Compact camera with microlens array for ultra-short-range imaging

Abstract

A compact camera for ultra-short distance imaging and a method for ultra-short distance imaging are provided. The compact camera includes an image sensor, a transparent layer, and a microlens (ML) layer between the image sensor and the transparent layer. The ML layer forms (a) a first ML array having a plurality of first MLs, and (b) a second ML array having a plurality of second MLs interlaced with the plurality of first MLs. The compact camera also includes a baffle layer between the ML layer and the image sensor, the baffle layer forming a plurality of first aperture stops and a plurality of second aperture stops, the first aperture stops are each aligned with a different first ML in the first MLs, and the second aperture stops are each aligned with a different second ML in the second MLs. The first MLs each have a first set of optical properties, and the second MLs each have a second set of optical properties different from the first set of optical properties.

Description

Technical Field

[0001] The present invention relates to the field of compact cameras, and in particular to a compact camera for ultra-short-range imaging and a method for ultra-short-range imaging. Background Art

[0002] Compact and low-profile cameras are key components of today's smartphones, tablets, laptops, game consoles, and a variety of portable devices that require one or more embedded cameras. Applications where the imaged object is at a distance of two millimeters or less include biometric authentication (e.g., fingerprint, heart rate, or vein recognition) and tag and / or barcode reading, and therefore require ultra-short-range imaging.

[0003] Ultra-short range imaging is challenging for conventional cameras that employ a single lens or a single group of lenses that covers a full field of view (FOV), especially when the total length of the module is less than two millimeters, which is a requirement for most smartphones and handheld devices. In addition, larger lenses typically have poor image quality near the edges of their FOV. FIGS. 1A and 1B illustrate an example prior art camera 100 that is made compact and low profile by using an array 101 (also referred to as a lenslet array) of microlenses (MLs) 102 and a spacing 104. FIG. 1A is a top schematic diagram illustrating the array 101 of MLs 102, and FIG. 1B illustrates a section AA through the camera 100 of FIG. 1A. As shown in FIG. 1B, the camera 100 also includes a filter 122, a baffle layer 124 having a plurality of aperture stops 126 (each aperture stop is positioned relative to each ML 102), a glass cover 128, and a support structure 130.

[0004] Each ML 102 captures only a partial FOV 106 over the area of ​​the image sensor 120, and software stitches together each of the captured image areas to form a complete image (illustratively shown in dashed outline) representing the full FOV 108. Because each ML's partial FOV 106 covers only a portion of the full FOV 108, its focal length, as well as the overall module length, is reduced.

[0005] In prior art cameras, the array 101 is a regular pattern (e.g., a square with a pitch 104) of identical MLs 102, where each ML 102 individually images a circular FOV 106 (or an inscribed square thereof) that overlaps the FOVs of the other MLs. In general, image quality (including MTF and distortion) and brightness gradually degrade from the center to the border of the lens' FOV, so some portions (e.g., portion 110) of the full FOV 108, especially near the border of an individual FOV 106, cannot be efficiently covered by the ML array 101. As a result, image quality and brightness vary significantly at different locations on the full FOV 108. That is, within the partial FOV 106 of each ML, image quality and brightness gradually degrade from the center to the border of the FOV 106, and because the FOVs 106 overlap only at the borders, the portion 110 of the full FOV 108 at the overlapping borders of the individual FOVs 106 is not efficiently covered by the array 101 of the ML 102, and the resulting image of the full FOV 108 is not optimal. Summary of the invention

[0006] In one aspect, a compact camera for ultra-short-range imaging includes an image sensor, a transparent layer, a microlens (ML) layer, and a baffle layer. The ML layer is between the image sensor and the transparent layer, forming (a) a first ML array having a plurality of first MLs, and (b) a second ML array having a plurality of second MLs interlaced with the plurality of first MLs. The baffle layer is between the ML layer and the image sensor, forming a plurality of first aperture stops and a plurality of second aperture stops, each of the first aperture stops being aligned with a different first ML in the first MLs, and each of the second aperture stops being aligned with a different second ML in the second MLs. Each of the first MLs has a first set of optical properties, and each of the second MLs has a second set of optical properties different from the first set of optical properties.

[0007] In some embodiments, the compact camera further includes a filter layer positioned between the baffle layer and the image sensor.

[0008] In some embodiments, the compact camera further includes a filter layer positioned between the ML layer and the transparent layer.

[0009] In some embodiments, the first ML array and the second ML array each form a periodic pattern.

[0010] In some embodiments, the periodic pattern is a square pattern.

[0011] In some embodiments, each first ML has a diameter d1, and each second ML has a diameter d2, wherein d1 is greater than d2, and the ratio R=d1 / d2, wherein

[0012] In some embodiments, each first ML has a diameter d1, and the first ML array has a pitch P, where 2 <P / d1<10。

[0013] In some embodiments, the ML layers are formed of a single lens material, and the first ML and the second ML have a back focal length (BFL) greater than or equal to 0.1 mm and less than 2 mm.

[0014] In some embodiments, each of the first MLs is positioned to form a first image on a corresponding first area of ​​the image sensor, and each of the second MLs is positioned to form a second image on a corresponding second area of ​​the image sensor different from the first area.

[0015] In some embodiments, the compact camera further includes a plurality of first color filters and a plurality of second color filters, each first color filter being formed in a corresponding first aperture stop in the first aperture stop, and each second color filter being formed in a corresponding second aperture stop in the second aperture stop.

[0016] In some embodiments, the compact camera further comprises a processor; and a memory storing a stitching algorithm having machine-readable instructions that, when executed by the processor, stitch the first image and the second image together to form a full image having a higher spectral range.

[0017] In some embodiments, the compact camera further comprises a plurality of visible light bandpass filters and a plurality of IR bandpass filters, each visible light bandpass filter being formed in a different first aperture stop in the first aperture stop, and each IR bandpass filter being formed in a different second aperture stop in the second aperture stop.

[0018] In some embodiments, the difference between the first set of optical properties and the second set of optical properties comprises a difference in f-number.

[0019] In some embodiments, the baffle layer includes a visible light bandpass filter layer forming a plurality of second aperture stops and an IR bandpass filter layer forming a plurality of first aperture stops.

[0020] In some embodiments, each of the plurality of first aperture stops has a transmission coefficient of a visible light bandpass filter layer, and each of the plurality of second aperture stops has a transmission coefficient of an IR bandpass filter layer.

[0021] In another aspect, a method for ultra-short-range imaging includes forming a corresponding first image in a plurality of first images at each of a plurality of first regions of an image sensor, and forming a corresponding second image in a plurality of second images at each of a plurality of second regions of the image sensor. The plurality of first images and the plurality of second images are captured using an image sensor, and the captured plurality of first images and the captured plurality of second images are stitched together to form a complete image.

[0022] In some embodiments, the step of forming the plurality of first images includes forming a first periodic array of the plurality of first images, and the step of forming the plurality of second images includes forming a second periodic array of the plurality of second images.

[0023] In some embodiments, the complete image is an image of a scene, and forming each of the plurality of first images includes imaging a corresponding first scene area among a plurality of first scene areas of the scene using a corresponding first ML among a plurality of first MLs of a first ML array, each of the first MLs having a first set of optical properties; and forming each of the plurality of second images includes imaging a corresponding second scene area among a plurality of second scene areas of the scene using a corresponding second ML among a plurality of second MLs of a second ML array, each of the second MLs having a second set of optical properties different from the first set of optical properties.

[0024] In some embodiments, the difference between the first set of optical properties and the second set of optical properties is the ML diameter.

[0025] In some embodiments, the difference between the first set of optical properties and the second set of optical properties comprises a difference in f-number. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 1A and 1B illustrate a prior art camera made compact and low profile by using a microlens (ML) array.

[0027] Figure 2 is a schematic top view of an example compact camera incorporating two distinct ML arrays for ultra-short range imaging in an embodiment.

[0028] Figure 3 In the embodiment, Figure 2 A cross section of a compact camera illustrating the image sensor and two distinct ML arrays with further example details.

[0029] Figure 4A yes Figure 3 Schematic diagram of a portion of an image sensor, illustrating the Figure 2 The two distinct ML arrays form a first image region.

[0030] Figure 4B A portion of an example complete image generated in an embodiment by stitching together images from a first image region and a second image region is shown.

[0031] Figure 5 In the embodiment shown, Figure 2 An example device of a compact camera to FIG. 4 .

[0032] Figure 6 is a schematic top view of an example compact camera incorporating two distinct ML arrays for ultra-short range imaging in an embodiment.

[0033] Figure 7 In the embodiment, Figure 6 Cross-section of a compact camera, illustrating the included filters.

[0034] Figure 8 is a cross-sectional view showing an example compact camera configured with visible light bandpass and infrared (IR) bandpass filters at aperture stops corresponding to two distinct ML arrays in an embodiment.

[0035] Fig. 9 is a cross-sectional diagram illustrating an example compact camera having a distinct ML array configured for high dynamic range (HDR) imaging in an embodiment.

[0036] Fig.10 is a cross-sectional view showing an example compact camera having two distinct ML arrays and a baffle layer formed of a visible light bandpass filter and an IR bandpass filter cascaded in two layers in an embodiment.

[0037] Fig.11A It is a diagram showing that in the embodiment Fig.10 Graphs of example transmittance spectra of a visible bandpass filter and an IR bandpass filter.

[0038] Fig. 11B is a diagram illustrating the embodiment with Fig.10 Graph of example transmittance spectra of an IR bandpass filter cascaded with a visible bandpass filter.

[0039] Fig.12 is a cross-sectional view showing an example compact camera with two distinct ML arrays and repositioned filters in an embodiment. DETAILED DESCRIPTION

[0040] Embodiments of the camera disclosed herein address the non-uniformity issues of image quality and brightness by combining two interleaved ML arrays. Each ML array has different characteristics, such as one or more of the following: size, shape, field of view (FOV), etc.

[0041] Figure 2 is a schematic top view of an example compact camera 200 incorporating two distinct microlens (ML) arrays for ultra-short range imaging. Figure 3 It passes through Figure 2 BB of compact camera 200 illustrates further example details. Figure 2 and Figure 3 It is best viewed in conjunction with the following description. For clarity of illustration, not all components are numbered.

[0042] The camera 200 includes an image sensor 300 having a plurality of pixels 301, a baffle layer 304 (e.g., an optically opaque layer) having a plurality of first-sized aperture stops 306 and a plurality of second-sized aperture stops 308, an ML layer 310, and a transparent layer 312 (e.g., glass) supported by sidewalls 314. The camera 200 may also include a filter layer 302 positioned between the image sensor 300 and the baffle layer 304. The filter layer 302 is positioned to filter all light impinging on the image sensor 300. In embodiments where the camera 200 captures visible light, the filter layer 302 is a visible light bandpass filter that only allows visible light to pass. In embodiments where the camera 200 captures IR light, the filter layer 302 is an IR bandpass filter that only allows IR light to pass. Thus, the selection of the filter layer 302 (or the omission of the filter layer 302 in the case where both visible and IR light are to be captured) depends on the intended application of the camera 200. Visible light bandpass filters allow visible light (e.g., approximately 400-700 nm) to pass and block ultraviolet (UV) light and infrared (IR) light. IR bandpass filters allow near infrared light (e.g., approximately 700-1000 nm wavelength) to pass and block all other wavelengths of light (e.g., <700 nm and >1000 nm).

[0043] The ML layer 310 forms (a) a first ML array 201 having a plurality of first MLs 202, each of which has a first optical characteristic, and (b) a second ML array 211 having a plurality of second MLs 212, each of which has a second optical characteristic different from the first optical characteristic. Figure 2As shown in , both the first ML array 201 and the second ML array 211 are formed into a staggered periodic pattern (e.g., a regular square pattern with a pitch P). However, other patterns may be implemented without departing from the scope of the present invention. Each first-sized aperture stop 306 is substantially aligned with a different first ML 202, and each second-sized aperture stop 308 is substantially aligned with a different second ML 212. In some embodiments, the first optical characteristic includes a first diameter for the first ML 202, and the second optical characteristic includes a second diameter for the second ML 212 that is different from the first diameter. For simplicity of illustration, the first ML array 201 is shown as a 5×4 matrix and the second ML array 211 is shown as a 4×3 array; however, each of the first ML array 201 and the second ML array 211 may have more MLs without departing from the scope of the present invention. In one embodiment, the first ML array 201 is formed as a periodic array of M×N first MLs 202, and the second ML array 211 is formed as a periodic array of P×Q second MLs 212, where P is 1 less than M, and Q is 1 less than N. For example, the first ML array 201 is formed as a periodic array of 14×10 first MLs 202, and the second ML array 211 is formed as a periodic array of 13×9 second MLs 212. The diameter of the ML can range from 50 μm to 250 μm, and can cover 100 (=10×10) to 10000 (=100×100) pixels. In one embodiment, the diameters of the first ML 202 and the second ML 212 are 140 μm and 90 μm (micrometers), respectively. In the case where the first ML array 201 is 14×10 and the pitch P=600 μm, the physical size of the ML layer 310 and the corresponding captured full image are, for example, about 8.4×6 mm.

[0044] Each first ML 202 has a corresponding partial FOV 206. The partial FOVs 206 overlap to collectively cover substantially all of the full FOV 208, where the full FOV 208 may represent an equivalent combined FOV of the cameras 200. The second MLs 212 each have a smaller individual FOV 216 and are positioned to capture images with good quality at locations that were captured with lower quality by the first MLs 202. As shown, the second MLs 212 are positioned so that the smaller individual FOVs 216 are at the intersection boundaries of the partial FOVs 206.

[0045] ML layer 310 may be formed of a single lens material, whereby first ML 202 and second ML 212 are shaped to form an image of object plane 316 at an image plane of image sensor 300 and have a back focal length (BFL). The back focal length may be between 0.1 mm and 2 mm. In particular, first ML 202 and second ML 212 are formed to image at least a portion (e.g., corresponding to full FOV 208) of object plane 316 at an image plane captured by pixels 301 of image sensor 300.

[0046] like Figure 2 As shown in , d1 is the diameter of ML 202 and d2 is the diameter of ML 212. The size ratio R between d1 and d2 can be calculated as d1 / d2. When R is less than or equal to 1.1, this size difference is basically equivalent to the process tolerance. R values ​​of 1.1 are also generally unfavorable because the brightness of the captured image may vary by more than an acceptable amount to produce a good image using a single exposure. Therefore, it is desirable to have values ​​between 1.1 and Similarly, a suitable ratio of pitch to size (eg, P / d1) can strike a balance between image quality and process feasibility. Therefore, a suitable ratio of pitch to size is between 2 and 10.

[0047] Figure 4A is a schematic diagram of a portion of the image sensor 300, illustrating first image regions 402 each formed by a corresponding first ML 202 and second image regions 412 each formed by a corresponding second ML 212. Each first image region 402 has a corresponding first effective pixel 404 that captures an area of ​​the full FOV 208 imaged by the corresponding first ML 202. Each second image region 412 has a corresponding second effective pixel 414 that captures a portion of the full FOV 208 imaged by the corresponding second ML 212. Each ML 202 is aligned with a corresponding image region 412. For example, the first image region 402 is centered where the optical axis of the ML 202 intersects the image sensor 300. Pixels of the image sensor 300 that are not assigned to any of the first effective pixel 404 and the second effective pixel 414 are unused and are considered invalid.

[0048] Figure 4BA portion of an example complete image 450 is shown generated by stitching together a first image 452 captured by a first effective pixel 404 (e.g., an image formed by the first ML array 201) and a second image 462 captured by a second effective pixel 414 (e.g., an image formed by the second ML array 211), such that the complete image 450 has better image quality and uniformity of brightness than an image captured by a single ML array. Thus, the complete image 450 represents an "equivalent single camera" with a full field of view defined by the boundaries of the composite image. Advantageously, by increasing the size of the image sensor 300, the size of the captured full image is also increased.

[0049] Figure 5 Shows the combination Figure 2 An example device 500 of the compact camera 200 of FIG. 4 is shown. Figure 5 In the example of , device 500 is shown as a smartphone that uses compact camera 200 to capture fingerprints. However, device 500 may represent any device that requires compact camera 200. In some embodiments, processor 502 and memory 504 may be combined with compact camera 200 to form an integrated device capable of generating complete image 450.

[0050] The device 500 includes a digital processor 502 communicatively coupled to a memory 504 (e.g., RAM, ROM, flash memory, etc.), the memory 504 storing a camera firmware 506, the camera firmware 506 including machine-readable instructions that, when executed by the processor 502, control the operation of the compact camera 200 to generate a complete image 450 (e.g., a fingerprint image). The camera firmware 506 is shown with a stitching algorithm 508 that is invoked to stitch together a first image 452 and a second image 462 to form the complete image 450. In one example of operation, the camera firmware 506 causes the processor 502 to control the compact camera 200 to capture the first image 452 and the second image 462 and store them in the memory 504. The camera firmware 506 then invokes the stitching algorithm 508 to process the first image 452 and the second image 462 and generate the complete image 450.

[0051] Although shown as separate images, in certain embodiments, first image 452 and second image 462 are contained in separate portions of a single image output by image sensor 300. Accordingly, stitching algorithm 508 processes the separate portions to generate complete image 450.

[0052] Multispectral, RGB-IR and / or HDR imaging

[0053] Figure 2The embodiments to FIG. 4 can be extended for multi-spectral, RGB-IR, and HDR imaging. For biometric authentication such as fingerprint sensing or vein recognition, images with different spectral content can provide additional information that can be used for anti-spoofing, and thus can enhance the security level of biometric authentication. The reflective, transmissive, and / or absorptive properties of biological skin / tissue are different from those of spoofed (e.g., fake or non-biological) samples, particularly in different spectral bands. For example, light at longer wavelengths (such as red or infrared light) penetrates and transmits through skin / tissue better than light at shorter wavelengths (blue or green light).

[0054] therefore, Figure 2 4 can be extended for multi-color and / or multi-spectral imaging. By including two different color or spectral filters within aperture stop 306 and aperture stop 308, each ML array 201 and 211 allows image sensor 300 to capture different spectral content based on the respective responsivities of the filters.

[0055] Figure 6 is a schematic top view of an example compact camera 600 incorporating an ML array for ultra-short range imaging. Figure 7 It passes through Figure 6 Section CC of compact camera 600 illustrates the included filters 722 and 724. Figure 6 and Figure 7 It is best viewed in conjunction with the following description. For clarity of illustration, not all components are numbered.

[0056] Compact Camera 600 Similar Figure 2 4 , but ML 602 is configured such that partial FOV 606 is wider than partial FOV 206, such that partial FOV 606 collectively covers substantially all of object plane 316. In addition, camera 600 includes a first type of filter 722 positioned within each aperture stop 706 aligned with ML 602 and partial FOV 606, and a second type of filter 724 positioned within each aperture stop 708 aligned with ML 612 and individual FOV 616.

[0057] The camera 600 includes an image sensor 300 having a plurality of pixels 301, a filter layer 302 positioned above the image sensor 300, a baffle layer 704 (e.g., an optically opaque layer) forming a plurality of aperture stops 706 and a plurality of aperture stops 708, an ML layer 710, and a transparent layer 312 (e.g., glass) supported by sidewalls 714. In some embodiments, the aperture stops 706 can have a different size than the aperture stops 708. The ML layer 710 forms (a) a first ML array 601 having a plurality of first MLs 602, each of the first MLs 602 having a first optical characteristic, and (b) a second ML array 611 having a plurality of second MLs 612, each of the second MLs 612 having a second optical characteristic different from the first optical characteristic. Figure 6 As shown in FIG. 1 , both the first ML array 601 and the second ML array 611 are formed in a staggered regular pattern (e.g., a square pattern with a pitch P). However, other patterns may be implemented without departing from the scope of the present invention. Each aperture stop 706 is substantially aligned with a different first ML 602, and each aperture stop 708 is substantially aligned with a different second ML 612. In some embodiments, the first optical characteristic includes a first diameter of the first ML 602, and the second optical characteristic includes a second diameter of the second ML 612 that is different from the first diameter.

[0058] Each first ML 602 has a partial FOV 606 that overlaps the partial FOV 606 of the adjacent first ML 602 to collectively cover substantially all of the full FOV 608, where the full FOV 608 represents the FOV of the camera 600. The second MLs 612 each have a smaller individual FOV 616 and are positioned to capture images with good quality at locations that the first ML 602 failed to capture with the same high quality. As shown, the second MLs 612 are positioned so that the smaller individual FOVs 616 are at the intersection boundaries of the partial FOVs 606.

[0059] The ML layer 710 may be formed of a single lens material, whereby the first ML 602 and the second ML 612 are formed to focus an image of the object plane 316 at the image plane of the image sensor 300 and have a back focal length (BFL) between 0.1 mm and 2 mm. In particular, the first ML 602 and the second ML 612 are formed to image at least a portion (e.g., corresponding to the full FOV 608) of the object plane 316 at the image plane captured by the pixels 301 of the image sensor 300.

[0060] like Figure 6 and Figure 7As shown in , the partial FOVs 606 overlap each other (eg, more than the partial FOV 206 ), and thus, the partial FOVs 606 collectively cover substantially all of the full FOV 608 and the object plane 316 .

[0061] In one embodiment, the filter 722 has a first transmission spectrum and the filter 724 has a second transmission spectrum that is different from the first transmission spectrum. For example, the filter 722 may transmit only one of red light, green light, and blue light while blocking the other two lights, while the filter 724 may transmit light of at least one color blocked by the filter 722. Therefore, when the image of the partial FOV 606 from the first ML array 601 and the image of the separate FOV 616 from the second ML array 611 are stitched and processed together, the compact camera 600 captures a complete image (e.g., similar to the complete image 450 of FIG. 4 ) including additional spectral information. Although the combined FOV 616 does not cover the entire object plane 316, the image captured by the image area 414, which is considered a "sample", provides additional spectral information that can be used to enhance the image captured by the image area 404. For example, during stitching and processing, the image captured by the image area 414 is processed together with the image captured by the image area 404 to improve one or more of white balance and color temperature correction. In the case where the compact camera 600 is used for biometric authentication, spectral information from only a portion of an object has been shown to be useful for anti-spoofing. Therefore, the spectral information captured by the image area 414 can be used for anti-spoofing.

[0062] Figure 8 is a cross-sectional view of an example compact camera 800 that is configured with visible light bandpass filters and IR bandpass filters at the aperture stops corresponding to two different ML arrays. The camera 800 is similar to Figure 6 and Figure 7 8. The camera 800 of claim 800 includes an image sensor 300 having a plurality of pixels 301, a baffle layer 704, an ML layer 710, and a transparent layer 312. The transparent layer 312 is supported by a sidewall 814 similar to the sidewall 314. In this embodiment, the camera 800 does not include a filter layer 302 because the image sensor 300 will capture both visible light and IR light. A visible light bandpass filter 822 is positioned at each aperture stop 706, and an IR bandpass filter 824 is positioned at the aperture stop 708. The visible light bandpass filter 822 blocks infrared light and passes visible light, while the IR bandpass filter 824 blocks visible light and passes infrared light. The camera 800 may include a transparent adhesive layer (not shown) between the image sensor 300 and the ML layer 710, the transparent adhesive layer bonding the ML layer 710 to the image sensor 300; however, this transparent adhesive layer has a negligible effect on the optical performance of the camera 800.

[0063] Each of the two ML arrays 601 and 611 can be optimized for the spectrum of light passed by their corresponding filters 822 and 824. For example, the first ML 602 is formed to create an image of the object plane 316 at the image plane of the image sensor 300 at visible wavelengths, while the second ML 612 is formed to create an image of the object plane 316 at the image plane of the image sensor 300 at infrared wavelengths. As with the camera 600, the first ML 602 and the second ML 612 have the same back focal length (BFL) at the wavelengths transmitted by the filters 822 and 824, respectively.

[0064] Thus, when an image of a partial FOV 606 from the first ML array 601 and an image of a separate FOV 616 from the second ML array 611 are captured and stitched together to form an image having a larger spectral range, the compact camera 800 captures a complete image (e.g., similar to the complete image 450 of FIG. 4 ) including additional spectral information. In certain embodiments, the first ML array 601 and the second ML array 611 are designed and manufactured to allow for the generation of two separate images, each having different spectral content. In these embodiments, the first ML array 601 and the second ML array 611 have different characteristics and may be designed and optimized for different spectral ranges. In an embodiment, the FOV 606 do not overlap because such an overlap is not required for certain applications. Advantageously, as discussed above, the RGB-IR image is beneficial for anti-spoofing applications in which the camera 800 is used for biometric authentication.

[0065] Fig. 9 is a cross-sectional view showing an example compact camera 900 having a different ML array configured for high dynamic range (HDR) imaging. The camera 900 includes an image sensor 300 having a plurality of pixels 301, a baffle layer 904 forming a plurality of aperture stops 906 and a plurality of aperture stops 908, an ML layer 910, and a transparent layer 312 supported by sidewalls 914. The camera 900 may also include a filter layer 302. The ML layer 910 is similar to Figure 7 The ML layer 710, and as Figure 6 As shown in FIG. 6 , (a) a first ML array 601 having a plurality of first MLs 602, each of which has a first optical characteristic, and (b) a second ML array 611 having a plurality of second MLs 612, each of which has a second optical characteristic different from the first optical characteristic, are formed. In this embodiment, the two ML arrays 601 and 611 and / or the baffle layer 904 are designed to have different light collection qualities, such as having different f-numbers. As with the camera 600, the first ML 602 and the second ML 612 have the same back focal length (BFL).

[0066] Thus, when the image of the partial FOV 606 from the first ML array 601 and the image of the separate FOV 616 from the second ML array 611 are stitched together, the compact camera 800 captures a complete image with a higher dynamic range (e.g., similar to the complete image 450 of FIG. 4 ). Advantageously, the HDR image enhances the signal-to-noise ratio of biometric images captured in certain situations (such as strong lighting or with cold or wet fingers) when normally captured images have low contrast.

[0067] Simplified process

[0068] Fig.10 1 is a cross-sectional view showing an example compact camera 1000 having two distinct ML arrays for capturing both visible and infrared wavelengths using a baffle layer 1004 formed by two cascaded filter layers. The camera 1000 is similar to Figure 8 The camera 800 of FIG. 1000 includes an image sensor 300 having a plurality of pixels 301, a baffle layer 1004, an ML layer 710, and a transparent layer 312 supported by a sidewall 1014. The camera 1000 may include a transparent adhesive layer (not shown) that bonds the ML layer 710 to the image sensor 300; however, this transparent adhesive layer has a negligible effect on the optical performance of the camera 1000.

[0069] exist Fig.10In an embodiment of the present invention, the baffle layer 1004 is not a single optically opaque layer having an aperture. Instead, the baffle layer 1004 is formed using two different layers: a visible light bandpass filter layer 1022 (e.g., formed of a visible light bandpass filter material for blocking wavelengths between 400 nm and 675 nm) and an IR bandpass filter layer 1024 (e.g., formed of an IR bandpass filter material that blocks visible light and allows wavelengths above 700 nm to pass). The visible light bandpass filter layer 1022 forms a plurality of partial band aperture stops 1008, each of which is aligned with a different one of the MLs 612. The IR bandpass filter layer 1024 forms a plurality of partial band aperture stops 1006, each of which is aligned with a different one of the MLs 602. Thus, only the visible light bandpass filter layer 1022 is present within the partial-band aperture stop 1006 having a transmission coefficient of the visible light bandpass filter material, and only the IR bandpass filter layer 1024 is present within the partial-band aperture stop 1008 having a transmission coefficient of the IR bandpass filter material. Where both layers 1022 and 1024 are present (e.g., between the partial-band aperture stop 1006 and the partial-band aperture stop 1008), the visible light bandpass filter layer 1022 and the IR bandpass filter layer 1024 are cascaded and effectively form an optically opaque layer that blocks all light at wavelengths detectable by the image sensor 300. Advantageously, the manufacturing process of the camera 1000 is simplified because no separate layer is required to block all light.

[0070] Fig.11A is a graph 1100 illustrating example transmittance spectra of visible light bandpass filter layer 1022 (indicated by line 1102 ) and IR bandpass filter layer 1024 (indicated by line 1104 ). Fig. 11B is a graph 1150 illustrating an example transmittance spectrum of visible light bandpass filter layer 1022 (indicated by line 1152 ) cascaded with IR bandpass filter layer 1024 .

[0071] Fig.12 1 is a cross-sectional view showing an example compact camera 1200 having two different ML arrays and a repositioned filter 1202. The camera 1200 is similar to Figure 2 and Figure 3 The camera 200 includes an image sensor 300 having a plurality of pixels 301, a filter 1202, a baffle layer 304 having a plurality of aperture stops 306 of a first size and a plurality of aperture stops 308 of a second size, an ML layer 310, and a transparent layer 1212 supported by a sidewall 1214.

[0072] Unlike compact camera 200, in which filter layer 302 is formed (e.g., deposited directly) onto image sensor 300, in compact camera 1200, filter 1202 is deposited onto the lower surface of transparent layer 1212. Advantageously, this can reduce the manufacturing cost of camera 1200 because difficult filter coating of image sensor 300 is avoided, which can prevent yield loss. Camera 1200 may include a transparent adhesive layer (not shown) located above pixel 301 that bonds the MLA and its supporting layer to image sensor 300; however, this transparent adhesive layer has a negligible effect on the optical performance of camera 1200.

[0073] Summary of advantages

[0074] The embodiments described herein have several advantages over the prior art. For example, Figure 2 , Figure 6 , Figure 8 , Fig. 9 , Fig.10 and Fig.12 The compact cameras 200, 600, 800, 900, 1000 and 1200 are respectively reflowable modules with low profile. The compact cameras 200, 600, 800, 900, 1000 and 1200 have uniformity of image quality and brightness over the full FOV, which is greatly improved over the prior art. The compact cameras 200, 600, 800, 900, 1000 and 1200 allow wafer-level assembly to achieve cost-effective mass production. The concept of utilizing different MLAs is extended to multi-color, RGB-IR and HDR imaging, whereby the compact cameras 200, 600, 800, 900, 1000 and 1200 simultaneously capture images with different spectral contents and provide data for anti-spoofing use in biometric authentication such as optical fingerprint or vein recognition.

[0075] Changes may be made to the above methods and systems without departing from the scope of this document. It should therefore be noted that the content contained in the above description or shown in the accompanying drawings is to be understood as illustrative and not restrictive. The following claims are intended to cover all general and specific features described herein, as well as all statements of the scope of the present methods and systems, which, as far as language is concerned, can be said to be intermediate.

Claims

1. A compact camera for ultra-short-range imaging, comprising: Image sensor; Transparent layer; a microlens ML layer between the image sensor and the transparent layer, the microlens ML layer forming (a) a first ML array having a plurality of first MLs, and (b) a second ML array having a plurality of second MLs interlaced with the plurality of first MLs; a baffle layer, the baffle layer being between the ML layer and the image sensor, forming a plurality of first aperture stops and a plurality of second aperture stops, the plurality of first aperture stops being respectively aligned with a different first ML of the plurality of first MLs, and the plurality of second aperture stops being respectively aligned with a different second ML of the plurality of second MLs; as well as Each first ML of the plurality of first MLs has a first set of optical properties including a diameter d1, and each second ML of the plurality of second MLs has a second set of optical properties different from the first set of optical properties; The first ML array has a pitch P, where 2 <P / d1<10。 2 . The compact camera of claim 1 , further comprising a filter layer positioned between the baffle layer and the image sensor. 3 . The compact camera of claim 1 , further comprising a filter layer positioned between the ML layer and the transparent layer. 4 . The compact camera of claim 1 , wherein the first ML array and the second ML array each form a periodic pattern. The compact camera of claim 4 , wherein the periodic pattern is a square pattern.

6. The compact camera of claim 1, wherein each first ML has a diameter d1, each second ML has a diameter d2, wherein d1 is greater than d2, and the ratio R=d1 / d2, wherein 1.1 <R<√10。 7 . The compact camera of claim 1 , wherein the ML layer is formed of a single lens material, and the first ML and the second ML have a back focal length (BFL) greater than or equal to 0.1 mm and less than 2 mm.

8. The compact camera of claim 1 , wherein the baffle layer comprises: a visible light bandpass filter layer, the visible light bandpass filter layer forming the plurality of second aperture stops; as well as An IR bandpass filter layer forms the plurality of first aperture stops. 9 . The compact camera according to claim 8 , wherein each of the plurality of first aperture stops has a transmission coefficient of the visible light bandpass filter layer, and each of the plurality of second aperture stops has a transmission coefficient of the IR bandpass filter layer.

10. A compact camera for ultra-short-range imaging, comprising: Image sensor; Transparent layer; a microlens ML layer between the image sensor and the transparent layer, the microlens ML layer forming (a) a first ML array having a plurality of first MLs, and (b) a second ML array having a plurality of second MLs interlaced with the plurality of first MLs; a baffle layer, the baffle layer being between the ML layer and the image sensor, forming a plurality of first aperture stops and a plurality of second aperture stops, the plurality of first aperture stops being respectively aligned with a different first ML of the plurality of first MLs, and the plurality of second aperture stops being respectively aligned with a different second ML of the plurality of second MLs; Each first ML of the plurality of first MLs (i) is located over a plurality of pixels of the image sensor and (ii) has a first set of optical characteristics; as well as Each second ML of the plurality of second MLs (i) is located over a plurality of pixels of the image sensor and (ii) has a second set of optical properties different from the first set of optical properties; Each of the first MLs is positioned to form a first image on a corresponding first area of ​​the image sensor, and each of the second MLs is positioned to form a second image on a corresponding second area of ​​the image sensor different from the first area.

11. The compact camera according to claim 10, further comprising a plurality of first color filters and a plurality of second color filters, each of the first color filters being formed in a corresponding first aperture stop in the first aperture stop, and each of the second color filters being formed in a corresponding second aperture stop in the second aperture stop.

12. The compact camera according to claim 11, further comprising: processor; as well as A memory storing a stitching algorithm having machine-readable instructions that, when executed by the processor, stitch the first image and the second image together to form a full image with a higher spectral range.

13. The compact camera according to claim 10 further comprises a plurality of visible light bandpass filters and a plurality of IR bandpass filters, each visible light bandpass filter being formed in a different first aperture stop in the first aperture stop, and each IR bandpass filter being formed in a different second aperture stop in the second aperture stop.

14. The compact camera of claim 10, wherein the difference between the first set of optical characteristics and the second set of optical characteristics comprises a difference in f-number.

15. A method for ultra-short distance imaging, comprising: forming a corresponding first image of a plurality of first images at each of a plurality of first regions of the image sensor; forming a respective second image of a plurality of second images at each of a plurality of second regions of the image sensor; capturing the plurality of first images and the plurality of second images using the image sensor; as well as stitching the captured plurality of first images and the captured plurality of second images together to form an image of the scene; wherein: forming each of the plurality of first images comprises imaging a corresponding first scene region of a plurality of first scene regions of the scene using a corresponding first microlens of a plurality of first microlenses of a first microlens array, each of the first microlenses having a first set of optical properties; forming each of the plurality of second images comprises imaging a corresponding second scene region of a plurality of second scene regions of the scene using a corresponding second microlens of a plurality of second microlenses of a second microlens array, each of the plurality of second microlenses having a second set of optical properties different from the first set of optical properties; and The plurality of second microlenses are interlaced with the plurality of first microlenses.

16. The method of claim 15, wherein the step of forming the plurality of first images comprises forming a first periodic array of the plurality of first images, and the step of forming the plurality of second images comprises forming a second periodic array of the plurality of second images.

17. The method of claim 15, wherein a difference between the first set of optical properties and the second set of optical properties is a difference between a first diameter for the first microlens and a second diameter for the second microlens.

18. The method of claim 15, wherein the difference between the first set of optical properties and the second set of optical properties comprises a difference in f-number.

19. The method according to claim 15, wherein each of the plurality of first microlenses has a diameter d1, and the first microlens array has a pitch P, wherein 2 <P / d1<10。 20. The method according to claim 15, Each of the plurality of first microlenses is located above a plurality of pixels of the image sensor; and Each of the plurality of second microlenses is located above a plurality of pixels of the image sensor.

Images