Portable laser scanning system and scanning methods having a resonant motor control circuit

Claim 2

A miniature, hand-held scanning device for repetitively scanning a target, said device having a laser beam generating means, at least one high speed scanning motor and a resonant motor circuit for controlling said scanning motor, said resonant motor circuit comprising: first circuit means for automatically tuning a scanning motor to resonance; and second circuit means for automatically controlling the amplitude of oscillation of the scanning motor; said tuning means and said controlling means being driven from a single feedback signal obtained directly from the scanning motor, said single feedback signal being a second harmonic of a voltage induced in said resonant motor.

Claim 3

The scanning device of claim 1, wherein said resonant motor circuit further including means coupled to the scanning motor for obtaining said second harmonic voltage induced within direct current stator windings of the motor to function as said single feedback signal and for providing said second harmonic voltage to said first and second circuit means.

Claim 4

The scanning device of claim 1 wherein said first circuit means is a feedback system comprising: a means for obtaining and amplifying an induced second harmonic voltage from direct current stator windings of the scanning motor to function as said single feedback signal; a signal multiplier means for electronically multiplying said amplified induced second harmonic means and providing an error signal output waveform; an integrator means for integrating and causing a polarity inversion in the error signal output waveform and providing an output control signal; and a controlled direct current power supply means for supplying current to the direct current stator windings of the scanning motor in response to said output control signal to tune the scanning motor to resonance.

Claim 5

The scanning device of claim 1 wherein said second circuit mean is a feedback system comprising: a pre-amplifier means for obtaining and amplifying an induced second harmonic voltage from direct current stator windings of the scanning motor to function as said single feedback signal; a voltage comparator means for comparing the amplified induced second harmonic voltage to a predetermined signal generated by a signal generating means and providing an error signal output waveform; an integrator means for integrating and causing a polarity inversion in the error signal output waveform and providing an output control signal; and a controlled alternating current power supply means for supplying current to alternating current stator windings of the scanning motor in response to said output control signal to control the amplitude of oscillation of the motor.

Claim 6

A miniature, hand-held scanning device for repetitively scanning a target with laser light, said device having a laser beam generating means and at least one high speed scanning motor, said motor having a stator, d.c. stator windings energized by a d.c. current, a.c. stator windings energized by an a.c. current, a permanent magnet rotor, a shaft connected to said rotor having light reflecting means attached thereto and being operable to oscillate in alternate circumferential directions, and a resonant motor circuit for automatically controlling the frequency and amplitude of oscillation of said scanning motor, said circuit comprising: feedback means coupled to the d.c. stator windings for obtaining a feedback signal, said feedback signal being a second harmonic of a voltage induced in the d.c. stator windings; frequency error signal means coupled to said feedback means for combining said feedback signal with a first reference signal having a frequency twice that of the a.c. current to output a frequency error signal representative of a difference between the natural frequency of oscillation of the shaft of the scanning motor and the a.c. current frequency; d.c. motor control means coupled to said error signal means and the d.c. stator windings for supplying said d.c. current to said d.c stator windings for adjusting the natural frequency of oscillation of the scanning motor in response to the frequency error signal; amplitude error signal means coupled to said feedback means for combining said feedback signal with a second reference signal which is proportional to the square of a predetermined amplitude to output an amplitude error signal representative of a difference between the amplitude of oscillation of the shaft of the scanning motor and the the predetermined amplitude; and a.c. motor control means coupled to said amplitude error signal means and the a.c. stator windings for supplying said a.c. current to said a.c. stator windings for adjusting the amplitude of oscillation of the scanning motor in response to the amplitude error signal.

Claim 7

A miniature, hand-held scanning device for repetitively scanning a target with laser light, said device having a laser beam generating means and at least one high speed scanning motor, said motor having a stator, d.c. stator windings energized by a d.c. current, a.c. stator windings energized by an a.c. current, a permanent magnet rotor, a shaft connected to said rotor having light reflecting means attached thereto and being operable to oscillate in alternate circumferential directions, and a resonant motor circuit for automatically controlling the frequency and amplitude of oscillation of said scanning motor, said circuit comprising: feedback means coupled to the d.c. stator windings for obtaining a feedback signal, said feedback signal being a second harmonic of a voltage induced in the d.c. stator windings; frequency error signal means coupled to said feedback means for combining said feedback signal with a first reference signal having a frequency twice that of the a.c. current to output a frequency error signal representative of a difference between the natural frequency of oscillation of the shaft of the scanning motor and the a.c. current frequency; d.c. motor control means coupled to said error signal means and the d.c. stator windings for supplying said d.c. current to said d.c stator windings for adjusting the natural frequency of oscillation of the scanning motor in response to the frequency error signal; amplitude error signal means coupled to said feedback means for combining said feedback signal with a second reference signal which is proportional to the square of a predetermined amplitude to output an amplitude error signal representative of a difference between the amplitude of oscillation of the shaft of the scanning motor and the the predetermined amplitude; and a.c. motor control means coupled to said amplitude error signal means and the a.c. stator windings for supplying said a.c. current to said a.c. stator windings for adjusting the amplitude of oscillation of the scanning motor in response to the amplitude error signal.

Claim 8

The scanning device of claim 5 wherein said feedback means includes a pre-amplifier for amplifying the second harmonic induced voltage.

Claim 9

The scanning device of claim 6 wherein said frequency error signal means includes a multiplier for electronically multiplying the second harmonic induced voltage and the first reference signal to provide said output frequency error signal.

Claim 10

The scanning device of claim 7 wherein said frequency error signal means further includes an integrator for integrating said output frequency error signal.

Claim 11

The scanning device of claim 8 further including a signal generating means coupled to said multiplier for providing said first reference signal.

Claim 12

The scanning device of claim 9 wherein said signal generating means provides a reference signal having a frequency equal to twice the frequency of the a.c. current driving the scanning motor.

Claim 13

The scanning device of claim 6 wherein said amplitude error signal means includes a comparator for comparing the amplitude of the second harmonic induced voltage with the amplitude of said second reference signal stored in said comparator to provide said output amplitude error signal.

Claim 14

The scanning device of claim 11 wherein said amplitude error signal means further includes an integrator for integrating said output amplitude error signal.

Claim 15

The scanning device of claim 12 wherein said frequency error signal means includes a multiplier for electronically multiplying the second harmonic induced voltage and the first reference signal to provide said output frequency error signal, and an integrator for integrating said output frequency error signal supplied to said d.c. motor control means.

Claim 16

The scanning device of claim 13 further including a signal generating means coupled to said multiplier and to said a.c. motor control means for providing said first reference signal to said multiplier and for providing an a.c. control signal to said a.c. motor control means.

Claim 17

The scanning device of claim 14 wherein said signal generating means provides a reference signal having a frequency equal to twice the frequency of the a.c. current driving the scanning motor.

Claim 20

The method of claim 16 wherein the step of obtaining a single feedback signal includes obtaining said second harmonic voltage induced within d.c. stator windings of the motor.

Claim 21

The method of claim 17 wherein said tuning step comprises comparing the phase of said feedback signal to that of a first reference signal having a predetermined frequency and phase and changing the current to the d.c. stator windings to reduce a difference in the frequencies of the feedback and first reference signals.

Claim 22

The method of claim 18 wherein said adjusting step comprises comparing the amplitude of said feedback signal to a second reference signal having a predetermined amplitude and changing the current to the a.c. stator windings of the motor to reduce a difference in the amplitudes of the feedback and second reference signals.

Claim 23

The method of claim 19 wherein the frequency comparing step includes providing the first reference signal with said predetermined frequency being equal to twice the frequency of the a.c. current.

Claim 26

The method of claim 21 wherein said feedback signal obtaining step includes amplifying the second harmonic induced voltage.

Claim 27

The method of claim 22 wherein said frequency combining step includes multiplying the second harmonic induced voltage and the first reference signal to provide said output frequency error signal.

Claim 28

The method of claim 23 wherein said frequency combining step further includes integrating said output frequency error signal.

Claim 29

The method of claim 24 further including providing said first reference signal with a frequency equal to twice the resonant frequency of the a.c. current.

Claim 30

The method of claim 22 wherein said amplitude combining step includes comparing the amplitude of said feedback signal with the of said second reference signal to provide said output amplitude error signal.

Claim 31

The method of claim 26 wherein said amplitude combining step further includes integrating said output amplitude error signal.

Claim 32

The method of claim 27 wherein said frequency combining step includes electronically multiplying the second harmonic induced voltage and the first reference signal to provide said output frequency error signal, and integrating said output frequency error signal.

Claim 33

The method of claim 28 further including providing said first reference signal with a frequency equal to twice the frequency of the a.c. current driving the motor.