Optical system having a filter carrier

Abstract

The invention relates to an optical system, which comprises a light source (1), a detector (6) and a sample holder. A first beam path (2) runs from the light source (1) to the sample holder, and a second beam path (5), which is separated from the first beam path (2), runs from the sample holder to the detector (6). The optical system also has a filter carrier (9, 14, 20, 21, 22, 23), which has a plurality of filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b). Filter pairs are formed by two filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) each. The filter carrier (9, 14, 20, 21, 22, 23) is disposed in the optical system such that the first beam path (2) runs through one filter (10a, 11a, 12a, 13a) of a filter pair and the second beam path (5) runs through the other filter (10b, 11b, 12b, 13b) of the same filter pair.

Description

[0001] Description

[0002] title

[0003] Optical system with filter carrier

[0004] The present invention relates to an optical system with a filter carrier which has a plurality of filters combined in filter pairs and to a use of the filter carrier in an optical system.

[0005] State of the art

[0006] In optical systems, individual components such as optical filters are automatically exchanged during operation. Mechanical exchange units are used for this, which exchange the filters in front of an aperture. One example of this is filter wheels, where the filters are arranged on a rotating disk and rotated in front of the aperture. Many optical systems have two apertures for two different light paths. The two filters are selected independently of each other and form a filter pair. A trivial solution is to use two filter wheels, with one filter wheel covering each aperture and each filter wheel only carrying the filters for the corresponding aperture. The two filter wheels can then be provided with a common drive.

[0007] In US 6,313,960 B2, it is proposed to arrange all filters on a common filter wheel. The filters are arranged along a circle around the center of rotation of the filter wheel at equal distances from it. The two filters of a filter pair are arranged opposite each other on a line with the center of rotation. The two apertures are arranged in a housing such that they are each spaced from the center of rotation by the radius of the circle of the filters and are also arranged on a line with the center of rotation. A filter pair thus occupies both apertures simultaneously. The filter wheel is used here for two identical beam paths. So-called "filter cubes" are also known from fluorescence microscopy; these consist of two filters and a dichroic mirror or a beam splitter. The filter cubes are mounted on a wheel, allowing both filters to be changed simultaneously.One filter is placed in the beam path from the source to the dichroic mirror, and another filter is placed in the beam path between the dichroic mirror and the detector. A common beam path is used from the dichroic mirror to the sample.

[0008] Disclosure of the invention

[0009] An optical system is proposed that includes a light source, a detector, and a sample holder. A first beam path runs from the light source to the sample holder, and a second beam path runs from the sample holder to the detector. The first and second beam paths meet only at the sample holder, but are otherwise spatially separated. The light from the light source and the light to the detector thus travel along separate paths.

[0010] The optical system also has a filter carrier which has a plurality of optical filters. Two filters are selected to match each other for a particular application and form a filter pair. The filters of the filter pair can preferably block different frequency ranges. The filter carrier is arranged in the optical system such that the first beam path runs through one filter of a filter pair and the second beam path runs through the other filter of the same filter pair. Thus, one side of the filter pair is assigned to the first beam path from the light source to the sample and the other side of the filter pair is assigned to the second beam path from the sample to the detector. By one side of the filter pairs it should be understood that these filters are assigned to the same beam path and thus the same aperture and do not form a common filter pair.The filter carrier makes it easy to switch between the filter pairs, and the matching filters of each filter pair are placed in the two completely separate beam paths. Specifically, the optical system is a fluorescence measurement system. Excitation light from the light source travels along the first beam path and through the first filter of the filter pair to the sample. The filter can be a bandpass filter that only allows the excitation light to pass through. The excitation light excites fluorescence in the sample, causing it to emit fluorescent light. The fluorescent light is directed into the second beam path and, separated from the excitation light, travels along the second beam path through the second filter of the filter pair to the detector, which records the fluorescent light.The second filter allows the fluorescent light to pass through and blocks the frequencies of the excitation light, preventing any scattered excitation light from reaching the detector. In a fluorescence measurement system, the filter pairs can be selected depending on the excitation light. Using the filter carrier is advantageous here, as the filter pair can be easily swapped when the excitation light changes.

[0011] In one variant, the filter carrier can be a filter wheel. The filter wheel is preferably a disk, in particular a circular disk, and the filters are arranged on the front side. In particular, the filters have a square shape. Such a square shape is easier to manufacture than, for example, a round shape. The filter wheel can be rotated about a center of rotation, which is preferably located at the center of the filter wheel. This moves the filters and allows them to be aligned with a corresponding aperture. All filters belonging to one side of the filter pairs are arranged at the same distance from the center of rotation. This applies to both sides of the filter pairs. By one side of the filter pairs, it should be understood that these filters are assigned to the same beam path and thus the same aperture and do not form a common filter pair.For each side, the corresponding aperture is positioned at the same distance from the center of rotation as the filters, so that the filters on that side can be aligned with the corresponding aperture. Preferably, the filters are equidistant from their neighbors on the same side. This allows the filter wheel to be rotated by the same angle when changing filters.

[0012] Preferably, however, the two filters of a filter pair are not at the same distance from the center of rotation. Thus, the filters of the filter pair do not lie on a circle with the same radius around the center of rotation, but can be distributed on the filter wheel. Alternatively or additionally, it can be provided that the two filters of a filter pair and the center of rotation do not lie on a common straight line. Thus, the filters of the filter pair are arranged offset in relation to the center of rotation. As a result, in both methods, the surface of the filter wheel is better utilized for the arrangement of the filters. Accordingly, the diameter of the filter wheel can be selected to be smaller, which is particularly advantageous in terms of the small installation space, but also in terms of lower material costs. A combination of the two methods further improves the utilization of the surface area. The apertures are arranged such that they are aligned with a filter pair in at least one position of the filter wheel.Since, as described above, the filters on one side of the filter pairs are arranged at the same distance from the center of rotation for each of the two sides, the respective filters are aligned with the apertures by turning the filter wheel.

[0013] A preferred arrangement of the filters on the filter wheel represents two concentric circles with different radii around the center of rotation. The filters on one side of the filter pairs are arranged along one circle, and the filters on the other side are arranged along the other circle. Because the two circles have different radii, the filters in a filter pair are at different distances from the center of rotation. Additionally, the filters can be arranged on the circles so that the filters in a filter pair do not form a common line with the center of rotation.

[0014] For example, eight filters forming four filter pairs can be provided. A particularly preferred arrangement of four filter pairs on the filter wheel represents a square whose center lies at the center of rotation of the filter wheel. The filters are arranged along the sides, including the corners, of the square and are preferably distributed equidistantly along the sides. In particular, the filters on one side of the filter pairs are arranged at the corners of the square. Thus, one of the circles described above runs through the corners of the square. The filters on the other side of the filter pairs are then each arranged at a point on the side of the square, for example the center point of the respective side. Thus, the other circle runs through these points.Due to its symmetry, the square offers a simple way of arranging the filters of a filter pair at different distances from the center of rotation and at the same time arranging the filters on one side of the filter pairs at the same distance from the center of rotation. Especially with square filters, this arrangement can save space on the filter wheel compared to an arrangement along a single circle. The eight filters can advantageously be arranged along the sides of the square by arranging one of the filters in the filter pair in a corner of the square and the corresponding other filter on one side of the square, particularly preferably in the center of the side. Accordingly, all filters on one side of the filter pairs are arranged in the corners of the square and all filters on the other side of the filter pairs are arranged on the sides of the square, particularly preferably in the center of the sides.The distance from the center of rotation to a corner of the square is the greatest and, due to symmetry, is the same for every corner. The distance to a side of the square, and especially to the center of the side, is smaller and, due to symmetry, can also be chosen to be the same for all sides. Furthermore, starting from a corner, only the opposite corner of the square and no other points on the sides of the square lie on a common line with the center of rotation.

[0015] For example, ten filters forming five filter pairs can be provided, with five filters on one side of the filter pairs arranged along an inner circle on a pentagon, and another five filters on the other side of the filter pairs arranged along an outer circle on a pentagon. Thus, the five filters on the inner circle form a pentagon, and the five filters on the outer circle form another pentagon surrounding the first-mentioned pentagon.

[0016] In general, for n (ne N) filter pairs, the filters are preferably arranged on n-corners.

[0017] In a further variant, the filter carrier can be a filter slider on which all of the filters are arranged. The filter slider can be moved along a straight line in the optical system. The filters on each side of the filter pair are arranged in rows one behind the other. The filters are the same distance from each other, both on each side of the filter pair and within the filter pairs. The rows on each side of the filter pair are arranged in the direction of the straight line along which the filter slider is moved. The filter slider allows the filters of a filter pair to be moved together and brought into the two beam paths. Since the filters are all arranged on the same filter slider, only this one slider needs to be moved when changing them.

[0018] In a further variant, the filter carrier can have several individual sliders arranged one behind the other in the direction of the beam paths, which together function as a single filter carrier and are also viewed as such. Only the two filters of a single filter pair are arranged in each individual slider. In addition, two openings are provided in each individual slider. Each individual slider can be moved to a first position in which the filters of the filter pair are brought into the two beam paths. In addition, each individual slider can be moved to a second position in which the two openings are arranged in the beam paths. The individual slider with the selected filter pair is moved to the first position and the other individual sliders are moved to the second position so that the beam paths run through the openings of the other individual sliders and only pass through the selected filter pair.The individual sliders also offer the advantage of allowing multiple filter pairs to be placed in both beam paths simultaneously. This allows, for example, a high-pass filter and a low-pass filter to be used together.

[0019] Short description of the drawings

[0020] Embodiments of the invention are illustrated in the drawings and explained in more detail in the following description.

[0021] Figures 1 a and b each show a schematic representation of a first embodiment of the optical system according to the invention with a filter wheel.

[0022] Figure 2 shows a schematic representation of a second embodiment of the optical system according to the invention with a common filter slider.

[0023] Figure 3 shows a schematic representation of a third embodiment of the optical system according to the invention with several individual sliders.

[0024] Embodiments of the invention Figures 1 to 3 show several optical filters 10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b. The filters 10a, 11a, 12a, 13a marked with "a" together with the corresponding filters 10b, 11b, 12b, 13b with the same number marked with "b" form filter pairs 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b. The filters of the same filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b are designed to be complementary. The filters 5a, 6a, 7a, 8a, and 9a, marked with "a," which belong to one side of the filter pair, are hereinafter referred to as the "first filters." Accordingly, the filters 5b, 6b, 7b, 8b, and 9b, marked with "b," which belong to the other side of the filter pair, are hereinafter referred to as the "second filters." The optical systems shown here are fluorescence measurement systems and are used for fluorescence spectroscopy.For this purpose, the first filters 10a, 11a, 12a, 13a are designed as bandpass filters that only allow the excitation light to pass, and the second filters 10b, 11b, 12b, 13b can be designed as highpass or lowpass filters that block the excitation light and only allow the fluorescent light to pass.

[0025] Figures 1a and b each show a first embodiment of the optical system for fluorescence spectroscopy. A broadband light source 1, for example a white LED, a phosphor-based light source, or a gas discharge lamp, emits excitation light. The excitation light travels along a first beam path 2 to a mirror 3 and is deflected by the latter toward a sample 4. The sample 4 is held in a sample holder (not shown). The sample 4 is excited by the excitation light and emits fluorescent light along a second beam path 5. The fluorescent light travels along the second beam path 5 to a detector 6 and is received by the latter. The detector 6 is configured to detect at least selected detection bands. A semiconductor detector, in particular a photodiode, is preferably used here.In Figure 1a, the mirror 3 directs the excitation light laterally into the sample 4, so that the excitation light is radiated along the first beam path 2 from a different side than the fluorescent light is emitted along the second beam path 5. In Figure 1b, the mirror 3 directs the excitation light along the first beam path 2 over the same side as the fluorescent light is emitted along the second beam path 5 into the sample 4. In both cases, the first beam path 2 and the second beam path 5 only intersect in the sample 4. The optical system can have various optical elements that shape and direct the light. The exact design depends on the radiation characteristics of the light source 1, the active area of ​​the detector 6, and the general sample and device concept. Examples that can be used include lenses, mirrors, deflection prisms, concave mirrors, waveguides, holographic, or diffractive optical elements.A first aperture 7 is provided in the first beam path 2, and a second aperture 8 is provided in the second beam path 5. The light culminates through the apertures 7 and 8.

[0026] In the first embodiment according to Figure 1, the filters 10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b are arranged on a filter wheel 9 to cover the apertures 7, 8. The filter wheel 9 is a circular disk and is rotatably mounted about a center of rotation 2 at its center. To rotate the filter wheel 9, the optical system has a mechanical or electromechanical device (not shown here) with which the rotation can be controlled externally. As explained in detail below, the filters 10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b are aligned with the apertures 7, 8 and cover them. In this case, only one filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b simultaneously covers the two apertures 7, 8. In this embodiment, the filter pairs 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b are arranged along a square whose center lies at the rotation center of the filter wheel 9.The first filters 10a, 11a, 12a, 13a are arranged at the corners of square Q. A first concentric circle (not shown) runs through the corners of square Q, with the rotation center of filter wheel 9 as its center point, so that the first filters 10a, 11a, 12a, 13a are arranged on the first circle. The second filters 10b, 11b, 12b, 13b of the corresponding filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b are arranged at the centers of the opposite sides of the square. Starting from the corner, the same opposite side is always selected, e.g., the left opposite side. A second concentric circle, also not shown, runs through these centers, so that the second 10b, 11b, 12b, 13b are arranged on the second circle.The radius of the second circle is smaller than the radius of the first circle; accordingly, the distance from the center of rotation of the filter wheel 9 to the first filters 10a, 11a, 12a, 13a is greater than the distance from the center of rotation to the second filters 10b, 11b, 12b, 13b. The second aperture 8 is arranged so that it falls on one corner (in Figure 1, for example, the right corner) of the square, and the first aperture 7 is arranged so that it falls on the center of the opposite side of the square. The apertures 7, 8 can also be arranged the other way around.Since the center of rotation of the filter wheel 9 and the center of the square coincide, when the filter wheel 9 rotates, due to the symmetry of the square, the first filters 10a, 11a, 12a, 13a in the corners of the square pass through the first aperture 7 and, accordingly, the associated second filters 10b, 11b, 12b, 13b of the same filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b on the sides of the square pass through the second aperture 8 at the same time. The filters 10a, 11a, 12a, 13a and 10b, 11b, 12b, 13b are each arranged at the same distance from each other, so that the rotation for changing the filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b always takes place by the same angle. The corners of the square and the centers of the sides of the square are at different distances from the center of rotation of the filter wheel 9 and, moreover, are not on a common straight line with the center of rotation.

[0027] However, other geometries can be provided for the filters of the filter wheel, such as pentagons or generally n-gons.

[0028] Figures 2 and 3 show a second and third embodiment of the optical system for fluorescence spectroscopy, respectively. The optical systems according to the second embodiment and the third embodiment differ from the first embodiment only in the filter carrier. For the remaining construction, reference is made to the above description. The optical system can be designed as shown in Figure 1a or as shown in Figure 1b with regard to the mirror 3 and the path of the first beam path 2.

[0029] In the second embodiment according to Figure 2, the filters 10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b are arranged on a filter slide 14 to cover the apertures 7, 8. The filter slide 14 can be moved along the displacement direction 14. The filters 10a, 11a, 12a, 13a of one side of the filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b are arranged in a row 16 one behind the other in the displacement direction 15. Likewise, the filters 10b, 11b, 12b, 13b of the side of the filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b in a row 17 are arranged one behind the other in the displacement direction 15, in the same order as the corresponding filter of the filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b in the other row 16. The distance between the rows 16, 17 is constant and the distances between the filters 10a, 11a, 12a, 13a and 10b, 11b, 12b, 13b in the respective rows 16 and 17 are the same.The apertures 7, 8 are arranged above the two rows 16, 17 and are spaced the same distance apart as the rows 16, 17. The first aperture 7 is arranged above the row 16 of filters 10a, 11a, 12a, 13a on one side of the filter pairs 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b and the second aperture 8 is arranged above the row 17 of filters 10b, 11b, 12b, 13b on the other side of the filter pairs 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b. By moving the filter slider 14 along the direction of movement 15, a filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b covers both apertures 7, 8 at the same time.

[0030] In the third embodiment according to Figure 3, several individual sliders 20, 21, 22, 23 are provided, which together function as a filter carrier. The individual sliders 20, 21, 22, 23 are arranged one behind the other in the direction of the first beam path 2 and in the direction of the second beam path 5. A first individual slider 20 has a first filter pair 10a, 10b, a second individual slider 21 has a second filter pair 11a, 11b, a third individual slider 22 has a third filter pair 12a, 12b, and a fourth individual slider 23 has a fourth filter pair 13a, 13b. Each individual slider can be moved between a first position in which the two filters of the corresponding filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b are placed in the beam paths 2, 5, and a second position in which the two openings 24, 25 are placed in the two beam paths 2, 5, along a displacement direction.The individual sliders 20, 21, 22, and 23 can be moved independently of one another. To move the individual sliders 20, 21, 22, and 23, the optical system includes a mechanical or electromechanical device (not shown here) that allows the movement to be controlled externally. The filters of each filter pair 10a & 10b, 11a & 11b, 12a & 12b, and 13a & 13b are each equidistant from one another. Each individual slide 20, 21, 22, 23 also has an opening 24 which is arranged in the direction of displacement 26 next to a filter 10a, 11a, 12a, 13a on one side of the filter pairs 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b, and an opening 25 which is arranged in the direction of displacement 26 next to a filter 10b, 11b, 12b, 13b on the other side of the filter pairs 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b.The openings 24, 25 are spaced apart from each other at the same distance as the filters of each filter pair 10a & 10b, 11a & 11b, 12a & 12b, 13a & 13b, and are offset from the respective filters 10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b by the same distance in the same direction. The openings 24 are designed such that the first beam path 2 passes through them unhindered, and the opening 25 is designed such that the second beam path 5 passes through them unhindered when the associated individual slider 20, 21, 22,.

[0031] 23 in the second position shifts the openings 24, 25 into the beam paths 2, 5. The openings 24, 25 and the filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) serve as the aperture. In Figure 3, for example, the third individual slider 22 is in the first position and the other individual sliders 20, 21, 23 are in the second position. The excitation light thus passes along the first beam path 2 through the opening 24 of the first individual slider 20, the opening 24 of the second individual slider 21, the filter 12a of the third individual slider 22, and the opening 24 of the fourth individual slider 23. Similarly, the fluorescent light passes along the second beam path 5 through the opening 25 of the fourth individual slider 23, the filter 12b of the third individual slider 22, the opening 25 of the second individual slider 21, and the opening 25 of the first individual slider 20.

Claims

Claims 1. An optical system comprising a light source (1), a detector (6), and a sample holder, wherein a first beam path (2) extends from the light source (1) to the sample holder and a second beam path (5), which is separate from the first beam path (2), extends from the sample holder to the detector (6), characterized by a filter carrier (9, 14, 20, 21, 22, 23) comprising several filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b), wherein two filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) form a filter pair, and wherein the filter carrier (9, 14, 20, 21, 22, 23) is arranged in the optical system such that the first beam path (2) passes through a filter (10a, 11a, 12a, 13a) of a filter pair and the second beam path (5) passes through the other filter (10b, 11b, 12b, 13b) of the same filter pair.

2. Optical system according to claim 1, characterized in that the optical system is a fluorescence measurement system, wherein an excitation light passes along the first beam path (2) through one filter (10a, 11a, 12a, 13a) of the filter pair and a fluorescence light passes separately from the excitation light along the second beam path (5) through the other filter (10b, 11b, 12b, 13b) of the filter pair.

3. Optical system according to one of claims 1 or 2, characterized in that the filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) of a filter pair block different frequency ranges.

4. Optical system according to one of claims 1 to 3, characterized in that the filter carrier is a filter wheel (9), wherein the filter wheel (9) is rotatably mounted about a center of rotation.

5. Optical system according to claim 4, characterized in that the filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) of a filter pair have different distances to the center of rotation and / or the filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) of a filter pair and the The center of rotation does not lie on a common straight line. Optical system according to claim 4, characterized in that the filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) are arranged along two concentric circles around the center of rotation. Optical system according to any one of claims 1 to 3, characterized in that the filter carrier is a filter slider (14), wherein the filter slider (14) is displaceable along a straight line, and wherein the filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) on each side of the filter pair are arranged in rows in the direction of the straight line.Optical system according to one of claims 1 to 3, characterized in that the filter carrier has several individual sliders (20, 21, 22, 23) arranged one behind the other in the direction of the beam paths, wherein a filter pair (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) and two openings (24, 25) are provided in each individual slider (20, 21, 22, 23) and the individual sliders (20, 21, 22, 23) are each arranged in a first position in which the filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) of the filter pair are arranged in the beam paths (2, 5), and in a second position in which both openings (24, 25) are in the beam paths (2, 5). 5) are arranged, are movable.Use of a filter carrier (9, 14, 20, 21, 22, 23) in an optical system with a light source (1), a detector (6) and a sample holder, wherein a first beam path (2) of the optical system extends from the light source (1) to the sample holder and a second beam path (5) of the optical system, which is separate from the first beam path (2), extends from the sample holder to the detector (6), characterized in that the filter carrier (9, 14, 20, 21, 22, 23) comprises several filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b), wherein two filters (10a, 10b, 11a, 11b, 12a, 12b, 13a, 13b) form a filter pair and wherein the filter carrier (9, 14, 20, 21, 22, 23) is arranged in the optical system such that the first beam path (2) passes through one filter (10a, 11a, 12a, 13a) of a filter pair and the second beam path (5) passes through the other filter (10b, 11b, 12b, 13b) of the same filter pair.

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