Particle and gas detection method and apparatus

Abstract

It solves the problems of related devices. An apparatus for detecting a property of a gas includes a light source (20) configured to emit light along at least one propagation axis (30). The apparatus includes a light detection device (40) including a light sensor (70) configured to output a sensor signal (75) and a lens device (50) having a lens surface (60) and configured to direct light emitted from the light source (20) and scattered by the gas to the light sensor (70). The apparatus further includes an actuator assembly (110) configured to move the light sensor (70) in a direction parallel to at least a first axis (150). The first axis (150), the propagation axis (30), and the lens surface (60) intersect such that the Scheimpflug condition (61) is achieved.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE This disclosure relates to laser projection systems, and more particularly to systems for detecting gases and gas properties. [Background technology]

[0002] LIDAR, or laser radar, is an optical detection and ranging device that can be used in a wide range of environments, from industrial furnaces to ecosystem monitoring. Unlike currently popular topographic LIDAR systems that detect and range hard targets, atmospheric LIDAR is sensitive enough to acquire continuous molecular echoes from perfectly clean air. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] US 11,169,272 Summary of the Invention [Problem to be solved by the invention]

[0004] Differential Absorption LIDAR (DIAL) is a type of highly specific atmospheric LIDAR method. With this method, it is possible to obtain the molecular absorption lines and concentration characteristics of a target-specific gas for a pulsed wavelength-variable laser. In practice, high peak power (MW), short pulses (ns), narrow bandwidth (<pm), and wavelength variability are mutually contradictory. Such a DIAL system generally requires a small team of laser physics doctors for its operation. Some progress has been reported on a lighter and smaller DIAL system using a micro LIDAR, but its time resolution is still on the order of several tens of minutes. Therefore, the DIAL system is extremely expensive and there are only a handful of operations worldwide. The low resolution, (high) cost, and bulkiness of the DIAL system hinder many practical applications such as industrial process optimization and mapping of greenhouse gas sources and flows.

[0005] A known alternative LIDAR method is described in U.S. Pat. No. 1,169,272. This document describes an optical device for using the Scheimpflug condition to analyze gas absorption lines at different distances within the same field of view. One problem with this device is that the system requires a complex optical sensor device suitable for focusing and sampling the received light corresponding to different distances. Such a system additionally requires the satisfaction of several conditions, such as the Scheimpflug and hinge rules, during operation. However, operational flexibility is very limited, and parameters cannot be easily changed during runtime because the optical conditions must be met. Furthermore, this type of array or two-dimensional imaging sensor can be very expensive, especially for wavelengths longer than the silicon wavelength, due to the kHz speed requirements. Furthermore, such devices are typically inherently coupled to the imaging sensor and processing, which imposes non-trivial demands on the sensor assembly and the processing unit in terms of speed. This means that installation, operation and maintenance can be complex and time consuming.

[0006] The examples of the present disclosure aim to address the above problems. [Means for solving the problem]

[0007] According to one aspect of the present disclosure, there is provided an apparatus for detecting a property of a gas, the apparatus comprising: a light source configured to emit light along at least one propagation axis; a light sensor configured to output a sensor signal; and a light detection device including a lens device including a lens surface and configured to direct light emitted from the light source and scattered by the gas toward the light sensor; and an actuator assembly configured to move the light sensor in a direction parallel to at least a first axis, wherein the first axis, the propagation axis, and the lens surface intersect such that a Scheimpflug condition is achieved.

[0008] Optionally, the actuator assembly is further configured to move the light sensor in a direction parallel to a second axis corresponding to an optical axis of the lens arrangement.

[0009] Optionally, the actuator assembly is further configured to move the optical sensor in a direction parallel to a third axis orthogonal to the second axis and in a plane defined by the first axis and the second axis.

[0010] Optionally, the actuator assembly is configured to move the optical sensor in a direction parallel to a fourth axis that is normal to a plane defined by the first axis and the second axis.

[0011] Optionally, the optical sensor is disposed in a sensor assembly.

[0012] Optionally, the light sensor is movable relative to the sensor assembly, and the actuator assembly includes a first actuator configured to move the light sensor.

[0013] Optionally, the sensor assembly is movable relative to the housing of the device, and the actuator assembly includes a second actuator configured to move the sensor assembly.

[0014] Optionally, the sensor assembly is movable relative to the housing of the device along a rail.

[0015] Optionally, the light sensor comprises at least one of a single pixel, a quadrant of pixels, an array of pixels, a pixel matrix, a position sensitive device (PSD) pixel.

[0016] Optionally, the light sensor includes at least one column of pixels aligned parallel to the first axis.

[0017] Optionally, the photosensor includes at least one row of pixels aligned parallel to a fourth axis.

[0018] Optionally, the optical sensor comprises at least one of a photodiode, an avalanche photodiode, a photomultiplier tube (PMT), and a CMOS sensor.

[0019] Optionally, the optical sensor comprises at least one of a transimpedance amplifier, a free silicon amplifier, a current amplifier, and a dynode amplifier.

[0020] Optionally, the optical sensor is configured to detect signals produced by at least one of wavelength modulation spectroscopy, direct absorption spectroscopy and / or frequency modulation spectroscopy.

[0021] Optionally, the light source is a tunable laser diode.

[0022] Optionally, the light source is controlled in a TDLAS manner.

[0023] Optionally, the light source is controlled in a DIAL manner.

[0024] Optionally, the light source comprises an array of individual light sources arranged parallel to a fifth axis or parallel to a fourth axis orthogonal to the axis of propagation.

[0025] Optionally, the light sensor comprises a single sensor pixel.

[0026] Optionally, the apparatus includes a sensor window positioned between the light sensor and the lens arrangement.

[0027] Optionally, the sensor window includes a slit having an adjustable width in a direction along the first axis.

[0028] In another aspect of the present disclosure, a method for detecting a property of a gas is provided, the method including: emitting light along at least one propagation axis; directing light scattered by the gas toward a light sensor using a lens device having a lens surface; and imaging a volume of the gas at a specific distance from the device by moving the light sensor to a corresponding position along the first axis, wherein the first axis, the propagation axis, and the lens surface intersect such that the Scheimpflug condition is met.

[0029] These and other aspects, features, and possible advantages of the example or embodiments of the present disclosure will be apparent and will become apparent from the following description of the example or embodiments of the present disclosure, which description refers to the accompanying drawings. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a schematic plan view of an apparatus according to an example of the present disclosure. [Figure 2] FIG. 1 is a diagram of an application example according to an example of the present disclosure. [Figure 3] 1 is a schematic plan view of an apparatus according to an example of the present disclosure. [Figure 4] 1 is a diagram of an apparatus according to an example of the present disclosure. [Figure 5a] 1 is a schematic plan view of an apparatus according to an example of the present disclosure. [Figure 5b] 1 is a schematic plan view of an apparatus according to an example of the present disclosure. [Figure 6] 1 is a schematic perspective view of an apparatus according to an example of the present disclosure; [Figure 7a] 1 is an enlarged view of a portion of an apparatus according to an example of the present disclosure. [Figure 7b] 1 is an enlarged view of a portion of an apparatus according to an example of the present disclosure. [Figure 8] FIG. 10 is another enlarged view of a portion of an apparatus according to an example of the present disclosure. [Figure 9a] FIG. 10 is another enlarged view of a portion of an apparatus according to an example of the present disclosure. [Figure 9b] FIG. 10 is another enlarged view of a portion of an apparatus according to an example of the present disclosure. [Figure 10] 1 is a flowchart of a method according to an example of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0031] Below, examples of the present disclosure are provided for one particular example of a gas and particle detection device 100. Throughout the specification, the same drawing reference numerals are used to identify corresponding elements.

[0032] FIG. 1 illustrates one embodiment of the device 100. In some examples, the device 100 is a gas detection device 100, and in some examples, the device 100 is a particle 90 detection device (particle detection device) 100. The device 100 is configured to direct light from a light source 20 and receive scattered light from one or more particles 90. The one or more particles 90 are gases or hard matter that are remote from the device 100. This can be both gas particles 90 and / or hard particles 90. The one or more particles 90 can be ozone, nitrogen oxides (e.g., NO ), or other gases. X ), sulfur oxides (e.g., SO X), water, oxygen, nitrogen, hydrogen (H), CO, CO, CH, acetylene CH, formaldehyde HCO, hydrogen sulfide HS, hydrogen chloride HCl, ammonia NH, ethane CH, hydrogen fluoride HF, or any other gas naturally occurring or emitted in the atmosphere. In some other examples, one or more particles 90 may additionally or alternatively be particulate contaminants, such as dust, soot, or smoke.

[0033] In some instances, one or more particles 90 · Coarse particles with a diameter of more than 10 μm 90; ·(PM 10-2.5 Coarse particles 90 (also known as coarse particles 90): particles 90 having a diameter generally greater than 2.5 μm and less than or equal to 10 μm; ·(PM 2.5 Also known as) fine particles 90: particles 90 generally having a diameter of 2.5 μm or less; Ultrafine particles and nanoparticles with a diameter of less than 2.5 μm (nanoparticles) It could be.

[0034] In general, the identification (detection) of coarse particles 90, fine particles 90, ultrafine particles 90, and nanoparticles 90 is desirable because these particles 90 can enter the lungs and damage the respiratory system. Furthermore, even ignoring the impact of particles 90 on human health, the identification (detection) and monitoring of particles 90 is extremely important for industries where particles 90 directly affect the quality of products, such as the processing industry and cleanroom environments. Particles 90 can include one or more of sulfate ions, nitrate ions, ammonium ions, elemental carbon ions, organic carbon ions, silicon ions, and sodium ions. In some examples, particles 90 can be any particles 90 in the atmosphere having the above sizes. Measuring the size of particles 90 is well known and will not be further described.

[0035] The apparatus 100 includes a data processing device 10 that, during operation, is configured to send control signals to one or more components of the apparatus 100. The data processing device 10 is also configured to generate an indication of whether one or more particles 90 are detected in the gas. In this manner, the data processing device 10 is configured to drive the light source 20 and process the sensor signal 75 to determine the properties of the gas.

[0036] In some examples, data processing device 10 may be implemented by dedicated software (or firmware) running on one or more general-purpose or special-purpose computing devices (computers) 10. In this sense, the "elements" or "means" of such computing devices 10 may be understood to be conceptually equivalent to respective method steps; however, there is not necessarily a one-to-one correspondence between elements / means and specific pieces of hardware or software routines. A piece of hardware may include different elements / means. For example, a processing unit may function as one element / means when executing one instruction, and as another element / means when executing another instruction. Furthermore, one element / means may be implemented by one instruction in some cases and by multiple instructions in other cases. Such a software-controlled computing device 10 may include one or more processing units, such as a CPU (“Central Processing Unit”), DSP (“Digital Signal Processor”), ASIC (“Application-Specific Integrated Circuit”), analog and / or digital discrete components, or other programmable logic devices 10 such as an FPGA (“Field Programmable Gate Array”). The data processing device 10 may further include a system memory and a system bus that couples various system components, including the system memory, to the processing unit. The system bus may be any of several types of bus structures, including a memory bus or memory controller, a peripheral bus, and a local bus, using any of a variety of bus architectures. The system memory may include computer storage media in the form of volatile and / or nonvolatile memory, such as read-only memory (ROM), random access memory (RAM), and flash memory.The dedicated software may be stored in system memory or other removable / non-removable, volatile / non-volatile computer storage media included in or accessible to computing device 10, such as magnetic media, optical media, flash memory cards, digital tape, solid state RAM, solid state ROM, etc. Data processing device 10 may include one or more communication interfaces, such as a serial interface, a parallel interface, a USB interface, a wireless interface, a network adapter, etc., and one or more data acquisition devices

[10] , such as an analog-to-digital converter. The dedicated software may be provided on any suitable computer-readable medium, including recording media and read-only memory, of data processing device 10.

[0037] Distinguishing between co-polarized and de-polarized light in LIDAR can provide microstructural information about LIDAR targets. Single-scattering aerosol LIDAR can be defined as a type of atmospheric LIDAR sensitive to receiving echoes from clean air. In single-scattering aerosol LIDAR, the depolarization ratio (DoLP), defined as the intensity ratio between the perpendicular and parallel components of scattered light, allows for differentiation between spherical particles 90 and particles with edges or irregular shapes, such as droplets and ice crystals. Furthermore, particle sizing can be determined based on signal intensity by distinguishing signals from any of several wavelengths or with a priori knowledge of the particle distribution in the gas.

[0038] The data processing device 10 is configured to send a control signal 25 to the light source 20 such that the light source 20 emits light along a propagation axis 30 .

[0039] Light emitted from the light source 20 travels along a propagation axis 30 until it reaches a particle 90 in the atmosphere. At least a portion of the emitted light from the light source 20 is backscattered from the particle 90 along a second axis 160 towards the light detection device 40. The second axis 160 is the received light path axis 160, e.g., the path that the scattered light follows from the particle 90 to the device 100.

[0040] The light detection device 40 includes a lens arrangement 50 having a lens surface 60. The lens arrangement 50 shown in Figure 1 is aligned along a second axis 160. While the second axis 160 is effectively one backscattering axis, there may be multiple different backscattering axes from different particles 90 at different distances from the light detection device 40. The lens arrangement 50 is configured to direct light scattered by the scattering particles 90 towards the light sensor 70.

[0041] In one embodiment, the optical sensor 70 has an array of pixels aligned with an image plane and is configured to output a sensor signal 75 to the data processing device 10. The image plane may be aligned along a first axis 150. The first axis 150, the lens surface 60, and the propagation axis 30 intersect at a first intersection point 61 such that the Scheimpflug condition is met.

[0042] Furthermore, in some examples, the displaced image plane 82, the front focal plane 62 of the lens arrangement 50, and the propagation axis 30 of the light source 20 optionally satisfy a hinge rule at a second intersection 63. The data processing device 10 processes the sensor signals 75 from the light detection arrangement 40 to determine pixel signals for one or more pixels of the light sensor 70. Satisfying the hinge rule relationship between the light source 20 and the light detection arrangement 40 is optional.

[0043] The lens arrangement 50 may include at least one of an imaging lens including one or more refractive components and a mirror lens including catadioptric components. The lens arrangement 50 may include an F-number, F / #, an aperture, TIFF2025536381000002.tif716 and focal length frec Lens apparatus 50 may further include one or more optical filters. In some examples, the optical filters include interference-type optical filters, and in some examples, the optical filters include color-coated optical filters, which may be bandpass, shortpass, longpass, or a combination thereof.

[0044] The light sensor 70 may be a CMOS array detector or a low pixel count array detector, or a single pixel detector such as a photodiode. By making the light sensor 70 a single pixel, the light sensor 70 is less complex. The light sensor 70 is optionally placed after the sensor window 702. Furthermore, the pixels of the light sensor 70 are smaller, thereby improving resolution. The light sensor 70 is movable, and the movement of the light sensor 70 is described in more detail below with reference to Figures 3, 4, 5a, 5b and 6. The light sensor 70 is further configured to output a sensor signal 75. The movable light sensor 70 may be configured to move along the sensor length. TIFF2025536381000003.tif721, which has the sensor tilt angle (θ) and a number of pixels. The pixels are pixel heights. TIFF2025536381000004.tif817 and pixel width (w pix )

[0045] In some examples, the photosensor 70 includes a single movable pixel. In other examples, the height and width of the movable pixel are variable through one or more slits in front of the pixel and behind the sensor window 702. The sensor window 702 is shown in FIGS. 7a and 7b and described in more detail below. The sensor window 702 can optionally include an adjustable slit component configured to control scattered light received by the photosensor 70. The adjustable slit component is described in more detail below with respect to FIGS. 7a and 7b. In other examples, the photosensor 70 includes a small array of movable pixels. For example, the photosensor 70 includes a 2x2, 3x3, 4x4, 5x5, or nxn array of pixels, where n can be any number from 1 to 20, and the height and width of the array are variable through one or more slits in front of the pixel and behind the sensor window 702.

[0046] In other less preferred examples, the optical sensor 70 may include a movable linear CMOS array detector and may include at least one row of pixels aligned with an image plane aligned with the first axis 150. The movable linear CMOS array detector optical sensor 70 is further configured to output a sensor signal 75. The optical sensor 70 may include a sensor length TIFF2025536381000005.tif721, which has the sensor tilt angle (θ) and a number of pixels. The pixels are pixel heights. TIFF2025536381000006.tif817 and pixel width (w pix )

[0047] After applying the Scheimpflug principle or the Scheimpflug principle and hinge law, several design parameters remain to be considered. The device 100 may be designed with the following variables in mind: transmitter-receiver baseline separation distance TIFF2025536381000007.tif79, Receiver focal length f rec, and the tilt θ of the sensor relative to the lens plane 60. The transmitter-receiver baseline separation distance is defined as the perpendicular distance between the lens assembly 50 and the propagation axis 30. The receiver focal length is defined as the perpendicular distance between the lens plane 60 and the front focal plane 62.

[0048] The device 100 includes an actuator assembly 110 configured to move the light sensor 70 parallel to or along the first axis 150. This means that rather than providing a larger sensor spread over a larger area, the position of the light sensor 70 is adjustable. Thus, the light sensor 70 can be simulated as a larger sensor by using the actuator assembly 110 to move the light sensor 70 through a volume of space.

[0049] This simplifies the operation of the device 100 by allowing the use of a smaller, less complex optical sensor 70. Because the optical sensor 70 moves along the first axis 150, the Scheimpflug principle and hinge law can be easily maintained without the use of a complex sensor. Adjusting the lens assembly 50 to change the focus onto the optical sensor 70 makes the optical arrangement more complex, increasing the likelihood that the Scheimpflug principle and / or hinge law will not be maintained over a wide range of configurations.

[0050] 2 shows the photodetector device 40 of the device 100. The photodetector device 40 includes a base 200, which is a rigid structure for mounting one or more components of the device 100 thereto. The base 200 is a planar structure extending in a plane parallel to the first axis 150 and the second axis 160. In some examples, the base 200 is a metal structure or other suitable rigid structure. This means that the components mounted on the base 200 can be fixed relative to each other such that their spatial and optical relationships are maintained.

[0051] Base 200 itself may optionally include one or more mounting holes 202 for securing device 100 to a work surface (not shown) or other object. Alternatively, mounting holes 202 are for attaching a lid (not shown) to protect device 100 during use. Mounting holes 202 are optionally located at the corners of base 200 and include threaded holes 706 for receiving threaded bolts (not shown).

[0052] Base 200 optionally includes a component mounting plate 204 configured to receive components of apparatus 100. In some examples, component mounting plate 204 is machined from a stiff metal plate with predetermined mounting locations for receiving components of apparatus 100. In other examples, base 200 does not have component mounting plate 204, and instead, components are mounted directly to base 200.

[0053] As shown in Figure 2, the lens device 50 is attached to the first end 206 of the base 200. As previously mentioned, the lens device 50 may include at least one of an imaging lens, which includes one or more optical refractive components, and a mirror lens, which includes a catadioptric system. The lens device 50 may be configured with an F-number, F / #, an aperture, TIFF2025536381000008.tif716, and focal length f rec Lens apparatus 50 may further include one or more optical filters. In some examples, the optical filters include interference-type optical filters, and in some examples, the optical filters include color-coated optical filters, and the optical filters may be band-pass, short-pass, long-pass, or a combination of these types. Lens apparatus 50 is aligned on second axis 160.

[0054] Lens arrangement 50 is also shown in Figure 8, and will now be briefly described with reference to Figure 8, which shows a perspective view of lens arrangement 50.

[0055] Lens apparatus 50 includes a lens frame 800 to which one or more lenses and one or more optical filters (not shown for clarity) are attached. Lens frame 800 includes two mounting bolts 802, 804 for attaching lens apparatus 50 to corresponding mounting holes in optional component mounting plate 204.

[0056] In some examples, the lens arrangement 50 includes an adjustment mechanism 806. The adjustment mechanism 806 is configured to fine-tune the position of the lens arrangement 50 relative to the base 200 after the lens arrangement 50 is attached to the base 200 and, optionally, the component mounting plate 204. In some examples, the adjustment mechanism 806 is configured to move the lens arrangement 50 in a direction parallel to the fourth axis 180, which is an axis perpendicular to the second axis 160. In this manner, the adjustment mechanism 806 is configured to adjust the height of the lens arrangement 50 above the base 200, which helps align the lens arrangement 50 on the second axis 160. In some examples, a means for adjusting the position of the lens arrangement 50 relative to the base 200, such as the adjustment mechanism 806, is motorized to allow for controlled and / or automatic adjustment. In some examples, the adjustment mechanism 806 is an actuator, such as a stepper motor. However, in other examples, the adjustment mechanism 806 is a manually adjusted adjustment screw. This allows for optimization of maximizing the overlap of the imaged radiation 30 along the second axis 160 and the light (30) collected by the light sensor 70 (imaged radiation).

[0057] 2 is decoupled from the position of the lens arrangement 50. This means that even if there is some misalignment of the light sensor 70, the misalignment can be corrected by the adjustment mechanism 806 of the lens arrangement 50 when the light sensor 70 is moved along the first axis 150. The misalignment can be simultaneously corrected by the adjustment mechanism 806 when the light sensor 70 is moved. This is in contrast to prior art solutions in which the position of the lens arrangement cannot be decoupled from the position of the light sensor in a conventional array sensor, and therefore the positional height of the lens arrangement needs to be aligned with the emitted light.

[0058] Returning to FIG. 2 , the light source 20 will now be described in more detail. In some examples, the light source 20 is a tunable diode laser. The light source 20 may include one or more of a narrowband single-mode light source, a broadband multimode light source, a high-power multimode diode laser, a high-power multimode fiber laser, a high-power tapered amplifier seeded with a tunable single-mode diode laser, a high-power fiber amplifier seeded with a tunable single-mode diode laser, and a high-power tunable CO or solid-state crystal laser. In fact, the light source 20 may be any light source 20 suitable for generating light to be delivered to the gas to be analyzed. In other examples, the light source 20 may be other types of light sources 20, such as a non-coherent light source such as an LED or an incandescent light bulb.

[0059] In one embodiment, the light source 20 is a 10 W, 761 nm, 2 nm FWHM (full width at half maximum) CW (continuous wave) multimode laser diode. Acquisition of approximately 400 elastic spectral bands is performed in the 760 nm to 762 nm range. This allows for the resolution of a large number of O2 absorption lines. While O2 absorption lines are mentioned, this is exemplary; other absorption lines of other gas molecules or particles 90 molecules can be resolved. For example, any absorption line of a gas or the light scattering characteristics of particles 90 mentioned in this disclosure can be detected. Absorption lines provide information about air concentration, pressure, and temperature. Generally, the O2 concentration in the atmosphere is 21%, but local depletion after metabolism or combustion can create O2 holes. A decrease in O2 corresponds to an increase in CO2 and H2O. Therefore, a decrease in O2 can provide information about the current metabolic rate, for example. Alternatively, determining (measuring) engine fuel consumption can provide a means for standardizing aerosol emissions or evaluating engine quality. This technique allows for indirect assessment of CO2, pressure and temperature profiling.

[0060] To ensure good gas sensitivity of light source 20, data processing device 10 is configured to provide control of one or more parameters of light source 20. In some examples, data processing device 10 is configured to provide fine control of temperature, current, and voltage driving characteristics of light source 20. Furthermore, data processing device 10 is configured to provide interference prevention for light source 20.

[0061] In some examples, the data processing device 10 is optionally configured to provide temperature control of the light source 20, which is achieved by using a thermistor (not shown), such as a negative temperature coefficient (NTC) thermistor, and a thermoelectric cooler (TEC) in a feedback loop. High-precision thermistor sampling is well known and can be achieved using a biased or unbiased scheme and sampled by an analog-to-digital converter. The temperature can then be easily obtained by linearizing the voltage.

[0062] However, controlling and driving a TEC is rather challenging because large currents must be switched in a controlled manner in two directions: one for heating and the other for cooling. The large currents (up to several amperes) and the required speeds typically result in an H-bridge configuration, similar to driving an electric motor. However, this approach has significant drawbacks in highly sensitive optical systems such as those described in this disclosure because the large currents require switching electronics that can easily induce unwanted noise caused by both the switching hardware itself and the large currents.

[0063] Thus, in some examples, data processing device 10 is optionally configured to generate and control current by using a step-down regulator or step-down converter (not shown). Such converters typically cannot sink current and are not suitable for current-driven applications. However, in one example, one or more step-down converters are used in a synchronous topology, since they can both sink and source current. By using two such step-down converters, each output voltage can be adjusted independently, thus achieving control of the direction of current flow. The advantage is the high frequency at which these devices inherently operate, which can be in the range of several MHz, making them essentially quieter in terms of equipment operating at lower frequencies. This is a major advantage and important for achieving good sensitivity. Furthermore, this example also allows for a smaller footprint because fewer components are required. In addition, the driving scheme does not require dead-time insertion, as is required in the well-known H-bridge configuration, and can operate at 100% duty cycle, providing a more energy-efficient and noise-free solution.

[0064] In another example, the drive configuration of light source 20 is optionally addressed. Current implementations often rely on manual or semi-automated calibration and testing procedures by an operator during manufacturing, where drive characteristics, such as voltage, current, temperature, and relaxation of optical interference characteristics, are determined. This is completely decoupled from light source 20 itself, making this a cumbersome, time-consuming, costly, and human-error-prone process.

[0065] In this example, a storage device (not shown) is optionally integrated into the light source itself. Such storage device may be read-only memory, such as EEPROM, flash, F-RAM, or other types of persistent storage. Alternatively, such storage device may be a read-write device with persistent storage characteristics. The storage device contains light source model and calibration values ​​that can be read by the instrument to automate instrument testing and calibration steps. Such information may be important for the optical gas detection subject matter described in this disclosure, and slight deviations from optimal conditions can easily significantly degrade the quality and performance of the instrument. In another example, data processing device 10 can write data back to the storage device; in this way, identified potential problems, e.g., related to lifetime, aging, current, voltage, and temperature deviations, are logged in light source 20, which can be used to improve processes, troubleshooting, and traceability.

[0066] In another example, mitigation against optical interference can be optionally addressed. This can be very important for long-coherence-length light sources 20, i.e., narrow-bandwidth light sources 20 for gas and particle detection. In some examples, the data processing device 10 is configured to provide a form of dithering used to average out laser speckle, which is the dominant optical noise contributor in the instrument. Dithering can be achieved by movement of a lens close to the light source 20, the light source 20 itself, movement of a diffusive element, or the entire light source 20 assembly itself. This can be achieved by motors, piezoelectric crystals, liquid lenses, or impulse devices. Driving these devices often requires very high voltages, often in the range of ±100 V. Because the voltage range differs significantly from the rest of the sensitive hardware, noise immunity and configurability are critical to the design.

[0067] For example, hardware reconfiguration is always necessary if the load changes or deteriorates over time. In some examples, a universal, integrated solution is optionally provided that can drive loads regardless of their electrical characteristics, such as different capacitances, resistances, and inductances. This is achieved by a buck-boost converter (not shown) that acts as a high-voltage amplifier. Such a buck-boost converter is used, for example, in haptic devices, providing automatic feedback and loops for different types of loads that may also be time-varying simultaneously when different drive patterns are used. In some examples, this buck-boost converter driver is combined with a simple digital-to-analog converter that generates an arbitrary waveform that the high-voltage buck-boost converter outputs to a dithering device, making it load-independent and self-referenced to ensure proper function and operation of the dithering device.

[0068] In some examples, the data processing device 10 is configured to send control signals 25 to the laser diode of the light source 20 to control the laser diode in a TDLAS (Tunable Diode Laser Absorption Spectroscopy) mode of operation and / or a DIAL (Differential Absorption Lidar) mode of operation. Both the TDLAS and DIAL modes of operation are known and will not be described further. In some examples, the control signals sent from the data processing device 10 to the light source 20 may be one or more of control signals configured to control temperature (double buck), dithering (high voltage amplifier), and / or light source drive current (embedded data storage), as previously described.

[0069] 9a and 9b show an example of a light source 20 in plan and side views, respectively.

[0070] In Figure 2, the light source 20 is shown positioned to the side of the base 200. The position of the light source 200

[20] is fixed relative to the base 200 during operation. In some examples, the light source 20 is fixedly attached to the base 200 or to an accessory that is fixed relative to the base 200, as shown in Figures 9a and 9b.

[0071] For example, in some instances, the base 200 can extend below the light source 20 so that the light source 20 can be secured to an optional component mounting plate 204. As shown in FIG. 9 a, the base 200 of the light detection device 40 is coupled to a lateral rail assembly 900. The lateral rail assembly 900 is fixed relative to the base 200. The light source 20 is mounted on a light source carriage 902 that is movable on the lateral rail assembly 900. The light source carriage 902 is configured to be fixed relative to the lateral rail assembly 900 by a clamp (not shown) or other suitable releasable fastener. The lateral rail assembly 900 includes a pair of rails 904 along which the light source carriage 902 slides. The rails 904 allow movement in a direction along a fifth axis 190 that is angled relative to the propagation axis 30. In some examples, the fifth axis 190 is perpendicular to the propagation axis 30, while in other examples, the fifth axis 190 can be angled at any suitable angle relative to the propagation axis 30. Movement of the light source carriage 902 along the fifth axis 190 means that the propagation axis 30 can move relative to the light detection device 40. In other examples, the light source carriage 902 also allows relative movement of the light source 20 and the propagation axis 30 relative to the light detection device 40 along different axes and different directions. The light source carriage 902 optionally includes a pivot mount 908 that allows the light source 20 to pivot in a first pivot direction 906 relative to the light source carriage 902, which can tilt the propagation axis 30 relative to the base 200. Additionally or alternatively, the pivot mount 908 allows the light source 20 to pivot in a second pivot direction 910 relative to the light source carriage 902. In this manner, the first pivot direction 906 and the second pivot direction 910 are orthogonal. The first pivot direction 906 is perpendicular to the plane of the light source carriage 902. The second pivot direction 910 is parallel to the plane of the light source carriage 902. In other examples, the pivot mount 908 allows for other movement relative to the light detection device 40. In other examples, additionally or alternatively, the light detection device 40 is configured to move relative to the light source 20.That is, light detector 40 is optionally configured to tilt, pivot, or rotate relative to light source 20 .

[0072] In some other instances, the light source carriage 902 and lateral rail assembly 900 are not used. Alternatively, the base 200 and light source 20 are both mounted to the same rigid object, such as a workbench.

[0073] In some examples, the light source 20 includes multiple individual light sources 20 arranged parallel to a fourth axis 180 that is perpendicular to the transmission axis 30. In some examples, additionally or alternatively, the light source 20 includes multiple individual light sources 20 arranged parallel to a fifth axis 190 that is perpendicular to the propagation axis 30. This means that multiple light beams can propagate along the propagation axis 30. The multiple light sources 20 can be the same or different. This can mean that the light source 20 includes a greater output power, or that multiple different frequency light sources 20 or multiple polarizations can be emitted simultaneously or temporally multiplexed, for example.

[0074] The light detection device 40 will now be described in more detail with reference to Figures 3 and 4. Figure 3 is a schematic diagram of the light detection device 40. Figure 4 is a plan view of the light detection device 40. The light detection device 40 includes a sensor assembly 120. The sensor assembly 120 is attached to the base 200 via a component mounting plate 204 at a second end 208 of the base 200.

[0075] The sensor assembly 120 is mounted to the component mounting plate 204 via a sensor carriage 400. The sensor carriage 400 can be fixed relative to the base 200. In some other examples described below with reference to Figures 5a, 5b, and 6, the sensor carriage 400 can be movable relative to the base 200.

[0076] 4, the sensor assembly 120 includes a sensor plate 212 (best shown in FIG. 7a) that is aligned with or parallel to the first axis 150. The face of the sensor plate 212 is aligned with the first axis 150.

[0077] The optical sensor 70 includes an optical sensor housing 210 slidably mounted along a sensor plate 212 of the sensor assembly 120 via at least one sensor rail 700, for example, a pair of sensor rails 700 (best shown in FIGS. 7a and 7b). The sensor plate 212 includes a sensor window 702. The sensor window 702 is elongated and extends in a direction parallel to the first axis 150. The sensor window is also configured to intersect the second axis 160, allowing backscattered light to be received through the sensor window 702. The optical sensor 70 directs the sensor window 702 toward the lens arrangement 50. The sensor window 702, as shown in FIG. 4, is separate from the optical sensor 70. In some other examples, the sensor window 702 is integrated into the optical sensor housing 210. In some examples, the sensor window 702 may be a circular hole rather than an elongated slot as shown in FIGS. 7a and 7b. In this case, the sensor window 702 is provided (formed) on an additional plate (not shown) attached to the light sensor housing 210. In this case, the sensor window 702 is fixed relative to the light sensor 70, and both the sensor window 702 and the light sensor 70 move together along the first axis 150. In some examples, the sensor window 702 optionally includes an adjustable slit component (not shown). The adjustable slit component is configured to change the position, size, and / or orientation of an aperture between the light sensor 70 and the lens arrangement 50. This means that the adjustable slit component can select the amount of scattered light received by the light sensor 70. In some examples, the adjustable slit component is integrated into the sensor window 702. Alternatively, the adjustable slit component is a separate element attached in front of the light sensor 70 or the sensor window 702.

[0078] The adjustable slit component includes an adjustable aperture configured to allow adjustment of the slit width. In some examples, the slit width extends in a direction parallel to the first axis 150, and the slit height extends along a direction parallel to the fourth axis 180. Thus, the adjustable slit component can selectively adjust the width of the slit in the direction of the first axis 150. This means that the adjustable slit component can be adjusted to provide the most relevant optical signal to the light sensor 70. The adjustable slit component includes a slit actuator (not shown) configured to adjust the size of the slit. The slit actuator can be operatively coupled to any suitable mechanism for adjusting the slit width, such as two movable plates, an iris, etc.

[0079] The optical sensor 70 is mounted on a pair of sensor rails 700 such that the optical sensor 70 is aligned with the sensor window 702. The optical sensor 70 is configured to be aligned with the sensor window 702 when the optical sensor 70 is moved relative to the sensor plate 212. The pair of sensor rails 700 ensure that the optical sensor 70 moves parallel to the first axis 150.

[0080] As described above, the optical sensor 70 is movable via the actuator assembly 110. In a first example, the optical sensor 70 is movable relative to the base 200 along a first axis 150. The movement of the optical sensor 70 is shown schematically in FIG. 3 by arrow 300. The actuator assembly 110 includes a first actuator 130 operatively coupled to an optical sensor housing 210, such that the optical sensor 70 moves relative to a sensor plate 212 when the first actuator 130 is actuated.

[0081] In some examples, the optical sensor 70 and the optical sensor housing 210 are attached to a rod 704 having a helical thread that is attached to a threaded hole 706 in the sensor plate 212. As the rod 704 rotates, the helical thread of the rod 704 moves in and out of the threaded hole 706 in the sensor plate 212. This causes the optical sensor 70 to move along the first axis 150 toward or away from the first intersection 61. This advantageously maintains the Scheimpflug condition 61. In some examples, the first actuator 130 is an electric motor (not shown) and includes a drive gear attached to a drive shaft of the electric motor that is operatively coupled to the helical thread. Thus, rotation of the drive shaft of the electric motor moves the rod 704, adjusting the position of the optical sensor 70.

[0082] In some other examples, first actuator 130 may be other types of actuators, such as a pneumatic linear actuator, a hydraulic linear actuator, a linear servo, a stepper motor, a piezoelectric motor, or any other suitable linear drive mechanism.

[0083] 3 and 4 depict device 100 in which optical sensor 70 is movable along only one degree of freedom, e.g., along first axis 150. In some other examples, optical sensor 70 is movable in multiple different directions in addition to being movable along first axis 150. Figures 5a and 5b show schematic configurations of device 100 in which optical sensor 70 is movable in more than one direction relative to light detection device 40.

[0084] 5a shows that the optical sensor 70 is movable along a first axis 150 and along or parallel to a second axis 160, which is the optical axis of the lens arrangement 50. The movement of the optical sensor 70 and the arrangement for providing the movement of the optical sensor 70 along the first axis 150 are the same as those described with reference to the previous figures.

[0085] Movement of the optical sensor 70 along the second axis 160 is provided by moving the sensor carriage 400 in a direction parallel to the second axis 160. The sensor carriage 400 includes a protruding foot (not shown) slidable within a carriage slot 402. The carriage slot 402 limits relative movement of the protruding foot from the sensor carriage 400 in a direction along or parallel to the second axis 160, as indicated by arrow 500. The sensor carriage 400 is operatively coupled to a second actuator 140. The second actuator 140 is configured to move the sensor carriage 400 toward the first end 206 of the base 200 or toward the second end 208 of the base 200. In some examples, the second actuator 140 is another linear actuator. In some examples, the second actuator 140 is the same as the first actuator 130. In some other examples, second actuator 140 may be any other suitable linear actuator, such as a pneumatic linear actuator, a hydraulic linear actuator, a linear servo, a stepper motor, a piezoelectric motor, or any other suitable linear actuation mechanism.

[0086] Because the optical sensor 70 is configured to move along the first axis 150 and the second axis 160, the optical sensor 70 is movable both parallel and perpendicular to the second axis 160. This means that the optical sensor 70 is movable to cover most of the light detection device 40.

[0087] FIG. 5b shows a configuration identical to that shown in FIG. 5a, except that the optical sensor 70 is configured to move in another direction. In this example, the actuator assembly 110 includes a third actuator (not shown). The third actuator is configured to move the optical sensor 70 along a third axis 170 or in a direction parallel to the third axis 170, as indicated by arrow 502. The third axis 170 is an axis perpendicular to the second axis 160, e.g., the optical axis of the lens arrangement 50. In some examples, a secondary sensor carriage (not shown) is attached to the sensor carriage 400. The secondary sensor carriage is attached to the sensor carriage 400 via a plurality of rails extending in a direction parallel to the third axis 170. The secondary sensor carriage is slidable relative to the sensor carriage 400 along a direction parallel to the third axis 170. The third actuator is identical to the second actuator 140 and is attached to the sensor carriage 400.

[0088] FIG. 6 illustrates a configuration identical to that illustrated in FIG. 5b, except that the optical sensor 70 is configured to move along another direction. In this example, the actuator assembly 110 includes a fourth actuator (not shown). The fourth actuator is configured to move the optical sensor 70 along a fourth axis 180 or in a direction parallel to the fourth axis 180, as indicated by arrow 600. The fourth axis 180 is an axis perpendicular to the second axis 160, e.g., the optical axis of the lens arrangement 50, and the third axis 170. In other words, moving the optical sensor 70 along the fourth axis 180 adjusts the height of the optical sensor 70 above the base 200. In some examples, the sensor carriage 400 includes a sensor plate 212 attached to the sensor carriage 400 via a scissor linkage, a worm gear motor, a stepper motor, or a piezo motor, and may be driven by the fourth actuator. These types of actuators, such as scissor linkages, worm gear motors, stepper motors, and piezo motors, can all be actively or passively locked into position. The sensor plate 212 is movable relative to the sensor carriage 400 along a direction parallel to the fourth axis 180 in response to extension and contraction of the scissor linkage. The fourth actuator is identical to the second actuator 140 and is attached to the sensor carriage 400. Alternatively, any other suitable mechanism can be used to adjust the height of the optical sensor 70 above the base 200.

[0089] In some examples, the light sensor 70 includes at least one of a single pixel, a quadrant of pixels, an array of pixels, a pixel matrix, and a position sensitive device (PSD) pixel. The light sensor 70 may have at least one column of pixels aligned parallel to the first axis 150. The light sensor 70 includes at least one row of pixels aligned parallel to the fourth axis 180.

[0090] In some examples, the optical sensor 70 includes at least one of a photodiode, an avalanche photodiode, or a photomultiplier tube (pmt). The optical sensor 70 may include at least one of a transimpedance amplifier, a free silicon amplifier, and a dynode amplifier.

[0091] In some examples, optical sensor 70 is configured to detect signals generated by at least one of wavelength modulation spectroscopy, direct absorption spectroscopy, and / or frequency modulation spectroscopy.

[0092] The operation of the device 100 will now be described with reference to Figure 10. Figure 10 shows a flow chart of an example of how the device 100 operates.

[0093] In one embodiment, a data processing device 10 is configured to operate the device 100. The data processing device 10 sends a control signal to emit light along the transmission axis 30 as shown in step 1000.

[0094] The data processing device 10 is configured to position (arrange) the optical sensor 70 and / or the sensor window 702 and / or the sensor window 702 (e.g., as shown in FIGS. 7a and 7b) at a predetermined position along a plane formed by the sensor axes, as shown in steps 1004, 1006, 1008, and 1010 and described in more detail below. The device 100 directs light scattered by the gas toward the optical sensor 70, as shown in step 1002. In some examples, the optical sensor 70 includes a single movable pixel. In this case, moving the sensor window 702 and / or the slit together with the optical sensor 70 enables better signal detection. Optionally, the slit width and sensor positions are adjusted to be individually optimized for a target volume in space, including distance.

[0095] The data processing device 10 is configured to image a volume of gas at a particular distance in step 1012. In step 1012, the data processing device 10 is optionally configured to process the sensor signal 75 to determine a signal S when the light source 20 is activated and to determine a background signal B when the light source 20 is not activated.

[0096] In step 1012, the data processing device 10 is also optionally configured to normalize the signal S using the background signal B. In one embodiment, the background signal B is subtracted from the signal S.

[0097] In step 1012, the data processing device 10 is optionally also configured to apply appropriate thresholds and corrections for non-constant range dependency. The result of the normalization step is an intensity signal as a function of sensor position, which needs to be converted into an intensity signal as a function of distance. Thus, this step involves converting the raw intensity signal as a function of sensor position into an intensity signal as a function of distance.

[0098] In step 1012, the data processing device 10 is also optionally configured to process the intensity signal as a function of distance to determine the presence of a gas absorption imprint by obtaining a baseline model available from a multimode setup or by scanning a single mode laser observing light that is in resonance and not in resonance with the gas of interest. The data processing device 10 can also optionally detect and analyze particles 90.

[0099] In step 1012, the data processing device 10 is optionally also configured to correlate the results of the processing step of the intensity signal as a function of distance with previously determined results for noise reduction and / or to provide time information regarding those results.

[0100] The data processing device 10 is further configured to repeat one or more of the above steps as necessary.

[0101] As mentioned above, the data processing device 10 is configured to perform processing steps to configure the device 100 to move the optical sensor 70 to the correct position in steps 1004, 1006, 1008 and 1010, which will be described in more detail (below).

[0102] The data processing device 10 is configured to send a control signal to the first actuator 130 to move the optical sensor 70 along the first axis 150, as shown in step 1004 of FIG. 10 . In some examples, the data processing device 10 receives a sensor signal 75 from the optical sensor 70 as the first actuator 130 moves the optical sensor 70 along the first axis 150. When the data processing device 10 determines that the optical sensor 70 is in the correct position along the first axis 150, the data processing device 10 sends a control signal to the first actuator 130. Movement along the first axis 150 corresponds to the distance of detected light scattered back from the particle 90 toward the optical detection device 40. In some examples, the data processing device 10 sends a control signal to the first actuator 130 to move the optical sensor 70 along the first axis 150. In other examples, the data processing device 10 moves the first actuator 130 over the entire distance (or range) of movement of the first axis 150. The data processing device 10 then determines the strength of the detected light signal scattered back from the particle 90 as a function of distance. In this manner, the data processing device 10 is configured to determine the distance of the particle 90 from the light detection device 40.

[0103] Once the data processing device 10 has moved the optical sensor 70 along the first axis 150 to the required position, the data processing device 10 is further configured to image a volume of gas at a particular distance from the device 100, as shown in step 1012. If the data processing device 10 is configured to only perform movement of the optical sensor 70 in the first axis 150, the data processing device 10 proceeds from step 1004 to step 1012, as indicated by the arrow connecting step 1004 and step 1012.

[0104] Additionally or alternatively, the data processing device 10 is configured to move the optical sensor 70 in the second axis 160, the third axis 170, and / or the fourth axis 180. In this case, the data processing device 10 proceeds from step 1004 to step 1006, step 1008, and step 1010. Furthermore, the data processing device 10 can skip from any of steps 1006, 1008, and 1010 to step 1012 without performing any of the other steps 1006, 1008, and 1010.

[0105] In some alternative examples, the data processing device 10 is configured to continuously scan the optical sensor 70 to sequentially acquire all distances by moving the optical sensor 70 along the first axis 150. In some examples, the data processing device 10 is configured to adjust the slit width of the adjustable slit component to increase the spatial resolution of the test volume at a particular distance.

[0106] In some examples, in steps 1002, 1004, 1006, 1008, or 1010, the data processing device 10 optionally sends a control signal to the slit actuator to fully open the slit. This results in a high signal and poor spatial resolution, but the data processing device 10 can perform a coarse scan along the first axis 150. The data processing device 10 then determines that the signals received in the narrow range are of interest. In this manner, the data processing device 10 is configured to "lock on" to a specific range (or distance) of interest. The data processing device 10 may use one or more parameters of the received optical signal, such as intensity, distance of the particle 90, etc., to select the specific range of interest. The data processing device 10 then sends a control signal to the slit actuator to narrow the slit width. By narrowing the slit width, the data processing device 10 is configured to improve the distance resolution while simultaneously increasing the data collection time.

[0107] Optionally, the data processing device 10 is further configured to send a control signal to the second actuator 140 to move the optical sensor 70 along the second axis 160. Optionally, the data processing device 10 is further configured to send a control signal to the third actuator to move the optical sensor 70 along the second axis 160. Optionally, the data processing device 10 is further configured to send a control signal to the fourth actuator to move the optical sensor 70 along the fourth axis 180. The data processing device 10 is configured to control the movement of the second actuator 140, the third actuator and the fourth actuator in the same manner as described for the first actuator 130.

[0108] The present disclosure has been described above primarily with reference to certain exemplary embodiments. However, as those skilled in the art will readily appreciate, embodiments other than those disclosed above are equally possible within the scope and spirit of the present disclosure, which is defined and limited only by the appended claims.

[0109] In another example, two or more examples are combined, i.e., features of one example can be combined with features of other examples.

[0110] Although the embodiments of the present disclosure have been described with particular reference to the illustrated embodiments, it will be apparent that variations and modifications can be made to the described embodiments within the scope of the present disclosure.

Claims

1. 1. An apparatus for detecting a property of a gas, comprising: The device (100) comprises: a light source (20) configured to emit light along at least one propagation axis (30); A light detection device (40), wherein the light detection device (40) an optical sensor (70) configured to output a sensor signal (75); and a lens device (50) including a lens surface (60) and configured to direct light emitted from the light source (20) and scattered by the gas toward the light sensor (70); Including, an actuator assembly (110) configured to move the optical sensor (70) in a direction parallel to at least a first axis (150); Including, The first axis (150), the propagation axis (30) and the lens surface (60) intersect so that the Scheimpflug condition (61) is met. An apparatus characterized by:

2. 10. The apparatus of claim 1, The actuator assembly (110) is further configured to move the optical sensor (70) in a direction parallel to a second axis (160) corresponding to the optical axis of the lens arrangement (50). An apparatus characterized by:

3. 3. The apparatus of claim 2, The actuator assembly (110) is further configured to move the optical sensor (70) in a direction parallel to a third axis (170) perpendicular to the second axis (160) and in a plane defined by the first axis (150) and the second axis (160). An apparatus characterized by:

4. 4. The device according to claim 2 or 3, The actuator assembly (110) is configured to move the optical sensor (70) in a direction parallel to a fourth axis (180) that is normal to the plane defined by the first axis (150) and the second axis (160). An apparatus characterized by:

5. In the device according to any one of claims 1 to 4, The optical sensor (70) is disposed in a sensor assembly (120). An apparatus characterized by:

6. 6. The apparatus of claim 5, The optical sensor (70) is movable relative to the sensor assembly (120), and the actuator assembly (110) includes a first actuator (130) configured to move the optical sensor (70). An apparatus characterized by:

7. 6. The apparatus of claim 5, The sensor assembly (120) is movable relative to a housing of the device (100), and the actuator assembly (110) includes a second actuator (140) configured to move the sensor assembly (120). An apparatus characterized by:

8. 8. The apparatus of claim 7, The sensor assembly (120) is movable relative to the housing of the device (100) along a rail (700). An apparatus characterized by:

9. The device according to any one of claims 1 to 8, The optical sensor (70) includes at least one of a single pixel, a quadrant of pixels, an array of pixels, a pixel matrix, and a position sensitive device (PSD) pixel. An apparatus characterized by:

10. The device according to any one of claims 1 to 9, The optical sensor (70) includes at least one column of pixels aligned parallel to the first axis (150). An apparatus characterized by:

11. The device according to any one of claims 4 to 10, The optical sensor (70) includes at least one row of pixels aligned parallel to the fourth axis (180). An apparatus characterized by:

12. The device according to any one of claims 1 to 11, The optical sensor (70) includes at least one of a photodiode, an avalanche photodiode, a photomultiplier tube (pmt), and a cmos sensor. An apparatus characterized by:

13. The device according to any one of claims 1 to 12, The optical sensor (70) includes at least one of a transimpedance amplifier, a free silicon amplifier, a current amplifier, and a dynode amplifier. An apparatus characterized by:

14. The device according to any one of claims 1 to 13, The optical sensor (70) is configured to detect signals generated by at least one of wavelength modulation spectroscopy, direct absorption spectroscopy, and / or frequency modulation spectroscopy. An apparatus characterized by:

15. The device according to any one of claims 1 to 14, The light source (20) is a wavelength-tunable laser diode. An apparatus characterized by:

16. 16. The apparatus of claim 15, The light source (20) is controlled by the TDLAS method. An apparatus characterized by:

17. 16. The apparatus of claim 15, The light source (20) is controlled by a DIAL method. An apparatus characterized by:

18. The device according to any one of claims 4 to 17, The light source (20) comprises an array of individual light sources arranged parallel to a fifth axis (190) perpendicular to the propagation axis (30) or parallel to the fourth axis (180). An apparatus characterized by:

19. The device according to any one of claims 1 to 18, The optical sensor (70) includes a single sensor pixel. An apparatus characterized by:

20. The device according to any one of claims 1 to 19, The device (100) includes a sensor window (702) positioned between the optical sensor (70) and the lens arrangement (50). An apparatus characterized by:

21. 21. The apparatus of claim 20, the sensor window (702) includes a slit having an adjustable width in a direction along the first axis (150); An apparatus characterized by:

22. 1. A method for detecting a property of a gas, comprising: The method comprises: emitting light along at least one propagation axis (30); directing the light scattered by the gas toward a light sensor using a lens arrangement having a lens surface; Imaging a volume of gas at a particular distance from the device (100) by moving the optical sensor (70) to a corresponding position along a first axis (150). containing, The first axis (150), the propagation axis (30) and the lens surface (60) intersect so that the Scheimpflug condition (61) is fulfilled. A method characterized by:

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