Optical sensing performance of under-screen optical sensor module for on-screen fingerprint sensing
Devices and optical sensor modules are provided for provide on-screen optical sensing of fingerprints by using an under-screen optical sensor module that captures and detects returned light that is emitted by the display screen for displaying images and that is reflected back by the top surface of the screen assembly. Optical collimators are provided in the under-screen optical sensor module to enhance the optical imaging performance. Techniques for reducing the environmental light in the optical sensing are provided.
1. An optical sensor module, for being arranged under a display panel to capture a fingerprint pattern of a finger above the display panel, the optical sensor module comprising:
an optical sensor array of optical detectors for receiving probe light that is returned from the finger and carrying fingerprint information, and converting the probe light into detector signals representing a fingerprint pattern, wherein the returned probe light is generated when the finger is illuminated and is transmitted through the display panel; and
an array of optical collimators located between the display panel and the optical sensor array, for collecting angled probe light returned from the display panel, and directing the angled probe light to the corresponding optical detectors of the optical sensor array;
wherein the optical sensor module is structured to measure probe light at two or more different wavelengths to compare characteristics of the probe light at the two or more different wavelengths to determine of whether the probe light is from a live person, the probe light at two or more different wavelengths correspond to light emitted by light emitting display pixels in the display panel, and the characteristics of the probe light at the two or more different wavelengths comprises an extinction ratio of the probe light at the two or more different wavelengths.
2. The optical sensor module as in claim 1 , wherein the array of optical collimators and spacing between the array of optical collimators and the optical sensor array are structured to cause images of a field of view of the optical collimators at the optical sensor array to be spatially separated.
3. The optical sensor module as in claim 1 , wherein the optical collimators has an optical axis that is slanted with respect to the display panel, so that the angled probe light returned from the display panel is capable of passing through the optical collimators and reaching the optical detectors of the optical sensor array.
4. The optical sensor module as in claim 3 , wherein the array of optical collimators is built by combing an array of aligned holes in different light block layers and transparent layers which are interleaved between the light block layers to provide separation.
5. The optical sensor module as in claim 4 , wherein the light block layers are metal layers, and the transparent layers are oxide layer.
6. The optical sensor module as in claim 5 , wherein an aperture of the aligned holes in a metal layer is different from that in another metal layer.
7. The optical sensor module as in claim 4 , further comprising: a micro lens array comprising a plurality of micro lenses arranged on the array of optical collimators, wherein each micro lens is located with respect to a corresponding optical collimator.
8. The optical sensor module as in claim 1 , further comprising: an optical layer between the optical collimators and the display panel to select the angled probe light returned from the display panel to enter the optical collimators while reducing an amount of the probe light that is perpendicular to the display panel and enters the optical collimators.
9. The optical sensor module as in claim 8 , wherein the optical layer comprises an optical diffraction pattern that diffracts the probe light to direct the angled probe light returned from the display panel to enter the optical collimators.
10. The optical sensor module as in claim 8 , wherein the optical collimators has an optical axis perpendicular to the display panel, and the optical layer between the optical collimators and the display is structured to direct the angled probe light from the display panel to be substantially perpendicular to the display panel to enter the optical collimators while directing a portion of the probe light from the display panel that is perpendicular to the display panel to be away from the direction of the optical collimators.
11. An optical sensor module, for being arranged under a display panel to capture a fingerprint pattern of a finger above the display panel, the optical sensor module comprising:
an optical sensor array of optical detectors for receiving probe light that is returned from the finger and carrying fingerprint information, and converting the probe light into detector signals representing a fingerprint pattern, wherein the returned probe light is generated when the finger is illuminated and is transmitted through the display panel; and
an array of optical collimators located between the display panel and the optical sensor array, for collecting angled probe light returned from the display panel, and directing the angled probe light to the corresponding optical detectors of the optical sensor array;
wherein the optical collimators has an optical axis that is slanted with respect to the display panel, so that the angled probe light returned from the display panel is capable of passing through the optical collimators and reaching the optical detectors of the optical sensor array;
and wherein the array of optical collimators is formed by combing an array of aligned holes in different metal layers and insulating layers which are interleaved between the light block layers to provide separation;
wherein an aperture of the aligned holes in a metal layer is different from that in another metal layer, and a micro lens array comprising a plurality of micro lenses arranged on the array of optical collimators, wherein each micro lens is located with respect to a corresponding optical collimator.
12. The optical sensor module as in claim 11 , wherein the optical sensor module is further structured to measure probe light at two or more different wavelengths to compare characteristics of the probe light at the two or more different wavelengths to determine of whether the probe light is from a live person.
13. The optical sensor module as in claim 11 , wherein the optical sensor module is further structured to capture different fingerprint patterns at different times to monitor time-domain evolution of the fingerprint ridge pattern deformation that indicates time-domain evolution of a press force from the finger.
14. The optical sensor module as in claim 11 , wherein the array of optical collimators and spacing between the array of optical collimators and the optical sensor array are structured to cause images of a field of view of the optical collimators at the optical sensor array to be spatially separated.
15. The optical sensor module as in claim 1 , wherein the optical sensor module is further structured to capture different fingerprint patterns at different times to monitor time-domain evolution of the fingerprint ridge pattern deformation that indicates time-domain evolution of a press force from the finger.