The present invention relates to a specimen-holder system for upright microscopes.
Upright microscopes used at the present time have a stage upon the surface of which the specimen to be examined is placed and which is generally displaceable, for focusing purposes, in the direction of the optical axis. For this purpose, two separate adjustments, a so-called coarse adjustment and a so-called fine adjustment, are required in order, on the one hand, to adapt the focal plane to greatly varying dimensions of the specimens and, on the other hand, to permit accurate focusing in the range of high magnification.
Since coarse and fine adjustments are effected coaxially, this focusing mechanism is relatively expensive to manufacture, particularly if value is placed on high stability of the stage. Manipulations of the specimen or displacements of the specimen upon scanning should cause the specimen to migrate as little as possible out of the focal plane of the microscope.
In inverse-type microscopes, the specimens to be examined are placed almost generally on a fixed stage so that the surface of the specimen in the case of reflected-light specimens always falls in the focal plane of the microscope. For small focusing strokes, merely a fine adjustment is required, whereby the lens turret can be displaced vertically.
This has the disadvantage that the user cannot directly observe the specimen surface which is being examined at the time, as is for instance very useful when seeking specimen regions of interest. When operating with oil immersion, the oil must be applied to the downward-facing preparation-side of the specimen slide and therefore, upon scanning of the specimen, the oil easily flows into the mechanism of preparation protection of the objective lens.
The focusing by displacement of the lens turret which is known in inverse-type microscopes cannot be applied directly to upright microscopes since larger focusing strokes (such as are required to enable examination of specimens of different dimensions) require the use of a special optical system. With the lenses widely used up to the present time, and designed for a finite tube length, only slight focusing strokes can be effected without negatively affecting the quality of the intermediate image.
West German Pat. No. 2,449,291 discloses a device for applying specimen slides to microscopes. The device consists of a fixed stage against the lower edge of which standardized transmitted-light specimen slides can be applied by means of a suction unit; as a result, specimen planes of the specimens always agree with the focal plane of the microscope used. Aside from the fact that this device requires a vacuum conduit, which is not available in the case of simple microscopes, other specimens, for instance reflected-light specimens of different dimensions, cannot be used in this apparatus. Even examinations of blood-count chambers, which are frequently viewed in clinical operations alternately with standard specimen slides, cannot be carried out on this apparatus since normal blood-count chambers differ in all dimensions (i.e., thickness, cover-glass thickness, width, length) from the corresponding values for standard specimen slides.
West German utility model Pat No. 1,973,676 discloses a so-called auto-levelling stage for reflected-light specimens; this auto levelling stage is placed on the actual stage of an upright microscope and within it specimens of different thickness are pressed, in each case by spring force, against the lower side of an annular diaphragm. With such auto-levelling stages, the specimen plane is moved upward by a constant amount, namely the height of the auto-levelling stage, and remains the same for all specimens which vary within the height of the auto-levelling stage. Of course, the use of this auto-levelling stage is possible only on microscopes which have a coarse adjustment or some other stage adjustment by which the focal plane of the microscope can be readjusted by that amount which corresponds to the displacement of the specimen plane which is attributable to the height of the auto-levelling stage.