A method on improvement of wavelength resolution of grating spectrometers

A novel concept on the optical structure of the grating spectrometer is introduced to improve the wavelength resolution. Having entering the spectrometer from the entrance, the light is transformed into the parallel beam by a lens and a concave mirror in order to compress the size on the image plane of spectrometer, which efficiently reduces the full width at half maximum of the spectral lines. Having been dispersed by the grating, the beam is converged on the image plane by a concave mirror and a lens with a spectrum range smaller than that only by a concave mirror. By using a spectrometer home-developed and a Charge Coupled Device camera, the lines of 588.9951nm and 589.5924nm from a hollow cathode lamp with sodium element are recorded with three types of optical structure, respectively, and a Charge Coupled Device camera. The experimental results are well in agreement with theoretic results.