding undesirable
blinking of the light source detectable by human eye. It should be
noted that, the values provide in the embodiments of the present
invention are theoretical values for illustrative purposes, but not
actual values. The actual values may vary due to the parameters of
different devices.
[0145] Alternatively, as for a first modulated driving current for
driving the light source to emit the visible light signal with
varied frequencies at different time points, for example, with
varied frequencies f.sub.3a, f.sub.3c and f.sub.3e at different
time points within time intervals .DELTA.T1, .DELTA.T2 and
.DELTA.T3 as shown in FIG. 3g, the driving signal may be modulated,
in the similar manner as shown in FIGS. 4a and 4b, so that luminous
flux of the light source driven by the first modulated driving
current in .DELTA.T1, .DELTA.T2, .DELTA.T3 is equal to luminous
flux of the light source driving by the un-modulated driving
current.
[0146] According to some embodiments of the present invention,
optionally, the method 100 may comprise a step of emitting the
visible light signal on the basis of a second modulated driving
current which is greater than an un-modulated driving current
together with a high frequency carrier wave signal, so that
luminous flux of the light source driven by the second modulated
driving current is constant among periods comprising peak levels
and bottom levels.
[0147] FIG. 4c is the schematic diagram of a modulated driving
current greater than the un-modulated driving current without high
frequency carrier wave signal according to an embodiment of the
present invention. As shown in FIG. 4c, within different time
intervals .DELTA.T1 and .DELTA.T2, the peak levels and bottom
levels may have different durations of peak levels and bottom
levels for transmitting different codes, as shown in FIG. 4c,
resulting in different luminous fluxes of the light source driven
by the modulated driving current, causing the light source to
blink. For example, as shown in FIG. 4c, within a time interval
.DELTA.T1 representing code "1", the driving current is modulated
to have a total duration of peak level of
.DELTA.T1.sub.peak=1/2*.DELTA.T1, giving a luminous flux of 50%;
and within another time interval .DELTA.T2 representing code "2",
the driving current is modulated to have a total duration of peak
level of .DELTA.T2.sub.peak=2/3*.DELTA.T2, giving a luminous flux
of 66.7%. Therefore, the luminous flux within .DELTA.T1
representing code "1" is less than that within .DELTA.T2
representing code "2", causing the light source to blink.
[0148] In order to avoid the blinking of the light source when
transmitting different codes, the driving current which is greater
than un-modulated driving current is further modulated with a high
frequency carrier wave signal. By modulating with a high frequency
carrier wave signal, within different time intervals, the durations
of peak levels and bottom levels of the driving current for
transmitting different codes are same, giving the same luminous
flux among periods comprising the peak levels and bottom levels,
and thus avoiding the blinking of the light source. For example, as
shown in FIG. 4d, within time interval .DELTA.T1 representing code
"1", the driving current is further modulated with a high frequency
carrier wave to have a total duration of peak levels of
.DELTA.T1.sub.peak=1/2*.DELTA.T1*66.7%, giving a luminous flux of
33.3%; within time interval .DELTA.T2 representing code "2", the
driving current is further modulated with a high frequency carrier
wave to have a total duration of peak levels of
.DELTA.T2.sub.peak=2/3*.DELTA.T2*50%, giving a luminous flux of
33.3%. Therefore, the luminous flux within .DELTA.T1 representing
code "1" is equal to that within .DELTA.T2 representing code "2",
avoiding undesirable blinking of the light source detectable by
human eye.
[0149] For the purpose of illustration, the visible light signals
shown in FIG. 4c and FIG. 4d have the same frequency within
different intervals .DELTA.T1 and .DELTA.T2. It should be noted by
those skilled in the art that a modulated driving current for
driving the light source to emit the visible light signal with
varied frequencies at different time points may be modulated in the
similar manner as shown in FIGS. 4c and 4d, so that the luminous
flux of the light source driven by the modulated driving current is
equal to the luminous flux of the light source driving by the
un-modulated driving current.
[0150] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits, which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0151] With the first modulated driving current as shown in FIG.
3g, the images as shown in FIGS. 3b, 3d and 3f may be obtained at
different time points within time intervals .DELTA.T1, .DELTA.T2
and .DELTA.T3. The identification information corresponding to the
varied numbers of bright or dark stripes in the images as shown in
FIGS. 3b, 3d and 3f may be transmitted. The identification
information transmitted may comprise data bits which comprise data
corresponding to the varied frequencies, such as f.sub.3a, f.sub.3c
and f.sub.3e at different time points within time intervals
.DELTA.T1, .DELTA.T2 and .DELTA.T3. Each data bit corresponds to a
number among the varied numbers of bright or dark stripes. For
example, 10 dark stripes and 11 bright stripes as shown in FIG. 3b
may represent code "1", 5 dark stripes and 6 bright stripes as
shown in FIG. 3d may represent code "2", and 3 dark stripes and 4
bright stripes as shown in FIG. 3f may represent code "3". Of
course, the first modulated driving current may have other
combinations of signals with different frequencies or different
durations.
[0152] According to an embodiment of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more starts bit
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits
[0153] FIG. 5a is the schematic diagram of the identification
information corresponding to the varied numbers of bright or dark
stripes comprising a start bit according to an embodiment of the
present invention. As shown in FIG. 5a, a start bit is added at the
beginning of the data bits. Alternatively, more than one start bits
may be included.
[0154] FIG. 5b is the schematic diagram of the identification
information corresponding to the varied numbers of bright or dark
stripes comprising a start bit and an error correction bit
according to an embodiment of the present invention. As shown in
FIG. 5b, besides a start bit, an error correction bit is also added
at the end of the data bits. Alternatively, more than one error
correction bits may be included. Alternatively, the one or more
error correction bits may be added to the data bits without the
start bit.
[0155] According to some embodiments of the present invention, the
first modulated driving voltage or the first modulated driving
current is used for driving the light source to emit a visible
light signal with a frequency from 100 Hz to 1.37 MHz, and duration
of each bottom level of the visible light signal is fixed, or
duration of each peak level of the light pulse signal is fixed.
[0156] Optionally, the image may be obtained by an image capturing
device comprising an image sensor whose exposure mode is the
rolling shutter mode. The exposure time of the image sensor is
defined as the exposure time of pixels in each row (or column) of
the rolling shutter based image sensor.
[0157] When a frame rate of the image sensor is 30 Hz and a
resolution is 640*480 (V-line*H-line), time required for capturing
one image is 1 s/frame rate=1 s/30 Hz=0.033 s=33 ms, and time
required for capturing each row is 1 s/(frame rate*H-line)=33
ms/480=69 us.apprxeq.70 us. In order to obtain a clear image
containing bright or dark stripes with each stripe being
corresponding to each row, the exposure time of each is less than
70 us, the duration of alternating the peak and bottom levels of
the visible light signal emitted by the light source should be
equal to or larger than 70 us and thus the frequency of the visible
light signal is less than or equal to 1 s/(duration required for
bright stripes+duration required for dark stripes)=1 s/(1 s/(Frame
rate*H-line)+1 s/(Frame rate*H-line))=1 s/(70 us+70 us)=7.14
kHz.
[0158] When a frame rate of the image sensor is 30 Hz, a resolution
is 3 billion Hz with V-line:H-line=1:1, the frequency of the
visible light signal is less than or equal to 1 s/(duration
required for bright stripes+duration required for dark stripes)=1
s/(1 s/(Frame rate*H-line)+1 s/(Frame rate*H-line))=0.5*30
Hz*(3000000000).sup.0.5=1.37 MHz. Since the light blinking
frequency detectable by human eyes is less than 100 Hz, the
frequency of visible light signal is from 100 Hz to 1.37 MHz.
[0159] Referring to FIG. 3g again, the first modulated driving
current has the frequency of f.sub.3a at time points within the
time interval .DELTA.T1, the frequency of f.sub.3c at time points
within the time interval .DELTA.T2, and frequency of f.sub.3e at
time points within the time interval .DELTA.T3. Different time
intervals .DELTA.T1, .DELTA.T2 and .DELTA.T3 have same duration,
and the numbers of the peak levels or bottom levels are different.
For example, there are three peak levels or bottom levels within
.DELTA.T1; there are two peak levels or bottom levels within
.DELTA.T2; and there is one peak level or bottom level within
.DELTA.T3. As shown in FIG. 3g, the duration of each bottom level
of the visible light signal is fixed. Therefore, after emitting the
visible light signal on the basis of the first modulated driving
current as shown in FIG. 3g, the images as shown in FIGS. 3b, 3d
and 3f may be obtained at different time points within .DELTA.T1,
.DELTA.T2 and .DELTA.T3, and the dark stripes in the images as
shown in FIGS. 3b, 3d and 3f have the same width. Alternatively,
the duration of each peak level of the visible light signal may be
fixed, and the bright stripes in the images have the same
width.
[0160] According to some embodiments of the present invention,
optionally, the method 100 may further comprise steps of detecting
the presence of a human being within an illumination scope of the
light source, and emitting a visible light signal on the basis of
un-modulated driving signal in the absence of a human being.
[0161] FIG. 6 shows a light source emitting visible light signal
for transmitting identification information in response to the
presence of a human being. As shown in FIG. 6, when no human being
is presented within an illumination scope of the light source, such
as at "position a" shown in FIG. 6, a visible light signal is
emitted on the basis of un-modulated driving signal and no
identification information is transmitted. When a human being is
presented within the illumination scope of the light source, such
as at "position b" shown in FIG. 6, the presence of the human being
is detected, the driving signal of the light source is modulated on
the basis of the identification information to be transmitted, the
visible light signal is emitted on the basis of the modulated
driving signal, and the identification information corresponding to
the varied numbers of bright or dark stripes shown in one or more
images obtained from the visible light signal is transmitted. When
the human being leaves the illumination scope of the light source,
such as at "position c" shown in FIG. 6, a visible light signal on
the basis of un-modulated driving signal is emitted, and no
identification information is transmitted.
[0162] It should be noted by those skilled in the art that the
frequencies, waveforms, or widths of the peak levels and bottom
levels of the modulated driving current are not limited to the
above exemplary values, but may be set to have any values as
required. Similarly, the frequencies, waveforms, or widths of the
peak levels and bottom levels of the high frequency signal wave
signal are not limited to the above exemplary values, but may be
set to have any values as required.
[0163] According to a second aspect of the present invention, there
is provided a method for obtaining identification information of a
light source from visible light signal. FIG. 7 is a flow chart
illustrating the method 200 for obtaining identification
information of a light source from visible light signal according
to an embodiment of the present invention.
[0164] As shown in FIG. 7, the method 200 begins with a step 210 of
obtaining one or more images at one or more time points from a
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time points
emitted by a light source. As shown in FIG. 7, after the step 210,
step 220 of the method 200 is performed, wherein the varied numbers
of bright or dark stripes in the one or more images is measured and
the varied numbers of bright or dark stripes are corresponding to
the varied frequencies. After step 220, step 230 of the method 200
is performed, wherein identification information corresponding to
the varied numbers of the bright or dark stripes is obtained.
[0165] According to a third aspect of the present invention, there
is provided a method 300 for positioning by visible light signals.
FIG. 8 is a flow chart illustrating the method 300 for positioning
by visible light signal according to an embodiment of the present
invention.
[0166] Embodiments of the third aspect of the present invention
also apply to the second aspect of the present invention, thus only
the embodiments of the third aspect will be described in details
hereinafter, and same embodiments of the second aspect will not be
described repeatedly for the sake of conciseness.
[0167] As shown in FIG. 8, the method 300 begins with a step 310 of
obtaining one or more images at one or more time points from a
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time points
emitted by a light source.
[0168] According to some embodiments of the present invention, the
visible light signal may be emitted by the light source on the
basis of a modulated driving signal, which drives the light source
to emit visible light signal having its level changed between a
peak level and a bottom level with varied frequencies at different
time points, as described hereinbefore in details with respect to
the method 100.
[0169] According to some embodiments of the present invention, the
modulated driving signal may be modulated by the PWM scheme.
Optionally, the modulated driving signals may be modulated driving
voltages or modulated driving currents.
[0170] Optionally, the modulated driving current may be greater
than un-modulated driving current, so that luminous flux of the
light source driven by the modulated driving current is equal to
luminous flux of light source driven by the un-modulated driving
current, as described hereinbefore in details with respect to the
method 100 making reference to FIGS. 4a and 4b.
[0171] Optionally, the modulated driving current may be greater
than un-modulated driving currents together with a high frequency
carrier wave signal, so that the luminous flux of the light source
driven by the driving current is constant among periods comprising
peak levels and bottom levels, as described hereinbefore in details
with respect to the method 100 making reference to FIGS. 4c and
4d.
[0172] The above embodiments have been described in details
previously with respect to the method 100, and will not be iterated
herein for the sake of conciseness.
[0173] According to some embodiments of the present invention, the
image obtained from the visible light signal may be an image
containing bright or dark stripes as shown in FIGS. 3b, 3d, 3f,
where varied numbers of bright or dark stripes correspond to the
varied frequencies of the visible light signal.
[0174] According to some embodiments of the present invention, the
step 210 may comprise obtaining at the position one or more images
at one or more time points by an image capturing device comprising
an image sensor whose exposure mode is rolling shutter mode, and a
sampling rate of the rolling shutter is higher than the frame rate
of the image sensor. The image capturing device is used for
capturing the one or more images obtained from the visible light
signal emitted by the light source. The image capturing device may
be a smartphone, laptop computer, or other electronic device
equipped with camera(s). Alternatively, the image capturing device
may be an embedded system integrated in other devices or objects,
for example, piece jewelry, key, card, pen, etc. The image sensor
may be a photosensitive component.
[0175] For an image sensor whose exposure mode is rolling shutter
mode, different parts of the image sensor, each row or each column,
may be exposed at different time. The image sensor may obtain one
or more images containing bright or dark stripes, such as those
shown in FIG. 3b, 3d or 3f, when capturing one or more images at
different time points of a rapidly changing light source driven by
the modulated driving signal, such as those shown in FIG. 3g.
Optionally, the sampling rate of the rolling shutter is higher than
the frame rate of the image sensor, so as to obtain a clear image
containing bright or dark stripes with each stripe being
corresponding to each row. For example, for a frame rate of the
image sensor of 30 Hz and a resolution of 640*480, time required
for capturing one image is 1 s/30 Hz=0.033 s=33 ms, and time
required for capturing each row is 33 ms/480=69 us. In order to
obtain a clear image containing bright or dark stripes with each
stripe being corresponding to each row, the exposure time of each
is less than 69 us and the sampling rate is higher than 30 Hz.
[0176] According to some embodiments of the present invention, the
step 210 may comprise capturing at the position on an image sensor
with a rolling shutter the one or more images in which different
portions of the image sensor are exposed at different time points.
Optionally, the image sensor may be a complementary
metal-oxide-semiconductor (CMOS) image sensor or a Charge-Coupled
Device (CCD) image sensor.
[0177] As shown in FIG. 8, after the step 310 described
hereinbefore, step 320 of the method 300 is performed, wherein
varied numbers of bright or dark stripes in the one or more images
is measured, and the varied numbers of bright or dark stripes are
corresponding to the varied frequencies.
[0178] According to some embodiments of the present invention,
varied numbers of bright or dark stripes in the one or more images
obtained from the visible light signal may be measured by, for
example, an image processor or a general purpose processor. After
the image is projected onto the image sensor surface, the optical
signal detected by the image sensor is converted into electrical
signal by the image sensor. The analog electrical signals are
converted into digital signals by an analog-to-digital-converter
(ADC) of the image sensor or the processor. The processor is
applied to further process the digital signal and generate a
digital image, which may be displayed on a monitor. Optionally, a
digital signal processing (DSP) module of the processor may be
applied to process the digital signal and generate a digital
image.
[0179] As shown in FIG. 8, after the step 320 described
hereinbefore, step 330 of the method 200 may be performed, wherein
identification information of the light source corresponding to the
varied numbers of the bright or dark stripes is obtained.
[0180] According to some embodiments of the present invention, the
identification information of the light source corresponding to the
pattern of the color stripes may be any type of identification
information, for example, the identifier (ID) of the light source,
and other identification information.
[0181] According to some embodiments of the present invention, the
varied numbers of bright or dark stripes in the one or more images
are derived from the varied frequencies of the visible light signal
at different time points. According to some embodiments of the
present invention, the identification information of the light
source corresponding to the varied numbers of bright or dark
stripes may be decoded. By this way, the initial identification
information carried on the visible light signal can be
recovered.
[0182] As shown in FIGS. 3b, 3d and 3f, the images captured by an
image sensor can be generated from the light source emitting
visible light signal at different time points, which is driven by
the modulated driving signal as shown in FIG. 3g. When decoding the
identification information corresponding to the varied numbers of
bright or dark stripes, the analysis of the captured images is
based on the measurements of varied numbers of bright or dark
stripes. For example, the image shown in FIG. 3b has 10 dark
stripes and 11 bright stripes, and its decoded wave form
corresponds to that in FIG. 3a or within .DELTA.T1 as shown in FIG.
3g; the image shown in FIG. 3d has 5 dark stripes and 6 bright
stripes, and its decoded wave form corresponds to that in FIG. 3c
or within .DELTA.T2 as shown in FIG. 3g; the image shown in FIG. 3e
has 3 dark stripes and 4 bright stripes, and its decoded wave form
corresponds to that in FIG. 3e or within .DELTA.T3 as shown in FIG.
3g.
[0183] It should be noted that although varied frequencies of the
visible light signals at different time points are used during
coding, the transmitted identification information of the light
source may be decoded by comparing the relative frequencies
corresponding to the numbers of the bright or dark stripes, instead
of the absolute frequencies of the visible light signals.
[0184] According to some embodiments of the present invention, the
light source may be one or more light sources. One or more images
from visible light signal emitted by the light source may be
obtained at one or more time points. Each image obtained may have
one or more exposed regions, and each exposed region may contain
bright or dark stripes corresponding to one light source.
[0185] FIG. 9 is a schematic diagram of an image containing one or
more exposed regions corresponding to one or more light sources
according to an embodiment of the present invention. In FIG. 9, the
image obtained has three exposed regions, and each exposed region
contains bright or dark stripes, such as those shown in FIG. 3b, 3d
or 3f, corresponding to one light source driven by the modulated
driving signal, such as those shown in FIG. 3a, 3c or 3e.
[0186] The step 310 may comprise: obtaining one or more images at
one or more time points from visible light signal having its level
changed between a peak level and a bottom level with varied
frequencies at different time points emitted by the one or more
light sources, wherein one or more exposed regions in each image
correspond to the one or more light sources. The image having one
or more exposed regions obtained from one or more light source, for
example the image shown in FIG. 9, may be obtained in the similar
way as that obtained from one light source as mentioned above,
which will not be iterated herein for the sake of conciseness.
Further, the step 320 may comprise measuring the varied numbers of
the bright or dark stripes of the one or more exposed regions in
each image. The varied numbers of bright or dark stripes of each
exposed region corresponding to each set light source may be
measured in the similar way as mentioned above. For example, varied
numbers of bright or dark stripes of each exposed region
corresponding to each light source shown in FIG. 9 may be
respectively measured in the similar way as those shown in FIGS.
3b, 3d and 3f, which will not be iterated herein for the sake of
conciseness. Still further, the step 330 may comprise obtaining
identification information corresponding to the varied numbers of
the bright or dark stripes of the one or more exposed regions in
each image. The identification information corresponding to the
varied number of bright or dark stripes of each exposed regions in
the image may be obtained respectively, in the similar way as that
from one light source as mention above. For example, identification
information corresponding to the varied number of bright or dark
stripes of each exposed region corresponding to each light source
shown in FIG. 9 may be respectively obtained in the similar way as
that corresponding to those shown in FIGS. 3b, 3d and 3f, which
will not be iterated herein for the sake of conciseness.
[0187] When the incident light is not in perpendicular with the
plane of the image sensor, the shape of the light spot projected on
the image sensor may have distortion, for example, from a circular
to an ellipse. In this case, acceleration meter, gravity sensor,
tilt sensor, gyro, or magnetic sensor may be applied to measure the
angle of inclination, which may be used to obtain the
identification information of one or more light sources
corresponding to the varied numbers of bright or dark stripes of
the one or more exposed regions in the image.
[0188] As shown in FIG. 8, after the step 330 described
hereinbefore, step 340 of the method 300 is performed, wherein the
position is determined by checking the identification information
in a predetermined map database. According to some embodiments of
the present invention, the predetermined map database contains
identification information and the corresponding position
information of each light source. By checking the identification
information in the map database, the position of the light source
can be determined.
[0189] According to some embodiments of the present invention,
optionally, before step 330, method 300 may further comprise
determining an area of the position by means of one or more
wireless positioning schemes. After the area of the position is
determined, the position can be then determined by checking the
identification information with data of the area in the
predetermined map database.
[0190] According to some embodiments of the present invention,
identification information of a light source is unique for an area
at which the light source is located.
[0191] According to some embodiments of the present invention, the
wireless positioning scheme comprises positioning by means of GPS,
GPRS, GSM, CDMA, WIFI, Zigbee, Bluetooth, and RFID.
[0192] By determining an area of the position by means of one or
more wireless positioning schemes, the area where the light source
is located can be determined, providing the rough position of the
light source. Then, the position of the light source within the
area can be determined by checking the identification information
with data of the area in the predetermined map database, providing
the accurate position of the light source. By this way, each area
may have independent map database. The identification information
of the light source in one area may be different from that in a
different area.
[0193] Alternatively, the identification information of the light
source in one area may be same as that in a different area, and
under such circumstances, the area where the light source is
located should be determined firstly and then the position of the
light source within the area can be determined on the basis of the
identification information which unique in the area. Such
embodiment allows easier coding and shorter length of the
identification information, and faster transmission of the
identification information.
[0194] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0195] With the modulated driving current as shown in FIG. 3g, the
images as shown in FIGS. 3b, 3d and 3f may be obtained at different
time points within time intervals .DELTA.T1, .DELTA.T2 and
.DELTA.T3. The identification information corresponding to the
varied numbers of bright or dark stripes in the images as shown in
FIGS. 3b, 3d and 3f may be transmitted. The identification
information of the light source transmitted may comprise data bits
which comprise data corresponding to the varied frequencies, such
as f.sub.3a, f.sub.3c and f.sub.3e at different time points within
time intervals .DELTA.T1, .DELTA.T2 and .DELTA.T3. Each data bit
corresponds to a number among the varied numbers of bright or dark
stripes. For example, 10 dark stripes and 11 bright stripes as
shown in FIG. 3b may represent code "1", 5 dark stripes and 6
bright stripes as shown in FIG. 3d may represent code "2", and 3
dark stripes and 4 bright stripes as shown in FIG. 3f may represent
code "3". Of course, the modulated driving current may have other
combinations of signals with different frequencies or different
durations.
[0196] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more start bits
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits.
[0197] Referring to FIG. 5a again, the identification information
corresponding to the varied numbers of bright or dark stripes may
comprise a start bit according to an embodiment of the present
invention. Optionally, a start bit is added at the beginning of the
data bits. Alternatively, more than one start bits may be
included.
[0198] Referring to FIG. 5b again, the identification information
corresponding to the varied numbers of bright or dark stripes may
comprise a start bit and an error correction bit according to an
embodiment of the present invention. Optionally, besides a start
bit, an error correction bit is also added at the end of the data
bits. Alternatively, more than one error correction bits may be
included. Alternatively, the one or more error correction bits may
be added to the data bits without the start bit.
[0199] According to a fourth aspect of the present invention, there
is provided a light source 400 for transmitting identification
information by visible light signal. As shown in FIG. 10, the light
source 400 may be a lamp, for example a LED lamp, LED backlight,
LED flat light, etc. However, the light source 400 is not limited
to the above example, but may be any light source capable of
transmitting visible light signals.
[0200] As shown in FIG. 10, the light source 400 may comprise a
modulator 410 and an emitter 420. The modulator 410 may be a
modulator driven by an electric signal with constant current,
constant voltage, constant electric power, constant optical power,
or by an electric signal modulated by PWM. The emitter 420 may be a
LED which may emit visible light signal having its level changed
between a peak level and a bottom level with varied frequencies at
different time points. As for one-way LED driving, the emitter 420
may be one or more LEDs connected in one string, including 1 to
dozens of LEDs. Alternatively, the emitter 420 may be one or more
LEDs connected in more strings with each string including 1 to
dozens of LEDs. According to some embodiments of the present
invention, the emitter 420 comprises more LEDs. However, the
modulator 410 or the emitter 420 is not limited to the above
example, but may be any modulator or emitter.
[0201] The modulator 410 may be configured to modulate, on the
basis of the identification information to be transmitted, a
driving signal of the light source to obtain a modulated driving
signal for driving the light source to emit visible light signal
having its level changed between a peak level and a bottom level
with varied frequencies at different time points.
[0202] The emitter 420 may be configured to emit the visible light
signal having its level changed between a peak level and a bottom
level with varied frequencies at different time points on the basis
of the modulated driving signal, so as to transmit identification
information corresponding to the varied numbers of bright or dark
stripes shown in one or more images obtained from the visible light
signal at one or more time points, which numbers are corresponding
to the varied frequencies.
[0203] According to some embodiments of the present invention, the
modulator 410 may be configured to modulate on the basis of the
identification information to be transmitted a driving voltage or a
driving current of the light source to obtain a first modulated
driving voltage or a first modulated driving current.
[0204] According to some embodiments of the present invention, the
first modulated driving current is greater than the un-modulated
driving current, so that the luminous flux of the light source
driven by the first modulated driving current is equal to the
luminous flux of the light source driven by the un-modulated
driving current.
[0205] According to some embodiments of the present invention, the
emitter 420 can be configured to emit the visible light signal on
the basis of a second modulated driving current which is greater
than the un-modulated driving current together with a high
frequency carrier wave signal, so that luminous flux of the light
source driven by the second modulated driving current is constant
among periods comprising peak levels and bottom levels.
[0206] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0207] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes may further comprise one or more starts bit
and/or one or more error correction bits, the start bits are used
to identify a start position of a set of data bits, and the one or
more error correction bits are used to check error in the data
bits.
[0208] According to some embodiments of the present invention, the
first modulated driving voltage or the first modulated driving
current is used for driving the light source to emit a visible
light signal with a frequency from 100 Hz to 1.37 MHz, and duration
of each bottom level of the visible light signal is fixed, or
duration of each peak level of the light pulse signal is fixed.
[0209] According to some embodiments of the present invention, the
light source 400 may further comprise a detector configured to
detect the presence of a human being within an illumination scope
of the light source, and the emitter is configured to emit a
visible light signal on the basis of un-modulated driving signal in
the absence of a human being.
[0210] The above detailed descriptions for the method 100 also
apply to the embodiments of the light source 400 according to the
present invention, and are thus not iterated for the sake of
conciseness. In particular, the step 110 in the method 100 can be
performed by the modulator 410, and the step 120 in the method 100
can be performed by the emitter 420.
[0211] According to a fifth aspect of the present invention, there
is provided a device 500 for obtaining identification information
from visible light signal. For example, the device may be a mobile
device with a camera, such as a smartphone, tablet, laptop
computer, or other electronic device. However, the device 500 is
not limited to these examples, but can be any electronic device
with photosensitive component.
[0212] As shown in FIG. 10, the device 500 for obtaining
identification information of light source from visible light
signal may comprise an image sensor 510, a memory 520, and a
processor 530. The image sensor 510 may be for example a camera,
photodiode, and photodiode array. The memory 520 may be for example
volatile memory, non-volatile memory, etc. The processor 530 may be
general purpose processor, dedicated processor, etc.
[0213] The image sensor 510 can be configured to obtain one or more
images at one or more time points from a visible light signal
having its level changed between a peak level and a bottom level
with varied frequencies at different time points emitted by a light
source. The memory 520 can be configured to store the one or more
images obtained by the image sensor at one or more time points. The
processor 530 can be configured to measure varied numbers of bright
or dark stripes in the one or more images stored in the memory 520
and obtain identification information corresponding to the varied
numbers of the bright or dark stripes, and the varied numbers of
bright or dark stripes are corresponding to the varied
frequencies.
[0214] According to a sixth aspect of the present invention, there
is provided a device for positioning by visible light signal. For
example, the device may be a mobile device with a camera, such as a
smartphone, tablet, laptop computer, or other electronic device.
However, the device is not limited to these examples, but can be
any electronic device with photosensitive component.
[0215] Embodiments of the sixth aspect of the present invention
also apply to the fifth aspect of the present invention, thus only
the embodiments of the sixth aspect will be described in details
hereinafter, and same embodiments of the fifth aspect will not be
described repeatedly for the sake of conciseness.
[0216] Embodiments of device according to the sixth aspect of the
present invention will be described with reference to FIG. 10 again
hereinafter, and same reference numbers with the fifth aspect will
be used.
[0217] As shown in FIG. 10, the device 500 for positioning by
visible light signal may comprise an image sensor 510, a memory
520, and a processor 530. The image sensor 510 may be for example a
camera, photodiode, and photodiode array. The memory 520 may be for
example volatile memory, non-volatile memory, etc. The processor
530 may be general purpose processor, dedicated processor, etc.
[0218] The image sensor 510 can be configured to obtain at a
position one or more images at one or more time points from a
visible light signal having its level changed between a peak level
and a bottom level with varied frequencies at different time points
emitted by a light source. The memory 520 can be configured to
store the one or more images obtained by the image sensor at one or
more time points. The processor 530 can be configured to measure
varied numbers of bright or dark stripes in the one or more images
stored in the memory 520, obtain identification information
corresponding to the varied numbers of the bright or dark stripes,
and determine the position by checking the identification
information in a predetermined map database, the varied numbers of
bright or dark stripes being corresponding to the varied
frequencies.
[0219] According to some embodiments of the present invention, the
processor 530 is configured to before determining the position by
checking the identification information in a predetermined map
database, determine an area of the position by means of one or more
wireless positioning schemes; and the processor 530 is configured
to determine the position by checking the identification
information with data of the area in the predetermined map
database. According to some embodiments of the present invention,
the wireless positioning scheme comprises positioning by means of
GPS, GPRS, GSM, CDMA, WIFI, Zigbee, Bluetooth, and RFID.
[0220] According to some embodiments of the present invention,
identification information of a light source 400 is unique for an
area at which the light source 400 is located.
[0221] By determining an area of the position by means of one or
more wireless positioning schemes, the area where the light source
is located can be determined, providing the rough position of the
light source. Then, the position of the light source within the
area can be determined by checking the identification information
with data of the area in the predetermined map database, providing
the accurate position of the light source. By this way, each area
may have independent map database. The identification information
of the light source in one area may be different from that in a
different area.
[0222] Alternatively, the identification information of the light
source in one area may be same as that in a different area, and
under such circumstances, the area where the light source is
located should be determined firstly and then the position of the
light source within the area can be determined on the basis of the
identification information which unique in the area. Such
embodiment allows easier coding and shorter length of the
identification information, and faster transmission of the
identification information.
[0223] According to some embodiments of the present invention,
exposure mode of the image sensor is rolling shutter mode, and a
sampling rate of the rolling shutter is higher than the frame rate
of the image sensor.
[0224] According to some embodiments of the present invention, the
image sensor 510 is an image sensor with a rolling shutter and is
configured to obtain the one or more images in which different
portions of the image sensor are exposed at different time points.
Optionally, the image sensor 510 may be a complementary
metal-oxide-semiconductor (CMOS) image sensor or a Charge-Coupled
Device (CCD) image sensor.
[0225] According to some embodiments of the present invention, the
visible light signal is emitted by the light source 400 on the
basis of a modulated driving signal, which drives the light source
400 to emit the visible light signal having its level changed
between a peak level and a bottom level with varied frequencies at
different time points.
[0226] According to some embodiments of the present invention, the
light source 400 may be one or more sets of light sources, and the
image sensor 510 can be configured to obtain one or more images at
one or more time points from visible light signal having their
level changed between peak levels and bottom levels with varied
frequencies at different time points emitted by the one or more
light sources, wherein one or more exposed regions in each image
correspond to the one or more light sources; the memory 520 can be
configured to store the one or more images obtained by the image
sensor at one or more time points; and the processor 530 can be
configured to measure the varied numbers of the bright or dark
stripes of the one or more exposed regions in each image, and
obtain identification information corresponding to the varied
numbers of the bright or dark stripes of the one or more exposed
regions in each image.
[0227] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes comprises data bits which comprise data
corresponding to the varied frequencies, and each data bit
corresponds to a number among the varied numbers of bright or dark
stripes.
[0228] According to some embodiments of the present invention, the
identification information corresponding to the varied numbers of
bright or dark stripes further comprises one or more start bits
and/or one or more error correction bits, the one or more start
bits being used to identify a start position of a set of data bits,
and the one or more error correction bits being used to check error
in the data bits.
[0229] The above detailed descriptions for the method 300 also
apply to the embodiments of the device 500 according to the sixth
aspect of the present invention, and are thus not iterated for the
sake of conciseness. In particular, the step 310 in the method 300
as described above can be performed by the image sensor 510 and
memory 520, and the steps 330, 340 and 350 in the method 300 can be
performed by the processor 530.
[0230] According to some embodiments of the present invention, the
device for positioning by visible light signal may be a mobile
device. FIG. 11 shows a flow chart of a process that a mobile
device accesses the indoor map. The mobile device starts the
software for indoor positioning, initializes the wireless network,
determines an area of the position by means of one or more wireless
positioning schemes. The software searches where there is the map
of the current position in the predetermined may database of the
mobile device. If no, the map of the current position is downloaded
to the mobile device through wireless network. If yes, the mobile
device checks the map of the current position and determines the
position by checking the identification information in the map.
[0231] According to some embodiments of the present invention, a
mobile device may be integrated with a positioning software. FIG.
12 shows the diagram of a mobile device integrated with a
positioning software. The identification information and a
predetermined map database can be stored in the memory of the
mobile device. Therefore, the mobile device can compare the
received identification information with the map database, and show
the map of the position on the display of the mobile device. As
described above, the working flow of a mobile device integrated
with a positioning software is as follows: one or more images of
the light source are captured by the image sensor; the captured
images are sent to the processor to decode the identification
information; the recovered identification information is compared
with the predetermined map database and the accurate position is
shown on the display of the mobile device.
[0232] According to some embodiments of the present invention, a
predetermined map database contains the identification information
of the light sources. FIG. 13 is the diagram of the relation
between the map database and the identification information of
light sources. The predetermined map database containing
identification information may be stored in a mobile device.
Alternatively, the predetermined map database containing
identification information may be stored in a remote server. After
recovering the identification information, the mobile device can
access the predetermined map database on the remote server through
network. Then, the mobile device compares the received
identification information with the map database, and the accurate
position is shown on the display of the mobile device.
[0233] There are two conventional ways to modify the identification
information stored in the light source: Disassembling the memory
chip from the light source, and modifying the identification
information by a compiler, which can rewrite the memory chip; and
reserving an interface for modifying identification information on
the light source, connecting the interface with a compiler which
can rewrite the memory chip through a cable to modify the memory
chip. Both ways are complex and consequently lead to a high
maintenance cost.
[0234] According to some embodiments of the present invention, the
identification information of the light source may be modified by a
mobile modification device via wireless communication. FIG. 14 is
the diagram of a light source with a mobile modification device
comprising a receiver and a transmitter. The light source can
receive the wireless signal sent by the mobile device and update
the identification information stored in the integrated memory. The
wireless signal could be a light signal, RF signal or other kind of
wireless signals. The visible light signal is chosen as an example
to further explain the method and related devices. The present
invention provides an easy and low cost way to modify
identification information stored in the integrated memory in light
sources.
[0235] According to some embodiments of the present invention, a
mobile modification device can update the information stored in the
light source as shown in FIG. 15. The light detection module is
applied for receiving the visible light signal sent by the mobile
device for updating the identification information in the light
source; and updating the identification information in the
integrated memory in light sources.
[0236] According to some embodiments of the present invention, the
identification information of the light source may be updated
through the mobile modification device as shown in FIG. 16. A light
detection module is integrated in the light source. This light
detection module is applied for receiving the visible light signal
sent by the mobile modification device for updating the
identification information in the light source. When the light
detection module receives a signal which is confirmed as correct
identification information, the processor updates the
identification information in the integrated memory in the light
source.
[0237] FIG. 17 is the flow chart of updating the identification
information of a light source. Mobile modification device receives
the visible light signal sent by the light source; demodulates the
visible light signal with a microprocessor; and shows the
demodulated identification information on a display. Meanwhile, the
microprocessor search the memory for the identification information
of the light source and display the identification information to
be updated on the display, determine whether the demodulated
identification information is the same as the identification
information. If they are not the same, the transmitter sends the
visible light signal modulated by the modulator to the light
source. The light source receives the visible light signal, the
microprocessor demodulates the identification information and
updates the identification information.
[0238] FIG. 18 is the flow chart of searching the identification
information of a light source. After the identification information
is updated, the light source sends the updated identification
information to the mobile modification device. The receiver of the
mobile modification device receives the information, the
microprocessor demodulates the identification information of the
light source and display a confirmation message after updating is
completed. If the received updated identification information is
the same as the identification information to be updated, then the
process ends. Otherwise, the mobile modification device resends the
visible light signal containing the identification information to
the light source.
[0239] According to some embodiments of the present invention, FIG.
19a shows that the image sensor is placed horizontally for
capturing image. The image sensor is placed below the light source
for capturing the image from the visible light signals of multiple
light sources. FIG. 19b shows the captured image under when the
image sensor is placed horizontally. The captured image contains
three exposed regions corresponding to three light sources. The
current position of the mobile device can be calculated by the
position of the corresponding three light sources. The distance
between point A and B is:
D.sub.AB=((X.sub.A,-X.sub.B).sup.2+(Y.sub.A-Y.sub.B).sup.2).sup.0.5.
This distance may be pre-stored in the database. The ratio Q.sub.Y
between the actual distance and the distance of the pixel points on
the image may be obtained by the actual distance D/D.sub.AB on Y
direction. The distance between point A and C is:
D.sub.Ac=((X.sub.A,-X.sub.C).sup.2+(Y.sub.A-Y.sub.C).sup.2).sup.0.5.
This distance may be pre-stored in the database. The ratio Q.sub.X
between the actual distance and the distance of the pixel points on
the image may be obtained by the actual distance D/D.sub.AC on X
direction. The actual coordinates of the midpoint
(X.sub.mid,Y.sub.mid) may be determined by the midpoint
(X.sub.mid,Y.sub.mid) and anyone of A, B C. The actual coordinates
of the midpoint (X,Y) may be calculated as X=X.sub.B(actual
coordinate)+(X.sub.mid-X.sub.B)*Q.sub.X, Y=Y.sub.B(actual
coordinate)+(Y.sub.mid-Y.sub.B)*Q.sub.Y.
[0240] According to some embodiments of the present invention, FIG.
20a shows that the image sensor for capturing image is tilted from
the horizontal plane. When the image sensor is inclined, the
surface of the image sensor is not perpendicular to the direction
of the incident light, causing the midpoint of the captured image
is different from the midpoint of the image captured when the image
sensor is placed horizontally. An angular transducer or other
devices capable of detecting angle integrated in the mobile device
may be used, in order to compensate the decoding error caused by
the tilting angle. Alternatively, the different distance between
each light source and the image sensor may also be reflected by the
intensity of the visible light signal emitted by the light source
and received by the image sensor. Therefore, the position of the
mobile device may be calculated through the intensity of the
visible light signal emitted by the light source and received by
the image sensor. FIG. 20b shows the image captured by the image
sensor when the image sensor is tilted from the horizontal plane,
that is, the surface of the image sensor is not perpendicular to
the direction of the incident light. In this case, the position of
the mobile device needed to be calibrated by calculating the
tilting angle of the mobile device.
[0241] According to some embodiments of the present invention, FIG.
21 shows the diagram on how to calculate the midpoint of the image.
The midpoint of the image may be calculated through the exposed
regions on the image. 01, the angle between the surface of the
mobile device and G direction, may be obtained by the gyroscope in
the mobile device. As shown in the figure,
.theta..sub.2=90-.theta..sub.1. The distance h between the mobile
device and the floor is generally about 1.0.about.1.2 meters.
Therefore, the distance between the mobile device and the ceiling
is: H=h-1.2 m. The distance from the midpoint to the actual
location point is d=H*Tan .theta..sub.2, where d is the distance
from the physical location of the mobile device when capturing
image to the midpoint of the image.
[0242] According to some embodiments of the present invention, FIG.
22a shows the schematic diagram of a gyroscope. The gyroscope can
be applied for measuring the angular relationship between X, Y, Z
axis and the angle between the surface of the image sensor and the
incident light. The rotation angle of the mobile device is
.phi..sub.n=.phi..sub.n-1+1sgl, where .phi..sub.n is the angle at
the present moment, .phi..sub.n-1 is the angle at the previous
moment, .omega. is the angular velocity measured by the gyroscope,
dt is the sampling interval. The rotation angle of the mobile
device may be obtained by calculating the angular velocity along X,
Y, Z axis, respectively. FIG. 22b is a schematic diagram of the
coordinate system an accelerometer of the mobile device. A mobile
device is placed facing up, X, Y axis is in the horizontal plane
and the Z axis is along the gravity direction and perpendicular to
the horizontal plane.
[0243] According to some embodiments of the present invention, FIG.
23 shows the schematic diagram on how to calculate the midpoint of
the captured image. According to the projection in horizontal plane
of the angle between the surface of the image sensor and the
incident light, as well as the angular relationship with X axis,
the actual position of the mobile device may be calculated. The
rotation angle of the mobile device is
.phi..sub.n=.phi..sub.n-1+.omega.dt. As shown in FIG. 21, the
distance from the midpoint to the actual location point where the
mobile device is capturing the image is d. The position information
of the light source may be obtained from the predetermined may
database. According to the image information and the position
information of light sources A and B, the midpoint of the image is
(X.sub.mid,Y.sub.mid). The distance between point A and B is:
D.sub.AB=((X.sub.A,-X.sub.B).sup.2+(Y.sub.A-Y.sub.B).sup.2).sup.0.5.
This distance may be pre-stored in the database. The ratio Q.sub.Y
between the actual distance and the distance of the pixel points on
the image may be obtained by the actual distance D/D.sub.AB on Y
direction. The distance between point A and C is:
D.sub.Ac=((X.sub.A,-Xc).sup.2+(Y.sub.A-Yc).sup.2).sup.0.5. This
distance may be pre-stored in the database. The ratio Q.sub.X
between the actual distance and the distance of the pixel points on
the image may be obtained by the actual distance D/D.sub.AC on X
direction. The actual coordinates of the midpoint
(X.sub.mid,Y.sub.mid) may be determined by the midpoint
(X.sub.mid,Y.sub.mid) and anyone of A, B C. The actual coordinates
of the midpoint (X,Y) may be calculated as X=X.sub.B(actual
coordinate)+(X.sub.mid-X.sub.B)*Q.sub.X, Y=Y.sub.B(actual
coordinate)+(Y.sub.mid-Y.sub.B)*Q.sub.Y. The actual coordinate of
the midpoint is (X+d*cos .phi.,Y+d*sin .phi.).
[0244] According to some embodiments of the present invention, FIG.
24 is the schematic diagram of the format of the data stored in the
databases. The mobile device receives the visible light signal sent
by the light source; the identification information is recovered by
the software integrated in the mobile device, the identification
information is sent to the database through network; by comparing
the identification information with the database, the position of
the mobile device is determined; the identification information is
transmitted to the mobile device by the database computer through
wireless schemes, such as, GPRS, GSM, CDMA, WIFI, Zigbee and
Bluetooth, etc. The position information of the mobile device is
displayed in the map shown in the display of the mobile device.
[0245] According to some embodiments of the present invention, FIG.
25 is the schematic diagram of information related to the
identification information of the light source. The identification
information of the light source may correspond to the following
information: the coordinates of the position in the map database;
other related information, such as advertisements information,
service information, reminder information, etc.
[0246] Magnetometer and gyroscope could be used to measure the
direction of motion. The positioning can be realized only by
visible light signal, or by combining with other positioning
methods, such as, GPS, GPRS, GSM, CDMA, Wi-Fi, Zigbee, Bluetooth,
RFID, accelerometer, angular transducer, gyroscope, ultrasonic,
etc. Between two light sources, more methods as mentioned above may
be applied, to improve the consistency and continuity of the
positioning. For example, accelerometer is applied to measure the
frequency of human steps; then the walking speed can be estimated
by a normal length of ty of the positiangular transducer is applied
to measure the walking direction. In this way, when moving between
two light sources, the position of the mobile device still can be
roughly positioned.
[0247] According to some embodiments of the present invention, FIG.
26 is the schematic diagram of recording a route. A magnetic sensor
is applied to determine the initial direction, the gyroscope is
applied to measure the walking direction, a gravity sensor is
applied to determine human steps when he is walking. According to
the speed of walking and a normal length of "one step", the walking
direction and speed may be roughly determined and can be indicated
on the map.
[0248] According to some embodiments of the present invention, FIG.
27 is the schematic diagram of the captured image of two light
sources. When the mobile device is under the light sources, the
position may be determined by capturing the image of the light
signals emitted by the light sources. The two light sources may be
placed such that the distance between them is e less than 0.5 m,
which allows the two light sources can be captured within one
image.
[0249] According to some embodiments of the present invention, FIG.
28 is the schematic diagram of the captured image of two light
sources which is calibrated. The two light sources are installed in
a south-north orientation. The last bit in the identification
information indicates the orientation. For example, "For example,
orientation.led in The mobile device captures the image of the two
light source, receives the identification information of these two
light sources, calibrated with gyroscope multiple times, to insure
the accuracy of the orientation obtained.
[0250] According to some embodiments of the present invention, a
map database may be used for positioning. The mobile device
receives the light signal sent by the light source; the position of
the mobile device is determined by comparing the identification
codes with the database; the current position of the mobile device
is shown on the display of the mobile device. This positioning
system can be applied for the navigation in a shopping mall or
super market, and can be used for business statistics, market
expansion, online support, SNS (Social Networking Services),
Management profiles, or other position-related applications.
[0251] According to some embodiments of the present invention, the
light source 400 may further comprises an AC/DC converter, a
micro-controller and a memory, as shown in FIG. 29. The AC/DC
converter is configured to convert the AC power of the light source
400 obtained from electric power supply to DC power. The
micro-controller is configured to compile the pre-stored
identification information in the memory to modulation signal based
on pre-defined coding method. The modulator is configured to
receive the modulation signal and modulate, on the basis of the
identification information to be transmitted, a driving signal of
the light source to obtain a modulated driving signal for driving
the light source to emit visible light signal having its level
changed between a peak level and a bottom level with varied
frequencies at different time points.
[0252] According to some embodiments of the present invention, the
exposure time of the image sensor 510 may be adjusted before
capturing an image. FIG. 30a is a flowchart of a process that the
exposure time of the image sensor 510 is adjusted before capturing
an image according to an embodiment of the present invention. An
image sensor is turned on and the exposure time is adjusted.
Optionally, the frame rate is 30 Hz and the resolution of each
frame is 640*480. Since the light source is close to the image
sensor, the light intensity is high. The exposure time of the image
sensor may be set at a small value, such as 1/14400 s. When the
exposure time of the image senor is less than 1/14400 s, such
exposure time is fixed by software. Then, the image senor is ready
to capture an image. By adjusting the exposure time of the image
sensor, when the exposure time of the image sensor is short enough,
images with bright or dark strips can be captured clearly for
transmitting identification information. By this way, the
communication between the light source and the image sensor is
achieved.
[0253] According to some embodiments of the present invention, in
order to capture images with bright or dark stripes clearly, the
sampling duration rate of the image sensor may be smaller or equal
to the duration of the peak level or bottom level of the visible
light signal emitted by the light source, as shown in FIG. 30b. For
instance, in FIG. 30b, the duration of the bottom level is smaller
compared to that of the peak level. In order to capture dark
stripes clearly, which corresponds to the bottom level, the
sampling duration of the image sensor is smaller or equal to the
duration of the bottom level. In the case that the frequency of the
visible light signal is fixed, the smaller the sampling duration,
the clearer the bright or dark stripes obtained. For instance, as
shown in FIG. 30c, within the duration of the bottom level of the
visible light signal, a dark stripe having of 3 rows is obtained;
and within the duration of the peak level of the visible light
signal, a bright stripe having 13 rows is obtained. Similarly, an
image as shown in FIG. 30d may be obtained, which contains bright
or dark stripes as shown in FIG. 30c.
[0254] According to some embodiments of the present invention,
after the image is captured, the exposed region in the image is
detected as shown in FIGS. 31a and 31b. Alternatively, the exposed
region may be detected by software in following way: searching the
exposed regions from the center of the image outwards along a
spiral route; detecting the exposed region; and adjusting the
exposure parameters of the image sensor according to the brightness
of the exposed region.
[0255] According to some embodiments of the present invention, when
the light source is one or more light source, each image captured
may contain one or more exposed regions corresponding to one or
more light sources. The one or more exposed regions in the image
may be detected as shown in FIGS. 32a-32c. FIG. 32a shows an image
captured by an image sensor from one or more light sources. The one
or more exposed regions on each image may be detected as shown in
FIG. 32b in following way: searching the exposed regions from the
center of the image outwards along a spiral route; dividing the
image into one more regions corresponding to the one or more light
sources; detecting each exposed region corresponding to each light
source as shown in FIG. 32c; determining the number of the stripes;
and obtaining the identification information transmitted.
[0256] According to some embodiments of the present invention, the
exposure time of the image sensor 510 may be adjusted before
capturing an image. FIG. 33 is a flowchart of a process that the
exposure time of the image sensor 510 is adjusted before capturing
an image according to an embodiment of the present invention. When
the light source is far away from the image sensor and the light
intensity detected by the image sensor is low, the exposure time of
the image sensor may be adjusted to a suitable value, based on the
brightness in the center of the light source. When the exposure
time of the image senor is less than the suitable value, such
exposure time is fixed by software. Then, the image senor is ready
to capture an image. Optionally, the frame rate is 30 Hz and the
resolution of each frame is 640*480. The time for the image sensor
to capture one image is 1 s/30 Hz=0.033 s=33 ms, and the time for
capturing each row is 33 ms/480=69 us.apprxeq.10 us. When the
exposure time is fixed to 1/2000 s corresponds to the time for
capturing ( 1/2000 s)/70 us=7.2 rows. In order to capture images
with bright and dark strips clearly for transmitting identification
information, the duration of the bottom level corresponding to dark
stripes or the duration of the peak level corresponding to bright
stripes should be larger than the exposure time 1/2000 s, and thus
the width of the dark or bright stripes should be larger than 7
rows. Optionally, the exposure time may be set as an interface
according to underlying software agreement and this interface can
be directly applied to the application software. When an image
sensor is turned on, the exposure time is set directly by the
application layer interface.
[0257] According to some embodiments of the present invention, the
captured image containing bright and dark stripes may be decoded,
optionally by decoding software, in the following manner: capturing
one or more images from the visible light signal emitted by a light
source; determining one or more exposed regions in each image;
measuring the number of the bright or dark strips where different
number represents different code; and recovering the transmitted
identification information.
[0258] FIG. 34a is a schematic diagram of the image captured by the
image sensor, according to embodiments of the present
invention.
[0259] Alternatively, the exposed region within the image is
searched from the center of the image outwards along a spiral
route, optionally, by pre-installed software, as shown in FIG. 34b,
according to embodiments of the present invention. Alternatively,
the exposed region may be determined by searching pixels with gray
scale values higher than a threshold value. For instance, for an
image to be analyzed with a resolution of 640*480, a threshold
value is set to the average value of the gray scale of all pixels;
the exposed region is searched from the center of the image
outwards along a spiral route; when there are a plurality of pixels
with gray scale values higher than the threshold in a region, this
region is determined as a exposed region. Alternatively, the
determined exposed region may be a rectangular region in the image
according to embodiments of the present invention, as shown in FIG.
34c, with the coordinates of the four corners of the rectangle
(x.sub.min, y.sub.min), (x.sub.max, y.sub.min), (x.sub.min,
y.sub.max) and (x.sub.max, y.sub.max). Here, x.sub.min and
x.sub.max are the minimum and maximum coordinates on the x-axis of
the pixels with gray scale values higher than the threshold,
respectively; y.sub.min and y.sub.max are the minimum and maximum
coordinates on the y-axis of the pixels with gray scale values
higher than the threshold, respectively. And the center of the
exposed region is: (x.sub.mid, y.sub.mid), where
x.sub.mid=(x.sub.min+x.sub.max)/2 and
y.sub.mid=(y.sub.min+y.sub.max)/2. Alternatively, the coordinates
may be obtained by scanning, comparing and screening each pixel in
the image, as shown in FIG. 34d. Alternatively, since the light
source generally has a circular shape, the determined exposed
region may be further optimized to eliminate the interference from
the non-exposed region though the center (x.sub.mid, y.sub.mid),
that is, the coordinates of the four corners of the exposed region
is determined as (x.sub.mid-5,y.sub.min), (x.sub.mid+5,y.sub.min),
(x.sub.mid-5,y.sub.max) and (x.sub.mid+5,y.sub.max) as shown in
FIG. 34e.
[0260] Alternatively, the number of the bright or dark strips
within the optimized exposed region may be measured by measuring
the gray scale value within the optimized exposed region according
to embodiments of the present invention, as shown in FIG. 34f. The
RGB-based color image is converted to the gray-scale image and the
gray scale value of each pixel in the image is measured.
Optionally, the minimum and maximum gray scale values are set to 0
and 255, respectively, corresponding to brightness levels from the
darkest to the brightest. Optionally, a gray scale threshold is set
to the average of the maximum and minimum gray scale values, or the
average of the gray scale values of all pixels within the exposed
region. The measured gray scale value of each pixel is compared
with the gray scale threshold; and if the measured gray scale value
of a pixel is higher the gray scale threshold, the pixel is
assigned a gray scale dualization value of "1", otherwise the pixel
is assigned a gray scale dualization value of "0". The gray scale
dualizaton values of the pixels in the same row are summed and
compared with a dualization threshold. Optionally, the dualization
threshold is set to the average of the maximum and minimum of the
sum of gray scale dualizaton values in a row, or is set to the
average of the sum of gray scale dualizaton values in all rows
within the exposed region. If the sum of gray scale dualizaton
values of the pixels in the row is higher than the dualization
threshold, the dualization value of the row is set to "1",
representing bright stripe; otherwise, the dualization value of the
row is set to "0", representing dark stripe.
[0261] Alternatively, the number of the bright or dark strips may
be measured according to embodiments of the present invention, as
shown in FIG. 34f. As described above, the dualization value "1"
represents bright stripe and the dualization value "0" represents
dark stripe. When the dualization value of a row is "0" and the
dualization value of the next row is "1", it means the transition
from a dark stripe to a bright stripe; when the dualization value
of a row is "1" and the dualization value of the next row is "0",
it means the transition from a bright stripe to a dark stripe; when
the dualization value of a row is "1" and the dualization value of
the next row is still "1", it means the two rows of pixels are
still within one bright stripe; when the dualization value of a row
is "0" and the dualization value of the next row is still "0", it
means the two rows of pixels are still within one dark stripe. By
this way, the transmitted identification information may be decoded
by measuring the number of the dark stripes, by measuring the
number of the bright stripes, or by collectively measuring the
number of the bright or dark stripes, where different number
represents different code. For example, in FIG. 34f, the number of
the dark stripes is 5, the number of the bright stripes is 6, and
the number of the bright or dark stripes is 11.
[0262] Alternatively, the number of the bright or dark strips may
be measured according to another embodiment of the present
invention, as shown in FIG. 34g. In FIG. 34g, the first-order
derivative of the sum of gray scale dualization values is
calculated. The sign (positive or negative) of the first-order
derivatives is further derivated. If the derivative of the sign is
larger than 0, it means the transition from a bright stripe to a
dark stripe or from a dark stripe to a bright stripe. The number of
the bright or dark stripes may be obtained by calculating the
number of the derivative of the sign larger than 0.
[0263] According to some embodiments of the present invention, the
device 400 may contain multiple image sensors as shown in FIG. 35.
When using multiple image sensors in the device, it is necessary to
pre-determine which image sensor is activated. Optionally, the
strategy may be as follows: activating all image sensors; choosing
the image sensor which receives the light signal first as an
activated image sensor, and switching off other image sensors.
Optionally, the strategy may be manually choosing one image sensor
as an activated image sensor. Optionally, the strategy may be
choosing one image sensor as an activated image sensor based on the
identification information collected by other image sensors or
processors to obtain the identification information corresponding
to the varied numbers of bright or dark stripes of the one or more
exposed regions in the image.
[0264] According to some embodiments of the present invention, a
software program may be used to trigger the image sensor in the
device for obtaining identification information from visible light
signal to start receiving the visible light signal. Optionally, the
real-time image and the identification information obtained
therefrom may be displayed in the program during the process of
capturing image, as shown in FIG. 36A. Optionally, only the
identification information obtained from the image may be displayed
in the program during the process of capturing image, as shown in
FIG. 36B.
[0265] According to some embodiments of the present invention, a
light source for transmitting identification information by visible
light signal comprising a modulator and an emitter according to the
present invention may be included in a transmitter as shown in FIG.
37. The transmitter may further comprise a power supply, and a
microprocessor, e.g., a micro controller unit (MCU). Before the
visible light signal is ready to be emitted by the transmitter, the
image sensor should be activated in advance. Optionally, the image
sensor may be activated by an activation signal sent by the
transmitter, as shown in FIG. 18. The activation may be realized by
a software-based switch. When this switch is turned on, the image
sensor starts receiving the visible light signal. Alternatively,
the image sensor may be activated by other manners. For instance,
when the software begins to operate, the image sensor is activated
at the same time. Optionally, the activation can also be achieved
by other switches, sensors or network.
[0266] According to some embodiments of the present invention, when
the image sensor is activated to receive the visible light signal,
the transmitter is informed to send the visible light signal. This
can be realized by a hardware-based switch installed on the
transmitter, as shown in FIG. 38. When this switch is turned, the
transmitter starts to send the visible light signal; when the
switch is turned off, the transmitter stops sending the visible
light signal. Alternatively, the transmitter may be informed by
other manners, such as, buttons, physical contact, sensors, and
network.
[0267] According to some embodiments of the present invention, a
photosensitive device may be integrated in the transmitter to
detect the state of the image sensor, such as whether the image
sensor is ready to capture images. Before the transmitter sends the
visible light signal, the photosensitive device may first check the
state of the image sensor. Optionally, when the image sensor is
ready to capture images, the light emitting component of the image
sensor changes the brightness at a certain frequency, and such
changes of the brightness can be detected by the photosensitive
device integrated in the transmitter; and then the transmitter
starts to send the visible light signal, as shown in FIG. 39.
Alternatively, the state of the image sensor may be detected by
other sensors, such as, sound sensor, gravity sensor, acceleration
meter, etc. Alternatively, the state of the image sensor may be
detected by other manners, such as, network adaptors, for example
GPRS, GSM, CDMA, WiFi, Zigbee, Bluetooth, RFID, etc.
[0268] According to some embodiments of the present invention, the
transmitter may transmit multiple types of identification
information, comprising but not limited to, identifier (ID) of the
transmitter, voice, text, audio, pictures, video, etc., which may
be stored in the memory, as shown in FIG. 40.
[0269] According to some embodiments of the present invention, the
transmitter may comprise a light source according to the present
invention, a microprocessor (for example a MCU), and a battery, as
shown in FIG. 41. The microprocessor encodes the driving
current/voltage of the light source, a modulator in the light
source may modulate the driving current/voltage of the light source
on the basis of the identification information to be transmitted,
and an emitter in the light source may emit the visible light
signal on the basis of the modulated driving current/voltage. The
light source may emit visible light signal having its level changed
between a peak level and a bottom level with varied frequencies at
different time points. The battery may be used to provide energy
for the light source and the microprocessor. Optionally, as shown
in FIG. 41, the transmitter may further comprise a charging circuit
applied for charging the battery or protecting the battery from
being overcharged or overheated, etc.
[0270] According to some embodiments of the present invention, the
transmitter may further comprise a sensor as shown in FIG. 42. The
sensor may be applied for measuring electrical parameters, such as
temperature, humidity, voltage, and current, or biological
parameters, such as human heart rate, body temperature, and blood
pressure.
[0271] According to some embodiments of the present invention, the
transmitter may further comprise a memory as shown in FIG. 43. The
memory is applied for storing identification information, such as
pre-stored data, and identification information collected by
sensors.
[0272] According to some embodiments of the present invention, the
transmitter may further comprise a display as shown in FIG. 43. The
display is applied for showing the transmitted identification
information.
[0273] According to some embodiments of the present invention, the
device for obtaining identification information may comprise an
image sensor, a microprocessor (for example a MCU) and a power
supply, as shown in FIG. 44. The image sensor is applied for
capturing the visible light signals mitted by the light source. The
processor is applied for measuring the varied numbers of bright or
dark stripes contained in the captured image and obtaining
identification information corresponding to the varied numbers of
bright or dark stripes. The power supply is used to provide energy
for the processor.
[0274] According to some embodiments of the present invention, the
device for obtaining identification information from visible light
signal having its level changed between a peak level and a bottom
level with varied frequencies according to embodiments of the
present invention may further comprise a communication module, as
shown in FIG. 44. The communication module may be wired or
wireless, and may be applied for data transmission between the
device and other electronic devices, or connecting the device to
Internet.
[0275] According to some embodiments of the present invention, the
transmitter could be a lamp. The transmitter may be an embedded
system integrated in other devices, such as an integrated part of a
ring, as shown in FIG. 45.
[0276] According to some embodiments of the present invention, the
basic working principle of the system for transmitting and
obtaining identification information by visible light signal
comprising a light source for transmitting identification
information by visible light signal having its level changed
between a peak level and a bottom level with varied frequencies at
different time points and a device for obtaining identification
information from visible light signal from light source according
to embodiments of the present invention is as follows: the image
sensor in the device captures the visible light signal emitted by
the light source and obtain one or more images therefrom, and the
processor in the device measures the varied numbers of bright or
dark stripes in each image and recovers the identification
information corresponding to the varied numbers of bright or dark
stripes.
[0277] According to some embodiments of the present invention, the
transmitter may be integrated in a wearable electronic device,
providing advantages of small in volume, easy to carry, and low in
power consumption. The wearable electronic device may be a jewelry,
such as a ring, an earrings, a necklace, a watches, etc., or maybe
a key, a card, a pen, etc. When the transmitter is integrated in
the wearable electronic device, such wearable electronic device can
emit visible light signals for transmitting identification
information.
[0278] According to some embodiments of the present invention, the
transmitter may be integrated in a wearable electronic device, such
as a ring powered by a battery, as shown in FIG. 46. It should be
noted that the ring is only used for illustrating the present
invention, but should not be considered as the limitation to the
present invention. The battery is used to provide energy for the
transmitter. The light source included in the transmitter can emit
visible light having its level changed between a peak level and a
bottom level with varied frequencies at different time points and
each light source may be modulated independently.
[0279] According to some embodiments of the present invention, the
transmitter may comprise one or more light sources that can emit
visible light signals having their level changed between peak
levels and bottom levels with varied frequencies at different time
points, as shown in FIG. 47. One or more exposed regions in each
image correspond to the one or more light sources. As described
before, the transmitter may be integrated in a wearable electronic
device.
[0280] According to some embodiments of the present invention, the
transmitter may further comprise a driver, as shown in FIG. 48. As
described before, the transmitter may be integrated in a wearable
electronic device. The driver is added to drive the light source.
The driver can supply larger driving current or driving voltage to
drive high-power light source. In this way, the transmission
distance of transmitter can be increased.
[0281] According to some embodiments of the present invention, the
transmitter may further comprise a battery charging circuit, as
shown in FIG. 49. As described before, the transmitter may be
integrated in a wearable electronic device. The charging circuit is
applied not only for charging the battery, but also for limiting
the charging current/voltage or checking the temperature, etc., so
as to protect the battery from being overcharged or overheated.
Optionally, the charging circuit can be powered by an external
power source, such as power mains, solar panel, generator, or
energy harvesting system, etc. Optionally, the charging circuit can
be a wireless charging system.
[0282] According to some embodiments of the present invention, the
transmitter may further comprise a memory as shown in FIG. 50. As
described before, the transmitter may be integrated in a wearable
electronic device. The memory is applied for storing identification
information, such as pre-stored data, and the identification
information collected by the image sensor.
[0283] According to some embodiments of the present invention, the
transmitter may further comprise a sensor as shown in FIG. 51. As
described before, the transmitter may be integrated in a wearable
electronic device. The sensor may be applied for measuring
parameters, such as temperature, humidity, voltage and current, or
biological parameters, such as human heart rate, body temperature
and blood pressure. Such sensor could be a temperature sensor,
humidity sensor, optical sensor, sound sensor, accelerometer,
pressure sensor, etc. The transmitter may also comprise a
voltage/current sensing circuit, which is applied for detecting the
state of the battery. If a low battery is detected, the transmitter
may inform the user by signal of light, sound, vibration, etc.
[0284] According to some embodiments of the present invention, the
transmitter may further comprise a network adaptor as shown in FIG.
52. As described before, the transmitter may be integrated in a
wearable electronic device. The network adapter is applied for data
exchange between the device for obtaining identification
information from visible light signal and other electronic devices
with network capability, e.g., a computer; or sending commands to
control other devices. Optionally, the network adapter may use
following communication technologies: GPRS, GSM, CDMA, WiFi,
Zigbee, Bluetooth, RFID, etc.
[0285] According to some embodiments of the present invention,
before the transmitter sends the visible light signal, the
transmitter may first check the state of the image sensor in the
device for obtaining identification information from visible light
signal. Optionally, when the image sensor is ready to capture
images, the screen of the light emitting component changes the
brightness at a certain frequency, and such changes of the
brightness can be detected by the photosensitive device (e.g., a
sensor) integrated in the transmitter; and then the transmitter
starts to send the visible light signal, as shown in FIG. 53.
Optionally, when the device for obtaining identification
information from is a smartphone, a LED flashlight embedded in the
smartphone may be used to send signals to the transmitter.
Alternatively, the state of the device for obtaining identification
information from visible light signals may be detected by other
sensors, such as, sound sensor, gravity sensor, acceleration meter,
etc. Alternatively, the state of the device for obtaining
identification information from visible light signals may be
detected by other manners, such as, network adaptors, for example
GPRS, GSM, CDMA, WiFi, Zigbee, Bluetooth, RFID, etc. Alternatively,
the device for obtaining identification information from visible
light signal may be a laptop computer or other electronic devices
which have photosensitive component(s).
[0286] According to some embodiments of the present invention, the
transmitter is integrated in a wearable electronic device. When the
wearable electronic device starts to send the visible light
signals, its transmitter should be turned on. This can be realized
by a hardware-based switch installed on the transmitter, or other
sensor-based switch connected to the transmitter. When the wearable
electronic device receives the switch-on signal, it starts to send
light signal. The above described process is illustrated in FIG.
54.
[0287] According to some embodiments of the present invention,
after a transmitter starts to send the visible light signal, the
working flow of the image sensor in the device for obtaining
identification information from visible light signal is as follows,
as shown in FIG. 55: starting the receiving program, initializing
the image sensor, setting the exposure parameters, sending request
for receiving the visible light signal and waiting for the visible
light signal; after receiving the visible light signal, checking
the start code, analyzing the captured images, measuring the varied
numbers of bright or dark stripes in the images, and recovering the
identification information.
[0288] According to some embodiments of the present invention, it
provides a positioning system based on the visible light signal as
shown in FIG. 56. Optionally, the device for obtaining
identification information from visible light signals comprising an
image sensor may be a mobile device containing photosensitive
components. Optionally, such mobile device could be a smartphone.
The light source (e.g., in a transmitter) may be modulated to emit
the above mentioned visible light signal; the emitted visible light
signal contains the unique ID of the corresponding light source; an
image sensor in the smartphone, captures images of the light
sources, measures the varied number of bright or dark stripes in
these images, decodes the ID identification information, and
compares the decoded ID with the data stored in a map database. In
this way, the accurate position of the image sensor can be
determined from the position of the light source.
[0289] In conclusion, the embodiments of the present invention
provide an efficient and effective approach for
transmitting/obtaining identification information and positioning
by visible light signal, which can achieve indoor positioning,
transmit/obtain identification information much faster and more
accurate, and the identification information transmitted/obtained
may contain more data bits. Further, the embodiments of the present
invention effectively avoid the undesirable blinking of the light
source detectable by human eyes.
[0290] It should be noted that the aforesaid embodiments are
exemplary rather than limiting the present invention, substitute an
alternative embodiments may be designed by those skilled in the art
without departing from the scope of the claims enclosed. The word
"include" does not exclude elements or steps which are present but
not listed in the claims. The word "a" or "an" preceding the
elements does not exclude the presence of a plurality of such
elements. In the apparatus claims that list several components,
several ones among these components can be specifically embodied in
the same hardware item. The use of such words as first, second,
third does not represent any order, which can be simply explained
as names.
* * * * *