The key technology of microminiature APS CMOS star tracker

At present,most star tracker use CCD as a photosensitive detector,which has the characteristics of high sensitivity,wide dynamic range,uniform pixel response and so on,which is very suitable for high-precision occasions,which is why it has occupied the mainstream in the past 20 years.

In recent years,the development of CMOS technology,especially APS CMOS technology,has greatly improved the sensitivity of photosensitive detectors.So it is currently widely believed that APS CMOS photodetectors will replace CCD as the mainstream of the next generation of miniature sensors

Why will APS CMOS sensor replace CCD to become the mainstream of a new generation of micro star tracker?

The APS CMOS sensor integrates an amplifier and readout circuit in each pixel,which is different from the charge transfer mode of CCD.This property makes it more resistant to radiation than CCDS.At the same time,the CCD processing technology is compatible with the common CMOS process.

The difference between APS CMOS and CCD imaging principles:

There is a significant difference between these two.The CCD whole frame image is exposed once,while CMOS uses a roller shutter exposure imaging method.The APS CMOS photosensitive detector has a completely different structure from CCD.Each pixel unit not only has a photosensitive area,but also has signal amplification and readout control signals.In theory,APS CMOS can directly read out the response value of each pixel by accessing memory.

Effective Separation of Noise and Signal:Star Map Filtering Algorithm

A major drawback of APS CMOS image sensors compared to CCD image sensors is that there is relatively high noise,especially mode noise.At the same time,the signal-to-noise ratio of APS CMOS star sensors also has a certain gap compared to CCD,which leads to a decrease in the signal-to-noise ratio of APS CMOS star sensors compared to traditional CCD star sensors.So in order to effectively separate noise and signal,extracting star points is a key aspect of filtering imaging algorithms,which is also a key factor in the success or failure of star sensors.

Real time processing methods for star maps:

The traditional star sensor star map processing algorithm adopts a software processing scheme,which is very slow.With the development of electronic technology,the array of image sensors continues to increase.In order to improve the measurement accuracy of a single star in the star sensor,the effective information ratio of star points in the image sensor is reduced.If traditional algorithms are used,a large amount of computation is required.

Therefore,a real-time star map filtering algorithm based on hardware structure is proposed,which performs image filtering while image exposure and reading,and realizes the real-time star image processing of star sensor.

This article mainly introduces the key technologies of micro APS CMOS star sensors from several aspects.Understood the technical differences between CCD and APS CMOS.