Introduction and Types of Infrared Sensors
Infrared sensor is the use of infrared physical properties to measure the sensor. Infrared also known as infrared light, it has reflection, refraction, scattering, interference, absorption and other properties. Any substance that has a certain temperature of its own (above absolute zero) can emit infrared radiation. Infrared sensor measurement does not directly contact with the measured object, so there is no friction, and has the advantages of high sensitivity, fast response.
Infrared sensor includes optical system, detecting element and conversion circuit. Optical system can be divided into transmission type and reflection type according to different structure. The detecting element can be divided into thermal detecting element and photoelectric detecting element according to the working principle. Thermistors are the most widely used thermistors. When thermistor is subjected to infrared radiation, the temperature increases, and the resistance changes (this change may be larger or smaller, because thermistor can be divided into positive temperature coefficient thermistor and negative temperature coefficient thermistor), which can be converted into electrical signal output through the conversion circuit. Photoelectric detection elements are commonly used as photosensitive elements, usually made of lead sulfide, lead selenide, indium arsenide, antimony arsenide, mercury cadmium telluride ternary alloy, germanium and silicon doped materials.
Infrared sensors, in particular, make use of the sensitivity of the far infrared range for human physical examination, infrared wavelengths are longer than visible light and shorter than radio waves. Infrared makes people think that it is only emitted by hot objects, but in fact it is not so. All objects existing in nature, such as human beings, fire, ice and so on, all emit infrared rays, but their wavelength is different because of the temperature of the object. The body temperature is about 36 ~ 37°C, which emits a far infrared ray with a peak value of 9 ~ 10μm. In addition, the object heated to 400 ~ 700°C can emit a middle infrared ray with a peak value of 3 ~ 5μm.
The infrared sensor can be divided into its actions:
(1) The infrared line is transformed into heat, and the heat type of the changing resistance value and the output signal such as the electric dynamic potential are removed by heat.
(2) The optical effect of the semiconductor migration phenomenon and the quantum type of the photoelectric potential effect due to PN connection.
The thermal phenomenon is commonly known as pyrothermal effect, and the most representative are radiation detector (Thermal Bolometer), thermoelectric reactor (Thermopile) and thermoelectric (Pyroelectric) elements.
The advantages of thermal type are: can operate at room temperature action, wavelength dependence (different wavelength sensory changes) does not exist, the cost is cheap;
Disadvantages: low sensitivity, slow response (mS spectrum).
Advantages of quantum type: high sensitivity, rapid response (the spectrum of S);
Disadvantages: must cool (liquid nitrogen), wavelength dependence, high price;
Infrared sensor includes optical system, detecting element and conversion circuit. Optical system can be divided into transmission type and reflection type according to different structure. The detecting element can be divided into thermal detecting element and photoelectric detecting element according to the working principle. Thermistors are the most widely used thermistors. When thermistor is subjected to infrared radiation, the temperature increases, and the resistance changes (this change may be larger or smaller, because thermistor can be divided into positive temperature coefficient thermistor and negative temperature coefficient thermistor), which can be converted into electrical signal output through the conversion circuit. Photoelectric detection elements are commonly used as photosensitive elements, usually made of lead sulfide, lead selenide, indium arsenide, antimony arsenide, mercury cadmium telluride ternary alloy, germanium and silicon doped materials.
Infrared sensors, in particular, make use of the sensitivity of the far infrared range for human physical examination, infrared wavelengths are longer than visible light and shorter than radio waves. Infrared makes people think that it is only emitted by hot objects, but in fact it is not so. All objects existing in nature, such as human beings, fire, ice and so on, all emit infrared rays, but their wavelength is different because of the temperature of the object. The body temperature is about 36 ~ 37°C, which emits a far infrared ray with a peak value of 9 ~ 10μm. In addition, the object heated to 400 ~ 700°C can emit a middle infrared ray with a peak value of 3 ~ 5μm.
The infrared sensor can be divided into its actions:
(1) The infrared line is transformed into heat, and the heat type of the changing resistance value and the output signal such as the electric dynamic potential are removed by heat.
(2) The optical effect of the semiconductor migration phenomenon and the quantum type of the photoelectric potential effect due to PN connection.
The thermal phenomenon is commonly known as pyrothermal effect, and the most representative are radiation detector (Thermal Bolometer), thermoelectric reactor (Thermopile) and thermoelectric (Pyroelectric) elements.
The advantages of thermal type are: can operate at room temperature action, wavelength dependence (different wavelength sensory changes) does not exist, the cost is cheap;
Disadvantages: low sensitivity, slow response (mS spectrum).
Advantages of quantum type: high sensitivity, rapid response (the spectrum of S);
Disadvantages: must cool (liquid nitrogen), wavelength dependence, high price;
