Multiple focus optical system for data reading applications

• US 5,438,187 A
• Filed: 06/18/1993
• Issued: 08/01/1995
• Est. Priority Date: 11/01/1991
• Status: Expired due to Fees

• Current Assignee: PSC Scanning, Inc. (Datalogic ADC Incorporated)
• Original Assignee: Spectra-Physics Scanning Systems, Inc.
• Inventors: Arends, Thomas C., Reddersen, Brad R.
• Primary Examiner(s): SHEPPERD, JOHN W
• Application Number:
  US08/080,036
• Time in Patent Office: 774 Days
• Field of Search: 359/721, 359/710, 359/708, 359/737, 359/724, 359/642, 359/315, 359/319, 359/204, 359/214, 359/741, 359/742, 235/462, 235/467, 235/472, 235/457, 235/454, 235/468, 250/271, 250/235, 250/555, 250/236
• US Class Current: 235/462.22
• CPC Class Codes: G06K 2207/1013 Multi-focal
• CPC Class Codes: G06K 7/10811 Focalisation

Abstract

An optical system and method for data reading having a light source which generates an optical beam directed toward an object to be read and a focusing system in the outgoing light path which establishes multiple beam functions. In a preferred application, a scanning system includes a multifocal lens having a single lens element having an inner lens portion of a first focal length and an outer annular lens portion with a second focal length, the scanning system therefore establishing two separate focal positions from a single light source. Alternately, the system includes a focusing lens system with an corrector element disposed in the outgoing optical path, the corrector element having a plurality of optical zones, each zone having a different optical characteristic for modifying a portion of the outgoing optical beam. A zone may be a refractive region, a reflective region, a diffractive region, an empty region, a window region, or combinations thereof.

Claims

1. An optical system for data reading, comprising:

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

a scanning mechanism for scanning the outgoing beam along at least one axis to produce at least one scan line;

a multifocal lens system positioned in the outgoing optical path between the single light source and the scanning mechanism, the multifocal lens system including at least an inner lens portion having a first focal length and an outer lens portion having a second focal length, the multifocal lens system dividing the outgoing optical beam at least into a first beam section and a second beam section, the first beam section being focused by the inner lens portion simultaneously with the second beam section being focused by the outer lens portion;

a detector for detecting light reflecting off the object, the detector being positioned to receive the light reflecting from the object without the light passing through the multifocal lens system.

2. An optical system according to claim 1 wherein the inner lens portion focuses light at a first focal point and the outer lens portion focuses light at a second focal point, the second focal point being further from the multifocal lens system than is the first focal point.

3. An optical system according to claim 1 wherein the inner lens portion focuses light at a first focal point and the outer lens portion focuses light at a second focal point, the second focal point being closer to the multifocal lens system than is the first focal point.

4. An optical system according to claim 1 wherein the light source is selected from the group consisting of:

lasers, laser diodes, coherent light sources, light emitting diodes and non-coherent light sources.

5. An optical system according to claim 1 wherein the inner lens portion and the outer lens portion are selected from the group consisting of:

spherical lenses, Fresnel lenses, holographic optical elements, aspheric lenses, and combinations thereof.

6. An optical system according to claim 1 wherein the multifocal lens system comprises a primary lens element and the inner lens portion comprises a lenslet attached to and positioned on one side of the primary lens element.

7. An optical system according to claim 1 wherein the optical system comprises a laser scanner.

8. An optical system according to claim 1 wherein the multifocal lens system further includes a third lens portion between the inner lens portion and the outer lens portion, the third lens portion having a third focal length.

9. An optical system according to claim 1 wherein the first beam section is coaxial with the second beam section.

10. An optical system according to claim 1 wherein the inner lens portion focuses light in a resolving axis at a first waist location and the outer lens portion focuses light in the resolving axis at a second waist location, the first waist location being separate from the second waist location.

11. An optical system for data reading, comprising:

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

a scanning mechanism for scanning the outgoing beam along at least one axis to produce at least one scan line;

a multifocal lens system comprising at least two lens focusing portions positioned in the outgoing optical path between the light source and the scanning mechanism, the at least two lens focusing portions dividing the optical beam into at least a first cone of light and a second cone of light for simultaneous transmission outward along the outgoing optical path, the first cone of light having a first focal point and the second cone of light having a second focal point, the first focal point being separate from the second focal point, the first cone of light being coaxial with the second cone of light and being transmitted simultaneously therewith;

a detector for detecting light reflecting off the object, the detector being positioned to receive the light reflecting from the object without the light passing through the multifocal lens system.

12. An optical system according to claim 11 wherein the multifocal lens system is selected from the group consisting of:

spherical lenses, Fresnel lenses, holographic optical elements, aspheric lenses, and combinations thereof.

13. An optical system according to claim 11 wherein the multifocal lens system comprises a primary lens element and a lenslet attached to and positioned on one side of the primary lens element.

14. An optical system according to claim 11 wherein the multifocal lens system comprises a primary lens element and a secondary smaller lens element positioned adjacent the primary lens element.

15. An optical system according to claim 11 wherein the multifocal lens system further divides the optical beam into a third cone of light along the outgoing optical path, the third cone of light focusing at a third focal point, the third focal point being separate from and coaxial with the first focal point and second focal point.

16. An optical system according to claim 11 comprising a scanning system, wherein multifocal lens system includes a primary lens element and a corrector plate element positioned to one side of the primary lens element, the at least two lens focusing portions being provided by the optical corrector plate which comprises two optical zones namely a central optical zone and an outer annular optical zone, the central optical zone having a given size, shape and material which modifies a first optical beam portion passing therethrough to focus to a given first waist location at least along one axis, the outer annular optical zone having a given size, shape and material which modifies a second optical beam portion passing therethrough to focus to a given second waist location at least along one axis.

17. An optical system according to claim 16 wherein the central optical zone of the optical corrector plate comprises an elliptical-shaped opening having a diameter in a resolving axis smaller than that in a non-resolving axis.

18. A method for data reading comprising the steps of:

emitting an outgoing beam of light from a single light source toward an object to be read;

passing the outgoing beam of light through a multifocus lens system having at least a first focusing portion and a second focusing portion, the first focusing portion being coaxial with the second focusing portion;

dividing the outgoing beam of light into first and second beam portions by focusing the first beam portion of the outgoing beam of light passing through the first focusing portion at a first focal point and simultaneously focusing the second beam portion of the outgoing beam of light passing through the second focusing portion at a second focal point coaxially with the first beam portion being focused by the first focusing portion, the first focal point being separate from the second focal point;

scanning the outgoing beam, which has been focused to first and second focal points, with a scanning mechanism along at least one axis to produce at least one scan line; and

detecting return light reflecting off the object along a collection path without passing the return light through the multifocal lens system.

19. A method for data reading according to claim 18 wherein the carrier signal includes high and low levels, the method further comprising the step of subtracting out the carrier signal having a low level from the carrier signal having a high level.

20. A method for data reading according to claim 18 wherein the multifocus lens system comprises a multifocal lens element.

21. A method for data reading according to claim 20 wherein the first focusing portion comprises an inner portion of the multifocal lens element and the second focusing portion comprises an outer annular portion of the multifocal lens element which is coaxial with the inner portion.

22. A method for data reading according to claim 20 wherein the first focusing portion comprises an outer annular portion of the multifocal lens element and the second focusing portion comprises an inner portion of the multifocal lens element which is coaxial with the outer annular portion.

23. A method for data reading according to claim 18 wherein the step of emitting a beam of light comprises emitting a beam of light from a light source selected from the group consisting of:

lasers, laser diodes, coherent light sources, light emitting diodes and non-coherent light sources.

24. A method for data reading according to claim 18 wherein light is passed through a third focus portion of the multifocus lens system and further comprising the step of focusing light passing through the third focusing portion at a third focal point, the third focal point being separate from and coaxial with the first focal point and the second focal point.

25. A method for data reading according to claim 18 further comprising

passing the outgoing beam of light through a primary focusing lens element,

wherein the step of focusing a portion of the outgoing beam of light passing through the first focusing portion at a first focal point and the step of simultaneously focusing another portion of the outgoing beam of light passing through the second focusing portion at a second focal point comprise passing the outgoing beam through secondary focusing elements contained within a corrector plate element positioned to one side of the primary lens element.

26. A method for data reading according to claim 25 wherein the step of passing the outgoing beam through secondary focusing elements contained within the corrector plate element comprises passing the portion of the outgoing beam through a central optical zone of the corrector plate element to focus to the first focal point and passing the other portion of the outgoing beam through an outer annular optical zone of the corrector plate element to focus the beam portion to the second focal point.

27. An optical system for data reading, comprising:

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

a scanning mechanism for scanning the outgoing beam along at least one axis to produce at least one scan line;

a multifocal lens system positioned in the outgoing optical path between the light source and the scanning mechanism, the multifocal lens system including at least an inner lens portion having a first focal length and an outer lens portion having a second focal length, the multifocal lens system dividing the outgoing optical beam into at least coaxial first and second beam sections, the first beam section being focused by the inner lens portion simultaneously with the second beam section being focused by the outer lens portion;

a detector for detecting light reflecting off the object, the detector being positioned to receive the light reflecting from the object without the light passing through the multifocal lens system.

28. An optical system for data reading, comprising:

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

a scanning mechanism for scanning the outgoing beam along at least one axis to produce at least one scan line;

a multifocal lens system comprising at least two lens focusing portions positioned in the outgoing optical path between the light source and the scanning mechanism, the at least two lens focusing portions dividing the optical beam from the single light source into at least a first cone of light and a second cone of light for simultaneous transmission outward along the outgoing optical path, the first cone of light having a first focal point and the second cone of light having a second focal point, the first focal point being separate from the second focal point;

a detector for detecting light reflecting off the object, the detector being positioned to receive the light reflecting from the object without the light passing through the multifocal lens system.

29. 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; and

a focusing lens system positioned in the outgoing optical path for focusing the optical beam, the focusing lens system comprising

at least one focusing lens element which focuses the outgoing beam to a given waist location and

an optical corrector plate positioned in the outgoing optical path on a side of the focusing lens element opposite to the light source, the optical corrector plate including a plurality of optical zones which divide the outgoing optical beam into at least two respective optical beam portions, the optical corrector plate including a holder portion within which the focusing lens element is mounted in a unitary structure therewith.

30. An optical system according to claim 29 wherein the focusing lens element is comprised of glass material providing primary focusing for the system and the optical corrector plate is comprised of optical plastic material providing secondary focusing for the system.

31. 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; and

a focusing lens system positioned in the outgoing optical path for focusing the optical beam, the focusing lens system comprising

at least one focusing lens element which focuses the outgoing beam to a given waist location and

an optical corrector plate positioned in the outgoing optical path on a side of the focusing lens element opposite to the light source, the optical corrector plate including a plurality of optical zones which divide the outgoing optical beam into at least two respective optical beam portions, the optical corrector plate including a holder portion within which the focusing lens element is mounted in a unitary structure therewith, wherein the plurality of optical zones comprises a central optical zone and an outer annular optical zone, the central optical zone having a given size, shape and material which modifies the optical beam portion passing therethrough to focus at a given waist location, the outer annular optical zone having a given size, shape and material which modifies the optical beam portion passing therethrough to focus at a given waist location for simultaneous transmission along the outgoing optical path.

32. 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; and

a focusing lens system positioned in the outgoing optical path for focusing the optical beam, the focusing lens system comprising

at least one focusing lens element which focuses the outgoing beam to a given waist location and

an optical corrector plate positioned in the outgoing optical path on a side of the focusing lens element opposite to the light source, the optical corrector plate including a plurality of optical zones which divide the outgoing optical beam into at least two respective optical beam portions, the optical corrector plate including a holder portion within which the focusing lens element is mounted in a unitary structure therewith, wherein one of the optical zones of the optical corrector plate is dynamically variable, an optical characteristic of the one optical zone being varied by the application of an electrical voltage.

33. 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; and

a focusing lens system positioned in the outgoing optical path for focusing the optical beam, the focusing lens system comprising

at least one focusing lens element which focuses the outgoing beam to a given waist location and

an optical corrector plate positioned in the outgoing optical path on a side of the focusing lens element opposite to the light source, the optical corrector plate including a plurality of optical zones coaxially dividing the outgoing optical beam into at least respective first and second optical beam portions, the plurality of optical zones comprising a central optical zone and an outer annular optical zone, the central optical zone having a given size, shape and material which modifies the first optical beam portion passing therethrough to focus at a given waist location, the outer annular optical zone having a given size, shape and material which modifies the second optical beam portion passing therethrough to focus at a given waist location for simultaneous transmission along the outgoing optical path.

34. An optical system according to claim 33 wherein the central optical zone of the optical corrector plate comprises an elliptical-shaped opening having a diameter in a resolving axis smaller than that in a non-resolving axis.

35. An optical system according to claim 33 wherein the optical corrector plate includes a holder portion within which the focusing lens element is mounted in a unitary structure therewith.

36. An optical system for data reading according to claim 33 wherein the central optical zone of the optical corrector plate comprises an opening having a given diameter in a resolving axis, the opening being small enough to be within diffractive limit of the optical beam so as to shift the waist of the first optical beam portion to a given location.

37. 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; and

a focusing lens system positioned in the outgoing optical path for focusing the optical beam, the focusing lens system comprising

at least one focusing lens element and

an optical corrector plate positioned in the outgoing optical path, the optical corrector plate including a plurality of optical zones dividing the outgoing optical beam into respective outer and inner optical beams, the plurality of optical zones comprising a central optical zone and an outer annular optical zone, the central optical zone having a given size, shape and material which modifies the inner optical beam passing therethrough to focus at a given waist location, the outer annular optical zone having a given size, shape and material which modifies the outer optical beam passing therethrough to focus at least a portion of the outer optical beam at a given waist location for simultaneous transmission along the outgoing optical path, wherein the outer annular optical zone of the optical corrector plate comprises a beam splitter deflecting a portion of the outer optical beam impinging thereon along an alternate beam path.

38. 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; and

a focusing lens system positioned in the outgoing optical path for focusing the optical beam, the focusing lens system comprising

at least one focusing lens element which focuses the outgoing beam to a given waist location and

an optical corrector plate positioned in the outgoing optical path on a side of the focusing lens element opposite to the light source, the optical corrector plate including a plurality of optical zones which divide the outgoing optical beam into at least two respective optical beam portions, the optical corrector plate including a holder portion within which the focusing lens element is mounted in a unitary structure therewith, wherein one of the plurality of optical zones comprises a central optical zone comprised of an opening having a given diameter in a resolving axis, the opening being small enough to be within diffractive limit of the optical beam so as to shift the waist of the first optical beam portion to a given location.