JP5048599B2 - Imaging device - Google Patents

Description

The present invention relates to an imaging apparatus , and more particularly to an imaging apparatus that captures a through image and a moving image.

  In Patent Document 1, a screen division pattern is set, the brightness is compared for each area, detection of backlight or orderable light is performed based on the comparison result, and an automatic diaphragm device is detected based on the detection result. An image pickup apparatus is described that performs automatic exposure control during moving image shooting by changing the detection characteristics.

  In Patent Document 2, when the subject dynamic range is larger than the target dynamic range, the difference between the maximum luminance value of the target dynamic range and the maximum luminance value of the subject dynamic range, the minimum luminance value of the target dynamic range, and the subject dynamic range are disclosed. By controlling the aperture opening and closing operation so that the difference from the minimum luminance value matches the image, it is possible to uniformly generate overexposure and underexposure and capture a natural image corresponding to the subject. An apparatus is described.

In Patent Document 3, information on the dynamic range of the shooting scene is acquired and analyzed, and after setting the main shooting conditions based on the analysis result, shooting is performed by one or a plurality of exposures under different exposure conditions. For this reason, there has been described an imaging apparatus capable of obtaining a wide dynamic range image in which both a person and a background are displayed in an appropriate exposure state.
Japanese Patent Laid-Open No. 5-22650 Japanese Patent Laid-Open No. 2002-57939 JP 2002-223387 A

  However, in the invention described in Patent Document 1, there is a problem that the subject at the center of the screen is properly exposed, but other subjects may not be properly exposed.

  In addition, the invention described in Patent Document 2 has a problem that overexposure and underexposure cannot be eliminated.

  Further, in the invention described in Patent Document 3, since it is necessary to synthesize a plurality of images, there is a problem that it cannot be applied to a through image or a moving image.

The present invention has been made in view of such circumstances. Even when the brightness of a subject changes abruptly, the brightness does not change abruptly, and a stable through image without overexposure or underexposure occurs. An object of the present invention is to provide an imaging apparatus capable of obtaining a moving image .

In order to achieve the above object, an invention according to one aspect of the present invention includes an imaging unit that continuously captures an image of a subject and acquires a continuous image signal, and an image of the subject based on the image signal acquired by the imaging unit. Brightness detection means for detecting brightness and calculating an appropriate exposure value based on the detection result, sky detection means for detecting whether or not the subject image captured by the imaging means includes sky, and the brightness Determining means for determining whether to perform dynamic range expansion processing based on the brightness of the subject detected by the detection means , and when the sky detection unit detects sky, the dynamic range expansion processing is performed. determining means for determining to perform, when said determination means determines to perform the dynamic range expansion processing, the underexposure by a predetermined exposure correction value than the proper exposure value In addition to correcting the appropriate exposure value, the dynamic range expansion processing unit corrects the gradation of the image signal captured by the imaging unit according to the gamma curve corresponding to the exposure correction value, and the determination unit expands the dynamic range. If it is determined that no processing is performed, exposure is controlled based on the appropriate exposure value, and if it is determined that dynamic range expansion processing is performed, exposure control is performed that controls exposure based on the appropriate exposure value corrected by the exposure correction value. And the brightness detection means determines the brightness of the subject based on the image signal whose gradation has been corrected by the dynamic range expansion processing means when the determination means determines that the dynamic range expansion processing is to be performed. And the appropriate exposure value is calculated based on the detection result .

According to one aspect of the present invention, when sky is detected from a subject image , the gradation of an image signal that is captured under exposure by a predetermined exposure correction value with respect to the appropriate exposure value depends on the exposure correction value. Dynamic range expansion processing is performed to correct according to the gamma curve. Thereby, a through image or a moving image in which both the bright sky and other regions can be visually recognized can be taken.

According to another aspect of the present invention, an imaging unit that continuously captures an image of a subject and obtains a continuous image signal, and detects the brightness of the subject based on the image signal acquired by the imaging unit, Based on the brightness detection means for calculating the appropriate exposure value based on the detection result, the sensitivity setting means for setting the sensitivity of the imaging means, and the brightness of the subject image detected by the brightness detection means Sensitivity detection means for detecting sensitivity, and determination means for determining whether to perform dynamic range expansion processing based on the brightness of the subject detected by the brightness detection means, which is set by the sensitivity setting means And the sensitivity detected by the sensitivity detection means, and the sensitivity detected by the sensitivity detection means is lower than the sensitivity set by the sensitivity setting means When determining that the dynamic range expansion process is to be performed, and when the determination unit determines that the dynamic range expansion process is to be performed, the appropriate exposure value is set so as to be underexposed by a predetermined exposure correction value from the appropriate exposure value. A dynamic range expansion processing unit that corrects and corrects a gradation of an image signal captured by the imaging unit in accordance with a gamma curve corresponding to the exposure correction value, and the determination unit determines that the dynamic range expansion processing is not performed. Then, when it is determined that the exposure is controlled based on the appropriate exposure value and the dynamic range expansion process is performed, an exposure control unit that controls the exposure based on the appropriate exposure value corrected by the exposure correction value, and When the brightness detection unit determines that the determination unit performs a dynamic range expansion process, the brightness detection unit By detecting the brightness of the object based on an image signal gradation is corrected by the dynamic range expansion processing means, and calculates the proper exposure value based on the detection result.

According to another aspect of the present invention, when the detected sensitivity is lower than the sensitivity at the time of subject image acquisition, the gradation of the image signal imaged underexposure by a predetermined exposure correction value with respect to the appropriate exposure value is set as the exposure correction value. A dynamic range expansion process is performed in which correction is performed according to a gamma curve corresponding to. Thereby, even when shooting a bright subject that can be shot on the lowest sensitivity side, it is possible to shoot a through image or a moving image in which both a bright part and a dark part are visible.

The invention according to yet another aspect of the present invention is characterized in that the determination means changes the exposure correction value based on the brightness of the subject detected by the brightness detection means.

According to still another aspect of the present invention , the exposure correction value is changed based on the brightness of the subject. Thereby, the level of the dynamic range expansion processing, for example, 100%, 200%, 400%, etc. can be changed according to the brightness of the subject.

  According to the present invention, even when the brightness of a subject changes suddenly, it is possible to obtain a stable through image or moving image in which the brightness does not change suddenly and there is no overexposure or underexposure.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, the best mode for carrying out an imaging apparatus, an imaging method, and a program to which the invention is applied will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing a schematic electrical configuration inside a digital camera 1 which is an imaging apparatus according to the first embodiment.

  As shown in FIG. 1, the digital camera 1 mainly includes an imaging unit 10 (an optical unit 11, an imaging element 12, an analog signal processing unit 13, an A / D converter 14, a digital signal processing unit 15, a motor driving unit 16, Timing generator (TG) 17), CPU 20, memory I / F (interface) 22, RAM 24, ROM 26, compression / decompression processing circuit 28, LCD I / F (interface) 30, LCD 32, external memory I / F (interface) 34, memory A card 36, a charging unit 38, a flash 40, an AE (automatic exposure) control unit 41, a brightness detection unit 42, a dynamic range (D range) control unit 43, and the like.

  The optical unit 11 is mainly composed of a zoom lens, a focus lens, a diaphragm, and the like, and forms a subject image on the image sensor 12.

  The image pickup device 12 includes, for example, a large number of photodiodes (light receiving devices) through red (R), green (G), and blue (B) color filters arranged in a predetermined arrangement structure (Bayer, G stripe, etc.). Is two-dimensionally arranged on the light receiving surface, and electronically captures an image of the subject formed by the optical unit 11. The image sensor 12 is driven by a timing generator (TG) 17 that outputs a timing signal in response to a command from the CPU 20.

  The analog signal processing unit 13 samples and holds the R, G, B signals for each divided area with respect to the image signal output from the image sensor 12 (correlated double sampling processing), and outputs analog R, G, B signals. Is generated. The generated analog R, G, B signals are input to the A / D converter 14.

  The A / D converter 14 amplifies the analog R, G, and B signals input from the analog signal processing unit 13 and converts the analog R, G, and B signals into digital R, G, and B signals. Output to the digital signal processing unit 15.

  The digital signal processing unit 15 includes a synchronization circuit (a processing circuit that converts a color signal into a simultaneous expression by interpolating a spatial shift of the color signal associated with the color filter array of a single CCD), a white balance correction circuit, and a gamma correction. Circuit, contour correction circuit, luminance / color difference signal generation circuit, etc., and in accordance with a command from the CPU 20, the digital R, G, B signals inputted from the A / D converter 14 are subjected to necessary signal processing to obtain luminance. Image data (YUV data) composed of data (Y data) and color difference data (Cr, Cb data) is generated. The image data generated by the digital signal processing unit 15 is output to the compression / decompression processing circuit 28.

  The motor drive unit 16 drives the optical unit 11 in accordance with instructions from an operation unit (not shown) including various operation means such as a shutter switch and a mode change switch.

  The timing generator (TG) 17 provides timing signals to the image sensor 12, the analog signal processing unit 13, the A / D converter 14, and the digital signal processing unit 15. The processing of each unit is synchronized by the timing signal given from the TG 17.

  The CPU 20 performs overall control of the entire digital camera 1 according to a predetermined control program based on an operation signal input from the operation unit 111.

  A RAM 24 and a ROM 26 are connected to the CPU 20 via a bus 55 and a memory I / F 22. The ROM 26 stores a control program executed by the CPU 20 and various data necessary for the control, various setting information relating to the operation of the digital camera 1 such as photographer setting information. The RAM 24 is used as a calculation work area for the CPU 20 and as a temporary storage area for image data and the like.

  The CPU 20 includes an AF (autofocus) detection circuit. The AF detection circuit includes a high-pass filter that passes only high-frequency components of the G signal, an absolute value processing unit, and a predetermined focus area (for example, the center of the screen). An AF area detection unit that extracts signals and an integration unit that integrates absolute value data in the AF area are configured. During the AF control, the CPU 20 sequentially moves the focus lens from a closest position to a lens position corresponding to infinity, and at the same time, the high frequency component of the image signal based on the image signal of the AF area captured via the image sensor 12 for each lens position. The integrated evaluation value is acquired, a lens position where the evaluation value reaches a peak is obtained, and contrast AF is performed to move the focus lens in the optical unit 11 to the lens position.

  The compression / decompression processing circuit 28 performs compression processing of a predetermined format on the input image data in accordance with a command from the CPU 20 to generate compressed image data. Further, in accordance with a command from the CPU 20, the input compressed image data is subjected to a decompression process in a predetermined format to generate uncompressed image data.

  The LCD I / F 30 controls display on the LCD 32 in accordance with a command from the CPU 20. That is, in accordance with a command from the CPU 20, the input image signal is converted into a video signal (for example, an NTSC signal, a PAL signal, or a SCAM signal) for display on the LCD 32 and output to the LCD 32.

  The LCD 32 is composed of a liquid crystal display capable of color display. The LCD 32 is used as an image display panel for displaying a photographed image in the playback mode, and is used as a photographer interface display panel for performing various setting operations. In the photographing mode, a through image is displayed as necessary, and is used as an electronic viewfinder for checking the angle of view.

  The external memory I / F 34 controls reading / writing of data with respect to the memory card 36 loaded in the media slot in accordance with a command from the CPU 20, and stores the data compressed by the compression / decompression processing circuit 28 in accordance with a predetermined format. Record on card 36.

  The flash 40 emits a visible flash using a discharge of xenon gas and can be charged from the charging unit 38.

  The AE detection unit 41 calculates a physical quantity necessary for AE control and AWB (automatic white balance) control from the input image signal. For example, as a physical quantity necessary for AE control, the integrated value for each divided area calculated by the brightness detection unit 42 is weighted and averaged to detect the brightness of the subject (subject brightness), and an exposure value suitable for shooting (shooting) EV value) is calculated. The AE detection unit 41 outputs the calculated exposure value to the CPU 20.

  The brightness detection unit 42 divides one-screen image data output from the digital signal processing unit 15 into a plurality of areas (for example, 16 × 16), and an integrated value of R, G, and B image signals for each divided area. Calculate the brightness of the subject (subject brightness).

  The D range control unit 43 determines whether or not the dynamic range expansion process is necessary based on the brightness of the subject detected by the brightness detection unit 42 and outputs the determination result to the CPU 20 (the dynamic range expansion process). ON / OFF control). CPU20 controls each part according to the result output from D range control part 43, and picturizes an image with a wide dynamic range.

  For example, the D range control unit 43 may include (1) the amount of change in brightness between the current frame and the previous frame, (2) the width of variation in brightness, (3) the average screen brightness, and (4) the bright area divided area. On the basis of (5) the product sum of the luminance and the number of divided areas and (6) the luminance of the divided area having the highest luminance, ON / OFF of the dynamic range expansion processing is controlled.

  Here, the dynamic range expansion process will be described. In the dynamic range expansion process, the exposure value is corrected so that the exposure value is underexposed by a predetermined exposure correction value from the appropriate exposure value obtained by the AE detection unit 41, and the higher luminance side is compared with the normal gradation conversion curve. This is a process of shooting with a dynamic range wider than that in the normal shooting mode by performing a gamma conversion process using a gradation conversion curve that is flat (small in inclination) and has a large halftone. Here, the gradation conversion curve is set according to the exposure correction value.

  When dynamic range expansion processing is performed, it is possible to capture an image (broad dynamic image) in which the halftone has substantially the same brightness as in normal shooting and the gradation changes on the highlight side. Assuming that the normal dynamic range is 100%, when the exposure correction value is 1 EV, that is, when the image is taken 1 EV lower than the appropriate exposure, an image with the dynamic range expanded to 200% is obtained. In addition, when the exposure correction value is 2 EV, that is, 2 EV lower than the appropriate exposure, the dynamic range is expanded to 400%.

  Next, the operation of the digital camera 1 of the present embodiment configured as described above will be described. By setting the power / mode switch to the shooting position, the digital camera 1 is set to the shooting mode. When the digital camera 1 is set to the shooting mode, the optical unit 11 is extended to enter a shooting standby state.

(1) When controlling ON / OFF of dynamic range expansion processing based on the amount of change in brightness between the current frame and the previous frame The D range control unit 43 determines the amount of change in brightness between the current frame and the previous frame. In other words, the dynamic range expansion processing is turned on / off based on whether or not the change in brightness between the current frame and the previous frame (previous frame) is a predetermined threshold (screen brightness or differential value of G component). A photographing process in the case of control will be described with reference to FIG.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 first measures the brightness of the subject, forms an image of the subject light on the light receiving surface of the image sensor 12 with an exposure value corresponding to the brightness, A subject image for a through image is captured (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 forms an image of subject light on the light receiving surface of the image sensor 12 with the exposure value obtained by the AE detector 41 in step S8 (detailed later). A subject image for an image is captured (step S3).

  The subject light imaged on the light receiving surface of the image sensor 12 in step S2 or S3 is received by each photodiode, converted into a signal charge of an amount corresponding to the amount of incident light, and a signal based on a drive pulse supplied from the TG 17 It is sequentially read out as a voltage signal (image signal) corresponding to the electric charge, converted into digital R, G, B signals by the analog signal processing unit 13, the A / D converter 14, and the digital signal processing unit 15, and is compressed and expanded. The signal is added to the LCD I / F 30 via the circuit 28, converted into a signal format for display, and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 makes the brightness of the image (current frame image) displayed on the LCD 32 in step S4 brighter than a brightness of a previously captured image (previous frame image) by a predetermined threshold or more. It is determined whether it has changed (step S5). For the amount of change in brightness, the D range control unit 43 calculates the average brightness of the subject for each divided area calculated by the brightness detection unit 42 for the current frame image and the previous frame image, and the difference And is calculated by taking the derivative.

  If the brightness of the image of the current frame has not changed to a value brighter than the brightness of the image of the previous frame by a predetermined threshold or more (NO in step S5), the D range control unit 43 controls the dynamic range expansion process to OFF. The result is output to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  When the brightness of the image of the current frame has changed to a value brighter than the brightness of the image of the previous frame by a predetermined threshold or more (YES in step S5), the D range control unit 43 controls the dynamic range expansion process to be ON. The result is output to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 starts shooting processing. That is, the CPU 20 determines the aperture value and the shutter speed from the photographing EV value obtained by the AE detection unit 41 in step S9 and a predetermined program diagram. At the same time, the CPU 20 calculates focus evaluation values (AF evaluation values) at a plurality of AF detection points while moving the focus lens in the optical unit 11 based on the integrated value data, and the evaluation value is maximized. The position is determined as the focus position, and the focus lens is moved to the determined focus position. The CPU 20 exposes the image sensor 12 with the determined aperture value and shutter speed, and forms subject light on the light receiving surface of the image sensor 12 with an appropriate exposure amount, thereby capturing a subject image for a still image ( Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the amount of change between the brightness of the image of the current frame and the brightness of the image of the previous frame is greater than or equal to a predetermined threshold in step S5, that is, whether or not dynamic range expansion processing (step S7) has been performed. Judgment is made (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13. That is, the CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 calculates an average integrated value for each color of the R, G, and B signals for each divided area, and the calculation result is sent to the CPU 20. provide. The CPU 20 obtains the ratio of R / G and B / G for each divided area from the obtained R accumulated value, B accumulated value, and G accumulated value, and R of the obtained R / G and B / G values. The light source type is discriminated based on the distribution in the color space of / G and B / G. Then, according to the white balance adjustment value suitable for the discriminated light source type, for example, the value of each ratio is approximately 1 (that is, the RGB integration ratio is R: G: B≈1: 1: 1 on one screen). As described above, the gain value (white balance correction value) for the R, G, and B signals of the white balance adjustment circuit is controlled to correct the signal of each color channel. The digital signal that has been subjected to processing such as automatic white balance adjustment is taken into the compression / expansion processing circuit 28. The compression / expansion processing circuit 28 converts the digital signal into a luminance / color difference signal and outputs it to the RAM 24. The RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

(2) When ON / OFF of dynamic range expansion processing is controlled based on the dynamic range of the image The D range control unit 43 performs dynamic based on whether or not the dynamic range of the image of the current frame is greater than or equal to a predetermined threshold. An imaging process in the case of controlling ON / OFF of the range expansion process will be described with reference to FIG. The same parts as (1) are given the same reference numerals, and the description thereof is omitted.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 determines whether or not the variation width of the brightness of the image of the current frame is equal to or greater than a predetermined threshold (step S15). The width of the variation in brightness is calculated by taking the difference between the maximum value and the minimum value of the brightness for each divided area of the image of the current frame detected by the brightness detection unit 42 in the D range control unit 43. Is done.

  If the brightness variation width is not equal to or greater than the predetermined threshold (NO in step S15), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  If the brightness variation width is equal to or greater than the predetermined threshold (YES in step S15), the D range control unit 43 controls the dynamic range expansion process to be ON and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S16, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

(3) When ON / OFF of dynamic range expansion processing is controlled based on the average screen brightness The D range control unit 43 performs dynamic based on whether the screen average brightness is equal to or higher than a predetermined brightness (for example, 15 EV). An imaging process in the case of controlling ON / OFF of the range expansion process will be described with reference to FIG. The same parts as (1) are given the same reference numerals, and the description thereof is omitted.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 determines whether the screen average brightness of the image of the current frame is equal to or higher than a predetermined threshold (for example, 15 EV) (step S16). The average screen brightness is calculated by taking the average brightness for each divided area calculated by the brightness detector 42.

  If the screen average brightness is not equal to or greater than the predetermined threshold (NO in step S16), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  If the screen average brightness is equal to or higher than the predetermined threshold (YES in step S16), the D range control unit 43 controls the dynamic range expansion process to be ON and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S15, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

(4) When ON / OFF of dynamic range expansion processing is controlled based on the number of divided areas with high luminance The D range control unit 43 determines whether or not the number of divided areas with high luminance is equal to or greater than a predetermined threshold. An imaging process in the case of controlling ON / OFF of the dynamic range expansion process based on this will be described with reference to FIG. The same parts as (1) are given the same reference numerals, and the description thereof is omitted.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  In the current frame image, the D range control unit 43 determines whether the number of bright divided areas, that is, the number of divided areas whose luminance is equal to or greater than a predetermined threshold (for example, 15 EV) is equal to or greater than the predetermined threshold (for example, half) It is determined whether or not (step S17). The number of divided areas whose luminance is greater than or equal to a predetermined threshold is calculated by counting the number of divided areas in which brightness greater than or equal to the predetermined threshold is detected by the brightness detection unit 42.

  If the number of bright areas is not equal to or greater than the predetermined threshold (NO in step S17), the D range control unit 43 controls the dynamic range expansion process to OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  When the number of bright area divisions is equal to or greater than the predetermined threshold (YES in step S17), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S15, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

  In this embodiment, ON / OFF of the dynamic range expansion process is controlled based on whether or not the number of divided areas with high luminance is equal to or greater than a predetermined threshold. However, the luminance is not limited to the number of divided areas with high luminance. Various indices such as the area of a high area and the number of divided areas having the highest luminance when the image of the current frame is divided and measured can be used.

(5) When controlling ON / OFF of dynamic range expansion processing based on the product sum of luminance and the number of divided areas The D range control unit 43 has a product sum of luminance and the number of divided areas equal to or greater than a predetermined threshold. An imaging process in the case of controlling ON / OFF of the dynamic range expansion process based on whether or not will be described with reference to FIG. The same parts as (1) are given the same reference numerals, and the description thereof is omitted.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 determines whether or not the product sum of the brightness of the image of the current frame and the number of divided areas is equal to or greater than a predetermined threshold (step S18). For the product sum of the luminance and the number of divided areas, the D range control unit 43 first acquires the brightness of each divided area detected by the brightness detection unit 42, and then acquires the brightness for each acquired brightness. The number of divided areas having brightness is obtained. Then, for a divided area having a brightness of a predetermined value or more, the product of the brightness and the number of divided areas of the brightness is calculated for each brightness, and the sum of the values calculated for each brightness is calculated. It is obtained by calculating.

  Specifically, for example, the image of the current frame includes a divided area having a luminance of 12 EV to 15 EV, the divided area of 12 EV is A, the divided area of 13 EV is B, the divided area of 14 EV is C, If there are D divided areas of 14EV, the product of the luminance and the number of divided areas for each luminance (12EV × A = 12A, 13EV × B = 13B, 14EV × C = 14C, 15EV × D = 15D ) (12A + 13B + 14C + 15D) is the product sum of the luminance and the number of divided areas.

  If the product sum of the luminance and the number of divided areas is not equal to or greater than the predetermined threshold value (NO in step S18), the D range control unit 43 controls the dynamic range expansion process to OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  If the product sum of the luminance and the number of divided areas is equal to or greater than a predetermined threshold (YES in step S18), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Thereby, ON / OFF of the expansion of the dynamic range can be controlled in consideration of the variation in luminance of the image of the current frame.

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S15, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

(6) When ON / OFF of dynamic range expansion processing is controlled based on the highest luminance in the screen The D range control unit 43 determines whether or not there is a particularly bright portion in the image of the current frame, that is, the highest luminance. An imaging process in the case of controlling the ON / OFF of the dynamic range expansion process based on whether or not it is higher than the screen average brightness by a predetermined threshold will be described with reference to FIG. The same parts as (1) are given the same reference numerals, and the description thereof is omitted.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 is configured such that the highest luminance among the luminances (luminances) for each divided area of the image of the current frame detected by the brightness detection unit 42 is a predetermined threshold value (for example, 2 to 2). 3EV) It is determined whether or not it is higher (step S19). In this embodiment, it was determined whether or not the highest brightness in the screen is higher than the screen average brightness by a predetermined threshold or more. However, the comparison with the highest brightness in the screen is not limited to the screen average brightness. Various indexes such as the average luminance at the center and the lowest luminance in the current frame image can be used. That is, the method is not limited to this as long as it is possible to determine whether or not there is a possibility that the divided area is saturated because the luminance of some of the divided areas in the screen is high.

  When the highest luminance is not higher than the screen average luminance by a predetermined threshold or more (NO in step S19), the D range control unit 43 controls the dynamic range expansion processing to OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  If the highest luminance is higher than the screen average luminance by a predetermined threshold or more (YES in step S19), the D range control unit 43 controls the dynamic range expansion process to be ON and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S15, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

  As described above, the still images shot as shown in (1) to (6) are added to the compression / decompression processing circuit 28, compressed in accordance with a predetermined compression format (for example, JPEG format), and then stored in the RAM 24. The image file is in a predetermined image recording format (for example, Exif format) and then recorded on the memory card 36 via the external memory I / F 34.

  According to the present embodiment, even when the brightness suddenly changes during through image shooting, such as when the sky enters the shooting range while shooting after chasing a bird, the shot image The change in brightness can be moderated. This is particularly effective when the brightness of the image changes quickly and the AE process cannot follow.

  Further, according to the present embodiment, when the shooting range includes a subject and a bright region, for example, when a bird and sky or snow are included in the shooting range, a bright region such as sky or snow is present. It is possible to capture a through image in which the subject can be surely seen without causing problems such as overexposure or darkening of the subject.

  In the present embodiment, the D range control unit 43 controls the ON / OFF of the dynamic range expansion process. However, in addition to the ON / OFF control of the dynamic range expansion process, the dynamic range expansion level (200% or 400%) % Or the like) may be controlled. In this case, it is only necessary to control the level of underexposure by always turning on the dynamic range expansion processing and changing the exposure correction value (for example, selecting 1 EV or 2 EV). Further, ON / OFF control of the dynamic range expansion processing and level control may be combined and executed.

  In this embodiment, the D range control unit 43 always controls ON / OFF of the dynamic range expansion process when shooting a through image. However, the dynamic range expansion process is controlled to be ON / OFF according to the shooting mode. May be. For example, the dynamic range expansion process may be turned on in portrait photography mode and sports photography mode, and the dynamic range expansion process may be turned off in night view photography mode, landscape photography mode, and the like. Furthermore, the dynamic range ON / OFF control based on the shooting mode may be combined with the dynamic range ON / OFF control based on the brightness of the subject image.

  In the present embodiment, when the S2 signal is input to the CPU 20 (step S10), a still image is captured with the exposure value obtained by the AE detection unit 41 at the time of through image capturing. However, the CPU 20 receives the S2 signal or S1. AE control may be performed again when the signal is turned on, and a still image may be captured with the exposure value obtained there.

  In the present embodiment, ON / OFF of the dynamic range expansion processing of the current frame image is controlled based on the brightness of the current frame image detected by the brightness detection unit 42. Not only the brightness but also the ON / OFF of the dynamic range expansion process of the current frame may be controlled based on the brightness of the image of the previous frame, for example.

  In the present embodiment, the AE process for capturing an image of the next frame is performed based on the brightness of the image of the current frame detected by the brightness detection unit 42. However, based on the brightness of the image of the current frame. The AE processing performed in this way is not limited to the image shooting for the next frame, but may be for the image shooting after two frames, for example. In addition, an image of a subsequent frame may be captured using the result of AE processing performed on a plurality of frames. Further, the AE process may be performed every five frames without performing the AE process on all the captured images.

<Second Embodiment>
In the first embodiment of the present invention, the brightness of a photographed image is detected, and ON / OFF of the dynamic range expansion process is controlled based on the detected brightness. The method for controlling OFF is not limited to this.

  In the second embodiment of the present invention, a face is detected from a captured image, and ON / OFF of dynamic range expansion processing is controlled based on the result. Hereinafter, the digital camera 2 according to the second embodiment will be described. In addition, the same code | symbol is attached | subjected about the part same as 1st Embodiment, and description is abbreviate | omitted.

  FIG. 8 is a block diagram showing an electrical schematic configuration inside the digital camera 2 which is the imaging apparatus of the second embodiment. As shown in FIG. 8, the digital camera 2 mainly includes an imaging unit 10 (an optical unit 11, an imaging element 12, an analog signal processing unit 13, an A / D converter 14, a digital signal processing unit 15, a motor driving unit 16, Timing generator (TG) 17), CPU 20, memory I / F (interface) 22, RAM 24, ROM 26, compression / decompression processing circuit 28, LCD I / F (interface) 30, LCD 32, external memory I / F (interface) 34, memory A card 36, a charging unit 38, a flash 40, an AE (automatic exposure) control unit 41, a brightness detection unit 42, a dynamic range (D range) control unit 43, a face detection unit 44, and the like.

  The face detection unit 44 extracts a face area in the image from the input image data in accordance with a command from the CPU 20, and detects the position (for example, the center of gravity of the face area). In this face area extraction, for example, skin color data is extracted from an original image, and a cluster of photometric points determined to be in the skin color range is extracted as a face. In addition, as a method for extracting a face area from an image, a method for determining a face area by converting photometric data into hue and saturation, creating a two-dimensional histogram of the converted hue / saturation, and analyzing it. Or a method for extracting a face candidate region corresponding to the shape of a human face and determining the face region from the feature amount in the region, extracting a human face outline from an image, and determining a face region, There are known methods for extracting a human face by preparing a template having the shape of a human face, calculating the correlation between the template and an image, and using the correlation value as a face candidate region. Can be extracted.

  Next, the operation of the digital camera 2 of the present embodiment configured as described above will be described. FIG. 9 is a flowchart showing the flow of shooting processing of the digital camera 2.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 determines whether or not a face is detected from the image of the current frame by the face detection unit 44 (step S20).

  When the face is not detected (NO in step S20), the D range control unit 43 determines whether the brightness of the divided area around the face is higher than the brightness of the divided area corresponding to the face by a predetermined threshold or more. Is determined (step S21).

  When the face is not detected (NO in step S20) and the brightness of the divided area around the face is not brighter than a predetermined threshold value than the brightness of the divided area corresponding to the face (NO in step S21), The D range control unit 43 controls the dynamic range expansion process to OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  If the brightness of the divided area around the face is higher than the brightness of the divided area corresponding to the face by a predetermined threshold or more (YES in step S21), the D range control unit 43 controls the dynamic range expansion process to ON. The result is output to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 weights and averages the brightness of each divided area based on the image signal obtained in step S6 or S7 so that the brightness of the divided area corresponding to the face is emphasized. Brightness (subject brightness) is detected, and an exposure value (photographing EV value) suitable for photographing is calculated (step S11). As a result, the face of the subject can be visually recognized more reliably, and a through image without overexposure or underexposure can be taken.

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S15, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

  According to the present embodiment, since the dynamic range expansion process is performed when a face is detected, even if the brightness suddenly changes due to sudden backlighting during through image shooting, the captured image It is possible to shoot a through image in which the change in brightness is gradual and the face of the subject can be reliably recognized.

  In this embodiment, ON / OFF of the dynamic range expansion process is controlled based on the difference between the brightness of the detection area corresponding to the face and the brightness of the detection area around the face. However, when a face is detected. May perform dynamic range expansion processing.

<Third Embodiment>
In the first embodiment of the present invention, the brightness of a photographed image is detected, and ON / OFF of the dynamic range expansion process is controlled based on the detected brightness. The method for controlling OFF is not limited to this.

  In the third embodiment of the present invention, a moving object is detected from a photographed image, and ON / OFF of dynamic range expansion processing is controlled based on the result. Hereinafter, the digital camera 3 according to the third embodiment will be described. In addition, the same code | symbol is attached | subjected about the part same as 1st Embodiment, and description is abbreviate | omitted.

  FIG. 10 is a block diagram showing an electrical schematic configuration inside the digital camera 3 which is the image pickup apparatus of the third embodiment. As shown in FIG. 10, the digital camera 3 mainly includes an imaging unit 10 (an optical unit 11, an imaging element 12, an analog signal processing unit 13, an A / D converter 14, a digital signal processing unit 15, a motor driving unit 16, Timing generator (TG) 17), CPU 20, memory I / F (interface) 22, RAM 24, ROM 26, compression / decompression processing circuit 28, LCD I / F (interface) 30, LCD 32, external memory I / F (interface) 34, memory A card 36, a charging unit 38, a flash 40, an AE (automatic exposure) control unit 41, a brightness detection unit 42, a dynamic range (D range) control unit 43, a main subject detection unit 45, a moving object detection unit 46, and the like. Yes.

  The main subject detection unit 45 extracts feature points such as the edges of the subject from the image data of the previous frame and the image data of the current frame. The subject edge extracted from the image data of the previous frame is compared with the edge of the subject extracted from the image data of the current frame, and if they match, the main subject detection unit 45 extracts the extracted edges. The subject is detected as the main subject. When a plurality of subjects are extracted, the main subject detection unit 45 detects the moving object having the largest size as the main subject.

  The moving object detection unit 46 detects whether or not the position of the main subject detected from the image data of the previous frame by the main subject detection unit 45 matches the position of the main subject detected from the image data of the current frame. . If the position of the main subject detected from the image data of the previous frame does not match the position of the main subject detected from the image data of the current frame, the moving object detection unit 46 determines the main object from the image data of the current frame. The subject is detected as a moving object.

  Next, the operation of the digital camera 2 of the present embodiment configured as described above will be described. FIG. 11 is a flowchart showing the flow of shooting processing of the digital camera 3.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 determines whether or not a moving object has been detected from the image of the current frame by the moving object detection unit 46 (step S23).

  If a moving object is detected (YES in step S23), the D range control unit 43 determines whether the brightness of the detection area other than the moving object is brighter than a predetermined threshold value than the brightness of the detection area corresponding to the moving object. (Step S24).

  If no moving object is detected (NO in step S23) and the brightness of the detection area other than the moving object is not brighter than a predetermined threshold value than the brightness of the detection area corresponding to the moving object (NO in step S24), D The range control unit 43 controls the dynamic range expansion process to OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  When the brightness of the detection area other than the moving object is brighter than the brightness of the detection area corresponding to the moving object by a predetermined threshold or more (YES in step S24), the D range control unit 43 controls the dynamic range expansion process to ON, The result is output to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  The AE detection unit 41 weights and averages the brightness of each divided area so that the brightness of the divided area corresponding to the moving object is emphasized based on the image signal obtained in step S6 or S7. Brightness (subject brightness) and an exposure value (photographing EV value) suitable for photographing is calculated (step S25). Thereby, a moving subject can be visually recognized more reliably, and a through image without overexposure or underexposure can be taken.

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S15, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

  According to the present embodiment, when a moving object, that is, a moving subject is detected as a main subject, the dynamic range expansion process can be reliably performed. As a result, even if the brightness of the shooting range suddenly changes due to panning or tilting operations, it is possible to shoot a through image that can moderately change the brightness of the shot image and reliably see the moving object. it can.

  In this embodiment, ON / OFF of the dynamic range expansion process is controlled based on the brightness difference between the moving object detection area and the other detection areas. However, when a moving object is detected, the dynamic range expansion process is performed. May be performed.

<Fourth embodiment>
In the first embodiment of the present invention, the brightness of a photographed image is detected, and ON / OFF of the dynamic range expansion process is controlled based on the detected brightness. The method for controlling OFF is not limited to this.

  In the fourth embodiment of the present invention, sky is detected from a captured image, and ON / OFF of dynamic range expansion processing is controlled based on the result. Hereinafter, the digital camera 4 according to the fourth embodiment will be described. In addition, the same code | symbol is attached | subjected about the part same as 1st Embodiment, and description is abbreviate | omitted.

  FIG. 12 is a block diagram showing an electrical schematic configuration inside the digital camera 4 which is the image pickup apparatus of the fourth embodiment. As shown in FIG. 12, the digital camera 4 mainly includes an imaging unit 10 (an optical unit 11, an imaging element 12, an analog signal processing unit 13, an A / D converter 14, a digital signal processing unit 15, a motor driving unit 16, Timing generator (TG) 17), CPU 20, memory I / F (interface) 22, RAM 24, ROM 26, compression / decompression processing circuit 28, LCD I / F (interface) 30, LCD 32, external memory I / F (interface) 34, memory A card 36, a charging unit 38, a flash 40, an AE (automatic exposure) control unit 41, a brightness detection unit 42, a dynamic range (D range) control unit 43, a sky detection unit 47, and the like.

  The sky detection unit 47 extracts a region having a brightness equal to or higher than a predetermined threshold as a sky candidate region based on the brightness of each divided area detected by the brightness detection unit 42. Next, the sky detection unit 47 uses the R / G and B / G signals generated by the white balance correction circuit included in the digital signal processing unit 15 to detect the R / G and B in the extracted bright region. Find the ratio of / G. Then, the sky detection unit 47 detects a sky blue region as sky based on the obtained ratios of R / G and B / G.

  Next, the operation of the digital camera 3 of the present embodiment configured as described above will be described. FIG. 13 is a flowchart showing the flow of shooting processing of the digital camera 3.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 determines whether or not sky is detected from the current frame image by the sky detection unit 47 (step S26).

  If no sky is detected (NO in step S26), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  When the sky is detected (YES in step S22), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9, and captures a still image subject image. (Step S10). The captured still image subject image is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14.

  The CPU 20 determines whether or not the screen average brightness is determined to be greater than or equal to a predetermined threshold value in step S15, that is, whether or not dynamic range expansion processing (step S7) has been performed (step S11).

  When the dynamic range expansion process (step S7) is not performed (NO in step S11), the D range control unit 43 controls the dynamic range expansion process to be OFF and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 processes the image signal of the subject image for the still image with a normal dynamic range (100%) (step S12).

  When the dynamic range expansion process (step S7) is performed (YES in step S11), the D range control unit 43 controls the dynamic range expansion process to ON and outputs the result to the CPU 20. The CPU 20 outputs an instruction to the digital signal processing unit 15, and the digital signal processing unit 15 performs image signal processing of a subject image for a still image by dynamic range expansion processing (for example, 200%) (step S13).

  The CPU 20 performs automatic white balance adjustment on the image signal obtained in step S12 or S13, and inputs it to the compression / decompression processing circuit. The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S14). As a result, a still image is taken.

  According to the present embodiment, when the sky is detected, that is, when the brightness range of the subject image is estimated to be wide, the dynamic range expansion process can be reliably performed.

  Further, according to the present embodiment, it is possible to shoot a through image in which the sky does not fly out and the subject can be visually recognized even when the shooting range includes a subject and a bright sky.

  In this embodiment, the presence / absence of sky detection is determined in step S26, and ON / OFF of the dynamic range expansion processing is controlled based on the result. However, when sky is detected, the brightness detection unit 42 It is also possible to separately detect the brightness of the area where the sky is detected and other areas, and control the ON / OFF of the dynamic range expansion process based on the brightness. For example, when the average brightness of the area where the sky is detected is larger than the average brightness of the other areas by a predetermined threshold or more, the dynamic range expansion process may be performed.

  The sky detection unit 47 detects a sky blue area as sky based on R / G and B / G in a bright area. However, the sky detection method is not limited to this, and is not limited to a bright area. The sky blue area may be detected based on B / G.

<Fifth embodiment>
In the first embodiment of the present invention, the brightness of a photographed image is detected, and ON / OFF of the dynamic range expansion process is controlled based on the detected brightness. The method for controlling OFF is not limited to this.

  In the fifth embodiment of the present invention, the sensitivity of a photographed image is detected, and ON / OFF of dynamic range expansion processing is controlled based on the result. Hereinafter, a digital camera 5 according to a fifth embodiment will be described. In addition, the same code | symbol is attached | subjected about the part same as 1st Embodiment, and description is abbreviate | omitted.

  FIG. 14 is a block diagram showing a schematic electrical configuration inside the digital camera 5 which is the imaging apparatus of the fifth embodiment. As shown in FIG. 14, the digital camera 5 mainly includes an imaging unit 10 (an optical unit 11, an imaging element 12, an analog signal processing unit 13, an A / D converter 14, a digital signal processing unit 15, a motor driving unit 16, Timing generator (TG) 17), CPU 20, memory I / F (interface) 22, RAM 24, ROM 26, compression / decompression processing circuit 28, LCD I / F (interface) 30, LCD 32, external memory I / F (interface) 34, memory A card 36, a charging unit 38, a flash 40, an AE (automatic exposure) control unit 41, a brightness detection unit 42, a dynamic range (D range) control unit 43, a sensitivity setting unit 48, a sensitivity detection unit 49, and the like. .

  The sensitivity setting unit 48 sets the sensitivity of the image sensor 12.

  The sensitivity detection unit 49 detects an appropriate sensitivity for shooting based on the brightness detected by the brightness detection unit 42.

  Next, the operation of the digital camera 2 of the present embodiment configured as described above will be described. FIG. 15 is a flowchart showing a flow of shooting processing of the digital camera 2.

  It is determined whether or not the first shooting is in the standby state (step S1). In the case of the first shooting (YES in step 1), the CPU 20 captures a through-image subject image with an exposure value corresponding to the measured subject brightness (step S2).

  If it is not the first shooting (NO in step 1), the CPU 20 captures a subject image for a through image with the exposure value obtained by the AE detection unit 41 in step S9 (step S3).

  The subject image for the through image captured in step S2 or S3 is added to the LCD I / F 30 via the analog signal processing unit 13, the A / D converter 14, the digital signal processing unit 15, and the compression / decompression processing circuit 28. It is converted into a display signal format and output to the LCD 32. Thereby, the photographed subject image is displayed on the LCD 32 as a through image (step S4).

  The D range control unit 43 determines whether the sensitivity detected by the sensitivity detection unit 49 is lower than the sensitivity set by the sensitivity setting unit 48 (step S27). For example, when the sensitivity is set to ISO 400 by the sensitivity setting unit 48 and photographing is performed with this sensitivity, when the sensitivity detected by the sensitivity detection unit 49 is ISO 100, the sensitivity detection unit 49 detects the sensitivity. It is determined that the sensitivity is lower than the sensitivity set by the sensitivity setting unit 48.

  If it is not determined that the sensitivity detected by the sensitivity detection unit 49 is lower than the sensitivity set by the sensitivity setting unit 48, that is, if the set sensitivity is appropriate (NO in step S27), D The range control unit 43 controls the dynamic range expansion process to OFF and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the normal dynamic range (100%) (step S6).

  If it is determined that the sensitivity detected by the sensitivity detection unit 49 is lower than the sensitivity set by the sensitivity setting unit 48, that is, if the set sensitivity is not appropriate (YES in step S27), the amount of light is large. Therefore, the D range control unit 43 controls the dynamic range expansion process to ON, and outputs the result to the CPU 20. The CPU 20 controls each unit so as to process the image signal of the current frame in the dynamic range expansion process (for example, 200%) (step S7).

  Then, the AE detection unit 41 detects the brightness of the subject (subject brightness) based on the image signal obtained in step S6 or S7, and calculates an exposure value (shooting EV value) suitable for shooting (step S8). ).

  It is determined whether the S2 signal is input to the CPU 20, that is, whether the photographer has fully pressed the shutter button (step S9). If the S2 signal has not been input to the CPU 20 (NO in step S9), the process returns to the step of capturing a through image subject image with the exposure value calculated in step S8 (step S3).

  When the S2 signal is input to the CPU 20 (YES in step S9), the CPU 20 determines in the D range control unit 43 that the screen average luminance is equal to or higher than the predetermined threshold in step S15, that is, the dynamic range expansion process. It is determined whether (Step S7) has been performed (Step S11).

  When the dynamic range expansion process (step S7) is not performed, that is, when the set sensitivity is appropriate (NO in step S11), the CPU 20 determines the exposure value obtained by the AE detection unit 41 in step S9, Further, the image sensor 12 is exposed with the sensitivity set by the current sensitivity setting unit 48 to capture a still image subject image (step S28).

  When the dynamic range expansion process (step S7) is performed, that is, when the amount of light is too large (YES in step S11), the CPU 20 issues an instruction to the sensitivity setting unit 48, and the sensitivity setting unit 48 is currently set. Set the sensitivity one level lower than the current sensitivity. Then, the CPU 20 exposes the image sensor 12 with the exposure value obtained by the AE detection unit 41 in step S9 and the sensitivity set again by the sensitivity setting unit 48, thereby capturing a subject image for a still image (step S9). S29). In the case of still images, it is necessary to shoot beautiful images with less noise, so there is a possibility that overexposure or underexposure may occur, but it is possible to respond by reducing the sensitivity without selecting the dynamic range expansion processing .

  The still image subject image captured in step S28 or S29 is input to the digital signal processing unit 15 via the analog signal processing unit 13 and the A / D converter 14. The digital signal processing unit 15 performs processing such as processing in a normal dynamic range (100%) and automatic white balance adjustment on the obtained image signal, and inputs the processed signal to the compression / decompression processing circuit 28. . The compression / decompression processing circuit 28 converts this digital signal into a luminance / color difference signal and outputs it to the RAM 24, and the RAM 24 stores the luminance / color difference signal (step S26). As a result, a still image is taken.

  According to the present embodiment, it is possible to reliably perform the dynamic range expansion process when the amount of light is too large.

  In the first to fifth embodiments, the shooting of a through image has been described as an example. However, the present invention can be applied to a moving image as well as a through image. Also, the first to fifth embodiments can be implemented in combination.

  Note that the application of the present invention is not limited to a digital camera, and can be similarly applied to an imaging device such as a mobile phone with a camera and a video camera, an endoscope, and the like. It can also be provided as a program applied to a device such as a digital camera.

1 is a block diagram showing an electrical configuration of a digital camera 1 to which the present invention is applied. 6 is a flowchart showing a flow of a process of controlling the ON / OFF of a dynamic range expansion process based on the amount of change in brightness between a current frame and a previous frame, which is a shooting process of the digital camera 1. It is a flowchart which shows the imaging | photography process of the said digital camera 1, Comprising: The flow of the process which controls ON / OFF of a dynamic range expansion process based on the width of the dispersion | variation in brightness. It is a flowchart which shows the flow of a process which is the imaging | photography process of the said digital camera 1, Comprising: ON / OFF of a dynamic range expansion process is controlled based on a screen average brightness | luminance. It is a flowchart which shows the imaging | photography process of the said digital camera 1, Comprising: The flow of the process which controls ON / OFF of a dynamic range expansion process based on the number of division areas of a bright part. It is a flowchart which shows the imaging | photography process of the said digital camera 1, Comprising: The flow of the process which controls ON / OFF of a dynamic range expansion process based on the product sum of a brightness | luminance and the number of divided areas. FIG. 10 is a flowchart showing a flow of processing for controlling ON / OFF of dynamic range expansion processing based on the luminance of the divided area having the highest luminance, which is the photographing processing of the digital camera 1. 1 is a block diagram showing an electrical configuration of a digital camera 2 to which the present invention is applied. 3 is a flowchart showing a flow of photographing processing of the digital camera 2; It is a block diagram which shows the electric constitution of the digital camera 3 to which this invention was applied. 3 is a flowchart showing a flow of photographing processing of the digital camera 3; It is a block diagram which shows the electric constitution of the digital camera 4 to which this invention was applied. 3 is a flowchart showing a flow of photographing processing of the digital camera 4; It is a block diagram which shows the electric constitution of the digital camera 5 to which this invention was applied. 3 is a flowchart showing a flow of photographing processing of the digital camera 5;

Explanation of symbols

1, 2, 3, 4, 5: digital camera, 10: imaging unit, 11: optical unit, 12: imaging device, 13: analog signal processing unit, 14: A / D converter, 15: digital signal processing unit, 16: Motor drive unit, 17: Timing generator (TG), 20: CPU, 22 memory I / F, 24: RAM, 26: ROM, 28: Compression / decompression processing circuit, 30: LCD I / F, 32: LCD, 34 : External memory I / F, 36: Memory card, 38: Charging unit, 40: Flash, 41: AE (automatic exposure) detection unit, 42: Brightness detection unit, 43: Dynamic range (D range) control unit, 44 : Face detection unit, 45: moving object detection unit, 46: main subject detection unit, 47: sky detection unit, 48: sensitivity setting unit, 49: sensitivity detection unit

Claims (3)

Imaging means for continuously imaging a subject and acquiring continuous image signals;
Brightness detection means for detecting the brightness of the subject based on the image signal acquired by the imaging means, and calculating an appropriate exposure value based on the detection result;
Sky detection means for detecting whether or not the subject image captured by the imaging means includes sky;
A determination unit that determines whether to perform dynamic range expansion processing based on the brightness of the subject detected by the brightness detection unit, and when the sky is detected by the sky detection unit, expands the dynamic range. A determination means for determining to perform processing;
If the determination means determines that the dynamic range expansion processing is performed, the appropriate exposure value is corrected to be underexposed by a predetermined exposure correction value from the appropriate exposure value, and a gamma curve corresponding to the exposure correction value is obtained. Dynamic range expansion processing means for correcting the gradation of the image signal imaged by the imaging means according to
If the determination means determines not to perform dynamic range expansion processing, the exposure is controlled based on the appropriate exposure value, and if it is determined to perform dynamic range expansion processing, it is based on the appropriate exposure value corrected by the exposure correction value. Exposure control means for controlling the exposure,
The brightness detection unit, when said determination means determines to perform the dynamic range expansion processing, and detects the brightness of the object based on an image signal gradation is corrected by the dynamic range expansion processing means, the An imaging apparatus, wherein the appropriate exposure value is calculated based on a detection result . Imaging means for continuously imaging a subject and acquiring continuous image signals;
Brightness detection means for detecting the brightness of the subject based on the image signal acquired by the imaging means, and calculating an appropriate exposure value based on the detection result;
Sensitivity setting means for setting the sensitivity of the imaging means;
A sensitivity detection means for detecting an appropriate sensitivity based on the brightness of the subject image detected by the brightness detection means;
A determination unit that determines whether to perform dynamic range expansion processing based on the brightness of the subject detected by the brightness detection unit , the sensitivity set by the sensitivity setting unit, and the sensitivity detection unit A determination unit that compares the detected sensitivity and determines that the dynamic range expansion process is performed when the sensitivity detected by the sensitivity detection unit is lower than the sensitivity set by the sensitivity setting unit ;
If the determination means determines that the dynamic range expansion processing is performed, the appropriate exposure value is corrected to be underexposed by a predetermined exposure correction value from the appropriate exposure value, and a gamma curve corresponding to the exposure correction value is obtained. Dynamic range expansion processing means for correcting the gradation of the image signal imaged by the imaging means according to
If the determination means determines not to perform dynamic range expansion processing, the exposure is controlled based on the appropriate exposure value, and if it is determined to perform dynamic range expansion processing, it is based on the appropriate exposure value corrected by the exposure correction value. Exposure control means for controlling the exposure,
The brightness detection unit, when said determination means determines to perform the dynamic range expansion processing, and detects the brightness of the object based on an image signal gradation is corrected by the dynamic range expansion processing means, the An imaging apparatus, wherein the appropriate exposure value is calculated based on a detection result . The determining means is imaging apparatus according to claim 1 or 2, wherein changing the exposure correction value based on the brightness of the detected using the brightness detection means subject.

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