KR20160019112A - Modular optics for scanning engine - Google Patents

Abstract

The optoelectronic modules 130 and 148 include a beam radiator 104 that emits at least one light beam along a beam axis, and a photodiode that senses light received by the module along the light collecting axis of the photodetector parallel to the beam axis within the module (Not shown). The beam combining optical system 142, 150, 170 directs the beam and received light such that the beam axis is aligned with the light-collecting axis outside the module. The beam combining optical system includes a first surface 144, 160, 172 configured for at least internal reflection and a second surface 146, 151 including a beam splitter 158 intersecting both the beam axis and the condensing axis ≪ / RTI >

Description

[0001] MODULAR OPTICS FOR SCANNING ENGINE [0002]

The present invention relates generally to methods and devices for the projection and capture of optical radiation, and more particularly to optical scanning devices.

Various methods are known in the art for creating a 3D profile of an object's surface by processing optical images of the object, i.e., for optical 3D mapping. This kind of 3D profile is also called 3D map, depth map or depth image, and 3D mapping is also called depth mapping. The terms "optical" and "light" in connection with the present patent application and in the claims refer to electromagnetic radiation in some or all of the visible, infrared and ultraviolet wavelength ranges.

U.S. Patent Application Publication No. 2011/0279648 describes a method for constructing a 3D representation of a subject, including capturing a 2D image of the subject with a camera. The method includes scanning a modulated illumination beam across an object to illuminate a plurality of target areas of the object one at a time, and modulating the modulation aspect of light from the reflected illumination beam from each of the target areas, The method comprising the steps of: A moving-mirror beam scanner is used to scan the illumination beam, and a photodetector is used to measure the modulation aspect. The method further comprises calculating a depth aspect based on the modulation aspect measured for each of the target areas, and associating the depth aspect with a corresponding pixel of the 2D image.

U.S. Patent No. 8,018,579 discloses a three-dimensional imaging and display system in which a user input is optically detected in an imaging volume by measuring the path length of the amplitude-modulated scanned beam as a function of its phase shift, . Visual visual user feedback on the detected user input is presented.

U.S. Patent No. 7,952,781 - the disclosure of which is incorporated herein by reference - describes a method of scanning a light beam and a method of manufacturing a microelectromechanical system (MEMS) that may be included in a scanning device.

United States Patent Application Publication No. 2012/0236379 describes a LADAR system using MEMS scanning. A scanning mirror includes a substrate that is patterned to include a mirror region, a frame around the mirror region, and a base around the frame. A set of actuators is operative to rotate the mirror area relative to the frame about a first axis and a second set of actuators rotates the frame relative to the base about a second axis. Scanning mirrors can be fabricated using semiconductor processing techniques. Actuators for the scanning mirror may utilize feedback loops that operate the mirrors for triangular motion. Some embodiments of the scanning mirror may be used in a LADAR system for the Natural User Interface of a computing system.

The "MiniFaros" consortium, led by SICK AG (Hamburg, Germany), is supporting research on new laser scanners for automotive applications. Additional details are available on the minifaros.eu website.

Embodiments of the present invention described below provide improved apparatus and methods for optical beam transmission and reception.

Thus, in accordance with one embodiment of the present invention, there is provided an optoelectronic module, wherein the optoelectronic module comprises a beam transmitter configured to emit at least one light beam along a beam axis, And a light receiver configured to sense light received by the module along the axis of convergence of the receiver parallel to the axis. Beam-combining optics configured to direct the beam and the received light such that the beam axis is aligned with the light-collecting axis outside the module includes at least a first face configured for internal reflection, And a second surface including a beam splitter intersecting the first and second surfaces.

In some embodiments, the beam combining optical system includes a prism having a plurality of surfaces, wherein the beam axis is at an entrance angle and an exit angle near a minimum deviation angle, And escape from him. In the disclosed embodiment, the first and second surfaces are parallel to each other, and both the beam axis and the condensing axis pass through the second surface at different respective positions.

In the disclosed embodiment, the module comprises a micro-optical substrate, and the beam emitter comprises a laser die, while the receiver includes a detector die, And is mounted on the micro-optical substrate.

In some embodiments, the module includes a filter formed on one of the faces to block received light outside the emission band of the beam radiator. Additionally or alternatively, the beam splitter comprises a polarizing beam splitter coating on the second side. The beam combining optical system may include at least one lens configured to collimate at least one laser beam and to focus the received light onto a detector die.

In one embodiment, the plurality of planes include a third side, and the beam axis and the focusing axis exit the module through the third side at a location on the third side common to both the beam axis and the converging axis.

In the disclosed embodiment, the optical scanning head includes a scanning mirror configured to scan both the beam axis and the condenser axis at one time over the scan area and the module described above.

Further, according to an embodiment of the present invention, there is provided an optical method, wherein the optical method includes the step of emitting at least one light beam from the beam radiator in the optoelectronic module toward the scanner along the beam axis. The light is received from the scanner along a condensing axis parallel to the beam axis in the optoelectronic module. Using a beam combining optical system including a first surface configured for at least internal reflection and a second surface including a beam splitter intersecting both the beam axis and the condenser axis, And the beam and the received light are directed to and from the scanner.

In the disclosed embodiment, a method includes scanning a beam axis and a condensing axis both at once through a scan area using a scanner, wherein emitting at least one beam comprises emitting light pulses, Wherein the step of receiving light comprises measuring the time of flight of each of the pulses coming and going to objects in the scan region.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description of embodiments thereof, taken in conjunction with the drawings, in which: FIG.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of an optical scanning head according to an embodiment of the present invention; Fig.
Figures 2a and 2b are schematic side views of an optoelectronic module, according to another embodiment of the present invention.
Figure 3a is a schematic side view of an optoelectronic module, in accordance with an embodiment of the present invention.
Figure 3b is a schematic isometric view of the module of Figure 3a;
4 is a schematic side view of a prism, in accordance with an embodiment of the present invention;
5 is a schematic side view of a prism, according to another embodiment of the invention;

U.S. Patent Application No. 13 / 766,811 (published as US 2013/0206967 on Aug. 15, 2013) describes depth engines that generate 3D mapping data by measuring the flight time of a scanning beam. A light transmitter such as a laser directs short optical pulses toward the scanning mirror that scans the light beam over the scene of interest. A receiver such as a sensitive high-speed photodiode (e.g., avalanche photodiode) receives light returned from the scene via the same scanning mirror. The processing circuit measures the time delay between the emitted light pulse and the received light pulse at each point in the scan. This delay represents the distance traveled by the light beam and therefore the depth of the object at that point. The processing circuitry uses the extracted depth data to generate a 3D map of the scene.

Various possible configurations of the deep engine optics are described in U.S. Patent Application No. 13 / 766,811. Many disclosed embodiments use a single scanning mirror to transmit the beam output by the light emitter and to direct the returned light (typically by reflection) towards the receiver. Thus, the depth engine optical system includes a beam combining optical system for directing the output beam and the received light so that the beam axis of the output beam is aligned with the light-collecting axis of the received beam. A beam combining optical system typically includes a plurality of surfaces having functions of beam splitting, beam turning, and wavelength filtering, for example. In general, it is necessary to carefully align the optical surfaces with the illuminator, the receiver and the scanning mirror itself to ensure proper operation of the depth engine; Deviation of alignment during deep engine operation can lead to severe performance loss.

Embodiments of the present invention described below are based on optoelectronic modules and beam combining optics described in U.S. Patent Application No. 13 / 766,811 and add features that improve the ease of alignment and robustness of such modules. In these embodiments, the optoelectronic module includes a beam radiator that emits at least one laser beam along a beam axis, and a photodetector that senses light received by the module along the axis of condensation. The beam axis and the condensing axis are separate and parallel within the module. The beam combining optical system is configured such that, outside the module, the beam axis is aligned with the light-collecting axis outside the module (and thus the same scanning mirror can be used to scan both the beam axis and the condensing axis at a time over a given scan area) It directs both lights.

In the disclosed embodiments, the beam combining optical system includes an element (such as a prism) having a plurality of surfaces. One plane is configured for internal reflection so that the beam axis and the light collecting axis can be aligned by reflection of one of the axes in the element, as shown in the figures. The second side of the element includes a beam splitter that intersects both the beam axis and the condenser axis. The beam combining prism can be designed and arranged such that the beam axis enters and leaves the prism faces at an entrance angle and an exit angle near the minimum shift angle (defined below). This feature of the prism facilitates the alignment of the beams and improves the module's robustness against misalignment that may be present during use.

1 schematically illustrates elements of an optical scanning head 40 used in the system described in the aforementioned U.S. Patent Application No. 13 / 766,811. The optical scanning head 40 is shown and described herein as an example of the principles of a particular scanner to which embodiments of the present invention may be applied. The optical scanning head generally includes a number of optical components that must be carefully aligned for proper operation; These components are preferably replaced by elements of the kind shown in Figures 3 to 5 and described below.

However, the principles of the present invention are not limited to scanners of this type. Rather, optoelectronic modules based on these principles and beam combining optics can be applied in other types of optical transmitter / receiver devices having a boresighted (or otherwise parallel) transmission axis and a receiver axis .

A light emitter 44 within the head 40 emits light pulses to the polarization beam splitter 60. Typically, only a small area of the beam splitter that is directly in the optical path of the optical transmitter 44 is coated for reflection, while the remainder of the beam splitter transmits the transmitted light (Or even anti-reflective coatings for this range). The light from the light emitter 44 is reflected from the beam splitter 60 and then from a folding mirror 62 to the scanning micromirror 46. The MEMS scanner 64 scans the micromirror in the X-direction and the Y-direction with the desired scan frequency and amplitude. Details of micromirrors and scanners are described in U.S. Patent Application No. 13 / 766,811, which is outside the scope of the present patent application.

The optical pulses returned from the scene collide with the micromirror 46 and the micromirror 46 reflects the light through the folding mirror 62 and through the beam splitter 60. The photodetector 48 senses the returned optical pulses and generates corresponding electrical pulses. The entire area of the beam splitter 60 and the aperture of the photodetector 48 may be significantly larger than the area of the beam output by the light transmitter 44 to improve the sensitivity of detection. A bandpass filter (not shown in the figure) may be included in the receiver path, perhaps on the same substrate as the beam splitter 60, to limit the amount of undesired ambient light reaching the receiver 48.

2A and 2B are schematic side views of an optoelectronic module 130 according to another embodiment described in the aforementioned U.S. Patent Application No. 13 / 766,811. The module 130 may replace the light transmitter 44, the light receiver 48, the beam splitter 60 and the mirror 62 in the optical scanning head 40 (Fig. 1). The figure shown in Fig. 2b is rotated by 90 degrees with respect to the view in Fig. 2a, so the items shown in front of the figure of Fig. 2a are on the left side of Fig. 2b.

In module 130, the emitted beam is generated by laser die 104, while the received beam is detected by an avalanche photodiode (APD) 114, and both laser die 104 and APD 114 (Typically a SiOB (silicon optical bench) 102). Alternatively, the laser die may be integrated as a light emitter module on the SiOB, while the APD is mounted on a printed circuit board with the light emitter module. Although laser die 104 is shown as an edge-emitting device in the figures, in alternative embodiments (not shown in the figures), the light emitter is a vertical-cavity surface-emitting laser (VCSEL) Emitting devices. The term " surface-emitting devices " However, these aspects of the configuration of module 130 are shown and described herein by way of example only, and the principles of the present invention are equally applicable to a wide variety of different transmitter / receiver designs, It is possible.

The emitted beam and received beam are separate in module 130 and are aligned at the exit from the module by beam combiner 142 mounted on the substrate of the module. The embodiments shown in Figs. 3-5 may employ similar types of light emitters and receivers, but may provide improved beam combiners. Alternatively, the beam combiners shown in Figs. 3-5 may be used with other types of optical radiators and receivers.

The irradiation beam emitted by the laser die 104 is collimated by a ball lens 134 located in the groove 135 formed in the SiOB 102. [ The grooves 135 can be created in silicon (and other semiconductor materials) with lithographic precision by techniques known in the art, such as wet etching. Alternatively, or in addition, the ball lens can be attached directly to the SiOB by an accurate pick-and-place machine, without the groove 135. [ The diverting mirror 136 reflects the collimated beam away from the SiOB 102 and through the cover glass 137 protecting the optoelectronic components within the module 130. Related electronics components, such as the amplifier 116 coupled to the laser driver 106 and the APD 114, may also be mounted on the SiOB 102.

Because the ball lens 134 typically only achieves partial parallelization, a beam expander 138 may be used to extend the laser beam typically 3 to 10 times and thus improve its collimation. Although the beam expander 138 is shown here as a single element optical component, alternatively, multi-element beam expanders may be used.

The collimated beam output by the beam expander 138 is redirected by the reflector 144 in the beam combiner 142 and then redirected outward by the beam splitter 146 towards the scanning mirror. Assuming that the laser die 104 outputs a polarized beam, the beam splitter 146 may advantageously be polarization dependent and have polarizations opposite to those of the emitted beam and the received beam. The condensed beam returned from the scanning mirror passes through a beam splitter 146 and then is focused onto the APD 114 by a condenser lens 140. The condensing lens may optionally have an asymmetrical and elongate shape, as shown in Figures 2A and 2B, to maximize the condensing efficiency within the geometric constraints of the module 130. (In this case, the aperture of the condenser lens 140 is selected to accept all the rays from the scene reflected by the micromirror 46 with some tolerance, and the long shape of the lens coincides with the long shape of the mirror do.)

Figures 3A and 3B are schematic illustrations of an optoelectronic module 148, in accordance with an embodiment of the present invention. Figure 3a shows a side view, while Figure 3b shows an isometric view of the same elements. Module 148 may be used in place of module 130 in optical scanning head 40 as well as in other types of optical devices. As described above, elements of the module 148 that are similar in function to the components of the optical scanning head 40 and module 130 are identified by the same numbers as above, . ≪ / RTI > However, unlike the module 130, the beam combining optics in the module 148 include a back surface 151 (toward the light transmitter and receiver) and a front surface 153 (toward the micromirror 46) And a prism 150. The prism 150 includes a prism 150, The emitted beam enters the prism through the surface 151 and exits through the surface 153 toward the micromirror 46 while the received beam reflected from the micromirror is reflected by the surface 153 (as shown in Figure 4) Into the prism and exits through the surface 151. The micromirror 46 is mounted to rotate relative to the base 49 about the hinges 47, thus simultaneously scanning both the emitted beam and the received beam over the scan area.

을 충족시키는 각도 D를 말하고, 여기서 A는 프리즘의 각도(이 경우에, 도 3a에서의 프리즘의 상부 정점의 각도)이고, n은 프리즘의 굴절률이며, D는 입사 빔에 상대적인, 프리즘을 통해 송광된 빔의 편이각이다.The prism 150 is arranged so that the beam axis of the emitted beam is aligned with the light-collecting axis of the received beam outside the module 148, while both the beam axis and the light- And exit from it. The minimum deviation angle is defined by the relationship: < RTI ID = 0.0 >

Where A is the angle of the prism (in this case, the angle of the upper vertex of the prism in FIG. 3A), n is the refractive index of the prism, and D is the transmittance through the prism The angle of incidence of the beam is angle.

However, for various design reasons, such as compactness and manufacturability, the prism 150 may intentionally deviate from a precise minimum deviation angle. The beneficial effects of this type of minimum deviation design can still be recognized for deviations from the minimum deviation point up to about +/- 15 degrees. Beam angles within this ± 15 ° angular range are defined herein as being in the vicinity of the least offset angles, and the transmitter / receiver module designs in accordance with some embodiments of the present invention are designed such that the beam axes are in this neighborhood Refraction and internal reflection in the prism can be used as long as it enters and exits the faces of the prism at the entrance and exit angles.

4 is a schematic side view of a prism 150, in accordance with an embodiment of the present invention. The emitted beam 152 enters the backside 151 at an angle a with respect to each side and exits from the front side 153, where the side angle D = 180-2? -A. The received beam 154 also enters the plane 153 at the same angle a and exits from the back face 151. The beam axis of the emitted beam 152 and the condensing axis of the received beam 154 pass through the front face 153 at the same position common to both beams while the condensing axis passes through the emitted beam 152 through the back face, And passes through the back surface 151 at a position different from the entry point of the beam axis. (The beam axis and the condensing axis of the module are parallel to the beam 152 and the beam 154, respectively.) The received beam is internally reflected from the beam direction conversion surface 160 parallel to the surface 151.

To allow the prism 150 to function properly, suitable coatings are typically applied to the sides of the prism. The plane 151 has a beam splitter coating 158 (typically a polarizing beam splitter coating) in the area where the beam 152 enters the prism 150, while the plane 153 typically has a beam 152 from the prism And has an antireflective coating 162 in the region where the beam 154 enters. The beam deflecting surface 160 has a reflective coating (which may be metal or dielectric) for reflecting the received beam 154 in the prism 150. The surface 151 is formed by a narrow band filter coating 156 (as described in U.S. Patent Application No. 13 / 766,811, which corresponds to the emission band of the light emitter) in the region where the received beam exits the prism 150 towards the receiver. Lt; / RTI > pass band). The remaining areas of the faces of the prism 150 may be coated with a light absorbing coating to reduce the amount of stray light reaching the receiver.

The design of the prism 150 makes it simple to align the module 148 and allow for ease of alignment. Even though the prism is rotated several degrees, the beam 152 and beam 154 will maintain their alignment with respect to each other at the front face 153 and against the micromirror 46. Specifically, due to the minimum deviation criterion, when the prism is rotated by a small angle? About the axis passing through the paper surface of Fig. 4, the angle between the beams 152 and 154 and the surface 151 increases by? +? While the angle between the beams and the plane 153 will be reduced to? -? Or vice versa, so the total deviation angle remains the same. Because the face 160 is parallel to the face 151, the alignment between the two beams is maintained despite the rotation. As such, the scanner including the module 148 can be assembled at low cost, and will be robust against shocks in the field and changing thermal conditions.

The prism 150 can be easily mass produced from optical glass plates of appropriate thickness (e.g., 2 to 10 mm thickness, depending on application requirements). Prior to cutting the plate, coatings 156 and 158 are applied at appropriate locations on the side of the plate that will be surface 151 and a reflective coating is applied to the opposite side to be surface 160. [ The plate is then cut and polished at an appropriate angle to define a face 153, and then a coating 162 is applied to that face 153. Other non-functional surfaces are cut to singulate the prism 150 only after the coating processes are completed.

5 is a schematic side view of prism 170, in accordance with an alternative embodiment of the present invention. The coatings of the prismatic surfaces in this embodiment are identified using the same numbers as in Fig. As in prism 150, the emitted beam passes through prism 170 with a minimum deviation near the angle (in this case, not exactly the minimum deviation angle). However, the received beam at the prism 170 is reflected by the beam splitter coating 158 and then onto the redirecting surface 172 of the prism 170, before exiting the prism through a surface different from the entrance surface of the emitted beam ) By the total internal reflection at the point of time. This design allows less misalignment than the prism 150 because the minimum deviation criterion is partially relaxed in the design of the prism 170, but this kind of mitigation is important for physical compactness or for applications in which other design considerations are involved Lt; / RTI >

Alternative implementations of the principles described above will be apparent to those of ordinary skill in the art after reading this disclosure and are considered to be within the scope of the present invention. It will thus be appreciated that the embodiments described above are cited as examples and that the present invention is not limited to what has been shown and described in detail above. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described above, as well as variations and modifications thereof, which are not described in the prior art, which will occur to those skilled in the art upon reading the above description .

Claims (20)

As an optoelectronic module,
A beam transmitter configured to emit at least one light beam along a beam axis;
The receiver configured to sense the light received by the module along a condensing axis of a receiver parallel to the beam axis within the module; And
And a beam splitter configured to direct the beam and the received light so that the beam axis is aligned with the light-collecting axis outside the module, wherein at least a first face configured for internal reflection, And beam splitting optics comprising a prism having a plurality of surfaces including a second surface including a beam splitter intersecting the beam splitter optics. The optoelectronic module according to claim 1, wherein the beam axis enters and exits the faces of the prism at an entrance angle and an exit angle near a minimum deviation angle. 3. The optoelectronic module of claim 2, wherein the first surface and the second surface are parallel to each other. 3. The optoelectronic module according to claim 2, wherein both the beam axis and the condensing axis pass through the second surface at different positions. 3. The apparatus of claim 1, comprising a micro-optical substrate, wherein the beam emitter comprises a laser die, the receiver comprising a detector die, Optic module mounted on the micro-optical substrate. 6. The optoelectronic module according to any one of claims 1 to 5, comprising a filter formed on one of the faces to block the received light outside the emission band of the beam radiator. 6. The optoelectronic module according to any one of claims 1 to 5, wherein the beam splitter comprises a polarizing beam splitter coating on the second surface. 6. The apparatus according to any one of claims 1 to 5, wherein the plurality of surfaces comprise a third surface, the beam axis and the condensing axis are common to both the beam axis and the condensing axis, And exits the module through the third face at a second position. 6. A system according to any one of claims 1 to 5, wherein the beam combining optical system is configured to collimate at least one laser beam and to focus the received light onto the detector die The lens of the optoelectronic module. An optical scanning head comprising: a scanning mirror configured to scan both the beam axis and the condenser axis at one time over a scan area and a module according to any one of claims 1 to 5. As an optical method,
Emitting at least one light beam from the beam radiator in the optoelectronic module towards the scanner along the beam axis;
Receiving the light from the scanner along a light-collecting axis parallel to the beam axis in the optoelectronic module; And
Using a beam combining optical system including a prism having a first surface configured for at least internal reflection and a second surface including a beam splitter intersecting both the beam axis and the condenser axis, And directing the beam and the received light to and from the scanner such that an axis is aligned with the light-collecting axis in the scanner. 12. The optical method according to claim 11, wherein the beam axis enters and exits from the faces of the prism at an entrance angle and an exit angle near a minimum deviation angle. 13. The optical method of claim 12, wherein the first surface and the second surface are parallel to each other. 13. The optical method according to claim 12, wherein both the beam axis and the condensing axis pass through the second surface at different respective positions. 15. A method as claimed in any one of claims 11 to 14, comprising the step of forming a filter on one of said faces to block said received light outside the emission band of said beam radiator . 15. The optical method according to any one of claims 11 to 14, wherein the beam splitter comprises a polarizing beam splitter coating on the second surface. 15. The apparatus according to any one of claims 11 to 14, wherein the plurality of surfaces comprise a third surface, the beam axis and the condensing axis are on the third surface common to both the beam axis and the condensing axis And exits the optoelectronic module through the third face at a second position. 15. A method according to any one of claims 11 to 14, wherein the directing of the laser beam and the received light comprises at least a step for parallelizing at least one laser beam and for focusing the received light from the scanner And applying a single lens. 15. The optical method according to any one of claims 11 to 14, comprising using the scanner to scan both the beam axis and the condenser axis all at once through the scan area. 20. The method of claim 19, wherein emitting the at least one beam comprises emitting light pulses, wherein receiving light comprises: measuring a flight time of each of the pulses to and from objects in the scan region and measuring a time of flight.

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