Method and apparatus for reading bar coded data wherein the light source is periodically energized

• US 4,160,156 A
• Filed: 05/04/1978
• Issued: 07/03/1979
• Est. Priority Date: 05/04/1978
• Status: Expired due to Term

• Current Assignee: Symbol Technologies, Inc. (Zebra Technologies Corporation)
• Original Assignee: MSI Data Corp. (Zebra Technologies Corporation)
• Inventors: Sherer, Paul
• Primary Examiner(s): Cook, Daryl W.
• Application Number:
  US05/902,892
• Time in Patent Office: 425 Days
• Field of Search: 235/462, 235/463, 235/472, 250/555, 250/566, 250/568, 250/569
• US Class Current: 235/462.05
• CPC Class Codes: G06K 2207/1018 Source control
• CPC Class Codes: G06K 7/10881 constructional details of hand-held scanners
• CPC Class Codes: G06K 7/14 using light without selection of wavelength, e.g. sensing reflected white light G06K7/10831 - G06K7/1097 take precedence

Abstract

A method and apparatus for reading bar coded data for entry into portable data collection systems. The data is read by an optical wand wherein the light source is automatically and periodically energized for saving the energy of the system. The D.C. offset voltages are determined and stored in an up/down counter during reading or sampling intervals while the analog signal processing circuits are periodically de-energized. The light source is also calibrated to maximize the power savings and minimize reading errors.

Claims

1. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic comprising

optical sensing means for producing electrical signals representative of the optical characteristics of a surface presented thereto upon the production of relative movement between the surface and the sensing means, said sensing means having a light source and a light sensor for receiving the light rays from the light source reflected from the surface being sensed, the sensor output signals including an unknown offset voltage,

analog signal processing means for processing the signals from the sensor and providing analog signals representative of the sensed bars of the different optical characteristics,

digital signal processing means for storing and continuously signalling the analog value of the offset signals generated and coupled to the analog signal processing means, and

control circuit means including means for automatically and periodically energizing the light source and the analog signal processing means and maintaining the energization of same in response to a signal representative of a bar of one optical characteristic and automatically de-energizing said same elements in response to a signal representative of a bar of the other optical characteristic.

2. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic as defined in claim 1 wherein the digital signal processing means are further characterized as being continuously energized.

3. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic as defined in claim 2 wherein the digital signal processing means comprises means for controlling the conductivity of the light source for standardizing said analog output signals.

4. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic comprising

optical sensing means for producing electrical signals representative of the optical characteristics of a surface presented thereto upon the production of relative movement between the surface and the sensing means, said sensing means having a light source and a light sensor for receiving the light rays from the light source reflected from the surface being sensed, the sensor output signals including an unknown offset voltage,

means for automatically determining the value of the unknown offset voltage and continuously storing the value thereof, and

means for amplifying the difference between the signals from the signal processing means and the value of the stored unknown voltage and producing an output signal representative thereof,

means for automatically determining the reflective characteristic of the surface sensed as represented by the output signal from said amplifying means, and means for automatically and periodically energizing the light source, the amplifying means and the reflective characteristic determing means and maintaining the energization of said elements in response to an output signal representative of one reflective characteristic and automatically de-energizing the light source in response to an output signal representative of the other reflective characteristic.

5. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic as defined in claim 4 wherein said means for storing the offset voltage value includes up/down counting means.

6. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic as defined in claim 4 or 5 including means for standardizing the current through the light source.

7. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic as defined in claim 4 or 5 wherein the optical sensing means includes a spherical lens on the tip of the sensor.

8. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic comprising

optical sensing means for producing electrical signals representative of the optical characteristics of a surface presented thereto upon the production of relative movement between the surface and the sensing means, said sensing means having a light source and a light sensor for receiving the light rays from the light source reflected from the surface being sensed, the sensor output signals including an unknown offset voltage,

a binary coded up/down counting means for storing a count representative of the offset value,

a digital-to-analog circuit means for converting the count stored in said counter to a corresponding analog signal,

differential amplifying circuit means coupled to be responsive to said analog signals and the output signal from said optical sensing means for amplifying only the difference between the two,

first comparison circuit means coupled to be responsive to the difference between the output signal from said differential amplifying circuit means and a preselected threshold level for providing output signals representative of the reflective characteristic of the sensed surface,

second comparison circuit means coupled to be responsive to the output signal from the differential amplifying circuit means and a preselected bias level for providing an output signal for controlling the direction of counting the said up/down counting means,

means for presetting the up/down counting means to a preselected count upon the application of electrical power thereto, said preselected count causing an output signal to be produced at said second comparison circuit means for providing a count down signal, and

control circuit means coupled to the light source, the differential amplifying circuit means and the first and second comparison circuit means for automatically and periodically energizing each of said means and including means for maintaining the energization of each of said means in response to a sensed signal of one kind and automatically de-energizing each of said means in response to a sensed signal of the other kind, said control circuit means including means for providing strobe pulses coupled to said counting means, the second comparison circuit means providing a control signal for counting down the counting means in response to the source of pulses until the value of the offset voltage value is stored therein to thereby maintain the apparatus in a nonread mode, and thereafter in a read mode.

9. A method of optically reading bar coded data wherein binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic comprising the steps of

producing relative movement between the bar coded data and an optical bar coded sensor for producing electrical signals representative of the sensed binary bits,

the sensor including a light source and a light sensor for receiving the light rays reflected from the bar coded data representative of the sensed binary bits and producing corresponding electrical signals,

providing signal processing circuits for the signals produced by the sensor,

maintaining the light source and the associated signal processing circuits normally de-energized,

automatically and periodically energizing the light source and the associated signal processing circuits at a preselected rate,

determining the voltage value of the offset signals generated by the signal processing circuits and continually storing the value,

amplifying the difference between the stored offset value and the signals produced by the light sensor and the associated signal processing circuits,

determining the reflective characteristic of the surface exposed to the sensor by means of the resulting difference signal,

if no reflective surface is sensed, automatically de-energizing the light source and the associated signal processing circuits while maintaining the storage of the value of the offset signals,

if a reflective surface is sensed, maintaining the light source and the associated signal processing circuits energized, and

generating the electrical signals representative of the bar coded data while the light source and the signal processing circuits are maintained in energization.

10. A method of optically reading bar coded data wherein binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic as defined in claim 9 including the step of calibrating the current through the light source for standardizing the sensed output signals.

11. A method of optically reading bar coded data wherein binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic as defined in claim 9 or 10 including the step of maintaining the signal processing circuits in a "non-read" condition until the offset signals are determined.

12. A method of optically reading bar coded data wherein binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic as defined in claim 9 wherein the optical bar coded sensor includes a spherical lens on the tip of the sensor for contacting the surface to be sensed, and the offset signals include the signals generated by the internal reflection of the light rays against the spherical lens.

13. A method of optically reading bar coded data wherein binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic comprising the steps of

producing relative movement between the bar coded data and an optical bar coded sensor for producing electrical signals representative of the sensed binary bits,

the sensor including a light source and a light sensor for receiving the light rays reflected from the bar coded data representative of the sensed binary bits and producing corresponding electrical signals,

providing signal processing circuits for the signals produced by the sensor,

maintaining the light source and the associated signal processing circuits normally de-energized,

automatically and periodically energizing the light source and the associated signal processing circuits at a preselected rate,

continuously storing the voltage value of the offset signals generated by the signal processing circuits,

amplifying the difference between the stored offset signals and the signals produced by the light sensor and the associated signal processing circuits,

controlling the stored voltage value of the offset signal in accordance with the value of the amplified difference signal for maintaining the signal processing circuits in a "non-read" condition until the value of the stored offset signal has been obtained,

after the stored voltage of the offset signal has been obtained, determine the reflective characteristic of the surface exposed to the sensor by means of the signal processing circuits,

if no refective surface is sensed, automatically de-energizing the light source and the associated signal processing circuits,

if a reflective surface is sensed, maintaining the light source and the associated signal processing circuits energized, and

generating the electrical signals representative of the bar coded data while the light source and the signal processing circuits are maintained in energization.

14. A method of optically reading bar coded data wherein binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic as defined in claim 13 including the step of maintaining the stored value of the offset signal while the light source and associated signal processing signals are de-energized and continuously following the changes in the offset signal and storing the changed offset signal.

15. A method of optically reading bar coded data wherein binary bits are encoded in terms of bars of different widths of the same optical characteristics separated by areas of the opposite optical characteristic as defined in claim 14 including the steps of automatically calibrating the light sensor output for standardizing the output electrical signals representative of the sensed binary bits.

16. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic comprising

optical sensing means for producing electrical signals representative of the optical characteristics of a surface presented thereto upon the production of relative movement between the surface and the sensing means, said sensing means having a light source and a light sensor for receiving the light rays from the light source reflected from the surface being sensed, the sensor output signals including an unknown offset voltage,

first amplifying circuit means coupled to be responsive to the signals from the light sensor including the offset voltages,

a binary coded decimal up/down counting means for storing a count representative of the offset value,

digital-to-analog circuit means for converting the count stored in said counter to a corresponding analog signal,

differential amplifying circuit means coupled to be responsive to said analog signal and the output signal from said first amplifying means for amplifying only the difference between the two,

first comparison circuit means coupled to be responsive to the difference between the output signal from said differential amplifying circuit means and a preselected threshold level for providing output signals representative of the reflective characteristic of the sensed surface,

second comparison circuit means coupled to be responsive to the output signal from the differential amplifying circuit means and a preselected bias level for providing an output signal for controlling the direction of counting of said up/down counting means,

means for presetting the up/down counting means to a preselected count upon the application of electrical power thereto, said preselected count causing an output signal to be produced at said second comparison circuit means for providing a count down control signal,

control circuit means coupled to the light source, the first amplifying means, the differential amplifying circuit means and the first and second comparison circuit means for automatically and periodically energizing each of said means and including means for maintaining the energization of each of said means in response to a sensed signal of one kind and automatically de-energizing each of said means in response to a sensed signal of the other kind, said control circuit means including means for providing strobe pulses coupled to said counting means, the second comparison circuit means providing a control signal for counting down the counting means in response to the source of pulses until the value of the offset voltage value is stored therein to thereby maintain the apparatus in a non-read mode,

switching circuit means coupled to the light source for controlling the energization and light output thereof, said switching means including means coupled to be responsive to said strobe pulses for maintaining the light source de-energized during the initial counting down of said counting means from said preselected count,

a binary coded count down counting means for storing a preselected maximum count and preselected minimum count, means for presetting the count down counting means to the preselected maximum count upon the application of electrical power thereto, said counting means being adapted to be maintained at the preselected minimum count upon being counted down thereto,

control circuit means coupled to be responsive to the output signals from the first comparison circuit means and the output signal from the second comparison circuit means to count down the count down counting means when said signals are both of the same kind until the counting means is set to the preselected minimum count, and

digital-to-analog circuit means coupled to be responsive to the output signals from the counting means for providing a corresponding output signal, the resulting analog signal being coupled to the switching circuit means for setting the light output of the light source.

17. Apparatus for optically reading bar coded data wherein the binary bits are encoded in terms of bars of different widths of the same optical characteristic separated by areas of the opposite optical characteristic comprising

optical sensing means for producing electrical signals representative of the optical characteristics of a surface presented thereto upon the production of relative movement between the surface and the sensing means, said sensing means having a light source and a light sensor for receiving the light rays from the light source reflected from the surface being sensed, the sensor output signals including an unknown offset voltage,

first amplifying circuit means coupled to be responsive to the signals from the light sensor including the offset voltages,

a binary coded up/down counting means for storing a count representative of the offset value,

digital-to-analog circuit means for converting the count stored in said counter to a corresponding analog signal,

means for presetting the up/down counting means to a preselected minimum count upon the application of electrical power thereto,

switching circuit means coupled to the light source for controlling the conductivity and light output thereof,

differential amplifying circuit means coupled to be responsive to the signals from said first amplifying circuit means and a preselected offset threshold voltage signal and provides a difference output signal,

first comparison circuit means coupled to be responsive to the output signal from the differential amplifying circuit means and a preselected threshold level for providing output signals representative of the reflective characteristic of the sensed surface,

second comparison circuit means coupled to be responsive to the output signal from the differential amplifying circuit means and a preselected bias level for providing an output signal for controlling the direction of counting of said up/down counting means,

control circuit means coupled to the light source, the differential amplifying means and the first and second comparison circuit means for automatically and periodically energizing each of said means and including means for maintaining the energization of each of said means in response to a sensed signal of one kind and automatically de-energizing each of said means in response to a sensed signal of the other kind, said control circuit means including means for providing strobe pulses periodically occurring,

gating circuit means coupled to be responsive to the strobe pulses and the output signals from the second comparison circuit means for counting up the up/down counting means when said signals are both of the same kind, and

switching circuit means coupled to the light source for controlling the conductivity and the light output thereof and coupled to be responsive to the analog signal from the analog-to-digital converter for maintaining the light source de-energized until a preselected count is reached by said up/down counting means.