JPH0691880B2 - Color shift prevention device for still images - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color shift prevention device for preventing color shift of a still image generated based on an image pickup signal obtained by using a color sequential illumination system, In particular, the present invention relates to a color misregistration prevention device capable of easily obtaining a still image without color misregistration with a simple configuration.

[Conventional technology]

In recent years, a solid-state image sensor such as CCD is provided at the tip of an endoscope, and the inside of the body cavity is sequentially illuminated with three colors of light of red, green, and blue to color-image the inside of the body cavity, and a color image displayed on a monitor device is displayed. An endoscopic image pickup apparatus has been developed for performing diagnosis based on the above.
Since it is necessary to capture the three-color component images in order to capture one color image by this method, it takes time, and the color shift of the image easily occurs due to the movement of the subject or camera shake.

As means for preventing this color misregistration, in Japanese Patent Application Laid-Open No. 61-71790 filed by the applicant of the present application, a means for detecting color misregistration of an image based on the difference between images taken at different times by the imaging means. It is proposed that the imaging speed of the imaging means is controlled according to the output of the detection means. According to this method, the operation speed of the image pickup unit changes according to the operation speed of the subject, and it is possible to prevent color shift even in the case of a fast moving subject.

[Problems to be Solved by the Invention]

By the way, the color shift prevention means in the endoscope image pickup apparatus proposed in the above publication is designed to prevent color shift in a moving image. When the apparatus is instructed to stand still, the image pickup means is unconditionally operated based on the instruction to obtain a still image. Therefore, if a still instruction is issued when the position of the subject and the tip of the endoscope are relatively moving, color shift occurs in the still image. Since this color shift makes it difficult to see the original subject image, there is a risk that the observer may overlook the lesion or the like.

In order to obtain a still image in which no color shift has occurred, there is a problem that a complicated operation of repeating a still instruction and a still release is required until a still image without a color shift is obtained. Further, a method has been proposed in which, when a color shift occurs in a still image, the color shift is removed by performing image processing correction, but not only is the device large-scaled, but the peripheral portion of the image cannot be corrected. There was a flaw.

The present invention has been made to solve the above-mentioned problems in obtaining a still image in a conventional endoscope image pickup device, and a still image that can easily obtain a still image with no color shift with a simple configuration. It is an object of the present invention to provide a color misregistration prevention device.

[Means and Actions for Solving the Problems]

In order to solve the above problems, the present invention provides a color misregistration prevention device that prevents color misregistration of a still image generated based on an imaging signal obtained by using a color sequential illumination system, based on the imaging signal. The stillness instruction means for instructing stillness of the obtained image, the color misregistration detection means for detecting an amount corresponding to the amount of color misregistration in the image pickup signal, and outputting a signal based on the detected amount, and the stillness instruction means. The image stillness control unit controls the generation of a still image based on the image pickup signal according to a signal output based on a stillness instruction and a signal output from the color shift detection unit.

The subject of the endoscope is mainly the subject, and the subject often moves due to the heartbeat and breathing of the subject's heart, but there is a cycle of both heartbeat and respiration, and the subject either stands still or moves at a certain timing. Will be much less. Therefore, there is almost no color shift in the captured image at this point. This state is detected by the color misregistration detection means to generate an output signal, which is input to the image stillness control means together with the output signal from the image stillness instruction means, and a still image based on the image pickup signal is generated by the control signal from the control means. Control the generation and get a still image.

This makes it possible to easily obtain a still image without color misregistration, eliminating the need to perform a complicated operation of repeatedly instructing and releasing the stillness, and as a result, the examination time is shortened and the pain of the subject is reduced. be able to.

〔Example〕

Examples will be described below. FIG. 1 is a block diagram showing an embodiment of a color misregistration prevention device in an endoscope image pickup device according to the present invention. In the figure, reference numeral 1 denotes an electronic endoscope in which an objective lens 2 is arranged at a tip portion thereof, and an image pickup device 3 composed of a CCD or the like is provided at an image forming position thereof. Reference numeral 4 denotes a light guide made of glass fiber or the like for introducing illumination light into the living body.

Reference numeral 5 is a color filter disc provided with red, green, and blue transmission filters, which is rotatably arranged so as to face one end surface of the light guide 4 and is connected to a motor 6 to be driven. Has become. Reference numeral 7 denotes a lighting lamp including a xenon lamp or the like, which is connected to a lamp driving circuit 8. A condenser lens 9 is arranged at a position where the light emitted from the lamp 7 is condensed on one end surface of the light guide 4 through the color filter disc 5.

An image stationary switch 10 is provided in the operation unit of the electronic endoscope 1 and is connected to an image stationary signal holding circuit 11 composed of a latch or the like. Reference numeral 12 denotes a drive circuit for the image pickup device 3 such as a CCD, or a video circuit configured by a video amplifier or the like, to which the image pickup device 3 is connected. The output end of the video circuit 12 is A / D
It is connected to the converter 13, and the output terminal of the A / D converter 13 is connected to a common terminal of a changeover switch 14 including a semiconductor switch or the like. Each switching terminal of the changeover switch 14 has an image memory (R1) 1 composed of a semiconductor memory or the like.
5, connected to the image memory (G1) 16 and the image memory (B1) 17, respectively. Image memory (R1) 15, Image memory (G
1) 16, output terminals of image memory (B1) 17 are further connected to image memory (R2) 18, image memory (G2) 19, image memory (B2) 20, respectively, and image memory (R2) 18, image The outputs of the memory (G2) 19 and the image memory (B2) 20 are input to the D / A converter (R) 21, the D / A converter (G) 22, and the D / A converter (B) 23, respectively. Are connected as.

The outputs of the D / A converter (R) 21, the D / A converter (G) 22, and the D / A converter (B) 23 are sent to the TV monitor 24 and input to the color shift detection means 25. It is supposed to be done.
The output end of the color misregistration detecting means 25 is connected to one input end of the comparator 26, and the other input end of the comparator 26 is connected to the output end of the threshold setting means 27 composed of a variable resistor or the like. Has been done. Reference numeral 28 denotes an AMD circuit, to which the output of the comparator 26 and the output of the image still signal holding circuit 11 are input. The output of the AND circuit 28 is input to the image stillness control circuit 29, and the image stillness control circuit 29
The output of 29 is the image memory (R2) 18, the image memory (G
2) 19 and image memory (B2) 20 are input to each image stillness control terminal.

Next, the operation of the color misregistration prevention device in the thus configured endoscope imaging device will be described. The white light emitted from the lamp 7 passes through the color filter disc 5 which is rotationally driven by the motor 6 to generate R, G,
It becomes the color sequential light of B, and is incident on one end face of the light guide 4 of the electronic endoscope 1. The color-sequential light incident on the end surface of the light guide 4 is transmitted through the light guide 4, reaches the tip of the electronic endoscope 1, and is emitted from the other end surface of the light guide 4. The emitted color sequential light illuminates a subject such as the stomach wall, and an image of the subject is formed on the image sensor 3 by the objective lens 2. The image sensor 3 is driven by the video circuit 12, and its output is converted into a video signal by the video circuit 12.

The output of the video circuit 12 is digitized by the A / D converter 13, and the digital image data is switched by the changeover switch 14 for each of the R, G, B component image data, while the image memory (R1) 15 It is input and recorded in the memory (G1) 16 and the image memory (B1) 17, respectively. The changeover switch 14 is adapted to be sequentially changed over in synchronization with the rotation of the color filter disc 5 in accordance with the color of the color sequential light.

Next, each image data recorded in the image memory (R1) 15, the image memory (G1) 16, and the image memory (B1) 17 is the image memory (R2) 18, the image memory (G2) 19, the image memory (B2) 20. Transferred at high speed. This transfer operation is performed using the synchronization signal period of the television. The image data transferred to the image memory (R2) 18, the image memory (G2) 19, and the image memory (B2) 20 is read in synchronization with the television sync signal, and the D / A converter (R) 21 , D / A converter (G) 22 and D / A converter (B) 23 convert the analog signal and display it on the TV monitor 24. Normally, the above-mentioned transfer is performed for each frame, so that a moving image is observed on the TV monitor 24.

In the case of observing a still image, the operator depresses the image stillness switch 10 to give a stillness instruction. When the image stillness switch 10 is pressed, an image stillness instruction signal is sent to the image stillness signal holding circuit 11. And image still switch 10
Circuit for holding the image still signal even after the pressing operation of the
At 11, the stationary instruction signal is held.

On the other hand, the D / A converter (R) 21, D / A converter (G) 22, D / A
Each output of the converter (B) 23 is also input to the color shift detecting means 25, and the color shift detecting means 25 detects the color shift amount for each frame. Then, the color shift amount is compared with a value preset by the threshold setting means 27 by the comparator 26, and when the color shift amount becomes equal to or less than the set constant value, the comparator 26 is applied to one input terminal of the AND circuit 28. And output the true value. The output of the image still signal holding circuit 11 is input to the other input terminal of the AND circuit 28, and the AND circuit 28 outputs the image only when the outputs of the comparator 26 and the image still signal holding circuit 11 are both true values. Stationary control circuit
Send control signal to 29.

The image stillness control circuit 29 receives this control signal, and from the image memory (R1) 15, the image memory (G1) 16, the image memory (B1) 17, the image memory (R2) 18, the image memory (G2) at an appropriate timing. 19, Stop the transfer of image data to the image memory (B2) 20. As a result, a still image is recorded in the image memory (R2) 18, the image memory (G2) 19, and the image memory (B2) 20, and the still image is observed on the TV monitor 24.

At this time, the still image to be observed is a still image in a state in which the color misregistration is below a certain value, and is an easy-to-see image with almost no color misregistration.

To cancel the still image, the image still signal holding circuit 11 may be reset by a release switch (not shown), or the image still signal holding circuit 11 may be toggled by the image still switch 10.

The subject of the endoscope is mainly a living body, and as described above, the subject is often moving due to the subject's heart, heartbeat, or respiration. Is stationary or has very little movement. Therefore, as in the above-described embodiment, the color shift amount is monitored by the color shift detection means, and the state where the subject is stationary or the amount of color shift is extremely small and the color shift amount is below a certain value is detected. By making the image stand still by, a still image in which the influence of the color shift is removed can be obtained in practical use.

FIG. 2 is a block diagram showing a concrete configuration example of the color misregistration detecting means 25 in the embodiment shown in FIG.

When the relationship between the green (G) component and the blue (B) component of a normal endoscopic image is examined, it is as shown in FIG. From this figure, it is understood that the G component and the B component of each pixel forming the endoscopic image are scattered within a limited range centering on the function of the straight line. The variation varies depending on the subject, but many pixels exist near the center straight line. Therefore, it can be considered that the ratio of the G component to the B component of many pixels of a normal endoscopic image is almost constant.

Depending on the subject, the G component and the B component may be distributed in a polygonal line shape as shown in FIG. 4, but it is a simple polygonal line shape, and if the range of pixel data size is considered, G It can be said that the ratio of the component to the B component is almost constant.

The configuration example shown in FIG. 2 is adapted to detect a color shift from green and blue image signals based on the above fact. That is, the output of the D / A converter (G) 22 is input to one input terminal of the subtractor 30 and the integrator (1) 31, while the output of the D / A converter ( B) The output of 23 is
The signal is input to the other input terminal of the subtractor 30 via the variable gain amplifier 32 and also to the integrator (2) 33. Then, the integrator (1) 31 and the integrator (2) 33
Each output of is input to the gain control circuit 34 that controls the gain of the variable gain amplifier 32, and the output end of the gain control circuit 34 is connected to the gain control input end of the variable gain amplifier 32.

The output terminal of the subtractor 30 is connected to a window comparator 35, and the window comparator 35 is connected to a window setting device 37 for setting a window. The output terminal of the window comparator 35 is connected to the integrator (3) 36, and the output of the integrator (3) 36 is input to the comparator 26 as the output of the color misregistration detecting means 25. There is.

Next, the operation of the color misregistration detecting means configured as described above will be described. First, the output of the D / A converter (G) 22 is integrated by the integrator (1) 31 for one field or one frame period. On the other hand, the output of the D / A converter (B) 23 is amplified by the variable gain amplifier 32 and then integrated by the integrator (2) 33 for one field or one frame period. The outputs of the integrator (1) 31 and the integrator (2) 33 are compared by the gain control circuit 34, and the output of the gain control circuit 34 is obtained by the integrator (1) 31 and the integrator (2) 33. The gain of the variable gain amplifier 32 is controlled so that the outputs become equal.

As a result, in a normal endoscopic image, even though the G component is higher in level than the B component, the G component and B component of the image signal input to the subtractor 30 are within the field or frame period. And the integrated value becomes equal. The subtractor 30 outputs the difference between the output of the D / A converter (G) 22 and the output of the variable gain amplifier 32. If no color shift occurs, the pixel that makes the output of the subtractor 30 almost 0, That is, there are many pixels in which the values of the G component and the B component multiplied by the gain of the variable gain amplifier 32 are equal. On the contrary, when the color shift occurs, the number of pixels for which the output of the subtractor 30 is set to almost 0 becomes smaller than the above.

The window comparator 35 extracts only the pixel signals for which the output of the subtractor 30 is close to 0, and the integrator (3) 36 integrates the entire screen to obtain the color shift amount of the entire screen. Therefore, the output of the integrator (3) 36 indicates the amount of color shift, and by inputting this to the comparator 26, the control signal of the image stillness control circuit 29 can be obtained.

FIG. 5 is a block diagram showing another configuration example of the color misregistration detection means. The output of the D / A converter (G) 22 is input to one input terminal of the divider 38, while the D / A
The output of the converter (B) 23 is configured to be input to the other input terminal of the divider 38 via a level substitution circuit 39 that outputs a value other than 0 when the input is 0. There is. The output terminal of the divider 38 is connected to a high-pass filter 40 that blocks the DC component and passes only the AC component. The output of the high-pass filter 40 is input to an absolute value circuit 41 composed of a rectifying circuit or the like, and the output of the absolute value circuit 41 is an integrator 42 that performs an integrating operation only in one field or one frame period.
Entered in. The output of the integrator 42 is input to the comparator as the output of the color shift detecting means.

Next, the operation of the color misregistration detecting means configured as described above will be described. The level replacing circuit 39 replaces the output of the D / A converter (B) 23 with a value near 1 only when the value is near 0. This is to prevent the denominator of the divider 38 from being near 0. In the divider 38, (G component) /
Calculate (B component). As is apparent from FIGS. 3 and 4 described above, the value of (G component) / (B component), that is, the slope of the function of the straight line in FIG. 3, is as shown in FIG. There is a variation around a fixed value, and the degree of this variation indicates a color misregistration state.

FIG. 7 shows the temporal change of the output of the divider 38 within one field period. If the color shift does not occur, the variation is small, and if the color shift occurs, the variation does not occur. Is increasing. This variation is extracted in the form of an AC component by the high-pass filter 40, and the absolute value circuit 41 and the integrator 42 integrate the amount over the entire screen. The output of the integrator 42 indicates the amount of color misregistration and is input to the comparator 26 to obtain the image stillness control signal.

FIG. 8 is a block diagram showing another embodiment of the present invention, in which the same or equivalent components as those of the embodiment shown in FIG. 1 are designated by the same reference numerals. In the figure, 30 is a general fiberscope, which includes an objective lens 2 and a light guide.
4, an image guide 31, an eyepiece lens 32, and the like. Reference numeral 33 is a color-sequential TV camera head detachably attached to the eyepiece of the fiberscope 30, and the imaging lens 3
4, the image pickup device 3, the dark box 35, etc., and the image pickup device 3 is arranged at the image forming position of the end face of the image guide 31 by the image forming lens 34. Further, the image pickup device 3 is connected to the video circuit 12 via a connection cord 36.

Similar to the embodiment shown in FIG. 1, the light from the lamp 7 driven by the lamp driving circuit 8 is generated by the condenser lens 9 and the motor 6.
The light is focused on one end surface of the light guide 4 via the color filter disk 5 which is rotationally driven by.
10 is an image static switch composed of a foot switch,
The image still signal holding circuit 11 including a latch and the like and the timer 37 are connected.

The output of the video circuit 12 is A / D converted by an A / D converter 13.
The data is input and recorded in the image memory (R1) 15, the image memory (G1) 16, and the image memory (B1) 17 via the changeover switch 14, respectively. The output terminals of the image memory (R1) 15, image memory (G1) 16, and image memory (B1) 17 are
Image memory (R2) 18, image memory (G2) 19,
The outputs of the image memory (R2) 18, the image memory (G2) 19, and the image memory (B2) 20 are respectively connected to the image memory (B2) 20, and the outputs of the D / A converter (R) 21 and D / A, respectively. Converter (G) 2
The data is input to the 2, D / A converter (B) 23 and also input to the color misregistration detecting means 25 including a digital correlator.

The outputs of the D / A converters 21, 22, 23 are input to the TV monitor 24, the output of the color misregistration detecting means 25 is input to one input terminal of the comparator 26, and the other input terminal of the comparator 26. A threshold setting means 27 is connected to the. The output of the comparator 26 and the output of the image still signal holding circuit 11 are input to the AND circuit 28, and the output of the AND circuit 28 and the timer 3 are input.
The output of 7 is input to the OR circuit 38. The output of the OR circuit 38 is input to the image stillness control circuit 29, and the output terminal of the image stillness control circuit 29 has the image memory (R2) 18, the image memory (G2) 19, and the like as in the above-described embodiment. It is connected to each image stillness control terminal of the image memory (B2) 20.

The operation of this embodiment is almost the same as that of the embodiment shown in FIG. 1, but the different points are as follows. The subject image is the objective lens 2, image guide 31, eyepiece lens 32,
An image is formed on the image sensor 3 via the image forming lens 34, and the output signal thereof is input to the image circuit 12. Since the image stillness switch 10 is composed of a foot switch, the image stillness is instructed by operating this switch with a foot. The color misregistration detection means 25 includes an image memory (R2) 18, an image memory (G2
2) Since it is connected to the image memory 19 and the image memory (B2) 20, the digital image data is directly input to the color shift detecting means 25. Therefore, in the color shift detecting means 25, the second
The same process as the process in the color misregistration detection means shown in FIG. 5 or FIG. 5 is digitally performed.

The timer 37 is for coping with the case where the color shift of the captured image does not decrease and the signal is not output from the comparator 26 even after a lapse of a certain time after the image freeze switch 10 is operated to issue a freeze instruction. A signal is output from the timer 37 after a lapse of a certain time, and the image stillness control circuit 29 is forcibly driven via the OR circuit 38 to freeze the image, so that a still image is obtained.

In the color shift detection means shown in FIGS. 2 and 5,
The integrator (1) 31, the integrator (2) 33, the integrator (3) 36, the integrator 42, etc. are shown as integrated over the entire screen, but in an ordinary electronic endoscope, FIG. As indicated by the slanted lines in FIG. 3, the endoscopic image portion is a part. Therefore, when performing various integrations with each of the integrators, it is necessary to exclude pixels other than the endoscopic image portion. To do so, generate a mask signal indicating the endoscopic image part,
The function of the integrator may be controlled thereby.

Further, the color misregistration detection may not be performed for the entire endoscopic image, but may be performed, for example, only in the central portion of the image or only on a specific scanning line. In this case, an appropriate mask signal may be generated to detect the color misregistration only in a specific area.

Further, in the color shift detecting means shown in FIGS. 2 and 5, the color shift is detected using the green (G) component and the blue (B) component, but the invention is not limited to this. The color shift may be detected using another color component image. Furthermore, the image may be differentiated once, and the color misregistration may be detected by using the color component images of the two colors in which the contour is emphasized or extracted. In short, the color shift may be detected by some method.

In general, a video signal obtained from an electronic endoscope apparatus is gamma-corrected. However, in the present invention, before being input to the color misregistration detection means, it is made linear through a circuit having an inverse gamma characteristic before processing. You may comprise.

Further, the color misregistration prevention device according to the present invention may be incorporated in the electronic endoscope device, or may be configured separately from the electronic endoscope device and utilize a video signal obtained from the electronic endoscope device. Color misregistration may be detected and the image stationary operation of the electronic endoscope apparatus may be externally controlled.

〔The invention's effect〕

As described above based on the embodiment, according to the present invention, the color misregistration detection unit detects a state in which no color misregistration occurs, and controls the image stillness control unit by the detection signal and the image stillness instruction signal. Since the image is made to stand still, a still image without color shift can be easily obtained. Therefore, it is not necessary to perform a complicated operation of repeating the stationary instruction and the stationary cancellation, and accordingly, the examination time can be shortened and the pain of the examinee can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a color misregistration prevention device in an endoscope imaging apparatus according to the present invention, and FIG.
FIG. 3 is a block diagram showing an example of the configuration of the color misregistration detection means in the figure, FIGS. 3 and 4 are diagrams showing the distribution state of the green component and the blue component of each pixel forming the endoscopic image, and FIG. , A block diagram showing another configuration example of the color misregistration detection means, and FIG.
(Green component) / (Blue component) of each pixel that constitutes the endoscopic image
FIG. 7 is a conceptual diagram showing the distribution state of the values of FIG. 7, FIG. 7 is a diagram showing the temporal change of the output of the divider in FIG. 5 within one field period, and FIG. 8 is another embodiment of the present invention. FIG. 9 is a block diagram showing the configuration of the endoscope image section of the electronic endoscope. In the figure, 1 is an electronic endoscope, 3 is an image sensor, 4 is a light guide, 30 is a fiberscope, and 31 is an image guide.

Claims (1)

[Claims] 1. A color misregistration prevention apparatus for preventing color misregistration of a still image generated based on an image pickup signal obtained by using a color-sequential illumination method, and instructing stillness of an image obtained based on the image pickup signal. And a color shift detection means for detecting an amount corresponding to the color shift amount in the image pickup signal and outputting a signal based on the detected amount, and a color shift detection means for outputting a signal based on the static instruction by the static direction indicating means. A color misregistration prevention device for controlling the generation of a still image based on the image pickup signal according to a signal output from the color misregistration detection device and a signal output from the color misregistration detection device.