IMAGE DISPLAY APPARATUS

• US 3,821,721 A
• Filed: 03/15/1973
• Issued: 06/28/1974
• Est. Priority Date: 03/15/1972
• Status: Expired due to Term

• Current Assignee: Hughes G
• Original Assignee: Hughes G
• Inventors: HUGHES G
• Application Number:
  US05/341,652
• Time in Patent Office: 470 Days
• US Class Current: 345/63
• CPC Class Codes: G09F 13/26 Signs formed by electric discharge tubes by selective lighting G09F9/00
• CPC Class Codes: G09F 9/313 being gas discharge devices G09F9/302 takes precedence; gas discharge panels comprising a number of discharge gaps per se H01J17/49
• CPC Class Codes: G09G 3/296 Driving circuits for producing the waveforms applied to the driving electrodes
• CPC Class Codes: G09G 3/297 using opposed discharge type panels
• CPC Class Codes: H04N 3/125 using gas discharges, e.g. plasma

Abstract

Apparatus for displaying an image on an arrangement of gas discharge cells is disclosed in which a matrix of image display cells is formed by the interlacing of a number of elementary cell matrices. The elementary cells are so arranged that corresponding single cells from all the elementary matrices fall within each image display cell. The brightness of each image cell is therefore dependent upon the number of its elementary cells which are energised and the brightness level of those energised elementary cells. By arranging that the individual elementary cells of an image cell have different brightness levels and selecting appropriate combinations of these elementary cells to be energised a brightness range of at least 12:1 is possible for a single image cell, thus allowing the arrangement to display half-tone images acceptably. Tone separation of a displayed image is possible by reducing the brightness range of the display cells. The variations in brightness of the elementary cells may be achieved by, for example, the incorporation of optical filters, such as neutral density filters, to absorb light from some of the elementary cells within an image cell or by regulating the current permitted to flow in each elementary cell. The decoding of coded brightness information to control the energisation of the elementary cells during scanning of those cells within a display cell is disclosed.

Claims

1. Apparatus for displaying an image by a plurality of illuminable image cells arranged in rows and columns including a plurality of similar elementary cell matrices, the cell matrices each containing gas display cells arranged respectively in rows and columns corresponding to the rows and columns of the image cells, the elementary cells being selectively individually energizable to produce a glow discharge, the different elementary cell matrices being physically interlaced to displace corresponding ones of the elementary cells in different matrices one from another to locate within each image cell a corresponding single elementary cell from each different cell matrix respectively and means for selectively controlling the energization of the elementary cells of each image cell selectively to vary the illumination brightness of the image cells.

2. Apparatus as claimed in claim 1 in which the means for controlling the energization of the elementary cells includes means for registering image display information expressed as a brightness code specifying a level of brightness for each image cell and means for decoding the brightness code to select to be energised different combinations of the elementary cells of an image cell in dependence upon the different brightness levels expressible by said brightness code.

3. Apparatus as claimed in claim 2 in which the energization control means further includes means for selecting an image cell by selecting corresponding cells in each of the elementary cell matrices, means for sequentially scanning the selected elementary cells and means associated with said decoding means for strobing the decoded brightness code in synchronism with the scanning of the cells to permit the energization of only those elementary cells required to produce an image coil illumination of the specified brightness.

4. Apparatus as claimed in claim 3 in which all the cells of a single matrix are responsive to energization to produce illumination of substantially similar brightness and in which the cells of at least some matrices produce illumination of different brightness than those of other matrices.

5. Apparatus as claimed in claim 4 in which the means for controlling the energization of the elementary cells includes means for limiting current flowing in the cells, the current limiting means being arranged to permit different currents to flow in the cells of different matrices respectively.

6. Apparatus as claimed in claim 4 in which selected elementary cell matrices include means for optically reducing the visual brightness of energized cells.