There is a race to develop spaceborne high-resolution video cameras since Skybox’s success. For low manufacture cost and adaption to micro and small satellites, it is urgent to design and develop compact long focal length optical system with not only small volume, light weight and easy implementation, and also two dimensional field. Our focus is on the Coaxial Three-Mirror Anastigmat (CTMA) with intermediate real image for its no need outer hood and compactness and for its easy alignment, low-order aspheric surface and low cost. The means to deflect its image space beam for accessibility of focal plane array detector and to eliminate its inherent secondary obscuration from its primary mirror central hole and deflection flat mirror is discussed. The conditions to satisfy the above-mentioned requirements are presented with our derived relationship among its optical and structural parameters based on Gaussian optics and geometry. One flat mirror near its exit pupil can be used to deflect its image plane from its axis. And its total length can be decreased with other some flat mirrors. Method for determination of its initial structure with the derived formulae is described through one design example. Furthermore, optimized CTMA without secondary obscuration and with effective focal length (EFFL) of 10m is reported. Its full field, F-number and total length are respectively 1.1°×1°, F/14.3, and one eighth of its EFFL. And its imaging quality is near diffraction limit.
The blur due to the rapidly relative motion between scene and camera during exposure has the well-known influence on the quality of acquired image and then target detection. An improved coded exposure is introduced in this paper to remove the image blur and obtain high quality image, so that the test accuracy of the surface defect and edge contour of motion objects can be enhanced. The improved exposure method takes advantage of code look-up table to control exposure process and image restoration. The restored images have higher Peak Signal-to-Noise Ratio (PSNR) and Structure SIMilarity (SSIM) than traditional deblur algorithm such as Wiener and regularization filter methods. The edge contour and defect of part samples, which move at constant speed relative to the industry camera used in our experiment, are detected with Sobel operator from the restored images. Experimental results verify that the improved coded exposure is better suitable for imaging moving object and detecting moving target than the traditional.