WO2018059663A1 - Device and method for the ir spectroscopic examination of a sample using a diffused reflection - Google Patents

Abstract

The invention relates to a device and a method for the IR spectroscopic examination of a sample, in particular in order to detect the chemical composition and/or the chemical properties of a material. The invention discloses a device for the IR spectroscopic examination of a sample, wherein at least one light source, at least one detector, and a sample with a sample surface which is optionally uneven can be combined in a dynamic optical measurement system such that despite the unevenness in the sample material, a spectrum with a large proportion of absorption signals reflected in a diffuse manner can be obtained, the signal intensity of said signals being comparable. This is achieved by the mobility of all or two or one of the three components of the light source, detector, and sample and by a control and regulating system which measures the surface topography of the sample and adapts the placement of the components during the measurement.

Description

 DEVICE AND METHOD FOR THE IR-SPECTROSCOPIC EXAMINATION

 A SAMPLE OF DIFFUSER REFLECTION

description

The invention relates to a device and a method for IR spectroscopic examination of a sample, in particular for detecting the chemical composition and / or the chemical properties of a material.

A universally applicable method for non-contact and sterile, ie non-invasive, differentiation of materials is spectroscopy with electromagnetic radiation, in particular with infrared, UV / VIS, microwave and / or Raman radiation. In particular, for water-containing media is 900 and 2500 nm wavelength special ^¬ DERS the region of the NIR, in addition to suitable UV or Raman radiation, suitable as a penetration depth in the medium of up to a millimeter is possible here. At longer wavelengths, the interaction with the sample material is so strong that only near-surface Be ^¬ rich (about 1 / 10mm) can be detected.

Therefore, among other things, IR spectroscopy is used as a non-contact measuring method for the detection of the chemical properties or constituents of a material, for example a tissue sample. The general measurement method of IR spectroscopy is that illuminate ^¬ rich surface to be measured with a light source with a broad (infra red) Wellenlängenbe while recording the spectrum of the non-absorbed radiation. For spectral analysis of the material which diffusely reflected Strah ^¬ system is particularly suitable. This contains specific information about the sample. In strak reflective and / or shiny surfaces, a large part of the radiation, especially in the area of the specular angle is directly reflected and passes out of this Win ^¬ angle range in the detector. The result is that through saturation effects of the detector or individual detector areas the spectrum is distorted. The proportion of diffuse reflection in the measurement signal is in such cases negligible to the proportion of direct reflection. This distorts the measurement and / or renders it useless.

The object of the present invention is therefore to provide an apparatus and a method for IR spectroscopic examination of samples, in particular of water-containing samples such as tissue samples, by which the disadvantages of the prior art are overcome.

Solution of the problem and object of the present invention is a device for the IR-spectroscopic investigation of a sample, at least three components, a Aufnahmevor ^¬ direction of the examined sample, a detector and a light source comprising at least one light source, at least one receiving device and / or a detector are at least relative to one another or arranged to be movable to another part and means for measuring, Rege ^¬ lung and control before and / or during the spectroscopy are so positioned that the radiation and / or reflection in the glancing angle area of the sample material as low as possible is held. Likewise, the present invention is a process for the IR-spectroscopic investigation of a sample by means of a light source and a detector where ^¬ at be changed in their positions during the spectroscopy so by suitable means, the light source, the detector and the sample that unevenness and / or gloss effects on the sample surface are compensated by the relative movements of the light source and / or the detector relative to the sample surface, with the aim that the highest possible proportion of diffusely reflected radiation in the spectrum is recognizable.

General knowledge of the invention is that a direct reflection from the light source to the detector can always occur when any surface by movement or rotation is brought into the gloss angle range or a very uneven sample surface is present. Particularly in the case of moist surfaces, as present, for example, when measuring in an operation site, two different processes can occur, on the one hand a direct, ie specular, reflec- tion on the surface, which shows a very high light intensity of the backscattered signal and, on the other hand a diffuse reflection at the surface, which shows a low intensity of the backscattered signal but involves a high level of chemical information about the sample material.

According to one embodiment of the invention, the at least one detector and the at least one light source are arranged opposite to the sample to be examined such that the proportions of the diffusely reflected and the directly reflected light remain approximately the same upon the impact on the detector during the spectroscopic examination. This is particularly because it is detrimental to signal processing when there is a different ratio of the proportions of the two scattering modes in the signal.

To illustrate the Streumodi the specular, direct reflection and the diffuse reflectors indirect ^¬ tion is shown in FIG. 1

Figure 1 shows

a) the direct reflection

b) the diffuse reflection

c) a mixed form with direct and diffuse reflection

The three representations are structurally the same: FIG. 1a) There is a specular reflection 5 on the surface 1. On the surface 1 of the sample material 2 from the light source 3 - which ^halves the simplicity of the representation as sun is shown - from the beam 4 in the bright wind On the surface, so that it is reflected with maximum intensity in direct beam 5 to the detector 6 - again symbolized by an eye for simplicity - out. The intensity of the reflected beam 5 is high and gives a strong signal to the detector 6, which, however, contains little chemical information. It is measured a very high signal ^¬ intensity of the backscattered signal 5, which on the one hand often leads to over-steer of the detector 6, on the other hand is in the measured signal containing little information.

Figure lb)

It comes almost exclusively light from diffuse reflection 7 at the detector 6. This is almost exclusively information from the sample material in the signal. The latter is characterized by a low signal intensity of the backscattered light ge ^¬ , in which, however, a high level of material information is impressed.

Unlike Figure la) is hardly reflected here from the surface 1 of the sample material here, but also with a certain depth from the sample diffuse reflectors ^¬ advantage. The diffuse reflection 7 is produced at the detector 6 is a ge ^¬ ringere signal intensity, but a signal frequency and intensity comprises about Wellenlän ^¬ ge, a high content of chemical information.

FIG. 1c) at a certain measuring angle, a mixing between diffuse and direct reflection can occur, which again leads to a falsification of the measured signal.

On uneven sample surfaces 1 there is in addition to the problem of displacement of the angle of incidence or the prob ^¬ lem of shadowing when inevitably at some points is given by the lighting of a fixed by the geometry of the measuring set-up angles are too large topographical changes of the measured surface shadowing , This prevents that from being shadowed by them Make diffused light come to the detector. At these points in the spectrum there is a strong variation in signal intensity and a degraded signal-to-noise ratio Ver ^¬ because the signal from the shaded places ex- tremely low.

FIG. 2 shows how individual angles of incidence, as shown in FIGS. 1 a to 1 c, and / or shading influence the measured spectra. Spectroscopic measurements of one and the same substance were taken, measured at different angles between the detector and the light source. We found marked differences in the signal intensity ^¬, as well as changes in the shape of the spectrum such as missing and / or overlapping bands and without intersections of the signal lines zen.

To recognize is on the one hand, that each give, after irradiation angle strong differences in the signal intensity and on the other that strong changes in the shape of the spectrum of al- such as missing or overlapping band and Kreu ^¬ zen of the signal lines at different angles result.

As a result, FIGS. 1 and 2 show that a measurement setup which leads to spectrally detectable reflection of the type of diffuse reflection according to FIG. 1b provides the best spectra. This particular because ideally, to ^¬ approaching have the same signal intensity and an identical shape the spectra.

The inventively proposed system of one or more differently positioned and / or freely positionable light sources and one or more detectors, which are also freely positionable, so mobile, for example, also on a robot arm, arranged, the angular dependence of an IR and / or NIR - Absorption spectrum bypassed. Through different angles between the at least one Move ^¬ union detector and the at least one movable light source as well as by the continuous measurement of surface chenrauigkeit the sample surface, coupled with the see dynamic adaptation of the detector and / or light source position, it is now possible that a non-ideal Winkelkons ^¬ tion or measurement geometry can be changed accordingly to obtain largely measurement results as shown in Figure lb.

For measuring the surface inclinations and / or surface roughness and dynamically adapting the positions of the light source and the detector, a feedback system for checking the irradiation angles is used, for example, individually or in combination according to the following measuring principles:

 Camera observation of a reflex image, for example

Turning the robot arm,

 3D measurement

 Light field camera

- triangulation scanner ...

Thus, a device is provided by which the IR measurement method is independent of the sample surface and even independent of the geometry of the structure feasible. No matter how a sample surface is designed, there is at least one positioning of the detector which adequately measures the surface to be determined.

As light sources, for example, the following can be used:

Incandescent or halogen lamps

 LEDs

 laser diodes

- Laser

Central light sources whose light is distributed via fiber optic cables. Combination light source of the aforementioned, such as, LED and others.

As a detector, for example, the following components are suitable:

 probe

 spectrometer

Photodiodes or Arrays In the figures 3a to 3c, the invention with reference to ^¬ advantageous embodiments of the device which are shown schematically, explained in more detail. The figures show the food ^¬ tial components of the device, the principle of the measuring arrangement or measuring optics again prevail. In particular, the sample is partially, a section of the sample surface, a symbolically represented light source and one or more symbolically represented detector (s) shown in exemplary arrangements to each other. FIGS. 3 a to 3 c show exemplary arrangements of measuring structures each having a light source. Of the invention, of course, devices comprising a plurality of light sources, wherein a device according to the invention, for example, ^{¬ may} include a combination of all 3 measurement structures shown here.

In FIG. 3 a, the light source is represented symbolically by a sun 3, as in FIGS. 1 a to 1 c. The light sources, as mentioned above, are for example LEDs. The surface 1 of the sample to be measured is - as shown in Figure 1 - shown, as well as the sample material 2, hatched here and a dashed line area, where reflected radiation is expected. The detector symbolizes - as in Figure 1 - the schematic representation of an eye. 6

FIG. 3 a shows the simplest embodiment of the device with the uneven sample surface 1, the sample material 2 with the area 8 shown in dashed lines, from which certain Penetration diffuse reflection is detected and the light source 3 6. The irradiated light in close proximity to the detector - arrow 4 has a comparatively high intensity in ^¬ and is therefore slightly thicker painted. The directly reflected beam 5 is almost as thick and the diffuse

Litter guide, which provides the most information, is again represented by the arrow 7.

The penetration depth of the measurement always depends on the sample - in the case of liquids, the measuring depth may even be more than 1 cm. A penetration depth of about one millimeter, for example, in the application of tissue differentiation tumor vs. Not reached tumor in the neuro area. For example, when Ge ^¬ brain in vivo rate of the penetration depth is approximately 1-1.5 mm. Again with a fixed brain (after removal and treatment with paraformaldehyde) the penetration depth decreases to about 800ym.

At longer wavelengths, e.g. Medium infrared, the water absorption is so annoying that the measurement is rather difficult. The penetration depth then depends on the measuring method and the material.

In FIG. 3 b, the measuring device differs insofar as the light source 3 and the detector 6 are spatially farther apart. The detector 6 is arranged to measure the diffused reflected radiation 7.

FIG. 3 c is an embodiment with an annular detector 6 which measures the diffusely reflected radiation 7 in a certain radius around the incident beam 4.

Finally, FIG. 4 shows preferred embodiments of the device, in which the arrangement of the light source (s) and / or the detector (s) is shown on one or more robot arm (s). In the figures 4d, 4e, and 4f is shown in each case with a) the uner ^¬ desired direct reflection and with b) the ge ^¬ desired diffuse reflection. 4d shows the robot arm 9 with detector 6 ininin different positions b) and a) to the sample 2 with the uneven sample surface 1, the topology of example about "hori zontal ^¬" and "obliquely upward" is reproduced. The three Figures 4d to 4f show all devices with a single and fixedly mounted light source 3. Single ^¬ Lich a detector 6 to a robot arm 9 (not shown) according to a control and regulating unit moved over the Unebenhei ^¬ th of the sample surface. 1

FIG. 4 d shows the detector in positions b) a) b), wherein it absorbs in the positions b) the diffusely reflected radiation which is reflected back from the slope 11 of the sample surface 1 and the sample 2.

According to Figure 4e, the detector 6 is moved to the impinging on the Horizonta ^¬ len 10 of the sample surface 1 beam around. FIG. 4f shows the robot arm 9 on which the receiving device for sample reception of the sample 2 is fastened and moved with respect to a fixedly or movably mounted detector 6 and / or a fixed or movably mounted light source 3 in order to control the signal intensity and the signal intensity. To optimize the noise ratio of the spectrum.

It should be emphasized that according to the present invention by simple variation of the components, a device can be realized by the

- The placement of one or more detectors on a robot arm and the implementation of the feedback system possible is to perform independent of the topography of the measurement surface Mes ^¬ solutions;

 the placement of one or more light sources on a robot arm and the implementation of the feedback system is possible in order to be able to carry out measurements independently of the topography of the measurement surface;

the placement of / the detector / detectors and the light source (s) at one or more robot arm (s) and implementation of the feedback system is possible, in order regardless of the topography of measurements to the measurement surface imple ^¬ ren;

 - The placement of the sample on a platform (plate, plate, etc.), which is mounted on a robot arm and in conjunction with the feedback system can ensure optimal optical adjustment is possible.

In addition, a nearly perpendicular to the surface of translucent Be ^¬ lighting is used and the detection window can be kept constant at a defined angle thereto.

For an optimal signal strength of the reflected light, according to a further embodiment, for example, an annular detection window, see Figure 3c, is provided.

According to a further advantageous embodiment, an optical coupling is used, in which the light source and detector are closely adjacent and the angle of einfal ^¬ lendes beam is kept constant to the surface.

 Examples of applications include:

 In the medical field (surgery, dermatology, etc.) during a skin screen or surgery

- Detection of chemical ingredients and properties of bulk samples

 Detection of materials on conveyor belts

Identification of food or the cooking state in a stove Furthermore, the system can be used for any applications in which the spectrum of the illuminated surface is to be recorded by means of the reflection of light, or a recognition of the surface by means of the sample spectrum is to take place.

The invention discloses a device for IR spectroscopic investigation of a sample, wherein at least one light source, at least one detector and a sample having a sample surface, which is optionally uneven so can be combined in egg ^¬ ner dynamic measuring optics, in spite of the unevenness in Sample material is a spectrum with a high proportion of diffusely reflected absorption signals whose signal intensity is comparable, is available. This is achieved firstly by the mobility of all or two or one of the three components light source, detector and sample and secondly by the control system which measures the surface topography of the sample and adjusts the placement of the components during the measurement.

Claims

claims 1. A device for IR spectroscopic examination of a sample, at least three components, a receiving device for the sample to be examined, a detector and a Light source comprising at least one light source, ^{¬ at} least one recording ^device and / or at least one detector are arranged relative to each other or movable to another component and positioned by means for measurement, regulation and control before and / or during spectroscopy in that the irradiation and / or the reflection in the bright angle range of the sample material is kept as low as possible. 2. Device according to claim 1, wherein the means for measuring during spectroscopy continuously measure the surface of the sample to be measured and provide the values of the control unit. 3. Device according to one of claims 1 or 2, wherein the control unit adjusts the position of the movably mounted components dynamically during spectroscopy. 4. Device according to claims 2 and 3, wherein the values from the measurement of the surface are used for positioning the movably mounted components. 5. Device according to one of the preceding claims, wherein the movable mounting of the movably mounted components is on one or more robot arms. 6. Device according to one of the preceding claims, wherein the robot arms are independently controllable. 7. Device according to one of the preceding claims, both fixed-mounted and movably mounted components um ^¬ summarizing. 8. Device according to one of the preceding claims, as a component at least one light source selected from the group of the following light sources: Incandescent or halogen lamp, light emitting diode (LED), laser serdiode, lasers, central light source whose light can be distributed over glass fiber ^¬ lines, full . 9. Device according to one of the preceding claims, as an NEN components at least one detector selected from the Group of following detectors comprising:  Measuring head, spectrometer, photodiodes and / or photoarrays. 10. Device according to one of the preceding claims, as a means for measurement, control and control a system based on at least one of the following measuring principles: camera observation of a reflex image, 3-D measurement, light field camera and / or triangulation scanner, full . 11. Device according to one of the preceding claims, comprising an annular detector, such as an annular Detektionsfens- ter. 12. A method for IR spectroscopic examination of a sample by means of a light source and a detector, wherein by suitable means the light source, the detector and the sample in their positions during spectroscopy are so changed ^¬ changed that unevenness and / or gloss effects on the sample surface are so offset by the relative movements of the light source and / or the detector relative to the sample surface from ^¬, that the highest possible proportion of diffusely reflected radiation is visible in the spectrum.