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Microthermometer: a more economical thermal imaging technique

Microthermometer: a more economical thermal imaging technique

2021-05-11 11:10:07
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Microthermometer: a more economical thermal imaging technique

At room temperature and below room temperature, the real thermal effect is 3μm and above. imaging devices capable of capturing these thermal effects are generally considered true thermal imager. Infrared cameras refer not only to these thermal imaging devices —— because most of the signals they capture come from long-wave infrared radiation.

 

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The diagram shows the electromagnetic spectrum containing the infrared band.

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Scientists and camera manufacturers define infrared spectral bands differently. The definition boundary of the camera manufacturer depends on the technical characteristics of the detector in the thermal imager.

 

MWIR detectors can also be applied in the field of thermal imaging. However, they have a common disadvantage that is very expensive. 640×512 pixel detectors sell for a median price of about $70,000. These detectors are expensive because they must be cooled to about 75 K( or -198.15). the detector material itself is very sensitive to thermal radiation, thus causing the sensor to saturate immediately at room temperature. Among modern MWIR thermal imager, low temperature cooling is realized by closed circuit Stirling refrigerator located inside the camera fuselage. In the past, the cooling of such cameras required the use of atmospheric bottles filled with liquid nitrogen.


A more economical option is a thermal imager integrated with a microthermometer detector. Depending on the pixel resolution, detector noise level, and temperature measurement accuracy, the thermal imager can start at less than $1000 with a resolution of 80×60 pixels. The principle of micro-radiometer is completely different from that of typical photon capture detector, which is mainly based on micro thermal resistance pixels. Some of these thermal imager mainly use thermoelectric refrigeration components, easier to operate. When these pixels are exposed to infrared radiation (heat), their resistance changes. No low temperature refrigeration, simpler operation, lower cost.

LWIR each pixel in the camera has its physical mass, it needs to capture the thermal radiation of the pointed object to heat it. this is the time required for each pixel to preheat before the camera read resistance changes, given a fixed time constant. The constant is usually between 8 and 14 milliseconds, depending on the pixel size. The disadvantage of this detector is that when it comes to imaging of moving objects, the time constant brings no small challenge.

Eight milliseconds seems short. However, according to the camera's field of view angle and the speed of the imaging object, there may be obvious motion blur in the captured image. in the integral time (i.e., time constant), motion blur occurs when part of the object passes through the detector pixels. in other words, the pixel may not fully integrate the thermal radiation it is trying to capture before the object moves to an adjacent pixel. therefore, this leads to the temperature average effect, which leads to measurement errors and other problems.

 

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A non-cooled micro-radiometer detector is a more economical alternative to a refrigeration MWIR camera. the ability of the microthermometer detector to capture thermal imaging data is mainly based on the micro thermal resistance pixel, which changes its resistance when exposed to infrared radiation (heat), which can be used.

 

Motion blur is not the only blur type in thermal imaging. Since the contrast in the thermal image is caused by temperature changes, most thermal images look blurred. This ambiguity is not the result of focus or lack of focus. more precisely, this is caused by physical thermodynamic functions. Hi-resolution sensor.

Thermal energy flows from warmer regions with higher energy to cooler regions with lower energy. This behavior is completely dynamic, resulting in a temperature transition or thermal gradient. In the thermal image, the temperature changes as brightness changes: white represents the hotter area, black represents the colder area, and the gray transition occurs between the warmer and colder areas.

 

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The diagram shows the thermal image of the electrified circuit. The thermal image will only appear clear when the emissivity (emissivity) changes or when the warmer area is thermally isolated from the surrounding area. It is this dynamic behavior caused by thermal diffusion that indicates that thermal imaging may be more related to signal processing than image processing.

 


these transitions make the image edges look blurred. this effect usually does not appear in standard machine vision applications, which rely more on the effects produced by surface or characteristic reflected light. this reflection mode is constant and the contrast it produces in the image is constant. Only when the emissivity changes, or when the warmer area is thermally isolated from the surrounding area, the thermal image will appear clearer. It is this dynamic behavior caused by thermal diffusion that indicates that thermal imaging may be more related to signal processing than image processing.


As the global performance leading OEM in IR camera industry, ZIP Technology is the perfect solution for any IR application where accuracy, adaptability, low cost, and quality are imperative, brings you a high speed, high definition, dual thermal camera system solutions, ensuring maximum security and surveillance in many different scenarios.


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