GB2099174A

GB2099174A - Rod lens and lens combination and endoscope including the rod lens

Info

Publication number: GB2099174A
Application number: GB8206976A
Authority: GB
Original assignee: STORZ KARL
Current assignee: STORZ KARL
Priority date: 1981-04-01
Filing date: 1982-03-10
Publication date: 1982-12-01
Also published as: DE3113110C2; GB2099174B; DE3113110A1

Abstract

A rod lens (3) has radially enlarged ends (b, c) to permit cementing to larger diameter lenses (2, 4) without a radial step at the lens junction. The rod lens is of particular use in an endoscope and a spacer sleeve (5) can be provided within the endoscope tube between at least two adjacent lenses. <IMAGE>

Description

SPECIFICATION Rod lens and lens combination and endoscope including the rod lens The invention relates to a rod lens, particularly for fitting an endoscope, as well as an arrangement thereof in an endoscope.

Due to their small diameter and considerable length there is a risk of endoscope rod lenses shattering. During the handling of medical endoscopes in particular, it is unavoidable that they will be subjected to bending stress, so that shear forces are developed in the center. There is an especial risk to the cement layers used for fixing rod lenses together or fixing rod lenses to normal lenses.

According to the prior art the rod lenses always have a uniform diameter. However, if the ends are cemented to lenses having a larger diameter, an endangered cross-section is formed at this cementing point. If the rod lens arrangement is subject to bending stress within an endoscope, the cement layer may fracture.

The object of the invention is to so improve rod lenses that the cementing points at the ends thereof have a better resistance to shattering than hitherto.

The object is achieved by reducing the outer diameter of the rod lens at its center, so it is smaller than the outer diameter at its ends. As a result, the ends of the rod lens can have the same diameter as the diameter of an adjacent lens to which the ends are to be cemented. This leads to a much better hold by the endoscope shaft, because in the case of bending stress to two adjacent lenses which are cemented together are equally stressed, whereas hitherto it has been principally the larger diameter lens which has been exposed to the stress.

According to one aspect of the invention, there is provided a rod lens, particularly for installation in an endoscope, wherein the diameter of the rod lens approximately in the center of its axial length is smaller than the diameter at its ends.

According to another aspect of the invention, there is provided in combination: a plurality of lenses, at least one being a rod lens of the invention, and all of said lenses having at least a portion adjacent to both of their ends with the same diameter as the end diameter of said rod lens, and an endoscope tube embracing and holding said lenses, in contact with said lenses at said last-named diameters.

According to a further aspect of the invention, there is provided a rod lens having radially enlarged ends of the maximum outer diameter of the lens.

According to another aspect of the invention, there is provided a lens combination comprising a rod lens having radially enlarged ends ofthe maximum outer diameter of the lens coaxially cemented between two lenses wherein the respective abutting ends of the lense are of the same outer diameter.

The invention also provides an endoscope comprising a lens or lens combination in accordance with any ofthe preceding aspects.

In one embodiment of the invention, in the vicinity of the end portions there is an approximately conical transition from the larger to the smaller diameter extending over a central axial length of substantial extent. It is preferred however that there is a relatively gradual transition from the end diameters to the centre diameter, so that loading peaks and endangered cross-sections are, as far as possible, avoided. It is also preferred that the outer wall of the lens, viewed from the side lies on a radius whose centre is outside of the lens.

According to yet another preferred but optional feature of the invention, a spacer sleeve is placed in the endoscope tube between adjacent rod lenses or between groups of lenses that include a rod lens.

The spacer sleeves contribute to providing an additional protection against shattering and increasing the stability between the individual lenses or lens groups.

The invention is described in greater detail hereinafter relative to non-limitative embodiments and the attached drawings, in which; Fig. lisa side view of an embodiment with several lenses according to the prior art; Fig. 2 is a side view of a first embodiment according to the invention; and Fig. 3 is a side view of a second embodiment according to the invention.

Fig. 1 shows a prior art rod lens system, including from left to right lenses 1,2,3 and 4, which are cemented to one another. They can in all cases be rod lenses, but lenses 1,2 and 4 can also be normal lenses.

As can be seen, the diameter of the prior rod lens 3 is smaller than that of the remaining lenses. According to the prior art this rod lens 3 has a completely uniform diametera in the center and 6 and cat the ends. This leads to the disadvantage that even in the case of limited bending of the endoscope, the cement layers 6 and 7 at the ends of lens 3 are highly stressed. This is in particular due to the fact that only lenses 1, 2 and 4 are embraced by the endoscope shaft (not shown) while the other circumference of the rod lens 3 is not held by the endoscope shaft due to the smaller diameter of lens 3. Thus, in this known arrangement the cement layers 6 and 7 are greatly endangered and fracture easily.

However, according to the embodiment of the invention shown in Fig. 2 the center of rod lens 3 has a smaller diametera than that at its ends b and c. In the vicinity of said ends the diameter is the same as that of the adjacent lenses 2 on the left and 4 on the right. Thus, in this embodiment, the endangered cement areas at the ends of rod lens 3 are embraced by the not-shown endoscope shaft (not shown) and are also supported by the latter. In the case of a bending stress it is the central area of lens 3 with the smaller diameter a which bends first. The transition from the larger to the smaller diameter is gradual, and in this case is roughly conical. In this area the rod lens is slightly relief-ground.

Fig. 3 shows a further embodiment in which a radius R is provided in the represented manner in the center of region A of the length along rod lens 3.

Thus, in this case diametera is at a minimum in the center. Here again, the outer ends of rod lens 3 have diameters and c which coincide with the diameters of lenses 3 and 4 which are cemented to the faces thereof. To the right there is shown a spacer sleeve 5, which can additionally increase the strength of the cemented points.

Thus, the invention provides a lens arrangement having at least one rod lens, which has a much greater resistance to shattering.

This invention is not to be limited by the embodiments shown in the drawings and described in the description, which are given by way of example and not of limitation, but only in accordance with the scope of the following claims.

Claims

1. A rod lens, particularly for installation in an endoscope, wherein the diameter of the rod lens approximately in the center of its axial length is smaller than the diameter at its ends.

2. A rod lens as claimed in Claim 1, wherein in the vicinity ofthe end portions there is an approximately conical transition from the largerto the smaller diameter extending over a central axial length of substantial extent.

3. A rod lens as claimed in Claim 1, wherein in the center there is a gradual transition from the end diameters to the smaller diameter.

4. A rod lens as claimed in Claim 3, wherein the outer wall of the lens, viewed from the side lies on a radius whose center is outside ofthe lens.

5. A rod lens substantially as hereinbefore described with reference to and as shown in Figure 2.

6. A rod lens substantially as hereinbefore described with reference to and as shown in Figure 3.

7. In combination: a plurality of lenses, at least one being a rod lens as claimed in any one of the preceding Claims, and all of said lenses having at least a portion adjacent to both of their ends with the same diameter as the end diameter of said rod lens, and an endoscope tube embracing and holding said lenses, in contact with said lenses at said last-named diameters.

8. A combination as claimed in Claim 7 in which a spacer sleeve is held by an endoscope tube between at least two adjacent lenses.

9. A combination as claimed in Claim 7 and substantially as hereinbefore described with reference to and as shown in Figure 2.

10. A combination as claimed in Claim 7 and substantially as hereinbefore described with reference to and as shown in Figure 3.

11. A rod lens having radially enlarged ends of the maximum outer diameter of the lens.

12. A lens combination comprising a rod lens as claimed in Claim 11 coaxially cemented between two lenses wherein the respective abutting ends of the lense are of the same outer diameter.

13. An endoscope comprising a rod lens as claimed in any one of Claims 1 to 6 and 11.

14. An endoscope comprising a lens combination as claimed in any one of Claims 7 to 10 and 12.