# US 7,123,415 B2 · Optical instrument and optical element providing expanded exit pupil

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- Number: US 7,123,415 B2
- Document ID: US7123415B2
- Status: Granted
- Kind: B2
- Application number: 10/221,157
- Filed: 2001-03-20
- Published: 2003-02-06
- Granted: 2006-10-17
- Earliest claimed: 2000-03-20
- Assignees: Vision Engineering Limited
- Inventors: Graham Mercer
- Web page: https://patentgrep.com/patent/US7123415B2

## CPC

- G02B 27/0081: {with means for altering, e.g. enlarging, the entrance or exit pupil}
- G02B 5/18: Diffraction gratings {(holographic optical elements G02B5/32, G03H; integrally combined with optical fibres G02B6/02057; for coupling light guides G02B6/34; integrally combined with optical integrated light guides G02B6/12; grating systems G02B27/44)}
- G02B 21/02: Objectives
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

The invention provides an optical instrument including means (1, 2) to produce an optical image to be viewed by an observer including a diffractive element (7) located at an intermediate focal or image plane (4) of the optical instrument and comprising a pattern of a plurality of areas effective to cause diffraction interference in light passing through the optical instrument and thereby produce an expanded exit pupil (6) comprising a combination of a multiplicity of exit pupils displaced relative to one another transverse to an optical axis (3) of said instrument.

## Claims

### Claim 1

A diffractive element for use in an optical instrument, comprising a plurality of replications of a pattern of separated diffraction structures each effective to produce diffractive interference of polychromatic light passing through or reflected by the diffractive element, the plurality of diffraction structures including diffraction structures of different sizes and shape, and the plurality of replications are configured to produce a plurality of exit pupils which are displaced relative to one another transverse to an optical axis of the optical instrument such as to be viewable as a single, continuous expanded exit pupil and which have a light energy such that a light energy distribution across an extent of the expanded exit pupil is substantially uniform.

### Claim 2 (depends on 1)

A diffractive element as claimed in claim 1, wherein the diffraction structures of the plurality of diffraction structures are two-dimensional.

### Claim 3 (depends on 1)

A diffractive element as claimed in claim 1, wherein the diffraction structures of the plurality of diffraction structures are three-dimensional.

### Claim 4 (depends on 3)

A diffractive element as claimed in claim 3, wherein the diffraction structures of the plurality of diffraction structures comprise projections.

### Claim 5 (depends on 4)

A diffractive element as claimed in claim 4, wherein the projections are of one height.

### Claim 6 (depends on 4)

A diffractive element as claimed in claim 4, wherein the projections extend to more than one height.

### Claim 7 (depends on 3)

A diffractive element as claimed in claim 3, wherein the diffraction structures of the plurality of diffraction structures comprise depressions.

### Claim 8 (depends on 7)

A diffractive element as claimed in claim 7, wherein the depressions are of one depth.

### Claim 9 (depends on 7)

A diffractive element as claimed in claim 7, wherein the depressions lie at more than one depth.

### Claim 10 (depends on 1)

A diffractive element as claimed in claim 1, wherein the plurality of replications are such that the plurality of exit pupils are overlapping.

### Claim 11 (depends on 1)

An optical instrument for producing an optical image to be viewed by an observer, the optical instrument including the diffractive element of claim 1 located at an intermediate focal or image plane thereof.

### Claim 12 (depends on 11)

An optical instrument as claimed in claim 11, including an optical element, and wherein the diffractive element is formed on or is integral with a surface of the optical element.