JP4300936B2 - Imaging device - Google Patents

Description

  The present invention relates to an imaging apparatus. More specifically, the present invention relates to an imaging apparatus that can perform flash photography with an optimum light emission amount for a subject of a specific color.

  In the prior art, when shooting a low-luminance subject, in order to compensate for the shortage of the amount of light incident on the imaging device, shooting is performed by flashing the flash device (hereinafter referred to as flash shooting). It is determined by the distance to the subject.

  The distance to the subject is calculated based on the depth-of-field information used in the autofocus (AF) function, but when the focal length is short (the zoom lens is on the wide-angle side), the depth of field is There is a problem that deep and accurate subject distance information cannot be obtained.

  Therefore, in order to solve this problem, the flash device preliminarily emits light before taking an image, and the reflected light from the subject is detected and analyzed, so that the amount of light emitted at the time of photographing (hereinafter referred to as the amount of light emitted during actual photographing) is reduced. There is a technique of calculating (hereinafter, pre-dimming).

  In pre-dimming, an effective image frame of a photographed image is divided into blocks having a predetermined area, and the amount of reflected light from the subject during preliminary light emission is detected for each of the divided blocks (hereinafter referred to as detection frames). Each detection frame should match this characteristic based on characteristics such as a subject in the center of the effective image frame, a subject with a large area, and a subject with a close distance are likely to be the main subject. A large value of the weighting coefficient value is given to the detection frame, and the light emission amount of the main photographing is calculated based on the weighting coefficient value given to each detection frame and the detected reflected light amount.

  In addition, when flashing a person or the like, there is also a problem that the main subject cannot be identified and the subject cannot recognize which subject the flash emission amount is adjusted to.

Therefore, a non-flash image taken without flash emission and a flash image taken with flash emission are taken and compared, and the red-eye area detection unit detects a red-eye area in the flash image. An apparatus and method for detecting a person in an image by extracting a skin color area near the red-eye area detected by the red-eye detection section by the person-area detection section has been devised (for example, Patent Document 1).
JP 2003-30647 A (page 6-8, FIGS. 6 and 9)

  However, when shooting with flash, it is preferable to make the flash device emit light with an amount of light emitted so that a main subject such as a person has a proper exposure. Sometimes not done.

  For example, as shown in FIG. 10, the same person as the subject exists at the same position in the image frame 100A, one has a low background reflectance (FIG. 10A), and the other has a high background reflectance. In this case (FIG. 10B), when the flash device is preliminarily emitted and the amount of reflected light from the subject is detected and analyzed, the amount of reflected light is smaller when the reflectance of the background is higher, and the calculated main emission The amount increases with lower background reflectance.

  In such a case, the flash device should be able to shoot with the optimal exposure for the subject by calculating the amount of light emitted from the flash device based on the person who is the main subject. There is a problem that the value of the main light emission amount is affected by the reflectance, and the subject is not properly exposed.

  In addition, the above-mentioned Japanese Patent Application Laid-Open No. 2003-30647 discloses a non-flash image and a flash image taken by emitting a flash, compares both images, detects a person's red-eye region in the flash image, The skin color area in the vicinity of the detected red-eye area is extracted to identify the person in the image. In general, the red-eye is a certain condition in which the angle between the optical axis of the lens and the light of the person and the flash device is constant. This is a phenomenon that occurs when the condition is met.If this condition is not met, red eyes will not occur, so it is not always possible to identify a person such as when a person is sleeping or facing sideways. It is also difficult to detect this.

  Therefore, when performing flash photography, there is a problem that must be solved by determining a main subject and enabling photography with a light emission amount so that the determined subject has an appropriate exposure.

  In order to solve the above-described problems, an imaging apparatus according to the present invention is configured as follows.

(1) An image pickup apparatus that can take an image by emitting light from a flash device, and first image data that is taken without causing the flash device to emit light and second image data that is taken by making the flash device emit light. And the difference image generation means for generating the difference image data, and the imaging range of the image data is divided into measurement blocks of a predetermined area, and the reflected light amount of the image data and the difference image data for each measurement block Image data detection means capable of measuring the ratio of the specific color, and subject determination means for determining the presence or absence of a predetermined subject based on the ratio of the specific color of the difference image data measured by the image data detection means, When the predetermined object is determined by the object determining unit, a specific color coefficient value based on a specific color ratio of the difference image data is calculated for each measurement block Coefficient calculation means; and a light emission coefficient calculation means for calculating a light emission quantity coefficient value for determining the light emission quantity of the flash device for each measurement block based on the specific color coefficient value calculated by the specific color coefficient calculation means; A light emission amount calculating means for calculating a light emission amount of the flash device based on a reflected light amount of the second image data measured by the image data detection means and a light emission amount coefficient value calculated by the light emission coefficient calculation means; An imaging apparatus comprising: a light emission control unit that controls light emission of the flash device based on the light emission amount calculated by the light emission amount calculation unit.
(2) The imaging apparatus according to (1), wherein the difference image generation unit generates difference image data based on spectral characteristic data of the flash device stored in advance.
(3) The imaging apparatus according to (1), wherein the image data detection unit measures a specific color based on an imaging mode set according to a shooting condition and a scene.
(4) The light emission amount calculating means calculates the light emission amount of the flash device by performing a weighted average process on the reflected light amount of the second image data and the light emission amount coefficient value. The imaging device described.

(5) An image pickup apparatus capable of taking an image by emitting light from the flash device, wherein the first image data is taken without causing the flash device to emit light, and the second image data is taken by causing the flash device to emit light. And the difference image generation means for generating the difference image data, and the imaging range of the image data is divided into measurement blocks of a predetermined area, and the reflected light amount of the image data and the difference image data for each measurement block And a reflected light coefficient for calculating a reflected light coefficient value for each measurement block in accordance with the reflected light amount of the difference image data measured by the image data detecting means. A calculation unit; a subject determination unit that determines the presence or absence of a predetermined subject based on a ratio of a specific color of the difference image data measured by the image data detection unit; When the determination unit determines the predetermined subject, a specific color coefficient calculation unit that calculates a specific color coefficient value based on a ratio of the specific color of the difference image data for each measurement block; and the image data detection unit Based on a specific coefficient value preset in each measurement block, the reflected light coefficient value calculated by the reflection coefficient calculation means, and the specific color coefficient value calculated by the specific color coefficient calculation means, the flash light is measured for each measurement block. A light emission coefficient calculating means for calculating a light emission quantity coefficient value for determining a light emission quantity of the apparatus; a reflected light amount of the second image data measured by the image data detecting means; and a light emission quantity calculated by the light emission coefficient calculating means. A light emission amount calculating means for calculating the light emission amount of the flash device based on the coefficient value, and a light emission control for controlling the light emission of the flash device based on the light emission amount calculated by the light emission amount calculation means. Imaging apparatus characterized by comprising a means.
(6) The imaging apparatus according to (5), wherein the difference image generation unit generates difference image data based on spectral characteristic data of the flash device stored in advance.
(7) The imaging apparatus according to (5), wherein the image data detection unit measures a specific color based on an imaging mode set according to a shooting condition and a scene.
(8) The light emission amount calculating means calculates a light emission amount of the flash device by performing a weighted average process on the reflected light amount of the second image data and the light emission amount coefficient value. The imaging device described.

  With such a configuration, the first image data shot without emitting the flash device and the second image data shot with the flash device emitted are compared to generate difference image data, and the imaging range is set to a predetermined area. The difference image data is measured with the measurement blocks divided in step (b), the reflected light coefficient value corresponding to the amount of reflected light measured for each measurement block is calculated, and a predetermined color is measured based on the ratio of the specific color measured in each measurement block. The presence / absence of a subject is determined, and when a predetermined subject is determined, a specific color coefficient value based on the ratio of the specific color is calculated for each measurement block.

  At this time, the difference image data specifying the light source as the flash device can be obtained by generating the difference image data based on the spectral characteristic data of the flash device stored in advance.

  Then, a light emission amount coefficient value for determining the light emission amount of the flash device is calculated based on a specific coefficient value, a reflected light coefficient value, and a specific color coefficient value preset in each measurement block, and the second image data is reflected. The light emission amount of the flash device is calculated based on the light quantity and the light emission amount coefficient value, and the light emission control means controls the light emission of the flash device based on the light emission amount, so the imaging mode set according to the shooting conditions and scene It is possible to discriminate a subject of a specific color based on the above, and to control the flash device to emit light with a light emission amount suitable for the subject.

  The light emission amount calculating means calculates a light emission amount of the flash device by performing a weighted average process on the reflected light amount of the second image data and the calculated light emission amount coefficient value, thereby calculating the light emission amount calculated for each measurement block. The variation of the coefficient values is averaged, and the optimum light emission amount is calculated for the entire imaging range.

  During flash photography, the subject was photographed by emitting light (preliminary light emission) and a non-flash image photographed without emitting the flash device based on the spectral characteristic data of the flash device stored in advance before the actual photographing. By generating difference image data by comparing with the flash image, it is possible to remove the influence of external light at the time of shooting and obtain image data using only the light of the flash device as the light source, so accurate white balance correction As a result, the detection (measurement) of a specific color can be accurately performed.

  Further, the difference image data is detected (measured) by a detection frame (measurement block) obtained by dividing the imaging range by a predetermined area, and a predetermined subject (for example, according to the imaging mode) based on the ratio of a specific color in each measurement block (for example, When a predetermined subject is determined, a specific color coefficient value is calculated based on a specific color ratio for each measurement block, and light emission calculated in consideration of the specific color coefficient value The flash device's light emission amount is determined based on the coefficient value, and the flash device's light emission is controlled based on this light emission amount. Therefore, an object of a specific color corresponding to the imaging mode is detected, and the detected object is the optimum. This produces an excellent effect of being able to shoot with flash with a large amount of light emission.

  In addition, the light emission amount of the flash device is calculated by performing a weighted average process on the reflected light amount of the flash image taken by preliminary light emission and the above-described light emission amount coefficient value, so that the variation of the light emission amount coefficient value of each measurement block is changed. Since averaging is performed, there is an advantage that flash photography can be performed with an optimum light emission amount over the entire imaging range.

  Next, an embodiment of the imaging apparatus of the present invention will be described with reference to the drawings. However, the drawings are only for explanation, and do not limit the technical scope of the present invention.

  FIG. 1 is a block diagram illustrating a simplified configuration of the imaging apparatus 10, and includes a lens unit 11, a lens driver 12, an imaging element unit 13, an AGC circuit 14, an A / D conversion circuit 15, an image signal processing circuit 16, It comprises a detection circuit 17, a calculation unit 18, a light emitting circuit 19, a flash device 20, a memory 21, a recording unit 22, and the like.

  The lens unit 11 includes a diaphragm mechanism (iris) that limits the size of the lens and the opening of the lens and restricts the amount of incident light (signal). The lens unit 11 sends a lens driving signal and an iris sent from the lens driver 12. It operates according to the drive signal, adjusts the amount of light (signal) from the subject input via the lens by the diaphragm mechanism, and sends it to the image sensor section 13.

  The lens driver 12 generates a lens drive signal and an iris drive signal for controlling the lens unit 11 based on the lens control signal sent from the calculation unit 18 and sends the lens drive signal and the iris drive signal to the lens unit 11.

  The imaging element unit 13 is configured by an element such as a CCD (Charge Coupled Device), and in accordance with an electronic shutter control signal transmitted from the calculation unit 18, light (signal) transmitted from the lens unit 11 is converted into an image signal. (Analog signal) is converted and sent to the AGC circuit 14.

  The AGC circuit 14 adjusts the gain of the image signal (analog signal) converted by the image sensor unit 13 in accordance with the gain control signal sent from the calculation unit 18 and sends it to the A / D conversion circuit 15.

  The A / D conversion circuit 15 converts the image signal (analog signal) whose gain has been adjusted by the AGC circuit 14 into a digital signal and sends the digital signal to the image signal processing circuit 16.

  The image signal processing circuit 16 operates in cooperation with the arithmetic unit 18 and the memory 21 and adjusts and corrects the image signal converted into a digital signal by the A / D conversion circuit 15 (white balance adjustment, digital filter processing, (Aperture correction, gamma correction, etc.), etc., are subjected to predetermined signal processing, converted into predetermined image signals (luminance signal Y and color difference signal [RG] / [BG]), and detected by a detection circuit 17, an arithmetic unit 18, The data is sent to the memory 21 and the recording unit 22, and the adjustment amount / correction amount data (hereinafter referred to as correction data) when the image signal is adjusted or corrected is sent to the calculation unit 18. Further, the image signal stored in the memory 21 is read out and sent to the detection circuit 17, the calculation unit 18, and the recording unit 22.

  In the detection circuit 17, a detection frame for obtaining predetermined data necessary for controlling the light emission amount of the flash device 20 in accordance with the photographing mode or the like is set by the arithmetic unit 18, and the image signal processing circuit is set by this detection frame. 16 detects (measures) necessary data from the image signal (digital signal) sent from 16, and sends the detected measurement data to the calculation unit 18.

  The predetermined data necessary for controlling the light emission amount of the flash device 20 includes, for example, the amount of light reflected from the subject when shooting with the flash device 20 emitting light, and data of a specific color in the image signal.

  Specifically, as shown in FIG. 2A, a plurality of detection frames a to i in which an imaging range (hereinafter referred to as an effective image frame 100) is divided into blocks having a predetermined area are set, and FIG. As shown, the image signal sent from the image signal processing circuit 16 is detected (measured) in the set detection frames a to i, and the reflected light quantity and specific color of the image signal in the range corresponding to each detection frame are shown. The measurement data is sent to the calculation unit 18.

  For example, as shown in FIG. 2C, when the amount of reflected light when the flash device 20 is preliminarily emitted is detected (measured), the detection frame a → “20”, the detection frame b → “25”, and the detection frame c → "20", detection frame d → "130", detection frame e → "80", detection frame f → "25", detection frame g → "50", detection frame h → "60", detection frame i → " Measurement data such as 20 ″ is sent to the calculation unit 18.

  The calculation unit 18 generates various control signals based on the image signal (digital signal) and correction data sent from the image signal processing circuit 16 and the measurement data detected (measured) by the detection circuit 17, respectively. To the circuit.

  Specifically, a gain control signal for controlling the AGC circuit 14, an electronic shutter signal for controlling the imaging element unit 13, a lens control signal for controlling the lens driver 12, and a control for controlling the light emitting circuit 12 A flash control signal or the like is generated and sent to each circuit.

  The light emitting circuit 19 controls the light emission amount of the flash device 20 based on the flash control signal sent from the calculation unit 18.

  The flash device 20 emits a flash of a predetermined light emission amount for a predetermined time in accordance with the control of the light emitting circuit 19.

  The memory 21 has a function of storing an image signal (digital signal) sent from the image signal processing circuit 16 and reading out an image signal (digital signal) stored in accordance with the image signal processing circuit 16.

  The recording unit 22 records the image signal (digital signal) sent from the image signal processing circuit 16 on a recording device or a recording medium.

  Next, an operation when flash photography is performed by the imaging apparatus having the above-described configuration will be described with reference to the flowchart of FIG.

  When the release button is pressed to start shooting, the light input through the lens unit 11 is converted into an electric signal by the image sensor unit 13, and the gain of the electric signal is adjusted by the AGC circuit 14, and A / D It is converted into a digital image signal by the conversion circuit 15 and sent to the image signal processing circuit 16 (ST100).

  The image signal conversion circuit 16 performs signal processing such as white balance adjustment, digital filter processing, aperture correction, and gamma correction on the image signal sent from the A / D conversion circuit 15. The image signal converted into the luminance signal Y and the color difference signal [RG] / [BG] is sent to the detection circuit 17.

  In the detection circuit 17, the luminance signal Y of the image signal sent from the image signal processing circuit 16 is based on a detection frame set corresponding to the shooting mode (for example, portrait shooting mode, night scene shooting mode) or the like. The brightness level is detected (measured), and the detected value (hereinafter referred to as brightness level) is sent to the calculation unit 18.

  The calculation unit 18 determines whether or not the luminance level detected (measured) by the detection circuit 17 is a predetermined luminance level, that is, determines the brightness of external light at the time of shooting and causes the flash device 20 to emit light. Is selected (ST101).

  When the luminance level is equal to or higher than the predetermined luminance level, the process shifts to normal photographing operation control in which the flash device 20 is not caused to emit light (ST101 → ST200).

  When the brightness level is lower than the predetermined luminance level (or when the flash shooting is set by the user's setting operation), the calculation unit 18 detects the signal with the detection circuit 17 in order to execute the preliminary light emission operation by the flash device 20. Based on the (measured) brightness level, control values such as aperture diameter of the aperture mechanism, electronic shutter speed, and gain are calculated, and control signals (lens control signal, electronic shutter signal, gain control signal) corresponding to the calculated control values. Are transmitted to the lens unit 11, the image sensor unit 13, the AGC circuit 14 and the like (ST101 → ST102).

  In the lens unit 11, the image sensor unit 13, the AGC circuit 14, and the like, the aperture of the aperture mechanism and the speed of the electronic shutter according to control signals (lens control signal, electronic shutter signal, gain control signal) sent from the calculation unit 18. , Gain, etc. are set (ST102).

  When the aperture of the aperture mechanism, the speed of the electronic shutter, the gain, etc. are set in each part and each circuit, the shutter operation becomes possible. When the shutter operation is performed, first, the subject is photographed without causing the flash device 20 to emit light. Performed (ST103).

  An image photographed without causing the flash device 20 to emit light is processed by the image signal processing circuit 16 via the lens unit 11, the image sensor unit 13, the AGC circuit 14, and the A / D conversion circuit 15, and is stored as non-light emitting image data. 21 is stored.

  Subsequently, the flash device 20 emits light (preliminary light emission), and the subject is photographed (ST104).

  At this time, the light emitting circuit 19 causes the flash device 20 to emit light with a predetermined preliminary light emission amount necessary for obtaining data (a reflected light amount, a specific color, etc.) for calculating the optimum light emission amount of the flash device 20.

  An image photographed by preflashing the flash device 20 is processed by the image signal processing circuit 16 via the lens unit 11, the image sensor unit 13, the AGC circuit 14, and the A / D conversion circuit 15, and stored as preliminary light emitting image data. 21 is stored.

  It should be noted that the same values are set for the aperture of the aperture mechanism, the speed of the electronic shutter, and the gain, both when the flash device 20 is not emitting light and when the preliminary light is emitted. The aperture of the aperture mechanism is set so that when the flash device 20 is preliminarily fired and the subject is present at a short distance, the aperture is set so as not to cause a gradation failure, and in order to reduce the influence of external light as much as possible. The shutter speed is set to a high speed, and a lower gain is set to reduce noise in the image signal.

  At this time, the exposure timing and the timing of the light emission pulse for causing the flash device 20 to emit light are as shown in the time chart of FIG. 4, and the exposure time is designed to minimize the influence of external light according to the set speed of the electronic shutter. Time span.

  Next, the image signal processing circuit 16 reads the non-light emission image data and the preliminary light emission image data stored in the memory 21, compares the two image data in units of pixels, generates differential image data, and detects the detection circuit 17. (ST105).

  This difference image data is image data in which only the portion irradiated with the flash of the flash device 20 is extracted without the influence of external light at the time of shooting, in other words, when the light source is shot only with the flash device. Image data.

  Subsequently, the detection circuit 17 detects (measures) the difference image data calculated by the image signal processing circuit 16 using a detection frame (see FIG. 2) set corresponding to the imaging mode (ST106).

  First, by detecting (measuring) the luminance level of each detection frame, the amount of reflected light from the subject with respect to light emission (preliminary light emission) of the flash device 20 is obtained, and measurement data (hereinafter referred to as reflected light amount data) is sent to the calculation unit 18. To do.

  Similarly, for each detection frame, a specific color corresponding to the imaging mode or the like is detected (measured), and measurement data (hereinafter, specific color data) is sent to the calculation unit 18.

  The computing unit 18 calculates the reflected light coefficient value for each detection frame based on the reflected light amount data sent from the detection circuit 17 (ST107).

  The computing unit 18 also determines the ratio of the specific color to each detection frame based on the specific color data sent from the detection circuit 17, and the subject of the specific color exists in the photographed image. It is determined whether or not (ST108).

  Only when it is determined that the subject of the specific color exists, the specific color coefficient value for each detection frame is calculated (ST109).

  Next, the calculation unit 18 optimizes the light emission amount (hereinafter referred to as “main light emission amount”) for actual photographing of the subject based on the specific coefficient value, the reflected light coefficient value, and the specific color coefficient value set in each detection frame. The light emission amount coefficient value for determining the value is calculated (ST110).

  Subsequently, the main flash amount is calculated from the light emission amount coefficient value and the amount of reflected light from the subject (the amount of reflected light for each detection frame) when shooting with preliminary flash, and a flash control signal is generated based on the calculated main flash amount. Then, the light emitting circuit 19 is set (ST111).

  Then, the flash device 20 is caused to emit light based on the optimum light emission amount value set in the light emitting circuit 19, and the subject is actually photographed (ST112).

  Next, a determination method for determining a subject of a specific color in the flowchart of FIG. 3 described above will be specifically described.

  In the detection (measurement) of a specific color, it is assumed that “white balance correction” for correcting white so as to correctly capture white according to the color temperature that changes depending on the state of the light source in the shooting environment is performed correctly.

  Correct white balance correction means that when a white subject is photographed, the R [red] / G [green] / B [blue] levels of the image signal are the same, Fluorescent lamps, sunlight, and the like have non-uniform spectral characteristics, that is, R [red] / G [green] / B [blue] levels of each color component are non-uniform. In this case, an image with a large amount of B [blue] component is obtained, and an image becomes bluish as it is. Therefore, by increasing the gain of R [red] / G [green] by white balance correction, each color component (R [ (Red) / G [Green] / B [Blue]) are controlled to be equal to each other so that the subject color is corrected to be photographed as white.

  However, an output signal output from the image sensor unit 13 (an image sensor thereof), that is, each image signal converted into an R [red] / G [green] / B [blue] signal is a light source (R / G of the light source). / B) and the reflected light from the subject (each spectrum Rr / Gr / Br) is used as an input signal. Actually, various signals such as fluorescent lamps, incandescent lamps and sunlight are used. Since photographing is performed under a light source, the spectral characteristics of the light source are not known, and accurate white balance correction cannot be performed.

  For example, when a white subject is photographed with a reddish light source and when a red subject is photographed with a white light source, the output signal (image signal) from the image sensor unit 13 (the image sensor thereof) is exactly the same red. It is difficult to determine which color component should be adjusted when correcting the white balance.

  Here, if the spectral characteristics of the light source can be specified, when a white subject is photographed with a reddish light source, the G [green] / B [blue] component gain is increased because the light source is reddish. When a red subject is photographed with a white light source, the white balance can be appropriately corrected by equalizing the gains of R [red] / G [green] / B [blue] because the light source is white. .

  Therefore, according to the present invention, first, non-light-emitting image data (light source; external light) obtained by photographing the subject without causing the flash device 20 to emit light is stored in the memory 21, and then the flash device 20 is caused to emit light (preliminary light emission). Preliminary light emission image data (light source: outside light + light of the flash device 20) obtained by photographing the subject is stored in the memory 21, and the stored preliminary light emission image data and non-light emission image data are compared in pixel units to obtain a difference. Difference image data is generated.

  This difference image data is image data obtained by removing the influence of “external light” that is a light source of non-emission image data from “external light + light of the flash device” that is a light source of preliminary light emission image data. The light source of the image data is specified by the light from the flash device 20.

  The spectral characteristics (see FIG. 5A) of the flash device 20 are known in advance, and the same spectral characteristics are obtained whenever light is emitted. Further, since the spectral characteristics (see FIG. 5B) of the image sensor itself of the image sensor section 13 do not change, the spectral characteristics of the flash device 20 and the image sensor are stored in advance in the arithmetic unit 18 or the memory 21 as data. The image signal processing circuit 16 analyzes the spectral characteristics of the difference image data based on the spectral characteristic data stored in advance, and R [red] / G [green] / B [of the difference image data based on the analysis result. Adjust the gain of [Blue].

  That is, by specifying the light source as the flash device 20 and correcting the white balance, it is possible to correct the white balance accurately, and it is possible to accurately detect (measure) the specific color set according to the photographing mode.

  In this way, the difference image data generated by adjusting the white balance by the image signal processing circuit 16 is detected (measured) by the detection frame (see FIG. 2) corresponding to the imaging mode set in the detection circuit 17, and each In the case of a specific color corresponding to the photographing mode within the detection frame range, for example, portrait mode, the human skin color is detected (measured) as the specific color.

  The specific color to be detected (measured) by the detection circuit 17 is determined by the position (or range) in the color difference plane (two-dimensional coordinates in which the vertical axis is the color difference [RG] and the horizontal axis is the color difference [BG]). For example, in the color difference plane graph shown in FIG. 6, when the color corresponding to the upper left (second quadrant) range 200 is the specific color A, the difference image data (the color difference signal [RG] ] / [B−G]) is detected (measured), and specific color data indicating the ratio of the specific color A to each detection frame is sent to the calculation unit 18.

  When detecting (measuring) the skin color of a person as a specific color, the difference in skin color by race is almost within the same range (upper left of the graph; second quadrant) on the color difference plane graph, and the skin color by race There is little need to consider the difference.

  Then, the calculation unit 18 determines whether or not a specific color is detected (measured) in each detection frame based on the specific color data from the detection circuit 17, and specifies the range within the detection frame where the specific color exists. When the range occupied by the color occupies a range greater than or equal to a predetermined size, it is determined that a subject of a specific color exists (captured) in the detection frame.

  For example, when the specific color is skin color, in order to determine that the result of skin color detection is a person, the skin color part needs to have a certain size, and the detection circuit 17 is connected to each detection frame. The skin color portion is detected and the area is calculated and output to the calculation unit 18. When the area of the skin color portion in each detection frame is detected with a predetermined value or more, the calculation unit 18 detects the skin color portion within the corresponding detection frame. It is determined that there is a person.

  Next, the calculation process of the light emission amount (main light emission amount) of the flash device in the flowchart of FIG. 3 described above will be specifically described.

  The detection circuit 17, for the effective image frame 100 for the image signal (digital signal) captured as shown in FIG. 2A, is divided into a plurality of detection frames a˜ i is set, and each of the detection frames a to i is set with a unique weighting coefficient value (hereinafter referred to as a specific coefficient value).

  Usually, since a desired subject is often placed near the center of the effective image frame 100, for example, the largest weight is applied to the detection frame e in the center of the effective image frame 100 as shown in FIG. The coefficient value “20” is set, the weighting coefficient value “10” is set for the detection frames a, c, g, and i at the four corners, and the weighting coefficient value “15” is set for the other detection frames b, d, f, and h. Such unique weighting coefficient values are set.

  With such detection frames a to i, differential image data generated from the preliminary light emission image data and the non-light emission image data is detected (measured).

  In order to calculate the light emission amount (main light emission amount) of the flash device 20, first, the luminance level (luminance signal Y) of the difference image data in each of the detection frames a to i is detected (measured), and the light emission of the flash device 20 is performed. The amount of reflected light from the subject when (preliminary light emission) is obtained, detected (measured), and the amount of reflected light data is sent to the calculation unit 18.

  For example, as shown in FIG. 2C, the detection frame a → “20”, the detection frame b → “25”, the detection frame c → “20”, the detection frame d → “130”, and the detection frame e → “80”. Measurement data such as “, detection frame f →“ 25 ”, detection frame g →“ 50 ”, detection frame h →“ 60 ”, detection frame i →“ 20 ”is sent to the calculation unit 18.

  On the other hand, as described above, the difference image data (color difference signal [RG] / [BG]) is detected (measured) in each of the detection frames a to i, and the ratio indicating the ratio of the specific color with respect to each detection frame is specified. The color data is sent to the calculation unit 18.

  In the calculation unit 18, for each of the detection frames a to i, the reflection is a weight coefficient value for determining the main light emission amount of the flash device 20 at the time of photographing according to the reflected light amount data transmitted from the detection circuit 17. The light coefficient value is calculated.

  For example, when a large weight coefficient value is given to a detection frame with a large amount of reflected light based on the reflected light amount data in FIG. 2C, as shown in FIG. 7B, the detection frame a → “10”, Detection frame b → “10”, detection frame c → “10”, detection frame d → “20”, detection frame e → “15”, detection frame f → “10”, detection frame g → “12”, detection frame The weight coefficient values are h → “12” and detection frame i → “10”.

  In addition, the calculation unit 18 determines whether or not a specific color is detected (measured) in each detection frame a to i based on the specific color data transmitted from the detection circuit 17, and the specific color exists. When the range occupied by the specific color in the detection frame range occupies a range of a predetermined size or more, it is determined that the subject of the specific color exists in the detection frame and specified for the detection frames a to i. A specific color coefficient value that is a weight coefficient value corresponding to the color occupancy ratio is calculated.

  For example, when the shooting mode is portrait mode and the specific color is skin color, if a person and a bicycle image as shown in FIG. 2B are shot, as shown in FIG. In a detection frame e in which a face corresponding to a person's face, that is, a skin color of a specific color is detected, a weight coefficient value “30” is larger than in other detection frames, and in other detection frames, the detection frame e The small weight coefficient value is “10”.

  Subsequently, in order to determine the main light emission amount of the flash device 20 at the time of photographing, the calculation unit 18 determines each of the detection frames a to based on the intrinsic coefficient value, the reflected light coefficient value, and the specific color coefficient value (see FIG. 7). The light emission amount coefficient value for i is calculated.

  The light emission amount coefficient value is obtained by multiplying the intrinsic coefficient value corresponding to each detection frame, the reflected light coefficient value detected in each detection frame, and the specific color coefficient value.

  For example, in the case of the intrinsic coefficient value, reflected light coefficient value, and specific color coefficient value as shown in FIG. 8A, the detection frame e includes the specific coefficient value “20”, the reflected light coefficient value “15”, and the specific color. A light emission amount coefficient value “9000” obtained by multiplying the coefficient value “30” is calculated. Similarly, the other detection frames are light emission amount coefficient values calculated by multiplying the inherent coefficient value, the reflected light coefficient value, and the specific color coefficient value.

  Subsequently, when the calculation unit 18 calculates the light emission amount coefficient value of each detection frame a to i, the calculation unit 18 applies the light amount coefficient value and the reflected light amount data detected (measured) when preliminary light emission is performed to the flash device 20. A light emission target amount for emitting a desired light emission amount is calculated.

  The light emission target amount is obtained by first multiplying the light emission amount coefficient value in each detection frame a to i and the reflected (measured) reflected light amount data, and then adding each value calculated by this multiplication processing. The total value is calculated by performing a so-called weighted average process in which the total value is divided by the total value of the light emission amount coefficient values of the detection frames a to i. By this weighted average processing, variation in coefficient values of the detection frames a to i is averaged, and an appropriate emission target amount is calculated.

  In the case of the light emission amount coefficient value (see FIG. 8A) and the reflected light amount data (see FIG. 2C) as shown in FIG. 9A, for example, the detection frame e has a light emission amount coefficient value “9000”. And the reflected light coefficient value “80” are multiplied to calculate a value “720000”, and the other detection frames are similarly multiplied by the light emission amount coefficient value and the reflected light coefficient value to obtain a multiplication value (A). Calculated.

  Next, a total value “1413000” obtained by adding each value of the multiplication value (A) obtained by multiplying the light emission amount coefficient value and the reflected light coefficient value of each of the detection frames a to i is obtained. A light emission target amount “67.3” is calculated by dividing by the total value “21000” obtained by adding the light emission amount coefficient values of the detection frames a to i.

  When calculating the light emission target amount, the calculation unit 18 generates a flash control signal for controlling the light emission circuit 19 based on the light emission target amount, and sets the flash control signal in the light emission circuit 19. Based on the optimum light emission amount, that is, the light emission target amount, the flash device 20 is caused to emit light according to the set light emission amount, and the main photographing is performed.

It is the block diagram which simplified the structure which becomes main of the imaging device which concerns on this invention. It is explanatory drawing for demonstrating the detection frame set to the detection circuit of the imaging device shown in FIG. 2 is an operation flowchart of the imaging apparatus illustrated in FIG. 1. 2 is a time chart showing the exposure timing in the imaging apparatus shown in FIG. 1 and the timing of the light emission pulse of the flash device in a simplified manner. 2 is a graph schematically showing spectral characteristics of an imaging element of an imaging element unit and spectral characteristics of a flash device in the imaging apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram showing a simplified color difference plane as a reference when detecting (measuring) a specific color by the detection circuit of the imaging apparatus shown in FIG. 1. FIG. 2 is an explanatory diagram illustrating an example of a weighting coefficient value of a detection frame set in the detection circuit of the imaging apparatus illustrated in FIG. 1. It is explanatory drawing which showed schematically the calculation method of the light emission amount coefficient value. It is explanatory drawing which showed schematically the calculation method of the light emission target amount of a flash device. In prior art, it is explanatory drawing for demonstrating the difference in the emitted light amount of the flash device by the difference in the reflectance of a background.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10; Imaging device, 11; Lens part, 12: Lens driver, 13; Imaging element, 14; AGC circuit, 15; A / D conversion circuit, 16; Image signal processing circuit, 17; 19; Light emitting circuit, 20; Flash device, 21; Memory, 22; Recording unit 100; Effective image frame 200;

Claims (8)

An imaging device capable of shooting with a flash device emitting light,
Differential image generation means for comparing the first image data photographed without causing the flash device to emit light and the second image data photographed by causing the flash device to emit light, and generating the difference image data;
Image data detection means that divides the imaging range of image data into measurement blocks of a predetermined area, and can measure the amount of reflected light and the specific color of the image data and the difference image data for each measurement block;
Subject discriminating means for discriminating the presence or absence of a predetermined subject based on a ratio of a specific color of the difference image data measured by the image data detection means;
Specific color coefficient calculation means for calculating a specific color coefficient value based on a ratio of a specific color of the difference image data for each measurement block when the predetermined object is determined by the object determination means;
Based on the specific color coefficient value calculated by the specific color coefficient calculation means, a light emission coefficient calculation means for calculating a light emission quantity coefficient value for determining the light emission quantity of the flash device for each measurement block;
A light emission amount calculating means for calculating the light emission amount of the flash device based on the reflected light amount of the second image data measured by the image data detection means and the light emission amount coefficient value calculated by the light emission coefficient calculating means;
Light emission control means for controlling the light emission of the flash device based on the light emission quantity calculated by the light emission quantity calculation means;
An imaging apparatus comprising: The imaging apparatus according to claim 1, wherein the difference image generation unit generates difference image data based on spectral characteristic data of the flash device stored in advance. The imaging apparatus according to claim 1, wherein the image data detection unit measures a specific color based on an imaging mode set according to a shooting condition and a scene. 2. The imaging according to claim 1, wherein the light emission amount calculation unit calculates a light emission amount of the flash device by performing a weighted average process on the reflected light amount of the second image data and the light emission amount coefficient value. apparatus. An imaging device capable of shooting with a flash device emitting light,
Differential image generation means for comparing the first image data photographed without causing the flash device to emit light and the second image data photographed by causing the flash device to emit light, and generating the difference image data;
Image data detection means that divides the imaging range of image data into measurement blocks of a predetermined area, and can measure the amount of reflected light and the specific color of the image data and the difference image data for each measurement block;
Reflected light coefficient calculation means for calculating a reflected light coefficient value for each measurement block according to the reflected light amount of the difference image data measured by the image data detection means;
Subject discriminating means for discriminating the presence or absence of a predetermined subject based on a ratio of a specific color of the difference image data measured by the image data detection means;
A specific color coefficient calculating unit that calculates a specific color coefficient value based on a ratio of a specific color of the difference image data for each measurement block when the predetermined object is determined by the object determining unit;
Based on the specific coefficient value preset in each measurement block of the image data detection means, the reflected light coefficient value calculated by the reflection coefficient calculation means, and the specific color coefficient value calculated by the specific color coefficient calculation means, A light emission coefficient calculating means for calculating a light emission quantity coefficient value for determining the light emission quantity of the flash device for each measurement block;
A light emission amount calculating means for calculating the light emission amount of the flash device based on the reflected light amount of the second image data measured by the image data detection means and the light emission amount coefficient value calculated by the light emission coefficient calculating means;
Light emission control means for controlling the light emission of the flash device based on the light emission quantity calculated by the light emission quantity calculation means;
An imaging apparatus comprising: The imaging apparatus according to claim 5, wherein the difference image generation unit generates difference image data based on spectral characteristic data of the flash device stored in advance. The imaging apparatus according to claim 5, wherein the image data detection unit measures a specific color based on an imaging mode set according to a shooting condition and a scene. 6. The imaging according to claim 5, wherein the light emission amount calculating means calculates a light emission amount of the flash device by performing a weighted average process on the reflected light amount of the second image data and the light emission amount coefficient value. apparatus.

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