Multi-spectral filter

Abstract

The invention relates to a multispectral filter. The optical filter may include a substrate. The optical filter may include a first mirror and a second mirror. Each of the first mirror and the second mirror may include a plurality of quarter-wave stacks. The plurality of quarter-wave stacks may include a plurality of layers including a first material, a second material, and a third material. The optical filter may include a spacer disposed between the first mirror and the second mirror.

Description

[0001] Divisional Application Instructions

[0002] This application is a divisional application of the invention patent application with the application date of May 22, 2018, the application number of 202111322234.4, and the invention name of “Multi-spectrum filter”. This application is a divisional application of the invention patent application with the application date of May 22, 2018, the application number of 201810494349.3, and the invention name of “Multi-spectrum filter”.

[0003] This application is a divisional application filed in response to the unity opinion pointed out in the first examination opinion notice of the Chinese invention patent application with application number 202111322234.4 and name “Multi-spectral Filter” issued by the State Intellectual Property Office on July 11, 2023. Background Art

[0004] A multi-spectral sensor device can be used to capture information. For example, a multi-spectral sensor device can capture information related to a set of electromagnetic frequencies. A multi-spectral sensor device can include a set of sensor elements (e.g., optical sensors, spectral sensors, and / or image sensors) that capture information. For example, an array of sensor elements can be used to capture information related to multiple frequencies. A particular sensor element of the array of sensor elements can be associated with a filter that limits the range of frequencies for the particular sensor element. The filter can be associated with a particular bandwidth corresponding to the width of the spectral range that the filter passes toward the particular sensor element. Summary of the invention

[0005] According to some possible implementations, the optical filter may include a first mirror and a second mirror. Each of the first mirror and the second mirror may include a first one or more quarter-wave stacks. The quarter-wave stacks in the first one or more quarter-wave stacks may include a set of alternating layers of a first material and a second material. The first material may be associated with a higher refractive index than the second material. Each of the first mirror and the second mirror may include a second one or more quarter-wave stacks. The quarter-wave stacks in the second one or more quarter-wave stacks may include one or more alternating layers of a third material and a fourth material. The third material may be associated with a higher refractive index than the fourth material. The first material, the second material, the third material, and the fourth material may include three or more different materials. The optical filter may include a spacer disposed between the first mirror and the second mirror.

[0006] According to some possible implementations, the multispectral filter may include a first set of dielectric layers to reflect a portion of light directed toward the first set of dielectric layers. The first set of dielectric layers may include a first one or more quarter wave stacks. The first set of dielectric layers may include a first set of three or more different materials. The multispectral filter may include a set of spacer layers. Corresponding to a channel in a set of channels formed by a set of spacer layers, a layer in a set of spacer layers may be selected based on a refractive index of the layer and corresponding to a wavelength of light directed toward a sensor element in a set of sensor elements. The multispectral filter may include a second set of dielectric layers to reflect a portion of light directed toward the second set of dielectric layers. The second set of dielectric layers may include a second one or more quarter wave stacks. The second set of dielectric layers may include a second set of three or more different materials.

[0007] According to some possible implementations, the optical filter may include a substrate. The optical filter may include a first mirror and a second mirror. Each of the first mirror and the second mirror may include a plurality of quarter-wave stacks. The plurality of quarter-wave stacks may include a plurality of layers including a first material, a second material, and a third material. The optical filter may include a spacer disposed between the first mirror and the second mirror.

[0008] This application provides the following:

[0009] 1) An optical filter, comprising:

[0010] First mirror and second mirror,

[0011] Each of the first mirror and the second mirror comprises a first one or more quarter wave stacks,

[0012] A quarter wave stack of the first one or more quarter wave stacks comprises a set of alternating layers of a first material and a second material,

[0013] The first material is associated with a higher refractive index than the second material,

[0014] Each of the first mirror and the second mirror comprises a second one or more quarter wave stacks,

[0015] A quarter wave stack of the second one or more quarter wave stacks comprises one or more alternating layers of a third material and a fourth material,

[0016] said third material being associated with a higher refractive index than said fourth material,

[0017] the first material, the second material, the third material, and the fourth material include three or more different materials; and

[0018] A spacer is arranged between the first mirror and the second mirror.

[0019] 2) The optical filter according to claim 1, wherein at least one of the three or more different materials is an oxide material, the oxide material comprising at least one of the following:

[0020] Niobium titanium oxide (NbTiOx),

[0021] Silicon dioxide (SiO2),

[0022] Aluminum oxide (Al2O3),

[0023] Titanium dioxide (TiO2),

[0024] Niobium pentoxide (Nb2O5),

[0025] Tantalum pentoxide (Ta2O5),

[0026] Zirconium oxide (ZrO2),

[0027] Yttrium oxide (Y2O3),

[0028] Hafnium dioxide (HfO2), or

[0029] Its combination.

[0030] 3) The optical filter according to claim 1), wherein at least one of the three or more different materials comprises at least one of the following:

[0031] Nitride materials,

[0032] Fluoride materials,

[0033] Sulfide materials,

[0034] Selenide materials, or

[0035] Its combination.

[0036] 4) The optical filter according to claim 1), wherein at least one of the first mirror or the second mirror comprises a hydrogenated silicon (Si:H) material.

[0037] 5) The optical filter according to claim 1), wherein the spacer is a hydrogenated silicon (Si:H) spacer.

[0038] 6) An optical filter as claimed in claim 1), wherein at least one of the three or more different materials is associated with a refractive index greater than 200 at a spectral range between approximately 800 nm and approximately 1100 nm.

[0039] 7) An optical filter as described in claim 1), wherein at least one of the three or more different materials is associated with a refractive index less than 30.0 in the spectral range between approximately 800 nm and approximately 1100 nm.

[0040] 8) The optical filter of claim 1), wherein the optical filter is associated with a 50% relative bandwidth between approximately 0)9 nm and approximately 5)3 nm at a central wavelength of 932 nm.

[0041] 9) The optical filter of claim 1), wherein the optical filter is associated with a 50% relative bandwidth between approximately 3) 75 nm and approximately 5) 75 nm at a central wavelength of 800 nm.

[0042] 10) The optical filter of claim 1), wherein the optical filter is associated with a 50% relative bandwidth of between approximately 4 nm and approximately 8 nm at a central wavelength of 1100 nm.

[0043] 11) An optical filter as claimed in claim 1), wherein the optical filter is deposited on a substrate associated with a group of sensor elements in an array of sensor elements,

[0044] The spacer of the optical filter includes a plurality of layers that form a plurality of channels corresponding to the group of sensor elements in the array of sensor elements.

[0045] 12) The optical filter according to claim 1), wherein the optical filter is an array of optical filters corresponding to a group of sensor elements in a sensor element array.

[0046] 13) A multi-spectral filter, comprising:

[0047] a first set of dielectric layers, the first set of dielectric layers reflecting a portion of light directed toward the first set of dielectric layers,

[0048] the first set of dielectric layers comprising a first one or more quarter-wave stacks,

[0049] the first set of dielectric layers comprising a first set of three or more different materials;

[0050] a set of spacer layers,

[0051] A layer in the set of spacer layers is selected based on a refractive index of the layer and corresponds to a wavelength of light directed to a sensor element in a set of sensor elements corresponding to a channel in a set of channels formed by the set of spacer layers; and

[0052] a second set of dielectric layers, said second set of dielectric layers reflecting a portion of light directed toward said second set of dielectric layers,

[0053] the second set of dielectric layers comprising a second one or more quarter-wave stacks,

[0054] The second set of dielectric layers includes a second set of three or more different materials.

[0055] 14) The multi-spectral filter of claim 13), wherein the first group of three or more different materials and the second group of three or more different materials are a common set of three or more different materials.

[0056] 15) A multispectral filter as claimed in claim 13), wherein the first one or more quarter-wave stacks comprise:

[0057] The first quarter wave stack,

[0058] The first quarter wave stack includes a first material of the first set of three or more different materials and a second material of the first set of three or more different materials; and

[0059] The second quarter wave stack,

[0060] The second quarter-wave stack includes the first material and a third material of the second set of three or more different materials.

[0061] 16) The multi-spectral filter of claim 13), wherein the amount of channels in the set of channels is greater than or equal to a channel amount threshold, the channel amount threshold being one of the following:

[0062] 8 channels,

[0063] 16 channels,

[0064] 32 channels,

[0065] 64 channels, or

[0066] 128 channels.

[0067] 17) The multi-spectral filter of claim 13), wherein the thickness of at least one layer in the first set of dielectric layers and the second set of dielectric layers is detuned from a quarter wave thickness.

[0068] 18) The multispectral filter of claim 17), wherein the thickness is detuned by a threshold percentage, the threshold percentage comprising at least one of:

[0069] 10% reduction,

[0070] 20% reduction,

[0071] 30% reduction,

[0072] 40% reduction,

[0073] 50% reduction,

[0074] 10% increase,

[0075] 20% increase,

[0076] 30% increase,

[0077] 40% increase, or

[0078] 50% increase.

[0079] 19) An optical filter comprising:

[0080] Substrate,

[0081] First mirror and second mirror,

[0082] Each of the first mirror and the second mirror comprises a plurality of quarter-wave stacks,

[0083] The plurality of quarter wave stacks comprises a plurality of layers, the plurality of layers comprising a first material, a second material, and a third material; and

[0084] A spacer is arranged between the first mirror and the second mirror.

[0085] 20) An optical filter as described in claim 19), wherein the difference between the refractive index of the high refractive index material of the quarter-wave stack in the plurality of quarter-wave stacks and the low refractive index material of the quarter-wave stack in the plurality of quarter-wave stacks is greater than a threshold. BRIEF DESCRIPTION OF THE DRAWINGS

[0086] Figure 1 is a schematic diagram of an example implementation described herein;

[0087] Figures 2A-2D is a graph of characteristics associated with the multispectral filter described herein;

[0088] Figures 3A-3D is a graph of characteristics associated with the multispectral filter described herein;

[0089] Figures 4A-4C is a graph of characteristics associated with the multispectral filter described herein;

[0090] Figures 5A-5C is a graph of characteristics associated with the multispectral filter described herein;

[0091] Figures 6A-6C is a graph of characteristics associated with the multispectral filter described herein;

[0092] Figures 7A-7D is a graph of characteristics associated with the multispectral filter described herein; and

[0093] Figures 8A-8B is a graph of characteristics associated with the multispectral filter described in this article. DETAILED DESCRIPTION

[0094] The following detailed description of example implementations refers to the accompanying drawings.The same reference numbers in different drawings may identify the same or similar elements.

[0095] A sensor element (e.g., an optical sensor) may be incorporated into an optical sensor device to obtain information about a set of electromagnetic frequencies. For example, the optical sensor device may include an image sensor, a multi-spectral sensor, etc. that can perform sensor measurements of light. The optical sensor device may utilize one or more sensor technologies, such as complementary metal-oxide-semiconductor (CMOS) technology, charge coupled device (CCD) technology, etc. The optical sensor device may include a plurality of sensor elements (e.g., an array of sensor elements), each of the plurality of sensor elements being configured to obtain information.

[0096] The sensor element may be associated with a filter that filters light for the sensor element. For example, the sensor element may be aligned with a linear variable filter (LVF), a circular variable filter (CVF), a Fabry-Perot filter, etc., so that the portion of the filtered light is directed toward the sensor element. For a binary filter structure such as a Fabry-Perot filter, hydrogenated silicon (Si:H) may be selected as a layer of a spacer positioned between the mirrors of the filter. The mirrors may be made of a metal layer (e.g., silver) or a dielectric layer (e.g., a quarter-wave stack of alternating high refractive index layers and low refractive index layers (HL pairs)). For example, a multispectral filter may include a first mirror and a second mirror, the first mirror including a set of quarter-wave stacks of alternating hydrogenated silicon layers and silicon dioxide layers, and the second mirror including another set of quarter-wave stacks of alternating hydrogenated silicon layers and silicon dioxide layers. The multispectral filter may result in a specific filter response. For example, the multispectral filter may be associated with a specific center wavelength of a spectral range passed toward the sensor, a specific bandwidth of a spectral range passed toward the sensor element, etc. The filter response can be altered by changing the thickness of the spacers or by changing the amount of quarter wave stacks between which the spacers are positioned.

[0097] However, changing the thickness of the spacer of a single cavity type filter and / or changing the amount of quarter wave stacks may result in a change in the filter response that exceeds a threshold. For example, changing from a set of two quarter wave stacks of silicon hydride and silicon dioxide to a set of three quarter wave stacks of silicon hydride and silicon dioxide may reduce the bandwidth of the filter from a first bandwidth greater than a first threshold to a second bandwidth less than a second threshold. The implementations described herein may utilize mixed quarter wave stack configurations, altered quarter wave stack layer thicknesses, etc. to allow for alteration of the multispectral filter response. For example, the implementations described herein may utilize three or more coating materials for a quarter wave stack of a multispectral filter. In this case, the filter response of the multispectral filter may be changed from, for example, an initial bandwidth greater than a first threshold to a target bandwidth between the first threshold and the second threshold. In this way, greater granularity adjustment of the performance of the multispectral filter is achieved.

[0098] Figure 1 is a schematic diagram of an example implementation 100 described herein. Figure 1 As shown, the multi-spectral filter 105 (eg, a binary structured optical filter array) may include a first mirror 110 - 1 , a second mirror 110 - 2 , and a spacer 120 .

[0099] like Figure 1 As further shown, the first mirror 110-1 and the second mirror 110-2 can sandwich a spacer 120. In other words, the spacer 120 can separate the first mirror 110-1 and the second mirror 110-2 by a threshold distance, and / or a face of the spacer 120 can be enclosed by the first mirror 110-1 and the second mirror 110-2. In some implementations, the mirror 110 can be associated with a particular material. For example, the mirror 110 can include a set of dielectric mirror material layers (e.g., alternating hydrogenated silicon layers and silicon dioxide layers), etc., to reflect a portion of light directed from a light source toward a sensor element associated with the multi-spectral filter 105. The mirror 110 can be aligned with each sensor element in the sensor element array associated with each channel of the multi-spectral filter 105.

[0100] In some implementations, the spacer 120 can include one or more spacer layers 130. For example, the spacer 120 can include a set of spacer layers 130-1 to 130-5 (e.g., dielectric layers such as hydrogenated silicon layers). In some implementations, the thickness of the one or more spacer layers 130 can be associated with ensuring a minimum spacer thickness for a particular wavelength. In some implementations, the spacer 120 can be associated with a single cavity configuration. Additionally or alternatively, the spacer 120 can be associated with a multi-cavity configuration.

[0101] In some implementations, the thickness of one or more spacer layers 130 can depend on a binary progression. For example, spacer layer 130-3 can be associated with approximately half the thickness of spacer layer 130-2, spacer layer 130-4 can be associated with approximately half the thickness of spacer layer 130-3, and spacer layer 130-5 can be associated with approximately half the thickness of spacer layer 130-4.

[0102] In some implementations, the multispectral filter 105 can be deposited on a substrate associated with the optical sensor device. For example, the mirror 110-1 can be deposited (e.g., via a deposition process and / or a photolithography lift-off process) on a substrate including an array of sensor elements to capture information (e.g., spectral data). In some implementations, the spacer 120 can allow for the capture of information associated with multiple wavelengths. For example, a first portion of the spacer 120 aligned with a first sensor element (e.g., a rear-illuminated optical sensor or a front-illuminated optical sensor of an array of sensor elements) can be associated with a first thickness, and a second portion of the spacer 120 aligned with a second sensor element can be associated with a second thickness. In this case, light directed to the first sensor element via a first channel corresponding to the first portion and directed to the second sensor element via a second channel corresponding to the second portion can correspond to a first wavelength at the first sensor element based on the first thickness, and to a second wavelength at the second sensor element based on the second thickness. In this way, the multi-spectral filter 105 allows for multi-spectrum sensing by an optical sensor device using spacers (eg, spacer 120) associated with multiple portions associated with multiple thicknesses aligned to multiple sensor elements of the optical sensor device.

[0103] As indicated above, Figure 1 Provided only as an example. Other examples are possible and may be related to Figure 1 Different than described.

[0104] Figures 2A-2D It is a characteristic diagram related to multi-spectral filters. Figures 2A-2D An example of a multi-spectral filter is shown that employs a first set of two quarter-wave stacks and a second set of two quarter-wave stacks to sandwich a spacer.

[0105] like Figure 2AAs shown by diagram 200, filter 210 may include a substrate, a first set of two quarter wave stacks, a spacer, and a second set of two quarter wave stacks. The first set of quarter wave stacks includes layers 1 to 4 of alternating hydrogenated silicon (shown as "Si_H" or sometimes referred to as Si:H) layers and silicon dioxide (shown as SiO2) layers. The spacer may include layer 5 of hydrogenated silicon spacers. The second set of two quarter wave stacks includes layers 6 to 9 of alternating hydrogenated silicon layers and silicon dioxide layers.

[0106] The hydrogenated silicon layers of the first quarter wave stack and the second quarter wave stack can each be associated with a refractive index of approximately 3.7226 at a spectral range of approximately 932 nm, a physical thickness of approximately 62.6 nm, and a quarter wave optical thickness (shown as "QWOT") of approximately 932 nm. The quarter wave optical thickness of the layer corresponds to the physical thickness and refractive index of the layer. In some implementations, the high refractive index layer of the quarter wave stack (e.g., a hydrogenated silicon layer, which is associated with a higher refractive index than the low refractive index layer (silicon dioxide layer) of the quarter wave stack) can be associated with a refractive index greater than a threshold. For example, the high refractive index layer can be associated with a refractive index greater than approximately 2.0, a refractive index greater than approximately 2.5, a refractive index greater than approximately 3.0, a refractive index greater than approximately 3.5, a refractive index greater than approximately 3.6, a refractive index greater than approximately 3.7, etc. at a spectral range of approximately 800 nm to approximately 1100 nm. In some implementations, the difference between the refractive index of the high refractive index material layer and the refractive index of the low refractive index material layer can be greater than a threshold, such as greater than approximately 1.0, greater than approximately 1.5, greater than approximately 2.0, and so on.

[0107] The silicon dioxide layers of the first set of two quarter-wave stacks and the second set of two quarter-wave stacks can each be associated with a refractive index of approximately 1.4664 at a spectral range of approximately 932 nm, a physical thickness of approximately 158.9 nm, and a quarter-wave optical thickness of approximately 932 nm. In some implementations, the low refractive index layer (e.g., silicon dioxide layer) of the quarter-wave stack can be associated with a refractive index less than a threshold at a spectral range of approximately 800 nm, such as a refractive index smaller than the refractive index of the high refractive index layer, a refractive index less than approximately 3.0, a refractive index less than approximately 2.5, a refractive index less than approximately 2.0, a refractive index less than approximately 1.75, a refractive index less than approximately 1.5, and the like.

[0108] The hydrogenated silicon spacer layer is associated with a refractive index of approximately 3.7226, a physical thickness of approximately 152.2 nm, and a quarter wave optical thickness of approximately 1864. Although described herein as a hydrogenated silicon spacer layer, the hydrogenated silicon spacer layer may include multiple spacer layers of hydrogenated silicon of multiple thicknesses selected to form multiple channels. For example, in a first scenario, a plurality of layers forming 64 channels may be used to form the hydrogenated silicon spacer layer. Similarly, in a second scenario, a plurality of layers forming 128 channels may be used to form the hydrogenated silicon spacer layer. Additionally or alternatively, the spacer layer may be used to form another threshold amount of channels, such as 8 channels, 16 channels, 32 channels, 256 channels, etc. In some implementations, the spacer layer can be associated with a refractive index greater than a threshold at a spectral range of approximately 800 nm to approximately 1100 nm (such as a refractive index greater than approximately 2.0, a refractive index greater than approximately 2.5, a refractive index greater than approximately 3.0, a refractive index greater than approximately 3.5, a refractive index greater than approximately 3.6, a refractive index greater than approximately 3.7, etc.).

[0109] like Figure 2B As shown, chart 250 represents the refractive index profile of filter 210. As shown, filter 210 includes a substrate, a first mirror 252-1 disposed on the substrate, a second mirror 252-2, and a hydrogenated silicon spacer 254 disposed between the first mirror 252-1 and the second mirror 252-2. The first mirror 252-1 includes a first quarter wave stack 256-1 and a second quarter wave stack 256-2. Similarly, the second mirror 252-2 includes a third quarter wave stack 256-3 and a fourth quarter wave stack 256-4. Each quarter wave stack 256-1 to 256-4 includes a hydrogenated silicon layer and a silicon dioxide layer forming a high refractive index layer / low refractive index layer (HL) pair.

[0110] like Figure 2C As shown in FIG. 270 and as illustrated by graph 270; and Figure 2D As shown, and illustrated by graph 280, a filter response of filter 210 is provided. For example, filter 210 is associated with a transmittance (shown as "T [%]") greater than approximately 90% at a wavelength (shown as "λ [nm]") of approximately 932 nm. Figure 2D As shown and indicated by reference numeral 282, filter 210 is associated with a relative 50% bandwidth (e.g., a bandwidth of greater than 50% transmittance around a center wavelength representing peak transmittance) of approximately 5.3 nm in the spectral range from approximately 929.35 nm to approximately 934.65 nm.

[0111] As indicated above, Figures 2A-2D Provided only as an example. Other examples are possible and may be related to Figures 2A-2D Different than described.

[0112] Figures 3A-3D It is a characteristic diagram related to multi-spectral filters. Figures 3A-3D An example of a multi-spectral filter is shown that employs a first set of three quarter-wave stacks and a second set of three quarter-wave stacks to sandwich a spacer.

[0113] like Figure 3A As shown, a graph 350 represents a refractive index profile of the filter 310. As shown, the filter 310 includes a substrate, a first mirror 352-1 disposed on the substrate, a second mirror 352-2, and a hydrogenated silicon spacer 354 disposed between the first mirror 352-1 and the second mirror 352-2. The first mirror 352-1 includes a set of three quarter-wave stacks 356-1 to 356-3. The second mirror 352-2 includes a set of three quarter-wave stacks 356-4 to 356-6. Each quarter-wave stack 356 includes a hydrogenated silicon layer and a silicon dioxide layer forming an HL pair.

[0114] like Figure 3B As shown, and illustrated by graph 370; Figure 3C As shown in FIG. 3 and illustrated by graph 380; and Figure 3D As shown, and illustrated by graph 390, the filter response of filter 210 and the filter response of filter 310 are provided. Figure 3C As shown, and indicated by reference numerals 392 and 392', filter 310 is associated with reduced peak transmittance and reduced relative 50% bandwidth based on filter 310 including an additional hydrogenated silicon and silicon dioxide quarter wave stack for each mirror of filter 310 relative to filter 210. In this case, as Figure 3C As shown and indicated by reference numeral 392, filter 210 is associated with a transmittance of approximately 92% at approximately 932 nm and a 50% relative bandwidth of 5.3 nm. Figure 3C As shown and indicated by reference numeral 392', filter 310 is associated with a peak transmittance of approximately 76% at approximately 932 nm, and is associated with a 50% relative bandwidth of approximately 0.9 nm. Figure 3D As shown, and indicated by reference numerals 396 and 396', filter 310 is associated with reduced out-of-band transmission relative to filter 210, and the minimum transmittance of filter 310 is reduced from approximately 0.1% to approximately 0.005% relative to filter 210. In some implementations, the transmittance of filter 310 can also be improved by matching the configuration of filter 310 to a substrate and another medium (e.g., air).

[0115] In these cases, changing the amount of quarter wave stacks in the mirrors of the multispectral filter (e.g., changing from two quarter wave stacks in each mirror to three quarter wave stacks in each mirror) causes a change in the optical characteristics of the multispectral filter, thereby enabling the multispectral filter to be tuned for a particular spectral range, a particular transmittance, etc. However, the change in optical characteristics may be greater than a threshold change. For example, the multispectral filter may be expected to be associated with a 50% relative bandwidth between approximately 0.9 nm and approximately 5.3 nm.

[0116] As indicated above, Figures 3A-3D Provided only as an example. Other examples are possible and may be related to Figures 3A-3D Different than described.

[0117] Figures 4A-4C It is a characteristic diagram related to multi-spectral filters. Figures 4A-4C An example of a multispectral filter having an additional low refractive index layer deposited adjacent to each of a first set of three quarter-wave stacks and a second set of three quarter-wave stacks and a spacer disposed between the first set of three quarter-wave stacks, the second set of three quarter-wave stacks, and the additional low refractive index layer is shown.

[0118] like Figure 4A As shown, a graph 450 represents a refractive index profile of the filter 410. As shown, the filter 410 includes a substrate, a first mirror 452-1 disposed on the substrate, a second mirror 452-2, and a spacer 454 disposed between the first mirror 452-1 and the second mirror 452-2. The first mirror 452-1 includes a set of quarter-wave stacks 456-1 to 456-3 and an unpaired silicon dioxide layer 458-1 (e.g., a low refractive index silicon dioxide layer that is not paired with a high refractive index hydrogenated silicon layer or another high refractive index layer). Similarly, the second mirror 452-2 includes a set of quarter-wave stacks 456-4 to 456-6 and an unpaired silicon dioxide layer 458-2. Each quarter-wave stack 456 is disposed between the unpaired silicon dioxide layers 458-1 and 458-2 and includes a hydrogenated silicon layer and a silicon dioxide layer that form an HL pair. Although the silicon dioxide layers 458 are not paired with a corresponding high refractive index layer (e.g., a hydrogenated silicon layer), each silicon dioxide layer 458 can be referred to as a quarter wave stack of a corresponding mirror 452. In some implementations, the filter 410 can be an array of optical filters aligned to a set of sensor elements of the sensor element array.

[0119] like Figure 4B As shown in FIG. 4 and as shown in FIG. 470 ; and Figure 4CAs shown, and illustrated by graph 480, a set of filter responses for filter 210, filter 310, and filter 410 are provided. Figure 4B As shown, and indicated by reference numerals 492, 492', and 492", filter 410 is associated with a peak transmittance at approximately 932 nm between filter 210 and filter 310 and a 50% relative bandwidth between filter 210 and filter 310 based on filter 410 including a set of unpaired silica layers for each mirror of filter 410. In this case, as Figure 4B As shown and indicated by reference numeral 492, filter 210 is associated with a peak transmittance greater than 90% at approximately 932 nm and is associated with a 50% relative bandwidth of approximately 5.3 nm. Figure 4B As shown and indicated by reference numeral 492', filter 310 is associated with a peak transmittance of approximately 75% at approximately 932 nm and a 50% relative bandwidth of approximately 0.9 nm. Figure 4B As shown and indicated by reference numeral 492", filter 410 is associated with a peak transmission of approximately 80% at approximately 932 nm and a 50% relative bandwidth of approximately 1.4 nm.

[0120] In this case, adding unpaired sets of silica layers causes the optical characteristics of the multispectral filter to change, thereby enabling the multispectral filter to be tuned for a specific spectral range, a specific transmittance, a specific bandwidth, etc. in a more granular manner than changing the amount of a quarter-wave stack.

[0121] As indicated above, Figures 4A-4C Provided only as an example. Other examples are possible and may be related to Figures 4A-4C Different than described.

[0122] Figures 5A-5C It is a characteristic diagram related to multi-spectral filters. Figures 5A-5C An example of a multi-spectral filter is shown that employs a mixed set of quarter wave stacks and spacers disposed between the mixed set of quarter wave stacks.

[0123] like Figure 5AAs shown, a graph 550 represents a refractive index profile of the filter 510. As shown, the filter 510 includes a substrate, a first mirror 552-1 disposed on the substrate, a second mirror 552-2, and a spacer 554 disposed between the first mirror 552-1 and the second mirror 552-2. The first mirror 552-1 includes a set of quarter-wave stacks 556-1 and 556-1, a quarter-wave stack 558-1, and an unpaired silicon dioxide layer 560-1. Similarly, the second mirror 552-2 includes a set of quarter-wave stacks 556-3 and 556-4, a quarter-wave stack 558-2, and an unpaired silicon dioxide layer 560-2. Each quarter-wave stack 556 includes hydrogenated silicon and silicon dioxide forming an HL pair. Each quarter-wave stack 558 includes niobium titanium oxide (NbTiO x ). In this case, the filter 510 utilizes a mixed set of quarter wave stacks, with each mirror 552 comprising a different type of HL pair. Utilizing a mixed set of quarter wave stacks allows the characteristics of the filter 510 to be controlled with greater granularity than another technique that controls the characteristics by increasing or decreasing the amount of quarter wave stacks. Although the quarter-wave stack of filter 510 is described herein in terms of niobium titanium oxide, silicon dioxide, and hydrogenated silicon, another set of three or more materials may be used for a set of mixed quarter-wave stacks, such as utilizing oxide materials such as silicon dioxide (SiO2), niobium pentoxide (Nb2O5), tantalum pentoxide (Ta2O5), titanium dioxide (TiO2), aluminum oxide (Al2O3), zirconium oxide (ZrO2), yttrium oxide (Y2O3), hafnium dioxide (HfO2), etc.; nitride materials such as silicon nitride (Si3N4); fluoride materials such as magnesium fluoride (MgF); sulfide materials such as zinc sulfide (ZnS); zinc selenide materials such as zinc selenide (ZnSe); combinations thereof; and the like.

[0124] like Figure 5B As shown, and illustrated by graph 570; Figure 5C As shown, and illustrated by graph 580, the filter response of filter 210, the filter response of filter 310, and the filter response of filter 510 are provided. Figure 5B As shown, and indicated by reference numerals 592, 592', and 592", filter 510 is associated with a peak transmittance of approximately 932 nm and a 50% relative bandwidth between filter 210 and filter 310 based on filter 510 including a set of unpaired silica layers 560 and utilizing a hybrid set of quarter-wave stacks. In this case, as Figure 5BAs shown and indicated by reference numeral 592, filter 210 is associated with a peak transmittance greater than 90% at approximately 932 nm and a 50% relative bandwidth of approximately 5.3 nm, and as shown Figure 5B As shown and indicated by reference numeral 592', filter 310 is associated with a peak transmittance of approximately 75% at approximately 932 nm and a 50% relative bandwidth of approximately 0.9 nm. Figure 5B As shown and indicated by reference numeral 592", filter 510 is associated with a peak transmission of approximately 90% at approximately 932 nm and a 50% relative bandwidth of approximately 3.1 nm.

[0125] In this case, utilizing a set of mixed quarter-wave stacks causes the optical characteristics of the multispectral filter to change, thereby enabling the multispectral filter to be adjusted for a specific spectral range, a specific transmittance, etc. in a more granular manner than by changing the amount of quarter-wave stacks.

[0126] As indicated above, Figures 5A-5C Provided only as an example. Other examples are possible and may be related to Figures 5A-5C Different than described.

[0127] Figures 6A-6C It is a characteristic diagram related to multi-spectral filters. Figures 6A-6C An example of a multi-spectral filter employing detuned sets of quarter wave stacks and spacers disposed between the detuned sets of quarter wave stacks is shown.

[0128] like Fig. 6A As shown, chart 650 shows a comparison of the refractive index profile of filter 410 and the refractive index profile of filter 610. As shown, filter 610 includes a substrate, a first mirror 652-1 disposed on the substrate, a second mirror 652-2, and a hydrogenated silicon spacer 654 disposed between the first mirror 652-1 and the second mirror 652-2. The first mirror 652-1 includes a set of quarter-wave stacks 656-1 to 656-3 and an unpaired silicon dioxide layer 658-1. Similarly, the second mirror 652-2 includes a set of quarter-wave stacks 656-4 to 656-6 and an unpaired silicon dioxide layer 658-2. Each quarter-wave stack 656 includes a hydrogenated silicon layer and a silicon dioxide layer forming an HL pair. In some implementations, another set of materials can be used for the quarter-wave stack 656. In some implementations, the quarter-wave stack 656 can be a mixed set of quarter-wave stacks using three or more materials.

[0129] like Fig. 6AAs further shown, and indicated by reference numeral 660, filter 610 (e.g., of mirror 652) includes a silicon dioxide layer associated with a threshold reduction in thickness relative to the silicon dioxide layer of filter 410 (e.g., of mirror 454). As indicated by the reference numerals, filter 610 includes a hydrogenated silicon layer associated with a threshold increase in thickness relative to the hydrogenated silicon layer of filter 410. In some implementations, the threshold increase or decrease can be selected to detune the quarter-wave stack from a quarter-wave thickness (e.g., a thickness associated with a center wavelength of light to be incident on the quarter-wave stack) to center filter 610 at a selected center wavelength of peak transmittance and / or alter the 50% relative bandwidth of filter 610, such as by utilizing an approximately 30% increase or approximately 30% decrease in thickness. Additionally or alternatively, an increase or decrease in thickness of between approximately 25% and 30%, between approximately 20% and 40%, between approximately 10% and 50%, etc. may be selected for filter 610.

[0130] like Figure 6B , and as shown by graph 670; and Figure 6C As shown, and illustrated by graph 680, a set of filter responses for filter 210, filter 310, and filter 610 are provided. For example, Figure 6B As shown, and indicated by reference numerals 692, 692', and 692", filter 610 is associated with a peak transmittance at approximately 932 nm and a 50% relative bandwidth between filter 210 and filter 310 based on filter 610 comprising a set of detuned quarter wave stacks (e.g., quarter wave stacks using modified layer thicknesses). In this case, as Figure 6B As shown and indicated by reference numeral 692, filter 210 is associated with a peak transmittance greater than 90% at approximately 932 nm and a 50% relative bandwidth of approximately 5.3, and as shown Figure 6B As shown and indicated by reference numeral 592', filter 310 is associated with a peak transmittance of approximately 75% at approximately 932 nm and a 50% relative bandwidth of approximately 0.9 nm. Figure 6B As shown and indicated by reference numeral 692", filter 610 is associated with a peak transmission of approximately 87% at approximately 932 nm and a 50% relative bandwidth of approximately 2.0 nm.

[0131] In this case, utilizing a set of detuned quarter wave stacks causes the optical characteristics of the multispectral filter to change, thereby enabling the multispectral filter to be tuned for a particular spectral range, a particular transmittance, etc., in a more granular manner than changing the amount of quarter wave stacks. For example, the thickness of the detuned quarter wave stacks allows the optical filter to be configured with a selected bandwidth, such as a bandwidth between bandwidths associated with different amounts of quarter wave stacks, a bandwidth that overlaps bandwidths associated with different amounts of quarter wave stacks, etc.

[0132] As indicated above, Figures 6A-6C Provided only as an example. Other examples are possible and may be related to Figures 6A-6C Different than described.

[0133] Figures 7A-7D is a graph of the characteristics associated with a set of multispectral filters. Figures 7A-7D An example of a multispectral filter with a hybrid collection of quarter-wave stacks is shown.

[0134] like Fig. 7A As shown, a graph 705 represents a refractive index profile of an optical filter 710. As shown, the optical filter 710 includes a substrate, a first mirror 712-1 disposed on the substrate, a second mirror 712-2, and a hydrogenated silicon spacer 714 disposed between the first mirror 712-1 and the second mirror 712-2. The first mirror 712-1 includes a set of quarter-wave stacks 716-1 and 716-2 of hydrogenated silicon and silicon dioxide as an HL pair and a quarter-wave stack 718-1 of niobium titanium oxide and silicon dioxide as an HL pair. The second mirror 712-2 includes a set of quarter-wave stacks 716-3 and 716-4 of hydrogenated silicon and silicon dioxide as an HL pair and a quarter-wave stack 718-2 of niobium titanium oxide and silicon dioxide as an HL pair. In this case, the quarter-wave stack 718-1 is disposed between the quarter-wave stack 716-2 and the hydrogenated silicon spacer 714, and the quarter-wave stack 718-2 is disposed between the quarter-wave stack 716-3 and the hydrogenated silicon spacer 714.

[0135] like Figure 7BAs shown, a graph 735 represents a refractive index profile of an optical filter 740. As shown, the optical filter 740 includes a substrate, a first mirror 742-1 disposed on the substrate, a second mirror 742-2, and a hydrogenated silicon spacer 744 disposed between the first mirror 742-1 and the second mirror 742-2. The first mirror 742-1 includes a set of quarter-wave stacks 746-1 and 746-2 of hydrogenated silicon and silicon dioxide as an HL pair, a quarter-wave stack 748-1 of niobium titanium oxide and silicon dioxide as an HL pair, and an unpaired silicon dioxide layer 750-1. Similarly, the second mirror 742-2 includes a set of quarter-wave stacks 746-3 and 746-4 of hydrogenated silicon and silicon dioxide as an HL pair, a quarter-wave stack 748-2 of niobium titanium oxide and silicon dioxide as an HL pair, and an unpaired silicon dioxide layer 750-2. In this case, quarter wave stack 748 - 1 is disposed between quarter wave stacks 746 - 1 and 746 - 2 , and quarter wave stack 748 - 2 is disposed between quarter wave stacks 746 - 3 and 746 - 4 .

[0136] like Figure 7C As shown, a graph 755 represents a refractive index profile of an optical filter 760. As shown, the optical filter 760 includes a substrate, a first mirror 762-1 disposed on the substrate, a second mirror 762-2, and a hydrogenated silicon spacer 764 disposed between the first mirror 762-1 and the second mirror 762-2. The first mirror 762-1 includes a quarter-wave stack 766-1 of hydrogenated silicon and tantalum pentoxide (Ta2O5) as an HL pair, a set of two quarter-wave stacks 768-1 and 768-2 of hydrogenated silicon and silicon dioxide as an HL pair, and an unpaired tantalum pentoxide layer 770-1. Similarly, the second mirror 762-2 includes a quarter-wave stack 766-2 of hydrogenated silicon and tantalum pentoxide as an HL pair, a set of two quarter-wave stacks 768-3 and 768-4 of hydrogenated silicon and silicon dioxide as an HL pair, and an unpaired tantalum pentoxide layer 770-2. In this case, quarter-wave stacks 768-1 and 768-2 are disposed between quarter-wave stack 766-1 and hydrogenated silicon spacer 764, and quarter-wave stacks 768-3 and 768-4 are disposed between quarter-wave stack 766-2 and hydrogenated silicon spacer 764.

[0137] like Fig.7DAs shown, a graph 775 represents a refractive index profile of an optical filter 780. As shown, the optical filter 780 includes a substrate, a first mirror 782-1 disposed on the substrate, a second mirror 782-2, and a hydrogenated silicon spacer 784 disposed between the first mirror 782-1 and the second mirror 782-2. The first mirror 782-1 includes a set of quarter-wave stacks 786-1 and 786-2 of hydrogenated silicon and niobium titanium as an HL pair, a set of two quarter-wave stacks 788-1 and 788-2 of hydrogenated silicon and silicon dioxide as an HL pair, and an unpaired niobium titanium layer 790-1. Similarly, the second mirror 782-2 includes a set of quarter-wave stacks 786-3 and 786-4 of hydrogenated silicon and niobium titanium as an HL pair, a set of two quarter-wave stacks 788-3 and 788-4 of hydrogenated silicon and silicon dioxide as an HL pair, and an unpaired tantalum pentoxide layer 790-2. In this case, quarter-wave stacks 788-1 and 788-2 are disposed between quarter-wave stack 786-2 and hydrogenated silicon spacer 784, and quarter-wave stacks 788-3 and 788-4 are disposed between quarter-wave stack 786-3 and hydrogenated silicon spacer 784.

[0138] As indicated above, Figures 7A-7D Provided only as an example. Other examples are possible and may be related to Figures 7A-7D Different than described.

[0139] Figures 8A-8B is a graph of the characteristics associated with a set of multispectral filters. Fig. 8A and 8B An example of a 50% relative bandwidth of the filters described herein is shown.

[0140] like Fig. 8AAs shown, and illustrated by table 800, a set of 50% relative bandwidths for the filters described herein is provided for a center wavelength of approximately 932 nm. As shown, filter 210 is associated with a 50% relative bandwidth of approximately 5.3 nm. Adding an additional quarter-wave stack to form filter 310 results in a 50% relative bandwidth of approximately 0.9 nm. As described herein, a number of techniques may be utilized to adjust the multispectral filter with a greater degree of granularity (e.g., to adjust the multispectral filter to a 50% relative bandwidth between approximately 0.9 nm and approximately 5.3 nm or another range of 50% relative bandwidths associated with another set of multispectral filters). For example, filter 410 results in a 50% relative bandwidth of approximately 1.4 nm, filter 510 results in a 50% relative bandwidth of approximately 3.1 nm, filter 610 results in a 50% relative bandwidth of approximately 2.0 nm, filter 710 results in a 50% relative bandwidth of approximately 2.8 nm, filter 740 results in a 50% relative bandwidth of approximately 3.1 nm, filter 760 results in a 50% relative bandwidth of approximately 5.3 nm, and filter 780 results in a 50% relative bandwidth of approximately 3.0 nm. In this way, a multispectral filter can utilize three or more different materials of a quarter wave stack mirror, detuned quarter wave stack thicknesses, unpaired quarter wave stack layers, etc. to achieve a specific spectral range, transmittance, etc.

[0141] like Figure 8B As shown, and illustrated by graph 850, a set of 50% relative bandwidths of the filters described herein are provided at a set of center wavelengths. For example, based on tuning the multispectral filter described herein to a particular center wavelength (e.g., by changing the spacer thickness of the multispectral filter), the 50% relative bandwidth can be determined. As shown, for a spectral range with a center wavelength between approximately 800 nm and approximately 1100 nm, each of filters 410, 510, 610, 710, 740, 760, and 780 is associated with a 50% relative bandwidth between filters 210 and 310. For example, at a center wavelength of approximately 800 nm, filters 410, 510, 610, 710, 740, 760, and 780 are associated with a 50% relative bandwidth between approximately 3.75 nm and approximately 5.75 nm. Similarly, at a center wavelength of approximately 1100 nm, filters 410, 510, 610, 710, 740, 760, and 780 are associated with a 50% relative bandwidth between approximately 4 nm and approximately 8 nm.

[0142] As indicated above, Figures 8A-8B Provided only as an example. Other examples are possible and may be related to Fig. 8A and 8B Different than described.

[0143] Although some implementations described herein are described in terms of granularity of adjusting a spectral range relative to another optical filter having two quarter-wave stacks or three quarter-wave stacks, the implementations described herein may provide greater granularity of adjustment relative to other amounts of quarter-wave stacks. For example, utilizing a third coating material, a fourth coating material, etc., or the thickness of a detuned quarter-wave stack may allow for improved granularity of adjustment of an optical filter for a particular spectral range, transmittance, etc., relative to adding or subtracting one quarter-wave stack, adding or subtracting two quarter-wave stacks, adding or subtracting three quarter-wave stacks, adding or subtracting four quarter-wave stacks, etc.

[0144] In this way, utilizing a hybrid set of quarter wave stacks and a detuned set of quarter wave stacks yields greater granularity for controlling transmittance, bandwidth, etc. relative to another technique involving utilizing an additional amount of quarter wave stacks. Based on the improved granularity of control over the multispectral filter, improved sensing is provided for the sensor element attached to the multispectral filter.

[0145] The foregoing disclosure provides illustration and description, but is not intended to be exhaustive or to limit implementations to the precise form disclosed.Modifications and variations are possible in light of the above disclosure or may be acquired from practice of implementations.

[0146] Some implementations are described herein in conjunction with thresholds. As used herein, satisfying a threshold may refer to a value being greater than a threshold, more than a threshold, above a threshold, greater than or equal to a threshold, less than a threshold, less than a threshold, below a threshold, less than or equal to a threshold, equal to a threshold, and the like.

[0147] Although particular combinations of features are recited in the claims and / or disclosed in the specification, these combinations are not intended to limit the disclosure of possible implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and / or disclosed in the specification. Although each dependent claim may only be directly dependent on one claim, the disclosure of possible implementations includes the combination of each dependent claim with every other claim of the entire set of claims.

[0148] Elements, behaviors or instructions used herein should not be understood as being decisive or necessary unless explicitly described as such. In addition, as used herein, the articles "individual" and "one" are intended to include one or more items and can be used interchangeably with "one or more". In addition, as used herein, the term "group" is intended to include one or more items (e.g., related items, unrelated items, combinations of related items, and multiple unrelated items, etc.), and can be used interchangeably with "one or more". In the case of meaning only one item, the term "one" or similar language is used. In addition, as used herein, the term "having" etc. is intended to be an open term. In addition, shorter than "based on" is intended to represent "based at least in part", unless explicitly specified otherwise.

Claims

1. A multi-spectral filter, comprising: a first set of dielectric layers, the first set of dielectric layers reflecting a portion of light directed toward the first set of dielectric layers, the first set of dielectric layers comprising a first one or more quarter-wave stacks, a second set of dielectric layers, said second set of dielectric layers reflecting a portion of light directed toward said second set of dielectric layers, The second set of dielectric layers includes a second one or more quarter-wave stacks, and The thickness of at least one layer of the first set of dielectric layers or the second set of dielectric layers is detuned from a quarter wave thickness.

2. The multispectral filter according to claim 1, wherein: The quarter wave thickness is a thickness associated with a center wavelength of light to be incident on at least one of the first one or more quarter wave stacks or the second one or more quarter wave stacks.

3. The multispectral filter according to claim 1, wherein: The thickness is detuned by increases between 10% and 50%.

4. The multispectral filter according to claim 1, wherein: The first set of dielectric layers includes a set of three or more different materials.

5. The multispectral filter according to claim 4, wherein: The second set of dielectric layers includes a different set of three or more different materials.

6. The multispectral filter according to claim 5, wherein: The set of three or more different materials and the different set of three or more different materials are a common set of three or more different materials.

7. The multispectral filter according to claim 1, wherein: The first set of dielectric layers includes a set of three or more different materials, and Wherein, the first one or more quarter-wave stacks include: a first quarter wave stack comprising a first material from the set of three or more different materials and a second material from the set of three or more different materials; and A second quarter wave stack includes the first material and a third material.

8. The multispectral filter according to claim 7, wherein: the second set of dielectric layers comprises a different set of three or more different materials, and Wherein, the different set of three or more different materials includes the third material.

9. The multispectral filter according to claim 1, further comprising: a set of spacer layers, A layer in the set of spacer layers is selected based on a refractive index of the layer.

10. The multispectral filter according to claim 9, wherein: The layer corresponds to a wavelength of light directed to a sensor element in a set of sensor elements corresponding to a channel in a set of channels formed by the set of spacer layers.

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