Holographic laser scanning system employing holographic scanning disc having dual-fringe contrast regions for optimized laser beam scanning and light collection operations

• US 6,003,772 A
• Filed: 09/30/1997
• Issued: 12/21/1999
• 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:
  US08/941,716
• Time in Patent Office: 812 Days
• Field of Search: 235/462.01, 235/462.2, 235/462.21, 235/462.22, 235/462.25, 235/462.26, 235/462.32, 235/462.38, 235/462.4, 235/462.36, 235/454 , 235/472.01, 359/3, 359/4, 359/24, 359/29
• US Class Current: 235/462.01
• 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

Holographic laser scanning system employing a holographic scanning disc with holographic facets having dual-fringe contrast regions optimized for scanning and light collection operations. In the preferred embodiments, the first region of each holographic facet is optimized for laser light having a first polarization state, whereas the second portion thereof is optimized for laser light having a second polarization state. The dual-fringe contrast scanning disc construction of the present invention provides for improved laser scanning efficiency during scanning operation, and improved laser light collection efficiency during laser light collection/detection operation within the system.

Claims

1. A holographic laser scanning system comprising:

a laser scanning disc rotatable about an axis of rotation and having a plurality of holographic optical elements for scanning a laser beam and producing a laser scanning pattern for scanning code symbols, each said holographic optical element having dual-fringe contrast regions including

a first region characterized by a first fringe contrast optimized for scanning said laser beam across a code symbol in said laser scanning pattern, and

a second region characterized by a second fringe contrast optimized for collecting light reflected off said code symbol scanned by said laser beam during scanning operations.

2. The holographic laser scanning system of claim 1, wherein said laser scanning disc has an outer radius and an inner radius, and said first regions are located adjacent said outer radius and said second regions are located adjacent said inner radius.

3. The holographic laser scanning system of claim 2, which further comprises a plurality of laser beam sources for producing a plurality of laser beams for transmission through said holographic elements as said laser scanning disc rotates about said axis of rotation.

4. The holographic laser scanning system of claim 3, wherein said first regions of said holographic optical elements are optimized for laser light having a first polarization state, and said second regions of said holographic optical elements are optimized for laser light having a second polarization state.

5. A method of constructing a holographic scanning disc having one or more holographic optical elements for scanning a laser beam and producing a laser scanning pattern for scanning code symbols, said method comprising the steps of:

(a) for each said holographic optical element, making a first portion of said holographic optical element with a first modulation index and

(b) making the second portion of said holographic optical element with a second modulation index which is different than said first modulation index.

6. The method of claim 5, wherein step (a) comprises exposing a layer of photosensitive material to a first object beam and a first reference beam having relative intensities which result in the formation of the first portion of said selected holographic optical element having said first modulation index, and wherein step (b) comprises exposing a layer of photosensitive material to a second object beam and a second reference beam having relative intensities which result in the formation of the second portion of said selected holographic optical element having said second modulation index.

7. The method of claim 5, wherein step (a) comprises making said first portion of each said holographic optical element optimized for laser light having a first polarization state, and wherein step (b) comprises making said second portion of each said holographic optical element optimized for laser light having a second polarization state.