Remote optical display designator

• US 4,150,285 A
• Filed: 12/27/1977
• Issued: 04/17/1979
• Est. Priority Date: 12/27/1977
• Status: Expired due to Term

• Current Assignee: Siemens Rail Automation Ltd. (Siemens AG)
• Original Assignee: United Technologies Corporation (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: Gordon, Jason M., Brienza, Michael J.
• Primary Examiner(s): Segal, Robert
• Application Number:
  US05/864,956
• Time in Patent Office: 476 Days
• Field of Search: 358/107 (U.S. only), 250/203, 250/227, 364/521
• US Class Current: 356/622
• CPC Class Codes: G06F 3/0386 for light pen

Abstract

An optical designator system employs a remote source of electromagnetic energy, such as a small hand-held infrared LED or the like, to generate an identifying beam which is directed to the same faceplate through which a displayed image is viewed. A diffuser medium is disposed at the image plane along the rear surface of the faceplate and scatters the incident beam of electromagnetic energy toward orthogonal pairs of photodetectors located adjacent to the edges of the faceplate. The output signals from the photodetectors are presented to a normalizer circuit which compensates for intensity variations of the source of electromagnetic energy into the faceplate. Therefore, the output signal from each normalizer circuit varies in a relationship which is proportional to the distance between the photodetectors at which the incident beam strikes the diffuser medium. The remote energy source is preferably modulated with a waveform which is discernible both from background ambient light and that of the displayed image. Optical and electrical filters associated with the photodetectors insure that normalizer circuits respond only to electromagnetic energy from the remote source.

Claims

1. A remote designator apparatus for identifying locations on a display area, comprising:

a faceplate means having a diffusing surface on one face thereof forming an image plane;

a source means for directing a beam of electromagnetic energy to the diffusing surface of said faceplate means;

photoresponsive means disposed at the perimeter of said faceplate for receiving electromagnetic energy scattered along said faceplate by said diffusing surface; and

means coupled to said photoresponsive means for providing an output signal indicating the location on said diffusing surface impinged by the incident beam of electromagnetic energy from said source means.

2. A designator apparatus according to claim 1, wherein said photoresponsive means includes two pair of photodiodes, said photodiodes of each pair positioned adjacent opposite edge portions of said faceplate means, and further including a normalizer circuit coupled to each pair of photodiodes for indicating the respective orthogonal distance along the faceplate impinged by said incident beam of electromagnetic energy.

3. A remote designator according to claim 2, wherein said normalizer circuit comprises a summing node, a subtracting node, and an analog divider having a pair of inputs, and wherein said photodiodes are electrically coupled to said summing node and said subtracting node, and wherein said summing supplies an electrical signal to one input of said analog divider proportional to the sum of the signals supplied by the photodiodes, and wherein the subtracting node supplied a signal to the other input of said analog divider whose magnitude is proportional to the location of the point impinged by the incident beam of electromagnetic energy from said source means.

4. A designator apparatus according to claim 1, wherein said source means includes a generator for creating a beam of electromagnetic energy having a wavelength outside the visible frequency spectrum, and wherein said source means further includes a selectively actuable oscillator means for modulating an identifiable signal onto the beam of electromagnetic energy generated by said generator means, and filter means turned to the frequency of said identifying signal.

5. A designator apparatus according to claim 1, wherein said faceplate means is a part of a cathode ray tube or the like, and wherein said diffusing surface is the phosphor coating on the inside face of said CRT, and wherein said photoresponsive means is a pair of photodiodes disposed adjacent to the opposite edge portions of the faceplate of said cathode ray tube.

6. A designator apparatus according to claim 4, further including an optical filter means disposed between each of said photoresponsive elements and said faceplate means, said optical filter passing electromagnetic energy of the same wavelength as that generated by said source means.

7. A designator apparatus according to claim 1, wherein said faceplate means is a part of a liquid crystal display device.

8. A designator apparatus according to claim 1, wherein said faceplate means is a part of a plasma display panel.

9. A designator apparatus according to claim 1, wherein said faceplate means is a part of a light emitting diode display.

10. A designator apparatus according to claim 1, wherein said faceplate means is a part of a photographic display, and wherein an image can be projected from either side of said faceplate means to form an image on said diffusing surface.