NL2030738B1

NL2030738B1 - Laser apparatus, method and computer program

Info

Publication number: NL2030738B1
Application number: NL2030738A
Authority: NL
Inventors: Mertens Michiel
Original assignee: P Laser N V
Priority date: 2022-01-27
Filing date: 2022-01-27
Publication date: 2023-08-07
Also published as: BE1030227A1; BE1030227B1

Abstract

There is provided a laser apparatus for irradiating an object with a laser beam. The laser apparatus comprises laser scan head for directing the laser beam to the object, a 5 transport unit for moving the object and the laser scan head relative to each other, and a control unit configured to control the laser scan head to perform a first scan movement of the laser beam and a second scan movement of the laser beam. The control unit is configured to control the transport unit to move the object and the laser scan head relative to each other in a transport direction during the first scan movement and during the second scan movement. 10 The laser scan head is configured to move the laser beam along a first scan direction to irradiate a first line on the object. The laser scan head is configured to move the laser beam along a second scan direction to irradiate a second line on the object. (Fig. 1)

Description

P35412NLO0 27 januari 2022

Laser apparatus, method and computer program

The invention relates to a laser apparatus, especially a cleaning laser apparatus. The invention further relates to a method for irradiating an object with a laser beam, and to a computer program having instructions to be executed by a control unit of a laser apparatus.

Further, the invention relates to a laser scan head and to a control unit for use in a laser apparatus.

For laser cleaning of an object, a laser apparatus is provided that irradiates the object with a laser beam. By irradiating the object, the laser beam irradiates contamination on the object, such as particles, rust, or coatings that are to be removed. The energy of the laser beam causes a reaction of the contamination on the surface of the object. The reaction may cause the contamination to evaporate or to sublimate. The reaction may cause a chemical reaction, such as oxidating of the contamination. The energy of the laser beam per unit of surface area needs to be high enough to cause the desired reaction of the contamination.

However, the energy of the laser beam per unit of surface area needs to be low enough to prevent damage to the object.

When cleaning an object with a laser cleaning apparatus, it is important that the laser beam from the laser cleaning apparatus irradiates the object as uniformly as possible. By uniformly irradiating the object, the desired reaction of the contamination is obtained over the entire object, whereas damage to the object is prevented. In case the object is not irradiated uniformly, contamination may remain on some areas on the object due to a lack of sufficient radiation, whereas some other areas of the object may be damaged due to an excessive amount of radiation.

However, the laser apparatus should not only obtain a desired cleanliness of the object, but the laser apparatus should also irradiate sufficient surface area of the object per unit of time. The more surface area the laser apparatus irradiates per unit of time, the higher the cleaning capacity of the laser apparatus is.

To improve the cleaning capacity, the object typically moves relative to the laser apparatus in a transport direction. The known laser apparatus scans the laser beam back and forth over the width of the object. During each scan across the object, a line across the object is irradiated.

While the laser beam is scanned across the object, the object moves relative to the laser beam in the transport direction. As a result, the laser beam irradiates a pattern of zig- zag lines on the object. As a result of the zig-zag pattern, some parts of the object receive less radiation from the laser beam than other parts. As a result, the transport speed is set to a low value, to ensure the object is properly cleaned at the areas that receive the least radiation. As a result, the cleaning capacity of the known laser apparatus is low.

In a known laser apparatus disclosed in PCT patent application WO2010/086865, the object to be cleaned is placed at an angle with the transport direction. When scanning the laser beam perpendicular to the transport direction, the transport speed causes the laser beam to describe a line along the object that corresponds to the angle with the transport direction. This way, parallel lines are irradiated on the object instead of a pattern of zig-zag lines.

However, during a scan, the laser beam moves from one side of the object to the opposite side. At the end of the scan, the laser beam is redirected back to the starting side of the object to start the following scan. As a result, the known laser apparatus has a limited cleaning capacity.

It is an objective of the invention to provide an improved laser apparatus, or to at least provide an alternative laser apparatus. Optionally, the improved laser apparatus is able to irradiate a larger surface area per unit of time and/or to irradiate a surface area with a more uniform irradiation across the surface area than the known laser apparatus.

The objective of the invention is obtained by a laser apparatus for irradiating an object with a laser beam. The laser apparatus comprises a laser scan head for directing the laser beam to the object, a transport unit for moving the object and the laser scan head relative to each other, and a control unit configured to control the laser scan head to perform a first scan movement of the laser beam and a second scan movement of the laser beam. The control unit is configured to control the transport unit to move the object and the laser scan head relative to each other in a transport direction during the first scan movement and during the second scan movement. The laser scan head is configured to perform the first scan movement by moving the laser beam along a first scan direction to irradiate a first line on the object. The laser scan head is configured to perform the second scan movement by moving the laser beam along a second scan direction to irradiate a second line on the object. The first scan direction extends across at least part of a width of the object. The width is in a direction perpendicular to the transport direction. The second scan direction extends across at least part of the width of the object opposite to the first scan direction. The control unit is configured to control the second scan direction based on the first scan direction and a vector in the transport direction.

Because of the first scan movement of the laser beam, the laser scan head irradiates the first line on the object. During the first scan movement, the laser beam moves along the first scan direction. Depending on the first scan direction, the first line has a certain orientation on the object. For example, the first line is arranged on the object perpendicular to the transport direction, or at an oblique angle relative to the transport direction.

During the second scan movement of the laser beam, the laser scan irradiates the second line on the object. During the second scan movement, the laser beam moves along the second scan direction. Whereas during the first scan movement, the laser beam moves across at least part of the width of the object in one direction, during the second scan the laser beam moves across at least part of the width of the object in the opposite direction. So by moving the laser beam with the first scan movement and the second scan movement, the laser beam moves back and forth across the width of the object.

In the known laser apparatus, the movement of the laser beam back and forth across the width of the object would result in a pattern of zig-zag lines on the object, because the known laser apparatus moves the laser beam back and forth over the same scan direction.

However, the laser apparatus according to the invention comprises the control unit configured control the second scan direction based on the first scan direction and a vector in the transport direction. The control unit controls the second scan direction by using the first scan direction as a basis and correcting this basis with the vector in the transport direction. By correcting this basis with the vector in the transport direction, the second scan direction is not parallel to the first scan direction. This way, the second scan direction takes the movement of the laser scan head relative to the object into account during the second scan movement.

This allows the laser scan head to irradiate the second line more accurately relative to the first line to obtain a more uniform irradiation of the object.

The laser apparatus is, for example, a cleaning laser apparatus for cleaning the object.

The cleaning laser is adapted to remove undesired particles or coatings from the object. The laser apparatus is, for example, adapted to perform a surface treatment of the object, such as laser polishing. The laser apparatus is, for example, adapted to perform laser beam machining for creating features in the object by removing material of the object. For example, the laser apparatus is configured to emit a pulsed laser beam with an energy between 1-100 mJ and a frequency between 1 kHz - 1 MHz. For example, the laser apparatus is to operate as a Class 1 laser, which is safe under all conditions of normal use. For example, the laser apparatus comprises a laser source for generating the laser beam. In another example, the laser apparatus is adapted to be coupled to a laser source for generating the laser beam. For example, the laser apparatus comprises a coupling for an optical guide, such as an optical fiber or an optical wave guide, to receive the laser beam from the laser source.

The object is any object that may be irradiated with the laser beam. For example, the object is made of metal or ceramic. For example, the object has a surface with corrosion to be removed by the laser beam. For example, the object is part of a battery. For example, the object has a flat surface to receive the laser beam, and/or a curved surface to receive the laser beam. For example, the surface of the object that is to be irradiated with the laser has openings, such as through holes or recesses.

The laser scan head directs the laser beam from the laser source to the object. For example, the laser scan head has one or more moveable mirrors to receive the laser beam from the laser source and to direct the laser beam to the object. The laser scan head is, for example, adapted to move at least one the moveable mirror to move the laser beam in a scan movement. For example, the laser scan head has one or more optical components to adjust a property of the laser beam, such as a cross-section of the laser beam or a focus point.

The transport unit is for moving the object and the laser scan head relative to each other. The transport unit is adapted to move the object relative to a stationary laser scan head, to move the laser scan head relative to a stationary object, or to move both the object and the laser scan head. For example, the transport unit comprises a stage system or a conveyor system to support the object. By operating the stage system or the conveyor system, the object is moved relative to the laser scan head. For example, the transport unit comprises a lathe to rotate the object relative to the laser scan head. For example, transport unit comprises stage system or a gantry to support the laser scan head. By operating the stage system or the gantry system, the laser scan head is moved relative to the object.

The control unit is configured to control the laser scan head. For example, the control unit is connected to the laser scan head to provide a control signal to the laser scan head.

Based on the control signal, the laser scan head moves one or more moveable mirrors to direct the laser beam to the object and to perform a scan movement.

The control unit is configured to control the transport unit to move the object and the laser scan head relative to each other in a transport direction. For example, the control unit is connected to the transport unit to provide a transport control signal to the transport unit.

Based on the transport control signal, the transport unit moves the object relative to the laser scan head. For example, the control unit controls the transport unit to move the object and the laser scan head relative to each with a constant speed. For example, the transport unit comprises a motor adapted to move in response to the transport control signal.

The control unit comprises, for example, a processor for executing software, and a memory for storing the software. For example, the software comprise instructions representing the directions of the first scan direction and the second scan direction. For example, the instructions are the result of off-line calculations in which the second scan direction is calculated based on the first scan direction and the vector. For example, the control unit comprises a Programmable Logic Controller (PLC) or a Field-Programmable Gate

Array (FPGA). The control unit comprises, for example, an interface. Via the interface, an operator is able to interact with the control unit to operate the laser apparatus. The interface comprises, for example, a touch screen or a keyboard or a communication device. The communication device is for example adapted for wired communication or for wireless communication, such as Bluetooth. The interface comprises, for example, a connector to connect with a data carrier, such as an USB flash drive, a SD-card, a CD-R or a DVD-R. The control unit is, for example, implemented as a single unit or as multiple units. For example, the part of the control unit that is configured to control the laser scan head is implemented in a different unit than the part of the control unit that is configured to control the transport unit.

The control unit is configured to control the laser scan head to perform the first scan movement and the second scan movement while the transport unit moves the object relative tothe laser scan head. So when the object is being irradiated during the first scan movement and the second scan movement, the object is moving relative to the laser scan head.

During the first scan movement, the laser scan head moves the laser beam in the first scan direction. The laser beams describes a trajectory relative to the laser scan head along the first scan direction. The first scan direction extends across at least part of the width of the object. The first scan direction is in a direction parallel to the direction of the width, or the first scan direction is in a direction that has a component in the direction of the width and a component in the transport direction. During the first scan movement, the laser beam moves across the whole width of the object, i.e., starting at one side of the object and stopping at the opposite side of the object, or the laser beam moves a part of the width of the object. For example, the first line starts at a distance from the nearest edge of the object, and/or the first line ends at a distance from the nearest edge of the object. In some applications, it is not necessary or desired to irradiate the entire object, so moving the laser beam across only a part of the width of the object is sufficient.

The second scan direction extends across at least part of the width of the object opposite to the first scan direction. For example, the first scan direction is from left to right across the width of the object. Then the second scan direction is from right to left across the width of the object. The second scan direction is in a direction parallel to the direction of the width, or the second scan direction is in a direction that has a component in the direction of the width and a component in the transport direction. During the second scan movement, the laser beam moves across the whole width of the object, i.e., starting at one side of the object and stopping at the opposite side of the object, or the laser beam moves a part of the width of the object. Preferably, the laser beams moves the same amount in the direction of the width of the object during the first scan movement and the second scan movement.

During the first scan movement, the laser beam moves along the first scan direction and irradiates the first line on the object. The length of the first line is determined by the distance that the laser beam moves during the first scan movement. The width of the first line is determined by a width of the laser beam, e.g., the diameter of the laser beam. The width of the laser beam is perpendicular to the first scan direction. The first and second lines are referred to as lines because, because the length of such a line is typically several mm’s or more, whereas the width of the line is typically about 50-200 um. So the lengths of the first line and the second are substantially larger than their widths. During the first scan movement, the laser beam forms an irradiated area on the object along the first line. The irradiated area is, for example, formed by a plurality of laser pulses. The laser pulses are, for example, adjacent to each other without overlapping each other or overlapping each other. For example, the amount of overlapping is 5% or 10% or 20% of the diameter of the laser beam.

The amount of overlap, for example, differs along the first line. The first line is a straight line ora curved line.

During the second scan movement, the laser beam moves along the second scan direction and irradiates the second line on the object. The length of the second line is determined by the distance that the laser beam moves during the first scan movement. For example, the second line has the same length as the first line. The width of the second line is determined by the width of the laser beam, e.g., the diameter of the laser beam. The width of the laser beam is perpendicular to the second scan direction. During the second scan movement, the laser beam forms an irradiated area on the object along the second line. The irradiated area is, for example, formed by a plurality of laser pulses. The laser pulses are, for example, adjacent to each other without overlapping each other or overlapping each other.

For example, the amount of overlapping is 5% or 10% or 20% of the diameter of the laser beam. The amount of overlap, for example, differs along the second line. The second line is a straight line or a curved line. For example, the second line has the same shape as the first line. For example, the laser scan head irradiates the second line to partly overlap with the first line. For example, the amount of overlapping is 5% or 10% or 20% of the diameter of the laser beam.

The control unit is configured to control the second scan direction based on the first scan direction and a vector in the transport direction.

In a first example, the first scan direction is perpendicular to the transport direction. The first line starts at a first start point and ends at a first end point. Because the first scan direction is perpendicular to the transport direction, the first line is arranged on the object oblique relative to the transport direction, wherein the first start point is the leading end, and the first end point is the trailing end of the first line. The second scan movement starts to irradiate the second line near the first end point and stops to irradiate the second line near the first start point. To arrange the second line parallel to the first line, the second scan direction is determined by the first scan direction and a vector in the transport direction. The vector in the transport direction needs to be large enough to account for the oblique angle of the first line and the transport speed.

In a second example, the first line is perpendicular to the transport direction. Because the abject moves in the transport direction during the first scan movement, the first scan direction has a vector in the transport direction. The first line starts at the first start point and ends at the first end point. The second scan movement starts to irradiate the second line near the first end point and stops to irradiate the second line near the first start point. To arrange the second line parallel to the first line, the second scan direction is determined by the first scan direction and the vector in the transport direction. Because the second scan direction is partly opposite to the first scan direction, the vector at least partly compensates the vector that was included in the first scan direction. In addition, the vector includes the transport speed.

In a third example, the second scan direction is perpendicular to the transport direction.

To irradiate the first line and the second line parallel to each other, the first scan direction would have a large component in the transport direction. So when the control unit controls the second scan direction based on the first scan direction and the vector, the vector takes the large component in the transport direction of the first scan direction into account.

In an embodiment, the control unit is configured to control the laser scan head to arrange the first line and the second line on the object parallel to each other.

When creating a first line and a second line in a zig-zag pattern with a known laser apparatus, the laser beam would end at a distance from where the laser beam started. The distance is in the transport direction. The transport speed of the known laser apparatus is limited to ensure that the distance is sufficiently small to ensure proper irradiation. According to the invention, the laser beam moves with first scan movement and the second scan movement back and forth over the object. By arranging the first line and the second line parallel to each other, the laser beam ends at a distance from where the laser beam started with the first scan movement that is only half the distance compared to that of the known laser apparatus. The transport speed and the scan speed of the laser beam for both situations are the same. As a result, the embodiment allows a higher transport speed while still achieving proper irradiation of the object. For example, the transport speed is increased with a factor of two.

In an embodiment, the control unit is configured to control the laser scan head to arrange the first line and the second line adjacent to each other.

According to this embodiment, the first line and the second line are arranged adjacent to each other on the object. For example, the first line and the second line are arranged adjacent to each other without overlapping with each other, or overlapping each other. For example, the amount of overlapping is 5% or 10% or 20% of the diameter of the laser beam.

By arranging the first line and the second line are arranged adjacent to each other on the object, an improved irradiation of the object is achieved.

In an embodiment, the vector in the transport direction is based on a scan speed of the second scan movement. The scan speed is a speed at which the laser scan head moves the laser beam along the second scan direction to irradiate the second line.

According to this embodiment, the vector depends on the scan speed. In case the scan speed is high, the second scan movement is done in a small amount of time. In this small amount of time, there is only a small movement of the object relative to the laser scan head.

As a result, vector in the transport direction is small. In case the scan speed is low, the second scan movement is done in a large amount of time. In this large amount of time, there is a large movement of the object relative to the laser scan head. As a result, vector in the transport direction is large. By taken the scan speed of the second scan movement into account, the control unit is able to determine the second scan direction more accurately. For example, the scan speed of the second scan movement is the same as the scan speed of the first scan movement. In another example, the scan speed of the second scan movement is different from the scan speed of the first scan movement.

In an embodiment, the control unit is configured to control the transport unit to move the object and the laser scan head relative to each other in the transport direction at a transport speed. The vector in the transport direction is based on the transport speed.

The transport speed determines how much the object moves relative to the laser scan head per unit of time. In case the transport speed is low the second scan direction is less affected by the vector in the transport direction. In case the transport speed is high the second scan direction is affected more by the vector in the transport direction. For example, the vector in the transport direction is based on the transport speed and the scan speed, for example a ration between the transport speed and the scan speed.

In an embodiment, the control unit is configured to control the second scan direction based on an inverse of the first scan direction.

According to this embodiment, the control unit bases the second scan direction on an inverse of the first scan direction. The first scan direction extends across part of the width of the object. By basing the second scan direction on the inverse of the first scan direction, the second scan direction extends across at least part of the width opposite to the first scan direction. The control unit bases the second scan direction on the inverse of the first scan direction and the vector in the transport direction to take into account the movement of the object relative to the laser scan head.

In an embodiment, the laser scan head comprises at least one mirror and at least one galvo-scanner motor. The at least one mirror is arranged to reflect the laser beam towards the object. The at least one galvo-scanner motor is configured to rotate the at least one mirror.

The control unit is configured to control the at least one galvo-scanner motor to control the first scan movement and the second scan movement.

According to this embodiment, the laser scan head has one or more mirrors. A galvo- scanner motor is provided for each of the mirrors to rotate the mirrors. By rotating the mirrors, the mirrors reflect the laser beam to move according to the first scan movement and the second scan movement. For example, the galvo-scanner motor has two mirrors, each with a galvo-scanner motor. Each galvo-scanner motor is arranged to rotate one of the mirrors. The two mirrors are arranged to reflect the laser beam to move the laser beam across a two- dimensional surface across the object. For example, the control unit is configured to control the galvo-scanner motors to rotate the two mirrors.

In an embodiment, the laser scan head is configured to start the first scan movement at a first start point on the first line, to stop the first scan movement at a first end point on the first line, to start the second scan movement at a second start point on the second line, and to stop the second scan movement at a second end point on the second line. The laser scan head is configured to arrange the first end point and the second start point on the object at a distance from each other. The distance is in a direction perpendicular to the first line. The distance is equal to or less than a diameter of the laser beam.

According to this embodiment, during the first scan movement, the laser beam moves along the object from the first start point to the first end point. During the second scan movement, the laser beam moves along the object from the second start point to the second end point. When the laser beam is at the second end point, the laser beam is at the distance from the first start point. Because this distance is less than a diameter of the laser beam, there is no surface or only an acceptable small surface between the first line and the second line that is not irradiated by the laser beam. As a result, the object is irradiated by the laser beam in an improved way. In case the distance is equal to the diameter of the laser beam, the irradiated areas of the first line and the second line are adjacent to each other without overlap. In case the distance is smaller than the diameter of the laser beam, the irradiated areas of the first line and the second line partly overlap each other. In case the laser beam has a round cross-section, the diameter is the diameter of the round cross-section. In case the cross-section has the shape of a polygon, the diameter corresponds to the largest diagonal of the cross-section shape. In case the first line is curved, the distance is in a direction perpendicular to a tangent of the first line at the first end point.

In an embodiment, the distance is less than 80% of the diameter of the laser beam.

According to this embodiment, by selecting the distance of less than 80% of the diameter of the laser beam, the irradiation of the object is improved. By selecting this distance, there is sufficient overlap between the irradiated area of the first line and the irradiated area of the second line to ensure a proper irradiation of the object. In an example the laser beam has a round cross-section and is a pulsed laser beam. By selecting the distance of less than 80% of the diameter of the laser beam, there will be no or only very little surface between the pulses on the object that is not sufficiently irradiated by the laser beam.

In an embodiment, laser scan head is configured to arrange the laser beam in a first laser start position to irradiate the first start point, arrange the laser beam in a first laser end position to irradiate the first end point, arrange the laser beam in a second laser start position to irradiate the second start point, arrange the laser beam in a second laser end position to irradiate the second end point. The first laser start position, the first laser end position, the second laser start position, and the second laser end position are relative to the laser scan head. The laser beam in the second laser start position is arranged opposite to the transport direction relative to the laser beam in the first end position.

According to this embodiment, the laser beam moves relative to the laser scan head from the first laser start position to the first laser end position during the first scan movement.

The laser beam moves relative to the laser scan head from the second laser start position to the second laser end position during the second scan movement. The laser scan head starts the second scan movement at the second laser start position relative to the first laser end position upstream in the transport direction. This way, the laser scan head is able to arrange the first laser start position, the first laser end position, the second laser start position, and the second laser end position closer together, which simplifies the mechanical design of the laser scan head. For example, the laser beam is interrupted between the first laser end position and the second laser start position.

In an embodiment, the second laser start position is the same as the first laser end position.

According to this embodiment, the laser scan head ends the first line with the laser beam in the first laser end position, and starts the second line with the laser beam in the same laser position. The laser scan head waits with the laser beam in the first laser end position, until the object has moved sufficiently along the transport direction before starting with the second line. This helps to simplify the control of the laser beam. In an example, the laser scan head brings back the laser beam to the first laser start position after irradiating a certain number of lines, for example 10 lines or 50 lines or more than 100 lines.

In an embodiment, the laser beam in the second laser end position is arranged in the transport direction relative to the laser beam in the first laser start position.

According to this embodiment, the laser beam moves relative to the laser scan head from the second laser start position to the second laser end position during the second scan movement. To take into account the vector in the transport direction, the second laser end position is arranged in the transport direction relative to the laser beam in the first laser start position.

In an embodiment, the laser scan head is configured to perform the first scan movement to irradiate a third line on the object. The laser scan head is configured to start the third scan movement at a third start point on the third line, stop the third scan movement at a third end point on the third line, direct the laser beam to the first laser start position to irradiate the third start point, and direct the laser beam to the first laser end position to irradiate the third end point. The first line and the third line are on opposite sides of the second line.

According to this embodiment, the laser scan head is able to irradiate the third line in a similar way as the first line. This way, the laser scan head is able to repeat the irradiation of lines to irradiate a desired surface area of the object.

In an embodiment, the laser scan head is configured to irradiate the first line. The first line is perpendicular to the transport direction.

According to this embodiment, the first line is at an angle of 90 degrees with the transport direction. Irradiating the first line perpendicular to the transport direction is especially beneficial if the first line has a relatively long length, for example more than 30 mm or more than 40 mm or more than 100 mm. By arranging the first line perpendicular to the transport direction, the first line is as short as possible while still extending across the width of the object as much as possible. Since the length of the first line is relatively long, laser scan head is able to obtain a large scan speed and/or a large average scan speed. The inertia of moving parts, such as rotating mirrors, in the laser scan head do not have a substantial impact on average scan speed. This way, the laser scan head may obtain, for example, a maximum scan speed. The maximum scan speed is the maximum scan speed for which the laser scan head is designed.

In an embodiment, the laser scan head is configured to irradiate the first line. The first line has an oblique angle to the transport direction.

According to this embodiment, the first line is at an angle different than 90 degrees with the transport direction. The angle is between 0-90 degrees. Irradiating the first line at the oblique angle to the transport direction is especially beneficial if the width of the object that is to be irradiated has a relatively short length, for example less than 50 mm or more less than 40 mm or less than 30 mm. By arranging the first line at the oblique angle to the transport direction, the first line can be made longer while extending across the width of the object. By making the first line longer in this way, the laser scan head is able to obtain a larger scan speed and/or a larger average scan speed. The inertia of moving parts, such as rotating mirrors, in the laser scan head do not have a substantial impact on average scan speed. This way, the laser scan head may obtain, for example, a maximum scan speed. The maximum scan speed is the maximum scan speed for which the laser scan head is designed. In comparison, if the first line would have a same short length as the width, the inertia of the moving parts would limit the average scan speed. For example, the laser scan head would not be able to achieve the maximum scan speed.

It is noted that the required scan length to obtain the maximum scan speed, the amount of inertia of the moving parts, and the maximum speed depend on the design of the laser scan head. If a certain laser scan head is not able to obtain its maximum scan speed, or obtains the maximum scan speed only for a small portion of the scan movement while irradiating a line perpendicular to the transport direction, the scan speed can be increased by arranging the line at the oblique angle. As a result of the increased scan speed, the amount of irradiated surface per unit of time increases.

In an embodiment, the first line extends along a scan width of the object. The scan width is perpendicular to the transport direction. The laser scan head is configured to have a first average scan speed for a scan movement along a length of the scan width. The laser scan head is configured to have a second average scan speed for the first scan movement.

The second average scan speed is higher than the first average scan speed.

According to this embodiment, the laser scan head has a certain average scan speed when irradiating a line with the length of the scan width. The scan width is the width of the surface area of the object that is to be irradiated. Because the scan width is too short, the laser scan head would not achieve a maximum average scan speed when performing a scan movement over the length of the scan width. Because of the oblique angle, the first line is longer than the scan width. Because of the longer length, the laser scan head is able to achieve a higher average scan speed, for example the maximum average scan speed, when irradiating the first line.

In an embodiment, the laser apparatus comprises a further laser scan head for directing a further laser beam to the object. The further laser scan head and the laser scan head are arranged relative to each other along the direction perpendicular to the transport direction.

The control unit is configured to control the further laser scan head to perform a further first scan movement of the further laser beam and a further second scan movement of the further laser beam. The control unit is configured to control the transport unit to move the object and the further laser scan head relative to each other in the transport direction during the further first scan movement and during the further second scan movement. The further laser scan head is configured to perform the further first scan movement by moving the further laser beam along a further first scan direction to irradiate a further first line on the object. The further laser scan head is configured to perform the further second scan movement by moving the further laser beam along a further second scan direction to irradiate a further second line on the object. The further first scan direction extends across at least part of the width of the object. The width is in a direction perpendicular to the transport direction. The further second scan direction extends across at least part of the width of the object opposite to the further first scan direction. The control unit is configured to control the further second scan direction based on the further first scan direction and a further vector in the transport direction.

According to this embodiment, another laser scan head is arranged next to the laser scan head in the direction of the width of the object. For example, the laser scan head and the further laser scan head are aligned in the direction of the width, or are arranged at an offset. The laser scan head and the further laser scan head are arranged next to each other such that one part of the object is irradiated via the laser scan head and another part of the object via the further laser scan head. For example, the laser scan head irradiates a left side of the object, whereas the further laser scan head irradiates a right side of the object. For example, there is a small portion of the object that is irradiated by both laser scan heads, for example along a center line of the object. By irradiating the small portion by both laser scan heads, it is ensured that this portion is properly irradiated.

The further laser scan head irradiates different lines than the laser scan head. The further laser scan head performs scan movement similar to the laser scan head. However, the directions and/or speeds of the further first scan movement and the further second scan movement are, for example, different from the first scan movement and the second scan movement respectively. The further laser scan directs the laser beam for the further scan movement along the further second scan direction. The control unit controls the further second scan direction based on the further first scan direction and the further vector in the transport direction. The further vector is the same as the vector in the transport direction, or is different that the vector in the transport direction. By controlling based on the further vector in the transport direction, the further second scan direction is not parallel to the further first scan direction. This way, the further second scan direction takes the movement of the further laser scan head relative to the object into account during the further second scan movement. This allows the further laser scan head to irradiate the further second line more accurately relative to the first line to obtain a more uniform irradiation of the object.

By arranging the two laser scan heads next to each other, more surface area can be irradiated per unit of time compared to providing a single laser scan head with the double amount of laser power. For example, using the two laser scan heads each with a laser power of 100 W results in substantially more irradiated surface per unit of time compared to using a single laser scan head with a laser power of 200 W. High power laser sources with a high pulse frequency are readily available. However, laser scan heads are not able to scan fast enough to distribute all that power over an object in a short amount of time. By using two laser scan heads, each laser scan head needs to scan only a portion of the width, for example only half the width. This way, the two laser scan heads are able to distribute the double amount of laser power in the same amount of time, which increases the amount of irradiated surface per unit of time.

In an embodiment, the laser scan head and the further laser scan head are arranged to arrange the first line and the further first line adjacent to each other on the object, and to arrange the second line and the further second line adjacent to each other on the object.

According to this embodiment, the first line and the further first line are adjacent to each other, and the second line and the further second line adjacent to each other. Because the lines are adjacent to each other, a continuous irradiated surface is created by the two laser scan heads. This way, a wide surface area of the object can be irradiated efficiently. The lines are adjacent to each other without overlap or overlapping each other. For example, the overlap is 5% or 10% or 20% of the diameter of the laser beam.

In an embodiment, the laser apparatus is a laser cleaning apparatus.

According to this embodiment, the laser apparatus is adapted to remove contamination from the object.

In an embodiment, there is provided a laser scan head for use in the laser apparatus according to any one of the embodiments above.

In an embodiment, there is provided a control unit for use in the laser apparatus according to any one of the embodiments above.

In a second aspect of the invention, there is provided a method for irradiating an object with a laser beam. The method comprises the steps of: directing the laser beam with a laser scan head to the object, performing a first scan movement with the laser scan head by moving the laser beam along a first scan direction to irradiate a first line on the object, while moving the object and the laser scan head relative to each other in a transport direction, performing a second scan movement with the laser scan head by moving the laser beam along a second scan direction to irradiate a second line on the object, while moving the object and the laser scan head relative to each other in the transport direction. The first scan direction extends across at least part of a width of the object. The width is in a direction perpendicular to the transport direction. The second scan direction extends across at least part of the width of the object opposite to the first scan direction. The method comprises the step of controlling the second scan direction based on the first scan direction and a vector in the transport direction.

In an embodiment, the method comprises the step of arranging the first line and the second line on the object parallel to each other.

In an embodiment, the method comprises the step of arranging the first line and the second line on the object adjacent to each other.

In an embodiment, the method comprises the step of moving the laser beam along the second scan direction to irradiate the second line at a scan speed. The step of controlling the second scan direction based on the vector in the transport direction comprises controlling the second scan direction based on the scan speed.

In an embodiment, the method comprises the step of moving the object and the laser scan head relative to each other in the transport direction at a transport speed. The step of controlling the second scan direction based on the vector in the transport direction comprises controlling the second scan direction based on the transport speed.

In an embodiment, the method comprises the step of controlling the second scan direction based on the first scan direction comprises controlling the second scan direction based on an inverse of the first scan direction.

In an embodiment, the method comprises the steps of: starting the first scan movement at a first start point on the first line, stopping the first scan movement at a first end point on the first line, starting the second scan movement at a second start point on the second line, stopping the second scan movement at a second end point on the second line, arranging the first end point and the second start point on the object at a distance from each other. The distance is in a direction perpendicular to the first line. The distance is equal to or less than a diameter of the laser beam.

In an embodiment, the method comprises the steps of: arranging the laser beam in a first laser start position to irradiate the first start point, arranging the laser beam in a first laser end position to irradiate the first end point, arranging the laser beam in a second laser start position to irradiate the second start point, arranging the laser beam in a second laser end position to irradiate the second end point, arranging the laser beam in the second laser start position opposite to the transport direction from the laser beam in the first laser end position. The first laser start position, the first laser end position, the second laser start position, and the second laser end position are relative to the laser scan head.

In an embodiment, the method comprises step of performing the first scan movement comprises irradiating the first line, the first line having an oblique angle to the transport direction.

In an embodiment, the method comprises the steps of: providing a further laser scan head for directing a further laser beam to the object, performing the method according to any one of claims 24-30 with the further laser scan head to irradiate a further first line and a second first line,

arranging the further first line adjacent to the first line, arranging the further second line adjacent to the second line.

In a third aspect of the invention, there is provided a computer program having instructions which when executed by a control unit of a laser apparatus, wherein the laser apparatus comprises a laser scan head for directing a laser beam to an object, and a transport unit for moving the object and the laser scan head relative to each other, cause the control unit to perform the method according to any one of the embodiments above.

The invention will be described in more detail below under reference to the figures, in which in a non-limiting manner exemplary embodiments of the invention are shown. The figures show in:

Fig. 1: a first embodiment of a laser apparatus according to the invention.

Figs. 2A-2B: irradiating the first line according to the first embodiment.

Figs. 3A-3B: irradiating the second line according to the first embodiment.

Fig. 4: the first and second scan directions according to the first embodiment.

Fig. 5: the first and second scan directions according to a second embodiment of the invention.

Fig. 6: the amount of irradiated surface area per unit of time according to the invention.

Fig. 7: a third embodiment of a laser apparatus according to the invention.

Fig. 8: a fourth embodiment of the invention.

Fig. 9: a method according to an embodiment of the invention.

To aid in the explanation of the invention, a Cartesian coordinate system is included in the figures.

Fig. 1 depicts a first embodiment of a laser apparatus 100 according to the invention.

The laser apparatus 100 is for irradiating an object 101 with a laser beam 102. The laser apparatus 100 is for example a laser cleaning apparatus. The laser scan head 103 is for directing the laser beam 102 to the object 101. The transport unit 104 is for moving the object 101 and the laser scan head 103 relative to each other. The control unit 105 is configured to control the laser scan head 103 to perform a first scan movement of the laser beam 102 and a second scan movement of the laser beam 102. The control unit 105 is configured to control the transport unit 104 to move the object 101 and the laser scan head 103 relative to each other in a transport direction 113 during the first scan movement and during the second scan movement. The transport direction 113 is indicated with the arrow and is directed in the x- direction.

The laser scan head 103 is configured to perform the first scan movement by moving the laser beam 102 along a first scan direction 111 to irradiate a first line 121 on the object

101. The laser scan head 103 is configured to perform the second scan movement by moving the laser beam along a second scan direction 112 to irradiate a second line 122 on the object 101. The first scan direction 111 extends across at least part of a width of the object 101. The width is in a direction perpendicular to the transport direction 113, i.e, in the y-direction. The second scan direction 112 extends across at least part of the width of the object 101 opposite to the first scan direction 111. As shown in Fig. 1, the first scan direction 111 is largely in the positive y-direction, whereas the second scan direction 112 is largely in the negative y- direction.

The control unit 105 is configured to control the laser scan head 103 to arrange the first line 121 and the second line 122 on the object 101 parallel to each other. The first line 121 is perpendicular to the transport direction 113. The lines in Fig. 1 are depicted as being separated from each other to clearly shown the individual lines. In practice, the lines are adjacent to each other and optionally partly overlapping with each other to form a continuous irradiated surface on the object 101.

The laser scan head 103 comprises at least one mirror and at least one galvo-scanner motor. The at least one mirror is arranged to reflect the laser beam 102 towards the object 101. The at least one galvo-scanner motor is configured to rotate the at least one mirror. The control unit 105 is configured to control the at least one galvo-scanner motor to control the first scan movement and the second scan movement. For example, the laser scan head 103 has two mirrors and two galvo-scanner motors, one for each mirror. The two mirrors are rotatable by the two galvo-scanner motors to move the laser beam 102 across the object 101 in a two-dimensional plane.

Figs. 2A and 2B depict irradiating the first line 121 according to the first embodiment.

The laser scan head 103 starts the first scan movement by irradiating the first start point 221 on the first line 121, as shown in Fig. 2A. While the object 101 moves in the transport direction 113, the laser beam 102 moves along the first scan direction 111. The laser beam 102 is a pulsed laser beam that provides laser pulses 200 on the object 101 at a certain frequency while moving along the first scan direction. The laser pulses 200 are indicated by the circles. Note that there is some overlap between the laser pulses 200. As the object 101 moves in the transport direction 113, the laser beam 102 moves to the right of the figure.

In the situation in Fig. 2B, the laser scan head 103 has completed the first scan movement and has just irradiated the first end point 222 of the first line 121. The result of the first scan movement is that the first line 121 is irradiated with the laser pulses 200 as indicated with the solid lines. The laser pulses 200 indicated with the dashed lines indicate how the first line 121 was irradiated in the time before the situation in Fig. 2B.

The first line 121 has moved in the transport direction 113 with a distance 202. The distance 202 corresponds to a diameter of the cross-section of the laser beam 102.

Figs. 3A and 3B depict irradiating the second line 122 according to the first embodiment. The laser scan head 103 starts the second scan movement by irradiating the second start point 321 on the second line 122, as shown in Fig. 3A. The laser scan head 103 is configured to arrange the first end point 222 and the second start point 321 on the object 101 at the distance 202 from each other. The distance 202 is in a direction perpendicular to the first line 121. The distance 202 is equal to the diameter of the laser beam 102. Optionally, the distance 202 is less than the diameter of the laser beam 102. Optionally, the distance 202 has a component perpendicular to the transport direction 113.

While the object 101 moves in the transport direction 113, the laser beam 102 moves along the second scan direction 112. The laser beam 102 provides laser pulses 200 on the object 101 at the certain frequency while moving along the second scan direction 112. As the object 101 moves in the transport direction 113, the laser beam 102 moves to the left of the figure.

In the situation in Fig. 3B, the laser scan head 103 has completed the second scan movement and has just irradiated the second end point 322 of the second line 122. The result of the second scan movement is that the second line 122 is irradiated with the laser pulses as indicated with the solid lines. The laser pulses 200 indicated with the dashed lines indicate how the second line 122 was irradiated in the time before the situation in Fig. 3B.

The control unit 105 is configured to control the laser scan head 103 to arrange the first line 121 and the second line 122 adjacent to each other.

The laser scan head 103 is configured to perform the first scan movement to irradiate a third line 321 on the object 101. The third line 321 is at the location indicated by the dashed line. From the point of view of the laser scan head 103, the third line 321 is at the location where the second line 122 was in the situation of Fig. 3A. The laser scan head 103 is configured to start the third scan movement at a third start point 331 on the third line 321, and to stop the third scan movement at a third end point 332 on the third line 321. The first line 121 and the third line 321 are on opposite sides of the second line 122.

Fig. 4 depicts the first scan direction 111 and second scan direction 112 according to the first embodiment. The first scan direction 111 is directed from the bottom left to the top right of the figure. The first scan direction 111 extends in the transport direction 113 and in the direction of the width. The first scan direction 111 has a component in the transport direction 113 and a component in the direction of the width. The angle of the first scan direction 111 is set in relation to the transport speed and the scan speed to irradiate the first line 121 perpendicular to the transport direction 113.

When the first scan movement is finished, the laser beam 102 is directed at the right side of the figure. During the second scan movement, the laser beam 102 moves from the right side of the figure to the left side.

The control unit 105 is configured to control the second scan direction 112 based on the first scan direction 111 and a vector 402 in the transport direction 113. The vector 402 is shown in Fig. 4. The control is configured to control the second scan direction 112 based on an inverse 400 of the first scan direction 111. However, if the laser beam 102 would move in the direction of the inverse 400, the second line 122 would be arranged at a large angle relative to the first line 121. The large angle would be caused by the movement of the object 101 in the transport direction 113, and caused by the component of the inverse 400 in the direction opposite to the transport direction 113. Therefore, the control unit 105 takes the vector 402 in the transport direction 113 into account.

The vector 402 in the transport direction 113 is based on a scan speed of the second scan movement. The scan speed is a speed at which the laser scan head 103 moves the laser beam 102 along the second scan direction 112 to irradiate the second line 122. The control unit 105 is configured to control the transport unit 104 to move the object 101 and the laser scan head 103 relative to each other in the transport direction 113 at a transport speed.

The vector 402 in the transport direction 113 is based on the transport speed. Optionally, the vector 402 is based on only one of the scan speed and the transport speed. The second scan direction is, for example, a sum of the vector 402 of the inverse 400 and the vector 402 in the transport direction 113. By taken the vector 402 in the transport direction 113 into account, the second scan direction 112 is directed from the bottom right of the figure to the top left. As aresult of the second scan direction 112, the second line 122 is arranged parallel to the first line 121.

The laser scan head 103 is configured to arrange the laser beam 102 in a first laser start position 411 to irradiate the first start point 221, to arrange the laser beam 102 in a first laser end position 412 to irradiate the first end point 222, to arrange the laser beam 102 in a second laser start position 421 to irradiate the second start point 321, and to arrange the laser beam 102 in a second laser end position 422 to irradiate the second end point 322. The first laser start position 411, the first laser end position 412, the second laser start position 421, and the second laser end position 422 are relative to the laser scan head 103. The laser beam 102 in the second laser start position 421 is arranged opposite to the transport direction 113 relative to the laser beam 102 in the first laser end position 412.

The laser scan head 103 directs the laser beam 102 to the first laser start position 411 to irradiate the third start point 331. The laser scan head 103 directs the laser beam 102 to the first laser end position 412 to irradiate the third end point 332.

Fig. 5 depicts the first scan direction 11 1 and the second scan direction 112 according to a second embodiment of the invention. The second embodiment has, for example, the same elements as the first embodiment, except for the following. For example, the second embodiment comprises the laser apparatus 100 of the first embodiment, or at least part of the laser apparatus 100 of the first embodiment.

The laser scan head 103 is configured to irradiate the first line 121, wherein the first line 121 has an oblique angle 500 to the transport direction 113. The first line 121 extends along a scan width 502 of the object 101. The scan width 502 is perpendicular to the transport direction 113. The scan width 502 is the width of the surface area of the object 101 that is to be irradiated by the laser beam 102.

The laser scan head 103 is configured to have a first average scan speed for a scan movement along a length of the scan width 502. The laser scan head 103 is configured to have a second average scan speed for the first scan movement. The second average scan speed is higher than the first average scan speed. As is clear from Fig. 5, by arranging the first line 121 at the oblique angle 500, the length of the first line 121 is substantially longer than the scan width 502. As a result, the laser scan head 103 is able to obtain a higher average scan speed when irradiating the first line 121. Similarly, the average scan speed of the second scan movement is higher.

Note that the first scan direction 111 and the second scan direction 112 of the second embodiment resemble the first scan direction 111 and the second scan direction 112 of the first embodiment, except that that they are rotated to obtain the oblique angle 500 of the first line 121. The oblique angle 500 can be selected between 0 and 90 degrees to obtain a desired length of the first line 121 at which the average scan speed is high or is maximal.

Fig. 6 depicts an example of the amount of irradiated surface area per unit of time according to the invention. The x-axis indicates the scan width 502 in mm. The y-axis indicates the amount of irradiated surface area per unit of time in m2/hour.

Line 601 indicates the output of irradiating a zig-zag pattern using a known laser apparatus 100. Due to the zig-zag pattern, the transport speed needs to be low to ensure that the zig-zag lines are sufficiently adjacent to each other. Further, for a small scan width 502 of less than 40 mm, the transport speed is further reduced, because the laser scan head 103 is not able to move the laser beam 102 fast enough back and forth across the width of the object 101. The inertia of the moving parts of the laser scan head 103 prevent the laser beam 102 from moving back and forth faster.

Line 602 indicates the output of the first embodiment of the invention. Because the first embodiment has the control unit 105 configured to control the second scan direction 112 based on the first scan direction 111 and the vector 402, a proper irradiation of the object 101 is obtained at a much higher transport speed, about two times as fast as with the zig-zag pattern. As is shown, the output is limited for scan width 502 of less than 40 mm, because the laser scan head 103 is not able to move the laser beam 102 along the first scan movement and the second scan movement any faster due to the inertia of the moving parts of the laser scan head 103. For a scan width 502 of 40 mm and larger, the laser scan head 103 is able to achieve a maximum average scan speed.

Line 603 indicates the output of the second embodiment of the invention. Because of the oblique angle 500 of the first line 121, a first line 121 of 40 mm or more can be scanned by the laser scan head 103 for a scan width 502 of less than 40 mm. This way, the laser scan head 103 is able to achieve the maximum average scan speed independently of the scan width 502. As a result, the second embodiment has a high output independently of the scan width 502.

Fig. 7 depicts a third embodiment of a laser apparatus 100 according to the invention.

The third embodiment has, for example, the same elements as the first embodiment and/or as the second embodiment, except for the following.

The laser apparatus 100 comprises a further laser scan head 703 for directing a further laser beam 702 to the object 101. The further laser scan head 703 and the laser scan head 103 are arranged relative to each other along the direction perpendicular to the transport direction 113. The further laser scan head 703 and the laser scan head 103 are arranged next to each other in the y-direction.

The control unit 105 is configured to control the further laser scan head 703 to perform a further first scan movement of the further laser beam 702 and a further second scan movement of the further laser beam 702. The control unit 105 is configured to control the transport unit 104 to move the object 101 and the further laser scan head 703 relative to each other in the transport direction 113 during the further first scan movement and during the further second scan movement. The further laser scan head 703 is configured to perform the further first scan movement by moving the further laser beam 702 along a further first scan direction 711 to irradiate a further first line 721 on the object 101. The further laser scan head 703 is configured to perform the further second scan movement by moving the further laser beam 702 along a further second scan direction 712 to irradiate a further second line 822 on the abject 101. The further first scan direction 711 extends across at least part of the width of the object 101. The width is in a direction perpendicular to the transport direction 113. The further second scan direction 712 extends across at least part of the width of the object 101 opposite to the further first scan direction 711. The control unit 105 is configured to control the further second scan direction 712 based on the further first scan direction 711 and a further vector in the transport direction 113.

The further vector is, for example, determined in the same way as the vector 402 as explained in the first embodiment and shown in Fig. 4.

The laser scan head 103 and the further laser scan head 703 are arranged to irradiate the first line 121 and the further first line 721 adjacent to each other on the object 101, and to irradiate the second line 122 and the further second line 822 adjacent to each other on the object 101. The second further line 822 is shown in Fig. 8. As shown in Fig. 7, the first line 121 and the further first line 721 together form a single continuous line. Similarly, the second line 122 and the further second line 822 together form a single continuous line.

Fig. 8 depicts a fourth embodiment of the invention. The fourth embodiment is a combination of the second embodiment and the third embodiment. The control unit 105 is configured to arrange the first line 121 and the second line 122 at the oblique angle 500, and to arrange the further first line 721 and the further second line 822 at a further oblique angle 800 to the transport direction 113. The further first scan movement and the further second scan movement are mirror symmetrical in the transport direction 113 relative to the first scan movement and the second scan movement. As a result, the irradiated pattern formed by the first line 121, the second line 122, the further first line 721 and the further second line 822 is a

V-shaped pattern. The lines may partly overlap in the point of the V-shaped pattern on the center line of the object 101 to ensure that the surface is properly irradiated near the point of the V-shaped pattern.

The laser scan head 103 irradiates the left half 801 of the object 101. The further laser scan head 703 irradiates the right half 802 of the object 101.

Fig. 9 depicts a method according to an embodiment of the invention. The method is for irradiating the object 101 with the laser beam 102. The method comprises the step 900 of directing the laser beam 102 with a laser scan head 103 to the object 101. The method comprises the step 901 of performing the first scan movement with the laser scan head 103 by moving the laser beam 102 along the first scan direction 111 to irradiate the first line 121 on the object 101, while moving the object 101 and the laser scan head 103 relative to each other in the transport direction 113. The method comprises the step 902 of performing the second scan movement with the laser scan head 103 by moving the laser beam 102 along the second scan direction 112 to irradiate a second line 122 on the object 101, while moving the object 101 and the laser scan head 103 relative to each other in the transport direction 113. The first scan direction 111 extends across at least part of the width of the object 101.

The width is in a direction perpendicular to the transport direction 113. The second scan direction 112 extends across at least part of the width of the object 101 opposite to the first scan direction 111. The method comprises the step 903 of controlling the second scan direction 112 based on the first scan direction 111 and the vector 402 in the transport direction 113.

This document describes detailed embodiments of the invention. However it must be understood that the disclosed embodiments serve exclusively as examples, and that the invention may be implemented in other forms.

Claims

CONCLUSIONS

A laser device (100) for irradiating an object (101) with a laser beam (102), comprising: a laser scanning head (103) for directing the laser beam (102) onto the object (101); a transport unit (104) for moving the object (101) and the laser scanning head (103) relative to each other; a controller (105) configured to control the laser scanning head (103) to perform a first scanning movement of the laser beam (102) and a second scanning movement of the laser beam (102); wherein the control unit (105) is configured to control the transport unit (104) to move the object (101) and the laser scan head (103) relative to each other in a transport direction (113) during the first scanning movement and during the second scanning movement; wherein the laser scanning head (103) is configured to perform a first scanning movement by moving the laser beam (102) along a first scanning direction (111) to irradiate a first line (121) on the object (101), wherein the laser scanning head ( 103) is configured to perform second scanning motion by moving the laser beam (102) along a second scanning direction (112) to irradiate a second line (122) on the object (101), with the first scanning direction (111) extending over at least part of a width of the object (101), the width being perpendicular to the transport direction (113), the second scanning direction (112) extending over at least part of the width of the object (101) opposite to the first scan direction (111), the controller (105) being configured to control the second scan direction (112) based on the first scan direction (111) and a vector (402) in the transport direction (113).

The laser device (100) of claim 1, wherein the controller (105) is configured to control the laser scan head (103) to make the first line (121) and the second line (122) on the object (101) parallel to each other. places.

The laser device (100) of claim 2, wherein the controller (105) is configured to control the laser scan head (103) to juxtapose the first line (121) and the second line (122).

A laser device (100) according to any one of the preceding claims, wherein the vector (402} in the transport direction (113) is based on a scanning speed of the second scanning movement, the scanning speed being a speed at which the laser scanning head (103) transmits the laser beam ( 102) moves along the second scanning direction (112) to irradiate the second line (122).

A laser device (100) according to any one of the preceding claims, wherein the control unit (105) is configured to control the transport unit (104) to move the object (101) and the laser scanning head (103) relative to each other in the transport direction (113). ) to move at a transport speed, where the vector (402) in the transport direction (113) is based on the transport speed.

The laser device (100) of claim 4 or 5, wherein the controller (105) is configured to control the second scan direction (112) based on an inverse (400) of the first scan direction (111).

The laser device (100) of any preceding claim, wherein the laser scan head (103) comprises at least one mirror and at least one galvo scanner motor; the at least one mirror being positioned to reflect the laser beam (102) toward the object (101), the at least one galvo scanner motor being configured to rotate the at least one mirror; wherein the controller (105) is configured to drive the at least one galvo scanner motor to control the first scan move and the second scan move.

A laser device (100) according to any one of the preceding claims, wherein the laser scan head (103) is configured to start the first scan move at a first start point (221) on the first line (121), to stop the first scan move at a first end point (222) on the first line (121), to start the second scan move at a second start point (321) on the second line (122), to stop the second scan move at a second end point (322) on the second line (122),

wherein the laser scan head (103) is configured to position the first end point (222) and the second start point (321) on the object (101) at a distance (202) from each other, the distance (202) being perpendicular to the first line (121) where the distance (202) is equal to or less than a diameter of the laser beam (102).

The laser device (100) of claim 8, wherein the distance (202) is less than 80% of the diameter of the laser beam (102).

The laser device (100) of claim 8 or 9, wherein the laser scan head (103) is configured to: position the laser beam (102) at a first laser start position (411) to irradiate the first start point (221); position the laser beam (102) at a first laser end position (412) to irradiate the first end point (222); position the laser beam (102) at a second laser start position (421) to irradiate the second start point (321); position the laser beam (102) at a second laser end position (422) to irradiate the second end point (322); wherein the first laser start position (411), the first laser end position (412), the second laser start position (421), and the second laser end position (422) are relative to the laser scanning head (103); wherein the laser beam (102) in the second laser start position (421) is placed opposite to the transport direction (113) with respect to the laser beam (102) in the first laser end position (412).

The laser device (100) of claim 9, wherein the second laser start position (421) is the same as the first laser end position (412).

A laser device (100) according to claim 9 or 10, wherein the laser beam (102) is positioned in the second laser end position (422) in the transport direction (113) relative to the laser beam (102) in the first laser start position (411).

The laser device (100) of claim 12, wherein the laser scanning head (103) is configured to perform the first scanning motion to irradiate a third line (321) on the object (101); wherein the laser scan head (103) is configured to: start the third scan pass at a third starting point (331) on the third line (321),

stop the third scanning motion at a third end point (332) on the third line (321), direct the laser beam (102) to the first laser start position (411) to irradiate the third start point (331); directing the laser beam (102) to the first laser end position (412) to irradiate the third end point (332); wherein the first line (121) and the third line (321) are on opposite sides of the second line (122).

A laser device (100) according to any one of the preceding claims, wherein the laser scan head (103) is configured to irradiate the first line (121), the first line (121) being perpendicular to the transport direction (113).

The laser device (100) of any one of claims 1 to 13, wherein the laser scan head (103) is configured to irradiate the first line (121), the first line (121) having an oblique angle (500) relative to the transport direction (113).

The laser device (100) of claim 15, wherein the first line (121) extends over a scanning width (502) of the object (101), the scanning width (502) being perpendicular to the transport direction (113), the laser scanning head (103) is configured to have a first average scan speed for a scan move over a length of the scan width (502), the laser scan head (103) being configured to have a second average scan speed for the first scan move, the second average scan speed higher than the first average scan rate.

A laser device (100) according to any one of the preceding claims, comprising a further laser scan head (703) for directing a further laser beam (702) onto the object (101), the further laser scan head (703) and the laser scan head (103 ) are arranged relative to each other along the direction perpendicular to the transport direction (113), the controller (105) being configured to control the further laser scanning head (703) to perform a further first scanning movement of the further laser beam (702) and a further perform second scanning movement of the further laser beam (702), wherein the control unit (105) is configured to control the transport unit (104) to move the object (101) and the further laser scanning head (703) relative to each other in the transport direction ( 113) during the further first scanning movement and during the further second scanning movement;

with the further laser scan head (703) configured, perform the further first scan move by moving the further laser beam (702) along a further first scan direction (711) to irradiate a further first line (721) on the object (101) wherein the further laser scan head (703) is configured to perform the further second scan move by moving the further laser beam (702) along a further second scanning direction (712) to create a further second line (822) on the object (101). irradiating, wherein the further first scanning direction (711) extends over at least part of the width of the object (101), wherein the further second scanning direction (712) extends over at least part of the width of the object (101 ) opposite to the further first scan direction (711), the controller (105) being configured to control the further second scan direction (712) based on the further first scan direction (711) and a further vector in the transport direction (113).

The laser device (100) of claim 17, wherein the laser scan head (103) and the further laser scan head (703) are arranged to position the first line (121) and the further first line (721) side by side on the object (101) , and to place the second line (122) and the further second line (822) side by side on the object (101).

A laser device (100) according to any one of the preceding claims, wherein the laser device (100) is a laser cleaning device.

A laser scanning head (103) for use in the laser device (100) according to any one of claims 1 to 19.

A control unit (105) for use in the laser device (100) according to any one of claims 1 to 19.

22. A method of irradiating an object (101) with a laser beam (102), the method comprising the steps of: directing the laser beam (102) at the object (101) with a laser scanning head (103), performing a first scanning movement with the laser scanning head (103) by moving the laser beam (102) along a first scanning direction (111) to irradiate a first line (121) on the object (101) while the object (101) and the laser scanning head ( 103) are moved relative to each other in a transport direction (113); performing a second scan move with the laser scan head (103) by moving the laser beam (102) along a second scanning direction (112) to form a second line (122)

on the object (101) while the object (101) and the laser scanning head (103) are moved relative to each other in the transport direction (113), the first scanning direction (111) extending over at least a part of a width of the object (101), the width being perpendicular to the transport direction (113), the second scanning direction (112) extending over at least a portion of the width of the object (101) opposite to the first scanning direction (111 ), the method comprising the step of controlling the second scan direction (112) based on the first scan direction (111) and a vector (402) in the transport direction (113).

The method of claim 22, including the step of aligning the first line (121) and the second line (122) on the object (101) parallel to each other.

The method of claim 23, including the step of juxtaposing the first line (121) and the second line (122) on the object (101).

The method of any one of claims 22 to 24, comprising the step of moving the laser beam (102) along the second scanning direction (112) to irradiate the second line (122) at a scanning rate; wherein the step of controlling the second scanning direction (112) based on the vector (402) in the transport direction (113) comprises controlling the second scanning direction (112) based on the scanning speed.

The method of claim 25, comprising the step of moving the object (101) and the laser scanning head (103) relative to each other in the transport direction (113) at a transport speed; wherein the step of controlling the second scan direction (112) based on the vector (402) in the transport direction (113) comprises controlling the second scan direction (112) based on the transport speed.

The method of any one of claims 22 to 26, wherein the step of controlling the second scanning direction (112) based on the first scanning direction (111) comprises controlling the second scanning direction (112) based on a inverse (400) of the first scanning direction (111).

A method according to any one of claims 22 to 27, comprising the steps of:

starting the first scan move at a first start point (221) on the first line (121), stopping the first scan move at a first end point (222) on the first line (121), starting the second scan move at a second start point (321) on the second line (122), stopping the second scan motion at a second end point (322) on the second line (122), setting up the first end point (222) and the second start point (321) on the object (101) at a distance (202) from each other, the distance (202) being perpendicular to the first line (121), the distance (202) being equal to or less than a diameter of the laser beam (102 ).

The method of any one of claims 22 to 28, comprising the steps of: placing the laser beam (102) at a first laser start position (411) to irradiate the first starting point (221), placing the laser beam (102) at a first laser end position (412) to irradiate the first end point (222); placing the laser beam (102) at a second laser start position (421) to irradiate the second start point (321); placing the laser beam (102) at a second laser end position (422) to irradiate the second end point (322); placing the laser beam (102) in the second laser start position (421) opposite to the transport direction (113) of the laser beam (102) in the first laser end position (412); wherein the first laser start position (411), the first laser end position (412), the second laser start position (421), and the second laser end position (422) are relative to the laser scan head (103).

The method of any one of claims 22 to 29, wherein the step of performing the first scanning pass comprises irradiating the first line (121), the first line (121) having an oblique angle (500) relative to relative to the transport direction (113).

A method according to any one of claims 22 to 30, comprising the steps of: providing a further laser scanning head (703} for directing a further laser beam (702) onto the object (101),

performing the method according to any one of claims 22 to 30 with the further laser scanning head (703) to irradiate a further first line (721) and a second first line (121), arranging the further first line (721 ) next to the first line (121), positioning the further second line (822) next to the second line (122).

32. Computer program containing instructions which, when executed by a control unit (105) of a laser device (100), the laser device (100) comprising a laser scanning head (103) for directing a laser beam (102) at an object {101 }, and a transport unit (104) for moving the object (101) and the laser scan head (103) relative to each other, cause the control unit (105) to perform the method according to any one of claims 22 to 31.