WO2016164995A2 - A measuring head applicable to a spectrometer, and a spectrometer - Google Patents

Abstract

One describes a measuring head (1) applicable to a spectrometer (40), the measuring head (1) having a cylindrical shape defining a plane surface and a convex face, the measuring head (1) being configured so as to receive a plurality of semi-conductive components (20, 21) on the plane surface. The measuring head (1) being further provided with a center (10) arranged on the plane surface, so that in the center there is a first semi-conductive component (21) of the plurality of semi-conductive components (20, 21), and around the center (10) there are a set of semi- conductive components (20) of the plurality of semi-conductive components (20, 21). The present invention further relates to a spectrometer provided with the proposed measuring head.

Description

Specification of the Patent of Invention for: "A MEASURING HEAD APPLICABLE TO A SPECTROMETER, AMD A SPECTROMETER"

[1 ] This application claims priority of the Brazilian patent application no. BR102015008771 -3, filed on April 17, 2015, the contents of which are integrally incorporated here by reference. The present invention relates to a measuring head applicable to a spectrometer, used for discriminating alterations in the composition of liquid and solid compositions. The invention further deals with a spectrometer using the measuring head proposed.

[2] The present invention approaches principles of optical physics that deal with the interaction of electromagnetic radiation with the matter to be analyzed by the spectrometer. This area is called optical Spectrometry or absorption Spectrophotometry, which consists of the incidence of a light beam onto the sample (substance under analysis) and the capture by a photodetector of the light transmitted, or reflected and/or spread.

[3] Among the techniques that compose spectrophotometry, the most widely used are transmission spectrophotometry, which is characterized by supplying information of absorbance and transmittance of the sample, and diffuse reflectance, which is characterized by supplying complementary or similar information about the sample under analysis.

[4] For samples of low concentrations, the most widely used technique is transmission spectrophotometry, but in the case of highly concentrated samples and that still have, in their composition, particles in suspension, powders, micelles, among others, the most widely used technique is diffuse reflectance.

[5] The use of diffuse reflectance in an industrial environment has been occupying space as a tool for monitoring the production and quality control process. As a marking example, one cites the varied composition raw milk with respect to quality: normal, instable, acidic and adulterated. Other examples are found in the studies and analysis of intact soils, surface compositions, pigments for paint and cosmetic industries, and many more.

[6] The present invention is based on the principles of diffuse reflectance using small source of light, that is, light emitting diodes (LED) by virtue of their convenience, low consumption of energy and small volume.

[7] More specifically, the present invention relates to a measuring head and a spectrometer provided with such a component. Said spectrometer and, consequently, its measuring head is considered tunable because it operates in narrow bands of the electromagnetic spectrum, according to the absorption bands of the substance under analysis and also because it enables easily the change of the set of LEDs according to the spectral band of interest.

[8] The use of a spectrometer may take place at both an industrial plant (food, dairy products and others) and in the field, close to the production site and/or near the place where the product to be analyzed is collected. It can be arranged on trucks intended for collection of raw materials such as raw milk, agricultural machines, among many others.

[9] Besides, it can be installed on tanks for observation of products in liquid form for the purpose of monitoring the variation in the quality of the products along the storage time. Therefore, it is an instrument that can also be dipped into the liquid under analysis, without the need for any protective apparatus.

[10] One should mention that the applicability of the spectrometer/measuring head described in the present invention is not restricted to the examples mentioned above.

[1 1 ] With regard to the knowledge disclosed in the prior art, one can cite a few documents that deal with spectrometers for the same purpose as that of the present invention. However, as will be seen later, the prior-art spectrometers exhibit differences, chiefly when the measuring head used therein is compared with the one of the present invention.

[12] More specifically, the marking differences between the prior-art equipment and the creation proposed herein are the configuration of the measuring head (optical arrangement) and the arrangements of its components, so that it can be used either dipped in liquid or not. In this regard, it is valid to point out the contents disclosed in documents WO 2008/124542, WO2000/64242 and US 8,844,931 . [13] With regard to document WO2000 64242, it discloses a measuring head in planar base configuration, composed by a number of LEDs distributed around a conical optical guide, that is, the LEDs are arranged circularly on a plane base in the form of a disc.

[14] Such a disc is connected to molded concentric rings forming two cavities, so that, in one of them an acrylic ring is fitted, which plays the role of an optical outlet window and, in the other, in the center of the mold, a conical formation (optical guide) stands out, the plane base of which is the optical inlet window,

[15] At the top of said optical guide there is the photodetector. The

LEDs surround the optical guide concentrically, as can be observed in figures 3 and 4 of said international publication.

[16] The distribution of light that emerges from the measuring head of

WO 2000/64242 is similar to that of a flashlight since it does not have the light beams collimated to a focal region. So the light beam illuminates divergently the sample surface that reflects the light diffusely.

[17] It is important to point out that there is no light collimation on the sample to enhance the efficiency of capture of this light by the photodetector. Some of the diffusely spread light returns to the measuring head, following the optical guide until it reaches the photodetector.

[18] Thus, the capture of light is not efficient, since the beams of light spread in low angles are not detected, because they do not penetrate the optical guide. It is not a robust system because it contains movable parts that are close together and may be easily damaged.

[19] Further, it may be an open device (exposed optical components); it may not be used ion direct contact with the sample, let alone be dipped into liquids. The measuring head disclosed in WO 2000/64242 always needs a transparent protective window. So the use of this device requires the sample to always be in a container (sample-holder) for carrying out the analysis.

[20] The measuring head and the spectrometer proposed in the present invention differ from the matter disclosed in WO 2000/64242 in the configuration and functionality of the optical system, ion the robustness thereof, the mounting simplicity and in a number of applications.

[21 ] In the present invention, the measuring head is a single piece that serves for both exit of converging light and entrance of light that is reflected and collimated in the photodetector region. More specifically, the diffuse or reflected light is oriented always in the direction of the photodetector due to the effect of the shape of the converging lens, enhancing the capture of light and improving the signal/noise relation.

[22] The mounting of the components is of great convenience, since it does not involve various individual pieces to be integrated to the spectrometer. When there are different pieces to be mounted, the chance of losing the optical alignment is great, and this may cause deficiency in the operation, requiring correction.

[23] In the present invention, there is no such diversity of pieces to mount. So the difficulty set forth above does not occur. This is a great advantage, because, since this is a single piece, there is no need for maintenance in order to correct the optical alignment. Once it has been mounted, it will remain in the same way.

[24] Further, since the measuring head proposed here in is a sealed device, it may be dipped directly into the liquid, or else if may further operate in aggressive environments (taking certain precautions as to the operation distance), like in spectroscopic studies of intact soils, that is, in loco, which is not the case with the device described in WO 2000/84242, since, as already said, its components are exposed.

[25] Using the head disclosed in WO 2000/64242, the sample will always be conditioned to a container with transparent walls, whereas in the present invention the use of a container for receiving the sample is optional.

[26] On the other hand, US 6,844,931 discloses a device formed by a number of mounted and fixed parts, optical components such as lenses, mirrors and LEDs.

[27] The device disclosed herein has a circular shape with the LEDs arranged in concentric circles, so that for each LED there is a set of lenses associated. The lights of the LEDs pass through the set of lenses that coliimate on the surface of mirrors arranged at various angles to direct the beams of light in a focal area on the sample.

[28] This array of lenses and mirrors with different angles results from the fact that the device has more than one concentric circle of LEDs. So the angles should be different in order to compensate the radial distances of each circle with a view to obtain a lighted focal region on the sample.

[29] Further, the device uses a combination of white and ultraviolet

LEDs and an additional array of blue, green and fed (RGB) LEDs, which, when mixed, distribute the spectrum visually. In the center of the circle there is a wide lens that serves to capture the reflected light.

[30] Thus, this is a sample illuminating head whose diffusely reflected light is caught perpendicularly to the sample surface and some of the reflected light is directed and coilimated by the lens at a focal point where one can install a photodetector or an optical fiber cable, and the latter, in turn, leads the light as far as the entrance of a monochromator or an integrating sphere.

[31 ] The mounting of the device disclosed in this US patent is complex due to the multiple angles of the mirrors to direct the beams of light in the focal area on the sample. Additionally, the lenses should be installed on blocks and with different focal lengths. Due to this complexify, this device has low robustness for field operation.

[32] Additionally, the illumination is polychromatic, which needs a monochromator or an interference filter to decompose the reflected light and obtain the reflectance spectrum of the sample. For protection of the optical system there is an optical window closing the set of semiconductive components and the lenses. In this regard, it is known that the more optical components in the path of the light the more intensity loss there will be and the worse the signal/noise will be. So, due to the construction mode of this device low intensity of light reaching the photodetector is expected.

[33] Comparing the measuring head proposed in the present invention with that disclosed in US 6,844,931 , significant differences can be observed: in the present invention, the measuring head does not need sets of lenses and mirrors for orientation and collimation of light, its configuration in the form of converging lens with the LEDs installed parallel to the optical axis of the lens in a single block enables collimation and detection of light without the need for multi-angles for orientation of the beams of light.

[34] Further, the LEDs used on the measuring head proposed herein are monochromatic with the wavelengths installed according to the application or the interval of interest. On the other hand, the device disclosed in US 6,844,931 cannot be used in the "dippable" mode because the optical components are exposed and housed in open cavities.

[35] Since the device of US 6,844,931 has movable parts, with complex and weak mounting, it is not so robust and convenient as the measuring head and spectrometer proposed in the present invention.

[36] With regard to WO 2008/124542, the measuring head disclosed therein is quite similar to that of US 6,844,931 as to the conception of its parts.

[37] WO 2008/124542 discloses eight LEDs arranged in circle and housed in a piece called "diffuser collar" (reference number 15), which in turn fits into the so-called "aperture cone" (reference number 18). Each LED has a lens for light collimation, which in turn is directed to the wall of the reflecting piece "aperture cone", following to the cone outlet, where the sample is placed.

[38] In this document WO 2008/124542 one also uses a coliimating lens to capture the light reflected from the sample and focus it in the region of an interference filter or at one of the ends of an optical fiber cable. One can consider that the device disclosed in the document under analysis is a miniature of the measuring head disclosed in US 6,844,931 , the main difference lies in the fact that in the device disclosed in WO 2008/124542 eight ultraviolet (395 nanometer (nm)) or blue (about 470 nm) LEDs associated to the films made from fluorescent materials are used, such as yellow phosphor, for conversion to white light. From these LEDs only one does not receive the fluorescent covering.

[39] Said fluorescent covering is the innovative part of this device, while in the US patent the lights of the different LEDs are combined to form the white emission (principle of functioning of computer and TV-set screens), the detection principle disclosed in WO 2008/124542 takes place by means of an interference filter associated to a matrix of photodetectors arranged linearly of the type "Charge Coupled Device" (CCD) or through an optical fiber cable the external end of which is distributed over the CCD window.

[40] The interference filter decomposes the reflected light into wavelengths and distributes it over the CCD, In this way, each wavelength is detected by one of the photodiodes that compose the CCD. Therefore, it is important to point out that the marking or innovative difference between the two devices lies in the use of fluorescent materials associated to a type of LED.

[41 ] Further about this sensor device, the electronic circuit of feed, control and detection is mounted on the same printed circuit board together with the LEDs. In this way, it does not enable replacement of the set of LEDs easily. Additionally, it is not robust and has a high degree of complexity due to the various integrating parts, as well as to the type of interference filter.

[42] In comparison with the measuring head proposed in the present invention, the collimation effect is naturally achieved through the shape of converting lens of the head, not by a spread or reflecting surface. The LEDs are monochromatic, as determined by the manufacturers, and do not need introduction of films or color filters (or fluorescent materials) to obtain the desired spectral band.

[43] Due to the ease of mounting and dismounting this device, the set of LEDs, distributed circularly, operating at a determined interval of wavelength, may be removed or replaced by others of different spectral bands, without any modification in the system. In this way, the spectrometer (and the measuring head) of the present invention can be tunable to spectral bands of interest.

[44] The detector is a phototransistor photodiode of wide response, of spectral broadness ranging from 350 to 1 150 nm, covering the w3hole band of interest. The photodetector is in the focal region of the measuring head, capturing the whole light that goes into the material of this device. Thus, the same lens that collimates the light incident upon the sample is also the same one that catches and collimates onto the detector the light reflected therefrom.

[45] This characteristic is extremely advantageous, since it dispenses with the use of an extra lens in the front of the detector to make this capture of spread light, as can be seen in the prior-art documents cited before. In such documents, one observes that the collimating lens is a fundamental component in the functioning of the devices described.

[46] Since the photodetector used in the spectrometer (and the measuring head) described in the present invention is of broad spectral defection band and is in the focal region inside the measuring head, then, depending on the application, it dispenses with the arrays with CCD or optical fiber that raises the cost of the equipment, corresponding to an optimized system in terms of construction and detection of light.

[47] The use of the CCD is advantageous when one desires rapid detection versus small number of wavelengths to be determined. For a small number of LEDs, the cost/benefit relation is high due to the price of a CCD versus that of a photodiode or a phototransistor of general purpose, that is, the CCD may cost tens or hundreds of dollars as compared to the cost of a few cents of a phototransistor (photodetector) of general purpose.

[48] The measuring head proposed in the present invention presents the advantages of having the LEDs distributed circularly around the axle of a cylindrical piece, the photodetector being in the center. Since the LEDs are actuated in pairs, the collimated beam of light forms a symmetric area in the focal region.

[49] In the documents cited before there is no such symmetric distribution of light for a given wavelength, being limited to the emission of a LED at a time (WO 2000/64242) or of all the emitters simultaneously, as described in documents WO 2008/124542 and US 6,844,931 .

[50] The direct use of LEDs that emit in the region of interest it is more effective if compared to the above-cited art. The symmetric distribution of light over the sample provides high signal/noise relation and easy detection, as is the case of the measuring head and spectrometer proposed in the present invention. Further, the use of fluorescent substances or combination of LEDs does not guarantee homogeneous illumination at all the wavelengths.

[51 ] Thus, as demonstrated above, the devices disclosed in the prior- art documents presents advantages in both structural and operational nature I with respect to the measuring head and spectrometer proposed in the present invention.

Objectives of the invention

[52] The present invention has the objective of providing a measuring head and a spectrometer provided with such a measuring head, wherein the structural configuration specifically of the measuring head and its components optimize the optical coupling of the parts.

[53] A second objective of the present invention is to provide a measuring head and a spectrometer provided with such a measuring head that is portable, computerized and tunable to wavelengths of the electromagnetic radiation.

[54] An additional objective of the present invention is to provide a measuring head and a spectrometer provided with such a measuring head that can be used directly in contact with a liquid sample.

[55] The present invention has also the objective of providing a measuring head and a spectrometer provided with such a measuring head that can be used in both an industrial plant and in the field, close to the production site and/or place of collection of the product to be analyzed.

[56] A further objective of the present invention is to provide a measuring head and a spectrometer provided with such a measuring head wherein the data on the sample can be obtained rapidly, in less than 30 seconds.

[57] It is also an additional objective of the present invention to provide a measuring head and a spectrometer provided with such a measuring head, capable of being used on raw-material collection trucks. [58] Additionally, the present invention has the objective of providing a measuring head and a spectrometer provided with such a measuring head, wherein the LEDs are arranged diametrically around a center, which point receives a photodetector.

Brief description of the invention

[59] The present invention relates to a measuring head applicable to a spectrometer, the measuring head being provided with a cylindrical shape defining a plane (back) surface and a convex (frontal) face.

[60] The measuring head is configured so as to receive a plurality of semi-conductive components inserted into cavities, longitudinal to the cylindrical shape, open in the plane surface and arranged radially around a central point, and is further provided with a central cavity arranged on the plane surface, the depth of which should be reach the focal region inside the cylindrical body of this head, of the convex lens (front face).

[61 ] In the central cavity, a first semi-conductive component of the plurality of semi-conductive components is accommodated, and circularly around the center there are a set of semi-conductive components of the plurality of semi-conductive components. The present invention further relates to a spectrometer provided with said measuring head.

Brief description of the drawings

[62] The present invention will now be described in greater detail with reference to an example of embodiment represented in the drawings. The figures show:

[63] Figure 1 is a perspective view of the measuring head proposed in the present invention;

[64] Figure 2 is a cross-sectional view of the measuring head proposed in the present invention;

[65] Figure 3 is a cross-sectional additional view of the measuring head proposed in the present invention;

[66] Figure 4 is a representation of the array of the arrangement of the light emitting diodes and of the photodetector on the measuring head proposed in the present invention; [67] Figure 5 is a cross-sectional view representing the beams of light emitted, reflected internally and transmitted to the external medium, using the measuring head proposed in the present invention;

[68] Figure 6 is a cross-sectional view representing the beams of lights emitted, reflected internally, reflected due to the sample and transmitted to the external medium;

[69] Figure 7 is a representation of the beam of light that configures the total internal reflection, as discussed in the present invention;

[70] Figure 8 is a representation of the support body for fixation of the measuring head proposed in the present invention;

[71 ] Figure 9 is a representation of a mode of use of the spectrometer and measuring head proposed in the present invention;

[72] Figure 10 is a representation of the reflector that can be used as an accessory to the spectrometer and the measuring head proposed in the present invention;

[73] Figure 1 1 is a representation of the shield cabinet that can be used as an accessory to the spectrometer and the measuring head proposed in the present invention;

[74] Figure 12 is a representation of the body that can be used as an accessory to the spectrometer and the measuring head proposed in the present invention;

[75] Figure 13 is an alternative representation of the shield cabinet that can be used as an accessory to the spectrometer and the measuring head proposed in the present invention;

[76] Figure 14 is an alternative representation of the body that can be used as an accessory to the spectrometer and the measuring head proposed in the present invention;

[77] Figure 15 is a representation of the shield cover that can be used as an accessory to the spectrometer and the measuring head proposed in the present invention;

[78] Figure 16 is a representation of an additional mode of use of the spectrometer and measuring head proposed in the present invention; [79] Figure 17 is a representation of the support that can be used as an accessory to the spectrometer and the measuring head proposed in the present invention;

[80] Figure 18 is an illustration of a first mode of practical use of the spectrometer and measuring head proposed ion the present invention;

[81 ] Figure 19 is an illustration of a second practical use of the spectrometer and the measuring head proposed in the present invention;

[82] Figure 20 is an illustration of a third mode of practical use of the spectrometer and the measuring head proposed in the present invention;

[83] Figure 21 is an illustration of a fourth mode of practical use of the spectrometer and the measuring head proposed in the present invention;

[84] Figure 22 is an illustration of the spectrometer and the measuring head associated to a signal conditioner.

Detailed description of the figures

[85] Figure 1 illustrates a perspective view of the measuring head (1 ) proposed in the repent invention. The measuring head (1 ) is a single piece, made from a transparent material, such as polymers polymethylmethacrylate

(PMMA) or acrylic, polycarbonate, polyethylene terephthalate (PET.

[86] The measuring head (1 ) may also be made of glasses with spectroscopic quality (Borosiiicate - BK7), quartz and molten silica, or any other transparent materials, in the spectral region of interest, which can be molded in the form shown in Figure 1.

[87] In this preferred embodiment, the material used for making the measuring head (1 ) is acrylic (PMMA), since the latter is a polymer of high optical transparency, with refraction index close to that of water, glass, quartz and silica (n= 1 .5 to 1 ,55), transparent from the ultraviolet (300 nm) region, through the visible region, to a part of the near red (1200 nm).

[88] Further, acrylic is more resistant to mechanical shock than glass, easy to work on a mechanical turning machine and provides optimum final finish.

[89] One observes in figure 1 that the measuring head (1 ) proposed herein has cylindrical shape, defining a plane surface and a convex face, the end or convex face forms a converging lens (1 1 ), the focal region of which is 4 centimeters from the center of this face. The radius of curvature of the converging lens (1 1 ) is the same as that of the cylindrical face, but it may be worked to provide lenses with different focal distances, according to the need of the application.

[90] Specifically with regard to the plane surface, the latter is capable of receiving a plurality of semi-conductive components (20) and (21 ), the latter been described hereinafter:

[91 ] More specifically, a first semi-conductive component (21 ) is positioned in the center (10) of the plane surface by means of a second coupling cavity (3). In this preferred embodiment of the measuring head (1 ), the first semi-conductive component (21 ) is a photodetector. Thus, from this point onwards the semi-conductive component (21 ) will be referred to as photodetector (21 ).

[92] Circularly around the center (10) there are a set of semi- conductive components (20) of the plurality of semi-conductive components. In this preferred embodiment, such a set of semi-conductive components (20) are light emitting diodes (LEDs), hereinafter called LEDs (20). Such LEDs (20) are accommodated in the coupling cavities (2).

[93] The LEDs (20) and the photodetector (21 ) face the converging lens (1 1 ) of the measuring head (1 ) and are oriented parallel to the optical axis of the lens, as can be seen in figure 1 or 2.

[94] The coupling cavities ((2) and (3) can be better viewed in figures

2 and 3, which are cross-sectional views of the measuring head (1 ) proposed.

[95] The cavities (2) and (3) serve to receive (house) the semiconductor components, LEDs (20) and the photodetector (21 ) (FD). Preferably, such cavities are circular and have a 3- or 5-cenfimeter diameter, depending only on the size of the LEDs (20) and photodetector (21 ) used.

[96] The region of the cavities (2) and (3) that will receive the LEDs

(20) (tops of the cavities (2) and (3)) and the photodetector (21 ) is rounded in shape, cooperating with the shape of the light emitting diodes (20) and the photodeiector (21 ). The reason for the top of the cavities (2) and (3) to be of the same shape as the semi-conductors (20) and (21 ) is that is should maximize the optical coupling between the lens of the encapsulation of the semi-conductors (20) and (21 ) and the material of the measuring head (1 ).

[97] The tops of the cavities (2) and (3) are polished to prevent light from spreading to various directions, improving the optical coupling between the encapsulation of the semi-conductors and the material of the measuring head (1 ).

[98] As already mentioned, since the materials of the lens and of the semi-conductors (20) and (21 ) and of the measuring head (1 ) have refraction index values very close or similar, as in the case of acrylic (PMMA), if is expected that, upon coupling the parts, there will be no significant loss by internal reflections in this interface, as if it were a single body. In this way, the light emitted by the LEDs (20) will follow to the measuring head (1 ) (to the converging lens (1 1 )) as if there were no different in the medium.

[99] The depth of the coupling cavities (2) and (3) depends on the focal distance of the converging lens (1 1 ) (lens (1 1 )), since, if it is greater, close to the curvature of the lens (1 1 ), this may cause luminous interference with the photodetector (21 ).

[100] In this preferred embodiment of the present invention, and with reference to figure 3, one observes that the phototetector (21 ) is located at a first distance D1 from the center of the convex surface of the measuring head (1 ). On the other hand, the LEDs (20) are arranged at a second distance D2 also from the center of the convex surface of the measuring head (1 ). One observes that the first distance D1 is shorter than the second distance D2 when taken from the center of the convex surface. In other words, one should have the LEDs (20) behind the photodetector (21 ). One observes that if the distance D2 is taken from the center of the convex surface of the measuring head (1 ), its value should be higher than D1 plus twice the length of the encapsulation of the LED.

[101 ] The first distance D1 , when taken from the center of the convex surface, defines also the focal (internal) region of the converging lens. In this preferred embodiment of the measuring head the internal focal region is away from the center of the convex surface by values between the radius of curvature of the lens and twice this radius.

[102] Further with reference to figure 3 and according to this preferred embodiment of the measuring head (1 ), the cavities (2) in which the LEDs (20) are fitted (accommodated) are away by a third distance D3 from a border (3) of the plane surface.

[103] For a better understanding of the present invention, the border (13) should be understood as the junction of the plane surface with the cylindrical wall that extends and configures the converging lens (1 1 ).

[104] In this preferred embodiment, the third distance D3 may assume values ranging from 5 to 15 mm. thus, the LEDs (2) are distributed circularly around the central region (10), and in this region there is the second coupling cavity (3) for arrangement of the photodetector (21 ). Preferably, the value fo the third distance D3 is 10 mm and, as can be seen in figure 3, the distance D3 is taken from the center of the cavity that houses the LEDs to the side border (13) of the measuring head (1 ).

[105] One should observe that the dimensions mentioned should be adjusted upon variation in the size of the measuring head and/or alteration in the number of LEDs (20). Moreover, one should bear in mind that, if the LED cavity is displaced towards the center, this may result in problems on the sensor and, if it is displaces closer to the border, this may cause total internal reflection, the two situations being undesirable.

[106] With respect specifically to the arrangement of the LEDs (20) and of the photodetector (21 ), and making reference to figure 4, in this preferred embodiment of the measurement head (1 ) one uses eight different wavelengths chosen in the intervals Ultraviolet (UV) / Visible (Vis)/ near Infrared (NIR) (300 - 1200 nm), according to the need of the application and the spectral width.

[107] Thus, in this preferred embodiment of the measurement head (1 ) one uses 16 coupling cavities (2) for the LEDs (20) and one cavity (second cavity (3)) for the photodetector (21 ). Preferably, and with a view to prevent the terminals of the semi-conductor components (LEDs (20) and photodetector (21 )) from coming into short-circuit within the coupling cavities (2) and (3), at least one of these terminals of each component should be electrically insulated by a piece of plastic cover.

[108] The distribution of the LEDs (20) takes place in pairs, according to the wavelength. So, LEDs (20) of equal wavelengths are diametrically accommodated around the center (10) of the plane surface.

[109] More specifically and with reference to figure 4, if the LED (20A) has wavelength 470 nm (blue light), diametrically in the circle there will be another LED 20A'), also emitting blue light, with the same wavelength. The blue light emerging to the external medium forms the focal region composed by these two beams. Thereby one obtains the effect of symmetric distribution of light over the surface of the sample, producing distribution of energy over it.

[1 10] Similarly, the LEDs (20A0, (20B), (20C), (30E), (20F), (20G) and (20C), (20D'), (20Ε'), (20F), (20G'), and (20H^:), respectively, !t should be reminded that the actuation of the LEDs takes place in pairs.

[1 1 1 ] Figure 5 represents the same cross-sectional view illustrated in figure 2, but now pointing out the lines representative of the beams of light emitted (5), reflected internally (6) and transmitted to the outer medium (7), forming points or focal regions inside and outside the measuring head (1 ).

[1 12] The beams of light represented were obtained by considering the preferred arrangement of the LEDs (20) and photodetector (21 ) commented above, that is, for the values of the first, second and third distances D1 , D2 and D3 mentioned. Such a configuration brings about the fact that the beam reflected by the sample reaches the internal focal region of the lens (1 1 ), and more specifically reach the photodetector (21 ), as can be better observed in figure 6.

[1 13] Further specifically with respect to figure 6, the latter evidences the reflective effect of the beams transmitted to the outer medium (7) when these meet the surface of an optical window (25), or of the sample above the latter. [1 14] One considers that, in figure 6, the optical window (25) is sufficiently thin not to cause significant diversions in the beams of light reflected (7A) due to the surfaces of the optical window (25), that is, multiple reflections. One has assumed that the reflected beam (7A) and (7B) is chiefly due to the sample. These beams, upon returning to the measuring head (1 ) diffract following a path (7B) to the focal region inside the material, where the photodetector (21 ) is located. This orientation of the beam of light maximizes the signal/noise relation and can capture it from different directions. Preferably, the optical window (25) is embodied in the form of a disc having preferably plane and parallel faces, made from a transparent material in the interval of wavelength of interest. One may employ glass, quartz, transparent polymers, among others, in making them.

[1 15] Studies showed that, depending on the position of the LEDs (20) with respect to their distance to the center (10) or to the side border (13) of the measuring head (1 ), different reflection effects may occur.

[1 16] For example, if the LEDs (20) are arranged too close to the center (10), then the beam reflected internally (beam 6) in figure 6) may reach the photodetector (21 ) together with the beam reflected by the sample (beam ((7B) in figure 6).

[1 17] This fact is undesired for the application of the measuring head (1 ) proposed in the present invention, since the beam of light from the sample (beam (7B) in figure 6)) would have its detection impaired by the beam reflected internally (beam (6) in figure 6)) at the border of the lens (1 1 ), generating a saturated signal, that is, optical saturation of the photodetector (21 ).

[1 18] On the other hand, if the LEDs (20) are located too close to the border (13), the beam of light emitted undergoes total internal reflection, surrounds the surface of the lens (1 1 ) and emerges on the opposite side radially to the position of the LED (20) that emitted it, that is, the beam does not come out to the external medium and returns to the convex face and returns to the plane face and emerges from it. Theoretically, in this case the sample would not receive light, and so the detection of the beam reflected from the sample would be negligible,

[1 19] Said total internal reflection is illustrated in figure 7, in which one observes the behavior of the internally reflected beam (6).

[120] It is important to mention that figure 7 shows the illustration of tests carried out in laboratory, using laser beam equipment (not LEDs). However, if one had used LEDs, the behavior of the internally reflected beam (6) would be the same. Therefore, figure 7 is valid for a better understanding of said total internal reflection.

[121 ] Thus, one has determined an intermediate position (LEDs (20) arranged at a distance D3 from the border (13), such that the internally reflected beam would pass through the photodetector (21 ) or have total infernal reflection.

[122] Then, the structural embodiment of the measuring head (1 ) and as shown in figures 2, 3, 5 and 6, the latter further comprises a protrusion (4) that serves to fix the measuring head (1 ) to the support thereof.

[123] Such a protrusion (4) is capable of receiving a fixing element such as a screw, thus preventing circular movement of the measuring head (1 ) and preventing irreparable damage to the LEDs (20) and to the photodetector (21 ).

[124] In an alternative embodiment of the measuring head (1 ) proposed in the present invention, the LEDs (20) and the photodetector (21 ) might be arranged (encapsulated) directly in the material of this device, eliminating the individual envelope of the LEDs (20) and photodetector (21 ), thus preventing the construction of the coupling cavities (20) and (3) for fitting, and so the emission will be totally direct.

[125] The present invention also relates to a spectrometer (40) that makes use of the measuring head (1 ) proposed in the present invention. Said spectrometer may be used in different manners, each of them requiring or not requiring the use of additional components.

[126] Hereinafter, the various possible uses for the spectrometer (40) will be addressed, as well as the components required for each of these uses. [127] For instance, the measuring head (1 ) may be fixed to a support body (8), shown in figure 8 of the present invention.

[128] The support body (8) is preferably made from PVC. However, other materials might be used, such as metallic (aluminum) materials.

[129] The support body (8) comprises an inner portion (41 ) defining a first cavity (9), in which a printed-circuit board should be arranged for fixation (19) of the plurality of semi-conductive components (20) and (21 ).

[130] The support body (8) further comprises a second cavity (12), which has the function of accommodating sealing means (14), preferably rubber rings (o-ring) to prevent the entry of liquids into the first cavity (9). Thus, the first cavity (9) is fiuidly isolated (sealed) from the second cavity (12), preventing contact of liquids with the printed-circuit board for fixation (19), which is arranged in the cavity (9).

[131 ] The fluid isolation (sealing) between the cavities (9) and (12) is important, since this enables one to dip the spectrometer (40) directly into the liquid, without the electronic components being affected.

[132] Once the measuring head (1 ) has been coupled (arranged) in the second cavity (12), it is locked by a first fixation means, such as a screw that should be inserted into the orifice (42), and the latter engages with the protrusion (4) of the measuring head (1 ), shown in figures 2, 3, 5 and 6.

[133] The support body (8) further comprises, at its back portion), a cover (15) made preferably from the same material as the body (8) and that has the purpose of closing the first cavity (9) and also to serve as support for an electric connector (16) responsible for preventing electric polarization of the LEDs (20) and photodetector (21 ) and receiving the electric signal from the potodetector (21 ).

[134] The fixation of the cover (15) to the connector (18) is made, preferably with screws (18) passing through the orifices (26), and (27) and then screwed into the orifice (28).

[135] The spectrometer (40) with the measuring head 91 ) duly associated to the fixation body (8) is illustrated in figure 9.

[136] In figure 9 one further observes that the connector (16) is connected to the printed-circuit board (19) by means of electric cables (36), where electric currents pass, which feed the LEDs (20) and the electric signals proportional to the intensifies of light reflected by the sample.

[137] The electric cable (36) is welded directly to the printed-circuit board (19), following the eiectric connection scheme previously defined. In the preferred embodiment of this invention, the connector (16) is of the DB25 type, and 20 pins are used to meet the needs of communication with the data collection system (datalogger), which will be described later.

[138] The LEDs (20), photodetector (21 ) and eiectric cables (36) are welded to one of the faces of the printed-circuit board (19), while the other face receives no welding, with a view not to impair the coupling of this board to the wail of the first cavity (9).

[139] Once ail the components have been mounted, the fixation plate (19) is inserted into the first cavity (9) and the LEDs (20) and photodetector (21 ) penetrate the coupling cavities (2) and (3) as far as they reach the top thereof.

[140] The printed-circuit board (19) is not fixed by means of screws inside the first cavity (9). It is only fitted into the cavity, since it has virtually the same diameter thereof.

[141 ] In order to keep it fitted, the eiectric cables (36) play the role of a low Hook constant spring, !n case there is the need to remove the board (19), it is enough to remove the cover (15) together with the connector (16). Then the whole electric set of LEDs (20) and photodetector (21 ) is also removed. This is a rapid and practical action, since there are not fragile integral parts in the system.

[142] In this preferred embodiment of the spectrometer (40), the electronic control and feed circuit is not mounted together with the LEDs (20) and the photodetector (21 ). This makes the system easy to mount, more simple and robust, since, if there is the need to remove the measuring head (1 ), the electronic system will not be affected.

[143] Depending on the use of the spectrometer (40), the latter may receive a deflector (37), as shown in figure 10. This deflector (37) is a cylindrical piece that may be made from both metal and resistant plastic.

[144] As shown in figure 10, internally there is a conical surface (38) that should be mirrored. If the deflector (37) material is metallic, it should be polished so as to obtain a mirrored conical surface (38).

[145] If the material is plastic, it should receive a metallic covering by evaporation so as to form the mirrored conical surface (38).

[146] The deflector (37) has the objective of redirecting the laterally spread light back to the sample and from the latter to the measuring head (1 ). The measuring head (1 ) penetrates the conical opening from the narrow side of the deflector (27) (lower side), which in turn is fixed to the inner base of a large shield cabinet (29).

[147] If is important to mention that the deflector (37) is an accessory that enhances the intensity of the signal detected by 5%, but the spectrometer (40) may function without it, since the spectral response dos not alter, but only improve the signal/noise relation.

[148] Said shield cabinet (29) (cabinet (29)) is illustrated in figure 1 1 . The cabinet (29) is a cylindrical piece that involves the measuring head and is further provided with a portion (31 ) connectable to the support body (8) and with a sampling portion (30), said sampling portion being configured so as to receive at least one portion of a sample to be analyzed by the spectrometer (40).

[149] One observes in figure 1 1 that the cabinet (29) further comprises a through-cavity (42) of the measuring head (1 ) and a sealing ring (43) for sealing the cabinet (29) with the measuring head (1 ).

[150] The cabinet (29) should be made from a blackened material such as black polyacetal or another polymer, and even from a metallic material, as long as its inside is painted black.

[151 ] Depending on the use of the spectrometer (40) with the cabinet (29), one should also use a sample-holder (23), as shown in figure 12.

[152] In this preferred embodiment, the sample-holder (23) is referred to as a beaker (23). This beaker (23) may be manufactured from the following materials: polymers such as polyethylene terephfhalate (PET) or ^

poiy(ethylene)terephthalate, polymethylmethacrylate (PM A - acrylic) or polycarbonate, polyacetal, metal (aluminum) with a transparent window in the bottom, glass and other materials that do not absorb in the spectral region of interest.

[153] If the beaker (23) is of a polymeric material, it may be disposable in order to prevent contamination between samples. Further, the latter is useful when the sample is intended not to come into direct contact with the measuring head (1 ).

[154] The shield cabinet (29) represented in figure 1 1 is structurally configured for use with the beaker (23) of figure 12, In this case, the beaker (23) descends smoothly in the sampling portion (30) due to the air that is expelled slowly out of the beaker (23) cavity by gravitational action. This configuration of the beaker (23) illustrated in figure 12 might be used with the model of shield cabinet (29A) shown in figure 13 as well.

[155] On the latter, in addition to the elements already mentioned in the description of figure 1 1 , there is a side fitting (SOB) at the same height as the body portion that receives the sample, or the upper body cavity (24).

[156] The shield cabinet (29A) represented in figure 13 may also be used with the body (23A) of figure 14. In comparison with the beaker (23), one observes that the body (23A) does not have a lower cavity (32), as shown in figure 12. So, it should be supported on the fitting border (30B) of the cabinet (29A). In this way, the latter or any other body (sample-holder) is prevented from remaining in direct contact with the measurement head (10).

[157] The shield cabinet (29) or (29A)is an important piece in the functioning of the spectrometer (40), since it protects the measurement head (1 ) against entry of external light, damage, dirt, and enables the sample surface to be always at the same distance from the measuring head (1 ).

[158] In order to prevent influence of external light, the top of the cabinet (29) (29A) may be closed by a shield cover (34) made from the same black material, as shown in figure 15.

[159] One observes that the shield cover (34) has a protrusion that serves as a handle and a cannei (35) for coupling to the border of the beaker (23) or (23A). This carinei (35) seals the border of the beaker (23) or (23A), so that the liquid, or particulate solid, will not leak out of it. In this way, the sample and the spectrometer will remain protected against external influences. The structure illustrated for the cover (34) in figure 15 is only a preferred embodiment.

[160] Figure 16 illustrates the spectrometer (40) provided with the support body (8), beaker (23), deflector (37), shield cabinet (29), shield cover (34) and still a sample (30C). the central top of the lens on the measuring head (1 ) is located 1 mm from the optical window (25), which means that the external focal region is within the sample (30C), since this region too is 4 cm above the center of the convex surface.

[161 ] Specifically with respect to the sample (30C), the latter may occupy the whole volume of the internal area of the beaker (23) or (23A)), or a part thereof, according to the absorption length of the substance being analyzed. When the sample (30C) to be analyzed is a liquid, it is recommended that the whole volume of the beaker (23) (23A) be occupied, preventing light reflection due to the wall thereof.

[162] Upon using the spectrometer (40) in analyzing liquids, it should be arranged in a vertical position. For this purpose a support (43) may be used, as preferably illustrated in figure 17. As said before, the illustrated embodiment of the support (43) is only a preferred one, so that any other structural embodiment that can achieve the objective of arranging the spectrometer (40) in a vertical position may be used.

[163] Specifically with regard to the use of the spectrometer (40) for analysis of solid and liquid samples, there are six options of use, namely: i) the sample arranged within the beaker (23) (23A) and using the shield cabinet (29) (29A), as shown in figure 16;

ii) for field analysis (intact soils), it is enough to remove the shield cover (34) and, without any body within the shield cabinet (29) (29A), to remove the spectrometer from the support (43), turn it with the cabinet (29) (29A) mouth facing downward and place it on the duly leveled soil (figure 18). This mode is very useful in the field or on any surface with the material (sample) which one wishes to analyze;

alternatively, one may use the spectrometer as illustrated in figure

19. In this mode, the beaker (23) (23A), or any other body or container of appropriate dimensions, may be filled with sample (30C). The spectrometer (40) is placed on it with the mouth facing downward until the latter reaches the border of the fitting (30B) or the deflector (37). The sample surface should be distant between one and four millimeter below the central top of the measuring head (1 );

alternatively, one may use the spectrometer as illustrated in figure

20. For this purpose, one removes the deflector (37) and any other beaker (23) (23A). Then the shield cabinet (29) (29A), with the mouth facing upward, may be filled with the sample (30C). !n this case, the measuring head (1 ) remains dipped into the sample (30C). Thus, one may use the spectrometer (40) dipped into water (rivers, lagoons and lakes) for constant monitoring of polluting state, chlorophyll and dissolved sediments;

the spectrometer may further be used for analyzing liquids stored in big contained and under cooling, such as milk in storage and collection tanks. For this purpose, one removes the shield cabinet (29) (29A) and installs the spectrometer (40) directly on the reservoir or tubing wall, as shown in figure 21 ;

the spectrometer may still be sued dipped and without the shield cabinet (29) (29A). In this case, one removes the cabinet (29) (29A), leaving the measuring head (1 ) exposed. Using a body (29) (29A) of any shape filled with liquid, one dips only the head (1 ) into the liquid. Then the measurement is carried out. The bodies may have opaque walls, so that the surrounding light will not interfere with the measurement.

Regardless of how the spectrometer (40) is used, in order for if to data about the sample, electronic circuits for acquiring data and electric feed are associated, forming a datalogger, or signal conditioner (44) [165] Said signal conditioner (44) may preferably comprise a keyboard on which the operator enters the commands and fills in the information required to carry out the acquisitions. The electronic circuit of the signal conditioner should comprise a microprocessor provided with an embarked program, written in machine language, which activates a Multiplex circuit and the latter actuates a gain amplifier together with a pair of LEDs (exciters) of the same wavelength,

[166] For example, a determined pair of LEDs (20) will illuminate the sample (30C), be the latter on the beaker (23) (23A) or on one of the above- mentioned modes. The reflected light is detected by the photodefector (21 ) and its electric signal is proportional to the intensity of the reflected light.

[167] This signal goes to the analog/digital (A/D) converter of the microprocessor in order to digitize it, convert it into valid data and store it in the Memory. This procedure is repeated for all the pairs of LEDs (20) of the same wavelength. The spectral scanning lasts 20 seconds (time acceptable for arranging the LEDs sequentially, without the need to use CCD), enabling a number of repetitions for subsequent statistic treatment, determination of the average value and standard deviation.

[168] The stored data may further be processed so as to appear on a display and/or be sent to another computer via serial communication interface RS232 or USB, or still by Bluetooth, or any other desired protocol.

[169] The program embarked on this computer controls remote acquisition, reception of data for statistical analysis and storage thereof in a mass memory unit.

[170] The electric feed to the spectrometer (40) may be based on battery (12V) and/or by the conventional electric network for recharge or direct use. It may also be fed by the battery of a sample-collection truck or an agricultural machine.

[171 ] Figure 22 is only a preferred representation of the spectrometer (40) connected to said signal conditioner (44).

[172] For correct use of the spectrometer (40) and measuring head (1 ) proposed in the present invention, one should first carry out calibration thereof. Such calibration is due to the fact that the LEDs (20) have varied intensities as a function of their wavelengths (low in the ultraviolet, increasing in the visible and decreasing in the infrared).

[173] Thus, there is not constant energetic response throughout the wavelength of the spectrum. Also the photodiodes (21 ) do not respond linearly as a function of the wavelength. Most commercial semi-conductor photodiodes (photodetector) (21 ) have a maximum of response ion the near infrared, extending downward in the infrared toward the high wavelengths, while monotonously (slowly) decreasing in the visible region as far as the ultraviolet one.

[174] Therefore, the emission curve of the LEDs (20) and that of response of the photodetector (21 ) overlap each other, resulting in the spectral response curve of the instrument. In order to compensate for this instrument response curve, one carries out the measurement of the base line, or "the white", by obtaining a spectrum of the reference sample used for spectral normalization.

[175] This process takes place automatically on double-beam spectrometers, where the electric signal on the detector, due to the reference beam of light, is used to normalize the electric signal obtained from the beam of light emerging from the sample.

[176] Thus, considering the spectrometer (40) and the measuring head (1 ) proposed in the present invention, one has projected a gain circuit for the photodetector (21 ) as a function of the actuated LED 20, called a gain amplifier (already mentioned),

[177] Since for each LED (20) there is a gain in sensitivity of the photodetector (21 ), this consists in increasing or decreasing the electric polarization of this semi-conductor, for instance: for ultraviolet LED (20), which supplies low light intensity, the photodetector (21 ) is also less sensitive. Then its electric polarization value is increased, thus causing a decrease in the photo-sensitivity of this detector. Once this procedure has been carried out, the spectrometer can be duly calibrated. [178] The manner how such calibration should take place does not represent the preferred aspect of the present invention. As already mentioned, one may: (i) adjust the gain amplifier for each LED (20), (ii) obtain the spectrum of a white substance as reflectance reference, (iii) use a standard substance with known spectrum for comparison or (iv) use interference or color filters with known spectra.

[179] As to the procedures for analysis of the sample (30C), they are referenced hereinafter.

[180] First, it is necessary to obtain the spectrum of the empty spectrometer (40), without any device or sample (30C), using only the shield cabinet (29) (29A) dosed by the shield cover (34).

[181 ] Thus, the response of the spectrometer (40) in the darkness condition is obtained. This procedure is valid for use with or without the beaker (23) (23A), but it is not necessary to carry it out every time a measurement of a sample (30C) is made. These data may already be stored in the memory of the signal conditions (44) prior to measurement.

[182] Then, it is necessary to obtain the spectrum with an empty beaker (23) (23A). This procedure is compulsory for use with the beaker (23) (23A) as a sample (30C) support. If is also necessary to obtain the spectrum of a device made of PTFE (polyterephthfluorethylen - Teflon), introducing if into the beaker (23) (23A) and then into the cabinet (29) (29A) with the shield cover (34). Once this has been done, the data is kept in a memory of the signal conditioner (44) for subsequent use.

[183] Subsequently, one should obtain the spectrum of the sample (30C) placed on the beaker (23) (23A), by introducing the beaker (23) (23A) into the shield cabinet (29) (29A) and using the shield cover (34). Once the spectrum and the data stored in the signal conditioner (44) are obtained, one may carry out normalization of the samples.

[184] When the spectrometer (40) is used by dipping into the sample (30C), but without using the beaker (23) (23A) and cabinet (29) (29A), one should use two bodies (23) (23A), one made of PTFE and the other black, without optical window, with the solvent that contains the solute to be analyzed.

[185] The black beaker (23) (23A) with solvent (water) - is used for obtaining the spectral response of the spectrometer 40 in the dark or low- reflectance, whereas the white beaker (23) (23A) (PTFE), also with the solvent, serves to obtain the reference of high reflection and spread.

[186] These data are used for determining the spectrum of the liquid sample (30C) in the condition of dipping into the spectrometer (40). On the other hand, the sample (30C) which one wishes to analyze should be placed in the beaker (23) (23A) for obtaining its spectrum.

[187] When the spectrometer 40 is used without the beaker (23) (23A), the first step cited above should be carried out (obtaining the empty spectrum, without sample, only with the cabinet (29) (29A) and the cover (34).

[188] The white reference should be placed at the same distance between the measuring head (1 ) and the sample (30C). For this purpose, it is enough to turn the spectrometer with the cabinet (29) (29A) facing downward, without cover (34), and couple to the white surface, followed by electronic actuation for carrying out the measurement.

[189] For measurements of particulate solid samples - for example, soils - one should take care to level the surfaces thereof. Different distances generate displacement of the signal level, rendering it difficult to make comparisons with other samples (30C). the next step is to carry out the normalization on the spectrometer.

[190] The normalization is made for obtaining the reference spectrum of the sample (30C) and/or the equivalent absorbance. For this purpose, one applies the equation below (equation 1 ):

S_r— S₍i

[191 ] In equation 1 , Sa, Sd, Sr and R refer to the signals referring to the sample, to the empty spectrometer or with the black beaker, to the white reference (PTFE) or white beaker and the reflectance of the sample, respectively. In order to obtain the spectrum equivalent to that of absorbance, one applies the equation 1 in the Kubelka-Munk (K-M) function, below: K (1 - J?)²

Ριιηςζο (KM) =— = _2R

[192] In equation KM, S, K and R are the parameters referring to the spreading, to the absorption of the sample and to the light reflection given by the equation 1 , respectively.

[193] Considering the beaker (23) (23A) for the sample (30C), there may be variations in its material constituents and/or defects, making it necessary to obtain, first, the base line spectrum with every use of a new beaker (23) (23A). This is carried out by placing the PTFE device, or another of high reflectance, into the beaker (23) (23A) and obtaining the spectral curve of this assembly. If this variation condition is not significant, then this procedure may be eliminated. After this, one uses the beaker (23) (23A) with the sample (30C) for analysis.

[194] Thus, the present invention discloses a measuring head (1 ) and spectrometer (40) that have advantages over the devices known from the prior art. For example, according to the diameter of the measuring head (1 ), one may place more LEDs (20) of different wavelengths without the need to orient the mirror.

[195] Consequently, by increasing the number of emitters at a defined interval of wavelength, one will increase the spectral resolution according to the criterion of band width.

[196] In the present invention, the number of LEDs (20) distributed diametrically may be either increased or decreases according to the application, that is, whether spectroscopic or process-monitoring application, or still for determining the presence of a constituent of interest in one substance.

[197] In the spectroscopic case, the increase in the number of LEDs (20) with wavelengths distributed along the visible spectrum, for instance, provides conditions for defining the spectral profile of the samples, chiefly when the latter provide spectra with wide absorption bands.

[198] In various agronomical applications, it is not necessary to determine the complete spectrum of the sample (30C), such as soils. In the case of monitoring the quality of foods, taking a determined substance present in the product as a marker is often a conventional procedure.

[199] Thus, taking milk as an example, the fat may be used as a substance to be monitored to know how the handling for a specific animal was carried out.

[200] Further, another advantage of the present invention lies in the fact that the LEDs (20) and the photodiode (21 ) are installed on the measuring head (1 ), but since these electronic components have rounded shapes, then the tops of coupling cavities (2) and (3), where they are installed, have them as well. These tops have the same dimensions as the body of the LEDs (20) and of the photodetector (21 ), and their walls (tops) are polished for optimizing the optical coupling. This situation is not observed in the prior-art documents cited before.

[201 ] Another advantage is the fact that the spectrometer (40) with the measuring head (1 ) is a spectrophotometric portable device, computerized, tunable on wavelength ranges of the electromagnetic radiation.

[202] The spectrometer (40) is considered tunable because it operates on narrow bands of the electromagnetic spectrum, according to the absorbance bands of the sample (30C) under analysis and also because it enables the change of the LEDs (20) according to the spectral band of interest.

[203] The achievement of spectra or data on the sample (30C) is rapid, 20 seconds, since it does not have movable parts that make the analysis difficult due to inertia. Further, the spectrometer (40) may be used in different ways: by dipping (one should use the cabinet (29) (29A)) in the liquid (direct contact) or using a sample support, or still on the sample, but without contact.

[204] Since it is convenient because it does not need previous preparation, the use thereof may take place both at an industrial plant (foods, dairy products, and others) and in the field, close to the production site and/or product-collection site to e analyzed. When it is arranged directly on tubing, it should be used without the cabinet (29) (29A). !t may also be arranged on truck intended for collection of raw materials such as raw milk, agricultural machines, among many others. [205] Preferred embodiment examples having been describes, one should understand that the scope of the present invention embraces other possible variations, being limited only by the contents of the accompanying claims, which include the possible equivalents.

Claims

1 . A measuring head (1 ) applicable to a spectrometer (40), the measuring head (1 ) being characterized by: having a cylindrical shape defining a plane surface and a convex face, the measuring head (1 ) being configured so as to receive a plurality of semi-conductive components (20, 21 ) on the plane surface, and the measuring head (1 ) being further provided with a center (10) arranged on the plane surface, so that in the center there is a first semi-conductive component (21 ) of the plurality of semi-conductive components (20, 21 ), and around the center (10) there are a set of semi-conductive components (20) of the plurality of semi-conductive components (20, 21 ).

2. The measuring head (1 ) according to claim 1 , characterized by comprising a plurality of coupling cavities (2, 3) configured so as to receive the plurality of semi-conductive components (20, 21 ),

3. The measuring head (1 ) according to claims 1 and 2, characterized in that the first semi-conductive component (21 ) and the set of semi- conductive components (20) are accommodated, respectively, in the center (10) and around the center (10) by means of a plurality of coupling cavities (2, 3).

4. The measuring head (1 ) according to claims 1 to 3, characterized ion that the convex face defines a converging lens (1 1 ), the inner focal region of which is away from the convex surface by a first distance (D1 ) longer than the convergence radius or equal to twice this radius.

5. The measuring head (1 ) according to claims 1 to 4, characterized ion that the plurality of semi-conductive components (20, 21 ) faces the converging lens (1 1 ) of the measuring head (1 ), said components being oriented parallel to the optical axis of the converging lens (1 1 ).

6. The measuring head (1 ) according to claims 1 to 5, characterized in that the first semi-conductive component (21 ) is at a first distance D1 ) from the convex surface of the measuring head (1 ) and the set of semi-conductive components (20) is at a second distance (D2) from the convex surface of the measuring head (1 ), the first distance (D1 ) being shorter than the second distance (D2),

7. The measuring head (1 ) according to claims 1 to 6, characterized in that the set of semi-conductive components (20) are accommodated at a third distance (D3) from a border (13) of the plane surface of the measuring head (1 ), the third distance (3) having a value ranging from 5 millimeters to 15 millimeters,

8. The measuring head (1 ) according to claims 1 to 7, characterized in that the first semi-conductive component (21 ) is a photodetector and the set of semi-conductive components (20) are light emitting diodes.

9. The measuring head (1 ) according to claims 1 to 8, characterized in that the light emitting diodes of the same wavelength are diametrically accommodated around the center (10) of the plane surface.

10. A spectrometer (40) characterized by comprising the measuring head (1 ) as defined in claim 1 and comprising a support body (8) defining an internal portion (41 ), and comprising means for fixing the measuring head (1 ) to the internal portion (41 ) of the support body (8).

1 1 . The spectrometer (40) according to claim 10, characterized in that the internal portion (41 ) of the support body (8) comprises a first cavity (9) for arrangement of a printed-circuit board for fixation (19) of the plurality of semi-conductive components (20, 21 ).

12. The spectrometer (40) according to claims 10 and 1 1 , characterized in that the internal portion (41 ) of the support body (8) comprises a second cavity (12) fluidiy isolated from the first cavity (9), the second cavity (12) associated to a first means for fixing the measuring head

(1 ) to the support body (8).

13. The spectrometer (40) according to claims 10 to 12, characterized by further comprising a shield cabinet (29), the shield cabinet (29) being configured so as to involve the measuring head (10) and being provided with a portion (31 ) connectabie to the support body (8) and further provided with a sampling portion (30), the sampling portion (30) being capable of receiving at least one portion of a sample to be analyzed by the spectrometer (40),

14. The spectrometer (40) according to claims 10 to 13, characterized in that the sampling portion (30) is capable of further receiving a sample- holder (23), said sample-holder (23) being provided with an internal area in which at least a portion of the sample to be analyzed by the spectrometer (40) is arranged.

15. The spectrometer (40) according to claims 1 1 -14, characterized in that the shield cabinet (29) is made from a blackened material, the shield cabinet (29) further comprising a shield cover (34) configured so as to involve the sampling portion (30), the shield cover (34) being also made from a blackened material.