Sensor Assembly with Optical Metasurface Films

Abstract

A fingerprint sensor assembly using a metasurface array. The sensor assembly includes an image sensor having a sensor pixel array and a metasurface array on the sensor pixel array. An optical filter, such as an IR cut filter or a notch filter, can be disposed on the metasurface array. The assembly can also include a substrate, an optical spacer, or an optically transparent adhesive between the sensor pixel array and the metasurface array. The fingerprint sensor assembly can be incorporated into a mobile device.

Description

[Background technology]

[0001] Optical metasurfaces (OMS) are synthetic composite materials that contain arrays of subwavelength elements called meta-atoms with dimensions on the order of tens or hundreds of nanometers for visible light applications. Optical metasurfaces locally affect the amplitude, phase, or polarization of light, imparting a phase shift of the light that varies as a function of position on the surface. Metasurfaces can be engineered to exhibit properties that are not readily obtainable using conventional materials and techniques.

[0002] Metasurfaces, which have nanoscale surface features, have recently found applications in optics, biosensing, semiconductors, and other electronic devices, including compact near infrared (NIR) cameras for automotive applications, endoscopic camera optics, polarization imaging systems, and dynamic beam steering optics for light detection and ranging (LIDAR).

[0003] Systems or assemblies composed of conventional optical elements (e.g., compound lenses based on refractive lenses) and an OMS can be designed to improve overall optical performance. In these systems, the conventional elements provide the majority of the optical functions, and the OMS corrects or corrects the system for aberrations, aberrations, or astigmatism. Summary of the Invention

[0004] Embodiments of the present invention include a sensor assembly having an array or elements of optical metasurfaces, which may be useful as a fingerprint sensor. [Brief description of the drawings]

[0005] [Figure 1A] FIG. 2 is a side view of a microlens array / sensor assembly. [Figure 1B]FIG. 11. Side view of the metasurface array / sensor-on-glass assembly. [Figure 1C] FIG. 11. Side view of the assembly of metasurface array / film on a sensor. [Figure 1D] FIG. 11A is a side view of the metasurface-on-film array / sensor assembly. [Diagram 2] FIG. 1 is a side view of a multi-wavelength, multi-focal OMS array used in a sensor assembly to enable image capture and biodetection. [Diagram 3] FIG. 13 is a side view of the assembly of a metasurface array on a sensor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0006] Described herein are enhanced sensor assemblies for detecting visible and near-infrared light. The assemblies comprise a pixelated sensor or sensor pixel array, an optical film, and at least one optical metasurface array. The combination of these three elements is expected to provide enhanced functionality and performance for visible, near-infrared, and ultraviolet (UV) imaging. Potential enhancements include improved signal-to-noise ratio (S / N), hyperspectral imaging capabilities, polarization imaging, biodetection, and smaller physical profiles. These enhanced sensors are useful, for example, in consumer electronic devices.

[0007] The articles described herein may be useful in numerous applications, including, but not limited to, fingerprint or vein pattern sensors capable of sensing both image and pattern location or orientation, and fingerprint or vein pattern sensor assemblies for visible and near infrared light sources, including, but not limited to, 400-600 nm and 850-940 nm. In particular, the articles and assemblies described herein may be used in the wavelength ranges of 400 nm to 700 nm for the visible range, 700 nm to 2000 nm for the NIR, and 100 nm to 400 nm for the UV.

[0008] Sensor Assembly 1~3 These assemblies are designed and fabricated for sensor enhancement films as part of under-panel fingerprint sensors (FPS) for use in mobile phones or other devices. The films use optical elements, including a refractive microlens array, an infrared (IR) cutoff filter, and an aperture array as an angular filter. Overall, the films help improve the signal-to-noise performance of the sensor by collimating and filtering the light (FIG. 1A). The assembly in FIG. 1A includes the following elements arranged as shown: a microlens array 10, an IR cut filter 12, a pinhole array 14, and an image sensor 18 with a pixelated sensor array 16.

[0009] Three other assemblies (FIGS. 1B, 1C, and 1D) comprise a sensor (CMOS, TFT, or organic photo detector (OPD)), a metasurface array, and an optical film. In each case, the metasurface array is a regular arrangement of individual metalenses with a size and pitch comparable to that of the corresponding sensor pixels. The metasurface array is separate and distinct from a single large area metalens that is disposed adjacent to the surface of the sensor. Each metalens in the array may be identical (e.g., in the case of an imaging sensor), or there may be a series of metalens types (e.g., with different focal lengths, different spectral ranges) that are spatially distributed. The metalens array may or may not be aligned with the underlying sensor pixels on a pixel basis. The metalens array may be embedded in another material, such as an optical resin or other material. The metalens may be on the order of the size of a pixel, or may be larger, covering many pixels, or smaller, covering a portion of a pixel. The function of the metalens element can be to focus light, change the angle of light, polarize light, diffuse light, or filter light. The filtering function can be spectral, polarization-based, angular, or spatial. These functions can be applied to the emitter (or emitter array), the detector (or detector array), or both. The function can be for imaging or non-imaging applications.

[0010] Figure 1B shows an embodiment of a sensor assembly in which the optical film is a notch filter and the metasurface is disposed on a rigid transparent substrate. The assembly in Figure 1B includes the following elements arranged as shown: an optical film 20, a metasurface array 22, a rigid transparent substrate 24, and an image sensor 28 having a sensor pixel array 26.

[0011] Figure 1C shows a second embodiment in which a metasurface array is disposed on a sensor with an intervening optical spacer layer. The assembly of Figure 1C includes the following elements arranged as shown: an optical film 30, a metasurface array 32, an optical spacer 34, and an image sensor 38 having a sensor pixel array 36.

[0012] Figure ID shows a third embodiment in which the metasurface is disposed on an optical film. The assembly of Figure ID includes the following elements arranged as shown: an optical film 40, a metasurface array 42, and an image sensor 46 having a sensor pixel array 44.

[0013] In the embodiments of FIGS. 1B, 1C, and 1D, it is also possible to align the sensor array and the metalens array.

[0014] Sensor Assembly 4 Another sensor assembly embodiment is capable of photoplethysmography (PPG) to enable both security and health or biometric sensing simultaneously during the fingerprint authentication process (FIG. 2). The assembly of FIG. 2 includes the following elements arranged as shown to sense finger 48: MOF notch filter 50, metasurface array 52, rigid transparent substrate 54, and image sensor 58 having sensor pixel array 56.

[0015] The system includes a multi-wavelength, multi-focal length OMS lens array, an image sensor, and a notch filter film. The OMS array is tuned to at least two wavelengths and two focal lengths: a wavelength λ1 suitable for imaging the fingerprint surface, which is focused on the finger surface (DOF1), and an optimal wavelength for vein imaging (λ1, e.g., 850 nm), which is focused within the first few microns of live tissue (DOF2). The OMS performs a spatial filtering function: one metasurface pixel focuses λ1 at f1 and filters λ2, and the other metasurface pixel focuses λ2 at f2 and filters λ1. The multi-layer optical film (MOF) also allows both λ1 and λ2 to pass.

[0016] Optionally, the system may be equipped with polarized lenses and polarized light sources of various polarization states to reduce subcutaneous scattering, allowing for vein imaging in the red or NIR spectral regions.

[0017] Sensor Assembly 5 Another embodiment of a sensor assembly in which a metasurface is used without the separate optical film shown in Figures 1B, 1C, and 1D is shown in Figure 3. This embodiment can optionally use a dual wavelength metalens, where the focal length of a first wavelength is optimized for pinhole formation and the focal length of a second wavelength is optimized for optical function. The assembly of Figure 3 includes the following elements arranged as shown: a metasurface array 60, a transparent substrate 62, a pinhole array 64, an optically clear adhesive (OCA) 66, and an image sensor 70 having a sensor pixel array 68.

[0018] In this embodiment (FIG. 3), the metasurface lens array is disposed on one surface of a transparent substrate having a second surface generally parallel to and spaced a uniform distance d from the first surface. In a preferred embodiment, the thickness d of the substrate is selected such that collimated light incident normally on the metasurface lens array is focused at the second surface of the substrate. An optically opaque coating covers most of the second surface of the transparent substrate, except where normally incident light is focused by the lens array. This coating layer is sometimes referred to as a pinhole array. These openings allow light incident on the lens array from a narrow range of angles, e.g., ±4° around the normal, to pass through the pinhole array to the detector, while blocking light incident on the metasurface from other angles. The coating on the pinhole array is preferably an optically absorbing material to minimize light scattering within the film. Examples of suitable coatings include carbon black, or roughened and / or blackened metals.

[0019] In a preferred embodiment, the metasurface lens array is designed with high wavelength dispersion characteristics to focus only light in a narrow wavelength range, such as light between 400 nm and 600 nm, or light between 800 nm and 1000 nm, through the pinhole array, and light having wavelengths outside of this range is either not focused at all, or is focused somewhere other than the pinhole array and is not efficiently transmitted through the pinhole array to the detector.

[0020] The film can be bonded to the detector array by an adhesive, such as an optically clear adhesive. The film can also be bonded to the back of the display module by an optically clear adhesive. The detector array or the display module can comprise a planar or curved substrate. One advantage of the metasurface array approach over microlens arrays is that metasurface arrays can be made with flat top surfaces that are suitable for direct optical bonding.

[0021] Metasurface elements such as those described herein serve as both angular and spectral filters for large area fingerprint sensors. Spectral filtering can be further improved by adding dyes or pigments that absorb undesired wavelengths of light to the transparent substrate and / or by adding such dyes or pigments to the adhesive layer used to bond the transparent substrate to the detector and / or display module.

[0022] The assembly described herein can be used as a fingerprint sensor when a finger is placed directly (in physical contact) on or in sufficient proximity to the top component of the assembly, opposite the image sensor.

Claims

1. a sensor pixel array; and a metasurface array on the sensor pixel array; and an IR cut filter on an opposite side of the metasurface array from the sensor pixel array; A sensor assembly comprising:

2. 10. The sensor assembly of claim 1 , wherein the Metasurface array includes a metalens having a size and pitch comparable to a size and pitch of the corresponding sensor pixel array.

3. 10. The sensor assembly of claim 1 , wherein the metasurface array comprises metalenses, each of the metalenses covering a plurality of pixels in the sensor pixel array.

4. a sensor pixel array; and a transparent substrate over the sensor pixel array; and a metasurface array on an opposite side of the transparent substrate from the sensor pixel array; a notch filter on the metasurface array opposite the transparent substrate; A sensor assembly comprising:

5. 5. The sensor assembly of claim 4, wherein the Metasurface array includes a metalens having a size and pitch comparable to a size and pitch of the corresponding sensor pixel array.

6. 5. The sensor assembly of claim 4, wherein the metasurface array comprises metalenses, each of the metalenses covering a plurality of pixels in the sensor pixel array.

7. a sensor pixel array; and an optically clear adhesive on the sensor pixel array; a pinhole array on a side of the optically transparent adhesive opposite the sensor pixel array; a transparent substrate on a side of the pinhole array opposite the optically clear adhesive; a metasurface array on an opposite side of the transparent substrate from the pinhole array; A sensor assembly comprising:

8. 8. The sensor assembly of claim 7, wherein the Metasurface array includes a metalens having a size and pitch comparable to a size and pitch of the corresponding sensor pixel array.

9. 8. The sensor assembly of claim 7, wherein the metasurface array comprises metalenses, each of the metalenses covering a plurality of pixels in the sensor pixel array.

10. A mobile device comprising any of the sensor assemblies according to claims 1 to 9, the mobile device having an imaging sensor for imaging a body part of a user arranged in proximity to the mobile device.

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