Proximity sensor having an array of single photon avalanche diodes and circuitry for switching off illumination source and associated method, computer readable medium and firmware
View Patent ↗A proximity detector may include an array of single photon avalanche diodes (SPADs) and an illumination source. Illumination from the illumination source may be reflected by a target to the array of single photon avalanche diodes. The SPADs may be operable to detect events. A number of events detected may be dependent on a level of illumination incident on the SPADs. The proximity detector may then determine a quality metric and calculate an output when the quality metric is at a predetermined level. A related method may include regulating the quality of the data on which such a proximity detector apparatus calculates its output.
1. A proximity detection apparatus comprising:
an illumination source; and
an array of single photon avalanche diodes (SPADs) configured so that illumination from said illumination source is reflected by a target to said array of SPADs; and
circuitry coupled to said array of SPADs and configured to
detect a number of events based upon a level of illumination on said array of SPADs,
determine a quality metric,
calculate an output when the quality metric is at a threshold level, and
switch off said illumination source when the threshold level is reached.
2. The proximity detection apparatus of claim 1 , wherein the quality metric is based upon a total number of the events detected by said array of SPADs.
3. The proximity detection apparatus of claim 1 , wherein the quality metric is based upon a number of events detected under ambient illumination conditions.
4. The proximity detection apparatus of claim 1 , wherein said circuitry is configured to repeat cycles of a detection phase and a calculation phase; and wherein the quality metric is determined for each detection phase such that a duration of each detection phase is based upon a value of its corresponding quality metric.
5. The proximity detection apparatus of claim 4 , wherein said circuitry is configured to be in a low power mode where the detection phases are at intervals in a threshold range.
6. The proximity detection apparatus of claim 1 , wherein said array of SPADs are arranged in rows and columns.
7. The proximity detection apparatus of claim 1 , wherein said circuitry comprises a multiplexer and a counter coupled to said array of SPADs and configured to enable measurement of the reflected illumination.
8. The proximity detection apparatus of claim 1 , wherein said circuitry is configured to calculate the output using a range equation based upon a phase difference between the illumination provided and the reflected illumination.
9. The proximity detection apparatus of claim 8 , wherein said circuitry is configured to determine the phase difference by dividing time into two equal duration intervals which alternate repeatedly, the duration of each interval being based upon a modulation frequency of the illumination source, the phase difference being based upon an interval in which the events were detected.
10. A method of regulating the quality of data on which an output of a proximity detector is calculated, the proximity detector comprising an array of single photon avalanche diodes (SPADs) and a illumination source, the method comprising:
turning on the illumination source so that illumination from the illumination source is reflected by a target to the array of SPADs;
counting a number of events detected by the array of SPADs, the number of events being based upon a level of illumination on the array of SPADs;
determining a quality metric from the number of events counted;
calculating, when the quality metric is at a threshold level, and from a number of events which exceed the threshold level, the output based upon a proximity of the target; and
turning off the illumination source when the threshold level is reached.
11. The method of claim 10 , wherein the quality metric is based upon a total number of events detected by the array of SPADs.
12. The method of claim 10 , wherein the quality metric is based upon a number of events detected under ambient illumination conditions.
13. The method of claim 10 , further comprising repeating cycles of a detection phase and a calculation phase, wherein the quality metric is determined for each detection phase such that a duration of each detection phase is based upon a value of its corresponding quality metric.
14. The method of claim 13 , wherein the detection phases are at intervals in a threshold range.
15. The method of claim 10 , wherein the array of SPADs is arranged in rows and columns.
16. The method of claim 10 , wherein the array of SPADs is coupled to a multiplexer and a counter for measuring the reflected illumination.
17. The method of claim 10 , wherein the output is calculated using a range equation based upon a phase difference between the illumination from the illumination source and reflected illumination.
18. The method of claim 17 , wherein the phase difference is determined by dividing time into two equal duration intervals which alternate repeatedly, the duration of each interval being based upon a modulation frequency of the illumination source, and the phase difference being based upon an interval in which the events were detected.
19. A non-transitory computer readable medium for use with a proximity detection apparatus and comprising an array of single photon avalanche diodes (SPADs) and a illumination source, and having computer-executable instructions for causing the proximity detection apparatus to perform the steps comprising:
turning on an illumination source so that illumination from the illumination source is reflected by a target to the array of SPADs;
counting a number of events detected by the array of SPADs, the number of events being based upon a level of illumination on the array of SPADs;
determining a quality metric from the number of events counted;
calculating, when the quality metric is at a threshold level, and from a number of events which exceed the threshold level, the output based upon a proximity of the target; and
turning off the illumination source when the threshold level is reached.
20. The non-transitory computer-readable medium of claim 19 , wherein the quality metric is based upon a total number of events detected by the array of SPADs.
21. The non-transitory computer-readable medium of claim 19 , wherein the quality metric is based upon a number of events detected under ambient illumination conditions.
22. The non-transitory computer-readable medium of claim 19 , wherein the computer-executable instructions are for repeating cycles of a detection phase and a calculation phase, wherein the quality metric is determined for each detection phase such that a duration of each detection phase is based upon a value of its corresponding quality metric.
23. The non-transitory computer-readable medium of claim 19 , wherein the computer-executable instructions are for calculating the output using a range equation based upon a phase difference between the illumination from the illumination source and reflected illumination.
24. The non-transitory computer-readable medium of claim 23 , wherein the computer-executable instructions are for determining the phase difference by dividing time into two equal duration intervals which alternate repeatedly, the duration of each interval being based upon a modulation frequency of the illumination source, and the phase difference being based upon an interval in which the events were detected.