# US 2014/0198141 A1 · Image display apparatus > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0198141 A1 - Document ID: US20140198141A1 - Status: Published application - Kind: A1 - Application number: 13/988,197 - Filed: 2012-10-18 - Published: 2014-07-17 - Earliest claimed: 2011-10-20 - Assignees: Panasonic Corporation - Applicants: Panasonic Corporation - Inventors: Kenichi Kasazumi; Keiji Sugiyama; Kakuya Yamamoto - Web page: https://patentgrep.com/patent/US20140198141A1 ## CPC - G09G 3/02: by tracing or scanning a light beam on a screen - G02B 5/1842: {Gratings for image generation (G02B5/1847 takes precedence)} - G02B 26/0808: {by means of one or more diffracting elements} - G02B 30/50: the image being built up from image elements distributed over a three-dimensional [3D] volume, e.g. voxels - G03H 1/2286: {Particular reconstruction light (G03H1/24 takes precedence); Beam properties} - G03H 1/2294: {Addressing the hologram to an active spatial light modulator} - G09G 3/3611: {Control of matrices with row and column drivers} - G03H 2222/18: RGB trichrome light - G03H 2240/51: Intensity, power or luminance (G03H2240/52 takes precedence) - G09G 2320/0233: Improving the luminance or brightness uniformity across the screen - G09G 2320/0626: for control of overall brightness - G09G 2320/0646: Modulation of illumination source brightness and image signal correlated to each other - G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) - G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS - G03H: HOLOGRAPHIC PROCESSES OR APPARATUS (holograms, e.g. point holograms, used as ordinary optical elements G02B5/32; producing stereoscopic or other three-dimensional effects G02B30/00; diffraction-grating systems G02B27/44; systems using moiré fringes G02B27/60; optical logic elements G02F3/00; stereo-photography G03B35/00; photosensitive materials or processes for photographic purposes G03C; {stereo-photographic or similar processes G03C9/00}; apparatus for processing exposed photographic materials G03D; analogue computers performing mathematical operations with the aid of optical elements G06E3/00; authentication by radiation, of concealed information carried by holograms or diffraction gratings G06K19/16; holographic storage G11B7/0065, G11C13/04; {stereoscopic or other three dimensional effects in television systems H04N13/00}) ## Abstract An image display apparatus, including: a light source which emits coherent light; a spatial modulation element which diffracts the coherent light by displaying a diffraction grating pattern corresponding to an input image and which displays a virtual image by the diffracted light; and a control unit which calculates a total brightness representing a sum total of brightnesses of all pixels of the input image, and controls at least one of the light source and the spatial modulation element in such a manner that, if the total brightness has decreased, the virtual image is displayed at a lower brightness than a reference virtual image displayed when the input image is used directly. ## Claims ### Claim 1 An image display apparatus, comprising: a light source which emits coherent light; a spatial modulation element which diffracts the coherent light by displaying a diffraction grating pattern corresponding to an input image and which displays a virtual image by the diffracted light; and a control unit which calculates a total brightness representing a sum total of brightnesses of all pixels of the input image, and controls at least one of the light source and the spatial modulation element in such a manner that, if the total brightness has decreased, the virtual image is displayed at a lower brightness than a reference virtual image displayed when the input image is used directly. ### Claim 2 (depends on 1) The image display apparatus according to claim 1, further comprising a light shielding section which shields a portion of light emitted from the spatial modulation element, wherein the control unit adds a light shielding pattern that generates light directed towards the light shielding section, to the input image, and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image to which the light shielding pattern has been added. ### Claim 3 (depends on 2) The image display apparatus according to claim 2, wherein the light generated by the light shielding pattern includes zero-order diffracted light emitted from the spatial modulation element. ### Claim 4 (depends on 1) The image display apparatus according to claim 1, wherein, when the total brightness has decreased, the control unit enlarges a partial image of high brightness constituting the input image, and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image in which the partial image has been enlarged. ### Claim 5 (depends on 4) The image display apparatus according to claim 4, wherein the input image includes a plurality of text information images representing text characters as the partial image, and when the number of the text information images has decreased, the control unit changes a font size of the text information images in such a manner that the font size of the text information images becomes larger and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image in which the text information images have been changed. ### Claim 6 (depends on 4) The image display apparatus according to claim 4, wherein the input image includes a plurality of text information images representing text characters as the partial image, and when the number of the text information images has decreased, the control unit changes a font of the text information images in such a manner that the font of the text information images becomes thicker and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image in which the text information images have been changed. ### Claim 7 (depends on 1) The image display apparatus according to claim 1, wherein, when the total brightness has decreased, the control unit adds a control pattern to the input image in such a manner that the virtual image is displayed at a lower brightness than the reference virtual image, and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image to which the control pattern has been added. ### Claim 8 (depends on 7) The image display apparatus according to claim 7, wherein the control pattern includes an outer frame pattern of high brightness which is added at an outer periphery of the input image, and when the total brightness has decreased, the control unit changes the outer frame pattern in such a manner that a thickness of the outer frame pattern is increased, or in such a manner that a brightness of the outer frame pattern is increased, and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image in which the outer frame pattern has been changed. ### Claim 9 (depends on 7) The image display apparatus according to claim 7, wherein the control pattern includes a text string image containing a prescribed text string relating to the image display apparatus, and when the total brightness has decreased, the control unit changes the text string image in such a manner that the text string image becomes larger, or in such a manner that a brightness of the text string image is increased, and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image in which the text string image has been changed. ### Claim 10 (depends on 7) The image display apparatus according to claim 7, wherein the control pattern includes a uniform pattern having a uniform brightness with respect to the whole of the input image, and when the total brightness has decreased, the control unit changes a brightness of the uniform pattern in such a manner that the brightness of the uniform pattern is increased, and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image in which the brightness of the uniform pattern has been changed. ### Claim 11 (depends on 7) The image display apparatus according to claim 7, wherein the control pattern includes a distributed pattern which is distributed with respect to the whole of the input image, a brightness thereof in peripheral portions being lower than a brightness in a central portion of the input image, and when the total brightness has decreased, the control unit changes a brightness of the distributed pattern in such a manner that the brightness of the central portion of the distributed pattern is increased, and controls the spatial modulation element so as to display a diffraction grating pattern corresponding to the input image in which the brightness of the distributed pattern has been changed. ### Claim 12 (depends on 1) The image display apparatus according to claim 1, wherein the control unit controls an output of the light source in accordance with the total brightness. ### Claim 13 (depends on 1) The image display apparatus according to claim 1, wherein the control unit controls a lighting period of the light source in accordance with the total brightness. ### Claim 14 (depends on 1) The image display apparatus according to claim 1, further comprising an illumination optics system which converts the coherent light from the light source into illumination light and emits the illumination light to the spatial modulation element.