Filter array with focused light and reduced stray light

Abstract

To provide a favorable filter array with reduced stray focused light.SOLUTION: An apparatus is disclosed comprising an optical filter array (10) including an array of optical filter elements; where each optical filter element has opposing mutually parallel principal faces connected by sidewalls including at least one pair of opposing trapezoidal sidewalls and at least one pair of opposing sidewalls that are not mutually parallel; and where the opposing mutually parallel principal faces of the filter elements collectively define optical entrance and exit apertures of the optical filter array and include interference filters. Further disclosed is a method of illuminating such a filter array.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] (Cross-reference of related applications) This application claims priority to U.S. Provisional Patent Application No. 62 / 250,272, filed on 3 November 2015. The complete disclosure of this patent application is incorporated herein by reference in its entirety.

[0002] The following pertains to optical technology, optical filter technology, spectroscopy technology, pricing information distribution technology, and related technologies. [Background technology]

[0003] Optical interference filters, exhibiting high spectral selectivity, comprise a stack of layers with alternating refractive index values. These filters can be designed to provide passband, stopband, high-pass, low-pass, and notch filter outputs. The optical layers are typically deposited on an optically transparent substrate plate for the design-based spectrum; therefore, the filter is sometimes referred to as a filter plate, and is optically uniform across the plate's area.

[0004] On the other hand, optical interference filters, which have different passbands or stopbands or cutoff wavelengths within different areas of a plate, are useful for a variety of multispectral applications such as spectrometers or spectral analysis devices. Because it is difficult to control the variation of layer thickness across the substrate plate during layer deposition, such multispectral filters are sometimes manufactured as so-called "parquet" filter arrays. To construct a parquet filter array, a set of filter plates with different filter characteristics (e.g., different passbands or stopbands and / or bandwidths) are formed by appropriate layer deposition. Each filter plate is designed to be uniform across the area of ​​the plate. The filter plates are then die-cut to form filter elements in the form of strips, which are then joined together in a designed pattern to form the parquet filter array. A two-dimensional filter array is manufactured by a similar process, except that the filter plates are die-cut to form filter elements, which are then joined together in the desired two-dimensional array.

[0005] Several illustrative multispectral arrays of the aforementioned type are described, for example, in Downing et al.'s U.S. Publication No. 2014 / 0307309A1, published on October 16, 2014 (which is incorporated herein by reference in its entirety).

[0006] Several improvements are disclosed herein. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] U.S. Publication No. 2014 / 0307309A1 Specification [Overview of the project] [Means for solving the problem]

[0008] This disclosure relates to an apparatus comprising an optical filter array, which includes an array of optical filter elements, wherein each optical filter element has opposing, parallel principal surfaces connected by side walls, each comprising at least one pair of opposing trapezoidal side walls and at least one pair of opposing side walls that are not parallel to each other, and the opposing, parallel principal surfaces of the filter elements collectively define optical inlet and outlet apertures of the optical filter array and include interference filters.

[0009] The disclosure also provides the aforementioned filter array and relates to a method for illuminating an optical filter array with convergent or divergent light having a local angle that conforms to the sidewall angle of the sidewalls of the filter elements.

[0010] In addition, the present disclosure relates to an apparatus including an optical filter array comprising an array of internal optical filter elements, not the outermost optical filter elements of the optical filter array, each internal optical filter element having larger and smaller opposing parallel principal surfaces connected by side walls, each including at least one pair of opposing trapezoidal side walls and at least one pair of opposing side walls that are not parallel to each other, wherein the larger principal surface of the internal optical filter element provides a divergent aperture of the optical filter array, and the smaller principal surface of the internal optical filter element provides a convergent aperture of the optical filter array. This specification also provides, for example, the following items: (Item 1) It is a device, An optical filter array comprising an array of optical filter elements, Each optical filter element has opposing, parallel principal surfaces connected by side walls, including at least one pair of opposing trapezoidal side walls and at least one pair of opposing side walls that are not parallel to each other. The opposing, parallel principal surfaces of the filter elements collectively define the optical inlet and outlet apertures of the optical filter array, including interference filters. Device. (Item 2) The device according to item 1, wherein each filter element is a strip with side walls including a pair of opposing trapezoidal end side walls and a pair of opposing long side walls that are not parallel to each other. (Item 3) The device according to item 2, further comprising a linear or cylindrical light source having a major axis parallel to the long side walls of the filter element. (Item 4) The device according to item 1, wherein each filter element includes two pairs of opposing trapezoidal side walls where each pair of opposing trapezoidal side walls are not parallel to each other. (Item 5) The device according to item 1, further comprising an optical system configured to generate convergent or divergent light, and at least one pair of opposing side walls of each filter element is aligned with the local angle of the convergent or divergent light. (Item 6) The device according to item 1, wherein the main surface of the filter elements other than the outermost filter element of the filter array has an area larger than the other of the optical inlet opening and the optical outlet opening at one of the optical inlet opening and the optical outlet opening. (Item 7) The device according to item 1, wherein the optical filter element comprises a plurality of optical filter elements of different optical filter types defined by different interference filters. (Item 8) The device according to item 1, wherein the interference filter of the optical filter element comprises a passband filter or a notch filter. (Item 9) A method comprising: providing the optical filter array according to item 1; illuminating the optical filter array with convergent or divergent light having a local angle adapted to the side wall angle of the side walls of the filter element. A method comprising the above steps. (Item 10) A device comprising: an optical filter array comprising an array of internal optical filter elements that are not the outermost optical filter elements of the optical filter array. Each internal optical filter element includes a larger and a smaller opposing parallel major surface connected by sidewalls including at least one pair of opposing trapezoidal sidewalls and at least one pair of opposing sidewalls that are not parallel to each other. An apparatus, wherein the larger major surface of the internal optical filter element has a diverging aperture of the optical filter array, and the smaller major surface of the internal optical filter element has a converging aperture of the optical filter array. (Item 11) The apparatus according to item 10, wherein each internal optical filter element is a strip with a pair of opposing trapezoidal end sidewalls and a pair of opposing long sidewalls that are not parallel to each other. (Item 12) The apparatus according to item 10, wherein each internal optical filter element includes two pairs of opposing trapezoidal sidewalls where each pair of opposing trapezoidal sidewalls are not parallel to each other. (Item 13) The apparatus according to item 10, further comprising an optical system that generates converging light that enters the optical filter array at the diverging aperture and exits the optical filter array at the converging aperture. (Item 14) The apparatus according to item 10, further comprising an optical system that generates diverging light that enters the optical filter array at the converging aperture and exits the optical filter array at the diverging aperture.

[0011] These and other non-limiting aspects and / or objectives of the present disclosure will be described more specifically below.

Brief Description of the Drawings

[0012] The following is a brief description of the drawings presented for the purpose of illustrating exemplary embodiments disclosed herein and not for the purpose of limiting them.

[0013] [Figure 1] FIG. 1 schematically shows a side cross-sectional view of a filter array for filtering converging light in conjunction with a ray tracing and photodetector array illustrating the converging light. [Figure 2] Figure 2 schematically shows a cross-sectional view of one side of the optical filter array shown in Figure 1. [Figure 3] Figure 3 schematically shows a cross-sectional view of a single optical filter element, which is an example of the filter arrays shown in Figures 1 and 2. [Figure 4] Figures 4, 5, 6, and 7 schematically show the front, top, right, and perspective views of the filter arrays in Figures 1 and 2, respectively. In Figures 4-7, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. [Figure 5] Figures 4, 5, 6, and 7 schematically show the front, top, right, and perspective views of the filter arrays in Figures 1 and 2, respectively. In Figures 4-7, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. [Figure 6] Figures 4, 5, 6, and 7 schematically show the front, top, right, and perspective views of the filter arrays in Figures 1 and 2, respectively. In Figures 4-7, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. [Figure 7] Figures 4, 5, 6, and 7 schematically show the front, top, right, and perspective views of the filter arrays in Figures 1 and 2, respectively. In Figures 4-7, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. [Figure 8] Figures 8, 9, 10, and 11 schematically show the front, top, right, and perspective views of a deformable filter array for light that converges or diverges in only one dimension, for example, generated by an illustrated linear or cylindrical light source. As in Figure 4-7, and again in Figures 8-11, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figure. [Figure 9]Figures 8, 9, 10, and 11 schematically show the front, top, right, and perspective views of a deformable filter array for light that converges or diverges in only one dimension, for example, generated by an illustrated linear or cylindrical light source. As in Figure 4-7, and again in Figures 8-11, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figure. [Figure 10] Figures 8, 9, 10, and 11 schematically show the front, top, right, and perspective views of a deformable filter array for light that converges or diverges in only one dimension, for example, generated by an illustrated linear or cylindrical light source. As in Figure 4-7, and again in Figures 8-11, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figure. [Figure 11] Figures 8, 9, 10, and 11 schematically show the front, top, right, and perspective views of a deformable filter array for light that converges or diverges in only one dimension, for example, generated by an illustrated linear or cylindrical light source. As in Figure 4-7, and again in Figures 8-11, the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figure. [Modes for carrying out the invention]

[0014] A more complete understanding of the processes and apparatus disclosed herein can be obtained by referring to the accompanying drawings. These drawings are merely schematic diagrams based on convenience and ease of demonstrating the existing art and / or the present development, and are therefore not intended to show the relative sizes and dimensions of the assemblies or their components.

[0015] Specific terms are used in the following description for clarity, but these terms are intended to refer only to specific structures of embodiments selected for illustration in the drawings and are not intended to define or limit the scope of this disclosure. In the drawings and the following description, similar numerical designations should be understood to refer to components of similar function.

[0016] The singular forms "a," "an," and "the" also include plural references unless explicitly indicated otherwise by the context.

[0017] The modifier "about" used in relation to a quantity includes the stated value and has meaning indicated by the context (for example, at least the degree of error associated with the measurement of a particular quantity). When used with a specific value, it should also be considered to disclose that value. For example, the term "about 2" also discloses the value "2," and the range "about 2 to about 4" also discloses the range "2 to 4."

[0018] Referring to Figure 1, the disadvantage of the parquet-type filter arrays recognized herein is that they are not suitable for many practical optical systems that have a finite focal plane and act on convergent or divergent light beams. Figure 1 illustrates a ray tracing for such a system having a focal plane P at a finite position along the optical axis OA. Due to the finite location of the focal plane P, light passing through the optical system (illustrated by the illustrative ray L) forms a conical beam with a cone half-angle A as shown in Figure 1, which converges at the focal plane P. In illustrative Figure 1, the ray L travels from left to right in the drawing and is detected by a detector array 8 located in the plane adjacent to the focal plane P; i.e., ray L is therefore a convergent ray. Alternatively, if the light travels away from the finite focal plane, for example, if it originates from a small light source at the focal plane, the ray can diverge (alternative not shown). In either case, the ray forms either a convergent (as illustrated) or divergent beam.

[0019] A parquet-type filter array consists of filter elements in the form of strips (for a one-dimensional array) or blocks (for a two-dimensional array) cut from a filter plate. A dicing saw produces vertical sidewalls for the strips or blocks. Downing et al., U.S. Publication 2014 / 0307309A1, discloses an improvement for use when the angle of incidence of light is not perpendicular to the surface of the filter array. In the design disclosed in Downing et al., U.S. Publication 2014 / 0307309A1, the strips or blocks are diced so that they have sidewalls at an angle selected to match the angle of incidence of light. This reduces light scattering and loss at the boundaries between filter elements.

[0020] In this specification, for convergent or divergent light, such filter arrays are recognized to produce light scattering and loss at the boundaries between adjacent filter elements. This scattering and optical loss cannot be reduced using the approach of Downing et al., U.S. Publication 2014 / 0307309A1, because the incident angle of the convergent or divergent light is not defined.

[0021] Continuing with reference to Figure 1 and further with reference to Figure 2, the improved optical filter array 10 has optical filter elements 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, and 12j with non-parallel sidewalls, the angles of which are designed to match the local convergence or divergence angles of the light ray L for each filter element (optionally, excluding the outer sidewalls of the outermost filter elements 12a and 12j that form the periphery of the filter array 10). The sidewall joints of adjacent filter elements are at the same local location on the surface of the filter array 10 and therefore have the same sidewall angle. As recognized herein, this coincidence of neighboring sidewall angles allows the filter elements to be fixed together at the sidewall joints, for example, using adhesive or other bonding, to form the filter array 10. As an example, as indicated at the interface 14 between filter elements 12b and 12c in Figure 2, the joint of the side walls of filter elements 12b and 12c has the same side wall angle.

[0022] As can be seen further in Figures 1 and 2, the sidewall angle increases with increasing distance from the optical axis OA, corresponding to the increase in the angle of the converging or diverging light beam with increasing distance from the optical axis OA.

[0023] Continuing to refer to Figures 1 and 2, and further to Figure 3, the sidewalls of a given filter element are not parallel to each other. Rather, the central sidewalls of a given filter element have a smaller sidewall angle than the outer sidewalls ("central" and "outer" indicate being relatively close to the optical axis OA and relatively far from it, respectively). For illustrative purposes, Figure 3 shows filter element 12d alone. With respect to filter element 12d, the central sidewall 16 has a sidewall angle A of the outer sidewall 18. O Compared to, a smaller side wall angle A I It has (measured from the direction of the optical axis OA).

[0024] Continuing to refer to Figure 3, for each filter element (e.g., illustrative filter element 12d), the filter element comprises a transparent substrate or body 20, bounded by four sidewalls 16, 18 extending between opposing main surfaces 22, 24 (including two additional sidewalls not depicted in the side section view of Figure 3). One or both of these main surfaces include interference filters; for example, the illustrative main surface 22 of filter element 12d includes an interference filter 26, which may be deposited by techniques such as sputtering, vacuum deposition, or plasma deposition. The interference filter 26 typically consists of a designed stack of layers that provide optical interference, offering a design-based passband, stopband, high-pass, low-pass, or notch filter. The wavelength, full width at half maximum (FWHM), or other spectral characteristics of the interference filter 26 are designed for a specific application. Furthermore, since the filter array 10 is typically a multispectral filter, each filter element 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j generally has a different interference filter (however, some filter elements may be selected similarly. For example, if the filter array 10 is intended to be symmetrical about the optical axis OA, then the interference filters for filter elements 12a, 12j are the same, the interference filters for filter elements 12b, 12i are the same, the interference filters for filter elements 12c, 12h are the same, the interference filters for filter elements 12d, 12g are the same, and the interference filters for filter elements 12e, 12f are the same). Although not shown, an interference filter may be included additionally or alternatively on the main surface 24 of filter element 12d.

[0025] Filter elements may generally be designed for any passband or stopband within the ultraviolet wavelength range, the visible wavelength range, or the infrared wavelength range. In an illustrative example, the filter element (or more specifically, the filter element body or substrate, e.g., the filter element body or substrate 20 of the illustrative filter element 12d in Figure 3) may be made from a light-transmitting material such as glass, sapphire, or another material having suitable transparency within the operating optical range. The interference filter 26 may include alternating layers of tantalum oxide (Ta2O5) and silicon dioxide (SiO2), or more generally, alternating layers of two (or more) materials with different refractive indices. The layers constituting the interference filter 26 are also preferably light-transmitting for the operating optical range, but because they are thin layers, some optical absorption within the operating optical range may be acceptable. For example, in another illustrative example, the layers may be metal / metal oxide layers such as titanium / titanium dioxide (Ti / TiO2). Known techniques for designing interference filters can be employed to design layer thicknesses for a given passband or notch filter stopband, or to provide desired high-pass or low-pass filtering characteristics.

[0026] Figures 1 and 2 depict the filter 10 in a side cross-sectional view. This side view does not capture the three-dimensional shape of the focusing light L or the filter array 10.

[0027] Referring to Figure 4-6, the three-dimensional shape is schematically depicted by front (Figure 4), top (Figure 5), and right (Figure 6) views of the filter 10, and Figure 7 shows a perspective view of the filter 10 in its optical environment, including the converged light beam L and detector array 8 shown in the perspective view. In Figure 4-7, for schematic simplification, the number of filter elements shown is reduced to a 4x4 array of filter elements. It should be understood that the number of filter elements is a design parameter that is suitably selected based on the desired filter resolution and the total area of ​​the filter array.

[0028] The filter element has two mutually parallel bases 22, 24 (i.e., the bases 22, 24 are parallel to each other) with the same number of vertices (four vertices for the rectangular bases 22, 24 of the exemplary filter array 10), and at least two trapezoidal side walls 16, 18 that are not parallelograms (due to different side wall angles, e.g., different angles A I , A O ), and has the shape of a frustum of a pyramid (specifically, refer to the exemplary filter element 12d in FIG. 3). The two parallel bases 22, 24 of the filter elements within the assembled filter array 10 collectively define the optical inlet aperture and the outlet aperture (or vice versa) of the filter array 10, as best seen in FIGS. 1 and 7.

[0029] Continuing to refer to FIGS. 4 - 7 and further referring to FIGS. 8 - 11, for a two - dimensionally diverging or converging light beam, all four side walls of the filter element are trapezoidal side walls, as best seen in FIGS. 4, 6, and 7. In these embodiments, each pair of opposing trapezoidal side walls (e.g., side walls 16, 18 in FIG. 3) are not parallel to each other (i.e., not mutually parallel). On the other hand, as seen in FIGS. 8 - 11, for a light beam that diverges or converges in only one dimension and is parallel in the orthogonal dimension (e.g., generated by a cylindrical or linear light source 30) and is spectrally filtered only in the direction of divergence or convergence, the deformed filter array 40 has filter elements in the form of strips, and each filter element has two end side walls 46 that are trapezoidal trap and long side walls 46 that are parallelograms par . In this embodiment, the two trapezoidal end side walls 46 trap are opposing side walls that are parallel to each other (i.e., mutually parallel), while the two parallelogram long side walls 46 par are opposing side walls that are not parallel to each other. The linear or cylindrical light source 30 has a long axis 32 that is parallel to the long side walls 46 of the filter element par and is transverse to the trapezoidal end side walls 46 trap .

[0030] Referring back to Figures 1 and 2, generally, the internal filter elements (i.e., filter elements 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, not the outermost filter elements 12a, 12j of the filter array 10) have one principal surface (principal surface 22 in Figure 3) that has a larger area than the other principal surfaces (principal surface 24 in Figure 3). The larger area principal surfaces of the internal filter elements collectively constitute the divergent aperture 50 (labeled in Figure 2) of the filter array 10. The smaller area principal surfaces of the internal filter elements collectively constitute the convergent aperture 52 of the filter array 10. In Figures 1 and 2, the left side of the filter array 10 is the divergent aperture 50, while the right side of the filter array 10 is the convergent aperture 52. When the filter is applied to focused light (as illustrated in Figure 1), the diverging aperture is the inlet aperture (i.e., focused light enters the diverging aperture 50), and the focusing aperture is the outlet aperture (i.e., focused light exits the focusing aperture 52 of the filter array 10). Conversely, when the filter is applied to diverging light (as in the embodiment of Figure 11), the focusing aperture (the upper aperture of the filter array 40 as shown in Figure 11) is the inlet aperture, and the diverging aperture (invisible in the perspective view shown in Figure 11) is the outlet aperture.

[0031] The outermost filter elements may optionally be made "square" so as a whole they have non-sloping peripheral sidewalls for the filter array 10 (as seen in the outermost filter elements 12a and 12j, where the left principal face is smaller than the right principal face), which may be an exception to the aforementioned geometric shape as it may affect the area of ​​the principal faces.

[0032] The angle of the sidewall of the filter element (for example, angle A for the illustrative filter element 12d in Figure 3) I and A O When designing a filter, the local angle of diverging or converging light L at the sidewall is taken into consideration. This angle is preferably the angle in the material of the filter element, rather than the angle in the air, due to the bending of light according to Snell's law. The angle θ of the light ray within the filter element material fe This is the angle θ of light rays in the air according to Snell's Law, i.e., sin(θ)=nfe sin(θ fe In relation to ), in the formula, n fe n is the refractive index of the filter element, and the surroundings are assumed to be air, vacuum, or another environment with a refractive index n=1. For example, if the local ray angle is θ=15° at the sidewall of the filter element, then n fe If = 1.5, [ka] Therefore, the side walls in this location are 10 o It is preferably selected as (where the surrounding area is different from n = 1). ambient If it is an oil or some other material accompanied by n, Snell's Law is true. ambient sin(θ)=n fe sin(θ fe This generalizes to the following: The filter elements may be processed in various ways, such as first die-cutting a parallelepiped filter element, and then polishing the individual die-cut filter elements to form sidewall angles. Alternatively, die-cutting can be performed using a suitably angled cutting saw or an angled wafer mounting jig.

[0033] It should be understood that the various features and functions disclosed herein, as well as other features and functions or their substitutes, may preferably be combined with many other different systems or applications. Furthermore, it should be understood that various currently unexpected or unforeseen substitutes, modifications, variations, or improvements may be subsequently made by those skilled in the art, and these too are intended to be covered by the following claims.

Claims

1. An apparatus comprising an optical filter array comprising an array of optical filter elements, The optical filter element includes an outermost optical filter element and an array of internal optical filter elements that are not the outermost optical filter element of the optical filter array. The optical filter elements of the optical filter array are in the form of strips, and each optical filter element comprises a substrate bounded by four side walls, including a pair of opposing trapezoidal end side walls that are parallel to each other and a pair of opposing elongated side walls that are not parallel to each other, the pair of opposing elongated side walls being in the shape of a parallelogram, At least each internal optical filter element of the optical filter array has opposing parallel principal surfaces connected by four side walls, including the pair of opposing trapezoidal end side walls that are parallel to each other and the pair of opposing elongated side walls that are not parallel to each other, and the opposing parallel principal surfaces of each internal optical filter element include larger and smaller opposing parallel principal surfaces. One or both of the opposing, mutually parallel main surfaces include an interference filter layer stack, the interference filter layer stack is bounded by the four side walls, which include the pair of opposing trapezoidal end side walls and the pair of opposing elongated side walls, and has corresponding shapes defined by the four side walls. Each long sidewall of the optical filter element has a sidewall angle configured to match the local angle of divergent or converging rays in the material of the optical filter element at the long sidewall, The larger main surface of the internal optical filter element is provided with a divergent aperture of the optical filter array, and the smaller main surface of the internal optical filter element is provided with a converging aperture of the optical filter array. An apparatus in which adjacent internal optical filter elements are fixed together at the joint of the long sidewalls having a matched sidewall angle.

2. The apparatus according to claim 1, wherein the substrate of each optical filter element of the optical filter array comprises a light-transmitting material that is transparent over the operating optical range of the optical filter array.

3. The apparatus according to claim 1, further comprising a linear or cylindrical light source having a major axis parallel to the long side wall of the optical filter element and lateral to the trapezoidal end side wall.

4. The apparatus according to claim 3, wherein the linear or cylindrical light source is configured to generate convergent or divergent light, and the pair of opposing long sidewalls of each optical filter element are matched to the local angle of the convergent or divergent light.

5. The apparatus according to claim 1, wherein the interference filter layer stack comprises alternating layers of two or more materials having different refractive index values.

6. The aforementioned interference filter layer stack is Alternating layers of tantalum oxide and silicon dioxide, or Titanium and titanium dioxide The apparatus according to claim 5, comprising one of the following.

7. The apparatus according to claim 1, further comprising an optical system configured to generate converging or diverging light, wherein the pair of opposing long sidewalls of each internal optical filter element are matched to the local angle of the converging or diverging light.

8. The apparatus according to claim 1, wherein the main surface of the internal optical filter element has a rectangular shape.

9. The aforementioned optical filter element is The apparatus according to claim 1, comprising a plurality of optical filter elements of different optical filter types defined by different interference filter layer stacks.

10. The apparatus according to claim 1, wherein the outermost optical filter element of the optical filter array comprises non-inclined peripheral side walls arranged perpendicular to the opposing, mutually parallel main surfaces.

11. The apparatus according to claim 1, wherein the interference filter layer stack of the optical filter element comprises a passband filter or a notch filter.

12. The apparatus according to claim 1, further comprising an optical system for generating converged light that enters the optical filter array at the diverging aperture and exits the optical filter array at the converging aperture.

13. The apparatus according to claim 1, further comprising an optical system for generating divergent light that enters the optical filter array at the converging aperture and exits the optical filter array at the diverging aperture.

14. To provide the optical filter array described in claim 1, Illuminating the optical filter array with focused or divergent light having a local angle that matches the side wall angle of the long side wall of the optical filter element, A method that includes this.

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