OPTICAL SYSTEM

Description

[0001] The present invention relates to an optical system for multiple deflection of an electromagnetic radiation field, which system comprises a first reflective surface and a second reflective surface, which first reflective surface defines a first reflective surface plane and which second reflective surface defines a second reflective surface plane, which first reflective surface comprises a first electromagnetic radiation-reflecting coating and which second reflective surface comprises a second electromagnetic radiation-reflecting coating, wherein the first reflective surface and the second reflective surface are spaced apart from each other.wherein the first reflective surface plane and the second reflective surface plane are inclined to each other and enclose an angle of inclination, and wherein the first reflective surface and / or the second reflective surface has at least one optical coupling aperture for coupling an optical radiation field between the first and the second reflective coating.

[0002] Furthermore, the present invention relates to a measuring device for measuring the power of an electromagnetic radiation field with a radiation pressure measuring device.

[0003] Furthermore, the present invention relates to an absorption measuring device for measuring the absorption of electromagnetic radiation in a sample, comprising a sample cell for receiving the sample.

[0004] Furthermore, the present invention relates to a distance measuring device comprising an interferometer.

[0005] Furthermore, the present invention relates to a scanning device for deflecting a radiation field comprising a deflection device.

[0006] Optical systems of the type described above are particularly well-known in the form of optical delay lines and optical phase shifters. Optical delay lines are used in many scientific and technical applications. Their primary purpose is to delay an existing optical pulse by a defined time relative to another event.

[0007] In a phase shifter, the phase of a continuous or pulsed optical radiation source is shifted spatially or temporally by a specific amount. In principle, this is also an optical delay line, except that the defined delay is not relative to an event, but rather relative to a specific phase position.

[0008] Two methods are particularly well-known for implementing optical delay lines and phase shifters. Firstly, the actual path length of the optical light can be varied; secondly, the optical group velocity in different materials can be reduced so that the optical light, or more precisely the radiation field, experiences a delay.

[0009] In known concepts for designing optical delay lines, particularly those aimed at making them as compact, fast, and precise as possible, three properties typically compete for attention. Long delay times usually come at the cost of very low dynamic speed. Conversely, high dynamic speeds often make it impossible to achieve long delay times. Furthermore, most known systems operate continuously, preventing the setting of static delay times.

[0010] US 2008 / 0080584 A1 discloses an amplification module for a solid-state laser. Methods and devices for pumping a laser are described in US 2006 / 0165151 A1. US 2010 / 0265512 A1 discloses a multiplier with an optomechanical optical delay line for microelectromechanical systems. US 2002 / 0057725 A1 discloses a laser with an amplification medium for providing an integrated optical pumping cavity. US 2017 / 0229835 A1 relates to laser amplifiers. US 2016 / 0294146 A1 discloses a spatial chirped cavity for the temporary stretching and compression of optical pulses. Finally, WO 2011 / 027731 A1 discloses a plane waveguide laser device.

[0011] It is therefore an object of the present invention to design an optical system of the type described above as simply and compactly as possible.

[0012] This problem is solved according to the invention in an optical system of the type described above by the fact that the at least one optical coupling aperture is designed in the form of a wavelength-dependent and angle-of-incidence coupling aperture for an optical radiation field and that the first reflective coating and / or the second reflective coating define or comprise the at least one wavelength-dependent and angle-of-incidence coupling aperture.

[0013] With the proposed advanced optical system, it is particularly possible to achieve multiple passes of a radiation field in a simple manner, namely through multiple reflections at the first reflective coating and at the second reflective coating. The radiation field thus remains within the system between the two coatings for the multiple passes or cycles, specifically more than one round trip between the two coatings. The radiation field is therefore effectively trapped between the first and second reflective coatings and reflected back and forth multiple times.Depending on the chosen angle of inclination, it is possible, even with a very small distance between the two coatings, to shift a radiation field with a diameter of several millimeters laterally by only a fraction of its own diameter with each pass, so that after each pass almost the same space between the coatings is traversed again. An entry aperture, in this context, refers specifically to any opening that allows the radiation field to pass through, thus enabling its entry into a region or space between the coatings.In particular, this refers not only to a spatial opening, but also to an optical opening that allows the radiation field to penetrate between the two coatings under certain conditions, for example for a specific wavelength or a specific wavelength range under a specific angle of incidence or a specific angle of incidence range and / or depending on a polarization of the radiation field.In particular, the aforementioned optional dependencies make it possible to selectively define an opening for a radiation field on the entire first reflective surface and / or the entire second reflective surface, thus eliminating the need for optimal focusing of the radiation field on a specific area of ​​the reflective surfaces. For example, an input aperture formed by an uncoated area of ​​the first or second reflective surface, i.e., one free of a reflective coating, is not required. The proposed further development of the optical system thus fundamentally avoids the complex optical arrangements known from the prior art, especially those involving mirrors and drive devices for varying an optical delay line.This simplifies the design of optical systems for multiple deflections of an electromagnetic radiation field and can also lead to significant cost savings. A compact design also reduces the overall system weight, which is particularly advantageous for space applications. Low weight, especially of the first and / or second reflective surfaces, is particularly beneficial in applications where the delay path length or phase needs to be varied, as only small masses need to be moved. These can be moved much faster than large masses. The first and second reflective surfaces do not need to define perfect planes in the mathematical sense.It is particularly advantageous if irregularities on the first reflective surface and / or the second reflective surface enclose an angle smaller than the angle of inclination. For example, the optical system can be used to create a microphone if, as a result of pressure fluctuations, such as those caused by sound waves, the refractive index of the medium between the reflective surfaces changes, leading to a change in the orbital period of the radiation field in a region between the reflective surfaces. The pressure fluctuations can then be determined from the changed orbital periods. Furthermore, it is advantageous if the at least one optical coupling aperture is designed as a wavelength-dependent and angle-of-incidence coupling aperture for an optical radiation field. Such a coupling aperture can, in particular, extend over an entire region of the first reflective surface or the second reflective surface.In this way, radiation fields, especially those with a large diameter, can be easily coupled into and trapped in the area between the two reflective surfaces. According to the invention, the first reflective coating and / or the second reflective coating define or comprise the at least one wavelength-dependent and angle-of-incidence coupling aperture. Thus, the coupling aperture can be defined by the respective coating itself. The coupling aperture also forms the output coupling aperture, enabling the radiation field to exit the area between the two coatings under appropriate conditions, i.e., depending on the wavelength and the angle of incidence.

[0014] It is advantageous if the first and second reflective surfaces are arranged so that they can move relative to each other. In particular, the angle of inclination can remain constant when the first and / or second reflective surfaces are moved. A movable arrangement has the particular advantage that the distance, and thus the length of a delay path, can be changed by moving one or both reflective surfaces relative to each other. To achieve a linear extension depending on the movement of the first and / or second reflective surfaces, it is advantageous if the angle of inclination remains constant. Depending on the number of passes or cycles between the two reflective surfaces—that is, one return journey between each surface—the light path can thus be easily increased by a factor corresponding to the number of cycles simply by changing the distance.In particular, the movable arrangement of the first and second reflective surfaces relative to each other allows for the creation of a microphone. A movement of the first and second reflective surfaces relative to each other, resulting from a pressure fluctuation, for example in the form of sound waves, in the medium surrounding the optical system, leads to a changing path of the electromagnetic radiation field between the reflective surfaces, resulting in a change in the travel time of the radiation field. The pressure fluctuations can be determined from measured changes in travel time. Furthermore, the movable arrangement of the reflective surfaces relative to each other allows for the creation of an accelerometer if one of the two reflective surfaces is mounted on a test mass that can be deflected against the action of a restoring device.The reset mechanism can, for example, comprise one or more reset elements in the form of spring elements. The movement of the reflective surfaces relative to each other, resulting from acceleration forces acting on the test mass, in turn changes the rotational period of the radiation field in the area between the reflective surfaces. From this change in rotational period, the acting acceleration forces can then be determined, given the system parameters.

[0015] It is advantageous if the optical system comprises a first reflective element and a second reflective element, with the first reflective element comprising the first reflective surface and the second reflective element comprising the second reflective surface. If no such reflective elements are provided, the first reflective surface and / or the second reflective surface, with their respective coatings, can also be self-supporting.

[0016] The reflective elements simplify the handling of the optical system. In particular, reflective elements can be used in the form of carriers for the coatings, with the reflective surfaces being formed or defined primarily by the coatings. However, the coatings can also be applied directly to components of other devices to create the desired reflective surfaces, for example, to the weighing platform of a scale.

[0017] Furthermore, it can be advantageous if the first reflective surface is displaceable relative to the first reflective surface plane, in particular perpendicularly or substantially perpendicularly, and / or if the second reflective surface is displaceable relative to the second reflective surface plane, in particular perpendicularly or substantially perpendicularly. In particular, the first and / or the second reflective element can also be displaceable relative to the first reflective surface plane or the second reflective surface plane, in particular perpendicularly or substantially perpendicularly. This arrangement allows, in particular, a linear multiplication of, for example, a delay distance depending on the number of revolutions of a radiation field between the reflective surfaces and a displacement of the reflective surfaces.Such an arrangement is particularly advantageous in a measuring device for measuring the power of an electromagnetic radiation field with a radiation pressure measuring device.

[0018] A light path can be easily changed if the optical system includes a distance-changing device for altering the distance between the first and second reflective surfaces. The distance-changing device can be configured, in particular or alternatively, to move the first and / or the second reflective surface. Specifically, it can also be configured to move the first and / or the second reflective element.

[0019] The optical system can be easily configured if the distance-changing device is designed to move the first reflective surface perpendicular to the first reflective surface plane and / or the second reflective surface perpendicular to the second reflective surface plane. In particular, the distance-changing device can be configured to move the first and / or second reflective element perpendicular to the first and second reflective surface planes, respectively. In particular, the distance-changing device can be configured to move the first reflective element and / or the second reflective element parallel to itself. In particular, the distance-changing device can include a drive mechanism for moving the first reflective surface and / or the second reflective surface, or for moving the first coating and / or the second coating.

[0020] The optical system can be designed to be particularly compact if the distance-changing device includes an electromagnetic or piezomechanical drive unit.

[0021] Distances can be changed particularly quickly if the distance-changing device includes at least one piezoelectric actuator. In the described embodiments of optical systems, such a piezoelectric actuator has the particular advantage that the first and / or the second reflective surface can be moved very quickly by a displacement path to change the distance between the reflective surfaces. However, due to the special design of the optical system, the path traveled by the radiation field is multiplied by a multiple of the displacement path, depending on the number of revolutions or passes between the two coatings.

[0022] To minimize possible losses in the radiation field, it is advantageous if the first reflective surface and the second reflective surface are arranged or designed to point towards each other.

[0023] It is advantageous if the first reflective coating is designed as a highly reflective coating or as a wavelength- and / or angle-of-incidence-dependent reflective coating. If the coating is highly reflective, the optical coupling aperture can be defined, in particular, by a region of the first or second reflective surface that is not covered with the highly reflective coating. If, on the other hand, the reflection of the coating is wavelength- and / or angle-of-incidence-dependent, the entire first or second reflective surface can be used, in particular, to couple a radiation field between the surfaces.This has advantages insofar as essentially the entire area defined by the first reflective surface or by the second reflective surface can be used to couple the radiation field, so that essentially the entire area between the two reflective surfaces is penetrated by the radiation field.

[0024] Furthermore, it is advantageous if the second reflective coating is designed as a highly reflective coating or as a wavelength- and / or angle-of-incidence-dependent reflective coating. The same principles apply here as those described above regarding the different forms of the first reflective coating. In particular, any combination of highly reflective coatings and wavelength- and / or angle-of-incidence-dependent reflective coatings is possible on the first and second reflective surfaces. For example, a wavelength- and angle-of-incidence-dependent reflective coating could be applied to the first reflective surface, and a highly reflective coating to the underside. A reversed coating configuration is also conceivable.Furthermore, both coatings can be highly reflective, or both coatings can be reflective depending on the wavelength and / or angle of incidence.

[0025] It is advantageous if the first and / or second coating is designed as an angle-of-incidence-dependent edge filter or a single or double bandpass filter. Such coatings make it possible, in particular, to couple a radiation field between the two reflective surfaces as a function of the angle of incidence. For example, for an edge filter, a radiation field can be coupled between the two reflective surfaces above or below a specific wavelength range for a given angle of incidence. Due to the relative inclination of the reflective surfaces, the radiation field is tilted slightly after entering the area between the reflective surfaces between successive reflections, always by twice the angle of inclination.This causes the angle at which the radiation field strikes the coatings to change after each reflection in the region between the two reflective surfaces. If, at the angle of incidence from the outside, an entry condition for the radiation field into the region between the reflective surfaces is met, the radiation field remains trapped between the two reflective surfaces if, after the first internal back reflection in the region between the reflective surfaces, the entry or exit condition for the radiation field is no longer met. Ideally, the exit condition for the radiation field is no longer met after just one internal reflection between the two reflective surfaces, so that the radiation field can no longer pass through the coating that defines the coupling aperture at the external angle of incidence. Instead, the radiation field is now predominantly, and in particular completely, reflected back.In other words, the optical density of the coating changes depending on the angle at which the radiation field strikes the coating. This allows a radiation field to be selectively coupled between the two reflective surfaces and trapped between them.

[0026] It is advantageous if the edge filter or the single or double bandpass filter has a slope of at least 1 OD / 3 nm. Preferably, the slope is in the range of approximately 1 OD / 3 nm to approximately 3 OD / 3 nm. In particular, the slope is approximately 2 OD / 3 nm. An optical density of approximately 10 dB is present. With a minimum slope as specified, a radiation field can be coupled into a region between the reflective surfaces at a specific angle of incidence and trapped therein in the manner described. The greater the slope, the lower the losses during coupling of the radiation field, for example, due to reflection on an outer surface of the first or second reflective surface or due to partial transmission of the radiation field through the first or second coating out of the region between the reflective surfaces.In principle, it is desirable to provide the steepest possible slope.

[0027] The optical system becomes particularly efficient when the edge filter or the single or double bandpass filter has a high cancellation ratio. In particular, the optical density of the filters is at least 3. More preferably, the optical density of the filters is at least 6.

[0028] Advantageously, the first and / or second coating is designed as a dichroic coating. Dichroic coatings are characterized by the fact that their reflectivity depends primarily on the angle of incidence, wavelength, and polarization of the light. In particular, dichroic coatings can also be designed to exhibit bandpass characteristics and a transmission behavior that is almost independent of polarization and varies with the angle of incidence.

[0029] Advantageously, the first and / or second coating is polarization-independent. This has the particular advantage that the reflectivity of the first and / or second coating depends only on the angle of incidence and the wavelength of the radiation field.

[0030] To obtain the highest possible number of multiple reflections within the solid, it is advantageous for the angle of inclination to be in the range of approximately 0° to approximately 3°. More preferably, the angle of inclination is in the range of approximately 0.5° to approximately 1.5°. In particular, it can be approximately 1°. The smaller the angle of inclination, the greater the number of possible multiple reflections in the area between the two reflective surfaces. However, depending on the properties of the first coating and / or the second coating, especially the steepness of its edges, a larger angle of inclination may be advantageous in order to couple as much of the radiation field as possible into and trap it within the solid.

[0031] It is advantageous if the first and / or the second reflecting element are designed in the form of a solid that is transparent to electromagnetic radiation. This allows the radiation field to be easily guided through the first and / or the second reflecting element.

[0032] The optical system can be designed particularly simply and cost-effectively if the solid is in the form of a crystal or made of glass. For example, the first and / or the second reflective element can serve as carriers for the first and second coatings. A side face of the respective reflective element then forms the first or second reflective surface, respectively, which is coated with the first or second coating.

[0033] It is advantageous if the crystal is made of yttrium aluminum garnet, sapphire, or a semiconductor. Such crystals can be formed in a particularly simple and defined manner.

[0034] It is advantageous if the first and / or the second reflective element has a thickness in the range of approximately 1 mm to approximately 10 mm. In particular, a thickness in the range of approximately 2 mm to approximately 5 mm is acceptable. This allows for the creation of very lightweight reflective elements as substrates for the first or second coating.

[0035] A wavelength- and incidence-angle-dependent coating of the first and / or second reflective surface can be omitted, in particular, if the at least one optical coupling aperture is designed as a coating-free coupling zone on the first reflective surface or as a coating-free coupling zone on the second reflective surface. Thus, with the exception of the coupling zone, both the first and second reflective surfaces can be provided with a highly reflective coating. This makes it possible, in particular, to couple a radiation field through the coupling aperture thus designed into the region between the reflective surfaces.If the coupling area is sufficiently small, after a back reflection at the opposite reflective surface, the radiation field can no longer escape from the area between the two reflective surfaces, because it is reflected back at the highly reflective coating next to the uncoated coupling area into the area between the reflective surfaces, namely towards the other reflective surface. "Uncoated" refers exclusively to the first or second coating. The uncoated coupling area can optionally be provided with an anti-reflective coating.

[0036] It is advantageous if the first and / or the second reflective element are disc-shaped or cuboid-shaped. Such reflective elements can be easily designed, especially as substrates for coatings.

[0037] It is advantageous if the first reflective coating and / or the second reflective coating are in the form of a VersaChrome® < TBP01-900 / 11 coating or an LP02-1064RE coating. Such coatings are available, in particular, from Semrock, Inc.

[0038] It is advantageous if the first and / or second coating is designed to reflect electromagnetic radiation in a wavelength range of approximately 300 nm to approximately 1700 nm. Such an optical system can be used, in particular, as a delay line or phase shifter for radiation fields with wavelengths in the specified range.

[0039] Furthermore, it can be advantageous to arrange or form an electro-optic layer or element between the first and second reflective surfaces. An electro-optic layer or element makes it possible, particularly by changing its refractive index due to an electromagnetic field, to selectively modify the group velocity of the radiation field as it passes through the electro-optic element or layer. Thus, by activating the electro-optic layer or element, the path of the light can be altered, thereby creating a delay line or a phase shifter, even and especially when the first and second reflective surfaces are fixed relative to each other.

[0040] An optical system can be easily constructed if the electro-optical layer comprises a liquid crystal. For example, if a space between the two reflective surfaces is sealed on all sides, a liquid crystal can be introduced into such a structure.

[0041] According to a further preferred embodiment of the invention, the optical system may include a radiation source for generating an electromagnetic radiation field. For example, the radiation source may be a laser.

[0042] It is advantageous if the electromagnetic radiation field is directed at the first or second coating at a radiation field angle relative to a surface normal of the first or second reflective surface. This facilitates, in particular, the coupling of the radiation field into the region between the two reflective surfaces.

[0043] The handling of the optical system can be further simplified if the radiation field is collimated. In particular, one or more collimating lenses can be used for this purpose.

[0044] The problem posed at the outset is solved according to the invention in a measuring device of the type described above by the fact that the radiation pressure measuring device comprises one of the optical systems described above. In this way, the radiation field can be directed onto a radiation pressure measuring device multiple times, depending on how many revolutions between the two reflective surfaces are made possible. This allows even small powers of radiation fields, especially small laser powers on the order of only a few watts, to be measured reliably and precisely.

[0045] It is advantageous if the radiation pressure measuring device includes at least one pressure sensor and if the first or second coating is rigidly coupled to, or mounted on, or held against this pressure sensor. The multiply reflected radiation field thus strikes the pressure sensor multiple times, so that the pressure force exerted by the radiation field is multiplied according to the number of revolutions. This allows for significantly more precise measurement of radiation pressure forces.

[0046] It is advantageous if the radiation pressure measuring device includes a scale and if the scale includes at least one pressure sensor. One of the two coatings can then be arranged or formed on the scale, for example, on a weighing pan of the scale. Alternatively, a reflective element, which carries or includes one of the two coatings, can also be arranged on the scale.

[0047] The problem stated at the outset is further solved according to the invention in an absorption measuring device for measuring the absorption of electromagnetic radiation in a sample by the absorption measuring device comprising one of the optical systems described above. If the sample cell is arranged, in particular, between the two reflective coatings, the number of passes of the radiation field through the sample can be multiplied according to the number of passes of the radiation field between the two reflective coatings. In this way, the interaction between the radiation field and the sample can be multiplied in a very small space.

[0048] Advantageously, the sample cell is positioned or formed between the first and second coatings. As mentioned earlier, this allows for a simple increase in the interaction between the radiation field and the sample.

[0049] According to a further preferred embodiment of the invention, the absorption measuring device may comprise a radiation source for generating electromagnetic radiation and a detector for detecting electromagnetic radiation, wherein the radiation source is arranged to impart radiation to the sample and wherein the detector is arranged or configured to measure the radiation transmitted through the sample. In the manner described, for example, an absorption spectrometer can be designed which can be operated and used completely autonomously to measure absorptions, particularly in highly dilute samples, such as gaseous samples.

[0050] It is advantageous if the absorption measuring device includes an imaging device comprising at least one first imaging element and at least one second imaging element, wherein the sample cell is arranged or formed in a beam path between the at least one first imaging element and the at least one second imaging element. This allows, in particular, the radiation field to be easily expanded before passing through the sample in order to interact with the largest possible spatial area of ​​the sample. Furthermore, the imaging device also makes it possible, in particular, to increase the distance between the two coatings without impairing the function of the optical system.

[0051] It is advantageous if the imaging device is designed as a 4f imaging device. Such a device can be designed particularly easily and allows the two coatings of the system to be separated sufficiently far from each other to enable even large-volume samples to be irradiated with the radiation field.

[0052] The problem stated at the outset is further solved according to the invention in a distance measuring device of the type described above by the fact that it comprises one of the optical systems described above. For example, the optical system can be used to determine the displacement of a mirror of the interferometer with high precision.

[0053] It is particularly advantageous if the interferometer includes a movable mirror, and if the movable mirror encompasses or carries the first or second coating. Specifically, the mirror can carry or encompass the first or second reflective element. When the movable mirror is moved, the distance between the two reflective coatings changes in the manner already described above, so that the displacement of the mirror can be determined with high precision by measuring a deceleration.

[0054] The problem stated at the outset is further solved according to the invention in a scanning device of the type described above by the fact that the deflection device comprises one of the optical systems described above. The deflection device can, in particular, comprise a mirror formed by the second reflective element with the second coating. Preferably, the wedge-shaped coatings, inclined relative to each other, define a plane of symmetry. If the optical system, and in particular its two reflective elements, is arranged to pivot about a pivot axis, a radiation field incident on the optical system can be deflected. The pivot axis preferably runs in both the plane of symmetry and the second reflective plane. Optionally, the scanning device can include a pivot drive to tilt the optical system in a defined manner about the pivot axis, for example, continuously.In this way, the incident radiation field can be spatially separated from the emitted radiation field, particularly when viewed through the optical system. Specifically, a small swivel angle around the swivel axis increases the angle between the incident and emitted radiation fields proportionally to twice the number of rotations of the radiation field in the area between the two coatings. This allows a radiation field to be deflected very efficiently by a small change in the swivel angle, resulting in significantly higher scan rates compared to a deflection device consisting of only a simple mirror.

[0055] Furthermore, the use of one of the optical systems described above is proposed for forming an optical delay line or a phase shifter or an absorption measuring device or a measuring instrument for measuring the power of an electromagnetic radiation field or a scanner or scanning device.

[0056] The following description of preferred embodiments of the invention, in conjunction with the drawings, serves for further explanation. The drawings show: Figure 1: a schematic representation of a main beam path of a radiation field; Figure 2: an enlarged close-up view of the in Figure 1Figure 1: the main beam path rotated by 45°; Figure 3: a schematic representation of multiple reflections in a region between two reflective surfaces; Figure 4: a schematic representation of an optical system as part of a distance measuring device; Figure 5: a schematic representation of an optical system as part of a measuring device for measuring the power of an electromagnetic radiation field with a radiation pressure measuring device; Figure 6: a schematic representation of an optical system as part of an absorption measuring device for measuring the absorption of electromagnetic radiation in a sample; Figure 7: a schematic representation of an optical system comprising an electro-optical layer in the region between the reflective coatings; Figure 8: a schematic representation of a main beam path of a double pass;Figure 9: a schematic representation of an optical system which is arranged or designed to be tiltable relative to the radiation field; Figure 10: a schematic representation of the optical density of the VersaChrome® coating < TBP01-900 / 11 for angles of incidence of 0° and 60°; Figure 11: a schematic representation of an optical system with a radiation field that is too shallow to penetrate between the two reflective surfaces; Figure 12: a similar schematic representation; Figure 11for a radiation field that strikes the first coating at too steep an angle of incidence, so that the radiation field cannot penetrate between the two reflective surfaces; Figure 13: a schematic arrangement of a distance measuring device comprising an interferometer; Figure 14: a schematic representation of the optical density at 0° and 30° as a function of wavelength for a coating of type LP02-1064RE from Semrock, Inc.; Figure 15: a schematic representation of another embodiment of an optical system for forming a microphone; Figure 16: a schematic representation of another embodiment of an optical system for forming a microphone; and Figure 17: a schematic representation of another embodiment of an optical system for forming an accelerometer.

[0057] Figure 1Figure 1 schematically shows a first embodiment of an optical system, designated overall by reference numeral 10, for multiple deflection of an electromagnetic radiation field 12.

[0058] System 10 comprises a first reflective surface 14 and a second reflective surface 16.

[0059] The first reflective surface 14 defines a first reflective surface plane 18. The second reflective surface 16 defines a second reflective surface plane 20.

[0060] The first reflective surface 14 comprises a first electromagnetic radiation-reflecting coating 22. The second reflective surface 16 comprises a second electromagnetic radiation-reflecting coating 24.

[0061] The first reflective surface 14 and the second reflective surface 16 are arranged at a distance from each other.

[0062] The first reflective surface plane 18 and the second reflective surface plane 20 are also arranged inclined to each other and enclose an angle of inclination 26.

[0063] To generate the radiation field 12, the optical system 10 can optionally include a radiation source 28. For example, the radiation source 28 can be in the form of a laser, such as a laser diode, a disk laser, or a fiber laser.

[0064] The first coating 22 and the second coating 24 are designed as reflective coatings. These can be designed in different ways. For example, they can be highly reflective regardless of wavelength, or highly reflective depending on wavelength and angle of incidence. Possible variants are explained in detail below.

[0065] The first coating 22 forms a simple bandpass filter 30. Its properties are shown schematically in Figure 10 The diagram shows a schematic representation of the optical density of the first coating 22 for the bandpass filter 30 at an angle of incidence of 0° and at an angle of incidence of 60°. Accordingly, electromagnetic radiation can penetrate the first coating 22 within a transmittance range 32 for wavelengths from approximately 890 nm to approximately 910 nm. The optical density of the first coating 22 is zero for radiation incident perpendicularly on the first coating 22 within the specified wavelength range.

[0066] With decreasing wavelength, the optical density of the first coating 22 increases; with increasing wavelength above 910 nm, the optical density of the first coating 22 also increases. Both a short-wavelength edge 34 and a long-wavelength edge 36 of the optical density profile of the coating exhibit a slope of approximately 2 OD / 3 nm.

[0067] When electromagnetic radiation strikes the first coating 22 at an angle of 60°, the following results: Figure 10 The left side shows the optical density as a function of wavelength. For example, a transmittance range 38 from approximately 775 nm to approximately 795 nm with an optical density of 0 is observed. Here, too, a short-wavelength slope 40 and a long-wavelength slope 42 are present, each with a gradient of approximately 2 OD / 3 nm.

[0068] The in connection with Figure 10The property of the first coating 22, as exemplified above, makes it possible, in particular, to couple electromagnetic radiation of a specific wavelength at a predetermined angle of incidence into a region 44 between the two reflective surfaces 14 and 16. This can be achieved, for example, at a wavelength of 780 nm and an angle of 60° for a first coating 22, with the properties described in Figure 10 Permeability properties shown.

[0069] If the angle at which electromagnetic radiation with a wavelength of 780 nm strikes the first coating 22 becomes smaller or larger, the optical density of the first coating 22 decreases for both smaller and larger angles. Therefore, if the radiation strikes the first coating 22 at a different angle after passing through it and reflecting off the second coating 24, the special properties of the first coating 22 may result in the electromagnetic radiation entering the region 44 no longer fulfilling the transmittance condition for the angle of incidence at which the radiation strikes the first coating 22 a second time. If the optical density for the radiation at the new angle of incidence is greater than 0, the radiation is at least partially reflected off the first coating 22.

[0070] This change in the angle of incidence of the radiation on the first coating 22 after a back-and-forth pass of the radiation through the region 44 results from the relative inclination of the reflective surfaces 14 and 16. Due to the law of reflection, after each double pass through the region 44, the angle at which the radiation strikes the first coating 22 is reduced by twice the inclination angle 26.

[0071] This means that the first coating 22 forms an optical coupling aperture 46 for the radiation field 12, depending on its wavelength and the angle of incidence at which the radiation field first strikes the first coating 22. If, after a back-and-forth pass through the region 44, during which the radiation is completely reflected back at the second coating 24, the described condition is met—namely, that for the respective wavelength, an optical density of the first coating 22 is satisfied for the angle of incidence of the radiation on the first coating 22 changed by twice the inclination angle 26—then the radiation is reflected at the first coating with increasing proportions and thus passes through the region 44 multiple times.

[0072] The number of passes or cycles in area 44 therefore depends on both the inclination angle 26 and the angle of incidence 48 of the radiation on the first coating 22.

[0073] The in Figure 1 The illustrated embodiment of the optical system 10 comprises a first reflective element 50 and a second reflective element 52. These each form a support for the first coating 22 and the second coating 24, respectively.

[0074] The first reflective element defines the first reflective surface 14 with one side surface, the second reflective element 52 defines the second reflective surface 16 with one side surface. The reflective elements 50 and 52 are arranged such that the reflective surfaces 14 and 16 are arranged facing each other.

[0075] The first reflecting element 50 and the second reflecting element 52 are designed as solids transparent to electromagnetic radiation. This makes it possible, in particular, to reflect the radiation field 12, as schematically shown in Figure 1 shown to direct the light through the first reflective element 50 onto the first coating 22.

[0076] Alternatively, the second reflective element 52 can be made of a material that is opaque to electromagnetic radiation. In particular, no coupling aperture can be provided on the second reflective surface 16, so that the radiation field 12 can be coupled exclusively through the coupling aperture 46, which is formed by the first coating 22, into the region 44 between the two coatings 22 and 24.

[0077] The first reflecting element 50 is preferably made of a crystal or glass. For example, the crystal can be yttrium aluminum garnet or sapphire, or a semiconductor crystal.

[0078] The thickness 54 or 56 of the reflective elements 50 and 52 is preferably in the range of about 1 mm to about 10 mm. In the case of the Figure 3 In the schematically illustrated embodiment, the thicknesses 54 and 56 are approximately 2.5 mm and approximately 4 mm respectively.

[0079] The reflection elements 50 and 52 shown as examples in the figures are disc-shaped. Alternatively, they can also be cuboid-shaped.

[0080] The coupling of a radiation field 12 into the region 44 between the coatings 22 and 24 is exemplified in Figure 4 depicted.

[0081] The radiation field 12 strikes the first reflecting element 50 at a radiation field angle 58 with respect to a surface normal 60 to a top surface 62. In the optically denser first reflecting element 50, the radiation field 12 is refracted towards the surface normal 60 according to the laws of optics, so that the radiation field 12 strikes the first coating 22 at an angle of incidence 64, which is smaller than the radiation field angle 58.

[0082] For example, one wavelength of the radiation field is 12,780 nm. The inclination angle 26 is 1°. The first coating 22 is formed by the coating of a VersaChrome® filter from Semrock, Inc., designated TBP01-900 / 11.

[0083] The tilting behavior of this coating can be calculated in a known manner according to the following formula: λ θ = λ 0 1 − sin 2 θ n eff 2

[0084] This is λ ( θ ) the wavelength at a given angle of incidence, where 0° corresponds to a perpendicular angle of incidence on the coating, and n eff The effective refractive index of the coating is 22. Θ The angle of incidence is 64° relative to the surface normal of 60°.

[0085] The radiation field 12 enters the area 44 through the coating 22 and is completely reflected by the highly reflective second coating 24.

[0086] If the radiation field 12 hits the first coating 22 again at an angle of incidence of 64° of 60°, after reflection at the second coating 24 it hits the first coating 22 again at an angle of 60°-2°=58° and is largely reflected back towards the second coating 24.

[0087] Taking into account the inclination angle 26 and the incidence angle 64, a total of 33 double reflections of the radiation field 12 result in the area 44.

[0088] Taking into account the decreasing angle of incidence of the radiation field 12 after each reflection at the second coating 24 onto the first coating 22, the radiation field 12 practically travels back along the same path and then exits the area 44 at almost the same point.

[0089] In Figure 3The optical densities of the first coating 22 after the first six back reflections at the second coating 24 are shown schematically.

[0090] The second coating 24 is highly reflective, regardless of the wavelength and the angle of incidence.

[0091] With suitable coatings, radiation fields 12 with any wavelengths in the range 44 can, in principle, be captured in the manner described.

[0092] The first coating 22, in particular the previously mentioned coating from Semrock, Inc., designated LP02-1064RE, can be used. This coating forms a long-pass filter that transmits long wavelengths.

[0093] The average distance between the two reflective surfaces 14 and 16 is preferably in the range of about 200 µm to about 2000 µm. The wavelength of the radiation field can, for example, be 941 nm. The radiation field 12 can, in particular, be P-polarized.

[0094] If the radiation field angle 58 is chosen such that the angle of incidence 64 is 48°, the radiation field will have a total of 48 revolutions in the area 44.

[0095] The coating LP02-1064RE has the advantage over the coating TBP01-900 / 11 that the transmittance of the coating decreases by several optical densities after just one revolution, so that secondary rays do not represent any significant sources of loss or interference and thus the energy of the radiation field 12 is reduced by only a few percent.

[0096] To further increase the number of revolutions, the tilt angle 26 must be reduced. A prerequisite for achieving the aforementioned revolution loss values ​​is, in particular, the P-polarization of the radiation field 12.

[0097] To counteract the described direct reflection of the radiation field 12, it is possible to slightly rotate the optical system 10 relative to the radiation field 12, i.e. to rotate the radiation field 12 at the angle of incidence 48 with respect to a plane of symmetry 68 perpendicular to the top surface 62 and thus also to the bottom surface 66 of the first reflecting element 50 which carries the first coating 22.

[0098] For disc-shaped reflecting elements 50 and 52 with a diameter 70, an inclination angle 26 of 1°, and an incidence angle 48 of 5°, the radiation field 12 exhibits a profile as shown schematically in Figures 1 and 2. These two figures merely illustrate rays that exceed 98% of the radiation power of the radiation field 12.

[0099] Figure 1 shows the beam path in a view from the Y direction.

[0100] In Figure 2 An example is a close-up view of the first reflection element 50, which is rotated by 45° with respect to the Y-axis.

[0101] In Figure 2 It is clearly evident that the radiation field emerging from area 44 forms a small angle with the incident radiation field 12 and can thus be easily separated spatially.

[0102] A course of the radiation field 12 in the wedge-shaped region 44 between the coatings 22 and 24 is shown in Figure 2 schematically represented. The path follows an arc here, so that the radiation field 12 exits area 44 again at a different angle.

[0103] The number of reflections is essentially independent of the position of the radiation field 12 on the first reflective element 50. Only one dimension of the arc-shaped path and thus of the light path is determined by the respective local thickness of the area 44, i.e. by a distance between the two coatings 22 and 24.

[0104] The optical system 10 can be used in particular to form a delay line for the radiation field 12. The one mentioned above in connection with the Figures 2 and 3The described light path in region 44 can be changed, and thus the length of a delay line defined by the optical system 10 can be changed, if the coatings 22 and 24 are arranged so that they can be moved relative to each other. This is exemplified in Figure 4 The second reflection element 52 is shown here so that it can be moved parallel to itself.

[0105] A distance-adjustment device 72 is used to move the second reflecting element 52, allowing the reflecting elements 50 and 52 to be moved towards and away from each other. The distance-adjustment device allows the distance between the reflecting surfaces 14 and 16 to be changed.

[0106] In Figure 4Figure 1 shows an embodiment in which the distance-changing device 72 is designed to move the second reflective surface 16, namely by moving the second reflective element 52, perpendicular to the second reflective surface plane 20. Alternatively or additionally, the distance-changing device 72 can also be designed such that the first reflective surface 14 can be moved with it, for example by moving the first reflective element 50, perpendicular to the first reflective surface plane.

[0107] The delay path, or light path, of the radiation field 12 in region 44 can be changed by altering the position of the second reflecting element 52 as follows. If the second reflecting element 52 is shifted parallel to itself by a displacement 74 of Δd, the length of the light path in region 44 changes proportionally to n· Δd, where nindicates the number of forward and backward reflections within the area 44.

[0108] Such an optical system 10 therefore makes it possible in particular to achieve an extension of the light path by a multiple of this displacement path 74 by means of a small displacement path 74.

[0109] If the distance-changing device 72 includes a drive device 76, for example in the form of an electromagnetic or piezomechanical drive, for example in the form of a piezo actuator 78, an adjustment or change of the light path can be carried out at high speed.

[0110] With a like in Figure 4In particular, a distance measuring device 80 can be designed using the optical system 10 shown, as schematically depicted in Figure 13. It comprises a conventional interferometer 82 with a radiation source 84 for generating a radiation field 86, which is directed onto a beam splitter 88. Here, the radiation field 86 is split and divided between a stationary mirror 90 and a movable mirror 92. After reflection from the mirrors 90 and 92, the two components of the radiation field 86 formed by the splitting at the beam splitter 88 re-enter the beam splitter 88 and are at least partially directed onto a detector 94. The superimposed intensity of the components of the radiation field 86 can be measured with this detector.

[0111] The optical system 10 of the distance measuring device 80 comprises a first, stationary reflecting element 50 and a second reflecting element 52. The first reflecting element 50 is arranged in the beam path between the beam splitter 88 and the movable mirror 92. The movable mirror 92 forms the second reflecting element 52. Its second reflective surface 16, facing the first reflecting element 50, is provided with a highly reflective coating, which reflects the radiation field 86 back after it passes through the first reflecting element 50.

[0112] The first reflective surface 14 is provided with the first coating 22, which, as described above, forms a wavelength- and angle-dependent optical coupling aperture 46. In this way, a delay path is formed between the two coatings 22 and 24 of the optical system.

[0113] If the movable mirror 92 is shifted by a displacement 74, the delay distance of the optical system 10 changes by a multiple of this displacement 74. Thus, by a small displacement of the movable mirror 92, especially with a fast drive such as a piezoelectric actuator, the interferometer can be tuned. This can therefore be done very quickly and precisely.

[0114] Another application of the optical system 10 is possible in a measuring device 96 for measuring the power of the electromagnetic radiation field 12. The measuring device 96 includes a radiation pressure measuring device 98 in the form of a scale 100.

[0115] The scale 100 includes a pressure measuring sensor 102. The first coating 22 and the second coating 24 are arranged to be movable relative to each other. In the case of the Figure 5In the illustrated embodiment, the second coating 24 is immovably coupled to, or arranged on, or held by, the pressure sensor 102. This is achieved by directly coupling the second reflective element 52, which carries the second coating 24, to the pressure sensor 102.

[0116] The measuring device 96 basically works on the principle that the radiation field 12 exerts a force on the surface from which it is reflected as a result of reflection. However, these pressure forces exerted by the radiation field 12 are very small. The optical system 10 now enables a multiplication of the acting radiation pressure force F by a factor n, which corresponds to the number of forward and backward reflections in the area 44 between the two coatings 22 and 24. In this way, even very small powers of radiation fields 12 can be measured, even if they amount to only a few watts.

[0117] An optical system 10 can, for example, also be used to form an absorption measuring device 104 for measuring the absorption of electromagnetic radiation in a sample 106.

[0118] The absorption measuring device 104 comprises a sample cell 108 for receiving the sample 106. The sample 106 is in particular a gaseous sample, so that a simple passage of the radiation field 12 through the sample 106 results in only a small interaction between the radiation field 12 and the sample 106.

[0119] If the absorption measuring device 104 includes an optical system 10, the sample cell 108 can be arranged or formed between the first coating 22 and the second coating 24.

[0120] The absorption measuring device 104 comprises a radiation source 110 for generating electromagnetic radiation and a detector 112 for detecting electromagnetic radiation.

[0121] The radiation source 110 is arranged to bombard the sample 106 with radiation. The detector 112 is arranged to measure the radiation transmitted through the sample 106.

[0122] The optical system 10 is, as schematically shown in the Figure 1 and 2 As shown and described above, the radiation field 12 is tilted slightly to the direction of incidence, so that the incident radiation and the radiation exiting the optical system 10 do not directly overlap, but are spatially separated from each other.

[0123] If two lenses 114 are inserted into the beam path between the coatings 22 and 24, the radiation field 12 can be expanded, for example with a 4f image, by these lenses 114 before passing through the sample 106. The lenses 114 together form an imaging device 128, which can also include other optical elements such as lenses, prisms, mirrors, or gratings. In this way, a large-aperture yet compact absorption measurement device 104 can be formed.

[0124] Another variant of an optical system 10 is shown schematically in Figure 7 As shown, an electro-optic layer 116 or an electro-optic element is arranged or formed between the first reflective surface 14 and the second reflective surface 16. For example, the electro-optic layer 116 can comprise a liquid crystal 118.

[0125] By applying an electric field, the refractive index of the electro-optic layer 116 can be changed, and thus a group velocity of the radiation field 12 in the electro-optic layer 116 can be changed. If the two coatings 22 and 24 are arranged in a fixed position relative to each other, the orbital period of the radiation field 12 in the region 44 between the coatings 22 and 24 can be changed by changing the refractive index of the electro-optic layer 116 while maintaining a constant light path.

[0126] Such an optical system can also be used as a delay line.

[0127] If further cycles through the optical system 10 are to take place, the radiation field 12 can, for example, be deflected again onto the optical system 10 via additional mirrors 120a and 120b. This is shown schematically in Figure 8This illustrates how the number of forward and backward reflections in area 44 of optical system 10 can be easily doubled.

[0128] Depending on the properties of the coatings 22 and 24, the number of revolutions of the radiation field 12 in the area 44 can also be further increased with additional mirrors.

[0129] Figure 9 Figure 10 shows another variant of an optical system. The wedge-shaped arrangement of the coatings 22 and 24 is symmetrically aligned with the plane of symmetry 68.

[0130] The overall arrangement of the two reflective elements 50 and 52, which carry the coatings 22 and 24, is pivotable about a pivot axis 122.

[0131] The pivot axis 122 runs in both the plane of symmetry 68 and the second reflection plane 20.

[0132] Optionally, a swivel drive 124 can be provided to tilt the optical system 10 about the swivel axis 122 in a defined manner, for example, continuously. In this way, a scanning device can be designed with which the incident radiation field 12 on the optical system 10 can be spatially separated from the emitted radiation field 12. A small swivel angle about the swivel axis 122 increases the angle between the incident radiation field 12 and the emitted radiation field 12, proportionally to twice the number of revolutions of the radiation field in the region 44. In this way, a radiation field can be deflected very efficiently by a small change in the swivel angle by a multiple of its original value, thereby enabling higher scan rates.

[0133] Figure 14Figure 1 shows the optical density of a first coating 22 of type LP02-1064RE from Semrock, Inc. The tilting behavior can also be calculated using the formula provided by Semrock, Inc. λ θ = λ 0 1 − sin 2 θ n eff 2 be described, whereby in turn λ ( θ ) the wavelength at a given angle of incidence and n eff The effective refractive index of the coating is given by . An angle of incidence of 0° corresponds to a perpendicular incidence on the coating 22.

[0134] It is clearly visible that the optical density of the coating, at perpendicular incidence (i.e., at an angle of incidence of 0°), corresponds to an optical density of 7 at a wavelength of approximately 1010 nm, and then drops steeply to 0 with increasing wavelength. At an angle of incidence of 30°, the optical density of P-polarized radiation decreases from 7 to 0 at a wavelength of approximately 1067 nm.

[0135] With the described coating 22 of type LP02-1064RE, one obtains in turn the in Figure 3 Principle diagram of the structure of an optical system 10.

[0136] The second coating 24 is highly reflective, independent of wavelength. At an inclination angle 26 of 0.5°, the path of the radiation field through the region 44 shown is obtained for glass substrates of type BK7 with a wavelength of 1030 nm. An antireflective layer is preferably applied to the top surface 62. In this case, the second coating 24 forms a pure long-pass filter, i.e., an edge filter.

[0137] In the described arrangement, the radiation field 12 is reflected twice 45 times. The radiation field 12 thus exerts approximately 45 times the light pressure on the two reflecting elements 50 and 52.

[0138] The Figure 11 and 12Figure 1 illustrates conditions under which the first coating 22 prevents the coupling of the radiation field 12 into region 44 of the optical system 10. If the radiation field angle 58 is so large that the angle of incidence 64 also exceeds a limit value of the first coating 22, the radiation field 12 is reflected or substantially reflected by the first coating. Coupling into region 44 is therefore not possible. Under this condition, the coupling aperture 46 is closed to the radiation field 12.

[0139] In the schematic arrangement in Figure 12 The radiation field angle 58 is chosen to be so small that the angle of incidence 64, determined by refraction in the first reflecting element 50, is also too small to allow the coupling of the radiation field 12 into the region 44. In this case as well, reflection essentially takes place at the first coating 22.

[0140] The orders from the Figure 11 and 12 This applies in particular to radiation sources 28 that are not monochromatic. Of these generated radiation fields 12, only a section of the electromagnetic spectrum, i.e., a defined wavelength range, is captured in the region 44 between the coatings 22 and 24.

[0141] Possible combinations for this include the use of dispersive elements, in particular in the form of prisms, gratings, lenses, or glass blocks, which approximate the spectral angular behavior from the equation above via a non-monochromatic spectrum of the radiation source 28. In particular, it is possible to collimate different wavelengths of the radiation field 12 at different angles, thereby enabling, at least theoretically, the coupling of the non-monochromatic radiation field 12 into the region 44 in a single step.

[0142] The above-described embodiments of optical systems 10 enable in particular a simple and compact construction of optical delay lines, which are used for temporal optical scanning.

[0143] Such optical systems 10 can also be used as optical phase shifters for communication technology or laser technology.

[0144] Furthermore, it can also be used as a laser power meter, for example in the form of the measuring device 96 described above. This device can be used, in particular, to check laser power. Since very small laser powers can be measured by multiplying the effect of the radiation pressure of the radiation field 12, it is sufficient to couple out only a very small part of the radiation field 12 for power measurement to check the laser power.

[0145] Figure 15Figure 1 schematically shows another embodiment of an optical system 10 which can be used to form a microphone 128.

[0146] The first reflection element 50, arranged to be displaceable parallel to itself, can, as a result of an external excitation by means of sound waves 130, be moved from a basic position against the effect of the Figure 15The spring elements 132, shown schematically as an example, which form a return mechanism, are deflected towards and away from the second reflection element 52. Due to the movement of the first reflection element 50, the path and thus the orbital period of the radiation field 12 in the region 44 between the coatings 22 and 24 change. By measuring the change in the orbital period, time-varying pressures in the medium surrounding the optical system can be determined. From the determination of the changes in the orbital period, sound waves can therefore not only be detected but also evaluated, for example, to convert noise and speech into optical and subsequently electrical signals.

[0147] Another embodiment of an optical system 10 is shown schematically in Figure 16The sound waves 130, or time-varying pressures in a medium surrounding the optical system 10, lead to a change in the refractive index of the medium enclosed in region 44. This is shown in Figure 16 In the right part, in region 44, the optically denser and thinner areas are indicated purely schematically. Due to the change in the refractive index, the path of the light also changes, and thus the orbital period of the radiation field 12 in region 44. Thus, similar to the example in Figure 15 In the illustrated embodiment of the optical system 10, the optical system 10 can be used to detect temporal pressure fluctuations, for example as part of a microphone 128. In this embodiment, the coatings 22 and 24 do not need to be arranged so as to be movable relative to each other.

[0148] Another embodiment of an optical system 10 is shown schematically in Figure 17The first reflective element 50 is designed in the form of an edge filter 134 and is provided with the first coating 22, which points towards a second coating 24 of a second reflective element 52. The second reflective element 52 is designed in the form of a test mass, which is movably connected to a housing 136 via spring elements 138 that define a return mechanism. The first reflective element 50 is fixed to the housing 136. The coatings 22 and 24 are inclined relative to each other by an angle of inclination 26 in a manner as described above.

[0149] When the test mass, i.e., the second reflective element 52, is accelerated, it is deflected from its initial position against the action of the spring elements 138. This changes the path of the light and thus the orbital period of the radiation field 12 in the region 44 between the coatings 22 and 24. At least theoretically, under acceleration, the distance between the coatings 22 and 24 changes proportionally to the acceleration. The described arrangement allows for a high dynamic range and, in particular, high sensitivity for measuring accelerations.

[0150] At the in Figure 17 In the illustrated embodiment of the optical system 10, the reflection elements 50 and 52 can also be arranged in reverse order, i.e. alternatively, the first reflection element can be arranged on the housing 136 by means of a return element and the second reflection element 52 can be fixed to the housing 136.

[0151] In the optical systems 10 described above, the second coating 24 is preferably highly reflective. Optionally, a coating can also be provided that defines a further coupling or extraction aperture for the radiation field 12. Such an arrangement makes it particularly easy to spatially separate the radiation field 12 between the coupling and extraction points from the region 44 than by tilting the optical system 10 as described above.

[0152] The first coating 22 and the second coating 24 can, in principle, be self-supporting. For example, when used in conjunction with a laser power meter, it is possible to apply the first coating 22 or the second coating 24 directly to parts of the pressure sensor 102, for example, directly to a surface of the pressure sensor 102.

[0153] Overall, a very compact optical system 10 can be designed with which a radiation field 12 can be selectively deflected multiple times. By selecting parameters of the system 12, in particular the tilt angle 26, the type of coatings 22 and 24, as well as the radiation field angle 58 and the resulting angle of incidence 64, the number of rotations between the coatings 22 and 24 can be set as desired. This allows a path of the radiation field 12 in the region 44 to be defined and, as described above, modified as desired. Reference symbol list

[0154] 10 Optical system 12 Radiation field 14 First reflective surface 16 Second reflective surface 18 First reflective surface plane 20 Second reflective surface plane 22 First coating 24 Second coating 26 Inclination angle 28 Radiation source 30 Bandpass filter 32 Transmittance range 34 Flank 36 Flank 38 Transmittance range 40 Flank 42 Flank 44 Range 46 Coupling aperture 48 Angle of incidence 50 First reflective element 52 Second reflective element 54 Thickness 56 Thickness 58 Radiation field angle 60 Surface normal 62 Top 64 Angle of incidence 66 Bottom 68 Plane of symmetry 70 Diameter 72 Distance adjustment device 74 Displacement 76 Drive device 78 Piezo actuator 80 Distance measuring device 82 Interferometer 84 Radiation source 86 Radiation field 88 Beam splitter 90 Mirror 92 Mirror 94 Detector 96 Measuring device 98 Radiation pressure measuring device 100 Balance 102 Pressure measuring sensor 104 Absorption measuring device 106 Sample 108 Sample cell 110 Radiation source 112 Detector 114 Lens 116 Electro-optic layer 118 Liquid crystal 120a Mirror120b Mirror 122 Swivel axis 124 Swivel drive 126 Anti-reflective coating 128 Imaging device 130 Sound waves 132 Spring element 134 Edge filter 136 Housing 138 Spring element

Claims

1. Optical system (10) for multiple redirection of an electromagnetic radiation field (12), which system (10) comprises a first reflective surface (14) and a second reflective surface (16), which first reflective surface (14) defines a first reflective surface plane (18) and which second reflective surface (16) defines a second reflective surface plane (20), which first reflective surface (14) comprises a first electromagnetic radiation reflective coating (22) and which second reflective surface (16) comprises a second electromagnetic radiation reflective coating (24), wherein the first reflective surface (14) and the second reflective surface (16) are spaced apart from one another, wherein the first reflective surface plane (18) and the second reflective surface plane (20) are inclined relative to one another and form between them an angle of inclination (26), and wherein the first reflective surface (14) and / or the second reflective surface (16) comprises at least one optical incoupling opening (46) for incoupling an optical radiation field (12) between the first and the second reflective coating (22, 24), characterized in that the at least one optical incoupling opening (46) is configured in the form of a wavelength-dependent and angle-of-incidence-dependent incoupling opening (46) for an optical radiation field (12) and in that the first reflective coating (22) and / or the second reflective coating (24) defines or comprises the at least one wavelength-dependent and angle-of-incidence-dependent incoupling opening (46).

2. Optical system in accordance with claim 1, characterized in that the first reflective surface (14) and the second reflective surface (16) are arranged in movable relation to one another, in particular wherein the angle of inclination (26) is unchangeable.

3. Optical system in accordance with any one of the preceding claims, characterized in that a) the optical system comprises a first reflective element (50) and a second reflective element (52), which first reflective element (50) comprises the first reflective surface (14) and which second reflective element comprises the second reflective surface (16), and / or b) the first reflective surface (14), in particular the first reflective element (50), is arranged or supported for displacement relative to the first reflective surface plane (18) and / or in that the second reflective surface (16), in particular the second reflective element (52), is arranged or supported for displacement relative to the second reflective surface plane (20), and / or c) the optical system comprises a distance changing device (72) for changing a distance between the first reflective surface (14) and the second reflective surface (16), in particular wherein the distance changing device (72) is configured for displacing the first reflective surface (14), in particular the first reflective element (50), perpendicularly to the first reflective surface plane (18) and / or for displacing the second reflective surface (16), in particular the second reflective element (52), perpendicularly to the second reflective surface plane (20), further in particular wherein the distance changing device (72) - comprises an electromagnetic or a piezomechanical drive device (76), and / or - comprises at least one piezo actuator (78).

4. Optical system in accordance with any one of the preceding claims, characterized in that the first reflective surface (14) and the second reflective surface (16) are arranged or formed such that they point towards one another.

5. Optical system in accordance with any one of the preceding claims, characterized in that a) the first reflective coating (22) is configured in the form of a highly reflective coating or in the form of a wavelength-dependent and angle-of-incidence-dependent reflective coating, and / or b) the second reflective coating (24) is configured in the form of a highly reflective coating or in the form of a wavelength-dependent and angle-of-incident-dependent reflective coating, in particular wherein the first coating (22) and / or the second coating (24) is configured in the form of an angle-of-incidence-dependent edge filter or a single or dual bandpass filter (30), further in particular wherein the edge filter or the single or dual bandpass filter (30) - has an edge steepness of at least 1 OD / 3 nm, preferably in a range of approximately 1 OD / 3 nm to approximately 3 OD / 3 nm, in particular approximately 2 OD / 3 nm, and / or - has a high cancellation ratio, in particular an optical density of at least 3, further in particular of at least 6.

6. Optical system in accordance with any one of the preceding claims, characterized in that a) the first coating (22) and / or the second coating (24) is configured in the form of a dichroic coating, and / or b) the first coating (22) and / or the second coating (24) is of polarization-independent configuration, and / or c) the angle of inclination (26) is in a range of approximately 0° to approximately 3°, in particular in a range of approximately 0.5° to approximately 1.5°, further preferably approximately 1°.

7. Optical system in accordance with any one of claims 3 to 6, characterized in that the first reflective element (50) and / or the second reflective element (52) a) is configured in the form of a solid body that is transmissive to electromagnetic radiation, in particular wherein the solid body is configured in the form of a crystal or is formed from glass, further in particular wherein the crystal is formed from yttrium aluminium garnet, or sapphire, or from a semiconductor, and / or b) has a thickness (54, 56) in a range of approximately 1 mm to approximately 10 mm, in particular in a range of approximately 2 mm to approximately 5 mm, and / or c) is configured in the shape of a disk or a cuboid.

8. Optical system in accordance with any one of the preceding claims, characterized in that a) the at least one optical incoupling opening is configured in the form of a coating-free incoupling area on the first reflective surface or in the form of a coating-free incoupling area on the second reflective surface, and / or b) the first reflective coating (22) and / or the second reflective coating (24) is configured in the form of a VersaChrome® TBP01-900 / 11 coating or in the form of an LP02-1064RE coating, available from Semrock, Inc., and / or c) the first coating (22) and / or the second coating (24) is configured for reflecting electromagnetic radiation in a range of wavelengths of approximately 300 nm to approximately 1700 nm, and / or d) an electrooptical layer (116) or an electrooptical element is arranged or formed between the first reflective surface (14) and the second reflective surface (16), in particular wherein the electrooptical layer (116) comprises a liquid crystal (118).

9. Optical system in accordance with any one of the preceding claims, characterized by a radiation source (28) for generating an electromagnetic radiation field (12), in particular wherein a) the electromagnetic radiation field (12) is oriented towards the first or the second coating (22, 24) at a radiation field angle (58) with respect to a surface normal (60) of the first reflective surface (14) or the second reflective surface (16), and / or b) the radiation field (12) is collimated.

10. Measurement instrument (96) for measuring a power of an electromagnetic radiation field (12) using a radiation pressure measurement device (98), characterized in that the radiation pressure measurement device (98) comprises an optical system (10) in accordance with any one of the preceding claims, in particular wherein the radiation pressure measurement device (98) comprises at least one pressure measurement sensor (102), and wherein the first coating (22), in particular the first reflective element (50), or the second coating (24), in particular the second reflective element (52), is non-movably coupled to the at least one pressure measurement sensor (102) or arranged thereon or held thereto, further in particular wherein the radiation pressure measurement device (98) comprises a scale (100), and wherein the scale (100) comprises the at least one pressure measurement sensor (102).

11. Absorption measurement device (104) for measuring the absorption of electromagnetic radiation in a sample (106), comprising a sample cell (108) for receiving the sample (106), characterized by an optical system (10) in accordance with any one of claims 1 to 9.

12. Absorption measurement device in accordance with claim 11, characterized in that a) the sample cell (108) is arranged or formed between the first coating (22) and the second coating (24), and / or b) the absorption measurement device comprises a radiation source (110) for generating electromagnetic radiation and a detector (112) for detecting electromagnetic radiation, wherein the radiation source (110) is arranged for exposing the sample (106) to radiation and wherein the detector (112) is arranged or formed for measuring the radiation transmitted through the sample (106), and / or c) the absorption measurement device comprises an imaging device (128), comprising at least one first imaging element (114) and at least one second imaging element (114), wherein the sample cell is arranged or formed in a beam path between the at least one first imaging element and the at least one second imaging element, further in particular wherein the imaging device (128) is configured in the form of a 4f imaging device.

13. Distance measurement device (80), comprising an interferometer (82), characterized by an optical system in accordance with any one of claims 1 to 9, in particular wherein the interferometer comprises a movable mirror (92), and wherein the movable mirror (92) comprises or carries the first coating (22), in particular the first reflective element (50), or the second coating (24), in particular the second reflective element (52).

14. Scan apparatus (130) for deflecting a radiation field (12), comprising a deflection device, characterized in that the deflection device comprises an optical system in accordance with any one of claims 1 to 9.

15. Use of an optical system (10) in accordance with any one of claims 1 to 9 for forming an optical delay path, or a phase shifter, or an absorption measurement device (104), or a measurement instrument (96) for measuring a power of an electromagnetic radiation field (12), or a scan apparatus (130), or a microphone, or an acceleration sensor.