WO1996035531A1

WO1996035531A1 - Small endoscope prism and manufacturing process

Info

Publication number: WO1996035531A1
Application number: PCT/US1996/007117
Authority: WO
Inventors: Christopher C. Gregory
Original assignee: Galileo Electro-Optics Corporation
Priority date: 1995-05-11
Filing date: 1996-05-13
Publication date: 1996-11-14

Abstract

A prism designed for endoscopes, consisting of a hollow internal region (36). The internal section defined by surfaces (40 and 42) are composed of a material with a higher index of refraction than the material which forms regions (32 and 34). The differences in the index of refraction between the hollow region (36) and the outer region of the prism (32 and 34) allow for total internal reflection of a light ray (38) within the hollow section. Consequently, light is then more focused, thereby permitting sharper images to be seen from the endoscope in question.

Description

SMALLENDOSCOPE PRISMANDMANUFACTURINGPROCESS

BACKGROUND OF THE INVENTION

The invention relates to an endoscope, and in particular to a

prism for an endoscope formed as reflective surfaces in a cavity.

Small diameter rigid endoscopes have been in use in the

medical field for decades. A large number of these devices require off

axis viewing at angles up to or even greater than or even greater than

90°. Almost all of the known rigid endoscopes use prism sections in

their objective assemblies to produce the off axis viewing angle. To

maintain the orientation of the image, these prisms usually produce

two reflections in the image path canceling each other out. These prisms are as small as 0.3 mm on an edge and are conceivably even smaller. The very small size of these prisms restricts their availability

at reasonable cost. The grinding, polishing and coating of these

prisms is tedious work requiring great skill.

Two exemplary known reflection endoscope prisms are

illustrated in Figs. 8A and 8B. The prisms produce two reflections

resulting in reasonable reflection angles and correct image orientation.

In the prism 10 of Fig. 8A, the prism comprises an upper layer of glass

12, a lower layer of glass 14, and a middle layer of glass 16. The upper layer 12 and middle layer 16 have an index of refraction N^ and

the lower layer 14 has an index of refraction N₂. To allow total internal

reflection as an option, N₂ is less than N In the configuration shown in Fig. 8A, the lower section 14 does not transmit light and is mirrored. The upper section 12 does so only to allow the wide spread of rays to reach the center layer 16. The interface 18 between the upper two

pieces cannot be fully silvered to allow wide angle rays, thus making

manufacturing more difficult. The entire assembly is ground cylindrical for easy mounting.

The prism 20 arrangement of Fig. 8B is somewhat easier to

make because it has fewer elements including mirrored surfaces 22.

However, it is quite difficult to mount. Also, as one attempts to reduce

the size, the difficulty of manufacturing the prism 20 increases.

SUMMARY OF THE INVENTION

The present invention is based upon the discovery that a small

prism may be manufactured by forming a cavity having reflective surfaces in a non-optical body. The cavity provides an optical path and the reflective surfaces correct the image orientation.

In one embodiment, the prism comprises a body formed with a

through cavity defining an optical path and having at least two reflective surfaces for reorienting the image. The body may be a molded organic, inorganic or refractory

material. The cavity may be filled with air or may be filled with organic

or inorganic optical material having an index of refraction greater than

1. The prism may be manufactured by a process including a

machining or molding step to form the cavity within the body and to

finish the reflective surfaces therein. The prism may further include a

molded optical filler having an index of refraction different from 1.

DESCRIPTION OF THE DRAWINGS

Fig. 1 illustrates a side sectional view of a prism manufactured

in accordance with the present invention;

Fig. 2 illustrates an end view of the prism of Fig. 1 ;

Fig. 3 is an illustration of an alternative embodiment of the

invention in which the cavity of the prism is filled with a castable

material;

Fig. 4 is an illustration of another embodiment of the invention

in which the cavity is filled with a glass wedge; Fig. 5 is an illustration of embodiment of the invention in which

the cavity is filled with a high index material such as molten glass;

Fig. 6 is an alternative embodiment of the invention in which the cavity in the body is formed by a x-ray lithography process;

Fig. 7 is another embodiment of the invention in which portions

of the upper and lower portions of the body are extruded and

positioned together to form the prism; and

Fig. 8A and 8B are illustrations of known prisms. DESCRIPTION OF THE INVENTION

Figs. 1 and 2 illustrate a prism 30 manufactured in accordance

with the present invention. The prism 30 is manufactured by a

technique which departs from traditional optical manufacturing

techniques for the manufacturing of these type structures. In the

arrangement, the prism 30 includes outer sections 32 and 34 and a

central cavity 36 forming an optical path 38. Reflective surfaces 40

and 42 are formed on opposite sides of the cavity 36, as shown. In the

arrangement illustrated, the outer sections 32 and 34 are light opaque

so that light does not pass through any part of the prism except the

center section 36.

The upper and lower sections 32 and 34 may be made from any

suitable material such as organic, inorganic or refractory materials.

The reflective surfaces 40 and 42 may be made by suitable processes including molding and machining. The outer sections 32 and 34 may be connected outside of the optical path 38 forming the cavity 36 inside for light to pass therethrough along the optical path 38. As

hereinafter described, the cavity may be unfilled, it may be filled with

a gas or it may be filled with light transparent materials with a selected

index of refraction, such as glass, organic and the like. The filler

material may be shaped to fit the space or may be casted or molded

therein.

In an embodiment of the invention illustrated in Fig. 3, wherein

like reference numerals are used for similar elements, the prism 44 having a shape as illustrated in Figs. 1 and 2 or a similar shape, may be made by molding a non-optical material. The cavity 36 may be

coated with reflective coatings 46 and 48 to produce the reflective

surfaces 40 and 42. If the material forming the prism 44 is a reflective

material, the reflective surfaces 40 and 42 may be produced directly

by molding and without the coatings.

If the interior of the prism requires an index of refraction higher

than 1 (e.g., air), the cavity 36 may be filled with a castable material

50, such as acrylic. Polished surfaces 52 (shown in phantom) may be

held against the entrance and exit faces 54 and 56, resulting in optically adequate surfaces thereat.

Alternatively, as shown in Fig. 4, prism 60 having a shape as

shown in Figs. 1 and 2 or a similar shape, may be made by molding of

a non-optical material, and may be coated to produce the reflective surfaces 42 and 44, if the material is not already reflective. If the

interior of the prism requires an index higher than 1 and the entrance

does not require a wide opening, the space may be filled with a wedge

of glass 64 and the respective entrance and exit faces 54 and 56 may be polished optically smooth. In another embodiment illustrated in Fig. 5, the prism 70 having

a shape as shown in Figs. 1 and 2 or something similar, may be made

by molding a non-optical material and coating to produce reflective

surfaces if the material is not already reflective. If the cavity 36 of the prism 70 requires an index much greater than 1 , for example 1.16, the space may be filled with a molten glass 72. Polished surfaces 50 shown in phantom are held against the entrance and exit faces 54 and

56 resulting in optically adequate surfaces thereat. Further surface finishing may be useful. In yet another embodiment shown in Fig. 6, the prism 80 having a shape as shown in Figs. 1 and 2 or a similar shape, may be made by

micromachining of a block of material 82. Micromachining may be accomplished by a deep edge x-ray lithography process in which resist materials 84 and 64 are placed on the entrance and exit faces 54 and 56 to form an etch mask. In addition to the deep etch x-ray lithography

(LIGA), other machining techniques related to the manufacture of electronic components may be employed. The prism 80 may be completed by one or more of the techniques described hereinabove.

In yet another embodiment of the invention illustrated in Fig. 7, the prism 90 having a shape as shown in Figs. 1 and 2 or a similar shape, may be made by extruding a profile of material in the shape of upper and lower sections 92 and 94. These surfaces may be coated if not already reflective and the sections may be positioned relative to each other, and the space or cavity 36 therebetween may remain unfilled or may be filled as hereinabove described. In this case, the filling material could be an extension of optical material. This could act to position sections 92 and 94. After assembly, the part could be

shaped for insertion into an endoscope assembly. The use of the above described non-traditional techniques for the manufacture of optical components could reduce the cost of the prisms and endoscopes by an order of magnitude. The use of

micromachining and the production of endoscope objects has great potential, but its most immediate uses in the manufacture of flat elements such as prisms.

While there have been described what are at present

considered to be the preferred embodiments of the present invention,

it will be apparent to those skilled in the art that various changes and

modifications may be made therein without departing from the invention, and it is intended in the appended claims to cover such changes and modifications as fall within the spirit and scope of the invention.

Claims

WHAT IS CLAIMED IS:

1. A prism for transmitting an image comprising:

a body having a cavity formed therein, said cavity defining an

optical path;

said cavity having internal reflective surface on the optical path

for transmitting the image.

2. The prism of claim 1 wherein the internal reflective surface comprises first and second surface portions lying in opposition for

twice reflecting thereby reorienting the image.

3. The prism of claim 1 wherein the body comprises a molded

non-optical material.

4. The prism of claim 1 wherein the cavity remains unfilled.

5. The prism of claim 4 wherein the body comprises a molded

plastic (polymer) material.

6. The prism of claim 1 wherein an optical material is located

in a cavity.

7. The prism of claim 5 wherein the optical material has an

index of refraction greater than 1.

8. The prism of claim 6 wherein the optical material comprises gas, organic and inorganic material.

9. The prism of claim 1 wherein the body comprises a molded refractory material.

10. The prism of claim 5 wherein the reflective surface includes

a reflective coating.

11. A method for manufacturing a prism for transmitting light comprising forming a body; forming a cavity within the body having open interconnected ends defining an optical path and forming

reflective internal surfaces within the cavity.

12. The method of claim 11 wherein the forming steps include drilling, machining, molding and extrusion.

13. The method of claim 11 further comprising filling the cavity with an optical material having an index of refraction of at least 1.

14. The method of claim 11 further comprising coating the reflective surfaces with a reflective material.

15. The method of claim 11 further comprising polishing the reflective surfaces.

16. The method of claim 11 further comprising filling the cavity with a castable material and locating polished surfaces at the ends of the cavity for establishing finished surfaces thereat.

17. The method of claim 11 further comprising polishing the filled material at the first and second ends coplanar therewith.

18. The method of claim 11 wherein the forming step includes depositing an etch mask having aperture therein on the body and etching through the apertures in the mask to form the cavity.