Optical head for an authenticity identifying system

Abstract: A highly simple and compact optical head (5) for optically determining authenticity of an article (1) by impinging a light beam upon an identification region (4) provided on the article and having a selected reflective directivity, and receiving light reflected by the identification region. The identification region may consist of a holograph, a diffraction grating or a multiplicity of parallel grooves. The optical head comprises a light emitting element (8) fixedly secured to a casing (6); and a light receiving element (12) placed coaxially in a light path of a light beam emitted from the light emitting element and having an opening (14) for allowing the light beam to pass through; the light receiving surface facing away from the light emitting element and being divided into a plurality of sectors (12a through 12h) defined around an axial center line of the light emitting element with each of the sectors being capable of individually detecting a magnitude of light impinging thereon.

Description: TECHNICAL FIELD The present invention relates to a system for determining or identifying the authenticity of such articles as information storage cards by means of a reader/writer to prevent unauthorized fabrication and alteration of such articles or cards, and in particular to an optical head which is suitable for use in such a system. The information storage cards include, not exclusively, magnetic cards, IC cards, optical cards and so on which are capable of exchanging information with reader/writers. BACKGROUND OF THE INVENTION Conventionally, to the end of preventing the forgery of, for instance, a magnetic card, it has been practiced to use a laminated structure for its magnetic layer, and to punch holes in the magnetic card when the magnetic card is not intended for repeated use. However, such structures can be duplicated with deceitful intention by the forgers with relative ease, and may not be sufficient to discourage attempts to illegally duplicate and alter the card. The internal structure of the card may be made more complex by known means, but it will lead to the complication and cost increase of the reader/writers for reading and writing information into and out of the card. A holograph or other optically conditioned region having a prescribed directivity may be used for identification purpose, but the system for optically identifying it tends to be complex, expensive and large in size. DE-A-24 44 961 discloses a character recognition system which employs an optical head having a plurality of light receiving sectors arranged concentrically. The light emitting element is not shown in the drawings. It simply and generally illuminates the document to be read. Further, the said document suggests the use of a single wafer including an array of photo-diodes. It does, however, not suggest any opening in the wafer for defining an aperture for the light emitting element. Also, the said document does not suggest the use of a hologram. It is the object of the invention to provide an optical head for optically determining authenticity of an article by impinging a light beam upon an identification region provided on the article and having a selected reflective directivity, and receiving light reflected by the identification region, which is highly compact in structure. A further object is to provide such an optical head which is economical to manufacture. These and other objects of the present invention can be accomplished by the teaching of claim 1. BRIEF DESCRIPTION OF THE DRAWINGS Now the present invention is described in the following with reference to the appended drawings, in which: Figure 1 is a perspective view of a card and an essential part of a card reader/writer to which the present invention is applied; Figures 2 is a sectional view of the optical head according to the present invention taken along line II-II of Figure 1; and Figure 3 is a bottom view of the optical head as seen in the direction indicated by III in Figure 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows a card reader/writer to which a preferred embodiment of the present invention is applied. The card 1 is conveyed in the direction indicated by the arrows or substantially laterally as seen in Figure 1 by means of conveyer rollers or the like not shown in the drawing, and a magnetic head 3 writes into and reads out of a magnetic stripe 2 provided on a major surface 1a of the card 1 when it has reached such a position. A holograph region 4 is provided on a suitable location of the major surface 1a of the card 1. This holograph region 4 consists of a reflective holograph having such a reflective property that incident light having a certain wave length and projected perpendicularly upon the holograph is reflected in a certain prescribed direction or certain prescribed directions. The identification region may consist of a holograph, a diffraction grating or a multiplicity of parallel grooves. The reader/writer is provided with an optical head 5 according to the present invention for projecting a coherent beam of laser light perpendicularly upon the major surface 1a of the card 1, in particular upon the holograph region 4, and receiving the light reflected therefrom as described hereinafter. An identification circuit 19 is connected to the optical head 5 to determine the authenticity of each card. In carrying out such a card identification process, the card 1 inserted in the card reader/writer is retained perpendicularly to the illuminating light beam from the optical head 5, and the illuminating light or the incident light from the optical head 5 is projected upon the holograph region 4. The authenticity of the card 1 can be identified when the light reflected by the holograph region 4 is collected by the optical head 5 in a certain pattern, and its intensity is detected to be of a certain level by the identification circuit 19. Therefore, even when a forger obtained such a card, not only it would be difficult for him to analyze and duplicate the holograph but also a significant cost is required to fabricate an identical holograph. Thereby, it offers a strong discouraging effect upon potential forgers. Figures 2 and 3 show the preferred embodiment of the optical head according to the present invention. This optical head 5 comprises an annular casing 6 made of synthetic resin and provided with a flange 6a at a bottom end thereof, a light emitting element 8 consisting of a semiconductor laser device at a top end of a central bore 7 defined in the casing 6, and a lens 8 fixedly fitted into an enlarged part 7a of the central bore 7 in a lower part thereof. The bottom end (the lower end as seen in Figure 2) of the central bore 7 is closed by a circuit board 11 having an octagonal shape as illustrated in Figure 3. A semiconductor chip 12 consisting of a silicon chip is mounted on the bottom surface of the circuit board 11. The circuit board 11 is provided with a central opening 13 for allowing a coherent light beam emitted from the light emitting element 8 and collimated by the lens 10 to pass through. The central opening 13 of the circuit board 11 serves as a diaphragm which limits the aperture of the lens 10. The semiconductor chip 12 is divided into eight sectors 12a through 12h of an equal size, and is provided with a central opening 14 which is coaxial with the opening 13 of the circuit board 11 and is larger in diameter than the opening 13. Each of the sectors 12a through 12h is formed as an individual photodiode. The identification of the identification region can be accomplished by detecting the pattern of light received by these sectors. The opening 13 or the central aperture serves as a diaphragm. A flexible circuit board 9 is attached to an axial upper end surface of the casing 6 remote from the flange 6a, and a part of the flexible circuit board 9 extends along a side of the casing 6. Pins 15 connected to the sectors 12a through 12h of the semiconductor chip 12 along with pins extending from the light emitting element 8 are soldered to appropriate parts of the flexible circuit board 9. The flexible circuit board 9 carries various circuit elements 16, and lead wires 18 are connected to appropriate parts of the circuit formed on the flexible circuit board 9 via a connector 17. According to the present invention, the light receiving surface may be simply divided into a plurality of sectors 12a through 12h arranged around the central opening 14 as illustrated in Figure 3, or, alternatively, may be divided into two or more rows of sectors arranged around the central opening 14.

Claims: An optical head (5) for optically determining the authenticity of an article (1) by impinging a light beam upon an identification region (4) provided on said article (1) and having a selected reflective directivity, and receiving light reflected by said identification region, comprising: a light emitting element (8) for providing a coherent beam of light a generally planar mounting means (11); a generally planar array of photodiodes (12) mounted on said mounting means (11) whereby said photodiodes do not receive direct light from said light emitting element, said array of photodiodes (12) being arranged around an axial centre line of said coherent light beam, each of said photodiodes (12a -12h) being adapted to individually detect a magnitude of light reflected from said identification region (4) of said article(1) and impinged thereon, characterized in that the optical head further comprises an annular casing (6) defining a central bore (7) therein; said light emitting element is received coaxially at one end of said central bore (7) with a light emitting surface thereof facing interior of said central bore; said mounting means (11) is provided at an other end of said central bore (7) remote from said one end and includes an opening (13), disposed in a light path of said coherent light beam for allowing said coherent light beam to pass there through; said generally planar array of photodiodes is mounted on a surface of said mounting means facing away from said light emitting element (8) and is arranged around said opening (13). An optical head according to claim 1, wherein said planar array of photodiodes consists of a concentric array of photodiodes each having a sector-shaped light receiving surface. An optical head according to claim 2, wherein said sector-shaped light receiving surfaces are arranged in two rows around said aperture. An optical head according to claim 1, further comprising a circuit board (9) attached to said one end of said annular casing, said light emitting elements being mounted on said circuit board via leads of said light emitting element, said light receiving elements being provided with leads (15) which are passed through the annular casing and electrically and mechanical connected to said circuit board. An optical head according to claim 4, wherein said circuit board consists of a flexible circuit board, and is provided with an extension extending along a side of said annular casing and carrying at least one circuit element (16) for said light emitting element or said light receiving element. An optical head according to claim 1, wherein said array of photodiodes consisting of a single wafer having a central opening (14) passed through said wafer, and said sectors defined around said central opening. An optical head according to claim 1, wherein said light emitting element consists of a semiconductor laser device. An optical head according to claim 1, wherein said identification region consists of a holograph, a diffraction grating or a multiplicity of parallel grooves.

Inventors: HOSHINO HIDEKAZU, NISHIGUMA HIROAKI, SEKI YOSHIAKI, HOSHINO, HIDEKAZU, NISHIGUMA, HIROAKI, SEKI, YOSHIAKI, HOSHINO, HIDEKAZU, C/O NHK SPRING CO., LTD., Nishiguma, Hiroaki, c/o NHK Spring Co., Ltd., SEKI, YOSHIAKI, C/O NHK SPRING CO., LTD.
Applicants: NHK SPRING CO LTD, NHK SPRING CO.LTD.
Application year: 1992
Main classification: G06K7
IPC codes: G06K7, G06K19