# US 10,864,820 B2 · Virtual image display optical system and image display device > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,864,820 B2 - Document ID: US10864820B2 - Status: Granted - Kind: B2 - Application number: 16/345,939 - Filed: 2017-10-30 - Published: 2020-02-20 - Granted: 2020-12-15 - Earliest claimed: 2016-10-31 - Assignees: Konica Minolta, Inc. - Applicants: Konica Minolta, Inc. - Inventors: Kentarou Nakamura; Norihide Yamada; Eiji Nomura; Junji Hashimura; Shinichiro Saito - Web page: https://patentgrep.com/patent/US10864820B2 ## CPC - G02B 27/0101: {characterised by optical features (G02B27/0172 takes precedence)} - B60K 35/22: Display screens - B60K 35/235: with means for detecting the driver's gaze direction or eye points - B60K 35/60: Instruments characterised by their location or relative disposition in or on vehicles (arrangements of lighting devices on dashboards B60Q3/10) - B60K 35/81: for controlling displays - B60K 37/20: Dashboard panels - G02B 27/0149: {characterised by mechanical features (G02B27/0176 takes precedence)} - B60K 2360/334: Projection means - G02B 2027/0127: {comprising devices increasing the depth of field} - G02B 2027/0145: {creating an intermediate image} - G02B 2027/0154: {with movable elements} - G02B 2027/0185: {Displaying image at variable distance} - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - B60K: ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES ## Abstract An object of the present invention is to provide a virtual image display optical system that is capable of substantially simultaneously displaying virtual images at a plurality of distances even with a simple configuration, and an image display device using the virtual image display optical system. A virtual image display optical system (30) according to the present invention is provided with: a display element (11); a projection optical system (15) that enlarges an image formed on the display element (11); a diffusing screen (16) that has a diffusing function, and is positioned on the light emission side of the projection optical system (15); and a virtual image forming optical system (17) that converts an image on the diffusing screen (16) into a virtual image, wherein the virtual image display optical system (30) is further provided with a positioning changing device (62) that changes a position of the diffusing screen (16). ## Claims ### Claim 1 A virtual image display optical system comprising: a display element that sequentially forms a plurality of images, each of the plurality of images being different from each other; a projection optical system that receives and enlarges the plurality of images formed on the display element; a diffusing screen that has a diffusing function, and is positioned on a light emission side of the projection optical system; and a virtual image forming optical system that converts a plurality of images on the diffusing screen into a plurality of virtual images, wherein the virtual image display optical system further comprises a positioning changing device that moves the diffusing screen in an optical axis direction to sequentially arrange the diffusing screen at a plurality of positions in the optical axis direction, each of the plurality of images corresponding to a respective one of the plurality positions. ### Claim 2 (depends on 1) The virtual image display optical system according to claim 1, wherein the display element has a two-dimensional display surface. ### Claim 3 (depends on 1) The virtual image display optical system according to claim 1, wherein the diffusing screen is positioned at an imaging position of the projection optical system, and causes a virtual image distance to change by being driven so as to reciprocate in the optical axis direction within a focal depth. ### Claim 4 (depends on 1) The virtual image display optical system according to claim 1, wherein the diffusing screen is a rotating body having a plurality of regions that differ in position related to the optical axis direction, and that can be positioned at imaging positions of the projection optical system, and a virtual image distance is changed by rotating the rotating body to move the plurality of regions so as to cross an optical axis. ### Claim 5 (depends on 1) The virtual image display optical system according to claim 1, wherein the diffusing screen is a rotating body having a disk shape, in which a diffusing surface and a bottom surface form a pair of surfaces, and in which a thickness in the optical axis direction differs in a circumferential direction, and a virtual image distance is changed by rotating the rotating body to move the diffusing surface of the rotating body so as to cross the optical axis. ### Claim 6 (depends on 4) The virtual image display optical system according to claim 4, wherein the rotating body is controlled to forwardly rotate by an outer motor. ### Claim 7 (depends on 4) The virtual image display optical system according to claim 4, wherein the display element is controlled by using rotation pulses of the rotating body as triggers. ### Claim 8 (depends on 4) The virtual image display optical system according to claim 4, wherein the diffusing screen is surrounded by a cover that is substantially cylindrical and hollow, and that has optical transparency. ### Claim 9 (depends on 1) The virtual image display optical system according to claim 1, wherein the diffusing screen moves in synchronization with display operation of the display element. ### Claim 10 (depends on 9) The virtual image display optical system according to claim 9, wherein the display element operates at a frame rate of 30 fps or more. ### Claim 11 (depends on 1) The virtual image display optical system according to claim 1, wherein the projection optical system has a diaphragm, and the diaphragm is arranged most on the diffusing screen side of the projection optical system. ### Claim 12 (depends on 1) An image display device that is equipped with the virtual image display optical system according to claim 1. ### Claim 13 (depends on 2) The virtual image display optical system according to claim 2, wherein the diffusing screen is positioned at an imaging position of the projection optical system, and causes a virtual image distance to change by being driven so as to reciprocate in the optical axis direction within a focal depth. ### Claim 14 (depends on 2) The virtual image display optical system according to claim 2, wherein the diffusing screen is a rotating body having a plurality of regions that differ in position related to the optical axis direction, and that can be positioned at imaging positions of the projection optical system, and a virtual image distance is changed by rotating the rotating body to move the plurality of regions so as to cross an optical axis. ### Claim 15 (depends on 2) The virtual image display optical system according to claim 2, wherein the diffusing screen is a rotating body having a disk shape, in which a diffusing surface and a bottom surface form a pair of surfaces, and in which a thickness in the optical axis direction differs in a circumferential direction, and a virtual image distance is changed by rotating the rotating body to move the diffusing surface of the rotating body so as to cross the optical axis. ### Claim 16 (depends on 2) The virtual image display optical system according to claim 2, wherein the diffusing screen moves in synchronization with display operation of the display element. ### Claim 17 A virtual image display optical system comprising: a display element; a projection optical system that enlarges an image formed on the display element; a diffusing screen that has a diffusing function, and is positioned on a light emission side of the projection optical system; and a virtual image forming optical system that converts an image on the diffusing screen into a virtual image, wherein the virtual image display optical system further comprises a positioning changing device that changes a position of the diffusing screen, the diffusing screen is a rotating body having a plurality of regions that differ in position related to an optical axis direction, and that can be positioned at imaging positions of the projection optical system, a virtual image distance is changed by rotating the rotating body to move the plurality of regions so as to cross an optical axis, and a number of rotations of the rotating body is controlled on the basis of rotation angle information of the rotating body. ### Claim 18 A virtual image display optical system comprising: a display element; a projection optical system that enlarges an image formed on the display element; a diffusing screen that has a diffusing function, and is positioned on a light emission side of the projection optical system; and a virtual image forming optical system that converts an image on the diffusing screen into a virtual image, wherein the virtual image display optical system further comprises a positioning changing device that changes a position of the diffusing screen, and the virtual image display optical system satisfies the following conditional expression: 2≤FOV/(m×H)≤4 where: FOV is a viewing angle [rad] of the virtual image forming optical system; m is an optical magnification of the projection optical system; and H is a horizontal directional length [m] of the display element. ### Claim 19 A virtual image display optical system comprising: a display element; a projection optical system that enlarges an image formed on the display element; a diffusing screen that has a diffusing function, and is positioned on a light emission side of the projection optical system; and a virtual image forming optical system that converts an image on the diffusing screen into a virtual image, wherein the virtual image display optical system further comprises a positioning changing device that changes a position of the diffusing screen, and the virtual image forming optical system satisfies the following conditional expression: 2≤M/L≤4 where: M is an optical magnification of the virtual image forming optical system; and L is a distance [m] from an observation position to a virtual image. ### Claim 20 A virtual image display optical system comprising: a display element; a projection optical system that enlarges an image formed on the display element; a diffusing screen that has a diffusing function, and is positioned on a light emission side of the projection optical system; and a virtual image forming optical system that converts an image on the diffusing screen into a virtual image, wherein the virtual image display optical system further comprises a positioning changing device that changes a position of the diffusing screen, and an F-number of the projection optical system is set so as to satisfy the following conditional expression: 0.8≤2×F×P×m2/δ≤1.2 where: F is an F-number on the display element side of the projection optical system; P is a pixel pitch [mm] of the display element; and δ is a diffusing screen moving distance [mm] required to obtain a desired virtual image distance range.