# US 5,710,668 A · Multi-color head-up display system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,710,668 A - Document ID: US5710668A - Status: Granted - Kind: A - Application number: 08/451,301 - Filed: 1995-05-26 - Granted: 1998-01-20 - Earliest claimed: 1995-05-26 - Assignees: Flight Dynamics, Inc. - Inventors: Jeffrey A. Gohman; Robert D. Brown; Robert B. Wood - Web page: https://patentgrep.com/patent/US5710668A ## CPC - G02B 27/0103: {comprising holographic elements} - G02B 5/28: Interference filters - G02B 2027/0145: {creating an intermediate image} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS ## Abstract A multi-color optical display system (10) employs a multi-powered reflective combiner (20) that together with a monochromatic or partly color-corrected relay lens (16) longitudinally corrects a multi-colored image. The combiner typically includes two surfaces (82, 90) of different optical powers with a reflective coating (106, 108) on each of the surfaces. The coatings are chosen to each reflect a specific wavelength range of colored light used in the system and to transmit all other wavelengths. The curvature of each surface is dictated by the aberrations in the color image created by the relay lens. Specifically, each surface is positioned so that its focus (86, 94) coincides with the focal point (58, 60) of the corresponding color component in an intermediate image (18) created by the relay lens so that the final virtual image (22) reflected by the combiner is longitudinally color corrected. ## Claims ### Claim 1 A multi-color optical display system for producing longitudinally color-corrected multi-colored images and presenting them for observation in combination with an observer's visual exterior view of an outside world scene, comprising: an image source providing a multi-colored image carried by multiple wavelengths of light propagating along an optical path; an optical combiner positioned so that an observer can see the exterior view through it and so that at least some of the multiple wavelengths of light reflect off the combiner to provide an image for observation by the observer; a lens positioned along the optical path between the combiner and the image source but out of the observer's direct exterior view, the lens receiving the multi-colored image, producing an intermediate image, and introducing longitudinal color aberrations into the multiple wavelengths of light as they propagate through the lens; and the combiner receiving the multiple wavelengths of light propagating from the lens, the combiner including multiple substrates having curved surfaces of different shapes and carrying reflective coatings of different wavelength selective properties so that the substrates cooperate to reflect the multiple wavelengths of light propagating from the lens to present to the observer a multi-colored final image superimposed on the outside world scene and substantially free from longitudinal color aberrations. ### Claim 2 (depends on 1) The system of claim 1 in which the reflective coatings are transmissive to selected ranges of the multiple wavelengths of light. ### Claim 3 (depends on 1) The system of claim 1 in which substantially all the wavelengths of light carrying the final image are focused at or near optical infinity. ### Claim 4 (depends on 1) The system of claim 1 in which the multi-colored image comprises a first colored light and a second colored light each having a focal point in the intermediate image and the multiple substrates comprise a first curved surface having a focus that coincides with the focal point of the first colored light and a second curved surface having a focus that coincides with the focal point of the second colored light. ### Claim 5 (depends on 4) The system of claim 4 in which the multi-colored image further comprises a third colored light having a focal point in the intermediate image and the multiple substrates further comprise a third curved surface having a focus that coincides with the focal point of the third colored light. ### Claim 6 (depends on 1) The system of claim 1 in which the multi-colored image comprises green and red light and in which the multiple substrates comprise a first curved surface having a reflective coating that reflects the green light and a second curved surface having a reflective coating that reflects the red light. ### Claim 7 (depends on 6) The system of claim 6 in which the multi-colored image further comprises blue light and in which the multiple substrates further comprise a third curved surface having a reflective coating that reflects the blue light. ### Claim 8 (depends on 1) The system of claim 1 in which at least one of the reflective coatings comprises a reflective material taken from the group consisting essentially of a holographic recording material, a dielectric, and a thin film. ### Claim 9 (depends on 1) The system of claim 1 in which the lens is of a monochromatic or partly color corrected type.