Light tunnel and its manufacturing method

Abstract

To provide a light tunnel and a method of manufacturing the same.SOLUTION: An optical device comprises two flat plates each having a reflective flat surface, and two flat spacer plates of a thickness H each having a reflective sidewall. The flat plates and flat spacer plates are arranged as a stack with the reflective flat surfaces facing each other, and the flat spacer plates are arranged in a single plane and disposed between the two flat plates with the reflective sidewalls facing each other with a gap between the two reflective sidewalls. The facing reflective flat surfaces and the facing reflective sidewalls define a light tunnel passage with a dimension H in a direction transverse to the single plane. The facing reflective sidewalls may be mutually parallel and spaced by a constant gap W to provide a light tunnel passage with a constant cross-section H×W, or may be oriented at an angle to provide a tapered light tunnel passage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 665,152, filed May 1, 2018, which is incorporated herein by reference in its entirety. [Background technology]

[0002] The following relates to optical device technology, photonics technology, light tunnel device technology, and their applications, such as light mixing, light projector systems, projection televisions, etc.

[0003] A light tunnel comprises a tube with a reflective inner surface. In optical designs in which the light tunnel connects a light source to downstream optical components, the light tunnel acts as an optical integrator rod to homogenize the light. For example, in a projection display device, a projector lamp may be focused at the input aperture of the light tunnel, causing the light exiting the output aperture of the light tunnel to be more uniform across the area of ​​the output aperture. Light tunnels are primarily etendue-preserving; therefore, the divergence characteristics of the light output at the exit aperture can be engineered with an appropriate taper within the light tunnel. Light tunnels can provide additional or other benefits, such as providing a sealed optical path for connecting a high-temperature incandescent lamp to heat-sensitive downstream optics. Light tunnels can also be used to shape light. For example, in a projector system for a pixelated display device, a light tunnel with a rectangular cross-section can be designed with a rectangular light source at the output aperture to fit a rectangular digital micromirror device (DMD), a pixelated LCD display, or the like.

[0004] Light tunnels rely on strong interactions between light and the reflective inside surfaces of the light tunnel to provide an optical integrator (light mixing) effect. In geometric ray modeling, this corresponds to multiple reflections (on average) of light rays passing through the light tunnel. Therefore, for high optical efficiency, the interior surfaces of the light tunnel should have very high reflectivity. If there are (on average) N reflections and the surfaces have reflectivity r, the power output is rN and the loss is (1-rN). For example, if there are N=4 reflections on average at r=95%, the light loss is (1-0.954)=18% loss. Increasing the reflectivity to r=97% reduces this to 11% loss, and at r=98%, the loss reduces to 7.8%. One approach to fabricating a rectangular cross-section light tunnel with high optical efficiency involves placing four glass plates with highly reflective coatings end-to-end, each oriented at 90° to its neighbors, with the highly reflective coating forming the interior surface of the light tunnel. A mandrel can be used to temporarily hold the four glass plates together and glue or otherwise secure their adjacent edges together.

[0005] Here, some improvements are disclosed. Summary of the Invention [Means for solving the problem]

[0006] In some exemplary embodiments disclosed herein, an optical device is disclosed that includes a first element having a first reflective plane, a second element having a second reflective plane, and two flat spacer plates, each having a reflective sidewall. The two flat spacer plates are arranged in a single plane with the reflective sidewalls of the two flat spacer plates facing each other and with a gap between the two opposing reflective sidewalls. The first reflective plane is arranged parallel to the single plane including the two flat spacer plates and is in contact with the two flat spacer plates. The second reflective plane is arranged parallel to the single plane including the two flat spacer plates and is in contact with the two flat spacer plates. The first and second reflective planes are arranged on either side of the single plane.

[0007] In some exemplary embodiments disclosed herein, an optical device includes a first element having a first reflective plane, a second element having a second reflective plane opposite the first reflective plane, and two flat spacer plates with a thickness H arranged in a single plane with opposing reflective spacer plate sidewalls. The two flat spacer plates are disposed between the opposing first and second reflective planes and space the opposing first and second reflective planes apart by the thickness H.

[0008] In some exemplary embodiments disclosed herein, an optical device includes two flat plates, each having a reflective flat surface, and two flat spacer plates of thickness H, each having a reflective sidewall. The two flat plates and the two flat spacer plates are arranged as a stack with the plates having the reflective flat surfaces of the two flat plates facing each other and the two flat spacer plates arranged in a single plane, with the reflective sidewalls facing each other and disposed between the two flat plates with a gap between the two reflective sidewalls of the two flat spacer plates. The opposing reflective flat surfaces of the two flat plates and the opposing reflective sidewalls of the two flat spacer plates define a light tunnel passage having a dimension H transverse to the single plane.

[0009] In some exemplary embodiments disclosed herein, a method for manufacturing a light tunnel is disclosed. Two flat surfaces are coated with a reflective coating to define two reflective flat surfaces. At least one sidewall of each of two flat spacer plates is coated with a reflective coating to define spacer plates each having a reflective sidewall. The two flat surfaces and the two spacer plates are fixed together with the two flat surfaces facing each other and the two flat spacer plates arranged in a single plane between the two facing surfaces and the reflective sidewalls facing each other. In this way, a light tunnel passage is defined by the two facing flat surfaces and the two facing reflective sidewalls. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 shows a schematic end view of a light tunnel. [Figure 2] FIG. 2 shows a schematic representation of the cross section SS shown in FIG. [Figure 3] FIG. 3 shows a schematic manufacturing process for producing the light tunnel shown in FIGS. [Figure 4] FIG. 4 shows an alternative tapered light tunnel in an exploded cross-sectional view. [Figure 5] FIG. 5 shows an alternative tapered light tunnel in a SS cross section. DETAILED DESCRIPTION OF THE INVENTION

[0011] The method of manufacturing a rectangular light tunnel by arranging four glass plates to form a rectangle with the highly reflective surfaces of the glass plates facing inward to form the interior surface of the light tunnel works well for typical light tunnel sizes, e.g., having an open area of ​​about one square centimeter to several square centimeters or more. However, this method has proven difficult to fabricate smaller light tunnels, having cross-sectional areas on the order of sub-millimeter to several square millimeters, due to the tedious handling, positioning, and assembly of the component glass plates. The embodiments disclosed herein offer improved manufacturability due to improved handling and easier part positioning and assembly. The embodiments disclosed herein are also scalable for high-throughput manufacturing. Furthermore, the embodiments disclosed herein are readily adapted for tapered light tunnels.

[0012] Referring to FIG. 1, an end view of light tunnel 8 is shown. FIG. 2 illustrates cross section SS shown in FIG. 1. Light tunnel 8 includes a first element 10 and a second element 12. First element 10 has a first reflective planar surface 14, and second element 12 has a second reflective planar surface 16. In a preferred embodiment, the two elements 10 and 12 are flat plates, such as flat glass plates. Light tunnel 8 also includes two flat spacer plates 20 and 22. Flat spacer plate 20 has a reflective sidewall 24, and flat spacer plate 22 has a reflective sidewall 26. In a preferred embodiment, the two flat spacer plates 10 and 12 are flat glass plates.

[0013] The reflective surfaces 12, 14 and the reflective sidewalls 24, 26 preferably have high reflectivity, e.g., reflectivity r>90%, more preferably r>95%, and even more preferably r>98%. For example, the reflective surfaces 14, 16 and the reflective sidewalls 24, 26 may each include a reflective multi-layer optical interference filter coating designed using conventional interference filter design methods to provide the desired high reflectivity for a design criteria spectral wavelength or wavelength range. As a non-limiting example, the reflective surfaces 14, 16 and the sidewalls 24, 26 may have an interference filter coating composed of alternating layers of silicon (a-Si:H) and a lower refractive index dielectric, such as SiO, silicon oxynitride (SiOxNy), tantalum pentoxide (Ta2O5), niobium pentoxide (Nb2O5), or titanium dioxide (TiO2). Instead of interference filters, the reflective surfaces 14, 16 and reflective sidewalls 24, 26 may comprise a reflective metal such as silver (Ag, up to r=98%, depending on wavelength), aluminum (Al, up to r=95%, depending on wavelength), or the like, and may optionally have higher reflectivity provided by surface passivation or other surface treatment / coating layers. In some embodiments, the reflective coatings on the reflective surfaces 14, 16 and reflective sidewalls 24, 26 have a reflectivity of at least 0.95 over a wavelength range that includes 400-700 nanometers. More generally, the reflective surfaces 14, 16 and reflective sidewalls 24, 26 preferably have a reflectivity of 0.9 or greater (i.e., 90% or greater) for the design wavelength or wavelength range, and more preferably have a reflectivity of 0.95 or greater (i.e., 95% or greater) for the design wavelength or wavelength range.

[0014] As best shown in FIG. 1 , in the light tunnel 8, the two flat spacer plates 20, 22 are arranged in a single plane (e.g., the plane of the illustrated cross section SS) with the reflective sidewalls 24, 26 of the two flat spacer plates 20, 22 facing each other and with a gap W (shown in cross section SS in FIG. 2 ) between the two opposing reflective sidewalls 24, 26. This gap W defines the width W of the light tunnel 8. Note that the drawings are schematic. Generally, the reflective coatings applied to form the reflective surfaces 14, 16 and reflective sidewalls 24, 26 are assumed to have negligible thicknesses, on the order of microns. If the coating thickness is not negligible, the location of each reflective surface 14, 16 and each reflective sidewall 24, 26 is defined as the upper exposed reflective surface of the reflective coating.

[0015] Additionally, within light tunnel 8, first reflective plane 14 is positioned parallel to a single plane (i.e., parallel to the cross-sectional plane of cross-section SS shown in FIG. 1 ) that accommodates two flat spacer plates 20, 22. Furthermore, two reflective planes 14, 16 are positioned opposite each other on either side of the single plane (i.e., exemplary cross-sectional plane SS) and are in contact with the two flat spacer plates 20, 22. This arrangement results in light tunnel 8 having a rectangular cross-section with the aforementioned width W and a height H equal to the thickness of the two flat spacer plates 20, 22 (assuming they have the same thickness within design tolerances). Generally, height H and width W need not be equal, although these dimensions can be equal if appropriate for a particular light tunnel design. The light tunnel 8 has a rectangular passage 30 of dimensions H x W defined by (1) two opposing reflective surfaces 14, 16 of each of the first and second elements 10 and 12, each having a thickness H, and (2) two opposing reflective sidewalls 24, 26 of two flat spacer plates 20, 22. While the exemplary sidewalls 24, 26 are straight and orthogonal to the reflective surfaces 14, 16, it should be noted that this is not strictly necessary; however, any deviation from a straight orthogonal sidewall profile and orientation should be analyzed for its effect on light loss. On the other hand, having reflective sidewalls 24, 26 with some convex or concave curvature can advantageously aid in light mixing.

[0016] Note that in the S-S cross-section of FIG. 2 , the two flat spacer plates 20, 22 are depicted as opaque, so the underlying reflective surface 14 of the first element 10 is not visible, except for the gap W between the reflective surfaces 24, 26 of the two flat spacer plates 20, 22. Of course, if the two flat spacer plates 20, 22 were made of a transparent material such as glass, the S-S cross-section would actually have the reflective surface 14 visible through the transparent flat spacer plates 20, 22. However, the two opposing reflective surfaces 14, 16 and the two opposing reflective sidewalls 24, 26 together form a continuous perimeter of a rectangular passage 30 having dimensions H x W. Therefore, the transparency or opacity of the flat spacer plates 20, 22, or, for that matter, the transparency or opacity of the elements 10, 12, does not affect the optical properties of the rectangular passage 30, which is an optical light tunnel.

[0017] 1 and 2 will now be described with reference to FIG. 3. The first and second elements 10, 12, in this illustrative example, are fabricated from a glass plate 40 (e.g., a glass microscope slide, as a non-limiting illustrative example) by coating two flat surfaces of the glass plate 40 with a reflective coating to define two flat reflective surfaces 14, 16. In some embodiments, this can be done by coating a single surface of a larger glass plate, which is then cut (i.e., diced) to form the individual glass plates 10, 12 with the reflective coatings 14, 16. Of course, scalability is readily achieved, as large-scale, industrial-scale coating machines can coat many such elements in a single batch process.

[0018] In parallel, two flat spacer plates 20, 22 are formed as individual parts, possibly in a large-scale batch process. As shown schematically in FIG. 3, two constituent glass plates 42, each having a thickness H, are assembled with other interchangeable glass plates 42 to form a plate stack 44. In this stack, all sidewalls on one side of the stack 44 are parallel and face the same direction. Therefore, all of these sidewalls can be coated in a single batch coating process, producing a coated stack 46 having coated sidewalls. Furthermore, the thinner thickness H of the glass plates 42 allows more such plates to be assembled in the stack 44. As a result, scalability increases substantially with the reduction in thickness H (and thus the resulting reduction in the dimension H of the light tunnel passage 30). The individual plates of the coated stack 46 are then disassembled, and any two constituent coated plates of the interchangeable plate stack 46 are selected as two flat spacer plates 20, 22, each having coated sidewalls 24, 26.

[0019] Finally, as shown in FIG. 3, the four component pieces 10, 12, 20, 22 are fixed together with two opposing flat surfaces 14, 16, two flat spacer plates 20, 22 arranged in a single plane between the two opposing flat surfaces 14, 16, and opposing reflective side walls 24, 26, whereby the light tunnel passage 30 is defined by the two opposing flat surfaces 14, 16 and the two opposing reflective side walls 24, 26.

[0020] Continuing to refer to Figure 3, in an alternative embodiment shown in brackets, stack 44 is coated on two opposing sides to produce coated stack 47. The advantage of this approach is improved handling and reduced chance of assembly errors.

[0021] The light tunnel passage 30 has a rectangular cross-section of dimensions H x W, where dimension H is constant transverse to a single plane (i.e., the cross-sectional plane of cross-section SS in exemplary FIGS. 1 and 2) and dimension W is constant parallel to the single plane. When the two opposing sidewalls 24, 26 are parallel to one another, dimensions H and W are constant along the entire length of the light tunnel. Dimension H is determined by the thickness of the two spacer plates 20, 22 (ignoring the thickness of any glue or other adhesive that may optionally be applied to bond the surfaces 14, 16 to the spacer plates 20, 22. In some embodiments, no adhesive is used; instead, the assembly is clamped together). This dimension H can be as small as the actual thickness of the stock glass plate or plates from which the plate 42 is cut or obtained. For example, in some contemplated embodiments, H is 4 millimeters or less, although larger values ​​for H are contemplated. Similarly, the gap W between the opposing reflective sidewalls 24, 26 can be almost arbitrarily small. For example, a mandrel (or spacer) can be inserted into the assembly to provide a defined gap W, which can then be removed after assembly. Thus, the gap W may be 4 millimeters or less in some embodiments, although larger values ​​for the gap W are also contemplated. In some embodiments, the dimensions of the opening H×W are contemplated to define a sub-millimeter opening; that is, H and / or W may be less than 1 millimeter.

[0022] Referring to Figures 4 and 5, an alternative embodiment is shown in an exploded cross-sectional view along section SS (Figure 4) and an assembled cross-sectional view along section SS (Figure 5). In this embodiment, the two rectangular spacer plates 20, 22 are replaced with wedge-shaped spacer plates 120, 122. As a result, the two flat spacer plates 120, 122 are arranged in a single plane (e.g., cross-section SS) with opposing reflective sidewalls 124, 126 disposed at an angle to one another. (Alternatively, although not shown in this alternative embodiment, rectangular plates 24, 26 can be used to tilt the plates relative to one another to define an angle.) In this way, as best shown in Figure 5, a tapered light tunnel passage is defined between opposing first and second reflective planes (similar to the embodiment of Figures 1 and 2). The opposing reflective sidewalls 124, 126 are disposed at an angle to one another. The tapered light tunnel passage has a constant dimension H transverse to the single plane. Dimension H, as in the embodiment of Figures 1 and 2, is defined by the thickness of the flat spacer plates 120, 122. However, in the embodiment of Figures 4 and 5, the constant dimension W of the embodiment of Figures 1 and 2 (resulting from the opposing sidewalls 24, 26 being parallel to one another) is replaced with a non-constant dimension that varies linearly along the length of the light tunnel passageway due to the angle of the opposing reflective sidewalls 124, 126. More generally, a non-linear taper can be achieved by having the opposing reflective sidewalls of a parabolic or other curvature cut using, for example, a diamond saw or other precision glass cutting machine.

[0023] In the exemplary embodiment, plates 10, 12, 20, and 22 are glass plates, but plates of any other material, such as metal plates, can be used. In the case of metal plates made of a metal with a sufficiently high reflectivity (e.g., aluminum), a separate reflective coating can be omitted.

[0024] It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. It will be understood that various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements may subsequently occur to those skilled in the art, which are also intended to be encompassed by the following claims.

Claims

1. a first flat plate having a first reflective surface; a second flat plate having a second reflective surface; two flat spacer plates each having a reflective sidewall and two major surfaces; An optical device comprising: the two flat spacer plates are arranged in a single plane with the reflective sidewalls of the two flat spacer plates facing each other with a gap W between the opposing reflective sidewalls; the first reflecting surface is arranged parallel to the single plane including the two flat spacer plates and is in contact with the two flat spacer plates; the second reflecting surface is disposed parallel to the single plane including the two flat spacer plates and is in contact with the two flat spacer plates; the first reflecting surface and the second reflecting surface are disposed on opposite sides of the single plane, the two main surfaces of the two flat spacer plates in contact with the first and second reflecting surfaces are parallel to the single plane; The two flat spacer plates each have a thickness H; the first flat plate, the second flat plate, and the two flat spacer plates are clamped together to form an adhesive-free assembly; the assembly having a rectangular light tunnel passage defined by the first reflective surface, the second reflective surface, and the opposing reflective sidewalls; The optical device according to claim 1, wherein the light tunnel passage has a constant height dimension equal to the thickness H in a direction transverse to the single plane.

2. 2. The optical device of claim 1, wherein the first flat plate is arranged parallel to the single plane, and the second flat plate is arranged parallel to the single plane.

3. the first flat plate, the second flat plate and the two flat spacer plates are each a glass plate; 2. The optical device of claim 1, wherein the first reflective surface, the second reflective surface, and the opposing reflective sidewalls are each defined by a reflective coating on each of the glass plates.

4. the first flat plate, the second flat plate and the two flat spacer plates are each a metal plate; 2. The optical device of claim 1, wherein the first reflective surface, the second reflective surface, and the opposing reflective sidewall are each defined by a respective one of the metal plates.

5. 5. The optical device of claim 1, wherein the light tunnel passage has a rectangular cross section with dimensions HxW.

6. 6. The optical device according to claim 1, wherein the gap W is constant.

7. the opposing reflective sidewalls are not parallel to one another; 6. The optical device according to claim 1, wherein the gap W between the opposing reflective sidewalls is not constant.

8. 8. The optical device of claim 7, wherein the opposing reflective sidewalls each have a curvature such that the variation of the gap W over the length of the light tunnel passage is non-linear.

9. 8. The optical device of claim 7, wherein the opposing reflective sidewalls are disposed at an angle relative to one another such that the gap W varies linearly over the length of the light tunnel passage.

10. a first flat plate having a first reflective surface; a second flat plate having a second reflective surface; two flat spacer plates each having a reflective sidewall and two major surfaces; An optical device comprising: the two flat spacer plates are arranged in a single plane with the reflective sidewalls of the two flat spacer plates facing each other with a gap W between the opposing reflective sidewalls, and the two flat spacer plates each have a thickness H; the first reflecting surface is arranged parallel to the single plane including the two flat spacer plates and is in contact with the two flat spacer plates; the second reflecting surface is disposed parallel to the single plane including the two flat spacer plates and is in contact with the two flat spacer plates; the first reflecting surface and the second reflecting surface are disposed on opposite sides of the single plane, the two main surfaces of the two flat spacer plates in contact with the first and second reflecting surfaces are parallel to the single plane; the first flat plate, the second flat plate, and the two flat spacer plates are fixed together to form an assembly such that the first reflective surface contacts the two flat spacer plates and the second reflective surface contacts the two flat spacer plates; the assembly includes a rectangular light tunnel passage defined by the first reflective surface, the second reflective surface, and the opposing reflective sidewalls, the light tunnel passage having a constant height dimension; no adhesive is present between the first reflective surface, the second reflective surface, and the opposing reflective sidewalls such that the thickness H of the opposing reflective sidewalls is equal to the constant height dimension of the light tunnel passage; 10. An optical device, wherein the thickness H and the constant height dimension are measured in a direction transverse to the single plane.

11. 11. The optical device of claim 10, wherein the first flat plate, the second flat plate and the two flat spacer plates are clamped together and fixed.

12. 12. An optical device according to claim 10 or 11, wherein the light tunnel passage has a rectangular cross section with dimensions HxW.

13. 13. The optical device according to claim 10, wherein the gap W is constant over the length of the light tunnel passage.

14. 13. The optical device of claim 10, wherein the gap W varies linearly over the length of the light tunnel passage.

15. 15. The optical device of claim 14, wherein the two flat spacer plates are wedge-shaped so that the opposing reflective sidewalls are disposed at an angle to each other.

16. 16. The optical device according to claim 10, wherein the two flat spacer plates, the first flat plate and the second flat plate each consist of a glass plate provided with a reflective coating.

17. 16. The optical device according to any one of claims 10 to 15, wherein the two flat spacer plates, the first flat plate and the second flat plate, consist of reflective metal plates.

18. 1. A method of forming a light tunnel, comprising: a step of disposing a first spacer plate on a first reflecting plane of a first element, the first spacer plate having two main surfaces, an upper surface and a lower surface parallel to the upper surface and the first reflecting plane of the first element; disposing a second spacer plate on the first reflecting plane, the second spacer plate having two major surfaces, a top surface and a bottom surface parallel to the top surface and the first reflecting plane, the first spacer plate and the second spacer plate each having opposing reflective sidewalls, separated by a gap W, and the first spacer plate and the second spacer plate each having a thickness H; disposing a second element having a second reflecting plane on the first spacer plate and the second spacer plate, the second reflecting plane facing the first reflecting plane and spaced apart from the first reflecting plane by a dimension H equal to the thickness H of the first spacer plate and the second spacer plate, the second reflecting plane being parallel to the first reflecting plane of the first element; securing the first spacer plate, the first element, the second spacer plate, and the second element together to form the light tunnel with a light tunnel passage having dimensions H x W; Including, 2. The method of claim 1, wherein no adhesive is used to secure the first spacer plate, the first component, the second spacer plate, and the second component together.

19. 20. The method of claim 18, wherein the step of securing the first spacer plate, the first element, the second spacer plate, and the second element together is secured by a clamp.

20. the first element comprises a first flat plate, and the second element comprises a second flat plate; 20. The method of claim 18 or 19, wherein the first reflecting plane of the first flat plate is parallel to the second reflecting plane of the second flat plate.

21. The fixing step includes: inserting spacers into spaces between the first spacer plate, the first element, the second spacer plate, and the second element; clamping the first spacer plate, the first element, the second spacer plate, and the second element together; removing the spacer to form the light tunnel passage; The method according to any one of claims 18 to 20, comprising:

22. forming the first element by applying a first reflective coating to a first planar surface of a first glass plate, the first reflective coating forming the first planar reflective surface of the first element; forming the second element by applying a second reflective coating to a second planar surface of a second glass plate, the second reflective coating forming the second planar surface of the second element; forming the first spacer plate by applying a third reflective coating to a first sidewall of a third glass plate, the third reflective coating forming the reflective sidewall of the first spacer plate; forming the second spacer plate by applying a fourth reflective coating to a second sidewall of a fourth glass plate, the fourth reflective coating forming the reflective sidewall of the second spacer plate; The method of any one of claims 18 to 21, further comprising:

23. 23. The method according to any one of claims 18 to 22, wherein the thickness H of the first spacer plate and the thickness H of the second spacer plate are constant.

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