HOLOGRAM IDENTIFICATION SYSTEM

• US 3,735,374 A
• Filed: 06/25/1970
• Issued: 05/22/1973
• Est. Priority Date: 07/09/1969
• Status: Expired due to Term

• Current Assignee: Michel Rembault
• Original Assignee: Michel Rembault
• Inventors: Rembault, Michel
• Primary Examiner(s): Habecker, Thomas B.
• Application Number:
  US05/049,612
• Time in Patent Office: 1,062 Days
• Field of Search: 340/149A,146.3P,213 356/71 350/3.5
• US Class Current: 356/71
• CPC Class Codes: G03H 1/041 Optical element in the object space affecting the object beam, not otherwise provided for
• CPC Class Codes: G06V 10/88 Image or video recognition using optical means, e.g. reference filters, holographic masks, frequency domain filters or spatial domain filters

Abstract

An identification arrangement comprises light sources and photodetectors arranged in accordance with a predetermined correspondence code. An appropriate key hologram produces, in respect of each of these sources, respective real images on the above photo-detector. Threshold circuits are connected to these photo-detectors and an assembly of coincidence circuits produces a signal when signals of predetermined levels are simultaneously applied to the outputs of all the photo-detectors.

Claims

1. A hologram identification system, for identifying objects carrying at least one hologram key means storing a pattern of interference fringes constructed from light beams respectively emitted by m point reference sources and focused on n luminous object points;

the locations of said point sources and said object points in relation to said hologram key means being characteristic of a predetermined correspondence code ;

said identification system comprising;

m point light sources and n point photo-detectors located in respective predetermined locations determined by said correspondence code, m and n being positive integers higher than one;

means for positioning said hologram key means in a location where said hologram key means actually focuses said sources onto said photo-detectors ;

logic circuit means connected to said photo-detectors and having an output for supplying a first control signal when, upon insertion of said hologram key means in said location, said n photodetectors simultaneously supply respective signals ; and

supply mans for supplying electrical energy to said sources and said logic circuit means.

2. A system as claimed in claim 1 , wherein said logic circuit means comprise threshold circuits for said control signal to be supplied if said photo-detector signals have respective amplitudes simultaneously higher than respective predetermined thresholds.

3. A system as claimed in claim 2 , wherein said logic circuit means comprise :

n variable threshold circuits connected respectively to said photo-detectors and having each a threshold level control input;

m evaluating circuits, coupled respectively to said light sources and having outputs respectively connected to said control inputs of said threshold circuits which are connected to said photo-detectors corresponding respectively to said sources, for evaluating the light intensities respectively supplied by said sources and for supplying threshold control signals; and

coincidence circuit means having n inputs respectively connected to said threshold circuits and an output for supplying said first control signal.

4. A system as claimed in claim 3 , wherein said inserting means comprise means for inserting a plurality of key holograms in series, at least the first of which operates by transmission, the real point images supplied by one of said holograms serving as point light sources for the next one of said holograms.

5. A system as claimed in claim 3 , wherein said key hologram is an hologram operating by reflection, said sources are white light sources and said photo-detectors are selected for being sensitive to the wavelengths of the light radiations reflected by said hologram.

6. A system as claimed in claim 3 , wherein said evaluating circuits comprise each an auxiliary photo-detector and said key hologram forms an extra real image of the corresponding light source on a predetermined location where said auxiliary photo-detector is located.

7. A system as claimed in claim 1 , wherein said logic circuit means further comprise an alarm arrangement for signalling that the illumination of said photo-detectors is different from the illumination according to said code.

8. A system as claimed in claim 7 , wherein said arrangement comprises an alarm circuit and an extra photo-detector connected to said alarm circuit.

9. A system as claimed in claim 8 , wherein said arrangement further comprises an inverter, connected to said output of said logic circuit means and having an output connected to said alarm circuit.