# US 4,398,787 A · Optical leverage telecentric scanning apparatus

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- Number: US 4,398,787 A
- Document ID: US4398787A
- Status: Granted
- Kind: A
- Application number: 06/274,602
- Filed: 1981-06-17
- Granted: 1983-08-16
- Earliest claimed: 1981-06-17
- Assignees: The United States of America as represented by the Secretary of the Army
- Inventors: N. Balasubramanian
- Web page: https://patentgrep.com/patent/US4398787A

## CPC

- G02B 26/108: {having one or more prisms as scanning elements}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical leverage telecentric scanning apparatus for scanning a large fat film transparency at a given location is disclosed, wherein the scan pattern from the transparency is detected for optical power spectrum analysis. The scanning apparatus includes a collimated laser beam supply and a refraction device for laterally translating the collimated beam across the transparency. To magnify the collimated beam, an optical leverage device is provided including a first lens arranged between the laser beam supply device and the refraction device, and a scanning concave parabolic mirror arranged between the diffraction device and the transparency. The degree of magnification afforded by the optical leverage device is equal to the ratio of the focal lengths of the mirror to the first lens, respectively. A detector arranged on the opposite side of the transparency from the refraction device detects the scan pattern produced by the laser beam passing through the transparency.

## Claims

### Claim 1

Optical leverage telecentric scanning apparatus for scanning a large format film transparency for optical power spectrum analysis, comprising
(a) means supporting the transparency at a given location;
(b) means supplying a collimated laser beam;
(c) refraction means for laterally translating said collimated beam across the transparency;
(d) optical leverage means for magnifying said collimated beam, said optical leverage means including
(1) a first lens arranged between said laser beam supply means and said refraction means, and
(2) a concave parabolic mirror arranged between said refraction means of magnification afforded by said first lens and said mirror being equal to the ratio of the focal lengths of said mirror to said first lens, respectively;
(e) detector means arranged on the opposite side of the transparency from said refraction means for detecting the scan pattern produced by the laser beam which is passed through the transparency, whereby said refraction means and said optical leverage means produce a magnified scan pattern for optical power spectrum analysis of said transparency; and a transform concave parabolic mirror arranged between the transparency and said detector means for focusing said scan pattern from the transparency on said detector means.

### Claim 2 (depends on 1)

Apparatus as defined in claim 1, wherein said refraction means comprises rotating polygonal prism means.

### Claim 3 (depends on 2)

Apparatus as defined in claim 2, wherein said rotating polygonal prism means comprises a pair of polygonal prisms the axes of which are arranged perpendicularly, whereby one of said pair of prisms laterally translates said scanning beam along a first axis, and the other of said pair of prisms translates said scanning beam along a second axis perpendicular to said first axis to scan the area of said film transparency.

### Claim 4 (depends on 1)

Apparatus as defined in claim 1, wherein said collimated laser beam supply means comprises
(a) laser beam supply means; and
(b) spatial filter collimator means for collimating said laser beam.

### Claim 5 (depends on 4)

Apparatus as defined in claim 4, wherein said spatial filter collimator means comprises a pair of lenses arranged in afocal relation.

### Claim 6 (depends on 4)

Apparatus as defined in claim 4, wherein said spatial filter collimator means further comprises an apertured member arranged between said pair of afocal lenses, whereby the diameter of said collimated scanning laser beam is related to the size of the aperture.

### Claim 7 (depends on 1)

Apparatus as defined in claim 1, further including:
a mirror arranged between said concave parabolic mirror and said transparency for passing said collimated beam normal to the plane of said transparency.