Fully compensated optical gas sensing device

Abstract

Systems and devices for robust portable gas detection. In particular, the present disclosure describes devices and systems for optical gas detection in a compact package using two optical paths. There is a need for a very compact, low power gas detection system for gases such as CO2, NOx, water vapor, methane, etc. The present disclosure provides an ultra-compact, highly stable and efficient optical measurement system based on the principle of optical absorption spectroscopy using substantially collinear paths.

Description

[0001] Cross-references to related applications

[0002] This application relates to and claims priority to the following: U.S. Provisional Patent Application No. 63 / 051,042, filed July 13, 2020, entitled “Fully Compensated Optical Gas Sensing System”; and U.S. Non-Provisional Patent Application No. 17 / 327,172, filed May 21, 2021, entitled “Fully Compensated Optical Gas Sensing System and Apparatus”; and U.S. Patent Application No. 10,866,185, filed May 30, 2018, entitled “Compact Optical Gas Detection System and Apparatus”; and U.S. Patent Application No. 16 / 872,758, filed May 12, 2020, entitled “Gas Detection Using Differential Path Length Measurement”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to portable gas detection. More specifically, this disclosure describes apparatus and systems for optical gas detection using differential path length. Background Technology

[0004] A nondispersive infrared sensor (or NDIR sensor) is a simple spectral sensor commonly used as a gas detector. It is nondispersive in the sense of optical dispersion because it allows infrared energy to pass through an atmospheric sampling chamber without distortion.

[0005] It is also non-dispersive because there are no dispersive elements (e.g., prisms or diffraction gratings, typically found in other spectrometers) to separate broadband light (such as monochromators) into a narrow spectrum suitable for gas sensing. Most NDIR sensors use a broadband light source and filters to select a narrow spectral region that overlaps with the absorption region of the gas of interest. In this case, the narrow bandwidth can be 50–300 nm. Modern NDIR sensors can use microelectromechanical systems (MEMS) or mid-infrared LED light sources, with or without filters.

[0006] The main components of an NDIR sensor are an infrared source (lamp), a sample chamber or lamp, a filter, and an infrared detector. IR light is directed to the detector through the sample chamber. Parallel to this, there is another chamber containing a sealed reference gas (usually nitrogen). According to Beer-Lambert's law, the gas in the sample chamber causes absorption at specific wavelengths; the detector measures the attenuation of these wavelengths to determine the gas concentration. A filter is located in front of the detector, which eliminates all light except for wavelengths that the selected gas molecules can absorb.

[0007] Ideally, other gas molecules would not absorb light at that wavelength and would not affect the amount of light reaching the detector; however, some cross-sensitivity is unavoidable. For example, many measurements in the IR region are cross-sensitive to H2O, and gases such as CO2, SO2, and NO2 typically induce cross-sensitivity at low concentrations.

[0008] A common application is the use of NDIR (non-dispersive infrared absorption) sensors to monitor CO2. Most molecules can absorb infrared light, causing them to bend, stretch, or twist. The amount of infrared light absorbed is proportional to the concentration. The energy of photons is insufficient to cause ionization, so the detection principle is very different from that of a photoionization detector (PID). Ultimately, the energy is converted into kinetic energy, accelerating the molecules and thus heating the gas. A common infrared light source is the household incandescent light bulb. Each molecule absorbs infrared light at a wavelength representing the type of bond present.

[0009] Many techniques have been proposed, typically consisting of broadband light sources. Unfortunately, they require relatively long optical paths, which reduces light collection efficiency. The inventors of this disclosure have recognized these drawbacks and the need for a more elegant, robust, and compact optical gas detection and measurement system with high collection efficiency. Specifically, the inventors propose a compact, low-power optical gas detection device that can be mass-produced through packaging without compromising accuracy.

[0010] Furthermore, existing technologies utilize color wheels or filters positioned at the photodetector. Specifically, absorption measurements for a particular gas are taken at one color (wavelength λ1). A reference measurement is typically performed at another color (wavelength λ2) via a color wheel or a second sensor, with the filter centered at λ2. Gas concentration per unit volume is based on the absorption spectrum. However, these techniques cannot account for variations in several parameters, particularly thermal drift, filter bandwidth and sensitivity, and variations in the source as a function of wavelength.

[0011] This overview is intended to provide an overview of the subject matter of this patent application. It is not intended to provide an exclusive or exhaustive explanation of the invention. Further limitations and disadvantages of conventional and traditional methods will become apparent to those skilled in the art by comparing these systems with some aspects of the invention set forth in the remainder of this application with reference to the accompanying drawings. Summary of the Invention

[0012] Systems and apparatuses for robust portable gas detection. Specifically, this disclosure describes apparatuses and systems for optical gas detection in a compact package using two optical paths. There is a need for a very compact, low-power gas detection system for gases such as CO2, NOx, water vapor, and methane. This disclosure provides an ultra-compact, highly stable, and efficient optical measurement system based on the principle of optical absorption spectroscopy using fundamental collinear paths.

[0013] It not only reduces the size and power consumption of the instrument by more than an order of magnitude, enabling widespread deployment, but also improves accuracy. This is achieved by measuring the lengths of two optical paths under identical conditions, yielding results similar to those of others. The need for a large number of distributed gas sensors has been identified to improve human health, the environment, and conserve energy.

[0014] According to one aspect of this disclosure, a gas absorption measuring apparatus measures the differential path length ratio at two wavelengths – a first wavelength set at the absorption wavelength of the target gas and a second wavelength set such that it is not absorbed by any gas present in the measured gas mixture.

[0015] According to another aspect of this disclosure, in a gas absorption measuring device, two wavelengths pass through a gas sampling optics along substantially the same optical path, starting from an optical filter.

[0016] According to another aspect of this disclosure, the gas absorption measuring device originates from the formation of RoR as described according to the novel differential path length (DPL) ratio.

[0017] According to another aspect of this disclosure, a gas absorption measuring device is provided, wherein a second LED is placed adjacent to a first LED, and the first LED acts as a second reflector of the second LED, such that the light path from the second LED after being scattered by the first LED is substantially the same.

[0018] According to another aspect of this disclosure, a gas absorption measuring device is provided, wherein a first / second LED is placed below or stacked on top of a second / first LED.

[0019] According to another aspect of this disclosure, a gas absorption measuring device is provided, wherein a physical LED generates two different wavelengths that can be controlled by an electric current.

[0020] According to another aspect of this disclosure, a gas absorption measuring device is provided, wherein a first LED and a filter together have an absorption region extending beyond the target gas to include another gas, while a second LED and a filter have absorption only at the other gas.

[0021] According to one aspect of this disclosure, a gas absorption measuring device (or working fluid absorption device) includes a light source forming a common optical path, one or more filters filtering the common optical path, a collimator disposed in the common optical path, and two or more detectors for dividing the common optical path, each detector for collecting the divided optical path.

[0022] According to another aspect of this disclosure, the gas absorption measuring device (or working fluid absorption device) is configured to place two or more detectors at two (or more correspondingly) different distances from the light source, wherein each detector measures light transmission after two different gas absorption path lengths.

[0023] According to another aspect of this disclosure, the gas absorption measuring device (or working fluid absorption device) also includes a collector optics preceding the detector.

[0024] According to another aspect of this disclosure, in a gas absorption measuring device (or working fluid absorption device), the beam splitter may be a polarizing beam splitter (PBS), a half-wave plate, a half-silvered mirror, a Fresnel prism, or any other suitable optical device.

[0025] According to another aspect of this disclosure, the gas absorption measuring device (or working fluid absorption device) further includes one or more waveguides.

[0026] According to another aspect of this disclosure, the waveguide provides an opening for the diffusion of gas molecules.

[0027] According to another aspect of this disclosure, the filter may include an absorption filter and / or an interference filter or a dichroic filter.

[0028] According to another aspect of this disclosure, the light source may include a light-emitting device (LED) or other suitable device.

[0029] According to another aspect of this disclosure, the collecting optical device may include a convex lens or a concave lens.

[0030] According to another aspect of this disclosure, the detector is a photosensitive element and may be one or more of the following: a photodetector, a photodiode (PD), an avalanche photodiode (APD), a single-photon avalanche photodiode, or a photomultiplier tube (PMT).

[0031] According to another aspect of this disclosure, after filtering the light source for specific gas absorption, a difference in path length is employed.

[0032] According to another aspect of the gas absorption measuring device (or working fluid absorption device), the concentration of the working fluid is measured by using the ratio of the signals from two detectors.

[0033] According to another aspect of the gas absorption measuring device (or working fluid absorption device), the ratio of the two detectors is saved under known conditions during the calibration step and subsequently used for future calculations.

[0034] The concentration of a predetermined gas is calculated based on another aspect of the gas absorption measuring device (or working fluid absorption device).

[0035] According to another aspect of this disclosure, the predetermined gas may be CO2, water vapor, methane (CH4), NO, and vapors of various alcohols.

[0036] According to another aspect of this disclosure, the predetermined gas can be any gas used in anesthesia.

[0037] According to another aspect of this disclosure, the predetermined gas may be vapor of diesel, kerosene or gasoline.

[0038] According to another aspect of this disclosure, multiple gases can be detected simultaneously by using multiple detectors and filters selected for each gas, and by using a broadband light source.

[0039] According to another aspect of this disclosure, the predetermined gas may be CO2 and ethanol vapor, which are simultaneously detected for width analysis.

[0040] According to another aspect of this disclosure, the predetermined gas can be water and alcohol vapor, which are simultaneously detected for width analysis.

[0041] According to another aspect of this disclosure, a gas absorption measuring device (or working fluid absorption device) is disposed on a substrate.

[0042] According to another aspect of this disclosure, the gas absorption measuring device (or working fluid absorption device) also includes an optical cap fixed to the substrate.

[0043] According to another aspect of this disclosure, the internal shape of the cap forms a mirror, wherein the mirror shape originates from two elliptical mirrors that are substantially tilted at 45 degrees to provide a high collection of light source to the detector.

[0044] According to another aspect of this disclosure, the cap provides an opening for the diffusion of gas molecules.

[0045] According to another aspect of this disclosure, the substrate and the cap are provided with a method for aligning each other.

[0046] According to another aspect of this disclosure, the optoelectronic package for measuring light absorption also includes a substrate on which at least two detectors are disposed.

[0047] According to another aspect of this disclosure, the first detector is used as a reference detector that measures light such that its signal is substantially insensitive to the absorption of a predetermined gas.

[0048] According to another aspect of this disclosure, the second detector may have a filter attached thereto or disposed thereon to make it substantially sensitive to the absorption of a predetermined gas.

[0049] According to another aspect of this disclosure, the optoelectronic package for measuring light absorption also includes a plurality of detectors, wherein at least one detector serves as a reference detector, and filters have been applied to the other detectors to detect different gases present in the cavity.

[0050] According to another aspect of this disclosure, the light source can be a thermal light source.

[0051] According to another aspect of this disclosure, the optoelectronic package for measuring light absorption also includes a substrate on which a light source is disposed. The center wavelength of the LED can be from 0.2 to 12 μm.

[0052] According to another aspect of this disclosure, the detector may use direct photon absorption or may use an indirect measurement method, which includes converting light into heat to measure the light flux.

[0053] According to another aspect of this disclosure, the direct photon detector includes a detector made of PbSe, PbS, HgCdTe, GaSb / InAs superlattice, etc.

[0054] According to another aspect of this disclosure, indirect thermal detectors include thermoelectrics, calorimeters, etc.

[0055] According to another aspect of this disclosure, the optoelectronic package for measuring light absorption further includes: the opening of the cavity forming the cap can be covered with a fine mesh to prevent larger dust particles from entering the cavity.

[0056] According to another aspect of this disclosure, the optoelectronic package for measuring light absorption further includes a "base package" that can be tested separately from the gas chamber and combined by assembly to form a complete gas detection system.

[0057] The accompanying drawings illustrate exemplary gas detection circuitry and configurations. Variations to these circuits, such as changing the location of the circuitry, adding or removing certain components, do not depart from the scope of the invention. The smoke detectors, configurations, and supplementary devices shown are intended to complement the support provided in the detailed description. Attached Figure Description

[0058] When with attachment Figure 1This disclosure is best understood from the following detailed description. It should be emphasized that, in accordance with industry standard practice, various features are not necessarily drawn to scale and are for illustrative purposes only. Where scale is explicitly or implicitly shown, it is merely an illustrative example. In other embodiments, the dimensions of various features may be increased or decreased arbitrarily for clarity of discussion.

[0059] To more fully understand the nature and advantages of the present invention, reference is made to the following detailed description of preferred embodiments, taken in conjunction with the accompanying drawings, wherein:

[0060] Figure 1 An exemplary differential path length measurement system for measuring gas concentration using absorption spectroscopy is described, based on some embodiments of the disclosure provided herein.

[0061] Figure 2 An exemplary differential path length measurement system for measuring gas concentration using a beam splitter, according to other embodiments of the present disclosure provided herein, is described;

[0062] Figure 3 Exemplary differential path length measurement systems using alternative beam path optics according to other embodiments of the present disclosure provided herein are depicted; and

[0063] Figure 4 An exemplary differential path length measurement system using alternative beam path optics is shown according to other embodiments of the present disclosure provided herein. Detailed Implementation

[0064] This disclosure relates to portable gas detection. More specifically, this disclosure describes apparatus and systems for optical gas detection using differential paths. The inventors of this invention envision filtering a common beam path, splitting it to measure light absorption at two different light length paths, and then calculating the concentration of a predetermined gas.

[0065] The following description and accompanying drawings illustrate certain illustrative embodiments of the present disclosure, indicating several exemplary ways in which the various principles of the present disclosure can be performed. However, these illustrative examples are not exhaustive of the many possible embodiments of the present disclosure. Other objects, advantages, and novel features of the present disclosure are set forth in the procedure, in conjunction with the accompanying drawings, where applicable.

[0066] One of the most popular techniques for the quantitative measurement of important industrial gases (such as CO2, NOx, water vapor, methane, etc.) is optical absorption. Most of these gases have strong vibrational absorption spectra in the electromagnetic spectrum range of 1-12 μm, including a variety of vibrational modes and their overtones.

[0067] A fundamental measurement technique involves measuring the extinction change of a light source at a specific wavelength of interest as the concentration of the target gas changes. This technique is commonly referred to as nondispersive infrared (NDIR) technology.

[0068] Many devices are available on the market. They typically consist of a broadband light source (a thermal light source, such as a bulb, compact heater, or LED), whose output passes through an optical system that provides a relatively long path length for gas absorption and whose extinction is measured by a detector system. A small aperture in the optical system allows the gas to diffuse into the optical path.

[0069] The detector system itself can consist of two detectors. One detector provides a reference signal and is specifically tuned to reduce or avoid the absorption line of the gas of interest. The other detector is tuned to the absorption wavelength of the gas to be measured.

[0070] Many configurations of optical systems have been proposed in the past, and some of these devices are commercially available. One of the most popular measuring gases is CO2. In the following discussion of novel optical packaging designs, the focus will be on CO2 gas to make the discussion more concrete, but the principles apply to many of the industrial-related gases mentioned above, and are very common.

[0071] Furthermore, this disclosure focuses on systems that use room temperature detectors and are not cooled, as cooling increases cost, power consumption, and system complexity. However, active and / or passive cooling is not beyond the scope of this invention.

[0072] A better method for measuring absolute gas concentration is disclosed. This method is also applicable to absorbance measurements in liquids. The method is suitable for any fluid (gas or liquid) that can be placed in the path between the light source and the two detectors.

[0073] There is a large body of literature on the use of reference detectors to measure gas concentrations. The largest market is for nondispersive IR measurements (NDIR), where filters are used to isolate the absorbance of the gas of interest.

[0074] Some systems use a single detector and source, along with a pre-calibrated lookup table, to compensate for temperature, humidity, aging, etc., while more precise systems use two different detectors with different filter characteristics, or use the same detector with timely filter changes. Current technological status and... Figure 1 resemblance.

[0075] Figure 1 Exemplary optical gas detection and measurement systems utilizing filters positioned near the detector are illustrated according to some embodiments of the disclosure provided herein. In some embodiments, a light source is powered to illuminate the sampling tube. The light source is typically broadband, but this embodiment uses an infrared (IR) source suitable for detecting CO2 gas.

[0076] CO2-containing gas passes through a sampling tube via a vent or port. Some light absorption occurs as a function of the target gas's concentration and chemical composition. That is, different gases absorb different wavelengths of light (actually, bandwidths). Therefore, a higher concentration of the target gas absorbs more light of that relevant wavelength. The goal of any NDIR system is to accurately determine how much light is absorbed / scattered in order to infer the gas density (i.e., the gas's partial pressure).

[0077] According to Beer-Lambert's law, gases in a sample chamber cause absorption at specific wavelengths, and detectors measure the attenuation of these wavelengths to determine the gas concentration. Carbon dioxide has a characteristic absorption band in the infrared (IR) region at a wavelength of 4.26 μm. This means that when infrared radiation passes through a gas containing CO2, some of the radiation is absorbed. Therefore, the amount of radiation passing through the gas depends on the amount of CO2 present, which can be detected using an infrared detector.

[0078] This is achieved using two optical bandpass filters and two thermopile. A thermopile is an electronic device that converts heat energy into electrical energy. It consists of multiple thermocouples, which are usually connected in series or, less commonly, in parallel. This device works based on the thermoelectric effect, where a voltage is generated when its different metals (thermocouples) are exposed to a temperature difference.

[0079] A bandpass filter is used as a reference frequency band and typically does not significantly overlap with the absorption signal band. As mentioned earlier, the absorption signal band corresponds to the target gas. By comparing the two (e.g., ratio, etc.), the concentration of the target gas can be determined.

[0080] Such a system does require calibration. Specifically, some measurement baseline needs to be obtained before the target gas is detected. However, this system is susceptible to wavelength drift from the light source, which represents one of the drawbacks of existing technologies.

[0081] Although this embodiment can detect multiple gases simultaneously, this system differs from the previous embodiment. Specifically, this system requires calibration and is susceptible to wavelength and intensity drift, especially since it lacks a reference channel measurement.

[0082] The core idea behind state-of-the-art systems is that the ratio of reference channels to filter channels (corresponding to a specific gas) eliminates the influence of source intensity variations over time, as well as common variations in detector performance. However, in these methods for measuring gas concentration, variations in the wavelength spectrum of light and subtle changes in the optical filters cannot be directly removed from the measurement. While some drift issues are mitigated, complex calibration is still required.

[0083] Some state-of-the-art systems (such as the Vaisala) use Fabry-Perot (FP) cavity-based systems that employ the same detector that receives radiation from a single source, as the filter is alternately tuned between "gas-upper absorptivity" and "gas-lower absorptivity" to measure gas absorptivity. However, this cannot adequately compensate for spectral shifts in the source or filter. In most gas infrared measurements, the "non-absorbing filter" must differ from the "absorbing filter" by more than 100 nm due to the width of the absorption feature. This is sufficiently separated in wavelength, so the ratio cannot fully compensate for changes in the spectral shape of LEDs and other light sources over time and temperature.

[0084] In all prior designs reviewed by the inventors, the reference channel used a different filter than the measurement channel to track changes in light source intensity. In the Vaisala sensor, an FP cavity was used, and the filter was tuned to alternately turn the gas absorption wavelength on and off in time.

[0085] Those skilled in the art will understand the following novel features of this disclosure. Other benefits are not beyond the scope of this disclosure. This disclosure is highly independent of the performance of the LED and filter to temperature, intensity, etc., and of any variations in the wavelength spectrum of the light source, filter, and other optical components.

[0086] Furthermore, all spectral variations are naturally removed from the measurement. This includes intensity variations caused by drift in the electrical or optical systems.

[0087] This disclosure provides the advantage of ratio measurement, even when both detectors are manufactured to the same degree.

[0088] This disclosure also provides a highly simplified calibration performed with a single measurement at known concentrations of the species of interest.

[0089] Finally, this disclosure is easy to implement because the current solution is easier to handle. Therefore, the calibration procedure is highly simplified during manufacturing.

[0090] Figure 1 An exemplary differential path length measurement system 100 for measuring gas concentration using absorption spectroscopy, according to some embodiments of the present disclosure provided herein, is depicted. The differential path length measurement system 100 includes a light source 110, a filter 120, a collimating lens 130, a beam splitter 140, a reference collecting lens 170, a reference detector 180, a signal collecting lens 110, and a signal detector 160.

[0091] In one or more embodiments, the light source 110 is a light-emitting diode (LED), such as an infrared (IR) LED. However, other embodiments may have LEDs with shorter wavelengths, such as those in the visible or ultraviolet regions. In other embodiments, multiple wavelengths may be used. Any suitable, compact light-generating device is within the scope of this disclosure, whether it is a broadband lamp, a coherent, incandescent, or incoherent light bulb, a laser, or even hot blackbody radiation.

[0092] In one or more embodiments, filter 120 is at least partially a dichroic filter. A dichroic filter, thin-film filter, or interference filter is a very precise color filter used to selectively pass light through a small range of colors while reflecting other colors. In contrast, dichroic mirrors and dichroic mirrors are often characterized by the color of the reflected light, rather than the color that passes through.

[0093] Although a dichroic filter is used in this embodiment, other filters are not outside the scope of the invention, such as interference, absorption, diffraction, gratings, Fabry-Perot filters, etc. An interference filter consists of multiple thin layers of dielectric material with different refractive indices. Metal layers may also be present. In its broadest sense, the interference filter also includes an etalon that can be implemented as a tunable interference filter. The interference filter exhibits wavelength selectivity due to the interference effect occurring between the incident and reflected waves at the thin film boundary. In other embodiments, a color wheel with an optical chopper can be used as filter 120.

[0094] Collimating lens 130 is a collimator. In optics, a collimator can consist of a curved mirror or a lens, having some type of light source and / or image at its focal point. This can be used to reproduce a target focused at infinity with almost no parallax. The purpose of collimating lens 130 is to direct light rays in a coaxial optical path toward beam splitter 140.

[0095] Beam splitter 140 is a beam splitter known in the art. A beam splitter (or beam divider) is an optical device that splits a beam of light into two. It is a key component of many optical experimental and measurement systems (such as interferometers) and is also widely used in fiber optic communications.

[0096] In the most common cubic form, the beam splitter 140 is made of two triangular glass prisms bonded together at their bases using a polyester, epoxy, or urethane-based adhesive. The thickness of the resin layer is adjusted so that (for a specific wavelength) half of the light incident through one "port" (i.e., the surface of the cube) is reflected, while the other half is transmitted due to suppressed total internal reflection. Polarizing beam splitters, such as the Wollaston prism, use birefringent materials to split light into two orthogonally polarized beams.

[0097] In other embodiments, beam splitter 140 is a half-silvered reflector. This includes an optical substrate, typically a sheet of glass or plastic, with a partially transparent thin metallic coating. The thin coating may be aluminum deposited from aluminum vapor using a physical vapor deposition method. The thickness of the deposit is controlled such that a portion (typically half) of the light incident at a 45-degree angle and not absorbed by the coating or substrate material is transmitted, while the remainder is reflected.

[0098] The very thin, semi-silvered mirrors used in photography are often called thin-film mirrors, and they can also be used in some embodiments. To reduce light loss due to absorption by the reflective coating, so-called "Swiss cheese" beam splitters are used. Initially, these are highly polished metal plates perforated to achieve the desired reflectivity and transmittance. Later, the metal is sputtered onto the glass to form a discontinuous coating, or small areas of a continuous coating are removed by chemical or mechanical action to produce the literal "semi-silvered" surface.

[0099] In another embodiment, a dichroic optical coating can be used instead of a metallic coating. Depending on its properties, the ratio of reflection to transmission will vary according to the wavelength of the incident light. Dichroic mirrors are used in some ellipsoidal reflector spotlights to separate unwanted infrared (thermal) radiation and as output couplers in laser configurations.

[0100] In yet another embodiment, a third form of beam splitter 140 is a dichroic mirror prism assembly, which uses a dichroic optical coating to split the incident beam into multiple output beams with different spectra. This device has been used in three-pickup color television cameras and three-line color cinema cameras. It is currently used in modern three-CCD cameras. In three-LCD projectors, an optically similar system is used in reverse as a beam combiner, where light from three separate monochrome LCD displays is combined into a single full-color image for projection.

[0101] As listed, any beam splitter or optical circulator can be used. Optical circulators are power-saving but significantly increase complexity and cost. However, any suitable optical device, such as a polarizing beam splitter, a half-wave plate, a half-silvered mirror, etc., is within the scope of this invention.

[0102] In practice, the collimated light from collimating lens 130 is split into two beams, 195 and 190. Beam 195 is used as a reference beam, and beam 190 is used as a signal beam. Their geometry and their respective path lengths are known. Their importance will be described in more detail later in this disclosure.

[0103] In one or more embodiments, the reference collecting lens 370 and the signal collecting lens 150 are optical lenses. An optical lens is a transmissive optical device that focuses or scatters a beam of light through refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of multiple simple lenses (elements) typically arranged along a common axis. Lenses are made of materials such as glass or plastic and are ground, polished, or molded into the desired shape.

[0104] A lens can focus light to form an image, unlike a prism, which refracts light without focusing. Similarly, devices that focus or disperse waves and radiation other than visible light are also called lenses, such as microwave lenses, electron lenses, acoustic lenses, or explosion lenses.

[0105] Most lenses are spherical lenses: their two surfaces are part of a sphere. Each surface can be convex (bulging outwards from the lens), concave (recessed into the lens), or flat. The line connecting the centers of the sphere that form the lens surfaces is called the lens axis.

[0106] Lenses are classified according to the curvature of their two optical surfaces. If both surfaces are convex, the lens is biconvex (or simply convex). If both surfaces have the same radius of curvature, the lens is isoconvex. A lens with two concave surfaces is biconcave (or simply concave). If one surface is flat, the lens is plano-convex or plano-concave, depending on the curvature of the other surface. A lens with one convex side and one concave side is convex-concave or meniscus. This type of lens is most commonly used for corrective lenses.

[0107] If the lens is biconvex or plano-convex, the collimated light beam passing through the lens converges to a single point behind the lens (the focal point). In this case, the lens is called a positive lens or a converging lens. For a thin lens in air, the distance from the lens to the light spot is the focal length of the lens, usually represented by f in diagrams and equations. An extended hemispherical lens is a special type of plano-convex lens in which the surface of the lens is a complete hemisphere, and the thickness of the lens is much greater than its radius of curvature.

[0108] If the lens is biconcave or planoconcave, the collimated beam passing through the lens diverges (spreads); therefore, the lens is called a negative lens or a diverging lens. After passing through the lens, the beam appears to originate from a specific point on the front axis of the lens. For a thin lens in air, the distance from this point to the lens is the focal length, although it is negative relative to the focal length of a converging lens.

[0109] A convex-concave (meniscus) lens can be positive or negative, depending on the relative curvature of its two surfaces. A negative meniscus lens has a steeper concave surface and is thinner at the center than at the periphery. Conversely, a positive meniscus lens has a steeper convex surface and is thicker at the center than at the periphery. An ideal thin lens with two surfaces of equal curvature would have zero optical power, meaning it would neither converge nor diverge light.

[0110] However, all real lenses have a non-zero thickness, which makes real lenses with the same curvature slightly positive. To obtain precise zero power, a meniscus lens must have slightly unequal curvature to account for the effect of lens thickness.

[0111] In practice, both focusing lenses are used to focus light onto photodetectors 160 and 180, which are sensors for light or other electromagnetic energy. Photodetectors 160 and 180 have pn junctions that convert photons into current. Absorbed photons form electron-hole pairs in the depletion region, used to detect the intensity of the received light. In some embodiments, photodetectors 160 and 180 are photodiodes or phototransistors. However, any light detection device, such as an avalanche diode, photomultiplier tube, etc., is within the scope of this disclosure.

[0112] according to Figure 1 It can be proven that:

[0113]

[0114] Therefore, we see that all changes in the light source and filter cancel each other out. If the detector's responsivity ratio... If the ratio is known or calibrated at a known gas concentration, it can be used to directly determine any concentration of the gas.

[0115] This elimination of light source characteristics makes the entire detection system independent of the light source's intensity and spectral changes over time, temperature, mechanical stress, and many other parameters that may change the characteristics of the LS and filter over time.

[0116] The calibration procedure can be written as follows:

[0117]

[0118] And this ratio is recorded and saved as part of the instrument calibration.

[0119] Now, the measured value at any gas concentration can be determined as:

[0120]

[0121] or

[0122]

[0123] There are many implementations that can implement differential paths of ΔL. Some of them are... Figure 2 As shown.

[0124] Figure 2 An exemplary differential path length measurement system for measuring gas concentration using a beam splitter is described according to other embodiments of the present disclosure provided herein.

[0125] Differential path length (DPL) automatically eliminates variations in LED and filter performance characteristics, such as intensity or wavelength, and contributes to robust measurements of gas absorption. For example, within a temperature range of -40 to 70°C, the product of LED intensity and photodiode responsivity over the gas absorption wavelength range can vary by approximately 10X-30X. The DPL method eliminates most of this variation, and the ratio stabilizes to a few percent over the same temperature range. However, mechanical variations in the optical path still leave residual variations.

[0126] Ideally, we want to stabilize this ratio to 0.1% or better under temperature and other environmental conditions. The remaining uncompensated variations in the DPL method appear to originate from changes in the optical path itself. In this disclosure, we build upon the DPL method and compensate for changes in the optical path, as well as any other residual variations in the detector and amplifier, to make the measurement of gas absorption robust.

[0127] Changes in the optical path lead to changes in the measured intensity, and these changes cannot be distinguished from those caused by gas absorption (even after using the DPL method). These include: vibration; temperature-induced changes in optical surface dimensions and deformation; humidity-induced changes in optical surface dimensions and deformation; changes in surface reflectivity; and changes in the responsivity of the photodiode as a function of temperature and environment.

[0128] By implementing a new method of ratio (RoR), all the above changes can be automatically compensated for. RoR will be described in detail below.

[0129] There are three methods that essentially follow the same optical path by using non-resonant LEDs (second LEDs) of different wavelengths: the second LED is reflected away from the surface of the first LED; additional packaging design—special filter design; using two stacked LEDs to provide two colors; and placing the second LED very close to the first LED, thereby ensuring a similar path by using optics that map two slightly separated LED sources to the same reference and main photodiode.

[0130] In practice, it has been achieved as follows Figure 2 The exemplary design is shown. Figure 2 This is a side view of the module that performs differential path length measurement. Figure 2An exemplary differential path length measurement system for measuring gas concentration using a beam splitter is described according to other embodiments of the present disclosure provided herein.

[0131] The differential path length module 200 includes a substrate 210, an LED 220, a reference detector 230, a main detector 240, an ASIC 250, an optical filter 255, a mirror 260, a mirror 285, a mirror 270, and a beam splitter 275. The filter 255 is positioned directly above the light source 220 and is fabricated on the silicon substrate 210. The complex reflector shape collimates a portion of the filtered light toward the main detector 240, while another portion is focused toward the reference detector 230. In one or more embodiments, the composite reflector shape serves as the beam splitter 275, which will now be discussed in more detail.

[0132] Beam splitter 275 includes mirrors 260 and 285. Mirror 260 is an off-axis parabola, and mirror 285 is an elliptical mirror. In some embodiments, two-dimensional and three-dimensional parabolic / parabolic surfaces and elliptical / ellipsoidal surfaces are preferred. However, other conical cross-sections and other shapes and surfaces are not beyond the scope of this disclosure. For example, a polarizing beam splitter (PBS) with a plane mirror can be used. Mirror 270 collects collimated light passing through the gas and focuses it onto the main detector 240. In some embodiments, mirror 270 has a conical cross-section, while in other embodiments it is a concave collimating lens. Any suitable reflective shape or material is not beyond the scope of this disclosure.

[0133] In practice and in some embodiments, light source 220 generates broadband light, which is filtered by filter 255. Optical filter 255 may be a bandpass filter selected based on the type of target gas being absorbed. That is, the color of the light is selected based on the gas to be detected. In other embodiments, a rotating color wheel, similar to an optical chopper, can be implemented. An optical chopper is a device that periodically interrupts the light beam. This results in the simultaneous detection of a large number of gases.

[0134] The filtered light is split into two paths: a collimated portion reflected from mirror 260, which passes through the gas absorption region 280 of the chamber and is received by the main detector 240; and a portion reflected to the reference detector 230. Then, in one or more embodiments, an ASIC is used to process the detector signal, while also handling any necessary ratios. An application-specific integrated circuit (ASIC) is an integrated circuit (IC) chip customized for a specific purpose rather than for general use.

[0135] Other circuits not exceeding the scope of this disclosure include, for example, FPGAs, ADCs, and AFEs. A Field-Programmable Gate Array (FPGA) is an integrated circuit designed to be configured by a customer or designer after manufacturing, hence the term "field-programmable." An analog-to-digital converter (ADC, A / D, or A-to-D) is a system that converts analog signals (such as sound picked up by a microphone or light entering a digital camera) into digital signals. An analog front-end (AFE or Analog Front-End Controller AFEC) is a set of analog signal conditioning circuitry that provides the configurable and flexible electronic function blocks needed to connect various sensors to antennas, analog-to-digital converters, or in some cases, to microcontrollers.

[0136] As mentioned above, the intensity and wavelength shift of the LED are eliminated by temperature and other environmental parameters. Note that the common-mode shift in the temperature performance of the photodetector and amplifier, denoted by D, is also compensated for.

[0137] The following equation is shown (reprinted from DPL):

[0138]

[0139] Note that η represents the light splitting efficiency of the LED light when a portion of the light is sent to the main detector and the other portion to the reference detector. As can be seen from the equation, the optical splitting is not canceled out, and the ratio η... Main / η Ref Any change in η cannot be distinguished from the exponential term representing gas absorption. For example, if the beam splitter moves relative to the LED / PD for any reason (e.g., due to stress or expansion / contraction caused by temperature), it can increase the light to the master PD and decrease it to the reference PD, thus changing the ratio η. Main / η Ref This idea is also intended to address this issue.

[0140] Now imagine we have set up a second light source that follows essentially the same optical path but is not absorbed by the gas. Now we perform two measurements. First, we use the first LED to measure gas absorption, and then immediately use the second LED, which is known not to be absorbed by any other possible gas. The ratio at the wavelength of the second LED will be similar to equation (1), except that the absorption term is missing. Its contents are as follows:

[0141]

[0142] We can now establish the ratio (RoR), and it's easy to see that η also cancels it out. Therefore, RoR will eliminate any drift caused by mechanical displacement of the optical element due to stress or temperature. RoR is:

[0143]

[0144] Consider the first term: This ratio is measured on physically identical detectors connected to the same electronic equipment. Any variations in detector characteristics common to both wavelengths, such as amplifier gain, detector shunt impedance, etc., will be offset as a function of temperature or certain other environmental parameters. Potentially small residual wavelength-dependent variations in these parameters may remain uncompensated. But the second term... Having the same characteristics – because it is made of the same material and manufactured together during the manufacturing process, and will include the first term and the pre-factor in equation (3),

[0145]

[0146] As independent of environmental factors as possible. Now, we can continue calibrating the gas concentration device as discussed in DPL.

[0147] Without any gas, we can write equation (4) as:

[0148] RoR(c gas =0)=γ#(5)

[0149] This ratio can be stored in memory, and then the gas concentration can be measured in the following ways:

[0150]

[0151] When the independent variable of the exponent is small, the approximate right-hand term in equation (6) is applicable.

[0152] Using this method, we achieved direct, calibration-free measurement of gas concentration. It only requires the optical path length and the average gas absorption α. gas This knowledge is relevant. Note that for many popular gases, such as CO2 or CH4, the absorption cross-section of a given LED and filter can be calculated.

[0153] Typically, the second LED and the first LED after passing through the filter can share a common absorption region. In this case, the common absorption region will still be eliminated.

[0154] Methods for implementing RoR

[0155] Method 1: The second LED reflects light from the surface of the first LED.

[0156] In this method, we take advantage of the fact that we have a filter surface (such as...) Figure 3 (As shown). We add another LED in the near-infrared region, which can be transmitted through the filter F, and place it near the main LED or the first LED. By patterning the filter as shown in the figure below, we can force the light from the second LED to follow the path of the first LED.

[0157] Figure 3 An exemplary differential path length measurement system 300 using alternative beam path optics is depicted according to other embodiments of the present disclosure provided herein. The differential path length measurement system 300 includes a primary / first LED 320, a secondary LED 330, a mirror 310, a filter 350, and a substrate 370.

[0158] Figure 3 This is a cross-section of the region near the first LED 320 used to measure gas absorption. The second LED 330 is placed near the first LED. Figure 3 An exemplary range of placement of the secondary LED 330 is shown. Light from the secondary LED 330 is reflected away from the reflector 310. The reflector 330 may be made of silver plating, a dielectric coating, or any other suitable method known in the art. In this embodiment, the reflectors 330 reflect light at or near the bandwidth of the LED 330. At a minimum, their bandwidths should overlap such that light from the LED 330 is substantially reflected.

[0159] Applying a metallic reflective layer to glass is commonly referred to as "silver plating," even though the metal may not actually be silver. The main processes currently used are electroplating, "wet" chemical deposition, and vacuum deposition. Front-coated metallic mirrors can achieve 90–95% reflectivity under new conditions.

[0160] Dielectric coatings can achieve higher reflectivity or greater durability, but bandwidth is not critical. Dielectric coatings can achieve reflectivity up to 99.997% over a limited wavelength range. Because they are generally chemically stable and non-conductive, dielectric coatings are almost always applied via vacuum deposition, most commonly by evaporation deposition. Since the coatings are typically transparent, absorption losses are negligible. Unlike metals, the reflectivity of a single dielectric coating is a function of Snell's law (known as the Fresnel equation), determined by the difference in refractive index between layers. Therefore, the coating thickness and refractive index can be tuned to be centered at any wavelength. Vacuum deposition can be achieved in various ways, including sputtering, evaporation deposition, arc deposition, reactive gas deposition, and ion plating.

[0161] The reflector 310 is modified and patterned to have an opening on top of the first LED, while the rest of the surface is metallized or used as a high-reflectivity reflector 310 at the wavelength of the second LED 330.

[0162] When the second LED 330 is turned on, light is reflected from the mirror, and some of this light illuminates the first LED 320, which is very close to it. This is limited by the distance between the first and second LEDs and the emitting cone. That is, if the distance between them is too large or if the light cone is too narrow, the light from the second LED 330 will not properly illuminate the first LED 320.

[0163] Consistently, the rough surface of the first LED 320 or other structures nearby (e.g., bonding pads or bonding lines) will scatter light in the same direction as the light from the first LED 320. This scattered light is the only light that will reach the rest of the optics and follow the same path as the first LED 320. Therefore, we have achieved the goal of having both LEDs have substantially the same path. Note that the intensity of the light from the second LED is not important, as shown in other embodiments, particularly those incorporated herein by reference. However, it should be sufficient to produce high-quality measurements for forming the RoR calculation.

[0164] In one embodiment, the substrate on which the filter is formed is silicon, therefore the second LED must be in a wavelength region that is substantially transparent to silicon. The filter 350 can be manufactured according to the foregoing discussion in this disclosure. The center wavelength of the filter 350 is selected for a specific application. For example, it can be bandpass for a specific gas to be detected.

[0165] In practice, the light from the secondary LED 330 is reflected away from the reflector 310. This light then strikes the primary LED 320. (As...) Figure 3 As shown, the primary LED has an emission cone 375. The primary optical measurement path 360 continues to the rest of the system optics. Those skilled in the art will understand that, after scattering and / or reflection from the primary LED 320, some light from the secondary LED will travel collinearly with path 360.

[0166] Method 2: Using stacked LEDs

[0167] In this configuration, a larger LED is placed at the bottom, and another LED at the top. Because both LEDs are within the focal region of the lens and are practically very close to each other, the light from each LED follows the same path. Figure 4 As shown.

[0168] Figure 4An exemplary differential path length measurement system using alternative beam path optics is shown according to other embodiments of the present disclosure provided herein. Figure 4 An exemplary differential path length measurement system 400 using alternative beam path optics is depicted according to other embodiments of the present disclosure provided herein. The differential path length measurement system 400 includes a primary / first LED 420, a secondary LED 430, a filter 450, a printed circuit board (PCB) 410, and a substrate 470.

[0169] Figure 4 This is a cross-section of the region near the first LED 420 used for measuring gas absorption. A second LED 430 is placed near the first LED. In one or more embodiments, the first LED 420 is positioned on top of the second LED 430. Light from the secondary LED 430 produces light propagation 465 that is approximately collinear with the light propagation of the primary optical measurement path 460.

[0170] Therefore, we have achieved the goal of having the two LEDs with substantially the same path. Note that the intensity of the light from the second LED is not important, as shown in other embodiments, particularly those incorporated by reference. However, it should be sufficient to produce high-quality measurements for forming the RoR calculation.

[0171] In one embodiment, the substrate on which the filter is formed is silicon, therefore the second LED must be in a wavelength region that is substantially transparent to silicon. The filter 450 can be manufactured according to the foregoing discussion in this disclosure. The center wavelength of the filter 450 is selected for a specific application. For example, it can be bandpass for a specific gas to be detected.

[0172] In fact, such as Figure 4 As shown, light from the secondary LED 430 and the primary LED 420 produces substantially similar emission cones 475. Primary optical measurement paths 460, 465 continue to the rest of the system optics. Those skilled in the art will understand that some light from the secondary LED will travel collinearly with the primary optical measurement path 460.

[0173] In this scenario, we leverage the fact that the collecting optics are designed to collect light from the surface of an LED, which may span several hundred micrometers. Light from the entire surface of the LED needs to be collected and imaged onto the detector surface. Therefore, two LEDs placed on top of each other will be indistinguishable and will still form an image on the detector surface. The choice of which wavelength should be larger for an LED will depend on cost and electrical convenience.

[0174] Clearly, if the LED is configured to emit at two different wavelengths and electrically selected to emit at either wavelength, the method can be extended and become almost perfect.

[0175] While the discussion uses specific optical modules as examples to describe the invention, it is not limited to any particular optical arrangement of beam splitters and collimating optics. It should be understood that the measurement of RoR is independent of how the differential path length is specifically arranged. In many cases, it is necessary to measure extremely low concentrations of gas.

[0176] In this scenario, the optical path length must be long enough to provide sufficient absorption. However, with changes in the environment such as temperature, stress, or humidity, a longer differential path length is more likely to be affected by mechanical variations in optical collection efficiency. Simultaneously, due to the low gas concentration, smaller variations need to be measured. The method disclosed herein becomes more powerful for ultrasensitive absorption measurements because it fully compensates for mechanical variations and those of LEDs, PDs, amplifiers, etc., leaving only gas absorption as a measurement parameter. When perfected, the solution shown in this invention can be used to calibrate gas concentrations directly based on first-principles measurements.

[0177] Historically, in most cases, physical devices have never achieved inherent stability to their environment; rather, it has been achieved through long and arduous calibration. A lookup table is created to compensate for anticipated variations by measuring environmental parameters such as temperature and humidity. For ultra-precise measurements, the entire device remains temperature-stable. We are able to do this without resorting to any of these expensive and laborious measures.

[0178] Select Example

[0179] Example 1 provides an apparatus for optical differential path length gas detection, comprising: a first light source generating a first light centered on a first wavelength, a second light source generating a second light centered on a second wavelength, a filter disposed near the first light source and configured to allow the second light to pass through; and a reflector configured to reflect the second light onto the beam splitter first light source.

[0180] Example 2 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: circuitry configured to calculate a ratio of signals representing the measured intensities of the first and second light.

[0181] Example 3 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, wherein the circuitry is an ASIC.

[0182] Example 4 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, wherein the circuitry is an AFE.

[0183] Example 5 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: a controller configured to control electricity to the first and second light sources.

[0184] Example 6 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: a first photodetector configured to detect light centered at the first wavelength, the first photodetector generating a first signal indicating the measured intensity.

[0185] Example 7 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: a first photodetector configured to detect light centered at the second wavelength, and a second photodetector generating a second signal indicating the measured intensity.

[0186] Example 8 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: circuitry configured to calculate a first ratio based at least on the first and second signals.

[0187] Example 9 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, wherein the circuitry is also configured to calculate a ratio of the ratio based at least on the first ratio.

[0188] Example 10 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: a second filter configured to allow the first light to pass through.

[0189] Example 11 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: a time multiplexer configured to alternate between first and second signals.

[0190] Example 12 provides an apparatus for optical differential path length gas detection, comprising: a first light source generating a first light cone centered on a first wavelength, a second light source generating a second light cone centered on a second wavelength, and a filter disposed near the first light source and configured to allow the second light to pass through, wherein the first and second light cones substantially overlap.

[0191] Example 13 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, wherein the first light source is positioned directly adjacent to the second light source.

[0192] Example 14 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, wherein the first light source is positioned directly on top of the second light source.

[0193] Example 15 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: circuitry configured to calculate a first ratio of a signal representing the measured intensity of the first and second lights.

[0194] Example 16 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, wherein the circuitry is also configured to calculate a ratio of the ratio based at least on the first ratio.

[0195] Example 17 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, wherein the first light source and the second light source are LEDs.

[0196] Example 18 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: a controller configured to control the current to the first and second light sources.

[0197] Example 19 provides an optical differential path length gas detector according to any of the foregoing and / or ongoing examples, further comprising: a second filter configured to allow the second light to pass through.

[0198] Example 20 provides a method for calculating the optical differential path length of gas detection, comprising emitting a first light from a first LED centered at a first wavelength; emitting a second light from a second LED centered at a second wavelength; reflecting the second light away from the first LED; measuring the first light; measuring the second light; and calculating a ratio based at least on the measurements of the first light and the second light.

[0199] The above description of the illustrated embodiments, including those described in the abstract, is not intended to be exhaustive or to limit the precise forms disclosed. While specific implementations and examples of various embodiments or concepts have been described herein for illustrative purposes, various equivalent modifications may be possible, as will be recognized by those skilled in the art. These modifications can be made based on the above detailed description, abstract, drawings, or claims.

[0200] Having described several aspects and embodiments of the technology described herein, it should be understood that various changes, modifications, and improvements will be readily apparent to those skilled in the art. Such changes, modifications, and improvements are intended to be within the spirit and scope of the technology described herein. For example, those skilled in the art will readily conceive of various other means and / or structures for performing the functions described herein and / or obtaining results and / or one or more advantages, and each of these changes and / or modifications is considered to be within the scope of the embodiments described herein.

[0201] Those skilled in the art will recognize, or be able to determine, many equivalents of the particular embodiments described herein using only conventional experimentation. Therefore, it should be understood that the above embodiments are presented by way of example only, and embodiments of the invention may be practiced in ways different from those specifically described within the scope of the appended claims and their equivalents. Furthermore, any combination of two or more features, systems, articles, materials, kits, and / or methods described herein, provided that such features, systems, articles, materials, kits, and / or methods are not inconsistent with each other, is included within the scope of this disclosure.

[0202] The foregoing outlines features of one or more embodiments of the subject matter disclosed herein. These embodiments are provided to enable those skilled in the art (PHOSITA) to better understand various aspects of this disclosure. Certain well-known terms and underlying technologies and / or standards may be referenced without detailed description. It is anticipated that PHOSITA will possess or be entitled to background knowledge or information on those technologies and standards sufficient to practice the teachings of this disclosure.

[0203] PHOSITA will understand that they can readily use this disclosure as the basis for designing or modifying other processes, structures, or variations to achieve the same purpose and / or benefits as the embodiments described herein. PHOSITA will also recognize that such equivalent constructions do not depart from the spirit and scope of this disclosure, and that they can be modified, substituted, and altered in various ways without departing from the spirit and scope of this disclosure.

[0204] The above embodiments can be implemented in any of a variety of ways. One or more aspects and embodiments of this application relating to the execution of processes or methods can utilize program instructions executable by a device (e.g., a computer, processor, or other device) to perform or control the processes or methods.

[0205] In this respect, various inventive concepts can be embodied in a computer-readable storage medium (or multiple computer-readable storage media) (e.g., computer memory, one or more floppy disks, optical disks, magnetic tapes, flash memory, or other tangible computer storage media) encoded with circuit configurations in one or more programmable gate arrays or other semiconductor devices or other tangible computer storage media, which, when executed on one or more computers or other processors, executes a program that implements one or more of the methods described in the various embodiments above.

[0206] One or more computer-readable media may be transportable, such that a program stored thereon may be loaded onto one or more different computers or other processors to implement the aspects described above. In some embodiments, the computer-readable medium may be a non-transitory medium.

[0207] Note that the activities discussed in the above reference diagram apply to any integrated circuit that involves signal processing (e.g., gesture signal processing, video signal processing, audio signal processing, analog-to-digital conversion, digital-to-analog conversion), especially those integrated circuits that can execute dedicated software programs or algorithms, some of which may be associated with processing digitized real-time data.

[0208] In some cases, the teachings of this disclosure may be encoded into one or more tangible, non-transitory computer-readable media having executable instructions stored thereon, which, when executed, instruct a programmable device (e.g., a processor or DSP) to perform the methods or functions disclosed herein. Where the teachings of this disclosure are at least partially embodied in a hardware device (e.g., an ASIC, IP block, or SoC), the non-transitory medium may include hardware device hardware programmed to perform the methods or functions disclosed herein. The teachings may also be practiced in register-transfer level (RTL) or other hardware description languages ​​(e.g., VHDL or Verilog), which can be used to program manufacturing processes to produce the disclosed hardware elements.

[0209] In the example implementations, at least some portions of the processing activities outlined herein may also be implemented in software. In some embodiments, one or more of these features may be implemented in hardware provided externally to the elements of the disclosed figures, or may be incorporated in any suitable manner to achieve the intended functionality. Various components may include software (or reciprocating software) that can be coordinated to perform the operations outlined herein. In other embodiments, these elements may include any suitable algorithms, hardware, software, components, modules, interfaces, or objects that facilitate their operation.

[0210] Any properly configured processor component can execute any type of instructions associated with data to perform the operations detailed herein. Any processor disclosed herein can transform an element or item (e.g., data) from one state or thing to another. In another example, some of the activities outlined herein can be implemented using fixed or programmable logic (e.g., software and / or computer instructions executed by a processor), electrically erasable programmable read-only memory (EEPROM), including digital logic, software, code, electronic instructions, flash memory, optical discs, CD-ROMs, DVD-ROMs, magnetic cards or optical cards, other types of machine-readable media suitable for storing electronic instructions, or any suitable combination thereof, in an ASIC.

[0211] In operation, the processor can store information in any suitable type of non-transitory storage medium (e.g., random access memory (RAM), read-only memory (ROM), FPGA, EPROM, electrically erasable programmable ROM (EEPROM), etc.), software, hardware, or any other suitable component, device, element, or object, where appropriate and based on specific needs. Furthermore, based on specific requirements and implementation, information tracked, sent, received, or stored in the processor can be provided in any database, register, table, cache, queue, control list, or storage structure, all of which can be referenced at any suitable time period.

[0212] Any memory item discussed herein should be understood as being included within the broad term "memory". Similarly, any potential processing element, module, and machine described herein should be understood as being included within the broad term "microprocessor" or "processor". Furthermore, in various embodiments, the processors, memories, network interface cards, buses, storage devices, associated peripherals, and other hardware elements described herein may be implemented by processors, memories, and other associated devices configured by software or firmware to emulate or virtualize the functionality of these hardware elements.

[0213] Furthermore, it should be understood that, as a non-limiting example, a computer can be implemented in any of a variety of forms, such as a rack-mounted computer, a desktop computer, a laptop computer, or a tablet computer. Additionally, a computer can be embedded in a device that is not typically considered a computer but has appropriate processing capabilities, including a personal digital assistant (PDA), a smartphone, a mobile phone, an iPad, or any other suitable portable or fixed electronic device.

[0214] In addition, a computer may have one or more input and output devices. Among other things, these devices can be used to present a user interface. Examples of output devices that can be used to provide a user interface include printers or displays for visual presentation of output and speakers or other sound-generating devices for auditory presentation of output. Examples of input devices that can be used for a user interface include keyboards and pointing devices such as mice, touchpads, and digitizing tablets. As another example, a computer may receive input information through speech recognition or in other audible formats.

[0215] Such computers can be interconnected in any suitable form through one or more networks, including local area networks (LANs) or wide area networks (WANs), such as corporate networks, as well as intelligent networks (INs) or the Internet. Such networks can be based on any suitable technology and can operate according to any suitable protocol, and can include wireless or wired networks.

[0216] Computer-executable instructions can take many forms, such as program modules, and can be executed by one or more computers or other devices. Typically, program modules include routines, programs, objects, components, data structures, etc., that perform specific tasks or implement specific abstract data types. In various embodiments, the functionality of program modules can typically be combined or distributed as needed.

[0217] The terms "program" or "software" as used herein generally refer to any type of computer code or set of computer-executable instructions that can be used to program a computer or other processor to implement the various aspects described above. Furthermore, it should be understood that, according to one aspect, when performing the methods of this application, one or more computer programs do not need to reside on a single computer or processor, but can be distributed in a modular manner across multiple different computers or processors to implement the various aspects of this application.

[0218] Furthermore, data structures can be stored in any suitable form on a computer-readable medium. For simplicity, a data structure can be shown as having fields related by their location within the data structure. Such relationships can also be implemented by assigning storage locations to fields in a computer-readable medium, where these storage locations convey the relationships between the fields. However, any suitable mechanism can be used to establish relationships between information within the fields of a data structure, including the use of pointers, labels, or other mechanisms for establishing relationships between data elements.

[0219] When implemented in software, the software code can be executed on any suitable processor or set of processors, whether it is provided in a single computer or distributed among multiple computers.

[0220] The computer program logic that implements all or part of the functionality described herein is embodied in various forms, including but not limited to source code, computer-executable form, hardware description form, and various intermediate forms (e.g., masked operation or form generated by an assembler, compiler, linker, or locator). In one example, the source code comprises a series of computer program instructions implemented in various programming languages, such as object code, assembly language, or high-level languages ​​such as OpenCL, RTL, Verilog, VHDL, Fortran, C, C++, JAVA, or HTML, for various operating systems or operating environments. The source code can define and use various data structures and communication messages. The source code can be in a computer-executable form (e.g., via an interpreter), or the source code can be transformed (e.g., by a translator, assembler, or compiler) into a computer-executable form.

[0221] In some embodiments, any number of circuits shown in the figure can be implemented on a board of the relevant electronic device. This board can be a general-purpose circuit board that holds various components of the internal electronic system of the electronic device and further provides connectors for other peripheral devices. More specifically, the board can provide electrical connections through which other components of the system can communicate electrically. Any suitable processor (including digital signal processors, microprocessors, supporting chipsets, etc.), memory elements, etc., can be appropriately coupled to the board based on specific configuration requirements, processing requirements, computer design, etc.

[0222] Other components, such as external memory, additional sensors, controllers for audio / video displays, and peripherals, can be plug-in cards, connected to the board via cables, or integrated into the board itself. In another example embodiment, the circuitry of the figure can be implemented as a standalone module (e.g., a device with associated components and circuitry configured to perform a particular application or function) or as a plug-in module in the application-specific hardware of an electronic device.

[0223] Note that the interactions can be described using two, three, four, or more electrical components in the numerous examples provided herein. However, this is done merely for clarity and illustration. It should be understood that the system can be incorporated in any suitable manner. Along similar design alternatives, any components, modules, and elements shown in the figures can be combined in a wide variety of possible configurations, all of which are clearly within the broad scope of this disclosure.

[0224] In some cases, it is easier to describe one or more functions of a given set of flows by referring to only a limited number of electrical components. It should be understood that the diagrams and the circuits they teach are readily expandable and can accommodate a large number of components as well as more complex / complex arrangements and configurations. Therefore, the examples provided should not limit the scope of the circuits or inhibit their broad teaching, as the circuits can be applied to countless other architectures.

[0225] Furthermore, as described, some aspects can be embodied as one or more methods. Actions performed as part of a method can be ordered in any suitable manner. Therefore, embodiments can be constructed in which actions are performed in a different order than those shown, which may include performing some actions simultaneously, even if they are shown as sequential actions in the illustrative embodiments.

[0226] Terminology Explanation

[0227] All definitions defined and used herein should be understood to be the control dictionary definitions, definitions in files merged by reference, and / or the general meaning of defining terms. Unless the context expressly requires otherwise, throughout the specification and claims:

[0228] "Including" and "containing" should be interpreted as inclusive, rather than exclusive or exhaustive; that is, in the sense of "including but not limited to".

[0229] "Connection", "coupling" or any variation thereof means a direct or indirect connection or coupling between two or more elements; the coupling or connection between elements can be physical, logical or a combination thereof.

[0230] When terms such as “here,” “above,” “below,” and similar terms are used to describe this specification, they should refer to the specification as a whole, not any specific part of it.

[0231] "Or" refers to a list of two or more items, including all of the following interpretations of the word: any item in the list, all items in the list, and any combination of items in the list.

[0232] The singular forms “a,” “an,” and “the” also include the meaning of any appropriate plural form.

[0233] Directional terms such as “vertical,” “lateral,” “horizontal,” “up,” “down,” “forward,” “backward,” “inward,” “outward,” “left,” “right,” “front,” “back,” “top,” “bottom,” “below,” “above,” “under,” etc., used in this specification and any appended claims (if any), depend on the specific orientation of the described and illustrated device. The subject matter described herein can take on various alternative orientations. Therefore, these directional terms are not strictly defined and should not be interpreted narrowly.

[0234] The terms "a" and "an" as used in this specification and claims, unless expressly stated otherwise, shall be construed as meaning "at least one".

[0235] The phrase “and / or” as used herein in the specification and claims should be understood to mean “one or two” of the elements so combined, that is, elements that exist together in some cases and separately in others. Multiple elements listed with “and / or” should be interpreted in the same way, that is, “one or more” elements so combined.

[0236] Other elements may optionally be present, whether or not they are related to those explicitly identified by the “and / or” clause. Thus, as a non-limiting example, in one embodiment, when used in conjunction with open-ended language such as “comprising,” a reference to “a and / or B” may refer only to a (optionally including elements other than B); in another embodiment, it may be limited to B (optionally including elements other than A); in yet another embodiment, it may connect to both A and B (optionally including other elements); and so on.

[0237] As used herein in the specification and claims, the phrase "at least one," referring to a list of one or more elements, should be understood to mean at least one element selected from any one or more elements in the list, but not necessarily including at least one of every element specifically listed in the list, and does not exclude any combination of elements in the list. This definition also allows for the optional presence of an element outside of the specifically identified elements in the list of elements referred to by the phrase "at least one," whether or not it is related to those specifically identified elements.

[0238] Therefore, as a non-limiting example, in one embodiment, “at least one of a and B” (or equivalently, “one of A or B”, or equivalently, “at least one of A and / or B”) may refer to at least one, optionally including more than one A, while B is absent (and optionally including elements other than B); in another embodiment, at least one, optionally including more than one B, while A is absent (and optionally including elements other than A); in yet another embodiment, it relates to at least one, optionally including more than one A, and at least one, optionally including less than one B (and optionally including other elements); etc.

[0239] As used herein, unless otherwise stated, the term "both parties" shall be included. For example, "between A and B" includes both A and B unless otherwise stated.

[0240] Furthermore, the wording and terminology used herein are for descriptive purposes and should not be considered limiting. As used herein, “containing,” “including,” “having,” “comprising,” “involving,” and variations thereof mean “including the items listed thereafter and their equivalents” as well as other items.

[0241] In the claims and the foregoing description, all transitional phrases such as “containing,” “including,” “carrying,” “having,” “comprise,” “involving,” “holding,” and “forming” should be understood as open-ended, meaning including but not limited to. Only the transitional phrases “by” and “mainly by” should be closed or semi-closed transitional phrases, respectively.

[0242] Those skilled in the art can identify many other changes, substitutions, variations, alterations, and modifications, and this disclosure is intended to include all such changes, substitutions, variations, alterations, and modifications that fall within the scope of the appended claims.

[0243] In order to assist the United States Patent and Trademark Office (USPTO) and any reader of any patent in this application in interpreting the appended claims, the applicant wishes to draw the attention of the applicant that: (a) the applicant does not intend to invoke any appended claims existing as of the date of filing of this application under section 112(f) of Title 35 of the United States Code, unless the word “means” or “step” is specifically used in a particular claim; and (b) the applicant does not intend to limit this disclosure in any way not otherwise reflected in the appended claims by any statement in the disclosure.

[0244] Therefore, this invention should not be considered limited to the specific embodiments described above. Various modifications, equivalent methods, and multiple structures applicable to this invention will be apparent to those skilled in the art upon review of this disclosure.

Claims

1. An optical differential path length gas detector, comprising: A first light source that produces first light centered on a first wavelength; A second light source that generates a second light centered on a second wavelength; A filter is disposed near the first light source and configured to selectively allow the second light to pass through; and A reflector is configured to reflect the second light back onto the first light source, wherein a portion of the reflected second light travels collinearly with the first light. The second light source has a surface from which the second light is emitted, the first light source has a surface on which the second light is reflected, and the main surface of the filter and the main surface of the reflector are substantially parallel to the surfaces of the first light source and the second light source.

2. The optical differential path length gas detector of claim 1, further comprising circuitry configured to calculate a ratio of signals representing the respective measured intensities of the first light and the second light.

3. The optical differential path length gas detector according to claim 2, wherein the circuit is a dedicated integrated circuit.

4. The optical differential path length gas detector according to claim 2, wherein the circuit is an analog front end.

5. The optical differential path length gas detector according to claim 1, further comprising a controller configured to control the current to the first light source and the second light source.

6. The optical differential path length gas detector of claim 1, further comprising a first photodetector configured to detect light centered on the first wavelength, the first photodetector generating a first signal indicating a first measurement intensity.

7. The optical differential path length gas detector of claim 6 further includes a second photodetector configured to detect light centered on the second wavelength, the second photodetector generating a second signal indicating a second measurement intensity.

8. The optical differential path length gas detector of claim 7, further comprising circuitry configured to calculate a first ratio based at least on the first signal and the second signal.

9. The optical differential path length gas detector of claim 8, wherein the circuitry is further configured to calculate a ratio of the ratio based at least on the first ratio.

10. The optical differential path length gas detector of claim 1, further comprising a second filter configured to allow the first light to pass through.

11. The optical differential path length gas detector of claim 7, further comprising a time multiplexer configured to alternate between the first signal and the second signal.

12. An optical differential path length gas detector, comprising: The first light source generates a first light cone centered on a first wavelength; The second light source generates a second light cone centered on the second wavelength; A filter is disposed near the first light source and configured to selectively allow the second light cone to pass through; and A reflector is configured to reflect the second light cone onto the first light source, wherein a portion of the reflected second light cone travels collinearly with the first light cone. The first light cone and the second light cone substantially overlap. The second light source has a surface from which the second light cone is emitted, the first light source has a surface on which the second light cone is reflected, and the main surface of the filter and the main surface of the mirror are substantially parallel to the surfaces of the first light source and the second light source.

13. The optical differential path length gas detector according to claim 12, wherein the first light source is disposed directly adjacent to the second light source.

14. The optical differential path length gas detector of claim 12, further comprising circuitry configured to calculate a first ratio of signals representing the respective measured intensities of the first optical cone and the second optical cone.

15. The optical differential path length gas detector of claim 14, wherein the circuitry is further configured to calculate a ratio of the ratio based at least on the first ratio.

16. The optical differential path length gas detector according to claim 12, wherein the first light source is a first light-emitting diode, and the second light source is a second light-emitting diode.

17. The optical differential path length gas detector of claim 12, further comprising a controller configured to control current to the first light source and the second light source.

18. The optical differential path length gas detector of claim 12, further comprising a second filter configured to selectively allow the second light cone to pass through.

19. A method for calculating the optical differential path length for gas detection, comprising: A first light is emitted from a first light-emitting diode, the first light having a first wavelength as its center; A second light is emitted from a second light-emitting diode, and the second light is centered on a second wavelength; A mirror is used to reflect the second light onto the surface of the first light-emitting diode; Use a filter to selectively allow the second light to pass through; Measure the first light; Measure the second light; and The ratio is calculated based at least on measurements of the first light and the second light. The second light-emitting diode has a surface from which the second light is emitted, wherein the first light-emitting diode has a surface on which the second light is reflected, and wherein the main surface of the filter and the main surface of the reflector are substantially parallel to the surfaces of the first light-emitting diode and the second light-emitting diode.

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