JPH03206412A - Halation removing device for endoscope and electronic endoscope - Google Patents

Abstract

PURPOSE:To preclude halation effect and to make a film image shape by specifying the angle between the optical axes of circular polarized light filter on the sides of a light guide and an image guide. CONSTITUTION:The angle between the optical axes of the circular polarized light filters 4 and 10 on the light-guide and image-guide sides is set to 80-90 deg.. Consequently, halation is nearly eliminated. Namely, a light beam which is made incident on the mucous membrane of the stomach from the light-guide side is clockwise circular polarized light, but reflected to become counterclock wise polarized light. A circular polarizing plate on the image-guide side, how ever, is a clockwise polarizing plate, so the reflecting counterclockwise polariz ing plate is an image-side 1/4-wavelength plate and the light is reconverted into linear polarized light, so that its considerably large part is cut off and removed by a linear polarizing film. Consequently, the halation is eliminated and the uniform and sharp image is obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention attaches a circularly polarizing filter to the tip of an endoscope or electronic endoscope, making it possible to take clear film images. In particular, it relates to a Halley thin removal device that aims to make the film clear when the operator looks directly into the finder of the endoscope, or when diagnosing television images via the solid-state imaging device of the electronic endoscope or mirror. [Conventional technology and its problems] When conventionally using an endoscope to film the stomach wall, etc., the light intensity irradiated from the light source, through the light guide fiber, to the stomach wall, etc. is linearly polarized light or circularly polarized light. Contains a certain amount. By the way, if we take the stomach wall as an example, on the surface of the stomach wall, there are 5 layers of gastric juice, 5 layers of water 1as, and 5 layers of gastric mucosa layer 1b, respectively, as shown in FIG.
It is layered to a thickness of approximately 00 μm. Therefore, the light emitted from the tip of the light guide fiber is scattered and reaches the stomach wall surface, but the gastric juice, water layer 1a, and gastric mucosal layer 1b
acts like a lens, and after the light is bent and converged by this lens, it is reflected from one side of the stomach wall. Therefore, when the reflected light passes through the objective lens, passes through the image guide fiber, and is exposed to the film surface, it causes a halation effect. In other words, when light is irradiated onto a lesion or mucosal surface, the central spot becomes too bright and becomes white, while the surrounding area forms a suitable image. The reason for this is thought to be that the light from the light source contains direct polarized light and circularly polarized light, and the refractive index of the lens on the stomach wall surface is at random. Especially in the case of endoscopes, the distance between the light irradiation point and the subject is 1~
Since the distance is within 2 cm, the reflection of the spot surface as described above is brought into close-up. (c) Means for Solving the Problems and Their Effects] In order to solve the above-mentioned problems of the conventional endoscope, the present invention takes the following precautions. That is, a circularly polarizing filter 4 has a linearly polarizing film 102 and a quarter wavelength plate 103 superimposed between the incident and reflective objective lenses 2 and 2a and the light guide fiber 3, image guide fiber 3a, or solid-state image sensor CCD. , 4a, in an endoscope or electronic endoscope in which the 1/4 wavelength slope 103 is set at the same phase angle toward the objective lenses 2 and 2a, (a) circular polarization filters on the light guide side and the image guide side The angle formed by the optical axes of 4 and 4a was set to 80@~90'', (b) and a 32 Volaizer was used as the linear polarizing filter 102 of circular polarizing filter 4.4a, (c) 1/4 Wavelength 14 to be cut by wave plate 103
This structure employs the following structure: 5ns±5n. By adopting the above-mentioned precepts, the present invention has succeeded in obtaining captured images with extremely low halation. [Explanation of an embodiment of an endoscope] First, an embodiment in which the device of the present invention is applied to an endoscope will be described. The present applicant previously filed an application as Japanese Patent Application No. 1-130245 for a Halley stain removal device having the following structure. In the drawing, 1 is the stomach wall, 1a is the gastric juice and water layer on its surface, and lb is the gastric mucosal layer. 2 and 2a are incident side and reflection side objective lenses, 3 and 3a are light guide fibers and image guide fibers, respectively. 4 and 4a are provided between the objective lenses 2 and 2a and the light guide fiber 3 and image guide fiber 3a. It is a circular polarizing filter. 5 refers to the endoscope. The effect will be explained below. The reflection removing device of the present invention replaces the filter conventionally used in television displays with the objective lens of an endoscope.
, 2a and the light guide fiber 3 and image guide fiber 3a. This filter has a laminate structure in which multi-coated glass 101, gray polarizing film 102, quarter-wave plate 103, and glass 104 are layered. However, glasses 1-4 may be multi-coated glasses. Multi-coated glass 101 significantly reduces troublesome reflections on the display surface, making it possible to create a clear screen. The gray polarizing film 102 and the quarter-wave plate 103 constitute the circularly polarizing filter 4 of the present invention. This filter has the following effects. (a) The gray polarizing film 102 provides a suitable contrast and provides an easy-to-read screen. (b) The circular polarization effect suppresses display flickering and improves resolution. (c) Reflection on the iiji image plane can be almost eliminated. That is, the reflectance of the multi-coated glass 104 is significantly lower in the wavelength range of 450 to 650 nm than in the case without coating. Furthermore, as shown in FIG. 7, the light transmittance is extremely large at wavelengths of 400 nm or more, so it has a significant effect on reflectance and transmittance in light sources used in endoscopes. (d) It can block harmful ultraviolet rays. By the way, the function of the circularly polarizing filter 4.4a (the two may be integrated) is explained as follows. The light emitted from the light guide fiber 3 first passes through the gray linearly polarizing film 102 of the circularly polarizing filter 4 and then transmits through the 1/4 wavelength slope 103. In the linearly polarizing film 102, circularly polarized lights other than the linearly polarized lights are cut off. And this linearly polarized light is 174 wavelength slope 103
When the light passes through it, a 45° phase difference occurs in the direction of vibration, resulting in circularly polarized light as shown in Figure 4. This circularly polarized light may also become elliptically polarized light. As shown in FIG. 2, this circularly polarized light passes through the entrance objective lens 2 to the stomach wall l, and then
It is reflected by the stomach wall 1, passes through the reflective objective lens 2a, passes through the reflective circular polarizing filter 4a again, and enters the image guide fiber 3a. The film is then exposed to light in the same way as before. By the way, in the present invention, the following precautions are adopted in the above-mentioned prior art Hareshigon removal device I. That is, (1) the angle formed by the optical axes of the linearly polarizing film 102 on the light guide side and the image guide side is 90° to 801°, a 32 Volaizer is used as the Q linearly polarizing film 102, and 145±5n is used as the 0 1/4 wavelength plate; In other words, a circularly polarizing filter of 560 to 600n was used. The details are explained below. Explanation of ■: As shown in Figure 6a, the optical axis of the linearly polarizing film is represented by the angle of the transmission axis as O'', 45°.901.As shown in Figure 6b, the 1/4 wavelength plate is also The angle of the axis is O@, 45°,
Expressed as 906. And linear polarizing film, 1/
If the 4-wave plate is round, by rotating it in the direction of the hour hand from the 0° position as shown in Figure 6c and d, its leading axis will be set to 0.
It will change to 45°, 90@. The angle is also displayed in the following cases: A circularly polarizing plate is usually made by combining a linearly polarizing plate and a quarter-wave plate. When a linear polarizing plate and a quarter-wave plate are combined, it is necessary to decide in what direction their respective optical axes, that is, the optical axes, should be combined. For example, as shown in Figure 6e, the optical axis direction of the linear polarizing plate is 90°.
The combination of this and the optical axis of the 174-wave plate at 45 degrees is as shown in Figure 6f. The combination of optical axes in Figure 6r is displayed as in Figure 6g. When making a front gate polarizing plate, it will be made by combining a linear polarizing plate and a quarter wavelength plate, so it will look like the one shown in Figure 6h. This expression is used not only for the combination of a linear polarizer and an h-wave plate, but also for the combination of linear polarizers. That is, the sixth
In Figure ■, it is said that the linear polarizers are parallel to each other. As shown in Figure 7, if it is ■, it is a right-handed circularly polarizing plate, and if it is ■, it is a left-handed circularly polarizing plate. In the present invention, as shown in FIG. 8, the circularly polarizing plates on the light guide side and the image guide side are both right-handed circularly polarizing plates or both are left-handed circularly polarizing plates. In the present invention, by adopting such a configuration, light that enters as right-polarized light from the light guide side becomes left-polarized light when it hits the stomach wall and is reflected. As a result, the light that is reflected and becomes left-handed circularly polarized light enters the right-handed circularly polarizing plate, and since the optical axis angle of the linearly polarizing film and the % wave plate is 45 degrees, the circular wave plate on the image side forms a 90' straight line. Since it is polarized light, a large amount of light is blocked by a linear polarizing plate, which has an optical axis of 0°. In this way, the reflected light that causes hareshi blemishes is removed. ■Explanation , I will explain about it. The product name of POLAX-32N is "POLAX-32N".
is a polarizing plate with the most average characteristics such as single transmittance and polarization performance among the visible light circularly polarizing plates of the POLAX series. The single transmittance is approximately 32%, which is sufficient for use in polarizing filters for cameras, circularly polarizing filters, etc. In addition, the orthogonal transmittance is 10-3 to 10-5 in the used wavelength range of 700 nm to 350 nm.
It also combines order and excellent performance. This polarizing plate is ideal for applications that require a polarizing plate that is totally balanced, rather than polarizing a single element such as transmittance or extinction ratio. POLAX-32N has received high praise for its well-balanced characteristics in the field of polarizing filters for cameras, circular polarizing filters, and optical measurement equipment such as strain testers. ' Conventionally, a 38 polarizer was used in this type of endoscope, but in the present invention, a 32 polarizer was used, and a significant improvement was achieved in the halation removal effect. The test results are shown in Figures 9 to 11, and the test results of the 38 Volaizer are shown in Figure 12. Figure 9 shows the test results using a 32 Volaizer and a round wave plate of 145 nm, Figure 1 shows the test results using a 140 nm Arashi wave plate, and Figure 1 l shows the test results using a 150 nm Arashi wave plate.The horizontal axis of these graphs is the image guide. It shows the angle between the optical axis of the circularly polarizing filter on the side and the light guide side. Furthermore, Figure 12 shows the test results when using a linear polarizing plate of 38 Volalyzer and h wavelength plate Etax, %λ-5800. @Explanation% A wavelength plate of 140±5 nm, that is, a circularly polarizing plate of 560 to 600 nm, was used because the wavelength range of light transmitted by this wavelength plate has the original color tone of the stomach wall, which is bluish. This is because it matches the reddish-purple color. (Explanation of Embodiment of Electronic Endoscope) FIG. 13 shows a case where the present invention is applied to an electronic endoscope. In this case, the circularly polarizing filter on the solid-state image sensor CCD side is placed between the objective lens 2a and the solid-state image sensor CCD. In general form, it is attached to a solid-state image sensor COD. Although two light guide fibers are arranged in parallel in both the endoscope and the electronic endoscope, they are shown as one in Figures 3 and 12. (Others) The present invention can also be used for jewelry appraisal, metal cross-section inspection, precision parts inspection, etc. (Effects of the invention) ■ Since the angle formed by the optical axes of the circularly polarizing filters on the light guide side and the image guide side is set to 90" to 800, halation almost disappears as shown in Figure 6. In other words, from the light guide side to the stomach The light beam incident on the mucous membrane is right-handed circularly polarized light, but when it is reflected and changed to left-handed circularly polarized light, the circular light plate on the image guide side is converted back to linearly polarized light by the coronal wave plate on the image side. As a result, halation is extremely reduced. Figures 9 to 11 show the case where a 32 polarizer is used as a linearly polarizing film. In other words, Figures 9 to 11 show a case where a 32 polarizer is used as a linearly polarizing film of a circularly polarizing film. The case where a polarizer is used and a 14Snm±5nm h wavelength plate is used.As shown in Figures 9 to 11, the angle formed by the optical axis of the circularly polarizing plate with the image guide side and the light guide side is 90°. In the case of °, the wavelength is 500 to 350 nm, and 650 to 350 nm.
The 700nm portion is extremely small, indicating that the blue afterglow is reduced. In other words, halation disappeared and a uniform, clear image was obtained. ■ In the present invention, 32 Volaizer was used as the linearly polarizing film. This shows that the light transmittance is lower and the halation removal effect is greater than when the conventional 38 Volaizer was used. In other words, when comparing the case where a 32 polarizer is used as shown in Figures 9 to 11 and the case where a 38 polarizer is used as shown in Figure 12, in the case of a 38 polarizer, the wavelength range of 450 to 400 nm is extremely large. It grows larger and the blue afterglow is extremely large. In this respect, when using the 32 Volaizer, there is very little blue afterglow, indicating that images with little halation can be obtained. ■ Also, since we used a round wave plate with a wavelength of 145±5 nm, it matches the original color tone of the stomach wall, and the color tone of the image matches that of the original stomach wall.

[Brief explanation of drawings]

Fig. 1: Partial sectional view of the stomach wall, Fig. 2: Skeleton diagram of the device of the present invention, Fig. 3: Also a sketch of the main parts, Fig. 4: An explanatory diagram of the action of the gray polarizing film 102 and the storm wave plate 103. Figure 5 2 Explanatory diagram of the circularly polarizing filter 4 of the present invention, Figure 6 ■
~ ■: Explanation of how to display the optical axis, Figure 7 ■, ■: Explanatory diagram of left and right circularly polarizing plates, Figure 8: Explanatory diagram of the arrangement of circularly polarizing plates of the present invention, Figure 9: 32 polarizer, optical wavelength Graph of test results using a 145 nm plate, Figure 10: Graph when using a 140 nm wavelength plate, Figure 11: Graph when using a 150 nm wavelength plate, Figure 12: Using a 38 polarizer Fig. 13 Schematic diagram for a two-electron endoscope, l: stomach wall, la: gastric mucus layer, 2-2a: incident side, reflection side objective lens, 3.3a: light guide fiber, image guide fiber 4 , 4a: Incident side, reflective side polarizing filter 10l: multi-coated glass, 102: gray polarizing film, 102s: vertical slit, 103: round wavelength plate, 104: glass, 5: endoscope. Engraving of drawings 1st Engraving of drawings 2nd Engraving of drawings X 3rd Engraving of drawings 5 ” Fig. 6 Fig. 6 Fig. 6 Fig. 6 Fig. 6 Fig. 6 Fig. 6 h Fig. 6

Claims (1)

[Claims] 1) Circularly polarized light obtained by superimposing a linear polarizing film 102 and a quarter-wave plate 103 between the incident and reflective objective lenses 2 and 2a, the light guide fiber 3, and the image guide fiber 3a. Filters 4, 4a, 1/4 wavelength plate 1
03 is attached to the objective lenses 2 and 2a in the same phase, and the angle between the optical axes of the linear polarizing films 102 on the light guide side and the image guide side is 90° to 80°. Device. 2) Circular polarizing filters 4, 4a in which a linear polarizing film 102 and a quarter-wave plate 103 are superimposed between the incident and reflective objective lenses 2, 2a, the light guide fiber 3, and the solid-state imaging device (CCD). In an endoscope in which the quarter-wave plate 103 is attached in the same phase toward the objective lenses 2 and 2a, the linear polarizing film 1 on the light guide side and the solid-state image sensor side is
A halation removal device, wherein the angle formed by the optical axis of 02 is 90° to 80°, particularly 90°. 3) The halation removal device according to claim 1 or 2, wherein a 32 polarizer is used as the linearly polarizing film 103. 4) The halation removal device according to claim 1 or 2, wherein the quarter wavelength plate 103 has a wavelength of 145 nm±5 nm, that is, the circular polarizing filter has a wavelength of 560 to 600 nm. 5) The halation removal device according to any one of claims 1 to 4, wherein multi-coated glass 101 which is multi-coated on the outside is bonded to both sides of the linear polarizing film 102 and the quarter-wave plate 103. 6) The halation removal device according to claim 2, wherein a solid-state image sensor CCD is attached to the circularly polarizing filter 4a.