Filter array with focused light with reduced stray light

Abstract

To provide a suitable filter array having focused light with reduced stray light. An apparatus is disclosed that includes an optical filter array (10) including an array of optical filter elements, each having opposing parallel major surfaces connected by sidewalls, the opposing parallel major surfaces including at least one pair of opposing trapezoidal sidewalls and at least one pair of opposing sidewalls that are not parallel to one another, the opposing parallel major surfaces of the filter elements collectively defining optical entrance and exit apertures of the optical filter array and including an interference filter. Also disclosed is a method of illuminating such a filter array.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 62 / 250,272, filed November 3, 2015, the complete disclosure of which is incorporated herein by reference in its entirety.

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

[0003] Optical interference filters with 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, or notch filter outputs. The optical layers are typically deposited on a substrate plate that is optically transparent for the design-based spectrum; therefore, the filter, sometimes referred to as a filter plate, is optically uniform across the area of ​​the plate.

[0004] On the other hand, optical interference filters with different passbands or stopbands or cutoff wavelengths within different areas of the plate are useful for a variety of multispectral applications, such as spectrometers or spectral analysis devices. Because it is difficult to controllably vary layer thickness across a substrate plate during layer deposition, such multispectral filters are sometimes manufactured as so-called "marquetry" filter arrays. To construct a marquetry 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 plate's area. The filter plates are then diced to form filter elements in the form of strips, which are then bonded together in a designed pattern to form the marquetry filter array. Two-dimensional filter arrays are manufactured by a similar process, except that the filter plates are diced to form filter elements, which are then bonded together into the desired two-dimensional array.

[0005] Some illustrative multispectral arrays of the foregoing type are described, for example, in U.S. Publication No. 2014 / 0307309A1 to Downing et al., published 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] US Publication No. 2014 / 0307309A1 Summary of the Invention [Means for solving the problem]

[0008] The present disclosure relates to an apparatus comprising an optical filter array comprising an array of optical filter elements, each optical filter element having opposing parallel major surfaces connected by sidewalls, the opposing parallel major surfaces including at least one pair of opposing trapezoidal sidewalls and at least one pair of opposing sidewalls that are not parallel to one another, and the opposing parallel major surfaces of the filter elements collectively define optical entrance and exit apertures of the optical filter array and include an interference filter.

[0009] The present disclosure is also directed to a method of providing the aforementioned filter array and illuminating the optical filter array with converging or diverging light having a local angle that matches the sidewall angle of the sidewalls of the filter elements.

[0010] Additionally, the present disclosure is directed to an apparatus including 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 having larger and smaller opposing parallel major surfaces connected by sidewalls, the larger major surface of the internal optical filter element comprising a diverging aperture of the optical filter array, and the smaller major surface of the internal optical filter element comprising a converging aperture of the optical filter array, the internal optical filter elements being not the outermost optical filter elements of the optical filter array, the larger major surface of the internal optical filter element comprising a diverging aperture of the optical filter array, and the smaller major surface of the internal optical filter element comprising a converging aperture of the optical filter array. The present specification also provides, for example, the following items: (Item 1) 1. An apparatus comprising: an optical filter array comprising an array of optical filter elements; each optical filter element has opposing parallel major surfaces 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 one another; the opposing parallel major surfaces of the filter elements collectively define optical entrance and exit apertures of the optical filter array and include interference filters; Device. (Item 2) Item 10. The apparatus of item 1, wherein each filter element is a strip with sidewalls including a pair of opposing trapezoidal end sidewalls and a pair of opposing long sidewalls that are not parallel to one another. (Item 3) Item 3. The apparatus of item 2, further comprising a linear or cylindrical light source having a long axis parallel to a long sidewall of the filter element. (Item 4) Item 1. The apparatus of item 1, wherein each filter element includes two pairs of opposing trapezoidal sidewalls, wherein the opposing trapezoidal sidewalls of each pair are not parallel to one another. (Item 5) Item 1, the apparatus further comprising an optical system configured to generate converging or diverging light, wherein opposing side walls of at least one pair of each filter element are aligned with a local angle of the converging or diverging light. (Item 6) Item 2. The device of item 1, wherein a major surface of a filter element other than an outermost filter element of the filter array has a larger area at one of the optical entrance opening and optical exit opening than at the other of the optical entrance opening and optical exit opening. (Item 7) Item 10. The device of 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) Item 10. The apparatus of item 1, wherein the interference filter of the optical filter element comprises a passband filter or a notch filter. (Item 9) 1. A method comprising: Providing an optical filter array according to item 1; illuminating the optical filter array with converging or diverging light having a local angle that matches the sidewall angle of the sidewalls of the filter elements; A method comprising: (Item 10) 1. An apparatus comprising: an optical filter array comprising an array of interior optical filter elements that are not outermost optical filter elements of the optical filter array; each internal optical filter element includes larger and smaller opposing parallel major faces 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 one another; The apparatus wherein a larger major surface of the internal optical filter element comprises a diverging aperture of the optical filter array and a smaller major surface of the internal optical filter element comprises a converging aperture of the optical filter array. (Item 11) Item 11. The device of 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) Item 11. The device of item 10, wherein each internal optical filter element includes two pairs of opposing trapezoidal sidewalls, each pair of opposing trapezoidal sidewalls being non-parallel to one another. (Item 13) Item 11. The apparatus of 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) Item 11. The apparatus of item 10, further comprising an optical system that generates divergent 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 objects of the present disclosure are more particularly described below. [Brief explanation of the drawings]

[0012] The following is a brief description of the drawings, presented for purposes of illustrating, but not limiting, exemplary embodiments disclosed herein.

[0013] [Figure 1] FIG. 1 shows a schematic side cross-sectional view of a filter array for filtering convergent light, along with ray tracing illustrating the convergent light and a photodetector array. [Figure 2] FIG. 2 shows a schematic cross-sectional side view of the optical filter array of FIG. [Figure 3] FIG. 3 shows a schematic cross-sectional side view of an exemplary optical filter element of the filter array of FIGS. [Figure 4] Figures 4, 5, 6, and 7 diagrammatically show the front, top, right, and perspective views, respectively, of the filter array of Figures 1 and 2. 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 diagrammatically show the front, top, right, and perspective views, respectively, of the filter array of Figures 1 and 2. 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 diagrammatically show the front, top, right, and perspective views, respectively, of the filter array of Figures 1 and 2. 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 diagrammatically show the front, top, right, and perspective views, respectively, of the filter array of Figures 1 and 2. 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 diagrammatically show front, top, right, and perspective views, respectively, of modified filter arrays for light converging or diverging in only one dimension, such as that generated by illustrative linear or cylindrical light sources. As in Figures 4-7, in Figures 8-11 the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. [Figure 9]Figures 8, 9, 10, and 11 diagrammatically show front, top, right, and perspective views, respectively, of modified filter arrays for light converging or diverging in only one dimension, such as that generated by illustrative linear or cylindrical light sources. As in Figures 4-7, in Figures 8-11 the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. [Figure 10] Figures 8, 9, 10, and 11 diagrammatically show front, top, right, and perspective views, respectively, of modified filter arrays for light converging or diverging in only one dimension, such as that generated by illustrative linear or cylindrical light sources. As in Figures 4-7, in Figures 8-11 the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. [Figure 11] Figures 8, 9, 10, and 11 diagrammatically show front, top, right, and perspective views, respectively, of modified filter arrays for light converging or diverging in only one dimension, such as that generated by illustrative linear or cylindrical light sources. As in Figures 4-7, in Figures 8-11 the number of illustrative optical filter elements has been reduced to a 4x4 array to reduce the complexity of the figures. DETAILED DESCRIPTION OF THE INVENTION

[0014] A more complete understanding of the processes and apparatus disclosed herein may be obtained by reference to the accompanying drawings, which are merely schematic representations for convenience and ease of illustrating existing technology and / or the present developments, and as such are not intended to indicate the relative size and dimensions of the assembly or its components.

[0015] Although specific terms are used in the following description for purposes of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings and are not intended to define or limit the scope of the present disclosure. In the drawings and the description that follows, it should be understood that like numerical designations refer to components of similar function.

[0016] The singular forms "a," "an," and "the" include plural references unless the context clearly indicates otherwise.

[0017] The modifier "about" used in connection with a quantity is inclusive of the stated value and has the meaning dictated by the context (e.g., includes at least the degree of error associated with measurement of the particular quantity). When used in conjunction 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 FIG. 1 , a disadvantage of the parquet-type filter arrays recognized herein is that they are incompatible with many practical optical systems that have a finite focal plane and operate on converging or diverging light beams. FIG. 1 illustrates 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 (schematically represented by illustrative ray L) forms a conical beam with a conical half-angle A as shown in FIG. 1 , which converges at the focal plane P. In illustrative FIG. 1 , ray L travels from left to right on the drawing and is detected by detector array 8, which is located in a plane close to the focal plane P; i.e., ray L is therefore a converging ray. Alternatively, if the light is traveling away from the finite focal plane, e.g., emanating from a small light source at the focal plane, the light rays may diverge (alternative not shown). In either case, the light rays form either a converging (as shown) or diverging beam.

[0019] Marquetry-type filter arrays are composed of filter elements in the form of strips (for one-dimensional arrays) or blocks (for two-dimensional arrays) cut from a filter plate. A dicing saw produces vertical sidewalls for the strips or blocks. U.S. Publication No. 2014 / 0307309A1 to Downing et al. 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 U.S. Publication No. 2014 / 0307309A1 to Downing et al., the strips or blocks are diced with sidewalls at an angle selected to match the angle of incidence of the light. This reduces light scattering and loss at the boundaries between the filter elements.

[0020] It is recognized herein that, for converging or diverging light, such filter arrays produce optical scattering and losses at the boundaries between adjacent filter elements. This scattering and optical losses cannot be reduced using the approach of Downing et al., U.S. Publication No. 2014 / 0307309 A1, because the angle of incidence of the converging or diverging light is not defined.

[0021] With continued reference to FIG. 1 and further reference to FIG. 2, the improved optical filter array 10 has optical filter elements 12 a, 12 b, 12 c, 12 d, 12 e, 12 f, 12 g, 12 h, 12 i, 12 j with non-parallel sidewalls, the angles of which are designed to match the local convergence or divergence angles of light rays L for each filter element (optionally excluding the outer sidewalls of the outermost filter elements 12 a, 12 j, which form the perimeter 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 matching of neighboring sidewall angles allows the filter elements to be affixed together at the sidewall joints, for example, using an adhesive or other bond, to form the filter array 10. Illustratively, the sidewall joints of filter elements 12b and 12c have the same sidewall angle, as labeled at interface 14 between filter elements 12b and 12c in FIG.

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

[0023] With continued reference to Figures 1 and 2, and with further reference to Figure 3, the sidewalls of a given filter element are not parallel to one another. Rather, the inboard sidewalls of a given filter element have smaller sidewall angles than the outboard sidewalls ("inboard" and "outboard" indicate relative proximity to and relative distance from the optical axis OA, respectively). By way of example, Figure 3 shows filter element 12d alone. For filter element 12d, inboard sidewall 16 has a sidewall angle A smaller than that of outboard sidewall 18. O Compared to the smaller sidewall angle A I (measured from the direction of the optical axis OA).

[0024] Continuing with reference to FIG. 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 major surfaces 22, 24 (including sidewalls 16, 18 plus two sidewalls not depicted in the cross-sectional side view of FIG. 3 ). One or both of these major surfaces may include an interference filter; for example, illustrative major surface 22 of filter element 12d includes an interference filter 26, which may be deposited by techniques such as sputtering, vacuum evaporation, plasma deposition, etc. Interference filter 26 is typically composed of an engineered stack of layers providing optical interference to provide 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 this interference filter 26 are designed for a particular application. Furthermore, because filter array 10 is typically a multispectral filter, each filter element 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, and 12j generally has a different interference filter (although some filter elements may be selected identically. For example, if filter array 10 is intended to be symmetric about optical axis OA, the interference filters for filter elements 12a and 12j would be the same, the interference filters for filter elements 12b and 12i would be the same, the interference filters for filter elements 12c and 12h would be the same, the interference filters for filter elements 12d and 12g would be the same, and the interference filters for filter elements 12e and 12f would be the same). Although not shown, an interference filter may additionally or alternatively be included on major surface 24 of filter element 12d.

[0025] Filter elements may generally be designed for any passband or stopband within the ultraviolet, visible, or infrared wavelength ranges. As 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 of FIG. 3) may be made of an optically transmissive material such as glass, sapphire, or another material with suitable transparency within the operating optical range. The interference filter 26 may include alternating layers of tantalum oxide (TaO) and silicon dioxide (SiO), or more generally, alternating layers of two (or more) materials with different refractive index values. The layers that make up the interference filter 26 are also preferably optically transmissive for the operating optical range, but because they are thin, some optical absorption within the operating optical range may be acceptable. For example, as another illustrative example, the layers may be metal / metal oxide layers such as titanium / titanium dioxide (Ti / TiO). 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] 1 and 2 depict filter 10 in a cross-sectional side view. This side view does not capture the three-dimensional shape of the convergent light L or filter array 10.

[0027] With reference to Figures 4-6, this three-dimensional shape is depicted diagrammatically by front (Figure 4), top (Figure 5), and right (Figure 6) views of filter 10, and Figure 7 shows a perspective view of filter 10 within its optical environment, including a converging light beam L and detector array 8 shown in a perspective view. In Figures 4-7, for diagrammatic simplicity, the number of filter elements shown has been 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 chosen based on the desired filter resolution and the total area of ​​the filter array.

[0028] The filter elements have two parallel bases 22, 24 (i.e., the bases 22, 24 are parallel to one another) with the same number of vertices (four vertices for the rectangular bases 22, 24 of the illustrative filter array 10), and are not parallelograms (different sidewall angles, e.g., different angle A for filter element 12d in illustrative FIG. 3). I , A O 1 and 7, each filter element has a truncated pyramidal shape (see particularly illustrative filter element 12d in FIG. 3), with at least two trapezoidal sidewalls 16, 18. The two parallel base sides 22, 24 of the filter elements in the assembled filter array 10 collectively define the optical entrance and exit apertures (or vice versa) of the filter array 10, as best seen in FIGS.

[0029] With continued reference to Figures 4-7, and further reference to Figures 8-11, for light beams that diverge or converge in two dimensions, all four sidewalls of the filter elements are trapezoidal sidewalls, as best seen in Figures 4, 6, and 7. In these embodiments, the opposing trapezoidal sidewalls of each pair (e.g., sidewalls 16, 18 in Figure 3) are not parallel to one another (i.e., not mutually parallel). On the other hand, for light beams that diverge or converge in only one dimension and are parallel in the orthogonal dimension (e.g., generated by a cylindrical or linear light source 30), as seen in Figures 8-11, and that are to be multispectrally filtered only in the direction of divergence or convergence, the modified filter array 40 has filter elements in the form of strips, each filter element having two end sidewalls 46 that are trapezoidal. trap and the long side wall 46, which is a parallelogram. par In this embodiment, the 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 opposed side walls that are not parallel to each other. The linear or cylindrical light source 30 is aligned with the long side wall 46 of the filter element. par and parallel to the trapezoidal end side wall 46 trap It has a major axis 32 that is transverse to the

[0030] 1 and 2, generally, the interior filter elements (i.e., filter elements 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, but not outermost filter elements 12a, 12j of filter array 10) have one major surface (major surface 22 in FIG. 3) that has a larger area than the other major surface (major surface 24 in FIG. 3). The larger area major surfaces of the interior filter elements collectively constitute diverging aperture 50 (labeled in FIG. 2) of filter array 10. The smaller area major surfaces of the interior filter elements collectively constitute converging aperture 52 of filter array 10. In FIGS. 1 and 2, the left side of filter array 10 is diverging aperture 50, while the right side of filter array 10 is converging aperture 52. When a filter is applied to converging light (as in illustrative FIG. 1), the diverging aperture is the entrance aperture (i.e., the converging light enters diverging aperture 50) and the converging aperture is the exit aperture (i.e., the converging light exits converging aperture 52 of filter array 10). Conversely, when a filter is applied to diverging light (as in the embodiment of FIG. 11), the converging aperture (the upper aperture of filter array 40, as shown in FIG. 11) is the entrance aperture and the diverging aperture (not visible in the perspective view shown in FIG. 11) is the exit aperture.

[0031] The outermost filter elements may optionally be "squared off" to have non-sloped peripheral sidewalls for the filter array 10 as a whole (as seen in outermost filter elements 12a and 12j, where the left major surface is smaller than the right major surface), which may be an exception to the aforementioned geometry as this may affect the area of ​​the major surfaces.

[0032] The sidewall angle of the filter element (e.g., angle A for illustrative filter element 12d in FIG. 3) I and A O When designing the filter element, the local angle of diverging or converging light L at the sidewall is taken into account. This angle is preferably the angle in the material of the filter element, not the angle in air, due to the bending of light, according to Snell's law. The angle θ of the light ray in the filter element material fe is the angle θ of the ray in the air according to Snell's law, i.e., sin(θ)=nfe sin(θ fe ), wherein n fe is the refractive index of the filter element, and the surroundings are assumed to be air, vacuum, or another surrounding with refractive index n=1. For example, if the local ray angle is θ=15° at the filter element sidewall and n fe = 1.5, [ka] The side walls in this tournament are 10 o (The surrounding area is different from 1.) ambient If the temperature is oil or some other material with ambient sin(θ)=n fe sin(θ fe ) The filter elements may be fabricated in a variety of ways, such as by first dicing a parallelepiped filter element and then grinding the individual diced filter elements to form the sidewall angles. Alternatively, dicing can employ a suitably angled cutting saw or an angled wafer mounting jig.

[0033] It is to be understood that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications.Furthermore, it is to be understood that various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art, which are also intended to be encompassed by the following claims.

Claims

1. 1. An apparatus comprising an optical filter array comprising an array of optical filter elements, the optical filter elements include an outermost optical filter element and an array of interior optical filter elements that are not the outermost optical filter elements of the optical filter array; the optical filter elements of the optical filter array are in the form of strips, each optical filter element comprising a substrate bounded by four sidewalls including a pair of opposing trapezoidal end sidewalls that are parallel to one another and a pair of opposing long sidewalls that are not parallel to one another, the pair of opposing long sidewalls being parallelogram-shaped; At least each internal optical filter element of the optical filter array has opposing parallel major surfaces connected by the four sidewalls, including the pair of opposing trapezoidal end sidewalls that are parallel to each other and the pair of opposing long sidewalls that are not parallel to each other, and the opposing parallel major surfaces of each internal optical filter element include larger and smaller opposing parallel major surfaces; one or both of the opposing parallel major surfaces includes an interference filter layer stack, the interference filter layer stack being bounded by the four sidewalls, including the pair of opposing trapezoidal end sidewalls and the pair of opposing long sidewalls, and having a corresponding shape defined by the four sidewalls; each long sidewall of the optical filter element has a sidewall angle configured to match a local angle of diverging or converging light rays within the material of the optical filter element at the long sidewall; The apparatus wherein the larger major surface of the internal optical filter element comprises a diverging aperture of the optical filter array and the smaller major surface of the internal optical filter element comprises a converging aperture of the optical filter array.

2. The apparatus of claim 1 , wherein the substrate of each optical filter element of the optical filter array comprises an optically transmissive material that is transparent over an operating optical range of the optical filter array.

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

4. 4. The apparatus of claim 3, wherein the linear or cylindrical light source is configured to generate converging or diverging light, and the pair of opposing long side walls of each optical filter element are aligned with a local angle of the converging or diverging light.

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

6. The interference filter layer stack comprises: Alternating layers of tantalum oxide and silicon dioxide, or Titanium and Titanium Dioxide The apparatus of claim 5 , comprising one of:

7. 10. The apparatus of claim 1, further comprising an optical system configured to generate converging or diverging light, wherein the pair of opposing long side walls of each internal optical filter element are aligned with the local angle of the converging or diverging light rays.

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

9. The optical filter element comprises: The apparatus of claim 1 comprising a plurality of optical filter elements of different optical filter types defined by different interference filter layer stacks.

10. The apparatus of claim 1 , wherein the outermost optical filter elements of the optical filter array have non-sloped peripheral sidewalls disposed perpendicular to the opposing parallel major faces.

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

12. The apparatus of claim 1 , 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.

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

14. Providing an optical filter array according to claim 1; illuminating the optical filter array with converging or diverging light having a local angle that matches a sidewall angle of the long sidewall of the optical filter element; A method comprising:

Images