System for reading two-dimensional images using ambient and/or projected light

• US 20020075481A1
• Filed: 01/02/2002
• Published: 06/20/2002
• Est. Priority Date: 10/26/1994
• Status: Active Grant

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Roustaei, Alexander R.
• Granted Patent: US 6,729,546 B2
• Time in Patent Office: Days
• US Class Current: 356/388
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G06K 7/10811 Focalisation

Abstract

A system for reading a two-dimensional image, and for comparing the two-dimensional image to stored data representative of a known image. The optical scanning device comprises a sensor for capturing the two-dimensional image, which sensor includes a light source for projecting an emitted light towards the two-dimensional image and an optical assembly for focussing light, which may be ambient and or emitted light from the light source, reflected from the framed two-dimensional image onto a CMOS or CCD detector for detecting the focussed light, the detector including a photodiode array for sensing the focussed light and generating a signal therefrom. Aiming of the sensor to read the two-dimensional image is facilitated by a frame locator consisting of a laser diode which emits a beam that is modified by optics, including diffractive optics, to divide the beam into beamlets which having a spacing therebetween that expands to match the dimensions of the field of view of the sensor, forming points of light at the target to define the edges of the field of view.

Claims

1. An optical scanning device for reading a two-dimensional image having a first width wherein an ambient light impinges upon said two-dimensional image, said optical scanning device comprising:

a printed circuit board having a front edge with a second width;

a light source mounted on said printed circuit board, said light source for projecting an emitted beam of light onto said two-dimensional image, said emitted beam of light having substantially said second width at said front edge of said printed circuit board and a first height and a third width at said two-dimensional image, said third width being greater than said second width and at least as large as said first width;

a framing means disposed on said printed circuit board for framing said two-dimensional image to identify an area to be scanned by said sensor, wherein said framing means comprises at least one laser diode for emitting a laser beam and at least one diffractive optic for transforming said laser beam into a plurality of diverging beamlets, said diverging beamlets having a beam edge and a beamlet spacing at said two-dimensional image at least as large as said first width;

an optical assembly disposed on said printed circuit board along an optical path for focussing light reflected from said framed two-dimensional image to obtain a focussed light, said reflected light comprising at least one of said ambient light and said emitted beam of light;

a detector disposed on said printed circuit board along said optical path behind said optical assembly for detecting at least a portion of said focussed light within a field of view of said detector, said field of view having said first height and said third width, said detector for sensing said focussed light to obtain a sensed two-dimensional image;

a controller for generating a plurality of control signals for controlling activation of said light source and said detector;

a processor for processing said sensed two-dimensional image to obtain an electrical image signal; and

an output means for converting said electrical image signal into image data.

2. The optical scanning device recited in claim 1 further comprising a photodetector for determining a level of light received at said detector and providing an input signal to said controller, wherein said controller causes said light source to be activated when said level of light is lower than needed to obtain said sensed two-dimensional image.

3. The optical scanning device recited in claim 1 wherein said diffractive optic comprises at least one diffraction grating for transforming said laser beam into at least two diverging beamlets for defining at least two spots along an edge of said field of view.

4. The optical scanning device recited in claim 3 wherein said at least one diffraction grating comprises two diffraction gratings disposed at 90 degrees to each other so that four diverging beamlets are formed for defining four spots along said beam edge.

5. The optical scanning device recited in claim 4 wherein said beam is square and each of said four spots is disposed at a corner of the square beam.

6. The optical scanning device recited in claim 1 wherein said diffractive optic includes a mirror assembly comprising a plurality of discrete reflective surfaces for reflecting said at least two diverging beamlets so that they diverge along a beam path centered along said optical path.

7. The optical scanning device as recited in claim 6 wherein said mirror assembly further comprises a base on which said plurality of discrete reflective surfaces are formed, said base being transparent to said ambient light and said light source.

8. The optical scanning device recited in claim 1 wherein said diffractive optic comprises a binary optic for transforming said laser beam into at least two diverging beamlets for defining at least two spots along said beam edge.

9. The optical scanning device recited in claim 1 wherein said light source comprises an array of LEDs.

10. The optical scanning device recited in claim 9 wherein each LED of said array is an infrared LED.

11. The optical scanning device recited in claim 1 further comprising a beam splitter disposed within said optical path for aligning said diverging beamlets along said optical path.

13. The frame locator recited in claim 12 wherein said diffractive optic comprises at least one diffraction grating for transforming said laser beam into at least two diverging beamlets for defining at least two spots along said beam edge.

14. The frame locator recited in claim 13 wherein said at least one diffraction grating comprises two diffraction gratings disposed at 90 degrees to each other so that four diverging beamlets are formed for defining four spots along said beam edge.

15. The frame locator recited in claim 14 wherein said beam is square and each of said four spots is disposed at a corner of the square beam.

16. The frame locator recited in claim 12 wherein said diffracting optic includes a mirror assembly comprising a plurality of discrete reflective surfaces for reflecting said at least two diverging beamlets so that they diverge along a beam path centered along said optical path.

17. The frame locator as recited in claim 16 wherein said mirror assembly further comprises a base on which said plurality of discrete reflective surfaces are formed, said base being transparent to said ambient light and said illuminating source.

18. The frame locator recited in claim 17 wherein said diffracting optic comprises a binary optic for transforming said laser beam into at least two diverging beamlets for defining at least two spots along said beam edge.

20. The optical scanning device recited in claim 19 wherein said diffractive optic comprises two diffraction gratings disposed at 90 degrees to each other so that four said diverging beamlets are formed for defining four spots along said beam edge.

12. A frame locator for an optical scanner having a light source and a detector with a field of view for locating a target image within the field of view of the optical scanner, said detector for detecting an ambient light and an illuminating light from said light source, the frame locator comprising:

at least one laser diode disposed within the optical scanner for emitting a laser beam; and

a diffractive optic for transforming said laser beam into a plurality of diverging beamlet, said diverging beamlets defining a beam edge and a beam width at said target image substantially equal to a width of the field of view.

19. An optical scanning device for reading a two-dimensional image having a first width wherein an ambient light impinges upon said two-dimensional image, said optical scanning device comprising:

a sensor for capturing said two-dimensional image, said sensor including;

a printed circuit board having a front edge with a second width;

a light source mounted on said printed circuit board, said light source for projecting an emitted beam of light onto said two-dimensional image, said emitted beam of light having substantially said second width at said front edge of said printed circuit board and a first height and a third width at said two-dimensional image, said third width being greater than said second width and at least as large as said first width;

a framing means disposed on said printed circuit board for framing said two-dimensional image to identify an area to be scanned by said sensor, wherein said framing means comprises at least one laser diode for emitting a laser beam and at least one diffractive optic for transforming said laser beam into a plurality of diverging beamlets, said diverging beamlets having a beam edge and a beamlet spacing at said two-dimensional image at least as large as said first width;

an optical assembly disposed on said printed circuit board along an optical path for focussing light reflected from said framed two-dimensional image to obtain a focussed light, said reflected light comprising at least one of said ambient light and said emitted beam of light;

a detector disposed on said printed circuit board along said optical path behind said optical assembly for detecting at least a portion of said focussed light within a field of view of said detector, said field of view having said first height and said third width, said detector for sensing said focussed light to obtain a sensed two-dimensional image;

a controller for generating a plurality of control signals for controlling activation of said light source and said detector;

a processor for processing said sensed two-dimensional image to obtain an electrical image signal;

a compressor for compressing said electrical image signal, said compressor employing a compression algorithm to obtain a compressed image signal; and

a decoder for decoding said compressed image signal to obtain image data representative of said two-dimensional image.