Beam shaping is well known in material processing. The normal Gaussian beam profile may be is converted to a top hat (flat top) to more efficiently utilize the full energy of the beam.
The same beam shaping optics can also be used to improve image quality from a confocal microscope. Here is an abstract from an interesting paper published on the subject:
Uniform illumination of a working field is very important in optical systems of confocal microscopy and various implementations of fluorescence microscopy like TIR, SSIM, STORM, PALM to enhance performance of these laser-based research techniques. Widely used TEM00 laser sources are characterized by essentially non-uniform Gaussian intensity profile which leads usually to non-uniform intensity distribution in a microscope working field or in a field of microlenses array of a confocal microscope optical system, this non-uniform illumination results in instability of measuring procedure and reducing precision of quantitative measurements. Therefore transformation of typical Gaussian distribution of a TEM00 laser to flat-top (top hat) profile is an actual technical task, it is solved by applying beam shaping optics. Due to high demands to optical image quality the mentioned techniques have specific requirements to a uniform laser beam: flatness of phase front and extended depth of field, – from this point of view the microscopy techniques are similar to holography and interferometry. There are different refractive and diffractive beam shaping approaches used in laser industrial and scientific applications, but only few of them are capable to fulfil the optimum conditions for beam quality required in discussed microscopy techniques. We suggest applying refractive field mapping beam shapers Shaper, which operational principle presumes almost lossless transformation of Gaussian to flat-top beam with flatness of output wavefront, conserving of beam consistency, providing collimated low divergent output beam, high transmittance, extended depth of field, negligible wave aberration, and achromatic design provides capability to work with several lasers with different wavelengths simultaneously. The main function of a beam shaper is transformation of laser intensity profile, further beam transformation to provide optimum for a particular technique spot size and shape has to be realized by an imaging optical system which can include microscope objectives and tube lenses.
This paper will describe design basics of refractive beam shapers and optical layouts of their applying in microscopy systems. Examples of real implementations and experimental results will be presented as well.
Download the entire paper here:
Laser beam shaping for biomedical microscopy techniques SPIE PE April 2016___farbig.pdf
Confocal microscopes may use a high speed polygon scanner to achieve video 3D rate imaging.