Infrared sensor, sensing system, and infrared sensing method
An infrared sensor according to the present disclosure includes an output pixel, and a switcher. The output pixel includes infrared photodetectors. The switcher switches each of the infrared photodetectors between a first state and a second state independently with a predetermined period P. In the first state, the infrared photodetector is able to change in temperature in response to receiving infrared radiation. In the second state, the infrared photodetector is maintained at a predetermined temperature. Switching of the infrared photodetectors from the second state S 2 to the first state S 1 is executed sequentially in the period P at a predetermined time interval ti. The output pixel includes N infrared photodetectors. The time interval ti divided by the period P is greater than or equal to 1/(N+1) and less than or equal to 1/(N−1).
1 . An infrared sensor comprising:
an output pixel that includes infrared photodetectors, the output pixel generating an output signal on the basis of outputs from the infrared photodetectors, the outputs corresponding one-to-one to the infrared photodetectors; and
a switcher that switches each of the infrared photodetectors between a first state and a second state independently in a predetermined period, the first state being a state in which the infrared photodetector is able to change in temperature in response to receiving infrared radiation, the second state being a state in which the infrared photodetector is maintained at a predetermined temperature,
wherein each of the infrared photodetectors is maintained in the first state for a specific amount of time in the predetermined period,
wherein the infrared photodetectors are switched from the second state to the first state sequentially in the predetermined period, the switches from the second state to the first state corresponding one-to-one to the infrared photodetectors, a time interval provided between a first switch among the switches and a second switch among the switches being a predetermined time interval, the second switch being provided immediately after the first switch among the switches,
wherein the infrared photodetectors are switched from the first state to the second state sequentially in the predetermined period,
wherein a total number of the infrared photodetectors is N,
wherein N is an integer greater than or equal to 2, and
wherein the predetermined time interval divided by the predetermined period is greater than or equal to 1/(N+1) and less than or equal to 1/(N−1).
2 . The infrared sensor according to claim 1 , wherein the specific amount of time divided by the predetermined period is greater than or equal to 0.5/N and less than or equal to 2/N.
3 . The infrared sensor according to claim 1 , wherein in the generating the output signal, the outputs from the infrared photodetectors include an output from an infrared photodetector of the infrared photodetectors that is in the second state is regarded as zero.
4 . The infrared sensor according to claim 1 , wherein the output pixel includes a square number of the infrared photodetectors disposed adjacent to each other.
5 . The infrared sensor according to claim 1 , wherein the predetermined period is less than a thermal relaxation time of each of the infrared photodetectors, the thermal relaxation time being a time required for a temperature of the infrared photodetector to stabilize to a steady state after end of reception of infrared radiation.
6 . The infrared sensor according to claim 1 , further comprising:
a first wiring line through which a signal from each of the infrared photodetectors is to be transferred; and
a second wiring line independent from the first wiring line, the second wiring line being a wiring line through which a control signal for the switcher is to be transferred.
7 . The infrared sensor according to claim 1 , further comprising
a component constituting a heat bath,
wherein each of the infrared photodetectors includes a stack of at least two materials with different thermal expansion coefficients, and
wherein in switching from the first state to the second state, each of the infrared photodetectors deforms in response to application of a control signal, and at least part of the infrared photodetector comes into contact with the component, the control signal having an electric current value greater than or equal to a predetermined value.
8 . A sensing system comprising:
the infrared sensor according to claim 1 ; and
a load device that applies a load to an object to be sensed by the infrared sensor, the load being a load that varies with the predetermined period.
9 . An infrared sensing method comprising:
generating an output signal from an output pixel on the basis of outputs from infrared photodetectors, the output pixel including infrared photodetectors, the outputs corresponding one-to-one to the infrared photodetectors;
switching each of the infrared photodetectors between a first state and a second state independently in a predetermined period, the first state being a state in which the infrared photodetector is able to change in temperature in response to receiving infrared radiation, the second state being a state in which the infrared photodetector is maintained at a predetermined temperature;
maintaining each of the infrared photodetectors in the first state for a specific amount of time in the predetermined period;
switching the infrared photodetectors from the second state to the first state sequentially in the predetermined period, the switches from the second state to the first state corresponding one-to-one to the infrared photodetectors, a time interval provided between a first switch among the switches and a second switch among the switches being a predetermined time interval, the second switch being provided immediately after the first switch among the switches; and
switching the infrared photodetectors from the first state to the second state sequentially in the predetermined period,
wherein a total number of the photodetectors is N,
wherein N is an integer greater than or equal to 2,
wherein the predetermined time interval divided by the period is greater than or equal to 1/(N+1) and less than or equal to 1/(N−1).
10 . The infrared sensing method according to claim 9 , comprising applying a load to an object to be sensed, the load being a load that varies with the predetermined period.
11 . An infrared sensor comprising:
a pixel including a first cell including a first infrared photodetector, . . . , and an Nth cell including an Nth infrared photodetector; and
a first thermoelectric cooler that cools the first infrared photodetector, . . . , and an Nth thermoelectric cooler that cools the Nth infrared photodetector,
wherein the first thermoelectric cooler is supplied with an electric current from a time m×T to a time {m×T+ta(1)}, and from a time {m×T+ta(1)+tb(1)} to a time (m+1)×T, and as a result, the first infrared photodetector is cooled, . . . , and the Nth thermoelectric cooler is supplied with an electric current from the time m×T to a time {m×T+ta(N)}, and from a time {m×T+ta(N)+tb(N)} to the time (m+1)×T, and as a result, the Nth infrared photodetector is cooled,
wherein the first thermoelectric cooler is supplied with no electric current from the time {m×T+ta(1)} to the time {m×T+ta(1)+tb(1)}, . . . , and the Nth thermoelectric cooler is supplied with no electric current from the time {m×T+ta(N)} to the time {m×T+ta(N)+tb(N)},
wherein N is a natural number greater than or equal to 2,
wherein m is an integer greater than or equal to 0,
wherein {1/(N+1)}≤{(ta(2)−ta(1))/T}≤{1/(N−1)}, . . . , and {1/(N+1)}≤{(ta(N)−ta(N−1))/T}≤{1/(N−1)},
wherein the pixel outputs a signal Om,
wherein the signal Om is based on one or more detection values detected by the first cell from the time {m×T+ta(1)} to the time {m×T+ta(1)+tb(1)}, . . . , and the signal Om is based on one or more detection values detected by the Nth cell from the time {m×T+ta(N)} to the time {m×T+ta(N)+tb(N)}, and
wherein the signal Om is not based on one or more detection values detected by the first cell from the time m×T to the time {m×T+ta(1)}, and is not based on one or more detection values detected by the first cell from the time {m×T+ta(1)+tb(1)} to the time (m+1)×T, . . . , and the signal Om is not based on one or more detection values detected by the Nth cell from the time m×T to the time {m×T+ta(N)}, and is not based on one or more detection values detected by the Nth cell from the time {m×T+ta(N)+tb(N)} to the time (m+1)×T.
12 . The infrared sensing method according to claim 9 , wherein
in the generating the output signal, the outputs from the infrared photodetectors include an output from an infrared photodetector of the infrared photodetectors that is in the second state is regarded as zero.