Abstract: According to some aspects, a low-field magnetic resonance imaging system is provided. The low-field magnetic resonance imaging (MRI) system comprises a magnetics system having a plurality of magnetics components configured to produce magnetic fields for performing MRI, the magnetics system comprising, a B0 magnet configured to produce a B0 field for the MRI system at a low-field strength of less than 0.

Abstract: According to some aspects, a low-field magnetic resonance imaging system is provided. The low-field magnetic resonance imaging system comprises a magnetics system having a plurality of magnetics components configured to produce magnetic fields for performing magnetic resonance imaging, the magnetics system comprising, a B0 magnet configured to produce a B0 field for the magnetic resonance imaging system at a low-field strength of less than 0.

Abstract: A modified diffraction grating having a predetermined amount of astigmatic power correction is substituted for the plane diffraction grating in an Ebert type spectrograph having a single concave collimating and focusing mirror for directing a light beam onto the surface of the modified diffraction grating. The surface of the modified diffraction grating is curved to introduce the proper amount of astigmatic power correction to converge the sagittal focus and the tangential focus of the diffracted beam to produce a stigmatic image. The modified diffraction grating may have a pure cylindrical surface or a toroidal surface. Another embodiment replaces the plane grating in a two mirror Czerny-Turner type of instrument with a modified grating according to this invention to reduce or eliminate astigmatism in that type of instrument as well.

Abstract: An improved method and apparatus for focused stigmatic imaging with spherical concave diffraction gratings incorporates a concave spherical diffraction grating with parallel, normally ruled lines. An entrance light beam source or projector propagates a beam of light to be analyzed through an entrance point and onto the surface of the diffraction grating. A light detector or analyzer is positioned at or near a detection point for detecting or characterizing the light diffracted from the grating. The entrance point and detection point are positioned in spaced-apart relation to each other and to the grating according to disclosed formulae, such that they are in respectively corresponding stigmatic or near stigmatic focus with each other.