Method and apparatus for determining mirror position in a fourier-transform infrared spectrometer

Claim 2

Apparatus for use in determining the position of the moving mirror in a Fourier-transform infrared spectrometer of the type which includes an interferometer with a moving mirror, a laser which directs its beam into the interferometer, a laser detector for detecting the intensity of the laser light exiting from the interferometer, and a microcomputer system adapted to utilize information on the postion of the moving mirror to control the motion of the moving mirror and to correlate the position of the moving mirror with the signal obtained from an infrared detector in the spectrometer, comprising: (a) incremental counter means, connected to the laser detector and to the microcomputer, for counting pulses from the laser detector up or down in response to an up or down control signal and having a maximum bit capacity, with the count kept by the counter means returning to zero when the maximum bit capacity of the counter means is exceeded or returning to the maximum bit capacity number when the count in the counter means is decremented below zero, the output of the counter means being connected to the microcomputer system for access by the microcomputer system; and (b) means connected to the laser light detector for discriminating the direction of motion of the moving mirror in the FTIR spectrometer and providing an up control signal to the incremental counter means when the moving mirror is moving in one direction and a down control signal to the incremental counter means when the moving mirror is moving in the other direction.

Claim 3

The apparatus of claim 1 including latch means, connected between the incremental counter means and the microcomputer system, for responding to a control signal to load and hold the output count from the incremental counter means in response to the control signal, and timing control means connected to the latch means for providing an enable control signal to the latch means to cause the latch means to load new data from the incremental counter means in a time period which is less than the time required for the incremental counter means to advance one-half of its maximum number of counts.

Claim 4

The apparatus of claim 2 wherein the means for discriminating the direction of the moving mirror is connected to the microcomputer system, wherein the incremental counter means is capable of counting in only one direction, and wherein the incremental counter means is cleared upon a change in direction of the moving mirror and the timing control means provides an additional control signal when the moving mirror changes direction.

Claim 5

The apparatus of claim 1 including latch means, connected between the incremental counter means and the microcomputer system, for responding to a control signal to load and hold the output count from the incremental counter means in response to the control signal, and control means connected to the latch means for providing an enable control signal to the latch means to cause the latch means to load new data from the incremental counter means when maximum bit capacity of the counter means is exceeded or when the count in the counter means is decremented below zero.

Claim 6

The apparatus of claim 1 wherein the incremental counter means includes a plurality of up/down counters connected in a cascaded configuration with the lowest significant bit input of each counter except the least significant bit counter connected to receive the overflow bit from the next least significant bit counter.

Claim 7

The apparatus of claim 1 wherein the laser detector includes two separate detectors arranged such that the detectors provide output pulse signals which are out of phase with each other and with the output of one detector leading the output of the other detector when the moving mirror is moving in one direction and trailing when the moving mirror is moving in the opposite direction, the means for discriminating the direction of motion connected to the two detectors to determine which detector is providing a pulse signal which is leading the other detector and providing a high output signal if a first of the detectors is leading and a low output signal if the second of the detectors is leading.

Claim 8

The apparatus of claim 1 wherein the microcomputer has a random access memory and maintains an absolute position count in its memory of the sum of the existing content of its memory with the new incremental count, either positive or negative, obtained from the incremental counter means.

Claim 9

The apparatus of claim 7 wherein the absolute position count is updated when the incremental counter means is accessed by the microcomputer.

Claim 10

An infrared spectrometer comprising: (a) a Michelson interferometer with a moving mirror; (b) a positioning laser having a light beam directed into the interferometer; (c) a laser detector for detecting the intensity of laser light exiting from the interferometer; (d) an infrared detector for detecting the intensity of infrared exiting from the spectrometer; (e) a microcomputer system having an absolute positive register in its memory for storing the position of the moving mirror and adapted to utilize information on the position of the moving mirror to control the motion of the moving mirror and to correlate the position of the moving mirror with the signal obtained from the infrared detector in the spectrometer; (f) incremental counter means connected to the laser detector and to the microcomputer for counting pulses from the laser detector and having a maximum bit capacity, the output of the counter means being connected to the microcomputer system for access by the microcomputer system; (g) means, connected to the laser light detector for discriminating the direction of motion of the moving mirror in the FTIR spectrometer and providing an up control signal when the moving mirror is moving in one direction and a down control signal when the moving mirror is moving in the other direction; and (h) means, receiving the up and down control signals from the means for discriminating the direction of motion, for coordinating the count of the incremental counter means with the up and down control signals to properly increment or decrement the absolute position count maintained in the absolute position register of the microcomputer system.

Claim 11

An infrared spectrometer comprising: (a) a Michelson interferometer with a moving mirror; (b) a positioning laser having a light beam directed into the interferometer; (c) a laser detector for detecting the intensity of laser light exiting from the interferometer; (d) an infrared detector for detecting the intensity of infrared exiting from the spectrometer; (e) a microcomputer system having an absolute positive register in its memory for storing the position of the moving mirror and adapted to utilize information on the position of the moving mirror to control the motion of the moving mirror and to correlate the position of the moving mirror with the signal obtained from the infrared detector in the spectrometer; (f) incremental counter means connected to the laser detector and to the microcomputer for counting pulses from the laser detector and having a maximum bit capacity, the output of the counter means being connected to the microcomputer system for access by the microcomputer system; (g) means, connected to the laser light detector for discriminating the direction of motion of the moving mirror in the FTIR spectrometer and providing an up control signal when the moving mirror is moving in one direction and a down control signal when the moving mirror is moving in the other direction; and (h) means, receiving the up and down control signals from the means for discriminating the direction of motion, for coordinating the count of the incremental counter means with the up and down control signals to properly increment or decrement the absolute position count maintained in the absolute position register of the microcomputer system.

Claim 12

The infrared spectrometer of claim 9 including latch means, connected between the incremental counter means and the microcomputer system, for responding to a control signal to load and hold the output count from the incremental counter means in response to the control signal, and timing control means connected to the latch means for providing an enable control signal to the latch means to cause the latch means to load new data from the incremental counter means in a time period which is less than the time required for the incremental counter means to advance one-half of its maximum number of counts.

Claim 13

The infrared spectrometer of claim 9 wherein the incremental counter means responds to the up or down control signal to count up to a maximum bit capacity and then return to zero or to count down to zero and then return to a maximum bit capacity.

Claim 14

The infrared spectrometer of claim 11 including latch means, connected between the incremental counter means and the microcomputer system, for responding to a control signal to load and hold the output count from the incremental counter means in response to the control signal, and control means connected to the latch means for providing an enable control signal to the latch means to cause the latch means to load new data from the incremental counter means when maximum bit capacity of the counter means is exceeded or when the count in the counter means is decremented below zero.

Claim 15

The infrared spectrometer of claim 11 wherein the incremental counter means includes a plurality of up/down counters connected in a cascaded configuration with the lowest significant bit input of each counter except the least significant bit counter connected to receive the overflow bit from the next least significant bit counter.

Claim 16

The infrared spectrometer of claim 9 wherein the means for discriminating the direction of the moving mirror is connected to the microcomputer system, wherein the incremental counter means is capable of counting in only one direction, and wherein the incremental counter means is cleared upon a change in direction of the moving mirror and the timing control means provides an additional control signal when the moving mirror changes direction.

Claim 17

The infrared spectrometer of claim 9 wherein the laser detector includes two separate detectors arranged such that the detectors provide output pulse signals which are out of phase with each other and with the output of one detector leading the output of the other detector when the moving mirror is moving in one direction and trailing when the moving mirror is moving in the opposite direction, the means for discriminating the direction of motion connected to the two detectors to determine which detector is providing a pulse signal which is leading the other detector and providing a high output signal if a first of the detectors is leading and a low output signal if the second of the detectors is leading.

Claim 18

The infrared spectrometer of claim 9 wherein the microcomputer has a random access memory and maintains an absolute position count in its memory of the sum of the existing content of its memory with the new incremental count, either positive or negative, obtained from the incremental counter means.

Claim 19

The infrared spectrometer of claim 16 wherein the absolute position count is updated when the incremental counter means is accessed by the microcomputer.

Claim 22

The method of claim 18 wherein the microcomputer has a random access memory and maintains an absolute position count in its memory of the sum of the existing content of its memory with the new incremental count, either positive or negative, obtained from the incremental counter means.

Claim 23

The method of claim 19 further comprising the step of updating the absolute position count of the microcomputer when the output of the counter is accessed by the microcomputer.