# US 10,122,473 B2 · System and method for pulsed based receiver photo sensor

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- Number: US 10,122,473 B2
- Document ID: US10122473B2
- Status: Granted
- Kind: B2
- Application number: 15/463,566
- Filed: 2017-03-20
- Published: 2017-12-21
- Granted: 2018-11-06
- Earliest claimed: 2016-06-20
- Assignees: Rockwell Automation Technologies, Inc.
- Applicants: Rockwell Automation Technologies, Inc.
- Inventors: Donald L. Charlantini; Gregory J. Reimann; Derek W. Gallon; Frederic Boutaud
- Web page: https://patentgrep.com/patent/US10122473B2

## CPC

- H04B 10/691: {Arrangements for optimizing the photodetector in the receiver}
- G01V 8/12: using one transmitter and one receiver
- H04B 10/40: Transceivers
- H04B 10/50: Transmitters
- H04B 10/60: Receivers
- G02B 6/3598: {Switching means directly located between an optoelectronic element and waveguides, including direct displacement of either the element or the waveguide, e.g. optical pulse generation (based on changing the optical properties of the medium G02F1/00; optical pulse generation in optical transmitters H04B10/508; optical pulse generation by controlling laser operation H01S3/00)}
- H01S 3/00: Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range (semiconductors lasers H01S5/00)
- H04B 1/7174: {Pulse generation (in general H04L25/03834)}
- H04B 7/17: employing pulse modulation, e.g. pulse code modulation
- H04B: TRANSMISSION
- G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

## Abstract

A photoelectric sensor uses a selective pulse detection technique and associated synchronization techniques to improve the quality of pulse detection, the operating range of the sensor, and the sensor's immunity to noise. These improvements also yield faster sensor response times and reduce the design cycle time. A modulated light beam emitted by the sensor's emitter comprises multiple pulse periods, with a pulse being transmitted within each period. The pulses are positioned within their respective periods at a defined offset time relative to the start of the periods, where the offset time can vary between periods according to a defined pattern. The receiver can selectively sample the signal based on synchronization information to determine whether the received signal contains the emitted pulse pattern. Through-beam sensor embodiments can generate the synchronization information internally based on an analysis of the analog signal corresponding to the modulated signal.

## Claims

### Claim 1

A photoelectric sensor, comprising:
a photo-detector component configured to receive optical information and convert the optical information to an analog signal, the optical information including a light beam having a modulated signal comprising a series of pulses emitted at a rate of one pulse per pulse period;
a synchronization component configured to generate synchronization information for a receiver of the photoelectric sensor based on an analysis of the analog signal;
a pulse identification component configured to identify presence and timings of the pulses in the analog signal based on digital sample information obtained for the analog signal;
a timing analysis component configured to, for one or more sample windows comprising multiple pulse periods, determine whether a defined minimum number of the pulses within the respective one or more sample windows are identified at locations within the respective pulse periods indicated by the synchronization information; and
an output control component configured to control an output based on a result generated by the timing analysis component.

### Claim 2 (depends on 1)

The photoelectric sensor of claim 1, further comprising a digital sampling component configured to digitally sample the analog signal at a sample timing defined by the synchronization information to yield the digital sample information.

### Claim 3 (depends on 1)

The photoelectric sensor of claim 1, wherein the one or more sample windows comprise at least one of multiple non-contiguous sample windows or multiple sample windows that overlap in time.

### Claim 4 (depends on 1)

The photoelectric sensor of claim 1, wherein the series of pulses have fixed timings within respective pulse periods of the multiple pulse periods.

### Claim 5 (depends on 1)

The photoelectric sensor of claim 1, wherein the series of pulses have timings within respective pulse periods, of the multiple pulse periods, that vary between the pulse periods according to a defined pattern.

### Claim 6 (depends on 5)

The photoelectric sensor of claim 5, wherein the defined pattern varies between the one or more sample windows.

### Claim 7 (depends on 1)

The photoelectric sensor of claim 1, wherein the one or more sample windows have a first duration that is less than a second duration of a burst of pulses.

### Claim 8 (depends on 1)

The photoelectric sensor of claim 1, wherein
the series of pulses have a fixed timing between the pulses, and
the synchronization component is configured to:
identify presence of pulses within the analog signal,
determine, as at least a first portion of the synchronization information, respective durations between consecutive pulses of the series of pulses within the analog signal, and
calculate, as at least a second portion of the synchronization information, an estimated average pulse period based in part on an average of the respective durations.

### Claim 9 (depends on 1)

The photoelectric sensor of claim 1, wherein
the digital sampling component is configured to collect, as the digital sample information for a pulse period of the multiple pulse periods, a first sample at a first time prior to an expected location of a pulse within the pulse period, a second sample at a second time corresponding to the expected location of the pulse within the pulse period, and a third sample at a third time after the expected location of the pulse within the pulse period, and
wherein the digital sampling component determines the expected location based on the synchronization information.

### Claim 10 (depends on 9)

The photoelectric sensor of claim 9, wherein the pulse identification component is configured determine an amplitude value based at least on values of the first sample, the second sample, and the third sample, and to identify presence of the pulse within the pulse period in response to determining that the amplitude value satisfies a criterion indicative of a presence of a pulse.

### Claim 11 (depends on 8)

The photoelectric sensor of claim 8, wherein
the pulse identification component is further configured to determine a relative magnitude of the amplitude value relative to at least one other amplitude value calculated for at least one other pulse period of the pulse periods, and
the output control component is further configured to control the output further based a determination of whether the relative magnitude corresponds to an expected relative magnitude indicative of a defined amplitude pattern.

### Claim 12

A method, comprising:
converting, by a photoelectric sensor comprising at least one processor, received optical information to an analog signal, the optical information comprising a light beam with a modulated signal comprising a series of pulses emitted at a rate of one pulse per pulse period;
generating, by the photoelectric sensor, synchronization information for a receiver of the photoelectric sensor based on an analysis of the analog signal;
identifying, by the photoelectric sensor, presence and timings of the pulses in the analog signal based on digital sample information collected from the analog signal;
determining, by the photoelectric sensor for one or more sample windows comprising multiple pulse periods, whether a defined minimum number of the pulses within the respective one or more sample windows have timings, relative to starts of the multiple pulse periods, that correspond to timings defined by the synchronization information; and
controlling, by the photoelectric sensor, an output based on a result of the determining.

### Claim 13 (depends on 12)

The method of claim 12, wherein the identifying comprises digitally sampling the analog signal at a sample timing defined by the synchronization information to yield the digital sample information.

### Claim 14 (depends on 12)

The method of claim 12, wherein the determining comprises defining the one or more sample windows to be one of multiple non-contiguous sample windows or multiple sample windows that overlap in time.

### Claim 15 (depends on 12)

The method of claim 12, further comprising receiving, by the photoelectric sensor, the modulated signal with fixed timings between the series of pulses.

### Claim 16 (depends on 12)

The method of claim 12, further comprising receiving, by the photoelectric sensor, the modulated signal with timings between the series of pulses that vary according to a defined pattern.

### Claim 17 (depends on 16)

The method of claim 16, wherein the defined pattern varies between the one or more sample windows.

### Claim 18

A non-transitory computer-readable medium having stored thereon executable components that, in response to execution, cause a processor to perform operations, the operations comprising:
converting optical information received at a photoelectric sensor to an analog signal, wherein the optical information comprises a light beam having a modulated signal comprising a series of pulses emitted at a rate of one pulse per pulse period;
deriving synchronization information for a receiver of the photoelectric sensor based on an analysis of the analog signal;
identifying presence and timings of the pulses in the analog signal based on digital sample information derived from the analog signal;
determining, for one or more sample windows comprising multiple pulse periods, whether a defined minimum number of the pulses within respective sample windows of the one or more sample windows have timings relative to start times of the respective pulse periods that correspond to timings defined by the synchronization information; and
setting an output based on a result of the determining.

### Claim 19 (depends on 18)

The non-transitory computer-readable medium of claim 18, wherein the identifying comprises digitally sampling the analog signal at a sample timing defined by the synchronization information to yield the digital sample information.

### Claim 20 (depends on 18)

The non-transitory computer-readable medium of claim 18, wherein the determining comprises defining the one or more sample windows to be one of multiple non-contiguous sample windows or multiple sample windows that overlap in time.