Camera module integrating metasurfaces

Abstract

The device includes a camera module. The camera module includes an image sensor, a lens unit disposed on the image sensor, and an aperture diaphragm. The lens unit includes at least two encapsulated metasurfaces stacked vertically on top of each other.

Description

Technology Field

[0001] This application relates to a camera module. Background Technology

[0002] Various types of small camera modules are available. Time-of-flight (ToF) sensor modules can be used, for example, to detect the distance to an object. Generally, indirect time-of-flight (iToF) systems are based on phase measurement techniques of emitted intensity-modulated light reflected by the scene. The reflected light is imaged onto the sensor, and photogenerated electrons are demodulated within the sensor. Based on phase information, the distance to a point within the scene for each pixel is determined by the processing circuitry associated with the sensor. Additionally, ToF-based systems can provide depth and / or distance information through pulse measurement techniques. In pulse measurement techniques, the distance is determined based on the time it takes for the emitted light to be reflected back onto the sensor.

[0003] However, integrating camera modules (e.g., ToF sensors including their lenses) into devices such as smartphones, tablets, and other handheld devices can be challenging for several reasons. For instance, space within a host device is typically very limited. Consequently, there is a need to achieve precision ToF sensors and other camera modules with a relatively small height. Additionally, it may be desirable for the ToF sensor module to have a low F-number (representing the ratio of focal length (f) to entry pupil diameter (EPD)), and it may be advantageous to have a low effective F-number (i.e., a low F-number for all viewpoints). However, achieving such F-numbers can present challenges when using conventional lens configurations. For instance, achieving a similarly low effective F-number may require a somewhat complex and large conventional lens stack. means of solving the problem

[0004] In one embodiment, the present disclosure describes an apparatus comprising a camera module. The camera module comprises an image sensor, a lens unit disposed on the image sensor, and an aperture stop. The lens unit comprises at least two encapsulated metasurfaces stacked vertically on top of each other.

[0005] The lens unit may have a front side and a back side, and the back side of the lens unit is closer to the image sensor than the front side of the lens unit. In some embodiments, the aperture is positioned on the front side of the lens unit.

[0006] Some embodiments include one or more of the following features. For example, in some embodiments, the lens unit includes an optical filter, said optical filter includes an angle-of-incidence (AOI) filter operable to selectively block or attenuate a beam of electromagnetic radiation greater than a specific angle of incidence at a specific wavelength. In some embodiments, the lens unit includes a first and a second optical filter, each optical filter including an angle-of-incidence (AOI) filter, wherein the first AOI filter is positioned after a first metasurface within the lens unit and has a first blocking angle, and the second AOI filter is positioned after a second metasurface within the lens unit and has a second blocking angle different from the first blocking angle.

[0007] In some embodiments, the camera module includes an optical filter, and the optical filter includes a bandpass filter operable to selectively block or attenuate rays of electromagnetic radiation outside a defined passband of wavelength. In some embodiments, the optical filter includes a coating in or on the lens unit. In some embodiments, the optical filter is a separate component bonded to the rear surface of the lens unit. In some embodiments, the optical filter is closer to the metasurface in the lens unit than to the image sensor.

[0008] In some embodiments, the camera module further includes a barrel disposed within a holder, a lens unit disposed within the barrel, and an optical filter is a separate component disposed within the barrel or within the holder.

[0009] In some embodiments, the aperture is located at the front of the lens unit. In some embodiments, the lens unit further includes at least one baffle to prevent at least some stray light from reaching the photosensitive surface of the image sensor. In some embodiments, at least one baffle includes a first baffle disposed at the rear of the lens unit. In some embodiments, at least two encapsulated metasurfaces include a first metasurface and a second metasurface, and at least one baffle further includes a second baffle disposed between the first metasurface and the second metasurface. The baffle(s) may be composed of, for example, black resist or black chrome.

[0010] In some embodiments, the aperture is defined by an aperture layer composed of black chrome or black resist. In some embodiments, the sidewalls of the lens unit are at least partially blackened. In some embodiments, the lens unit includes an anti-reflection coating (ARC).

[0011] In some embodiments, at least two encapsulated metasurfaces comprise a first metasurface and a second metasurface on opposite sides of a single glass substrate. In some embodiments, at least two encapsulated metasurfaces comprise a first metasurface on a first glass substrate and a second metasurface on a second glass substrate bonded to the first glass substrate. In some embodiments, the first glass substrate and the second glass substrate are bonded to each other by an adhesive. The adhesive may be optically transparent at a specific wavelength (e.g., an operating wavelength for a camera module). In some embodiments, the adhesive is refractive index matched to the first glass substrate and the second glass substrate.

[0012] In some embodiments, at least one of the metasurfaces is encapsulated by a polymer. In some embodiments, at least one of the metasurfaces is encapsulated by an adhesive that bonds the first glass substrate and the second glass substrate together. In some embodiments, each of at least two metasurfaces is encapsulated by a respective encapsulation layer composed of a material that is optically transparent at a specific wavelength.

[0013] In some embodiments, the camera module further comprises a cover glass and a spacer over an image sensor, a lens unit is bonded to the spacer, and the spacer is bonded again to the cover glass. In some embodiments, the lens unit is bonded to the active surface of the image sensor or to the cover glass over the image sensor. In some embodiments, the lens unit is bonded to the active surface of the image sensor without any gaps between them.

[0014] In some embodiments, the device further includes an electronic circuit board, and an image sensor is mounted on the electronic circuit board. In some embodiments, a lens unit is mounted in a barrel aligned within a holder attached to the circuit board. In some embodiments, the camera module is a Time-of-Flight (ToF) sensor module.

[0015] One or more of the following advantages may be achieved in some embodiments. For example, the use of optical elements employing planar technology (i.e., MOE) may help reduce the overall size of the camera module (e.g., diameter and height) in some cases. In some cases, incorporating a stack of metasurfaces into the lens unit may facilitate improved thermal and mechanical stability. In some cases, incorporating a stack of metasurfaces into the lens unit may facilitate a wide range of optical functions by correcting various aberrations of the optical system, thereby improving or enhancing the optical performance of the camera module.

[0016] Other embodiments, features, and advantages will become readily apparent from the following detailed description, the accompanying drawings, and the claims. Brief explanation of the drawing

[0017] Figure 1 illustrates a first example of a camera module. Figure 2 illustrates a second example of a camera module. Figure 3 illustrates a third example of a camera module. Figure 4 illustrates a fourth example of a camera module. FIGS. 5 to 9 illustrate examples of camera modules including optical filters. FIGS. 10 to 14 illustrate examples of a camera module including at least one baffle. FIGS. 15 to 17 illustrate an example of a camera module including a spacer between a lens unit and an image sensor. Specific details for implementing the invention

[0018] The present disclosure describes various small camera modules. In the following paragraphs, examples of applications using time-of-flight sensors are described. However, camera modules may also be used in other applications that incorporate other types of image sensors.

[0019] As illustrated in FIG. 1, an exemplary camera module is a ToF sensor module (20) comprising an image sensor (e.g., a ToF sensor) (22) and a lens unit (26) placed over the sensor. The ToF sensor (22) may be mounted and electrically coupled to an electronic circuit board (e.g., a printed circuit board (PCB)) (24) by means of, for example, wire bonds or conductive pads (23). The electronic circuit board (24) may eventually be electrically connected to other components within a host device (e.g., a smartphone or tablet). Other components may include, for example, one or more light sources (e.g., a vertical cavity surface emitting laser (VCSEL); a light-emitting diode (LED)) and a processing circuit.

[0020] The ToF sensor (22) may include, for example, an array of spatially distributed photosensitive elements (e.g., active demodulation detection pixels) as well as a photosensitive area (25) containing a reference pixel. The detection pixel provides a primary signal for determining the distance to an object outside the module (20). The signal from the reference pixel may be used, for example, to compensate for drift and / or provide zero distance measurements. The sensor (22) may be implemented on a semiconductor chip using, for example, charge-coupled device (CCD) or complementary metal oxide semiconductor (CMOS) technology or single photon avalanche diode (SPAD) technology. In some embodiments, a cover glass (44) may be provided over the ToF sensor (22).

[0021] Depending on the specific use case, the operating wavelength for the module may be, for example, in the visible light range (400 - 700 nm), near-infrared range (700 - 1400 nm), short-wavelength infrared range (1.4 - 3 μm), mid-wavelength infrared range (3 - 8 μm), or low-wavelength infrared range (8 - 14 μm).

[0022] The lens unit (26) comprises one or more substrates (30) having at least two metasurfaces (28A, 28B) stacked vertically above each other. Each metasurface (28A, 28B), together with the substrate disposed thereon, forms a metalens. Incorporating a stack of metasurfaces into the lens unit (26) can facilitate a wide range of optical functions by having resonant interactions between the stacked metasurfaces in some cases. The metasurfaces (28A, 28B) may be disposed on an optically transparent or at least partially transparent substrate (30) (e.g., glass, plastic, or polymer material). In the example illustrated in FIG. 1, the metasurfaces (28A, 28B) are disposed on opposite sides of the same substrate (30), and the substrate is, for example, glass (e.g., D 263 manufactured by Schott). ® It can be composed of borosilicate glass (such as glass) and can provide mechanical support to the metasurface (28A, 28B).

[0023] Each metasurface (28A, 28B) has carefully arranged "unit cells" or "meta atoms" having a sub-wavelength structure (e.g., nanostructures). The term "sub-wavelength" indicates that the nanostructure has at least one lateral dimension (parallel to the substrate on which it is placed) smaller than the wavelength of light incident thereon. The meta atoms may be composed of, for example, silicon. Generally, the dimensions of the nanostructure are proportional to the shortest wavelength of interest. For example, in some embodiments, the nanostructure may be in the form of nanoscale features having dimensions of less than 1 micron. By adjusting the geometry of these unit cell elements, the phase on the elements can be modified in response to plane waves. It is possible to create metalens with any phase profile by having knowledge of the phase in terms of geometric parameters and placing meta atoms at the required locations. Generally, the derivative of the phase profile determines the refraction of the light. Each metasurface (28A, 28B) on the substrate (30) forms a metal optical element (MOE) that employs planar optical technology. The use of optical elements that employ planar technology can, in some cases, help to reduce the overall size (e.g., diameter and height) of the module (20).

[0024] As shown in FIG. 1, each of the metasurfaces (28A, 28B) may be encapsulated. This arrangement may provide protection for the metasurfaces. In some embodiments, each metasurface (28A, 28B) is encapsulated by each encapsulation layer (32) composed of a material that is optically transparent at the applied wavelength. For example, in some cases, the encapsulation layer (32) is composed of a polymer. The encapsulation layer (32) may be relatively thin (e.g., 1-5 μm in some cases) to reduce the degree of any adverse effect on optical performance. In some embodiments, other materials and / or thicknesses may be used for the encapsulation layer (32).

[0025] Some embodiments include an anti-reflective coating (ARC) on an encapsulation layer (32) on an upper metasurface (28A) (i.e., a metasurface further away from the ToF sensor (22)). In some embodiments, the ARC is applied to other air-glass interfaces of the lens unit.

[0026] As additionally illustrated in the example of FIG. 1, the aperture layer (34) is provided on the front of the lens unit (26) (e.g., on, above, or near the first metasurface (28A) where light is incident on the module). The aperture layer (34) defines an aperture aperture that operates to limit the solid angle of a ray passing through the system from an axial object point, which defines a light cone reaching the image plane of the ToF sensor (22). The aperture layer (34) may be composed of, for example, black chrome or black resist.

[0027] The outer sidewalls of the substrate (30) and the encapsulation layer (32), as well as the ARC (if present), may be blackened or at least partially blackened with a layer (38) of, for example, a black polymer material or other opaque material to prevent or reduce stray light from entering the lens unit (26). The lens unit (26) may be held within a barrel (40), and the barrel is again held by a holder (42) that maintains a specific distance between, for example, the ToF sensor (22) and the lens unit (26). The lower end(s) of the holder may be placed on, for example, the surface of an electronic circuit board (24). Thus, the lens unit (26) may be mounted within the barrel (40) aligned within the holder (42) attached to the circuit board (24).

[0028] In some embodiments, various modifications may be made to the lens unit. For example, in some cases, instead of two metasurfaces on opposite sides of the same substrate as shown in FIG. 2, the lens unit (26A) comprises metasurfaces (28A, 28B) disposed on each of the respective different substrates (30A, 30B). The substrates (30A, 30B) may be bonded back-to-back together by an adhesive (46) (e.g., a thin layer of polymer glue) that is optically transparent at the operating wavelength for the module (20A). In some embodiments, the adhesive (46) is refractive index matched to the glass substrates (30A, 30B). Also, in some embodiments, as shown in the exemplary module (20B) of FIG. 3, the two substrates (30A, 30B) of the lens unit (26B) are bonded together in a front-to-back arrangement. That is, the front side of the second substrate (30B) (i.e., the side where the encapsulated metasurface (28B) is present) is bonded to the rear side of the first substrate (30A) (i.e., the side opposite the encapsulated metasurface (28A)). In some embodiments of the front-to-rear arrangement, as shown in the lens unit (26C) of the module (20C) of FIG. 4, the metasurface (28B) on the second substrate (30B) may be encapsulated by an adhesive (46) that bonds the two substrates (30A, 30B) together. In that case, a separate encapsulation material (32) for the second metasurface (28B) may be omitted. In each of the examples of FIG. 1 to FIG. 4, there is no gap between the metasurfaces (28A, 28B) within the lens unit.

[0029] Any of the embodiments described above may include, in some cases, an optical filter positioned between, for example, the lens unit (26) and the ToF sensor (22). The optical filter may be implemented, for example, as a narrowband filter (e.g., a bandpass filter (BPF)) and / or an angle of incidence (AOI) filter. The AOI filter may be selective, for example, with respect to the angle of incidence of the incident light. The narrow bandwidth characteristic will allow only light with a small angle to pass through and block light with an angle greater than the cut-off angle. That is, the optical filter can be operated to block or significantly attenuate light greater than a specific angle of incidence (i.e., cut-off angle) for a given wavelength (e.g., 940 nm). In this regard, the angle of incidence (α) refers to the angle formed between a light ray striking the surface and a line perpendicular to the surface.

[0030] In some embodiments, providing an optical filter that selectively blocks or attenuates rays of electromagnetic radiation greater than a specific angle of incidence may provide optical performance advantages (e.g., stray light filtering). For example, in some cases, the optical output from the lens unit (26) includes an imaging ray and a ray of a higher diffraction order, where the higher diffraction order is a higher diffraction order than the imaging order. An AOI filter optically positioned between the lens unit (26) and the ToF sensor (22) may help reduce the amount of light from at least one of the higher diffraction order rays reaching the photosensitive surface of the image sensor. In some cases, to improve functionality, the position of the AOI filter is closer to the second metasurface (28B) than to the ToF sensor (22).

[0031] For example, in some embodiments, the imaging order is a first transmission convergence order (m: ±1), and higher diffraction orders include one or more higher transmission convergence or divergence orders (m: ±2, ±3, ...), and the incident angle filter can be operated to prevent at least some rays of the second transmission order (m: ±2) and / or higher orders (m: ±3, ±4, ...) from reaching the photosensitive surface of the image sensor. More generally, the unwanted diffraction orders are all orders other than the imaging order. The unwanted orders may arise, for example, from each MOE surface, and combinations of these unwanted orders may exist in the optical stack. A zero-order diffraction order may also be included among the unwanted orders. In some situations, the unwanted orders will have a higher incident angle toward the sensor than the imaging order, thereby being reduced or partially blocked by the optical filter.

[0032] Implementing the optical filter as a narrowband filter (e.g., a BPF) allows the optical filter to be selective for a specific wavelength spectrum used in ToF applications and can be configured to pass only light of a specific wavelength used in the illumination portion of the ToF system. Additionally, the BPF can assist the AOI filter in blocking and / or reducing unwanted orders at very high angles. Thus, in some embodiments, the optical filter may be operable to block or significantly attenuate light using both the BPF and the AOI filter. For example, the BPF can block and / or reduce wavelengths that are not primarily used in the illumination portion of the ToF application, whereas the AOI filter can reduce light with an angle of incidence toward the sensor that is higher than the imaging order. The F-number of the optical design determines the blocking angle. In this regard, the angle of incidence (α) refers to the angle formed between a light ray striking a surface and a line perpendicular to the surface. Depending on the application, the filter may block light rays by one or more of absorption, reflection, or deflection, for example, to move the incident light rays away from the image sensor area.

[0033] In some embodiments, the optical filter comprises both a BPF and an AOI filter arranged such that the light rays blocked by the BPF have a higher diffraction order than the diffraction order reduced by the AOI filter. In some cases, the optical filter may be implemented as an optical interference bandpass filter that exhibits some degree of shift depending on the angle of incidence. In some embodiments, the characteristics of the AOI filter depend on position; for example, they may vary radially.

[0034] FIG. 5 illustrates an example in which an optical filter (e.g., AOI filter and / or BPF) as described above is implemented as a coating (48) on the surface of a glass substrate (30B) opposite the surface on which the metasurface (28B) is placed. In other cases, as illustrated in the examples of FIG. 6 and FIG. 7, the optical filter may be implemented as a separate component bonded to a lens stack (e.g., by an adhesive such as polymer glue). In FIG. 6, the optical filter (50) is bonded by an adhesive (52) to an encapsulating material (32) that encapsulates the second metasurface (28B). In FIG. 7, the optical filter (50) is bonded directly to the glass substrate (30) by an adhesive (52) (e.g., polymer glue). In the latter embodiment, the adhesive (52) also serves to encapsulate the second metasurface (28B). In the examples described above in FIGS. 5 to 7, another layer (38) of black chrome or opaque material may extend along the sidewall of the optical filter.

[0035] In some embodiments, the optical filter (50) may be spaced somewhat apart from the lens stack (26) and held in place by the barrel (40). For example, in some cases, as shown in FIG. 8, the optical filter (50) may be attached to one or more supports (54) extending laterally inward from the holder. In other cases, as shown in FIG. 9, the optical filter (50) may be held by the holder (42). For example, the optical filter (50) may be attached to one or more supports (56) extending laterally inward from the holder (42).

[0036] Some embodiments of the ToF module include one or more baffles. In some cases, the baffle(s) can prevent at least some stray light (e.g., light originating from higher diffraction orders, Fresnel reflections, or other scattered light) from reaching the photosensitive surface of the ToF sensor (22). In some embodiments, incorporating baffle(s) into the ToF module can help prevent artifacts originating from stray light at one or more higher diffraction orders or other scattered light from appearing on the photosensitive surface of the ToF sensor (22). In some cases, providing baffle(s) in combination with a metalens can prevent stray light from unwanted light beyond what is achievable using a conventional (e.g., refractive) optical system. That is, in addition to preventing stray light from scattered rays, providing baffle(s) in combination with a metalens can, in some cases, help prevent stray light from unwanted diffraction orders or combinations of orders and / or stray light caused by "non-transmitted" rays appearing under certain conditions in the generalized Snell's Law.

[0037] FIGS. 10 and 11 illustrate an example of a ToF module in which a first baffle (60A) is positioned on the lower surface of a lens unit (i.e., between the metalens and the ToF sensor). FIGS. 12 and 13 illustrate an example also comprising a second baffle (60B) positioned within a lens unit between the first metalens and the second metalens. In some embodiments (see FIG. 14) that also include an AOI filter or a BPF, the baffle(s) may be configured to block unwanted light rays that are not blocked by the AOI filter and / or the BPF. Generally, the AOI filter (50) may be positioned after any metasurface, but preferably after the last metasurface (i.e., the metasurface closest to the ToF sensor). In such a case, the distance from the AOI filter to the ToF sensor must be longer than the half-optical path length between the metasurface and the sensor. It is also possible to have more than one AOI filter within the lens unit. For example, a first AOI filter may be placed after a first metasurface and have a first cut-off angle, and a second AOI filter may be placed after a second metasurface and have a second cut-off angle different from the first cut-off angle. Each cut-off angle is determined by a corresponding metasurface to allow imaging orders to pass through and to reduce unwanted orders having higher angles of incidence.

[0038] The baffle(s) may be composed of, for example, black resist, black chrome, or other light-blocking materials. In some cases, there is a distance (d) that provides a clearance between the edge of the baffle and the light rays for the imaging order(s). Such an arrangement can prevent the baffle from interfering with the imaging order(s) for all field points to avoid vignetting. In some embodiments, the respective positions of the baffle (60B) and the aperture (34) may be interchanged so that the baffle is positioned on the front metasurface and the aperture is positioned between two metasurfaces.

[0039] In the exemplary embodiments of FIGS. 1 through 14, the lens unit (e.g., 26) is held by a barrel (40) placed within a holder (42), and the holder is mounted on an electronic circuit board (24) identical to the ToF sensor itself (on the ToF sensor (22)). However, in other embodiments, the lens unit may be mounted, for example, on a cover glass (44) placed on the ToF sensor (22). For example, as shown in FIG. 15, the lens unit (26) is bonded to a glass spacer (62) (e.g. by an adhesive (64A)), which is then bonded to the cover glass (44) (by an adhesive (64B)). The adhesives (64A, 64B) may be, for example, a polymer glue that is optically transparent at the operating wavelength of the ToF module. In some embodiments, instead of a glass spacer, a lens unit (26) is bonded to an optical filter (50) (e.g., an AOI filter or a BPF) (e.g., by an adhesive (64A)), which is then bonded to a cover glass (44) (e.g., by an adhesive (64B)) (see FIG. 16). Thus, in this example, the optical filter (50) also serves as a spacer. In some embodiments, as shown in FIG. 17, the spacer (62) has an opening (66) so that a gap exists between the lens unit (e.g., 26) and the cover glass (44). In the example of FIG. 17, the spacer (62) does not need to be transparent to the operating wavelength. In each of the examples of FIG. 14 through 16, the spacer may help provide a specific distance between the lens unit and the ToF sensor.

[0040] The above-described examples of FIGS. 1 through 17 include a gap between the cover glass (44) and the image sensor (22), but some embodiments include a refractive index-matched adhesive (e.g., bonding glue) or other optically transparent material between the cover glass (44) and the image sensor (22) so that no gap exists. Additionally, in some embodiments, the cover glass (44) may be omitted, and in some cases, a refractive index-matched adhesive (e.g., bonding glue) or other optically transparent material may be provided to directly bond an optical filter (50) (e.g., BPF or AOI filter) or a spacer (62) to the image sensor (22) so that no gap exists between the lens unit and the image sensor.

[0041] Although this specification contains many specific details, they should not be interpreted as limitations on the scope of the disclosure or the scope of claims, but rather as descriptions of features specific to specific embodiments. Specific features described in this specification in the context of distinct embodiments may also be combined in the same embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination. Various modifications may be made to the examples described above. Accordingly, other embodiments are also within the scope of the claims.

Claims

Claim 1 A device comprising a camera module, wherein the camera module comprises: an image sensor; a lens unit comprising at least two encapsulated metasurfaces stacked vertically above and below each other, wherein the lens unit is positioned above the image sensor and has a front surface and a rear surface, wherein the rear surface of the lens unit is closer to the image sensor than the front surface of the lens unit; and an aperture diaphragm. Claim 2 In paragraph 1, the aperture is a device located on the front of the lens unit. Claim 3 The device according to claim 1, wherein the camera module further comprises an optical filter, and the optical filter comprises an angle of incidence (AOI) filter operable to selectively block or attenuate a beam of electromagnetic radiation greater than a specific angle of incidence at a specific wavelength. Claim 4 The device according to claim 1, wherein the lens unit further comprises first and second optical filters, each optical filter comprises an angle of incidence (AOI) filter, the first AOI filter is positioned after a first metasurface within the lens unit and has a first blocking angle, and the second AOI filter is positioned after a second metasurface within the lens unit and has a different second blocking angle. Claim 5 The device according to claim 1, wherein the camera module further comprises an optical filter, and the optical filter comprises a bandpass filter operable to selectively block or attenuate a beam of electromagnetic radiation outside a defined passband of wavelength. Claim 6 A device according to any one of paragraphs 2 to 5, wherein the optical filter comprises a coating within or on the lens unit. Claim 7 A device according to any one of paragraphs 2 to 5, wherein the optical filter is a separate component bonded to the rear surface of the lens unit. Claim 8 A device according to any one of claims 2 to 5, wherein the camera module further comprises a barrel disposed within a holder, the lens unit disposed within the barrel, and the optical filter is a separate component disposed within the barrel. Claim 9 A device according to any one of claims 2 to 5, wherein the camera module further comprises a barrel disposed within a holder, the lens unit disposed within the barrel, and the optical filter is a separate component disposed within the holder. Claim 10 A device according to any one of claims 2 to 9, wherein the optical filter is closer to the metasurface within the lens unit than to the image sensor. Claim 11 A device according to any one of claims 1 to 9, wherein the lens unit further comprises at least one baffle for preventing at least some stray light from reaching the photosensitive surface of the image sensor. Claim 12 In claim 10, the device comprises at least one baffle including a first baffle disposed on the rear surface of the lens unit. Claim 13 An apparatus according to claim 12, wherein the at least two encapsulated metasurfaces comprise a first metasurface and a second metasurface, and the at least one baffle further comprises a second baffle disposed between the first metasurface and the second metasurface. Claim 14 A device according to any one of claims 11 to 13, wherein at least one baffle is composed of black resist or black chrome. Claim 15 A device according to any one of claims 1 to 14, wherein the side wall of the lens unit is at least partially blackened. Claim 16 A device according to any one of claims 1 to 15, wherein the lens unit comprises an anti-reflective coating (ARC). Claim 17 An apparatus according to any one of claims 1 to 16, wherein the at least two encapsulated metasurfaces comprise a first metasurface and a second metasurface on opposite sides of a single glass substrate. Claim 18 An apparatus according to any one of claims 1 to 16, wherein the at least two encapsulated metasurfaces comprise: a first metasurface on a first glass substrate; and a second metasurface on a second glass substrate bonded to the first glass substrate. Claim 19 An apparatus according to any one of claims 1 to 16, wherein the first and second glass substrates are joined together by an adhesive. Claim 20 In paragraph 19, the above adhesive is an optically transparent device at a specific wavelength. Claim 21 In claim 19 or 20, the device wherein the adhesive is refractive index matched to the first glass substrate and the second glass substrate. Claim 22 In claim 19, the device wherein at least one of the metasurfaces is encapsulated by a polymer. Claim 23 In claim 19, the device wherein at least one of the metasurfaces is encapsulated by an adhesive that bonds the first glass substrate and the second glass substrate together. Claim 24 An apparatus according to any one of claims 1 to 23, wherein each of the at least two metasurfaces is encapsulated by a respective encapsulation layer composed of a material that is optically transparent at a specific wavelength. Claim 25 A device according to any one of claims 1 to 24, wherein the aperture aperture is defined by an aperture layer composed of black chrome or black resist. Claim 26 An apparatus according to any one of claims 1 to 25, wherein the camera module further comprises: a cover glass over the image sensor; and a spacer, wherein the lens unit is bonded to the spacer, and the spacer is bonded in turn to the cover glass. Claim 27 A device according to any one of claims 1 to 25, wherein the lens unit is bonded to the active surface of the image sensor or to the cover glass above the image sensor. Claim 28 In claim 27, the device wherein the lens unit is bonded to the active surface of the image sensor without any gaps between them. Claim 29 A device according to any one of claims 1 to 28, further comprising an electronic circuit board, wherein the image sensor is mounted on the electronic circuit board. Claim 30 In claim 29, the lens unit is a device mounted in a barrel aligned within a holder attached to a circuit board. Claim 31 A device according to any one of claims 1 to 30, wherein the camera module is part of a time-of-flight (ToF) sensor module.

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