Optical filtering system for a laser bar code scanner having narrow band-pass characteristics employing spatially separated filtering elements including a scanner window

• US 6,209,789 B1
• Filed: 11/09/1999
• Issued: 04/03/2001
• Est. Priority Date: 09/17/1991
• Status: Expired due to Fees

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Rockstein, George, Wilz, David M. Sr., Amundsen, Thomas, Blake, Robert, Knowles, Carl H.
• Primary Examiner(s): LE, THIEN MINH
• Application Number:
  US09/436,742
• Time in Patent Office: 511 Days
• Field of Search: 235/462.01, 235/462.2, 235/462.22, 235/462.25, 235/462.29, 235/462.28, 235/462.32, 235/462.36, 235/462.43, 235/472.01 , 235/462.45, 235/462.35
• US Class Current: 235/472.01
• 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 2207/1016 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 7/10564 Light sources
• 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 7/10693 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 7/10851 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 7/10881 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 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G06K 7/1443 locating of the code in an image

Abstract

A novel optical filtering system for a laser bar code scanner having narrow band-pass characteristics is disclosed. The optical filtering system has two different optical filtering elements which are disposed in a scanner housing in a spatially separate relationship. One of the optical filtering elements is positioned inside of the scanner housing in front of and close to the light detection element. The other optical filtering element is positioned in the light transmission aperture of the scanner housing and forms the scanning window. The optical filtering characteristics of the scanning window obscure the internal components of the scanner from plain view making the scanner appear more aesthetically pleasing. Together the optical filtering element cooperate to form a narrow-band pass filter to provide for better light collection and scanning.

Claims

1. A laser symbol scanning system, comprising:

a housing having a light transmission aperture through which light can enter and exit said housing;

laser beam source in said housing for producing a laser beam characterized by a predetermined wavelength;

laser beam scanning element in said housing for projecting said laser beam through said aperture and scanning said laser beam across a code symbol on an object located within at least a portion of a scan field defined external to said housing;

light collection element for collecting laser light reflected off said code symbol and pas sing through said aperture;

laser light detection element in said housing disposed in said laser light path, for detecting the intensity of laser light reflected off said code symbol and collected by said light collection element;

a laser beam directing element mounted to the surface of said light collection element for directing the laser beam produced by said laser beam production element to said laser beam scanning mechanism; and

a pair of optical filter elements in said housing, spatially separated from each other, each optical filter element having wavelength-selective filtering characteristics, said pair of optical filter elements cooperating so as to form a band-pass optical filtering system having a narrow wavelength bandwidth positioned about said predetermined wavelength such light reflected off said code symbol having wavelengths only within said narrow wavelength bandwidth reach said laser light detection element and wherein one of said pair of optical filtering elements is disposed in said light transmission aperture and functions as a scanning window in said housing.

2. The laser code symbol scanning system of claim 1, wherein said predetermined wavelength is about 670 nanometers.

3. The laser code symbol scanning system of claim 1 wherein one of said pair of optical filtering elements is disposed adjacent said light detecting means.

4. The laser code symbol scanning system of claim 1 wherein said wavelength filtering characteristics of said scanning window obscures each of said elements positioned in said housing from plain view.

5. The laser code symbol scanning system of claim 1 wherein said wavelength filtering characteristics of said scanning window appear reddish in color.

6. The laser code symbol scanning system of claim 1 wherein in said housing is a compact hand-supportable housing.

7. The laser code symbol scanning system of claim 1 wherein said laser light collection element is concave mirror.

8. The laser code symbol scanning system of claim 1 wherein said laser light directing element is a plane mirror.

9. The laser code symbol scanning system of claim 1 wherein said laser light directing element is mounted off center of the laser light collection element.

10. The laser bar code symbol scanning system of claim 1 wherein said housing a compact fixed-mounted housing.

11. A method for scanning a bar code on an object, comprising the steps of:

positioning a bar code scanning field of a bar code reader over a bar code on an object to be scanned;

producing a laser beam having a predetermined wavelength from a laser source;

directing said laser beam from said laser source to a scanning element;

scanning said produced laser beam across said bar code scanning field and said barcode;

reflecting light including said laser beam from said bar code to said bar code reader; and

preventing certain wavelengths of light reflected from said bar code from passing through a scanning window having wavelength-selective filtering characteristics and into said bar code reader.

12. The method for scanning a bar code of claim 11, further comprising the steps of:

collecting said reflected light from said bar code and passed through said scanning window;

focussing said collected light onto a light detection element in said bar code reader; and

preventing wavelengths of light, other than said predetermined wavelength which are reflected from said bar code and passed through said scanning window, from passing into said light detection element.

13. A method for scanning a bar code on an object, comprising the steps of:

positioning a bar code scanning field of a bar code reader over a bar code on an object to be scanned;

producing a laser beam having a predetermined wavelength from a laser source;

scanning said produced laser beam across said bar code scanning field and said bar code;

reflecting light including said laser beam from said bar code to said bar code reader;

preventing certain wavelengths of light reflected from said bar code from passing through a scanning window having wavelength-selective filtering characteristics and into said bar code reader;

collecting said reflected light from said bar code and passed through said scanning window;

focussing said collected light onto a light detection element in said bar code reader; and

preventing wavelengths of light, other than said predetermined wavelength which are reflected from said bar code and passed through said scanning window, from passing into said light detection element.