JP2004179852A - Digital camera - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a digital camera capable of always suppressing the effect of smear and transferring data to a frame memory at a low speed even when photographing is carried out without using a mechanical shutter. <P>SOLUTION: A CCD 116 is driven at a high speed at an ordinary photographing, white balance adjustment and gamma correction are applied to obtained image data to reduce the data amount and a frame memory 140 stores the resulting data so as to suppress the effect of smear even when photographing is carried out without using a mechanical shutter. The CCD 116 is driven at a low speed at flash photographing, the obtained image data are once stored in the frame memory 140 without modification, after the image data are read from the frame memory 140 and subjected to the white balance adjustment and the gamma correction, the resulting data are stored again in the frame memory 140 to suppress the effect of smear and to transfer the data to the frame memory 140 at a low speed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a digital camera capable of performing shooting without using a mechanical shutter.
[0002]
[Prior art]
When taking a picture without using a mechanical shutter in a digital camera, the light receiving surface of an image sensor using a CCD (Charge Coupled Device) or the like is continuously irradiated, so that the reading speed is faster than the signal generation speed of the image sensor. Is delayed, there arises a problem that a smear, that is, a false signal is generated in a line shape above and below or right and left of a high-luminance subject. Therefore, in order to suppress the influence of smear, it is necessary to read out signals from the image sensor at high speed. However, for this purpose, since the signal processing speed and transmission speed of the entire system must be increased, it is necessary to increase the writing speed to the frame memory or increase the bus width. An increase in the writing speed to the frame memory leads to an increase in power consumption, and an increase in the bus width of the frame memory leads to an increase in the price of the signal transmission system and the frame memory.
[0003]
Therefore, in many digital cameras, a signal read out from an image sensor at high speed is subjected to automatic white balance (hereinafter referred to as AWB) processing, γ correction processing, and the like to compress (reduce) the amount of data, and then to frame memory. Is used. (See Patent Document 1, Patent Document 2, etc.)
[0004]
[Patent Document 1]
JP 2000-102025 A [Patent Document 1]
Japanese Patent Laid-Open No. 2000-184381
[Problems to be solved by the invention]
However, in order to properly perform AWB processing, γ correction processing, and the like, it is necessary to count evaluation values for calculating AWB and γ correction processing parameters from the obtained image data. When a through image is displayed on a finder or the like, it is possible to obtain an evaluation value from the image and perform AWB processing or gamma correction processing. It is difficult to perform an appropriate AWB process depending on the state.
[0006]
The present invention has been made in view of the above circumstances, and its object is to always suppress the influence of smear even when shooting without using a mechanical shutter and to transfer data to the frame memory at a low speed. It is to provide a digital camera that can perform.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a digital camera capable of selectively executing normal shooting for shooting without using a flash light source and flash shooting for shooting with a flash light source. An image sensor for picking up images and converting them into electrical signals, a through image display means for displaying a through image of the image data obtained by the image sensor, and an automatic for automatically adjusting the white balance of the image data obtained by the image sensor. A white balance processing means; a γ correction processing means for γ correcting the output from the automatic white balance processing means; a frame memory for storing image data obtained by the image sensor; and a driving speed of the image sensor. Switching means for setting either high speed or low speed, and During normal shooting, the drive speed of the image sensor is set to a high speed, and the image data obtained by the image sensor is adjusted based on the evaluation value obtained from the through image of the previous image data. After processing and γ correction processing, it is stored in the frame memory. At the time of flash photography, the drive speed of the image sensor is set to a low speed, and the image data obtained by the image sensor is temporarily stored in the frame memory. Then, after the white balance adjustment process and the γ correction process based on the evaluation value obtained from the through image of the image data, the image data is re-stored in the frame memory.
[0008]
As described above, during normal shooting, the image sensor drive speed is set to a high speed, and the image data obtained by the image sensor is whitened based on the evaluation value obtained from the through image of the image data one frame before. After the balance adjustment process and the γ correction process are stored in the frame memory, the influence of smear can be suppressed even when shooting is performed without using the mechanical shutter. Also, at the time of flash photography, the image sensor drive speed is set to a low speed, the image data obtained by the image sensor is temporarily stored in the frame memory as it is, and based on the evaluation value obtained from the through image of the image data After the white balance adjustment process and the γ correction process, the effect of smear can be suppressed and data transfer to the frame memory can be performed at a low speed by re-storing in the frame memory.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0010]
FIG. 1 is a block diagram showing a configuration example of a digital camera according to the present invention. The digital camera 100 includes an imaging unit 110, an A / D converter 120, a system LSI 130, a frame memory 140, an operation panel 150, a media interface 160, an LCD driver 170, and the like.
[0011]
The imaging unit 110 includes an optical system 115 including an AF (Automatic Focus) lens 111 and a diaphragm 112, and a CCD (Charge-Coupled Devices) 116 that is an image sensor. The optical system 115 forms a subject image on the light receiving surface of the CCD 116. The CCD 116 outputs an image signal corresponding to the amount of light incident on the light receiving unit to the A / D converter 120. The A / D converter 120 converts the input analog image signal into a 12-bit digital image signal and outputs it to the system LSI 130.
[0012]
The system LSI 130 includes functional blocks such as an integration unit 131, an AWB processing unit 132, a γ correction processing unit 133, various signal processing units 134, and a data control unit 135. These functional blocks include a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random) that constitute the system LSI 130.
(Access Memory).
[0013]
Raw image data input from the A / D converter 120 to the system LSI 130 is temporarily stored in the RAM in the system LSI 130, converted to a display size, and then passed to the monitor LCD 175 via the LCD driver 170. Displayed.
[0014]
The integration unit 131 integrates the AF control value, AWB control value, AE control value, and the like of the through image. The obtained integrated value is temporarily stored in the RAM.
[0015]
The AWB processing unit 132 automatically adjusts the white balance of the image data sent from the A / D converter 120 based on the evaluation value obtained from the through image of the image data one frame before. The evaluation value is calculated using the result of integration by the integration unit 131.
[0016]
The γ correction processing unit 133 performs γ correction on the output from the AWB processing unit 132. Various signal processing units 134 perform RGB interpolation processing, YC separation processing, YC → RGB conversion processing, aperture processing, compression / decompression processing, and the like on the image data after the γ correction processing.
[0017]
The various signal processing units 134 compress the image data stored in the frame memory 140 by a predetermined compression method such as the JPEG method and record the compressed image data on the portable recording medium 165 or read the image data read from the portable recording medium 165. Or decompress the data. Further, the various signal processing unit 134 converts the YC separation signal into a luminance signal and the color difference signal into an RGB signal when displaying the image data recorded on the portable recording medium 165 on the monitor LCD 175. The LCD driver 170 drives the monitor LCD 175 based on the RGB signals, whereby a color image is displayed on the monitor LCD 175.
[0018]
The data control unit 135 switches the driving speed of the CCD 116 to 24 MHz (high speed) during normal shooting and 12 MHz (low speed) during flash shooting. The flow of image data processing in the system LSI 130 is switched between normal shooting and flash shooting, and writing and reading of image data to and from the frame memory 140 are controlled. As the frame memory 140, an SDRAM (Synchronous Dynamic Random Access Memory) is used. The data control unit 135 performs bus arbitration to write and read data to and from the frame memory 140.
[0019]
As the portable recording medium 165, a small memory card or the like equipped with a flash memory is used. Writing / reading of image data to / from the portable recording medium 165 is performed via the media interface 160 and the media driver 161.
[0020]
The operation panel 150 is provided with a release button 151, a shooting mode switching button 152, and the like. The release button 151 is an operator for instructing the digital camera 100 to start shooting. When the release button 151 is pressed halfway, focus control and aperture control of the optical system 115 are performed, and when the button is completely pressed, Captured images are captured by the CCD 116 and the A / D converter 120. At that time, the optical system 115 is controlled by a photometry / ranging CPU (not shown), and the CCD 116 is controlled by a system LSI 130. In addition, a charging / light emission control circuit (not shown) is activated in accordance with the photographing timing, and the flash light source (not shown) is driven to emit light.
[0021]
The shooting mode switching button 152 is an operator for switching between normal shooting and flash shooting. Each time this button is pressed, the shooting mode of the digital camera 100 is switched alternately between normal shooting and flash shooting. It has become.
[0022]
Next, the operation of the digital camera 100 configured as described above will be described.
[0023]
During normal shooting, as shown in FIG. 1A, the drive speed of the CCD 116 is set to 24 MHz (high speed). The image data output from the CCD 116 is converted into 12-bit digital image data (raw image data) by the A / D converter 120 and input to the system LSI 130. The image data input to the system LSI 130 is temporarily stored in the RAM and input to the data control unit 135. The raw image data temporarily stored in the RAM is converted into a display size and then displayed as a through image on the monitor LCD 175 via the LCD driver 170. At the same time, an AF control value, an AWB control value, an AE control value, and the like of the through image are integrated by the integrating unit 131, and the obtained integrated value is temporarily stored in the RAM.
[0024]
The image data input to the data control unit 135 is sent to the AWB processing unit 132, where the white balance is adjusted based on the evaluation value obtained from the through image of the image data one frame before, and the γ correction processing unit. At 133, gamma correction processing is performed. By the processing so far, the bit rate of the image data is reduced from the initial 12 bits to 8 bits. The image data after the γ correction processing is stored in the frame memory 140 via the data control unit 135.
[0025]
Thereafter, the data control unit 135 reads the image data after the γ correction processing from the frame memory 140 and sends the image data to various signal processing units 134 to perform RGB interpolation processing, YC separation processing, YC → RGB conversion processing, aperture processing, compression / compression A decompression process or the like is performed, and the data is stored again in the frame memory 140. The re-stored image data is recorded on the portable recording medium 165 or displayed on the monitor LCD 175 after undergoing a predetermined process.
[0026]
On the other hand, during flash photography, as shown in FIG. 1B, the drive speed of the CCD 116 is set to 12 MHz (low speed). The image data output from the CCD 116 is converted into 12-bit digital image data (raw image data) by the A / D converter 120 and input to the system LSI 130. The image data input to the system LSI 130 is temporarily stored in the RAM and input to the data control unit 135. The raw image data temporarily stored in the RAM is converted into a display size and then displayed as a through image on the monitor LCD 175 via the LCD driver 170. At the same time, an AF control value, an AWB control value, an AE control value, and the like of the through image are integrated by the integrating unit 131, and the obtained integrated value is temporarily stored in the RAM.
[0027]
The image data input to the data control unit 135 is temporarily stored in the frame memory 140 as 12-bit raw image data.
[0028]
Thereafter, the data control unit 135 reads the raw image data from the frame memory 140 and sends it to the AWB processing unit 132. The AWB processing unit 132 performs white balance adjustment based on the evaluation value obtained from the through image of the image data read from the frame memory 140. The data control unit 135 sends the image data output from the AWB processing unit 132 to the γ correction processing unit 133 to perform γ correction processing, and then sends the image data to various signal processing units 134 to perform RGB interpolation processing, YC separation processing, YC → RGB conversion processing, aperture processing, compression / decompression processing, and the like are performed, and the data is stored again in the frame memory 140. The re-stored image data is recorded on the portable recording medium 165 or displayed on the monitor LCD 175 after undergoing a predetermined process.
[0029]
As described above, during normal shooting, the drive speed of the CCD 116 is set to a high speed, and the image data obtained by the CCD 116 is adjusted based on the evaluation value obtained from the through image of the previous image data. After the processing and the γ correction processing are stored in the frame memory 140, the influence of smear can be suppressed even when shooting is performed without using the mechanical shutter.
[0030]
Further, at the time of flash photography, the drive speed of the CCD 116 is set to a low speed, and the image data obtained by the CCD 116 is temporarily stored as it is in the frame memory 140, and the white data is obtained based on the evaluation value obtained from the through image of the image data. By performing the balance adjustment process and the γ correction process and then storing them again in the frame memory 140, the influence of smear can be suppressed and the data transfer to the frame memory 140 can be performed at a low speed. Therefore, power consumption can be reduced, and there is no need to increase the bus width of the frame memory 140.
[0031]
In the above embodiment, switching between normal shooting and flash shooting is performed by operating the shooting mode switching button 152, but the digital camera 100 detects the brightness of the subject and the subject is dark. May automatically switch to flash photography.
[0032]
In the above example, the monitor LCD 175 has both a playback image display function and a viewfinder function. However, the monitor LCD 175 displays the playback image, and the through image is displayed only on the viewfinder (not shown). You may make it do.
[0033]
Further, the numerical values such as the CCD driving speed and the number of bits of the image data in the above-described embodiment are examples, and the present invention is not limited to these values.
[0034]
【The invention's effect】
As described above, according to the digital camera of the present invention, during normal shooting, the image sensor is driven at high speed, and the obtained image data is subjected to white balance adjustment processing and γ correction processing to reduce the amount of data. The image sensor is driven at a low speed during flash photography, the obtained image data is temporarily stored in the frame memory, and white balance adjustment processing and γ correction processing are performed on the image data read from the frame memory. After that, since it is re-stored in the frame memory, it is possible to always suppress the influence of smear and perform data transfer to the frame memory at a low speed even when shooting without using the mechanical shutter. it can.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration example of a digital camera according to the present invention.
[Explanation of symbols]
100: Digital camera 110: Imaging unit 116: CCD (image sensor)
120: A / D converter 140: Frame memory 131: Integration unit 132: Automatic white balance processing unit 133: γ correction processing unit 135: Data control unit 152: Shooting mode switching button (switching means)
175: LCD (through image display means)

Claims (1)

In a digital camera that can selectively execute normal shooting for shooting without using a flash light source and flash shooting for shooting with a flash light source,
An image sensor for imaging a subject and converting it into an electrical signal;
Through image display means for displaying a through image of image data obtained by the image sensor;
Automatic white balance processing means for automatically adjusting white balance of image data obtained by the image sensor;
Γ correction processing means for γ correcting the output from the automatic white balance processing means;
A frame memory for storing image data obtained by the image sensor;
Switching means for setting the drive speed of the image sensor to either high speed or low speed,
During the normal shooting,
The drive speed of the image sensor is set to a high speed, and the image data obtained by the image sensor is subjected to white balance adjustment processing and γ correction processing based on an evaluation value obtained from a through image of image data one frame before Is stored in the frame memory,
At the time of flash photography,
The drive speed of the image sensor is set to a low speed, the image data obtained by the image sensor is temporarily stored in the frame memory as it is, and the white balance is adjusted based on the evaluation value obtained from the through image of the image data A digital camera configured to be stored again in the frame memory after performing processing and γ correction processing.

Images