JPH05307144A - Halation removing device for endoscope and electronic endoscope - Google Patents

Abstract

PURPOSE:To eliminate halation from the picked-up image in an endoscope or electronic endoscope, thereby to form the bright image. CONSTITUTION:This halation removing device has about 90 deg. angle formed by the optical axes of quarter-wave plates 103, 103a and linear polarizing plates 102, 102a on the light guide side and image guide side of the endoscope or electronic endoscope having incident and reflection side objective lenses and circular polarizing filters 4, 4a superposed with the linear polarizing plates 102, 102a and the quarter-wave plates 103, 103a mounted between a light guide fiber 3 and an image guide fiber 3a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention has a circular polarization filter attached to the tip of an endoscope or an electronic endoscope so that a film image can be clearly captured.

In particular, the present invention relates to a halation removing device for sharpening a film image when an operator directly looks into a viewfinder of an endoscope or makes a television image diagnosis through a solid-state image pickup device of an electronic endoscope.

[0003]

2. Description of the Related Art Conventionally, when a film of a stomach wall or the like is imaged using an endoscope, a light component emitted from a light source to a stomach wall or the like through a light guide fiber is
It contains linearly polarized light and circularly polarized light components.

Taking the stomach wall as an example, on the surface of the stomach wall, as shown in FIG. 1, gastric juice, water layer 1a and obtained mucous membrane layer 1b are each layered to a thickness of about 500 μm. Therefore, the light emitted from the tip of the light guide fiber diffuses and reaches the stomach wall surface, but the gastric juice, the water layer 1a, and the gastric mucosa layer 1b act as if they were lenses, and the light at this lens portion. After bending and converging, it will be reflected from one surface 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, a halation effect occurs. That is, the light applied to the lesion or mucosal surface makes the central spot portion too bright and white, and the peripheral portion forms an appropriate image.

It is considered that the reason for this is that the light from the light source contains linearly polarized light and circularly polarized light components, and the refractive index at the lens portion on the surface of the stomach wall is at random.

Particularly in the case of an endoscope, since the distance between the light irradiation point and the object is within 1 to 2 cm, the reflection on the spot surface as described above is greatly emphasized.

[0008]

MEANS FOR SOLVING PROBLEMS AND ACTION THEREOF The present invention has the following constitution in order to solve the problems of the conventional endoscopes described above.

That is, the incident and reflecting side objective lenses 2 and 2
a, a light guide fiber 3, an image guide fiber 3a, or a solid-state image sensor CCD, and a circular polarization filter 4, 4a in which a linear polarization plate 102 and a quarter-wave plate 103 are superposed on each other. In the endoscope, the angles formed by the optical axes of the light guide side and image guide side circular polarization filters 4 and 4a, the linear polarization plates 102 and 102a, and the circular polarization filters 103 and 103a are set to 90 degrees inside and outside.

According to the present invention, by adopting the above configuration,
It succeeded in obtaining a captured image with extremely little halation.

(Description of Embodiment of Endoscope) First, an embodiment in which the device of the present invention is adopted for an endoscope will be described below.

FIG. 3 shows the case where the present invention is applied to an endoscope. 1 is a stomach wall, 1a is a layer of gastric juice and water on its surface, 1b
Is the gastric mucosal layer.

Reference numerals 2 and 2a denote incident side and reflection side objective lenses,
3 and 3a are light guide fibers and image guide fibers, and 4 and 4a are objective lenses 2 and 2a and light guide fibers 3 and image guide fibers 3 respectively.
It is a circularly polarized filter provided between a and a. Reference numeral 5 denotes an endoscope.

The circular polarization filters 4 and 4a are, as shown in FIG. 2, multi-coated glass 101 and 101a.
And linear polarization plates 102, 10 such as a gray polarization film
2a, quarter-wave plates 103 and 103a, and glass 10
4, 104a are superposed.

The optical axes of the quarter-wave plate 103 and the linear polarizing plate 102 are orthogonal to each other as shown in FIGS.

FIG. 5a shows a linear polarizing plate 10 on the light guide side.
FIG. 5B shows the optical axes of the 2 and 1/4 wave plates 103, and FIG.
The optical axis of a is shown.

FIG. 6 shows the optical axes of the circular polarization filters 4 and 4a on the light guide side and the image guide side collectively.

The operation will be described below with reference to FIG. On the light guide side, the acute-angle reflected ray that causes halation is initially natural light that is a combination of longitudinal and transverse waves.

Then, it passes through the linear polarizing plate 102 and becomes a longitudinal wave. This is because the optical axis of the linear polarizing plate 102 on the light guide side is in the vertical direction in FIG.

When the light passes through the quarter-wave plate 103, it becomes circularly polarized light that turns left with respect to the traveling direction and is specularly reflected on the gastric mucus layer 1a on the stomach wall.

Then, the light turns right with respect to the traveling direction and returns. Therefore, when the light passes through the quarter-wave plate 103a on the light guide side, a linear polarization plate 102 is generated by a longitudinal wave.
This longitudinal wave is cut by a.

That is, since the specularly reflected light that causes halation is almost cut off, the connected image becomes clear without halation.

The test results are shown in FIGS.
% Circularly polarized filter, and FIG. 11 shows the test results of the circularly polarized filter having a transmittance of 38%. FIG. 8 shows a transmittance of 32.
% Linearly polarizing plate and a quarter wave plate having a phase difference of 145 nm.
Shows the test results using a quarter wave plate having a phase difference of 140 nm, and FIG. 10 shows the test results using a quarter wave plate having a phase difference of 150 nm. The horizontal axes of those graphs are circular polarization filters on the image guide side and the light guide side. Shows the angle formed by the optical axis of.

FIG. 11 shows the test results when a linear polarizing plate having a transmittance of 38% and a quarter wave plate having a phase difference of 145 nm are used.

As shown in FIGS. 8 to 11, linear polarization plates 102 and 102a of the circular polarization filters 4 and 4a on the light guide side and the image guide side, and quarter wave plates 103 and 1 are used.
When the optical axis of 03a is 90 °, the amount of afterglow is close to zero.

(Description of Embodiment of Electronic Endoscope) FIG. 12 shows a case where the present invention is applied to an electronic endoscope. In this case, the circular polarization filter 4a on the solid-state image sensor CCD side is placed between the objective lens 2a and the solid-state image sensor CCD. As a general form, it is attached to a solid-state image sensor CCD. Other configurations are the same as those of the endoscope.

13 to 18 show the positional relationship of the optical axes of the circularly polarizing filter which is the object of the present invention.

FIG. 13 shows a case where the left circular polarization filters 102 and 103 are arranged in two rows on the light guide side, and the left circular polarization filters 102a and 103a whose optical axes are orthogonal to each other are arranged on the image guide side. ing.

The light guide side left circular polarization filters 102 and 103 in the upper and lower four stages of FIG. 13 rotate their optical axes in the counterclockwise direction by 90 ° sequentially from the upper stage to the lower stage. Corresponding to this, the polarization filters 102a, 10 on the image guide side
3a also rotates its optical axis 90 ° counterclockwise.

FIG. 14 shows a case where the left circular polarization filters 102 and 103 on the light guide side of FIG. 13 are vertically inverted. FIG. 15 shows a case where one row of the left circular polarization filters 102 and 103 on the light guide side of FIG. 13 has the same vertical relationship as that of FIG. 13, and the other row is inverted by 180 ° from that of FIG.

Next, FIG. 16 shows a case where the upper and lower four stages of the right circular polarization filters 102 and 103 on the light guide side are sequentially rotated clockwise by 90 ° from the upper stage to the lower stage.

FIG. 17 shows a case where two rows of the right circular polarization filters 102 and 103 on the light guide side in FIG.

FIG. 18 shows a case where the right circular polarization filters 102 and 103 on the light guide side of FIG. 16 have the same vertical relationship as in FIG.

16 to 18, the optical axes of the image guide side polarization filters 102a and 103a are orthogonal to those of the right guide polarization filters 102 and 103 on the light guide side, respectively.

[0035]

[Effects of the Invention] The linear polarizing plate 102 on the light guide side,
Since the angle formed by the optical axes of the 102a and the quarter-wave plates 103 and 103a is set to 90 ° inside or outside, it is possible to obtain an image without halation.

[Brief description of drawings]

FIG. 1 is a partial sectional view of a stomach wall,

FIG. 2 is a skeleton diagram of the device of the present invention,

[Fig. 3] Similarly, a sketch of the main part,

FIG. 4 shows linear polarization plates 102 and 102a and a quarter wavelength plate 1.
In the operation explanatory view of 03 and 103a, the case where left-handed circularly polarized light with respect to the light traveling direction is shown.

FIG. 5 shows the directions of the optical axes of the linear polarizing plate 102 and the quarter-wave plate 103 on the light guide side.

FIG. 6 also shows the direction of the optical axis on the image guide side.

FIG. 7 collectively shows the optical axes of the light guide side and the image side.

FIG. 8 is a linearly polarizing plate with a transmittance of 32% and a phase difference of 145 nm.
Graph of the test results using the 1/4 wavelength plate of

FIG. 9 is a graph when a wave plate phase difference of 140 nm is used,

FIG. 10 is a graph similarly when a wave plate phase difference of 150 nm is used,

FIG. 11 is a linear polarizing plate having a transmittance of 38%,

FIG. 12 is a sketch of an electronic endoscope,

FIG. 13 is a layout diagram of optical axes when left circular polarization filters 102 and 103 are used as circular polarization filters on the light guide side.

FIG. 14 shows a case where the left circular polarization filter of FIG. 13 is vertically inverted.

FIG. 15 shows a case where one row of the left circularly polarized light filter of FIG. 13 has the same vertical relationship and the other row has been vertically inverted by 180 °.

FIG. 16 is a circular polarization filter 102 on the light guide side,
Arrangement diagram of the optical axis when a right circular polarization filter is used for 103,

FIG. 17 shows a right circular polarization filter of FIG.
Shows the case of rotation.

FIG. 18 shows a case where one row of the right circular polarization filter of FIG. 16 has the same vertical relationship and the other row has been inverted upside down 180 °.

[Explanation of reference numerals] 1: stomach wall, 1a: gastric mucus layer, 2, 2a: incident side, reflective side objective lens, 3, 3a: light guide fiber, image guide fiber, 4, 4a: incident side, reflective side circularly polarized light Filter, 101: Multi-coated glass, 1
02, 102a: linear polarizing plate, 103, 103a: 1 /
Four-wave plate, 104: glass, 5: endoscope.

Claims (2)

[Claims] 1. Linear polarizing plates 102, 102a, a quarter-wave plate 103, between the incident and reflecting objective lenses and the light guide fiber 3 and the image guide fiber 3a.
In the endoscope equipped with the circular polarization filters 4 and 4a in which 103a are overlapped, a quarter wave plate 10 on the light guide side and the image guide side is provided.
A halation removing device in which the angle formed by the optical axes of the optical fibers 3, 103a and the linear polarizing plates 102, 102a is within 90 °. 2. An electronic endoscope provided with circular polarization filters 4, 4a between a light guide fiber 3 and a solid-state image sensor (CCD), wherein linear polarization on the light guide side and the solid-state image sensor (CCD) side. Plates 102 and 102a and quarter-wave plates 103 and 103
A halation removing device in which the angle formed by the optical axis of a is 90 ° or outside.