Optical device and method for changing polarization of a polarized light beam

Abstract

The invention further relates to an optical device (10) for changing a polarization of a polarized light beam (12).

Description

[0001]14.03.2025 DS16778P4019WO0 5 10 Optical device and method for changing the polarization of a polarized light beam Description The invention relates to an optical device and a method for changing the polarization of a polarized light beam. Optical devices in the form of a λ / 2 plate and / or a λ / 4 plate for changing the polarization of a polarized light beam are known. Typically, the λ / 2 plate or the λ / 4 plate is formed from a birefringent material through which the polarized light beam passes to change the polarization. For a polarized light beam with high power and / or for wavelengths of a polarized light beam for which no birefringent materials are available, the polarization is often changed by reflecting the polarized light beam off a phase-shifting mirror.A phase-shifting mirror can be understood as a mirror that reflects a light beam with a phase shift between a P-polarization component and an S-polarization component of the light beam with respect to a plane of incidence of the light beam onto the phase-shifting mirror. A phase-shifting mirror can, for example, have a phase shift of 90°, although any other amounts of phase shift are also conceivable. A phase shift of 90° can be understood as a phase shift of λ / 4. Thus, the phase-shifting mirror with the phase shift of 90° can reflect a linearly polarized light beam, which is incident on the phase-shifting mirror in such a way that the P-polarization component and the S-polarization component are equal in their amounts, as a circularly polarized light beam.5 A phase-shifting mirror can be a mirror that has a phase shift of at least 5°. A mirror that has a phase shift of less than 5° cannot be a phase-shifting mirror. The object of the present invention is to provide an optical device and a method for changing the polarization of a polarized light beam, each of which has improved properties, particularly for a polarized light beam with high power and / or for wavelengths of a polarized light beam for which no birefringent materials are available, enabling the polarization of the polarized light beam to be changed. 15 The invention solves this problem with an optical device having the features of claim 1 and a method for changing the polarization of a polarized light beam having the features of claim 9.Advantageous embodiments and further developments of the invention emerge from the dependent claims. 20 An optical device according to the invention is designed to change the polarization of a polarized light beam. The optical device has an optical device with a first optical arrangement and a second optical arrangement. The first optical arrangement has a plurality, for example 3, 4, 5 or 6, of reflection optics 25 for reflecting the light beam. The first optical arrangement is rotatably mounted about a first axis of rotation of the optical device. The second optical arrangement has a plurality, for example 3, 4, 5 or 6, of reflection optics for reflecting the light beam. The second optical arrangement is rotatably mounted about a second axis of rotation of the optical device.The first optical arrangement and the second optical arrangement are arranged such that the polarized light beam passes through the first optical arrangement and the second optical arrangement, in particular one after the other, for the purpose of changing the polarization. The optical device is designed to change the polarization of the polarized light beam as a function of a rotational position of the first optical arrangement and a rotational position of the second optical arrangement by reflecting the polarized light beam by means of the plurality of reflection optics of the first optical arrangement and by reflecting the polarized light beam by means of the plurality of reflection optics of the second optical arrangement. Advantageously, the change in the polarization of the polarized light beam can be adjustable by rotating the first optical arrangement about the first axis of rotation and / or by rotating the second optical arrangement about the second axis of rotation.As a result, for example, the polarization of the polarized light beam can be changed to a predetermined polarization by means of the optical device. 10 A further aspect of the invention is that by using the first optical arrangement and the second optical arrangement, the change in the polarization of the polarized light beam can be adjusted particularly quickly. In particular, the change in polarization can be adjusted by rotating the first and / or second optical arrangement by particularly small angles of rotation. As a result, less space can be required for rotating the first and / or second optical arrangement, whereby the first optical arrangement and the second optical arrangement enable a particularly compact design of the optical device.Further advantageously, by using 20 reflection optics, the optical device can change the polarization of the polarized light beam even when the polarized light beam has a high power and / or a wavelength for which no birefringent materials are available. As a result, the invention can enable a particularly simple and variable change in the 25 polarization of the polarized light beam. For the purpose of changing its polarization, the polarized light beam can be guided over the plurality of reflection optics of the first optical arrangement and over the plurality of reflection optics of the second optical arrangement. 30 The polarization of the polarized light beam, in particular before passing through the optical device, can be linear polarization, elliptical polarization, or circular polarization.For example, a linear polarization of the polarized light beam can be changed into a circular polarization by means of the optical device. 35 For example, an elliptical polarization of the polarized light beam can be changed into a circular or linear polarization by means of the optical device. For example, a circular polarization of the polarized light beam can be changed into a linear polarization by means of the optical device. 5 The light beam can be a laser beam. The light beam can be a light beam from a CO2 laser. The power of the light beam can have a value in a first range from 50 W (watts) to 300 W, in particular 100 W to 200 W, and / or in a second range from 8 kW (kilowatts) to 50 kW, in particular 10 kW to 30 kW. A wavelength of the light beam can have a value in a range of 9 µm (micrometers) to 12 µm, 10 in particular 10 µm to 11 µm.For example, the wavelength of the light beam can be 10.6 µm. Each reflection optic of the first optical arrangement and / or the second optical arrangement can be designed as a mirror, in particular a Bragg mirror. 15 The plurality of reflection optics of the first optical arrangement can have at least one phase-shifting mirror for changing the polarization of the light beam. The plurality of reflection optics of the second optical arrangement can have at least one phase-shifting mirror for changing the polarization of the light beam. Each 20 phase-shifting mirror of the optical device can have a phase shift with an amount in a range of 2.5° to 175°, in particular from 3.5° to 120°, in particular from 5° to 90°, in particular 10° to 80°.The phase shift of the phase-shifting mirror can be a change in phase between a portion of a P-polarization component and a portion of an S-polarization component of the polarized light beam, which the polarized light beam has after being reflected by the phase-shifting mirror. The first optical arrangement can have a housing that is rotatably mounted about the first axis of rotation. The housing of the first optical arrangement can have an interior space 30 in which the plurality of reflection optics of the first optical arrangement are arranged. The plurality of reflection optics of the first optical arrangement can be attached to the housing of the first optical arrangement. The second optical arrangement can have a housing that is rotatably mounted about the second axis of rotation 35.The housing of the second optical arrangement may have an interior space in which the plurality of reflection optics of the second optical arrangement are arranged. The plurality of reflection optics of the second optical arrangement may be attached to the housing of the second optical arrangement. 5 The polarized light beam may have an X-polarization component in an X-direction and a Y-polarization component in a Y-direction orthogonal to the X-direction.Changing the polarization of the polarized light beam can be understood as changing an amplitude ratio between the X-polarization component of the polarization of the polarized light beam and the Y-polarization component of the polarization of the polarized light beam and / or changing a phase shift between the X-polarization component of the polarization of the polarized light beam and the Y-polarization component of the polarization of the polarized light beam. The polarized light beam can define an incidence plane upon impinging on a reflection optic of the optical device. A proportion of a P-polarization component and a proportion of an S-polarization component on each reflection optic of the first optical arrangement can depend on the rotational position of the first optical arrangement.By rotating the first optical arrangement 20 about the first rotation axis, the proportion of the P-polarization component and the proportion of the S-polarization component on each reflection optic of the first optical arrangement can be changed. A proportion of a P-polarization component and a proportion of an S-polarization component 25 on each reflection optic of the second optical arrangement can depend on the rotational position of the second optical arrangement. By rotating the second optical arrangement about the second rotation axis, the proportion of the P-polarization component and the proportion of the S-polarization component on each reflection optic of the second optical arrangement can be changed.30 For example, with an elliptical polarization of the polarized light beam, the proportion of the P-polarization component and the proportion of the S-polarization component on the reflection optics of the first optical arrangement can be changed by rotating the first optical arrangement about the first axis of rotation. Thus, by rotating the first optical arrangement about the first axis of rotation, an amplitude ratio between the X-polarization component and the Y-polarization component and a phase shift between the X-polarization component and the Y-polarization component can be changed if at least one reflection optic of the first optical arrangement is designed as a phase-shifting mirror.5 For example, with an elliptical polarization of the polarized light beam, the proportion of the P-polarization component and the proportion of the S-polarization component on the reflection optics of the second optical arrangement can be changed by rotating the second optical arrangement about the second axis of rotation. Thus, by rotating the second optical arrangement about the second axis of rotation, the amplitude ratio between the X-polarization component and the Y-polarization component and the phase shift between the X-polarization component and the Y-polarization component can be changed if at least one reflection optic of the second optical arrangement is designed as a phase-shifting mirror.15 A further aspect of the invention is that, through the use of the first optical arrangement and the second optical arrangement, the amplitude ratio between the X-polarization component and the Y-polarization component of the polarized light beam and the phase shift between the X-polarization component and the Y-polarization component of the polarized light beam can be adjusted in a range of arbitrary combinations. For example, the second optical arrangement can assume a rotational position in which a change in the amplitude ratio or a change in the phase shift is partially or completely compensated by the first optical arrangement. 25 The first optical arrangement can be mounted so as to be rotatable about the first axis of rotation independently of the second optical arrangement, in particular independently of a rotational position of the second optical arrangement.The second optical arrangement can be mounted so as to be rotatable about the second rotation axis independently of the first optical arrangement, in particular independently of a rotational position of the first optical arrangement. For example, the first optical arrangement can change an amplitude ratio between the X-polarization component and the Y-polarization component of the polarized light beam and simultaneously cause an unwanted phase shift between the X-polarization component and the Y-polarization component of the polarized light beam. The unwanted phase shift can be compensated for by means of the second optical arrangement.For example, the first optical arrangement can change a phase shift between the X-polarization component and the Y-polarization component of the polarized light beam and simultaneously cause an undesired amplitude ratio between the X-polarization component and the Y-polarization component of the polarized light beam. The undesired amplitude ratio can be compensated by the second optical arrangement. 10 In other words, after passing through the optical device, the polarized light beam can have a desired amplitude ratio between the X-polarization component and the Y-polarization component of the polarized light beam and a desired phase shift between the X-polarization component and the Y-polarization component of the polarized light beam.In a further development of the optical device, the plurality of reflection optics of the first optical arrangement, in particular as a whole, have a phase shift with an amount in a range from 40° to 80°, in particular 50° to 80°, in particular 50° to 70°. Additionally or alternatively, the plurality of reflection optics of the second optical arrangement, in particular as a whole, have a phase shift with an amount in a range from 40° to 80°, in particular 50° to 80°, in particular 50° to 70°. This makes it possible to change the polarization of the polarized light beam over a particularly large range. 25 The phase shift of the first optical arrangement can be a change in a phase between a portion of a P-polarization component and a portion of an S-polarization component of the polarized light beam, which change the phase of the polarized light beam after passing through the first optical arrangement.30 The phase shift of the second optical arrangement can be a change in phase between a portion of a P-polarization component and a portion of an S-polarization component of the polarized light beam, which change the phase of the polarized light beam after passing through the second optical arrangement. 35 The plurality of reflection optics of the first optical arrangement can, in particular overall, have a phase shift with an amount of approximately 60°. Additionally or alternatively, the plurality of reflection optics of the second optical arrangement can have a phase shift with an amount of approximately 60°. 5 In a development of the optical device, the plurality of reflection optics of the first optical arrangement has a first phase shift mirror and a second phase shift mirror.Additionally or alternatively, the plurality of reflection optics of the second optical arrangement comprises a first phase-shifting mirror 10 and a second phase-shifting mirror. The first phase-shifting mirror of the first optical arrangement and the second phase-shifting mirror of the first optical arrangement can each have a phase shift having an amount equal to half the amount 15 of the phase shift of the first optical arrangement. In particular, the first phase-shifting mirror of the first optical arrangement and the second phase-shifting mirror of the first optical arrangement can each have a phase shift having an amount in a range of 5° to 45°, in particular 20° to 40°. For example, the first phase-shifting mirror of the first optical arrangement and the second phase-shifting mirror of the first optical arrangement can each have a phase shift having an amount of approximately 30°.The first phase-shifting mirror of the second optical arrangement and the second phase-shifting mirror of the second optical arrangement can each have a phase shift having an amount equal to half the amount of the phase shift of the second optical arrangement. In particular, the first phase-shifting mirror of the second optical arrangement and the second phase-shifting mirror of the second optical arrangement can each have a phase shift having an amount in a range from 5° to 45°, in particular 20° to 40°. 30 For example, the first phase-shifting mirror of the second optical arrangement and the second phase-shifting mirror of the second optical arrangement can each have a phase shift having an amount of approximately 30°.In a further development of the optical device, the first optical arrangement for changing the polarization of the polarized light beam has a rotational position in which the first optical arrangement is configured to change an amplitude ratio between an X-polarization component of the polarized light beam and a Y-polarization component of the polarized light beam that is orthogonal to the X-polarization component to a greater extent than the second optical arrangement, and in which the first 5 optical arrangement is configured to change a phase shift between the X-polarization component of the polarized light beam and the Y-polarization component of the polarized light beam to a lesser extent than the second optical arrangement.In a further development of the optical device, the plurality of reflection optics of the first optical arrangement are arranged such that a beam axis of the polarized light beam, after passing through the first optical arrangement, in particular regardless of the rotational position of the first optical arrangement, forms a continuation of a beam axis of the polarized light beam, in particular immediately before passing through the first optical arrangement. Additionally or alternatively, the plurality of reflection optics of the second optical arrangement are arranged such that a beam axis of the polarized light beam, after passing through the second optical arrangement, in particular regardless of the rotational position of the second optical arrangement, forms a continuation of a beam axis of the polarized light beam, in particular immediately before passing through the second optical arrangement.Advantageously, a propagation direction of the polarized light beam after passing through the first optical arrangement and / or the second optical arrangement can thereby be the same as a propagation direction of the polarized light beam, in particular immediately before passing through the first optical arrangement and / or the second optical arrangement. In other words, a change in the propagation direction of the polarized light beam cannot occur as a result of passing through the first optical arrangement and / or the second optical arrangement. The beam axis of the polarized light beam, in particular immediately before passing through the first optical arrangement, can be aligned parallel to the first axis of rotation. The beam axis of the polarized light beam, in particular immediately before passing through the second optical arrangement, can be aligned parallel to the second axis of rotation.The plurality of reflection optics of the first optical arrangement and the plurality of reflection optics of the second optical arrangement can be arranged such that a beam axis of the polarized light beam, after passing through the optical device, forms a continuation of a beam axis of the polarized light beam, in particular immediately before passing through the optical device. In a further development of the optical device, the polarized light beam, before passing through the optical device, has an X-polarization component in an X-direction and a Y-polarization component in a Y-direction orthogonal to the X-direction. A phase shift of the first optical arrangement and a phase shift of the second optical arrangement are the same.A change in an amplitude ratio between the X-polarization component and the Y-polarization component of the polarized light beam after passing through the optical device satisfies the condition ^^^^ = ^^^^௧sin(2^^^) + ^^^^௧sin(2^^ଶ), where ^^^^ is the change in the amplitude ratio between the X-polarization component and the Y-polarization component of the polarized light beam, ^^. ^^௧ a phase shift of the first optical arrangement or a phase shift of the second optical arrangement, ^^ ^ a rotation angle of the first optical arrangement about the first rotation axis relative to the X-direction and ^^ ଶis a rotation angle of the second optical arrangement about the second rotation axis relative to the X-direction. A change in a phase shift between the X-polarization component and the Y-polarization component of the polarized light beam after passing through the optical device satisfies the condition ^^^^ = ^^^^௧cos(2^^^) + ^^^^௧cos(2^^ଶ), where ^^^^ is the change in the phase shift between the X-polarization component and the Y-polarization component of the polarized light beam. The condition for the change in the amplitude ratio ^^^^ and / or the condition for the change in the phase shift ^^^^ can apply if ^^ ^^௧has an amount in a range from 0° to 10°. In a further development of the optical device, the first optical arrangement and the second optical arrangement are of identical construction. This can advantageously simplify assembly of the first optical arrangement and the second optical arrangement. Advantageously, costs can be saved due to economies of scale by using identical components for the first optical arrangement and the second optical arrangement. In a further development of the optical device, the first axis of rotation and the second axis of rotation are aligned parallel to one another. The first axis of rotation can be arranged such that the second axis of rotation forms a continuation of the first axis of rotation. 5 A method according to the invention is set up for changing a polarization of a polarized light beam.The method comprises the steps of: a) generating the polarized light beam; b) adjusting a rotational position of a first optical arrangement, wherein the first optical arrangement has a plurality of reflection optics for reflecting the light beam; c) adjusting a rotational position of a second optical arrangement, wherein the second optical arrangement has a plurality of reflection optics for reflecting the light beam; and d) changing the polarization of the polarized light beam depending on the rotational position of the first optical arrangement and the rotational position of the second optical arrangement by reflecting the polarized light beam by means of the plurality of reflection optics of the first optical arrangement and by means of the plurality of reflection optics of the second optical arrangement. The method can be suitable for operating a previously described optical device.20 Steps b) and c) can take place simultaneously or sequentially in any order. Steps b) and c) can take place before or after step a). Steps b) and c) can each take place for the purpose of changing the polarization of the polarized light beam. For example, steps b) and c) can each take place in such a way that the change in the polarization of the polarized light beam in step d) to a desired polarization takes place. Step b) can take place by rotating the first optical arrangement about a first axis of rotation of an optical device. Step c) can take place by rotating the second optical arrangement about a second axis of rotation of the optical device. The optical device can have the first optical arrangement and the second optical arrangement.In a further development of the method, the polarized light beam has an X-polarization component in an X-direction and a Y-polarization component in a Y-direction orthogonal to the X-direction. The method comprises the steps: e) specifying a target amplitude ratio between the X-polarization component and the Y-polarization component; f) specifying a target phase shift between the X-polarization component and the Y-polarization component; g) measuring an actual amplitude ratio between the X-polarization component and the Y-polarization component; h) measuring an actual phase shift between the X-polarization component and the Y-polarization component; and i) determining a target rotational position of the first optical arrangement and a target rotational position of the second optical arrangement based on the target amplitude ratio, the target phase shift, the actual amplitude ratio, and the actual phase shift.Step b) is carried out by setting the desired rotational position of the first optical arrangement. Step c) is carried out by setting the desired rotational position of the second optical arrangement. The measurement of step g) and / or the measurement of step h) can take place upstream of the first optical arrangement in the direction of propagation of the polarized light beam or downstream of the second optical arrangement in the direction of propagation of the polarized light beam. For example, the measurement of step g) and the measurement of step h) can take place before the polarized light beam passes through the first optical arrangement, wherein the desired rotational position of the first optical arrangement determined in step i) and the desired rotational position of the second optical arrangement determined in step i) are each an absolute desired rotational position.For example, the measuring of step g) and the measuring of step h) can take place after the polarized light beam has passed through the second optical arrangement, wherein the target rotational position of the first optical arrangement determined in step i) and the target rotational position of the second optical arrangement determined in step i) are each a relative target rotational position. The relative target rotational positions can each indicate a change in the rotational position of the first optical arrangement and a change in the rotational position of the second optical arrangement. Steps e) and f) can take place before steps b) and i). Steps g) and h) can take place before steps b) and i). Step i) can take place before step b). The method can comprise the step: k) specifying a phase shift of the first optical arrangement and a phase shift of the second optical arrangement.Step k) can be performed before step i). The phase shift of the first optical arrangement and the phase shift of the second optical arrangement can be equal. Step i) can be based on the conditions 2^^^ = arctan ^௱^. ^ೞ ௱ఏ^ೞ ^ + arccos and 2^^ଶ = arctan ^௱^ ^ೞ ௱ఏ ^ೞ ^ − arccos ^ ^ ଶ ^ ^ ௱^ ^ೞ ଶ ଶ ఋ ^^^ ^ + ^ ௱ఏ ^ೞ ఋ ^^^ ^ ^ where ^^ ^ the target rotational position of the first optical arrangement, ^^ ଶ the target rotational position of the second optical arrangement, ^^^^ ^^ the difference between the actual amplitude ratio and the target amplitude ratio and ^^^^ ^^ is the difference between the actual phase shift and the desired phase shift. The condition for the desired rotational position of the first optical arrangement ^^ ^and / or the condition for the desired rotational position of the second optical arrangement ^^ ଶ can apply if ^^ ^^௧has an amount in a range from 0° to 10°. Further advantages and advantageous embodiments of the invention can be found in the figures, their description and the claims. All features disclosed in the figures, their description and the claims can be essential to the invention both individually and in any combination with one another. Shown are: Fig. 1 a schematic view of an optical device, Fig. 2 a schematic view of a polarization of a polarized light beam, Fig. 3 a graph of a rotation range of a first optical arrangement and a second optical arrangement of the optical device from Fig. 1, Fig. 4 a schematic representation of a further embodiment of a first optical arrangement, Fig. 5 a schematic representation of a further embodiment of a first optical arrangement, and Fig. 6 a further schematic representation of the first optical arrangement from Fig. 5. 5 Fig.1 shows an optical device 10 for changing the polarization of a polarized light beam 12. The light beam 12 is a laser beam from a CO2 laser. The power of the light beam 12 is 100 W to 200 W, and the wavelength of the light beam 12 is 10.6 µm. The light beam 12 can be an elliptically polarized light beam 12. For example, the polarization of the light beam 12 can be influenced by reflections from optical components of the CO2 laser generating the light beam 12 through different reflection values ​​for a P-polarization component and an S-polarization component such that the light beam 12 has the elliptical polarization. A polarization ellipse 14 of the light beam 12 is schematically shown in FIG. 2. The polarized light beam 12 has an X-polarization component 18 in an X-direction 16 and a Y-polarization component 22 in a Y-direction 20 orthogonal to the X-direction 16.20 The Y-polarization component 22 is smaller than the X-polarization component 18. The amplitude ratio between the X-polarization component 18 and the Y-polarization component 22 is 1:0.8 or, in other words, 1.25. The major axis of the polarization ellipse 14 is rotated by an angle 24 with respect to the X-direction 16. The phase shift between the X-polarization component 18 and the Y-polarization component 22 is 65°. The optical device 10 is designed to change the polarization of the polarized light beam 12 by changing the amplitude ratio and the phase shift between the X-polarization component 18 and the Y-polarization component 22 of the polarized light beam 12. 30 For this purpose, optical device 10 has an optical device 26 with a first optical arrangement 28 and a second optical arrangement 30.The first optical arrangement 28 has a plurality of reflection optics 32 in the form of mirrors for reflecting the polarized light beam 12. The reflection optics 32 of the first optical arrangement 28 are arranged in a plane. The light beam 12 is guided over the plurality of reflection optics 32 of the first optical arrangement 28. Each reflection optic 32 of the first optical arrangement 28 is designed as a Bragg mirror. 5 In total, the first optical arrangement 28 has four mirrors. However, it is also conceivable for the first optical arrangement to have three, five or six reflection optics. The light beam 12 passes through the first optical arrangement 28. The light beam 12 is first reflected by a first mirror 34, then by a second mirror 36, then by a third mirror 38 and then by a fourth mirror 40 of the first optical arrangement 28.The second mirror 36 and the third mirror 38 of the first optical arrangement 28 are designed as phase-shifting mirrors. The second mirror 36 and the third mirror 38 of the first optical arrangement 28 each have a phase shift of 30°. The phase shift is a phase angle which the respective phase-shifting mirror causes between a P-polarization component of the light beam 12 and an S-polarization component of the light beam 12 with respect to a plane of incidence of the light beam 12 onto the respective mirror 36, 38 when reflecting the light beam 12. The first mirror 34 and the fourth mirror 40 of the first optical arrangement 28 are designed as mirrors without phase shift. This results in an overall phase shift of the first optical arrangement 28 of 60°. The first optical arrangement 28 is mounted so as to be rotatable about a first axis of rotation 42 of the optical device 26.The first axis of rotation 42 is arranged such that the first axis of rotation 42 runs through the first mirror 34 and the fourth mirror 40 of the first optical arrangement 28. By rotating the first optical arrangement 28, the arrangement of the reflection optics 32 of the first optical arrangement 28 relative to one another is not changed. By rotating the first optical arrangement 28 about the first axis of rotation 42, the proportions of the P-polarization components and the S-polarization components of the light beam 12 on the second and third mirrors 36, 38 of the first optical arrangement 28 are changed. As a result, the amplitude ratio and the phase shift between the X-polarization component 18 and the Y-polarization component 22 of the 35-polarized light beam 12 are changed depending on the rotational position of the first optical arrangement 28.Consequently, the polarization of the light beam 12 is changed by the first optical arrangement 28 depending on its rotational position. The plurality of reflection optics 32 of the first optical arrangement 28 are arranged such that a beam axis 44 of the polarized light beam 12, after passing through the first optical arrangement 28, forms a continuation of a beam axis 46 of the polarized light beam 12 before passing through the first optical arrangement 28, regardless of the rotational position of the first optical arrangement 28. In the illustrated embodiment of Fig. 1, the beam axis 46 of the light beam 12 is aligned parallel to the first rotational axis 42 before passing through the first optical arrangement 28. The second optical arrangement 30 is structurally identical to the first optical arrangement 28.The first optical arrangement 28 and the second optical arrangement 30 are arranged relative to one another such that the polarized light beam 12 passes through the first optical arrangement 28 and the second optical arrangement 30 one after the other. 20 The second optical arrangement 30 has a plurality of reflection optics 48 in the form of mirrors for reflecting the polarized light beam 12. The reflection optics 48 of the second optical arrangement 30 are arranged in a plane. The light beam 12 is guided over the plurality of reflection optics 48 of the second optical arrangement 30. 25 Each reflection optic 48 of the second optical arrangement 30 is designed as a Bragg mirror. In total, the second optical arrangement 30 has four mirrors. However, it is also conceivable for the second optical arrangement to have three, five, or six reflection optics. 30 The light beam 12 passes through the second optical arrangement 30.The light beam 12 is first reflected by a first mirror 50, then by a second mirror 52, then by a third mirror 54, and finally by a fourth mirror 56 of the second optical arrangement 30. The second mirror 52 and the third mirror 54 of the second optical arrangement 30 are designed as phase-shifting mirrors. The second mirror 52 and the third mirror 54 each have a phase shift of 30°. The first mirror 50 and the fourth mirror 56 of the second optical arrangement 30 are designed as mirrors without phase shift. This results in a phase shift of the second optical arrangement 30 of 60°. The second optical arrangement 30 is mounted so as to be rotatable about a second axis of rotation 58 of the optical device 10 26. The second optical arrangement 30 is designed to be rotatable about the second axis of rotation 58 independently of the first optical arrangement 28.The second axis of rotation 58 is arranged such that the second axis of rotation 58 runs through the first mirror 50 and the fourth mirror 56 of the second optical arrangement 30. Rotating the second optical arrangement 30 does not change the arrangement of the reflection optics 48 of the second optical arrangement 30 relative to one another. Rotating the second optical arrangement 30 about the second axis of rotation 58 changes the proportions of the P-polarization components and the S-polarization components of the light beam 12 on the second and third mirrors 52, 54 of the second optical arrangement 30. As a result, the amplitude ratio and the phase shift between the X-polarization component 18 and the Y-polarization component 22 of the polarized light beam 12 are changed depending on the rotational position of the second optical arrangement 30.Consequently, the polarization of the light beam 12 changes due to the second optical arrangement 30 depending on its rotational position. 25 The plurality of reflection optics 48 of the second optical arrangement 30 are arranged such that the beam axis 60 of the polarized light beam 12, after passing through the second optical arrangement 30, forms a continuation of the beam axis 44 of the polarized light beam 12 before passing through the second optical arrangement 30, regardless of the rotational position of the second optical arrangement 30. 30 In the illustrated embodiment of Fig. 1, the beam axis 44 of the light beam 12 is aligned parallel to the second axis of rotation 58 before passing through the second optical arrangement 30. The first axis of rotation 42 and the second axis of rotation 58 are aligned parallel to one another.The first axis of rotation 42 and the second axis of rotation 58 are arranged relative to one another such that the second axis of rotation 58 forms a continuation of the first axis of rotation 42. The reflection optics 32 of the first optical arrangement 28 and the reflection optics 48 of the second optical arrangement 30 are arranged such that a propagation direction 62 of the polarized light beam 12 before passing through the optical device 26 is the same as a propagation direction 64 of the polarized light beam 12 after passing through the optical device 26. In other words, the optical device 26 does not cause any change in the propagation direction 62 of the polarized light beam 12.10 By means of the first optical arrangement 28 and the second optical arrangement 30, the optical device 26 is designed to change the polarization of the polarized light beam 12 as a function of the rotational position of the first optical arrangement 28 and the rotational position of the second optical arrangement 30 by reflecting the polarized light beam 12 at the reflection optics 32, 48 of the first and second optical arrangements 28, 30. The change in the polarization of the polarized light beam 12 can be adjusted by rotating the first optical arrangement 28 about the first axis of rotation 42 and / or by rotating the second optical arrangement 30 about the second axis of rotation 58. 20 Fig.3 shows a graph from which the change in the amplitude ratio and the change in the phase shift between the X-polarization component 18 and the Y-polarization component 22 of the polarized light beam 12 after passing through the optical device 26 for a phase shift of the first optical arrangement 28 25 of 60 ° and a phase shift of the second optical arrangement 30 of 60 °, formulated differently: ^^^^௧ = 60 °, and for different angles of rotation ^^^ of the first optical arrangement 28 and for different angles of rotation ^^. ଶof the second optical arrangement 30. The graph in Fig. 3 was calculated for a linear input polarization in the Y direction and for a circular output polarization. The 30 changes shown in the graph in Fig. 3 refer to the circular output polarization. From Fig. 3, for example, it can be seen that at a point A, the first optical arrangement 28 has a rotation angle of 154.5° and the second optical arrangement 30 has a rotation angle of 118°, each relative to the X direction 16. At such rotation angles, the optical device 26 causes a change in the polarization of the polarized light beam 12 such that its amplitude ratio changes by 0.25 and its phase shift changes by 10° after passing through the optical device 26. Through this change in the amplitude ratio and the phase shift, the circular output polarization of the light beam 12 can be achieved. 5 Further,Fig.3 that the phase shift and the amplitude ratio between the X-polarization component 18 and the Y-polarization component 22 of the polarized light beam 12 can be adjusted independently of one another by means of the optical device 26. 10 For example, the optical device 26 causes a change in the amplitude ratio of 0 and a change in the phase shift of 10° at a point B. In order to get from point A to point B without changing the phase shift by the optical device 26, a simultaneous adjustment of the angles of rotation of the first optical arrangement 28 and the second optical arrangement 30 is required. 15 In other words, by means of the optical device 26, the amplitude ratio between the X-polarization component 18 and the Y-polarization component 22 of the polarized light beam 12 can be changed without changing the phase shift between the X-polarization component 18 and theY-polarization component 22 of the polarized light beam 12. For example, the optical device 26 causes a change in the amplitude ratio of 0.25 and a change in the phase shift of -20° at a point C. In order to get from point A to point C without changing the amplitude ratio by the optical device 26, a simultaneous adjustment of the angles of rotation of the first optical arrangement 28 and the second optical arrangement 30 is required. In other words, by means of the optical device 26, the phase shift between the X-polarization component 18 and the Y-polarization component 22 of the polarized light beam 12 can be changed without changing the amplitude ratio between the X-polarization component 18 and the Y-polarization component 22 of the polarized light beam 12. In other words, the first optical arrangement 28 and the second optical arrangement 30 enable theAdjusting the amplitude ratio between the X-polarization component and the Y-polarization component of the polarized light beam 12 and the phase shift between the X-polarization component and the Y-polarization component of the polarized light beam 12 independently of one another. 5 In the illustrated embodiment of Figs. 1 to 3, the polarization of the elliptically polarized light beam 12 is to be changed by means of the optical device 26 such that the light beam 12 has a circular polarization. For this purpose, the polarization of the light beam 12 is measured in front of the optical device 26. The light beam 12 has an amplitude ratio between the X-polarization component 18 and the Y-polarization component 22 of 1.25 and a phase shift between the X-polarization component 18 and the Y-polarization component 22 of 65°. The circular polarization requires an amplitude ratio between theX-polarization component and the Y-polarization component of 1 and a phase shift between the X-polarization component and the Y-polarization component of 90°. 15 Fig. 3 shows at a point D that the optical device 26, with a rotation angle of the first optical arrangement 28 of 174° and a rotation angle of the second optical arrangement 30 of 118°, reduces the amplitude ratio between the X-polarization component 18 and the Y-polarization component 22 of the light beam 12 by 0.25 and increases the phase shift between the X-polarization component 18 and the Y-polarization component 22 by 25°. In other words, at a rotation angle of the first optical arrangement 28 of 174° and a rotation angle of the second optical arrangement 30 of 118°, the optical device 26 changes the elliptical polarization of the light beam 12 into a circular polarization. 25 The optical device 10 is designed to carry out a method for changing the polarizationof the polarized light beam 12. The method comprises the steps: k) specifying a phase shift of the first optical arrangement 28 and a phase shift of the second optical arrangement 30; e) specifying a desired 30 amplitude ratio between the X-polarization component 18 and the Y-polarization component 22; f) specifying a desired phase shift between the X-polarization component 18 and the Y-polarization component 22; a) generating the polarized light beam 12; g) measuring an actual amplitude ratio between the X-polarization component 18 and the Y-polarization component 22; h) measuring an actual 35 phase shift between the X-polarization component 18 and the Y-polarization component 22; i) Determining a desired rotational position of the first optical arrangement 28 and a desired rotational position of the second optical arrangement 30 based on the phase shift of the first optical arrangement 28, the phase shiftthe second optical arrangement 30, the target amplitude ratio, the target phase shift, the actual amplitude ratio, and the actual phase shift; b) setting the target rotational position of the first optical arrangement 28; c) setting the target rotational position of the second optical arrangement 30; d) changing the polarization of the polarized light beam 12 depending on the set target rotational position of the first optical arrangement 28 and the set target rotational position of the second optical arrangement 30 by reflecting the polarized light beam 12 by means of the plurality of reflection optics 32 of the first optical arrangement 28 and by reflecting the polarized light beam 12 by means of the plurality of reflection optics 48 of the second optical arrangement 30. 15 In the illustrated embodiment, in step k) the phase shift ^^ ^^௧= 60° of the first optical arrangement 28 and the phase shift ^^^^௧ = 60° of the second optical arrangement 30 are specified. In step e), the target amplitude ratio of 1 is specified. In step f), the target phase shift of 90° is specified. In step g), the actual amplitude ratio of 1.25 is measured. In step h), the actual phase shift of 65° is measured. Fig. 4 schematically shows a further embodiment of a first optical arrangement 28, wherein in the embodiment of Figs. 1 to 3 and in the embodiment of Fig. 4, the same reference numerals are used for identical and functionally equivalent elements and in this respect reference can be made to the explanations for the embodiment of Figs. 1 to 3, so that essentially only the existing differences in the embodiment of Fig. 4 will be discussed. In the embodiment of Fig.4, the angles of incidence of the light beam 12 on the first mirror 34 and on the fourth mirror 34 are each more than 45°. This results in angles of incidence on the second and third mirrors 36, 38 of less than 45°. A desired large change in the phase shift can be achieved particularly easily with large angles of incidence. Fig. 4 shows that the reflection optics 48 of the first optical arrangement 28 are arranged such that a propagation path of the light beam 12 from the first mirror 34 to the second mirror 36 and a propagation path of the light beam 12 from the third mirror 38 to the fourth mirror 40 intersect. Figs. 5 and 6 schematically show a further embodiment of a first optical arrangement 28, wherein in the embodiment of Figs. 1 to 3 and in the embodiment of Fig.5 and 6, the same reference numerals are used for identical and functionally equivalent elements 10 and in this respect reference can be made to the explanations for the embodiment of Figs. 1 to 3, so that essentially only the existing differences in the embodiment of Figs. 5 and 6 will be discussed. In the embodiment of Fig. 5, the angles of incidence of the light beam 12 on the first mirror 34 and on the fourth mirror 34 are each less than 45°. The angles of incidence of the light beam 12 on the second and third mirrors 36, 38 are each less than 45°. In addition, the reflection optics 32 of the first optical arrangement 28 in the embodiment of Figs. 5 and 6 are not arranged in a plane. The second mirror 36 is further away from a viewer in Fig. 5 than the third mirror 38. In other words, the second mirror 36 is perpendicular to the plane of the drawing in Fig. 5 to the rear, away from the viewer in Fig.5 away, offset. In the rotational position of the first optical arrangement 28 shown in Fig. 5, the second mirror 36 is spaced 25 in the X direction from the first mirror 34, wherein the distance has a positive value. The third mirror 38 is offset perpendicular to the plane of the drawing in Fig. 5 towards the front, towards the viewer in Fig. 5. In the rotational position of the first optical arrangement 28 shown in Fig. 5, the third mirror 38 is spaced 30 in the X direction from the first mirror 34, wherein the distance has a negative value. Fig. 6 shows the first optical arrangement 28 in a side view. The fourth mirror 40 is obscured by the first mirror 34 in Fig. 6 and therefore not visible in Fig. 6. The light beam 12 strikes the first mirror 34, wherein the first mirror 34 is arranged 35 such that the light beam 12 is directed 30 onto the second mirror 36.The second mirror 36 directs the light beam 12 onto the third mirror 38 and the third mirror 38 directs the light beam 12 onto the fourth mirror 40.

Claims

1. An optical device (10) for changing a polarization of a polarized light beam (12), comprising: 5 - an optical device (26) with a first optical arrangement (28) and a second optical arrangement (30), - wherein the first optical arrangement (28) has a plurality of reflection optics (32) for reflecting the polarized light beam (12), - wherein the first optical arrangement (28) is rotatably mounted about a first axis of rotation (42) of the optical device (26), - wherein the second optical arrangement (30) has a plurality of reflection optics (48) for reflecting the polarized light beam (12), - wherein the second optical arrangement (30) is rotatably mounted about a second axis of rotation (58) of the optical device (26), - wherein the first optical arrangement (28) and the second optical arrangement (30) are arranged such thatthat the polarized light beam (12) passes through the first optical arrangement (28) and the second optical arrangement (30) for the purpose of changing the polarization, - wherein the optical device (26) is designed to change the polarization of the polarized light beam (12) depending on a rotational position of the first optical arrangement (28) and a rotational position of the second optical arrangement (30) by reflecting the polarized light beam (12) by means of the plurality of reflection optics (32) of the first optical arrangement (28) and by means of the plurality of reflection optics (48) of the second optical arrangement (30).

2. Optical device (10) according to claim 1, - wherein the plurality of reflection optics (32) of the first optical arrangement (28) have a phase shift with an amount in a range of 50° to 80°, in particular 50° to 70°, preferably with an amount of 60°,and / or - wherein the plurality of reflection optics (48) of the second optical arrangement (30) have a phase shift with an amount in a range of 50° to 80°, in particular 50° to 70°, preferably with an amount of 60°.

3. Optical device (10) according to claim 2, - wherein the plurality of reflection optics (32) of the first optical arrangement (28) comprise a first phase-shifting mirror (36) and a second phase-shifting mirror (38), and / or - wherein the plurality of reflection optics (48) of the second optical arrangement (30) comprise a first phase-shifting mirror (52) and a second phase-shifting mirror (54). 4.Optical device (10) according to one of the preceding claims, - wherein the first optical arrangement (28) for changing the polarization of the polarized light beam (12) has a rotational position in which the first optical arrangement (28) changes an amplitude ratio between an X-polarization component (18) of the polarized light beam (12) and a Y-polarization component (22) of the polarized light beam (12) orthogonal to the X-polarization component (18) more than the second optical arrangement (30) and / or in which the first optical arrangement (28) changes a phase shift between the X-polarization component (18) of the polarized light beam (12) and the Y-polarization component (22) of the polarized light beam (12) less than the second optical arrangement (30).Optical device (10) according to one of the preceding claims, - wherein the plurality of reflection optics (32) of the first optical arrangement (28) are arranged such that a beam axis of the polarized light beam (12) after passing through the first optical arrangement (28) forms a continuation of a beam axis of the polarized light beam (12) before passing through the first optical arrangement (28), and / or - wherein the plurality of reflection optics (48) of the second optical arrangement (30) are arranged such that a beam axis of the polarized light beam (12) after passing through the second optical arrangement (30) forms a continuation of a beam axis of the polarized light beam (12) before passing through the second optical arrangement (30). 6.Optical device (10) according to one of the preceding claims, - wherein the polarized light beam (12) has an X-polarization component (18) in an X-direction and a Y-polarization component (22) in a Y-direction orthogonal to the X-direction before passing through the optical device (26). - wherein a phase shift of the first optical arrangement (28) and a phase shift of the second optical arrangement (30) are equal, - wherein an amplitude ratio change between the X-polarization component (18) and the Y-polarization component (22) of the polarized light beam (12) after passing through the optical device (26) satisfies the condition ^^^^ = ^^^^௧sin(2^^^) +^^ ^^௧ sin(2^^ ଶ ), where ^^^^ is the amplitude ratio change between the X-polarization component (18) and the Y-polarization component (22) of the polarized light beam (12), ^^ ^^௧a phase shift of the first optical arrangement (28), ^^ ^ an angle of rotation of the first optical arrangement (28) about the first axis of rotation (42) relative to the X-direction and ^^ ଶ a rotation angle of the second optical arrangement (30) about the second rotation axis (58) relative to the X-direction, - wherein a phase shift change between the X-polarization component (18) and the Y-polarization component (22) of the polarized light beam (12) after passing through the optical device (26) satisfies the condition ^^^^ = ^^^^௧cos(2^^^) +^^ ^^௧ cos ( 2^^ ଶ )where ^^^^ is the phase shift change between the X-polarization component (18) and the Y-polarization component (22) of the polarized light beam (12).

7. Optical device (10) according to one of the preceding claims, - wherein the first optical arrangement (28) and the second optical arrangement (30) are structurally identical.

8. Optical device (10) according to one of the preceding claims, - wherein the first axis of rotation (42) and the second axis of rotation (58) are aligned parallel to one another.

9. Method for changing a polarization of a polarized light beam (12), the method comprising the steps of: a) generating the polarized light beam (12), b) adjusting a rotational position of a first optical arrangement (28), the first optical arrangement (28) comprising a plurality of reflection optics (32) for reflecting the light beam (12), c) adjusting a rotational position of a second optical arrangement (30), wherein the second optical arrangement (30) has a plurality of reflection optics (48) for reflecting the light beam (12), and d) changing the polarization of the polarized light beam (12) as a function of the rotational position of the first optical arrangement (28) and the rotational position of the second optical arrangement (30) by reflecting the polarized light beam (12) by means of the plurality of reflection optics (32) of the first optical arrangement (28) and by means of the plurality of reflection optics (48) of the second optical arrangement (30).

10. The method according to claim 9, wherein the polarized light beam (12) has an X-polarization component (18) in an X-direction and a Y-polarization component (22) in a Y-direction orthogonal to the X-direction.wherein the method comprises the steps of: - specifying a target amplitude ratio between the X-polarization component (18) and the Y-polarization component (22), - specifying a target phase shift between the X-polarization component (18) and the Y-polarization component (22), - measuring an actual amplitude ratio between the X-polarization component (18) and the Y-polarization component (22), - measuring an actual phase shift between the X-polarization component (18) and the Y-polarization component (22), and - determining a target rotational position of the first optical arrangement (28) and a target rotational position of the second optical arrangement (30) based on the target amplitude ratio, the target phase shift, the actual amplitude ratio, and the actual phase shift, - wherein step b) comprises setting the target rotational position of the first optical arrangement (28),- wherein step c) comprises setting the desired rotational position of the second optical arrangement (30).,

Images