Image correction in virtual reality and heads up displays

• US 5,673,151 A
• Filed: 06/06/1995
• Issued: 09/30/1997
• Est. Priority Date: 02/07/1992
• Status: Expired due to Fees

• Current Assignee: i-O Display Systems LLC (Ilixco, Inc.)
• Original Assignee: Virtual I/O
• Inventors: Rallison, Richard Dennis
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): Robbins, Thomas
• Application Number:
  US08/473,559
• Time in Patent Office: 847 Days
• Field of Search: 385/116, 385/119, 385/120, 385/121, 359/631, 359/630, 359/633
• US Class Current: 359/631
• CPC Class Codes: G02B 2027/011 comprising device for correcting geometrical aberrations, distortion
• CPC Class Codes: G02B 2027/0116 comprising devices for correcting chromatic aberration
• CPC Class Codes: G02B 2027/0132 comprising binocular systems
• CPC Class Codes: G02B 2027/0174 holographic
• CPC Class Codes: G02B 2027/0178 Eyeglass type eyeglass details G02C
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G02B 27/0172 characterised by optical features
• CPC Class Codes: G02B 5/30 Polarising elements light-modulating devices with active elements G02F1/00
• CPC Class Codes: G02B 6/08 with fibre bundle in form of plate

Abstract

The present invention eliminates the relay lens systems found in conventional helmet mounted displays (HMDs) by removing field distortions and aberrations with a contoured fiber optic faceplate placed in close proximity to a liquid crystal display (LCD) or cathode ray tube. The optical system typically consists of a spherical dielectric or holographically made collimator-combiner, a dielectric or holographically made fold mirror, and a contoured fiber optic faceplate. The fold mirror is flat, and the collimator-combiner is made by coating a spherical eye glass blank. The system is configured as a folded and tilted catadioptric projector with the novel feature being the contoured faceplate. There are no dispersive elements in the imaging assembly which means it can be completely polychromatic (full color) without the need for additional color correction optics as found in all refractive color systems. When designed for full color, highest brightness, and see through capability it must be made with two or three narrow spectral and angular sensitive coatings on the fold mirror and on the collimator-combiner. These coatings allow the use of a tilt of the collimator-combiner with respect to the fold mirror which induces a small amount of astigmatism and keystone distortion but at the same time allows image light to pass through the folded optics to the eye with a minimum of loss. The elimination of a corrective refractive lens relay system makes this design polychromatic, less expensive, and lighter in weight, compared to a similar system with an achromatized and corrected refractive lens.

Claims

1. A method for providing a head-mounted display for a user comprising:

generating a plurality of image pixels to provide image light using an image generator wherein said pixels have edges, said pixels define a pixel size;

blurring the edges of the pixels by transmission through a fiber optic means, said fiber optic means defining a distance between said fiber optic means and said image generator having a numerical aperture approximately equal to twice the pixel size of said pixels divided by the distance between said fiber optic means and said image generator;

redirecting said image light output by said fiber optic means in a first direction away from the eye of the user;

redirecting said light from said first direction to a second direction for transmission to the eye of the user.

2. Head-mounted display apparatus for a user, said user having at least one eye comprising:

an image generator generating a plurality of pixels and defining a pixel size;

means for providing a numerical aperture approximately equal to twice the pixel size of the image generator divided by a distance between a fiber optic faceplate and said pixels;

a fold mirror for reflecting image light away from the eye of the user; and

a reflector for redirecting said light transmitted in said first direction to a second direction for transmission to the eye of the user.

3. Apparatus as claimed in claim 2 wherein said numerical aperture is between about 0.2 and about 0.4.

4. Apparatus as claimed in claim 3 wherein said distance is about 1.2 millimeters.

5. Head-mounted display apparatus comprising:

an image generator generating a plurality of pixels and defining a pixel size wherein said pixels have edges;

first means for blurring the edges of the pixels of said image light, said first means defining a distance between said first means and said pixels, said first means defining a numerical aperture approximately equal to twice the pixel size of the image generator divided by the distance between said first means and said pixels.

6. A method for reducing field curvature, spherical aberration, and keystone distortion in a folded catadioptric HMD having a spherical-surface collimator-combiner which delivers an image to an eye position without using refractive relay lenses, comprising:

replacing the refractive lenses with a fiber optic faceplate having an output surface; and

shaping the output surface of said fiber optic faceplate to provide a non-toric output surface which matches a locus of focused points generated by ray tracing many parallel bundles of rays from the eye position to said spherical surface of said collimator-combiner and thence to the points where the collimator-combiner focuses said parallel bundles of rays.