WO2001014923A1

WO2001014923A1 - Method of production for a light integrator, a light integrator and utilization thereof

Info

Publication number: WO2001014923A1
Application number: PCT/EP2000/008090
Authority: WO
Inventors: Peter Dannenberg; Bernhard Wagner
Original assignee: Carl Zeiss Jena Gmbh
Priority date: 1999-08-25
Filing date: 2000-08-18
Publication date: 2001-03-01
Also published as: DE19940305C2; DE19940305A1; EP1121620A1

Abstract

The invention relates to a production method for a light integrator (2) in which an inwardly reflecting hollow space of the integrator (2) is created and is characterized by the following steps: fabrication of at least two components (14, 14') from which the light integrator can be assembled and exposure of the surfaces of said integrator provided as inner sides of the hollow space; edgeless reflective layer application on at least the surfaces of the components (14, 14') which provided as inner sides of the hollow space; assembling and securing the components (14, 14').

Description

Manufacturing method for a light integrator, a light integrator and a use thereof

The invention relates to a production method for a light integrator and a light integrator for homogenizing a light bundle incident in an input surface and emerging from an output surface. The invention further relates to the use of the same.

Light integrators are known. In principle, they consist of a body that is evenly coated with reflective material into which the light is introduced, which then reflects back and forth several times on the reflective surfaces. Due to the multiple reflection, the origin of the light is largely lost for the light bundles emerging at the exit. A homogenized lighting surface is thus achieved.

Integrators are used wherever particularly uniform lighting is required, for example in imaging technology, where each part of the image to be imaged should receive an equal amount of light. For example, EP 0 734 183 A2 proposes a light tunnel which is inserted between an illumination optics and an LCD matrix to be illuminated. This so-called light tunnel is, for example, an elongated cuboid, the opposite surfaces of which are used on both sides of a longitudinal axis determining the main direction of the light as light entry and exit surfaces. The other surfaces perpendicular to the main direction of propagation of the light serve as mirror surfaces.

It is also stated in this publication that total reflection can also be exploited by simply producing this cuboid from a piece of smoothly polished glass and selecting the angles for coupling in such that the reflection on the sides takes place via total reflection.

The total reflection is extremely advantageous for these purposes, since little loss can be expected. The only losses that occur theoretically with such light integrators are caused by absorption of the material, which can be suppressed very much if one takes appropriate pure glass for the manufacture of such an integrator.

However, there are difficulties in mounting such a light tunnel or mixing rod. Any contact with the outer surface reduces and interferes with the total reflection, so that corresponding losses are to be feared due to spreading.

The principle of image generation, as exemplified in the European patent specification, is based on the fact that the light rays parallelized again after the light tunnel are directed onto at least one LCD matrix. For the image generation, the LCD matrix is activated, for example, with a control device for the display of video images. In principle, you could now display a video image using the technology known from slide projection as a large image on a screen or similar to that of the Episcope, for back-mirrored LCD matrixes, project the reflected light.

This large picture technology is considered to be future-oriented, since the electronic picture tube technology can no longer be used with very large pictures.

When using the incident light projection method, a mirror matrix can also be provided for image generation instead of the LCD matrix. Such a matrix is e.g. available as a circuit from Texas Instruments. In this circuit, several tilting mirrors arranged in a matrix are digitally controlled, one for each pixel. In one of the digital states, each tilting mirror reflects the full light intensity; in the other state, the mirror receives and reflects the light at an angle at which it can no longer be thrown onto the screen, ie the corresponding image point is open except for a small amount of scattered light the screen dark.

The different light brightness for representing a gray or color value of a pixel can be brought about by applying pulses to the mirrors, whereby only an intermediate value between full light intensity and darkness is detected in the eye of an observer for each pixel on average.

However, the large projection methods mentioned place very high demands on the light integrator. With large-scale projection, you cannot allow yourself large losses of light, so that there is sufficient light for an image projected onto a screen. As has already become clear above, in principle only total reflection is suitable for this, but the storage of a mixing stick is difficult because it can lead to large light losses. Furthermore, the light entry and exit surface is exposed to a high energy flow of light, and can become discolored. Dust on the entrance and / or exit surface further reduces the luminous flux unavoidable and uncontrollable. Because of these disadvantages, it would be highly desirable to use other light integrators.

So that the reflection is not disturbed, as with total reflection, one could think of mirroring all the outer surfaces in the above-mentioned cuboid rod. Then there is another disadvantage, the light losses through the material and the mirror add up.

In order to at least eliminate losses through the material, one could think of guiding the light inside an internally mirrored cavity. However, this idea can hardly be realized optimally in practice, because every specialist knows that uniform internal mirroring with sufficient mirror quality to keep losses low is practically impossible to achieve.

The object of the invention is to provide an integrator which is optimized with regard to the amount of light transmitted, but does not have the disadvantages of a totally reflecting rod.

The object is achieved by a production method for a light integrator, which has the following steps for forming an internally mirrored cavity of the integrator:

Manufacture of at least two parts from which the light integrator can be assembled and the surfaces of which are provided as the inside of the cavity are exposed.

rimless mirroring of at least the inside of the

Cavity provided surfaces of the parts.

Assemble and fasten the parts.

This creates a light integrator according to the invention for homogenizing an incident in an input surface and emerging from an output surface light beam, which is characterized in that it for

Light pipe has an internally mirrored cavity, the Light integrator is composed of at least two parts, the surfaces of which are exposed before assembly and which face inward after assembly are provided with a mirror layer.

The interior mirrored cavity is therefore selected from the alternatives discussed above. As previously explained in detail, this alternative would not have been sensible at all and the expert would not have considered it at all, since mirroring inside with tolerable small losses would not have been possible at all. Prior to the invention, one would have had to rely on, for example, vapor deposition of a silver layer in the interior, which, however, easily oxidizes if it is not provided with a protective layer. This protective layer would also cause absorption.

In particular, it can easily be calculated that at 96% reflectance and 5 reflections, 20% of the light was already lost in the integrator, it being questionable whether such a high reflectance can be achieved at all. Only when the cavity is disassembled according to the invention, i.e. divided into at least two parts of the integrator, the inside of the cavity being exposed when it is mirrored, is it possible to produce highly playful layers with 98% reflectance, for example by applying dielectric layers to the metal layer. With a degree of reflection of 98%, which is quite achievable, 5 reflections give more than 90% transmission, so you only have to reckon with a loss of 10%.

Furthermore, an essentially dielectric mirror can be applied, with a thin metal layer possibly underneath as a backing layer, and thus the losses can be reduced even further.

The light propagates essentially in air in a cavity integrator, so that the losses are determined solely by the mirror layers and, through corresponding efforts, any tolerable losses in the integrator which are as small as possible can be achieved. However, the assembly of the parts, for example by glue at the gluing points, could cause further losses. In particular, care should be taken to ensure that glue does not accidentally get on the mirror layers, since the reject would then be correspondingly large. Attaching the parts to one another with an adhesive or by means of a screw connection would also be time-consuming, which would unnecessarily increase the effort for producing such an integrator if no other possibility was found.

According to a preferred development of the invention in this regard, it is provided that the fastening step is carried out by the following substeps:

Covering the assembled parts with a shrink tube;

Shrink the tubing until the cavity integrator reaches a suitable strength.

In this way, a light integrator according to a further development is characterized in that the parts are held together by at least one shrink tube.

The process of providing parts with a shrink tube is known from electrical engineering. There, a hose that is larger than the point to be insulated, for example a soldering point, is placed over it for quick insulation. With thermal treatment, for example by hot air, the hose shrinks and completely surrounds the solder joint mentioned as an example.

So far, this method has only been used for insulation and has proven itself for a fast working method. It is used here for the first time for an attachment. This type of attachment is not only characterized by easy and quick handling. Due to the elasticity of the shrink tube, the pressure is automatically distributed to the assembled parts, which are preferably made of glass, and breakage or other damage to the parts is avoided.

Furthermore, due to its elastic tension, the shrink tube ensures that the parts to be fastened are pressed very close together. With degrees of polishing, as are common in optics, this means that the parts can practically be light-tight. For light within the cavity, there is therefore only a low probability of falling into the area between adjacent surfaces of the parts from which the light integrator is composed, where it would then no longer be available for illumination. This result could only be achieved to a small extent with an adhesive and would also not be reproducible, since the distance between the parts would then essentially be determined by the amount of adhesive.

When manufacturing from glass with glue, for example, only positional tolerances of the opening of +0.2 mm could be realized, when fastening with plastic, however, less than 0.05 mm.

Above all, two alternatives are preferred for attaching the shrink tube:

1. Fastening by holding the parts together using a shrink tube attached centrally between the entrance surface and the exit surface.

2. Fastening by holding the parts together in the vicinity of its input and output surface by two enclosing the integrator

Heat Shrink.

The following further developments essentially deal with the shaping of the parts in order to obtain the cheapest possible integrator To create manufacturing, effort and reproducibility. Such preferred further developments are characterized by:

that a nose is provided on one part, which engages in a recess of the other part after assembly.

- That the inside and outside of the cavity forming the

Light integrators are flat, the light integrator has the shape of a geometric prism with rectangular base and cover surfaces provided as exit and entry surfaces, and the nose and the recess are rectangular, in particular square.

- That the light integrator from two T-shaped and two I-shaped

Side parts is composed.

Above all, the nose in the recess not only ensures a reproducible assembly, but also reduces a possible gap in which light could be lost, the remaining gap being able to be kept very small by means of pressing, for example using the shrink tube mentioned above.

The above-mentioned shape with a rectangular nose or recess above all simplifies production. In particular, the assembly of two T-shaped and two I-shaped side parts simplifies the application of the mirror layers. Furthermore, there are only two types of parts, namely the T-shaped and the I-shaped, which can then be easily mass-produced. The exemplary embodiments shown later explain the most favorable shape of the individual parts once again in more detail.

Due to the low loss of light, the use of such integrators for homogenizing the light originating from a light source, which is provided for illuminating an electronically controllable matrix for displaying picture elements, is particularly advantageous. While the lighting of LCD If matrixes are known, the invention also provides for the matrix to be a tilting mirror matrix when used in this way.

Further special features of the invention result from the following description of exemplary embodiments with reference to the attached drawing. Show it:

Figure 1 is a schematic representation of the operation of a light integrator using the example of the projection with a matrix, in particular a tilting mirror matrix.

2 shows a perspective illustration of an integrator according to the invention;

Fig. 3 front view of the integrator of Fig. 2;

Fig. 4 shows another embodiment of an integrator according to the invention.

1 schematically shows the use of an integrator 2 for illuminating an LCD matrix or DMD matrix, which is also referred to here as a tilting mirror matrix. The application is not limited to such matrices for electronic image display, but it is extremely expedient to use such an integrator when illuminating such matrices, since in particular a tilting mirror matrix 4 has very small dimensions below 1 mm ^* 1 mm, an area which, when focused with high luminance alone cannot be illuminated uniformly, since the light spot usually has the same dimensions when focusing the light of a lamp with high luminance.

The entire arrangement shown in FIG. 1 is arranged on a single optical axis 6. This is also not restrictive. Such an arrangement can be put together, for example, optics whose optical axes are offset from one another. A light beam 8 shown by way of example, which can be generated with the aid of a lamp provided with a parabolic mirror, is introduced into the input surface 12 of the integrator 2 through a coupling optic 10. Within the integrator 2, which is mirrored on the inside of the side parts 14 or if the integrator 2 consists of a medium of a suitable refractive index for total reflection, the light beam 8 is reflected back and forth several times. This results in a pseudostochastic distribution of the incoming light beams 8 in the light exit surface 16.

Because of the pseudostochastic distribution, the light beam 8 is highly homogenized at the output of the integrator. It can be parallelized again by a decoupling optic 18, as can be seen schematically in FIG. 1. The light beam thus homogenized is then directed onto the tilting mirror matrix 4, from where it is then passed into a projection optical system which throws the image electronically generated by the tilting mirror of the tilting mirror matrix 4 onto a screen and thereby makes it visible to an observer.

An integrator 2 according to the invention is shown in FIG. 2, which is particularly advantageous for use with a tilting mirror matrix 4. The integrator 2 is a cavity integrator, which is mirrored on the inside of the side parts 14, 14 '. A cavity integrator is characterized above all by the fact that the inlet surface 12 and the outlet surface 16 remain unloaded thermally, so that no discoloration occurs at high light output or dust particles can settle there. An integrator 2, which is designed as a cavity integrator, is particularly advantageous when using small tilting mirror arrays, since high luminance levels are used in particular there.

In order to be able to simply mirror it inside, the cavity integrator is composed of four parts, two T-shaped 14 'and two I-shaped 14. The arrangement and shape of the parts can also be seen in particular from FIG. 3. The T- and I-shaped parts are shaped and fitted together so that they do not allow any shear movement against each other. You could also choose a different shape of the parts and this in the manner of tongue and groove with a Fit the recess to ensure the exact right-angled geometry. Due to the illustrated I-shaped parts 14 and the T-shaped parts 14 ', in which a corner 20 of the I-shaped part fits exactly in a recess 22 of the T-shaped part, a particularly good hold is always guaranteed, whereby a Tilting but not breaking the material.

The entire integrator 2 is held together by a shrink tube 24.

A manufacturing method for an integrator shown in FIGS. 2 and 3 is accordingly relatively simple. The individual parts 14 and 14 'are, for example, made of plastic by injection molding from glass or the like. manufactured and mirrored rimless on the inside. Silver is particularly suitable for mirroring because of the high degree of reflection. At degrees of reflection, which should be significantly higher than 96%, it is advisable to provide a dielectric mirror layer, which can also serve as a protective layer.

The mirroring takes place essentially without a rim, so that when fitting into one another according to FIG. 3, all surfaces of the parts 14 and 14 'which are open to the inside are mirrored with a high degree of reflection. After assembly, a shrink tube 24 is placed over it. This hose shrinks due to thermal treatment and also holds the parts 14 and 14 'together with the greatest possible stability due to the corner 20 which fits into the recess 22. The elasticity of the shrink tube allows simple assembly, in particular also with a view to reducing the risk of breakage when fastening, if the parts 14, 14 'are, as usual, made of fragile material, in particular glass.

4 shows an integrator similar to that shown in FIG. 2, but with two slight changes. First, instead of a single shrink tube 24, two shrink tubes 24 ′ and 24 ″ are provided, which in particular on the Give ends a better grip. Secondly, a cutout 26 is kept free in the area of the input surface 12 in order to increase the compactness of a practically implemented device according to FIG. 1. In the exemplary embodiment, an otherwise disturbing screw head was accommodated in the recess 26. The loss of light such. The cutout is correspondingly small if the angles achieved by the coupling optics 10 are large enough for this cutout 26 to lie outside the first reflection.

It can also be seen from FIG. 4 that shapes other than two T-shaped and two I-shaped parts 14, 14 'are also possible.

For this purpose it must be stated that the invention can even be implemented if only two right-angled parts are joined together with corresponding cutouts. In the case of glass production in particular, however, the configuration of four parts is much cheaper, since there are always flat surfaces that can be ground and polished accordingly.

Above all, the preceding exemplary embodiments illustrated the simplicity of the design and thus a less complex manufacturing process for such an integrator 2. Furthermore, the person skilled in the art will immediately recognize some possible changes that are within the scope of the invention. For example, instead of a single shrink tube 24, two or three shrink tubes can also be used. In addition, the shape of the parts 14 and 14 'can be modified accordingly, for example by providing a tongue and groove connection between the parts.

Such changes are possible. However, the exemplary embodiments of FIGS. 2 to 4 are particularly preferred, among other things also because, for example, a tongue and groove connection, for example if inserted incorrectly, the risk of breakage at the edges of the groove or the corners of the tongue would increase. The examples shown are also particularly optimized for simple and quick assembly of the parts 14 and 14 'when manufacturing the integrator 2.

Claims

Expectations

1. Manufacturing method for a light integrator (2), characterized by the following steps for forming an internally mirrored cavity of the integrator (2):

Manufacture of at least two parts (14, 14 ') from which the light integrator (2) can be assembled and the surfaces of which are provided as the inside of the cavity are exposed;

rimless mirroring of at least the surfaces of the parts (14, 14 ') provided as the inside of the cavity;

Assembling and fastening the parts (14, 14 ')

2. Manufacturing method for a light integrator (2) according to claim 1, characterized in that the attachment is carried out by the following steps:

Covering the assembled parts (14, 14 ') with a shrink tube (24, 24', 24 ");

Shrink the tubing until the cavity integrator has reached a suitable strength.

3. Light integrator (2) for homogenizing a light bundle incident in an input surface (12) and emerging from an output surface (16), characterized in that it has an internally mirrored cavity for light conduction, the light integrator (2) comprising at least two parts (14 , 14 ') is composed - whose before

Assembling exposed and after assembling inward-facing surfaces are provided with a mirror layer.

4. Light integrator (2) according to claim 3, characterized in that on one of the parts a nose (20) is provided which engages a recess (22) of the other parts after assembly.

5. Light integrator (2) according to claim 4, characterized in that the inner and outer sides of the light integrator forming the cavity are flat, the light integrator (2) has the shape of a geometric prism with a rectangular base provided as exit and entry surfaces (16, 12) - Has and top surfaces and the nose and the recess (22) are rectangular, in particular square.

6. Light integrator (2) according to claim 5, characterized in that the light integrator is composed of two T-shaped (14 ') and two I-shaped (14) side parts.

7. Light integrator (2) according to one of claims 1 to 6, characterized in that the parts (14, 14 ') are held together by at least one shrink tube (24).

8. Light integrator (2) according to claim 7, characterized in that it is applied to hold the parts (14, 14 ') in the middle between the input surface (12) and the output surface (16)

Has shrink tube (24).

9. Light integrator (2) according to claim 7, characterized in that it holds the parts (14, 14 ') together in the vicinity of its inputs and Output surface (12, 16) has two shrink sleeves (24 ', 24 ") comprising the light integrator.

10. Use of the light integrator (2) according to one of claims 3 to 9 for homogenizing the light originating from a light source, which is provided for illuminating an electronically controllable matrix (4) for displaying picture elements.

11. Use according to claim 10, characterized in that the matrix (4) is a tilting mirror matrix.