Laser Diode Collimator and a Pattern Projecting Device Using Same

Abstract

An optical collimating unit is provided that comprises a laser unit, and a lens having three optical surfaces, being a first refractive surface, a second reflective surface and a third refractive surface. Also provided is a light projection device comprising an optical collimating unit that comprises a laser unit, a lens and an optical component configured to shape laser beams being emitted into respective desired light patterns.

Claims

1. An optical collimating unit comprising a laser unit, and a lens having three optical surfaces, being a first refractive surface, a second reflective surface and a third refractive surface.

2. The optical collimating unit of claim 1, wherein any of the at least three optical surfaces, is a member selected from a group that comprises a convex surface, a concave surface, a spherical surface, an aspherical surface, a bi-conic surface, a cylindrical surface, a toric surface or a freeform shape, and wherein the shape of the at least three surfaces is selected to enable controlling a shape and direction of a beam refracted by the lens.

3. The optical collimating unit of claim 1, further comprising an external reflective element attached thereto that enables emitting a light beam shaped to a desired cross-section distribution of phase and amplitude, thereby said emitted light beam is focused at a desired distance from said lens.

4. A light projection device comprising an optical collimating unit comprising at least one laser unit, at least one lens and at least one optical component configured to shape laser beams being emitted, into respective desired light patterns.

5. The light projection device of claim 4, wherein said at least one optical component is selected from a group that consists of a phase-modulating component, a diffuser, and a microlens array (MLA).

6. The light projection device of claim 4, wherein said at least one optical component configured to shape emitted laser beams into respective desired light patterns, is implemented on one or more of the lens' surfaces.

7. A pattern projecting device, comprising a laser diode unit having at least two separated apertures and configured to emit electromagnetic radiation simultaneously from the at least two separated apertures of said laser diode unit.

8. The pattern projecting device of claim 7, wherein said laser diode unit is an edge-emitting laser diode chip configured to emit electromagnetic radiation simultaneously from both ends of said laser diode chip.

9. The pattern projecting device of claim 8, further comprising optical collimating units each fixed next to a respective end of said laser diode.

10. The pattern projecting device of claim 7, comprising a plurality of surfaces each having a pre-defined curvature to enable collimating a fast axis and a slow axis of a light beam, and at least two microstructured components, each configured to generate a respective pattern out of a respective light beam that passes there-through.

11. The pattern projecting device of claim 10, wherein projected light patterns are at least partially overlapping each other.

12. The pattern projecting device of claim 10, wherein light patterns projected by said pattern projecting device are spatially combined to provide a wide field of illumination subtending a wide angle of at least 90° in one or two transverse dimensions.

13. The pattern projecting device of claim 10, wherein the projected light patterns are different from each other.

14. The pattern projecting device of claim 10, wherein the adjustment of the amount of light is achieved by reflecting part of the emitted light through the respective aperture, back into the laser unit.

15. The pattern projecting device of claim 10, wherein optical power associated with the at least two light patterns, is adjustable in a range extending from providing an equal optical power to all projected light patterns derived from the electromagnetic radiation emitted simultaneously from the at least two separated apertures, to providing a near-zero optical power associated with one of said projected light patterns.

16. An optical apparatus comprising a pair of controllable photonic devices that are associated with pattern projecting device of claim 10, wherein each of the pair of controllable photonic devices is configured to adjust power transmitted from a respective end of the laser diode unit of said pattern projecting device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0042] For a more complete understanding of the present invention, reference is now made to the following detailed description taken in conjunction with the accompanying drawing wherein:

[0043] FIG. 1—illustrates an exemplary prior art single-sided projector;

[0044] FIG. 2 illustrates a laser and lens according to an embodiment of the present invention;

[0045] FIG. 3 exemplifies a single-sided projector construed according to an embodiment of the present invention;

[0046] FIG. 4—illustrates a two-sided projector construed according to an embodiment of the present invention;

[0047] FIG. 5—exemplifies a Field of Illumination represented in angle space, and divided into two slightly-overlapping regions;

[0048] FIG. 6—exemplifies a slanted folding lens surface and accordingly slanted exit surface for projection of pattern into a tilted FOI;

[0049] FIG. 7—exemplifies non-overlapping complementary projection areas presented in angle space; and

[0050] FIG. 8—illustrates Power behavior of the two beams as a function of the controlling device reflection coefficient; and

[0051] FIG. 9—exemplifies a double-sided projector construed according to another embodiment of the present invention.

DETAILED DESCRIPTION

[0052] In this disclosure, the term “comprising” is intended to have an open-ended meaning so that when a first element is stated as comprising a second element, the first element may also include one or more other elements that are not necessarily identified or described herein, or recited in the claims.

[0053] In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a better understanding of the present invention by way of examples. It should be apparent, however, that the present invention may be practiced without these specific details.

[0054] Known patterns (e.g. grids or bars) are often projected by structured-light sensors or stereo sensors onto a scene. The deformation of these known patterns as it appears to the sensor camera when the pattern strikes surfaces, allows vision systems to calculate depth and surface information of the objects present in the scene, as used for example in structured light 3D scanners.

[0055] A pattern projector may comprise a light source, one or more optical components, and a package (housing). The purpose of this device is to project a light pattern. This typically may be achieved by manipulating light emitted from a source or an array of sources, and shaping it into the desired pattern at the desired intensity. In numerous projector modules, a laser or array of lasers are utilized, optionally a lens and a pattern-shaping element, a micro-structured optical element, such as a diffuser or DOE.

[0056] According to the present invention, the laser diode is preferably of an edge-emitter type, mounted on a surface (“laser substrate plane”, usually a sub-mount substrate), which is perpendicular or nearly-perpendicular to the central axis of the desired pattern projection FOI.

[0057] FIG. 1 illustrates a prior art projector, being a conventional edge-emitting laser configured to emit light from only a single edge of the laser chip, while its opposite edge is configured not to emit light (e.g. by having a highly-reflective coating thereat. An optical component is placed next to the laser aperture at the appropriate location and alignment.

[0058] In the embodiment illustrated in FIG. 2, the purpose of the optical component placed next to the laser aperture is collimation of the laser diode light and folding it in the normal direction (or near-normal) to the laser substrate plane. To that end, the first surface (1) of the optical component is a cylindrical aspheric surface or a toroidal aspheric surface, and acts mainly on the fast axis of the laser diode beam. Its shape and distance from the laser aperture is chosen according to the desired beam size, which in turn is determined by DOE size in that direction. The second surface (2) folds the beam path, reflecting it in a direction which is normal or near-normal to the laser substrate surface. Surface (2) is a flat surface which reflects the light through total internal reflection (TIR), or by using a metallized or dielectric coating. In case of a dielectric coating—it may be used to filter additional wavelengths in the laser diode beam out of the optical path or combine them thereto. The third surface (3) is also an aspheric toroid or aspheric cylinder, and it collimates the slow axis of the laser beam. In this example, the optical component functions both as a collimating lens and as a folding mirror. This configuration is particularly useful for general laser-based devices which require compact laser collimator. In the case of using a compact pattern projector, after leaving the optical component, the beam passes through a microstructured component which forms the pattern.

[0059] In another example of the single-sided projector illustrated in FIG. 3, surface (1) collimates the fast axis, surface (2) is a curved surface which reflects the beam (again either by implementing TIR, or by using metal or dielectric coating or attaching a reflecting component) and collimates the slow axis. Surface (3) is a planar surface which emits the preconditioned (collimated) beam into the microstructured component (4).

[0060] By a further example of the single-sided projector illustrated in FIG. 3, but with the exception that the microstructure is integrated with surface (3) of the optical component, thereby effectively merging the two optical parts in the projector into a single one. In this example, the optical component has mainly three functions: collimating the beam, folding it and forming the pattern. This example is advantageous when compared with the previous single sided projectors described above, due to a lower Bill of Materials (“BOM”) and assembly costs, precise alignment between microstructure and the other optical surfaces, improved thermo-mechanical and thermo-optic robustness, substantially smaller size and reduced power loss due to the fact that reflection at two surfaces has been eliminated.

[0061] By another example, the first surface collimates the slow axis of the laser beam and possibly also acts optically on the slow axis (such as to enable partial collimation of the beam), and the second surface is a curved surface with a relief pattern applied thereon, forming a curved diffractive surface. The surface is metallized, to provide adequate reflection. Same as in the previous example, the optical component serves as a folding prism, a collimator and a DOE.

[0062] By still another example, surface 1 is a flat surface. Surfaces 2 and 3 are curved and are configured to provide beam collimation.

[0063] Possible configurations of the three surfaces of the optical component are summarized in the following table:

TABLE-US-00001 Configuration Surface 1 Surface 2 Surface 3 1 Curved, fast Flat Slow axis axis collimator collimator 2 Curved, fast Curved, slow Flat surface axis axis collimator collimator 3 Curved, fast Curved, slow Planar axis axis collimator microstructure collimator (DOE) A Curved, fast Curved Flat Surface axis microstructure; collimator slow axis collimator and DOE 5 Flat Curved Curved optionally with optionally with microstructure microstructure

[0064] FIG. 4 illustrates an exemplary two-sided projector construed according to an embodiment of the present invention which is configured to project two patterns. In angular space, the projected patterns may completely or partially overlap each other, or in the alternative, may be non-overlapping. The optical layouts described in the above examples, are implemented at each end of the laser diode, thereby forming a pattern per each beam emitted from a respective end of the laser chip.

[0065] In another example illustrated in FIG. 9, the optical components located at the two sides of the laser diode, may be manufactured as a single piece.

[0066] The FOI of the two-sided projector illustrated in FIG. 4 is divided into 2 slightly-overlapping regions, as shown in FIG. 5. The overall FOI illustrated in this figure, is 2*θx by 2*θy, and if overlapping may be neglected, one side of the projector projects a pattern onto a respective part of the FOI, whose angular extent is from (−θx.sub.0) to 0 in the horizontal direction and (−θy.sub.0) to θy.sub.0 in the vertical direction, whereas the other side of the projector projects the pattern associated therewith at the complimentary part of the FOI, namely, from 0 to θx.sub.0 in the horizontal direction and from (−θy.sub.0) to θy.sub.0 in the vertical direction.

[0067] Optionally, it may be advantageous to configure a design which implements the optical component with a different fold angle, where the beam within the component is folded not normally to the laser substrate surface but at a half of the θx.sub.0 angle (or perhaps close to that value), while the exit surface (3) and the DOE are both slanted by θx.sub.0 angle. Such an embodiment is illustrated in FIG. 6. In this example, the DOE creates a pattern which spans an angular space which is symmetric in both dimensions relative to the direction of the beam incident on the DOE.

[0068] In some applications, it may be of interest to separate the FOI into two different patterns which are symmetric around the FOI center, as illustrated in FIG. 7, and project either one of the patterns or both of them together. In this case, each side of the projector is aligned as shown in FIG. 3, i.e. the projection is done at both sides in a direction which is normal to the substrate surface plane. In such configurations, where the two DOEs are coplanar, they can be manufactured as a single unit. For the case illustrated in FIG. 7, one side of the projector includes a DOE which covers the central FOI, while the other side DOE projects a pattern which may include or not the central area (the central rectangle).

[0069] According to another embodiment of the present invention, one of the edges of the two-sided laser has a different coating from that of the other edge. Consequently, the total power of the laser is divided differently between its two ends. This may be useful sometimes, for example, in applications where the two projected patterns require different optical power levels.

[0070] In accordance with another embodiment, a controllable photonic device is installed next to one of the laser apertures, where this controllable photonic device is configured to adjust the amount of light emitted from that respective edge, e.g. by reflecting the rest of the light back into the laser. In this arrangement, optical power may be controllably divided between the two ends of the laser, and the ratio of power of the two patterns may be adjusted between equal power provided to both ends, to near-zero power provided for the pattern projected from the laser end where the controllable photonic device is installed. This option is exemplified in FIG. 8.

[0071] In another embodiment of the present invention, there are two controllable light-reflection devices as described above with reference to FIG. 8, each installed at a respective end of the laser device, wherein each of the two-controllable light-reflection devices is controlled separately from the other. By implementing such an arrangement, when the two reflection coefficients and the laser current are controlled, the optical power of each of the two projected patterns can be separately controlled, allowing all laser power capacity to be directed to any one of the patterns while the other is switched off, or alternatively have the power divided between the two ends of the laser at any desired ratio.

[0072] The solution provided by the present invention described hereinabove offers a number of advantages. Among which are: [0073] 1. A symmetric design enables coverage of a wide field of view (“FOV”) by using a single projection module with a single laser device. [0074] 2. Folding of the optical path enables to place the edge-emitting laser on the surface which is normal to the pattern propagation direction, which in turn provides two advantages: [0075] a. Small size [0076] b. Improved heat dissipation [0077] 3. Excluding the DOE, this laser device of the present invention may be used as a very thin laser collimator, for any systems which utilize collimated lasers. [0078] 4. Monolithic, low-cost design: three components may be manufactured within a single device, whereas in the symmetric case, six components may be manufactured as a single part, as exemplified in FIG. 9. [0079] 5. Enabling projection of two patterns using a single device. [0080] 6. Allowing division of power between two patterns, whether they overlap each other or not.

[0081] In summary, the projector provided by the present invention enables emitting light beams from both ends of the projector, rather than from one of its ends. Around each end, an arrangement of optical components is preferably aligned, in order to form a desired pattern out of the emitted beam. There is a large variety of possible arrangements of optical components, where each of these arrangements may serve a different application. In a specific arrangement, an optical component is designed, which can serve three functions simultaneously. When this component is placed at the laser aperture, a pattern may be produced by using only two components, the laser and the optical component. In case of a high-FOI projector, a laser unit (e.g. a laser chip) which emits light from both ends is chosen, and one such optical component is placed at each end of the laser symmetrically, so that each side is configured to project a pattern towards one part (out of two) of the FOI. This configuration enables reaching a FOI of up to twice the FOI of conventional projectors (e.g. 180 degrees), for example when dividing the required high FOI into two halves, and projecting a light pattern to each of these two halves by a different end of the laser unit.

[0082] In the description and claims of the present application, each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb.

[0083] The present invention has been described using detailed descriptions of embodiments thereof that are provided by way of example and are not intended to limit the scope of the invention in any way. The described embodiments comprise different features, not all of which are required in all embodiments of the invention. Some embodiments of the present invention utilize only some of the features or possible combinations of the features. Variations of embodiments of the present invention that are described and embodiments of the present invention comprising different combinations of features noted in the described embodiments will occur to persons of the art. The scope of the invention is limited only by the following claims.