Servo feedback control based on designated scanning servo beam in scanning beam display systems with light-emitting screens

1. A scanning beam display system, comprising:

a light module to direct and scan at least one excitation beam having optical pulses that carry image information and at least one servo beam at a servo beam wavelength different from a wavelength of the excitation beam;

a screen positioned to receive the scanning excitation beam and the servo beam and comprising a light-emitting layer of parallel light-emitting stripes which absorb light of the excitation beam to emit visible light to produce images carried by the scanning excitation beam, the screen configured to reflect light of the servo beam towards the light module to produce servo feedback light; and

an optical servo sensor module positioned to receive the servo feedback light and to produce a servo feedback signal indicative of positioning of the servo beam on the screen,

wherein the light module is responsive to the positioning of the servo beam on the screen in the servo feedback signal to adjust timing of the optical pulses carried by the scanning excitation beam to control the spatial alignment of spatial positions of the optical pulses in the excitation beam on the screen.

2. The system as in claim 1 , wherein:

the screen comprises servo feedback marks that have facets facing the excitation light source that are specularly reflective to light of the servo beam, and areas outside the servo feedback marks that are diffusively reflective to light of the servo beam;

wherein the system comprises a Fresnel lens located between the screen and the light module to direct the scanning servo beam and excitation beam to be at a substantially normal incidence to the screen, and

wherein the Fresnel lens has an optic axis symmetrically in a center of the Fresnel lens to be parallel to and offset from an optic axis of the light module to direct light of the servo beam that is specularly reflected by a servo feedback mark into the optical servo sensor while light of the servo beam that is diffusely reflected by the screen outside a servo feedback mark is spread by the Fresnel lens over an area greater than the optical servo sensor to direct a fraction of diffusely reflected light of the servo beam into the optical servo sensor.

3. The system as in claim 2 , wherein:

the servo feedback marks are parallel stripes that are parallel to the parallel light-emitting stripes in the screen and have facets facing the excitation light source that are specularly reflective to light of the servo beam.

4. The system as in claim 1 , comprising:

a second optical servo sensor module located relative to the screen to receive a portion of the visible light emitted by the screen to produce a second servo feedback signal, and

wherein the control unit is operable to calibrate positioning of the servo beam on the screen in the servo feedback signal with respect to positioning information in the second servo feedback signal.

5. The system as in claim 4 , wherein:

the second optical servo sensor module include a plurality of optical detectors to respectively detect visible light of different colors emitted by the screen.

6. The system as in claim 1 , wherein:

the servo beam is an IR beam.

7. A method for controlling a scanning beam display system, comprising:

scanning one or more excitation beams modulated with optical pulses to carry images on a screen to excite parallel light-emitting strips to emit visible light which forms the images;

scanning a servo beam at an optical wavelength different from an optical wavelength of the one or more excitation beams, on the screen;

detecting light of the servo beam from the screen to obtain a servo signal indicative of positioning of the servo beam on the screen; and

in response to the positioning of the servo beam on the screen, controlling the one or more scanning excitation beams to control the spatial alignment of spatial positions of the optical pulses in each excitation beam on the screen.

8. The method as in claim 7 , comprising:

detecting a portion of reflected light of the one or more excitation beams from the screen to provide a second servo signal indicative of positioning of an excitation beam on the screen; and

using information in the servo signal and the second servo signal to control the spatial alignment of spatial positions of the optical pulses in each excitation beam on the screen.

9. The method as in claim 7 , comprising:

detecting a portion of visible light of emitted from the screen to provide a second servo signal indicative of positioning of an excitation beam on the screen; and

using information in the servo signal and the second servo signal to control the spatial alignment of spatial positions of the optical pulses in each excitation beam on the screen.

10. The method as in claim 7 , comprising:

detecting light reflected from a reference line mark on the screen that is spaced away from and is parallel to the parallel light-emitting strips on the screen as a start of line reference to measure a position of a beam relative to an edge of the parallel light-emitting strips; and

using the measured position from the reference line mark to control timing of the optical pulses in each excitation beam in displaying the images on the screen.