JP4993670B2 - Imaging apparatus and control method thereof - Google Patents

Description

The present invention relates to an imaging apparatus and its control how having a photoelectric conversion element, particularly relates to an imaging apparatus and its control how using a CMOS image sensor.

  Conventionally, CCD image sensors and CMOS image sensors have been widely used as solid-state imaging devices. The CCD image sensor converts light into signal charges with photoelectric conversion elements arranged in the pixels, and simultaneously reads and transfers the signal charges from all pixels to the CCD, and converts the transferred signal charges into electrical signals for output. It has a function to do. On the other hand, a CMOS image sensor has a function of converting light into a signal charge by a photoelectric conversion element arranged in a pixel and outputting the signal charge as an electric signal amplified for each pixel. The CMOS image sensor has a feature that is not available in a CCD image sensor that reads out image signals of all pixel areas simultaneously because it can partially read out from a part of the pixel area of the imaging unit (hereinafter referred to as “partial reading”). Have.

FIG. 15 is a conceptual diagram of electronic zoom by partial reading (hereinafter referred to as “electronic zoom”) using the characteristics of a CMOS image sensor. Reference numeral 1301 denotes an effective pixel area of the CMOS image sensor, in which a × b pixels are arranged. In this case, the electronic zoom magnification is 1 (× 1). Reference numeral 1302 denotes a pixel area where partial reading is performed when the electronic zoom magnification is double (× 2), and (a / 2) × (b / 2) pixels are read out. Reference numeral 1303 denotes a pixel area where partial readout is performed when the electronic zoom magnification is 3 times (× 3), and (a / 3) × (b / 3) pixels are read out. An image signal output from the CMOS image sensor and converted into a digital signal by an A / D converter (not shown) is shown in FIG. 16 by a Bayer arrangement in which one block is composed of repetition of R, G, G, and B. Is divided into a plurality of blocks. Then, color evaluation values Cx, Cy, and Y are calculated for each block based on Equation 1.
Cx = (R−B) / Y
Cy = (R + B-2G) / Y
Y = (R + G + B) / 2
... (Formula 1)
The color evaluation values Cx and Cy of each block calculated using Expression 1 are compared with a preset white detection area.

  FIG. 17 is a graph showing the white detection area. The white detection area 101 is obtained as follows. First, a white object such as a reference white plate (not shown) is photographed using a light source having an arbitrary color temperature interval from a high color temperature to a low color temperature. Next, the color evaluation values Cx and Cy are calculated based on Equation 1 based on the signal value obtained from the imaging unit 200. Then, with respect to Cx and Cy obtained for each light source, the plotted points with the horizontal axis as Cx and the vertical axis as Cy are connected with a straight line, or the plotted points are approximated using a plurality of straight lines. Thereby, the white detection axis 102 from the high color temperature to the low color temperature is obtained. Actually, even if the white color is the same, there is variation in the spectrum. Therefore, the white detection region 102 having a width with respect to the Y-axis direction is defined as the white detection region 101.

When the calculated color evaluation values Cx and Cy are included in the white detection region 101, it is assumed that the block is white, and the integrated values (SumR, SumG, SumB) of the color pixels of each block assumed to be white are calculated. To do. Then, white balance gains kWB_R, kWB_G, and kWB_B for each color of RGB are calculated from the integral values calculated using Equation 2.
kWB_R = 1.0 / SumR
kWB_G = 1.0 / SumG
kWB_B = 1.0 / SumB
... (Formula 2)
Japanese Patent No. 03515066

  However, the white balance correction in the conventional CMOS image sensor has the following problems. For example, the color evaluation value of a white subject under a solar light source is distributed as shown by a region 103 in FIG. When shooting a face up under a high color temperature light source such as sunlight using electronic zoom by partial reading during moving image shooting or EVF display, the color evaluation value of human skin is distributed as in region 105. . The area 105 substantially coincides with the area 104 where white color evaluation values photographed under a low color temperature light source such as white tungsten are distributed. For this reason, when the area of the skin color increases, such as when the face is up, it may be erroneously determined that the image was taken under a light source with a color temperature lower than the actual color temperature.

  The present invention has been made in view of the problem of generating an image by performing partial readout from a pixel area of an imaging unit, and an object of the present invention is to perform appropriate white balance processing even in such a case. .

A first aspect of the present invention relates to an imaging apparatus, and includes an imaging unit having a first pixel area and a second pixel area different from the first pixel area, and an image signal from the first pixel area. Control is performed so that the image signal is read out from a divided region obtained by dividing the second pixel region into a plurality of intervals between readings a plurality of times, and each time an image signal is read out from the divided region obtained by dividing the second pixel region. White balance of the image signal read from the first pixel area based on control means for controlling the pixel signal to be read from the area and image signals read from a plurality of different divided areas of the second pixel area ; Correction means for correcting.

According to a second aspect of the present invention, there is provided a control method for an imaging apparatus including an imaging unit having a second pixel region different from the first pixel region and the first pixel region, wherein the first pixel every interval to read a plurality of times an image signal from the area, together with to read out the image signals from the divided areas obtained by dividing the second pixel region into a plurality reads image signals from the divided region second dividing a pixel region to read out the pixel signals from the different divided regions, based on the image signals read out from a plurality of different divided regions of the second pixel region, to correct the white balance of an image signal read from the first pixel region It is characterized by controlling as follows.

  A third aspect of the present invention relates to a program, and causes a computer to execute the above-described imaging apparatus control method.

  According to the present invention, appropriate white balance processing can be performed even when an image is generated by performing partial readout from the pixel region of the imaging unit.

  Preferred embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is an overview of an imaging unit using a CMOS image sensor. B11 to Bmn (m and n are integers; the same applies hereinafter) are pixels arranged two-dimensionally on the imaging surface. Each pixel includes at least a photoelectric conversion element and a transistor that amplifies and outputs the signal charge converted by the photoelectric conversion element for each pixel. The vertical shift register 220 outputs a control pulse for reading an electrical signal from the pixel for each of the horizontal output lines VSEL1 to VSELm. The electrical signals of the respective pixels selected by the horizontal output lines VSEL1 to VSELm are read by the vertical output lines VSIG1 to VSIGn and accumulated in the adding circuit 221. The electrical signals accumulated in the adder circuit 221 are sequentially read and scanned by the horizontal shift register 222 and output in time series.

  When performing the partial reading described above, a control pulse is output from the vertical shift register 220 to a horizontal output line connected to a pixel that is a target of partial reading out of the horizontal output lines VSEL1 to VSELm. Then, a control pulse is output from the horizontal shift register 222 to a vertical output line connected to a pixel that is a target of partial readout among the vertical output lines VSIG1 to VSIGn. The electric signal of each pixel selected by the control pulse of the horizontal output line is read to the adder circuit 221 by the control pulse of the vertical output line, and passes through the adder circuit 221 without being accumulated in the adder circuit 221. For example, in the case of reading out at an electronic zoom magnification of 2 (× 2), pixels for two pixels in the horizontal direction (also for two pixels in the vertical direction when an adder circuit is arranged in the vertical shift register) Do not add. On the other hand, as shown in FIG. 15, when the entire effective pixel area of the imaging unit 200 is read (electronic zoom magnification 1 × (× 1)), for the n pixels in the horizontal direction (addition circuit in the vertical shift register). Is also added to m pixels in the vertical direction).

  FIG. 2 is a diagram showing an outline of an imaging system using the imaging unit of FIG. Reference numeral 501 denotes a lens portion (referred to as “lens” in FIG. 2) as an optical system, 502 denotes a lens driving portion, 503 denotes a mechanical shutter (noted as mechanical shutter), and 504 denotes a mechanical shutter driving portion (“shutter driving portion” in FIG. 2). 505) denotes an A / D converter. Reference numeral 200 denotes an imaging unit having the configuration shown in FIG. Reference numeral 506 denotes an imaging signal processing circuit, 507 denotes a timing generation unit, 508 denotes a memory unit, 509 denotes a control unit, 510 denotes a recording medium control interface unit (indicated as “recording medium control I / F unit” in FIG. 2), 511. Indicates a display. Reference numeral 512 denotes a recording medium, 513 denotes an external interface unit (indicated as “external I / F unit” in FIG. 2), 514 denotes a photometric unit, and 515 denotes a distance measuring unit. The imaging signal processing circuit 506 includes a WB circuit 516 that performs white balance processing based on a signal from the A / D converter 505. Details of processing in the WB circuit 516 will be described later with reference to FIG.

  The subject image that has passed through the lens unit 501 is formed in the vicinity of the imaging unit 200. A subject image formed in the vicinity of the imaging unit 200 is captured by the imaging unit 200 as an image signal. The imaging signal processing circuit 506 amplifies the image signal output from the imaging unit 200, converts the analog signal into a digital signal (A / D conversion), and converts the R, G, G, and B signals after A / D conversion. obtain. The imaging signal processing circuit 506 performs various corrections, compression of image data, and the like.

  The lens unit 501 is driven and controlled by a lens driving unit 502 such as zoom, focus, and diaphragm. The mechanical shutter 503 is a shutter mechanism having only a curtain corresponding to the rear curtain of a focal plane type shutter used in a single-lens reflex camera. The mechanical shutter 503 is driven and controlled by a shutter driving unit 504. The timing generation unit 507 outputs various timing signals to the imaging unit 200 and the imaging signal processing circuit 506. A control unit 509 performs control of the entire imaging system and various calculations. The memory unit 508 temporarily stores image data. The recording medium control interface unit 510 records image data on the recording medium 512 and reads or reads image data from the recording medium 512. The display unit 511 displays image data. The recording medium 512 is a detachable storage medium such as a semiconductor memory, and records image data. The external interface unit 513 is an interface for communicating with an external computer or the like. The photometry unit 514 detects the brightness information of the subject, and the distance measurement unit 515 detects the distance information to the subject. Reference numeral 516 denotes a white balance circuit (WB circuit). Note that the operation unit 517 sets the operation mode of the image pickup apparatus (auto mode, person shooting mode for shooting a person, landscape shooting mode for shooting a landscape, manual mode for setting a white balance correction value by a user, etc.). .

(First embodiment)
FIG. 3 is a diagram schematically showing a method of electronic zoom by partial reading in the imaging apparatus according to the preferred first embodiment of the present invention. The outer pixel area 301 is an effective pixel area of the imaging unit 200. The inner pixel region 302 is a pixel region that is partially read by electronic zoom. A to I are pixel areas that are read out during reading of a moving image recording frame or display frame at the time of electronic zoom, and are obtained by dividing a pixel area other than the pixel area E that is partially read out by electronic zoom into a plurality of areas. It is an area. Each control according to the present embodiment is performed by the control unit 509.

  In order to increase the accuracy of the white balance processing in the WB circuit 516 in FIG. 2, it is necessary to increase the pixel region (view angle) for acquiring the white balance coefficient. Therefore, the pixel area for acquiring the white balance coefficient is read between the predetermined number of frames for moving image recording or display frame (area E). For example, at the time of moving image shooting, the image capturing unit 200 divides the pixel area E from E → A → E → B → E → C → E → D → E → F → E → G → E → H → E → I. Read the area alternately. Further, for example, each time the pixel area E is read M (M is an integer equal to or greater than 2) times (hereinafter referred to as “E (read M times)”), the divided areas may be read. That is, E (M times reading) → A → E (M times reading) → B → E (M times reading) → C → E (M times reading) → D → E (M times reading) → F → E (M (Reading times) → G → E (reading M times) → H → E (reading M times) → I. The pixel area for obtaining the white balance coefficient may or may not include the pixel area E. The electric signal of the pixel area (divided area) for obtaining the white balance coefficient is temporarily stored in the recording medium 512 and accumulated until the entire pixel area 301 (one screen) is collected. When the electric signal of the entire pixel area 301 is accumulated in the recording medium 512, a white balance coefficient is calculated.

  In FIG. 3, the pixel region is divided into nine, but the number of division is not limited to this. Further, the readout order of the divided regions is not limited to the above, and other readout orders may be used. Further, it is not necessary to read out the divided areas until the entire pixel area 301 (for one screen) is gathered between reading the pixel areas E, and it is only necessary to collect electrical signals in a pixel area wider than the pixel area E. Even in such a case, the accuracy of white balance in the case of moving image recording or EVF can be increased.

  Divided areas that are read out between pixel areas may be read out by thinning out reading. The thinning-out reading can be performed by reducing the number of B11 to Bmn selected by the horizontal shift register 222 and the vertical shift register 220 in FIG. Further, a part of the plurality of signals read from B11 to Bmn in FIG. Also in this case, the number of signals read from the horizontal shift register 222 can be reduced. Also in the case of thinning readout, as described above, when an electrical signal of a predetermined pixel region (typically, the entire pixel region 301) is accumulated in the recording medium 512, a white balance coefficient as a correction value is calculated. Hereinafter, the image is assumed to have a full angle of view obtained by dividing the divided areas.

  FIG. 4 is a block diagram showing a schematic configuration of the WB circuit 516 according to the preferred first embodiment of the present invention. Reference numeral 30 denotes a mode determination unit that determines the operation mode of the imaging apparatus set by the operation unit 517. Reference numeral 31 denotes an evaluation block dividing unit that divides an output signal from the imaging unit 200 into a plurality of evaluation blocks as shown in FIG. A white detection area storage unit 32 stores a reference white detection area (hereinafter referred to as “reference white detection area”). Reference numeral 33 denotes a white detection region variable unit that appropriately changes the white detection region using a limit value. A pattern storage unit 34 stores a combination pattern of a position on the imaging screen and a white determination region changed by the white detection region variable unit used for white determination of the evaluation block at the position, for each mode. is there. A white determination unit 35 determines whether each evaluation block divided by the evaluation block dividing unit 31 is white. Reference numeral 36 denotes a WB coefficient calculation unit that calculates a WB coefficient used for white balance (WB) correction from the image signal of the evaluation block determined to be white by the white determination unit 35. Reference numeral 37 denotes a WB coefficient storage unit that stores the WB coefficient calculated by the WB coefficient calculation unit 36. Reference numeral 38 denotes a WB correction unit that performs WB correction on the output signal from the imaging unit 200 using the WB coefficient stored in the WB coefficient storage unit 37. Note that the white detection area storage unit 32, the pattern storage unit 34, and the WB coefficient storage unit 37 may be configured by one memory or an arbitrary plurality of memories.

  Here, the reference white detection area stored in the white detection area storage unit 32 will be described. The case where a primary color filter is used as the imaging unit 200 will be described as an example.

  In FIG. 5, 201 is a first white detection area, and 202 is a white detection axis. As described above, a white subject such as a reference white plate (not shown) is photographed using a light source having an arbitrary color temperature interval from a high color temperature to a low color temperature, and the above-described signal value obtained from the imaging unit 200 The color evaluation values Cx and Cy are calculated based on Equation 1 below. Then, with respect to Cx and Cy obtained for each light source, the plotted points with the horizontal axis as Cx and the vertical axis as Cy are connected with a straight line, or the plotted points are approximated using a plurality of straight lines. Thereby, the white detection axis 202 from the high color temperature to the low color temperature is obtained. The horizontal axis corresponds to the color temperature of the light source, and the vertical axis corresponds to the correction amount in the green direction (in other words, the luminance color temperature direction and the fluorescent lamp color temperature direction). Actually, there is a slight variation in the spectrum even with the same white, so the first white detection region 201 is defined as having a slight width in the Y-axis direction with respect to the white detection axis 202. The data of the first white detection area 201 determined in this way is stored in the white detection area storage unit 32 when the WB circuit 516 is manufactured or shipped.

  In FIG. 5, the second white detection area 203 is obtained by limiting the Cx range between Ll1 and Lh1 by setting white detection limiters Ll1 and Lh1 for the first white detection area 201. . The third white detection region 204 has a Cx range so that a region with a low color temperature is cut from the second white detection region 203 by setting white detection limiters Ll2 and Lh2 with respect to the white detection region 201. Is limited between Ll2 and Lh2.

  The white determination unit 35 performs white determination on the evaluation block. In addition, the white determination unit 35 calculates a WB coefficient (white balance gain) from the integrated value of the pixel values of the evaluation block determined to be white by the WB coefficient calculation unit 36 and stores it in the WB coefficient storage unit 37. The WB correction unit 38 performs WB correction of the input image using the WB coefficient stored in the WB coefficient storage unit 37.

  Next, white determination processing will be described with reference to FIGS.

  6A shows a pattern setting example in the auto mode and FIG. 6B shows a pattern setting example in the person photographing mode stored in the pattern storage unit 34 in FIG. The outer rectangular area 401 is the maximum field angle of the imaging unit 200, and the inner rectangular area 402 is a pixel area (view angle) that is partially read by electronic zoom. The region (1) is a region obtained by removing the circular region 403a or the circular region 403b from the rectangular region 401. The area (2) corresponds to the circular area 403a or the circular area 403b and is hatched. The width of the area (2) can be fixed according to the shooting mode, or can be enlarged / reduced with the change of the angle of view by the electronic zoom. The pattern represented by the area (1) and the area (2) is a combination of the position of each evaluation block and the size of the variable white detection area used for white evaluation of the evaluation block at the position of the block. Indicates. These patterns may be stored in advance in the pattern storage unit 34 when the WB circuit 516 is manufactured or shipped, or the user may be able to change the area setting.

  Next, FIG. 7 shows a series of processing flows in the white determination processing sequence.

  In step S <b> 11, the mode determination unit 30 determines which of the auto mode and the portrait shooting mode is set by the operation unit 517. If the auto mode is set, the process proceeds to step S12, and if the person shooting mode is set, the process proceeds to step S13.

  In step S <b> 12, the white determination unit 35 acquires area data of the pattern shown in FIG. 6A from the pattern storage unit 34.

  In step S <b> 13, the white determination unit 35 acquires area data of the pattern shown in FIG. 6B from the pattern storage unit 34.

  In step S14, the white determination unit 35 determines whether each evaluation block is in the region (1) or the region (2). If it is in the region (1) (YES in step S14), the process proceeds to step S15. If it is in the region (2) (NO in step S14), the process proceeds to step S16.

  In step S <b> 15, the white determination unit 35 compares the color evaluation value of the evaluation block with the white detection region 203 shown in FIG. 4A, the region of which is limited by the white detection region variable unit 33.

  In step S <b> 16, the white determination unit 35 compares the color evaluation value of the evaluation block with the white detection region 204 shown in FIG. 4B, the region of which is limited by the white detection region variable unit 33.

  Since there is a high possibility that human faces are included in the center area of the imaging screen, setting the lower limit on the low color temperature side higher than that of the surrounding areas for the center area will make the human skin white. Is limited to the white detection area 204 so as not to be misidentified.

  In both step S15 and step S16, if the color evaluation value of the evaluation block is in the white detection area 203 or 204, the white determination unit 35 proceeds to step S17. If it is not in the white detection area 203 or 204, the white determination unit 35 proceeds to step S18.

  In step S17, the white determination unit 35 determines that the evaluation block determined to be within the white detection region 203 or 204 in step S15 or step S16 is white.

  In step S18, the white determination unit 35 determines that the evaluation block determined not to be in the white detection region 203 or 204 in step S15 or step S16 is not white.

  Thus, the evaluation block determined to be white with reference to a signal having a wider angle of view than the electronic zoom is integrated with the pixel value to calculate the white balance gain (WB coefficient) as described above. The

  In step S19, the white determination unit 35 determines whether it is determined whether or not all evaluation blocks are white, and repeats steps S14 to S18 until the determination of all evaluation blocks is completed.

  In addition, according to an experiment, when the low color temperature side white detection limiter Ll2 is fixed to about 5000K, a good result can be obtained. However, the present invention is not limited to 5000K and can be changed as appropriate.

  Further, according to the first embodiment, a signal of a pixel region (view angle) wider than a pixel region that is partially read by electronic zoom is read, and a different white detection region is used depending on the position on the imaging screen. As a result, erroneous determination of white determination can be reduced. As a result, it is possible to perform better white balance correction.

  Further, when the camera shooting mode is set to the person shooting mode, by increasing the area of the central region (2) as shown in FIG. 6B, the erroneous determination of white determination due to human skin is reduced. Can do. However, although it is considered that there is a high possibility that human skin is present at the center of the imaging screen in the human photographing mode, there are many cases where human skin is not present in the central portion of the imaging screen in the auto mode.

  When there is no human skin at the center of the imaging screen, for example, the color temperature result based on an image photographed under a certain light source becomes higher than the actual light source color temperature. This is because the color temperature detection result at the center of the imaging screen does not become lower than the white detection limiter Ll2 (for example, 5000K) on the low color temperature side when the above-described imaging screen setting and white limiter setting are performed. is there.

  Therefore, as described below, the presence / absence of human skin is determined prior to the operation shown in step S12 of FIG. 7, and when it is determined that there is human skin, the operation after step S12 is performed, so that the accuracy is higher. White balance correction can be realized. This operation will be described with reference to the flowchart of FIG.

  In step S21, the white determination unit 35 uses the same white detection region for all the evaluation blocks in the central portion of the imaging screen (region (2) in FIG. 4A) and the peripheral portion (region (1) in FIG. 4A). Is used to detect an evaluation block in which the image data is determined to be white (hereinafter referred to as “white evaluation block”). Here, the “same white detection region” refers to a region in which the color temperature region of human skin is included in a region limited by the same white detection limiter or a white detection region that is not limited. For example, one of the white detection area 201 and the white detection area 203 corresponds to this.

  In step S22, the light source color temperature CtAround is calculated from the data obtained by integrating and averaging the image data of the white evaluation block at the periphery of the imaging screen.

  In step S23, the light source color temperature CtCenter is calculated from the data obtained by integrating and averaging the image data of the white evaluation block at the center of the imaging screen. Note that the order of the processing in step S22 and step S23 may be reversed or simultaneous.

  In step S24, CtAround and CtCenter are compared. If the color temperature CtCenter obtained from the center of the imaging screen is lower than the color temperature CtAround obtained from the periphery of the imaging screen, it is determined in step S25 that the possibility that the center of the imaging screen is human skin is high. That is, if CtCenter <CtAround is established, the central portion of the imaging screen is determined to be human skin, and the auto mode white determination shown in FIGS. 5 to 7 is performed to calculate the light source color temperature (step S26).

  On the other hand, when the color temperature CtCenter from the central portion of the imaging screen is substantially the same as or higher than the color temperature CtAround from the peripheral portion of the imaging screen, it is determined that there is a high possibility that the central portion of the imaging screen is not human skin (step S27). That is, if CtCenter ≧ CtAround, it is determined that there is no human skin, all evaluation blocks are compared with a common white detection area, a white evaluation block is detected, and the obtained light source color temperature is adopted (step S28).

  By adding the above processing, erroneous determination of white determination can be further reduced, and good white balance correction can be performed.

  When it is determined in the mode determination in step S11 in FIG. 7 that the manual mode is selected, all evaluation blocks are compared with a common white detection area in the same manner as when it is determined that there is no human skin. To detect. Then, the light source color temperature obtained from the image data in the white evaluation block may be adopted.

  Up to this point, the divided areas obtained by dividing the effective pixel area of the imaging unit 200 are combined to create one image, and then the white balance is obtained. However, white balance may be obtained for each divided region, and white balance correction may be performed using an average value for all the view angles.

(Second Embodiment)
FIG. 9 is a diagram illustrating a pattern setting example for suppressing erroneous determination of a blue sky as white. FIG. 9A shows a pattern example in the auto mode, and FIG. 9B shows a pattern example in the landscape shooting mode. The outer rectangular area 701 is the maximum field angle of the imaging unit 200, and the inner rectangular area 702 is a pixel area (view angle) that is partially read by electronic zoom. The area (1) is an area obtained by excluding the area (2) indicated by diagonal lines from the rectangular area 701. Similar to the first embodiment, it is determined whether or not the evaluation block is white by comparing with the white detection area limited by using different white detection limiters in the area (1) and the area (2). .

  Since the color evaluation value of the evaluation block of the image area in which the sky close to the sky or the sky close to the horizon has the same distribution as the color evaluation value of the shaded white point as described above, the evaluation block of the empty image portion Is mistaken for white. That is, the angle of view becomes wider and the sky area increases, so that the sky is mistakenly identified as white having a high color temperature.

  Therefore, as shown in FIG. 9A, the white detection limiter which is different on the high color temperature side by the white detection region variable unit 33 between the upper part of the imaging screen (area (2)) and the lower part of the imaging screen (area (1)). A white determination is performed using a different white detection region to which restrictions are added using.

  As shown in FIG. 10, the high color temperature for determining the evaluation block at the lower part of the imaging screen is the high color temperature side white detection limiter Lh4 that limits the white detection area for determining the evaluation block at the upper part of the imaging screen. It is set on the low color temperature side as compared with the white detection limiter Lh3 on the side. This prevents light blue from being misidentified as white.

  According to experiments, when the white detection limiter Lh4 is set to about 5500K, good results can be obtained. However, the present invention is not limited to 5500K and can be changed as appropriate.

  As described above, according to the second embodiment, by using different white detection areas depending on the position on the imaging screen, even when the angle of view becomes wider and the number of empty areas increases, erroneous determination of white determination is reduced. Therefore, better white balance correction can be performed.

  Further, when the camera shooting mode is set to the landscape shooting mode, the area of the upper region (2) is increased as shown in FIG. Can do.

  In the second embodiment, the brightness Bv of the subject is detected from the photographed image data, and a detection pattern for white detection as shown in FIGS. 9A and 9B is used according to the brightness. It may be changed. For example, as shown in FIG. 11, when Bv is larger than a preset value Bv2, the rate of shooting outside is high (the proportion of the empty area is large), so the white detection area 209 shown in FIG. The ratio of the evaluation block at the top of the imaging screen where the white detection range is limited is increased. On the other hand, when Bv is smaller than Bv1 (<Bv2) set in advance, the indoor probability is high, so the ratio of the evaluation block at the top of the imaging screen is reduced. When the brightness of the subject is between Bv1 and Bv2, the ratio of the evaluation block at the upper part of the imaging screen in which the white detection range is limited by the white detection area 209 is determined by linear calculation at Bv as shown in the graph. . By such processing, more appropriate white balance correction can be performed.

  Up to this point, the divided areas obtained by dividing the effective pixel area of the imaging unit 200 are combined to create one image, and then the white balance is obtained. However, white balance may be obtained for each divided region, and white balance correction may be performed using an average value for all the view angles.

(Third embodiment)
FIG. 12 is a diagram illustrating a pattern setting example for suppressing erroneous determination of white determination for both human skin and sky. The outer rectangular area 901 is the maximum field angle of the imaging unit 200, and the inner rectangular area 902 is a pixel area (view angle) that is partially read by electronic zoom. The rectangular area 901 and the rectangular area 902 are vertically divided by a boundary line 905. Similarly, the central circular region is also divided into a semicircular region 903 and a semicircular region 904 by a boundary line 905. The region (3) corresponds to the semicircular region 903, and the region (4) corresponds to the semicircular region 904. The area (1) is an area obtained by excluding the areas (2) to (4) from the rectangular area 901. The region (2) is a region obtained by removing the region (1), the region (3), and the region (4) from the rectangular region 901. The widths of the area (3) and the area (4) can be fixed depending on the shooting mode, or can be enlarged / reduced with a change in the angle of view by the electronic zoom. Here, for example, for the white determination of the evaluation block in the region (1) in FIG.
High color temperature side white detection limiter Lh5: 5500K
Low color temperature side white detection limiter Ll5: Brightness variable (FIG. 13A)
And for region (2) in FIG.
High color temperature side white detection limiter Lh6: variable brightness Low color temperature side white detection limiter Ll6: variable brightness (FIG. 13B)
And for region (3) in FIG.
High color temperature side white detection limiter Lh7: 5500K
Low color temperature side white detection limiter Ll7: 5000K (FIG. 14A)
And for region (4) in FIG.
High color temperature side white detection limiter Lh8: Brightness variable Low color temperature side white detection limiter Ll8: 5000K (FIG. 14B)
Good results can be obtained. Note that the values indicated as the white detection limiters Lh5, Lh7, Ll7, and Ll8 are merely examples, and the present invention is not limited thereto and can be changed as appropriate.

  As described above, according to the third embodiment, the white determination is performed using a pattern obtained by finely dividing the area of the imaging screen and using a white detection area that differs depending on the position on the imaging screen. For this reason, it is possible to suppress erroneous white determination in both human skin and the sky and perform white balance correction with higher accuracy.

  Note that, as in the first embodiment, the pattern to be used can be changed depending on the shooting mode.

  Up to this point, the divided areas obtained by dividing the effective pixel area of the imaging unit 200 are combined to create one image, and then the white balance is obtained. However, white balance may be obtained for each divided region, and white balance correction may be performed using an average value for all the view angles.

(Fourth embodiment)
In the first to third embodiments, the white balance coefficient is calculated based on the electrical signal read from the divided area obtained by dividing the effective pixel area of the imaging unit 200 into a plurality of areas.

  However, it is also possible to divide into a plurality of arbitrary blocks as shown in FIG. 16 and calculate the color evaluation values Cx, Cy, Y for each block based on Equation 1 above.

  The color evaluation values Cx and Cy of each block calculated by the above mathematical formula 1 are compared with a later-described white detection region set in advance. If it is included in the white detection area, it is assumed that the block is white, and the integrated values (SumR, SumG, SumB) of the respective color pixels of the block assumed to be white are calculated.

  Then, the white balance gains kWB_R, kWB_G, and kWB_B for each of the RGB colors are calculated from the integral value using the following formula from the above formula 2.

  The WB circuit 516 may perform white balance correction using the white balance gain obtained in this way.

(Fifth embodiment)
The software configuration and the hardware configuration according to the first to fourth embodiments can be appropriately replaced. Moreover, you may make it this invention combine the above-mentioned each embodiment or those technical elements as needed. Further, in the present invention, the configuration of the claims or the whole or a part of the configuration of the embodiment may form one apparatus. Further, it may be combined with other devices such as an imaging device such as a digital camera or a video camera, or a signal processing device that processes a signal obtained from the imaging device, or may be an element constituting the device. It may be anything.

  The object of each embodiment is also achieved by the following method. That is, a storage medium in which a program code of software that realizes the functions of the above-described embodiments is recorded is supplied to the system or apparatus. Then, the computer (or CPU or MPU) of the system or apparatus reads and executes the program code stored in the storage medium. In this case, the program code itself read from the storage medium realizes the functions of the above-described embodiments, and the storage medium storing the program code constitutes the present invention.

It is a general-view figure of the image pick-up part using a CMOS image sensor. 1 is a schematic diagram of an imaging system according to a preferred embodiment of the present invention. It is a figure which shows the signal read-out system which concerns on the suitable 1st Embodiment of this invention. 1 is a block diagram showing a schematic configuration of a WB circuit according to a preferred first embodiment of the present invention. It is a figure which shows the white detection area | region which concerns on suitable 1st Embodiment of this invention. It is a figure which shows the imaging screen division which concerns on suitable 1st Embodiment of this invention. It is a flowchart which shows the white determination process which concerns on suitable 1st Embodiment of this invention. It is a flowchart which shows the process which determines the presence or absence of the human skin at the time of the auto mode which concerns on suitable 1st Embodiment of this invention. It is a figure which shows the imaging screen division | segmentation which concerns on the suitable 2nd Embodiment of this invention. It is a figure which shows the white detection area | region which concerns on suitable 2nd Embodiment of this invention. In the suitable 2nd Embodiment of this invention, it is a figure which shows an example of the detection pattern for detecting the white area | region on the imaging screen of the display part corresponding to the brightness of a to-be-photographed object. It is a figure which shows the imaging screen division | segmentation which concerns on the suitable 3rd Embodiment of this invention. It is a figure which shows the white detection area | region which concerns on suitable 3rd Embodiment of this invention. It is a figure which shows the white detection area | region which concerns on suitable 3rd Embodiment of this invention. It is a conceptual diagram of electronic zoom It is a figure which shows the example of the imaging screen division | segmentation which shows the unit for performing white determination. It is a figure which shows a white detection area | region.

Explanation of symbols

200 Imaging unit 509 Control unit

Claims (6)

Imaging means having a second pixel area different from the first pixel area and the first pixel area;
In the interval between reading the image signal from the first pixel region a plurality of times, the image signal is read out from the divided region obtained by dividing the second pixel region into a plurality of regions, and the second pixel region is divided. Control means for controlling to read pixel signals from different divided areas each time an image signal is read from the area ;
Correction means for correcting white balance of the image signal read from the first pixel area based on the image signal read from a plurality of different divided areas of the second pixel area ;
An imaging apparatus comprising:   The control means controls to alternately read out an image signal from the first pixel area and read out an image signal from a divided area obtained by dividing the second pixel area. Item 2. The imaging device according to Item 1.   2. The control unit according to claim 1, wherein each time the image signal is read from the first pixel region a plurality of times, the control unit controls to read the image signal from a divided region obtained by dividing the second pixel region. The imaging device described. The imaging apparatus according to any one of claims 1 to 3, characterized in that images of the divided regions comprises a white determining means for determining whether or not white. A control method for an imaging apparatus including an imaging means having a second pixel area different from the first pixel area and the first pixel area,
In between reading a plurality of times an image signal from the first pixel region, together to read out the image signals from the divided areas obtained by dividing the second pixel region into a plurality, from the divided areas obtained by dividing the second pixel region to read out the pixel signals from the different divided area for each read out image signal, based on the image signals read out from a plurality of different divided regions of the second pixel region, of said first image signal read from the pixel area A control method for an imaging apparatus, wherein control is performed so as to correct white balance. A program for causing a computer to execute each step of the method for controlling the imaging apparatus according to claim 5 .

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