High precision laboratory geometric calibration is the basis for the validity of on-orbit data of the Directional Polarimetric Camera. However, the difference in refractive index between the laboratory geometric calibration environment and the on-orbit vacuum environment can lead to changes in instrument geometric performance. The geometric performance difference of the instrument in the standard atmospheric environment and vacuum environment was analyzed by Zemax. The image point position deviation of the instrument in the two environments increases monotonically with the FOV. The image point position in the standard atmospheric environment is further away from the optical axis. When the FOV of the incident beam is 60o , the image points position deviation in all bands is greater than 1.42 pixels. Then, the laboratory carried out the environmental difference verification experiment based on the geometric performance verification light source. The experimental results are in good agreement with the Zemax analysis results, and the average deviation in the 670 nm band is less than 0.01 pixel. Finally, the laboratory geometric model parameters of the Directional Polarimetric Camera are corrected according to the Zemax analysis results. The corrected geometric model parameters will effectively improve the on-orbit geolocation and image registration accuracy of the Directional Polarimetric Camera.
KEYWORDS: Instrumentation engineering, Charge-coupled devices, Imaging systems, Signal to noise ratio, Analog electronics, Sensors, Signal processing, Cameras, Polarization, Polarimetry
A CCD imaging system in the Directional Polarimetric Camera is developed, which is comprised of timing driving unit, pro-processing and analog-front-end unit, FPGA main control unit, internal communication and remote measurement unit, image transmission interface unit, and so on. A CCD driving timing method with twice frame transfer and once horizontal readout is proposed to effectively eliminate the residual charge of last frame image and improve the signal-to-noise ratio. The performance of this CCD imaging system is verified. The experimental results show that the 14bit image data can output steadily with a frame frequency of 2.02 frames per second. The imaging signal-to-noise ratio can reach 54.93dB when the CCD is lower than saturated. The dynamic range of the CCD detectable signals is 68.98 dB and the nonlinearity error under different wavelengths is less than 1%. The instrumentation can satisfy the operational requirements such as stable output, excellent linear performance, high signal-to-noise ratio and large dynamic range.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.