JP2000078606A - White balance adjuster - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable adjustment with high precision without inconveniences that a gain setting, which cannot be taken for a luminance, is performed even when a limiter area is changed by the luminance of a subject by regulating the gain of an output from an imaging device to the limiter area set in accordance with a kind of light source corresponding to the luminance of the subject. SOLUTION: A signal processing circuit 313 adjusts a gain from a picture signal from an imaging device 303 and a dimmer circuit 304 receives a reflected light of an incorporated flash 5 by a dimmer sensor 305. By this light reception, an overall control part 211 decides a subject luminance and controls an amount of light emission of the incorporated flash 5 and a white balance circuit 207 through a flash control circuit 214. As a result, the overall control part 211 regulates a gain ratio to a limiter area corresponding to photographing of outdoor and indoor excluding and including a set fluorescent light area. Thus, it is possible to appropriately adjust highly precise white balance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a white balance adjusting device used for digital cameras, video cameras and the like.

[0002]

2. Description of the Related Art An automatic white balance function is provided.
In a digital camera or a video camera, an overcorrection of a scene with a biased color deteriorates the color. For this reason, generally, a white balance is often adjusted by providing a limiter for regulating a gain for a color faria scene biased to a single color.

[0003] As such a white balance adjusting device, one described in Japanese Patent Application Laid-Open No. Hei 7-162890 is known. This white balance adjustment device measures the luminance of the subject and changes the limiter area by the limiter means according to the measured luminance.For example, in the case of outdoor light, indoors such as yellow, green, and skin color under outdoor light are used. The effect of chromatic colors in the light area is avoided, and a highly accurate white balance can be obtained.

[0004]

However, in the above-mentioned conventional white balance adjusting device, the limiter area for gain control merely enlarges or reduces the area range according to the luminance of the subject. In particular, even though the balanced gain control value differs considerably depending on the type of light source, the gain control value cannot cope with this, and it may not be possible to adjust the white balance with high accuracy.

The present invention has been made in view of such a technical background, and a white balance that adjusts a white balance by changing a limiter region that regulates an output gain of an image sensor according to the luminance of a subject. It is an object of the present invention to provide an adjustment device capable of performing highly accurate white balance adjustment.

[0006]

SUMMARY OF THE INVENTION The object of the present invention is to provide an image pickup device, gain control means for controlling the gain of the output from the image pickup device, limiter means for restricting the gain to a limiter area, and measuring the brightness of the object. In a white balance adjustment device including a luminance measuring unit and a changing unit that changes a limiter region by the limiter unit according to the luminance of the subject, the limiter region corresponds to a light source type corresponding to the luminance of the subject. The problem is solved by a white balance adjustment device characterized by being set.

In this white balance adjustment device, since the limiter area is set according to the type of the light source, even if the limiter area is changed by the brightness of the subject, balanced and highly accurate gain control is performed. .

In particular, the limiter area has a limiter area for outdoor shooting and a limiter area for indoor shooting. An area corresponding to a fluorescent lamp is set in the limiter area for indoor shooting, while a limiter area for outdoor shooting is set. When an area corresponding to a fluorescent lamp is excluded, an accurate white balance is performed according to the presence or absence of the fluorescent lamp.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <Structure of Digital Camera> As shown in FIGS. 1 to 3, a digital camera 1 is composed of a box-shaped camera body 2 and a rectangular parallelepiped imaging unit 3. FIG. The imaging unit 3 is detachably attached to the right side of the camera body 2 when viewed from the front (the front side in FIG. 1), and is rotatably mounted in a plane parallel to the right side.

The image pickup section 3 has an image pickup device including a photographing lens formed by a macro zoom and a photoelectric conversion element such as a CCD (Charge Coupled Device). It is converted into an image composed of signals and taken in. On the other hand, the camera body 2 has a display unit 10 formed of an LCD (Liquid Crystal Display), a mounting unit 17 for a memory card 8, and a connection terminal 13 to which a personal computer (hereinafter referred to as a personal computer) is externally connected. After subjecting the image signal captured by the imaging unit 3 to predetermined signal processing, processing such as display on the LCD display unit 10, recording on the memory card 8, and transfer to a personal computer is performed.

A photographing lens 301 composed of a macro zoom lens is provided inside the image pickup section 3, and a CCD color area sensor 3 is provided at an appropriate position behind the photographing lens 301.
03 (FIG. 4) is provided. Further, a dimming circuit 30 including a dimming sensor 305 that receives reflected light of the flash light from the subject at an appropriate position in the imaging unit 3.
4 (FIG. 4) are provided.

As shown in FIG. 1, on the front surface of the camera body 2, a grip portion 4 is provided at an appropriate position on a left end portion, and a built-in flash 5 is provided at an appropriate upper portion on a right end portion. As shown in FIG. 1, on the upper surface of the camera body 2, switches 6 and 7 for frame advance when reproducing a recorded image are provided substantially at the center. The switch 6 is used to advance the recorded image in the direction in which the frame number increases (the direction of the photographing order) (hereinafter referred to as the Up key). (Hereinafter referred to as Down key). Also, when viewed from the back side (the front side in FIG. 2), Dow
An erase switch D for erasing an image recorded on the memory card 8 is provided on the left side of the n key 7, and a shutter button 9 is provided on the right side of the Up key 6.

As shown in FIG. 2, on the rear surface of the camera body 2, a monitor display (corresponding to a viewfinder) of a photographed image and the LCD display for reproducing and displaying a recorded image are provided substantially at the center of the left end. A unit 10 is provided. A compression rate setting slide switch 12 for switching and setting a compression rate K of the image data recorded on the memory card 8 is provided below the LCD display section 10. PS is provided. The connection terminal 13 for connecting a personal computer 1000 (FIG. 4) is provided on a side surface of the camera body 2 on the side of the imaging unit 3.

The digital camera 1 has a flash mode (hereinafter, flash is sometimes referred to as FL) flash mode, an "auto flash mode" in which the built-in flash 5 is automatically flashed in accordance with the brightness of the subject. A “forced light emission mode” for forcibly emitting light from the built-in flash 5 and a “light emission prohibited mode” for forbidden light emission from the built-in flash 5 are provided regardless of the FL. Mode setting key 11
Each time is pressed, each mode of "automatic light emission", "forced light emission" and "light emission inhibition" is cyclically switched, and any one of the modes is selectively set. In the digital camera 1, two compression ratios K of 1/8 and 1/20 can be selected and set. For example, when the compression ratio setting switch 12 is slid to the right, the compression ratio K = 1/8 is set. Slide to the left, the compression ratio K = 1/20 is set. In the present embodiment, two types of compression ratios K can be selected and set, but three or more types of compression ratios K
May be selectively set.

Further, a photographing / playback mode setting switch 14 for switching between a "photographing mode" and a "playback mode" is provided at the upper right end of the rear surface of the camera body 2. The photographing mode is a mode in which a photograph is taken, and the playback mode is a mode in which a photographed image recorded in the
This is a mode for reproducing and displaying on the D display unit 10. The shooting / playback mode setting switch 14 also includes a two-contact slide switch. For example, sliding to the right sets the playback mode, and sliding to the left sets the shooting mode.

A battery loading chamber 1 is provided on the bottom of the camera body 2.
8 and a card loading chamber 17 for the memory card 8 are provided.
The loading ports of the loading chambers 17 and 18 are closed by a clamshell type lid 15. The digital camera 1 according to the present embodiment uses a power supply battery formed by connecting four AA batteries in series as a drive source.

FIG. 4 is a block diagram showing a control system of the digital camera 1.

In the image pickup section 3, the CCD 303
Transforms an optical image of a subject formed by the macro zoom lens 301 into image signals of R (red), G (green), and B (blue) color components (from a signal train of pixel signals received by each pixel). ) And output. The timing generator 314 generates various timing pulses for controlling driving of the CCD 303.

The exposure control in the image pickup unit 3 is performed by adjusting the exposure amount of the CCD 303, that is, the charge accumulation time of the CCD 303 corresponding to the shutter speed, since the stop is a fixed stop. If the appropriate shutter speed cannot be set when the subject brightness is low,
By adjusting the level of the image signal output from D303, improper exposure due to insufficient exposure is corrected. That is, when the luminance is low, the exposure control is performed by combining the shutter speed and the gain adjustment. The level adjustment of the image signal is performed in the gain adjustment of the AGC circuit in the signal processing circuit 313.

The timing generator 314 generates a drive control signal for the CCD 303 based on a reference clock transmitted from the timing control circuit 202.
The timing generator 314 generates clock signals such as integration start / end (exposure start / end) timing signals and light-receiving signal readout control signals (horizontal synchronization signal, vertical synchronization signal, transfer signal, etc.) for each pixel. Output to the CCD 303.

The signal processing circuit 313 performs predetermined analog signal processing on an image signal (analog signal) output from the CCD 303. The signal processing circuit 313
It has a DS (correlated double sampling) circuit and an AGC (auto gain control) circuit. The CDS circuit reduces the noise of the image signal, and the level of the image signal is adjusted by adjusting the gain of the AGC circuit.

The light control circuit 304 controls the light emission amount of the built-in flash 5 in flash photography to a predetermined light emission amount set by the overall control unit 211. In flash photography, the reflected light of flash light from the subject is received by the light control sensor 305 at the same time as the start of exposure, and when the amount of received light reaches a predetermined light emission amount, the light control circuit 3
An emission stop signal is output from 04 to the flash control circuit 214 via the overall control unit 211. The flash control circuit 214 forcibly stops the light emission of the built-in flash 5 in response to the light emission stop signal, whereby the light emission amount of the built-in flash 5 is controlled to a predetermined light emission amount.

In the camera body 2, the A / D converter 205 converts each pixel signal of the image signal into a 10-bit digital signal. The A / D converter 205 is
A / D input from an A / D clock generation circuit (not shown)
Each pixel signal (analog signal) is converted into a 10-bit digital signal based on a clock for D conversion.

In the camera body 2, a timing control circuit 202 for generating a reference clock, a timing generator 314, and a clock for the A / D converter 205 is provided. The timing control circuit 202 is controlled by the overall control unit 211. Black level correction circuit 206
Is for correcting the black level of the pixel signal (hereinafter, referred to as pixel data) A / D-converted by the A / D converter 205 to a reference black level.

The white balance circuit 207 adjusts R and R so that the white balance is also adjusted after the γ correction.
The level conversion of the pixel data of each of the G and B color components is performed. The white balance circuit 207 is a general control unit 2
11 using the level conversion table input from R,
The level of the pixel data of each color component of G and B is converted. The conversion coefficient (gradient of the characteristic) of each color component in the level conversion table is set by the overall control unit 211 for each captured image. The white balance adjustment control will be further described later.

The gamma correction circuit 208 corrects gamma characteristics of pixel data. The γ correction circuit 208 has, for example, six types of γ correction tables having different γ characteristics, and performs γ correction of pixel data using a predetermined γ correction table according to a shooting scene or shooting conditions.

The image memory 209 is a memory for storing pixel data output from the gamma correction circuit 208. The image memory 209 has a storage capacity for one frame. That is, in the image memory 209, the CCD 303
In the case of having pixels in rows and m columns, it has a storage capacity for pixel data of n × m pixels, and each pixel data is stored in a corresponding pixel position.

The VRAM 210 is a buffer memory for image data reproduced and displayed on the LCD display unit 10. VR
The AM 210 has a storage capacity for image data corresponding to the number of pixels of the LCD display unit 10.

In the shooting standby state, each pixel data of an image picked up by the image pickup unit 3 every 1/30 (second) is
After being subjected to predetermined signal processing by the A / D converters 205 to γ correction circuit 208, the signals are stored in the image memory 209, transferred to the VRAM 210 via the overall control unit 211, and displayed on the LCD display unit 10. You. Thus, the photographer can visually recognize the subject image from the image displayed on the LCD display unit 10. In the playback mode, after the image read from the memory card 8 is subjected to predetermined signal processing by the overall control unit 211, the VRAM 210
And reproduced and displayed on the LCD display unit 10.

The card I / F 212 is an interface for writing image data to the memory card 8 and reading image data. Also, the communication I / F 21
Reference numeral 3 denotes an interface for externally connecting the digital camera 1 to the personal computer 19 in a communicable manner.
It conforms to the B standard.

The flash control circuit 214 is a circuit for controlling light emission of the built-in flash 5. The flash control circuit 214 controls the presence / absence of light emission of the built-in flash 5, the amount of light emission, the light emission timing, and the like based on the control signal of the overall control unit 211, and based on the light emission stop signal STP input from the dimming circuit 304. Is controlled.

The RTC 219 is a clock circuit for managing the shooting date and time, and is driven by another power source (not shown).

The operation unit 250 includes the Up key 6,
It comprises a Down key 7, a shutter button 9, an FL mode setting key 11, a compression ratio setting switch 12, a shooting / reproduction mode setting switch 14, and the like.

The overall control section 211 is composed of a microcomputer, and controls the driving of each member in the image pickup section 3 and the camera main body section 2 in an organic manner to control the photographing operation of the digital camera 1 in an integrated manner. is there.

Further, as shown in FIG.
Reference numeral 1 includes a luminance determination unit 211a for setting an exposure control value (shutter speed (SS)) and a shutter speed (SS) setting unit 211b. Brightness judgment unit 2
11a is for determining the brightness of the subject using an image captured every 1/30 (second) by the CCD 303 in the shooting standby state. That is, the luminance determination unit 211a determines the brightness of the subject using the image data that is renewedly stored in the image memory 209.

The luminance determination unit 211a is provided with an image memory 209
Is divided into nine blocks, luminance data representing each block is calculated using pixel data of a G (green) color component included in each block, and when the subject luminance is equal to or higher than a predetermined level, It is determined that the scene is an outdoor shooting scene, and when the predetermined level is not reached, it is determined that the scene is an indoor shooting scene.

The shutter speed setting section 211b is a shutter speed (integration time of the CCD 303) based on the result of the brightness determination of the subject by the brightness determination section 211a.
Is set. Shutter speed setting unit 21
1b has a shutter speed table.

The shutter speed is set to 1 when the camera is started.
/ 128 (seconds), and in the shooting standby state, the shutter speed setting unit 211b shifts one step from the initial value to the high-speed side or the low-speed side according to the result of the brightness determination of the subject by the brightness determination unit 211a. Change and set each time.

The general control unit 211 sets “short luminance scene”, “medium luminance normal scene”, “middle luminance normal scene”, A scene determination unit 211c that determines four types of shooting scenes, that is, a “medium brightness backlight scene” and a “high brightness scene” is provided. "Low brightness scene"
Is usually used for flash 5 like indoor photography and night photography.
The “medium-luminance normal scene” is a scene in which illumination light (including natural light and artificial light) for the main subject is in normal light and its brightness is appropriate and there is no auxiliary light. This is a scene that can be taken with. The “medium brightness backlight scene” is a scene in which the overall brightness is appropriate, but the flash light is preferable because the illumination light for the main subject is backlight, and the “high brightness scene” is, for example, a clear sea scene. It is a very bright scene like shooting at a ski resort. The determination result by the scene determination unit 211c is stored in the memory 211d.

Further, the overall control unit 211 determines whether the captured image is a normal photographed image of a landscape, a person, or the like (hereinafter, such a captured image is referred to as a natural image) or is drawn on a whiteboard or the like. Images of characters, charts, etc.
An image similar to the value image is called a character image. ) Is provided.

The image determining unit 211e is provided with an image memory 209
A histogram of the luminance data at each pixel position is created based on the pixel data constituting the captured image stored in the storage device, and the content of the captured image is determined based on the histogram. In general, a histogram of luminance data of a captured image is a so-called one-peak distribution having a single peak value with a small bias in the luminance distribution in the case of a natural image. In the case of a character image, a bias in the luminance distribution is observed in each of a white background portion and a black character portion.
Mountain distribution. Therefore, the image determination unit 211e determines whether the histogram of the luminance data of the captured image has a single peak distribution,
It is determined whether the captured image is a natural image or a character image by determining whether the image is a mountain distribution. Then, this determination result is also stored in the memory 211d.

The overall control unit 211 includes a filter unit 211f for performing a filtering process and a recorded image generating unit 211g for generating a thumbnail image and a compressed image in order to perform the recording process of the photographed image. In order to reproduce the reproduced image on the LCD display unit 10, a reproduction image generation unit 211h that generates a reproduction image is provided.

The filter section 211f corrects high-frequency components of an image to be recorded by a digital filter, thereby correcting image quality related to contours. Filter unit 21
1f is a digital filter for performing a standard contour correction for each of the compression ratios K = 1/8 and 1/20, and two types of digital filters for enhancing the contour and the contour for the standard contour correction. A total of five types of digital filters, two types of digital filters to be weakened, are provided.

The recording image generating section 211g reads out pixel data from the image memory 209 and generates a thumbnail image and a compressed image to be recorded on the memory card 8. The recording image generation unit 211g reads pixel data for every eight pixels in both the horizontal direction and the vertical direction while scanning from the image memory 209 in the raster scanning direction, and sequentially transfers the pixel data to the memory card 8, thereby obtaining the thumbnail image. Is recorded on the memory card 8 while generating.

The recording image generation unit 211g reads out all pixel data from the image memory 209, and converts these pixel data into JPE data such as two-dimensional DCT transform and Huffman coding.
A predetermined compression process according to the G method is performed to generate image data of a compressed image, and the compressed image data is recorded in the main image area of the memory card 8.

In the photographing mode, when photographing is instructed by the shutter button 9 in the photographing mode, the overall control unit 211 displays the thumbnail image of the image taken in the image memory 209 after the photographing instruction and the compression ratio set by the compression ratio setting switch 12. A compressed image compressed by the JPEG method using K is generated, and tag information (frame number, exposure value, shutter speed, compression ratio K, shooting date, flash on / off data at shooting, scene information, image Both information is stored in the memory card 8 together with the information such as the judgment result of the above.

The memory card 8 has a compression ratio of 1/20
Zero frames of images can be stored, and each frame includes a tag portion and high-resolution image data (64
0 × 480 pixels) and image data for thumbnail display (8
0 × 60 pixels). For example, each frame can be handled as an image file in the EXIF format.

<Adjustment of White Balance> As described above, the white balance adjustment control in the white balance circuit 207 is performed, in the case of a primary color CCD, by adding predetermined gains obtained by calculation to the RGB signals output from the CCD. It is implemented by multiplying. Generally, the gain is determined so that the entire screen becomes gray. However, in a scene where the color is biased toward a specific color, such as a blue sky or a sunflower field that fills the entire screen, the tint is impaired.

Therefore, the range in which the gains of R and B can be set based on the G gain is determined in advance from the spectral characteristics and the light source state, and the color tone can be maintained by controlling so as not to exceed the range.

For example, assuming that a tungsten light source is a light source A, a daylight outdoor (under sunlight) is a light source B, and a cloudy daytime shade is a light source C in the daytime, as shown in FIG. The range of gain ratios that can be taken is set in a first limiter region L1 surrounded by a solid line. On the other hand, the range of gain ratios that can be taken for the fluorescent light area, the dusk area (dusk scene), and the B light source area is set in the second limiter area L2 surrounded by the wavy line.

Then, as described above, the overall control unit 21
If the brightness determination unit 211a determines that the subject brightness is equal to or higher than the predetermined level and the scene is an outdoor shooting scene, the white balance circuit 207 and the overall control unit 211 set the gain ratio in the first limiter area L1 indicated by the solid line. To be controlled. When the calculated value is present in the first limiter area L1, the gain ratio is an appropriate value, so that value is adopted. The calculated value is the first limiter area L1
Is exceeded, the value of the gain ratio in the closest limit area is adopted. For example, when the calculation result is a gain ratio indicated by x, the gain ratio is set by a value of the gain ratio indicated by ○.

On the other hand, when it is determined that the scene is an indoor photographing scene because the subject luminance is less than the predetermined level, control is performed so that the gain ratio is set in the second limiter area L2 indicated by the broken line. The calculated value is the second limiter area L
If the gain ratio is within 2, the gain ratio is an appropriate value, so that value is used as a coefficient. When the calculated value exceeds the second limiter area L2, the value of the gain ratio in the closest limiter area is taken.

As described above, when it is determined that the scene is an outdoor photographing scene, the gain ratio corresponding to the unnecessary fluorescent light region or the like is excluded from the limiter region, and the gain ratio corresponding to the necessary C light source region is added. When it is determined that the scene is an indoor photographing scene, an inappropriate gain ratio is adopted by adding a gain ratio corresponding to a necessary fluorescent light region and omitting a gain ratio corresponding to an unnecessary C light source region. No more fear,
Accuracy can be increased.

In the above embodiment, the present invention is applied to a white balance adjusting device in a digital camera.
The present invention may be applied to a white balance adjustment device in a video camera.

Also, the case where two limiter areas, ie, a first limiter area L1 corresponding to an outdoor shooting scene and a second limiter area L2 corresponding to an indoor shooting scene, are set, is shown. Switching may be performed by setting three or more limiter areas according to the type of light source to be used.

[0056]

As described above, according to the present invention, since the limiter area is set according to the type of the light source, even if the limiter area is changed according to the luminance of the subject, the limiter area cannot be obtained. The inconvenience of gain setting is eliminated, and highly accurate white balance adjustment can be performed.

The limiter area has a limiter area for outdoor shooting and a limiter area for indoor shooting. An area corresponding to a fluorescent lamp is set in the limiter area for indoor shooting, while a limiter area for outdoor shooting is set. In the case where the region corresponding to the fluorescent lamp is excluded, an accurate white balance can be performed according to the presence or absence of the fluorescent lamp.

[Brief description of the drawings]

FIG. 1 is a front view of a digital camera according to an embodiment of the present invention.

FIG. 2 is a rear view of the digital camera.

FIG. 3 is a bottom view of the digital camera.

FIG. 4 is a block diagram showing a control system of the digital camera shown in FIGS.

FIG. 5 is a block diagram showing a configuration of an overall control unit in FIG. 4;

FIG. 6 is a diagram illustrating a limiter range;

[Explanation of symbols]

 1 ... Digital camera 207 ... White balance circuit 211 ... Overall control unit 211a ... Luminance determination unit 301 ... Shooting lens 303 ... Imaging device L1, L2 ... Limiter area

Continued on the front page F term (reference) 5C052 AA17 AB04 CC03 CC06 CC11 DD02 EE02 EE03 EE08 5C066 AA01 BA20 CA08 DD07 EA04 EA14 EA16 EC05 GA02 GA05 GA31 HA02 KA08 KA09 KA12 KD06 KE01 KE09 KE17 KE10 KM10

Claims (2)

[Claims] An image sensor; gain control means for controlling a gain of an output from the image sensor; limiter means for limiting the gain to a limiter area; luminance measuring means for measuring a luminance of a subject; A white balance adjustment device comprising: a change unit that changes a limiter region by the limiter unit according to luminance; wherein the limiter region is set according to a light source type corresponding to luminance of a subject. White balance adjustment device. 2. The limiter area has a limiter area for outdoor shooting and a limiter area for indoor shooting. An area corresponding to a fluorescent lamp is set as the limiter area for indoor shooting, while a limiter area for outdoor shooting is set. 2. An area corresponding to a fluorescent lamp is excluded from the above.
The white balance adjustment device according to item 1.