DE102009054295A1 - Method for detecting e.g. three-dimensional surface and relief, involves measuring penetration depths of profiles of surface structures at points, such that pressure is delivered to sensor surface that is arranged opposite to profiles - Google Patents

Abstract

The method involves pressing surface structures of a three-dimensional surface into thick, relatively-soft material e.g. foam material (60). Penetration depths of profiles (61) of the surface structures are measured at points in such a manner that pressure transferred by the soft material is delivered to a sensor surface that is arranged opposite to the profiles. The sensor surface is provided with printed circuit boards (64), where characteristics of the soft material are changed during penetration of the surface structure into the soft material. An independent claim is also included for an arrangement for detecting a three-dimensional surface and a relief.

Description

The invention relates to a method for detecting three-dimensional surfaces and reliefs according to the preamble of claim 1.

The detection of a surface relief can be done optically (eg with laser), or by a specific spatial scanning. The systems known in the prior art in this respect are characterized by a high level of equipment complexity, are relatively expensive and / or require a relatively large amount of effort during use and during production.

Optical surface detections are technically elegant but can not be used in all situations and materials without any problems (eg black foam-like materials).

A successive, tactile scan of the surface of a relief is possible, but i. a. but quite expensive. Sampling by means of a measuring plunger (measuring tip) is carried out by first positioning the measuring tip in the x, y direction and then measuring the respective height profile point at each x, y position that can be taken in such a way that the measuring plunger reaches the surface of the object to be measured Object is guided in z-direction. At the first contact of the measuring tip with the surface to be measured, the height of the plunger z. B. registered by a displacement sensor and determines the height of the profile at this point.

If a touch of the surface or its immediate vicinity can be detected with the probe tip, then the surface can be scanned continuously when all x, y points are combined with the measured z values with a computer.

The recognition of a surface contact with the measuring tip can be done in very different ways, for. As with a pressure or force measurement, conductive surfaces also by establishing an electrical connection. (Such techniques are known in principle from force field microscopes (scanning electron microscopes)).

Although such a measurement here is classified as "tactile" or designated, in these cases, the actual measurement is carried out by a direct or indirect path measurement or otherwise.

If the pen is moved continuously from a time zero on, then it is sufficient u. U. to detect the time of surface contact, indirectly determine the movement length and from this determine the given at this time (x, y, z) -point position.

However, such a spatial sampling requires a relatively long time: z. For example, if an area of 50 × 50 cm is to be scanned with a resolution of 1 mm, then 250000 measuring points are to be approached and measured. Be here for each individual measurement z. B. only 0.05 seconds needed, (a relatively small value, because the sensor so first in the x, y-plane and then relatively gently on the surface of the relief to the contact must be lowered) then a measuring time of more to schedule as 3 hours. Measuring times of more than 5 minutes are in the intended applications but already outside an acceptable measurement period.

Will you - z. B. to reduce the measuring time - the tactile sensor process faster, then the necessary amount of technology, the wear, the cost of development and the material requirements of such a system, etc. are greater. With a progressive improvement of the technique required for such a (serial) scan, the effort to be made usually increases very rapidly.

To accelerate the measuring time, it is also possible to use a sensor system with measuring probes operating in parallel, in a sense using a "sensor pin cushion" with resilient pins. Such a pin arrangement (cf. ) divides the total area to be detected into equally sized patches depending on the number of pens, thus providing a faster spatial scan. (In the figures, the same details are often designated with the same identifier and also several times)

shows a possible construction ( 1 ): In a solid plastic or metal block ( 15 ) are holes ( 5 ) at periodic intervals, into the springs ( 2 ) and (top and bottom) end caps ( 7 ) 12 ) are used. The upper end piece ( 7 ) carries the actual measuring pen ( 6 ). Top and bottom end plates ( 3 ) 8th ), in which holes ( 4 ) 9 ) z. B. as breakthroughs for the measuring pins ( 6 ) are located. The lower end piece ( 12 ) has in this example short pins that pass through holes ( 9 ) in the lower end plate ( 8th ) protrude downwards and thus pass the force of the springs downwards.

A surface to be measured is detected much more quickly with such an arrangement (still by tactile needles, but) by the parallel measuring pins: Now, such a pincushion grid arrangement with a 1 cm x, y measuring point distance would be the one mentioned in the example above Relief 50 × 50 cm, scan at the same resolution (1 mm) and the same speed in only 100 s.

However, the effort is also extremely expensive and again can not be easily used on all materials. In addition, this is really useful only for relatively flat profiles, because the pin guide can be problematic from a certain length.

Such a pin construction (cf. and ) is also very sensitive to mechanically coarse influences (shocks), because the needles u. U. can bend. Already the bending of a single needle but u. U. already dramatic consequences, because a z. B. a bent needle into the object to be measured (and that may also be a human) would penetrate.

The price and the sensitivity of such sensors thus significantly complicates the decision to use motor-driven sensor systems. Only a drastically falling price can make such a technology competitive with other (optical) working methods.

In this context, the problem to be solved is to provide a simple method by which a surface or a relief can be detected with a total depth of a few cm. This must be done with a simple, d. H. inexpensive to manufacture and easy to use, also be fast sensor possible. Measurement times of significantly less than 2 minutes were to be maintained, a depth resolution of about 0.3 mm had to be achieved and a "spatial" (x, y) resolution of 2 mm had to be minimally fulfilled.

Furthermore, constructions according to the invention had to be provided for very different applications, above all in the size of the reliefs of up to 1 m length to be registered. However, the target objects to be detected by the sensor were of a more rounded shape, or had surface structures with rounded edges or relatively edgeless structures, but their course should be recorded as accurately as possible, because truly circular curves almost never occurred.

This problem is solved by the characterizing features of claim 1. Thereafter, by means of a, adapted to the maximum profile height, soft flexible support, realized with the spring function equivalents and so wegproportionale forces are generated, spatial profiles sensory detected that detects these power distribution functions by means of flat force pressure sensors become.

Thick foam mats, which can pass on a dependent of the profile height force to the ground, then meet u. Already to a profile detection by these transmitted from the foam mat forces with the surface, pressure or force sensor are detected by sensors. At a (dependent on the respective force sensor) punctual resolution of z. B. 1 mm in the (x, y) direction, and a force or pressure sensitivity of less than 0.05 g, the profile can be detected by the force equivalents caused by the profile often already with sufficient accuracy. Much more accurate measurements are possible.

The sensor thus detects a given relief depth by converting the height profile into a force profile and the measurement of this force profile, however, also requires a specially adapted signal and measured value processing.

From the physical teaching ( ) it is known that pressure ( 2 ) or tension springs against a force acting on them ( 10 ) which upsets these feathers ( 11 ) or stretched, exercise in equilibrium an equal counterforce. So if a spring is the force on a solid wall, z. B. a suspension (in a tension spring) or a support position (in a compression spring ( )), then it exerts on this wall exactly the same, to its deflection s ( 11 ) proportional force F ( 13 ) out. The transmission mechanism for transmitting this force to a sensor point ( 12 ) can be designed differently.

The compressive force values or tensile force values result from the fact that the spring ( 2 ) deforms linearly under the action of a force in accordance with F = F ₀ + α · s (F ₀ as zero value). The force F is (for not too great strains or compression) for the deflection s ( 11 ) directly proportional. The proportionality factor α is the so-called spring constant.

So you can use this to measure the measurement path s ( 11 ) (ie, the deflection length of such a "spring sensor") equivalent to the force F ( 13 ), with which the spring ( 2 ) on a measuring plate (in and not shown).

If you think of the bottom plate (the wall) at any point where a spring of a sensor tip (from a sensor array) is located, a force sensor that measures this force, then you have already solved part of the task.

If one imagines a mechanical spring over each point of a relief to be measured, which is pressed perpendicularly to the relief at the respectively defined x, y position, then this spring acts on a force corresponding to its deformation, which transmits it against the bottom plate , Since each spring is compressed (or pulled apart) at its respective position by the respective relief height given there, the spring experiences this Position a deflection proportional to the relief height. Each such deflection generates proportional to the height of the profile by the proportional force that is passed from the probe tip to the sensor on the bottom plate.

This force can be measured with sufficient spatial resolution with a planar sensor arrangement which contains force pressure sensors in the x, y direction with a defined resolution. In addition, if in the z-direction, the path can be detected by such a path-force conversion with sufficient accuracy, the task is achieved. If the pressure / tension of the spring functions is detected at each (x, y) position, then the surface of the relief as a whole can be determined and / or reconstructed.

The prerequisite is that the spring functions of all springs have a largely linear proportionality factor α over the entire measuring path (which is not always the case), or that the respective characteristic is known (which can almost always be fulfilled).

At each point where there is a spring, the spring force can be detected by z. B. a piezoactive film is placed between cross-row and column lines. Alternatively, other pressure-sensitive (resistive, capacitive or inductive) film materials or plastic or foam material coverings - which may be confused with the displacement-force transducer support for profile detection - are also suitable. The printed circuit board positioned to the spring arrangement must u. U. consist of a thin, flexible, pressure-permeable material. However, this is not a high-quality problem in the state of the art. Pressure-sensitive material applied to the printed circuit board in a punctiform or planar manner (by screen printing) also poses no problem.

For example, the DE 197 50 671 A1 For example, a method of measuring mechanical forces may be used which uses conductive or conductive foams to measure the changing resistance caused by an external force and to deduce the force from it. The construction of two-dimensional arrays with such sensors is also described. Here, the resistance in (located on a bottom plate) electrode cells at the location of the respective electrodes (not described) are measured. It should be noted that compressions can be measured down to the cm range. Not described is the detection of a height relief measurement or its derivation from a "compression measurement".

Such or similar arrangements are suitable in principle for large-area detection of compressive force values and thus for profile detection.

For further processing, the measured values are digitized. Since, due to the necessary high number of lines and columns, a direct digitization of each individual supply line seems too expensive, sequential sampling is to be preferred. Therefore, a multiplexer arrangement is used in order to be able to sample the measured values formed in each crossing point exactly once within a defined time interval (in each case determined by the size of the arrangement).

It is u. It may make sense not to perform the entire sampling with an analog-to-digital converter (ADC), but rather to combine several rows (or columns) via multiplexers into function blocks, each with one analog-to-digital converter. For example, you can blocks with z. B. 16, 32 or 48 columns (or rows) each assign an analog-to-digital converter. Other group sizes are possible.

The circuit in and represent such multiplexer arrangement with 32 rows or columns by way of example. This size represents here the preferred unit of a base unit.

Each row group, which is grouped by the multiplexer arrangement in subgroups of eight rows (or columns), is a higher-level multiplexer unit (generally a single electronic unit with 8 inputs ( 30 ), an output ( 31 ), two supply lines and at least four control lines ( 32 ) or a microprocessor, etc .; see. ). There are four ICs ( 33 ) provided as a multiplexer blocks with a total of 4 × 8 inputs.

The outputs of the multiplexer unit (if at the level of the up to eight multiplexers are present) either fed to another multiplexer or passed directly to a microprocessor, which performs both the sequential control of the multiplexer, as well as the values by means of analog-to-digital converter converts.

Preferred embodiments are for each four multiplexer ICs (see. ) with 8 inputs each for 1, 2 or 3 basic groups, ie for modules with 32, 64, and 96 rows or columns. This planning is adapted to the choice of microprocessors used (not shown), both the control of the multiplexer modules via the control lines ( 32 ), as well as the analog-to-digital converters (ADC). The microprocessor with an ADC and an internal analog 12-channel multiplexer pre-set can handle up to 12 Multiplexer outputs (12 x 8 = 96 lines / columns) process and also take over the control of the multiplexer control by 3 bits for row (column) control and 12 activation lines for the individual ICs.

It can therefore (as preferred base units) integer multiples of 32 rows and 32 columns to form a single construct summarize and thus realize integer multiples of 1024 sensor intersection points.

The achievable at a board production resolution is about 0.1 mm. The here preferred minimum cell resolution of 0.8 mm is therefore just barely feasible even with these simple board manufacturing process.

shows a multiplexer unit for activating individual column lines with group units also combined on a base of 8 lines ( 35 ) (here 4 × 8, so again 32 column assignments).

shows by way of example the structure of individual measuring cells, which consist of repetitive, two-sided comb arrangements ( . ) and is right and left ) and up and down ( ) repeat again and again. Neighboring lines each consist of interlocking, asymmetrical, comb-like structures designed according to the length of the sensor ( ). Each two adjacent row combs ( 52 ) and ( 53 ) together with perpendicular, also adjacent column combs ( 50 ) and ( 51 ), a small central section ( 54 ) in the overlapping structures. The zones ( 55 ) 56 ) 57 ) around these glades ( 54 ) around represents the area of the actual measuring cell. If the cell contacts are to be interpreted on one side, u. U. vias ( )

Basic modules are designed with resolutions of 0.5, 1, 2, 3, 4, 5 mm, corresponding to a size of 32 mm, 64 mm, 128 mm, 256 mm, 784 mm with a circumference of 32, 48, 64, 89, 96 row / column. Modular construction can be used meaningfully.

The measured value acquisition takes place using such structures with a multiplexer arrangement, the and is indicated, so using circuits that control the lines of the lying in the x-direction row (or column) lines and the lying in the y-direction column (or line) lines (circuit of ) and as differential measurements (circuit of ) and to an analogue-to-digital converter, possibly only after a suitable electronic processing (eg analog output ( 31 )).

In the sensor intersection points formed by the tracks of the boards, between which a pressure-sensitive element (eg a piezo film, a pressure-sensitive resistance material, or the like) is introduced, force-proportional stresses or parameters are applied (from the pressure acting on the intersection point). Resistance values or capacitance values) are generated and connected to the measuring arrangement via the multiplexer arrangement.

In a successive in x and then in y-direction scanning of the voltages on the tracks with a measuring time of about 0.1 ms per single measurement (including required for the multiplexer switching duration of about 10 microseconds and an ADC conversion time of approx. 10 μs) for an array with 64 × 64 measuring points, ie with a total of 4096 measuring points, a complete scanning, ie the acquisition of the complete relief, could be carried out in approx. 0.4 s.

Since only 1024 spatial test points are allocated and scanned to an ADC as a result of the block formation, conversion times of less than 0.1 s are achieved with the same technical data as before, which can be reduced to 0.01 s with suitable technical measures.

The most important element of the 3D relief sensor is the force or pressure value acquisition for forces occurring in a certain area. The relevant sensor consists of a structured in rows and columns comb arrangement in the crossing points pressure or force-dependent, piezoactive or resistive elements are. In another embodiment, piezoelectric ceramic materials are used, which are applied to the rigid circuit board for coating.

Other materials can be used. A semiconductor coating at the crossing points would be very effective, because in this way individual sensors can be explicitly positioned at the crossing point. The sampling could then be of a completely different kind in that a row (or column) pair takes over the supply line of a supply voltage and the measured value can be taken directly on the column (row) pairs. Due to the cost, however, this will only be used in special cases.

To stabilize the arrangement, it may be necessary that under the stable board in addition a (hard) base plate, z. B. of metal, stone or ceramic, is attached, which "restrains evenly" this entire arrangement the forces acting.

This sensor unit is referred to as a sensor or as a main module or as a base module.

To provide a complete sensor device for the three-dimensional detection of a relief surface, a displacement force transducer module must be added to the sensor module. Such modules can be designed in very different ways and adapted to a wide variety of applications:
A certain number of compression springs, which are positioned distributed over the respective sensor surface, give in a deformation at each point a wegproportionale force on the floor surface. The way in which the springs or other materials with the same function can be used is manifold:
For the detection of relatively coarse structures (eg in the case of body shapes), spring arrangements in "leading structures" have proven useful. For example honeycomb or tubular plastic mats can be used to insert into each tube or honeycomb a spring with a defined length and a defined spring constant. The mats provided on the one side with the (rigid) base module assembly as surface sensors, which are closed on the other side with a, easily stretchable, soft film allow resolutions in the x, y direction, by the given tube or spring diameter are limited.

Such honeycomb plastic mats are commercially available as bedsores. In every honeycomb you can z. B. stuck a (soft) spring, which are held stable by the respective honeycomb in the x, y-direction and (almost) only in the z-direction of the applied force can follow.

A pressed against the flexible film surface relief or body profile produced at each spring position dependent on the height of the relief spring deformation and thus acting on the side of the surface sensor, proportional to the relief height, mechanical force.

Although the measurement principle is relatively simple in itself, the metrological detection has some pitfalls, which must be solved by adapting to the particular application in each case:
Each spring (each spring element or spring equivalent) in such an arrangement has an initial tension dependent on the structure and already then generates a force acting on the measuring plate, even if no profile has yet been pressed onto the surface. This results in a non-zero value even without a measuring object, ie an offset value that depends on the manufacturing process, the manufacturing tolerance, the temperature, the material, etc., and must be calculated out for each measurement.

This initial value or offset value will be different at each point, that is to say for each spring, and must be recorded as a correction variable (correction image) for the entire measuring arrangement by a start calibration, which is preferably carried out before each measurement, and recorded in an electronic memory.

Since the force of the spring F = α · s applies, also applies to a calibration measurement F ₀ = α · s ₀ and thus results by subtraction (F - F ₀ ) = α · (s - s ₀ ), provided the spring constant α remains constant in the given measuring range. This leads to s = (F - F ₀ ) / α + s ₀ = F / α - F ₀ / α + s ₀ . By means of calibration measurement, F ₀ and s ₀ can therefore be determined and included in the following measurements.

If one knows s, one can also determine with s ₀ = F ₀ / α and s ₁ = F ₁ / α: α = s ₀ / F ₀ , α = s ₁ / F ₁ and α = (s - s ₀ ) / (F - F ₀ ). During the penetration of a profile, all spring parameters can thus be continuously determined and monitored.

To avoid z. B. Temperature effects is determined immediately before each measurement and continuously during the penetration of the profile calibration measurements and even stored as a complete characteristic.

For some applications it is sufficient to use for the calibrations preferably predefined calibration profiles, so that a defined calibration relief depth can be generated over each measuring point of the sensor. The recorded measured values are then included in both an (updated) calibration measurement and in each measurement. Since, by definition, zero is set, F _{0 is} the measured value directly at the start of the measurement and the course of penetration by the known calibration profile is known, all variables can be determined at each x, y position. If the measured values are recorded from the beginning of the profile penetration, then the characteristic curves for each spring position can be determined for all parameters.

So while a profile ( 61 ) ( ) in z. B. a foam ( 60 ) penetrates, can continuously the respective force value with the sensor board ( 64 ), which here on a vibratory plate ( 62 ) and a solid ground ( 63 ), and the pressure exerted by the soft foam mat ( 60 ) is detected and stored within 0.1 s.

Since the beginning of the penetration of the profile ( 61 ) in the foam mat ( 60 ), all values can be recorded continuously and continuously all relevant parameters can be recorded. As the depth of penetration progresses, the profile ( 61 ) a continuously increasing pressure in the material ( 60 ) built up. The force transferred to the ground depends on the depth of penetration of the profile ( 61 ) in the Foam material ( 60 ) and the spring constant (here the equivalent). The lowest point ( 68 ) creates the greatest pressure on the sensor plate ( 64 ). A lower penetration depth ( 69 ) generates a lower pressure. Therefore, the evaluation can conclude from the force data on the respective penetration depth. If during the continuous introduction of the profile, the spring constant α (here its equivalent) has been determined, then it can be concluded that the real penetration depth.

However, the principal errors to be evaluated differ:
Intrusion of the profile ( 61 ) into a soft material ( 60 ) leads to edge effects, which suggest an intrusion even where there is no intrusion ( 70 ), simply because the material as a whole will yield and dodge and thus pass on a pressure component in directions where intrusion does not exist ( 65 ).

The below shows how this can be seen: Firstly, the deeper penetrating profile ( 61 ) Material to the right or left ( 67 ), so that vectorially visible forces ( 66 ) in side zones. In addition, material under the pressure of the profile will be removed ( 67 ) and thus provide there more material, which will lead to a change in the spring constant.

This is where the know-how and the software comes into play when evaluating the data: On the one hand, the immediate effects of pressure transfer, material deviation and change of material constants under the conditions of vectorial and tensorial quantities must be calculated. However, this opens far-reaching correction options.

Since a profile that is already partially in the foam material ( 60 ) has impressed itself continuously during a further penetration movement over the entire already penetrated profile and the force values, thus the information from the sensor plate ( 61 ) should show just this, it can be concluded on changes in the material properties of the foam during penetration and thus very far reaching on the material parameters to be included in the correction calculation.

With properly performed calibration, it is possible to compensate for the error effects to a large extent by calculations with a suitable software. Additional measures can further improve this: in the was already a vibratory pad ( 62 ). With such a vibration, it is possible, the pad ( 64 ) of the foam mat ( 60 ) into sinusoidal vibrations. The total surface thereby periodically shortened and extended penetration depths ( 68 ) 69 ) 70 ), allow the calculation of the currently valid spring constant values.

This also allows extensive correction calculation.

The achievable resolution also depends on: Measuring a height profile (as a 3D function) at defined points in a uniform distance grid represents the spatial scanning of a function in space. Therefore, it must be remembered that each spatially punctual scanning with a pin arrangement, as known from sampled time functions subject to Shannon's sampling theorem.

If scanning positions z. B. from a scan with a stylus tip at a distance of 4 mm, then can be detected without errors in such a tactile scanning only structures, if they have no smaller structures than about 8 mm. For finer structures, sampling errors are provoked by an aliasing effect, which will then falsify the sampled profile. Even with a "high-precision" stylus scanning technique, however, one can not grasp finer, sharp contours.

Since the deformation of any deformable body behaves approximately like a spring, disengaging from the idea of using spring pins is therefore a consistent developmental step: a (softer) application foam has a spring-like behavior over a wide range and thus provides a substantial simplification. It is therefore sufficient, the planar pressure force sensor with an over positioned, thick, depending on the application to select, soft, easily deformable plastic or foam material (sponge, foam rubber, etc.) to occupy. The achievable with the described base sensor in such a case, very fine spatial resolution corresponds to a (quite helpful) spatial oversampling.

Since with a pin construction a minimum distance between the scanning points defined by the pin diameter can not be undershot, this spatial distance determines the spatial scanning rate and thus the properties of an aliasing.

Since even with the (arbitrarily precisely manufactured) pen spring design only a sampling of a spatial function in the distance of the pins is possible, and thus only (spatial frequency) structures can be detected, which correspond to twice the distance of the pen distance, also possibly only roughly crafted or coarse foam structure a u. U. same, often even better scan achieve.

Even if a very precise measurement of a profile is desired at different positions, so a pin construction with a possibly high-precision guidance and force or pressure measurements is not necessarily preferable to such a simple construction.

The know-how required for a measurement makes a significant contribution to error reduction. These parts, represented by algorithms and programs, include the use of calibration plate measurements, which must also be carried out once during production for the respective attachment and for the base unit.

For this purpose, various standard relief, measuring or calibration plates are used in the production and the data obtained, for. B. characteristic curves, the sensor in the form of a readable memory (eg stored in a memory).

The Basisiseichmessung at the time of manufacture of the planar force sensor is also carried out with standard essays (more precisely: with Eichreliefs) once and given to the base unit in a non-volatile memory.

• – Basiseinheit zur Druck/Kraftmessung mit Multiplexereinheit + Mikroprozessor + nichtflüchtigem Speicher
• – Diverse Aufsätze mit und ohne eine Speichereinheit zur Speicherung von Kennlinien (ohne Speichereinheit ist die Eichmessung vom Anwender zuvor jeweils selbst durchzuführen.)
• – geeignete Eichplatten mit definierten Eichprofilen als Zubehör (runde Formen, Pyramiden, Rechtecke, usw., z. B. auch Löcher)
• – Schnittstellenzubehör für die Verbindung einer Basiseinheit zu einer Rechnereinheit und zur Datenübertragung (die auch drahtlos erfolgen kann),
• – Software, die evtl. auf die jeweilige Anforderung angepasst werden muss.

Thus, the following components are available for real use:

• - Basic unit for pressure / force measurement with multiplexer unit + microprocessor + non-volatile memory
• - Various essays with and without a memory unit for the storage of characteristic curves (without memory unit the calibration measurement has to be carried out by the user himself before).
• - suitable calibration plates with defined calibration profiles as accessories (round shapes, pyramids, rectangles, etc., eg also holes)
• - Interface accessories for the connection of a base unit to a computer unit and for data transmission (which can also be wireless),
• - Software that may have to be adapted to the respective requirement.

If recurring, similar profiles are to be measured, an oak specimen, which was once interpreted correctly, can be used as a reference for later to be measured profiles. In this way, one obtains a suitable reference profile from the respective development process and can achieve such cases a resolution <0.1 mm - even with simple techniques - because only the differences to the calibration profile need to be included in the measurement.

Foam rubber inserts, also sponge attachments or plastics made of very soft material can be used in the process and can, for example, well capture a facial contour.

With some small technical and mathematical tricks and know-how, the resolution can be increased in most cases in addition: If, for example, n measurements are carried out with different contact pressure, then z. B. the respective spring constant over each measuring point in each case individually and each newly determined before a measurement. Since a profile to be measured remains the same when penetrating, a force change of F = α · s clearly implies the relationship ∂F / ∂z = ∂s / ∂z · α + ∂α / ∂z · s = α · s [(∂s / ∂z) / s + (∂a / ∂z) / z) (∂F / ∂z) / F = [(∂s / ∂z) / s + (∂α / ∂z) / α)] ∂ (lnF) / ∂z = [∂ (lns) / ∂z) + (∂ (lnα) / ∂z)].

Thus, if measurement sequences are also carried out in the time in which the profile to be measured penetrates ever further into the material and continuously the entire penetration process is detected, then (even non-linear) spring constants can be used (eg for measurements at very high profiles) be recorded and used for a correction measurement.

In addition, this "measurement of a complete penetration sequence" then allows almost completely to capture lateral and evasive effects of the material used and to reckon out errors caused by this profile. However, this also requires a suitably designed computing capacity and a u. U. large store.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19750671 A1 [0030]

Claims (7)

Method for detecting three-dimensional surfaces and reliefs, characterized in that the surface structures to be measured are pressed into thick, relatively soft materials such as foams and the penetration depths of the profile to be measured are detected at each point by the fact that the pressure transferred from these materials to one another takes place opposite the profile located sensor surface. A method according to claim 1, characterized in that the resolution in the xy direction is achieved by the achievable with the sensor surface in these directions resolution, wherein side and displacement effects are computationally corrected by recording the entire penetration during penetration of the profile in the soft material and evaluated. A method according to claim 1, characterized in that the resolution in the z-direction is achieved by the resolution achievable with the force sensors, wherein lateral, displacement and characteristic effects are mathematically corrected by the fact that the entire penetration during penetration of the profile recorded in the soft material and evaluated. Method according to at least one of Claims 1-3, characterized in that the resolution is increased by mathematically correcting pages, displacement effects and characteristic effects by recording and evaluating the entire penetration course when the profile penetrates into the soft material and additionally calibrating the entire arrangement is carried out by calibration profiles with a known penetration. Method according to at least one of claims 1-4, characterized in that a calibration of the entire arrangement takes place in that the zero values are recorded and stored at each position with overlying material but without a profile. Arrangement for detecting three-dimensional surfaces and reliefs, characterized in that the surface structures to be measured are pressed into thick, relatively soft materials such as sponges or foams and the penetration depths of the profile to be measured are detected by the fact that forwarded by these materials at each point pressure a sensor surface located opposite the profile takes place. Arrangement according to claim 6, characterized in that the sensor surfaces consist of boards in which cross over to the first x-directional lines and the second in the y-direction lines and positioned in the crossing points pressure-sensitive materials, so that a row and column by column scanning of the forces occurring at these crossing points is possible.

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