Infrared focal plane detector is the core component of thermal imaging system, which is used to detect and identify infrared information of objects. It is widely used in electric power, railway, petrochemical industry, security, medical and other fields. Infrared focal plane detectors are divided into refrigerated infrared focal plane detectors and uncooled infrared focal plane detectors. Thermal sensor is the core component of infrared detectors and the bridge between receiving infrared radiation and output signals. The thermal sensor of uncooled infrared focal plane detector is mainly composed of vanadium oxide and polysilicon. What is the difference between vanadium oxide and polysilicon?

The similarities between vanadium oxide and polysilicon

1. Same type of film

Vanadium oxide films and amorphous silicon films are semiconductor thermosensitive films and the film resistance temperature coefficient TCR is proportional to the resistivity.

2. Same production process

The microbolometer technology is compatible with the CMOS process and can be integrated with the CMOS readout circuit chip. It can be used for large-scale production based on the semiconductor manufacturing process. It is the main technology of the uncooled infrared focal plane detector.

The difference between vanadium oxide and polysilicon

1. Different imaging principles

An pixel of vanadium oxide detector is an accurate temperature. Polysilicon thin film is relatively insensitive to temperature changes due to the growth characteristics of materials. However, with the development of software algorithm, image algorithm program can be used to make up for it to a certain extent. The average temperature of N*N (N≥2) pixels is taken as a temperature measurement value by image algorithm, and a simulated artificial value is given in the adjacent area. Close observation is more accurate, remote observation, sometimes an object only a few pixels, often unable to recognize or analysis results error.

2. Different film performance indexes

Under the same resistance condition, vanadium oxide film TCR is superior to polysilicon film. Under the same TCR condition, the noise coefficient of polysilicon thin film is 1/ F higher than vanadium oxide thin film by two orders of magnitude, which greatly restricts the detector's inherent sensitivity and fixed graphic noise based on polysilicon thin film, and this constraint becomes more and more significant with the reduction of pixel size.

3. Different technical indicators

The thermal sensitivity of vanadium oxide detectors can reach 20 ~ 30mk, while that of polysilicon detectors is usually high

Between 50 and 60mk. The residual fixed pattern noise of polysilicon is large, which is more than one order of magnitude higher than that of vanadium oxide. The specific performance is that the image has gauze sense and the infrared image senses are not transparent enough.

The performance of vanadium oxide and polysilicon detectors are different and have their own advantages. With the progress of infrared technology, the performance of detectors will be more optimized.