Off axis rotation of diffraction grating
AssigneeLinear Instruments
InventorsRaymond G. Bryan, Louis Hlousek
Life of this patent
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Abstract
In a spectrophotometer application where high speed positioning is critical, a galvanometer in conjunction with a microprocessor controlled hybrid digital/analog servo system is used to rotate a diffraction grating for wavelength selection. A table containing digital position information for all wavelengths is accessed by the microprocessor to perform wavelength changes. The use of the table permits the determination of grating position to yield a desired wavelength for a system where the axis of rotation does not intersect a point on the surface of the diffraction grating. That is, the diffraction grating can be rotated about an axis coinciding with its center of gravity.
Claims10
An optical system comprising:
- a substrate;
- a diffraction grating formed on a surface of the substrate;
- means for rotating the substrate on an axis of rotation which intersects the substrate at a point other than at the surface on which is formed the diffraction grating.
An optical system comprising:
- a diffraction grating for propagation of incident light at an angle relative to an optical plane;
- and
- means for rotating the diffraction grating on an axis of rotation which intersects the diffraction grating an a point other than at the optical plane.
A method for providing light of a desired wavelength propagated from a diffraction grating formed on a surface of a substrate, the substrate having an axis of rotation passing through the substrate at a point not intersecting the surface, comprising the steps of:
- determining an angle of rotation of the substrate on the axis of rotation which corresponds to the desired wavelength;
- and
- rotating the substrate to the angle of rotation determined in the previous step.
An optical system comprising:
- a substrate;
- an optical element formed on a surface of the substrate;
- and
- means for rotating the substrate on an axis of rotation which intersects the substrate at a point other than at the surface on which is formed the optical element,
- wherein the means for rotating comprises:
- drive means connected to the substrate for rotating the substrate to a predetermined angle on the axis of rotation;
- control means for determining the desired wavelength of light to be propagated by the optical element upon the optical element being struck by incident light;
- and
- wherein the calculating means for calculating the predetermined angle, wherein the calculating means solves a trigonometric equation, one of the known quantities of such equation being the distance between the axis of rotation and the optical surface.
An optical system comprising:
- a substrate;
- an optical element formed on a surface of the substrate;
- and
- means for rotating the substrate on an axis of rotation which intersects the substrate at a point other other than at the surface on which is formed the optical element,
- wherein the means for rotating comprises:
- drive means connected to the substrate for rotating the substrate to a predetermined angle on the axis of rotation;
- control means for determining the desired wavelength of light to be propagated by the optical element upon the optical element being struck by incident light;
- and
- means for providing the predetermined angle as a function of the desired wavelength from a lookup table.
Dependencies are inferred from the claim text.