Analysis of the process of visualisation of transparent objects using the phase-contrast method with a photothermal Zernike cell

Basic characteristics of the process of visualisation of transparent objects using the phase-contrast method with a photothermal Zernike cell are analysed and evaluated. It is shown that, in spite of nonlocality of the process, visualisation is accomplished with the resolution close to the diffraction limit. The results of the visualisation process analysis in the scheme with a photothermal sell are compared with those obtained in a similar scheme with a Zernike cell based on the local Kerr nonlinearity. (optical image processing)