JP2001136546A - Electronic camera - Google Patents

Abstract

(57) [Summary] To detect a skin color from a focus detection area and determine a white balance adjustment gain. An image pickup device for picking up a subject image through an interchangeable lens, and an image pickup device for the interchangeable lens.
3, a color sensor 86 that receives the subject image and outputs color data, and a plurality of detection areas,
A focus detection device 36 for detecting the in-focus state of the interchangeable lens 90 in the detection area selected by the area selection switches 19a to 19d
And a white balance detection circuit 35 (FIG. 2) for determining a white balance adjustment gain based on the color data read from the color sensor 86 corresponding to the focus detection area. The white balance detection circuit 35 (FIG. 2) calculates R / G and B / G from the color data to detect a skin color, and determines a white balance adjustment gain using a correlated color temperature obtained from the detected skin color. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic camera for capturing an image of a subject and recording the captured image as electronic image data.

[0002]

2. Description of the Related Art An image pickup device such as a CCD for picking up an image of a subject passing through a photographing lens and outputting image data, and adjusting an amplification gain for image data output from the image pickup device to adjust white balance and γ. 2. Description of the Related Art An electronic camera including an image processing circuit that performs image processing such as an electronic camera is known. The image processing circuit calculates parameters such as R gain and B gain for white balance adjustment or a gradation curve for γ correction based on image data output from the imaging device by a predetermined algorithm. Is performed.

[0003]

In the above-described conventional electronic camera, a white balance adjustment coefficient is calculated such that the average value of color information of a captured main subject and a background is an achromatic color such as white or gray. Then, white balance adjustment is performed on the image data using the calculated adjustment coefficient. When performing close-up photographing of a person using such a camera as in portrait photographing, if there are many highly saturated colors such as flowers and greens in the background, the color information is often not achromatic even if the color information is averaged. As a result, poor adjustment of the white balance adjustment coefficient is likely to occur, and the skin tone of the person may change.

An object of the present invention is to provide an electronic camera in which the skin color of a main subject is detected from a predetermined image area such as a focus detection area and the white balance is adjusted so that the skin color of a person remains unchanged. It is in.

[0005]

FIG. 1 shows an embodiment of the present invention.
The present invention will be described with reference to FIG. (1) An electronic camera according to the first aspect of the present invention includes a photographing lens.
An imaging device 26 that captures a subject image passing through 90 and outputs image data, and is disposed at a position conjugate with the imaging device 26 with respect to the photographing lens 90, receives the subject image, and detects color temperature information Color temperature detecting means 86, and detects a skin color from the color temperature information of the color temperature detecting means 86 corresponding to a predetermined area of the object scene,
Gain calculating means 35C for calculating a gain using this skin color
The above-described object is achieved by providing a gain adjusting unit 103 that performs gain adjustment by multiplying the image data output from the imaging device 26 by the gain calculated by the gain calculating unit 35C. (2) The electronic camera according to the first aspect of the present invention is the electronic camera according to the first aspect, wherein the photographing lens 90 is provided in a plurality of regions within the object scene.
Focus detection means 36 for detecting the focus adjustment state, focus detection area selection means 19a to 19d for selecting a detection area by the focus detection means 36 from among a plurality of areas, and the focus adjustment state detected by the focus detection means 36 Lens driving means 37 for driving the photographing lens 90 to the in-focus position based on the above, and the gain calculating means 35C comprises a color temperature detecting means 86 corresponding to the detection area selected by the focus detecting area selecting means 19a to 19d. Is characterized in that a skin color is detected from the color temperature information and a gain is calculated using the skin color. (3) In the electronic camera according to the third aspect, in the electronic camera according to the second aspect, the gain calculating unit 35C calculates the gain using the skin color detected when the focus adjustment driving by the lens driving unit 37 ends. The gain adjusting unit 103 is characterized in that the gain is adjusted by applying the gain to the image data output from the imaging device 26. (4) The electronic camera according to any one of the first to third aspects, wherein the photometer 86 detects the brightness of the subject image in a plurality of regions of the object scene. And a photometric region selecting unit 19a to 19d for selecting a photometric region by the photometric unit 86, and the gain calculating unit 35C is provided with a color temperature detecting unit 86 corresponding to the photometric region selected by the photometric region selecting unit 19a to 19d. Detect skin color from temperature information,
The gain is calculated using the skin color.

[0006] In the section of the means for solving the above-mentioned problems, which explains the configuration of the present invention, the drawings of the embodiments are used to make the present invention easier to understand. However, the present invention is not limited to this.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a single-lens reflex digital still camera according to this embodiment includes a camera body 70 and a finder device 8 attached to and detached from the camera body 70.
0, a lens 91 and an aperture 92, and a camera body 70
And an interchangeable lens 90 attached to and detached from the camera. The subject light enters the camera body 70 through the interchangeable lens 90. Before the release, the quick return mirror 7 located at the position indicated by the dotted line
The finder mat 8 is guided to the finder device 80 at 1
1, and also forms an image on the focus detection device 36. The subject light that forms an image on the viewfinder mat 81 is further guided to an eyepiece 83 by a pentaprism 82. Before the release, the subject light passes through the prism 84 and the imaging lens 85 and enters the color sensor 86 to form a subject image. After the release, the quick return mirror 71 rotates to the position shown by the solid line, and the subject light forms an image on the imaging device 73 for photography via the shutter 72. The color sensor 86
It is arranged at a position conjugate with the imaging device 73 with respect to the taking lens 91.

FIG. 2 is a block diagram showing a circuit of a digital camera according to an embodiment of the present invention. The CPU 21 receives a half-press signal and a full-press signal from a half-press switch 22 and a full-press switch 23 linked to the release button, respectively. The CPU 21 has an AE lock switch 17 for holding a photometry result described later, an AF lock switch 18 for holding a focus detection result described later, and area selection switches 19a to 19d for selecting a focus detection area and a photometry area.
Is input. In response to a command from the CPU 21, the focus detection device 36 detects the focus adjustment state of the photographing lens 91, and the lens driving device 37 is controlled so that the subject light incident on the interchangeable lens 90 forms an image on the imaging device 26 of the imaging device 73. The lens 91 is driven to a focus position. The focus detection device 36 has a plurality of focus detection areas, and detects a focus adjustment state in any one of the selected focus detection areas. The CPU 21 includes a timing generator 24
And the driver 25 to control the driving of the imaging element 26 of the imaging device 73. Then, the operation timing of the analog processing circuit 27 and the A / D conversion circuit 28 is controlled by the timing generator 24.

When the full-press switch 23 is turned on after the half-press switch 22 is turned on, the quick return mirror 71 rotates upward, and subject light from the interchangeable lens 90 is applied to the light receiving surface of the image sensor 26. Image. The image sensor 26 is a CCD, and accumulates signal charges corresponding to the brightness of the subject image. The signal charges stored in the image sensor 26 are swept out by the driver 25 and input to an analog signal processing circuit 27 including an AGC circuit and a CDS circuit.
After analog processing such as gain control and noise removal is performed on the analog image signal by the analog signal processing circuit 27, the analog image signal is converted into a digital signal by the A / D conversion circuit 28. The digitally converted signal is, for example, AS
The image is guided to an image processing CPU 29 configured as an IC, where image preprocessing such as white balance adjustment, contour compensation, and gamma correction, which will be described later, is performed.

The image data subjected to the image pre-processing is further subjected to a format process (image post-process) for JPEG compression, and the image data after the format process is temporarily stored in the buffer memory 30. You.

The image data stored in the buffer memory 30 is processed into image data for display by a display image creation circuit 31 and displayed as a photographing result on a viewfinder 32 such as an LCD. The image data stored in the buffer memory 30 is subjected to data compression at a predetermined ratio by the compression circuit 33 according to the JPEG method, and is recorded on a recording medium (memory card) 34 such as a flash memory.

FIG. 3 is a block diagram showing details of the image processing CPU 29 in the digital camera operating as described above. FIG. 3 shows a line processing circuit 100 that performs signal processing on image data from the image sensor 26 line by line, and performs the above-described image preprocessing. This line processing circuit 1
Reference numeral 00 denotes various types of signal processing described below for the 12-bit R, G, and B signals output from the A / D conversion circuit 28. The digital clamp circuit 101, the gain setting circuit 102, and the gain It has an adjustment circuit 103, a black level circuit 104, and a γ correction circuit 105.

The 12-bit R, G, and B signals output from the A / D conversion circuit 28 are dot-sequentially output line by line with respect to the output of the image sensor 26, and the defective pixel (the address of which is specified in advance) After that, the data is input to the digital clamp circuit 101 after being corrected. The digital clamp circuit 101
The output of the image sensor 26 is dot-sequential for each line,
A weighted average of a plurality of pixel data used as optical black is subtracted from each pixel data of the line.

A gain setting circuit 102 sets an adjustment gain for pixel data of each of R, G, and B colors. The adjustment gain is set such that a gain is given to each pixel data of each color output from the imaging element 26, and the output level of each color becomes a predetermined level by the given gain. Even when the output level of the pixel data output from the image sensor 26 varies due to the variation of the image sensor 26, the gain adjustment circuit 1
The image data level input to 03 is corrected to a predetermined level regardless of the instrumental error of the image sensor 26. The gain adjustment circuit 103 performs white balance adjustment by multiplying the input R and B color pixel data by R gain and B gain for white balance adjustment. These R gain and B gain are calculated by a white balance detection circuit 35 described later and stored in the memory 35D.

The black level circuit 104 outputs a predetermined value stored in the register of the CPU 21 to R,
G and B signals are added. The gamma correction circuit 105 performs gamma correction on the output of the image sensor 26 in a dot-sequential manner for each line using a gradation look-up table.

-White Balance Detection- The white balance detection processing performed by the white balance detection circuit 35 of FIG. 2 will be described in detail. The white balance detection circuit 35 generates the white balance adjustment coefficient based on the above-described color sensor 86, an A / D conversion circuit 35B that converts an analog signal from the color sensor 86 into a digital signal, and the converted digital signal. CPU3
5C and a memory 35D in which a lookup table for reference is recorded. The CPU 35C detects a white balance from digital data captured by the color sensor 86 and determines a white balance adjustment gain. In the present embodiment, the CPU 35C detects a skin color based on color information of digital data, and determines a white balance adjustment coefficient, that is, an R gain and a B gain for white balance adjustment, according to the detected skin color. In this specification, a gain adjustment that makes a skin color more flesh-colored is also referred to as white balance adjustment.

The color sensor 86 is a single two-dimensional image sensor having 480 pixels divided into, for example, 24 columns × 20 columns as shown in FIG. On the surface of the image sensor 86, 48 rows of 24 columns × 20 rows corresponding to 480 pixels
An RGB color filter 861 divided into 0 blocks is provided. By capturing the subject light through such a color filter, the subject light is decomposed into an R color signal, a G color signal, and a B color signal and captured. CPU3
When detecting color information in 5C, a focus detection device 3 described later
The color sensor 86 corresponds to the focus detection area selected in Step 6.
, The color data of the subject light is read out.

In FIG. 4, points 86V to 86W represent positions on the color sensor 86 corresponding to the focus detection area. For example, when the focus detection area is set at the center of the object scene by the setting of the focus detection area described later, a square area of 6 pixels horizontally × 4 pixels vertically centered on the center point 86W of the color sensor 86 is used. The color data of the R, G, and B colors (shown by hatching in FIG. 4) are read.

Regarding the read color data, a set of R, G, and B color data adjacent in the horizontal direction is referred to as a target pixel i, and for each target pixel i read from the rectangular area,
A ratio R / G between the R color data and the G color data and a ratio B / G between the B color data and the / G color data are calculated. By using the following equations (1) and (2) for the calculated R / G and B / G, data suitable for skin color is detected.

SRGLOWER <Fi (R / G) <SRGUPPER (1) SBGLOWER <Fi (B / G) <SBGUPPER (2) where SRGLOWER and SRGUPPER are the lower and upper thresholds of the R color ratio at the time of skin color judgment. Yes, SBGLOWER and SBGUPPER are a lower threshold and an upper threshold of the B color ratio at the time of skin color determination. Further, Fi (R / G) and Fi (B / G) are the ratio of the R signal to the G signal and the ratio of the B signal to the G signal in the target pixel i. These thresholds are stored in the memory 35D in advance, and for example, 0.9 <Fi
(R / G) <1.1 and 0.7 <Fi (B / G) <0.9.

Assuming that the skin-color-like data satisfying the above equations (1) and (2) is the target pixel j, the average value of R / G of all target pixels j and the average value of B / G of all target pixels j Is
It is calculated by (3) and (4).

(Equation 2)

The correlated color temperature is determined based on the calculated average values of R / G and B / G. FIG. 5 is a diagram showing a correlated color temperature curve, where the horizontal axis is R / G and the vertical axis is B / G. By dividing the R signal and the B signal by the G signal, the red component and the blue component of the color of the subject can be represented without the influence of the luminance difference of the subject. As the color temperature increases, the blue component increases, and as the color temperature decreases, the red component increases. Since the correlated color temperature curve of FIG. 5 is stored in the memory 35D in advance as a look-up table, the correlated color temperature is read from the memory 35D according to the results calculated by the above equations (3) and (4). The white balance adjustment R gain for the R data and the white balance adjustment B gain for the B data are determined from the read correlated color temperature using FIG.

FIG. 6 is a diagram showing the relationship between the correlated color temperature and the R gain and the B gain. The values of the R gain and the B gain are determined in advance based on the actually measured data so as to bring the detected skin-like color closer to the skin color, and are expressed as a function of the color temperature. These R gain and B
The gain value is stored in a memory 35D as a lookup table.
And is read from the memory 35D according to the correlated color temperature obtained as described above. The read R gain and B gain values are determined as white balance adjustment coefficients used at the time of white balance adjustment. This white balance adjustment gain is stored in the memory 35D and sent to the image processing CPU 29 via the CPU 21.

The white balance adjustment coefficient determined as described above is used at the time of white balance adjustment performed by the gain adjustment circuit 103 on image data picked up by the image pickup device 26 thereafter. White balance adjustment is performed regardless of the white balance detection area.
This is performed by multiplying the R signal and the B signal of the entire area imaged in step 6 by the R gain and the B gain for white balance adjustment, respectively.

-Focus Detection- The configuration of the focus detection device 36 and the principle of the focus detection operation by the focus detection device 36 will be described with reference to FIG. The focus detection device 36 is controlled by the CPU 21 and includes an infrared light cut filter 700, a field mask 900, a field lens 300, an aperture mask 400, and a re-imaging lens 5.
01 and 502, and an image sensor 310. An area 800 is an exit pupil of the photographing lens 91 (FIG. 1). Areas 801 and 802 are areas where an image obtained by back-projecting the openings 401 and 402 formed in the aperture mask 400 onto the area 800 by the field lens 300 is present. Note that the infrared light cut filter 700
May be on the right or left side of the field mask 900. The light beams incident through the regions 801 and 802 are focused on the equivalent surface 600 of the image sensor 26, and then are focused on the infrared light cut filter 700, the field mask 900, the field lenses 300, the openings 401 and 402, and The image sensor array 310a passes through the image lenses 501 and 502,
An image is formed on 310b.

These image sensor arrays 310a, 310a
A pair of subject images formed on 10 b
Are close to each other in a so-called front focus state in which a sharp image of the subject is formed before (subject side) the equivalent surface 600 of the image sensor 26, and conversely, in a so-called rear focus state in which a sharp image of the subject is formed behind the equivalent surface 600 of the image sensor 26. In the pin state, they move away from each other. Then, the image sensor arrays 310a and 310b
A sharp image of the subject is located on the equivalent surface 600 of the image sensor 26 when the subject image formed above has a predetermined interval.
Therefore, the pair of subject images are photoelectrically converted by the image sensor arrays 310a and 310b to be converted into electric signals, and these signals are subjected to arithmetic processing to obtain the relative distance between the pair of subject images. That is, the position where a sharp image is formed by the interchangeable lens 90 is
In which direction and how far from the equivalent surface 600 of the image sensor 26, that is, the shift amount is obtained. In FIG. 7, the focus detection areas are the image sensor array 310a,
310b is projected back by the re-imaging lenses 501 and 502, and corresponds to a portion overlapping near the equivalent surface 600 of the image sensor 26.

The focus detection area in the photographing screen is set as follows. FIG. 8 is a diagram illustrating the area selection switches 19a to 19d provided on the back of the digital still camera, and FIG. 9 is a diagram illustrating a screen observed through the eyepiece 83. In FIG. 9, five marks 9V to 9Z
Indicates a focus detection area. The change of the focus detection area is performed by operating the area selection switches 19a to 19d until a predetermined time elapses after the half-push switch 22 is operated.

When the half-push switch 22 is operated, the area selection switches 19a to 19d are enabled for a predetermined time. When the switch 19a is operated during this time, when the switch 19a is operated, a position above the currently set focus detection area 9W in FIG. Is changed to the focus detection area 9V. Subsequently, when the area selection switch 19b is operated, the area is changed to the focus detection area 9W again. When the area selection switch 19c is operated, the focus detection area 9Y is changed to the focus detection area 9Y located on the left of the focus detection area 9W. Similarly, by operating the area selection switch 19d, it is possible to change to the focus detection area 9Z located to the right of the set focus detection area 9W. The selected focus detection area is displayed in an emphasized manner as compared with markers in other areas, for example, as in an area 9Y in FIG. Marks 9V to 9 on the main subject by the photographer
By selecting any one of Z, the adjustment state of the focus position described above is detected in the focus detection area in the shooting screen corresponding to the selected mark.

FIG. 7 shows one focus detection area for explaining the principle of focus detection. When a plurality of focus detection areas are provided in the field as shown in FIG. 9, a plurality of openings are formed in the field mask 9 corresponding to the focus detection areas.
00 is provided. Then, an optical system is provided so that the light beams passing through the plurality of openings of the field mask 900 are respectively formed as a pair of subject images.

The focus detecting operation by the focus detecting device 36 is as follows.
When the AF lock switch 18 is turned on, the photographing lens 91 is moved to the in-focus position by the lens drive circuit 37 based on the focus adjustment state detected at that time, and the subsequent focus detection operation is performed until the photographing process ends. Stop. Information on the focus detection area used in the focus detection operation is also used as an area for performing white balance detection as described above.
That is, points 86V to 86Z on the color sensor 86 correspond to the focus detection areas 9V to 9Z, respectively. For example, FIG.
When the area 9Y is selected as the focus detection area in
In the above-described white balance detection, the point 86 in FIG.
The color data of the G, B, and R colors existing in a rectangular area of 6 pixels × 4 pixels centering on Y is read from the color sensor 86. Information on the focus detection area and the operation state of the AF lock switch 18 are also sent from the CPU 21 to the white balance detection circuit 35.

FIG. 10 is a flowchart showing the white balance detection processing according to the present embodiment. Step S
In 201, it is determined whether the AF lock switch 18 is turned on. A negative determination is made (step S
If (N of 201) and the process proceeds to step S202, and if an affirmative determination is made (Y of step S201), the process proceeds to step S210.
In step S202, signal charges are accumulated in the color sensor 86, and the accumulated charge signals are converted into the A / D conversion circuit 35B.
Is converted to digital data. In step S203, position information of a focus detection area where focus detection is performed by the focus detection device 36 is read from the memory 35D. In step S204, R, G, and B in a predetermined area centered on the position on the color sensor 86 corresponding to the focus detection area
For the color pixel data, the ratio between the R color data and the G color data and the ratio between the B color data and the / G color data are calculated.

In step S205, it is determined whether or not there is skin color data in the target pixel i using the above equations (1) and (2). When one or more target pixels j satisfying both equations are detected, an affirmative determination is made (Y in step S205), and the process proceeds to step S206. In step S206, m sets of R / G and B / B detected by the above equations (1) and (2) are used.
The average value of G is calculated by the above equations (3) and (4).

In step S207, the calculated R
The correlated color temperature is read from memory 35D based on the average values of / G and B / G. In step S208,
The white balance adjustment R gain for the R data and the white balance adjustment B gain for the B data are determined from the relationship between the correlated color temperature and the white balance adjustment gain in FIG. The determined R gain and B gain are stored in the memory 35D. Step S20
At 9, the R gain and the B gain for white balance adjustment are sent to the image processing CPU 29, and the processing in FIG. 10 ends.

When a negative determination is made in step S205 (N in step S205), step S2 is performed.
Proceeding to 11, the predetermined white balance adjustment R gain and B gain stored in the memory 35D are read. These R gain and B gain are previously stored in the memory 35D as default values.

On the other hand, in step S210, which proceeds when the result of the determination in step S201 is affirmative, the R gain and B gain stored in the previous step S208 are read from the memory 35D. That is, when the AF lock switch 18 is turned on, no new calculation of the white balance adjustment coefficient is performed. When the AF lock switch 18 is turned on, the white balance adjustment coefficient is determined based on the skin-like color detected at that time, and the subsequent white balance detection operation until the photographing process ends is stopped. The operation state of the AF lock switch 18 is C
It is also sent from the PU 21 to the white balance detection circuit 35.

The operation of the digital still camera thus configured will be described. FIG. 11 is a flowchart showing the photographing process. In step S301, AF
It is determined whether the lock switch 18 is turned on. If a negative determination is made (N in step S301), the process proceeds to step S302, and if an affirmative determination is made (Y in step S301), the process proceeds to step S303. In step S302, the focus adjustment state is detected by the focus detection device 36, and the lens driving device 37 drives the lens 91 to the in-focus position based on the detected focus adjustment state. Step S3
At 03, the above-described white balance detection processing of FIG. 10 is performed.

In step S304, the image sensor 26
Each pixel accumulates the light receiving signal, and after the accumulation is completed, the accumulated charges of all the pixels are sequentially read. The read image data is processed by an analog signal processing circuit 27 and then converted into digital image data by an A / D conversion circuit 28.
29. Predetermined image processing including the above-described white balance adjustment is performed by the image processing CPU 29, and a through image after the image processing is displayed on the viewfinder 32 in step S305.

In step S306, it is determined whether or not the half-press switch 22 has been operated, and an affirmative determination is made.
(Y in step S306) and the process proceeds to step S307, and if a negative determination is made (N in step S306), the process proceeds to step S30.
Return to 1. In step S307, a photometric operation for detecting the luminance of the subject is performed. The luminance of the subject is detected by the CPU 35C using the data output from the color sensor 86. The luminance data detected by the CPU 35C is
When output to 1, the CPU 21 performs an exposure calculation based on the luminance data. In step S308, it is determined whether the AF lock switch 18 is turned on. If a negative determination is made (N in step S308), the process proceeds to step S309, and if an affirmative determination is made (Y in step S308), the process proceeds to step S310.

In step S309, the focus adjustment state is detected by the focus detection device 36, and the lens driving device 37 drives the lens 91 to the in-focus position based on the detected focus adjustment state. It is determined in step S310 that the full-press switch 23 has been operated (step S31).
If 0), the quick return mirror jumps up, and the photographing sequence after step S311 is started. On the other hand, when a negative determination is made (N in step S310), the process proceeds to step S317, and a timeout determination is performed. No timeout is determined in step S317 (step S3
In the case of 17) (N), the process returns to step S310, and when the timeout is determined (Y in step S317), the processing in FIG.

In step S311, the image sensor 26
Each pixel accumulates the light receiving signal, and after the accumulation is completed, the accumulated charges of all the pixels are sequentially read. In step S312,
The read image data is processed by the analog signal processing circuit 27, converted into digital image data by the A / D conversion circuit 28, and input to the image processing CPU 29. Next, the process proceeds to step S313, and the image processing CPU 29 performs the above-described white balance adjustment, γ gradation correction, JPEG formatting, and the like. Upon completion of the image processing, the flow advances to step S314 to temporarily store the image data after the image processing in the buffer memory 30 and display a frozen image on the viewfinder 32. In step S315, the image data is read from the buffer memory 30, and the data is compressed by the JPEG compression circuit 33.
In step S316, the compressed image data is stored in the memory card 34, and the processing in FIG. 11 ends.

In the above description, the case of photographing under natural light has been described. However, when photographing under fluorescent light, it is necessary to adjust the white balance adjustment gain. Generally, the color temperature of the captured RGB data is higher when photographing under a fluorescent light than when photographing under natural light. This color temperature difference is determined by the R gain and the B gain shown in FIG.
It can be corrected by correcting the value of the gain by a predetermined amount. Therefore, two sets of lookup tables storing the values of the R gain and the B gain are prepared for photographing under natural light and for photographing under fluorescent light, and correspond to photographing light preset by the photographer. Make the lookup table read.

The features of this embodiment will be summarized. (1) A target pixel j likely to be skin color is detected from the output of the color sensor 86, an average of R / G and B / G at the detected target pixel j is calculated, and converted to data on R / GB / G coordinates. The correlated color temperature was determined. Further, according to the obtained correlated color temperature, R gain and B for white balance adjustment are set.
Since the gain is determined, the optimum white balance is adjusted for the skin color. Therefore, when performing portrait photography, the optimal white balance adjustment for the flesh color of the person is performed regardless of the background color. (2) The detection of the attention pixel j which looks like skin color according to the above (1)
This is performed using the color data read from the color sensor 86 corresponding to the focus detection area selected by the focus detection device 36. That is, when the focus detection area 9Y is selected in FIG. 9, the horizontal 6 around the point 86Y in FIG.
G, B and R existing in a rectangular area of pixel × 4 pixels
It is performed using the color data of the color. Generally, the focus detection area is set at the position where the main subject exists,
By using the color data of the color sensor 86 corresponding to this area, it is possible to obtain an effect of making it easy to detect skin color-like data in portrait shooting. (3) When the AF lock switch 18 is turned on, the white balance adjustment coefficient is determined based on the skin-like color detected at that time, and the subsequent white balance detection operation until the photographing process ends is stopped. I made it. For example, if the AF lock switch 18 is turned on so that the main subject is located in the selected focus detection area, and then the camera is panned and photographed, even when the main subject is taken out of the focus detection area and photographed, The optimum white balance adjustment coefficient and the in-focus state for the main subject are maintained. (4) Since the color sensor 86 is disposed in the finder device 80, the color sensor 86 receives white balance detection data before the mirror 71 is mirrored up by operating the full-press switch 23. The white balance adjustment gain can be determined and sent to the image processing CPU 29. Therefore, it is not necessary to determine the white balance adjustment gain in the photographing sequence from step S311 performed by operating the full-press switch 23, so that the photographing processing time is shorter than when the white balance detection data is received in the photographing sequence. Can be shortened. (5) Since the color sensor 86 is used for both white balance detection and subject brightness detection, the mounting space can be reduced as compared with the case where the color sensor 86 is not used for both purposes, and the cost can be reduced. Is obtained.

In the above description, a single-lens reflex digital still camera has been described. However, the present invention can be applied to a non-single-lens reflex digital camera. In this case, the image sensor 2 is formed using a beam splitter, a half mirror, or the like.
6 and the color sensor 86 separately form subject images.

In the above description, the image sensor 26 and the color sensor 86 are provided separately. However, the image sensor 26 may also be used as a color sensor. In this case, the white balance adjustment gain is determined as described above using the data captured by the image sensor 26. Then, white balance adjustment is performed on the subject image data captured when the release operation is performed by using the white balance adjustment gain.

In the above description, the image sensor 26 and the image sensor 310 of the focus detecting device 36 are provided separately. However, the image sensor 26 may be used also as the image sensor 310. Further, although the image sensor 310 and the color sensor 86 are provided separately, the image sensor 310 may also serve as the color sensor 86. Furthermore, the image sensor 26 can also be used as the image sensor 310 and the color sensor 86.

In the above description, when color information is detected by the CPU 35C, color data is read from a square area of 6 pixels × 4 pixels centered on a position corresponding to the focus detection area on the color sensor 86, For the read R, G, and B color data, the ratio between the R color data and the G color data and the ratio between the B color data and the / G color data are calculated. However, instead of the color data in the rectangular area, a set of R, G, and B color data close to a position corresponding to the focus detection area on the color sensor 86 is read, and the set of color data is used. R / G and B / G may be calculated by the following method.

In the above description, the detection of the target pixel j which looks like flesh color is performed in accordance with the focus detection area selected by the focus detection device 36. However, when the digital camera has a plurality of photometric areas in the object field and performs a spot photometric operation in any one of the selected photometric areas, a skin-color-like attention corresponding to the selected photometric area. The detection of the pixel j may be performed.
In the present embodiment, the brightness of the subject is detected from the magnitude of the value of the color data output from the color sensor 86, and an exposure calculation is performed based on the detected brightness value. Therefore, both the luminance detection and the white balance detection may be performed using the color data read from the color sensor 86 corresponding to the photometry area. Normally, the spot metering area is set in accordance with the main subject. By using the color data read from the color sensor 86 corresponding to the spot metering area, it is easy to detect skin color-like data in portrait shooting. Is obtained.

In step S201 of the flowchart of FIG. 10, it is determined whether or not the AF lock switch 18 is turned on. If it is determined that the AF lock switch 18 is turned on, the process proceeds to step S210, and the processing is continued until the photographing process ends. The subsequent white balance detection operation is stopped. In step S201, it may be determined whether or not the AE lock switch 17 is turned on instead of the AF lock switch 18. In this case, A
When the E-lock switch 17 is turned on, the white balance adjustment coefficient is determined based on the skin-like color detected at that time, and the subsequent white balance detection operation until the photographing process ends is stopped. For example, if the AE lock switch 17 is turned on so that the main subject is located at the center of the object scene, and then the camera is panned and photographed, even if the main object is taken out of the center of the object scene and photographed,
The optimum white balance adjustment and exposure calculation value for the main subject are held. The information on the photometry area and the operation state of the AE lock switch 17 are also sent from the CPU 21 to the white balance detection circuit 35.

Further, step S201 in FIG. 10 may be omitted. In this case, regardless of the operation state of the AF lock switch 18, the process always proceeds to step S
The white balance detection operation after 202 is performed. Furthermore, steps S301 and S308 of the flowchart of FIG. 11 may be omitted. In this case, step S302 and step S302
At 309, the focus detection operation by the focus detection device 36 is performed.

The correspondence between each component in the claims and each component in the embodiment of the present invention will be described.
6, the color sensor 86 serves as a color temperature detecting means and a photometric means, the CPU 35C serves as a gain calculating means, the gain adjusting circuit 103 serves as a gain adjusting means, and the focus detecting device 36 serves as a gain adjusting means.
Corresponds to the focus detection means, the lens driving device 37 corresponds to the lens driving means, and the area selection switches 19a to 19d correspond to the focus detection area selection means and the photometry area selection means, respectively.

[0050]

According to the present invention as described in detail above, the following effects can be obtained. (1) According to the first aspect of the present invention, the color temperature detecting means detects color temperature information corresponding to a predetermined area of the object scene, and an image is obtained with a gain calculated using the skin color detected from the color temperature information. Gain adjustment for data was performed. Therefore, for example, when performing close-up photographing of a person as in portrait photographing, if color temperature information is detected from the skin region of the person, even if there is a highly saturated color in other regions, the skin color , An optimum gain can be calculated.
As a result, the white balance can be correctly adjusted, and a high-quality image can be obtained. (2) According to the second and third aspects of the invention, in addition to the configuration of the first aspect, the color temperature information is detected corresponding to the focus detection area by the focus detection means. In general, the focus detection area is set at a position where the main subject is present. Therefore, by detecting color temperature information corresponding to this area, color temperature information of a person's skin is detected in portrait shooting. The likelihood increases. (3) According to the invention of claim 4, the color temperature information is detected corresponding to the photometry area by the photometry means. For example,
When spot metering is performed, the metering area is set at the position of the main subject. By detecting color temperature information corresponding to this area, color temperature information of a person's skin is detected in portrait shooting. It is more likely to be done.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of an embodiment of a single-lens reflex digital still camera.

FIG. 2 is a block diagram showing an embodiment of a signal processing system of the single-lens reflex digital still camera.

FIG. 3 is a block diagram illustrating a circuit that performs line processing in the signal processing system illustrated in FIG. 2;

FIG. 4 is a diagram showing a filter array of a color sensor.

FIG. 5 is a diagram of a color temperature curve represented on R / GB / G coordinates.

FIG. 6 is a diagram illustrating a relationship between a color temperature and a gain for white balance adjustment.

FIG. 7 is a diagram illustrating a focus detection device.

FIG. 8 is a diagram illustrating an area selection switch.

FIG. 9 is a diagram of a screen observed through an eyepiece.

FIG. 10 is a flowchart illustrating a white balance detection process.

FIG. 11 is a flowchart illustrating a photographing process.

[Explanation of symbols]

17: AE lock switch, 18: AF lock switch, 19a to 19d: area selection switch,
21: CPU, 22: Half-press switch,
23: Full-press switch, 26: Image sensor,
28: A / D conversion circuit, 29: Image processing CPU, 32: Viewfinder,
33: JPEG compression circuit, 35: White balance detection circuit, 35B: A / D conversion circuit,
35C CPU, 35D memory
36: focus detection device, 37: lens driving device, 73: imaging device, 86: color sensor, 90: interchangeable lens, 91 ...
Shooting lens, 92 ... Aperture, 100
... Line processing circuit, 102 ... Gain setting circuit, 103 ... Gain adjustment circuit

Continued on the front page F term (reference) 5C065 AA03 BB02 BB04 BB10 BB12 BB23 CC08 CC09 DD02 DD17 EE06 EE13 FF03 GG15 GG17 GG18 GG23 GG30 GG31 GG32 GG35 5C066 AA01 BA20 CA08 CA17 DD01 DD07 EA08 EA02 EC02 KE03 KE09 KE17 KE19 KE24 KF05 KM02 KM05

Claims (4)

[Claims] An image pickup device for picking up an image of a subject passing through a photographing lens and outputting image data; and an image pickup device disposed at a position conjugate to the image pickup device with respect to the photographing lens and receiving the image of the subject. Color temperature detecting means for detecting color temperature information, and gain calculating means for detecting a skin color from the color temperature information of the color temperature detecting means corresponding to a predetermined area of the object scene and calculating a gain using the skin color. An electronic camera, comprising: a gain adjustment unit configured to apply a gain calculated by the gain calculation unit to image data output from the imaging device to perform gain adjustment. 2. The electronic camera according to claim 1, wherein the focus detection means detects a focus adjustment state of the photographing lens in a plurality of areas in the object scene, and the focus detection means from the plurality of areas. Focus detection area selecting means for selecting a detection area according to the following; and lens driving means for driving the photographing lens to a focusing position based on the focus adjustment state detected by the focus detecting means, wherein the gain calculating means An electronic camera comprising: detecting a flesh color from color temperature information of the color temperature detecting means corresponding to a detection area selected by the focus detection area selecting means; and calculating a gain using the flesh color. 3. The electronic camera according to claim 2, wherein the gain calculating means calculates a gain using a skin color detected when the focus adjustment driving by the lens driving means is completed, and the gain adjustment is performed. An electronic camera, wherein the means adjusts the gain by applying the gain to image data output from the imaging device. 4. The electronic camera according to claim 1, wherein said photometering means detects a luminance of said subject image in a plurality of regions of the object scene, and said photometering means from among said plurality of regions. A photometric region selecting unit that selects a photometric region according to the above, wherein the gain calculating unit detects a flesh color from the color temperature information of the color temperature detecting unit corresponding to the photometric region selected by the photometric region selecting unit. An electronic camera which calculates a gain using a skin color.