Spectrograph with low focal ratio
First Claim
1. A spectrograph for analyzing lights of wavelengths of interest, comprising:
- (a) a first lens unit having at least one lens with at least one aspheric surface for collimating light from a light source, the first lens unit having a positive optical power and having a focal ratio of at most 1.7;
(b) a reflective diffraction grating for diffracting the collimated light from the first lens unit;
(c) a light detector; and
(d) a second lens unit having at least one lens with at least one aspheric surface for focusing the diffracted light on the light detector, the second lens unit having a focal length sufficient to provide an overall magnification of 0.8 to 2.0 on the light detector for said light source.
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Accused Products
Abstract
A spectrograph having a collimating lens unit, a reflective diffraction grating, a focusing lens unit, and a light detector is provided. The collimating lens unit has at least one optical element with at least one aspheric surface for collimating light from a light source. This lens unit has a positive optical power and a focal ratio of at most 1.7. The reflective diffraction grating diffracts the collimated light from the collimating lens unit. The focusing lens unit also has at least one lens with at least one aspheric surface. It focuses the first order diffracted light on the light detector and has a focal length that provides an overall magnification of 0.8 to 2.0 when combined with the collimating lens unit and the diffraction grating.
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Citations
19 Claims
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1. A spectrograph for analyzing lights of wavelengths of interest, comprising:
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(a) a first lens unit having at least one lens with at least one aspheric surface for collimating light from a light source, the first lens unit having a positive optical power and having a focal ratio of at most 1.7; (b) a reflective diffraction grating for diffracting the collimated light from the first lens unit; (c) a light detector; and (d) a second lens unit having at least one lens with at least one aspheric surface for focusing the diffracted light on the light detector, the second lens unit having a focal length sufficient to provide an overall magnification of 0.8 to 2.0 on the light detector for said light source. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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12. A spectrograph for analyzing a spectrum having a plurality of wavelengths of interest, comprising:
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(a) a first lens unit composed of a single lens with at least one ellipsoidal surface for collimating light from a light source, the first lens unit having a positive optical power and having a focal ratio of 1.0 to 1.7; (b) a planar, reflective diffraction grating for diffracting the collimated light from the first lens unit; (c) a light detector; and (d) a second lens unit composed of a single lens with at least one nonellipsoidal, nonparaboloidal, aspheric surface facing the diffracting grating for focusing the diffracted light on the light detector, the second lens unit having a focal length sufficient to provide an overall magnification of 0.8 to 2.0 on the light detector for light of the wavelengths of interest, wherein the diffraction grating is separated from the second lens unit by a distance sufficient for a beam of diffracted light of various wavelengths to spread in its narrow dimension to a size of 1.5 to 3 times the size of the light beam off the grating when impinging on the second lens unit.
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13. A method of analyzing light from a light source, comprising:
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(a) collimating light from the light source by a first lens unit having at least one optical element with at least one aspheric surface, the first lens unit having a positive optical power and having a focal ratio of at most 1.7; (b) diffracting the collimated light from the first lens unit with a diffraction grating; and (c) focusing onto a light detector the diffracted light from the diffraction grating with a second lens unit having at least one optical element with at least one aspheric surface, the second lens unit having a focal length that provides an overall magnification when combined with the first lens unit of 0.8 to 2.0 for said light source. - View Dependent Claims (14, 15, 16)
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17. A method of making a spectrograph for analyzing light from a light source, comprising:
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(a) mounting on a support a collimating lens unit having a focal ratio of 1.7 or less in a position relative to the light source such that light emitted from the light source is collimated to a generally parallel beam, said lens unit having at least one lens with at least one aspheric surface; (b) mounting on the support a planar diffraction grating in a position to diffract the collimated light beam such that the first order diffracted light forms an acute angle with the collimated beam; (c) mounting on the support a focusing lens unit in a position to focus the first order diffracted light, said focusing lens unit having at least one lens with at least one aspheric surface; and (d) mounting on the support a planar light detector such that the normal of the plane of the light detector forms an acute angle with the optical axis of the focusing lens to obtain distinct, compact images of the light source in different wavelengths on the light detector, the focusing lens unit having a focal length that provides an overall magnification on the detector of 0.8 to 2.0 for said light source. - View Dependent Claims (18, 19)
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Specification