PATENT DOCUMENT

Publication Number: US-11469573-B2
Application Number: US-202016779609-A
Country: US
Kind Code: B2

Title: Vertical emitters with integral microlenses

Abstract:
An optoelectronic device includes a semiconductor substrate having first and second faces. A first array of emitters are formed on the first face of the semiconductor substrate and are configured to emit respective beams of radiation through the substrate. Electrical connections are coupled to actuate selectively first and second sets of the emitters in the first array. A second array of microlenses are formed on the second face of the semiconductor substrate in respective alignment with the emitters in at least one of the first and second sets and are configured to focus the beams emitted from the emitters in the at least one of the first and second sets so that the beams are transmitted from the second face with different, respective first and second focal properties.

Claims:
The invention claimed is: 
     
       1. An optoelectronic device, comprising:
 a semiconductor substrate having first and second faces; 
 an emitter array comprising first and second sets of emitters, which are formed on the first face of the semiconductor substrate and are configured to emit respective first and second beams of radiation through the substrate; 
 electrical connections, which are coupled to actuate selectively the first and second sets of the emitters in the emitter array; and 
 a microlens array comprising microlenses, which are formed on the second face of the semiconductor substrate in respective alignment with the emitters in at least one of the first and second sets and are configured to focus the beams emitted from the emitters in the at least one of the first and second sets so that the first and second beams are transmitted from the second face with different, respective first and second focal properties. 
 
     
     
       2. The device according to  claim 1 , wherein the semiconductor substrate comprises a III-V semiconductor substrate, and wherein the device comprises a silicon substrate on which the electrical connections are formed, the electrical connections comprising bonding pads to which the emitters in the first array are respectively connected. 
     
     
       3. The device according to  claim 1 , wherein the emitters comprise vertical-cavity surface-emitting lasers (VCSELs). 
     
     
       4. An optoelectronic device, comprising:
 a semiconductor substrate having first and second faces; 
 an emitter array comprising emitters, which are formed on the first face of the semiconductor substrate and are configured to emit respective beams of radiation through the substrate; 
 electrical connections, which are coupled to actuate selectively first and second sets of the emitters in the emitter array; and 
 a microlens array comprising microlenses, which are formed on the second face of the semiconductor substrate in respective alignment with the emitters in at least one of the first and second sets and are configured to focus the beams emitted from the emitters in the at least one of the first and second sets so that the beams are transmitted from the second face with different, respective first and second focal properties; and 
 projection optics, which are configured to focus the beams from the emitters in the first set to form a pattern of structured light in an area of a far field while spreading the beams from the emitters in the second set so as to project flood illumination over the area. 
 
     
     
       5. The device according to  claim 4 , wherein the emitters in the first set are disposed across the semiconductor substrate in a predefined spatial distribution, and wherein the pattern of structured light comprises a pattern of spots reproducing the spatial distribution of the emitters in the first set. 
     
     
       6. The device according to  claim 4 , wherein the microlenses are formed only in alignment with the emitters in the second set. 
     
     
       7. The device according to  claim 4 , wherein the microlenses that are formed in alignment with the emitters in the second set are displaced transversely on the second face relative to respective ones of the emitters in the second set so as to focus the beams emitted from the emitters in the second set toward a peripheral region of a focal plane of the device, and wherein the projection optics comprises a diffuser disposed in the peripheral region of the focal plane and configured to spread the beams that pass through the peripheral region, while the beams that pass through a central region of the focal plane are not diffused. 
     
     
       8. The device according to  claim 7 , wherein the projection optics comprise a diffractive optical element (DOE), which is disposed in a central region of the focal plane and is configured to create multiple replicas of the pattern of structured light in the far field. 
     
     
       9. The device according to  claim 1 , wherein the microlenses in the second array comprise doublet lenses. 
     
     
       10. An optical device, comprising:
 a semiconductor substrate having a first face and a second face, which is etched to define a first array of first microlenses configured to focus optical radiation that has been transmitted through the substrate; and 
 a second array of second microlenses, which is disposed on the substrate over the first array in alignment with the first microlenses so as to form microlens doublets. 
 
     
     
       11. The device according to  claim 10 , wherein the semiconductor substrate comprises a III-V semiconductor substrate. 
     
     
       12. The device according to  claim 10 , and comprising a third array of emitters, which are formed on the first face of the semiconductor substrate in alignment with the first microlenses and are configured to emit respective beams of the optical radiation through the substrate. 
     
     
       13. The device according to  claim 12 , wherein the emitters comprise vertical-cavity surface-emitting lasers (VCSELs), and wherein the first and second microlenses are configured to focus multiple modes of each of the VCSELs to a respective beam waist outside the semiconductor substrate. 
     
     
       14. The device according to  claim 10 , wherein the second microlenses comprise a polymer. 
     
     
       15. The device according to  claim 10 , wherein the second microlenses comprise a glass. 
     
     
       16. The device according to  claim 10 , wherein the second microlenses are offset in a transverse direction along the second face relative to the first microlenses with which they are respectively aligned. 
     
     
       17. A method for manufacturing an optical device, the method comprising:
 etching a semiconductor substrate, having a first face and a second face, to define, on the second face, a first array of first microlenses configured to focus optical radiation that has been transmitted through the substrate; and 
 depositing a second array of second microlenses over the first array in alignment with the first microlenses so as to form microlens doublets. 
 
     
     
       18. The method according to  claim 17 , wherein depositing the second microlenses comprises molding a polymer over the second face to define the second microlenses. 
     
     
       19. The method according to  claim 17 , wherein depositing the second microlenses comprises applying a photolithographic process to a polymer layer extending over the second face to define the second microlenses. 
     
     
       20. The method according to  claim 17 , wherein depositing the second microlenses comprises detecting a misalignment between the first microlenses and emitters of the optical radiation disposed on the first face of the semiconductor substrate, and offsetting the second microlenses in a transverse direction along the second face relative to the first microlenses so as to compensate for the detected misalignment.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Patent Application 62/800,577, filed Feb. 4, 2019, and of U.S. Provisional Patent Application 62/869,577, filed Jul. 2, 2019. Bother of these related applications are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to optoelectronic devices, and particularly to projectors of patterned illumination using arrays of solid-state emitters, such as vertical-cavity surface-emitting lasers (VCSELs). 
     BACKGROUND 
     Integrated VCSEL arrays can be used to generate either flood illumination, in which a target area is uniformly illuminated, or structured illumination, in which a pattern, such as an array of spots, is projected onto a target area. Depending on the optical configuration, the light emitted from each VCSEL can be projected into a single spot, or alternatively, a diffractive optical element (DOE) can be used to split the light from each VCSEL into multiple spots. 
     In most VCSEL arrays, the drive circuits are constructed so that all of the VCSELs on a given chip are excited and emit light simultaneously. Recently-developed technologies, however, make it possible to drive the VCSELs selectively, for example by mounting a III-V chip with an array of VCSELs on a silicon substrate on which control circuits are formed, as described in PCT International Publication WO 2018/053378, whose disclosure is incorporated herein by reference. 
     Because of their very short resonator length and complex radial mode structure, VCSELs tend to have high native divergence. To mitigate this problem, some VCSELs and VCSEL arrays include integrated microlenses, which are respectively aligned with the VCSELs. For example, U.S. Pat. No. 9,746,369, whose disclosure is incorporated herein by reference, describes a beam generating device that includes a semiconductor substrate, such as a GaAs wafer, having an optical passband. A first array of VCSELs is formed on a first face of the semiconductor substrate and are configured to emit respective laser beams through the substrate at a wavelength within the passband. A second array of microlenses is formed on a second face of the semiconductor substrate, with the microlenses in respective alignment with the VCSELs so as to transmit the laser beams generated by the VCSELs. This sort of device is shown specifically in  FIGS. 11-12  of the above-mentioned patent and described in the specification starting at col. 14, line 19. 
     SUMMARY 
     Embodiments of the present invention that are described hereinbelow provide improved devices for generating and projecting optical radiation, as well as methods for manufacture of such devices. 
     There is therefore provided, in accordance with an embodiment of the invention, an optoelectronic device, including a semiconductor substrate having first and second faces. A first array of emitters are formed on the first face of the semiconductor substrate and are configured to emit respective beams of radiation through the substrate. Electrical connections are coupled to actuate selectively first and second sets of the emitters in the first array. A second array of microlenses are formed on the second face of the semiconductor substrate in respective alignment with the emitters in at least one of the first and second sets and are configured to focus the beams emitted from the emitters in the at least one of the first and second sets so that the beams are transmitted from the second face with different, respective first and second focal properties. 
     In a disclosed embodiment, the semiconductor substrate includes a III-V semiconductor substrate, and the device includes a silicon substrate on which the electrical connections are formed, the electrical connections including bonding pads to which the emitters in the first array are respectively connected. Additionally or alternatively, the emitters include vertical-cavity surface-emitting lasers (VCSELs). 
     In some embodiments, the device includes projection optics, which are configured to focus the beams from the emitters in the first set to form a pattern of structured light in an area of a far field while spreading the beams from the emitters in the second set so as to project flood illumination over the area. In a disclosed embodiment, the emitters in the first set are disposed across the semiconductor substrate in a predefined spatial distribution, and the pattern of structured light includes a pattern of spots reproducing the spatial distribution of the emitters in the first set. In one embodiment, the microlenses are formed only in alignment with the emitters in the second set. 
     Additionally or alternatively, the microlenses that are formed in alignment with the emitters in the second set are displaced transversely on the second surface relative to respective ones of the emitters in the second set so as to focus the beams emitted from the emitters in the second set toward a peripheral region of a focal plane of the device, and the projection optics includes a diffuser disposed in the peripheral region of the focal plane and configured to spread the beams that pass through the peripheral region, while the beams that pass through a central region of the focal plane are not diffused. In one embodiment, the projection optics include a diffractive optical element (DOE), which is disposed in a central region of the focal plane and is configured to create multiple replicas of the pattern of structured light in the far field. 
     In a disclosed embodiment, the microlenses in the second array include doublet lenses. 
     There is additionally provided, in accordance with an embodiment of the invention, an optical device, including a semiconductor substrate having a first face and a second face, which is etched to define a first array of first microlenses configured to focus optical radiation that has been transmitted through the substrate. A second array of second microlenses is disposed on the substrate over the first array in alignment with the first microlenses. 
     In a disclosed embodiment, the semiconductor substrate includes a III-V semiconductor substrate. 
     In some embodiments, the device includes a third array of emitters, which are formed on the first face of the semiconductor substrate in alignment with the first microlenses and are configured to emit respective beams of the optical radiation through the substrate. In a disclosed embodiment, the emitters include vertical-cavity surface-emitting lasers (VCSELs), and the first and second microlenses are configured to focus multiple modes of each of the VCSELs to a respective beam waist outside the semiconductor substrate. 
     In the disclosed embodiments, the second microlenses include a polymer and/or a glass. 
     In one embodiment, the second microlenses are offset in a transverse direction along the second face relative to the first microlenses with which they are respectively aligned. 
     There is additionally provided, in accordance with an embodiment of the invention, a method for manufacturing an optical device. The method includes etching a semiconductor substrate, having a first face and a second face, to define, on the second face, a first array of first microlenses configured to focus optical radiation that has been transmitted through the substrate. A second array of second microlenses is deposited over the first array in alignment with the first microlenses. 
     In a disclosed embodiment, depositing the second microlenses includes molding a polymer over the second face to define the second microlenses. Alternatively or additionally, depositing the second microlenses includes applying a photolithographic process to a polymer layer extending over the second face to define the second microlenses. 
     In one embodiment, depositing the second microlenses includes detecting a misalignment between the first microlenses and emitters of the optical radiation disposed on the first face of the semiconductor substrate, and offsetting the second microlenses in a transverse direction along the second face relative to the first microlenses so as to compensate for the detected misalignment. 
     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 
         FIGS. 1A and 1B  are schematic sectional and frontal views of an integrated emitter device, in accordance with an embodiment of the invention; 
         FIGS. 2A and 2B  are schematic, sectional detail views showing beams emitted by two different types of emitters in an integrated emitter array, in accordance with an embodiment of the invention; 
         FIG. 3  is a schematic sectional view of an optical projection system, in accordance with an embodiment of the invention; 
         FIG. 4  is a schematic frontal view of a beam-conditioning component in the system of  FIG. 3 , in accordance with an embodiment of the invention; 
         FIG. 5  is a schematic, sectional detail view of two types of emitters in an integrated emitter array, in accordance with an embodiment of the invention; 
         FIG. 6  is a schematic sectional view of an integrated emitter array, in accordance with another embodiment of the invention; 
         FIGS. 7A, 7B and 7C  are schematic sectional views showing successive stages in the production of an array of microlens doublets, in accordance with an embodiment of the invention; and 
         FIG. 8  is a schematic sectional view of an array of microlens doublets, in accordance with another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Overview 
     Projecting a structured-light pattern of high quality and low distortion over a wide field requires careful design of the optics used for projection. When conventional lenses are used for this purpose, the resulting design is often bulky and costly. 
     Some embodiments of the present invention that are described herein overcome these constraints by forming integrated microlenses over an array of VCSELs. Specifically, in an example embodiment, an array of VCSELs is fabricated on a GaAs substrate, after which the back side of the substrate is thinned, and microlenses are formed on the back side of the substrate in alignment with the locations of the VCSELs. The microlenses may be formed by etching of the GaAs substrate and/or deposition and processing (by molding or etching, for example) of additional layers, such as polymer layers. 
     In some embodiments, the microlenses are not centered over each VCSEL in the array, but rather, some or all of the microlenses are intentionally decentered for improved optical performance. For example, the microlenses of the VCSELs can be displaced inwardly, with greatest displacement at the edges of the array. Alternatively or additionally, the microlenses may be decentered for the purpose of beam steering. 
     In other embodiments, microlenses formed on the back side of a VCSEL array chip may have multiple refractive surfaces to achieve improved optical performance, particularly for handling of multiple laser modes, and particularly the more divergent, higher-order transverse modes. For example, “doublet” microlenses may be produced by fabricating a polymer lens over an etched GaAs lens. 
     In some embodiments, multiple different types of microlenses are formed over different VCSELs in an array in order to achieve different illumination properties; or alternatively, microlenses may be formed over some of the VCSELs but not others. For example, different sets of VCSELs in a single integrated array can be used to generate structured light (a pattern of spots) and flood illumination, respectively. In this example, microlenses are formed over one set of the VCSELs but not the other; but alternatively, both sets of VCSELs may have microlenses of different, respective curvatures. A switching circuit, implemented in silicon, for example, can be used to select the set of VCSELs to be actuated at any given time, depending on the type of illumination that is required. 
     Emitter Arrays with Integral Microlenses 
       FIGS. 1A and 1B  are schematic sectional and frontal views of an integrated emitter device  20 , in accordance with an embodiment of the invention. The drawings are not to scale. 
     Device  20  comprises a semiconductor substrate  22 , for example a substrate made from a wafer of GaAs or another III-V semiconductor. An array of emitters, such as VCSELs  24  and  26 , is formed on one face of semiconductor substrate  22  in a back-emitting configuration, meaning that beams  28  of radiation emitted by the VCSELs are transmitted through substrate  22 . For example, the VCSELs may emit the beams of radiation at a wavelength of 940 nm, at which GaAs is transparent. Alternatively, other sorts of substrates, as well as other sorts of emitters, such light-emitting diodes, which may emit radiation at other wavelengths, may be formed in this configuration. 
     In the pictured example, the VCSELs are divided into two sets, as explained further hereinbelow:
         VCSELs  24  are to be used in projecting flood radiation onto an area of the far field (i.e., at distances from device  20  large enough so that propagation of the optical waves from the emitters is substantially uniform); and   VCSELs  26  are to be used in forming a pattern of structured light on the area of the far field.
 
In this example, VCSELs  26  are disposed across semiconductor substrate  22  in a certain spatial distribution—in this case, an irregular distribution—and the structured light will comprise a pattern of spots that reproduces the spatial distribution of VCSELs  26 .
       

     Microlenses  30  are formed on the opposite face of semiconductor substrate  22 , in respective alignment with VCSELs  24 , in order to focus beams  28  emitted from these VCSELs, but no microlenses are formed over VCSELs  26 . Consequently, the beams originating from VCSELs  24  will be transmitted out of the rear face of substrate  22  with different focal properties from those of VCSELs  26 . Alternatively, the microlenses may be formed only in alignment with VCSELs  26 , rather than VCSELs  24 . Further alternatively, microlenses having different focal properties may be formed over both sets of the VCSELs. Microlenses  30  are typically formed by a suitable etching process, which is applied to the rear face (i.e., the upper face in the view shown in  FIG. 1A ) of semiconductor substrate  22 . 
     A silicon wafer  32  is bonded to the front side of VCSELs  24 ,  26  in order to make the electrical connections needed in order to actuate the two sets of VCSELs selectively. The electrical connections include circuit lines  36  and  38 , which connect to VCSELs  24  and  26 , respectively, via suitable bonding pads  34 , comprising solder bumps or other suitable conducting elements, for example. Application of a drive signal to line  36  will actuate VCSELs  24 , so that device  20  will emit flood illumination; whereas application of a drive signal to line  38  will actuate VCSELs  26 , resulting in emission of patterned light. Alternatively, the electrical connections may be made on the III-V semiconductor wafer on which VCSELs  24  and  26  are fabricated (particularly if the two sets of VCSELs are each grouped in a different, respective area or areas of the wafer). 
       FIGS. 2A and 2B  are schematic, sectional detail views showing beams  40  and  42  emitted by VCSELs  24  and  26 , respectively, in accordance with an embodiment of the invention. Microlenses  30  in this example are formed in alignment only with VCSELs  24 . Beams  40  are thus collimated as they exit substrate  22 , whereas beams  42  diverge. More specifically, in the pictured example, microlenses  30  are displaced transversely on the back surface of substrate  22  relative to the respective VCSELs  24 , with the result that beams  40  are directed in an oblique direction, rather than normal to the substrate. In the pictured example, beams  40  are all directed in the same direction; but alternatively, microlenses  30  may be displaced by different increments relative to VCSELs  24 , in which case the beams will be directed at different angles. 
       FIG. 3  is a schematic sectional view of an optical projection system  50 , which is based on device  20 , in accordance with an embodiment of the invention. Microlenses  30  are formed over substrate with the sort of transverse displacement that is shown in  FIGS. 2A /B, so that beams  40  and  42  are output as described above. Projection optics  52 , typically comprising a suitable lens or group of lenses, focus beams  42  to form a pattern of structured light in an area of the far field. As noted earlier, the structured light in this example may comprise a pattern of spots reproducing the spatial distribution of VCSELs  26  on substrate  22 . At the same time, beams  40  are focused toward the peripheral region of a beam-conditioning component  54  in the focal plane of optics  52 . Element  54  spreads beams  40  so as to project flood illumination  56  over the far-field area of interest. As noted earlier, system  50  is capable of selectively generating either patterned or flood illumination, or both simultaneously if desired. 
       FIG. 4  is a schematic frontal view of beam-conditioning component  54 , in accordance with an embodiment of the invention. The peripheral part of component  54  comprises a diffuser  60 , which spreads beams  40  over the appropriate angular range to create flood illumination  56 , which uniformly (or nearly uniformly) illuminates a chosen angular field of view. Diffuser  60  may be refractive or diffractive, for example. 
     Projection optics  52  focus beams  42  through a central region  62  of component  54 . In one embodiment, this central region comprises a diffractive optical element (DOE), which creates multiple replicas of the pattern of structured light in the far field. Thus, for example, the number of spots in the projected pattern may be a multiple of the number of VCSELs  26  in device  20 . In this case, diffuser  60  may also be diffractive, but with different diffractive properties from the central DOE, despite occupying the same physical substrate. 
     Emitter Arrays with Doublet Microlenses 
       FIG. 5  is a schematic, sectional detail view of two types of VCSELs  24  and  26  in an integrated array, including a microlens doublet  74  over VCSEL  24 , in accordance with an embodiment of the invention. VCSEL  26  has no microlens, as in the preceding embodiments. 
     VCSELs often emit light in high-order transverse modes, which given rise to a beam  72  that propagates through substrate  22  and exits with high divergence. Beam  72  has a beam waist located at the confinement layer of the VCSEL, below substrate  22 , and it is this beam waist that defines an optical aperture  70  of the beam. The minimum size of this beam waist is a function of the required output power and the VCSEL manufacturing process. Large optical apertures  70 , however, require more complex projection optics, of longer effective focal length, in order to project spot patterns with fine resolution. A singlet microlens can demagnify the optical aperture by focusing beam  72 , but at the cost of increasing the divergence of the VCSEL, and therefore increasing the complexity of the projection optics. 
     As a solution to this problem, doublet  74  uses a pair of microlenses  76  and  78  to recover (or even improve) the divergence of beam  72  after demagnification. Typically, microlens  76  is etched into the back surface of substrate  22 , and thus comprises the same semiconductor material as the substrate, such as GaAs. Microlens  78 , comprising a polymer or glass material, for example, is then deposited over microlens  76 . Typically (although not necessarily), an array of microlenses  78  is deposited over and in alignment with a corresponding array of microlenses  76  on a III-V semiconductor wafer, thus forming an array of doublets  74 , as shown in the figures that follow. Doublets  74  are aligned with respective VCSELs  24  (or other emitters) on the opposite side of the wafer. 
     Doublet  74  refocuses beam  72  to a waist  80  at or above the upper surface of microlens  78 . Waist  80 , and hence the effective size of the optical aperture of VCSEL  24 , may be smaller than the native aperture  70  of the VCSEL. As a consequence, the projection optics used with VCSEL  24  may have a short effective focal length and larger field of view than can practically be used with VCSEL  26 , or even with a VCSEL having only a singlet microlens. Furthermore, because doublet  74  projects waist  80  to a plane above substrate  22 , the lower surface of the projection optics can be brought into very close proximity with wafer  22 —so that waist  80  is located at the front focal plane of the optics notwithstanding the short effective focal length—without risk that the optics will contact and damage delicate structures on the wafer, such as bond wires. The use of doublets  74  thus enables the VCSEL array device to be integrated into a very compact optical package, with short focal length, close working range, and wide field of view. 
     Microlens doublets can also be useful in compensation for alignment tolerances between etched microlenses  76  on one side of substrate  22  and VCSELs  24  on the opposite side. Precise front-to-back alignment of this sort can be difficult to achieve, particularly for a GaAs substrate, which is opaque to visible light. Misalignment of the array of microlenses  76  will cause a global pointing error of the VCSEL beams, which must then be taken into account in the system optical design. In a doublet design, on the other hand, the arrays of additional microlenses that is formed over the etched microlenses can be intentionally offset in order to compensate for the misalignment of the GaAs microlens array. 
       FIG. 6  is a schematic sectional view of an integrated emitter array  90  of this sort, in accordance with another embodiment of the invention. In the pictured example, microlenses  76  were etched on the back side of substrate  22  with their optical centers unintentionally shifted relative to optical axes  92  of the corresponding VCSELs  24 , along a direction transverse to the face of the substrate. To compensate for this error, microlenses  94 , comprising a polymer material, for example, are offset in the opposite transverse direction, relative to microlenses  76 . The offset is chosen so as to correct the pointing error that would otherwise arise due to microlenses  76 , so that the VCSEL beams will be directed by the microlens doublets along optical axes that are approximately normal to substrate  22 . 
     Detection and compensation for misalignment of microlenses  76  can be a part of the manufacturing process of array  90 . For example, the misalignment between the microlenses  76  and VCSELs  24  can be detected by creating fiducial marks as part of the manufacturing processes of the VCSELs and microlenses on both sides of wafer  22 , and then measuring the offset between the fiducial marks using suitable metrology equipment. Alternatively or additionally, the offset can be measured by active optical testing of the VCSELs. Once the offset has been detected and measured, the required offset of microlenses  94  can be calculated, and the mold or mask that is used to produces microlenses  94  can then be shifted accordingly so as to compensate for the detected misalignment. The fiducial marks associated with microlenses  76  can be used to align microlenses  94  precisely in the desired position. 
       FIGS. 7A, 7B and 7C  are schematic sectional views showing successive stages in the production of an array  110  of microlens doublets, in accordance with an embodiment of the invention. At the initial stage shown in  FIG. 7A , it is assumed that semiconductor substrate  22  has already been etched to define an array of microlenses  76 , and is then coated with a layer of a curable, transparent polymer material  100 , for example a photoresist resin, such as SU-8. 
     In  FIG. 7B , a transparent mold  102 , including a negative microlens form  104 , is pressed against substrate  22 , thus shaping polymer material  100  into the form. Mold  102  typically comprises glass or fused silica, and form  104  can be produced using processes that are known in the art for fabricating microlenses on glass and fused silica substrates, for example. The polymer material  100  remaining below mold  102  is then irradiated through the mold with ultraviolet light, in order to cure the polymer in the desired shape. Mold  102  may include a photomask  106  so that the ultraviolet light is incident only in the desired areas of wafer  22 . Mold  102  is then removed, leaving array  110  with polymer microlenses  112  deposited over etched microlenses  76 , as shown in  FIG. 7C . 
     In an alternative embodiment, the polymer microlenses are produced by applying a photolithographic process to polymer material  100 . For this purpose, polymer material  100  may comprise a polymer, such as polymethyl methacrylate (PMMA), that can be etched using ultraviolet (UV) light, for example by a process of UV-induced scission. Material  100  is irradiated by UV light through a gray-scale photomask, which defines the shapes of microlenses  112 . Following UV exposure, a chemical developer is applied to remove the excess polymer material, leaving array  110  as shown in  FIG. 7C . 
       FIG. 8  is a schematic sectional view of an array  120  of microlens doublets, in accordance with yet another embodiment of the invention. This embodiment uses a glass substrate  122  on which an array of microlenses  124  has been formed, with the same pitch as the array of microlenses  76  on semiconductor substrate  22 . Microlenses  124  are produced using processes of glass microlens fabrication that are known in the art. After microlenses  76  have been etched into wafer  22 , a layer of transparent optical cement  126 , such as NOA 61 (produced by Norland Products, Cranbury, N.J.), is deposited over the wafer. Microlenses  124  are then aligned precisely over corresponding microlenses  76 , and UV light is directed through substrate  122  in order to cure cement  126 . At this stage, the process is complete. 
     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: 20200202
Publication Date: 20221011
Grant Date: 20221011
Priority Date: 20190204
Inventors: LYON, Keith
LAFLAQUIERE, ARNAUD
Assignee: APPLE INC
CPC Classifications: [{"code": "H01S5/18388", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0961", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/021", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/18305", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/4233", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/423", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01S5/18391", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/423", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/3013", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/02253", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/18388", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/0207", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0922", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B3/0037", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/423", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0944", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/02326", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/18302", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/18391", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/02255", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S2301/18", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/02255", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/0207", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/0905", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/18391", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/02255", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/0207", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/02253", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/021", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/3013", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/18305", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/026", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B27/4233", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/02326", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01S5/423", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/18388", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 69724175