Browse Prior Art Database

Optical Surface Microtopography Measurement And/Or Automatic Focussing

IP.com Disclosure Number: IPCOM000077332D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 2 page(s) / 32K

Publishing Venue

IBM

Related People

Frosch, A: AUTHOR [+4]

Abstract

Beam 2 exiting laser 1 is focussed by lens 3 at a first focal point 4 disposed in front of optical system 6, 7, which focuses the beam on the surface of object 8 at 9. The beam is reflected from 9 and passes optical system 6, 7 in the opposite direction.

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Optical Surface Microtopography Measurement And/Or Automatic Focussing

Beam 2 exiting laser 1 is focussed by lens 3 at a first focal point 4 disposed in front of optical system 6, 7, which focuses the beam on the surface of object 8 at 9. The beam is reflected from 9 and passes optical system 6, 7 in the opposite direction.

According to a first embodiment, a light detector 5 having a central hole at 4 is arranged in the path of the beam leaving optical system 6, 7. If beam 2 is in focus at 9, the reflected beam is again focussed at 4 and hence passes the central hole of light-detector 5 undisturbed. If beam 2 is out of focus at 9 the reflected beam is out of focus at 4, too, so that part of it is impinging on light detector 5. The signal at the output of light detector 5 is transformed at 10 into a control signal, which refocuses optical system 6, 7 via electromotor 11. Electro- optic element 12 may be provided to cyclically shift focal point of beam 2 at 9, thus providing an AC output of light detector 5.

According to another embodiment, in lieu of light detector 5, a first beam splitter 13 is arranged in the path of the beam leaving optical system 6, 7 which deflects the light reflected from 9 to second beam splitter 14 and mirror 15, and from there to light detectors 16 and 17 in front of which stops 18 and 19, having pinhole apertures, are arranged. The light reflected from 14 is focussed behind stop 18 while light reflected from 15 is focussed in front of st...