HEAD MOUNTED DISPLAY

• US 20120044573A1
• Filed: 04/27/2010
• Published: 02/23/2012
• Est. Priority Date: 04/29/2009
• Status: Active Grant

• Current Assignee: Snap, Inc.
• Original Assignee: BAE Systems Plc
• Inventors: Simmonds, Michael David, Valera, Mohmed Salim
• Granted Patent: US 8,842,368 B2
• Time in Patent Office: Days
• US Class Current: 359/631
• CPC Class Codes: G02B 2027/0123 comprising devices increasing the field of view
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 27/4205 having a diffractive optical element [DOE] contributing to image formation, e.g. whereby modulation transfer function MTF or optical aberrations are relevant
• CPC Class Codes: G02B 27/4272 having plural diffractive elements positioned sequentially along the optical path
• CPC Class Codes: G02B 27/44 Grating systems; Zone plate systems G02B27/46 takes precedence
• CPC Class Codes: G02B 5/02 Diffusing elements; Afocal elements

Abstract

A helmet or head-mounted apparatus has a visor or other curved optical element in front of at least one eye of a wearer, which element also is used as a waveguide. Image-bearing light is injected into the waveguide via an input diffractive element, and propagates through the visor to an output diffractive element which releases the light. The optical powers of the curved waveguide and the input and output diffractive elements are selected so that the released light is delivered as an image to the users eye.

Claims

1. A head-mounted or helmet-mounted display apparatus comprising:

an optical element which in use is disposed in front of an eye of a user and which is curved in both azimuth and elevation relative to the eye and configured to operate as a waveguide;

a source of image-bearing light; and

diffraction means for propagation of image-bearing light through the optical element and for releasing the image bearing light from the optical element, the optical element and the diffraction means having optical powers such that the released light provides a visible image to the user'"'"'s eye.

2. The apparatus of claim 1 wherein the diffraction means comprises an input diffractive element and an output diffractive element.

3. The apparatus of claim 2 wherein at least the output diffractive element has spherical optical power in azimuth and elevation relative to the user'"'"'s eye.

4. The apparatus of claim 3 where in spherical optical power is provided by non-parallel diffractive features of the output diffractive element.

5. The apparatus of claim 4 wherein the diffractive features comprise a curved diffractive component.

6. The apparatus of claim 1 wherein the output diffractive element has an angular bandwidth which is less than the angular field of view of the visible image provided to the user'"'"'s eye, the angle of diffraction of the output diffractive element varying across the element so as to present the image to the user'"'"'s eye.

7. The apparatus of claim 1 wherein an optical axis of a waveguide formed within the optical element lies in a plane containing a sagittal axis of symmetry of the optical element and an eye of the user.

8. The apparatus of claim 1 wherein the source of the image-bearing light comprises a display panel and means for illuminating it, or a self-illuminating display panel.

9. The apparatus of claim 1 wherein the optical powers of the optical element and the diffraction means are such that image-bearing light passes from the image-bearing light source to the diffraction means without being acted upon by an element having optical power.

10. The apparatus of claim 1 comprising a further said diffraction means configured with the optical element to provide a visible image to the user'"'"'s other eye.

11. The apparatus of claim 10 comprising a respective image-bearing light source for each diffraction means, the light sources being disposed such that relative angular movement of the light sources about an axis of symmetry of the optical element adjusts the inter-pupillary spacing of the image presented to the user'"'"'s eyes.

12. The apparatus of claim 10 comprising a common light source for each diffraction means, and means for switching the image-bearing light repeatedly between the first and further diffraction means whereby to provide a visible image to each of the user'"'"'s eyes.

13. The apparatus of claim 12 wherein the switching means is an input element which is common to both the first and the further diffraction means, and switchable between them.

14. The apparatus of claim 12 wherein the image-bearing light source is configured to modify the image synchronously with switching of the image-bearing light whereby to provide a pair of binocular images to the main eyes.

15. The apparatus of claim 1 wherein the curved optical element is a transparent element through which the user views the outside world.