JPH0228966B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the improvement of images in endoscopic devices, and in particular to the prevention of moiré fringes and the reduction of optical fiber mesh patterns caused by gaps between the cores of each optical fiber.

Originally, it is desirable for an endoscope to be able to display a clear image of the surface of the body to be observed (image of the affected area) due to its purpose of use. However, the image guide of an endoscope is a regularly arranged optical fiber consisting of a core made of a high refractive index material and a cladding layer surrounding the core with a low refractive material. The image is transmitted only by light passing through the core, and no light passes through the cladding layer or the gaps between the cladding layers, resulting in a black mesh pattern on the screen. If the ratio of the area occupied by this mesh pattern portion is large, the observed image becomes difficult to be recognized as an image, which impedes proper treatment. Furthermore, the observed image is converted into a video signal via an image sensor.
In addition to the above-mentioned problem, prevention of moire fringes becomes an important issue in endoscope devices equipped with video devices that display images on a display device such as a CRT. When moire fringes occur, the image of the affected area on the display becomes unclear, hindering proper treatment for the observer, and even endangering the patient's life. Therefore,
In endoscope devices, it is strongly required to reduce the black mesh pattern caused by gaps between fibers and to prevent the occurrence of moire fringes. As a solution to the above problem, a method has been proposed in which the eyepiece is minutely vibrated in the optical axis direction in an optical viewfinder endoscope in which images transmitted from an image guide are directly observed through the eyepiece. However, the above-mentioned method cannot be adopted in an endoscope apparatus equipped with a video device, and it is also not very effective as a measure to prevent moire.

Therefore, in view of the above-mentioned circumstances, the present invention attempts to solve the above-mentioned problems at once by micro-vibrating an image sensor that photoelectrically converts an image of an affected area in an endoscope device equipped with a video device in the optical axis direction.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing one embodiment of the present invention. In the figure, 1 is an image guide in which optical fibers consisting of a core and a cladding layer surrounding it are regularly arranged, and 2 is a transmission from the image guide. 3 is an eyepiece; 4 is an imaging lens for forming an image of one affected area of the image divided into two by the half mirror 2 on an image sensor 5; 5; 6 is an image pickup device in which a plurality of photodetectors are arranged in a matrix and has a light receiving section that converts an image of the affected area into an electrical signal and a scanning circuit that scans the electrical signal from the light receiving section; 6 is used to hold the imaging device 5; mount, 7 is a bimorph plate consisting of two flat plates 7a made of piezoelectric material and three flat electrodes 7b sandwiching the piezoelectric flat plates 7a, respectively;
8 is a mount for fixing the end of the bimorph plate 7;
Reference numeral 9 indicates an AC power source for vibrating the bimorph plate 7 at a predetermined frequency. The image of the affected area transmitted via the image guide 1 is transferred to the half mirror 2.
The beam is divided into two by the eyepiece lens 3, and one beam is
observed by the observer via the The other optical image flux passes through the imaging lens 4 and forms an image on the light-receiving surface of the image pickup device 5, and after being photoelectrically converted, it is converted into a video signal via an amplifier, a control circuit, and an encoder. and CRT,
It is projected on a display device such as an LCD and observed as an electronic image. In this configuration, the observer can also directly observe the affected area image through the eyepiece lens 3.
An electronic image imaged on a display device can also be observed, or both an optical image and an electronic image can be observed simultaneously. The bimorph plate 7 is two flat plates 7 made of piezoelectric material such as barium titanate.
Three plate-shaped electrodes 7b are arranged so as to sandwich each electrode 7b, and a voltage of the same polarity is applied to the two electrodes at both ends, and a voltage of the opposite polarity is applied to the middle electrode. It is configured. When a constant frequency and a constant voltage are applied from the AC power supply 9, an electric field whose direction changes alternately according to the frequency is applied to the two piezoelectric flat plates 7a. As a result, the piezoelectric flat plate 7a generates mechanical strain in the direction perpendicular to the direction of the electric field.Since both ends of the piezoelectric flat plate 7a are fixed, the piezoelectric flat plate 7a cannot change in the strain direction, and is distorted up and down in the direction of the electric field. Since the applied electric field changes depending on the frequency, the bimorph plate 7
vibrates in the electric field direction, that is, in the optical axis direction. This vibration is transmitted to the image sensor 5 attached to the bimorph plate via the mount 6, and the image sensor 5 vibrates in the optical axis direction. Any frequency can be obtained by changing the frequency of the AC power source 9, the applied voltage, the thickness of the piezoelectric flat plate, etc., and the amplitude can also be obtained by changing the applied voltage, the thickness of the piezoelectric flat plate, etc. Can be done. When the center point position of vibration matches the imaging position of the imaging lens 4, the image sensor 5 repeats vibration in the optical axis direction centering on the focused position, and the affected area is detected at the focused position and the positions before and after this. The image will be captured continuously, and at certain times in chronological order, the image will be captured at the focus position.
Sometimes I end up taking pictures at a position that is slightly off from the focal point. Since this operation is performed continuously, the in-focus state and the out-of-focus state occur almost alternately, so that the observer's eyes hardly notice any out-of-focus state. On the other hand, when the mesh pattern of optical fibers is out of focus, its contrast decreases and its relative strength is weakened. This makes it possible to make the mesh pattern of the optical fibers less noticeable without reducing the clarity of the screen. When an image is taken with moire fringes out of focus, the intensity of the moire fringes decreases, and the flashing stimulus to the observer's eyes weakens, weakening the moire fringes without reducing the clarity of the screen. be able to.

By vibrating the half mirror 2 in a direction perpendicular to the mirror surface as shown by the arrow 10, it is possible to vibrate it back and forth around the focus position, but due to the vibration, the image changes left and right with respect to the optical axis. It vibrates and is not effective. Another possible method is to vibrate the imaging lens 4 in the optical axis direction.
The imaging lens must allow light to pass through it, and it is undesirable to hold and vibrate the periphery of the lens due to mechanical structural problems. On the other hand, since the image sensor only receives light and does not need to transmit it, it can be easily vibrated in the optical axis direction from the back as shown in the figure, and can be vibrated using an extremely simple method.

Next, consider the vibration frequency. The display device displays on the screen a value obtained by integrating the amount of light within the time required to create one frame of screen. Therefore, if the frequency of the image sensor is lower than the readout frequency of the display device, it is undesirable to produce a continuous screen that is out of focus. When the frequency of the image sensor matches the readout frequency of the display device, one frame of the screen is composed of a value obtained by integrating one cycle of the vibration of the image sensor. This results in the same result as integrating a screen in which in-focus and out-of-focus states appear almost alternately. Therefore, the frequency must be at least higher than the readout frequency of the display device. Furthermore, if the frequency of the image sensor is set to an integral multiple of the readout frequency of the display device, the period of one frame of the screen of the display device matches the period of an integral multiple of the vibration of the image sensor, which greatly simplifies the configuration of the control circuit. be able to. If the amplitude of the vibration of the image sensor is too large, the focus will be too large, which is undesirable, but a minute vibration with an amplitude of about 400 μm can produce a sufficient effect.

As explained above, in an endoscope device equipped with a video device, the black mesh pattern of optical fibers can be reduced with a simple configuration by slightly vibrating the image sensor that converts the surface image of the object to be observed into an electrical signal in the optical axis direction. At the same time, a clear image with reduced moire fringes can be obtained.

[Brief explanation of drawings]

The figure shows a configuration diagram of an endoscope apparatus according to the present invention. 1... Image guide, 2... Half mirror,
3... Eyepiece lens, 4... Imaging lens, 5... Image sensor, 6... Image sensor mount, 7... Bimorph board, 8... Bimorph board mount, 9...
…AC source.

Claims (1)

[Scope of Claims] 1. In an endoscope apparatus including an image sensor that converts an optical image transmitted from an image guide into an electrical signal, and a device that converts the electrical signal from the image sensor into a video signal, the image sensor An endoscope device that converts an optical image into an electrical signal while vibrating in the optical axis direction. 2. The endoscope device according to claim 1, wherein the image sensor is vibrated in the optical axis direction at a frequency that is the same as or higher than a readout frequency of a display device that displays the video signal as an electronic image. . 3. The endoscope device according to claim 1, wherein the image sensor is vibrated in the optical axis direction at a frequency that is an integral multiple of a readout frequency of a display device that displays the video signal as an electronic image.