JPH04227226A - Color convergense error preventing device for endoscope image pick-up device - Google Patents

Abstract

PURPOSE:To easily obtain a standstill image free from color convergence error with a simple constitution by detecting the state where color divergence is not generated on the basis of the correlation between the images in each color, and controlling an image standstill means from the detection signal and an image standstill instruction signal. CONSTITUTION:A color convergence error detecting means 25 detects the color convergence error quantity by forming the correlation between the colors in each frame. The color convergence error quantity is compared with a set value by a comparator 26, and when the quantity becomes less than a set value or less, the comparator 26 outputs a true value for one input edge of an AND circuit 28. The output of an image standstill signal holding circuit 11 is inputted into the other input terminal of the AND circuit 28, which sends out a control signal into an image standstill control circuit 29 only in the case where both the outputs are true values. The control circuit 29 receives the control signal, and the transfer of the image data from image memories 15, 16 and 17 to the image memories 18, 19 and 20 is suspended, and the image memories 18, 19 and 20 are put into the state where the standstill image is recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for preventing color shift of still images in an endoscope imaging device using a color sequential illumination method.

0002

[Prior Art] In recent years, a solid-state image sensor such as a CCD is installed at the tip of an endoscope, and the interior of the body cavity is sequentially illuminated with three-color light of red, green, and blue to take a color image of the interior of the body cavity, which is then displayed on a monitor device. Endoscopic imaging devices have been developed that perform diagnosis based on displayed color images. To capture one color image using this method, it is necessary to capture component images of three colors, which takes time and tends to cause color shift in the image due to subject movement or camera shake.

As a means to prevent this color shift, Japanese Patent Application Laid-Open No. 71790/1989 filed by the present applicant proposes a method to prevent color shift in images based on the difference between images taken at different times by an imaging means. A device has been proposed that includes a detection device and controls the imaging speed of the imaging device in accordance with the output of the detection device. According to this method, the operating speed of the imaging means changes depending on the operating speed of the subject,
It is possible to prevent color shift from occurring even in the case of a fast-moving subject.

0004

[Problems to be Solved by the Invention] By the way, the color misregistration prevention means in the endoscope imaging device proposed in the above publication is designed to prevent color misregistration in moving images. In this case, conventionally, when an endoscope imaging device is instructed to stop, the imaging means is unconditionally stopped based on the instruction to obtain a still image. Therefore, if a still instruction is given at a time when the positions of the subject and the endoscope tip are moving relative to each other, color shift will occur in the still image. This color shift makes it difficult to see the original image of the subject, so there is a risk that the observer may miss a lesion or the like.

[0005] In order to obtain a still image with no color shift, there is a problem in that a complicated operation is required to repeatedly instruct and release the freeze until a still image without color shift is obtained. . In addition, when a color shift occurs in a still image, a method has been proposed in which the color shift is corrected using image processing to remove the color shift, but this method not only requires large-scale equipment but also cannot correct the peripheral areas of the image. There were drawbacks.

The present invention was made in order to solve the above-mentioned problems when obtaining still images using conventional endoscopic imaging devices, and it is possible to easily obtain still images without color shift with a simple configuration. An object of the present invention is to provide a device for preventing color shift in an endoscope imaging device.

[0007]

[Means and operations for solving the problems] In order to solve the above problems, the present invention provides a means for instructing an image to freeze, an image stilling means for freezing the image, and an amount of color shift based on the correlation between images of each color. and an image freeze control means that controls the image freeze means according to the output of the color shift detection means and the output of the image freeze instruction means. This constitutes a color misregistration prevention device in a mirror imaging device.

[0008] The subject of an endoscope is mainly a living body, and the subject often moves due to the subject's heartbeat and breathing, but both the heartbeat and breathing have a cycle, and at a certain timing the subject stops. Or there will be very little movement. Therefore, almost no color shift occurs in the photographed image at this point. In addition, as a feature of endoscopic images, the correlation between G and B is high, so a color shift detection means based on the correlation between images of each color accurately detects the state where color shift no longer occurs, and generates an output signal. The image stilling means is input to the image stilling control means together with the output signal from the image stilling instruction means, and the image stilling means is operated by the control signal from the control means to obtain a still image.

[0009] As a result, it is possible to easily obtain a still image with no color shift with high precision, and there is no need to repeat the complicated operations of instructing and canceling the still image.As a result, the examination time is shortened, and the examinee's It can be used to measure pain relief.

0010

[Example] Examples will be explained below. Figures 1 and 2
1 is a block diagram showing an embodiment of a color misregistration prevention device in an endoscope imaging device according to the present invention; FIG. 1 shows an electronic endoscope portion, and FIG. 2 shows a color misregistration prevention device portion. There is. The terminals a and b in FIG. 1 are the terminals a' and b in FIG.
’. In Figures 1 and 2,
Reference numeral 1 denotes an electronic endoscope, which has an objective lens 2 disposed at its tip, and an image sensor 3 composed of a CCD or the like at its imaging position.
is provided. Reference numeral 4 denotes a light guide made of glass fiber or the like, which is used to introduce illumination light into the living body.

Reference numeral 5 denotes a color filter disk provided with red, green, and blue transmission filters, which is rotatably arranged opposite to one end surface of the light guide 4, and is connected to and driven by a motor 6. It has become so. Reference numeral 7 denotes an illumination lamp composed of a xenon lamp or the like, and is connected to a lamp drive circuit 8. Reference numeral 9 denotes a condensing lens, which is arranged at a position to condense the light emitted from the lamp 7 onto one end surface of the light guide 4 via the color filter disk 5.

10 is an image stilling switch, and the electronic endoscope 1
The image still image signal holding circuit 11 is provided in the operation section of the control panel 1, and is connected to an image still signal holding circuit 11 composed of a latch or the like. 12 is CCD
The image sensor 3 is connected to a video circuit including a drive circuit for the image sensor 3, a video amplifier, and the like. The output end of the video circuit 12 is connected to an A/D converter 13,
The output terminal of the /D converter 13 is connected to a common terminal of a changeover switch 14 made up of a semiconductor switch or the like. Each switching terminal of the changeover switch 14 is connected to an image memory (R1) 15, an image memory (G1) 16, and an image memory (B1) 17, each of which is composed of a semiconductor memory or the like. The output terminals of image memory (R1) 15, image memory (G1) 16, and image memory (B1) 17 are further connected to image memory (R2) 18, image memory (G2) 19, and image memory (B2) 20, respectively. image memory (R2) 18, image memory (G2) 19
, the outputs of the image memory (B2) 20 are each D/A
Converter (R) 21, D/A converter (G) 22, D/
It is connected to be input to the A converter (B) 23.

[0013] Each output of the D/A converter (R) 21, D/A converter (G) 22, and D/A converter (B) 23 is
It is sent to the monitor 24 and also sent to the color shift detection means 25.
It is now entered into This color shift detection means 2
The output terminal of 5 is connected to one input terminal of a comparator 26, and the other input terminal of the comparator 26 is connected to the output terminal of a threshold value setting means 27 constituted by a variable resistor or the like. 28 is an AND circuit, and the comparator 26
The output of the still image signal holding circuit 11 and the output of the image still signal holding circuit 11 are input. The output of the AND circuit 28 is input to an image stilling control circuit 29, and the output of the image stilling control circuit 29 is input to each image of the image memory (R2) 18, image memory (G2) 19, and image memory (B2) 20. It is designed to be input to the stationary control terminal.

Next, the operation of the color misregistration prevention device in the endoscopic imaging device configured as described above will be explained. The white light emitted from the lamp 7 passes through the color filter disk 5 that is rotationally driven by the motor 6, and becomes R, G, and B color sequential light, which is transmitted to one side of the light guide 4 of the electronic endoscope 1. incident on the end face of The color-sequential light incident on the end face of the light guide 4 is transmitted through the light guide 4, reaches the tip of the electronic endoscope 1, and is transmitted through the light guide 4.
The light is emitted from the other end face. The emitted color sequential light illuminates a subject such as the stomach wall, and an image of the subject is formed on an image sensor 3 by an objective lens 2. The image sensor 3 is driven by a 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 sent to an A/D converter 13.
The digital image data is digitized by the image memory (R1) 15, while being switched for each R, G, and B component image data by the changeover switch 14.
Image memory (G1) 16, image memory (B1) 17
are entered and recorded. In addition, changeover switch 1
4 is adapted to be sequentially switched 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 image memory (R1) 15, image memory (G1) 16, and image memory (B1) 17 is transferred to image memory (R2) 18, image memory (G2) 19, and image memory ( B2) Transferred to 20 at high speed. This transfer operation is performed using the synchronization signal period of the television. Image memory (R2) 18,
The image data transferred to the image memory (G2) 19 and the image memory (B2) 20 are read out in synchronization with the television synchronization signal, and then sent to the D/A converter (R) 21 and D/A.
The signal is converted into an analog signal by a converter (G) 22 and a D/A converter (B) 23 and displayed on a TV monitor 24. Normally, the above transfer is performed for each frame, so T
A moving image is observed on the V monitor 24.

To observe the image still, the operator presses the image freeze switch 10 to issue a freeze instruction. When the image stilling switch 10 is pressed, an image stilling instruction signal is sent to the image stilling signal holding circuit 11. Even after the pressing operation of the image stilling switch 10 is released, the image stilling signal holding circuit 11 holds the stilling instruction signal.

On the other hand, the D/A converter (R) 21, D
The outputs of the /A converter (G) 22 and the D/A converter (B) 23 are also input to the color shift detection means 25, and the color shift detection means 25 detects the difference between each color image for each frame. The amount of color shift is detected by taking the correlation between the two. The amount of color shift is then compared by the comparator 26 with a value preset by the threshold setting means 27, and when the amount of color shift is less than the set constant value, the comparator 26
6 outputs the true value to one input terminal of the AND circuit 28. The output of the still image signal holding circuit 11 is input to the other input terminal of the AND circuit 28, and the AND circuit 28 is connected to the comparator 26 and the still image signal holding circuit 1.
Only when both outputs of 1 are true values, the image stillness control circuit 29
Sends control signals to.

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

[0020] At this time, the observed still image is a still image in a state where the color shift is less than a certain value, and is an easy-to-see image with almost no color shift occurring. To release the image from stilling, the image stilling signal holding circuit 11 may be reset using a release switch (not shown), or the image stilling signal holding circuit 11 may be toggled by using the image stilling switch 10.

[0021] The subject of an endoscope is mainly a living body, and as mentioned earlier, the subject is often moved by the subject's heart, heartbeat, and breathing, but both heartbeat and breathing have a cycle. When it comes to timing, the subject is either stationary or has very little movement. Therefore, as in the above embodiment, the color shift detection means monitors the amount of color shift, detects when the subject is stationary or moves very little and the amount of color shift falls below a certain value, and at that point By freezing the image at , it is possible to obtain a still image from which the effects of color shift are practically removed.

FIG. 3 is a block diagram showing a specific example of the configuration of the color misregistration detecting means 25 in the embodiment shown in FIGS. 1 and 2 above. Green (G) and blue (B) components of normal endoscopic images
When examining the relationship with the components, the results are as shown in FIG. From this figure, we can see that the G component and B component of each pixel constituting the endoscopic image
It can be seen that the components vary within a limited range around a linear function, and the correlation between B and G is high. 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 in a normal endoscopic image is approximately constant.

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

The configuration example shown in FIG. 3 is designed to accurately detect color shift from green and blue image signals based on the fact that the correlation between B and G, which is unique to the endoscopic image, is high. It is something. That is, the output of the D/A converter (G) 22 is input to one input terminal of the subtracter 30, and is also input to the integrator (1) 31;
The output of the converter (B) 23 is input to the other input terminal of the subtracter 30 via the variable gain amplifier 32, and is also input to the integrator (2) 33. The outputs of the integrator (1) 31 and the integrator (2) 33 are input to a gain control circuit 34 that controls the gain of the variable gain amplifier 32, and the output terminal of the gain control circuit 34 is connected to the gain of the variable gain amplifier 32. Connected to the control input terminal.

The output terminal of the subtracter 30 is connected to a window comparator 35.
A window setting device 37 for setting a window is connected to. The output terminal of the window comparator 35 is connected to an integrator (3) 36, and the integrator (3) 36
The output is configured to be input to the comparator 26 as the output of the color shift detection means 25.

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

As a result, in a normal endoscopic image, even though the G component has a higher level than the B component, the subtracter 3
The G component and B component of the image signal inputted to 0 have the same integral value within a field or frame period. The subtracter 30 outputs the difference between the output of the D/A converter (G) 22 and the output of the variable gain amplifier 32, but if no color shift occurs, a pixel that makes the output of the subtracter 30 almost 0; That is, there are many pixels in which the G component and the value obtained by multiplying the B component by the gain of the variable gain amplifier 32 are equal. On the other hand, when a color shift occurs, the number of pixels for which the output of the subtracter 30 becomes almost 0 is smaller than that described above.

By extracting only the pixel signal for which the output of the subtracter 30 is around 0 using the window comparator 35 and integrating it over the entire screen using the integrator (3) 36,
The amount of color shift for the entire screen can be obtained. Therefore, the integrator (3
) 36 indicates the amount of color shift, so by inputting this to the comparator 26, the image stillness control circuit 2
Nine control signals can be obtained.

FIG. 6 is a block diagram showing another example of the configuration of the color shift detection means. The output of the D/A converter (G) 22 is input to one input terminal of the divider 38, while the output of the D/A converter (B) 23 is input when the input is 0. It is configured to be input to the other input terminal of the divider 38 via a level replacement circuit 39 which outputs a value other than 0 when . The output end of the divider 38 is connected to a high-pass filter 40 that blocks direct current components and passes only alternating current components. The output of the high-pass filter 40 is input to an absolute value circuit 41 composed of a rectifier circuit, etc., and the output of the absolute value circuit 41 is input to an integrator 42 that performs an integration operation only for one field or one frame period. The output of the integrator 42 is configured to be input to the comparator 26 as the output of the color shift detection means 25.

Next, the operation of the color misregistration detection means configured as described above will be explained. The level replacement 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. The divider 38 calculates (G component)/(B component). As is clear from FIGS. 4 and 5 mentioned above, (G component)/
The value of (B component), that is, the slope of the straight line function in FIG. 4, varies around a constant value, as shown in FIG.
The degree of this variation indicates the state of color misregistration.

FIG. 8 shows the temporal change in the output of the divider 38 within one field period. If no color shift occurs, the variation is small, and if color shift occurs, the variation is small. are increasing. This degree of variation is extracted in the form of an alternating current component by a high-pass filter 40, and its amount is integrated over the entire screen by an absolute value circuit 41 and an integrator 42. The output of the integrator 42 indicates the amount of color shift, and is input to the comparator 26 to obtain an image stilling control signal.

FIGS. 9 and 10 are block diagrams showing other embodiments of the present invention, with FIG. 9 showing an endoscope section;
FIG. 10 shows a portion of the color misregistration prevention device. and figure 9
Terminals c and d of are connected to terminals c' and d' of FIG. 10, respectively. Also, in these figures,
Components that are the same or equivalent to those of the embodiment shown in FIGS. 1 and 2 are designated by the same reference numerals. In Figures 9 and 10, 30 is a general fiberscope, and objective lens 2
, a light guide 4, an image guide 31, an eyepiece 32, etc. Reference numeral 33 denotes a color-sequential TV camera head detachably attached to the eyepiece of the fiberscope 30, which is composed of an imaging lens 34, an imaging element 3, a dark box 35, etc., and the imaging element 3 is connected to the imaging lens 34. It is disposed at an imaging position on the end face of the image guide 31. Further, the image sensor 3 is connected to the video circuit 12 via a connection cord 36.

Similar to the embodiment shown in FIGS. 1 and 2, light from a lamp 7 driven by a lamp drive circuit 8 passes through a condenser lens 9 and a color filter disk 5 rotated by a motor 6. The light is focused on one end surface of the light guide 4 through the light guide. Reference numeral 10 denotes an image stilling switch composed of a foot switch, which is connected to an image stilling signal holding circuit 11 composed of a latch and the like and a timer 37.

The output of the video circuit 12 is A/D converted by an A/D converter 13, and sent via a changeover switch 14 to an image memory (R1) 15, an image memory (G1) 16,
Each image is input and recorded in the image memory (B1) 17. The output terminals of image memory (R1) 15, image memory (G1) 16, and image memory (B1) 17 are further connected to image memory (R2) 18, image memory (G2) 19, and image memory (B2) 20, respectively. connected, image memory (R2) 18, image memory (
The outputs of G2) 19 and image memory (B2) 20 are respectively connected to a D/A converter (R) 21 and a D/A converter (G).
22, is input to the D/A converter (B) 23, and
It is also input to a color shift detection means 25 which is composed of a digital correlator or the like.

The output of each D/A converter 21, 22, 23 is input to the TV monitor 24, and the output of the color shift detection means 25 is input to one input terminal of the comparator 26, and the output of the color shift detection means 25 is input to one input terminal of the comparator 26. Threshold value setting means 27 is connected to the input terminal of . 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 output of the timer 37 are input to the OR circuit 38. The output of the OR circuit 38 is input to the image stilling control circuit 29, and the output end of the image stilling control circuit 29 is connected to the image memory (R2) 18 and the image memory (G2), as in the previously described embodiment.
19, connected to each image freeze control terminal of the image memory (B2) 20.

The operation of this embodiment is almost the same as that of the embodiment shown in FIGS. 1 and 2, but the differences are as follows. The object image is formed on the image sensor 3 via the objective lens 2, image guide 31, eyepiece lens 32, and imaging lens 34, and its output signal is input to the video circuit 12. Since the image freeze switch 10 is composed of a foot switch, an instruction to freeze the image is given by operating this switch with the foot. Color shift detection means 25
are image memory (R2) 18, image memory (G2) 1
9. Since it is connected to the image memory (B2) 20,
Digital image data is directly input to this color shift detection means 25. Therefore, in this color misregistration detection means 25, the same processing as that in the color misregistration detection means shown in FIG. 3 or FIG. 6 is digitally performed.

The timer 37 is provided in order to cope with the case where the color shift in the captured image does not decrease and no signal is output from the comparator 26 even after a certain period of time has elapsed since the image freeze switch 10 was operated to instruct the image to freeze. It belongs to
The timer 37 outputs a signal after a certain period of time has elapsed, and the image stilling control circuit 29 is forcibly driven via the OR circuit 38 to freeze the image and obtain a still image.

In the color shift detection means shown in FIGS. 3 and 6, the integrator (1) 31, integrator (2) 33, integrator (3) 36, integrator 42, etc. perform integration over the entire screen. However, in a normal electronic endoscope, the endoscope image part is only a part, as shown by diagonal lines in FIG. Therefore, when performing various types of integration using each of the above-mentioned integrators, it is necessary to avoid pixels other than those in the endoscopic image area. To this end, it is sufficient to generate a mask signal indicating the endoscopic image area and to control the function of the integrator accordingly.

Furthermore, color shift detection may not be performed on the entire endoscopic image, but may be performed only on the central part of the image, or only on a specific scanning line, for example. In this case, it is sufficient to generate an appropriate mask signal and perform color shift detection only in a specific area.

Furthermore, although the color shift detection means shown in FIGS. 3 and 6 detect color shift using the green (G) component and the blue (B) component, the present invention is not limited to this. ,
The configuration may be such that color shift is detected using images of other color components. Furthermore, once again, perform differential processing of the image, etc.
A configuration may also be adopted in which color shift is detected using a two-color color component image whose contours have been emphasized or extracted. In short, it is sufficient to detect it by some means based on the correlation between images of each color.

Although video signals obtained from electronic endoscope devices are generally gamma-corrected, in the present invention, the video signals are linearized through a circuit having inverse gamma characteristics and then processed before being input to the color shift detection means. It may be configured to perform the following. Further, the color misregistration prevention device according to the present invention may be incorporated into an electronic endoscope device, or may be configured separately from the electronic endoscope device, and may be configured using a video signal obtained from the electronic endoscope device. The image freezing operation of the electronic endoscope device may be controlled from the outside by detecting color shift.

[0042]

[Effect of the invention] As explained above based on the embodiments,
According to the present invention, the color shift detecting means detects a state in which no color shift occurs based on the correlation between images of each color, and the image stilling control means is controlled based on the detection signal and the image stilling instruction signal to Since it is configured to stand still, it is possible to accurately detect color shifts by utilizing the characteristic feature of endoscopic images, which is the high correlation between each color image, and easily obtain still images without color shifts. . Therefore, it is no longer necessary to perform complicated operations to repeatedly instruct the patient to stand still and release the patient from rest, thereby providing advantages such as shortening the examination time and reducing the patient's pain.

Furthermore, since the present invention is an endoscope imaging device using a color sequential illumination method, it is originally an R. G. It has three types of memories (B), and since each color signal can be taken out from these memories and correlated to detect the amount of color shift, a separate extra memory is not required. In addition, in the color sequential illumination type endoscope imaging device, R. G. The B signals are combined and colored, and since the correlation between each color image can be determined during the colorization period, advantages such as being able to detect the amount of color shift almost in real time can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of an electronic endoscope portion of an embodiment of a color misregistration prevention device in an endoscope imaging device according to the present invention.

FIG. 2 is a block configuration diagram showing a color shift prevention device portion of an embodiment of the color shift prevention device in the endoscope imaging device according to the present invention.

FIG. 3 is a block diagram showing an example of the configuration of a color shift detection means in FIG. 2;

FIG. 4 is a diagram showing the distribution state of green components and blue components of each pixel constituting an endoscopic image.

FIG. 5 is a diagram showing another distribution state of green components and blue components of each pixel constituting an endoscopic image.

FIG. 6 is a block diagram showing another example of the configuration of the color shift detection means.

[Figure 7] (Green component)/( of each pixel composing the endoscopic image)
FIG. 3 is a conceptual diagram showing the distribution state of values of blue component).

FIG. 8 is a diagram showing a temporal change within one field period of the output of the divider in FIG. 6;

FIG. 9 is a diagram showing the configuration of an endoscope portion in another embodiment of the present invention.

FIG. 10 is a block configuration diagram showing a color misregistration prevention device portion in another embodiment of the present invention.

FIG. 11 is a diagram showing an endoscope image section in an electronic endoscope.

[Explanation of symbols]

1 Electronic endoscope 3 Imaging device 4 Light guide 30 Fiberscope 31 Image guide

Claims (1)

[Claims] 1. An endoscope imaging device using a color sequential illumination method, comprising means for issuing an image freeze instruction, an image freeze means for freezing the image, and a color detecting amount of color shift based on the correlation between images of each color. A color misregistration prevention device comprising: a misregistration detecting means; and an image stilling control means for controlling the image stilling means according to the output of the color misregistration detecting means and the output of the image stilling instruction means.