Semiautomatic zoom lens calibration based on the camera's rotation

摘要

Abstract. A zoom lens calibration consists of hundreds of monofo-ncal calibrations, each of which takes considerable time and effort withnconventional methods.We present a practical calibration method thatnconsists of two separate procedures—zoomcalibration and focus cal-nibration. The zoom calibration regards each zoom setting as a mono-nfocal camera, and takes advantage of both the pattern-based and thenrotation-based approaches. A rotation sensor is utilized to overcomenthe ill-posedness caused by the many parameter dimensions. Thenzoom calibration is followed by the focus calibration process, whichnis fully automatic and available even at a defocused setting wherenthe pattern detection is not possible. The focus calibration drasti-ncally reduces the number of required manual calibrations, from N2 tonN times. The experimental results are compared with the lens datansheets provided by the lens manufacturer. The overall calibration pro-ncedure is very quick compared to the conventional methods, owing tonthe proposed zoom and focus calibrations, and shows small enoughnparameter errors in the effective zoom-focus range. © 2011 SPIE andnIS&T. [DOI: 10.1117/1.3574403]