Method and apparatus for aperture sculpting in a microlens array film
View Patent ↗A collimating sheet, for use with a backlit display and the like, that includes a substrate, a plurality of microlenses on the output side of the substrate, a specularly reflective layer on the side of the substrate opposite the microlenses, and a plurality of apertures in the reflective layer in direct correspondence to the microlenses of the lens array. The specularly reflective layer can be relatively thinner than a diffuse reflective layer, which allows light to pass through the more readily. One or more layers of dielectric can be placed on top of one or more reflective material layers to further improves overall reflectivity. Apertures are preferably made in the light-absorptive and reflective layers with a laser ablation process wherein laser light illuminates the output side of the film. The laser light is brought to a focus by the lenslets of the lens array onto the light-absorptive layer, which then ablates a hole or aperture into the light-absorptive and reflective layer. In this way, the apertures are self-aligned with the lenslets.
1. A method for making a collimating sheet comprising:
providing a substrate with an optical input side and an optical output side; forming a plurality of microlenses on the output side of the substrate;
providing a light absorptive layer on the input side of the substrate;
providing a reflective material layer on the light absorptive layer; and
forming a plurality of apertures in the reflective material layer with a laser ablation process, by directing laser light from the optical output side through at least one of the microlenses and then through the light absorptive layer.
2. A method as in claim 1 wherein the apertures are formed within the reflective layer on the input side of the substrate such that one or more of the apertures have a predetermined spatial relationship with respect to an optical axis of the corresponding microlenses.
3. A method as in claim 2 wherein the apertures are substantially centered on the optical axis of the microlenses.
4. A method as in claim 2 wherein at least one resulting aperture is offset from the optical axis of a corresponding microlens, and at least a second aperture is formed with an off-angle laser ablation at a second angle with respect to the optical axis, wherein the resulting aperture and the second aperture are in the same reflective material layer.
5. A method as in claim 2 wherein the collimating sheet is attached to a rotating and translating drum, and a laser is incident to a nominal point of incidence on the drum.
6. A method as in claim 1 where the collimating sheet is attached to a rotating drum.
7. A method as in claim 6 wherein the collimating sheet is of a size large enough to serve as a sleeve for the rotating drum.
8. A method as in claim 5 wherein the laser is incident at a 90 degree angle with respect to the drum.
9. A method as in claim 6 wherein the rotating drum is located on a horizontal translating stage.
10. A method as in claim 9 wherein the drum is rotatable about a central axis of the drum, and the horizontal translating stage is caused to move such that a relatively large area of the collimating sheet can be exposed to the laser.
11. A method as in claim 5 wherein the aperture is sculpted to an arbitrary shape by varying an angle of incidence of the laser with respect to the drum.
12. A method as in claim 11 wherein the angle of incidence in a vertical plane is varied by raising or lowering the drum with a vertical translation stage.
13. A method as in claim 11 wherein the angle of incidence in the horizontal plane is varied by swiveling the drum about a vertical axis.
14. A method as in claim 11 wherein a sculpted aperture is ablated by performing several cycles of ablation, with each ablation cycle occurring at a different laser angle of incidence with the film, as determined by the orientation of the vertical and horizontal translation stages.
15. A method as in claim 2 wherein the substrate is of a size large enough to serve as a sleeve for the drum.
16. A method as in claim 2 wherein two or more apertures are made per lenslet, with each aperture selectively being sculpted.
17. A method as in claim 6 wherein two or more ablation steps are performed at different positions of the vertical translation stage.
18. A method as in claim 17 where two or more ablation steps are made at different positions of a horizontal swiveling rotational stage.
19. A method as in claim 1 wherein the collimating sheet is moved by one or more steps of spinning, swiveled, translating, raising or lowering with respect to the ablating laser beam.
20. A method as in claim 1 wherein the ablating laser is a YAG laser.
21. A method as in claim 1 wherein the directing laser light from the optical output side through at least one of the microlenses further comprises directing the laser light to a focal position at the light absorptive layer, wherein the laser ablation process selectively removes at least the light absorptive layer without any substantial removal of the substrate through which the laser light extends during the laser ablation process.
22. A method as in claim 1 wherein the providing the reflective material layer further comprises providing a specularly reflective material layer on the light absorptive layer.
23. A method as in claim 1 further comprising providing a dielectric film stack on the reflective material layer on the input side, wherein the forming the plurality of apertures in the reflective material layer further comprises forming the plurality of apertures in the dielectric film stack.
24. A method as in claim 1 further comprising providing another reflective material layer on the reflective material layer on the input side, wherein the forming the plurality of apertures in the reflective material layer further comprises forming the plurality of apertures in the another reflective material layer.
25. A method as in claim 1 wherein the forming the plurality of apertures in the reflective material layer further comprises forming at least one of a textured or optical power surface on a portion of the substrate in one or more of the plurality of apertures.
26. A method as in claim 1 further comprising providing at least one fill material in at least one of the plurality of apertures.
27. A method as in claim 26 wherein the at least one fill material is non-diffusive and substantially transparent.
28. A method as in claim 26 wherein the at least one fill material is diffusive.
29. A method as in claim 1 further comprising providing at least anti-reflective layer in at least one of the plurality of apertures.
30. A method as in claim 1 further comprising providing at least one anti-reflective microstructure over at least a portion of the input side of the substrate, wherein the providing the light absorptive layer is provided on the at least one anti-reflective micro structure.