HK40118572A - Multi-transmission optical filter - Google Patents

Description

Multi-transmission optical filter

Case Analysis

This application is a divisional application of PCT patent application with an international filing date of October 8, 2020, international application number PCT/US2020/070633, Chinese national phase application number 202080070708.8, and invention title "Multi-transmission optical filter".

Cross-references to related applications

This patent application claims priority to U.S. Provisional Patent Application No. 62/912,951, filed October 9, 2019, entitled “MULTI-TRANSMISSION OPTICAL FILTER,” and U.S. Non-Provisional Patent Application No. 16/948,960, filed October 7, 2020, entitled “MULTI-TRANSMISSION OPTICAL FILTER,” which are expressly incorporated herein by reference.

Background Technology

An interferometric filter is an optical filter that reflects one or more spectral bands or lines and transmits other spectral bands or lines. Due to the interference effect that occurs between the incident and reflected waves at the boundaries of the interferometric filter, it can be wavelength selective.

Summary of the Invention

According to some embodiments, an optical filter may include: an interference filter that allows at least two channels associated with at least two transmission peaks to pass through; and a plurality of blockers, wherein each of the plurality of blockers allows a corresponding channel associated with a corresponding transmission peak of the at least two transmission peaks to pass through, and blocks one or more channels other than the corresponding channel associated with the corresponding transmission peak.

According to some embodiments, a sensor device may include: an optical sensor that collects data using multiple channels; and an optical device including: a spacer; a first mirror and a second mirror, wherein the optical device is associated with at least two transmission peaks; and a plurality of blocks attached to the optical device, wherein each of the plurality of blocks allows a corresponding channel of the plurality of channels associated with a corresponding transmission peak of the at least two transmission peaks to pass through.

According to some embodiments, a binary multispectral filter may include: a plurality of interferometric filters; and a plurality of blockers, wherein each of the plurality of interferometric filters is configured to allow a corresponding channel pair associated with a corresponding transmission peak pair to pass through, wherein the interferometric filter of the plurality of interferometric filters is associated with a first blocker of the plurality of blockers, the first blocker being configured to allow a channel associated with a first transmission peak of a corresponding transmission peak pair to pass through and block a channel associated with a second transmission peak of a corresponding transmission peak pair, and wherein the interferometric filter is associated with a second blocker of the plurality of blockers, the second blocker being configured to allow a channel associated with a second transmission peak to pass through and block a channel associated with a first transmission peak.

Attached Figure Description

Figure 1 is a diagram of an example interference filter.

Figure 2 is a diagram of an example device containing an interference filter.

Figure 3 is a diagram illustrating an example transmission graph of an interference filter.

Figure 4 is a diagram illustrating an example transmission graph of an interferometric filter associated with multiple spacers of different thicknesses.

Figure 5 is a diagram illustrating an example transmission graph of an interference filter.

Detailed Implementation

The following detailed description of the exemplary embodiments is with reference to the accompanying drawings. The same reference numerals in different drawings may identify the same or similar elements.

Optical sensors can use filters to transmit light of desired frequencies for sensing operations. For example, an optical sensor can perform sensing about one or more frequency ranges (referred to herein as channels). In some cases, an optical sensor can use an interference filter to transmit the channel and block unwanted light frequencies. Interference filters (e.g., interferometers, Fabry-Perot interferometers, etalons, Leo filters, etc.) can transmit light associated with transmission peaks based on the geometry and material composition of the interference filter. In some embodiments, the interference filter can be configured to transmit channels associated with transmission peaks within the free spectral range (FSR) of the interference filter, allowing the optical sensor to perform sensing about the channels.

Using a single optical sensor to perform multi-channel sensing can be advantageous. To facilitate multi-channel sensing, the free-spectral density (FSR) of an interferometric filter can be manipulated by changing the filter's geometry and/or material composition. However, a larger FSR can lead to a larger resonator bandwidth, resulting in poorer spectral resolution; therefore, extending the FSR to broaden the range of addressable channels may not be a feasible solution in all use cases. If the optical sensor is to perform multi-channel sensing, the interferometric filter can be fabricated with two or more different spacer thicknesses, which may result in the interferometric filter transmitting through two or more corresponding channels. However, the use of multiple spacer thicknesses can complicate the fabrication of the optical filter and may be difficult or impossible to achieve using some deposition techniques.

If the interferometer is configured to transmit a channel associated with a transmission peak in certain regions of the FSR, it can also allow a second channel associated with a second transmission peak at a frequency different from the desired transmission peak (e.g., due to harmonic effects). For example, if the interferometer is configured to transmit a transmission peak appearing in a region of the FSR susceptible to harmonic effects, it can also transmit a second transmission peak that may overlap with the desired channel. In this case, if the interferometer (or another filter) is not configured to block unwanted harmonic transmission peaks, the optical sensor can detect noise in the desired channel.

The embodiments described herein provide an interference filter that transmits channels associated with two or more transmission peaks for measurement by an optical sensor: a first transmission peak (e.g., in the harmonic region of the FSR of the interference filter) and a second transmission peak associated with a harmonic of the corresponding first transmission peak. The interference filter may include two or more blockers corresponding to the two or more transmission peaks. Each blocker allows a corresponding channel associated with one of the two or more transmission peaks to pass through and may block one or more other transmission peaks among the two or more transmission peaks. The blockers may utilize transmission peaks in regions of the FSR that would otherwise result in harmonic interference. For example, this allows optical sensors to perform sensing in both the near-infrared (NIR) and visible spectral ranges (e.g., red light wavelength ranges, biologically significant wavelength ranges, etc.) without increasing design complexity or manufacturing difficulty compared to variable spacer designs.

Figure 1 is a diagram of an example interference filter 100. In some embodiments, the interference filter 100 may include a spectral filter, a multispectral filter (e.g., a binary multispectral filter, etc.), etc. In some aspects, the interference filter 100 may include a biometric sensor device, a security sensor device, a health monitoring sensor device, an object identification sensor device, a spectral identification sensor device, a sensor for wearable devices, etc. As shown, the interference filter 100 includes one or more spacers 110, a mirror group 120, and blocker groups 130-1 and 130-2. The propagation of light via the spacers 110 and the reflection of light by the mirrors 120 may create interference, and may allow light associated only with a specific channel or frequency range (e.g., a transmission peak) to pass through. The channel can be configured by changing the thickness of the spacers 110 or the material properties of the spacers 110 and/or the mirrors 120. For example, when the thickness of the spacers 110 is changed, the channel of the interference filter 100 may be shifted upward or downward. Similarly, if different regions of spacer 110 have different thicknesses, or if different spacers 110 of interference filter 100 have different thicknesses, different regions or different spacers 110 can allow channels associated with different transmission peaks to pass through. Furthermore, changing the material properties of spacers 110 and/or mirror 120 can shift the transmission peaks upwards or downwards. Spacers 110 can comprise any material capable of allowing light to pass through, such as glass, polymers, substrates, etc. For example, spacers 110 can comprise silicon dioxide (SiO2), silicon hydride (Si:H), niobium titanium oxide (NbTiOx), niobium tantalum oxide (NbTaOx), zinc oxide (ZnO), etc. Si:H can provide material absorption in regions where harmonic transmission peaks may occur in a given design, meaning that the use of Si:H can provide the functionality of blocker 130 with respect to harmonic transmission peaks. In some aspects, interference filter 100 can comprise a single blocker 130 blocking a first transmission peak and spacers 110 partially composed of Si:H blocking a second transmission peak. For example, the region of the interferometer filter 100 not covered by a single blocker 130 may include a spacer 110 composed of Si:H, thereby reducing the cost associated with implementing multiple blocks. Therefore, the blocker can be implemented in the silicon hydride spacer 110 of the interferometer filter 100. The mirror 120 may include a reflective layer, such as a reflective glass layer. The mirror 120 may be attached to the opposite side of the spacer 110. In some aspects, the mirror 120 may be composed of a reflective material, such as a silver layer. In some aspects, the mirror 120 and the spacer 110 may together have a thickness less than a threshold. For example, the mirror 120 and the spacer 110 may form a Fabry-Perot interferometer with a thickness of less than about 3 micrometers.

As shown, the interference filter 100 includes a plurality of blocks 130. Each block 130 includes a device capable of blocking (e.g., reflecting, absorbing, or a combination thereof) light associated with a first frequency and allowing (e.g., transmitting) light associated with a second frequency to pass through. For example, the block 130 may include an optical filter. In some embodiments, the blocks 130 may be attached to the surface of the interference filter 100. In some embodiments, the blocks 130 may not overlap each other on the surface of the interference filter 100.

In the example shown in Figure 1, blocker 130-1 is configured to allow a channel at approximately 1100 nm (indicated by the dashed ellipse around the right transmission peak in transmission chart 150) to pass through, and blocker 130-2 is configured to allow a channel at approximately 775 nm (indicated by the dashed ellipse around the left transmission peak in transmission chart 150) to pass through. Transmission chart 150 is described in more detail in conjunction with Figure 3.

Each blocker 130 can be configured to block one or more channels, rather than the channels through which the blocker 130 passes. For example, blocker 130-1 can be configured to block light of a wavelength associated with blocker 130-2 (e.g., approximately 775 nm), and blocker 130-2 can be configured to block light of a wavelength associated with blocker 130-1 (e.g., approximately 1100 nm). In this way, the interference filter 100 can utilize transmission peaks associated with harmonic transmission peaks by using blockers 130 to block unwanted frequencies, thereby reducing interference and improving the accuracy of measurements performed by the optical sensors associated with the interference filter 100.

Transmission peaks and their corresponding harmonic transmission peaks can be identified using methods for analyzing the propagation of electromagnetic waves through layered media. In one example, the transmission peak and its corresponding harmonic transmission peak can be determined using a transfer matrix method. For instance, the transfer matrix method can identify the harmonic response associated with mirror 120 and spacer 110 based at least in part on the geometry and material composition of mirror 120 and spacer 110. The harmonic response can indicate the transmission peak and one or more corresponding harmonic transmission peaks.

The interference filter 100 may include a plurality of spacers 110 of varying thicknesses. Each thickness of the spacer 110 may be associated with a corresponding pair of transmission peaks (or a plurality of corresponding transmission peaks) and a corresponding blocker group 130. An example of a transmission chart associated with this embodiment is shown in Figures 4 and 5. In some aspects, the spacers 110 and the mirror 120 may be configured such that the spacers 110 and the mirror 120 create transmission peaks and corresponding harmonic transmission peaks. For example, the thicknesses of the spacers 110 and the mirror 120, the material properties of the spacers 110 and the mirror 120, etc., may be configured such that the spacers 110 and the mirror 120 transmit transmission peaks and one or more corresponding harmonic transmission peaks.

As indicated above, Figure 1 is provided as an example only. Other examples may differ from those described with respect to Figure 1.

Figure 2 is a diagram of an example device 200 including an interference filter 100. Device 200 includes any device that includes the interference filter 100 and an optical sensor 210. In some aspects, device 200 is an optical device. The interference filter 100 is described in more detail elsewhere herein. In some embodiments, device 200 may be a sensor device, such as a spectrometer, a spectral sensor (e.g., a binary multispectral (BMS) sensor), etc. As shown, device 200 includes the interference filter 100 and the optical sensor 210. The optical sensor 210 includes a device capable of sensing light. For example, the optical sensor 210 may include an image sensor, a multispectral sensor, a spectral sensor, etc. In some embodiments, the optical sensor 210 may include a charge-coupled device (CCD) sensor, a complementary metal-oxide-semiconductor (CMOS) sensor, etc. In some embodiments, the optical sensor 210 may include a front illumination (FSI) sensor, a back illumination (BSI) sensor, etc. As indicated by reference numeral 220, the first blocker 130 of the interference filter 100 can pass through a channel associated with a first transmission peak. As indicated by reference numeral 230 in the figure, the second blocker 130 of the interference filter 100 allows the channel associated with the second transmission peak to pass through.

As indicated above, Figure 2 is provided as an example only. Other examples may differ from those described with respect to Figure 2.

Figure 3 is a diagram illustrating an example transmission chart 300 (e.g., transmission chart 150) for an interferometric filter 100. As shown, the transmission chart 300 includes a first transmission peak 310 and a second transmission peak 320. For example, the first transmission peak 310 may appear in a region of the free spectral range (FSR) 330 of the interferometric filter 100, which is associated with the harmonic transmission peak of the first transmission peak 310 (i.e., the second transmission peak 320).

Harmonic peaks can interfere with the sensing operation of a sensor device (e.g., device 200). For example, consider an interference filter configured to allow a first channel (e.g., as a primary channel, rather than as a harmonic of another channel) at approximately 775 nm and a second channel at approximately 1100 nm to pass through. In this case, in addition to the first channel at 775 nm, the interference filter can also allow the harmonic transmission peak of the second channel at 775 nm to pass through. Therefore, the interference filter may cause interference to the first channel at 775 nm due to the overlap between the first channel and the harmonic transmission peak.

By utilizing the blocker 130 and the harmonic transmission peak associated with the first transmission peak 310, the interference filter 100 can reduce interference, and the effective spectral range of the interference filter 100 can be increased. For example, instead of configuring two spacers to allow the first and second channels (which would likely cause interference between the harmonic transmission peaks of the first and second channels) to pass through, the interference filter 100 can use a single spacer to allow light associated with both the first and second channels to pass through. The corresponding blocker of the interference filter 100 can block one of the first and second channels. Therefore, the interference filter 100 can allow light associated with two transmission peaks at a single spacer thickness to pass through, thereby simplifying the fabrication of the interference filter 100 and increasing the number of channels that can be passed through by the interference filter 100 for a given spacer thickness distribution.

Figure 4 is a diagram illustrating an example transmission graph 400 for an interferometric filter (e.g., interferometric filter 100) associated with multiple spacers 110 of different thicknesses. Here, five of the eight regions of the interferometric filter are shown by way of example only, and regions not shown are indicated by ellipses. As indicated by reference numeral 410, the interferometric filter may include multiple spacers 110 of different thicknesses. As shown, each spacer 110 is associated with a corresponding mirror group 120 and a corresponding plurality (e.g., a corresponding pair) of stoppers 130.

Based on the respective thicknesses of the spacers 110 and/or the material properties of the spacers 110 and/or the mirrors 120, each region of the interferometric filter allows a corresponding channel to pass through. The corresponding channel is indicated by reference numeral 420. Furthermore, if the corresponding channel is within the FSR region associated with the corresponding harmonic transmission peak, each region of the interferometric filter allows the channel associated with that harmonic transmission peak to pass through. The corresponding channel associated with the harmonic transmission peak is indicated by reference numeral 430. As shown, each region of the interferometric filter associated with different spacer thicknesses can be associated with a corresponding pair of spacers 110. One spacer 110 in each pair can block the channel indicated by reference numeral 420, and the other spacers 110 in each pair can block the channel indicated by reference numeral 430. In this way, the number of channels that the interferometric filter allows to pass through is increased compared to a method where the interferometric filter is configured to allow a single channel outside the FSR region associated with harmonic effects to pass through.

Figure 5 is a diagram illustrating an example transmission graph 500 of an interferometric filter (e.g., interferometric filter 100). As shown in graph 500, in some embodiments, the interferometric filter may be a plurality of primary filter channels 510 and a plurality of secondary filter channels 520. Each secondary filter channel 520 may be associated with a harmonic transmission peak of a corresponding primary filter channel 510. As shown, the primary filter channels 510 and secondary filter channels 520 may be spaced approximately 5 nm apart from each other. This can be achieved by configuring the characteristics of the reflector 120 or spacer 110. Therefore, the spacing and number of channels addressable by a sensor device (e.g., device 200) can be increased relative to methods that do not use secondary filter channels 520.

As indicated above, Figure 5 is provided as an example. Other examples may differ from those described with respect to Figure 5.

The foregoing disclosure provides illustrations and descriptions, but is not intended to be exhaustive or to limit the embodiments to the precise forms disclosed. Modifications and variations may be made based on the foregoing disclosure, or may be derived from practice of the embodiments.

As used in this article, depending on the context, satisfying the threshold can mean a value greater than the threshold, more than the threshold, higher than the threshold, greater than or equal to the threshold, less than the threshold, less than the threshold, lower than the threshold, less than or equal to the threshold, equal to the threshold, etc.

Even though specific combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of the various embodiments. In fact, many of these features can be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one claim, the disclosure of the various embodiments includes each dependent claim combined with each other claim in the group of claims.

Unless explicitly stated otherwise, the elements, actions, or instructions used herein should not be construed as critical or necessary. Furthermore, as used herein, the articles “a” and “one” are intended to include one or more items and are interchangeable with “one or more.” Further, as used herein, the article “the” is intended to include one or more items referenced in conjunction with the article “the” and is interchangeable with “one or more.” Additionally, as used herein, the term “group” is intended to include one or more items (e.g., related items, unrelated items, a combination of related and unrelated items, etc.) and is interchangeable with “one or more.” In cases involving only one item, the phrase “only one” or similar language is used. Moreover, as used herein, the terms “has,” “have,” “having,” etc., are intended as open-ended terms. Further, unless explicitly stated otherwise, the phrase “based on” is intended to mean “at least partially based on.” Moreover, as used herein, unless otherwise expressly stated (e.g., if used in combination with “any one” or “only one of…”), the term “or” is intended to be inclusive when used in series and may be used interchangeably with “and/or”.

Claims (20)

1. An interferometric filter, comprising: The first blocker is attached to the surface and configured as follows: The first set of channels associated with the first set of transmission peaks are passed through, and Blocking the second set of channels associated with the second set of transmission peaks; and A second blocker is attached to the surface and configured as one or more of the following: Block the first set of channels, or Allow the second set of channels to pass through. 2. The interference filter according to claim 1, wherein the second blocker is configured as: Block the first set of channels, and Allow the second set of channels to pass through. 3. The interference filter according to claim 1, wherein the first blocker is configured to block the second group of channels as follows: Reflect or absorb light or reflect and absorb light associated with one or more frequency ranges corresponding to the second set of channels. 4. The interference filter according to claim 1, wherein the first blocker is an optical filter. 5. The interference filter of claim 1, wherein the first blocker and the second blocker do not overlap with each other. 6. The interference filter of claim 1, wherein the first set of channels includes a channel at approximately 1100 nm. 7. The interference filter of claim 1, wherein the second set of channels includes a channel at approximately 775 nm. 8. The interference filter according to claim 1, further comprising: One or more spacers; and A reflector, between the one or more spacers and a set of barriers, The set of blocks includes the first blocker and the second blocker. 9. The interference filter according to claim 8, The one or more spacers include a first spacer and a second spacer, and The first thickness of the first spacer is different from the second thickness of the second spacer. 10. An interference filter, comprising: The first blocker is configured to be attached to the surface and configured to: One or more first channels associated with one or more first transmission peaks pass through, and Blocking one or more second channels associated with one or more second transmission peaks; and The second blocker is configured to be attached to the surface and is configured to be one or more of the following: Blocking at least one of the one or more first channels, or At least one of the one or more second channels is passed through. The first and second blocks are configured to not overlap with each other on the surface. 11. The interference filter of claim 10, wherein the second blocker is configured to block at least one of the first channels as follows: Reflected light is associated with one or more frequency ranges corresponding to at least one of the first channels. 12. The interference filter according to claim 10, further comprising: Spacers; and The reflector is located between the spacer and a set of barriers. The set of blocks includes the first blocker and the second blocker, and The first thickness of the first region of the spacer is different from the second thickness of the second region of the spacer. 13. The interference filter according to claim 10, further comprising: One or more spacers; and A reflector, between the one or more spacers and a set of barriers, The set of blocks includes the first blocker and the second blocker, and The spacers mentioned above include silicon dioxide (SiO2), silicon hydride (Si:H), niobium titanium oxide (NbTiOx), niobium tantalum oxide (NbTaOx), or zinc oxide (ZnO). 14. The interference filter of claim 10, wherein the first transmission peak of the one or more first transmission peaks is a harmonic transmission peak of the second transmission peak of the one or more second transmission peaks. 15. A filter, comprising: The first blocker is attached to the surface and configured as follows: Make the first passage pass through, and Blocking the second passage; and The second blocker is configured to be attached to the surface and is configured to be one or more of the following: Block the first channel, or Allow the second channel to pass through. 16. The filter according to claim 15, The first channel is associated with the first transmission peak, and The second channel is associated with the second transmission peak. 17. The filter of claim 15, wherein the first blocker is configured to: block the second channel. Absorbs light associated with the frequency range corresponding to the second channel. 18. The filter of claim 15, further comprising: One or more spacers; and A reflector, between the one or more spacers and a set of barriers, The set of blocks includes the first blocker and the second blocker. 19. The filter of claim 18, wherein the one or more spacers comprise silicon hydride (Si:H). 20. The filter of claim 15, wherein the surface is the surface of a mirror.