Holographic laser scanning system employing light focusing optics below the holographic scanning disc

• US 6,076,736 A
• Filed: 10/27/1997
• Issued: 06/20/2000
• 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:
  US08/958,695
• Time in Patent Office: 967 Days
• Field of Search: 359/17, 359/18, 235/462, 235/472, 235/454, 235/469, 235/467, 235/470
• US Class Current: 235/472.01
• 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 and the like, comprising: a holographic scanning disc; a plurality of laser beam sources; a plurality of beam folding mirrors adjacent the holographic scanning disc; a plurality of light focusing elements disposed beneath the holographic scanning disc; and plurality of photodetectors disposed above the holographic scanning disc. The light focusisng elements below the holographic scanning disc focus reflected laser light collected through the elements of the holographic scanning disc and retransmit the same therethrough off Bragg for direct detection by the photodetectors which are proximately dispposed to and above the holographic scanning disc. Several important advantages are obtained by providing light collection optics disposed below the holographic scanning disc, and retransmitting focused/collected laser light through the holographic scanning disc at an angle substantially off a Bragg angle of about 44 degrees. In particular, it is now possible to design and construct holographic laser scanners employing miultiple laser scanning stations within compact scanner housings having minimized height dimensions, while avoiding interference among the multiple outgoing, incoming and retransmitted laser beams generated within the scanner housing during laser scanning and light collection operations.

Claims

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

a housing having a scanning window for transmission of laser light therethrough;

a holographic scanning disc disposed within said housing and being rotatable about an axis of rotation;

a laser beam source disposed within said housing, 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 plane within which a plurality of holographic optical elements are supported, for (i) scanning and focusing said plurality of laser beams during transmission of said plurality of laser beams through said holographic optical elements so as to produce a plurality of laser scanning planes, and also (ii) collecting light rays reflected off a code symbol scanned by one or more of said laser scanning planes for subsequent focusing and detection,

wherein each said holographic optical element has substantially the same Bragg angle, and said angle of incidence of each said holographic optical element is substantially equal to said Bragg angle;

a beam folding mirror disposed within said housing adjacent said holographic scanning disc, at an angle of inclination relative to the plane of said holographic scanning disc, for folding said plurality of laser scanning planes and projecting said folded laser scanning planes through said scanning window, for intersection within the spatial extent of a predefined 3-D scanning volume so as to produce a laser scanning pattern within said predefined 3-D scanning volume;

a light focusing element disposed beneath said holographic scanning disc, and having an optical axis disposed at an angle substantially different than said Bragg angle, for focusing towards a focal point above said holographic scanning disc, the reflected light rays collected by said holographic optical elements; and

a photodetector, disposed at said focal point proximate to and above said holographic scanning disc, and radially aligned with the optical axis of said light focusing element, for directly detecting the intensity of focused light rays retransmitted through said holographic optical elements as said holographic scanning disc rotates, and generating a scan data signal for subsequent processing.

2. The holographic laser scanning system of claim 1, wherein said light focusing element is realized as a parabolic mirror element.

3. The holographic laser scanning system of claim 2, wherein laser beam source comprises a visible laser diode.

4. The holographic laser scanning system of claim 3, wherein said Bragg angle is substantially greater than 22 degrees measured relative to normal vector drawn to the plane of said holographic scanning disc.

5. The holographic laser scanning system of claim 3, wherein said Bragg angle is about 44 degrees measured relative to

normal vector drawn to the plane of said holographic scanning disc.

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

a housing having a scanning window for transmission of laser light therethrough;

a holographic scanning disc disposed within said housing and being rotatable about an axis of rotation;

a plurality of laser beam sources disposed within said housing 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 plane within which a plurality of holographic optical elements are supported, for (i) scanning and focusing said plurality of laser beams during transmission of said plurality of laser beams through said holographic optical elements so as to produce a plurality of laser scanning planes, and (ii) collecting light rays reflected off a code symbol scanned by one or more of said laser scanning planes for subsequent focusing and detection,

wherein each said holographic optical element has substantially the same Bragg angle, and said angle of incidence of each said holographic optical element is substantially equal to said Bragg angle;

a plurality of beam folding mirrors disposed adjacent said holographic scanning disc, at an angle of inclination relative to plane of said holographic scanning disc, for folding said plurality of laser scanning planes and projecting said folded laser scanning planes through said scanning window, for intersection within the spatial extent of a predefined 3-D scanning volume so as to produce a laser scanning pattern within said predefined 3-D scanning volume;

a plurality of light focusing elements disposed beneath said holographic scanning disc, each said light focusing element having an optical axis disposed at an angle substantially different than said Bragg angle, for focusing towards a focal point above said holographic scanning disc, light rays reflected off said scanned coded symbol and collected by said holographic optical elements; and

a plurality of photodetectors, each said photodetector being proximately disposed at one said focal point above said holographic scanning disc, and being radially aligned with the optical axis of one said light focusing element, for directly detecting the intensity of focused light rays retransmitted through said holographic optical elements as said holographic scanning disc rotates, and generating a scan data signal for subsequent processing.

7. The holographic laser scanning system of claim 6, wherein said light focusing element is realized as a parabolic mirror element.

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

9. The holographic laser scanning system of claim 6, wherein said Bragg angle is substantially greater than 22 degrees measured relative to normal vector drawn to the plane of said holographic scanning disc.

10. The holographic laser scanning system of claim 6, wherein said Bragg angle is about 44 degrees measured relative to normal vector drawn to the plane of said holographic scanning disc.