Diode laser source with concurrently driven light emitting segments

• US 5,802,092 A
• Filed: 10/25/1996
• Issued: 09/01/1998
• Est. Priority Date: 12/07/1992
• Status: Expired due to Fees

• Current Assignee: Viavi Solutions, Inc. (Lumentum Holdings Inc.)
• Original Assignee: SDL PLC (RWS Holdings Plc)
• Inventors: Endriz, John
• Primary Examiner(s): Bovernick, Rodney B.
• Assistant Examiner(s): Leung, Quyen Phan
• Application Number:
  US08/738,216
• Time in Patent Office: 676 Days
• Field of Search: 372/50, 372/43, 372/75, 347/133, 347/233, 347/241, 347/244, 385/11, 359/622
• US Class Current: 372/50.23
• CPC Class Codes: B41J 2/45 using light-emitting diode [LED] or laser arrays
• CPC Class Codes: B41J 2/451 Special optical means therefor, e.g. lenses, mirrors, focusing means
• CPC Class Codes: G02B 19/0014 at least one surface having optical power
• CPC Class Codes: G02B 19/0057 in the form of a laser diode array, e.g. laser diode bar semiconductor laser arrays with beam combining arrangement H01S5/4012
• 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 27/0961 Lens arrays lens arrays per se G02B3/0006
• CPC Class Codes: G02B 27/0966 Cylindrical lenses cylindrical lenses per se G02B3/06
• CPC Class Codes: G02B 3/005 arranged along a single direction only, e.g. lenticular sheets G02B3/0043 takes precedence
• CPC Class Codes: G02B 3/0068 arranged in a single integral body or plate, e.g. laminates or hybrid structures with other optical elements G02B5/1885, G02B17/002, G02B30/27 take precedence
• CPC Class Codes: G02B 3/06 with cylindrical or toric faces
• CPC Class Codes: H01S 5/4012 Beam combining, e.g. by the use of fibres, gratings, polarisers, prisms
• CPC Class Codes: H01S 5/4025 Array arrangements, e.g. constituted by discrete laser diodes or laser bar H01S5/42 takes precedence
• CPC Class Codes: H01S 5/4031 Edge-emitting structures

Abstract

A diode laser source including a laser diode whose emitting element array or elements or subarray is divided into a plurality of concurrently driven laser segments. Beam filling and focusing optics are disposed in front of the segments so that light from the segments in each element or subarray converges to a single overlapping spot. The optics include a beam filling lens array collimating the light from the segments and either a single focusing lens or a second lens array focusing the collimated light to corresponding spots. In the case of a element laser diode array, each multi-segment element or subarray of the array is individually addressable so as to be driven independently from the other multi-elements array elements. The segmentation of laser elements improves laser life by reducing thermal gradients and isolating any local failures to a single segment, while separately focusing of the segments of each subarray to overlapping light spots increases the tolerance of the source to local failures. Two or more segments in a given element or subarray must fail before the source is considered to fail.

Claims

1. A multibeam optical unit comprising;

a plurality of laser elements formed in a monolithic laser diode array, each laser element comprising a plurality of laser emitters addressable as an emitter group providing an output of plural light beams;

means for electrically addressing said laser elements independently of one another;

beam optics disposed in front of each of said laser elements, said beam optics including a lens system disposed in front of and aligned with a corresponding one of said laser emitter groups to converge the light beams emitted from the plural emitters of an emitter group into a single overlapping spot for that group to preserve their overall brightness;

said emitter groups forming with said beam optics a plurality of high intensity, single overlapped light spots, each of which comprises light beams from all of the emitters of an emitter group so that, at a focal plane of said beam optics, a plurality of spatially aligned high intensity overlap spots is formed substantially aligned in a plane of said laser elements, failure of any one or emitters in any particular emitter group will cause only a slight decrease in optical power and brightness with substantially no size change in its single overlapped light spot.

2. The multibeam optical unit of claim 1 wherein said beam optics permits divergence of light from said laser emitters to said beam optics.

3. The multibeam optical unit of claim 1 wherein the number of laser emitters in each laser element is in a range from about 5 to about 20.

4. The multibeam optical unit of claim 1 wherein a width of each laser emitter is less than 20 μ

m.

5. The multibeam optical unit of claim 1 wherein a center-to-center spacing of the laser emitters forming each laser element is in a range from 20 μ

m to 50 μ

m.

6. The multibeam optical unit of claim 1 wherein the number of individually addressable laser elements is in a range from about 10 to about 20.

7. The multibeam optical unit of claim 1 wherein said lens system comprises a single monolithic lens arrays structure.

8. The multibeam optical unit of claim 1 wherein said lens system comprises a single monolithic binary diffractive optics lens array structure.

9. The multibeam optical unit of claim 1 wherein said unit is used in a laser printing system.

10. The multibeam optical unit of claim 9 wherein said laser printing system includes a light sensitive medium.

12. The multibeam optical unit of claim 1 wherein said optical means is a cylinder lens.

13. The multibeam optical unit of claim 1 wherein said beam application is a laser printing system.

14. The multibeam optical unit of claim 13 wherein said laser printing system includes a light sensitive medium.

11. A multibeam optical unit comprising:

a laser diode array comprising a plurality of laser diode emitters each emitting a separate diverging light beam from its respective emitter, said emitters being sufficiently separated from one another to permit separate operation among the emitters;

said laser diode array divided into a plurality of subarrays of diode lasers, said diode laser emitters of each subarray being driven as a group from a single current source so that said subarrays in said laser diode array are independently addressable;

optical means in alignment to receive the light beams from said array for reducing their divergence in at least one orthogonal direction; and

a plurality of lenslet arrays, one of said lenslet arrays for each of said subarrays and comprising a plurality of separate lenslets, one for each of the light beams of the subarray, for focusing each of the light beams in orthogonal beam directions in overlapped relation to form a single light spot for delivery to a beam application.

15. The multibeam optical unit of claim 11 wherein said optical means for each of said subarrays produces a plurality of aligned light spots of overlapped light beams from respective subarrays at the focal plane.

16. The multibeam optical unit of claim 11 wherein said lenslet comprises an input lens surface for collimating the light beam and an output lens surface for focusing the light beam to a light spot at said focal plane.

17. The multibeam optical unit of claim 16 wherein output lens surface focuses the light beam to said single light spot at said focal plane.

18. The multibeam optical unit of claim 16 wherein output lens surface lenslets is a separate lens unit positioned in optical alignment between said lenslet array and said focal plane.

19. The multibeam optical unit of claim 16 wherein at least one of said lenslet lens surfaces is a binary optics lens.

20. The multibeam optical unit of claim 16 wherein at least one of said lenslet lens surfaces is a refractive lens.

21. The multibeam optical unit of claim 16 wherein said input lens surface is a plurality of small lenslets.

22. The multibeam optical unit of claim 11 wherein said lenslet array is positioned from said subarray to permit each of the individual light beams of said subarray to optically fill a respective lenslet.

23. The multibeam optical unit of claim 11 wherein the number of subarrays in said array are in the range from about 5 to about 20.

24. The multibeam optical unit of claim 11 wherein said individually addressable subarrays are independently modulated.

25. A multibeam optical unit comprising:

a laser source comprising a plurality of subarrays with each subarray having a plurality of emitters spaced a predetermined distance from one another;

means for independently electrically addressing the emitters of each of said laser subarrays as a single group;

an optical lens unit for each of said laser subarrays comprising a first lens unit having a plurality of lenslets, one for each emitter of said laser subarrays to provide beam filling of said light beams within each of the respective lenslets so that the spacing between adjacent emitters at the source of each of said laser subarrays is reduced or substantially eliminated at said first lens unit.

26. The multibeam optical unit of claim 25 wherein said optical lens unit for each of said laser subarrays further comprises a second lens unit positioned between said laser subarray and said first lens unit for reducing beam divergence in at least one orthogonal direction.

27. The multibeam optical unit of claim 25 wherein said optical lens unit further focusing the respective light beams of said laser subarray in overlapped relation to form a single light spot for delivery to a beam application.

28. The multibeam optical unit of claim 27 further comprising adjacently aligned laser subarrays comprising said laser source producing a plurality of spatially aligned light spots each comprising overlapped light beams from a respective laser subarray for de to said beam application.

29. The multibeam optical unit of claim 25 wherein the number of subarrays in said laser source is in the range from about 5 to about 20.

30. The multibeam optical unit of claim 25 wherein said subarrays are independently modulated.

31. The multibeam optical unit of claim 25 wherein said optical lens unit includes a cylinder lens.

32. The multibeam optical unit of claim 25 wherein said optical lens unit includes a refractive lenslet or binary diffractive lenslet array.

33. The multibeam optical unit of claim 25 wherein said optical lens unit further includes a lens for delivery of said light spot to said beam application.

34. In a laser printing system, a multibeam optical unit comprising:

a laser source comprising a plurality of subarrays with each subarray having a plurality of emitters spaced a predetermined distance from one another and producing diverging light beams with intervening dead spacing;

means for independently electrically addressing the emitters of each of said laser subarrays as a single group;

an optical lens unit for each of said laser subarrays comprising a first lens unit having a plurality of lenslets, one for each emitter of said lager subarrays to provide beam filling of said light beams within each of the respective lenslets so that the intervening dead spacing between adjacent light beams at the source of each of said laser subarrays is reduced or substantially eliminated;

said optical lens unit further focusing the respective light beams of each said laser subarrays in overlapped relation to form a plurality of spatially separate light spots for delivery to the laser printing system.

35. In the laser printing system of claim 34, wherein said laser printing system includes a light sensitive medium.