JPH11113012A - Electronic image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a device which suppresses the deterioration of an image, gets a image signal that reproduces and shows a satisfactory image and also realizes miniaturization by controlling a resolution compensating means in accordance with a signal level from an image pickup device. SOLUTION: A CPU 20 controls an edge emphasis degree integrator 15 in accordance with an input level of an image signal from a CCD 2 and variably controls a coefficient, that is, contour (edge) emphasis degree in performing edge emphasis processing. Specifically, it controls so that an edge emphasis degree to a input that has a lower level becomes relatively low. Then, optimum edge emphasis processing is performed even at a low signal level without emphasizing noise too much. Moreover, gamma correction processing is performed and subtracting color is performed to 8-bit image data of each color on a preceding stage of a digital processing part and besides, various signal processing are executed. Thereby, it is possible to make a circuit scale small and to contribute to the miniaturization of this device itself.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic image pickup apparatus, and more particularly to an electronic image pickup apparatus for electronically recording an image taken by a solid-state image pickup device or the like.

[0002]

2. Description of the Related Art In recent years, a subject image optically photographed by a photographing optical system such as a photographing lens is photoelectrically converted by an image pickup means such as an image pickup device, and an image signal as an electric signal obtained by the photoelectric conversion is electronically converted. 2. Description of the Related Art Electronic imaging devices (hereinafter, referred to as electronic cameras) such as electronic cameras for recording are widely used.

In such an electronic camera, a solid-state imaging device such as a CCD is generally used as an imaging means. As a display device for reproducing and displaying an image captured and recorded by the electronic camera, a display device using a cathode ray tube such as a CRT, a liquid crystal display device (LCD), or the like is generally used.

The slope of the photoelectric conversion characteristic indicating the relationship between the amount of incident light (input) incident on the CCD of the electronic camera and the output signal, ie, the γ (gamma) characteristic, is generally constant and proportional over a wide range. It is desirable.

However, the electro-optical conversion characteristic (γ) of a normal display device has a non-linear characteristic, so that an image photographed by the electronic camera using such a display device can be favorably reproduced and displayed. For this purpose, it is necessary to perform gamma (γ) correction processing on the image output signal so that the intensity of the incident light of the electronic camera and the emission intensity of the display device are proportional.

For this purpose, in a conventional electronic camera, an image signal obtained by an image pickup means such as a CCD (hereinafter simply referred to as a CCD) is color-separated into R, G, and B color signals. After performing a gamma correction process on the image signal, a luminance signal (Y signal) and a color difference signal are generated from the image signal, and the reproduced signal is output to a display device to reproduce and display an image. Further, in a conventional electronic camera, in order to improve image quality, for example, a resolution compensating unit such as an outline emphasizing unit is provided to perform various signal processes.

An analog image signal photoelectrically converted by a CCD is usually converted into a digital signal through a two-stage process of sampling (sampling) and quantization in an A / D converter. . In general, the quantization number in the quantization process is set to a level (number of gradations) of about 8 to 10 bits per pixel in order to obtain an image signal capable of displaying a good image.

Here, a flow of signal processing when processing a digital signal of a conventional electronic camera is shown in a block diagram of a main part of FIG.

In an A / D converter (not shown) of the electronic camera, for example, a 10-bit quantization number is set to
When the D conversion is performed, the image signal converted into the digital signal is subjected to signal processing such as color correction in a main signal processing unit (circuit) as shown in FIG. Is the edge extraction processing in the edge extraction unit,
After a coring process or the like in the coring unit 14, a contour (edge) correction process or the like by the edge emphasis degree integrator 15 is performed. After the edge corrected Y signal and the main signal processed Y signal are added by the adder 11, a gamma correction process is performed in a gamma correction processing circuit 7A, and 8-bit data of each color is obtained. And output to a display processing unit (not shown) such as an LCD.

As described above, if the gamma correction process is performed after the various signal processes, each signal process is performed on an image signal having a data amount of 10 bits for each color. And a good image signal can be obtained.

However, in this case, since the amount of data to be handled becomes large, the circuit scale for performing signal processing becomes large, the device itself becomes large, and the manufacturing cost also increases. There is.

Therefore, as shown in the block diagram of the main part of FIG. 6, the configuration is such that the gamma correction processing is performed before the signal processing, and the image signal is reduced to 8-bit image data for each color. Performing various types of signal processing in this manner has the advantage that the above-described problem can be avoided and the circuit scale of the device can be designed to be small.

[0013]

In this case, however, there arises a problem that, for example, noise in a low-luminance portion (dark portion) increases, and as a result, the resolution and sharpness of an image reproduced and displayed are caused. Degree may deteriorate.

FIG. 7 is a diagram showing the relationship between input signals and output signals (γ characteristics) in a conventional electronic camera. In FIG. 7, for example, noises Ain, at the same level in a low-luminance part (dark part) and a high-luminance part (light part) of the input signal are shown.
Each noise Aou of each output signal with respect to Bin
Focusing on t and Bout, the noise Aou as shown in FIG.
There is a relationship of t> noise Bout. That is, the noise level of the output signal in the low luminance portion tends to be higher than the noise level of the output signal in the high luminance portion.

In order to suppress this, a means for suppressing noise by increasing the coring level in the coring process can be considered. However, in the coring process, the effect on the low luminance portion and the effect on the high luminance portion are different, and the effect on the low luminance portion is particularly small. Therefore, when the coring process is performed at a higher coring level, the coring process acts excessively on the high luminance portion, and the high luminance portion of the image may be deteriorated.

The present invention has been made in view of the above points, and has as its object to perform optimal signal processing on an image signal captured by a solid-state imaging device such as a CCD. An object of the present invention is to provide an electronic image pickup apparatus which can obtain an image signal capable of reproducing and displaying a better image while suppressing the deterioration of the image, and realize a downsizing.

[0017]

In order to achieve the above object, an electronic imaging apparatus according to a first aspect of the present invention uses a two-dimensional imaging element and includes an electronic imaging apparatus having a resolution compensating means. The resolution compensating means is controlled according to the signal level from

According to a second aspect of the present invention, in the electronic imaging apparatus according to the first aspect, the resolution compensating means is a contour enhancing means for performing a process of enhancing a contour signal by changing a contour enhancing degree. It is characterized by.

An electronic image pickup apparatus according to a third aspect of the present invention is an electronic image pickup apparatus using a two-dimensional image pickup element and having a resolution compensating means, for extracting a contour signal different from a gradation characteristic for a main signal. It is characterized by having gradation characteristics.

Therefore, the electronic image pickup apparatus according to the first aspect of the present invention obtains an image signal capable of displaying a good image by optimal signal processing by controlling the resolution compensating means according to the signal level from the image pickup device. .

Further, the electronic imaging apparatus according to the second aspect of the present invention performs processing for enhancing the contour signal by changing the degree of contour enhancement by the contour enhancing means which is the resolution compensating means in accordance with the signal level from the image sensor. Thus, an image signal capable of displaying a good image is obtained.

Further, the electronic image pickup apparatus according to the third aspect of the invention displays a good image by performing a gradation correction process using a gradation characteristic for extracting an outline signal different from the gradation characteristic for a main signal. Obtain the obtained image signal.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a block diagram showing the internal configuration of the electronic imaging apparatus according to the first embodiment of the present invention.

As shown in FIG. 1, the electronic image pickup apparatus according to the present embodiment includes a photographing optical system 1 including a photographing lens, a driving motor and a driving mechanism for driving the photographing lens, and the photographing optical system 1.
A solid-state imaging device (hereinafter, simply referred to as a CCD) 2 such as a CCD that photoelectrically converts an optical subject image formed by the CCD and generates an image signal of the subject image, and converts an image signal component from the output signal of the CCD 2 CDS circuit to extract (correlated double sampling) 3
And an amplifier (AMP) 4 which is a gain control means including an AGC circuit for adjusting the output signal level of the CDS circuit 3 to a predetermined gain value, and converts an analog signal output from the AMP 4 into a digital signal. An analog signal processing unit including an A / D converter 5 and a digital signal processing unit for processing a digital signal A / D converted by the A / D converter 5 are provided.

The digital signal processing section includes the CCD 2
And a pixel defect correction circuit 6 which is a pixel defect correction means for interpolating an image defect caused by a defect such as a white point defect (hereinafter referred to as a white point defect), and γ for performing gamma correction processing of an image signal
A correction circuit 7, a color separation circuit 8 for separating an image signal (main signal) which has been γ-corrected by the γ correction circuit 7 into three primary color signals of an RL signal, a GL signal, and a BL signal; And a color matrix circuit 9 for performing color correction for improving color, and converting each color signal of R, G, and B into a luminance signal YL and two color difference signals (RY signal and BY signal) to convert the hue and color. A main signal processing unit that handles main signals such as color signals among image signals obtained by the CCD 2 and a sub signal such as a luminance signal (Y signal), such as a color difference matrix circuit 10 that adjusts the degree of saturation, etc. And a sub-signal processing unit. The sub-signal processing unit extracts a luminance signal (Y signal) from the image signal output from the γ correction circuit 7 and generates the luminance signal (Y signal), and removes a low-frequency component from the Y signal. A high-pass filter (HPF) unit 13 for extracting an edge signal, a coring unit 14 for performing a coring process for suppressing or removing a noise component of the edge signal generated by the HPF 13 and improving an S / N ratio, and The signal is formed by a contour emphasizing means as a resolution compensating means constituted by an edge emphasizing degree accumulator 15 and the like for performing an edge emphasizing process by multiplying the Y signal subjected to the coring process by the ring unit 14 by a predetermined coefficient. ing.

Further, the electronic imaging device adds the edge-enhanced Y signal output from the edge enhancement degree integrator 15 and the luminance signal YL output from the color difference matrix circuit 10 to obtain a luminance. A liquid crystal display (LC) which is a display unit including an adder 11 for outputting the signal YH and a signal processing circuit for processing the image signal into a displayable form.
D) DR which is a built-in camera storage means including a display processing unit including 19 and a memory for temporarily storing image signals.
A recording unit including an AM 16, a compression / expansion circuit 17 for performing compression processing and expansion processing on an image signal, and a recording medium 18 such as a memory card for storing the image signal. An operation unit 21 including a plurality of switches such as a trigger switch capable of generating a trigger signal to be generated, a temperature sensor unit 22 serving as a temperature detecting unit for detecting a temperature state of the CCD 2 and a synchronizing signal such as a driving pulse of the CCD 2 are generated. Timing generator (TG) 23 and signal generator (SG)
24 and other components such as a control unit.

The components described above are electrically connected to a CPU 20 serving as control means, and the entire electronic image pickup apparatus of the present embodiment is controlled by the CPU 20 as a whole.

In the electronic imaging apparatus according to the present embodiment having the above-described configuration, the CPU 20 includes the CCD 2
The edge emphasizing degree integrator 15 is controlled in accordance with the input level of the image signal from the CPU to variably control the coefficient when performing the edge emphasizing process, that is, the contour (edge) emphasizing degree. Specifically, control is performed so that the degree of edge enhancement for a lower level input is relatively low. Therefore, even at a low signal level, the noise is not excessively enhanced, and the optimum edge enhancement processing is performed.

As described above, according to the first embodiment, the edge enhancement degree is variably controlled in accordance with the input level of the image signal, and the optimum edge enhancement processing is performed in accordance with the input level. Therefore, it is possible to obtain an image signal capable of displaying a good image without deteriorating the image.

In addition, since the gamma correction process is performed in the preceding stage of the digital signal processing unit, the color data is reduced to 8-bit image data for each color, and various signal processes are performed, the circuit scale is reduced. This can contribute to downsizing of the device itself.

Next, an electronic imaging apparatus according to a second embodiment of the present invention will be described below. FIG. 2 is a block diagram showing the internal configuration of the electronic imaging device according to the second embodiment of the present invention. The second embodiment has substantially the same configuration as that of the first embodiment described above, and differs only in the configuration of the digital signal processing unit. Therefore, the same components as those in the above-described first embodiment are denoted by the same reference numerals, detailed description thereof will be omitted, and only different portions will be described below.

The digital signal processing unit in the electronic imaging apparatus according to the present embodiment has the same configuration as that of the first embodiment.
It is composed of a main signal processing unit that handles a main signal such as each color signal among the image signals obtained by D2, and a sub signal processing unit that handles a sub signal such as a luminance signal (Y signal).

The main signal processing section includes a pixel defect correction circuit 6 which is a pixel defect correction means for interpolating an image defect and a first γ correction circuit for performing gamma correction processing on the main signal of the image signal (in FIG. 2, γ (1) correction circuit) 27, a color separation circuit 8 for separating color signals, a color matrix circuit 9 for performing color correction processing, a luminance signal YL, and two color difference signals (RY).
Color difference matrix circuit 1 for converting a
0 or the like.

Further, the sub-signal processing unit performs the first γ
A second γ correction circuit 25 (shown as a γ (2) correction circuit in FIG. 2) for performing a gamma correction process for extracting an outline signal (hereinafter, referred to as an edge signal) on the image signal output from the correction circuit 27; , A Y signal generation unit 12 for extracting a luminance signal (Y signal), and a high-pass filter (HP
F) Unit 13 and coring unit 14 for performing coring processing
And an edge emphasizing means 15 for performing edge emphasizing processing for multiplying a correlated Y signal by a predetermined coefficient (edge emphasizing degree). Have been.
Other configurations are completely the same as those of the first embodiment.

The flow of signal processing in the digital signal processing section for processing digital signals in the electronic image pickup apparatus of the present embodiment thus configured is as shown in the block diagram of the main part of FIG.

That is, when the A / D converter 5 performs A / D conversion by setting a quantization number of, for example, 10 bits, the image signal converted into a digital signal is as shown in FIG. First, in the first γ correction circuit 27, a gamma correction process is performed based on the gradation characteristics for the main signal, that is, the first gamma characteristics γ (1), and the color is reduced to 8-bit gradation image data for each color. The main signal processing section (circuit) performs signal processing such as normal color correction on the main signal.

On the other hand, in the sub signal processor,
The gamma correction circuit 25 performs a gamma correction process based on a second gamma characteristic γ (2), which is a gradation characteristic for extracting an edge signal, which is different from the gradation characteristic for the main signal. The luminance signal (Y signal) in the Y signal generation unit 12
Is extracted, and the low-frequency component is removed from the Y signal in the HPF unit 13 to extract an edge signal (edge extraction processing).

Next, a coring process is performed on the edge signal in the coring unit 14, and the edge enhancement is performed by multiplying the correlated Y signal by a predetermined coefficient in the edge enhancement degree integrator 15 or the like. Processing is performed.

The edge-corrected Y signal and the Y signal subjected to the main signal processing in the main signal processing unit are used.
The signal (reference numeral YL in FIG. 1) is added by the adder 11 and then output as a Y signal (YH). In addition, the two signals are output from the color difference matrix circuit 10 together with two color difference signals (R− Along with the Y signal and the BY signal), they are output to an LCD 19 (not shown in FIG. 2) which constitutes a display processing unit. Note that the image signal output here is image data having 8-bit gradation for each color.

In this case, the relationship (γ characteristic) between the input signal and the output signal of the electronic imaging device is as shown in FIG.

In FIG. 4, noise A of the same level in a low-luminance portion (dark portion) and a high-luminance portion (bright portion) of the input signal is shown.
The respective output signals for in and Bin are subjected to γ correction only by the first gamma characteristic γ (1),
The noise level Aout (1) of the output signal in the low luminance portion and the noise level Bout (1) of the output signal in the high luminance portion are as follows.
Noise Aout (1)> Noise Bout (1)
As described above, the difference is extremely large.

On the other hand, in this embodiment, the second
Since the gamma correction process based on the gamma characteristic γ (2) is performed, when the first and second gamma characteristics gamma (1) and γ (2) are synthesized, “γ (1)” shown in FIG. * Γ (2) ”. Accordingly, the noise level of each output signal with respect to the noise Ain and Bin of the same level in the low luminance portion (dark portion) and the high luminance portion (bright portion) of the input signal is determined by the noise Aout (2) and the noise Bout (2). As shown, the difference is small enough. Therefore, good noise characteristics can be obtained over the entire luminance.

As described above, according to the second embodiment,
Using the second gamma characteristic γ (2), which is a gradation characteristic for extracting edge signals, different from the first gamma characteristic γ (1), which is the gradation characteristic for the main signal, the sub signal (Y signal) is Since the signal processing is performed, optimal signal processing can be performed so that the resolution and the noise are in a well-balanced state over substantially the entire luminance of the image signal obtained by the CCD 2. Therefore, it is possible to obtain an image signal capable of reproducing and displaying a better image while suppressing deterioration of the image.

Also, various signal processing for the digitally converted image signal is performed by 8-bit image data of each color (image data of a necessary gradation capable of reproducing and displaying a good image). The scale can be designed to be small. Therefore, it can contribute to downsizing of the device itself.

[0045]

As described above, according to the present invention, CC
By performing optimal signal processing on an image signal captured by a solid-state imaging device such as D, image deterioration can be suppressed, and an image signal capable of reproducing and displaying a better image can be obtained. Can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the internal configuration of an electronic imaging apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of an electronic imaging device according to a second embodiment of the present invention.

FIG. 3 is a main block diagram showing a digital signal processing unit in the electronic imaging apparatus of FIG. 2;

FIG. 4 is a diagram showing a relationship (γ characteristic) between an input signal and an output signal in the electronic imaging device of FIG. 2;

FIG. 5 is a main block diagram showing a digital signal processing unit in a conventional electronic camera.

FIG. 6 is a main block diagram showing another digital signal processing unit in a conventional electronic camera.

FIG. 7 is a diagram showing a relationship (γ characteristic) between an input signal and an output signal in the electronic camera of FIG. 6;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Optical imaging system 2 ... CCD (solid-state imaging device) 3 ... CDS circuit (correlated double sampling circuit) 4 ... AMP (amplifier, gain control means) 5 ... A / D converter 6 ... Pixel Defect correction circuit (pixel defect correction means) 7, 7A... Gamma (γ) correction circuit 8... Color separation circuit 9... Color matrix circuit 10... Color difference matrix circuit 11. (Luminance signal generator) 13 HPF section (high-pass filter section, contour emphasizing means) 14 coring section (contour emphasizing means) 15 ... edge emphasis degree integrator (contour emphasizing means) 19 LCD (liquid crystal display) Display; display device, display means) 20 CPU (control means) 21 operation unit (trigger switch etc.) 25 second gamma (γ) correction circuit 27 first gamma (γ) correction circuit

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 9/69 H04N 9/69

Claims (3)

[Claims] 1. An electronic image pickup apparatus using a two-dimensional image pickup device and having a resolution compensation means, wherein the electronic image pickup apparatus controls the resolution compensation means according to a signal level from the image pickup element. . 2. The electronic imaging apparatus according to claim 1, wherein said resolution compensating means is a contour emphasizing means for performing a process of emphasizing a contour signal by changing a contour emphasis degree. 3. An electronic image pickup apparatus using a two-dimensional image pickup device and provided with a resolution compensating means, characterized in that the electronic image pickup apparatus has a gradation characteristic for extracting a contour signal different from a gradation characteristic for a main signal. Image pickup device.