Optical aberrations and modulation transfer function of a thermal lens for use in imaging.

The optical aberrations of the thermal lens formed in a liquid are reported for the first time as expressed in terms of the Zernike polynomials coefficients. Convection of the liquid in which the thermal lens is formed is shown to strongly modify the lens imaging properties, even for the case of vertical heating laser illumination, as studied herein. The time evolution of the optical properties of the thermal lens is investigated. The direction from which the heating laser beam illuminates the thermo-optical liquid, in which the thermal lens is formed, has been found to be crucial for the lens optical power, type, and level of aberrations observed and the way these lens properties change in time.