Optical: systems and elements – Lens – With support
Reexamination Certificate
2001-08-16
2003-02-25
Epps, Georgia (Department: 2873)
Optical: systems and elements
Lens
With support
C359S813000, C359S819000
Reexamination Certificate
active
06525888
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
This application claims priority of German Application No. 100 42 844.4, filed Aug. 17, 2000, the complete disclosure of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a radially adjustable lens mounting like the one known from FR 2428852.
b) Description of the Related Art
Lens mountings are used for the precise mechanical mounting of optical lenses in precise positions within a lens system, meaning at particular distances and alignments to each other. Particularly in high-performance lenses, minute positional deviations of individual lenses can have undesired systematic errors as their consequence. For this reason, an adjustment is done after assembly of at least those lenses whose positional deviation has a critical effect on the lens system.
Only by means of these measures can the total error of the lens system be optimally corrected while taking all production tolerances of the individual lenses and of the mechanical components into consideration.
The exact alignment of the lens plane (the plane that is vertical to optical axis of the lens) relative to the optical axis of the lens is of particular importance for the adjustment of a high-performance lens. Centering the lenses on the optical axis of the lens system also has a very great influence on its precision. Both are achieved by an adjustment which is radial to the optical axis and as sensitive as possible while it avoids tilting the lens. Depending on the use of the optical system, other requirements with regards to thermal stability or positional security relative to mechanical stresses are added.
The devices necessary for this can be combined into radially adjustable lens mountings.
In such devices, the mounted or unmounted individual lens is moved on its lens plane relative to a mechanical base; the latter can be a lens tube, a mounting or an auxiliary mounting adjustable inside the main mounting.
Here, the decisive factor for the precision of adjustment is achieved in particular by means of a delicate movement and fixing of the lens without misadjustment.
From DE 37 12 179 A1 a radially adjustable lens mounting is known where a lens tube provides the mechanical base for the adjustment.
At an offset of 90 degrees, two auxiliary devices engage on the circumference of the lens tube; each of them consists of a so-called spring element and a so-called micrometer attachment arranged diametrically opposite to it. The spring element and the micrometer attachment are special mechanical subassemblies which can be removed and used for identical adjustments somewhere else after the adjusted lens has been fixed in place by means of another device provided for this purpose. The displacement in one direction is done by means of an adjustment screw guided in the spring element.
The overall solution including the auxiliary device and the fixing device integrated in the lens tube is a constructionally complicated solution. It is disadvantageous for the adjustment process that when the lens is moved in one adjusting direction this is always done against forces which are vertical to the direction of the adjusting movement and are being generated by the second auxiliary device. The friction created by this has the effect of causing a backwards sliding movement (slide-back) and thus reduces the sensitivity of the adjustment. Furthermore, the arrangement for fixing cited here, which for example consists of three clamping jaws, does not guarantee a no-tilt fixing, since they are tightened individually.
From DE 206 591 B1 an arrangement is known for which an auxiliary lens mounting (mechanical mounting) is arranged so as to be radially displaceable at right angles to the axis of the lens tube (axis of the device) within a gimbal mounted main mounting (holder). The displacement of the auxiliary lens mounting within the main mounting as well as the holding of the auxiliary lens mounting is done via radially engaging adjusting elements. Since the adjusting elements also fulfill a holding function, only mechanical adjusting screws can be used as adjusting elements. They all have to be released for the adjustment which means that the auxiliary lens mounting can slip out of alignment during the adjustment. The lens is fixed in position by tightening the adjustment screws. So that the fixing of the auxiliary lens mounting does not lead to a maladjustment, the adjustment screws must be tightened with an even force after contacting the auxiliary lens mounting; in practice, this appears to be difficult.
A solution comparable to DD 206 591 B1 with regards to the radial adjustment is described in OE-Reports, No. 67, p.13, July 1989, published by SPIE. An auxiliary lens mounting with two plane surfaces inside of which the lens is fixed can be adjusted vertical to the optical axis by means of adjusting elements within a main lens mounting. One of the plane surfaces of the auxiliary lens mounting rests on a plane surface of the main lens mounting so that friction results during the adjustment; this can lead to slide-back and thus counteracts the sensitivity of the adjustment. In contrast to the previous solution, though, the fixing is here done by means of the application of glue; this means that a maladjustment during fixing can not take place, since no mechanical forces are active, but it has to be said that the adjustment is also irreversible.
DE PS 37 30 094 C2 describes an arrangement where an auxiliary mounting which can be moved inside a main mounting is indirectly pushed against a base surface by means of the force of a spring acting vertical to the direction of displacement.
The forces determining this clamp-like connection have to be overcome during an adjustment radial to the optical axis and therefore counteract sensitivity.
For all solutions mentioned, the adjustment takes place in two orthogonal directions of adjustment relative to a mechanical base and by means of adjustment screws or headless setscrews. During an adjustment in one direction of adjustment, the adjustment screws or setscrews must either be released or their force of pressure must be overcome; both are disadvantageous for the adjustment process. If they are released when they are also fulfilling a holding function as well as the adjustment function, this can result in a renewed maladjustment in the already adjusted direction.
If they are not released, friction is created which can lead to slide-back. For solutions where an additional holding arrangement is present, this is normally either activated after the end of the adjustment process (DE 37 12 79) or its effect is at least partially cancelled during the adjustment process, as known from DE 44 00 869.
For the latter, piezo translators are inserted which generate a force which counteracts and partially compensates for the force of pressure generated in a main mounting (first mounting) for the defined holding of the auxiliary lens mounting during the adjustment so that a displacement of the auxiliary lens mounting is possible with little radial force. For this solution, too, the movement of mechanical parts against each other causes friction, which can lead to the slide-back previously mentioned.
Beyond the criticisms made, the application of all solutions described so far is limited when it comes to thermal or mechanical stresses.
In a mounting according to FR428852, the centering of a lens is done with barely any friction. Between lens and mounting, spring elements are arranged in indirect contact with the peripheral surface of the lens which effect an almost evenly distributed radially acting spring force between the mounting and the lens and are supposed to center the lens on the axis of the mounting. This spring force can be generated by a flat spring of different types which almost encloses the lens completely or by a large number of individual spring elements like compression springs or purpose-shaped leaf springs. By means of an adjusting screw engaging indirectly with the lens, an adjustment in on
JENOPTIK Laser, Optik, Systeme GmbH
Reed Smith LLP
Seyrafi Saeed
LandOfFree
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