Objective lens design of image guide fiber bundle with large field and low distortion

In the design of front lens for the large cross-section image guide fiber bundle, the negative-positive structure with telecentric structure in image space, even aspheric surface and crescent thick lens were applied for solving the problems on off-axial aberrations and illumination uniformity on the image plane, as well as keeping the lens compact and small. After theoretical calculation and optimization, the design was developed whose operating wavelength, focal length, angle of view and relative aperture were 660 nm, 1.22 mm, 60 and 1∶3, respectively. The results showed that the MTF value of the lens was higher than 0.8 at the spatial frequency of 40 lp/mm, the relative distortion of the lens in the largest field was less than 0.05% and the field curvature was lower than 50 m. With the fine quality of imaging, the lens could be used for observation and measurement.