Patent Application
20050244126
Optical devices, such as digital projectors include numerous components to process light from a light source to, for example, a screen. One of these components is a light guide, also referred to in the art as integrated rod or a spatial homogenizer.
Light guides include a hollow tunnel, with the internal walls being highly reflective. The light from a light source is typically not uniform. For example, the intensity of the light may be significantly greater at the center of the beam than at the perimeter. To correct for this non-uniformity, a light guide is positioned in the light path between the source and an image processing portion. Thus, the light exiting the guide has a substantially homogeneous cross-section and is delivered to the image processing portion.
The cross-section of the light exiting the guide in various designs is dimensioned to correspond to the desired aspect ratio of the final image. For example, certain media formats require an aspect ratio of 16:9. For such cases, the cross-section of the light exiting the guide must also have an aspect ratio of 16:9. In order to achieve this, light guides are generally designed to have very precise dimensions.
One embodiment of the invention relates to a guide, such as a light guide. The guide includes a plurality of plates positioned to form a tunnel. Each of the plates has a reflective internal surface with first and second opposing ends, and a side edge along the first opposing end. The side edge along the first opposing end of each plate abuts an internal surface of a first adjacent plate, and the internal surface of each plate is abutted by a side edge of a second adjacent plate.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and exemplary only, and are not restrictive of the invention as claimed.
FIGS. 6A-D illustrate a method for making the light guide of
In the figures, like numerals are used to represent like elements.
Light from the light source 112 is passed through a light guide 114. Light guides are also known in the art as light homogenizers, a spatial homogenizers or integrated rods. The light guide 114 outputs a substantially homogeneous beam of light for delivery to the image processing portion 130.
Referring to
Each of the plates has an internal surface 31b, 32b, 33b, 34b, respectively, with first and second opposing ends. The internal surfaces 31b, 32b, 33b, 34b of each plate 31, 32, 33, 34, respectively, are formed to be highly reflective. In a particular embodiment, the internal surfaces are provided with a dielectric mirror or reflective coating. Thus, light entering the guide 30 can strike the walls of the tunnel 36 and be reflected as it travels through the tunnel 36 with minimal loss of intensity.
Each of the plates 31-34 has side edges (31a, 31c, etc.) along the opposing ends. In the exemplary embodiment of
The light guide 30 is formed by arranging the plates 31-34 such that one side edge of each plate abuts an internal surface of one adjacent plate, and a side edge of another adjacent plate abuts the internal surface of the plate. Thus, the left side edge 31c of the top plate 31 abuts the internal surface 33b of the adjacent left vertical plate 33, while the edge 34c of the adjacent right vertical plate 34 abuts the internal surface 31b of the top plate 31. Each of the other plates 32-34 forming the light guide 30 is similarly situated between two adjacent plates.
In this configuration, each plate 31-34 is not required to be dimensioned with great precision, thereby reducing the cost of fabricating the plates. As can be seen in the illustration of
Referring now to
A central block 42 is disposed on the base 41 and serves as a template for the light guide to be formed. The central block 42 is raised from the surface of the base 41 sufficiently to support the plates used to form the light guide 30 and includes walls to position the plates according to the desired aspect ratio. Thus, the formation of the block should be sufficiently precise to satisfy the requirements of the final product (e.g., the light guide, digital projector, etc.).
In particular, the four walls of the central block 42 should be dimensioned to correspond to the dimensions of the light guide. In this regard, the central block 42 includes top wall 44a, bottom wall 44b, left wall 46a, and right wall 46b. Adjacent walls are separated by a corner cutaway 48 which may facilitate assembly of the light guide.
A plate securing arrangement 50 is provided across from each wall 44a, 44b, 46a, 46b of the central block 42 for positioning and securing a plate of a light guide against the wall of the central block 42. In the illustrated embodiment, each plate securing arrangement 50 includes a rigid support 52 fixedly attached to the base 40 and in a fixed position relative to the central block 42. The plate securing arrangement 50 of the illustrated embodiment also includes a fastener 54 projecting through a hole 52a in the rigid support 52. The fastener 54 is adapted to be selectively moved forward or backward to secure or release a plate against a wall of the central block 42. The fastener 54 and the through hole 52a may be correspondingly threaded to facilitate the selective movement.
An initial positioning support 56 is provided fixedly positioned on the base 41 to facilitate positioning of the first plate in the formation of the light guide. While the walls of the central block 42 and the plate securing arrangement 50 facilitate proper positioning of an internal surface of a plate, the initial positioning support 56 forms a guide for the proper positioning of a side edge of the first plate to be positioned during the light-guide formation process. In this regard, the initial positioning support 56 of the illustrated embodiment includes a positioning surface 56a. The positioning surface 56a is adapted to position a side edge of a plate on the left wall 46a such that the side edge is aligned with the plane of the bottom wall 44b. Thus, in the illustrated embodiment, the positioning surface 56a is formed as a flat surface aligned with the plane of the bottom wall 44b.
The initial positioning support 56 of the illustrated embodiment is formed in a triangular shape. Of course, those skilled in the art will recognize that many other shapes are possible to provide a positioning surface 56a for aligning a plate edge with the bottom wall 44b. In the illustrated embodiment, while one leg of the triangle forms the positioning surface 56a, the other leg forms a surface 56b that is offset from the plane of the left wall 46a. As illustrated below in
As noted above, the positioning surface 56a of the initial positioning support 56 is aligned with the bottom surface 44b of the central block 42. In a particular embodiment, this alignment is facilitated by forming the apparatus 40 in two segments. In this regard, the base 41 is divided into two separate sections 41a, 41b. The separation of the two sections 41a, 41b is indicated by the dashed line in
The formation of an exemplary light guide using the apparatus illustrated in
Next, as shown in
The third plate (right plate 34 with side edges 34a, 34c and internal surface 34b) is similarly positioned against the right wall 46b, as shown in
Referring now to
In certain embodiments, the initial positioning support 56 may be eliminated. In these embodiments, the first plate (e.g., the left plate 33) may be positioned against the left wall 46a in a position that allows the top plate 31 to abut the internal surface 33b. When the fourth plate (bottom plate 32) is positioned against the bottom wall 44b and abutting the internal surface 34b of the right plate 34, the first plate 33 may be released by the plate securing arrangement and allowed to slide until the side edge 33c abuts the internal surface 32b of the bottom plate 32.
With the plates 31-34 secured in place by the plate securing arrangements 50, an adhesive may be applied to external corners at the junction of adjacent plates to complete the light-guide formation.
It is noted that the figures and description above refer to light guides and the formation of light guides having a rectangular cross section. It will be understood by those skilled in the art that light guides having any other cross-sectional configuration may also be similarly provided. All such configurations are contemplated within the scope of the invention.
The foregoing description of embodiments of the invention have been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variation are possible in light of the above teachings or may be acquired from practice of the invention. The embodiment was chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modification as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
