WO2008138976A1 - Object imaging method and system - Google Patents

Abstract

The invention relates to a method and a system for imaging objects. A surface area of the object is locally stimulated using encoded stimulating radiation, and the object radiation emanating from a detection range of the object is detected in a cooperating manner. The object radiation comprises the radiation generated by the stimulation. The surface area is represented on the basis of the detected object radiation. Preferably, the object radiation is detected at a frequency that differs from the frequency of the stimulating radiation. The locally stimulated surface area is also preferably smaller than or has the same size as the detection range.

Description

 Method and system for imaging objects

The invention relates to an imaging method for imaging an object and in particular a surface or a near-surface region of the object by stimulating the surface with electromagnetic radiation and a system for carrying out this method.

Methods and apparatus for displaying surfaces of objects are known. Thus, in particular in a method generally referred to as thermography, the object to be examined or the object surface to be examined is excited by means of electromagnetic radiation or ultrasound and the heat radiation emitted by the object surface due to this excitation is detected with a thermographic camera (see, for example, A. Dillenz and G. Busse, "Non-contact detection of laminate damage using Lockin thermography", http://www.zfp.uni-stuttgart.de/downloads/kk99.pdf) The thermography camera used to record the thermal radiation emitted by the object is an infrared Camera which images the area of the object surface to be examined The achievable resolution is limited by the camera used or the imaging optics used.

The present invention seeks to provide a new method and system for imaging object surfaces. In particular, the invention is intended to allow the imaging of a surface cost-effectively with a high resolution.

The invention is defined by the features of the independent claims. Preferred embodiments are defined in the dependent claims.

The invention is based on the basic idea of generating or stimulating a predetermined area of the object surface locally by means of coded stimulation radiation in order to generate images of near-surface object properties and to detect or detect the object radiation emitted by the object in a cooperative manner. Radiation of a frequency which differs from the frequency of the stimulation radiation is preferably detected here. The detected radiation includes the radiation caused by the stimulation. The radiation caused by the stimulation is to be understood as radiation that can be generated, changed or even influenced by the stimulation radiation. By coordinating between the coding of the stimulation radiation and the cooperating detection, the radiation caused by the stimulation can be filtered out of the detected radiation. For example, the stimulation radiation can be coded by amplitude or frequency modulation and the detection can be synchronized with this coding or modulation.

In one embodiment, a region of the object surface is stimulated which is smaller than the detection region, which defines from which region the object radiation is detected. However, the detection area may also be the same size as the area of local stimulation or even larger. According to a preferred embodiment, in each case only a very small area of the object surface is stimulated by a laser beam, for example, and radiation emitted by essentially the entire object surface is detected. Such a local stimulation can be achieved by the cooperative detection accurate location information of the radiation generated by the stimulation and thus increase the resolution of the imaging. If different areas of the object surface are successively excited by the local stimulation, an image of the entire object surface can be generated by scanning the object surface. If, in this case, the detection device covers only a part of the object surface to be examined, the detection device is moved along accordingly. The scanning of the object surface can be done by successively stimulating defined areas (pixels) of the surface. These areas can, for example, be traversed in rows, columns or meanders to cover the entire surface to be examined. In order to avoid a possible influence of adjacent pixels, the surface can also be scanned in a jump method.

According to the present invention, the excitation and corresponding detection can be done using thermal effects. For example, the Object surface are locally heated by a laser beam and the heat radiation emitted due to this heating can be detected. To generate thermal effects, laser radiation in the visible or infrared range is preferably used. The detection is preferably carried out in the microwave range. The utilization of fluorescence or scattering effects is also possible in which the frequency of the fluorescence radiation differs from the frequency of the excitation radiation. Exemplary of this are two-photon fluorescence effects, wherein the excitation is carried out by the simultaneous absorption of two photons, or the Raman effect. Furthermore, particle beams, for example electron beams or ion beams, can be used in particular for stimulating the object surface.

Also, several stimulation devices can be used simultaneously or in parallel in order to be able to carry out the method more quickly. In this case, the different stimulation beams are coded differently.

By means of the method and the system of the present invention, an examination of the object surface can take place, ie the immediate object surface but also areas near the surface. Thus, for example, the thermal excitation of the object surface, the heat is introduced by thermal conduction in deeper layers of the object surface. These areas also contribute to the generation of the observed thermal radiation.

The present invention allows a representation of a surface area of an object to be examined. Due to the local stimulation of an object surface area, location information can be obtained from the globally or globally observed radiation without having to use imaging optics for the observation. The coding of the stimulation radiation and the cooperative detection can furthermore provide temporal information which can be used to filter out the background radiation which is not caused by the local stimulation and thus to obtain information about the radiation actually generated by the stimulation and to use for imaging. The above-described ideas and aspects of the present invention as well as alternative and / or additional aspects of the present invention will be described with reference to the following preferred aspects of the invention:

A system for imaging comprising means for locally stimulating an object surface area by means of coded stimulation radiation and means for cooperatively detecting object radiation emanating from the object, comprising radiation caused by the stimulation.

2. System according to aspect 1, wherein the detection device is designed to detect an object radiation of a frequency which differs from the frequency of the stimulation radiation.

3. System according to aspect 1 or 2, wherein the detection device is designed to detect object radiation from a detection area of the object, wherein the area of the local stimulation is less than or equal to the detection area.

4. System according to aspect 1, 2 or 3, further comprising a control device which is adapted to coordinate the detection with the stimulation, wherein the coordination is preferably carried out using and / or controlling the coding of the stimulation radiation.

5. System according to one of the preceding aspects, wherein the (a) control device is designed to filter from the detected radiation caused by the stimulation radiation, preferably by using and / or controlling the coding of the stimulation radiation.

6. System according to one of the preceding aspects, wherein the (a) control means is adapted to generate based on the stimulation caused by the radiation image information, preferably for display on a display of the stimulated area. 7. System according to one of the preceding aspects, wherein the means for local stimulation is adapted to stimulate successively different, defined areas.

8. The system according to one of the preceding aspects, wherein the control device is designed to generate image information of the different stimulated regions on the basis of the detected radiation caused by the stimulation of different defined stimulated regions and to generate an image of an object surface section from this image information.

9. System according to one of the preceding aspects, wherein the stimulation device is designed to generate amplitude and / or frequency modulated stimulation beams.

10. System according to one of the preceding aspects, wherein the detection device is designed to synchronize the detection with the coded stimulation radiation.

11. System according to one of the preceding aspects, wherein the stimulation device is designed to generate electromagnetic radiation in the visible and / or infrared range and / or wherein the detection device is adapted to detect electromagnetic radiation of a frequency, preferably in the microwave range, the deeper is, as the frequency of the stimulation radiation.

12. System according to one of the preceding aspects, wherein the stimulation device is designed to generate particle radiation.

13. System according to any of aspects 6 to 12, wherein the image information comprises material and / or geometry information relating to the stimulated area.

14. System according to one of the preceding aspects, wherein the stimulation means is adapted to fluorescence in the observed To generate object, and the detection device is adapted to detect the fluorescence radiation.

15. System according to one of the preceding aspects, wherein the detection device is designed to detect scattered radiation on the object surface, for example due to the Raman effect.

16. A method of imaging an object comprising the steps of: locally stimulating a surface area of the object with coded stimulation radiation; cooperatively detecting the object radiation emanating from a detection region of the object, comprising radiation caused by the stimulation; and

Representing the surface area on the basis of the detected object radiation.

17. The method of aspect 16, wherein object radiation is detected at a frequency different from the frequency of the stimulation radiation.

18. The method of aspect 16 or 17, wherein the locally stimulated surface area is less than or equal to the detection area.

19. The method of aspect 16, 17 or 18, wherein the detection is coordinated with the stimulation, wherein the coordination is preferably done using and / or controlling the coding of the stimulation radiation.

20. The method according to any one of aspects 16 to 19, wherein the stimulation radiation is amplitude and / or frequency modulated.

21. The method of any one of aspects 16 to 20, wherein the detection is synchronized with the coded stimulation radiation.

22. Method according to one of the aspects 16 to 21, wherein the radiation produced by the stimulation is filtered out of the detected radiation, preferably using and / or controlling the coding of the stimulation radiation.

23. Method according to one of the aspects 16 to 22, wherein image information of the stimulated area is generated on the basis of the radiation caused by the stimulation, for the representation of the surface area.

24. Method according to one of the aspects 16 to 23, wherein successively different, defined surface areas of the object are stimulated.

25. Method according to one of the aspects 16 to 24, wherein image information of the different stimulated areas is generated on the basis of the respective detected radiation caused by the stimulation of different stimulated areas and an image of a section of the object surface is generated from this image information.

26. The method according to any of aspects 16 to 25, wherein the stimulation radiation is electromagnetic radiation in the visible and / or infrared range and / or electromagnetic radiation of a frequency is detected which is lower than the frequency of the stimulation radiation.

27. The method according to any one of aspects 16 to 26, wherein fluorescence is excited by the local stimulation and the fluorescence radiation is detected.

28. The method of any one of aspects 16 to 27, wherein the stimulation radiation is particle radiation.

29. Method according to one of the aspects 16 to 28, wherein radiation scattered on the object surface, for example due to the Raman effect, is detected.

30. Use of a system according to any one of aspects 1 to 15 for carrying out a method according to one of the aspects 16 to 29. 31. Use of a system according to one of the aspects 1 to 15 and / or a method according to one of the aspects 16 to 29 for the representation of an object.

Preferred embodiments of the invention will be described in more detail below with reference to the accompanying figures.

Fig. 1 shows schematically the area of local stimulation and the detection area according to an embodiment of the invention;

Fig. 2 shows schematically a system according to an embodiment of the invention;

Fig. 3 shows (a) a measurement object and (b) the representation of this measurement object obtained by a method according to the present invention; and

FIGS. 4 (a) and (b) show another measured object and the corresponding one

Representation by a preferred method according to the invention.

In particular, according to the present invention, an image is generated by means of a system in which the re-emission of electromagnetic waves is used. Images of the distribution of near-surface object properties are obtained by stimulation of the object surface by means of locally introduced modulated electromagnetic radiation, for example by a laser oscillator, and subsequent time-variable change of the local macro-object properties, such as temperature, emissivity, heat flow or local microproperties, such as quantum states of surface molecules. These local property changes manifest themselves in a corresponding electromagnetic emission in a broad frequency spectrum, which is spatially determined spatially by a receiver, for example in the microwave range.

Sources of re-emission of electromagnetic waves may be thermal effects resulting from the heating of the object, and / or fluorescence or scattering effects, such as the Raman effect, that result from excitation of the object material. In general, the frequency of the stimulation radiation differs from the detected radiation. Thus, independent optimization of the stimulation and selection of the detection radiation is possible depending on the effects stimulated by the stimulation. For example, a low operating frequency makes it possible to reduce the costs for the detection device. By a modulated stimulation and a synchronized detection, a high geometric resolution can be achieved, in which only the stimulator is focused. Preferably, the receiver is not focused or not continuously. Also, an increase in dynamic amplification is possible.

1 schematically shows the region A _{Lss &} the local stimulation of an object surface, for example by irradiation of a laser and the larger area Ao of the detection according to an embodiment of the invention. The size of the laser beam-stimulated area A _L aser of the surface is significantly smaller in this embodiment than the area Ao observed by the detection means. Due to the small size of the excited region A _LaS he high geometric resolution can be achieved.

The expected power of the re-radiated signal, in the case of the use of thermal effects assuming blackbody radiation, can be estimated as follows, but this estimate is not suitable for exploiting a fluorescence effect or Raman effect and the dynamic expansion measures shown are not direct either transferable to these are:

A

= BM T + laser AT

A

Here, B is the bandwidth of the receiver, k is the bolt constant, To is the ambient temperature and ΔT is the temperature rise due to the stimulation. The ambient noise power PA, ENV can in turn be estimated using the following formula:

P = KkT The difference between P _A and PA, ENV gives an estimate of the power of the signal re-emitted due to the stimulation.

In order to improve the dynamic range of the system, therefore, on the one hand, the stimulated area Ai_a _S e _{r can be} increased, which leads to a higher signal level, but also to a lower geometric resolution. On the other hand, it is possible to downsize the observed area Ao, which in turn increases the radiated signal, but has the disadvantage that the object to be observed or the detection device has to be moved in order to be able to observe a larger area. Furthermore, to increase the dynamic range, improved system components may also be used, such as an improved mixer in the mmW radiometer, low noise IF amplifiers, or by amplifying the RF signal before conversion.

Fig. 2 schematically shows a system according to an embodiment of the present invention. According to FIG. 2, the local stimulation of the object surface 1 takes place by means of a stimulation device 2, which has a laser 21. The beam generated by the laser device 21 is coded, for example amplitude-modulated, which in the simplest case represents an on-off sequence that can be generated, for example, by an aperture wheel. However, other amplitude or frequency modulations are possible. With the aid of a mirror pivoting device 22, the surface 1 of the object to be examined is scanned in succession, cell by cell, for example from cell ai via cell aι _< to cell a _n . The control of the modulation and the pivoting device 22 is effected by a central control 4, for example a computer. The central controller 4 is thus aware of the location of the instantaneous stimulation on the object surface 1.

By means of a detection unit 3, which according to the embodiment shown in FIG. 2 has an antenna 31 and a receiver 32 connected thereto, the radiation emitted by the entire object surface 1 is detected, for example radiation in the microwave range. This detected radiation also includes the radiation resulting from a change in surface property in the locally stimulated surface portion caused by the stimulation radiation. If, for example, the stimulated surface area is stimulated by the stimulation beam heated, heat radiation is generated in this surface area and this can be detected by the detection device 3. The change in the surface property caused by the stimulation thus manifests itself in a correspondingly altered emission of electromagnetic radiation, which can then be detected by the detection device 3. A corresponding signal is then forwarded by the detection device 3 to the central controller 4. This signal can be processed by the controller 4 and thus on a display unit 5, for example a computer screen, an image of the surface property can be generated by dividing it from the individual picture elements b _k in lines 1 to m and columns 1 to n to the end Image element b _{e is} built.

A pictorial representation thus results according to the invention in that while a particular object surface cell a _{k is} stimulated, the result of the receiver signal is displayed at the equivalent image location b _k , for example on a screen. The stimulation beam is successively swiveled over the entire object surface from cell ai to a _e , for example with a mirror scanner, and at the same time the image is built cell by cell. According to the invention, the receiver recognizes the correct object surface cell at the identifier introduced there by the modulation of the stimulator, according to the principle of a coded cell, while at the same time all other areas of the surface which are not stimulated emit only background noise. For this purpose, the receiver can be equipped with a special filter for the modulation frequency, for example a synchronous detector or an FFT filter, which can be realized by software.

According to the invention, the image generation can be accelerated by simultaneously scanning a plurality of stimulation beams of the same carrier frequency on different, for example parallel tracks and with different modulation frequencies, the receiver simultaneously recognizing the different modulation signals and their statements being displayed in parallel. Furthermore, according to the invention, images of different surface properties can be produced simultaneously by scanning several stimulation beams of different carrier frequencies, which correspond to the sought-after properties, with their own modulation code, and the receiver selectively scans the surface Receives carrier frequencies at the same time, recognizes the modulation and representing the carrier frequencies corresponding statements on one or different screens simultaneously.

It is thus mixed with the stimulation beam from a stimulator, e.g. from a laser, which is also coded, for example, amplitude-modulated, the surface of an object in succession, scanned cell by cell, e.g. by means of a mirror swivel device (scanner), which is supplied by a central control. As a result, the location of the instantaneous stimulation on the object surface is known in the central control. If, at this point, a change in the surface property, e.g. caused by the temperature, which manifests itself in a correspondingly altered emission of electromagnetic radiation, then this radiation can be picked up by a matching receiver, which passes on its signal to the central control. On a presentation unit, e.g. a computer screen, an image of the surface property can then be generated, which is built from the individual picture elements.

The stimulation device 2 and / or the detection device 3 are thus connected to one another via the central control device and are controlled by the latter. This allows a coordinated and coordinated control of stimulation site, coding of the stimulation and / or detection and thus preferably allows an improved representation of the object or the object surface.

Fig. 3 (a) exemplifies a measurement object whose surface is to be imaged by the method according to the present invention. The object is a

Aluminum sheet, which has different sized holes. The surface of the

Aluminum sheet was covered with paper so that the holes can not be visually observed. Fig. 3 (b) shows the image of the aluminum sheet taken with a system according to Fig. 2. The detection signal measured and processed during the stimulation of the individual object areas is color-coded.

In Fig. 3 (a), discolorations of the paper cover caused by the differential heat absorption in this area are clearly observed at the locations of the holes. Is under the paper one Arranged portion of the aluminum sheet, the surface of the aluminum sheet is heated through the paper through the excitation beam and the heat relatively quickly passed into deeper areas of the aluminum sheet. On the other hand, if the area in which the holes are arranged is stimulated, only the paper used for the cover is hit by the laser beam, heat can not be given off to a material arranged underneath. The radiation produced in areas with or without aluminum sheet differs thereby, which also translates into different colors of the corresponding sections.

The receiver device 32 has various filter and synchronization devices for coded detection. The coding, for example, by simply switching on, allows to detect radiation only at the times in which the stimulation takes place. The coordination of the detection with the coded stimulation can also be carried out by the central control itself, for example by the fact that although continuously measured by the detection device 3, this continuous measurement is compared with the coded radiation in the central control, and so the required temporal Resolution takes place.

The difference of the present invention over a conventional BiId- production, consisting of a simultaneously covering the whole area

Lighting (eg by the sun, headlights, etc.) and the simultaneous detection of the light portions reflected from the illumination beam (with a necessarily imaging optics) consists, inter alia, in that this classical method only provides information about the reflectivity of the surface at the illumination frequency (color ) and requires a complex imaging recording optics, which may contains temporally parallel signal processing (e.g., retina of the eye and brain) and thus can be fast.

The method of the present invention, which may also be referred to as STIREEM (Stimulated Re-Emission), on the other hand, works serially and, because of the cooperation between the stimulation location and the pixel location on the presentation unit, does not require imaging optics which may be tracked Optics must be designed and can be costly. Detecting properties of an object near the surface, not just directly on or on but also in areas below the surface, for example to a depth of a few millimeters, allows insights that are not possible with classical methods (only "passive" reflection).

The STIREEM method according to the present invention provides a geometric resolution that is not limited by the frequency of the excitation system or the apparatus of the antenna. Within the scope of an embodiment of the present invention, the "illumination" of the sample can be achieved by stimulating the sample at a relatively high frequency, for example with a laser The receiving device, operating, for example, in the microwave range, detects the signal radiated back from the object surface At a lower frequency, for example, using an optical mirror scanner as shown in Figure 2, the stimulation beam is passed over the sample surface, thereby "activating" the molecules in the region of the laser spot. Depending on the type of molecules and the stimulation frequency, re-emission by the molecules takes place at a certain frequency or in a frequency range. If the receiver is set to this frequency or a frequency from the frequency range, a signal can be measured.

The lateral resolution here depends only on the size of the stimulation area. If a CO ₂ laser with a frequency of approximately 30 THz, corresponding to a wavelength of 10.6 μm, is used for the stimulation, the size of the laser spot is approximately 10 ^-8 m ² Even if the measuring range is several orders of magnitude greater, such as For example, with a measurement range of 10 ^"2 m ² for a receive antenna system operating at a frequency of 30 GHz, corresponding to a wavelength of 1 cm, with an aperture of 0.1 m and a measurement distance of 1 m, a resolution improvement by a factor of 10 ⁶ possible. The assignment of the observed pixel to the image pixel is achieved by a central controller. Here, the scan angle of the stimulation beam at a particular time is used to calculate the image pixel position, which is then associated with the receive signal at that time at the receive frequency. The stimulation time at the pixel on the sample depends on the effect used for the re-emission and the imaging application. To increase the sensitivity, the stimulation beam can be modulated, for example, by an aperture wheel or an optical chopper. The synchronization of a lock-in amplifier with the modulation frequency leads to a received signal that contains only information about the stimulation area and no longer covers the entire detection area. The lock-in technique can provide a good signal-to-noise ratio for the imaging system.

This is illustrated by the following examples:

a) Solid bodies or structures with solid / liquid boundaries that have different locations in the surface heat storage or thermal conductivity can be observed radiometrically with the STIREEM method, even if in conventional observation by reflection on a (uniform) reflective Area no details are recognizable. This may in particular be the case when the observation-facing side of a body has been coated by protective films (e.g., oxides, varnishes, plastic layers). Due to the different heat dissipation from the energy supplied by the stimulation beam into the body background, a different background behind a protective or camouflage film can be detected. This can be particularly important in manufacturing controls, if a part of the protective film has detached itself from the body. Also, delamination of an intermediate layer in multilayer material can be detected and displayed. Furthermore, with the method according to the invention, blind holes can be recognized from the rear side on the visually uniform surface, as described with reference to FIG. 3 above.

b) In a second group of STIREEM applications, not heat effects but frequency shifts on surfaces are exploited. The receiver must then be tuned to the re-emission frequency shifted from the pacing rate (if necessary to several re-emission frequencies). Frequency-shifting effects can be: linear or non-linear (2-photon) fluorescence and the Raman effect with its STOKES and anti-STOKES lines in molecules. Both effects have been used for a long time in the detection of pollutants or substances in the gaseous atmosphere and in Waters (environmental diagnostics) as well as for several years in cell diagnostics with special microscopes in biology and medicine.

In particular, the invention can be used in the observation of "technical" surfaces, such as bio-chips coated with organic material, or in biological / chemical weapons, such as bacteria in envelopes or

Plastic explosive under clothes and similar cases. Finally, the frequency-shifting effects also include the formation of harmonics

(integer multiples) of the stimulation frequency f _s ; the receiver must then be tuned to these harmonic frequencies nf _s (n = 2,3,4 ...).

c) The use of these effects according to the STIREEM principle could be used in the observation and analysis of processes in laser material processing such as e.g. in the semiconductor manufacturing or in the laser material processing (cutting, welding, joining) of importance. In these methods, the position of the laser beam is known at all times, so that information about the process properties can be obtained via a suitable evaluation.

d) The properties of the laser beam (low beam spread over long distances) allow the application of the STIREEM principle to longer distance targets. This type of remote sensing can be used for security-related and military tasks. These include material analysis over long distances, detection of cavities under surfaces as well as all above-mentioned tasks.

The resolving power in the method according to the present invention depends only on the stimulation frequency f _s or the associated wavelength X ₃ ; in a normal atmosphere (as the medium upstream of the target surface) λ _s = C ₀ / f _s with C ₀ = 3-10 ⁸ m / s. One measure of the resolution is the distance Δx from two points that are barely distinguishable from each other. In a commonly used laser for stimulation, it may be assumed that the waist of a Gaussian beam with the waist diameter 2w ₀ on the target surface produces a Δx = 2w ₀ = 2 λs there. In the case of a "green" laser with λs = 500 nm, a resolution of Δx = 1 μm would thus be possible If this value is compared with the diameter of the spot DR ₆ , from which a re-emission receiver picks up signals - and thus could also dissolve locally without STIREEM process - so you can see that in all cases of f _Re "f _s a significant increase in resolution can be reached. In the radiometric example, we choose f _s = 30 THz or λ _s = 10 μm and f _Re = 30 GHz or λ _Re = 1 cm. Even if the microwave receiver were focused on the stimulation area, with a Gaussian beam waist of 2λ _Re = 2 cm, this would result in a resolution of Δx = λ _s = 20 μm and thus an improvement by a factor of 1000.

Another characteristic of the method of the present invention is the fact that the stimulation beam is coded, in the simplest case amplitude-modulated. The scan speed depends on this modulation process. In general, the faster it can be modulated, the faster the beam angle may be changed.

For the "heat-change" effects described above, which are slow, the modulation frequency f ^ should not be higher than, for example, 10 Hz, and the residence times of the stimulation beam on a cell at the target surface are correspondingly long, typically about 10 periods T _M = 1 / f _M , in this example 10 T _M = 1 s. For a target field on the surface of eg 10 columns and 10 lines of object elements ak then a total sampling time of 10-10-1 is calculated s = 100 s The image structure in the rendering unit is just as fast: If the mechanisms of the re-emission are much faster, eg when using the Raman effect or also with the linear fluorescence, the object scan and thus the image composition can also be done The mirror swivel mechanism of the scanner and the signal processing electronics in this case do not give the limits.

As sources for the stimulation process, all generators can be used to produce monochromatic, coherent "light": from lasers in the UV region to FIR / THz lasers, provided they have a sufficient amplitude with sufficient stability over time The stimulation frequency f _s is dependent on the effect which one wishes to use, in particular also on the absorption coefficient at f _s on the respective surface In the experimental investigations with thermal effects previously carried out in the context of the invention, a CO ₂ laser (FIG. at λ = 10 micron wavelength), since in this Wavelength many substances reflect little, ie the stimulation frequency is well absorbed and thus causes heat effects.

The frequency position of the re-emission receiver depends on the effect used. For radiometric reception in the case of heat change effects, the entire microwave range available on the device can be used. In experiments, for example, a 150 GHz receiver with about 1 GHz bandwidth was used.

Another example of the application of the present invention is shown in Figures 4 (a) and 4 (b). Fig. 4 (a) shows a wood block in which Teflon, cardboard and ceramic are embedded in certain places. In the image of the object by the method of the present invention, as shown in Fig. 4 (b), the presence of these different substances within the wood block can be detected.

The method of the present invention is thus based in particular on local coded stimulation, reception preferably at a different wavelength for exploiting thermal or nonthermal near-surface effects, recognition of the image signal from the coding and instantaneous location of the stimulation and high-resolution representation of object features that do not or with conventional imaging methods can not be won so high.

The imaging device thus operates according to the STIREEM principle, ie local stimulation of the object surface with a coded radiation, eg the frequency fs and image generation from the cooperative reception of radiation preferably at a different frequency f _R ee due to re-emission of the stimulated surface Detection of material and geometry differences in the object surface.

The frequency fsa of the stimulating radiation may be in the spectral range between ultraviolet and far-infrared, and the frequency f _{Ree of} the re-emitted radiation may be lower frequency than f _sti dominant broadband in the spectral range of the microwaves. A specific frequency fsti can be selectively absorbed by a part of the surface, thereby stimulating f _Ree as fluorescence radiation, whereby the kind of substance of this surface part becomes recognizable.

From a narrow-band fsti, for example, parts of the surface can be stimulated by the Raman effect f _Rec as STOKES or anti-STOKES lines for re-emission, whereby these parts are recognizable in their material type.

In front of the object, that is to say between the stimulation source and the re-emission receiver and the object surface, there may be a cover layer which is transparent to f _S t and f _{R e} , which hinders normal visual transparency, but nevertheless allows STIREEM imaging.

The stimulating radiation can not be electromagnetic type, but consist of particles with non-zero rest mass (Korpuskeln), the object may be in a vacuum, the re-emitted electromagnetic radiation but also outside the vacuum vessel can be received.

At the same time, several stimulating beams with their own coding (modulation) and / or their own frequency _fst j can scan the surface of the object at different locations and enable a faster image buildup by cooperatively receiving the re-emitting radiation generated simultaneously by the various points.

The frequencies f _R ee of the re-emitted radiation may be higher harmonics (n-≤) of the stimulation frequency fsti.

The device can be used in laser material processing or laser tissue processing in manufacturing technology or medicine.

Claims

claims A system for imaging comprising means for locally stimulating an object surface area by means of coded stimulation radiation and means for cooperatively detecting object radiation emanating from the object, comprising radiation caused by the stimulation. The system of claim 1, wherein the detection means is arranged to detect an object radiation of a frequency different from the frequency of the stimulation radiation. 3. The system of claim 1, wherein the detection device is configured to detect object radiation from a detection area of the object, wherein the area of the local stimulation is less than or equal to the detection area. The system of claim 1, 2 or 3, further comprising a controller adapted to coordinate the detection with the stimulation, wherein the coordination is preferably done using and / or controlling the coding of the stimulation radiation. 5. System according to any one of the preceding claims, wherein the (one) control means is adapted to filter from the detected radiation caused by the stimulation radiation, preferably by using and / or controlling the coding of the stimulation radiation. A system according to any one of the preceding claims, wherein the control means is arranged to generate image information of the stimulated area based on the radiation caused by the stimulation. A system according to any one of the preceding claims, wherein the means for local stimulation is arranged to successively stimulate different, defined areas. 8. The system of claim 1, wherein the control device is designed to generate image information of the different stimulated regions on the basis of the detected stimulation-induced radiation of different defined stimulated regions and to generate an image of an object surface section from this image information. 9. System according to any one of the preceding claims, wherein the Stimulationseinrichturig is adapted to generate amplitude and / or frequency-modulated stimulation beams. 10. System according to any one of the preceding claims, wherein the detection means is adapted to synchronize the detection with the coded stimulation radiation. 11. System according to one of the preceding claims, wherein the stimulation device is designed to generate electromagnetic radiation in the visible and / or infrared range and / or wherein the detection device is adapted to detect electromagnetic radiation of a frequency which is lower than the frequency of stimulating radiation. 12. System according to any one of the preceding claims, wherein the stimulation device is designed to generate particle radiation. 13. System according to any one of claims 6 to 12, wherein the image information comprises material and / or geometry information concerning the stimulated area. 14. System according to any one of the preceding claims, wherein the stimulation means is adapted to generate a fluorescence in the object to be observed, and the detection means is adapted to detect the fluorescence radiation. 15. System according to one of the preceding claims, wherein the detection device is designed to detect scattered radiation on the object surface, for example due to the Raman effect. 16. A method of imaging an object comprising the steps of: locally stimulating a surface area of the object with coded stimulation radiation; cooperatively detecting the object radiation emanating from a detection region of the object, comprising radiation caused by the stimulation; and Representing the surface area on the basis of the detected object radiation. 17. The method of claim 16, wherein object radiation is detected at a frequency different from the frequency of the stimulation radiation. 18. The method of claim 16 or 17, wherein the locally stimulated surface area is less than or equal to the detection area. 19. The method of claim 16, 17 or 18, wherein the detection is coordinated with the stimulation, wherein the coordination is preferably carried out using and / or controlling the coding of the stimulation radiation. 20. The method according to any one of claims 16 to 19, wherein the stimulation radiation is amplitude and / or frequency modulated. 21. The method according to any one of claims 16 to 20, wherein the detection is synchronized with the coded stimulation radiation. 22. The method according to any one of claims 16 to 21, wherein from the detected radiation, the radiation caused by the stimulation is filtered, preferably using and / or controlling the coding of the stimulation radiation. 23. The method according to any one of claims 16 to 22, wherein on the basis of the stimulation caused by the radiation image information of the stimulated area is generated, for displaying the surface area. 24. The method according to any one of claims 16 to 23, wherein successively different, defined surface areas of the object are stimulated. 25. The method according to any one of claims 16 to 24, wherein on the basis of the respectively detected caused by the stimulation radiation of different stimulated areas image information of the different stimulated areas are generated and from this image information, an image of a portion of the object surface is generated. 26. The method according to any one of claims 16 to 25, wherein the stimulation radiation is electromagnetic radiation in the visible and / or infrared range and / or electromagnetic radiation of a frequency is detected, which is lower than the frequency of the stimulation radiation. 27. The method according to any one of claims 16 to 26, wherein fluorescence is excited by the local stimulation and the fluorescence radiation is detected. 28. The method according to any one of claims 16 to 27, wherein the stimulation radiation is particle radiation. 29. The method according to any one of claims 16 to 28, wherein radiation scattered on the object surface, for example due to the Raman effect, is detected. 30. Use of a system according to one of claims 1 to 15 for carrying out a method according to one of claims 16 to 29. 31. Use of a system according to one of claims 1 to 15 and / or a method according to one of claims 16 to 29 for the representation of an object.