Lateral Light Pipes

Abstract

The light pipe includes at least two optical structures with different refractive indices. The interface between the two optical structures is oblique to the longitudinal axis of the light pipe such that output light rays from the output surface at the distal end of the light pipe are non-parallel to input light rays that are parallel to the longitudinal axis at the input surface at the proximal end of the light pipe. Light refracts within the light pipe between the (at least) two optical structures, changing the direction of the light's optical path through the light pipe, thereby allowing greater freedom for selecting the deviation angle (fold angle) of the light pipe. By optimizing various parameters of the light pipe, a desired output optical axis angle (i.e., fold angle) suitable for a desired optical engine envelope can be achieved.

Description

[Technical field]

[0001] The present invention relates generally to optical light pipes, and more particularly to light pipes that can be used to illuminate electronic display sources (such as liquid crystal on silicon (LCOS) microdisplays used to inject images into light guides in near-eye displays) having an optical axis (light path) that can be folded at any desired folding angle relative to associated system components. [Background technology]

[0002] In augmented reality systems, the challenge is to fit the shape and form factor of the optical system into an aesthetic wearable frame, especially when it is necessary to mix colors from different light (e.g., LED) sources. One way to mix different light source channels is to use light pipes for the generation of illumination. For aesthetic reasons, it is desirable to align the light pipes with the eyeglass frame. However, light pipes are relatively long elements, and therefore often protrude from the desired optical engine envelope. Therefore, to achieve an aesthetic shape, it is important to bend the light pipes in any desired direction.

[0003] In addition to being a relatively long element, the light pipe is also typically relatively straight. To somehow maintain the light pipe within the desired optical engine envelope, curved light pipe designs have been proposed that implement the light pipe as a banded optical fiber. However, banded optical fiber implementations result in low efficiency due to the fact that light rays propagating in a curved banded optical fiber cannot propagate by total internal reflection along the propagation axis. Alternative folding solutions have been proposed in which the light pipe is folded using a right angle prism (i.e., a 90 degree prism) with a reflective coating (i.e., a mirror coating). Although such solutions result in higher efficiency, these solutions are significantly limited to certain folding angles. Summary of the Invention

[0004] In accordance with the teachings of the present embodiment, an apparatus is provided, the apparatus including a light pipe including at least (i) a first optical structure having a first refractive index, an input surface at a proximal end of the light pipe, and a second surface, and (ii) a second optical structure having a second refractive index not equal to the first refractive index, a third surface, and an output surface at a distal end of the light pipe, the light pipe having a longitudinal axis parallel to a long dimension of the first optical structure in a direction between the input surface and the second surface, and an interface between the second surface and the third surface that is oblique to the longitudinal axis of the light pipe such that an input light ray input to the input surface parallel to the longitudinal axis is output from the output surface as an output light ray that is not parallel to the input light ray.

[0005] In an optional embodiment, the angle between the input light beam and the output light beam is the optical deflection angle of the light pipe, the optical deflection angle being other than zero degrees. In another optional embodiment, the angle between the longitudinal axis and the output surface normal is the mechanical deflection angle of the light pipe, the mechanical deflection angle being other than zero degrees, and the output surface normal being perpendicular to the output surface of the second optical structure.

[0006] In another optional embodiment, at least the first and second optical structures define an optical path of light through the light pipe, the optical path being defined at least in part by light coupling in through the input surface, traversing the first optical structure, refracting through an interface from the first to the second optical structure and from the second to the third surface, traversing the second optical structure, and coupling out of the second optical structure through the output surface. In another optional embodiment, an outer sidewall of at least one of the first and second optical structures is coated with a reflective coating, the reflective coating constraining the optical path within the light pipe.

[0007] In another optional embodiment, an anti-reflective coating is added to at least one surface of at least the first and second optical structures. In another optional embodiment, the second surface is adjacent to a third surface. In another optional embodiment, the second surface is separated from the third surface by a gap. In another optional embodiment, the gap is filled with a material selected from the group consisting of air, optical adhesive, and optical gel. In another optional embodiment, the third surface is configured at a gap angle with respect to the second surface.

[0008] In another optional embodiment, the first optical structure has a first width and the second optical structure has a fifth width, the fifth width being greater than the first width. In another optional embodiment, the third width of the first optical structure and / or the fourth width of the second optical structure vary along the longitudinal axis of the light pipe. In another optional embodiment, the output face is at an eighth angle and / or the input face is at an eleventh angle relative to the longitudinal axis of the light pipe.

[0009] In another optional embodiment, the light source further includes a light source providing input light to the input surface of the light pipe. In another optional embodiment, the light pipe further includes a projection optical system, the light pipe configured to provide an output light beam as an input to the projection optical system.

[0010] In another optional embodiment, the major dimension of the light pipe is at least an order of magnitude greater than the width of the light pipe.

[0011] According to the teachings of this embodiment, an apparatus is provided, the apparatus including a light pipe including at least a first optical structure having a first refractive index, an input surface at a proximal end of the light pipe, and a second surface, and a second optical structure having the first refractive index, a third surface, and an output surface at a distal end of the light pipe, the light pipe having a longitudinal axis parallel to a long dimension of the first optical structure in a direction between the input surface and the second surface, and an interface between the second surface and a third surface that is oblique to the longitudinal axis of the light pipe such that an input light ray input to the input surface parallel to the longitudinal axis is output from the output surface as an output light ray that is not parallel to the input light ray, the second surface being separated from the third surface by a gap. [Brief description of the drawings]

[0012] Some embodiments of the present invention are described herein, by way of example only, with reference to the accompanying drawings. With particular reference to the drawings in detail, it is emphasized that the details shown are by way of example and are for the purpose of illustrative discussion of embodiments of the present invention. In this regard, the description accompanying the drawings will make apparent to those skilled in the art how embodiments of the present invention may be practiced. Turning now to the drawings, in which like reference numbers or letters indicate corresponding or similar elements, the drawings are as follows:

[0013] [Figure 1] 1 is a schematic diagram of an exemplary typical usage. [Figure 2A] This is an expression of the refraction of the light path. [Figure 2B] 2B is a variation of the embodiment illustrated in FIG. 2A. [Diagram 3] 2C is a schematic diagram of a light pipe corresponding to FIG. 2B. [Figure 4] 4 is a schematic diagram of a light pipe similar to that of FIG. 3. [Diagram 5] 5 is a schematic diagram of a light pipe similar to that of FIG. 4. [Figure 6] 2C is a variation of the embodiment illustrated in FIG. 2B. [Figure 7] 7 is a schematic diagram of a light pipe according to the embodiment of FIG. 6. [Figure 8] 10 illustrates a modification of the embodiment illustrated in FIG. [Figure 9] 1 is a schematic diagram of a light pipe with a tapered outer sidewall. [Figure 10] 1 is a schematic diagram of a light pipe having structures separated by air gaps. [Figure 11] The distance between the outer sidewalls of the light pipe is constant. [Figure 12] The distance between the outer sidewalls is increased. [Figure 13A] 1 is a schematic diagram of a light pipe constructed from a single base optical structure. [Figure 13B] 13B is a schematic diagram of the light pie of FIG. 13A, where light enters at different angles. [Figure 13C] 13C is a schematic diagram of a light pipe including the variations of FIGS. 13A and 13B. [Figure 13D] 13D is a schematic diagram of the light pipe of FIG. 13C showing coupling-in losses. [Figure 13E] FIG. 13D is a schematic diagram of the light pipe of FIGS. 13C and 13D with TIR. [Figure 13F] 13D is a schematic diagram of a light pipe that is a variation of FIG. 13C. [Figure 13G] 13D is a schematic diagram of a variation of FIG. 13C. [Figure 13H] FIG. 13H is a schematic diagram of a variation of FIG. 13G. [Figure 13I] FIG. 13B is a schematic diagram of a variation of FIGS. 13A and 13G. [Figure 14A] 1 is a schematic diagram of an alternative implementation of a light pipe. [Figure 14B] FIG. 14B is a schematic diagram of a variation of FIG. 14A. [Figure 14C] 13C, 13E, and 13G, in which a diffuser is disposed at the output of an additional optical structure. [Figure 15A] 13A-13I are schematic side and top views of the light pipe of FIG. 13C-I. [Figure 16A] 1 is a schematic diagram of a conventional folded light pipe using a reflective coating. [Figure 16B] 1 is a schematic diagram of an improved light pipe. [Figure 16C] 16B in three dimensions (3D) and with alternative tilts and rotations of the input and output planes.

[0014] Detailed Description - First Embodiment - Figures 1 to 16C SUMMARY OF THE PRESENT EMBODIMENTS Embodiments of the present invention are directed to light pipes that provide a light path that can be folded at any desired folding angle.

[0015] Unless otherwise defined, all technical and / or scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention pertains. Although methods and materials similar or equivalent to those described herein may be used in carrying out or testing embodiments of the present invention, exemplary methods and / or materials are described below. In case of conflict, the present patent specification, including definitions, shall prevail. In carrying out or testing embodiments of the present invention, exemplary methods and / or materials are described below. In case of conflict, the present patent specification, including definitions, shall prevail. In addition, the materials, methods, and examples are merely illustrative and are not necessarily intended to be limiting.

[0016] Before describing at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details and arrangements of construction of the components and / or methods set forth in the following description and / or illustrated in the drawings and / or examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

[0017] Please note that for simplicity of the drawings, generally only one ray is depicted. A ray can also be referred to as a "light" or a "beam". Those skilled in the art will recognize that the depicted light (ray) is a sample beam of actual light, usually formed by multiple beams at slightly different angles. Unless specifically mentioned as an extreme (edge) of light, the illustrated ray is usually the centroid of the light. If the light corresponds to an image, the central ray is the central ray from the center of the image or the central pixel of the image. If the light comes from a light source, the central ray is usually the center (and maximum intensity) of the cone of illumination propagating from the light source.

[0018] An illumination light pipe according to an embodiment of the invention is formed from a combination of at least two (i.e., two or more) optical structures (e.g., prisms), i.e., a first optical structure and a second optical structure. The first optical structure is formed from a material having a first refractive index, and the second optical structure is formed from a material having a second refractive index different from the first refractive index. Light refracts in the light pipe between the (at least) two optical structures according to Snell's law. Thus, the light path of the light pipe is bent before the light exits the optical structure, thereby allowing more freedom for the selection of the folding angle (defined below). By optimizing various parameters of the light pipe, a desired output optical axis angle (i.e., folding angle) suitable for a desired optical engine envelope can be achieved. Optimizable parameters include, for example, the refractive index of the optical structures, the angles of the internal optical junctions, the orientation angles of the outer surfaces of the optical structures, and the orientation angles of the entrance and exit faces of the optical structures.

[0019] The following paragraphs describe different embodiments of the light pipe of the present invention. The following embodiments are merely exemplary, and the present invention should not be limited to the specific embodiments described herein. Other embodiments of the light pipe are also contemplated.

[0020] Referring now to FIG. 1, there is shown a schematic diagram of an exemplary typical use of an embodiment of a light pipe 600 of the present invention. For aesthetic reasons, the light pipe 600 is preferably aligned (parallel) with the frame of the eyeglasses, and in this figure, the longitudinal axis R1 of the light pipe 600 is shown parallel to the frame. A light source beam from a light source 610 provides input light to the light pipe 600, in this case an input surface (not shown) along an input surface normal R01. The light pipe turns the optical axis, thereby changing the direction of the light path through the light pipe 600, such that the output light rays along the output surface normal R23 are non-parallel to the input light rays along the input surface normal R01. In this case, the illumination output of the light pipe 600 is directed to a projection optics 612 that provides an image to an image expansion module for viewing by a user's eye. In the context of this document, the light pipe turning the optical axis may be referred to as "folding" the optical axis.

[0021] Referring to FIG. 2A, there is shown a representation of the refraction of the light path of a light pipe according to an embodiment of the present invention in which two optical structures are used. For clarity, the exterior of the light pipe is not shown. The light pipe 600A has an input end 602 disposed in a first base medium P0 (e.g., air) having a base refractive index η0. In the figure, the light pipe is generally referred to as element 600, and the specific embodiment is referred to as element 600x, where "x" is a letter. It will be clear to one skilled in the art that some of the descriptions of the specific embodiment 600x are applicable to the general light pipe 600 and other specific embodiments 600x. The first optical structure P1 (e.g., a component or element such as a prism) has a first refractive index of η1, and the second optical structure P2 (component, element) has a second refractive index of η2. The medium at the output end 604 of the light pipe 600 is generally the same as the medium at the input end 602 of the light pipe 600. This implementation is not limiting and the output end 604 can be in a second medium P3 other than the first base medium P0. For clarity of this description, the medium at the output end 604 of the light pipe 100 is generally referred to as the second medium P3. If the second medium P3 has a different refractive index than the first medium P0 base refractive index η0, the refractive index of the second medium P3 is referred to as a third refractive index η3. In this example, the second medium P3 has a base refractive index η0, which is the same refractive index, the same medium, as the base medium P0. In this example, the refractive indexes of the first P1 and second P2 optical structures are different. This implementation is not limiting and in alternative configurations, as described below, the refractive indexes of the optical structures can be substantially equal.

[0022] The light source 610 provides light to the light pipe 600A. Light sources are known in the art, for example, a group of LEDs, each LED emitting light of one color, and the color combination is the light provided by the light source. A typical exemplary light source provides a color combination from three LEDs, one LED producing red light, one LED producing green light, and one LED producing blue light. The light source 610 provides light, represented as an input light ray L0 (also called a "beam" or "input beam"). The color combination, also known as a light source channel, is mixed by the light pipe to generate the lighting output, typically substantially white light.

[0023] Since the base medium P0 and the first optical structure P1 have different refractive indices, the input light ray L0 is refracted at the external input surface S01 to become a light ray L1 inside the first optical structure P1 (light ray L1 of the first optical structure P1). The external input surface S01 of the first optical structure P1 of the light pipe 600A has a normal shown as the dashed input surface normal R01 in the direction of the base medium P0. Correspondingly, the input surface normal R01 is also perpendicular to the first optical structure P1 inside the input surface S01, the inside being opposite to the outside of the input surface S01. A first angle, the external input angle θ 01 is defined between the input ray L0 and the input surface normal R01. Similarly, a second angle is defined as an internal input angle θ 10 It is.

[0024] The light ray L1 propagates from the external input surface S01 to the second surface S12 through the first optical structure P1. In this case, the second surface S12 is the output surface of the first optical structure P1 in the direction of the second optical structure P2. The second surface S12 is adjacent to the third surface S21, which is the input surface to the second optical structure P2. Usually, the second surface S12 and the third surface S21 are arranged adjacent to each other in contact, thereby effectively implementing a single interface 620 between the first optical structure P1 and the second optical structure P2. In this description, for convenience, the interface 620 of the second surface S12 and the third surface S21 is generally referred to simply as the "second surface S12". Note that in this figure, the second surface S12 and the third surface S21 are each represented by a slightly separated line on the drawing (rather than using a single line, which is the practical implementation of this embodiment) for clarity. This implementation is not limiting, and below we describe implementations in which the surfaces of the optical structures are not adjacent.

[0025] Since the first optical structure P1 and the second optical structure P2 have different refractive indices, the light ray L1 is refracted at the second surface S12 and becomes a light ray L2 inside the second optical structure P2 (light ray L2 of the second optical structure P2). The second surface S12 of the first optical structure P1 has a normal shown as the second surface normal R12, which is a dashed line, in the direction of the first optical structure P1. Correspondingly, the second surface normal R12 is also perpendicular to the second optical structure P2 inside the third surface S21. The third angle is the output angle θ of the second surface. 12 is defined between the ray L1 and the normal R12 of the second surface. Similarly, the fourth angle is the input angle θ 21 and is defined between the ray L2 and the normal R12 of the second surface.

[0026] The light ray L2 propagates from the third surface S21 to the output surface S23 through the second optical structure P2. In this case, the output surface S23 is the fourth surface of the second optical structure P2 in the direction of the second medium P3. Since the second optical structure P2 and the second medium P3 have different refractive indices, the light ray L2 refracts at the output surface S23 and becomes a light ray L3 inside the second medium P3 (light ray L3 of the second medium P3). The light ray L3 is the output light of the light pipe 600. The output surface S23 of the second optical structure P2 has an output normal (also called the fourth surface normal in the context of this document) shown as the output surface normal R23, which is a dashed line, in the direction of the second optical structure P2. Correspondingly, the output surface normal R23 is also perpendicular to the second medium P3 outside the output surface S23. The fifth angle, the output angle θ of the fourth surface 23 is defined between ray L2 and output surface normal R23. Similarly, a sixth angle is defined as the output angle θ 32 It is.

[0027] In this figure, two construction lines are used. The second reference line S2 and the third reference line S3 are both parallel to the input surface S01. The second reference line S2 intersects with the second surface S12. A seventh angle (δ, “delta”) is defined between the second reference line S2 and the second surface S12 (and in this case also the third surface S21). The seventh angle (δ) is used to help define the surface orientation between the first optical structure P1 and the second optical structure P2. Similarly, the third reference line S3 intersects with the output surface S23. An eighth angle (γ, “gamma”) is defined between the third reference line S3 and the output surface S23. The eighth angle (γ) is used to help define the surface orientation between the second optical structure P2 and the second medium P3.

[0028] The input optical axis is defined to coincide with the input ray L0, which is the central ray of the input light as described above. The rays, in this case ray L1 and ray L2, form the optical axis, or path, of propagation through the light pipe 600 (through the first P1 and second P2 optical structures). The output optical axis is defined to coincide with the output ray L3, which is the central ray of the output light. References to an "optical path", e.g., propagation through the light pipe 600, and bending of the optical path, can also be references to an "optical axis", e.g., the optical axis of the light propagating through the light pipe 600, and bending of the optical axis. Those skilled in the art will appreciate that off-axis (non-perpendicular to the input face S01, non-parallel to the input face normal R01) input rays are typically reflected several times on the walls of the light pipe 600. An exemplary off-axis optical path L9 is shown in this figure.

[0029] In this embodiment, the optical path (optical axis) is refracted at least three times. First, the input optical axis (light ray L0) of the optical path is refracted from a first medium P0 having a refractive index η0 to a first optical structure P1 having a refractive index η1. Next, the optical path is refracted from the first optical structure P1 having a refractive index η1 to a second optical structure P2 having a refractive index η2. Next, the optical path is refracted from the second optical structure P2 having a refractive index η2 to a second medium P3 having a refractive index η0.

[0030] The angles of incidence and refraction are: η0*sin(θ 01 )=η1*sin(θ 10 ) η1*sin(θ 12 )=η2*sin(θ 21 ) η2*sin(θ 23 )=η0*sin(θ 32 ) θ 12 =θ 10 -δ θ 23 =θ 21 -(δ-γ)

[0031] In addition, both of the two refractive indices η1 to η2 are greater than the refractive index of the base medium η0. The first refractive index η1 and the second refractive index η2 are each greater than the base refractive index η0. Thus, either η1≧η2≧η0 or η2≧η1≧η0.

[0032] Considering the above discussion and using the exemplary embodiment, we can now consider the definition of the folding angle of the light pipe 600. In the context of this document, the term "deviation angle" (or "fold angle") can be defined with respect to the light, i.e., from the "light point of view" ("optical deviation angle" or "optical folding angle"), or with respect to the direction of the input optical axis (optical input ray L0) and the output optical axis (optical output ray L3) ("mechanical deviation angle" or "mechanical folding angle"). When the term "deviation angle" or "fold angle" is used without specifying the optical or mechanical, a person skilled in the art will understand that the reference includes both the optical and the mechanical. In this case, the optical folding angle of the light pipe 600 is the angle defined between the input ray L0 and the output ray L3. As discussed above, by selecting, configuring, and optimizing various parameters of the light pipe 600, a desired folding angle can be achieved that matches the desired optical engine envelope. Examples of parameters include the refractive indices (η0, η1, η2, η3) of the optical structures (P0, P1, P2, P3), the angles of the internal optical junctions (δ), the orientation angles of the outer surfaces of the optical structures (α, β), and the orientation angles of the entrance and exit surfaces of the optical structures (ψ, γ). Note that element notations not mentioned above will be described later.

[0033] Based on this description, given the desired direction of output light ray L3, the fold angle can be determined and the light pipe 600 can be designed for any fold angle including 0 degrees (0°) and 90°, and particularly for any fold angle other than 0 degrees (0°) and 90°, i.e., where the output optical axis is other than linear and perpendicular to the input optical axis.

[0034] FIG. 2B shows a variation of the embodiment illustrated in FIG. 2A. Optionally, the outer sidewall (also referred to as "outer wall" in the context of this document) can be coated with a reflective coating layer. In this embodiment, the first outer sidewall S24 of the light pipe 600B can be coated with a reflective coating layer so that the light path (in this case, the light ray L2) is further reflected by the first outer sidewall S24 at a certain angle (the ninth angle, α, "alpha") within the light pipe 600B to become the light ray L21. Alternatively or additionally, the light pipe 600 can be configured such that the outer sidewall (in this case, the first outer sidewall S24) reflects one or more portions of the light path using total internal reflection (TIR). The fourth reference line S4 is a construction line perpendicular to the input surface S01. The fourth reference line S4 intersects with the first outer sidewall S24. A ninth angle (α) is defined between the fourth reference line S4 and the first outer sidewall S24. The ninth angle (α) is used to help define the orientation of the first outer sidewall S24 relative to other surfaces of the light pipe 600. In this embodiment, the incidence angle θ of the light ray L21 before returning to the base medium 23 is the formula θ 23 =θ 21 It is given by -(δ-γ)-2α.

[0035] 3 is a schematic diagram of a light pipe 600C corresponding to FIG. 2B, whereby the light path (L0, L1, L2, L21, L3) is at least partially refracted by the change in refractive index of the two optical structures (P1, P2) and reflected by one of the outer sidewalls (first outer sidewall S24) of the light pipe 600. Note that in this figure, the input light ray L0 is perpendicular to the external input surface S01, the input light ray L0 is parallel to the input surface normal R01, and the input light ray L0 is incident on the external input angle θ 01 is 90°, and the internal input angle θ 10 is 90°. The output ray L3 is perpendicular to the output surface S23, the output ray L3 is parallel to the output surface normal R23, and the output angle θ 23 is 90°, and the external output angle θ 32 Also note that is 90°.

[0036] In the above description, the folding angles were defined with respect to light, i.e., from the "light point of view" or with respect to the direction of the light input ray L0 and the light output ray L3. Alternatively, the folding angles can be described with respect to the mechanical configuration of the elements of the light pipe 600. The longitudinal axis R1 is defined parallel to the long dimension 606 of the first optical structure P1. It should be noted that the longitudinal axis R1 is not limited to being perpendicular to the input surface S01 or parallel to the input ray L0. In this embodiment, the longitudinal axis R1 is perpendicular to the input surface S01 and parallel to the input ray L0. In the example of Figures 2A and 2B, the longitudinal axis R1 may or may not be perpendicular to the input surface S01 and may not be parallel to the input ray L0. The longitudinal axis R1 serves as the input reference for the folding angle. The output surface normal R23 serves as the output reference for the folding angle. The mechanical bend angle is then defined by the angle between the longitudinal axis R1 and the output surface normal R23.

[0037] In the figures, the input surface S01 is generally depicted as perpendicular to the longitudinal axis R1 of the first optical structure P1, but this implementation is not limiting and, as described elsewhere, the input surface S01 may be non-perpendicular (inclined at an angle other than 90° or oblique) to the longitudinal axis R1 of the first optical structure P1.

[0038] Since the second optical structure P2 is generally aligned with the first optical structure P1, the second longitudinal axis R2 of the second optical structure P2 is generally aligned with, parallel to, or substantially aligned with the first longitudinal axis R1 of the first optical structure P1. This implementation is not limiting, and those skilled in the art will understand that the second longitudinal axis R2 of the second optical structure P2 may be aligned in a direction other than that of the first longitudinal axis R1. In this description, the output of the second optical structure P2 is defined relative to the first optical structure P1 (and the first longitudinal axis R1) to help clearly define the overall effect of the light pipe 600. In the figures, for simplicity, the optical structure surfaces (e.g., the input surface S01, the first outer side wall S24, and the output surface S23) are generally depicted as flat surfaces (straight lines), but this implementation is not limiting, and the surfaces of the optical structures may be of other shapes, such as curved surfaces. For example, the input surface S01, the second surface S12, and / or the output surface S23 may be curved and lenses may be implemented at the respective inputs and outputs of the light pipes.

[0039] Output face S23 can have a variety of shapes, but a straight surface that is also perpendicular to the side of light pipe 600 is often preferred for ease of manufacturing and mechanical attachment to subsequent devices.

[0040] In the figures, the first width W1 of the first optical structure P1 is generally depicted as being substantially equal to the second width W2 of the second optical structure P2. As in some examples detailed below, the widths of the optical structures are not necessarily equal. The width of the optical structure is generally along the minor axis of the light pipe 600 as compared to the major axis (e.g., the longitudinal axis R1) of the light pipe 600, or in other words, generally perpendicular to the longitudinal axis R1.

[0041] Figure 4 is a schematic diagram of a light pipe 600D similar to the light pipe 600C of Figure 3. In this figure, the light path, ray L1, undergoes an additional reflection 640 by Fresnel reflection inside the first optical structure P1 at the second surface S12, thereby reflecting ray L12 towards the fourth outer side wall S15 of the light pipe 600D. A second additional reflection 642 (by total internal reflection) at the fourth outer side wall S15 reflects ray L13 towards the second surface S12. Ray L13 refracts from the first optical component P1 to the second optical component P2 and continues along the light path as described above.

[0042] FIG. 5 is a schematic diagram of a light pipe 600E according to another embodiment, similar to the light pipe 600D of FIG. 4. In this embodiment, the optical structure is implemented as two prisms constructed from the same material and separated by a gap 650, in this case an air gap. In this case, the interface 620 includes the second surface S12, the third surface S21, and the area of ​​the gap 650. The first prism is a first optical structure P1 having a first refractive index η1, and the second prism P11 is another optical structure having a first refractive index η1. As mentioned above, this exemplary implementation is not limiting and more than two optical structures can be used. Two or more of the optical structures can have different refractive indices, or two or more of the optical structures can have the same refractive index. The outer sidewalls are designated as the first outer sidewall S24, the second outer sidewall S25 for the second optical structure P2, and the third outer sidewall S14, the fourth outer sidewall S15 for the first optical structure P1. The angles and spacing of the (air) gap 650 relative to the outer sidewalls (S14, S15, S24, S25) of the prisms (P1, P11) and the angles of the optical structure faces (e.g., the second face S12 and the third face S21 can be parallel or non-parallel to each other) are determined so that the full range of useful light rays propagating in the light pipe (among the light rays 652) reflects in the gap by total internal reflection, then reflects from the fourth outer sidewall S15 (by total internal reflection), and again enters the gap at an angle less than the critical angle, thereby being transmitted from the first prism P1 through the gap 650 to the second prism P11. As a result, the beam (between rays 652) is narrowed (range between beams 654) and diverted. Note that if the reflection at the gap 650 following reflection from the upper fourth outer sidewall S15 of the first prism P1 is incident at or below a critical angle that prevents transmission at the gap 650, a mirror (e.g., a reflective coating or surface) may be applied to the area of ​​the upper fourth outer sidewall S15 where the reflection occurs.

[0043] FIG. 6 shows a variation of the embodiment illustrated in FIG. 2B with an additional component shown in FIG. 7, in which there are two internal reflections of the main ray (paths L0, L1, L2, L21, L22, L3). In this embodiment, in the second optical structure P2, the first outer sidewall S24 of the light pipe 600F can be coated with a reflective coating layer so that the light path (in this case, ray L2) is further reflected by the first outer sidewall S24 in the light pipe 600F at a certain angle (the ninth angle, α, “alpha”) to become ray L21. Similarly, the second outer sidewall S25 of the light pipe 600F can be coated with a reflective coating layer so that the light path (in this case, ray L21) is further reflected by the second outer sidewall S25 in the light pipe 600F at a certain angle (the tenth angle, β) to become ray L22. Alternatively or additionally, the light pipe 600 may be configured such that the outer sidewalls (in this case the first outer sidewall S24 and the second outer sidewall S25) reflect one or more portions of the light path using total internal reflection (TIR).

[0044] The fifth reference line S5 is a construction line perpendicular to the input surface S01. The fifth reference line S5 intersects with the second outer sidewall S25. A tenth angle (β) is defined between the fifth reference line S5 and the second outer sidewall S25. The tenth angle (β) is used to help define the orientation of the second outer sidewall S25 relative to the other surfaces of the light pipe 600. In this embodiment, the incidence angle θ of the optical axis before returning to the second medium P3 is 23 is the formula θ 23 =θ 21 It is given by -(δ-γ)-2*α-2*β.

[0045] Figure 7 is a schematic diagram of a light pipe 600F according to the embodiment of Figure 6. For clarity, not all elements of Figure 6 are shown. In this figure, the side walls (S24, S25) of the second optical structure P2 are parallel to each other and perpendicular to the input face S01. Thus, the fourth reference line S4 is parallel and therefore coincides with the first outer side wall S24, and the ninth angle (α) is zero (0°). Similarly, the fifth reference line S5 is parallel and therefore coincides with the second outer side wall S25, and the tenth angle (β) is zero (0°).

[0046] FIG. 8 shows a representation of a variation of the embodiment shown in FIG. 9, further including that the input surface S01 is angled. In combination with any of the above-mentioned embodiments, the light pipe 600 can be angled such that the external input surface S01, which is the incident surface (i.e., the interface between the base medium P0 and the first optical structure P1), is inclined at a certain angle (the eleventh angle Ψ, "psi"). Note that the representation shown in FIG. 8 is the representation shown in FIG. 6 with an additional inclination angle Ψ. The inclination angle can also be applied to other representations such as FIG. 2B. As in the above description, the sixth reference line S6 is a construction line that is used as a reference instead of the input surface S01 since the input surface S01 is inclined. The sixth reference line S6 intersects with the input surface S01. The eleventh angle (Ψ) is defined between the sixth reference line S6 and the input surface S01. The eleventh angle (Ψ) is used to help define the orientation of the input surface S01 with respect to the other surfaces of the light pipe 600G.

[0047] 9 is a schematic diagram of a light pipe 600G according to another embodiment of the present invention, in which the outer sidewalls of the light pipe (i.e., the outer sidewalls of the two optical structures) are tapered, resulting in a light pipe with tapered sidewalls. The first optical structure P1 has a first width W1 at the input end 602, which is also the width of the input surface S01 in this figure. The first optical structure P1 increases in width along the longitudinal axis R1 in the direction of the optical path (light ray L1) and has a third width W11 near the second surface S12. The second optical structure P2 has a fourth width W22 near the third surface S21. The second optical structure P2 decreases in width along the longitudinal axis R1 in the direction of the optical path (L2, L21, L22) from the second surface S12 to the output surface S23 and has a second width W2 near the output surface S23. Alternatively, the first optical structure P1 (not shown in this figure) may decrease or remain constant in width along the longitudinal axis R1, and the second optical structure P2 may increase or remain constant in width.

[0048] In this figure, the ninth angle (α) and the fourth reference line S4 of the first outer sidewall S24, and the tenth angle (β) and the fifth reference line S5 of the second outer sidewall S25 are shown. Corresponding reference lines and angles are not shown for the third outer sidewall S14 and the fourth outer sidewall S15. Based on this description, one skilled in the art will be able to properly handle these elements.

[0049] FIG. 10 is a schematic diagram of a light pipe 600I in which different structures (portions) of the light pipe with equal joint surface angles are separated by an air gap 660. In this exemplary diagram, the optical structures are two structures (P1, P2) that can have the same or different refractive index. This diagram is similar to FIG. 5. In this exemplary diagram, the second surface S12 and the third surface S21 are at a gap angle 1000 with each other, compared to the exemplary embodiment of FIG. 5 in which the second surface S12 and the third surface S21 are parallel to each other. In this case, the interface 620 includes the area of ​​the second surface S12, the third surface S21, and the gap 660. The second surface S12 is perpendicular to the longitudinal axis R1 (and parallel to the input surface S01), while the third surface S21 is oblique to the longitudinal axis R1, so that the interface 620 is considered to be oblique to the longitudinal axis R1 of the light pipe 600.

[0050] 11 and 12 are schematic diagrams of light pipes (600J, 600K) in which different optical structures (P1, P2) are separated by a gap 670, optionally filled with an optical medium 672 having a corresponding gap refractive index η4. In this case, the interface 620 includes a region of the second surface S12, the third surface S21, the gap 670, and the optical medium 672. Optical media include, for example, optical adhesives and optical gels. At least two different refractive indices must be used for the three structures [first optical structure P1 (η1), second optical structure P2 (η2), gap 670 (η4)] so that the light path is refracted along the longitudinal axis R1. Although the figures are depicted with the gap 670 between parallel surfaces, in this case the second surface S12 and the third surface S21, this implementation is not limiting and the gap 670 can include a gap angle 1000, as described with reference to FIG. 10. In implementations where the separation is by an optical medium, it is possible to increase the distance (width) between the outer sidewalls of the light pipe (i.e., make the light pipe wider) in the section of the light pipe after the interface 620 of the two different refractive indexes to improve efficiency. In this case, widening the second optical structure P2. Optionally, one or more anti-reflective coatings can be added between the different optical structures, for example to improve the efficiency of light transmission from the first P1 to the second P2 optical component.

[0051] 11 shows a light pipe 600J where the distance between the outer sidewalls remains constant, resulting in light loss, i.e., reduced efficiency. In this figure, the first width W1 of the first optical structure P1 is substantially equal to the second width W2 of the second optical structure P2. A portion of the output ray L33 does not leave the light pipe 600J with the rest of the beam (output ray L3) and falls within a band W33 where it is lost to the system (not output within the usable range of output angle from the output surface S23) due to additional reflection from the top surface (first outer sidewall S24).

[0052] FIG. 12 shows a light pipe 600K in which the distance between the outer sidewalls (first outer sidewall S24 and second outer sidewall S25) in the section after the interface 620 (after the gap 670, second optical structure P2) is increased from the second width W2 to a fifth width W23, thereby maintaining efficiency as can be seen from all of the output light rays L31 being output from the output surface S23. In this case, the fifth width W23 is larger than the second width W2. As a result, the light pipe 600K has a second section (corresponding to the second optical structure P2, i.e., the prism) that is wider than the first section (corresponding to the first optical structure P1, i.e., the prism).

[0053] 13A is a schematic diagram of a light pipe 1300A comprised of a single base optical structure 1310 formed as a slab type structure with angled entrance 1302 and exit 1304 faces. The optical structure 1310 may be formed by taking a rectangular slab and making corresponding bevel cuts at the ends of the slab. As a result, the light pipe 1300A has a trapezoidal cross section on the page. When implemented as an isosceles trapezoid, the angle of incidence of input light L0 entering the light pipe 1300A through entrance face 1302 and the angle of light coupled out of the light pipe 1300A's L4 through exit face 1304 are equal.

[0054] Figure 13B is a schematic diagram of the light pipe 1300A of Figure 13A where the input light L0 is at a different angle relative to the input face 1302. The light pipe 1300A shown in Figure 13A has the advantage of being formed from a single structure (base 1310), however, the light pipe 1300A may suffer from coupling out light loss, i.e. reduced efficiency, indicated by output light L5 coupling out from the outer wall of the light pipe 1300A and not from the output face 1304.

[0055] FIG. 13C is a schematic diagram of a light pipe 1300B including a variation of the embodiment shown in FIG. 13A and FIG. 13B. The light pipe 1300B of this embodiment avoids the loss of the coupling-out light L5, thereby maintaining efficiency. In this embodiment, an additional optical structure 1312 in the form of a coupling-out wedge (e.g., a prism) is attached to the single-base optical structure 1310. In this case, the previous exit surface 1304 of the single-base optical structure can be replaced by forming the exit surface 1306 of the single-base optical structure 1310 by making a vertical cut at the right end of the single-base optical structure 1310 (non-limiting directional reference as drawn on the sheet) resulting in a right trapezoid in cross section on the paper. The two optical structures (1310, 1312) may have different refractive indices or may have the same refractive index to prevent undesired reflection / refraction at the joint surface (i.e., interface 620) between the two optical structures (1310, 1312). The light pipe 1300B now has a new output face 1308 from an additional optical structure 1312.

[0056] 13D is a schematic diagram of the light pipe 1300B of FIG. 13C showing coupling-in losses. Although this light pipe 1300B avoids coupling-out light losses L5, the light pipe 1300B may incur coupling-in light losses L6 due at least in part to the refractive index of the material from which the single base optical structure 1310 is formed. As seen in this figure, if the refractive index of the single base optical structure 1310 is not high enough, some of the light rays L0 entering the single base optical structure 1310 through the entrance surface 1302 may be refracted at a steep angle such that the refracted light rays are not totally internally reflected within the single base optical structure 1310 when they hit the bottom surface of the single base optical structure 1310. Therefore, the material from which the two optical structures (1310, 1312) are formed preferably has a sufficiently high refractive index (preferably 1.60 or greater) so that a light ray L0 entering the single base optical structure 1310 through the incident surface 1302 is refracted at a shallow enough angle to undergo total internal reflection (TIR) ​​when it hits the bottom surface of the single base optical structure 1310.

[0057] FIG. 13E is a schematic diagram of the light pipe 1300B of FIGS. 13C and 13D, in which the single base optical structure 1310 is made from a material with a sufficiently high refractive index such that the input light L0 refracts at a sufficiently high angle at the input surface 1302, resulting in TIR when it hits the bottom surface of the single base optical structure 1310.

[0058] Figure 13F is a schematic diagram of a light pipe 1300C that is a variation of light pipe 1300B of Figure 13C. In this figure, input face 1302A is "flipped" vertically on the sheet from input face 1302, thereby providing a single base optical structure 1310 with input face 1302A rotated 90 degrees from input face 1302 of light pipe 1300B described earlier. The functionality of both light pipes (1300B, 1300C) is maintained.

[0059] FIG. 13G is a schematic diagram of a variation of the embodiment shown in FIG. 13C. The light pipe 1300B is part of an optical device in which a collimating lens 1320 is disposed at or near the input surface 1302 of a single base optical structure 1310 (i.e., a trapezoidal structure). The use of a collimating lens narrows the angular range of the light source beam L7 and reduces coupling-in losses of the input light beam L0 into the light pipe 600. The collimating lens 1320 may be attached to the input surface 1302 via an optical adhesive or may be disposed near the input surface 1302 with an air gap maintained between the collimating lens 1320 and the input surface 1302. In embodiments in which an air gap is maintained, the collimating lens 1320 may be held in place via a mechanical arrangement. The light source 610 provides light to the collimating lens 1320, which collimates the provided light and outputs a collimated beam of light L01 to the input surface 1302. This configuration provides a collimated output beam L31.

[0060] Fig. 13H is a schematic diagram of a variation of the embodiment shown in Fig. 13G. In this embodiment, a Fresnel lens 1330 is used instead of the collimating lens 1320. The use of the Fresnel lens 1330 has the advantage of providing the light beam L01 covering a wider range of angles to the entrance surface of the single-base optical structure 1310 compared to the use of the collimating lens 1320. Another advantage of using the Fresnel lens 1330 is mechanical, providing a smaller focal length in the same volume compared to the collimating lens 1320. The Fresnel lens 1330 can be configured in an optical device having a single-base optical structure 1310, for example, using an optical adhesive or an air gap, similar to the provision of the collimating lens 1320 described above.

[0061] FIG. 13I is a schematic diagram of a variation of the embodiment shown in FIG. 13A and FIG. 13G. In this embodiment, a cone 1340 (e.g., made of glass or plastic) is used instead of the collimating lens 1320. Using the cone 1340 has the advantage of using reflection instead of refraction. The cone 1340 collects the source beam L7 better than the collimating lens 1320, in part because the light source 610 (e.g., an LED) can be brought into contact with the entrance of the cone 1340. Typically, when using a normal lens such as the collimating lens 1320, a distance between the light source 610 and the lens surface must be maintained. For example, the lens may not work properly if the light source is not in the focal plane of the lens. As a result, high angle rays are lost from the source beam L7. The cone 1340 can be used to collect relatively high angle rays from the source beam L7. In an alternative embodiment, instead of using the cone 1340, a reflective lens with curved (non-straight) sidewalls can be used. The cone 1340 can be configured in the optical device 1300D having the single base optical structure 1310, similar to the provision of the collimating lens 1320 described above, using, for example, an optical adhesive or an air gap.

[0062] In this figure, the output of the single base optical structure 1310 is an exit surface 1304, as described above with reference to Figure 13A. In this embodiment, a diffuser 1350 is configured adjacent to the exit surface 1304. One exemplary advantage of using a diffuser is improved color mixing. The use of a diffuser at the output of the light pipe and as a component of the optical device is an optional embodiment.

[0063] According to certain embodiments, the optical structures forming the light pipe may be arranged such that the optical axis R01 at the entrance surface / opening S01 (i.e., the interface between the base medium P0 and the first optical structure P1) is perpendicular to the optical axis R23 at the exit surface / opening S23 (i.e., the interface between the second optical structure P2 and the base medium P3).

[0064] According to certain embodiments, an anti-reflective coating may be applied to the interface between the two optical structures that form the light pipe (i.e., the interface 620 where the two surfaces abut, or on the surface adjacent to the air gap).

[0065] According to certain embodiments, a reflective coating may be applied to some or all of the exterior surface (outer sidewall) of the light pipe.

[0066] According to certain embodiments, an index-matched optical adhesive or gel can be disposed between the two optical structures forming the light pipe. The index of refraction of the optical adhesive or gel can be matched to one of the juxtaposed materials from which the optical structures are constructed.

[0067] According to certain embodiments, an intentionally index-mismatched optical adhesive or gel can be placed between the two optical structures that form the light pipe.

[0068] Those skilled in the art will appreciate the typical dimensions and requirements for general light pipe operation. For example, the major dimension (606) of the light pipe (600), typically referred to as the length of the light pipe 600, is significantly longer (e.g., an order of magnitude larger) than the minor dimension (width) of the light pipe. The cross section of the light pipe 600 is typically rectangular, although this is not limiting and other cross sections, for example, circular, can be used. A typical thickness of the light pipe 600 is 1-5 mm. A typical length of the light pipe 600 is 10-60 mm.

[0069] The light pipe 600 transmits light (input ray L0) from input face S01 to output face S23, preferably with negligible illuminance loss. An embodiment of the invention redirects the incoming light so that light enters the light pipe 600 at a given aperture and exits the light pipe 600 at a substantially similar aperture. The optical path of the light is redirected, resulting in a deviation of the optical path through the light pipe 600.

[0070] The range of angles of the input light can be various. For example, the external input angle θ of the input light L 01 L0 may be any ray of a cone of light originating from the light source 610 and striking the external input surface S01. As another non-limiting example, the input light L0 may be asymmetric about the input surface normal R01, for example at an angle of -30° to +40°. Currently used LED light sources include possible inputs of +-90°. Similarly, the output light L3 may have an output angle θ of 0° to +-60° (for simplicity, referred to simply as +-60°). 32In another non-limiting example, the output light L3 may be asymmetric around the output surface normal R23, for example, at angles between -20° and +30°. One preferred implementation is an output range of +-40°. The light pipe 600G of FIG. 9 may be used to change the angular range of the output light L3. For example, tapering the second optical structure P2 may be used to reduce the range of output angles and / or to focus the propagating light rays to a desired angle. Similarly, if the range of input angles is wider (larger) than the desired range at the output, the second optical structure P2 may be tapered to reduce the angular range of the output. Similarly, if the range of input angles is narrower (smaller) than the desired range at the output, the second optical structure P2 may be widened (W22 to W2) to increase the angular range of the output.

[0071] FIG. 14A is a schematic diagram of an alternative implementation of a light pipe. While the embodiments described so far have involved a light pipe constructed from two main optical structures (e.g., prisms, e.g., first optical structure P1 and second optical structure P2) with different refractive indices, other embodiments are possible in which a single main optical structure (i.e., block, here first optical structure P1) is used in combination with, for example, an array of microprisms 1360 arranged at the output face S12 of the block. The figure shows an embodiment in which the light pipe remains in a single main block (P1) and the direction of the emitted light L31 at the block output can be adjusted via the array of microprisms 1360 at the block output. The array of microprisms 1360 can be used to change the direction of the emitted light L31 to be non-perpendicular to the face S12. Alternatively, the same or similar functionality can be achieved by providing a commercially available redirecting film (DTF) at the block output S12.

[0072] 14B is a schematic diagram of a variation of the embodiment shown in FIG. 14A. In this figure, a diffuser 1360 is provided at the output of the array of microprisms 1360. The diffuser 1350 has the effect of further diffusing the light output by the microprism array, covering a wider range of angles L32 and / or improving color mixing. The diffuser 1350 can be used to achieve a range of angles around a central ray (of the output ray L31), shown as angle L32.

[0073] The diffuser 1350 in FIGS. 14B, 14C diffuses the light L32 output by the additional optical structure 1312 to cover a wider range of angles and / or improve color mixing.

[0074] FIG. 15A is a schematic diagram of a side view 1500 and a top view 1502 of the light pipe of FIGS. 13C-13I. This diagram defines the dimensions of the outcoupling wedge (additional optical structure 1312) to avoid, at least in part, the loss of light from the single base optical structure 1310 that is output from the new output face 1308. "Y" is the minimum length of the outcoupling wedge (along the edge from the single base optical structure to the output face), "h" is the height of the single base optical structure 1310, "Z" is the length of the light pipe from the input face to the output face, "a" is the angle at which the incident light ray reflects off the side of the light pipe and the extension of the wedge intersects with the other face of the light pipe, "H" is the height of the outcoupled light ray (from the edge of the wedge / additional optical structure 1312 to the output face), "V" is the height of the wedge beyond the base optical structure 1310 of the light pipe, and "θ" is the angle of the wedge between the output face and the face of the base optical structure 1310.

[0075] "Y=h tan a Z" is the minimum length of the outcoupling wedge (additional optical structure 1312) to avoid loss of propagating light in the light pipe 1500 due to TIR.

[0076] "H=h+[V / [1+[tan θ / tan a]]]" where "H" is the minimum height of the outcoupling wedge (additional optical structure 1312).

[0077] A typical ratio to allow sufficient color mixing is 5<[Z / h]<10.

[0078] 16A is a schematic diagram of a conventional folded light pipe 1600 that uses a reflective coating 1606 (i.e., a mirror coating) to redirect the light path of input light 1602 to output light 1603. In this configuration, light may be lost during propagation through the light pipe 1600 via at least two ray arrangements, e.g., input light 1604 couples out as lost output light 1605 and input light 1608 couples out (escapes) as lost output light 1609.

[0079] In this and subsequent figures, for clarity, bending of the optical path is not shown.

[0080] 16B is a schematic diagram of a modified light pipe 1610. In this embodiment, an interface 1620 is configured between the first optical structure P1 and the fourth optical structure P4, and also between the fourth optical structure P4 and the second optical structure P2. The fourth optical structure P4 has a mirrored inner surface 1606 configured on a side of the fourth optical structure P4 other than the side adjacent to the first P1 and second P2 optics.

[0081] 16B is a schematic diagram of a modified light pipe 1610. In this embodiment, an interface 1620 is configured between the first optical structure P1 and the fourth optical structure P4, and also between the fourth optical structure P4 and the second optical structure P2.

[0082] The fourth optical structure P4 has a mirrored inner surface 1606 configured on a side of the fourth optical structure P4 other than the side adjacent to the first P1 and second P2 optical structures. A regular interface 1620 uses a low index optical adhesive. This low index interface 1620 allows low angles (relative to the surface normal) of the propagating light rays to pass through the interface 1620, while high angles of the propagating light rays are reflected by TIR.

[0083] The interfaces 1620 (each interface shown as exemplary interfaces 1620A and 1620B) at least partially create the TIR 1616 (shown as respective exemplary TIRs 1616A and 1616B) and avoid light loss. In this figure, the interfaces 1620 create the TIR in the region 1616. The propagating input light 1604 experiences the TIR 1616B at the interface 1620B, and the light continues through the second optical structure P2 and exits the output face of the light pipe 1610 as output light 1615. The propagating input light 1608 experiences the TIR 1616A at the interface 1620A, and the light continues through the second optical structure P2 and exits the output face of the light pipe 1610 as output light 1619. Thus, the two ray configurations (FIG. 16A, 1605, 1609) that were lost in the conventional implementation (input rays 1604 and 1608) are maintained (1615, 1619) using this embodiment of the additional low index interface 1620.

[0084] In an alternative embodiment, the interface 1620 may be implemented with an air gap. In this figure, in a non-limiting implementation, the input surface S01 and the output surface S23 are tilted in opposite directions (e.g., perpendicular) to the tilt of the mirror 1606. As described above, the tilt of the input surface S01 can be described using an eleventh angle (Ψ) and the tilt of the output surface S23 can be described using an eighth angle (γ).

[0085] FIG. 16C is a schematic diagram of the modified light pipe 1610 of FIG. 16B, but shown in three dimensions (3D) and with alternative tilts and rotations of the input and output faces. In this embodiment of the light pipe 1630, the input face S01 and the output face S23 are tilted in the same direction (e.g., parallel) to the tilt of the mirror 1606. As discussed above, the input face S01 and the output face S23 can be tilted at any angle relative to the axis of the light pipe 600. Preferably, the input face S01 and the output face S23 are tilted between 0° (zero) and 45°, and most preferably at 45°. The input faces can also lack tilt, i.e., be straight, as discussed above with reference to the light pipes 600A of FIG. 2A and 600C of FIG. 3, for example.

[0086] Also, in this embodiment, the input surface S01 and the output surface S23 are rotated. The input surface S01 is rotated with respect to the (first) longitudinal axis R1 of the first optical structure P1 as shown by the arrow 1601. Similarly, the output surface S23 is rotated with respect to the second longitudinal axis R2 of the second optical structure P2 as shown by the arrow 1623. The input surface S01 and the output surface S23 can be rotated at any angle with respect to the axis of the light pipe 600. Preferably, the input surface S01 and the output surface S23 are rotated in 90° increments (0°, 90°, 180°, 270°).

[0087] Based on this description, one skilled in the art will be able to select and design the refractive index of the interface 1620 (e.g., by selecting an optical adhesive with an appropriate refractive index) that is close enough to the refractive index of the optical structures (P1, P2) to avoid light rays being reflected backwards (towards the input surface) by TIR, but different enough (far enough) from the refractive index of the optical structures (P1, P2) to implement sufficient TIR so that light does not escape out the sides of the light pipe 600.

[0088] It should be noted that the rotations discussed with reference to light pipe 1630 in this figure are applicable to all of the light pipes 600 discussed above.

[0089] It should be noted that the above examples, the numerical values ​​used, and the exemplary calculations are intended to aid in the explanation of the present embodiment, and that inadvertent typographical errors, mathematical errors, and / or the use of simplified calculations do not detract from the utility and fundamental advantages of the present invention.

[0090] To the extent that the appended claims have been drafted without multiple dependencies, this has been done solely to accommodate formal requirements in jurisdictions that do not permit such multiple dependencies. It should be noted that all possible combinations of features implied by making the claims multiple dependent are expressly contemplated and should be considered part of the present invention.

[0091] The description of various embodiments of the present disclosure has been presented for illustrative purposes, but is not intended to be exhaustive or limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terms used herein are selected to best explain the principles of the embodiments, practical applications or technical improvements to the technology found in the market, or to enable those skilled in the art to understand the embodiments disclosed herein.

[0092] As used herein, the singular forms "a," "an," and "the" include plural references unless the context clearly dictates otherwise.

[0093] The word "exemplary" is used herein to mean "serving as an example, instance, or illustration." Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and / or to exclude the incorporation of features from other embodiments.

[0094] It is understood that certain features of the invention that are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, for brevity, various features of the invention that are described in the context of a single embodiment may also be provided separately or in any suitable subcombination or as preferred in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperable without those elements.

Claims

1. An apparatus comprising: A light pipe (600) comprising at least: (i) the first refractive index (η １ a first optical structure (P1) having an input surface (S01) at a proximal end of the light pipe (600) where light from a light source is input into the light pipe (600), and a second surface (S12); (ii) a second refractive index (η ２ a second optical structure (P2) having a third surface (S21), and an output surface (S23) at a distal end of the light pipe (600) where light is output from the light pipe (600); The light pipe (600) further comprises: a longitudinal axis (R1) parallel to a major dimension (606) of the first optical structure (P1) in a direction between the input surface (S01) and the second surface (S12); an interface (620) between the second surface (S12) and the third surface (S21) that is oblique to the longitudinal axis (R1) of the light pipe (600) such that an input light ray (L0) to the input surface (S01) parallel to the longitudinal axis (R1) is output from the output surface (S23) as an output light ray (L3) that is not parallel to the input light ray (L0); The light pipe (600) is coupled to a frame of a mechanical body that supports the device on a user's head, and the light pipe (600) is aligned with the frame so that the longitudinal axis (R1) of the light pipe (600) is parallel to the elongation direction of the frame.

2. 2. The apparatus of claim 1, wherein an angle between the input light ray (L0) and the output light ray (L3) is an optical deviation angle of the light pipe (600), the optical deviation angle being other than zero degrees (0°).

3. 2. The device of claim 1, wherein the angle between the longitudinal axis (R1) and an output surface normal (R23) is a mechanical deflection angle of the light pipe (600), the mechanical deflection angle being other than zero degrees (0°), and the output surface normal (R23) being perpendicular to the output surface (S23) of the second optical structure (P2).

4. At least the first (P1) and second (P2) optical structures define an optical path for light through the light pipe (600), the optical path comprising: (a) coupling in via the input surface (S01); (b) traversing the first optical structure (P1); (c) refracting the first (P1) to the second (P2) optical structure through the interface (620) from the second (S12) to the third (S21) surface; (d) traversing the second optical structure (P2); and 2. The apparatus of claim 1, wherein: (e) a first optical axis is at least partially defined by the light coupling out of the second optical structure (P2) via the output face (S23).

5. The apparatus of claim 4, wherein at least one outer sidewall (S14, S15, S24, S25) of the first (P1) and second (P2) optical structures is coated with a reflective coating, the reflective coating constraining the optical path within the light pipe (600).

6. 2. The device according to claim 1, wherein an anti-reflective coating is added to at least one surface (S01, S12, S21, S23) of said at least first (P1) and said second (P2) optical structures.

7. The apparatus of claim 1 , wherein the second surface (S12) is adjacent to the third surface (S21).

8. The apparatus of claim 1 , wherein the second surface (S12) is separated from the third surface (S21) by a gap (660, 670).

9. The gap is (a) air, (b) an optical adhesive; and 10. The device of claim 8, wherein the device is filled with a material selected from the group consisting of: (c) optical gels.

10. 9. The apparatus of claim 8, wherein the third surface (S21) is arranged at a gap angle (1000) with respect to the second surface (S12).

11. 9. The device of claim 8, wherein the first optical structure (P1) has a first width (W1) and the second optical structure (P2) has a fifth width (W23), the fifth width (W23) being greater than the first width (W1).

12. 2. The device of claim 1, wherein a third width (W11) of the first optical structure (P1) and / or a fourth width (W22) of the second optical structure (P2) vary along the longitudinal axis (R1) of the light pipe (600).

13. 2. The device of claim 1, wherein the output face (S23) is at an eighth angle (γ, “gamma”) and / or the input face (S01) is at an eleventh angle (φ, “si”) with respect to the longitudinal axis (R1) of the light pipe (600).

14. The apparatus of claim 1 , further comprising a light source (610) providing input light (L0, L7) to the input face (S01) of the light pipe (600).

15. The apparatus of claim 1 , further comprising a projection optical system (612), the light pipe (600) configured to provide the output light beam (L3) as an input to the projection optical system (612).

16. The apparatus of claim 1 , wherein the major dimension (606) of the light pipe (600) is at least an order of magnitude greater than a width (W1, W11, W2, W22) of the light pipe (600).

17. An apparatus comprising: A light pipe (600) comprising at least: (i) the first refractive index (η １ a first optical structure (P1) having an input surface (S01) at a proximal end of the light pipe (600) where light from a light source is input into the light pipe (600), and a second surface (S12); (ii) the first refractive index (η １ a second optical structure (P2) having a third surface (S21), and an output surface (S23) at a distal end of the light pipe (600) where light is output from the light pipe (600); The light pipe (600) further comprises: a longitudinal axis (R1) parallel to a major dimension (606) of the first optical structure (P1) in a direction between the input surface (S01) and the second surface (S12); an interface (620) between the second surface (S12) and the third surface (S21) that is oblique to the longitudinal axis (R1) of the light pipe (600) such that an input light ray (L0) to the input surface (S01) parallel to the longitudinal axis (R1) is output from the output surface (S23) as an output light ray (L3) that is not parallel to the input light ray (L0); the second surface (S12) is separated from the third surface (S21) by a gap (660, 670); The light pipe (600) is coupled to a frame of a mechanical body that supports the device on a user's head, and the light pipe (600) is aligned with the frame so that the longitudinal axis (R1) of the light pipe (600) is parallel to the elongation direction of the frame.

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