JP2010147817A - Imaging apparatus, method and program for controlling same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable adequate exposure control in accordance with a face detected, even under the condition that luminance of an image changes rapidly, by preventing flickering caused by unstable photometric value of the detected face. <P>SOLUTION: The imaging apparatus executes exposure control depending on a photometric value corrected with amount of correction for the photometric values obtained from the complete area of the images picked up sequentially by computing the amount of correction in accordance with the photometric value obtained from the face area detected from the image. The imaging apparatus sets, in the computation and exposure control, a first time constant indicating response characteristic of the amount of correction for changes in the photometric values in the face area larger than a second time constant indicating response characteristic of the exposure control result for changes of the photometric values in the complete area of the image. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus, a control method thereof, and a program.

  2. Description of the Related Art Conventionally, an imaging apparatus such as a digital still camera or a digital camcorder has an automatic exposure control (AE) function that performs photometry based on a captured image and automatically determines the exposure based on the obtained photometric value. There is something to do. In this imaging device having the AE function, photometry is performed on a face area detected by face detection in a captured image so that a human face is properly exposed, and exposure control is performed in consideration of the obtained photometric value. There is something to do (Patent Document 1).

  Further, as an exposure control method for properly exposing a person's face, as shown in FIG. 4, only a photometric value of a person's face is acquired separately from a range (photometric frame) for acquiring a photometric value of the entire screen. There is a method of setting and using a face-only metering frame. As shown in FIG. 4, the face-specific photometry frame is set according to the position and face size of a person's face detected on the screen. In Patent Document 2, the face photometric value acquired from the face photometric frame is compared with the photometric value of the entire screen, and exposure control is performed using the larger photometric value, thereby appropriately controlling the exposure. A method has been proposed. As a result, when the photometric value of the face is brighter than that of the entire screen, exposure control based on the photometric value of the face is performed, so that overexposure of the face can be suppressed.

  In addition, as an exposure control method that uses the photometric value of the entire screen and the photometric value of the face, a correction amount (face correction value) necessary for properly converging the face exposure from the face photometric value is calculated. There is an exposure control method in which the face correction value is taken into consideration for the photometric value of the entire screen. However, in the exposure control method in which the face correction value is taken into consideration for the photometric value of the entire screen, as shown in FIG. 5, when the photometric value is acquired from the face position, the photometric value may become unstable. For example, because a person is not always facing the front, it is obtained from the photometry frame set for the face position by measuring light other than the part of the human skin that you want to measure, such as hair, or by changing the light source condition such as shade or sun. It is conceivable that the measured photometric value is not stable.

When exposure control is performed in which the face correction value calculated with the unstable face metering value is taken into account for the metering value of the entire screen, the metering value of the entire screen is not stable and does not converge. May flicker. Therefore, in order to prevent changes in the brightness of the entire screen due to instability of the photometric value of the face, the face detects the time constant of exposure control when performing exposure control that considers the face correction value to the photometric value of the entire screen. Responsiveness is slowed by making it larger than when it is not. Thereby, it is possible to absorb an unstable change in the photometric value of the face and prevent flicker due to a change in the brightness of the entire screen.
JP 2003-107555 A JP 2008-70562 A

  However, in the above prior art, when the face is detected, the time constant of exposure control is changed to a larger value, so that it has not been possible to cope with a sudden change in luminance of the entire screen due to a scene change or the like. For example, when a large luminance change suddenly occurs on the entire screen, a phenomenon occurs in which the exposure control of the entire screen cannot follow the luminance change because of the slow exposure control due to the time constant. As a result, it takes time until the exposure of the entire screen converges properly, and thus an image that is not properly exposed is displayed for a long time.

  The present invention has been made for the purpose of solving such problems of the prior art. An object of the present invention is to prevent flickering due to instability of a photometric value of a detected face when performing exposure control in consideration of the face of a subject, and to perform appropriate exposure even if an image brightness change suddenly occurs. An imaging apparatus that enables control, a control method thereof, and a program are provided.

  In order to achieve the above object, an imaging apparatus according to the present invention includes an imaging unit, a face detection unit that detects a human face region from an image captured by the imaging unit, the entire region of the image, and the face detection. Metering means for acquiring a photometric value from the face area detected by the means, and calculating means for calculating a correction amount for the photometric value acquired from the entire area of the image according to the photometric value acquired from the face area; Exposure control means for performing exposure control based on a photometric value obtained by correcting the photometric value acquired from the entire area of the image with the correction amount, and a response of the correction amount to a change in the photometric value of the face region The first time constant indicating the responsiveness is set to be larger than the second time constant indicating the responsiveness of the exposure control result to the change in the photometric value of the entire area of the image.

  According to the present invention, when exposure control is performed in consideration of the face of the subject, flicker due to instability of the photometric value of the detected face is prevented, and appropriate exposure can be achieved even if the brightness of the image suddenly changes. Control can be performed.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiments. Further, the embodiment of the present invention shows the most preferable mode of the invention, and does not limit the scope of the invention.

  FIG. 1 is a block diagram illustrating an example of a schematic configuration of an imaging apparatus 100 according to an embodiment of the present invention. As shown in FIG. 1, the imaging apparatus 100 is a so-called digital still camera, digital camcorder, or the like, and includes an imaging element 8 for capturing a subject image.

  The lens 1 guides light incident from the outside of the imaging device 100 to the inside of the imaging device 100. In FIG. 1, a single lens is illustrated in a simplified manner, but the lens 1 is usually composed of a plurality of lenses.

  The diaphragm 2 is a diaphragm blade that adjusts the amount of incident light. The aperture drive motor 3 drives the aperture 2 according to the drive power supplied from the aperture mechanism drive unit 13. The diaphragm state detection circuit 4 detects the driving state of the diaphragm 2 and outputs the detection result to the microcomputer 12. In the present embodiment, an imaging apparatus in which the diaphragm 2 is driven by the diaphragm drive motor 3 is illustrated, but an imaging apparatus with a fixed diaphragm or an imaging apparatus without a diaphragm may be used. Such an imaging apparatus does not need to be provided with the diaphragm drive motor 3 and the diaphragm state detection circuit 4.

  An ND filter 5 (ND: Neutral Density) attenuates light incident from the lens 1. The ND filter drive motor 6 drives the ND filter 5 according to the drive power supplied by the ND filter drive unit 15. The ND filter drive detection circuit 7 detects the drive state of the ND filter 5 and outputs the detection result to the microcomputer 12. In the present embodiment, an imaging device in which the ND filter 5 is driven by the ND filter drive motor 6 is illustrated, but an imaging device in which the ND filter 5 is fixed or an imaging device without the ND filter 5 may be used. Such an imaging apparatus does not need to provide the ND filter drive motor 6 and the ND filter drive detection circuit 7.

  The image sensor 8 images a subject by photoelectric conversion. The image sensor 8 used in the present embodiment may be a CCD (Charge Coupled Device), a CMOS (Complementary Metal Oxide Semiconductor) image sensor, or the like.

  The CDS / AGC circuit 9 samples and amplifies image information based on charges (image signals) stored in each pixel of the image sensor 8. In sampling, correlated double sampling (CDS) is performed, and in automatic amplification, automatic gain control (AGC) is performed.

  The A / D converter 10 converts the image information (analog signal) output from the CDS / AGC circuit 9 into a digital signal. The digital signal processing circuit 11 performs various signal processing on the image information (digital signal) output from the A / D converter 10.

  The microcomputer 12 is a circuit called a microcontroller or simply a controller, and comprehensively controls the operation of the imaging apparatus 100. For example, the microcomputer 12 receives various information such as luminance and color from the digital signal processing circuit 11 and performs various arithmetic processes. Details of the control performed by the microcomputer 12 will be described later.

  The aperture mechanism drive unit 13 supplies drive power to the aperture drive motor 3 based on control by the microcomputer 12. For example, the diaphragm mechanism driving unit 13 supplies driving power for narrowing or opening the diaphragm 2 under the control of the microcomputer 12 in accordance with the photometric value (luminance value) of the image captured by the image sensor 8. Thereby, in the imaging apparatus, it is possible to perform aperture adjustment so that an appropriate amount of light enters the imaging element 8.

  Based on the control by the microcomputer 12, the image sensor driving unit 14 supplies a drive pulse or the like for driving the image sensor 8 to the image sensor 8, and reads an image captured by the image sensor 8 and adjusts an exposure time. . For example, the image sensor drive unit 14 supplies drive pulses for exposing the image sensor 8 with a predetermined exposure time under the control of the microcomputer 12 in accordance with the photometric value of the image captured by the image sensor 8. Thereby, in the imaging device, it is possible to adjust the exposure time of the imaging element 8 according to the photometric value of the captured image and read the image.

  The ND filter drive unit 15 supplies drive power to the ND filter drive motor 6 based on control by the microcomputer 12. For example, the ND filter drive unit 15 generates drive power for increasing or decreasing the attenuation of light incident on the ND filter 5 by the control of the microcomputer 12 according to the photometric value of the image captured by the image sensor 8. Supply. Thereby, in the imaging device, it is possible to adjust the attenuation amount of the light incident on the imaging element 8 according to the photometric value of the captured image.

  In the case of an imaging device with a fixed aperture or an imaging device without an aperture, the aperture mechanism drive unit 13 may not be provided. Similarly, in the case of an imaging device with the ND filter 5 fixed or an imaging device without the ND filter 5, the ND filter driving unit 15 may not be provided.

  The face detection circuit 16 performs human face detection (face position and size) in the image from information of the entire image. Specifically, when an image after being sequentially captured by the image sensor 8 and processed by the digital signal processing circuit 11 is sequentially input from the microcomputer 12, the position of the person's face is in the entire area of the image. Or the size of the face area is detected. The detection result of the face area is output to the microcomputer 12.

  A known technique can be applied to the human face detection method in the face detection circuit 16 and is not directly related to the present invention. It should be noted that as a known face detection technique, a method based on learning using a neural network or the like, template matching is used to search a part having features in the shape of eyes, nose, mouth, etc. from an image. There is a method to consider that. In addition, many other methods have been proposed, such as a method that detects image feature amounts such as skin color and eye shape and uses statistical analysis. In general, a plurality of these methods are combined to improve face detection accuracy. Specific examples include a face detection method using wavelet transform and image feature amount as described in JP-A-2002-251380.

  The luminance information detection circuit 17 detects a photometric value based on digital image data output from the microcomputer 12. The luminance information calculation circuit 18 calculates and normalizes the photometric value detected by the luminance information detection circuit 17 and converts it into a photometric value that can be easily calculated by the microcomputer 12.

  The storage unit 19 is a RAM (Random Access Memory) or the like, and temporarily stores data. For example, the storage unit 19 temporarily stores image data after being captured by the image sensor 8 and processed by the digital signal processing circuit 11. The recording medium 20 is a semiconductor memory, an optical disk, or the like, and records image data and the like after being imaged by the image sensor 8 and processed by the digital signal processing circuit 11. Note that the recording of data on the recording medium 20 or the reading of the data recorded on the recording medium 20 is performed via an optical drive or a connection interface (not shown) that is driven under the control of the microcomputer 12. .

<Operation by conventional method>
In the operation of the imaging apparatus 100 according to the conventional method, when exposure control for appropriately correcting the photometric value of the face in the images sequentially captured by the image sensor 8 is performed under the control of the microcomputer 12, first, the subject to be imaged Is sensed by the image sensor 8. Then, the electric charge stored in each pixel of the image sensor 8 is output as an image signal in accordance with the drive pulse of the image sensor drive unit 14. The image signal output from the image sensor 8 is sampled and amplified by the CDS / AGC circuit 9. The image signal output from the CDS / AGC circuit 9 after sampling and amplification is converted into a digital signal by the A / D converter 10 and sent to the digital signal processing circuit 11.

  The digital signal processing circuit 11 performs various signal processing on the digital image signal output from the A / D converter 10. The microcomputer 12 sends the processing result (image signal) of the digital signal processing circuit 11 to the face detection circuit 16. The face detection circuit 16 detects the face position and face size of the person in the image based on the image signal output from the microcomputer 12, and outputs the detection result to the microcomputer 12.

  After that, when the face detection circuit 16 detects the face position and the face size of the person, the microcomputer 12 acquires the photometric value of the face position in the image. Get photometric value. Next, the microcomputer 12 outputs the photometric value of the face measured by the luminance information detecting circuit 17 to the luminance information calculating circuit 18, and the calculated and normalized face photometric value is calculated by the luminance information calculating circuit 18. At the same time, the microcomputer 12 also obtains photometric values for the entire area of the image from the luminance information detection circuit 17, and obtains photometric values for the entire area of the image calculated and normalized by the luminance information calculation circuit 18.

  Next, the microcomputer 12 calculates a difference value from a face target value set in advance so that the photometric value of the face properly converges. Thereafter, the microcomputer 12 calculates a face correction value from the calculated difference value, and adds the face correction value to the photometric value of the entire image. In the exposure control by the microcomputer 12, the photometric value of the entire image including the face correction value is converged to the preset target value of the entire image so that the exposure of the face becomes appropriate. Specifically, in the exposure control, the microcomputer 12 uses the exposure time of the image sensor 8 by the image sensor drive unit 14 and the aperture mechanism drive unit 13 so that the detected photometric value becomes a preset target value. The opening degree of the diaphragm 2 is controlled.

  At this time, the microcomputer 12 sets the exposure control time constant for the entire image to a larger value than when the face detection circuit 16 does not detect a human face, thereby changing the exposure amount due to exposure control. Reduce the amount. The time constant in exposure control is a value indicating how quickly the exposure amount, which is a controlled variable, changes per unit time with respect to the difference between the target photometric value and the current photometric value, that is, the response of exposure control. It is a value indicating sex.

  When this time constant is set to a large value, the change in the exposure amount with respect to the difference between the target photometric value and the current photometric value is slow, and the response is low. When this time constant is set to a small value, the exposure amount changes quickly with respect to the difference between the target photometric value and the current photometric value, and the responsiveness increases.

  For example, in the exposure control, the exposure amount is changed to converge to the target value according to the difference between the current photometric value and the target value. However, when the time constant is large, the change in the exposure amount is delayed. Therefore, it takes time to converge. On the other hand, when the time constant is small, the change in the exposure amount becomes faster, so that it converges immediately. Therefore, by setting the exposure control time constant to a large value, the exposure control does not become unstable even when a sudden brightness change occurs in the face of a person, but the brightness change of the image is abrupt. Appropriate exposure control is not possible when

<Operation in this embodiment>
In the operation of the imaging apparatus 100 according to the present embodiment, when exposure control for appropriately correcting the photometric value of the face in the images sequentially captured by the image sensor 8 is performed under the control of the microcomputer 12, first, imaging is performed. The image sensor 8 senses the subject. Then, the electric charge stored in each pixel of the image sensor 8 is output as an image signal according to the drive pulse of the image sensor drive unit 14. The image signal output from the image sensor 8 is sampled and amplified by the CDS / AGC circuit 9. The image signal output from the CDS / AGC circuit 9 after sampling and amplification is converted into a digital signal by the A / D converter 10 and sent to the digital signal processing circuit 11.

  The digital signal processing circuit 11 performs various signal processing on the digital image signal output from the A / D converter 10. The microcomputer 12 sends the processing result (image signal) of the digital signal processing circuit 11 to the face detection circuit 16. The face detection circuit 16 detects the face position and face size (face area) of the person in the image (all areas of the image) based on the image signal output from the microcomputer 12, and the detection result is detected by the microcomputer 12. Output to.

  After that, when the face detection circuit 16 detects the face position and the face size of the person, the microcomputer 12 acquires the photometric value of the face position in the image. Get photometric value. Next, the microcomputer 12 outputs the photometric value of the face measured by the luminance information detecting circuit 17 to the luminance information calculating circuit 18, and the calculated and normalized face photometric value is calculated by the luminance information calculating circuit 18. At the same time, the microcomputer 12 acquires the photometric value of the entire image from the luminance information detection circuit 17, and acquires the photometric value of the entire image calculated and normalized by the luminance information calculation circuit 18.

  Next, the microcomputer 12 calculates a difference value from a face target value (face area target photometric value) set in advance so that the face photometric value converges appropriately. Thereafter, the microcomputer 12 calculates a face correction value (correction amount) with a time constant larger than the exposure control time constant based on the calculated difference value, and uses the face correction value as a photometric value for the entire image. to add. In the exposure control by the microcomputer 12, the photometric value of the entire image including the face correction value is converged to the preset target value of the entire image so that the exposure of the face becomes appropriate.

  At this time, the exposure control of the entire image is a time constant different from the time constant used for calculating the face correction value (first time constant), and a time constant smaller than that time constant (second time constant). Constant) is used. In other words, the time constant indicating the responsiveness of the face correction value to the change in the photometric value of the face area is set larger than the time constant indicating the responsiveness of the exposure control result to the change of the photometric value of the entire area of the image. Yes.

  For example, in the exposure control of the entire image, a normal time constant is used without being affected by the presence or absence of detection of a human face. Then, by using a large time constant for calculating the face correction value in the exposure control of the entire image, even if the photometric value suddenly changes at the face position detected by the face detection circuit 16, the change in the face correction value The amount is reduced. Therefore, it is possible to perform stable exposure control that suppresses flickering with respect to changes in the brightness of the face. Even when a face of a person is detected by the face detection circuit 16, the exposure control for the entire image has a time constant smaller than the time constant of the face correction value (for example, a time constant that is not different from the normal time). ) Is used, it is possible to respond sensitively to changes in luminance of the entire image.

  In the present embodiment, as shown in FIG. 1, the configuration of all independent circuit units is shown. However, all or a part of the configuration may be configured in the microcomputer 12.

  Next, a control method performed by the microcomputer 12 in the imaging apparatus 100 of the present embodiment will be described with reference to FIGS. FIG. 2 is a flowchart illustrating a method for controlling the imaging apparatus 100 according to the embodiment of the present invention. Specifically, FIG. 2 shows exposure control in the imaging apparatus 100. FIG. 3A to FIG. 3D are diagrams showing actual operations in the present embodiment. Specifically, FIG. 3A is a diagram illustrating calculation of a difference between the face photometric value and the face target value. FIG. 3B is a diagram illustrating calculation of face correction values. FIG. 3C is a diagram illustrating the addition of the face correction value to the photometric value of the entire screen. FIG. 3D shows exposure control.

  As shown in FIG. 2, when the process is started, the microcomputer 12 acquires a photometric value of the entire screen imaged by the image sensor 8 in S101. Next, in S102, the microcomputer 12 calculates an evaluation value (target value) for exposure control from the acquired photometric value.

  Next, in S <b> 103, the microcomputer 12 determines whether or not a human face exists in the image captured by the face detection circuit 16. If the result of the determination in S103 is that a person's face does not exist in the captured image, the microcomputer 12 performs normal exposure control for the entire screen in S108 without performing processing related to the face correction value described later, The process ends.

  On the other hand, if the result of the determination in S103 is that a human face is present in the captured image, the microcomputer 12 advances the process to S104. Next, in S <b> 104, the microcomputer 12 sets a face photometric frame at the face position detected in S <b> 103 and acquires a photometric value in the set face photometric frame from the luminance information detection circuit 17. That is, in S104, the photometric value of the person's face in the captured image is acquired. If there are a plurality of faces detected in S103, photometric values of a plurality of faces may be acquired.

  Next, the microcomputer 12 calculates and normalizes the acquired photometric value by the luminance information calculation circuit 18, and calculates a face evaluation value (face target value) in S105. Next, in S106, the microcomputer 12 calculates a face correction value using a large time constant for the face.

  Specifically, in S106, as shown in FIG. 3A, the difference between the face target value set so that the face photometric value converges properly and the face photometric value is calculated. Thereafter, as shown in FIG. 3B, a face correction value using a large time constant for the face is calculated. That is, instead of adding the difference value with the face target value as the face correction value to the photometric value of the entire screen as it is, the face correction value with a small change amount with respect to time is added to the photometric value of the entire screen. To do. Thereby, it is possible to prevent the exposure control of the entire screen from becoming unstable due to a rapid change in luminance of the face.

  Next, in S107, the microcomputer 12 adds the face correction value calculated in S106 to the photometric value of the entire screen as shown in FIG. 3C (the photometric value of the face is in the minus direction from the face target value). Because there is a negative face correction value is added). Next, in S108, the microcomputer 12 performs exposure control so that the photometric value of the entire screen including the face correction value converges to the target value (evaluation value) of the entire screen so that the exposure of the face becomes appropriate. To.

  In conventional exposure control during face detection, the time constant of exposure control for the entire screen is increased and the amount of change in exposure is reduced, so that it converges to the appropriate exposure by switching scenes on the entire screen where the difference in brightness is large. It took time to do. On the other hand, in the exposure control of the entire screen in S108, the time constant of the exposure control is not changed regardless of the presence or absence of face detection.

  Therefore, even when a face is detected, the exposure control time constant is not changed to a large value, and the exposure is quickly and appropriately adjusted when the photometric value changes suddenly, such as when the scene changes. Can be converged. In addition, by setting the time constant for the face correction value and the time constant for exposure control of the entire screen individually, and making the time constant for the face correction value larger than the time constant for exposure control, face photometry Even if the value is unstable, exposure control with reduced flickering can be performed.

  Through the above-described series of processing of S101 to S108, the imaging apparatus 100 executes exposure control for the entire screen using the face correction value when a human face is detected.

  As described above, in the imaging apparatus 100, in order to make a person's face have proper exposure, the time constant for calculating the face correction value from the photometric value of the face is separated from the time constant for exposure control of the entire screen. The time constant for the face correction value is larger than the time constant for exposure control of the entire screen. This makes it possible to perform exposure control that suppresses flickering due to instability of the face's photometric value, and to quickly and properly converge the exposure even when the photometric value of the entire screen changes suddenly, such as when switching scenes. Exposure control can be performed. Therefore, in this embodiment, it is possible to perform stable exposure control that suppresses flickering with respect to a change in the brightness of the face as compared with the conventional method, and to perform exposure control that quickly and appropriately exposes the entire screen. Is possible.

  Note that the description in the above-described embodiment shows an example, and the present invention is not limited to this. The configuration and operation in the embodiment described above can be changed as appropriate.

(Other embodiments)
The above-described embodiment can also be realized in software by a computer of a system or apparatus (or CPU, MPU, etc.). Therefore, the computer program itself supplied to the computer in order to implement the above-described embodiment by the computer also realizes the present invention. That is, the computer program itself for realizing the functions of the above-described embodiments is also one aspect of the present invention.

  The computer program for realizing the above-described embodiment may be in any form as long as it can be read by a computer. For example, it can be composed of object code, a program executed by an interpreter, script data supplied to the OS, but is not limited thereto. A computer program for realizing the above-described embodiment is supplied to a computer via a storage medium or wired / wireless communication. Examples of the storage medium for supplying the program include a magnetic storage medium such as a flexible disk, a hard disk, and a magnetic tape, an optical / magneto-optical storage medium such as an MO, CD, and DVD, and a nonvolatile semiconductor memory.

  As a computer program supply method using wired / wireless communication, there is a method of using a server on a computer network. In this case, a data file (program file) that can be a computer program forming the present invention is stored in the server. The program file may be an executable format or a source code. The program file is supplied by downloading to a client computer that has accessed the server. In this case, the program file can be divided into a plurality of segment files, and the segment files can be distributed and arranged on different servers. That is, a server apparatus that provides a client computer with a program file for realizing the above-described embodiment is also one aspect of the present invention.

  In addition, a storage medium in which the computer program for realizing the above-described embodiment is encrypted and distributed is distributed, and key information for decrypting is supplied to a user who satisfies a predetermined condition, and the user's computer Installation may be allowed. The key information can be supplied by being downloaded from a homepage via the Internet, for example. Further, the computer program for realizing the above-described embodiment may use an OS function already running on the computer. Further, a part of the computer program for realizing the above-described embodiment may be configured by firmware such as an expansion board attached to the computer, or may be executed by a CPU provided in the expansion board. Good.

1 is a block diagram illustrating an example of a schematic configuration of an imaging apparatus according to an embodiment of the present invention. 3 is a flowchart illustrating a method for controlling the imaging apparatus according to the embodiment of the present invention. (A) is a figure showing calculation of the difference of a face photometric value and a face target value, (b) is a figure showing calculation of a face correction value, (c) is a photometric value of the whole screen. It is a figure showing addition of the face correction value of (d), and (d) is a figure showing exposure control. It is a figure which shows the relationship between the photometry frame of a face in the prior art, and the photometry frame of the whole screen. It is a figure which illustrates the state of the face in which the photometric value of a face becomes unstable in a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image pick-up device 1 Lens 2 Diaphragm 3 Diaphragm drive motor 4 Diaphragm state detection circuit 5 ND filter 6 ND filter drive motor 7 ND filter drive detection circuit 8 Image sensor 9 CDS / AGC circuit 10 A / D converter 11 Digital signal processing circuit 12 Microcomputer 13 Aperture mechanism drive unit 14 Image sensor drive unit 15 ND filter drive unit 16 Face detection circuit 17 Luminance information detection circuit 18 Luminance information calculation circuit 19 Storage unit 20 Recording medium

Claims (5)

Imaging means;
Face detection means for detecting a face area of a person from an image captured by the imaging means;
A photometric means for obtaining a photometric value from the entire area of the image and the face area detected by the face detecting means;
Calculation means for calculating a correction amount for the photometric value acquired from the entire area of the image according to the photometric value acquired from the face area;
Exposure control means for performing exposure control based on a photometric value obtained by correcting the photometric value acquired from the entire area of the image with the correction amount;
With
From the second time constant indicating the responsiveness of the exposure control result to the change of the photometric value of the entire area of the image, the first time constant indicating the responsiveness of the correction amount to the change of the photometric value of the face area. An imaging device characterized by increasing the size of the image pickup apparatus. The calculating means calculates the correction amount from a difference value between a target photometric value of the face area and a photometric value acquired from the face area;
The imaging apparatus according to claim 1, wherein the first time constant indicates responsiveness of the correction amount with respect to a change in the difference value.   The imaging apparatus according to claim 1, wherein the second time constant does not change depending on whether or not the face area is detected. A method for controlling an imaging apparatus having imaging means,
A face detection step of detecting a human face area from the image captured by the imaging means;
A photometric step of obtaining a photometric value from the entire region of the image and the face region detected in the face detection step;
A calculation step of calculating a correction amount for the photometric value acquired from the entire area of the image according to the photometric value acquired from the face area;
An exposure control step for performing exposure control based on a photometric value obtained by correcting the photometric value acquired from the entire area of the image with the correction amount;
Including
From the second time constant indicating the responsiveness of the exposure control result to the change of the photometric value of the entire area of the image, the first time constant indicating the responsiveness of the correction amount to the change of the photometric value of the face area. A method for controlling the imaging apparatus.   The program for making a computer perform each process of the control method of the imaging device of Claim 4.

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