In a space project, a digital CCD camera which can image more clearly in the 1 Lux light environment has been
asked to design . The CCD sensor ICX285AL produced by SONY Co.Ltd has been used in the CCD camera. The FPGA
(Field Programmable Gate Array) chip XQR2V1000 has been used as a timing generator and a signal processor inside
the CCD camera. But in the low-light environment, two kinds of random noise become apparent because of the
improving of CCD camera's variable gain, one is dark current noise in the image background, the other is vertical
transfer noise. The real time method for eliminating noise based on FPGA inside the CCD camera would be introduced.
The causes and characteristics of the random noise have been analyzed. First, several ideas for eliminating dark current
noise had been motioned; then they were emulated by VC++ in order to compare their speed and effect; Gauss filter has
been chosen because of the filtering effect. The vertical transfer vertical noise has the character that the vertical noise
points have regular ordinate in the image two-dimensional coordinates; and the performance of the noise is fixed, the
gray value of the noise points is 16-20 less than the surrounding pixels. According to these characters, local median
filter has been used to clear up the vertical noise. Finally, these algorithms had been transplanted into the FPGA chip
inside the CCD camera. A large number of experiments had proved that the pretreatment has better real-time features.
The pretreatment makes the digital CCD camera improve the signal-to-noise ratio of 3-5dB in the low-light environment.
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