Device for supporting large optical components

Abstract

The apparatus (10) for supporting a large optical component (50) includes a support plate (12) and a rigid support surface (14a) disposed on the support plate (12) and configured to support a bottom surface (52) of the large optical component (50) in a predetermined position and orientation. The rigid support surface (14a) is further configured to support the large optical component (50) at a Bessel point (BP1) of the large optical component (50). The apparatus (10) further includes an elastic support surface (16a) disposed on the support plate (12) and configured to elastically support the bottom surface (52) of the large optical component (50).

Description

[Technical field]

[0001] The present invention relates to an apparatus for supporting large optical components. [Background technology]

[0002] Large optics, i.e. optics with a diagonal of more than 200 mm (preferably more than 500 mm), such as large lenses, are part of many laser systems. In particular, large optics are used in the production of OLED (Organic Light Emitting Diode) displays for smartphones, tablet PCs, televisions, etc. In this case, line-shaped laser irradiation is used for thermal processing of the workpiece. Another widely used application of sequential irradiation of a workpiece with a defined laser line is the line-by-line melting of amorphous silicon on a support plate. The laser line moves at a defined speed relative to the surface of the workpiece, similar to the production of OLED displays. By melting and subsequent cooling, the relatively cheap amorphous silicon can be converted into higher quality polycrystalline silicon. In practice, this type of application is often called solid-state laser annealing (laser annealing, SLA), sequential lateral solidification (SLS) or excimer laser annealing (ELA). Large optics are frequently used in particular to generate long and defined laser lines. To obtain a precise laser line, the precision of the optical system of the laser system plays a decisive role. For this, not only the quality of the optical components themselves is important, but also their attitude or position in space and their orientation. Thus, for example, a slight change in the attitude and orientation of a lens with a high refractive index can have a significant impact on the quality of the laser line on the processing surface. Similarly, an incorrect position or orientation, for example, of a deflection mirror, can have a significant effect on the beam path of the laser and, as a result, on the shape of the laser line on the processing surface. In this respect, the support of optical components, especially large optical components, is often a major challenge.

[0003] One method of supporting an optical component is to use a device that supports or holds the optical component at its edges. However, such support causes the greatest deflection in the center of the optical component. While this effect is not significant for small optical components, for large optical components weighing 40 kg or more, there is a risk of significant deflection when supporting the optical component in this manner. This is especially true for large, elongated optical components.

[0004] To minimize the deflection, it is common to support elongated large optical components at so-called Bessel points, which are by definition two symmetrically arranged support points of an elongated support at which the elongated support is least deformed by gravity. In other words, a Bessel point is a support point of an elongated support (or in this case a large optical component) at which a tangent to the optical component runs horizontally at the support point.

[0005] However, the problem with supporting large optical components at Bessel points is that they generate localized stresses at or in the area of ​​the optical component. These stresses result in optical anisotropy in the optical material. This means that when a light wave train passes through the optical material, it is split into two parts with different vibration planes. As a result, the propagation speed and the refractive index of light become directionally dependent. This phenomenon is called stress birefringence. In particular, as mentioned above, it changes the polarization of the incident laser beam. This means that polarization-sensitive methods such as solid-state laser annealing (SLA) can no longer be performed accurately.

[0006] Even if the laser processing process itself is not polarization sensitive, if the downstream measurement system is polarization sensitive, any changes in the polarization of the laser beam caused by large optical components can have adverse effects. In some circumstances, measurements from a polarization sensitive camera can indicate a malfunction of the optical system if the measurement results are misinterpreted, even though the optical components themselves are perfectly functional. Summary of the Invention [Problem to be solved by the invention]

[0007] Against this background, the object of the present invention is to provide an apparatus which can support large (especially elongated) optical components as flexibly and stress-free as possible, in particular to avoid local stresses within the large optical components. [Means for solving the problem]

[0008] According to one aspect of the present invention, to solve this problem, an apparatus for supporting a large optical component is proposed, which comprises a rigid support surface (hereinafter referred to as "rigid support surface") arranged on a support plate and configured to support the bottom surface of the large optical component in a predetermined position and orientation, and a further elastic support surface (hereinafter referred to as "elastic support surface") arranged on the support plate of the apparatus and configured to elastically support the bottom surface of the large optical component. In other words, the novel apparatus comprises a first support surface ("rigid support surface") and a second support surface ("elastic support surface"), where the first support surface is (substantially) less elastic than the second support surface. The terms "rigid" and "elastic" are interpreted such that "rigid" means "less elastic" compared to "elastic" or "elastic" means "less rigid" compared to "rigid". The elastic support surface or the elastic support by the second support surface can also be interpreted as a "floating" support.

[0009] The new device is able to distribute the weight of the optical component over a large area, including small residual forces. Unlike the prior art, there is (essentially) no point or line rigid support, but a flat and therefore more uniform support. In fact, the elastic support surface is configured to fit itself tightly against the surface of the large optical component, thereby (better) supporting it. This reduces the localized forces on the large optical component from the rigid support surface, and significantly reduces the polarization effects resulting from localized stresses.

[0010] Typically, the rigid support surface consists of a narrow rigid web that runs along the short axis of the bottom surface (base) of the large optical component. The material of the rigid support surface must be selected so that it does not flex, or only flexes very little, under the influence of the gravity of the large optical component supported thereon. In other words, a rigid material must be selected that can support the optical component over time and does not flex. A hard metal, such as steel, can be selected as the material for the rigid support surface. As a rule, the large optical component is supported so that its bottom surface, i.e. the base, is parallel to the support plate. The support plate is usually arranged horizontally.

[0011] In addition to one rigid support surface, it is also possible to use several, in particular two, separate rigid support surfaces. In practice, two rigid support surfaces are used in many devices for support, since this makes it easier to adjust or align the large optical component. In particular, two rigid support surfaces and a defined structure of the large optical component on these two support surfaces make it possible to avoid rotations or tilts of the large optical component.

[0012] In order to support the large optical component in a fixed position and orientation, one or more (rigid) contact surfaces may further be provided that are configured to support a side of the large optical component in a predetermined position and / or orientation.

[0013] The term "rigid" with respect to a rigid support surface (or rigid contact surface) does not imply that the support surface (or contact surface) is not adjustable, however, there is a need to make an adjustable support or contact surface fixable, thereby allowing fixed support of large optical components.

[0014] Preferably, the rigid support surface has a strength of at least 20 kN / mm 2 , and / or up to 500kN / mm 2 , in particular at least 40 kN / mm 2 , and / or up to 250kN / mm 2 For example, the rigid support surface has a modulus of elasticity of 5,000 mm 2In relation to the surface area of ​​the contact surface with the large optical component, the spring constant is at least 10 MN / mm and / or at most 1,000 MN / mm, preferably at least 100 MN / mm and / or at most 500 MN / mm.

[0015] With regard to the elastic support surface, the term "elastic" should be understood to mean that the elastic support surface flexes, preferably to a defined extent, when loaded with a weight, in particular the weight of a large optical component. For example, the elastic support surface can have a pre-defined preload, which preload allows the support surface to flex in a defined manner when loaded with the weight of the large optical component. The flexing of the elastic support surface under the influence of the weight of the large optical component has the consequence that the large optical component can be supported in a floating state.

[0016] Basically, it is also conceivable to use multiple elastic support surfaces. Preferably, the multiple elastic support surfaces are arranged evenly, so that the bottom surface of the large optical component can be supported evenly. Depending on the shape of the large optical component, it is advantageous to arrange the multiple elastic support surfaces in one (or multiple) rows transversely and / or parallel to the long side (or longitudinal axis) of the support plate or the large optical component. Arranging multiple rows of elastic support surfaces in a direction parallel to the longitudinal direction of the support plate is particularly advantageous when the large optical component has a thickness (transverse direction) of several centimeters. For example, the multiple elastic support surfaces can be multiple spring pressure pieces.

[0017] The support plate of the present apparatus may be formed as a separate plate adapted to be inserted into a frame for large optical components, however, the support plate may also be part of such a frame.

[0018] In a preferred embodiment, the rigid support surface of the device is configured to support the large optical component at a Bessel point of the large optical component or at an end point of the bottom surface of the large optical component.

[0019] The Bessel point of a large optical component is defined in this case as one of two symmetrical points at which the deformation of the large optical component is minimal when supported. The end points are understood to be the points at either end of the longitudinal axis of the large optical component, whereby the two points are usually those at which an imaginary connecting line between them is perpendicular to the direction of incidence of the laser beam in the laser system.

[0020] In a further embodiment, a metal film and / or a plastic film is arranged on the rigid support surface. The use of such a film is particularly useful when the device comprises a plurality of rigid support surfaces, which are not aligned exactly parallel or have different heights relative to the support plate. Even slight differences in height are sufficient to cause undesirable stress peaks in the large optical components supported thereon. In order to avoid such stress peaks, the metal film and / or the plastic film can be provided on at least one of the rigid support surfaces and towards the bottom side of the large optical components, whereby the film extends parallel to the bottom side of the large optical components. As the metal film, preferably a tin film or an aluminum film is used. Basically, alternatively or additionally, the use of a plastic film, for example a polytetrafluoroethylene (PTFE) film, is also conceivable. It is also conceivable to use several metal or plastic films arranged on top of one another, for example a tin film and an aluminum film, which films can be arranged on top of one another in any way. The use of such a film allows the height difference to be easily adjusted.

[0021] In a further embodiment, more than 50% of the gravity of the large optical component acts on the elastic support surface, preferably 70-95% of the gravity, more preferably 85-95% of the gravity.

[0022] Thus, less than 50% of the gravity of a large optical component acts on the rigid support surface (or rigid support surfaces), preferably 5-30% of the gravity, more preferably 5-15% of the gravity.

[0023] On the one hand, this embodiment ensures that the stresses induced locally on the optical component by the rigid support surface are reduced as much as possible. On the other hand, it ensures that a sufficient gravitational force is still borne by the rigid support surface to ensure accurate positioning and alignment of the large optical component or to ensure a reliable and clear contact at the contact points of the device. It is particularly preferred that 90% of the gravitational force of the large optical component is borne by the elastic support surface and 10% of the gravitational force is borne by the rigid support surface (or rigid support surfaces).

[0024] In a further embodiment of the device, the elastic support surface comprises a spring strip having a number of elastic springs.

[0025] The spring strip is formed in a straight line from a series of springs, the springs being connected to one another at at least one point. The arrangement of the spring strip in the device is preferably selected so that the longitudinal direction of the spring strip (i.e. along its longer side) is parallel to the longitudinal axis of the support plate (or to the longitudinal axis of the large optical component, if one is attached thereto). The shape of the spring is essentially arbitrary. In particular, springs having a curvature in the direction away from the support plate, thereby pointing towards the bottom surface of the large optical component to be mounted, are suitable. Likewise suitable are springs having elastic (or resilient) arms pointing away from the support plate, preferably at an angle between 30° and 50° from the (surface of) the support plate.

[0026] In a further embodiment, the gradient of the spring characteristic curve of the elastic springs of the spring strip is between 0.1 N / mm and 10 N / mm, preferably between 0.5 N / mm and 2 N / mm, more preferably between 0.8 N / mm and 1.2 N / mm, for example 1 N / mm. The spring constant of the entire spring strip depends on the number of individual springs and the length of the strip. The spring characteristic curve of a spring describes the behavior of the spring during operation. More precisely, the spring characteristic curve shows the relationship between the spring force and the spring displacement. Depending on the spring shape or the spring system used, a distinction is made between linear, progressive, depressive or combined spring characteristics. Basically, springs with a small gradient of the spring characteristic curve (small force change relative to displacement change) are more suitable than springs with a large gradient of the spring characteristic curve. In this respect, very elastic springs are particularly preferred, since they can better accommodate possible tolerances or ensure a more even weight distribution.

[0027] In particular, it can be provided that the spring strip comprises at least 50 and / or at most 400 elastic springs, preferably at least 100 and / or at most 300 elastic springs, particularly preferably at least 150 and / or at most 250 elastic springs.

[0028] For example, the spring strip has a length between 50 mm and 1000 mm, preferably between 100 mm and 600 mm.

[0029] In a preferred embodiment of the device, the material of the spring strip comprises metal and / or plastic.

[0030] Possible metals are in particular copper or copper alloys such as copper beryllium (CuBe), bronze (CuSn) or brass (CuZu), stainless steel, stainless steel alloys or aluminium alloys. In particular, copper beryllium is suitable as a material for the spring strips, since, despite its high strength, it is easy to form, has a high resistance to relaxation and is very durable (it does not rust in particular).

[0031] Possible plastics for the spring strips are, for example, elastomers, carbon fiber reinforced plastics (CFK) or glass fiber reinforced plastics (GFK), in particular carbon fiber reinforced elastomers or glass fiber reinforced elastomers. Polyetherimides (e.g. 1,4-bis(4-nitrophthalimido)-phenylene) are also particularly suitable. Spring strips made from suitable plastics have high strength, good fatigue behavior, few corrosion problems and are lightweight.

[0032] However, metal spring strips are usually preferred because plastic has limited resistance to UV light and in some cases can outgas, which can interfere with sensitive optical processes.

[0033] Depending on the size or thickness of the large optical component, it is advantageous to arrange multiple springs in a row on the support plate so that they extend parallel or transverse to the longitudinal axis of the large optical component when the large optical component is fixed to the support plate.

[0034] Additionally, the spring strips preferably have a predetermined metal thickness and / or preload.

[0035] In a further embodiment, the resilient support surface comprises a plurality of threaded screws, preferably a plurality of threaded screws with resilient springs.

[0036] Any number of threaded screws may be used. Essentially, the more threaded screws used, the more weight of the large optical component can be transferred to the threaded screws, and the greater the load on the rigid support surface(s). The multiple threaded screws are distributed as much as possible on the support plate to evenly support the large optical component.

[0037] Preferably, the threaded screw is a spring-loaded screw or a screw with a spring-loaded thrust piece, whereby the spring-loaded thrust piece can be embedded in the core of the screw, however, screws with a spring arranged on the outside of the thread are also conceivable.

[0038] In a further embodiment, the resilient support surface comprises a plurality of resilient plastic supports, preferably elastomeric supports.

[0039] The plastic support may be in the form of, for example, an O-ring.

[0040] In a further embodiment of the apparatus, the resilient support surface comprises at least one of a hydrostatic support, a hydrodynamic support, an aerostatic support, and an aerodynamic support.

[0041] For example, the elastic support surface may include a gas pressure spring. Gas pressure springs usually contain nitrogen as the gas, making them particularly suitable for the clean room conditions usually required in laser applications. However, the problem with gas pressure springs is that the piston rod is usually sealed by oil filling and sealing. The oil means that the piston rod is always wet with oil. For this reason, this type of gas pressure spring is not suitable for clean rooms. However, the use of gas pressure springs is fundamentally conceivable if a suitable lubrication system is used or if a suitable cover is used for the exposed piston rod.

[0042] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations shown in each case, but also in other combinations or alone, without going beyond the scope of the invention.

[0043] Exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description. [Brief description of the drawings]

[0044] [Figure 1A]FIG. 1 is a simplified schematic diagram of a support structure for a large optical component at a Bessel point and associated compressive and bending stress curves. [Figure 1B] FIG. 1 shows a simplified schematic diagram of a support structure for a large optical component at its end points and associated compressive and bending stress curves. [Diagram 2] 1 is a graph showing a line profile of a large optical component. [Diagram 3] FIG. 1 is a perspective view of a first embodiment of the novel device. [Figure 4] FIG. 1 shows a perspective view of a second embodiment of the novel device. [Diagram 5] FIG. 1 is a perspective view of a second embodiment of the novel device with large optical components mounted thereon. [Figure 6] FIG. 1 is a cross-sectional view of a second embodiment of the novel device with large optical components mounted thereon. [Figure 7A] FIG. 2 illustrates an embodiment of a spring strip. [Figure 7B] FIG. 13 shows another embodiment of a spring strip. [Figure 7C] FIG. 13 shows another embodiment of a spring strip. [Figure 7D] FIG. 13 shows another embodiment of a spring strip. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] 1A shows a simplified schematic diagram of a support structure for a large optical component, indicated by reference number 50. In the diagram shown, the (elongated) large optical component 50 is supported at Bessel points BP1 and BP2 (belonging to its long sides) via rigid support surfaces 14a and 14b. Furthermore, a compressive stress curve D and a bending stress curve B over the length L of the large optical component caused by the support structure are shown diagrammatically. From the stress curves D and B, it can be seen that the gravity of the large optical component 50 leads to compressive and bending stresses in the region of the Bessel points BP1 and BP2. Furthermore, it can be seen that the bending stress B alternates between compressive and tensile stresses over the length of the large optical component. The compressive stresses are maximum at the support surfaces 14a or 14b, whereas the tensile stresses are maximum in the middle of the long sides of the large optical component.

[0046] 1B is a simplified schematic representation of a support structure for a large optical component 50 at the end points R1 and R2 and the associated compressive stress curve D and bending stress curve B over the length of the large optical component 50. From FIG. 1B, it can be seen that the gravity of the large optical component 50 induces compressive stresses in the area of ​​the rigid support surfaces 14a, 14b, i.e., in the area of ​​the end points R1, R2. Indeed, the greater the gravity of the large optical component and the smaller the support surfaces 14a, 14b, the greater the stresses. This also applies to the support structure shown in FIG. 1A.

[0047] For economic reasons, the length of the large optical component 50 may be selected to be equal to or less than the line length of the laser beam generated on the working surface. This means that the stresses generated in each large optical component by the support structure shown in Figures 1A and 1B are within the optically usable range. Even if the optical components are selected slightly larger than the typical line length, for example, for a line length of 1500 mm and an optical component length of 1800 mm, the generated stresses are often within the optically usable range. Thus, the stress curves in Figures 1A and 1B impressively show the need for an improved support structure.

[0048] The effect of the stresses induced by the supports at the Bessel points in the large optic is shown in Figure 2. Figure 2 shows the intensity profile of a laser line passing through the large optic in focus. This profile was recorded along the long side (x direction) of the large optic. The lower figure contains several superimposed longitudinal sections of the shown intensity profile, or sections along various y positions, where the y direction represents the direction of spread of the laser line. If the camera (as in this case) is not completely insensitive to polarization, the areas in the large optic that are assigned to areas where the polarization is rotated by the stresses (induced by the rigid supports) will have an intensity change in the intensity profile. However, if one is not aware of this effect, when looking at the intensity profile, one would assume that the line profile has a higher intensity in these areas, i.e. at the support points 14a and 14b. However, this is not actually the case or is simply caused by the polarization rotation.

[0049] FIG. 3 indicates, overall, with the reference number 10, a first embodiment of the novel device. The device 10 is shown in a perspective view and comprises a flat support plate 12 and a rigid support surface 14a arranged on the support plate 12. The rigid support surface 14a is formed as a rigid flat body. In the region of the rigid support surface 14a, rigid contact surfaces 18a and 18b are arranged on the support plate and are configured, like the rigid support surface 14a, to hold a large optical component (not shown here) in a predetermined position (and orientation). Although not shown, the rigid contact surfaces can in principle be adjustable and / or have screws with spring preloading, which are configured to press against the large optical component. Furthermore, two elastic support surfaces 16a, 16b in the form of single spring strips are arranged on the support plate 12. The spring strips have a predetermined elasticity or preloading and are configured to elastically support the large optical component. In particular, the spring strips act as support elements for the rigid support surface 14 a to counteract (from below) the gravitational force of the large optical component 50 .

[0050] Figure 4 is a perspective view of a second embodiment of the novel device 10. In particular, Figure 4 shows a support plate 12 belonging to the device 10, two rigid support surfaces 14a and 14b and three resilient support surfaces 16a, 16b and 16c arranged on the support plate, where the support plate is part of a frame commonly used for laser applications with large optical components.

[0051] Each of the elastic support surfaces 16a, 16b, and 16c includes a metal spring strip that is arranged to run parallel to the longitudinal direction y of the support plate 12. This allows the elastic support surfaces to support the large optical component 50 over its entire length in the mounted state.

[0052] 4, a large optical component 50 is adapted to be supported within a frame on support plate 12 by rigid support surfaces 14a, 14b and resilient support surfaces 16a, 16b, 16c. In this embodiment, large optical component 50 comprises a large plano-convex lens having a bottom surface 52 (not shown), four side surfaces 54a, 54b, 54c, 54d, and a top surface 56.

[0053] 5 is a perspective view of a second embodiment of the novel apparatus 10 with a large optical component 50 attached thereto, in which the large optical component 50 covers most of the support plate 12, the rigid support surfaces 14a and 14b, and the resilient support surfaces 16a, 16b, and 16c.

[0054] 6 is a cross-sectional view of a second embodiment of the novel device 10 with a large optical component 50 attached thereto. The large optical component 50 is transparent so that it is possible to see how the large optical component 50 rests on the rigid support surface 14a and on the resilient support surface 16a.

[0055] 7A-7D show various embodiments of spring strips as examples of the elastic support surface 16a. Each of the illustrated spring strips consists of a series of individual elastic springs 162 arranged in a row, where the springs 162 are connected to each other at least at certain points. In each of the illustrated embodiments, the illustrated spring strips consist of a bent thin metal sheet. In this case, the spring strips or individual springs 162 are formed to have a curved portion. When the spring strips or springs 162 are attached to the support plate 12 of the novel device 10, the spring strips or springs 162 are arranged so that the curved portion faces away from the support plate 12. Thereby, when the large optical component 50 is attached on the support plate, the curved portion faces toward the bottom surface 52 of the large optical component, and the large optical component can be supported (surface-wise). [Explanation of symbols]

[0056] 10 equipment 12 Support plate 14a Rigid support surface 16a Elastic support surface 162 Elastic Spring 50 Large Optical Components 52 Bottom surface BP1 Bessel point

Claims

1. An apparatus (10) for supporting a large optical component (50), comprising: A support plate (12); a rigid support surface (14a) disposed on the support plate (12) and configured to support a bottom surface (52) of the large optical component (50) in a predetermined position and orientation; and a resilient support surface (16a) arranged on the support plate (12) and configured to resiliently support the bottom surface (52) of the large optical component (50), 1. An apparatus (10), wherein the rigid support surface (14a) is configured to support the large optical component (50) at a Bessel point (BP1) of the large optical component (50).

2. 2. The device (10) according to claim 1, characterized in that a metal film and / or a plastic film is arranged on the rigid support surface.

3. The device (10) according to claim 1 or 2, characterized in that more than 50% of the gravity of the large optical component (50) acts on the elastic support surface (16a), preferably 70 to 95% of the gravity, and more preferably 85 to 95% of the gravity.

4. The device (10) according to any one of claims 1 to 3, characterized in that the resilient support surface (16a) comprises a spring strip having a plurality of resilient springs (162).

5. The device (10) according to claim 4, characterized in that the gradient of the spring characteristic curve of the elastic spring (162) of the spring strip is between 0.1 N / mm and 10 N / mm.

6. The device (10) according to claim 4 or 5, characterized in that the material of the spring strip comprises metal and / or plastic.

7. The device (10) according to any one of claims 1 to 6, characterized in that the elastic support surface (16a) comprises a plurality of threaded screws, preferably a plurality of threaded screws with elastic springs.

8. Device (10) according to any one of the preceding claims, characterized in that the elastic support surface (16a) comprises a plastic support, preferably an elastomeric support.

9. The device (10) according to any one of the preceding claims, characterized in that the elastic support surface (16a) comprises at least one of a hydrostatic support, a hydrodynamic support, an aerostatic support and an aerodynamic support.

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