DE102019132003A1 - Optical unit and method for operating an optical unit - Google Patents

Abstract

The present invention relates to an optical unit (100) with a refractive element (105) which is designed to refract a beam (122) of electromagnetic radiation emitted from a radiation source (125) onto an object (135). Furthermore, the optical unit (100) comprises a sensor element (140) which is designed to detect a temperature in at least a partial area (148) of the breaking element (105) without contact and to output a temperature signal (142) in response to the temperature.

Description

State of the art

The invention relates to an optical unit and a method for operating an optical unit according to the main claims.

In optical systems, this optical element is often heated by the irradiation of electromagnetic radiation on optical elements, for example in the case of the irradiation of a laser beam on a lens or a prism, so that on the one hand the refractive index of the optical element can change and on the other hand a certain one thermal expansion of this element takes place, which subsequently leads to the optical function of this optical element being changed and a desired refraction by this optical element no longer being achieved.

Starting from this, an optical unit and a method for operating this optical unit according to the main claims are presented. Advantageous developments of the subjects of the main claims are defined by the dependent claims.

• - einem Brechelement, das ausgebildet ist, um einen Strahl einer von einer Strahlungsquelle auf ein Objekt ausgestrahlten elektromagnetischen Strahlung zu brechen; und
• - ein Sensorelement, das ausgebildet ist, um eine Temperatur auf zumindest einem Teilbereich des Brechelementes berührungslos zu erfassen und ansprechend auf die Temperatur ein Temperatursignal auszugeben.

An optical unit with the following features is presented here:

• a refractive element which is designed to refract a beam of electromagnetic radiation emitted by a radiation source onto an object; and
• a sensor element which is designed to detect a temperature in at least a partial area of the breaking element without contact and to output a temperature signal in response to the temperature.

An embodiment of the approach presented here is particularly advantageous in which a focusing unit is provided which is designed to change a distance between the refractive element and the object and / or between the radiation source and the refractive element or the object depending on the temperature signal and / or to change a position of an auxiliary element in a beam path of the beam in order to focus the beam on the object.

A refractive element can be understood as an optical element which can refract or deflect a beam of electromagnetic radiation. For example, such a refractive element can be a lens or a prism. The refractive element can also have a plurality of sub-elements which themselves again act as optically refractive elements. Electromagnetic radiation can be understood to mean, for example, light radiation that is emitted, for example, by a light source or a laser source as the radiation source. It is also conceivable that the electromagnetic radiation is infrared radiation. A sensor element can be understood to be an element which can detect temperatures without contact, for example by detecting and recording infrared radiation. A temperature signal can be understood to mean an electrical signal which represents a temperature in a partial area of the breaking element. A partial area of the refractive element can be understood, for example, as a surface of this refractive element, for example in a central section or middle area of this refractive element, this partial area being penetrated by the beam of electromagnetic radiation, for example. A focusing unit can for example be understood as a mechanical unit which can move different components with respect to one another in order to change a focal point or intersection of rays through the optical unit. An auxiliary element can be understood to mean, for example, a further optical element such as a lens, a prism, a disk or a beam expander, which is arranged in the beam path of the beam.

It should be noted here that the focusing unit (which can be designed as a “motor” here for example) does not necessarily have to be present. The focusing could also take place “externally”, for example by changing the workpiece position or the breaking element via a lifting table.

The approach presented here is based on the knowledge that by determining and using the temperature signal for focusing there is a possibility of correcting a misalignment of the refractive element due to a change in temperature in a partial area of the refractive element, in particular through which the beam or the beam path runs to be able to. This results in a significantly more efficient use of the electromagnetic radiation for a desired purpose. A contactless detection of the temperature on the at least one partial area of the refractive element also ensures a very fast and measurement error-robust detection of this temperature, so that a prompt readjustment of the focusing of the light beam can be achieved.

An embodiment of the approach presented here is favorable in which the sensor element is designed to also set a temperature on at least one further sub-area of the The refractive element and / or a part of a holding element carrying the refractive element to detect contactlessly in order to output a further temperature signal, wherein the focusing unit is designed to change a distance between the refractive element and the object and / or between the radiation source and depending on the further temperature signal to change the refractive element or the object and / or to change a position of an auxiliary element in a beam path of the beam in order to focus the beam on the object. A holding element can for example be understood as a housing part which receives or holds the breaking element. The further sub-area of the breaking element can be, for example, another sub-area of the same components of the breaking element at which the sensor element has also detected the temperature. For example, the sensor element can detect the temperature in a central part of a lens as a refractive element, which is in the beam path of the electromagnetic radiation, and also detect a temperature in an edge region of the lens as a refractive element that is not in the beam path of the electromagnetic radiation. In this way, for example, by comparing the two recorded temperatures, it can also be seen whether a temperature increase in the central middle part of the refractive element is possibly caused by the radiation of the electromagnetic radiation, or whether an increase in the ambient temperature, which has the same effect on both subregions of the refractive element , is the cause of a detected change in temperature. In this way, a much more precise adjustment of the focusing of the optical unit can be achieved.

Furthermore, an embodiment of the approach presented here is particularly favorable in which the sensor element has at least two spaced apart sensors (also called sensor units), a first sensor unit being designed to detect the temperature of a first sub-element of the breaking element and a second sensor unit being designed, to detect the temperature of a second sub-element of the breaking element and / or wherein the first sensor unit is designed to detect the temperature of the sub-area and the second sensor unit is designed to detect the temperature of the further sub-area. Such an embodiment offers the advantage of achieving the greatest possible independence when detecting the temperature of the sub-area and the detection of the temperature of the further sub-area or the temperatures of different sub-elements of the breaking element due to the spaced apart sensors.

Furthermore, an embodiment of the approach proposed here is conceivable in which the sensor element is designed to detect the temperature of the breaking element from a position in a housing receiving the breaking element. Such an embodiment offers the advantage of being able to react particularly sensitively to temperature changes in an interior of the optical unit without thermal environmental influences outside the optical unit excessively influencing a measurement of this temperature / temperatures.

An embodiment of the approach proposed here is also advantageous, in which the sensor element is designed to detect the temperature of the breaking element through a window in a housing carrying the breaking element. Such an embodiment offers the advantage of a particularly favorable implementation option for the sensor element, wherein influencing a measurement of the sensor element by heating up the breaking element or at least parts of the breaking element can also be avoided as far as possible.

Furthermore, according to a further embodiment of the approach presented here, the sensor element can also be designed to detect the temperature in a central area of the refractive element and / or wherein the refractive element is designed as an optical lens. Such an embodiment offers the advantage of being able to monitor particularly well that area of the refractive element through which the beam path of the electromagnetic radiation or the beam leads and in which a strongest change in temperature can therefore be expected. In this respect, the beam can be focused very quickly and precisely.

According to a further embodiment, a radiation source control unit can also be provided for controlling or regulating a radiation output by the radiation source, the radiation source control unit being designed to control or regulate the radiation output using the temperature signal. Such an embodiment offers the advantage of being able to readjust or reduce the power output by the radiation source when a critical temperature is detected in a partial area of the refractive element.

Furthermore, an embodiment of the approach proposed here is particularly favorable, in which the sensor element is arranged outside a beam path of the electromagnetic radiation which extends through the refractive element. In this way, heating of the sensor element as a result of irradiation of the electromagnetic radiation can be avoided, which results in a robust measurement of the Temperature in which at least a part of the same element is possible.

According to a further embodiment, the breaking element can also have at least two sub-elements, the sensor element being designed to detect at least one temperature each on one of the sub-elements in order to provide the temperature signal. Partial elements of such a refractive element can, for example, be lenses, prisms, diffusion disks or the like that are separate from one another. Such an embodiment of the approach proposed here offers the advantage of being able to monitor different, optically effective components of the refractive element by the sensor element, so that thermal effects at different positions of the optical unit can also be monitored or compensated for.

It is particularly advantageous to use a variant of the optical unit presented here in a material processing device, an image projection device and / or an ultraviolet exposure device. A material processing device can be understood to mean, for example, a laser material processing tool. An image projection device can be understood to mean, for example, a projector for outputting images onto a screen, for example in a cinema. Such an embodiment offers the advantage of being able to implement very good and rapid monitoring of the efficient use of the electromagnetic radiation emitted by the radiation source, particularly in areas with high light powers irradiated onto the optical elements and thus associated high thermal effects.

• - berührungsloses Erfassen einer Temperatur auf zumindest einem Teilbereich des Brechelementes zu erfassen, um ansprechend auf die Temperatur ein Temperatursignal auszugeben; und
• - abhängig von dem Temperatursignal, Verändern eines Abstands zwischen dem Brechelement und dem Objekt und/oder zwischen der Strahlungsquelle und dem Brechelement oder dem Objekt /oder um eine Position eines Hilfselements in einem Strahlengang des Strahls, um den Strahl auf das Objekt zu fokussieren.

According to a further embodiment, a method for operating a variant of the optical unit presented here is also proposed, the method having the following steps:

• - to detect contactless detection of a temperature on at least a partial area of the breaking element in order to output a temperature signal in response to the temperature; and
• - Depending on the temperature signal, changing a distance between the refractive element and the object and / or between the radiation source and the refractive element or the object / or around a position of an auxiliary element in a beam path of the beam in order to focus the beam on the object.

• - berührungsloses Erfassen der Temperatur an dem Brechelement oder einer anderen Komponente der optischen Einheit;
• - Erfassen von zumindest einem weiteren System- und Verfahrensparameter, insbesondere eines Zeitverlaufs einer auf das Brechelement ausgestrahlten elektromagnetischen Strahlung (wie beispielsweise einer Laserleistung), einer Pulsdauer und/oder einer Pulshöhe der auf das Brechelement ausgestrahlten elektromagnetischen Strahlung;
• - Erfassen einer Strahllage der elektromagnetischen Strahlung bei einem variierbaren Strahl durch die optische Einheit Scanneroptiken (z. B. einen Zeitverlauf der Strahlposition bei F-Theta-Objektiven); und
• - Kombination der Parameter und Ableitung von Zustandsparametern (z. B. Zeitverlauf der Absorption) und daraus abgeleitete Ausfallprognose, um die optische Einheit zu analysieren.

An embodiment of the approach presented here as a method for analyzing the properties of the optical unit is also particularly favorable, the method having the following steps:

• - Contactless detection of the temperature on the refractive element or another component of the optical unit;
• - Detection of at least one further system and method parameter, in particular a time curve of electromagnetic radiation emitted onto the refractive element (such as, for example, a laser power), a pulse duration and / or a pulse height of the electromagnetic radiation emitted onto the refractive element;
• - Detection of a beam position of the electromagnetic radiation in the case of a variable beam by the optical unit scanner optics (e.g. a time curve of the beam position in F-theta lenses); and
• - Combination of parameters and derivation of state parameters (e.g. time course of absorption) and failure forecast derived therefrom in order to analyze the optical unit.

Variants of this method can be implemented particularly favorably, for example in software or hardware or in a mixed form of software and hardware, for example in a control device.

The approach presented here also creates a control device which is designed to carry out, control or implement the steps of a variant of a method presented here in corresponding devices. This embodiment variant of the invention in the form of a control device also enables the object on which the invention is based to be achieved quickly and efficiently.

With the approach presented here, a computer program is also presented that can be stored on a machine-readable carrier or storage medium. The program can be used to carry out and / or control the steps of the method according to one of the embodiments described above if the program product or program is executed on a computer or a device.

• 1 schematische Querschnitt-Darstellung einer optischen Einheit gemäß einem Ausführungsbeispiel des hier vorgestellten Ansatzes;
• 2 eine schematische Querschnitt-Darstellung einer optischen Einheit gemäß einem anderen Ausführungsbeispiel des hier vorgeschlagenen Ansatzes;
• 3A eine schematische Querschnitt-Darstellung eines Teils eines weiteren Ausführungsbeispiels der optischen Einheit;
• 3B eine perspektivische Ansicht der in der 3A dargestellten Komponenten;
• 4A eine schematische Querschnitt-Darstellung eines Teils eines weiteren Ausführungsbeispiels der optischen Einheit;
• 4B eine perspektivische Ansicht der in der 4A dargestellten Komponenten;
• 5A eine schematische Querschnitt-Darstellung eines Teils eines weiteren Ausführungsbeispiels einer optischen Einheit;
• 5B eine perspektivische Ansicht der in der 5A dargestellten Komponenten;
• 6 eine schematische Querschnitt-Darstellung eines Teils eines weiteren Ausführungsbeispiels der optischen Einheit; und
• 7 ein Ablaufdiagramm eines Verfahrens gemäß einem Ausführungsbeispiel.

Favorable exemplary embodiments of the approach presented here are shown in the drawings and explained in more detail in the description below. It shows:

• 1 schematic cross-sectional representation of an optical unit according to an exemplary embodiment of the approach presented here;
• 2 a schematic cross-sectional representation of an optical unit according to a another embodiment of the approach proposed here;
• 3A a schematic cross-sectional representation of part of a further embodiment of the optical unit;
• 3B a perspective view of the in FIG 3A illustrated components;
• 4A a schematic cross-sectional representation of part of a further embodiment of the optical unit;
• 4B a perspective view of the in FIG 4A illustrated components;
• 5A a schematic cross-sectional representation of part of a further embodiment of an optical unit;
• 5B a perspective view of the in FIG 5A illustrated components;
• 6th a schematic cross-sectional representation of part of a further embodiment of the optical unit; and
• 7th a flowchart of a method according to an embodiment.

In the described advantageous exemplary embodiments of the present invention, the same or similar reference numerals are used in the various figures for similarly acting elements, a repeated description of these elements being dispensed with.

1 shows a schematic cross-sectional representation of an optical unit 100 according to an embodiment of the approach presented here. The optical unit 100 here comprises a breaking element 105 , which in this embodiment consists of two sub-elements 110 and 115 composed, the first sub-element 110 is shaped as a diverging lens and the second sub-element 115 as a collecting lens. The part elements 110 and 115 of the crushing element 105 are here in a beam path 120 arranged on which a beam 122 electromagnetic radiation through the optical unit 100 runs. This ray 122 can for example be a light and / or laser beam emitted by a radiation source 125 , for example a laser diode, is emitted and after passing the breaking element 105 for example on a mirror 130 distracted and on an object 135 is focused. This object 135 can be, for example, a workpiece which is through the from the radiation source 125 emitted laser beam as a beam 122 the electromagnetic radiation is heated, structured or otherwise processed. Is now from the radiation source 124 a very energetic beam 122 , as in the present case the laser beam, for processing a material of the object 135 , is sent out when one or more components of the refractive element are irradiated 105 usually the area through which the beam is heated 122 on the respective sub-element 110 or. 115 of the crushing element 105 runs. As a result, on the one hand, as already briefly described above, the refractive index of the material of this sub-element of the refractive element 105 changed, resulting in a change in the breaking behavior of this sub-element 110 or. 115 of the crushing element 105 leads and thus influences the focal length of the sub-elements concerned 110 or. 115 when a beam passes through these sub-elements at the respective heated sub-areas, compared to a beam that passes through unheated sub-areas of these components of the refractive element 105 runs. In addition, the heated areas of the sub-elements can also be 110 or. 115 of the crushing element 105 expand locally, which also leads to a change in the breaking behavior of these sub-areas of the sub-elements 110 or. 115 of the crushing element 105 leads.

To now such a change in the refractive behavior of components of the optical unit 100 To be able to recognize or compensate, it is now proposed according to an exemplary embodiment of the approach presented here, a sensor element 140 to provide, which is designed to provide a temperature on at least one sub-area (at least one sub-element 110 or. 115 ) of the crushing element 105 to detect contactless and a corresponding temperature signal 142 to spend. For example, such a contactless measurement of the temperature using an infrared radiation detector in the sensor element 140 be performed. In the present exemplary embodiment, the sensor element comprises 140 furthermore a first sensor unit 145 that are in or on an enclosure 147 the optical unit 100 is attached and the one temperature of a middle range 148 of the first sub-element 110 detected. In addition, in the 1 illustrated embodiment a second sensor unit 150 provided, which is also in or on the housing 147 the optical unit 100 is attached and the one temperature of a middle range 152 of the second sub-element 115 detected. More precisely, by the first sensor unit 145 a temperature of the radiation source 124 facing away surface of the first sub-element 110 are detected, whereas by the second sensor unit 150 a temperature of the radiation source 125 facing surface of the second sub-element 115 can be captured. Through the first sensor unit 145 can then use one of the temperature of the partial area of the first partial element 110 representing temperature signal 142 a focusing unit 160 , more precisely a first partial focusing unit 162 the focusing unit 160 , are controlled, which is designed, for example, a position of a first holding element 165 for holding the first sub-element 110 to change and thus influence the focal length of the optical unit 100 to take. Alternatively or in addition, the second sensor unit 150 by means of the temperature of the sub-area of the second sub-element 115 representing temperature signal 142 ' the focusing unit 160 , more precisely here a second partial focusing unit 167 the focusing unit 160 are controlled, which is formed, for example, a position of a second holding element 170 for holding the second sub-element 115 to change and thus also influence the focal length of the optical unit 100 to take. For example, the first partial focusing unit 162 and / or the second partial focusing unit 167 be designed to linear movement of the first holding element 165 or the second holding element 170 in the direction of the beam path 120 to effect. Such a design of the optical unit 100 a significant improvement in (ie, in particular, more efficient) utilization of the radiation source can thus be achieved 125 provided beam 122 by precisely focusing this beam 122 on the object 135 realize.

It is also also conceivable that, for example, by the first sensor unit 145 the temperature of an edge area 175 of the first sub-element 110 detected and in another temperature signal 177 to the focusing unit 160 , here especially the first partial focusing unit 162 is transmitted. An evaluation of a temperature difference in the temperature in the middle range can then be performed here 148 above the temperature in the edge area 175 , for example in the first partial focusing unit 162 be made that draw a conclusion about the by the beam 122 caused temperature increase in the middle area 148 of the first sub-element 110 supplies. In this way, temperature changes in the environment around the optical unit 100 can be recognized and when re-adjusting components of the breaking element 105 be taken into account.

The focusing unit can also 160 for example a radiation source control unit 180 having that with the radiation source 125 is coupled and which is designed to emit the electromagnetic radiation by the radiation source 125 to control or regulate. In this way, for example, components of the optical unit can be overheated 100 such as the sub-elements 110 and 115 of the crushing element 105 avoid.

In the 1 became the approach of an optical unit presented here 100 presented in connection with the use in a material processing device, through which, for example, the material of the object 135 can be edited. However, it is also conceivable to use the optical unit 100 for example in connection with an image projection device, for example in a cinema projector, in which case the object 135 would be the screen on which an image is to be depicted appropriately in focus. Another possible application of the optical unit presented here can also be, for example, a UV exposure device such as is used for structuring wafers in semiconductor manufacture. In this case the object would be 135 to assume a corresponding wafer, which is now for example with a photoresist layer, which is to be exposed to UV light as electromagnetic radiation.

2 shows a schematic cross-sectional representation of an optical unit 100 according to another exemplary embodiment of the approach proposed here, the radiation source according to the illustration from FIG 1 in the 2 is not explicitly shown for reasons of clarity. Here is the breaking element, for example 105 at a beam exit 200 the optical unit 100 arranged, whereby initially a temperature of a sub-area of one or more sub-elements (as here the sub-elements 110 and 115 ) through the sensor element 140 is captured. A temperature signal representing this temperature 142 is then attached to the focusing unit 160 transmitted which a change in a position of at least one auxiliary element 210 can cause, for example using a linear drive element 215 . This auxiliary element 110 can for example in the one in the 2 illustrated embodiment as a combination of a converging lens and a diverging lens, so that the auxiliary element 210 can develop an optical refractive effect if the beam 122 the optical unit 100 shines through. In this way, the focusing of the beam can also be improved 122 can be realized on an object.

3A shows a schematic cross-sectional representation of part of a further exemplary embodiment of the optical unit 100 . Here is in the 3A a sensor element 140 reproduced, which is outside the holding unit 165 is arranged and, for example, also outside one in the 3A housing not shown 147 as shown in the 1 can be arranged. The sensor element detects 140 the temperature of the breaking element 105 , which in this embodiment comprises only a single component in the form of a converging lens, using a mirror 300 that can, for example, reflect infrared radiation. Further is the mirror 300 designed to be a Detection direction of the sensor element 140 through a window 310 in the (first) holding element 165 or one around the holding element 165 housing arranged around 167 on a sub-area, such as the central area here 148 of the crushing element 105 , can direct. For example, this mirror can also 300 be designed to be movable or tiltable, so that, for example, a temperature in an area outside the central area 148 of the crushing element 105 from the sensor element 140 can be captured when the window 310 is big enough. In this way it can be advantageously ensured, for example, that the sensor element 140 at a greater spatial distance from the crushing element 105 so that, for example, an increase in temperature on the breaking element 105 The least possible repercussions on a temperature increase at the sensor element 140 Has.

3B FIG. 13 is a perspective view of FIG 3A illustrated components.

4A shows a schematic cross-sectional representation of part of a further exemplary embodiment of the optical unit 100 . Here again is a sensor element 140 provided which a first sensor unit 145 and a second sensor unit 150 includes, each in turn outside a housing 147 or a holding element 165 for at least one component of the breaking element 105 is arranged. From the representation from the 4A it can also be seen that the first sensor unit 145 a temperature of a sub-area of the first sub-element 110 can monitor, whereas now, for example, the second sensor unit 150 a temperature of a partial area of a windshield 400 as the second sub-element of the breaking element 105 can monitor. For example, this front window 400 consist of glass, the refractive index of which changes with a change in temperature, so that this front pane too 400 when passing a beam 122 is optically effective or distracting.

4B FIG. 13 is a perspective view of FIG 4A illustrated components.

5A shows a schematic cross-sectional representation of part of a further exemplary embodiment of an optical unit 100 . It can be seen here that again two outside a housing 147 arranged sensor units 145 and 150 of the sensor element 140 are arranged, the temperatures in different subregions of the breaking element 105 or a component of the crushing element 105 like the windshield here 400 to capture. For example, the first sensor unit 140 a temperature in a peripheral area 175 the windshield 400 detect, whereas the second sensor unit 150 a temperature in a mid-range 148 the windshield as a component of the breaking element 105 can capture.

5B FIG. 13 is a perspective view of FIG 5A illustrated components.

6th shows a schematic cross-sectional representation of part of a further exemplary embodiment of the optical unit 100 . Here again is the sensor element 140 outside the case 147 or the holding element 165 arranged and can through a window 310 in the case 147 or the holding element 165 look through it and a temperature from a pane 400 in the beam path 120 of the beam 122 to capture.

7th shows a flow chart of a method 700 for operating a variant of an optical unit presented here. The procedure 700 includes one step 710 of the contactless detection of a temperature on at least a partial area of the breaking element in order to output a temperature signal in response to the temperature. The method also includes 700 one step depending on the temperature signal 720 of changing a distance between the refractive element and the object and / or between the radiation source and the refractive element or the object / or by a position of an auxiliary element in a beam path of the beam in order to focus the beam on the object.

As far as the relationship between the temperature of the measuring point and the change in the optical properties of the system z. B. are known from a calculation or simulation, the control loop can be closed directly via the actuator. The transfer function of the control loop can also be found experimentally. In this way, non-linearities, dynamic properties and also with specimen scatter can be found and corrected. The correction can be made even more precisely.

It is also possible to relate the temperature measurement data to other parameters measured in the system. In this way one can recognize changes in the system behavior that go beyond the control loop usage. If z. B. the heating per set laser power, there may be a changed absorption, which heralds an impending system damage / failure.

In addition to the evaluation of the temperature and system measurement data based on a-priori knowledge, pattern recognition algorithms can also be implemented in the control system, which make appropriate predictions after they have been trained with data from machines observed in the field.

• - berührungsloses Erfassen der Temperatur
• - Erfassen von weiteren System- und Verfahrensparametern, insbesondere des Zeitverlaufs der Laserleistung, den Pulsdauern, den Pulshöhen
• - Erfassen der Strahllage bei Scanneroptiken (z. B. Zeitverlauf der Strahlposition bei F-Theta-Objektiven)
• - Kombination der Parameter und Ableitung von Zustandsparametern (z. B. Zeitverlauf der Absorption) und daraus abgeleitete Ausfallprognose

A method for analyzing the properties of the optical unit with the following sequence is also presented:

• - Contactless recording of the temperature
• - Acquisition of further system and process parameters, in particular the time course of the laser power, the pulse durations, the pulse heights
• - Detection of the beam position with scanner optics (e.g. time course of the beam position with F-Theta lenses)
• - Combination of parameters and derivation of state parameters (e.g. time course of absorption) and failure prognosis derived therefrom

In summary, it should be stated that with the approach presented in the present case according to exemplary embodiments, a temperature-monitored lens with a control loop for focus tracking is presented. The background to the approach presented here can be seen in the fact that the refractive index of optical glasses changes with temperature, which means that the focal length of lenses also changes with temperature. Furthermore, the temperature of the housing deviates significantly from the effective lens temperature in the event of rapid temperature changes from the outside or if the lenses are heated from the inside, since glass conducts heat poorly. However, if a non-contact temperature sensor is suitably integrated into the lens, the effective temperature can be regulated very well and the focus can be kept more stable. For example, a lens with integrated, non-contact temperature sensors and a method and method for regulating the focusing by means of these sensors are presented, this being done using an internal lens controller or using an external controller that is connected to the lens via an interface . In this way, the focus of a lens can be kept stable under changing thermal loads.

1. (A) Objektiv mit fest integrierten Sensoren und optional Fokus-Stellgliedern für die exemplarischen Einsatzszenarien:
   1. (1) Lasermaterialbearbeitungsobjektive vom Typ F-Theta, Beamexpander, Kollimator
   2. (2) Hochleistungsprojektionsobjektive für kinematografische Anwendungen
   3. (3) Projektionsobjektive zur Halbleiter-Herstellung
2. (B) Optische Systeme mit zusätzlichen Sensoren zur Überwachung der Optiken und mit Aktoren und Reglern, welchen den Fokusregelkreis schließen können, für die exemplarischen Einsatzszenarien:
   • (4) Lasermaterialbearbeitungsmaschinen
   • (5) Bildprojektoren
   • (6) UV-Belichtungsmaschinen
3. (C) Sicherheitsfunktion bei optischen Elementen, die unter hoher optischer Leistung betrieben werden für die exemplarischen Einsatzszenarien:
   • (7) Schutzfenster
   • (8) (dielektrische) Spiegel
   • (9) strukturierte Elemente (z. B. DOEs)

The approach presented here can be used in several applications, for example as:

1. (A) Lens with permanently integrated sensors and optional focus actuators for the exemplary application scenarios:
   1. (1) F-Theta type laser material processing lenses, beam expander, collimator
   2. (2) High performance projection lenses for cinematographic applications
   3. (3) Projection lenses for semiconductor manufacturing
2. (B) Optical systems with additional sensors for monitoring the optics and with actuators and controllers that can close the focus control loop for the exemplary application scenarios:
   • (4) Laser material processing machines
   • (5) image projectors
   • (6) UV exposure machines
3. (C) Safety function for optical elements that are operated with high optical power for the exemplary application scenarios:
   • (7) Protective window
   • (8) (dielectric) mirrors
   • (9) structured elements (e.g. DOEs)

Several aspects can be cited as advantages of the approach presented here. In particular, the measured temperature value reflects the actual focal length relevant value. He reacts quickly and precisely. The lenses equipped in this way can perform their target function under stronger interference and thus experience an effective increase in imaging performance. In addition, in applications for laser material processing, it is also expected that the warming interference can be regulated and thus higher optical powers can be usefully guided through the optical system and used. Finally, a temperature reading in laser material processing also provides information on secondary component properties. Pollution can lead to the destruction of elements through the mechanism of absorption / heating / progressive element damage. Such sensors can therefore also be used for condition monitoring and increase plant safety / availability. Furthermore, the possibility that the sensors are small and inexpensive is particularly favorable and thus allow the improved functionality to be integrated into existing systems. The cost of producing the new functionality and integrating the functionality into existing systems is low.

1. (1) Lasermaterialbearbeitung (F-Theta, Beamexpander, Kollimatoren, überwachte Einzelfunktionalitäten (z. B. Fenster, Abschwächer, Strahlteiler)
2. (2) kinematographischen Projektionsobjektive
3. (3) UV-Belichtungsoptiken

For example, the approach presented here can be used in new products in the following areas

1. (1) Laser material processing (F-Theta, beam expanders, collimators, monitored individual functions (e.g. window, attenuator, beam splitter)
2. (2) cinematographic projection lenses
3. (3) UV exposure optics

The relationship between the increase in the lens surface temperature, which is caused by the absorption of laser power during operation, and the change in focal length of an objective can be derived from thermodynamic equations. It was also recognized that the focal length extension hardly depends on which areas of the F-theta lens used as an example are used for programmed writing.

Known sensors can be used to measure IR radiation, so that this type of sensor can also be used for non-contact temperature measurement. They are available with different angle sensitivity characteristics. Since the sensors should be outside the free diameter of the optics, but the measuring point is centrally located in the beam path, a more directed measurement sensitivity is required for the temperature measurement described here. If characteristics smaller than the 5 ° FOV characteristics are favorable, an additional lens (e.g. refractive single lens or concave mirror) can adapt the measuring point to the application.

If some mechanical elements in the vicinity of the lens or z. B. the entire lens tube as an optical unit 100 , the display value of the non-contact temperature measurement is made up of a radiation component from the lens to be tested and a component reflected by the test object from the radiation from the surrounding elements. In order to be able to correctly deduce the lens temperature, at least one measurement of the temperature should be carried out on one of these mechanical elements, or such a measurement is advantageous.

For a lens with sufficiently large air gaps, the temperature of the adjacent lenses can be measured directly via an access in the lens barrel, since the heating effects caused by the heat radiation of the refractive element are not too great here.

In the case of lenses with very small lens spacings, it is advantageous to place the sensors outside the lens or the housing of the optical unit 100 to attach. The distance between the sensors and the area of the lens to be tested is advantageously chosen so that a sufficiently large, central area of the lens is appropriate. For modular arrangements, the distance between the sensor and the lens should be smaller than the working distance of the lens.

The free diameters of collimators are not as large as with scanner lenses and the beam does not travel over the lens surface. The temperature can be measured on one or more lenses. A measurement of the housing temperature to improve the interpretation of the lens measurement values is advantageous. The sensors can be housed in the housing of the lens or measure into the lens from outside.

If, in addition to the sensor (s), the lens also contains actuators (e.g. motorized lenses that can be adjusted in Z) and if, for example, the sensors are connected to the actuators via a controller, the disruptive change in focus can be seen from the lens temperature Cancel refocusing.

The temperature of an optical element also provides information about its operating status. The temperature of a window depends on the amount of absorbed laser power. With stable conditions in and around the window, you can measure the laser power.

A change in absorption is e.g. B. caused by pollution. An increase in temperature can lead to further damage to the window / component via a positive feedback effect. With an appropriate sensor arrangement, it is possible to react to such a deterioration in the operating state before the system fails (cleaning or replacing the window, reducing the laser power, etc.)

In an optical system, focusing is often achieved by changing the working distance. A corresponding control loop in accordance with the approach presented here can also take place with a temperature measurement value from a critical element.

1. 1. einem Laser (Strahlungsquelle)
2. 2. einem Strahlaufweiter (Brechelement)
3. 3. einem Scanner
4. 4. einem Scanobjektiv und
5. 5. einem Werkstück-Handlingsystem (Fokussiereinheit)

According to a further exemplary embodiment, the optical unit 100 for a laser material processing system also have the following components:

1. 1. a laser (radiation source)
2. 2. a beam expander (refractive element)
3. 3. a scanner
4. 4. a scanning lens and
5. 5. a workpiece handling system (focusing unit)

The temperature of the lens can make the main contribution to the focus shift. However, the focus is elsewhere. Typical would be e.g. B. the change in the working distance to the workpiece via the handling system or the focusing unit. The use of an additional focusing element in the beam guide downstream of the laser can also be advantageous.

For a projection system (cinematographic or for semiconductor exposure) the z. B. Temperature of a particularly strong refractive power-bearing component in the pupil with high radiance be the determining element. If its temperature is measured without contact, focusing z. B. be done by changing the working distance on the object side.

If an exemplary embodiment comprises an “and / or” link between a first feature and a second feature, this should be read in such a way that the exemplary embodiment according to one embodiment has both the first feature and the second feature and, according to a further embodiment, either only the has the first feature or only the second feature.

Claims (15)

Optical unit (100) with the following features: - A refractive element (105) which is designed to refract a beam (122) of electromagnetic radiation emitted by a radiation source (125) onto an object (135); and - A sensor element (140) which is designed to detect a temperature in at least a partial area (148) of the breaking element (105) without contact and to output a temperature signal (142) in response to the temperature. Optical unit (100) according to Claim 1 , characterized by a focusing unit (160) which is designed to determine, depending on the temperature signal (142), a distance between the refractive element (105) and the object (135) and / or between the radiation source (125) and the refractive element (105 ) or to change the object (135) and / or to change a position of an auxiliary element (210) in a beam path (120) of the beam (122) in order to focus the beam (122) on the object (135). Optical unit (100) according to Claim 1 or 2 , characterized in that the sensor element (140) is designed to further detect a temperature in at least one further sub-area (175) of the breaking element (105) and / or part of a holding element (167) carrying the breaking element (105) without contact, to output a further temperature signal (142 '), wherein the focusing unit (160) is designed to change a distance between the refractive element (105) and the object (135) and / or between the To change the radiation source (125) and the refractive element (105) or the object (135) and / or to change a position of an auxiliary element (210) in a beam path (120) of the beam (122) in order to open the beam (122) to focus the object (135). Optical unit (100) according to one of the preceding claims, characterized in that the sensor element (140) has at least two spaced apart sensor units (145, 150), wherein a first sensor unit (145) is formed, the temperature of a first sub-element (110) of the breaking element (105) and a second sensor unit (150) is designed to detect the temperature of a second sub-element (115) of the breaking element (105) and / or the first sensor unit (145) is designed to detect the temperature of the sub-area ( 148) and the second sensor unit (150) is designed to detect the temperature of the further sub-area (175). Optical unit (100) according to one of the preceding claims, characterized in that the sensor element (140) is designed to detect the temperature of the refractive element (105) from a position in a housing (147) receiving the refractive element (105). Optical unit (100) according to one of the preceding claims, characterized in that the sensor element (140) is designed to measure the temperature of the refractive element (105) through a window (310) in a housing (147) carrying the refractive element (105) to capture. Optical unit (100) according to one of the preceding claims, characterized in that the sensor element (140) is designed to detect the temperature in a central area (148) of the refractive element (105) and / or wherein the refractive element (105) as optical lens is formed. Optical unit (100) according to one of the preceding claims, characterized in that a radiation source control unit (180) for controlling or regulating a radiation output by the radiation source (125) is further provided, wherein the radiation source control unit (180) is designed to use the radiation output the temperature signal (142, 142 ') to control or regulate. Optical unit (100) according to one of the preceding claims, characterized in that the sensor element (140) is arranged outside a beam path (120) of the electromagnetic radiation which extends through the refractive element (105). Optical unit (100) according to one of the preceding claims, characterized in that that the breaking element (105) has at least two sub-elements, the sensor element (140) being designed to detect at least one temperature each on one of the sub-elements (110, 115) in order to provide the temperature signal (142). Use of an optical unit (100) according to one of the preceding Claims 1 to 10 in a material processing device, an image projection device and / or an ultraviolet exposure device. Method (700) for operating an optical unit (100) according to one of the Claims 1 to 9 , wherein the method (700) comprises the following steps: - contactless detection (710) of a temperature on at least a partial area of the breaking element (105) to detect in order to output a temperature signal (142) in response to the temperature; and - depending on the temperature signal (142), changing (720) a distance between the refractive element (105) and the object (135) and / or between the radiation source (125) and the refractive element (105) or the object (135) / or a position of an auxiliary element (210) in a beam path of the beam (122) in order to focus the beam (122) on the object (135). Method for analyzing the properties of the optical unit (100) according to one of the preceding Claims 1 to 10 , wherein the method comprises the following steps: - contactless detection of the temperature at the breaking element (105) as a parameter; - Detection of at least one further system and / or method parameter, in particular a time curve of electromagnetic radiation emitted onto the refractive element, a pulse duration and / or a pulse height of the electromagnetic radiation emitted onto the refractive element; - Detection of a beam position of the electromagnetic radiation with a variable beam by the optical unit (100); and - combination of the parameter, the further system or method parameters and / or at least one derivative of the parameter, the further system or method parameters and a failure prognosis derived therefrom in order to analyze the optical unit (100). Computer program which is set up to carry out the steps of the method (700) according to Claim 12 or 13 execute and / or control. Machine-readable storage medium on which the computer program is based Claim 14 is stored.

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