DE10013725A1 - Measurement device directs beam to measurement scale and receives reflections of beam to produce phase shifted interference signals which are then evaluated - Google Patents

Abstract

A radiation source (4) directs a beam to a measurement scale (8). The beam is reflected from a diffraction grating of the measurement scale into the waveguides (12,18) of a waveguide coupler (10) that outputs phase shifted interference signals which are detected by photodiodes (30,32,34) and analyzed by an evaluation unit. An Independent claim is also included for a miniaturized optical scanning head.

Description

The invention relates to a measuring device as well a method of measuring a path of a relative movement between the measuring device and a measure stab on a measuring track with a diffraction grating has.

For measuring a path with a relative movement between a measuring device and a scale, at for example to control machine tools as well in coordinate measuring systems, are predominantly incorrect mental encoders, magnetic length measuring systems and La Serinterferometer used. Laser interferometer are for example in the form of sensor heads for in industrial applications available. You point for example waveguide couplers as beam splitters and external evaluation units, whereby their ferti supply, for example, either based on silicon optics and electrical integrated on a chip Coupling to the evaluation unit or through inte grilled optics on glass if necessary with fiber coupling Detectors and the laser to the evaluation unit can follow. With such interferometers high resolutions in the nanometer range can be achieved. In principle, however, there is a dependency on  the laser wavelength and the refractive index distribution of the Measuring section that requires extensive corrections.

Another disadvantage of the well-known Interfero meters is that they have a relatively large space have structure and therefore for example for are not suitable for use in microsystems.

The invention has for its object a Measuring device for measuring a path in a re relative movement between the measuring device and a Specify the scale for the dependencies of the measurement result of the wavelength of the used Radiation and the refractive index distribution of the measuring section are reduced and at the same time low Have space requirements.

This task is duch in claim 1 given teaching solved.

According to the invention, a waveguide coupler is used, such as that used in connection with a fiber, for example from the article "Integrated optics on glass and silicon for sensor applications" by E. Voges in "Technisches Messen" 58 ( 1991 ), pp. 140-145 integrated optical interferometer is known. In contrast to the known interferometers, in the measuring device according to the invention, the radiation of the radiation source, for example a laser, is in principle only split at the grating, with coupling of the radiation from the radiation source into the waveguide coupler only after the diffraction on the scale he follows. This makes it possible to attach the radiation source as an independent component to a substrate having the waveguide coupler.

In this way, the space requirement is invented inventive measuring device compared to that from the  State of the art measuring devices essential Lich reduced. In particular, the inventions measuring device according to the invention as a miniaturized measuring implement a device that is versatile, for example in machine tools and coordinates measuring systems and for the regulation of micro drives.

When operating the measuring device according to the invention there are phase shifted interference signals at the output of the waveguide coupler, the evaluation of which is generally known from the prior art, for example by the article "Interferometric real-time path system with completely dielectric, integrated optical sensor head" by H. Grübel and G. Nitsch in Technischen Messen 58 ( 1991 ), pp. 165-169. If, for example, a 3 × 3 coupler is used, at whose three outputs three interference signals that are phase-shifted by 120 ° can be detected, these interference signals can first be detected with the aid of photodiodes. The voltages corresponding to the interference signals at the output of the photodiodes form a three-phase system consisting of three rotary pointers which are 120 ° out of phase with one another. When the measuring device moves relative to the scale, the rotary pointers rotate in the coordinate system, where their phase relationship relative to one another remains constant. Here, the angle through which the rotary pointers turn is a measure of the distance traveled in the relative movement between the measuring device and the scale. By measuring the angle around which the rotary pointers rotate, a measurement of the path in the relative movement between the measuring device and the scale is thus made possible. In addition, the direction in which the measuring device moves relative to the scale is made possible in this way. Furthermore, with the measuring device according to the invention, with appropriate training of the evaluation means, variables derived from the path, for example the speed or acceleration of the measuring device relative to the scale, can be measured.

The use of a scale has the advantage that reference marks can be realized in a simple manner leave one to one during the relative movement clear and constantly reproducible reference This way you can easily Realize measuring devices that measure the when moving along the scale between two punk The scale of the distance covered lichen and for which, in addition, based on the ref enzmarke always a clear reference to a fixed Reference point on the scale is given.

With the measuring device according to the invention Path measurements with any relative movements possible light, especially the measurement of lengths with linea ren relative movements and the measurement of angles Angular movements.

According to the invention, any waveguide can be used couplers are used to overlay the radiation diffracted at the diffraction grating for formation phase-shifted interference signals are suitable. The waveguide coupler is expediently one n × m coupler, especially a 3 × 3 coupler like this provides an embodiment. The manufacturing tech nisch is the simplest form of such an n × m coupler a 2 × 2 coupler, in which the two outputs of the Wel lenleiterkopplers phase-shifted interference signals deliver le that can be detected with photodiodes. A disadvantage of such a 2 × 2 coupler, however, is that  that the waveguide coupler fluctuates in intensity of the beam from the radiation source is not compensated. To compensate for such fluctuations in intensity an additional is then possible, for example Liche monitor diode required, the intensity measures. In contrast, a 3 × 3 coupler is used Compensation for fluctuations in intensity.

A further development of the embodiment with the 3 × 3 coupler provides that the interference signals on Phase the output of the waveguide coupler by approximately 120 ° are moved. Designed in this embodiment the evaluation of the output signals of the waves conductor coupler particularly simple. It is also possible couplers with a larger number of outputs to use the out-of-phase interference deliver signals. However, such couplers are on more agile to manufacture and therefore more expensive. Except they increase the space requirement of the measuring device.

Another embodiment provides that the Scale inclined to the direction of incidence of the radiation is arranged. This embodiment has the front part that for decoupling the beam of the beam simple optical elements can be used can. In these embodiments the 0th diffraction order of the diffracted radiation is not reflected back into the radiation source, so that interference caused by such back reflections gene, especially the radiation source avoided are.

Basically, it can be sufficient to have one Use radiation source, for example Generates radiation with two wavelengths. To measure However, increasing security sees a further development extension of the measuring device according to the invention that  the radiation source he monochromatic radiation testifies.

According to another development, the Radiation source coherent radiation. In this way the measurement reliability can be increased further.

According to the invention, any radiation source are used, if necessary Beu by diffraction on the diffraction grating is generated. It is expedient that radiation source according to the invention a laser, esp especially a laser diode. Lasers are cheap available components and enable a high measurement reliability.

According to another training, the Radiation source emits radiation through a waveguide ter, especially an optical fiber, to size Rod.

Another embodiment provides that the Radiation source than on an active optical sub strat, for example gallium arsenide, integrated Component is formed. That way it's at possible, for example, the radiation source between the arms of an integrated waveguide coupler in to integrate the substrate of the coupler. To this This results in a particularly compact structure.

In the sense of a compact structure and a knockout cost-effective production, it is also advantageous that the waveguide coupler as on a substrate, in particular glass substrate, integrated component is formed.

In the embodiments with the integrated Radiation source and the integrated waveguide couplers can basically both components on one and the same substrate. Advantageously  are the radiation source and the waveguide coupler, however, as separate integrated components trained, which are firmly connected. On in this way the manufacture is simplified. The Radiation source and the waveguide coupler can be glued together, for example.

If it is not necessary, regarding the position of the measuring device along the whole Measurement path a clear reference to a fixed Be to get traction point on the scale, but le diglich when moving the measuring device along of the scale between two points relative to the To measure the distance traveled, that's it sufficient if the scale has a single measuring track has. If on the other hand a clear reference to a fixed reference point on the scale is required is an extremely advantageous next education of the teaching according to the invention that the measure stab has a second measuring track or a second Scale with a second measuring track is provided that the radiation source or a second radiation source directs a beam onto the second measuring track and that a second waveguide coupler with at least two waveguides is provided, which on the second measuring track are directed that of the second Measurement track reflected or transmitted through this and on this diffracted radiation into the waveguide of the second waveguide coupler, wherein in a superposition of the second waveguide coupler radiation coupled into the waveguide takes place to form out-of-phase interference signals Outputs of the second waveguide coupler, the second waveguide coupler with the detection means is connected to the detection of the interference signals.  

In this embodiment, two at the Irradiation of the two measurement tracks generated, of each other other independent diffraction patterns evaluated. On this is the area of uniqueness, i. H. the Area in which the relative movement between the Scale and the measuring device a clear reference the position of the measuring device to a fixed loading traction point on the scale, enlarged. By appropriate training of the measuring tracks, it is prin possible to uniquely hold, which is larger than that when moving the Meßvor direction along the scale relative to this is the maximum distance traveled. That way along the entire path that the measuring device relative to the scale, a clear one Relation of the position of the measuring device to a fixed one Given the reference point on the scale. So that is measuring device according to the invention, for example can be used to control micro drives. Is also in the embodiment with only one measurement track and a diffraction grating a uniqueness area available; however, this is for practical use conditions in which there is a clear reference to the position of the Measuring device to a fixed reference point on the Scale is required, usually too small.

Another development of the embodiment with the second measuring track provides that this is a Beu has grating, wherein the diffraction grating two measuring tracks relative to each other have a constant. When using a second Beu is compared to the embodiment, in which a re reference mark is used, the uniqueness range increased, within which an absolute position determination  is possible.

If both in the sense of a simple structure Measurement tracks with one and the same radiation source one embodiment sees before that means are provided that the radiation the radiation source for irradiating the two measuring split tracks.

A training of the aforementioned execution form provides that the two measurement tracks are relative to each other and inclined away from the radiation source Surfaces are arranged that line up on an edge adjoin others such that the edge is the radiation the radiation source for irradiating the two measuring splits tracks. This embodiment is special simple and therefore inexpensive to manufacture.

However, the second measurement track can be irradiated a separate radiation source can also be provided, as is provided by another embodiment.

Can according to the respective requirements Means for substantially vertical coupling of the reflected on the measuring track or trans through it averaged radiation into the waveguide of the waves conductor coupler may be provided. These funds can for example, in the radiation direction behind the Radiation source arranged grating coupler or Pris Menkoppler be formed.

If necessary, according to another Aus a decoupling optics can be provided, the the radiation from the radiation source onto the measurement track directs.

Another development of the invention Teaching provides that for the coupling of the Beu Diffraction grating diffracted radiation into the waveguide a coupling optics of the waveguide coupler, in particular  a lens is provided.

Finally sees a further training of the inventor inventive measuring device that the detection have medium photodiodes. Because photodiodes as one fold and inexpensive standard components available stand in this way is the structure of the Measuring device according to the invention simple and therefore ko designed at low cost.

The radiation source and the waveguide coupler can according to an embodiment of the Invention according teaching on the same side of the scale be arranged such that from the scale reflect beam and diffracted by its diffraction grating into the waveguide of the waveguide coupler couples.

However, the scale can also be in radiation direction between the radiation source and the waveguide ter be arranged such that by the scale transmitted and diffracted at its diffraction grating Radiation in the waveguide of the waveguide coupler lers couples in as this is another embodiment provides.

The invention further relates to a miniaturi based optical scanning head according to claim 24. Er According to the invention, the beam is in this readhead source and the waveguide coupler than on one Integrated components formed substrate. This he enables a particularly compact design of the scanning head. Developments of the scanning according to the invention head are given in claims 25 to 27.

A method according to the invention is claimed 28 and a further development of this method in the An pronounced 29.

The invention is described below with reference to the accompanying  highly schematic drawing tert, are shown in the exemplary embodiments.

It shows

Fig. 1 shows a schematic side view of a first embodiment of he inventive measuring device,

Fig. 2 in the same representation as Fig. 1 shows a second embodiment of he inventive measuring device,

Fig. 3 shows a schematic plan view of an embodiment of a TES drit OF INVENTION to the invention the measuring device,

Fig. 4, in the same representation as Fig. 3 shows a fourth embodiment of he inventive measuring device without the scale

Fig. 5 is a side view of the measuring apparatus according to Fig. 4 with the scale,

Fig. 6 is the same view as FIG. 3, a fifth embodiment in which a scale is used with two measuring tracks of he inventive measuring device,

Fig. 7, the two measuring tracks of the scale in the measuring apparatus according to Fig. 6,

Fig. 8 is the same view as FIG. 3, a sixth embodiment of a measuring device according to the invention, in which the radiation from the radiation source is split for the irradiation of the two measuring tracks on one edge,

Fig. 9, the two measuring tracks of the scale of the measuring device shown in FIG. 8,

Fig. 10, in the same representation as Fig. 3 shows a seventh embodiment of an inventive measuring device it without the scale

Fig. 11 is a side view of the measuring device shown in FIG. 10 with the scale,

Fig. 12, the two measuring tracks of the scale of the measuring device shown in FIG. 10,

Fig. 13 in the same representation as Fig. 11, an eighth embodiment of a measuring device according to the invention and

Fig. 14, the two measuring tracks of the scale of the measuring device of FIG. 13.

The same or corresponding components are in the figures of the drawing with the same reference characters.

In Fig. 1, a first embodiment of a measuring device according to the invention is shown, which has a radiation source 4 in the form of a laser, which directs a laser beam to a scale 8 via a coupling optics 6 .

The scale 8 has on its surface facing the radiation 4 a measuring track with a diffraction grating, as shown in FIG. 7 above. The grating of the diffraction grating runs into the drawing plane in FIG. 1, the measuring device 2 being movable relative to the scale 8 parallel to the diffraction grating, ie into the drawing plane in FIG. 1 and out of the drawing plane.

The measuring device 2 also has a waveguide coupler 10 , of which only one waveguide 12 can be seen in FIG. 1. The waveguide coupler 10 is designed in the manner explained in more detail below with reference to FIG. 3 as a 3 × 3 coupler and, in addition to the waveguide 12, has a further wel conductor, the two waveguides leading to three outputs of the waveguide coupler. The Wel lenleiter 12 and the other, in Fig. 1 not recognizable waveguide of the waveguide coupler 10 are directed to the scale 8 such that reflected from the scale 8 and diffracted at the diffraction grating radiation are coupled into the waveguide. A coupling optics 14 is provided for this. The waveguide coupler 10 is designed as a component integrated on a substrate 16 . If required Lich, the waveguides 12 , 14 for coupling the radiation diffracted on the scale 8 in the drawing, waveguides, not shown, can be pre-switched. Further, the outputs of the Wellenlei may be arranged downstream of terkopplers waveguide 10, which supply the reflected and overlaid in the waveguide 10 radiation detection means. Furthermore, the radiation source 4 can irradiate the scale 8 via a waveguide.

In Fig. 2, a second embodiment of a measuring device according to the invention is shown, which differs from the embodiment of FIG. 1 in that the scale 8 is arranged inclined to the measuring device 2 . This has the advantage that the decoupling optics 6 of the radiation source 4 can be formed by a simpler optical element compared to FIG. 1.

In Fig. 3, a third embodiment of a measuring device 2 according to the invention is shown, which differs from the embodiment of FIG. 1 in that the radiation source 4 is formed as a component integrated on an active optical substrate, 10 of the substrate 16 of the waveguide coupler 10 separate component . From Fig. 3 it is clear that the radiation source 4 between the waveguide 12 and another waveguide 18 of the waveguide coupler 10 is arranged and connected to the substrate 16 of the waveguide coupler 10 . From Fig. 3 it can also be seen that the Wel lenleiterkoupler 10 is designed as a 3 × 3 coupler and has three outputs 20 , 22 , 24 .

The measuring device 2 is movable in front of the scale 8 and parallel to the diffraction grating in the direction of a double arrow 26 relative to the scale 8.

The coupling-out optics of the radiation source 4 and the coupling-in optics of the waveguide coupler 10 are only indicated schematically at 28 in this exemplary embodiment.

As detection means for the detection of the output signals at the outputs 22 , 24 , 26 of the waveguide coupler 10 , photodiodes 30 , 32 , 34 are provided in this exemplary embodiment, the output voltages of which are supplied with evaluations, not shown in the drawing.

When the measuring device 2 according to the invention is in operation, the radiation source 4 directs a beam onto the scale 8, the beam being diffracted at the diffraction grating and reflected by the scale 8. Different diffraction orders of the diffracted radiation are coupled into the waveguide 12 , 18 of the waveguide 10 and are superimposed in this to form phase-shifted interference signals in such a way that three 120 ° phase-shifted interference signals are present at the outputs 20 , 22 , 24 . The interference signals at the outputs 20 , 22 , 24 are detected by the photodiodes 30 , 32 , 34 , the output voltages of which are fed to the evaluation means.

The output voltages of the photodiodes 30 , 32 , 34 form a three-phase rotary pointer system, the rotary pointers of which are out of phase with one another by 120 °. When the measuring device 2 moves relative to the measuring rod 8 , the rotary pointers rotate in their coordinate system, their phase relationship to one another being maintained. The angle by which the rotary pointers rotate during a relative movement between the measuring device 2 and the scale 8 is a measure of the distance covered during this relative movement. By determining this angle, it is thus known, as is known per se from the prior art, that the path covered during the relative movement between the measuring device 2 and the scale 8 can be determined. By determining the direction in which the rotary pointers turn, the direction in which the measuring device moves relative to the scale can also be seen. Furthermore, variables derived from the path, for example the speed and acceleration of the measuring device relative to the scale, can be determined.

Characterized in that the incident radiation of the radiation source 4 is only split at the diffraction grating of the scale 8 and only the partial beams reflected at the diffraction grating are coupled into the waveguide 12 , 18 of the waveguide coupler 10 , the radiation source 4 can be used as an independent component to fix the substrate 16 , as is the case with the exemplary embodiments according to FIGS . 1 and 3.

In this way, a miniaturized measuring device direction formed, for example in microsystem men can be used.

In FIG. 4, a fourth embodiment of a measuring device 2 according to the invention, which differs from the embodiment shown in FIG. 3 that the coupling of the light reflected on the scale and diffracted at the diffraction grating radiation in the waveguides 12, 18 of the waveguide coupler 10 via a grating coupler 36 takes place. This has the advantage that ver can be dispensed with with regard to the coupling to external beam shape optics. This facilitates the assembly and adjustment of the measuring device 2 . Furthermore, the measuring device 2 is implemented in this way with a minimal number of external components. It is then, however, a coupling grating or a coupling prism required for coupling the radiation from the radiation source 4 . When using active optical substrates in this embodiment, the radiation source can be integrated on the substrate 16 of the waveguide coupler 10 and manufactured with it in one production step. The radiation source 4 can be surface-emitting or can be realized with a grating coupler or prism coupler.

Fig. 5 illustrates the arrangement of the scale 8 relative to the measuring device 2 in the execution example according to Fig. 4.

In Fig. 6, a fifth embodiment of a measuring device 2 according to the invention is shown, which differs from the previous embodiments in that the scale 8 in addition to a first measuring track 38 with a first diffraction grating 40 has a second measuring track 42 with a second diffraction grating 44 . The diffraction gratings 40 , 44 run parallel to one another and have non-prime lattice constants.

In the embodiment according to FIG. 6, the output optical system 6 generates two partial beams 46 'and 46 ", of which the sub-beam 46' on the first diffraction grating of the first measuring track 38 and the sub-beam 46 'is directed to the second diffraction grating 44 of the second measuring track 42 .

For evaluation of a beam by diffraction of the part 46 "of the second diffraction grating 44, he testified diffraction image, a second waveguide coupler 48 is provided which is constructed and ar beitet, as has been described above for the waveguide 10 degrees. The evaluation of the output signals of the second waveguide coupler 48 is carried out in the same manner as that previously described for the evaluation of the output signals of the waveguide coupler 10 .

Because two independent diffraction patterns are evaluated in the exemplary embodiment according to FIG. 5, there is always a clear relationship between the position of the measuring device 2 and a fixed reference point on the scale 8. It can thus be clearly determined in what position the measuring device 2 is currently relative to the scale 8. If the measuring device 2 according to the invention is used, for example, to control a micro drive, it is not only possible to ascertain which path the micro drive has covered during a movement; rather, it can also be determined in which position the micro drive is currently relative to a fixed reference point on the scale.

In Fig. 8, a sixth embodiment of a measuring device 2 according to the invention is shown, which differs from the embodiment of FIG. 6 in that the measuring tracks 38 , 42 of the scale 8 relative to each other and from the radiation source 4 inclined surfaces 50 , 52nd of a body 54 are arranged, the surfaces 50 , 52 adjoining one another at an edge 56 . The formation of the partial beams 46 ', 46 "takes place in this exemplary embodiment, not through the decoupling optics 6 of the radiation source 4 , but through the edge 56 .

Fig. 9 shows the measuring tracks 38 , 42 of the scale 8, the measuring track 38 in this embodiment example having a reference mark, which is sufficient for determining the absolute position of the measuring device 2 in relation to the scale 8. A detector 59 in the form of a photodiode (cf. FIG. 8) is provided for detecting the reference mark.

Fig. 10 shows a seventh embodiment of a measuring device 2 according to the invention, which differs from the embodiment according to FIGS. 6 and 8 in that the formation of the partial beams len 46 ', 46 "for irradiating the measuring tracks 38 , 42 takes place through a grating 58 In this exemplary embodiment, the first measuring track 38 has a reference mark (cf. FIG. 12) A detector 59 in the form of a photodiode is provided for detecting the reference mark.

Fig. 11 illustrates the arrangement of the scale 8 relative to the gauge 2.

From Fig. 12, which shows the measuring tracks 38 , 42 of the measuring rod 8 in the embodiment according to FIG. 10, it can be seen that the first measuring track 38 has a reference mark and the second measuring track 42 has a diffraction grating.

Fig. 13, an eighth embodiment shows a measuring device according to the invention 2, in which the two waveguide couplers 10, 48, which are necessary for evaluation of the two diffraction images which are generated by irradiation of the two measuring tracks 38, 42, on two superposed substrates 60, 62 are realized.

Fig. 14 shows the measuring tracks 38 , 42 used in the measuring device 2 according to FIG. 13, the diffraction grating 40 , 44 with mutually alien lattice constant constant.

Claims (29)

1. Measuring device for measuring a path during a relative movement between the measuring device ( 2 ) and a scale (8), which has at least one measuring track ( 38 ) with a diffraction grating ( 40 ),
with at least one radiation source ( 4 ) for directing a beam onto the scale (8),
with at least one waveguide coupler ( 10 ) with at least two waveguides ( 12 , 18 ), which are directed to the scale (8) in such a way that on the diffraction grating ( 40 ) of the scale (8) diffraction radiation into the waveguide ( 12 , 18), couples in the waveguide being (10) a superposition of, in the waveguides (12, 18) coupled radiation is effected for the formation of phase-shifted interference signals as output signals of the waveguide coupler (10)
with detection means for detecting the interference signals and
with evaluation means for evaluating the detected signals. 2. Measuring device according to claim 1, characterized in that the waveguide coupler ( 10 ) is an n × m coupler, in particular a 3 × 3 coupler. 3. Measuring device according to claim 2, characterized in that the interference signals at the outputs ( 20 , 22 , 24 ) of the waveguide coupler ( 10 ) are out of phase by approximately 120 °. 4. Measuring device according to claim 1, characterized records that the scale (8) to the direction of incidence the radiation is arranged inclined. 5. Measuring device according to claim 1, characterized in that the radiation source ( 4 ) generates monochromatic radiation. 6. Measuring device according to claim 1, characterized in that the radiation source ( 4 ) generates coherent radiation. 7. Measuring device according to claim 1, characterized in that the radiation source ( 4 ) is a laser, in particular a laser diode. 8. Measuring device according to claim 1, characterized in that the radiation source ( 4 ) is formed as an integrated on an active optical substrate, for example Gallium arsenide. 9. Measuring device according to claim 1, characterized in that the radiation source ( 4 ) directs the radiation via a waveguide, in particular an optical fiber, to the scale (8). 10. Measuring device according to claim 1, characterized in that the waveguide coupler ( 10 ) as a on a substrate, in particular glass substrate, integrat tes component is formed. 11. Measuring device according to claim 1, characterized in that the radiation source ( 4 ) and the Wel lenleiterkoppler ( 10 ) are formed as separate integrated construction parts that are firmly connected to each other. 12. Measuring device according to claim 1, characterized shows that the scale has a reference mark and that a detector for detecting the reference mark is provided. 13. Measuring device according to claim 1, characterized in that the scale (8) has a second measuring track ( 42 ) or that a second scale is provided with a second measuring track,
that the radiation source ( 4 ) or a second radiation source directs a beam onto the second measuring track ( 42 ),
that a second waveguide coupler ( 48 ) with at least two waveguides is provided, which are directed towards the second measuring track ( 42 ) in such a way that from the second measuring track ( 42 ) is reflected or transmitted by the se and diffracted at this radiation into the waveguide of the second waveguide coupler (48) couples, in the second waveguide coupler (48) are a superposition of the ter in the Wellenlei radiation coupled to the formation of phase-shifted interference signals at outputs of the second waveguide coupler (48), said second waveguide (48) with the detection means for detecting the interference signals at its output is connected. 14. Measuring device according to claim 12, characterized in that the second measuring track ( 42 ) has a second diffraction grating ( 44 ), the diffraction grating ter ( 40 , 44 ) of the two measuring tracks ( 38 , 42 ) having mutually alien grating constants. 15. Measuring device according to claim 12, characterized in that means are provided which divide the radiation development of the radiation source ( 4 ) for irradiating the two measurement tracks ( 38 , 42 ). 16. Measuring device according to claim 12, characterized in that the two measuring tracks ( 38 , 42 ) on rela tive to each other and from the radiation source ( 4 ) away inclined surfaces ( 50 , 52 ) are arranged, which on one edge ( 56 ) to each other adjoin such that the edge ( 56 ) divides the radiation from the radiation source ( 4 ) for irradiating the two measuring tracks ( 38 , 42 ). 17. Measuring device according to claim 12, characterized in that a separate radiation source is provided for irradiating the second measuring track ( 42 ). 18. Measuring device according to claim 1, characterized in that means for substantially vertical coupling of the diffraction grating ( 40 ) diffracted radiation into the waveguide ( 12 , 18 ) of the waveguide coupler ( 10 ) are provided. 19. Measuring device according to claim 1, characterized in that a decoupling lens ( 6 ) is provided which directs the radiation of the radiation source ( 4 ) onto the measuring track ( 38 or 42 ). 20. Measuring device according to claim 1, characterized in that a coupling optics ( 14 ), in particular a lens, is provided for coupling the radiation diffracted at the diffraction grating into the waveguide ( 12 , 18 ) of the waveguide coupler ( 10 ). 21. Measuring device according to claim 1, characterized in that the detection means have photodiodes ( 30 , 32 , 34 ). 22. Measuring device according to claim 1, characterized in that the radiation source ( 4 ) and the Wel lenleiterkoppler ( 10 ) on the same side of the measuring rod ( 8 ) are arranged such that from the measuring rod ( 8 ) reflected and on whose diffraction grating ( 40 ) couples diffracted radiation into the waveguides ( 12 , 18 ) of the waveguide coupler ( 10 ). 23. Measuring device according to claim 1, characterized in that the scale (8) is arranged in the radiation direction between the radiation source ( 4 ) and the waveguide coupler ( 10 ), such that transmitted by the scale (8) and at its diffraction grating ( 40 ) couples diffracted radiation into the waveguide ( 12 , 18 ) of the waveguide coupler ( 10 ). 24. Miniaturized optical scanning head, in particular for use in a measuring device according to one of the preceding claims,
with a radiation source ( 4 ) designed as a component integrated on a substrate and
with a waveguide coupler ( 10 ) designed as a component integrated on a substrate, which is connected to the radiation source. 25. Read head according to claim 24, characterized in that the radiation source ( 4 ) and the Wel lenleiterkoppler ( 10 ) are formed as separate, firmly connected integrated components. 26. Read head according to claim 24, characterized in that the substrate on which the waveguide coupler ( 10 ) is integrated, an optically active sub strate and that the radiation source ( 4 ) is integrated on the substrate of the waveguide coupler. 27. Read head according to claim 24, characterized in that the radiation source ( 4 ) is a Laserdio de. 28. A method for measuring a path during a relative movement between a measuring device and a scale, which has a measuring track with a diffraction grating.
in which radiation from a radiation source is directed onto the scale and diffracted at the diffraction grating, in which the diffracted radiation is coupled into a waveguide coupler with at least two waveguides, and
in which the coupled into the waveguide of the waveguide coupler radiation is superimposed to form phase-shifted interference signals as output signals from the waveguide coupler and
in which the interference signals are detected by detection means and the detected signals are supplied to evaluation means. 29. The method according to claim 28, characterized in net that a measuring device according to one of the claims 1 to 23 is used.