JPH06327621A - Chromatic aberration correcting equipment - Google Patents

Abstract

PURPOSE:To make undistinguishable the border between a chromatic aberration- corrected portion and a non-corrected portion, to correct the chromatic aberration according to an amount of chromatic aberration without making a circuit large and in a natural color tone. CONSTITUTION:Characteristics of a subject shown in a color distribution is obtained by a chromatic aberration correcting portion 1 only from an image without chromatic aberration, and by using the obtained results the degree of chromatic aberration per picture element is detected. Since a composing portion 3 composes an original image and corrected data made in a corrected image drawing up portion 2 according to the degree of the chromatic aberration per picture element, it is possible to compose without any harm to the information of the original image, and more natural corrections are enabled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color misregistration correction device for correcting color misregistration associated with a frame sequential imaging system.

[0002]

2. Description of the Related Art A frame sequential electronic endoscope captures R, G, B three primary color images one by one every 1/60 seconds. Therefore, when a moving object is imaged, R,
Since the three primary colors G and B cannot be captured, the colors of the object are separated. This separated state is called color shift.

The method for correcting color shift disclosed in Japanese Patent Publication No. 52-9095 discloses an original signal and a three-field delay signal, that is, each primary color signal of the original signal and a primary color signal of the same color three fields before. To compare. Then, in the comparison result, when the difference signal exceeds a certain value, it is determined that the position is the moving position of the image in which color breakup occurs. At this time, a motion position determination signal (pulse) is issued to perform gain control and band control of the carrier signal to completely remove or suppress the carrier color signal at the motion position of the image to reduce color breakup of the three primary colors. Is. Alternatively, when there is a large amount of movement, it is a switching method of two or more switching to switch to a narrow band pass filter. A field-sequential color television imaging system that reduces such color breakup is disclosed.

[0004]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 52-9095
In the method of switching the pass band with a different filter in the publication, the boundary between the color misregistration correction unit and the non-correction unit becomes conspicuous.
Further, in the method of switching a plurality of filters in order to cope with a large movement, a large number of filter circuits are required and a large mounting area is required.

Further, in the method of changing the band region of the color signal according to the degree of color misregistration, if the band limitation is increased, the color becomes weaker and the color misregistration becomes less noticeable. Become.

The present invention has been made in view of the above circumstances, and makes the boundary between the color misregistration correction section and the non-correction section inconspicuous,
An object of the present invention is to provide a color misregistration correction device that corrects with a natural color tone by performing correction according to the amount of color misregistration without increasing the size of the circuit.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a color shift amount or a factor associated with the color shift is determined in pixel units or in predetermined book units from a color image signal obtained by an image pickup unit that images a subject in a frame sequential manner. A color shift detection means for detecting the color shift of the color image signal, a means for creating color shift correction data for correcting the color shift of the color image signal in pixel units or in predetermined block units, a color image signal of the image pickup means, and The synthesizing unit controls the synthesizing ratio with the color shift correction data of the creating unit in pixel units or in predetermined block units based on the degree of color shift detected by the color shift detecting unit.

[0008]

In contrast to the normal (subject) image, the endoscopic image has a feature that the colors forming the image are considerably deviated because the subject is, for example, an image in a body cavity. On the other hand, the color of the color-shifted portion lacks any one of R, G, and B in the color space and the color plane. Is different.

Therefore, the color misregistration detecting means detects the amount of color misregistration or a factor associated with the color misregistration as a degree of color misregistration in pixel units or in predetermined book units from the color image signal of the image pickup means.

In the synthesizing means, the color image signal which is the original image and the color misregistration correction data are synthesized in pixel units or in predetermined block units according to the degree of color misregistration. This enables more natural correction.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. The present invention will be described below by taking a color misregistration correction device as an example.

FIG. 1 shows the basic structure of a color misregistration correction device. The color misregistration correction device includes a color misregistration detection unit 1 that inputs an original image obtained by an imaging unit (not shown) and detects color misregistration pixels, and a correction image creation unit 2 that creates a correction image from the original image. , A combining unit 3 for combining the original image and the corrected image by changing the combining ratio according to the degree of color misregistration of the color misregistration detection unit
And have. The imaging means is adapted to perform frame sequential imaging based on frame sequential illumination light.

FIG. 2 shows the configuration of the color shift detecting section 1. The color misregistration detection unit 1 is based on a change point detection circuit 10 that detects a pixel having a color change in each of the R, G, and B images picked up by the image pickup unit, and a result of the change point detection circuit 10. And a first histogram creating circuit 11 for creating a color plane histogram for one field.

The color misregistration detection section 1 has a CPU block 12 and a color misregistration determination circuit 13. The C
The PU block 12 is for normalizing the histogram data from the histogram creating circuit 11. The color misregistration determination circuit 13 retrieves the pixel density normalized by the CPU block 12 from the color coordinates of each image, then converts the pixel density into a color misregistration degree, and outputs the result of the change point detection circuit 10. The degree of color misregistration is output based on

FIG. 5 shows the configuration of the corrected image creating section 2.

The corrected image creating section 2 is composed of a second histogram creating circuit 40, a CPU block 41, a color converting circuit 42, and an arithmetic circuit 43.

The second histogram creating circuit 40 is
A color space histogram for one field is created based on the result of the change point detection circuit 10. CPU
The block 41 searches for a representative color from the color space histogram. The color conversion circuit 42 applies the CP to the original image.
The color is converted into the color retrieved by the U block 41. The arithmetic circuit 43 creates a corrected image from the color obtained by the color conversion circuit 42 and the luminance signal of the original image.

FIG. 6 shows the structure of the synthesizing unit 3. The synthesizing unit 3 includes a coefficient calculating circuit 30 for calculating a coefficient to be given to two multipliers inside the spatial filter LSI 31 and a spatial filter LSI 31 from the color shift degree output from the color shift detecting unit 1. Have The spatial filter LSI 31 has the first arithmetic operation performed by the coefficient arithmetic circuit 30.
It has a multiplier 31a that multiplies the coefficient and the original image, a multiplier 31b that multiplies the second coefficient and the corrected image, and an adder 31c that adds the two multiplication results.

FIG. 3 and FIG. 4 show the internal construction of the blocks constituting the color shift detecting section 1 shown in FIG.

FIG. 3 shows the configuration of the change point detection circuit 10. The change point detection circuit 10 includes a matrix circuit 14 for calculating two color signals Cr and Cb from R, G and B signals.
And 4 field delay memories 15a and 15b for delaying the calculated Cr and Cb signals by 4 fields, and a difference between the 4 field Cr and Cb signals delayed by 4 fields and the Cr and Cb signals calculated by the matrix circuit 14. Difference detection circuits 16a and 16b for detecting and difference detection circuit 16
It is composed of a logical sum 17 for obtaining the logical sum of the detection results of a and 16b.

FIG. 4 shows the histogram creating circuit 11, CP.
3 is a configuration diagram of a U block 12 and a color shift determination circuit 13. FIG.

The histogram creating circuit 11 selects the Cr and Cb signals calculated by the matrix circuit 14 and the color signal data read from the last image field memories 19a and 19b.
8b, last image field memories 19a and 19b for storing one field of color signals selected by the selectors 18a and 18b, and color signals from one field of color signals stored in the last image field memories 19a and 19b. It is composed of a histogram LSI 20 for creating a distribution.

The CPU block 12 normalizes the histogram data created by the histogram LSI 20.

The color shift judging circuit 13 is a memory 2 for recording the color plane data normalized by the CPU block 12.
2, a low-pass filter (hereinafter LPF) 23 for smoothing the color plane recorded in the memory 22, and a coordinate-pixel density conversion memory 2 for storing the color signal smoothed by the LPF 23.
4 and a field memory 25 for delaying the Cr and Cb signals calculated by the matrix circuit 14 for one field time.
a, 25b, a cancel curve memory 26 for obtaining the pixel density in the coordinate-to-pixel density conversion memory 24 from the color signals delayed by the field memories 25a, 25b, and searching the degree of color misregistration from the pixel density, and change point detection. A field memory 27 for delaying the output of the circuit 10 by one field time,
And a selector 28 for selecting the degree of color misregistration at the color change point portion.

FIG. 5 shows the configuration of the corrected image creating section 2, which comprises a histogram creating circuit 40, a CPU block 41, a color converting circuit 42, and an arithmetic circuit 43.

The histogram generating circuit 40 is provided with R,
A selector 44 for selecting the G and B signals and the signal read from the last image field memory 41, a last image field memory 41 for storing the signal selected by the selector 44 for one field, and a last image field memory Histogram LSI 46 that creates a color distribution from the signal for one field stored in 41
It is composed of.

The CPU block 41 selects a representative color from the histogram data created by the histogram LSI 46.

The color conversion circuit 42 comprises a CPU block 4
Look-up tables 48a to 48f (typically 48) for storing the representative colors selected in 1 and a field memory 49a for delaying the R, G, B signals by one field time.
49b and 49c, multipliers 50a to 50f for weighting the converted colors, and adders 51a and 51b for adding the color signals weighted by the multipliers 50a to 50f.

The arithmetic circuit 43 is the matrix circuit 14
A field memory 52 for delaying the luminance signal Y generated in step 1 for one field time, and a matrix circuit 53 for generating an image from the color signals generated by the adders 51a and 51b and the luminance signal Y delayed by the field memory 52. Has been done.

The synthesizing section 3 shown in FIG.
And a spatial filter LSI 31. The coefficient calculator 30 includes a gradation converter 32 and a subtractor 33 for calculating coefficients in the two multipliers 31a and 31b based on the color shift degree output from the color shift detector 1.

A multiplier 31a for multiplying the first coefficient calculated by the coefficient calculator 30 and the original image, and a multiplier 31a for multiplying the second coefficient calculated by the coefficient calculator 30 and the corrected image. 31b and 2 of the multiplier 31a and the multiplier 31b
It is composed of an adder 31c for adding two multiplication results. Since three R, G, and B images are combined, three spatial filter LSIs 31 are required.

In the above structure, the change point detection circuit 10 of the color shift detection unit 1 compares the color signals having the time difference of 4 fields, so that the digital R, G, B signals are arranged in the matrix circuit 14.
Are converted into color signals Cr and Cb. The color signal is usually R-
Y and B-Y are used, but when R, G, and B each have 8 bits, the calculation results in 9 bits. Cr and Cb are signals in which the width is set to 8 bits.

The two signals Cr and Cb are input to the 4-field delay memories 15a and 15b and delayed by 4 fields. The difference detection circuits 16a and 16b perform subtraction between the color signal output from the matrix circuit 14 and the color signal delayed by the 4-field delay memories 19a and 19b. If the result is positive, the positive comparison is performed, and if the result is negative, the negative comparison is performed. By comparing with each predetermined value,
Determine the color change. Since the color signal is composed of two types, Cr and Cb, if any one of them determines that they do not match, it means that the color has changed. Therefore, the outputs of the two difference detection circuits 16a and 16b are output through the logical sum 17.

The histogram circuit 11 creates a color plane histogram from pixel data of an image for one field without color shift. For this reason, the field memories 19a and 1b, which are input to the selectors 18a and 18b for selecting only the pixels having no color change and store the image for one field, are stored.
It is stored in 9b. Histogram LSI20 with Cr, C
Create a color plane histogram for b.

Incidentally, the field memories 19a, 1 which store the pixel data of the image for one field without color shift.
9b has a FIFO structure and therefore has no contents after being read out. Therefore, it is fed back to the selectors 18a and 18b to accumulate and store pixels having no color shift.

In the CPU block 12, the color distribution state of the color plane of the image for one field is represented by a histogram LSI.
It is read from 20 as 16-bit data. When the read value is larger than the predetermined value, an upper limit process for setting the predetermined value is performed, the lower bits are deleted, and 8-bit data is written to the memory.

The color shift judging section 13 smoothes the color plane of the histogram data, and the smoothing section of the color plane discriminates the difference between the colors by the naked eye because the adjacent coordinates in the color plane are similar to each other. Hard to do. Further, in order to reduce variations in pixel density between adjacent coordinates of the histogram data, the color plane is expanded and the color distribution is smoothed through the LPF.
Therefore, the memory 22 and the LPF unit 23 regard the 16 * 16 color plane data written in the memory 22 as a 64 * 64 color plane and read it out, and apply a spatial filter to the color plane to perform coordinate-to-pixel density conversion. Write to the memory 24.

Since the color signals Cr and Cb are histograms for one field and are calculated by the CPU, processing time for one field is required.
One field is delayed by 5a and 25b, input to the address of the coordinate / pixel density conversion memory 24, and output as 8-bit pixel density data. The cancel curve memory 26 records a color shift degree according to the pixel density, inputs pixel density data to an address, and outputs the color shift degree.

The degree of color misregistration is recorded in gradations from "0" to "255", and "0" means no color misregistration. The selector 28 is for outputting the degree of color misregistration in the pixel determined to have a change from the output of the change inspection output circuit 10. At this time, the output of the selector 28 for the pixels determined to have no change is "0", that is, there is no color shift. The change point data is passed through the field memory 27 and input to the selector 28 for the same reason as the color signal.

With the above configuration and operation, it is possible to detect only the color misregistration portion by using the pixel distribution of the color plane histogram among the pixels having the color change.

The corrected image creating section 2 comprises a histogram creating circuit 40, a CPU block 41, a color converting circuit 42, and an arithmetic circuit 43.

Since the histogram circuit 40 creates a histogram of the color space from the pixel data of the image for one field having no color shift, the RGB signal is input to the selector 44 for selecting the pixel having no color change. It is stored in the last image field memory 45 which stores images for fields. The histogram LSI 46 is
A color space histogram is created by using the upper 3 bits of each of 8 bits of G and B.

The field memory 45 storing the pixel data of the image for one field without color shift is F
Since the contents are lost after being read because of the IFO (Forth-In-First-Out) structure, the contents are fed back to the selector 44, and the pixels having no color shift immediately before the color shift occurs are stored.

In the CPU block 41, R, G, B = 8 × 8 in step S1 according to the flowchart of FIG.
In selecting a representative color from the × 8 color space, a method of selecting the other two colors based on one color is adopted. For example, when R is used as a reference, G and B are selected from the color space to form one set of R (original image color), G '(estimated color), and B' (estimated color). The method is to change R from "10H" to R =
Eight G-B planes are prepared for eight divisions up to F0H, and in step S2, the highest density portion on each plane is selected, and the G and B coordinate values of that portion are recorded as estimated colors. For example, in the G-B plane when R = F0H, if the highest density portion is the thick frame portion in the figure, the coordinate values of G and B are "D0H" and "B0," respectively.
Since it is H ″, this is an estimated color. These are also searched for on the other 7 GB planes, and 8 points of data for estimating G from R and 8 for estimating B from R are obtained. The data of points are obtained, and the RB plane and the R-G plane are also searched to create Chart 9.

However, what is obtained here is the R, G, B data for both input and output, and not the color data that is finally needed. Therefore, in step S3, a matrix operation is performed to convert R to Cr, Cb. 8 points each, G to C
Correspondences from r, Cb, B to Cr, Cb are created as shown in FIG.

Next, in steps S4 and S5, interpolation processing is performed from the data of 8 points to 256 points and the result is written in the lookup tables 48a to 48f.

In the color conversion circuit 42, the multiplier 50a multiplies the three sets of color data of the look-up tables 48a to 48f into which the representative colors selected by the CPU block 41 are written.
.About.50f, and weighted and added for each color data to obtain color signals Cr and Cb. In this embodiment, the multiplier 50
a and 50b are "* 0.30", multipliers 50c and 50d are "* 0.59", and multipliers 50e and 50f are "* 0.1".
The weight is 1 ".

Next, the operation circuit 43 performs a matrix operation on the corrected color signal Cr, Cb created by the color conversion circuit 42 and the original image luminance signal Y created by the matrix circuit 14 to perform R operation. , G, B corrected images are obtained. The luminance signal Y is delayed by the field memory 52 and input to the matrix calculator 53 because one field time is required to create the color distribution.

The synthesizing section 3 comprises a coefficient computing circuit 30 and a synthesizing computing circuit 31. The coefficient calculation circuit 30 includes a gradation conversion circuit 32 and a subtractor 33. The gradation conversion circuit 3
Reference numeral 2 is a circuit for eliminating the need for division from the operation output of the synthesis operation circuit 31. The gradation of the color misregistration degree, which is the output of the color misregistration detection unit 1, is converted to 2 (nth power +1) using a multiplier. Convert.
The gradation conversion circuit 32 is, for example, (2 to the 7th power + 1) =
Convert to 129 gradations. The gradation-shifted color shift degree is output to the multiplier 31a as the first coefficient, and the first coefficient is output to the subtractor 33 to obtain the second coefficient. The second coefficient is (128
-First coefficient) and output to the multiplier 31b.

The synthesis operation circuit 31 includes a gradation conversion circuit 3
A multiplier 31a that multiplies the first coefficient calculated in 2 with the original image, a multiplier 31b that multiplies the second coefficient calculated in the subtractor 33 with the corrected image, and a multiplier 31a.
And an adder 31 for adding the two multiplication results of the multiplier 31b
It is composed of c and.

The results calculated by the two multipliers 31a and 31b are added by the adder 31c, the lower 7 bits are removed, and the result is output. Further, if the output of the color misregistration detection unit 1 is output with the gradation of 2 (nth power +1), the gradation conversion circuit 32 becomes unnecessary.

Usually, in order to calculate the composite output Y of the image A and the image B, the formula Y = A × K + B × (1−K) (1) is used. Is in the range 0 ≦
Since K ≦ 1, the arithmetic operation circuit becomes enormous when the decimal operation is performed, and the component cost and the mounting area become large, which is not good.

Here, if the range of the coefficient K is an integer from 00H to 80H, which is 2 to the 7th power + 1, then the equation (1) is expressed as Y = {A × K + B × (80H−K)} / 80H.・ It can be replaced with (2) and 129 kinds of synthesis can be performed.

Here, K is assigned to the first coefficient and the value (80H-K) is assigned to the second coefficient.

Originally, it is clear from the equation (2) that division by 80H must be performed, but since the divisor is 2 to the 7th power, the same effect as division can be obtained by omitting the lower 7 lines from the calculation result. Therefore, in this embodiment, the number of parts can be further reduced.

In the present embodiment, the color shift detection unit 1 creates a color distribution only from an image having no color shift and obtains the pixel density thereof to grasp the color characteristics of the target subject. Here, unlike an ordinary image, an endoscopic image is an image in a body cavity, and thus the colors forming the image are considerably deviated, so that the pixel density of a part of the color space and the color plane becomes high. On the other hand, the color of the color-shifted portion shows a portion different from the color distribution in the subject, for example, the body cavity, because the color space and the color plane, for example, R, G, or B are missing. .
Therefore, if the pixel density corresponding to the color coordinate of each pixel is calculated, the color in the body cavity and the color shift can be distinguished, and the degree of the color shift can be detected from the pixel density.

Further, since the color misregistration image creating unit 2 calculates a color having a high pixel density in the color space, it is possible to replace the color misregistration image with a color close to that in the body cavity.

Further, since the synthesizing unit 3 synthesizes the color image signal which is the original image and the color shift correction data for each pixel or for each predetermined block according to the degree of color shift, the information of the original image is lost. It can be combined without any need for more natural correction.

In the present embodiment, since a large number of filters are not required and synthesis is performed according to the degree of color misregistration, the boundary between the color misregistration correction unit and the non-correction unit can be made conspicuous without increasing the circuit scale. It can be corrected with a natural color tone.

In the present embodiment, the detection and the processing are performed in pixel units, but the same processing can be performed in a predetermined block unit composed of a plurality of pixels.

[0061]

As described above, according to the present invention, since composition is performed according to the degree of color misregistration, the circuit scale is not increased and the boundary between the color misregistration correction unit and the non-correction unit is not conspicuous. The effect is that it is possible to correct with a natural color tone.

[Brief description of drawings]

FIG. 1 is a block diagram showing a basic configuration of a color misregistration correction device.

FIG. 2 is a block diagram showing a configuration of a color shift detection unit.

FIG. 3 is an internal configuration diagram of a configuration block of a color misregistration detection unit shown in FIG.

FIG. 4 is an internal configuration diagram of a configuration block of the color misregistration detection unit shown in FIG.

FIG. 5 is a block diagram showing a configuration of a corrected image creating unit.

FIG. 6 is a block diagram showing a configuration of a combining unit.

FIG. 7 is a flowchart for selecting a representative color from a color space.

FIG. 8 is an explanatory diagram of selecting a representative color from a color space.

FIG. 9 is a diagram showing RGB color planes and estimated colors.

FIG. 10 is a chart regarding each color plane of RGB, each color plane of Cr and Cb, and an estimated color.

[Explanation of symbols]

 1 ... Color shift detection section 2 ... Corrected image creation section 3 ... Compositing section

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[Procedure amendment]

[Submission date] July 2, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

SUMMARY OF THE INVENTION According to the present invention, a color shift amount is determined on a pixel-by-pixel basis or a predetermined block-by-block basis from a color image signal obtained by an image pickup means for picking up a subject in a frame sequential manner. A color shift detection means for detecting the color shift of the color image signal, a means for creating color shift correction data for correcting the color shift of the color image signal in pixel units or in predetermined block units, a color image signal of the image pickup means, and The synthesizing unit controls the synthesizing ratio with the color shift correction data of the creating unit in pixel units or in predetermined block units based on the degree of color shift detected by the color shift detecting unit.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction content]

Therefore, the color misregistration detection means detects the amount of color misregistration or a factor associated with the color misregistration as the degree of color misregistration in pixel units or in predetermined block units from the color image signal of the image pickup means.

Claims (1)

[Claims] 1. A color misregistration detection for detecting, as a degree of color misregistration, a color misregistration amount or a factor associated with the color misregistration on a pixel-by-pixel basis or on a predetermined book-by-book basis basis from a color image signal obtained by an imaging means for imaging a subject in a frame sequential manner. Means, means for creating color misregistration correction data for correcting the color misregistration of the color image signal in pixel units or in units of predetermined blocks, color image signals of the imaging means, and color misregistration correction data of the creating means And a synthesizing unit that controls a synthesizing ratio of the ## EQU1 ## in pixel units or in predetermined block units based on the degree of color lag detected by the color lag detecting unit.