HK1258878B - Induced transmission filter - Google Patents

Description

Induced transmission filter

Technical Field

The present invention relates to optical filters.

Background Art

An optical sensor device can be used to capture information. For example, the optical sensor device can capture information related to a set of electromagnetic frequencies. The optical 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. In one example, the array of sensor elements can be used to capture information about a set of color bands of light in the sensor element array, such as a first sensor element in the sensor element array capturing information about a red band of light; a second sensor element in the sensor element array capturing information about a green band of light; a third sensor element in the sensor element array capturing information about a blue band of light, and so on.

The sensor elements of the sensor element array can be associated with a filter. The filter can include a passband associated with a first spectral range of light transmitted to the sensor element. The filter can be associated with blocking a second spectral range of light from being transmitted to a second sensor element. In one example, the sensor element array can be associated with a filter (e.g., a red-green-blue (RGB) filter) that includes passbands of different colors (such as a red passband, a blue passband, a green passband, etc.). In another example, the sensor element array can be associated with a near-infrared (NIR) blocking filter, an infrared (IR) blocking filter, a long-wave pass (LWP) filter, a short-wave pass (SWP) filter, a photopic filter, a tristimulus filter, etc.

Summary of the Invention

According to some possible embodiments, an optical filter may include a first set of layers. The first set of layers may include alternating layers of a first dielectric material from the set of dielectric materials and a second dielectric material from the set of dielectric materials. The optical filter may include a second set of layers. The second set of layers may include alternating layers of a third dielectric material from the set of dielectric materials and a fourth dielectric material from the set of dielectric materials. The optical filter may include a third set of layers. The third set of layers may include alternating layers of a fifth dielectric material from the set of dielectric materials, a sixth dielectric material from the set of dielectric materials, and a metal material. The third set of layers may be disposed between the first set of layers and the second set of layers.

According to some possible implementations, an induced transmission filter may include a first all-dielectric portion comprising a first set of dielectric layers. The induced transmission filter may include a second all-dielectric portion comprising a second set of dielectric layers. The induced transmission filter may include a metal/dielectric portion comprising a third set of dielectric layers and one or more metal layers. The metal/dielectric portion may be disposed between the first all-dielectric portion and the second all-dielectric portion.

According to some possible embodiments, a hybrid metal/dielectric optical filter may include a substrate. The hybrid metal/dielectric optical filter may include a first all-dielectric portion comprising alternating silicon dioxide layers and niobium titanium oxide layers. The hybrid metal/dielectric optical filter may include a second all-dielectric portion comprising alternating silicon dioxide layers and niobium titanium oxide layers. The hybrid metal/dielectric optical filter may include a metal/dielectric portion comprising one or more layer groups. A layer group in the one or more layer groups may include a silver layer, two zinc oxide layers, and two niobium titanium oxide layers. The silver layer may be disposed between the two zinc oxide layers. The two zinc oxide layers may be disposed between the two niobium titanium oxide layers. The metal/dielectric portion may be disposed between the first all-dielectric portion and the second all-dielectric portion.

BRIEF DESCRIPTION OF THE DRAWINGS

1A-1C are schematic diagrams of example implementations described herein;

2A-2C are graphs showing characteristics of the all-dielectric optical filter described herein;

3A-3C are graphs showing the characteristics of low-angle shift induced transmission optical (ITF) filters described herein;

4A-4C are graphs showing characteristics of hybrid metal/dielectric optical filters described herein;

5A-5C are graphs showing characteristics of hybrid metal/dielectric optical filters described herein;

6A and 6B are graphs showing characteristics of a set of optical filters described herein; and

7A-7G are graphs showing characteristics of a set of optical filters described herein.

DETAILED DESCRIPTION

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

The optical sensor device may include a sensor element array of sensor elements to receive light originating from a light source (such as an optical emitter, a light bulb, an ambient light source, etc.). 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 sensor elements (e.g., optical sensors) of the optical sensor device may obtain information (e.g., spectral data) about a set of electromagnetic frequencies.

The sensor element can be associated with an optical filter that filters light for the sensor element so that the sensor element can obtain information about a specific spectral range of electromagnetic frequencies. For example, the sensor element can be aligned with a red-green-blue (RGB) filter, a near-infrared (NIR) blocking filter, an infrared (IR) blocking filter, a long-wave pass (LWP) filter, a short-wave pass (SWP) filter, a photopic filter, a tristimulus filter, etc., to filter the portion of light directed toward the sensor element. The filter can include a set of dielectric layers to filter portions of the light. For example, the filter can include a dielectric filter stack of alternating high and low refractive index layers, such as alternating layers of niobium titanium oxide ( _NbTiOx ) and silicon dioxide ( _SiO2 ). However, all-dielectric filters can be associated with a shift in the threshold angle as the angle of incidence increases. For example, an all-dielectric filter may be associated with an angular shift of greater than approximately 10 nm at an angle of incidence of 20 degrees, greater than approximately 20 nm at an angle of incidence of 30 degrees, greater than approximately 40 nm at an angle of incidence of 40 degrees, greater than approximately 50 nm at an angle of incidence of 50 degrees, and so on.

Low angle shift (LAS) filters having alternating layers of high-refractive-index dielectrics, low-refractive-index dielectrics, and metals can be selected to reduce angular shift relative to all-dielectric filters. For example, a low angle shift filter can utilize layers of niobium titanium oxide, zinc oxide, and silver to reduce angular shift relative to an all-dielectric filter. However, a low angle shift filter can be associated with a transmittance in the passband of the low angle shift filter that does not meet a threshold. For example, a low angle shift filter can be associated with a transmittance of less than approximately 70% at an angle of incidence ranging from 0 degrees to 50 degrees.

Some implementations described herein provide hybrid dielectric/metallic filters having alternating dielectric layer sections that sandwich dielectric and metallic layer sections. For example, the optical filter can include a first section having a set of alternating high-refractive-index layers of niobium titanium oxide and low-refractive-index layers of silicon dioxide, a second section having another set of alternating high-refractive-index layers of niobium titanium oxide and low-refractive-index layers of silicon dioxide, and a third section having alternating layers of high-refractive-index layers of niobium titanium oxide, low-refractive-index layers of silicon dioxide, and metallic layers of silver disposed between the first and second sections. In this way, the filter can filter light at less than a threshold angular shift and at greater than a threshold level of transmission. For example, a hybrid dielectric/metallic filter can be associated with an angular shift of less than approximately 30 nm at an incident angle of 0 to 50 degrees, an angular shift of less than approximately 20 nm at an incident angle of 0 to 40 degrees, an angular shift of less than approximately 10 nm at an incident angle of 0 to 20 degrees, and so on. Similarly, a hybrid dielectric/metallic filter may be associated with a transmittance greater than approximately 70% at an angle of incidence from 0 to 50 degrees, a transmittance greater than approximately 75% at an angle of incidence from 0 to 50 degrees, and so on.

1A-1C are schematic diagrams of example implementations 100/100'/100" described herein. As shown in FIG1A , example implementation 100 includes a sensor system 110. Sensor system 110 can be part of an optical system and can provide an electrical output corresponding to a sensor determination. Sensor system 110 includes an optical filter structure 120, which includes an optical filter 130 and an optical sensor 140. For example, optical filter structure 120 can include an optical filter 130 that performs a passband filtering function. In another example, optical filter 130 can be aligned with an array of sensor elements of optical sensor 140.

Although the implementations described herein may be described in terms of an optical filter in an optical filter, the implementations described herein may be used in another type of system, may be used outside of a sensor system, and so on.

1A , and indicated by reference numeral 150, an input optical signal is directed toward the optical filter structure 120. The input optical signal may include, but is not limited to, visible spectrum (VIS) and NIR light (e.g., ambient light from the environment in which the sensor system 110 is utilized). In another example, the optical emitter may direct light in another spectral range for another function, such as a test function, a measurement function, a communication function, etc.

As further shown in FIG1A , and indicated by reference numeral 160, a first portion of the optical signal having a first spectral range does not pass through the optical filter 130 and the optical filter structure 120. For example, a dielectric filter stack, which may include a high refractive index material layer, a low refractive index material layer, and a silver/dielectric filter stack of the optical filter 130, may cause the first portion of the light to be reflected, absorbed, etc. in a first direction. As indicated by reference numeral 170, a second portion of the optical signal passes through the optical filter 130 and the optical filter structure 120. For example, the second portion of the light having a second spectral range may pass through the optical filter 130 in a second direction toward the optical sensor 140.

As further shown in FIG1A and indicated by reference numeral 180, based on passing the second portion of the optical signal to the optical sensor 140, the optical sensor 140 can provide an output electrical signal to the sensor system 110, such as for use in imaging, ambient light sensing, detecting the presence of an object, taking measurements, facilitating communications, etc. In some implementations, another arrangement of the optical filter 130 and the optical sensor 140 can be utilized. For example, instead of passing the second portion of the optical signal co-linearly with the input optical signal, the optical filter 130 can direct the second portion of the optical signal in another direction to the optical sensor 140 at a different location.

As shown in FIG1B , a similar example implementation 100′ includes sensor elements of a sensor element array 140 integrated into a substrate 120 of an optical filter structure. In this case, an optical filter 130 is provided on the substrate 120. Input optical signals 150-1 and 150-2 are received at one set of angles, and a first portion of the input optical signals 150-1 and 150-2 is reflected at another set of angles. In this case, a second portion of the input optical signals 150-1 and 150-2 passes through the optical filter 130 to the sensor element array 140, which provides an output electrical signal 180.

As shown in FIG1C , another similar example implementation 100 ″ includes sensor elements of a sensor element array 140 separated from an optical filter structure 120, and an optical filter 130 is disposed on the optical filter structure 130. In this case, the optical filter structure 130 and the sensor element array 140 may be separated by free space, for example. At the optical filter 130 , input optical signals 150 - 1 and 150 - 2 are received at a set of angles. First portions 160 of the input optical signals 150 - 1 and 150 - 2 are reflected, and second portions 170 are passed by the optical filter 130 and the optical filter structure 120 to the sensor element array 140, which provides an output electrical signal 180.

As indicated above, Figures 1A-1C are provided merely as examples. Other examples are possible and may differ from what is described with respect to Figures 1A-1C.

2A-2C are characteristic diagrams related to optical filters. 2A-2C illustrate examples of all-dielectric filters.

As shown in FIG2A and by diagram 200, the optical filter 210 may include a substrate and a set of dielectric stacks. The substrate may include silicon nitride ( _Si3N4 and shown as _Si3N4 ), a glass substrate, a polymer substrate, another transparent substrate, etc. In some implementations, the substrate may be attached to the set of dielectric stacks using an epoxy (e.g., clear glue), an air gap (e.g., having the epoxy outside the optical path), etc. Additionally or alternatively, the set of dielectric stacks may be directly disposed on a detector, a detector array, a sensor element array, etc., which may form the substrate of the set of dielectric stacks. For example, the sensor element array may include a top layer of silicon nitride, and the set of dielectric stacks may be attached to the top layer. In another example, such as for a back-illuminated detector, another type of substrate, such as a silicon substrate, may be used. In some implementations, the substrate may be the inlet dielectric, outlet dielectric, etc., for the set of dielectric stacks. One set of dielectric stacks includes alternating layers of niobium titanium oxide ( _NbTiO5 , shown as NbTiO5) and silicon dioxide ( _SiO2 , shown as SiO2). For example, filter 210 may include a first niobium titanium oxide layer having a thickness of 99.8 nanometers (nm) deposited on a substrate, and a first silicon dioxide layer having a thickness of 172.1 nm deposited on the niobium titanium oxide layer. Similarly, filter 210 may include a second niobium titanium oxide layer deposited at a thickness of 105.2 nm on the first silicon dioxide layer, and a second silicon dioxide layer having a thickness of 180.5 nm deposited on the second niobium titanium oxide layer. In this case, filter 210 is associated with a total thickness of approximately 5.36 micrometers (μm), which may result in excessive deposition time and costs associated with the increased deposition time. Furthermore, this total thickness may result in a threshold amount of compressive stress, which may cause warping of substrates having thicknesses less than the threshold, and may result in excessive difficulties and yield loss when separating the substrate with multiple filters deposited thereon into multiple discrete filters.

As shown in FIG2B and illustrated by graph 220, the filter response of the filter 210 exposed to the outlet medium of air is provided. For example, the filter 210 is associated with a cutoff wavelength of approximately 660 nm at an angle of incidence (AOI) of 0 degrees (e.g., at which the transmittance of the filter 210 decreases to a threshold rate). In contrast, at angles of incidence of 10 degrees, 20 degrees, 30 degrees, 40 degrees, and 50 degrees, the filter 210 is associated with threshold shifts in cutoff wavelength of approximately 5 nm, approximately 12 nm, approximately 25 nm, approximately 42 nm, and approximately 52 nm, respectively. Furthermore, for angles of incidence of 30 degrees, 40 degrees, and 50 degrees, the filter 210 is associated with a transmittance of approximately 4% at approximately 880 nm, approximately 31% at approximately 850 nm, and approximately 14% at approximately 805 nm, respectively. In addition, filter 210 is associated with a decrease in transmittance below a threshold transmittance between approximately 480 nm and approximately 505 nm at an AOI of 50 degrees (e.g., a decrease to a transmittance between approximately 58% and approximately 68%), and filter 210 is associated with an increase in transmittance greater than a threshold transmittance at a spectral range greater than approximately 1000 nm for an AOI of 50 degrees (e.g., an increase to a transmittance greater than approximately 1%). In order to use filter 210 to provide a passband between approximately 420 nm and approximately 620 nm, the threshold angle shift and the decrease and increase in threshold transmittance result in relatively poor filter performance.

As shown in FIG2C and illustrated by chart 230, a color diagram (e.g., the Commission Internationale de l'Eclairage (CIE) 1931 color diagram) of filter 210 is provided. As shown by reference numeral 232, filter 210 is associated with a CIE color diagram that identifies a threshold color shift between approximately (0.33, 0.33) and approximately (0.30, 0.33) when shifting from a 0-degree AOI to a 50-degree AOI. This threshold color shift results in relatively poor filter performance.

As indicated above, Figures 2A-2C are provided merely as examples. Other examples are possible and may differ from what is described with respect to Figures 2A-2C.

3A-3C are graphs of characteristics associated with optical filters. Figures 3A-3C illustrate an example of a low-angle shift-induced transmission optical filter (ITF) having a dielectric/metal filter stack.

As shown in FIG3A and by diagram 300, an optical filter 310 may include a substrate, a set of dielectric layers, and a set of metal layers. The substrate may include a silicon nitride substrate. The set of dielectric layers and the set of metal layers include alternating layers of niobium titanium oxide, zinc oxide (ZnO), and silver (Ag). For example, a first layer of niobium titanium oxide having a thickness of 28.0 nm is deposited on the silicon nitride substrate, a second layer of zinc oxide having a thickness of 2.0 nm is deposited on the first layer, a third layer of silver having a thickness of 11.3 nm is deposited on the second layer, a fourth layer of zinc oxide having a thickness of 2.0 nm is deposited on the third layer, and a fifth layer of niobium titanium oxide having a thickness of 53.8 nm is deposited on the fourth layer. In this case, the fifth layer of niobium titanium oxide may be a plurality of layers of niobium titanium oxide. In other words, a first portion of the fifth layer may sandwich the second to fourth layers with the first layer, and a second portion of the fifth layer may sandwich the sixth to eighth layers with a portion of the ninth layer. Although filter 310 is described as a particular set of layer thicknesses, other layer thicknesses are possible and may differ from that shown in FIG. 3A .

As shown in FIG3B and illustrated by graph 320, the filter response of filter 310 exposed to the outlet medium of air is provided. As indicated by reference numeral 322, filter 310 is associated with reduced angular shift relative to filter 210. For example, filter 310 is associated with an angular shift of the cutoff wavelength of less than approximately 20 nm for incident angles varying from 0 degrees to 10 degrees, 20 degrees, 30 degrees, 40 degrees, or 50 degrees, compared to an angular shift of greater than 20 nm for incident angles varying from 0 degrees to 30 degrees, 40 degrees, or 50 degrees. However, as indicated by reference numeral 324, filter 310 is associated with reduced transmittance relative to filter 210. For example, filter 310 is associated with an average transmittance of between approximately 62% and 65% for incident angles between 0 degrees and 50 degrees within the spectral range of the passband between approximately 420 nm and approximately 620 nm. In this case, the transmittance in the infrared (IR) blocking spectral range of approximately 750 nm to approximately 1100 nm is approximately 0.41% for an AOI of 0 degrees and approximately 0.37% for an AOI of 40 degrees.

3C , and illustrated by graph 330, a CIE 1931 color diagram is provided for filter 310. As shown by reference numeral 332, for a shift from a 0 degree angle of incidence to a 50 degree angle of incidence, filter 310 is associated with a color shift that decreases relative to filter 210. For example, filter 310 is associated with a color shift that is less than a threshold value (e.g., less than 0.2, less than 0.1, less than 0.05, etc.).

As indicated above, Figures 3A-3C are provided merely as examples. Other examples are possible and may differ from what is described with respect to Figures 3A-3C.

Figures 4A-4C are characteristic diagrams related to hybrid metal/dielectric optical filters. Figures 4A-4C illustrate examples of optical filters having a dielectric filter stack having high and low refractive index layers, and a metal (e.g., silver) dielectric filter stack disposed between the dielectric filter stacks.

As shown in FIG4A and by diagram 400, optical filter 410 may include a substrate, a set of dielectric layers, and a set of metal layers. As indicated by reference numeral 412, a first portion of optical filter 410 (e.g., a first all-dielectric portion) includes an all-dielectric layer of alternating high and low refractive index layers. In this case, the alternating high and low refractive index layers are niobium titanium oxide layers and silicon dioxide layers, respectively. For example, the first layer deposited on the silicon nitride substrate is a niobium titanium oxide layer having a thickness of 95.5 nm (shown as layer 1), the second layer deposited on the first layer is silicon dioxide having a thickness of 48.3 nm (shown as layer 2), and so on. In some implementations, another type of substrate, such as a glass substrate, may be used. In some implementations, another high refractive index material may be used, such as a material having a refractive index greater than approximately 2.0, greater than approximately 2.5, greater than approximately 3.0, greater than approximately 3.5, greater than approximately 3.6, greater than approximately 3.7, and so on. In some implementations, another low refractive index material can be used, such as a material having a refractive index less than approximately 3.0, less than approximately 2.5, less than approximately 2.0, less than approximately 1.5, etc. In some implementations, one or more layers may utilize, as a dielectric material, oxide materials such as silicon dioxide (SiO ₂ ), niobium pentoxide (Nb ₂ O ₅ ), tantalum pentoxide (Ta ₂ O ₅ ), titanium dioxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ), hafnium dioxide (HfO ₂ ), etc.; nitride materials such as silicon nitride (Si 3 N 4 ); fluoride materials such as magnesium fluoride (MgF); sulfide materials such as zinc sulfide (ZnS); zinc selenide materials such as zinc selenide (ZnSe); nitride materials such as silicon hydride or germanium hydride; such as germanium nitride; combinations thereof; and the like.

As further shown in FIG4A and indicated by reference numeral 414, the second portion of the filter 410 includes a mixed metal/dielectric layer. In this case, the second portion of the filter 410 includes multiple layer groups of one or more niobium titanium oxide layers, one or more zinc oxide layers, and one or more silver layers. For example, the first layer group (layers 7 to 11) includes a layer of niobium titanium oxide having a thickness of 139.1 nm (e.g., shown as layer 7, a first portion of which may be part of the first portion of the filter 410 and a second portion of which may be part of the second portion of the filter 410), a layer of zinc oxide having a thickness of 2.0 nm (shown as layer 8), a layer of silver having a thickness of 9.9 nm (shown as layer 9), a layer of zinc oxide having a thickness of 2.0 nm (shown as layer 10), and a layer of niobium titanium oxide having a thickness of 51.9 nm (shown as layer 11, a first portion of which may be part of the first layer group and a second portion of which may be part of the second layer group). For another example, the second layer group (layers 11 to 15) includes the second portion of niobium titanium oxide layer 11, zinc oxide layer 12, silver layer 13, zinc oxide layer 14, and the first portion of niobium titanium oxide layer 15 (for example, the second portion of which may be part of the third layer group). In another example, another metallic material may be used.

As further shown in FIG4A and indicated by reference numeral 416, the third portion of filter 410 (e.g., the second all-dielectric portion) comprises an all-dielectric layer of alternating high and low refractive index layers. In this case, the alternating high and low refractive index layers are layers of niobium titanium oxide and silicon dioxide, respectively. For example, the first layer is a portion of layer 23 of niobium titanium oxide, the second layer is layer 24 of silicon dioxide, the third layer is layer 25 of niobium titanium oxide, the fourth layer is layer 26 of silicon dioxide, and so on. In this case, filter 410 utilizes three different dielectric materials. In another example, filter 410 can utilize two different dielectric materials. In some implementations, filter 410 can be matched to an outlet medium of air. In some implementations, filter 410 can be matched to another outlet medium, such as a polymer material, a color dye, an RGB dye, an epoxy material, a glass material, and the like. In some implementations, the filter 410 can be an RGB filter (e.g., a filter having passbands corresponding to the red spectral range of light, the green spectral range of light, or the blue spectral range of light), an NIR light barrier, an LWP filter, a SWP filter, a photopic filter, an ambient light sensor filter, a tristimulus filter, etc. Although the filter 410 is described as a particular set of layer thicknesses, other layer thicknesses are possible and can differ from that shown in FIG4A .

As shown in FIG4B and illustrated by graph 420, and as shown in FIG4C and illustrated by graph 430, filter 410 is associated with reduced angular and color shift relative to filter 210 and improved transmittance relative to filter 310. For example, as shown by reference numeral 432 in FIG4B , filter 410 is associated with a transmittance of approximately 80% at approximately 420 nm and an angle of incidence of 0 degrees, and is associated with a transmittance of greater than 70% over the spectral range between approximately 420 nm and 550 nm for angles of incidence between 0 degrees and 50 degrees. Similarly, as shown by reference numeral 434 in FIG4B , filter 410 is associated with an angular shift of less than approximately 40 nm over the spectral range between approximately 400 nm and approximately 1100 nm and angles of incidence between 0 degrees and 50 degrees.

4C , and illustrated by graph 430, a CIE 1931 color diagram is provided for filter 310. As shown by reference numeral 436, for a shift from a 0 degree angle of incidence to a 50 degree angle of incidence, filter 410 is associated with a color shift that decreases relative to filter 210. For example, filter 410 is associated with a color shift that is less than a threshold value (e.g., less than 0.2, less than 0.1, less than 0.05, etc.).

As indicated above, Figures 4A-4C are provided merely as examples. Other examples are possible and may differ from what is described with respect to Figures 4A-4C.

Figures 5A-5C are characteristic graphs associated with another hybrid metal/dielectric optical filter. Figures 5A-5C illustrate another example of an induced transmission optical filter having a dielectric filter stack with high and low refractive index layers and a metal (e.g., silver) dielectric filter stack.

As shown in FIG5A and by diagram 500, optical filter 510 may include a substrate, a set of dielectric layers, and a set of metal layers. As indicated by reference numeral 512, a first portion of layers 1 through 10 of optical filter 510 comprises all-dielectric layers of alternating high and low refractive index layers. In this case, the alternating high and low refractive index layers are niobium titanium oxide layers and silicon dioxide layers, respectively. As indicated by reference numeral 514, a second portion of layers 10 through 25 of optical filter 510 comprises metal-dielectric layers. In this case, the second portion of optical filter 510 comprises multiple layer groups of one or more niobium titanium oxide layers, one or more zinc oxide layers, and one or more silver layers. As indicated by reference numeral 516, a third portion of layers 25 through 30 of optical filter 510 comprises all-dielectric layers of alternating high and low refractive index layers. In this case, the alternating high and low refractive index layers are niobium titanium oxide layers and silicon dioxide layers, respectively. Although filter 510 is described as a particular set of layer thicknesses, other layer thicknesses are possible and may differ from that shown in FIG. 5A .

As shown in FIG5B and illustrated by graph 520, and as shown in FIG5C and illustrated by graph 530, filter 510 is associated with reduced angular and color shift relative to filter 210 and improved transmittance relative to filter 310. For example, as shown by reference numeral 532 in FIG5B , filter 510 is associated with a transmittance of approximately 80% at approximately 500 nm and at angles of incidence between 0 and 50 degrees, and is associated with a transmittance greater than approximately 70% for the spectral range between approximately 460 nm and 590 nm for angles of incidence between 0 and 50 degrees. Similarly, as shown by reference numeral 534, filter 510 is associated with an angular shift of less than approximately 30 nm for the spectral range between approximately 400 nm and approximately 1100 nm and for angles of incidence between 0 and 50 degrees.

5C , and illustrated by graph 530, a CIE 1931 color diagram is provided for filter 510. As shown by reference numeral 536, for a shift from a 0 degree angle of incidence to a 50 degree angle of incidence, filter 510 is associated with a color shift that decreases relative to filter 210. For example, filter 510 is associated with a color shift that is less than a threshold value (e.g., less than 0.2, less than 0.1, less than 0.05, etc.).

As indicated above, Figures 5A-5C are provided merely as examples. Other examples are possible and may differ from what is described with respect to Figures 5A-5C.

Figures 6A and 6B are graphs of characteristics associated with a set of optical filters. Figures 6A and 6B illustrate a comparison of the characteristics of the filters described herein.

As shown in FIG6A and illustrated by graph 600, a comparison of the angular shifts in the cutoff wavelengths for filters 210, 310, 410, and 510 is provided. In this case, at each angle of incidence from 0 to 50 degrees, filters 410 and 510 are associated with a decreasing angular shift in the cutoff wavelength relative to filter 210. For example, at an angle of incidence of 40 degrees, filter 410 is associated with an angular shift in the cutoff wavelength of approximately 18 nm. Similarly, at an angle of incidence of 40 degrees, filter 510 is associated with an angular shift in the cutoff wavelength of approximately 20 nm. In contrast, at an angle of incidence of 20 degrees, filter 210 is associated with a change in the cutoff wavelength of approximately 42 nm.

As shown in FIG6B and illustrated by graph 610, a comparison of the average transmittance of the passband of filters 210, 310, 410, and 510 over a spectral range of approximately 420 nm to approximately 620 nm is provided. In this case, filters 410 and 510 are associated with improved transmittance relative to filter 310 at each angle of incidence from 0 to 50 degrees. For example, at an angle of incidence of 40 degrees, filter 410 and filter 510 are associated with average transmittances of approximately 72% and approximately 75%, respectively. In contrast, at an angle of incidence of 40 degrees, filter 310 is associated with an average transmittance of approximately 63%.

As indicated above, Figures 6A and 6B are provided merely as examples. Other examples are possible and may differ from what is described with respect to Figures 6A and 6B.

Figures 7A-7G are graphs of characteristics associated with a set of optical filters. Figures 7A-7G show a comparison of characteristics of green-type filters described herein.

As shown in FIG7A , an example stack of optical filter 702 is provided. Filter 702 can be a green filter comprising alternating layers of silicon dioxide (SiO ₂ ) and niobium titanium oxide (NbTiO ₅ ). Filter 702 can be associated with an inlet dielectric of silicon nitride (Si ₃ N ₄ ) and an outlet dielectric of air. Filter 702 can be an all-dielectric type filter and can be similar to filter 210, as shown in FIG2A .

As shown in FIG7B , an example stack of filter 704 is provided. Filter 704 can be a green filter comprising layers of niobium titanium oxide (NbTiO ₅ ), zinc oxide (ZnO), and silver (Ag), an inlet dielectric of silicon nitride (Si ₃ N ₄ ), and an outlet dielectric of air. Filter 704 can be similar to filter 310, as shown in FIG3A .

As shown in FIG7C , an example stack of optical filter 706 is provided. Filter 706 can be a green filter comprising layers of niobium titanium oxide (NbTiO ₅ ), silicon dioxide (SiO ₂ ), zinc oxide (ZnO), and silver (Ag), an inlet dielectric of silicon nitride (Si ₃ N ₄ ), and an outlet dielectric of air. Filter 706 can be similar to filter 410 shown in FIG4A . For example, filter 706 can include a first portion such as layers 1 through 13 (comprising alternating dielectric layers); a second portion such as layers 13 through 25 (comprising alternating dielectric and metal layers); and a third portion such as layers 25 through 37 (comprising alternating dielectric layers).

As shown in FIG7D , and illustrated by graphs 708 and 710, a filter response of filter 702 is provided. For example, filter 702 is associated with an angular shift for changes in angle of incidence (AOI) from approximately 0 degrees to approximately 50 degrees between approximately 50 nm and approximately 80 nm for a spectral range between approximately 450 nm and approximately 575 nm. Furthermore, filter 702 is associated with a peak transmittance in the passband that drops from approximately 100% at an angle of incidence of approximately 0 degrees to approximately 90% at an angle of incidence of approximately 50 degrees.

Furthermore, filter 702 is associated with a color shift in the CIE 1931 color diagram from approximately [0.08, 0.47] to approximately [0.25, 0.69].

As shown in FIG7E , and illustrated by graphs 712 and 714 , the filter response of filter 704 is provided. For example, filter 704 is associated with an angular shift for changes in the angle of incidence (AOI) from approximately 0 degrees to approximately 50 degrees between approximately 25 nm and approximately 40 nm for a spectral range between approximately 450 nm and approximately 575 nm. Furthermore, filter 704 is associated with a decrease in peak transmittance in the passband from approximately 72% at an angle of incidence of approximately 0 degrees to approximately 66% at an angle of incidence of approximately 50 degrees. Furthermore, filter 704 is associated with a color shift from approximately [0.17, 0.58] to approximately [0.26, 0.63] in the CIE 1931 color diagram.

As shown in FIG7F , and illustrated by graphs 716 and 718 , the filter response of filter 706 is provided. For example, filter 706 is associated with an angular shift for changes in angle of incidence (AOI) from approximately 0 degrees to approximately 50 degrees between approximately 25 nm and approximately 40 nm for a spectral range between approximately 450 nm and approximately 575 nm. Furthermore, filter 706 is associated with a decrease in peak transmittance in the passband from approximately 78% at an angle of incidence of approximately 0 degrees to approximately 70% at an angle of incidence of approximately 50 degrees. Furthermore, filter 706 is associated with a color shift from approximately [0.18, 0.62] to approximately [0.26, 0.65] in the CIE 1931 color diagram. In this way, filter 706 is associated with reduced angular shift and reduced color shift relative to filter 702, and improved transmittance relative to filter 704.

As shown in FIG7G , and illustrated by graphs 720 and 722, a comparison of the change in center wavelength and the average transmittance in the passband from approximately 510 nm to approximately 550 nm is provided for filter 702, filter 704, and filter 706, respectively. As shown in graph 720, for angles of incidence from approximately 10 degrees to approximately 50 degrees, filter 706 is associated with a reduced change in center wavelength relative to filter 702. As shown in graph 722, filter 706 is associated with an improved average transmittance in the passband relative to filter 704 for angles of incidence from approximately 0 degrees to approximately 50 degrees, and an improved average transmittance in the passband relative to filter 706 for angles of incidence from approximately 40 degrees to approximately 50 degrees.

As indicated above, Figures 7A-7G are provided merely as examples. Other examples are possible and may differ from what is described with respect to Figures 7A-7G.

In this way, the use of a filter comprising a first portion of a dielectric layer, a second portion of a mixed dielectric layer and a metal layer, and a third portion of a dielectric layer provides filtering with reduced angular shift and improved transmittance relative to an all-dielectric filter or a LAS ITF filter. Based on the reduced angular shift and improved transmittance, the accuracy of data obtained by a sensor element aligned to the filter is improved relative to the accuracy of data obtained by a sensor element aligned to another type of filter.

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 the implementations.

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, higher than a threshold, greater than or equal to a threshold, less than a threshold, less than a threshold, lower than a threshold, less than or equal to a threshold, equal to a threshold, and the like.

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. Indeed, many of these features can be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each of the following dependent claims may only be directly dependent on one claim, the disclosure of possible implementations includes the combination of each dependent claim with every other claim in the entire set of claims.

None of the elements, behaviors or instructions used herein should be understood to be 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, a combination 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 mean "at least partially based on", unless explicitly stated otherwise.

Claims (20)

1. An optical filter, comprising: First layer, The first set of layers includes at least four alternating layers of a first dielectric material and a second dielectric material in a set of dielectric materials; The second layer, The second set of layers includes at least four alternating layers of a third dielectric material and a fourth dielectric material from the set of dielectric materials; and The third layer, The third layer comprises alternating layers of a fifth dielectric material, a sixth dielectric material, and a metallic material from the group of dielectric materials. The third layer is positioned between the first layer and the second layer, and The optical filter filters light in a manner that shifts the light by less than a threshold angle and transmits light at a level greater than a threshold. 2. The optical filter of claim 1, wherein the set of dielectric materials is composed of two materials. 3. The optical filter of claim 1, wherein the set of dielectric materials is composed of three materials. 4. The optical filter of claim 1, wherein the set of dielectric materials comprises at least one of the following: Niobium titanium oxide ( _NbTiO₂x ) Silicon dioxide ( _SiO2 ), Aluminum oxide _{( Al₂O₃} ), Titanium dioxide ( _TiO2 ), Niobium pentoxide _{( Nb₂O₅} ), Tantalum pentoxide _{( Ta₂O₅} ), Zirconium oxide ( _ZrO₂ ), _Yttrium oxide ( _Y₂O₃ ), Hafnium dioxide (HfO ₂ ), or Its combination. 5. The optical filter of claim 1, wherein the set of dielectric materials comprises at least one of the following: Nitride materials, Fluoride materials, Sulfide materials, Selenide materials, or Its combination. 6. The optical filter of claim 1, wherein the metal material is silver. 7. The optical filter of claim 1, further comprising: Glass substrate, The first set of layers is deposited on the glass substrate. The third layer is deposited on top of the first layer. The second set of layers is deposited on the third set of layers. 8. The optical filter of claim 1, further comprising: The detector includes a detector substrate. The first set of layers is deposited on the detector substrate. The third layer is deposited on top of the first layer. The second set of layers is deposited on the third set of layers. 9. The optical filter of claim 8, wherein the detector is at least one of the following: Complementary metal-oxide-semiconductor (CMOS) detector, Charge-coupled device detector, Front lighting detector, or Rear illumination detector. 10. The optical filter of claim 1, wherein the first set of layers and the second set of layers do not include a metal layer. 11. The optical filter of claim 1, wherein at least one of the dielectric materials in the group is associated with a refractive index greater than 2.0. 12. The optical filter of claim 1, wherein at least one of the dielectric materials in the group is associated with a refractive index of less than 3.0. 13. The optical filter of claim 1, wherein the threshold angle shift is approximately 30 nm. 14. The optical filter of claim 1, wherein the threshold transmission level is approximately 70%. 15. An induced transmission filter, comprising: The first all-dielectric portion includes a first group of four or more dielectric layers; The second all-dielectric portion includes a second group of four or more dielectric layers; and The metal/dielectric portion includes a third set of dielectric layers and one or more metal layers. The metal/dielectric portion is disposed between the first all-dielectric portion and the second all-dielectric portion, and The induced transmission filter filters light in a manner that shifts the light at an angle less than a threshold and at a transmission level greater than a threshold. 16. The induced transmission filter of claim 15, wherein the first set of dielectric layers and the second set of dielectric layers each comprise alternating layers of a first dielectric material having a first refractive index and a second dielectric material having a second refractive index. The first refractive index is higher than the second refractive index. 17. The induced transmission filter of claim 15, wherein the first set of dielectric layers, the second set of dielectric layers, and the third set of dielectric layers each comprise at least one common material. 18. The induced transmission filter of claim 15, wherein the metal/dielectric portion comprises a set of layers arranged in a layered manner. The layer group includes multiple layers in the order of a first layer of a first dielectric material, a second layer of a second dielectric material, a third layer of a metallic material, a fourth layer of a second dielectric material, and a fifth layer of a first dielectric material. 19. A hybrid metal/dielectric optical filter, comprising: Substrate; The first all-dielectric portion includes alternating layers of silicon dioxide and niobium titanium oxide; The second all-dielectric portion comprises alternating layers of silicon dioxide and niobium titanium oxide; and The metal/dielectric portion includes one or more layers. One or more layers may comprise a silver layer, two zinc oxide layers, and two niobium titanium oxide layers. The silver layer is disposed between the two zinc oxide layers. The two zinc oxide layers are disposed between the two niobium titanium oxide layers. The metal/dielectric portion is disposed between the first all-dielectric portion and the second all-dielectric portion. 20. The hybrid metal/dielectric optical filter of claim 19, comprising at least one of the following: Color filter, Bandpass filter, Near-infrared light blocking component, Long wave pass (LWP) filter, Short-pass (SWP) filter, Clearview filter, or Three-color filter.