A toroidal diffraction grating is a sort of concave gratings. The toroidal shape is defined by two curvature radii at each central axis. Toroidal shapes where *R _{h}* is a horizontal curvature radius and

*R*is a vertical curvature radius. The toroidal shapes are expressed in the following equation.

_{v}The paraxial focal positions of a toroidal grating in Fig.8 are defined by equations (17) and (18). Here *r* is the entrance length, *r' _{h}* is the horizontal focal length, and

*r'*is the vertical focal length.

_{v}*α*and

*β*satisfy the grating equation (2)'.

Fig.8 The different focus of the Spherical diffraction grating

The spherical diffraction gratings are formed on spherical blanks( *R _{h}*=

*R*) that has two focal lengths(

_{v}*r'*,

_{h}*r'*) has astigmatisms, The toroidal diffraction gratings are formed on toroidal (aspheric) blanks(

_{v}*R*≠

_{h}*R*) that can correct astigmatisms.

_{v}- SHIMADZU DIFFRACTION GRATINGS
- 01. Introduction to Diffraction Gratings
- 02. What are Diffraction Gratings
- 03. The Grating Equations
- 04. Dispersion
- 05. Grating Resolution
- 06. Free Spectral Range
- 07. Blaze Wavelength
- 08. Diffraction Efficiency & Relationship between Diffraction Efficiency and Polarization
- 09. Anomalies
- 10. Profile of Grating Grooves
**11. Toroidal Diffraction Gratings**- 12. Replicas
- 13. Coatings
- 14. Transmission Gratings
- 15. Choice of a Grating
- 16. Handling of Gratings