Optical system for data reading having large depth of field

• US 5,945,670 A
• Filed: 05/19/1997
• Issued: 08/31/1999
• 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:
  US08/858,597
• Time in Patent Office: 834 Days
• Field of Search: 250/235, 250/555-557, 250/566, 250/568, 250/234, 250/236, 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 an electronically actuable mechanism with no moving parts which may include 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 obtaining a large depth of field in a scan volume for a data reader, comprising the steps of

projecting an optical beam along an outgoing optical path;

passing the optical beam through a control module;

actively changing focus of the optical beam in the scan volume to selected distances from the data reader by electronic actuation without moving parts of the control module;

collecting light from the optical beam reflecting and/or scattering off an object in the scan volume.

2. A method according to claim 1 further comprising forming the optical beam from a laser diode and positioning the control module on a side of the focusing system opposite to the laser diode.

3. A method 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 control module upstream of the focusing system and adjacent thereto.

4. A method according to claim 1 further comprising

forming the optical beam from a laser diode;

focusing the optical beam to a given waist location with a fixed focusing lens system; and

wherein the step of actively focusing the optical beam comprises passing the optical beam through an LCD mechanism of the control module.

5. A method according to claim 1 further comprising

lowering amplitude of the optical beam in the scan volume corresponding to focus being changed to a distance nearer to the data reader.

6. A method according to claim 1 further comprising maintaining a relatively constant waist diameter while changing focus of the optical beam.

7. A method for data reading comprising the steps of

projecting an optical beam along an outgoing optical path;

passing the optical beam through a control module;

actively focusing the optical beam to selected distances from the data reader by electronic actuation without moving parts of the control module;

forming the optical beam from a laser diode;

focusing the beam with a focusing system; and

positioning the control module downstream of the focusing system.

8. A method for data reading comprising the steps of

projecting an optical beam along an outgoing optical path;

passing the optical beam through a control module;

actively focusing the optical beam to selected distances from the data reader by electronic actuation without moving parts of the control module;

forming the beam 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 control module between the focusing system and the scanning mechanism.

9. A method for data reading comprising the steps of

projecting an optical beam along an outgoing optical path;

passing the optical beam through a control module;

actively focusing the optical beam to selected distances from the data reader by electronic actuation without moving parts of the control module;

forming the beam from a laser diode;

focusing the beam with a focusing system; and

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

10. A method for data reading comprising the steps of

projecting an optical beam along an outgoing optical path;

passing the optical beam through a control module;

actively focusing the optical beam to selected distances from the data reader by electronic actuation without moving parts of the control module;

compensating for temperature fluctuation.

11. A method for data reading according to claim 10 wherein the step of compensating for temperature fluctuation comprises the steps of

obtaining a temperature readout from a temperature device,

calculating a focus adjustment based upon the temperature readout obtained,

making the focus adjustment on the control module.

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

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

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

an electronically actuable aperture mechanism having no moving parts and positioned in the outgoing optical path, for adjusting distance of the waist from the light source.

13. A laser scanner according to claim 12 wherein the aperture mechanism is positioned in the outgoing optical path at a position downstream from one focal length upstream of the focusing lens.

14. A scanner comprising:

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

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

an electronically actuable aperture mechanism having no moving parts and positioned in the outgoing optical path, for adjusting location of the waist;

a scanning mechanism positioned downstream of the focusing lens for scanning the outgoing optical beam, wherein the aperture mechanism is positioned between the focusing lens and the scanning mechanism.

15. A data reading device, comprising:

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

a focusing optical element positioned in the outgoing optical path for focusing the laser beam to a waist at a given distance from the light source;

a diffractive device positioned in the outgoing optical path, the diffractive device comprising at least a first panel, the first panel being partially light transmissive, the diffractive device moving the waist nearer to the light source dependent upon degree of transmissivity of the first panel.

16. A data reading device according to claim 15 wherein the first panel forms a circular aperture.

17. A data reading device according to claim 15 wherein the first panel forms a rectangular aperture.

18. A data reading device according to claim 15 wherein the light source comprises a laser diode.

19. A data reading device according to claim 15 wherein the focusing optical element comprises a lens.

20. A data reading device comprising:

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

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

a diffractive device positioned in the outgoing optical path, the diffractive device comprising at least a first panel, the first panel being partially light transmissive;

a second panel for forming an aperture between the first and second panels.

21. A data reading device according to claim 20 wherein the aperture is rectangular.

22. A data reading device according to claim 20 wherein both the first and second panels are partially light transmissive.

23. A data reading device according to claim 20 wherein both the first and second panels comprise electrically actuated liquid crystal devices.

24. A data reading device comprising:

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

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

a diffractive device positioned in the outgoing optical path, the diffractive device comprising at least a first panel, the first panel being partially light transmissive, wherein the diffractive device refocuses the laser beam to waist at a new location nearer to the light source than the given location.

25. An optical system for data reading, comprising

a light source generating an optical beam along an outgoing optical path toward an object to be read;

a focusing system positioned in the outgoing optical path for focusing the optical beam to a given distance;

an aperture device positioned in the outgoing optical path, the aperture device forming an opening which is offset from a center of the outgoing beam.

26. An optical system according to claim 25 wherein the aperture device includes a section which is partially light transmissive.

27. An optical system according to claim 25 wherein the aperture device refocuses the laser beam to waist at a new location nearer to the light source than the given location.

28. A data reader, comprising:

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

a focusing lens positioned in the outgoing optical path for focusing the optical beam to a waist at a given distance from the lens in a scan volume;

an electronically-operated focusing control module positioned in the outgoing optical path, the control module adjusting distance of the waist from the light source onto an object in the scan volume without use of moving parts;

a detector for detecting light from the optical beam reflecting off the object.

29. A data reader according to claim 28 wherein the control module includes a diffractive optical element positioned in the outgoing optical path at a position downstream from one focal length upstream of the focusing lens.

30. A data reader according to claim 28 wherein the data reader comprises a laser bar code scanner.

31. A data reader according to claim 28 wherein the control module comprises an diffractive aperture device including at least one LCD panel for forming an aperture along at least one optical axis of the outgoing optical beam.

32. A data reader comprising

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

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

an electronically-operated focusing control module positioned in the outgoing optical path, the control module adjusting location of the waist without use of moving parts wherein the control module includes a diffractive optical element positioned in the outgoing optical path;

a scanning mechanism positioned downstream of the focusing lens for scanning the outgoing optical beam, wherein the diffractive optical element is positioned between the focusing lens and the scanning mechanism.

33. A data reader, comprising:

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

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

an electronically-operated focusing control module positioned in the outgoing optical path, the control module including a temperature sensor and a controller for adjusting focusing of the control module according to temperature in the control module as sensed by the temperature sensor.