Systems and methods for reducing unwanted reflections in display systems incorporating an under display biometric sensor
An optical sensor system includes a display substrate, display pixel circuitry including a plurality of light emitting display elements or pixels disposed over the display substrate, a first circular polarizer disposed over the display substrate and the display pixel circuitry, and a transparent cover sheet disposed over the first circular polarizer. A top surface of the transparent cover sheet provides a sensing surface for an object such as a finger. The optical sensor system also includes a sensor layer disposed below the display substrate, the sensor layer having a plurality of photosensors, and a second circular polarizer disposed between the sensor layer and the display substrate.
1. An optical sensor system, comprising:
a display substrate;
display pixel circuitry disposed over the display substrate;
a first circular polarizer disposed over the display substrate and the display pixel circuitry;
a transparent cover sheet disposed over the first circular polarizer, wherein a top surface of the transparent cover sheet provides a sensing surface for an object;
a quarter wave retarder disposed over the first circular polarizer;
a sensor layer disposed below the display substrate, the sensor layer having a plurality of photosensors; and
a second circular polarizer disposed between the sensor layer and the display substrate.
2. The optical sensor system of claim 1 , further including an angular selective structure disposed between the plurality of photosensors and the second circular polarizer.
3. The optical sensor device of claim 2 , wherein the angular selective structure includes a plurality of collimator filter elements.
4. The optical sensor device of claim 1 , further including a plurality of light emitters disposed over the display substrate, wherein the plurality of photosensors are configured to detect light emitted from the plurality of light emitters and returned through both the first circular polarizer and the second circular polarizer.
5. The optical sensor device of claim 1 , further including a light source disposed below the display substrate.
6. The optical sensor device of claim 5 , further including a diffuser element disposed between the light source and the display substrate.
7. The optical sensor device of claim 1 , further including a birefringent material correction layer to correct for angular polarization effects disposed between the sensor layer and the second circular polarizer.
8. The optical sensor device of claim 1 , wherein the quarter wave retarder is disposed over the transparent cover sheet.
9. The optical sensor device of claim 1 , wherein a handedness of the first circular polarizer is the same as a handedness of the second circular polarizer.
10. An optical display device, comprising:
a display substrate;
display pixel circuitry disposed over the display substrate;
a circular polarizer disposed over the display substrate and the display pixel circuitry;
a transparent cover sheet disposed over the circular polarizer, wherein a top surface of the transparent cover sheet provides a sensing surface for an object; and
a quarter wave retarder disposed over the circular polarizer.
11. The device of claim 10 , wherein the quarter wave retarder is disposed over the top surface of the transparent cover sheet, wherein a top surface of the quarter wave retarder proximal the top surface of the transparent cover sheet provides the sensing surface for the object.
12. The device of claim 10 , wherein the quarter wave retarder is disposed between the transparent cover sheet and the circular polarizer.
13. The device of claim 10 , wherein the quarter wave retarder comprises a liquid crystal (LC) quarter wave retarder and a plurality of electrodes, wherein application of a voltage to the plurality of electrodes controls an activation state of the LC quarter wave retarder.
14. The device of claim 13 , further comprising:
an optical image sensor disposed below the LC quarter wave retarder, wherein the optical image sensor is configured to obtain a first image when the LC quarter wave retarder is activated and obtain a second image when the LC quarter wave retarder is de-activated.
15. The device of claim 10 , further including a second circular polarizer disposed below the display substrate.
16. The device of claim 10 , further including a sensor layer comprising a plurality of photosensors disposed below the circular polarizer.
17. An optical fingerprint sensor device, comprising:
an image sensor layer having a plurality of photosensors;
an angular selective structure disposed over the image sensor layer;
a circular polarizer disposed over the image sensor layer, wherein the circular polarizer includes a quarter wave retarder layer disposed over a linear polarizer layer; and
a quarter wave retarder disposed over the circular polarizer.
18. The optical sensor device of claim 17 , wherein the angular selective structure includes a plurality of collimator filter elements.
19. The optical sensor device of claim 18 , further including a light source configured to illuminate a sensing area over the angular selective structure.