DE19940305C2 - Manufacturing process for a light integrator, a light integrator and a use thereof - Google Patents

Description

The invention relates to a manufacturing method for a light integrator, the following Steps to form an internally mirrored cavity of the light integrator comprises: Manufacture of at least two parts from which the light integrator can be assembled and whose as Surfaces provided on the inside of the cavity are exposed; rimless mirroring of the as Inside of the cavity provided surfaces of the parts, and assembling and Attach the parts. The invention further relates to a light integrator for Homogenize one falling into an input surface and out of an output surface failing light beam, which has an internally mirrored cavity for light conduction and is composed of at least two parts, the one before assembly exposed and inward-facing surfaces after assembly with a Mirror layer are provided, and on the use of such a light integrator.

Light integrators are known. In principle, they consist of a body that is even with reflective material is coated, in which the light is introduced, which then to the reflecting surfaces reflected back and forth several times. Due to the multiple reflection goes 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 uniform lighting is required are, for example in imaging technology, where each image portion to be imaged is an equal amount To receive light.  

For example, EP 0 734 183 A2 proposes a light tunnel between an illumination optics and an LCD matrix to be illuminated is inserted. This so-called light tunnel is, for example, an elongated cuboid, the opposite surfaces of which one on both sides The main continuation direction of the light determines the longitudinal axis as Light entry and exit surfaces can be used. The other areas perpendicular to the main direction of propagation of the light serve as Mirror surfaces.

It is also stated in this document that total reflection is also possible can be exploited by simply polishing this cuboid out of one piece Glass is produced and the angles for coupling are chosen so that the reflection on the sides takes place via total reflection.

The total reflection is extremely advantageous for these purposes, since with little Losses must be expected. The only losses that theoretically Such light integrators occur due to absorption of the material causes, which you can suppress very far if you corresponding pure glass for the manufacture of such an integrator takes.

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

The principle of image generation, as exemplified in the European Patent specification is based on the fact that after the light tunnel again parallelized light beams are directed onto at least one LCD matrix. The LCD matrix is used, for example, to generate an image Control device for the display of video images controlled. Basically you could now create a video image with the one known from slide projection Display technology as a large picture on a screen or similar to the  Episcope, with back-mirrored LCD matrixes, the reflected light project.

This large-screen technique is viewed as forward-looking because the Electronic picture tube technology can no longer be used for very large pictures is.

When using the incident light projection method, you can replace the LCD matrix also provide a mirror matrix for image generation. Such is a matrix z. B. available as a circuit from Texas Instruments. With this Circuit are several tilting mirrors arranged in a matrix for one every pixel, digitally controlled. Reflected in one of the digital states each tilt mirror receives the full light intensity, in the other state and the mirror reflects the light at an angle at which it is no longer on the screen can be thrown, d. that is, except for small amounts of scattered light the corresponding pixel on the screen is dark.

The different light brightness to represent a gray or color value A pixel can be brought about by the mirrors having pulse trains be acted on, which means that at each pixel in the time average only one Intermediate value between full light intensity and dark in the eye of one Observer is detected.

However, the large projection methods mentioned place very high demands to the light integrator. You can’t get one with the large projection large light losses allow a sufficient amount of light for a a screen projected image is present. As already clear above only total reflection is suitable for this, but the Storage of a mixing stick is difficult because it is too large Loss of light can result. Furthermore, the light entry and exit surface is one exposed to high levels of energy from light, and can become discolored. Dust on the entrance and / or exit surface further reduces the luminous flux  unavoidable and uncontrollable. Because of these drawbacks, it would be highly desirable use other light integrators.

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

To at least eliminate losses from the material, one could remember that Conduct light within an internally mirrored cavity. However, this idea is practical hardly possible to realize optimally, because every specialist knows that an even Internal mirroring with sufficient mirror quality to keep losses low, practical is not feasible.

For example, EP 0 493 365 A2 describes a light integrator that consists of four mirrors is built, the inside of which form the cavity of the light integrator and are mirrored accordingly. Two opposite mirrors can are moved against each other to adjust the diameter of the light integrator. The movable mirrors are made of correspondingly adjustable screws or a Stepper motor operated.

US 5,828,505 also discloses a light integrator with an internally mirrored cavity. The light integrator is constructed from disc-shaped material, whereby it is can in particular be micromechanically processable wafers whose interior forming edges or edge surfaces are mirrored. These discs are either with a Bracket held together or glued together with cement.

The object of the invention is to provide a light integrator and a corresponding one Specify manufacturing processes so that simple manufacture is possible.

The object is achieved by a manufacturing process for a light integrator, the following Steps to form an internally mirrored cavity of the light integrator comprises: Manufacture of at least two parts from which the light integrator can be assembled and whose as Surfaces provided on the inside of the cavity are exposed; rimless mirroring of the as Inside of the cavity provided areas of the part, and assembling and Fasten the parts, with the following steps to fasten the parts: Tighten the assembled parts with a shrink tube and shrink the tube up to achieve a suitable strength of the light integrator.  

The object is further achieved by a light integrator for homogenizing one into one Entry surface incident and emerging from an exit surface light beam to the Light pipe has an internally mirrored cavity and at least two parts is composed, whose exposed before the assembly and after the Composing inward-facing surfaces are provided with a mirror layer, whereby the parts are held together by at least one shrink tube.

The internally mirrored cavity thus becomes one of the previously discussed alternatives select. As has already been explained in detail, the interior mirroring is one Light mixing rod with tolerable low losses not possible. You could For example, evaporate a layer of silver in the interior, which, however, easily oxidizes when it is is not provided with a protective layer. A protective layer would in turn absorb cause.

In particular, it can easily be calculated that at 96% reflectance and 5 reflections 20% of the light in the integrator has already been lost, although it is questionable whether such a high one Reflectance is attainable at all. Only by producing the Cavity, whereby the inside of the cavity is exposed when mirroring, it will possible, highly reflective layers with 98% reflectance, for example by application to produce dielectric layers on the metal layer. With a reflectance of 98%, how it can be achieved is obtained with 5 reflections above 90% transmission therefore only expect a loss of 10%.

You can also use a substantially dielectric mirror, possibly with a Apply the underlying thin metal layer as a backing layer, and so the losses further decrease.

The light propagates essentially in air in a hollow integrator, so that the losses are determined solely by the mirror layers and are arbitrary with a corresponding effort low tolerable losses can be achieved in the integrator. However, it could Assembling the parts, for example by glue at the gluing points further losses cause. In particular, care should be taken to ensure that glue does not happen accidentally the mirror layers get there because the committee would be correspondingly large. An attachment the parts together with an adhesive or through a screw connection would also be time-consuming, making the effort to manufacture such an integrator unnecessary would increase if no other possibility was found.  

Therefore, according to the invention, a covering of the assembled parts with a Shrink tubing and shrinking the tubing until a suitable one is reached Strength of the hollow integrator, provided.

The process of providing parts with a shrink tube is from electrical engineering known. There is a hose that is larger than the one to be insulated for quick insulation Place, for example a solder joint, put on. With thermal treatment, for example by hot air, the hose shrinks and completely surrounds the solder joint.

This method was previously only intended for isolation and has been used for a fast way of working has proven itself. It is used here for the first time for an attachment.  

This type of attachment is not only characterized by light and quick handling. Because of the elasticity of the shrink tube the pressure is automatically distributed to the assembled parts yes are preferably made of glass, and it is thus a breaking or avoided other damage to the parts.

The shrink tube also ensures due to its elastic tension to ensure that the parts to be fastened are pressed very closely together. With degrees of polishing, as are common in optics, this means that practical a light-tight contact of the parts is possible. For light within the This means that there is only a slight probability of being in the cavity Area between adjacent surfaces of the parts that make up the light integrator is composed to fall where it is no longer used for lighting Available. This result could only be achieved with a small amount of glue Reach dimensions and would also not be reproducible because of the distance between the parts then essentially determined by the amount of glue.

For example, when manufacturing from glass with glue Positional tolerances of the opening of +0.2 mm when fastening with plastic on the other hand, less than 0.05 mm.

Two alternatives are particularly preferred for attaching the shrink tube:

• 1. Attachment by holding the parts together using a center between the entrance surface and the exit surface Shrink tubing.
• 2. Attachment by holding the parts together near their and output area by two comprising the integrator Heat Shrink.

The following further developments essentially deal with the shaping of the parts in order to create an integrator which is as inexpensive as possible with regard to manufacture, expenditure and reproducibility. Such preferred further developments are characterized by:

• - That a nose is provided on one part, which in a recess of the other part intervenes after assembling.
• - That the inside and outside of the cavity forming the Light integrators are flat, the light integrator is in the form of a geometric prism with intended as exit and entry surfaces has rectangular base and top surfaces and the nose as well as 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 that it can be reproduced Joining together also diminishes a possible gap in the light could be lost, the remaining gap being pressed, for example with the shrink tube mentioned above, very low can be held.

The aforementioned shape with a rectangular nose or recess is simplified especially manufacturing. In particular the combination of two T- shaped and two I-shaped side panels simplifies the application of Mirror layers. Furthermore, there are only two types of parts, namely the T- shaped and the I-shaped, which are then easily mass-produced can be. The exemplary embodiments shown later explain the The most favorable shape of the individual parts in more detail.

Due to the low loss of light, one particular use is such integrators for homogenizing the from a light source originating light, which is used to illuminate an electronically controllable Matrix for displaying picture elements is provided, extremely advantageous. While the lighting of LCD  Matrixes is known, the invention also provides that the matrix at such use is a tilting mirror matrix.

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.

Fig. 2 is a perspective view of an integrator according to the invention;

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

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

In Fig. 1, the use of an integrator 2 is shown for illuminating an LCD matrix or DMD array schematically, which is further referred to herein 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 of less than 1 mm. 1 mm, an area which, when focused 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, for. B. assemble from 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 from FIG. 1. The light beam thus homogenized is then directed onto the tilting mirror matrix 4 , from where it is then directed 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 now 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 unstressed, so that there are no discolorations with 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 matrices, since in particular high luminance levels are used 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 fit them in the manner of tongue and groove with a recess to always ensure the exact rectangular 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 of a state shown in Fig. 2 and Fig. 3 integrator is therefore relatively simple. The individual parts 14 and 14 'are, for example, made of plastic by injection molding from glass or the like and mirrored on the inside without a rim. Silver is particularly suitable for mirroring because of its 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 put 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.

In FIG. 4, a similar integrator as shown in Fig. 2 is shown, but with two light changes. First, instead of a single shrink tube 24, two shrink tubes 24 'and 24 "are provided, which in particular provide an improved hold at the ends. Second, a recess 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 light loss of such a recess is correspondingly low if the angles achieved by the coupling-in optics 10 are large enough for this recess 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.

To this end, it must be stated that the invention can even be implemented, if only two right-angled parts with corresponding recesses be put together. However, especially when manufacturing from glass the design of four parts much cheaper because it is always flat There are surfaces that are ground and polished accordingly can.

Above all, the preceding exemplary embodiments illustrated the simplicity of the structure 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 which 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. The embodiments of FIG. 2 to FIG. 4, however, are particularly preferred, because, for example, a groove / spring connection would increase, for example, in case of incorrect insertion of the risk of breakage at the edges of the groove or the corners of the spring, among others. The examples shown are also particularly optimized for simple and quick assembly of the parts 14 and 14 'when manufacturing the integrator 2 .

Claims (9)

1. A manufacturing method for a light integrator, which has the following steps for forming an internally mirrored cavity of the light integrator ( 2 ):

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

characterized by the following steps for fastening the parts ( 14 , 14 '):

• - Covering the assembled parts ( 14 , 14 ') with a shrink tube ( 24 , 24 ', 24 ") and
• - Shrinking the tube ( 24 , 24 ', 24 ") until the light integrator ( 2 ) has reached a suitable strength.

2. Light integrator ( 2 ) for homogenizing an incident in an input surface ( 12 ) and emerging from an output surface ( 16 ) light bundle, which has an internally mirrored cavity for light conduction and is composed of at least two parts ( 14 , 14 '), the front of which Assembling exposed and after the assembling facing surfaces are provided with a mirror layer, characterized in that the parts ( 14 , 14 ') are held together by at least one shrink tube ( 24 ). 3. Light integrator ( 2 ) according to claim 2, characterized in that on one of the parts ( 14 , 14 ') a nose ( 20 ) is provided which in a recess ( 22 ) of the other parts ( 14 , 14 ') according to Assembling intervenes. 4. Light integrator ( 2 ) according to claim 3, 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 ) - And cover surfaces, and the nose and the recess ( 22 ) are rectangular, in particular square. 5. Light integrator ( 2 ) according to claim 4, characterized in that the light integrator is composed of two T-shaped ( 14 ') and two I-shaped ( 14 ) side parts. 6. Light integrator ( 2 ) according to claim 2, characterized in that it has a shrink tube ( 24 ) applied centrally between the input surface ( 12 ) and output surface ( 16 ) to hold the parts ( 14 , 14 ') together. 7. light integrator ( 2 ) according to claim 2, characterized in that it holds the parts ( 14 , 14 ') in the vicinity of its input and output surface ( 12 , 16 ) two the light integrator comprising shrink sleeves ( 24 ', 24 ") having. 8. Use of the light integrator ( 2 ) according to one of claims 2 to 7 for homogenizing the light originating from a light source, which is provided for illuminating an electronically controllable matrix ( 4 ) for displaying picture elements. 9. Use according to claim 8, characterized in that the matrix ( 4 ) is a tilting mirror matrix.