JP2000299799A - Image processor, method therefor and computer-readable storage medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a video image from being faintly left on a screen in the case that fade-in is started from a white image on the screen and fade-out is finished in a white image on the screen when a noise reduction circuit is placed to a post-stage of a fader circuit. SOLUTION: Cyclic noise reduction sections 24, 28 are provided in a post- stage of fader sections 23, 27 of a luminance signal and a chrominance signal. In the case of fade-out, a multiple coefficient of a multiplier circuit being a component of the cyclic noise reduction sections 24, 28 is closer to zero as a mixing ratio of an input image to the fader section 23, 27 to an image in a prescribed color uniform on the screen gets higher as its control. Furthermore, in the case of fade-in, the multiple coefficient is closer to '1' as the mixing ratio gets lower.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus and method suitable for use in an image pickup apparatus such as a video camera provided with a noise reduction circuit for removing noise of a video signal, and a computer-readable apparatus used in the method. It relates to a storage medium.

[0002]

2. Description of the Related Art A video camera is provided with a noise reduction circuit for removing noise from a video signal. The noise reduction circuit is a DV cassette (SD
With the advent of formats), digitization is progressing together with other various video signal processing circuits. Such digital noise reduction circuits are generally of the recursive type using a field memory, and because of the recent low cost of memory, they are likely to be installed in popular video cameras for consumer use. Became.

FIG. 6 is a block diagram showing a conventional cyclic noise reduction circuit. In FIG. 6, a cyclic noise reduction circuit includes an input terminal 51, an addition circuit 52,
Subtraction circuit 53, multiplication circuit 54, field memory 55,
It comprises a limiter 56, an output terminal 57 and the like.

Next, the operation will be described. Input terminal 51
Is supplied to an addition circuit 52 and a subtraction circuit 53. In the subtraction circuit 53, the signal Si and the signal Sf delayed by the field memory 55 are subtracted, and a noise signal Sn1 between fields is detected. Signal Sn1
Is supplied to the limiter 56. Since the signal Sn1 also includes a motion component, the motion component is removed by the limiter 56 to obtain a signal Sn2. The signal Sn2 is supplied to the multiplication circuit 5
4 is multiplied by a coefficient K (hereinafter referred to as a cyclic coefficient) given from the outside, and becomes a signal K · Sn2.
2 is supplied. In the adder circuit 52, the signal Si and the signal K
Remove noise components from the signal Si by adding Sn2. The output signal So of the addition circuit 52 is
It is supplied to the field memory 55 and the output terminal 57
Output from

Here, in order to simplify the description, Sn1 =
Assuming that Sn2 = Sn, the signal Sn is as follows: Sn = Sf-Si (1) Becomes

Considering a method of obtaining a signal So having a smaller noise component from the above equation (2), the signal Si contains a noise component, and the signal Sf is a delayed signal of the signal So from which the noise component has been removed. Therefore, it can be seen that the cyclic coefficient K should be approximated to "1" without limit. Conversely, when the cyclic coefficient K is set to “0”, the signal Si becomes the signal So as it is.

[0007]

As described above, the closer the cyclic coefficient K is to "1", the more effective it is at removing noise. On the other hand, since the influence of the previous field becomes strong, an afterimage becomes conspicuous particularly in a scene having motion. As a countermeasure against this, a scene under sufficient illuminance or a scene under low illuminance is obtained by using parameters for controlling exposure such as an aperture value, an electronic shutter speed, and an AGC gain. Is determined, and only in the case of a shooting scene under low illuminance where the noise component increases, a process of increasing the cyclic coefficient K is performed so as to minimize residual images.

However, a fade-out in which a captured image is faded to an image of a uniform color (for example, white) over the entire surface (hereinafter, referred to as a fade image) or a reverse fade-in (hereinafter, the above-described fade-in, fade-out) In the case of a system configuration in which a noise reduction circuit is located behind a fader circuit that performs a process of (also referred to as an auto-fade together with the function of (1)), an afterimage appears significantly during auto-fade.

This problem will be described with reference to FIG. FIG.
(A), (b), and (c) are four colors (from left, yellow, blue, green, and red)
FIG. 6 is a diagram showing a video signal when a color bar chart 61 is photographed. Here, the color of the image at the end of the fade-out and at the start of the fade-in is white. FIG. 7 (a)
Is the state in which the auto fade is off, (b) is the state in which the auto fade is on and halfway out,
(C) shows the state of the end of the fade-out. 62 indicates a horizontal synchronizing signal, and 63 indicates a burst signal.

Reference numerals 64 and 65 denote signal amounts to be added to the input signal of the fader circuit (hereinafter referred to as a fade level), 64 denotes a fade level in the middle of a fade-out, and 65 denotes a fade level at the end of the fade-out. Indicates a fade level (the level at this time is assumed to be 100%).

Here, the fade level is also a value indicating the mixing ratio of the captured image and the image of the fade image. When the fade level = 0%, the captured image: the image of the fade image = 1: 0 fade When the level is 100%, the ratio of “captured image: fade image = 0: 1”.

The video signal output in FIG.
When the fade-out operation is started by turning on the auto fade, as shown in FIG. 7B, the fade level is simultaneously increased while the luminance and color gains are reduced. At the end of the fade-out, FIG.
As shown in (c), the gain of the luminance and the color is 0 in the fader circuit, the fade level reaches 100%, and the effect of the afterimage of the noise reduction processing in the subsequent stage despite the fact that the entire screen should be a white screen. Therefore, in the signal after the noise reduction circuit, the luminance and the color level do not reach 0, and the image becomes such that the four colors of the color bar chart 61 are lightly colored on a white screen.

The effect of this afterimage extends for several seconds depending on the cyclic coefficient K. Even when the fade-in operation starts, the video signal becomes the same as that in FIG. 7C (detailed description of the fade-in operation is omitted).

SUMMARY OF THE INVENTION The present invention has been made to solve the above problem, and has as its object to realize good noise reduction processing regardless of the system configuration even at the time of fade-in / out.

[0015]

In order to achieve the above object, in an image processing apparatus according to the present invention, an input image signal is set based on a first control value so as to be a predetermined color which is uniform over the entire screen. Fade means for fading, noise reduction means arranged at a subsequent stage of the fade means for removing noise of the image signal to be faded based on a second control value, and according to the first control value of the fade means Control means for changing the second control value of the noise reduction means.

Further, in the image processing method according to the present invention, after the input image signal is faded based on the first control value so as to have a predetermined color uniform over the entire screen, the noise of the faded image signal is reduced. Is removed based on the second control value, the second control value is changed according to the first control value.

In the storage medium according to the present invention,
The first step is to make the input image signal a predetermined color uniform over the entire screen.
A fade process for fading based on the control value of the second and a noise of the image signal obtained by the fade process in the second process.
And a program for executing a noise reduction process for removing based on the first control value and a control process for changing the second control value in accordance with the first control value.

[0018]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an imaging device such as a video camera to which the image processing device according to the present invention is applied. In FIG. 1, reference numeral 11 denotes a lens for forming an image of a subject,
Reference numeral 12 denotes an aperture for adjusting the amount of light, 13 denotes an image sensor such as a CCD that converts input light into an electric signal, 14 denotes a sample and hold unit that samples and holds an imaged signal,
15 is an AGC unit for automatically controlling the gain, and 16 is an A / D
A conversion unit 17 is a video signal processing unit that processes a signal to generate a video signal, 18 is a system control unit that controls the entire imaging device, and 19 is a field memory that stores an image for one field.

FIG. 2 is a block diagram showing a detailed configuration of the video signal processing section 17 of FIG. In FIG. 2, reference numeral 21 denotes a Y / C separation unit for separating an input signal into a luminance component and a color component;
Reference numeral 2 denotes a luminance signal processing unit that includes an aperture correction circuit and a gamma correction circuit and performs predetermined signal processing. Reference numeral 26 denotes a color signal processing unit that includes a matrix circuit, a white balance circuit, a gamma correction circuit, and a color difference matrix circuit and performs predetermined signal processing. ,
Reference numeral 23 denotes a fader unit for auto-fading the luminance signal.
7 is a fader for auto-fading the color signal; 24 is a noise reduction unit for removing noise of the luminance component;
8 is a noise reduction unit for removing noise of color components,
Reference numerals 25 and 29 denote D / A converters, reference numeral 30 denotes a video signal generation unit for generating a video signal, and reference numeral 31 denotes an interface which is a data input / output unit of the video signal processing unit 17.

The noise reduction units 24, 28
The circuit is the same as the circuit shown in FIG. 6 except that the field memory 55 is removed from the cyclic noise reduction circuit, and the equivalent of the field memory 55 in FIG.
9

Next, the operation will be described. The amount of light from the subject received from the lens 11 is adjusted by the aperture 12 and formed on the image sensor surface of the image sensor 13. Here, after being converted into an electric signal, the A / D converter 16 converts the signal into an A / D signal via the sample / hold unit 14 and the AGC unit 15.
The converted signal is input to the video signal processing unit 17.

In the video signal processing section 17, the input signal is separated into a luminance component and a color component by a Y / C separation section 21, and the luminance component is output to the processing section 22 and the color component is output to the color signal processing section 26. Is done. In the luminance signal processing unit 22, aperture correction and gamma correction are performed in the horizontal and vertical directions. The color signal processing unit 26 separates the color component signal into three primary colors,
White balance adjustment and gamma correction are performed, and a color difference signal is formed.

The outputs of the luminance signal processing unit 22 and the color signal processing unit 26 are controlled by the system control unit 18 by faders 23 and 27 to control the luminance and color gain and the fade level. It is output after being faded to a color, for example, white. Next, in the noise reduction units 24 and 28, the cyclic coefficient K is controlled by the system control unit 18 to remove noise of luminance and color components. After that, the signal passed through the D / A converters 25 and 29 is
The video signal is output to the video signal generation unit 30 to generate a video signal.

The system control unit 18 switches on / off of auto fade by an external fade trigger signal, and switches between fade in / out by a fade mode selection signal. The system control unit 18 controls the video signal processing unit 17 via the interface unit 31.

Next, the operation of the system control unit 18 for the faders 23 and 27 and the noise reduction units 24 and 28 will be described with reference to FIGS. 3, 4, and 5. FIG.
The graph shows the relationship between the gain, the fade level, and the cyclic coefficient, with the horizontal axis representing the gain and the fade level and the vertical axis representing the cyclic coefficient. FIG. 4 is a diagram showing video signals at the end of the fade-out or at the start of the fade-in when the color bar chart 61 is photographed. Incidentally, reference numerals 61, 62, 63 and 65 in FIG. 4 are the same as the signals of the same numbers in FIG. FIG. 5 is a flowchart showing the control operation of the system control unit 18 for the faders 23 and 27 and the noise reduction units 24 and 2.

At the time of normal photographing, that is, when auto-fade is off and no fade trigger signal is input, the process branches to step S702 in step S701 (hereinafter abbreviated as step), branches to step S712 in step S702, and sets
For 7, the gain is set to 1 and the fade level is set to 0%. Next, in S713, the fade operation is naturally turned off. In step S714, the noise reduction units 24, 2 and 2 are switched from the fade level set in step S712.
The cyclic coefficient K = 255/256 is calculated for 8. S
At 715, the control values set at S712 and S714 are output, and the process returns to S701 and repeats the same operation.

As a result, the inputs are output as they are to the faders 23 and 27, and the noise reduction units 24 and 28
Then, a signal corresponding to the above equation (2) used in the description of FIG. 6 is output.

Next, the operation when the auto fade is on will be described. Switching of the fade operation from off to on is performed by inputting a fade trigger signal. The system control unit 18 branches from S701 to S702,
If it is determined in 702 that a fade trigger signal has been input, the flow branches to S703. In S703, when the fade-out is selected by the fade mode selection signal, the flow branches to S704.

In S704, the gain is set to 1 within a predetermined time.
The gain and the fade level are changed so that the fade level can be shifted from 0% to 100% from 0 to 100%. In S705, the fade level is 100
If it is determined that the percentage has not been reached, S70
In step S707, the fade operation is turned off, and if it is determined that 100% has been reached, the fade operation is turned off in step S707.

From S706 and S707, the process proceeds to S714, in which a cyclic coefficient on the vertical axis with respect to the fade level on the horizontal axis of the graph of FIG. 3 is calculated from the fade level set in S704. In S715, S704 and S
The control value set in 714 is output, and the process returns to S701.
Since the fade operation is on until it is determined in S705 that the fade level has reached 100%, the process branches to S703 in S701, and the same operation is repeated thereafter.

As a result, the afterimage phenomenon is reduced as the fade level approaches 100%. When the fade level reaches 100%, the cyclic coefficient K becomes 0, and the noise reduction units 24 and 28 output the input signals as they are. The luminance and color gains of the signals after the noise reduction units 24 and 28 as well as the faders 23 and 27 become 0 as in the video signal shown in FIG. 4, and the entire screen becomes a uniform white screen.

On the other hand, if it is determined in step S703 that fade-in has been selected by the fade mode selection signal,
Branch to 708. In S708, the gain and the fade level are changed so that the gain can be shifted from 0 to 1 and the fade level from 100% to 0% within a predetermined time. In S709, the fade level is 0
If it is determined that the percentage has not been reached, S71
If 0, the fade operation is turned on, and if it is determined that 0% is reached, the fade operation is turned off in S711.

The process proceeds from S710 and S711 to S714, and calculates the cyclic coefficient on the vertical axis with respect to the fade level on the horizontal axis of the graph of FIG. 3 from the fade level set in S708. In step S715, the control values set in steps S708 and S714 are output, and the process returns to step S701. In S709,
Until it is determined that the fade level has reached 0%, the fade operation is on.
The process branches to 03 and the same operation is repeated thereafter. Thereby, the white screen at the start of the fade-in also becomes a uniform white screen as in the video signal shown in FIG.

In this embodiment, the fade level is 0.
If the cyclic coefficient K changes to a value that approximates 0 to a change from percent to 100 percent, the value of each cyclic coefficient K for the fade level shown in FIG. 3 is not limited.

Similarly, for the sake of simplicity, the cyclic coefficients K supplied to the noise reduction units 24 and 28 are set to be the same, but may be different values, and the values of the cyclic coefficients K are not limited.

Similarly, in this embodiment, the cyclic coefficient K is a fixed value not only under a sufficient illuminance but also under a low illuminance at the time of normal photographing (auto fade is off). As described above, the cyclic coefficient K may be varied according to the illuminance, and the value of the cyclic coefficient K at the time of normal photographing is not limited.

Although the present embodiment has been described for the case where the present invention is applied to an image pickup apparatus, the same effect can be obtained by applying the present invention to a camera-integrated VTR in which a recording apparatus is integrated.
Further, the present invention is applicable even when a fader circuit and a noise reduction circuit exist on the recording apparatus side.

Next, a storage medium according to another embodiment of the present invention will be described. The system according to the configuration of FIG.
It may be configured as hardware, or may be configured as a computer system including a CPU, a memory, and the like. When configured in a computer system, the memory forms a storage medium according to the present invention. The storage medium stores a program for executing the processing described in the above embodiment.

As the storage medium, ROM, R
Semiconductor memory such as AM, optical disk, magneto-optical disk,
A magnetic recording medium or the like may be used, and these may be a CD-ROM,
The present invention may be applied to an FD, a magnetic card, a magnetic tape, a nonvolatile memory card, or the like.

Therefore, this storage medium is used in a system or apparatus other than the system according to the above embodiment,
By reading and executing the program code stored in the storage medium by the system or the computer, the same functions as those of the above embodiment can be realized, and the same effects can be obtained. Can be achieved.

An OS running on a computer
When performing part or all of the processing, or after the program code read from the storage medium is written to a memory provided in an extended function board or an extended function unit connected to the computer, Even when the CPU or the like provided in the extended function board or the extended function unit performs a part or all of the processing based on the instruction of the program code, the same functions as those of the above embodiment can be realized and the same effects can be obtained. Can be obtained, and the object of the present invention can be achieved.

[0042]

As described above, according to the present invention, a system configuration in which the noise reduction means is located downstream of the fader means due to various restrictions such as miniaturization and cost reduction. However, the second control value such as the cyclic coefficient of the noise reduction means is changed in accordance with the first control value such as the mixing ratio of an image of an arbitrary color uniform over the entire screen with respect to the input image of the fade means. This makes it possible to always maintain a good image at the time of fade-in / out without being affected by the noise reduction processing.

In particular, by making the cyclic coefficient close to 0 as the mixing ratio is increased, and approximating the cyclic coefficient to 1 as the mixing ratio is reduced, at the start of fade-in and at the end of fade-out, ,
It is possible to prevent a color other than the desired color from fading on the screen.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an imaging device using an image processing device according to the present invention.

FIG. 2 is a block diagram illustrating a detailed configuration of a video signal processing unit in FIG. 1;

FIG. 3 is a graph showing a relationship between a gain and a fade level and a cyclic coefficient.

FIG. 4 is a waveform diagram showing a video signal at the end of fade-out.

FIG. 5 is a flowchart illustrating an operation of the system control unit in FIG. 1;

FIG. 6 is a block diagram showing a conventional cyclic noise reduction circuit.

FIG. 7 is a waveform chart for explaining the effect of noise reduction at the time of conventional auto-fading.

[Description of Signs] 13 Image sensor 14 Sample and hold unit 12 AGC unit 15 A / D conversion unit 16 Video signal processing unit 18 System control unit 19 Field memory 51 Input terminal 52 Addition circuit 53 Subtraction circuit 54 Multiplication circuit 57 Output terminal K Cyclic coefficient

Claims (9)

[Claims] 1. A fader for fading an input image signal based on a first control value so as to have a predetermined color uniform over the entire screen, and a noise of the faded image signal which is arranged at a subsequent stage of the fader. And a control means for changing the second control value of the noise reduction means according to the first control value of the fade means. An image processing apparatus characterized by the above-mentioned. 2. The apparatus according to claim 1, wherein the first control value is a value for setting a mixing ratio between the input image signal and the image signal of a predetermined color uniform over the entire screen. Image processing device. 3. An image processing apparatus according to claim 1, wherein said noise reduction means is a cyclic noise reduction circuit including a delay circuit, an addition circuit, and a multiplication circuit. 4. The system according to claim 3, wherein the second control value is a value for setting a multiplication coefficient of the multiplication circuit.
The image processing apparatus according to any one of the preceding claims. 5. The noise reduction means is a cyclic noise reduction circuit comprising a delay circuit, an addition circuit, and a multiplication circuit, and the second control value is a value for setting a multiplication coefficient of the multiplication circuit. Wherein the control means comprises:
3. The image processing apparatus according to claim 2, wherein the multiplication coefficient is approximated to 0 as the mixing ratio increases. 6. The noise reduction means is a cyclic noise reduction circuit composed of a delay circuit, an addition circuit, and a multiplication circuit, and the second control value is a value for setting a multiplication coefficient of the multiplication circuit. Wherein the control means comprises:
3. The image processing apparatus according to claim 2, wherein the multiplication coefficient is approximated to 1 as the mixture ratio decreases. 7. The image processing apparatus according to claim 1, wherein the input image signal is a signal captured by an imaging unit. 8. After fading an input image signal based on a first control value so as to have a predetermined color uniform over the entire screen,
An image processing method, comprising: changing the second control value according to the first control value when removing the noise of the faded image signal based on the second control value. 9. A fade process for fading an input image signal based on a first control value so that the input image signal has a uniform color over a whole screen, and a second control value for reducing noise of the image signal obtained by the fade process. A computer-readable storage medium storing a program for executing a noise reduction process for removing based on the first control value and a control process for changing the second control value in accordance with the first control value.