Digital Camera Patent Abstract
A digital camera capable of photography using a flash exposure to
illuminate a photographic subject is provided with an image sensor
having a plurality of photoreceptor elements and capable of independently
reading the electrical load of a specific photoreceptor element
among the plurality of photoreceptor elements, and a detector for
detecting the amount of load accumulation due to light exposure
of a specific photoreceptor element when using a flash exposure.
A controller stops the flash emission when the detection result
of the detector reaches a predetermined level. In this way, light
adjusting control is accomplished in real time. Digital Camera Patent Claims
What is claimed is:
1. A digital camera capable of flash photography by illuminating
a photographic object, the digital camera comprising: an image sensor
for sensing an image of the photographic object, the image sensor
including a plurality of photoreceptor elements, the image sensor
being adapted for reading an electrical load accumulation of each
of at least one predetermined photoreceptor element among the plurality
of photoreceptor elements; a detector for detecting an amount of
the electrical load accumulation of each of the at least one predetermined
photoreceptor element due to light exposure on the at least one
predetermined photoreceptor element during a flash exposure for
a duration of the flash exposure, and for outputting a corresponding
detection signal; an interpolator for interpolating photographic
data of photoreceptor elements, the photoreceptor elements of identical
color and adjacent to each of the at least one predetermined photoreceptor
element, the interpolator thus generating respective interpolated
photographic data for each of the at least one predetermined photoreceptor
element; and a controller for accomplishing light adjusting control
of the flash exposure based on the thus outputted detection signal.
2. A digital camera in accordance with claim 1, wherein the at
least one predetermined photoreceptor element is adapted for being
reset to start a new electrical load accumulation from an initial
state.
3. A digital camera in accordance with claim 2, wherein the detector
can detect the amount of the electrical load accumulation of each
of the at least one predetermined photoreceptor element by repeatedly
resetting each of the at least one predetermined photoreceptor element
during load accumulation, reading the electrical load accumulation
prior to each resetting, and performing cumulative addition of the
electrical load accumulation obtained by each reading.
4. A digital camera in accordance with claim 1, wherein the flash
exposure is a plurality of high-speed light pulses at predetermined
intervals.
5. A digital camera in accordance with claim 4, wherein the controller
accomplishes light adjusting control of the flash exposure by controlling
a number of the plurality of high-speed light pulses.
6. A digital camera in accordance with claim 1, wherein the outputted
detection signal corresponds to an average of the amount of the
electrical load accumulation of each of the at least one predetermined
photoreceptor element.
7. A digital camera in accordance with claim 6, wherein the average
of the amount of the electrical load accumulation of each of the
at least one predetermined photoreceptor element is a weighted average.
8. A digital camera in accordance with claim 1, further comprising:
a data replacement unit for replacing the electrical load accumulation
of each of the at least one predetermined photoreceptor element
with corresponding replacement data.
9. A digital camera in accordance with claim 8, wherein the replacement
data is respective interpolated photographic data.
10. A digital camera in accordance with claim 8, wherein the replacement
data is an average of respective interpolated photographic data
and electrical load accumulation.
11. A digital camera in accordance with claim 10, wherein the average
of respective interpolated photographic data and electrical load
accumulation is a weighted average.
12. A digital camera in accordance with claim 8, wherein the replacement
data is a predetermined one of respective interpolated photographic
data and electrical load accumulation.
13. A digital camera in accordance with claim 1, wherein a location
of each of the at least one predetermined photoreceptor element
is adjusted according to photographic conditions.
14. A digital camera capable of flash photography by illuminating
a photographic object, the digital camera comprising: a flash unit
for producing a flash exposure including at least one light pulse;
an image sensor for sensing an image of the photographic object,
the image sensor including a plurality of photoreceptor elements,
the image sensor being adapted for reading an electrical load accumulation
of each of at least one predetermined photoreceptor element among
the plurality of photoreceptor elements; a detector for detecting
an amount of the electrical load accumulation of each of the at
least one predetermined photoreceptor element due to light exposure
on each of the at least one predetermined photoreceptor element
during a flash exposure for a duration of the flash exposure, and
for outputting a corresponding detection signal; an interpolator
for interpolating photographic data of photoreceptor elements, the
photoreceptor elements of identical color and adjacent to each of
the at least one predetermined photoreceptor element, the interpolator
thus generating respective interpolated photographic data for each
of the at least one predetermined photoreceptor element; and a controller
for accomplishing light adjusting control of the flash exposure
based on the thus outputted detection signal, the controller controlling
a duration of the flash exposure.
15. A digital camera in accordance with claim 14, wherein each
of the at least one predetermined photoreceptor element is adapted
for being reset to start a new electrical load accumulation from
an initial state, and wherein the detector can detect the amount
of the electrical load accumulation of each of the at least one
predetermined photoreceptor element by repeatedly resetting each
of the at least one predetermined photoreceptor element during load
accumulation, reading the electrical load accumulation prior to
each resetting, and performing cumulative addition of the electrical
load accumulation obtained by each reading.
16. A digital camera in accordance with claim 14, further comprising:
a data replacement unit for replacing the electrical load accumulation
of each of the at least one predetermined photoreceptor element
with respective interpolated photographic data.
17. A digital camera in accordance with claim 14, wherein a location
of each of the at least one predetermined photoreceptor element
is adjusted according to photographic conditions.
18. A method for light adjusting control of a digital camera capable
of flash photography by illuminating a photographic object, the
digital camera including an image sensor with a plurality of photoreceptor
elements for sensing an image of the photographic object, the method
comprising the steps of: accumulating an electrical load due to
light exposure of each of at least one predetermined photoreceptor
element among the plurality of photoreceptor elements when using
a flash exposure; detecting an amount of the thus accumulated electrical
load of each of the at least one predetermined photoreceptor; outputting
a detection signal corresponding to the thus detected amount of
accumulated electrical load during the flash exposure for a duration
of the flash exposure; and interpolating photographic data of photoreceptor
elements of identical color and adjacent to each of the at least
one predetermined photoreceptor element, the interpolating thus
generating respective interpolated photographic data for each of
the at least one predetermined photoreceptor element; and accomplishing
light adjusting control of the flash exposure based on the thus
outputted detection signal.
19. A method for light adjusting control of a digital camera capable
of flash photography in accordance with claim 18, wherein the at
least one predetermined photoreceptor element is adapted for being
reset to start a new electrical load accumulation from an initial
state, and wherein the step of detecting an amount of the thus accumulated
electrical load includes: repeatedly resetting each of the at least
one predetermined photoreceptor element during the accumulating
of an electrical load step; reading the accumulated electrical load
prior to each resetting; and performing cumulative addition of the
accumulated electrical load obtained by each reading.
20. A method for light adjusting control of a digital camera capable
of flash photography in accordance with claim 18, the flash exposure
being a plurality of high-speed light pulses at predetermined intervals,
wherein the step of accomplishing light adjusting control includes
controlling a number of the plurality of high-speed light pulses.
Digital Camera Patent Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based on Patent Application No. 11-78218 filed
in Japan, the content of which is hereby incorporated by reference.
FIELD OF THE INVENTION
The present invention relates to a digital camera, and specifically
relates to the art of light adjusting control of flash used in a
digital camera.
BACKGROUND OF THE INVENTION
Digital cameras using an image sensor generally are capable of
exposure control using image data read by the image sensor. However,
because the image data are read after the flash exposure during
flash photography, light adjusting control cannot be performed during
the flash emission using the read image data.
Conventionally, the following light adjusting control methods are
often used. One light adjusting control method is an external light
adjusting control method wherein flash exposure light reflected
from a photographic subject is received by an external light adjusting
control element without passing through a photographic lens, so
as to control the flash exposure based on the output signals from
this external light adjusting control element. Another light adjusting
control method performs a preliminary flash exposure prior to a
main flash exposure, and controls the main flash exposure based
on the image data from an image sensing element during the preliminary
flash exposure.
In the case of the former light adjusting control method, since
the light reflected from the photographic subject does not pass
through the photographic lens, a shift may be generated in the light
adjusting control range relative to changes in the field angle accompanying
dislocation of the lens position as when a zoom lens is used as
the taking lens. This shift in the light adjusting control range
may be directly and disadvantageously linked to a shift in the light
adjusting control precision. In the case of the latter light adjusting
control method, there is no concern of a shift in the light adjusting
control range caused by change in field angle because the flash
exposure light reflected by the photographic subject passes through
the taking lens. However, a time lag may be disadvantageously generated
in the light adjusting control because a flash exposure must be
performed twice, once in the preliminary flash exposure and once
in the main flash exposure.
Another well-known light adjusting control method separate from
the above mentioned methods controls luminance and is a method wherein
light reflected from a photographic subject and passing through
a photographic lens is reflected by the photoreceptor surface of
the image sensor, and this reflected light is received by a separately
provided photoreceptor element which measures the amount of reflected
light received to accomplish light adjusting control. In this instance,
however, the degree of precise flatness of the photoreceptor surface
of the image sensor is readily affected by the material forming
the photoreceptor surface, e.g., metal, protective glass and the
like, such that light adjusting control data does not have a high
reliability.
An object of the present invention is to eliminate the previously
described disadvantages by providing a digital camera capable of
highly reliable light adjusting control in real time without fear
of dislocation of the light adjusting control range due to change
of field angle during flash photography.
SUMMARY OF THE INVENTION
These objects are attained by a digital camera having the construction
described below. A digital camera capable of flash photography by
illuminating a photographic object, the digital camera comprising:
an image sensor for sensing an image of the photographic object,
the image sensor including a plurality of photoreceptor elements,
the image sensor being adapted for reading an electrical load accumulation
of each of the at least one predetermined photoreceptor element
among the plurality of photoreceptor elements; a detector for detecting
an amount of the electrical load accumulation of each of the at
least one predetermined photoreceptor element due to light exposure
on the at least one predetermined photoreceptor element when using
a flash exposure for a duration of the flash exposure, and for outputting
a corresponding detection signal; and a controller for accomplishing
light adjusting control of the flash exposure based on the thus
outputted detection signal.
In this digital camera, the controller accomplishes a flash emission
until the amount of load accumulation in a specific photoreceptor
element detected by the detector attains a predetermined level.
Then, when the amount of load accumulation attains a predetermined
level, the controller stops the flash emission. In this way, since
luminance is controlled using the amount of load accumulation of
a specific photoreceptor element of the image sensor, there is no
dislocation of the light adjusting control range due to a change
of field angle as in the external light adjusting control method.
Since the amount of load accumulation during an on-going flash photograph
is used, light adjusting control is accomplished in real time. Furthermore,
highly reliable control is achieved because this method does not
use the light reflected by the photoreceptor surface of the image
sensor.
An example of a sensor usable as the image sensor is a CMOS sensor.
If a CMOS sensor is used, reliable detection of the amount of load
accumulation in a specific photoreceptor element can be obtained
by the detector.
Furthermore, this specific photoreceptor element can be reset independently
to start a new load accumulation operation from an initial state.
The detector also may be constructed to detect the amount of load
accumulation by repeatedly resetting the specific photoreceptor
element during load accumulation, reading the load prior to each
resetting, and performing cumulative addition of the accumulated
loads obtained by each reading.
When a load continuously accumulates in a specific photoreceptor
element, the load accumulation level of the photoreceptor element
may approach saturation level before the accumulation amount attains
a predetermined level, causing concern that an accurate load accumulation
amount may not be obtained. Conversely, when a new accumulation
operation is performed from an initial state, the operation of reading
the load accumulated by this accumulation operation can be repeated,
and the data obtained by the respective reading operations may be
cumulatively added. In this way, if normally using an operating
range (i.e., the range up to a saturation level) appropriate for
the operating characteristics of the specific photoreceptor element,
accurate load accumulation can be obtained for more precise light
adjusting control.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following description, like parts are designated by like
reference numbers throughout the several drawings.
FIG. 1 is a block diagram showing the electrical structure of an
embodiment of the digital camera of the present invention;
FIG. 2 is a structural view showing the drive unit of an image
sensor used in an embodiment of the digital camera of the present
invention;
FIG. 3 is an enlarged view of the drive unit of FIG. 2;
FIG. 4 illustrates the timing of each operation during flash photography
in an embodiment of the digital camera of the present invention;
FIGS. 5(A) and 5(B) illustrate the operation timing relating to
light adjusting control during flash photography in an embodiment
of the digital camera of the present invention;
FIGS. 6(A)-6(C) illustrate the interpolation process relating to
the photoreceptor element used for light adjusting control in the
image sensor of FIG. 1;
FIG. 7 is a flow chart showing the light adjusting control sequence
during flash photography in an embodiment of the digital camera
of the present invention; and
FIG. 8 is a diagram showing another example of an arrangement pattern
of the photoreceptor elements used for light adjusting control in
an image sensor.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The embodiments of the present invention are described hereinafter
with reference to the accompanying drawings.
FIG. 1 is a block diagram showing the electrical structure of an
embodiment of the digital camera of the present invention.
In FIG. 1, a digital camera 1 comprises a camera body 2 provided
with various circuits described later, and a taking lens unit 3
installed on the front surface of the camera body 2.
The taking lens unit 3 is provided with a taking lens 4 for capturing
an optical image of a photographic object, a stop 5 for restricting
the amount of light, a mechanical shutter 6 and the like.
The camera body 2 may be constructed using the body of a camera
originally designed for silver halide film use or the like. An image
sensor 8 is provided at a position corresponding to the position
occupied by a silver halide film in the camera body 2, and is arranged
with the photoreceptor surface facing toward the taking lens 4 side.
The image sensor 8 photoelectrically converts the light of the formed
object image on the optical path of the taking lens 4. The image
sensor 8 may be, for example, an area sensor which reads all pixels
having a color mosaic filter or the like; in the present embodiment
a CMOS sensor is used which is provided with photoreceptor elements
comprising a plurality of CMOS type photodiodes.
A detachable high-speed intermittent flash unit 7 is installed
on the camera body 2. A shutter button 9 is provided on the camera
body 2, and a display unit 10 is installed on the camera body 2.
The display unit 10 comprises a liquid crystal display (LCD), and
displays photographic images and live view images when previewing.
The camera body 2 is provided with, in addition to the image sensor
8, an image processing circuit 11, exposure calculator 12, stop
driver 13, shutter driver 14, and sensor timing control circuit
15. The camera body 2 is further provided with, although not shown
in the illustration, an image memory for temporary storage of image
data, and a removable memory card or the like for storing photographic
images.
The image processing circuit 11 converts analog image signals output
from the image sensor 8 to digital image signals, and thereafter
these digital signals are subjected to image processing such as
pixel interpolation, white balance, gamma correction and the like.
The image processing circuit 11 displays preview images and photographic
images on the display unit 10. The processed image signals are subjected
to matrix conversion to luminance signals within the image processing
circuit 11, and input to the exposure calculator 12.
The exposure calculator 12 generates exposure control signals in
accordance with the luminance by comparing the luminance signals
to reference signals. The exposure control value of the exposure
control signal is substituted in the load accumulation time and
stop parameters based on a pre-established table. The exposure calculator
12 is provided with an addition circuit 12a for cumulative addition
of each load accumulation amount obtained by repeated load accumulation
by the light adjusting control photoreceptor element during flash
photography. When the load accumulation obtained by the addition
circuit 12a attains a predetermined level, the exposure calculator
12 stops the emission by the flash unit 7. That is, the addition
circuit 12a functions as a detection means for detecting the amount
of load accumulation by the light adjusting control photoreceptor
element.
The sensor timing control circuit 15 controls the load accumulation
time and reading timing of the image sensor 8 in accordance with
commands from the exposure calculator 12. The load accumulation
start timing of the image sensor 8 is controlled based on the signals
from the sensor timing control circuit 15. The shutter driver 14
controls the opening and closing of the mechanical shutter 6 based
on instructions from the exposure calculator 12. The load accumulation
stop timing of the image sensor 8 is set by the timing for closing
the mechanical shutter 6.
The stop driver 13 controls the aperture diameter of the stop 5
in accordance with a predetermined stop amount set by the exposure
calculator 12.
After the stop amount has been set by the stop driver 13, when
the photoreceptor element of the image sensor 8 is reset after the
mechanical shutter 6 opens, load accumulation starts. When a predetermined
load accumulation time elapses, the mechanical shutter 6 is closed,
the image sensor 8 is entirely shielded from light, and in this
state, the signals of each photoreceptor element are read.
The image sensor 8 includes pixels of photoreceptor elements P1-Pn
comprising a plurality of CMOS photodiodes arrayed in a matrix,
as shown in FIGS. 2 and 3. Each photoreceptor element P1-Pn converts
the formed optical image via photoelectric conversion and accumulates
an electrical load corresponding to the amount of light exposure.
As shown in FIG. 2, a portion of all photoreceptor elements P1-Pn,
e.g., a plurality of individual photoreceptor elements Pm, are provided
as light adjusting control photoreceptor elements for the flash
unit 7.
FIG. 3 shows the drive unit of the image sensor 8. In FIG. 3, the
photoreceptor elements of each third horizontal and vertical row
are set as the previously mentioned light adjusting control photoreceptor
element Pm.
Reset switches RS are connected to each photoreceptor element P1-Pn
to discharge (to zero) the accumulated load of the photoreceptor
element. Reset lines RL are connected to each horizontal row groups
M1-Mn of reset switches RS. The reset line RL transmits a reset
signal from the vertical scan circuit VSC to the reset switch RS.
The reset switches RS of a horizontal row group are closed at the
time a reset signal is received by the horizontal row group. After
an accumulated load has been discharged during the prior photoelectric
conversion, the reset switch RS is immediately opened, and each
photoreceptor element P1-Pn returns to an activation state (a state
wherein a load can accumulate via light exposure).
A special reset line RLo is connected to the light adjusting control
photoreceptor ent Pm. The light adjusting control photoreceptor
element Pm is reset by reset line RLo, which is independent of reset
line RL.
Vertical readout switches VS are respectively connected to the
photoreceptor elements P1-Pn. A plurality of address lines AL are
respectively connected to each horizontal row group of vertical
readout switches VS. The address lines AL transmit address signals
from the vertical scan circuit VSC output with a predetermined timing
to the vertical readout switch VS so as to control the vertical
readout switch VS.
The photoreceptor elements P1-Pn are provided with a plurality
of signal lines SL for capturing line the load of the photoreceptor
elements P1-Pn to the output OL, and which are connected to the
vertical readout switches VS. Horizontal readout switches HS, which
are opened and closed by a horizontal scan circuit HSC, are inserted
between each signal line SL and output line OL.
A timing generator circuit TC receives a synchronization input
signal from the sensor timing control circuit 15, and controls the
operations of the vertical scan circuit VSC and the horizontal scan
circuit HSC.
That is, control signals from the timing generator circuit TC are
transmitted to the vertical scan circuit VSC and the horizontal
scan circuit HSC, to selectively control the opening and closing
of the vertical readout switch VS and the horizontal readout switch
HS. As a result, the load of the photoreceptor elements P1-Pn at
each address is discharged through the signal line SL to the output
line OL, amplified by an output amplifier AMP connected to the output
line OL, and transmitted to the image processing circuit 11.
An exposure pattern generator circuit EXC independently resets
the light adjusting control photoreceptor Pm and reads out pixel
data during flash photography.
The operation of the present embodiment of the digital camera of
the present invention is described hereinafter.
During normal light photography which does not use a flash unit,
when the shutter button 9 is depressed half way, the mechanical
shutter 6 is first opened. Thereafter, the photoreceptor elements
P1-Pn of the image sensor 8 are reset by a signal from the timing
generator circuit TC and enter the activated state.
After a predetermined time has elapsed, the vertical readout switch
VS and the horizontal readout switch HS are selectively opened/closed,
and image signals from the photoreceptor elements P1-Pn are output
in the indicated number sequence through the signal line SL to the
output line OL. After the image signal is amplified by the output
amplifier AMP connected to the output line OL, the image signal
is processed in the image processing circuit 11, and displayed on
the display unit 10. The luminance is calculated by the image processing
circuit 11 based on the obtained image data, and a suitable stop
value and exposure time are calculated by the exposure calculator
12 based on the luminance calculation. A live view image is displayed
on the display unit 10 as a result of repeating this operation over
a predetermined time frame period.
Then, when the shutter button 9 is fully depressed, the stop 5
is controlled based on the exposure control value calculated immediately
before by the exposure calculator 12, and the sensor timing control
circuit 15 controls the image sensor 8. Consequently, there is a
suitable exposure for the image sensor 8.
During photography using normal light, the image data obtained
by the light adjusting control photoreceptor element Pm are used
as part of the image data similar to the other photoreceptor elements.
Photography using the flash unit 7 is described below.
During flash photography, the amount of load accumulation by the
light adjusting control photoreceptor element Pm in the image sensor
8 is detected by the exposure calculator 12, and the amount of accumulation
detected by the exposure calculator 12 is monitored to control the
flash unit 7.
Specifics of light adjusting control are described below with reference
to FIGS. 4 and 5. FIG. 4 illustrates the timing of each operation
during flash photography. FIGS. 5(A) and 5(B) illustrate the operation
timing related to light adjusting control of the flash unit 7. FIG.
5(A) shows an instance of a photographic object a short distance
away, or when the reflectivity from the object is high. FIG. 5(B)
shows an instance of a photographic object a long distance away,
or when the reflectivity from the object is low. While the example
shown in FIGS. 4 and 5 illustrates use with a flash unit that produces
multiple light pulses, the light adjusting control method can also
be used with a flash unit which produces a single, long pulse by
controlling the duration of the single pulse.
The mechanical shutter 6 is opened at time t1, and exposure begins.
A reset signal is applied to all photoreceptor elements of the image
sensor 8 at time t1a, and actual load accumulation begins.
The flash emission operation by the flash unit 7 begins at time
t2, and the flash unit 7 emits a high-speed pulse at predetermined
intervals.
With each pulse emission by the flash unit 7, or a percentage of
a single cycle of a number of pulse emissions, reset signals are
transmitted to the light adjusting control photoreceptor Pm independently
from the vertical scan circuit VS via the reset line RLo. The light
adjusting control photoreceptor Pm is reset to an initial state
each time the aforesaid reset signal is received, and a new load
accumulation begins. On the other hand, the amount of accumulated
load immediately before the light adjusting control photoreceptor
element Pm is reset is read out whenever required and transmitted
to the addition circuit 12a of the exposure calculator 12, and cumulatively
added by the addition circuit 12a. That is, the light adjusting
control photoreceptor element Pm is repeatedly reset during load
accumulation for light adjusting control, and each time the load
accumulation starts from the initial state. In this way, load accumulation
is repeatedly executed and read out in a suitable operation range
before a saturation level is attained, to obtain an amount of accumulation
of more reliable image data. Of course, the load accumulation may
be consecutively executed without resetting.
Since the data cumulatively added by the adding circuit 12a are
equal to data obtained by consecutive accumulation operations without
saturation, when the cumulatively added value attains a standard
flash OFF level, an emission stop signal is output from the exposure
calculator 12a at time t3 to stop emission operation of the flash
unit 7. As shown in FIG. 5(A), when the photographic object is a
short distance away, or when the reflectivity from the object is
high, the added value of the data from the light adjusting control
photoreceptor elements Pm attains the flash OFF level in a short
time. On the other hand, as shown in FIG. 5(B), when a photographic
object is a long distance away, or when the reflectivity from the
object is low, a long time is required until the flash OFF level
is reached, and during this time the high-speed pulse flash is operated
continuously.
Flash light adjusting control can be performed simultaneously with
photography.
When a plurality of individual light adjusting control photoreceptor
elements Pm are provided, for example, the cumulatively added values
obtained by the respective light adjusting control photoreceptor
elements may be averaged, and a determination made as to whether
or not the average value has attained the flash OFF level.
Thereafter, the mechanical shutter 6 is closed at time t4, and
this ends the actual exposure. The actual load accumulation time
extends from time t1a to time t4. Thereafter, the accumulated load
of each pixel other than the light adjusting control photoreceptor
elements Pm are read out, and flash photography ends.
As described above, the image data from the light adjusting control
photoreceptor element Pm during flash photography are used for light
adjusting control and are not used as photographic image data. For
this reason, during flash photography, photographic data relating
to the light adjusting control photoreceptor element Pm are omitted.
Interpolation of the omitted pixels is performed as shown in FIGS.
6(A)-6(C). FIG. 6(B) shows an interpolation filter when a G (green)
pixel is used as the light adjusting control photoreceptor element
Pm in the layout pattern of pixels (filter) P of the image sensor
8 shown in FIG. 6(A). On the other hand, FIG. 6(C) shows an interpolation
filter when an R (red) or B (blue) pixel is used as the light adjusting
control photoreceptor element Pm. In either case, adjacent pixels
of identical color are used, and their values averaged for interpolation.
FIG. 7 is a flow chart showing the light adjusting control sequence
during flash photography. In the drawing and throughout the following
description, the term "step" is abbreviated to "S."
In the case of the conventional light adjusting control method
using a preliminary flash, the preliminary flash is emitted simultaneously
when the mechanical shutter opens, and the image data are read once.
The flash emission time is calculated based on the read image data.
Thereafter, the main flash light is emitted, and the image data
are subjected to image processing after the mechanical shutter is
closed.
In contrast, in the light adjusting control method of the present
embodiment, after the mechanical shutter 6 is opened in S101 via
a release operation each photoreceptor element of image sensor 8
including the light adjusting control photoreceptor element Pm is
reset in S102, and load accumulation begins.
Then, the flash unit 7 starts high-speed intermittent emission
in S103. During this time, in S104, the load of the light adjusting
control photoreceptor element Pm is read each time synchronously
with the emission operation, and the data are added by the addition
circuit 12a. In S105, a determination is made as to whether or not
the added cumulative value has attained a predetermined signal level.
When the predetermined level has been reached (S105: YES), in S106
the emission from flash unit 7 is stopped. When the predetermined
level has not been reached (S105: NO), the routine returns to S103,
and flash emission continues.
After the emission operation of flash unit 7 is stopped, the mechanical
shutter 6 is closed in S107. Then, in S108, the process of reading
the loads of the photoreceptor element excepting the light adjusting
control photoreceptor element Pm is performed, and in S109, the
image data corresponding to the read load are temporarily stored
in memory.
Thereafter, in S110, an interpolation process is performed relative
to the omitted pixels of the light adjusting control photoreceptor
element Pm, and an image regeneration process is executed in S111.
In S112, the image is displayed on the display unit 10, and in S113,
the image data are written to a memory card.
Alternatively, as the loads of the light adjusting control photoreceptor
element Pm are cumulatively added, the cumulatively added loads
may be used without requiring interpolation of adjacent identical
color photographic data for replacement of the photoreceptor element
Pm photographic data. As a further alternative, both the cumulatively
added load data and the interpolated adjacent identical color photographic
data may be compared. In this case, the cumulatively added load
data and the interpolated adjacent identical color photographic
data may be averaged, or the larger or smaller of the data may be
used as required.
The distribution of light adjusting control photoreceptor elements
Pm in the image sensor 8 is optional, and an example of a layout
having a vertical and horizontal distribution in the center of the
photoreceptor surface is shown in FIG. 8.
In the present embodiment, the light adjusting control photoreceptor
element Pm is specified beforehand. However, the present invention
is not limited to this arrangement, and a special reset line RLo
may be connected to all photoreceptor elements P or photoreceptor
elements P in a predetermined region beforehand, such that an optimal
photoreceptor element may be set as the light adjusting control
photoreceptor element Pm according to photographic conditions.
Although the flash unit is constructed as being detachable from
the camera body 2 in the previously described embodiment, it is
to be noted that the flash unit also may be built into the camera
body.
The present invention as described above uses a specific photoreceptor
element of the image sensor as a light adjusting control photoreceptor
element, and uses the data from this photoreceptor element for light
adjusting control. Accordingly, there is no dislocation of the luminance
range due to change in the field angle as occurs in external light
adjusting control methods, and highly reliable light adjusting control
can be accomplished in real time.
Furthermore, when a CMOS sensor is used as the image sensor, the
amount of load accumulation of the light adjusting control photoreceptor
element can be reliably detected, providing light adjusting control
of even greater reliability.
The present invention repeatedly resets the light adjusting control
photoreceptor element, reads the data therefrom, and cumulatively
adds the data obtained by the respective readings. As a result,
the operating range used is suitable for the operating characteristics
of the light adjusting control photoreceptor element and avoids
the saturation range of the light adjusting control photoreceptor
element, whereby reliable load accumulation is obtained, and even
higher precision light adjusting control is possible.
Although the present invention has been fully described by way
of examples with reference to the accompanying drawings, it is to
be noted that various changes and modification will be apparent
to those skilled in the art. Therefore, unless otherwise such changes
and modifications depart from the scope of the present invention,
they should be construed as being included therein. |