Patent Description:
An optical module can include, for example, an image sensor module, a light projector module, etc. An image sensor module typically includes an image sensor, which can include one or more image sensor chips, and one or more lenses. The one or more lenses can gather incident light and focus the light towards a light receiving surface of the image sensor. The image sensor includes light sensing elements (e.g., photodiodes) that can receive the incident light that passes through the one or more lenses via the light receiving surface, and convert the received light to electrical signals. The electrical signals can represent, for example, intensities of light from a scene. Based on the electrical signals, an image processor can generate an image of the scene. On the other hand, a light projector module may include a light source and one or more lens. The light source can emit light, which can pass through the lens and propagate to a far field. The assembly of the one or more lenses with the image sensor /light source can affect various properties of the optical module.

Patent application nos. <CIT>, <CIT>, <CIT>, and <CIT> are useful for understanding the present invention.

The disclosure relates generally to an optical module, and more specifically to an optical module comprising one or more lenses.

According to the present invention there is provided an apparatus in accordance with claim <NUM>.

In some aspects, each of the one or more polymer layers is made of a cyclic olefin copolymer (COC) material.

In some aspects, each of the one or more polymer layers is made of at least one of: a polycarbonate material, or a polyester material.

In some aspects, each of the one or more polymer layers is made from one or more injection molding processes.

In some aspects, a footprint of the lens assembly is substantially identical to a footprint of the image sensor.

In some aspects, the bonding layer is distributed around a perimeter of the image sensor to surround a light receiving surface of the image sensor facing the lens portions of the one or more polymer layers.

In some aspects, the lens assembly further comprises a light outputting surface. The bonding layer is optionally distributed over a light receiving surface of the image sensor to bond the light receiving surface of the image sensor with the light outputting surface of the lens assembly.

The extension portion of a pair of polymer layers of the plurality of polymer layers are optionally bonded via an adhesive.

The lens assembly optionally further includes a plurality of spacers comprising a first spacer, the first spacer being sandwiched between the extension portion of a pair of polymer layers of the plurality of polymer layers.

In some aspects, the first spacer is bonded to the extension portion of the pair of polymer layers.

In some aspects, the plurality of spacers are made of an opaque material comprising one of: a polymer, or a metal.

The lens portion of a pair of polymer layers of the plurality of polymer layers are optionally bonded via an adhesive.

In some aspects, the apparatus further comprises an opaque coating on exterior surfaces of the lens assembly, wherein the exterior surfaces do not face the image sensor.

In some aspects, the image sensor comprises a substantially flat substrate and an integrated circuit die. The light sensed by the image sensor passes through the substrate. The lens assembly is bonded to the substrate.

In some aspects, the apparatus further comprises a printed circuit board (PCB). The image sensor die is conductively bonded to the PCB.

In some aspects, the image sensor is conductively bonded with the PCB via solder balls by a reflow process.

In some aspects, a temperature of the reflow process is higher than a melting temperature of the one or more polymer layers.

In some aspects, the bonding layer is formed by a curing process at a temperature lower than a temperature of the reflow process to bond the image sensor to the lens assembly.

In some aspects, the PCB provides mechanical support for the image sensor. The PCB, the image sensor, and the bonding layer provide mechanical support for the lens assembly.

In some aspects, the bonding layer is formed by a curing processing involving an ultraviolet light to bond the image sensor to the lens assembly.

In some aspects, the apparatus further comprises an opaque lens holder to hold the one or more polymer layers. The opaque lens holder comprises a housing and a retainer. The housing is configured to hold the one or more polymer layers. The retainer is configured to retain the one or more polymer layers within the housing. The image sensor is bonded to either the housing or the retainer.

In some aspects, at least a part of the retainer is sandwiched between the housing and the image sensor.

In some aspects, the housing includes a first bottom surface surrounding a bottom opening of the housing facing the retainer and bonded with a top surface of the retainer via a first adhesive.

In some aspects, the retainer includes a middle surface to mount a filter, and a second bottom surface to bond with the image sensor via a second adhesive.

In some aspects, the first bottom surface of the housing comprises a first uneven surface. The top surface of the retainer comprises a second uneven surface. The first uneven surface and the second uneven surface are complimentary to each other and are bonded with each other via the first adhesive.

In some aspects, the housing comprises a barrel and a base portion. The base portion includes the first uneven surface to bond with the second uneven surface of the retainer.

In some aspects, the housing and the retainer are made of a polymer material using an injection molding process.

In some aspects, the lens holder holds the one or more lenses at one or more first locations and sets one or more first orientations of the one or more lenses.

In some aspects, the filter comprises an array of filters.

In some aspects, the image sensor comprises an image sensor die, and the second bottom surface is bonded with the image sensor die via the second adhesive.

In some aspects, a length and a width of a footprint of the apparatus on a PCB is less than <NUM> millimeter (mm). A narrowest width of the second bottom surface of the retainer is longer than <NUM>.

Optionally, a method comprises: forming a lens assembly comprising one or more lenses; performing a reflow process to conductively bond an image sensor onto a printed circuit board (PCB) to form an image sensor stack; forming a layer of adhesive on at least one of the image sensor stack or the lens assembly; connecting the lens assembly and the image sensor stack via the layer of adhesive; moving at least one of the lens assembly or the image sensor stack to align the image sensor with the one or more lenses; and with the image sensor stack and the lens assembly at their respective aligned positions and orientations, curing the layer of adhesive to bond the image sensor stack with the lens assembly.

In some aspects, forming the lens assembly comprises fabricating each of the one or more lenses using a mold-injection process.

In some aspects, forming the lens assembly comprises enclosing the one or more lenses in an opaque lens holder to form the lens assembly.

In some aspects, forming the lens assembly comprises loading the one or more lenses into a housing and attaching a retainer on a bottom surface of the housing to prevent the one or more lenses from falling out of the housing.

In some aspects, the one or more lenses comprise a plurality of lenses. Forming the lens assembly comprises: stacking the plurality of lenses with a plurality of spacers to form a lens stack, wherein each pair of lens of the plurality of lenses is separated by an opaque spacer of the plurality of spacers in the lens stack; and coating four sides of the lens stack with an opaque material.

In some aspects, the method further comprises: fabricating an image sensor die; packaging the image sensor die in a flip-chip package; depositing solder balls on the flip-chip package; and bringing the flip-chip packages having the solder balls into contact with contact pads of the PCB. The reflow process is performed to reflow the solder balls of the flip-chip packages into a liquid state to form conductive bonds with the contact pads.

In some aspects, the method further comprises forming a glass substrate on a light receiving surface of the image sensor die.

In some aspects, the layer of adhesive is formed on a perimeter of the glass substrate.

In some aspects, the lens assembly further comprises a light outputting surface. The layer of adhesive is distributed on a region of glass substrate to bond with the light outputting surface.

In some aspects, moving at least one of the lens assembly or the image sensor stack to align the image sensor with the one or more lenses comprises: controlling the image sensor to generate sensor data of light received by the image sensor via the one or more lenses; determining a degree of alignment between the image sensor and the one or more lenses based on the sensor data; and moving at least one of the lens assembly or the image sensor stack based on the degree of alignment.

In some aspects, curing the layer of adhesive comprises subjecting the layer of adhesive to ultraviolet light.

Illustrative examples are described with reference to the following figures.

The figures depict examples of the present disclosure for purposes of illustration only. One skilled in the art will readily recognize from the following description that alternative examples of the structures and methods illustrated may be employed without departing from the principles, or benefits touted, of this disclosure.

In the appended figures, similar components and/or features may have the same reference label.

An optical module can include, for example, an image sensor module, a light projector module, etc. An image sensor module typically includes an image sensor and one or more lenses. The one or more lenses can gather incident light and focus the light towards a light receiving surface of the image sensor. The image sensor can include an array of pixel cells to generate electrical signals representing a distribution of light intensities received by the image sensor. Based on the electrical signals, an image processor can generate an image of the scene. The image sensor module can be soldered onto a printed circuit board (PCB) which also includes an image processor. The PCB include electrical traces to transmit the electrical signals from the image sensor module to the image sensor, which can generate an image of the scene based on the electrical signals. On the other hand, a light projector module may include a light source and one or more lens. The light source can be soldered onto a PCB and controlled by electrical signals from the PCB to emit light. The light can pass through the lens to become, for example, collimated light beams.

The physical properties of the lens of the optical module can determine the optical properties as well as the performance of the optical module. Specifically, the curvature and refractive index of the lens can determine the focal length of the lens, which can define the field of view of the image sensor module. The field of view, in turn, can determine an area of the scene to be captured by the image sensor module. Moreover, the Abbe number of the lens can determine the variation of refractive index versus wavelength. Further, the birefringence of the lens can determine the variation of the refractive index of the lens with respect to the polarization and propagation direction of the incident light. Both Abbe number and birefringence can control the dispersion of light by the lens and can be determined by the material of the lens. All these optical properties can affect the quality of an image (e.g., amount of information captured, blurriness, distortion) captured by the image sensor module, the dispersion of light produced by the light projector module, etc..

The assembly of the one or more lenses and the image sensor in the image sensor module can also affect the optical properties as well as the performance of the image sensor module. Specifically, the alignment of the image sensor with respect to the lens (e.g., relative orientations, positions) can also affect the reception of the light by the image sensor. For example, the light receiving surface of the image sensor needs to be at the focal point of the lens, and be perpendicular with the optical axis, so that different points of the light receiving surface can receive the focused light to enable the image sensor to have the field of view defined by the focal length of the one or more lenses. But if the light receiving surface of the image sensor is not at the focal point of the one or more lenses and/or not perpendicular to the optical axis, at least some locations of the light receiving surface may receive divergent/dispersed incident light, and the resulting image may become blurred and distorted. The performance of the light projector module can also be affected in a similar way by the alignment between the light source and the lens.

Moreover, the assembly of the lens with the image sensor in the image sensor module can also affect the footprint of the image sensor module. For example, a housing may be used to hold the lens and the image sensor together at their respective aligned positions and orientations. But if the housing surrounds the image sensor, the housing can add to the footprint of the image sensor module such that the image sensor module occupies a larger area on the PCB than the image sensor. The increased footprint can be undesirable especially for integrating the image sensor in a mobile device, such as a wearable device, a smart glass, etc., where space is very limited. The same is true for integrating a light projector in a mobile device.

This disclosure relates to an image sensor module that can provide improved optical properties as well as reduced form factor, as well as a method of fabricating the image sensor module. The image sensor module includes a lens assembly including one or more lenses, and an image sensor. Each of the plurality of lens can be held by a housing, which can be in the form of a barrel. The lenses can be separated by spacers to form a lens stack. The entire lens stack (including the housing, the spacers, etc.) can be positioned on the image sensor, with the lens holder and/or spacers defining the position of each lens in the lens stack with respect to the light receiving surface of the image sensor. The lens holder and the spacers can provide mechanical support and rigidity to prevent the deformation of lens stack, which can degrade the overall optical properties of the image sensor module, while not adding to the footprint of the image sensor module. The lens assembly can be bonded to a light receiving surface of the image sensor via a layer of adhesive, whereas the image sensor can be soldered onto a PCB. The light receiving surface can be on a glass substrate placed on the image sensor. As the entirety of the lens assembly is positioned on the image sensor, the footprint of the image sensor module (on the PCB) can be reduced to become substantially identical to the footprint of the image sensor.

In some examples, the one or more lenses of the lens assembly can be made of a polymer material (e.g., Cyclo Olefin Polymer) and can be fabricated using high precision processes such as injection molding. The high precision fabrication of the one or more lenses provide improved control of the physical properties (e.g., curvature, shape, size, etc.) of the lens, whereas the polymer material can reduce the Abbe number and the birefringence of the lens, both of which can provide improved control of the optical properties of the lens and the overall performance of the image sensor module.

In some examples, the optical elements of an image sensor module may include, in addition to the lenses stack, a filter. The filter can include a filter array to select different frequency components of the light to be detected by the image sensor, or a single frequency component of the light to be detected by all pixel cells. The image sensor includes light sensing elements (e.g., photodiodes) that can receive the different frequency components of the light selected by the filter array via the light receiving surface, and convert the frequency components to electrical signals. The electrical signals can represent, for example, intensities of the different frequency components of light from a scene. Moreover, the filter array can also be part of a projector to select the frequency range of output light, such as an infrared frequency range.

In a case where the image sensor module includes a filter, the image sensor module may include, in additional to the housing, a retainer. Both the housing and the retainer can be made of, for example, a polycarbonate (PC) material, a polymer material (e.g., liquid crystal polymer, LCP) using an injection molding process, etc., and can together form a holder structure. The filter can be mounted in the retainer, while the retainer can be mounted within the housing between the lenses stack and a bottom opening of the housing. Within the housing, the retainer can be positioned away from the bottom opening so that the retainer does not protrude out of the bottom opening. Moreover, the retainer is also pushed against the lenses stack. Such arrangements can provide additional physical support to the lenses stack and prevent the lenses stack from falling out of the bottom opening. A bottom surface of the housing around the bottom opening can be bonded (e.g., via an adhesive followed by ultraviolet light curing) onto the light receiving surface of the image sensor, to set the alignments and orientations of the lenses and the filter with respect to the image sensor. Light can then enter the housing via the top opening and become focused by the lenses stack and filtered by the filter. The filtered light can then exit out of the bottom opening and enter the image sensor.

With examples of the present disclosure, the footprint of the image sensor module can be reduced as the entirety of the lens assembly can be positioned on the image sensor. Moreover, the optical properties of the image sensor module can be improved by, for example, including lens that are fabricated using a high precision process (e.g., injection molding) and using materials that provide low birefringence and Abbe numbers. The alignment of the lens with respect to the image sensor can also be improved by the alignment process involving the light sensor operation by the image sensor as the data generated by the image sensor can provide an accurate account of the degree of alignment between the image sensor and the lens assembly.

Although the above arrangements can shrink the footprint of the image sensor module, the mounting of the retainer within the housing can create various issues which can affect the assembly of the image sensor module as well as the optical properties and performance of the image sensor module. Specifically, the bottom surface of the housing provides a very limited area for applying the adhesive, which makes the bonding of the housing to the image sensor difficult. Specifically, the bottom opening can be enlarged to allows more pixel cells to receive light through the lenses and filter, which can improve the imaging resolution. But the bottom surface of the housing, which surrounds the bottom opening and the retainer, adds to the footprint and may need to be shrunk to reduce the footprint of the image sensor module. As a result, the available area for applying the adhesive can be reduced. The reduced bonding area can lead to weaker bonding between the housing and the image sensor. Moreover, due to the reduced bonding area, the amount of adhesive applied, as well as the locations where the adhesive is applied, need to be controlled with very high precision. This is to prevent the adhesive applied to the bottom surface of the housing from spilling into the bottom opening when the housing and the image sensor are brought together. But the requisite precision may become unachievable as the footprint of the image sensor module continues to shrink. The weaker bonding between the housing and the image sensor can introduce variations in the alignments and orientations of the lenses and the filter with respect to the image sensor. Moreover, the adhesive spilled into the bottom opening can obfuscate the filter and/or the pixel cells of the image sensor. All these can degrade the light sensing performance of the image sensor module. In addition, by mounting the retainer within the housing, the bottom surface of the housing and the surface of the retainer add up and increases the footprint of the image sensor module.

In some examples, to further reduce the footprint of the image sensor and to further improve the bonding between the housing and image sensor, the retainer is mounted on a bottom surface of the housing at a bottom opening of the housing, and sandwiched between the housing and the image sensor, such that the housing, the retainer, and the image sensor forms a stack. The retainer includes a first surface to bond with the bottom surface of the housing. The first surface is also stacked against the lenses stack to provide additional physical support to the lenses, and to prevent the lenses stack from falling out of the bottom opening. The retainer further includes a second surface opposite from the first surface. The second surface can be bonded to the light receiving surface of the image sensor via, for example, an adhesive.

With the disclosed techniques in which the housing, the retainer, and the image sensor form a stack. Such arrangements can reduce the surface area surrounding the filter and the footprint of the image sensor module. Moreover, the retainer surface can be made larger to provide a larger area for applying the adhesive for bonding with the image sensor, which can improve the bonding between the retainer and the image sensor and relax the precision requirements for application of adhesive. As the retainer does not surround the lenses stack, unlike the housing, the retainer surface can be increased without a corresponding increase in the footprint of the image sensor module. As a result, the footprint of the image sensor module can be reduced, while the bonding between the image sensor and the holder structure (including the housing and the retainer) can be improved to provide improve control of the alignments and orientations of the lenses and the filter with respect to the image sensor. All of these can further reduce the footprint and improve the performance of the image sensor module.

The image sensor can be bonded to the lens assembly, which may include the housing, the lenses stack, the filter, etc., via a layer of adhesive. The image sensor can be bonded to the housing directly, or to the retainer of the filter, of the lens assembly. Prior to the bonding, the image sensor can be soldered onto the PCB via a reflow process which typically occurs at a high temperature, to prevent the reflow process from deforming the lens in the lens assembly. During the fabrication of the image sensor module, the adhesive can be applied on the lens assembly and/or the image sensor, and the image sensor can be attached to the lens assembly via the adhesive to form the bonding. While the adhesive is still in a liquid state, an alignment process involving an light sensing operation by the image sensor can be performed to adjust the position and/or orientation of the image sensor with respect to the lens assembly. In the alignment process, light can be projected to the lens assembly, and the image sensor can be operated to generate sensor data based on the light that passes through the lens assembly. The sensor data can reflect a degree of alignment (e.g., based on a measurement of blurriness, distortion) between the lens assembly and the image sensor. The position and/or orientation of the image sensor can be adjusted until, for example, a target alignment is achieved. The image sensor can then be fixed at its aligned position/orientation based on curing the adhesive to harden the adhesive. The adhesive can be cured by, for example, ultraviolet light, a thermal process at a temperature lower than the melting point of the one or more lenses, etc., such that the curing process also does not deform the lens. The techniques described above can also be used to form a light projector system with reduced footprint and improved performance.

The disclosed techniques may include or be implemented in conjunction with an artificial reality system. Artificial reality is a form of reality that has been adjusted in some manner before presentation to a user, which may include, e.g., a virtual reality (VR), an augmented reality (AR), a mixed reality (MR), a hybrid reality, or some combination and/or derivatives thereof. Artificial reality content may include completely generated content or generated content combined with captured (e.g., real-world) content. The artificial reality content may include video, audio, haptic feedback, or some combination thereof, any of which may be presented in a single channel or in multiple channels (such as stereo video that produces a three-dimensional effect to the viewer). Additionally, in some examples, artificial reality may also be associated with applications, products, accessories, services, or some combination thereof, that are used to, for example, create content in an artificial reality and/or are otherwise used in (e.g., perform activities in) an artificial reality. The artificial reality system that provides the artificial reality content may be implemented on various platforms, including a head-mounted display (HMD) connected to a host computer system, a standalone HMD, a mobile device or computing system, or any other hardware platform capable of providing artificial reality content to one or more viewers.

<FIG> is a diagram of an example of a near-eye display <NUM>. Near-eye display <NUM> presents media to a user. Examples of media presented by near-eye display <NUM> include one or more images, video, and/or audio. In some examples, audio is presented via an external device (e.g., speakers and/or headphones) that receives audio information from the near-eye display <NUM>, a console, or both, and presents audio data based on the audio information. Near-eye display <NUM> is generally configured to operate as a virtual reality (VR) display. In some examples, near-eye display <NUM> is modified to operate as an augmented reality (AR) display and/or a mixed reality (MR) display.

Near-eye display <NUM> includes a frame <NUM> and a display <NUM>. Frame <NUM> is coupled to one or more optical elements. Display <NUM> is configured for the user to see content presented by near-eye display <NUM>. In some examples, display <NUM> comprises a waveguide display assembly for directing light from one or more images to an eye of the user.

Near-eye display <NUM> further includes image sensor modules 120a, 120b, 120c, and 120d. Each of image sensor modules 120a, 120b, 120c, and 120d may include a pixel array configured to generate image data representing different fields of views along different directions. For example, sensor modules 120a and 120b may be configured to provide image data representing two fields of view towards a direction A along the Z axis, whereas sensor 120c may be configured to provide image data representing a field of view towards a direction B along the X axis, and sensor 120d may be configured to provide image data representing a field of view towards a direction C along the X axis.

In some examples, sensor modules 120a-120d can be configured as input devices to control or influence the display content of the near-eye display <NUM>, to provide an interactive VR/AR/MR experience to a user who wears near-eye display <NUM>. For example, sensor modules 120a-120d can generate physical image data of a physical environment in which the user is located. The physical image data can be provided to a location tracking system to track a location and/or a path of movement of the user in the physical environment. A system can then update the image data provided to display <NUM> based on, for example, the location and orientation of the user, to provide the interactive experience. In some examples, the location tracking system may operate a simultaneous localization and mapping algorithm to track a set of objects in the physical environment and within a view of field of the user as the user moves within the physical environment. The location tracking system can construct and update a map of the physical environment based on the set of objects, and track the location of the user within the map. By providing image data corresponding to multiple fields of views, sensor modules 120a-120d can provide the location tracking system a more holistic view of the physical environment, which can lead to more objects to be included in the construction and updating of the map. With such an arrangement, the accuracy and robustness of tracking a location of the user within the physical environment can be improved.

In some examples, near-eye display <NUM> may further include one or more active illuminators <NUM> to project light into the physical environment. The light projected can be associated with different frequency spectrums (e.g., visible light, infrared light, ultraviolet light, etc.), and can serve various purposes. For example, illuminator <NUM> may project light in a dark environment (or in an environment with low intensity of infrared light, ultraviolet light, etc.) to assist sensor modules 120a-120d in capturing images of different objects within the dark environment to, for example, enable location tracking of the user. Illuminator <NUM> may project certain markers onto the objects within the environment, to assist the location tracking system in identifying the objects for map construction/updating.

In some examples, illuminator <NUM> may also enable stereoscopic imaging. For example, one or more of sensor modules 120a or 120b can include both a first pixel array for visible light sensing and a second pixel array for infrared (IR) light sensing. The first pixel array can be overlaid with a color filter (e.g., a Bayer filter), with each pixel of the first pixel array being configured to measure intensity of light associated with a particular color (e.g., one of red, green or blue colors). The second pixel array (for IR light sensing) can also be overlaid with a filter that allows only IR light through, with each pixel of the second pixel array being configured to measure intensity of IR lights. The pixel arrays can generate a red-green-blue (RGB) image and an IR image of an object, with each pixel of the IR image being mapped to each pixel of the RGB image. Illuminator <NUM> may project a set of IR markers on the object, the images of which can be captured by the IR pixel array. Based on a distribution of the IR markers of the object as shown in the image, the system can estimate a distance of different parts of the object from the IR pixel array, and generate a stereoscopic image of the object based on the distances. Based on the stereoscopic image of the object, the system can determine, for example, a relative position of the object with respect to the user, and can update the image data provided to display <NUM> based on the relative position information to provide the interactive experience.

As discussed above, near-eye display <NUM> may be operated in environments associated with a very wide range of light intensities. For example, near-eye display <NUM> may be operated in an indoor environment or in an outdoor environment, and/or at different times of the day. Near-eye display <NUM> may also operate with or without active illuminator <NUM> being turned on. As a result, image sensor modules 120a-120d may need to have a wide dynamic range to be able to operate properly (e.g., to generate an output that correlates with the intensity of incident light) across a very wide range of light intensities associated with different operating environments for near-eye display <NUM>.

<FIG> is a diagram of another example of near-eye display <NUM>. <FIG> illustrates a side of near-eye display <NUM> that faces the eyeball(s) <NUM> of the user who wears near-eye display <NUM>. As shown in <FIG>, near-eye display <NUM> may further include a plurality of illuminators 140a, 140b, 140c, 140d, 140e, and 140f. Near-eye display <NUM> further includes a plurality of image sensor modules 150a and 150b. Illuminators 140a, 140b, and 140c may emit lights of certain frequency range (e.g., near infrared range (NIR)) towards direction D (which is opposite to direction A of <FIG>). The emitted light may be associated with a certain pattern, and can be reflected by the left eyeball of the user. Sensor module 150a may include a pixel array to receive the reflected light and generate an image of the reflected pattern. Similarly, illuminators 140d, 140e, and 140f may emit NIR lights carrying the pattern. The NIR lights can be reflected by the right eyeball of the user, and may be received by sensor module 150b. Sensor module 150b may also include a pixel array to generate an image of the reflected pattern. Based on the images of the reflected pattern from sensor modules 150a and 150b, the system can determine a gaze point of the user, and update the image data provided to display <NUM> based on the determined gaze point to provide an interactive experience to the user.

As discussed above, to avoid damaging the eyeballs of the user, illuminators 140a, 140b, 140c, 140d, 140e, and 140f are typically configured to output lights of very low intensities. In a case where image sensor modules 150a and 150b comprise the same sensor devices as image sensor modules 120a-120d of <FIG>, the image sensor modules 120a-120d may need to be able to generate an output that correlates with the intensity of incident light when the intensity of the incident light is very low, which may further increase the dynamic range requirement of the image sensor modules.

Moreover, the image sensor modules 120a-120d may need to be able to generate an output at a high speed to track the movements of the eyeballs. For example, a user's eyeball can perform a very rapid movement (e.g., a saccade movement) in which there can be a quick jump from one eyeball position to another. To track the rapid movement of the user's eyeball, image sensor modules 120a-120d need to generate images of the eyeball at high speed. For example, the rate at which the image sensor modules generate an image frame (the frame rate) needs to at least match the speed of movement of the eyeball. The high frame rate requires short total exposure time for all of the pixel cells involved in generating the image frame, as well as high speed for converting the sensor outputs into digital values for image generation. Moreover, as discussed above, the image sensor modules also need to be able to operate at an environment with low light intensity.

<FIG> illustrates a close-up view of near-eye display <NUM>. As shown in <FIG>, frame <NUM> may house image sensor module 120a and illuminator <NUM>. Image sensor module 120a and illuminator <NUM> may be connected to a printed circuit board (PCB) which provides electrical connections between different subsystems of near-eye display <NUM>. The footprint of image sensor module 120a (e.g., along the x and y axes) on PCB <NUM>, as well as other subsystems connected to PCB <NUM> can determine a thickness (labelled "t" in <FIG>) of frame <NUM> needed to house PCB <NUM>. It may be desirable to reduce the thickness of frame <NUM> to reduce the weight of frame <NUM>, to increase the area of display <NUM>, and to improve aesthetics, all of which can improve the user experience. To reduce the thickness of frame <NUM>, the footprints of the sub-systems on PCB <NUM>, such as image sensor module 120a, illuminator <NUM>, etc., may need to be reduced.

<FIG> is an example of a cross section <NUM> of near-eye display <NUM> illustrated in <FIG>. Display <NUM> includes at least one waveguide display assembly <NUM>. An exit pupil <NUM> is a location where a single eyeball <NUM> of the user is positioned in an eyebox region when the user wears the near-eye display <NUM>. For purposes of illustration, <FIG> shows the cross section <NUM> associated eyeball <NUM> and a single waveguide display assembly <NUM>, but a second waveguide display is used for a second eye of a user.

Waveguide display assembly <NUM> is configured to direct image light to an eyebox located at exit pupil <NUM> and to eyeball <NUM>. Waveguide display assembly <NUM> may be composed of one or more materials (e.g., plastic, glass, etc.) with one or more refractive indices. In some examples, near-eye display <NUM> includes one or more optical elements between waveguide display assembly <NUM> and eyeball <NUM>.

In some examples, waveguide display assembly <NUM> includes a stack of one or more waveguide displays including, but not restricted to, a stacked waveguide display, a varifocal waveguide display, etc. The stacked waveguide display is a polychromatic display (e.g., a RGB display) created by stacking waveguide displays whose respective monochromatic sources are of different colors. The stacked waveguide display is also a polychromatic display that can be projected on multiple planes (e.g., multi-planar colored display). In some configurations, the stacked waveguide display is a monochromatic display that can be projected on multiple planes (e.g., multi-planar monochromatic display). The varifocal waveguide display is a display that can adjust a focal position of image light emitted from the waveguide display. In alternate examples, waveguide display assembly <NUM> may include the stacked waveguide display and the varifocal waveguide display.

<FIG> illustrates an isometric view of an example of a waveguide display <NUM>. In some examples, waveguide display <NUM> is a component (e.g., waveguide display assembly <NUM>) of near-eye display <NUM>. In some examples, waveguide display <NUM> is part of some other near-eye display or other system that directs image light to a particular location.

Waveguide display <NUM> includes a source assembly <NUM>, an output waveguide <NUM>, and a controller <NUM>. For purposes of illustration, <FIG> shows the waveguide display <NUM> associated with a single eyeball <NUM>, but in some examples, another waveguide display separate, or partially separate, from the waveguide display <NUM> provides image light to another eye of the user.

Source assembly <NUM> generates image light <NUM>. Source assembly <NUM> generates and outputs image light <NUM> to a coupling element <NUM> located on a first side <NUM>-<NUM> of output waveguide <NUM>. Output waveguide <NUM> is an optical waveguide that outputs expanded image light <NUM> to an eyeball <NUM> of a user. Output waveguide <NUM> receives image light <NUM> at one or more coupling elements <NUM> located on the first side <NUM>-<NUM> and guides received input image light <NUM> to a directing element <NUM>. In some examples, coupling element <NUM> couples the image light <NUM> from source assembly <NUM> into output waveguide <NUM>. Coupling element <NUM> may be, for example , a diffraction grating, a holographic grating, one or more cascaded reflectors, one or more prismatic surface elements, and/or an array of holographic reflectors.

Directing element <NUM> redirects the received input image light <NUM> to decoupling element <NUM> such that the received input image light <NUM> is decoupled out of output waveguide <NUM> via decoupling element <NUM>. Directing element <NUM> is part of, or affixed to, first side <NUM>-<NUM> of output waveguide <NUM>. Decoupling element <NUM> is part of, or affixed to, second side <NUM>-<NUM> of output waveguide <NUM>, such that directing element <NUM> is opposed to the decoupling element <NUM>. Directing element <NUM> and/or decoupling element <NUM> may be, for example, a diffraction grating, a holographic grating, one or more cascaded reflectors, one or more prismatic surface elements, and/or an array of holographic reflectors.

Second side <NUM>-<NUM> represents a plane along an x-dimension and a y-dimension. Output waveguide <NUM> may be composed of one or more materials that facilitate total internal reflection of image light <NUM>. Output waveguide <NUM> may be composed of for example, silicon, plastic, glass, and/or polymers. Output waveguide <NUM> has a relatively small form factor. For example, output waveguide <NUM> may be approximately <NUM> wide along x-dimension, <NUM> long along y-dimension and <NUM>-<NUM> thick along a z-dimension.

Controller <NUM> controls scanning operations of source assembly <NUM>. The controller <NUM> determines scanning instructions for the source assembly <NUM>. In some examples, the output waveguide <NUM> outputs expanded image light <NUM> to the user's eyeball <NUM> with a large field of view (FOV). For example, the expanded image light <NUM> is provided to the user's eyeball <NUM> with a diagonal FOV (in x and y) of <NUM> degrees and/or greater and/or <NUM> degrees and/or less. The output waveguide <NUM> is configured to provide an eyebox with a length of <NUM> or greater and/or equal to or less than <NUM>; and/or a width of <NUM> or greater and/or equal to or less than <NUM>.

Moreover, controller <NUM> also controls image light <NUM> generated by source assembly <NUM>, based on image data provided by image sensor module <NUM>. Image sensor module <NUM> may be located on first side <NUM>-<NUM> and may include, for example, image sensor modules 120a-120d of <FIG> to generate image data of a physical environment in front of the user (e.g., for location determination). Image sensor module <NUM> may also be located on second side <NUM>-<NUM> and may include image sensor modules 150a and 150b of <FIG> to generate image data of eyeball <NUM> (e.g., for gaze point determination) of the user. Image sensor module <NUM> may interface with a remote console that is not located within waveguide display <NUM>. Image sensor module <NUM> may provide image data to the remote console, which may determine, for example, a location of the user, a gaze point of the user, etc., and determine the content of the images to be displayed to the user. The remote console can transmit instructions to controller <NUM> related to the determined content. Based on the instructions, controller <NUM> can control the generation and outputting of image light <NUM> by source assembly <NUM>.

<FIG> illustrates an example of a cross section <NUM> of the waveguide display <NUM>. The cross section <NUM> includes source assembly <NUM>, output waveguide <NUM>, and image sensor module <NUM>. In the example of <FIG>, image sensor module <NUM> may include a set of pixel cells <NUM> located on first side <NUM>-<NUM> to generate an image of the physical environment in front of the user. In some examples, there can be a mechanical shutter <NUM> interposed between the set of pixel cells <NUM> and the physical environment to control the exposure of the set of pixel cells <NUM>. In some examples, the mechanical shutter <NUM> can be replaced by an electronic shutter gate, as to be discussed below. Each of pixel cells <NUM> may correspond to one pixel of the image. Although not shown in <FIG>, it is understood that each of pixel cells <NUM> may also be overlaid with a filter to control the frequency range of the light to be sensed by the pixel cells.

After receiving instructions from the remote console, mechanical shutter <NUM> can open and expose the set of pixel cells <NUM> in an exposure period. During the exposure period, image sensor module <NUM> can obtain samples of lights incident on the set of pixel cells <NUM>, and generate image data based on an intensity distribution of the incident light samples detected by the set of pixel cells <NUM>. Image sensor module <NUM> can then provide the image data to the remote console, which determines the display content, and provide the display content information to controller <NUM>. Controller <NUM> can then determine image light <NUM> based on the display content information.

Source assembly <NUM> generates image light <NUM> in accordance with instructions from the controller <NUM>. Source assembly <NUM> includes a source <NUM> and an optics system <NUM>. Source <NUM> is a light source that generates coherent or partially coherent light. Source <NUM> may be, for example, a laser diode, a vertical cavity surface emitting laser, and/or a light emitting diode.

Optics system <NUM> includes one or more optical components that condition the light from source <NUM>. Conditioning light from source <NUM> may include, for example, expanding, collimating, and/or adjusting orientation in accordance with instructions from controller <NUM>. The one or more optical components may include one or more lenses, liquid lenses, mirrors, apertures, and/or gratings. In some examples, optics system <NUM> includes a liquid lens with a plurality of electrodes that allows scanning of a beam of light with a threshold value of scanning angle to shift the beam of light to a region outside the liquid lens. Light emitted from the optics system <NUM> (and also source assembly <NUM>) is referred to as image light <NUM>.

Output waveguide <NUM> receives image light <NUM>. Coupling element <NUM> couples image light <NUM> from source assembly <NUM> into output waveguide <NUM>. In examples where coupling element <NUM> is diffraction grating, a pitch of the diffraction grating is chosen such that total internal reflection occurs in output waveguide <NUM>, and image light <NUM> propagates internally in output waveguide <NUM> (e.g., by total internal reflection), toward decoupling element <NUM>.

Directing element <NUM> redirects image light <NUM> toward decoupling element <NUM> for decoupling from output waveguide <NUM>. In examples where directing element <NUM> is a diffraction grating, the pitch of the diffraction grating is chosen to cause incident image light <NUM> to exit output waveguide <NUM> at angle(s) of inclination relative to a surface of decoupling element <NUM>.

In some examples, directing element <NUM> and/or decoupling element <NUM> are structurally similar. Expanded image light <NUM> exiting output waveguide <NUM> is expanded along one or more dimensions (e.g., may be elongated along x-dimension). In some examples, waveguide display <NUM> includes a plurality of source assemblies <NUM> and a plurality of output waveguides <NUM>. Each of source assemblies <NUM> emits a monochromatic image light of a specific band of wavelength corresponding to a primary color (e.g., red, green, or blue). Each of output waveguides <NUM> may be stacked together with a distance of separation to output an expanded image light <NUM> that is multi-colored.

<FIG> is a block diagram of an example of a system <NUM> including the near-eye display <NUM>. The system <NUM> comprises near-eye display <NUM>, an imaging device <NUM>, an input/output interface <NUM>, and image sensor modules 120a-120d and 150a-150b that are each coupled to control circuitries <NUM>. System <NUM> can be configured as a head-mounted device, a wearable device, etc..

Near-eye display <NUM> is a display that presents media to a user. Examples of media presented by the near-eye display <NUM> include one or more images, video, and/or audio. In some examples, audio is presented via an external device (e.g., speakers and/or headphones) that receives audio information from near-eye display <NUM> and/or control circuitries <NUM> and presents audio data based on the audio information to a user. In some examples, near-eye display <NUM> may also act as an AR eyewear glass. In some examples, near-eye display <NUM> augments views of a physical, real-world environment, with computer-generated elements (e.g., images, video, sound, etc.).

Near-eye display <NUM> includes waveguide display assembly <NUM>, one or more position sensor modules <NUM>, and/or an inertial measurement unit (IMU) <NUM>. Waveguide display assembly <NUM> includes source assembly <NUM>, output waveguide <NUM>, and controller <NUM>.

IMU <NUM> is an electronic device that generates fast calibration data indicating an estimated position of near-eye display <NUM> relative to an initial position of near-eye display <NUM> based on measurement signals received from one or more of position sensor modules <NUM>.

Imaging device <NUM> may generate image data for various applications. For example, imaging device <NUM> may generate image data to provide slow calibration data in accordance with calibration parameters received from control circuitries <NUM>. Imaging device <NUM> may include, for example, image sensor modules 120a-120d of <FIG> for generating image data of a physical environment in which the user is located, for performing location tracking of the user. Imaging device <NUM> may further include, for example, image sensor modules 150a-150b of <FIG> for generating image data for determining a gaze point of the user, to identify an object of interest of the user.

The input/output interface <NUM> is a device that allows a user to send action requests to the control circuitries <NUM>. An action request is a request to perform a particular action. For example, an action request may be to start or end an application or to perform a particular action within the application.

Control circuitries <NUM> provide media to near-eye display <NUM> for presentation to the user in accordance with information received from one or more of: imaging device <NUM>, near-eye display <NUM>, and input/output interface <NUM>. In some examples, control circuitries <NUM> can be housed within system <NUM> configured as a head-mounted device. In some examples, control circuitries <NUM> can be a standalone console device communicatively coupled with other components of system <NUM>. In the example shown in <FIG>, control circuitries <NUM> include an application store <NUM>, a tracking module <NUM>, and an engine <NUM>.

The application store <NUM> stores one or more applications for execution by the control circuitries <NUM>. An application is a group of instructions, that, when executed by a processor, generates content for presentation to the user. Examples of applications include: gaming applications, conferencing applications, video playback applications, or other suitable applications.

Tracking module <NUM> calibrates system <NUM> using one or more calibration parameters and may adjust one or more calibration parameters to reduce error in determination of the position of the near-eye display <NUM>.

Tracking module <NUM> tracks movements of near-eye display <NUM> using slow calibration information from the imaging device <NUM>. Tracking module <NUM> also determines positions of a reference point of near-eye display <NUM> using position information from the fast calibration information.

Engine <NUM> executes applications within system <NUM> and receives position information, acceleration information, velocity information, and/or predicted future positions of near-eye display <NUM> from tracking module <NUM>. In some examples, information received by engine <NUM> may be used for producing a signal (e.g., display instructions) to waveguide display assembly <NUM> that determines a type of content presented to the user. For example, to provide an interactive experience, engine <NUM> may determine the content to be presented to the user based on a location of the user (e.g., provided by tracking module <NUM>), or a gaze point of the user (e.g., based on image data provided by imaging device <NUM>), a distance between an object and user (e.g., based on image data provided by imaging device <NUM>).

<FIG> and <FIG> illustrate examples of an image sensor module <NUM> and its operations. Image sensor module <NUM> can be part of image sensor modules 120a-120d and 150a-150b of <FIG> and <FIG>, and part of image sensor module <NUM> of <FIG>. As shown in <FIG>, image sensor module <NUM> includes one or more lenses <NUM> and an image sensor <NUM>, which can include one or more image sensor dies/chips. One or more lenses <NUM> can include a single lens <NUM> (e.g., as shown in <FIG> and <FIG>) or multiple lens aligned in a stack along a propagation direction of light (e.g., along the z-axis). One or more lenses <NUM> can gather light <NUM> and light <NUM> and focus light <NUM> and light <NUM> towards image sensor <NUM>. Image sensor <NUM> includes a light receiving surface <NUM> to receive the focused light <NUM>. Light receiving surface <NUM> can be separated from lens <NUM> by a distance f. The distance f in <FIG> can correspond to a distance between lens <NUM> and image sensor <NUM> for capturing an image of an object at an infinite distance away from lens <NUM>. Distance f can be adjusted based on, for example, the distance between the object and lens <NUM>. Provided that light receiving surface <NUM> is at distance f from lens <NUM>, that light receiving surface <NUM> is perpendicular to the optical axis <NUM> of lens <NUM>, and that center of light receiving surface <NUM> aligns with optical axis <NUM>, light receiving surface <NUM> can receive focused light with a field of view <NUM> defined based on the length f of lens <NUM>. Image sensor <NUM> further includes an array of pixel cells <NUM> below the light receiving surface <NUM> to convert the focused light <NUM> to electrical signals. Different pixel cells may receive different intensities of light via lens <NUM> to generate the electrical signals, and an image of field of view <NUM> can be constructed based on the electrical signals from the pixel cells.

The optical properties of Image sensor module <NUM>, such as field of view <NUM>, can be determined by the physical properties of lens <NUM>. Specifically, the curvature and refractive index of lens <NUM> can determine the focal length f. Moreover, the Abbe number of lens <NUM> can determine the variation of refractive index versus wavelength. Further, the birefringence of lens <NUM> can determine the variation of the refractive index of the lens with respect to the polarization and propagation direction of the incident light. Both Abbe number and birefringence can control the dispersion of light <NUM> by lens <NUM> and can be determined by the material of lens <NUM>. All these optical properties can affect the quality of an image (e.g., amount of information captured in the field of view, blurriness and distortion caused by the dispersion of light) captured by the image sensor module <NUM>.

The assembly of one or more lenses <NUM> and image sensor <NUM> in image sensor module <NUM> can also affect the optical properties as well as the performance of image sensor module <NUM>. Specifically, the alignment of the image sensor with respect to the lens (e.g., relative orientations, positions) can also affect the reception of the light by image sensor <NUM>. As described above, for proper alignment, light receiving surface <NUM> should be separated from lens <NUM> by the distance f. Moreover, light receiving surface <NUM> should be perpendicular to the optical axis <NUM> of lens <NUM>, whereas the center of light receiving surface <NUM> should align with optical axis <NUM>. <FIG> illustrates examples of misalignment between lens <NUM> and image sensor <NUM> and their effects. As shown in <FIG>, image sensor <NUM> (and light receiving surface <NUM>) can become tilted with respect to optical axis <NUM> and lens <NUM>. As a result, various locations of light receiving surface <NUM> (e.g., locations labelled "P" and "Q") may be separated from lens <NUM> by a distance that is either shorter than or longer than distance f. As a result, light receiving surface <NUM> may receive dispersed light <NUM> at locations P and Q, and the resulting image may appear to be out-of-focus at those locations and become distorted. In addition, the center of light receiving surface <NUM> does not align with optical axis <NUM>, which can reduce the field of view captured by light receiving surface <NUM>.

<FIG> illustrates an example of an image sensor module <NUM> that can provide improved alignment between lens <NUM> and image sensor <NUM>. As shown in <FIG>, image sensor module <NUM> includes a housing <NUM> that houses one or more lenses <NUM>, a substrate <NUM> (e.g., a glass substrate), and image sensor <NUM>. One or more lenses <NUM> can include multiple lenses forming a lens stack and mounted on the internal wall of housing <NUM>. Housing <NUM> further includes a shoulder structure <NUM> that are on the vertical sides of image sensor <NUM> (e.g., sides that are perpendicular to light receiving surface <NUM>). There can be an air gap <NUM> between the vertical sides of image sensor <NUM> and shoulder structure <NUM>, and an air gap <NUM> between one or more lenses <NUM> and light receiving surface <NUM> of image sensor <NUM>. Both air gaps <NUM> and <NUM> can provide space for aligning one or more lenses <NUM> with respect to image sensor <NUM>.

Both housing <NUM> and image sensor <NUM> are bonded onto a PCB <NUM>. For example, shoulder structure <NUM> can be bonded to PCB <NUM> via an adhesive bondline <NUM>, whereas image sensor <NUM> can be soldered onto PCB <NUM> via solder balls <NUM> to form conductive bonds. Bondline <NUM> can be used to align one or more lenses <NUM> with respect to image sensor <NUM>. Specifically, bondline <NUM> can include adhesives that are flexible when in a liquid state but can become hardened when cured. When bondline <NUM> is in a liquid state, housing <NUM> (with one or more lenses <NUM> mounted within) can be moved in the x, y, and z directions and/or rotated around the x, y, and z axes to align with image sensor <NUM>. The target alignment can be such that, for example, optical axis <NUM> of one or more lenses <NUM> aligns with the center of the image sensor <NUM>, light receiving surface <NUM> is perpendicular to the optical axis <NUM> and is separated from one or more lenses <NUM> by a pre-determined distance d, etc. Once the target alignment is achieved, the adhesives can be cured to form bondline <NUM> to fix the location and orientation of the one or more lenses <NUM> with respect to image sensor <NUM>.

Although housing <NUM> of <FIG> can provide improved alignment between one or more lenses <NUM> and image sensor <NUM>, the shoulder structure <NUM> of housing <NUM> increases the footprint of image sensor module <NUM>, which is undesirable for a wearable device such as near-eye display <NUM>. As explained above, the increased footprint of image sensor module <NUM> can lead to increase in the thickness of frame <NUM>, which can increase the weight of frame <NUM>, reduce the area of display <NUM>, and affect aesthetics, all of which can degrade the user experience. Meanwhile, in order to shrink the footprint of image sensor module <NUM>, the footprint of image sensor <NUM> may need to shrink, which can reduce the number of pixel cells included in image sensor <NUM> and reduce the resolution of image capture. The performance of image sensor module <NUM> may be degraded as a result.

<FIG> illustrates another example of an image sensor module <NUM> with reduced footprint, whereas <FIG> and <FIG> illustrate an example fabrication method of image sensor module <NUM>. As shown in <FIG>, image sensor module <NUM> may include lens 602a (of one or more lenses <NUM>) formed on a glass substrate <NUM>. Glass substrate <NUM> can be bonded to image sensor <NUM> via, for example, an bonding layer <NUM>. Additional glass substrates can be stacked on top of glass substrate <NUM> to include additional lens. For example, a glass substrate <NUM> having a cavity <NUM> can be stacked on top of glass substrate <NUM> with cavity <NUM> accommodating lens 602a, and another glass substrate <NUM> including lens 602b can be stacked on top of glass substrates <NUM> and <NUM>, with lenses 602a and 602b aligned along the same optical axis <NUM>. Image sensor <NUM> can be soldered onto PCB <NUM> via solder balls <NUM> to form conductive bonds.

Compared with image sensor module <NUM> of <FIG>, image sensor module <NUM> can provide a reduced footprint. Specifically, as shown in <FIG>, the footprint of glass substrates <NUM>, <NUM>, and <NUM> can be substantially the same or smaller than image sensor <NUM>, unlike image sensor module <NUM> where shoulder structure <NUM> extends outwards from image sensor <NUM>. As a result, the footprint of image sensor module <NUM> (represented by L<NUM>) can be substantially the same as the footprint of image sensor <NUM> (represented by L<NUM>).

The glass substrates in image sensor module <NUM> can also provide a certain degree of alignment between lens <NUM> and image sensor <NUM>, such as defining the vertical distance (labelled "d" in <FIG>) between the lens and the image sensor die. However, the degree of alignment can be limited by the fabrication of image sensor module <NUM> which is typically based on a wafer-level optics process.

<FIG> illustrates an example of a wafer-level optics process. As shown in <FIG>, multiple lenses 602a can be formed on a glass wafer <NUM>. Moreover, multiple cavities <NUM> can be formed on a glass wafer <NUM>, whereas multiple lenses 602b can be formed on a glass wafer <NUM>. Glass wafers <NUM>, <NUM>, and <NUM> can be stacked, and each glass wafer can be moved along the x and y axes to align each lens 602a, cavity <NUM>, and lens 602b along the same optical axis <NUM> as shown in <FIG>. An alignment process can be performed to align glass wafers <NUM>, <NUM>, and <NUM>. Specifically, images of alignment marks <NUM>, <NUM>, and <NUM> on, respectively, glass wafers <NUM>, <NUM>, and <NUM> can be captured by cameras <NUM> and <NUM>, and a degree of alignment among the wafers can be determined based on the images. Each wafer can be moved against each other until the images of alignment marks <NUM>, <NUM>, and <NUM> indicate that a target degree of alignment is reached. After the glass wafers are stacked and aligned, the glass wafer stack can then be stacked on a semiconductor wafer <NUM> including multiple image sensor dies <NUM>, with each die corresponding to image sensor <NUM>. The glass wafer stack can also be moved along the x and y axes to align the lens with the image sensor dies <NUM>. The alignment of the glass wafer stack with respect to semiconductor wafer <NUM> can also be based on images of alignment marks <NUM>/<NUM>/<NUM> of the glass wafer stack and alignment mark <NUM> on semiconductor wafer <NUM> captured by cameras <NUM> and <NUM>. After the alignment process completes, the glass wafer stack and the image sensor dies can be diced to form individual image sensor module <NUM>.

The alignment process in <FIG> can only provide a limited degree of alignment between lens <NUM> and image sensor <NUM>. This is because the alignment is on a wafer-level and cannot completely eliminate the location/orientation differences of lens <NUM> between different image sensor modules. <FIG> illustrates an example of the limited alignment. As shown in <FIG>, two lens 602a1 and 602a2 are separated by a horizontal distance d1 and a vertical distance Δz on glass wafer <NUM>, whereas two image sensor dies 852a and 852b are separated by a horizontal distance d2 on semiconductor wafer <NUM>. Based on alignment between glass wafer <NUM> and semiconductor wafer <NUM>, each of lenses 602a1 and 602a2 may misalign with, respectively, image sensor dies 852a and 852b by half of the difference between d1 and d2. Moreover, as wafer <NUM> is only moved along the x/y axes to align with semiconductor wafer <NUM>, the misalignment along the vertical axis, caused by Δz, may remain for image sensor die 852b. Moreover, there is also no rotation of wafer <NUM> (or image sensor <NUM>) around the x, y, and z axes to correct the alignment.

In some examples, the alignment between the stack of glass substrates <NUM>, <NUM>, and <NUM> and image sensor <NUM> in the wafer-level optics process can be performed after the glass substrates stack are diced to form a lens stack (including diced glass substrates <NUM>, <NUM>, and <NUM> as well as lenses 602a and 602b) for each image sensor <NUM>. The lens stack can be moved with respect to an image sensor <NUM> and along the x/y axes based on, for example, alignment between edges of the lens stack and features of image sensor <NUM>. However, there is also no rotation of wafer <NUM> (or image sensor <NUM>) around the x, y, and z axes to correct the alignment. Therefore, only a limited degree of alignment between lens <NUM> and image sensor <NUM> can be achieved.

<FIG> illustrate examples of an image sensor module that can provide both reduced footprint and improved optical properties. As shown in <FIG>, an image sensor module <NUM> can include a lens assembly <NUM> and image sensor <NUM> of <FIG>. Image sensor <NUM> can be positioned below lens assembly <NUM> and can be bonded to lens assembly <NUM> via a bonding layer <NUM>. As lens assembly <NUM> does not include any shoulder structures that are adjacent to the sides of image sensor <NUM>, lens assembly <NUM> does not add to the footprint of image sensor module <NUM>. The footprint of image sensor module <NUM> is mostly contributed by image sensor <NUM>.

Lens assembly <NUM> can include one or more layers <NUM> and one or more spacers <NUM>, with each layer having a lens portion formed as lens <NUM> and an extension portion <NUM>. The lens portion is configured to gather and direct light towards image sensor <NUM>, whereas extension portion <NUM> can provide mechanical support for the lens portion. For example, extension portion <NUM> can rest on or be supported by spacer <NUM>, which includes an opening to fit the lens portion of layer <NUM>. Each layer can be made of, for example, a polymer material such as a cyclic olefin copolymer (COC) material which can provide a lower Abbe number and reduced birefringence, both of which can reduce light dispersion by lens <NUM>. Other polymer materials that can be used to fabricate layers <NUM> may include, for example, APEL5014CL, OKP1, OKP4, EP8000. APEL5014CL can be a COC. OKP1 and OKP4 can be a polyester, whereas EP8000 can be a polycarbonate. Each layer can also be made of other materials such as, for example, glass. Spacers <NUM> can also be made of an opaque material such as, for example, an opaque polymer, metal, etc..

In a case where lens assembly <NUM> includes multiple lenses <NUM> (e.g., three lenses 602a, 602b, and 602c as shown in <FIG>), each layer <NUM> (e.g., layers 908a, 908b, and 908c) can stack on top of each other and bonded to a spacer <NUM>, which can provide mechanical support and define the location and orientation of lens <NUM> within lens assembly <NUM>. For example, extension portion 911a of layer 908a can be bonded to spacer 910a, which includes an opening <NUM> for outputting light to image sensor <NUM>. In some examples, opening <NUM> can be filled with part of lens 602a to form a light outputting surface. Moreover, spacer 910b can be inserted between layers 908b and 908a with extension portion 911b of layer 908b bonded to spacer 910b, whereas spacer 910c can be inserted between layers 908c and 908b with extension portion 911c of layer 908c bonded to spacer 910c. Lens assembly <NUM> further includes a top cover <NUM> which includes an aperture <NUM> for receiving incident light.

In some examples, an opaque/dark coating layer <NUM> (shown in <FIG>) can be applied on the external vertical surfaces of lens assembly <NUM> to prevent light from entering through the side of lens assembly <NUM> to ensure that light only enters through aperture <NUM>. In some examples, as shown in <FIG>,.

In some examples, some of the spacers <NUM> between layers <NUM> can be omitted in lens assembly <NUM>. The extension portion <NUM> and/or lens <NUM> of two layers <NUM> can be bonded to form a stack. For example, extension <NUM> c of layer 908c and extension 911b of layer 908b can be bonded together, whereas extension 911b of layer 908b and extension 911a of layer 908a can also be bonded together, to form lens assembly <NUM>. As another example, lenses 602c and 602b can be bonded together, whereas 602b and 602c can also be bonded together, to form lens assembly <NUM>.

Layers 908a, 908b, and 908c can be fabricated by high precision processes, such as injection molding, to provide improved control over the physical dimensions (e.g., curvatures) of lenses 602a, 602b, and 602c and the resulting optical properties of lens assembly <NUM>. Moreover, spacers 910a, 910b, and 910c, as well as top cover <NUM>, can also be fabricated by injection molding to provide tighter fit between the layers, the spacers, and the covers, which can improve the rigidity of lens assembly <NUM>. In some examples, spacers 910a, 910b, and 910c, as well as top cover <NUM> can be made of stamped or machined metal.

Image sensor <NUM>, which can include glass substrate <NUM> (shown as a separate component in the figures), can be bonded to lens assembly <NUM> via a bonding layer <NUM>. Bonding layer <NUM> can be formed by applying a layer of adhesive material onto image sensor <NUM> after image sensor <NUM> is soldered onto PCB <NUM> via solder balls <NUM> in a reflow process. Image sensor <NUM> (soldered onto PCB <NUM>) and lens assembly <NUM> can then be brought together so that spacer 910a comes into contact with the adhesive material. The adhesive material can then be hardened in a curing process to form bonding layer <NUM>, which can provide permanent bonding between image sensor <NUM> and lens assembly <NUM>.

Bonding layer <NUM> can be used to maintain the alignment between image sensor <NUM> with lens <NUM> of lens assembly <NUM> obtained from an alignment process prior to the curing process, when the adhesive material remains in a liquid state. <FIG> illustrates an example of the alignment process, in which the position and orientation of image sensor <NUM> with respect to lens assembly <NUM> can be adjusted based on sensor data generated by image sensor <NUM> which reflects a degree of alignment. Referring to <FIG>, image sensor <NUM> can be enabled (powered on) to sense light that passes through lens assembly <NUM> during the alignment process. In one example, lens assembly <NUM> can be held at a fixed location and a fixed orientation, whereas image sensor <NUM> (and PCB <NUM>) can be supported on a platform (not shown in <FIG>) that can support six degrees of movements including linear movements along each of the x, y, and z axes, as well as rotations about each of the x, y, and z axes. In another example, image sensor <NUM> (and PCB <NUM>) can be held at a fixed location and a fixed orientation, whereas lens assembly <NUM> can be moved/rotated. A light projector <NUM> can project a light pattern <NUM> (e.g., a twodimensional light pattern of an image) to lens assembly <NUM>, which can direct light pattern <NUM> towards image sensor <NUM>, which can generate sensor data <NUM> of the image based on the sensing of light pattern <NUM>. As described above, a degree of alignment between image sensor <NUM> and lens <NUM> (e.g., how far image sensor <NUM> is from the focal point of lens <NUM>, or the orientation and position of image sensor <NUM> with respect to optical axis <NUM> of lens <NUM>) can determine a quality of image generated by image sensor <NUM> from the sensing of light pattern <NUM>. A controller <NUM> can analyze sensor data <NUM> to determine, for example, a degree of blurriness, a degree of distortion, etc., of the image represented by sensor data <NUM>, from which controller <NUM> can determine a degree of alignment between image sensor <NUM> and lens <NUM>. Based on the degree of alignment, controller <NUM> can control a movement of lens assembly <NUM> and/or image sensor <NUM> (e.g., based on linear movements along each of the x, y, and z axes, rotations about each of the x, y, and z axes, etc.) to align image sensor <NUM> with respect to lens assembly <NUM> when the adhesive between image sensor <NUM> and lens assembly <NUM> remains in the liquid state. The adhesive can be squeezed or stretched to allow the movement.

Controller <NUM> can continue moving at least one of image sensor <NUM> or lens assembly <NUM> to adjust the alignment until a target degree of alignment is reached. For example, a target degree of alignment is reached when optical axis <NUM> (not shown in <FIG>) of one or more lenses <NUM> aligns with the center of the image sensor <NUM>, light receiving surface <NUM> is perpendicular to the optical axis <NUM> and is separated from one or more lenses <NUM> by a predetermined distance, etc. When the target degree of alignment is reached, the adhesive can be hardened in a curing process. The curing process can be based on, for example, ultraviolet light, a thermal process at a temperature lower than the melting point of the polymer lens (to avoid deforming the lens), or both. When the adhesive is hardened, bonding layer <NUM> can be formed to bond image sensor <NUM> with lens assembly <NUM> while maintaining image sensor <NUM> at the aligned position and orientation with respect to lens assembly <NUM>. As image sensor <NUM> can be moved with respect to lens assembly <NUM> based on linear movements along each of the x, y, and z axes, rotations about each of the x, y, and z axes, and based on sensor data generated by image sensor <NUM> which can provide an accurate account of the instantaneous degree of alignment, the achievable degree of achievable alignment between lens <NUM> and image sensor <NUM> can be substantially increased.

There are various ways of distributing the adhesive to form bonding layer <NUM>. In one example, as shown in the left diagram of <FIG>, bonding layer <NUM> can be formed around a perimeter of image sensor <NUM> surrounding a region <NUM>. Region <NUM> can be over light receiving surface <NUM> of image sensor <NUM> and faces opening <NUM> of spacer 910a of lens assembly <NUM>. With such arrangements, adhesives that become opaque or otherwise have a low light transmittance upon becoming hardened can be used to form bonding layer <NUM> without blocking the light from reaching image sensor <NUM>, but the application of the adhesive is restricted such that the adhesives do not spill into region <NUM> when squeezed during the alignment process. In another example, as shown in the right diagram of <FIG>, bonding layer <NUM> can be formed over region <NUM> to bond with, for example, the part of lens 602a that fills opening <NUM>. With such arrangements, there can be fewer restrictions on the application of the adhesive on image sensor <NUM>, but the adhesive needs to be transparent or at least have a high light transmittance upon becoming hardened by the curing process. In some examples, the adhesive can also be formed on lens assembly <NUM> (e.g., on a surface of spacer 910a facing image sensor <NUM>) to bond with image sensor <NUM>.

<FIG> illustrates another example of an image sensor module that can provide both reduced footprint and improved optical properties. As shown in <FIG>, an image sensor module <NUM> can include a lens assembly <NUM> and image sensor <NUM> of <FIG>. Lens assembly <NUM> can include an opaque/dark lens housing <NUM>, which can be in the form of a barrel, that holds one or more lenses <NUM>. Housing <NUM> can be made of, for example, a polymer material, a metal, etc. Image sensor <NUM> can be positioned below housing <NUM> and can be bonded to lens assembly <NUM> via bonding layer <NUM>. As lens assembly <NUM> does not include any shoulder structure that are adjacent to the sides of image sensor <NUM>, lens assembly <NUM> does not add to the footprint of image sensor module <NUM>. The footprint of image sensor module <NUM> is mostly contributed by image sensor <NUM>.

In some examples, as shown in <FIG>, each of one or more lenses <NUM> can be part of a layer <NUM> including an extension portion <NUM>. Lens assembly <NUM> may also include one or more spacers <NUM>. The lens portion of layer <NUM> is configured to gather and direct light towards image sensor <NUM>, whereas the extension portion <NUM> can provide mechanical support to the lens portion. For example, extension portion <NUM> can rest on or be supported by spacer <NUM>, which includes an opening to fit the lens portion of layer <NUM>. Each layer <NUM> and spacer <NUM> are mechanically coupled (e.g., via adhesive) to the inner wall of housing <NUM>. Each layer <NUM> can be made of the same material as layer <NUM> including, for example, a polymer material (e.g., COC, polycarbonate), a glass material, etc. Spacers <NUM> can also be made of an opaque material such as polymer and metal. In a case where lens assembly <NUM> includes multiple lenses <NUM> (e.g., three lenses 602a, 602b, and 602c as shown in <FIG>), each layer <NUM> (e.g., layers 1006a, 1006b, and 1006c) can stack on top of each other and separated by a spacer <NUM>, which can provide mechanical support and define the location and orientation of lens <NUM> within lens assembly <NUM>. For example, extension portion 1008a of layer 1006a and extension portion 1008b of layer 1006b can be separated by spacer 1010a, whereas extension portion 1008b of layer 1006b and extension portion 1008c of layer 1006c can be separated by spacer 1010b. Housing <NUM> further includes an aperture <NUM> for receiving incident light.

Similar to image sensor module <NUM>, each layer <NUM> can be fabricated by high precision processes, such as injection molding, to provide improved control over the physical dimensions (e.g., curvatures) of lenses 602a, 602b, and 602c and the resulting optical properties of lens assembly <NUM>. Moreover, spacers <NUM> can also be fabricated by injection molding, machined/stamped metals, etc., to provide tighter fit between the layers and the spacers to improve the rigidity of lens assembly <NUM>. Moreover, bonding layer <NUM> can be used to maintain the alignment between image sensor <NUM> (of image sensor <NUM>) with lens <NUM> of lens assembly <NUM> obtained from an alignment process as described in <FIG>.

In some examples, the optical elements of an image sensor module, such as image sensor modules <NUM>, <NUM>, <NUM>, and <NUM> of <FIG> - <FIG>, may include a filter. The filter can include a filter array to select different frequency components of the light to be detected by different pixel cells the image sensor, or a single frequency component of the light to be detected by all pixel cells. The image sensor includes light sensing elements (e.g., photodiodes) that can receive the different frequency components of the light selected by the filter array via the light receiving surface and convert the frequency components to electrical signals. The electrical signals can represent, for example, intensities of the different frequency components of light from a scene.

<FIG>, <FIG>, and <FIG> illustrate examples of an image sensor module <NUM> including a filter. Image sensor module <NUM> can be part of image sensor modules 120a-120d and 150a-150b of <FIG>, <FIG>, and <FIG>, and part of image sensor module <NUM> of <FIG>. Image sensor module <NUM> may include components of image sensor modules <NUM>, <NUM>, <NUM>, and <NUM> of <FIG>, such as one or more lenses <NUM> and image sensor <NUM>. As shown on the left of <FIG>, which represents an internal side view of image sensor module <NUM>, image sensor module <NUM> includes one or more lenses <NUM>, a filter <NUM>, and image sensor <NUM> including an array of pixel cells <NUM> as shown in <FIG>. One or more lenses <NUM> (shown as an unified body in <FIG> for simplicity) can include a single lens or multiple lens separated by spacers and aligned in a stack along a propagation direction of light (e.g., along the z-axis) to pass the light, as shown in <FIG>. In some examples, the light can be focused and can converge at a focal point. The light can be filtered by filter <NUM>, which can select one or more frequency components of the light to be detected by image sensor <NUM>. In some examples, filter <NUM> can select a single frequency range (e.g., a visible frequency range, an infrared frequency range, etc.) of light to be detected by image sensor <NUM>. In some examples, filter <NUM> can include a filter array to select different frequency ranges (e.g., a red frequency range, a blue frequency range, a green frequency range, an infrared frequency range) of light to be detected by image sensor <NUM>.

Array of pixel cells <NUM> below light receiving surface <NUM> of image sensor <NUM> can convert different frequency components of the light to electrical signals. The electrical signals can represent, for example, intensities of the different frequency components of light from a scene. Based on the electrical signals, an image processor can generate an image of the scene. The image sensor module can be soldered onto a printed circuit board (PCB) <NUM> which also includes an image processor (not shown in the figures). PCB <NUM>, as described in <FIG>, includes electrical traces to transmit the electrical signals from the image sensor module to the image processor, which can generate an image of the scene based on the electrical signals.

Image sensor module <NUM> includes a holder structure <NUM> to hold and physically support one or more lenses <NUM> and filter <NUM>. Specifically, as shown in <FIG>, holder structure <NUM> may include a housing <NUM>, which can be include housing <NUM> of <FIG>, and a retainer <NUM>. Both housing <NUM> and retainer <NUM> can be made of, for example, a polycarbonate (PC) material, and/or a polymer material (e.g., liquid crystal polymer, LCP) using injection molding. Housing <NUM>, which can be in the form of a barrel, includes a top opening <NUM> to receive light and a bottom opening <NUM> to output light to image sensor <NUM>. Referring to <FIG>, one or more lenses <NUM> can be loaded into housing <NUM> through bottom opening <NUM> towards top opening <NUM> (indicated by direction labelled "A"). One or more lenses <NUM> can be mounted at pre-determined positions within housing <NUM> between top opening <NUM> and bottom opening <NUM> to form a lenses stack, where housing <NUM> can provide physical support to the lenses stack. In addition, housing <NUM> is stacked on image sensor <NUM> along the z-axis.

Referring back to <FIG>, bottom surface <NUM> of housing <NUM>, which surrounds bottom opening <NUM>, can be bonded to light receiving surface <NUM> of image sensor <NUM> via, for example, an adhesive <NUM> followed by UV curing to harden the adhesive, similar to the formation of bonding layer <NUM>/<NUM> in <FIG> - <FIG>. Based on the bonding with image sensor <NUM>, housing <NUM> can set the orientation and position of one or more lenses <NUM> with respect to image sensor <NUM>. In some examples, bottom surface <NUM> is bonded to the image sensor die of image sensor <NUM>. In some examples, bottom surface <NUM> is bonded to other components of image sensor <NUM>, such as glass substrate <NUM> (not shown in <FIG>), a package of image sensor <NUM>, etc..

In addition, retainer <NUM> can be mounted within housing <NUM> between the lenses stack and bottom opening <NUM>. Referring to <FIG>, retainer <NUM> can include an upper surface <NUM> (highlighted with a dotted line) to support one or more lenses <NUM> to prevent the lenses from falling out of bottom opening <NUM>, and a middle surface <NUM> (highlighted with a dotted line) to mount filter <NUM> (e.g., via a layer of adhesive not shown in the figures). Retainer <NUM> is positioned away from bottom opening <NUM> and further includes a recessed bottom surface <NUM> to prevent retainer <NUM> from protruding out of housing, when accounting for tolerance in the placement of retainer <NUM> within housing <NUM>. Such arrangements can ensure that bottom surface <NUM> of housing <NUM> is in contact with image sensor <NUM> when holder structure <NUM> is placed on image sensor <NUM>, while no part of retainer <NUM> is in contact with image sensor <NUM>. To maintain the position of retainer <NUM> within housing <NUM>, an adhesive <NUM> can be applied on recessed bottom surface <NUM> of retainer <NUM> and inner wall of housing <NUM>, followed by UV curing, to bond housing <NUM> with retainer <NUM>.

Although <FIG> illustrates that housing <NUM> includes a cylindrical portion and a rectangular/square portion, and that bottom opening <NUM> has a circular shape, it is understood that housing <NUM> and bottom opening <NUM> can have other geometric shapes. For example, housing <NUM> can include only a cylindrical barrel, a rectangular/square barrel, etc., whereas the bottom opening can have a rectangular/square shape.

The arrangements of <FIG>, in which housing <NUM> is attached on image sensor <NUM> to form a stack, can reduce the footprint of the image sensor module <NUM> on PCB <NUM>. The reduced footprint can be desirable especially for integrating image sensor module <NUM> in a mobile device, such as near-eye display <NUM>, where space is very limited. For example, referring back to <FIG>, in order to fit image sensor module <NUM> into frame <NUM>, a width of image sensor module <NUM> needs to be made shorter than the thickness (t) of frame <NUM>. Moreover, a length of image sensor <NUM> (e.g., of sensor 120a) also needs to be reduced so that pixel cells <NUM> of image sensor <NUM> can be positioned close to illuminator <NUM>, to improve the imaging operation (e.g., 3D sensing, stereoscopic imaging) involving illuminator <NUM> and sensor <NUM>. By shrinking the footprint of image sensor module <NUM>, it becomes more likely to fit image sensor module <NUM> into near-eye display <NUM>.

Although the arrangements in <FIG>, in which holder structure <NUM> forms a stack with image sensor <NUM>, can shrink the footprint of image sensor module <NUM> in a similar way as shown in <FIG>, the mounting of the retainer <NUM> within housing <NUM> can create various issues. Those issues can affect the assembly of the image sensor module as well as the optical properties and performance of the image sensor module. Specifically, as described above, housing <NUM> is bonded to image sensor <NUM> only via bottom surface <NUM>, while retainer <NUM> is not in contact with image sensor <NUM>. But bottom surface <NUM> of housing <NUM> provides a very limited area for applying adhesive <NUM>, which makes the bonding of housing <NUM> to image sensor <NUM> difficult. Moreover, bottom opening <NUM> may be enlarged to allow more pixel cells <NUM> of image sensor <NUM> to receive light, which can improve imaging resolution. But given that housing <NUM> surrounds the lens and retainer <NUM>, which increases the footprint, the thickness of housing <NUM> needs to be reduced to reduce the footprint. But reducing the thickness of housing <NUM> reduces bottom surface <NUM> of housing <NUM> as well as the available area for applying adhesive <NUM>. In one example, as shown in <FIG> and <FIG>, where the x/y dimension of image sensor <NUM> is around <NUM> millimeter (mm), a minimum width of bottom surface <NUM> of housing <NUM> can be shrunk to about <NUM>. The reduced bonding area can lead to a weaker bonding between housing <NUM> and image sensor <NUM>. The weak bonding may allow housing <NUM> to shift with respect to image sensor <NUM>, which changes the orientations and alignment of the lenses stack with respect to image sensor <NUM> and degrades the light sensing performance of image sensor module <NUM>.

Moreover, due to the reduced bonding area, the amount of adhesive <NUM> applied, as well as the locations on bottom surface <NUM> where adhesive <NUM> is applied, need to be controlled with a very high precision. This is to prevent the adhesive applied to bottom surface <NUM> of housing <NUM> from spilling into bottom opening <NUM> when housing <NUM> and image sensor <NUM> are brought together. But the requisite precision may become unachievable as the area of bottom surface <NUM> shrinks to reduce the footprint of image sensor module <NUM>. For example, it becomes very difficult to control the application of adhesive <NUM> in an <NUM> region of bottom surface <NUM> due to limits imposed by, for example, the diameter of a nozzle that applies the adhesive. The adhesive spilled into bottom opening <NUM> can obfuscate filter <NUM> and/or the pixel cells <NUM> of image sensor <NUM>. All these can degrade the light sensing performance of the image sensor module.

<FIG>, <FIG>, and <FIG> illustrate examples of an image sensor module <NUM> that can address at least some of the issues above. <FIG> illustrates an external side view of image sensor module <NUM>, whereas <FIG> illustrates an internal side view of image sensor module <NUM>. As shown in <FIG> and <FIG>, image sensor module <NUM> includes a holder structure <NUM> to hold and physically support one more lenses <NUM> and filter <NUM>. Holder structure <NUM> can be mounted on image sensor <NUM>, which in turn is mounted on PCB <NUM>. Holder structure <NUM> includes a housing <NUM> and a retainer <NUM>. Housing <NUM> can be in the form of a barrel in which one or more lenses <NUM> are mounted to form a lenses stack, whereas filter <NUM> can be mounted on retainer <NUM>, as in image sensor module <NUM> of <FIG> - <FIG>. However, unlike in image sensor module <NUM> in which retainer <NUM> is mounted within housing <NUM> in image sensor module <NUM>, at least a part of retainer <NUM> is sandwiched between housing <NUM> and image sensor <NUM>, such that housing <NUM>, retainer <NUM>, and image sensor <NUM> form a stack (e.g., along the z-axis). In addition, retainer <NUM> is bonded with image sensor <NUM> via an adhesive to set the orientation and position of one or more lenses <NUM> with respect to image sensor <NUM>.

Referring to <FIG>, housing <NUM>, which can be in the form of a barrel, includes a top opening <NUM> to receive light and a bottom opening <NUM> to output light to image sensor <NUM>. As in image sensor module <NUM>, one or more lenses <NUM> can be loaded into housing <NUM> of image sensor module <NUM> through bottom opening <NUM> towards top opening <NUM>. One or more lenses <NUM> can be mounted at predetermined positions within housing <NUM> between top opening <NUM> and bottom opening <NUM> to form a lenses stack, with housing <NUM> to provide physical support to the lenses stack. Housing <NUM> further includes a bottom surface <NUM> which surrounds bottom opening <NUM> and can be bonded with a top surface <NUM> of retainer <NUM> via an adhesive layer <NUM>.

<FIG> illustrates a magnified internal side view (left diagram) and a bottom view (right diagram) of retainer <NUM>. As shown in <FIG>, retainer <NUM> includes, in addition to top surface <NUM>, a middle surface <NUM> and a bottom surface <NUM>. An outer portion of top surface <NUM> of retainer <NUM> is bonded to bottom surface <NUM> of housing <NUM> via an adhesive <NUM>, whereas an inner portion of top surface <NUM> supports one or more lenses <NUM> to prevent the lenses from falling out of bottom opening <NUM> of housing <NUM>. Moreover, middle surface <NUM> provides a surface to mount filter <NUM>. In addition, bottom surface <NUM> of retainer <NUM> is flat and is bonded with light receiving surface <NUM> of image sensor <NUM> via an adhesive <NUM>. Both adhesives <NUM> and <NUM> can be cured by, for example, UV light to form a bonding layer.

Compared with bottom surface <NUM> of housing <NUM> of <FIG>, the width of bottom surface <NUM> of retainer <NUM>, as well as the width of bottom surface <NUM> of housing <NUM>, can be enlarged to increase the bonding area between retainer <NUM> and image sensor <NUM>. In addition, the footprint of image sensor module <NUM> imposes less restriction on the width of bottom surface <NUM> of retainer <NUM>. Specifically, referring back to <FIG>, bottom surface <NUM> of housing <NUM> surrounds both retainer <NUM> and filter <NUM>. As a result, bottom surface <NUM> needs to be made narrower to accommodate the width of retainer <NUM> and filter <NUM> for a given footprint. In contrast, in <FIG>, bottom surface <NUM> of retainer <NUM> may surround filter <NUM> only, whereas bottom surface <NUM> of housing <NUM> only surrounds one or more lenses <NUM>. Therefore, even for the same footprint and with the same filter <NUM>, bottom surface <NUM> of retainer <NUM> of <FIG>can be made wider and provide a larger bonding area between retainer <NUM> and image sensor <NUM>, compared with bottom surface <NUM> of housing <NUM> of <FIG>. Moreover, bottom surface <NUM> of housing <NUM> can also be made wider and provide a larger bonding area between housing <NUM> and retainer <NUM>, compared with the bonding area between housing <NUM> and retainer <NUM> of <FIG> - <FIG>.

In one example, as shown in <FIG>, with a footprint of <NUM> x <NUM> (e.g., same as image sensor module <NUM>), the minimum width of bottom surface <NUM> of retainer <NUM> is about <NUM>, about four times of the minimum width of bottom surface <NUM> of housing <NUM>. In addition, the minimum width of bottom surface <NUM> of housing <NUM> is about <NUM>, about twice of the minimum width of bottom surface <NUM> of housing <NUM>. As a result, an enlarged bonding area can be provided to improve bonding between retainer <NUM> and image sensor <NUM>, and between housing <NUM> and retainer <NUM>. In addition, with a larger bonding area, the precision requirement for application of adhesive <NUM> on bottom surface <NUM> can also be relaxed. It also becomes less likely that adhesive <NUM> spills over from bottom surface <NUM> and obfuscates filter <NUM> and/or pixel cells <NUM> of image sensor <NUM>. All these can improve the performance of image sensor module <NUM>.

Although <FIG> illustrates that retainer <NUM> includes has a rectangular footprint and that filter <NUM> has a circular shape, it is understood that retainer <NUM> and filter <NUM> can have other geometric shapes. For example, retainer <NUM> can have a cylindrical shape, whereas filter <NUM> can have a rectangular/square shape.

<FIG> and <FIG> illustrate examples of an image sensor module <NUM> having additional features to improve bonding between housing <NUM> and retainer <NUM>. The left of <FIG> illustrates an external view of image sensor module <NUM>, whereas the right of <FIG> illustrates a partial internal view of image sensor module <NUM>. As shown in <FIG>, housing <NUM> can include a barrel <NUM> as well as a rectangular base <NUM> which surrounds a part of barrel <NUM> and bonds with retainer <NUM>, whereas barrel <NUM> surrounds and holds one or more lenses <NUM>. Housing <NUM> and retainer <NUM> can include complimentary uneven bonding surfaces. The uneven bonding surfaces increases the total area for applying adhesive <NUM>, which can improve the bonding between housing <NUM> and retainer <NUM>.

The complimentary uneven bonding surfaces can be provided at various locations of housing <NUM> and retainer <NUM>. For example, as shown in <FIG>, the bottom of rectangular base <NUM> can include a protrusion <NUM> to provide an uneven bottom surface <NUM>, whereas the top of retainer <NUM> can include a complimentary notch <NUM> to provide an uneven top surface <NUM>. As another example, as shown in <FIG>, top of retainer <NUM> can include, as part of uneven top surface <NUM>, an outer top surface <NUM> and an inner top surface <NUM>. Outer top surface <NUM> can have the same rectangular footprint and dimension as bottom surface of rectangular base <NUM>, and bond with the bottom surface of rectangular base <NUM>. Moreover, inner top surface <NUM> can have the same rectangular footprint and dimension as the bottom surface of barrel <NUM>, and bond with the bottom surface of barrel <NUM>. The rectangular footprint of outer top surface <NUM> and rectangular base <NUM> can increase the bonding area and further improve the bonding between housing <NUM> and retainer <NUM>.

The techniques described above in <FIG> - <FIG> can also be used to reduce the footprint and improve the performance of a light projector module, such as illuminator <NUM> of <FIG>. For example, image sensor <NUM> in image sensor modules <NUM> and <NUM> can be replaced by a light source (e.g., an light emitting diode (LED), a laser diode). Light emitted by the light source can pass through filter <NUM> and one or more lenses <NUM> to form, for example, collimated light beams having a certain frequency range (e.g., infrared).

<FIG> - <FIG> illustrates a method <NUM> of forming an image sensor module, such as image sensor modules <NUM>, <NUM>, <NUM>, and <NUM> of <FIG>, on a PCB <NUM>. Referring to <FIG>, method <NUM> can start with step <NUM>, in which a lens assembly comprising one or more lenses is formed. In some examples, referring to <FIG>, lens assembly <NUM> of image sensor module <NUM> can be formed by first fabricating layers <NUM> and polymer spacers <NUM> by an injection molding process, in step 1402a, followed by stacking the layers and spacers to form a lens stack, in step 1402b, and then followed by coating four sides of the lens stack with an opaque material to form coating layer <NUM>, in step 1402c.

In some examples, referring to <FIG>, lens assembly <NUM> of image sensor module <NUM> can be formed by first fabricating housing <NUM>, layers <NUM>, and spacers <NUM> (e.g., by an injection molding process), in step 1402e, followed by inserting the layers <NUM> and spacers <NUM> into housing <NUM> to form lens assembly <NUM>, in step 1402f. In some examples, referring to <FIG>, one or more lenses <NUM>, which can include lens assembly <NUM>, can be loaded into a housing (e.g., housing <NUM>/<NUM>) through a bottom opening of the housing, followed by mounting a retainer either within the housing (e.g., retainer <NUM> as in <FIG> - <FIG>) or by mounting a retainer on bottom surfaces of the housing (e.g., retainer <NUM> as in <FIG> - <FIG>) in step 1402f, with the retainer providing a surface to attach a filter.

Referring back to <FIG>, image sensor <NUM> can be fabricated, in step <NUM>. The fabrication of image sensor <NUM> may include fabricating an image sensor die, packaging the image sensor die in a flip-chip package, and depositing solder balls <NUM> on the flip-chip package. The fabrication of image sensor <NUM> further includes forming glass substrate <NUM> on light receiving surface <NUM> of the image sensor die.

Following step <NUM>, a reflow process can be performed to conductively bond image sensor <NUM> onto PCB <NUM> to form an image sensor stack, in step <NUM>. The reflow process can be performed to reflow solder balls <NUM> of the flip-chip packages into a liquid state to form conductive bonds with the contact pads of PCB <NUM>.

Following step <NUM>, a layer of adhesive can be formed on at least one of the image sensor stack or the lens assembly. As shown in <FIG>, in a case where the adhesive is opaque upon curing, the adhesive can be formed on, for example, a perimeter of glass substrate <NUM> (of image sensor <NUM>) around a region <NUM> facing the light outputting surface of the lens assembly. Moreover, in a case where the adhesive is clear/transparent upon curing, the adhesive can be formed in region <NUM> as well to bond glass substrate <NUM> with the light outputting surface of the lens assembly. In some examples, as described with respect to <FIG> - <FIG>, the adhesive (e.g., adhesive <NUM>) can be formed on a bottom surface of the retainer. The adhesive can be cured to form a bonding layer in subsequent steps.

Although <FIG> illustrates that the fabrication of image sensor <NUM>, the reflow process, and the formation of the adhesive layer in steps <NUM> to <NUM> occur after the formation of the lens assembly in step <NUM>, it is understood that step <NUM> can be formed simultaneously or after any of steps <NUM>, <NUM>, or <NUM>. Referring to <FIG>, at the end of step <NUM>, a lens assembly <NUM>/<NUM> and/or an image sensor module <NUM>/<NUM> comprising a holder structure <NUM>/<NUM>, image sensor <NUM>, and PCB <NUM> are formed.

In step <NUM>, the lens assembly and the image sensor stack can be brought together and connected via the layer of adhesive. In step <NUM>, at least one of the lens assembly or the image sensor stack can be moved to align the image sensor with the one or more lenses while the image sensor stack is connected with the lens assembly. Referring back to <FIG>, the movement of the image sensor stack (and/or the lens assembly) can be based on an alignment process, in which the image sensor can be controlled to generate sensor data of light received by the image sensor via the one or more lenses. A degree of alignment between the image sensor stack and the one or more lenses can be determined based on the sensor data. The position and orientation of the image sensor stack with respect to the lens assembly can be adjusted until a target degree of alignment is reached.

In step <NUM>, with the image sensor stack and the lens assembly at their respective aligned position and orientation, a curing process can be performed to harden the adhesive layer to form bonding layer <NUM> to bond the image sensor stack with the lens assembly. The curing process can be based on ultraviolet light and/or a heat process at a temperature lower than the melting point of the one or more lenses.

Claim 1:
An apparatus comprising:
a lens assembly (<NUM>, <NUM>) comprising:
a plurality of polymer layers (<NUM>, <NUM>) comprising a first polymer layer and a second polymer layer forming a stack, the first polymer layer (<NUM>, <NUM>) including a lens portion (<NUM>) and an extension portion (<NUM>, <NUM>), and the second polymer layer (<NUM>, <NUM>) including a lens portion (<NUM>);
at least one rigid spacer (<NUM>, <NUM>) having an opening and sandwiched between the first polymer layer (<NUM>, <NUM>) and the second polymer layer (<NUM>, <NUM>), the extension portion (<NUM>, <NUM>) of the first polymer layer (<NUM>, <NUM>) being mechanically supported on and bonded to the at least one rigid spacer (<NUM>, <NUM>) via a first bonding layer (<NUM>) to allow the lens portion (<NUM>) of the first polymer layer (<NUM>, <NUM>) to be suspended over the opening (<NUM>) and over the lens portion (<NUM>) of the second polymer layer (<NUM>, <NUM>); and
an image sensor (<NUM>) positioned below the lens assembly (<NUM>, <NUM>) and bonded to the lens assembly (<NUM>, <NUM>) via a bonding layer (<NUM>, <NUM>) and configured to sense light that passes through the lens portions (<NUM>) of the plurality of polymer layers (<NUM>, <NUM>);
wherein the lens portions (<NUM>) of the plurality of polymer layers (<NUM>, <NUM>) are configured to gather and direct light towards the image sensor (<NUM>).