GB2359374A

GB2359374A - Flexible concave mirror adjustable using a vacuum pump

Info

Publication number: GB2359374A
Application number: GB0003460A
Authority: GB
Inventors: Stephen David Faulkner
Original assignee: Individual
Current assignee: Individual
Priority date: 2000-02-16
Filing date: 2000-02-16
Publication date: 2001-08-22
Also published as: GB0003460D0

Abstract

The mirror uses a flexible reflective membrane 6, which is supported by a sealed hollow body 5, with a variable vacuum pump and valve device 3 that sucks in the mirrored surface to form a concave shape. Increasing or decreasing the vacuum or adjusting the membrane tensioner 1 which fits on airtight rim 2 varies the field focus of the mirror. The mirror is suitable for use in a Cassegrain reflector telescope where an image (such as starlight) is bounced from the reflective membrane 6 onto secondary mirror 10. The narrowed field is then directed through a clear non-reflective centre 7 in the middle of the mirror and through a clear bulkhead 8 into a standard eyepiece 11 or camera device held in a mount 12.

Description

2359374 1 Adjustable Concave Mirror

Description

This invention relates to an adjustable mirrored membrane, mounted in a sealed drum-type body for a telescope application.

Most Cassegrain reflector telescopes require a concave primary mirror, precision ground from glass, which is both heavy, expensive to produce, limited to its size of diameter, and has a fixed concave focal surface.

The object of this invention is to replace this primary mirror with a lightweight, adjustable concave mirror surface of low cost and of a far greater diameter size.

This invention achieves these claims by using a flexible plastic mirror membrane, which is formed into a perfect concave shape, by the use of a vacuum, supported inside of a sealed drum body.

This new mirror concept could be incorporated into a new telescope design or built separately to individual specification to upgrade older models

The concept of this invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 shows a side view of the mirror body FIGURE 2 shows the concave mirror front elevation FIGURE 3 shows the clear glass bulkhead rear elevation FIGURE 4 shows a side elevation as a 'cut-away' section FIGURE 5 shows the whole concept as it might be incorporated into a Cassegrain type telescope Figure 1 shows the main cylindrical body 5, with an airtight adjustable rim 2, securing the flexible mirror membrane 6. Halfway along the body is a controllable vacuum pump and valve device 3 and on the rear end is an airtight rim 4 to support the bulkhead.

2 Figure 3 shows the bulkhead 8 to be non-flexible but it could be made of clear glass, Perspex or aluminium depending on the position of the eyepiece 11 for side or rear viewing telescopes.

Figure 2 shows the mirror membrane 6 stretched across the front of the cylindrical body 5 and held airtight by the rim 2, which can be increased or decreased in tension by membrane tensioner 1. This membrane 6 can be incorporated with a clear cellophane centre 7 for rear-view telescopes.

Figure 4 shows the cross section of the body 5 and how, when the vacuum 9 is altered, via the vacuum controller 3, the mirror membrane6 is adjusted in its concave shape for a higherllower field focus.

Figure 5 shows a 3dangle, cut-away projection of how the adjustable concave mirror would be adapted into a modern Cassegrain type telescope, whereby, the starlight enters the concave reflective membrane 6, is bounced back onto the secondary mirror 1 O.The narrowed field is then directed through the clear cellophane centre 7 and through the clear glass/perspex bulkhead 8, into a standard eyepiece 11 or camera device held in a mount 12.

3

Claims

An adjustable mirror using a flexible plastic membrane which is supported by a sealed hollow body with a variable vacuum that forms the mirrored surface into a concave shape.
2. An adjustable mirror as claimed in Claim 1 whereby the concave shape of the membrane is altered by increasing or decreasing the vacuum inside the sealed body of this apparatus.
3. An adjustable mirror as claimed in Claim 1 or Claim 2 where the flexible mirror membrane is held in a position around the body by a rim which, when adjusted, would cause the membrane to tension or de-tension.
4. An adjustable mirror as in Claims 1,2 and 3, where the centre of the flexible membrane is clear and the rear bulkhead of the sealed body is also clear to allow light to pass through without distortion.
5. An adjustable mirror as claimed in any proceeding claim which is incorporated into a telescope mechanism for observation purposes.
6.

An adjustable mirror as claimed in any proceeding claim which is made from aluminium, plastic material and glass or from a combination of these materials.
7. An adjustable mirror substantially as herein described and illustrated in the accompanying drawings.