Filter array with reduced stray focused light

Abstract

The present application provides a filter array with reduced stray focused light. The present application discloses a device, comprising: an optical filter array (10) comprising an array of optical filter elements; wherein each optical filter element has opposite mutually parallel main faces connected by side walls, the side walls comprising at least one pair of opposite trapezoidal side walls and at least one pair of opposite mutually non-parallel side walls; and wherein the opposite mutually parallel main faces of the filter elements jointly define an optical entrance hole and an optical exit hole of the optical filter array, and include an interference filter. The present application further discloses a method of irradiating such a filter array.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application is a divisional application of the Chinese patent application with application number 201680064153.X. The Chinese patent application with application number 201680064153.X is a Chinese national phase application of international application PCT / US2016 / 059335, which claims priority to U.S. provisional patent application serial number 62 / 250,272 filed on November 3, 2015. The complete disclosure of the patent application is incorporated herein by reference in its entirety. Technical Field

[0003] The following involves optical technology, optical filter technology, spectral technology, pricing information distribution technology and related technologies. Background Art

[0004] Optical interference filters with high spectral selectivity include stacks of layers with alternating refractive index values. These filters can be designed to provide passband, stopband, highpass, lowpass, or notch filter outputs. Typically, the optical layers are deposited on a substrate that is optically transparent to the designed spectrum. For this reason, filters are sometimes referred to as filter plates and are optically uniform over the area of ​​the plate.

[0005] On the other hand, for different multispectral applications (such as spectrometers or spectrum analyzer devices), optical interference filters with different passbands or stopbands or cut-off wavelengths in different areas of the plate are useful. Because it is difficult to controllably vary the layer thickness across the substrate during layer deposition, such multispectral filters are sometimes manufactured as so-called "butcher block" filter arrays. To construct a butcher block filter array, a set of filter plates with different filter characteristics (e.g., different passband or stopband wavelengths and / or bandwidths) are formed by appropriate layer deposition. Each filter plate is designed to be uniform over the area of ​​the plate. The filter plates are then cut to form banded filter elements, which are then bonded together in a desired pattern to form a butcher block filter array. Two-dimensional filter arrays are manufactured by a similar process, except that after the filter plates are cut to form the filter elements, the filter elements are bonded together in the desired two-dimensional array.

[0006] Some illustrative multispectral filter arrays of the above type are described, for example, in U.S. Publication 2014 / 0307309 A1 to Downing et al., published on October 16, 2014, the entire contents of which are incorporated herein by reference in their entirety.

[0007] This article discloses some improvements. Summary of the invention

[0008] The present disclosure relates to a device, comprising: an optical filter array, the optical filter array comprising an array of optical filter elements; wherein each optical filter element has opposing mutually parallel major faces connected by side walls, the side walls comprising at least one pair of opposing trapezoidal side walls and at least one pair of opposing mutually non-parallel side walls; and wherein the opposing mutually parallel major faces of the filter elements jointly define an optical entrance aperture and an optical exit aperture of the optical filter array, and comprise an interference filter.

[0009] The present disclosure also relates to a method of providing the above filter array and illuminating the optical filter array with converging or diverging light having a local angle matching the sidewall angle of the sidewalls of the filter elements.

[0010] Additionally, the present disclosure relates to a device comprising: an optical filter array comprising an array of inner optical filter elements, the inner optical filter elements being different from outermost optical filter elements of the optical filter array; wherein each inner optical filter element has larger and smaller opposing mutually parallel major faces connected by side walls, the side walls comprising at least one pair of opposing trapezoidal side walls and at least one pair of opposing mutually non-parallel side walls; and wherein the larger major faces of the inner optical filter elements comprise diverging apertures of the optical filter array and the smaller major faces of the inner optical filter elements comprise converging apertures of the optical filter array.

[0011] These and other non-limiting aspects and / or objects of the present disclosure are more particularly described below. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0013] Figure 1 schematically illustrates a side cross-sectional view of a filter array for filtering converging light, together with a ray trace of the converging light and a photodetector array;

[0014] Figure 2 Schematically shows Figure 1 An isolated side cross-sectional view of an optical filter array in FIG.

[0015] Figure 3 Schematically shows Figure 1 and Figure 2 an isolated side cross-sectional view of an illustrative optical filter element of the filter array in;

[0016] Figure 4 , Figure 5 , Figure 6and Figure 7 They are schematically shown Figure 1 and Figure 2 Front, top, right, and perspective views of the filter array in . Figures 4 to 7 In the example, the number of optical filter elements is reduced to a 4×4 array to reduce drawing complexity; and

[0017] Figure 8 , Fig. 9 , Fig.10 and Fig.11 Schematically depicting the front, top, right, and perspective views, respectively, of a filter array variant for light that converges or diverges in only one dimension (e.g., as produced by a linear light source or a cylindrical light source as shown). Figures 4 to 7 Similar, in Figures 8 to 11 In FIG. 5 , the number of exemplary optical filter elements is reduced to a 4×4 array to reduce drawing complexity. DETAILED DESCRIPTION

[0018] By referring to the accompanying drawings, the processes and devices disclosed herein can be more fully understood. These drawings are only schematic representations given for convenience and ease of explaining the prior art and / or the present disclosure, and therefore, are not intended to indicate the relative sizes and dimensions of its components or parts.

[0019] Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the specific structures of the embodiments selected for illustration in the accompanying drawings, and are not intended to define or limit the scope of the present disclosure. In the following drawings and the following description, it should be understood that the same number marks represent components with similar functions.

[0020] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0021] 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., it includes at least the degree of error associated with measurement of the particular quantity). When used with a particular value, it should be considered to disclose that value as well. For example, the term "about 2" also discloses the value "2", and the range "from about 2 to about 4" also discloses the range "from 2 to 4".

[0022] refer to Figure 1 , a disadvantage of anvil-type filter arrays pointed out in this paper is that they are not suitable for many practical optical systems that have a finite focal plane and operate on converging or diverging beams. Figure 1FIG. 1 shows a ray trace for a system having a focal plane P at a finite position along the optical axis OA. Due to the finite position of the focal plane P, light passing through the optical system (schematically represented by illustrative light rays L) forms a ray trace having a Figure 1 The cone beam has a cone half angle A shown, and the cone beam converges at the focal plane P. Figure 1 In the figure, the light L travels from left to right in the figure and is detected by the detector array 8 located in the plane near the focal plane P, so the light L is a converging light. Alternatively, if the light spreads away from a finite focal plane, such as from a small light source at the focal plane, the light may be divergent (optional, not shown). In either case, the light will form a converging (as shown) or diverging beam.

[0023] Anvil filter arrays are made of filter elements in the form of strips (for one-dimensional arrays) or blocks (for two-dimensional arrays) cut from a filter plate. A cutter creates vertical sidewalls for the "strips" or "blocks". U.S. Publication 2014 / 0307309A1 by Downing et al. discloses improvements 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 2014 / 0307309A1 by Downing et al., the "strips" or "blocks" are cut into sidewalls with angles that match the angle of incidence of the selected light. This reduces light scattering and light loss at the boundaries between filter elements.

[0024] It is recognized that in the case of converging or diverging light, such filter arrays can generate light scattering and light losses at the boundaries between adjacent filter elements. Such light scattering and light losses cannot be reduced using the method of Downing et al. in U.S. Publication 2014 / 0307309A1 because there is no defined angle of incidence for converging or diverging light.

[0025] Continue to refer Figure 1 And further reference Figure 2, the improved optical filter array 10 has optical filter elements 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j with non-parallel sidewalls, and for each filter element, the angle of the sidewalls (optionally, except for the outer sidewalls of the outermost filter elements 12a, 12j that form the perimeter of the filter array 10) is designed to match the local convergence angle or divergence angle of light rays L. The joined sidewalls of adjacent filter elements are at the same local position on the surface of the filter array 10, and therefore have the same sidewall angle. As recognized herein, this consistency of adjacent sidewall angles allows the filter elements to be fixed together at the joined sidewalls, for example, using an adhesive or other bonding method, to form the filter array 10. By way of illustration, as Figure 2 As marked in , at the interface 14 between the filter elements 12b and 12c, the joined sidewalls of the filter elements 12b and 12c have the same sidewall angle.

[0026] As in Figure 1 and Figure 2 As further seen in , the side wall angle increases with increasing distance from the optical axis OA, so as to coincide with the increasing angle of the converging or diverging light beam as the distance from the optical axis OA increases.

[0027] Continue to refer Figure 1 and 2 And further reference Figure 3 , the side walls of a given filter element are not parallel to each other. Moreover, the inner side wall of a given filter element has a smaller side wall angle than the outer side wall (wherein "inner" and "outer" mean relatively closer to the optical axis OA and relatively farther from the optical axis OA, respectively). By way of illustration, Figure 3 Filter element 12d is shown separately. For filter element 12d, the side wall angle A with the outer side wall 18 O In comparison, the inner side wall 16 has a smaller side wall angle A I (measured in the direction of the optical axis OA).

[0028] Continue to refer Figure 3 For each filter element (e.g., exemplary filter element 12d), the filter element includes a transparent substrate or body 20 bounded by four side walls 16, 18 (including two side walls other than side walls 16, 18, Figure 31 ), the side walls 16, 18 extend between opposing major faces 22, 24. One or both of these major faces include an interference filter, for example, the exemplary major face 22 of the filter element 12d includes an interference filter 26, which can be deposited by techniques such as sputtering, vacuum evaporation, plasma deposition, etc. The interference film 26 is typically composed of a designed stack of layers that provide optical interference to provide a passband, stopband, high pass, low pass, or notch filter based on the design. 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 filter array 10 is typically a multispectral filter, each filter element 12a, 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i, 12j typically has a different interference filter (although some filter elements are selected to be identical—e.g., if filter array 10 is intended to be symmetrical about optical axis OA, the interference filters for filter elements 12a, 12j are identical; the interference filters for filter elements 12b, 12i are identical; the interference filters for filter elements 12c, 12h are identical; the interference filters for filter elements 12d, 12g are identical; and the interference filters for filter elements 12e, 12f are identical). Although not shown, filter element 12d may additionally or alternatively include an interference filter on its major face 24.

[0029] In general, the filter element can be designed for any passband or stopband in the ultraviolet, visible, or infrared wavelength ranges. By way of illustrative example, the filter element (or more specifically, the filter element body or substrate, e.g. Figure 3 The filter element body or substrate 20 of the exemplary filter element 12d can be made of a light-transmitting material such as glass, sapphire, or other material with suitable transparency within the operable optical range. The interference filter 26 can include alternating layers of tantalum oxide (Ta2O5) and silicon dioxide (SiO2), or more generally alternating layers of two (or more) materials with different refractive index values. For the operable optical range, the layers making up the interference filter 26 are also preferably light-transmitting, but because they are thin layers, some optical absorption within the operable optical range is acceptable. For example, as another illustrative example, the layers can be metal layers / metal oxide layers, such as titanium / titanium dioxide (Ti / TiO2). Known techniques for designing interference filters can be used to design the layer thickness for a given passband or notch filter stopband, or to provide a desired high-pass or low-pass filtering characteristic.

[0030] Figure 1 and Figure 2The filter 10 is depicted in a side cross-sectional view. This side view does not capture the converging light L or the three-dimensional shape of the filter array 10.

[0031] refer to Figures 4 to 6 , which passes through the front side of the filter 10 ( Figure 4 ),top( Figure 5 ) and the right side ( Figure 6 ) view schematically depicts the three-dimensional shape, Figure 7 A perspective view of the filter 10 is shown in its optical environment, which includes a converging light beam L and a detector array 8 shown in perspective. Figures 4 to 7 In order to simplify the illustration, the number of filter elements shown is reduced to a 4×4 filter element array. It should be understood that the number of filter elements is a design parameter that is appropriately selected based on the required filter resolution and the total area of ​​the filter array.

[0032] The filter element has a pyramidal shape (see Figure 3 10) having two mutually parallel bases 22, 24 with the same number of vertices (four vertices for the rectangular bases 22, 24 of the exemplary filter array 10) (i.e., the bases 22, 24 are parallel to each other), and at least two non-parallelograms (due to different sidewall angles, such as in the exemplary filter array 10). Figure 3 In the example, the different angles A of the filter element 12d are I , A O ) of the trapezoidal side walls 16, 18. The two parallel bases 22, 24 of the filter elements in the assembled filter array 10 together define the optical entrance aperture and the optical exit aperture of the filter array 10 (or vice versa), as shown in Figure 1 and Figure 7 as shown in .

[0033] Continue to refer Figures 4 to 7 And further reference Figures 8 to 11 For a beam that diverges or converges in two dimensions, the four side walls of the filter element are all trapezoidal side walls, as shown in Figure 4 , Figure 6 and Figure 7 In these embodiments, each pair of opposing trapezoidal side walls (e.g., Figure 3 The side walls 16, 18) are not parallel to each other (i.e., they are not parallel to each other). Figures 8 to 11 As shown, for a light beam that is divergent or convergent in only one dimension, parallel in an orthogonal dimension (e.g., produced by a cylindrical light source or a linear light source 30), and multi-spectrally filtered only in the divergent or convergent direction, a filter array variant 40 has strip filter elements, each of which has two trapezoidal end sidewalls 46. trap and the long side wall 46 of the parallelogrampar In this embodiment, the two trapezoidal end side walls 46 trap are mutually parallel (ie, parallel to each other) opposite side walls, and the long side walls 46 of the two parallelograms par The linear or cylindrical light source 30 has long side walls 46 that are parallel to each other. par Parallel and transverse to the trapezoidal end side wall 46 trap The major axis is 32.

[0034] Return to reference Figure 1 and Figure 2 Typically, the inner filter elements (i.e., the filter elements 12b, 12c, 12d, 12e, 12f, 12g, 12h, 12i that are not the outermost filter elements 12a, 12j of the filter array 10) have a major surface ( Figure 3 The main surface 22) has a larger surface area than the other main surface ( Figure 3 The larger area of ​​the main surface 24 of the inner filter element together includes the diverging aperture 50 of the filter array 10 (at Figure 2 The smaller major surfaces of the inner filter elements together comprise the converging aperture 52 of the filter array 10. Figure 1 and Figure 2 In FIG. 1 , the left side of the filter array 10 is a diverging aperture 50, and the right side of the filter array 10 is a converging aperture 52. Figure 1 ) applies the filter to converging light, the diverging aperture is the entrance aperture (i.e., the converging light is input to the diverging aperture 50), and the converging aperture is the exit aperture (i.e., the converging light is emitted from the filter array 10 through the converging aperture 52). Conversely, if the filter is applied to diverging light (as shown in Fig.11 ), then the converging holes (such as Fig.11 The top hole of the filter array 40 shown is the entrance hole, while the diverging hole ( Fig.11 (not visible in the perspective view shown) is the exit aperture.

[0035] The outermost filter elements may be an exception to the above-described geometry in that they may optionally be "squared off" as a whole to have non-sloped peripheral sidewalls for the filter array 10 (as seen in the outermost filter elements 12a and 12j, where the left major surface is smaller than the right major surface), which affects the area of ​​the major surfaces.

[0036] When designing the sidewall angles of the filter element (e.g. Figure 3 Angle A of an exemplary filter element 12d I and A O), the local angle of the diverging or converging light L at the sidewall is considered. According to Snell's law, due to the bending of light, this angle is preferably the angle in the filter element material, not the angle in air. According to Snell's law, the angle θ of the light in the filter element material is related to the angle θ of the light in air, that is, sin(θ)=n fe sin(θ fe ), where n fe is the refractive index of the filter element, and the environment is assumed to be air, vacuum, or other environment with a refractive index of n = 1. For example, if the local ray angle at the sidewall of the filter element is θ = 15°, and n fe =1.5, then And the side wall at this position is appropriately selected to be 10°. (If the environment is n ambient non-uniform oil or some other material, then Snell's law generalizes to n ambient sin(θ)=n fe sin(θ fe ))). The filter elements can be manufactured in various ways, such as by initially cutting parallelepiped filter elements and then grinding each cut filter element to form the side wall angle. Optionally, the cutting can be performed using a cutting machine with a suitable angle or an angled wafer mounting jig.

[0037] It should be understood that the above-disclosed and other various features and functions and their alternatives can be combined into many other different systems or applications as needed. It will be further understood that various currently unforeseen or unanticipated alternatives, modifications, variations or improvements can be made by those skilled in the art subsequently, and these alternatives, modifications, variations or improvements are also intended to be included in the following claims.

[0038] project

[0039] Item 1. A device comprising:

[0040] An optical filter array, comprising an array of optical filter elements;

[0041] wherein each optical filter element has opposing mutually parallel major faces connected by side walls, the side walls comprising at least one pair of opposing trapezoidal side walls and at least one pair of opposing mutually non-parallel side walls;

[0042] The above-mentioned opposite and mutually parallel main surfaces of the filter element jointly define the optical entrance hole and the optical exit hole of the optical filter array, and include an interference filter.

[0043] Item 2. According to the device described in Item 1, each filter element is a strip having side walls, wherein the strip includes a pair of opposing trapezoidal end side walls and a pair of opposing non-parallel long side walls.

[0044] Item 3. The device according to Item 2, further comprising:

[0045] A linear or cylindrical light source having a long axis parallel to the long sidewalls of the filter element.

[0046] Item 4. The device according to Item 1 is characterized in that each filter element includes two pairs of opposite trapezoidal side walls, wherein each pair of opposite trapezoidal side walls are not parallel to each other.

[0047] Item 5. The device according to Item 1, further comprising:

[0048] An optical system for producing converging or diverging light, wherein at least one pair of opposing side walls of each filter element is aligned with a local angle of the converging or diverging light.

[0049] Item 6. The device according to Item 1 is characterized in that, unlike the outermost filter element in the filter array, the main surface of the filter element has a larger area at one of the optical entrance hole and the optical exit hole than at other locations in the optical entrance hole and the optical exit hole.

[0050] Item 7. The device according to Item 1, wherein the optical filter element comprises:

[0051] A plurality of optical filter elements of different optical filter types defined by different interference filters.

[0052] Item 8. The device according to Item 1 is characterized in that the interference filter of the optical filter element includes a passband filter or a notch filter.

[0053] Item 9. A method comprising:

[0054] Providing an optical filter array according to item 1; and

[0055] The optical filter array is illuminated with converging or diverging light having a local angle that matches the sidewall angle of the sidewalls of the filter elements.

[0056] Item 10. A device comprising:

[0057] an optical filter array comprising an array of internal optical filter elements, said internal optical filter elements not being outermost optical filter elements of said optical filter array;

[0058] wherein each internal optical filter element has larger and smaller opposed mutually parallel major faces connected by side walls, the side walls comprising at least one pair of opposed trapezoidal side walls and at least one pair of opposed mutually non-parallel side walls;

[0059] Wherein the larger major face of the internal optical filter element comprises the diverging apertures of the optical filter array, and the smaller major face of the internal optical filter element comprises the converging apertures of the optical filter array.

[0060] Item 11. The apparatus of Item 10, wherein each internal optical filter element is a strip having a pair of opposing trapezoidal end side walls and a pair of opposing mutually non-parallel long side walls.

[0061] Item 12. The device according to Item 10, characterized in that each internal optical filter element includes two pairs of opposing trapezoidal side walls, wherein each pair of opposing trapezoidal side walls are non-parallel to each other.

[0062] Item 13. The apparatus according to Item 10, further comprising:

[0063] An optical system produces converging light that enters the optical filter array at the diverging aperture and exits the optical filter array at the converging aperture.

[0064] Item 14. The apparatus according to Item 10, further comprising:

[0065] An optical system produces divergent light that enters the optical filter array at the converging aperture and exits the optical filter array at the diverging aperture.

Claims

1. An optical filter array, characterized in that: include: an optical filter element array having an array of inner optical filter elements that are not outermost optical filter elements of the optical filter array; wherein at least each internal optical filter element comprises a base defined by four trapezoidal side walls, the trapezoidal side walls being configured as two pairs of opposing side walls; wherein at least each internal optical filter element of the optical filter array has opposing mutually parallel major surfaces connected by two pairs of opposing trapezoidal side walls, wherein each pair of the opposing trapezoidal side walls are not parallel to each other, and the opposing mutually parallel major surfaces of each internal optical filter element include larger and smaller opposing mutually parallel major surfaces; wherein the larger principal face of the internal optical filter element comprises the diverging apertures of the optical filter array and the smaller principal face of the internal optical filter element comprises the converging apertures of the optical filter array, wherein one or both of the opposed mutually parallel major faces comprise an interference filter stack, the interference filter stack being bounded by the four trapezoidal side walls and having a corresponding shape defined by the trapezoidal side walls; wherein at least each trapezoidal sidewall of the internal optical filter element has a sidewall angle configured to match a local angle of converging or diverging light in the optical filter element material at the trapezoidal sidewall; and, Wherein, the sidewall angle of at least the inner optical filter element increases with increasing distance from the optical axis to be consistent with the increasing angle of converging or diverging light with increasing distance from the optical axis.

2. The optical filter array according to claim 1, characterized in that: The interference filter stack comprises alternating layers of two or more materials, wherein the two or more materials have different refractive indices.

3. The optical filter array according to claim 2, characterized in that: The interference filter stack comprises one of the following alternating layers: Tantalum oxide and silicon dioxide; or, Titanium and titanium dioxide.

4. An optical filter array according to any one of the preceding claims, characterized in that The optical filter array comprises blocks cut from a filter plate.

5. The optical filter array according to any one of claims 1 to 3, characterized in that: The substrate of each of the optical filter elements comprises a light transmissive material that is transparent within the operable optical range of the optical filter array.

6. The optical filter array according to any one of claims 1 to 3, characterized in that: The major face of each of the internal optical filter elements has a rectangular shape.

7. The optical filter array according to any one of claims 1 to 3, characterized in that: At least each internal optical filter element has a pyramidal shape.

8. The optical filter array according to claim 1, wherein: The optical filter array further comprises: An optical system for generating converging light or diverging light, wherein each pair of opposing trapezoidal side walls of each internal optical filter element is aligned with the local angle of the converging light or diverging light.

9. The optical filter array according to any one of claims 1 to 3, characterized in that: The interference filter stack of one or more of the optical filter elements comprises a passband filter or a notch filter.

10. The optical filter array according to any one of claims 1 to 3, characterized in that: Adjacent optical filter elements have the same sidewall angle, wherein the adjacent optical filter elements are fixed together at the joined trapezoidal sidewalls to form the optical filter array.

11. The optical filter array according to claim 1, wherein: The optical filter array further comprises: An optical system produces converging light that enters the optical filter array at the diverging aperture and exits the optical filter array at the converging aperture.

12. The optical filter array according to any one of claims 1 to 3, characterized in that: The optical filter element comprises: A plurality of optical filter elements of different optical filter types defined by different interference filter stacks.

13. The optical filter array according to claim 1, wherein: The optical filter array further comprises: An optical system produces divergent light that enters the optical filter array at the converging aperture and exits the optical filter array at the diverging aperture.

14. A method for filtering convergent light or divergent light, characterized in that: The method comprises: Providing an optical filter array according to any one of claims 1 to 3; and The internal optical filter array is illuminated with converging or diverging light having a local angle that matches the sidewall angle of the trapezoidal sidewalls of the optical filter elements.

15. The method according to claim 14, characterized in that The irradiation is performed by a light beam that diverges or converges in two dimensions.

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