1 May 2005 Autofocus system for space cameras
Author Affiliations +
Optical Engineering, 44(5), 053001 (2005). doi:10.1117/1.1901686
A novel autofocusing technique using a self-imaging approach is developed for a space camera having large aperture and long focus. Its optical system consists of an emitting system, receiving system, and two pentagonal prisms. The emitting system has three parts: a light source, beamsplitter, and aim slit. The receiving system includes a field lens, two separate lenses, and CCD. Using two little pentaprisms instead of a large planar mirror makes the autofocus system simple and compact. A defocused signal is acquired by measuring the change of the slit self-image position imaged on the CCD. The algorithm to calculate the movement of the slit self-image position is analyzed to achieve subpixel position estimation. The results of the experiments show a ±10-µm precision of autofocusing in a range of ±5-mm defocusing. The system demonstrates high resolution, easy adjustment, and high reliability. Also this method can meet the requirements of various accurate focus measurement systems.
Zhaohui Li, Keyong Wu, "Autofocus system for space cameras," Optical Engineering 44(5), 053001 (1 May 2005). http://dx.doi.org/10.1117/1.1901686


Imaging systems

Charge-coupled devices


Signal to noise ratio

Light sources

Beam splitters

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