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The main performance parameters of infrared camera
National standard GB/T19870-2005 "Industrial Detection Infrared Thermal Imager" clearly states: brightness temperature, system optical coaxiality, modulation transfer function (MTF), uniformity, FOV (Field of View) And focal length are the core performance parameters of infrared cameras. With the development of infrared thermal imaging technology, its core performance parameters have been expanded. The following is a detailed introduction:
1. Brightness temperature:
Does brightness also have temperature? Professionally speaking, the brightness temperature refers to the temperature of a black body whose radiance is equal to the effective radiance of the measured heat radiator in a given wavelength range. If you can’t understand it, you can understand it. This temperature is the temperature obtained by measuring the heat radiator with a thermal imager. The accuracy is generally provided by the instruction manual.
2. Noise equivalent temperature difference:
From a broad perspective, the signals generated by various reasons and affecting the measurement results are collectively called noise. In actual operation, the rms noise voltage can be used as an input signal to generate a signal-to-noise ratio of 1. The thermal imaging camera scans the target object. If the peak value of the signal voltage and the rms of the noise voltage output by the system reference electronic filter are the same, the temperature difference between the target and the background of the black body radiation source can become the noise equivalent temperature difference. When the noise equivalent temperature difference is smaller, the better the imaging image of the thermal imager, the less the temperature measurement near room temperature is.
3. Field of view FOV:
The angle of view is the angle between the difference between the main plane of the system and the optical axis to check the target object or the line length of the imaging screen. That is to say, in the process of using the thermal imager, the opening angle of the height and width that the lens of the thermal imager can see is the angle of view. The larger the angle of view, the greater the temperature measurement range.
4. SiTF (Signal Transfer Function):
The signal transfer function is also called the responsivity function, which is the conversion of the input and output of the fixed target size and the variable target size intensity, showing an S-shaped curve. For a DC-coupled system, dark current limits the minimum detectable signal, saturation limits the maximum detectable signal, and the ratio between the maximum detectable signal and the minimum detectable signal is the dynamic range. The response degree and response time of the instrument also represent the temperature measurement performance of the instrument.
5. Infrared detector:
The infrared detector is the heart of the infrared temperature measuring instrument. The infrared temperature measurement target temperature enters the infrared detector through the optical system, and then the circuit is read out by the detector. After image and data processing, it is reflected on the display screen of the thermal imager. The process of transforming the infrared radiation information of an object into an electrical signal. The size of the detector indicates the size of a detection element on the detector. As the size of the detection element decreases, the clarity of the thermal image gradually increases, and the measurement results More and more accurate.
The resolution is an important basis for evaluating the quality of the infrared thermal image detector. The resolution indicates the number of unit detection elements in the focal plane on the detector. The more detection elements, the higher the temperature image quality.
7. Focal length:
Thermal imaging cameras are imaging instruments, and naturally have a focal length, which refers to the distance from the center of the lens to its focal point. The general thermal imager is equipped with a standard lens (different according to the manufacturer's configuration) at the factory. When measuring a small target, a macro lens can be added, and when measuring a far target, a telephoto lens can be added. The larger the focal length, the farther the distance for clear imaging.
8. MRTD (Minimum Resolvable Temperature Difference):
The minimum resolution temperature difference, also known as thermal sensitivity, also reflects the spatial resolution of the thermal imager. When the temperature of the measured target fluctuates greatly and the temperature difference is small, you need to select a thermal imager with high thermal sensitivity for temperature measurement to accurately measure its temperature change.