Conical diffuse reflector for homogeneous illumination

Abstract

The invention relates to an optical unit (114) for a spectrometer device (112) for analyzing at least one sample (116). The optical unit (114) comprises a plurality of light emitting elements (120) configured for emitting light for illuminating the sample (116); a conical light guide (122) comprising at least one scattering element (124) arranged between opposing, differently sized openings (126) of the conical light guide (122), the conical light guide (122) being configured for scattering at least part of the light emitted by the light emitting elements (120); at least one reflector (128) configured for reflecting at least part of the light scattered by the light guide (122) in a direction toward the sample (116), wherein the light emitting elements (120) and the reflector (128) are arranged on a side of the conical light guide (122) having the bigger opening (130), wherein the sample (116) is placeable on a side of the conical light guide (122) having the smaller opening (132). Further disclosed are a spectrometer device (112), a spectrometer system (110) and various uses of the spectrometer device (112).

Description

[0001] Conical Diffuse Reflector for Homogeneous Illumination

[0002] Technical Field

[0003] The invention relates to an optical unit for a spectrometer device for analyzing a sample, to a spectrometer device, to a spectrometer system as well as to various uses of the spectrometer device. Such devices and systems can, in general, be used for investigation or monitoring purposes, in particular, in the infrared (IR) spectral region, especially in the near-infrared (NIR) and the mid infrared (MidlR) spectral regions, and for a detection of heat, flames, fire, or smoke. However, further kinds of applications are possible.

[0004] Background art

[0005] Various optical units, spectrometer devices and systems for investigations in the IR spectral region, in particular in the NIR and MidlR spectral regions, are known. Especially, optical units and spectrometer devices that comprise a combination of parabolic mirrors and incandescent lamps have been proposed. Therein, the incandescent lamps are commonly used to cover the required wavelength range with their broad spectrum formed as a black-body radiator by Planck’s law. These setups however generally require precise component placement and narrow manufacturing tolerances, since even small deviations tend to trigger high spatial dependency of the illumination of the sample. The resulting high alignment efforts usually render large- scale production uneconomical.

[0006] One generally accepted approach for overcoming this issue is performing multiple measurements at different locations. Specifically, multiple measurements are typically performed, thereby converging in an averaging prediction about a material parameter to be measured. However, performing multiple measurements is cumbersome and costly.

[0007] Problem to be solved

[0008] It is therefore desirable to provide an optical unit, a spectrometer device and a spectrometer system that may, in particular, be suited for investigations in the IR spectral region, especially in the NIR and MidlR spectral regions, and which at least substantially avoid the disadvantages of known devices and systems of this type. In particular, it would be desirous to provide an improved, simple, cost-efficient and still reliable optical unit for a spectrometer device.

[0009] Summary

[0010] This problem is addressed by an optical unit, a spectrometer device, a spectrometer system and a use of a spectrometer device with the features of the independent claims. Advantageous embodiments which might be realized in an isolated fashion or in any arbitrary combinations are listed in the dependent claims as well as throughout the specification. In a first aspect, the present invention relates to an optical unit for a spectrometer device for analyzing a sample. The optical unit comprises: a plurality of light emitting elements, i.e. at least two light emitting elements, configured for emitting light for illuminating the sample; a conical light guide, e.g. configured for homogenizing the light emitted by the light emitting elements, comprising at least one scattering element arranged between opposing, differently sized openings of the conical light guide, the conical light guide, specifically by its scattering element, being configured for scattering, i.e. diffusely reflecting, at least part of the light emitted by the light emitting elements, i.e. the part of the emitted light illuminating the scattering element; at least one reflector configured for reflecting at least part of the light scattered by the light guide in a direction toward the sample, wherein the light emitting elements and the reflector are arranged on a side of the conical light guide having the bigger opening, wherein the sample is placeable on a side of the conical light guide having the smaller opening.

[0011] The term “optical unit” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The time specifically may refer, without limitation, a part of a spectrometer device configured for guiding the electromagnetic radiation, i.e. light, through and / or within the spectrometer device, such as for controlling a light path, to and from the sample.

[0012] The term “spectrometer device” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an apparatus that is by guiding electromagnetic radiation to and from at least one sample, e.g. by its optical unit, capable of determining spectral information of the sample, such as information on at least one spectrum of the at least one sample, by recording at least one measured value for at least one signal intensity, i.e. an intensity of electromagnetic radiation, such as a light intensity. The signal may specifically be generated, preferably as an electrical signal, by a detector of the spectrometer device with respect to a corresponding wavelength of light, or a partition thereof. The signal intensity may then be used for deriving an optical property of the sample. As an example, the spectrometer device may be configured for analyzing the sample by performing diffusive reflectance spectroscopy.

[0013] The term “sample” as used herein is a broad term of this to be given its ordinary and customary meaning to person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary object or element, chosen from a living object or a nonliving object, and having at least one optical property. The determination of the optical property, preferably, being of interest to a user when using the spectrometer device. The sample may specifically have any kind of characteristics, for example an inhomogeneous character, as will be outlined in further detail below. As used herein, the term “light-emitting element” is a broad term and is to be given its ordinary and customary meaning to person of ordinary skill in the art and is not to be limited to special or customized meaning. The term specifically may refer to an element configured for emitting light. In particular, the light-emitting element may be or may comprise at least one light source which is known to provide sufficient emission, i.e. for the spectrometer device to detect, in a predefined optical spectral range, i.e. in infrared spectral range, such as in the near infrared spectral range and / or in the mid-infrared spectral range and / or in the far infrared spectral range. Specifically, the light-emitting element may be selected from at least one of the following light sources: a thermal radiator, specifically an incandescent lamp, such as an incandescent light bulb, and / or a thermal infrared emitter; a heat source; a laser, such as a laser diode; a light-emitting diode (LED); a miniaturized thin-film emitter; a structured light source; a gas discharge lamp.

[0014] Herein, the term “light” may generally refer to a partition of electromagnetic radiation which is, usually, referred to as “optical spectral range” and which specifically comprises one or more of the visible spectral range, the ultraviolet spectral range and the infrared spectral range. The terms “ultraviolet spectral range” or “UV” generally refer to electromagnetic radiation having a wavelength of 1 nm to 380 nm, preferably of 100 nm to 380 nm. Further, in partial accordance with standard ISO-21348 in a valid version at the date of this document, the term “visible spectral range”, generally, refers to electromagnetic radiation having a wavelength of 380 nm to 760 nm. The terms “infrared spectral range” or “IR” generally refer to electromagnetic radiation having a wavelength of 760 nm to 1000 pm, wherein the range of 760 nm to 1 .5 pm is usually denominated as “near infrared spectral range” or “NIR”, while the range from 1 .5 p to 15 pm is denoted as “mid infrared spectral range” or “Midi R” and the range from 15 pm to 1000 pm as “far infrared spectral range” or “FIR”. Light used for the typical purposes of the present invention may specifically be light in the I R spectral range, preferably in the NIR spectral range, more preferred having a wavelength of 800 nm to 3000 nm, even more preferred having a wavelength of 1100 nm to 2500 nm.

[0015] In particular, the light emitted by the light-emitting element may be within the near infrared spectral range, i.e. comprising electromagnetic radiation having wavelengths A of 760 nm < A < 3 pm.

[0016] As generally used, the term “incandescent lamp” refers to an electric light having a heatable element, such as a wire filament heated, which may be heated to a temperature that it may emit light, especially infrared light. Since the incandescent lamp can, therefore, be considered as a thermal emitter within the infrared spectral range, an emission power of the incandescent lamp decreases with increasing wavelength.

[0017] The term “light guide” as used herein is a broad term and is to be given its ordinary and customary meaning to person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a pipe shaped reflector element configured for guiding and homogenizing the light emitted by the light-emitting element by one or more internal reflections, i.e. by diffuse reflections. In particular, the light guide is a conical light guide forming a pipe and comprises at least one scattering element, such as a reflective surface, for scattering, i.e. diffusely reflecting, light that illuminates the scattering element. The term “conical”, specifically with regard to an optical element, such as the light guide, refers to a shape of the optical element which can be described as a truncated cone. Thus, the conical light guide has at least two opposing openings of different size.

[0018] The term “scattering element” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary object and / or element having a surface that, when illuminated by light, diffusely reflects at least part of that light, i.e. at least light of a predefined spectrum, in a plurality of directions. As an example, the diffusely reflecting surface of the scattering element may be or may comprise a rough and / or rugged surface made of a reflecting material, e.g. a reflector material. In particular, the scattering element may be or may comprise a material that, when illuminated by light in the near infrared spectrum, reflects more than 80%, preferably more than 90%, more preferred more than 95%, of the light.

[0019] The term “reflector” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an arbitrary object and / or element comprising an even and / or smooth surface made of a reflecting material. In particular, the reflector, may be configured for, when illuminated by light, specularly reflecting the light, such that the angle of incidence equals the angle of reflection. As an example, the reflector, specifically it’s surface, may comprise one or more of a mirror, a metal, a glass and a ceramic material.

[0020] As an example, the scattering element may comprise an uneven, irregularly patterned, reflective surface. Specifically, the scattering element may have a surface having an uneven and / or irregular shape. As an example, the surface may be a diffusor surface configured for total reflection.

[0021] The term “diffusor configured for total reflection” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an object and / or element configured for, when illuminated by light within the near infrared spectrum, diffusing and / or scattering, such as diffusively reflecting, over 95% of the light, preferably more than 97% of the light. Thus, the diffusor configured for total reflection may in particular absorb < 5%, preferably < 3%, of light in the near infrared spectrum.

[0022] The scattering element may specifically comprise at least one material selected from the group consisting of: a metal and / or metallic material, such as copper, gold, silver, aluminum, platin; a glass, e.g. Quartz glass; a plastic material; a ceramic. As an example, the conical light guide may be hollow or may at least partially be filled with at least one optically transparent material. Thus, there may be at least one optically transparent material, ambient air or even a vacuum within the truncated cone of the conical light guide. As an example, in case the conical light guide encloses ambient air, the material on the outside of the light guide may be the same as the material inside the light guide. Additionally or alternatively, the conical light guide may enclose an optically transparent material being different from the ambient material, for example a glass material.

[0023] An area ai of the smaller opening may be smaller than an area a2 of the bigger opening of the conical light guide by at least a factor of 1 .1 , specifically by at least a factor of 1 .5, more specifically by at least a factor of 1.7. Thus, as an example, a2> 1.1 ai, specifically, a2> 1.5 ai; more specifically a2> 1.7 ai.

[0024] The light emitting elements may particularly be arranged at least partially intruding into the bigger opening of the conical light guide. Thus, the light emitting elements may at least partially intrude into the bigger opening of the conical light guide, such as by being partially arranged within the bigger opening of the light guide. Additionally or alternatively, the light emitting elements may fully be arranged within the bigger opening of the light guide.

[0025] The light emitting elements may be arranged around a center point and / or a central light axis of the optical unit. For example, the light emitting elements may be arranged around a central axis of the conical light guide. The light emitting elements may be arranged around the center point and / or central light axis of the optical unit and / or around the axis of the conical light guide in shape of a circle or an oval. As an example, the light emitting elements may be arranged equidistantly around the center point and / or central light axis. In particular, the light emitting elements may be distributed equally around the center point and / or the central light axis, preferably in shape of a circle or an oval.

[0026] The term “central light axis” or “central axis” as used herein may specifically refer, without limitation, to an axis of the optical unit and / or the conical light guide, e.g. to an axis along which light is guided through the optical unit and / or through the conical light guide. Thus, specifically, the central light axis may be the symmetry axis of the truncated cone shape of the conical light guide.

[0027] In particular, the light emitting elements may be arranged around the center point and / or the central light axis of the optical unit, e.g. such that they are not directly in line with the sample. In detail, the light emitting elements may be placed at a distance from the central light axis. For example, the distance between the light elements and the central light axis may be at least half of a diameter of the smaller opening of the conical light guide. Specifically, in a plane view from above, i.e. in a view parallel to the central light axis, the light emitting elements may be arranged outside of the smaller opening of the conical light guide. As an example, the light emitting elements may not be placed directly under the sample. Instead, the light emitting elements may be placed in such a way that a majority of the light emitted by the light emitting elements may be scattered by the scattering element at least once before reaching the smaller opening, e.g. before illuminating the sample.

[0028] At least one of the light emitting elements, preferably all of the light emitting elements, may be selected from the group consisting of: a thermal radiator, specifically an incandescent lamp, such as an in-candescent lightbulb, or a thermal infrared emitter; a heat source; a laser, such as a laser diode; a light emitting diode (LED); a miniaturized thin-film emitter; a structured light source; a gas discharge lamp.

[0029] In a further aspect, the present invention relates to a spectrometer device for analyzing at least one sample. The spectrometer device comprises: an optical unit as described herein; at least one optical detector configured for generating at least one detector signal according to the illumination of the optical detector by at least a portion of the light emitted by the light emitting element and reflected by the sample; wherein the optical unit is arranged between the optical detector and the sample.

[0030] The spectrometer device comprises the optical unit as outlined above or as described in more detail below. Thus, specifically with regard to the definition of terms reference may be made to the description of the optical unit.

[0031] The term “optical detector” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to an optical sensor configured for detecting and / or measuring optical radiation, such as for detecting and illumination and / or a light spot generated by at least one light beam and / or ray of light. The detector may specifically comprise at least one photosensitive region. The photosensitive region may be configured for being illuminated, or in other words for receiving optical radiation, and for generating at least one signal, such as an electronic signal, in response to the illumination. The photosensitive region may be located on a surface of the photodetector. The photosensitive region may specifically be a single, closed, uniform photosensitive region. However, other options may also be feasible.

[0032] In particular, the optical detector may be a detector array comprising a plurality of detector elements, wherein the detector array is configured for generating the at least one detector signal according to an illumination of the plurality of detector elements.

[0033] As an example, the spectrometer device may be a portable spectrometer device. The term “portable” as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to the property of at least one object of being moved by human force, such as by a single user. Specifically, the object characterized by the term “portable” may have a weight not exceeding 10 kg, specifically not exceeding 5 kg, more specifically not exceeding 1 kg or even not exceeding 500 g. Additionally or alternatively, the dimensions of the object characterized by the term “portable” may be such that the object extends by no more than 0.3 m into any dimension, specifically by no more than 0.2 m into any dimension. The object, specifically, may have a volume of no more than 0.03 m3, specifically of no more than 0.01 m3or even no more than 0.001 m3.

[0034] In a further aspect, the present invention relates to a spectrometer system for analyzing at least one sample. The spectrometer system comprises at least one sample and at least one spectrometer device as described herein, wherein the sample and the spectrometer device are arranged and configured for essentially homogeneously illuminating at least one measurement area of the sample by the light emitted by the light emitting elements.

[0035] The spectrometer system comprises the spectrometer device as outlined above or as described in more detail below. Thus, specifically with regard to the definition of terms reference may be made to the description of the spectrometer device as well as to the description of the optical unit comprised by the spectrometer device.

[0036] The term essentially homogeneously illuminating as used herein is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a procedure of essentially homogenous light reaching and / or impinging on an arbitrary object or element. The term essentially homogenous as used herein, specifically may refer to a characteristic of light, wherein the light has constant intensity distribution lCOnst over a predefined area within a tolerance of ± 20%, specifically within a tolerance of ± 15%. In particular, essentially homogenous elimination of the sample may refer to a procedure of optical radiation having, within a tolerance of ± 20%, specifically within a tolerance of ± 15%, a constant light intensity, impinging within a predefined area, i.e. within the measurement area, on the sample.

[0037] The term “measurement area” as used herein, and also referred to as “sample spot area”, is a broad term and is to be given its ordinary and customary meaning to a person of ordinary skill in the art and is not to be limited to a special or customized meaning. The term specifically may refer, without limitation, to a spatially limited area of a sample surface on which the analyzation of the sample by the spectrometer device is based on. In particular, a size and / or extension as well as a shape of the measurement area may be dependent on at least one property of the spectrometer device or one or more of its components, i.e. on a size and / or power of the light emitting element.

[0038] The sample may, at least in the at least one measurement area, comprise at least one inhomogeneous characteristic. In particular, the sample may comprise a distinctly non-uniformity in at least one composition or character. As an example, the sample’s characteristic may be selected from the group consisting of the sample’s color, the sample’s shape, the sample’s particle size, sample’s weight distribution, such as its mass distribution, the sample’s density, the sample’s material, the sample’s texture and the sample’s temperature. In particular, the characteristic of the sample may be selected from the group consisting of: a color, a shape, a particle size, such as a grain size or a been size, a mass distribution, a density, a material, a texture, a temperature.

[0039] In particular, the sample may have a degree of variance, such as a quantitatively or qualitatively measurable deviation from an average and / or nominal value of one or more of its characteristics, i.e. within the measurement area. In particular, the degree of variance of the at least one characteristic in the measurement area of the sample may be at least 10 %, specifically at least 20 %. For example, at least 10 %, specifically at least 20 %, of the sample shown within and / or corresponding to the measurement area may be different or may have a different characteristic than the rest of the sample within the measurement area.

[0040] As an example, the sample may be or may comprise a conglomerate of particles, such as a bulk material, for example grain kernels, coffee beans or the like. In this case specifically, the measurement area may be larger than at least one sample particle, i.e. by at least a factor of 2. Thus, as an example, at least one characteristic, such as a size and / or power, of the spectrometer device and / or of one or more of its components may be selected according to the sample to be analyzed.

[0041] In a further aspect, a use of a spectrometer device according to any one of the embodiments disclosed above or below in further detail referring to a spectrometer device is disclosed. Therein, the use of the spectrometer device for a purpose of analyzing the sample, for example of determining information related to a spectrum of the sample, is proposed. In particular, the spectrometer device may be used for a purpose of use selected from the group consisting of: an infrared detection application; a spectroscopy application; an exhaust gas monitoring application; a combustion process monitoring application; a pollution monitoring application; an industrial process monitoring application; a mixing or blending process monitoring; a chemical process monitoring application; a food processing process monitoring application; a food preparation process monitoring; a water quality monitoring application; an air quality monitoring application; a quality control application; a temperature control application; a motion control application; an exhaust control application; a gas sensing application; a gas analytics application; a motion sensing application; a chemical sensing application; a mobile application; a medical application; a mobile spectroscopy application; a food analysis application; an agricultural application, in particular characterization of soil, silage, feed, crop or produce, monitoring plant health; a plastics identification and / or recycling application.

[0042] The above-described optical unit, the spectrometer device, the spectrometer system and the proposed uses of a spectrometer device have considerable advantages over the prior art. Thus, generally, a simple, cost-efficient and still reliable optical unit for a spectrometer device for analyzing at least one sample is provided.

[0043] Specifically, the devices, systems and used as proposed herein may allow for a facilitated analyzing of samples, specifically of inhomogeneous samples. In particular, the conical light guide, by scattering the light emitted by the light emitting elements, may increase randomization of an initial light distribution of the light emitted by the light emitting elements. Thereby, for example, a homogeneity of the light may be increased. An increased homogeneity of the light may specifically decrease dependency of the distribution of the light used for analyzing the sample from manufacturing tolerances, for example from precise positioning of light emitting elements. In particular, a position within the sample spot at which a given ray impinges may not correlate to the position or angle distribution of the light emitting elements, i.e. of the source of the light. As an example, the precise position of the light emitting elements, e.g. of lightbulbs or filament within the lightbulbs, may be irrelevant and may not influence a shape of the intensity distribution. The present devices and systems may thus compared to know systems and devices decrease sensitivity to manufacturing and constructional tolerances and may increase measurement reliability and safety, e.g. even over typical quality fluctuations.

[0044] Compared to known devices and systems, the present devices and systems, specifically by being less sensible to fluctuations in manufacturing tolerances, i.e. manufacturing tolerances in the production of the light emitting elements, may allow for a higher reproducibility and better series manufacturability, thereby allowing for economical large-scale production.

[0045] In particular, when analyzing the sample with the proposed spectrometer device, such as when performing diffusive reflectance spectroscopy by using the propose optical unit for a spectrometer device, on the sample, e.g. even on inhomogeneous samples, such as on grain kernels or coffee beans, the proposed optical unit may allow for a higher measurement reproducibility and thus may increase reliability of measurement results. This may specifically be the case if the measurement area, such as a measured sample spot area, exceeds, e.g. by a factor of at least 2, the typical grain size of the sample and / or if the illumination is homogeneous across the sample area.

[0046] The present devices and systems may further be scalable, allowing for a more precise adaption of the devices to the intended field of use and / or application. In particular, a size of the conical light guide may be scalable and thus may be compatible with various light emitting elements of arbitrary size. Thereby, compared to known systems and devices, the present systems and devices, specifically the proposed optical unit for a spectrometer device, may allow for an adaption of its size to a wide variety of applications. In particular, the present devices may allow for being miniaturized, such as for being integrated into a wide variety of consumer electronics, e.g. into smartphones, wearables and / or tablets. Further, the present devices may allow for being maximized, such as for being integrated into large-scale monitoring and / or observation systems, for example in the field of recycling.

[0047] Furthermore, the use of the conical light guide may allow for multiple advantages of the proposed optical unit and the spectrometer device comprising the optical unit compared to known devices, e.g. making use of parabolic reflectors. In particular, the conical light guide by being insensitive to variations of placement and shape of the light emitting element, i.e. of the light source, may allow for robustly illuminating the sample with homogeneous light. Thereby, homogeneous sample illumination may be secured and in turn a required measurement time may be reduced and user handling may be facilitated.

[0048] In addition, the conical light guide of the optical unit for the spectrometer device may allow for a higher luminous efficacy, thereby lessening a required energy. In particular, the conical light guide, by scattering the light emitted by the light emitting elements, may increase the amount of light, i.e. the total light power, reaching the smaller opening of the conical light guide. In particular, due to the finite reflectivity of any real material, light may in general be partially absorbed upon incidence. Hence, the total light power in the reflector may decrease with increasing number of reflections off the surface. In known devices and systems, where surfaces reflect but do not scatter the light, a significant fraction of the light rays may travel around the reflector axis many times, losing some of their power with every reflection. The proposed optical unit, by scattering light by the conical light guide, may increase the probability that a light ray is scattered towards the sample before the ray has lost a significant fraction of its power. Thus, the proposed spectrometer device may be more environmentally friendly than known devices and systems.

[0049] As used herein, the terms “have”, “comprise” or “include” or any arbitrary grammatical variations thereof are used in a non-exclusive way. Thus, these terms may both refer to a situation in which, besides the feature introduced by these terms, no further features are present in the entity described in this context and to a situation in which one or more further features are present. As an example, the expressions “A has B”, “A comprises B” and “A includes B” may both refer to a situation in which, besides B, no other element is present in A (i.e. a situation in which A solely and exclusively consists of B) and to a situation in which, besides B, one or more further elements are present in entity A, such as element C, elements C and D or even further elements.

[0050] Further, it shall be noted that the terms “at least one”, “one or more” or similar expressions indicating that a feature or element may be present once or more than once typically are used only once when introducing the respective feature or element. In most cases, when referring to the respective feature or element, the expressions “at least one” or “one or more” are not repeated, nonwithstanding the fact that the respective feature or element may be present once or more than once.

[0051] Further, as used herein, the terms "preferably", "more preferably", "particularly", "more particularly", "specifically", "more specifically" or similar terms are used in conjunction with optional features, without restricting alternative possibilities. Thus, features introduced by these terms are optional features and are not intended to restrict the scope of the claims in any way. The invention may, as the skilled person will recognize, be performed by using alternative features. Similarly, features introduced by "in an embodiment of the invention" or similar expressions are intended to be optional features, without any restriction regarding alternative embodiments of the invention, without any restrictions regarding the scope of the invention and without any restriction regarding the possibility of combining the features introduced in such way with other optional or non-optional features of the invention.

[0052] Summarizing and without excluding further possible embodiments, the following embodiments may be envisaged:

[0053] Embodiment 1 : An optical unit for a spectrometer device for analyzing at least one sample, comprising a plurality of light emitting elements, i.e. at least two light emitting elements, configured for emitting light for illuminating the sample; a conical light guide, e.g. configured for homogenizing the light emitted by the light emitting elements, comprising at least one scattering element arranged between opposing, differently sized openings of the conical light guide, the conical light guide, specifically by its scattering element, being configured for scattering, i.e. diffusely reflecting, at least part of the light emitted by the light emitting elements, i.e. the part of the emitted light illuminating the scattering element; at least one reflector configured for reflecting at least part of the light scattered by the light guide in a direction toward the sample, wherein the light emitting elements and the reflector are arranged on a side of the conical light guide having the bigger opening, wherein the sample is placeable on a side of the conical light guide having the smaller opening.

[0054] Embodiment 2: The optical unit according to the preceding embodiment, wherein the scattering element comprises an uneven, irregularly patterned, reflective surface.

[0055] Embodiment 3: The optical unit according to the preceding embodiment, wherein the surface comprises a diffuser configured for total reflection.

[0056] Embodiment 4: The optical unit according to any one of the preceding embodiments, wherein the scattering element comprises at least one material selected from the group consisting of: a metal and / or metallic material, such as copper, gold, silver, aluminum, platin; a glass, e.g.

[0057] Quartz glass; a plastic material; a ceramic.

[0058] Embodiment 5: The optical unit according to any one of the preceding embodiments, wherein the conical light guide is hollow or is at least partially filled with at least one optically transparent material.

[0059] Embodiment 6: The optical unit according to any one of the preceding embodiments, wherein an area ai of the smaller opening is smaller than an area a2 of the bigger opening of the conical light guide by at least a factor of 1 .1 , such that such that a2 1.1 ai, specifically a2> 1.5 ai; more specifically a2 1 .7 ai. Embodiment 7: The optical unit according to any one of the preceding embodiments, wherein the light emitting elements are arranged at least partially intruding into the bigger opening of the conical light guide.

[0060] Embodiment 8: The optical unit according to any one of the preceding embodiments, wherein the light emitting elements are arranged around a center point and / or a central light axis of the optical unit, such as around a central axis of the conical light guide, preferably in shape of a circle or an oval.

[0061] Embodiment 9: The optical unit according to the preceding embodiment, wherein the light emitting elements are arranged equidistantly around the center point and / or central light axis.

[0062] Embodiment 10: The optical unit according to any one of the two preceding claims, wherein the light emitting elements are arranged at a distance from the central light axis of at least half of a diameter of the smaller opening of the conical light guide.

[0063] Embodiment 11 : The optical unit according to any one of the preceding embodiments, wherein at least one of the light emitting elements, preferably all of the light emitting elements, is selected from the group consisting of: a thermal radiator, specifically an incandescent lamp, such as an incandescent lightbulb, or a thermal infrared emitter; a heat source; a laser, such as a laser diode; a light emitting diode (LED); a miniaturized thin-film emitter; a structured light source; a gas discharge lamp.

[0064] Embodiment 12: A spectrometer device for analyzing at least one sample, comprising: an optical unit according to any one of the preceding embodiments; at least one optical detector configured for generating at least one detector signal according to the illumination of the optical detector by at least a portion of the light emitted by the light emitting element and reflected by the sample; wherein the optical unit is arranged between the optical detector and the sample.

[0065] Embodiment 13: The spectrometer device according to the preceding embodiment, wherein the optical detector is a detector array comprising a plurality of detector elements, wherein the detector array is configured for generating the at least one detector signal according to an illumination of the plurality of detector elements.

[0066] Embodiment 14: A spectrometer system for analyzing at least one sample, the spectrometer system comprising at least one sample and at least one spectrometer device according to any one of the preceding embodiments referring to a spectrometer device, wherein the sample and the spectrometer device are arranged and configured for essentially homogeneously illuminating at least one measurement area of the sample by the light emitted by the light emitting elements. Embodiment 15: The spectrometer system according to the preceding embodiment, wherein the sample, at least in the at least one measurement area, comprises at least one inhomogeneous characteristic, specifically a distinctly non-uniformity in at least one composition or character of the sample.

[0067] Embodiment 16: The spectrometer system according to the preceding embodiment, wherein a degree of variance of the at least one characteristic in the measurement area of the sample is at least 10 %, specifically at least 20 %.

[0068] Embodiment 17: The spectrometer system according to any one of the two preceding embodiments, wherein the characteristic of the sample is selected from the group consisting of: a color, a shape, a particle size, such as a grain size or bean size, a mass distribution, a density, a material, a texture, a temperature.

[0069] Embodiment 18: A use of a spectrometer device according to any one of the preceding embodiments referring to a spectrometer device in one or more of: an infrared detection application; a spectroscopy application; an exhaust gas monitoring application; a combustion process monitoring application; a pollution monitoring application; an industrial process monitoring application; a mixing or blending process monitoring; a chemical process monitoring application; a food processing process monitoring application; a food preparation process monitoring; a water quality monitoring application; an air quality monitoring application; a quality control application; a temperature control application; a motion control application; an exhaust control application; a gas sensing application; a gas analytics application; a motion sensing application; a chemical sensing application; a mobile application; a medical application; a mobile spectroscopy application; a food analysis application; an agricultural application, in particular characterization of soil, silage, feed, crop or produce, monitoring plant health; a plastics identification and / or recycling application.

[0070] Short description of the Figures

[0071] Further optional features and embodiments will be disclosed in more detail in the subsequent description of embodiments, preferably in conjunction with the dependent claims. Therein, the respective optional features may be realized in an isolated fashion as well as in any arbitrary feasible combination, as the skilled person will realize. The scope of the invention is not restricted by the preferred embodiments. The embodiments are schematically depicted in the Figures. Therein, identical reference numbers in these Figures refer to identical or functionally comparable elements.

[0072] In the Figures:

[0073] Figure 1 shows an embodiment of a spectrometer system with an embodiment of a spectrometer device comprising an embodiment of an optical unit in a perspective view; Figure 2 shows an embodiment of a spectrometer device with an embodiment of an optical unit in a sectional perspective view;

[0074] Figure 3 shows an embodiment of an optical unit in a sectional view;

[0075] Figure 4 schematically illustrates a difference between specular reflection and diffuse reflection of light on a surface;

[0076] Figure 5 illustrates a measured intensity distribution within a sample spot of an embodiment of an optical unit;

[0077] Figure 6 illustrates a horizontal and vertical cut through the intensity distribution illustrated in Figure 5;

[0078] Figure 7 illustrates a graph of an efficiency of a scattering element of an embodiment of an optical unit over a scatter fraction for different reflectivities of the surface;

[0079] Figures 8 to 13 illustrate measured intensity distributions within a sample spot of an embodiment of an optical unit wherein for each of the figures the light emitting elements were are arranged differently; and

[0080] Figure 14 illustrates an exemplary embodiment of a measurement area of an inhomogeneous sample.

[0081] Detailed description of the embodiments

[0082] Figure 1 shows, in a perspective view, an embodiment of a spectrometer system 110 with an embodiment of a spectrometer device 112 comprising an embodiment of an optical unit 114. The spectrometer system 110 is configured for analyzing at least one sample 116 and comprises the sample 116 and the spectrometer device 112.

[0083] In a sectional perspective view, Figure 2 illustrates an embodiment of a spectrometer device 112, specifically the same embodiment of the spectrometer device 112 as illustrated in Figure 1 , with an embodiment of an optical unit 114. The spectrometer device 112 comprises the embodiment of the optical unit 114 and at least one optical detector 118 configured for generating at least one detector signal according to the illumination of the optical detector 118 by at least a portion of light emitted by a plurality of light emitting elements 120 of the optical unit 114 and reflected by the sample 116.

[0084] Figure 3 shows, in a sectional view, an embodiment of an optical unit 114, specifically the same embodiment of the optical unit 114 as illustrated in Figures 1 and 2. The optical unit 114 comprises the plurality of light emitting elements 120 configured for emitting light for illuminating the sample 116. The optical unit 114 further comprises a conical light guide 122 for example configured for homogenizing the light emitted by the light emitting elements 120. The conical light guide 122 comprises at least one scattering element 124 arranged between opposing, differently sized openings 126 of the conical light guide 122. The conical light guide 122, specifically by its scattering element 124, is configured for scattering, i.e. diffusely reflecting, at least part of the light emitted by the light emitting elements 120, i.e. the part of the emitted light illuminating the scattering element 124. Further, the optical unit 114 comprises at least one reflector 128 configured for reflecting at least part of the light scattered by the light guide 122 in a direction toward the sample 116. The light emitting elements 120 and the reflector 128 are arranged on a side of the conical light guide 122 having the bigger opening 130, wherein the sample 116 is placeable on a side of the conical light guide 122 having the smaller opening 132.

[0085] Exemplary beam paths of the light emitted by the light emitting elements 120 are illustrated in Figure 3 by dotted arrows. As illustrated, a part of the light emitted by the light emitting elements 120 may directly travel through the smaller opening 132, i.e. in a direction towards the sample 116, specifically in a direct beam path 134. Another part of the light emitted by the light emitting elements 120 may travel reflected beam paths 136 as exemplarily illustrated in Figure 3, by being diffusely reflected by the scattering element 122 and subsequently reflected by the reflector 128, i.e. by specular reflection, towards the smaller opening 132.

[0086] A schematic illustration of the difference between specular reflection and diffuse reflection of light on a surface 138 is illustrated in Figure 4. In the specular reflection, an incoming beam of light 140 is reflected by the surface 138, such that an angle of incidence equals angle of reflection, i.e. the angle of reflection of an specular outgoing beam of light 142 is the same as the angle of incidence of the incoming beam of light 140. In the diffuse reflection, the incoming beam of light 140 is scattered into a plurality of scattered outgoing beams of light 144.

[0087] In the spectrometer system 110, the sample 116 and the spectrometer device 112 are arranged and configured for essentially homogeneously illuminating at least one measurement area 146 of the sample 116, i.e. as exemplarily illustrated in Figure 14, by the light emitted by the light emitting elements 120. The measurement area 146 of the sample 116 may correspond to a sample spot 148 of the spectrometer device 112, specifically to the smaller opening 132 of the conical light guide 122 on which the sample 116 may be placed.

[0088] Figure 5 illustrates a measured intensity distribution within the sample spot 148 of an embodiment of an optical unit 114 and Figure 6 illustrates a horizontal and vertical cut through the intensity distribution illustrated in Figure 5. In particular, Figures 5 and 6 may show a measured homogeneous intensity distribution of light that illuminates the measurement area 146 of the sample 116 positioned on top of the smaller opening 132 of the conical light guide 122, i.e. of light illuminating the sample spot 148 of the optical unit, e.g. at least partially scattered by its conical reflector. In Figure 6, the x-axis 150 refers to the position, while the y-axis 152 refers to the intensity measured in counts. Further, in the graphs, the dotted line 154 represents the vertical cut through the intensity distribution illustrated in Figure 5 and the dashed line 156 represents the horizontal cut through the intensity distribution illustrated in Figure 5.

[0089] Figure 7 shows a graph of an efficiency of a scattering element of an embodiment of an optical unit 114 over a scatter fraction for different reflectivities of the surface. In this graph, the x-axis 150 refers to the scatter fraction, i.e. between 0.5 and 1 .0, wherein the y-axis 152 refers to the efficiency. As an example, results of a simulation of the efficiency of a scattering reflector versus scatter fraction for different reflectivities of the surface may be shown. Therein, the efficiency may be the ratio of the light power exiting through the smaller opening 132 and the total light power emitted by the light emitting elements 120, i.e. by the light sources. The scatter fraction may be the fraction of reflected light that is scattered upon incidence, while the rest is specularly reflected. The reflectivity may be the fraction of light that is reflected upon incidence on the surface, wherein the rest may be absorbed. In particular, Figure 7 may illustrate the efficiency for a plurality of scattering elements 124 having different reflectivities. As an example, a 0.95-graph 158 may illustrate the efficiency over the scatter fraction for a scattering element 124 having a reflectivitiy of 95%, a 0.96-graph 160 may illustrate the efficiency over the scatter fraction for a scattering element 124 having a reflectivitiy of 96%, a 0.98-graph 162 may illustrate the efficiency over the scatter fraction for a scattering element 124 having a reflectivitiy of 98%, a 0.95- graph 164 may illustrate the efficiency over the scatter fraction for a scattering element 124 having a reflectivitiy of 99% and a 1 .00-graph 166 may illustrate the efficiency over the scatter fraction for a scattering element 124 having a reflectivitiy of 100%.

[0090] Figures 8 to 13 illustrate measured intensity distributions within a sample spot 148 of an embodiment of an optical unit 114, wherein for each of the Figures the light emitting elements 120 were arranged differently. In the graphs, both the x-axis 150 and the y-axis 152 refer to a position in mm, wherein each dot refers to the number of counts and thus, the darker one area is, the higher the number of counts for that position on the sample spot 148.

[0091] Figure 14 illustrates an exemplary embodiment of a measurement area 146 of an inhomogeneous sample 116 of a spectrometer system 110. In particular, the inhomogeneous sample 116, specifically in a section corresponding to the measurement area 146, may comprise a distinctly non-uniformity in at least one of its composition or character, e.g. in its particle size. List of reference numbers spectrometer system spectrometer device optical unit sample optical detector light emitting element light guide scattering element opening reflector bigger opening smaller opening direct beam path reflected beam path surface incoming beam of light specular outgoing beam of light scattered outgoing beam of light measurement area sample spot x-axis y-axis dotted line dashed line

[0092] 0.95-graph

[0093] 0.96-graph

[0094] 0.98-graph

[0095] 0.99-graph

[0096] 1 .00-graph

Claims

Claims1 . An optical unit (114) for a spectrometer device (112) for analyzing at least one sample (116), comprising a plurality of light emitting elements (120) configured for emitting light for illuminating the sample (116); a conical light guide (122) comprising at least one scattering element (124) arranged between opposing, differently sized openings (126) of the conical light guide (122), the conical light guide (122) being configured for scattering at least part of the light emitted by the light emitting elements (120); at least one reflector (128) configured for reflecting at least part of the light scattered by the light guide (122) in a direction toward the sample (116), wherein the light emitting elements (120) and the reflector (128) are arranged on a side of the conical light guide (122) having the bigger opening (130), wherein the sample (116) is placeable on a side of the conical light guide (122) having the smaller opening (132).

2. The optical unit (114) according to the preceding claim, wherein the scattering element (124) comprises an uneven, irregularly patterned, reflective surface.

3. The optical unit (114) according to the preceding claim, wherein the surface comprises a diffuser configured for total reflection.

4. The optical unit (114) according to any one of the preceding claims, wherein the scattering element (124) comprises at least one material selected from the group consisting of: a metal and / or metallic material; a glass; a plastic material; a ceramic.

5. The optical unit (114) according to any one of the preceding claims, wherein the conical light guide (122) is hollow or is at least partially filled with at least one optically transparent material.

6. The optical unit (114) according to any one of the preceding claims, wherein an area ai of the smaller opening (132) is smaller than an area a2 of the bigger opening (130) of the conical light guide (122) by at least a factor of 1 .1 , such that a2 1.1 ai.

7. The optical unit (114) according to any one of the preceding claims, wherein the light emitting elements (120) are arranged at least partially intruding into the bigger opening (130) of the conical light guide (122).

8. The optical unit (114) according to any one of the preceding claims, wherein the light emitting elements (120) are arranged around a center point and / or a central light axis of the optical unit (114), wherein the light emitting elements are arranged at a distance from thecentral light axis of at least half of a diameter of the smaller opening of the conical light guide.

9. The optical unit (114) according to any one of the preceding claims, wherein at least one of the light emitting elements (120) is selected from the group consisting of: a thermal radiator; a heat source; a laser; a light emitting diode (LED); a miniaturized thin-film emitter; a structured light source; a gas discharge lamp.

10. A spectrometer device (112) for analyzing at least one sample (116), comprising: an optical unit (114) according to any one of the preceding claims; at least one optical detector (118) configured for generating at least one detector signal according to the illumination of the optical detector (118) by at least a portion of the light emitted by the light emitting element (120) and reflected by the sample (116); wherein the optical unit (114) is arranged between the optical detector (118) and the sample (116).

11. A spectrometer system (110) for analyzing at least one sample (116), the spectrometer system (110) comprising at least one sample (116) and at least one spectrometer device (112) according to any one of the preceding claims referring to a spectrometer device (112), wherein the sample (116) and the spectrometer device (112) are arranged and configured for essentially homogeneously illuminating at least one measurement area (146) of the sample (116) by the light emitted by the light emitting elements (120).

12. The spectrometer system (110) according to the preceding claim, wherein the sample (116), at least in the at least one measurement area (146), comprises at least one inhomogeneous characteristic.

13. The spectrometer system (110) according to the preceding claim, wherein a degree of variance of the at least one characteristic in the measurement area (146) of the sample (116) is at least 10 %.

14. The spectrometer system (110) according to any one of the two preceding claims, wherein the characteristic of the sample (116) is selected from the group consisting of: a color, a shape, a particle size, a mass distribution, a density, a material, a texture, a temperature.

15. A use of a spectrometer device (112) according to any one of the preceding claims referring to a spectrometer device (112) in one or more of: an infrared detection application; a spectroscopy application; an exhaust gas monitoring application; a combustion process monitoring application; a pollution monitoring application; an industrial process monitoring application; a mixing or blending process monitoring; a chemical process monitoring application; a food processing process monitoring application; a food preparation process mon-itoring; a water quality monitoring application; an air quality monitoring application; a quality control application; a temperature control application; a motion control application; an exhaust control application; a gas sensing application; a gas analytics application; a motion sensing application; a chemical sensing application; a mobile application; a medical application; a mobile spectroscopy application; a food analysis application; an agricultural application, in particular characterization of soil, silage, feed, crop or produce, monitoring plant health; a plastics identification and / or recycling application.

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