U.S. patent application number 12/461227 was filed with the patent office on 2009-12-03 for illuminative light communication device.
This patent application is currently assigned to Nakagawa Laboratories, Inc.. Invention is credited to Shinichiro Haruyama, Toshihiko Komine, Masao Nakagawa.
Application Number | 20090297166 12/461227 |
Document ID | / |
Family ID | 32180882 |
Filed Date | 2009-12-03 |
United States Patent
Application |
20090297166 |
Kind Code |
A1 |
Nakagawa; Masao ; et
al. |
December 3, 2009 |
Illuminative light communication device
Abstract
The illuminating end communication device is equipped with an
illuminating light source. An electric power fed to the light
source is modulated with a modulating unit responding to
transmission data, and the modulated light is sent out as
illuminating light. The illumination light is received by the light
receiving unit of a terminal end communication device to maintain a
downlink. Light emitted from the light emitting unit of the
terminal end communication device is received by the light
receiving unit of the illuminating end communication device to keep
an uplink. Or, illuminating light is modulated on the basis of data
when it is reflected, whereby data can be transmitted to the
illuminating end communication device. It is preferable that
illuminating light is reflected by CCR. A high-quality
communication is realized using illuminating light of high
power.
Inventors: |
Nakagawa; Masao; (Kanagawa,
JP) ; Komine; Toshihiko; (Shizuoka, JP) ;
Haruyama; Shinichiro; (Kanagawa, JP) |
Correspondence
Address: |
RADER FISHMAN & GRAUER PLLC
LION BUILDING, 1233 20TH STREET N.W., SUITE 501
WASHINGTON
DC
20036
US
|
Assignee: |
Nakagawa Laboratories, Inc.
Tokyo
JP
|
Family ID: |
32180882 |
Appl. No.: |
12/461227 |
Filed: |
August 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10532250 |
Sep 29, 2005 |
7583901 |
|
|
PCT/JP2003/013539 |
Oct 23, 2003 |
|
|
|
12461227 |
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Current U.S.
Class: |
398/172 |
Current CPC
Class: |
F21V 33/0052 20130101;
H04B 2203/5412 20130101; H04B 10/1141 20130101; H04B 2203/5458
20130101; H01L 25/0753 20130101; F21K 9/20 20160801; H05B 47/185
20200101; G09F 9/33 20130101; F21Y 2115/10 20160801; H05B 47/19
20200101; H04B 10/1149 20130101; H04B 10/116 20130101; H05B 47/195
20200101; H01L 2224/48091 20130101; H01L 2224/48247 20130101; H04B
3/54 20130101; H01L 2924/3025 20130101; F21K 9/65 20160801; H01L
2224/48091 20130101; H01L 2924/00014 20130101; H01L 2224/48091
20130101; H01L 2924/00 20130101; H01L 2924/3025 20130101; H01L
2924/00 20130101 |
Class at
Publication: |
398/172 |
International
Class: |
H04B 10/00 20060101
H04B010/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 24, 2002 |
JP |
2002-309557 |
Dec 4, 2002 |
JP |
2002-352075 |
Jan 10, 2003 |
JP |
2003-004560 |
Feb 17, 2003 |
JP |
2003-037746 |
Mar 14, 2003 |
JP |
2003-070673 |
Mar 25, 2003 |
JP |
2003-082278 |
Mar 26, 2003 |
JP |
2003-084819 |
Jun 6, 2003 |
JP |
2003-161859 |
Jun 23, 2003 |
JP |
2003-177816 |
Sep 16, 2003 |
JP |
2003-323052 |
Claims
1. An illuminative light communication device, comprising: a
lighting unit that emits light for lighting; a modulator that
controls blinking or light intensity of the lighting unit in
accordance with data, thereby modulating the emitted light; and a
light receiving unit that receives modulated light transmitted from
the outside; wherein data is transmitted via the light emitted by
the lighting unit, and the data is received by the light receiving
unit.
2. The illuminative light communication device according to claim
1, wherein the lighting unit is made up of one or a plurality of
LEDs.
3. The illuminative light communication device according to claim
1, wherein the light receiving unit receives infrared light as the
modulated light.
4. The illuminative light communication device according to claim
1, wherein the light receiving unit receives visible light as the
modulated light.
5. The illuminative light communication device according to claim
1, wherein the light receiving unit is a two-dimensional
sensor.
6. An illuminative light communication device, comprising: a light
receiving unit that receives illuminative light modulated in
accordance with data, thereby capturing the data; and a light
emitting unit that emits light modulated in accordance with data to
be transmitted.
7. The illuminative light communication device according to claim
1, wherein the light emitting unit emits infrared light.
8. The illuminative light communication device according to claim
1, wherein the light emitting unit emits visible light.
9. The illuminative light communication device according to claim
6, wherein the light emitting unit comprises a tracking unit that
guides the emitted light to an external light receiving unit.
10. An illuminative light communication device, comprising: a light
receiving unit that receives illuminative light modulated in
accordance with data, thereby capturing the data; and a reflecting
and modulating unit that reflects the illuminative light and
transmits reflected light modulated in accordance with data to be
transmitted.
11. The illuminative light communication device according to claim
10, wherein the reflecting and modulating unit is structured
including one or a plurality of corner cube reflectors, and
transmits reflected light to a light source of the illuminative
light.
12. The illuminative light communication device according to claim
10, wherein the reflecting and modulating unit uses an optical
shutter to carry out modulation.
13. The illuminative light communication device according to claim
11, wherein the reflecting and modulating unit modulates through
deforming a reflecting surface of the corner cube reflector.
14. The illuminative light communication device according to claim
10, wherein the reflecting and modulating unit comprises: a corner
cube modulation array comprising a plurality of corner cube
reflectors; a lens that is deployed to form an image on the corner
cube modulation array; and a modulator that controls every one or
every group of the corner cube reflectors in the corner cube
modulation array to modulate reflected light.
15. The illuminative light communication device according to claim
14, wherein the modulator is an optical shutter.
16. The illuminative light communication device according to claim
14, wherein the modulator modulates through deforming a reflecting
surface of the corner cube reflector.
Description
CROSS-REFERENCES TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S patent application
Ser. No. 10/532,250 filed Oct. 23, 2003, as International
Application No. PCT/JP03/013539, now pending, the contents of
which, including specification, claims and drawings, are
incorporated herein by reference in their entirety. This
application claims priority from Japanese Patent Application Serial
No. 2003-004560 filed Jan. 10, 2003, the contents of which are
incorporated herein by reference in their entireties.
TECHNICAL FIELD
[0002] The present invention relates to a technology that
contributes to illuminative light communication.
BACKGROUND ART
[0003] In recent years, a radio wave communication system has
become available along with portable terminals. Recently, shorter
wavelength infrared rays have been widely used due to available
frequency depletion. Other than available frequency depletion,
radio waves may influence medical devices or various precision
equipment. Moreover, there is fear that infrared rays may adversely
influence the human body (e.g., eyes). As a result, optical
communication is in the spotlight as a safe communication
method.
[0004] Meanwhile, white LEDs are developed owing to the success of
development of blue LEDs. The features of white LEDs are: extremely
lower power consumption than that of conventional incandescent
lamps or fluorescent lamps, small size, and long life. Accordingly,
use of white LEDs as a illuminative light source is considered.
Another feature of white LEDs is a fast response speed relative to
supplied power. Paying attention to these features, a study of
electrically controlling blinking or light intensity and thereby
transferring a signal has been conducted.
[0005] A study of integration of such signal transfer using white
LED lights with the aforementioned power-line communication system
has been conducted. For example, a proposal regarding that study
has been disclosed in `INTEGRATED SYSTEM OF WHITE LED VISIBLE-LIGHT
COMMUNICATION AND POWER-LINE COMMUNICATION` written by inventors:
T. Komine, Y. Tanaka, and M. Nakagawa, Institute of Electronics,
Information, and Communication Engineers Technical Research Report,
The Institute of Electronics, Information, and Communication
Engineers, Mar. 12, 2002, Vol. 101, No. 726, pp. 99-104. Since such
system utilizes lights, there are no effects on the human body,
allowing safe communication. In addition, other applications are
expected.
DISCLOSURE OF THE INVENTION
[0006] The present invention aims to provide an illuminative light
communication device that establishes a downlink using illuminative
light, and also allows uplink optical (including infrared rays)
communication, or provides, bidirectional optical
communication.
[0007] According to such objective, an illuminative light
communication device, which is positioned on the transmission side
for a downlink and positioned on the reception side for an uplink,
includes a lighting unit that emits light for lighting a modulator
that controls blinking or light intensity of the lighting unit in
accordance with data, thereby modulating the emitted light, and a
light receiving unit that receives modulated light transmitted from
the outside. Data is transmitted via the light emitted by the
lighting unit, and the data is received by the light receiving
unit. This structure allows establishment of a downlink using
illuminative light and an optical uplink by the light receiving
unit, thereby allowing bidirectional optical communication.
[0008] Note that the lighting unit can be made up of one or
multiple LEDs, allowing establishment of a downlink using
illuminative light based on the characteristics of the LEDs. In
addition, the light receiving unit can receive infrared light or
visible light as the modulated light. Furthermore, the light
receiving unit may be a two-dimensional sensor. This allows
effective removal of noise such as scattered light using received
modulated light signals and the other signals. In addition,
modulated light can be separated and received from multiple
positions using an optical system such as a lens, and uplink data
can be received from multiple light emitting sources.
[0009] An illuminative light communication device, which is
positioned on the transmission side for a downlink and positioned
on the reception side for an uplink, includes a light receiving
unit that receives illuminative light modulated in accordance with
data, thereby capturing the data, and a light emitting unit that
emits light modulated in accordance with data to be transmitted.
With such structure, the light receiving unit receives downlink
illuminative light while the light emitting unit establishes an
optical uplink. This allows bidirectional optical communication. A
mobile terminal, for example, can carry out bidirectional
communication.
[0010] Light emitted by the light emitting unit may be infrared
light or visible light. In addition, the light emitting unit
includes a tracking unit that guides the emitted light to an
external light receiving unit, thereby allowing further reliable
uplink communication.
[0011] An illuminative light communication device, which is
positioned on the transmission side for a downlink and positioned
on the reception side for an uplink, includes a light receiving
unit that receives illuminative light modulated in accordance with
data, thereby capturing the data, and a reflecting and modulating
unit that reflects the illuminative light and transmits reflected
light modulated in accordance with data to be transmitted. Even
this structure can provide bidirectional optical communication,
where a downlink can be established using illuminative light while
an uplink can be established using illuminative reflected light.
Furthermore, as described above, illuminative light has very large
electric power, and when it is used for an uplink, further reliable
communication is possible. In addition, since a new light emitting
unit is unnecessary, power consumption can be suppressed to a
degree of electric power provided for modulation, which
considerably contributes to power saving.
[0012] The reflecting and modulating unit may include one or
multiple corner cube reflectors (hereafter, referred to as CCR).
The CCR is characterized in that incident light is reflected in the
same incident direction, and transmits reflected light to a light
source of the illuminative light used for a downlink. The reflected
light is used for establishing an uplink. With such structure, a
tracking unit for guiding light used for an uplink to a light
receiving unit is unnecessary. In addition, since incident light
from multiple light sources can be reflected in the same direction,
respectively, when downlink data is received using illuminative
light from multiple light sources, reflected light for an uplink
can be transmitted to the respective light sources, thereby
allowing reduction in communication error, and improvement in
communication quality.
[0013] Note that an optical shutter can be used to carry out
modulation through controlling reflected light to pass through or
be shut off. Alternatively, modulation can be carried out through
deforming a reflecting surface of the CCR to change the reflection
characteristics of the CCR.
[0014] The reflecting and modulating unit may be made up of a
corner cube modulation array is made up of multiple CCRs, a lens
that is deployed to form an image on the corner cube modulation
array, and a modulator that controls every one or every group of
the CCRs in the corner cube modulation array to modulate reflected
light. As described above, the CCR is characterized in that
incident light is reflected in the same incident direction, the CCR
on which an image is formed by a light source of illuminative light
transmits reflected light to that light source. If there is
multiple light sources, the CCRs on which images are formed by the
respective light sources transmit reflected light to the
corresponding light sources. Therefore, parallel transmission is
possible through modulating reflected light for every one or every
group of the CCRs corresponding to the respective light
sources.
[0015] Note that a structure such that an optical shutter is used
as a modulator that controls every one or every group of the CCRs
to modulate reflected light, or a structure such that the modulator
modulates through deforming a reflecting surface of the CCR is
possible.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic block diagram of a first embodiment
according to the present invention;
[0017] FIG. 2 is a diagram describing a modified example of a light
receiving unit 213 in a lighting side communication device 201;
[0018] FIG. 3 is a diagram describing a modified example of a light
emitting unit 222 in a terminal side communication device 202;
[0019] FIG. 4 is a schematic block diagram of a second embodiment
according to the present invention;
[0020] FIG. 5 is a diagram describing an exemplary structure using
a mirror as a reflector/modulator 224;
[0021] FIG. 6 is a diagram describing a general view of a corner
cube reflector (CCR);
[0022] FIGS. 7A-7C each is a diagram describing an exemplary
modulation method using the CCR; FIG. 7A is a diagram of a
structure using an optical shutter; FIG. 7B is a diagram of a
structure using a dielectric; and FIG. 7C is a diagram of a
structure using an actuator;
[0023] FIGS. 8A and 8B each is a graph describing exemplary
waveforms of an incident light to the reflector/modulator 224 and a
modulated, reflected light; FIG. 8A shows a case where a downlink
data transfer rate is faster than an uplink data transfer rate; and
FIG. 8B shows a case where the downlink data transfer rate is
roughly equal to or less than the uplink data transfer rate;
[0024] FIG. 9 is a diagram describing an exemplary usage of an
illuminative communication device in which a CCR is provided as the
reflector/modulator 224;
[0025] FIG. 10 is a diagram describing an exemplary method of
combining received signals when multiple lighting side
communication devices are provided in the exemplary usage of an
illuminative light communication device in which a CCR is provided
as the reflector/modulator 224; and
[0026] FIG. 11 is a diagram describing an exemplary structure of
the reflector/modulator 224 in the terminal side communication
device 2 capable of carrying out parallel transmission.
BEST MODE FOR CARRYING OUT THE INVENTION
[0027] FIG. 1 is a schematic block diagram of a first embodiment
according to the present invention. In the drawing, 201 denotes a
lighting side communication device, 202 denotes a terminal side
communication device, 211 denotes a modulator, 212 denotes
illuminative light sources, 213 denotes a light receiving unit, 214
denotes a filter, 221 denotes a light receiving unit, 222 denotes a
light emitting unit, and 223 denotes a processor. The lighting side
communication device 201 is used as a lighting element to
illuminate the vicinity thereof, and includes the illuminative
light sources 212, which emit light for lighting. In this exemplary
structure, a light source is LEDs, but is not limited to them.
Alternatively, LDs or other light emitting devices with a fast
response speed are available.
[0028] The lighting side communication device 201 also includes the
modulator 211 and the light receiving unit 213 for illuminative
light communication. The modulator 211 ,which is deployed for a
downlink, controls electric power, which is supplied to the
illuminative light sources 212, in accordance with data to be
transmitted. This allows control of light intensity or blinking of
the illuminative light sources 212 and emission of light modulated
in accordance with data. The terminal side communication device 202
to be described later then receives the modulated illuminative
light, thereby allowing data transmission from the lighting side
communication device 201 to the terminal side communication device
202 (downlink).
[0029] An arbitrary modulation system, such as on-off keying (OOK)
or binary phase shift keying (BPSK), is available. In addition, all
of or some of the illuminative light sources 212 for lighting may
be LEDs, which are controlled to change light intensity or
blinking. Note that since LEDs have a high-speed response
characteristic as described above, change in light intensity and/or
blinking is imperceptible to the human eye, and seems as if light
is emitted continuously. Accordingly, the illuminative light
sources 212 may be used for lighting besides data
communication.
[0030] The light receiving unit 213, which is provided for
receiving modulated light (such as infrared rays, visible light,
ultraviolet light) emitted from the terminal side communication
device 202, includes a light receiving device such as a photodiode.
In addition, in this exemplary structure, a filter 214 is provided
for selectively receiving modulated light emitted from the terminal
side communication device 202. For example, to receive infrared
rays, the filter 214 that allows infrared rays to pass through
should be provided. Needless to say, a structure without the filter
214 is possible. In this case, received light is converted into an
electric signal, which is then demodulated. Consequently, data from
the terminal side communication device 202 is reconstructed and
then output.
[0031] Note that data to be transmitted via illuminative light may
be data received from the outside, or data retained in or generated
by the lighting side communication device 201. Alternatively, data
received by the light receiving unit 213 may be output to the
outside or processed in the lighting side communication device
201.
[0032] The terminal side communication device 202 may be an
arbitrary terminal device, and may include the light receiving unit
221 and the light emitting unit 222 for illuminative light
communication and the processor 223 for various kinds of
processing. The light receiving unit 221 receives and demodulates
modulated light emitted from the lighting side communication device
201, and transmits the demodulated results to the processor 223. In
this manner, reception of data transmitted from the lighting side
communication device 201 via illuminative light is possible, or
establishment of a downlink is possible.
[0033] The light emitting unit 222, which includes a light source
such as LEDs or LDs, and a control circuit for turning on and off
the light sources, receives data to be transmitted from the
processor 223, controls light intensity or blinking of the light
sources in accordance with data, and emits the resulting modulated
light. At this time, any modulation system can be used for that
modulation. Alternatively, infrared rays, visible light, or
ultraviolet light may be used as light to be emitted. The light
receiving unit 213 of the lighting side communication device 201
described above then receives the modulated light, or an uplink is
established.
[0034] As described above, the lighting side communication device
201 has the illuminative light sources 212 illuminate the vicinity
thereof, and modulates the illuminative light in accordance with
data, allowing transmitting the data via the illuminative light.
The light receiving unit 221 in the terminal side communication
device 202 then receives this illuminative light, thereby receiving
data transmitted from the lighting side communication device 201.
In this manner, a downlink is established. In addition, the
terminal side communication device 202 has the light emitting unit
222 emit modulated light in accordance with data, thereby
transmitting data. The light receiving unit 213 of the lighting
side communication device 201 then receives this modulated light,
and thus the lighting side communication device 201 receives data
transmitted from the terminal side communication device 202. In
this manner, an uplink is established. In this manner, either
downlink or uplink optical communication is possible, or
bidirectional optical communication is possible.
[0035] For example, the terminal side communication device 202 may
be a mobile, portable terminal device, such as a notebook computer,
a PDA, or a cellular phone, which does not need cable connection.
More specifically, in the case of a PDA with a camera or a cellular
phone with a camera, the camera may be used as the light receiving
unit 221. In addition, the terminal side communication device 202
is available in an environment where radio wave communication is
restricted, such as a hospital, a train, an airplane, a spaceship,
or a site where pacemaker users exist, and no license for use
thereof is required. Needless to say, it is available in various
environments, such as ordinary offices, stores, homes, and public
facilities. In addition, not limited to indoors, it is available
for various applications, such as neon signs, lighting for
advertisement, and communication among automobiles or among
facilities on the street and automobiles in a transportation
system.
[0036] Moreover, optical wavelength is short, allowing very
higher-speed communication than radio wave communication.
Furthermore, typically, lighting elements are widely provided, and
lighting is naturally provided in an environment where terminal
devices are used. Such lighting elements may be used as the
lighting side communication device 201 for communication, resulting
in considerable reduction in installation cost.
[0037] Note that in an environment such as an office where multiple
lighting elements are provided, respective lighting elements may be
used as the lighting side communication device 201, and multiple
lighting side communication devices 201 can be deployed. In this
case, light emitted from a single terminal side communication
device 202 can be received by the multiple lighting side
communication devices 201. In this manner, light is received by the
multiple lighting side communication devices 201, allowing
improvement in communication quality. In addition, even when a
single lighting side communication device 201 cannot receive light
due to shadowing developed by a passerby, other lighting side
communication devices 201 can receive that light, solving such
problem of shadowing.
[0038] Next, several major modified examples of the first
embodiment are described. FIG. 2 is a diagram describing a modified
example of the light receiving unit 213 in the lighting side
communication device 201. In the drawing, 231 denotes a
two-dimensional sensor, and 232 denotes a lens. The two-dimensional
sensor 231 is used as the light receiving unit 213 in the lighting
side communication device 201, and the lens 232 is used to form an
image on the light receiving surface. With such structure, an image
due to light emitted from the terminal side communication device
202 is formed on the light receiving surface of the two-dimensional
sensor 231, and that light is received by some of a great number of
light receiving cells provided in the two-dimensional sensor 231.
At this time, since the other light receiving cells receive
environmental light, background noise can be removed using it,
allowing high-quality communication.
[0039] In addition, when there are multiple terminal side
communication devices 202 and 202', for example, in the light
receiving area, an image due to lights emitted from the respective
terminal side communication devices 202 and 202' are formed at
different positions of the two-dimensional sensor 231, as shown in
FIG. 2. This allows parallel reception of data from the respective
terminal side communication device 202 and 202'. Needless to say, a
case of three or more terminal side communication devices provided
provides the same advantage.
[0040] In addition, in an environment where multiple lighting side
communication devices 201 are provided, light emitted form the
respective terminal side communication devices 202 and 202' can be
received by the two-dimensional sensors 231, which are provided in
the respective lighting side communication devices 201. In this
case, communication quality can be improved by identifying light
received points in the respective two-dimensional sensors 231 from
the light received positions in the respective two-dimensional
sensors 231 and the position of the lighting side communication
device 201.
[0041] FIG. 3 is a diagram describing a modified example of the
light emitting unit 222 in the terminal side communication device
202. In the drawing, 241 denotes a tracking unit, 242 denotes LED
light sources, 243 denotes a mirror surface, and 244 denotes a
lens. According to the basic structure shown in FIG. 1, when the
LED light sources 242 are used as the light source of the light
emitting unit 222 in the terminal side communication device 202
emitted light diverges, resulting in decrease in intensity of light
received by the lighting side communication device 201. FIG. 3
shows an exemplary structure having the mirror surface 243 and the
lens 244 provided to prevent such divergence of emitted light and
narrow a light beam. Light emitted from the LED light sources 242
may be effectively provided to the lighting side communication
device 201 using such an optical system, allowing preferable
communication. Needless to say, when LDs with high directivity are
used as the light source, the mirror surface 243 and the lens 244
are unnecessary.
[0042] In addition, in the case of narrowing the light beam or
using LDs as a light source, communication quality decreases or
communication is impossible when emitted light does not correctly
hit the light receiving unit 213 in the lighting side communication
device 201. Therefore, in the exemplary structure shown in FIG. 3,
the tracking unit 241 is provided to guide the light beam to the
light receiving unit 213 in the lighting side communication device
201. The tracking unit 241 may be structured with a movable
mechanism that allows manual change in light beam direction.
Alternatively, it may be structured to automatically operate
according to illuminative light or operate under control of a
terminal device itself. Alternatively, it may be structured to be
controlled by the lighting side communication device 201 via a
downlink. In this manner, there are a variety of structures to
embody the tracking unit 241.
[0043] A modified example of the light receiving unit 213 in the
lighting side communication device 201 and a modified example of
the light emitting unit 222 in the terminal side communication
device 202 have been described above. The present invention is not
limited to those examples. For example, the structure shown in FIG.
2 may be applicable to the light receiving unit 221 in the terminal
side communication device 202. This allows parallel illuminative
light transmission of different pieces of data from multiple
lighting side communication devices and selective reception of
those pieces of data by the terminal side communication device
202.
[0044] In addition, data to be transmitted from the lighting side
communication device 201 and data received therefrom may be
transferred via a dedicated data line or may be superimposed on an
electric power waveform and transmitted via a power line, which
supplies electric power for lighting. Needless to say, besides the
above-mentioned systems, various modifications thereof are
possible.
[0045] FIG. 4 is a schematic block diagram of a second embodiment
according to of the present invention. In the drawing, the same
symbols are given to the same parts as those in FIG. 1, and
repetitive descriptions thereof are thus omitted. 224 denotes a
reflector/modulator. In the aforementioned first embodiment, an
exemplary structure such that the light emitting unit 222 is
provided in the terminal side communication device 202 to emit
light for establishment of an uplink is shown. On the other hand,
the second embodiment shows a structure such that illuminative
light for a downlink is used as is, and reflected light is used for
an uplink. As described above, illuminative light has large
electric power, and when it is used for an uplink, further reliable
communication is possible. In addition, since the light emitting
unit 222 is unnecessary in the terminal side communication device
202, power consumption of the terminal side communication device
202 can be considerably suppressed, greatly contributing to power
saving. Note that since the structure of the lighting side
communication device 201 can be the same as those of the
aforementioned first embodiment and the modified example thereof,
repetitive descriptions thereof are thus omitted, and the modulator
211 is not shown in the drawing. In addition, the light receiving
unit 221 in the terminal side communication device 202 may be the
same as those of the aforementioned first embodiment and the
modified example thereof.
[0046] The reflector/modulator 224 is provided in the terminal side
communication device 202, which allows use of illuminative light
for an uplink. The reflector/modulator 224 reflects illuminative
light and transmits the resulting reflected light, which is
modulated in conformity with to-be-transmitted data via an
uplink.
[0047] FIG. 5 is a diagram describing an exemplary structure with a
mirror used as the reflector/modulator 224. In the drawing, 251
denotes a mirror, 252 denotes an optical shutter, 253 denote a
shielding wall, and 254 denotes a tracking unit. The mirror 251 is
simply used for reflecting illuminative light, and the reflection
direction is controlled by the tracking unit 254, which is similar
to the tracking unit 241 of the modified example shown in FIG. 3.
In addition, modulation can be carried out using the optical
shutter 252 allowing incident light to the mirror 251 and reflected
light from the mirror 251 to pass through or be shut off. For
example, a liquid crystal shutter may be used as the optical
shutter 252 for modulation, which controls the orientation of
liquid crystal in accordance with data so as to allow reflected
light to pass through or be shut off. Needless to say, other
modulation methods may be used alternatively. For example,
reflection direction of the mirror surface may be changed in
accordance with data. In other words, since change in reflection
direction of the mirror surface changes the intensity of incident
light to the light receiving unit 213 in the lighting side
communication device 201, data can be captured by detecting this
change. In this case, the tracking unit 254 may also be used as a
modulation means.
[0048] In addition, in the exemplary structure shown in FIG. 5, the
shielding wall 253 is provided surrounding the mirror 251. This is
provided for protecting user's eyes from the brightness of
reflected light traveling from the mirror 251, which reflects light
emitted by a light source other than the light source in the
lighting side communication device 201 for communication. When the
illuminative light source 212 and the light receiving unit 213 of
the lighting side communication device 201 are provided closely,
only light from the illuminative light source 212 should be
reflected, returning to the light receiving unit 213, and thus
reflection of other lights is unnecessary. The shielding wall 253
is provided for preventing such unnecessary reflection.
Alternatively, the inner surface of the shielding wall 253 may be
formed to be a mirror, thereby increasing reflected light
intensity. Needless to say, a structure without the shielding wall
253 is possible.
[0049] Note that the unit shown in FIG. 5 may be used as a single
structure or multiple units may be provided.
[0050] A corner cube reflector (CCR) may be used as an illuminative
light reflecting means in the reflector/modulator 224. FIG. 6 is a
diagram describing a general view of the CCR. The CCR has three
reflecting surfaces orthogonal to each other in an inward
direction. For example, as shown in FIG. 6, it can be structured
with three inner reflecting surfaces of a cube or a rectangular,
which have a shared apex and are orthogonal to one another.
[0051] The CCR is characterized in that incident light is reflected
in the same incident direction. Accordingly, when illuminative
light hits, the illuminative light is then reflected toward the
light source of the illuminative light. According to the present
invention, illuminative light is used for a downlink, and the
illuminative light used for the downlink is reflected and also used
for an uplink. More specifically, since the illuminative light is
reflected toward the illuminative light source, the reflected light
can be received by the light receiving unit 213 arranged very close
to the illuminative light source in the lighting side communication
device 201. In addition, since high directivity/strongly reflected
light hits the light receiving unit 213 in the lighting side
communication device 201, there is an advantage that peripheral
light is difficult to adversely influence that light. Note that the
lighting side communication device 201 can be provided in an
arbitrary area, and even when the terminal side communication
device 202 is provided in an arbitrary area, reflected light is
reflected toward the lighting side communication device 201.
[0052] FIGS. 7A-7C each is a diagram describing an exemplary
modulation method using the CCR. In the drawing, 261 denotes the
CCR, 262 denotes an optical shutter, 263 denotes a dielectric, and
264 denotes an actuator. Illuminative light can be reflected by the
CCR toward the lighting side communication device 201 in the
aforementioned manner. Several methods of modulating this reflected
light in accordance with data are shown forthwith. FIG. 7A shows an
example of modulating with the optical shutter 262 arranged in
front of the CCR. The optical shutter 262 may be structured with a
liquid crystal shutter using a liquid crystal display. The liquid
crystal orientation of the liquid crystal shutter changes due to
application of a voltage, thereby switching over between a light
pass-through mode and a light shut-off mode. When this liquid
crystal shutter is controlled to allow light to pass through,
illuminative light from the lighting side communication device 201
hits the CCR 261, and the resulting reflected light then travels to
the lighting side communication device 201, as described above. On
the other hand, when the liquid crystal shutter is controlled to
shut off light, both incident light to the CCR 251 and reflected
light are shut off, and the light receiving unit 213 in the
lighting side communication device 201 cannot receive reflected
light. In this manner, the control of liquid crystal orientation of
the liquid crystal shutter allows reflected light to pass through
or be shut off. Reflected light modulated through such a shutter
operation in accordance with data may be transmitted to the
lighting side communication device 201. Needless to say, there are
various kinds of liquid crystal, and they are available as needed.
For example, a type of liquid crystal capable of changing over
between a light pass-through mode and a light reflecting mode is
available. In addition, in this exemplary structure, a liquid
crystal shutter is used as the optical shutter 262. Alternatively,
any type of shutter mechanism capable of being controlled to allow
illuminative light and reflected light entered to pass through to
the CCR 261 or prevent them from passing through is available
regardless of its structure.
[0053] In the example shown in FIG. 7B, the dielectric 263 is
deployed very close (.lamda./3) to part of or entirety of the
mirror surface, which constitutes the CCR 261, so as to decrease
the total amount of reflection from the inner surfaces. The
intensity of reflected light from the CCR 261 may be controlled by
changing the position of the dielectric in accordance with data,
allowing transmission of modulated, reflected light to the lighting
side communication device 201. Note that this method utilizes
coherence, and use thereof is limited to the case where LDs are
used as a light source in the lighting side communication device
201.
[0054] In the example shown in FIG. 7C, the actuator 264 is
attached to one of the mirror surfaces, which constitute the CCR
261, so as to change the mirror surface in accordance with data.
For example, by changing an angle or deforming the mirror surface,
a light reflected angle between adjacent mirror surfaces of the CCR
261 changes. As a result, the relationship between incident light
and reflected light such that the latter returns along the former
can be broken. Such control in accordance with data allows
transmission of modulated, reflected light to the lighting side
communication device 201. The actuator 264 may be a structure using
a driving capability of a mechanical micro machine or distortion of
a piezo element.
[0055] FIG. 8 is a graph describing exemplary waveforms of incident
light to the reflector/modulator 224 and modulated reflected light,
respectively. As described above, incident light to the
reflector/modulator 224 is illuminative light that is modulated and
emitted from the lighting side communication device 201.
Accordingly, light intensity or blinking is controlled in
accordance with data transmitted via a downlink. When the light is
reflected by the CCR 261, the reflected light on which data
transmitted via the downlink is still being superimposed is then
provided. However, when the uplink data transfer rate is slower
than the downlink transfer rate, there is no problem. For example,
if the uplink data transfer rate is slow, illuminative light
intensity changes many times during a single data transfer due to
high-speed change in illuminative light intensity as shown in FIG.
8A. For example, when modulation is carried out and incident light
is reflected by the CCR 261 as described in FIG. 7, average light
intensity between a bright and a dark area during a single data
transfer is received by the light receiving unit 213 in the
lighting side communication device 201. On the other hand, when the
CCR 261 does not reflect light toward the light source, the light
receiving unit 213 in the lighting side communication device 201
cannot even receive average light intensity. Therefore, data can be
reliably transferred even using illuminative light on which data
for a downlink is still being superimposed for an uplink.
[0056] On the other hand, when the downlink data transfer rate is
roughly equal to or lower than the uplink data transfer rate,
reflected illuminative light is available for an uplink if there is
no time when illuminative light is completely shut off. FIG. 8B
shows a case of the downlink data transfer rate being equal to the
uplink data transfer rate. In this example, sub carrier binary
phase shift keying (BPSK) is used as a downlink data modulation
system. In this case, since illuminative light intensity never
continuously stay in zero during single data transfer, the light
receiving unit 213 in the lighting side communication device 201
can receive uplink data through sensing change in received light
intensity even when modulation is carried out by allowing
illuminative light to pass through or be shut off for an
uplink.
[0057] In this manner, even when illuminative light is modulated,
an uplink from the terminal side communication device 202 to the
illumination light communication device 201 can be established by
reflecting the modulated illuminative light and then modulating it
in conformity with uplink data. Illuminative light has large
electric power, and reflected light thereof also has large electric
power. This allows high-quality uplink communication. In addition,
since with a structure of using the CCR 261, reflected light
returns to the incident light source, there is no need for
tracking, and an uplink can be established with a simple structure.
Moreover, there is an advantage that it is unnecessary to
synchronize with the downlink. Furthermore, when using the CCR 261,
irregular reflected light scarcely hits users' eyes, and thus the
users scarcely sense brightness.
[0058] FIG. 9 is a diagram describing an exemplary application of
the illuminative light communication device which has the CCR as
the reflector/modulator 224. FIG. 10 is a diagram describing an
exemplary received signal combining method for the multiple
lighting side communication devices. In the drawing, 271 denotes
light receiving devices, 272 denotes delay correcting units, 273
denotes a combining unit, and 274 denotes a demodulator. As
described above, the CCR is characterized in that it returns
reflected light toward the light source. This feature is the same
as that in the case where incident lights from multiple directions
hit. For example, as shown in FIG. 9, when multiple lighting side
communication devices 201, 201', and 201'' emit respective
illuminative lights, which then enter the terminal side
communication device 202, illuminative light from the lighting side
communication device 201 is reflected thereto by the CCR in the
terminal side communication device 202, illuminative light from the
lighting side communication device 201' is reflected thereto, and
illuminative light from the lighting side communication device
201'' is reflected thereto. As a result, uplink data transmitted
from the terminal side communication device 202 is received by the
multiple lighting side communication devices 201, 201', and
201''.
[0059] The multiple lighting side communication devices 201,201',
and 201'' can reliably receive data by combining electric signals
obtained through reception of light. An exemplary circuit structure
in this case is shown in FIG. 10. The light receiving devices 271
in the respective light receiving units 213 of the respective
lighting side communication devices 201, 201', and 201'' convert
received lights to electric signals. The electric signals from the
light receiving devices 271 are corrected for specified amounts of
delays for respective lighting side communication devices 201,
201', and 201'' by the delay correcting unit 272, and the resulting
corrected electric signals are then combined by the combining unit
273. This may be done through simple addition, average electric
power calculation, and/or weighting. The higher the signal
intensity, the larger weight to be added. The combined electronic
signals are demodulated by the demodulator, allowing data
transmitted from the terminal side communication device 202 to be
captured.
[0060] In this manner, since uplink data can be transmitted to the
multiple lighting side communication devices, even if shadowing
develops due to a passerby, which may cause disturbance of optical
transmission to a lighting side communication device, other
lighting side communication devices can receive light, allowing
reliable communication. In this case, a CCR tracking mechanism is
unnecessary, and disturbance of optical communication or shadowing
can be solved by a simple structure. Note that three lighting side
communication devices are shown in FIG. 9, but the present
invention is not limited to this. Alternatively, two or four
devices are available.
[0061] A case of using a single CCR has been described above;
alternatively, multiple CCRs may be provided, for example,
two-dimensionally. When multiple CCRs are provided, a modulating
structure as shown in FIG. 7 should be provided for each of CCRs
261. By controlling all of them in the same manner, they can
operate in the same manner as in the case of using a single CCR.
For example, with a structure where the optical shutter 262 is used
for modulation as shown in FIG. 7A, the optical shutter 262 may be
shared by multiple CCRs.
[0062] In the case of providing multiple CCRs, it is possible to
control respective multiple CCRs or respective groups of multiple
CCRs to modulate. With such a structure, parallel data transmission
from the terminal side communication device 202 is possible. FIG.
11 is a diagram describing an exemplary structure which allows
parallel transmission of the reflector/modulator 224 in the
terminal side communication device 202. In the drawing, 281 denotes
a CCR array, and 282 denotes a lens. The CCR array 281, which is
made up of multiple CCRs, is structured such that respective
multiple CCRs or respective groups of multiple CCRs can be
controlled for modulation. When modulation for individual CCRs 281
is required using the optical shutter 262 shown in FIG. 7A, an
optical shutter capable of controlling for respective multiple CCRs
or respective groups of multiple CCRs should be provided. In
addition, with the structure allowing CCR mirror surfaces to change
as shown in FIG. 7C, the same structure can be provided for
individual CCRs, and control for respective multiple CCRs or
respective groups of multiple CCRs is possible.
[0063] The lens 282 is provided at the entrance (or exit) of the
CCR array 281 and is controlled to form an image for illuminative
lights, which have traveled from the lighting side communication
devices 201 and 201' on the CCR mirror surface or in the vicinity
thereof. With such a structure, incident lights emitted from the
lighting side communication devices 201 and 201' hit only some of
the CCRs in the CCR array 281. According to the characteristics of
the CCR, some of the CCRs that incident illuminative light from the
lighting side communication device 201 hits return reflected light
thereto, while some of the CCRs that incident illuminative light
from the lighting side communication device 201' hits return
reflected light thereto. At this time, when the CCRs that
respective incident illuminative lights hit are controlled to
modulate in the same manner, the same data can be transmitted to
the multiple lighting side communication devices 201 and 201' as
described in FIG. 9.
[0064] Alternatively, CCRs that respective incident illuminative
lights hit may be controlled to modulate in accordance with
different pieces of data. In other words, the CCRs that incident
illuminative light from the lighting side communication device 201
hits and that return reflected light thereto may be controlled to
modulate in accordance with a first data while CCRs that incident
illuminative light from the lighting side communication device 201'
hits and that return reflected light thereto may be controlled to
modulate in accordance with a second data. This allows transmission
of the first data to the lighting side communication device 201 and
the second data to the lighting side communication device 201'.
Those pieces of data can be transmitted in parallel, allowing
parallel communication.
[0065] Note that: CCRs that incident illuminative light hits may be
predetermined; a simply structured light reception device may be
provided together with CCRs; a light reception device may be
combined with the CCR mirror surface; and/or a two-dimensional
sensor and a lens system may be used as the light receiving unit
221 in the terminal side communication device 202 to allow
identification of the position of the lighting side communication
device. Needless to say, other structures are available.
[0066] The example of using reflected illuminative light for an
uplink has been described above as the second embodiment. As with
the aforementioned first embodiment, in the second embodiment, the
lighting side communication device 201 may be provided in the same
manner as conventionally available lighting elements, and the
terminal side communication device 202 may be a portable terminal
device, such as a notebook computer, a PDA, or a cellular phone. In
addition, it is available in ordinary offices, stores, homes,
public facilities, and an environment where radio wave
communication is restricted such as hospitals, trains, airplanes,
spaceships, and a site in which pacemaker users exist. Furthermore,
use thereof is not limited to the indoors, and it is available for
various applications, such as neon signs, lighting for
advertisement, or communication among automobiles or among
facilities on the street and automobiles in a transportation
system.
[0067] Moreover, the second embodiment may be modified into various
modifications as with the aforementioned first embodiment. The
structure of the light receiving unit 213 in the lighting side
communication device 201 shown in FIG. 2 and structure of the light
emitting unit 222 in the terminal side communication device 202
shown in FIG. 3 may be used, and power line communication for data
transmitted from and received by the lighting side communication
device 201 is available. Needless to say, besides such
modifications, a variety of other modifications are possible.
[0068] As described above, the conventional illuminative light
communication allows only downlink optical communication. However,
the present invention allows uplink optical communication, allowing
bi-directional optical communication.
[0069] In addition, reflected illuminative light may be used for an
uplink. In this case, high-quality communication is possible using
illuminative light with large electric power. Furthermore, use of
CCRs allows establishment of uplink optical communication with a
simple structure that does not need tracking.
* * * * *