Tensioning system

1. A tensioning system comprising:

a layer of a device;

a flexible overlay film that is configured to cover the layer of the device; and

a tensioning mechanism that is configured to tension the flexible overlay film against the layer of the device throughout a periphery, the tensioning mechanism being configured to apply forces to the flexible overlay film in two directions such that the flexible overlay film translates toward the layer of the device while causing contact between a portion of the flexible overlay film and the layer of the device without using adhesive at the portion of the flexible overlay film to adhere the portion of the flexible overlay film to the layer of the device, the portion of the flexible overlay film being at least a majority of the flexible overlay film.

2. The tensioning system of claim 1 , wherein the tensioning mechanism is configured to hold the flexible overlay film tight in a third dimension that is perpendicular to the two dimensions in which the flexible overlay film is allowed to move.

3. The tensioning system of claim 1 , wherein the portion of the flexible overlay film comprises an entire surface of the flexible overlay film and the tensioning mechanism is configured to tension the flexible overlay film in close proximity to the layer of the device over an entire surface of the layer of the device.

4. The tensioning system of claim 1 , wherein the tensioning mechanism is configured to allow expansion and contraction of the flexible overlay film in two dimensions.

5. The tensioning system of claim 1 , wherein the tensioning mechanism includes stiffeners that are attached to the flexible overlay film, that transfer forces to the flexible overlay film, and that spread point loads over a larger area.

6. The tensioning system of claim 5 , wherein the stiffeners distribute high tension across each edge of the flexible overlay film and provide a relatively uniform tension on a perimeter of the flexible overlay film.

7. The tensioning system of claim 5 , wherein the stiffeners comprise material that has a coefficient of thermal expansion that is equal to or greater than a coefficient of thermal expansion of the flexible overlay film such that the stiffeners expand and contract with the flexible overlay film.

8. The tensioning system of claim 1 , wherein the tensioning mechanism includes tension clips that are configured to translate a linear pull direction into horizontal and vertical directions.

9. The tensioning system of claim 8 , wherein the tension clips comprise a spring like material.

10. The tensioning system of claim 8 , wherein the tension clips enable bi-directional movement by having an applied force in a first plane and a reaction force in a second plane that is different than the first plane, thereby causing a rotational moment that rotates the flexible overlay film toward the layer of the device.

11. The tensioning system of claim 8 , wherein the tensioning mechanism includes flexures that provide lever arms configured to induce the linear pull on the tension clips.

12. The tensioning system of claim 1 , wherein the tensioning mechanism includes at least one tension adjusting mechanism that is configured to adjust tension of the flexible overlay film.

13. The tensioning system of claim 1 , further comprising a fastening mechanism configured to secure the layer of the device in a manner that decouples thermal expansion of the layer of the device from the tensioned flexible overlay film.

14. The tensioning system of claim 13 , wherein the fastening mechanism comprises a series of radial machined slots and fasteners that enable movement of the layer of the device in first and second directions and restrict movement of the layer of the device in a third direction, the first direction being different than the second direction and the third direction being different than the first and second directions.

15. The tensioning system of claim 14 , wherein the fastening mechanism comprises a mounting hole pattern that is radial from a center fastener and symmetric, the center fastener securing the layer of the device relatively tightly and other fasteners having slotted configurations that allow expansion and contraction of the layer of the device.

16. The tensioning system of claim 1 , further comprising a fastening mechanism configured to secure the layer of the device in a manner that allows movement of the layer of the device in first and second directions while restricting movement of the layer of the device in a third direction, the first direction being different than the second direction and the third direction being different than the first and second directions.

17. The tensioning system of claim 16 , wherein the fastening mechanism comprises a slotted hole that allows movement of the layer of the device in the first and second directions and a shoulder part that restricts movement of the layer of the device in the third direction.

18. The tensioning system of claim 1 , wherein the layer of the device is an optical waveguide configured to receive radiation and to cause at least some radiation to undergo total internal reflection within the optical waveguide, and the tensioning mechanism is configured to allow an air gap to be maintained between the flexible overlay film and the layer of the device such that total internal reflection of radiation within the optical waveguide occurs.

19. A touch-screen device comprising:

a radiation source configured to emit radiation;

an optical waveguide configured to receive radiation emitted from the radiation source and to cause at least some of the received radiation to undergo total internal reflection within the optical waveguide;

a flexible overlay film that is configured to cover the optical waveguide;

a tensioning mechanism that is configured to tension the flexible overlay film against the optical waveguide throughout a periphery while maintaining an air gap between at least part of the flexible overlay film and the optical waveguide and that is configured to apply forces to the flexible overlay film in two directions such that the flexible overlay film translates toward the layer of the device; and

an imaging sensor configured to detect radiation that is coupled out of the optical waveguide when frustrated by a touch input.