JP2002369211A - Electronic still camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photographed image having an overall proper balance over the entire image, even when photographing is conducted using the stroboscopic light as an auxiliary light. SOLUTION: Photographing is conducted automatically under the ambient light as pre-exposure prior to emitting the light from a strobe 200, and the luminance information obtained from this operation is stored in an image memory 204 for luminance information to determine the color of the ambient light. The luminance information of an image formally photographed by emitting light from the strobe 200, and the luminance information at the time of pre- photographing are compared, by means of a luminance information comparator 205, and from an obtained signal level ratio, the color of a light source at each point in the image is calculated; and by taking white balance based on the calculated colors of light sources, such as image, is obtained that has proper white balance over the entire image.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the white balance of an electronic still camera equipped with a strobe flash, and more particularly to an electronic still camera device capable of obtaining an image with good color reproducibility.

[0002]

2. Description of the Related Art In general, an electronic still camera is disclosed in Japanese Patent Application Laid-Open No. 4-70 to judge shooting conditions and automatically adjust an exposure amount and a white balance so as to obtain a clear image.
A function as described in Japanese Patent No. 179 is installed. This function is used, for example, when the lighting is dark and underexposure is likely to occur, the built-in strobe flash is fired and the white balance setting is adjusted under the light source where the ambient light of the subject and the strobe flash light are mixed. By correcting the gain control signal of the white balance at the time of photographing in accordance with the amount of light emitted from the strobe, it is possible to obtain an image with good color reproducibility.

As shown in FIG. 12, reflected light from a subject 102 near an electronic still camera 101 enters a white balance sensor, and a subject 10
No. 2 provides an image with good white balance and good S / N.

However, a subject 10 far from the camera
3 is that if the strobe flash light weakens in inverse proportion to the square of the subject distance, the ambient light, such as a fluorescent lamp or a light bulb, becomes the main light source, and this is taken in a white balance state that matches the subject 102 close to the camera. In this case, the white image is shot in a yellow or reddish state.

[0005] Therefore, in the case of stroboscopic flash photography indoors, a subject having a short subject distance can be photographed with a white balance, but a distant subject can be photographed only in a yellow or reddish state. Occurs.

[0006]

In the above-described conventional electronic still camera, when shooting with a strobe as auxiliary light, the white balance of the background cannot be obtained because the white balance is set in accordance with the strobe light. There was a problem.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an electronic still camera device capable of obtaining a shot image with a white balance over the entire image even when shooting using strobe light as auxiliary light.

[0008]

In order to solve the above-mentioned problems, in an electronic still camera apparatus according to the present invention, prior to a strobe flash photographing, a means for estimating a light source color from a photographed image, and a luminance of the image, Means for storing information; means for determining a white balance setting condition from a signal level ratio of the same area of the luminance information of the image captured by the strobe flash and the stored luminance information; and a signal in accordance with the white balance setting. Signal processing means for performing processing.

According to this means, even in the case of photographing using an auxiliary light such as a strobe flash, an image with a white balance can be obtained over the entire screen regardless of the distance to the subject.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram for explaining a first embodiment of the present invention, and FIG. 2 is a timing chart for explaining the operation of FIG.

When the power is turned on or the shutter button is half-pressed, a pre-imaging state is set in which the flash of the strobe 200 as the auxiliary light is not emitted. In this pre-imaging, only ambient light is given to the subject as illumination. The subject image is formed on the solid-state imaging device 202 by the lens 201. The video signal photoelectrically converted by the solid-state imaging device 202 is input to the color separation circuit 203 and output as a video signal of three primary colors.

A red signal (R) and a blue signal (B) of the three primary color video signals are respectively supplied to white balance amplifiers 206 and 2.
07, the camera process matrix circuit 208
To output a luminance signal and two color difference signals. The integrators 209 and 210 output the average value of the two color difference signals to the gain control circuit 211. Color separation circuit 2 as luminance information
The G signal of 03 is supplied to the luminance information comparator 205 and the luminance information image memory 204, respectively.

The luminance information image memory 204 stores an input signal during pre-imaging and outputs the same signal as the input. The luminance information comparator 205 outputs Ks = [(G signal of the color separation circuit 203) / (output of the image memory 204)]-1 (1) as the ratio of the amount of strobe flash light to the ambient light. Since the same signal is input to the luminance information comparator 205, the ratio of the light amount of the strobe flash light becomes 0 during the pre-photographing.

Therefore, the gain control circuit 211 performs a white balance operation only on the integrated value of the two color difference signals.
This is because the white balance amplifier 2 is set so that the average value of the two color difference signals output from the integrators 209 and 210 becomes zero.
06, 207, and white balance can be achieved with ambient light.

When the shutter button is pressed for photographing, writing to the luminance information image memory 204 is stopped at the end of the image field of the solid-state imaging device 202, and the pre-photographed image shown in FIG. 3 is stored.

The gain settings of the white balance amplifiers 206 and 207 at this point are Grp and Gbp, respectively.
And stored in the gain control circuit 211. The flash of the strobe 200 is illuminated during the vertical flyback period, and the main imaging signal is output from the solid-state imaging device 202.

The G image signal of the color separation circuit 203 at the time of actual photographing is obtained by using the subject 10 having a short subject distance as shown in FIG.
2 is brighter, but the distant subject 103 is hardly hit by the strobe flash light, so that the subject 103 is shot with almost the same brightness as in FIG.

Therefore, by comparing the G output signal of the color separation circuit 203 during the actual photographing shown in FIG. 4 with the signal of the same pixel of the signal stored in the luminance information image memory 204 shown in FIG. The ratio of the auxiliary light to the captured image signal can be automatically determined by the electronic still camera, and the white balance can be obtained for each pixel. This can be achieved by the following process.

First, the two signal levels of the same pixel supplied to the luminance information comparator 205 are compared with each other, and the light quantity ratio of the strobe flash light to the light quantity of the ambient light for the subject corresponding to this pixel is expressed by the following equation (1). And outputs Ks. Since the emission spectrum of the flash of the strobe 200 is constant, the gain setting Grs of the white balance R amplifier 206 for the strobe flash light and the B amplifier 207
Is set at the time of adjusting the assembly of the electronic still camera. Since the amount of strobe flash light that is Ks times the amount of ambient light hits the subject, the signal ratios R / G and B / G when shooting a white subject are: R / G (Ks) = (1 / Grp + Ks / Grs) / (1 + Ks) (2) B / G (Ks) = (1 / Gbp + Ks / Gbs) / (1 + Ks) (3)

Accordingly, the gain of the amplifiers 206 and 207 for each pixel is calculated as follows: Gr (Ks) = (1 + Ks) / (1 / Grp + Ks / Grs) (4) Gb (Ks) = (1 + Ks) / (1 / Gbp + Ks / Gbs)... (5), it is possible to obtain an image with a white balance over the entire screen even when the color temperatures of the auxiliary light and the ambient light are different.

FIG. 5 is a block diagram for explaining a second embodiment of the present invention. This embodiment is different from the configuration in FIG. 1 in that a liquid crystal display 502 is provided so that a photographed image can be confirmed and a photographing range at the time of photographing can be confirmed.

In an electronic still camera, the number of pixels of an image sensor is generally several million in order to improve the image quality. In order to improve portability, those having millions of pixels are used. When checking the captured image, the memory card
4, the image data is read from the image data compression / decompression unit 2
12, the image data is restored, and the image data is output to the liquid crystal interface 501. The liquid crystal interface 501 generally has several image display modes as shown in FIG.

FIG. 6A shows an image list display mode, which is a display mode used when designating an image for which it is desired to confirm that the image has been properly captured and designating it in order to reduce unnecessary images. In this mode, a predetermined address area of the display memory in the liquid crystal interface 501 is
This is realized by sequentially writing the image data 601 from the memory card 214 while thinning it out.

The full-screen display of the image shown in FIG. 6B is a mode mainly used for checking the composition, and is realized by writing image data from the memory card 214 to the display memory address area while thinning the image data. I have.

FIG. 6C shows an enlarged display for detail confirmation.
A mode used for determining the presence / absence of defocus, etc.
02 is sequentially written in the display memory area in the liquid crystal interface 501.

The display mode shown in FIG. 6B is also used for confirming the composition at the time of photographing. In this case, if the time delay from the photographing to the display is long, a time delay occurs between the camera operation and the displayed image, which hinders the operation of determining the photographing range by a person.

In order to quickly determine the photographing range, thinning-out scanning is performed at the time of reading out signals from the solid-state image pickup device 202 as shown in FIG. 7 to reduce the number of pixels constituting one screen, thereby reducing the number of pixels per screen. Output time is shortened and display delay is reduced. Therefore, in the pre-imaging state, only the image signal output by the thinning-out scanning is provided in the luminance information image memory 204. The luminance information has a resolution that allows the photographer to determine what the photographed image is. In the signal output period at the time of stroboscopic photographing, the scanning signal thinned out by the interpolation circuit 503 is obtained by, for example, linearly interpolating the scanning output signal for vertical thinning and outputting it to the luminance information comparator 205. The luminance signal ratio can be calculated, and a white balance can be obtained for the entire screen.

Next, a third embodiment of the present invention will be described with reference to FIGS. FIG. 8 is an explanatory diagram showing the positions of sampling points for explaining the interpolation method.
FIG. 9 is a block diagram. The same components as those in FIG. 5 are denoted by the same reference numerals, and description thereof will be omitted.

Of the thinning-out scanning signal outputs, the mark “○” in FIG. 8 indicates the one stored in the luminance information image memory 204,
Marks indicate those that are not stored in the luminance information image memory 204. 8 indicate pixels for determining the color temperature condition.

The luminance information comparator 205 determines the color temperature condition at the position indicated by the circle in FIG. 8 and outputs it to the interpolation circuit 503.
The interpolation circuit 503 determines which of the luminance information indicated by a triangle in FIG. 8 is closest to the luminance information indicated by a circle in FIG. 8 at the position of the vertex of the triangle surrounding the triangle. The color temperature condition at the position of the mark “を” is output as the color temperature condition of the mark “△” in FIG.

The delay circuits 901 to 903 are provided for synchronizing the color temperature condition and the image information. The delay circuits 901 to 903 hold the output signal from the image pickup device for one pixel like an electronic still camera and sequentially read out the signals. This is unnecessary when performing signal processing.

As described above, the storage capacity of the luminance information memory and the amount of calculation for calculating the color temperature condition are reduced by thinning out the luminance information two-dimensionally, and interpolation is performed using the luminance information. The color temperature information can be changed in a shape along the part.

10 and 11 relate to a fourth embodiment of the present invention. FIG. 10 is a block diagram,
FIG. 11 is an explanatory diagram for explaining a method for measuring the emission color of the strobe light. 10, the same components as those in FIG. 9 are denoted by the same reference numerals, and description thereof will be omitted.

When the amount of light is insufficient indoors, a strobe with a large amount of light may be required. In this case, the emission colors of the external flash and the built-in flash differ due to the influence of the lens member and the like.

For this reason, as shown in FIG. 10, the built-in flash data 1001 and the external flash data 1002 are held in the electronic still camera, and the switch 1003 is switched depending on whether the internal flash 2001 or the external flash 2002 is used. And a good white balance can be realized.

The external strobe 2002 is selected by the user according to the purpose of use. For this reason, all the emission color data of the external strobe 2002 cannot be aligned, so that a white subject 1103 is photographed using the external strobe 2002 as shown in FIG.
By controlling the gain of each of the R amplifier 206B and the amplifier 207 so that the color difference signal becomes 0 by the microprocessor 1004 in 1, the emission color of the external strobe 2002 is measured and stored in the external strobe data 1002. Good white balance characteristics can be provided for any strobe.

Further, by providing a switch 1005 for connecting this measuring method during the manufacturing inspection process so as to be used when adjusting the internal strobe data 1001, it is also possible to realize automatic strobe adjustment at the time of manufacturing. .

[0039]

As described above, according to the electronic still camera apparatus of the present invention, even when shooting is performed using an auxiliary light such as a strobe flash or the like, regardless of the distance to the subject, the screen is displayed. It is possible to obtain an image with a good white balance over the entire area.

[Brief description of the drawings]

FIG. 1 is a block diagram for explaining a first embodiment of the present invention.

FIG. 2 is a timing chart for explaining the operation of FIG. 1;

FIG. 3 is an explanatory diagram for explaining the yellow image capturing according to the present invention;

FIG. 4 is an explanatory diagram for explaining main shooting according to the present invention.

FIG. 5 is a block diagram for explaining a second embodiment of the present invention.

FIG. 6 is an explanatory diagram for describing a display example of an image mode displayed on the liquid crystal display of FIG. 5;

FIG. 7 is an explanatory diagram for describing a technique for quickly determining a photographing range.

FIG. 8 is an explanatory diagram for describing sampling point positions in an image interpolation method used in the third embodiment of the present invention.

FIG. 9 is a block diagram for explaining a third embodiment of the present invention.

FIG. 10 is a block diagram for explaining a fourth embodiment of the present invention.

FIG. 11 is an explanatory diagram for explaining a method for measuring the emission color of strobe light.

FIG. 12 is an explanatory diagram for describing a problem of a conventional electronic still camera.

[Explanation of symbols]

200, 2001, 2002: strobe, 202: solid-state imaging device, 203: color separation circuit, 204: image memory for luminance information, 205: luminance information comparator, 206, 207
... Amplifier, 208, 209, 210 ... Integrator, 211
... Gain control circuit, 212 ... Image data compressor / decompressor, 21
3 Memory card interface, 214 Memory card, 501 Liquid crystal interface, 502 Liquid crystal display, 901 to 903 Delay circuit, 1001 Built-in flash data, 1002 External flash data, 10
03,1005 ... Switch.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04N 9/73 H04N 9/73 A 5C066 // H04N 101: 00 101: 00 F term (reference) 2H002 DB25 2H053 CA41 2H054 AA01 5C022 AA13 AB15 AC03 AC42 AC69 5C065 AA03 BB02 BB03 BB04 BB41 CC02 CC03 CC08 DD02 DD17 GG21 GG23 GG30 GG32 5C066 AA01 AA05 CA21 EA03 EA15 EA17 EC01 EE04 FA02 GA01 KA01 KA01 KA01 KA01 KA01 KA01 KA01

Claims (6)

[Claims] 1. A means for estimating a light source color from an image photographed prior to a flash photography, a means for storing luminance information of the image, and a luminance information of an image photographed by a flash. An electronic still camera device comprising: means for determining a white balance setting condition from a signal level ratio of the same area as luminance information; and means for performing signal processing according to the white balance setting. 2. The method according to claim 1, wherein the number of pixels of the luminance information stored in the luminance information storage means is smaller than the number of pixels of the luminance information of the image to be captured by the strobe flash, and is stored when the signal level ratio of the same area is obtained. The electronic still camera device according to claim 1, wherein interpolation processing is performed on luminance information of the image. 3. A method according to claim 1, wherein the number of pixels of the luminance information stored in the means for storing the luminance information is smaller than the number of pixels of the luminance information of the image to be photographed by the strobe flash. The white balance setting condition is obtained from a level ratio, an interpolation process is performed on the white balance setting condition, and signal processing is performed according to the interpolated white balance setting condition. Electronic still camera device. 4. The electronic still camera according to claim 2, wherein the interpolation processing performed on the luminance information of the stored image determines an interpolation pattern based on the luminance information of the image captured by the strobe flash. apparatus. 5. The electronic still camera device according to claim 1, further comprising means for measuring a color of emitted strobe flash light. 6. The electronic still camera device according to claim 1, further comprising means for storing a plurality of emission colors of the strobe flash light and selecting the stored plurality of emission colors.