Self-Calibrating Spectral Sensor Module

Abstract

An example system includes a housing defining a cavity and an aperture, a photodetector disposed within the cavity, a voltage-adjustable interferometer disposed within the cavity between the aperture and the photodetector, a first light source disposed within the cavity, and electronic control equipment. The electronic control equipment is operable to vary an input voltage applied to the interferometer while simultaneously causing the first light source to emit light toward the interferometer and measure light reflected from the interferometer using the photodetector. The electronic control equipment is further operable to determine a calibrated input voltage based on the light reflected from the interferometer and measured by the photodetector. The electronic control equipment is further operable to apply the calibrated input voltage to the interferometer while simultaneously obtaining one or more spectral measurements using the photodetector.

Description

Technical Field

[0001] The present disclosure relates to a spectral sensor module for use in a spectrometer. Background Art

[0002] A spectrometer is an instrument used to measure the spectrum of sample light (eg, to determine the spectral components of ultraviolet, visible, and / or infrared light). In some embodiments, a spectrometer can determine the intensity of light as a function of wavelength or frequency.

[0003] Spectrometers are used in a variety of applications. For example, they are used for environmental analysis, industrial monitoring, color measurement, and pharmacology research.

[0004] Spectra can be measured using different methods, such as direct or indirect measurement. As an example, a spectrometer configured for direct measurement can spatially separate light of different wavelengths (e.g., using a wavelength dispersive device such as a diffraction grating or prism) and measure the power distribution of each wavelength of light separately (e.g., measuring the spectrum "directly" with respect to a specific wavelength).

[0005] As another example, a spectrometer configured for indirect measurement can modulate light according to a series of known spectral modulation patterns and obtain measurements of the modulated light. Each measurement provides information carried by multiple wavelengths and weighted differently, and can be used to reconstruct the spectrum of the original light (e.g., using multiplexing techniques). Summary of the Invention

[0006] A spectrometer system can be used to determine information about a sample (e.g., an object) based on properties of light reflected from and / or transmitted through the sample. For example, a spectrometer system can include a light source that emits light (e.g., light having known spectral properties) toward the sample, and a detector that measures the light reflected from and / or transmitted through the sample. The spectrometer system can determine the spectral properties of the reflected and / or transmitted light (e.g., the distribution of the light over a range of wavelengths) and determine information about the sample based on these measurements. For example, the spectrometer system can determine the physical shape or contour of the sample, characteristics of the sample surface, and / or the composition of the sample.

[0007] In some embodiments, a spectrometer system can measure light at specific wavelengths or wavelength ranges. This can be useful, for example, because measurements of light at certain wavelengths or wavelength ranges may be particularly useful in determining properties of a sample (e.g., compared to measurements of light at other wavelengths or wavelength ranges). Thus, the spectrometer system can selectively measure light at specific wavelengths or wavelength ranges (e.g., those that provide more information and / or more desirable information about the sample) while not measuring light at other wavelengths or wavelength ranges (e.g., those that provide less information and / or less desirable information about the sample) to improve measurement efficiency and accuracy.

[0008] In some embodiments, a spectrometer system can use an interferometer to measure light at specific wavelengths or wavelength ranges. An interferometer is a device that uses light interference (e.g., by superimposing light waves) to extract information from light. For example, an interferometer can receive reflected and / or transmitted light from a sample and, by superimposing the received light at different phases, selectively transmit a subset of light having a specific wavelength or wavelength range to a detector for measurement. Thus, the detector does not measure all of the light received from the sample, but rather a limited subset of the received light selectively transmitted by the interferometer.

[0009] In some embodiments, the interferometer can be "tunable," allowing the system or user to specify a specific wavelength or range of wavelengths of light to be transmitted by the interferometer for measurement. For example, the output of a tunable interferometer can depend on an input voltage applied to the interferometer. The input voltage can be varied to adjust the wavelength or range of wavelengths of light that the interferometer selectively transmits to a detector for measurement.

[0010] However, in some embodiments, the output of the interferometer may also depend on other factors, such as the temperature of the surrounding environment. In addition, the output of the interferometer may change during the lifetime of the interferometer. For example, the output of the interferometer may change due to oxidation of one or more components (e.g., the interferometer's mirrors), which may change the performance of the interferometer over time (e.g., causing a drift in the nominal center wavelength of the interferometer output, changing the effective length of the interferometer's cavity, etc.). As another example, over time, moisture ingestion into the interferometer's materials may cause additional strain on the interferometer's components, causing physical changes that may change the performance of the interferometer over time (e.g., bending due to increased volume). As another example, some materials may lose volume over time, resulting in changes in the mechanical configuration of the interferometer and corresponding changes in performance.

[0011] Thus, in response to a particular input voltage, the interferometer may output light of different wavelengths or wavelength ranges (e.g., due to temperature fluctuations in the surrounding environment, aging of the device, etc.). These variations can reduce the accuracy and / or precision of the measurements made by the spectrometer system, particularly when the spectrometer system is used in different and / or unregulated environments.

[0012] To improve its performance, the spectrometer system can calibrate the input voltage of the interferometer to account for these variations. As an example, the spectrometer system can transmit light to the interferometer (e.g., using an internal light source), measure the intensity of the light reflected from the interferometer (e.g., using a photodetector), and calibrate the input voltage of the interferometer based on this measurement.

[0013] The intensity of light reflected from the interferometer can vary depending on the characteristics of the emitted light and the transmission characteristics of the interferometer. For example, if the light source emits light according to a particular wavelength or wavelength range, and the interferometer is adjusted to transmit light according to that wavelength or wavelength range, the light reflected from the interferometer will be relatively low (e.g., because the emitted light is substantially transmitted through the interferometer rather than reflected from it). However, if the light source emits light according to a particular wavelength or wavelength range, and the interferometer is adjusted to transmit light according to a different wavelength or wavelength range, the light reflected from the interferometer will be relatively high (e.g., because the emitted light is substantially not transmitted through the interferometer).

[0014] Thus, the spectrometer can sweep the interferometer's input voltage across a voltage range while simultaneously transmitting light into the interferometer and measuring the intensity of the reflected light. Based on the measurements, the spectrometer can determine a relationship between the interferometer's input voltage and the resulting wavelength or wavelength range of light output by the interferometer (e.g., corresponding to a measured decrease in the intensity of the reflected light). The spectrometer can then calibrate the input voltage based on this relationship (e.g., by modifying the applied input voltage so that the interferometer's output is more accurately controlled).

[0015] In some embodiments, this self-calibration technique enables the spectrometer system to compensate for temperature and performance fluctuations, and enables the spectrometer system to make more accurate and / or more precise measurements. In addition, this self-calibration technique enables the spectrometer system to be used in a wider range of environments and conditions and extends the useful operating life of the spectrometer system.

[0016] In one aspect, a system includes a housing defining a cavity and an aperture, a photodetector disposed within the cavity, a voltage-adjustable interferometer disposed within the cavity between the aperture and the photodetector, a first light source disposed within the cavity, and electronic control equipment. The electronic control equipment is operable to vary an input voltage applied to the interferometer and, while varying the input voltage applied to the interferometer, cause the first light source to emit light toward the interferometer and measure light reflected from the interferometer using the photodetector. The electronic control equipment is further operable to determine a calibrated input voltage based on the light reflected from the interferometer and measured by the photodetector. The electronic control equipment is operable to apply the calibrated input voltage to the interferometer and, while applying the calibrated input voltage to the interferometer, obtain one or more spectral measurements using the photodetector.

[0017] Implementations of this aspect may include one or more of the following features.

[0018] In some embodiments, the electronic control device can determine the calibrated input voltage by determining the value of the input voltage corresponding to the minimum intensity of light reflected from the interferometer as measured.

[0019] In some embodiments, the electronic control device may determine the calibrated input voltage by determining that the value of the input voltage corresponding to the minimum intensity of light reflected from the interferometer measured is the calibrated input voltage.

[0020] In some embodiments, the first light source can include a plurality of light emitting elements.

[0021] In some embodiments, the electronic control device is operable to cause the first light source to emit light toward the interferometer by causing the plurality of light emitting elements to emit light in sequence.

[0022] In some embodiments, the electronic control device is operable to cause the first light source to emit light toward the interferometer by causing the plurality of light emitting elements to emit light simultaneously.

[0023] In some embodiments, the first light source can include one or more vertical-cavity surface-emitting laser (VCSEL) emitters.

[0024] In some embodiments, the interferometer may include a Fabry-Perot interferometer (FPI).

[0025] In some embodiments, the system may include a second light source disposed outside the cavity.The electronic control device is operable to obtain one or more spectral measurements by causing the second light source to emit sample light toward the object and measuring the sample light reflected from the object using the photodetector.

[0026] In some embodiments, the first light source is operable to emit light within a first wavelength range. The second light source is operable to emit light within a second wavelength range. The first wavelength range can be different from the second wavelength range.

[0027] In some embodiments, the first wavelength range can be narrower than the second wavelength range.

[0028] In some embodiments, the system can include a host device. The housing, photodetector, interferometer, light source, and control electronics can be at least partially disposed in the host device.

[0029] In some implementations, the host device may be at least one of a smartphone or a wearable device.

[0030] In another aspect, a method includes varying an input voltage applied to a voltage-tunable interferometer and, while varying the input voltage applied to the interferometer, emitting light into the interferometer and measuring light reflected from the interferometer. The method also includes determining a calibrated input voltage based on the measured light reflected from the interferometer. The method also includes applying the calibrated input voltage to the interferometer and, while applying the calibrated input voltage to the interferometer, obtaining one or more spectral measurements using a photodetector.

[0031] Implementations of this aspect may include one or more of the following features.

[0032] In some implementations, determining the calibrated input voltage can include determining a value of the input voltage corresponding to a minimum intensity of light measured reflected from the interferometer.

[0033] In some implementations, determining the calibrated input voltage can include determining that a value of the input voltage corresponding to a minimum intensity of light measured reflected from the interferometer is the calibrated input voltage.

[0034] In some embodiments, emitting light into the interferometer can include emitting light sequentially by a plurality of light emitting elements.

[0035] In some embodiments, emitting light into the interferometer can include emitting light simultaneously by a plurality of light emitting elements.

[0036] In some implementations, obtaining one or more spectral measurements can include emitting sample light toward the object, and measuring the sample light reflected from the object.

[0037] In some embodiments, the light may be within a first wavelength range and the sample light may be within a second wavelength range. The first wavelength range may be different from the second wavelength range.

[0038] In some embodiments, the first wavelength range can be narrower than the second wavelength range.

[0039] The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features and advantages will be apparent from the description and drawings, and from the claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a schematic diagram of an example spectrometer system.

[0041] Figure 2A is a graph illustrating an example relationship between an input voltage applied to an interferometer and the corresponding wavelength of light output by the interferometer.

[0042] Figure 2B is a graph showing an example relationship between the input voltage applied to an interferometer and the corresponding wavelength of light output by the interferometer for several different temperatures.

[0043] Figure 3 is a diagram of an example sensor module.

[0044] Figure 4A Included is a graph depicting the wavelength range of light output by the sensor module's internal light source and the wavelength range of light transmitted by the sensor module's interferometer.

[0045] Figure 4B A further graph is included that depicts the wavelength range of light output by the sensor module's internal light source and the wavelength range of light transmitted by the sensor module's interferometer.

[0046] Figure 4C Included is a graph of the measured intensity of reflected light versus the input voltage sweep range of the sensor module.

[0047] Figure 5 is a diagram of another example sensor module.

[0048] Figure 6 is a diagram of another example sensor module.

[0049] Figure 7 is a flow chart of an example process for measuring the spectral distribution of light reflected from and / or transmitted through a sample.

[0050] Figure 8 is a schematic diagram of an example computer system. DETAILED DESCRIPTION

[0051] The present disclosure describes embodiments of a spectrometer system for measuring the spectral distribution of light reflected from and / or transmitted through a sample. Embodiments of the spectrometer system include a voltage-tunable interferometer for selecting light of a particular wavelength or range of wavelengths for measurement. To account for variations in the interferometer output (e.g., due to fluctuations in ambient temperature, system aging, etc.), the spectrometer system can self-calibrate the input voltage applied to the interferometer. In some embodiments, this enables the spectrometer system to compensate for variations in operation and enables the spectrometer system to make more accurate and / or more precise measurements. Furthermore, this self-calibration technique enables the spectrometer system to be used over a wider range of environments and environmental conditions and extends the effective operating life of the spectrometer system.

[0052] Figure 1 An example spectrometer system 100 is shown. The spectrometer system 100 can be implemented as a standalone device (e.g., as a separate instrument) or as part of another device (e.g., as part of a multi-purpose device). In some embodiments, the spectrometer system 100 can be implemented as part of a mobile device (e.g., a smartphone, a tablet computer, or a wearable computer).

[0053] like Figure 1 As shown, spectrometer system 100 includes a light source 102 and a sensor module 150 having an interferometer 104, a voltage source 106, a detector 108, and electronic control equipment 110. In an example use of spectrometer system 100, light source 102 generates light 112, which is emitted toward a sample 114 (e.g., an object located in a sample region 160). At least some of sample light 116 reflected by and / or transmitted through sample 114 is incident on interferometer 104. Based on an input voltage generated by voltage source 106, interferometer 104 selectively transmits a subset of sample light 118 (e.g., sample light within a particular wavelength or wavelength range) to detector 108. Detector 108 measures a characteristic of the subset of sample light 118 and provides the measurement to electronic control equipment 110. Based on the measurements, the electronic control device 110 determines information about the sample 114 (eg, a histogram 120 representing the spectral distribution of a subset of the sample light 118 , characteristics of the sample 114 , etc.).

[0054] The light source 102 is a component operable to generate light and emit the light toward the sample area 160. The light source 102 may include one or more light emitting elements. As an example, the light source 102 may include one or more light emitting diodes (LEDs), vertical cavity surface emitting lasers (VCSELs), organic light emitting diodes (OLEDs), or other devices that selectively generate light.

[0055] Interferometer 104 is a component operable to extract information from light using optical interference. As an example, the interferometer can receive sample light 116 and selectively transmit a subset of sample light 118 having a specific wavelength or wavelength range to detector 108 for measurement by superimposing the sample light 116 according to different phases. Interferometer 104 is "tunable" so that the system or user can specify the specific wavelength or wavelength range of light transmitted by interferometer 104 to detector 108. For example, the output of interferometer 104 can depend on the input voltage V generated by voltage source 106 and applied to interferometer 104. in . The input voltage V in to adjust the wavelength or wavelength range of light selectively transmitted by interferometer 104 to detector 108. In some embodiments, interferometer 104 may include one or more micro-electro-mechanical system (MEMS) based tunable Fabry-Perot (FI) interferometers.

[0056] The voltage source 106 is operable to generate an input voltage V in The voltage source 106 may include one or more digital and / or analog circuit components for generating a voltage. In some embodiments, the voltage source 106 may include one or more batteries or generators. In some embodiments, the voltage source 106 may receive electrical energy from an external source (e.g., an external power supply) and use the received electrical energy to generate an input voltage V in In some embodiments, the voltage source 106 can be communicatively coupled to the electronic control device 110 and can be configured to operate based on a command signal s received from the electronic control device 110. voltage Generates an input voltage V with a specific voltage value in .although Figure 1 The voltage source 106 is depicted as part of the sensor module 150 , but in some embodiments, the voltage source 106 may be implemented as a separate component (eg, as part of the spectrometer system 100 or another device).

[0057] The detector 108 is a component operable to measure characteristics of a subset of the sample light 118 received from the interferometer 104. In some embodiments, the detector 108 may include one or more photodetectors or other light-sensitive sensors. The detector 108 may measure various characteristics of the subset of the sample light 118. For example, the detector 108 may measure the intensity of the light and / or spectral characteristics of the reflected light with respect to certain wavelengths and / or wavelength ranges. In some embodiments, the detector 108 may be operable to measure the subset of the sample light 118 according to one or more discrete points in time. In some embodiments, the detector 108 may be operable to measure the light continuously, periodically, intermittently, or according to some other pattern.

[0058] The electronic control device 110 is a component operable to control one or more functions of the spectrometer system 100. For example, the electronic control device 110 can be communicatively coupled to the light source 102 and can send command signals to the light source 102 to selectively turn the light source 102 on or off (e.g., to generate light during selected time periods (e.g., during measurement operations)) and / or to specify characteristics of the generated light (e.g., to generate light according to a particular pattern, spectral composition, etc.). As another example, the electronic control device 110 can be communicatively coupled to the voltage source 106 and can send command signals to the voltage source 106. voltage To generate an input voltage V with a specific voltage value in (E.g., for adjusting the output of interferometer 104.) As another example, electronic control device 110 may be communicatively coupled to detector 108 and may obtain measurements from detector 108.

[0059] Additionally, the electronic control device 110 may determine information from the sample 114 based on the measurements. For example, the electronic control device 110 may generate a histogram 120 representing the spectral distribution of a subset of the sample light 118. As another example, the electronic control device 110 may determine other characteristics of the sample 114 based on the measurements, such as the physical shape or contour of the sample, characteristics of the sample surface, and / or the composition of the sample.

[0060] In some embodiments, the electronic control device 110 can be implemented in conjunction with one or more other components of the spectrometer system 100 and / or the sensor module 150 (e.g., as a single integrated device). In some embodiments, the electronic control device 110 can be implemented as a separate device from one or more other components of the spectrometer system 100 and / or the sensor module 150. For example, the electronic control device 110 can be a separate and distinct computer system (e.g., a client computer system or a server computer system) or computer processor from one or more other components of the spectrometer system 100 and / or the sensor module 150.

[0061] As described above, the output of the interferometer 104 may depend on the input voltage V applied to the interferometer 104. in . The input voltage V in to adjust the wavelength or wavelength range of light selectively transmitted by the interferometer 104 to the detector 108.

[0062] In some embodiments, the input voltage V applied to the interferometer in The relationship between and the corresponding wavelength of light at the interferometer output is nonlinear. For example, Figure 2A A graph 200 is included that illustrates the input voltage V applied to the interferometer 104 of the spectrometer system. in and the corresponding wavelength of light output by the interferometer 104, which includes an exemplary MEMS-based tunable FI interferometer. In this example, an input voltage V is applied to the interferometer 104. in This will result in the output of light with a wavelength range having a central wavelength of approximately 1550nm, while light of other wavelengths outside this range is essentially not output by the interferometer. In this example, the relationship can be approximated by the following equation:

[0063]

[0064] where k is the spring constant, x is the wavelength change (e.g., the displacement of the interferometer cavity), ε0 is the vacuum dielectric constant, and ε a is the relative static permittivity, A is the area of the isoparallel plates of the interferometer, V is the voltage applied between the electrodes, and T is a parameter related to the geometry and permittivity of the medium under consideration (e.g., where g is the thickness of the cavity without applied voltage, t d is the thickness of the layer on top of the electrode, with a relative static dielectric constant of ε b ).

[0065] However, in some embodiments, the interferometer output may also depend on the temperature of the surrounding environment. Thus, in response to a specific input voltage, the interferometer may output light of different wavelengths or wavelength ranges depending on fluctuations in the ambient temperature. These variations can reduce the accuracy and / or precision of the spectrometer system's measurements, particularly when the spectrometer system is used in different and / or unregulated environments. For example, while the electronic control device 110 may specify that a specific wavelength of light be transmitted to the detector 108 for measurement, light of different wavelengths may be transmitted, resulting in variations in the measurements and / or errors in the interpretation of those measurements.

[0066] As an example, Figure 2B A graph 210 is shown which depicts (i) the input voltage V applied to the interferometer 104 inand (ii) the relationship between the corresponding center wavelengths of the wavelength ranges of light output by the interferometer 104 at seven different temperatures (40°C, -20°C, 5°C, 25°C, 45°C, 65°C, and 85°C) ranging from -40°C to 85°C. Figure 2B As shown, in response to a specific input voltage V in , an interferometer can output light in different wavelength ranges depending on the temperature. Therefore, the resulting measurements may vary due to temperature fluctuations during and between each measurement.

[0067] Furthermore, in some embodiments, the output of the interferometer may vary over the life of the interferometer. For example, as the interferometer ages, the input voltage V applied to the interferometer 104 may change. in The relationship between the wavelengths of the light and the corresponding center wavelengths of the wavelength range output by the interferometer 104 may shift or "drift." As a result, the resulting measurement may vary as the device ages.

[0068] To improve its performance, the spectrometer system can self-calibrate the input voltage V applied to the interferometer 104. in , to take these changes into account. Figure 3 An example sensor module 150 for performing self-calibration is shown in FIG.

[0069] The sensor module 150 includes a housing 300 defining a cavity 302 and an aperture 304 . Figure 3 Some or all of the components of the illustrated sensor module 150 may be similar to Figure 1 For example, the sensor module 150 may include a detector 108 disposed within the cavity 302 (e.g., on the substrate 306), and an interferometer 104 disposed within the cavity between the hole 304 and the detector 108 (e.g., on the substrate 306). In an example operation of the sensor module 150, the light source (e.g., Figure 1 The light source 102 described above) is directed to the sample (e.g., Figure 1 At least some of the light reflected by and / or transmitted through the sample passes through aperture 304 and is incident on interferometer 104. Figure 1 Based on an input voltage generated by a voltage source 106 (described above), the interferometer 104 selectively transmits a subset of the sample light (e.g., sample light within a particular wavelength or wavelength range) to a detector 108. The detector 108 measures a characteristic of the subset of the sample light and provides the measurement to an electronic control device (e.g., a reference to a source). Figure 1 Based on the measurements, the electronic control device determines information about the sample (eg, a histogram representing the spectral distribution of a subset of the sample light, characteristics of the sample, etc.).

[0070] The sensor module 150 also includes an internal light source 308 and a temperature sensitive sensor 314 located within the cavity 302 (eg, on the substrate 306 ) to facilitate self-calibration.

[0071] The temperature sensitive sensor 314 outputs a measurement signal that varies according to the ambient temperature (eg, the temperature within the cavity 302). For example, the temperature sensitive sensor 314 may include one or more temperature sensitive thermistors.

[0072] The internal light source 308 is a component operable to generate light and emit the light to the interferometer 104. The internal light source 308 may include one or more light emitting elements. As an example, the internal light source 308 may include one or more light emitting diodes (LEDs), vertical cavity surface emitting lasers (VCSELs), organic light emitting diodes (OLEDs), or other devices that selectively generate light. In some embodiments, the internal light source 308 may generate light according to a specific wavelength or wavelength range λ. emission In some embodiments, the internal light source 308 can emit light according to a relatively narrow wavelength range (e.g., a range less than 1 nm). In some cases, the internal light source 308 can emit light according to a wavelength range that is narrower than the wavelength range of the light source 108.

[0073] In some embodiments, the internal light source 308 can emit light (eg, at a wavelength or wavelength range λ) based on the measurement signal from the temperature sensitive sensor 314. emission As an example, the emission of the VCSEL-based internal light source 308 may vary by a specific amount (e.g., approximately 0.07 nm / °C) based on temperature. The electronic control device 110 may determine the temperature of the cavity 302 based on the temperature sensitive sensor 314 and adjust the internal light source 308 so that light of a desired wavelength or wavelength range is emitted.

[0074] In an example self-calibration process of sensor module 150, sensor module 150 uses internal light source 308 to transmit light 310 to interferometer 104 and uses detector 108 to measure the intensity of light 312 reflected from interferometer 104. Sensor module 150 calibrates the input voltage V applied to the interferometer based on this measurement. in .

[0075] The intensity of light 312 reflected from interferometer 104 may vary depending on the characteristics of emitted light 310 and the transmission characteristics of interferometer 104. As an example, Figure 4A , which depicts the wavelength range λ of the light output by the internal light source 308. emission400a, and a graph depicting a first wavelength range λ of light transmitted by the interferometer 104 transmission,1 Graph 400b (eg, corresponding to a first input voltage V applied to the interferometer 104) in,1 In this example, the wavelength ranges do not substantially overlap (e.g., λ emission Basically in λ transmission,1 ). Thus, the measured intensity of light reflected from interferometer 104 will be relatively high (e.g., because substantially no emitted light is transmitted through interferometer 104).

[0076] As another example, Figure 4B , which depicts the wavelength range λ of the light output by the internal light source 308. emission 402a, and a graph depicting a second wavelength range λ of light transmitted by the interferometer 104 transmission,2 Graph 402b (eg, corresponding to a second input voltage V applied to the interferometer 104) in,2 In this example, the wavelength ranges substantially overlap (e.g., λ emission Basically in λ transmission,2 Thus, the measured intensity of light reflected from interferometer 104 will be relatively low (e.g., because the emitted light is substantially transmitted through the interferometer rather than reflected from it).

[0077] The sensor module 150 can sweep the input voltage V applied to the interferometer 104 across a voltage range in , while transmitting light 310 to the interferometer 104 and measuring the intensity of the reflected light 312. Based on this measurement, the sensor module 150 can determine the input voltage V in and the resulting wavelength or wavelength range of light output by the interferometer 104 (e.g., corresponding to the measured decrease in the intensity or minimum intensity of the reflected light 312). The sensor module 150 can calibrate the input voltage V based on the relationship. in (For example, by modifying the applied input voltage so that the output of the interferometer is more accurately controlled).

[0078] As an example, Figure 4C shows the measured intensity of the reflected light 312 relative to the input voltage V in The scanning range of the curve 404. When the input voltage is V in,a and V in,b However, when the input voltage begins to exceed V in,b , the measured intensity of the reflected light 312 begins to decrease, and when the input voltage is V in,c When the input voltage starts to exceed Vin,c The measured intensity of the reflected light 312 begins to increase when the input voltage is V in,d and V in,e Between , the measured intensity of reflected light 312 is again relatively high.

[0079] Input voltage V in,c Corresponding to the maximum transmittance of the interferometer (eg, coincident with the resonant frequency of the interferometer). If the wavelength or wavelength range of the emitted light 312 is known (eg, λ emission ), then the input voltage V in,c and wavelength or wavelength range λ emission (For example, the input voltage / output wavelength data point pair (V in,c ,λ emission )) establishes a relationship between them. In practice, this means that when the input voltage V in,c When applied to the interferometer 104, the interferometer responds to the wavelength or wavelength range λ emission Transmitted light.

[0080] In some embodiments, the sensor module 150 can perform self-calibration based on a single data point. For example, the electronic control device 110 can instruct the internal light source 308 to emit light according to a single wavelength or wavelength range λ. emission The light is emitted to the interferometer 104. While emitting the light, the electronic control device 100 can instruct the voltage source 106 to apply the input voltage V to the interferometer. in The scanning range is set as shown in FIG1 and the intensity of the reflected light is measured using the detector 108. The electronic control device 110 can determine a data point pair indicating (i) the input voltage V′ corresponding to the minimum intensity of the measured reflected light. in , and (ii) the wavelength or wavelength range λ of the light emitted by the internal light source 308 emission (For example, the data point pair (V′ in ,λ emission Based on this determination, the electronic control device 110 can determine whether the output of the interferometer has deviated from its reference characteristic (e.g., by comparing the data point pair to one or more previously determined data point pairs or a calibration lookup table, a default setting programmed during the manufacture of the processor, etc.), and adjust the input voltage based on this determination. For example, if the electronic control device 110 determines, based on the data point pair, that a particular input voltage Vin causes the interferometer to output light of a different wavelength or range of optical wavelengths than expected, the electronic control device 110 can adjust the input voltage during operation to account for this difference (e.g., increase or decrease the input voltage to achieve the desired output). Data regarding the calibration process (e.g., data point pairs, input voltage adjustments, etc.) can be stored (e.g., in a data storage device) for future retrieval and use.

[0081] In some embodiments, the sensor module 150 can perform self-calibration based on multiple data points. For example, the electronic control device 110 can instruct the internal light source 308 to emit light according to the first wavelength or wavelength range λ. emission,1 The light is emitted to the interferometer 104. While emitting the light, the electronic control device 110 can instruct the voltage source 106 to apply the input voltage V to the interferometer. in The electronic control device 110 may determine a first pair of data points indicating (i) a first input voltage V′ corresponding to a minimum intensity of the reflected light measured during the voltage sweep; and (ii) a second pair of data points indicating (i) a first input voltage V′ corresponding to a minimum intensity of the reflected light measured during the voltage sweep. in,1 , and (ii) a first wavelength or wavelength range λ of light emitted by the internal light source 308 during scanning emission,1 (For example, the data point pair (V′ in,1 ,λ emission,1 )). The electronic control device 110 can repeat the process one or more times according to the different wavelengths or wavelength ranges of the emitted light to obtain additional data point pairs (e.g. (V′ in,2 ,λ emission,2 ),(V′ in,3 ,λ emission,3 ),...(V′ in,n ,λ emission,n )).

[0082] Based on these data point pairs, the electronic control device 110 can determine whether the output of the interferometer has deviated from its reference characteristics (e.g., by comparing the data point pairs to one or more previously determined data point pairs or a calibration lookup table, default settings programmed during manufacture of the processor, etc.), and adjust the input voltage based on this determination. For example, if the electronic control device 110 determines based on the data point pairs that a particular input voltage V in causes the interferometer to output light of a different wavelength or range of wavelengths than expected, the electronic control device 110 may adjust the input voltage during operation to account for the difference (eg, increase or decrease the input voltage to achieve the desired output).

[0083] In some embodiments, the electronic control device can calibrate the input voltage function based on multiple data points. The input voltage function can describe, for example, the relationship between a given input voltage and a corresponding wavelength or wavelength range of light output by the interferometer (e.g., Figure 2A and 2BAs shown). As an example, the electronic control device 110 can calibrate the input voltage function by performing a curve fit (e.g., using a regression technique, such as polynomial regression) relative to the input voltage function using one or more data point pairs as fitting parameters. As another example, the electronic control device 110 can calibrate the input voltage function by shifting the input voltage function based on one or more data point pairs (e.g., relative to the input voltage dimension and / or the output wavelength dimension). In some embodiments, the electronic control device 110 can adjust a lookup table based on the data points. The lookup table can indicate, for example, a plurality of discrete input voltages and their corresponding wavelengths or wavelength ranges of light output by the interferometer (e.g., in the form of a data table). Data about the calibration process (e.g., data point pairs, input voltage adjustments, calibrated input voltage functions, adjusted lookup tags, etc.) can be stored (e.g., in a data storage device) for future retrieval and use.

[0084] In some embodiments, the electronic control device 110 can perform a self-calibration before each spectral measurement. For example, the electronic control device 110 can perform a self-calibration using the internal light source 308 and then apply a calibrated input voltage V to the interferometer. in , to perform spectral measurements about a selected wavelength or wavelength range (eg, using light source 102). This may be advantageous, for example, in improving the precision and / or accuracy of the spectrometer system.

[0085] In some embodiments, the electronic control device 110 may periodically perform self-calibration during operation. For example, the electronic control device 110 may perform self-calibration using the internal light source 308 every N spectral measurements and / or once every time interval T. The electronic control device 110 may then apply a calibrated input voltage V to the interferometer. in , to perform one or more spectral measurements about a selected wavelength or wavelength range (e.g., using light source 102). This may, for example, be advantageous in improving the precision and / or accuracy of the spectrometer system (e.g., compared to not performing any self-calibration at all) while reducing the amount of time spent performing the self-calibration process (e.g., compared to performing self-calibration before each spectral measurement).

[0086] In some embodiments, the light source 102 can be integrated into the sensor module. As an example, Figure 5 A sensor module 500 is shown. Aspects of the sensor module 500 may be similar to those of the reference Figure 3The sensor module 150 shown and described. For example, the sensor module 500 includes a housing 300 defining a cavity 302 and an aperture 304. The sensor module 150 also includes a detector 108 disposed within the cavity 302 (e.g., on a substrate 306), and an interferometer 104 disposed within the cavity (e.g., on the substrate 306) between the aperture 304 and the detector 108. The sensor module 150 also includes an internal light source 308 and a temperature sensitive sensor 314 located within the cavity 302 (e.g., on the substrate 306) to facilitate self-calibration (e.g., as described with reference to FIG. Figure 3 and Figures 4A-4C described above).

[0087] Furthermore, the sensor module 500 includes a light source 102 disposed within the second cavity 502 of the housing 300. In an exemplary operation of the sensor module 500, the light source 102 emits light toward the sample through the second aperture 504 of the housing 300. At least some of the light reflected by and / or transmitted through the sample returns to the sensor module 500 through the aperture 304 and is incident on the interferometer 104. Figure 1 Based on an input voltage generated by a voltage source 106 (described above), the interferometer 104 selectively transmits a subset of the sample light (e.g., sample light within a particular wavelength or wavelength range) to a detector 108. The detector 108 measures a characteristic of the subset of the sample light and provides the measurement to an electronic control device (e.g., a reference to a source). Figure 1 Based on the measurements, the electronic control device determines information about the sample (eg, a histogram representing the spectral distribution of a subset of the sample light, characteristics of the sample, etc.).

[0088] In some embodiments, the sensor module can include multiple internal light sources (e.g., multiple laser emitters, LEDs, etc.). At least some of the internal light sources can be configured to emit light according to a different wavelength or wavelength range than the other internal light sources. This can be useful, for example, because it enables the sensor module 150 to perform self-calibration with respect to multiple different wavelengths or wavelength ranges. As an example, Figure 6 A sensor module 600 is shown having two internal light sources 600a and 600b disposed within the cavity 302 of the housing 300 (eg, on the substrate 306). Figure 6 Two internal light sources are shown in FIG, but in practice, the sensor module may include any number of internal light sources (eg, one, two, three, four, or more).

[0089] In some cases, one or more internal light sources can be configured to emit light so as to increase or maximize the contrast signal at the detector. For example, the one or more light sources can include lenses or microlenses to direct light at a specific angle at the interferometer so that the reflected light is substantially incident on the detector.

[0090] In some cases, a sensor module can be configured to sequentially emit light using multiple internal light sources (e.g., to scan across multiple different wavelengths or wavelength ranges of emitted light). This can be useful, for example, to reduce the peak power load of the sensor module (e.g., because not all internal light sources emit light simultaneously).

[0091] In some cases, the sensor module can be configured to use multiple internal light sources to emit light simultaneously (e.g., to simultaneously emit light having multiple wavelengths or wavelength ranges). This can help, for example, reduce the amount of time required to perform a self-calibration process.

[0092] In some cases, the sensor module can be configured to detect when the sensor module has been damaged. Figure 3 and Figures 4A-4C In a similar manner as described above, the sensor module can use an internal light source to transmit light to the interferometer and use a detector to measure the reflected light. If the measured reflected light is zero or substantially zero (e.g., across the range of input voltages scanned), the sensor module can determine that the sensor module is damaged. This may occur, for example, if the internal light source, detector, and / or interferometer are damaged or otherwise impaired. The spectrometer system can indicate such damage to the user (e.g., via a display screen, indicator light, audio speaker, etc.).

[0093] Example Process

[0094] Figure 7 An example process 700 for using a spectrometer system is shown. Process 700 can be performed to measure the spectral distribution of light reflected from and / or transmitted through a sample. In some embodiments, process 700 can be performed by Figure 1 、 Figure 3 、 Figure 5 and Figure 6 This may be performed by one or more of the spectrometer systems and / or sensor modules shown.

[0095] In process 700, the input voltage applied to the voltage-tunable interferometer is changed (step 702). Figure 1 As shown, the voltage source 106 can apply an input voltage to the interferometer 104 based on instructions from the electronic control device 110 and vary the input voltage over a period of time.

[0096] While varying the input voltage applied to the interferometer, light is emitted to the interferometer and the light reflected from the interferometer is measured (step 704). Figure 3 and Figure 5As shown, the internal light source 308 can emit light to the interferometer 104. In some embodiments, the light can be emitted sequentially by multiple light emitting elements. In some embodiments, the light can be emitted simultaneously by multiple light emitting elements. For example, Figure 6 As shown, light may be emitted by two internal light sources 600a and 600b, either sequentially or simultaneously.

[0097] A calibrated input voltage is determined based on the measured light reflected from the interferometer (step 706). In some embodiments, the calibrated input voltage can be determined by determining the value of the input voltage corresponding to the minimum intensity of the light reflected from the interferometer. Furthermore, the value of the input voltage corresponding to the minimum intensity of the light reflected from the interferometer can be determined to be the calibrated input voltage. For example, referring to Figures 4A-4C Example techniques for determining a calibrated input voltage are described.

[0098] The calibrated input voltage is applied to the interferometer (step 708). As an example, Figure 1 As shown, the voltage source 106 may apply a calibrated input voltage to the interferometer 104 based on instructions from the electronic control device 110 (eg, based on the calibration techniques described herein).

[0099] While applying a calibrated input voltage to the interferometer, one or more spectral measurements are obtained using a photodetector (step 710). Obtaining the one or more spectral measurements may include emitting sample light toward an object and measuring the sample light reflected from the object. In some embodiments, the initially emitted light may be within a first wavelength range and the sample light may be within a second wavelength range. The first wavelength range may be different from the second wavelength range. In some embodiments, the first wavelength range may be narrower than the second wavelength range.

[0100] Example System

[0101] Some embodiments of the subject matter and operations described in this specification may be implemented in digital electronic circuitry, or in computer software, firmware, or hardware including the structures disclosed in this specification and their structural equivalents, or in a combination of one or more of them. For example, in some embodiments, one or more components of the spectrometer system 100 and / or sensor modules 150, 500, or 600 (e.g., the electronic control device 110) may be implemented using digital electronic circuitry, or in computer software, firmware, or hardware, or in a combination of one or more of them. In another example, Figure 7 The processes shown may be implemented using digital electronic circuitry, or in computer software, firmware, or hardware, or in a combination of one or more of them.

[0102] Some embodiments described in this specification can be implemented as one or more groups or modules of digital electronic circuits, computer software, firmware, or hardware, or a combination of one or more of them. Although different modules can be used, each module does not have to be different, and multiple modules can be implemented on the same digital electronic circuits, computer software, firmware, or hardware, or a combination thereof.

[0103] Some embodiments described in this specification may be implemented as one or more computer programs, i.e., one or more modules of computer program instructions encoded on a computer storage medium, for execution by a data processing apparatus or for controlling the operation of a data processing apparatus. A computer storage medium may be or may be included in a computer-readable storage device, a computer-readable storage substrate, a random or serial access memory array or device, or a combination of one or more of these. In addition, although a computer storage medium is not a propagation signal, a computer storage medium may be a source or destination of computer program instructions encoded in an artificially generated propagation signal. A computer storage medium may also be or be included in one or more separate physical components or media (e.g., multiple CDs, disks, or other storage devices).

[0104] The term "data processing apparatus" includes all kinds of apparatuses, devices and machines for processing data, including, for example, a programmable processor, a computer, a system on a chip, or a plurality or combination thereof. The apparatus may include dedicated logic circuitry, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC). In addition to hardware, the apparatus may also include code that creates an execution environment for the computer program in question, for example, code constituting processor firmware, a protocol stack, a database management system, an operating system, a cross-platform runtime environment, a virtual machine, or a combination of one or more of these. The apparatus and execution environment may implement a variety of different computing model infrastructures, such as network services, distributed computing, and grid computing infrastructures.

[0105] A computer program (also referred to as a program, software, software application, script, or code) may be written in any form of programming language, including compiled or interpreted languages, declarative or procedural languages. A computer program may (but need not) correspond to a file in a file system. A program may be stored as part of a file that holds other programs or data (e.g., one or more scripts stored in a markup language document), in a single file dedicated to the program in question, or in multiple coordinated files (e.g., files that store one or more modules, subroutines, or portions of code). A computer program may be deployed to execute on a single computer or on multiple computers located at a single site or distributed across multiple sites and interconnected by a communications network.

[0106] Some of the processes and logic flows described in this specification can be performed by one or more programmable processors executing one or more computer programs to perform actions by operating on input data and generating output. These processes and logic flows can also be performed by special purpose logic circuitry, and the apparatus can also be implemented as special purpose logic circuitry, such as a field programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0107] For example, processors suitable for executing computer programs include general-purpose and special-purpose microprocessors, as well as processors of any type of digital computer. Typically, a processor will receive instructions and data from read-only memory or random access memory, or both. A computer includes a processor for performing actions in accordance with instructions and one or more memory devices for storing instructions and data. A computer may also include or be operatively coupled to one or more mass storage devices (e.g., magnetic, magneto-optical, or optical disks) for storing data, to receive data from or transfer data to the one or more mass storage devices, or both. However, a computer need not have such devices. Devices suitable for storing computer program instructions and data include all forms of non-volatile memory, media, and storage devices, including, for example, semiconductor memory devices (e.g., EPROM, EEPROM, flash memory devices, etc.), magnetic disks (e.g., internal hard disks, removable disks, etc.), magneto-optical disks, and CD-ROM and DVD-ROM disks. The processor and memory may be supplemented by or incorporated into dedicated logic circuitry.

[0108] To provide for interaction with a user, operations may be implemented on a computer having a display device (e.g., a monitor or another type of display device) for displaying information to the user and a keyboard and pointing device (e.g., a mouse, trackball, tablet, touch-sensitive screen, or another type of pointing device) through which the user can provide input to the computer. Other types of devices may also be used to provide for interaction with the user; for example, feedback provided to the user may be any form of sensory feedback, such as visual feedback, auditory feedback, or tactile feedback; and input from the user may be received in any form, including sound, voice, or tactile input. In addition, a computer may interact with a user by sending documents to and receiving documents from a device used by the user; for example, by sending a web page to a web browser on a user's client device in response to a request received from the web browser.

[0109] A computer system may include a single computing device or multiple computers that operate near or substantially remote from each other and typically interact through a communication network. Examples of communication networks include local area networks ("LANs") and wide area networks ("WANs"), internetworks (such as the Internet), networks including satellite links, and peer-to-peer networks (such as adhoc peer-to-peer networks). The relationship of client and server may arise by virtue of computer programs running on the respective computers and having a client-server relationship to each other.

[0110] Figure 8 An example computer system 800 is shown that includes a processor 810, a memory 820, a storage device 830, and an input / output device 840. Each of the components 810, 820, 830, and 840 can be interconnected, for example, via a system bus 850. In some embodiments, the computer system 800 can be used to control the operation of a spectrometer. For example, Figure 1 The illustrated electronic control device 110 may include a computer system 800 to control the operation of one or more components of the spectrometer and / or process measurement data. A processor 810 is capable of processing instructions for execution within the system 800. In some embodiments, the processor 810 is a single-threaded processor, a multi-threaded processor, or another type of processor. The processor 810 is capable of processing instructions stored in a memory 820 or on a storage device 830. The memory 820 and the storage device 830 can store information within the system 800.

[0111] Input / output devices 840 provide input / output operations for system 800. In some embodiments, input / output devices 840 may include one or more of a network interface device (e.g., an Ethernet card), a serial communication device (e.g., an RS-232 port), and / or a wireless interface device (e.g., an 802.11 card, a 3G wireless modem, a 4G wireless modem, a 5G wireless modem, etc.). In some embodiments, input / output devices may include driver devices configured to receive input data and send output data to other input / output devices (e.g., a keyboard, a printer, and a display device 860). In some embodiments, mobile computing devices, mobile communication devices, and other devices may be used.

[0112] Although this specification contains many details, these details should not be construed as limitations on the scope of what is claimed, but rather as descriptions of features specific to particular examples. Certain features described in this specification in the context of separate embodiments may also be combined. Conversely, various features described in the context of a single embodiment may also be implemented separately or in any suitable subcombination in multiple embodiments.

[0113] A number of embodiments have been described. However, various modifications may be made without departing from the scope of this disclosure. Therefore, other embodiments are within the scope of the following claims.

Claims

1. A self-calibrating spectral sensor system comprising: a housing defining the cavity and the aperture; a photodetector disposed within the cavity; a first light source disposed within the cavity; a voltage-tunable interferometer disposed within the cavity between the aperture, the photodetector, and the first light source; as well as An electronic control device operable to: By varying the input voltage applied to the interferometer, causing the first light source to emit light toward the interferometer while varying the input voltage applied to the interferometer, and measuring light reflected from the interferometer using the photodetector, determining a calibrated input voltage based on light reflected from the interferometer and measured by the photodetector, applying the calibrated input voltage to the interferometer, and One or more spectral measurements are obtained using the photodetector while applying the calibrated input voltage to the interferometer.

2. The system of claim 1 , wherein the electronic control device is operable to determine the calibrated input voltage by determining a value of the input voltage corresponding to a minimum intensity of the measured light reflected from the interferometer.

3. The system of claim 2, wherein the electronic control device is operable to determine the calibrated input voltage by determining that the value of the input voltage corresponding to the minimum intensity of the measured light reflected from the interferometer is the calibrated input voltage. The system of claim 1 , wherein the first light source comprises a plurality of light emitting elements.

5. The system of claim 4, wherein the electronic control device is operable to cause the first light source to emit light toward the interferometer by causing the plurality of light emitting elements to emit light in sequence.

6. The system of claim 4, wherein the electronic control device is operable to cause the first light source to emit light toward the interferometer by causing the plurality of light emitting elements to emit light simultaneously.

7. The system of claim 1, wherein the first light source comprises one or more vertical cavity surface emitting laser emitters.

8. The system of claim 1, wherein the interferometer comprises a Fabry-Perot interferometer.

9. The system of claim 1 , further comprising a second light source disposed outside the cavity, and wherein the electronic control device is operable to obtain the one or more spectral measurements by: causing the second light source to emit sample light toward the object, and Sample light reflected from the object is measured using the photodetector.

10. The system of claim 9, wherein the first light source is operable to emit light within a first wavelength range, wherein the second light source is operable to emit light within a second wavelength range, and wherein the first wavelength range is different from the second wavelength range. The system of claim 10 , wherein the first wavelength range is narrower than the second wavelength range.

12. The system of claim 1, further comprising a host device, and The housing, the photodetector, the interferometer, the light source and the electronic control device are at least partially disposed in the host device.

13. The system of claim 12, wherein the host device is at least one of a smartphone or a wearable device.

14. A method for operating a self-calibrating spectral sensor system, comprising: changing an input voltage applied to a voltage-tunable interferometer disposed within the cavity; While varying the input voltage applied to the interferometer: transmitting light from a light source disposed within the cavity toward the interferometer, and measuring light reflected from the interferometer using a photodetector disposed within the cavity; determining a calibrated input voltage based on the measured light reflected from the interferometer; applying the calibrated input voltage to the interferometer; as well as One or more spectral measurements are obtained using the photodetector while applying the calibrated input voltage to the interferometer.

15. The method of claim 14, wherein determining the calibrated input voltage comprises: A value of the input voltage corresponding to a minimum intensity of light measured reflected from the interferometer is determined.

16. The method of claim 15, wherein determining the calibrated input voltage comprises: The value of the input voltage corresponding to the minimum intensity of the light reflected from the interferometer measured is determined to be the calibrated input voltage. The method of claim 14 , wherein emitting light into the interferometer comprises emitting light sequentially from a plurality of light emitting elements. The method of claim 14 , wherein emitting light toward the interferometer comprises emitting light simultaneously by a plurality of light emitting elements.

19. The method of claim 14, wherein obtaining the one or more spectral measurements comprises: emitting sample light toward the object, and Sample light reflected from the object is measured.

20. The method of claim 19, wherein the light emitted to the interferometer is within a first wavelength range, wherein the sample light is within a second wavelength range, and wherein the first wavelength range is different from the second wavelength range. The method of claim 20 , wherein the first wavelength range is narrower than the second wavelength range.

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