Photodetector and portable electronic equipment
Effects of ambient light are suppressed, and distance to a detection object is measured with high precision. A ranging sensor includes a VCSEL, a SPAD array that has multiple SPADs that detect photons of pulse light emitted by the VCSEL, a SPAD array that has multiple SPADs that detect photons of reflected light where the pulse light has been reflected by a detection object, a DLL that measures a time difference between a pulse signal output from the SPADs of the SPAD array and a pulse signal output from the SPADs of the SPAD array, an ambient-light-incident SPAD determining unit that determines a SPAD on which ambient light is incident, based on pulse signals output from SPADs of the SPAD array when the VCSEL is not emitting light, and a SPAD front-end circuit that stops operation of the SPAD for which determination is made that ambient light is incident.
1. A photodetector, comprising:
a light-emitting element;
a first light-receiving unit that has a plurality of avalanche photodiodes as a first light-receiving element that detects, in Geiger mode, photons of pulse light emitted by the light-emitting element;
a second light-receiving unit that has a plurality of avalanche photodiodes as a second light-receiving element that detects, in Geiger mode, photons of reflected light where the pulse light has been reflected by a detection object;
a time difference measuring unit that measures a time difference between a puke signal output from the first light-receiving element of the first light-receiving unit and a pulse signal output from the second light-receiving element of the second light-receiving unit;
an ambient-light-incident light-receiving-element determining unit that determines the second light-receiving element on which ambient light is incident, based on pulse signals output from second light-receiving elements of the second light-receiving unit when the light-emitting element is not emitting light; and
an operation stopping unit that stops operation of the second light-receiving elements for which determination is made that ambient light is incident.
2. The photodetector according to claim 1 , wherein, in a case where a number of pulses per unit time of a pulse signal output from the second light-receiving element is greater than a predetermined value, the ambient-light-incident light-receiving-element determining unit determines that ambient light is incident on the second light-receiving element that has output the pulse signal.
3. The photodetector according to claim 1 , further comprising:
a coefficient multiplying unit that multiplies a pulse signal of the second light-receiving element by a weighting coefficient corresponding to a position of the second light-receiving element, in the second light-receiving unit,
wherein, in a case where a number of pulses per unit time of the pulse signal multiplied by the weighting coefficient is greater than a predetermined value, the ambient-light-incident light-receiving-element determining unit determines that ambient light is incident on the second light-receiving element that has output the pulse signal.
4. The photodetector according to claim 3 , wherein the weighting coefficient is smallest at a middle portion of the second light-receiving unit and becomes larger in a direction from the middle portion toward a perimeter portion of the second light-receiving unit.
5. The photodetector according to claim 1 , wherein, in a case where a number of pulses of a pulse signal output from the second light-receiving element is greater than a first predetermined value, and a difference or a ratio between the numbers of pulses when the light-emitting element is emitting light and not emitting light is smaller than a second predetermined value, determination is made that ambient light is incident on the second light-receiving element outputting the pulse signal.
6. The photodetector according to claim 5 , further comprising:
a light-emission intensity control unit that reduces light-emission intensity of the light-emitting element in a case where the difference or the ratio between the numbers of pulses when the light-emitting element is emitting light and not emitting light is greater than a predetermined value.
7. The photodetector according to claim 5 , further comprising:
a light emission angle control unit that controls a light emission angle of the light-emitting element in a case where the difference or the ratio between the numbers of pulses when the light-emitting element is emitting light and not emitting light is greater than a predetermined value.
8. The photodetector according to claim 1 , further comprising:
a concentrating lens disposed on a side of the second light-receiving unit on which light is incident.
9. Portable electronic equipment, comprising: the photodetector according to claim 1 .