U.S. patent application number 15/497905 was filed with the patent office on 2017-09-28 for method for controlling flash timing of extension flash module.
The applicant listed for this patent is EOSMEM Corporation. Invention is credited to Jiunn-Kuang Chen, Meng-Hsien Hsieh, Rong-Jie Tu.
Application Number | 20170280032 15/497905 |
Document ID | / |
Family ID | 56077819 |
Filed Date | 2017-09-28 |
United States Patent
Application |
20170280032 |
Kind Code |
A1 |
Chen; Jiunn-Kuang ; et
al. |
September 28, 2017 |
Method for Controlling Flash Timing of Extension Flash Module
Abstract
The present invention discloses a method for controlling flash
timing of an extension flash module cooperating with a mobile
device to provide supplemental light. The method includes:
detecting a specific event before a flashable time period, wherein
the flashable time is a period from the time at which a last photo
sensor row of a specific frame begins exposure to the time at which
a first photo sensor row in the specific frame ends exposure,
wherein the time period from when the specific event occurs to a
flashable time in the flashable time period has a fixed length of
time; and triggering a flash instruction after a delay time from
when the specific event occurs, such that the flash timing of the
extension flash module is in the flashable time period.
Inventors: |
Chen; Jiunn-Kuang; (Zhubei
City, TW) ; Hsieh; Meng-Hsien; (Zhubei City, TW)
; Tu; Rong-Jie; (Zhubei City, TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
EOSMEM Corporation |
Zhubei City |
|
TW |
|
|
Family ID: |
56077819 |
Appl. No.: |
15/497905 |
Filed: |
April 26, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14943227 |
Nov 17, 2015 |
9674416 |
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15497905 |
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14643905 |
Mar 10, 2015 |
9706096 |
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14943227 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04N 5/2354 20130101;
H04N 5/2256 20130101 |
International
Class: |
H04N 5/225 20060101
H04N005/225; H04N 5/235 20060101 H04N005/235 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 19, 2014 |
TW |
103140180 |
Mar 9, 2015 |
TW |
104107362 |
Claims
1. A method for controlling flash timing of an extension flash
module cooperating with a mobile device to provide supplemental
light when the mobile device having an image retrieval device is
taking a photo, the image retrieval device including pixels
arranged in rows, the method comprising: detecting a specific event
before a flashable time period, wherein the flashable time period
is a period from the time at which a last row in a specific frame
begins exposure to the time at which a first row in the specific
frame ends exposure, wherein the time period from when the specific
event occurs to a flashable time in the flashable time period has a
fixed length of time; and informing the extension flash module the
occurrence of the specific event, so that the extension flash
module triggers a flash instruction after a delay time from when
the specific event occurs, such that the flash timing of the
extension flash module is in the flashable time period.
2. The method of claim 1, wherein the delay time is determined
according to a flash delay time and the time period from when the
specific event occurs to the flashable time in the flashable time
period, wherein the flash delay time is a period from the time at
which the extension flash module starts to execute the flash
instruction to the time at which the extension flash module
actually flashes.
3. The method of claim 2, wherein the time at which the specific
event occurs is t0, the time at which the last row in the specific
frame begins exposure is t1, and the time at which the first row in
the specific frame ends exposure is t2, and wherein the delay time
which begins at t0 has a duration of td1, and the flash delay time
has a duration of td, wherein an initial time point of the duration
of td is the time at which the extension flash module starts to
execute the flash instruction, then the following relationship is
fulfilled: (t1-td-t0)<td1<(t2-td-t0).
4-6. (canceled)
7. The method of claim 1, wherein the delay time is pre-stored in a
driver program of the extension flash module or an application
program of the mobile device.
8. The method of claim 1, wherein the delay time is stored in a
memory device included in the extension flash module.
9. The method of claim 1, wherein the specific event includes: the
time at which one of the rows of the pixels in the specific frame
begins exposure; the time at which one of the rows of the pixels in
the previous Nth frame prior to the specific frame begins exposure;
or the time at which one of the rows of the pixels in the previous
Nth frame prior to the specific frame ends exposure; wherein N is a
natural number.
10. A method for controlling flash timing of an extension flash
module cooperating with a mobile device to provide supplemental
light when the mobile device having an image retrieval device is
taking a photo, the image retrieval device including pixels
arranged in rows, the method comprising: sensing a light emitting
time point at which the mobile device emits light; and triggering a
flash instruction after a delay time from the light emitting time
point at which the mobile device emits light, such that the flash
timing of the extension flash module is in a flashable time period;
wherein the flashable time period is a period from the time at
which a last row in a specific frame begins exposure to the time at
which a first row in the specific frame ends exposure.
11. The method of claim 10, wherein the light emitting time point
is: a time point at which a built-in light emitting diode (LED)
supplement lamp of the mobile device begins to emit light for the
first time or a time point at which the built-in LED supplement
lamp begins to emit light for the second time.
12-14. (canceled)
15. The method of claim 10, wherein the delay time is pre-stored in
a driver program of the extension flash module or an application
program of the mobile device.
16. The method of claim 10, wherein the delay time is stored in a
memory device included in the extension flash module.
17. A method for controlling flash timing of an extension flash
module cooperating with a mobile device to provide supplemental
light when the mobile device having an image retrieval device is
taking a photo, the image retrieval device including pixels
arranged in rows, the method comprising: detecting a specific event
before a flashable time period by receiving information of an
occurrence of the specific event from the mobile device by the
extension flash module, wherein the flashable time period is a
period from the time at which a last row in a specific frame begins
exposure to the time at which a first row in the specific frame
ends exposure, wherein the time period from when the specific event
occurs to a flashable time in the flashable time period has a fixed
length of time; and triggering a flash instruction so that the
extension flash module flashes during the flashable time period
according to a flash delay time and the period from the specific
event to the flashable time, wherein the flash delay time is a
period from the time at which the extension flash module starts to
execute the flash instruction to the time at which the extension
flash module actually flashes.
18. The method as claimed in claim 17, wherein the specific event
comprises the time at which the first row in the specific frame
begins exposure, and the fixed length of time is the period from
the time at which the first row begins exposure to the time at
which the last row begins exposure.
19. The method as claimed in claim 17, wherein the specific event
comprises the time at which a K.sup.th row in the specific frame
begins exposure, and the fixed length of time is the period from
the time at which the K.sup.th row begins exposure to the time at
which the last row begins exposure, N and K both being natural
numbers.
20. The method as claimed in claim 17, wherein the specific event
comprises the time at which the K.sup.th row in a previous Nth
frame prior to the specific frame begins exposure, and the fixed
length of time is N frame times plus the period from the time at
which the K.sup.th row begins exposure to the time at which the
last row begins exposure, N and K being natural numbers.
21. The method as claimed in claim 17, wherein the specific event
comprises the time at which the K.sup.th row in a previous Nth
frame prior to the specific frame ends exposure, and the fixed
length of time is N or N-1 frame times plus the period from the
time at which the K.sup.th row begins exposure to the time at which
the last row begins exposure, N and K being natural numbers.
22. The method as claimed in claim 17, wherein the specific event
comprises the time at which a built-in LED of the mobile device
begins lighting for a first time after a user presses a shutter or
the time at which a built-in LED of the mobile device begins
lighting for a second time after a user presses a shutter, wherein
the extension flash module comprises a photometry module, and
wherein when the photometry module in the extension flash module
detects light from the built-in LED, the extension flash module
triggers a flash instruction according to a flash delay time and
the period from the time at which the built-in LED begins lighting
for the first time or for the second time to the flashable time in
the flashable time period, so that the extension flash module
flashes during the flashable time period, wherein the flash delay
time is a period from the time at which the extension flash module
starts to execute the flash instruction to the time at which the
extension flash module actually flashes.
23. The method as claimed in claim 17, wherein an error of the
fixed length of time is smaller than half of the flashable time
period.
24. The method of claim 10, further comprising: sensing the light
emitting time point at which the mobile device emits light, by a
photometry module of the extension flash module.
Description
CROSS REFERENCE
[0001] The present invention claims priority to TW 103140180, filed
on Nov. 19, 2014, and TW 104107362, filed on Mar. 9, 2015. The
present invention is a continuation-in-part application of U.S.
Ser. No. 14/643,905, filed on Mar. 10, 2015.
BACKGROUND OF THE INVENTION
[0002] Field of Invention
[0003] The present invention relates in general to the technology
of flash lamp, and more particularly to a method for controlling
flash timing of an extension flash module of a mobile device.
[0004] Description of Related Art
[0005] With continuous advance in pixels and quality of digital
photography, it has become a trend for mobile devices, such as
mobile phones and tablets, to carry the function of taking photos.
However, these built-in digital cameras have not been able to
perform so well as conventional digital cameras under the
circumstances of low lighting or backlighting.
[0006] Although some built-in digital cameras also carry a
light-emitting diode (LED) supplement lamp, both the battery
capacity of mobile devices and the heat dissipation issue of LEDs
seriously confine the volume of fill light provided by the LED
supplement lamp. When the distance between the object being
photographed and the LED supplement lamp exceeds one meter, the LED
fill light cannot provide adequate light source to allow pixels of
a photo sensor to be properly exposed.
[0007] Xenon high-intensity discharge lamps (HIDs) can provide a
large amount of supplementary lighting within a short period of
time. Therefore, conventional digital cameras usually carry a xenon
HID. A charger in a xenon HID converts low-voltage battery power
supply into high-voltage power supply and stores it in a
high-capacitance high-voltage capacitor. Operating in coordination
with a mechanical shutter, the xenon HID is then triggered at a
proper timing to convert the electricity stored in the high-voltage
capacitor into high-brightness supplementary lighting within a very
short period of time so that the pixels of a photo sensor are
properly exposed under circumstances of low lighting or
backlighting. A xenon HID requires a high-voltage capacitor having
a capacitance from dozens to hundreds of pF and able to withstand
300 to 400 volts. In pursuit of lighter, thinner and more compact
mobile devices, the very large volume of such a high-voltage
capacitor fails to meet the requirements of current mobile devices.
Therefore, in order not to increase the volume and weight of
existing mobile devices, extension HID flash modules become a
feasible and even necessary option.
[0008] According to the specifications of the capacitance in
high-voltage capacitors and HID lamp tubes, the flash time of HID
flash modules lasts from dozens to hundreds of microseconds
(.mu.s). How to flash at the right timing so that all pixels in a
photo sensor are evenly exposed is an important issue to be solved
for extension HID flash modules to become a feasible option. Mobile
devices which carry a photo-taking device normally adopt a
complementary metal-oxide semiconductor (CMOS) photo sensor and a
rolling shutter instead of a mechanical shutter, as shown in FIG.
1. FIG. 1 is a schematic drawing of a rolling shutter in the
conventional art. In FIG. 1, every line represents the time during
which a row in the photo sensor performs light-sensing operation.
Although the length of exposure for every photo sensor row in a
frame is the same, there is a delay between the time when a photo
sensor row begins or ends exposure and the time when its preceding
photo sensor row begins or ends exposure. During the delay time,
the photo-taking device reads the exposure data in the photo sensor
row and resets the pixels so as to prepare for the exposure in the
next frame. Since photos are taken in different environments and
photo-taking devices are also set differently, the exposure time of
one photo sensor row is in a wide range, lasting approximately from
a few milliseconds to hundreds of milliseconds.
[0009] However, in coordination with a rolling shutter, an
extension HID flash module usually cannot locate the optimal flash
timing and fails to improve the quality of photos.
SUMMARY OF THE INVENTION
[0010] From one perspective, the present invention provides a
method for controlling flash timing of an extension flash module
cooperating with a mobile device to provide supplemental light when
the mobile device having an image retrieval device is taking a
photo, the image retrieval device including pixels arranged in
rows, the method comprising: detecting a specific event before a
flashable time period, wherein the flashable time period is a
period from the time at which a last row in a specific frame begins
exposure to the time at which a first row in the specific frame
ends exposure, wherein the time period from when the specific event
occurs to a flashable time in the flashable time period has a fixed
length of time; and informing the extension flash module the
occurrence of the specific event, so that the extension flash
module triggers a flash instruction after a delay time from when
the specific event occurs, such that the flash timing of the
extension flash module is in the flashable time period.
[0011] In one embodiment, the delay time is determined according to
a flash delay time and the time period from when the specific event
occurs to the flashable time in the flashable time period, wherein
the flash delay time is a period from the time at which the
extension flash module starts to execute the flash instruction to
the time at which the extension flash module actually flashes.
[0012] In one embodiment, the time at which the specific event
occurs is t0, the time at which the last row in the specific frame
begins exposure is t1, and the time at which the first row in the
specific frame ends exposure is t2, and wherein the delay time
which begins at t0 has a duration of td1, and the flash delay time
has a duration of td, wherein an initial time point of the duration
of td is the time at which the extension flash module starts to
execute the flash instruction, then the following relationship is
fulfilled: (t1-td-t0)<td1<(t2-td-t0).
[0013] In one embodiment, the delay time is determined by steps
including: (A) exposing a frame according to a given delay time;
(B) checking the exposed frame and comparing brightnesses of the
pixels with a reference threshold, to determine whether a pixel has
a brightness lower than the reference threshold; (C1) when none of
the pixels has a brightness lower than the reference threshold,
setting the given delay time as a default delay time; (C2) when one
or more of the pixels have a brightness lower than the reference
threshold, and the pixel having brightness lower than the reference
threshold is exposed earlier than half of the other pixels,
shortening the delay time; and (C3) when one or more of the pixels
have a brightness lower than the reference threshold, and the pixel
having brightness lower than the reference threshold is exposed
later than half of the other pixels, prolonging the delay time.
[0014] In one embodiment, the reference threshold of brightness is
set by steps including: performing an exposure without flashing the
extension flash module; and taking a lowest, highest, or average
brightness among all pixels, or a brightness of a pixel at a
predetermined position, as the reference threshold.
[0015] In one embodiment, the method further comprises: lowering
the reference threshold when an ambient light is relatively dimmer,
and raising the reference threshold when the ambient light is
relatively brighter.
[0016] In one embodiment, the delay time is pre-stored in a driver
program of the extension flash module or an application program of
the mobile device.
[0017] In one embodiment, the delay time is stored in a memory
device included in the extension flash module.
[0018] In one embodiment, the specific event includes: the time at
which one of the rows of the pixels in the specific frame begins
exposure; the time at which one of the rows of the pixels in the
previous Nth frame prior to the specific frame begins exposure; or
the time at which one of the rows of the pixels in the previous Nth
frame prior to the specific frame ends exposure; wherein N is a
natural number.
[0019] From yet another perspective, the present invention provides
a method for controlling flash timing of an extension flash module
cooperating with a mobile device to provide supplemental light when
the mobile device having an image retrieval device is taking a
photo, the image retrieval device including pixels arranged in
rows, the method comprising: sensing a light emitting time point at
which the mobile device emits light; and triggering a flash
instruction after a delay time from the light emitting time point
at which the mobile device emits light, such that the flash timing
of the extension flash module is in a flashable time period;
wherein the flashable time period is a period from the time at
which a last row in a specific frame begins exposure to the time at
which a first row in the specific frame ends exposure.
[0020] In one embodiment, the light emitting time point is: a time
point at which a built-in light emitting diode (LED) supplement
lamp of the mobile device begins to emit light for the first time
or a time point at which the built-in LED supplement lamp begins to
emit light for the second time.
[0021] From yet another perspective, the present invention provides
a method for controlling flash timing of an extension flash module
cooperating with a mobile device to provide supplemental light when
the mobile device having an image retrieval device is taking a
photo, the image retrieval device including pixels arranged in
rows, the method comprising: detecting a specific event before a
flashable time period, wherein the flashable time period is a
period from the time at which a last row in a specific frame begins
exposure to the time at which a first row in the specific frame
ends exposure, wherein the time period from when the specific event
occurs to a flashable time in the flashable time period has a fixed
length of time; and triggering a flash instruction so that the
extension flash module flashes during the flashable time period
according to a flash delay time and the period from the specific
event to the flashable time, wherein the flash delay time is a
period from the time at which the extension flash module starts to
execute the flash instruction to the time at which the extension
flash module actually flashes.
[0022] In one embodiment, the specific event comprises the time at
which the first row in the specific frame begins exposure, and the
fixed length of time is the period from the time at which the first
row begins exposure to the time at which the last row begins
exposure.
[0023] In one embodiment, the specific event comprises the time at
which a K.sup.th row in the specific frame begins exposure, and the
fixed length of time is the period from the time at which the
K.sup.th row begins exposure to the time at which the last row
begins exposure, N and K both being natural numbers.
[0024] In one embodiment, the specific event comprises the time at
which the K.sup.th row in a previous Nth frame prior to the
specific frame begins exposure, and the fixed length of time is N
frame times plus the period from the time at which the K.sup.th row
begins exposure to the time at which the last row begins exposure,
N and K being natural numbers.
[0025] In one embodiment, the specific event comprises the time at
which the K.sup.th row in a previous Nth frame prior to the
specific frame ends exposure, and the fixed length of time is N or
N-1 frame times plus the period from the time at which the K.sup.th
row begins exposure to the time at which the last row begins
exposure, N and K being natural numbers.
[0026] In one embodiment, the specific event comprises the time at
which a built-in LED of the mobile device begins lighting for a
first time after a user presses a shutter or the time at which a
built-in LED of the mobile device begins lighting for a second time
after a user presses a shutter, wherein the extension flash module
comprises a photometry module, and wherein when the photometry
module in the extension flash module detects light from the
built-in LED, the extension flash module triggers a flash
instruction according to a flash delay time and the period from the
time at which the built-in LED begins lighting for the first time
or for the second time to the flashable time in the flashable time
period, so that the extension flash module flashes during the
flashable time period, wherein the flash delay time is a period
from the time at which the extension flash module starts to execute
the flash instruction to the time at which the extension flash
module actually flashes.
[0027] The spirit of the present invention is to use a specific
event as a reference time point; the time at which the specific
event occurs is relatively fixed and known compared to the
flashable time. Meanwhile, the delay time of the flash module is
also taken into account, such that the extension flash module is
triggered at a proper timing and flashes during the flashable time
period. Therefore, with the method for taking photos provided by
the present invention, pixels are properly exposed under a low
lighting or backlighting environment, whereby the quality of photos
taken by the mobile device is enhanced.
[0028] The objectives, technical details, attribute or parameters,
and effects of the present invention will be better understood with
regard to the detailed description of the embodiments below, with
reference to the attached drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0029] FIG. 1 is a schematic drawing explaining how a rolling
shutter operates according to the conventional art.
[0030] FIG. 2 is a schematic drawing showing a flashable time
period according to an embodiment of the present invention.
[0031] FIG. 3 shows the flow chart of a method for taking photos
according to a preferred embodiment of the present invention.
[0032] FIG. 4 shows the oscillogram of signals from a built-in LED
supplement lamp of a mobile device adopting the method for taking
photos according to a preferred embodiment of the present
invention.
[0033] FIG. 5 shows a system block diagram of an extension flash
module according to a preferred embodiment of the present
invention.
[0034] FIG. 6 shows another preferred embodiment of the present
invention.
[0035] FIGS. 7-8 show yet another preferred embodiments of the
present invention.
[0036] FIG. 9 shows still another preferred embodiment of the
present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0037] The present invention will become more fully understood from
the detailed description given hereinafter. The drawings as
referred to throughout the description of the present invention are
for illustration only, but not drawn according to actual scale.
[0038] According to the present invention, an extension flash
module such as an HID flash module cooperates with a mobile device
to provide supplemental light when the mobile device is taking a
photo. The mobile device has an image retrieval device such as a
photo sensor, and the image retrieval device includes pixels
arranged in rows. FIG. 2 is a schematic drawing showing a flashable
time period according to an embodiment of the present invention.
Referring to FIG. 2, the flashable time period is between (and
includes) t1 and t2, because the flash light within this period can
be received by every photo sensor row; that is, any time point in
this flashable time period is a flashable time. If the flash timing
is earlier than t1, the subsequent photo sensor rows are not
exposed. If the flash timing is later than t2, the previous rows of
the photo sensor are not exposed. However, since a mobile device is
capable of multi-tasking and may be concurrently performing other
tasks, such other tasks can affect the execution timing of the
flash control; as a result, the delay time between the time when a
user presses the shutter and the actual flash timing is uncertain,
which means that the time from when a user presses the shutter to
t1 or t2 is not fixed. Conventionally, there is not a feasible and
reliable way to ensure that the flash timing of the extension flash
module is stably controlled between t1 and t2, but flashing at an
imprecise timing seriously and critically compromises the function
of an extension HID flash module. However, the present invention
solves this problem. A method for taking photos is provided by the
present invention, as shown in FIG. 2, and described below, in
which the flash timing of the extension flash module can be stably
controlled between t1 and t2.
[0039] FIG. 3 shows the flow chart of a method for taking photo
according to a preferred embodiment of the present invention. An
extension HID flash module is used to supplement light when the
mobile device is taking a photo. The method includes the following
steps:
[0040] Step S300: Start.
[0041] Step S301: Detecting a specific event before a flashable
time. Referring to FIG. 2, in one embodiment, the image retrieval
device equipped in a mobile device adopts a rolling shutter
mechanism, in which the photo sensor rows of the image retrieval
device are sequentially exposed row by row, and the exposure of a
photo sensor row is processed in a form of integration. As shown in
FIG. 2, the flashable time of a retrieved specific frame falls
between (and includes) t1 and t2. Referring to FIGS. 2, t1 and t2
are the time at which the last row begins exposure (integration
begins) and the time at which the first row ends exposure
(integration ends), respectively. If the flash module flashes
during the period between t1 and t2 (the flashable time period),
every row can receive the flash light during its exposure.
[0042] After a mobile device confirms that a user has pressed the
shutter giving a shutter instruction, the mobile device will
perform preparation actions, such as performing photometry and
focusing, and determine a specific frame to be retrieved and the
exposure time of a photo sensor. At and after a certain moment, the
flashable time period t1-t2 of the extension flash module becomes
known, i.e., it has a fixed relationship, which will no longer be
affected by any other task that the mobile device may be
performing, with a certain event (referred to as a "specific event"
in this specification) that occurs at that certain moment. Based on
this, for instance, a designer may predict the time of the specific
frame by designing a certain application program or use a signal
from a certain hardware to determine the time of the specific
frame. That is, when the specific event occurs, the time period
from when the specific event occurs to the flashable time is fixed
and is a relatively stable and known period. There is a fixed
length of time between the occurrence of the specific event and the
flashable time. (The flashable time can be any designated time
point within the flashable time period.) Therefore, in one aspect,
the present invention adopts the time of a specific event as the
basis for prediction.
[0043] In one embodiment, the prediction of the flashable time and
the flash control can be implemented by a mobile device application
program (e.g., a mobile phone application program), and for
example, the mobile phone application program can retrieve the time
at which the first photo sensor row begins exposure (in a specific
frame desired to be retrieved) as the specific event. In this
example, the fixed length of time is the period from the time at
which the first photo sensor row begins exposure to the time at
which the last photo sensor row begins exposure. For another
example, the specific event can be the time at which the Kth photo
sensor row (in a specific frame desired to be retrieved) begins
exposure. In this example, the fixed length of time is the period
from the time at which the Kth photo sensor row begins exposure to
the time at which the last photo sensor row begins exposure. For
another example, the specific event can be the time at which the
Kth photo sensor row in the previous Nth frame begins exposure. In
this example, the fixed length of time is N frame times plus the
period from the time at which the Kth photo sensor row begins
exposure to the time at which the last photo sensor row begins
exposure. For another example, the specific event can be the time
at which the Kth photo sensor row in the previous Nth frame ends
exposure. If the Kth photo sensor row ends exposure earlier than
the time at which the last photo sensor row begins exposure, then
in this example, the fixed length of time is N frame times plus the
period from the time at which the Kth photo sensor row ends
exposure to the time at which the last photo sensor row begins
exposure. If the Kth photo sensor row ends exposure later than the
time at which the last photo sensor row begins exposure, then in
this example, the fixed length of time is N-1 frame times plus the
period from the time at which the Kth photo sensor row ends
exposure to the time at which the last photo sensor row begins
exposure. In the above examples, the fixed length of time, which
corresponds to the period from the specific event to the flashable
time, is calculated with reference to the last time point (t2) of
the flashable time period. However, equivalently, the fixed length
of time can calculated with reference to any time point between
(and including) t1 and t2.
[0044] In another embodiment, the prediction of the flashable time
and the flash control can be implemented by referring to a hardware
signal. For example, the specific event may be a signal from a
built-in LED supplement lamp of the mobile device. FIG. 4 shows the
oscillogram of signals from a built-in LED supplement lamp of a
mobile device adopting the method for taking photo according to a
preferred embodiment of the present invention. Referring to FIG. 4,
when the mobile device is taking a photo, the built-in LED
supplement lamp lights up for a first time to indicate that the
lens is focusing and lights up for a second time to show that an
image is being retrieved (sensed). In this example, in the step
S301 of the present invention, the specific event may be the event
that the LED supplement lamp lights up for the first time or for
the second time.
[0045] Step S302: Triggering a flash instruction so that the
extension flash module flashes during the flashable time period
according to a flash delay time and the period from the specific
event to the flashable time. "Trigger a flash instruction" in the
context of this specification means that the extension flash module
starts to execute a flash instruction that it receives or has
received. As far as the extension flash module is concerned, a
flash delay time td exists between the time at which the extension
flash module starts to execute a flash instruction and the time at
which the actual flashing of the extension flash module occurs.
Therefore, the flash control should take into account, in addition
to the period from the specific event to the flashable time, the
delay time of the extension flash module itself. That is, because
the above-mentioned period from the specific event to the flashable
time is a constant and the delay time of the extension flash module
is a known value, the method of this embodiment can determine when
to trigger the flash instruction according to such constant and
known value. For example, if the delay time from the time at which
the flash instruction is received by the extension flash module to
the time at which the actual flashing of the extension flash module
occurs is td (td is calculated with reference to the time at which
the flash instruction is received), then the time point for
triggering the flash instruction should be between (t1-td) and
(t2-td). Or, if the reference initial time point of the delay time
td is the time at which the specific event occurs (the delay time
td starts being counted at the time when the specific event occurs)
and assuming that such time at which the specific event occurs is
t0, then the flash timing needs to fulfill the relationship:
(t1-t0)<td<(t2-t0). The extension flash module flashes when
the delay time td ends. If the delay time td is calculated with
reference to a certain other time point which has a time difference
from the time at which the specific event occurs, such time
difference can be taken into account, depending on the definition
of the delay time td (i.e., depending on when to start counting the
delay time td).
[0046] The above embodiments give examples as to how the flash
timing can be controlled when the extension flash module is
connected by hardware (e.g. via a universal serial bus (USB), or a
headset socket) to the mobile device, in coordination with the
internal software of the mobile device to determine the specific
event. In another embodiment which is in compliance with the spirit
of the present invention, the extension flash module may also be
optically coupled to control the flash timing. FIG. 5 shows a
system block diagram of an extension flash module adopting the
method according to one embodiment of the present invention.
Referring to FIG. 5, an extension flash module 50 may be, for
example, an extension flash module which is not electrically
connected to the mobile device 51 and can even be a separated
non-contact module to the mobile device 51. The extension flash
module 50 includes an optical sensor circuit 501, a delay circuit
502, a flash lamp drive circuit 503, and an HID lamp 504. When the
LEDs in the mobile device 51 light up, such an event is detected by
the optical sensor circuit 501 as the specific event and triggers
the HID lamp 504 to flash during the flashable time (t1.about.t2).
Typically, the LEDs in the mobile device 51 light up twice (first
for focusing and second for flashing), and the specific event can
be defined as either one of them.
[0047] Please note that optical coupling is only one among many
possible ways to embody the present invention; people ordinarily
skilled in the art would readily conceive, in light of the
teachings of the present invention, that the present invention may
also be implemented wirelessly--such as via Wi-Fi, near field
communication (NFC) or Bluetooth--or by detecting a sound produced
by the shutter of the mobile device. The present invention is not
limited to the embodiments described herein.
[0048] The above description describes a "fixed length of time"
from when a specific event occurs to the flashable time, which is a
relatively stable and known time period. However, there can still
be insignificant variations or errors caused by unknown sources;
therefore even designers themselves cannot guarantee that the
"fixed length of time" absolutely does not contain any minor
variation. Nevertheless, from the standpoint of practical
application, as long as such a variation is within than an
acceptable range, a good flashing control can still be achieved.
For example, if an error in calculating the "fixed length of time"
is smaller than half of the flashable time period, such an error is
tolerable and still falls within the scope defined by the present
invention.
[0049] In addition, because the flash module is used as an
extension hardware to be attached to a mobile device, the extension
flash module must be able to cooperate with different types of
mobile devices. Although as far as a single mobile device is
concerned, the period from the specific event to the flashable time
is a constant, different types of mobile devices have different
constants. In one embodiment, if the constants of some types of
mobile devices are known, different known constants can be
pre-stored in a driver program of the extension flash module or an
application program of the mobile device. Please refer to FIG. 6.
For example, when a mobile device is to be equipped with an
extension flash module, an application program can be installed
therein. This application program identifies the type or a certain
attribute or parameter of the mobile device, and correspondingly
determines the delay time td1 of the delay circuit 502. As
described above, there is a delay time td from the time at which
the flash instruction is received by the extension flash module to
the time at which the actual flashing of the extension flash module
occurs (td is calculated with reference to the time at which the
flash instruction is received), so the delay time td1 of the delay
circuit 502 should be controlled, such that the time point for
triggering the flash instruction is between (t1-td) to (t2-td).
Assuming that the time at which the specific event occurs is t0 and
the delay time td1 begins at t0, the following relationship should
be fulfilled: (t1-td-t0)<td1<(t2-td-t0).
[0050] In another embodiment, different known constants can be
stored in the hardware circuit. Please refer to FIG. 7 in
conjugation with FIG. 8. In this embodiment, first, storing one or
more time constants from the specific event to the flashable time,
corresponding to one or more mobile devices, in a memory device
(memory 505) of the extension flash module (step S801). When it is
desired to take a photo, the extension flash module 50 communicates
with the mobile device, to obtain the type or a certain attribute
or parameter of the mobile device (step S802). The extension flash
module 50 determines the delay time td1 according to the time
constant stored in the memory device with reference to the type or
the attribute or parameter of the mobile device (step S803). Next,
a specific event occurs and is detected (step S804). A flash
instruction is triggered after a delay time td1 from when the
specific event occurs (step S805).
[0051] In another embodiment, referring to FIG. 9, when the time
constants for some types of mobile devices are unknown, an optimum
delay time can be determined through a checking process. In this
embodiment, first, a photo-taking testing procedure can be taken,
for example but not limited to, when a mobile device is equipped
with an extension flash module and it is prepared to take a first
photo, or when a driver program of the extension flash module is
being installed, or at any other suitable moment (step S901). In
this photo-taking testing procedure, the image retrieval device
(such as a photo sensor) in the mobile device exposes a frame, and
the extension flash module flashes according to a given delay time
(step S902). Next, this embodiment checks the exposed frame, i.e.,
comparing the brightnesses of the pixels with a reference threshold
(step S903), to determine whether there is a pixel having a
brightness lower than the reference threshold (step S904). When
none of the pixels has a brightness lower than the reference
threshold, the given delay time can be set as the default delay
time (step S905). When there is one pixel (or a predetermined
number of pixels) having a brightness lower than the reference
threshold, and the pixel having the lower brightness is exposed
earlier than most (such as half of) other pixels (e.g., the first
row or the first several rows of pixels in FIG. 1) (step S906 and
step S907), then the delay time is shortened (i.e., the time for
triggering the flash instruction is moved earlier) (step S908), and
the process returns to the step S902. When there is one pixel (or a
predetermined number of pixels) having a brightness lower than the
reference threshold, and the pixel having the lower brightness is
exposed later than most (such as half of) other pixels (e.g., the
Nth row or the last several rows of pixels in FIG. 1) (step S906
and step S909), then the delay time is prolonged (i.e., the time
for triggering the flash instruction is moved later) (step S910),
and the process returns to the step S902. Thus, an appropriate
delay time can be obtained.
[0052] To avoid misjudgments, a pixel number threshold can be set,
such that: the delay time is adjusted only when the number of the
pixels having a brightness lower than the reference threshold
exceeds the pixel number threshold.
[0053] In addition, in one embodiment, the reference threshold of
brightness can be determined by, for example but not limited to:
exposing the pixels without flashing the extension flash module,
and taking the thus obtained brightness (which can be, e.g., a
lowest, highest, or average brightness among all pixels, or a
brightness of a pixel at a specific position such as the center, a
peripheral location, or a corner) as the reference threshold.
[0054] In one embodiment, the reference threshold of brightness can
be adjusted according to the sensing of the ambient light. For
example, if the mobile device is equipped with an ambient light
sensor, the sensed value of the ambient light can be taken as a
reference to correspondingly lower the reference threshold when the
ambient light is relatively dimmer, and correspondingly raise the
reference threshold when the ambient light is relatively
brighter.
[0055] In light of the above, the spirit of the present invention
is to use a specific event as a reference time point; the time at
which the specific event occurs is relatively fixed and known
compared to the flashable time. Meanwhile, the delay time of the
flash module is also taken into account, such that the extension
flash module is triggered at a proper timing and flashes during the
flashable time period. Therefore, with the method for taking photos
provided by the present invention, pixels are properly exposed
under a low lighting or backlighting environment, whereby the
quality of photos taken by the mobile device is enhanced.
[0056] While certain exemplary embodiments have been described and
shown in the accompanying drawings, it is to be understood that
such embodiments are merely illustrative of and not restrictive on
the broad invention, and that this invention should not be limited
to the specific construction and arrangement shown and described,
since various other modifications may occur to those ordinarily
skilled in the art. It will be apparent that various changes and
modifications can be made without departing from the spirit and
scope of the invention as defined in the appended claims.
* * * * *