| Popis: |
The Fourier transform optical systems, creating an image and/or realizing its accurate spectral characterization, suffer from appearing remarkable level of side-lobes in the image intensity distribution that reduce performances, in particular, the dynamic range of these systems. Therefore, suppressing side-lobes in the image plane represents an actual practical task being important for various scientific and technical applications such as, for example, direct imaging and spectral characterization of Earth-like extra-solar planets or spectrum analysis of ultra-high frequency radio-wave signals with exploiting an advanced acousto-optical technique. We suggest applying as apodization systems novel refractive optical beam shapers of the field mapping type, which are able to convert the input (more or less) uniform intensity distribution, peculiar to the majority of usually exploited sources of light, to arbitrary pre-scripted intensity distributions. In the case of choosing, for instance, Gaussian, cosine on a pedestal, etc. distributions, these shapers make it possible to minimize the total level of side-lobes significantly and to increase, in doing so, the dynamic range of optical data processing up to 40 dB or more. The operation principle of these beam shapers is based on inducing, in a control manner, spherical aberration in order to provide the required intensity profile transformation and further compensation of that aberration. As a result, the beam shapers operate as telescopes of special type; they produce a low divergence collimated beam with a target intensity distribution and flat wave front. We describe the beam shaper design, implementation examples, and results of practical applications to the acousto-optical technique of precise multi-channel spectrum analysis. |
