Advanced computational pixel imagers with multiple in-pixel counters
A computational pixel imaging device can include multiple digitizing counters per pixel that can be used to execute simultaneous signal-processing threads on acquired image data. The imaging device can also include infinite dynamic range sensing and perform signal down-sampling.
1. A pixel integrated circuit comprising:
a b-bit counter;
a data line arranged to transmit a value of a most significant bit of the b-bit counter; and
read-out circuitry configured to:
read the most significant bit at a higher read-out rate than a read-out rate for other bits of the b-bit counter;
determine a count rate from a first count accumulated by the b-bit counter for a first time period; and
determine one or more times at which to read-out the MSB of the b-bit counter for a second count accumulated by the b-bit counter for a second time period that is longer than the first time period.
2. The pixel integrated circuit of claim 1 , wherein the read-out circuitry is further configured to record a number of times greater than 1 that the b-1 bits of the b-bit counter have rolled over.
3. The pixel integrated circuit of claim 2 , wherein the read-out circuitry is further configured to record an address of the counter.
4. The pixel integrated circuit of claim 1 , wherein the read-out circuitry is further configured to automatically detect a toggling of the most significant bit from a first logic level to a second logic level and automatically reset the value of the most significant bit in response to detecting the toggling.
5. The pixel integrated circuit of claim 1 , wherein the b-bit counter comprises a plurality of flip-flops.
6. The pixel integrated circuit of claim 5 , wherein an output of a flip-flop corresponding to the most significant bit connects to a tri-state buffer.
7. The pixel integrated circuit of claim 5 , further comprising:
data input multiplexers connected to a data inputs of the flip-flops; and
clock input multiplexers connected to the clock inputs of the flip-flops.
8. The pixel integrated circuit of claim 7 , wherein the b-bit counter can be configured as a counter and as a shift register by selecting different data inputs and different clock inputs.
9. The pixel integrated circuit of claim 1 , further comprising:
a detector; and
a current-to-frequency converter arranged to receive an output from the detector and output a series of pulses in response to a detected signal, wherein an output of the current-to-frequency converter connects to an input of the b-bit counter.
10. The pixel integrated circuit of claim 1 included in an array having a plurality of the pixel integrated circuits arranged on a substrate.
11. The pixel integrated circuit of claim 10 , wherein the array is located adjacent to an imaging plane of an optical assembly.
12. A method of accumulating counts with a b-bit counter, the method comprising:
accumulating counts on the b-bit counter; and
reading, by read-out circuitry, data from a most significant bit of the b-bit counter at a higher read-out rate than a read-out rate for other bits of the b-bit counter;
determining a count rate from a first count accumulated by the b-bit counter for a first time period; and
determining, from the first count and time period, one or more times at which to read-out the MSB of the b-bit counter for a second count accumulated by the b-bit counter for a second time period that is longer than the first time period.
13. The method of claim 12 , further comprising:
transmitting over a data line a value of the most significant bit;
automatically detecting a toggling of the most significant bit from a first logic level to a second logic level; and
recording in memory a number of times greater than 1 that the b-1 bits of the b-bit counter have rolled over.
14. The method of claim 13 , further comprising:
performing a first operation with the number of times recorded in memory that mirrors or complies with a second operation performed with count values stored in the b-bit counter, wherein the second operation is performed on a chip that contains the b-bit counter.
15. The method of claim 12 further comprising:
automatically resetting the value of the most significant bit in response to detecting the toggling; and
recording an address of the b-bit counter.