WO2024046686A1

WO2024046686A1 - Method and device for laser projection

Info

Publication number: WO2024046686A1
Application number: PCT/EP2023/071280
Authority: WO
Inventors: Markus Brunk; Martin Greggersen
Original assignee: Lap Gmbh Laser Applikationen
Priority date: 2022-09-01
Filing date: 2023-08-01
Publication date: 2024-03-07
Also published as: DE102022122155B3

Abstract

The invention relates to a method for laser projection and to a laser device (10) for carrying out said method. According to the invention, the method involves using a laser device (10) comprising a laser generation unit (12) by means of which a laser beam (14) can be generated, a deflection apparatus (16) by means of which an emission angle of the laser beam (14) can be adjusted in order to direct the laser beam (14) along a specified trajectory (18), and a control apparatus (20), coupled to the laser generation unit (12), by means of which the power of the laser beam (14) can be adjusted, wherein in a first step for the navigation of the laser beam (14) along the specified trajectory (18) a plurality of navigation angles to be achieved by means of the deflection apparatus (16) are determined, wherein a starting power is assigned to the navigation angles, which starting power specifies the power of the laser beam (14) during deflection between two navigation angles, and wherein in a next step depending on the number of navigation angles to be achieved directly in succession and with which the laser beam (14) reaches a navigation section (22) of a reference surface (24), an expected residence time of the laser beam (14) in the navigation section (22) is ascertained and at least for a subset of the navigation angles with which the laser beam (14) reaches the navigation section (22), the respective starting power of the laser beam (14) is adjusted to a specifiable target power depending on the ascertained residence time.

Description

METHOD AND DEVICE FOR LASER PROJECTION

The present invention relates to a method for laser projection using a laser device and to a laser device which is designed to carry out the method according to the invention.

Laser projectors are used in a wide variety of technical areas to project outlines and markings onto objects. As a rule, their lines can be projected clearly visibly onto a flat or curved surface, or onto a surface of any other contour, in a single-color projection, for example in a red, green or blue projection, or in a multi-color projection, in particular in a mixed-color projection. The basis for the projection is often CAD data, which is processed into projection data and transmitted to one or more projectors. Industrial laser projection systems create virtual but visible stencils on objects to be processed that do not touch or contaminate the surfaces. Technically, the projection is usually carried out using one or more galvanometers, which can be used to change the orientation of a mirror in relation to a laser beam. The laser beam is deflected by the mirror, with the angle of rotation of the mirror determining the direction of deflection. If two or more galvanometers are combined with each other, every accessible point in the room can be illuminated.

In order to comply with safety guidelines regarding the deployment and use of lasers, it is necessary to limit the power emitted by the laser projector depending on various variables such as location or intended use. The risk of injury to people who are in a radiation area that can be reached by the laser plays a particular role. In particular, an unprotected look at high-power laser light can lead to injuries to the retina and thus possibly to impaired vision. The invention is based on the object of providing a method and a device for laser projection which allows the intensity of the laser beam to be adjusted to a predeterminable level using simple means.

The object is achieved by a method according to the invention according to claim 1 and by a device according to the invention according to claim 17. Advantageous embodiments are specified in the subclaims.

According to the invention, there is a method for laser projection using a laser device comprising a laser generation unit by means of which a laser beam can be generated, a deflection device by means of which a beam angle of the laser beam can be adjusted for steering the laser beam along a predetermined trajectory, and a control device coupled to the laser generation unit by means of which the power of the Laser beam can be adjusted, wherein in a first step for the navigation of the laser beam along the predetermined trajectory, several navigation angles to be controlled by means of the deflection device are determined, with the navigation angles each being assigned a starting power, which specifies the power of the laser beam when deflecting between two navigation angles , and wherein in a next step, depending on the number of navigation angles to be controlled immediately one after the other, with which the laser beam reaches a navigation section of a reference surface, an expected dwell time of the laser beam in the navigation section is determined and that at least for a subset of the navigation angles with which the Laser beam reaches the navigation section, the respective starting power of the laser beam is set to a predeterminable target power depending on the determined dwell time.

The present invention makes it possible to provide a laser projector that can be operated in compliance with specified laser safety classes. For example, by using the method according to the invention, a laser projector can be provided that meets the specified safety guidelines The removable criteria for laser class 2 and laser class 3B are met. If certain laser classes are met, it can be achieved, for example, that a laser projector according to the invention can also be used without a laser protection officer who is otherwise necessary for operation in the company. Compliance with certain laser classes can be achieved by limiting the total power that can be emitted by the laser projection device. For example, laser class 3B compliance can be achieved if the laser projection device does not exceed a total power of 500 mW.

Laser class 2 could also be achieved by selecting laser diodes with a maximum emitted power of 1 mW. However, the power of 1 mW is unsuitable for use in a projector, as the projection would not be bright enough for its intended purpose due to the usual distance to the projection surface and the high speeds at which the laser beam is usually deflected.

In order to solve this problem, a safety area can be defined, whereby predeterminable criteria outside the safety area, such as the criteria for laser class 2, are met and within the safety area other criteria are met that require classification in a higher laser class. The method according to the invention is based on the idea of using safety criteria for pulsed beam sources, in particular regardless of whether a pulsed or an unpulsed radiation source is used to generate the laser beam. For example, based on currently valid safety guidelines, the energy of the laser beam when crossing an aperture of 7 mm can now be considered instead of the power to ensure compliance with the criteria necessary for a specific laser class.

The energy of the laser beam when sweeping over a specific area section can be determined by knowing the emitting power of the laser generation unit depending on the residence time of the laser beam within the area section determine. In a method of the type according to the invention, the trajectory to be swept by the laser beam is usually determined by the sequential control of individual predetermined navigation angles using the deflection device. The navigation angles are controlled one after the other at a short time interval from one another. Each navigation angle is usually also assigned a laser power, which determines the laser power for this navigation angle.

If the time intervals between the individual controlled navigation angles are at least largely the same, the duration of the laser beam in a specific navigation section can be determined, for example, by multiplying the number of navigation angles to be controlled one after the other, with which the navigation section is reached, and the time interval. For example, the time interval between two navigation angles controlled one after the other can be 2 ps. The time interval can be specified by a time constant that a controller uses as process time between individual control steps.

In order to specify a curve to be projected with the laser device, it can be provided in a first step to provide vector graphics, for example in SVG or DXF format. These vector graphics are usually processed using a computer processing method set up for this purpose and broken down into individual elements such as circle sections, lines and splines. This data is then transmitted to the laser projection device. The laser projection device receives the data and processes it using a control device in such a way that an angle phi, an angle theta and a specific laser power are assigned in predeterminable time intervals of, for example, 2 ps. The solid angle to be controlled by the deflection device, consisting of the angle Phi and the angle Theta, can also be referred to as the navigation angle. This processing is called trajectoryization. After the trajectory, a further step takes place in which method steps according to the invention are carried out in order to enable compliance with a specific laser class. After processing according to the invention, the data can be transferred to a controller, which uses the galvanometer drives and the laser drivers to cyclically and in real time follow the specified trajectory based on the navigation angles. The rotation frequencies, i.e. the repetition rates of a trajectory, are typically between 30 - 50 Hz.

When setting the target power of the laser beam according to the invention, it is intended that the output power emitted by the laser generation unit is adjusted. When using a laser generation unit with several laser sources, the laser powers of the individual sources are preferably adjusted in order not to exceed an expected energy in a navigation section resulting from the power of the laser beam and the dwell time.

In one embodiment, it is envisaged that for the setting of the starting powers to the target powers, an expected actual energy to be applied by means of the laser beam in the navigation section of the reference surface is determined on the basis of the predetermined starting powers of the laser beam and, if exceeded the actual energy over a first predeterminable limit energy, the starting powers are reduced to target powers in such a way that an expected actual energy is achieved which is less than or equal to the limit energy.

The setting of the starting powers assigned to the navigation angles to the target powers can be carried out in such a way that all starting powers to be set are reduced or increased by a specific factor. When using several laser sources, in which the laser powers of the individual laser sources are assigned to the navigation angles, for example, each starting power to be adjusted is reduced or increased by a certain factor. In the method according to the invention, it is intended that the setting of the starting power to the target power takes place before the activation of the laser, so that the laser does not exceed the predeterminable power or energy limit values when activated and thus immediately upon activation of the laser Compliance with certain laser classes is guaranteed.

In addition to reducing the starting power to the target power, increasing the starting power can also be considered. An increase can be carried out, for example, if the actual energy of the laser beam to be expected in a navigation section is lower than a predeterminable limit energy. If the duration of the laser beam in the navigation section does not exceed a certain level, so that a predetermined limit energy or limit power of the laser beam in the navigation section under consideration is already undershot without adjustment, provision can also be made to leave the starting powers unchanged .

The expected actual energy to be applied by means of the laser beam in the navigation section of the reference surface can be calculated, for example, using the equation Eq. n

^{Eist =} 2 ti x Pi x Si (Eq) i=a

Whereby the following applies to equation Eq and the following: E _is the actual energy;

is the time interval between a previous and the considered navigation angle i; j is the starting power of the laser source of the laser beam assigned to the navigation angle i under consideration; S _t is a scaling factor of the laser source; a is the first navigation angle considered and n is the last navigation angle considered. In equation Eq, the sum is formed for a number of consecutive navigation angles a to n, whereby the time duration is multiplied by the laser power P _t and a scaling factor of the laser source. If there is more than one source, the equation must be expanded accordingly to include the laser power P _xl and the scaling factor S _xi of the other sources. For example, the actual energy can be determined using equation G2 when using a laser generation unit with two laser sources.

In the case of laser projectors of the generic type, the time period t _£ between two navigation angles i is usually the same. The time period is therefore formed, for example, by a time constant t _K , in particular a controller constant. In one application, the time constant t _K can be 2ps.

The limit energy can be determined for different laser power classes to be achieved. For example, a limit energy for laser class 2 can be determined using equation G3.

Elimit = 7 X IO" ⁴ XT ^0.75 XC ₆ (G3)

Where the following applies to equation G3 and beyond: E _limit is the limit energy; T is the dwell time of the laser beam in the navigation section under consideration; C ₆ is a rating factor for the degree of focusing of the laser beam. When using a parallel, i.e. collimated, laser light in which the beam diameter is in particular 7 mm or less than 7 mm, a value of 1 can be selected for the design factor C ₆ , for example. When using an expanded laser beam, this expansion is taken into account in the design factor. Preferably in the case according to the invention The method uses a collimated laser beam with a beam diameter of less than 7 mm.

The limit energy for laser class 3R can be determined, for example, using equation G4.

Earenz = 3.5 X IO ^-3 XT ⁰ ' ⁷⁵ (G4)

The dwell time T results from the sum of the time intervals between the navigation angles i considered. If the time intervals are the same, i.e. are present as a time constant, the dwell time T can be formed by multiplying the time constant by the number of navigation angles to be controlled immediately one after the other with which the laser beam reaches the navigation section of the reference surface under consideration.

If the determined actual energy is higher than the limit energy to be undercut, it is considered to multiply the starting powers of the navigation angles under consideration by a correction factor in order to adjust the expected actual energy of the laser in the navigation section under consideration reduce that is at or below the limit energy. The correction factor can be determined, for example, using equation G5.

According to a preferred embodiment, it can further be provided that an expected section power to be emitted by means of the laser beam in a navigation section of the first reference surface is determined on the basis of the target powers of the laser beam, and the section power is compared with a predeterminable limit power, and whereby if the expected section performance exceeds the limit performance at least for a subset of the Navigation angle with which the laser beam reaches the navigation section, the target powers are reduced in such a way that the expected section power is less than or equal to the limit power.

This checks whether the section power achieved with specified target powers or starting powers, as long as the powers assigned to the navigation angles have not been changed, is below a limit power outside a certain protection area. If the expected section power at the distance from the protection area is greater than the limit power to be undershot, then the target powers of at least part of the, in particular all, navigation angles at which the laser beam reaches the navigation section under consideration are proportionally reduced.

In this embodiment, it is also considered that in order to determine the section power, a section energy to be expected to be applied in the navigation section is first determined and linked to a repetition rate of the predetermined trajectory.

The section energy can be determined, for example, using equation Eq, or when using multiple laser sources using an adapted equation such as equation G2, where the actual energy corresponds to the section energy. The section power can be determined, for example using equation G6, by multiplying the section energy by the repetition rate of the trajectory.

^Section ~ ^Section frR (66)

Where for equation G6 and further applies: Psection is the section power; ^Section is the section energy and f _TR is the frequency or repetition rate of the trajectory, for example the number of repetitions of the trajectory that should be projected per second. In a further embodiment, it is envisaged that trajectory segments of the predetermined trajectory for which the laser beam reaches this navigation section are identified for at least one navigation section of the reference surface. By identifying trajectory segments with which the laser beam reaches the navigation section under consideration, it can first be recognized whether more than one trajectory section lies within the navigation section under consideration. In the following, a total energy of different combinations of these trajectory segments can be taken into account in order to determine whether a predeterminable limit energy is exceeded. The trajectory segments are sections of the predetermined trajectory, each of which is composed of immediately successive navigation angles with which the laser beam reaches the navigation section under consideration.

It is also envisaged that when more than one trajectory segment lying within the navigation section is identified for at least one combination, in particular for each combination, consisting of a first trajectory segment and one or more further immediately successive trajectory segments, a number of navigation angles assigned to the combination the trajectory section of the predetermined trajectory comprising the trajectory segments is determined, starting with a first navigation angle of the first trajectory segment of the combination and ending with a last navigation angle of the last trajectory segment of the combination along the trajectory section.

The number of possible combinations of different trajectory segments, each of which lies in the navigation section under consideration, increases with the number of identified segments. The number of combinations can be found using equation G7. The area of the predetermined trajectory, which includes identified trajectory segments of a combination, is a trajectory section assigned to the navigation section. A trajectory section is assigned to each combination of trajectory segments. A Trajectory section begins with a first navigation angle of a first trajectory segment lying within the navigation section

Combination and it ends with a last navigation angle of a last trajectory segment lying within the navigation section

Combination. Such a trajectory section therefore includes all immediately successive navigation angles starting with a first navigation angle of a first trajectory segment and ending with a last navigation angle of a last trajectory segment of the combination.

Whereby the following applies to equation G7 and beyond: N _K is the possible number of combinations, which results from the number n _TS of trajectory segments lying within the navigation section under consideration.

When considering a combination, a first trajectory segment and one or more further trajectory segments immediately following one another are taken into account. Immediately successive trajectory segments are those segments of the trajectory that follow one another directly in the direction of the temporal sequence of the navigation angle to be controlled or in the direction of movement of the laser along the trajectory, i.e. without skipping over segments in between, and also lie in the navigation section under consideration. A combination can therefore consist of two or more than two trajectory segments located within the navigation section under consideration. It goes without saying that only a single run of the trajectory within a period is considered here. The trajectory segments that lie within a navigation section under consideration are therefore each different segments of a single run of the trajectory. It is further envisaged that for at least one combination, in particular for each combination, a reference duration is determined depending on the number of navigation angles assigned to the combination, a combination limit energy assigned to the combination being determined depending on the reference duration, and where An expected actual combination energy for the combination is determined from the sum of segment energies, each of which corresponds to the expected energy of the trajectory segments of the combination, and the actual combination energy is compared with the combination limit energy , and whereby when the combination actual energy exceeds the combination limit energy, at least for a subset of the navigation angles of the trajectory section, the starting power or target power of the laser beam assigned to the navigation angles is reduced in such a way that the expected combination -Actual energy is less than or equal to the combination limit energy.

Like the limit energy E _limit, the combination limit energy can also be determined for different laser power classes to be achieved. Analogous to equation G3, the combination limit energy can be determined for laser class 2, for example, using equation G8.

E _KG E = 7 X IO“ ⁴ X RD ^0.75 XC ₆ (G8)

Where the following applies to equation G8 and beyond: E _KGE is the combination limit energy; RD is the reference duration for the combination under consideration; C ₆ is the design factor to take into account the degree of focusing of the laser beam, which, as explained above, can be 1, for example.

The combination limit energy for laser class 3R can be determined, for example, using equation G4 analogously. The reference duration RD can be determined from the sum of the time intervals between the individual navigation angles of the combination under consideration, starting with a first navigation angle of the first trajectory segment of the combination and ending with a last navigation angle of the last trajectory segment of the combination along the trajectory section. So not only the navigation angles of the individual trajectory segments of the combination are taken into account, but also those between two immediately successive trajectory segments. The reference duration RD can therefore be determined, for example, using equation G9.

Where the following applies to equation G9 and beyond: RD is the reference duration for the combination under consideration; t _t is the time interval between a previous and the considered navigation angle i; a is the first navigation angle considered and n is the last navigation angle considered.

If the time intervals between two immediately successive navigation angles are the same, i.e. there is a time constant t _K , the reference duration can be determined from multiplying the time constant t _K by the number of navigation angles n considered, i.e. in particular using equation G10.

RD = n X t _K (G10)

The segment energies can be determined using equation Gi l. Equation Eq Equation G2 can be applied. To avoid repetition, further explanations are therefore omitted.

Whereby the following applies to equation Eq. 1 and further: E _SE is the segment energy of a trajectory segment under consideration; t _t is the time interval between a previous and the considered navigation angle i; P[ is the starting power assigned to the navigation angle i under consideration or the target power of the laser source of the laser beam adjusted after previous method steps have been applied; Si is a scaling factor of the laser source; a is the first navigation angle and n is the last navigation angle of the trajectory segment under consideration.

The time duration for laser projectors of the generic type is analogous to the explanations for equations Gl and G2

between two navigation angles i preferably the same.

In order to adjust the power of the laser beam to a level at which the combination actual energy is less than or equal to the combination limit energy, provision can be made to set the power previously assigned to the navigation angles under consideration to a new power. Analogous to the previous explanations, the laser power previously assigned to the navigation angles considered, i.e. the starting or target power set up to this method step, can be multiplied by a factor. This means that the performance values of the navigation angles under consideration are changed proportionally. The power setting can be done, for example, using equation Eq. 2.

Where the following applies to equation G12 and further: P _new is the set new power assigned to a navigation angle under consideration; P _att is the old power associated with a navigation angle under consideration; E _KGE is the combination limit energy; E _KIE is the combination-actual energy.

According to a preferred embodiment, it is envisaged that the power of the laser beam is adjusted using pulse width modulation.

Furthermore, it can be provided that a distance from objects detected in the detection range of the distance sensor to the laser device is monitored by means of a distance sensor. This makes it possible to recognize that an object is within a predetermined safety distance. The priority is to use the distance sensor to detect people, in particular the head of a person, who are within a safe distance.

In the first regard, it is provided that the distance sensor only detects when an object is within a set safety distance. It is therefore not necessary to record the actual distance. A suitable distance sensor could therefore be set up to detect an object located in the security area based on a threshold value being exceeded. Alternatively or additionally, it can be provided that the distance sensor is designed and set up to determine a distance from a detected object or to generate a signal by means of which a distance to the object can be determined.

To increase laser safety, it can be provided that the power of the laser beam depends on the distance monitored by the distance sensor is set, the laser generation unit being deactivated, in particular if the safety distance falls below a predeterminable safety distance.

In one embodiment of the invention it can be provided that the reference surface is calculated as a virtual surface which extends over an angular range, in particular over the entire angular range, of a navigation range that can be reached by the laser beam. The navigation area that can be reached by the laser beam is essentially determined based on the exit opening of the laser device of the solid angle that can be reached with the deflection device.

For an equidistant distribution of the navigation sections over the projection area of the laser device, it is intended that the virtual reference surface has a spherical shape and extends at a distance from the laser projection device, the distance of the virtual reference surface corresponding in particular to the safety distance. The distance of the virtual reference surface can be selected, for example, according to local conditions and/or according to predeterminable safety criteria. By means of the method according to the invention, compliance with laser class 2 or compliance with another laser safety class such as laser class 3R is ensured in the distance ranges that exceed the safety distance. It goes without saying that the method according to the invention can also be carried out with several different reference surfaces at different distances, for example to ensure compliance with different laser safety classes in different distance ranges.

Furthermore, it is envisaged that the reference area is divided into a grid comprising several grid cells, with each grid cell corresponding to a navigation section that can be reached by the laser beam. A navigation section can, for example, have a rectangular outer contour. In particular, it can be provided that the outer contour of a navigation section is square. For the edge length of a rectangular or square In principle, any value can be selected in the navigation section, for example a value based on certain standardized specifications. For example, the edge length can be a value between 4 mm, or less than 4 mm, and 10 mm, or more than 10 mm. Preferably, a square outer contour with an edge length of 7 mm is considered.

In particular, to generate different colored laser projections, it can be provided that the laser generating unit has two or more than two laser beam sources, with the beams generated by the two or more than two laser beam sources being superimposed to generate the laser beam. For example, it can be provided that a red laser with a starting power assigned to the navigation angles of 100% of its maximum power is used together with a green laser with a starting power assigned to the navigation angles of 50% of its maximum power. A different power setting of the laser sources enables the projection of different mixed colors. In the case of a power reduction according to the invention in order to comply with limit energies, both sources can be reduced proportionally, for example the red laser to 50% and the green laser to 25% of their respective maximum power. When using multiple laser sources, the individual sources must be individually adjusted, for example using individually adjustable pulse width modulation.

To deflect the laser beam in different spatial directions, it is intended that the deflection device has at least one movable mirror, in particular at least one galvanometer mirror, by means of which the laser beam can be deflected to adjust the beam angle.

A safety problem can arise if the deflection device unintentionally remains inoperative or does not reach the desired deflection speed due to malfunctions. The actual duration of the laser beam in a specific navigation section can be longer than the calculated one Length of stay. In order to reduce this safety risk, it is considered that a predetermined speed of a drive unit of the deflection device is monitored by means of a monitoring device. This monitoring can, for example, be intended to determine whether the actual angle of the deflection device corresponds to the intended target angle. Deviations between the actual angle and the target angle are also called “following errors”. Alternatively or additionally, provision can be made to check the resulting speed from both mirror movements against a limit speed. With this monitoring, mirrors that remain completely non-functional, i.e. “sticky” mirrors, can be detected.

If the deflection device falls below a target speed, provision can be made to reduce the laser power to a level that is not critical to safety. Alternatively or additionally, provision can be made to deactivate the laser device when the speed falls below a target speed.

Finally, according to the invention there is also a laser device for laser projection comprising a laser generation unit by means of which a laser beam can be generated, a deflection device by means of which a beam angle of the laser beam can be adjusted for steering the laser beam along a predeterminable trajectory, and a control device coupled to the laser generation unit by means of which the power of the laser beam is controlled is adjustable, the laser device being designed and set up to carry out a method according to the invention according to one of the previously explained embodiments.

Advantages, details and further refinements of the laser device according to the invention result in particular from the explanations of the refinements of the method according to the invention.

Further details and refinements of the invention are explained using figures. Show it: 1 is a schematic view of a laser device according to the invention,

2 shows a schematic representation of navigation angles to be controlled by means of a laser device according to the invention,

3 shows a detail of a reference area with navigation sections in a schematic representation,

4 shows a navigation section of the reference area from FIG. 3 in a schematic representation,

5a shows a navigation section of a reference surface with a trajectory section intersecting the navigation section in a schematic representation, and

Fig. 5b is a schematic representation of individual trajectory segments that lie within the navigation section from Fig. 5a.

Figure 1 shows a laser device 10, also generally referred to as a projector, with a laser generating unit 12 which generates a laser beam 14. The laser beam 14 is directed by means of a deflection device 16 in such a way that the laser beam 14 sweeps over a predeterminable trajectory 18 in space. The power setting of the laser generation unit can be carried out by means of a control device 20 coupled to the laser generation unit 12. The control device 20 and/or a further control device provided for this purpose can control the deflection device 16 in such a way that a predetermined navigation angle X (FIG. 2) is controlled. A distance sensor 30 can be provided to detect objects in a detection range of the distance sensor 30. The deflection device 16 can be set up to direct the laser beam 14 into any navigation angle X located in a navigation area 28. The navigation area 28 can be in Radiation area of the laser device 10 may be conical. The detection range of the distance sensor 30 is preferably larger or at least as large as the navigation range 28 that can be reached with the laser beam 14.

As indicated schematically in Figure 1, the laser generating device 12, the control device 20 and the deflection device 16 can be arranged in a common housing 26. The distance sensor can also be arranged inside, but also on or outside of the housing.

In the navigation area 28 of the laser device 10, a reference surface 24 is formed - here shaped spherically to the deflection point of the laser beam 14 on the deflection device 16. This reference surface 24 can in particular be arranged at a safety distance that corresponds to a safety area monitored by the distance sensor 30. The reference surface 24 is a virtually generated spatial surface that serves to adjust the power of the laser device 10 according to the invention.

In a specific example that can be used as a basis for every embodiment of the invention, provision can be made in a first criterion 1 to adjust the power of the laser sources of the laser device by two mechanisms. By setting a diode current of a laser diode on the laser driver, the maximum laser power that should be emitted can be specified. This value is preferably set once and is preferably unchangeable. On the other hand, a largely linear adjustment of the emitted power can be achieved by pulse width modulation of the signal at the laser diode. This intensity value, which can be adjusted using a power value, is determined for each point of the trajectory and is used, for example, to make the projected figure appear equally bright. The power setting can be influenced in order to avoid any violation of the laser class. The basic frequency of this pulse width modulation is, for example, 20 MHz and therefore has a period of 50 ns, which in turn can be divided into 271 stages of 184 ps each. This Pulses therefore have a minimum length of 184 ps and a maximum length of 50 ns. They therefore fall under this criterion 1.

2 shows purely schematically a simple example of a spatial trajectory 18 to be controlled with the laser beam 14 of a laser device 10. The trajectory 18 is formed by controlling several navigation angles X. The navigation angles Xi to Xi shown in FIG. 2 for purposes of illustration are controlled one after the other by means of the deflection device 16. Since the navigation angles

The navigation angle X is formed from two angle information phi and theta. With this pair of angles phi and theta, any solid angle within the navigation area 28 of the laser device 10 can be controlled. The angle information phi and theta are used to set the deflection device 16.

Each navigation angle

Figure 3 shows a virtual reference surface 24 in a schematic representation. The reference surface 24 is divided into a grid with square grid cells 32 in the present example, each grid cell 32 corresponding to a navigation section 22 that can be reached by the laser beam 14. 3 also shows purely schematically a trajectory 18 swept over by the laser beam 14. As shown, the laser beam 14 reaches different navigation sections 22 when controlling the navigation angles X of the trajectory 18. Figure 4 shows a navigation section 22 from Figure 3 in detail. In this schematic detailed representation, successively controlled navigation angles X of a segment of the trajectory 18 lying within the navigation section 22 are shown. The area of the trajectory 18 that lies within the navigation section 22 is referred to as the trajectory segment TS. In this schematic representation, eleven navigation angles X lie within the navigation section 22. With a constant time interval between the navigation angles For example, if the time constant is 2 ps, the dwell time is 22 ps (11 x 2 ps).

In a specific example, which can be used as a basis for any embodiment of the invention, provision can be made in a second criterion 2, as already explained above, to divide a trajectory projection 18 in the projection area 28 onto a grid 32 of a reference surface 24. In mathematical terms, this grid 32 is preferably at the distance of the security area from the projector 10 and more preferably has a spherical shape. The entire theoretically reachable area 28 of the projector 10 is covered by the sphere. The preferably square cells of the grid 32 of the sphere preferably have an edge length of 7 mm in both directions on the spherical surface. Each point of the trajectory 18 is assigned to a cell or a navigation section 22 of the grid or the reference surface 24 based on its coordinates or navigation angle X.

For each navigation section 22 of the reference surface 24 it is known when the laser beam 14 enters the navigation section 22 and exits again. The part between the entry and exit of a cell represents a pulse or a trajectory segment TS. If the same navigation section 22 is hit again at a later time in the trajectory 18, this is assessed as a further trajectory segment TS. Figure 4 schematically shows, for example, a single cell or a single navigation section 22 from the example in Figure 3. The sub-area of the trajectory 18 is symbolized by points representing navigation angle ps of trajectory 18 represents.

For criterion 2, the energy for each 2 ps step is determined from the known maximum laser power of the sources and the adjustable power using pulse width modulation. The sum of all 2 ps steps in this pulse is the pulse energy. The permissible limit value is obtained, for example, using equation G3, with the time being determined by the number of pulses multiplied by 2ps.

With this example, compliance with laser class 2 can be made possible in a certain safety area. Analogous to the procedure for determining laser class 2 at the distance of the safety area, compliance with laser class 3R can be made possible for the distance of, for example, 100 mm in front of the projector. In both cases, a grid with an edge length of 7 mm can be used, which leads to different pulse lengths of the trajectory segments TS and power setting values for the navigation angles X under consideration. In both cases, when the calculated limit values are exceeded, the power values for the navigation angles

In a further specific example, which can be used as a basis for any embodiment of the invention, provision can be made in a third criterion 3 to re-evaluate the power settings of the navigation angle X corrected, for example, after taking criterion 2 into account. According to this criterion 3, the sum of the energies for all pulses or trajectory segments TS is considered, which are in a grid cell or in a navigation section 22 within a certain time, of, for example, 0.25 seconds. This also includes the repetitions of the pulses or trajectory segments TS, which occur within the navigation section 22 under consideration due to the projection frequency of, for example, 25 to 50 Hz. With this criterion 3 it can be provided that the total power of a cell or a navigation section 22 may not be greater than 1 mW at a distance from the protected area and not more than 5 mW at a distance of 100 mm (cf. laser class 2 or 3R). If the limit is exceeded, a correction is carried out for the entire cell, i.e. for all navigation angles X with which the laser beam 14 reaches the navigation section 22. For this purpose, all power values of the navigation angles

5a shows a schematic representation of another example of a navigation section 22 with a section of a trajectory 18, with four sub-segments TS1 to TS4 lying within the navigation section.

Figure 5b shows schematically the compilation of various combinations of sub-segments TS1 to TS4 from Figure 5a located within the navigation section 22. Between the sub-segments TS1 to TS4, intermediate pieces ZI to Z3 are indicated, which represent the trajectory areas which lie along the trajectory 18 between the first trajectory segment TS1 reaching the navigation section 22 and the last trajectory segment TS4 reaching the navigation section 22 and thus outside the navigation section 22.

In the present case, in one run of the trajectory 18, there are four trajectory segments TS within the navigation area 22. According to equation GL7, six combinations K1 to K6 can be formed, each of which is formed from two or more than two trajectory segments TS immediately following one another. In the present case, the combination Kl consists of the trajectory segments TS 1 and TS2. Combination K2 consists of the trajectory segments TS1, TS2 and TS3. The The remaining combinations K3 to K6 are formed accordingly. Each combination K defines a trajectory section TA, which includes the navigation angles X of the trajectory 18, starting with a first navigation angle X of the first trajectory segment TS of the combination K under consideration and ending with the last navigation angle In the present case, the trajectory section TAI includes, for example, all navigation angles are defined accordingly.

In a specific example that can be used as a basis for every embodiment of the invention, provision can be made in a fourth criterion 4 to consider multiple pulses, i.e. several trajectory segments TS occurring in a navigation section 22 within a period T. This occurs, for example, when the trajectory 18 intersects itself. An example of a cell or a navigation section 22 with several trajectory segments TS within a period T is - as mentioned - shown in Figure 5a. In Figure 5b, the time course of the four trajectory segments TS1 to TS4 within this cell or the navigation section 22 is indicated schematically. All four trajectory segments TS are passed through within a period T of a trajectory 18. This can be seen in the time sequence in the diagram in FIG. 5b. The diagram shows purely schematically the power P of the trajectory segments TS over time. First, the navigation angle X of the trajectory segment TS1 is controlled, then the trajectory segments TS2 to TS4 follow. Then the period T ends and a new run begins.

The four individual pulses TS1 to TS4 can already be taken into account in criterion 2. However, since the pulses can occur irregularly in number, length and distance within a periodic cycle, additional virtual pulses must also be included Trajectory sections called TA, against which limits from criterion 2 are checked. This can be done for different laser classes, for example for both laser class 2 and laser class 3R. The virtual pulses or trajectory sections TA are defined by considering several consecutive pulses together. The successive pulses or trajectory segments TS of a virtual pulse are also referred to here as combination K. This can be seen specifically in Figure 5b. In this example cell with four pulses TS1 to TS4, six additional virtual pulses or trajectory sections TAI to TA6 are defined. Using the power and the duration of each trajectory section TA, depending on the power class under consideration, equations G3 and G4 from criterion 2 can, for example, be used to determine the limit value for the respective virtual pulse or the respective trajectory section TA. The virtual pulses or trajectory sections TAI to TA6 are each shown in Figure 5b as an arrow under the diagram. For the first virtual pulse TAI, the sum of the energies of the first two individual pulses TS1 and TS2 of the combination Kl is determined as well as the length, i.e. the reference duration RD, of the trajectory section TAI from the beginning of the trajectory segment TS1 to the end of the trajectory segment TS2. For the second virtual pulse TA2, the sum of the energies of the first three individual pulses TS1 to TS3 is determined as well as the length, i.e. the reference duration RD, of the trajectory section TA2 from the beginning of the trajectory segment TS1 to the end of the trajectory segment TS3. The other virtual pulses TA3 to TA6 are considered accordingly.

REFERENCE SYMBOL LIST

10 laser device

12 laser generation unit

14 laser beam

16 deflection device

18 trajectory

20 control device

22 navigation section

24 reference surface

26 housings

28 Navigation area

30 distance sensor

32 grids

X navigation angle

TS trajectory segment

K combination

Z intermediate pieces

TA trajectory section

Claims

EXPECTATIONS

1. Method for laser projection using a laser device (10) comprising a laser generation unit (12) by means of which a laser beam (14) can be generated, a deflection device (16) by means of which a beam angle of the laser beam (14) can be adjusted for steering the laser beam (14) along a predetermined trajectory (18), and a control device (20) coupled to the laser generation unit (12) by means of which the power of the laser beam (14) can be adjusted, characterized in that in a first step for navigating the laser beam (14) along of the predetermined trajectory (18), several navigation angles (Xi) to be controlled by means of the deflection device (16) are determined, with the navigation angles (X) each being assigned a starting power which corresponds to the power of the laser beam (14) when deflecting between two navigation angles ( X) specifies, and in a next step depending on the number of navigation angles (X) to be controlled immediately one after the other, with which the laser beam (14).

Navigation section (22) of a reference surface (24) is reached, an expected dwell time of the laser beam (14) in the navigation section (22) is determined and that at least for a subset of the navigation angles (X) with which the laser beam (14) reaches the navigation section ( 22), the respective starting power (Pstart) of the laser beam (14) is set to a predeterminable target power depending on the determined dwell time.

2. The method according to claim 1, characterized in that for the setting of the starting powers (Pstart) to the target powers (Psou) based on the predetermined starting powers (Pstart) of the laser beam (14), an expected one, by means of the Laser beam (14) in the navigation section (22) of the reference surface (24) the actual energy (Ei _S t) to be applied is determined and when the actual energy (Eist) is exceeded via a first predeterminable limit energy (Elimit), the start Services (Pstart) are reduced to target services (Psoii) in such a way that an expected actual energy (Eist) is achieved that is less than or equal to the limit energy (Elimit). Method according to claim 1 or 2, characterized in that, on the basis of the target powers (Psoii) of the laser beam (14), an expected section power to be delivered by means of the laser beam (14) in a navigation section (22) of the first reference surface (24). (P section) is determined, and wherein the section power is compared with a predeterminable limit power (Plimit), and where if the expected section power is exceeded, the limit power (Plimit) is exceeded at least for a subset of the navigation angles (Xi) with which the Laser beam (14) reaches the navigation section (22), the target powers (Psoii) are reduced in such a way that the expected section power (P section) is less than or equal to the limit power (Plimit). Method according to claim 3, characterized in that to determine the section power, a section energy to be applied in the navigation section (22) is first determined and is linked to a repetition rate of the predetermined trajectory (18). Method according to one of the preceding claims, characterized in that for at least one navigation section (22) of the reference surface (24), trajectory segments (TS) of the predetermined trajectory (18) are identified, for which the laser beam (14) reaches this navigation section (22). Method according to claim 5, characterized in that when identifying more than one trajectory segment (TS) lying within the navigation section (22) for at least one combination (K), in particular for each combination (K), consisting of a first trajectory segment (TS) and one or more further immediately successive trajectory segments (TS) a number of assigned to the combination (K). Navigation angle (X) of a trajectory section (TA) of the predetermined trajectory (18) comprising the trajectory segments (TS) is determined, starting with a first navigation angle (X) of the first trajectory segment (TS) of the combination (K) and ending with a last one Navigation angle (X) of the last trajectory segment (TS) of the combination (K) along the trajectory section (TA). Method according to claim 6, characterized in that a reference duration (RD) is determined for at least one combination (K), in particular for each combination (K), depending on the number of navigation angles (X) assigned to the combination (K), whereby in Depending on the reference duration (RD), a combination limit energy (EKGE) assigned to the combination (K) is determined, and an expected combination actual energy (EKIE) is determined for the combination (K) from the sum of segment - Energies (ESE), which each correspond to the expected energy of the trajectory segments (TS) of the combination (K), and where the combination actual energy (EKIE) is compared with the combination limit energy (EKGE), and where when the combination actual energy (EKIE) is exceeded over the combination limit energy (EKGE), at least for a subset of the navigation angles (X) of the trajectory section (TA), the starting power or target power assigned to the navigation angles (X). of the laser beam (14) is reduced in such a way that the expected combination actual energy (EKIE) is less than or equal to the combination limit energy (EKGE). Method according to one of the preceding claims, characterized in that the power of the laser beam (14) is adjusted by means of pulse width modulation. Method according to one of the preceding claims, characterized in that a distance of im Detection range of the distance sensor (30) of detected objects to the laser device (10) is monitored. Method according to claim 7, characterized in that the power of the laser beam (14) is adjusted as a function of the distance monitored by means of the distance sensor (30), the laser generation unit (12) being deactivated, in particular if the laser generation unit (12) is undershot when a predeterminable safety distance is undershot. Method according to one of the preceding claims, characterized in that the reference surface (24) is calculated as a virtual surface which extends over an angular range, in particular over the entire

Angular range, one that can be reached by the laser beam (14).

Navigation area (28) extends. Method according to claim 11, characterized in that the virtual reference surface (24) has a spherical shape and extends at a distance from the laser projection device (10), the distance of the virtual reference surface (24) corresponding in particular to the safety distance. Method according to one of the preceding claims, characterized in that the reference surface (24) is divided into a grid (32) comprising several grid cells, each grid cell corresponding to a navigation section (22) that can be reached by the laser beam (14). Method according to one of the preceding claims, characterized in that the laser generating unit (12) has two or more than two laser beam sources, the beams generated by the two or more than two laser beam sources being superimposed to generate the laser beam (14). Method according to one of the preceding claims, characterized in that the deflection device (16) has at least one movable mirror, in particular at least one galvanometer mirror, by means of which the laser beam (14) can be deflected to adjust the radiation angle. Method according to one of the preceding claims, characterized in that a predetermined speed of a drive unit of the deflection device (16) is monitored by means of a monitoring device. Laser device (10) for laser projection, comprising a laser generation unit (12) by means of which a laser beam (14) can be generated, a deflection device (16) by means of which a beam angle of the laser beam (14) can be adjusted for steering the laser beam (14) along a predeterminable trajectory ( 18), and a control device (20) coupled to the laser generation unit (12), by means of which the power of the laser beam (14) can be adjusted, the laser device (10) being designed and set up to carry out a method according to one of claims 1 to 16.