Compensation for Spatial Variation in Displayed Image in Scanning Beam Display Systems Using Light-Emitting Screens

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

scanning a beam of excitation light modulated with optical pulses on a screen with a fluorescent layer to excite the fluorescent layer to emit visible fluorescent light which forms images; and

adjusting optical power of the optical pulses in the beam of excitation light as the beam of excitation light moves from one screen position to another based on a spatial variation in pixel brightness of the screen to negate the spatial variation in pixel brightness of the screen.

2 . The method as in claim 1 , wherein:

the screen comprises a multilayer film layer that transmits the excitation light and reflects the visible fluorescent light emitted by the fluorescent layer and the optical transmission of the multilayer film layer varies with position of light on the multilayer film layer, and

the optical power of the optical pulses in the beam of excitation light is adjusted to negate spatial variation in optical transmission of the multilayer film layer.

3 . The method as in claim 1 , wherein:

the fluorescent layer in the screen has a spatial variation, and

the optical power of the optical pulses in the beam of excitation light is adjusted to negate the spatial variation of the fluorescent layer.

4 . The method as in claim 1 , wherein:

an optical component in an optical path of the beam of excitation light causes a spatial variation in the beam of excitation light in scanning through different locations on the screen, and

the optical power of the optical pulses in the beam of excitation light is adjusted to negate the spatial variation of the optical component.

5 . The method as in claim 1 , comprising:

obtaining a map of pixel brightness for the screen; and

controlling the optical power of the optical pulses in the beam of excitation light based on the map to negate the spatial variation in pixel brightness of the screen.

6 . The method as in claim 5 , wherein:

the map of pixel brightness for the screen is obtained in a calibration process which includes:

controlling the beam of excitation light to carry a test image pattern in a process of calibrating the scanning beam display system; and

measuring brightness of each pixel of the screen when the test image pattern is displayed to collect measured pixel brightness of the screen.

7 . A scanning beam display system, comprising:

an optical module operable to produce a beam of excitation light having optical pulses that can carry image information;

a beam scanning module to scan the beam of excitation light along a first direction and a second, perpendicular direction;

a screen comprising a light-emitting area having a plurality of parallel light-emitting stripes each along the first direction and spatially displaced from one another along the second direction, wherein light-emitting stripes absorb the excitation light and emit visible light to produce images carried by the scanning beam of excitation light; and

a control unit operable to adjust optical power of the optical pulses in the beam of excitation light as the beam of excitation light moves from one screen position to another based on a spatial variation in pixel brightness of the screen to negate the spatial variation in pixel brightness of the screen.

8 . The system as in claim 7 , wherein:

the beam scanning module comprises:

a first beam scanner to scan the beam of excitation light along the first direction;

a second beam scanner to scan the beam of excitation light received from the first beam scanner along the second direction; and

a scan lens placed in an optical path of the beam of light between the first and the second beam scanners to direct the beam of excitation light from the first beam scanner along a line on the second beam scanner and to focus the beam of excitation light onto the screen.

9 . The system as in claim 8 , wherein:

the first beam scanner scans at a first scanning rate higher than a second scanning rate of the second beam scanner.

10 . The system as in claim 9 , wherein:

the first beam scanner is a polygon scanner comprising a plurality of different reflective facets, and

the second beam scanner is a 1-dimensional beam scanner.

11 . The system as in claim 8 , comprising:

two optical reflectors located in a folded optical path between the second beam scanner and the screen to direct the beam of excitation light onto the screen.

12 . The system as in claim 7 , wherein:

the beam scanning module comprises:

a first beam scanner to scan the beam of excitation light along the first direction;

a second beam scanner to scan the beam of excitation light received from the first beam scanner along the second direction; and

a scan lens placed in an optical path of the beam of light downstream from the second beam scanner to direct and focus the beam of excitation light from the second beam scanner onto the screen.

13 . The system as in claim 12 , comprising:

two optical reflectors located in a folded optical path between the scan lens and the screen to direct the beam of excitation light from the scan lens onto the screen.

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

scanning a beam of excitation light modulated with optical pulses on a screen with parallel light-emitting stripes in a beam scanning direction perpendicular to the light-emitting stripes to excite the fluorescent strips to emit visible light-emitting light which forms images;

modulating the beam of excitation light to carry a test image pattern which is displayed on the screen for calibrating the scanning beam display system;

measuring brightness of each pixel of the screen when the test image pattern is displayed to collect measured pixel brightness of the screen to represent spatial variation in pixel brightness of the screen; and

storing the measured pixel brightness of the screen for adjusting optical power of the optical pulses in the beam of excitation light, during a normal display of images on the screen, as the beam of excitation light moves from one screen position to another to negate the spatial variation in pixel brightness of the screen.