DOE-based systems and devices for producing laser beams having modified beam characteristics

• US 7,123,413 B2
• Filed: 07/17/2001
• Issued: 10/17/2006
• Est. Priority Date: 12/18/1995
• Status: Expired due to Fees

• Current Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Original Assignee: Metrologic Instruments Incorporated (Honeywell International Inc.)
• Inventors: Good, Timothy A., Knowles, C. Harry, Dickson, LeRoy, Amundsen, Thomas C., Carullo, Thomas, Groot, John
• Primary Examiner(s): Assaf, Fayez G.
• Application Number:
  US09/907,491
• Publication Number:
  US 20020114076A1
• Time in Patent Office: 1,918 Days
• Field of Search: 339 15- 18, 339/566, 339/568, 339/569, 339/565, 339/573
• US Class Current: 359/566
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• CPC Class Codes: G02B 19/0028 refractive and reflective surfaces, e.g. non-imaging catadioptric systems
• CPC Class Codes: G02B 19/0052 the light source comprising a laser diode coupling into light guides using intermediate optical elements G02B6/4204; semiconductor lasers having optical devices external to the laser cavity H01S5/005
• CPC Class Codes: G02B 26/106 having diffraction gratings as scanning elements, e.g. holographic scanners holographic optical elements G02B5/32, holography G03H
• CPC Class Codes: G02B 27/09 Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for adapting the beam shape of a laser diode G02B19/0052; adapting the beam shape of an LED G02B19/0061; coupling into light guides using intermediate optical elements G02B6/4204; beam shaping specially adapted for lasers H01S3/005
• CPC Class Codes: G02B 27/0944 Diffractive optical elements, e.g. gratings, holograms gratings per se G02B5/18; holograms used as optical elements per se G02B5/32
• CPC Class Codes: G02B 5/1842 Gratings for image generation G02B5/1847 takes precedence
• CPC Class Codes: G02B 5/32 Holograms used as optical elements
• CPC Class Codes: G06K 17/0022 arrangements or provisious for transferring data to distant stations, e.g. from a sensing device "transfer between computer elements G06F13/00 "; data-transmission H04L
• CPC Class Codes: G06K 2207/1013 Multi-focal
• CPC Class Codes: G06K 7/10 by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
• CPC Class Codes: G06K 7/10564 Light sources
• CPC Class Codes: G06K 7/10584 Source control
• CPC Class Codes: G06K 7/10594 Beam path
• CPC Class Codes: G06K 7/10603 Basic scanning using moving elements
• CPC Class Codes: G06K 7/10663 using hologram
• CPC Class Codes: G06K 7/10673 Parallel lines
• CPC Class Codes: G06K 7/10693 for omnidirectional scanning
• CPC Class Codes: G06K 7/10702 Particularities of propagating elements, e.g. lenses, mirrors G06K7/10831 takes precedence
• CPC Class Codes: G06K 7/10792 Special measures in relation to the object to be scanned
• CPC Class Codes: G06K 7/10801 : Multidistance reading
• CPC Class Codes: G06K 7/10811 : Focalisation
• CPC Class Codes: G06K 7/10851 : Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device basic electronic circuitry H03
• CPC Class Codes: G06K 7/10861 : sensing of data fields affixed to objects or articles, e.g. coded labels postal sorting B07C3/14, conveying articles B65G47/48
• CPC Class Codes: G06K 7/10871 : randomly oriented data-fields, code-marks therefore, e.g. concentric circles-code
• CPC Class Codes: G06K 7/10881 : constructional details of hand-held scanners
• CPC Class Codes: G06K 7/10891 : the scanner to be worn on a finger or on a wrist
• CPC Class Codes: G06K 7/109 : adaptations to make the hand-held scanner useable as a fixed scanner
• CPC Class Codes: G06K 7/14 : using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence
• CPC Class Codes: G07G 1/0054 : with control of supplementary check-parameters, e.g. weight or number of articles
• CPC Class Codes: H01S 5/005 : Optical components external to the laser cavity, specially adapted therefor, e.g. for homogenisation or merging of the beams or for manipulating laser pulses, e.g. pulse shaping H01S5/026, H01S5/18388 take precedence
• CPC Class Codes: H01S 5/4025 : Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence

Abstract

Novel methods are disclosed for designing and constructing miniature optical systems and devices employing light diffractive optical elements (DOEs) for modifying the size and shape of laser beams produced from a commercial-grade laser diodes, over an extended range hitherto unachievable using conventional techniques. The systems and devices of the present invention have uses in a wide range of applications, including laser scanning, optical-based information storage, medical and analytical instrumentation, and the like. In the illustrative embodiments, various techniques are disclosed for implementing the DOEs as holographic optical elements (HOEs), computer-generated holograms (CGHs), as well as other diffractive optical elements.

Claims

1. A laser beam production module for producing a laser beam having a desired beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism, said laser beam producing module comprising:

a module housing;

a visible laser diode (VLD), mounted within said module housing, for producing a laser beam from its junction having divergent and elliptical beam characteristics;

a collimating lens (L1), mounted in said module housing, spaced from said VLD by a distance D, for collimating the laser beam as it is transmitted through said collimating lens L1 and through components in said module;

a first fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M1; and

a second fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M2,

wherein the collimated laser beam exiting said collimating lens L1 is transmitted through said first DOE, and the collimated laser beam exiting said first DOE is transmitted through said second DOE, and wherein;

(a) the collimating lens has a downstream focus location, in the direction of said collimating lens L1, that is calculated to adjust or eliminate astigmatism in the beam propagating beyond the second DOE;

(b) for the calculated downstream focus location, D is selected to provide a desired beam spot size, thereby determining an upstream focus location for the lens, in the direction of said VLD; and

(d) the focal length of the collimating lens is selected according to the upstream and downstream focus locations,

whereby the collimated laser beam exiting said second DOE exits has a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism; and

wherein said laser beam is transmitted through said collimating lens L1 and through said module in a S-incident manner; and

wherein the total beam-shaping factor (M=M1M2) for the laser beam producing module is less than unity, and the laser beam leaving said collimating lens (L1) is compressed in one dimension, and has a circularized beam aspect-ratio, minimized (or reduced to zero beam dispersion, and corrected astigmatism.

2. The laser beam production module of claim 1, wherein said collimating lens (L1) is realized by an optical element selected from the group consisting of a refractive lens, a HOE, a CGH, other type of DOE, a grin lens, and one or more zone plate(s).

3. The laser beam production module of claim 1, wherein each said DOE is realized by an optical element selected from the group consisting of a HOE, a computer-generated hologram (CGHs), and a surface-relief hologram.

4. The laser beam production module of claim 1, wherein said collimating lens (L1) is realized by an optical element selected from the group consisting of a refractive lens, a HOE, a CGH, other type of DOE, a grin lens, and one or more zone plate(s).

5. The laser beam production module of claim 1, wherein each said DOE is realized by an optical element selected from the group consisting of a HOE, a computer-generated hologram (CGHs), and a surface-relief hologram.

6. The laser beam production module of claim 1,

wherein the first fixed spatial-frequency diffractive optical element (DOE) has fringe surface spacing d₁ and is mounted in said module housing such that the angle of diffraction of the laser beam from the first DOE is θ

_d1; and

wherein the second fixed spatial-frequency diffractive optical element (DOE) has a fringe surface spacing d₂ and is mounted in said module housing, such that the angle of incidence of the laser beam on the second DOE is θ

_i2;

and where d₂ cos θ

_i2=d₁ cos θ

_d1.

7. The laser beam production module of claim 1, which further comprises a blocking plate or surface between the first DOE and the second DOE to block any zero-order beam from the first DOE.

8. A laser beam production module for producing a laser beam having a desired beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism, said laser beam producing module comprising:

a module housing;

a visible laser diode (VLD), mounted within said module housing, for producing a laser beam from its junction having divergent and elliptical beam characteristics;

a collimating lens (L1), mounted in said module housing, spaced from said VLD by a distance D, for collimating the laser beam as it is transmitted through said collimating lens L1 and through components in said module;

a first fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M1; and

a second fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M2,

wherein the collimated laser beam exiting said collimating lens L1 is transmitted through said first DOE, and the collimated laser beam exiting said first DOE is transmitted through said second DOE, and wherein;

(a) the collimating lens has a downstream focus location, in the direction of said collimating lens L1, that is calculated to adjust or eliminate astigmatism in the beam propagating beyond the second DOE;

(b) for the calculated downstream focus location, D is selected to provide a desired beam spot size, thereby determining an upstream focus location for the lens, in the direction of said VLD; and

(d) the focal length of the collimating lens is selected according to the upstream and downstream focus locations,

whereby the collimated laser beam exiting said second DOE exits has a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism; and

wherein said laser beam is transmitted through said collimating lens L1 and through said module in a P-incident manner; and

wherein the total beam-shaping factor (M=M1M2) for the laser beam producing module is greater than unity (1), and thus the laser beam leaving said collimating lens (L1) is expanded in one dimension and has a circularized beam aspect-ratio, minimized (or reduced to zero) beam dispersion, and corrected astigmatism.

9. The laser beam producing module of claim 8, wherein said collimating lens (L1) is realized by an optical element selected from the group consisting of a refractive lens, a HOE, a CGH, other type of DOE, a grin lens, and one or more zone plate(s).

10. A laser beam production module for producing a laser beam having a desired beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism, said laser beam producing module comprising:

a module housing;

a visible laser diode (VLD), mounted within said module housing, for producing a laser beam from its junction having divergent and elliptical beam characteristics;

a collimating lens (L1), mounted in said module housing, spaced from said VLD by a distance D, for collimating the laser beam as it is transmitted through said collimating lens L1 and through components in said module;

a first fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M1; and

a second fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M2,

wherein the collimated laser beam exiting said collimating lens L1 is transmitted through said first DOE, and the collimated laser beam exiting said first DOE is transmitted through said second DOE, and wherein;

(a) the collimating lens has a downstream focus location, in the direction of said collimating lens L1, that is calculated to adjust or eliminate astigmatism in the beam propagating beyond the second DOE;

(b) for the calculated downstream focus location, D is selected to provide a desired beam spot size, thereby determining an upstream focus location for the lens, in the direction of said VLD; and

(d) the focal length of the collimating lens is selected according to the upstream and downstream focus locations,

whereby the collimated laser beam exiting said second DOE exits has a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism;

wherein said laser beam is transmitted through said collimating lens L1 and through said module in a P-incident manner;

wherein the total beam-shaping factor (M=M1M2) for the laser beam producing module is greater than unity (1), and thus the laser beam leaving said collimating lens (L1) is expanded in one dimension and has a circularized beam aspect-ratio, minimized or reduced to zero beam dispersion, and corrected astigmatism; and

wherein each said DOE is realized by an optical element selected from the group consisting of a HOE, a computer-generated hologram (CGHs), a surface-relief hologram, and other diffractive optical element.

11. The laser beam producing module of claim 10,

wherein the first fixed spatial-frequency diffractive optical element (DOE) has fringe surface spacing d₁ and is mounted in said module housing such that the angle of diffraction of the laser beam from the first DOE is θ

_d1; and

wherein the second fixed spatial frequency diffractive optical element (DOE) has a fringe surface spacing d₂ and is mounted in said module housing, such that the angle of incidence of the laser beam on the second DOE is θ

_i2;

and where d₂ cos θ

_i2=d₁ cos θ

_d1.

12. The laser beam production module of claim 10, which further comprises a blocking plate or surface between the first DOE and the second DOE to block any zero-order beam from the first DOE.

13. A laser beam production module for producing a laser beam having a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism, said laser beam producing module comprising:

a module housing;

a visible laser diode (VLD), mounted within said module housing, for producing a laser beam from its junction having divergent and elliptical beam characteristics and having a narrower dimension and a wider dimension;

a collimating lens (L1), mounted in said module housing, for collimating the laser beam as it is transmitted through said collimating lens L1 and through components in said module;

a first fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M1; and

a second fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M2,

wherein the collimated laser beam exiting said collimating lens L1 is transmitted through said first DOE, and the collimated laser beam exiting said first DOE is transmitted through said second DOE, and wherein

(a) the first and second DOEs expand the narrower dimension or compress the wider dimension and

(b) the lens causes the beam incident on the first DOE to converge, such that the collimated laser beam exiting said second DOE exits having a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism; and

wherein the first fixed spatial-frequency diffractive optical element (DOE) has fringe surface spacing d₁ and is mounted in said module housing such that the angle of diffraction of the laser beam from the first DOE is θ

_d1; and

wherein the second fixed spatial-frequency diffractive optical element (DOE) has a fringe surface spacing d₂ and is mounted in said module housing, such that the angle of incidence of the laser beam on the second DOE is θ

_i2;

and where d₂ cos θ

_i2=d₁ cos θ

_d1.

14. The laser beam production module of claim 13, wherein said collimating lens (L1) is realized by an optical element selected from the group consisting of a refractive lens, a HOE, a CGH, other type of DOE, a grin lens, and one or more zone plate(s).

15. The laser beam production module of claim 13, wherein each said DOE is realized by an optical element selected from the group consisting of a HOE, a computer-generated hologram (CGHs), and a surface-relief hologram.

16. A laser beam production module for producing a laser beam having a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism said laser beam producing module comprising:

a module housing;

a visible laser diode (VLD) mounted within said module housing, for producing a laser beam from its junction having divergent and elliptical beam characteristics and having a narrower dimension and a wider dimension;

a collimating lens (L1) mounted in said module housing, for collimating the laser beam as it is transmitted through said collimating lens L1 and through components in said module;

a first fixed spatial-frequency diffractive optical element (DOE) mounted in said module housing, having a beam expansion factor M1; and

a second fixed spatial-frequency diffractive optical element (DOE), mounted in said module housing, having a beam expansion factor M2,

wherein the collimated laser beam exiting said collimating lens L1 is transmitted through said first DOE, and the collimated laser beam exiting said first DOE is transmitted through said second DOE, and wherein

(a) the first and second DOEs compress the narrower dimension or expand the wider dimension and

(b) the lens causes the beam incident on the first DOE to diverge, such that the collimated laser beam exiting said second DOE exits having a controlled beam aspect-ratio, a minimized or reduced to zero beam dispersion, and corrected astigmatism;

wherein the first fixed spatial-frequency diffractive optical element (DOE) has fringe surface spacing d₁ and is mounted in said module housing such that the angle of diffraction of the laser beam from the first DOE is θ

_d1; and

wherein the second fixed spatial-frequency diffractive optical element (DOE) has a fringe surface spacing d₂ and is mounted in said module housing, such that the angle of incidence of the laser beam on the second DOE is θ

_i2;

and where d₂ cos θ

_i2=d₁ cos θ

_d1.

17. The laser beam production module of claim 16, wherein said collimating lens (L1) is realized by an optical element selected from the group consisting of a refractive lens, a HOE, a CGH, other type of DOE, a grin lens, and one or more zone plate(s).

18. The laser beam production module of claim 16, wherein each said DOE is realized by an optical element selected from the group consisting of a HOE, a computer-generated hologram (CGHs), and a surface-relief hologram.

19. The laser beam production module of claim 16, which further comprises a blocking plate or surface between the first DOE and the second DOE to block any zero-order beam from the first DOE.

20. The laser beam production module of claim 16, which further comprises a blocking plate or surface between the first DOE and the second DOE to block any zero-order beam from the first DOE.

21. A method of manufacturing a laser beam production module to have a module housing;

a visible laser diode (VLD) to be mounted within said module housing, for producing a laser beam from its junction having divergent and elliptical beam characteristics;

a collimating lens (L1) to be mounted in said module housing, spaced from said VLD by a distance D, for collimating the laser beam, a first fixed spatial-frequency diffractive optical element (DOE) to be mounted in said module housing, having a beam expansion factor M1; and

a second fixed spatial-frequency diffractive optical element (DOE) to be mounted in said module housing, having a beam expansion factor M2, such that, in operation, the collimated laser beam exiting said collimating lens L1 is transmitted through said first DOE, and the collimated laser beam exiting said first DOE is transmitted through said second DOE,

wherein the first fixed spatial-frequency diffractive optical element (DOE) has fringe surface spacing d₁ and is to be mounted in said module housing such that the angle of diffraction of the laser beam from the first DOE is θ

_d1; and

wherein the second fixed spatial-frequency diffractive optical element (DOE) has a fringe surface spacing d₂ and is to be mounted in said module housing, such that the angle of incidence of the laser beam on the second DOE is θ

_i2;

wherein the method is characterized by;

(a) calculating a downstream focus location for the collimating lens to adjust or eliminate astigmatism in the beam propagating beyond the second DOE;

(b) calculating values for d₁, d₂, θ

_i2, and θ

_d1 such that d₂ cos θ

_i2=d₁ cos θ

_d1;

(c) selecting a value for D according to the calculated downstream focus location, to provide a desired beam spot size,

(d) determining an upstream focus location for the lens;

(e) selecting a collimating lens according to the upstream and downstream focus locations; and

(f) manufacturing the laser beam production module in accordance with the selected value for D and the selected lens and values for d₁, d₂, θ

_i2, and θ

_d1, such that a collimated laser beam exiting said second DOE has a controlled beam aspect-ratio, a minimized (or reduced to zero) beam dispersion, and corrected astigmatism.

22. The laser beam producing module manufactured according to claim 21.