Laser scanner using two scan motors independently controlled by a single signal
First Claim
1. A speed control arrangement in an electro-optical scanner for reading light-reflective indicia, said scanner having first and second scan motors driven by a single common digital signal having an input frequency and a duty cycle, said motors being operative for scanning a light beam in a scan pattern over an indicium to be read, said arrangement comprising:
- (a) first control means responsive to the single common signal, for varying the speed of the first scan motor in proportion to the input frequency of the single common signal; and
(b) second control means responsive to the single common signal, for varying the speed of the second scan motor in proportion to the input frequency and the duty cycle of the single common signal.
2 Assignments
0 Petitions
Accused Products
Abstract
A dual motor speed control circuit for providing independent speed control of two motors in a laser scanning device is disclosed herein. This apparatus utilizes a single input signal having variable frequency and duty cycle components. The speed of the first motor is controlled by utilizing the frequency component of said input signal while the speed of the second motor is controlled by utilizing the frequency and duty cycle components of said input signal. Specifically, a DC signal is generated that is dependent upon the duty cycle component of said input signal and said DC signal is utilized to offset the speed of the second motor from the speed value as determined by the frequency component of said input signal.
39 Citations
19 Claims
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1. A speed control arrangement in an electro-optical scanner for reading light-reflective indicia, said scanner having first and second scan motors driven by a single common digital signal having an input frequency and a duty cycle, said motors being operative for scanning a light beam in a scan pattern over an indicium to be read, said arrangement comprising:
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(a) first control means responsive to the single common signal, for varying the speed of the first scan motor in proportion to the input frequency of the single common signal; and (b) second control means responsive to the single common signal, for varying the speed of the second scan motor in proportion to the input frequency and the duty cycle of the single common signal. - View Dependent Claims (4, 5, 14, 15, 16)
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2. The arrangement of claim 2, wherein the first and second control means share a first input circuit means for generating a frequency control signal having a control frequency proportional to the input frequency of the common signal;
- and wherein the first control means includes a first control circuit for controlling the speed of the first scan motor in direct proportion to the control frequency; and
wherein the second control means includes a second input circuit for generating a direct current voltage signal having a variable voltage dependent on the duty cycle, and a second control circuit for controlling the speed of the second scan motor, independently of the speed of the first scan motor, as a function of the control frequency and the direct current voltage signal. - View Dependent Claims (3)
- and wherein the first control means includes a first control circuit for controlling the speed of the first scan motor in direct proportion to the control frequency; and
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6. A method of controlling first and second scan motors in an electro-optical scanner for reading light-reflective indicia, scan motors being operative for scanning a light beam in a scan pattern over an indicium to be read, said method comprising the steps of:
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(a) generating a single common signal having an input frequency and a duty cycle; (b) varying the speed of the first scan motor in proportion to the input frequency of the single common signal; and (c) varying the speed of the second scan motor in proportion to the input frequency and the duty cycle of the single common signal. - View Dependent Claims (7, 8, 9)
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10. A speed control arrangement in an electro-optical scanner for reading light-reflective indicia, said scanner having first and second scan motors driven by a common digital signal having an input frequency and a duty cycle, said motors being operative for scanning a light beam in a scan pattern over an indicium to be read, said arrangement comprising:
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(a) first control means responsive to the common signal, for controlling the speed of the first scan motor as a function of the input frequency of the common signal; (b) second control means responsive to the common signal, for controlling the speed of the second scan motor as a function of the input frequency and the duty cycle of the common signal; (c) said first and second control means sharing a first input circuit means for generating a frequency control signal having a control frequency proportional to the input frequency of the common signal, said first input circuit means including a counter means for converting the common signal to the frequency control signal whose control frequency substantially corresponds to an operating speed at which the first scan motor is required to operate; (d) said first control means including a first control circuit for controlling the speed of the first scan motor in direct proportion to the control frequency; and (e) said second control means including a second input circuit for generating a direct current voltage signal having a variable voltage dependent on the duty cycle, and a second control circuit for controlling the speed of the second scan motor, independently of the speed of the first scan motor, as a function of the control frequency and the direct current voltage signal. - View Dependent Claims (11)
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12. A speed control arrangement in an electro-optical scanner for reading light-reflective indicia, said scanner having first and second scan motors driven by a common digital signal having an input frequency and a duty cycle, said motors being operative for scanning a light beam in a scan pattern over an indicium to be read, said arrangement comprising:
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(a) first control means responsive to the common signal, for controlling the speed of the first scan motor as a function of the input frequency of the common signal; (b) second control means responsive to the common signal, for controlling the speed of the second scan motor as a function of the input frequency and the duty cycle of the common signal; (c) said first and second control means sharing a first input circuit means for generating a frequency control signal having a control frequency proportional to the input frequency of the common signal; (d) said first control means including a first control circuit for controlling the speed of the first scan motor in direct proportion to the control frequency, said first control circuit including; (i) a first speed sensor means for generating a first motor speed signal having a first motor frequency proportional to an operating speed of the first scan motor, (ii) a first signal processor means for obtaining a first difference signal having a voltage and being representative of the frequency difference between the frequency control signal and the first motor speed signal, (iii) a first amplifier means for comparing the voltage of the first difference signal with a predetermined voltage of a reference signal, and for outputting a first frequency error correction signal for correcting the operating speed of the first scan motor, (iv) a first motor driver means coupled to the first amplifier means and the first scan motor, for converting the first frequency error correction signal into a first drive signal for the first scan motor, and (v) the first speed sensor means, the first signal processor means, the first amplifier means, the first motor driver means and the first scan motor all being connected in a closed feedback loop; and (e) said second control means including a second input circuit for generating a direct current voltage signal having a variable voltage dependent on the duty cycle, and a second control circuit for controlling the speed of the second scan motor, independently of the speed of the first scan motor, as a function of the control frequency and the direct current voltage signal. - View Dependent Claims (13, 17)
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18. A method of controlling first and second scan motors in an electro-optical scanner for reading light-reflective indicia, scan motors being operative for scanning a light beam in a scan pattern over an indicium to be read, said method comprising the steps of:
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(a) generating a digital common signal having an input frequency and a duty cycle; (b) controlling the speed of the first scan motor as a function of the input frequency of the common signal; (c) controlling the speed of the second scan motor as a function of the input frequency and the duty cycle of the common signal; (d) generating a frequency control signal having a control frequency proportional to the input frequency of the common signal; (e) said step (b) being performed by controlling the speed of the first scan motor in direct proportion to the control frequency; (f) said step (c) being performed by generating a direct current voltage signal having a variable voltage dependent on the duty cycle, and controlling the speed of the second scan motor, independently of the speed of the first scan motor, as a function of the control frequency and the direct current voltage signal; and (g) said step (b) being further performed by generating a first motor speed signal having a first motor frequency proportional to an operating speed of the first scan motor, obtaining a first difference signal having a voltage and being representative of the frequency difference between the frequency control signal and the first motor speed signal, comparing the voltage of the first difference signal with a predetermined voltage of a reference signal, and outputting a first frequency error correction signal for correcting the operating speed of the first scan motor, and converting the first frequency error correction signal into a first drive signal for the first scan motor. - View Dependent Claims (19)
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Specification