Sensor device and method for operating a sensor device

1 . A sensor device comprising

a plurality of sensors each of which is configured to detect an intensity of an influence on the sensor and to detect as an event a positive or a negative change of the intensity of the influence that is larger than a respective predetermined threshold;

processing circuitry configured to randomly select for readout a part of a plurality of events detected by the plurality of sensor during at least one predetermined time period;

a memory configured to store history data of detected events and/or of readout selection operations of the processing circuitry; and

an output interface configured to receive and output the selected part of the plurality of events from the processing circuitry for each of the at least one predetermined time period, wherein

the processing circuitry is configured to perform the random selection repeatedly for a series of the at least one predetermined time period including performing the random selection for a current predetermined time period based on the history data of detected events and/or of readout selection operations for a previous predetermined time period,

the plurality of sensors, the processing circuitry, the memory, and the output interface are all part of a single sensor chip,

during each predetermined time period the memory is configured to store as the history data events and a number of the events detected during the predetermined time period,

the processing circuitry is configured to

compare the stored number of events with an event selection threshold,

when the stored number of events is larger than the event selection threshold, carry out the random selection on the events stored in the memory, and

when the stored number of events is smaller than the event selection threshold, not carry out the random selection on the events stored in the memory, and

the processing circuitry is configured to set a probability for forwarding an event out of the stored events to the output interface as a ratio of the event selection threshold and the stored number of events.

2 . The sensor device according to claim 1 , wherein the processing circuitry is configured to carry out random selection of multiple events stored in the memory in parallel.

3 . The sensor device according to claim 1 , wherein the processing circuitry is configured to carry out random selection by

randomly choosing one or more event of the stored events for forwarding to the output interface without choosing a same stored event twice,

counting a number of the forwarded events, and

when the number of forwarded events has reached the event selection threshold, stopping forwarding of the stored events.

4 . The sensor device according to claim 1 , wherein

the memory has at least one memory space to store a number of N events at a same time; and

for each predetermined time period the processing circuitry is configured to

store each newly detected event into the memory space until the number of N events are stored therein, and

decide thereafter randomly whether or not to overwrite events stored in the memory space by newly detected events.

5 . The sensor device according to claim 4 , wherein for randomly deciding whether or not to overwrite the events stored in the memory space the processing circuitry is configured to:

count a number of detected events,

store the counted number in the memory as the history data,

generate for each of the newly detected events a random number between 1 and a momentary number of detected events,

if the random number is larger than the number N, discard the newly detected event, and

if the random number is smaller or equal to N, overwrite an event stored in the memory space at a position corresponding to the random number.

6 . The sensor device according to claim 1 , wherein

the memory is configured to store as the history data a number of events detected during the at least one predetermined time period; and

the processing circuitry is configured to randomly select events during the current predetermined time period with a probability that depends on a number of detected events of the previous predetermined time period.

7 . The sensor device according to claim 1 , wherein

the plurality of sensor are divided into groups of sensor, each containing a same number of sensor; and

the processing circuitry is configured to separately carry out the random selection of the detected events for each of the groups of sensor.

8 . The sensor device according to claim 7 , wherein

the memory is configured to store as the history data a total number of events detected during the at least one predetermined time period as well as a number of events detected within each of the groups of sensor; and

the processing circuitry is configured to determine a probability for randomly selecting an event detected in one specific group of the groups of sensors in the current predetermined time period based on the total number of events and the number of events counted for the specific group in the previous predetermined time period.

9 . The sensor device according to claim 7 , wherein the processing circuitry is configured to:

assign to each of the groups of sensor a desired number of events to be read out from the respective group, and

carry out the random selection with a probability that is based on the assigned desired number.

10 . The sensor device according to claim 1 , wherein the processing circuitry is configured to carry out the random selection by:

grouping all or a subset of events detected during one predetermined time period into an event vector, and

performing a bit-wise logical operation between the event vector and a random vector containing a randomly distributed number of 1s and otherwise 0s.

11 . The sensor device according to claim 1 , wherein

the sensor device is a solid state imaging device; and

the plurality of sensor are imaging pixels arranged in a pixel array, each of which is configured to sense intensity of light falling on the imaging pixel and to detect as the event a positive or a negative change of light intensity that is larger than the respective predetermined threshold.

12 . A method for operating a sensor device according to claim 1 , the method comprising:

detecting the plurality of events with the plurality of sensor;

randomly selecting for readout the part of the plurality of events detected by the plurality of sensor during the at least one predetermined time period;

storing history data of detected events and/or of readout selection operations; and

outputting the selected part of the plurality of events for each of the at least one predetermined time period; wherein

the random selection is performed repeatedly for a series of the at least one predetermined time period including performing the random selection for a current predetermined time period based on the history data of detected events and/or of readout selection operations for a previous predetermined time period.

13 . A method comprising:

detecting a plurality of events with a plurality of sensors each of which is configured to detect an intensity of an influence on the sensor and to detect as an event a positive or a negative change of the intensity of the influence that is larger than a respective predetermined threshold;

randomly selecting for readout a part of the plurality of events detected by the plurality of sensors during at least one predetermined time period;

storing history data of detected events and/or of readout selection operations; and

outputting the selected part of the plurality of events for each of the at least one predetermined time period; wherein

the random selection is performed repeatedly for a series of the at least one predetermined time period including performing the random selection for a current predetermined time period based on the history data of detected events and/or of readout selection operations for a previous predetermined time period.

14 . A method comprising:

detecting a plurality of events;

randomly selecting for readout a part of the plurality of events during at least one predetermined time period;

storing history data of detected events and/or of readout selection operations; and

outputting the selected part of the plurality of events for each of the at least one predetermined time period; wherein

the random selection is performed repeatedly for a series of the at least one predetermined time period including performing the random selection for a current predetermined time period based on the history data of detected events and/or of readout selection operations for a previous predetermined time period.