# US 7,746,515 B2 · Circuit for detecting a clock error in a swept-beam system and related systems and methods

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- Number: US 7,746,515 B2
- Document ID: US7746515B2
- Status: Granted
- Kind: B2
- Application number: 11/316,326
- Filed: 2005-12-21
- Published: 2006-11-30
- Granted: 2010-06-29
- Earliest claimed: 2004-12-21
- Assignees: Microvision, Inc.
- Inventors: Scott Straka; Jari Honkanen; Philip C. Black; James G. Moore
- Web page: https://patentgrep.com/patent/US7746515B2

## CPC

- G02B 26/105: {with one or more pivoting mirrors or galvano-mirrors (G02B26/101 takes precedence)}
- G09G 3/02: by tracing or scanning a light beam on a screen
- H03L 7/0812: {and where no voltage or current controlled oscillator is used}
- H04N 1/047: Detection, control or error compensation of scanning velocity or position ({H04N1/0402 and } H04N1/17 take precedence)
- H03L 7/07: using several loops, e.g. for redundant clock signal generation
- H04N 1/1135: {for the main-scan only}
- H04N 2201/0082: Image hardcopy reproducer (H04N2201/0091 - H04N2201/0094 take precedence)
- H04N 2201/04712: using unbroken arrays of detectors, i.e. detectors mounted on the same substrate
- H04N 2201/04713: Details of the detector arrangement, e.g. non-standard position, optical details (H04N2201/04712 takes precedence)
- H04N 2201/04729: in the main-scan direction
- H04N 2201/04731: in the sub-scan direction
- H04N 2201/04732: Detecting at infrequent intervals, e.g. once or twice per line for main-scan control
- H04N 2201/04744: by detecting the scanned beam or a reference beam
- H04N 2201/04751: Detecting position relative to a step, e.g. using L-shaped masks, marks or gratings
- H04N 2201/04781: Controlling the phase of the signals
- H04N 2201/04789: in the main-scan direction
- H04N 2201/04791: in the sub-scan direction
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)
- H03L: AUTOMATIC CONTROL, STARTING, SYNCHRONISATION OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES (generation of oscillations H03B)
- H04N: PICTORIAL COMMUNICATION, e.g. TELEVISION

## Abstract

A circuit for detecting a phase error between a clock signal and a beam position includes a beam generator, sensor, and phase detector. The beam generator directs a beam toward a beam sweeper in response to a clock signal. The sensor, which is disposed at a mid line of a region that the beam sweeper scans, detects the beam from the beam sweeper, and the phase detector detects an error in the clock phase from the detected beam. Such a circuit can automatically detect the phase error in the pixel clock and correct this error, thus eliminating the need for a manual phase-error corrector.

## Claims

### Claim 1

A method, comprising:
activating a beam in response to a first portion of a clock that corresponds to a first predetermined location in a first line of a scan region as the beam moves in a direction, the clock having a phase;
measuring a first intensity of the activated beam as the beam moves in the direction;
activating the beam in response to a second portion of the clock that corresponds to a second predetermined location in a second line of the scan region as the beam moves in an opposite direction;
measuring a second intensity of the activated beam as the beam moves in the opposite direction;
weighting the first intensity by an amount that is related to the first location;
weighting the second intensity by an amount that is related to the second location; and
detecting an error in the phase of the clock from the weighted first and second intensities.

### Claim 2 (depends on 1)

The method of claim 1 wherein:
the first predetermined location comprises a first pixel location in the first line;
the second predetermined location comprises a second pixel location in the second line;
weighting the first intensity comprises multiplying the first intensity by a location number of the first pixel location; and
weighting the second intensity comprises multiplying the second intensity by a location number of the second pixel location.

### Claim 3 (depends on 2)

The method of claim 2 wherein:
the first predetermined location comprises a pixel location in the first line;
the second predetermined location comprises the pixel location in the second line;
weighting the first intensity comprises multiplying the first intensity by a location number of the pixel location;
weighting the second intensity comprises multiplying the second intensity by the location number; and
detecting the error in the phase of the clock comprises determining a difference between the weighted first and second intensities.

### Claim 4 (depends on 2)

The method of claim 2, further comprising:
wherein the first predetermined location comprises a pixel location in the first line;
wherein the second predetermined location comprises the pixel location in the second line;
wherein weighting the first intensity comprises multiplying the first intensity by a location number of the pixel location;
wherein weighting the second intensity comprises multiplying the second intensity by the location number;
wherein detecting the error in the phase of the clock comprises determining a difference between the weighted first and second intensities; and
correcting the error by shifting the phase of the clock such that the difference between the weighted first and second intensities decreases.

### Claim 5

A method, comprising:
activating a beam in response to a clock as the beam moves in a direction across a scan region, the clock having a phase;
measuring a first intensity of a first portion of the activated beam that strikes an edge region of a sensor located along a midline of the scan region as the beam moves in the direction;
activating the beam in response to the clock as the beam moves in an opposite direction;
measuring a second intensity of a second portion of the activated beam that strikes the edge region of the sensor as the beam moves in the opposite direction; and
calculating an error in the phase of the clock as being proportional to a difference between the first and second intensities.

### Claim 6 (depends on 5)

The method of claim 5 wherein:
activating the beam as it moves in the direction comprises activating the beam in response to a cycle of the clock that corresponds to a predetermined pixel in a first line of a scan region; and
activating the beam as it moves in the opposite direction comprises activating the beam in response to a cycle of the clock that corresponds to the predetermined pixel in a second line of the scan region.

### Claim 7 (depends on 5)

The method of claim 5, further comprising correcting the error by shifting the phase of the clock so as to cause a reduction in the difference between the first and second intensities.

### Claim 8 (depends on 5)

The method of claim 5 wherein the edge region of the sensor is defined by an edge of the sensor.

### Claim 9 (depends on 5)

The method of claim 5 wherein the edge region of the sensor is defined by a structure that is disposed over the sensor.