WO2003021330A1

WO2003021330A1 - Light integrator

Info

Publication number: WO2003021330A1
Application number: PCT/EP2002/009742
Authority: WO
Inventors: Dr. Lars Bewig; Dr. Wolfram Maring; Thomas Kuepper; Dr. Christoph Moelle; Frank Koppe
Original assignee: Schott Glas; Carl-Zeiss-Stiftung Trading As Schott Glas; Carl-Zeiss-Stiftung
Priority date: 2001-09-03
Filing date: 2002-08-30
Publication date: 2003-03-13
Also published as: AU2002337052A1; DE10143134A1

Abstract

Light integrators which are typically used for lighting arrangements, consist, inter alia and alongside solid rods, of a longitudinal hollow body which is silvered on the inside. Hollow bodies having a quadrilateral inner cross-section thus have a special importance. In prior art, such hollow bodies are glued together from individual parts, which is time-consuming and thus expensive, and reduces the temperature resistance of the light integrator. According to the invention, this can be avoided if the hollow body is a monolithic, seam-free body and has a defined rounding in the transition regions between the inner surfaces, with a radius of < 1mm.

Description

light integrator

The invention relates to a light integrator for lighting arrangements, consisting of an elongated hollow body with a square inner cross section and applied internal mirroring.

Illumination devices for optical systems have light sources, for example with a filament that emits a luminous flux with inhomogeneous light distribution over its cross section. Light distribution is understood to mean the luminous flux per surface element of a cross section of the light field, or the illuminance per surface element.

In many optical systems, however, the illumination of an optical component by means of a shaped luminous flux with a distinctly homogeneous light distribution over its cross section is required. A current example of such an optical system is digital light processing, in which light valves, preferably in combination with a color wheel for a colored projection, are acted upon by means of a luminous flux with a sharp-edged rectangular or square cross-section and with the most homogeneous light distribution possible over the entire cross-section.

Such a system is described, for example, in EP 0 631 434 A1 or has become known through the scanning color recuperation (SCR) technology from Texas Instruments.

BESTATIGUNGSKOPIE In order to homogenize and shape the inhomogeneous luminous flux emanating from the light source, it is known to switch between the light source and the optical component to be illuminated, a so-called light integrator, which represents a substitute light source, so to speak, and which also shows an approximately uniform light distribution at its exit end, when an inhomogeneous light flux is applied to the entrance end. Here, for example, a collector lens arrangement is provided between the light entry end of the light integrator and the light source in order to largely couple the light flux emanating from the light source into the integrator. An elliptical arrangement with the light source in one focal point and the light entry end of the light integrator in the other focal point is also known.

The homogenization and shaping of a light beam by a light integrator includes for the highest possible light output, i.e. on the highest possible transmission factor. The light that enters an integrator propagates through a variety of reflections on the inner surfaces of the integrator. Depending on the design of the integrator, this can be a total reflection or a mirror reflection. The number of reflections that the light experiences inside the integrator depends on the angle of incidence at the entrance of the integrator and the length of the integrator. The degree of homogenization of the light energy distribution increases with the number of reflections on the inner surfaces of an integrator, but the transmission factor decreases with the number of reflections due to absorption losses.

Light integrators can be designed in different ways. DE 24 10 079 A1 shows a light integrator in the form of a monofilament light rod in the context of a device for illuminating a character carrier in the photo set. Here, the integrating effect of the monofilament light rod used to create a replacement light source with approximately uniform light distribution at the exit end. Separately from the light rod, a set of collector lenses is arranged in front of its entry end, which images the light source onto the entry end. Furthermore, a condenser lens set is arranged separately from the light rod after its exit end, which enlarges the light field on the subsequent projection surface.

Such a light integrator in the form of a light rod generates a luminous flux with a round cross section. However, the round cross-section causes a high loss of light intensity if it is to be used to illuminate a square element, e.g. the light valves in today's digital systems. Furthermore, a high absorption of light energy in the material of the light rod causes a further loss of light intensity. Another disadvantage is the high sensitivity of a monofilament light rod to external mechanical damage, which also leads to visual impairments.

In order to implement a light integrator with an emerging luminous flux, the cross section of which deviates from the round shape, US 5,680,257 describes a conical or rectangular solid light integrator made of a light-refracting material. The tapering towards the end of the light exit is intended to maximize the reflection of light on the inner surface of the integrator. Furthermore, a small light exit cross section can be realized with a large light entry cross section. In order to couple as large a portion of the light flowing in from the light source into the light integrator, a concave configuration of the light entry surface is proposed. With this light integrator, too, absorption losses in the homogenization of the light and high mechanical sensitivity can be expected.

EP 0 691 552 A2 (= US 5,625,738), DE 1 027504 C, Wo 98/37448 and FR 1.121.971 show not only light integrators made of solid rod-shaped light-guiding bodies but also tubular, i.e. hollow light integrators with mirrored inner surface, which act as light-guiding channels. The EP and FR documents also show a light integrator in the form of a square, hollow, light-guiding channel for generating a square-shaped light beam, as is advantageously required in the digital systems described at the beginning for illuminating the square light valves.

The production of such a light integrator with a square inner cross section is not without problems. While the aforementioned WO and FR writings do not provide any information on the manufacture of the light integrator, according to the aforementioned EP 0691 552 A2 the square, hollow, light-guiding channel is produced from four elongated plates mirrored on the inside by forming these plates into a square tube, for example with an epoxy resin adhesive. The interior of the light channel can optionally be filled with a light-conducting, solid material composition of a glass or plastic. This manufacturing technique is complex and costly. Furthermore, the thermal load capacity is limited by the relatively low temperature load capacity of the organic adhesive. Since the light intensity of projectors in which the light integrators are used, so-called beamers, is continuously increased, the highest possible thermal stability is, however, a requirement for modern light integrators. The invention is based on the object of designing the light integrator for lighting arrangements described at the outset in such a way that it has a

- High luminous efficacy with homogeneous light distribution over the cross-section of the light beam

- Exact, sharp-edged shaping of the light exit bundle

- High thermomechanical stability

owns, as well as simple and inexpensive to manufacture. is ..

This object is achieved with a light integrator for lighting arrangements, consisting of an elongated hollow body with at least a square inner cross-section and applied internal mirroring according to the invention in that the hollow body is a monolithic, seamless body and has a defined rounding in the transitions between the inner surfaces , with a radius that is <1 mm.

An essential feature of the invention is the monolithic design of the light integrator. According to Brockhaus, encyclopedia, a monolithic body is understood to mean a body that forms an inseparable unit, i.e. is made from one piece coherent and seamless.

Since the monolithic integrator according to the invention does not have any seams, its thermal stability is not limited by joining materials whose thermal stability is less than that of the material from which the integrator is made. The monolithic integrator according to the invention therefore has high thermal stability and is also easier and cheaper to manufacture than in the known case due to the one-piece design.

If you put the light integrator together from plates, the transition between the inner surfaces can be very sharp, i.e. be practically trained without rounding. During the production of a monolithic hollow body, in particular if it consists of glass or glass ceramic, roundings typically occur which impair the homogeneity of the intensity distribution over the cross section. The light integrator according to the invention is designed such that it has a defined rounding in the transitions, with a radius that is <1 mm. The smaller the radius, the more homogeneous the light distribution. Therefore, a rounding with a radius <0.5 mm, and preferably <0.3 mm, is advantageously formed.

According to a development of the invention, the hollow body forming the light integrator is designed such that the angle in the transitions between the inner surfaces is 90 °, forming a rectangular or square inner cross section.

However, the hollow body can also be designed such that a cross section deviates from the rectangular or square configuration, for example by the angles in the transitions between the inner surfaces differ from one another to form a trapezoidal or diamond-shaped cross section. Formations with a half-sided diamond or a half-sided trapezoid are also conceivable.

It is also important to achieve high thermomechanical stability, ie high resistance to thermal stresses the wall thickness of the hollow body forming the light integrator. In order to keep the thermal stresses as low as possible, the wall thickness should be as thin as possible, but while maintaining the mechanical "basic stability".

The wall thickness in the light integrator according to the invention is in the range between 0.1 mm and 5.0 mm, preferably in the range between 0.3 mm and 3.0 mm and preferably in the range between 0.5 mm to 2 mm.

Further refinements of the invention are characterized in the corresponding subclaims and also result from the description of the figures.

The invention is described in more detail on the basis of the description of three exemplary embodiments of the light integrator according to the invention shown in the drawings and its preferred application in a “projector”. The figures for the exemplary embodiments each have three figure parts A, B, C, with a perspective view in the figure part A, a cross-sectional view in part B and a longitudinal section in part C.

Show it:

1 shows an exemplary embodiment of the monolithic light integrator according to the invention with a square inner and outer cross section, FIG. 2 shows an exemplary embodiment corresponding to FIG. 1, but with a rectangular inner and outer cross section, FIG. 3 shows an exemplary embodiment corresponding to FIG. 2 with a rectangular inner cross section and rounded

External cross section, and Fig. 4 shows a lighting arrangement with the monolithic light integrator according to the invention for digital signal processing (projector).

FIG. 1 shows a monolithic light integrator 1, which is made from one piece in a coherent and seamless manner, preferably from glass or glass ceramic. It consists of an elongated hollow body of length I, which is in the range from 5 to 200 mm, preferably in the range from 10 to 120 mm and preferably in the range from 10 to 30 mm, and which has a square internal and external cross section. The inner surfaces of the square inner channel are mirrored. The edge length b of the square inner cross section is 6 mm.

The wall thickness of the elongated hollow body is in the range between 0.1 mm and 5.0 mm, preferably between 0.3 mm and 3.0 mm, and preferably between 0.5 mm and 2 mm. The edge length a of the square outer cross section is correspondingly greater than the edge length b of the inner cross section.

In the transitions between the inner surfaces, a sharp-edged transition is sought, so that the light reflections and thus the homogeneity of the light distribution over the cross section are not adversely affected. In terms of production technology, a certain rounding cannot be avoided; however, it is set in a defined manner. The rounding radius R _a is <1 mm, preferably <0.5 mm and preferably <0.3 mm.

The outer edges of the elongated hollow body are also rounded due to the manufacturing process, as is evident when using a tubular, round starting body. The outer rounding radius R is of the order of 0.5 - 50 mm. The outer rounding advantageously results in a low mechanical sensitivity.

FIG. 2 shows a further embodiment of an elongated hollow body of length I as in the case of FIG. 1, but which has a rectangular inner cross section with the edge dimensions c = approx. 7 mm and d = approx. 5 mm. With the dimensions of the wall thicknesses specified for FIG. 1, the edge dimensions a, b of the rectangular outer cross section are correspondingly larger. With regard to the inner rounding radius R _a , the statements made with regard to FIG. 1 apply accordingly. The outer rounding radius Rb is of the same order of magnitude as in the case of the embodiment according to FIG. 1.

3 shows a third exemplary embodiment of the monolithic light integrator according to the invention with a rectangular inner cross section with dimensions a = approximately 4.7 mm and b = approximately 3.7 mm. The outer cross section is rounded compared to the designs according to FIGS. 1 and 2 with outer rounding diameters R _b , R _c and R _d ,. The dimensions of these radii are in the range of 0.5 - 50 mm.

The statements made with regard to FIG. 1 apply accordingly to the inner rounding radius R _a and the length I.

In order to avoid light leaks at the end faces of the elongated hollow bodies shown, they are at least translucent, e.g. by roughening. They can also be opaque, e.g. by being coated with a high temperature resistant black paint.

The elongated hollow bodies of the light integrator according to FIGS. 1-3 can be produced in various ways, for example by pressing or forming from a round glass or glass ceramic tube. Special advantages, in particular with regard to a small rounding radius, are achieved by the technology of vacuum shrinking, in which a glass or glass ceramic tube, after it has been plasticized, for example in a hood furnace, on a metallic core, the cross section of which corresponds to the desired internal cross section of the light integrator, with the application of a vacuum is shrunk inside the pipe. After the shrinking process, the forming core is removed and the inside of the tube is mirrored. The individual light integrators are then cut to length from the shaped tube in a conventional manner.

Vacuum shrink technology typically leads to relatively thick-walled hollow bodies. The hollow bodies can also be produced in such a way that glass / glass ceramic tubes are drawn over a mandrel, preferably over a graphite dome, the diameter of which is larger than the inside diameter of the tube. The hollow bodies then become thinner.

The mirroring is carried out by known deposition processes, such as depositions from the gas phase (CVD, also thermal CVD processes (in particular PECVD and PICVD processes), or from the liquid phase (in particular galvanic or wet chemical (electroless) processes) or by sputtering, preferably metals such as silver, aluminum or chromium are deposited, typically in conjunction with an outer protective layer or a base layer adhering well to glass or glass ceramic, for example chromium can be electrodeposited as a mirror surface on a Cu / Ni base layer become. The mirror layer is preferably applied by gas flow sputtering, a cathode sputtering, as is described, for example, in the report of the “43rd Annual Technical Conference Proceedings-Denver, April 15-20, 2000, pages 287-292”. The cathode to be atomized is, for example made of silver, aluminum or chromium, from which the metallic particles are knocked out by the ions of the inert gas and deposited on the substrate .. Following this first step of metallic atomization, reactive gases, for example SiO ₂ or TiO ₂ particles, are fed in deposited as a protective layer, whereby a very temperature-stable mirroring is available.

In principle, the mirroring can also be carried out by applying a dielectric interference pact. This package consists of alternating high and low refractive index materials, which creates the desired mirror surface. For example, Si0 ₂ and Ti0 ₂ layers can be used.

The exemplary embodiments show light integrators with a square cross section. This is the preferred cross section. However, pentagonal, hexagonal, etc. cross-sections can also be formed, especially if they approximate a square in the manner of a polygene.

The light integrator according to the invention is preferably provided in a system for digital light processing. Such a system for digital light processing is practically a digital projector. 4 shows a schematic structure for generating a homogeneous light field for a digital projector, also called “projector”. The light source 4 generates light beams 2. The light beams are bundled and pass through the opening of a plate 3 into the light integrator 1 designed according to the invention. The Plate 3 is optionally attached to the entry side of the light integrator 1. In the light integrator 1, the light beams 2 are homogenized by multiple reflection. The homogenized light beams 2 hit a color wheel 5. The color wheel divides the homogenized light into the three primary colors and sequentially displays them on an imaging element 7 of the digital projector via a lens 6.

Claims

claims

1. Light integrator for lighting arrangements, consisting of an elongated hollow body with at least square internal cross-section and applied internal mirroring, characterized in that the hollow body (1) is a monolithic, seamless body and has a defined rounding in the transitions between the inner surfaces, with a Radius that is <1 mm.

2. Light integrator according to claim 1, characterized in that the radius of the rounding is <0.5 mm.

3. Light integrator according to claim 1, characterized in that the radius is <0.3 mm.

4. Light integrator according to one of claims 1 to 3, characterized in that in each case the angle in the transitions between the inner surfaces to form a rectangular or square inner cross section is 90 °.

5. Light integrator according to one of claims 1 to 3, characterized in that the angles in the transitions between the inner surfaces differ from one another to form a trapezoidal or diamond-shaped cross section.

6. Light integrator according to one of claims 1 to 5, characterized in that the wall thickness of the elongated hollow body is in the range between 0.1 mm and 5.0 mm.

7. Light integrator according to claim 6, characterized in that the wall thickness is in the range between 0.3 and 3.0 mm.

8. Light integrator according to claim 6, characterized in that wall thickness is in the range between 0.5 mm to 2 mm.

9. Light integrator according to one of claims 1 to 8, characterized in that the end faces of the elongated hollow body are translucent.

10. Light integrator according to one of claims 1 to 8, characterized in that the end faces of the elongated hollow body are opaque, preferably coated with a temperature-resistant black color.

11. Light integrator according to one of claims 1 to 10, characterized in that the elongated hollow body is produced by vacuum shrinking onto a square core.

12. Light integrator according to one of claims 1 to 10, characterized in that the elongated hollow body is produced by pulling a glass tube over a mandrel with a square cross-section.

13. Light integrator according to one of claims 1 to 11, characterized in that the internal mirroring is applied according to the technology of gas flow sputtering.

14. Light integrator according to claim 13, characterized in that initially by metallic Spray a silver or aluminum layer and then reactively apply a cover layer, preferably made of SiO ₂ .