Photoresist as an opaque aperture mask on a multispectral filter array

Abstract

To provide a favorable photoresist as an opaque aperture mask on multispectral filter arrays.SOLUTION: An apparatus (e.g., a multi-spectral optical filter array, an optical wafer, an optical component) has an aperture mask printed directly thereon, the aperture mask including a positive or negative photoresist. The apparatus includes a substrate having the aperture mask printed on at least one of a light entrance surface and a light exit surface of the substrate so as to provide an aperture over a portion of the substrate. The photoresist from which the aperture mask is formed is photosensitive or non-photosensitive, and is deposited / printed to form the aperture mask on the substrate.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This application claims the benefit of U.S. Provisional Application No. 62 / 557,909, filed on September 13, 2017, entitled "PHOTO RESIST AS OPAQUE APERTURE MASK ON MULTISPECTRAL FILTER ARRAYS". U.S. Provisional Application No. 62 / 557,909, filed on September 13, 2017, entitled "PHOTO RESIST AS OPAQUE APERTURE MASK ON MULTISPECTRAL FILTER ARRAYS", is hereby incorporated by reference in its entirety into the specification of this application.

Background Art

[0002] This disclosure relates to optical technology, optical filter technology, spectroscopy technology, and related technologies.

[0003] Optical filters with high spectral selectivity can be manufactured using stacks of layers with alternating layers of two (or more) constituent materials having different refractive index values. Such filters are sometimes referred to as interference filters and can be designed to provide a designed passband, stopband, high-frequency, or low-frequency output. For passband filters, the width of the passband can typically be made narrower as desired by using more layer periods in the stack, even if there is some transmission loss at the peak transmission wavelength as a possibility. Notch filters can be similarly designed by constructing a stack of layers to form a Bragg reflector that blocks the stopband. The layer stack is light-transmissive with respect to the wavelength or range of wavelengths to be transmitted and is deposited on a substrate, which can be, for example, a glass plate for an optical filter operating within the visible spectrum. This results in a filter plate whose structural rigidity is provided by the substrate.

[0004] In such optical filters, a given filter plate operates within a single, clearly defined passband or stopband. The layers of the stack are typically required to have precise thicknesses that satisfy the wavelength and bandwidth defined with respect to the passband or stopband.

[0005] However, varying layer thickness across a substrate plate in a controlled manner, either during or after deposition, to provide different passbands or stopbands within different areas of the plate, is difficult or impossible. Such arrangements are useful for spectrometers, spectral analyzers, or other "multispectral" applications.

[0006] A filter array addresses this problem by fabricating a set of filter plates with different filtering characteristics (e.g., different passband or stopband wavelengths and / or bandwidths). The filter plates are then die-cut to form filter elements in the shape of strips. These strips are then joined together in the desired pattern to form a filter array. The resulting filter array is sometimes referred to as a "laminated timber" due to the similarity of its joined structural elements (here, the filter elements, and for reference, the wood elements in the case of actual laminated timber). This approach isolates the optical properties of each filter element in the filter array from those of the other filter elements, allowing for virtually any combination of filter elements within a single filter array.

[0007] In optical technology, if the image to be viewed is too bright, stray light can cause the bright area to blur or eliminate the boundary between the bright and dark areas, blurring the boundary between them. This can be particularly problematic when two bright areas are separated by a small dark area, as the illumination can effectively eliminate the separating dark area. This can result in a state where there is too much glare for any significant detail to be seen.

[0008] To mitigate the aforementioned problems, aperture masks are often used. A mask, often dark in color, is placed across the filter array, and the mask contains the aperture. When properly constructed and positioned, aperture masks greatly reduce glare and dazzling light, reduce illumination, eliminate diffraction effects, thereby improving contrast and avoiding undesirable blurring of bright areas into dark areas. Generally, aperture masks function by reducing a wide range of resolution to the resolution of an unoccluded refractor having apertures of the same size as the apertures within the aperture mask. However, in many cases, it may be desirable to have a sharp, stable image with reduced resolution instead of a bright image lacking any detail. The use of aperture masks provides a wide range of this desired sharp, stable image.

[0009] Conventionally, aperture masks are deposited in a manner similar to that of the optical coating itself. A first layer is deposited on the optical coating. A chemical compound is then applied to the first layer in a design corresponding to the desired apertures. This forms a mask on the first layer, masking those portions that should remain. An etching compound is then applied, which removes the unmasked portions of the first layer. The chemical compound is then removed via the application of a suitable chemical, leaving the aperture mask formed from the first layer. This process requires the use of a coating with optical dark mirror coating (DMC) on which the aperture mask is printed, and further requires certain conditions regarding the chemicals, such as temperature, stress, and a long lift-off process.

[0010] Therefore, it would be desirable to provide an aperture mask that eliminates the need for optical DMC coating and eliminates certain conditions required for coating, such as temperature and stress in the chemicals and long lift-off processes. Several improved aperture masks are disclosed herein. [Overview of the project] [Means for solving the problem]

[0011] This disclosure relates to a method and apparatus (e.g., a multispectral optical filter array, an optical wafer, an optical component) having an aperture mask deposited / printed thereon.

[0012] Disclosed in various embodiments is an apparatus comprising a substrate having an aperture mask printed on at least one of the light incident surface or light exit surface of the substrate so as to provide an aperture over a portion of the substrate. The aperture mask includes, or in other words, is formed from, a photoresist.

[0013] The photoresist may be opaque. In certain embodiments, the substrate does not include an optical coating between the aperture mask and at least one of the light incident surface or light exit surface on which the aperture mask is printed. The aperture mask can be printed on both the light incident surface and the light exit surface of the substrate.

[0014] The substrate to be coated can be a multispectral optical filter array, an optical wafer, or another optical component.

[0015] Photoresist can be positive or negative, and can be photosensitive or non-photosensitive.

[0016] A method is also disclosed that includes the steps of: providing a substrate to be film-coated; printing an aperture mask on an optical coating on at least one of the top or bottom of the substrate to be film-coated so as to provide an aperture over a portion of the substrate; and depositing a photoresist, wherein the photoresist is printed and forms an aperture mask on the substrate.

[0017] The method may further include the step of curing the photoresist deposited on the substrate (for example, via an ultraviolet lamp) to thereby form an aperture mask thereon.

[0018] Also disclosed herein is a multispectral optical filter array having a filter element substrate on which an opaque aperture mask is printed, the aperture mask being formed from a photoresist. This specification also provides, for example, the following items: (Item 1) An optical device, A substrate, wherein the substrate has an aperture mask printed on at least one of the light incident surface or light emission surface of the substrate so as to provide an opening over a portion of the substrate. Equipped with, The aperture mask is an optical device containing a photoresist. (Item 2) The apparatus described in item 1, wherein the photoresist is opaque. (Item 3) The apparatus according to any one of items 1-2, wherein the optical coating is not present between the substrate and the aperture mask. (Item 4) The apparatus according to any one of items 1-3, wherein the aperture mask is printed on both the light incident surface and the light exit surface of the substrate. (Item 5) The apparatus according to any one of items 1-4, wherein the substrate is selected from the group consisting of a multispectral optical filter array, an optical wafer, and optical components. (Item 6) The apparatus according to any one of items 1-5, wherein the photoresist is photosensitive. (Item 7) The apparatus according to any one of items 1-6, wherein the photoresist is a positive-type photoresist. (Item 8) The apparatus according to any one of items 1-6, wherein the photoresist is a negative-type photoresist. (Item 9) A method for forming an opening mask, Depositing a photoresist layer on the surface of an optical substrate, Exposing a portion of the aforementioned photoresist layer to light, Developing the photoresist layer to form the aperture mask on the surface of the optical substrate, and A method comprising. (Item 10) The method according to item 9, wherein an optical coating is not provided between the substrate and the photoresist layer. (Item 11) The method according to any one of items 9-10, wherein the photoresist layer is deposited on both the light incident surface and the light exit surface of the optical substrate. (Item 12) The method according to any one of items 9-11, wherein the optical substrate is selected from the group consisting of a multi-spectral optical filter array, an optical wafer, and an optical component. (Item 13) The method according to any one of items 9-12, wherein the photoresist is a positive photoresist. (Item 14) The method according to any one of items 9-12, wherein the photoresist is a negative photoresist. (Item 15) The method according to any one of items 9-14, wherein the photoresist is photosensitive. (Item 16) A multi-spectral optical filter array, wherein the multi-spectral optical filter array has a filter element substrate, and an opaque aperture mask is printed on the filter element substrate, and the aperture mask is formed from a photoresist. (Item 17) The multi-spectral optical filter array according to item 16, wherein the aperture mask is printed on both the light incident surface and the light exit surface of the substrate. (Item 18) An optical device, A multispectral optical filter array comprising a plurality of optical filter elements, wherein the plurality of optical filter elements are joined together to form the multispectral optical filter array, An aperture mask formed on the light incident surface and / or light output surface of the multispectral optical filter array, wherein the aperture mask comprises a photoresist or a non-photosensitive polyimide. An optical device equipped with the following features. (Item 19) The aperture mask comprises a positive-type photoresist or a negative-type photoresist, as described in item 18. (Item 20) The aperture mask comprises a non-photosensitive polyimide, as described in item 18. (Item 21) The optical device according to any one of items 18-20, wherein each optical filter element comprises a filter element substrate and a filter layer stack forming an interference filter having a passband or a stopband, the filter layer stack being supported by the filter element substrate. (Item 22) Each optical filter element has a different passband or stopband, as described in any one of items 18-21 of the optical device.

[0019] These and other non-limiting characteristics of this disclosure are specifically disclosed below. [Brief explanation of the drawing]

[0020] The following is a brief description of the drawings, which are presented for illustrative purposes only and not intended to limit the exemplary embodiments disclosed herein.

[0021] [Figure 1] Figure 1 schematically shows a side view of a first exemplary filter array having an aperture mask that includes or is formed from a photoresist that can be printed thereon.

[0022] [Figure 2] Figure 2 schematically shows a perspective view of the filter array in Figure 1.

[0023] [Figure 3] Figure 3 schematically illustrates the method for manufacturing a filter array. [Modes for carrying out the invention]

[0024] A more complete understanding of the components, processes, and apparatus disclosed herein can be obtained by reference to the accompanying drawings. These drawings are merely schematic diagrams based on convenience and ease of demonstrating the disclosure and are therefore not intended to show the relative sizes and dimensions of the device or its components, and / or to define or limit the scope of the exemplary embodiments.

[0025] Specific terminology is 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.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art. In case of any conflict, this document, including its definitions, shall prevail. Preferred methods and materials are described below, but similar or equivalent methods and materials may also be used in the practice or testing of this disclosure. All publications, patent applications, patents, and other references referenced herein are incorporated herein in their entirety by reference. The materials, methods, and articles disclosed herein are illustrative and not intended to be limiting.

[0027] Unless the context explicitly indicates otherwise, the singular forms "a," "an," and "the" refer to multiple objects.

[0028] As used herein and in the claims, the term “comprising” may include embodiments of “consisting of” and “consisting essentially of.” The terms “comprise,” “include,” “having,” “has,” “can,” “contain,” and their variations are intended to be non-restrictive transitional phrases, terms, or words that require the presence of an expressed ingredient / step and allow for the presence of other ingredients / steps, as used herein. However, such descriptions should also be interpreted as describing a composition or process as “consisting of” and “essentially consisting of” the enumerated ingredients / steps, which allows for the presence of only the expressed ingredients / steps and excludes other ingredients / steps, in addition to any unavoidable impurities that may arise therefrom.

[0029] Numerical values ​​in the specification and claims of this application should be understood to include numerical values ​​that, when rounded to the same number of significant figures to determine the value, become identical, and numerical values ​​that differ from the stated value by less than the experimental error of the conventional measurement technique of the type described herein.

[0030] All ranges disclosed herein include the listed endpoints and are independently combinable (for example, the range "2 grams to 10 grams" includes the endpoints, i.e., 2 grams and 10 grams, and all intermediate values).

[0031] The terms “approximately” and “about” can be used to include any number that can vary without changing the fundamental function of its value. When used with a range, “approximately” and “about” also disclose a range defined by the absolute values ​​of two endpoints; for example, “approximately 2 to approximately 4” also discloses the range “2 to 4”. Generally, the terms “approximately” and “about” can refer to ±10% of the number being expressed.

[0032] This disclosure may refer to temperatures for certain process steps. It should be noted that these generally refer to the temperatures at which a heat source (i.e., a furnace, oven, etc.) is set, and not necessarily to the temperatures that must be achieved by the material being exposed to the heat.

[0033] As used herein, the term "room temperature" refers to a temperature within the range of 20°C to 25°C.

[0034] It should be noted that the coefficient of thermal expansion is typically reported as the average between the starting temperature and the reported temperature.

[0035] It should be noted that, as used herein, “opening mask,” “mask,” and “opaque coating” may be used synonymously unless understood in the context below to refer to distinctly different embodiments. For example, “opening mask” may include other coatings other than “opaque,” ​​and the use herein is intended solely to assist the reader and is not intended to limit the application of this disclosure to opening masks for opaque coating materials.

[0036] As described in more detail below, this disclosure provides exemplary embodiments of methods and apparatus, including the application of opaque aperture masks comprising or formed therefrom on various optical components (e.g., filter arrays). According to some embodiments described herein, the application may be carried out on one or both sides of a filter, creating an aperture mask on the incident and / or exit surfaces. It should be understood that non-limiting embodiments of this disclosure describe and illustrate embodiments in which the aperture mask may be offset from the incident and / or exit surfaces, taking into account the angle of incidence of the light ray.

[0037] As shown in Figure 1, an existing or pre-fabricated optical filter array (i.e., a substrate) is provided. In a particular illustrative embodiment, the substrate is a multispectral optical filter array. The substrate may comprise an optical wafer. The substrate in Figure 1 corresponds to an angled array. The perspective view in Figure 2 shows the “bar-like” geometry of the optical filter elements of this one-dimensional filter array. As seen in both Figures 1 and 2, the filter elements have inclined sidewalls 140 (labeled only in Figure 1). However, the outermost optical filter elements of the filter array (identified as numbers “1” and “4”) have straight “outer” sidewalls 141 that form the edge of the assembled filter array. This may be advantageous insofar as the assembled filter array has the shape of a right-angled parallelepiped. An alternative (not shown) would employ optical filter elements with inclined sidewalls on both sides and include additional triangular filler elements to provide straight outermost sidewalls to the geometry of the assembled filter. The filter array depicted in Figure 1 is shown as an angled filter array. However, the substrate / filter array of this disclosure can generally be any desired structure and is limited only by the aperture mask applied thereon.

[0038] Referring to Figure 1, the improved filter array is shown in a side cross-sectional view. In this schematic illustrative embodiment, the filter array includes four filter elements labeled "1" through "4". (This is illustrative only; generally, a filter array may have tens or hundreds of filter elements.) Each filter element is die-cut from a filter plate on which filter layer stacks having different optical properties (e.g., different passbands or stopbands in terms of center wavelength and / or bandwidth) are deposited. Thus, as shown in Figure 1, each filter element may include a filter layer stack 112 supported by a filter element substrate 114. The filter layer stack 112 may be embodied, for example, as multiple layers of optical coatings arranged on the filter element substrate 114, forming an interference filter.

[0039] Typically, each filter element is die-cut from a single filter plate. Filter elements may generally be designed for any passband or stopband within the ultraviolet, visible, or infrared wavelength range. In an illustrative example, a filter element operating in the visible range may include a filter element substrate 114 of glass, sapphire, or another material having suitable transparency in the optical range, and the filter stack 112 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. In another illustrative example, the layers may be metal / metal oxide layers such as titanium / titanium dioxide (Ti / TiO2). Known techniques for designing interference filter optical stacks can also 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. The die-cut filter elements are joined together using adhesive or other bonding agents 116. The joined optical filter elements may include multiple optical filter elements defined by different interference filters. The interference filters of the optical filter elements may include passband filters or notch filters that operate in the visible spectrum, ultraviolet spectrum, and / or infrared spectrum (in various embodiments).

[0040] Continuing with Figure 1, the illustrative filter array is designed to be illuminated by light. Again, the filter array depicted in Figure 1 is shown as an angled filter array such that light will be incident on the array at a certain angle. As will be understood by those skilled in the art as described above, the substrate / filter array of the present disclosure can generally be any desired structure and is limited only by the aperture mask applied thereon.

[0041] During use, light strikes the light incident surface 123 of the filter array. Printed on the light incident surface 123 of the filter array is the incident aperture 120. The incident aperture 120 defines an aperture mask on the light incident surface 123 of the filter array. According to this disclosure, the aperture mask defined by the incident aperture 120 includes a photoresist on which the aperture is applied at a predetermined location on the array. The incident aperture 120 reduces optical crosstalk at the light incident surface 123 of the filter array (e.g., blocking stray light).

[0042] Light then passes through the filter layer stack 112 of the filter element and through the filter element substrate 114, and exits from the light-emitting surface 124 of the filter array. Printed on the light-emitting surface 124 is the exit aperture 122. The exit aperture 122 defines an aperture mask on the light-emitting surface 124 of the filter array. According to this disclosure, the aperture mask defined by the exit aperture 122 includes a photoresist on which the aperture is applied at a predetermined location on the array. The exit aperture 122 reduces optical crosstalk at the light-emitting surface 124 of the filter array (e.g., blocking stray light).

[0043] The light emitted from the light-emitting surface of each filter element is filtered by the filter layer stack 112 of that filter element, and therefore contains only the spectral components of the incident light within the passband (or, in the case of a notch filter, only the spectral components outside the stopband, or in the case of a high-pass filter element, only the spectral components above the cutoff wavelength, or in the case of a low-pass filter element, only the spectral components below the cutoff wavelength, etc.). In Figure 1, the filter layer stack 112 of each filter element is positioned on the light-incident surface of the filter element (or more precisely, on the light-incident surface of the filter element substrate 114). Alternatively, it is also possible to position the filter layer stack on the light-emitting surface, or on both the light-incident and light-emitting surfaces (either the same type to provide a sharper spectral bandwidth or cutoff, or a different type to provide more complex filter characteristics, e.g., two stopbands in a two-band notch filter).

[0044] As described above, the incident and exit apertures 120 and 122 define aperture masks on the incident and exit surfaces 123 and 124 of the filter array, respectively, and after the assembly of the filter elements, an opaque coating is patterned and deposited on the boundaries between the optical filter elements. In particular, the aperture masks include, or in other words, are formed from, photoresist. Due to the use of photoresist, the aperture masks can be printed directly onto the incident or exit surfaces 123 and 124 of the filter array (i.e., without an optical coating applied between the apertures and the incident or exit surfaces). This is advantageous in that it eliminates the need for an optical coating between the aperture mask and the substrate, and further eliminates certain conditions required for coating, such as temperature and stress in the chemicals and a long lift-off process. It should also be understood that such an implementation would also help eliminate stray light and crosstalk between optical bands.

[0045] Again, the aperture mask comprises or is formed from a photoresist, which advantageously eliminates the need to apply an optical coating to the substrate. Depending on the desired application of the filter array, the photoresist can be negative or positive. Similarly, again, depending on the desired application of the filter array, the photoresist can be photosensitive or non-photosensitive (e.g., a polyimide that is not photosensitive, i.e., neither a positive nor a negative photoresist). Preferred embodiments of positive photoresists capable of functioning as described above include SK-9010, S-1813, or S-1818, for illustrative purposes only and not for limiting purposes. Preferred embodiments of negative photoresists capable of functioning as described above include AZ P4620, AZ NLof 2020, or AZ NLof 2070, for illustrative purposes only and not for limiting purposes. Preferred examples of non-photosensitive photoresists capable of functioning as described above include polyimides, for illustrative purposes only and not to limit thereto.

[0046] As will be understood by those skilled in the art, the application of an aperture mask containing a photoresist to a substrate according to this disclosure can be achieved by any preferred means. For illustrative purposes only, and not limiting purposes, an aperture mask can be applied to any desired pattern using additive manufacturing techniques such as printing via an inkjet-type additive manufacturing printer, printing via an extrusion-type printer (i.e., a fused filament printing printer), any other 3D printing technique, fused deposition modeling, or printing via any standard photolithography technique, including, but not limited to, contact printing, spraying, or any other exposure or development method. A separate mask is then used to expose the photoresist to light. The photoresist is then developed by the application of a developer, which removes undesirable portions of the photoresist layer, leaving the desired portions as an aperture mask. In other words, the photoresist is used to form an aperture mask rather than being used as a means to form a desired aperture mask pattern within an optical DMC coating and then remove it from the optical DMC coating.

[0047] Accordingly, in some embodiments, the optical device comprises a multispectral optical filter array comprising a plurality of optical filter elements joined together to form a multispectral optical filter array, and an aperture mask formed on the light incident surface and / or light exit surface of the multispectral optical filter array, wherein the aperture mask comprises a photoresist or a non-photosensitive polyimide. In some embodiments, each optical filter element comprises a filter element substrate and a filter layer stack forming an interference filter having a passband or stopband, the filter layer stack being supported by the filter element substrate. In some embodiments, each optical filter element has a different passband or stopband.

[0048] Continuing with reference to Figures 1 and 2, and further to Figure 3, an illustrative method for manufacturing an aperture mask for a filter array is described. In operation S1, a photoresist layer is deposited on the surface of an optical substrate, i.e., on an existing or pre-fabricated optical filter array. To fabricate an entrance aperture 120, the photoresist layer is appropriately deposited on the light entrance surface 123 of the filter array. To fabricate an exit aperture 124, the photoresist layer is appropriately deposited on the light exit surface 124 of the filter array. In operation S2, a portion of the photoresist layer is exposed to light. In operation S3, the photoresist layer is developed to form an aperture mask (e.g., entrance aperture 120 and / or exit aperture 122) on the surface of the optical substrate.

[0049] The apparatus of this disclosure (e.g., multispectral optical filter arrays, optical wafers, optical components) can be manufactured by any preferred means, as will be understood by those skilled in the art. For example, the manufacture of the filter arrays of Figures 1 and 2 may include the fabrication of filter plates on a bulk substrate for each of the filter elements 1-4. Typically, this involves the steps of placing a substrate (e.g., a glass substrate for several visible-range designs) in a deposition system and depositing a stack of filter layers by sputtering, vacuum deposition, plasma deposition, or another technique, such that the thickness of the constituent layers of the filter stack on each filter plate is designed to provide the filter properties of the corresponding filter type. The result of this process is a set of filter plates, e.g., four filter plates corresponding to filter elements 1, 2, 3, and 4 for fabricating the illustrative filter arrays of Figures 1 and 2. The filter elements of the desired type can then be mounted in a bonding jig and bonded together at the sidewalls (e.g., inclined sidewalls for angled arrays, such as those depicted in Figures 1 and 2) or otherwise bonded together using an adhesive to form a multispectral filter array. Finally, the entrance and / or exit apertures 120, 122 and other components (e.g., photodetectors) are added to the filter array to form a complete multispectral optical system.

[0050] This specification is written with reference to exemplary embodiments. Modifications and alterations will be recalled to those skilled in the art upon careful reading and understanding of this specification. This disclosure is intended to be construed as including all such modifications and alterations to the extent that they fall within the scope of the appended claims or their equivalents.

Claims

1. An optical device, A substrate having a light incident surface and a light emission surface, wherein the substrate is A multispectral optical filter array comprising a plurality of optical filter elements, the plurality of optical filter elements joined together to form the multispectral optical filter array, and each optical filter element including a filter layer stack, or Optical wafer One of them is the circuit board, An aperture mask is printed directly on the light incident surface of the substrate to provide an incident aperture over a portion of the substrate. Equipped with, The aperture mask includes a photoresist, and the photoresist is developed such that a portion of the photoresist is removed, leaving another portion of the photoresist that forms the aperture mask on the light incident surface of the substrate. The photoresist is deposited directly onto the substrate without optical coating. On the substrate where the optical coating is absent, the remaining portion of the photoresist after development constitutes the aperture mask. The aforementioned aperture mask does not include a dark mirror coating. An optical device in which a dark mirror coating is not present between the substrate and the aperture mask.

2. The apparatus according to claim 1, wherein the substrate comprises the filter layer stack on the light incident surface of the substrate, and the aperture mask is disposed on the filter layer stack.

3. The apparatus according to any one of claims 1 to 2, wherein the substrate is an optical wafer and the photoresist is a positive-type photoresist.

4. The apparatus according to claim 1, wherein the substrate comprises a first optical filter element which is bonded together with a second optical filter element at its boundary, and the aperture mask is printed directly on the boundary.

5. The apparatus according to claim 4, wherein the substrate is provided with an adhesive at the boundary between the first and second optical filter elements.

6. The apparatus according to any one of claims 1 to 5, wherein the photoresist is opaque.

7. The apparatus according to any one of claims 1 to 6, wherein the aperture mask is printed on both the light incident surface and the light emission surface of the substrate.

8. The apparatus according to any one of claims 1 to 7, wherein the photoresist is photosensitive.

9. A method for forming an opening mask, The method involves depositing a photoresist layer on the light incident surface of an optical substrate, wherein the optical substrate is either a multispectral optical filter array or an optical wafer, the optical substrate comprises a filter layer stack on the light incident surface, the photoresist layer is deposited directly on the filter layer stack, and no optical coating is installed between the filter layer stack and the photoresist layer. Using a separate mask to expose a portion of the photoresist layer to light, By developing the photoresist layer by applying a developer to the photoresist layer on the optical substrate where the optical coating is not installed, a portion of the photoresist layer is removed, leaving another portion of the photoresist layer that forms the aperture mask on the surface of the optical substrate. Includes, The aforementioned photoresist layer is not a dark mirror coating.

10. The method according to claim 9, wherein the optical substrate comprises a plurality of optical filter elements, and the plurality of optical filter elements are joined together at their boundaries to form the multispectral optical filter array.

11. The method according to claim 10, wherein the aperture mask is positioned on the boundary between the plurality of optical filter elements.

12. The method according to any one of claims 10-11, wherein the multispectral optical filter array is provided with adhesive at the boundaries between the plurality of optical filter elements.

13. The method according to any one of claims 9-12, wherein the photoresist layer is deposited on both the light incident surface and the light emission surface of the optical substrate.

14. The method according to any one of claims 9 or 13, wherein the photoresist layer is photosensitive.

15. The method according to any one of claims 9-14, wherein the photoresist layer is a positive-type photoresist or a negative-type photoresist.

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