In order to eliminate the distortion caused by the astigmatism from a compensate prism to improve the image quality of the optical system in a old no-distortion fingerprint scanner

a new method for eliminating the distortion using a cylindrical system combined with a telecentric lens is proposed. The double cylindrical system can reduce magnification in one direction that the prism doesn't do it

and the telecentric system can eliminate the trapezoid distortion when the objective and image is tilted. A computer model is established using this idea to adjust the suitable merit function to optimize the aberration

a higher imaging quality result is obtained comparing with the prism compensated method. From the example design

it is shown that using cylindrical system and telecentric lens method

the MTF in finger capture position is bigger than 0.377 in 5 lp/mm(equivalent 40 lp/mm in image area)and bigger than 0.139 lp/mm in 10 lp/mm(equivalent 80 lp/mm in image area) in most of the fields of view

the MTF value is 1.6 times as large as that obtained by the prism compensate method

also the image quality is much even in every field of view.