A Wavefront Coding microscopy system is implemented in order to extend the depth of field of an optical system. An LC - SLM is used to display the profile of a phase mask. A set of optically coded images is recorded in an axial range [−1, 1.5] mm. To accelerate the deconvolution process, a routine developed directly on a GPU is implemented. Using this GPU based approach, the deconvolution time is reduced by providing an additional speed up to the visualization. Digital images are acquired using an experimental setup and results are presented.
Wavefront coding refers to the use of a phase modulating element in conjunction with deconvolution to extend the depth of focus of an imaging system. The coding element is an asymmetrical phase plate shape, for most applications in the form of a trefoil or a cubic polynomial. Phase plates with trefoil shape generate not only the desired amount of trefoil aberration but also spherical aberration. It has been recently shown that a wavefront coding based optical system shows high tolerance to spherical aberration for monochromatic images; however, the depth of focus is considerably shortened for color images. In this work, we will show how to modify the shape of a phase plate in order to optimize its performance for color imaging. The design parameters of the phase plate are obtained by minimizing a merit function by means of genetic algorithms developed for this purpose. The evaluation of the optical characteristics of the phase plates for a feedback with the optimization algorithm is obtained by Zemax. Results will be illustrated by numerical simulations of color images.
Wavefront Coding (WFC) technique is typically used to compensate for optical aberrations related to defocus. An advantage of WFC are that the depth of field (DOF) will be increased and the weight and size of an optical system are reduced. In this work a WFC system is analyzed to extend the DOF of the microscope objective. The Point Spread Function (PSF) is used to modify in such a way that it is invariant to defocus in a range of axial distances. A liquid crystal display light modulator (LC − SLM) in a 4f imaging system is used for the implementation of the phase masks (PM). LC− SLM screens modulate both the amplitude and the phase of the input beam. This display allows a flexible implementation of different profiles of phase masks that are generated from different families of functions, this is because the parameters can be dynamically modified. In this document, we propose an experimental setup for extended DOF in optical microscopy. Experimental results are presented using a LC - SLM.