Electronically scanned beam display

• US 20020158814A1
• Filed: 04/09/2002
• Published: 10/31/2002
• Est. Priority Date: 04/09/2001
• Status: Active Grant

• Current Assignee: Microvision, Inc.
• Original Assignee: Microvision, Inc.
• Inventors: Moore, James G., Tegreene, Clarence T., Urey, Hakan, Lewis, John R., Black, Philip C., Straka, Scott W., Bright, Gregory Scott
• Granted Patent: US 7,061,450 B2
• Time in Patent Office: Days
• US Class Current: 345/7
• CPC Class Codes: G02B 27/017 Head mounted
• CPC Class Codes: G09G 3/001 using specific devices not provided for in groups G09G3/02 - G09G3/36, e.g. using an intermediate record carrier such as a film slide; Projection systems; Display of non-alphanumerical information, solely or in combination with alphanumerical information, e.g. digital display on projected diapositive as background slide projectors per se G03B23/00 = 42 HP
• CPC Class Codes: G09G 3/025 with scanning or deflecting the beams in two directions or dimensions
• CPC Class Codes: H04N 3/08 having a moving reflector
• CPC Class Codes: H04N 5/04 Synchronising for television systems using pulse code modulation H04N7/56
• CPC Class Codes: H04N 5/06 Generation of synchronising signals
• CPC Class Codes: H04N 5/126 whereby the synchronisation signal indirectly commands a frequency generator
• CPC Class Codes: H04N 9/3132 using one-dimensional electronic spatial light modulators
• CPC Class Codes: H04N 9/641 Multi-purpose receivers, e.g. for auxiliary information H04N9/642 takes precedence

Abstract

A scanning control circuit generates a clock signal corresponding to an expected scan timing of a resonant scanner. In one approach, the control circuit uses a pair of direct digital synthesis (DDS) integrated circuits. A first DDS chip provides a system clock that is synchronized to the monitored period of the scanner. A second DDS chip generates a frequency chirped signal that has a frequency profile corresponding to a desired pixel clock timing. To control phase precisely, four complementary clock signals are weighted and mixed at light source drivers to produce relative phase shifts for different light sources.

Claims

1. A scanned beam display system responsive to an image signal to produce an image for viewing, comprising:

a light source operative to emit a beam of light responsive to a driver signal;

a driver circuit responsive to the image signal and a data clock to produce the driver signal;

a scanner positioned to receive the beam of light and operative to direct the beam of light through a periodic scan pattern;

a sensor responsive to the position, speed or acceleration of a portion of the scanner to produce a detector signal; and

a control circuit having an input for receiving the image signal and a detector input coupled to the sensor, the control circuit including;

a clock generator circuit responsive to the detector signal to produce a chirped signal; and

a filtering circuit responsive to the chirped signal to produce a data clock.

2. A scanning beam display responsive to an image signal having a plurality of components, comprising:

a first light source that emits a first beam of light along a first vector the first beam of light having an intensity defined by a first of the components;

a second light source that emits a second beam of light along a second vector intersecting the first vector at a first location, the second beam of light having an intensity defined by a second of the components; and

a scanner at the first location that receives the first and second light beams and redirects the first and second light beams toward an image field such that the first light beam strikes a first pixel area of the image field at a first time and a second light beam strikes the first pixel area at a second time following the first time.

3. The scanning beam display of claim 2 further comprising an electronic controller that receives the image signal and generates a first drive signal corresponding to the first component and a second drive signal corresponding to the second component.

4. The scanning beam display of claim 3 wherein image signal includes data representing a selected pixel of an image and the electronic controller is responsive to the data to delay the second drive signal relative to the first signal in an amount corresponding to an angle between the first and second vectors.

5. A scanning control circuit for a scanning system having a plurality of sweep intervals, comprising:

a primary clock signal circuit that produces a base pixel clock; and

a phase correction circuit that shifts the base pixel clock by a selected initial phase shift at a starting scan time and shifts the base pixel clock by a phase shift that varies sequentially during a selected sweep interval.

6. The scanning control circuit of claim 5 wherein the sequentially varying phase shift of the phase correction circuit is defined by a linear approximation of a desired phase shift.

7. The scanning control circuit of claim 5 further including a phase shift control circuit including:

a generator circuit that produces a sine wave;

a complementary generator circuit that produces a complementary signal synchronized to the sine wave; and

a mixing circuit that combines the sine wave and the complementary signal to produce a phase control signal.

8. The scanning control circuit of claim 7 further including a lookup table containing data representing relative amplitudes, wherein the mixing circuit is responsive to the lookup table to combine the sine wave and complementary signal with a phase defined by the data representing relative amplitudes.

9. A method of producing a pixel timing clock, comprising the sets of:

generating a chirped frequency component as a base clock signal with a first circuit;

generating a phase correction component with a second circuit; and

combining the frequency component and the phase correction component to produce the pixel timing clock.

10. The method of claim 9 further including determining a phase shift component induced by a physical element of an optical scanning system, wherein the phase correction component is defined by the determined phase shift component.

11. A method of addressing optical distortion in a scanning system, comprising the steps of:

determining a base frequency chirped pixel clock;

determining a desired pixel clock that offsets the optical distortion; and

adjusting the base frequency chirped pixel clock toward the desired pixel clock.

13. The method of claim 12 wherein chirping a signal with a frequency pattern corresponding to the determined aberration includes digitally synthesizing a waveform from a series of pulses.

15. The display of claim 14 wherein the first and second wavelengths are different.

16. The display of claim 14 further including a third light source responsive to a third control signal to emit a third light beam of a third wavelength along a third beam path that substantially converges with the first beam path, wherein the scanner is oriented to direct the third light beam through a third scan path in the image field, the first, second and third scan paths being substantially overlapping in the image field, with the third beam trailing the second beam by a second lag angle.

17. The display of claim 16 wherein the control circuit is responsive to a third color component of the image signal corresponding to the third wavelength to produce the third control signal, the third control signal lagging the second control signal by a delay corresponding to the second lag angle.

12. A method of correcting optical aberrations in a scanning beam system having a periodic pattern of scanning including a plurality of scan lines, comprising the steps of:

determining for each of the scan lines a respective aberration;

determining a period of scanning of the periodic scan;

for each determined respective aberration, chirping a signal with a frequency pattern corresponding to the determined aberration;

constructing from the chirped signal a pixel clock; and

modulating the scanning beam according to a timing responsive to the pixel clock.

14. A display responsive to an image signal to produce an image having a plurality of wavelengths in an image field, comprising:

a first light source responsive to a first control signal to emit a first light beam of a first wavelength along a first beam path;

a second light source responsive to a second control signal to emit a second light beam of a second wavelength along a second beam path that substantially converges with the first beam path;

a scanner positioned in the first and second light paths and oriented to direct the first light beam through a first scan path in the image field and to direct the second light beam through a second scan path in the image field, the first and second scan paths being substantially overlapping in the image field, with the second beam trailing the first beam by a first lag angle;

an electronic control system responsive to a first color component corresponding to the first wavelength of the image signal to produce the first control signal and responsive to a second color component of the image signal to produce the second control signal, the second control signal lagging the first control signal by a delay corresponding to the first lag angle.