Optical EngineeringImaging theory of plane-symmetric varied line-space grating systems
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We review the focusing properties of a general planesymmetric dispersive system containing a varied line-space (VLS) grating as its dispersive element. A VLS grating is one whose grooves are straight and parallel (when viewed looking down the grating normal) but unequally spaced. Aberration terms for VLS gratings are related to those for holographically produced gratings. The groove pattern is represented by a groove function, which, although less intuitive than the groove spacing, contains information that clearly corresponds to the imaging properties of the grating. The projection of the groove pattern onto the plane tangent to the grating at its center is shown to be useful in describing the focusing properties of the grating; consequently the imaging effects of the curvature of the grating blank itself can be considered separately.