WO2015180755A1 - Optical sensor for a coordinate measuring machine and illumination module for such an optical sensor and method for measuring female threads or drilled holes of a workpiece using the optical sensor or illumination module - Google Patents

Abstract

The invention relates to an optical sensor (31a; 31b; 31c; 31d; 31e) or an illumination module (41a; 41b; 41c; 41d; 41e) for a coordinate measuring machine, wherein a deflection element (6a; 6f) ensures a deflection onto the surface (7a) of a workpiece (7) to be measured on the outward path of the light, wherein the focal region of the sensor (31a; 31b; 31c; 31d; 31e) has an at least partly arcuate embodiment as a result of the deflection element (6a; 6f) and wherein a detector (10) of the sensor (31a; 31b; 31c; 31d; 31e) is embodied in a planar manner for registering intensity signals of light from this focal region, wherein a diffractive optical element (5f) and/or an optical element with a free-form surface (5f; 6f) is arranged on the outward path, wherein a movable and/or changeable optical element (MMA; 3) is arranged between the light source (1) and the diffractive optical element and/or the optical element with the free-form surface (5f; 6f) and wherein the point of incidence of the light on the diffractive optical element (5f) and/or on the optical element with the free-form surface (5f; 6f) on the outward path can be modified with the aid of the movable and/or changeable optical element (MMA; 3).

Description

 description

Optical sensor for a coordinate measuring machine and illumination module for such an optical sensor and method for measuring internal threads or boreholes of a workpiece with the optical sensor or lighting module

The invention relates to an optical sensor for a coordinate inatenmessgerät and a lighting module for such an optical sensor and a method for measuring internal threads or boreholes of a workpiece by means of the optical sensor or lighting module.

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Deflection mirror used to direct the focus or the focus zone of the white light interferometer on a point or a region with a small lateral extent of the inner wall to measure the distance of this point or area of the inner wall. The disadvantage is However, that for complete measurement of only one contour line of the inner wall, the periscope or the deflection mirror must be successively rotated in different rotational positions by a total of 360 ° and one measurement point must be recorded per rotational position. This results in a large amount of time for the complete measurement of one or more contour lines of the inner wall of a borehole or internal thread.

The simultaneous detection of whole contour lines of inner walls of boreholes is disclosed in connection with FIG. 5 of the patent US Pat. No. 4,453,082 by means of a rotationally symmetrical parabolic mirror for a confocal sensor. The disadvantage, however, is that the full focus ring generated by the parabolic mirror is not variable in diameter by the fixed shape of the parabolic mirror and so for different

Borehole diameter different sensors with different parabolic mirrors must be used. This problem of focus variation solves the publication EP 2 093 536 AI in that instead of a parabolic mirror, a cone is used and the generation of the focus ring is brought about by the generation or use of inclined only to the optical axis of light beams. In this case, in the exemplary embodiment of FIG. 1 of the cited publication, two diaphragms are used for selecting light beams inclined only to the optical axis, and in the exemplary embodiment to FIG. 11 an axicon for producing light beams inclined only to the optical axis. Through this

Inclination of the light rays to the optical axis ensures that this

Light rays on one side of the cone form a focus and that after reflection on the inner wall of a borehole these light rays can also run back on the same side of the cone to a detector. Without this inclination, the at the

 Inner wall reflected rays on the way back no longer hit the cone. This is the reason why in many prior art documents, which generally use light aligned parallel to the optical axis for focusing through a lens, a deflecting mirror or periscope is used after the lens to redirect the focus point Elements is ensured that both the inner wall or the

Focus incoming rays as well as the returning reflected rays are completely detected by the deflection mirror or the periscope. The adaptation to different borehole diameter is described in the publication EP 2 093

536 realized in that the distance of the cone from the rest of the sensor is changeable. For this purpose, however, it is necessary to move the cone and / or the associated housing in which the cone is embedded. As a result, on the one hand relatively large masses must be moved and on the other hand, the movement of the cone must be very precisely controlled. The large masses lead to an increase in the necessary measuring or conversion time for different borehole diameters or for boreholes with larger diameter fluctuations, as they are given for example in internal threads. The inaccuracy in the movement of the cone leads to a reduced accuracy of measurement as soon as the cone has to be moved during a measurement.

Object of the present invention is therefore to provide a sensor or a lighting module for a coordinate measuring machine for measuring boreholes or internal threads, the or over the prior art, a high absolute

Measurement accuracy and a reduced measurement time for the complete detection of the coordinates of inner walls of a well with larger diameter variations, in particular an internal thread allowed.

This object is achieved by an optical sensor comprising at least one light source and at least one detector and optical elements for guiding the light on the one hand on the way from the at least one light source to the surface of the workpiece to be measured and on the other hand on the way back from the surface of the to be measured Workpiece to the at least one detector, wherein some of said optical elements both for the beam guidance on the way and for the

Beam guide to be used on the way back and wherein at least one of said optical elements is a deflecting element on the way out for a

Deflection of the light on the surface of the workpiece to be measured and on the way back for a deflection of the light to the at least one detector, wherein on the way through the deflecting the focus area of the sensor is at least partially arcuate and wherein the at least one detector in terms of area Detection of intensity signals of light from this at least partially arcuate focus area is formed, wherein a diffractive optical element and / or an optical element with a freeform surface at least on the way of the light to Surface of the workpiece between the at least one light source and the surface of the workpiece is arranged, wherein between the at least one light source and the diffrativen optical element and / or the optical element with the free-form surface is arranged a movable and / or variable optical element and wherein by means of of the movable and / or variable optical element of the location of the light on the diffractive optical element and / or the optical element with the

Freiformoberfläche can be changed at least on the way from the at least one light source to the surface of the workpiece to be measured. Furthermore, the object is achieved by an illumination module for an optical sensor for detecting surface coordinates of a workpiece by means of a coordinate measuring device comprising at least one light source and optical elements for guiding the light on the one hand on the way from the at least one light source to the surface of the workpiece to be measured and on the other hand, on the way back from the surface of the workpiece to be measured to at least one detector of the optical sensor, wherein some of said optical elements are used both for the beam on the way out and for the beam path in the return path and wherein at least one of said optical Elements is a deflection that provides on the way for a deflection of the light on the surface of the workpiece to be measured and on the way back for a deflection of the light to the at least one detector, wherein on the way through the deflection The diffractive optical element and / or an optical element with a free-form surface is arranged at least on the way of the light to the surface of the workpiece between the at least one light source and the surface of the workpiece , wherein between the at least one

Light source and the diffrativen optical element and / or the optical element with the free-form surface, a movable and / or variable optical element is arranged and wherein with the aid of the movable and / or variable optical element of the impact of the light on the diffractive optical element and / or optical element with the free-form surface can be changed at least on the way from the at least one light source to the surface of the workpiece to be measured. According to the invention, it was recognized that different focal positions can be assigned to different surfaces of the surface of a diffractive optical element and / or an optical element having a free-form optical system, such that the light of the light source can be detected by a movable and / or changeable optical element of the sensor or illumination module according to the invention Different locations can be supplied to change the focus position of the sensor or lighting module. The fact that the movable and / or variable optical element is used on the way of the light from the light source to the surface of the workpiece and between the diffractive optical element and / or the optical element with free-form optics and the light source, the influence of a reduced Deformation of the movable and / or variable optical element on the measurement error of the sensor compared to the prior art considerably. In this case, the distance of a cone to the rest of the sensor is changed for another focus position. However, since the movable cone in the prior art is responsible for both the way of the light to the surface, as well as for the return of the light to the detector and thus for data acquisition or data generation, goes one

Deformation of the movable cone in the prior art as a further contribution directly into the measurement error of the optical sensor. In addition, the sensor according to the invention or the illumination module according to the invention has the advantage that much lighter moving optical elements can be used as a cone to change the focal position, thereby shortening the time required to change the focus position. In particular, when using so-called multi-mirror arrangements (Mu lti -M i rror- array s, MMA), as is well known in projectors, a change in focus position in interaction with the diffractive optical element and / or the freeform optics in ms, in particular even be made in.

Due to the short changeover time for changing the focus position, the sensor according to the invention or the illumination module according to the invention is capable of, for example

Internal threads or undercuts in holes in terms of their

Complete coverage of surface coordinates in a very short time. As a result, it is possible, for example, to significantly increase the measuring point density in comparison to conventional sensors, so that the roughness or the surface texture can also be determined from the surface data of the sensor. In one embodiment, the diffractive optical element has a rotationally symmetrical diffraction characteristic and / or has the optical element with a

Freiformoberfläche a rotationally symmetrical free-form surface, so that when adjusting the movable and / or variable optical element to the effect that the points of incidence of the light have a constant distance to the axis of symmetry of the diffractive optical element and / or the optical element with free-form surface, resulting thereof, at least partially arcuate, in particular annular closed focus region of the sensor for measuring inner walls of bores or internal threads of the workpiece has a constant radial distance to the optical sensor or to its optical axis. For measuring circular

 Drill holes or internal threads, it is useful to use a closed as possible annular focus area around the sensor for the detection of surface coordinates of the holes or internal threads. Such a focus range can be in the sensor according to the invention by a diffractive optical element with a

Achieve rotationally symmetric diffraction characteristics and / or by an optical element with a freeform optics with a rotationally symmetric freeform surface.

In a further embodiment, the optical element having a free-form surface has an aspherical free-form surface, wherein different zones of incidence of the light with mutually different lateral distances to the symmetry axis of the diffractive optical element and / or the optical element with freeform surface different focus positions for bundling of the zones associated with passing light. In this way it is possible, during the measurement of boreholes and in particular of internal threads, to switch between different focal positions by illuminating another zone of the diffractive optical element and / or the optical element with freeform surface by the movable and / or variable optical element.

In one embodiment, the rotationally symmetric and aspherical

Freeform surface with a plane containing the symmetry axis of the free-form surface on a curve and this average curve corresponds at least partially

Curve section of a spiral, where the spiral is given from the group: Corny, Euler or Clothoid spiral. Spirals usually point along their arc length continuously changing diameters in your diameter. Through a

Free-form element, which follows along a main direction of curvature of a spiral shape, it is thus possible to continuously generate changing focal positions depending on the lateral zone distance.

In a further embodiment, the optical element with free-form surface in the form of a cylinder is designed as a deflecting element, the underside of which with a

Mirror coating is provided and is formed by the free-form surface. Such an optical element has the advantage that the mirrored free-form surface is protected by the cylinder when entering bores or internal threads, so that this sensitive surface is not scratched in collisions with the workpiece.

In one embodiment, the movable optical element is given by an axicon movably mounted along its axis of symmetry. Such an optical element can be produced inexpensively.

In another embodiment, the variable optical element is a

Micro Mirror Array (MMA). As a result, extremely short switching times between different focal positions can be realized.

In a further embodiment, the light source is given by a white light source, in particular a superluminescent diode, and the sensor or the illumination module comprises a beam splitter, a collimating lens and at least two for the

Illustration of lenses provided on the detector. The use of a white light source, in particular a superluminescent diode allows the realization of different

Measuring principles. On the one hand, it is conceivable to operate the sensor like a microscope or a camera and by the movable and / or variable optical element

make different focus variations, with a subsequent evaluation of the depth of field. Or the sensor can be called a two-dimensional confocal

Distance sensor, in particular operated as a chromatic confocal sensor. Or the sensor can be configured as a so-called white light interferometer due to the white light source. In the case of the two latter measuring principles as well, the movable and / or variable optical element interacts with the latter diffractive optical element and / or the optical element with the free-form surface made a change in the focus position.

In one embodiment, the sensor or the illumination module has a beam splitter, which proportionally splits the light arriving from the light source into a detection beam path, at the end of which the surface of the workpiece to be measured is located, and a reference beam path, at whose end there is a reference mirror. This splitting of the light of the light source into a detection beam path and a reference beam path through a beam splitter allows the use of interferometri see

Methods for coordinate determination.

In a further embodiment, the beam splitter brings together the light reflected from the reference mirror and the light reflected from the surface of the workpiece in the direction of the detector so that the composite signal is emitted from the detector at the detector

Referenzstrahlengeng and the detection beam can be evaluated. As a result, an interferometric superposition of the beam paths of the detection beam path and the reference beam path at the detector of the sensor is made possible.

In one embodiment, the reference mirror may be changed in its distance from the beam splitter with time, whereby the composite signal at the detector as

 Interference signal in the time domain (English time domain, TD) can be analyzed. Due to the variable reference mirror, the measuring method of white light interferometry known under the heading TD-OCT is made possible in connection with the sensor or illumination module according to the invention.

In another embodiment, means for spectrally separating the composite signal are provided between the beam splitter and the detector so that the composite signal can be analyzed at the detector as an interference signal (English frequency domain, FD) decomposed into a plurality of spectral channels. Due to the means for spectral separation, the known under the keyword FD-OCT measurement method of

 White light interferometry in connection with the sensor according to the invention or

Lighting module allows. In one embodiment, the sensor or the illumination module has a

 Change interface for coupling a or the lighting module to the sensor. This will allow one lighting module to go against another

Lighting module can be replaced on the sensor. For example, the different lighting modules can be designed for different diameters or for different measuring methods.

The object of the present invention is further solved by a method

Measuring a borehole in particular an internal thread of a workpiece by means of a coordinate measuring machine with the aid of the sensor or illumination module according to the invention, wherein in a first step the sensor or the illumination module is moved through the

Coordinate measuring machine to a desired position within the borehole or

Internal thread of the workpiece is moved and wherein in a second step by means of a movable and / or variable optical element of the incidence of the light of the at least one light source on a diffractive optical element and / or an optical element with a freeform surface at least on the way from the at least a light source is changed to the surface of the workpiece to be measured such that the provided for surveying portions of the surface of the workpiece reach the focus area of the sensor or the illumination module.

According to the invention, it has been recognized that different focal positions can be assigned to different surfaces of a diffractive optical element and / or an optical element having a freeform optical system, such that the light of the light source can be detected by a movable and / or changeable optical element of the sensor or illumination module according to the invention Different locations can be supplied to change the focus position of the sensor or the lighting module. Thus, after the introduction of the sensor or illumination module into a borehole or internal thread, it is possible for the focal position to be achieved by the interaction of the movable and / or variable optical element with the diffractive optical element and / or the element with a freeform optical system, for example an initially set low

Distance to the sensor or lighting module is changed continuously or in individual steps to a large distance, so that during this scan always different sub-areas of the surface to be measured, the distances just set Corresponding distance of the focal position, can be detected by the sensor or the lighting module.

In one embodiment of the method according to the invention, in a third step, intensity signals from the focus area of the sensor or the illumination module are detected by a detector of the sensor configured to detect intensity signals as a function of the position of the movable and / or variable optical element of the sensor or of the illumination module and / or in dependence on the position of a reference mirror, which is movable in its normal direction, of the sensor and / or in

Dependence of the frequency or wavelength of the detected light detected by the detector. By this third step, the assignment of intensity signals from the focus area to the differently set focal positions and thus the assignment of different sub-areas of the surface to be measured takes place at different distances.

In a further embodiment of the method according to the invention, the second step is for a focus area changed in its lateral distance from the sensor or illumination module while maintaining the position approached in the first step or the first step for another desired position within the borehole or internal thread in the case of FIG Maintaining the position set in the second step of the movable and / or variable optical element of the sensor or the lighting module repeatedly carried out until in the subsequent third step, the complete information about the surface data of the section to be measured of the borehole or internal thread is present ,

In particular, for internal threads where, for example, in metric ISO threads, the difference of core and outside diameter (nominal diameter) is between 0.3 mm (at M1) and 7 mm (at M64), it is necessary to do both a scan along the axis of the internal thread, as well as a focus scan over different diameters or focal positions with the sensor or the illumination module to perform the full

Surface information of the internal thread with respect to the thread, the

Thread flanks and the thread depths z obtained. Due to the large difference between core and outer diameter (nominal diameter) with internal threads, it is usually not possible to work with only one focus position for a survey. It is understood that the scan along the axis by the change in position of the sensor or the

Illumination module can be performed by means of the coordinate measuring machine and the focus scan of the sensor or lighting module independently and in any combination with each other to obtain complete information about the surface coordinates of the internal thread.

Further features and advantages of the invention will become apparent from the following

Description of embodiments of the invention with reference to the figures, which

show details essential to the invention, and from the claims. The single ones

 Features may be implemented individually for themselves or for several in any combination in a variant of the invention.

Embodiments of the invention will be explained in more detail with reference to FIGS. In these shows

Figure 1 is a schematic representation of an optical sensor of the prior

 Technique according to FIG. 11 from EP 2 093 536 A I; Figure 2 is a schematic representation of a first embodiment of

 sensor or lighting module according to the invention with a movable axicon and a diffractive optical element;

Figure 3 is a schematic representation of a second embodiment of the

 inventive sensor or lighting module with a multi-mirror arrangement and a diffractive optical element;

Figure 4 is a schematic representation of a third embodiment of

 inventive sensor or lighting module with a multi-mirror arrangement and a mirrored free-form surface;

Figure 5 is a schematic representation of a fourth embodiment of the

inventive sensor or lighting module as White light interferometer with a multi-mirror arrangement and a mirrored freeform surface; and

Figure 6 is a schematic representation of another invention

 Illumination module for an optical sensor.

1 shows a prior art optical sensor 30 for a coordinate measuring device for detecting surface coordinates of a workpiece 7 comprising at least one light source 1 and at least one detector 10 and optical elements 2, 3, 4, 5, 6 and 9 for guiding the Light on the one hand on the way from the at least one light source 1 on the surface 7a of the workpiece to be measured 7 and on the other hand on the way back from the surface 7a of the workpiece to be measured 7 to the at least one detector 10, wherein some of said optical elements 4, 5th , 6 and 6a are used both for the beam guidance on the way out and for the beam guidance on the way back and wherein at least one of said optical elements is a deflection element 6a on the way out for a deflection of the light on the surface 7a of the to be measured workpiece 7 and on the way back for a deflection of the light to the at least one Detek tor 10, wherein on the way through the deflecting element 6a, the focus area of the sensor 30 is at least partially arcuate and wherein the at least one detector 10 in terms of area for detecting intensity signals of light from this at least partially arcuate focus area is formed.

The optical sensor 30 shown in FIG. 1, together with the reference symbols, corresponds to the sensor disclosed in FIG. 11 of EP 2 093 536 A, only the reference symbol 7a for the surface of the workpiece 7 has been added. Further, the optical element 6 in the

Figure 1 not in a stepped form as shown in Figure 1 1 of EP 2 093 536 AI but as a solid cylinder. In addition, in FIG. 1, in contrast to FIG. 11, more space has been allocated for the light path between the collimation lens 2 and the axicon 3. A further difference of the present here Figure 1 to Figure 1 1 of EP 2 093 536 AI results from the fact that the position of the aperture 8 in Figure 1 1 below the lens 9 corresponds to the position of a pupil plane and the position of the aperture 8 in of the present Figure 1 was selected above the lens 9 according to the location of the smallest constriction of the light beams. It should also be noted that in FIG. 11 of EP 1 093 536 A1 light beams are shown above the beam splitter 4, which do not exist in reality. This relates to the outermost light beams at the detector 10 of Figure 1 1 of EP 2 093 536 AI. Presumably, these nonexistent light beams were taken to illustrate the pupil plane and thus the position of the diaphragm 8 in Figure 1 1 of EP 2 093 536 AI. A correct representation of the light rays without these nonexistent light rays, however, can be found in the following Figure 12 of EP 2 093 536 AI.

The mode of operation of the sensor 30 shown in FIG. 1 will be briefly explained below. In addition, reference is made to the disclosure of EP 2 093 536 with regard to the operation of this sensor, which is hereby incorporated by reference in its entirety for the description of the sensor 30 of FIG.

The sensor 30 shown in Figure 1 is particularly suitable for measuring the

Surface coordinates of the inner sides of boreholes of a workpiece 7, since the sensor 30 is capable of fully projecting the focused on the inner wall or surface 7 a in the form of a ring focus area of the sensor 30 by means of only one measurement on the detector 10. For this purpose, the light of the light source 1 is first collimated by a collimating lens 2, that is aligned almost parallel to the optical axis. A subsequent axicon 3 ensures a decomposition of the parallel aligned light in a circumferentially closed ring bundle, wherein the ring bundle subsequently has a constant inclination to the optical axis. A beam splitter 4 following the axicon 3 in the direction of the light deflects the ring bundle in the direction of a lens 5. Due to the fact that the axicon 3 is approximately at the plane of the front focal length of the subsequent lens 5, those light beams of the ring bundle which have previously passed approximately through the tip of the axicon and thus from a point of the optical axis take their exit, aligned by the lens 5 parallel to the optical axis. The lateral distance of these rays to the optical axis or the so-called height h after the lens 5 is then corresponding to h = f * sin a, where f is the focal length of the lens 5 and a is the angle of inclination with respect to the optical axis at the axicon 3. Due to the parallel alignment of these beams to the optical axis, these rays pass through the plano-optics following the lens 5, in particular the one into one Transparent cylinder 6 embedded or incorporated deflection cone 6a almost perpendicular to the inner wall to be measured 7a of the borehole or workpiece 7 and are therefore reflected in itself, whereby these rays occupy the same path for the outward and return path between beam splitter 4 and surface 7a , On the way back, however, these beams pass through the beam splitter 4 and reach the detector 10.

The annular focus area now arises because not only the rays from the axicon tip but all the rays after the axicon 3 have the same angle of inclination to the optical axis. Since the axicon 3 is approximately at the focal point of the lens 5, the plane of the axicon represents an illumination pupil plane of the sensor 3. According to the general optical Fourier relationships between field and pupil planes, which are given even for a single lens 5, all rays which start in an illumination pupil plane of an optic of the focal length f with the same inclination angle <x, collect in the illumination field plane at a point with the lateral distance h = f * sin α to the optical axis. That in other words, the generation of a circularly symmetric to the optical axis ring bundle with a constant inclination of the rays of the ring bundle to the optical axis in the illumination pupil plane of the sensor 30 through the axicon 3 automatically results in the generation of an annular focus area due to the optical Fourier relationship of field and pupil planes in the field plane of the sensor 30. This generated by the inclined beams annular focus area is deflected in the sensor 30 of Figure 1 by a mirrored cone 6a at the end of a transparent cylinder member 6 on the surface to be measured 7a of the workpiece 7.

Without the generation of inclined rays by the axicon 3, all otherwise parallel rays due to h = f * sin 0 ° = 0 mm would be in a focal point on the optical

Collect axle. As a result, it would not be possible to redirect the beams with the deflecting cone 6a on the way out and on the way back. In this case, the beams would cut the optical axis above the cone on the return path and thus miss the cone for a further deflection in the direction of the detector 10.

In EP 2 093 536 AI is in connection with the local figure 1 another

Embodiment of a sensor 30 of the prior art shown. In this

Embodiment be successively staggered aperture as another option specific selection of inclined or skewed rays disclosed. However, this solution results in greater light losses due to the apertures.

The illuminated by the annular focus area surface portions of the surface 7a in the sensor 30 of Figure 1 by two lenses 5 and 9 on a

two-dimensional detector, for example a CCD or CMOS chip. That In other words, recordings of the illuminated surface sections are made by means of a digital camera. To determine the coordinates of the illuminated

Surface sections can then be determined from the taken recordings the broadening of the recorded focus line according to the method discussed in connection with FIG. 12 of EP 2 093 536 A I. Reference is made to EP 2 093 536 A, which is incorporated by reference in its entirety, and to the description of the figures relating to FIG. 12 therein. However, it is also possible to vary the distance of the cylinder 6 and thus of the deflection cone 6a from the rest of the sensor 30 and thus to make different shots of the illuminated surface portion at different focal positions. Subsequently, the best focus position and thus its coordinate can then be determined by software for the respective subsection by means of a contrast or image enhancement of the images. This method is known as focus variation.

Alternatively, the correct focus position in the focus variation can also be determined confocally by means of one or more apertures 8. In this case, the focus is not optimized on the sharpness of the image but on its intensity. In this alternative confocal measurement technique, however, it may be necessary to use one or more variable apertures 8 drivable along the optical axis to obtain the optimum position and the optimum

Diameter of the aperture 8 depending on the selected focus position. Such apertures are known from digital photography.

It should also be noted that in the case of the sensor 30 of FIG. 1, even when the axicon 3 is exchanged for another axicon which generates light beams with a larger inclination angle β, this is due to β> α to a larger distance h '= f * sin β > h = f * sin α of the rays to the optical axis following the lens 5 would lead, however, the

Focus position of the sensor 30 would not change this, since this depends only on the focal length of the lens 5 and possibly also in addition to the distance of the deflection cone 6a to the rest of the sensor. In other words, all rays emanating from a pupil plane accumulate in one and the same field level, those with a large angle in the pupil gather at a large field height and the small angle in the pupil accumulate at a small field height. However, it is not possible to shift the position of the field plane along the optical axis with a variation of the angles in the pupil.

FIG. 2 shows a first embodiment of the sensor 31a or lighting module 41a according to the invention, which additionally has an axially movable axicon 3 and a diffractive optical element 5f or optical fiber 5f shown in broken lines in relation to the sensor 30 of the prior art Element having a free-form surface 5f. The illumination module 41 a is the part of the sensor 31 a shown in the lower part of FIG. 2. The dashed line between the upper part of the sensor 3 la from the lens 9 upwards and the illumination module 41 a from the aperture 8 downwards represents a possible and useful separation plane between these two parts of the sensor 31 a. In this level, an exchange interface for replacement or coupling different lighting modules to be provided to the sensor 31 a. These exchangeable illumination modules can be based on various measuring techniques mentioned in the introduction, be executed according to FIGS. 3 to 5 or adapted for different measuring tasks. FIGS. 3 to 5 have corresponding parting planes for exchanging or coupling different inventive illumination modules to sensors according to the invention. By contrast, FIG. 6 shows an alternative

Lighting module 41 e, which is for replacement or coupling to the

inventive sensor 31 e is provided with an alternative parting plane.

2, what happens when the axicon 3 in a sensor 0 of the prior art from its position shown in FIG. 1 to the displacement vector a shown in FIG axially offset in the direction of the light source 1. By this displacement of the axicon 3, the inclination of the rays does not change. That is, the rays start at the former position of the axicon 3 and thus in the pupil with the same inclination to the optical axis. However, in the axicon 3 displaced by the vector a, the ring bundle is now laterally widened in the pupil, ie, the locations of the rays of the ring bundle in the pupil are further away from the optical axis than in FIG. 1. This is shown in FIG represented graphically that the rays of the Axikonspitze, which have formed in Figure 1 nor the outer edge of the ring bundle on the subsequent lens 5, in Figure 2 now represent the inner edge of the ring bundle on the subsequent lens 5. Thus, in FIG. 2, the ring bundle passes through a region of the lens 5 which is located further outside than in FIG. 1.

In principle, rays of the same inclination in the pupil meet with ideal lenses according to the Fourier relation at the same field point. A real lens, on the other hand, differs slightly from this ideal because of its aberrations, and in particular the aberration of spherical aberration is responsible for collimating rays of light which meet a lens farther out at a focal point closer to the lens. These

Focus deviation of the real lens 5 from an ideal lens due to the spherical aberration is represented in FIG. 2 as a shift of the focal position by the vector b. With the help of this changed focus position, it would then be possible to measure another hole 7 with a smaller diameter. Such a borehole is shown by dashed lines in FIG. According shortened to the sensor 30 out

Focus position also reduces the diameter of the borehole on the detector 10 by the vector c. The vector c is exaggerated in the figures and therefore not

shown to scale. However, the lens 5 is also provided in the optical sensor 30 and the optical sensor according to the invention 31 a for imaging on the detector 10 and optically selected so that it does not have a large spherical aberration, which the imaging and the data acquisition on the detector 10 would complicate. Thus, the strong focus effect of the lens 5 shown in FIG. 2 in the prior art sensor 30 is, for example, insufficient to achieve the variation of several millimeters in the focus position necessary for the measurement of an internal thread

solely by a change in the position of the axicon 3 provide.

According to the invention, it is therefore proposed to provide an optical element 5f which, instead of or in addition to the lens 5, varies the focal position by a plurality

Millimeters at a change of location of the incident on the element 5f light rays allows. Such an element 5 f can now be a diffractive optical element (DOE) and / or an optical element with a free-form optical system. Both mentioned optical elements or an element which combines both properties mentioned are or will be able to provide a corresponding focus depending on the respective impact of the rays on the element. In the case of the optical element with free-form optics, it would be conceivable, for example, to choose a rotationally symmetrical aspherical surface form analogous to the Schmidt plate known for mirror telescopes. Such a Schmidt plate can be produced inexpensively. Also holograms, in particular so-called computer-generated holograms (CGH) are subsumed in the context of this application under the term diffractive optical elements. The inventive sensor 31a or the illumination module 41a according to the invention of FIG. 2 is thus characterized in that a diffractive optical element 5f and / or an optical element with a free-form surface 5f at least on the way of the light to the surface 7a of the workpiece 7 between the at least a light source 1 and the surface 7a of the workpiece 7 is arranged, wherein between the at least one light source 1 and the diffrativen optical element 5f and / or the optical element with the free-form surface 5f, a movable and / or variable optical element 3 is arranged and wherein Help of the movable and / or variable optical element 3 of the location of the light on the diffractive optical element 5f and / or the optical element with the free-form surface 5f changed at least on the way from the at least one light source 1 to the surface 7a of the workpiece 7 to be measured will ka nn.

In the case of the sensor 31a or the illumination module 41a according to the invention, the focus variation amounts to between 0.5 and 200 mm in order to both

Internal thread and cylinder bores within engine blocks can measure. Corresponding diffractive optical elements 5f and / or optical elements with a free-form optics 5f, which have a focal length variation of 200 mm, are without much technological effort for the visible, ultraviolet or infrared

Wavelength range manufacturable. For example, injection molds for producing aspherical plastic lenses for digital cameras have been known for many years.

As an optical element with a free-form optics 5f and toroidal optical element such as a ring lens or an arrangement of several nested one another understood separate ring lenses. Accordingly, an optical element with

Freeform optics 5f also consist of juxtaposed individual optical elements whose optically effective surfaces represent subsections of a freeform surface.

As an alternative to an axicon 3 shown in FIG. 2, it is also possible to use a so-called refractive optical element whose surface parcels locally simulate the inclination of the axial surfaces in accordance with a Fresnel lens. Furthermore, the

Functionality of an axicon 3 are also modeled by a diffractive optical element. However, both mentioned alternatives are associated with increased cost of manufacture.

The evaluation of the intensity signals recorded at the detector 10 of the sensor 3 1 a according to the invention can be carried out according to the methods already discussed above in connection with the sensor 30 of FIG. 1. In this case, in particular for kon focal methods, a ring aperture 8 instead of the diaphragm 8 shown in Figure 2 are used.

FIG. 3 shows a second exemplary embodiment of a sensor 31b according to the invention or an illumination module 41b in which the axially movable axicon 3 has been exchanged for a variable multiple mirror arrangement (MMA). This multiple mirror arrangement MMA can vary by other angular positions of the individual micro-tilting mirror the impact on the optical element 5f and thus its focus position. Since multi-mirror arrangements for projectors are well known in their mode of operation, a detailed discussion in the context of this application is dispensed with. Multiple mirror arrangements MMAs can be obtained as separate units cost-effectively from different manufacturers including corresponding control software. This MMAs provided for projectors can also be used directly for the sensor 31b according to the invention or the illumination module 41b according to the invention, since the optical requirements for size, tilt angle, size of the micromirrors and wavelengths are different for the sensor 31b or the illumination module 41b do not differ from those requesting a projector to project a computer screen onto a screen. FIG. 4 shows a third exemplary embodiment of a sensor 31c or illumination module 41c according to the invention in which, compared to FIG. 3, the function of the optical element 5f has been integrated into the surface shape of the deflection element 6f. This deflection element 6f has a free-form surface whose focal positions are dependent on which points of incidence the deflecting element 6f deflects the rays. in particular, a deflection element 6f, in which the rotationally symmetrical and aspherical free-form surface having a plane containing the symmetry axis of the freeform surface has an intersection curve and this intersection curve at least partially a

Curve section corresponds to a spiral and the spiral is given from the group: Corny, Euler or clothoid spiral, offers the possibility of continuous with the

Impacts changing focus positions. Spiral curves usually have continuously varying curvatures with the arc length and thus continuously variable focal positions with the point of incidence. Representative of these many

4, only two different focal positions with the vectors b and B and the resulting location displacements on the detector 10 with the vectors c and C are shown in FIG.

However, instead of being formed on the underside of the transparent cylinder 6 in the form of a mirrored surface 6f as deflecting element, the freeform surface can also be formed on the upper side and / or the circumferential surface of the cylinder 6. Alternatively, the focus variation can also be realized by a diffractive optical element formed on the upper side and / or the lateral surface of the cylinder 6. Furthermore, correspondingly differently shaped cylinders 6 can be exchanged for one another between the elements 4 and 5 or the elements 5 and 6 by means of a swiveling element 1, not shown in the figures. In addition, mechanical protective sleeves for the cylinder 6 can be provided. When using optically transparent material for these mechanical protective sleeves different wall thicknesses and / or different

Refractive indices of these protective sleeves for further adaptation to different

Borehole diameter can be used. In this respect are accordingly interchangeable

Protective sleeves conceivable for further adaptive adaptation. For a measurement of rotationally symmetrical boreholes or internal threads, in the optical sensors according to the invention shown in FIGS. 2 to 6, the diffr active optical element 5f has a rotationally symmetric diffraction characteristic and / or has the optical element with a free-form surface 5f; 6f a rotationally symmetric

Freiformoberfläche, so that when adjusting the movable and / or variable optical element MMA; 3, in that the locations of incidence of the light are at a constant distance from the axis of symmetry of the diffractive optical element 5f and / or the free-form surface optical element 5f; 6f, the resulting, at least partially arcuate, in particular annularly closed focus region of the sensor for measuring inner walls 7a of bores or internal threads of the workpiece 7 has a constant radial distance from the optical sensor.

Advantageously, the optical element with freeform surface 6f in the form of a cylinder 6 in the optical sensors or lighting modules according to the invention of Figures 4 to 6 is designed as a deflection, the underside is provided with a mirror coating and is formed by the free-form surface 6f. The mirrored freeform surface 6f is thus sufficiently protected by the surrounding cylinder 6 from scratches and other damage in collisions with the workpiece 7. 5 shows a further embodiment of a sensor 3 dd or illumination module 41 d based on white-light interferometry, also known as optical coherence radar or OCT The basic structure of the sensor 31 d shown in FIG. 5 corresponds to the sensor 31 c shown in FIG. A multi-mirror arrangement MMA, in conjunction with a deflection element 6f with free-form surface, provides for a

Focus variation within the borehole 7. However, the beam splitter 4a in the

Embodiment of the sensor 3 Id of Figure 5 for the fact that only a proportion of light coming from the light source 1 is deflected in the detection beam path in the direction of the element 6f. The remaining part of the light passes through the beam splitter 4a and thus enters the reference beam path in the direction of a reference mirror R. It should be noted that due to the representation of FIG. 5 in DIN A4 format, the reference beam path is shown shortened relative to the detection beam path. With the basic structure of a Michelson interferometer shown in FIG. 5, in connection with a white light source 1, for example a superluminescent diode and a reference mirror R adjustable in the direction of light by piezoelectric actuators, for example, the intensity signals at the detector 10 can be evaluated as a function of the reference mirror position. The intensity signals of the detector 10 result from a superposition of the reflected light coming from the reference beam path and the detection beam path through the beam splitter 4a by means of the lens 9. If the light paths in the reference beam path and in the detection beam path are over, a constructive interference of the light results and thus a Intensity signal at the detector. With increasing path length difference Δζ between the detection beam path and the reference beam path, however, this intensity signal at the detector decreases. Consequently, with the optical sensor 31d shown in FIG. 5, the composite signal at the detector 10 can be analyzed as an interference signal in the time domain (TD) as a function of the time-varying distance of the reference mirror R to the beam splitter 4a. The reference mirror R is for this purpose, for example, by piezo actuators

Vibrations excited about its zero position and the corresponding interference signal will determine depending on the position of the mirror. The zero position of the reference mirror R can be tuned by the piezo actuators or other additional actuators to the respective set focus position. Furthermore, it is conceivable alternatively a

Rotationally symmetric stepped reference mirror to use, each stage corresponds to a different focus position.

As an alternative to the basic structure shown in FIG

Reference mirror R of the optical sensor 31 d between the beam splitter 4a and the detector 10 also have means for spectral separation of the composite signal, so that the composite signal as a decomposed into several spectral channels interference signal (English frequency domain, FD) are analyzed at the detector 10 can. For this purpose, the detector 10 may be subdivided into a plurality of areas which receive the different interference signals for different wavelengths, or a plurality of detectors 10 may be used next to each other or spatially offset from one another. By analyzing different interference signals at different wavelengths, it is possible to determine which wavelength at the fixed reference mirror R is a

corresponding interference. As a rule, this is a Fourier transformation of the frequency spectrum to obtain the corresponding spatial information. From this it is then possible to deduce the length of the detection beam path and thus the distance of the surface to be measured. For further details of the measurement methods TD-OCT and FD-OCT will be on

 Special literature and in particular in connection with the coordinate metrology to the published patent applications DE 10 2004 012 426 and US 2010/03 12524 and the references cited therein. FIG. 6 shows a further illumination module 41e according to the invention for a sensor 31e according to the invention. In contrast to the exchangeable lighting modules of FIGS. 2 to 5, the illumination module 41e of FIG. 6 can be retrofitted, so that it can be connected to already existing optical systems. The illumination module 41e shown in FIG. 6 differs from the illumination modules shown in FIGS. 2 to 5 in that it does not contain the lens 5 and thus the remaining part of the sensor 3 le with the lens 5 even without the illumination module forms a complete optical system optical measurement of workpieces 7 forms. 6 can be coupled to existing optical systems in order to equip or retrofit these systems with a functionality for measuring boreholes or internal threads. Corresponding optical systems are disclosed, for example, in publications WO 2014/023332 and WO 2014/023780. For coupling, the illumination module 41e has a not shown

Wechselschnittstclle, with which it can be coupled to existing optical systems manually or automatically. This change should be made according to the changeover interface of the illumination modules or sensors of FIGS. 2 to 5. Corresponding interchangeable interfaces are known, for example, from published patent application WO 2013/167167. It is understood that the illumination module 41 e shown in Figure 6 is not limited to the illustrated design, but may have any discussed in connection with Figures 2 to 5 design of a lighting module.

FIGS. 2 to 6 consequently disclose illumination modules 41a to 41e for an optical sensor 3 1 a to 3 1 e for detecting surface coordinates of a workpiece 7 by means of a coordinate measuring machine comprising at least one light source 1 and optical Elements 2, MMA; 3, 4; 4a; 5; 6, 6a; 6f for guiding the light on the one hand on the way from the at least one light source 1 on the surface 7a of the to be measured

Workpiece 7 and on the other hand on the way back from the surface 7a of the workpiece to be measured 7 to at least one detector 10 of the optical sensor 3 1a to 31 e, wherein some of said optical elements 4; 4a; 5; 6, 6a; 6f are used both for the beam guidance on the way out and for the beam guidance on the return path and wherein at least one of said optical elements 6a; 6f a deflecting element 6a; 6f is on the way for a deflection of the light on the surface 7a to

measuring workpiece 7 and on the way back for a deflection of the light to the at least one detector 10, wherein on the way through the deflecting element 6a; 6f the focal region of the sensor 3a to 31e is at least partially arc-shaped, and wherein a diffractive optical element 5f and / or an optical element with a free-form surface 5f; 6f is arranged at least on the way of the light to the surface 7a of the workpiece 7 between the at least one light source 1 and the surface 7a of the workpiece 7, wherein between the at least one light source 1 and the diffrativen optical element 5f and / or the optical element with the

Free-form surface 5f; 6f a movable and / or variable optical element MMA; 3 is arranged and wherein by means of the movable and / or variable optical element MMA; 3 the location of the light on the diffractive optical element 5f and / or the optical element with the free-form surface 5f; 6f can be changed at least on the way from the at least one light source 1 to the surface 7a of the workpiece 7 to be measured.

It is understood that in all inventive sensors 31 a to 3 l e or

Lighting modules 41 a to 41 e an axicon 3 instead of a multi-mirror assembly MMA for varying the Lichtstrah running hangers and vice versa a multi-mirror assembly MMA instead of an axicon 3 can be used.

Furthermore, it is understood that in all inventive sensors 3 1a to 31 e or

Lighting modules 41 a to 41 e a diffractive optical element 5f and / or an optical element with free-form surface 5f instead of an optical deflection element with free-form surface 6f for focus variation and vice versa can be used. In addition, it is understood that in the inventive sensors 31a; 31b; 31 c and 31 e and lighting modules 41 a; 41b; 41c and 41e alternatively to that in the

Embodiment of Figure 4 described superluminescent diode laser, LED (UV, VIS, IR), incandescent, halogen or (short) arc lamps can be used as the light source 1. By using a broadband light source, a targeted longitudinal chromatic aberration of the optics used in the inventive sensors 31 a; 31b; 31 c and 31 e and lighting modules 41 a; 41b; 41c and 41e to the effect that a confocal measurement technique that images of images with color separations or by pixel-by-pixel color measurement are carried out with corresponding sensors. Furthermore, the different wavelengths due to their different scattering properties can also be used for spatially resolved roughness measurements, for example via the parallel measurement of different color separations.

With the aid of the sensors and illumination modules shown in FIGS. 2 to 6, it is possible to drill holes and, in particular, internal threads of a workpiece (7) by means of a

Coordinate measuring device measured by the sensor or the illumination module is moved by the coordinate measuring machine to a desired position within the borehole or internal thread of the workpiece (7) and in a second step by means of a movable and / or variable optical element (MMA; 3) of the sensor or of the illumination module, the location of incidence of the light of the at least one light source (1) on a diffractive optical element (5f) and / or an optical element with the free-form surface (5f; 6f) of the sensor or the

Illuminating module is changed at least on the way from the at least one light source (1) to the surface (7a) of the workpiece to be measured (7) such that the provided for surveying portions of the surface (7a) of the workpiece in the

Focus range of the sensor or lighting module arrive.

In a third step, intensity signals from the focus area of the sensor or the illumination module are detected by a detector (10) designed to detect intensity signals as a function of the position of the movable and / or variable optical element (MMA; Lighting module and / or depending on the position of a movable in its normal direction

Reference level (R) of the sensor or lighting module and / or in dependence of Frequency or wavelength of the light detected by the detector (10) determined.

Here, the second step for one in its lateral distance to the sensor or

Lighting module changed focus area in the maintenance of the approached in the first step position or the first step for another desired position within the internal thread while maintaining the second step set position of the movable and / or variable optical element (MMA; 3) of the sensor or Illuminating module are repeatedly carried out until in each subsequent third step, the complete information about the surface data of the section of the internal thread to be measured is present. These surface data can then be analyzed by known 3D point cloud mapping techniques

Determining the geometry of the measurement object into the corresponding geometric elements such as circle, ellipse, cylinder, ellipsoid, etc. are decomposed. It goes without saying that the method according to the invention or the sensors according to the invention can be calibrated or referenced using thread standards and / or can be returned to a normal. For this purpose workpieces are placed with several well-known internal threads on the measuring table of a coordinate measuring machine and it is carried out the inventive method by means of the sensors according to the invention and the detected dimensions of the internal thread are calibrated on the basis of the known dimensions of the internal thread.

Claims

claims: 1. Optical sensor (31a, 31b, 31c, 31d, 31e) for a coordinate measuring machine for  Detecting surface coordinates of a workpiece (7) comprising at least one light source (1) and at least one detector (10) and optical elements (2, MMA; 3, 4; 4a, 5, 6, 6a; 6f, 9) for guiding the light on the one hand on the way from the at least one light source (1) on the surface (7a) of the to be measured Workpiece (7) and, on the other hand, on the way back from the surface (7a) of the workpiece (7) to be measured to the at least one detector (10), some of said optical elements (4; 4a, 5, 6, 6a; 6f) be used both for the beam guidance on the way out and for the beam guidance on the return path and wherein at least one of said optical elements (6a, 6f) a  Deflection element (6a; 6f), which on the way out for a deflection of the light on the surface (7a) of the workpiece to be measured (7) and on the way back for a deflection of the light to the at least one detector (10), on the way through the deflecting element (6a; 6f), the focus area of the sensor (31a; 3 1 b; 31 c; 31 d; 3 1 e) is at least partially arcuate, and wherein the at least one detector (10) measures in terms of area is formed of intensity signals of light from this at least partially arcuate focus area, characterized in that a diffractive optical element (5f) and / or an optical element with a freeform surface (5f; 6f) at least on the way of the light to the surface (7a) of the Workpiece (7) between the at least one light source (1) and the surface (7a) of the workpiece (7) is arranged, wherein between the at least one light source (1) and the diffrativen optical elements t (5f) and / or the optical element with the free-form surface (5f; 6f) a movable and / or variable optical element (MMA; 3) is arranged, and wherein by means of the movable and / or variable optical element (3) the location of the light on the diffractive optical element (5f) and / or the optical element with the free-form surface (5f; 6f) at least on the way from the at least one light source (1) to the surface (7a) of the to be measured workpiece (7) can be changed. 2. Illumination module (41 a, 41 b, 41 c, 41 d, 41 e) for an optical sensor (31 a, 31 b, 31 c, 31 d, 31 e) for detecting surface coordinates of a workpiece (7) by means of a coordinate measuring machine at least one light source (1) and optical elements (2, MMA; 3, 4; 4a; 5; 6, 6a; 6f) for guiding the light on the one hand on the way from the at least one light source (1) to the surface (7a). of the workpiece (7) to be measured and, on the other hand, on the return path from the surface (7a) of the workpiece (7) to be measured to at least one detector (10) of the optical sensor (31), some of said optical elements (4; 5, 6, 6a, 6f) are used both for the beam guidance on the way out and for the beam guidance on the way back, and wherein at least one of said optical elements (6a, 6f) is a deflection element (6a, 6f) on the way for a deflection of the light on the upper surface (7 a) of the We to be measured R ckstücks (7) and on the way back for a deflection of the light to the at least one detector (10), wherein on the way through the  Deflection element (6a, 6f) of the focus area of the illumination module (41 a; 41 b; 41 c; 41 d; 41 e) or sensor (31 a; 31 b: 3 1 c; 31d; 31 e) is at least partially arcuate, characterized characterized in that a diffr active optical element (5f) and / or an optical element with a Fre i form surface (5f; 6f) at least on the way of the light to the surface (7a) of the workpiece (7) between the at least one Light source (1) and the surface (7a) of the workpiece (7) is arranged, wherein between the at least one light source (1) and the diffrativen optical element (5f) and / or the optical element with the  3) is arranged, and wherein with the aid of the movable and / or variable optical element (MMA; 3) the location of the light on the diffractive optical element (5f) is arranged on the free-form surface (5f; 6f). and / or the optical element with the free-form surface (5f; 6f) can be changed at least on the way from the at least one light source (1) to the surface (7a) of the workpiece (7) to be measured. 3. Optical sensor (31 a, 31 b, 31 c, 31 d, 3 1 e) according to claim 1, wherein the diffractive optical element (5f) has a rotationally symmetric diffraction characteristic and / or the optical element with a free-form surface (5f; ) one rotat on ssym m etri see free-form surface, so that when adjusting the movable and / or variable optical element (MMA; 3) to the effect that the points of incidence of the light at a constant distance from the axis of symmetry of the diffractive optical element (5f) and / or of the optical element with  6f), the resulting, at least partially arcuate, in particular annularly closed focus region of the sensor (31a; 3 1 b; 31 c; 3 1 d; 31 e) for measuring inner walls (7a) of bores or internal threads of the workpiece (7) has a constant radial distance from the optical sensor (31a; 31b; 31c: 31d; 31e). 4. Optical sensor (3 1 a; 3 1 b; 31 c; 3 ld; 3 le) according to claim 1 or 3 or  The illumination module (41a; 41b; 41c; 41d; 41e) according to claim 2, wherein the optical element having a free-form surface (5f; 61) has an aspheric free-form surface, wherein different zones of incidence of the light with mutually different lateral distances to the axis of symmetry of the diffractive optical element (5f) and / or the optical element with free-form surface (5f; 6f) are assigned different focus positions for focusing the light passing through the zones. 5. Optical sensor (3 1 c, 3 ld, 31 c) or lighting module (41 c, 41 d, 41 e) after  Claim 4, wherein the rotationally symmetric and aspherical freeform surface having a plane containing the axis of symmetry of the freeform surface has a cut curve and this cut curve at least partially corresponds to a curve portion of a spiral and the spiral is given from the group: Corny, Euler or clothoid spiral. 6. Optical sensor (31c; 31 d; 31 e) according to any one of claims 1, 3, 4 or 5 or Lighting module (41 c, 41 d, 41 e) according to any one of claims 1, 2, 4 or 5, wherein the optical element with free-form surface (6f) in the form of a cylinder (6) is designed as a deflection, the underside of which is provided with a mirror coating is formed by the free-form surface (6f). 7. An optical sensor (31 a, 31 b, 31 c, 31 d, 31 e) according to claim 1, 3, 4, 5 or 6 or lighting module (41 a, 41 b, 41 c, 41 d, 41 e) according to one of claims 1, 2, 4, 5 or 6, wherein the movable optical element (3) is given by a movably mounted axicon (3) along its axis of symmetry. 8. Optical sensor (3 lb; 3 1 c; 31 d; 31 e) according to any one of claims I, 3, 4, 5 or 6 or  The illumination module (41b; 41c; 41d; 41e) according to any of claims 1, 2, 4, 5 or 6, wherein the variable optical element (MMA) is provided by a micro mirror array (MMA). 9. Optical sensor (31 a, 31 b, 31 c, 31 d, 31 e) according to one of claims 1, 3 to 7 or 8 or lighting module (41 a, 41 b, 41 c, 41 d, 41 e) one of claims 1, 2, 4 to 7 or 8, wherein the light source (1) is given by a white light source, in particular a superluminescent diode, and the sensor (31 a; 3 1 b; 3 1 c; 3 1 d; 3 le) or the illumination module (41a; 41b; 41c; 41d; 41e) comprises a beam splitter (4; 4a) and a collimating lens (2). 10. An optical sensor (31a; 31b; 31c; 31d; 31e) according to any one of claims 1, 3 to 8 or 9, wherein the sensor (31a; 31b; 31c; 31d; 31e) at least two lenses (5, 9) provided for imaging on the detector (10). 1 1. Optical sensor (3 Id) according to any one of claims 1, 3 to 9 or 10 or  Lighting module (41 d) according to any one of claims 1, 2, 4 to 8 or 9, wherein the sensor (31 d) or the illumination module (41 d) comprises a beam splitter (4a) which splits the incoming light from the light source proportionally in a  Detection beam, at the end of which the surface (7a) of the workpiece to be measured (7) is located and a reference beam path, at whose end there is a reference mirror (R). 12. Optical sensor (3 Id) or lighting module (41d) according to claim 1 1, wherein the beam splitter (4a) merges the light reflected from the reference mirror (R) and the surface of the workpiece light in the direction of the detector (10), such that at the detector (10) the composite signal from the reference beam path and the Detekti on sstrah 1 engan g can be evaluated. 13. Optical sensor (31d) or lighting module (41d) according to claim 12, wherein the reference mirror (R) in its distance from the beam splitter (4a) can be changed over time, whereby the composite signal at the detector (10) as  Interference signal in the time domain (English time domain, TD) can be analyzed. 14. Optical sensor (3 Id) or lighting module (41d) according to claim 12, wherein between the beam splitter (4a) and the detector (10) means for spectrally separating the composite signal are provided so that the detector (10) the composite Signal as a decomposed into several spectral channels  Interference signal (English frequency domain, FD) can be analyzed. An optical sensor (31a; 31b; 31c; 31d; 3 le) according to any one of claims 1, 3 to 13 or 14 or lighting module (41a; 41b; 41c; 41d; 41e) according to any one of claims 1 to 2 . 4 to 9, or 11 to 14, wherein the sensor (31a; 31b; 1c; 31d; 31e) and the  Illumination module (41a, 41b, 41c, 41d, 41e) has an exchange interface to the  Coupling one or the illumination module (41a; 41b; 41c; 41d; 41e) to the sensor (31a: 31b; 1c; 31d; 31e). 16. A method for measuring a borehole, in particular an internal thread of a workpiece (7) by means of a coordinate measuring machine with the aid of a sensor (31a; 3 lb; 3 lc; 3 ld; 3 le) or a lighting module (41a; 41b; 41c; 41d; 41e) according to one of the preceding claims, wherein in a first step the sensor (31a; 31b; 31c; 31d; 31e) or the lighting module (41a 41b: 41c, 41d, 41e) through the Coordinate inatenmessgerät to a desired position within the borehole or internal thread of the workpiece (7) is moved, characterized in that in a second step by means of a movable and / or variable optical element (MMA; 3) of the sensor (31a, 31b; 31c, 31d, 31e) and the Illumination module (41a: 41b; 41c; 4 ld; 41e) is the location of the light from the at least one light source (1) of the sensor (31a; 31b; 31c; 31d; 31e) or the illumination module (41a; 41b; 41c; 4 ld; 4Ie) on a diffractive optical element (5f) and / or an optical element with the free-form surface (5f; 6f) At least on the way from the at least one light source (1) to the surface (7a) of the workpiece to be measured, the sensor (31a; 31b; 31c; 31d; 31e) or the illumination module (41a; 41b; 41c; 41d; 41e) (7) is changed such that the portions of the surface (7a) of the workpiece to be surveyed are moved into the focus area of the sensor (31a; 31b; 31c; 31d; 31e) or the illumination module (41a; 41b; 41c; 41d; 41e ) reach. 17. The method according to claim 13, wherein in a third step intensity signals from the focal region of the sensor (31a; 31b; 31c; 31d; 31e) or of the illumination module (41a; 41b; 41c; 41d; 41e) from one surface for the registration of  Depending on the position of the movable and / or variable optical element (MMA; 3) of the sensor (31a; 31b; 31c; 31d; 3), the detector (10) of the sensor (31a; 31b; 31c; 31d; le) or the  Illumination module (41) and / or in dependence on the position of a reference mirror (R) of the sensor (31a; 31b; 31c; 31d; 1e) or of the light illumination module (41a; 41b; 41c; 41d; 41e) which is movable in its normal direction and / or or as a function of the frequency or wavelength of the light detected by the detector (10). 18. The method according to claim 14, wherein the second step contributes to a focal region which is changed in its lateral distance from the sensor (31a; 31b; 31c; 31d; 31e) or to the illumination module (41a; 41b; 41c; 41d; 41e) maintaining the position approached in the first step or the first step for another desired position within the internal thread while maintaining the position of the movable and / or variable optical element (MMA; 3) of the sensor (31a; 31b; 31c 3 ld; 31c) or the illumination module (41a; 41b; 41c; 41d; 41e) are repeatedly executed until, in the third step that follows each time, the complete information about the  Surface data of the section of the internal thread to be measured is present.