JP2002023067A - Optical system device for electronic endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To effectively utilize light outputted from a light source even in a configuration using an optical objective system as an optical observation path and as an optical illumination path. SOLUTION: On the back side of an optical objective system 12, a 1/4 wavelength plate 16 and a cubic polarizing prism 17 having an optical transmission path L1 for outputting the light of the light source and an optical reflection path L2 for guiding the light from the optical objective system 12 to the side of a CCD 18 are provided. Concerning the prism 17, two rectangular prisms are combined to have a polarized light separation plane and a p-polarized light reflection film 27 is formed on this polarized light separation plane. Thus, the p-polarized light of the light source converted by the prism 17 is turned into circularly polarized light by the 1/4 wavelength plate 16 and irradiated from the optical objective system 12. Whereas, reflected light from an object to be observed is converted to s-polarized light by the 1/4 wavelength plate 16 and guided through the prism 17 to the CCD 18 by the optical reflection path L2. As a result, the loss of the light from the light source can be reduced to 1/2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system for an electronic endoscope, and more particularly to illuminating an object to be observed through a light guide and observing the object to be imaged by an image sensor through an objective optical system. The present invention relates to a configuration of an optical system member of an electronic endoscope.

[0002]

2. Description of the Related Art In an electronic endoscope apparatus, an object to be observed (inside) is illuminated by emitting light from a distal end portion of a scope through a light guide formed of an optical fiber bundle. And captured by the image sensor. In this type of electronic endoscope apparatus, for example, two light guides are provided up to the distal end, and the objective optical system is disposed at a position sandwiched between the two light guides.
Thereby, the object to be observed is illuminated well.

In the above-mentioned electronic endoscope apparatus, since the scope is inserted into an observation site such as a thin body cavity, it is required to reduce the diameter of the distal end portion and the insertion portion. , The diameter is reduced, and the arrangement is devised. However, bright illumination light is required for good observation, and it is not advisable to reduce the diameter of the light guide too much.

[0004] Further, with such an endoscope, it is relatively difficult to perform uniform illumination with no unevenness on the imaging position captured by the objective optical system. That is, as described above, when two light guides are provided, since both lights overlap at a predetermined position, illumination unevenness occurs in a peripheral portion thereof. In addition, when one light guide is used, strictly speaking, light impinges obliquely on the irradiation position, so that illumination unevenness similarly occurs in the peripheral portion. Therefore, as disclosed in Japanese Patent Application Laid-Open No. 10-99268, the present applicant has proposed an apparatus that uses an objective optical system member that captures an image of an object to be observed as an illumination optical path.

[0005]

However, in the optical system of the electronic endoscope, a semi-transmissive film is used in an optical path coupling optical element for securing an optical path from a light source and an optical path leading to an image pickup device. However, the light incident on the image sensor becomes about 1/4 of the light of the light source, and there is a disadvantage that the output light of the light source cannot be used effectively. That is, the light from the light source becomes と き when passing through the semi-transmissive film, and becomes と き に when light from the object is reflected by the semi-transmissive film. It becomes 4.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an electronic endoscope which can effectively use light output from a light source even when an objective optical system is used as an observation optical path and an illumination optical path. An object of the present invention is to provide a mirror optical system device.

[0007]

In order to achieve the above object, an optical system for an electronic endoscope according to the first aspect of the present invention outputs illumination light and is illuminated with the illumination light. An objective optical system arranged to capture an image of the object to be observed, and a polarizer function arranged behind the objective optical system and separating incident light into two polarization components orthogonal to each other. A polarization separation optical element that secures a transmission optical path that transmits a polarization component and a reflection optical path that reflects the other polarization component,
An illumination unit optically connected to one of a transmission optical path and a reflection optical path set by the polarization separation optical element, an imaging element optically connected to the other of the optical paths, and the polarization separation optical element. A polarization component conversion element disposed on the side of the objective optical system for converting between linearly polarized light and circularly polarized light.

According to a second aspect of the present invention, a full-conversion-type polarization component conversion element that has a polarizer function of the polarization separation optical element and converts all of the light from the light source into one linear polarization component is provided in the illumination means. It is characterized by having been provided.

According to the above arrangement, the random light guided from the light source via the light guide is separated into s-polarized light and p-polarized light by the polarizer function of the polarization splitting optical element, and then, for example, only the p-polarized light is transmitted. After that, the light is converted into circularly polarized light by the polarization component conversion element. Then, the circularly polarized light is irradiated as illumination light on the object to be observed via the objective optical system. on the other hand,
When circularly polarized light reflected from the object to be observed is captured by the objective optical system, the reflected circularly polarized light is converted into s-polarized light by the polarization component conversion element, and is guided to the polarization splitting optical element. In this polarization splitting optical element, the s-polarized light is reflected by the polarizer function and supplied to the imaging device, and the object image is formed on the imaging surface by the s-polarized light.

Accordingly, a uniform and efficient illumination state in which the illumination region and the observation region are matched can be obtained, and the random light amount from the light source is only halved by the polarizer. 4 has the advantage that the output light of the light source can be used effectively. Further, according to the configuration of the second aspect, since the full-conversion-type polarization component conversion element that converts all of the light from the light source into a linearly polarized light component is used, in this case, all of the light output from the light source is used for imaging. Becomes possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a main structure of an optical system of an electronic endoscope according to a first embodiment of the present invention. The configuration is shown. First, in FIGS. 2 and 3, the distal end portion 10 has an objective optical system member (barrel) 12 held by a holding member 11.
The objective optical system member 12 includes not only an objective lens but also an aperture, a filter, and the like. Also,
A forceps port 14 is provided on the distal end surface of the distal end portion 10, a treatment tool insertion channel 15 is connected to the forceps port 14, and various treatment tools such as forceps are led out of the forceps port 14 through the treatment tool insertion channel 15. it can.

Further, on the rear side of the objective optical system member 12,
As shown in FIG. 1, a quarter-wave plate 16 as a polarization component conversion element and a cubic prism 17 as a polarization splitting optical element incorporating a polarizer are optically connected. On the side, a CCD (Char
ge Coupled Device) 18 is optically connected. The CCD 18 is housed and connected in a CCD package 20 sealed with a cover glass 19.
Is adhered to the lower surface of the prism 17. The above C
A wiring pattern is formed on the CD package 20, and a signal line 21 for connection to the outside is connected via the wiring pattern.

In FIG. 1, the cubic prism 17
Is composed of a polarizing prism (polarizing beam splitter) in which two right-angle prisms are joined and the joining surface (inclined surface) becomes the polarization splitting surface 17A. (May be polarized light)
A polarization reflection film (linear polarization reflection film) 27 is formed. According to the cubic prism 17, the s-polarized reflection film 2
The randomized light, which is the light source light, is separated into s-polarized light and p-polarized light by the polarized light separating surface 17A to which the s-polarized light is applied. Further, a transmission light path (straight traveling light path) L1 for passing the light from the light source to the objective optical system member 12 is set, and the light incident from the objective optical system member 12 is transmitted from the polarization separation surface 17A to the CCD 18, which is a lower right angle direction. A reflected light path L2 for reflection is formed.

The quarter-wave plate 16 on the front side of the cubic prism 17 converts the p-polarized light output from the prism 17 into circularly polarized light, and converts the reflected light from the object to be observed due to the circularly polarized light into s. Convert to polarized light. Therefore, this 1 /
The s-polarized light emitted from the four-wavelength plate 16 forms an image of the object under observation on the CCD 18 via the reflection optical path L2.

Further, a light guide 25 is disposed behind the cubic prism 17 via a condenser lens 23 and a diffusion plate 24, and the light guide 25 is connected to a light emitting end of the light source device. . The diffusion plate 24 has a ground glass surface, and serves to prevent the shape of the fiber bundle on the end face of the light guide 25 from being back-projected to the CCD 18 side.

The first example has the above configuration, and its operation will be described below. As shown in FIG. 1, light guided from the light source device via the light guide 25 passes through the diffusion plate 24 and is incident on the rear surface of the cubic prism 17 by the condenser lens 23. This light source light is random light, and the random light is linearly polarized component (s
(Polarized light, p-polarized light), one linearly polarized light component is transmitted, and the other linearly polarized light component is reflected upward by the polarization separation surface 17A. If, for example, the p-polarized light travels along the transmission optical path L1 (the s-polarized light is reflected), the p-polarized light becomes circularly polarized light by the quarter-wave plate 16, and is observed as illumination light via the objective optical system member 12. The illumination light is emitted to the body, and the illumination light passes through the optical path of the objective optical system member 12 that captures the image of the object to be observed.

On the other hand, the object image illuminated by the circularly polarized light is captured by the objective optical system member 12, and the circularly polarized light reflected from the object to be observed passes through the optical path in the objective optical system member 12 and becomes １ ／.
The light is converted into s-polarized light having a polarization direction different by 90 degrees by the wave plate 16 and supplied to the cubic prism 17. Then, in the cubic prism 17, the s-polarized light is
The reflected light path L in the direction perpendicular to the polarization separating surface 17A having
2 is reflected to the CCD 1 as shown in FIG.
An image of the object to be observed is formed on the imaging surface 8 by s-polarized light.

According to the first example, the conventional semi-transmissive film in which the random light output from the light source becomes only the p-polarized light by the cubic prism 17 and the light amount becomes １ ／, and the light amount becomes １ ／. The light source light can be used more effectively. Then, as can be understood from FIGS. 2 and 3, the objective optical system member 12
The light guide 25 and the light guide 25 are arranged in series instead of in parallel.
There is an advantage that the diameter of the distal end portion 10 can be reduced, and an illumination pattern optimal for an imaging area can be obtained. Therefore, illumination unevenness can be eliminated and good imaging can be performed.

In the first example, the cubic prism 1
Although the s-polarized light reflective film 27 was formed as the linearly polarized light-reflective film 7, a p-polarized light reflective film may be formed instead. In this case, the s-polarized light is transmitted through the cubic (polarized) prism 17, It will be configured to reflect polarized light.

FIGS. 4 and 5 show the structure of a second example of the embodiment. This second example has a polarizer function and performs a total conversion for converting all of the light from the light source into linearly polarized light. It is provided with a type polarization component conversion element. In this second example, FIG.
As shown in FIG.
The configuration up to this point is the same, and a full conversion type polarization component conversion element 28 for converting the light source light into, for example, p-polarized light is disposed between the cubic prism 17 and the light source.

FIG. 5 shows an example of the configuration of the full conversion type polarization component conversion element 28.
No. 2417. In FIG. 5, a cubic prism (polarizing beam splitter) 28a that receives light from a light source has, for example, a polarization splitting surface 28b that transmits p-polarized light and reflects s-polarized light. A reflector 28c is disposed in the optical path of the s-polarized light output from the cubic prism 28a, and a half-wave plate 28d is disposed in the reflective optical path of the reflector 28c.

According to such a configuration, the random light as the light source light is separated into p-polarized light and s-polarized light by the cubic prism 28a, and the p-polarized light is output straight, but the s-polarized light is guided upward. The s-polarized light is reflected at a right angle by the reflection plate 28c, then converted into p-polarized light by passing through the half-wave plate 28d, and the p-polarized light is guided to the output direction. Therefore, according to the full conversion polarization component conversion element 28, all of the light from the light source is converted into p-polarized light and output.

The above-mentioned all conversion type polarization component conversion element 2
The p-polarized light output from 8 is supplied to a cubic prism 17 which is a polarization splitting optical element via a light guide 25 and the like, and all the p-polarized light incident on the cubic prism 17 passes through a 波長 wavelength plate 16. It is guided to the objective optical system member 12. Therefore, in the second example, there is an advantage that an image of an object to be observed can be formed on the CCD 18 using all of the light from the light source without loss.

In the above embodiment, the CCD 18 is provided below the cubic prism 17 and the light guide 25 is provided on the rear side.
A light guide 25 is provided below the CCD 18 and a CCD 18
May be arranged.

[0025]

As described above, according to the present invention,
In an optical system of an electronic endoscope that also uses an observation optical path of an objective optical system as an illumination optical path, a polarization separation optical element having a polarizer function of separating two polarization components, and securing a transmission optical path and a reflection optical path, Since the polarization component conversion element for converting linearly polarized light and circularly polarized light is provided, it is possible to effectively use the light output from the light source with a device that achieves uniform illumination without reducing the diameter and unevenness.

According to the second aspect of the present invention, since the full conversion type polarization component conversion element for converting all of the light output from the light source into one linearly polarized light component is provided, the light source light can be used for imaging the object to be observed. There is the advantage that everything can be used.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of an optical system device of an electronic endoscope according to a first example of an embodiment of the present invention.

FIG. 2 is a side sectional view showing a configuration of a distal end portion of the electronic endoscope of the first example.

FIG. 3 is a view of the distal end portion of FIG. 2 as viewed from the rear side.

FIG. 4 is an explanatory diagram illustrating a configuration of an optical system device of an electronic endoscope according to a second example of the embodiment.

FIG. 5 is a configuration diagram illustrating an example of a second conversion type polarization component conversion element according to a second example.

[Explanation of symbols]

 Reference numeral 10: tip, 12: objective optical system member, 16: quarter-wave plate, 17: cubic prism (polarizing prism), 18: CCD, 25: light guide, 27: s-polarized reflection film, 28: all conversion type Polarization component conversion element.

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Claims (2)

[Claims] 1. An objective optical system arranged to output illumination light and capture an image of an object to be observed illuminated by the illumination light, and an incident light arranged behind the objective optical system and incident thereon. A polarization splitting optical element that has a polarizer function of splitting into two polarization components orthogonal to each other, and secures a transmission optical path for transmitting one polarization component and a reflection optical path for reflecting the other polarization component. An illumination unit optically connected to one of the transmission optical path and the reflection optical path set in the above, an imaging element optically connected to the other of the optical paths, and the objective optical system side of the polarization separation optical element Placed in
An optical system for an electronic endoscope, comprising: a polarization component conversion element that converts linearly polarized light and circularly polarized light. 2. The illumination device according to claim 1, further comprising a full-conversion-type polarization component conversion element having a polarizer function of the polarization separation optical element and converting all of the light from the light source into one linear polarization component. The optical system of an electronic endoscope according to claim 1.