WO2014057352A1

WO2014057352A1 - Measuring sensor and method for measuring a surface

Info

Publication number: WO2014057352A1
Application number: PCT/IB2013/002621
Authority: WO
Inventors: Bruno Knobel; Charles Findeisen
Original assignee: Naviswiss Ag
Priority date: 2012-10-08
Filing date: 2013-10-08
Publication date: 2014-04-17
Also published as: DE112013004917A5

Abstract

The invention relates to a measuring sensor for measuring a surface, comprising a sensor body and a fixing device for fixing the sensor body to a finger, and to a method for measuring a surface, wherein the sensor body is fixed to the finger such that the finger can touch the surface together with the sensor body.

Description

Probe and method for measuring a surface

The invention relates to a probe for measuring a surface with a probe body and a fastening device for fastening the probe body to a finger and a method for measuring a surface.

[2] Mobile 3D measuring technology plays a major role in industrial metrology. For example, the shape of any objects such as bent tubes or car molds is measured with buttons. During the measurement, the measuring person guides the probe of the probe, for example, along a trajectory on the surface of the material to be measured. The surface of the material to be measured can also be touched point by point.

Such measuring systems are also used to position and spatial orientation of objects, such as pairs of flanges to detect absolute or relative to each other. Also in surgery, surfaces are scanned with rigid styli whose position and orientation are measured with surgical navigation systems.

[4] All these measuring systems have in common that the measuring person must operate the button in such a way that the probe tip has conclusive contact with the surface of the measuring material for the measurements. There is always the possibility that the probe tip slips sideways away from the material being measured or slips from the desired measuring point. This can lead to measurement errors. This problem can be alleviated in part by the measuring person operating, for example, the push-button with one hand and with the other hand pressing the push-button tip onto the surface of the measured object.

[5] Measurements are problematic at locations such as expanding cavities, which are neither directly accessible visually nor with the probe. For such measurements, the button must be preformed accordingly. Also in this case, the stylus tip can slide off the target measurement point. US Pat. No. 7,742,802 B2, US patent application 2005/0199250 A1 and patent application DE 10 2005 010 335 A1 describe systems, devices and methods for determining the position of a point on an object. In this case, a stylus tip, with which the desired position is felt on the object, mounted with a structure on a finger of the measuring person. A surgical navigation system tracks a hand-mounted sensor that is connected in a defined manner to a hand-held positioner. The task of the positioning device is to determine the position of the probe tip relative to the sensor. The structure on the finger is movable with respect to the sensor. The probe tip can trigger a targeted measurement and it is able to communicate with the positioning device. The entire arrangement allows the determination of the global position of the probe tip in the coordinate system of the navigation system.

[7] The invention is based on the object to facilitate the palpation of the relevant points of an object surface.

This is achieved with a system and a method in which a probe interacts with areas that allows the simultaneous haptic perception of both the product and a part of the probe tip.

In terms of device, this is achieved with a generic probe in which the probe body is attached to the finger so that the finger can touch the surface next to the probe body.

[10] Haptic perception is understood to mean the active feeling of size, contours, surface texture, weight, etc. of an object through integration of the senses of the skin and sensitivity to depth. In particular, the terminal tactile ball of a fingertip, i. the fingertip, on the inside of each finger equipped with many receptors that allow the scanning of a surface. The totality of haptic perceptions allows the brain to localize and evaluate, for example, mechanical stimuli. Changing stimuli, such as those produced by scanning a surface, are perceived to be particularly haptic.

[1 1] While the fingertip can feel a surface with the many nerve endings, a stylus only measures the position of a point or successively many points. The device according to the invention makes it possible to combine the two principles by making it possible, during the measurement of a point of the fingertip, to feel the surface around or around the point.

[12] It is advantageous if the probe body is a ball or a tip. The tip may also protrude from a spherical body or it may be formed as a cone or pyramid. Depending on the application, different probe body shapes are advantageous.

In particular, to track edges or structures on surfaces easier, it is proposed that the probe body has a curved guide. Such a curved guide may be a short curved piece of wire or a curved surface. The bend may describe a concave arc or the curved guide may also be roof-shaped or formed as an angled surface.

[14] In order to achieve a high measuring precision, it is advantageous that the probe body is particularly small. On the other hand, the probe body must also be rigidly connectable to the fastening device, and the probe body should make it possible to be pressed into the fingertip preferably in such a way that the area of the fingertip surrounding the probe body can touch the surface which also contacts the probe body. It has been found that it is advantageous if the probe is between 1 and 10 mm and preferably between 2 and 5 mm long. This length is the diameter of a spherical probe and the maximum extension between two surface points of the body in another Tastkörperform.

[15] A simple embodiment provides that the fastening device has a finger ring. Such a ring can be easily slipped over the finger and thus allows attachment of the probe body and the entire probe on the finger. The ring can be pushed over the fingertip between the first and second limb of a finger or surround the finger syringe in the area of the fingertip.

[16] The fastening device becomes individually adaptable if it has a plastically deformable sleeve. Such a sleeve can also be shaped like a ring. The plastic deformability makes it possible to adapt the sleeve to a special finger shape and to attach it. In this case, the material of the sleeve is to be chosen so firmly that it is on the one hand for adaptation plastically deformable and on the other hand during use of the fastening device, the sleeve is so rigid that the probe body is firmly connected to the finger. For this, the sleeve may also be in cross-section U-shaped or O-shaped with an open slot, so that the sleeve - preferably elastic - is easily bendable to pull it over the finger.

[17] So that the Tastballen can come into simultaneous contact with the probe body and with the surface to be measured, it is proposed that the fastening device comprises a wire which holds the probe body. A thin, stiff wire or several thin stiff pieces of wire make it possible on the one hand to keep the probe safely and on the other hand, not to hinder the scanning of the surface with the finger. The wire should have a cross section such as a tube cross-section or a T-shape to allow high stability. It can also be used highly stable plastics.

A simple embodiment provides that the probe body is rigidly connected to a measuring arm. About the measuring arm, the position of the probe can be determined without a camera system is necessary.

[19] Alternatively or cumulatively, it is provided that the probe has a camera system that is aligned with the marker area. This increases the mobility of the probe.

[0001] In terms of the method, the object underlying the invention is achieved by a method for measuring a surface, in which a feeler body is moved with a finger on a surface in such a way that the finger touches the surface while the feeler body touches the surface.

It is advantageous if the position of the probe is determined and stored. Individual points on the surface of an object can be measured. In particular for the measurement of roughnesses or shapes, it is proposed that the position of the feeler be continuously measured. [22] For measuring it is provided that the position of the probe is measured in the room. That is, there is a space coordinate system in relation to which the position of the probe is set in the measurement.

[23] Alternatively or cumulatively, it is proposed that the position be measured relative to the position of the surface. While several measurement points define the position of the surface, individual points serve to determine the deviation from a surface shape. It is advantageous if the sol surface of an object to be measured is known and the method is used to determine a deviation from the surface of the sol. In this example, bumps in a piece of pipe can be determined or surveys on a bone, which differ from the usual bone shape. During the measurement, a surface shape can first be determined by interpolating between the locations of the points by means of a multiplicity of points in order to determine a basic shape. A more accurate measurement can subsequently determine a deviation from this basic shape, such as, for example, surface irregularities or roughnesses or even macroscopic elevations on a previously determined desired shape.

[24] In order for the user, i. If the measuring person is able to activate a camera system or parts of the measuring system or the entire measuring system on the basis of a special haptic perception, it is proposed that a measuring system be activated after the finger has touched the surface. This is preferably realized by a switch or voice control. Depending on the haptic perception, the measuring system can thus be switched on or off.

[25] When talking about a finger or a fingertip, this refers either to the area of the skin of the finger or, for example, when a glove is worn, to the corresponding area on the glove.

[26] When it comes to determining the position of the probe, this is achieved either via a measuring arm or via a camera system.

[27] A measuring arm is fixed with one end firmly in the space and thereby can by the determination of the movement of the measuring arm on the position of the other end of the arm getting closed. Alternatively, the probe can also have a probe body and optical recognition features for the position and orientation determination.

[28] The invention will now be described by way of example without limiting the general inventive concept by means of exemplary embodiments with reference to the drawings, which are expressly referred to in the rest with respect to the disclosure of all details of the invention not explained in detail. Show it:

FIG. 1 schematically shows the device with optical camera system, the probe with an area for haptic perception and the material to be measured,

FIG. 2 schematically shows a possible embodiment of the probe with an area for the haptic perception,

Figure 3 schematically another possible embodiment of the probe with a

Area for haptic perception,

FIG. 4 schematically shows two possible embodiments of the scanning range of the device,

Figure 5 schematically shows two possible designs for guides in the sensing range of

Contraption,

FIG. 6 shows schematically the cross-section of the sensing area of the device with a ball as a rigid probe body,

FIG. 7 schematically shows the longitudinal section of the scanning region of the device with a ball as a rigid probe body,

FIG. 8 schematically shows the cross-section of the sensing area of the device with a

Combination of a hemisphere and a cone as a rigid probe body,

FIG. 9 schematically shows the device with optical camera system, the probe with a further form of the rigid probe body, the marker region and the probe body,

10 shows schematically the device with optical camera system, the probe with rigid probe body, marker region and probe body and another marker with pattern rigidly connected to the object,

11 shows schematically the device with optical camera system, the probe with a rigid probe body, marker region and probe body and another, rigidly connected to the table marker with pattern,

Figure 12 schematically shows the device with the object rigidly connected optical

Camera system, the probe with a rigid probe body, marker area and probe body,

13 shows schematically the device with a rigidly connected to the probe optical camera system, the probe with a rigid stylus body, marker region and probe and a rigidly connected to the object marker with pattern and

Figure 14 schematically a suitable device for the measurement of hard to reach places of a workpiece.

[29] Figure 1 shows schematically the arrangement of all components of a device based on optical methods. On the measuring table 100 is the measured material 200 such as an engine block or a bent pipe. The measuring person 300 holds a probe 501 with a rigid shield 500, on which optically visible markings are mounted. The spatial positions and spatial orientations of these markings are measured by at least one camera 400 with image sensor and the viewing area 410 using methods known in the art. For example, the cameras can be fixed to a wall, ceiling, rack or tripod with a 440 magnet, screw, bayonet or click-lock. The orientation of the cameras to each other is calibrated by means of a reference body 600 with optical markings. Appropriate calibration methods are known in the art.

[30] Details of the probe are shown schematically in FIG. The rigid shield 500 is connected by means of the rigid connection 532 with the ring 531, to which the rigid ball 530 is attached. The probe 501 is by means of the ring 531 from the finger 311 of the hand 310 of Held measuring person. The measuring person guides the ball 531 of the probe 501 along the surface of the object 200 such that the touch ball 312 of the fingertip 311 contacts both the surface of the object 200 and the ball 530.

[31] The marks 510 on the shield can be passive. They can also be actively lit, such as with LED or OLED.

With methods known in the art, spatial position and spatial orientation of the markings 510 measured by the cameras are determined on the shield 500 in the camera coordinate system. Since the shield 500 is connected to the rigid ball 530 via the rigid connection 532 and the ring 531, the orientation and orientation of the ball 530 for each measurement is also known.

The sphere can be made of a quartz glass, of steel or of any other suitable material, which can clearly detect the surface of the material to be measured. For example, the ball has a diameter of 2 to 5 millimeters. This makes it possible for the measuring person to simultaneously perceive both the ball 530 and the surface of the object 200 haptically. The geometry of the material to be measured 200 can thus be detected by the person measuring leads her finger with the probe gently over the material to be measured in a pleasant speed, for example 50 to 150 mm / s. At the same time, the contact line or the contact point is detected by the camera system at any time via the ball contact with the material to be measured. Depending on requirements, other fingers such as the thumb 313 are used to scan the material 200 to be measured and guide the ball 530.

[34] Using methods known in the art, the sphere geometry is taken into account when determining the surface geometry of the material to be measured.

[35] The scanning of the material to be measured makes it possible that a visual contact between the measuring person 300 and the sample 200 is not required during the measurement. Sampling is more intuitive thanks to tactile perception. For example, during the scan, the subject may view a monitor with the analyzed measurement data. For example, the measuring person can judge the quality of the measurement data himself and decide whether certain object locations need to be measured again. [36] The scanning preferably produces not only single spot measurements but rather areas of pads. It is the task of the analysis algorithm to calculate the surface of the article 200 from the measured points of contact. If the ball 530 always remains in contact with the object 200, a continuous measurement can also be made which detects lines in the space lying on the surface of the object.

FIG. 3 schematically shows a further device with the probe 1, which consists of the probe body 2, the marker region 3 and the probe body 13. The probe body 2 is attached by means of the fastening device 5 to a finger 7 on the hand 6 of the measuring person. The attachment between the wire 2 of the fastening device 5 and the finger 7 need not be rigid and should allow only a movement of the probe body 13. With the probe 1, the surface 9 of an object part 8 is measured. The touch area 4 is located in the probe body 13. The probe body 13 may be, for example, a ball or a tip.

[38] The rigid marker region 3 and the rigid probe body 13 are rigidly connected to the rigid probe body 2. Thus, the probe 1 is a substantially rigid object.

The probe 1 is attached to a hand 6, that firstly the probe body 2 is guided along a finger 7, secondly the Tastballen 10 of the fingertip of this finger is at the touch area 4 and third, the marker area 3 at the back of the hand, wrist or forearm of the measuring person. The finger 7 may be, for example, the index finger, the middle finger or otherwise a finger.

[40] The measuring person can wear gloves during the measurement. This must be taken into account in the design of the touch area. For example, the surgeon must wear gloves in the operating room. Or the measuring person in the production line must protect himself with gloves against sharp edges of the object to be measured or against oily surfaces.

[41] The fastening device 5 may comprise an elastic tube. The attachment may also have an easily deformable, plastically deformable sleeve, the for attaching the probe 1 on the finger can be easily compressed and then connects the sleeve firmly with the finger. Other options for attachment can be easily handled clamps or straps. The attachment should be easy to remove after use. The attachment of the probe to the finger is temporary. The attachment should be comfortable for the measuring person. The attachment ensures that the probe 1 does not slip off the finger 7.

[42] The optically contrasting pattern 11 is applied to the surface of the marker region 3. For example, this is realized by means of laser engraving. The surface of the marker region to which the pattern is applied is preferably flat. Preferably, the pattern has no gloss on the surface of the marker region, i. the surface is dull. The marker region 3 can consist of one or more such flat surfaces on which the high-contrast patterns 11 are applied.

[43] Each pattern 11 on a flat area of the marker area contains areas at least for the pattern identification and for the determination of the position and orientation of the pattern in the coordinate system of the camera system. Other pattern areas may include redundancy to account for effects of, for example, a soiled pattern in determining identification, location, and orientation.

[44] Each pattern is assigned its own coordinate system.

[45] Two or more patterns 11 may be arranged on the marker area 3 such that at least one pattern is measurable by the camera system 12.

[46] The camera system measures the optically contrasting patterns 1 1 and uses them to determine the position and orientation of the pattern coordinate system with respect to the coordinate system of the camera system.

[47] The position and orientation of the probe in the coordinate system with respect to the pattern on the marker region is known either through the manufacturing process or through calibration. This calibration is state of the art. Thus, the position and orientation of the probe in the coordinate system of the camera system is known from the measured position and orientation of the pattern. [48] In the arrangement in Figure 3, the camera system and the object must not be moved during the measurement.

The objects 8 are in surgery, for example, the surfaces of acetabular cups, in particular the edge of the acetabulum, other joints such as knee, ankle, shoulder joint or generally bone or hard structures. In industrial productions, for example, the objects 8 may be any molded parts or bearings in gears.

[50] The touch area 4 is designed such that, when the surface 9 of the touchpad 10 of the fingertip is measured in the touch area 4 of the probe 1, it simultaneously comes into contact with the object surface 9 and with the feeler body 13. For example, by means of the haptic perception, the measuring person ensures that the probe body 13 is located on the object surface 9 at the desired position and / or that the probe body 13 touches the object surface 9.

[51] Due to the haptic perception by means of the finger 7, the measuring person can move the probe body 13 to the desired surface position. It may also be helpful to use the other fingers that are not connected to the probe for haptic perception.

Due to the haptic perception, the measuring person can activate the camera system, parts of the measuring system or the entire measuring system by means of activation modules such as switches or voice control for the measurement.

[53] The shape and size of the probe body 13 depend, for example, on the haptic perception of the person measuring with gloves or on the object surface 9. For example, too small balls can reduce their haptic perception with respect to the object surface. Too large balls cover too much of the touch area and can also reduce haptic perception.

[54] In Figures 4a and 4b, the scanning range is shown schematically. The objects directly touched by the touch ball of the fingertip are, for example, the probe body 13, parts of the probe body 14, 15 and object surface parts 16 of the object surface 9. [55] FIGS. 5a and 5b schematically show guide aids for the probe. The touch area around the rigid feeler body 13 can be configured with a rigid guide aid 20 (FIG. 5a). This substantially facilitates the guidance of the feeler body 13, for example, along the edge of the object surface 9. The guide aid 20 may be attached to the stylus body 2.

[56] The tactile area around the rigid probe body 13 can be configured with a guide aid 21 made of flexible and / or plastically deformable material (FIG. 5b). This substantially facilitates the guidance of the feeler body 13 along the object surface 9. The shape of this guide aid substantially supports the displacement of the feeler body along the object surface. In the case of an object edge, the guidance aid, for example in the form of a saddle, can be helpful.

[57] For a better illustration of these guide aids the Tastballen 10 is shown with the fingernail 50 in Figures 5a and 5b.

FIG. 6 shows schematically the cross-section of the sensing area 4 of the device with a ball 13 as a probe body. The touchpad 10 of the fingertip touches the ball 13 and at the points 24, the object surface 9 of the object 8. For a better illustration of the cross section of the fingernail 50 is shown in the figure 6.

FIG. 7 shows schematically the longitudinal section of the scanning region 4 of the device with a ball 13 on the rigid stylus body 2. The stylet 10 of the fingertip touches the ball 13 and, at the points 25, the object surface 9 of the object 8.

[60] FIG. 8 shows schematically the cross-section of the sensing area of the device with a hemisphere 26 and a cone 27 as a probe body. The tactile ball 10 of the fingertip feels the hemisphere 26 and the object surface 9, while the tip of the cone 27 slides over the object surface 9.

[61] For surgical purposes, the attachment and probe must be sterile. For example, the probe consists of materials suitable for multiple sterilization in an autoclave without compromising the probe geometry or the optical properties of the sample. [62] The probe can be completely passive. It can be designed as a lightweight measuring instrument. For example, its weight is less than 50g.

[63] Measuring probes can be manufactured with different patterns, marker areas, stylus body lengths, stylus configurations or different materials. The probe can be made of a piece of metal or plastic. The patterns are applied to the marker region, for example by means of laser engraving.

[64] The surface to be scanned must not be visible to the measuring person. Thanks to the haptic perception in the touch area, the positioning of the probe on the object is made much easier. This ensures, for example, that the probe touches the object surface safely. By moving the scanning area along the object surface, the measuring person can safely aim for the desired positioning of the probe body.

[65] The camera system can be part of a tracking system or a navigation system. It can be used stationary or mobile, be light and portable, have its own power supply and / or communicate wirelessly.

[66] The camera system can carry out the measurements continuously. As soon as samples are measured in the measuring range of the camera system, their position and orientation are transmitted to the user software. This calculates the positions and orientations of the probe in the camera coordinate system. Thus, the contact points of the probe body are calculated on the object surface with methods known in the art.

[67] The camera system measures the optically contrasting patterns of the probe and thus the position and orientation of the probe. Thanks to the haptic perception, the measuring person assesses the position of the probe with respect to the object surface. In general, only measurement data relating to the object surface should be acquired with the camera system. Due to the haptic perception, the measuring person can activate the camera system as needed for measurement. The activation can be carried out, for example, by a foot switch or by a switch or push button integrated in the camera system. The activation of the camera system triggers a single measurement, which indicates the position and orientation of the pattern and the tactile results. Activation of the camera system may, if necessary, trigger a series of individual measurements. In this case, the measuring person can guide the measuring probe along the object surface in a targeted manner by means of haptic perception and thus acquire measurement data.

[68] Continuous measurement without activation of the measuring system is particularly easy when the shape of the object to be measured, such as a pipe or a car door, is known. In this case, for example, by measuring fewer measuring points on the surface of the object, the position of the object in space can be determined, and then the deviation from a desired shape can be determined in further measurements.

FIG. 9 schematically shows another form of the rigid stylus body 2. The stylus body 2 is arranged laterally by the finger 7. Other implementations of the stylus body are possible as along both finger sides, above the finger over the fingernail or at the finger bottom along the Tastballens. The stylus bodies can be made of components of simple geometry or anatomically shaped to provide a high wearing comfort.

FIG. 10 schematically shows the device with optical camera system 12, the probe 1 with a rigid probe body 2, marker region 3 with pattern 11 and probe body 13 and a further marker 3a rigidly connected to the object 8 and having the pattern I 1a. The identifications of the patterns 11 and 11a are different. The measured coordinates of the probe body 13 can be calculated in the coordinate system of the second pattern I Ia. The camera system can be moved freely with respect to the two markers. The camera system 12 can be held by the measuring person with the other hand in order to carry out measurements if necessary. Both camera system 12 and object 8 are allowed to move relative to each other.

FIG. 11 schematically shows the device with optical camera system, the probe 1 with a rigid probe body 2, marker region 3 with pattern 11 and probe body 13 and a further marker 3a rigidly connected to the table 30. The object 8 must not be moved in the measurement with respect to the table marker 3a. The camera system 12 can be moved freely with respect to the two markers 3 and 3a. FIG. 12 schematically shows a device in which the rigid object 8 is rigidly connected to an optical camera system 40. The probe 1 has a rigid probe body 2, a marker region 3 with pattern 11 and a probe body 13. The camera system is preferably lightweight and portable. It has its own power supply and communicates wirelessly.

FIG. 13 schematically shows the device with an optical camera system 50 rigidly connected to the probe 1, the probe 1 with a rigid stylus body 2 and a stylus 13 and a marker 3 a rigidly connected to the rigid object 8 with a pattern I 1 a. The camera system and the probe are, if necessary, rigidly connected to each other by means of the adapter 51. The lightweight, portable camera system has its own power supply and communicates wirelessly. For the surface measurement of the probe is preferably performed with one hand along the surface and with the other hand, the camera system is held if necessary and / or activated for measurement by means of switches or buttons.

FIG. 14 schematically illustrates a possible device for measurements at hard-to-reach locations of a workpiece 1200. In this case, the probe ball 530 is connected to the shield 500 by means of the connecting piece 1201. With the hinge 1012, the pattern 510 on the sign can be aligned with the camera system as needed. The center of the ball 530 lies on the axis of rotation 1010. The correct position of the test ball on the workpiece surface is scanned with the finger 311.

[75] The application of this haptic measuring device is possible in various areas: in quality control, in assembly, in mold and plant construction, in sheet metal working, in welding technology and in many more. Especially in processes where highest ergonomics and high throughput of measurements are required, the measurement process can be integrated into the respective work step.

[76] A particularly preferred application uses two probes simultaneously, which are measured individually by the measuring system. Both hands are equipped with a measuring probe. This allows objects to be measured very efficiently in an intuitive way. The optimal circle of action is about one meter. The surgeon can make the object ergonomic Grasp and move properly with both hands to deposit it at a specific location or to control the item after processing. At the same time, the object is determined and measured.

[77] Often, a machined object is taken out of the machining center by the mechanic and haptically scanned to sense unevenness. This process can be performed simultaneously for measuring and measuring the object.

[78] The object can be examined for roughness by means of suitable tactile balls by gently rubbing the operator over the material to be measured. Based on the change in position of the ball and the depth variation perpendicular to the measurement plane, the roughness is determined.

Haptic scanning according to the invention can be combined with Augmented Reality. For example, a target shape is known. Through a surface treatment such as milling, Meissein material is removed from an object. The measuring system immediately records the current shape by scanning. This can be communicated to the surgeon via an optical system without, for example, constantly having to use another measuring instrument such as a surface scanner.

[80] Instead of the optical measuring system, a measuring arm known to the experts can also be used. The probe is attached directly to the measuring arm by means of a suitable adapter. The shield 500 shown schematically in FIG. 2 with the optical markings 510 or the marker 3 with the pattern 11 in FIG. 3 can thus be dispensed with. The measurements of the probe take place in the coordinate system of the measuring arm.

Claims

claims

1. probe for measuring a surface with a probe body and a fastening device for fastening the probe body to a finger, characterized in that the probe body is attached to the finger so that the finger can touch the surface next to the probe body.

2. Probe according to claim 1, characterized in that the probe body is a ball or a tip.

3. Probe according to one of the preceding claims, characterized in that the probe body has a curved guide.

4. Probe according to one of the preceding claims, characterized in that the probe body is between 1 and 10 mm and preferably between 2 and 5 mm long.

5. Probe according to one of the preceding claims, characterized in that the fastening device has a finger ring.

6. Probe according to one of the preceding claims, characterized in that the fastening device comprises a plastically deformable sleeve.

7. Probe according to one of the preceding claims, characterized in that the fastening device comprises a wire which holds the probe body.

8. Probe according to one of the preceding claims, characterized in that the probe body is rigidly connected to a measuring arm.

9. probe according to one of the preceding claims, characterized in that the probe body is rigidly connected to a marker region.

10. Probe according to one of the preceding claims, characterized in that it comprises a camera system which is aligned with the marker region.

1 1. A method for measuring a surface in which a probe body so with a Finger on a surface is moved so that the finger touches the surface while the probe touches the surface.

12. The method according to claim 11, characterized in that the position of the probe is determined and stored.

13. The method according to claim 11 or 12, characterized in that the position of the probe body is measured continuously.

14. The method according to any one of claims 11 to 13, characterized in that the position is measured in space.

15. The method according to any one of claims 11 to 14, characterized in that the position is measured relative to the position of the surface.

16. The method according to any one of claims 11 to 15, characterized in that after the finger has touched the surface, a measuring system is activated.