Research On Computer Aided Adjustment Technology Of Flat Field Concave Diffraction Grating

Since the wide application of spectro-analysis, the spectrum analyticalinstruments have always been the "guests" to laboratories and institutes though theyare usually bulky and expensive. With the development of technology, thespectro-analysis application is still expanding while the users have a growing demandfor portable, low-cost analytical instruments.The appearance of flat-field concave grating makes it possible for spectrumanalytical instruments to be small-sized and portable. The flat-field concave grating,with both dispersion and imaging functions, completely replaces the collimator lens,dispersion grating, imaging lens that belong to conventional spectrometers, so as togreatly simplify the optical path in the analytical instruments. However, the opticalpath structure based on the flat-field concave grating belongs to an off-axis opticalsystem, so its assembly and debugging can hardly be done by means of aprecision-machined rack as a coaxial optical system can. Additionally, with itsstructure more complex than most other optical devices, the alignment of the flat-fieldconcave grating will, when in a traditional alignment mode, be longer in cycle, higherin cost, lower in precision and consistency of the aligned instruments.By referring to some Chinese and foreign literature, this paper offers thecomputer-aided alignment for the flat-field concave grating, as follows:1. Research into traditional alignment methods in order to utilize their goodideas and avoid their problems.2. Research into the properties of the flat-field concave grating, mastering therelation expression between its assembly error and its optical aberration. Due to itsspecial structure, the mal-alignment of the flat-field concave grating will lead toco-existence of a variety of aberrations. I here propose an algorithm based on thepoint spread function and spatial autocorrelation for the treatment of such aberrationalco-existence.3. A full set of alignment solutions are offered here, including: an uppercomputer, a lower computer, a mechanical actuator and a kind of detecting light source. Therein, the upper computer is programmed with LabVIEW language forhuman-computer interaction and scientific computing; the lower computer, with aMega328p SCM as its core, works as the bridge between the upper computer and themechanical actuator; the actuator is in a parallel robot structure, which is high inprecision and easy in inverse solutions of computing locations; the detecting lightsource is a constant current source with gradient, which is designed for the specialcurrent requirements by three deep-ultraviolet LED.