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Digital Camera Patent Abstract
To provide a camera which enables photographing while intentionally,
subtly shifting operation timing from that of another camera. A
digital camera has a timing computing circuit. The timing computing
circuit receives a reset request from another digital camera by
way of a communications interface. The timing computing circuit
awaits a reset request for a standby period shown by the reset request,
and outputs a reset command to a reset circuit. The reset circuit
outputs a reset signal to a timing generator (TG) in accordance
with the reset command.
Digital Camera Patent Claims
1. A digital camera for performing photographing in cooperation
with another digital camera connected thereto by way of a network,
the camera comprising: an image sensor; a timing generator for outputting
a vertical synchronization signal to the image sensor; a reset circuit
for outputting to the timing generator a reset signal used for resetting
output timing of the vertical synchronization signal; a communications
interface for receiving a reset request from the other digital camera;
a reset control circuit for controlling the reset circuit so as
to output a reset signal after having received the reset request
and waited during a standby period which is determined on the basis
of a photographing parameter of the digital camera or that of the
other digital camera; and a sensor control circuit for controlling
the image sensor so as to start performing exposure in synchronism
with the reset vertical synchronization signal.
2. The digital camera according to claim 1, wherein the reset control
circuit transmits a reset request to the other digital camera by
way of the communications interface when the reset circuit outputs
a reset signal.
3. The digital camera according to claim 2, wherein the reset control
circuit transmits the reset request while the reset request includes
the photographing parameter of the digital camera.
4. The digital camera according to any one of claims 1 through
3, wherein the photographing parameter includes an exposure period
employed when the digital camera or the other digital camera performs
photographing.
5. The digital camera according to any one of claims 1 through
4, wherein the photographing parameter includes a flash firing period
employed when the digital camera or the other digital camera performs
photographing.
6. A digital camera for performing photographing in cooperation
with another digital camera connected thereto by way of a network,
the camera comprising: an image sensor; a timing generator for outputting
a vertical synchronization signal to the image sensor; a reset circuit
for outputting to the timing generator a reset signal used for resetting
output timing of the vertical synchronization signal; and a reset
control circuit for transmitting a reset request, which includes
the photographing parameter of the digital camera, to the other
digital camera when the reset circuit outputs a reset signal.
Digital Camera Patent Description
FIELD OF THE INVENTION
[0001] The present invention relates to a digital camera which
performs photographing operation in cooperation with another digital
camera connected to the digital camera by way of a network.
BACKGROUND OF THE INVENTION
[0002] A photographing system utilizing a plurality of cameras
includes, e.g., a system which displays images captured by a plurality
of cameras on a multi-screen; a system for generating a three-dimensional
image of a subject; a system for measuring a distance to a subject;
and a system for generating a wide-range image, such as a panoramic
image. In such a photographing system, a plurality of cameras must
be synchronized.
[0003] In relation to the photographing system such as that mentioned
above, a technique for synchronizing a plurality of cameras is described
in U.S. Published Application Publication 2002/0135682 to Oka et
al. According to Oka et al, a master camera generates a time stamp
used for synchronizing frame synchronization signals of all cameras
(including the master camera). All the cameras generate frame synchronization
signals on the basis of the time stamp generated by the master camera,
to thus synchronize the plurality of cameras.
[0004] By way of the technique described in Oka et al, the plurality
of cameras can be synchronized. However, difficulty is encountered
in causing cameras to perform photographing while intentionally,
subtly shifting operation timing from one camera to another camera,
by way of merely synchronizing a plurality of cameras; for instance,
a slave camera starting performing exposure immediately after a
master camera has completed exposure to thus perform continuous
photographing of a single subject while eliminating a blank period
during which a single subject is not exposed.
SUMMARY OF THE INVENTION
[0005] Accordingly, the present invention provides a camera which
enables photographing while intentionally, subtly shifting operation
timing from that of another camera.
[0006] The present invention provides a digital camera for performing
photographing in cooperation with another digital camera connected
thereto by way of a network, the camera comprising:
[0007] an image sensor;
[0008] a timing generator for outputting a vertical synchronization
signal to the image sensor;
[0009] a reset circuit for outputting to the timing generator a
reset signal used for resetting output timing of the vertical synchronization
signal;
[0010] a communications interface for receiving a reset request
from the other digital camera;
[0011] a reset control circuit which acquires a standby period
from when the reset request has been received until when the reset
circuit outputs a reset signal and controls the reset circuit so
as to output a reset signal after having waited the acquired standby
period; and
[0012] a sensor control circuit for controlling the image sensor
so as to start performing exposure in synchronism with the reset
vertical synchronization signal. The standby period is determined
on the basis of a photographing parameter of the digital camera
or that of the other digital camera
[0013] According to the present invention, upon receipt of a reset
request, the digital camera resets a vertical synchronization signal
after having waited for a standby period which is determined by
a photographing parameter. Thereby, the digital camera can shift
output timing of a vertical synchronization signal from a timing
at which another digital camera outputs a vertical synchronization
signal, by a time corresponding to the photographing parameter.
Accordingly, the digital camera can perform photographing while
subtly shifting operation timing from that of another digital camera
according to the photographing parameter.
[0014] The invention will be more clearly comprehended by reference
to the embodiments provided below. However, the scope of the invention
is not limited to those embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] Preferred embodiments of the present invention will be described
in detail based on the following figures, wherein:
[0016] FIG. 1 is a view showing a schematic configuration of a
photographic system according to an embodiment of the present invention;
[0017] FIG. 2 is a view showing functional blocks of a camera in
the photographic system;
[0018] FIG. 3 is a timing chart acquired when a master camera and
a slave camera perform photographing in a continuous exposure mode;
[0019] FIG. 4A is a flowchart showing photographing procedures
of the master camera;
[0020] FIG. 4B is a flowchart showing photographing procedures
of the slave camera;
[0021] FIG. 5 is a timing chart acquired when the master camera
and the slave camera perform photographing in a first synchronous
mode;
[0022] FIG. 6 is a timing chart acquired when the master camera
and the slave camera perform photographing in a second synchronous
mode;
[0023] FIG. 7 is a timing chart acquired when the master camera
and a plurality of slave cameras perform continuous exposure during
a single exposure period;
[0024] FIG. 8 is a timing chart acquired when the master camera
and the plurality of slave cameras perform continuous exposure during
different exposure periods; and
[0025] FIG. 9 is a timing chart acquired when the master camera
and the plurality of slave cameras perform photographing at the
same photographing interval.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] The best mode for carrying out the present invention (hereinafter
called an "embodiment") will be described hereinbelow
by reference to the drawings.
[0027] FIG. 1 is a view showing the schematic configuration of
a photographing system according to an embodiment of the present
invention. As shown in FIG. 1, the present system includes two digital
cameras 10 (hereinafter simply called "cameras 10"). Each
camera 10 can operate in two modes; i.e., a master mode and a slave
mode. In the present embodiment, a camera set to a slave mode (hereinafter
called a "slave camera") controls output timing of a vertical
synchronization signal in accordance with a command from a camera
set to the master mode (hereinafter called a "master camera").
Each of the cameras 10 can operate in a plurality of photographing
modes. Each of the cameras 10 controls output timing of a vertical
synchronization signal in accordance with a photographing mode selected
by the user, and the respective cameras 10 photograph a subject
12 in cooperation with each other and in accordance with the controlled
vertical synchronization signal. The term "photographing mode"
used herein signifies operation procedures which specify exposure
timing and timing of firing a flash for each camera 10 in such a
way that a desired photograph is acquired. A specific example of
photographing mode will be described later.
[0028] FIG. 2 is a view showing functional blocks of each of the
cameras 10 constituting the present photographing system. In FIG.
2, a CPU 20 is a central processing unit which controls the overall
camera 10, and performs arithmetic processing operations and control
of respective circuits, or the like, which constitute the camera
10. An optical system 30 includes a lens and a diaphragm which are
used for allowing light from the subject enter an image sensor 32
such that a desired image signal is obtained.
[0029] The image sensor 32 converts incident light into signal
charges through photoelectric conversion performed by a light-receiving
element array, and outputs the signal charges. The light-receiving
element array of the image sensor 32 is formed from L(vertical).times.N(horizontal)
(L, N are integers) pixels to which R (red), G (green), and B (blue)
color filters are affixed. The image signal output from the image
sensor 32 has RGB components. The image sensor 32 is activated in
a preview mode, where a simplified image signal for monitoring purpose
including some pixels--into which a vertical image has been diminished
to 1/1 ("1" is an integer)--is output, and a still mode
where an image signal for recording purpose, including all pixels,
is output.
[0030] A CDS (Correlated Double Sampling)-AD (Analog/Digital) circuit
34 reduces noise in the image signal output from the image sensor
32 by way of correlated double sampling to thereby convert the image
signal into a digital signal. An image-processing circuit 36 subjects
the image signal output from the CDS-AD circuit 34 to predetermined
image processing. A storage device 38 saves, as image data, a video
signal for recording purpose which has been subjected to predetermined
image processing by way of the image-processing circuit 36. For
monitoring purpose, a display section 40 displays on a screen a
motion picture based on the simplified image signal.
[0031] An operation section 42 is a user interface used by the
user to operate the camera 10, such as a shutter button which can
be pressed halfway down or all the way down. A communications interface
44 controls communication with another camera 10 by way of radio
communication such as WiFi or wire communication.
[0032] A timing generator (TG) 50 outputs a horizontal synchronization
signal (HD) and a vertical synchronization signal (VD), which are
required to control the light-receiving element array included in
the image sensor 32, as well as outputting a synchronization signal
required by the CDS-AD circuit 34 to perform signal processing,
thereby synchronizing the image sensor 32 and the CDS-AD circuit
34. A reset circuit 52 outputs a reset signal to the timing generator
50. By way of the input reset signal, the timing generator 50 controls
output timings of the respective synchronization signals. More specifically,
the reset circuit 52 temporarily switches a reference pulse, which
is output from an oscillator circuit (not shown) to the timing generator
50, from High to Low, and further switches from Low to High at another
predetermined timing. The timing when the reset circuit 53 switches
the reference pulse from Low to High corresponds to a timing when
the reset signal is output. As mentioned above, the reset circuit
52 controls output timings of the respective synchronization signals
output by the timing generator 50, by way of switching of the reference
pulse between Low and High.
[0033] A timing-computing circuit 54 outputs to the reset circuit
52 a reset command used for commanding output of a reset signal.
When outputting a reset command, the timing-computing circuit (hereinafter
called a "timing-computing circuit [M]," and the same
also applies to other circuits and the like) of the master camera
transmits a reset request for requesting the slave camera to output
a reset signal. The reset request shows a standby period T.sub.W
starting from receipt of the request by the timing-computing circuit
(hereinafter called a "timing-computing circuit [S],"
and the same also applies to other circuits and the like) of the
slave camera and ending with output of a reset command is. Specifically,
upon receipt of a reset request, the timing-computing circuit [S]
outputs a reset command to the reset circuit [S] after having waited
during the standby period T.sub.W shown in the request. The synchronization
signal output from the timing generator [M] and the synchronization
signal output from the timing generator [S] are shifted from each
other by a period corresponding to the standby period T.sub.W.
[0034] In the present photographing system, the method for computing
a standby period T.sub.W, which is computed by the timing-computing
circuit 54, is changed according to the photographing mode. Thereby,
the synchronization signal (the vertical synchronization signal)
is intentionally shifted for each camera 10, to thus shift an exposure
period.
[0035] The method for computing the standby period T.sub.W will
now be described by way of taking a continuous exposure mode, which
is one of the photographing modes, as an example. In the present
embodiment, the continuous exposure mode signifies a photographing
mode where a slave camera starts performing exposure immediately
after the master camera has completed exposure to thus perform continuous
exposure of a single subject while eliminating a blank period during
which exposure is not carried out.
[0036] FIG. 3 is a view showing a timing chart acquired when the
master camera and the slave camera perform photographing in the
continuous exposure mode. In FIG. 3, the timing-computing circuit
[M] first commands the reset circuit [M] to prepare resetting operation
(S10), whereby the reference pulse [M] is switched from High to
Low. Subsequently, the timing-computing circuit [M] outputs a reset
command to the reset circuit [M] after having waited for a given
period of time (S12), whereby the reference pulse [M] is switched
from Low to High, and the output timing of the vertical synchronization
signal [M] is reset. It is better to set a time, which is sufficient
for switching the synchronization pulse [M] from Low to High, for
the predetermined period. Simultaneously with outputting a reset
command in S12, the timing-computing circuit [M] transmits to the
timing-computing circuit [S] a reset request, which shows the standby
period T.sub.W (S14).
[0037] In the meantime, upon receipt of the reset request (S16),
the timing-computing circuit [S] immediately commands the reset
circuit [S] to prepare for resetting operation, whereby the reference
pulse [S] is switched from High to Low. Subsequently, the timing-computing
circuit [S] waits during the standby period T.sub.W after having
received the reset request, and outputs a reset command to the reset
circuit [S] (S18). The reference pulse [S] is then switched from
Low to High, whereby the output timing of the vertical synchronization
signal [S] is reset.
[0038] When the reset vertical synchronization signal first turns
into a negative polarity, each of the master and slave cameras switches
the drive mode of the image sensor from the preview mode to the
still mode, thereby initiating exposure. A single value, such as
30 fps (frames/sec.), is set as a cycle of the vertical synchronization
signal (i.e., a frame rate) for the master camera and the slave
camera in the preview mode. Consequently, the time from when the
master camera has started exposure until the slave camera starts
exposure can be controlled by way of controlling the time from when
the master camera has reset the vertical synchronization signal
until when the slave camera resets the vertical synchronization
signal. In short, the timings at which the master camera and the
slave camera start exposure can be controlled, by way of controlling
the standby period T.sub.W.
[0039] When the slave camera starts exposure immediately after
the exposure period T.sub.E1 of the master camera has been completed,
it is better, as can be seen from FIG. 3, to shift the timing at
which the master camera outputs the vertical synchronization signal
(hereinafter simply called a "V-sync signal output timing")
from the V-sync signal output timing of the slave camera, by the
amount corresponding to the exposure period T.sub.E1. Specifically,
the period from when the master camera has reset the vertical synchronization
signal until when the slave camera resets the vertical synchronization
signal is taken as the exposure period T.sub.E1. A communication
time T.sub.D is consumed from when the timing-computing circuit
[M] has transmitted the reset request until when the timing-computing
circuit [S] receives the reset request. Accordingly, the timing-computing
circuit [M] computes the standby period T.sub.W according to the
following expression (1) in consideration of the communication time
T.sub.D, whereby the V-sync signal output timing of the master camera
can be shifted from the V-sync signal output timing of the slave
camera by the amount corresponding to the exposure period T.sub.E1.T.sub.W=T.sub.E1-T.sub.D
(1)
[0040] It is better to determine the communication time T.sub.D
on the basis of an actually-measured value obtained by means of
actually measuring a time during which communication is established
between the master camera and the slave camera.
[0041] Next, photographing procedures of the master camera will
be described by reference to a flowchart shown in FIG. 4A, and photographing
procedures of the slave camera will be described by reference to
a flowchart shown in FIG. 4B. The user performs operation in advance
to set each of the cameras 10 into a master mode or a slave mode,
and further sets the photographing mode of the camera 10. Moreover,
the user places the respective cameras 10, for which various settings
have been made, at predetermined positions.
[0042] In FIG. 4A, the master camera determines whether or not
the preparation for photographing has been completed (S100). Specifically,
the shutter button of the master camera is pressed halfway down,
to thereby perform auto-focusing (AF) processing or auto-exposure
(AE) processing. Thereby, the standby period T.sub.W is computed
after deriving photographing parameters required for photographing,
such as a focal distance, an exposure period, firing/unfiring of
a flash, and a period of firing of a flash. When computation of
the standby period T.sub.W has been completed and the shutter button
has been pressed all the way down, the master camera determines
completion of the preparation for photographing. When the preparation
for photographing has been completed, the master camera resets the
vertical synchronization signal by way of outputting a reset signal
while transmitting a reset request, which shows the standby period
T.sub.W, to the slave camera (S102). Subsequently, the master camera
performs photographing (S104).
[0043] In FIG. 4B, when having been set in the slave mode, the
slave camera performs AF processing and AE processing and then enters
a standby condition until it receives a reset request from the master
camera. The slave camera may be caused to start AF processing and
AE processing as a result of the user having pressed the shutter
button halfway down as in the case of the master camera, to thus
enter a standby condition. Upon receipt of a reset request from
the master camera (S110), the slave camera in the standby condition
outputs a reset signal after elapse of the standby period T.sub.W
indicated by the reset request, to thus reset the vertical synchronization
signal (S112). Subsequently, the slave camera performs photographing
(S114).
[0044] As above, according to the present embodiment, the respective
cameras 10 perform exposure in accordance with the vertical synchronization
signals whose output timings are shifted from one camera to another
camera, so that photographing can be performed while the exposure
periods are intentionally shifted.
[0045] The present embodiment has described the example where the
master camera computes the standby period T.sub.W in consideration
of the exposure period T.sub.E1 of the master camera. The master
camera may transmit the reset request, which shows the exposure
period T.sub.E1, to the slave cameras without computing the standby
period T.sub.W, and the slave camera may compute the standby period
T.sub.W by use of the exposure period T.sub.E1. Further, if the
master camera and the slave camera are given the same photographing
conditions and the same exposure period, the slave camera may compute
the standby period T.sub.W on the basis of an exposure period T.sub.E2
of the slave camera. Specifically, when outputting the reset signal,
the master camera transmits to the slave camera the reset request
which does not show the standby period T.sub.W. Upon receipt of
the reset request, the slave camera waits during the standby period
T.sub.W, which is computed by the slave camera on the basis of the
exposure period T.sub.E2 of the slave camera, and then outputs the
reset signal. Thus, when the master camera and the slave camera
perform photographing under the same photographing conditions, the
slave camera may compute the standby period T.sub.W on the basis
of the exposure period T.sub.E2 of the slave camera.
[0046] Subsequently, there will be described a method for computing
the standby period T.sub.W in connection with the photographing
mode, where the master camera and the slave camera perform photographing
while sharing a single flash, while taking two modes (hereinafter
called a "first synchronous mode" and a "second synchronous
mode") as examples.
[0047] First, there will be described a method for computing the
standby period T.sub.W in the first synchronous mode. FIG. 5 shows
a timing chart acquired when the master camera and the slave camera
perform photographing in the first synchronous mode. As shown in
FIG. 5, either the master camera or the slave camera fires a flash
once in the first synchronous mode. The master camera performs photographing
through so-called rear-curtain synchronization by firing a flash
through. In contrast, the slave camera performs photographing through
so-called front-curtain synchronization by firing a flash. Specifically,
in the first synchronization mode, each of the cameras controls
the firing timing of a flash so as to come immediately before completion
of the exposure period of the master camera and immediately after
the slave camera has started the exposure period. As shown in FIG.
5, in the first synchronization mode, the timing at which the slave
camera outputs a reset signal is advanced ahead of the continuous
exposure mode by an amount corresponding to a flash firing period
R.sub.F. Specifically, in the first synchronous mode, the slave
camera waits, upon receipt of a reset request, during the standby
period T.sub.W computed according to the following equation (2),
and outputs the reset signal.T.sub.W=T.sub.E1-T.sub.D-T.sub.F (2)
[0048] When the master camera fires a flash, the master camera
computes the standby period T.sub.W, and transmits to the slave
camera a reset request, which shows the standby period T.sub.W.
Alternatively, the master camera transmits to the slave camera a
reset request, which shows the exposure period T.sub.E1, and the
flash firing period T.sub.F, and the slave camera computes the standby
period T.sub.W. In the meantime, when the slave camera fires a flash,
the master camera transmits to the slave camera a reset request,
which shows the exposure period T.sub.E1 of the master camera. The
slave camera computes the standby period T.sub.W by use of the exposure
period T.sub.E1 which is shown by the reset request.
[0049] As above, as a result of photographing being performed in
the first synchronous mode, the image captured by the front-curtain
synchronization and the image captured by the rear-curtain synchronization
can be obtained by firing of a single flash.
[0050] There will now be described a method for computing the standby
period T.sub.W in the second synchronous mode. FIG. 6 shows a timing
chart acquired when the master camera and the slave camera perform
photographing in the second synchronous mode. As shown in FIG. 6,
in the second synchronous mode the exposure period T.sub.E2 of the
slave camera is made shorter than the exposure period T.sub.E1 of
the master camera. By way of a single flash fired by the master
camera or the slave camera, the master camera and the slave camera
perform photographing in rear-curtain synchronization. In order
to effect such photographing, the timing at which the slave camera
outputs the reset signal is shifted from the timing at which the
master camera outputs the reset signal, by the amount corresponding
to a difference (T.sub.E1-T.sub.E2) between the exposure period
T.sub.E1 of the master camera and the exposure period T.sub.E2 of
the slave camera. In short, in the second synchronous mode, the
slave camera is essentially required to wait for the standby period
T.sub.W computed according to the following equation (3) upon receipt
of the reset request and output a reset signal.T.sub.W=T.sub.E1-T.sub.E2-T.sub.D
(3)
[0051] In the second synchronous mode, even when any of the cameras
fires a flash, the timing-computing circuit [S] of the slave camera
computes the standby period T.sub.W.
[0052] As mentioned above, as a result of photographing being performed
in the second synchronous mode, the images, which have been captured
through two rear-curtain synchronization operations having different
exposure periods, can be obtained by way of firing a single flash.
For instance, when a night view, including a person, is photographed
in the second synchronous mode, there can be acquired an image having
different image quality in a distant view of a scene where no flash
light reaches.
[0053] Subsequently, there will be described a method for computing
the standby period T.sub.W of each of the slave cameras in the continuous
exposure mode when two or more slave cameras are present.
[0054] As shown in FIG. 7, when the respective cameras have the
same exposure period and the cameras sequentially perform exposure,
the standby period T.sub.Wn, of the n.sup.th slave camera can be
computed according to the following equation (4).T.sub.Wn=n.times.T.sub.E1-T.sub.D
(4)
[0055] In this case, for instance, the timing-computing circuit
[M] of the master camera computes the standby period of each of
the slave cameras according to Equation (4), and transmits to the
respective slave cameras reset requests, which show the thus-computed
respective standby periods. In this case, the master camera stores
the sequence of the respective slave cameras in advance in association
with identification information (e.g., an IP address) about the
respective slave cameras.
[0056] As shown in FIG. 8, when the exposure periods of the respective
cameras differ from each other, the master camera transmits to the
first slave camera a reset request which shows a standby period
computed according to Equation (1). In the meantime, each of the
slave cameras computes a standby period for the next slave camera
according to the following equation (5). Specifically, the slave
camera subtracts the communication time T.sub.D from the exposure
period T.sub.En thereof, to thus compute the standby period of the
next slave camera. When outputting the reset signal, the slave camera
transmits to the next slave camera the reset request, which shows
the standby period.T.sub.Wn=T.sub.En-1-T.sub.D (5)
[0057] As above, even when exposure periods of the respective cameras
differ from each other, continuous photographing, which does not
have any blanks in an exposure period, can be realized by use of
a plurality of cameras.
[0058] As shown in FIG. 9, even when exposure periods of the respective
cameras differ from each other, the respective cameras can start
photographing, where exposure is effected at a given interval provides
a camera which enables photographing while intentionally, subtly
shifting operation timing from that of another camera, in cooperation
with each other, so long as the standby periods of the respective
slave cameras can be computed according to the following equation
(6).T.sub.Wn=n.times.T.sub.Q-T.sub.D (6)
[0059] An interval T.sub.Q may be arbitrary. However, in the case
of, for instance, a photographing time T.sub.M and the number of
cameras N, the interval may be computed from the following equation
(7).T.sub.Q=T.sub.M/N (7)
[0060] As above, according to the present embodiment, the standby
period T.sub.W from when each of the cameras has received a reset
request until when the camera outputs a reset signal is changed
according to the photographing mode, so that photographing can be
performed while the output timing of the vertical synchronization
signal can be intentionally, subtly shifted from one camera to another
camera.
[0061] Provided that the camera, which is to become the master
camera, outputs a reset request to the respective slave cameras
in synchronism with a timing where the vertical synchronization
signal changes to negative polarity in the preview mode, the master
camera does not reset the vertical synchronization signal. Therefore,
in this case, the master camera can shift the V-sync signal output
timing of the slave camera for a desired period of time while maintaining
the V-sync signal output timing acquired at this point in time.
[0062] The above descriptions have described the embodiment where
the standby period T.sub.W is computed in consideration of the communication
time T.sub.D to establish communication between the master camera
and the slave cameras. However, so long as the master camera is
configured to output a reset command after having waited for the
communication time T.sub.D since output of the reset request, the
standby period T.sub.W can be computed without subtracting the communication
time T.sub.D. So long as the communication time T.sub.D is considerably
shorter than the exposure period T.sub.E, the standby period T.sub.W
may be computed without subtracting the communication time T.sub.D.
Further, when the communication time T.sub.D is drastically shorter
than the exposure period T.sub.E, the standby period T.sub.W may
be computed without subtracting the communication time T.sub.D.
[0063] Further, the above embodiment has described a case where
the master camera and the slave cameras start performing exposure
after the reset signal has been output. However, the master camera
and the slave cameras can perform exposure at arbitrary timings
after the vertical synchronization signal has been reset. Moreover,
each of the cameras may start performing exposure by way of waiting
again for a photographing start command after having reset the vertical
synchronization signal.
[0064] The invention has been described in detail with particular
reference to certain preferred embodiments thereof, but it will
be understood that variations and modifications can be effected
within the spirit and scope of the invention. TABLE-US-00001 PARTS
LIST 10 camera 12 subject 20 CPU 30 optical system 32 image sensor
34 CDS-AD circuit 36 image-processing circuit 42 operation section
38 storage device 44 interface 50 timing generator 52 reset circuit
53 reset circuit
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