JP2010237700A - Image capturing apparatus and program therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image capturing apparatus that prevent degradation in image quality in strobe consecutive shooting, and to provide a program therefor. <P>SOLUTION: When a strobe consecutive shooting mode is set, the image capturing apparatus sets a pixel addition mode in which the image data of a CCD 5 are read out by pixel addition drive (S7), performs light control operation by preliminary light emission (S8), and calculates appropriate emitted light quantity on the basis of the light control operation (S9). whether light emission can be successively performed three times with the calculated emitted light quantity is determined (S10). When it is determined that light emission can be successively performed three times with the calculated emitted light quantity (Y in S10), strobe consecutive shooting is successively performed with the calculated emitted light quantity (S13 to S17). When it is determined that strobe consecutive shooting cannot be performed with the calculated emitted light quantity (N in S10), the emitted light quantity is limited to the maximum within a range where strobe light emission can be successively performed three times (S11). Then, strobe consecutive shooting is performed with the limited emitted light quantity (S13 to S17). <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an imaging apparatus and a program thereof, and more particularly, to an imaging apparatus that shoots a subject by flash emission and a program thereof.

In recent years, in an imaging apparatus, for example, a digital camera, it is necessary to shoot with a strobe emitting light every time shooting is performed when shooting a subject continuously in a dark situation.
However, if the strobe is caused to emit light continuously, the voltage stored in the capacitor decreases, so that sufficient exposure for photographing cannot be obtained.
In view of this, a technique has been developed in which flash photography is performed for each number of light emission times corresponding to the time code and the number of continuous shots, and the underexposure amount is compensated by increasing gain (Patent Document).

Japanese Patent Laid-Open No. 5-167910

  However, according to the above-mentioned patent document, since the underexposure is compensated by increasing the gain, there is a problem that the image quality is deteriorated.

  Therefore, the present invention has been made in view of such conventional problems, and an object of the present invention is to provide an imaging apparatus and a program for the same that can prevent deterioration in image quality during strobe continuous shooting.

In order to achieve the above object, an imaging device according to the first aspect of the present invention includes an imaging device that converts light of a subject into image data;
A strobe that flashes light,
Photographing means for performing strobe photography using the image sensor and strobe;
Calculating means for calculating the amount of light emitted from the strobe to obtain an appropriate exposure;
Determining means for determining whether or not a predetermined number of times of light emission is possible based on the light emission amount calculated by the calculating means;
If the determination unit determines that the predetermined number of times of light emission is possible, the image pickup unit continuously performs the predetermined number of times of flash photography based on the light emission amount calculated by the calculation unit. Control means;
It is provided with.

For example, as described in claim 2, the determination unit includes:
Determining whether or not the predetermined number of times of light emission is possible with the light emission amount obtained by the calculating means;
The photographing control means includes
When the determination means determines that the predetermined number of times of light emission is possible, the image pickup means is configured to continuously execute the predetermined number of times of flash photography with the light emission amount calculated by the calculation means. Also good.

For example, as described in claim 3, the determination unit includes:
Bracketing the light emission amount calculated by the calculation means to determine whether or not the predetermined number of times of light emission is possible,
The photographing control means includes
When it is determined by the determination means that the predetermined number of times of light emission is possible, the amount of light emission calculated by the calculation means is bracketed, and the predetermined number of times of flash photography is continuously executed by the image pickup means. You may make it make it.

Further, for example, as described in claim 4, the photographing control unit includes:
If it is determined by the determination means that the predetermined number of times of light emission is not possible, the predetermined number of times of strobe shooting is continuously performed on the image pickup means with a light emission amount capable of the predetermined number of times of strobe light emission. You may make it perform.

Further, for example, as described in claim 5, the photographing control unit includes:
The photographing unit may continuously execute the predetermined number of times of flash photography within a range in which the predetermined number of times of flash emission is possible and substantially the maximum light emission amount.

Further, for example, as described in claim 6, a setting unit for setting the strobe continuous shooting mode is provided,
The photographing control means includes
When the strobe continuous shooting mode is set by the setting means, the photographing means may be caused to execute the strobe photographing for the predetermined number of times by driving the image pickup device to add pixels.

For example, as described in claim 7, the photographing control unit includes
Including means for causing the photographing means to perform preliminary strobe photographing by preliminary light emission by driving the image pickup device to add pixels;
The calculating means includes
You may make it calculate the light emission amount of the flash | flash which can obtain appropriate exposure based on the image data obtained by the preliminary | backup strobe imaging | photography by the said imaging | photography control means.

For example, as described in claim 8, the photographing control unit includes:
Only when the determination unit determines that the predetermined number of times of light emission is not possible, the image pickup unit may be caused to perform the predetermined number of times of strobe shooting by causing the image pickup device to perform pixel addition driving. .

Further, for example, as described in claim 9, the photographing control unit includes:
You may make it make the said imaging | photography means perform the flash photography of the predetermined number of times by changing the light emission time of the said flash.

  Further, for example, as described in claim 10, brightness correction means for performing brightness correction processing by gamma correction on the image data obtained by the photographing control means may be provided.

For example, as described in claim 11, the brightness correction unit includes:
When the determination unit determines that the predetermined number of times of light emission is not possible, brightness correction processing by gamma correction may be performed on the image data obtained by the photographing control unit.

Further, for example, as described in claim 12, the image processing apparatus includes a determination unit that determines whether the image data obtained by the photographing control unit has appropriate brightness,
The brightness correction means includes
Brightness correction processing by gamma correction may be performed only on image data that is determined not to have appropriate brightness by the determination means.

In order to achieve the above object, an imaging device according to a thirteenth aspect of the present invention is an imaging device that converts light of a subject into image data;
A strobe that flashes light,
Photographing means for performing strobe photography using the image sensor and strobe;
Setting means for setting the strobe mode,
When the strobe continuous shooting mode is set by the setting means, shooting control means for causing the shooting means to continuously perform flash shooting by driving the image sensor to add pixels; and
It is provided with.

In order to achieve the above object, a program according to a fourteenth aspect of the present invention is directed to a shooting process for performing strobe shooting using an imaging element that converts light of a subject into image data and a strobe that flashes light.
A calculation process for calculating the light emission amount of the strobe for obtaining an appropriate exposure;
A determination process for determining whether or not a predetermined number of times of light emission is possible based on the light emission amount calculated by the calculation process;
If the determination process determines that the predetermined number of times of light emission is possible, the image pickup process causes the shooting process to continuously execute the predetermined number of times of flash photography based on the light emission amount calculated by the calculation process. Control processing,
And having the computer execute the processes described above.

  According to the first aspect of the present invention, there is provided an imaging device that converts light of a subject into image data, a strobe that flashes light, a photographing unit that performs strobe photography using the imaging device and the strobe, and an appropriate exposure. A calculating means for calculating the light emission amount of the strobe obtained; a determination means for determining whether or not a predetermined number of times of light emission is possible based on the light emission amount calculated by the calculating means; and the determination means for the predetermined number of times. And a photographing control unit that causes the photographing unit to continuously perform the predetermined number of times of flash photography based on the light emission amount calculated by the calculating unit. Therefore, continuous flash photography can be performed with appropriate exposure without degrading the image quality.

  According to a second aspect of the present invention, the determining means determines whether or not the predetermined number of times of light emission is possible with the light emission amount obtained by the calculating means, and the imaging control means is determined by the determining means. When it is determined that the predetermined number of times of light emission is possible, the image pickup unit continuously performs the predetermined number of times of flash photography with the amount of light emission calculated by the calculation unit. Strobe continuous shooting can be performed without lowering, and image data that is not underexposed can be obtained.

  According to a third aspect of the present invention, the determination unit determines whether or not the predetermined number of times of light emission is possible by bracketing the light emission amount calculated by the calculation unit, and the photographing control unit includes: When it is determined by the determination means that the predetermined number of times of light emission is possible, the amount of light emission calculated by the calculation means is bracketed, and the predetermined number of times of flash photography is continuously executed by the image pickup means. Therefore, it is possible to perform strobe bracketing shooting with appropriate exposure without degrading the image quality.

  According to a fourth aspect of the present invention, when the determination unit determines that the predetermined number of times of light emission is not possible, the photographing control unit uses a light emission amount that allows the predetermined number of times of strobe light emission. Since the photographing unit continuously executes the strobe photographing for the predetermined number of times, it is possible to prevent image quality deterioration.

  According to a fifth aspect of the present invention, the photographing control means continuously performs the predetermined number of times of flash photography within the range in which the predetermined number of times of strobe light emission is possible and substantially the maximum light emission amount. Therefore, it is possible to prevent the image quality from deteriorating and to prevent underexposure as much as possible.

  According to a sixth aspect of the present invention, there is provided setting means for setting a strobe continuous shooting mode, and when the setting control means sets the strobe continuous shooting mode, the imaging control means drives the image pickup device to a pixel. Since the photographing unit is caused to perform the predetermined number of times of flash photography by performing addition driving, the brightness of the entire image data is increased, and image data with no underexposure or underexposure is prevented as much as possible. Obtainable.

According to a seventh aspect of the present invention, the photographing control means includes means for causing the photographing means to perform preliminary strobe photographing by preliminary light emission by causing the image pickup device to be driven by pixel addition driving, and the calculating means includes Since the amount of stroboscopic light emission with which appropriate exposure is obtained is calculated based on the image data obtained by the pre-strobe photographing by the photographing control means, the stroboscopic light emission is based on the image data whose luminance is increased by the pixel addition driving. The amount of light can be calculated, and an appropriate amount of light emission can be calculated.
Further, since the flash emission amount is calculated based on the image data with increased brightness, the calculated emission amount is reduced, and it is determined that the predetermined number of flash photography cannot be performed continuously based on the calculated emission amount. As a result, it is possible to make it easy to obtain image data that does not have a shortage of light, and to prevent deterioration in image quality.

According to an eighth aspect of the present invention, the imaging control means causes the pixel addition drive to drive the image sensor only when the determination means determines that the predetermined number of times of light emission is not possible. Since the photographing unit is caused to execute a predetermined number of strobe shootings, if the predetermined number of strobe shootings cannot be performed with the calculated light emission amount, pixel addition driving is performed to increase the brightness of the image data. Therefore, underexposure can be prevented as much as possible, and deterioration in image quality can be prevented as much as possible.
Further, when the predetermined number of times of flash photography can be performed with the light emission amount calculated in the previous period, it is possible to obtain image data in which the light amount is not insufficient without performing pixel addition driving.

  According to the ninth aspect of the invention, since the photographing control unit causes the photographing unit to perform the predetermined number of times of flash photography by changing the light emission time of the strobe, an appropriate exposure amount is obtained. Can be obtained.

  According to the tenth aspect of the present invention, since the image data obtained by the photographing control means is provided with the correction means for performing the brightness correction processing by the gamma correction, the image data without underexposure is obtained. be able to.

  According to an eleventh aspect of the present invention, the brightness correction unit applies the image data obtained by the photographing control unit when the determination unit determines that the predetermined number of times of light emission is not possible. Since the brightness correction processing by the gamma correction is performed, even when it is determined that the predetermined number of times of light emission is not possible, image data that is not underexposed can be obtained.

  According to the twelfth aspect of the present invention, it is provided with a determination unit that determines whether or not the image data obtained by the photographing control unit has an appropriate brightness, and the brightness correction unit is more appropriate by the determination unit. Since only the image data determined not to have sufficient brightness is subjected to brightness correction processing by gamma correction, it is possible to obtain image data that is not underexposed and to prevent image quality deterioration as much as possible. it can.

  According to the thirteenth aspect of the present invention, there is provided an imaging device for converting light of a subject into image data, a strobe for flashing light, a photographing means for performing strobe photography using the imaging device and the strobe, and strobe continuous shooting. A setting unit for setting a mode, and a shooting control for causing the shooting unit to continuously perform flash shooting when the setting unit is set to the strobe continuous shooting mode by driving the image sensor to pixel addition driving. Therefore, the brightness of image data obtained by flash photography can be increased without degrading the image quality.

  According to the fourteenth aspect of the present invention, the image pickup apparatus of the present invention can be realized by being read by a digital camera, a personal computer, or the like.

1 is a block diagram of a digital camera according to an embodiment of the present invention. It is a flowchart which shows operation | movement of the digital camera of embodiment. It is a flowchart which shows operation | movement of the digital camera of embodiment. It is a time chart which shows the voltage of the built-in capacitor | condenser C in strobe continuous shooting mode, strobe light emission pulse, and the operation | movement of a camera. It is a figure which shows the mode of a correction coefficient table. It is a figure for demonstrating the judgment whether image data is appropriate brightness, and the brightness correction by a gamma correction.

Hereinafter, this embodiment will be described in detail with reference to the drawings as an example applied to a digital camera.
[Embodiment]
A. Configuration of Digital Camera FIG. 1 is a block diagram showing a schematic electrical configuration of a digital camera 1 that implements the imaging apparatus of the present invention.
The digital camera 1 includes a focus lens 2, a zoom lens 3, a lens driving circuit 4, a CCD 5, a vertical driver 6, a TG (timing generator) 7, a unit circuit 8, a memory 9, a CPU 10, a DRAM 11, an image display unit 12, and a flash memory 13. , A key input unit 14, a strobe device 15, and a bus 16.

The focus lens 2 and the zoom lens 3 are composed of a plurality of lens groups (not shown), and a lens driving circuit 4 is connected to the focus lens 2 and the zoom lens 3.
The lens driving circuit 4 includes a motor (not shown) that moves the focus lens 2 and the zoom lens 3 in the optical axis direction, and a motor driver that drives the focus motor and the zoom motor in accordance with a control signal sent from the CPU 10, respectively. (Not shown).

  The CCD 5 is scanned and driven by the vertical driver 6, photoelectrically converts the intensity of light of each color of the RGB value of the subject image at a constant period, and outputs it to the unit circuit 8 as an imaging signal. The operation timings of the vertical driver 6 and unit circuit 8 are controlled by the CPU 10 via the TG 7.

  A TG 7 is connected to the unit circuit 8, a CDS (Correlated Double Sampling) circuit that holds the imaging signal output from the CCD 5 by correlated double sampling, and an AGC (Automatic Gain Adjustment of the imaging signal after the sampling) An automatic gain control) circuit and an A / D converter that converts the analog image pickup signal after the automatic gain adjustment into a digital signal. The image pickup signal of the CCD 5 is sent to the CPU 10 through the unit circuit 8 as a digital signal. It is done.

The CPU 10 performs image processing such as gamma correction, interpolation processing, white balance processing, histogram generation processing, luminance color difference signal (YUV data) generation processing on image data sent from the unit circuit 8, image data compression / compression. This is a one-chip microcomputer that has a function of performing decompression (for example, JPEG compression / decompression) processing and controls each part of the digital camera 1.
In particular, in the present embodiment, the CPU 10 controls the light emission start and the light emission time of the strobe device 15, calculates the light emission amount based on the light control operation and the result, the strobe continuous shooting, and the brightness correction processing. It has the function to give.

The memory 9 stores a control program and necessary data necessary for controlling each part of the CPU 10, and the CPU 10 operates according to the program.
Further, the memory 9 stores a correction coefficient table in which correction coefficients for the emission times of the number of images that are continuously shot in the continuous flash photography are recorded. This correction coefficient table will be described later. The memory 9 also has a light emission time storage area for storing the light emission time of the strobe and a number storage area for storing the number of shots.

The DRAM 11 is used as a buffer memory for temporarily storing image data sent to the CPU 10 after being imaged by the CCD 5 and also as a working memory for the CPU 10.
The image display unit 12 includes a color LCD and its drive circuit, and displays the subject imaged by the CCD 5 as a through image when in a shooting standby state, and is read out from the flash memory 13 and decompressed when a recorded image is reproduced. The recorded image is displayed.

The flash memory 13 is a recording medium that stores image data captured by the CCD 5.
The key input unit 14 includes a plurality of operation keys such as a shutter button and a mode switching key, and outputs an operation signal corresponding to the user's key operation to the CPU 10.

  The strobe device 15 includes a built-in capacitor C, a charging circuit (not shown), a light emitting circuit (not shown) including a xenon tube, a charging voltage detection circuit (not shown) of the capacitor C, and the charging circuit supplies power to the built-in capacitor C. The light-emitting circuit supplies the charge in the built-in capacitor C to the xenon tube serving as a light source to flash light. The strobe device 15 is controlled by the CPU 10 to start charging, emit light, and emit time, and emit light according to the control. The charging voltage detection circuit in the strobe device 15 sends the detected charging voltage to the CPU 10.

D. Operation of Digital Camera 1 The operation of the digital camera 1 in the embodiment will be described based on the flowcharts of FIGS. 2 and 3 and the time chart of FIG. FIG. 4 is a time chart showing the voltage of the built-in capacitor C, the strobe light emission pulse, and the operation of the camera in the strobe continuous shooting mode.

  When the strobe shooting is set by operating the mode switching key of the user key input unit 14, the CPU 10 starts imaging of the subject by the CCD 5, generates a luminance color difference signal from the image data obtained by the imaging, The generated image data of the luminance / color difference signal is stored in the buffer memory (DRAM 11), and through image display is started in which the stored image data of the subject is displayed on the image display unit 12 (step S1).

  Next, the CPU 10 determines whether or not the strobe continuous shooting mode has been selected by the user (step S2). This determination is made based on whether or not an operation signal corresponding to the operation for selecting the strobe continuous shooting mode is sent from the key input unit 14. The strobe continuous shooting mode refers to a mode in which a subject is continuously photographed (here, three consecutive times are photographed), and a strobe is emitted for each photographing.

If it is determined in step S2 that the flash continuous shooting mode is not selected, the CPU 10 determines whether or not the flash single shooting mode is selected (step S3). This determination is made based on whether or not an operation signal corresponding to the operation for selecting the strobe single shooting mode has been sent from the key input unit 14. The strobe single shooting mode refers to shooting a subject once by emitting a strobe.
If it is determined in step S3 that the single flash mode is not selected, the process returns to step S2.

On the other hand, if it is determined in step S2 that the flash continuous shooting mode is set, the CPU 10 starts charging the built-in capacitor C by sending a control signal to the flash device 15 (step S4). At this time, the charging circuit of the strobe device 15 charges the built-in capacitor C according to the control signal of the CPU 10.
When charging is started, the CPU 10 determines whether or not the charging is completed (step S5). This determination is made based on the charging voltage information sent from the charging voltage detection circuit of the strobe device 15 to determine whether or not the charging is completed.

If it is determined in step S5 that charging has not been completed, the process stays in step S5 until completion. If it is determined that charging has been completed, the CPU 10 determines whether or not the shutter button has been pressed (step S6). This determination is made based on whether or not an operation signal corresponding to pressing of the shutter button is sent from the key input unit 14.
As shown in FIG. 4, as the charging starts, the voltage of the built-in capacitor C increases. When the voltage of the built-in capacitor C reaches a certain voltage (300 V in this case), the charging is completed, and the voltage further increases. I understand that there is no.

If it is determined in step S6 that the shutter button has been pressed, the CPU 10 sets the pixel addition mode (step S7). At this time, the number of pixels to be added is also set. This pixel addition mode refers to a mode in which charges accumulated in the CCD 5 are read out by pixel addition driving. Since pixel addition driving is already a well-known technique, description thereof is omitted.
Here, the pixel addition mode is set because, when continuous shooting (continuous shooting) is performed, the voltage of the built-in capacitor C is divided into three to cause strobe light emission. By reading out the electric charge accumulated in the light source, the shortage of light quantity can be compensated, and the charge reading speed of the CCD 5 can be increased, so that the frame rate can be increased, so that continuous shooting can be performed quickly.

Next, the CPU 10 performs a dimming operation by preliminary light emission (step S8). In other words, the CPU 10 sends a control signal to the strobe device 15 to cause the strobe to preliminarily emit light, and at the same time, causes the CCD 5 to perform a photographing (charge accumulation) operation, and then reads out the charge accumulated in the CCD 5 by pixel addition driving. Do. At this time, since it is preliminary light emission, the light emission time is shorter than that at the time of flash photography, and here it is 10 μsec.
Referring to FIG. 4, during the dimming operation, the CPU 10 sends a light emission start and light emission time control signal (strobe light emission pulse) to the strobe device 15, and the light emission circuit of the strobe device 15 discharges the charge in the built-in capacitor C. By doing so, the light is flashed, and it can be seen that the voltage in the built-in capacitor C drops from 300V to 295V.

Next, the CPU 10 calculates the light emission amount of the strobe light based on the dimming operation result (step S9).
The light emission amount is calculated based on the average value of the luminance of the image data (or a part of the image data) read out by the pixel addition drive, and the light emission amount of the strobe light for obtaining the appropriate exposure. Here, the strobe light emission time of the first sheet (first time) so that the calculated light emission amount is obtained is calculated and stored in the light emission time storage area of the memory 9.

Next, the CPU 10 determines whether or not continuous flash photography can be performed with the calculated light emission amount (step S10). That is, since the continuous flash photography is performed three times continuously, it is determined whether or not the voltage for causing the flash to emit light three times continuously with the calculated light emission amount is stored in the built-in capacitor C. .
Here, it is determined whether or not the first flash emission time calculated in step S9 is equal to or less than a limit value (24 μsec here), and if it is determined to be 24 μsec or less, the calculated light emission amount is three times. It is determined that the voltage for continuously emitting the strobe is stored in the built-in capacitor C.

Here, the reason for determining whether or not it is possible to emit light continuously three times with the calculated light emission amount will be specifically described below based on whether or not the first light emission time is 24 μsec or less.
First, if shooting is performed three times continuously with the same light emission amount, as shown in FIG. 4, the voltage of the built-in capacitor C decreases every time the light is emitted, so that light is emitted three times continuously with the same light emission amount. In order to achieve this, the light emission time must be lengthened according to the number of times of light emission. The flash emission time in each shooting can be obtained from the correction coefficient table stored in the memory 9, and the flash emission time t in each shooting is t = correction coefficient × first emission time.

FIG. 5 shows the state of the correction coefficient table stored in the memory 9.
5A, since the correction coefficient for the first light emission time is 1.00, the first light emission time is 1.00 × first light emission time, and the correction coefficient for the second light emission time is Since 1.18, the second light emission time is 1.18 × first light emission time, and the third light emission time correction coefficient is 1.36, so the third light emission time is 1.36 × 1 time. It can be seen that the emission time is.
It should be noted that although the light emission time for each photographing varies depending on the correction coefficient, it goes without saying that a correction coefficient is provided so that the light emission amount does not change.

Further, referring to FIG. 4, 260 V is the minimum light emission possible voltage, which is the minimum voltage necessary for the third light emission.
From this situation, if the first light emission time is known, the second light emission time can also be known, and thereby the voltage of the built-in capacitor C at the end of the second light emission can also be known.

For example, when the first strobe light emission time is 28 μsec, the second strobe light emission time is about 33 μsec, and the voltage of the built-in capacitor C at the third strobe light emission (at the end of the second strobe light emission) is 256 V. Therefore, the third strobe light cannot be emitted. When the first flash emission time is 24 μsec, the second flash emission time is about 28 μsec, and the voltage of the built-in capacitor at the third flash emission is 267 V, so the third flash emission is performed. Can do.
Therefore, here, it is determined whether or not the strobe light can be emitted three times continuously with the same light emission amount, depending on whether or not the first strobe light emission time is 24 μsec or less.

If it is determined in step S10 that continuous flash photography cannot be performed with the calculated light emission amount, that is, if it is determined that the first light emission time is not 24 μsec or less, the first flash light emission amount is limited to 24 μsec ( The process proceeds to step S11) and step S12. That is, if it is determined that the first light emission time is not 24 μsec or less, the memory in the light emission time storage area of the memory 9 is updated to 24 μsec.
On the other hand, if it is determined in step S10 that continuous flash photography can be performed with the calculated light emission amount, that is, if it is determined that the calculated first light emission time is 24 μsec or less, the process proceeds directly to step S12.

In step S12, the CPU 10 determines the light emission amount based on the light emission time stored in the memory 9 as the absolute light emission amount.
That is, if the light emission time calculated in step S9 (because the light emission time and the light emission amount are proportional) is 24 μsec or less, the calculated light emission time is determined as the absolute light emission amount, and the light emission time calculated in step S9 Is longer than 24 μsec, 24 μsec is determined as the absolute light emission amount.
At this time, the number of shots n is set to 1, that is, 1 is stored in the number storage area of the memory 9. Here, the determined light emission time is 24 μsec.

Next, the CPU 10 corrects the strobe light emission time (step S13). In this correction, a correction coefficient corresponding to the number of shots (number of times) stored in the number storage area of the memory 9 is read from the correction coefficient table, and the read correction coefficient and the determined emission time (in the emission time storage area). This is performed by multiplying the stored emission time).
Here, since the determined light emission time is 24 μsec and the stored number of shots is 1, the correction coefficient corresponding to the first image is 1.00, so that the light emission after correction is 24 μsec × 1.00. The time is 24 μsec.

Next, the CPU 10 sets the corrected light emission time as the strobe light emission time (step S14), and performs the strobe shooting operation (the exposure operation of the CCD 5 and the light emission operation of the strobe device 15) based on the set strobe light emission time. This is performed (step S15). In this strobe photographing operation, the charges accumulated in the CCD 5 are read out by pixel addition driving, and still image data obtained by this strobe photographing is stored in a buffer memory.
Next, the CPU 10 determines whether or not the flash photography has been performed three times (step S16). If the CPU 10 determines that the flash photography has not been performed three times, the CPU 10 increments the number of shots n (step S17), and the step. Returning to S13, if it is determined in step S16 that the flash photography has been performed three times, the process proceeds to step S24.
Whether or not the three-time flash photography has been performed is determined by whether or not the number stored in the number storage area has reached three. Further, incrementing the number of shots n is performed by storing a number obtained by adding 1 to the number stored in the number storage area.

On the other hand, if it is determined in step S3 that the mode is the single flash mode, the CPU 10 sends a control signal to the flash device 15 to start charging the built-in capacitor C (step S18).
When charging is started, the CPU 10 determines whether or not the charging is completed (step S19).

If it is determined in step S19 that charging has not been completed, the process stays in step S19 until completion. If it is determined that charging has been completed, the CPU 10 determines whether or not the shutter button has been pressed (step S20).
If it is determined in step S20 that the shutter button is not pressed, the process stays in step S20 until the shutter button is pressed. When the shutter button is pressed, the CPU 10 performs a light control operation by preliminary light emission (step S21). In the dimming operation here, the pixels of the CCD 5 are read out by normal reading driving (all pixel reading driving other than pixel adding driving, partial pixel reading driving, etc.) without performing pixel addition driving.

Next, the CPU 10 sets a light emission amount for obtaining proper exposure based on the result of the light control operation (step S22), performs a flash photographing operation based on the set light emission amount (step S23), and step Proceed to S24. In this strobe photographing operation, the charges accumulated in the CCD 5 are read out by normal reading driving, and still image data obtained by this strobe photographing is stored in a buffer memory.
Note that, in the same shooting situation, the light control operation in the flash continuous shooting mode and the light control operation in the flash single shooting mode are calculated based on the result of the light control operation in step S9 in FIG. The light emission amount is smaller than the light emission amount set based on the result of the dimming operation in step S22. This is because, in the strobe continuous shooting mode, the image data of the CCD 5 is read out by pixel addition driving, so that the brightness of the entire image increases.

  In step S24, the CPU 10 determines whether or not still image data (Bayer data) obtained by flash photography has appropriate brightness. At this time, when a plurality of still image data is obtained by continuous flash photography, the CPU 10 determines whether or not each obtained still image data has appropriate brightness.

The CPU 10 performs brightness correction by gamma correction on the still image data of the Bayer data that is determined not to have the appropriate brightness in step S24 (step S25), and records it in the flash memory 13. At this time, when recording still image data, the CPU 10 performs image processing such as luminance color difference signal generation processing, and compresses and records the applied image data.
On the other hand, the still image data of the Bayer data determined to have appropriate brightness in step S24 is recorded in the flash memory 13 as it is. Also at this time, when recording still image data, the CPU 10 performs image processing such as luminance color difference signal generation processing, and compresses and records the applied image data.

An example of a method of determining whether or not the still image data has appropriate brightness and a brightness correction method by gamma correction processing will be briefly described below.
Whether or not the still image data has appropriate brightness is determined by generating a histogram for each RGB from Bayer data, which is still image data obtained by shooting, and reaching a high luminance ratio for each RGB (for example, , A level reaching 3% from the high luminance side). Then, the highest value among the levels (hereinafter referred to as peak levels) reaching the high luminance ratio for each RGB is selected, and if the selected value is higher than the threshold value, the still image data has an appropriate brightness. It is judged that it has.

FIG. 6A shows a histogram generated for each of RGB, which is represented by 10-bit digital values (1024 values) as “black” on the left and “white” on the right.
The hatched portion in the histogram for each of RGB in FIG. 6A shows the portion until reaching 3% from the high luminance side, and the portion reaching just 3% is the peak level. The peak levels for each RGB are R-PEAK, G-PEAK, and B-PEAK.

In FIG. 6A, for example, when R-PEAK = 547, G-PEAK = 541, and B-PEAK = 543, the highest value is R-PEAK = 547.
In FIG. 6A, since the highest value R-PEAK = 547 is not higher than the threshold value, it is determined that the still image data does not have appropriate brightness.

  Next, in the brightness correction method using gamma correction processing, a correction magnification is calculated such that the selected highest value becomes a threshold value. Then, as shown in FIG. 6B, the input range is narrowed according to the value of the correction magnification, such as 1.5 times or 2.0 times, using a preset gamma curve of 1.0 times as a standard. Change the direction. Thereby, for example, if the gamma curve is changed to 1.5 times, the output value b2 is obtained with respect to the input value a1, and a brighter value than the output value b1 in the standard curve can be obtained.

D. As described above, in the embodiment, it is determined whether or not strobe light can be emitted three times continuously with the light emission amount calculated based on the result of the light control operation, and the strobe light is emitted continuously. If it is determined that the image can be reproduced, the flash is continuously photographed with the calculated light emission amount, so that image data that is not underexposed can be obtained without degrading the image quality.

  If it is determined that continuous flash firing is not possible, the flash output is limited to the maximum possible range for continuous flash shooting, and continuous flash photography is possible with the limited flash output. Therefore, underexposure can be prevented as much as possible without degrading the image quality.

When the strobe continuous shooting mode is set, the CCD 5 drive is set to the pixel addition drive, the light control operation is performed, and the light emission amount is calculated based on the result, so that the entire image data read from the CCD 5 is calculated. The brightness increases, and the calculated light emission amount can be reduced. In addition, since the calculated light emission amount can be reduced, the ratio at which it is determined that continuous flash photography cannot be performed with the calculated light emission amount is reduced, and it is easy to obtain image data that is not insufficient in light amount.
In addition, since flash photography is performed by pixel addition driving, the brightness of the entire image data obtained by photography is increased, and it is easy to obtain image data that is not insufficient in light quantity.

  Further, it is determined whether or not each image data has proper brightness, and brightness correction by gamma correction is performed on image data that does not have proper brightness. Obtainable. Even when brightness correction is performed, the image data is obtained with the maximum amount of light emission within the range where continuous flash photography is possible. Degradation can be prevented as much as possible.

[Modification]
The above-described embodiment can be modified as follows.
(1) In the above embodiment, when the strobe continuous shooting mode is set, the strobe shooting is performed continuously for three images. However, the number of images is not limited to three and may be any number. In addition, the user may be able to set an arbitrary strobe continuous shooting number by a key operation.
In this case, a limit value corresponding to the number of images to be continuously shot is provided, and it is determined whether or not continuous flash photography can be performed based on whether or not the calculated flash emission time is longer than this limit value. It will be.

(2) In the above embodiment, when the strobe continuous shooting mode is set, the pixel addition driving mode is set. However, in step S10 in FIG. 2, continuous flash photography is performed with the calculated light emission amount. The pixel addition drive mode may be set only when it is determined that this is not possible.
When strobe continuous shooting is not possible with the calculated flash amount, the flash light amount is limited, so an appropriate exposure amount cannot be obtained, and the brightness of the entire image data can be increased by pixel addition driving, A bright image can be obtained. In addition, when continuous flash photography can be performed with the calculated light emission amount, continuous flash photography can be performed by normal driving other than pixel addition driving, and a bright image can be obtained.
In this case, the dimming operation by the preliminary light emission in step S8 in FIG. 2 reads out the image data of the CCD 5 by normal driving that is not pixel addition driving.

(3) In the above embodiment, the correction coefficient is set so that the exposure amount (light emission amount) of the first sheet to the third sheet is uniform. However, the exposure amount is bracketed. A correction coefficient table may be provided, and using this correction coefficient, the exposure amount of the first to third sheets may be bracketed to perform flash photography.
FIG. 5B is a diagram showing a state of a correction coefficient table for bracketing exposure. Looking at the correction coefficient table in FIG. 5B, the correction coefficient is gradually reduced. Therefore, when the flash photography is performed using the correction coefficient table, the bracketing photography in which the exposure amount is gradually reduced is performed. be able to.
In this case, a limit value corresponding to the bracketing amount is provided, and it is determined whether or not strobe bracketing photography can be performed based on whether or not the calculated strobe light emission time is longer than the limit value. Become.

  (4) In the above embodiment, only one correction coefficient table is provided. However, a plurality of correction coefficient tables in which the correction coefficient is changed according to the light emission time of the first sheet may be provided.

  (5) In the above embodiment, the second and third light emission times are corrected by multiplying the correction coefficient based on the first light emission time. The correction coefficient value may be finely adjusted according to the voltage of the built-in capacitor C immediately after the flash photography.

  (6) Also, in the above embodiment, it is determined whether or not each image data obtained by photographing has an appropriate brightness, and the brightness by gamma correction is determined for the image data determined to be not the appropriate brightness. However, only when it is determined in step S10 that continuous flash photography cannot be performed with the calculated light emission amount, the three pieces of image data obtained by continuous flash photography are processed. Alternatively, brightness correction by gamma correction may be performed.

  (7) Moreover, you may make it change into embodiment which combined said (1)-(6) arbitrarily.

  (8) Furthermore, the digital camera 1 in the above embodiment is not limited to the above embodiment, but is a mobile phone with a camera, a PDA with a camera, a personal computer with a camera, an IC recorder with a camera, or a digital video camera. In short, any device capable of performing strobe continuous shooting may be used.

1 Digital Camera 2 Focus Lens 3 Zoom Lens 4 Lens Drive Circuit 5 CCD
6 Vertical driver 7 TG
8 Unit circuit 9 Memory 10 CPU
11 DRAM
12 Image display unit 13 Flash memory 14 Key input unit 15 Strobe device 16 Bus

Claims (14)

An image sensor that converts light of a subject into image data;
A strobe that flashes light,
Photographing means for performing strobe photography using the image sensor and strobe;
Calculating means for calculating the amount of light emitted from the strobe to obtain an appropriate exposure;
Determining means for determining whether or not a predetermined number of times of light emission is possible based on the light emission amount calculated by the calculating means;
If the determination unit determines that the predetermined number of times of light emission is possible, the image pickup unit continuously performs the predetermined number of times of flash photography based on the light emission amount calculated by the calculation unit. Control means;
An imaging apparatus comprising: The determination means includes
Determining whether or not the predetermined number of times of light emission is possible with the light emission amount obtained by the calculating means;
The photographing control means includes
When the determination unit determines that the predetermined number of times of light emission is possible, the image pickup unit continuously performs the predetermined number of times of flash photography with the light emission amount calculated by the calculation unit. The imaging apparatus according to claim 1. The determination means includes
Bracketing the light emission amount calculated by the calculation means to determine whether or not the predetermined number of times of light emission is possible,
The photographing control means includes
When it is determined by the determination means that the predetermined number of times of light emission is possible, the amount of light emission calculated by the calculation means is bracketed, and the predetermined number of times of flash photography is continuously executed by the image pickup means. The imaging apparatus according to claim 1, wherein: The photographing control means includes
If it is determined by the determination means that the predetermined number of times of light emission is not possible, the predetermined number of times of strobe shooting is continuously performed on the image pickup means with a light emission amount capable of the predetermined number of times of strobe light emission. The imaging apparatus according to claim 1, wherein the imaging apparatus is executed. The photographing control means includes
The imaging apparatus according to claim 4, wherein the photographing unit continuously performs the predetermined number of times of strobe photographing within a range in which the strobe light can be emitted for the predetermined number of times and substantially the maximum light emission amount. It has setting means to set the strobe mode,
The photographing control means includes
6. The apparatus according to claim 1, wherein when the strobe continuous shooting mode is set by the setting means, the photographing means is caused to execute the predetermined number of times of strobe photography by driving the image pickup device to add pixels. The imaging device according to any one of the above. The photographing control means includes
Including means for causing the photographing means to perform preliminary strobe photographing by preliminary light emission by driving the image pickup device to add pixels;
The calculating means includes
The imaging apparatus according to claim 6, wherein a light emission amount of a strobe for obtaining an appropriate exposure is calculated based on image data obtained by preliminary strobe photographing by the photographing control unit. The photographing control means includes
Only when the determination unit determines that the predetermined number of times of light emission is not possible, the image pickup unit is caused to perform the predetermined number of times of strobe shooting by causing the image pickup device to perform pixel addition driving. The imaging device according to claim 6. The photographing control means includes
The imaging apparatus according to claim 1, wherein the photographing unit is caused to execute the strobe photographing for the predetermined number of times by changing a light emission time of the strobe. The imaging apparatus according to claim 1, further comprising a brightness correction unit that performs brightness correction processing by gamma correction on the image data obtained by the photographing control unit. The brightness correction means includes
The brightness correction process by gamma correction is performed on the image data obtained by the photographing control unit when the determination unit determines that the predetermined number of times of light emission is not possible. The imaging device according to 10. Determination means for determining whether or not the image data obtained by the photographing control means has appropriate brightness,
The brightness correction means includes
The imaging apparatus according to claim 10, wherein brightness correction processing by gamma correction is performed only on image data that is determined not to have appropriate brightness by the determination unit. An image sensor that converts light of a subject into image data;
A strobe that flashes light,
Photographing means for performing strobe photography using the image sensor and strobe;
Setting means for setting the strobe mode,
When the strobe continuous shooting mode is set by the setting means, shooting control means for causing the shooting means to continuously perform flash shooting by driving the image sensor to add pixels; and
An imaging apparatus comprising: An imaging device that converts the light of the subject into image data and a shooting process that performs flash photography using a flash that emits light; and
A calculation process for calculating the light emission amount of the strobe for obtaining an appropriate exposure;
A determination process for determining whether or not a predetermined number of times of light emission is possible based on the light emission amount calculated by the calculation process;
If the determination process determines that the predetermined number of times of light emission is possible, the image pickup process causes the shooting process to continuously execute the predetermined number of times of flash photography based on the light emission amount calculated by the calculation process. Control processing,
And causing a computer to execute each of the processes described above.

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