Linear Optical System

Abstract

The present invention relates to a line optical system (10) for generating a predetermined laser line (24) on a work surface (26), said line optical system comprising at least one laser source (12) for generating at least one laser beam (20) and an optical device suitable for generating an illumination beam (22) from said at least one laser beam (20) along a beam path, said illumination beam (22) defining a beam direction across said work surface (26), said illumination beam (22) forming said predetermined laser line (24) in the area of ​​said work surface (26), said optical device (14) comprising a focusing objective lens (28) for focusing said illumination beam (22) in said beam path. The optical device (14) has a beam unit (18) and the focusing objective lens (28) is movable parallel to the beam direction; a camera system (36) suitable for observing the illumination beam (22) at a predetermined position below the focusing objective lens (28) in the beam path, the illumination beam (22) having a focus state at the predetermined position; and a control device (44) suitable for readjusting the position of the focusing objective lens (28) parallel to the beam direction based on a change in the focus state at the at least one predetermined position.

Description

[Technical field]

[0001] The present invention relates to a line optics system for producing a predetermined laser line on a work surface. [Background technology]

[0002] Such a line optical system is known on its basis from US Pat. No. 5,399,633.

[0003] The linear form of the laser radiation of such a line optical system can advantageously be used for thermal processing of a workpiece. The workpiece can be, for example, a synthetic resin material on a glass plate used as a carrier material. The synthetic resin material can in particular be a thin film on which organic light emitting diodes, so-called OLEDs, and / or thin film transistors are produced. OLED films are increasingly used in smartphone displays, tablet PCs, televisions and other devices with screen displays. After the electronic structures are produced, the thin film must be removed from the glass carrier. This is done with a laser radiation in the form of a thin laser line, which moves at a defined speed relative to the glass plate and, in so doing, penetrates through the glass plate and releases the adhesive bond of the thin film. Such an application is often denoted in practice as LLO or laser lift-off.

[0004] Another popular application of sequentially irradiating a workpiece with a given laser line can be melting amorphous silicon line by line on a carrier plate. The laser line moves with a given speed relative to the workpiece in this specification. Through melting and subsequent cooling, the relatively cost-effective amorphous silicon can be transformed into better quality polycrystalline silicon. Such applications are often actually written as solid-state laser annealing (SLA), sequential planar solidification (SLS) or excimer laser annealing (ELA).

[0005] In such applications, a laser line is required on the working surface that is as long as possible in one direction in order to obtain the largest possible working surface, and in comparison, very short in another direction in order to provide the energy density required for the respective process. Correspondingly, a long and thin laser line with a very large aspect ratio of line length to line width is desirable. In typical applications, line lengths of 100 mm or more and line widths of as much as 20 μm may be desirable. The direction along which the laser line runs is usually designated as the major axis (LA), and the line width as the so-called minor axis (SA, minor axis) of the beam distribution. In general, the laser line should have a certain intensity gradient in both axes. It is often desirable for the laser line to have an intensity distribution that is as rectangular or trapezoidal as possible in the major axis, where a trapezoidal intensity distribution can be advantageous if several laser lines are adjacent to each other for a longer total length. In the minor axis, a rectangular intensity distribution (so-called top hat distribution) or a Gaussian distribution is often desirable depending on the application.

[0006] The patent application EP 1 399 636 A1 discloses a device for generating such a laser line with numerous details regarding the elements of the optical device. The optical device in the application includes a collimator for parallelizing the laser beam, a beam converter, a homogenizer, and a focusing stage. The beam converter receives the parallelized raw beam and expands it in the longitudinal direction. In principle, the beam converter can also receive and combine several raw laser beams from several laser sources into one expanded laser beam with higher power. The homogenizer generates the desired beam distribution in the longitudinal direction. The focusing stage focuses the deformed laser beam at a predetermined position in the area of ​​the working surface. The known device is suitable for LLO and SLA applications and can set laser beams with wavelengths from the infrared range (IR) to the ultraviolet range (UV).

[0007] At high laser powers, line focus systems can experience changes in their optical properties, for example due to thermal lensing or mechanical expansion of optical components due to temperature fluctuations, which leads to shifts in the focal position of the laser line.

[0008] This problem is known for cutting lenses and line focus systems. To compensate for this, the focusing optics of the line focus system has been adjusted up to now based on a characteristic curve. This characteristic curve represents the position of the focusing optics as a function of time. The characteristic curve can be determined beforehand, for example in a calibration process, and used, for example in the form of control data from a control unit of the line focus system, to adjust the focusing optics during operation.

[0009] For example, in (Patent Document 3), an optical system for generating an illumination line is shown. The optical system includes a laser source generating a laser beam along an optical axis. The optical system further includes a beam forming device suitable for forming a laser beam such that the beam distribution of the laser beam has a major axis and a minor axis, and an imaging device (e.g., a focusing objective lens) arranged after the beam forming device in the beam path of the laser beam, suitable for imaging the formed laser beam as an illumination line. The beam forming device includes at least one telescope device including a first lens group and a second lens group, the first lens group and the second lens group having optical refractive power at least with respect to the minor axis. The optical system includes a first moving device for moving at least one of the first and second lens groups along the optical axis. The optical system includes a second moving device for moving the imaging device along the optical axis. The optical system further includes a control unit suitable for controlling the first and second moving devices, and at least one of the first and second lens groups and the imaging device are moved while the laser source generates the laser beam. Control data is stored in a memory of the control unit for controlling the first and second mobile devices.

[0010] However, known line optical systems still leave room for improvement, particularly with regard to the adjustment of the focusing optics. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] US Patent Application Publication No. 2006 / 182155 [Patent Document 2] International Publication No. 2018 / 019374 Brochure [Patent Document 3] German Patent Application Publication No. 102018200078A1 Summary of the Invention [Problem to be solved by the invention]

[0012] Against this background, it is an object of the present invention to provide a line optical system with improved adjustment of the focusing optics. [Means for solving the problem]

[0013] According to one aspect, the object is solved by a line optical system for generating a predefined laser line on a working surface. The line optical system comprises at least one laser light source generating at least one laser beam, an optical device, a camera system and a control device. The optical device is suitable for generating an illumination beam along a beam path from the at least one laser beam. The illumination beam defines a beam direction across the working surface. The illumination beam forms a predefined laser line in the region of the working surface. The optical device comprises in the beam path a focusing unit with a focusing objective for focusing the illumination beam. The focusing objective is movable parallel to the beam direction. The camera system is suitable for observing the illumination beam at a predefined position below the focusing objective in the beam path. The illumination beam has a focus state at the predefined position. The control device is suitable for readjusting the position of the focusing objective parallel to the beam direction based on a change in the focus state at the predefined position.

[0014] The at least one laser light source may be a UV laser light source generating a UV laser beam or an IR laser light source generating an IR laser beam. The at least one laser light source may be suitable for generating two or more laser beams. In particular, a number of laser light sources may be provided, each of which is suitable for generating one laser beam.

[0015] The optical device is suitable for generating an illumination beam from at least one laser beam along a beam path. The illumination beam has a linear beam distribution in the region of the working surface. The illumination beam thus generates a predetermined laser line in the working surface. In other words, the illumination beam has a beam distribution in the region of the working surface, which beam distribution has a major axis with a major beam width perpendicular to the beam direction and a minor axis with a minor beam width. To generate the illumination beam from the at least one laser line, the optical device may have a series of optical components that guide the beam along the beam path and form the beam. The optical device may furthermore be movable along a movement direction relative to the working surface, preferably parallel to the working surface, in order to process the workpiece with the illumination beam.

[0016] The optical device comprises a focusing unit, which is suitable for focusing the radiation beam. In particular, the focusing unit can focus the radiation beam in the direction of the minor axis. In other words, the focusing unit is used to focus the minor axis of the laser line. The focusing unit is preferably arranged in the beam path after the beam steering and beam forming optics.

[0017] To focus the illumination beam, the focusing unit has a focusing objective. The focusing objective may have one or several optical components. The focal point of the focusing objective is at a focal position below the focusing objective in the beam path. In other words, the focal position of the focal point of the focusing objective is the position below the focusing objective in the beam path, at which the focusing objective focuses the illumination beam. The focal position therefore defines the distance, below the beam path, at which the focal point of the focusing objective is located. The term "below the beam path" is to be interpreted with respect to the beam path and beam direction of the illumination beam and means that something is arranged in the beam path or subsequent to the beam direction. In other words, the focal position of the focal point of the focusing objective is after the focusing objective in the beam path or in the beam direction of the illumination beam, in other words behind it.

[0018] The focusing objective lens is furthermore movable parallel to the beam direction. In other words, the focusing objective lens is arranged so that it can be moved parallel to the beam direction. To move the focusing objective lens, the focusing unit can for example have a moving device. By moving the focusing objective lens, the position of the focus of the focusing objective lens can be adjusted.

[0019] The line optical system may further comprise other optical components in the beam path below the focusing unit, such as, for example, protective glasses, turning mirrors, etc. Those other optical components preferably do not have a beam forming or beam steering function.

[0020] The camera system is suitable for observing the illumination beam at a predetermined position in the beam path below the focusing objective lens. Observing means that the camera system acquires, for example, one or more images of the illumination beam, in which the illumination beam at the predetermined position is depicted. The predetermined position is arranged after the focusing objective lens in the beam direction of the illumination beam.

[0021] The focusing objective lens has a distance relative to the given position in the beam direction. The illumination beam has a focus state at the given position. The focus state describes the focusing at the given position relative to the focusing objective lens, in other words the focusing at a distance relative to the focusing objective lens. In particular the focus state describes how strongly the illumination beam is focused at the given position. In other words the focus state describes the degree of focusing at that position. At the focus position, in other words at the focal point of the focusing objective lens, the focusing is maximum. Moving away from the focus position parallel to the illumination direction the focusing becomes weaker. If the focal position of the focal point of the focusing objective lens is changed the focus state at the given position changes.

[0022] A change in the focus state is called a focus state change. The focus position can change, for example, in two cases: on the one hand, if the focusing objective is displaced parallel to the beam direction, and on the other hand, due to changes in the optical properties of the focusing objective, in particular due to thermal changes. If the focus state at a given position changes, then the focus state of the illumination beam in the working plane also changes. Camera systems are particularly suitable for observing the focus state at a given position, in particular the focus state changes at a given position.

[0023] The control device is suitable for readjusting the position of the focusing objective lens parallel to the beam direction based on the focus state change at the predetermined position. The control device preferably analyzes the focus state at the predetermined position observed by means of the camera and determines the focus state change on the basis thereof. To determine the focus state change, the control device can, for example, observe the focus state at the predetermined position at a determined time point and compare it with a predefined focus state. Alternatively, the control device can observe the focus state at two or more determined time points and compare the observed focus states with each other.

[0024] Based on the determined or observed change in focus state, the control device can appropriately readjust the position of the focusing objective. For this readjustment, for example, based on the determined change in focus state, a direction and / or a step width for shifting the position of the focusing objective parallel to the beam direction can be determined. In particular, the position of the focusing objective is then adjusted to shift the focal position to the working surface. In this way, the short axis of the laser line is focused on the working surface.

[0025] The readjustment of the position of the focusing objective lens is therefore performed in the form of a feedback loop, whereby a first focus state change at a given position is first observed and the position of the focusing objective lens is appropriately readjusted, which leads to a second focus state change at the given position.

[0026] The readjustment can be performed passively or actively. Passive readjustment means that the focus state of the focusing objective is observed over time while it is placed in a position. A focus state change caused by a change in the optical properties of the focusing objective, in particular a thermally induced change, can then be determined. The position of the focusing objective is adjusted in such a way that this determined focus state change is counteracted. In other words, the readjustment causes a focus state change which reverses the determined focus state change. The readjustment is therefore performed in this case according to the negative feedback principle. In particular in the case of passive readjustment, the focusing objective can be initially positioned such that the focus position is located in the working surface. With the readjustment in the negative feedback principle, the position of the focusing objective can be readjusted based on the observed focus state change so that the focus position returns to the working surface again. Active readjustment means that the focus state is observed over time while the position of the focusing objective is changed. Depending on the focus state change determined in this way, the position of the focusing objective lens can be appropriately readjusted.

[0027] In a preferred embodiment, the predetermined position of the beam direction is at the same height as the working surface. In this case, the illumination beam has the same focus state at the predetermined position observed with the camera system and in the working surface. In particular, when the camera system observes that the focus state at the predetermined position is optimal, the illumination beam is focused in the working surface, which means that the focus position is in the working surface. This embodiment is particularly suitable for active readjustment. The position of the focusing objective can then be readjusted based on the observed focus state change to optimally adjust the focus state at the predetermined position, whereby the focus position is shifted to the working surface. This can in particular be done repeatedly. Repeatedly means in this document that the readjustment is performed in several successive steps. The direction and / or step width of the position change of the focusing objective is then determined based on the focus state change in each of these steps.

[0028] The control device may in particular comprise an adjustment unit and a data processing unit. The data processing unit may for example execute a calculation step for determining the focus state change. The adjustment unit may for example generate control instructions for adjusting the position of the focusing objective. For example, the control instructions may be used to control a movement device suitable for moving the focusing objective.

[0029] The line optical system according to the invention is designed in such a way that the focal position can be easily adjusted online, i.e. during operation, depending on the observed changes in the focus state. In this way, the radiation beam, in particular the laser line, can be focused in the working plane during operation. The adjustment according to the characteristic curve, which has been used up to now in the prior art, has the disadvantage that in the case of UV line focus systems, this characteristic curve is difficult to convert. Furthermore, contamination and changes in process parameters require new characteristic curves. On the contrary, the proposed readjustment in response to the observed changes in the focus state can be used in these cases. The line optical system according to the invention therefore allows the focusing objective to be adjusted better and for a wider range of applications.

[0030] The problem posed at the outset is thus completely solved.

[0031] In a first configuration of the line optical system, the camera system is arranged in the beam path below the work surface.

[0032] Thus, the illumination beam is observed in the beam path after the work surface. Furthermore, the illumination beam can be observed either after it has passed through the work surface or after it has been reflected by the work surface.

[0033] In particular, the camera system may be arranged so that a reflected beam of the illumination beam can be observed on the working surface. The reflected beam is a back reflection of the illumination beam on the working surface. In particular, during operation, the illumination beam can be reflected on the surface of a workpiece that is arranged on the working surface and is to be processed with the laser beam. The back reflection can be observed using the camera system. In this way, the defocus as well as changes in the working surface can be compensated for.

[0034] Alternatively, the camera system can also be arranged behind the work surface, which is then between the camera system and the focusing unit. The camera system can thereby observe the illuminating beam passing through the work surface. With this arrangement of the camera system, the focal position can be determined and adjusted when no workpiece is placed on the work surface or when the workpiece can be completely traversed with the laser line so that the laser line passes through the work surface and reaches the camera system.

[0035] In another embodiment, the line optical system comprises an additional optical component arranged in the beam path below the focusing unit, the additional optical component being suitable for splitting the illumination beam, a part of the illumination beam running in the direction of the working surface and another part of the illumination beam running in the direction of the camera system.

[0036] As already explained before, additional optical components, such as for example a turning mirror or a protective glass, may be arranged in the beam path after the focusing unit, through which the illumination beam reaches the direction of the working surface. The additional optical components may for example split the illumination beam into two parts. In particular, the additional optical components may be arranged to reflect one part of the illumination beam and to pass, in other words transmit, another part of the illumination beam. Either the transmitted or the reflected part runs in the direction of the working surface, whereas the corresponding other part of the illumination beam runs in the direction of the camera system and is observed by this camera system. The reflected part of the illumination beam may be described as a back reflection of the illumination beam at the additional optical components.

[0037] In particular, the camera system may be suitable for observing the back reflection of the illumination beam on the additional optical component, which is particularly advantageous if the additional optical component has a protective glass through which the illumination beam passes in the direction of the working surface, the camera system then being used to observe the back reflection on the protective glass.

[0038] Alternatively, the camera system may also be suitable for observing the transmitted portion of the illumination beam. For example, the additional optical component may further comprise a partially transparent, in particular semi-transparent, deflection mirror, which deflects, in other words reflects, the illumination beam towards the working surface. The transmitted portion of the illumination beam that passes through the deflection mirror may then be observed by means of the camera system.

[0039] In another embodiment of the line optical system, the camera system comprises a camera adapted to obtain a first image of the illumination beam at a first time, where the first image comprises an image of the illumination beam at a given position at the first time.

[0040] In other words, the camera is suitable for acquiring an image at a given time point, in which the illumination beam is imaged in a defined focus state. As already explained at the beginning, the focus state depends on the one hand on the distance parallel to the illumination direction relative to the focusing objective lens, and on the other hand on the optical properties of the focusing objective lens, in other words on the position of the focus position relative to the position of the focusing objective lens. The imaging sharpness of the imaging of the illumination beam in the acquired image depends on the focus state.

[0041] In another form of the line optical system, the control device is adapted to determine a focus state of the illumination beam at a predetermined position based on the first image, and to determine a focus state change based on the determined focus state and a default focus state.

[0042] In particular, the focusing objective may be initially arranged in the laser beam optical device such that the focal position is located in the working plane. The predefined focal state then corresponds to the focal state that the radiation beam assumes when the focal position is located in the working plane. The predefined focal state may, for example, be pre-fixed or calculated. Alternatively, for example, the predefined focal state in an initialization process may be determined on the basis of an image that is initially acquired by means of a camera. In this case, the focal position is preferably located in the working plane in the initialization process. The predefined focal state may therefore also be referred to as predefined or pre- or initial focal state. The adjustment of the position of the focusing objective may then be carried out so as to adjust the predefined focal state again. In other words, the readjustment may be carried out according to the negative feedback principle.

[0043] In another form of the line optical system, the camera is adapted to obtain a second image of the illumination beam at a second time, the second image comprising an image of the illumination beam at the predetermined position at the second time, and the controller is adapted to determine a focus state of the illumination beam at the predetermined position at the first time based on the first image, determine a focus state of the illumination beam at the predetermined position at the second time based on the second image, and determine a focus state change based on the focus states determined at the first and second times.

[0044] The first and second time points are different from each other. In other words, the camera is suitable for acquiring images of the illumination beam at a given position at different time points, respectively. In particular, the camera may also be suitable for acquiring images at three or more time points. Based on the acquired images, the control device can compare the focus states observed in the acquired images with each other and thereby determine, in particular, a focus state change at a given position between two time points. The control device can adjust the position of the focusing objective lens based on the determined focus state change. If images are acquired at three or more time points using the camera, the control device can, for example, determine a focus state change, respectively, between two successive time points and appropriately readjust the position of the focusing objective lens based on the determined focus state change. The readjustment is then performed iteratively. For adjusting the position of the focusing objective lens, it is also possible to take into account multiple focus state changes, for example the last two or three, in order to fix in particular the direction of movement and / or the step width of the focusing objective lens.

[0045] In another form of the line optical system, the controller is adapted to adjust a position of the focusing objective lens such that the focusing objective lens is positioned to capture a first image at a first position and a second image at a second position.

[0046] In this way, the focusing objective can be actively moved to search for the optimal focus state. In particular, the position of the camera system in the beam direction relative to the work surface, i.e. the position of the predetermined position, is predefined, i.e. known. This is particularly advantageous if the predetermined position at which the camera system observes the illumination beam is at the height of the work surface in the beam direction. By actively moving the focusing objective and simultaneously observing the focus state, the optimal focus state can be adjusted.

[0047] In another embodiment of the line optical system, the control device is adapted to determine a focus value of the focus state based on a beam distribution of the illumination beam at the predetermined position at the first and / or second time point in order to determine the respective focus state, in particular the control device is adapted to determine a focus state change based on a comparison of the focus values ​​of the focus states.

[0048] The focus value indicates the degree of focusing of the illumination beam in the beam direction at a given position, in other words the imaging sharpness. The focus value has a global extreme value at the focus position of the focus of the focusing objective lens. In particular the curve of the focus value in the beam direction can be modeled as a curve on a parabola. The positions of the extreme values ​​then correspond to the focus position. To determine the focus value, for example the beam distribution of the image of the illumination beam can be observed in the direction of the short axis. In particular the control device can be suitable for determining the beam distribution of the illumination beam in the direction of the short axis for the image of the illumination beam in the corresponding image, in which case the focus value can be determined on the basis of the beam distribution of the image. The beam distribution is an intensity distribution which represents the intensity curve of the illumination beam in the direction of the short axis at the given position. The beam distribution can in particular be determined on the basis of the projection of the pixels of the image in the corresponding image along the direction of the major axis into the direction of the short axis. The beam distribution can preferably be a square-shaped intensity distribution (so-called top hat distribution) or a Gaussian distribution. The focus value can for example be the inclination of the beam distribution (also called lateral inclination). The inclination represents the gradient in the edge region of the beam distribution, in other words on one side of the beam distribution. The smaller the value or inclination, the steeper the side. The focus value may for example be the inverse of the inclination. The smaller the focus value, the steeper the edge. Alternatively, the focus value may be the width of the beam distribution. In particular, the width of the beam distribution may be taken as the width of the region of the beam distribution. The intensity value is then 1 / e of the maximum value of the beam distribution. 2, 50% or 90% or more. At the focus position, the slope of the beam distribution is maximum and the inverse of the slope and the width of the beam distribution are minimum. The focus state change can be determined, for example, based on the difference in focus values ​​of the focus states to be compared. In particular, based on the difference in focus values, a direction and / or a step width for shifting the position of the focusing objective parallel to the beam direction for readjustment can be fixed.

[0049] In another embodiment, the line optical system comprises a moving device for moving the focusing objective parallel to the beam direction, the control device being adapted to control the moving device to adjust the position of the focusing objective.

[0050] For example, the control device can send a control command to the displacement device, which then displaces the focusing objective according to the control command. The displacement device can for example have a linear guide along which the focusing objective can be displaced parallel to the beam direction. The linear guide thus guides the focusing objective parallel to the beam direction. The displacement device can furthermore have a drive device, which can displace the focusing objective parallel to the beam direction, in particular along the linear guide. In particular, the control device can control the drive device.

[0051] In another form of the line optical system, the optical device further comprises beam steering and beam forming optics adapted to generate the radiation beam from the at least one laser beam.

[0052] The optical device preferably comprises a series of beam guiding and beam shaping optics along the beam path, with which the radiation beam is generated. These optics are preferably arranged in front of the focusing unit in the beam path. The radiation beam generated by the beam guiding and beam shaping optics is focused in the working plane by the focusing unit. As beam guiding and beam shaping optics, the optical device may comprise, for example, a beam converter, a homogenizer and a large area lens. The beam converter may be arranged in the beam path after the laser source. The beam converter is suitable for expanding at least one laser beam in a direction transverse to the beam direction, in particular in the direction of the longitudinal axis. In particular, the beam converter is used to optimize the aspect ratio of the radiation beam even more and / or more efficiently with respect to the desired laser line. The homogenizer may be arranged in the beam path after the beam converter. The homogenizer is suitable for dispersing at least one, preferably expanded, laser beam homogenously in the longitudinal direction. The homogenizer is thus used to obtain a homogenous intensity distribution of the radiation beam along the longitudinal axis. The large area lens is preferably arranged after the homogenizer in the beam path. The large area lens is used to shape the beam distribution in the working surface. The large area lens may, for example, have one or more optical elements (e.g., Fourier lenses) along the beam path. The optical elements generate a linear beam distribution in the area of ​​the working surface.

[0053] It will be understood that the features mentioned above and which will be further explained hereinafter can be used not only in the respective indicated combinations, but also in other combinations or alone, without departing from the scope of the invention.

[0054] 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]

[0055] [Figure 1] 1 shows a schematic diagram of a first embodiment of a novel line optical system. [Diagram 2]A diagram showing the imaging of an illumination beam using a focusing objective lens is shown. [Diagram 3] Two figures are shown with the focus position of the focusing objective lens shifted. [Figure 4] 1 shows four diagrams illustrating different arrangements of a camera system within the beam path of a line optical system. [Diagram 5] 1 shows a schematic diagram of an example of a line optical system that is retuned according to a characteristic curve. [Figure 6] FIG. 13 shows a schematic diagram of a second embodiment of a line optical system realigned via a camera system. [Figure 7] FIG. 13 shows a schematic diagram of a third embodiment of a line optical system realigned via a camera system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] In FIG. 1, an embodiment of the novel line optical system is generally indicated with the reference number 10. The line optical system 10 generates a laser line 24 in the region of a working surface 26 to process a workpiece (not shown here) arranged in the region of the working surface 26. The laser line 24 runs in a direction denoted as the x-axis below. The laser line has a line width observed in the direction of a y-axis, which runs orthogonally to the x-axis here. In the following, the x-axis therefore corresponds to the major axis of the beam distribution formed on the working surface 26, and the y-axis corresponds to the minor axis of said beam distribution. In other words, the beam distribution has a major axis with a major beam width in the x-direction and a minor axis with a minor beam width in the y-direction. The respective beam width may be defined, for example, as the width of the intensity distribution I(x,y) at 50% of the maximum intensity (FWHM, full width at half maximum), or, for example, as the width between 90% intensity values ​​(full width at 90% value, FW@90%), or in another way.

[0057] In some embodiments, the workpiece may include a surface layer made of amorphous silicon, which is converted to polycrystalline silicon using the laser beam 24, which may be moved in a moving direction relative to the working surface 26 for processing. In other embodiments, the workpiece may be a transparent carrier plate from which a deposited film, for example an OLED film, is to be removed.

[0058] The line optics system 10 includes at least one laser light source 12. In a preferred embodiment, the laser light source 12 may be a solid-state laser. The laser light source 12 generates at least one laser beam 20. In a preferred embodiment, the laser light source 12 may generate multiple laser beams. In an alternative embodiment, the line optics system 10 includes multiple laser light sources 12, each of which generates at least one laser beam 20.

[0059] The line optical system 10 further comprises an optical device 14. The optical device 14 is suitable for generating an illumination beam 22 from the at least one laser beam 20 along a beam path. The illumination beam 22 defines a beam direction across a working surface 26. The illumination beam 22 has a beam distribution in the area of ​​the working surface 26, which beam distribution has, perpendicular to the beam direction, a major axis with a major beam width and a minor axis with a minor beam width. In other words, the illumination beam 22 has a linear shaped beam distribution in the area of ​​the working surface 26. The illumination beam 22 thus generates a laser line 24 in the working surface 26.

[0060] The optical system comprises along the beam path a series of beam steering and beam shaping optics 16 and a focusing unit 18. The focusing unit 18 is disposed in the beam path below the beam steering and beam shaping optics 16.

[0061] The beam steering and beam shaping optics 16 are suitable for generating a radiation beam 22 from at least one laser line 20. As the beam steering and beam shaping optics 16, the optical device may comprise, for example, a beam converter, a homogenizer and a large area lens. The focusing unit 18 is suitable for focusing the radiation beam 22. In particular, the focusing unit 18 focuses the radiation beam 22 in the direction of the short axis.

[0062] To focus the radiation beam 22, the focusing unit 18 comprises a focusing objective 28. The focusing objective 28 comprises one or more optical components. The focusing objective 28 is movable parallel to the beam direction. The focusing unit 18 comprises a movement device 30, which is suitable for moving the focusing objective 28 parallel to the beam direction. The movement device 30 comprises a linear guide 32 and a drive device 34. The linear guide 32 thus guides the focusing objective 28 parallel to the beam direction. Along the linear guide 32 the focusing objective 28 is movable. The drive device 34 is suitable for moving the focusing objective 28 parallel to the beam direction, in particular along the linear guide 32.

[0063] The line optical system 10 further comprises a camera system 36. The camera system 36 is suitable for observing the illumination beam 22 below the focusing objective 28 in the beam path. In particular, the camera system 36 is suitable for observing the illumination beam 22 at a predefined position in the beam path below the focusing objective 28. The illumination beam 22 has a defined focus state at this predefined position. The camera system 36 comprises an imaging system 38 and a camera 40. The imaging system 38 images the illumination beam 22 onto the camera 40. The camera 40 is suitable for acquiring an image of the illumination beam 22 at a defined time point. In particular, the camera 40 is arranged to acquire an image of the illumination beam 22 at a predefined position in the beam path below the focusing objective 28. The image thus comprises an image of the illumination beam 22 at the predefined position. Preferably, the camera is suitable for acquiring an image of the illumination beam 22 at a plurality of time points, for example at a first and a second time point, respectively at the predefined position.

[0064] The line optical system 10 further comprises a control device 44. The control device 44 is suitable for adjusting the position of the focusing objective 28 parallel to the beam direction. The control device 44 can further, for example, send corresponding control commands to the movement device 30. The movement device 30 can move the focusing objective 28 along the linear guide 32 by means of the drive device 34 according to the control command. The control device 44 can further receive data from the camera system 36. These data can comprise one or several captured images. The control device 44 adjusts the position of the focusing objective based on the data of the camera system 36.

[0065] To adjust the position of the focusing objective 28, the control device 26 may, for example, comprise various subunits, each of which may perform control and / or data processing of the components of the laser beam optical device 10. The control device 44 may further comprise, for example, an adjustment unit and a data processing unit. The adjustment unit may, for example, generate control instructions, with which the position of the focusing objective is adjusted. The data processing unit may, for example, perform calculation steps, in which the data received from the camera system 36 are analyzed. Based on this analysis, it generates, in particular, corresponding control instructions, for appropriately adjusting the position of the focusing objective 28.

[0066] The control device 44 may be connected to or may comprise a non-volatile data memory in which a computer program is stored. In some embodiments, the control device 4 is a general-purpose computer, such as a commercially available personal computer operating under Windows, Linux or MacOS, and the computer program from the memory comprises a program code, which is designed and configured to perform the adjustment of the focusing objective lens 28. Alternatively, in an embodiment, the control device 44 is a logic circuit, such as a field programmable gate array (FPGA), an application specific integrated circuit (ASIC), a microcontroller or any other suitable programmable electronic circuit. The logic circuit can be used to perform the adjustment of the focusing objective lens 28, in particular the control and measurement steps, and thus the logic circuit is designed and configured to perform the adjustment of the focusing objective lens 28. To perform the adjustment of the focusing objective lens 28 in the logic circuit, any suitable programming language or hardware description language, such as C, VHDL, etc., can be used.

[0067] The control device 44 is suitable for readjusting the position of the focusing objective lens 28 parallel to the beam direction based on the focus state change at the predetermined position. For example, the control device 44 can analyze one or more focus states observed by means of a camera system to determine the focus state change. Based on the determined focus state change, the control device 44 can appropriately readjust the position of the focusing objective lens 28. In particular, the position of the focusing objective lens 28 can be adjusted such that the focus position is shifted to the working surface 26. In other words, the readjustment is performed in the form of a feedback loop. Based on the focus state change observed at the predetermined position, the position of the focusing objective lens 28 is readjusted, which again leads to a focus state change.

[0068] In Fig. 2(A) a focusing objective lens 28 is shown as an example, with the illumination beam being focused at a focal position 46. In Fig. 2(B) and Fig. 2(C) two beam distributions of the illumination beam 22 in the direction of the short axis are shown: Fig. 2(B) shows a Gaussian distribution, and Fig. 2(C) shows a rectangular beam distribution, the so-called top hat distribution.

[0069] The two beam distributions from Figures 2(B) and (C) have a slope in the side or edge region of the beam distribution. The slope represents the intensity drop y over an interval x at the side of the beam distribution, i.e. in the edge region. The side is the edge region of the distribution, where the gradient is maximum. The slope is therefore defined by the quotient y / x. The inverse of the slope is therefore defined as the quotient x / y.

[0070] Both beam distributions from Figures 2B and 2C furthermore have a width. In particular, the width of the beam distribution can be taken as the width of the area of ​​the beam distribution. The intensity value then is 1 / e 2 , 50% or 90% or more.

[0071] At the focal position 46, the beam distribution of the illumination beam in the direction of the short axis has a minimum width and a maximum slope. As one moves away from the focal position 46 parallel to the beam direction, the slope of the beam distribution decreases and the inverse of the width and slope of the beam distribution increases.

[0072] Therefore, the slope, inverse slope or width of the beam distribution can be used to describe the focus state of the illumination beam at a given position in the beam direction. In other words, the slope, inverse slope or width of the beam distribution can be the focus value of the focus state.

[0073] The control device 44 determines the focus state change, for example by comparing the focus values ​​of two focus states. In particular, the control device 44 can determine the focus state change based on a difference between corresponding focus values ​​of the focus states. The two focus states to be compared can then be, for example, two focus states at a given position at different times.

[0074] 3A shows, by way of example, how the position of the focusing objective lens 28 remains constant, whereas the focal position 46 of the focusing objective lens 28 can shift during operation due to thermal effects. The initial focal position is designated by reference numeral 46. The shifted focal position is designated by reference numeral 46'.

[0075] FIG. 3B shows, by way of example, how the focal position 46 of the focusing objective lens 28 can be adjusted. The focusing objective lens 28 can be moved along the linear guide 32. In the representation of FIG. 3B, the focusing objective lens is, by way of example, displaced in the direction of the focal position, the displaced position of the focusing objective lens being designated by reference number 28''. Due to the displacement of the focusing objective lens 28, the focal position 46 is accordingly displaced, the displaced focal position being designated by reference number 46''.

[0076] FIG. 4 illustrates four exemplary positions of the camera system 36 in the beam path of the line optical system 10 at which the camera system 36 can observe the illumination beam 22 .

[0077] In Figure 4A, camera system 36 is positioned behind work surface 26. In this position, camera system 36 views illumination beam 22 as it passes through the work surface.

[0078] 4B, a turning mirror 48 is disposed in the beam path between the focusing objective lens 28 and the work surface 26. The turning mirror turns the illumination beam 22 toward the work surface 26. The turning mirror 48 is partially transparent. The camera system 36 is positioned such that the portion of the illumination beam 22 that passes through the turning mirror 48 runs toward the camera system 36. In this arrangement, the camera system 36 views the portion of the illumination beam 22 that passes through the turning mirror 48.

[0079] 4C, illumination beam 22 reflects off work surface 26. Camera system 36 is positioned such that the illumination beam reflected from work surface 26 travels towards camera system 36. In this position, camera system 36 observes illumination beam 22 reflected from the work surface.

[0080] In Fig. 4(D) an additional optical element 50, e.g. a protective glass, is arranged in the beam path between the focusing objective lens 28 and the working surface 26. The illumination beam 22 passes through the protective glass in the direction of the working surface 26. A part of the illumination beam 22 is reflected by the additional optical element 50. The camera system 36 is arranged such that the part of the illumination beam 22 reflected by the additional optical element 50 runs in the direction of the camera system 36. In this arrangement the camera system 36 observes the part of the illumination beam 22 reflected by the additional optical element 50.

[0081] Figure 5 shows an example of a line optical system 10 in which the repositioning of the focusing objective is performed according to a characteristic curve. The line optical system 10 from Figure 5 has a similar configuration to the line optical system from Figure 1. However, the line optical system 10 from Figure 5 does not have a camera system 36.

[0082] The line optical system 1 includes one or more beam-forming / beam-guiding optics 16 (e.g. homogenizers or large-area lenses). Further focusing in the short axis is performed by means of a focusing objective 28, which consists of one or more optical components, which can be moved along the beam direction on linear guides 32. A turning mirror 52 may be arranged in the beam path between the optical components 16 and the focusing objective 28. The focusing objective 28 is followed by one or more additional optical components 50 (e.g. optical protective glass or processing chamber protective glass). The illumination beam 22 is focused on a working surface 26, on which a workpiece may be arranged, the surface of the workpiece being in the working surface 26. The surface of the workpiece may also be called a substrate surface.

[0083] Regardless of the described behavior, it is desirable to maintain a specific, particularly focused, beam distribution on the working surface. The time behavior can be compensated for through the fluctuation of the position of the objective lens according to a predefined characteristic curve. This characteristic curve depends, among other things, on the power received. This characteristic curve can be determined in advance, for example by a calibration process.

[0084] As already explained before, readjustment according to a characteristic curve has some disadvantages. As already described before, the new line optical system 10 in particular provides, instead of adjusting through a characteristic curve, furthermore using a camera system 36 in the beam path below the focusing objective 28 for observing the illumination beam 22 at a predetermined position and readjusting the position of the focusing objective 28 according to a feedback loop based on the focus state changes observed at the predetermined position. In figures 6 and 7 two additional embodiments of the new line optical system 10 are shown. The line optical system shown in figures 6 and 7 substantially corresponds to the line optical system 10 from figure 1, showing the beam path in a detailed representation. In particular a turning mirror may be arranged between the optical component 16 and the focusing objective 28. Furthermore the focusing objective 28 is followed by one or more additional optical components 50 (for example optical protective glass or protective glass of the processing room).

[0085] In particular, the camera system 36 can be used to observe the various reflected beams of the illumination beam 22. Figures 6 and 7 show various exemplary arrangements of the camera system 36 within the linear optical system 36. These arrangements of the camera system 36 correspond to the arrangements from Figures 4(C) and (D).

[0086] Illumination beam 22 may be reflected, for example, at work surface 26, in particular at a substrate surface disposed on work surface 26. The beam reflected at work surface 26 is designated by reference numeral 54 and may also be referred to as reflection 54 at work surface 26. Reflection 54 may pass through optical component 50. Camera system 36 is positioned in FIG. 6 such that reflection 54 can be observed.

[0087] Moreover, the illumination beam 22 may as well be reflected at one of the additional optical components 50, for example at the surface of a protective glass. The beam reflected at the additional optical component 50 is designated by the reference numeral 56 and may as well be referred to as a reflection 56 of the illumination beam 22 at the additional optical component 50. The camera system 36 is positioned in Fig. 7 so as to be able to observe the reflection 54.

[0088] Based on the reflections 54, 56 of the illumination beam 22, the control device 44 can appropriately readjust the position of the focusing objective lens 28 along the linear guide 32 through the proposed feedback loop. When observing the reflection 54 at the work surface 26, the defocus as well as the variations in the work surface can thus be compensated for. [Explanation of symbols]

[0089] 10-line optical system 12 Laser light source 16 Beam steering and beam forming optics 18 Focusing Unit 20 Laser Beam 22 Irradiation beam 24 Laser Lines 26 Work Surface 28 Focusing Objective Lens 28'' shifted focusing objective position 32 Linear guide 34 Drive unit 36 Camera System 38 Imaging System 40 Camera 44 Control device 46 Focus position 46' Out of focus 48 additional optics 50 additional optics 52 Turning Mirror 54 reflection 56 reflection

Claims

1. A line optics system for generating a predetermined laser line (24) on a work surface (26), comprising: at least one laser source (12) generating at least one laser beam (20); an optical device suitable for generating an illumination beam (22) along a beam path from said at least one laser beam (20), said optical device comprising: the illumination beam (22) defines a beam direction across the work surface (26); The radiation beam (22) forms the predetermined laser line (24) in the area of ​​the work surface (26); the optical device (14) comprises in the beam path a focusing unit (18) comprising a focusing objective lens (28) for focusing the illumination beam (22), an optical device (14), in which the focusing objective lens (28) is movable parallel to the beam direction; a camera system (36) suitable for observing the illumination beam (22) at a predetermined position in the beam path below the focusing objective lens (28), the illumination beam (22) having a focus state at the predetermined position; a control device (44) adapted to readjust the position of the focusing objective lens (28) parallel to the beam direction based on a change in focus condition at the predetermined position; A line optical system (10) having

2. 2. The line optical system (10) of claim 1, wherein the camera system (36) is disposed in a beam path below the work surface (26).

3. 2. The line optical system (10) of claim 1, further comprising additional optical components (48, 50) arranged below the focusing unit (18) in the beam path, the additional optical components (48, 50) being suitable for splitting the illumination beam (22), a portion of the illumination beam (22) running in the direction of the working surface (26) and another portion of the illumination beam (22) running in the direction of the camera system (36).

4. The line optical system (10) of any one of claims 1 to 3, wherein the camera system (36) comprises a camera (40) suitable for acquiring a first image of the illumination beam (22) at a first time, the first image comprising an image of the illumination beam (22) at the predetermined position at the first time.

5. 5. The line optical system (10) of claim 4, wherein the control device (44) is adapted to determine the focus state of the illumination beam (22) at the predetermined position based on the first image, and to determine the focus state change based on the determined focus state and a default focus state.

6. 6. The line optical system (10) of claim 4 or 5, wherein the camera (40) is adapted to acquire a second image of the illumination beam (22) at a second time point, the second image having an image of the illumination beam (22) at the predetermined position at the second time point, and the control device (44) is adapted to determine the focus state of the illumination beam at the predetermined position at the first time point based on the first image, determine the focus state of the illumination beam at the predetermined position at the second time point based on the second image, and determine the focus state change based on the focus states determined at the first and second time points.

7. 7. The line optical system (10) of claim 6, wherein the control device (44) is adapted to adjust the position of the focusing objective lens (28) such that the focusing objective lens (28) is positioned to acquire a first image at a first position and to acquire a second image at a second position.

8. The line optical system (10) according to any one of claims 5 to 7, wherein the control device (44) is adapted to determine a focus value of the focus state based on a beam distribution of the illumination beam (22) at the predetermined position at a first and / or second time point in order to determine each focus state, in particular the control device (44) is adapted to determine the focus state change based on a comparison of the focus values ​​of the focus states.

9. The line optical system (10) of any one of claims 1 to 8, wherein the line optical system (10) has a moving device (30) for moving the focusing objective lens (28) parallel to the beam direction, and the control device (44) is suitable for controlling the moving device (30) to adjust the position of the focusing objective lens (28).

10. The line optical system (10) of any one of claims 1 to 9, wherein the optical device (14) further comprises beam steering and beam forming optics (16), the optics being suitable for generating the illumination beam (22) from the at least one laser beam (20).

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