JPH0659195A - Optical system device for endoscope - Google Patents

Abstract

PURPOSE:To remove a ghost occurring due to irregular reflection in a prism by a light shielding means. CONSTITUTION:In the prism 16 making incident the luminous flux from an objective lens system 12 and leading the luminous flux to a CCD 19, the light shielding means shielding a beam 100 incident on the CCD 19 through a reflection optical path excepting the reflection optical path set by the prism is provided. As the light shielding means, those as a light shielding plate 20, a light shielding coating film arranged on an incident surface, a holding tool of a lens barrel or the light shielding plate formed integrally in a lens holding tool, and further, a light shielding film formed on a low-pass filter, etc., may be adopted. Moreover, an air groove formed on a position shielding the unneeded beam 100 in the prism 16 as well is possible, and by these light shielding means, the beam 100 causing a ghost is removed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system device for an endoscope, and more particularly to a structure of an optical system device for forming an image obtained from an observation window on a solid-state image pickup device using a prism.

[0002]

2. Description of the Related Art An electronic endoscope apparatus is known in which an electronic endoscope (electronic scope) is inserted into a body to be observed and an image of the body to be observed is displayed on a monitor. It is formed by guiding an image captured by a window, an objective lens or the like to a solid-state image sensor, for example, a CCD (Charge Coupled Device).

FIG. 6 shows the structure of a conventional optical system device for an electronic endoscope. In the figure, an objective lens system 2 is connected to an observation window 1 arranged at the tip of the electronic endoscope. Is
A prism 3 is arranged at the subsequent stage of the objective lens system 2.
In addition, the prism 3 is covered with C through a cover glass 4.
A CD 5 is attached, and the CCD 5 is configured to form an image within the image area E shown in the figure. Therefore, the light flux in the horizontal direction that has entered the observation window 1 and the objective lens system 2 is bent in the vertical direction by the prism 3 and reaches the image area E of the CCD 5, and the object imaged in this image area E is imaged. The image in the observation body will be displayed on the monitor after signal processing.

[0004]

By the way, in the above-mentioned conventional endoscope apparatus, as shown in FIG. 6, the light beam incident on the prism 3 reaches the image area E of the CCD 5 after being reflected by the slope 3A. Is the regular optical path. However, for example, a part of the light ray 100 that has passed through the outer peripheral portion of the prism 3 is reflected by the slope 3A and then the incident surface 3B.
There is a problem in that the light is further reflected on the rear surface and reaches the image area E of the CCD 5, which causes a ghost.

That is, as shown in FIG. 7, recently, C
Due to the miniaturization and high density of the CD 5, the image area E of the CCD 5 is set so as to be inscribed in the incident light area (visual field area) 200 formed by the optical system member (the chain line 6 is the monitor screen). Accordingly, the size of the prism 3 is also reduced accordingly, and the diameter of the electronic endoscope is reduced accordingly. However, in this case, since the incident light area 200 is wider than the image area E, an originally unnecessary light ray also enters the prism 3 like the light ray 100 in FIG. 100 is reflected by the rear surface of the incident surface 3B and reaches the image area E. As a result, a ghost 300 is generated at the end of the image area E as shown in FIG. 7, and the image becomes difficult to see.

In the above case, the prism 3 shown in FIG.
Although it suffices to cut a portion other than the image area E shown in (1), processing and assembling the prism 3 as close as possible to the boundary of the effective light beam is as follows.
It is difficult to manufacture the prism 3 and, in addition, an outer peripheral space is required to connect with the lens barrel holding the objective lens system 2 in the previous stage. Therefore, it is impossible to solve the above problem by cutting the outer circumference of the prism 3.

The present invention has been made in view of the above problems, and an object thereof is to provide an endoscope optical system device capable of eliminating a ghost caused by irregular reflection in a prism.

[0008]

In order to achieve the above object, the invention according to the first aspect of the present invention is such that an objective lens system connected to a distal end observation window and a light beam from this objective lens system are incident on the objective lens system. A prism for guiding this light flux to the solid-state image sensor,
In the endoscope optical system device having a light-shielding means for blocking light that passes through the outer peripheral portion of the prism and is incident on the solid-state imaging device by a reflected light path other than the reflected light path set by the prism. It is characterized by

According to a second aspect of the present invention, the light-shielding means is a light-shielding mask formed of a light-shielding plate or a light-shielding film, and the light-shielding mask is provided on the incident surface of the prism or in the preceding stage thereof. And According to a third aspect of the present invention, the light-shielding means is configured by forming a light-shielding film on a low-pass filter provided before the prism. According to a fourth aspect of the invention, the light shielding means is
An air groove for blocking an optical path other than the regular reflected optical path is formed in the prism.

[0010]

According to the above construction, the light-shielding mask is provided at the incident surface of the prism or at the position blocking the optical path of unnecessary light rays in the preceding stage. As this light-shielding mask, the light-shielding plate or the light-shielding plate arranged on the incident surface is used. It may be a coating film, or a light shielding plate formed integrally with the holder of the lens barrel or the lens holder, or a light shielding film formed on a low pass filter. Furthermore, inside the prism, an air groove may be formed at a position that blocks an optical path of an unnecessary ray, and these configurations remove the ray that causes a ghost.

[0011]

FIG. 1 shows the configuration of an optical system device for an electronic endoscope according to a first embodiment. As shown in the drawing, in the optical system device, an objective lens is connected to an observation window 11. Lens system 12
Is provided. A diaphragm 13 is provided in the objective lens system 12.
The observation window 11 and the objective lens system 12 are held by a cylindrical lens holder 14 to form a lens barrel. The lens barrel is held by a cylindrical lens barrel holder 15, a prism 16 is attached to the rear stage of the lens barrel holder 15, and a cover glass 18 is provided on the bottom surface side of the prism 16.
The CCD 19 is connected via. In the CCD 19, as in the conventional case, the image of the object to be observed is formed in the image area E.

In the first embodiment, the light shielding plate 20 is arranged on the incident surface of the prism 16 of the optical system device having such a structure. As shown in FIG. 2, the light shielding plate 20 has a rectangular opening 21 having a size corresponding to the image area E of the CCD 19, and a light beam forming a reflected light path other than the regular reflected light path by the outer peripheral frame portion. It is designed to shut off. In the case of the embodiment, as shown in the figure, there is a ray 100 that causes a ghost only in the upper part of the prism 16 and such a ray does not exist in the lower part, so it is not necessary to provide a light shielding plate on the lower side. The light shielding plate 20 is formed over the lower side in consideration of the ease of manufacturing and assembling.

According to this, the light beam 11 passing through the regular optical path
Although 0 and 120 reach the image area E of the CCD 19 after being reflected by the inclined surface 16A of the prism 16, light rays other than the normal optical path, that is, the light ray 100 reflected again by the incident surface 16B of the prism 16 are shielded by the light shielding plate 20. Is cut off by.
Therefore, unlike the conventional case, a ghost does not occur at the edge of the screen. Further, instead of the light shielding plate 20, it is possible to form a light shielding film on the entrance surface 16B of the prism 16 by coating, and the same light shielding effect can be obtained by this light shielding coating film.

FIG. 3 shows the structure of a second embodiment of the present invention. In this second embodiment, a light shielding plate is integrally formed with a conventional constituent member. That is, as shown in the figure, the light shielding plate 23 protruding inward is integrally formed at the end of the lens barrel holder 15 arranged in front of the prism 16, and this also allows the regular light shielding plate 23 to be formed. It is possible to block light rays 100 that form an optical path other than the optical path. Further, as shown by a chain line, it is possible to integrally form the light shielding plate 24 on the lens holder 14 that constitutes the lens barrel.

FIG. 4 shows the configuration of the third embodiment. In this third embodiment, a light-shielding film is formed on a low pass filter. That is, as shown in FIG.
In the preceding stage of 6, for example, a polarizing plate that allows light in the vertical direction, an interference plate,
A low-pass filter 26 is provided in which a polarizing plate that transmits light in the lateral direction is attached. The low-pass filter 26 removes unnecessary incident light. In the third embodiment,
A light shielding film 27 is formed on the incident surface of the low pass filter 26 by coating. This also makes it possible to block the ray 100 that causes a ghost.

FIG. 5 shows the configuration of the fourth embodiment. In the fourth embodiment, the prism 16 itself is provided with light-shielding means for air grooves. That is, as shown in the drawing, the prism 16 is arranged in an optical path other than the regular optical path, in the case of the embodiment, in the optical path through which the light ray 100 passes,
A V-shaped groove 28 is formed from the inclined surface 16A of the prism 16. According to this, since the inside of the V-shaped groove 28 becomes an air layer, the light ray 100 is blocked by the air layer of the V-shaped groove 28. Further, instead of the above V-shaped groove 28, the prism 1
It is possible to form the V-shaped groove 29 at a position where the light ray 100 is blocked from the incident surface 16B of No. 6 of FIG. The V-shaped grooves 28 and 29 may be U-shaped or other shapes.

For example, as shown by the chain line in FIG. 5, a right triangle triangular groove 30 may be formed on the slope 16A of the prism 16 so that only the portion of the slope 16A where the light beam 100 is reflected is cut.

Although the prism 16 in the above embodiment is a right triangle, the prism 1 having another shape is used in the endoscope.
6 can be used. In this case, the optical path that causes the ghost is different from that in the above-mentioned embodiment, but the ghost can be effectively removed by providing the light shielding plate at a position that shields the light other than the regular optical path by the peripheral light. Is.

[0019]

As described above, according to the present invention,
A light-shielding plate or light-shielding coating film disposed on the entrance surface of the prism, a light-shielding plate formed integrally with the holder of the lens barrel or a lens holder, and further, a light-shielding film formed on the low-pass filter, and further inside the prism. Since a light blocking means such as an air groove formed at a position to block unnecessary light rays is provided,
With this light-shielding means, it is possible to eliminate the ghost that has conventionally occurred at the edge of the screen. Moreover, there is an advantage that the diameter of the electronic endoscope can be reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of an endoscope optical system device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of a light shielding plate according to the first embodiment.

FIG. 3 is a sectional view showing a configuration of a second exemplary embodiment of the present invention.

FIG. 4 is a sectional view showing a configuration of a third exemplary embodiment of the present invention.

FIG. 5 is a sectional view showing the configuration of a fourth exemplary embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a configuration of a conventional endoscope optical system device.

FIG. 7 is a diagram showing a relationship between an incident light area of an observation window and an image area of a CCD.

[Explanation of symbols]

 1, 11 ... Observation window, 2, 12 ... Objective lens system, 3, 16 ... Prism, 5, 19 ... CCD, 20, 23, 24 ... Shading plate, 27 ... Shading film, 28, 29 ... V-shaped groove, 30 … Groove.

Claims (4)

[Claims] 1. An optical system for an endoscope, comprising: an objective lens system connected to a distal end observation window; and a prism for introducing a light beam from the objective lens system and guiding the light beam to a solid-state image sensor. The endoscope is characterized in that the device is provided with a light-shielding means for blocking light that passes through the outer peripheral portion of the prism and is incident on the solid-state imaging device by a reflected light path other than the reflected light path set by the prism. Optical system device. 2. The light-shielding means is a light-shielding mask composed of a light-shielding plate or a light-shielding film, and the light-shielding mask is provided on the incident surface of the prism or in the preceding stage thereof. An optical system device for an endoscope according to the description. 3. The optical system device for an endoscope according to claim 2, wherein the light-shielding means is configured by forming a light-shielding film on a low-pass filter provided in the preceding stage of the prism. 4. The endoscope according to claim 1, wherein the light blocking means is formed by forming an air groove in the prism for blocking an optical path other than the regular reflected optical path. Optical system device.