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Laser Scanning Microscope With Micromechanical Scale

IP.com Disclosure Number: IPCOM000100188D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 83K

Publishing Venue

IBM

Related People

Kallmeyer, M: AUTHOR [+2]

Abstract

A high-precision laser scanning microscope comprises a micromechanical scale with integrated photoreceptors in its intermediary image plane for locating the scanning laser beam exactly in two dimensions. Such a microscope may be used for laser beam position measurements in the Angstrom range.

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Laser Scanning Microscope With Micromechanical Scale

       A high-precision laser scanning microscope comprises a
micromechanical scale with integrated photoreceptors in its
intermediary image plane for locating the scanning laser beam exactly
in two dimensions.  Such a microscope may be used for laser beam
position measurements in the Angstrom range.

      Fig. 1 shows the schematic optical set-up of the laser scanning
microscope with a laser 1, a pair of scanning devices 2, 4 for
deflecting the laser beam in two orthogonal directions, a relay lens
3 for focussing the laser beam in the intermediary image plane IM of
the object lens 8, and a crossed phase grating 5 for splitting up the
laser beam into five partial beams 6 such that the deflected beams
6a, 6b impinge upon micromechanical scale 7, whereas the undiffracted
central beam 6c is focussed on object 9.  The scanning devices 2, 4
may be mirrors oscillating around two perpendicular axes.

      Fig. 2A is a plan view of the two-dimensional micromechanical
scale 7 with a central opening 20 for the undiffracted beam 6c and
four groups of linear photodetectors 21a - 21d (in periodic
arrangement with a period interval P) for the diffracted beams 6a, b,
e, f. For optimal signal evaluation, the two photodetector groups for
each direction are offset relative to each other by a quarter of a
period length P/4.

      In the micromechanical embodiment of scale 7, which is shown in
Fig. 2B in a cross-section (along line A-B of Fig. 2A), the
photodiodes 21 are formed at the bottom of a cavity extending along
either side of central opening 20 in a...