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1 December 1991 Alignment and focus control of a telescope using image sharpening
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Two alternative methods have traditionally been used to maintain telescope alignment and focus. The direct method measures rigid body changes (decentration, tilt and despace) using internal sensors and predicts the resulting performance degradation. The indirect method measures the performance degradation with a wavefront sensor and predicts the rigid body changes. An alternative indirect method uses an image sharpening merit function value derived from the image irradiance data . The image sharpening function has the property that it achieves its maximum value when the image has no residual aberrations. An aberrated image can be improved by introducing aberration corrections using an active mirror until the merit function value is optimized. Therefore, by forming a closed loop between the image detector and the active optical element, a telescope can be realigned and refocused to optimum performance without the use of a separate wavefront sensor or internal alignment/focus sensors. A comparison of the direct and indirect methods and recent experimental results of the image sharpening method are presented.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Peter A. Jones "Alignment and focus control of a telescope using image sharpening", Proc. SPIE 1542, Active and Adaptive Optical Systems, (1 December 1991);


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