Method for calibrating an integrating cavity

Abstract

A method of using an integrating cavity to obtain a calibration measurement of a sample is provided. The method includes the steps of obtaining sample spectral information by using the integrating cavity with the sample placed inside the integrating cavity (110), obtaining generated cavity characterization spectral information by using the integrating cavity with a standard object (120), and obtaining a measurement result from the sample spectral information by employing a mathematical operation that takes the cavity characterization spectral information as input (130).

Description

Technical Field

[0001] The present invention relates to methods and apparatus for calibrating integrating cavities, for example, for spectroscopic purposes. Background Technology

[0002] Many properties of a sample can be measured in an integrating cavity, see, for example, CIE 130-1998 "Practical methods for measuring reflectance and transmittance," which, for example, discusses the measurement of directional hemispherical incident reflectance, diffuse reflectance, directional hemispherical incident transmittance, and diffuse transmittance of radiation. Integrating cavities can also be used in analytical physics, for example, in spectrophotometers for spectral measurements of samples, see, for example, WO 2104 / 080322. If a radiant flux is introduced into an integrating cavity (e.g., a sphere) through a small entrance aperture, the power distribution inside the cavity will quickly (i.e., after several bounces) become uniform and isotropic due to the diffuse reflection properties of the reflections at the sphere's walls. When a portion of this diffusely reflected (i.e., uniform and isotropic) power escapes from the cavity through an opening in the wall (called an exit window), the distribution of the escaping rays is Lambertian relative to the plane of the opening. In a spherical cavity filled with ideal diffuse radiation, radiation reflected from any point on the wall will radiate equally to all other points on the surface. Therefore, in practice, a spherical or near-spherical shape is usually preferred because this minimizes the number of bounces when mixing occurs.

[0003] When an absorbent sample is placed inside the integrating cavity, the power density of the diffuse reflection field inside the cavity decreases. This decrease can be measured using a photodetector, which can be located inside the cavity or, more commonly, outside the cavity and "looking out" at the exit window. The absorption-like spectrum of the sample can be measured in the same way as when using a conventional transmission cuvette, i.e., by measuring the detector intensity H obtained from the sample inside the cavity. sample (λ) (where λ is the wavelength of light) divided by the detector intensity H measured using a reference object inside the cavity (in this case, the cavity is usually an empty sphere, i.e., the interior is only air). ref (λ). For example, when using the decimal logarithm, the absorption spectrum is A(λ) = –log(λ). 10 (H sample (λ) / H ref (λ). The method of measuring samples inside the integrating cavity is particularly useful for samples with low absorption coefficients because the effective absorption optical path length is amplified by multiple sample interactions of diffuse reflected light inside the cavity, and the measurement results are almost unaffected by changes in sample geometry, scattering inside the sample, and reflection from the sample surface. Summary of the Invention

[0004] According to a first aspect of the present invention, a method for obtaining calibration measurements of a sample using an integrating cavity is provided. The method includes: obtaining sample spectral information by using the integrating cavity while the sample is placed inside the integrating cavity; obtaining generated cavity characterization spectral information by using the integrating cavity with a standard object; and obtaining a measurement result from the sample spectral information by employing mathematical operations that take the cavity characterization spectral information as input.

[0005] Various embodiments of the first aspect may include at least one feature from the following bulleted list:

[0006] • Cavity characterization spectral information is obtained by using an integrating cavity with a standard object placed inside it;

[0007] • Cavity characterization spectral information is obtained by using an integrating cavity with a standard object replacing part of the inner surface of the integrating cavity;

[0008] The method further includes acquiring second cavity characterization spectral information and comparing it with cavity characterization spectral information, and in response to the comparison indicating that the second cavity characterization spectral information is different from the cavity characterization spectral information, using the second cavity characterization spectral information to acquire measurement results;

[0009] The sample includes at least one of solid samples, liquid samples, and gas samples;

[0010] • Samples may include solid samples, and each sample may include at least one plant seed;

[0011] • A standard object includes an object that has an optical black layer on it;

[0012] The object has at least one hole that penetrates the optical black layer;

[0013] The object was encased in glass;

[0014] Glass includes fused silica or borosilicate glass;

[0015] • Glass welding is performed on the glass to encapsulate the object;

[0016] • A standard object includes a volume-absorbing material, which is equivalent to a volume absorbent.

[0017] According to a second aspect of the invention, a standard object is provided. The standard object includes a metal object having an optical black layer thereon, a transparent encapsulation for encapsulating the metal object, and the optical black layer.

[0018] Various embodiments of the second aspect may include at least one feature from the following bulleted list:

[0019] The metallic object also has at least one hole that penetrates the optical black layer;

[0020] • Metallic objects have multiple holes that penetrate the optical black layer;

[0021] • Transparent encapsulation components include fused silica or borosilicate glass;

[0022] • One of the following methods for encapsulating metal objects: glass welding, melting, and gluing.

[0023] According to a third aspect of the invention, a standard object is provided. The standard object comprises a volumetric absorbent material, equivalent to a volumetric absorbent. The volumetric absorbent material has been configured to have a specific predetermined absorption cross-section. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the workflow of the method of the present invention for correcting absorption spectra;

[0025] Figure 2 A schematic setup of an optical analyzer with an optical integrating cavity is shown in cross-section;

[0026] Figure 3 An integrating sphere of a standard object with automatic operation is schematically shown;

[0027] Figure 4 An embodiment of a standard object according to the present invention is shown; and

[0028] Figure 5 An example of a computer system intended for use in this invention is shown. Detailed Implementation

[0029] One drawback of using this integrating cavity when the sample is inside the cavity is the dependence on the reference spectrum H. ref (λ) Measurement method. Unlike when the sample is outside the integrating cavity, when using an integrating cavity with the sample inside, the cavity's optical properties (i.e., diffuse reflection or diffuse transmission geometry) must remain stable over a long period. The reason is as follows: Regardless of the sample's position, drift phenomena from the light source, detector sensitivity, and the transmission factor or other efficiency factors of any optical elements outside the sphere will always offset the spectral reference ratio H. sample / H ref However, the sphere's own transmission factor is only offset from the reference ratio when the sample is located outside the sphere.

[0030] This invention relates to an apparatus and method for controlling the drift effects of an integrating cavity's optical properties from the resulting absorption or absorption-like spectra when the sample is located inside a sphere. The standardized measurements disclosed in this invention improve spectral reference. The spectral reference ratio H... sample / H ref Eliminate drift originating from components outside the sphere, including short-term drift of the lamps and detectors. Reference spectrum H ref (λ) Therefore, it can be remeasured quite frequently, typically every few minutes, generally at least once a day. On the other hand, the sphere normalization method disclosed in this invention is only needed when the optical properties of the sphere change (which is usually less frequent). If the sphere is used very carefully, for example in a laboratory, the properties of the sphere may remain unchanged for many years. However, even in this case, it is desirable for the laboratory to have, for example, a second sphere available as a backup. The normalization method disclosed in this invention is also useful in this case because after the two spheres are normalized to their own long-term stable standard objects for the laboratory, these spheres behave identically in measuring absorbance or other types of absorption spectra, and therefore can be quickly switched if necessary, i.e., without recalibrating the settings. In other words, a simple calibration transfer is achieved.

[0031] Many applications of spheres are based on precision spectroscopic measurements, for example, when it is necessary to measure small absorption bands that overlap with the larger and more varied absorptions of other components in the sample. This situation is called matrix absorbance. In these and other precision applications, especially when quantitative analysis using chemometric models is required, the methods disclosed in this invention can be advantageously used to maintain the analytical accuracy of the cavity measurement system. Chemometric models can be developed using the spectra of a “young” cavity. Over time, subsequent drift in the optical response can introduce errors and reduce the original accuracy of the sphere. Numerous physical effects and behaviors contribute to the aging of spheres, including temperature sensitivity, ultraviolet (UV) light sensitivity, mold sensitivity, moisture sensitivity, dirt buildup, paint aging, mechanical damage to corners and edges, scratches on surfaces and windows, and / or any other long-term chemical or physical changes in the quality of the white diffuse reflective material.

[0032] Therefore, a simple and accurate method is needed to standardize the optical response of the integrator cavity.

[0033] This invention helps improve the quality of spectral information acquired when the sample is located inside an integrating cavity (such as an integrating sphere). It provides a simple and accurate way to normalize the optical response of the integrating cavity. Spectral information, such as absorption spectra, can be rendered using an absolute scale, thus allowing nearly identical absorption spectra to be obtained from any given sample using different integrating cavities.

[0034] Advantages of this invention include the use of scaled spectra instead of the original measured spectra. Chemometric models can be developed based on scaled spectra, which maintains analytical accuracy for a longer period (theoretically even indefinitely) because the effects of "sphere aging" may be diminished or even eliminated. Another important advantage is the ability to build a chemometric model on one sphere and then transfer it to other spheres, because differences between individual spheres can be eliminated in scaled spectra, as the scaled spectrum references a standard object, rather than an empty sphere as in the original spectrum. Similar advantages apply to cases where the sphere is intentionally modified.

[0035] At least in principle, an integrating cavity used to measure the optical properties of a sample placed within it can be of any shape. However, spherical or near-spherical shapes are advantageous because they offer the strongest diffuse reflection, meaning that less reflection is required inside the cavity to uniformly distribute incident light across the entire surface compared to other shapes. In the embodiments described below, the integrating cavity is spherical, but the invention is not limited to any particular shape of cavity.

[0036] When the sample is located inside a cavity with a small aperture serving as a light entry and exit window, the measurement results depend on the cavity's optical properties. When the inner surface of the cavity is covered with a diffuse white reflective coating, it becomes a so-called integrating cavity. The diffuse white coating approximates a Lambertian mirror, meaning that light incident on the inner surface is diffusely reflected and loses information about its original direction of arrival after several reflections. After one or more such diffuse reflections, the light is uniformly distributed across the entire surface. Thus, through the diffuse reflection effect inside the integrating cavity, the original direction of the light is "forgotten."

[0037] For example, the chemical composition of a sample can be determined based on spectral information measured inside an integrating sphere. Spectral information may include, for example, absorption spectra or absorbance values ​​at selected wavelengths.

[0038] In practice, samples to be analyzed are more frequently placed outside the integrating sphere, for example, by covering windows in the machined sphere wall. However, the advantages of placing the sample inside the integrating cavity include:

[0039] • Absorption signal amplification due to spherical multiplication factor;

[0040] • Virtual elimination of sample delivery errors;

[0041] • Sample loading is simple (both particulate and liquid samples are handled equally well);

[0042] • The detector has high irradiance;

[0043] • Photodetectors and electronic devices have a small dynamic range; and

[0044] • It is easy to obtain a linear and reliable absorption response from the sample.

[0045] Modern spheres are coated with or made of materials with very high diffuse reflectance, typically ρ > 0.95. These modern materials are also spectrally non-selective (not strongly dependent on wavelength), non-fluorescent, and long-term stable. Nevertheless, especially under harsh operating conditions, the optical properties of the sphere can still change over the long term. Most spheres used in practice have diameters ranging from approximately 50 mm to 1 meter. The apertures used for the light source and detector are called windows, and the total area of ​​all windows is typically less than 5% of the sphere's surface area.

[0046] When using an integrating sphere with the sample placed outside the sphere—that is, when measuring diffuse reflectance or diffuse transmittance characteristics—the aging effect of the sphere cancels out in the spectral reference ratio when the measurement results are obtained. In other words, the fact that the optical or spectral properties of the sphere change over time when the sample is outside the sphere is not a problem.

[0047] When the sample to be analyzed is located inside the sphere, the aging effect of the sphere will not be canceled out. The method of spectral reference measurement when air is used instead of the sample (i.e., the sample is removed from the sphere) differs from the method when the sample to be analyzed is located outside the sphere. For example, when measuring the absorption spectrum A = –log 10 (H sample / Href When the optical properties of the sphere are not offset, the drift of the sphere's optical properties will not be canceled out, because the effect caused by the change in the sphere's optical properties is mathematically approximated by the change in optical path length in the case of traditional cuvette transmission spectroscopy.

[0048] Since aging effects cannot be negated, controlling for aging becomes crucial when using an integrating sphere in a mode where the sample to be analyzed is located inside the sphere. "Inside the sphere" (or more colloquially, the integrating cavity) means the sample is completely inside the cavity. Alternatively, "inside the cavity" could mean more than half the sample's volume is inside the cavity. While paint aging, dirt buildup, and other effects may be minor, some measurements require stability of around 0.01% over time for successful execution. For example, some near-infrared analyte measurements fall into this category, where small analyte peaks need to be subtracted from a large and varying background. The integrating sphere's lifespan can be several years, meaning sufficiently large variations can occur during its lifetime to significantly impact measurement accuracy.

[0049] According to the present invention, standard objects or reference materials with good long-term stable optical properties can be used to detect and correct changes in the properties of the integrating sphere.

[0050] For example, a standard with a stable absorption cross section can be provided, and this standard can be measured within the sphere during assembly to obtain cavity characterization spectral information that characterizes the sphere at the time of assembly. This cavity characterization spectral information can be combined with the measurement sample using the sphere, thus projecting the spectral information obtained from the sample by comparing it to the standard object rather than an empty sphere. Because the standard object is stable, unlike an empty sphere, the sample can be measured stably, and the aging effect of the sphere can be significantly reduced.

[0051] Over time, new measurements can be performed on the same standard or another nominally identical standard using the same sphere to obtain new cavity characterization spectral information. When the new cavity characterization spectral information differs from the previous information, it can be combined with subsequent measurements of the sample because it now more accurately reflects the state of the sphere. In this case, the new cavity characterization spectral information can be used to compare the spectral information obtained from the sample with that of the standard, while time-related changes in the sphere itself can be eliminated or at least significantly attenuated, thereby improving measurement accuracy.

[0052] For example, in absorption spectroscopy – log 10 (H sample / H ref When performing a standardization procedure, the following steps can be taken. First, measure the absorption spectrum A of the standard object. std (λ)=–log 10 (H std (λ) / H ref,std (λ)) and save it to memory. Next, routine measurements of the absorption spectra of one or more samples can begin, i.e., A(λ) = –log 10 (H sample (λ) / H ref (λ)). Typically, the reference spectrum H of the sample. ref (λ) can, in principle, be related to the reference spectrum H used to calculate the absorption spectrum of the standard. ref,std (λ) is the same, but more commonly a new or recent reference spectrum will be measured. The third step is to divide the sample's absorption spectrum A(λ) by the standard object's absorption spectrum A. std (λ), thus obtaining the normalized absorption spectrum A of the sample. n (λ)=A(λ) / A std (λ). Similar to, for example, H sample (λ) / H refSimilar to other spectral ratios of (λ), the division sign in the formula is equivalent to the ". / " symbol in MathWorks' MATLAB software, meaning that division is performed point-by-point at each wavelength. In the example of spectral measurement, the measurement variable can be over several wavelength bands, thus storing the variable as a vector rather than a scalar in memory. For the normalized spectrum A... n (λ) Quantitative analysis yields more reliable and long-term stable results because drift in the optical properties of the sphere can be eliminated by simply measuring and storing the recent absorption spectrum of the standard and using it to normalize the sample spectrum. This is far simpler than the current practice of recalibrating the entire setup. The only requirement is that the optical properties of the standard object itself remain stable over the long term.

[0053] This process applies not only to absorption spectra A(λ) = –log 10 (H sample (λ) / H ref (λ)), and is applicable to ratio-based H sample / H ref Other absorption-like spectra. To simplify notation, λ can be omitted from the formula. Dividing by the absorption-like spectrum of the standard helps restore the stability of the analysis.

[0054] For a conventional absorption spectrum – log10(...) – which uses decimal logarithms and where the numerical output is expressed in the so-called absorbance unit AU, the correction is very effective for small absorbance values ​​(i.e., at most about 0.3 AU) and also quite effective for larger absorbance values.

[0055] Alternative locations can be selected using the natural logarithm A. e =–log e (H sample / H ref In this case, the same argument applies, except that the range of values ​​for which the correction is most effective increases to about 0.7, i.e., 0.3 x 2.303.

[0056] Absorbance A e The first-order Taylor series approximation is A1 = ((H) ref / H sample –1). Surprisingly, this correction method was found to be very effective for the A1(λ) spectrum. In other words, the normalization process A1(λ) / A 1,STD (λ) corrects for drift in the sphere very well over the wide dynamic range of A1.

[0057] All absorption formulas are valid within a certain range. In practice, it is therefore possible to find formulas that are favorable for both quantitative analysis (i.e., Lambert-Beer behavior of the sample) and spherical correction.

[0058] Please note that the above correction effect is not attributable to the "double ratio" effect, because the two spectra involved are compared to H. Sample (t) / H Ref (t) and H Std (t1) / H Ref (t1) (where t is time) are not directly divisible by each other. The correction effect is not attributable to a simple optical path length correction. If it were, the correction would be for the normal absorption spectrum A = –log 10 (...) is most effective, but this is not the case, because the correction is for the A1 spectrum A1=((H ref / H sample )–1) is most effective. Conversely, the stabilization effect produced by dividing the absorbance or absorption-like spectrum of the sample by the similar or even different absorption-like spectrum of a long-term stable standard is a fortunate result of the intricate physical behavior exhibited by the integrating sphere when the sample is located inside the sphere.

[0059] Standard objects may include, for example, strips of metal or plastic, with an optically black layer on or within them. Optically black means that it absorbs almost all incident light. The optically black layer can be, for example, inorganic. An exemplary material used for the optically black layer is so-called "black nickel," a commercially available coating for metals. Due to an electrodeposition process, the layer also grows uniformly at the edges and internal corners of the workpiece. A variety of other materials can also be used to fabricate the optically black layer, including various coatings and surface treatments. For an overview, see the following two papers: (a) Stephen M. Pompea and Robert P. Breault, CHARACTERIZATION AND USE OF BLACK SURFACES FOR OPTICAL SYSTEMS, Handbook of Optics, Chapter 6, 3rd Edition, Volume 4: Optical Properties of Materials, Nonlinear Optics, Quantum Optics, M. Bass (ed.), McGraw-Hil, 2010; and (b) Jennifer L. Marshall, PatrickWilliams, Jean-Philippe Rheault, Travis Prochaska, Richard D. Allen and DL DePoy, CHARACTERIZATION OF THE REFLECTIVITY OF VARIOUS BLACK MATERIALS, July 30, 2014 (page 8), published in Proc. SPIE Int. Soc. Opt. Eng. 9147 (2014) 91474F.

[0060] Standard objects may contain a volumetric absorbent material, essentially a so-called volumetric absorber, in place of a black layer (also known as a surface absorber). There is no clear distinction between surface and volumetric absorbers, but the material used within a volumetric absorber typically has a much lower absorption coefficient than that used in a surface absorber. Examples of materials well-suited for realizing standard objects as volumetric absorbers include light-absorbing plastics, particularly gray plastics, where the total mass can be used to determine the resulting absorption cross-section, and its shape can be optimized because injection molding can be used as the manufacturing process. Another example of suitable volumetric absorbent materials is a powder mixture containing graphite, especially a mixture containing non-absorbing powders such as glass or Teflon particles, making graphite the sole absorber, where the desired absorbance can be adjusted using the mixing ratio. The powder mixture can be encapsulated in glass, as described below. Volumetric absorbers can be configured to have a specific, predetermined light absorption cross-section.

[0061] Standard objects can be encased in glass to enhance their stability and facilitate cleaning, removing fingerprints and other contaminants that may accumulate. The glass material can include fused silica, as it transmits ultraviolet and longer-range near-infrared radiation that might be absorbed by other types of glass. Borosilicate glass can be used alternatively, depending on the application. Currently available glass welding can be used to encapsulate the standard object within the glass. Glass fusion can also be used instead of glass welding to encapsulate the standard object within the glass. Where the standard is based on surface absorption, at least the areas of the black layer exposed to light should be protected with glass; protection of other parts of the object is less critical.

[0062] The standard may include one or more holes. The holes may be in a metal or plastic object. These holes may penetrate an optical black layer. Penetrating the optical black layer can also mean that the optical black layer covers the inner edge of the one or more holes, so that the one or more holes penetrate the metal or plastic object before the optical black layer is applied.

[0063] The advantage of having one or more holes is that the risk of affecting the diffuse reflection characteristics of the light field inside the sphere is minimized when a standard object is placed inside the sphere. In other words, the possibility of shading effects is minimized. This is advantageous because, ideally, the absorption effect caused by the standard object should be completely independent of its position within the sphere, which is only achieved when there are no shading effects. In some embodiments, at least two holes are present. In other embodiments, the holes cover more than 50% of the surface of the standard object.

[0064] Based on practical experience, and considering the overall final accuracy and efficient use of measurement time, it is advantageous to select a standard object's absorption cross-section such that the diffuse reflection photon density established inside the sphere is reduced to approximately half when the standard object is placed inside the sphere. In other words, and more specifically, over the entire wavelength range of the measurement, the ratio H... std (λ) / H ref,std The value of (λ) is preferably in the range of about 0.4 to 0.7.

[0065] Figure 1 This describes the workflow of at least some embodiments of the method of the present invention for calibrating absorption spectra measured from samples. (The following is a description of the workflow:) Figure 2 The diagram shows an integrating cavity with an internal surface that is essentially diffusely reflective, used to introduce radiated power into a radiation source within the cavity, and a detector sensitive to radiated power is positioned therein.

[0066] Phase 110 includes: acquiring sample spectral information by using the integrating cavity with the sample placed inside. The sample spectral information may include the spectral information of the sample. Phase 120 includes: acquiring cavity characterization spectral information generated by using the integrating cavity with a standard object. When generating the cavity characterization spectral information, the standard object may be located inside the cavity, or the standard object may be arranged to partially replace the cavity wall without being located inside the cavity. Acquiring the cavity characterization spectral information may, for example, include retrieving the cavity characterization spectral information from memory. Phase 130 includes: acquiring a measurement result from the sample spectral information by employing mathematical operations with the cavity characterization spectral information as input. Optionally, Phase 140 includes: comparing second cavity characterization spectral information with the cavity characterization spectral information, and, in response to the comparison indicating that the second cavity characterization spectral information differs from the cavity characterization spectral information, using the second cavity characterization spectral information to acquire the measurement result. Like the cavity characterization spectral information, the second cavity characterization spectral information can be generated with the standard object located in the cavity. The second cavity characterization spectral information may be more up-to-date than the cavity characterization spectral information.

[0067] Figure 2 An exemplary optical analyzer with an integrating sphere is shown. The sample is held in place by a sample holder. In the case of grain seeds or other particulate materials, the sample holder may be constructed of glass 27. On glass 27, for example, grains or other agricultural particles are held in place and distributed across the entire surface to form an optically thin layer. Optically thin means that the sample is, in most cases, transparent to diffuse light from inside the integrating cavity. Furthermore, a [missing information - likely a typo, should be inserted here] can be placed between glass plates 29a and 29b. Figure 4 The standard object.

[0068] Standard objects for spheres can be used inside handheld or in-line optical instruments. In the case of handheld devices, the standard object can be manually inserted and removed. In the case of in-line instruments, the standard object can be operated automatically and can be permanently located on or inside the instrument.

[0069] Figure 2A schematic configuration of an optical analyzer with an optical integrating cavity 20 is shown in cross-section. The optical integrating cavity 20 is formed by two hemispheres 21, 24, which are connected to each other, for example, using a bayonet closure. A sample holder 27 can be fixed to the device housing (not shown) or the lower hemisphere 24. The optical integrating cavity can be opened and closed using a frame 22, which forms a shape fit with at least one of the hemispheres 21, 24. The frame 22 can be made of plastic or metal, provided that the diffuse reflectance of the material is high enough not to impede the integrating capability of the optical integrating cavity 20. An optional protective glass 29a is used to protect the interior of the upper hemisphere 21, including the front of the light source 23, which extends from the hemisphere for easy replacement, since the protective glass 29a may be non-removable. Similarly, an optional second protective glass 29b protects the white diffuse reflective wall 24a of the lower hemisphere 24 for optimal light homogenization.

[0070] Incident light from light source 23 is reflected by baffle 28, strikes the diffuse inner wall 2la of the upper hemisphere 21, and is diffusely reflected into the integrating sphere. Sample holder 27 can be removed from the sphere 20 and can be filled with a sample in place or removed for sample filling. Sample holder 27 can also accommodate standard objects (see...). Figure 4 The standard object can, for example, slide into the support. The frame 22 can be designed to securely fasten the sample holder 27 to the two hemispheres 21, 24, and can be permanently attached to the sample holder 27.

[0071] Diffuse light can pass through opening 25 in the lower hemisphere 24 and be directed to the spectral sensor 26. The sensor may include beam-guiding elements such as lenses 26a and 26b, a linearly variable bandpass filter 26c, and finally, a detector array 26d. Each pixel of the detector array (e.g., a row of 256 pixels) corresponds to a wavelength of interest, and the filter 26c is responsible for transmitting the correct wavelength to the corresponding pixel. The linearly variable optical filter 26c can be replaced by a grating or prism, and the spectral sensor 26 as a whole can be replaced by other spectral sensors.

[0072] Figure 3 An integrating sphere 31 with an automatically operating standard object 34 is schematically shown. According to some embodiments, a standard object 34 with a diffuse white coating region and an optical black coating region is used. The black coating region represents the standard object. In the case of a very dark black coating (i.e., diffuse reflectance <5%), the absorption cross-section of the standard object is almost identical to the geometry of the exposed black coating region. The integrating sphere 31 has a bulb 33 and a spectrometer detector 35, both equipped with baffles 38. The integrating sphere 31 is used to analyze a sample stream (e.g., a grain stream) falling into and passing through a sample holder (i.e., through a glass tube 39 of the sphere 31).

[0073] A delivery screw 36, driven by motor 37, provides a continuous sample flow to the sphere. An automatic standard 34 is located behind an opening in the sphere wall. The opening is either covered by a white surface, effectively “filling the opening,” or covered by a black surface, thus functioning as a standard. Mechanically, there is only one moving part, namely a disk or plate with at least one white field and one black field. Most of the time, the opening is covered by the white surface. A mechanical actuator (not shown) is only activated when a new standard measurement H is performed. std (k) takes a short time to move the dark surface onto the opening, thus exposing the standard object.

[0074] The spectral reference measurement of the empty sphere is performed by stopping the sample flow by stopping the conveyor screw 36. Once the flow has stopped and the sphere is empty, two measurements can be performed: one for the empty sphere to obtain the spectral reference H. Ref (λ), another is the measurement of H of the standard under the condition of exposure to black standard. Std (λ). The proximity of the time between two measurements helps to detect minute drifts in the properties of the sphere.

[0075] The automatic deployment of the standard object can be achieved in a different mechanical way than described above, for example, as follows: First, the black standard object can move in and out through a narrow slit in the sphere's wall. Second, the black area can be fixedly located within the sphere's wall. The black area can be covered by a movable white diffuse reflective material, making it appear white, and the white diffuse reflective material can be removed to expose the black area. When the movable white reflective material is removed, it may stop on adjacent white areas, making the total amount of white area on the sphere appear constant.

[0076] exist Figure 4 An embodiment of a standard object is shown for use in a system operating according to the principles of the present invention. Figure 4 The standard object comprises a transparent glass cover plate 41, a transparent glass back plate 42, a transparent glass frame 43 located between the cover plate and the back plate, and a perforated optical black metal sheet 44 disposed within the space defined by the frame and the cover plate and the back plate. The metal sheet 44 can be cut into the desired shape using, for example, laser cutting. The glass sheets can be joined by at least one of the following methods: glass welding, glass melting, and using a small amount of renewable adhesive. Requirements for the standard object include long-term stability of its optical properties. In practice, this means that the standard object should be mechanically and chemically stable, and stable relative to temperature and ultraviolet light. The standard object should also be mildew-proof and moisture-proof. The standard object should also be easy to clean, inspect, and reproduce. Figure 4 The standard object constructed as shown satisfies all of these requirements.

[0077] Figure 5An exemplary computer system 50 capable of supporting at least some embodiments of the present invention is illustrated. The computer system 50 includes a processor 51, which may include, for example, a single-core or multi-core processor, wherein a single-core processor includes one processing core, and a multi-core processor includes more than one processing core. The processor 51 may include more than one processor. The processing core may include, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core manufactured by Advanced Micro Devices Corporation. The processor 51 may include at least one Qualcomm Snapdragon and / or Intel Atom processor.

[0078] Processor 51 may include at least one application-specific integrated circuit (ASIC). Processor 51 may include at least one field-programmable gate array (FPGA). Processor 51 may be an apparatus for performing method steps in device 50. Processor 51 may be configured at least in part by computer instructions to perform some actions.

[0079] Computer system 50 also includes memory 52. ​​Memory 52 may include random access memory and / or permanent memory. Memory 52 may include at least one RAM chip. Memory 52 may include, for example, solid-state, magnetic, optical, and / or holographic memory. Memory 52 may be at least partially accessed by processor 51. Memory 52 may be at least partially included in processor 51. Memory 52 includes computer instructions that processor 51 is configured to execute. When computer instructions configured to cause processor 51 to perform certain actions are stored in memory 52, and device 50 as a whole is configured to operate under the guidance of processor 51 using computer instructions from memory 52, processor 51 and / or at least one of its processing cores may be considered to be configured to perform said certain actions.

[0080] Computer system 50 may include a data output port or transmitter 53, and may also include an input port or receiver 54. Ports 53 and 54 may be configured to send and receive information respectively according to at least one protocol designed to enable data exchange between the various components of the apparatus of the present invention (i.e., the light source, the sphere, the photodetector, and the spectroscopic device). Other external resources, such as databases, the Internet, etc., may also be accessible. The ports may be wired or wireless.

[0081] The computer system 50 may also include a near-field communication (NFC) transceiver 55 as an alternative or supplement to providing data exchange between components of the device of the present invention. The NFC transceiver 55 may support at least one NFC technology, such as NFC, Bluetooth, Wibree, or similar technologies.

[0082] Additionally, a user interface 56 may be used. The user interface (UI) 56 may include at least one of a display, a keyboard, and a touchscreen. Users can operate the device 50 via the UI 56, thereby managing measurements, for example.

[0083] The computer system 50 may be configured to accept at least one external data carrier module 57. Such a module may be, for example, an external memory card containing configuration or calibration information.

[0084] Processor 51 may be equipped with a transmitter arranged to output information from processor 51 to other devices included in computer system 50 via internal electrical leads of device 50. Such a transmitter may include a serial bus transmitter arranged, for example, to output information to memory 52 via at least one electrical lead for storing information in memory 52. ​​The transmitter may include a parallel bus transmitter as an alternative to a serial bus. Similarly, processor 51 may include a receiver arranged to receive information from other devices included in computer system 50 via internal electrical leads of computer system 50. Such a receiver may include a serial bus receiver arranged, for example, to receive information from receiver 54 via at least one electrical lead for processing in processor 51. The receiver may include a parallel bus receiver as an alternative to a serial bus.

[0085] Computer system 50 may include Figure 5 Other devices not shown. For example, computer system 50 may include at least one digital camera.

[0086] The processor 51, memory 52, transmitter 53, receiver 54, NFC transceiver 55, UI 56, and / or external module 57 can be interconnected in various ways via electrical leads within the device 50. For example, each of the aforementioned devices can be connected to a main bus within the device 50 to allow the devices to exchange information. However, as those skilled in the art will understand, this is merely an example, and depending on the embodiment, various ways of interconnecting at least two of the aforementioned devices can be chosen without departing from the scope of the invention.

[0087] It should be understood that the embodiments of the invention disclosed herein are not limited to the specific structures, processes, or materials disclosed herein, but extend to their equivalents, as will be recognized by those skilled in the art. It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and not for limitation.

[0088] Throughout this specification, reference to an embodiment or an example means that a particular feature, structure, or characteristic described in connection with that embodiment is included in at least one embodiment of the invention. Therefore, the phrases "in one embodiment" or "in one example" appearing throughout the specification do not necessarily refer to the same embodiment. Where numerical values ​​are mentioned using terms such as approximately or substantially, precise numerical values ​​are also disclosed.

[0089] As used herein, for convenience, multiple items, structural elements, constituent elements, and / or materials may be presented in a common list. However, these lists should be understood as if each item in the list were considered a separate and unique item. Therefore, unless stated otherwise, no single item in such a list should be construed as an equivalent to other items in the same list simply because they are presented in a common group. Furthermore, various embodiments and examples of the invention herein may be described together with alternative components of its various components. It should be understood that such embodiments, examples, and alternatives should not be construed as actual equivalents of each other, but should be considered as separate and independent presentations of the invention.

[0090] Furthermore, the described features, structures, or characteristics can be combined in any suitable manner in one or more embodiments. Numerous specific details, such as examples of length, width, shape, etc., are provided in the foregoing description to provide a thorough understanding of embodiments of the invention. However, those skilled in the art will recognize that the invention can be practiced without one or more of these specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations have not been shown or described in detail to avoid obscuring various aspects of the invention.

[0091] While the foregoing examples illustrate the principles of the invention in one or more specific applications, it will be apparent to those skilled in the art that various modifications can be made to the form, usage, and details of implementation without any inventive effort and without departing from the principles and concept of the invention. Accordingly, the invention is not limited except by the claims listed below.

[0092] The verbs “comprising” and “including” are used in this document as open-ended restrictions, neither excluding nor requiring the presence of any unrecorded features. Unless otherwise expressly stated, the features recited in the dependent claims may be freely combined with each other. Furthermore, it should be understood that the use of “a” or “an” throughout the document, i.e., the singular form, does not exclude a plurality.

[0093] Industrial applicability

[0094] At least some embodiments of the present invention have been industrially applied to improve the accuracy of spectral measurements.

[0095] List of abbreviations

[0096] CIE (International Commission on Illumination)

[0097] NFC (Near-Field Communication)

Claims

1. A method for obtaining calibration measurements of a sample using an integrating cavity, comprising: With the sample placed inside the integrating cavity, the sample spectral information is obtained by using the integrating cavity; The first cavity characterization spectral information is obtained by using the integrating cavity and a standard object inside the integrating cavity; Measurement results are obtained from the sample spectral information by employing mathematical operations that take cavity characterization spectral information as input. as well as After acquiring the first cavity characterization spectral information, the integrating cavity and a standard object inside the integrating cavity are used to acquire the second cavity characterization spectral information, and the second cavity characterization spectral information is compared with the first cavity characterization spectral information. In response to the comparison indicating that the second cavity characterization spectral information is different from the first cavity characterization spectral information, the second cavity characterization spectral information is used to acquire the measurement result; otherwise, the first cavity characterization spectral information is used to acquire the measurement result. The standard object includes an object containing an optical black layer.

2. The method according to claim 1, wherein, The cavity characterization spectral information is obtained by using the integrating cavity with the standard object replacing a portion of the inner surface of the integrating cavity.

3. The method according to claim 1 or 2, wherein, The cavity characterization spectral information is used to project the spectral information obtained from the sample by comparing it with the standard object rather than by comparing it alone with the integrating cavity.

4. The method according to claim 1, wherein, The sample includes at least one of solid samples, liquid samples, and gas samples.

5. The method according to claim 1, wherein, The samples include agricultural samples.

6. The method according to claim 5, wherein, The sample includes at least one plant seed.

7. The method according to claim 1, wherein, The standard object has at least one hole that penetrates the optical black layer.

8. The method according to claim 1, wherein, The standard object has multiple holes, wherein the optical black layer covers the inner edges of the holes.

9. The method according to claim 8, wherein, The standard object is encapsulated in glass.

10. The method according to claim 9, wherein, The glass comprises fused silica or borosilicate glass.

11. The method according to claim 9 or 10, wherein, The glass is glass-welded to encapsulate the standard object.

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