Local dimming on light-emitting screens for improved image uniformity in scanning beam display systems
Systems and techniques for scanning-beam display are provided to use local dimming on the optical energy of at least one optical beam to minimize the non-uniform image brightness across the screen. This local dimming during the beam scanning can be achieved by adjusting optical energy of at least one optical beam during the scanning based on (1) the location of the scanning optical beam and (2) the predetermined distortion information at the location.
1. A display system, comprising:
light sources that produce optical beams at optical wavelengths in a violet spectral range or ultra violet (UV) spectral range;
a signal modulation controller in communication with the light sources to cause the optical beams to be modulated in form of a time domain signal modulation as optical pulses that carry images to be displayed;
a screen that receives the optical beams to display images carried by the optical beams and includes light-emitting regions that absorb light of the optical beams to emit visible light forming the images and one or more reference marks to produce feedback light from the screen from the illumination of the optical beams;
an optical scanning module that scans optical beams onto the screen to transform, via spatially scanning each optical beam along a scanning path on the screen, the time domain signal modulation in each optical beam into spatial images on the screen;
a designated optical detector located off the screen can to collect the optical feedback light from the screen to convert the collected optical feedback light into a detector signal that contains position information of each optical beam on the screen;
wherein the signal modulation controller receives the detector signal from the designated optical detector and operates to control the light sources, based on the time domain signal modulation and the position information of each optical beam on the screen in the received detector signal, to adjust optical energies of the optical pulses of the optical beams with respect to positions of the scanning optical beams on the screen to render the images on the screen via spatially scanning each optical beam on the screen, and
wherein the signal modulation controller, in addition to adjusting optical energies of the optical pulses for transforming, via spatially scanning each optical beam along a scanning path on the screen, the time domain signal modulation in each optical beam into spatial images on the screen, adjusts optical energies of the optical pulses of at least one optical beam, based on information of a predetermined spatial variation of each optical beam in connection with the location of the optical beam on the screen caused by one or more distortions in scanning the optical beam onto the screen, to reduce the one or more distortions in the images displayed on the screen.
2. The system as in claim 1 , wherein:
the predetermined spatial variation of the optical beam in connection with the location of the optical beam on the screen includes a variation in a beam spot size of the optical beam on the screen as the optical beam is scanned through different locations on the screen.
3. The system as in claim 2 , wherein:
the signal modulation controller decreases an optical energy of an optical pulse as the beam spot size on the screen decreases and increases an optical energy of an optical pulse as the beam spot size on the screen increases.
4. The system as in claim 1 , wherein:
the predetermined spatial variation of the optical beam in connection with the location of the optical beam on the screen includes a variation in spacing between two adjacent scanning lines produced by scanning of the optical beams on the screen.
5. The system as in claim 4 , wherein:
the predetermined spatial variation of the optical beam in connection with the location of the optical beam on the screen includes a variation in spacing between two adjacent scanning lines produced by scanning of the one or more optical beams on the screen caused by a pyramidal error in a polygon scanner that is used to scan the one or more optical beams on the screen.
6. The system as in claim 4 , wherein:
the optical scanning module includes optical lenses through which the optical beams transmit before reaching the screen; and
the predetermined spatial variation of the optical beam in connection with the location of the optical beam on the screen includes a variation in spacing between two adjacent scanning lines produced by scanning of the optical beams on the screen caused by the optical lenses.
7. The system as in claim 4 , wherein:
the signal modulation controller decreases an optical energy of an optical pulse as the spacing between two adjacent scanning lines produced by scanning of the one or more optical beams on the screen decreases and increases an optical energy of an optical pulse as the spacing between two adjacent scanning lines produced by scanning of the optical beams on the screen increases.
8. The system as in claim 1 , wherein:
the one or more optical reference marks include a start of line reference mark that is located in a peripheral area on the screen that is outside an image displaying area where the images are displayed, and
each optical beam is scanned through the start of line reference mark before reaching the image displaying area of the screen.
9. The system as in claim 1 , wherein:
the one or more optical reference marks include an end of line reference mark that is located in a peripheral area on the screen that is outside an image displaying area where the images are displayed, and
each optical beam is scanned through the image displaying area of the screen before reaching the end of line reference mark.
10. The system as in claim 1 , wherein:
the signal modulation controller is configured to adjust both a beam size and optical energy of the optical pulses of at least one optical beam, based on the predetermined spatial variation of the optical beam, to reduce the one or more distortions in the images displayed on the screen.