JP2003037775A - Imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imaging device used for a video camera or the like, that provides gradation characteristic, in response to modes, such as a moving image mode or a still picture mode and a photographing state. SOLUTION: The image pickup device is provided with a gradation condition detection means 16, a microcomputer 15, gradation characteristic setting means 17a to 17c, and gradation correction means 18a to 18c. The gradation condition detection means 16 detects a condition of a gradation characteristic, depending on the intention of the user or a scene to be photographed or the like, the microcomputer 15 obtains adjustment conditions of the gradation characteristic by the gradation condition detection means 16, the gradation characteristic setting means 17a to 17c updates the setting value of the gradation characteristic by a command of the microcomputer 15, and the gradation correction means 18a to 18c apply gradation corrections to the input signal, depending on the gradation characteristic set by the gradation characteristic setting means 17a to 17c.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup device used in a video camera or the like.

[0002]

2. Description of the Related Art A conventional image pickup apparatus will be described with reference to the drawings. FIG. 7 is a configuration diagram showing a configuration of a conventional image pickup apparatus. Here, a single-chip system that has one solid-state image pickup device and obtains a video signal by separating into a luminance signal and a color difference signal by signal processing will be described. The image pickup apparatus includes a three-plate system using three solid-state image pickup devices and the like, and the configuration is different, but the concept of processing does not change. Therefore, only the single-plate system will be described here.

In FIG. 7, 1 is a solid-state image sensor, and 2 is C.
DS circuit (correlated double sampling circuit), 3 gain control (GC) circuit, 4 analog / digital (AD) converter, 5 camera signal processing circuit, 6 luminance color separation circuit, 7 high pass filter, 8a , 8b and 8c are gamma ROMs, 9 is an aperture gain control circuit, 10 is a waveform shaping circuit, 11 is an adding circuit, 12 is an output terminal, 13 is a matrix circuit, 19 is an optical lens, 20
Is the aperture.

In the conventional image pickup apparatus, incident light entering through the optical lens 19 and the diaphragm 20 is photoelectrically converted on the surface of the solid-state image pickup device 1 and a signal corresponding to the light incident intensity is output.
The output signal of the solid-state image sensor 1 is noise-reduced by the CDS circuit, gain-controlled by the gain control circuit 3, AD-converted by the AD conversion circuit 4, and input to the camera signal processing circuit 5.

In the camera signal processing circuit 5, the input signal is input to the luminance / color separation circuit 6, and the luminance signal Y and the color signal C among the output signals of the solid-state image sensor are output. Here, the color signal C is output as R (red), G (green), and B (blue) primary color signals. The high-pass filter (HPF) 7 separates the high-frequency component of the luminance signal Y output from the luminance-color separation circuit 6 and outputs it as an aperture signal AP.

Further, the luminance signal Y is subjected to gradation correction corresponding to a gamma characteristic of 0.45 in the gamma ROM 8a and is output as a luminance signal Y'after gamma. Further, the luminance signal Y is input to the gamma ROM 8b and output as a gain Gap corresponding to a gamma characteristic of 0.45.

Here, the gamma ROM is a ROM in which an incident signal level is used as an address and an output signal level corresponding to the incident signal level is written. Aperture signal AP and gain G
ap is input to the aperture gain control circuit 9,
The gain-controlled aperture signal APg is output. In the waveform shaping circuit 10, the gain-controlled aperture signal APg is input, subjected to coring processing to suppress a small amplitude signal, and output as APc. In the adder 11, the luminance signal Y ′ output from the gamma ROM 8a and the aperture signal APc output from the waveform shaping circuit 10 are added, and the output luminance signal Yout is output.
Is output from the output terminal 12a.

The color signal C output from the luminance color separation circuit 6 is 0.
The gradation correction corresponding to the gamma characteristic of 45 is performed and the color signal C ′ after gamma is output. Matrix circuit 13
Then, the color signal C ′ after gamma is subjected to matrix processing, and is output from the output terminal 12b as the RY and BY color difference signals Cout.

FIG. 8 shows the signal waveform of each part when a gray scale is imaged.

In FIG. 8, the horizontal axis represents the horizontal pixel position and the vertical axis represents the signal level. The broken line represents the luminance signal Y, the thick line represents the gamma-corrected luminance signal Y ′, and the thin line represents the output luminance signal Y.
out. Gradation correction is performed by gamma correction so that steps from low luminance to high luminance are stepped at substantially constant intervals.

[0011]

However, the above structure has some problems as described below.

A video camera and a digital still camera have a moving image mode for shooting as a moving image and a still image mode for shooting as a still image. However, since the moving image mode is mainly displayed on a television monitor, a gamma curve of 0.45 is preferable. In the still image mode, 0.55 is preferable, which matches the gradation of prints and personal computer monitors. On the other hand, in the conventional imaging device, since the gradation correction characteristic is determined by the gamma ROM, there is a problem that the gradation correction characteristic cannot be changed.

Further, when an image of a low illuminance object is picked up, the aperture of the lens is usually adjusted to be opened, but when the object is open, the adjustment cannot be performed any more, and the screen becomes darker for a further low illuminance object. Will end up. Therefore, generally, FIG.
The level is adjusted by correcting the gain in the gain control circuit 3 of. However, the gain control circuit 3
By increasing the gain of, not only the signal component but also the noise component is emphasized, and noise is conspicuous especially in the low luminance portion where the gain is high, resulting in an unnatural image. In such a case, the noise is usually suppressed by lowering the gain of the aperture gain control circuit 9 or raising the coring level of the waveform shaping circuit 10. If the gain is lowered, the level of the aperture signal is lowered on the entire screen, which causes deterioration of resolution, and if the coring level is raised, distortion due to nonlinear processing becomes conspicuous, resulting in an unnatural image.

[0014]

In order to solve the above-mentioned problems, the present invention provides a gradation condition detecting means for detecting or setting a condition of gradation characteristics according to a user's intention or a scene to be photographed, and a gradation condition. According to the gradation characteristic set by the gradation characteristic setting means, the microcomputer for obtaining the adjustment condition of the gradation characteristic by the detecting means, the gradation characteristic setting means for changing the setting value of the gradation characteristic by the instruction of the microcomputer. And a gradation correction means for performing gradation correction on the input signal.

As a result, it becomes possible to adaptively control the gradation characteristics and obtain an appropriate image quality.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention comprises a gradation condition detecting means, a microcomputer, a gradation characteristic setting means and a gradation correcting means, and the gradation condition detecting means is in an operating state. The gradation characteristic condition is detected according to (user's intention, scene to be photographed, output form, etc.), the microcomputer obtains the gradation characteristic adjusting condition by the gradation condition detecting means, and the gradation characteristic setting means The setting value of the gradation characteristic is changed according to a command from the microcomputer, and the gradation correction means performs the gradation correction on the input signal according to the gradation characteristic set by the gradation characteristic setting means.

The invention according to claim 2 of the present invention is
The gradation condition detecting means is a mode change switch, and changes the gradation correction characteristic in the gradation correcting means according to the mode switching state.

The invention according to claim 3 of the present invention is
The gradation condition detecting means has a signal level adjusting means for adjusting the level of the input signal, and the gradation condition detecting means is a brightness detecting means for detecting the brightness of the object, and the signal according to the brightness level detected by the brightness detecting means. The output signal level of the level adjusting means is controlled and the gradation correction characteristic of the gradation correcting means is changed.

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

(Embodiment 1) An image pickup apparatus according to Embodiment 1 of the present invention is a video camera, a digital still camera, or the like, and has a mode (operation mode, such as a moving image mode for taking a moving image or a still image mode for taking a still image). It is possible to give gradation characteristics according to the output mode, etc.).

FIG. 1 is a block diagram showing the structure of an image pickup apparatus according to the first embodiment of the present invention. Here, a single-chip system that has one solid-state image pickup device and obtains a video signal by separating into a luminance signal and a color difference signal by signal processing will be described. The image pickup device has a three-plate type that uses three solid-state image pickup elements, etc., and the configuration is different, but the idea of processing does not change, so
Here, only the single plate method will be described.

In FIG. 1, 1 is a solid-state image sensor (CC
D), 2 is a CDS circuit, 3 is a gain control circuit,
4 is an AD converter, 5 is a camera signal processing circuit, 6 is a luminance color separation circuit, 7 is a high-pass filter, 9 is an aperture gain control circuit, 10 is a waveform shaping circuit, 11 is an addition circuit, 12 is an output terminal, 13 is A matrix circuit; 15 a microcomputer; 16 a mode changeover switch as a gradation condition detecting means; 17 a gradation characteristic setting circuit;
Reference numeral 18 is a gradation correction circuit, 19 is an optical lens, and 20 is a diaphragm.

Incident light incident through the optical lens 19 and diaphragm 20 is photoelectrically converted on the surface of the solid-state image pickup device 1 and a signal corresponding to the light incident intensity is output. The output signal of the solid-state image sensor 1 is noise reduced by the CDS circuit.
The gain is controlled by the gain control circuit 3, the AD conversion is performed by the AD conversion circuit 4, and the signal is input to the camera signal processing circuit 5.

In the camera signal processing circuit 5, the input signal is input to the luminance / color separation circuit 6, and the luminance signal Y and the color signal C among the output signals of the solid-state image pickup device are output. Here, the color signal C is output as R, G, and B primary color signals. The high-pass filter 7 separates the high-frequency component of the luminance signal Y output from the luminance-color separation circuit 6, and the aperture signal AP
Is output as.

Here, the mode selector switch 16 selects the moving image mode. Mode switch 16
The mode switching signal obtained from the microcomputer 1
5, and the microcomputer 15 detects the moving image mode. Accordingly, the microcomputer 15 sets the gradation characteristic setting circuits 17a, 17b and 17c to 0.4
The gradation characteristic data corresponding to the gamma characteristic 5 is set. It should be noted that the gamma characteristic of 0.45 is 0.
It means a characteristic having a curve of 45th power.

As a result, the luminance signal Y becomes the gradation correction circuit 1
In 8a, gradation correction corresponding to a gamma characteristic of 0.45 is performed, and the luminance signal Y ′ after gamma is output. Further, the brightness signal Y is input to the gradation correction circuit 18b and output as a gain Gap corresponding to a gamma characteristic of 0.45.

Here, the gradation correction circuits 18a and 18b
Is composed of a RAM in which an input signal level is an address and an output signal corresponding to the input signal level is written. The data in the RAM of the gradation correction circuit 18 is rewritten by the set value of the gradation correction characteristic setting circuit 17.

The aperture signal AP and the gain Gap are input to the aperture gain control circuit 9 and output as the gain-controlled aperture signal APg. In the waveform shaping circuit 10, the gain-controlled aperture signal APg is input, subjected to coring processing to suppress a small amplitude signal, and output as APc. In the adder 11, the luminance signal Y ′ output from the gradation correction circuit 18a and the aperture signal APc output from the waveform shaping circuit 10 are added and output from the output terminal 12a as an output luminance signal Yout.

Further, the color signal C output from the luminance color separation circuit 6 is subjected to gradation correction corresponding to the gamma characteristic of 0.45 in the gradation correction circuit 18c in the same manner as the luminance signal Y, and after gamma correction. The color signal C'is output. In the matrix circuit 13, matrix processing is performed on the color signal C ′ after gamma, and the color signal Cout of RY and BY is output from the output terminal 12b.

Next, the still picture mode is selected by the mode selector switch 16. The mode switching signal obtained from the mode switching switch 16 is the microcomputer 15
, And the microcomputer 15 detects the still image mode. Accordingly, the microcomputer 15 sets the gradation characteristic setting circuits 17a, 17b and 17c to 0.5.
The gradation characteristic data corresponding to the gamma characteristic of 5 (characteristic having a curve of 0.55 to the input signal) is set.

The operations other than the gradation correction circuits 18a to 18c are the same as those in the moving image mode. FIG. 2 shows the waveform of each part in the moving image mode, and FIG. 3 shows the waveform of each part in the still image mode.

2 and 3, the horizontal axis represents the horizontal pixel position and the vertical axis represents the signal level. The broken line indicates the luminance signal Y, the thick line indicates the luminance signal Y ′ after gamma correction, and the thin line indicates the output luminance signal Yout.

Compared with FIG. 2, FIG. 3 tends to suppress the contrast in the low-luminance portion in accordance with the gradation characteristics of prints and personal computer monitors.

The effect of the present invention is that the mode changeover switch as the gradation condition detecting means can detect the moving image mode or the still image mode, and accordingly, the optimum gradation correction can be performed for each characteristic. Is.

In this embodiment, the mode changeover switch is used to switch between the moving image mode and the still image mode, but the mode switching is not limited to two types. It is possible to select gradation characteristics that reflect the user's preference by using the high contrast mode in which the gamma slope is steeper than 0.45 and the low contrast mode in which the gamma slope is gentler than 0.55. Can be

Further, the gamma characteristic given by the gradation characteristic setting means may be a curve capable of back light correction by making the inclination of the low luminance portion and the high luminance portion steep and making the middle inclination gentle.

Further, in the present embodiment, the single plate type having a single image pickup element has been described, but the same effect can be obtained also in an image pickup apparatus having a plurality of image pickup elements, for example, a three plate type. In this case, the configuration of the camera signal processing circuit will be slightly different.

In this embodiment, the RAM is used as the gradation correction circuit, but the same effect can be obtained by using other means such as polygonal line approximation.

(Second Embodiment) In the first embodiment, the gradation characteristic is set according to the user's intention or output form by using the mode changeover switch as the gradation condition detecting means. A configuration in which the gradation characteristics are adjusted is also possible.

An image pickup apparatus according to the second embodiment of the present invention will be described below with reference to the drawings.

In the present embodiment, the output signal level of the signal level adjusting means is controlled according to the brightness level detected by the brightness detecting means, and the gradation correction characteristic of the gradation correcting means is changed. To prevent resolution degradation,
The objective is to obtain a noise suppression method that produces a natural image with less noticeable distortion due to nonlinear processing.

FIG. 4 is a block diagram showing the structure of the image pickup apparatus according to the second embodiment.

In FIG. 4, 1 is a solid-state image sensor, 2 is C
DS circuit, 3 gain control circuit, 4 AD converter, 5 camera signal processing circuit, 6 luminance color separation circuit, 7
Is a high-pass filter, 9 is an aperture gain control circuit, 10 is a waveform shaping circuit, 11 is an addition circuit, and 12a.
And 12b are output terminals, 13 is a matrix circuit, and 14
Is a level detection circuit, 15 is a microcomputer, 17
Is a gradation characteristic setting circuit, 18 is a gradation correction circuit, 19 is an optical lens, and 20 is an aperture.

Incident light incident through the optical lens 19 and the diaphragm 20 is photoelectrically converted on the surface of the solid-state image pickup device 1 and a signal corresponding to the light intensity is output. The output signal of the solid-state imaging device 1 is noise-reduced by the CDS circuit, gain-controlled by the gain control circuit 3, AD-converted by the AD conversion circuit 4, and input to the camera signal processing circuit 5.

In the camera signal processing circuit 5, the input signal is input to the luminance / color separation circuit 6, and the luminance signal Y and the color signal C among the output signals of the solid-state image pickup device are output. Here, the color signal C is output as R, G, and B primary color signals. The high-pass filter 7 separates the high-frequency component of the luminance signal Y output from the luminance-color separation circuit 6, and the aperture signal AP
Is output as.

In a normal photographing state, the microcomputer 15 sets gradation characteristic data according to the gamma characteristic of 0.45 in the gradation characteristic setting circuits 17a, 17b and 17c.

As a result, the luminance signal Y is transferred to the gradation correction circuit 1
In 8a, gradation correction corresponding to a gamma characteristic of 0.45 is performed, and the luminance signal Y ′ after gamma is output. Further, the brightness signal Y is input to the gradation correction circuit 18b and output as a gain Gap corresponding to a gamma characteristic of 0.45. The aperture signal AP and the gain Gap are input to the aperture gain control circuit 9 and output as a gain-controlled aperture signal APg. In the waveform shaping circuit 10, the gain-controlled aperture signal AP
g is input, a coring process for suppressing a small amplitude signal is performed, and the signal is output as APc. In the adder 11, the luminance signal Y ′ output from the gradation correction circuit 18a and the aperture signal APc output from the waveform shaping circuit 10 are added and output from the output terminal 12a as an output luminance signal Yout.

Further, the color signal C output from the luminance color separation circuit 6 is subjected to gradation correction corresponding to a gamma characteristic of 0.45 in the gradation correction circuit 18c in the same manner as the luminance signal Y, and after gamma, The color signal C'is output. In the matrix circuit 13, matrix processing is performed on the color signal C ′ after gamma, and the color signal Cout of RY and BY is output from the output terminal 12b.

Here, the case where the illuminance of the subject is extremely lowered will be described. Level detection circuit 14 in FIG.
The luminance signal Y output from the luminance color separation circuit 6 is input, an average value of signals for one screen is calculated, and the average value is input to the microcomputer 15. When the illuminance of the subject decreases, the average value detected by the level detection circuit 14 decreases, so the microcomputer 15 issues a command to open the aperture value of the aperture 20 through the aperture drive circuit 21, and the level detection circuit 14 obtains it. The aperture is controlled so that the average value of the signal is kept constant.

However, when the illuminance of the subject is extremely lowered, the diaphragm 20 is opened, and the signal level cannot be increased further by diaphragm control. Therefore, the microcomputer 15 raises the signal level by raising the amplification factor of the input signal in the gain control circuit 3.

Next, the microcomputer 15 issues a command to the gradation characteristic setting circuits 17a to 17c so that the maximum value of the slope of the gamma curve is set to a fixed value or less. Other than the inclination of the gamma curve, it is the same as the normal shooting state.

FIG. 5 and FIG. 6 show waveforms of various parts at the time of gray scale imaging when noise is mixed. here,
FIG. 5 shows a normal image pickup, and FIG. 6 shows a gain up. 5 and 6, the horizontal axis represents the horizontal pixel position and the vertical axis represents the signal level. The broken line indicates the luminance signal Y, the thick line indicates the luminance signal Y ′ after gamma correction, and the thin line indicates the output luminance signal Yout.

It can be seen from FIG. 6 that the noise component in the low luminance portion, which is particularly noticeable, is suppressed because the inclination is suppressed.

The effect of the present invention is to control the output signal level of the signal level adjusting means in accordance with the brightness level detected by the brightness detecting means and to change the gradation correction characteristic in the gradation correcting means. To prevent resolution degradation,
Distortion due to non-linear processing is inconspicuous, and a noise suppression method that produces a natural image can be obtained.

In the present embodiment, the single-chip system having a single image pickup element has been described, but the same effect can be obtained for an image pickup apparatus having a plurality of image pickup elements, for example, a three-plate system. In this case, the configuration of the camera signal processing circuit will be slightly different.

Further, in the present embodiment, the RAM is used as the gradation correction circuit, but the same effect can be obtained by using other means such as polygonal line approximation.

Further, it is also possible to use the first embodiment and the second embodiment in combination. That is, the tone correction characteristics may be changed according to the brightness level with reference to the gamma characteristics in the moving image mode or the still image mode.

[0058]

The effect of the present invention is to detect the moving image mode or the still image mode by the mode changeover switch as the gradation condition detecting means, and perform the optimum gradation correction for each characteristic according to the detection. That is.

Another effect of the present invention is that the output signal level of the signal level adjusting means is controlled according to the brightness level detected by the brightness detecting means and the gradation correction characteristic in the gradation correcting means is changed. Thus, it is possible to obtain a noise suppression method that suppresses deterioration of resolution and makes distortion due to non-linear processing inconspicuous, resulting in a natural image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image pickup apparatus according to a first embodiment of the present invention.

FIG. 2 is a waveform diagram showing a signal waveform in each part of the image pickup apparatus in a moving image mode.

FIG. 3 is a waveform diagram showing a signal waveform in each unit in the still image mode of the image pickup apparatus.

FIG. 4 is a block diagram showing a configuration of an image pickup apparatus according to a second embodiment of the present invention.

FIG. 5 is a waveform diagram showing signal waveforms in various parts of the imaging apparatus in a normal state.

FIG. 6 is a waveform diagram showing signal waveforms at various parts when the gain of the image pickup apparatus is increased.

FIG. 7 is a block diagram showing a configuration of a conventional imaging device.

FIG. 8 is a waveform diagram showing a signal waveform in each part of the conventional imaging device.

[Explanation of symbols]

1 Solid-state imaging device 2 CDS circuit 3 Gain control circuit 4 AD converter 5 Camera signal processing circuit 6 Luminance color separation circuit 7 High-pass filter 8 Gamma ROM 9 Aperture gain control circuit 10 Waveform shaping circuit 11 Addition circuit 12 Output terminal 13 Matrix circuit 14 Level detection circuit 15 Microcomputer 16 Mode selection switch 17 as gradation condition detection means 17 Gradation characteristic setting circuit 18 Gradation correction circuit 19 Optical lens 20 Aperture 21 Aperture drive circuit

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Bunki Shibuya             1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric             Sangyo Co., Ltd. F term (reference) 5B057 CA08 CB08 CE11 CH06 CH07                       CH18                 5C021 PA58 RB03 XA03 XA34 ZA02                 5C022 AA13 AB20 AC42 AC69                 5C066 AA01 CA17 EC05 GA04 KM02                 5C077 LL19 MP01 NN02 NN19 PP15                       PQ08 PQ12 PQ23 RR05 TT09

Claims (3)

[Claims] 1. A gradation condition detecting means for detecting or setting conditions of gradation characteristics according to a user's intention or a scene to be photographed, and a microcomputer for obtaining adjustment conditions of gradation characteristics by said gradation condition detecting means. And a gradation characteristic setting means for changing the setting value of the gradation characteristic according to a command of the microcomputer, and a step for performing gradation correction on an input signal according to the gradation characteristic set by the gradation characteristic setting means. An image pickup apparatus comprising: an adjustment device. 2. The image pickup apparatus according to claim 1, wherein the gradation condition detection means is a mode changeover switch, and changes the gradation correction characteristic in the gradation correction means according to the mode switching state. 3. A signal level adjusting means for adjusting the level of an input signal is provided, and the gradation condition detecting means is a brightness detecting means for detecting the brightness of a subject, which is detected by the brightness detecting means. The image pickup apparatus according to claim 1, wherein the output signal level of the signal level adjusting means is controlled according to the brightness level, and the gradation correction characteristic of the gradation correction means is changed.