Today I will introduce to you what are the performance parameters of short wave infrared sensors.
1. Voltage response
When the modulated infrared radiation is irradiated on the sensitive surface of the SWIR image sensors, the ratio of the output voltage of the sensor to the input infrared radiation power is called the voltage response rate of the sensor.
2. Response wavelength range:
(1) The response wavelength range (or spectral response) is the relationship between the voltage response rate of the sensor and the wavelength of the incident infrared radiation, which is generally represented by a curve.
(2) Generally, the wavelength corresponding to the maximum response rate is called the peak wavelength.
(3) The wavelength at which the response rate drops to half of the response value is called the cutoff wavelength, which represents the wavelength range used by the short wave infrared sensor.
3. Noise equivalent power
If the output voltage generated by the radiation power projected on the sensitive element of the infrared sensor is exactly equal to the noise voltage of the sensor itself, then this radiation power is called "noise equivalent power".
The higher the detection rate of the infrared sensor is, the smaller the minimum radiation power that the sensor can detect, and the more sensitive the sensor is.
4. Specific detection rate
Specific detection rate is also called normalized detection rate, or detection sensitivity. Essentially, when the area of the sensitive element of the sensor is a unit area and the bandwidth of the amplifier is 1 Hz, the specific detection rate is what we call the ratio of the signal voltage obtained by the radiation of a unit power to the noise voltage.
5. Time constant
The time constant represents the rate at which the output signal of the short wave infrared sensor changes with infrared radiation.
The time that the output signal lags behind the infrared radiation is called the time constant of the sensor, which is: τ = 1/2πfc in value
Where fc is the modulation frequency when the response rate drops to the maximum value of 0.707 (3dB).
The thermal inertia parameter of the thermal sensor is relatively large, and its time constant is larger than that of the photon sensor, generally it is of millisecond or longer; while the time constant of the photon sensor is generally microsecond.