Optical system for data reading having wide range of focus

• US 5,641,958 A
• Filed: 06/07/1995
• Issued: 06/24/1997
• Est. Priority Date: 12/18/1992
• Status: Expired due to Term

• Current Assignee: PSC Scanning, Inc. (Datalogic ADC Incorporated)
• Original Assignee: Spectra-Physics Scanning Systems, Inc.
• Inventors: Rudeen, Robert W.
• Primary Examiner(s): ALLEN, STEPHONE B
• Application Number:
  US08/475,757
• Time in Patent Office: 748 Days
• Field of Search: 250/235, 250/555-557, 250/566, 250/568, 235/462, 235/467, 235/472, 359/370
• US Class Current: 250/235
• CPC Class Codes: G02B 26/105 with one or more pivoting mirrors or galvano-mirrors G02B26/101 takes precedence
• CPC Class Codes: G02B 5/005 Diaphragms for cameras G03B9/02
• CPC Class Codes: G06K 2207/1013 Multi-focal
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence
• CPC Class Codes: G06K 7/10801 Multidistance reading
• CPC Class Codes: G06K 7/10811 Focalisation

Abstract

An optical system and method for data reading in which a light source generates an optical beam directed toward an object to be read and a variable aperture mechanism positioned in the outgoing light path establishes at least two separate focal planes. The variable aperture device may comprise a variable aperture system in which the size of the aperture is selectively varied about a range within the diffractive limit of the light beam. A preferred aperture mechanism is a liquid crystal aperture with one or more aperture regions which are selectively or consecutively activated. The optical system therefore establishes two or more separate waist locations from a single light source resulting in greater depth of field or multiple depths of field.

Claims

1. A method for data reading comprising the steps of

projecting a beam of light along an outgoing optical path;

passing the optical beam through a diffractive module having a first outer aperture and a second inner aperture, the second inner aperture being formed by at least one panel which is partially light transmissive.

2. A method for data reading according to claim 1 further comprising forming the beam of light from a laser diode and positioning the diffractive module on a side of the focusing system opposite to the laser diode.

3. A method for data reading according to claim 1 further comprising

forming the beam of light from a laser diode;

focusing the beam with a focusing system; and

positioning the diffractive module downstream of the focusing system.

4. A method for data reading according to claim 1 further comprising

forming the beam of light from a laser diode;

focusing the beam with a focusing system;

scanning the beam that has been focused with a scanning mechanism; and

positioning the diffractive module between the focusing system and the scanning mechanism.

5. A method for data reading according to claim 1 further comprising

forming the beam of light from a laser diode;

focusing the beam with a focusing system; and

positioning the diffractive module upstream of the focusing system and adjacent thereto.

6. A method for data reading according to claim 1 further comprising

forming the beam of light from a laser diode;

focusing the beam with a focusing system; and

positioning the diffractive module downstream from the laser diode beyond a point one system focal length upstream of the focusing system.

7. A method for data reading according to claim 1 further comprising concentrically positioning the second inner aperture in the outgoing optical path.

8. A laser scanner for bar code reading, comprising:

a discrete light source generating a laser beam along an outgoing optical path;

a focusing lens positioned in the outgoing optical path for focusing the laser beam to a waist at a given location;

a diffractive aperture device positioned in the outgoing optical path, the diffractive aperture device having a first outer aperture and a second inner aperture, the second inner aperture being formed by at least one panel, the panel being comprised of a material which allows for partial light transmission therethrough.

9. A laser scanner according to claim 8 wherein the diffractive aperture device is positioned in the outgoing optical path at a position downstream from one focal length upstream of the focusing lens.

10. A laser scanner according to claim 8 further comprising a scanning mechanism positioned downstream of the focusing lens for scanning the outgoing optical beam, wherein the diffractive aperture device is positioned between the focusing lens and the scanning mechanism.

11. A laser scanner according to claim 8 wherein the second inner aperture is rectangular.

12. A laser scanner according to claim 8 wherein the second inner aperture is circular.

13. A laser scanner according to claim 8 wherein the at least one panel comprises a single panel forming a circular second inner aperture.

14. A laser scanner according to claim 8 wherein the second inner aperture is fully transmissive.

15. A laser scanner according to claim 8 wherein the second inner aperture is concentrically positioned in the outgoing optical path.

16. A data reading device, comprising:

a light source generating a laser beam along an outgoing optical path;

a focusing lens positioned in the outgoing optical path for focusing the laser beam to a waist at a given location;

a diffractive aperture device positioned in the outgoing optical path, the diffractive aperture device having an outer aperture and an inner aperture, the inner aperture being formed by at least a first panel, the first panel being partially light transmissive.

17. A data reading device according to claim 16 wherein both the first and second panels are partially light transmissive.

18. A data reading device according to claim 16 further comprising a second panel, wherein the inner aperture is formed between the first and second panels.

19. A data reading device according to claim 18 wherein the inner aperture is rectangular.