[Detection System for High-Resolution and Broadband-2D Spectrogram].

In order to meet the demand of detecting the high-resolution and broadband-2D spectrogram for echelle-prism cross-dispersion, the design method is given, and the 2D spectrogram detection system with high-resolution and low noise is designed by analyzing the relation between the detector and the optical system and proving designing method of detecting the area spectrogram. The system includes a main control unit, a detector driving unit, a signal processing unit, a data storage unit and a data transmission unit, etc. With Hamamatsu's S10141-1109S CCD as the detector, the detection system features high sensitivity, broadband spectrogram, high signal to noise ratio. Combined with the echelle-prism cross-dispersion optical path to perform experiments, the results show that, the detection system can acquire high-resolution 2D spectrogram image in the range of 200 to 600 nm, the monochromatic image at 253.652 nm of Hg lamp covers 5 pixels, and the resolvable wavelength reaches 6.3 pm.

[Optical path difference in off-plane quasi-Littrow dispersion mountings].

The present paper analyzes the relative relation between the meridian and sagittal rays in off-plane quasi-Littrow (OP-QL) dispersion mountings. It's concluded that the off-plane angle will cause the rotation of the beam and result in the mismatch between the sagittal beams on different optical elements. Therefore the total optical path difference (OPD) should be an accumulation of corresponding beams instead of the sagittal beam of each element itself. Then, a directional derivative based method is put forward to calculate the OPD for spherical mirrors in various directions. Based on the method, the numerical OPD for OP-QL mountings is solved. Finally, this methodology is validated with both echelette and echelle examples.

[Coma and resolution in wide spectral region Czerny-Turner spectrometer].

The Czerny-Turner layout, which is most frequently used in miniature spectrometers, should follow Shafer's coma-free condition and Fastie's flat-field principal to eliminate the central wave's primary coma and maximize its resolution. However, the design process does not take the comas and resolutions at non-central waves into consideration. Based on the theory of primary coma in reflection optical system, the present paper points out that in the crossed beam design, the resolutions at wide 'spectral region present a "V" shape, while in the M design, the resolutions change little over the whole region, and present an approximately straight line shape, so the latter kind of spectrometer maintains a far more consistent resolution than the former one. Accordingly, this paper designs two kinds of spectrometers with spectrum regions from 400 to 600 nm, and carries out theoretical simulation and contrast experiment. The result demonstrates that for the two designs the resolutions at the fringe wavelength are 3.8 times and 1.5 times respectively that at the central wavelength, which accords with the conclusion of the theoretical simulation.

[Comparison of dispersion parts of conventional spectrometers].

Innovation of conventional spectrometers is of actual technical and economical value. It is also an important way to accelerate the development of spectroscopic instruments. When improving a conventional spectrometer, its dispersion part is pivotal, because it is decisive to the basic performance of the spectrometer. In the present paper, the typical dispersion parts of conventional spectrometers are compared to feature them and find the evolution force among them. The basic characters of the dispersion parts, including spectral range, dispersion power, resolution and throughput, are compared separately and comprehensively by reviewing their decisive factor, formula and typical data. The results not only conclude the feature and the complementariness of the dispersion parts, but also indicate that the trade-off between resolution and throughput is ubiquitous in traditional spectrometers. Further reviewing from this point, the evolution history of traditional spectrometers shows that the conflict between resolution and throughput is an important evolution force. This is a new way to understand the evolution of traditional spectrometers. Moreover, dealing with the trade-off between resolution and throughput correctly will help to analyze and settle the core problem of spectrometers.

[Global modeling and analyzing of grating spectrometers].

A method for globally modeling and analyzing grating spectrometers is put forward in the present paper. Different from existing methods which are confined to parts of a spectrometer, the method takes a grating spectrometer as four functional parts, namely imaging optics, detector, reconstruction and display. Effects of each part on spectrum are considered and a global model of the spectrometer is developed, accompanied with its transfer function. With the help of the model and the transfer function, laws of each part affecting the holistic performance are summed up. It is suggested that high quality spectrogram needs enhancing baseband response and reducing spurious response, and reconstruction is an effective way.

[Algorithm for restoring spectrogram with sub-pixel resolution].

Insufficient spatial resolution of detectors is an obstacle to capturing spectra with high resolution. An effective solution is sub-pixel restoration, which can restore a high resolution spectrogram from sub-pixel shifted low resolution ones. In the present paper, an algorithm for sub-pixel restoration is suggested. It utilizes the bidirectional recursive relation between sub-pixel values and estimates each sub-pixel value from both directions of head-end and end-head. As a result, the averaged value will be accepted as the sub-pixel value. Numerical experiments on single gauss profile and superposition ones verified the effectiveness of the algorithm.

[Blind deconvolution algorithm for spectrogram super-resolution restoration].

Deconvolution is an important way to realize spectrogram super-resolution restoration. Blind deconvolution is superior to the traditional one in that it does not need a well prepared convolution core. Taking advantages of the features of spectrogram and the existing achievements of spectrogram deconvolution, the authors bring forward a scheme to adapt the space domain iterative blind deconvolution method to spectroscopy application. Moreover, after probing into the spectrogram degradation described by convolution, computational models for spectrum convolution and Gauss fitting are worked out to meet the requirements of blind deconvolution algorithm. Accompanying results are simulations with MATLAB7.0. They shows that for the given spectrum and point spread function of Gauss type the blind deconvolution algorithm works well and a resolution enhancement of 30% can be achieved under a signal-to-noise ratio of 50 dB.

[The effect of the photoelectric detector on the accuracy of the spectrometer].

An optimized photoelectric detector will increase the precision of a spectrometer, thus indicates an important way to develop high performance spectrometer. With an eye to this, a model describing the process that spectrogram is integrated and sampled by photoelectric detector and restored after low-pass filtering is developed. Based on the model, the influence of the characteristic parameters of the detector on the spectral line in the frequency domain is analyzed and the relation between the full width half maximum (FWHM) of the spectra line and the integral interval, sampling space and sensitivity of the detector is deduced. The conclusion indicates that both the integral interval and sampling space should be 1/6 of the FWHM for a spectral line with gaussian profile as a result of compromise between accuracy and feasibility. Moreover, the critical point deciding the right situation for scanner and array detector is given. Other guide line to optimize the photoelectric detector and increase accuracy is suggested also.