Gratings with imaging properties for modern dispersive systems
Zeiss produces concave gratings holographically. The radii of curvature available are finely graded within a wide range. Relative apertures of as wide as 1:1 are obtainable. Concave gratings combine the dispersive properties of plane gratings with the imaging properties of concave mirrors. The spectrum is produced without auxiliary optical means. Aberrations, especially astigmatism, occur as in image formation with concave mirrors. Because of an aspheric surface production of its own, Zeiss is able to offer gratings also on toric, elliptic or other aspheric surfaces which show fewer aberrations than conventional concave gratings.
Aberrationcorrected concave gratings with considerably reduced aberrations Aberration-corrected concave gratings are recorded in an interferometer set-up adapted to the potential use of the grating. As with holograms, this ensures aberrationfree images at the operating wavelength required. Astigmatism is completely compensated for specific wavelengths and also considerably reduced over a wide wavelength range. This permits the use of high-aperture gratings with large diffraction angles, resulting in particularly effective dispersive systems.
Cost advantages due to simple spectrometer design
With corrected concave gratings it is in contrast to the classical Rowland gratings possible to vary the position of the focal curves in a wide range. From it novel simple versions of the optical design of dispersive systems can follow.
- Monochromator arrangements consisting only of a fixed entrance and exit slit and a grating rotating around its axis.
- Spectrometers of the polychromator type without movable parts, with a fixed grating and a flat diode array covering all wavelengths of interest.
- Spectrographs with a fixed entrance slit, fixed grating and e.g.a camera with considerably reduced astigmatic deformation of the spectral lines
- Even in classical arrangements, e.g. with entrance and exit slits on a Rowland circle, aberrationcorrected gratings can be used to best advantage.
Your benefit from these advantages
The aberration correction of holographic concave gratings guarantees high resolving power and small bandwidths even at high apertures.
Dispersive systems of high light- gathering power and compactness can be implemented using gratings with wide apertures. The light-gathering power is further increased by the high efficiency of the Zeiss holographic gratings
Straylight is considerably reduced by simple design using fewer scattering surfaces. Less astigmatism allows the use of smaller slit diameter with reduced transmission of straylight. Zeiss holographic gratings are virtually straylight-free
Cost advantages due to the elimination of collimating and other imaging components and the use of a simplified mechanical system including easy adjustment
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