Compact camera module with META optics

Abstract

A method that includes providing an optical stack, where the optical stack includes a first meta lens, a second meta lens, and a first bonding layer that bonds the first meta lens to the second meta lens, attaching a camera module spacer section to a bottom side of the optical stack to form at least a portion of a camera module, wherein the camera module spacer section includes a spacer layer, and where the camera module spacer section is configured such that, when the camera module spacer section is attached to the optical stack, a object distance of the camera module is based on an adjustment length of the camera module spacer section.

Description

NIL Technology ApSF&R Ref.: 47717-0071 WO1 PCT ApplicationCOMPACT CAMERA MODULE WITH META OPTICSTECHNICAL FIELD

[0001] The present disclosure relates to camera modules that include meta optics.BACKGROUND

[0002] In many camera modules, multiple refractive lenses are stacked together, for example in a lens barrel or using wafer level optics. Refractive systems, however, include a change in refractive index between different optical surfaces. At each interface with changing refractive index, undesirable reflections can occur, and anti-reflective coatings may need to be added at all or some of the interfaces.SUMMARY

[0003] In some aspects, the present disclosure describes a method that includes providing an optical stack, where the optical stack includes a first meta lens, a second meta lens, and a first bonding layer that bonds the first meta lens to the second meta lens, attaching a camera module spacer section to a bottom side of the optical stack to form at least a portion of a camera module, wherein the camera module spacer section includes a spacer layer, and where the camera module spacer section is configured such that, when the camera module spacer section is attached to the optical stack, an object distance of the camera module is based on an adjustment length of the camera module spacer section.

[0004] Implementations of the method may include one or more of the following. The camera module spacer section includes a second bonding layer in contact with a top side of the spacer layer and a third bonding layer in contact with a bottom side of the spacer layer, and where the adjustment length of the camera module spacer section is based on a thickness of the second bonding layer, a thickness of the spacer layer, and a thickness of the third bonding layer.

[0005] Implementations of the method may include one or more of the following. The method includes attaching the camera module spacer layer to the bottom side of the optical stack includes bonding the optical stack to the spacer layer using the secondbonding layer. The method includes bonding the camera module spacer layer to a camera module image sensor section using the third bonding layer. The camera module image sensor section includes an image sensor, and the camera module spacer layer is bonded directly to the image sensor using the third bonding layer. The camera module image sensor section includes an image sensor and a cover glass positioned over the image sensor, and the camera module spacer layer is bonded directly to the cover glass using the third bonding layer.

[0006] Implementations of the method may include one or more of the following. The spacer layer includes an optical filter. The optical filter includes a bandpass filter. The method includes providing the optical stack by providing a first wafer comprising the first meta lens, forming the first bonding layer on the first wafer, providing a second wafer comprising the second meta lens on the first bonding layer to form a wafer stack, curing the first bonding layer, and singulating the wafer stack to provide optical stack.Implementations of the method may include one or more of the following. The optical stack includes an aperture layer between the first meta lens and the second meta lens.The optical stack includes an aperture layer on a top side of the first meta lens, where the first bonding layer is on a bottom side of the first meta lens. A top side of the first meta lens includes a first set of meta structures. A bottom side of the second meta lens includes a second set of meta structures.

[0007] Implementations of the method may include one or more of the following. The method includes providing the optical stack by encapsulating the top side of the optical stack in a first encapsulation layer. The method includes providing the optical stack by encapsulating the bottom side of the optical stack in a second encapsulation layer. The second bonding layer is index matched to the second meta lens and to the spacer layer. The third bonding layer is index matched to the spacer layer. Each of the second bonding layers and the third bonding layer has a refractive index in the range of 1.3 to 1.7. The spacer layer includes a glass spacer. The method includes providing the optical stack by forming an anti-reflection coating on a top side of the first meta lens.

[0008] In some aspects, the present disclosure describes a camera module spacer section including a spacer layer, a first bonding layer on a top side of the spacer layer, a second bonding layer on a bottom side of the spacer layer, where an adjustment thickness of the camera module spacer section is configured such that, when the camera module spacer section is affixed to a meta optical stack in a camera module, the camera module includes a predetermined object distance that is based on the adjustment thickness of the camera module spacer section. The spacer layer includes an optical filter. The optical filter includes a bandpass filter. Each of the first bonding layer and the second bonding layer is index matched to the spacer layer. A refractive index of each of the first bonding layer and the second bonding layer is between 1.3 and 1.7.

[0009] In some aspects, the present disclosure describes a meta lens camera module including an optical stack, wherein the optical stack includes a first meta lens, a second meta lens, and a first bonding layer that bonds the first meta lens to the second meta lens, a camera module spacer section attached to a bottom side of the optical stack, and an image sensor section attached to a bottom side of the camera module spacer section, where the camera module spacer section includes a spacer layer, and where the camera module spacer section is configured such that an object distance of the camera module is based on an adjustment length of the camera module spacer section.

[0010] The meta lens camera module may include one or more of the following. The camera module spacer section comprises a second bonding layer in contact with a top side of the spacer layer and a third bonding layer in contact with a bottom side of the spacer layer, and wherein the adjustment length of the camera module spacer section is based on a thickness of the second bonding layer, a thickness of the spacer layer, and a thickness of the third bonding layer.

[0011] The camera module image sensor section includes an image sensor, and the camera module spacer layer is bonded directly to the image sensor using the third bonding layer. The camera module image sensor section includes an image sensor and a cover glass positioned over the image sensor, and the camera module spacer layer is bonded directly to the cover glass using the third bonding layer. The spacer layerincludes an optical filter. The optical filter includes a bandpass filter. The optical stack includes an aperture layer between the first meta lens and the second meta lens. The optical stack includes an aperture layer on a top side of the first meta lens, where the first bonding layer is on a bottom side of the first meta lens. Atop side of the first meta lens includes a first set of meta structures. A bottom side of the second meta lens includes a second set of meta structures. In some implementations, both sides of the first and / or second meta lens can include meta structures. The optical stack includes a first encapsulation layer on a top side of the optical stack. The optical stack includes a second encapsulation layer on a bottom side of the optical stack. The second bonding layer is index matched to the second meta lens and to the spacer layer. The third bonding layer is index matched to the spacer layer. Each of the second bonding layer and the third bonding layer has a refractive index in the range of 1.3 to 1.7. The spacer layer includes a glass spacer.

[0012] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG. 1 shows an example of a meta lens camera module.

[0014] FIGs. 2A and 2B illustrate examples of meta lens camera modules with a first adjust distance and a second adjust distance.

[0015] FIGs. 3A and 3B illustrate examples of camera modules which are fabricated with varying spacer sections 104.

[0016] FIG. 4A illustrates a bar chart demonstrating optical performance of meta lens camera modules having different adjustment thicknesses.

[0017] FIGS. 4B-4D illustrate bar charts demonstrating optical performance of meta lens camera modules having fixed adjustment thicknesses.

[0018] FIGs. 5A-5D show an example process for forming an optical stack.

[0019] FIGS. 6A-6B show an example process for forming a camera module.

[0020] Like reference symbols in the various drawings indicate like elements.DETAILED DESCRIPTION

[0021] The present disclosure describes optical systems, such as camera modules, that include meta optics. Meta optical elements (MOEs) employ a flat optic technology and have a metasurface that includes distributed small subwavelength structures (e.g., referred to as nanostructures or “meta-atoms”) arranged to interact with light in a particular manner. For example, a metasurface, which may be referred to as a metastructure, can be a surface with a distributed array of nanostructures. The nanostructures may, individually or collectively, interact with light waves. The meta- atoms may be sub-wavelength nanostructures, which indicates that the structures have lateral dimensions, parallel to the substrate surface, that are less than a wavelength of light that is to be incident on to the structures. For example, in some instances, the nanostructures can be in the form of nanoscale features having dimensions less than 1 micron. Optical devices with different properties can be formed by adjusting the geometry of the meta-atoms / unit cell elements formed on a meta structure. The nanostructures or other meta-atoms may change a local amplitude, a local phase, or both, of an incoming light wave. In some instances, metasurfaces may perform optical functions that are traditionally performed by refractive optical elements. In some cases, MOEs can provide several potential advantages compared to refractive elements. For example, compared to refractive lenses, MOEs can have fewer surfaces and less performance degradation. Optical systems that include fewer surfaces together with the use of MOEs are, in some implementations, less sensitive to performance losses that occur when varying the adjustment thickness of the system. The meta-atoms of MOEs may be arranged, in some cases, in a pattern so that the metasurface functions as an optical element such as, for example, a lens, lens array, beam splitter, grating (e.g., a diffraction grating), grating coupler, fanout grating, diffuser, or other optical element. In other instances, the meta-atoms need not be arranged in a pattern. In someimplementations, the metasurfaces may perform other functions, including polarization control, negative refractive index transmission, beam deflection, vortex generation, polarization conversion, optical filtering, and plasmonic optical functions.

[0022] In general, in some aspects, the present disclosure is directed to an optical apparatus, such as a camera module, that includes an optical stack, which in turn includes at least two meta lenses that are stacked one over the other. The optical stack is attached to a camera module spacer section to form at least a portion of the camera module, in which the camera module spacer section includes a spacer layer. The optical stack and camera module spacer section may have no air gaps between their various optical elements and layers. Such an arrangement can help reduce or eliminate unwanted reflections that might otherwise occur, for example, at air / lens interfaces.

[0023] Optical systems are often associated with a parameter referred to as an object distance, which may be understood to encompass a distance from the object being imaged to the front of the optical system (e.g., to the front lens of the optical system). In designing optical systems, the object distance impacts the depth of field (DOF), which is the range within which the object appears sharp. Typically, a longer object distance results in a greater depth of field, but it can also lead to a decrease in the ability of the optical system to capture fine details as effectively. Conversely, a shorter object distance will have a shallower DOF, but potentially perform better within that range to resolve fine details of the object. One way to measure an optical system’s performance is through a parameter referred to as modulation transfer function (MTF). MTF is a measure of the optical system’s ability to transfer contrast at different spatial frequencies from the object to the image. It essentially describes how well detail from the object can be reproduced at the image plane. MTF is usually plotted as a curve that shows how the contrast of the image changes with the spatial frequency (e.g., measured in line pairs or “cycles” per millimeter, c / mm).

[0024] Optical systems may be optimized for a particular object distance. In systems based on refractive optics, altering the optical system to achieve a different object distance is not straightforward and may adversely affect performance of the system,requiring re-design. For instance, it may be necessary to change the lens components and / or arrangement, which can take substantial time and cost.

[0025] In contrast, for optical systems based on flat lenses such as MOE lenses, diffractive optical element (DOE) lenses, and / or gradient refractive index (GRIN) lenses, the inventors of the present subject matter have discovered that the object distance of the optical system can be adjusted, in certain implementations, without requiring significant re-design and without a degradation in performance. Such modifications can be obtained by varying a so-called adjustment thickness of the optical system (e.g., a camera module), where the adjustment thickness is based on a thickness of one or more optical components within the optical system. As explained herein, such optical components may include, but are not limited to, one or more bonding layers and / or one or more spacer layers. By varying the thickness of these components, the adjustment thickness of the optical system is varied, which in turn modifies the object distance of the optical system without a substantial change of performance.

[0026] FIG. 1 shows an example of an optical system according to the present disclosure. In the particular example of FIG. 1 , the optical system includes a meta lens camera module 100. However, the optical systems disclosed herein are not limited to camera modules and can include other optical systems, such as, e.g., microscope modules, barcode readers, among other systems, and any description herein of the camera module 100 may also apply to those other systems. The optical systems can be standalone or can form part of larger systems such as, e.g., augmented reality (AR) systems, virtual reality (VR) systems, mixed reality (MR) systems. The optical systems disclosed herein can be included in eyeglasses, mirrors (e.g., rearview mirrors), or windows (e.g., windshields).

[0027] As shown in FIG. 1, the meta lens camera module 100 may be arranged into multiple sections. These sections include an optical stack 102, a camera module spacer section 104 (also referred to simply as a spacer section), and an image sensor section 106. For the purposes of this disclosure, the optical stack 102 may be understood to be toward the “front” of the camera module 100, where light is received into the camera module100, and the image sensor section 106 may be understood to be toward the “rear” of the camera module 100.

[0028] The optical stack section 102 includes a first MOE substrate 108, a second MOE substrate 110, and an adhesive 112 that bonds the first MOE substrate 108 to the second MOE substrate 110. The first MOE substrate 108 is optically transparent and can be composed of, e.g., glass. In the context of the present application, optically transparent indicates that the material is optically transparent for a specified operational wavelength (e.g., in the infra-red, UV, or visible part of the spectrum). The first MOE substrate 108 can include an MOE 113 on a first surface of the substrate 108. Though shown as being formed on a front surface of substrate 108, the MOE 113 can alternatively be formed on an opposite or rear surface of the substrate 108. In some implementations, a first MOE is formed on the front surface of the substrate 108, and a second MOE is formed on the rear surface of the substrate 108. The MOE 113 may be encapsulated (e.g., embedded or buried) by an encapsulant layer 111, which can be composed, e.g., of optically transparent material such as glass or a polymer. The material for the encapsulant layer 111 should be substantially index matched optically to the substrate 108. The second MOE substrate 110 is also optically transparent and can be composed of, e.g., glass. The second MOE substrate 110 can include another MOE 117. The MOE 117 can be formed on a first (e.g., rear) surface of the MOE substrate 110, a second (e.g., front) surface of the MOE, or on both a first and second surface of the MOE substrate 110. The adhesive 112 that bonds the first MOE substrate 108 to the second MOE substrate 110 is preferably optically transparent and index matched to each of the first MOE substrate 108 and the second MOE substrate 110. In some implementations, the adhesive 112 can serve as an encapsulant for an MOE formed on the first and / or second MOE substrates.

[0029] In some implementations, the optical stack section 102 includes an antireflection coating (ARC) layer 109 applied to the encapsulation layer 111. In some implementations, the optical stack section 102 further includes a patterned layer 107 on the encapsulation layer 111 or on the ARC layer 109. The patterned layer 107 can definean aperture stope 101, and may be formed from, e.g., black chrome or black resist. Alternatively or in addition, the optical stack section 102 can include a second aperture stop 123 located between the first MOE substrate 108 and the second MOE substrate 110. The aperture stop 123 can be defined by a patterned layer 115 that, similar to layer 107, can be formed, e.g., from black chrome or black resist. In general, the optical stack section 102 has no air gaps between elements of the stack 102.

[0030] The optical stack section 102 can be affixed to the spacer section 104. The spacer section 104 can include, e.g., a spacer layer 116. In some implementations, the spacer layer 116 is a substrate that is optically transparent and is composed of, e.g., glass. In some implementations, the spacer layer 116 is an optical filter (e.g., a bandpass filter or an angle-of incidence filter). The spacer layer 116 may be affixed to the optical stack section 102 through an adhesive layer 114 (e.g., bonding glue). The spacer layer 116 can further be affixed to the image sensor section 106 through another adhesive layer 118. Each of adhesive layers 114 and 118 are preferably optically transparent and index matched to the spacer layer 116. In general, the spacer section 104 has no air gaps between elements of the section 104 or between section 104 and stack 102 and image sensor section 106. However, in some implementations the spacer section 104 incorporates a spacer with a central hole where a central axis of the hole is aligned with the optical axis of the system 100 and filled with air or vacuum.

[0031] The image sensor section 106 includes a support substrate 122 on which an image sensor 126 is formed. The support substrate may include, but is not limited to, a silicon chip or a printed circuit board (PCB) that has external electrical connections (e.g., a ball grid array) 124 on its rear surface. The image sensor 126 can include, e.g., an array of pixels, each including light sensitive elements, e.g., silicon photodiodes. In some implementations, the image sensor section 106 further includes a cover glass 120. The cover glass 120 can be provided over the image sensor 126 and can be attached, for example, to the support substrate 122 by a spacer 121. The spacer 121 may be formed, e.g., from a polymer, such as a resist. In the illustrated example, the front side of the cover glass 120 is attached to a rear side of the spacer section 104 through adhesive 118.As explained herein, the various optical elements and layers of the camera module 100 are substantially index matched optically to one another. That is, preferably the respective refractive indices of the various optical elements and layers (e.g., the substrates, encapsulants and bonding glues) do not deviate from one another by more than 0.2 in refractive index.

[0032] As illustrated in FIG. 1, there are no air gaps between the various optical elements and layers in the optical stack section 102 or the spacer section 104. Such an arrangement can help reduce or eliminate unwanted reflections that might otherwise occur, for example, at air / lens interfaces.

[0033] Various implementations may include additional and / or different elements in the module 100. For example, some implementations include multiple MOEs on respective substrates. In some implementations, the optical stack section 102 includes a single substrate with MOEs on one or more surfaces. In some implementations, the optical stack section 102 includes more than two substrates with MOEs on one or more surfaces of the substrates. In some implementations, the location of the apertures may differ from the example of FIG. 1. The aperture stop may be on the same substrate as an MOE or on a separate substrate. Further, in some implementations, the location of the optical filter in the stack may differ from that of FIG. 1. The number of spacer layers (e.g., filters) within the spacer section 104 also may differ (e.g., two or more).

[0034] In some implementations, the camera module 100 is modular such that the different sections are produced separately for later fixing to one another to form a full camera module. For instance, in some cases, the optical stack section 102 is formed separately from the spacer section 104, which may be formed separately from the image sensor section 106.

[0035] In certain implementations, the optical stack section 102 may be designed for a particular focal distance. Nonetheless, it may be possible to adjust the object distance of the module by altering the “adjustment thickness” of the spacer section 104. The adjustment thickness of the spacer section may be understood to be the combined thickness of the different optical components and layers of the spacer section 104. Byvarying the thickness of these components, the adjustment thickness of the optical system is varied, which in turn modifies the object distance of the optical system without a substantial change performance. That is to say, the adjustment thickness can be used to refocus the optical system to obtain a sharp image at different object distances.

[0036] FIGS. 2A and 2B illustrate a generalized example of how the object distance varies with the adjustment thickness. Each of FIG. 2A and FIG. 2B illustrates an example of a camera module, such as the camera module 100 shown in FIG. 1. Each of the camera modules 200, 250 includes an optical stack section 102, a spacer section 104, and an image sensor section 106. The optical stack sections 102 and image sensor sections 106 of each module 200, 250 are the same. That is, they include the same components where each component has the same thickness and is arranged in the same position in both modules 200, 250. Like module 100, each spacer section 104 includes a spacer layer 216 and adhesive layers 214, 218 on either side of the spacer layer 216. However, the spacer section 104 of module 200 has an overall thickness (e.g., an adjustment thickness) that is greater than an overall thickness of the spacer section 104 of module 250. As shown in FIG. 2A, the greater thickness is due to a thicker adhesive layer 218 of module 200. The larger adjustment thickness associated with module 200 in turn leads to an object distance 201 that is less than an object distance 203 for module 250, which has a thinner adjustment thickness. Accordingly, a large range of object distances can be achieved by changing only the adjustment thickness of the camera module.

[0037] Although the difference in adjustment thickness is shown as being due to a difference in the thickness of the single adhesive layer 218 between the two modules, the adjustment thickness may be modified in various ways. For example, the adjustment thickness can alternatively or additionally be varied by changing the thickness of the spacer layer 216 and / or of the other adhesive layer 214. In some implementations, the adjustment thickness can be varied by changing the thickness of other components within the optical module, such as by changing the thickness of adhesive layers or the cover glass in the image sensor section 106.

[0038] FIGS. 3 A and 3B illustrate examples of camera modules which are fabricated with varying spacer sections 104. Each of FIG. 3 A and 3B illustrates an example of a camera module, such as the camera module 100 shown in FIG. 1. The spacer section 104 ranges from 100 pm to 2000 pm. As explained, the change in adjustment thickness can be achieved by varying a thickness of one or more components of the spacer section 104. For instance, the spacer sections 104 shown in FIGS. 3 A and 3B include a first bonding layer 302, a second bonding layer 306 and a spacer layer 304. The spacer layer 304 may include, e.g., a bandpass filter. The different adjustment thickness shown in FIG. 3B can be achieved by increasing the thickness of spacer layer 304 and decreasing a thickness of bonding layer 306.

[0039] In some implementations, varying the thickness of the spacer layer and varying the thickness of the first and / or second adhesive layers can result in different thickness of the spacer section of the camera module 100. This variation in the thickness of the adjustment thickness of the spacer section of the camera module will lead to an adjustment in the optimum object distance and depth of field of the camera module 100.

[0040] Despite the change in adjustment thickness, and corresponding change in object distance for the modules, the performance of the modules may not substantially change. Characterization of the modules’ optical performances may be determined by looking at the modulation transfer function (MTF) for the modules. For instance, in some implementations, a change in the object distance may correspond to a change in the adjustment thickness of the module, without the MTF falling below a predetermined value.

[0041] In some implementations, the adjustment thickness of the spacer section can be designed to improve the performance of the camera module over a long object distance. As an example, FIG. 4A is a bar plot that demonstrates a simulated optical performance of a meta lens camera module having the configuration shown in FIG. 1. The plot shown in FIG. 4A illustrates MTF (vertical axis) at half the Nyquist frequency as measured at the on-axis field point and at an off-axis field point of the camera module. The MTF is simulated for different adjustment thicknesses of the spacer section (e.g.,spacer section 104), where each adjustment thickness is selected to provide an optimal performance for a corresponding object distance. The corresponding object distances are listed along the horizontal axis of the plot. By changing the adjustment thickness of the camera module, the module is effectively “refocused” for specific object distances.

[0042] As can be seen from the plot of FIG. 4A, despite changing the adjustment thickness, the performance of the camera module (reflected by the MTF values both on- axis and off-axis) remains consistent with relatively high MTF values close to 0.6. Accordingly, only the adjustment thickness need be changed to maintain high performance for the camera module without more substantial camera redesign. In other words, the camera module design allows one to change an adjustment thickness for refocusing the camera module, without a substantial loss in performance.

[0043] FIGS. 4B-4D are plots illustrating simulated optical performances of meta lens camera modules having the configuration shown in FIG. 1. Unlike FIG. 4A, the plots of FIGS. 4B-4D reflect simulated MTF values for camera modules with fixed adjustment thicknesses. That is, FIGS. 4B-4D are plots illustrating simulated MTF values at one quarter of the Nyquist frequency for an adjustment thickness that corresponds to a particular optimized object distance. The depth of field (DOF) as a function of the MTF is also illustrated for each different configuration. In contrast to FIG. 4A, the object distances along the horizontal axis of FIGS. 4B-4D do not correspond different adjustment thicknesses of the camera module, as that value is fixed for each different plot. Rather, the horizontal axis values reflect the position of where an actual object may be located relative to a camera module that is designed to operate at a single optimal object distance.

[0044] For instance, FIG. 4B is a plot of on-axis and off-axis MTF values at one quarter of the Nyquists frequency for a camera module where the adjustment thickness of the spacer section (e.g., section 104) of the camera module is selected so that the camera module has an optimal object distance corresponding to approximately 18 mm. FIG. 4C is a plot of on-axis and off-axis MTF values for a camera module where the adjustment thickness of the spacer section (e.g., 104) of the camera module is selected so that thecamera module has an optimal object distance of approximately 50 mm. FIG. 4D is a plot of on-axis and off-axis MTF values for a camera module where the adjustment thickness of the spacer section (e.g., 104) of the camera module is selected so that the camera module has an optimal object distance of approximately 10 mm.

[0045] As explained herein, for refractive based optical systems, a longer object distance results in a greater depth of field, but it can also lead to a decrease in the ability of the optical system to capture fine details as effectively. Conversely, for those systems, a shorter object distance will have a shallower DOF, but potentially perform better within that range to resolve fine details of the object. However, as shown in the simulation results shown in FIGS. 4B-4D, it can be seen that performance of MOE-based optical systems, such as those disclosed herein, may be maintained at relatively high values despite longer object distances. For instance, as shown in FIG. 4B, for a camera module designed for an optimal object distance of about 18 mm, the module achieves MTF values of approximately 0.8 over a depth of field of about 15 mm. As shown in FIG. 4C, for a camera module designed for an optimal object distance that is substantially larger (about 50 mm), the camera module maintains MTF values near 0.8 over a depth of field between 25 mm and infinity. These values are comparable to the MTF values obtained for a camera module designed with a much shorter optimal object distance of approximately 10 mm, as shown in FIG. 4D.

[0046] FIGs. 5A-5D are schematics that show an example process of forming an optical stack, such as the optical stack section 102 shown in FIG. 1. As illustrated in FIG. 5A, a first substrate 502 on to a second substrate 504 are first provided. The first substrate 502 and the second substrate 504 may be formed, e.g., of glass, polymer or silicon, among other materials. As described herein, the substrates 502, 504 may be optically transparent to one or more operating wavelengths of the to-be-formed optical module. The first substrate 502 may be a first MOE substrate that includes a plurality of nanostructures on a first surface of the first substrate 502. The squares illustrated on the substrate 502 may represent, e.g., the areas corresponding to different camera modules, respectively. The second substrate 504 may be a second MOE substrate that includes aplurality of nanostructures on a first surface of the second substrate 504. The squares illustrated on the substrate 504 may represent, e.g., the areas corresponding to different camera modules, respectively. The first substrate 502 and the second substrate 504 may each be optically transparent.

[0047] A layer of bonding adhesive is deposited directly to at least one of the first and second substrates 502, 504. For example, in some implementations, the bonding adhesive is applied directly to the first surface of the second substrate 504. This surface may include the plurality of nanostructures or may be opposite to a surface of substrate 504 that includes the plurality of nanostructures. Alternatively, or in addition, the bonding adhesive may be applied to the first surface of the substrate 502. This surface may include the plurality of nanostructures or may be opposite to a surface of substrate 502 that includes the plurality of nanostructures. As an example, the bonding adhesive may be applied as a uniform layer on substrate 502 and / or substrate 504 by a spin coating method.

[0048] Each of the first substrate 502 and the second substrate 504 may include one or more alignment marks which are used to appropriately align the substrates during bonding. As shown in FIG. 5B, when the two substrates are appropriately aligned, the first substrate 502 is affixed to the second substrate 504 via the bonding adhesive to form the optical stack 506.

[0049] As illustrated in FIG. 5C, the bonding adhesive between the first substrate 502 and the second substrate 504 of the optical stack 506 then is cured. The bonding adhesive may be a glue that is UV-curable, and the meta lens stack is exposed to UV light to cure the bonding adhesive layer. In some implementations, the bonding adhesive layer may be thermally curable glue. In these implementations, the first bonding adhesive layer is cured when the optical stack is exposed to heat.

[0050] As illustrated in FIG. 5D, the optical stack then is diced into individual modules, the location of which is represented by the squares in the figure. In some implementations, dicing may involve using a diamond-tipped blade to cut the layers of wafer substrates into individual layered modules. For example, a high-speed, diamond-tipped blade can be used to cut the layers of wafers along one or more predefined lines. In some implementations, dicing involves using a laser to cut the layers of wafer substrates into individual layered modules. For example, a high precision laser can be used to ablate the layers of wafers along one or more defined lines.

[0051] The optical stack formed by the process shown in FIGS. 5A-5D may form a module that can be combined with a spacer section and an image sensor section, as described herein, to form a camera module. In some implementations, the spacer section and image sensor section may be formed as separate modules (e.g., in separate fabrication processes) that are combinable with the optical stack module. In some implementations the optical stack section and the spacer section are bonded on wafer level as part of a single fabrication process, rather than as separate modules that are then combined. In some implementations, the spacer section and the image sensor section are formed together as a single module that, in turn, is combined with the optical stack module to form the camera module. In some implementations, the optical stack section, the spacer section, and the image sensor section are formed together to provide the camera module as part of a single fabrication process, rather than as separate modules that are then combined.

[0052] FIGS. 6A-6B show an example method of fabricating an optical system that includes a meta lens camera module according to the present disclosure. As shown in FIG. 6 A, the method of fabrication includes providing an optical stack 506, such as the optical stack section 102 of module 100, that includes one or more MOEs. The optical stack 506 may be formed using the process described in FIGS. 5A-5D. Although shown as a wafer stack, the optical stack 506 may be in the form of individual modules that have been diced, and that can be sold separately for combining with other components to form the camera module.

[0053] The optical stack 506 may be affixed (601) to a spacer wafer 602. The spacer wafer 602 can include, e.g., a substrate that is optically transparent to the wavelengths to be imaged by the camera module. For example, the spacer wafer 602 may be a glass or polymer substrate. In some implementations, the spacer wafer 602 may be configured tofunction as an optical filter, such as a bandpass filter, which can be implemented through, as an example, using an optical coating on one or both sides of the substrate. Affixing the optical stack 506 to the spacer wafer 602 may include applying an adhesive to a bottom surface of the stack 506 and / or to a top surface of the spacer wafer 602, contacting the optical stack 506 to the spacer wafer 602, and then curing the adhesive. The adhesive may be applied using, e.g., a spin-in technique or drop-dispensing technique. The adhesive may be cured using, e.g., a UV-based and / or thermally based process. Affixing the optical stack 506 to the spacer wafer 602 forms a combined optical / spacer stack 604.

[0054] The optical / spacer stack 604 then is affixed (603) to an image sensor wafer 606, as shown in FIG. 6B. The image sensor wafer 606 includes multiple image sensors 608 formed in or on its surface. The image sensor wafer 606 may be a silicon substate in which the image sensors have been fabricated. Each image sensor 608 may include one or more pixels in which an image sensing circuit, such as a photodetector, is provided. In some cases, the image sensor wafer 606 includes a separate cover glass positioned over the image sensors 608. Although shown as wafers, each of the optical / spacer stack 604 and the image sensor wafer 606 may be pre-diced into individual chips or modules.

[0055] Affixing the optical / spacer stack 604 to the image sensor wafer 606 may include applying an adhesive to a bottom surface of the stack 604 and / or to a top surface of the image sensor wafer 606, contacting the optical / spacer stack 604 to the image sensor wafer 606, and then curing the adhesive. The adhesive may be applied using, e.g., a spin-in technique or drop-dispensing technique. The adhesive may be cured using, e.g., a UV-based and / or thermally based process. Affixing the optical / spacer stack 604 to the image sensor wafer 606 forms a combined camera module stack 610. The camera module stack 610 then may be diced to form individual camera modules.

[0056] The thickness of the adhesives used to affix the optical stack wafer to the spacer wafer and to affix the optical / spacer stack wafer to the image sensor wafer, and the thickness of the spacer wafer together may be defined to set the adjustment thickness of the resulting camera module. The thickness of the adhesives may be controlled in the stacking process or in a controlled pick-and-place process. If the adhesives are spun on,e.g., as in a wafer-based process, the thickness of the adhesives may be controlled by adjusting the spin speed and / or time.

[0057] As mentioned, the bonding adhesives may be a bonding glue that have refractive indices that match refractive indices of the one or more meta lenses, spacers, and / or cover glass used in the optical system. For example, the refractive index of the bonding adhesives may be between 1.3 and 1.7. In some implementations, the refractive indices of the bonding adhesives deviate from the refractive index of the other components to which they are index matched by less than 0.2.

[0058] A number of implementations of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other implementations are within the scope of the following claims.

Claims

WHAT IS CLAIMED IS:

1. A method comprising: providing an optical stack, wherein the optical stack comprises a first meta lens, a second meta lens, and a first bonding layer that bonds the first meta lens to the second meta lens; attaching a camera module spacer section to a bottom side of the optical stack to form at least a portion of a camera module, wherein the camera module spacer section comprises a spacer layer, and wherein the camera module spacer section is configured such that, when the camera module spacer section is attached to the optical stack, an object distance of the camera module is based on an adjustment length of the camera module spacer section.

2. The method of claim 1, wherein the camera module spacer section comprises a second bonding layer in contact with a top side of the spacer layer and a third bonding layer in contact with a bottom side of the spacer layer, and wherein the adjustment length of the camera module spacer section is based on a thickness of the second bonding layer, a thickness of the spacer layer, and a thickness of the third bonding layer.

3. The method of claim 2, wherein attaching the camera module spacer layer to the bottom side of the optical stack comprises bonding the optical stack to the spacer layer using the second bonding layer.

4. The method of any of claims 2-3, comprising bonding the camera module spacer layer to a camera module image sensor section using the third bonding layer.

5. The method of claim 4, wherein the camera module image sensor section comprises an image sensor, and the camera module spacer layer is bonded directly to the image sensor using the third bonding layer.

6. The method of claim 4, wherein the camera module image sensor section comprises an image sensor and a cover glass positioned over the image sensor, and the camera module spacer layer is bonded directly to the cover glass using the third bonding layer.

7. The method of any of claims 1 -6, wherein the spacer layer comprises an optical filter.

8. The method of claim 7, wherein the optical filter comprises a bandpass filter.

9. The method of any of claims 1-8, wherein providing the optical stack comprises: providing a first wafer comprising the first meta lens; forming the first bonding layer on the first wafer; providing a second wafer comprising the second meta lens on the first bonding layer to form a wafer stack; curing the first bonding layer; and singulating the wafer stack to provide optical stack.

10. The method of any of claims 1-9, wherein the optical stack comprises an aperture layer between the first meta lens and the second meta lens.

11. The method of any of claims 1 -9, wherein the optical stack comprises an aperture layer on a top side of the first meta lens, wherein the first bonding layer is on a bottom side of the first meta lens.

12. The method of any of claims 1-11, wherein a top side of the first meta lens includes a first set of meta structures.

13. The method of any of claims 1-12, wherein a bottom side of the second meta lens includes a second set of meta structures.

14. The method of any of claims 1-13, wherein providing the optical stack comprises encapsulating the top side of the optical stack in a first encapsulation layer.

15. The method of any of claims 1-14, wherein providing the optical stack comprises encapsulating the bottom side of the optical stack in a second encapsulation layer.

16. The method of any of claims 1-15, wherein the second bonding layer is index matched to the second meta lens and to the spacer layer.

17. The method of any of claims 1-16, wherein the third bonding layer is index matched to the spacer layer.

18. The method of any of claims 1-17, wherein each of the second bonding layer and the third bonding layer has a refractive index in the range of 1.3 to 1.7.

19. The method of any of claims 1-18, wherein the spacer layer comprises a glass spacer.

20. The method of any of claims 1-19, wherein providing the optical stack comprises forming an anti-reflection coating on a top side of the first meta lens.

21. A camera module spacer section comprising: a spacer layer; a first bonding layer on a top side of the spacer layer; a second bonding layer on a bottom side of the spacer layer, wherein an adjustment thickness of the camera module spacer section is configured such that, when the camera module spacer section is affixed to a meta optical stack in a camera module,the camera module comprises a predetermined object distance that is based on the adjustment thickness of the camera module spacer section.

22. The camera module spacer section of claim 21, wherein the spacer layer comprises an optical filter.

23. The camera module spacer section of claim 22, wherein the optical filter comprises a bandpass filter.

24. The camera module spacer section of any of claims 21-23, wherein each of the first bonding layer and the second bonding layer is index matched to the spacer layer.

25. The camera module spacer section of any of claims 21-24, wherein a refractive index of each of the first bonding layer and the second bonding layer is between 1.3 and 1.7.

26. A meta lens camera module comprising: an optical stack, wherein the optical stack comprises a first meta lens, a second meta lens, and a first bonding layer that bonds the first meta lens to the second meta lens; a camera module spacer section attached to a bottom side of the optical stack; and an image sensor section attached to a bottom side of the camera module spacer section, wherein the camera module spacer section comprises a spacer layer, and wherein the camera module spacer section is configured such that an object distance of the camera module is based on an adjustment length of the camera module spacer section.

27. The meta lens camera module of claim 26, wherein the camera module spacer section comprises a second bonding layer in contact with a top side of the spacer layer 1and a third bonding layer in contact with a bottom side of the spacer layer, and wherein the adjustment length of the camera module spacer section is based on a thickness of the second bonding layer, a thickness of the spacer layer, and a thickness of the third bonding layer.

28. The meta lens camera module of any of claims 26-27, wherein the camera module image sensor section comprises an image sensor, and the camera module spacer layer is bonded directly to the image sensor using the third bonding layer.

29. The meta lens camera module of any of claims 26-27, wherein the camera module image sensor section comprises an image sensor and a cover glass positioned over the image sensor, and the camera module spacer layer is bonded directly to the cover glass using the third bonding layer.

30. The meta lens camera module of any of claims 26-29, wherein the spacer layer comprises an optical filter.

31. The meta lens camera module of claim 30, wherein the optical filter comprises a bandpass filter.

32. The meta lens camera module of any of claims 26-31, wherein the optical stack comprises an aperture layer between the first meta lens and the second meta lens.

33. The meta lens camera module of any of claims 26-31, wherein the optical stack comprises an aperture layer on a top side of the first meta lens, wherein the first bonding layer is on a bottom side of the first meta lens.

34. The meta lens camera module of any of claims 26-33, wherein a top side of the first meta lens includes a first set of meta structures.2335. The meta lens camera module of any of claims 26-34, wherein a bottom side of the second meta lens includes a second set of meta structures.

36. The meta lens camera module of any of claims 26-35, wherein the optical stack comprises a first encapsulation layer on a top side of the optical stack.

37. The meta lens camera module of any of claims 26-36, wherein the optical stack comprises a second encapsulation layer on a bottom side of the optical stack.

38. The meta lens camera module of any of claims 26-37, wherein the second bonding layer is index matched to the second meta lens and to the spacer layer.

39. The meta lens camera module of any of claims 26-38, wherein the third bonding layer is index matched to the spacer layer.

40. The meta lens camera module of any of claims 26-39, wherein each of the second bonding layer and the third bonding layer has a refractive index in the range of 1.3 to 1.7.

41. The meta lens camera module of any of claims 26-40, wherein the spacer layer comprises a glass spacer.

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