Motionless microscopy with tunable thermal lens.

The ability to modify the lens focal length has an advantage of giving sharp images without moving the lens. This work presents for the first time the use of the thermal lens as a tunable imaging element of the microscope. It shows also that the thermal lens can modify the image of a selected area of the sample, leaving the rest part of the image unaffected. Thus, appropriate tuning of thermal lens can lead to a simultaneously sharp image of two objects lying in different object planes separated by a distance exceeding the depth of field of the imaging optics.