System for calibrating a monochromator
First Claim
1. A method for calibrating a monochromator, to compensate for mechanical imperfections is its defraction grating and grating drive assembly which cause positioning error in spectral emission lines, comprising the steps of:
- (a) measuring the positioning error of a first pre-selected set of emission lines to establish a coarse correction to the positioning error attributable to said imperfections; and
(b) obtaining a polynomial fit to determine a set of multiple positioning correction terms for an expanded preselected set of emission line utilizing an iterative self-consistent Fourier transform.
3 Assignments
0 Petitions
Accused Products
Abstract
A method for calibrating a monochromator to compensate for mechanical imperfections in its diffraction grating and grating drive assembly employs a two stage interactive procedure which permits the use of small (0.2 nm) spectral regions for the identification of emission lines. An iterative, self-consistent, discrete Fourier transform is used for the determination of multiple positioning correction terms. When the Fourier calculations are completed, the results of the calibration procedure are presented by the system to the analyst for acceptance. If accepted, the positioning error of the primary calibration line is measured, stored and used by the system to maintain a zero centered distribution of positioning errors each time the monochromator is reinitialized.
25 Citations
52 Claims
-
1. A method for calibrating a monochromator, to compensate for mechanical imperfections is its defraction grating and grating drive assembly which cause positioning error in spectral emission lines, comprising the steps of:
-
(a) measuring the positioning error of a first pre-selected set of emission lines to establish a coarse correction to the positioning error attributable to said imperfections; and (b) obtaining a polynomial fit to determine a set of multiple positioning correction terms for an expanded preselected set of emission line utilizing an iterative self-consistent Fourier transform. - View Dependent Claims (2, 3, 4, 5)
-
-
6. In a monochromator having a grating and grating drive assembly, a method for compensating for mechanical imperfections in the diffraction grating and drive assembly causing positioning errors having an aperiodic component comprising the steps of:
-
(a) generating a light beam; (b) introducing the light beam into said monochromator; (c) directing the light beam to strike said diffraction grating to create a spectrum; (d) positioning said diffraction grating to locate a first set of preselected spectral lines in said spectrum by rotating said drive assembly a discrete number of steps and using a first preselected spectral window to isolate each line in said first set; (e) measuring the positioning error, Δ
steps, for each isolated spectral line in said first set; and(f) fitting a polynomial, P(steps), to said measured positioning errors plotted against the wavelength of said isolated lines from said first set to thereby obtain a coarse correction for said mechanical imperfections. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
-
-
19. A method for compensating for mechanical imperfections in the diffraction grating and grating drive assembly of a monochromator, comprising the steps of:
-
(a) generating a light beam; (b) introducing the light beam into said monochromator; (c) directing the light beam to strike said diffraction grating to create a spectrum; (d) positioning said diffraction grating to locate a first set of preselected spectral lines in said spectrum by rotating said drive assembly a discrete number of steps and using a first preselected spectral window to isolate each line in said first set; (e) measuring the positioning error, Δ
steps, for each isolated spectral line in said first set;(f) fitting a polynomial, P(steps), to said measured positioning errors plotted against the wavelengths of said isolated lines from said first set to thereby obtain a coarse correction for said mechanical imperfections; (g) utilizing said coarse correction to position said diffraction grating to locate a second set of preselected spectral lines in said spectrum wherein a second preselected spectral window, smaller then said first window, is used to isolate each line in said second set; (h) measuring the positioning errors for each line located in said second set by subtracting the first corrected step value for a given line in said second set from the actual number of steps required to locate said line, where each first corrected step value is calculated by adding the theoretical step value for a given line to the value of P(steps) for said line; (i) fitting a polynomial, P'"'"'(steps), to the measured positioning error versus wavelength, for each isolated line in said second set; (j) adding the coefficients of P(steps) and P'"'"'(steps) algebraically to obtain the coefficients of a polynomial, P2 (steps), which is an improved estimate of the aperiodic component of the positioning error; and (k) constructing a set of residual errors, R0, by subtracting P'"'"'(steps) from the measured positioning error for each line in said second set. - View Dependent Claims (20, 21, 22, 23, 24, 25)
-
-
26. A system, including computer means and program, for calibrating a monochromator having a grating and grating drive assembly to compensate for mechanical imperfections in the monochromator diffraction grating and grating drive assembly, comprising:
-
(a) means for measuring the positioning error of a first preselected set of emission lines to establish a coarse correction to the positioning error attributable to said imperfections; and (b) means for obtaining a polynomial fit to determine a set of multiple positioning correction terms for an expanded preselected set of emission lines utilizing an iterative self-consistent Fourier transform. - View Dependent Claims (27, 28, 29, 30, 31, 32)
-
-
33. A system, including a monochromator having a grating, grating drive assembly, and computer means and program, for compensating for mechanical imperfections in the diffraction grating and grating assembly comprising:
-
(a) means for generating a light beam; (b) means for introducing the light beam into said monochromator; (c) means for directing the light beam to strike said diffraction grating to create a spectrum; and (d) means operating under the control of said computer means and program for positioning said diffraction grating to locate a first set of preselected spectral lines in said spectrum by rotating said drive assembly a discrete number of steps, utilizing a first preselected spectral window to isolate each line in said first set. - View Dependent Claims (34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52)
-
Specification