Optical arrangement having a concave mirror or concave grating

DETAILED DESCRIPTION It is an object of the invention to provide the simplest possible correction of astigmatism in concave mirrors and concave gratings, or in the case of holographically produced concave gratings to obtain a greater degree of freedom in terms of correction possibilities.
To form an image of a relatively small or slit-like surface, this object is attained in accordance with the invention by mounting a slab waveguide at the surface at which an image is formed, or is to be formed.
To correct further image aberrations, such as sagittal coma, it may be advantageous for the reflecting surfaces of the slab waveguide to be curved.
It is particularly advantageous to embody the reflecting surfaces as concentric spherical surfaces.
Especially in the case of wavelength multiplexers, it is advantageous to dispose the reflecting surfaces wedgewise with respect to one another, in order to compensate for wavelength tolerances in the radiation sources.
One advantageous embodiment of the invention is characterized by an illumination device having a concave mirror and a source of illumination.
With such a device, the slab waveguide makes it possible to carry a greater radiant flux from the source of illumination, for instance, into a light-conducting fiber.
Spectrometers having concave gratings are examples of other advantageous embodiments; because of the slab waveguide, considerable economy in terms of energy is attained.
Other advantageous embodiments include wavelength multiplexers and demultiplexers having a concave grating, in which the radiation is introduced and conducted away, for instance, by light-conducting fibers.
In advantageous embodiments, the concave grating is made up in a known manner of at least two zones, which are ruled using differently shaped diamond styluses.
In this way, good energy conditions are attainable over a wide wavelength range.
Combining the device with a second one having a concave mirror or concave grating is particularly advantageous; then the same slab waveguide is used for both devices