Optical: systems and elements – Light control by opaque element or medium movable in or... – Slit type
Reexamination Certificate
2000-03-10
2001-06-26
Phan, James (Department: 2872)
Optical: systems and elements
Light control by opaque element or medium movable in or...
Slit type
C359S227000, C359S230000
Reexamination Certificate
active
06252696
ABSTRACT:
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to a subassembly for generating an optically active slit with a changeable slit width s, preferably for slit lamps, with two slit plates or slit jaws which are displaceable relative to one another at a straight-line guide and between which the slit is formed, wherein one of two guide paths is allocated to each slit jaw.
b) Description of the Related Art
In optical instrument engineering, it is frequently necessary to generate illuminated fields of different geometric shapes with a virtually uniform illumination. One shape of illuminated field that is very frequently required is a light slit which is adjustable in width and length with an exactly parallel limiting of the slit width. Precision guidance of the slit-shaping structural component parts and a high edge quality at the slit jaws are needed to generate a light gap of this kind with high-contrast, sharp image borders.
A preferred application for subassemblies for generating an optically active slit is the slit lamp, which is frequently used for ophthalmologic diagnosis. It comprises essentially a stereo microscope and a projection device, both of which are arranged so as to be movable on a carrying system and coordinated with one another. The projection device makes it possible to generate geometrically different light fields. It is coupled with the stereo microscope in such a way that the center of the illumination field plane generally coincides with the center of the observation plane.
For example, a slit width which is adjustable from “zero” to 14 mm in a continuous and sensitive manner is required for applications of the kind mentioned above, wherein “zero” signifies an absolutely tight closing of the slit. The length of the slit can be between 0.3 mm and 14 mm, for example; further, the slit must often be swivelable by at least ±90° about the optical axis.
A significant problem in slit-forming optical subassemblies continues to be that the function-related caused proximity of the light housing which contains the illumination source giving off heat causes temperature fluctuations which disadvantageously affect the parallelism of the slit and which require a slit jaw guide that still generates a light slit satisfying requirements with respect to quality in spite of the influence of temperature.
The slit jaw guides known from the prior art have straight guide elements based on sliding friction or rolling friction in which two slit jaws which are displaceable relative to one another for changing the slit width are pretensioned against a guide path arranged at the frame by means of correspondingly constructed sliding or rolling guide elements so as to be free of play.
A disadvantage in all of the known technical solutions in this respect is the transmission of thermal and mechanical influences to the slit jaws which still occurs to an undesirably high degree and the consequent unwanted influence on the slit parallelism which manifests itself, for example, in the inability of the slit to close absolutely tight. To this extent, in spite of the large number of solutions that are already known, there is still a need for development, the aim of which is to reduce the troublesome influences and their consequences.
OBJECT AND SUMMARY OF THE INVENTION
Based on this prior art, it is the primary object of the invention to further develop a subassembly of the type mentioned above for generating an optically active slit in such a way that the consequences of external influences on the parallelism of the light slit are further reduced.
According to the invention, it is provided in a subassembly for generating an optically active slit of the type mentioned above that the guide paths are formed at portions of a guide rail which project out freely from a clamping position at the frame in the displacement directions of the slit jaws.
Due to the fact that the guide rails project out freely, this guide rail can expand without hindrance under the influence of temperature in the displacement direction.
In a preferred constructional variant of the invention, the guide paths are formed at two portions of a guide rail which project in opposite directions in a cantilevering manner from a clamping position. It is therefore possible to compensate for changes in length through unimpeded longitudinal expansion of these two portions in opposite directions.
In another constructional variant of the invention, it is provided that the guide paths are formed at two portions of the guide rail which project in one direction from a clamping position, wherein the end portion of the guide rail located opposite to the clamping position is supported in a floating manner. This guarantees compensation of changes in length of the guide rail in this direction proceeding from the clamping position. The guide rail can expand in the displacement direction, whereas changes in its position vertical to the displacement direction are impossible.
Further, in an advantageous manner, means for bending the guide rail are provided in the middle between the clamping position and the opposite end portion which is supported in a sliding manner, wherein the alignment of the two guide paths can be corrected by this bending. When the rail is bent using these means and the relative alignment of the two guide paths is adjusted, the parallelism of the slit can be influenced in this way. Accordingly, an adjustment possibility is provided which can preferably be carried out for an optimal adjustment of the slit parallelism prior to mounting the subassembly, according to the invention, in an optical device, for example, in a slit lamp.
In this connection, a particularly preferred construction consists in that a threaded pin is provided as means for bending the guide rail, wherein a bending of the guide rail in the longitudinal direction of the slit is accomplished by advancing the threaded pin. For this purpose, the guide rail, the clamping means for the guide rail, and the threaded pin should be made from the same material with the lowest possible coefficient of expansion, preferably stainless steel, so that changes in length caused by temperature influences can be compensated.
In a further construction of the invention, it is provided that slides are located across from the guide paths and are outfitted either with sliding guides or rolling body guides, the slit jaws being fastened thereto. The rolling body guides can be constructed in such a way, for example, that they engage around the guide paths.
Alternatively, it can also be provided that V-grooves which slide against the guide paths are formed at the slides. In this connection, it is advantageous when tension springs and/or pressure springs are provided for generating a pretensioning force between the slides and the guide paths, wherein one end of the spring is fixed with respect to the frame and the other end of the spring is attached to one of the slides. This ensures that the V-grooves always make contact with the associated guide paths and are thus also always aligned in the guide direction.
In one construction, tension springs are provided for this purpose and are arranged in such a way that their spring force causes the pretensioning of the V-grooves against the respective associated guide path with a first component F
1
and, with a second component F
2
, causes a pretensioning of the respective slide against an actuating member which is used to adjust a distance between the slides in the displacement direction and accordingly serves for adjustment. In this way, the contact of the V-grooves against the guide path and the contact of the slide against the actuating member are ensured with a spring allocated to a slide and to a slit jaw, respectively. In addition the tension springs can be arranged in such a way that the spring force, with a third component F
3
, prevents a rotation of the slit jaws around the displacement direction as will be shown in detail in the embodiment example.
In an advantageous manner, rolling bearings can be prov
Koschmieder Ingo
Link Guenter
Luther Egon
Steinmetz Dietmar
Carl Zeiss Jena GmbH
Phan James
Reed Smith LLP
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