Laser scanning system employing parabolic light collection surfaces having optical axes disposed off the Bragg angle of the holographic optical elements of the holographic scanning disc thereof
First Claim
1. A holographic laser scanning system for scanning bar code symbols, comprising:
- a holographic scanning disc;
a laser beam source for producing a laser beam and directing said laser beam at an angle of incidence to said holographic scanning disc;
said holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning said laser beam and producing a laser scanning pattern for scanning a code symbol, and collecting light rays reflected off said scanned code symbol for subsequent focusing and detection,wherein each said holographic optical element has substantially the same Bragg angle;
a parabolic light reflective surface disposed beneath said holographic scanning disc, and having an optical axis disposed off the Bragg angle of said holographic optical elements, for focusing towards a focal point above said holographic scanning disc the reflected light rays collected by each said holographic optical element; and
a photodetector, disposed at said focal point above said holographic scanning disc, and radially aligned with the optical axis of said parabolic light reflective surface, for detecting the intensity of collected light rays focused by said parabolic light reflective surface and transmitted through said holographic optical elements to said photodetector for detection and generation of a scan data signal for subsequent processing;
wherein the light diffraction efficiency of each said holographic optical element at said angle of incidence of said laser beam during said scanning is substantially greater than the light diffraction efficiency of said holographic optical element at the angle at which said focused laser light is transmitted from said parabolic light reflective surface through said holographic optical elements towards said photodetector during light detection.
10 Assignments
0 Petitions
Accused Products
Abstract
A holographic laser scanning system for scanning bar code symbols. The system comprises a holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning the plurality of laser beams directed at the same incident angle. Each holographic optical element as substantially the same Bragg angle. The parabolic light reflective surfaces are disposed beneath the holographic scanning disc. Each parabolic light reflective surface has an optical axis disposed off the Bragg angle of the holographic optical elements, for focusing towards a focal point above the holographic scanning disc, the reflected light rays collected by each holographic optical element. A photodetector is disposed at the focal point of the corresponding parabolic light reflective surface above the holographic scanning disc, and is radially aligned with the optical axis of one parabolic light reflective surface. The light diffraction efficiency of each holographic optical element at the angle of incidence of each laser beam during scanning is substantially greater than the light diffraction efficiency of the focused laser light transmitted from each parabolic light reflective surface through the holographic optical elements towards corresponding photodetector during light detection. This enables the collected light rays, focused by the parabolic light reflective surface, to be efficiently transmitted through the holographic optical elements, to the photodetector for detection and generation of a scan data signal for subsequent processing. By virtue of this novel arrangement, the present invention enables the construction of a holographic laser scanner having substantially reduced height characteristics.
-
Citations
18 Claims
-
1. A holographic laser scanning system for scanning bar code symbols, comprising:
-
a holographic scanning disc; a laser beam source for producing a laser beam and directing said laser beam at an angle of incidence to said holographic scanning disc; said holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning said laser beam and producing a laser scanning pattern for scanning a code symbol, and collecting light rays reflected off said scanned code symbol for subsequent focusing and detection, wherein each said holographic optical element has substantially the same Bragg angle; a parabolic light reflective surface disposed beneath said holographic scanning disc, and having an optical axis disposed off the Bragg angle of said holographic optical elements, for focusing towards a focal point above said holographic scanning disc the reflected light rays collected by each said holographic optical element; and a photodetector, disposed at said focal point above said holographic scanning disc, and radially aligned with the optical axis of said parabolic light reflective surface, for detecting the intensity of collected light rays focused by said parabolic light reflective surface and transmitted through said holographic optical elements to said photodetector for detection and generation of a scan data signal for subsequent processing; wherein the light diffraction efficiency of each said holographic optical element at said angle of incidence of said laser beam during said scanning is substantially greater than the light diffraction efficiency of said holographic optical element at the angle at which said focused laser light is transmitted from said parabolic light reflective surface through said holographic optical elements towards said photodetector during light detection. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A holographic laser scanning system for scanning bar code symbols, comprising:
-
a holographic scanning disc; a plurality of laser beam sources for producing a plurality of laser beams and directing said plurality of laser beams at an angle of incidence to said holographic scanning disc; said holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning said plurality of laser beams and producing laser scanning pattern for scanning a code symbol, and collecting light rays reflected off said scanned code symbol for subsequent focusing and detection, wherein each said holographic optical element has substantially the same Bragg angle; a plurality of parabolic light reflective surfaces disposed beneath said holographic scanning disc, and each having an optical axis disposed off the Bragg angle of said holographic optical elements, for focusing towards a focal point above said holographic scanning disc, the reflected light rays collected by each said holographic optical element; and a plurality of photodetectors, each being disposed at said focal point above said holographic scanning disc, and radially aligned with the optical axis of one said parabolic light reflective surface, for detecting the intensity of collected light rays focused by said one parabolic light reflective surface and transmitted through said holographic optical elements to said photodetector for detection and generation of a scan data signal for subsequent processing; wherein the light diffraction efficiency of each said holographic optical element at said angle of incidence of each said laser beam during said scanning is substantially greater than the light diffraction efficiency of said holographic optical element at the angle at which said focused laser light is transmitted from each said parabolic light reflective surface through said holographic optical elements towards said corresponding photodetector during light detection. - View Dependent Claims (7, 8, 9, 10, 11, 12)
-
-
13. A holographic laser scanning system for scanning bar code symbols, comprising:
-
a holographic scanning disc; a laser beam source for producing a laser beam and directing said laser beam at an angle of incidence to said holographic scanning disc; said holographic scanning disc having a plurality of holographic optical elements disposed thereon for scanning said laser beam and producing a laser scanning pattern for scanning a code symbol, and collected light rays reflected off said scanned code symbol for subsequent focusing and detection, wherein each said holographic optical element has substantially the same Bragg angle; and a parabolic light reflective surface disposed beneath said holographic scanning disc, and having an optical axis disposed off the Bragg angle of said holographic optical elements, for focusing towards a focal point above said holographic scanning disc, the reflected light rays collected by each said holographic optical element. - View Dependent Claims (14, 15, 16, 17, 18)
-
Specification