Image sensor packages with tunable polarization layers
Imaging systems may include tunable polarization filters. A tunable polarization filter may be integrated directly into an image sensor package. For example, the tunable polarization filter may serve as cover glass for the image sensor package. Tunable polarization package glass may be incorporated into image sensor packages that have air gaps between the image sensor and the cover glass or that have transparent adhesive between the image sensor and the cover glass. The tunable polarization layer may be controlled at a global level, at a sub-array level, or at a pixel level. In some cases, the tunable polarization layer may be a tunable polarization filter. In this example, the direction of the polarization filter is tuned. In other cases, the tunable polarization layer may be a tunable polarization rotator. In this example, the tunable polarization layer selectively rotates the polarization of light that passes through the tunable polarization layer.
1. An imaging system comprising:
a substrate;
an image sensor having an array of imaging pixels formed on the substrate and microlenses formed over the array of imaging pixels;
a tunable polarization layer that covers the image sensor, wherein the tunable polarization layer and the substrate form a package for the image sensor;
transparent adhesive formed between the substrate and the tunable polarization layer; and
a low-index layer formed between the microlenses and the transparent adhesive.
2. The imaging system defined in claim 1 , wherein the tunable polarization layer comprises a layer of liquid crystal material.
3. The imaging system defined in claim 2 , wherein the tunable polarization layer comprises first and second electrodes and wherein the layer of liquid crystal material is interposed between the first and second electrodes.
4. The imaging system defined in claim 3 , wherein the tunable polarization layer comprises first and second transparent substrates, wherein the first electrode is interposed between the layer of liquid crystal material and the first transparent substrate, and wherein the second electrode is interposed between the layer of liquid crystal material and the second transparent substrate.
5. The imaging system defined in claim 4 , further comprising a linear polarizer formed on the first transparent substrate, wherein the layer of liquid crystal material is interposed between the linear polarizer and the image sensor.
6. The imaging system defined in claim 5 , further comprising:
a dam attached to the substrate; and
adhesive that couples the dam to the second transparent substrate.
7. The imaging system defined in claim 4 , further comprising:
a first linear polarizer formed on the first transparent substrate, wherein the layer of liquid crystal material is interposed between the first linear polarizer and the image sensor; and
a second linear polarizer formed between the layer of liquid crystal material and the image sensor.
8. The imaging system defined in claim 7 , further comprising:
a dam attached to the substrate; and
adhesive that couples the dam to the second linear polarizer.
9. The imaging system defined in claim 4 , wherein the image sensor is formed on an upper surface of the substrate, the imaging system further comprising:
a plurality of solder balls on a lower surface of the substrate.
10. The imaging system defined in claim 1 , wherein the tunable polarization layer has a continuous, adjustable portion that covers the entire image sensor.
11. The imaging system defined in claim 1 , wherein the tunable polarization layer has a plurality of independent segments that each cover a subset of the image sensor.
12. The imaging system defined in claim 1 , wherein the tunable polarization layer comprises a tunable polarization filter configured to selectively pass light to the image sensor.
13. The imaging system defined in claim 1 , wherein the tunable polarization layer comprises a tunable polarization rotator configured to selectively rotate a polarization of light.