Optical system with cross-track error reduction

Abstract

There is provided an optical system (100) comprising a scanning mirror (103) having a reflective face (105) and a plurality of optical elements (M1, 117, M2) defining a beam path (P) from a first position (109) via a plurality of face reflections (FR1, FR2) on the face (105) to a second position (111), the beam path (P) comprising a relay segment (P2-P4) from one face reflection (FR1) to the next face reflection (FR2). There is also provided a method comprising: directing light from a light source (109) along a beam path (P) from a first location (109) via a plurality of facet reflections (FR1, FR2) on a rotating reflective facet (105) of a scanning mirror (103) to a second location (111); and relaying one face reflection (FR1) on the face (105) to the next face reflection (FR2) while rotating the face (105).

Description

Technical Field

[0001] The present disclosure relates to an optical system that includes a scanning mirror having a reflective surface and a plurality of optical elements that define a beam path from a first position to a second position. The scanning mirror may include a rotating polygon mirror. Background Art

[0002] Scanning mirrors are widely known for scanning a beam from a light source over a target area by reflecting the beam on the reflective surface of the mirror and rotating (also referred to as "scanning") the mirror and thus the reflective surface. A rotating polygon mirror (also referred to as a polygon scanner) is a high-speed scanner having a mirror with a plurality of mirror faces attached to an axis that rotates about its central axis. The mirror is attached to an axis that rotates about its central axis. The axis may be mounted with suitable bearings, such as magnetic bearings, ball bearings, and / or air bearings, for higher speed applications. In a raster scanning application, the rotation of the mirror may define a fast axis and a slow axis perpendicular to the fast axis. The rotation of the face produces a scan line, and when using a polygon mirror, each passing reflective polygon face produces a separate (fast axis) scan line. However, due to machining defects of the mirror and / or defects of the bearings, the scanning mirror tends to cause a certain cross-scanning error perpendicular to the fast axis scanning direction defined by the rotation axis. For a polygon mirror, the cross-scanning error (or "dynamic track error") may also or especially be caused by defects of the polygon faces. Depending on the application, if this error is too high, it may pose a problem.

[0003] WO2020 / 263094 discloses the use of a polygon scanner for raster scanning in a confocal microscope. If in this case the dynamic track error is constant but not equal for each face, each fast axis scan line moves transversely to the scan line. This results in a non-uniformly illuminated raster scan pattern, which may lead to perceptible brightness bands on the final image.

[0004] There have been several methods to reduce the dynamic track error of a polygon mirror. For example: G. Marshall and G. Stutz, Handbook of Optical and Laser Scanning, Second Edition, Series in Optical Science and Engineering, Taylor & Francis, 2011, which describes the use of a retroreflective prism; EP0465136A2, which discloses the use of a cylindrical lens; and DE4300739A1, which discloses the use of active beam steering to correct (known) face errors, such as using acousto-optic beam steering or a galvanometer. See also US5614961 and A. S. Khattak et al., "Refractive Scanner Economically Eliminates Tracking Error", Laser Focus World, 28(3), March 1992, pp. 73 - 77, 79, ISSN: 1043 - 8092.

[0005] However, these solutions either cannot fully correct the errors, or require an increase in the size of the polygon faces, or require precise timing. For a polygon of a given size, increasing the size of the polygon faces may force a reduction in the number of faces. Tighter tolerances in the machining of the polygon can also reduce manufacturing errors, but this increases the cost of such units.

[0006] Therefore, it is desirable to reduce the cross-scanning error of the scanning mirror. SUMMARY OF THE INVENTION

[0007] In view of the foregoing, the present disclosure provides an optical system including a scanning mirror having a reflective surface and a plurality of optical elements that determine a beam path from a first position to a second position by a plurality of surface reflections on the surface, including a relay section from one surface reflection to the next surface reflection.

[0008] Providing a relay section from one surface reflection to the next surface reflection, during use, the plurality of surface reflections on the reflective surface can be rotated by the scanning mirror to guide the light emitted from the light source along the beam path from the first position to the second position, relaying one surface reflection to the next surface reflection, thereby reversing the angle of the beam from one surface reflection to the next surface reflection. Thus, the reflection angle error can be eliminated. This can prevent or at least reduce the position error at the second position due to the reflection error (rotation) of the surface. Through relaying, the optical characteristics of the beam can be not affected otherwise.

[0009] Therefore, the illumination of the target at the second position by the light from the first position can be well controlled. The illumination can be used for one or more of irradiating, writing, printing, cutting, welding, melting, curing, etc. of at least a part of the target; the target can be or include an object and / or one or more flowable substances, such as a photocurable substance for additive manufacturing. The illumination can include causing the target to emit light of another wavelength different from the light of the beam, particularly through fluorescence and / or phosphorescence. Additionally or alternatively, another optical effect can be produced, such as reflecting and / or emitting light with another polarization different from the incident light.

[0010] The next surface reflection can preferably be the directly next surface reflection on the surface, without another surface reflection therebetween, so that no further / or other tracking errors are accumulated.

[0011] The scanning mirror can include a rotating polygonal mirror having a plurality of reflective surfaces, and one surface reflection and the next surface reflection can be on the same surface. Thus, the cross-scanning error of each surface can be reduced or prevented, and the overall dynamic scanning error of the polygonal mirror can be reduced from one surface to the next.

[0012] One surface reflection and the next surface reflection can be at the same location, e.g., partially or fully overlapping on the surface. This can achieve one or more of the following: simplify alignment, assist alignment inspection, minimize (introduce) other errors, reduce the size of the system.

[0013] The scanning mirror can be a first scanning mirror, and the optical system can include a second scanning mirror having a reflecting surface between the first scanning mirror and a second position. The scanning mirror can then be arranged to scan in a direction different from that of the first scanning mirror, preferably in a vertical direction. Thus, scanning of surface areas other than line scanning can be facilitated, which can assist confocal microscopy of samples wider than the scanning line. Vertical scanning can assist, for example, in improving resolution, reducing errors, reducing scanning time, facilitating alignment, and one or more of alignment inspection.

[0014] The system can also include a plurality of optical elements that define another relay section from the surface reflection on the first scanning mirror to the surface reflection on the second scanning mirror. Similar to the above, this can prevent cross-scanning errors and improve scanning quality. The system can be particularly used in confocal microscopy, where the second scanning mirror can be used to reflect the scanning light and the target light in opposite directions. Then, the image quality of the target can also be improved.

[0015] The system can include a detector and / or an aperture; and then the system can also include a beam splitter, such as a dichroic mirror and / or a polarization beam splitter, for guiding (e.g., reflecting) light having a first optical property (e.g., having a first wavelength and / or a first polarization) of the light source from a first position along the beam path to a second position, and guiding (e.g., transmitting) light having a second optical property (e.g., having a second wavelength and / or a second polarization) differently along the beam path and via the beam splitter to the detector and / or the aperture.

[0016] Such a system can be used for scanning imaging, particularly confocal imaging, where light having a first optical property (e.g., a first wavelength) can be used to irradiate at least a part of the target, and light having a second optical property (e.g., a second wavelength) can be detected by the detector; the detector can be arranged behind the aperture, which can be used for spatial filtering of the light having the second optical property and then arranged at the focal point of the lens.

[0017] Note that in this document, unless otherwise stated, the word "lens" can refer to a single lens element or to a compound lens including a plurality of individual lens elements, such as an eyepiece, an achromatic lens (such as an achromatic doublet), a collimated beam expander, etc.

[0018] Embodiments can include a detector and an aperture as may be described above, and it can include

[0019] A beam splitter, such as a dichroic element (such as a dichroic mirror) and / or a polarization beam splitter, is used to direct light having a first optical characteristic (e.g., at a first wavelength and / or polarization) from a light source from a first position to a second position, and direct light having a second optical characteristic (e.g., at a second wavelength and / or polarization) (preferably from the second position) through an aperture towards a detector, and

[0020] A second plurality of optical elements define a second beam path from the aperture to the detector, the second beam path including a second relay section that is reflected via a plurality of second surfaces, including from one second surface reflection to the next second surface reflection. Then, when the scanning mirror includes a rotating polygon mirror having a plurality of reflecting surfaces, one second surface reflection and the next second surface reflection can be on the same surface of the rotating polygon mirror, preferably on the same surface as a previously specified one surface reflection and the next surface reflection.

[0021] Such a system allows for re-scanning of a confocal microscope. The beam path and any other elements and aspects mentioned above can then be related to the scanning path and the re-scanning path. The next second surface reflection can preferably be the directly next second surface reflection on the surface.

[0022] Such embodiments can include a third scanning mirror having a reflecting surface that scans in a direction perpendicular to the first scanning mirror between the scanning mirror and the detector, particularly in a direction parallel to the second scanning mirror (if present).

[0023] Then, such a system can further include a plurality of optical elements that define a second additional relay beam path segment from the first scanning mirror to the third scanning mirror.

[0024] One or more of the second beam path, the second relay section, the second plurality of optical elements, the third scanning mirror, the second additional relay beam path segment, etc. can provide any features and / or any benefits as set forth by any one of the (first) beam path, the second scanning mirror, the (first and / or additional) relay section, the (first) plurality of optical elements, etc. of any embodiment of the system discussed above, with necessary modifications.

[0025] The system can include a light source for directing light from a first position to a second position along the beam path and / or a target holder configured to hold a target at the second position. Such a target holder can be configured to hold a microscope objective at the second position, possibly including an objective lens system

[0026] The surface reflection can be arranged on one side of the scanning mirror, and the relay section and / or (if applicable) the second relay section can then be at least partially located on the opposite side of the scanning mirror, for example extending around the scanning mirror and preferably extending in a plane perpendicular to the scanning axis of the scanning mirror. This helps to construct the system in a relatively small space.

[0027] Associated with the foregoing and providing associated benefits, on the other hand, includes an optical method.

[0028] The method includes: guiding light from a light source from a first position to a second position along a beam path via a plurality of surface reflections on a rotating reflective surface of a scanning mirror, including relaying one surface reflection to the next surface reflection on the surface when rotating the surface.

[0029] Relaying one surface reflection to the next surface reflection on the surface when rotating the surface (including the surface of the lens) allows for reducing or preventing cross-scanning errors, as discussed elsewhere herein.

[0030] The scanning mirror can include a rotating polygonal mirror having a plurality of reflective surfaces, and one surface reflection and the next surface reflection are on the same surface.

[0031] The use of a polygonal mirror is beneficial for providing uniform illumination of the scan lines on the target; a scanning mirror that scans back and forth tends to have a sinusoidal rotational speed due to the acceleration and deceleration of the lens oscillating around the scanning axis. Therefore, the illumination of the target via surface reflections may result in a locally varying average illumination power along the scan line. A polygonal mirror is beneficial for scanning at a constant rotational speed and thus scanning along the scan line with a constant average illumination power.

[0032] One surface reflection and the next surface reflection can be at the same position.

[0033] The scanning mirror can be a first scanning mirror, and the method can then include guiding the light from the first scanning mirror to a second scanning mirror having a reflective surface, and using the second scanning mirror to scan in a second direction perpendicular to the first scanning direction of the first scanning mirror between the first scanning mirror and the second position.

[0034] The method can then include relaying the surface reflection on the first scanning mirror to the next surface reflection on the second scanning mirror.

[0035] The method can include: using a beam splitter such as a dichroic mirror and / or a polarization beam splitter to guide the light of a light source having a first optical property (e.g., at a first wavelength and / or a first polarization), and guiding the guided light from the first position to the second position along the beam path, and transmitting light having a second optical property (e.g., at a second wavelength and / or a second polarization) along the beam path and through the dichroic mirror towards a detector and / or an aperture.

[0036] The method may include detecting light of a second wavelength for a particular process of detecting at least a portion of a target disposed at a second location, such as writing, printing, cutting, welding, melting, curing, etc. In particular, the method may be used in a confocal microscope. An aperture may be used for imaging and / or spatial filtering of light of the second wavelength.

[0037] The method may include: guiding light having a first optical characteristic (e.g., having a first wavelength and / or a first polarization) of a light source from a first location to a second location along a beam path via a beam splitter (e.g., a dichroic element such as a dichroic mirror); and guiding light having a second optical characteristic (e.g., having a second wavelength and / or a second polarization) along the beam path and using the beam splitter through an aperture towards a detector, and

[0038] guiding light having a second optical characteristic (e.g., having a second wavelength) from the aperture to the detector via multiple second surface reflections on a rotating reflective surface of a scanning mirror, including relaying one second surface reflection to the next second surface reflection when rotating the surface,

[0039] wherein, when the scanning mirror includes a rotating polygon mirror having a surface with multiple reflective surfaces, one second surface reflection and the next second surface reflection may be on the same surface of the rotating polygon mirror, preferably on the same surface as one surface reflection and the next surface reflection in the above method.

[0040] The scanning mirror may be a first scanning mirror, and the method may include guiding light from the first scanning mirror to a third scanning mirror having a reflective surface, and scanning with the third scanning mirror in a third scanning direction perpendicular to a first scanning direction of the first scanning mirror between the first scanning mirror and the detector, in particular, the third scanning direction is parallel to the second scanning direction mentioned above.

[0041] The method may include holding the target at the second location and irradiating a portion of the target with light.

[0042] The target may include a microscope sample, and the method may further include: if the detector is provided, imaging at least a portion of the sample light using the detector.

[0043] Thus, improvements in rescan confocal imaging (especially confocal microscopy) can be achieved, not only in the scan and descan beam paths, but also in the rescan beam path.

[0044] In this method, relaying one surface reflection to the next surface reflection may include directing light from one surface reflection to the next surface reflection on the opposite side of the scanning mirror, e.g., at least partially around the scanning mirror and preferably in a plane perpendicular to the scanning axis of the scanning mirror. Additionally or alternatively, if applicable, relaying one second surface reflection to the next second surface reflection may include directing light from one second surface reflection to the next second surface reflection on the opposite side of the scanning mirror, e.g., at least partially around the scanning mirror and preferably in a plane perpendicular to the scanning axis of the scanning mirror.

[0045] Accordingly, an optical system is provided herein that includes a scanning mirror having a reflective surface, particularly a multi-faceted mirror having a plurality of reflective surfaces;

[0046] One or more first optical elements that define a first beam path segment from a light source to a surface location of the scanning mirror to provide a first surface reflection of light from the light source, thereby providing once-reflected light;

[0047] One or more second optical elements that define a second beam path segment from surface location to surface location to provide a second surface reflection of light from the light source, thereby providing twice-reflected light;

[0048] One or more third optical elements that define a third beam path segment from the surface location towards a target location to direct the twice-reflected light towards the target location;

[0049] Wherein, the one or more second optical elements include a relay optical system that is arranged to define the second beam path segment as a relay beam path from a first reflection to a second reflection.

[0050] The scanning mirror may be a faceted mirror having a plurality of reflective surfaces. The surface location may be determined by at least a portion of the surface and / or by the position where or expected to be where the surface of the faceted mirror is located during rotation of the faceted mirror to cause a surface reflection.

[0051] The third optical element may include a second scanning mirror having a reflective surface, and the third optical element may then optionally include an additional relay optical system that is arranged to define a portion of the third beam path segment as a relay beam path from the surface location to a surface reflection location on the second scanning mirror to provide additional reflected light from the twice-reflected light and direct the additional reflected light to the target location.

[0052] The optical system may include a detector and / or an aperture. The aperture may have a fixed size or an adjustable size; e.g., an adjustable aperture.

[0053] One or more of the first optical element, the second optical element, or the third optical element may include a beam splitter for guiding (e.g., transmitting) light having a first optical property (e.g., having a first wavelength and / or a first polarization) in one direction along a respective one of the first beam path segment, the second beam path segment, and the third beam path segment, and guiding (e.g., reflecting) light having a second optical property (e.g., having a second wavelength and / or a second polarization) differently in another direction along a respective one of the first beam path segment, the second beam path segment, and the third beam path segment.

[0054] The optical system may include one or more fourth optical elements that define a fourth beam path segment from the aperture to the second surface position (which may be the same as the (first) surface position) of the scanning mirror to provide a third surface reflection, thereby providing triple-reflected light;

[0055] One or more fifth optical elements that define a fifth beam path segment from the surface position to the surface position to provide a fourth surface reflection, thereby providing quadruple-reflected light;

[0056] One or more sixth optical elements that define a sixth beam path segment from the fourth surface position toward a second target position, particularly a detector position, to guide the quadruple-reflected light toward the second target position;

[0057] Wherein, the one or more fifth optical elements include a relay optical system that is arranged to define the fifth beam path as a relay beam path from the third surface reflection to the fourth surface reflection.

[0058] The sixth optical element may include a third scanning mirror having a reflective surface and may optionally include a second additional relay optical system that is arranged to define a portion of the sixth beam path segment as a relay beam path from the fourth surface position to a surface reflection position on the third scanning mirror to provide a second additional reflected light from the quadruple-reflected light and guide the second additional reflected light to the second target position. Description of the Drawings

[0059] The above aspects will be explained in more detail below with reference to the drawings, which illustrate a plurality of embodiments by way of example.

[0060] Figure 1 A multifaceted mirror and some basic concepts are shown;

[0061] Figure 2 The use of a multifaceted mirror is shown;

[0062] Figure 3 A relay system is shown;

[0063] Figure 4 shows a first embodiment of an improved optical system;

[0064] Figure 5 shows a second embodiment of an improved optical system;

[0065] FIG. 6A shows the cross-scan error measurement results of the Figure 3 system as a comparative example; FIG. 6B shows the cross-scan error measurement results of the Figure 5 embodiment;

[0066] Figure 7 shows a third embodiment of an improved optical system;

[0067] Figure 8 shows a fourth embodiment of an improved optical system. DETAILED DESCRIPTION

[0068] It should be noted that the drawings are schematic and not necessarily drawn to scale, and details that are not necessary for understanding the present invention may have been omitted. Unless otherwise specified, terms such as "upward", "downward", "below", "above", etc. refer to the embodiments oriented as in the drawings. In addition, elements that are at least substantially the same or perform at least substantially the same function are denoted by the same numerals, which may be individualized with alphabetical suffixes.

[0069] Furthermore, unless otherwise specified, terms such as "detachable" and "detachably connected" are intended to mean that the corresponding components can be disconnected substantially without damaging or destroying either component, e.g., not including structures where the components are integral (e.g., welded or molded as one piece), but including structures where the components are attached by mating connectors, fasteners, releasable self-fastening features, etc. The verb "facilitate" is intended to mean "make easier and / or less complex", rather than "enable".

[0070] Figure 1 Shows a polygon mirror 1 as an exemplary scanning mirror, which has a lens 3 provided with a plurality of mirror surfaces 5 (e.g., eight surfaces 5), and is attached to a shaft 7 that rotates about its central axis A.

[0071] Each surface 5 is planar and has a surface normal. A light beam incident on the surface will be reflected on the surface; in this document, for the purpose of distinguishing it from other reflections, "surface reflection" is used to denote the reflection on the reflecting surface of a scanning mirror (e.g., a polygon mirror surface). Ideally, the surface normal of each surface 5 is radial and in a radial plane with respect to the axis A.

[0072] Figure 2 Shows a view in the axial direction along the axis A (hereinafter also referred to as "top view"), whileFigure 1 is a view of a portion of the multifaceted mirror 3 (side view) and of the light source 9 (here a laser), which light source 9 causes a light beam to travel along a light beam path P (light beam segments P1, P2) from the light source 9 to the camera 11 or other target via a surface reflection FR on the surface 5 of the multifaceted mirror 3. In Figure 2 the light beam path is also defined by lenses 13, 15 (e.g., a collimating lens 13 and an imaging lens 15).

[0073] Cross-scan errors can be caused by the elevation angle ε or -ε of the normal relative to the ideal direction (upward or downward in Figure 1 ; here the error is shown as a symmetric error) in relation to the tangential plane mechanical angle relative to the axis A, as shown in the figure. Thus, a light beam L1 incident on the surface 5 in the radial direction will be reflected as a reflected light beam R1 (R1) deviated from the radial plane by an angle 2ε (-2ε), as indicated.

[0074] Cross-scan errors can be caused by the wobbling of the surface relative to the ideal and fixed axis direction and / or by the surface normal of different orientations of different surfaces of the multifaceted mirror in the case of a multifaceted mirror. According to Marshall and Stutz mentioned above, the dynamic track error of the multifaceted scanner as a whole can be defined as the total mechanical angle change of the surface perpendicular to the scan direction. This is the peak-to-peak (P2P) mechanical change, which results in twice the optical change.

[0075] Thus, each passing surface has a certain angular optical "zero-to-peak" (Z2P) error with respect to the "expected" surface normal. A relay optical system can be used to invert and reverse scan the cross-scan errors caused by the surface normal elevation axis errors, especially the Z2P errors.

[0076] Figure 3 A relay optical system 17 (or simply "relay system" / "relay optics") is indicated, which is known per se. For example, it can include a set of two lenses 19, which two lenses 19 have a front focal length and a rear focal length f, and the lenses 19 are operatively arranged to have coinciding foci along the optical axis (not indicated), thereby creating three focal planes FP1, FP2, FP3 along and perpendicular to the optical axis. The lenses 19 can be the same or different, and the same ones are preferably used. A collimated light beam propagating along the optical axis will be focused between the lenses 19 on the optical axis and will propagate in the reverse direction around the optical axis (OA) after passing through the relay section 19. As Figure 2 shown, a collimated light beam CB propagating at an angle 2ε to the optical axis will be focused between lenses 19 offset from the optical axis and will propagate in the reverse direction relative to the optical axis after passing through the relay section 19. Thus, the angle 2ε turns four focal lengths f along the optical axis and the sign changes to -2ε.

[0077] This angle is equal but negative at this point compared to the starting position. These two characteristics of the relay optical system (relaying and sign inversion of any incident angle) can be used to eliminate unwanted cross-scanning errors by simply relaying the beam scanned by the polygonal face back to the same polygonal face, as also shown below. As explained with respect to Figure 1 As explained, the beam reflected at the reflection position on the reflecting surface 5 has an orientation error (e.g., elevation error +ε) with respect to the optical axis, and an error in the +2ε direction with respect to the optical axis will be obtained. If the first focal plane FP1 of the relay optical system 17 coincides with the reflection position, the beam will be focused in the second focal plane FP2 offset from the optical axis, and after passing through the relay optical system 17, the beam will propagate at an inverted angle of -2ε with respect to the optical axis. If the third focal plane FP3 coincides with the position of the reflecting surface 5, the reflecting surface 5 has an elevation error of -ε opposite to the surface that caused the initial reflection, and the beam is further reflected while negating the initial error, so that the beam then propagates along the optical axis again.

[0078] Figure 4 Indicates the optical system 100 as a first embodiment. Note that in order to clarify the general structure of any of the figures herein, each figure is schematic and not drawn to scale, and the beam angles may not be correct upon reflection.

[0079] The optical system 100 includes a scanning mirror 103 having a reflecting surface 105 and a plurality of optical elements (e.g., static mirrors M1, M2), which define a beam path P (with path segments P1 - P5) from a light source 109 at a first position via a plurality of surface reflections FR1, FR2 on the surface 105 to a target 111 at a second position. The optical system 100 further includes a relay optical system 117 that provides a relay section P2 - P4 from one surface reflection FR1 to the next surface reflection FR2: the reflection positions of the surface reflections FR1, FR2 on the surface 105 are located at the corresponding focal planes of the relay optical system 117.

[0080] As indicated by the arrows, the scanning mirror 103 can rotate about a scanning axis (not shown), causing a related rotation of the beam path segments. The surface 105 is scanned and rotated about the scanning axis at a scanning angle of 2ζ, which may produce an angular error ε, resulting in a doubling of the scanning deflection of the beam segments of each surface reflection FR1, FR2, and the angular error ε is eliminated due to the relay section P2 - P4.

[0081] Figure 5Indicates an optical system 200 as a second embodiment, which includes a rotating polygon mirror 203 as a scanning mirror having a reflecting surface 205, and a plurality of optical elements (e.g., mirrors M1, M2), the plurality of optical elements defining a beam path P (having path segments P1 - P5) from a laser as a light source 209 at a first position to a camera 211 at a second position, the beam path P passing through a plurality of surface reflections FR1, FR2 on the surface 205 along the beam path P. Different from Figure 4 , here the surface reflections FR1, FR2 are at the same position on the surface. The optical system 200 further includes a relay system 217, which provides a relay section (P2 - P4) from one surface reflection FR1 to the next surface reflection FR2: the reflection positions of the surface reflections R1, R2 on the surface 205 are located at corresponding focal planes of the relay system 217. Note that as an option, the relay section (P2 - P4) intersects at least one other beam segment, here the beam path segment P1. This is beneficial for a compact construction.

[0082] To test the effectiveness of the proposed method, an eight-sided rotating polygon scanner was used for comparison Figure 2 and Figure 5 settings. For each face, a collimated beam is reflected from the polygon face, and directly measured ( Figure 2 ) or first relayed back to the same polygon face ( Figure 5 ). The beam reflected from the polygon is (finally) focused onto the image plane of the camera, and the position of the resulting focused spot is determined. FIGS. 6A and 6B show the deviations of the eight faces as measurement results, the deviations in FIG. 6A are from the average trend line of the comparison example of Figure 2 , and the deviations in FIG. 6B are from the average trend line of the embodiment of Figure 5 including the relay system. The relay system significantly reduces the cross-axis error.

[0083] Figure 7 Schematically shows an optical system 300 for rescan confocal microscopy according to this concept.

[0084] The system 300 includes a rotating mirror 303, which includes a reflecting surface 305. Here, the mirror 303 is a polygon mirror, and the mirror 303 and thus the surface 305 rotate about an axis in the Y direction in the X - Z plane.

[0085] A plurality of optical elements including a dichroic mirror DM define a beam path P (having segments P1 - P8) from a laser light source 309 to a microscope 311, the beam path P passing through a plurality of surface reflections FR1, FR2 on the surface 305 along the beam path segments P1 - P8, including a first relay section 317A from one surface reflection on the surface to the next surface reflection.

[0086] System 300 further includes a dichroic mirror DM that serves as a beam splitter, a pinhole PH that serves as an aperture, and a CMOS camera 321 that serves as an exemplary detector.

[0087] A second plurality of optical elements define a second beam path R having a segment R1-R8 from the aperture PH via a plurality of second surface reflections FR3, FR4 to the detector 321, the plurality of second surface reflections FR3, FR4 including a second relay segment 317B from one second surface reflection FR3 to the next second surface reflection FR4 on the same surface as the surface reflections FR1, FR2.

[0088] In system 300, the scanning mirror 303 is the first scanning mirror. The optical system 300 includes a second scanning mirror 323 having a reflective surface and disposed along the beam path P between the first scanning mirror 303 and the microscope 311. The second scanning mirror 323 is arranged to scan light along the beam path P in a direction perpendicular to the first scanning mirror 303, and the second scanning mirror 323 rotates about an axis in the X-Z plane. A plurality of optical elements 317C define another relay segment P6-P7 from the surface reflection FR2 on the first scanning mirror 303 to the surface reflection on the second scanning mirror 323.

[0089] The optical system 300 further includes a third scanning mirror 325 having a reflective surface and disposed along the beam path R between the first scanning mirror 303 and the detector 321. The third scanning mirror 325 is arranged to scan light along the beam path R in a direction perpendicular to the first scanning mirror 303, and the third scanning mirror 325 rotates about an axis in the X-Z plane. A plurality of optical elements 317D define a second additional relay segment R6-R7 from the surface reflection FR4 on the first scanning mirror 303 to the surface reflection on the third scanning mirror 325.

[0090] The laser 309 provides light of a first wavelength along a segment P1-P8 of the beam path P along a sample (not shown) in the microscope 311. The sample light emitted from the sample is collected and guided in the opposite direction along a segment P8-P1 of the beam path P; the sample light of the second wavelength is transmitted through the dichroic mirror DM along the beam path segment P9-P10 towards the aperture PH. The aperture PH is disposed between the lenses BP, AP, and the lenses BP, AP are focused on the aperture PH in a spatial filtering arrangement.

[0091] The sample light passing through the aperture PH is guided by the second plurality of optical elements along the second beam path R (R1-R8) to the camera 321.

[0092] As described above, the scanning rotation of the surface 305 about the scanning axis (not shown) by the scanning angle 2ζ as indicated by the arrow (which may vary to εζ) causes the corresponding beam segments P3 - P7 to be scanned and rotated accordingly as indicated by the corresponding arrows to the second scanning mirror 323 and from there to the sample arranged appropriately (e.g., in the focal point of the microscope 311). By scanning the second scanning mirror 323 (or: "second scanning / de-scanning mirror") in the vertical direction, the beam is scanned on the sample in two directions (i.e.: 2D scanning).

[0093] Conversely, the emitted light from the sample is de-scanned in two directions by the two scanning mirrors 323, 303 on the reverse path to reach the pinhole PH. After that, the sample light that is scanned by the first mirror surface 305 and then guided through the pinhole PH in the vertical direction by the third scanning mirror 325 or "second re-scanning mirror" and along the second beam path R (R1 - R8) to the camera 321 is also scanned on the image plane of the camera 321, just like the scanning explained above.

[0094] The beam path segments P2 - P10 - R1 - R2 form a static path, and all other path segments are dynamic when the first mirror 303 and possibly the second and / or third scanning mirrors 323, 325 rotate.

[0095] By providing relay optical systems 317A and 317C / relay segments P3 - P5 and P6 - P7 respectively, the cross-scanning error of the first reflecting mirror (surface) is canceled out onto the reflection of the second reflecting mirror surface, and the second reflecting mirror can scan the sample. According to this principle, a plurality of additional optical elements can be provided to convert the shown beam path P8 into a beam path from the second scanning reflecting mirror 323 to the microscope 311 via multiple surface reflections on the reflecting surface of the second scanning reflecting mirror 323, which beam path includes relay segments from one surface reflection on the reflecting surface to the next surface reflection, so as to reduce or eliminate the cross-scanning error from the second scanning reflecting mirror 323. With the necessary modifications, the same applies to the relay systems 317B and 317D / relay segments R3 - R5 and R6 - R7 respectively for the third scanning reflecting mirror 325 and the beam path R8 of the camera 321.

[0096] In Figure 7 several horse heads are indicated; the horse heads show the "sample image" as seen if looking directly at the incident sample emission beam at this point along the optical path. Importantly, the horse heads "look" in the same direction to which the (re-)scanning beam moves. Again, note that the image is not drawn to scale, and the beam angles on the surfaces are also incorrect, deliberately so for clarity.

[0097] Figure 8 Another optical system for re-scanning confocal microscopy according to this concept is shown.

[0098] System 400 includes a scanning mirror 403, which includes a reflecting surface 405 that rotates about a scanning axis perpendicular to the plane of the figure; the mirror 403 can be a rotating polygon mirror. System 400 includes a dichroic mirror DM as a beam splitter and a pinhole PH. Figure 8 Also shown are a light source 409 for emitting excitation light of a first wavelength, a microscope 411, and a detector 321.

[0099] A plurality of optical elements includes the dichroic mirror DM, static mirrors SM1 - SM4, and lenses SL1 - SL2, which define a beam path P for the excitation light from the light source 409 to the microscope 411 (sample), along beam path segments P1 - P7 via multiple reflections PF on the surface 405, thereby providing a scanned beam path. Note that in this embodiment, the dichroic mirror transmits the light from the light source 409.

[0100] Lenses SL1 and SL2 provide a relay optical system that defines a first relay segment P2 - P6 in the beam path P from one reflection PF on a surface to the next reflection PF on a surface.

[0101] Similar to Figure 7 the system and explanation, sample light of a second wavelength from the sample is guided along the beam path P in a direction opposite to that along segments P7 - P1, and after being reflected by the dichroic mirror DM, P8 is guided onto the pinhole PH, thereby providing an unscanned beam path.

[0102] The sample light passing through the pinhole PH is guided by a second plurality of optical elements including static mirrors SPM, RM1 - RM4, and lenses RL1, RL2 along a second beam path R (having path segments R1 - R8) defined by the second plurality of optical elements to the detector 321, thereby forming a rescan beam path. Lenses RL1 and RL2 provide a second relay system that defines a second relay segment R3 - R7 from one reflection PF on a surface in the beam path R to the next reflection PF on a surface.

[0103] Paths P1 - P8 - R1 - R2 are static paths.

[0104] The relay segment P2 - P6 and the second relay segment R3 - R7 are partially located on the side of the scanning mirror 403 opposite to the reflections on the surface, extend around the scanning mirror 406, and optionally extend in a plane perpendicular to the scanning axis of the scanning mirror 403. The relay beam segments optionally cross other beam path segments.

[0105] The present disclosure is not limited to the above embodiments and can vary in many ways within the scope of the claims.

[0106] For example, unless otherwise explicitly stated, elements and aspects discussed with respect to a particular embodiment or in connection with a particular embodiment may be combined appropriately with elements and aspects of other embodiments.

Claims

1. An optical system (100, 200, 300, 400), comprising: A rotating scanning mirror (103, 203, 303, 403) having a reflecting surface (105, 205, 305, 405), and A plurality of optical elements (117, 213, 215, 217, 317A, 323, M1 - M2, CL, SL, SL1 - SL2, SM1 - SM4) defining a beam path (P) from a first position (at 109, 209, 309, 409) via multiple reflections (FR1, FR2, PF) on the surface (105, 205, 305, 405) to a second position (at 111, 211, 311, 411). Characterized in that it includes a relay section (100&200: P2 - P4; 300: P3 - P5; 400: P2 - P6) with reflections from one surface (FR1, FR2, PF) to the next (FR2, FR1, PF).

2. The optical system (100, 200, 300, 400) according to claim 1, wherein, The scanning mirror (103, 203, 303, 403) includes a rotating multi - mirror having a plurality of reflecting surfaces (105, 205, 305, 405), and the one surface reflection (FR1, FR2, PF) and the next surface reflection (FR2, FR1, PF) occur on the same surface (105, 205, 305, 405).

3. The optical system (100, 200, 300, 400) according to any one of the preceding claims, wherein, The one surface reflection (FR1, FR2, PF) and the next surface reflection (FR2, FR1, PF) occur at the same position.

4. The optical system (300) according to any one of the preceding claims, wherein, The scanning mirror (303) is a first scanning mirror, and the optical system includes a second scanning mirror (323) having a reflecting surface between the first scanning mirror (303) and the second position (311), and the second scanning mirror (323) is arranged to scan in a direction different from that of the first scanning mirror (303), preferably in the vertical direction.

5. The optical system (300) according to claim 4, including a plurality of optical elements (317C) defining another relay section (P6, P7) of reflections from a surface (FR2) on the first scanning mirror (303) to a surface on the second scanning mirror (323).

6. The optical system (300, 400) according to any one of the preceding claims, including a detector (321, 421) and / or an aperture (PH), such as a pinhole, And including a beam splitter (DM) for guiding, for example, reflecting light from a light source (309, 409) having a first optical property along the beam path (P) from the first position (309, 409) to the second position (311, 411), and guiding light having a second optical property along the beam path (P) and through the beam splitter (DM) in a different way, for example, transmitting it, to the detector (321, 421) and / or the aperture (PH).

7. The optical system (300, 400) according to any one of the preceding claims, comprising a detector (321, 421) and an aperture, such as a pinhole (PH), possibly the optical system (300, 400) according to claim 6, and comprising a beam splitter (DM), such as a dichroic element, such as a dichroic mirror, for guiding light having a first optical characteristic, such as light at a first wavelength, from the light source (309, 409) from the first position (at 309, 409) to the second position (at 311, 411) and for guiding light having a second optical characteristic, such as light at a second wavelength, preferably from the second position (at 311, 411) through the aperture (PH) towards the detector (321, 421), A second plurality of optical elements (AP, M4 - M6, 317B, 317D, 325, RL) define a second beam path (R) from the aperture (PH) via a plurality of second surface reflections (FR3, FR4) to the detector (321), the plurality of second surface reflections including a second relay section (R3 - R5) from one second surface reflection (FR3) to the next second surface reflection (FR4), Among them, When the scanning mirror (303) comprises a rotating polygon mirror having a plurality of reflecting surfaces (305), the one second surface reflection (FR3) and the next second surface reflection (FR4) may be on the same surface (305) of the rotating polygon mirror, preferably on the same surface as the one surface reflection (FR1) and the next surface reflection (FR2) according to claim 2.

8. The optical system (300) according to any one of the preceding claims, comprising a third scanning mirror (325), the third scanning mirror having a reflecting surface that scans a direction perpendicular to the first scanning mirror (303) between the scanning mirror (303) and the detector (321), in particular in the case of the optical system (300) according to at least claim 4, the reflecting surface scans a direction parallel to the second scanning mirror (323).

9. The optical system (300) according to claim 8, comprising a plurality of optical elements (317D), the plurality of optical elements (317D) defining a second additional relay beam path segment (R6 - R7) from the first scanning mirror (303) to the third scanning mirror (325).

10. The optical system (100, 200, 300, 400) according to any one of the preceding claims, comprising a light source (109, 209, 309, 409) for guiding light from the first position (at 109, 209, 309, 409) to the second position (at 111, 211, 311, 411) along the beam path (P).

11. The optical system (100, 200, 300, 400) according to any one of the preceding claims, comprising a target holder configured to hold a target at the second position (at 111, 211, 311, 411).

12. The optical system (100, 200, 300, 400) according to claim 11, wherein, The objective holder is configured to hold the microscope objective at the second positions (at 111, 211, 311, 411), and the objective holder may include an objective lens system.

13. The optical system (400) according to any one of the preceding claims, wherein, The plane reflection (PF) is arranged on one side of the scanning mirror (403). Wherein, the relay section (P2 - P6) and / or, if present, the second relay section (R3 - R7) is at least partially located on the opposite side of the scanning mirror (403), for example, extends around the scanning mirror (403), and preferably extends in a plane (X - Z plane) perpendicular to the scanning axis of the scanning mirror.

14. A method, comprising: Along the light beam path (P), light from a light source is guided from a first position (109, 209, 309, 409) to a second position (111, 211, 311, 411) via a plurality of plane reflections (FR1, FR2, PF) on the rotating reflecting surface (105, 205, 305, 405) of the scanning mirror (103, 203, 303, 403). It is characterized in that while rotating the surface (105, 205, 305, 405), one plane reflection (FR1, FR2, PF) is relayed to the next plane reflection (FR2, FR1, PF) on the surface.

15. The method according to claim 14, wherein, The scanning mirror (103, 203, 303, 403) includes a rotating polygonal mirror having a plurality of reflecting surfaces (105, 205, 305, 405), and the one plane reflection (FR1, FR2, PF) and the next plane reflection (FR2, FR1, PF) are on the same surface (105, 205, 305, 405).

16. The method according to any one of claims 14 - 15, wherein, The one plane reflection (FR1, FR2, PF) and the next plane reflection (FR2, FR1, PF) are at the same position.

17. The method according to any one of claims 14-16, wherein, The scanning mirror (303) is a first scanning mirror, and the method includes guiding light from the first scanning mirror (303) to a second scanning mirror (323) having a reflecting surface, and using the second scanning mirror (323) to scan in a second direction perpendicular to the first scanning direction of the first scanning mirror (303) between the first scanning mirror (303) and the second position (311).

18. The method according to claim 17, including relaying the plane reflection (FR2) on the first scanning mirror (303) to the next plane reflection on the second scanning mirror (323).

19. The method according to any one of claims 14 - 18, comprising guiding light of a light source (309, 409) having a first optical property, e.g., having a first wavelength, e.g., reflected light, with a beam splitter (DM), and guiding the guided light along the beam path (P) from a first position (at 309, 409) to a second position (at 311, 411), and guiding differently, e.g., emitting light having a second optical property, e.g., having a second wavelength, along the beam path (P) and through the beam splitter (DM) towards the detector (at 321, 411), e.g., transmitting light having a second optical property, e.g., having a second wavelength, along the beam path (P) and through the beam splitter (DM) towards the detector (321, 421) and / or an aperture (PH), such as a pinhole.

20. The method according to any one of claims 14 - 19, further comprising guiding, via a beam splitter (DM), e.g., a dichroic element such as a dichroic mirror, light of a light source (309, 409) having a first optical property, e.g., having a first wavelength, from a first position (at 309, 409) to a second position (at 311, 411) along the beam path (P), and guiding light having a second optical property, e.g., having a second wavelength, along the beam path (P) and using the beam splitter (DM) towards a detector (321, 421) through an aperture (PH) such as a pinhole, and guiding light having a second optical property, e.g., having a second wavelength, from the aperture (PH) to the detector (321, 421) via a plurality of second surface reflections (FR3, FR4, PF) on a rotating reflecting surface (305, 405) of the scanning mirror (303, 403), including relaying one second surface reflection (FR3) to the next second surface reflection (FR4) while rotating the surface (305, 405), Among them, when the scanning mirror (303, 403) comprises a rotating polygonal mirror having a plurality of reflecting surfaces (305, 405), the one second surface reflection (FR3, PF) and the next second surface reflection (FR4, PF) can be on the same surface (305, 405) of the rotating polygonal mirror (303, 403), preferably on the same surface as the one surface reflection and the next surface reflection in the method according to at least claim 15.

21. The method according to any one of claims 14 - 20, wherein, The scanning mirror (303) is a first scanning mirror, and the method comprises guiding light from the first scanning mirror (303) to a third scanning mirror (325) having a reflecting surface, and scanning with the third scanning mirror (325) in a third scanning direction perpendicular to a first scanning direction of the first scanning mirror (303) between the first scanning mirror (303) and the detector (321), in particular, in the method according to at least claim 17, the third scanning direction is parallel to the second scanning direction.

22. The method according to any one of claims 14 - 21 further comprises holding the target at the second position (at 111, 211, 311, 411) and irradiating a part of the target with the light.

23. The method according to any one of claims 14-22, wherein The target comprises a microscope sample, and in the case of the method according to at least claim 19 or 20, the method further comprises imaging at least a part of the sample light with the detector (321, 421).

24. The method according to any one of claims 14-23, wherein Relaying the one surface reflection (PF) to the next surface reflection (PF) comprises: guiding light from the one surface reflection (PF) to the next surface reflection (PF) on the opposite side of the scanning mirror (403), for example at least partially around the scanning mirror (403) and preferably in a plane (X - Z plane) perpendicular to the scanning axis of the scanning mirror (403); and / or if applicable wherein relaying the one second surface reflection (PF) to the next second surface reflection (PF) comprises guiding light from the one second surface reflection (PF) to the next second surface reflection (PF) on the opposite side of the scanning mirror (403), for example at least partially around the scanning mirror (403), and preferably in a plane (X - Z plane) perpendicular to the scanning axis of the scanning mirror (403).

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