Optical system design for lens with relative aperture of 1∶1

A spectral camera lens with the relative aperture of 1∶1 is introduced. The complicated Petzval structure is converted into a triplet structure based on aspheric surface. The primary optical properties are: f′=120mm, F=1, τ≥90%. The spatial frequency is greater than 20lp/mm when the MTF value of the optical system is equal to 0.85. The lens structure is optimized to facilitate the machining of the aspheric surface. Several kinds of aberration curves and the MTF data are given, and the further possible improvement for the optical system is explored.