Fine focusing table

Details Fine focusing table Fine focusing table

1999-05-24

2000-10-24

Nguyen, Thong

Optical: systems and elements

Compound lens system

Microscope

359391, 359392, G02B 2126

Patent

active

061376272

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention concerns a fine-focusing stage for microscopes, with an object carrier, a holder for the object carrier, and a positioning means which changes the vertical Z-axis position of the object carrier.
In ordinary microscopy, the object is focused by the microscope focusing drive. Positioning accuracy attainable with motors--usually DC motors--is about .+-.50 nm. Such values are inadequate, by a factor of more than two, so such focusing is not useful. External stepping motors are also often attached to the fine focusing drive of the microscope. By gearing down sufficiently, fine step divisions can be achieved; but the internal or external gearing needed very substantially limits movability.
Gear-free direct drives are already known in practice. Positioning accuracies in the nanometer range are attained with such direct drives. However, the range of motion is limited to a few hundred micrometers. There is the further problem here that such a direct drive, for instance, moves only one objective, which then projects far past the other objectives.
Z-stages which can be moved by piezoactive elements are also known in practice. However, the range of movement of such Z-stages is limited by the piezoelements. Piezo assemblies are also expensive because of the external measurement system required and because of the high-voltage control systems also needed.
Almost any desired Z scan rates can be attained with piezo control, including constant rapid and also very slot Z scan rates, such as 1000 .mu.m per second to 0.01 .mu.m per second. Speed tolerances less than .+-.0.5% can, in any case, be attained with geared motors only with extreme difficulty.
Now if a fine-adjustment stage is to be used in a conventional microscope, its design requires extreme flatness, with heights of about 5 mm desirable. Also, there must be a hole in the center of the stage for the light to pass through.
Z-stages with galvanometrically driven tilt plates have also been known in practice for some years. The disadvantage of such a system, though, is that the object is necessarily moved laterally as it is lifted, with large lift movements. If the object being observed is in the plane of the pivot of the tilt plate the error due to the lateral movement is negligibly small. For objects, or areas of objects, more distant from the plane of pivoting, though, this error becomes unacceptably large as the distance increases.


SUMMARY OF THE INVENTION

The invention is based on the objective of designing and developing a fine-focusing stage for microscopes of the type discussed here such that no error occurs even with large vertical movement of the object carrier. Furthermore, the fine-focusing stage should be simple in design and it should be possible to make it as thin as possible.
The fine-focusing stage according to the invention attains the objective above by being designed so that the holder comprises a mounting portion, preferably fastened to the microscope stage or to the microscope, and a connecting portion to the object carrier, and that hinged parallel arms extend between the mounting portion and the connecting portion through bending elements.
It is known according to the invention that adjustment errors which occur in the usual Z-stages can be avoided if the object carrier has a parallel lift characteristic. Therefore the holder has a mounting portion which can be attached rigidly to the holder. In the actual case, the mounting portion fastens either to the microscope stage or to the microscope itself. The holder also has a connecting portion to the object carrier, so that the object carrier is effectively connected to the mounting portion. Parallel arms hinged at bending elements extend between the mounting portion and the connecting portion, so that the bending elements occur between the mounting portion and the parallel arms, and also between the parallel arms or the connecting portion and the microscope stage.
The characteristic claimed here always assures that the horizontal position of the microsc

REFERENCES:
patent: 3407018 (1968-10-01), Miller
patent: 4095874 (1978-06-01), Wallace
patent: 4688908 (1987-08-01), Moore
patent: 5323712 (1994-06-01), Kikuiri
patent: 5864389 (1999-01-01), Osanai et al.

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