System and method for vibrating screens to reduce speckle
View Patent ↗The present disclosure includes systems and methods for solving speckle problems by exciting the screen with a more complex vibration spectrum. A range of frequencies provides, in effect, a collection of overlapping patterns of high and low displacement, so that all regions of the screen have enough motion to reduce visible speckle. As previously discussed acceptable speckle may be approximately 15% contrast or less, preferably approximately 5% contrast or less at approximately 15 feet from the screen.
1. A method for reducing speckle on a projection screen, comprising:
vibrating the projection screen within a predetermined frequency spectrum, wherein the vibration of the projection screen is out of the screen plane; and
locating vibrating elements behind masking to reduce acoustic transmission from the vibrating elements.
2. The method for reducing speckle on a projection screen of claim 1 , further comprising vibrating the projection screen with at least one primary transducer.
3. The method for reducing speckle on a projection screen of claim 2 , wherein the at least one primary transducer further comprises a voice coil.
4. The method for reducing speckle on a projection screen of claim 2 , further comprising mounting the at least one primary transducer to a mounting patch, wherein the mounting patch is attached to the projection screen.
5. The method for reducing speckle on a projection screen of claim 2 , further comprising detecting primary transducer failure by measuring the projection screen vibrations.
6. The method for reducing speckle on a projection screen of claim 5 , further comprising measuring projection screen vibrations with at least one accelerometer.
7. The method for reducing speckle on a projection screen of claim 5 , further comprising locating redundant transducers on the projection screen.
8. The method for reducing speckle on a projection screen of claim 7 , further comprising driving the redundant transducers only when a failure of at least one primary transducer is detected.
9. The method for reducing speckle on a projection screen of claim 1 , wherein the predetermined frequency spectrum power is primarily in the range of 30-500 Hertz.
10. The method for reducing speckle on a projection screen of claim 1 , wherein the speckle is reduced to less than 15 percent contrast at fifteen feet from the projection screen.
11. The method for reducing speckle on a projection screen of claim 1 , wherein the projection screen further comprises a high elastic modulus substrate.
12. The method for reducing speckle on a projection screen of claim 11 , wherein the high elastic modulus substrate has an elastic modulus of greater than 0.4 GPa.
13. The method for reducing speckle on a projection screen of claim 1 , further comprising attaching at least one vibrating element directly to the projection screen.
14. The method for reducing speckle on a projection screen of claim 1 , wherein vibrating the screen further comprises producing an acceptable level of audible noise of less than 40 dBm.
15. A projection screen system comprising:
a projection screen;
at least one primary vibrating element attached to the projection screen, wherein the vibrating element vibrates the screen within a predetermined frequency spectrum and vibrates the screen out of the screen plane; and
masking located to dampen audible acoustic transmission from the at least one primary vibrating element.
16. The projection screen of claim 15 , wherein the projection screen comprises a high elastic modulus substrate.
17. The projection screen of claim 16 , wherein the high elastic modulus substrate has an elastic modulus of greater than 0.4 GPa.
18. The projection screen of claim 15 , wherein the at least one primary vibrating element comprises at least one primary transducer.
19. The projection screen of claim 18 , wherein the at least one primary transducer comprises a voice coil.
20. The projection screen of claim 15 , wherein the predetermined frequency spectrum is in the range of 50-200 Hz.
21. The projection screen of claim 15 , wherein vibrating the screen reduces the speckle to less than 15 percent contrast at fifteen feet from the projection screen.
22. The projection screen of claim 15 , wherein the at least one primary vibrating element is mounted directly adjacent to the projection screen.
23. The projection screen of claim 15 , further comprising redundant vibrating elements in addition to the at least one primary vibrating element, wherein the redundant vibrating elements are driven only when a failure of at least one of the primary vibrating elements is detected.
24. The projection screen of claim 15 , wherein the masking is located on the front and the back of the projection screen.
25. The projection screen of claim 15 , wherein the masking further comprises noise absorbing material.