US4991934A — Varied space diffraction grating and in-focus mon…

Claim 1

Independent Claim 259 words

A grating which comprises: a. a concave surface; b. a plurality of substantially parallel diffracting elements spaced from each other by unequal distances as projected upon a chord of said concave surface, according to a density function; c. an object point substantially fixed in space; d. an image point substantially fixed in space; e. a first path length equal to the distance which extends between said fixed object point and a first one of said diffracting element plus the distance which extends between said first diffracting element and said fixed image point; f. a second path length equal to the distance which extends between said fixed object point and a second one of said differacted element plus the distance which extends between said second diffracting element and said fixed image point; wherein the difference between said first and second path lengths plus a distance equal to a non-zero integer times a chosen wavelength times an integer equal to one plus the number of diffracting elements intervening said first and said second diffracting elements, defines a path-length error function, said grating characterized in that said concave surface, density function and said object and image points are chosen such that said path-length error function when written as a sum of powers of said chord distance between said first and said second diffracting elements lacks both second and third power terms at more than one distinct said chosen wavelength diffracted from said fixed object to said fixed image, said distinct wavelengths being determined by rotation of said grating about a fixed axis.

Claim 2

Dependent Claim 259 words

A grating which comprises: a. a concave surface; b. a plurality of substantially parallel diffracting elements spaced from each other by unequal distances as projected upon a chord of said concave surface, according to a density function; c. an object point substantially fixed in space; d. an image point substantially fixed in space; e. a first path length equal to the distance which extends between said fixed object point and a first one of said diffracting element plus the distance which extends between said first diffracting element and said fixed image point; f. a second path length equal to the distance which extends between said fixed object point and a second one of said differacted element plus the distance which extends between said second diffracting element and said fixed image point; wherein the difference between said first and second path lengths plus a distance equal to a non-zero integer times a chosen wavelength times an integer equal to one plus the number of diffracting elements intervening said first and said second diffracting elements, defines a path-length error function, said grating characterized in that said concave surface, density function and said object and image points are chosen such that said path-length error function when written as a sum of powers of said chord distance between said first and said second diffracting elements lacks both second and third power terms at more than one distinct said chosen wavelength diffracted from said fixed object to said fixed image, said distinct wavelengths being determined by rotation of said grating about a fixed axis.

Claim 3

Dependent Claim 20 words

The grating of claim 1, in which said fixed axis is substantially tangent to one of said parallel diffracting elements.

Claim 4

Dependent Claim 15 words

The grating of claim 1, in which said concave surface is substantially spherical and reflecting.

Claim 5

Dependent Claim 72 words

The grating of claim 3, in which said density function is written as 1/σ=1/σ.sub.o +N.sub.2 w+N.sub.3 w.sup.2 +N.sub.4 w.sup.3 + where σ o , N 2 , N 3 , N 4 , etc. are constant coefficients, where σ is the said chord spacing between neighboring said diffracting elements, and where w is the said chord distance from a reference said diffracting element where said chord is tangent to said spherical surface.

Claim 6

Dependent Claim 181 words

The grating of claim 4, in which N.sub.2 =-(T.sub.1 +T'.sub.1)/(mλ.sub.1) N.sub.3 =3/2[T.sub.1 (sin α.sub.1)/r-T.sub.1 '(sin β.sub.1)/r']/(mλ.sub.1) where T=(cos.sup.2 α)/r-(cos α)/R,T'=(cos.sup.2 β)/r'-(cos β)/R and ##EQU3## 1/r'=δ/r-ε/R where a=γ sin α.sub.1 cos.sup.2 α.sub.1 -sin α.sub.2 cos.sup.2 α.sub.2 -γδ.sup.2 sin β.sub.1 cos.sup.2 β.sub.1 +δ.sup.2 sin β.sub.2 cos.sup.2 β.sub.2 b=-γ sin α.sub.1 cos α.sub.1 +sin α.sub.2 cos α.sub.2 +2γδε sin β.sub.1 cos .sup.2 β.sub.1 -2δε sin β.sub.2 cos.sup.2 β.sub.2 γδ sin β.sub.1 cos β.sub.1 -δ sin β.sub.2 cos β.sub.2 c=-γε.sup.2 sin β.sub.1 cos.sup.2 β.sub.1 +ε.sup.2 sin β.sub.2 cos.sup.2 β.sub.2 γε sin β.sub.1 cos β.sub.1 +ε sin β.sub.2 cos β.sub.2 δ=(γ cos.sup.2 α.sub.1 -cos.sup.2 α.sub.2)/(cos.sup.2 β.sub.2 -γ cos.sup.2 β.sub.1) ε=[γ(cos α.sub.1 +cos β.sub.1)-(cos α.sub.2 +cos β.sub.2)]/(cos.sup.2 β.sub.2 -γ cos.sup.2 β.sub.1) γ=λ.sub. /λ.sub.1 where subscripts 1 and 2 refer to the quantity as determined using α and β given by α=θ-arc sin [mλ/(2σ.sub.o cos θ)],β=2θ-α λ 1 and λ 2 being two said distinct wavelengths of choice, m being the spectral order, θ being an angle of choice, σ o being a spacing of choice, and where R is the radius of curvature of said spherical surface.

Claim 7

Dependent Claim 15 words

The grating of claim 1, in which said concave surface is a spherical and reflecting.

Claim 8

Dependent Claim 29 words

The grating of claim 1, in which the angle subtended by lines drawn from any said diffracting element to said fixed object and to said fixed image, exceeds 140°.

Claim 9

Dependent Claim 18 words

The grating of claim 1, in which said distinct wavelengths are electromagnetic wavelengths within the range 3-2500 Å.

Claim 10

Dependent Claim 68 words

An optical system comprising: a. a granting which comprises a surface having substantially parallel diffracting elements spaced from one another by unequal distances as measured along a straight line tangent to the grating surface at a point; b. means for rotating said grating about an axis substantially fixed in space; c. means for translating said grating in a direction substantially parallel to a tangent plane of said surface.

Claim 11

Dependent Claim 68 words

An optical system comprising: a. a granting which comprises a surface having substantially parallel diffracting elements spaced from one another by unequal distances as measured along a straight line tangent to the grating surface at a point; b. means for rotating said grating about an axis substantially fixed in space; c. means for translating said grating in a direction substantially parallel to a tangent plane of said surface.

Claim 12

Dependent Claim 12 words

The optical system of claim 9, in which said surface is concave.

Claim 13

Dependent Claim 16 words

The optical system of claim 10, in which said concave surface is substantially spherical and reflecting.

Claim 14

Dependent Claim 16 words

The optical system of claim 10, in which said concave surface is a spherical and reflecting.

Claim 15

Dependent Claim 13 words

The optical system of claim 9, in which said surface is substantially planar.

Claim 16

Dependent Claim 14 words

The optical system of claim 13, used in combination with an incident plane wave.

Claim 17

Dependent Claim 20 words

The optical system of claim 13, used in combination with a virtual object, providing a converging wave to said grating.

Claim 18

Dependent Claim 18 words

The optical system of claim 9, in which said rotation axis is substantially parallel to said diffracting elements.

Claim 19

Dependent Claim 19 words

The optical system of claim 9, in which said rotation axis lies substantially on said surface of said grating.

Claim 20

Dependent Claim 73 words

The optical system of claim 9, employed in combination with a source of radiation and a target means receiving said radiation, said grating located between said source and said target means, additionally comprising at least one optical element disposed in the path of light which travels between said source and said target means, said optical element arranged to cause said source radiation to focus in a plane substantially parallel to said diffracting elements.

Claim 21

Dependent Claim 35 words

The optical system of claim 18, in which said optical element comprises a concave reflecting surface having a normal which lies substantially within a plane which is parallel to a tangent of said grating surface.

Claim 22

Dependent Claim 15 words

The optical system of claim 19, in which said concave reflecting surface is a cylinder.

Claim 23

Dependent Claim 33 words

The optical system of claim 19, in which said concave reflecting surface is a sphere, which additionally causes said radiation to focus in the plane which is substantially perpendicular to said diffracting elements.

Claim 24

Dependent Claim 35 words

The optical system of claim 18, in which said optical element comprises a concave reflecting surface having a normal which lies substantially within the same plane as a normal to the surface of said grating.

Claim 25

Dependent Claim 15 words

The optical system of claim 22, in which said concave reflecting surface is a cylinder.

Claim 26

Dependent Claim 31 words

The optical system of claim 22, in which said concave reflecting surface is a sphere, which additionally focuses said radiation in the plane which is substantially perpendicular to said diffracting elements.

Claim 27

Dependent Claim 41 words

The optical system of claim 9, additionally comprising at least one narrow opening, or slit, located at a position substantially fixed in space, whereby said slit limits the passage of all but a narrow band of wavelengths diffracted by said grating.

Claim 28

Dependent Claim 19 words

The optical system of claim 9 used in combination with electromagnetic radiation having wavelengths in the range 3-2500 Å.

Claim 29

Dependent Claim 24 words

The optical system of claim 9, in which said means for rotating said grating and said means for translating said grating are mechanically coupled.

Claim 30

Dependent Claim 17 words

The optical system of claim 9, in which said means for rotating said grating comprise a cam.

Claim 31

Dependent Claim 17 words

The optical system of claim 9, in which said means for translating said grating comprise a cam.

Claim 32

Dependent Claim 21 words

The optical system of claim 9, wherein said means for rotating said grating comprise a bar which translates with said grating.

Claim 33

Dependent Claim 44 words

The optical system of claim 30, further including a body which translates in a linear direction, said body having a substantially planar surface which is in contact with said bar, said planar surface being inclined at a finite angle relative to said linear direction.

Claim 34

Dependent Claim 58 words

The optical system of claim 9, employed in combination with a source of radiation, additionally comprising an entrance slit and at least one optical element disposed in the path of light which travels between said source and said grating, said optical element arranged to cause said radiation to be efficiently directed to and transmitted through said entrance slit.

Claim 35

Independent Claim 79 words

A method for aligning varied-space gratings in spectrometers and monochromators comprising the steps of: a. employing a grating having a surface which is not rotationally symmetric about any line, and which comprises a plurality of substantially parallel diffracting elements spaced from each other by unequal distances as measured along a straight line tangent to said grating surface at a point; and b. translating said grating substantially along said surface and in a direction substantially perpendicular to said diffracting elements.

Claim 36

Independent Claim 79 words

A method for aligning varied-space gratings in spectrometers and monochromators comprising the steps of: a. employing a grating having a surface which is not rotationally symmetric about any line, and which comprises a plurality of substantially parallel diffracting elements spaced from each other by unequal distances as measured along a straight line tangent to said grating surface at a point; and b. translating said grating substantially along said surface and in a direction substantially perpendicular to said diffracting elements.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1994-02-11	1994-08-13	1995-02-12	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1998-02-11	1998-08-13	1999-02-12	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2002-02-11	2002-08-13	2003-02-12	$7700.00	Window Closed / Lapsed

Varied space diffraction grating and in-focus monochromator

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