Extended depth of field imaging system using chromatic aberration

• US 20080212168A1
• Filed: 03/22/2007
• Published: 09/04/2008
• Est. Priority Date: 01/31/2005
• Status: Active Grant

• Current Assignee: Datalogic Scanning Incorporated (Datalogic S.p.A.)
• Original Assignee: PSC Scanning, Inc. (Datalogic ADC Incorporated)
• Inventors: Olmstead, Bryan L., Shearin, Alan
• Granted Patent: US 7,626,769 B2
• Time in Patent Office: Days
• US Class Current: 359/355
• CPC Class Codes: G02B 27/0075 with means for altering, e.g. increasing, the depth of field or depth of focus
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence

Abstract

An imaging system (FIG. 3) is disclosed that has a wavelength dependent focal shift caused by longitudinal chromatic aberration in a lens assembly (203) that provides extended depth of field imaging due to focal shift (213,214) and increased resolution due to reduced lens system magnification. In use, multiple wavelengths of quasi-monochromatic illumination, from different wavelength LEDs (206,207) or the like, illuminate the target, either sequentially, or in parallel in conjunction with an imager (200) with wavelength selective (colored) filters. Images are captured with different wavelengths of illumination that have different focus positions (208,209), either sequentially or by processing the color planes of a color imager separately. Extended depth of field, plus high resolution are achieved. Additionally, information about the range to the target can be determined by analyzing the degree of focus of the various colored images.

Claims

1-28. -28. (canceled)

29. An extended depth of field imaging method comprising

illuminating a target with a light of a first quasi-monochromatic wavelength in the infrared range;

illuminating the target with a light of a second quasi-monochromatic wavelength different from the first wavelength;

receiving light reflected from the target at an electronic imaging location;

extending depth of target field within which an image of the illuminated target received is substantially in focus by interposing a lens having chromatic aberration between the illuminated target and the electronic imaging location.

30-50. -50. (canceled)

51. A system for imaging an object, comprising:

an illumination system generating light of first and second different quasi-monochromatic wavelengths wherein at least one of the first and second quasi-monochromatic wavelengths is in the infrared range;

a chromatically aberrant lens system having a first focal distance for the first wavelength light and a second focal distance for the second wavelength light; and

an imaging sensor receiving, via the lens system, light reflected from an object to be imaged, the sensor generating an image of the object by assembling first wavelength light focused thereon when a distance of the object from the lens system is the first focal distance and second wavelength light focused thereon when the distance of the object from the lens system is the second focal distance.

52. A system according to claim 51, wherein the lens system comprises one or more collection lenses.

53. A system according to claim 52 further comprising a wavelength dependent aperture is disposed between one of the collection lenses and the imaging sensor.

54. A system according to claim 51, wherein the first wavelength is about 850 nm, and the second wavelength is about 590 nm.

55. A system according to claim 51, wherein the lens system comprises a plano-concave lens element a plano-convex lens element.

56. A system according to claim 55 further comprising a wavelength dependent aperture is disposed between the plano-convex lens element and the plano-concave lens element.

57. The scanner according to claim 51, wherein the illumination system includes a first light source generating light of the first wavelength and a second light source generating light of the second wavelength.

53-1. A system according to claim 51, wherein the object comprises a bar code.

54-2. A system according to claim 51, wherein the imaging sensor is a solid-state imaging array.