Laser scanning system employing light collection surfaces having optical axes disposed off the bragg angle of the holographic optical elements of the holographic scanning disc thereof

• US 6,523,750 B1
• Filed: 11/15/1999
• Issued: 02/25/2003
• Est. Priority Date: 08/17/1994
• Status: Expired due to Fees

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Dickson, LeRoy, Amundsen, Thomas, Knowles, Carl Harry, Groot, John
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US09/440,560
• Time in Patent Office: 1,198 Days
• Field of Search: 399/565, 399/18, 399/566, 399/809, 399/569, 399/209, 399/210, 399/211, 399/17, 235/472.01, 235/468.01, 235/462.1, 235/462.07, 235/462.38, 235/462.44, 235/462.25
• US Class Current: 235/462.34
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G02B 26/10 Scanning systems
• CPC Class Codes: G02B 26/106 having diffraction gratings as scanning elements, e.g. holographic scanners holographic optical elements G02B5/32, holography G03H
• CPC Class Codes: G06K 17/0022 arrangements or provisious for transferring data to distant stations, e.g. from a sensing device "transfer between computer elements G06F13/00 "; data-transmission H04L
• CPC Class Codes: G06K 2207/1012 Special detection of object
• CPC Class Codes: G06K 2207/1013 Multi-focal
• CPC Class Codes: G06K 2207/1016 Motor control or optical moving unit control
• CPC Class Codes: G06K 2207/1017 Programmable
• CPC Class Codes: G06K 2207/1018 Source control
• CPC Class Codes: G06K 7/10 by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
• CPC Class Codes: G06K 7/10564 Light sources
• CPC Class Codes: G06K 7/10584 Source control
• CPC Class Codes: G06K 7/10594 Beam path
• CPC Class Codes: G06K 7/10603 Basic scanning using moving elements
• CPC Class Codes: G06K 7/10663 using hologram
• CPC Class Codes: G06K 7/10673 Parallel lines
• CPC Class Codes: G06K 7/10693 for omnidirectional scanning
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence
• CPC Class Codes: G06K 7/10792 Special measures in relation to the object to be scanned
• CPC Class Codes: G06K 7/10801 Multidistance reading
• CPC Class Codes: G06K 7/10811 : Focalisation
• CPC Class Codes: G06K 7/10851 : Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/10861 : sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48
• CPC Class Codes: G06K 7/10871 : randomly oriented data-fields, code-marks therefore, e.g. concentric circles-code
• CPC Class Codes: G06K 7/10881 : constructional details of hand-held scanners
• CPC Class Codes: G06K 7/10891 : the scanner to be worn on a finger or on a wrist
• CPC Class Codes: G06K 7/109 : adaptations to make the hand-held scanner useable as a fixed scanner
• CPC Class Codes: G06K 7/14 : using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G07F 9/002 : Vending machines being part of a centrally controlled network of vending machines
• CPC Class Codes: G07G 1/0045 : with a code reader for reading of an identifying code of the article to be registered, e.g. barcode reader or radio-frequency identity [RFID] reader
• CPC Class Codes: G07G 1/0054 : with control of supplementary check-parameters, e.g. weight or number of articles

Abstract

A holographic laser scanning system for scanning bar code symbols. The system comprises a holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning the plurality of laser beams directed at the same incident angle. Each holographic optical element as substantially the same Bragg angle. The parabolic light reflective surfaces are disposed beneath the holographic scanning discs. Each parabolic light reflective surface has an optical axis disposed off the Bragg angle of the holographic optical elements, for focusing towards a focal point above the holographic scanning disc, the reflected light rays collected by each holographic optical element. A photodetector is disposed at the focal point of the corresponding parabolic light reflective surface above the holographic scanning disc, and is radially aligned with the optical axis of one parabolic light reflective surface. The light diffraction efficiency of each holographic optical element at the angle of incidence of each laser beam during scanning is substantially greater than the light diffraction efficiency of the focused laser light transmitted from each parabolic light reflective surface through the holographic optical elements towards corresponding photodetector during light detection. This enables the collected light rays, focused by the parabolic light reflective surface, to be efficiently transmitted through the holographic optical elements, to the photodetector for detection and generation of a scan data signal for subsequent processing. By virtue of this novel arrangement, the present invention enables the construction of a holographic laser scanner having substantially reduced height characteristics.

Claims

1. A holographic laser scanning system for scanning bar code symbols, comprising:

a holographic scanning disc;

a laser beam source for producing a laser beam and directing said laser beam at an angle of incidence to said holographic scanning disc;

said holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning said laser beam and producing a laser scanning pattern for scanning a code symbol, and collecting light rays reflected off said scanned code symbol for subsequent focusing and detection,

wherein each said holographic optical element has substantially the same Bragg angle;

a light reflective surface disposed beneath said holographic scanning disc, and having an optical axis disposed off the Bragg angle of said holographic optical elements, for focusing towards a focal point above said holographic scanning disc the reflected light rays collected by each said holographic optical element; and

a photodetector, disposed at said focal point above said holographic scanning disc, and radially aligned with the optical axis of said light reflective surface, for detecting the intensity of collected light rays focused by said light reflective surface and transmitted through said holographic optical elements to said photodetector for detection and generation of a scan data signal for subsequent processing;

wherein the light diffraction efficiency of each said holographic optical element at said angle of incidence of said laser beam during said scanning is substantially greater than the light diffraction efficiency of said holographic optical element at the angle at which said focused laser light is transmitted from said light reflective surface through said holographic optical elements towards said photodetector during light detection.

2. The holographic laser scanning system of claim 1, wherein said light reflective surface is realized as a parabolic mirror element having parabolic surface patch characteristics.

3. The holographic laser scanning system of claim 1, which further comprises a light polarizing filter disposed before said photodetector.

4. The holographic laser scanning system of claim 3, wherein the polarization state of said incident laser beam is S polarization state, and the polarization state of said light polarizing filter is P polarization state.

5. The holographic laser scanning system of claim 1, wherein laser beam source comprises a visible laser diode.

6. A holographic laser scanning system for scanning bar code symbols, comprising:

a holographic scanning disc;

a plurality of laser beam sources for producing a plurality of laser beams and directing said plurality of laser beams at an angle of incidence to said holographic scanning disc;

said holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning said plurality of laser beams and producing laser scanning pattern for scanning a code symbol, and collecting light rays reflected off said scanned code symbol for subsequent focusing and detection,

wherein each said holographic optical element has substantially the same Bragg angle;

a plurality of light reflective surfaces disposed beneath said holographic scanning disc, and each having an optical axis disposed off the Bragg angle of said holographic optical elements, for focusing towards a focal point above said holographic scanning disc, the reflected light rays collected by each said holographic optical element; and

a plurality of photodetectors, each being disposed at said focal point above said holographic scanning disc, and radially aligned with the optical axis of one said light reflective surface, for detecting the intensity of collected light rays focused by said one light reflective surface and transmitted through said holographic optical elements to said photodetector for detection and generation of a scan data signal for subsequent processing;

wherein the light diffraction efficiency of each said holographic optical element at said angle of incidence of each said laser beam during said scanning is substantially greater than the light diffraction efficiency of said holographic optical element at the angle at which said focused laser light is transmitted from each said light reflective surface through said holographic optical elements towards said corresponding photodetector during light detection.

7. The holographic laser scanning system of claim 6, wherein said light reflective surface is realized as a parabolic mirror element having parabolic surface path characteristics.

8. The holographic laser scanning system of claim 6, which further comprises a light polarizing filter disposed before said photodetector.

9. The holographic laser scanning system of claim 6, wherein the polarization state of said incident laser beam is S polarization state, and the polarization state of said light polarizing filter is P polarization state.

10. The holographic laser scanning system of claim 6, wherein said plurality of laser beam sources comprises a plurality of visible laser diodes.

11. The holographic laser scanning system of claim 6, wherein said laser scanning pattern is substantially confined within a highly defined 3-D scanning volume.

12. The holographic laser scanning system of claim 11, wherein said laser scanning pattern is an omnidirectional scanning pattern substantially confined within said 3-D scanning volume.