JPH0686754A - Endoscope television system - Google Patents

Abstract

PURPOSE:To eliminate generation of an image having no moire nor color by providing an optical element having an optical characteristic for enough attenuating a frequency spectrum peculiar to an image guide fiber bundle, in an image pickup optical path. CONSTITUTION:This system prepares two filters of an optical low-pass filter 11a which can enough attenuate a frequency spectrum fF peculiar to an image guide fiber bundle for passing through the vicinity of a chrominance subcarrier frequency and the vicinity of a sampling frequency, and an optical low-pass filter 11b for lowering enough a response in the vicinity of the sampling frequency in order to prevent a false color phenomenon generated by a high-frequency component contained in a luminescent point of a mucous membrane, etc., in a coelom being an image pickup object, as a constitution for varying selectively the response of the optical low-pass filter. Also, they are installed so as to be changeable in an optical path in a video camera 10 by using a turret 26, etc.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an endoscope capable of selectively using a fiberscope and a rigid endoscope, and enables an image of the inside of a body cavity to be observed on a monitor television or the like. Regarding

[0002]

2. Description of the Related Art In recent years, an endoscopic television system in which a body cavity or the like is displayed on a monitor television or the like for observation has become widespread, and surgical operation in the body cavity to be performed under endoscopic observation has become popular. It's coming. An example of such an operation using an endoscope is a laparoscopic cholecystectomy in which the gallbladder is removed due to a disorder such as a gallstone. In addition, as a surgical technique which has recently received a great deal of attention, "Common Bile"
There is one called "Copy". This is because when a bile duct is found to be clogged with gallstones during the laparoscopic cholecystectomy, a rigid endoscope used for observation is operated with a scalpel, scissors, etc. from the forceps channel. This gallstone is removed by switching to a fiberscope that can perform.

An example of an endoscope television system used for such surgery will be described with reference to FIGS. 32 to 35. In FIG. 32, reference numeral 1 is a fiberscope using the image guide fiber 2 for the image transmission system, and 3 is a rigid scope using the relay lens 4 for the image transmission system. Reference numeral 5 is an objective lens provided at each of the distal end portions of the fiberscope 1 and the rigid endoscope 3, 6 is an eyepiece lens provided at each eyepiece 7, and 8 is an eyepiece having an imaging lens 9 built therein. This is an adapter for connecting the section 7 and the television camera 10 that does not have an imaging optical system. An optical low-pass filter 11 and a solid-state image sensor (CCD) 12 are sequentially arranged in the television camera 10.

When the fiberscope 1 is used for the endoscope, the illumination light transmitted by a light source and a light guide (not shown) illuminates the object M, and an image of the object M is formed by the objective lens 5. The image is transmitted by the image guide fiber 2. Then, an image is formed on the solid-state image sensor 12 via the eyepiece lens 6, the imaging lens 9 and the low-pass filter 11, and the camera control unit 1
3 is displayed as an endoscopic image on the monitor television 14. When the rigid endoscope 3 is used as the endoscope, the object M
Is transmitted by the relay lens 4, and is imaged on the solid-state image sensor 12 via the eyepiece lens 6, the imaging lens 9 and the low-pass filter 11 as in the case of using the fiberscope 1, and is displayed on the monitor television 14. It is projected.

FIG. 33 shows a system configuration using a camera head 15 incorporating an imaging lens 9, a low-pass filter 11 and a solid-state image sensor 12 instead of the adapter 8. Further, FIG. 34 shows a system configuration example when only the fiberscope 1 can be connected to the camera head 15, and FIG. 35 shows a system configuration example when the eyepiece lens 6 is not provided in the fiberscope 1. In the example shown in FIG. 35, the camera control unit 13 includes a camera head unit 13a including an imaging lens 9, a low-pass filter 11 and a solid-state image sensor 12, and a signal processing circuit 13b. Unlike the configuration, the fiberscope 1 is directly connected to the camera control unit 13. In addition to the fiber barscope 1 which is entirely composed of a flexible fiberscope, the insertion part is composed of a rigid part of the same quality as a rigid endoscope, and the image transmission part is composed of a flexible image guide fiber bundle. Also included are so-called rigid fiberscopes.

By the way, in each of the above-mentioned endoscope television systems, the image formed on the solid-state image pickup device, that is, the image transmitted to the solid-state image pickup device via the fiberscope or the rigid mirror becomes the subject. However, the endoscopic image obtained with the fiberscope has the following features. FIG. 36A shows the exit end face of the image guide fiber bundle having the hexagonal close-packed structure. 2a in the figure
Is a core of the image guide fiber bar 2, and 2b is a clad. Further, arrow A is the stacking direction of the fier bars 2, and arrow B is the horizontal scanning direction of the solid-state image sensor 12. When the exit end face is imaged by the solid-state imaging device 12 that is two-dimensionally arrayed as shown in FIG. 2B, the endoscopic image signal has an array pattern of both the image guide fiber 2 and the solid-state imaging device 12. Due to the strong frequency spectrum fF = 1
/ (Pf × β × sin 60 °) is included. Where P
f is the fiber image pitch, and β is the magnification of the imaging optical system. This frequency spectrum fF is a particularly strong first-order frequency spectrum, but if this spectrum is shown in a two-dimensional spatial frequency strictly with the stacking direction of the fibers shown in FIG. 36 as the horizontal axis, as shown in FIG. 37. It also has a large number of second-order and higher-order frequency spectra.

When the subject is the exit end face of the image guide fiber bundle formed by randomly arranging fibers as shown in FIG. 38, the frequency spectrum according to the arrangement pattern is fF = 1 / (Pf '×). It can be expressed as β). Here, Pf 'is the average pitch of randomly arranged fibers. In this case, unlike the case where the fiber array has a hexagonal close-packed structure, the frequency spectrum distribution is substantially isotropic.

As described above, in an optical device which uses the solid-state image pickup device to discretely spatially sample an object image and picks it up, when the object image contains a high frequency component equal to or higher than the Nyquist limit on the image pickup side. In addition, the beat between the high frequency component and the sampling frequency causes a false signal called aliasing, moire, or the like.

A single plate type solid-state image pickup device for an object is used by using a filter in which G (green), C (cyan), Mg (magenta), and Y (yellow) color filters shown in FIG. 39 are arranged in a checkered pattern. In the case of imaging with, when the pitch of one pixel of the filter is Px in the horizontal scanning direction and Py in the vertical direction, on the two-dimensional spatial frequency plane shown in FIG.
Coordinates (1 / 2Px, 0) (1 / 2Px, 0), (1/2
Px, 1 / 4Py) (-1 / 2Px, -1 / 4Py) and (1 / 2Px, -1 / 4Py) (-1 / 2Px, 1 /
A sampling point occurs at 4Py). Therefore, when the exit end face of the image guide fiber bundle having the hexagonal close-packed structure is imaged using such a filter, as shown in FIG. 41, the first-order frequency spectrum fF included in the image is near the sampling point of the filter. Because it exists
Strong moire is generated at this portion. In FIG. 41, the frequency spectrum fF is illustrated with a certain width, but this is because the case where the imaging lens is a zoom lens is taken into consideration.

In order to remove such moire, conventionally, as disclosed in JP-A-1-284225, a large number of birefringent plates are used and the intensity of the frequency spectrum fF existing near the sampling point. Was to be attenuated.

[0011]

By the way, in recent years, the number of pixels of the solid-state image pickup device has been increased, so that the moire generated at the color subcarrier frequency has become a serious problem. NT
In each of the SC, PAL, and SECAM systems, a composite signal output system that simultaneously outputs a luminance signal and a color difference signal is adopted. For example, in the case of the NTSC system, a signal waveform of a signal output to a monitor television on one scanning line. Is as shown in FIG. In this case, on the monitor TV side, the hue is changed to a color burst signal (signal frequency 3.5
8MHz) and color difference signal (color subcarrier frequency 3.58MH
Since the phase difference of z) and the saturation are judged by the amplitude of the color difference signal, if there is a component in the vicinity of 3.58 MHz which is almost equal to the color subcarrier frequency of the color difference signal in the luminance signal component (see FIG. (See b)), this may be regarded as a color difference signal, and an irrelevant color different from the original image may be displayed. If such a color subcarrier frequency is represented on the two-dimensional spatial frequency plane,
As shown in FIG. 43.

Conventionally, since the pixels of the solid-state image sensor are coarse, the sampling point and the color subcarrier frequency are close in frequency, and an optical low-pass that weakens the intensity of the frequency spectrum of the fiber existing in the vicinity of the sampling point. By using the filter, the frequency spectrum of the fiber existing near the color subcarrier frequency could be attenuated.

However, when a high-pixel solid-state image pickup device is used to pick up an endoscopic image obtained by a fiberscope, the strong frequency spectrum fF contained in the exit end face of the image guide fiber bundle interferes with the color subcarrier frequency. This causes moire in the image. In this case, the conventional optical low-pass filter described above has a problem that the intensity of the frequency spectrum fF existing in the vicinity of the color subcarrier frequency cannot be sufficiently attenuated, and the occurrence of such moire cannot be prevented.

Further, in an endoscope television system capable of connecting both the fiberscope 1 and the rigid endoscope 3 as shown in FIGS. 32 and 33, an optical low-pass filter for the fiberscope is usually installed inside. Therefore, even when a rigid endoscope is used, it is necessary to capture an image through this optical low-pass filter, and there is a problem in that the resolution deteriorates when the rigid endoscope is used.

On the other hand, recently, when an image plane of a subject including a high frequency component higher than a color subcarrier frequency that can cause moire is imaged, the color is changed according to the amplitude value of the aperture signal created from the high frequency component. A camera control unit has been proposed in which a signal suppression circuit works to reduce the color output of that portion to make color moire inconspicuous.
However, when the exit end face of the image guide fiber bundle as shown in FIG. 36 and FIG. 38 is imaged using such a camera control unit, the intensity of the aperture signal becomes strong because the high frequency component is very large in the image, and The color signal suppression circuit operates so as to weaken the output intensity of the information signal, that is, as if a colorless image is captured,
There is a problem that a clear endoscopic image cannot be obtained.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to prevent generation of an image without moire or color when a fiberscope is used. An object of the present invention is to provide an endoscopic television system capable of obtaining an endoscopic image with excellent resolution and contrast when a rigid endoscope is used.

[0017]

Means and Actions for Solving the Problems Means and actions of the present invention for achieving the above object will be sequentially described. (First Means) In the endoscope television system of the present invention, the image appearing on the exit end face of the image guide fiber bundle is formed on the solid-state image pickup device so that the image can be observed on the monitor television. In an endoscope television system, a frequency peculiar to an image guide fiber bundle that passes the vicinity of the color subcarrier frequency has an optical characteristic that sufficiently attenuates the frequency spectrum peculiar to the image guide fiber bundle, and a frequency peculiar to the image guide fiber bundle that passes the vicinity of the sampling frequency of the solid-state image sensor. It is characterized in that an optical element having an optical characteristic capable of sufficiently attenuating the spectrum is arranged in the imaging optical path.

When the exit end face of an image guide fiber bundle having a hexagonal close-packed structure as shown in FIG. 36 is imaged by a 1 / 2-inch size solid-state image pickup device which outputs a signal by the NTSC system, a strong 1 included in the image is detected. The next frequency spectrum fF has a value of about 20 to 80 (lines / mm) on the imaging surface. In addition, in the conventional endoscope TV system,
As a solid-state image sensor, for example, the pitch of one pixel is Px = 12.76 μm in the horizontal direction and Py = 9.86 μm in the vertical direction.
When a 1/2 inch size is used, the sampling point of this solid-state image sensor is 39.2 (lines / m
m).

On the other hand, when the color subcarrier frequency output by the NTSC system is converted into a spatial frequency, 3.58 MHz≈29.5 (lines / mm) is obtained. That is, the optical low-pass filter used in the conventional endoscope television system has an effect of removing moire caused by the interference between the sampling point and the frequency spectrum of the fiber, but the sampling frequency and the color subcarrier frequency And are close in frequency,
The moire generated due to the interference between the color subcarrier frequency and the frequency spectrum of the fiber was also effective in removing the moire to some extent.

However, recently, the pitch of one pixel is Px = 9.6 μm in the horizontal direction and Py = 9.9 μm in the vertical direction.
Some of them have a horizontal Nyquist limit of 5
It is calculated to be 2.1 (lines / mm). Therefore, in the conventional optical low-pass filter for removing moire caused by the interference between the sampling point and the frequency spectrum of the fiber, the color subcarrier frequency and the frequency spectrum fF of the fiber interfere with each other. It was not possible to remove the moire.

According to the present invention, not only the optical element for reducing the intensity of the frequency spectrum fF existing in the vicinity of the sampling point, but also the frequency spectrum fF existing in the vicinity of the color subcarrier frequency 29.5 (lines / mm). Since an optical element that reduces the intensity is provided in the imaging optical path, even when the subject is the exit end face of the image guide fiber bundle,
Even when the above-mentioned color signal suppression circuit is operated to increase the contrast of the luminance signal and the television signal output is adjusted, approximately 3.58 MHz ≈ 29.5 (lines /
The frequency spectrum fF which is equal to (mm) is not imaged on the solid-state image sensor. That is, since the image signal output from such a solid-state image sensor has a waveform as shown in FIG. 1, it is possible to prevent the phenomenon that the luminance signal is regarded as a color signal on the monitor television side, and obtain an endoscopic image without moire. be able to.

(Second Means) In the endoscope television system according to the second means of the present invention, at least a fiberscope using an image guide fiber bundle in the image transmission system or a rigid body using a relay lens in the image transmission system is used. It can be connected to a mirror, and an image obtained by either endoscope is formed on a solid-state image sensor, and an electric signal output from the solid-state image sensor is converted into a television signal by a camera control unit. In an endoscopic television system that outputs and obtains an endoscopic image, an optical element with optical characteristics that sufficiently attenuates the response at the sampling point of the solid-state image sensor, and an image guide fiber that passes near the color subcarrier frequency It has optical characteristics to sufficiently attenuate the frequency spectrum peculiar to the bundle and passes near the sampling frequency of the solid-state image sensor. The image guide is characterized in that any one of the optical elements with optical characteristics that sufficiently attenuates the frequency spectrum peculiar to the fiber bundle is selected and used in the imaging optical path according to the endoscope to be used. Is.

An optical low-pass filter for a solid-state image pickup device having a high number of pixels, which is capable of sufficiently attenuating the frequency spectrum fF peculiar to the image guide fiber bundle passing near the color subcarrier frequency, is provided with a fiberscope and a rigid endoscope. When used in an endoscope television system that can connect both of the two, the optical low-pass filter works even when a rigid endoscope is used, so images of frequency components above the color subcarrier frequency can be cut and reproduced by the filter. However, there is a problem that the resolution and contrast of the endoscopic image deteriorates when the rigid endoscope is used.

In the present invention, when the fiberscope is used, the optical characteristic is such that the frequency spectrum fF peculiar to the image guide fiber bundle passing near the color subcarrier frequency and near the sampling frequency is sufficiently attenuated, and the rigid scope is used. In order to prevent a false color phenomenon caused by a high frequency component contained in a bright spot such as a mucous membrane in a body cavity, which is an imaged object, a response near a sampling frequency is sufficiently lowered to have an optical characteristic. , The optical low-pass filter is appropriately exchanged and used according to the endoscope to be used, and the response of the filter is set so as to have an optical characteristic suitable for each.

As such a structure, for example, the optical system shown in FIGS. 2 and 3 can be cited. This is two variable power systems 2
5a and 25b, an intermediate image M'of the image M is formed by the first variable magnification system 25a on the object side including the optical low-pass filter 11, and this intermediate image is solid-state imaged by the second variable magnification system 25b. It is arranged for re-imaging on the element 12. 2 shows an optical system when a fiberscope is used, and FIG. 3 shows an optical system when a rigid endoscope is used. Since the first variable power system 25a on the object side includes the optical low-pass filter 11, the first variable power system 2a
The frequency component contained in the intermediate image M'formed by 5a varies depending on its size. Therefore, this intermediate image M'is converted by the second variable power system 25b into the solid-state image sensor 1
The solid-state imaging device 1
It is possible to change only the frequency component without changing the size of the image M on the image 2, that is, to make the characteristic of the optical low-pass filter 11 variable.

In this case, when the fiberscope is used, the optical characteristic is such that the frequency spectrum fF peculiar to the image guide fiber bundle passing near the color subcarrier frequency and near the sampling frequency is sufficiently attenuated, and when the rigid scope is used, imaging is performed. In order to prevent the false color phenomenon caused by the high frequency components contained in the bright spots of the mucous membrane, which is an object, the optical characteristics should be such that the response near the sampling frequency is sufficiently reduced when using the fiberscope. It is possible to realize an endoscope television system in which the occurrence of moire can be prevented and the resolution and contrast can be improved when a rigid endoscope is used.

An optical low-pass filter capable of sufficiently attenuating the frequency spectrum fF peculiar to the image guide fiber bundle passing near the color subcarrier frequency is
The condition is that the response in the frequency spectrum fF included in the band of [color subcarrier frequency ± 0.5 MHz] is 40% or less. An optical low-pass filter that sufficiently attenuates the frequency spectrum fF peculiar to the image guide fiber bundle passing near the sampling point is in the band of [sampling point frequency ± w MHz] when the frequency band of the color difference signal is w. The condition is that the response in the frequency spectrum fF included in is less than 40%.

As a structure for selectively changing the response of the optical low-pass filter, as shown in FIG. 4, the frequency spectrum fF peculiar to the image guide fiber bundle passing near the color subcarrier frequency and near the sampling frequency is sufficiently attenuated. The optical low-pass filter 11a that causes the noise and the response near the sampling frequency are sufficiently reduced in order to prevent a false color phenomenon caused by a high frequency component included in a bright spot such as a mucous membrane in a body cavity that is an imaging object. Two filters, the optical low-pass filter 11b, may be prepared, and these may be installed in the optical path in the television camera 10 so as to be exchangeable by using the turret 26 or the like.

Further, as shown in FIG. 5, an adapter 8 incorporating an imaging lens and the above-mentioned two optical low-pass filters 11a and 11b is prepared, and the adapter 8 is selected according to the endoscope to be used. You may do it. As shown in FIG. 6, the camera head 15 may be of a form in which the filter can be replaced, and the filter may be replaced appropriately according to the endoscope used. Further, as shown in FIG. 7, a plurality of adapters 8 and camera heads 15 each having an optical low pass filter are prepared with different filter characteristics, and these are appropriately selected according to the endoscope to be used. You may use it.

(Third Means) In the endoscope television system according to the third means of the present invention, at least the endoscope image appearing on the exit end face of the image guide fiber bundle is imaged on the solid-state image pickup device, and the solid-state image pickup device is formed. In an endoscopic television system in which an electric signal output from the image pickup device is converted into at least a composite television signal and output to obtain an endoscopic image, at the time of outputting the composite signal, the color sub signal of the luminance signal of the composite signal is output. It is characterized in that it has an electric means for selecting only a signal near the carrier frequency and lowering the level of the signal.

In an endoscope television system in which both a fiberscope and a rigid endoscope can be connected, for example, NTSC
In the case of the composite television signal of the system, moire occurs when a strong frequency spectrum fF included in the exit end face of the image guide fiber bundle exists in the vicinity of the color subcarrier frequency of 3.58 MHz as shown in FIG. In this case, if an optical low-pass filter that sufficiently attenuates the frequency response in the vicinity of 3.58 MHz is used, the 3.58 MHz component in the luminance signal is cut, so that the occurrence of moire can be prevented. However, when a rigid endoscope is used, the resolution and contrast cannot be improved even if a high-pixel solid-state image sensor is used, and the image quality is the same as when an image sensor with a small number of pixels is used.

According to the above configuration of the present invention, at the time of outputting the composite signal, it has an electric characteristic of sufficiently attenuating the amplitude of the signal near 3.58 MHz in the luminance signal component of the composite signal as shown in FIG. Therefore, the amplitude of the component near 3.58 MHz in the luminance signal is sufficiently attenuated and output (see FIG. 10). Therefore, even when the luminance signal of 3.58 MHz is regarded as a color signal on the monitor television side, the signal processing is performed as a color difference signal with extremely weak saturation, and moire generated when the fiberscope is used hardly interferes when observing the monitor television. It can be made inconspicuous to the extent that it is not. Therefore, it is possible to prevent moire caused by the frequency spectrum fF interfering with the color subcarrier frequency without using an optical low-pass filter in which the response near the color subcarrier frequency is sufficiently attenuated. Therefore, even if a high-pixel solid-state image sensor is used, moire can be removed when a fiberscope is used by simply using an optical low-pass filter that reduces the frequency spectrum fF existing near the sampling point.

As a means for realizing the above electrical characteristics, use of an aperture signal can be cited, for example. Figure 1
The operation of the aperture signal will be described with reference to FIG. In the figure, assuming that the figure (a) is an input signal for giving luminance information, this signal is subjected to signal processing to create the aperture signal shown in the figure (b). When this aperture signal is superimposed on the luminance signal again, a signal in which the contour (edge) of the image is emphasized is obtained as shown in FIG. Since this signal apparently has a negative point image intensity distribution, the apparent response exceeds 100%, whereby the image contrast can be improved. In this case, the frequency of the edge enhancement peak in the response of the output image can be changed by manipulating the delay time when creating the aperture signal. Therefore, as shown in FIG. 12, when using the fierberscope, the delay time of the peak Ap of the aperture signal is set so that the contrast of the luminance signal is sufficiently small in the vicinity of 3.58 MHz (see the same figure ( a)), the high frequency component of 3.58 MHz or more becomes relatively smaller than the frequency component of 3.58 MHz or less, and the above-described electrical characteristics can be obtained by normalizing the entire luminance signal. However, if this is left as it is, a resolution of 3.58 MHz or higher cannot be obtained when a rigid endoscope is used. Therefore, when the rigid endoscope is used, the delay time of the peak Ap of the aperture signal is set to a high frequency band where the cutoff frequency of contrast is 3.58 MHz or more (see FIG. 7B). Although the action of the aperture signal has been described with reference to the contour enhancement in the horizontal direction of the image, the same principle can be applied to the enhancement of the vertical or diagonal contour of the image.

With the above configuration, the value of 3.58 as shown in FIG. 9 is obtained.
Approximately realizes the electrical characteristics that sufficiently attenuate the amplitude of the signal near MHz, and as a result, 3.58M in the luminance signal is realized.
Since the amplitude of the Hz component becomes small, it is possible to make the occurrence of moire in the case of using the fierberscope inconspicuous to the extent that no trouble occurs when observing the monitor television.
According to the experiment, the luminance signal [3.58 ± 0.5] MHz
It has been confirmed that the moire removing effect is practically sufficient when the amplitude in the frequency band of is 40% or less with respect to the amplitudes in other frequency bands.

Further, the optical low-pass filter is configured so as to electrically remove moire generated by the interference between the frequency spectrum fF of the fierberscope and the color subcarrier frequency, so that the optical low-pass filter exists in the fiber near the sampling point. What has a characteristic of attenuating only the frequency spectrum fF of the scope may be used, and when such an optical low-pass filter is used together with a solid-state image pickup device with a high pixel when using a rigid endoscope, an endoscopic image excellent in resolution and contrast is obtained. be able to. The moire removing effect can be obtained even when the above configuration is applied to an endoscope television system dedicated to a fiberscope.

(Fourth Means) In the endoscope television system according to the fourth means of the present invention, at least the endoscopic image appearing on the exit end face of the image guide fiber bundle is imaged on the solid-state image pickup device, and the solid-state image pickup device is formed. In an endoscopic television system in which an electric signal output from the image pickup device is converted into at least a composite television signal and output to obtain an endoscopic image, the frequency spectrum peculiar to the image guide fiber bundle is the composite television signal. It is characterized in that an electric means is provided for switching the composite television signal to the component television signal when it exists in the vicinity of the color subcarrier frequency.

As described above, when the strong frequency spectrum fF included in the exit end face of the image guide fiber bundle exists in the vicinity of the color subcarrier frequency of 3.58 MHz, moire occurs (see FIG. 8). 3.5
If an optical low-pass filter that sufficiently attenuates the response in the vicinity of 8 MHz is used, the resolution and contrast when using a rigid endoscope cannot be improved even if a solid-state image sensor with high pixels is used.

According to the above configuration of the present invention, when at least the fiberscope is used, the television signal output is separated into the luminance signal and the color difference signal and can be output as the component television signal. Even if the frequency sub-carrier frequency includes the frequency spectrum fF, the monitor television does not regard it as a color difference signal, and it is possible to prevent moire due to signal interference.

As described above, the optical low-pass filter exists near the sampling point by electrically removing the moire generated by the interference between the frequency spectrum fF of the fierberscope and the color subcarrier frequency. It is sufficient to use a fiberscope that has a characteristic of attenuating only the frequency spectrum fF of the fiberscope. If such an optical low-pass filter is used together with a high-pixel solid-state image sensor when using a rigid endoscope, an endoscopic image excellent in resolution and contrast is obtained. Can be obtained. The moire removing effect can be obtained even when the above configuration is applied to an endoscope television system dedicated to a fiberscope.

(Fifth means) In the endoscope television system according to the fifth means of the present invention, the endoscope image appearing at the exit end face of the image guide fiber bundle having at least the hexagonal close-packed structure is formed on the solid-state image pickup device. In an endoscopic television system in which an image is formed and an electric signal output from the solid-state imaging device is converted into at least a composite television signal and output to obtain an endoscopic image, a frequency spectrum peculiar to the image guide fiber bundle is It is characterized in that the stacking direction of the image guide fiber bundle is formed at an angle of approximately 30 degrees with respect to the horizontal scanning direction of the solid-state image pickup device when it exists near the color subcarrier frequency of the composite television signal. It will be.

As described above, when the strong frequency spectrum fF included in the exit end face of the image guide fiber bundle exists near 3.58 MHz which is the color subcarrier frequency, moire occurs (see FIG. 8). If an optical low-pass filter that sufficiently attenuates the response in the vicinity of 3.58 MHz is used for removal, the resolution and contrast when using a rigid endoscope cannot be improved even if a solid-state imaging device with high pixels is used.

According to the above-mentioned structure of the present invention, the stacking direction of the image guide fiber bundle is formed at an angle (30 °) with respect to the horizontal scanning direction of the solid-state image pickup device (see FIG. 13). As shown in FIG. 14, the primary frequency spectrum fF of the fiber on the two-dimensional spatial frequency plane is given a certain slope, and the primary frequency spectrum fF and the color subcarrier frequency can be separated in frequency.

A schematic diagram of such a configuration example is shown in FIG. In the figure, (a) is a conventional one, (b) and (c) are the exit end face of the image guide fiber bar bundle of the present invention, the solid-state imaging device 1.
2 and a monitor television 14 are shown, and arrows A and B are also shown.
Indicate the stacking direction of the fibers and the horizontal scanning direction of the solid-state imaging device 12, respectively. A mask (field stop) 27 is installed at the exit end of the fiberscope 2, and this end face image is displayed on the monitor television 14 via the solid-state image sensor 12. 15, in the configuration of FIG. 15B, the entire image guide fiber bundle is rotated by 30 degrees around the optical axis, as compared with the configuration of FIG. The cutout portion 27a of the mask 27 is a guide for performing the angle operation of the endoscope, and is thus set so that the position on the solid-state image sensor 12 does not change. Further, FIG. 11C shows a configuration in which the positions of the image guide fiber bar bundle and the mask 27 are configured in the same manner as in FIG. 11A, and only the solid-state image sensor 12 is rotated by 30 degrees around the optical axis. .

As described above, the moire generated by the interference between the frequency spectrum fF of the fierberscope and the color subcarrier frequency is mechanically removed, in other words, is removed by the structural feature of the fierberscope. Therefore, an optical low-pass filter may be used that has a characteristic of attenuating only the frequency spectrum fF of the fiberscope existing in the vicinity of the sampling point. If used, an endoscopic image excellent in resolution and contrast can be obtained. The moire removing effect can be obtained even when the above configuration is adapted to the endoscope television system dedicated to the fiber optic scope. In addition, the angle of the stacking direction of the image guide fiber bundles with respect to the horizontal scanning direction of the solid-state imaging device is set to the above-mentioned configuration example (30
.Degree.), The primary frequency spectrum fF of the fiber on the two-dimensional spatial frequency plane is given a certain inclination so that the primary frequency spectrum fF and the color subcarrier frequency can be separated in frequency. Set to an angle.

(Sixth Means) An endoscope television system according to the sixth means of the present invention is a rigid scope using at least a fiberscope using an image guide fiber bundle for an image transmission system or a relay lens for an image transmission system. The image obtained by any of the endoscopes is formed on the solid-state image sensor, and the electric signal output from the solid-state image sensor is converted into a television signal by the camera control unit and output. In an endoscopic television system adapted to obtain an endoscopic image, the camera control unit includes an electric circuit for controlling and outputting a signal magnitude of a color difference signal according to a spatial frequency component included in the image, and the electric circuit. And a switching means for selectively operating the circuit according to the characteristics of the image transmission system.

When using a rigid endoscope, in order to remove false color signals as much as possible and improve image resolution and contrast, a single birefringent plate is used and the cutoff frequency is set to the Nyquist limit of the solid-state image sensor. The optical low pass filter described above may be used. Further, even if the luminance signal is processed by the color signal suppressing circuit, the false color signal can be suppressed.

The operation of the color signal suppressing circuit will be described with reference to FIG. FIG. 16A is a block diagram of a main part of the camera control unit 13 using an analog circuit. In the figure, an electric signal output from the solid-state image sensor 12 in the television camera 10 is processed by a sample hold circuit and a γ correction circuit, respectively, and an electric low-pass filter 16 arranged in parallel in the camera control unit 13. And the electric bandpass filter 17 to pass the electric bandpass filter 17 and the electric bandpass filter 17, respectively, to divide the electric signal into luminance and color information. The luminance information is divided by the aperture signal generating circuit 18 into an electric signal for generating an aperture signal for edge enhancement and an electric signal which becomes a luminance signal of a television signal. Further, FIG. 2B is a block diagram of a main part of the camera control unit 13 using a digital circuit. In the figure, an electrical low-pass filter 16 and A /
The electric signal converted into the digital luminance information through the D conversion circuit 20 is input to the aperture signal generation circuit 18, and when the aperture signal generation circuit 18 generates the aperture signal, the absolute value circuit 21 amplitudes of the aperture signal. Takes the absolute value of and adjusts the output intensity of the electric signal that gives color information according to the value with the chroma gain controller 22,
Electrical band pass filter 1 with chroma suppressor circuit 23
The digital color difference signal output from the A / D conversion circuit 20 via the A.D.

By using the color signal suppressing circuit,
When a high frequency component contained in the bright spots of the mucous membrane in the body cavity, which is a general subject when using a rigid endoscope, enters, the intensity of the aperture signal is increased by this high frequency component, and the output intensity of the electrical signal that provides color information is weakened. The false color can be made inconspicuous by adjusting the direction. For this reason, when using a rigid endoscope, even if the cutoff frequency of the optical low-pass filter is set to a higher frequency side than the Nyquist limit of the solid-state image sensor using a single birefringent plate, sufficient false color will be obtained in actual use. Since the prevention effect is obtained, the contrast at the Nyquist frequency of the solid-state image sensor can be improved.

However, when the exit end face of the fierberscope is imaged as a subject and this video signal is subjected to signal processing by the color signal suppression circuit, a high frequency component is contained in the video signal, so that the aperture signal generation circuit 18 There is a problem that the amplitude of the aperture signal to be created becomes large and the chroma gain controller 22 adjusts the signal in the direction of lowering the overall signal level according to this value, that is, as if the image had no color. It was

According to the above construction of the present invention, as shown in FIG. 17, the switching means 24 is provided in the camera control unit 13, and the aperture signal is changed depending on whether the fibrescope is used or the rigid scope is used. The input state of the signal from the creating circuit 18 can be selected. The switching means 24 switches the signal connection between the aperture signal generating circuit 18 and the absolute value circuit 21,
When using the fiber bar scope, it is turned off to cut off both circuits, and when used with a rigid endoscope, it is turned on to connect both circuits. Thereby, color loss of the endoscopic image can be prevented when the fiberscope is used, and the color signal suppressing circuit can be operated when the rigid endoscope is used to obtain an endoscopic image excellent in resolution and contrast.

When the color difference signal output is 90% or less of the normal use state, the endoscopic image seems to have somehow disappeared in color, but it is acceptable in the image observation in actual use. The limit is 50 for normal use.
It has been clarified by experiments that the percentage is (below). Therefore, the switching means 24 is not limited to the ON / OFF switching type as shown in the figure, and the aperture signal generating circuit 18 to the absolute value circuit 21 may be within the allowable limit.
A method of continuously changing the magnitude of the aperture signal input to the terminal may be used. Further, the fiber bar scope to be used may be provided with a discriminating means so that it can be automatically changed according to the fiber scope. Furthermore, the amplitude of the aperture signal is fed back to the switching means to change the characteristics when using the fiberscope,
It may be configured to output a color.

Further, by appropriately using the above-mentioned first to fifth means together with the sixth means of the present invention, it is possible to further enhance the moire removing effect when the fiberscope is used. In addition, if both the characteristics of the resolution and the contrast of the endoscopic image when the fiberscope is used are improved within a certain allowable range, the endoscopic image formed on the solid-state imaging device is Moire can also be removed by slightly blurring the focus.

[0053]

The present invention will be described in detail below with reference to the illustrated embodiments. Regarding the optical low-pass filter for the fiberscope used in the first means of the present invention,
A description will be given in three examples. (First Embodiment) FIG. 18 shows an optical low-pass filter for a fiber bar scope according to this embodiment. In the figure,
Reference numeral 29 is an optical low-pass filter, which is composed of three birefringent plates 29a, 29b, and 29c and has thicknesses of 1.67 mm, 2.88 mm, and 1.67 mm from the object side, respectively. , And has the crystal axis direction shown in FIG.

Low-pass filter 29 having such a configuration
Has the trap characteristics shown in FIG. In the figure, Ux and Uy respectively represent two-dimensional spatial frequencies,
The trap lines 30a, 30b, 30c are respectively provided with the birefringent plate 29.
The frequencies at which the response is 0% are indicated by a, 29b, and 29c. The sampling points are two pixels in the horizontal scanning direction of the solid-state image sensor and four pixels in the vertical direction. That is, assuming that the pitch of one pixel of the solid-state image sensor is (horizontal 9.6 μm × vertical 9.9 μm), the sampling points are (Ux, Uy) = (52.1, 25.
3) (books / mm). In addition, this solid-state image sensor is
Assuming that of the TSC system, the color multi-carrier frequency occurs as points (Ux, Uy) = (29.5, 25.3) (lines / mm). The frequency spectrum fF included in the exit end surface of the image guide fiber bar bundle is about 20 to 80 assuming that the solid-state image sensor has a 1/2 inch size.
Values up to (books / mm) can be taken.

As is apparent from FIG. 19, the trap line 30b is set so as to substantially pass the color subcarrier frequency in consideration of the case where the frequency spectrum fF exists near the color subcarrier frequency. Also, the frequency spectrum fF
Is present near the sampling point, trap line 3
With 0a and 30c, the intensity of the frequency spectrum fF can be sufficiently attenuated. Since the trap line 30a is set to pass near the color subcarrier frequency almost at the same time, the resolution in the horizontal scanning direction is slightly lowered, but it is sufficient for practical use only by using three relatively expensive birefringent plates. It is possible to obtain an excellent moire removing effect.

With the above configuration, it is possible to prevent the occurrence of moire when the fiberscope is used. A similar response can be obtained by using an aspherical lens, a phase filter, or the like instead of the birefringent plates 29a, 29b, 29c.

(Second Embodiment) FIG. 20 shows an optical low-pass filter for a fiber bar scope according to this embodiment. In the figure, 31 is an optical low-pass filter,
This is the four birefringent plates 31a, 31b, 31c, 31d.
, 2.7mm and 2.7m from the object side, respectively.
The thickness is m, 1.7 mm, and 2.3 mm, and the crystal axis direction shown in FIG.

The low-pass filter 31 having such a configuration
Has the trap characteristics shown in FIG. In the figure, Ux and Uy respectively represent two-dimensional spatial frequencies,
The trap lines 32a, 32b, 32c and 32d indicate frequencies at which the response becomes 0% due to the birefringent plates 31a, 31b, 31c and 31d, respectively. Also, the trap line 3
2a ', 32b', 32c ', and 32d' are caused by the repetition of the trap lines 32a, 32b, 32c, and 32d, respectively, and prevent the folding distortion. In addition, the sampling point, the color subcarrier frequency, and the frequency spectrum fF included in the exit end face of the image guide fiber bundle
Are the same as those in the first embodiment.

With the above configuration, the trap lines 32a, 32b passing through the color multi-carrier frequency and the sampling point,
32c and 32d have the same effect as the optical low-pass filter 29 of the first embodiment described above, and further, by tilting the crystal axis direction of the birefringent plate as a whole, the aliasing distortion is also produced by utilizing the repeated effect of the trap line. It can be prevented.

(Third Embodiment) FIG. 22 shows an optical low-pass filter for a fiber bar scope according to this embodiment. In the figure, 33 is an optical low-pass filter,
This is four birefringent plates 33a, 33b, 33c, 33d
2.52 mm and 1.52 respectively from the object side.
It has thicknesses of mm, 1.63 mm, and 2.62 mm, and has the crystal axis direction shown in FIG.

Low-pass filter 33 having such a configuration
Has the trap characteristics shown in FIG. In the figure, Ux and Uy respectively represent two-dimensional spatial frequencies,
The trap lines 34a, 34b, 34c, 34d indicate frequencies at which the response becomes 0% due to the birefringent plates 33a, 33b, 33c, 33d, respectively. The sampling point, the color subcarrier frequency, and the frequency spectrum fF included in the exit end face of the image guide fiber bundle are all the same as those in the first embodiment.

According to this embodiment, different trap lines pass through the color multi-carrier frequency and the sampling point, so that the frequencies existing in the vicinity of each frequency are not unnecessarily lowered in the response in the horizontal scanning direction. The intensity of the spectrum fF can be effectively attenuated.

Next, an embodiment of the endoscope television system used in the second means of the present invention will be described. (Fourth Embodiment) FIGS. 24 (a) and 24 (b) are perspective views of a main part of such an endoscope television system. In the figure, the user has two types of camera heads, a television camera head 15a having a built-in optical low-pass filter suitable for the fiberscope and a television camera head 15b having a built-in optimal optical low-pass filter for the rigid endoscope. It can be selected according to the endoscope to be used and can be inserted into and removed from the camera control unit 13.

The one shown in FIG. 11A is a camera control unit 1 in the television camera heads 15a and 15b.
3 has a built-in electric circuit for obtaining an electric matching with the No. 3, and the electric characteristics can be adjusted according to the camera control unit 13. Also, FIG.
In the case shown in (1), even if a plurality of camera heads 15a and 15b are attached to one camera control unit 13,
TV camera head 15 so that color reproducibility does not change
The electrical characteristics can be corrected on the sides of a and 15b, and a plurality of television camera heads can be simultaneously attached to one camera control unit 13. In this case, since the camera control unit 13 processes the signals output from the plurality of TV camera heads 15a and 15b by one signal processing system, the switch 40 for selecting the TV camera head to be signal processed. Is provided. By configuring a plurality of TV camera heads to be used at the same time in this manner, switching during surgery becomes easy, and even if one camera head is broken during surgery, surgery can be continued using the other camera head. And so on.

In this case, the optical low-pass filter most suitable for the fiberscope has, for example, the structure described in the first to third embodiments, and the most suitable optical low-pass filter for the rigid endoscope is as follows. The one shown in FIG. 25 is exemplified. This optical low-pass filter 35 is
One birefringent plate 3 having the crystal axis direction shown in FIG.
As shown in FIG. 26, the cutoff frequency of 5b is 52.1 (lines / m) which is the Nyquist limit of the solid-state image sensor.
m). Reference numeral 35a is a glass plate for correcting the optical path length.

According to the present embodiment, for example, as a solid-state image pickup device, the pitch size of one pixel is Px = 9.6 in the horizontal direction.
μm and Py = 9.9 μm in the vertical direction, the horizontal Nyquist frequency is 52.1 (lines / m
m) is calculated. Therefore, while the optical low-pass filter for the fiberscope has a contrast of almost 0% at 29.5 (lines / mm), when the optical low-pass filter for the rigid endoscope is used, the response value at 3.58 MHz is obtained. Is MTF (3.58MHz) = cos {(π / 2) × (29.5 / 5
2.1)} ≈ 63%, which is very large, and the advantage of increasing the number of pixels in the solid-state image sensor can be fully utilized. Further, since the TV camera head can be replaced, the TV camera head is prevented from being upsized and the deterioration of image quality due to intrusion of dust is prevented.

FIG. 27A shows a television camera head 15 incorporating an optical low-pass filter dedicated to a rigid endoscope.
FIG. 3B is a perspective view of a main part of a rigid scope dedicated to television observation, which uses b and the imaging lens 9 for directly integrating the rigid scope from which the eyepiece 41 of the eyepiece is removed. Also, FIG.
Is a fiber for television observation using a television camera head 15a having a built-in optical low-pass filter dedicated to the fiberscope and an imaging lens 9 for directly integrating the fiberscope from which the eyepiece 41 of the eyepiece is removed. It is a principal part perspective view of a scope.

Next, embodiments of the optical low-pass filter for the fiberscope used in the endoscope television system used in the third to fifth means of the present invention will be described. (Fifth Embodiment) In the endoscope television system according to the third to fifth means, the moire caused by the interference between the frequency spectrum fF of the fiberscope and the color subcarrier frequency is an electric means for adjusting the signal level, or a signal. It is designed to be removed by using a mechanical means for switching. Therefore, the optical low-pass filter of this embodiment has no characteristic for removing moire, but has a characteristic of sufficiently attenuating the intensity of the frequency spectrum fF of the fiberscope existing in the vicinity of sampling.

FIG. 28 shows an optical low-pass filter according to this embodiment. In the figure, 36 is an optical low-pass filter, which is composed of four birefringent plates 36a, 36.
b, 36c, 36d, each of which is 1.
81 mm, 1.98 mm, 1.57 mm, 1.51 mm
And has the crystal axis direction shown in FIG. FIG. 29 shows the trap characteristic of the optical low pass filter 36. Note that FIG.
, The frequency spectrum fF contained in the sampling point and the exit end face of the image guide fiber bundle
Are all the same as in the first embodiment.

By combining the optical low-pass filter having the above characteristics with the above-mentioned electrical means or mechanical means, the advantage of increasing the number of pixels of the solid-state image pickup device can be utilized, and the resolution and contrast are excellent. It is possible to obtain an endoscopic image. The electrical and mechanical means for removing moiré are applicable to all composite television signal output systems, and N and
An output method other than the TSC, PAL, and SECAM methods may be used, and for example, it may be used for HD-TV.

As another configuration for electrically removing moire when using a fiberscope, there is a use of a still image recording device for recording an endoscopic image converted into an image signal by a solid-state image pickup device for each field. In this case, if an image is recorded on a video, a printer, or the like via the still image recording device, the saturation of the moire is reduced, and the moire generated when the fiberscope is used can be made inconspicuous.

Next, used in the sixth means of the present invention,
An embodiment of an endoscope television system using a camera control unit having a color signal suppression circuit will be described. (Sixth Embodiment) The camera control unit using the color signal suppressing circuit has been described with reference to FIGS. 11 and 16. However, if such a camera control unit is used, for example, one sheet used for a rigid endoscope can be used. Using a birefringent plate, as shown in FIG. 30 (a), the cutoff frequency is 52.1 (lines / m) which is the Nyquist limit of the solid-state imaging device.
The optical low-pass filter set in m) is shown in FIG.
As shown in, the cutoff frequency is 56.3 (pieces / mm)
Even if the optical low-pass filter is set to, the false color removal effect is practically sufficient.

For example, 1 / signal output in the NTSC system
3.58 when using a 2-inch size solid-state image sensor
When the response at MHz is 63%, MTF (3.58MHz) = cos {(π / 2) × (29.5 / 5) is obtained by using the camera control unit and the optical low pass filter.
6.3)} ≈68%, and the contrast can be improved as a whole. Also, the response at the Nyquist limit of the solid-state image sensor was 0%, but MTF (52.1 lines / mm) = cos {(π / 2) × (29.5 /
56.3)} ≈15%, and the resolution can be improved.

The cut-off frequency is set to 56.3 (lines / mm) as an optical low-pass filter used in a camera control unit having a color signal suppression circuit, but it depends on the characteristics of the color signal suppression circuit. If the optical characteristics are set so that false color does not become a problem when using a rigid endoscope, set the cutoff frequency by the optical low-pass filter to any frequency higher than the Nyquist limit of the solid-state image sensor. Alternatively, the optical low pass filter may not be used.

As described above, when the camera control unit having the color signal suppressing circuit is used, the effect more than that of the solid-state image pickup device having a higher number of pixels, that is, the improvement in the resolution and the contrast can be obtained, but the subject including a large amount of high frequency components is obtained. When the image is captured and signal-processed, the amplitude of the aperture signal is output with a large value, so that the endoscopic image is a colorless image.

FIG. 31 is a block diagram of the essential parts of the camera control unit of this embodiment. In the figure, the camera control unit 13 has two types of circuits, that is, a color signal suppressing circuit and a normal electric circuit, and an image signal input to these circuits is selectively switched by the switching means 24 at the input destination circuit. It can be switched. The switching means 24 is arranged in the next stage of the solid-state image sensor 12, but if the same effect as that shown in the figure is obtained,
It may be arranged at an appropriate position from the input side of the solid-state image sensor to the cathode ray tube of the monitor television.

According to this embodiment, by arranging the switching means capable of selecting the operation of the color signal suppression circuit according to the endoscope used at an appropriate position in the circuit, the above-mentioned endoscope image Color loss can be prevented. When the switching means is operated, the user may select it according to the endoscope used. In addition, a mechanism for determining the type of the endoscope is provided, and a mechanism for feeding back the information to the switching means is provided, so that the operation state of the color signal suppression circuit can be checked when each endoscope is connected. Can be controlled.

[0078]

As described above, according to the present invention, it is possible to prevent the generation of moire and color-free images when using a fiberscope, and to obtain an endoscopic image excellent in resolution and contrast when using a rigid scope. The obtained endoscopic television system can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing an output waveform of a solid-state image pickup device when an optical element of a first means in an endoscope television system of the present invention is arranged in an image pickup optical path.

FIG. 2A is a diagram showing an example of an optical system when a fiberscope of the second means is used in the endoscope television system of the present invention, and FIG. 2B is a diagram showing frequency characteristics.

FIG. 3A is a diagram showing an example of an optical system when a rigid scope of the second means is used in the endoscope television system of the present invention;
(B) is a figure which shows a frequency characteristic.

FIG. 4 is a diagram showing a configuration example of second means in the endoscope television system of the present invention.

FIG. 5 is a diagram showing another configuration example of the second means in the endoscope television system of the present invention.

FIG. 6 is a diagram showing still another configuration example of the second means in the endoscope television system of the present invention.

FIG. 7 is a diagram showing still another configuration example of the second means in the endoscope television system of the present invention.

FIG. 8 is a diagram showing frequency characteristics in an NTSC endoscopic television system connectable to both a fiberscope and a rigid endoscope.

FIG. 9 is a diagram showing frequency characteristics of a third means in the endoscopic television system of the present invention.

FIG. 10 is a third view of the endoscope television system of the present invention.
It is a figure which shows the output waveform of the solid-state image sensor of the means.

FIG. 11 is an explanatory diagram for creating an aperture signal, where (a) is a luminance signal, (b) is an aperture signal,
(C) is an aperture signal obtained by superimposing (b) on (a).

FIG. 12 is a diagram showing a contrast of a brightness signal when a peak of an aperture signal is delayed, (a) is a fiberscope, and (b) is a rigid scope.

FIG. 13A is a diagram illustrating an exit end surface when a fiber bundle is configured to form a constant angle, and FIG. 13B is a diagram illustrating a scanning direction of a solid-state image sensor.

14 is a diagram showing frequency characteristics of an image signal when the fiber bundle shown in FIG. 13 is used.

15A is a view showing an exit end face of a fiberscope according to a fifth means of the present invention and FIG. 15A is a view showing an imaging direction of a solid-state imaging device;

16A is a block diagram of a television signal creation circuit using an analog circuit, and FIG. 16B is a block diagram of a television signal creation circuit using a digital circuit including a color signal suppression circuit.

FIG. 17 is a sixth view of the endoscope television system of the present invention.
It is a diagram showing a configuration example of the means.

FIG. 18 is a diagram showing an optical low-pass filter according to a first embodiment of the present invention, (a) is a schematic plan view, and (b) is a diagram showing a crystal axis direction of a birefringent plate.

19 is a diagram showing a trap characteristic of the optical low-pass filter of FIG. 18 in a two-dimensional frequency plane.

20A and 20B are diagrams showing an optical low-pass filter according to a second embodiment of the present invention, FIG. 20A is a schematic plan view, and FIG. 20B is a diagram showing a crystal axis direction of a birefringent plate.

21 is a diagram showing a trap characteristic of the optical low-pass filter of FIG. 20 in a two-dimensional frequency plane.

22A and 22B are views showing an optical low-pass filter according to a third embodiment of the present invention, wherein FIG. 22A is a schematic plan view and FIG. 22B is a view showing a crystal axis direction of a birefringent plate.

23 is a diagram showing a trap characteristic of the optical low-pass filter of FIG. 22 in a two-dimensional frequency plane.

FIG. 24 is a perspective view of a main part of a fourth embodiment of the present invention,
(A) is a method of inserting and removing one camera head,
In (b), a plurality of camera heads are installed.

25A and 25B are views showing an optical low-pass filter according to a fourth embodiment, wherein FIG. 25A is a schematic plan view and FIG. 25B is a view showing a crystal axis direction of a birefringent plate.

26 is a diagram showing a trap characteristic of the optical low-pass filter of FIG. 25 in a two-dimensional frequency plane.

27A and 27B are perspective views of a main part showing another configuration of the fourth embodiment, in which FIG. 27A corresponds to a rigid endoscope, and FIG. 27B corresponds to a fiberscope.

28A and 28B are diagrams showing an optical low-pass filter according to a fifth embodiment of the present invention, wherein FIG. 28A is a schematic plan view and FIG. 28B is a diagram showing a crystal axis direction of a birefringent plate.

29 is a diagram showing a trap characteristic of the optical low-pass filter of FIG. 28 in a two-dimensional frequency plane.

FIG. 30A is a diagram showing frequency characteristics of an optical low-pass filter in which the cutoff frequency is set to the Nyquist limit, and FIG. 30B is a diagram showing frequency characteristics of an optical low-pass filter in which the cutoff frequency is set to the Nyquist limit or higher. .

FIG. 31 is a block diagram of a television signal creation circuit according to a sixth embodiment of the present invention.

FIG. 32 is a configuration diagram of a conventional endoscope television system.

FIG. 33 is another configuration diagram of the conventional endoscope television system.

FIG. 34 is a diagram showing still another configuration of the conventional endoscope television system.

FIG. 35 is a diagram showing still another configuration of the conventional endoscope television system.

FIG. 36 is a diagram showing the exit end surface of the image guide fiber bundle and the imaging direction of the solid-state imaging device.

37 is a diagram showing frequency characteristics of an image signal when the fiberscope shown in FIG. 36 is used.

FIG. 38 is a view showing an exit end face of an image guide fiber bundle having a random structure.

FIG. 39 is a diagram showing one configuration of a color filter.

FIG. 40 is a diagram showing frequency characteristics of an image signal output from the solid-state imaging device via the color filter of FIG. 39.

41 is a diagram showing frequency characteristics of an image signal when the fiberscope of FIG. 36 is imaged by the solid-state imaging device using the color filter of FIG. 39.

42A shows an output waveform of an NTSC solid-state image sensor, and FIG. 42B shows an output waveform of an NTSC solid-state image sensor when a luminance signal component has a component substantially equal to a color subcarrier frequency. It is a figure.

43 is a diagram showing the color subcarrier frequencies of FIG. 42 on a two-dimensional spatial frequency.

[Explanation of symbols]

 1 Fiberscope 3 Rigid Mirror 12 Solid-state Image Sensor 13 Camera Control Unit 14 Monitor Television 11, 29, 31, 33 Optical Low-pass Filter

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Kimihiko Nishioka 2-43-2 Hatagaya, Shibuya-ku, Tokyo Olympus Optical Co., Ltd.

Claims (6)

[Claims] 1. An endoscope television system in which an image appearing on the exit end face of an image guide fiber bundle is formed on a solid-state image pickup device so that the image can be observed on a monitor television. Having an optical characteristic of sufficiently attenuating the frequency spectrum peculiar to the image guide fiber bundle passing through, and an optical characteristic of sufficiently attenuating the frequency spectrum peculiar to the image guide fiber bundle passing near the sampling frequency of the solid-state imaging device. An endoscope television system characterized in that an optical element having the above is arranged in an imaging optical path. 2. A fiberscope using at least an image guide fiber bundle for an image transmission system or a rigid scope using a relay lens for an image transmission system, which is obtained by any of the endoscopes described above. In an endoscope television system in which an image is formed on a solid-state image sensor, an electric signal output from the solid-state image sensor is converted into a television signal by a camera control unit and the television signal is output to obtain an endoscopic image. An optical element having an optical characteristic capable of sufficiently attenuating a response of a sampling point of the solid-state image sensor, and an optical characteristic capable of sufficiently attenuating a frequency spectrum peculiar to the image guide fiber bundle passing near a color subcarrier frequency, and The frequency specific to the image guide fiber bundle passing near the sampling frequency of the solid-state image sensor Endoscopic television system characterized in that as selected and used in the imaging optical path in accordance with any of the optical elements of the optical properties, such as allowed to sufficiently attenuated, the endoscope using the spectrum. 3. An endoscopic image appearing at least on the exit end face of the image guide fiber bundle is formed on a solid-state image sensor, and an electric signal output from the solid-state image sensor is converted into at least a composite television signal and output. In an endoscopic television system for obtaining an endoscopic image, at the time of outputting the composite signal, an electrical signal that selects only a signal in the vicinity of a color subcarrier frequency of the luminance signal of the composite signal and lowers the level of the signal An endoscopic television system having means. 4. An endoscopic image appearing at least on the exit end face of the image guide fiber bundle is formed on a solid-state image sensor, and an electric signal output from the solid-state image sensor is converted into at least a composite television signal and output. In an endoscopic television system adapted to obtain an endoscopic image, if a frequency spectrum specific to the image guide fiber bundle exists near a color subcarrier frequency of the composite television signal, the composite television signal is converted into a component. An endoscopic television system provided with an electric means for switching to a television signal. 5. An endoscopic image appearing on the exit end face of an image guide fiber bundle having at least a hexagonal close-packed structure is formed on a solid-state image sensor, and an electric signal output from the solid-state image sensor is at least a composite television signal. In the endoscopic television system, which is adapted to convert and output to obtain an endoscopic image, when the frequency spectrum peculiar to the image guide fiber bundle exists in the vicinity of the color subcarrier frequency of the composite television signal, the image An endoscope television system, wherein the stacking direction of the guide fiber bundle is configured to form an angle of approximately 30 degrees with respect to the horizontal scanning direction of the solid-state imaging device. 6. A fiberscope using at least an image guide fiber bundle for an image transmission system or a rigid scope using a relay lens for an image transmission system, which is connectable to an image obtained by any one of the endoscopes. An endoscope television system in which an image is formed on a solid-state image sensor, an electric signal output from the solid-state image sensor is converted into a television signal by a camera control unit, and the television signal is output to obtain an endoscopic image. The camera control unit includes an electric circuit for controlling and outputting the magnitude of the color difference signal according to the spatial frequency component contained in the image, and a switching for selectively operating the electric circuit according to the characteristics of the image transmission system. An endoscope television system comprising: