Laser protection devices

Abstract

The present invention relates to a laser protection device (14a, 14b) comprising an optical element (16a, 16b) for reflecting and / or absorbing a laser beam (18) and a sensor (30a, 30b) arranged on or spaced apart from the optical element (16a, 16b) for detecting transmission of the laser beam (18) through the optical element (16a, 16b). The sensor (30a, 30b) has a substrate (42) with conductor tracks (44a, 44b) arranged on the surface of the substrate (42), the conductor tracks (44a, 44b) being guided in a labyrinth shape.

Description

[Technical Field]

[0001] Background of the Invention The present invention relates to an apparatus for laser protection. The present invention further relates to a laser protection system.

[0002] For example, devices for protection from laser beams in case of misdirection are known from the prior art.

[0003] WO 2015 / 172816 discloses a temperature sensor connected to a temperature monitoring unit to monitor the correct orientation of the laser beam as it passes through the aperture.

[0004] EP 2 119 531 A1 discloses a laser protection window in which secondary radiation generated by a laser beam at the laser protection window is detected by a sensor.

[0005] EP 2338635 discloses a laser protection wall designed to detect the sound emitted by a laser beam at the laser protection wall.

[0006] German utility model No. 202016008509 relates to a rollable gate for a building opening, which is equipped with a sensor for detecting a laser beam.

[0007] Optical elements can be penetrated and destroyed by laser beams, especially short-pulse laser beams, without the optical elements being heated, and in many such cases the destruction of the optical elements and the subsequent undesired beam direction of the laser beam are not detected by sensors, which are typically based on temperature measurement, used to detect the laser beam in the optical elements.

[0008] Problem to be solved by the invention It is therefore an object of the present invention to provide a device for protection against laser beams that reliably detects the transmission of an optical element, especially if the optical element is not significantly heated during transmission.It is also an object of the present invention to provide a laser protection system that includes such a device.

[0009] Description of the Invention This problem is solved according to the invention by a device as set forth in claim 1. The laser protection system according to the invention is characterized in claim 8.

[0010] The device according to the invention comprises the following elements: a) a reflective and / or absorptive optical element that can be irradiated by a laser beam; b) a sensor having a substrate and a meander-shaped electrical first conductor path arranged on a first side of the substrate, The sensor is disposed indirectly on the optical element or is disposed or configured directly on the optical element to detect damage to the optical element caused by the laser beam.

[0011] The sensor can be used to reliably determine whether the laser beam illuminates unwanted locations around the optical element, for example, whether the laser beam penetrates the optical element. As a result of the detection, the laser beam can be switched off to prevent further damage. The sensor is advantageously designed compactly and has a simple structure.

[0012] By guiding the conductor tracks in a meandering pattern, the conductor tracks are designed to cover a relatively large percentage of the substrate surface. When the laser beam strikes the conductor tracks, parts of the conductor tracks are removed or destroyed. In particular, parts of the conductor tracks melt, burst, or evaporate. This causes changes in the electrical characteristics of the conductor tracks, in particular their electrical resistance. When current flows through the conductor tracks, changes in these characteristics that fall outside a preset control range can be detected, allowing the laser to be switched off before it causes damage to the surrounding optical elements. In particular, an interruption in the current flow as a result of the destruction of the conductor tracks by the laser beam can be easily and reliably detected as a sudden increase in the resistance of the conductor tracks. The laser beam is detected advantageously without relying on temperature measurement. Switching the laser beam back on is preferably prevented.

[0013] Adjacent portions of the conductor track preferably have a sufficiently large spacing so that if the laser beam causes one portion of the conductor track to expand, for example by melting, the adjacent portions of the conductor track will not be connected to one another. In some embodiments, multiple sensors are connected in series.

[0014] The optical element is particularly configured as a mirror, a beam guide tube, and / or a diaphragm. The laser beam is generated in a laser source. The laser source particularly comprises a solid-state laser for generating the laser beam, preferably having a wavelength of 1030 nm. The substrate is particularly configured as a non-carbonizing substrate, for example made of ceramic. The sensor preferably forms part of the detection device, in particular a safety circuit.

[0015] The conductor tracks are preferably applied to the substrate by vapor deposition, squeegeeing, etching and / or gluing (especially using a carrier sheet), with an additional electrically insulating layer being used in particular in the application process in the case of conductive substrates.

[0016] In one advantageous embodiment of the device, the sensor has a meander-shaped electrical second conductor, with the first and second conductors being particularly perpendicular to each other. The second conductor covers additional portions of the surface of the substrate that are not covered by the first conductor. This increases the probability that the conductors are also illuminated by the laser beam that strikes the surface of the substrate. This therefore increases the probability that the laser beam is detected by the sensor.

[0017] In a preferred embodiment, the second electrical conductor path is disposed on a second surface of the substrate opposite the first surface of the substrate. This ensures that if the conductor path is damaged on one surface of the substrate, particularly by a laser beam, the conductor path is better protected on the other surface of the substrate. Furthermore, the sensor can be flexibly used with respect to its orientation.

[0018] In one advantageous variant, the first and second conductor paths are connected in parallel to one another. This embodiment allows for the detection of which side of the substrate the laser beam is hitting or whether the laser beam penetrates the substrate. The two conductor paths can be contacted independently of one another by a detection device. In this case, the sensor is configured with two channels.

[0019] The present invention also includes an embodiment of the device in which the first conductor path and the second conductor path are connected in series. In this case, the sensor is configured with a single channel. A change in the electrical characteristic of the conductor path at one point causes a change in the electrical characteristic of the entire sensor. This increases the detection reliability. In particular, an interruption of the current flow at one point of the conductor path causes an interruption of the current flow throughout the entire sensor.

[0020] In one preferred embodiment, the sensor is arranged or configured directly on the optical element, and the substrate is configured as part of the optical element, so that the device for laser protection is configured to be particularly compact and easily transportable.

[0021] The sensor preferably has a housing that surrounds at least the first conductor path and the substrate. The housing preferably surrounds the two aforementioned conductor paths and the substrate of the sensor. The housing is preferably made of aluminum. A housing made of aluminum has the advantage that it is easily processable and relatively suitable. The housing may also be made of copper. This has the advantage that the housing is particularly robust, especially against beams having a wavelength of 1030 nm. This housing prevents the laser beam from penetrating the sensor even if it penetrates the substrate. The housing is also used to hold the remaining components of the sensor. In some embodiments, the housing has a protective glass to reduce the risk of particles generated during irradiation of the sensor by the laser beam flowing around the sensor. The protective glass is particularly configured to be transparent to the laser beam used.

[0022] A laser protection system according to the present invention comprises the above-described laser protection device and a laser source for emitting a laser beam, with an optical element arranged in the beam path of the laser beam. In such a laser protection system, a sensor can reliably detect whether the laser penetrates the optical element or is reflected by the optical element to an undesired location. The laser source is particularly configured to generate laser pulses (e.g., short or ultrashort pulses). The sensor is preferably connected to the laser source in a signal-technical manner to switch off the laser source at a predetermined sensor signal (i.e., upon a predetermined change in an electrical characteristic of the sensor).

[0023] In one preferred embodiment, the laser protection system is preferably arranged on a laser housing, in which a laser source is additionally arranged, the laser source being preferably configured as a solid-state laser.

[0024] In one advantageous embodiment of the laser protection system, the sensor is arranged on the rear surface of the optical element in the beam direction of the laser beam, with the beam direction pointing towards the optical element. By spatially arranging the sensor directly on the rear surface of the optical element, the sensor can detect in time and with high precision whether the laser beam passes through the rear surface of the optical element and thus passes through the optical element from its front surface to its rear surface. The beam direction particularly relates to the (extended) beam direction of the laser beam in one part of the beam path of the laser beam between the optical element and another optical element that is closest to and located upstream of this optical element in the beam path. The sensor is particularly applied to the rear surface of the mirror, which may have one or more layers.

[0025] In an alternative embodiment of the laser protection system, the sensor is arranged behind and at a distance from the optical element in the beam direction of the laser beam, with the beam direction pointing towards the optical element, which allows for a more flexible positioning of the sensor, which allows for, for example, a better signal-technical connection with the detection device.

[0026] In one preferred embodiment of the laser protection system, an absorber is arranged between the sensor and the optical element in the beam direction of the laser beam toward the optical element. The absorber absorbs components of the laser beam that are transmitted through the optical element, for example, due to different frequencies of the laser pulses. The absorber also absorbs the beam that the optical element emits due to its own heating as a result of irradiation by the laser beam toward the sensor. This protects the sensor. The sensor and the optical element are particularly arranged directly on the absorber. The absorber is, for example, configured as a copper plate, and is particularly preferably thermally coupled to a cooling system for cooling.

[0027] In another embodiment, the laser protection system includes an EUV light source in the beam path of the laser beam. An optical element is arranged in the beam path of the laser beam between the laser source and the EUV (extreme ultraviolet) light source or after the EUV light source to deflect the laser beam in the desired direction. In this case, the sensor reliably indicates whether the laser beam penetrates the optical element and thus does not travel the desired beam path. Preferably, the laser pulses generated by the laser source are used to irradiate the EUV light source, in particular the tin droplets.

[0028] In one preferred embodiment, the laser protection system has a switch element for switching off the laser beam when the electrical resistance of one of the conductor paths of the sensor exceeds a preset control value, in particular when the current flow through the one of the conductor paths of the sensor is interrupted. By switching off the laser beam with the switch element, a faulty output coupling of the laser beam into the surroundings of the optical element is preferably prevented.

[0029] Further advantages of the present invention will be apparent from the description and drawings. Likewise, each of the features described above and further described subsequently can be used individually by itself or in any combination of several. The illustrated and described embodiments should not be understood as a complete enumeration, but rather have an exemplary nature for describing the invention. [Brief explanation of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram of a laser protection system. [Figure 2] 1 is a schematic cross-sectional view of a detection area of ​​a sensor of a laser protection system; [Figure 3] 1 is a schematic plan view of the substrate and conductor tracks of the sensor; [Figure 4] FIG.

[0031] Detailed Description of the Invention and Drawings 1 shows a schematic diagram of a laser protection system 10 including a laser source 12 and first and second devices 14a, 14b for protecting the periphery of a first optical element 16a and a second optical element 16b from a laser beam 18 from the laser source 12. The two devices 14a, 14b may be provided alternatively or together. The optical elements 16a, 16b are configured as mirrors and are arranged in a beam path 20 of the laser beam 18 from the laser source 12. The optical elements 16a, 16b deflect the laser beam 18 toward an EUV light source (in particular a "target" in the form of tin droplets) 22, which emits an EUV beam 24.

[0032] An absorber 28, e.g., in the form of a copper plate, is located on a back surface 26a of the first optical element 16a in the first direction RL1 of the laser beam 18 to absorb the laser beam transmitted through the first optical element 16a. A first sensor 30a is located on a back surface 26c of the absorber 28 at a distance from the first optical element 16a to detect the laser beam that is undesirably transmitted through both the first optical element 16a and the absorber 28. The first sensor 30a is positioned behind the first optical element 16a in the beam direction RL1 of the laser beam 18. When a current flows through the first sensor 30a and the laser beam 18 strikes the first sensor 30a, an electrical characteristic of the first sensor 30a changes.

[0033] A change in the electrical characteristic, and thus in the current flow, can be detected by a detection device 32 connected to the first sensor 30a via a first signal channel 34a. In the event of a change in the characteristic outside a predetermined control range, the detection device 32 sends a signal via a second signal channel 34b to a switch device 36 to switch off the laser source 12 and thus the laser beam 18 via a third signal channel 34c. This is particularly related to the electrical resistance of the conductor path of the first sensor 30a (see FIG. 3), through which the current flows. This prevents the laser beam 18 from irradiating unwanted areas around the first optical element 16a and causing damage.

[0034] The laser beam 18 is deflected from the first optical element 16a to a second optical element 16b, which is configured as part of the second device 14b for laser protection. A second sensor 30b is located on the back surface 26b of the second optical element 16b (toward the second optical element 16b in the second beam direction RL2 of the laser beam 18) to detect whether the laser beam 18 undesirably penetrates the second optical element 16b. Similar to the first sensor 30a, a current flows through the second sensor 30b. When the laser beam 18 penetrates the second optical element 16b and strikes the second sensor 30b, an electrical characteristic of the second sensor 30b changes. This change is signaled to the detection device 32 via a fourth signal channel 34d, which triggers the switching off of the laser source 12 if the change exceeds a control range.

[0035] FIG. 2 shows a schematic cross-section of the detection area 38 (see FIG. 4) of a sensor, here, by way of example, sensor 30a. A first conductor track 44a is arranged on a first surface 40a of a substrate 42 of sensor 30a. When the first conductor track 44a is illuminated by laser beam 18 (see FIG. 1), its electrical characteristic value changes. To increase detection reliability, a second conductor track 44b is arranged on a second surface 40b of substrate 42 opposite to the first surface 40a. The conductor tracks 44a and 44b may be connected in parallel or in series. The substrate 42 may be configured as part of optical elements 16a, 16b (see FIG. 1), for example, on the back surface of a mirror. The detection area 38 includes, among other things, the substrate 42 and the conductor tracks 44a, 44b.

[0036] 3 shows a schematic plan view of the substrate 42 and conductor paths 44a and 44b of a sensor, here, by way of example, sensor 30a. The first conductor path 44a is guided by a meandering portion 46 along the first surface 40a of the substrate 42 (see FIG. 2) from a first electrical terminal 48a to a second electrical terminal 48b. The first terminal 48a and the second terminal 48b allow a current to flow through the first conductor path 44a, thereby enabling changes in the electrical characteristic of the first conductor path 44a to be measured. Correspondingly, the second conductor path 44b is guided by the meandering portion 46 along the second surface 40b of the substrate 42 (see FIG. 2) from a third electrical terminal 48c to a fourth electrical terminal 48d. The third terminal 48c and the fourth terminal 48d allow a current to flow through the second conductor path 44b, thereby enabling changes in the electrical characteristic of the second conductor path 44b to be measured. Here, the first conductor path 44a and the second conductor path 44b are angled, in particular perpendicular, to one another. Corresponding portions of the conductor paths 44a, 44b (e.g., portions of the same length) in particular extend at right angles to one another.

[0037] FIG. 4 shows a cross section of a sensor, here, by way of example, sensor 30a. Substrate 42 (see FIG. 3) with conductor tracks 44a, 44b is enclosed by a housing 50 for protection. Housing 50 has an opening 52 at its bottom end and a cover 54 at its top end. Through opening 52, laser beam 18 (see FIG. 1) can enter housing 50 to irradiate substrate 42. Sealing rings 56a, 56b are attached to both sides of substrate 42. Protective glasses 58a, 58b are arranged on sealing rings 56a, 56b to provide additional protection for conductor tracks 44a, 44b on substrate 42. Protective glasses 58a, 58b and housing 50 surround, inter alia, sensor detection area 38. Protective glasses 58a, 58b further reduce the flow of particles around sensor 30a when laser beam 18 strikes substrate 42. The protective glasses 58 a , 58 b are preferably transparent to the beam of the laser beam 18 used in the laser protection system 10 .

[0038] With reference to all figures of the drawings together, the invention relates to a device for laser protection 14a, 14b comprising an optical element 16a, 16b for reflecting and / or absorbing a laser beam 18 and a sensor 30a, 30b arranged on the optical element 16a, 16b or arranged at a distance from the optical element 16a, 16b for detecting the transmission of the laser beam 18 through the optical element 16a, 16b. The sensor 30a, 30b has a substrate 42 with conductor tracks 44a, 44b arranged on its surface, the conductor tracks 44a, 44b being guided in a labyrinth shape. [Explanation of symbols]

[0039] 10 Laser Protection System 12 Laser Source 14a,b Devices for laser protection 16a,b Optical elements 18 Laser Beam 20 Beam Path 22 EUV light source 24 EUV beams 26a-c Back of components 28 Absorber 30a,b sensor 32 Detection device 34a~d Signal Channels 36 Switching device 38 Sensor detection area 40a,b Substrate surface 42 PCB 44a,b Conductor path 46 Meander-shaped section 48a~d terminals 50 Housing 52 Opening 54 Cover 56a,b Seal ring 58a,b Protective glass RL1,2 Laser beam direction

Claims

1. A device (14a, 14b) for laser protection, comprising: a) a reflective and / or absorptive optical element (16a, 16b) that can be irradiated by a laser beam (18); b) a substrate (42) and a sensor (30a, 30b) having a meander-shaped electrical first conductor path arranged on a first surface (40a) of the substrate (42), The sensors (30a, 30b) are arranged indirectly on the optical elements (16a, 16b) or directly on or configured to detect damage to the optical elements (16a, 16b) caused by the laser beam (18).

2. 2. The device according to claim 1, wherein the sensor (30a, 30b) has a meander-shaped electrical second conductor path (44b), the first conductor path (44a) and the second conductor path (44b) being particularly perpendicular to each other.

3. 3. The device according to claim 2, wherein the second conductor path (44b) is disposed on a second surface (40b) of the substrate (42) opposite the first surface (40a) of the substrate (42).

4. 4. The device according to claim 2, wherein the first conductor path (44a) and the second conductor path (44b) are connected in parallel with each other.

5. 4. The device according to claim 2, wherein the first conductor path (44a) and the second conductor path (44b) are connected in series.

6. 6. The device according to claim 1, wherein the sensor (30a, 30b) is arranged or configured directly on the optical element (16a, 16b), and the substrate (42) is configured, in particular, as part of the optical element (16a, 16b).

7. 7. The device according to claim 1, wherein the sensor (30a, 30b) has a housing (50) surrounding at least the first conductor track (44a) and the substrate (42).

8. 10. A laser protection system (10) comprising a device (14a, 14b) for laser protection according to any one of claims 1 to 7 and a laser source (12) for emitting the laser beam (18), wherein the optical elements (16a, 16b) are arranged in a beam path (20) of the laser beam (18).

9. 9. The laser protection system of claim 8, wherein the sensors are arranged on the back surfaces of the optical elements in a beam direction of the laser beam, the beam direction facing the optical elements.

10. 9. The laser protection system of claim 8, wherein the sensors are arranged behind and spaced apart from the optical elements in a beam direction of the laser beam, the beam direction pointing toward the optical elements.

11. 11. The laser protection system of claim 10, wherein an absorber is arranged between the sensor and the optical element in the beam direction of the laser beam directed toward the optical element.

12. The laser protection system according to any one of claims 8 to 11, comprising an EUV light source (22) in the beam path of the laser beam (18).

13. 13. The laser protection system according to claim 8, further comprising a switch element for switching off the laser beam if the electrical resistance of one of the conductor paths of the sensors exceeds a preset control value, in particular if the current flow through one of the conductor paths of the sensors is interrupted.

Images