Avalanche diode based object detection device
There is provided an object detection device including a light source, an avalanche diode, a first counter, a second counter and a processor. The light source emits light within a first interval, and is turned off within a second interval, a third interval and a fourth interval. The avalanche diode detects photons corresponding to the first interval, second, third and fourth intervals to trigger avalanche events. The first counter performs up-counting on the avalanche events in the first interval and performs down-counting on the avalanche events in the third interval to generate a first count value. The second counter performs up-counting on the avalanche events in the second interval and performs down-counting on the avalanche events in the fourth interval to generate a second count value. The processor calculates a time-of-flight according to the first count value and the second count value.
1. An object detection device, comprising
a light source configured to be turned on or turned off;
an avalanche diode configured to perform a bright exposure corresponding to the light source being turned on, and perform a dark exposure corresponding to the light source being turned off to generate electrical pulses;
two counters each comprising multiple stages of counting units, wherein the electrical pulses generated within an interval of the bright exposure of the avalanche diode are inputted to a first stage of the counting units, and the electrical pulses generated within an interval of the dark exposure of the avalanche diode are switched to be inputted to other counting units of the same counter behind the first stage of the counting units; and
a processor configured to calculate a time-of-flight according to count values within an exposure interval of the two counters, wherein the exposure interval comprises an interval of one bright exposure and intervals of multiple dark exposures, and the count values are results by eliminating ambient light influence without further subtraction operation in calculating the time-of-flight.
2. The object detection device as claimed in claim 1 , wherein the electrical pulses generated within an interval of another dark exposure of the avalanche diode are switched back to be inputted to the first stage of the counting units.
3. The object detection device as claimed in claim 1 , wherein
when the electrical pulses are inputted to the first stage of the counting units, said counting units are configured to perform an up-counting, and
when the electrical pulses are inputted to other counting units behind the first stage of the counting units, said counting units perform a down-counting.
4. The object detection device as claimed in claim 1 , wherein the processor is further configured to accumulate the count values of the two counters for a plurality of exposure intervals.
5. The object detection device as claimed in claim 1 , further comprising a sampling switch configured to connect the avalanche diode with one of the two counters.