JP2008065053A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus achieving optimum control of light emission even when photographing a subject including ambient light of a predetermined level or higher. <P>SOLUTION: The imaging apparatus includes: an imaging means for forming an image of a subject on a predetermined imaging face, thereby imaging a subject image; a light emitting means for illuminating a subject; a light emission control means for controlling emission of light from the light emitting means; an ambient light detecting means for determining presence of ambient light in the subject. When the ambient light detecting means determines no ambient light, a light emission control means subjects the light emitting means to first light emission control so that the light emitting means emits light until a quantity of light reflected from the subject reaches a predetermined quantity. When the ambient light detecting means determines the ambient light, the light emission control means subjects the light emitting means to second light emission control so that the light emitting means emits a quantity of light, calculated in advance according to the subject. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an imaging device such as a digital camera, and more specifically, imaging in which an optimum light-emitting method is selected from a plurality of light-emitting methods based on the presence or absence of constant light above a predetermined level included in a subject. Relates to the device.
In addition, the present invention is applicable to all imaging devices that have a plurality of light emission control methods and switch the light emission control method based on the presence or absence of stationary light.

  In an imaging device such as a digital camera, photographing is performed using an illumination device such as a strobe when the subject is dark, but the light emission control methods are roughly classified into the following two methods.

  The first method is a method adopted in a silver salt camera that mainly uses a photographic film to measure light reflected from an object using a photometric element provided on the front of the camera, In this method, light emission is continued until a predetermined amount of light is obtained. In this method, since the strobe light being photographed is metered, there is an advantage that preliminary metering is unnecessary and the metering does not take time. However, particularly in the case of a short distance, there is a possibility that accurate photometry cannot be performed due to a parallax problem.

  The second method is a method mainly used in digital cameras. The flash is preliminarily fired before shooting, the amount of light from the subject is measured with an image sensor, and the appropriate flash amount is set. It is a method. In the light emission control by this method, preliminary light emission is performed before photographing, the amount of light reflected from the subject is measured with an image sensor, and the proper main flash emission amount is calculated based on the luminance of the subject obtained by the photometry. At this time, by utilizing the fact that the light emission amount is attenuated in inverse proportion to the square of the distance to the subject, the light emission amount to the subject is calculated by measuring the distance to the subject by the distance measuring unit, and the preliminary light emission and Generally, the reference light emission amount in the main light emission is used. That is, in the preliminary light emission, light emission is performed with the reference light emission amount calculated from the subject distance, and in the main light emission, fine adjustment of the light emission amount reflecting the photometry result is performed on the reference light emission amount.

  However, in the light emission control by this method, the distance measurement error to the subject appears as it is as the error of the reference light emission amount. In terms of focusing, there is no practical problem even if the distance measurement accuracy is lowered by the extent that the depth of field becomes deeper as the distance increases. However, the light emission amount attenuates in inverse proportion to the square of the distance to the subject. ) Is not allowed from the viewpoint of exposure control. If the distance measurement error is within a certain range, it is possible to correct the light emission amount of the main flash from the photometry result of the preliminary flash.However, if the distance measurement result is significantly different, the correction based on the photometry result cannot be performed. Arise.

  As described above, the first and second light emission control methods have advantages and disadvantages, respectively. Therefore, a conventional device that performs light emission control by switching between the two control methods according to the distance to the subject and the result of the preliminary light emission measurement is patented. It is disclosed in Document 1.

  When the distance to the subject measured by the distance measuring means is determined to be closer than the limit distance determined based on the distance measurement accuracy, the device of Patent Document 1 determines the aperture and shutter speed based on the subject distance to the subject. Is a device that performs light emission control by light control based on the amount of reflected light from the subject when it is determined that the distance to the subject is farther than the limit distance.

JP-A-63-267926

  As described above, in the first method, light emission is controlled while light is emitted from a strobe and the amount of light reflected from the subject is measured by a photometric element. Therefore, if the first light emission control is performed when there is constant light of a predetermined level or higher, such as a light bulb, in the subject, there is a problem that the photometry element detects the constant light and stops the strobe light emission. is there. In other words, the metering element detects the steady light in the subject in addition to the reflected light from the subject, where the reflected light from the subject due to the strobe emission should continue to emit until the predetermined amount of light. However, there is a problem that the flash emission is stopped before the appropriate exposure amount is reached, and as a result, an extremely dark image can be taken.

  The present invention addresses the above problems and provides an image pickup apparatus capable of performing optimal light emission control even when shooting a subject including stationary light of a predetermined level or higher.

  That is, the present invention relates to an imaging means for imaging a subject image by forming a subject image on a predetermined imaging surface, a light emission means for subject illumination, a light emission control means for controlling light emission of the light emission means, An imaging device having a stationary light detection unit that determines whether or not there is stationary light of a predetermined level or more, wherein the light emission control unit is configured to detect from the subject when the stationary light detection unit determines that there is no stationary light. When the first light emission control is performed to control the light emitting means to emit light until the reflected light amount reaches a predetermined amount, and the steady light detecting means determines that the steady light is present, the first light emission control is performed in advance according to the subject. An image pickup apparatus characterized by performing second light emission control for controlling the light emitting means so as to emit light with the calculated light emission quantity.

  Further, the present invention is the imaging apparatus, wherein the steady light detecting means determines the presence or absence of the steady light using luminance information obtained from a subject before subject illumination by the light emitting means.

  Furthermore, the present invention is the imaging apparatus, wherein the stationary light detection unit divides the imaging surface into a plurality of blocks and acquires the luminance information for each block.

Furthermore, the present invention is an imaging apparatus characterized in that the stationary light detecting means determines that the stationary light is present by the following methods (1) to (4).
(1) When there is a block having a luminance equal to or higher than a first threshold among the plurality of blocks, it is determined that the stationary light is present.
(2) Among the plurality of blocks, it is determined that the stationary light is present when a plurality of blocks having a luminance equal to or higher than the first threshold are continuously present.
(3) Among the plurality of blocks, when there is a block whose luminance is equal to or higher than the second threshold value and whose luminance difference between the block and the adjacent block is equal to or higher than the third threshold value, Judge that there is steady light.
(4) Among the plurality of blocks, the luminance is equal to or greater than the second threshold value, and the luminance difference between one block adjacent to the block is equal to or greater than the third threshold value and is adjacent to the block. When there is a block whose luminance difference with the other block is equal to or less than the fourth threshold value, it is determined that the stationary light is present.

  Further, the present invention is the imaging apparatus, wherein the emitted light amount is calculated according to a distance to the subject.

  Furthermore, the present invention is the imaging apparatus, wherein the emitted light amount is calculated according to the reflected light amount from the subject when the light emitting means emits light as preliminary light emission before photographing.

  Based on the result of the steady light detecting means for detecting whether or not the constant light of a predetermined level or more exists in the subject, light emission is performed until the amount of reflected light from the subject reaches a predetermined amount. In order to switch between the first light emission control to be controlled and the second light emission control to be controlled so as to emit light with a light emission amount calculated in advance according to the subject, steady light of a predetermined level or more included in the subject This avoids the problem that the photometric element in the first light emission control detects steady light and stops the strobe light emission before reaching the appropriate exposure amount, and performs optimal light emission control according to the subject. Is possible.

  The steady light detection means detects the presence of the steady light before the strobe light emission because the steady light of the predetermined level or more is detected using the luminance information obtained from the subject before the light emission by the light emission control means. It becomes possible.

  Furthermore, the stationary light detection means can easily detect the presence or absence of stationary light above a predetermined level by dividing the imaging surface into a plurality of blocks and acquiring the luminance information for each block. In particular, it is possible to detect only stationary light having a predetermined size (region) as a determination target, or it is possible to detect relatively bright stationary light without an absolute amount of luminance.

  Before describing the best mode for carrying out the present invention, the conventional invention will be described in detail in order to clarify the difference between the present invention and the conventional invention.

Here, the steady light means light emitted from a light source existing in the subject image or reflected light reflected by the subject image of light emitted from the light source present outside the subject image. The light emitted is different from the reflected light reflected by the subject image.
Specifically, light emitted from a light source that emits light such as a lighting fixture or the sun, and light emitted from a reflector such as a mirror that reflects the light emitted from the light source toward the photometry unit may be used.
Furthermore, the steady light in the present invention particularly refers to light that is a predetermined level or more.

  In the case of the first light emission control method, control is performed so that light is emitted until the amount of light from the subject reaches a predetermined amount. However, in a conventional imaging device, if there is steady light of a certain level or more, steady light and light emission are performed. Therefore, there is a problem in that the light metering unit, which will be described later, detects the amount of light obtained by adding stationary light to the reflected light and stops the strobe before reaching the appropriate exposure amount. .

  For example, there is no means (steady light detection means) for recognizing the presence or absence of steady light before photographing for a subject that has a constant light level above a predetermined level and is dark around it. Consider a case in which shooting is performed using a conventional imaging device of a light emission control system that controls to emit light until the amount of light reaches a predetermined amount.

In this case, first, a dimming threshold value is set in the photometry unit in advance so as to stop light emission when a predetermined amount of light is obtained. Next, when the release button is pressed, the power supply to the photometry unit is turned on as light emission control, the steady light from the subject and the reflected light amount are converted into current values, and integrated into an integration circuit in the photometry unit.
At that time, the photometry unit integrates the amount of light obtained by adding the steady light to the reflected light, so that the light emission is stopped and the image is captured before the light amount is originally required. Sufficient reflected light could not be obtained, resulting in an extremely dark image.

The present invention solves the above problems.
Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

(Embodiment)
FIG. 1 is a functional block diagram of an imaging apparatus according to the present invention, in which 1 is a lens barrel unit, 2 is an image input unit, 3 is an audio input unit, 4 is an operation unit, 5 is a distance measuring unit, 6 is a ROM, 7 is a storage unit, 8 is a main memory, 9 is a monitor, 10 is an external I / O, 11 is an audio output unit, 12 is a strobe, 13 is a display unit, and 14 is a CPU.

FIG. 2 shows the lens barrel unit 1 and the image input unit 2 of FIG. 1 in more detail.
The lens barrel unit 1 includes a lens 21 (zoom, focus) for capturing an optical image of a subject into a CCD, a mechanical shutter 22, a diaphragm 23, and a motor driver 24. The motor driver 24 has a function of driving each motor (not shown) for moving the lens 21, the mechanical shutter 22, and the diaphragm 23.

  The image input unit 2 includes a CCD 25 and an image processing unit 26 (amplification rate control means) that processes the captured optical image. The CCD 25 is a solid-state image sensor for photoelectrically converting an optical image. The image processing unit 26 includes a correlated double sampling circuit for removing image noise, an amplification circuit, a white balance adjustment circuit, and a digital signal conversion circuit, and has a function of increasing / decreasing the overall brightness by changing the amplification factor. have. Further, the motor driver 24 and the image processing unit 26 are processed or controlled by a drive command from the CPU 14.

  Returning to the description of FIG. The voice input unit 3 includes a microphone for inputting a voice signal by the user, a microphone AMP for amplifying the input voice signal, and a voice recording circuit for recording the amplified voice signal. The operation unit 4 includes keys operated by the user. The distance measuring unit 5 is a device that measures the distance to the subject.

  The ROM 6 stores a control program and parameters for control, which are described in codes readable by the CPU 14. When the power supply of the imaging apparatus is turned on, the program stored in the ROM 6 is loaded into the main memory 8, and the CPU 14 controls the operation of each part of the apparatus according to the program and temporarily stores data necessary for the control. Is stored in the main memory 8. Further, by using a rewritable flash ROM as the ROM 6, it becomes possible to change the control program and parameters for control, and the function can be easily upgraded.

  The storage unit 7 is a memory for storing captured image data even when no memory card is attached to the memory card throttle.

  The main memory 8 is a place where the CPU 14 temporarily stores data necessary for control. Further, when the CPU 14 performs various processes on the image data, the image data is also temporarily stored. The stored image data is acquired from the CCD 25 via the image processing, for example, and the white balance setting is performed. "RAW-RGB image data" in which gamma is set, "YUV image data" in which luminance / chrominance data conversion is performed, "JPEG image data" compressed with JPEG, and the like.

  The monitor 9 is a monitor for confirming the state of the subject before photographing and the photographed image, and displaying image data recorded in a built-in memory such as a memory card or the storage unit 7.

  The external I / O 10 is a circuit for converting the output signal of the serial block in order to perform serial communication with an external device such as a personal computer.

  The audio output unit 11 includes an audio reproduction circuit that converts a recorded audio signal into a signal that can be output from a speaker, an audio AMP that amplifies the converted audio signal and drives the speaker, and a speaker that outputs the audio signal.

  The strobe 12 is for emitting a flash to the subject, and the display unit 13 is a diode or the like to indicate the state of the image pickup apparatus. For example, a power-on lamp or the like corresponds to this.

  The CPU 14 performs white balance setting and gamma setting on the output data of the image processing from the CCD 25, a control block for converting to luminance data / color difference data by filtering processing, a block for controlling the operation of each part of the apparatus, an external device such as a personal computer USB block for USB communication with devices, serial block for serial communication with external devices such as personal computers, blocks for JPEG compression / decompression, blocks for enlarging / reducing the size of image data by interpolation processing, It has a TV signal display block for converting to a video signal for display on an external display device such as a TV, and a memory card block for controlling a memory card for recording captured image data.

  FIG. 3 is a block diagram showing the CCD 25 and the image processing unit 26 as the image input unit 2 in more detail. The image processing unit 26 includes a front end processing unit IC (F / E-IC). The image processor 26 sets the amplification factor of the image signal.

  The CCD 25 is a solid-state imaging device for photoelectrically converting an optical image, and the image processing unit 26 is a CDS 26a that performs correlated double sampling for removing image noise of analog shooting data input from the CCD 25, and the amplitude variation of the shooting data. AGC 26b that automatically adjusts the gain of the amplifier so as to detect and keep the output signal constant, A / D 26c that converts the analog signal into a digital signal, the vertical synchronization signal VD, and the horizontal synchronization signal HD based on the CCD 25 and the image processing unit TG 26d for generating 26 drive timing signals.

  In the present invention, the steady light detection means refers to the luminance information of the image captured by the CCD 25 before the strobe 12 emits light, and the CPU 14 determines whether or not the constant light above the predetermined level exists in the subject. This is realized.

  FIG. 4 is a circuit block diagram of the strobe. 40 is a charging unit, 41 is a light emission control unit, 42 is a trigger unit, 43 is a light emission unit, and 44 is a photometry unit.

  The charging unit 40 includes a feedback circuit for boosting, charge storage, and storage voltage, boosts the power supply voltage, stores charge in the capacitor, returns the storage voltage to the CPU 14, and controls the charge voltage by a charge control signal of the CPU 14.

  The light emission control unit 41 outputs a signal to the trigger unit 42 when the light emission control signal supplied from the CPU 14 changes from Low to High. Then, the trigger unit 42 supplies a trigger signal to the charging unit 40, and the charge of the capacitor in the charging unit 40 is discharged to the light emitting unit 43, and light emission in the light emitting unit 43 starts. Light emission stops when the light emission control signal supplied from the CPU 14 changes from High to Low, and the amount of light emission is controlled in the time width during which the light emission control signal is High. In general, the light emission control unit 41 uses an insulated gate bipolar transistor (IGBT), a thyristor, or the like as a light emission control element. Further, the light emission amount necessary for photographing, that is, the time width that is high of the light emission control signal is obtained by the distance to the subject, the aperture, and the image amplification factor, and is stored in advance in a memory such as the ROM 6 as a table. . Although control of the charging voltage is omitted, for example, the charging voltage of the capacitor in the charging unit 40 may be divided and A / D converted and then monitored by the CPU 14.

  In the present embodiment, the preliminary light emission amount is varied by reading the pre-correction strobe light emission amount G into the light emission control unit 41 and controlling the light emission control unit 41 with the light emission control signal output from the CPU 14. .

The photometry unit 44 is a photometry circuit that measures the amount of reflected light from the subject.
When performing the light emission control by the first method in the present invention, the power supply to the photometry unit 44 is turned on, the amount of reflected light from the subject is converted into a current value, and an integration circuit (not shown) in the photometry unit 44 is shown. ). Then, a dimming threshold value that stops light emission when a predetermined amount of reflected light is obtained is set in the photometry unit 44 in advance. In this light emission control method, the CPU 14 supplies a sufficiently long light emission time to the light emission control unit 41, and the actual light emission stop process is performed by the photometry unit 44 sending a light emission stop signal to the light emission unit 43. Do.

Next, the second light emission control method in the present invention will be described. Here, preliminary light emission is performed using the strobe 12 as described above, and at this time, the difference between the photometric result received from the CCD 25 and the reference photometric light amount (reflected light amount with a standard reflectance of 18%) (preliminary light emission photometric value). The difference between the appropriate amount of light measurement ΔEV) is grasped, and a preset coefficient: K is added to the difference with respect to the reference amount of light to correct the light emission amount of the flash at the time of shooting. Appropriate strobe light emission with respect to the difference in reflectance can be obtained.
First, the pre-correction strobe light emission amount: G is obtained from the following equation (1) using a subject distance: L, an aperture: F, and a proportionality constant: K ₁ defined by the photographing gain.

G = L * F * K ₁ (1)

On the other hand, the corrected photographic light amount Gx is obtained by the following equation (2), where ΔEV * K ₂ is a difference ΔEV with respect to the reference light measurement amount obtained by the preliminary light emission and a correction value by a coefficient K ₂ .

Gx = G * sqr (2) ^ (ΔEV * K ₂ ) (2)

  Note that the coefficient K is a coefficient that changes depending on the value of ΔEV, and the correction amount can be changed in accordance with the state of the reflectivity by storing it as a table in advance in a memory such as the ROM 6.

  With reference to FIGS. 5 to 10, the operation of the imaging apparatus of the present invention will be described.

  FIG. 5 shows an example of a subject that requires strobe light emission and includes steady light of a predetermined level or higher. An example of such a subject is a construction site at night. The stationary light in the subject of FIG. 5 is the light bulb of the worker's helmet.

Next, with reference to FIG. 6, a photographing operation when photographing such a subject will be described.
When the process is started, the subject luminance for each block divided into a plurality of blocks is acquired (step 100), and it is determined whether or not there is a photographing request (for example, the release button is pressed) from the user (step 101). . If there is no photographing request from the user (No in Step 101), the process returns to Step 100 to acquire the subject brightness for each block.

The image pickup apparatus of the present invention always captures a subject image by the CCD 25 and outputs it to the display unit 13 while the image pickup operation is not being performed. For example, as shown in FIG. 7, the image data captured by the CCD 25 is obtained by dividing the imaging surface into 256 blocks of equal area of horizontal 16 × vertical 16 and periodically measuring subject luminance for each block.
At this time, the division of the blocks in the present invention is not limited as long as the presence of stationary light can be reliably detected, and the number of blocks and the area of the blocks are not limited.

  In the present embodiment, the luminance level is represented in 10 levels. This luminance information is used, for example, when performing automatic exposure control so that the brightness of the monitor output image is appropriate.

Specifically, the luminance is represented by an 8-bit integer value from 0 to 255, and the luminance level is divided into 10 levels by dividing the luminance into 10 equal parts, with luminance level 0 being the darkest and luminance level 9 being the brightest. To do.
At this time, the brightness and the brightness level may be expressed more finely, and the finer brightness can be reproduced as it becomes finer. Further, it is not necessary to divide the luminance level equally, and it is possible to improve the reproducibility of the luminance within the target range by dividing the luminance level.

Luminance level 0: 0 to 25
Luminance level 1: 26-51
Luminance level 2: 52-77
Luminance level 3: 78-102
Luminance level 4: 103-128
Luminance level 5: 129-153
Luminance level 6: 154-179
Brightness level 7: 180-204
Luminance level 8: 205-230
Luminance level 9: 231 to 255

  On the other hand, when there is a photographing request from the user (Yes in Step 101), the steady light detection means (CPU 14) uses the subject luminance information acquired in Step 100 to include steady light of a predetermined level or higher in the subject. To determine whether or not Here, the luminance level of the subject is scanned in the horizontal direction from the block of line A shown in FIG. 7 (step 102). As a result of this line scan, the stationary light detection means determines whether or not a block having a predetermined luminance or higher is included in the block of the line (step 103).

FIG. 8 shows details of the determination in step 103.
First, in the flowchart of FIG. 8, the luminance level of the first (left end) block of a predetermined line is extracted (step 120), and it is confirmed whether the luminance level of this block is equal to or higher than a predetermined first threshold value. (Step 121). If the luminance level of the block is less than the first threshold value (No in step 121), it is determined whether the block is the last block (right end) (step 124). (No in step 124), the target block is updated (step 125), and the luminance level of the next block is extracted (step 120). For example, in the case of line A in FIG. 7, the luminance levels of the blocks in the line are all “0”, which is less than the predetermined first threshold value (level 8 or higher in this embodiment). All determinations in step 121 are No. In step 124, if the luminance extracted block is the last block of the line (Yes in step 124), the stationary light detection unit determines that there is no stationary light of a predetermined level or more in the line ( Step 126).

Here, the case of FIG. 7 will be described as an example of the determination in step 103.
First, paying attention to the line E in FIG. 7, there is a block whose luminance level is the first threshold value (level 8 or higher) in the block of the line (blocks E5 and E6). Here, when the luminance level of the block E5 is extracted in step 120 of FIG. 8, it is determined in step 121 that the luminance level is equal to or higher than the first threshold value (Yes in step 121). Then, the brightness level of the next block E6 is extracted (step 122), and it is determined whether or not the brightness level of this block is equal to or higher than the first threshold value (step 123). Since the luminance level of the block E6 is “9”, this determination is affirmed (Yes in step 123). In other words, it is determined that there are consecutive blocks having the first threshold value or more in the line E, and as a result, the steady light detection means determines that there is steady light having a predetermined level or more in the line. (Step 127).

  In the present embodiment, it is determined that there is stationary light of a predetermined level or higher when there are two consecutive blocks that are equal to or higher than the first threshold, but this determination method is an example, For example, when there is only one block having a luminance level equal to or higher than the first threshold, or when there are three or more consecutive blocks, it may be determined that there is steady light having a predetermined level or higher. When there are a plurality of blocks having a luminance level equal to or higher than the first threshold value in a discrete manner, it may be determined that there is stationary light having a predetermined level or higher. Moreover, although the case where it continues on the same line (the case where it continues in the horizontal direction in a figure) was shown, when it continues on the same row | line | column of an adjacent line (when it continues in the vertical direction in a figure), it determines with regular light You may do it.

  The determination in step 103 in FIG. 6 is performed by the above method. As a result, if there is a block of a predetermined level or higher in the scan line (Yes in Step 103), the light emission control means (CPU 14) of the present invention selects the second light emission control as the light emission method (Step 110).

  In step 103, when there is no block of a predetermined level or higher (No in step 103), the stationary light detection means next has a block whose luminance difference with an adjacent block is a predetermined threshold value or more. It is determined whether or not to perform (step 104).

Here, step 104 will be described in detail with reference to FIG.
In the flowchart of FIG. 9, the stationary light detection means extracts the luminance level of the first (left end) block of the predetermined line (step 130), and determines whether or not it is equal to or higher than the predetermined second threshold (step 130). 131). In the present embodiment, the luminance level “5” is set as the second threshold value. Here, the second threshold value is set to a value smaller than the first threshold value described above. Although the details will be described later, the stationary light detection means in the present embodiment detects a relatively bright area (block) compared with the surrounding luminance level although the absolute value of the luminance level is low.

  In step 131, when the luminance level is less than the second threshold value (No in step 131), the stationary light detection unit determines whether the block is the last block in the scan line (step 136). If the block is not the final block (No in step 136), the target block is updated (step 137), and the luminance level of the next block is extracted (step 130). If the block is the final block (No in step 136), the stationary light detection means determines that there is no stationary light of a predetermined level or more in the line (step 138).

  On the other hand, if the luminance level is greater than or equal to the second threshold value in step 131 (Yes in step 131), the stationary light detection means determines the luminance of the block before the block and the block next to the block. Each level is extracted (steps 132 and 133). If the block is the leftmost block of the line, step 132 is skipped. If the block is the rightmost block of the line, step 133 is skipped.

  Next, the stationary light detection means determines whether or not the luminance difference between the block and the previous block is equal to or greater than a predetermined third threshold value (step 134). If the luminance difference between the block and the previous block is equal to or greater than a predetermined third threshold value (Yes in step 134), the stationary light detecting means has a predetermined fourth luminance difference with the next block. It is determined whether it is equal to or less than a threshold value (step 135). If the luminance difference with the next block is equal to or smaller than the fourth threshold value (Yes in step 135), the stationary light detection means determines that stationary light of a predetermined level or more exists in the line (step 141). ).

On the other hand, in step 134, if the luminance difference with the previous block is not equal to or greater than the predetermined third threshold value (No in step 134), the stationary light detection means has a predetermined luminance difference with the next block. It is determined whether or not the threshold value is 3 or more (step 139). If the luminance difference between the block and the next block is greater than or equal to a predetermined third threshold (Yes in step 139), the stationary light detection means has a predetermined fourth threshold value that is different from the preceding block. It is determined whether the value is equal to or less than the value (step 140). If the luminance difference from the previous block is equal to or smaller than the fourth threshold value (Yes in step 140), the stationary light detection means determines that there is stationary light of a predetermined level or more in the line (step 141). ).
That is, step 134 confirms the rise of the luminance with respect to the scan direction, and step 139 confirms the fall of the luminance.

  On the other hand, if the luminance difference with the next block is less than the third threshold value in step 139 (No in step 139), or the luminance difference with the preceding block is the fourth threshold value in step 140. Is exceeded (No in step 140), or in step 135, if the luminance difference from the previous block is less than the third threshold value (No in step 135), the stationary light detection means It is determined whether the block is the last block in the scan line (step 136). If the block is not the final block (No in step 136), the target block is updated (step 137), and the luminance level of the next block is extracted (step 130). If the block is the final block (No in step 136), the stationary light detection means determines that there is no stationary light of a predetermined level or more in the line (step 138).

An example of the determination at step 104 will be described with reference to FIG.
FIG. 10 is another example showing the luminance level for each block in the block division diagram of the subject. If there is no block having the first luminance level or higher in the subject, the determination in step 103 is negative and step 104 is performed. Is executed. Note that FIG. 7 and FIG. 10 are different in luminance level from block E4 to block E7.

  Here, focusing on the block E5 in FIG. 10, the operation of the stationary light detection means when the main block E5 is the target block will be described. In the present embodiment, the following are set as the second, third, and fourth threshold values, respectively.

Second threshold value: luminance level “5” or higher Third threshold value: The luminance difference between the target block and the adjacent block is not less than half the luminance level of the target block. Fourth threshold value: Target The brightness difference between the block and the adjacent block is less than brightness level “1”

  Here, the luminance difference between the third threshold value and the fourth threshold value means a luminance difference between the target block and the adjacent block. When the luminance of the adjacent block is smaller than the target block, When the luminance difference is a positive value and the luminance of a block adjacent to the target block is larger, the luminance difference is a negative value.

  First, in step 130, the luminance level “6” of the block E5 is extracted. Next, in step 131, the luminance level (level “6”) of the block E5 is compared with the second threshold value (luminance level “5”), and the process proceeds to step 132 as a result of the determination. In step 132, the luminance level “2” of the block before block E5, that is, block E4 is extracted. Subsequently, in step 133, the luminance level “7” of block E6 next to block E5 is extracted. Next, in step 134, the brightness difference “4” between the brightness level “6” of the block E5 and the brightness level “2” of the block E4 before the block E5 is compared with the third threshold value. Here, since the luminance level of the target block E5 is the level “6”, the third threshold value is a half value “3”. Therefore, the luminance difference “4” with respect to the block E4 is equal to or greater than the third threshold value, and step 134 is affirmed and the routine proceeds to step 135. In step 135, the luminance difference “−1” between the luminance level “6” of the block E5 and the luminance level “7” of the block E6 next to the block E5 is compared with the fourth threshold value (target block). Since the luminance level of E5 is smaller than the luminance level of the next block E6, the luminance difference is a negative value). Since the fourth threshold value has a luminance difference of level “1” or less, step 135 is affirmed and the routine proceeds to step 141. That is, in step 141, it is determined that the subject includes stationary light having a predetermined level or higher.

  Therefore, even when the absolute value of the luminance level of the steady light is less than the first threshold value, there is a certain luminance level (second threshold value), and the luminance difference from the surroundings is predetermined. Stationary light can be detected for a subject having a level (third threshold) or more.

  In the present embodiment, in addition to the luminance difference with the adjacent block being equal to or greater than the third threshold value, the luminance difference with the other adjacent block is equal to or less than the fourth threshold value. Although the stationary light is present when the stationary light has a certain area or more, the comparison with the fourth threshold value may be omitted (that is, the stationary light area may be small). ).

  The determination in step 104 in FIG. 6 is performed by the above method. As a result, if there is a block of a predetermined level or higher in the scan line (Yes in Step 104), the light emission control means (CPU 14) selects the second light emission control as the light emission method (Step 110). In step 104, when there is no block of a predetermined level or higher (No in step 104), the stationary light detection unit determines whether the scan line is the final line (step 105). If it is not the last line (No in Step 105), the scan line is updated (Step 106), and the next line scan is started (Step 102). If it is the last line (Yes in Step 105), the light emission control means selects the first light emission control as the light emission method (Step 107).

  Next, when the first light emission control is selected in step 107, the light emission control means calculates a dimming threshold value for obtaining an appropriate amount of reflected light from the set photographing gain, aperture, and the like. (Step 118), a light emission control mode is set so as to emit light by the reflected light photometry method, and a light emission (flash photography) operation is performed (Step S119). In other words, the light emission control in step 119 is a method in which the reflected light from the subject is measured by the photometry unit 44 and continues to emit light until a predetermined amount of light is obtained. Set the threshold value.

  On the other hand, when the second light emission control is selected in step 110, the light emission control means performs preliminary light emission with a predetermined light emission amount calculated according to the subject (step 111). Next, the light emission control means performs photometry of the amount of light reflected from the subject in preliminary light emission (step 112). Here, an analog image signal received via the CCD 25 is converted into a digital signal by the A / D 26c to extract the subject luminance Y, and a correction amount for obtaining an appropriate luminance is calculated. Then, the main light emission amount is corrected based on the calculated correction amount (step 113), the light emission control mode is set to perform the main light emission with the calculated light emission amount, and the main light emission (strobe shooting) with the specified light amount is performed. ) The operation is performed (step 114). In the main light emission control in step S118, since the function of the photometry unit 44 is not used, the power supplied to the photometry unit 44 is turned off.

  As described above, the imaging apparatus according to the present invention detects steady light from a subject based on the result of the steady light detection unit that detects whether or not the constant light of a predetermined level or more exists in the subject. Switching between the first light emission control for controlling to emit light until the reflected light amount reaches a predetermined amount and the second light emission control for controlling to emit light with a light amount calculated in advance according to the subject. Therefore, it is possible to avoid the problem that the light metering element in the first light emission control stops the light emission of the strobe before it reaches the appropriate exposure amount due to the steady light above the predetermined level included in the subject. Is possible.

  In the present embodiment, as the second light emission control, the preliminary light emission method for calculating the main light emission amount from the light measurement result of the preliminary light emission performed before the main light emission has been described, but the light emission amount according to the distance to the subject. The light emission control may be performed at. In addition, although the example in which the light emission control unit switches between the first and second light emission control based on the detection result of the steady light detection unit has been described, in addition to this condition, the first light emission control unit switches according to the distance to the subject. The first and second light emission controls may be switched, or the first and second light emission controls may be switched according to the result of preliminary light measurement.

It is a functional block diagram concerning the imaging device of the present invention. It is a lens barrel unit block diagram concerning the imaging device of the present invention. It is an image processing block diagram concerning the imaging device of the present invention. 1 is a strobe block diagram according to an imaging apparatus of the present invention. FIG. 3 is a block division diagram of a subject according to the present embodiment. 3 is a flowchart relating to control of the imaging apparatus according to the present invention. It is the luminance level for every block in the block division | segmentation figure of the to-be-photographed object which concerns on this Embodiment. It is a flowchart of the brightness | luminance determination (step 103) of the imaging device which concerns on this Embodiment. It is a flowchart of the brightness determination (step 104) of the imaging device which concerns on this Embodiment. It is another example of the luminance level for every block in the block division | segmentation figure of the to-be-photographed object which concerns on this Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lens barrel unit 2 Image input part 3 Voice input part 4 Operation part 5 Ranging part 6 ROM
7 Storage unit 8 Main memory 9 Monitor 10 External I / O
11 Audio Output Unit 12 Strobe 13 Instruction Unit 14 CPU
21 Lens (focus, zoom)
22 Mechanical shutter 23 Aperture 24 Motor driver 25 CCD
26 Image processing unit 26a CDS
26b AGC
26c A / D
26d TG
40 Charging part 41 Light emission control part 42 Trigger part 43 Light emission part 44 Photometry part

Claims (9)

Imaging means for imaging a subject image by forming a subject image on a predetermined imaging surface;
Light emitting means for subject illumination;
A light emission control means for controlling light emission of the light emission means;
A stationary light detecting means for determining the presence or absence of stationary light above a predetermined level in a subject,
The light emission control means includes
Performing a first light emission control for controlling the light emitting means to emit light until the amount of reflected light from the subject reaches a predetermined amount when the steady light detecting means determines that the steady light is absent;
When the steady light detecting means determines that the steady light is present, second light emission control is performed to control the light emitting means to emit light with a light emission amount calculated in advance according to the subject. An imaging device.   The imaging apparatus according to claim 1, wherein the stationary light detection unit determines presence or absence of the stationary light using luminance information obtained from a subject before subject illumination by the light emitting unit.   The imaging apparatus according to claim 2, wherein the stationary light detecting unit acquires the luminance information for each block by dividing the imaging surface into a plurality of blocks.   The imaging according to claim 3, wherein the stationary light detection unit determines that the stationary light is present when there is a block having a luminance equal to or higher than a first threshold among the plurality of blocks. apparatus.   The said stationary light detection means judges that there exists the said stationary light when the block from which a brightness | luminance becomes more than a 1st threshold value exists among several said blocks continuously. 3. The imaging device according to 3.   The stationary light detection means includes a block in which the luminance is equal to or higher than a second threshold value and the luminance difference between the block and an adjacent block is equal to or higher than a third threshold value among the plurality of blocks. The imaging apparatus according to claim 3, wherein it is determined that the stationary light is present.   The stationary light detection means has a luminance that is equal to or greater than a second threshold value among the plurality of blocks, and a luminance difference between one block adjacent to the block is equal to or greater than a third threshold value, The imaging apparatus according to claim 3, wherein when there is a block in which a luminance difference between the block and the other adjacent block is equal to or less than a fourth threshold, it is determined that the stationary light is present.   The imaging apparatus according to claim 1, wherein the light emission amount is calculated according to a distance to the subject.   The imaging apparatus according to claim 1, wherein the emitted light amount is calculated according to a reflected light amount from the subject when the light emitting unit emits light as preliminary light emission before photographing.