JP2010219606A - Device and method for white balance adjustment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and method for white balance adjustment, wherein the effect of stroboscopic light for white balance is estimated with high accuracy over the entire photographic image so as to accurately adjust the white balance of a photographed image, in stroboscopic photographing. <P>SOLUTION: The white balance adjustment device includes a color reproduction coefficient setting means 51 for estimating the color temperature of a light source illuminating an object and calculating the white balance coefficient of white balance adjustment, corresponding to the color temperature of the light source; a distance information detection part 200 for detecting distance information from an imaging apparatus to the object, in each image area where image data are formed in multiples, corresponding to the coordinates of pixels; and a white balance coefficient correction means 51c for specifying a main object area, on the basis of the distance information detected in the distance information detection part 200 for calculating the ratio Rs of the irradiation light quantity of a flash device 13 and environmental light quantity included in photographing light illuminating the main object area during photographing, and correcting the white balance coefficient on the basis of the calculated ratio Rs, and so on. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a white balance adjustment device and a white balance adjustment method in flash photography.

  2. Description of the Related Art Conventionally, in an imaging apparatus such as a digital camera, there is a technique for performing appropriate white balance control on a captured image obtained from a solid-state imaging device (for example, CCD: Charge Coupled Device or CMOS: Complementary Metal-Oxide Semiconductor). Are known.

  For example, in an imaging apparatus, a CCD sensor is constituted by a plurality of photoelectric conversion elements arranged two-dimensionally. On the surface of each photoelectric conversion element, for example, R (red), G (green), and B (blue) Any one of the color filters is provided, and is configured to generate and output an electrical signal corresponding to incident light transmitted through each color filter. Then, a color image reproduction unit provided at the subsequent stage of the CCD generates a color image using an electrical signal output from the CCD.

  When shooting, reflected light such as sunlight or illumination light is reflected through the subject, so the shot image is affected by the color temperature of the light source. Blue is produced in white, and red is produced when the color temperature is low. Therefore, a technique for adjusting white balance in order to reproduce appropriate white color under any light source is known.

  For example, in a digital camera, an imaging area close to an achromatic color is extracted from a color signal generated based on a shooting signal, and the gain of an amplifier for white balance adjustment is calculated based on the color information of the extracted imaging area. A technique for performing white balance control by adapting to temperature is disclosed (for example, see Patent Document 1).

  At this time, since it is difficult to accurately estimate the light source on a screen with many chromatic color areas, the screen is divided into a plurality of areas in advance, and an area close to an achromatic color is extracted for each divided area. .

  Also, in recent digital cameras, those equipped with a flash device such as a strobe (strobe is a trademark of Strobe Research Inc.) are generally used, and as a technique for adjusting white balance appropriately at the time of shooting, a strobe is used. Some have white balance adjustment values associated with the presence or absence of light emission and the shooting distance.

  For example, when a xenon tube is used for the light emitting part of the strobe device, white balance is adjusted to suppress blue in the entire screen in order to prevent the phenomenon that white objects are biased toward the blue side due to the strobe light. Is called.

  In strobe shooting, strobe light diffuses and attenuates as the distance from the subject increases. Therefore, for each pre-divided area of the shooting screen, the focus is adjusted to detect the distance to the subject, the degree of influence of the strobe light in each area is estimated according to the detected distance, and the white balance A technique for performing adjustment is disclosed (for example, see Patent Document 2).

JP 2003-224863 A Japanese Patent Laid-Open No. 7-301842

  However, according to the white balance adjustment technique described in Patent Document 2, the subject distance, the influence degree of the strobe light, and the like are estimated based on the predetermined degree of focus of the divided area. This estimation is not necessarily obtained with high accuracy, and there is room for further improvement. For example, when a plurality of subjects having different reflectivities are included in the shooting screen, the influence of strobe light changes depending on both the subject distance and the reflectivity.

  Further, according to the white balance adjustment technique described in Patent Document 2, since the subject distance is detected by using the focus function, each of the pairs is set to the number of areas in order to obtain the distance for each shooting area. Focus adjustment is necessary and the work may be complicated, and it is difficult to obtain distance information for each photographing region in an imaging apparatus that does not have a focus adjustment function.

  Therefore, the present invention provides a white balance adjustment device and white balance adjustment capable of accurately estimating the white balance of a photographed image by accurately estimating the influence of the strobe light on the white balance over the entire photographing screen in strobe photography. It aims to provide a method.

  In order to achieve this object, the invention according to claim 1 is directed to a flash means for irradiating a subject with a predetermined amount of light, and photoelectrically converting a photographed optical image for each pixel to output image data. A white balance adjustment device for adjusting a white balance of the image data in an imaging device comprising an imaging means, wherein the color temperature of a light source that illuminates the subject is estimated based on the image data, and is estimated White balance coefficient calculating means for calculating a white balance coefficient for white balance adjustment in association with the color temperature of the light source, and for each image region in which the image data is defined in a plurality in association with the coordinates of the pixel. Based on distance information detection means for detecting distance information from the imaging device for photographing the subject to the subject, and distance information detected by the distance information detection means. The main subject area is identified, and the ratio of the amount of light emitted from the flash means included in the photographing light that illuminates the subject area at the time of photographing and the amount of environmental light excluding the amount of illuminated light is calculated, and based on the calculated ratio And white balance coefficient correction means for correcting the white balance coefficient.

  According to the white balance adjusting device according to claim 1, distance information detection for detecting distance information from the imaging device to the subject for each image region in which image data is defined in plural in association with pixel coordinates. The main subject area is identified based on the distance information detected by the means and the distance information detection means, and the amount of light emitted from the flash means included in the photographing light that illuminates the main subject area at the time of photographing and the amount of environmental light excluding this amount of emitted light And a white balance coefficient correction means for correcting the white balance coefficient based on the calculated ratio, so that the white balance can be achieved in flash photography (hereinafter also referred to as strobe photography). Estimate the degree of influence of the light emitted from the flashing means (hereinafter also referred to as strobe light) with high accuracy over the entire screen and accurately determine the white balance of the captured image. It can be adjusted.

  Next, according to a second aspect of the present invention, in the white balance adjustment device according to the first aspect, the distance for detecting the distribution of the distance information on the photographing screen based on the distance information detected by the distance information detecting means. A distance detecting unit, a distance information defining unit that hierarchically defines the image data into a plurality of regions in association with the distribution of the distance information detected by the distance distribution detecting unit; and the distance information defining unit Main subject region selection means for selecting a main subject region from a plurality of regions defined in step (i), and the white balance coefficient correction means corrects the white balance coefficient by weighting the main subject region. It is characterized by.

  According to the white balance adjustment device of claim 2, based on the distance information detected by the distance information detection unit, the distance distribution detection unit that detects the distribution of the distance information on the photographing screen, and the distance distribution detection unit detects the distance information. In correspondence with the distribution of the distance information, distance information defining means for hierarchically defining image data into a plurality of areas, and selecting a main subject area from the plurality of areas defined by the distance information defining means And a white balance coefficient correction means configured to weight the main subject area and correct the white balance coefficient, so that the user can freely select white according to the distance information. It is possible to set a balance image area and improve convenience.

  Next, according to a third aspect of the present invention, in the white balance adjustment device according to the first or second aspect, the white balance coefficient correction unit is configured to perform the irradiation light amount and the environmental light amount for each of the plurality of regions. Is calculated, an average value of the calculated ratio is calculated, and the white balance coefficient is corrected in association with the calculated average value.

  According to the white balance adjusting device of the third aspect, the ratio of the irradiation light quantity and the environmental light quantity is calculated for each of the plurality of regions via the white balance coefficient correcting unit, and the average value of the calculated ratios is calculated. Since the calculation is performed and the white balance coefficient is corrected in association with the calculated average value, changes in the irradiation light quantity and the environmental light quantity can be reflected in the white balance adjustment.

  Next, the invention according to claim 4 is the white balance adjusting device according to any one of claims 1 to 3, further comprising preliminary light emitting means for performing preliminary light emission before the main photographing, wherein the distance information detecting means is Based on reference distance acquisition means for acquiring a reference value of distance information corresponding to a specific area in the shooting screen area and image data of the subject obtained by shooting without preliminary light emission, a predetermined number of pixels is set. Based on first luminance generation means for discretely sequentially generating a plurality of first luminances as a unit over a predetermined image area, and image data of the subject obtained by photographing with the preliminary light emission. Second luminance generating means for generating a plurality of second luminances each having the predetermined number of pixels as a unit so as to be paired with one luminance, and the first luminance from the second luminance for each unit. Subtract the preliminary light emission A luminance difference calculating means for calculating a luminance component of the light source, and for each unit, the first luminance and the luminance component of the irradiation light calculated in the luminance difference calculating procedure are respectively compared with a predetermined target luminance. Parameter generating means for generating first and second parameters by converting into distance information parameters, the first and second parameters, and an exposure value at the time of the preliminary light emission in the second luminance generation procedure. Based on the first distance information generating means for generating the first object distance information for each unit, and the reference value of the object distance information with respect to the first object distance information located in the specific area The first subject distance information is corrected using the correction value calculation means for calculating the difference between the first subject distance information and the correction value generated in the correction value calculation procedure for each unit. Second distance information generating means for generating , Characterized in that it comprises a.

  According to the white balance adjusting device of claim 4, first, a reference value of subject distance information corresponding to a specific region in the photographing screen region is obtained, and then a subject obtained by photographing without light emission of the flash device. Based on the image data, a plurality of first luminances each having a predetermined number of pixels as a unit are sequentially generated discretely over a predetermined image area, and then the image of the subject obtained by preliminary light emission of the flash device Based on the data, a plurality of second luminances are generated so as to be paired with the first luminance, and then the flash device irradiation is performed by subtracting the first luminance from the second luminance for each unit. The luminance component of light is calculated.

  Next, for each unit, the first luminance and the luminance component of the irradiation light calculated in the luminance difference calculation procedure are converted into distance information parameters by comparing with the predetermined target luminance, respectively. Two parameters are generated, and then first subject distance information is generated for each unit based on the first and second parameters and the exposure value at the time of flash device emission.

  Next, a difference in the reference value of the subject distance information is calculated for the first subject distance information located in the specific area, the first subject distance information is corrected using the calculated difference, and the second Subject distance information is generated. Accordingly, subject distance information (second subject distance information) can be measured in association with the first and second luminance coordinates discretely generated on the entire photographing screen.

  Accordingly, the white balance adjusting device according to claim 4 does not require focus adjustment so as to be paired with the number of regions for obtaining the distance for each photographing region. The work of white balance processing can be simplified. In addition, since the subject distance can be calculated in association with the luminance coordinates without being estimated based on the degree of focus of the divided area, the degree of influence of the strobe light in the white balance can be calculated with high accuracy, and white balance adjustment can be improved.

  Next, the invention described in claim 5 includes a flash unit that irradiates a subject with a predetermined amount of light, and an imaging unit that photoelectrically converts an optical image of the photographed subject for each pixel and outputs image data. A white balance adjustment method for adjusting a white balance of the image data in an imaging apparatus, wherein the color temperature of a light source that illuminates the subject is estimated based on the image data, and the color temperature correspondence of the estimated light source In addition, a white balance coefficient calculation procedure for calculating a white balance coefficient for white balance adjustment, and imaging for photographing the subject for each image area in which the image data is defined in plural in association with the coordinates of the pixel Based on the distance information detection procedure for detecting the distance information from the apparatus to the subject and the distance information detected by the distance information detecting means, the main subject region is specified and the photographing is performed. In this case, the ratio of the irradiation light amount of the flash means included in the photographing light that illuminates the main subject region and the environmental light amount excluding the irradiation light amount is calculated, and the white balance coefficient is corrected based on the calculated ratio. And a white balance coefficient correction procedure.

  According to the white balance adjustment method of claim 5, distance information detection for detecting distance information from the imaging device to the subject for each image area in which image data is defined in plural in association with pixel coordinates. The main subject region is identified based on the procedure and the distance information detected in the distance information detection procedure, and the amount of light emitted from the flash means included in the photographing light that illuminates the subject region at the time of photographing, and the amount of environmental light excluding this amount of emitted light The white balance coefficient correction procedure for correcting the white balance coefficient based on the calculated ratio is used, so that the flash (strobe) shooting is performed as in the first aspect of the invention. In this case, the influence of the light emitted from the flash means (so-called strobe light) in the white balance is estimated with high accuracy over the entire shooting screen, and the white balance of the shot image is calculated. Every time can be well-adjusted.

  Next, according to a sixth aspect of the present invention, in the white balance adjustment method according to the fifth aspect, the distance for detecting the distribution of the distance information on the photographing screen based on the distance information detected by the distance information detection procedure. A distance detection procedure, a distance information definition procedure for hierarchically defining the image data into a plurality of regions in association with a distribution of distance information detected by the distance distribution detection procedure, and the distance information definition procedure A main subject region selection procedure for selecting a main subject region from a plurality of regions defined in step (b), wherein the white balance coefficient correction procedure weights the main subject region to correct the white balance factor. It is characterized by.

  According to the white balance adjustment method of claim 6, based on the distance information detected by the distance information detection procedure, a distance distribution detection procedure for detecting a distribution of distance information on the photographing screen, and a detection by the distance distribution detection procedure The main subject area is selected from the distance information creation procedure that hierarchically defines the image data into a plurality of areas and the plurality of areas defined by the distance information creation procedure in association with the distribution of the distance information. The main subject area selection procedure is used, and the white balance coefficient is corrected by weighting the main subject area via the white balance coefficient correction procedure. Similarly, according to the distance information, the user can freely set an image area for white balance adjustment, and convenience can be improved.

  Next, according to a seventh aspect of the present invention, in the white balance adjustment method according to the fifth or sixth aspect, the white balance coefficient correction procedure includes the irradiation light amount and the environmental light amount for each of the plurality of regions. Is calculated, an average value of the calculated ratios is calculated, and the white balance coefficient is corrected in association with the calculated average value.

  According to the white balance adjustment method of claim 7, the ratio of the irradiation light quantity and the environmental light quantity is calculated for each of the plurality of areas through the white balance coefficient correction procedure, and the average value of the calculated ratios is calculated. Since the calculation is performed and the white balance coefficient is corrected in association with the calculated average value, the change in the irradiation light amount and the environmental light amount is used for the white balance adjustment as in the third aspect of the invention. Can be reflected.

  Next, the invention according to claim 8 is the white balance adjustment method according to any one of claims 5 to 7, further comprising a preliminary light emission procedure for performing preliminary light emission before the main photographing, wherein the distance information detection procedure includes: Based on a reference distance acquisition procedure for acquiring a reference value of distance information corresponding to a specific area in the shooting screen area and the image data of the subject obtained by shooting without the preliminary light emission, a predetermined number of pixels is set. Based on a first luminance generation procedure for discretely and sequentially generating a plurality of first luminances as a unit over a predetermined image region, and the image data of the subject obtained by photographing with the preliminary light emission, A second luminance generation procedure for generating a plurality of second luminances having the predetermined number of pixels as one unit so as to be paired with one luminance, and the first luminance from the second luminance for each unit. Subtract the preliminary light emission A luminance difference calculation procedure for calculating a luminance component of the light source, and for each unit, the first luminance and the luminance component of the irradiation light calculated in the luminance difference calculation procedure are respectively compared with a predetermined target luminance. To the parameter of the distance information to generate the first and second parameters, the first and second parameters, and the exposure value at the time of the preliminary light emission in the second luminance generation procedure. Based on the first distance information generation order for generating the first object distance information for each unit and the first object distance information located in the specific area, the reference value of the object distance information The first subject distance information is corrected using the correction value calculation procedure for calculating the difference between the first subject distance information and the correction value generated in the correction value calculation procedure for each unit, and the second subject distance information is obtained. A second distance information generation procedure to be generated; The use, characterized in that.

  According to the white balance adjusting method of the eighth aspect, similarly to the fourth aspect of the invention, each of the white balance adjustment methods is associated with the first and second luminance coordinates discretely generated on the entire photographing screen. , Subject distance information (second subject distance information) can be measured.

  Further, according to the white balance adjustment method described in claim 8, focus adjustment is not necessary so as to be paired with the number of regions for obtaining the distance for each photographing region. The work of white balance processing can be simplified compared to technology. In addition, since the subject distance can be calculated in association with the luminance coordinates without being estimated based on the degree of focus of the divided area, the degree of influence of the strobe light in the white balance can be calculated with high accuracy, and white balance adjustment can be improved.

  The white balance adjustment device and the white balance adjustment method of the present invention detect and detect distance information from an imaging device to a subject for each image area in which a plurality of image data is defined in association with pixel coordinates. The main subject area is identified based on the distance information, and the ratio of the amount of light emitted from the flashing means included in the photographing light that illuminates the main subject area at the time of shooting and the amount of environmental light excluding this amount of light is calculated. Since the white balance coefficient is corrected based on the ratio, the influence of the irradiation light (strobe light) on the white balance in flash photography (so-called strobe photography) The white balance of the captured image can be adjusted with high accuracy.

  Further, the white balance adjustment device and the white balance adjustment method of the present invention detect the distribution of distance information on the shooting screen based on the detected distance information, and associate the image data with the detected distribution of distance information. It is configured to hierarchically define multiple areas, select the main subject area from the defined areas, and weight the main subject area to correct the white balance coefficient. Accordingly, the user can freely set an image area for white balance adjustment, and convenience can be improved.

  Further, the white balance adjustment device and the white balance adjustment method of the present invention calculate the ratio between the irradiation light amount and the environmental light amount for each of a plurality of regions, calculate the average value of the calculated ratio, and calculate the average Since the white balance coefficient is corrected in association with the value, changes in the irradiation light amount and the environmental light amount can be reflected in the white balance adjustment.

  In addition, the white balance adjustment apparatus and the white balance adjustment method of the present invention associate the subject distance information (second object) with each of the first and second luminance coordinates discretely generated on the entire shooting screen. This is the object distance information), and the focus adjustment is not required so as to be paired with the number of areas for obtaining the distance for each photographing area, so that the work of white balance processing can be simplified. In addition, since the subject distance can be calculated in association with the luminance coordinates without being estimated based on the degree of focus of the divided area, the degree of influence of the strobe light in the white balance can be calculated with high accuracy, and white balance adjustment can be improved.

It is a block diagram showing the structure of the imaging device using the white balance adjustment apparatus of one Example of this invention. It is explanatory drawing which detects distribution of the distance information of the imaging | photography screen in the white balance adjustment apparatus of the Example. It is explanatory drawing which calculates the average value of ratio of the irradiation light quantity and environmental light quantity in the white balance adjustment apparatus of the Example. It is explanatory drawing of the to-be-photographed object distance information generation apparatus in the white balance adjustment apparatus of the Example. It is the Bayer array image data output from the imaging unit in the white balance adjustment apparatus of the embodiment. In the white balance adjustment apparatus of the embodiment, (a) is a graph showing information stored in the reference light source storage means on xy chromaticity coordinates, (b) is an explanatory diagram of evaluation area division of the block integration means, (C) is explanatory drawing of the color reproduction process of a color correction part. It is explanatory drawing which calculates a white vance coefficient and a color reproduction coefficient from xy chromaticity coordinates of the color reproduction coefficient calculation means in the white balance adjustment apparatus of the embodiment. It is explanatory drawing showing the procedure of the white balance adjustment method of one Example of this invention. It is a flash program diagram in the imaging device of the embodiment. It is explanatory drawing showing the detail of the procedure of distance information calculation for every block in the flowchart of FIG.

As shown in FIG. 1, the imaging apparatus 1 uses an imaging unit 100 that captures a subject (imaging signal S) and outputs a digital image signal (image data), and a digital image signal input from the imaging unit 100. A distance information detection unit 200 that detects distance information for each image region, an image processing unit 300 that generates a color image based on a digital image signal, and a white balance correction coefficient based on distance information detected by the distance information detection unit 200 A white balance coefficient correction means 50 for calculating the light intensity, an exposure setting unit 42 for adjusting the amount of incident light and the amount of light emitted from the flash device 13, a CPU 40, a ROM 41, and the like. The CPU 40 controls each function of the imaging device 1 in cooperation with the ROM 41. To do.
Note that the function of the white balance adjusting device according to the present invention is expressed by the distance information detection unit 200, the white balance coefficient correction unit 50, the image processing unit 300, the CPU 40, the ROM 41, and the like.

  The imaging unit 100 includes a front lens 2 that guides subject light into the imaging unit 100, an iris (aperture) 3, a focus lens 5, a shutter 6, and a filter that removes harmful infrared rays, reflected light, and the like (infrared removal filter and optical). 7 is an image sensor (CCD: Charge Coupled Devices) 8, AFE (Analog Front End) 9 which converts an analog image signal output from the image sensor 8 into a digital image signal, and outputs Iris 3. The Iris drive unit 15, the detection unit 16 that detects the drive amount of Iris 3 through the sensor 16a, the focus drive unit 17 that performs slide drive in the optical axis direction of the focus lens 5, and the slide amount of the focus lens 5 through the sensor 18a. The detection unit 18 to detect, the image sensor 8 and the AFE 9 are TG (Timing Generator) 19 for controlling the period, and the like are provided.

  In addition, the imaging unit 100 includes a flash device (for example, a strobe) that irradiates a subject with a predetermined amount of light, and a reference distance detection that detects a distance from the imaging unit 100 to the subject in association with a specific region of the imaging region. Means 14, etc. are provided. The imaging device 1 first performs preliminary light emission toward the subject using the flash device 13 before photographing the subject, and the distance to the subject and the irradiation light of the flash device 13 via the distance information detection unit 200. The reflectance of the subject is measured, and the exposure amount at the time of actual photographing is set based on the measurement results.

  The imaging element 8 is configured such that a plurality of photoelectric conversion elements are arranged in a matrix, and the imaging signal S is photoelectrically converted for each photoelectric conversion element to output an analog image signal. Specifically, as shown in FIG. 5, the light receiving surface of the image sensor 8 is provided with a color filter made up of a Bayer array of R (red), G (green), and B (blue) in association with each pixel. The signal output from each pixel has information for one color that has passed through the filter of each color. In FIG. 5, G located beside R is represented as Gr, and G located beside B is represented as Cb.

  The AFE 9 is a correlated double sampling circuit (CDS: Correlated Double Sampling) 10 that removes noise from an analog image signal output via the image sensor 8, and an image that has been correlated double sampled by the correlated double sampling circuit 10. A variable gain amplifier (AGC) 11 that varies the ISO sensitivity (SV) by amplifying the signal, and an analog image signal from the image sensor 8 input via the variable gain amplifier 11 is converted into a digital image signal. An image signal configured by the A / D converter 12 and the like and output from the image sensor 8 is converted into a digital image signal (hereinafter also referred to as a pixel signal) at a predetermined sampling frequency and output to the preprocessing unit 20. To do.

The reference distance detection unit 14 focuses when an appropriate focus degree is obtained in a specific area of the image area (in the present embodiment, the position B in FIG. 4A and the center of the screen). In association with the position information of the lens 5, a reference distance (so-called reference value of subject distance information in the present invention) DV _(base) from the focus lens 5 to the subject is detected. In the present embodiment, DV _(base) is an APEX value based on a distance of 1 m, and an actual distance L is calculated using an expression of DV _(base) = LOG ₂ (distance L / 1 m). Has been converted.

  The reference distance detection unit 14 is configured to detect the reference distance to the subject using the principle of triangulation or the like based on the reflected light from the subject corresponding to the specific area instead of the position information of the focus lens 5. May be. In this embodiment, the specific area when detecting the reference distance to the subject will be described as the position of the center of the screen (the position B in FIG. 4A). For example, in FIG. Other positions such as the position of A and the position of C may be selected according to the shooting conditions. The function of the reference distance acquisition means in the present invention is expressed by the reference distance detection means 14.

  Note that the imaging unit 100 may be configured using a CMOS (Complementary Metal Oxide Semiconductor) sensor instead of the imaging device 8, the correlated double sampling circuit 10, the variable gain amplifier 11, the A / D converter 12, and the like. .

  Next, the image data output from the imaging unit 100 is input to the distance information detection unit 200 and the image processing unit 300 via the preprocessing unit 20.

  A pre-processing unit (IFP: Image Front Processor) 20 offsets a dark current for each digital image signal output from the imaging unit 100. Specifically, the digital image signal output from the A / D converter 12 is acquired at a timing at which the amount of light is not incident on the image sensor 8, and the acquired digital image signal is used as the dark current offset value.

  The preprocessing unit 20 sets an effective pixel range of the image sensor 8 in the entire pixel range. Specifically, the degree of light and darkness and distortion of the image output in all the pixel areas are detected, and the allowable range is set as the effective pixel range. At this time, the effective pixel range has a rectangular shape corresponding to the screen of the display device (monitor or television receiver).

  Next, the distance information detection unit 200 generates a luminance signal with a predetermined number of pixels as a unit based on the digital image signal input from the imaging unit 100, and the luminance signal generation unit 21 generates the luminance signal. A luminance buffer 22 that stores the received luminance signal in association with the presence or absence of preliminary light emission, a strobe light luminance calculation means 25 that calculates a luminance signal of only the flash device 13 from the luminance signal with or without preliminary light emission, and subject distance information for each luminance coordinate Luminance coordinate distance information generation means 26 to be generated, reflectance calculation means 32 to calculate the reflectance of the subject for each luminance coordinate, subject distance information and reflectance calculation means for each luminance coordinate generated by the luminance coordinate distance information generation means 26 A control program that is configured by a recording unit 33 that records the reflectivity and the like for each luminance coordinate calculated in 32, and that is stored in the ROM 41 by the CPU 40. Therefore, to control the processes of the distance information detecting unit 200. The function of the distance information detection unit in the present invention is expressed by the distance information detection unit 200, the reference distance detection unit 14, and the like. The function of the preliminary light emission means in the present invention is expressed by the flash device 13.

  The luminance generation means 21 scans the digital image signal output from the AFE 9 and generates a luminance signal with four pixel signals of two pixels in the horizontal direction and two pixels in the vertical direction as a unit. As a result, a plurality of luminance signals are generated in a matrix in the imaging region, and each luminance signal is stored in the luminance buffer 22 in association with the unit of luminance coordinates (for example, the central coordinates of four pixels). Is done. Note that one unit for generating the luminance signal is not limited to two horizontal pixels and two vertical pixels, and may be set so that the luminance signal can be generated in a matrix in the imaging region.

The luminance buffer 22 is associated with presence / absence of preliminary light emission of the flash device 13, and stores a luminance signal (Ya _{(h, v)} ) obtained by photographing without preliminary light emission for each luminance coordinate. And a second luminance buffer 24 for storing a luminance signal (Yc _{(h, v)} ) obtained by photographing with preliminary light emission.

The strobe light luminance calculating means 25 stores the luminance signal (Yc _{(h, v)} ) stored in the second luminance buffer 24 for each luminance coordinate from the first luminance buffer 23 using (Equation 1). The luminance signal (Yb _{(h, v)} ) of only the strobe light at the time of preliminary light emission is calculated by subtracting the luminance signal (Ya _{(h, v)} ).
(Formula 1) Yb _{(h, v)} = Yc _{(h, v)} −Ya _{(h, v)}
Note that the subscripts _{(h, v} ) of Ya, Yb, and Yc in (Expression 1) represent luminance coordinates in the horizontal direction and the vertical direction of the imaging region. Note that the function of the brightness difference calculating means in the present invention is expressed by the strobe light brightness calculating means 25.

Next, the luminance coordinate distance information generating unit 26 uses, for each luminance coordinate, the luminance signal Ya stored in the first luminance buffer 23 and a predetermined luminance signal Yt that is set in advance using (Equation 2). The first parameter calculation unit 27 that calculates the first parameter MVa of the distance information based on the ratio, and the strobe light luminance Yb calculated by the strobe light luminance calculation unit 25 using (Equation 3) and a predetermined luminance A second parameter calculation unit 28 for calculating a second parameter MVb of the distance information based on the ratio to the signal Yt.
(Formula 2) MVa _{(h, v)} = LOG ₂ (Ya _{(h, v)} / Yt)
(Formula 3) MVb _{(h, v)} = LOG ₂ (Yb _{(h, v)} / Yt)
The function of the parameter generation means in the present invention is expressed by the first parameter calculation unit 27 and the second parameter calculation unit 28.

Further, the luminance coordinate distance information generating means 26, for each luminance coordinate, as shown in FIG. 4B from the first parameter MVa, the second parameter MVb, the exposure condition at the time of preliminary light emission, etc. A first distance information calculation unit 29 that calculates first subject distance information (DX _{(h, v)} ) for each luminance coordinate, as shown in FIG. A correction value calculation unit 30 that calculates a difference OFFSET of a reference value (DV _(base) ) of the subject distance with respect to the reference value, as shown in FIG. 4D, using the correction value OFFSET calculated by the correction value calculation unit 30. A second distance information calculation unit 31 that corrects the first subject distance information (DX _{(h, v)} ) and calculates the second subject distance information (DV _{(h, v)} ) is provided. The function of the first distance information generating unit in the present invention is expressed by the first distance information calculating unit 29, and the function of the correction value calculating unit in the present invention is expressed by the correction value calculating unit 30, The function of the second distance information generation means is expressed by the second distance information calculation unit 31.

Specifically, the first distance information calculation unit 29 calculates first subject distance information (DX _{(h, v)} ) for each luminance coordinate using (Equation 4).
(Formula 4) (DX _{(h, v)} ) = (MVa _{(h, v)} -MVb _{(h, v)} ) / 2- (5-TV-GV) / 2

  In (Expression 4), (5-TV-GV) in the term on the right-hand side is a parameter group representing the exposure conditions for preliminary light emission, where TV is the APEX value of the shutter speed, and GV is the preliminary light emission guide of the flash unit 13. The APEX value of the number, the numerical value 5, is a numerical value for correcting the guide number GV based on ISO100.

The correction value calculation unit 30 calculates the correction value (OFFSET) using (Equation 5), and the second distance information calculation unit 31 uses (Equation 6) to calculate the second subject for each luminance coordinate. Distance information (DV _{(h, v)} ) is calculated.
(Formula 5) OFFSET = DX _(base) −DV _(base)
(Formula 6) (DV _{(h, v)} ) = DX _{(h, v)} )-OFFSET

Next, the subject distance information measuring unit 200 includes the second parameter (MVb) calculated by the luminance coordinate distance information generating unit 26, the second subject distance information (DV _{(h, v)} ), and the exposure condition for the preliminary light emission. Based on the above, the reflectance calculation means 32 for calculating the reflectance of the subject for each luminance coordinate, the second subject distance information (DV _{(h, v)} ) calculated by the luminance coordinate distance information generation means 26 and the reflectance calculation. Recording means 33 for recording the reflectance (RV _{(h, v)} ) and the like calculated by the means 32 is provided.

Specifically, the reflectance calculation means 32 uses (Equation 7) to calculate the reflectance (RV _{(h, v)} ) of the subject for each luminance coordinate, as shown in FIG.
(Formula 7) (RV _{(h, v)} ) = MVb _{(h, v)} + 2 * DV _{(h, v)} − (GV−AV−5 + SV)
In (Expression 7), (GV−AV−5 + SV) in the term on the right side is a parameter group representing the exposure condition of preliminary light emission, where GV is the APEX value of the guide number of preliminary light emission of the flash device 13, and AV is Iris. The APEX value of the F number of (aperture) 3, the numerical value 5 is a correction value in which the guide number GV is associated with ISO 100, and SV is the APEX value of ISO sensitivity.

Further, the distance information detection unit 200 includes the second subject distance information DV _{(h, v)} measured by the luminance coordinate distance information generation unit 26 and the reflectance information RV _{(h, v)} calculated by the reflectance calculation unit 32 _. A subject measurement information display device (not shown) for displaying _v) in correspondence with luminance coordinates (which is also the coordinate position of the photographed image) is provided.

The distance information detection unit 200 refers to the second subject distance information and DV _{(h, v) and} reflectance RV _{(h, v)} when the user takes a picture, and mainly performs an interface (not shown ₎ via the interface. The subject portion can be selected.

Next, the exposure setting unit 42 includes the second subject distance information DV _{(h, v)} measured by the subject distance information generating unit 26 and the reflectance information (RV _{(h, v )} calculated by the reflectance calculating unit 32. _In accordance with ( ₎ ), a function of an exposure control device for controlling an exposure amount when photographing a subject is provided. Specifically, the exposure setting unit 42 sets the light emission amount (GV), shutter speed (TV), aperture value (AV), ISO sensitivity (SV), etc. of the flash device 13 based on a program diagram (not shown). .

  Next, as shown in FIG. 1, the white balance coefficient correction means 50 includes a distance distribution detection means 50a, a distance information definition means 50b, a main subject selection means 50c, an irradiation light ratio calculation means 50d, and a correction coefficient calculation means 50e. Based on the distance information detected by the distance information detection unit 200, the white balance coefficient and the color reproduction matrix coefficient correction coefficient are calculated. The function of the white balance coefficient correction means in the present invention is expressed by the white balance coefficient correction means 50. The distance distribution detection means of the present invention corresponds to the distance distribution detection means 50a, the distance information definition means of the present invention corresponds to the distance information definition means 50b, and the main subject region selection means of the present invention selects the main subject. This corresponds to means 50c.

Specifically, as shown in FIG. 2A, the distance distribution detection unit 50 a calculates the distribution of the second subject distance information DV _{(h, v)} for each luminance coordinate calculated by the second distance information calculation unit 31. To detect. In FIG. 2A, the horizontal axis is the numerical value of the distance, and the vertical axis is the number of detections.

  The distance information defining means 50b selects the distance value with the largest number of detections and the distance value with the next largest number of detections in the distribution diagram shown in FIG. The distance value (Dvd) is used as a separation point, and is defined into an image region on the near side and an image region on the far side from the separation point.

  The main subject selecting unit 50c selects any one of the image areas defined by the distance information defining unit 50b as a main subject area based on a command signal from the user. In this embodiment, the short distance side is the main subject area and the long distance side is the background via the separation point (DVd).

  The irradiation light ratio calculating unit 50d uses the evaluation value (luminance value) without preliminary light emission and the evaluation value (luminance value) with preliminary light emission detected by the distance information detection unit 200, and uses the strobe light and the environmental light for each block. The weight ratio of the main subject area is calculated, and the average value of the strobe light and the ambient light is calculated.

Specifically, for each of the blocks, first, the luminance value when there is preliminary light emission is expressed as Yp [n], and the luminance value when there is no preliminary light emission is expressed as Y0 [n]. The luminance value of light is calculated as Yp0 [n], and the luminance value of strobe light during preliminary light emission is calculated as Yp1 [n] using (Equation 8).
(Formula 8) Yp0 [n] = Y0 [n]
Yp1 [n] = Yp [n] −Yp0 [n]

Next, using (Equation 9), based on the ratio to the target luminance signal Yt [n], Yp0 [n] and Yp1 [n] calculated in Equation 8 are respectively converted to APEX values (MVp0 [n] ], MVp1 [n]).
(Formula 9) MVp0 [n] = LOG ₂ (Yp0 [n] / Yt [n])
MVp1 [n] = LOG ₂ (Yp1 [n] / Yt [n])

Next, the ratio PV [n] of strobe light to ambient light is calculated for each of all blocks using (Equation 10).
(Formula 10) PV [n] = (MVp0 [n] −MVp1 [n]) + (TVp−TVs + GVp−GVs)
In (Expression 10), the APEX value of the shutter speed when TVp performs preliminary light emission, GVp the APEX value of the guide number of the flash device 13 when preliminary light emission, and the shutter speed when TVs is the main light emission (main photographing). APEX value, GVs is the APEX value of the guide number of the flash device 13 light emission at the time of main light emission (main photographing).

Next, using (Equation 11), the ratio PV [n] of strobe light to ambient light is weighted and summed, and the sum is divided by the total value SUM (W [n] of weighting factors, and PV [ n] is calculated, and SUM is an operation symbol for calculating the total value.
(Formula 11) SUM (PV [n] × W [n]) / SUM (W [n])

  That is, as shown in FIG. 3, the shooting screen is defined as a main subject and a background, a weighting factor (α = W [n]) is set for the main subject, and the strobe light ratio is totaled. By dividing the value by the sum of the weighting factors, the average value PVave. Is calculated.

Next, the correction coefficient calculation unit 50e uses (Expression 12) to calculate the ratio PVave. Is converted into a ratio Rs of the strobe light to the photographing light quantity. For example, when the ambient light is 0% and the strobe light is 100%, Rs is 1.
(Formula 12) A = (Ys0 / Ys1) = 2 ^ (PVave.)
Rs = 1− (A / (A + 1))

  Next, the image processing unit 300 generates a white balance correction parameter 51 and a color reproduction coefficient setting unit 51 that generates a color reproduction coefficient of a color color based on the pixel signal, and a white balance correction generated by the color reproduction coefficient setting unit 51. The white balance processing unit 60 that corrects the white balance of the pixel signal based on the parameters of the image, the color reproduction processing unit 61 that adjusts the image data to a predetermined hue, and the like. The CPU 40 performs the image processing according to the program stored in the ROM 41. The unit 300 is controlled. Note that the function of the white balance coefficient calculation means in the present invention is expressed by the color reproduction coefficient setting means 51.

  The color reproduction coefficient setting unit 51 includes a block integration unit 51a, a light source estimation unit 51b, a correction unit 51c, a reference light source selection unit 51d, a reference light source data storage unit 51e, a color reproduction coefficient calculation unit 51f, and the like.

  The block integration unit 51a divides the RGB signal supplied from the imaging unit 100 via the preprocessing unit 20 into a plurality of M × N areas as shown in FIG. Accumulated addition is performed every time, and the integrated values SUM (R), SUM (G), and SUM (B) are sent to the light source estimating means 51b.

  The light source estimation unit 51b converts ΣR, ΣG, and ΣB input from the block calculation unit 51a into XYZ signals for each block by an XYZ conversion matrix calculation having three rows and three columns, and the obtained XYZ signal is expressed as x = X / (X + Y + Z), y = Y / (X + Y + Z) is substituted into an equation to obtain xy chromaticity coordinates, and the RGB color signal is converted into xy chromaticity coordinates in a two-dimensional space.

  The matrix coefficient of 3 rows and 3 columns used for the XYZ conversion matrix calculation described above is the value of the RGB color signal supplied from the imaging unit 100 when the achromatic imaging area under the reference light source is imaged, and the achromatic imaging. A region is stored in advance in a buffer so as to be associated with chromaticity coordinates actually measured using a measuring machine such as a chromaticity color meter. The association between the RGB color signal values and the xy chromaticity coordinates is calculated by using a corresponding selection method based on a plurality of light source data such as sunlight, white fluorescent lamp, and incandescent lamp.

  Further, the light source estimation means 51b associates the data converted into xy chromaticity coordinates for each block with a predetermined light source map, and the xy chromaticity coordinates are within the light source selection area shown in FIG. Determine whether or not. When the light source is within the light source selection area, the light source is determined to be a light source such as sunlight, a white fluorescent lamp, an incandescent lamp, etc., and the xy chromaticity coordinates are cumulatively added to calculate an average value (xa, ya), thereby correcting means 51c. Send to.

  The correction means 51c uses the chromaticity coordinates (xa, ya) input from the light source estimation means 51b, the correction coefficient Rs calculated by the white balance coefficient correction means 50, and the chromaticity coordinates (xb, yb) and the corrected chromaticity coordinates (xc, yc) are sent to the reference light source selection means 51d and the color reproduction coefficient calculation means 51f. The chromaticity coordinates (xb, yb) of the strobe light are stored in the reference light source data storage means 51e.

  Specifically, as shown in FIG. 7, along the x-axis and y-axis directions, a coordinate axis is generated with Rs in chromaticity coordinates of only ambient light being 0 and Rs in chromaticity coordinates of only strobe light being 1. The chromaticity coordinates (xc, yc) of the photographing light at the time of strobe photographing are obtained in association with the Rs value calculated by the correction coefficient calculating means 51e.

  The reference light source selection unit 51d refers to the reference light source data storage unit 51e in which the coefficient for calculating the reference light source is set and stored in advance, and the white balance coefficient and color of the corrected chromaticity coordinates (xc, yc) An interpolation reference light source is selected to calculate the reproduction coefficient. At this time, at least three interpolation reference light sources surrounding the chromaticity coordinates (xc, yc) are selected in association with the corrected chromaticity coordinates (xc, yc).

  In the reference light source data storage means 51e, as shown in FIG. 6A, xy chromaticity coordinates, white balance coefficients (Kr, Kg, Kb) corresponding to each of a plurality of reference light sources, 3 rows and 3 columns. The color reproduction matrix coefficients (ai) consisting of are created and stored in advance. In FIG. 6A, the coordinates of the x mark represent the chromaticity coordinates of the reference light source.

  A plurality of white balance coefficients (Kr, Kg, Kb) stored in the reference light source data storage means 51e, a color reproduction matrix coefficient (ai) composed of 3 rows and 3 columns, etc. It is a value adjusted based on actual shooting data taken under a reference light source.

  Then, the reference light source selection unit 51d associates the selected white balance coefficient (Kr, Kg, Kb) and color reproduction coefficient (ai) with each color interpolation coefficient in association with the selected interpolation reference coordinate. To 51f.

  The color reproduction coefficient calculating unit 51f uses the chromaticity coordinates (k) calculated by the correcting unit 51c using the white balance coefficients (Kr, Kg, Kb) and the color reproduction matrix coefficients (ai) set as the interpolation reference coordinates. The white balance coefficients (Kr, Kg, Kb) ′ and the color reproduction matrix coefficients (a to i) ′ corresponding to xc, yc) are calculated by interpolation. Thereby, Rs expresses a function as a correction coefficient for the white balance coefficient and the color reproduction coefficient.

  Next, the white balance processing unit 60 uses the white balance calculated by the color reproduction coefficient setting unit 51 to determine the level of the RGB digital image signal input from the imaging device 1 via the preprocessing unit 2 during the actual photographing. Adjustment is performed using the coefficients (Kr, Kg, Kb) ′, and the digital image signal is corrected so that the white color appears white. That is, the white balance processing unit 60 corrects the RGB signal levels so that R = G = B when an achromatic imaging region is imaged regardless of the type of light source.

  Next, the color reproduction processing unit 61 includes a color interpolation unit 62, a color correction unit 63, a γ conversion unit 64, and a YUV conversion unit 65.

  As described above, the image sensor 8 includes a color filter composed of a Bayer array of R (red), G (green), and B (blue) colors in association with pixels, and a signal output from each pixel passes through the filter of each color. Therefore, the color interpolation unit 62 determines the RGB three-color components for each pixel and generates color image data (also referred to as demosaic processing). Say).

  The color correcting unit 63 uses the color reproduction matrix coefficients (ai) ′ calculated by the color reproduction coefficient calculating unit 51f to convert the RGB digital image signal input via the white balance processing unit 60 and the color interpolation unit 62. Correct to a predetermined signal level. Specifically, the determinant calculation shown in FIG. 6C is performed to convert the RGB digital image signals into R ′, G ′, and B ′ image signals to correct the color image.

Next, since the digital image signal output from the imaging unit 100 is data that does not have a predetermined gradation (for example, 2 ⁸ = 256 gradations), the γ conversion unit 64 has a color correction unit 63. The gradation conversion of the digital image signal input via is performed.

  At this time, a gradation conversion table is stored in a buffer (not shown) with reference to a predetermined appropriate exposure amount for the image data.

  Further, the γ conversion unit 64 performs γ conversion by associating the gradation-converted digital image signal with the color display characteristics of the display on which the image data is displayed.

  The YUV conversion unit 65 converts the image signal output from the γ conversion unit 64 into a color space of a standard color image, and generates YUV color information for each pixel of the color image (Y is luminance information, U , V is color information.

  As described above, the white balance adjusting apparatus according to the present exemplary embodiment detects the distance information from the imaging unit 100 to the subject for each image area in which the image data is defined in plural in association with the pixel coordinates. A main subject region is identified based on the distance information detected by the information detection unit 26 and the distance information detection unit 26, and the irradiation light amount of the flash means included in the photographing light that illuminates the main subject region at the time of photographing and the irradiation light amount And a white balance coefficient correction means 50 for correcting the white balance coefficient based on the calculated ratio, and a flash device that occupies the white balance in flash photography. The degree of influence of 13 irradiation lights (hereinafter also referred to as strobe light) can be estimated with high accuracy over the entire shooting screen, and the white balance of the shot image can be adjusted with high accuracy.

  Further, the white balance adjusting apparatus of the present embodiment includes a distance distribution detecting unit 50a that detects a distribution of distance information on the photographing screen based on the distance information detected by the distance information detecting unit 26, and a distance distribution detecting unit 50a. Corresponding to the detected distribution of distance information, distance information defining means 50b for hierarchically defining image data into a plurality of areas, and the main subject from the plurality of areas defined by the distance information defining means 50b Main subject selection means 50c for selecting an area, and the white balance coefficient correction means 50 is configured to correct the white balance coefficient by weighting the main subject area. However, it is possible to freely set an image area for white balance adjustment and improve convenience.

  In addition, the white balance adjustment device of the present embodiment includes the distance information detection unit 26, so that it is not necessary to adjust the focus so as to be paired with the number of regions for obtaining the distance for each photographing region, The work of white balance processing can be simplified compared to the technique described in Patent Document 2. In addition, since the subject distance can be calculated in association with the luminance coordinates without being estimated based on the degree of focus of the divided area, the degree of influence of the strobe light in the white balance can be calculated with high accuracy, and white balance adjustment can be improved.

  Further, the white balance adjustment device of the present embodiment calculates the ratio of the irradiation light amount and the environmental light amount for each of a plurality of regions via the white balance coefficient correction unit 50, and calculates the average value of the calculated ratios. Since the white balance coefficient is corrected in association with the calculated average value, changes in the irradiation light amount and the environmental light amount can be reflected in the white balance adjustment.

  Next, the procedure of the white balance adjustment method and the image processing method in the imaging apparatus 1 will be described with reference to FIGS. This procedure is executed by the CPU 40 giving a command signal to each functional unit based on a program stored in the ROM 41. Further, S in FIGS. 8 and 9 represents a step.

  First, this procedure starts when an activation signal is input to the imaging apparatus 1 by the user.

  Next, as shown in FIG. 7, in S100, previously calculated information is initialized, and thereafter, the process proceeds to S110.

  Next, in S110, exposure conditions for preliminary light emission of the flash device 13 are set according to the shooting conditions, and then the process proceeds to S120.

Next, in S120, the reference distance detection unit 14 is used to acquire distance information (DV _(base) ) of a specific area at the time of shooting, and then the process proceeds to S130.

  Next, in S130, the subject is photographed without preliminary light emission from the flash device 14, and then the process proceeds to S140.

Next, in S140, the luminance signal generation means 21 is used to generate a first luminance signal (Ya _{(h, v)} ) having four pixels of two adjacent horizontal pixels and two vertical pixels as one unit. The information is stored in the first luminance buffer 23 in association with the luminance coordinate located at the center of the pixel, and then the process proceeds to S150.

  Next, in S150, the flash device 13 emits light toward the subject (preliminary light emission) according to the exposure condition set in S110, and the subject is photographed. Thereafter, the flow proceeds to S160.

Next, in S160, the luminance signal generating means 21 is used to generate a second luminance signal (Yc _{(h, v)} ) having four pixels of two adjacent horizontal pixels and two vertical pixels as one unit. The brightness coordinates are stored in the second brightness buffer 24 in association with the brightness coordinates located at the center of the pixel, and then the process proceeds to S170.

Next, in S170, distance information for each block of a predetermined size is calculated. Specifically, as shown in FIG. 9, in S171, the strobe light luminance calculation unit 25 is used to generate for each luminance coordinate from the second luminance signal (Yc _{(h, v)} ) generated in S160 in S140 for each luminance coordinate. The first luminance signal (Ya _{(h, v)} ) is subtracted to calculate the luminance component (Yb _{(h, v)} ) of only the strobe light in the preliminary light emission, and then the process proceeds to S172.

  Next, in S172, the first parameter calculator 27 is used to convert the first luminance signal Ya into the first parameter (MVa) of the distance information, and the second parameter calculator 28 is used to convert only the strobe light. The luminance component Yb is converted into the second parameter (MVb) of the distance information, and then the process proceeds to S173.

In step S173, the first distance information calculation unit 29 is used to determine the first subject distance information (DX _{(2) for} each luminance coordinate based on the first and second parameters, the exposure value of preliminary light emission set in step S110, and the like. _{h, v)} ) is calculated, and then the process proceeds to S174.

Next, in S174, using the correction value calculation unit 30, the difference between the reference value (DV _(base) ) of the distance information and the first subject distance information (DX _{(h, v)} ) in the specific area of S120 ( OFFSET) is calculated to obtain a correction value for the first subject distance information, and then the process proceeds to S175.

Next, in S175, the second distance information calculation unit 31 is used to subtract the correction value (OFFSET) calculated in S174 from the first object distance information calculated in S173, so that the second object distance is determined for each luminance coordinate. Information (DV _{(h, v)} ) is calculated, and then the process proceeds to S176.

Next, in S176, second subject distance information (DV _{(h, v)} ) is stored for each predetermined block, and thereafter, the process proceeds to S180 in FIG.

Next, in S180, the distance distribution detecting means 50a, the separation information defining means 50b, and the main subject selecting means 50c are used to detect the distance distribution to define an image area, and among the plurality of defined image areas. To select the main subject area. Specifically, as shown in FIG. 2A _, the distribution of the second subject distance information DV _{(h, v)} for each luminance coordinate calculated in S175 is detected, and the distance information defining unit 50b is used. The distance value with the largest number of detections and the distance value with the next largest number of detections are selected, and the distance value (Dvd) that is the valley of the distribution of the two is used as the separation point, and the image area closer to the separation point. And the far-distance image area, and the main subject selection means 50c is used to select one of the defined image areas as the main subject area based on a command signal from the user.

  Next, in S190, a weighting coefficient (α = W [n]) for calculating a strobe light ratio, which will be described later, is set for the main subject region selected in S180, and thereafter, the process proceeds to S200.

  Next, in S200, the irradiation light ratio calculation unit 50d uses the irradiation light ratio calculation unit 50d, and the irradiation light ratio calculation unit 50d evaluates the evaluation value (luminance value) without preliminary light emission and the evaluation value with preliminary light emission detected by the distance information detection unit 200 ( Luminance ratio), the ratio PV (n) of strobe light to ambient light is calculated for each block, and in S210, as shown in FIG. 3, the main subject area is multiplied by the weighting coefficient calculated in S190. Average value PVave. Of strobe light and ambient light. Is calculated.

  Next, in S220, the ratio PVave. Of the strobe light to the ambient light PVave. Is converted into a ratio Rs of the strobe light to the photographing light quantity, and then the process proceeds to S230.

  Next, in S230, the achromatic color region selection unit 51 and the color reproduction coefficient setting unit 51 are used to calculate the chromaticity coordinates (xc, yc) associated with the flash photography, and the white color associated with the chromaticity coordinates. The balance coefficients (Kr, Kg, Kb) ′ and the color reproduction matrix coefficients (a to i) ′ are calculated by interpolation, and then the process proceeds to S240. Specifically, the chromaticity coordinates (xa, ya) input from the light source estimation means 51b are corrected using the correction coefficient Rs calculated by the white balance coefficient correction means 50 and the chromaticity coordinates (xb, yb) of the strobe light. Then, chromaticity coordinates (xc, yc) are calculated, and then at least three interpolation reference light sources for obtaining the interpolation reference coordinates are selected in association with the corrected chromaticity coordinates (xc, yc). Using the white balance coefficient (Kr, Kg, Kb) and the color reproduction coefficient (ai), the white balance coefficient (Kr, Kg, Kb) ′ and the color reproduction coefficient (ai) ′ at the time of flash photography are obtained. calculate.

  Next, in S240, the BV coordinates of the current brightness information are acquired based on the exposure information on the preview screen before the main shooting, and the shutter speed (TV) and aperture for the main shooting are associated with the BV coordinates. A parameter group such as value (AV), ISO sensitivity (SV), and guide number of flash device 13 is set, and flash photography is performed based on the parameter group. Then, the process proceeds to S250.

  Next, in S250, the white balance coefficient (Kr, Kg, Kb) ′ obtained in S230 is applied to the image data (RGB) obtained by strobe photographing (main photographing) using the white balance processing unit 60. To perform white balance processing.

  Next, in S260, color image data is generated using the color interpolation unit 62, the color correction unit 63, the γ conversion unit 64, the YUV conversion unit 65, etc., and the procedures of the white balance adjustment method and the color image processing method are completed. To do.

  As described above, the white balance adjustment method according to the present embodiment detects distance information from the imaging device to the subject for each image area in which image data is defined in plural in association with the coordinates of the pixels. The main subject region is identified based on the detection procedure (S110 to S170) and the distance information detected in the distance information detection procedure, and the amount of light emitted from the flash means included in the photographing light that illuminates the main subject region at the time of photographing Since a white balance coefficient correction procedure (S180 to S230) for calculating a ratio with the ambient light quantity excluding the irradiation light quantity and correcting the white balance coefficient based on the calculated ratio is used. In shooting, the influence of the irradiation light (so-called strobe light) of the flash means (flash device 13) occupying the white balance is accurately estimated over the entire shooting screen. The white balance of the captured image can be adjusted accurately.

  Further, the white balance adjustment method of the present embodiment uses the distance information detection procedure (S110 to S170), so that it is not necessary to adjust the focus so as to be paired with the number of areas to obtain the distance for each shooting area. Therefore, the work of white balance processing can be simplified. In addition, since the subject distance can be calculated in association with the luminance coordinates without being estimated based on the degree of focus of the divided area, the degree of influence of the strobe light in the white balance can be calculated with high accuracy, and white balance adjustment can be improved.

  Also, the white balance adjustment method of the present embodiment detects the distribution of distance information on the shooting screen based on the distance information detected in the distance information detection procedure (S110 to S170), and the detected distance information distribution is detected. Correspondingly, a white balance coefficient correction procedure (S230) using a main subject region selection procedure (S180) for selecting a main subject region from a plurality of regions defined by hierarchically defining image data into a plurality of regions. ), The white balance coefficient is corrected by weighting the main subject area, so that the user can freely set the image area for white balance according to the distance information for each image area. Convenience can be improved.

  Further, the white balance adjustment method of the present embodiment calculates the ratio of the irradiation light amount and the environmental light amount for each of the plurality of regions through the white balance coefficient correction procedure (S230), and calculates the average value of the calculated ratios. Since the white balance coefficient is corrected in association with the calculated average value, changes in the irradiation light amount and the environmental light amount can be reflected in the white balance adjustment.

In addition, the imaging apparatus 1 and the imaging method described in the present embodiment calculate the relative position difference between the image areas defined based on the second subject distance information DV _{(h, v)} for each luminance coordinate. It is possible to adjust the white balance according to the information relating to the relative positional relationship between the subject portions detected and classified by the second subject distance information DV _{(h, v)} , and the convenience can be further improved.

  As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, Various aspects can be taken.

  The white balance adjustment device and adjustment method according to the present invention can be used when adjusting the white balance of an image obtained by flash photography.

  DESCRIPTION OF SYMBOLS 1 ... Imaging device, 2 ... Front lens, 3 ... Iris (aperture), 5 ... Focus lens, 6 ... Shutter, 7 ... Filter, 8 ... Imaging device (CCD: Charge Coupled Devices) 9 ... AFE (Analog Front End) DESCRIPTION OF SYMBOLS 10 ... Correlated Double Sampling Circuit (CDS: Correlated Double Sampling), 11 ... Variable Gain Amplifier (AGC), 12 ... A / D converter, 13 ... Flash device (for example, strobe), 14 Reference distance detecting means, 15 ... Iris driving unit, 16 ... detecting unit, 16a ... sensor, 17 ... focus driving unit, 18 ... detecting unit, 18a ... sensor, 19 ... TG (Timing Generator), 20 ... preprocessing unit, 21: Luminance signal generating means, DESCRIPTION OF SYMBOLS 2 ... Luminance buffer, 23 ... 1st luminance buffer, 24 ... 2nd luminance buffer, 25 ... Strobe light luminance calculation means, 26 ... Luminance coordinate distance information generation means, 27 ... 1st parameter calculation part, 28 ... 2nd parameter calculation , 29 ... 1st distance information calculation part, 30 ... Correction value calculation part, 31 ... 2nd distance information calculation part, 32 ... Reflectance calculation means, 33 ... Recording means, 40 ... CPU (Central Processing Unit), 41 ... ROM (Read Only Memory), 42 ... exposure setting unit, 50 ... white balance coefficient correction means, 50a ... distance distribution detection means, 50b ... distance information definition means, 50c ... main subject selection means, 50d ... irradiation light ratio calculation means , 50e ... correction coefficient calculating means, 51 ... color reproduction processing unit, 51 ... color reproduction coefficient setting means, 51a ... block integrating means, 51 b ... light source estimation means, 51c ... correction means, 51d ... reference light source selection means, 51e ... reference light source data storage means, 51f ... color reproduction coefficient calculation means, 60 ... white balance processing section, 61 ... color reproduction processing section, 62 ... Color interpolation unit, 63 ... color correction unit, 64 ... γ conversion unit, 65 ... YUV conversion unit, 100 ... imaging unit, 200 ... distance information detection unit, 300 ... image processing unit.

Claims (8)

Adjusting the white balance of the image data in an image pickup apparatus including a flash unit that irradiates a subject with a predetermined amount of light and an image pickup unit that photoelectrically converts an optical image of the photographed subject for each pixel and outputs image data A white balance adjusting device,
White balance coefficient calculating means for estimating a color temperature of a light source that illuminates the subject based on the image data, and calculating a white balance coefficient for white balance adjustment in association with the estimated color temperature of the light source;
Distance information detection means for detecting distance information from the imaging device that captures the subject to the subject for each image region in which the image data is defined in plural in association with the coordinates of the pixels;
The main subject area is identified based on the distance information detected by the distance information detecting means, and the amount of light emitted from the flash means included in the photographing light that illuminates the main subject area during photographing and the amount of environmental light excluding the amount of emitted light A white balance coefficient correction means for correcting the white balance coefficient based on the calculated ratio;
A white balance adjusting device comprising: Based on the distance information detected by the distance information detection means, distance distribution detection means for detecting the distribution of distance information on the shooting screen;
Distance information defining means for defining the image data hierarchically in a plurality of regions in association with the distribution of distance information detected by the distance distribution detecting means;
Main subject area selecting means for selecting the main subject area from a plurality of areas defined by the distance information defining means;
With
The white balance coefficient correction means corrects the white balance coefficient by weighting the main subject area;
The white balance adjusting device according to claim 1, wherein: The white balance coefficient correcting means is
For each of the plurality of regions, calculate a ratio between the irradiation light amount and the environmental light amount, calculate an average value of the calculated ratio,
Correcting the white balance coefficient in association with the calculated average value;
The white balance adjusting device according to claim 1 or 2, wherein Preliminary light emitting means to perform preliminary light emission before the main shooting,
The distance information detecting means is
Reference distance acquisition means for acquiring a reference value of distance information corresponding to a specific area in the shooting screen area;
A first luminance that discretely and sequentially generates a plurality of first luminances each having a predetermined number of pixels as a unit based on image data of the subject obtained by photographing without the preliminary light emission. Generating means;
Based on the image data of the subject obtained by photographing with the preliminary light emission, a plurality of second luminances having the predetermined number of pixels as one unit are generated so as to be paired with the first luminance. Two luminance generation means;
Luminance difference calculating means for subtracting the first luminance from the second luminance for each unit to calculate a luminance component for the preliminary light emission;
For each unit, the first luminance and the luminance component of the irradiation light calculated in the luminance difference calculation procedure are each converted into a parameter of distance information in comparison with a predetermined target luminance, Parameter generating means for generating a second parameter;
First distance information generation means for generating first subject distance information for each unit based on the first and second parameters and the exposure value in the preliminary light emission in the second luminance generation procedure. When,
Correction value calculation means for calculating a difference between reference values of the subject distance information with respect to the first subject distance information located in the specific area;
Second distance information generating means for correcting the first subject distance information and generating second subject distance information using the correction value generated in the correction value calculation procedure for each unit;
Comprising
The white balance adjusting device according to claim 1, wherein the white balance adjusting device is a white balance adjusting device. Adjusting the white balance of the image data in an image pickup apparatus including a flash unit that irradiates a subject with a predetermined amount of light and an image pickup unit that photoelectrically converts an optical image of the photographed subject for each pixel and outputs image data A white balance adjustment method,
A white balance coefficient calculating procedure for estimating a color temperature of a light source that illuminates the subject based on the image data, and calculating a white balance coefficient for white balance adjustment in association with the estimated color temperature of the light source;
A distance information detection procedure for detecting distance information from the imaging device that captures the subject to the subject for each image region in which the image data is defined in plural in association with the coordinates of the pixels;
The main subject area is identified based on the distance information detected by the distance information detection means, and the amount of illumination of the flash means included in the photographing light that illuminates the main subject area at the time of photographing and the amount of environmental light excluding the amount of illumination A white balance coefficient correction procedure for correcting the white balance coefficient based on the calculated ratio;
The white balance adjustment method characterized by using. Based on the distance information detected in the distance information detection procedure, a distance distribution detection procedure for detecting the distribution of distance information on the shooting screen;
In correspondence with the distribution of distance information detected in the distance distribution detection procedure, the distance information defining procedure for defining the image data hierarchically in a plurality of regions,
A main subject region selection procedure for selecting the main subject region from a plurality of regions defined by the distance information creation procedure;
Use
The white balance coefficient correction procedure weights the main subject area to correct the white balance coefficient;
The white balance adjustment method according to claim 5, wherein: The white balance coefficient correction procedure includes:
For each of the plurality of regions, calculate a ratio between the irradiation light amount and the environmental light amount, calculate an average value of the calculated ratio,
Correcting the white balance coefficient in association with the calculated average value;
The white balance adjustment method according to claim 5 or 6, wherein: Pre-flash procedure for pre-flash before actual shooting
The distance information detection procedure includes:
A reference distance acquisition procedure for acquiring a reference value of distance information corresponding to a specific area in the shooting screen area;
A first luminance that sequentially and discretely generates a plurality of first luminances having a predetermined number of pixels as a unit based on image data of the subject obtained by photographing without the preliminary light emission Generation procedure,
Based on the image data of the subject obtained by photographing with the preliminary light emission, a plurality of second luminances having the predetermined number of pixels as one unit are generated so as to be paired with the first luminance. A two-luminance generation procedure;
A luminance difference calculation procedure for subtracting the first luminance from the second luminance for each unit to calculate a luminance component for the preliminary light emission;
For each unit, the first luminance and the luminance component of the irradiation light calculated in the luminance difference calculation procedure are each converted into a parameter of distance information in comparison with a predetermined target luminance, A parameter generation procedure for generating a second parameter;
A first distance information generation order for generating first subject distance information for each unit based on the first and second parameters and the exposure value at the time of the preliminary light emission in the second luminance generation procedure. When,
A correction value calculation procedure for calculating a difference between reference values of the subject distance information with respect to the first subject distance information located in the specific region;
A second distance information generation procedure for correcting the first subject distance information and generating second subject distance information using the correction value generated in the correction value calculation procedure for each unit;
Use
8. The white balance adjusting method according to claim 5, wherein the white balance is adjusted.

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