DE9218289U1 - endoscope - Google Patents

Description

Patent Attorney's Office

GEyer&Fehners

European Patent Attorneys

Perhamerstrasse 31 ■ D-80687 Munich
Telephone: (089) 5 461520 Fax: (089) 5460392 Telex: 5218915 gefe d -Telegrams: gefepat muenchen

Attorney file: Gm 2032/19-92 Date: 13 September 1993

Henke-Sass, Wolf GmbH,

Kronenstrasse 16,

D-78532 Tuttlingen

endoscope

The invention relates to endoscopes with an optical system which essentially consists of an objective lens, a multi-stage guidance system and an eyepiece.

Such known optical systems consist of many optical glass and/or plastic lenses, which are fixed and mounted in a metal tube and are therefore particularly suitable for rigid endoscopes. The relatively large image transmission of the individual lenses or lens combinations does not allow use in flexible endoscopes.

Lenses made of glass are significantly more expensive than those made of plastic, because the processing of glass lenses is very time-consuming and difficult. With such glass lenses, the surfaces must be polished in order to achieve a flat, convex, concave or aspherical shape.

Glass lenses made from plastic are cheaper because they can be produced in large quantities using injection molding compared to glass lenses and cost about 1/10 of comparable glass lenses. However, the optical transmission qualities of plastic lenses are significantly worse than glass lenses.

Regardless of these price differences, however, such conventional optics made of glass or plastic also have qualitative defects, namely unavoidable imaging errors that arise due to the physical principle of light refraction.

Spherical aberration plays an important role in such optical systems. The image created by such optics appears blurred because rays that hit the edge area of the lens have a shorter focal length than those that fall close to the optical axis. To compensate for this aberration, lenses made of different materials and curvatures are arranged one behind the other.

Another disadvantage of such conventional optics is the chromatic aberration, which occurs because conventional lenses for blue light have a shorter focal length than for red light. This chromatic aberration has so far been corrected by gluing lenses made of materials with different dispersive properties together. However, such lens arrangements are complicated and expensive.

The above-mentioned circumstances meant that conventional endoscopes had to work with very complex lens systems that were very time-consuming and expensive to manufacture.

The object of the invention is to create endoscopes with optical systems which are simpler in their construction, require a smaller number of individual lenses and/or lens combinations and are also more cost-effective to manufacture, whereby the aim is in particular to ensure that spherical and chromatic aberrations and other image errors are excluded or eliminated as completely as possible and that their shafts can also be designed to be flexible.

This task is solved by the fact that in such an endoscope at least parts of the optical system consist of binary optical elements.

Binary optical elements are well known; they do not work through the above-described refraction of light, but break down the incident wave front into countless elementary waves on their surface, which overlap to form a new overall wave directed at the desired focal point. Such diffractive, i.e. light-bending elements are thinner than refractive optical elements and therefore also lighter, so they offer the advantage that endoscopes equipped with such binary optical elements are also lighter and thus easier for the surgeon to handle. Their use, however, has the particular advantage that no spherical aberration occurs.

In an advantageous development of the invention, the optical system consists entirely of binary optical elements.

This allows the number of individual lenses to be installed in an optical system for endoscopes to be greatly reduced, resulting in significantly better optical transmission and image quality, as fewer qualitative and quantitative losses occur on the individual lens surfaces.
5

In a further advantageous embodiment of the invention, a refractive optic is combined with a binary optic to form an achromatic optical system within the overall optical system.

With this combination, the chromatic aberration of conventional refractive optics can be compensated because binary optics have an opposite chromatic aberration, i.e. they have a longer focal length for blue light than for red light. The combination of a binary optic with a refractive optic therefore completely compensates for the chromatic aberration.

Finally, the individual binary optical elements can be made very thin and very small in diameter, thus allowing the production of miniature endoscopes.

Embodiments of the invention are described below with reference to the drawings.
20

Show it:

Fig. 1 shows the arrangement diagram of an achromatic endoscope lens system consisting of conventional refractive optics,
25

Fig. 2 shows the arrangement diagram of a rod lens system consisting of conventional refractive optics,

Fig. 3 shows the arrangement diagram of an achromatic lens system consisting of a combination of refractive and diffractive optics,

Fig. 4 is an enlarged detail of Fig. 3,

Fig. 5 the combination of a diffractive correction element with a conventional refractive lens,

Fig. 6 a diffractive lens with convex/flat surfaces,
Fig. 7 a diffractive lens with biconvex surfaces and

Fig. 8 a lens combination consisting of a diffractive and a refractor

tive lens, where the plano/convex lens can be made of a different material.

The conventional lens systems for rigid endoscopes shown in Fig. 1 and 2, i.e. consisting of refractile optics, essentially consist of a lens system forming an objective 1 or 1', a guide system 2 or 2' and an eyepiece 3 or 3', whereby an achromatic optical system is shown in Fig. 1 and a rod lens system is shown in Fig. 2.

In order to avoid spherical and/or chromatic aberration, combinations of refractive lenses are used in these known systems, whereby the optical system according to Fig. 1 is characterized by the fact that it has a very large number of lens combinations. The optical system according to Fig. 2 avoids the arrangement of a large number of lens combinations by using rod lenses.

Fig. 3 shows an optical system for an endoscope composed of refractive and diffractive optics, which in turn consists of an objective lens 1", a guidance system 2* and an eyepiece 3". The lens combinations shown in this figure each consist of a refractive and a diffractive lens. For this, reference is made to Fig. 4, in which the enlarged surface of the lens combination 4 from the guidance system 2" is shown.

As this enlarged surface of the binary optics shows, certain structures are incorporated into it which, in contrast to refractive lenses, achieve the optically desired result not through refraction but through diffraction of the light waves.

In Figs. 5 to 8, individual lens shapes are shown in section. Fig. 5 shows a combination of a conventional lens 5 with convex/flat surfaces 6 and 7, with a diffractive correction element 8 with its structured surface 9 lying opposite the convex surface 6. Both lenses 5 and 8 can be made of glass or plastic.

Fig. 6 shows a lens 10 with convex/planar surfaces 11 and 12, respectively, wherein the convex surface 11 has binary structures 13.

Fig.7 shows a similarly designed lens 14, which, however, instead of a flat surface, has a convex surface 15.

Finally, Fig. 8 shows an embodiment of a lens combination 16 with convex/flat surfaces 17 and 18, respectively, in which, however, the convex surface 17 having the binary structures consists of a glass or plastic part 19, which is glued or sprayed onto the flat surface 20 of the lens 16.

All of the lens combinations described above can be glass/glass, glass/plastic or plastic/plastic, and the surfaces of the lenses in these combinations can also be flat/convex or aspherical.

In contrast to the refractive optics that have been used up to now, binary optics are much more cost-effective to manufacture, for example by using simple etching to produce the surfaces, by using laser technology as used in semiconductor production, by using plastic-injected surfaces and also by making the anti-reflective coating that is often required for refractive lenses unnecessary.

By using binary optics, much more complicated lens shapes can be produced in a relatively unproblematic manner.

By using binary optics in endoscope optics systems, in addition to chromatic and spherical aberration, other image errors can also be corrected, such as distortion, vignetting, astigmatism, coma and optical path differences.

Finally, binary optical lenses can be manufactured with a diameter of only 0.1 mm, which makes it possible to build very thin endoscopes, which expands their use in medical technology, for example.
35

Claims (4)

Patent Attorney's Office GEYER & FEHNCRf) Europe!^ -Patent A;torne/j Perhamerstrasse 31 ■ D-80687 Munich Telephone: (089) 5461520 · Fax: (089) 54603 92 · Telex: 5218915 gefe d ■ Telegrams: gefepat muenchen Attorney file: Gm 2032/19-93 Date: 13 September 1993 Protection claims 1. Endoscope with an optical system consisting of an objective, a multi-stage guidance system and an eyepiece, characterized in that at least parts of the optical system consist of binary optical elements. 2. Endoscope according to claim 1, characterized in that the optical system consists entirely of binary optical elements. 3. Endoscope according to claim 1, characterized in that a refractive optic is combined with a binary optic to form an achromatic optical system within the entire optical system. 4. Endoscope according to claim 2, characterized in that the individual binary optical elements are very thin and small and the endoscope is designed to be correspondingly small.