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    United States Patent [19] [11] Patent Number: 4,655,541 Yamazaki et al. [45] Date of Patent: Apr. 7, 1987

    [54] HOLOGRAM SCANNER [52] US. Cl. ................................... .. 350/3.71; 350/62

    [75] Inventors: K020 Yam 1 . Zama; Fumio [58] Fleld of Search .............................. .. 350/ 3.71, 6.2

    Yamagishi, Ebina; Hiroyuki Ikeda, [56] References Cited YOkohama; Takefumi Inga, us. PATENT DOCUMENTS Kawasaki; Ichiro Sebata, Tokyo; shunji Kitagawa, Atsugi; Masayuki 4,165,464 8/1979 Ikeda et al. ...................... .. 350/171 Kato Atsugi; Toshiyuki Ichikawa 4,239,326 12/1980 Kramer ............................ .. 350/371

    Atsugi, all of Japan Primary ExaminerBruce Y. Arnold Assistant Examiner-David J. Edmondson

    [73] Assigneez Fujitsu Linuted, Kanagawa, Japan Attorney, Agent or Firm_staas & Halsey [21] Appl. No.: 675,870

    r [57] ABSTRACT

    [22] F?ed: Nov 28 1984 A hologram scanner includes a laser source, a rotary [30] Foreign Application Priority Data body having a rotational axis at least one hologram

    facet arranged on the rotary body for diffracting a laser beam from the laser source to scan an object and receive the scattered light from the object for detection thereof, a motor means for driving the rotary body, and an opti cal detector for detecting the scattered light received and diffracted by the hologram facet. The hologram

    Nov. 30, 1983 [JP] May 11, 1984 [JP] May 11, 1984 [JP] May 29, 1984 [JP] May 29, 1984 [JP]

    Japan .............................. .. 58-224325

    .. 5 9-092979

    Jul 30 1984 [JP] facet is inclined with respect to the rotational axis of the Jul. 30, 1984 [JP] rotary body Jul. 31, 1984 [JP] '

    [51] Int. Cl. ..................... .. G02B 26/10; GOZB 26/08 24 Claims, 35 Drawing Figures

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  • 4,655,541 1

    HOLOGRAM SCANNER

    BACKGROUND OF THE INVENTION

    The present invention relates to a hologram scanner which scans an object by using a laser beam diffracted by a hologram. A bar-code reader is used in a market control system

    in a supermarket or the like. Such a bar-code reader reads a bar-code printed on a commodity and inputs the information data to a computer to control the operation of the supermarket. A hologram scanner is used as a bar-code scanner of the bar-code reader. FIG. 1 is a view of a hologram scanner used as a

    bar-code reader according to the prior art. The scanner comprises a laser source 2, a beam expander 3, a holo gram disc 4 comprising a plurality of hologram facet elements, a motor 5 for driving the hologram disc 4, a mirror 9 having a throughhole 9a at the center thereof for passing a laser beam, a condensor lens 10, and an optical detector 11, within an outer box 1. A laser beam from the laser source 2 passes through the throughhole 9a of the mirror 9 and is diffracted by a rotating holo gram disc 4 so that the laser beam scans a bar-code 12 printed on a commodity 13, as a scanning beam 7 through a window 6. The laser beam 7 irradiated onto the bar-code 12 is scattered and a part 8 of the scattered light returns toward the hologram disc 4. The scattered light 8 is diffracted by the hologram 4, re?ected by the mirror 9, and detected by the detector 11 through the lens 10. Each component, such as the laser source 2, the holo

    gram disc 4, the motor 5, the mirror 9; and the detector 11, of the hologram scanner is individually attached to the outer box 1 of the bar-code reader, together with the other components such as a control circuit, an interface unit and a power source. Such a structure is not com pact and is inconvenient to handle, which causes diffi culties when assembling the bar-code reader since the positioning of the parts of the hologram scanner is not easy. The hologram disc 4 of the prior art scanner com

    prises a disc plate located perpendicularly to the rota tional axis thereof. Therefore, the diffraction angle 0 (FIG. 2) of the scanning beam7 must be large for elon gating the scanning line traced by the scanning point A with respect to the rotational angle of the hologram disc 4. However, if the diffraction angle 0 is enlarged, the amount of the scattered light 8 received by the holo gram disc 4 decreases, which results in the degradation of the reliability of the detection. The reading ability of the scanner is upgraded as the

    laser beam is strengthened. However, the eyes of the operator or customer may be damaged if the laser beam is excessively strengthened. The laser beam strength must not exceed the safety standards for the human eye. The prior art method for enhancing the allowable laser beam strength in accordance with the safety standards is illustrated in FIG. 3. The laser beam for scanning in one direction is divided into two beams which are separated from each other by more than 7 mm at the outside of the scanning window 50 (d

  • 4,655,541 3

    facet 24 on which a hologram (not shown) is con structed. The hologram facet 24 is inclined with respect to the rotary shaft 21. A Fresnel mirror 26 is disposed on the upper vinner surface of the rotary body 28 to re?ect and converge a parallel beam. A metallic re?ec tion film (not shown) is coated on the front surface or the rear surface (facing the upper inner surface of the rotary body 28) of the Fresnel mirror 26. The rotating body 28 has the shape illustrated in FIG.

    5. Two hologram facets 24 form a wedge at an end of a cylindrical body. Variations of the rotary body 28 are illustrated in FIGS. 6 to 9. The rotary body 28 of FIG. 6 comprises four hologram facets 24 forming a quadran gular pyramid at an end of a cylindrical body. The rotary body 28 of FIG. 7 comprises four hologram facets 24 forming a quadrangular pyramid at an end of a square pillar. The rotary body 28 of FIG. 8 comprises a conical facet 24 at an end of a cylindrical body. Two hologram facet elements 24a and 24b having different diffraction angles may be formed on the same plane, as illustrated in FIG. 9. The number of hologram facets may be three, four, ?ve, or more to form a pyramid. Each hologram facet 24 diffracts a scanning beam to irradiate an object and simultaneously receives scat tered light from the object for the detection thereof. Therefore, each hologram facet 24 must be large enough to receive a critical amount of the scattered light to be able to recognize the object. Taking this point into consideration, the rotary body 28comprising two hologram facets 24 illustrated in FIG. 5 is the most preferable from the standpoint of compactness and pro ductivity. A laser diode module 22 which emits a plane wave

    laser beam having an predetermined diameter and a mirror 23 for re?ecting the laser beam are secured to the frame 20 (FIG. 4). An optical detector 29 is also secured to the frame 20 at the position facing the lower end of the rotary body 28. A concave lens 27 is installed at the lower end of the rotary body 28 for the following reason. The scattered light (dash lines) from the object is converged toward the center of the lower end of the rotary body 28 by the function of the Fresnel mirror 26. It is desirable to make the converging area at the lower end of the rotary body 28 as small as possible toenlarge the hologram facet area. The optical detector 29 for detecting the converged beam is disposed at a distance below the lower end of the rotary body in such a man ner that the detector does not come in contact with the rotary body. Therefore, the concave lens 27 is needed to elongate the focus position from the proximity of the rotary body end to the optical detector 29. The upper plate 280 (FIG. 10) of the rotary body 28

    has a plurality of slits 38 in a circle to pass the laser beam therethrough. Another arrangement for passing the laser beam

    through the upper plate 28a of the rotary body 28 is illustrated in FIG. 11. In this arrangement, the upper plate 280 is made of a transparent material and the me tallic re?ection film is not coated along a circular track 39 on the front surface or the rear surface of the Fresnel lens 26 (FIG. 4) to pass the laser beam through the circular track 39. The track 39 is not embossed to form the Fresnel lens so that the beam passes straight there through. By this arrangem