Start of scan circuit for FTIR spectrometer
First Claim
1. A start of scan circuit for an FTIR spectrometer which includes an interferometer with a moving mirror, a positioning laser also directed into the interferometer, and a laser detector for detecting in-phase pulses of laser light exiting from the interferometer and generating a digital output signal, the start of scan circuit connected through a servo circuit to control motion of the moving mirror, the start of scan circuit comprising:
- a mode counter having a series of output lines which are clocked through a series of states, each state corresponding to a state of motion of the moving mirror, the mode counter output lines connected to the servo circuit to control the moving mirror motion;
a position counter circuit controllable selectively (i) to load a preselected numerical value into a position counter and (ii) to increment or decrement the numerical value therein;
physical position sensor means for detecting a position of the mirror; and
gating means for connecting the output lines of the mode counter selectively (i) to gate the digital output signal of the laser detector to the position counter to increment or decrement the numerical value therein and (ii) to actuate the position counter to load said preselected numerical value, the gating means also for connecting the output of the position counter to the input of the mode counter, the gating means is also connected so that the position counter sequentially;
(1) is loaded with a value when the physical position sensor means detects the position, the value representing a distance the mirror is moved beyond the physical position sensor means;
(2) counts until the mirror moves the distance;
(3) counts a distance the mirror retreats as it is stopped;
(4) counts back the distance the mirror retreated as it stopped;
(5) is loaded with a value representing a distance until the start of scan; and
(6) counts until the distance is reached.
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Accused Products
Abstract
A start of scan circuit for an FTIR spectrometer includes a mode counter, counting through various states of operation of the moving mirror in the FTIR interferometer, and a positioning counter circuit which counts laser pulses from a positioning laser also directed through the interferometer. By appropriately loading and counting up or down the counter in various states, as determined by the mode counter, the circuit can flexibly control the start of scan of the FTIR so that that start of scan can be selectively varied by switches and/or under software control.
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Citations
12 Claims
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1. A start of scan circuit for an FTIR spectrometer which includes an interferometer with a moving mirror, a positioning laser also directed into the interferometer, and a laser detector for detecting in-phase pulses of laser light exiting from the interferometer and generating a digital output signal, the start of scan circuit connected through a servo circuit to control motion of the moving mirror, the start of scan circuit comprising:
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a mode counter having a series of output lines which are clocked through a series of states, each state corresponding to a state of motion of the moving mirror, the mode counter output lines connected to the servo circuit to control the moving mirror motion; a position counter circuit controllable selectively (i) to load a preselected numerical value into a position counter and (ii) to increment or decrement the numerical value therein; physical position sensor means for detecting a position of the mirror; and gating means for connecting the output lines of the mode counter selectively (i) to gate the digital output signal of the laser detector to the position counter to increment or decrement the numerical value therein and (ii) to actuate the position counter to load said preselected numerical value, the gating means also for connecting the output of the position counter to the input of the mode counter, the gating means is also connected so that the position counter sequentially;
(1) is loaded with a value when the physical position sensor means detects the position, the value representing a distance the mirror is moved beyond the physical position sensor means;
(2) counts until the mirror moves the distance;
(3) counts a distance the mirror retreats as it is stopped;
(4) counts back the distance the mirror retreated as it stopped;
(5) is loaded with a value representing a distance until the start of scan; and
(6) counts until the distance is reached. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A Fourier-transform infrared spectrometer comprising:
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a Michelson interferometer having a moving mirror; a fixed position sensor responsive to a single position of the moving mirror; a positioning laser directed into the interferometer; a laser detector to detect in-phase laser light pulses exiting from the interferometer to thus indicate motion of the moving mirror; a servo circuit controlling the motion of the moving mirror; a position counter circuit selectively gated to count pulses from the laser detector to be thus counted up and down as the mirror moves; a mode counter means having a series of output lines connected to the servo circuit for controlling the mirror movement the mode counter means connected to the position counter circuit to control the gating of the laser pulses thereto depending on its state and also connected to the output of the fixed position sensor, the mode counter means operating sequentially in the following modes;
(1) a mode one, initiated by detection of the position of the moving mirror by the fixed position sensor as the mirror retreats, in which the position counter circuit is pulsed by output of the laser detector to count down a value loaded in the position counter circuit while the mirror retreats under power;
(2) a mode two, initiated by the end of the count of mode one, in which the power to the moving mirror is removed by the servo circuit, and during which the position counter circuit counts up pulses from the laser detector;
(3) a mode three, initiated by the physical stopping of the moving mirror, in which the mirror is driven forward and during which the value in the position counter circuit is counted down by pulses from the laser detector;
(4) a mode four, initiated by the end of the count of mode three, during which a numerical value is loaded in the position counter circuit and counted down by pulses from the laser detector to provide a selectable delay before spectrometry data is taken, and (5) a mode five, initiated by the end of the count of mode four, during which the spectrometry data is taken. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification