WO2013064395A1

WO2013064395A1 - Device for optically determining the surface geometry of a three-dimensional sample

Info

Publication number: WO2013064395A1
Application number: PCT/EP2012/070965
Authority: WO
Inventors: Miro Taphanel
Original assignee: Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.; Karlsruher Institut für Technologie
Priority date: 2011-11-03
Filing date: 2012-10-23
Publication date: 2013-05-10
Also published as: DE102011117523B3

Abstract

The invention relates to a device for optically determining the surface geometry of a three-dimensional sample, comprising a polychromatic light source, a slit diaphragm arranged in the beam path of the light source, a dispersive and focusing optical assembly arranged in said beam path after the slit diaphragm, said optical assembly being designed and/or arranged in such a way that said optical assembly focuses the image of the slit diaphragm for different wavelengths in the spectrum of the light source onto different lines lying at a distance from one another in space on a predefined surface (focus line surfaces), and an imaging optical assembly, which focuses at least sections of the focus line surface and/or several, preferably all of the focus lines onto one and the same line (scanning line) in space, which line is or can be scanned by a spatially resolving and wavelength resolving detection element, wherein the sample is or can be positioned in space in such a way that the sample intersects with the focus line surface.

Description

Apparatus for optically determining the surface geometry of a three-dimensional sample

The present invention relates to an apparatus for optically determining the surface geometry of a three-dimensional sample, which is also referred to below as a confocal chromatic line triangulation sensor. Confocal systems, confocal chromatic systems and also triangulation sensors for optical 3D surface measurement are already known from the prior art. See, for example, DIN EN ISO 25178-602: 2011-01. The corresponding confocal sensors usually have a punctiform measuring spot. If the three-dimensional structure of a surface of an object or a sample is to be detected, then the surface can be traced out in a grid pattern. Two principles have prevailed here.

In the first principle of a chromatic confocal sensor, a dispersive element focuses the light at different levels depending on the wavelength. Reflected light, which is focused on the surface, has a significantly higher intensity than light that is not focused (see also the aforementioned standard) .A spectrometer then identifies the wavelength with the highest intensity Distance surface

Sensor is possible. See also relevant commercial systems at www.microepsilon. com / displacement-position-sensors / confocal- sensor / index. html or www.precitec-optronik.de.

Disadvantages of these systems are the point-shaped measuring spot and the need for a spectrometer, so that the measuring speed is greatly reduced.

In the second principle (monochromatic confocal sensors, in which by means of a vibrating resonators ^¬ tors, the focus is varied), the resonator performs ei ^¬ ne harmonic vibration which changes the optical path. A detector detects the reflected intensity, which becomes maximum when the beam is focused. Disadvantages here are that the systems are technically very expensive (expensive sensors), also complex, error-prone movable optical elements must be used. See for example www. nanofocus. de / sprint sensor. html? & L = 0th

Another principle for scanning three-dimensional surface geometries is followed by so-called triangulation sensors which work with the aid of a laser point or a laser line. Disadvantages here include that these sensors fail with reflective surfaces. See for example

www. sick. com.

Generally, known systems for scanning a three-dimensional surface thus have the following disadvantages:

• A point sensor does not allow an efficient detection of a surface, as a meandering Ab ^¬ drive the entire surface with a lot of time is necessary.

• For a vertical measuring head arrangement following systems all Wellenlän ^¬ gen overlap in the measurement point, which the adverse use of a spectrometer to determine the wavelength with the highest intensity. However, the necessity of using a spectrometer additionally reduces the measuring speed.

• If several discrete measuring points are selected next to each other at a distance, the illumination of the individual measuring points is additionally superimposed. As a result, the intensity of the focused wavelength is less pronounced than the superimposed wavelengths. The measuring points must therefore not be too close to each other, so they must each have a distance from each other, so that the intensity of the laterally superimposed light is not too strong. See here e.g. the product

MPLS180 of the company Stil S.A. (Www.stilsa.com).

The object of the present invention is therefore to provide a device for optically determining the surface geometry of a three-dimensional sample, with the three-dimensional

Surface geometries of any, e.g. also specular samples reliably, with the highest possible resolution and, compared to the prior art, with increased speed can be determined. In addition, the task is to provide appropriate determination procedures and orders.

This object is achieved by a device according to claim 1, by an arrangement according to claim 11 and by a method according to claim 12.

Advantageous embodiments can be found in each case the dependent claims. Hereinafter, the present invention will first be described in general terms, then with reference to various Ausfüführungsbei- games in detail. The individual features and / or components of the devices or arrangements according to the invention implemented in the individual exemplary embodiments in combination with one another need not be realized exactly in the context of the present invention in the combinations shown in the exemplary embodiments. In particular, individual components shown can also be arranged or aligned differently or even omitted. Also, individual components shown in the exemplary embodiments or the features described within the scope of the exemplary embodiments can each contribute to the improvement of the prior art in each case (ie independently of the other components or features described in the exemplary embodiments). The present invention thus discloses all Liehe combinations of individual features of the various embodiments in the context of the expert appear reasonable.

The present invention enables an optical contactless measurement of the three-dimensional surface geometry of a sample or an object, wherein the surface is detected line by line. Thus, a plurality of individual measurement points in a row next to one another are simultaneously available for scanning, so that a certain width, that is to say an entire line, can be detected with one measurement process at a time. Moving the scanned object (or device relative to this object) then allows scanning of the next line. The present invention thus extends the idea of a confocal chromatic sensor known per se to the effect that not only one measuring point at a time is available, but at this time an entire line (ie a one-dimensional line) with measuring points lying close to each other at the same time can be evaluated.

The present invention initially starts from the confocal chromatic point sensor known per se, in which a polychromatic point source (light source together with a punctiform aperture arranged behind it) is split chromatically by a lens so that different focus points result on the optical axis. If a surface is held in this chromatically split light cone, the result is that exactly one wavelength is focused exactly on this point and all other wavelengths are focused either in front of or behind it. Although all monochromatic wavelengths are superimposed on the surface of the measurement spot (measurement spot), the intensity of the focused wavelength is significantly higher, but due to the superimposition, a spectrometer is required that can measure the wavelength of the intensity maximum.

A device according to the invention for optically determining the surface geometry of a three-dimensional sample now has: a polychromatic light source, a slit diaphragm arranged in the beam path of this light source, a dispersive and focusing optical arrangement arranged in the beam path after the slit diaphragm and designed and / or arranged in this way is that they are the image of the slit diaphragm for different wavelengths in the spectrum of Light source focused on different, on a predefined surface (hereinafter also referred to as focus line area) in the spatial space {hereinafter also by the world coordinate system with the three kartesi- see coordinates x, y and z) spaced lines (hereinafter also referred to as focus lines), and an imaging optical arrangement. The two func ^¬ NEN the dispersion and the focusing can be realized with a single optical element. Likewise, however, it is also possible to use a plurality of optical elements, for example a first element for the dispersion and a second element for the focusing. The imaging optical arrangement forms sections of the focal line area (preferably: the entire focus line area on which the individual wavelengths of the polychromatic spectrum of the light source come to rest) and / or at least several, but preferably all, of the focus lines on one and the same line that follow also referred to as a scan line, focused in space from. The scanning line can then be scanned by a spatially resolving and wavelength-resolving detection element (for example, a line detector comprising individual RGB pixels), ie optically detected.

To measure the sample, it is positioned in space (or inserted into the field of the focus lines) in such a way that the sample (or at least a surface portion of it) intersects the focal line area.

A spatially resolving and wavelength-resolving detection element is understood to mean a detector having different wavelengths in the spectrum can detect the polychromatic light source separately from each other, so the wavelength of each incident on the individual detector pixels light can determine. For example, it may be an RGB line sensor.

In the preferred variant of the present invention, the dispersive and focusing optical arrangement is designed and / or arranged such that the image of the slit diaphragm for several (preferably: all) wavelengths in the spectrum of the light source from one and the same side of the focus line surface on exactly this focal line area If (see also below) the predetermined focus line surface in the preferred case is a plane (focus line plane), then all optical elements of the device according to the invention lying on the radiation incident side (ie the light source, the slit diaphragm and the dispersive and focusing optical arrangement) are in Half space arranged on one side of the focus line plane, the dispersive and focusing optical arrangement then focused from this half space, the individual focus lines spaced apart on the focus line plane .The imaging optical arrangement and the detection element are then preferably on the other side of the focal line plane, that is arranged in the other half-space.

It is preferred here, is that the dispersive and focusing optical arrangement, adapted and / or arranged such that the focus line surface is not more cuts for the different wavelengths, the beam path after the jeweili ^¬ gen focus line. In the device according to the invention then cuts for each wavelength of the spectrum of the polychromatic light source the beam path the predetermined focus line area exactly once. If the focal line surface is a focal line plane, then the optical axis of the incident beam path (optical axis of the elements light source, slit diaphragm and dispersive and focusing optical arrangement) is preferably a finite angle of eg greater than 10 °, preferably greater than 20 °, preferably 30 ° inclined with respect to the focal line plane (the focus lines are thus not formed on the optical axis, but in a tilted plane).

In a further advantageous embodiment, the dispersive and focusing optical arrangement is thus formed and / or arranged such that the

Slit diaphragm for the different wavelengths on a predefined plane in space, the focus line plane, is shown focused. The (optionally a plurality of individual optical elemen ^¬ te comprehensive) dispersive and focusing optical arrangement of a hand, and the imaging optical arrangement, on the other hand (or at least each individual of the respective assembly-forming optical ele- ments) can be realized symmetrically seen relative to the focus line surface. Is the focus line surface has a focus line plane, this means that the dispersive and focusing optical array on one side of this plane and the imaging optical see arrangement on the other side of this plane seen ^¬ as in respect to this plane arranged mirror-symmetrical to each other and / or are aligned.

Like the radiation input side, the beam output side {eg half-space of the image Denden optical arrangement) have a preferably arranged directly in front of the detection element slit. This can, viewed in relation to the focal line area, be arranged symmetrically (in the case of a focal line plane: mirror-symmetrical with respect to this plane) to the slit diaphragm of the polychromatic light source. The gap width of the two slit diaphragms is preferably in the range between 10 μm and 300 μm.

In a particularly preferred embodiment, the dispersive and focusing optical arrangement as the essential optical imaging element on a simultaneously acting as a dispersive and as a focusing element reflective concave grid. Likewise, the imaging optical arrangement may have a reflective, concave grid acting simultaneously as a dispersive and a focusing element. Are both the incident side and the Ausf llsseite the radiation with such

Grid formed and the focus line surface is a plane, the two gratings are preferably arranged mirror-symmetrically to the focus line plane and aligned. Such reflective concave gratings, which act simultaneously as the primary dispersive element and as the primary focusing element, are known to those skilled in the art (see, for example, the so-called reflective concave blazed holographic gratings of Edmund Optics Inc. , 101 East Gloucester Pike, Barrington, NJ 08007-1380 USA).

Alternatively, however, according to the invention, a non-symmetrical arrangement is possible. The imaging optical arrangement then preferably comprises a lens (camera lens) and can be used as a simple line scan. mera (or area camera, in which only a single line is exploited) be formed. The objective then forms the focus line surface and / or the focus lines focused on a scan line lying in the focus line surface itself. In contrast to the above-described symmetrical arrangement of

on the one hand and the imaging optical arrangement on the other hand, in which the scanning line on the side of the imaging optical arrangement, e.g. is positioned in the corresponding half-space laterally of the focus line plane, the imaging optical arrangement can thus be positioned, formed and aligned so that it focuses a focused directly on the focus line surface scan line. In the case of a focal line plane, the imaging optical arrangement as well as the detection element are preferably also positioned in the focal line plane for this purpose.

In another embodiment, the dispersive and focusing optical arrangement may be formed in multiple parts from ^¬, ie it may be a dispersive element

(or a dispersive device) for realizing the dispersive function separately from a focusing element (or focusing optical system of a plurality of elements). The dispersive element of the dispersive and focusing optical arrangement is preferably a transmission grating or a prism (preferably a straight-line prism). In particular, the focusing part of the dispersive and focusing optical arrangement may be a focusing system comprising a plurality of lenses in one

Scheimpflug arrangement has. Accordingly, then

(preferably symmetrically thereto, see above) and the imaging optical arrangement separated from each other a dispersive element (or a dispersive device) and a focusing optical system (which may preferably also be designed in Scheimpflug arrangement) have.

Finally, other training courses are also available

dispersive and focusing arrangement conceivable, provided that they meet the prescribed function to focus terraced illustration of different focal lines ^¬ surface. For example, it is conceivable to form the dispersive and focusing optical arrangement as a lens system with wavelength-dependent refractive index.

Thus, according to the invention, a dispersive (that is, the refractive index changes with wavelength) and / or a diffractive (that is, the light is diffracted differently for different wavelengths) element, e.g. as the chromatic aberration ausnutzendes grid and / or prism can be formed, be arranged. This element (s) must then satisfy the above-mentioned condition of the focal line area, wherein a suitable imaging optics can be added for realizing the desired beam path, preferably incident from a single side on the focal line area.

In a further advantageous embodiment, the location and wavelength-resolution detection element in the beam path of the imaging optical arrangement may comprise a line sensor. This can be positioned at the point of scan line or seen in the beam path directly behind one of the abbilden- at the site of Abtastli ^¬ never positioned further slit diaphragm be arranged the optical arrangement. Likewise, however, the detection element can have an area sensor. In this case, a sensor line of this surface sensor is positioned at the location of the scanning line or, viewed in the beam path, arranged immediately behind a further slit diaphragm of the imaging optical arrangement positioned at this location. In principle, it is also conceivable, as seen in the beam path, to position a spectrometer as a detection element behind a further slit diaphragm positioned at the location of the scanning line with which the scanning line can be scanned in a spatially resolved manner. This, however, at the price of a reduced scanning speed.

The detection element may be, for example, a line sensor in the form of a one-dimensional line array or even an area sensor in the form of a two-dimensional area array of pixels which can detect, separate and detect the different wavelengths of the focus lines. For example, RGB cameras with corresponding pixels can be used for this purpose. It is exploited that monochromatic light can produce a color impression on an RGB sensor. By means of a calibration can be deduced from this color impression on a wavelength.

Not just a single, one-dimensional

To scan the cutting line of the surface of the sample, either the sample relative to the device or vice versa, the device must be moved relative to the sample. For this purpose, an arrangement is provided according to the invention comprising a device according to one of the preceding claims and a drive unit for realizing this relative movement. For example, the sample with a space x, y, z sliding sample holder through the

Focus line surface of the device immovably moved in the space x, y, z. Likewise, however, it is conceivable to provide a sample holder fixed in space, fixing the sample, and to position the device on a displacement table which is movable relative to the sample or to the sample holder. With such an example three-axis displacement table, on which the device is arranged, then the device (or the focus area realized by them in the space) can be moved relative to the sample.

The present invention will now be described with reference to several embodiments. Showing:

Figures la and lb a sketch to the basic

Operation of the present invention.

Figure 2 is a sketch for the incidence of

Radiation at a defined, finite angle to the focal plane {oblique incidence).

FIG. 3 shows a basic embodiment of the present invention with an imaging optical arrangement designed mirror-symmetrically to the dispersive and focusing optical arrangement.

FIG. 4 shows a plan view of an arrangement according to FIG. 3. Figure 5 shows a first concrete embodiment of the construction of a device according to the invention with a symmetry between the dispersive and focusing optical arrangement on the one hand and the imaging optical arrangement on the other. A second concrete embodiment of the present invention with a non-symmetrical structure. a third concrete Ausfüh ^¬ tion example with a separate from a dispersive element formed focusing system in both the dispersive and focusing optical arrangement and in the imaging optical arrangement. a non-inventive, alternative approach.

FIG. 1 a shows a sketch of a basic structure (without the imaging optical arrangement 6, cf. FIG. 3) for carrying out the invention in the Cartesian spatial space x, y, z.

In the beam path 2 of a polychromatic, emitting in the visible range between 350 nm and 750 nm light source 1 (for example, a xenon lamp, a halo ^¬ genlampe, a fluorescent tube or a geeig ^¬ designated broadband LED) is in the y-direction, a gap Aperture 3a (gap width between 10 and 300 μm) is arranged in the beam path 2 of the light source 1 behind the slit diaphragm 3a, which is designed and arranged such that it images the slit diaphragm 3a for the different wavelengths in the visible emission spectrum of the polychromatic light source 1, each focused on different, on a predefined surface, which is here a plane (focus line plane 5 parallel to the yz plane), spaced lines, the focus lines Discretely spaced apart individual wavelengths in the spectrum of the light source Thus, for example, the wavelength λι = 380 nm is focused by the dispersive and focusing optical arrangement on the focal line Ii, the wavelength λ ₂ = 510 nm in the -z direction apart of which on the focus line I2, the wavelength λ ₃ = 600 nm spaced therefrom to the focus line 1 ₃ and the wavelength λ ₄ = 700 nm turn further into

-z direction spaced therefrom to the focus line 1 ₄ . All focal lines Ii 1 to ₄ are parallel to the cleavage direction 3a in the y direction.

FIG. 1b now shows how this spatially variable, focused image of the focus lines 1 of different wavelengths λ on the focal line plane 5 can be used to detect the three-dimensional surface geometry of an arbitrarily shaped object (sample P). Bring to the surface to be scanned of the sample P in the region of the focal line level 5 a, that is so that this surface the focal lines ^¬ plane 5 intersects (see dashed line level 5 in Figure lb), it is, on a defi ny y-coordinate, only light of the source 1 of a single wavelength (at the y-coordinate shown in Figure lb here light of wavelength λ ₃ = 600 nm) focused on the corresponding y-coordinate of the intersection line between the surface of the sample P and the focus line level 5 shown. All other wavelengths, since their focus lines lie above or below the intersection line between the surface of the sample P and the focal line plane 5, are merely diffusely imaged onto the surface of the sample P at the corresponding y coordinate.

If one uses a suitable imaging optical arrangement 6 and one in the beam path after the same

(see Figures 3 to 7) arranged detector, e.g. in the form of a sensor with a pixel line aligned parallel to the y-direction, which can distinguish the individual wavelengths or colors of the visible light of the source 1 from one another, it is possible to obtain color information obtainable by means of this sensor for the above-described y-coordinate

{here in the case shown: λ ₃ = yellow) gain a corresponding height information for this y-coordinate due to the distribution of the focus lines of the different wavelengths or colors along the z-direction. In this case, as seen in the y direction, the entire cutting line (which may indeed vary in terms of its height or z coordinate) between the sample surface and the focal line plane 5 can be recorded simultaneously via the individual pixels of the corresponding detector or detection element. Thus, in the above-described color coding, the entire height information of a single contour line of the sample surface P can be detected simultaneously. On the basis of a relative movement of the sample P on the one hand and the On the other hand, in the direction of optical determination in the x direction, that is to say perpendicular to the focal plane 5, the entire object surface P can be scanned step by step or line by line. Components such as sliding tables, ekthalter, ... to realize the corresponding relative movement are known in the art.

With the structure of the present invention outlined in FIGS. 1a and 1b, the following advantages can be achieved in comparison with the prior art: A simple single-line pixel detector from, for example, RGB camera pixels can be used as the detector or detection element. As a result, a significant increase in the measurement speed can be achieved, since by using such as an RGB camera no more spectrometer must be used. In addition, fewer and less expensive components are needed to perform the 3D surface scan. Since all of the optical imaging elements used (compare, in particular, also below, FIGS. 4 to 7) can be designed and arranged as focusing or sharply imaging optical elements, it is possible to image surface points of the light source 1 that are arbitrarily close to each other (through the gap 3 a), without disturbing superimpositions of the wavelength or height information between adjacent imaging elements (or on the side of the imaging optical arrangement: pixels). There are thus realizable line sensors with prinzi ^¬ piell arbitrarily close measuring points.

Due to the essential technical feature that the chromatically split light 2 in the focal point or in the focus lines 1 is unmixed, there is a fo kissed light spot on a surface of monochromatic light. However, the color impression of monochromatic light can not be changed by the surface color of the sample P. For this very reason, a spectrometer can be dispensed with and the color impression of an RGB camera can be used to directly deduce the wavelength and thus the height information. In addition to the advantage that the individual measurement points, which are arranged in a row, belie- big may lie close to one another, can be (see also subsequent figures 3 to 5) into ^¬ particular by the use of an identical optics for illumination and imaging the Use present invention not only for non-reflective surfaces of the sample P, but also for specular ^¬ specimen surfaces P, since the condition angle of incidence = angle of failure is met. The present invention thus has independence from surface colors of the sample P and allows both diffuse and specular measurements

Surfaces (also of all mixed forms).

In particular, the present invention (see in particular also FIGS. 3 and 5) also has the advantage that the angle condition angle of incidence = angle of reflection is fulfilled in the beam path, so that reflecting surfaces P can also be measured. The device according to the invention is also not designed to be telecentric. Thus, the telecentric constructions inherent disadvantages that less

Light can be used and that the measurement line on the object is less than or equal to the size of the common lens avoided. In addition, of the products contained ^¬ constricting invention avoids the effect even when shifts of the sample in the scanning direction disadvantages that the pixels recorded by a line camera in displacement direction of movement are not square, as soon as the object height changes (with such a displacement of the sample). An improved lateral measurement is possible.

Thus, in the present invention (see also, for example, the structure of Fig. 3) of a polychromatic light source 1, a one-dimensional slit 2 is preset. The slit diaphragm is imaged wavelength-dependent by the dispersive and focusing optical arrangement 4. The optical arrangement 4 is so pronounced that the focus lines 1 are located one above the other in a focal line plane 5 in the z-direction. The demixing is achieved by organizing the focal lines of the individual wavelengths in one plane and the light 2 of the illumination 1 (relative to the optical axis of light source 1, slit 3a and optical arrangement 4) is incident on the plane 5 only from one side. Between the optical axis of the elements 1, 3a and 4 and the plane 5 is thus given a finite angle, which is about 30 ° to 40 ° here. (Of course, other angles between this optical axis and the plane 5 are possible, for example 20 ° to 25 ° or also angles> 45 °.)

This tilt angle is thus chosen so that all light rays incident on the side of the plane 5 of the focus lines 1. Such a tilting has the consequence that in the presence of a surface of a

Probe P demixing of the polychromatic light takes place in the plane 5 of the focus lines. In other words, the focused beam path in the focal line or at the focal point (see arrow in Figure lb) of any wavelength adjacent Überla ^¬ siege, so is monochromatic ago. It is not essential in the context of the present invention that the focus points are organized in one plane. With a suitable design of the dispersive and focusing optical arrangement, it is also conceivable, for example, to focus on the individual focal points or focus lines on a surface section of a sphere or an ellipsoid. Accordingly, then subsequently to be described imaging optical Anord ^¬ voltage must 6 are formed and arranged to image the focus points, or so-lines on the detection element, that only the sharply on the line of intersection between the object upper Smile Friend and the predefined focus line surface, that is Focused imaged wavelength is sharply imaged on the detection element (whereas all non-focused on the corresponding cutting line incident wavelengths then just not be allowed to focus on the detection element). Thus, the requirement of a separation of the wavelengths on the surface P is adhered to, the following condition must be satisfied: When the focal points or lines 1 of the different wavelengths λ, the Fokuslinienflä ^¬ che 5 form in a predefined geometric shape, then it must for these focal lines - or interface apply that any possible, emanating from the source 1 illumination beam in the beam path 2 from the same side (ie, for example, in Figure la from left to the focal plane 5 lying half space) from this focus line surface and never hits after exactly one-time impact again this focus line surface pierces.

Furthermore, the individual focus lines 1 need not be arranged vertically one above the other, for example also an oblique arrangement conceivable.

When using an identical imaging optics on the radiation incidence side and the radiation failure side, ie an identical dispersive and optical arrangement on the one hand and imaging optical arrangement on the other hand, these optics 4, 6 usually symmetric, e.g. mirror symmetry to a focal line plane 5, are arranged.

In order to fulfill in the case of a focus line plane 5 shown in FIG. 1 the condition that all possible light beams in the beam path 2 are incident from one side into the plane 5 of the focus points, the

Tilt angle between the optical axis of the elements 1, 3a and 4 on the one hand and the level 5 on the other ^{¬ be} selected in a range which is limited by the following two conditions (see also Figure 2, identical reference numerals designate identical elements of the device): The minimum tilting is achieved if the angle of the langwel ^¬ ligsten, still provided for imaging wavelength (here, the angle of the wavelength λ ₄₎ relative to the yz plane to zero. A smaller tilt from level 5 would cause this longest wavelength light to pierce level 5 from the other side. The maximum tilt angle is given by the angle of the shortest wave still provided for imaging light (here: λι) to the horizontal or to the xy plane. If an even greater tilt angles can be set, the object P would be illuminated from below, which is no longer with the detection element 8 (see below) according ^¬ weisbar. The usable area for the

Tilt angle results in its concrete size ultimately from the interaction of the Aperture diaphragm (angle of the cone of light in the beam path 2 after the slit diaphragm 3a), the wavelengths intended for imaging {the steepest and flattest beam of light) and the plane 5 of the focal points. If the above-described condition is fulfilled, then the light on the surface P segregates independently of the concrete surface geometry. However, the segregation takes place only at the point at which the plane 5 of the focus lines intersects the surface P. (This statement is strictly speaking only for one

Slit diaphragm with infinitely small slit width in front of the illumination; If a technically meaningful aperture is used as described above, the light again mixes slightly. This leads to a slight error, which is however tolerable or

can be deducted.)

FIG. 3 outlines a basic arrangement for the present invention in accordance with the principle sketched in FIGS. 1 and 2, which is characterized by a mirror-symmetrical arrangement of the focusing-plane 5 of the dispersive and focusing optical arrangement 4 on the one hand and the imaging optical arrangement 6 on the other hand. In this case {and also in the specific embodiments of the invention shown in FIGS. 5 and 7), the individual elements of the optical arrangement 4 on the one hand and the individual elements of the optical arrangement 6 on the other hand are arranged on both sides of the plane 5 in pairs mirror-symmetrically to this plane, designed and aligned unless otherwise stated below. In FIG. 3 (as well as in the following figures), identical reference numerals denote identical components in comparison with FIGS. 1 and 2. As already described with reference to FIGS. 1 and 2, the dispersive and focusing optical arrangement 4 is arranged and aligned on one side {left half space 5a) of the plane of symmetry 5 such that all the wavelengths λ used for imaging are made of this

Half space 5a to the level 5, so the incident rays in the beam path 2 cut this level 5 only once. On the

Half space 5a opposite side of the plane 5, the imaging optical arrangement 6 is now arranged and mirror-symmetrical to the arrangement 4 so formed and aligned that the focus lines 1χ to I4 in the beam path 2 by this imaging arrangement 6 focused on one and the same line, the scan line 7, are shown. The scanning line 7 is in the half space opposite half space 5a mirror-symmetrical {with respect to the plane 5) positioned to the gap opening 3a, so represents the superimposed with respect to the individual wavelength λ image of the gap 3a. At the location of the scan line 7 is

Detection element 8 in the form of a one-dimensional, mirror-symmetrical {with respect to the plane 5) to the gap 3a, so arranged in the y-direction, aligned RGB pixel detector. With this detection element 8, the varying z coordinates of a sample P introduced into the line field Ii to I (not shown here) can thus be detected spatially resolved and resolved in a wavelength-resolved manner along the focal lines or in the y direction.

According to Figure 3 thus a mirrored and identical optics of focal lines focuses the plane 5 to an RGB line sensor 8 7 at the location of the scan line ^¬ Al ternatively thereto but could also be a spatially resolving spectrometers are used as a detection element. 8

The fact that a demixing of the spectrum of On the one hand, no adjacent measuring points are superimposed (the color impression of monochromatic light can not be changed by surface color), so that the device presented is independent of the surface color of the sample P. Furthermore, the wavelength λ of monochromatic light can be determined within certain limits by the RGB sensor 8. Thus, when working with such an RGB sensor, the measurement speed can be significantly increased over a spectrometer. As FIG. 3 shows, a tilted structure of the illumination or radiation input side on the one hand and the imaging or radiation output side on the other hand is characteristic of the present invention.

According to FIG. 4, which shows a structure corresponding to FIG. 3 in plan view (that is, opposite to the z-direction), it is not absolutely necessary to use optically identical optics for the dispersive and focusing optical arrangement 4 on the beam output side, that is to say as the imaging optical arrangement 6 may even be advantageous if, as shown in FIG. 4, an arrangement 6 is used for the optical imaging, which collects more light (in the spatial dimension in the direction of the sensor, ie the y-direction, as far as possible all light should be exploited) , Also, it is not absolutely necessary that, as shown in Figures 1 to 4, the plane 5 of the focus lines is always parallel to the longitudinal direction of the gap 3a and the longitudinal direction of the line sensor 8. For example, a Scheimpflug arrangement could achieve an angle between this plane and this straight line. FIG. 5 now shows a concrete structure of the invention, in which the two optical tasks of the dispersive and focusing arrangement 4, ie the splitting of the light into its components as a function of wavelength (dispersive element) and the focusing of this split light onto the focal line surface 5 (focusing element) , is solved by a single assembly (reflective, concave grating 10). Identical reference symbols again designate identical components as in FIGS. 1 to 4.

The polychromatic light 2 of the source 1 is after the gap 3a first (to allow a compact space of the entire device) led to a first mirror 9a, the beam path 2 on a reflective concave holographic grating. 10a of the Edmund Optics Inc. company. The mirror 9a and the grating 10a taking over both the dispersive and the focusing function thus form the dispersive and focusing optical arrangement 4 in the half space 5a to the left (ie on the radiation input side of the) focus line plane 5.

Like the optical arrangement 4, the imaging optical arrangement 6 of the beam output side in the half space lying on the right of the plane 5 also has a reflective, concave, holographic grating 10b and, in the beam path thereafter, a plane mirror 9b. The two mirrors 9a and 9b are arranged mirror-symmetrically to the plane 5 and aligned and formed identically. The same applies to the two grids 10a and 10b.

The focal lines Ii, 1 ₂ ,... Of the plane 5 are thus focused on the mirror 10b via the mirror 9b Scanned line 7 shown. The beam path on the beam output side is mirror-symmetrical (to plane 5) to the beam path on the incident side.

Moreover, as shown in FIG. 5, outside the intersecting line between the plane 5 and the sample surface P, rays incident on the sample surface P and incident thereon on the grating 10b and the mirror 9b are imaged outside the scanning line 7 by the imaging optical device 6. Relative to the plane 5 mirror-symmetrical to the plane of incidence plane 3a, an imaging gap 3b is arranged on the radiation output side (which is identical to the column 3a), which additionally shields the single-line detector 8 positioned at the location of the scan line 7 against this beam component which is undesirable for the detection. However, this gap 3b is not necessary and can accordingly be omitted. An additional imaging optics in the form of e.g. a lens or the like for imaging the output beam path on the detection element 8 is thus not necessary.

The fact that only the focused wavelengths (in this case: wavelength λ 2 or focus line 1 ₂ ) are again imaged on the detection element 8 is due to the field diaphragm, ie the range that the sensor 8 observes. Although light outside this area is also imaged, it is adjacent to the line detector 8. Thus, light only impinges on the sensor 8 when the corresponding light beam passes through its focal point in the focal plane 5.

Finally, in the color-sensitive line sensor 8, a color measurement takes place: each incident wavelength is generated in the corresponding pixel along the y-axis. Direction a different color impression (at varying along the y-direction height z of the surface P), which uniquely identifies this wavelength and thus the local height. In this context, as a rule, a one-time calibration of the sensor 8 is necessary in order to determine the correlation wavelength / color on the one hand and the assigned height of the sample P in the z-direction on the other hand.

In an alternative embodiment (not ge here ^¬ shows), the two gratings 10a and 10b are so formed that the focal lines 1 do not lie on a plane but on a focus line surface in the form of a sphere portion. The construction results in this case by means of the so-called Rowland circle (compare, for example, also L. Candler, "Modern Interferometer", Higler & Watt, London, 1951.) The difference of a structure, the focus points, as shown in Figure 5, on a Arranging a plane, as well as a structure, which arranges the focus points on a sphere section, lies only in the form of the mirror, on which the grating element of the reflective, concave grating 10 a, 10 b is applied (If this mirror, the focus lines in a Plane is an aberration-corrected mirror.)

The corresponding grating must be calculated for the spectrum of the light source 1. Accordingly, it is of course not only possible to use light sources emitting in the visible range (about 350-750 nm) as the light source 1, but also, for example, as a light source. also in the UV range or in the IR range emitting.

Figure 6 shows a second concrete embodiment of the present invention, which basically How the embodiment shown in Figure 5 is realized, so that only the differences will be described below.

The radiation input side of the variant shown in FIG. 6, ie the elements 1, 3a, 9a and 10a in the incident beam path, is / are identical to the case shown in FIG. 5, aligned and arranged so that the differences only affect the beam output side, So refer to the starting from ^¬ optical arrangement 6 and the detection element 8.

Instead of a symmetrical positioning of the imaging optical arrangement, the optical arrangement 6, which in this case consists of a simple camera lens of an RGB camera, is arranged here in the focal line plane 5 just like the individual line of the RGB camera serving as detection element 8. 6 and 8 are formed in the camera body 13. The viewing direction of the camera 6, 8 is in the plane 5 in -z- direction, ie from above on the individual focus lines 1. Accordingly, the focal length of the camera lens designed as an optical arrangement 6 thus the field of the individual focus lines Ii, l _2f .. ., at least in sections sharply imaged on a single, in the plane 5 and parallel to the y-direction RGB line 8 as a detection element.

The variant shown has the advantage of a simpler construction than the variant of the invention shown in FIG. 5, since it only considers the focal line plane or the now colored surface of the sample P with a commercially available line scan camera. (Areas outside the section line between sample surface P and level 5 are indicated by the forming optical arrangement 6 to other, not used for evaluation, not lying in the plane 5 single lines of the line scan camera.} Prerequisite for the construction shown is that the depth of field of the camera used together with the lens sufficient to the entire desired measurement range, ie a Sufficient section of the plane 5 seen in the z-direction, sharp image. Corresponding ^¬ limiting limitations are not given in the structure shown in Figure 5: The depth of field problem does not occur in the confocal system shown in Figure 5, since only focused beam paths are considered ^¬ tet. In addition, the variant shown in FIG. 5 has the advantage that it works reliably in any, in particular also in the case of reflecting surfaces of the sample P (whereas in the variant shown in FIG. 6, a diffuse light emission in the z-direction is necessary, which is generally the case in the case of specularly reflected surfaces P is not possible).

FIG. 7 shows an arrangement which is fundamentally identical to the arrangement shown in FIG. 3, so that only the differences will be described below.

FIG. 7 shows a further concrete embodiment of the present invention, in which the dispersive and focusing optical arrangement 4 has a plurality of individual optical elements (ie, the dispersion and focusing functions are separate). The same then applies to the symmetrical to the focal plane 5 formed optical arrangement. 6

In the beam path 2 of the light source 1 after the slit diaphragm 3a of the incidence side, the dispersive and focusing arrangement 4 initially has a first collection point. Lens 12a ', through which the polychromatic light 1 is imaged after the slit diaphragm 3a to infinity. This parallel light impinges in the beam path 2 after the converging lens 12a ^' on a dispersive optical element IIa, which is here designed as a transmission grating and that the light decomposed into its spectral components (shown at the wavelengths λι to λ ₃ , the 3 correspond to wavelengths shown). As an alternative to the transmission grating, however, it is also possible to use a prism, in particular a straight-viewing prism (also called a dispersion prism).

Each wavelength λι to λ ₃ thus leaving the Transmissi- onsgitter IIa at a different angle and is incident on a second converging lens 12 '' of the arrangement 4. This second condenser lens 12a ^'' of the arrangement 4 focuses the light of the different wavelengths λ (each of which for the individual wavelengths λι to λ _{3 is} parallel, but in each case incident on the converging lens 12a '' at a different angle) on a virtual plane Ela. At this level Ela, a sharp intermediate image of the gap 3a arises for each wavelength. This plane Ela is used as the focal plane of a Scheimpflug arrangement.

The focus line plane 5 forms the image plane of these known to those skilled in Scheimpflug configuration and the lens main plane of the Scheimpflug is a further, third collecting lens 12a ^'' 'of the assembly 4 is positioned (this plane is indicated by the Bezugszei ^¬ chen E2a). In other words, the planes Ela, E2a and 5 intersecting in the common intersection line P _£ (in which the Scheimpflug condition is fulfilled) form the three planes for which the Scheimpflug condition is fulfilled

Scheimpflug condition will thus be the sharp Plots of the gap (ie, the focus lines of the gap) on the plane Ela imaged on the focal plane 5. For this purpose, the Scheimpflug condition in the line P _{s is} satisfied, ie the intermediate image plane Ela is optically focused by the converging lens 12a '''in the plane E2a on the focus line plane 5. In this dispersive and focusing optical arrangement thus form the three lenses 12a ^' to

12a '' 'a focusing system 12a, which is formed separately from the transmission grating IIa as a dispersive element of the arrangement 4.

With respect to the focal plane 5 mirror symmetrical to the dispersive and focusing optical arrangement 4, but in the half space 5 a of this arrangement opposite half space of the plane 5 and the focusing part of the imaging optical arrangement 6 is formed in Scheimpflug arrangement: along the z direction in focus lens plane Ii, l _2r ... are sharply imaged on the intermediate image plane Elb via the mirror-symmetrically arranged lens 12a ^''' in the main lens plane E2b, which images the image plane of the Scheimpflug device of the imaging optic. see arrangement 6 forms (the focal plane of the

Scheimpflug arrangement on the side of the imaging optical arrangement 6 is the focus line plane 5), the focus line plane 5, the plane E2b and the plane Elb thus also intersect in the

Cutting line forming this Scheimpflug arrangement

Straight line P _s . The intermediate images of the plane Elb are then on the converging lens 12b '', which is arranged mirror-symmetrically with respect to the plane 12 to the lens 12a '' on the optical transmission grating IIb of the An-order 6 (relative to the plane 5 mirror-symmetrical to the transmission grating IIa is arranged) formed by the transmission grating IIb combined to a common parallel beam path and by the (relative to the plane 5) mirror-symmetrically to the lens 12a 'arranged further converging lens 12b' of the assembly 6 in the image-side gap 3b, with respect to the plane 5th is arranged mirror-symmetrically to the gap 3a, lying scanning line 7 focused.

Thus, the symmetrical optical structure 6 takes over the imaging function on the detection element 8. The functions "focus" and "dispersion" therefore need not necessarily be solved by one and the same optical element (on the imaging side, the element IIb forms the dispersive element of the arrangement 6 and the three lenses 12b 'to 12b' '' form the focusing system 12b}.

FIG. 8 does not show the present invention but an alternative procedure: If the surface color of the sample P is known or if it is measured separately, the illumination by the source 1 does not necessarily have to be monochromatically demixed. It can be three light sources in eg blue, red and green (light sources λι-LQ, ...) via a Lin ^¬ se Scheimpflug arrangement (tilted lens 4 ') are mapped. Thus, a rainbow pattern can be projected using, for example, an RGB projector. The colors are laterally projected at an angle so that the color encodes a specific height. Alternatively, no RGB projector can be used, but a prism, in combination with white light. The actual illumination plane is defined blurred, so that the individual wavelengths in the plane 5 ', by the imaging optical assembly 6' with the Detection element 8 'is considered sitting in this plane 5', mix. This mixing results in a rainbow pattern. Thus, a correlation can again be found between the height in the z direction and the measured color. The disadvantage when no monochromatic light or monochromatic separation is used is that the surface color of the sample P falsifies the result. Thus, the surface color must be measured extra or only monochrome surfaces may be measured.

Another disadvantage is that shown in Figure 8 Anord ^¬ voltage that the color impression of the surface slope is dependent because the blended mix colors each at an angle. For example, the color blue at a different angle than the color red. Depending on the diffuse radiation (over the angle) of the surface is (sometimes more, sometimes less) red reflected back to blue and thus changes the measured color impression. This effect becomes most visible when a reflective surface is measured: Assuming that the blue light would have just the condition angle of incidence = angle of reflection, this would not apply to the red light and it would only blue light on the RGB sensor to meet. The measuring method shown in FIG. 8 thus fails with reflecting surfaces.

The present invention (Figures 1 to 5 and 7) can be used for any specular and non-specular objects for their surface measurement. Only with too dark objects, which reflect too little light, the invention can not be used. Due to the expected high speeds are also inline processes of interest, the device erfindungsgeraäße can thus be used in particular in the form of a workstation for complex processes. Particularly with reflective surfaces, for example la ^¬ For short- surfaces, the invention has great advantages in terms of fast and flexible measurement has. A concrete application is, for example, the conductor track or printed circuit board inspection.

Claims

claims

A device for optically determining the Oberflä ^¬ chengeometrie a three-dimensional sample (P) with a polychromatic light source (1), one in the beam path (2) of the light source (1) disposed slit (3a) of this beam path (2) to the slit aperture ( 3a) arranged, dispersive and focusing optical arrangement (4), which is formed and / or arranged so that it the image of the slit (3a) for different wavelengths {λι, ..., λ _η ) in the spectrum of the light source (1) focused on different, on a predefined surface (focus line surface 5) in space (x, y, z) spaced lines (focus lines l _lr ..., l _n ), and an imaging optical assembly (6) at least portions of the focal line area (5) and / or a plurality, preferably all of the focus lines (Ii, ..., l _n ) on one and the same, from a spatially resolving and wavelength-resolving detection element (8) scannable or scanned line ( Scanning line 7) in the space (x, y, z) focused, the sample (P) in the space (x, y, z)

is positionable or positioned to intersect the focus line surface (5). Device according to the preceding claim, characterized in that the dispersive and focusing optical arrangement (4) is designed and / or arranged so that the image of the slit diaphragm (3a) for several, in particular for all of the different wavelengths (λι, ..., _λ η) in the spectrum of the light source (1) of one and the same side (5a) of the focus line surface (5) is focused on this focal lines ^¬ surface (5), wherein the dispersive and focusing optical arrangement, {4} preferably also includes what is formed and / or arranged that for these several, in particular for all these different wavelengths (λι, .. ,, λ _η ) of the

Beam path (2) after the respective focus line (li, ..., l _n ) the focal line surface (5} no longer intersects.

Device according to one of the preceding claims, characterized in that the dispersive and focusing optical arrangement (4) is designed and / or arranged such that it forms the image of the slit diaphragm (3a) for the different wavelengths (λι, ..., λ _η ) focused in the spectrum of the light source (1) on unterschiedli ^¬ che, on a predefined level in the space (x _r y _r z) spaced focus lines (li, ..., l _n ), that is the Fo ^¬ kuslinienfläche (5) is a focus line plane. Device according to one of the preceding claims, that the dispersive and focusing optical Anord ^¬ voltage (4) on the one hand, and the imaging optical arrangement (6) on the other, or at least each individual optical elements (9a, 9b, 10a, 10b, IIa, IIb , 12a, 12b) of these two optical arrangements (4, 6), viewed relative to the Fokuslinienflä ^¬ che (5) symmetrically arranged, ^¬ aligned and / or are formed, preferably arranged mirror-symmetrically to the focal plane, aligned and / or formed.

Device according to one of the preceding claims, characterized in that the imaging optical arrangement (6) with respect to the slit (3a) viewed symmetrically to the focus line surface (5), preferably mirror-symmetrically to the focal line plane, arranged further slit diaphragm (3b).

Device according to one of the preceding claims, characterized in that the dispersive and focussing optical arrangement (4) has a reflecting, concave grating (10a) acting simultaneously as a dispersive and a focusing element and / or that the imaging optical arrangement (6) comprises a simultaneously dispersives and as focusing rendes element acting reflective, concave grating (10b), wherein in the preferred case of the presence of both gratings (10a, 10b), these are preferably symmet ^¬ driven to the focus line surface (5), are preferably mirror-symmetrical to the focal line plane, positioned and oriented.

Device according to one of the preceding ^¬ claims that preferably a lens comprising or designed as such a lens imaging optical arrangement (6) the portions of the Fokusli ^¬ nienfläche (5} / the focus line surface (5) and / or more / all focus lines

(Ii, ..., l _n ) is focused on a focus line surface (5), preferably on the focus line plane, lying scan line (7), wherein at the location of the scan line (7) preferably a line sensor or a line of a surface sensor as a detection element ( 8} is positioned.

Device according to one of the preceding claims, characterized in that the dispersive and focusing optical arrangement (4) is a dispersive element (IIa), preferably a transmission grating or a prism, preferably a straight-viewing prism, and in the beam ^path (2) behind the dispersive element ( ^II ). IIa) a focusing system (12a) comprising at least one convergent lens (12a ', 12a ^'' , 12a'''), in particular a lens system in Scheimpflug arrangement, and / or that the imaging optical arrangement (6) is a dispersive element (IIb), preferably a transmission grating or a prism, preferably a straight-viewing prism, and in the beam path (2) behind the dispersive element (IIb ) at least one converging lens

(12b ', 12b' ', 12b' '') comprising focusing system (12b), in particular a lens system in Scheimpflug arrangement, wherein the two optical arrangements (4, 6) are preferably formed according to claim 4.

Device according to one of the preceding claims, characterized in that the dispersive and focusing optical arrangement (4) is designed as a lens system with wavelength-dependent refractive index.

Device according to one of the preceding claims, characterized in that the location and wavelength-resolution detection element (8)

A line sensor which is positioned at the location of the scanning line (7) or which is arranged in the beam path (2) directly behind a further slit diaphragm (3b) of the imaging optical arrangement (6) positioned at this location, Having an area sensor, wherein a sensor row of this area sensor is positioned at the location of the scanning line (7) or viewed in the beam path (2) immediately behind a further slit diaphragm (3b) of the imaging optical arrangement (6) positioned at this location, or

• a preferred seen in the beam path (2)

has a spectrometer arranged behind a further slit diaphragm (3b) positioned at the location of the scanning line (7), with which the scanning line (7) can be scanned in a spatially resolved manner, and / or in that the position-sensitive and wavelength-resolving detection element (8) comprises a line sensor in the form of a one-dimensional row array or an area sensor in the form of a two-dimensional area arrays of the different wavelengths (λι, ..., λ _η ) different pixels, in particular RGB camera pixels comprises.

Arrangement comprising a device according to one of the preceding claims and a drive unit for realizing a relative movement between the sample (P) on the one hand and the device, in particular its focal line surface (5), on the other hand.

Method for optically determining the surface geometry of a three-dimensional sample (P), which is preferably carried out with a device according to one of the preceding claims, wherein in the beam path (2) a

polychromatic light source (1) a slit (3a) is arranged, wherein in the beam path (2) after the slit (3a) a dispersive and focusing optical assembly (4) is positioned, which is formed and / or arranged so that they the image the slit diaphragm (3a) for different wavelengths (λι, ..., λ _η ) in the spectrum of the light source (1) to different, on a predefined surface (focus line surface 5) in the space (x, y, z) spaced lines ( Focus lines li, ..., l _n ) focused, wherein in the beam path (2) after the dispersive and focusing optical arrangement (4) an imaging optical arrangement (6) is positioned so that it at least portions of the focal line surface (5} and / or several, preferably all, of the focus lines (li, ..., l _n ) are focused on one and the same line (scan line 7) scanned or scanned by a spatially resolving and wavelength-resolving detection element (8) in space (x, y, z) and wherein the sample (P) is positioned in the space (x, y, z) such that at least a portion of the sample surface intersects the focus line surface (5).