Portable laser scanning system and scanning methods having a motor amplitude regulator circuit

• US 5,003,164 A
• Filed: 10/30/1989
• Issued: 03/26/1991
• Est. Priority Date: 10/30/1989
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Inventors: Barkan, Edward
• Primary Examiner(s): Pitts, Harold I.
• Application Number:
  US07/428,834
• Time in Patent Office: 512 Days
• Field of Search: 235/467, 235/472, 350/6.1, 250/566
• US Class Current: 235/472.01
• CPC Class Codes: G06K 2207/1016 Motor control or optical moving unit control
• CPC Class Codes: G06K 7/10 by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners

Abstract

A lightweight hand-held scanning device for repetitively scanning a laser light source across a target having a laser light generating means and at least one high speed scanning motor controlled by a motor amplitude regulator circuit which automatically controls the amplitude of oscillation of the shaft of the high speed scanning motor. The amplitude control is accomplished by using a closed loop control system that supplies the ac stator windings of the scanning motor with periodic triangular current waveforms for energizing and de-energizing the ac stator coils. The signal that closes the control loop is a feedback signal obtained from the dc stator windings of the motor which indicates the amplitude of oscillation. By controlling the amplitude of oscillation, the high speed scanning motor can maintain a consistent scanning speed and use less power.

Claims

1. 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 motor amplitude regulator circuit for controlling said scanning motor, said motor amplitude regulator circuit comprising means for operating said scanning motor at resonance, and means for automatically controlling the amplitude of oscillation of the shaft of said scanning motor, said controlling means being driven from a single feedback signal obtained from the scanning motor.

2. The scanning device of claim 1, wherein said motor amplitude regulator circuit further includes means coupled to the scanning motor for obtaining a generated voltage induced within direct current stator windings of said scanning motor to function as said single feedback signal and for providing said generated voltage to said circuit means.

3. The scanning device of claim 1 wherein said circuit means is a feedback system comprising:

a means for obtaining and amplifying an induced generated voltage from the direct current stator windings of the scanning motor to function as said single feedback signal;

a peak detector means for converting said amplified generated voltage to a direct current voltage signal;

a different amplifier means for comparing said direct current voltage signal with a reference signal and providing an error signal output;

a variable controlled resistance means for providing a variable direct current voltage signal from said error signal output; and

a controlled power supply means for supplying a periodic current waveform to the ac stator windings of the scanning motor in response to said error signal to adjust the amplitude of said scanning motor shaft oscillation.

4. The scanning device of claim 3 wherein said feedback system further includes a means for providing a regulated current to the dc stator windings of said scanning motor.

5. 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, dc stator windings, ac stator windings, a rotor, a shaft connected to said rotor having light reflecting means attached thereto and being operable to oscillate in alternate circumferential directions, and a motor amplitude regulator circuit for automatically controlling the amplitude of oscillation of the shaft of said scanning motor and for operating said motor at or near resonance, said circuit comprising:

feedback means coupled to the dc stator windings for obtaining a feedback signal, said feedback signal being a generated voltage induced in the dc stator windings;

amplitude error signal means coupled to said feedback means for comparing said feedback signal with a reference signal having a predetermined voltage to output an amplitude error signal representative of a difference between the amplitude of oscillation of the shaft of the scanning motor and the reference signal; and

motor control means coupled to said error signal means and the ac stator windings for adjusting the amplitude of oscillation of the shaft of said scanning motor in response to the amplitude error signal.

6. The scanning device of claim 5 wherein said feedback means includes a motor drive integrated circuit for amplifying the induced generated voltage.

7. The scanning device of claim 6 wherein said motor drive integrated circuit includes a regulated current supply means for providing said dc stator windings of the scanning motor with a regulated current.

8. The scanning device of claim 6 wherein said feedback means further includes a peak detector circuit means for converting the induced generated voltage into a dc voltage signal.

9. The scanning device of claim 5 wherein said amplitude error signal means includes a differential amplifier for comparing the induced generated voltage and the reference signal to provide said amplitude error signal.

10. The scanning device of claim 9 wherein said amplitude error signal means further includes a voltage controlled resistance means for providing a constant dc voltage controlled resistance means for providing a constant dc voltage signal to said motor control means from said error signal means.

11. The scanning device of claim 5 wherein said motor control means includes a current supply means which supplies periodic current waveforms from said motor drive integrated circuit to said scanning motor to control the amplitude of oscillation of the shaft of said scanning motor.

12. A method for repetitively scanning a target with light by automatically controlling the amplitude of oscillation of a scanning motor having light reflective means mounted on a shaft thereof, comprising:

obtaining a single feedback signal from the scanning motor;

and adjusting the amplitude of oscillation of the motor shaft in response to the single feedback signal.

13. The method of claim 12 wherein the step of obtaining a single feedback signal includes obtaining a generated voltage induced within the dc stator windings of the scanning motor.

14. The method of claim 12 wherein said adjusting step comprises comparing the amplitude of said feedback signal to a reference signal having a predetermined amplitude and changing the current supplied to the ac stator windings of the scanning motor to reduce a difference in the amplitudes of the feedback and reference signals.

15. A method for repetitively scanning a target with light by automatically controlling the amplitude of oscillation of a scanning motor, said motor having a stator, dc stator windings, ac stator windings, a rotor and a shaft connected to the rotor having a light reflective means mounted thereon and being operable to oscillate in alternate circumferencial directions, said method comprising:

obtaining a feedback signal from the dc stator windings, said feedback signal being a generated voltage induced in the dc stator windings;

combining said feedback signal with a reference signal having a predetermined amplitude to output an amplitude error signal representative of the difference between the amplitude of oscillation of the shaft of the scanning motor and the reference signal amplitude; and

adjusting the amplitude of oscillation of the scanning motor shaft in response to the amplitude error signal.

16. The method of claim 15 wherein the step of obtaining said feedback signal includes amplifying the generated voltage.

17. The method of claim 16 wherein the step of obtaining said feedback signal further includes converting said induced voltage into a dc voltage signal.

18. The method of claim 15 wherein said combining step comprises comparing the generated voltage and a reference signal to provide said amplitude error signal.

19. The method of claim 15 wherein said combining step further comprises providing a constant dc voltage signal to current supply means, said current supply means outputting periodic current waveforms to said ac stator windings of said scanning motor to control the amplitude of said motor shaft oscillation.