Compensation for overlapping scan lines in a scanning-beam display system

1. A display system comprising:

a display screen;

a plurality of subsystems each including

a light source to generate at least one beam, the at least one beam including an excitation beam that carries image information,

a beam scanning module to receive the at least one beam and to direct the at least one beam onto a display region of the display screen, the beam scanning module configured to scan the at least one beam along a scanning direction across the display region, the display screen comprising at least one servo feedback mark in the display region,

a servo feedback detector positioned to receive feedback light of one or more of the at least one beam scanning on the display region, to detect the servo feedback mark from the feedback light, and to produce a monitor signal indicative of a position of the at least one beam on the display region, and

a control unit operable to adjust optical energies carried by the excitation beam using one or more scaling factors,

wherein two adjacent subsystems of the plurality of subsystems are configured such that in operation an area scanned by one or more excitation beams of a first subsystem of the adjacent subsystems overlaps with an area scanned by one or more excitation beams of a second subsystem of the adjacent subsystems in an overlap region; and

a control system coupled to the plurality of the subsystems and configured to

determine a range of the overlap region between the adjacent subsystems based on the monitor signals from the servo feedback detectors of the adjacent subsystems, and

determine the scaling factors for the excitation beams for the overlap region of the adjacent subsystems.

2. The display system of claim 1 , wherein the control system is configured to

determine a distance based on a time duration of a second monitor signal from the servo feedback detector, the distance being between the light source that generates the one or more of the at least one beam and the display region of the screen along a direction perpendicular to the scanning direction, and

determine a position of the excitation beam on the display region based on the determined distance.

3. The display system of claim 2 , wherein the control system is configured to

determine a variation of the range of the overlap region based on the determined position, and

adjust the respective scaling factors for the excitation beams associated with the overlap region of the adjacent subsystems.

4. The display system of claim 2 , wherein the control system is configured to:

for each of the adjacent subsystems, determine the position of the excitation beam on the display region based on the determined distance, the position of the one or more of the at least one beam, and predetermined spatial information between the one or more of the at least one beam and the excitation beam, and

determine the range of the overlap region based on the determined positions of the excitation beams of the adjacent subsystems.

5. The display system of claim 1 , wherein, in operation, the excitation beam scans over the display region to produce one or more scan lines on the display region extending along the scanning direction.

6. The display system of claim 5 , wherein the control system is configured to determine the range of the overlap region between the adjacent subsystems by

determining respective scan lines produced by the excitation beams of the first and second subsystems on first and second display regions of the display screen, the first and second display regions being adjacent along a direction perpendicular to the scanning direction, and

determining that one or more scan lines of the first subsystem and one or more scan lines of the second subsystem overlap within the overlap region.

7. The display system of claim 6 , wherein the determined one or more scan lines of the first subsystem are ordered from a first scan line to a last scan line along the direction, the first scan line of the first subsystem being closer to the second display region than the last scan line of the first subsystem, and

wherein the determined one or more scan lines of the second subsystem are ordered from a first scan line to a last scan line along the direction, the first scan line of the second subsystem being closer to the first display region than the last scan line of the second subsystem.

8. The display system of claim 7 , wherein the range of the overlap region is determined to be:

2Λ+( A−B ),

where Λ is a gap between two sequential scan lines in one of the first and second subsystems, A is the first scan line of the first subsystem in the overlap region, and B is the last scan line of the second subsystem in the overlap region.

9. The display system of claim 8 , wherein a respective scaling factor for each scan line of each of the first and second subsystems in the overlap region is determined to be:

n Λ/(2Λ+( A−B )),

where n represents an order number of the scan line in the one or more scan lines of the subsystem in the overlap region.

10. The display system of claim 9 , wherein the control unit of the subsystem is configured to adjust optical energies carried by the excitation beam based on adjustment of intensities of each scan line produced by the excitation beam in the overlap region by the respective scaling factor.

11. The display system of claim 1 , wherein the control system is configured to:

receive a first monitor signal indicative of a first position of a respective first servo beam on a first screen portion and a first time duration indicative a first distance between a first respective servo light source and the first screen portion along a direction perpendicular to the first screen portion, the first monitor signal being associated with a first servo feedback mark in the first screen portion,

receive a second monitor signal indicative of a second position of the first servo beam or a respective second servo beam on a second screen portion and a second time duration indicative of a second distance between the first respective servo light source or a second respective servo light source and the second screen portion along a direction perpendicular to the second screen portion, the second monitor signal being associated with a second servo feedback mark in the second screen portion, the first and second servo feedback marks being parallel along the scanning direction, and

determine a slope by dividing a difference between the first and second distances by a difference between the first and second positions.

12. The display system of claim 11 , wherein the control system is configured to

determine a variation of a length of the overlap region along a direction perpendicular to the scanning direction based on the determined slope, and

adjust the respective scaling factors for the excitation beams associated with the overlap region of the adjacent subsystems.

13. The display system of claim 11 , wherein the control system is configured to:

determine a maximum distance between two parallel servo feedback marks along the scanning direction based on a predetermined slope and a maximum distance tolerance perpendicular to the screen portions, and

wherein the first and second servo feedback marks are selected such that a distance between them is no more than the maximum distance.

14. The display system of claim 11 , wherein the first screen portion and the second screen portion are within a same display region provided by the same beam scanning module.

15. The display system of claim 14 , wherein the first servo feedback mark comprises a start of line (SOL) reference mark of the display region, and the second servo feedback mark comprises an end of line (EOL) reference mark of the display region.

16. The display system of claim 11 , wherein the first screen portion and the second screen portion are within two different display regions provided by different beam scanning modules.

17. The display system of claim 1 , wherein the one or more beams includes the excitation beam and a servo beam at a wavelength different than the excitation beam.

18. The display system of claim 1 , wherein the display region comprises a second servo feedback mark,

wherein the servo feedback detector is positioned to receive second servo feedback light of the one or more of the at least one beam scanning on the display region from the second servo feedback mark and to produce a second monitor signal indicative of a position offset of the one or more of the at least one beam on the display region along a direction perpendicular to the scanning direction, and

wherein the control system is configured to adjust the respective scaling factors for the excitation beams associated with the overlap region based on the position offset.

19. The display system of claim 18 , wherein the second servo feedback mark comprises a pair of triangle reference marks that are separated and spaced from each other in both the scanning direction and the direction perpendicular to the scanning direction to maintain an overlap along the scanning direction.

20. The display system of claim 1 , wherein the control system is configured to:

determine, by using an optical simulation model, an average position along a direction perpendicular to the scanning direction based on overlap regions over the entire display screen to ensure display brightness uniformity of images across the entire display screen;

normalize the overlap regions based on the determined average position; and

generate the scaling factors based on the normalized overlap regions.