JP2009088800A - Color imaging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color imaging device for exibiting sufficient effect in a color shading correction. <P>SOLUTION: The color imaging device is provided with: a first color imaging element (16) for imaging an image of a field formed by a photographic lens; a second color imaging element (22) provided in addition to the first color imaging element to detect a color distribution of the field; a determining means (29) for determining the type of illuminating light that illuminates the field on the basis of the color distribution detected by the second color imaging element; and a setting means (29) for setting an amount of color shading compensation to be applied to the image generated by the first color imaging element in accordance with the type determined by the determining means. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a color imaging apparatus.

Usually, the color shading of a color image sensor varies depending on the F value of the photographing lens, but it is empirically known that it also varies depending on the color temperature of the illumination light that illuminates the object scene. To cope with this, an electronic camera that determines the color temperature of illumination light based on an image (through image) generated by a color image sensor before imaging, and adjusts the amount of color shading correction according to the color temperature is proposed. (See Patent Document 1 and the like).
JP 2005-278004 A

  However, with the correction method described in Patent Document 1, it has been found that there is a possibility that the correction effect does not sufficiently appear depending on the use state of the electronic camera.

  SUMMARY An advantage of some aspects of the invention is that it provides a color imaging apparatus that can sufficiently bring out the correction effect of color shading correction.

  The color imaging device of the present invention is provided separately from the first color imaging element that captures an image of the field formed by the photographing lens and generates an image for storage, and the first color imaging element, A second color image sensor that detects a color distribution of the object scene; and a determination unit that determines a type of illumination light that illuminates the object field based on the color distribution detected by the second color image sensor; And a setting unit configured to set a correction amount of color shading correction to be applied to an image generated by the first color imaging device according to the type determined by the determination unit.

  The setting unit may set the correction amount based on the type determined by the determination unit, the F value of the photographing lens, and the position of the aperture stop of the photographing lens.

  In addition, any one of the color imaging devices according to the present invention may further include a correction unit that performs color shading correction on an image generated by the first color imaging device with a correction amount set by the setting unit.

  In addition, any one of the color imaging devices according to the present invention may further include a recording unit that stores the correction amount set by the setting unit together with the image generated by the first color imaging device.

  According to the present invention, it is possible to realize a color imaging apparatus that can sufficiently bring out the correction effect of color shading correction.

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described. The present embodiment is an embodiment of an electronic camera.

  First, the photographing mechanism of the electronic camera will be described. FIG. 1 is a schematic diagram showing a configuration of an optical system of an electronic camera. As shown in FIG. 1, the electronic camera includes a camera body 11 and a lens unit 13 that houses a photographing lens 12. The lens unit 13 is replaceably attached to the camera body 11 via a mount (not shown). In this state, the lens unit 13 is electrically connected to the camera body 11.

  In the camera body 11, a main mirror 14, a mechanical shutter 15, a color image sensor 16, and a finder optical system (17 to 20) are arranged. The main mirror 14, the mechanical shutter 15, and the color image sensor 16 are disposed along the optical axis of the photographing lens 12, and the finder optical system (17 to 20) is disposed in the upper region of the camera body 11.

  The main mirror 14 rotates around a rotation shaft (not shown), thereby switching between an observation state and a retracted state. The main mirror 14 in the observation state is inclined and disposed in front of the mechanical shutter 15 and the color image sensor 16. The main mirror 14 in the observation state reflects the light beam captured by the photographing lens 12 upward and guides it to the finder optical system (17 to 20). The center of the main mirror 14 is a half mirror, and a part of the light beam captured by the photographing lens 12 at this time is guided to a focus detection unit (not shown) via the half mirror and a sub mirror (not shown). It is burned.

  On the other hand, the retracted main mirror 14 is flipped upward and deviates from the optical path of the taking lens 12. When the main mirror 14 is in the retracted state, the entire light beam captured by the photographing lens 12 is guided to the mechanical shutter 15.

  The finder optical system (17 to 20) includes a focusing screen 17, a condenser lens 18, a pentaprism 19, and an eyepiece lens 20. In addition, a re-imaging lens 21 and a split photometric sensor 22 are disposed in the vicinity of the pentaprism 19.

  The focusing screen 17 is located above the main mirror 14 in the retracted state. The light beam formed by the focusing screen 17 enters the lower surface of the pentaprism 19 via the condenser lens 18. The light beam incident on the lower surface of the pentaprism 19 enters the interior of the pentaprism 19, reflects the inner surface of the pentaprism 19, and then passes from the surface (exit surface) perpendicular to the lower surface of the pentaprism 19 to the outside of the pentaprism 19. Ejected toward the eyepiece 20.

  A part of the light beam incident on the lower surface of the pentaprism 19 enters the inside of the pentaprism 19 and is reflected from the inner surface of the pentaprism 19, and then exits from the exit surface to the outside of the pentaprism 19 to be recombined. It goes to the split photometric sensor 22 through the image lens 21.

  Next, the circuit configuration of the electronic camera will be described. FIG. 2 is a block diagram showing a circuit configuration of the electronic camera. As shown in FIG. 2, the camera body 11 includes a color image sensor 16, an AFE 16a, a timing generator (TG) 16b, a divided photometric sensor 22, an A / D conversion circuit 22a, an image processing circuit 23, and a buffer memory. (MEM) 24, a recording interface (recording I / F) 25, an operation switch (SW) 26, a CPU 29, a RAM 28, a ROM 27, and a bus 31 are provided. Among these, the image processing circuit 23, the buffer memory 24, the recording interface 25, the CPU 29, the RAM 28, and the ROM 27 are connected to each other via a bus 31. The operation switch 26 is connected to the CPU 29.

  The color image sensor 16 is provided to generate a storage image (main image). The color imaging device 16 generates an image signal (analog signal) of the main image by photoelectrically converting the object scene image formed on the imaging surface.

  Note that, on the imaging surface of the color imaging device 16, three types of color filters of red (R), green (G), and blue (B) are arranged in, for example, a Bayer array in order to detect the color of the object scene image. ing. As a result, three types of pixels of R pixel, G pixel, and B pixel are arranged on the imaging surface of the color imaging element 16, and the image signal of the main image has three types of signals of R signal, G signal, and B signal. It will consist of Note that an optical low-pass filter, an infrared light cut filter, and the like are provided on the entire imaging surface of the color imaging element 16.

  The AFE 16a is an analog front-end circuit that performs signal processing on an image signal generated by the color image sensor 16. The AFE 16a performs correlated double sampling of the image signal, gain adjustment of the image signal, A / D conversion of the image signal, and the like. The image signal (digital signal) output from the AFE 16a is input to the image processing circuit 23 as image data of the main image.

  The timing generator 16b sends drive signals to each of the color image sensor 16 and the AFE 16a in accordance with instructions from the CPU 29, thereby controlling the drive timing of both.

  The divided photometric sensor 22 is a color image sensor provided for generating a monitor image (monitor image). The same object scene image as that formed on the imaging surface of the color image sensor 16 is formed on the imaging surface of the split photometric sensor 22. The split photometric sensor 22 photoelectrically converts the object scene image to generate an image signal (analog signal) of the monitor image.

  A color filter is disposed on the imaging surface of the split photometric sensor 22 for color detection of the object scene image. Therefore, the image signal of the monitor image is also composed of three types of signals, R signal, G signal, and B signal. The image signal output by the split photometric sensor 22 is input to the CPU 29 via the A / D conversion circuit 22a.

  The image processing circuit 23 performs various types of image processing on the image data of the main image output from the AFE 16a. The image processing circuit 23 includes a color shading correction unit 23a that performs color shading correction on image data, a white balance correction unit (WB) 23b that performs white balance correction on image data, and a color interpolation processing unit that performs color interpolation processing on image data. 23c, a processing unit (other processing unit) 23d for performing other processing such as color conversion processing on the image data is arranged. The color shading correction, white balance correction, color interpolation processing, and other processing in these processing units are pipeline processing, and are performed on the image data in this order.

The color shading correction is to multiply the R signal and B signal of the image data by gains g _r and g _b , respectively. However, since the color shading amount varies depending on the position (mainly image height) on the image, the values of the gains g _r and g _b vary depending on the blocks on the image. Here, the blocks on the image are a plurality of blocks that can be obtained by dividing the image, and are, for example, 750 blocks that can be obtained by dividing the image into 25 vertical and 30 horizontal. Hereinafter, the i-th block is referred to as "i-th block", the gain g _r to be multiplied by the R signal of each pixel in the i-th block "g _ri" Distant, B signals for each pixel in the i-th block The gain g _b multiplied by is set to “g _bi ”. Note that all gains (gain groups) g _r1 ,..., G _r750 , g _b1 ,..., G _b750 used in this color shading correction are calculated and set for each image by the CPU 29. Details of this calculation method will be described later.

The white balance correction is to multiply the R signal and B signal of the image data by gains G _r and G _b , respectively. The values of the gains G _r and G _b are common to all the blocks on the image. The gains C _r and G _b used in the white balance correction are also calculated and set for each image by the CPU 29. Details of this calculation method will be described later.

  The buffer memory 24 is a memory that temporarily stores the image data of the main image in order to compensate for the difference in speed between individual processes performed by the image processing circuit 23 and the CPU 29.

  The recording interface 25 is formed with a connector for connecting the storage medium 32. The recording interface 25 accesses the storage medium 32 connected to the connector, and writes and reads image data of the main image. The storage medium 32 is constituted by a hard disk, a memory card incorporating a semiconductor memory, or the like.

  The operation switch 26 is a release button, a command dial, a multi-selector, and the like, and gives a signal to the CPU 29 in accordance with the operation content by the user. For example, the user can give a shooting instruction to the CPU 29 by fully pressing the release button. Further, the user can give an instruction to switch the recording mode to the CPU 29 by operating the multi selector.

  The recording mode includes a normal recording mode and a RAW recording mode. The normal recording mode is a recording mode in which the CPU 29 stores the image data of the main image after image processing in the storage medium 32, and the RAW recording mode is the CPU 29. Is a recording mode in which the image data (RAW data) of the main image before image processing is stored in the storage medium 32.

  The CPU 29 is a processor that performs overall control of the electronic camera. The CPU 29 reads out a sequence program stored in advance in the ROM 27 to the RAM 28 and executes the program to calculate parameters for each process (such as the gain described above) and to control each unit of the electronic camera.

  When the CPU 29 designates the F value of the photographing lens 12 with respect to the lens CPU (not shown) of the lens unit 13, the lens CPU adjusts the diameter of the aperture stop (not shown) of the photographing lens 12. Thereby, the F value of the taking lens 12 is set.

  Further, when the CPU 29 gives the defocus signal generated in the focus detection unit (not shown) to the lens CPU of the lens unit 13, the lens CPU sets the shooting distance of the shooting lens 12 so that the defocus signal becomes zero. Change. Thereby, automatic focusing (AF) of the taking lens 12 is performed.

  Further, the CPU 29 extracts a luminance evaluation value from the image signal of the monitor image, and based on the luminance evaluation value and a program diagram prepared in advance, the opening time of the mechanical shutter 15, the charge accumulation time of the color image sensor 16, and photographing. Settings such as the F value of the lens 12 and the on / off state of strobe light emission are performed.

  Further, the CPU 29 can fetch lens information from a lens CPU (not shown) of the lens unit 13. The lens information includes information such as the focal length of the photographing lens 12, the subject distance, the aperture value (F value), and the exit pupil position (EPD). Incidentally, since the lens information is taken in by the CPU 29 every time the state of the photographing lens 12 changes or periodically, the CPU 29 can always recognize the latest lens information.

  The CPU 29 can also determine the type of illumination light (illumination type) that illuminates the object scene by executing the program. For this determination, for example, a criterion calculated in advance by supervised learning is used. The CPU 29 extracts the feature amount from the image signal of the monitor image, and determines the illumination type by comparing the feature amount with the discrimination criterion.

The ROM 27 calculates information necessary for the CPU 29 to determine the illumination type and the color shading correction gain groups g _r1 ,..., G _b750 , g _{b1 ,.} Information necessary for this is also stored in advance. The information includes a look-up table T _R for calculating the gain groups g _r1 ,..., G _r750 as shown in FIG. 3A and the gain groups g _{b1 ,. b750} is a lookup table T _B for calculating the. Hereinafter, these lookup tables T _R and T _B will be described in detail.

(Look-up table T _R )
The contents of the look-up table T _R is predetermined by the color shading for R pixels of the color image sensor 16 (= G pixel sensitivity distribution on the imaging plane of the relative sensitivity of the R pixel on the basis of).

  Usually, the color shading for the R pixel depends on the position on the image (mainly depends on the image height), but also changes depending on the combination of the F value of the photographing lens 12 and the EPD of the photographing lens 12. Furthermore, it changes also with illumination types as shown to Fig.4 (a).

  FIG. 4A is a conceptual diagram illustrating color shading relating to an R pixel when the F value and EPD are the same and only the illumination type is different. As shown in FIG. 4 (a), the color shading relating to the R pixel hardly occurs when the illumination type is a fluorescent lamp, a mercury lamp, a sodium lamp, or the like, but the illumination type is artificial sunlight, a halogen lamp, or a strobe. It often occurs in the case of light.

  The reason is that scenes of light sources such as fluorescent lamps, mercury lamps, and sodium lamps are likely to be scenes with little infrared light, whereas scenes of light sources such as artificial sunlight, halogen lamps, and strobe light are red. It is considered that there is a high possibility that the scene has a lot of outside light, and that color shading regarding the R pixel is increased as the absolute amount of incident infrared light is larger.

  Incidentally, the color temperature of the fluorescent lamp is about 4500K, the color temperature of the mercury lamp is about 4200K, the color temperature of the sodium lamp is about 2100K, the color temperature of artificial sunlight is about 5000 to about 6000K, and the color temperature of the halogen lamp is about 4200K. Since the color temperature of the strobe light is about 5000 to about 15000 K, the halogen lamp and the mercury lamp can be regarded as having the same color temperature. However, as is apparent from FIG. 4A, the color shading amount for the R pixel is different between the halogen lamp and the mercury lamp. Therefore, in this embodiment, the color shading amount regarding the R pixel is considered to depend on the type (illumination type), not the color temperature of the illumination light.

Therefore, in the present embodiment, the look-up table T _R, and various combinations of F values and EPD and lighting types, group gain suitable for each of these combinations g _r1, ..., stored in association with each other and g _R750 A three-dimensional lookup table is used. As shown in FIG. 3 (a), this when the look-up table T _R to F value and the EPD and the illumination type is entered, the F value and the EPD and the illumination type gain group g _r1 suitable combination of, ..., _g r750 is output from the look-up table T _R.

(Look-up table T _B)
The contents of the look-up table T _B is determined in advance by the color shading about B pixels of the color image sensor 16 (= G pixel sensitivity reference to distribution on the imaging plane of the relative sensitivity of B pixels of).

  Normally, the color shading for the B pixel depends on the position on the image (mainly on the image height), but also changes depending on the combination of the F value of the photographing lens 12 and the EPD of the photographing lens 12. However, as shown in FIG. 4B, the color shading for the B pixel hardly changes depending on the illumination type.

  FIG. 4B is a conceptual diagram illustrating color shading relating to the B pixel when the F value and EPD are the same and only the illumination type is different. As shown in FIG. 4B, the color shading for the B pixel is constant regardless of the illumination type. The reason is that the color shading for the B pixel hardly changes depending on the absolute amount of incident infrared light.

Therefore, in the present embodiment, the look-up table T _B, and various combinations of F values and EPD, group gain suitable for each of these combinations g _B1, ..., the two-dimensional look-stored in association with each other and g _B750 Up table. As shown in FIG. 3 (b), when the look-up table T F value and the EPD to _B is entered, the F value and the EPD gain group g _B1 suitable for combination with, ..., g _B750 lookup table is output from the T _B.

  Next, the flow of operation of the CPU 29 relating to shooting will be described. FIG. 5 is an operation flowchart of the CPU 29 regarding photographing. Here, it is assumed that the auto white balance function of the electronic camera is turned on and the recording mode of the electronic camera is set to the normal recording mode. At the start of the flowchart, the main mirror 14 is in the observation state, and the user can observe the object scene from the eyepiece 20.

  Step S101: The CPU 29 determines whether or not the release button is half-pressed. If the release button is half-pressed, the process proceeds to step S102, and if the release button is not half-pressed, the step S101 is repeated.

  Step S102: The CPU 29 starts continuous driving of the divided photometric sensor 22. As a result, the image signal of the monitor image starts to be output from the divided photometric sensor 22.

  Step S103: The CPU 29 performs automatic focus adjustment of the photographing lens 12 by giving a defocus signal generated by a focus detection unit (not shown) to the lens CPU, and also automatically exposes based on the luminance evaluation value extracted from the monitor image. Take control. As a result, shooting conditions (such as the opening time of the mechanical shutter 15, the charge accumulation time of the color imaging device 16, the F value of the shooting lens 12, the shooting distance of the shooting lens 12, the EPD of the shooting lens 12, the presence or absence of strobe light emission) are set. The

  Step S104: The CPU 29 extracts a feature amount from the monitor image, and compares the feature amount with the above-described discrimination criterion to determine the type of illumination that illuminates the current scene.

  Step S105: The CPU 29 determines whether or not the release button has been fully pressed. If the release button is not fully depressed, the process proceeds to S106, and if the release button is fully depressed, the process proceeds to S107.

  Step S106: The CPU 29 determines whether or not the half-press of the release button has been released. If the half-press of the release button has been released, the CPU 29 stops the operation of the divided photometric sensor 22 and returns to step S101. When the half-press of the release button is continued, the process returns to step S105.

  Step S107: The CPU 29 performs shooting (acquisition of image data of the main image) under the shooting conditions set in step S103. That is, the CPU 29 acquires the image data of the main image by driving the mechanical shutter 15 and the timing generator 16b with the main mirror 14 in the retracted state. At this time, the CPU 29 drives a strobe device (not shown) as necessary to emit strobe light. Note that the data of the main image acquired by this shooting is buffered in the buffer memory 24 after passing through the AFE 16a. When the photographing is finished, the main mirror 14 is returned to the observation state again.

Step S108: CPU 29 includes an illumination type determined in step S104, the latest F value, the latest 3 and EPD (a) to the gain group g _r1 by inputting to the look-up table T _R shown, ... , _Gr750 . However, when the object in step S107 was flash photography, regarded as the influence of the strobe light is dominant with respect to the object scene, CPU 29 is an illumination type to be input to the look-up table T _R, step S104 Regardless of the illumination type determined in step 1, “strobe light” is used.

Further, CPU 29 obtains the latest F value, the gain group g _b1 by inputting to the look-up table T _B showing the latest EPD in FIG 3 (b), ..., a g _B750. Then, the CPU 29 sets the acquired gain groups g _r1 ,..., G _r750 , g _b1 ,..., G _b750 to the color shading correction unit 23a.

Step S109: The CPU 29 calculates the correlated color temperature of the illumination light based on the illumination type determined in Step S104, and obtains the gain G _r , necessary for achromatic the region having the correlated color temperature in the main image. _Gb is calculated and set in the white balance correction unit 23b. The correlation color temperature is calculated, for example, according to the following procedures (1) to (3).

  (1) The CPU 29 divides the main image into a plurality of blocks, calculates the chromaticity of each block (average chromaticity in the block), and maps each block onto chromaticity coordinates according to the chromaticity. To do.

  (2) The CPU 29 finds a block group mapped to the chromaticity range corresponding to the current illumination type from these blocks, and calculates the center-of-gravity position on the chromaticity coordinates of these block groups. In the calculation, a larger number of blocks with high luminance may be counted.

  (3) The CPU 29 converts the calculated chromaticity of the center of gravity position into a correlated color temperature, and sets it as the correlated color temperature of the illumination light.

  Step S120: The CPU 29 gives an image processing instruction to the image processing circuit 23. At this time, the image processing circuit 23 performs color shading correction, white balance correction, color interpolation processing, and other processing on the image data of the main image. At this time, the gain set in step S108 is used in the color shading correction, and the gain set in step S109 is used in the white balance correction. The image data of the main image after the image processing is compressed by the CPU 29 and stored in the storage medium 32.

  As described above, the electronic camera according to the present embodiment includes the split photometric sensor 22 that generates a monitor image separately from the color imaging element 16 that generates the main image, and determines the illumination type based on the monitor image. Then, the electronic camera of this embodiment calculates a gain for color shading correction according to the illumination type.

  Therefore, the electronic camera of this embodiment does not need to drive the color image sensor 16 in order to calculate the gain for color shading correction. Therefore, the possibility that the color image sensor 16 rises in temperature is suppressed to a low level, and deterioration of the main image hardly occurs. Therefore, the effect of color shading correction on the main image is high.

  In addition, the electronic camera of the present embodiment calculates the gain of color shading correction for the R pixel according to the illumination type instead of calculating according to the color temperature of the illumination light. As described above, the color shading relating to the R pixel does not depend on the color temperature of the illumination light, but depends on the type of illumination. Therefore, according to this calculation method, the color shading correction gain is calculated with high accuracy, and the color shading is calculated. The effect of shading correction can be enhanced.

[Second Embodiment]
Hereinafter, a second embodiment of the present invention will be described. This embodiment is also an embodiment of an electronic camera. Here, only differences from the first embodiment will be described. The difference is in the lookup table stored in the ROM 27 and the processing in step S108.

The ROM27 of the present embodiment, as shown in FIG. 6 (a), (b) , (c), and a look-up table T _R of the two-dimensional, and a look-up table T _C one-dimensional, two-dimensional look-up and the table T _B are stored in advance.

As shown in FIG. 6 (a), the look-up table T _R has a variety of combinations of F values and EPD, combinations thereof each gain groups suitable for g _r1, ..., stored in association with the g _R750 together It is a two-dimensional lookup table. However, these gain groups g _r1 ,..., G _r750 are all gain groups suitable for standard illumination (for example, “fluorescent lamp”).

As shown in FIG. 6 (b), the look-up table T _C includes a variety of lighting types, their illumination each type of adjustment data group Delta] g is suitable for _r1, ..., one-dimensional stored in association with each other and Delta] g _R750 Lookup table. The adjustment data group Delta] g _r1, ..., Delta] g _R750 is gain group g _r1 suitable standard illumination, ..., the g _R750, the gain group g _r1 appropriate to the particular kind of lighting ', ..., g _R750' is adjusted to It is a data group for.

Here, it is assumed that the relationship g _ri ′ = g _ri −Δg _ri is satisfied for all i. Therefore, the adjustment data group _{Δg r1} ,..., _{Δg r750} corresponding to the “fluorescent lamp” is zero. Further, an adjustment data group _{Δg r1} ,..., _{Δg r750} corresponding to “ _synthetic sunlight”, “halogen lamp”, “strobe light”, etc. is an adjustment data group _Δg corresponding to “mercury lamp”, “sodium lamp”, etc. _r1 ,..., _{Δg r750} is larger.

As shown in FIG. 6 (c), the look-up table T _B includes various combinations of F values and EPD, combinations thereof each gain groups suitable for g _b1, ..., stored in association with the g _B750 mutually It is a two-dimensional lookup table.

  Then, the CPU 29 of this embodiment operates as follows (1) to (5) in step S108.

(1) CPU 29 includes the latest F value, the gain group g _r1 by inputting to the look-up table T _R showing the latest EPD in FIG 6 (a), ..., acquires g _R750.

(2) CPU 29, the adjustment data group Delta] g _r1 by inputting the lighting type determined in step S104 to the look-up table T _C shown in FIG. 6 (b), ..., acquires Delta] g _R750. However, when the object in step S107 was flash photography, CPU 29 is an illumination type to be input to the look-up table T _R, regardless of the illumination type determined in step S104 that the "strobe light".

(3) CPU 29 may gain group g _r1, ..., adjustment from each data group Delta] g _r1 of g _R750, ..., by subtracting Delta] g _R750, the gain group g _r1 suitable for the current illumination type ', ..., g _R750 'Get.

(4) CPU 29 is the latest F value, the gain group g _b1 by inputting to the look-up table T _B showing the latest EPD in FIG 6 (c), ..., acquires g _B750.

(5) The CPU 29 sets the acquired gain groups g _r1 ′,..., G _r750 ′, g _b1 , ..., g _b750 in the color shading correction unit 23a.

  That is, the electronic camera of this embodiment uses a combination of a two-dimensional lookup table and a one-dimensional lookup table instead of using a three-dimensional lookup table. Therefore, the amount of information to be stored in advance in the ROM 27 is suppressed more than that in the first embodiment.

[Others]
In the second embodiment, two look-up tables related to the R signal are converted into a two-dimensional look-up table (FIG. 6A) for calculating a gain group suitable for standard illumination, and the gain group is compared with the current gain group. Although the combination with a one-dimensional lookup table (FIG. 6B) for adjusting to a gain group suitable for the illumination type is used, the combination may be any of the following combinations (A) and (B). .

  (A) A combination of a two-dimensional lookup table for calculating a gain group suitable for the standard F value and a one-dimensional lookup table for adjusting the gain group to a gain group suitable for the current F value. In this case, information input to the two-dimensional lookup table is EPD and illumination type, and information input to the one-dimensional lookup table is an F value.

  (B) A combination of a two-dimensional lookup table for calculating a gain group suitable for standard EPD and a one-dimensional lookup table for adjusting the gain group to a gain group suitable for the current EPD. In this case, information input to the two-dimensional lookup table is the F value and the illumination type, and information input to the one-dimensional lookup table is EPD.

  In any of the above-described embodiments, the information stored in the lookup table is information on all blocks. However, the information amount of the lookup table is reduced by limiting the information to only some blocks. May be. Since the correction amount of color shading correction mainly depends on the image height, it may be limited to only information relating to each block in one area formed by dividing the image into four parts vertically and horizontally. In that case, CPU29 should just acquire the information of another block from the information regarding those blocks by calculation. However, in order to speed up image processing after shooting, it is desirable to store information on all blocks in the lookup table as in any of the embodiments described above.

  Further, in any of the embodiments described above, the illumination type determination result is held during the half-press period of the release button, but the illumination type determination is repeatedly performed during the half-press period of the release button, and the determination result is It may be updated each time.

  In any of the above-described embodiments, since it is assumed that the recording mode of the electronic camera is the normal recording mode, the image data after the image processing is stored. However, in the RAW recording mode, the CPU 29 The determined illumination type data may be recorded in the storage medium 32 together with the RAW data of the main image as supplementary information. Thereafter, when performing development processing of RAW data, the CPU 29 may read the RAW data from the storage medium 32 and execute the above-described step S108 and subsequent steps.

  In any of the above-described embodiments, the electronic camera executes the correction processing for the color shading correction, but the computer may execute part or all of the processing. In that case, a program necessary for processing is installed in the computer. The installation is performed via a storage medium such as a CD-ROM or the Internet.

It is a schematic diagram which shows the structure of an electronic camera. It is a block diagram which shows the circuit structure of an electronic camera. It is a figure explaining the look-up table used in 1st Embodiment. It is a conceptual diagram explaining the relationship between illumination kind and color shading. It is an operation | movement flowchart of CPU regarding imaging | photography. It is a figure explaining the lookup table used by 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Camera body, 16 ... Color imaging device, 16a ... AFE, 22 ... Divided photometry sensor, 22a ... A / D conversion circuit, 23 ... Image processing circuit, 24 ... Buffer memory, 25 ... Recording interface, 26 ... Operation switch, 29 ... CPU, 28 ... RAM, 27 ... ROM, 31 ... Bus

Claims (4)

A first color imaging device that captures an image of a field formed by the photographing lens and generates an image for storage;
A second color image sensor provided separately from the first color image sensor and detecting a color distribution of the object scene;
Determination means for determining the type of illumination light that illuminates the object scene based on the color distribution detected by the second color image sensor;
A color imaging apparatus comprising: setting means for setting a correction amount of color shading correction to be applied to an image generated by the first color imaging element according to the type determined by the determination means. The color imaging device according to claim 1,
The setting means includes
The color imaging apparatus, wherein the correction amount is set based on a type determined by the determination unit, an F value of the photographing lens, and an aperture stop position of the photographing lens. In the color imaging device according to claim 1 or 2,
A color imaging apparatus, further comprising: correction means for performing color shading correction on an image generated by the first color imaging device with a correction amount set by the setting means. In the color imaging device according to claim 1 or 2,
A color imaging apparatus, further comprising: a recording unit that stores the correction amount set by the setting unit together with the image generated by the first color imaging element.

Images