Aberration analysis and adjustment of nonspherical lens in the linear CCDs three-dimensional measurement system

Abstract

Linear CCDs three-dimensional measurement system is constituted with three one dimensional imaging units (ODIUs) composed of charge-couple device (CCD) linear image sensor paired with equivalent cylindrical lens cells. The cylindrical lens is needed for optical transformation from object point to its realistic image line in the ODIU, and the imaging quality of equivalent cylindrical lens (width and distortion aberration of the image line) directly affected the reconstruction precision of three dimension coordinates. At present, the methods of how to design an equivalent cylindrical lens with both high precision and wide field of view were not reported in literatures. An improved Double Gauss structured lenses by replacing the first spherical lens in the traditional Double Gauss lenses with a cylindrical lens is introduced to realize the point to line optical transformation and aberration adjustment. The coma aberration and distortion can be automatically adjusted due to the structure symmetry of composite lenses, and the spherical aberration, astigmatism and curvature of field can also be largely adjusted by appropriately selecting material, luminous flux, curvature, thickness, and distance of lenses. Under the computer simulating by Zemax (an optical systems design software), the composite cylindrical lens was designed and fabricated. Finally, the three-dimensional positioning system made up of above-mentioned composite cylindrical lens and corresponding circuits is constructed, and the direct linear transformation (DLT) is adopted to three dimension coordinated reconstruction. The result of reconstruction error of X, Y, Z axis with in the view field of 700x760x500 mm less than 1mm are obtained.