Cancelling noise caused by the flicker of ambient lights

Patent metadata

Field	Value
Publication number	US-9805237-B2
Application number	US-201615225190-A
Country	US
Kind code	B2
Filing date	Aug 1, 2016
Priority date	Sep 18, 2015
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

Systems and methods for cancelling noise caused by the flicker of ambient lights are provided. Such noise cancelling systems and methods may be incorporated in a laser-based barcode scanning device. In one example, a barcode scanning device includes a light source, a first sensor, a second sensor, and a noise cancelling circuit. The light source is configured to emit a beam of light. The first sensor is configured to detect a first optical signal indicative of light reflecting off of a barcode. The reflected light may originate from the light source and from at least one ambient light source in the vicinity of the barcode scanning device. The second sensor is configured to detect a second optical signal indicative of light originating from the at least one ambient light source. The noise cancelling circuit is configured to obtain a noise-cancelled scanning signal from the first and second optical signals.

First claim

The invention claimed is:

1. A barcode scanning device comprising:
a light source configured to emit a beam of light;
a first sensor configured to detect a first optical signal indicative of light reflecting off of a barcode, the reflected light originating from the light source and from at least one ambient light source in the vicinity of the barcode scanning device;
a second sensor configured to detect a second optical signal indicative of light originating from the at least one ambient light source;
a noise cancelling circuit configured to obtain a noise-cancelled scanning signal from the first and second optical signals; and
a mirror having an aperture in the center of the mirror, wherein the first sensor is configured to sense light illuminating through the aperture and the second sensor is configured to sense light reflected off of the mirror.

2. The barcode scanning device of claim 1 , wherein the noise cancelling circuit comprises a differential amplifier configured to subtract the second optical signal from the first optical signal to obtain the noise-cancelled scanning signal.

3. The barcode scanning device of claim 1 , wherein the first and second sensors include photodiodes for sensing light.

4. The barcode scanning device of claim 1 , wherein the first sensor includes a first field of view that encompasses at least a spot where the beam of light is directed on the barcode.

5. The barcode scanning device of claim 4 , wherein the second sensor includes a second field of view that encompasses an area proximate to the first field of view.

6. The barcode scanning device of claim 4 , wherein the second sensor includes multiple sensors having a second field of view that encompasses a first area on one side of the first field of view and a third field of view that encompasses a second area on an opposite side of the first field of view.

7. The barcode scanning device of claim 4 , wherein the second sensor includes a second field of view that encompasses an area that surrounds the first field of view.

8. The barcode scanning device of claim 1 , wherein the aperture is configured to allow substantially all of the reflected light originating from the light source to pass through the aperture in the center of the mirror to the first sensor rather than reflecting off the mirror to the second sensor.

9. The barcode scanning device of claim 7 , further comprising a spectral beam splitter configured to reflect light originating from the at least one ambient light source and further configured to pass light originating from the light source and from the at least one ambient light source, wherein the first sensor is configured to sense the light that passes through the spectral beam splitter and the second sensor is configured to sense the light reflected off of the spectral beam splitter.

10. The barcode scanning device of claim 1 , further comprising a laser filter lens configured to pass laser frequency light and direct the laser frequency light onto the first sensor.

11. A laser scanning apparatus comprising:
a housing;
a laser source configured to emit a beam of laser light to be scanned across a barcode;
a first photodiode disposed in the housing, the first photodiode configured to detect a first optical signal indicative of reflected light originating from the beam of laser light and ambient light originating from at least one ambient light source;
a noise cancelling circuit configured to provide at an output thereof a noise-cancelled scanning signal derived from the first optical signal and a second optical signal indicative of the ambient light originating from the at least one ambient light source; and
a mirror having an aperture in the center of the mirror, wherein the first photodiode is configured to detect light illuminating through the aperture.

12. The laser scanning apparatus of claim 11 , wherein the noise cancelling circuit comprises a differential amplifier configured to subtract the second optical signal from the first optical signal to obtain the noise-cancelled scanning signal.

13. The laser scanning apparatus of claim 11 , further comprising a second photodiode disposed outside the housing in the vicinity of the first photodiode, the second photodiode configured to sense a second optical signal comprising light reflected off of the mirror, wherein the first photodiode includes a first field of view that encompasses at least a spot where the beam of laser light is directed onto the barcode, and wherein the second photodiode includes a second field of view that encompasses at least an area adjacent to the first field of view.

14. A noise cancellation circuit comprising:
at least one optical sensor configured to detect a first optical signal in a first stage and detect a second optical signal in a second stage;
a differential amplifier configured to subtract the second optical signal from the first optical signal to thereby remove a noise component from the first optical signal;
a notch filter; and
a frequency matching circuit;
wherein the first optical signal includes a laser scanning component and the noise component, the noise component corresponding to ambient light from at least one ambient light source;
wherein the second optical signal includes the noise component; and
wherein the differential amplifier is configured to output a noise-cancelled scanning signal.

15. The noise cancellation circuit of claim 14 , wherein the at least one optical sensor includes a first optical sensor and a second optical sensor, the first optical sensor having a first field of view that encompasses at least a spot where a beam of light is directed, and the second optical sensor having a second field of view that encompasses an area adjacent to the first field of view.

16. The noise cancellation circuit of claim 14 , wherein the at least one optical sensor includes a single optical sensor.

17. The noise cancellation circuit of claim 16 , further comprising a transistor configured, in response to a modulating input signal, to switch a visible laser diode on and off, wherein the single optical sensor is configured to detect the first optical signal in the first stage and detect the second optical signal in the second stage, and wherein the first optical signal includes the laser scanning component from the visible laser diode.

18. The noise cancellation circuit of claim 16 , further comprising a phase shift circuit and a delay line, the phase shift circuit configured to receive the first optical signal, and the delay line configured to receive the second optical signal.

19. The noise cancellation circuit of claim 16 , further comprising a first sample and hold circuit and a second sample and hold circuit, the first sample and hold circuit configured to receive the first optical signal, and the second sample and hold circuit configured to receive the second optical signal.

20. The noise cancellation circuit of claim 16 , further comprising an active filter circuit for filtering the noise component with the notch filter.

Assignees

• Hand Held Prod Inc

Inventors

• Feng Chen
• Ren Jie
• Lu Jun
• Qu Haiming
• Zhang Qing

Classifications

• G06K7/10851 Primary

  Circuits for pulse shaping, amplifying, eliminating noise signals, checking the function of the sensing device (basic electronic circuitry H03) · CPC title

• G06K19/06028

  using bar codes · CPC title

• G06K7/10574

  Multiple sources · CPC title

• G06K7/10554

  Moving beam scanning · CPC title

• G01S17/00

  Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems · CPC title