The basic parameters that characterize the performance of infrared detectors include responsivity, noise equivalent power, detectivity, specific detectivity, time constant and spectral response, background-limited specific detectivity, etc. These parameters are an important basis for estimating system performance. In different systems, the choice of different detectors must also be selected according to these parameters.

 

1. Responsiveness

The responsivity of the detector is a parameter that characterizes the sensitivity of the detector to radiation. It characterizes the ability of the detector to convert the infrared radiation emitted by humans into electrical signals.

 

2. Noise equivalent power

In practical applications, infrared detection not only receives radiation signals emitted by humans, but also there is always noise in the detector. Obviously, the presence of noise limits the detector's ability to detect weak radiation signals, that is, the minimum radiation power that the detector can detect is limited. The noise equivalent power is defined as the radiation power emitted by a person onto the detector when the output signal power of the detector is equal to the noise power.

 

3. Detection rate and specific detection rate

The reciprocal of the noise equivalent power is called the detectivity.

 

4. Time constant

When radiation of a certain power is suddenly irradiated on the sensitive surface of the detector, it takes a certain time for the output voltage of the detector to rise to a value corresponding to the radiation power. When the radiation is suddenly cleared, it will take some time for the output voltage to drop to the value before the radiation exposure. Irradiate the detector with a rectangular radiation pulse, and observe its output signal waveform, it will be found that the rise or fall of the output signal falls after the rectangular pulse.

 

5. Spectral response

The monochromatic radiation of the same power is irradiated on the detector, and the relationship between the signal voltage generated and the radiation wavelength is called the spectral response of the detector. Usually, the responsivity R of the monochromatic radiation or the spectral specific detection rate D is used for the wavelength. Draw a graph to describe the spectral response of the detector.

 

6. Background limited detection rate

Ideal photon detectors will absorb all incident photons with wavelengths less than the cut-off wavelength, because these ideal detectors themselves do not generate noise, and their performance is limited by the noise generated by the fluctuation of the number of background radiation photons—photon noise.