Optical device

Embodiments of an optical device including at least two transparent layers are disclosed.

BACKGROUND

In the application of optical devices, such as reflective optical devices, it may be difficult to selectively reflect desirable imaging light.

DETAILED DESCRIPTION OF THE DRAWINGS

The present disclosure provides an apparatus, a method of manufacturing, and a method of using a reflective optical device. The optical device can be utilized in a wide variety of applications, such as optical display devices. For ease of illustration, the present disclosure will be discussed in terms of one embodiment, namely, a projection screen.

FIG. 1is a top view of one example embodiment of a reflective optical device10, such as a projection screen12, including a viewing surface14and a frame16. Frame16may support viewing surface14and may allow mounting of optical device10to a mounting surface, such as a conference room wall (not shown). In other embodiments, projection screen12may be free standing and, therefore, may be easily transported and may not require frame16.

FIG. 2is a cross-sectional side view of optical device10ofFIG. 1taken along line2-2, showing a base18including surface features20. Surface features20may refer to protrusions22and/or depressions24, and may also be referred to as a textured (seeFIG. 5) or a non-smooth surface, peaks, valleys, and grooves. The height, slope of sides, profile, and other aspects of the asperities can be varied to provide desired screen characteristics for particular applications. Generally, the dimensions of the asperities may be large relative to the wavelength of visible light to help avoid diffraction and interference effects, while small enough to help avoid pixilation or sparkle. Generally, when the distance from the screen to a viewer is larger, larger asperities can be used without resulting in undesirable pixilation or sparkle. Surface features20may or may not be diffractive elements such as a diffraction grating. In other words, in some embodiments surface features20may be a diffraction grating and in other embodiments surface features20may not be a diffraction grating. Surface features20may be an inherent quality of base18or base18may purposely be manufactured or processed to include surface features20. In one embodiment surface features48may be separately manufactured on base18. In the embodiment shown, surface features20may be random in size, shape and/or location, and may each define a height in a range of about 4 microns to about 500 microns or more, and for example, may have a height26toward the smaller range for indoor projection screen applications with closer viewing distances. Other applications such as large billboard screens may use larger surface features20, larger than 500 microns, where the viewing distances are much greater.

Each of surface features20may define, as shown in this cross-sectional view, a first side surface28and a second side surface30. During processing wherein base18may be moved in a direction32, for example, first side surface28may be referred to as a downstream surface and second side surface30may be referred to as an upstream surface. Base18may be a light absorbing material, such as a black, light absorbent material. In another embodiment, base18may be transparent and may include an absorbent coating material on an underside thereof.

Still referring toFIG. 2, in the example embodiment shown, first side surface28may include a first material34positioned thereon, and a second material36positioned on first material34. In this embodiment, first and second materials34and36are each positioned substantially only on first side surface28of surface features20. The terms “positioned substantially only on the first side surface” may mean that an effective amount of first material34is deposited on first side surface28to render first side surface28reflective of light and any amount of first material34that may be deposited on second side surface30of surface features20will allow second side surface30to absorb light.

First material34may be a clear or transparent material having a first index of refraction (R1). Second material36may be a clear or transparent material having a second index of refraction (R2), wherein the first index of refraction is different from the second index of refraction. Accordingly, when these two materials are deposited or coated on one another they will define an interface38that will reflect therefrom a percentage of light impinging on the interface. The material of base18may also have a different index of fraction from either or both of the coating materials. The base material may also be transparent, with an absorptive lower surface for example, wherein the first surface interface between the first coating material and the base may also act as a reflecting surface and aid in the overall reflective effect of device10.

In particular, the amount of reflection at an interface38of first side surfaces28of surface features20may be calculated as ((R1−R2)/(R1+R2))^2. For a first index of refraction of 1.5 of first material34and a second index of refraction of 1.0 of second material36, the reflection may be 0.04, or 4%. The percent reflection for each interface in a multilayer stack is additive such that seven layers of altering first and second materials34and36(seeFIG. 7, for example) will provide fourteen interfaces38and a reflected light42that is at least a 50% reflection, and is approximately a 75% reflection of source light40a(seeFIG. 4) impinging thereon. Twelve layers with twenty four interfaces38will provide reflected light42that is approximately a 96% reflection of source light40aimpinging thereon and twenty layers may provide a 99% reflection. In contrast, on second side surface30of surface features20, where there may be substantially no interface38because there is little or no first material34and because each layer on the second side may have a similar index of refraction to its adjacent layers, substantially all light40b(seeFIG. 4) traveling to second side surface30of surface features20, may be absorbed by base18as absorbed light44.

First and second materials34and36may not be metal layers but may be a non-conductive material, such as a dielectric material For example, aluminum by itself may not be utilized, nor may a metal sputtering process. Instead, it may be desirable that the first and second materials34and36are clear or transparent materials that may be deposited by inkjet, spray, reactive sputtering deposition, evaporation deposition, or similar deposition methods. The first and/or second materials34and36may also have a large index of refraction to enhance the reflectivity in that direction. In example embodiments, first material34and/or second material36may be chosen from the group including: zinc sulfide with an index of refraction of 2.32; titanium oxide with a index of refraction of 2.4; BiOCl with an index of refraction of 2.15; Sb2O5 with an index of refraction of 1.67; TiO2-ZrO2-SnO2 with an index of refraction in a range of 1.85 to 1.90 depending on the particular manufacturer; and ZnO2-Sb2O5 with an index of refraction of 1.7. Standard index matching fluids may be utilized and may have an index of refraction of approximately 1.5. The use of alternating first and second materials, or third, fourth, fifth, etc, materials, on only a first side28of surface features20of a base18, wherein the interfaces provide reflective interfaces similar to38, provides a highly reflective optical device for source light40a(seeFIG. 4) impinging on first side28of surface features20. In contrast, light40b(seeFIG. 4) impinging on second side30of surface features20of base18will not encounter reflective interfaces38and, therefore, the light will not be reflected and will be absorbed by base coating48or base18(if base coating48is transparent). In one embodiment, base coating48and base18may be manufactured of the same material.

FIG. 3shows a cross-section of an optical device10including a base18including surface features20having a first side surface28and a second side surface30. A first material34is deposited over an entirety of base18thereby coating first and second side surfaces28and30. Thereafter, a second material36is deposited substantially only on first side surfaces28so that an interface38between first and second materials34and36is present substantially only on first side surfaces28. Accordingly, light impinging on first side surfaces28will be at least partially reflected and light impinging on second side surface30will not be reflected and will be absorbed by base18.

Still referring toFIG. 3, each of first and second materials34and36may be deposited having a particular thickness34aand36a, respectively, to “tune” the optical device. The term “tune” may be defined as depositing a layer of material having a thickness chosen to enhance the optical properties of the device. For example, one may chose the thickness34aand36aof each of the layers of first and second materials34and36, respectively, to enhance and increase the overall reflective properties of device10for projection light40a(seeFIG. 4). For example, we can tune the thickness of layers34aand36ato have high reflectance in the visible radiation range and a low reflectance in the UV and IR radiation ranges. This may enhance and increase the overall absorptive properties of device10for non-projection light40b(seeFIG. 4).

FIG. 4shows a cross-section of an optical device10including a base18having a smooth top surface46. Top surface46of base18has a coating48thereon which defines surface features20having a first side surface28and a second side surface30. In this embodiment, the first and second side surfaces28and30are in a different orientation than the embodiment shown inFIGS. 2 and 3. In such an embodiment, coating48and base18may be referred to collectively as the base or support of multiple layers of first and second materials34and36. In this embodiment, first material34is deposited substantially only on first side surfaces28. Thereafter, second material36is deposited over an entirety of base18thereby coating first and second side surfaces28and30of surface features20so that interface38between first and second materials34and36is present substantially only on first side surfaces28. In such an embodiment, second material36may have an index of refraction that matches an index of refraction of coating48applied directly on top surface46of base18so that an interface49between coating48and second material36does not define a reflective interface38. Accordingly, light40aimpinging on first side surfaces28will be at least partially reflected as reflected light42and light40bimpinging on second side surface30will not be reflected and will be absorbed as absorbed light44by base18.

During use of optical device10, light40amay be an imaging light projected from a first direction40cwherein it may be desirable for such light to be reflected. For example, light40amay be one or more imaging, projection light(s) projected by a projector50. Light40bmay be ambient or room light originating from another direction40dfrom a source52wherein it may not be desirable for such light to be reflected. For example, light40bmay be light from non-projection sources, such as room lamps, LED displays, and direct or reflected sunlight. These non-projection sources of light40b, if reflected by optical device10, may reduce the brightness of a light image projected by optical device10or may be viewed by a viewer (not shown). Accordingly, the present specification discloses an optical device10that selectively absorbs light from one direction and selectively reflects light from a second direction.

In other embodiments, there may be several different desirable projection lights40a1,40a2, etc., each projected to device10from a different direction, and there may be several different undesirable lights40b1,40b2, etc., each originating from still another, different direction, wherein device10may reflect the desirable projection lights40a1,40a2, etc., and may be tuned to absorb the undesirable lights40b1,40b2, etc. Accordingly, for example, surface features20may be a three dimensional projection including four different sides (such as front, back, left side, and right side) (not shown). The four different sides of surface features20may be coated as desired to include a first side to reflect a first light40a1, a second side to absorb a second light40b1, a third side to reflect a third light40a2, and a fourth side to absorb a fourth light40b2.

FIG. 5shows a cross-section of an optical device10including a base18having a texture54on a top surface46. Texture54may include a pattern of repeating surface features20each having a first side surface28and a second side surface30. In this embodiment, first material34is deposited substantially only on first side surfaces28. Thereafter, second material36is deposited over an entirety of base18thereby coating first and second side surfaces28and30of surface features20so that interface38between first and second materials34and36is present substantially only on first side surfaces28.

FIG. 6shows a cross-section of an optical device10including a base18having depressions56on a top surface46. Depressions56may each have a first side surface28and a second side surface30. In this embodiment, first material34is deposited substantially only on first side surfaces28. Thereafter, second material36is deposited over an entirety of base18thereby coating first and second side surfaces28and30of surface features20so that interface38between first and second materials34and36is present substantially only on first side surfaces28.

FIG. 7shows a cross-section of an optical device10including a base18having surface features20, each having a first side surface28and a second side surface30. In this embodiment, a first layer of first material34is deposited substantially only on first side surfaces28. Thereafter, a layer of second material36is deposited over an entirety of base18thereby coating first and second side surfaces28and30of surface features20so that interface38between first and second materials34and36is present substantially only on first side surfaces28. This process is repeated four more times so that five layers of first material34are deposited on first side surfaces28and five layers of second material36are deposited on surface features20of optical device10in an alternating fashion. This will result in an interface38between each of the first and second materials34and36on first sides28of surface features20, thereby increasing the reflectance of the layer stack on base18at first sides28.

In contrast, multiple layers of substantially only second material36are coated on second sides30of surface features20. The interface58between each of the multiple layers of second material36on second side30may not be a reflective interface because the index of refraction for the second material is the same for each layer on second side30of surface features20. Accordingly, light40b(seeFIG. 4) impinging on second side surfaces30will substantially be transmitted by the layers of second material36and will be absorbed by base18.

FIG. 8shows one example method of making optical device10. In this embodiment, base18is moved in a direction60under a first spray nozzle62which may spray base18, including surface features20, with second transparent material36. Second material36may be a non-conductive material, namely, a dielectric material, for example. In one example, a spray axis64of first spray nozzle62may be positioned approximately perpendicular to a plane66(shown in side view) of base18and approximately perpendicular to the direction of movement60of base18. Any position of spray nozzle62may be utilized, and may be displaced from a perpendicular position, so as long as the coverage of the spray nozzle62results in an even coverage across surface features20. Accordingly, such positioning of spray nozzle62with respect to base18may allow first and second sides28and30of surface features20to be substantially evenly coated with second material36.

Thereafter, base18may be moved in direction60, for example, under a second spray nozzle68which may spray base18, including surface features20, with first transparent material34. In other embodiments, base18may be moved in a different direction than direction60for spraying by second spray nozzle68. In still other embodiments, the spray nozzle may be moved.

A spray axis70of first spray nozzle62may be positioned at a low angle72with respect to plane66(shown in side view) of base18and at a low angle with respect to the direction of movement60of base18. A low angle may be defined as an acute angle, and in some embodiments, may be an angle less than forty five degrees, with respect to plane66and direction of movement60. In the example embodiment shown, low angle72may be approximately fifteen degrees or less. This low angle positioning of spray nozzle68with respect to base18may allow substantially only first side28of surface features20to be substantially evenly coated with first material34because surface features20may substantially block first material34from coating second sides30of the surface features.

In another embodiment, second spray nozzle68, or similar positioning thereof of another spray nozzle, may be utilized for depositing both first and second materials34and36such that each of the first and second materials are deposited substantially only on first sides of surface features20, as shown in the embodiment ofFIG. 2.

In another embodiment, the last layer applied may be a transparent sealant or a protective coating to protect the underlying layers.

Other variations and modifications of the concepts described herein may be utilized and fall within the scope of the claims below.