Image sensors with metallic nanoparticle optical filters
View Patent ↗An imaging system may include one or more optical filters that include metallic nanoparticles in a matrix. The metallic nanoparticle optical filters may form a color filter array for an imager in the imaging system. Different metallic nanoparticle optical filters may be formed for each desired color. Properties of the metallic nanoparticles and matrices may be varied to achieve the desired optical filtering properties and pass the desired wavelength bands to the imager. As examples, the type of metal, the size of the nanoparticles, the shape of the nanoparticles, and the type of matrix in which the nanoparticles are formed may all influence the optical properties of the resulting metallic nanoparticle optical film.
1. An imager comprising:
an array of image sensing pixels; and
a color filter array associated with the array of image sensing pixels, wherein the color filter array comprises:
first and second regions that filter different colors;
a matrix; and
metallic nanoparticles within the matrix, wherein the metallic nanoparticles filter incident light, wherein the metallic nanoparticles include first metallic nanoparticles in the first region and second metallic nanoparticles in the second region, and wherein the first and second metallic nanoparticles are different in at least one of: size, shape, type of metal, and concentration within the matrix.
2. The imager defined in claim 1 wherein the matrix comprises a dielectric matrix.
3. The imager defined in claim 1 wherein the matrix comprises a conductive matrix and wherein the imager further comprises a conductive path shorting the conductive matrix to a ground terminal.
4. The imager defined in claim 1 wherein the first metallic nanoparticles are of a different size than the second metallic nanoparticles.
5. The imager defined in claim 1 wherein the first metallic nanoparticles have a different shape than the second metallic nanoparticles.
6. The imager defined in claim 1 wherein the first metallic nanoparticles are formed from a different type of metal than the second metallic nanoparticles.
7. The imager defined in claim 1 wherein the first metallic nanoparticles are formed in a greater concentration within the matrix than the second metallic nanoparticles.
8. The imager defined in claim 1 wherein the first region includes a first matrix and wherein the second region includes a second matrix formed from a different material than the first matrix.
9. The imager defined in claim 1 further comprising an in-pixel light grid formed from additional metallic nanoparticles in the matrix.
10. The imager defined in claim 1 wherein the color filter array comprises colored pigment or colored dye in the matrix, wherein the colored pigment or colored dye also filters incident light.
11. The imager defined in claim 1 wherein the color filter array comprises at least one layer separate from the matrix and wherein the at least one layer comprises color filter pigment or color filter dye.
12. The imager defined in claim 1 wherein the metallic nanoparticles are thermally treated with at least one of a plasma annealing process and a laser annealing process.
13. The imager defined in claim 1 further comprising:
a peripheral light blocking film including additional metallic nanoparticles within a medium.
14. The imager defined in claim 1 wherein the array of imaging sensing pixels includes a plurality of dark pixels, the imager further comprising:
a light blocking film including additional metallic nanoparticles within a medium, wherein the light blocking film shields the dark pixels from incident light.
15. The imager defined in claim 1 further comprising:
a plurality of reflective surfaces including a conductive in-pixel light grid or conductive lines interconnecting the image sensing pixels; and
a light blocking film covering the reflective surfaces, wherein the light blocking film comprises additional metallic nanoparticles within a medium.
16. A system, comprising:
a central processing unit;
memory;
input-output circuitry; and
an imaging device that includes:
an imager that contains an array of imaging pixels;
a color filter array; and
an infrared optical filter that shields the array of imaging pixels from incident infrared light, wherein the color filter array overlaps the infrared optical filter, and wherein the infrared optical filter comprises:
a matrix; and
metallic nanoparticles within the matrix, wherein the metallic nanoparticles filter the incident infrared light.
17. The system defined in claim 16 wherein the matrix comprises a dielectric matrix.
18. The system defined in claim 16 wherein the matrix comprises a conductive matrix and wherein the imaging device further comprises a conductive path shorting the conductive matrix to a ground terminal in the system.
19. The system defined in claim 16 wherein the imaging device further comprises a color filter array and wherein the infrared optical filter is disposed between the array of imaging pixels and the color filter array.
20. A method of forming an optical filter in an imaging device, the method comprising:
depositing a matrix;
adding metallic nanoparticles to the matrix, wherein the metallic nanoparticles filter light before the light is received by imaging pixels in the imaging device; and
after adding the metallic nanoparticles to the matrix, altering at least one of the size and shape of the metallic nanoparticles.
21. The method defined in claim 20 wherein the metallic nanoparticles are added to the matrix using at least one process selected from the group consisting of:
ion implantation, chemical vapor deposition, pulsed chemical vapor deposition, and atomic layer deposition.
22. The method defined in claim 20 wherein altering at least one of the size and shape of the metallic nanoparticles comprises subjecting the optical filter to an annealing process.