Devices and methods for obtaining three-dimensional shape information using polarization and time-of-flight detection pixel cells
In some embodiments, an imaging system is provided. The imaging system comprises an image sensor, a light source, control circuitry, and function logic. The image sensor comprises a pixel array that includes a plurality of polarization pixel cells and a plurality of time-of-flight pixel cells. The light source is configured to emit light pulses to an object. The control circuitry is coupled to the light source and the pixel array, and is configured to synchronize a timing of the emission of the light pulses with sensing of photons reflected from the object by the plurality of time-of-flight pixel cells to generate depth information. The function logic is configured to determine a set of ambiguous surface normals using signals generated by the plurality of polarization pixel cells, and to disambiguate the set of ambiguous surface normals using the depth information to generate a three-dimensional shape image.
1. An image sensor comprising a pixel array that includes:
a plurality of polarization pixel cells; and
a plurality of time-of-flight pixel cells that are distinct from the plurality of polarization pixel cells;
wherein the plurality of time-of-flight pixel cells includes a plurality of single time-of-flight pixel cells separated from each other at least one of horizontally and vertically by at least seven polarization pixel cells;
wherein the plurality of polarization pixel cells includes groups of four polarization pixel cells arranged in two-by-two squares; and
wherein each time-of-flight pixel cell of the plurality of single time-of-flight pixel cells is arranged within a group of four polarization pixel cells and replaces one polarization pixel cell in the group of four polarization pixel cells.
2. The imaging sensor of claim 1 , wherein each time-of-flight pixel cell includes:
a photosensor to sense photons reflected from the object; and
pixel support circuitry including:
charging control logic coupled to the photosensor to detect when the photosensor senses the photons reflected from the object, wherein the charging control logic is further coupled to receive timing signals representative of when light pulses are emitted from the light source to the object;
a controllable current source coupled to provide a charge current in response to a time of flight signal coupled to be received from the charging control logic, wherein the time of flight signal is representative of a time of flight of each one of the light pulses emitted from the light source until the photosensor senses a respective one of the photons reflected from the object;
a capacitor coupled to receive the charge current from the controllable current source in response to the time of flight signal, wherein a voltage on the capacitor is representative of a round trip distance to the object; and
a reset circuit coupled to reset the voltage on the capacitor after being charged a plurality number of times by the controllable current source in response to the time of flight signal.
3. The image sensor of claim 1 , wherein a first polarization pixel cell of each group of four polarization pixel cells is associated with polarization wires oriented in a first direction;
wherein a second polarization pixel cell of each group of four polarization pixel cells is associated with polarization wires oriented in a second direction;
wherein a third polarization pixel cell of each group of four polarization pixel cells is associated with polarization wires oriented in a third direction; and
wherein a fourth polarization pixel cell of each group of four polarization pixel cells is associated with polarization wires oriented in a fourth direction.
4. The image sensor of claim 1 , wherein the image sensor is configured to process polarization pixel cells in each group of four polarization pixel cells together as a pixel, and wherein the image sensor is configured to process each single time-of-flight pixel cell as a separate pixel.
5. The image sensor of claim 1 , wherein the image sensor is configured to process a group of pixel cells that includes a plurality of polarization pixel cells and at least one time-of-flight pixel cell together as a pixel.