WO2018138138A1 - Method and device for sensing the surface structure and the nature of a sample - Google Patents

Abstract

The invention relates to a method for sensing the surface structure and nature of a sample (P) by means of a sensor (2₁, 2₂), in particular for sensing chemical substances on and in the surface of the sample (P), wherein the sample (P) and the sensor (2₁, 2₂) are moved relative to one another, and wherein a) the sensor emits light (L ₁, L ₂) with at least two different characteristics, in particular two different wavelengths (λ ₁, λ ₂) and/or different phase positions, wherein in particular the wavelength (λ ₁) of the first light (L ₁) lies in the absorption region and/or the phase position lies in the contrast region of the sample (P), and in particular wavelengths (λ ₁, λ ₂) are used which correspond to the wavelength range of the absorption spectrum of the nature of the surface of the sample (P), in particular of a chemical substance (S) to be sensed, b) the light (R ₁, R ₂) reflected by the surface of the sample (P) is sensed and from deviations of the reflected light (R ₁, R ₂) from the emitted light (L ₁, L ₂) two digital images of the topography of the surface of the sample (P) and the intensity of the reflected light (R ₁, R ₂) are produced. The invention further relates to a device for carrying out said method.

Description

 and device for detecting the surface structure

 and condition of a sample

description

The invention relates to a method for detecting the surface structure and nature of a sample according to the preamble of claim 1 and to a device for detecting the surface structure and nature of a sample according to the preamble of claim 18.

From DE 10 201 1 1 1 1 168 A1 a device for detecting an impression on a track carrier is known, which has a track carrier support, a receiving head with a

Infrared receiving camera and a holder for the recording head, with which the recording head is held relative to the track carrier holder. The infrared camera picks up the infrared rays emitted and / or reflected by an imprint on the track carrier. The receiving head is arranged in a holder which contains a telescoping column for adjusting the distance of the receiving head from the track carrier, which can be moved horizontally along a bar held by two bars linear. The recording head additionally has a digital camera for creating images of an evidence stored on the track carrier and an infrared emitter, which can be moved in a circle around the infrared camera. A method for detecting a fingerprint is known from DE 100 22 143 A1, in which a picture of the fingerprint arranged on a track carrier is recorded in the invisible, infrared wavelength range by means of a camera so that the image is not only reflected by the reflection, as in the visible wavelength range or absorption of the incident light, but also by the emitted heat radiation. For this purpose, the track carrier is placed on a temperature-controlled pad and illuminated by a light source, which is arranged laterally and in height offset from the temperature-controlled pad. The image is taken by means of a camera, which is arranged above the track carrier located on the temperature-controlled substrate. The arrangement of spectral filters on the light source and the camera, the track carrier is illuminated with light of the desired wavelength range.

From DE 10 2014 203 918.5 an investigation of the nature of a sample by means of a light beam is generally known.

It is the object of the present invention to provide an improved method and an improved device for detecting the surface structure and nature of a sample which, in one or more high-resolution sampling operations, produces distortion and shadow-free images of the topography and the intensity image of a sample as well as If necessary, allow a color image (RGB image) with at least theoretically unlimited size of the surface of the sample. In this case, the method and the device should be particularly suitable for surfaces in which the backscatter of the surface is not constant. In such cases, the signal from the sample is difficult to differentiate from the signal from the surrounding sample.

This object is achieved by a method for detecting the surface structure and nature of a sample according to the features of claim 1.

The light emitted onto the sample, in particular in the form of light beams, has at least two different properties, such as two different wavelengths and / or two different phase positions. In this case, for example, the wavelength of the first light, in particular of the first light beam in the absorption region of the material to be detected, is the sample, eg fat. For example, this wavelength of the first light, in particular of the first light beam, may be adapted according to the nature of the sample (ie a chemical substance). Different chemical substances such as water or fat or special hydrocarbons have such absorption areas in the middle infrared.

The second light, in particular the second light beam, comprises e.g. based on the same substance to be detected the sample to a wavelength whose specific absorption - the expression is used as the expert from the spectroscopic measurement technology known - is less than in the first light / light beam. The approach that the first light / the first light beam at the maximum of an absorption peak and the second light / the second light beam at absorption must be equal to zero, however, does not apply on closer inspection. The measuring task can also be solved if the second light beam also absorbs light to a lesser extent.

The pad, so e.g. the evidence on the e.g. The fingerprint must be recognized as a sample, has its own absorption bands, so that they can also interfere with the evaluation and thereby the choice of the two wavelengths to be detected is influenced thereby. Rather, it is part of the process that the most favorable choice of the two wavelengths depends on the overall requirements of the measurement task.

Of course, the contrast will develop particularly well if the difference in specific absorptions is particularly large.

Analogously, for example, the phase angle of the first light beam is in the contrast range of the sample. The phase position of the second light, in particular the light beam, or further light beams are outside the contrast range. The reflected light from the surface of the sample - having different characteristics such as wavelength and / or phase angle - is detected and from deviations of the reflected light from the emitted light one or two digital images of the topography of the surface of the sample and the intensity of the reflected light rays generated. In the case of generating an image, the two or more pieces of information immediately associated with each point of the sheet objects will be merged by an algorithm. The detection of the reflected light can for example be done with an appropriate for the wavelength range IR camera with surface sensor and a suitable IR lens.

By using light with different properties, variations in the retroreflective power can be eliminated. Thus, e.g. two images of the sample are taken at different wavelengths in one step, one of which is in the range of the absorption maximum of the sample. The other image - a type of reference image - lies in a different wavelength range, preferably in an area in which the sample absorbs little or not. The method and the device for detecting the surface structure and nature of the sample by means of a scanning device can e.g. for detection of traces caused by contact of the skin of the human body on the surface of an object or recorded by means of a track carrier, used in medical technology for incident light observation in skin cancer examinations as well as in the industrial sector for the detection of surface coatings and for the thickness measurement of internal layers of an object.

However, samples can also be used in the search for MRSA (methicillin-resistant Staphylococcus aureus). In principle, the scan is the same as for fingerprint grease and other chemical substances. The first wavelength will align one absorption peak of the bacterium, the second will align with an area next to it. If it were not possible to detect a peak of the sample, one could contrast or use a different reaction procedure. The evaluation of multiple peaks, with multiple lasers, or a tuning is conceivable here.

The method ensures that, for example, with a single scan, the topography of a sample and an intensity image of the sample characterizing the chemical substances on and in the surface of the sample with high resolution and distortion-free and shadow-free recorded with at least theoretically unlimited size of the surface of the sample, ensures a safe function even with incident extraneous light and, if necessary, allows shots of a color image (RGB image).

In one embodiment, the surface of the sample is first of all irradiated by a scanning device with at least two emitted light beams in a planar manner, in particular pointwise or line by line. Flat in this context means that the at least two light beams are each not only guided along a straight line, but the lines cover a flat area on the sample. This can e.g. also be circular when the light rays are e.g. be guided spirally. The area can also be complex shaped, i. with a complex shaped boundary. The light beams may be laser beams or non-coherent light. The areal, in particular the line-by-line scanning of the surface of the sample is used with high resolution and with e.g. two or more different wavelengths a distortion and shadow-free recording of both the topography of the surface of the sample and the intensity of the reflected light rays and thus the nature of the sample or the chemical substances contained in the sample or surface of the sample ensures. The individual pixels of the areal, in particular line-by-line scanning can thus be combined to form a meaningful digital image of the topography of the surface of the sample and the intensity of the reflected light beam for assessing the nature of the sample or of the chemical substances contained in the sample or surface of the sample.

In one embodiment, the second wavelength of the at least second light beam is in the non-absorbent or low-absorbing region of the sample. This can efficiently generate a reference image. Furthermore, in one embodiment, at least one light beam may have a tunable, in particular thermally tunable, light source.

The light used can be coherent or non-coherent, so that in one embodiment the at least two light beams are generated by at least two laser sources or a broadband light source with subsequent beam splitting. The procedure of irradiation with the different wavelengths can - depending on the embodiment - done in different temporal ways:

 a) First, a first wavelength is irradiated to each individual point of the surface, then a second wavelength, the calculation of the results can be instantaneous or even after the intermediate results have been stored. b) The entire object is irradiated pointwise with the first wavelength, then with the second wavelength. After that the pictures will be charged

 c) Each individual pixel is irradiated simultaneously with the first wavelength and the second wavelength and transmitted via a suitable e.g. wavelength-selective o- after polarization selective or otherwise separating the two light beams detection method selected

 d) Both wavelengths are directed simultaneously, but to other locations of the sample, and collimated with e.g. detected two detectors and taken into account the location offset by appropriate offsetting.

 e) Mixture of the previously described methods possibly also with more than two wavelengths

In one embodiment, the light is passed through a filter device before impinging on the sample, wherein in the filter device at least two different filters are each transparent only for a specific property of the light, wherein the light is guided through only one of the filters, so that by changing the filter staggered images of the sample and the environment of the sample are made with light with different properties.

In a further embodiment, the scanning device emits at least one light beam in the infrared spectrum. The light beam emitted by the scanner is emitted either at a wavelength corresponding to the wavelength range of a previously determined significant absorption peak of the chemical substance to be detected on the surface of the sample, or the scanner is configured such that the light beam emitted from the scanner is in one Range of the infrared spectrum is emitted or tuned light. In the former case, the knowledge of the absorption peak of the sample to be examined is assumed, while in the second-mentioned case a "prescan" for determining the absorption peak of the sample or chemical substance takes place. Preferably, the surface of the sample with laser beam with a predetermined laser beam diameter of preferably less than or equal to 0, 1 mm in a laser beam diameter corresponding step size irradiated line by line, the reflected laser beams coaxially detected the emitted laser beams and the transit time of the laser beam reflected from the surface of the sample Creation of a topography of the surface of the sample corresponding distance image and the deviation of the reflected from the surface of the sample laser beams from the output from the scanning laser beam to create a chemical substance on and in the surface of the sample corresponding intensity image evaluated.

The use of a scanning device designed in particular as an IR laser scanner in conjunction with a collimation optics limiting the laser beam diameter ensures high resolution in the detection of chemical substances on the surface of the sample, while the detection of the reflected light beam coaxial with the emitted light beam a distortion and shadow-free Sampling ensures optimal representation and evaluation of the surface of the sample.

In order to determine the topography of the surface of the sample, the transit time of the laser beams emitted by the scanning device and reflected by the surface of the sample is determined by the spacing of the scanning device and evaluated to form a distance image corresponding to the topography of the surface of the sample. Or the phase shift between the laser beams emitted by the scanning device and the laser beam reflected from the surface of the sample is detected and evaluated to determine the topography of the surface of the sample.

This method can also be used to evaluate the thickness of internal layers of a sample which differ from external layers.

In one embodiment, at least one of the light beams, in particular one of the laser beams, is sinusoidally modulated and used to determine the phase shift between that emitted by the scanner and that from the surface of the scanner Sample reflected at least one light beam used and the detected by the scanning reflected at least one light beam is correlated with a synchronous to at least one light beam reference signal. In a preferred embodiment, the surface of the sample is scanned serially point by point with the at least one modulated light or laser beam and pixels of a digital image are emulated from the distance and intensity measurements arranged in a matrix. To generate an RGB image, the light or laser beams generated and reflected by separate light sources can be detected in the visible range by means of an RGB sensor for determining the color values of the scanned surface of the sample, processed in an RGB image processing unit and displayed on a display become. The object is also achieved by a device having the features of claim 18.

A device for detecting the surface structure and nature of a sample contains:

 a sample intake,

 a scanning device (2) with a light source for light (Li, L2) radiates with at least two different properties, in particular two different wavelengths (λι, λ2) and / or different phase positions, wherein in particular the wavelength (λι) of the first light (Li) in the absorption region and / or the phase position in the contrast region of the sample (P), and in particular wavelengths

(λι, λ2) are used, which correspond to the wavelength range of the absorption spectrum of the nature of the surface of the sample (P), in particular a chemical substance to be detected,

 an evaluation device (3), with which from the surface of the sample (P) reflected light (R1, R2) can be detected and from deviations of the reflected

Light (R1, R2) of the emitted light (Li, L2) are two digital images of the topography of the surface of the sample (P) and the intensity of the reflected light (R1, R2) can be generated. In one embodiment, the scanning device has a means for surface, in particular pointwise or line by line, irradiation of the surface of the sample.

To change the distance between the sample holder and the scanning device, in one embodiment, the sample holder and / or the scanning device is or are connected to a Z-axis drive unit, which is bidirectionally connected to the central computer unit via a Z-axis driver unit , To generate an RGB image in addition to the distance and intensity image, in another embodiment, an RGB image acquisition unit aligned with the surface of the sample can be provided, which is connected bidirectionally via a third computer unit to the central computer unit. While the light source of the scanner directs the emitted light beams onto the surface of the sample via transmission optics and the X-Y axis deflection unit, the light receiver of the scanner preferably incorporating an infrared photodiode receiver is connected to receiving optics on the receiving side receiving the reflected light beams.

In a preferred embodiment, the scanning device includes an infrared laser emitter which directs an IR laser beam via a modulator driven by a laser control electronics onto a collimator, which mirrors the IR laser beam with a limited laser beam diameter to a polygonal deflection mirror preferably driven by an electric motor existing deflector emits the IR laser beam line by line on the

Deflects the sample and deflects the reflected from the surface of the sample IR laser beams to a photodiode.

A beam splitter arranged in the beam path between the collimator and the deflection device on the one hand allows the IR laser beams emitted by the collimator to pass to the deflection device and on the other hand deflects the IR laser beams which are serially collected by the deflection device and reflected by the surface of the sample to the photodiode. The IR laser beams fanned out line by line by the deflection device and the reflected IR laser beams received by the deflection device are directed to the sample via a correction lens and a deflection mirror, with at least part of the IR laser beams fanned out line by line being deflected onto a synchronization photodiode ,

Embodiments are illustrated in the following drawings. It shows

1 shows a block diagram of a sampling and evaluation device with integrated RGB sensor.

Fig. 2 is a block diagram of the sampling and evaluation to explain the

 Functional principle of the optical pulse transit time measurement;

3 shows the time profile of an emitted light or laser beam and of a reference light or laser beam for explaining a phase difference measurement;

Fig. 4 is a schematic representation of the parallel beam path of the output from the scanning modulated light or laser beam and reflected modulated light or laser beam.

5 shows a reduction in the intensity of monochromatic light through an oil layer;

6 shows a schematic representation of the return of the layer thickness by absorption spectroscopy;

FIG. 7 shows a schematic representation of a sample with a fat layer located on the surface of the sample; FIG.

8 is a schematic representation of the absorption band versus the wavelength of a measurement of the surface of the sample at two selected measuring points with a spectroscope; 9 shows a schematic, two-dimensional representation of an intensity image; 10 is a schematic, three-dimensional representation of an intensity image and

Fig. 1 1 is a schematic, three-dimensional representation of an object as a gray scale and the chemical substance located on the surface in color representation;

12 shows a first embodiment for guiding two light beams onto a sample and the detection of the reflected light;

Fig. 13 shows a variation of the first embodiment with an optically imaging element;

 14 shows a second embodiment for guiding two light beams onto a sample and the detection of the reflected light;

Fig. 15 shows a variation of the second embodiment with an optically imaging element;

16 shows a third embodiment for guiding two light beams onto a sample and the detection of the reflected light;

17 shows a variation of the third embodiment with an optically imaging element;

Fig. 18 shows a fourth embodiment for guiding two light beams onto a sample and detecting the reflected light;

19 shows a fifth embodiment for guiding two light beams onto a sample and the detection of the reflected light;

FIG. 20 shows a picture of a typical sample background; FIG.

FIG. 21 shows a photograph of a fingerprint on the sample background according to FIG. 20 in the absorption peak; FIG. FIG. 22 shows a photograph of the fingerprint according to FIG. 21 using an embodiment of a method presented here.

Fig. 1 shows a block diagram of a device for detecting the surface structure and nature of a sample or a measurement object P. The sample or the measurement object P is placed on a sample holder 1, which is provided with a Z-axis drive unit 5 for adjusting the distance between two Scanning 2i, 22 and the sample holder 1 is connected. The dash-dotted framed scanning 2i, 22 each consist of a transmitter with an IR laser light source 22i, 222, a laser drive electronics 211, 212 and a transmission optics 23i, 232 and from a receiver with an IR photodiode receiver 25, a log in signal amplifier 24 and a receiving optical system 26. The IR laser light sources 22i, 222 are driven by the clocked by a pulse generator 81, 82 laser drive electronics 211, 2I 2. The wavelengths λι, λ2 of the IR laser light sources 22i, 222 differ by a certain amount. In addition, in one embodiment, one of the wavelengths λι, λ2 selected so that the sample P absorbs this wavelength as well as possible and the other just not. Basically, it is only necessary that the wavelengths λι, λ2 show different contrast behavior between sample P and sample environment.

The laser beams Li, L2 emitted by the IR laser light sources 22i, 222 are collimated by means of the transmitting optics 23i, 232, for example in the form of collimators, to laser beam diameters of less than or equal to 0.1 mm and to those on the sample holder

1 located sample P directed. The surface of the sample is traversed linearly by means of the laser beam Li, L2 in a step width corresponding to the laser beam diameter, and the laser beams R1, R2 reflected by the surface of the specimen are picked up by the receiving optics 26 and emitted to the IR photodiode receiver 25 on the output side connected to the log-in signal amplifier 24, the amplified measurement signals to a dot-dash framed evaluation 3 with a first computer unit 31 for calculating a topography of the surface of the sample corresponding distance image and a second computer unit 32 for calculating a chemical substance of the surface of the Sample corresponding intensity image outputs, which are also clocked by the pulse generator 8. The first and second computer unit 31, 32 are bidirectionally connected to a central processing unit (CPU) 30 to which a storage unit 61 and an external storage unit 62 are bidirectionally connected. The two laser beams L2 are thereby directed by a control unit 70 so that they are guided in a predeterminable manner on the receiving optics 26 and the IR photodiode receiver 25. As will be explained with reference to different embodiments (see FIGS. 12 to 19), the IR photodiode receiver 25 may have a plurality of photodiodes, for example. The deflection of the beams can also take place in different ways. In the context of these embodiments is also discussed how the use of two laser beams Li, L2 affects.

The laser beams Li emitted by the transmitter 211, 22i, 23i of the first scanning device 2i lie in the wavelength range of the absorption spectrum of the sample P to be examined. Alternatively, the transmitter 211, 222, 233 broadband emits a laser beam Li in the infrared spectrum to the surface of the sample, wherein the wavelength is changed into regions in 0.2 nm increments.

The laser beams Li, L2 emitted by the IR laser light sources 22i, 222 are collimated onto the surface of the sample in the transmission optics 23i, 232, to a diameter of less than or equal to 0.1 mm, and deflected by means of deflection means, for example by means of deflection means Polygon mirror or galvanometer line by line in a step corresponding to the beam diameter, so that by means of the deflector scanning of the surface of the sample in one (X-axis) and by the feed of the sample or the scanning device in the other (Y- Axis) for sampling the

XY surface is done.

A X-Y-axis deflecting unit 4 traveling either the scanning devices 2i, 22 or the sample receptacle 1 in the XY plane perpendicular to the Z axis causes the entire area of the surface of the sample to be scanned by means of the scanning devices 2i, 22 is scanned. By scanning the surface of the sample line-by-line in conjunction with the XY-axis adjustment, sample surfaces up to a width of 10 m and any length can be scanned. The XY axis deflection unit 4 is driven by an XY axis drive unit 40 and outputs to these position signals. The XY axis driver unit 40 is bidirectionally connected to the central processing unit 30. The Z-axis drive unit 5 is driven by a Z-axis drive unit 50 and outputs to these altitude position signals, and the Z-axis drive unit 50 is also bidirectionally connected to the central processing unit 30.

For determining color values of the surface of the sample scanned by the scanning devices 2i, 22, an external RGB image acquisition unit 7 can additionally be provided, which is directed onto the surface of the sample and connected to a third computer unit 33, which is also bidirectional to the central computer unit 30 is connected.

To record the topography or contour of the surface of the sample and the nature of the chemical substance of the sample P, in one embodiment the transit time of the laser light signals or laser light pulses can be measured, which depends on the distance of the individual points of the contour of the surface of the sample. so that an exact image of the topography of the surface of the sample is detected by calculating a distance image. The topography can also be obtained by triangulation or another method.

Since the chemical substance to be examined has specific absorption properties, the strength or intensity of the reflected laser beam R provides information about the nature or composition of the sample or surface of the sample. Thus, when scanning the surface of the sample, an intensity image of the surface of the sample can be recorded and evaluated from the individual intensity measuring points. For this purpose, each individual measuring point can be represented, for example, in the form of an intensity scaled from 0 to 100, an easily recognizable reproduction of the intensity image and corresponding imaging on an image display unit or by an assignment of different color scales to the intensity values

Display 9 will be enabled. The measurement of the distance between the individual points of the surface of the sample and the scanning device 2 required for determining the topography of the surface of the sample will be explained in more detail below with reference to FIGS. 2 and 3. For the sake of simplicity, this basic description is made only by means of a laser beam.

2 shows a schematic block diagram for explaining the operating principle of an optical pulse time-of-flight measurement (TOF time-of-flight). Analogous to the block diagram according to FIG. 1, a laser light source 22i is provided whose emitted laser beams Li are collimated by a transmitting optics 23i onto the surface of the sample of the sample P located on the sample holder 1. The reflected laser beams Ri are received by the receiving optics 26 and delivered to a photodiode receiver 25. Both the laser light source 22i and the photodiode receiver 25 output output signals to a time measuring device 27, which is the output side connected to a microprocessor 300. To the microprocessor 300, a digital output 28 and optionally an analog output 29 of the measuring device is connected.

The laser light source 22i triggers the time measuring device 27i simultaneously with the delivery of a laser light pulse Li. The laser light pulse Li impinges on the surface of the sample, is reflected therefrom and received as reflected laser light pulse Ri from the receiving optics 26 and detected by the photodiode receiver 25, which stops the time measuring means 27, so that the distance-dependent signal propagation time was measured immediately the distance of the respective Measuring point of the surface of the sample from the scanning device 2 corresponds. Since only very small differences in the distance-dependent signal propagation time of the laser beam Li are measured with very flat contours of the surface of the sample, the accuracy of the detection, evaluation and reproduction of the topography of the surface of the sample depends on the accuracy of the time measurement. For this reason, a method for distance measurement by means of phase shifting is used as an alternative, the functional principle of which is shown in FIG. 3 and which essentially consists of the same device as in FIG

2 makes use of a phase measuring device instead of the time measuring device 27.

In this method, the phase shift is measured, the optically modulated measurement signal due to its path-dependent signal propagation time relative to a reference signal experiences. In the case of the optical pulse travel time measurement, the laser light pulse Li is replaced by a sinusoidally modulated signal whose phase is determined by the signal received by the photodiode receiver 25 being correlated with a synchronous reference signal. The thus determined phase shift or phase difference Δφι is proportional to the propagation time of the laser light pulse Li from the laser light source 221 to the photodiode receiver 25.

In order to arrive at a three-dimensional distance measurement from the above-described one-dimensional transit time measurement, the surface of the sample is scanned with the aid of the scanning device 2i with the aid of the modulated laser light beam and the surface of the sample is measured serially point by point. The measurement results arranged in a matrix are picture elements of a digital image which reproduces a distance image and therewith the topography of the surface of the sample and an intensity image of the surface of the sample which corresponds to the nature of the surface of the sample. If an additional RGB sensor is used, an additional RGB image can be created from the determined color values of the measured points.

1, the measurement data, namely the distance values, intensity values and RGB color values are transmitted to the evaluation device 3, for example a PC or laptop, in which they are supplied with the aid of software a distance, intensity and possibly true color image composed and visualized on the image display unit or the display 9. In addition to the pictorial representation of the measured data, the evaluation device 3 also effects the recording control of the scanning devices 2i, 22, for example the selection of the area of the surface of the sample to be scanned, specification of the step size during the scanning process, height adjustment of the sample holder 1, etc. FIG. 4 also shows in more schematic form Representing the principal function of a scanning device 2i, 22 (for reasons of simplicity, only one scanning device 2 is shown in FIG. 4) for emitting the modulated IR laser beams Li, L2 and for receiving the reflected modulated IR laser beams R1, R2 whose transit time or phase shift relative to the modulated IR laser beam Li, L2 for determining a distance image and in order to determine the topography of the surface of the sample P and its absorption properties and thus chemical composition are combined to form an intensity image. The IR detectors 91, 92 and lenses 93, 94 are positioned obliquely to the sample receptacle 1, wherein the one IR detector 91 in the Y direction and the other IR detector 92 is aligned in the X direction.

The embodiment makes it possible to deduce the thickness of a chemical substance at each measuring point via the intensity measurement, which, in addition to the application areas mentioned at the outset, can also be used for the measurement of material coatings, adhesive layers on foils and in multilayer structures of internal layers. Examples of this are shown in FIGS. 5 to 10. 5 shows a schematic representation of the reduction of the intensity of monochromatic light through an oil film 101 on a metal strip 100 of a sample 1. On the sample 1 monochromatic light, for example a laser beam, is directed with the initial intensity lo. The intensity of the monochromatic light is determined by the coating thickness-dependent absorption of the oil film 101, the reflection IR at the boundary layer of the surface of the oil film 101, and the boundary layer between the oil film 101 and the film

Surface of the metal strip 100 and reduced by the stray light ls the coating.

FIG. 6 shows in a schematic representation of the absorption over the wavenumber the return of the layer thickness by the absorption spectroscopy of the arrangement according to FIG. 5.

FIG. 6 shows the peak Ai representing the layer thickness-dependent absorption of the oil film 101 and A2 the reduction of the intensity of the monochromatic light by the reflection at the surface of the oil film 101, the scattered light of the coating and the reflection of the boundary layer between the oil film 101 and the metal strip

100th

FIGS. 7 and 8 show an example of a measurement with a spectroscope. The sample used is a plate shown schematically in FIG. 7 with a fat layer located thereon and two measuring points Mi and M2. FIG. 8 shows two spectra which were measured on the disk sample with a layer of fat at the two measuring points Mi and M2. In the diagram according to FIG. 8, the absorption peaks with the associated functional groups are shown. In addition to the broad, strong absorption peak at about 1, 000 cm ^-1 , further absorption peaks occur at about 1, 500 cm ^-1 (methylene CH ₂ and methylene CH ₂ and methyl CH ₃ ), at about 1, 750 cm ^-1 (ketones C = 0), 2,700 cm ^-1 and 3,000 cm ^-1. A broad absorption peak occurs between 3,700 cm ^-1 and 3,350 cm ^-1 (H2O and OH). These additional peaks can all be attributed to the presence of the fat layer, the absorption peak of the OH group can originate from the fat or from the humidity that has deposited on the plate surface.

The absorption over the wave number shown in FIG. 8 at the two measuring points Mi and M2 according to FIG. 7 shows the peaks typical for certain materials in a wave number range between 800 and 3,750 cm ^-1 . At 2,850 cm ^-1 and at 2,900 cm ^-1 , the characteristic bands for finger trace ^fat can be seen. In the case of a finger-track scan, preferably only this band is evaluated, but not the entire absorption band over a range of 1-10 μηη wavelength. 9 shows a two-dimensional representation of an intensity image, showing the respective X / Y position of each pixel and the intensity of each pixel represented by means of a gray scale representation, resulting in a structural representation of the surface of the sample. FIG. 10 shows an imaging, three-dimensional representation of the intensity image of each individual measurement point on the surface of the sample and a scale of the spectral intensity, which is shown schematically in color and which corresponds to the respective color of the measurement points, so that in addition to a qualitative assessment of the surface the sample is also a quantitative assessment possible. The topography depicted in FIG. 10 in a gray scale can be displayed two-dimensionally, but also three-dimensionally, with the substance S thereon, as shown in FIG. 11, as in the illustration. 1 1 shows a schematic, two-dimensional representation of a sample P with the height profile Z1 of the sample P as a gray scale and the chemical substance S located on the surface of the sample P with the height profile Z2, for example in a red-level representation. Depending on the height Z2 of the substance S, it can be displayed in a two-dimensional image in a color palette from light red to dark red.

 With the scanning or scanning method according to the invention and the scanning device derived therefrom, a technology is realized which enables a shadow-free and tooth-free recording of the surface of the sample with a single scanning process by a distance image,

 an intensity image

 If required, an RGB image is created when an RGB sensor is arranged to determine the color values of the measured points with a distance resolution of approximately 1 mm, in particular less than or equal to 0.1 mm, with each sampled pixel providing image and distance information. Furthermore, the method according to the invention and the device according to the invention ensure the suppression of background light, so that a reliable function of the scanning method is ensured even with extraneous light.

Different embodiments are shown in FIGS. 12 to 19, with which two light beams I 2 are directed onto the sample P and the reflected light R i, R 2 is supplied to an evaluation.

In the first embodiment, two parallel light beams Li, L2 (e.g., laser beams) having different wavelengths are directed to the sample P via a partially transmissive mirror device 70 and a reflector 71. The reflector 71 is here and also designed as a vibrating mirror or rotating mirror.

The reflected rays R1, R2 with the respective wavelengths then strike the reflector 71 and the partially transmissive mirror device 70 again. From there they are directed onto a receiving optical system 26, which here has two diodes as detectors. For the details of the reception and the evaluation of the reflected light R1, R2 refer to the above description. In Fig. 13, a variation of the embodiment of FIG. 12 is shown. Here, an optically imaging element 72 is additionally arranged between the partially transparent mirror device 70 and the reflector 71. This has the task, for example, of a parallel beam path, as it may be favorable for the partially transmissive mirror to convert into a focused beam path, which has advantages for the point imaging and resolution.

In the embodiments of Figures 14 and 15, two light beams Li, L2 are simultaneously passed over a first dispersive element 73 (e.g., transmission grating). The merged laser beam L is then passed over a partially transparent mirror device 70 and a reflector 71 on the sample P.

The light R reflected by the sample is guided by the partially transmissive mirror device 70 onto a second dispersive element 74. The thus separated beams are passed to the receiving optics 26, which has two diodes as detectors here.

FIG. 15 shows a variation of the embodiment according to FIG. 14, wherein, as in the embodiment of FIG. 13, an optically imaging element 72 is arranged in the beam path between the partially transmissive mirror device 70 and the reflector 71. Here, too, the imaging element 72 transfers the part of the optics with a rather parallel beam path into the confocal part of the optic.

In the embodiments according to FIGS. 16 and 17, the light beams Li, L2 are irradiated in time in the form of light pulses onto the sample P. The time offset is through

Chopper or shutter 75,76 generated in the beam path in front of a dispersive element 73. The time offset can also be achieved via a corresponding control of the laser or a kind of controllable breaker. The merged beam L is then guided via the partially transmitting mirror device 70 and the reflector 71 onto the sample P. The reflected light R is then guided again via the reflector 71 and the partially transmissive mirror device 70 to a receiving optical system 26, which here makes do with a diode as a detector. FIG. 17 shows a variant of the embodiment according to FIG. 16. In this case, an optically imaging element 72 is additionally arranged in the beam path in front of the dispersive element 73. Hereby, the light can be parallelized and the wavelength splitting effect of the dispersive element 73 can be improved.

In FIG. 18, two parallel light beams Li, L2 are guided via an optically imaging element 72 onto a reflector 71. The diffusely reflected light radiation R is then received by a receiving optics 26 with a diode as a detector. The intensity of the recorded light will usually be weak, so that this variant seems suitable only for light surfaces and with increased amplification effort.

The embodiments of FIGS. 12 to 18 used laser light to obtain information about the sample P. In Fig. 19, an embodiment will be described in which non-coherent light, e.g. from a broadband MIR light source 75, is irradiated onto a partially transmissive mirror device 70. Via an optical imaging element 72 and a reflector 71, the light is guided onto the sample P. The partially transmissive mirror device 70 directs the reflected light R onto a dispersive element 73, which divides the light and supplies it to the receiving optics 26, here with two diodes as detectors.

According to the embodiments presented here with at least two light beams Li, L2, fluctuations in the reflection behavior of the surroundings of the sample P can be eliminated by taking a second image of the scan area and adjusting the laser wavelength such that the second image is not or not at all Absorbing area of the surface is absorbed. Thus, the first light beam Li is the targeted absorption, the second light beam L2 serves as a reference. Two images of the surface are obtained, one in the absorption maximum of e.g. examined organic

Substance and one outside this wavelength range. When using infrared radiation, a reference image is taken to the actual mid-infrared image.

It is thus possible to calculate a real extinction, as in classical means of infrared spectroscopy, namely for every pixel

 Ext = logy where the intensity lo is the intensity of the reflectance light of the reference wavelength in the non-absorbing region and I the wavelength absorbed by the organic substance (e.g., fat).

The variable extinction (Ext) would then be independent of the reflectance or brightness of the surface and scale linearly with the layer thickness of the overlying fat (Lamert-Beers law). The mathematical process of forming a logarithm linearizes the characteristic curve as a function of the layer thickness, so that in one embodiment the layer thickness of the greasy film can be stated directly.

Depending on the embodiment of the system according to the invention, the second wavelength A2 of the second light beam L2 can be obtained as a laser wavelength tuned thermally or otherwise, or by using a second laser or by splitting a broadband light source or by other means.

Also, a third light beam with a third laser wavelength and also with an even higher number of laser wavelengths, the contrast can be improved.

The recording can be carried out sequentially for each measuring point on the sample P or simultaneously during selection via wavelength-splitting dividing apparatuses when using a broadband light source 75.

The second image can be obtained independent of the first image. The same background can be scanned at the second, third, or another wavelength. Thus, measurements can also be carried out after a first measurement. In a further embodiment, the two light sources can be positioned next to each other, advantageously illuminate the sample P in close proximity and through the same optics. The two light spots are then imaged side by side on the sample P. The two images obtained are thus spatially offset and are moved after completion of the scan or even during the scan by a previously calibrated and stored in the device manner for the purpose of background suppression. Particularly advantageous in this embodiment is the low expenditure on equipment, since all optical parts can be used together.

Also, the height information can be recorded completely separated by laser triangulation or stripe light projection or by time-of-flight cameras, which significantly improves the measurement setup.

The method can also be performed on sloping surfaces, which represents a significant advantage in the scope of the inventive measuring system. Brightness fluctuations within the surface are suppressed by the quotient formation. Elaborate phase contrast or transit time difference measurements of the IR light are not necessary in the method shown here.

Depending on the sample requirements and availabilities of laser sources or other light sources, wavelengths with high intensity and low intensity can be used. The skilled artisan will choose the optimum compromise here because often weak or not fully powered laser light sources have a much longer life before they need to be replaced, on the other hand with a weaker signal more relative noise occurs. The method is not limited to the wavelengths in the absorption peak of

Fats. It can also be used outside absorption. Thus, different wavelengths can be used in an edge of absorption peaks. Again, the suppression of the background works by quotient formation. If, for example, an absorption peak of 3500-3600 cm ^-1 extends at a maximum at 3550 nm, then the choice of the wavelengths can also fall, for example, to 3550 nm and 3530 nm.

In the following example, a fingerprint is used as sample P, with fingerprints predominantly consisting of fat. In Fig. 20, the pure background is shown without fingerprint absorption. The fluctuation range in the reflection is significant.

FIG. 21 shows the same background with a fat fingerprint in the absorption peak. In Fig. 22, the application of the method described here and the achievable improvements are exemplified. In this measurement, the measuring arrangement Fig. 18 was used.

In addition to the expansion of the range of applications on sloping surfaces and the considerable contrast improvement, there is an extension of the possible applications to problematic surfaces. Even rough surfaces can thus be measured, which is a significant improvement over the prior art.

So far, the basic idea has been described with reference to the absorption of different wavelengths λι, λ2.

However, other embodiments may be other known differences of two light beams Li, L2, which ultimately lead to a contrast and visualization of the objects. To name here is the phase of the light rays, or in the result of the phase contrast, which comes from the duration of the light when penetrating the sought material. The transit time is dependent on the speed of light in the medium and thus on the refractive index, which may vary depending on the material to be examined.

LIST OF REFERENCE NUMBERS

1 sample intake

2i, 2 ₂ scanning device

 3 evaluation device

 4 XY axis deflection unit

 5 Z-axis drive unit

 7 RGB image acquisition unit (RGB sensor)

8 pulse generator

 9 image display unit (display)

21 i, 21 ₂ Laser control electronics

22i, 22 ₂ I R laser light source

23i, 23 ₂ Transmitting optics

 24 log-in signal amplifiers

 25 photodiode receivers

 26 receiving optics

 27 time or phase measuring device

28 digital output

 29 analog output

 30 central processing unit (CPU)

 40 X-Y axis driver unit

 50 Z-axis driver unit

 61 storage unit

 62 External storage unit

 70 Semitransparent mirror device

71 reflector (rotating mirror, oscillating mirror)

72 Optically imaging element

 73 First dispersive element

 74 Second dispersive element

 75 Light source for non-coherent light

91, 92 IR detectors

 93, 94 lenses

 100 sheet metal strips

 101 oil film

300 microprocessor Ai, A ₂ peaks

 I passed light

 IA layer thickness-dependent absorption lo initial intensity

 IR reflection

ls stray light

Li, L ₂ emitted laser beam

Mi, M ₂ measurement points and curves

Ri, R ₂ reflected laser beam

 S substance

 P sample or target

 Δφ phase shift or phase difference

Claims

claims 1 . Method for detecting the surface structure and nature of a sample by means of a scanning device, in particular for detecting chemical substances on and in the surface of the sample, wherein the sample and the scanning device are moved relative to one another, characterized in that a) the scanning device uses light ( L2), in particular light beams having at least two different properties, in particular two different wavelengths (λι, λ2) and / or two different phase angles, in particular the wavelength (λι) of the first light (Li), in particular the first light beam in the absorption range the sample (P) and / or the phase position of the first light (Li), in particular the first light beam in the contrast region of the sample (P), and in particular wavelengths (λι, λ2) are used, the wavelength range of the absorption spectrum of the nature of the surface the sample (P), in particular one to erfa b) the light reflected from the surface of the sample (R1, R2) and from deviations of the reflected light (R1, R2) from the emitted light (Li, L2) two digital images of the topography of the surface of the Sample (P) and the intensity of the reflected light (R1, R2) are generated. 2. The method according to claim 1, characterized in that the surface of the sample (P) of the scanning device (21, 22) with at least two emitted light beams (L1, L2), in particular laser light surface, in particular pointwise or line by line, is irradiated. 3. The method according to claim 1 or 2, characterized in that the second wavelength (λ2) of the at least second light, in particular the second light beam (L2) in the non-absorbent or little absorbing region of the sample (O). 4. The method according to at least one of the preceding claims, characterized in that at least one light beam (Li, L2) has a tuned, in particular thermally tuned wavelength (λι, λ2). 5. The method according to at least one of the preceding claims, characterized in that the at least two light beams (Li, L2) by at least two laser sources or a broadband light source (75) are generated with subsequent beam splitting. 6. The method according to at least one of the preceding claims, characterized in that the irradiation of the surface of the sample (P) of the scanning device (2i, 22) with the at least two emitted light beams (Li, L2) sequentially for each measuring point (M), in particular with a time offset or simultaneously. 7. The method according to at least one of the preceding claims, characterized in that the light (Li, L2) is passed through a filter device before impinging on the sample (P), wherein in the filter device at least two different filters each only for a specific property the light (Li, L2) are transparent, wherein the light (Li, L2) is guided in each case only by one of the filters, so that by changing the filter staggered recordings of the sample (P) and the environment of the sample (P) with Light (Li, L2) can be made with different properties. 8. The method according to at least one of the preceding claims, characterized in that the scanning device (2) emits at least one light beam (Li, L2) in the infrared spectrum. 9. The method according to at least one of the preceding claims, characterized in that the surface of the sample (P) with at least two laser beams (Li, L2) each with predetermined laser beam diameter in a laser beam diameter corresponding step size irradiated line by line, the reflected laser beams (R1, R2 ) are detected and evaluated coaxially with the emitted laser beams (Li, L2). 10. The method according to claim 9, characterized in that the emitted laser beams (Li, L2) to a laser beam diameter less than or equal to 1 mm, in particular less than or equal to 0, 1 mm, are collimated. 1 1. Method according to at least one of the preceding claims, characterized in that the thicknesses of internal layers of the sample (P), which differ from outer layers, are evaluated. 12. The method according to at least one of the preceding claims, characterized in that the distance of the scanning device (2i, 22) from the surface of the sample (P) dependent transit time of the scanning device (2) and emitted from the surface of the sample (P ) reflected laser beam (R1, R2) and evaluated to create a topography of the surface of the sample (P) corresponding distance image. 13. The method according to at least one of the preceding claims, characterized in that the phase shift (Δφ) between at least one of the scanning device (2) emitted light beam (Li, L2), in particular at least one laser beam (Li, L2) and the at least one of the surface of the sample (P) reflected light beam (R1, R2) is detected and evaluated to determine the topography of the surface of the sample (P). 14. The method according to at least one of the preceding claims, characterized in that the absorption-related deviation of the surface of the sample (P) reflected laser beam (R1, R2) emitted by the scanning device (2) light beam, in particular laser beam (Li, L2) to evaluate an intensity image corresponding to the chemical substance on and in the surface of the sample. 15. The method according to claim 13 or 14, characterized in that at least one of the light beams (Li, L2), in particular one of the laser beams (Li, L2) is sinusoidally modulated and for determining the phase shift (Δφ) between that of the scanning device (2 ) and the at least one light beam (R1, R2) reflected from the surface of the sample (P) is used and that of the Scanning (2) detected reflected at least one light beam (Ri, R2) is correlated with a at least one light beam (Li, L2) synchronous reference signal. 16. The method according to at least one of the preceding claims, characterized in that the surface of the sample (P) with the modulated light beam (Li, L2) scanned serially point by point and from the arranged in a matrix distance and intensity measurements pixels of a digital image. 17. The method according to at least one of the preceding claims, characterized in that the at least one reflected light beam (R1, R2) by means of an RGB image recording unit (7) for determining the color values of the scanned surface of the sample (P) is detected. 18. Device for detecting the surface structure and nature of a sample, in particular for carrying out the method according to at least one of the preceding claims, characterized by a sample holder (1),  - A scanning device (2) with a light source for light (Li, L2), in particular light beams with at least two different properties, in particular two different wavelengths (λι, λ2) and / or different phase angles radiates, in particular the wavelength (λι) of the first Light (Li), in particular of the first light beam in the absorption region and / or the phase position of the first light (Li), in particular the first light beam in the contrast region of the sample (P) are, and in particular wavelengths (λι, λ2) are used, the wavelength range of the absorption spectrum of the nature of the surface of the sample (P), in particular of a chemical substance to be detected, - An evaluation device (3), with which from the surface of the sample (P) reflected light (R1, R2) are detectable and from deviations of the reflected light (R1, R2) from the emitted light (Li, L2) two digital images the topography of the surface of the sample (P) and the intensity of the reflected light (R1, R2) are generated. 19. The apparatus according to claim 18, characterized by a means of the Abstasteinrichtung (2i, 22) for areal, in particular pointwise or line by line, irradiation of the surface of the sample (P). 20. The apparatus of claim 18 or 19, characterized in that the sample holder and / or the scanning device (2) connected to a Z-axis drive unit (5) for changing the distance between the sample holder (1) and the scanning device (2) is or are, which is bidirectionally connected via a Z-axis driver unit (5) to the central computer unit (30). 21. The device according to at least one of claims 18 to 20, characterized by an on the surface of the sample (P) aligned RGB image recording unit (7) bidirectionally via a third computer unit (33) for generating an RGB image with the central computer unit (30) is connected. 22. Device according to at least one of the preceding claims 18 to 21, characterized in that the light source (21, 22, 23) an IR laser light source (22), a transmission optics (23) for the emission of light beams (Li, L2 ) of the IR laser light source (22) on the surface of the sample (P) and a light source Ansteuerelekt- ronik (21) for driving the IR laser light source (22). 23. The device according to at least one of the preceding claims 18 to 22, characterized in that the light receiver (24, 25, 26) an IR Fotodioden- receiver (25), one on which the reflected light beams (R1, R2) receiving side receiving optics arranged (26) and a the output from the IR photodiode receiver (25) signals amplifying log-in signal amplifier (24). 24. The device according to at least one of the preceding claims 18 to 23, characterized in that a pulse generator (8), the light source drive electronics (21), the log-in signal amplifier (24) and the three computer units (31, 32, 33) controls. 25. Device according to at least one of the preceding claims 18 to 24, characterized in that the IR laser light source (22) at least one IR Laser beam (Li, L2) via a driven by a laser drive electronics (21) modulator (1 1) directed to a collimator (13), the at least one IR laser beam (Li, L2) with a limited laser beam diameter to a deflection (15), which deflects the at least one IR laser beam (Li, L2) line by line on the sample (P) and deflects the reflected from the surface of the sample IR laser beams (R1, R2) to an image pickup photodiode (12) , 26. The device according to claim 25, characterized in that in the beam path between the collimator (13) and the deflection device (15) a semitransparent mirror device (14) is arranged, on the one hand from the collimator (13) emitted IR laser beams (Li, L2 ) to the deflection device (15) and, on the other hand, deflects the IR laser beams (R), which are combined in series by the deflection device (15) and reflected by the surface of the sample (2), to form an image-recording photodiode (12). 27. The device according to at least one of claims 18 to 26, characterized in that the deflection of the device (15) fanned line by line IR laser beams (L) and the deflecting device (15) received reflected IR laser beams (R) via a correction lens (17) and a deflecting mirror (18) to the sample (P) are passed. 28. The device according to at least one of claims 18 to 27, characterized in that at least part of the deflecting device (15) line-by-line fanned out IR laser beams (Li, L2) is deflected to at least one synchronization photodiode. 29. Device according to one of the preceding claims 18 to 28, characterized in that the deflection device consists of an electric motor driven polygonal deflection mirror (15) or a galvanometer.