PATENT DOCUMENT

Publication Number: US-11899136-B2
Application Number: US-202217877955-A
Country: US
Kind Code: B2

Title: Increasing VCSEL projector spatial resolution

Abstract:
An optical device includes a radiation source, which is configured to emit a beam of light, and a scanning cell positioned to receive the beam of light. The scanning cell includes transparent entrance and exit faces, at least one of the faces including a flexible membrane. A transparent fluid is contained between the entrance and exit faces, so that the beam enters the transparent fluid through the entrance face and exits the transparent fluid through the exit face. At least one actuator is coupled to the flexible membrane, and configured, responsively to an applied electrical signal, to apply an asymmetrical deformation to the flexible membrane, thereby deflecting the beam by refraction in the transparent fluid.

Claims:
The invention claimed is: 
     
       1. An optical device, comprising:
 a radiation source, which is configured to emit a beam of light; and 
 a scanning cell positioned to receive the beam of light and comprising:
 transparent entrance and exit faces, at least one of the faces comprising a flexible membrane; 
 a transparent fluid contained between the entrance and exit faces, so that the beam enters the transparent fluid through the entrance face and exits the transparent fluid through the exit face; and 
 at least one actuator coupled to the flexible membrane, and configured, responsively to an applied electrical signal, to apply an asymmetrical deformation to the flexible membrane, thereby deflecting the beam by refraction in the transparent fluid. 
 
 
     
     
       2. The device according to  claim 1 , and comprising a controller, which is configured to vary the electrical signal applied to the at least one actuator so as to adjust a deflection angle of the beam. 
     
     
       3. The device according to  claim 2 , wherein the controller is configured to vary the electrical signal so as to scan the beam of light over an angular range. 
     
     
       4. The device according to  claim 3 , and comprising a lens, which is disposed to receive the beam exiting through the exit face of the scanning cell and to transmit and project the beam towards a scene. 
     
     
       5. The device according to  claim 4 , and comprising a receiver, which is configured to receive the light reflected from the scene and to output receiver signals in response to the received light, and processing circuitry, which is configured to process the receiver signals in order to map the scene in three dimensions. 
     
     
       6. The device according to  claim 1 , wherein the radiation source is configured to emit multiple beams of light into the scanning cell, and wherein the scanning cell is configured to deflect the multiple beams. 
     
     
       7. The device according to  claim 1 , wherein the at least one actuator is configured to apply the asymmetrical deformation to the flexible membrane in a single direction, so as to deflect the beam about a single deflection axis. 
     
     
       8. The device according to  claim 1 , wherein the transparent entrance face comprises a first flexible membrane, and the transparent exit face comprises a second flexible membrane, and wherein the at least one actuator is configured to apply a first asymmetrical deformation to the first flexible membrane in a first direction so as to deflect the beam about a first deflection axis and to apply a second asymmetrical deformation to the second flexible membrane in a second direction so as to deflect the beam about a second deflection axis, which is not parallel to the first deflection axis. 
     
     
       9. The device according to  claim 8 , wherein the at least one actuator comprises a first actuator coupled to deform the first flexible membrane and a second actuator coupled to deform the second flexible membrane. 
     
     
       10. The device according to  claim 9 , wherein the first and second actuators comprise piezoelectric elements. 
     
     
       11. The device according to  claim 8 , wherein the first and second directions are mutually orthogonal. 
     
     
       12. The device according to  claim 1 , wherein the at least one actuator comprises at least one piezoelectric element. 
     
     
       13. The device according to  claim 12 , wherein the at least one piezoelectric element comprises first and second piezoelectric elements coupled respectively to first and second sides of the flexible membrane. 
     
     
       14. The device according to  claim 13 , wherein actuating the first piezoelectric element causes the cell to deflect the beam in a first direction, and actuating the second piezoelectric element causes the cell to deflect the beam in a second direction, different from the first direction. 
     
     
       15. A method of scanning, comprising:
 directing a beam of light into a scanning cell having transparent entrance and exit faces and containing a transparent fluid between the entrance and exit faces, at least one of the faces comprising a flexible membrane, such that the beam enters the transparent fluid through the entrance face and exits the transparent fluid through the exit face; and 
 applying an electrical signal to at least one actuator coupled to the flexible membrane so as to create an asymmetrical deformation to the flexible membrane, thereby deflecting the beam by refraction in the transparent fluid. 
 
     
     
       16. The method according to  claim 15 , wherein applying the electrical signal comprises varying the electrical signal applied to the at least one actuator so as to scan the beam of light over an angular range. 
     
     
       17. The method according to  claim 15 , wherein applying the electrical signal comprises deforming the flexible membrane so as to deflect the beam about a single deflection axis. 
     
     
       18. The method according to  claim 15 , wherein the transparent entrance and exit faces respectively comprise first and second flexible membranes, and wherein applying the electrical signal comprises applying a first asymmetrical deformation to the first flexible membrane in a first direction so as to deflect the beam about a first deflection axis and applying a second asymmetrical deformation to the second flexible membrane in a second direction so as to deflect the beam about a second deflection axis, which is not parallel to the first deflection axis. 
     
     
       19. The method according to  claim 18 , wherein the first and second directions are mutually orthogonal. 
     
     
       20. The method according to  claim 15 , wherein the at least one actuator comprises at least one piezoelectric element.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. patent application Ser. No. 16/537,582, filed Aug. 11, 2019, which claims the benefit of U.S. Provisional Patent Application 62/733,656, filed Sep. 20, 2018, which is incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to opto-electronic devices, and particularly to light projectors. 
     BACKGROUND 
     Portable electronic devices, such as cellular phones, commonly employ one or more integral light sources. These light sources may provide illumination for a scene recorded by a camera integrated into the device. 
     As an example, United States Patent Application Publication 2018/0084241 describes a pattern projector, including a light source, configured to emit multiple beams of light. The beams are scanned in angular space by moving laterally a collimating lens of the projector. 
     As another example, United States Patent Application Publication 2018/0062345 describes another pattern projector, including a light source, configured to emit multiple beams of light. The beams are scanned in angular space by using several scanning mechanisms, including a lateral movement of a collimating lens, a lateral movement of the light source, rotating prisms, and a scanning mirror. 
     SUMMARY 
     Embodiments of the present invention that are described hereinbelow provide improved light projectors. 
     There is therefore provided, in accordance with an embodiment of the invention, an electro-optical device, including a radiation source, which is configured to emit multiple beams of light. A scanner includes an array of cells. Each cell is positioned to receive one or more of the beams of light and includes transparent entrance and exit faces, at least one of the faces including a flexible membrane, and a volume of a transparent fluid contained between the entrance and exit faces, so that the one or more of the beams enter the volume through the entrance face and exit the volume through the exit face. At least one actuator is coupled to the flexible membrane, and is configured, responsively to an applied electrical signal, to apply an asymmetrical deformation to the flexible membrane, thereby deflecting the one or more of the beams by refraction in the transparent fluid. A controller is configured to vary the electrical signal applied to each of the cells so as to scan the beams of light over respective angular ranges. 
     In some embodiments, the radiation source includes an addressable array of emitters, such as vertical-cavity surface-emitting lasers (VCSELs) In a disclosed embodiment, the addressable array includes a silicon substrate, on which the VCSELs are mounted and which includes circuitry configured to control each emitter independently. 
     In some embodiments, the device includes a lens, which is disposed to receive the beams exiting through the exit faces of the cells of the scanner and to transmit and project the beams towards a scene. The device may further include a receiver, which is configured to receive the light reflected from the scene and to output receiver signals in response to the received light, and processing circuitry, which is configured to process the receiver signals in order to map the scene in three dimensions. 
     In a disclosed embodiment, the at least one actuator is configured to apply the asymmetrical deformation to the flexible membrane, so as to deflect the one or more of the beams about a single deflection axis. 
     Additionally or alternatively, the transparent entrance face includes a first flexible membrane, and the transparent exit face includes a second flexible membrane, and the at least one actuator includes at least one first actuator coupled to the first flexible membrane and configured to apply a first asymmetrical deformation to the first flexible membrane so as to deflect the one or more of the beams about a first deflection axis, and at least one second actuator coupled to the second flexible membrane and configured to apply a second asymmetrical deformation to the second flexible membrane so as to deflect the one or more of the beams about a second deflection axis, which is not parallel to the first deflection axis. 
     In some embodiments, the at least one actuator includes at least one piezoelectric element. In a disclosed embodiment, the at least one piezoelectric element includes first and second piezoelectric elements positioned on two different sides of the flexible membrane, such that application of the electrical signal to the first piezoelectric element causes the cell to deflect the one or more of the beams in a first direction, while application of the electrical signal to the second piezoelectric element causes the cell to deflect the one or more of the beams in a second direction, different from the first direction. 
     In a disclosed embodiment, each cell is configured to receive and deflect a single one of the beams. Alternatively, each cell is configured to receive and deflect a group of the beams. Each cell may be configured to receive and deflect the one or more of the beams about a single deflection axis or about two deflection axes. In some embodiments, the controller is configured to apply different, respective electrical signals to different ones of the cells. 
     There is also provided, in accordance with an embodiment of the invention, a method of scanning, which includes directing multiple beams of light toward a scanner, including an array of cells. Each cell is positioned to receive one or more of the beams of light and includes transparent entrance and exit faces, at least one of the faces including a flexible membrane, and a volume of a transparent fluid contained between the entrance and exit faces, so that the one or more of the beams enter the volume through the entrance face and exit the volume through the exit face. At least one actuator is coupled to the at least one flexible membrane. An asymmetrical deformation is applied to the at least one flexible membrane by applying an electrical signal to the at least one actuator, thereby deflecting the one or more of the beams by refraction in the transparent fluid. The electrical signal applied to each of the cells is varied so as to scan the beams of light over respective angular ranges. 
     There is additionally provided, in accordance with an embodiment of the invention, a method of fabricating an electro-optical device, which includes providing a scanner, including an array of cells. Each cell includes transparent entrance and exit faces, at least one of the faces including a flexible membrane, a volume of a transparent fluid contained between the entrance and exit faces, and at least one actuator coupled to the flexible membrane, and configured, responsively to an applied electrical signal, to apply an asymmetrical deformation to the flexible membrane. The scanner is positioned in proximity to a radiation source, which is configured to emit multiple beams of light, so that each cell receives one or more of the beams of light such that the one or more of the beams enter the volume through the entrance face and exit the volume through the exit face. A controller is coupled to vary the electrical signal applied to each of the cells, thereby deflecting the one or more of the beams by refraction in the transparent fluid. 
     The present invention will be more fully understood from the following detailed description of the embodiments thereof, taken together with the drawings in which: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a schematic side view of an optical apparatus with beam scanning by a projector, in accordance with an embodiment of the invention; 
         FIGS.  2   a - 2   c    are schematic sectional views of a scanner cell for a one-dimensional scan, illuminated by a VCSEL, in different states of operation, in accordance with an embodiment of the invention; 
         FIG.  3    is a schematic sectional view of two scanner cells for two independent one-dimensional scans, illuminated by two mounted VCSELs, in accordance with an embodiment of the invention; 
         FIG.  4    is a schematic sectional view of two scanner cells for two independent two-dimensional scans, illuminated by two mounted VCSELs, in accordance with an embodiment of the invention; 
         FIGS.  5   a - 5   d    are schematic top views of VCSEL arrays and scanners, in accordance with embodiments of the invention; and 
         FIGS.  6   a - 6   b    are schematic perspective and sectional views, respectively, of an electro-optical device, in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Overview 
     Existing and emerging consumer applications have created an increasing need for beam projectors, which are used, for example, in real-time three-dimensional (3D) imagers, known also as 3D mappers. Some commonly-used 3D mappers utilize beam projectors comprising a laser array, projecting multiple optical beams onto the scene. The beam intercepts are imaged onto a detector array, and the distance to the intercept between each beam and the scene is measured either by measuring for each beam the time-of-flight from the laser array to the detector array via the scene, or by deriving the distance from the displacement of each intercept image on the detector array. 
     When the beams illuminating the scene are static (i.e., not scanned in a dimension transverse to the beams), a balance is struck between the total extent of the scene covered by the beams and the lateral spatial resolution on the scene (i.e., the resolution in a plane transverse to the beam axes): When a large area of the scene is covered, the lateral spatial resolution is limited to a linear extent of the illuminated scene divided by the number of beams along this linear extent. When the beams are projected closely together for a high lateral spatial resolution (small lateral separation between the beams), the extent of the illuminated target area is limited to a product of the spatial resolution and the number of beams across the linear dimension. 
     The embodiments of the present invention that are described herein address the above limitation so as to provide beam projectors illuminating a scene with high lateral spatial resolution. In the disclosed embodiments, a high lateral spatial resolution of the scene is achieved by scanning the beams emitted by a radiation source, such as an array of lasers or other emitters, in the angular space by transmitting the beams through fluid-filled cells that are deformable by an electrical signal, thus deflecting the beams responsively to the electrical signal. Depending on the configuration of the cells and addressability of the electrical signals, the beams may be scanned all together, or in separate groups, or separately and independently of one another. A small-angle angular scan is sufficient, as for a given array of illuminating beams the angular scan amplitude does not need to exceed the angular pitch of the array (although in some cases it may be advantageous to be capable of scanning over a slightly larger range, for example up to twice the angular pitch). This combination of an optical separation of the beams and a small-angle angular scan achieves a coverage of the entire extent of the scene, as well as a high spatial resolution, with the added advantage, in some embodiments, of an independent scan angle for each beam. 
     Another advantage can be achieved in some embodiments of the present invention by operating each emitter in the array individually. The combination of an individual control of both the presence of a beam and its direction enables a highly flexible generation of spot patterns on the scene, as well as a one-dimensional or two-dimensional (lateral) scan of the pattern, including changing the pattern during the scan. 
     In the disclosed embodiments, a radiation source emits multiple beams of light. (The terms “optical radiation” and “light” as used in the present description and in the claims refer generally to any and all of visible, infrared, and ultraviolet radiation.) The angular scan of one or more beams of light is accomplished by an array of fluid-optical cells. Each cell comprises transparent entrance and exit faces, wherein at least one of the faces is a flexible membrane. A volume of transparent fluid, such as a liquid or a gel, is contained between the entrance and exit faces, so that one or several beams of light enter the volume through the entrance face and exit through the exit face. One or more actuators are coupled to each flexible membrane. Applying electrical signals to the actuators of a given membrane causes the actuators to apply an asymmetrical deformation to the membrane, thereby deflecting the beams of light by refraction in the transparent fluid. A controller is configured to vary the electrical signals applied to the cells so as to scan the beams of light over respective angular ranges. 
     In some embodiments, the radiation source comprises an addressable array of emitters, for example vertical-cavity surface-emitting lasers (VCSELs). For addressability, the VCSELs can be grown on a III-V substrate, which is bonded to a silicon substrate with addressable drive circuits. These addressable drive circuits enable independent control of each of the VCSELs in the array. 
     A lens is positioned to receive the beams exiting through the exit faces of the cells of the scanner and to transmit and project the beams towards a scene. For mapping the scene in three dimensions (3D), a receiver is positioned to receive the light reflected from the scene and to output receiver signals in response to the received light. Processing circuitry processes the signals output by the receiver in order to produce a 3D map of the scene. 
     The cells of the scanner can be configured to deflect the beams about either one or two deflection axes. A cell having one flexible membrane and either one actuator or two actuators, which are coupled to and positioned on opposing sides of the membrane, will deflect a transmitted beam (or beams) about a single deflection axis. A cell in which both the entrance and exit faces comprise flexible membranes, with either one actuator or two actuators coupled to each membrane, and with the actuators of the two membranes oriented with respect to each other at angles other than 0° or 180°, will deflect a transmitted beam (or beams) about two non-parallel deflection axes. Typically, the actuators are configured so that the deflection axes are mutually perpendicular. 
     In some embodiments, the actuators used to deform the flexible membranes are piezoelectric elements, which bend under an applied electrical signal. Alternatively, other suitable types of actuators may be used, such as actuators based on micro-electro-mechanical systems (MEMS) technology. When two piezoelectric elements are positioned on two different sides of the flexible membrane, applying an electrical signal to one piezoelectric element causes the cell to deflect the beam (or beams) to one direction, while applying an electrical signal to the other piezoelectric element causes the cell to deflect the beam (or beams) to another direction. By positioning the actuators symmetrically around the membrane, the beam (or beams) is deflected about a single deflection axis to both sides of the un-deflected beam. 
     By a suitable configuration of the cells and the actuators with respect to the emitted beams, different scan modes may be implemented:
         1. each cell is configured to receive and deflect a single beam (point scan);   2. each cell is configured to receive and deflect a group of beams;   3. each cell is configured to receive and deflect a single beam or a group of beams about a single deflection axis (one-dimensional scan); and   4. each cell is configured to receive and deflect a single beam or a group of beams about two deflection axes (two-dimensional scan).       

     The controller driving the scanner can be configured to apply independent electrical signals to each of the cells, or to drive groups of the cells or all of the cells together. 
     System Description 
       FIG.  1    is a schematic side view of an optical apparatus  20  with beam scanning by a projector  22 , in accordance with an embodiment of the invention.  FIG.  1    illustrates an overall architecture of optical apparatus  20  that can be used for 3D mapping. Alternatively, projector  22  may be used in other applications that use a scanned array of beams of optical radiation. 
     Optical apparatus  20  comprises projector  22  and a receiver  24 . Projector  22  comprises a two-dimensional array  26  of emitters, comprising individual VCSELs  28  in this embodiment, in either a regular or irregular (for example, pseudo-random) spatial array. The VCSELs emit an array of beams  30  of light, which may be pulsed or continuous. Beams  30  impinge on a scanner  32  comprising a two-dimensional array of cells  34 , each cell positioned to receive one beam. Scanner  32  deflects beams  30  in two lateral dimensions, thus outputting corresponding beams  36 , which impinge on a lens  38 , which refracts, collimates, and projects them into beams  40 . 
     Beams  30  are emitted at VCSELs  28  with a typical cross-section of 10 μm and with a typical half-angle of 12°, expanding typically to several millimeters at lens  38 , and continuing from there as collimated beams  40  with a roughly constant cross-section. The local angular pitch of beams  40  is determined by the local spatial pitch of VCSEL array  26 , which is typically less than 50 μm, and the focal length of optics  38 . The directional angle of each of beams  40  is deflected by the corresponding cell  34  of scanner  32  so as to scan an angular range that is equal to or somewhat greater than the local angular pitch. This scan range will suffice to scan the entire field of view (FOV) of projector (as defined by the outermost of rays  40 ). A typical range of deflection is ±1°, and thus VCSEL array  26  comprising  30  elements in each linear direction is sufficient to scan a FOV of 60°. 
     Beams  40  impinge on a scene  42 , from which they are reflected towards receiver  24 . Receiver  24  comprises collection optics  44  and a detector array  46 . Detector array  46  receives an image of the pattern projected onto scene  42 , exemplified by light reflected from a point  48  on the scene and received at a point  50  on the detector array (shown schematically by rays  52 ). 
     A controller  54  drives VCSEL array  26  and scanner  32 , as well as receives signals from detector array  46  via processing circuitry  56  for calculating a depth map of scene  42 . As described above, the distance to scene  42  may be measured either by measuring the round-trip time of the optical beams from VCSEL array  26  to detector array  46 , or by capturing an image of the projected pattern on the detector array and deriving the distance from the local displacement of the pattern. 
     By driving individual cells  34  of scanner  32 , controller  54  scans beams  40  on scene  42  at a resolution that is much higher than the inherent beam separation for a discrete VCSEL array  26  with static beams (i.e., without scanning). Moreover, controller  54  may fire VCSELs  28  individually or in groups, thus controlling the pattern of beams  40  projected onto and scanned over scene  42 . 
     Although controller  54  and processing circuitry  56  are shown in  FIG.  1   , for the sake of convenience, as single functional blocks, in practice the functions of the “controller” and “processing circuitry” may be implemented in a single physical unit, such as a suitable integrated circuit, or in two or more separate physical units for each. These functions may be implemented in software or in hardware logic or in a combination of software and hardware functions. In either case, controller  54  and processing unit  56  have suitable interfaces for receiving and transmitting data and instructions to and from other elements of apparatus  20  as described. 
       FIGS.  2   a - 2   c    are schematic sectional views of a scanner cell  134  for a one-dimensional scan, illuminated by a VCSEL  128 , in different states of operation, in accordance with an embodiment of the invention. 
     Cell  134  comprises transparent entrance and exit faces  102  and  104 , respectively, wherein the entrance face comprises a flexible membrane and the exit face comprises a transparent window, for example glass. A volume of a transparent fluid  106  is contained between entrance face  102  and exit face  104 . Two actuators  108  and  110 , respectively, are attached to opposite sides of entrance face  102 . Two electrodes  112  and  114  are coupled respectively to actuators  108  and  110 . A controller  111  (similar to controller  54  in  FIG.  1   ) is coupled to electrodes  112  and  114 . Cell  134  further comprises two spacers  116  and  118  and a transparent window  120  (made out of, for example, glass), providing support and protection to the cell. A space  122  between exit face  104  and window  120  contains air or a transparent material. Transparent fluid  106  comprises either a liquid or a deformable polymer, which typically has a refractive index exceeding 1.3 and a thickness of tens or hundreds of microns. Actuators  108  and  110 , as well as the actuators in subsequent figures, are assumed to be piezoelectric elements, which bend under an applied electrical signal. 
       FIG.  2   a    shows cell  134  when no electrical signals are applied by controller  111  to electrodes  112  and  114 , and consequently no deformation is applied to the flexible membrane of entrance face  102  by actuators  108  and  110 . A beam  130  that is emitted by VCSEL  128 , with a Gaussian distribution of optical power within the beam shown schematically by a curve  124 , is transmitted by cell  134  to a beam  136  without any deflection. For the sake of clarity, optical refractions at planar interfaces are not shown in  FIGS.  2   a   - 2   c.    
       FIG.  2   b    shows cell  134  when an electrical signal is applied by controller  111  to electrode  114 . (As the elements in  FIGS.  2   b - 2   c    are identical to those in  FIG.  2   a   , only those specifically referred to in the text of  FIGS.  2   b - 2   c    are labelled.) Actuator  110  is bent due to the electrical signal, and the bending causes an asymmetric deformation of entrance face  102 . Due to this asymmetric deformation and the consequent asymmetric shape of the volume of transparent fluid  106  contained in cell  134 , beam  136  is deflected to the left. The amount of deflection is determined by the electrical signal applied by controller  111 . 
       FIG.  2   c    shows cell  134  when an electrical signal is applied by controller  111  to electrode  112 . Actuator  108  is bent due to the electrical signal, and the bending causes an asymmetric deformation, opposite to that in  FIG.  2   b   , of entrance face  102 . Due to this asymmetric deformation and the consequent asymmetric shape of the volume of a transparent fluid  106 , beam  136  is deflected to the right. 
       FIG.  3    is a schematic sectional view of two scanner cells  134   a  and  134   b  for two independent one-dimensional scans, illuminated by two mounted VCSELs  128   a  and  128   b , in accordance with an embodiment of the invention. 
       FIG.  3    shows the assembly of two of cells  134  of the type shown in  FIGS.  2   a - 2   c   , to create a two-cell scanner. Large-scale scanners, with tens or hundreds of beams, may be produced simply by extending the principles of this embodiment. The same labels are used as in  FIGS.  2   a - c   , with the addition of “a” and “b” for cells  134   a  and  134   b , respectively. VCSELs  128   a  and  128   b  are mounted on a silicon substrate  140  containing respective circuits  142   a  and  142   b , which are configured to control each VCSEL independently. Scanner cells  134   a  and  134   b  have been fabricated on a silicon substrate  144 , which was then thinned, with openings  146   a  and  146   b  formed to permit beams from VCSELs  28   a  and  28   b  to pass through the substrate. Electrodes  112   a  and  114   a  for cell  134   a  and electrodes  112   b  and  114   b  for cell  134   b  have been formed on silicon substrate  144 . An entrance face  150 , comprising a flexible membrane, and an exit face  152 , comprising a transparent window, are shared by cells  134   a  and  134   b , but each cell has its own actuators  108 ,  110  connected to its respective electrodes. A volume of a transparent fluid  154 , similar to transparent fluid  106  in  FIG.  2   , is contained between entrance and exit faces  150  and  152 . Spacers  156 ,  158 , and  160  are similar to spacers  116  and  118  in  FIG.  1   . A window  162  is similar to window  120  in  FIG.  2   , and is shared by cells  134   a  and  134   b.    
     A controller  148  (similar to controller  54  in  FIG.  1   ) is coupled to circuits  142   a  and  142   b , as well as to electrodes  112   a ,  112   b ,  114   a , and  114   b , and thus controls both the firing of VCSELs  128   a  and  128   b  and beam deflection by cells  134   a  and  134   b.    
     Although  FIG.  3    shows only two scanner cells, larger numbers of scanner cells may be fabricated either as a line array or as a two-dimensional array. Such arrays may have regular or irregular spacing between the cells. 
       FIG.  4    is a schematic sectional view of two scanner cells  234   a  and  234   b  for two independent two-dimensional scans, illuminated by two mounted VCSELs  228   a  and  228   b , in accordance with an embodiment of the invention. 
     Similarly to  FIG.  3   , VCSELs  228   a  and  228   b  are mounted on a silicon substrate  270  containing respective circuits  272   a  and  272   b , which are configured to control each VCSEL independently. Two flexible membranes  236  and  238  form the entrance and exit faces, respectively, for cells  234   a  and  234   b . Specifically, cells  234   a  and  234   b  have entrance faces  236   a  and  236   b  and exit faces are  238   a  and  238   b , respectively. A volume of a transparent fluid  240 , similar to transparent fluid  106  in  FIG.  2   , is contained between flexible membranes  236  and  238 . In order to present the exit face actuators and electrodes in the sectional view of  FIG.  4   , the actuators and electrodes coupled to exit faces  238   a  and  238   b  have been, for the figure, rotated by 90° around a z-axis of a Cartesian coordinate system  258 . 
     For the entrance faces, two actuators  242   a  and  244   a , respectively, are attached to opposite sides of entrance face  236   a . Similarly, two actuators  242   b  and  244   b , respectively, are attached to opposite sides of entrance face  236   b . Two electrodes  246   a  and  248   a  are coupled respectively to actuators  242   a  and  244   a . Similarly, two electrodes  246   b  and  248   b  are coupled respectively to actuators  242   b  and  244   b.    
     For the exit faces, two actuators  250   a  and  252   a , respectively, are attached to opposite sides of exit face  238   a . Similarly, two actuators  250   b  and  252   b , respectively, are attached to opposite sides of entrance face  236   b . Two electrodes  254   a  and  256   a  are coupled respectively to actuators  250   a  and  252   a . Similarly, two electrodes  254   b  and  256   b  are coupled respectively to actuators  250   b  and  252   b . For cell  234   a , actuators  250   a  and  252   a  coupled to exit face  238   a , together with respective electrodes  254   a  and  256   a , are orthogonal to actuators  242   a  and  244   a  coupled to entrance face  236   a  and their respective electrodes  246   a  and  248   a . Similarly for cell  234   b , the exit face actuators and their electrodes are orthogonal to the entrance face actuators and their electrodes. 
     A transparent window  260  protects cells  234   a  and  234   b  and is shared by them. Controller  274  (similar to controller  54  in  FIG.  1   ) is coupled to circuits  272   a  and  272   b , as well as to electrodes  246   a ,  246   b ,  248   a ,  248   b ,  254   a ,  254   b ,  256   a , and  256   b.    
     When no electrical signals are applied to any of the electrodes of cells  234   a  and  234   b , beams  230   a  and  230   b , emitted by VCSELs  228   a  and  228   b , respectively, are transmitted through the cells and emitted without deflection as beams  276   a  and  276   b , respectively. 
     By applying an electrical signal to electrode  246   a , actuator  242   a  is bent, and entrance face  236   a  is deformed asymmetrically. The subsequent deformation of volume of transparent fluid  240  adjacent to entrance face  236   a  causes beam  276   a  to deflect about the y-axis of Cartesian coordinate system  258 . By applying an electrical signal to the opposing electrode  244   a , beam  276   a  is, through a similar mechanism, deflected to an opposite direction about the y-axis. Similar deflection about the y-axis may be accomplished for beam  276   b  by applying electrical signals to electrodes  242   b  and  244   b.    
     A deflection of beam  276   a  about the x-axis of Cartesian coordinate system  258 , i.e., orthogonally with respect to the previously described direction, is accomplished by applying electrical signals to electrodes  250   a  and  252   a . Similarly, a deflection of beam  276   b  about x-axis is accomplished by applying electrical signals to electrodes  250   b  and  252   b.    
     By a simultaneous application of electrical signals to the mutually orthogonal electrodes of cell  234   a , beam  276   a  may be deflected simultaneously about both x- and y-axes, with the same applying to cell  234   b.    
     Electrodes  246   a ,  246   b ,  248   a , and  248   b , together with actuators  242   a ,  242   b ,  244   a ,  244   b  and membrane  236  have been fabricated on a silicon substrate  262 , which was then thinned, with openings  264   a  and  264   b  formed to permit the passage of beams from VCSELs  228   a  and  228   b . Similarly but separately, electrodes  254   a ,  254   b ,  256   a , and  256   b , together with actuators  250   a ,  250   b ,  252   a ,  252   b  and membrane  238  have been fabricated on a silicon substrate  266 , similarly thinned, with openings  268   a  and  268   b  formed to permit the passage of beams from VCSELs  228   a  and  228   b . After the above-described fabrication, thinned wafers  262  and  266  are brought into close proximity, with membranes  236  and  238  facing each other and with the openings in the two wafers aligned. The cavity between the membranes is then filled with transparent fluid  240 . 
     Although  FIG.  4    shows only two scanner cells, larger numbers of scanner cells may be fabricated either as a line array or as a two-dimensional array, as noted above. 
       FIGS.  5   a - 5   d    are schematic top views showing configurations of VCSEL arrays and scanners, in accordance with embodiments of the invention. 
       FIG.  5   a    shows a scanner  306  overlaid on a 2×3 array  302  of VCSELs  304 . Scanner  306  comprises a 2×3 array of cells  308 , such that each cell is aligned with a VCSEL  304 . Each cell  308  is a two-dimensional scanner cell, similar to cells  234   a  and  234   b  in  FIG.  4   , and comprises two actuators  310  and  312 , aligned along the x-axis of a Cartesian coordinate system  314 , and two actuators  316  and  318 , aligned along the y-axis of the Cartesian coordinate system. For the sake of clarity, all the actuators are fully visible in all of  FIGS.  5   a - 5   d    in the top view, although in the actual cells parts of the actuators would be covered in this view, but none of the other details in cells  308  are shown. A thinned silicon wafer  320  makes up one of the thinned wafers of scanner  306 , similar to one of thinned wafers  262  and  266  in  FIG.  4   . 
     Controller  330  (similar to controller  54  in  FIG.  1   ) is coupled to the electrodes of cells  308 , as well as to VCSELs  304  (through the respective driving circuits of the VCSELs). By applying electrical signals to actuators  310  and  312 , the beam emitted by each VCSEL  304  may be deflected about the x-axis, and by applying electrical signals to actuators  316  and  318 , the beam emitted by each VCSEL  304  may be deflected about the y-axis. By applying independent electrical signals simultaneously to both pairs of actuators, arbitrary deflection angles (within the maximal deflection achievable by cells  308 ) may be achieved. By driving, for example, all actuators  310  (or actuators  312 ) with the same signal, a synchronized scanning about x-axis is achieved. This sort of drive may be accomplished either by output of this same signal from controller  330  to each of cells  308  individually or by wiring all the electrodes of actuators  310  (and/or the electrodes of actuators  312 ) together for simplified wiring. Similar synchronized scanning may be achieved about the y-axis by driving all actuators  316  (or actuators  318 ) with the same signal. As each VCSEL  304  of VCSEL array  302  may be driven independently by controller  330 , single-beam scans (point scans), as well as other beam patterns, may be achieved. 
       FIG.  5   b    shows a scanner  344  overlaid on a VCSEL array  340  comprising three lines of VCSELs  342 , with eight VCSELs in each line. Scanner  344  comprises three cells  346 , such that each cell is aligned with a line of VCSELs  304  and encompasses all eight VCSELs in that line. Each cell  346  is a one-dimensional scanner cell similar to cells  134   a  and  134   b  in  FIG.  3   , and comprises two actuators  348  and  350 , aligned along the x-axis of Cartesian coordinate system  314 . A thinned silicon wafer  351  is similar to thinned wafer  144  of  FIG.  3   . 
     Controller  352  (similar to controller  54  in  FIG.  1   ) is coupled to the electrodes of actuators  348  and  350  of each cell  346 , as well as to VCSELs  342 . By applying electrical signals to actuators  348  and  350  of a given cell, the beams emitted by VCSELs  342  that are aligned with that cell may be deflected about the x-axis, thus performing a line scan. Cells  346  may be driven either independently or in unison by controller  352 . Alternatively, by wiring all electrodes for actuators  348  together and all electrodes of actuators  350  together, synchronized line scans are achieved with simplified wiring. One-dimensional point-scanning is achieved by driving one VCSEL  342  at a time. 
       FIG.  5   c    shows a 4×8 VCSEL array  360  comprising VCSELs  362 , overlaid by a single-cell scanner  364 , encompassing all of VCSELs  362 . Scanner  364  is a one-dimensional scanner similar to one of cells  134   a  and  134   b  in  FIG.  3   , and comprises two actuators  366  and  368 , aligned along the x-axis of Cartesian coordinate system  314 . A thinned silicon wafer  370  is similar to thinned wafer  144  of  FIG.  3   . 
     Controller  370  (similar to controller  54  in  FIG.  1   ) is coupled to the electrodes of actuators  366  and  368 , as well as to VCSELs  362 . By applying electrical signals to actuators  366  and  368 , the beams emitted by VCSELs  362  may be deflected about the x-axis, thus performing a one-dimensional array scan. One-dimensional point-scanning is achieved by driving one VCSEL  362  at a time. 
       FIG.  5   d    shows a 4×4 VCSEL array  380  comprising VCSELs  382 , overlaid by a single-cell scanner  384 , encompassing all VCSELs  382 . Scanner  384  is a two-dimensional scanner similar to one of cells  234   a  and  234   b  in  FIG.  4   , and comprises two orthogonal pairs of actuators, with actuators  386  and  388  aligned along the x-axis, and actuators  390  and  392  aligned along the y-axis. A thinned silicon wafer  394  makes up one of the thinned wafers of scanner  384 , similarly to one of thinned wafers  262  and  266  in  FIG.  4   . 
     Controller  392  (similar to controller  54  in  FIG.  1   ) is coupled to the electrodes of scanner  384 , as well as to VCSELs  382 . By applying electrical signals to actuators  386  and  388 , the beams emitted by VCSELs  382  may be deflected about the x-axis, and by applying electrical signals to actuators  390  and  392 , the beams emitted by the VCSELs may be deflected about the y-axis. Applying simultaneous but independent electrical signals to both pairs of actuators, an arbitrary deflection angle (within the maximal deflection of scanner  384 ) may be achieved. By selectively driving VCSELs  382  by controller  392 , any combination of beams from VCSEL array  380  may be emitted, as well as scanned in one or two dimensions. 
       FIGS.  6   a - 6   b    are schematic perspective and sectional views, respectively, of an electro-optical device  400 , in accordance with an embodiment of the invention. 
     Electro-optical device  400  comprises two VCSELs  402   a  and  402   b , mounted on a silicon substrate  404  containing respective circuits  405   a  and  405   b , which are configured to control each VCSEL independently, and a scanner  406  supported by spacers  408 . Scanner  406  comprises two cells  412   a  and  412   b  for two independent two-dimensional scans, similar to cells  234   a  and  234   b  in  FIG.  4   . Due to this similarity, the elements of cells  412   a  and  412   b  have not been labelled. The height of spacers  408  is determined so that the lower surfaces of cells  412   a  and  412   b  are within a small distance, for example 10 μm, of the top surfaces of VCSELs  402   a  and  402   b , respectively. This minimization of the gap between cell  412   a  and VCSEL  402   a  and between cell  412   b  and VCSEL  402   b  ensures that diverging beams  410   a  and  410   b , which are emitted by VCSELs  402   a  and  402   b , respectively, pass through cells  412   a  and  412   b  without the beams being clipped. 
     Both silicon substrate  404  and scanner  406 , together with spacers  408 , are mounted on a ceramic substrate  414  (not shown in  FIG.  6   a   ). A controller  420  (similar to controller  54  in  FIG.  1   ) is coupled to scanner  406 , as well as to circuits  405   a  and  405   b , via bonding pads  416  and wire bonds  418 . 
     Although  FIG.  6   b    shows only two scanner cells, larger numbers of scanner cells may be fabricated either as a line array or as a two-dimensional array. 
     It will be appreciated that the embodiments described above are cited by way of example, and that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof which would occur to persons skilled in the art upon reading the foregoing description and which are not disclosed in the prior art.

Metadata:
Filing Date: 20220731
Publication Date: 20240213
Grant Date: 20240213
Priority Date: 20180920
Inventors: LAFLAQUIÈRE, ARNAUD
Assignee: APPLE INC
CPC Classifications: [{"code": "G01S7/4817", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S17/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/004", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0875", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/10", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/042", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/423", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/0071", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S7/4817", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01S7/4817", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/004", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0875", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/423", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S7/4815", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/101", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/0875", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B26/004", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/423", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01S17/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/042", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B26/10", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 83149928