Patent Description:
An optical transmitter may emit light that is directed toward an object. For example, in a gesture recognition system, the optical transmitter may transmit near infrared light toward a user, and the near-infrared light may be reflected off the user toward an optical receiver. In this case, the optical receiver may capture information regarding the near-infrared light, and the information may be used to identify a gesture being performed by the user. In another example, information regarding the visible light, such as information regarding different wavelengths of visible light may be captured to image an object.

However, during propagation of light with a wavelength of interest toward a target and/or during reflection of the light from the target toward the optical receiver, ambient light may be introduced along with the wavelength of interest. For example, when an optical receiver is to receive near infrared light reflected off a target, the optical receiver may also receive visible light (e.g., from another light source, such as a light bulb or the sun). Thus, the optical receiver may be optically coupled to an optical filter, such as a bandpass filter, to filter ambient light and to allow one or more wavelengths of light to pass through toward the optical receiver. Additionally, or alternatively, when performing sensing of multiple wavelengths of light, a filter may be provided to ensure that each wavelength of light, of the multiple wavelengths of light, is directed to a different sensor.

A multispectral sensor device, which may be an optical receiver, may be utilized to capture information about the multiple wavelengths of light. The multispectral sensor device may include a set of sensor elements (e.g., optical sensors, spectral sensors, and/or image sensors) that capture the information and are coupled to a multispectral filter. For example, an array of sensor elements may be utilized to capture information relating to multiple frequencies, and the multispectral filter may direct, to each sensor element, light associated with a different frequency. In some cases, a single binary multispectral filter may be disposed to cover each sensor element of the sensor element array, and may form a set of channels for the sensor element array.

<CIT>, <CIT> and <CIT> provide examples of multilayer devices known in the art.

According to a first aspect of the present invention, there is provided a filter as set out in claim <NUM>.

The stepped medium may be stepped in one dimension.

The stepped medium may be stepped in two dimensions.

A wavelength range of the set of channels of the filter may be between approximately <NUM> nanometers (nm) and <NUM>.

The stepped medium may be associated with a greater than <NUM>% transmissivity at a wavelength range of the filter and is one of: an oxide based medium, a semiconductor based medium, a dielectric based medium, a polymer based medium, a nitride based medium, a phosphide based medium, or a carbide based medium.

The spacer may be associated with a refractive index greater than <NUM> and is one of: hydrogenated silicon based spacer, an oxide based spacer, a germanium based spacer, or a silicon germanium based spacer.

The spacer may be at least one of: a gaseous spacer, a polymer spacer, or a liquid spacer.

The stepped medium forms a set of pillars, and wherein at least one pillar, of the set of pillars, forms an inactive channel. According to a second aspect of the present invention, there is provided a system as set out in claim <NUM>.

A sensor element (e.g., an optical sensor) may be incorporated into an optical sensor device to obtain information (e.g., spectral data) regarding a set of electromagnetic frequencies. For example, the optical sensor device may include an image sensor, a multispectral sensor, and/or the like that may perform a sensor measurement of light. The optical sensor device may utilize one or more sensor technologies, such as a complementary metal-oxide-semiconductor (CMOS) technology, a charge-coupled device (CCD) technology, and/or the like. The optical sensor device may include multiple sensor elements (e.g., an array of sensor elements) each configured to obtain information about a different frequency of light.

A sensor element may be associated with a filter that filters light to 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, and/or the like to cause a portion of light directed toward the sensor element to be filtered. For a binary filter structure, such as a Fabry-Perot filter, a spacer may be positioned between reflectors (e.g., mirrors) of the binary filter structure. Configuration of refractive indices, thicknesses, and/or the like of layers of the reflectors, layers of the spacer, and/or the like may enable configuration of the binary filter structure to form a set of channels. A channel may be a portion of the filter that directs light of a particular wavelength range to a sensor element of a sensor element array. In this way, the sensor element array may obtain information regarding multiple different wavelengths of light.

However, a fixed set of channels configured based at least in part on selected refractive indices, spacer thicknesses, and/or the like may limit a sensor element array to performing measurements of a fixed set of wavelengths. Thus, to ensure that a binary multispectral filter, which may also be termed a multichannel filter, is configured to capture whichever wavelengths of light are of interest, the binary multispectral filter may be designed with greater than a threshold quantity of channels and a sensor element array may, correspondingly, include greater than a threshold quantity of sensor elements. This may result in excessive size and/or an excessive cost to ensure flexibility in using a binary multispectral filter.

Further, some binary multispectral filters use different spacer thicknesses to form different channels at different wavelength ranges. For these binary multispectral filters, the different spacer thicknesses may be formed by depositing multiple layers of a spacer material on top of a first flat mirror, which is deposited directly on a substrate. In this case, the multiple layers of the spacer material are deposited to form a stepped structure spacer, and a second mirror is deposited onto the stepped structure of the spacer. However, depositing multiple layers of the spacer material may result in imperfections, which may reduce optical performance of a binary multispectral filter. For example, when hydrogenated silicon is used for the spacer material, a surface of each layer of the hydrogenated silicon may partially oxidize into silicon dioxide in between layer depositions, which may result in a reduced transmissivity, an increased angle shift, and/or the like.

Some implementations, described herein, provide a multispectral filter array with an improved spacer. For example, a binary multispectral filter may include a stepped medium disposed between a substrate and a first mirror, causing the first mirror to have a stepped surface, a monolithic spacer disposed on the stepped surface of the mirror, and a second mirror disposed on a flat surface of the monolithic spacer. In this case, based on forming the spacer in a single procedure, rather than depositing multiple spacer layers to build a stepped structure, imperfections, such as surface oxidation, may be avoided, thereby improving optical performance. For example, a monolithic spacer may enable improved transmissivity, reduced angle shift, and/or the like.

Moreover, some implementations, described but not claimed herein, may enable the second mirror to be movable with respect to the first mirror, rather than disposed directly on the spacer and disposed in a fixed position. For example, the second mirror may be translatable relative to the first mirror (i.e., either the first mirror or the second mirror or both the first mirror and the second mirror may be moved), thereby enabling a gap between the first mirror and the second mirror, formed by the spacer, to vary in thickness as the second mirror is translated. In this way, a wavelength range of a set of channels may be dynamically reconfigurable, thereby increasing a quantity of spectral bands that can be captured by sensor elements aligned to the set of channels. Moreover, in this way, a quantity of channels in the multispectral filter to cover a particular spectral range may be decreased relative to a multispectral filter with a fixed gap between mirrors, thereby achieving reduced size, reduced cost, and/or the like.

<FIG> is a diagram of an example implementation of a multispectral filter <NUM> described herein. As shown in <FIG>, a multispectral filter <NUM> (e.g., a binary structure optical filter array) includes a substrate <NUM>, a medium <NUM>, a first mirror <NUM>-<NUM>, a second mirror <NUM>-<NUM>, and a spacer <NUM>.

In some implementations, substrate <NUM> may be associated with an optical sensor device. For example, substrate <NUM> may include an array of sensor elements to capture information (e.g., spectral data). Additionally, or alternatively, substrate <NUM> may not include sensor elements, and multispectral filter <NUM> may be aligned to sensor elements disposed on another substrate. Additionally, or alternatively, multispectral filter <NUM> may be designed without substrate <NUM>. For example, multispectral filter <NUM> may be positioned in free space, may be disposed onto a substrate of an optical sensor device not part of multispectral filter <NUM>, and/or the like.

In some implementations, multispectral filter <NUM> may be associated with a particular spectral range. For example, multispectral filter <NUM> may be associated with multiple channels in a visible spectral range, a near infrared (NIR) spectral range, a mid-infrared (MIR) spectral range, and/or the like. In this case, multispectral filter <NUM> may be associated with a spectral range of between approximately <NUM> nanometers (nm) and <NUM>, <NUM> nanometers (nm) and <NUM>, between approximately <NUM> and approximately <NUM>, between approximately <NUM> and approximately <NUM>, <NUM> and approximately <NUM>, between approximately <NUM> and approximately <NUM>, <NUM> and approximately <NUM>, <NUM> and approximately <NUM>, between approximately <NUM> and approximately <NUM>, between approximately <NUM> and approximately <NUM>, and/or the like. In some implementations, multispectral filter <NUM> may include a threshold quantity of channels, such as greater than or equal to <NUM> channels, <NUM> channels, <NUM> channels, <NUM> channels, <NUM> channels, <NUM> channels, and/or the like.

As further shown in <FIG>, medium <NUM> is associated with a stepped structure, which forms a set of channels for multispectral filter <NUM>. For example, medium <NUM> may be formed, as described in more detail herein, using a photolithographic procedure to form the stepped structure. In some implementations, medium <NUM> may be stepped along a single axis (i.e., stepped in one dimension), as shown. For example, medium <NUM> may be stepped to form a set of <NUM> different channels extending along the single axis. In some implementations, medium <NUM> may be stepped along multiple axes (i.e., stepped in two dimensions). For example, medium <NUM> may be stepped orthogonal to the single axis to form a total of <NUM> different channels. In some implementations, medium <NUM> may include one or more repeated channels. For example, as shown, Channel <NUM> formed by medium <NUM> may be disposed at edges of multispectral filter <NUM>, which provides structural stability for multispectral filter <NUM>. Medium <NUM> causes one or more channels to be inactive. For example, portions of first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM>, which are aligned with a pillar of medium <NUM> forming Channel <NUM>, do not sandwich a portion of spacer <NUM>. This results in Channel <NUM> being inactive (but remaining for structural support). Additionally, or alternatively, a portion of spacer <NUM> may be sandwiched by first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM> to cause Channel <NUM> to be an active channel.

In some implementations, medium <NUM> may be formed using a particular material. For example, medium <NUM> may be formed from a material that is transmissive to a wavelength range for which multispectral filter <NUM> is to capture spectral data. In this case, the material may include a tantalum based medium material, a niobium based medium material, a silicon dioxide based medium material, an oxide based medium material, a III-V semiconductor based medium material, a gallium phosphide based medium material, a germanium based medium material, germanium silicon based medium material, a dielectric based medium material, a polymer based medium material, a nitride based medium material, a phosphide based medium material, a carbide based medium material, a combination thereof, and/or the like.

As further shown in <FIG>, first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM> may sandwich spacer <NUM>. In other words, spacer <NUM> may separate first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM> by a set of distances and/or faces of spacer <NUM> may be enclosed by first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM>. In this case, the set of distances may form different channels. For example, a first portion of first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM> aligned to Channel <NUM> may be separated by a first distance, and may form a first channel that passes through a first wavelength band of light. Similarly, a second portion of first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM> aligned to Channel <NUM> may be separated by a second distance, as a result of medium <NUM> having a stepped structure and causing a stepped structure for spacer <NUM>, as described in more detail herein, and may form a second channel that passes through a second wavelength band of light. In this case, the first channel may be aligned to a first sensor element and may form a first component filter for obtaining spectral data regarding the first spectral range and the second channel may be aligned to a second sensor element and may form a second component filter for obtaining spectral data regarding the second spectral range.

In some implementations, mirrors <NUM> may be associated with a particular material. For example, mirrors <NUM> may include a set of metal mirror layers (e.g., silver), a set of dielectric mirror layers (e.g., alternating hydrogenated silicon layers and silicon dioxide layers), and/or the like to direct a portion of light directed from a light source toward sensor elements associated with multispectral filter <NUM>. In some implementations, mirrors <NUM> may align with each sensor element, of a sensor element array, associated with each channel of multispectral filter <NUM>.

In some implementations, spacer <NUM> may be a monolithically formed spacer, as described in more detail herein. For example, spacer <NUM> may be formed by depositing a material onto a stepped surface of first mirror <NUM>-<NUM>, such that a first surface of spacer <NUM> at an interface with first mirror <NUM>-<NUM> is a stepped surface and a second surface of spacer <NUM> at an interface with second mirror <NUM>-<NUM> is a flat surface. In some implementations, spacer <NUM> may be formed from a particular material to cause multispectral filter <NUM> to have a particular wavelength range, transmissivity (e.g., greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, greater than <NUM>%, etc.), and/or the like. For example, spacer <NUM> may be a hydrogenated silicon based spacer, an oxide based spacer, a germanium based spacer, a silicon germanium based spacer, a polymer spacer, a combination thereof, and/or the like. In some implementations, spacer <NUM> may have a refractive index greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, greater than <NUM>, and/or the like.

In some implementations, spacer <NUM> may include a non-solid spacer material. For example, spacer <NUM> may be formed from a gaseous material (e.g., air or another gaseous material) or a liquid material to enable a size of spacer <NUM> (i.e., a separation between first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM>) to be expanded or contracted, as described in more detail herein. In some implementations, spacer <NUM> may include multiple spacer materials. For example but not claimed, spacer <NUM> may include a solid spacer forming a first portion of spacer <NUM> and covering first mirror <NUM>-<NUM> and a liquid spacer forming a second portion of spacer <NUM> and enabling second mirror <NUM>-<NUM> to be translated with respect to first mirror <NUM>-<NUM>. Similarly but not claimed, spacer <NUM> may include a first solid spacer covering first mirror <NUM>-<NUM>, a second solid spacer covering second mirror <NUM>-<NUM>, and a third liquid spacer disposed between the first solid spacer and the second solid spacer to enable second mirror <NUM>-<NUM> to be translated with respect to first mirror <NUM>-<NUM>. In this way, based on having a stepped structure, spacer <NUM> enables different portions of multispectral filter <NUM> to pass different wavelength bands of light to form different channels. Further, based on being formed without multiple layers of material or with less than a threshold quantity of layers of material, spacer <NUM> may be associated with less than a threshold level of imperfections, such as less than a threshold amount of surface oxidation within spacer <NUM>, thereby improving optical performance of multispectral filter <NUM>.

In some implementations, layers forming, for example, medium <NUM>, first mirror <NUM>-<NUM>, second mirror <NUM>-<NUM>, spacer <NUM>, and/or the like may include a set of layers of a high refractive index material (H layers), such as silicon layers, hydrogenated silicon layers, silicon-germanium (SiGe) layers, hydrogenated germanium layers, hydrogenated silicon-germanium layers, and/or the like. In some implementations, the layers forming, for example, medium <NUM>, first mirror <NUM>-<NUM>, second mirror <NUM>-<NUM>, spacer <NUM>, and/or the like may include a set of a low refractive index material (L layers), such as silicon dioxide layers, silicon nitride layers, tantalum pentoxide (Ta<NUM>O<NUM>) layers, niobium pentoxide (Nb<NUM>O<NUM>) layers, titanium dioxide (TiO<NUM>) layers, aluminum oxide (Al<NUM>O<NUM>) layers, zirconium oxide (ZrO<NUM>) layers, yttrium oxide (Y<NUM>O<NUM>) layers, silicon nitride (Si<NUM>N<NUM>) layers, a combination thereof, and/or the like. Although some layers may be described as a particular material, such as silicon germanium, some layers may include (small quantities of) phosphor, boron, nitride, and/or the like.

In some implementations, the layers forming, for example, medium <NUM>, first mirror <NUM>-<NUM>, second mirror <NUM>-<NUM>, spacer <NUM>, and/or the like may be associated with a particular quantity of layers, such as alternating high refractive index layers and low refractive index layers, in a range of <NUM> layers to <NUM> layers. In some implementations, one or more layers may be fabricated using a sputtering procedure, a photolithographic procedure, an etching procedure, a lift off procedure, a scraping procedure, an annealing procedure, a molding procedure, a casting procedure, a machining procedure, a stamping procedure and/or the like.

In some implementations, each layer of the layers forming, for example, medium <NUM>, first mirror <NUM>-<NUM>, second mirror <NUM>-<NUM>, spacer <NUM>, and/or the like may be associated with a particular thickness. For example, each layer may be associated with a thickness of between approximately <NUM> and approximately <NUM>, between approximately <NUM> and approximately <NUM>, and/or the like. Additionally, or alternatively, multispectral filter <NUM> may be associated with a thickness of between approximately <NUM> and approximately <NUM>, approximately <NUM> and approximately <NUM>, and/or the like.

In this way, multispectral filter <NUM> forms multiple channels for capturing spectral data regarding multiple wavelength ranges with a reduced amount of imperfections formed in spacer <NUM>, thereby improving optical performance of multispectral filter <NUM>.

<FIG> is a diagram of an example implementation of a multispectral filter <NUM> described herein. As shown in <FIG>, multispectral filter <NUM> may include a first substrate <NUM>-<NUM>, a second substrate <NUM>-<NUM>, a medium <NUM>, a first mirror <NUM>-<NUM>, a second mirror <NUM>-<NUM>, and a spacer <NUM>.

In some implementations, second substrate <NUM>-<NUM> may be deposited onto second mirror <NUM>-<NUM>. For example, second mirror <NUM>-<NUM> may be deposited onto spacer <NUM>, and second substrate <NUM>-<NUM> may be deposited onto second mirror <NUM>-<NUM>. Additionally, or alternatively, second mirror <NUM>-<NUM> may be deposited onto second substrate <NUM>-<NUM>. For example, medium <NUM> may be deposited on first substrate <NUM>-<NUM>, first mirror <NUM>-<NUM> may be deposited on medium <NUM>, spacer <NUM> may be deposited onto first mirror <NUM>-<NUM>, second mirror <NUM>-<NUM> may be deposited on second substrate <NUM>-<NUM>, and second mirror <NUM>-<NUM> and second substrate <NUM>-<NUM> may be aligned to first mirror <NUM>-<NUM> and first substrate <NUM>-<NUM>.

<FIG> are diagrams of an implementation of a multispectral filter <NUM> described herein but not claimed. As shown in <FIG>, multispectral filter <NUM> may include a first substrate <NUM>-<NUM>, a second substrate <NUM>-<NUM>, a medium <NUM>, a first mirror <NUM>-<NUM>, a second mirror <NUM>-<NUM>, and a spacer <NUM>. As further shown in <FIG>, multispectral filter <NUM> is attached to one or more translation devices <NUM>.

As further shown in <FIG>, second mirror <NUM>-<NUM> of multispectral filter <NUM> may be movable with respect to first mirror <NUM>-<NUM> to cause spacer <NUM> to have a variable thickness, which may alter a spectral range of light passed by channels of multispectral filter <NUM>. Although described herein in terms of second mirror <NUM>-<NUM> being translated, tilted, or otherwise moved with respect to a fixed first mirror <NUM>-<NUM>, first mirror <NUM>-<NUM> may be moved with respect to second mirror <NUM>-<NUM>, both first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM> may be moved by translation devices <NUM>, and/or the like.

As shown in <FIG>, second mirror <NUM>-<NUM> is translated by translation device <NUM> with respect to first mirror <NUM>-<NUM>. For example, second substrate <NUM>-<NUM> and second mirror <NUM>-<NUM> may be moved further away from first substrate <NUM>-<NUM> and first mirror <NUM>-<NUM> with respect to a position shown in <FIG>. Translation device <NUM> may be a focusing element, a voice-coil motor, a piezo-electric transducer, a silicon micro-electro-mechanical system (MEMS) device, a thermomechanical device, a bi-stable beam switch, and/or the like.

As shown in <FIG>, second mirror <NUM>-<NUM> may be translated by translation device <NUM> such that second mirror <NUM>-<NUM> is tilted with respect to first mirror <NUM>-<NUM>. For example, second substrate <NUM>-<NUM> may be attached to a tilting device, multiple translation devices, and/or the like. In this way, a wavelength range of channels of multispectral filter <NUM> may be further configured by reducing a separation between second mirror <NUM>-<NUM> and first mirror <NUM>-<NUM> for a first portion of channels, increasing a separation between second mirror <NUM>-<NUM> and first mirror <NUM>-<NUM> for a second portion of channels, maintaining a separation between second mirror <NUM>-<NUM> and first mirror <NUM>-<NUM> for a third portion, and/or the like.

A movement device may move second mirror <NUM>-<NUM> with respect to first mirror <NUM>-<NUM> based on a particular timing configuration. For example, during a read-out of sensor elements aligned to channels of multispectral filter <NUM>, the movement device may be triggered to move second mirror <NUM>-<NUM> to cause some channels to be associated with different wavelength ranges and other channels to maintain a default wavelength range. As an example, when a multispectral filter includes multiple channels with a common wavelength range, as shown in <FIG> and <FIG> with regard to the multiple Channel <NUM>'s, the movement device may be triggered to cause a first sensor element of a first channel associated with the common wavelength range to read out at a first position of second mirror <NUM>-<NUM> and a second sensor element of a second channel associated with the common wavelength range to read out at a second position of second mirror <NUM>-<NUM>. In this way, the multispectral filter <NUM> may enable multiple spectral ranges using a common channel. Moreover, the movement device may cause the first sensor element to read out at the first position and at the second position, resulting in capture of multiple spectral ranges using a single channel.

Spacer <NUM> may be constrained to enable a variable spacer width based on translating second mirror <NUM>-<NUM> with respect to first mirror <NUM>-<NUM>. For example, spacer <NUM> may be a gaseous spacer or a liquid spacer that may be encapsulated by multispectral filter <NUM> to enable the gaseous spacer or the liquid spacer to expand and/or contract as second mirror <NUM>-<NUM> is translated with respect to first mirror <NUM>-<NUM>. Additionally, or alternatively, spacer <NUM> may be constrained such that additional gaseous spacer material or liquid spacer material may be provided into a gap between second mirror <NUM>-<NUM> and first mirror <NUM>-<NUM> and/or removed from the gap to enable the spacer to provide a variable thickness.

As shown in <FIG>, multiple spacers <NUM>, such as a first spacer <NUM>-<NUM> and a second spacer <NUM>-<NUM> may be disposed between first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM>. For example, first spacer <NUM>-<NUM> may be a solid spacer that covers first mirror <NUM>-<NUM>, and second spacer <NUM>-<NUM> may be a gaseous (or liquid) spacer that enables a variable separation between first mirror <NUM>-<NUM> and second mirror <NUM>-<NUM>.

As indicated above, <FIG> are provided merely as examples.

<FIG> is a flow chart of an example process <NUM> for manufacturing a multispectral filter described herein. In some implementations, one or more process blocks of <FIG> may be performed by a deposition device during a manufacturing procedure, such as by an etching device, a sputtering device, a photolithographic device, and/or the like.

As shown in <FIG>, process <NUM> may include disposing, on a substrate, a medium to form a stepped structure (block <NUM>). For example, a deposition device may deposit the medium on the substrate to form the stepped structure. In some implementations, the deposition device may deposit multiple layers of medium to form the stepped structure. For example, multiple layers of photolithographic material may be deposited and multiple layers of medium may be deposited to form the stepped structure. In this case, the multiple layers of photolithographic material may be exposed to light in connection with a photomask to selectively remove the photolithographic material and cause the multiple layers of medium to form the stepped structure. Photolithographic formation of the stepped structure for the medium is described in detail with regard to <FIG>. Additionally, or alternatively, the medium may be disposed on the substrate to form the stepped structure using an etching procedure. For example, a medium may be deposited onto a substrate and then etched to form a stepped structure. Although some implementations, described herein, are described in terms of a photolithographic procedure or an etching procedure, other procedures for forming a stepped medium structure are possible.

As shown in <FIG>, process <NUM> may include disposing, on the medium, a first mirror for a multichannel filter to form a stepped mirror structure (block <NUM>). For example, the deposition device may deposit the first mirror on the medium. In this case, the first mirror forms a stepped structure based on the medium, on which the first mirror is deposited, having a stepped structure.

As shown in <FIG>, process <NUM> may include disposing, on the first mirror, a spacer for the multichannel filter (block <NUM>). For example, the deposition device may deposit the spacer on the first mirror. In this case, the spacer may be a solid spacer deposited using a single deposition step, which may reduce surface layer oxidation based effects to optical performance relative to depositing the spacer using multiple deposition and etching steps. Additionally, or alternatively, the spacer may be a liquid spacer or a gaseous spacer that may be inserted into a cavity formed by the first mirror and a second mirror, which may enable a variable spacer binary multispectral filter with a translatable mirror (not claimed). In some implementations, the spacer may form a flat surface. For example, the spacer may be deposited onto the first mirror such that a first surface interfacing with a stepped mirror surface of the first mirror is stepped and such that a second surface on an opposite side of the spacer is flat. In this case, the spacer may be etched to remove a portion of the spacer to form the flat surface. In some implementations, the first mirror or the medium may form an etch stop for etching the spacer to form the flat surface.

As shown in <FIG>, process <NUM> may include disposing, on the second surface of the spacer, a second mirror to form a flat mirror for the multichannel filter (block <NUM>). For example, the deposition device may deposit the second mirror on the second surface of the spacer such that the mirror is a flat mirror. In some implementations, the second mirror may be aligned to the first mirror. For example, the second mirror may be deposited onto another substrate, and the second mirror and the other substrate may be aligned to the first mirror such that the second mirror and the other substrate are translatable with respect to the first mirror to form a variable thickness spacer (not claimed). In this way, a multispectral filter may be formed with multiple channels.

<FIG> are diagrams of an example implementation relating to process <NUM>. <FIG> show an example process for manufacturing a multispectral filter described herein.

As shown in <FIG>, and by diagram <NUM>, photoresist <NUM> may be deposited onto substrate <NUM>. As shown by diagram <NUM>, photomask <NUM> and <NUM> may positioned over photoresist <NUM>.

As shown in <FIG>, and by diagram <NUM>, photomask <NUM> and <NUM> and a portion of photoresist <NUM> not covered by photomask <NUM> and <NUM> may be exposed to light. As shown by diagram <NUM>, based on the exposure to light, the portion of photoresist <NUM> not covered by photomask <NUM> and <NUM> may remain disposed on substrate <NUM>.

As shown in <FIG>, and by diagram <NUM>, a layer of medium <NUM> may be deposited onto substrate <NUM> and the remaining portion of photoresist <NUM>. As shown by diagram <NUM>, the remaining portion of photoresist <NUM> may be removed. In this case, portions of the layer of medium <NUM> deposited onto substrate <NUM> may remain, forming a first step where the remaining portion of photoresist <NUM> was removed. As shown by diagram <NUM>, another layer of photoresist <NUM> may be deposited onto medium <NUM> and substrate <NUM>.

As shown in <FIG>, and by diagram <NUM>, based on using another photomask (not shown) and based on exposure to light, only a portion of the other layer of photoresist <NUM> may remain. As shown by diagram <NUM>, another layer of medium <NUM> may be deposited.

As shown in <FIG>, and by diagram <NUM>, the other layer of photoresist <NUM> may be removed, resulting in medium <NUM> forming two steps. As shown by diagram <NUM>, another layer of photoresist <NUM> may be deposited onto medium <NUM> and substrate <NUM>.

As shown in <FIG>, and by diagram <NUM>, the other layer of photoresist <NUM> may be removed, resulting in medium <NUM> forming three steps. As shown by diagram <NUM>, another layer of photoresist <NUM> may be deposited onto medium <NUM> and substrate <NUM>.

As shown in <FIG>, and by diagram <NUM>, based on using another photomask <NUM> and <NUM> (not shown) and based on exposure to light, only a portion of the other layer of photoresist <NUM> may remain. As shown by diagram <NUM>, another layer of medium <NUM> may be deposited.

As shown in <FIG>, and by diagram <NUM>, the other layer of photoresist <NUM> may be removed, resulting in medium <NUM> forming <NUM> steps. As shown by diagram <NUM>, after further photolithographic steps, a set of <NUM> steps may be formed by medium <NUM> with channels at each edge of the multispectral filter being a common channel.

As shown in <FIG>, and by diagram <NUM>, a first mirror <NUM> may be deposited onto the set of <NUM> steps formed by medium <NUM>. As shown by diagram <NUM>, a spacer <NUM> may be deposited onto first mirror <NUM>. In this case, a first surface of spacer <NUM> at an interface with first mirror <NUM> is stepped based on first mirror <NUM> having a stepped surface. Further, a second surface of spacer <NUM> is a non-flat surface.

As shown in <FIG>, and by diagram <NUM>, an etching procedure may remove a portion of the second surface of spacer <NUM> to cause the second surface of spacer <NUM> to be a flat surface. As shown by diagram <NUM>, a second mirror <NUM> is deposited on the flat second surface of spacer <NUM>. In this case, based on the first surface being stepped and the second surface being flat, spacer <NUM> forms multiple channels for the multispectral filter without multiple layers of deposition for spacer <NUM>.

<FIG> is a diagram of an example implementation <NUM> described herein. As shown in <FIG>, example implementation <NUM> includes a sensor system <NUM>. Sensor system <NUM> may be a portion of an optical system, and may provide an electrical output corresponding to a sensor determination. For example, sensor system <NUM> may be a portion of a biometric system, a security system, a health monitoring system, an object identification system, a spectroscopic identification system, an imaging system, and/or the like. Sensor system <NUM> includes an optical filter structure <NUM>, which includes an optical filter <NUM>, and a set of optical sensors <NUM> (e.g., a sensor element array). For example, optical filter structure <NUM> may include an optical filter <NUM> that performs a bandpass blocking functionality and/or the like. In some implementations, optical filter <NUM> may be a multispectral filter, such as a multispectral filter with a stepped medium and a monolithic spacer, a multispectral filter with a variable thickness spacer, and/or the like. Sensor system <NUM> includes an optical transmitter <NUM> that transmits an optical signal toward a target <NUM> (e.g., a person, an object, etc.).

Although implementations, described herein, may be described in terms of an optical filter in a sensor system, implementations described herein may be used in another type of system, may be used external to the sensor system, and/or the like.

In some implementations, another arrangement of optical filter <NUM> and optical sensor <NUM> may be utilized. For example, rather than passing the second portion of the optical signal collinearly with the input optical signal, optical filter <NUM> may direct the second portion of the optical signal in another direction toward a differently located optical sensor <NUM>. In some implementations, optical sensor <NUM> may be an avalanche photodiode, an Indium-Gallium-Arsenide (InGaAs) detector, an infrared detector, and/or the like.

As further shown in <FIG>, and by reference number <NUM>, an input optical signal is directed toward optical filter structure <NUM>. The input optical signal may include visible light, near-infrared light, mid-infrared light, and/or the like emitted by optical transmitter <NUM> and ambient light from the environment in which sensor system <NUM> is being utilized. For example, when optical filter <NUM> is a bandpass multispectral filter with multiple channels, optical transmitter <NUM> may direct multiple wavelength ranges of near-infrared light toward an object for a spectroscopic measurement, and the near-infrared light may be reflected off target <NUM> (e.g., the object) toward optical sensors <NUM> to permit optical sensors <NUM> to perform a measurement of the multiple wavelength ranges of near-infrared light. In this case, ambient light may be directed toward optical sensor <NUM> from one or more ambient light sources (e.g., a light bulb or the sun).

In another example, multiple light beams may be directed toward target <NUM> and a subset of the multiple light beams may be reflected toward optical filter structure <NUM>, which may be disposed at a tilt angle relative to optical sensor <NUM>, as shown. In some implementations, another tilt angle may be used. In some implementations, optical filter structure <NUM> may be disposed and/or formed directly onto optical sensors <NUM>, disposed a distance from optical sensors <NUM> (e.g., via free-space optics), and/or the like. For example, optical filter structure <NUM> may be coated and patterned onto optical sensors <NUM> using, for example, photolithography, a sputter deposition technique (e.g., using argon gas and helium gas as an inert gas mixture for sputter deposition), and/or the like.

In another example, optical transmitter <NUM> may direct near-infrared light toward another type of target <NUM>, such as for detecting a gesture in a gesture recognition system, detecting objects in proximity to a vehicle, detecting objects in proximity to a blind person, detecting a proximity to an object (e.g., using a LIDAR technique), and/or the like, and the near-infrared light and ambient light may be directed toward optical sensor <NUM> as a result.

In some implementations, a portion of the optical signal is passed by optical filter <NUM> and optical filter structure <NUM>. For example, differing spacer thicknesses of different channels of optical filter <NUM> may cause a first portion of light to be reflected and a second portion of light to be passed. In this case, optical filter <NUM> may include multiple channels formed by a spacer in connection with a stepped medium and each channel may pass a different wavelength of light. Additionally, or alternatively, two or more channels may pass a common wavelength of light.

As further shown in <FIG>, and by reference number <NUM>, based on the portion of the optical signal being passed to optical sensor <NUM>, optical sensor <NUM> may provide an output electrical signal for sensor system <NUM>, such as for use in performing a spectroscopic measurement, recognizing a gesture of the user, detecting the presence of an object, and/or the like.

Modifications and variations are possible within the scope of the appended claims.

Some implementations are described herein in connection with thresholds. As used herein, satisfying a threshold may refer to a value being greater than the threshold, more than the threshold, higher than the threshold, greater than or equal to the threshold, less than the threshold, fewer than the threshold, lower than the threshold, less than or equal to the threshold, equal to the threshold, and/or the like.

Claim 1:
A filter (<NUM>, <NUM>), comprising:
a substrate (<NUM>, <NUM>-<NUM>);
a stepped medium (<NUM>) disposed on the substrate (<NUM>, <NUM>-<NUM>);
a first mirror (<NUM>-<NUM>, <NUM>) disposed on the stepped medium (<NUM>);
wherein the first mirror (<NUM>-<NUM>, <NUM>) forms a stepped mirror surface,
wherein each step, of the stepped mirror surface corresponds to a channel, of a set of channels, of the filter (<NUM>);
a spacer (<NUM>, <NUM>) disposed on the stepped mirror surface; and
a second mirror (<NUM>-<NUM>, <NUM>( disposed on another surface of the spacer (<NUM>, <NUM>);
wherein the stepped medium (<NUM>) forms a set of pillars, and
characterised in that at least one pillar, of the set of pillars, forms an inactive channel (<NUM>), wherein a portion of the first mirror (<NUM>-<NUM>) and a portion of the second mirror (<NUM>-<NUM>) aligned with the at least one pillar does not sandwich a portion of spacer (<NUM>) such that structural support is provided at the inactive channel (<NUM>).