Polychromator gratings have been optimized for assembling with fixed entrance split, grating and linear detector arrays. In contrast to conventional concave gratings, the focal area is not curved but is a flat plane. This is possible because of holographic manufacturing processes. Aberrations such as astigmatism, spherical aberration and coma can be minimized across a wide spectral area. Unlike Rowland circle gratings, these aberration-corrected gratings exhibit grooves with a variable spacing and variable curvatures. This holographic design allows optimum adaptation of a grating’s imaging properties to the specific requirements of the spectral unit in which the grating will be used .This ensures that gratings are obtained whose imaging properties effectively concentrate the available light energy on the detector over a wide spectral range. Holographically corrected gratings are ideal for imaging the spectrum on a diode array or a CCD sensor. lt is therefore possible to produce modern, compact high-resolution spectrometers and spectrometer modules at justifiable cost.