# US 4,400,062 A · Wave plate retarder

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- Number: US 4,400,062 A
- Document ID: US4400062A
- Status: Granted
- Kind: A
- Application number: 06/074,308
- Filed: 1979-09-11
- Granted: 1983-08-23
- Earliest claimed: 1979-09-11
- Assignees: Sony Corporation
- Inventors: Hiroshi Mori; Mikio Sugiki
- Web page: https://patentgrep.com/patent/US4400062A

## CPC

- G02B 5/3083: {Birefringent or phase retarding elements (G02B5/3008, G02B5/3016 take precedence; systems for polarisation control G02B27/286; manufacturing phase modulating patterns by lithographic processes G03F7/001)}
- Y10S 359/90: Methods
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- Y10S: TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS

## Abstract

A wave plate retarder consists of a stacked plurality of doubly refracting or birefringent high molecular films laminated with a predetermined angle between their respective optical axes to establish a desired phase difference during transmission through the films of components of light polarized along orthogonal axes. The predetermined angle may be selected to provide a phase difference of 1/4 or 1/2 wavelength of light to thus produce a composite wave plate retarder which functions as a 1/4 or 1/2 wavelength plate regardless of the phase difference of components of light produced by transmission through a single film.

## Claims

### Claim 1

A method of making a wave plate retarder comprising the steps of:
placing a film of birefringent material having an optical axis with its surface normal to a linearly polarized beam of light;
rotating said film about an axis parallel to said beam of light;
measuring maximum and minimum values of a linearly polarized component of said beam of light after passing through said film during said rotating of the latter;
determining a retardation phase angle from the following relationship:
R=1/2(1+cos .GAMMA.)
in which R is the ratio of said minimum value to said maximum value, and .GAMMA. is the retardation phase angle for said film;
forming from said film two sheets having respective optical angles; and
overlapping said two sheets with an angle C between their optical axes which is determined from the following relationship:
R.sup.1 =(1/2 cos 2.GAMMA.-2 cos .GAMMA.+3/2) cos.sup.4 C+2(cos .GAMMA.-1) cos.sup.2 C+1
in which R.sup.1 is 1/2 for a 1/4 wave plate retarder or R.sup.1 is 1 for a 1/2 wave plate retarder.

### Claim 2 (depends on 1)

The method according to claim 1; wherein said film is polypropylene which has been uniaxially stretched during the manufacture thereof to define an optical axis parallel to the direction of stretch.