CH703647A1 - Position measuring device e.g. absolute encoder, for determining absolute position of e.g. lever in resting position, has light receiver including light receiver elements and formed as sensor regions co-operated with respective tracks - Google Patents

Abstract

The device i.e. encoder (10), has a light source i.e. organic LED, arranged at a distance from a light receiver, and a carrier plate provided with strip conductors on which a transparent substrate is arranged. The substrate and the plate are interconnected in a fixed manner by a flip-chip assembly. One of two tracks generates an incremental signal. The receiver is formed as sensor regions and includes a set of light receiver elements. One sensor region is co-operated with the track to generate the incremental signal, and the other region is co-operated with the other track i.e. encoded track. An independent claim is also included for a method for determining an absolute position of a movable part in a resting position.

Description

The invention relates to a position measuring device according to the preamble of claim 1 and a manufacturing method according to the preamble of claim 33.

State of the art

From US patent application no. 2006/0 007 541 a sensor head of a working with reflective light sensor head is known. This sensor head has a light source, which projects a light beam onto a physical scale, and two semiconductor substrates. The semiconductor substrates each comprise photodetectors to detect light which is reflected by a dimensional scale. Light source and semiconductor substrates are arranged in a box-like housing, wherein the light source at the bottom of the housing and the semiconductor substrates on the lid, with which the housing is closable, are arranged and fixed. The semiconductor substrates are fastened by turn-mounting on the lid.

The semiconductor substrates with the photodetectors are arranged opposite each other on both sides of the light source in a direction which is perpendicular to the direction of movement of the scale. Each semiconductor substrate has an electrical circuit, and the electrical circuits of both semiconductor substrates are connected to each other by electrical leads formed on the underside of the lid. Current-voltage transformers are formed directly on the semiconductor substrates in order to minimize disturbances.

A disadvantage of the previously known sensor head is its complex production. In this case, the semiconductor substrates must first be prepared and then attached to the housing cover. Then, the light source is placed and fixed to the bottom of the housing. Finally, the lid is mounted on the housing so that the light source is properly aligned with the semiconductor substrate. This must be done with the necessary precision so that the signals can be evaluated in the desired quality and ultimately the encoder works perfectly. Also, the production of the electrical connections to the two semiconductor substrates is complicated and expensive.

Object of the invention

It is an object of the present invention to provide a position measuring device which can be manufactured inexpensively in the desired precision required. Another object is to build a position measuring device with the smallest dimensions, with high accuracy and reliability. Yet another goal is to propose a position measuring device whose construction is insensitive to environmental influences. Another object is to provide a position measuring device which tolerates a certain installation tolerance and yet can ensure a reliable function.

description

This object is achieved in a position measuring device according to the preamble of claim 1, characterized in that on the side facing away from the dimensional side of the substrate, the light receiver is deposited in the form of a thin film structure consisting of several superimposed layers directly on the transparent substrate that at a distance from Light receiver is provided a light source and that a support plate is provided, on which the substrate is arranged. The light receiver is provided in the form of a thin film sensor in the mentioned layers is a recess for a light source., The light source is preferably formed so that it is involved in the processes for producing the sensors (light receiving elements), so that the dimensions and position of the Light receiver and the light source are given by masks. In this case, the light source can be formed by a diaphragm and an LED or by an OLED deposited directly on the substrate. In contrast to the prior art described above, no further adjustments are therefore necessary, which makes the production of the position measuring device considerably simpler, but also more reliable.

Embodiments of the position measuring device are described below, wherein the said preferred features - unless they exclude - can be implemented in any combination.

The method may moreover comprise, as method steps, the use of one or more of the mentioned preferred features of the device according to the invention (or the functions made possible by these features).

Thanks to the compact design of the sensor head, it is possible to produce encoders with other properties, such as position sensors with multiple sensor heads for the redundant detection of position values. Another possibility is to build very compact absolute encoders, which have built in the dimensional standard of a Manchester code or similar serial codes and make it possible to determine an absolute position value by a relative movement between the sensor head and dimensional scale.

These advantageous properties are best achieved when the scale of semicircular cylindrical reflectors is formed and the light source has certain dimensions. This in turn requires a precise position of the light source above the light sensor to obtain stable and reliable signals. The bundling of the entire amount of light incident on a division together with the compact sensor head makes it possible to build position detection units that have a high luminous efficacy and ensure the function with less light output. Thus, the inventive position measuring devices for battery devices are best used.

The use of a thin-film structure with an intrinsic layer has the advantage that reliable light receivers can be produced by simple means because of the presence of an inherently insulating intermediate layer. These layers have low dark currents and are particularly suitable for the construction of a sensor head for an encoder.

Advantageous embodiments of the position measuring device will become apparent from the features of the dependent claims.

The present invention is also a position measuring device, in particular encoder, comprising a support, a sensor head arranged on the support with a light source and a light receiver element, a measuring element which can be moved relative to the sensor head and has optical elements which can be mounted on a movable part of a device, for example a motor, and which can cooperate with the sensor head for determining an absolute position value, characterized that the sensor head is movably arranged on the support, and means are provided for displacing the sensor head relative to the support by a certain amount. The movable arrangement of the sensor head on the support has the advantage that the absolute position of a movable part, e.g. a shaft or other machine part can be determined in its rest position. This has great advantages in a work process and also in terms of safety.

Another independent aspect of the present invention relates to a method for determining the absolute position of a movable part in the rest position by means of a position measuring device, which allows the determination of the absolute position of the part by means of a relative to a sensor head movable measuring scale, with is coupled to the movable part, characterized in that is moved to determine the absolute position of the movable part in the rest position of the sensor head relative to the movable part.

The invention will be explained in more detail with reference to the drawing and an embodiment. It shows: <Tb> FIG. 1 <sep> Schematic and perspective view of the basic structure of an encoder consisting of a sensor head according to the invention and a physical scale spaced from the sensor head; <Tb> FIG. 2 <sep> schematically the structure of the sensor head consisting of glass substrate with sensor areas formed thereon, a carrier plate and an evaluation unit, which are each connected to one another in the flip-chip mounting method; <Tb> FIG. 3 <sep> the individual process steps for producing the sensor areas and contacting them; <Tb> FIG. 4 <sep> the individual process steps for the design of the light source; <Tb> FIG. 5 <sep> Schematically the assembly of the components on a wafer substrate; <Tb> FIG. 6 <sep> On average, a practical embodiment of an arranged in a housing encoder for small engines; <Tb> FIG. 7 Schematically, how, in a relative movement of the receiver element and the physical scale, the light intensities registered by the receiver element are converted into an analog signal and subsequently into a digital signal for the position determination; <Tb> FIG. Fig. 8 schematically illustrates the generation of an index signal by means of a single optical element and two receiver elements; <Tb> FIG. Fig. 9 schematically shows the generation of a position signal by means of two different optical elements, which are strung together according to a Manchester code, and two receiver elements; <Tb> FIG. FIG. 10 shows a plan view of a first exemplary embodiment of a sensor head according to the invention having a plurality of receiver elements with an incremental and an index track. FIG. <Tb> FIG. 11 <sep> is a plan view of a second embodiment of a sensor head according to the invention, in which the receiver elements are electrically connected by means of a separate conductor track; <Tb> FIG. 12 <sep> An embodiment of the invention with a light source having an LED disposed behind a shutter, the shutter substantially determining the dimensions of the light source; <Tb> FIG. 13 <sep> A circuit for optimum assignment of the index signal Zg formed by the scale embodiment; <Tb> FIG. 14 <sep> An embodiment of an absolute encoder with cold start position determination. <Tb> FIG. 15 <sep> is a perspective view of a kit encoder with motor; <Tb> FIG. 16 <sep> a back and side view of the housing with horizontal cable; <Tb> FIG. 17 <sep> is a sectional view of the housing of the kit encoder <Tb> FIG. 18 <sep> a preferred embodiment of the wave recording.

Fig. 1 shows an inventive encoder 10 comprising a sensor head 11 and a dimensional scale 13 which is movable relative to the sensor head 11 in a direction 15. Mass standardization in the context of the present invention is understood to mean a mass graduation or scale which is applied to a support or carrier and is suitable for reflecting and modulating a light beam when the material measure is moved relative to the sensor head. Such a dimensional embodiment may have the shape of a circular code disk or an elongated beam. The graduation itself has a pitch, each pitch being, by definition, capable of modulating a beam of light as the pitch is moved by the beam of light. Structures are known in which, for example, one half of the graduation is transparent and the other half is opaque. Advantageously, each division is represented by a reflective optical element suitable for focusing a light beam (e.g., hollow cylinder, concave mirror). However, it is also conceivable to use lattice structures, although their efficiency in light processing would be smaller than that of mirrors, by means of which the light beam is diffracted.

The sensor head 11 shown consists essentially of a support plate 17 and a transparent substrate 19, on the back side, i. that side, which faces the support plate 17, a light source 21 and light receiving elements 23 are arranged. The light source 21 emits a light beam whose major axis is designated by the reference numeral 22. Preferably, a light source is used which emits light in the visible range. For a better light signal with a smaller diffraction light with a wavelength below 460 nm is advantageous. The material measure 13 includes at least one first track 25 with first optical elements 27, which interacts with a first sensor area 29 of the material measure 13. In addition to the first track 25, according to the exemplary embodiment shown, a second track 31 with at least one individual optical element 33 is provided. This second track 31 cooperates with a second sensor area 35 of the sensor head 11. As can be seen from FIG. 1, the optical elements 27 of the graduation are arranged in a plane which is substantially parallel to the flat sides 37 of the substrate. In this case, the material measure 13 is arranged relative to the substrate 19 in such a way that the tracks 25, 31 in each case coincide with the sensor regions 29, 35 in a direction parallel to the axis 22 of the light beam.

The optical elements 27, 33 are formed as focussing lenses or mirrors, which collide incident light in each case focused on the sensor head 11. According to the embodiment shown, the optical elements 27, 33 have the shape of a circular half-cylinder. Here, the first track 25 serves to generate an incremental position signal, and the second track 31 to generate an index signal, as will be described in more detail below (description of FIGS. 7 and 8).

The position of the material measure relative to the sensor head is usually associated with a mounting tolerance, which directly affects the quality and reliability of the measurement signal. At assembly tolerance zero, the flat sides 37 of the substrate 19 are parallel to a plane passing through the scale 13, and the direction of movement 15 (= tangent to a circular path in the case of a provided on a circular scale) is perpendicular to a longitudinal central axis 39, which the sensor areas 29th , 35 and divides the light source 21 into two sections, respectively. Deviations from the exact relative orientation of the scale body 13 and substrate 19, which are indicated in Fig. 1 by arrow 41, the position signals from the two tracks 25 and 31 against each move (see below description of Fig. 10). At zero tolerance, the center line 43 of the scale embodiment will be substantially parallel to an axis 45 passing through the center of the light source 21, provided that the sensor areas 29, 35 are arranged symmetrically to the center of the light source. At zero tolerance of the distance between the material measure 13 and the sensor head 11, the nominal distance is determined primarily by the design of the optical elements 27, 33 of the material measure 13. In the context of the present invention, focusing optical elements and in particular three-dimensional (3D) reflectors are particularly preferred because they are particularly tolerant with respect to a variation of the center distance between the graduated body 13 and the substrate 19.

The inventive sensor head 11 according to FIG. 2 comprises the substrate 19 with the first and second sensor regions 29,35, the support plate 17 and an applied on the support plate 17 evaluation 47. Substrate 19, support plate 17 and evaluation 47 are by means of adhesive and Underfill mechanically firmly connected and sealed from the environment. The light source 21 is preferably an LED located behind a shutter which defines the dimension of the light source. Of importance for the present invention is that the sensor regions 29, 35 are deposited directly on the substrate in a multi-stage thin-film process, by means of which the sensors and the diaphragm are formed in a multi-stage etching process 49. This production method has the advantage that the relation between diaphragm 49 and sensor regions 29, 35 can be determined very precisely, so that these can be formed in an etching stage according to FIGS. 3 b and 4 b.

The electrical connection between the first and second sensor regions 29,35 and the support plate 17 is preferably done by means of flip-chip mounting. So that the heat-sensitive sensor areas 29,35 can not be damaged during the manufacturing process - which could be the case if "bumps" made of solder would be - for the electrical contact so-called "stud bumps" or ultrasonically mounted gold balls 53 on the off Aluminum formed top sensor portion 51 (Fig. 3a) applied. In turn, conductor tracks 55 are provided on the carrier plate 17. Above these tracks 55, a film 57 is attached, which at the location of the planned electrical connection recesses 59, which are filled prior to assembly with conductive adhesive 54 (Fig. 3e). By means of flip-chip mounting, substrate 19 and carrier plate 17 can now be connected to one another. In the non-conductive layer 57 recesses 59 are provided at the intended contact points. Suitable film formers are various plastics, such as e.g. Epoxy resins. After joining, the gap between the carrier plate 17 and the glass substrate 19 is then filled with a so-called "underfill" 61.

On the back 63 of the support plate 17 is the evaluation circuit 47, e.g. an AS1C, arranged. The connection of the evaluation circuit 47 with the support plate 17 can also be done by flip-chip mounting analogous to the connection between the glass substrate 19 and the support plate 17. For this purpose, 63 printed conductors 64 and a non-conductive layer 65 are applied with recesses 67 on the back. The recesses 67 coincide with the points of the evaluation circuit 47 to be contacted. In this, an electrically conductive adhesive is filled before the assembly of the support plate 17 with the evaluation circuit 47. The via from the front to the back is by means of apertures 69 in the support plate 17 which are connected to a conductive material, e.g. a solder or an electrically conductive adhesive are filled.

As is apparent from Fig. 2, in a recess 71 of the support plate 17, the light source 21, e.g. an LED, recorded. A spacer element 75 keeps the light source 21 at a distance from the glass substrate 19, so that between the aperture 49, an air gap 77 is provided. The air gap serves to reduce the internal reflection present in the substrate 19, and thus to achieve a better utilization of the light energy. The rear side of the LED light source 21 can be contacted by means of an electrically conductive adhesive 79.

Of importance for the application of the present invention is in particular the manner of manufacturing the sensor area and the aperture 49 in thin-film technology. In a first step, all layers which are necessary for the construction of the sensor regions are deposited over a large area onto a transparent substrate, preferably a glass substrate (FIG. 3 a). The large glass substrate is chosen so that a multiplicity of> 200, preferably> 2000 and particularly preferably> 10 000 sensor arrangements can be produced simultaneously. The selection of the substrate size is carried out depending on the existing coating device.

In the production of the light receiver, the following layers are preferably applied successively on the glass substrate 13 (FIG. 3 a), which preferably results in the construction of a PIN diode: <tb> 1. <sep> a conductive transparent layer 81, preferably a TCO (= Transparent Conducting Oxide ') layer, with a layer thickness between 10 and 100 nm, preferably 20 and 70 nm and particularly preferably between 25 and 50 nm. <tb> 2. <sep> a first n- or p + doped layer 83 with a layer thickness between 10 and 80 nm, preferably 20 and 70 nm and particularly preferably between 25 and 50 nm. <tb> 3. <sep> an intrinsic (intrisic) layer 85 with a layer thickness between 100 and 1500 nm, preferably 200 and 1000 nm and particularly preferably between 400 and 800 nm. <tb> 4. <sep> a second p + or n-doped layer 87 with a layer thickness between 10 and 80 nm, preferably 20 and 70 nm and particularly preferably between 25 and 50 nm and <tb> 5. <sep> a conductive upper layer 51 having a layer thickness between 200 and 2000 nm, preferably 500 and 1500 nm, and more preferably between 700 and 1200 nm.

The deposition of the various layers is preferably carried out by means of a CVD (chemical vapor deposition), PECVD (Plasma Enhanced Chemical Vapor Deposition) or other similar modified processes such as VHFCVD or HWCWD instead, i. E. a plasma enhanced chemical vapor deposition of preferably silane to produce an aSi: h (amorphous silicon) intrinsic layer. For the doping of the layers further gases are added to the silane containing the metals germanium (GeH) and / or boron (B, H).

After the glass substrate is coated with the above-mentioned layers, the shape and extent of the light-receiving elements and the light source is defined by applying a photoresist to the uppermost layer 51, exposing it to a mask with UV, and exposing either the unexposed or the exposed one Areas are replaced. Thereafter, in a first etching step, preferably by means of ion beam etching, the conductive covering layer 51, the second doped layer 87 and preferably a part of the amorphous silicon layer 85 are removed at those locations where the resist is detached. As a result, the structure of the light receiver is already formed (FIG. 3b). Instead of the amorphous silicon and similar materials could be used, which are preferably used for the formation of a PIN diode.

Thereafter, in a further step, the TCO layer is exposed at certain points, in which the amorphous silicon layer 85 and the first doped layer 83 essentially in a second etching step (ion beam etching and / or "reactive Ion Beam Etching" (RIE), or modified methods) are completely etched away (Figure 3c). The procedure may be analogous to the first etching process, i. the points not to be edited are masked first and then the non-masked points are edited. These process steps are well known to those skilled in the art, so that it need not be discussed in more detail at this point. The exposed areas form after removal of the amorphous silicon layer, the one electrical contact point 89 of the light receiver. The other contact point 91 is formed by the conductive cover layer 51.

Subsequently, the sensor region is preferably coated with a protective layer 93, preferably an SiO 2 layer (FIG. 3d). In this case, the contact points 89,91 are each left by etching or in the lift-off - method. It should be pointed out that FIGS. 3 and 4 serve exclusively to illustrate the production process and that the layer thicknesses shown do not coincide with the actual layer thicknesses.

As is apparent from Fig. 4, the aperture used in this embodiment for forming the light source by means of the same process steps as used for the preparation of the light receiving structures and the contacts, can be prepared. In this case, in the second etching step (FIG. 4c), the diaphragm 49 is formed by once again etching a point etched in the first etching process.

The LED may be adhered to the uppermost layer 51 by placing it on a spacer 75 (see Fig. 12). The spacer 75 provides a defined gap between the substrate 19 and the light source 21. This defines (reliably) a cavity for the adhesive 79.

Finally, the sensor areas are electrically connected to the support plate 17 by means of flip-chip mounting. In the same method step, the front side of the light source is also contacted with the metal layer 51 in which printed conductors not shown in detail are formed (contact point 95).

Fig. 5 shows an arrangement of a plurality of juxtaposed sensor heads on a large support plate 4.97 in the form of a wafer. The figure shows the sensor heads 11 which are mounted on the carrier material 97 by means of flip-chip mounting. The carrier material is a plate made of electrically nonconductive material, on which, in a preceding coating process, printed conductors for contacting a multiplicity of light receivers 11 and evaluation circuits 47 are applied both on the front and rear side. Incidentally, the light sources 21 may be previously applied either directly to the glass substrate 19, e.g. be integrated by gluing, or in a recess of the carrier material 97. Subsequently, the rear side of the carrier material 97 can be equipped with the evaluation circuits 47. The assembly of the evaluation circuit 47 can also be done in the flip-chip method. In this case, the substrate 19 can be connected to the light receiver elements 23 and the evaluation circuit 47 simultaneously with the carrier plate 17. If the sensor heads 11 are contacted with the evaluation circuits 47, the encoder function can already be tested. This can be done in an automated process. Only then is the carrier material sawed.

On one side edge of the carrier material 97, two indentations 99 are provided, in which pins 101 of a tool can engage. With the help of the indentations 99 and corresponding tools, the carrier material 97 can be precisely aligned during the various process steps. This allows a cost-effective production.

In Fig. 6, an example of a miniature motor is shown, where thanks to the compact design of the sensor head, a high quality sensor is grown. Should the dimensional standard of an absolute track according to FIG. 8 and an incremental track according to FIG. 6 be present, an absolute encoder can be constructed in the same construction volume and the same construction. In this case, it takes a movement of less than about 2 °, so that the absolute position can be determined or read on the scale by means of the sensor head. With current state-of-the-art encoders (with an index mark), an angular movement of up to 360 degrees is required to find an absolute reference point.

Fig. 6 shows an encoder 10 with a sensor head 11 and a code disk 155, on the surface of a dimensional scale (not shown) is arranged. The code disk 155 is connected to a shaft 157 and thereby rotatable. The sensor head 11 and the dimensional unit formed of optical elements (not shown) cooperate to generate a signal. For this purpose, the sensor head 11 in this embodiment, a light source 21, which emits light in the direction of the scale. The optical elements of the material measure are arranged on the sensor head 11 facing side of the code disk 155. They throw the light coming from the light source 21 in bundled form back onto the sensor head 11, where it is registered by the light receiving elements (not shown). Of course, the light source may also be disposed on the other side of the code disk 155 and transmit the light through the optical elements to the sensor head 11. However, the solution shown, in which the sensor head 11 has both one or more light sources and one or more light-receiving elements, is preferred. For a correct formation of the position signals, the light receiver elements must be arranged in a defined position relative to the optical elements. Instead, as known from the prior art, by means of a tool and / or an optical device directly adjust the position of the light receiving elements relative to the scale or the housing, this is indirectly achieved in the illustrated encoder 10 by matching the dimensions of the individual device parts. The sensor head holder 141 has a first structural element in the form of an opening 149 into which a part of the sensor head 11 can be inserted accurately, resulting in a positive connection. Advantageously, this part of the sensor head 11 is a transparent substrate 19 to which the light receiver elements are preferably applied by thin-film method. In such methods, a plurality of light-receiving elements is applied to a substrate plate, which is then cut into (smaller) substrates 19. Such a configuration of the sensor head 11 enables the position of the light receiving elements relative to the edges of the substrates to be determined by accurately cutting the substrate plate. The edge 151 of the substrate 19 can cooperate positively with said opening 149 in the sensor head holder 141. The opening 149 is precisely positioned relative to a second structural element, which is here the edge 153 of the sensor head holder 141. The edge 153 of the sensor head holder 141 cooperates positively with the inner wall of the housing 143, wherein the housing 143 is again arranged in a defined position relative to the dimensional scale. That is, the position of the sensor head 11 and the substrate 19 and thus also the position of the light receiver elements relative to the optical elements on the dimensional scale is indirectly determined by a plurality of matched in their dimensions device parts. The advantage is that a mechanical adjustment during assembly is eliminated. The sensor head holder 141 thus acts as an adapter. With regard to the stated dimensions or the defined positions, deviations of less than 0.2 mm, preferably less than 0.05 mm, are advantageously ensured, which is generally sufficient for a correct functioning of the measuring device. The housing 143 is closed by a cover 145 which presses against the sensor head holder 141 and thus fixes it in the housing 143. Housing 143 preferably has an opening between cover 145 and housing 143, through which contacting of the sensor head 11, e.g. by means of cable 159, preferably by means of a flex cable. This arrangement ensures easy mounting of the sensor head.

The code disk 155 is preferably adhered to the shaft 157. The through-hole of the code disk is advantageously designed so that one or more channels result between the code disk 155 and the shaft 157, in which the adhesive takes place. Advantageously, the code disk 155 and the material measure of plastic, preferably made of black-filled plastic, are formed. The material measure is then coated with a metal. A layer construction with gold or with aluminum, which is coated with synthetic resin, is preferred. In an alternative embodiment, the material measure is formed by means of hot stamping, wherein the film used advantageously has the following structure: a carrier material made of plastic, an aluminum layer and a plastic film for protecting the aluminum layer from oxidation.

By this arrangement a simple mounting of the sensor head is ensured.

The code disk is preferably adhered to the shaft. The through hole of the code disk is formed to form an order of a plurality of channels between the code disk and the shaft in which the adhesive finds place.

The code disk and the dimensional scale are made of plastic, preferably black filled plastic. The material measure is then coated with preferably gold or aluminum. On the aluminum layer, however, an additional protective layer, such as e.g. SiO2, are applied.

An alternative embodiment provides a film structure of the code disk. As a carrier material may serve a plastic on which an aluminum layer and a plastic film is provided as oxidation protection of the aluminum layer. The material measure can be formed by means of hot embossing on the side of the aluminum layer.

FIGS. 7, 8 and 9 show different embodiments of scale bodies 23 and light receiver elements 23 which serve to form at least one analogue signal 103. The analog signals 103a and 103b are processed in an evaluation circuit and optionally converted into a further-processable digital signal. The signals issued by the evaluation circuit are used to determine the position of the dimensional scale relative to the sensor head. The evaluation of the position data can be done by means of an analog or digital signal.

Fig. 8 shows an incremental track, Fig. 8 shows the track for the formation of an index which is evaluated at least once per revolution, Fig. 9 shows another track structure coded for the Manchester code, which together with the incremental Signal can define an absolute position. The three mentioned tracks, alone or in combination, can form the scale, which can be integrated on a carrier, such as a code disk, and preferably manufactured in the same operation as the carrier. The material measure is preferably formed with two tracks, the optical elements of both tracks having substantially the same focal length.

The illustrated in Fig. 7 track 25 of the scale embodiment consists of periodically spaced apart identical optical elements, which are arranged in the direction of movement 15 at regular intervals. In Figure 7, the optical elements are semi-circular cylindrical reflectors, which constitute the preferred embodiment within the scope of the present invention. The light emitted by the light source is focused by an optical element of the scale and focused on the sensor plane 100. There, the light hits a point 108. The adjacent regions 107 of the sensor plane, however, is not acted upon or only with little light. The distribution of the light intensity on the sensor plane is represented by the curve 101. The point 101h of the curve corresponds to a high energy density, the point 101t to a low energy density. The electrical conversion of the light intensity into an electrical signal is effected with at least two light receiver elements 23, which are preferably arranged offset from each other by approximately 180 °. That is, whenever the one light receiving element registers a maximum, the other light receiving element registers a minimum, and vice versa. With the two light receiver elements, two analog signals 103A + and 103A- are generated, which are forwarded to the evaluation circuit for further processing.

The evaluation circuit can then form a digital signal 104 from the analog signals 103.

Fig. 8 shows the index track 31 of a dimensional scale consisting of a single, approximately semicircular cylindrical reflector, which is centered about the axes 105. The width of this reflector will be between 100% and 300% of the width of a reflector of the incremental track. At the sensor level 100, the light is concentrated substantially at a point 108, the adjacent area 107 being exposed to only little light. The remaining area 109 is subjected to a substantially constant and unmodulated amount of light. The distribution of the light intensity on the sensor plane 100 is represented by the curve 101, wherein the point 101h corresponds to a high energy density and the point 101t to a low energy density. The conversion of the light intensity into an electrical signal preferably takes place with a special arrangement of light-receiving elements 23. According to a preferred embodiment, the light-receiving elements 23 consist of a main receiver 23Z + and two receivers 23Z-, which are arranged symmetrically to the main receiver 23Z + and electrically connected to each other. Advantageously, the total area of the receivers 23Z- is at least 10%, preferably at least 20%, and more preferably at least 30% larger than the total area of the main receiver 23Z +. This is important in connection with the evaluation of the signals. Because the area contents of the two light receiver elements Z + / Z- differ, it can be ensured that the signal 103a is clearly spaced from the signal 103b so that they can not intersect in the remaining area 109 at all. With this light receiver arrangement, two analog signals 103a and 103b are generated, which are further processed in the evaluation circuit. The signals may be e.g. in a comparator circuit, a crossing point of the two signals each representing a change in the digital level, i. one of the edges of the pulse 104 is generated.

For the formation of a stable digital pulse 104, it is important that the two signals 103a and 103b intersect with a large slope. This is achieved by the special arrangement of the light receiver elements 23: In the central position according to FIG. 8, the collimated light beam mainly strikes the central receiver element 23Z +, whereby the signal peak 103aa is formed. For the signal level 103ba to be as low as possible, the two light receivers 110Z, for example at point 107, should emit less light than normal, i. if the light beam is not modulated, receive. This is accomplished by having the slanted light receiving elements at the top, i. at the proximal end, slightly wider than at the distal end are formed. The illustrated configuration of the receivers 23Z +, 23Z- with a first elongate light receiving element 23Z + and two second elongated light receiving elements 23Z- arranged substantially mirror image symmetrical and at an angle to the longitudinal axis of the first receiver element 23Z + may be considered optimal. With this shape of the light receiving elements signals 103a and 103b can be formed, which have a large slope in the mutual crossing points, so that a reliable basic signal Zb for the index signal can be formed.

Preferably, the geometric center of gravity 102b of the two light receiver elements 23Z + and 23Z - coincides as possible at the same point. If the focal points do not coincide, i. if these are spaced from one another, then the level ratio between the two signals 103a and 103b changes as the distance between the graduated body 13 and the substrate 19 changes (see FIG. Thanks to the described advantageous geometric design of the receiver elements 23, the distance between scale and sensor head can vary within a relatively wide range, without the signal quality would suffer, whereby the rather large tolerance in the axial position of waves in small engines can be easily absorbed. This also has the advantage that complex adjustments are not required.

9 shows a track 31 of the dimensional scale. Like the incremental track shown in FIG. 7, the track includes a plurality of optical elements, but the optical elements are not all aligned the same. Each of the optical elements is configured and / or arranged to focus the light at either a first or a second point on the sensor plane. The two dots represent the 0 (zero) and the 1 (one) of a binary code, respectively. The sequence of zeros and ones (binary digits) defines a code, e.g. an 8-bit code in which 8 consecutive binary digits define a characteristic position value that occurs only once. In the present example, one point is to the left of axis 105 and the other to the right. However, it is also possible to provide three or more different points, i. to arrange and / or to design the optical elements correspondingly so that the sequence of the differently positioned impact points 108 on the sensor plane 100, e.g. a ternary code is created. However, preferred is a binary code, in particular a so-called Manchester code. On the sensor plane 100, the light is concentrated in a point 108, which is arranged in each case asymmetrically to the axis 105. Only a small amount of light falls on the area 107. The distribution of the light intensity on the sensor plane is represented by the curve 101. The electrical conversion of the light intensity into an electrical signal takes place with at least two light sensors 23 offset by 180 ° from one another two analog signals 103A + and 103A- are generated, which are supplied together with an incremental signal to an evaluation circuit. The evaluation circuit will use the incremental signal to evaluate the signals 103 such that the bit value of the division is determined and output in a digital signal. The reading of the bit value occurs every fourth falling edge of the index signal, at which time the difference between signal 103A + and 103A- is read.

The order of the bit values of the physical scale is selected such that, given a certain number of consecutive bits, an equivalent sequence can only be found once. The order is preferably formed according to Manchester code.

10 shows an arrangement of the light receiver elements 23 for a 3-channel encoder, wherein the main axis of the emitted light beam passing through the center of the light source intersects with the center line 43 of the dimensional scale (FIGS. 1, 2) (see FIG . 1). In the area 25 (first track of the physical scale), the light receiver elements for the incremental signal and in the area 31 (second track of the physical scale) that for the index signal are arranged. The same sensor head could also be used for an absolute encoder with Manchester code, in which case the area 25 remains unchanged and in the area 31 at least two receiver elements type are arranged as shown in FIG.

In order for the encoder to be insensitive to mounting tolerances, i. with respect to the centering of the light source and angular position of the sensor head with respect to the main axis 43 (see Fig. 1) of the scale, the following order of the light receiving elements is preferably selected with respect to the direction of movement 15: A + / B- A- / B + or A - / B + / A + / B-, ie a symmetrical arrangement of the light receiver elements relative to the axis 39 with respect to the two channels A and B (see Fig. 1). In this case, the light receiver elements A +, A- and B-, B + are offset by approximately 180 ° to each other. In this way, both for the channel A and for the channel B, two approximately sinusoidal curves, offset by 180 degrees, are obtained, which are converted into a digital signal in a comparator circuit. In this arrangement, the pads and the interconnection between the light receiving elements 23 are formed in the same material as the light receiving elements, i. that these areas are also opto-electronically active. It is then to be noted that the center of gravity of each of the 4 light receiver elements in area 25 is substantially the same distance from light source 21 (see line 102). Here, the points 102b each mark the center of gravity of a U-shaped receiver element. In the direction 15, the distances between the centers of gravity 102b should essentially coincide with the graduation of the dimensional embodiment. The normal width of a light receiver in the region 25 is preferably chosen between 40 and 80% of the width of a graduation of the graduation. Width is to be understood in this context that dimension of the light source which runs parallel to the main axis 43. In order to maintain the center of gravity of an array of light-receiving elements in the correct location, it is usually necessary to broaden the width of the receiver elements at certain points 106. Reference numeral 110 shows the contacts to the TCO layer.

Advantageously, the width of the light source 21 is resp. the aperture 49 selected between 60 and 150%, preferably 100% to 120% of the width of a division. If the width of the aperture 49 is too small, too little light energy is transmitted. If the width of the aperture 49 is too large, then the width of the light spot becomes too large, so that the signals are too flat to be reliably evaluated.

A similar arrangement of the light source and the optical receiver elements could be realized with other technologies, e.g. the light source 21 would be constructed as a light-emitting OLED directly on the substrate 19, and the light-receiving regions 35,25 would have a similar layer structure as the OLED. Both the OLED and the light-receiving elements are made of thin layers as shown in Fig. 3a, but different starting materials can be used.

Fig. 11 shows another arrangement of light receiving elements, wherein the individual receiver elements are electrically connected via vias through the SiO 2 layer with conductive paths, preferably aluminum, applied to the SiO 2 layer. The advantage of this arrangement is that the light receiver elements 23 are optimally designed without the transition lines and / or contact points can influence the formation of the analog signals. In this respect, such a solution will cost more, since additional layers and precautions must be taken. An arrangement of the receiver elements 23 in the direction of movement 15 has the same advantages as already indicated in the description of FIG.

FIG. 12 shows a preferred embodiment of the light source consisting of diaphragm and LED (see also FIG. 2). The LED is adhered to the glass substrate 19 as described in Fig. 4c and radiates through the opening recessed in the thin film structure. The LED 21 is received in the recess 71 of the support plate 17. Various variants are shown how the light source can be mounted on the glass substrate 19. Fig. 12a shows the light source with an emission layer 161 and a contact layer 163. Between the light source 21 and the coated glass substrate 19, a spacer 75 is provided, which keeps the light source at a distance from the substrate 19. It can be seen that in this construction there is a risk that laterally exiting light 165 will fall on the light receiver. The reference numeral 170 shows the light cone emitted by the light source in the direction of the material measure.

This arrangement is disadvantageous because the generated stray light can penetrate in the light sensor area, which can lead to signal interference.

FIG. 12 b shows an insulated light source in which the emission layer 161 is coated on the edge with a non-transparent cover layer 167. This can prevent scattered light from falling on the light receiver. According to FIG. 12c, the non-transparent cover layer 167 is not applied to the light source 21 but to the light receiver. Other precautions may be that an underfill material is selected which is opaque or has low transmission for light.

Fig. 13 shows a circuit with which mounting errors with respect to the angular position 41 of the sensor head with respect to the main axis of the physical scale can be compensated so that the index signal can function independently of such an angle error reliably.

Fig. 13a shows the signals A, B, Zb and Z. Signal Z is formed from the combination of the signals A and B and Zb. The signal Z shown in this Fig. 13a consists of two pulses, which is basically not desirable. By a recombination of the original signals A and B 13bandere signal states are generated in Fig., The signal Zb is almost centric to the region of the signals A and B in plus. The resulting signal thus consists of a single pulse. In order to achieve this, the input signals A and B are inverted and / or exchanged according to the truth table FIG. 13c, which combination is controlled by two signals X1 and X2, which equals a displacement of the signal Zb compared to the signals A and B.

The two channels A and B of FIG. 13b consist of the inverted input channel B for the channel A and the input channel A for the channel B. Thus, the combination of the signals from channel A and channel B and channel Zb forms an index signal a single pulse.

The signal processing according to the truth table can be performed by the depicted circuit (FIG. 13d). The circuit is driven by two control signals X1 and X2. The signals Ain 200 and Bin 201 are inverted by two inverters 206, 207. The circuit additionally contains 4 mutliplexers 208 which, depending on the state of the control signals X1, X2, pass on one of the two signals in the input to the respective output. The examples given in FIGS. 13a and 13b are the control signals X1 = 0 and X2 = 1, the thick-line switching paths being indicated in FIG.

In Fig. 14, a special structure of an absolute encoder is shown schematically, which can determine an absolute position signal even when lying still substrate or still lying wave, or in cold start. This is made possible by a special device which allows relative movement between the scale and the sensor head. The device has a pivot arm (or equivalent) on which the at least one sensor head is mounted. The swing arm is driven by a motor and generates a relative movement between the scale and the sensor head, which corresponds to a fraction, preferably less than 5 degrees, of a complete revolution. By evaluating the signals coming from the sensor head, the absolute position can be determined. This is in turn possible thanks to the compact design of the sensor head and the tolerance-friendly design of this arrangement.

Fig. 14 shows the schematic structure of the absolute encoder with a housing 1, a mounted shaft 2, a code disk 3 with a dimensional scale 4 preferably with an absolute track of FIG. 8 and an incremental track of FIG. 6, a fixed or a small angle pivotable carrier 10, on which at least one sensor head 3,4 is mounted. The code disk is mounted centrically on a shaft 201, which is in a housing 202 with at least one bearing 208 positively.

With a small movement of the axis of less than 3 °, a position number, whereby a position value of the code disc is determined. Thereafter, the position values are determined by counting the pulses from the incremental track. In addition, with such an absolute encoder, a redundant determination of the position values during the movement of the material measure can be performed by comparing the position values determined from the incremental counter with the position values determined from the absolute track. This results in additional security in determining the position values of the position measuring device.

Preferably, the Manchester code is read with one or more pairs of receiver elements (see Fig. 8). A position number is determined between 1 and a maximum number of position values by a movement of the material measure in relation to the sensor head. The length of the position number, expressed in binary form, is the number of bits determined by the length of the scale. The position number is determined by reading a number of consecutive bits. A position number is defined by the dimensional standard formed according to the Manchester code. For the entire length of the scale, the position numbers are singular, i. determine the position of the dimensional scale relative to the light receivers. The conversion of the read position number into a position value is done with the evaluation circuit.

A redundant determination of the position values can protect against read errors by registering several consecutive position numbers. This means that actually a prolonged position number is recorded. The extended position number is converted into several position values. If the position values can not be arranged in a row, then this would indicate a read error of the manchester code.

FIG. 14 shows an arrangement where the evaluation circuit is arranged outside the sensor. The evaluation circuit is connected to the encoder with 3 lines 186 (schematic representation). Two lines transmit the pulses from the channels A and B, 104 and the third line a digital signal, which maps the position numbers of the absolute track. Thus, position information is transmitted in a redundant manner between encoder 10 and evaluation circuit 187. This ensures a safe transmission of the position numbers and determination of the position values. The evaluation circuit passes by means of a conventional data bus, such. SPI, 12C, Profibus, etc., the data, for example, to a PLC control. The evaluation circuit preferably comprises a microprocessor 188, which carries out the translation of the position numbers into position values and preferably immediately forwards them to an external PLC control.

A disadvantage of an encoder system with Manchester code is that for the determination of the absolute position relative movement of the scale, and thus a movement of the machine parts to be measured is necessary to determine the absolute position values. This is not appreciated by the machine builder.

It is desirable that a position value when switching on the machine even before any movements take place, can be determined. This is achieved in that the code disk has a large number of tracks, the min. is assigned to one receiver element per track. This genus of position measuring device does not fit in small cases.

A further embodiment of the invention is therefore that means are provided which allow movement of the sensor head relative to the material measure internally in the sensor, so that at the touch of a button determination of the position value is possible without the machine must be set in motion , This is accomplished by placing the support, e.g. a Codescheibe.um is rotated about 3 °. This can, for example, with a motor 185 and an eccentric 184, which preferably engages positively in a slot 183 of the pivot arm. The signals generated by this movement (channel A, channel B and M code) can then be used to determine the position values.

14 shows a compact kit encoder, consisting of a housing 1, a sensor head 2, a code disk 3 and a flange 4 to be attached to the engine. The code disk is held centrically on a provisional bearing. The bearing has the function of keeping the code disk centric to the housing during the assembly process. The bearing itself may be a ball bearing or a bearing preferably made of Teflon. The flange 4 is mounted on the motor part centric with respect to a shaft and preferably fastened with screws. Subsequently, the housing is preferably snapped onto the flange and at the same time the code disc attached to the shaft. The code disk contains channels into which adhesive can be introduced. Fig. 15a shows a channel with slots and Fig. 15b channels, which are easier to produce on the tool side. In this case, a number of spaces can be formed where adhesive can find space.

The sensor head is mounted on a printed circuit board which is connected to a flat cable. Preferably, this circuit board is snapped into the housing. On the circuit board or on an additional support a bearing is attached. The bearing has an assembly function to fulfill, so that, for example, a sliding bearing made of Teflon is advantageous so that the rotation of the motor shaft is not loaded by this provisional bearing. The cable outputs are arranged so that the cable can be continued radially or tangentially within the housing diameter, which is realized by appropriate design of the housing.

Figs. 15 to 17 show a position measuring device. This is an encoder 10, which has a particularly compact design. This design is characterized by a specific arrangement of the code disk 155, the mounted thereon Masserverkörperung 13, the housing 143 and the sensor head 11, which cooperates with the scale 13 for generating a signal. The material measure 13 is located here on that side 249 of the code disk 155, which faces away from the housing 143. What is meant here is preferably a part of the housing 143 extending along or substantially parallel to the flat side of the code disk 155 and / or the upper part of the housing 143. Preferably, the code disk 155 is between the inside of the housing 143 (or the inside the said part of the housing) and the sensor head 11 or the printed circuit board 251 are arranged. The fact that the receptacle 267 for the shaft (or at least the greater part, in particular at least 70 or 90% of the length of the shaft receptacle) is arranged on the same side of the code disk 155 as the graduated mass 13 results in a substantial space saving. The reason for this is that the location of the measurement, that is to say the area between the scale 13 and the sensor head 11, is arranged next to the shaft or the shaft receiver 267. Advantageously, the sensor head 11 is mounted on a printed circuit board 251 which cooperates positively with the housing 143. This is particularly preferably done via a snap connection 153. A very simple mounting of the encoder 10 can be accomplished by the use of an adapter part 255, which has a first connection means 257 and a second connection means 259. The latter is then advantageously a snap connection 259, which is e.g. is formed by one or more projections 261 and one or more recesses 263. Projections 261 and depressions 263 can be arranged on the housing (in particular on the housing inner wall) and / or on the adapter part 255. Preferably, it is a detachable connection. Advantageously, the housing 143 has an assembly bearing 265 into which the code disk 155 and / or a receptacle 267 connected to the code disk 155 can be accommodated for a shaft. The latter reason, because the code disk 155 and the shaft receiving 267 can either be integrally formed, which is preferred, or just can represent interconnected items. In the case of the encoder 10 according to the invention, the housing 143 and / or the printed circuit board 251 and / or the code disk 155 and / or the connecting means 253 and / or 259 are preferably made of plastic. A particularly compact design is also achieved when the contacting of the sensor head 11 via a side opening 269 in the housing 143 takes place. This opening 269 is advantageously arranged on the side facing away from the code disk 155 side of the sensor head 11 and / or the circuit board 251. The contacting can thus be done on the underside of the sensor head 11 or - when the sensor head 11 is contacted via the printed circuit board 251 - on the underside of the printed circuit board 251. Said contacting can be accomplished via one or more cables 159, which pass through the opening 269 into the housing 143. These are preferably flat cables 159 as shown in the figures, flex cables being particularly preferred. The opening 269 therefore advantageously has an elongated shape and is preferably arranged substantially parallel to the code disk 155 and / or to the printed circuit board 251. The flat cable 159 is also aligned accordingly. If the housing 143 on a side 245 has a recess 273, which adjoins the opening, this is particularly advantageous. In particular, when the recess extends from the opening along side 245 of housing 143 to another side 247 or to an edge of housing 143 or to an edge of housing 143. The indentation 273 may extend from the opening 269, e.g. extend to the top 245 of the housing 143. The cable 159 may thus be positioned in the recess 273. If the housing 143 - which is preferred - has a cylindrical shape, the cable 159 is so preferably within the cylinder radius. Furthermore, it is advantageous if the position measuring device, or the encoder 10 has one or more of the features, as described in other parts of this document. In particular, the design of the sensor head 11 and the dimensional standard may be mentioned. For example, the scale preferably has at least two tracks, one track being an incremental track, and a second track preferably being either an index track or a coded track as described in this document.

Legend:

[0075] <Tb> 10 <sep> Encoder <Tb> 11 <sep> Sensor Head 'Tb> 13 <sep> graduation <tb> 15 <sep> Direction of movement of the graduation relative to the sensor head <Tb> 17 <sep> carrier plate <Tb> 19 <sep> Substrate <Tb> 21 <sep> Light Source <tb> 22 <sep> Main axis of the emitted light beam <Tb> 23 <sep> light receiving elements <tb> 25 <sep> first trace of the physical embodiment <tb> 27 <sep> first optical elements <tb> 29 <sep> first sensor area <tb> 31 <sep> Second trace of the Massification <tb> 33 <sep> second optical element <tb> 35 <sep> second sensor area <tb> 37 <sep> flat sides of the substrate <Tb> 39 <sep> longitudinal central axis <Tb> 41 <sep> Arrow <tb> 43 <sep> Center line of the scale <tb> 45 <sep> axis through the light source <Tb> 47 <sep> evaluation <Tb> 49 <sep> Aperture <tb> 51 <sep> Metal layer on sensors <Tb> 53 <sep> solder balls <tb> 55 <sep> Circuit traces on carrier plate <tb> 57 <sep> non-conductive layer (Permanent Resist) <Tb> 59 <sep> recesses <Tb> 61 <sep> underfill <tb> 63 <sep> Back side of the carrier plate <tb> 64 <sep> tracks on the back of the carrier plate <tb> 65 <sep> non-conductive layer <Tb> 67 <sep> recesses <tb> 69 <sep> breakthroughs in the carrier plate <tb> 71 <sep> recess for light source <Tb> 73 <sep> Holder <Tb> 75 <sep> spacer <Tb> 77 <sep> air gap <Tb> 79 <sep> Kleber <tb> 81 <sep> conductive transparent layer <tb> 83 <sep> First doped layer <tb> 85 <sep> amorphous silicon layer <tb> 87 <sep> second doped layer <tb> 89, 91 <sep> Contact points of the light receiver <Tb> 93 <sep> protective layer <tb> 95 <sep> contact point between light source and layer 51 <tb> 96 <sep> Pen of a tool <Tb> 97 <sep> substrate <Tb> 99 <sep> indentations <Tb> 100 <sep> sensor plane <tb> 101 <sep> curve of light intensity (h / 1) <tb> 102 <sep> Line on which the centers of gravity of the light receiving elements are arranged <tb> 102b <sep> Center of gravity of the light receiver elements <tb> 103a, 103b <sep> Analog signals (A + / A- / a / aa / ab / ac / b / ba / bb) <Tb> 104 <sep> Digital Signal <tb> 105 <sep> Axis of the optical element <Tb> 106 <sep> diode <tb> 107 <sep> Neighboring area to 108 <tb> 108 <sep> Impact point of light at 100 <tb> 109 <sep> Remaining area (i.e., without areas 107 and 108) <tb> 111 <sep> VIAS ?? (electrically conductive connections / layers between 23 ??) <Tb> 141 <sep> Sensor head holder <Tb> 143 <sep> Housing <Tb> 145 <sep> Lid <Tb> 147 <sep> depression <Tb> 149 <sep> Opening <tb> 151 <sep> Edge of the substrate / edge of the sensor head <tb> 153 <sep> Edge of sensor head holder <Tb> 155 <sep> code disk <Tb> 157 <sep> wave <Tb> 159 <sep> Cables <tb> 161 <sep> Emission layer of light source <Tb> 163 <sep> contact layer <tb> 165 <sep> light exiting sideways <Tb> 167 <sep> topcoat <Tb> 168 <sep> <Tb> 170 <sep> beam <Tb> 180 <sep> <Tb> 181 <sep> Position number <Tb> 182 <sep> arm <Tb> 183 <sep> slot <Tb> 184 <sep> eccentric <Tb> 185 <sep> Engine <Tb> 186 <sep> Connection line <Tb> 187 <sep> evaluation <Tb> 188 <sep> Microprocessor <Tb> 241 <sep> <Tb> 261 <sep> projections <Tb> 263 <sep> wells <Tb> 265 <sep> Mounting bearings <tb> 267 <sep> recording for Well <tb> 269 <sep> Lateral opening <tb> 271 <sep> side of the sensor head facing away from the code disk <Tb> 273 <sep> indentation

Claims (44)

1. Position measuring device with at least one dimensional standard having an optical structure, preferably an arrangement of 3-D reflectors, - A arranged at a distance from the scale of light source and - At least one arranged at a distance from the physical scale light receiver, and at least one transparent substrate present between the scale and the light receiver, characterized, that the light receiver in the form of a thin-film structure comprising a plurality of layers arranged one above the other is deposited directly on the transparent substrate on the side of the substrate which faces away from the dimensional embodiment, - That at a distance from the light receiver, a light source is provided, and - That a support plate is provided, on which the substrate is arranged. 2. Apparatus according to claim 1, characterized in that the light source is arranged behind a etched in said layers recess. 3. carrier plate on both flat sides of strip conductors for contacting with the light receiver and an evaluation circuit has. 4. Apparatus according to claim 1 or 2, characterized in that the transparent substrate and the carrier plate are connected by flip-chip mounting firmly together. 5. Device according to one of the preceding claims, characterized in that an evaluation circuit is provided, which is arranged on the carrier plate. 6. Device according to one of the preceding claims, characterized in that the light receiver is kontaktier with a metallic cover layer, preferably made of aluminum. 7. The device according to claim 6, characterized in that the electrically conductive metal is aluminum, which is preferably alloyed with 1 to 5% titanium. 8. Apparatus according to claim 6 or 7, characterized in that the electrical connection between the conductive cover layer and the conductor tracks of the carrier plate by means of solder balls, so-called "bumps" or "stud-bumps" is made. 9. Device according to one of claims 6 to 8, characterized in that the connection between the metallic cover layer or bumps on the one hand and the carrier plate on the other hand is made by means of an electrically conductive adhesive. 10. Device according to one of the preceding claims, characterized in that between the carrier plate and the substrate a permanent resist is provided for limiting the expansion of the adhesive. 11. Device according to one of the preceding claims, characterized in that the carrier plate has connections for connection of the position measuring device to an external display device. 12. Device according to one of the preceding claims, characterized in that the thin-film sensor is formed by a transparent, conductive layer, preferably a transparent, conductive oxide layer (= TCO layer), a first doped layer, an intrinsic layer, preferably an amorphous silicon layer, a second doped layer as well - An electrically conductive, metallic cover layer. 13. The device according to claim 12, characterized in that for the production of a structured sensor region partially the aluminum layer, the uppermost doped layer and preferably at least a portion of the intrinsic layer is etched away. 14. Device according to one of the preceding claims, characterized in that the light receiver is formed as a sensor region consisting of a plurality of light receiving elements, which are electrically connected to each other. 15. The device according to claim 14, characterized in that for the production of a structured sensor region partially the aluminum layer, the uppermost doped layer and preferably at least a portion of the intrinsic layer is etched away. 16. The device according to one of claims 13 to 15, characterized in that at least one first and a second sensor region is provided, which regions are each assigned to a material measure with an incremental, index or absolute track. 17. The device according to claim 16, characterized in that the first sensor region has first and second light receiver elements, which are nested one inside the other. 18. The apparatus of claim 16 or 17, characterized in that the first and second light receiving elements have an approximately U-shaped configuration. 19. Device according to one of claims 13 to 18, characterized in that the geometric center of gravity of the first and second light-receiving elements of the first sensor area are approximately on a straight line. 20. Device according to one of claims 13 to 19, characterized in that the first sensor region are each formed by a plurality of preferably strip-shaped light receiver elements, which light receiver elements at an angle of preferably between 0.5 and 15 degrees to each other and arranged in a certain direction one behind the other are, wherein the even and the odd light receiving elements are each electrically connected to each other. 21. The device according to claim 20, characterized in that the first and / or the second light-receiving elements are connected to each other by an additionally applied, electrically conductive layer, wherein between the metal layer and the additional conductive layer, an insulating layer is provided. 22. Device according to one of claims 13 to 21, characterized in that the first and second light-receiving elements of the first sensor region are arranged so that two 180 ° shifted, alternating signals in the order «AbaB» are obtained. 23. Device according to one of claims 13 to 22, characterized in that the second sensor region is provided for the generation of an index and a strip-shaped, first light-receiving element and two projecting at an angle from the first light-receiving element second light-receiving element is formed. 24. Device according to one of claims 13 to 23, characterized in that the geometric center of gravity of the surface of the first light-receiving element and the surface of the two second light-receiving element of the second sensor region substantially coincide. 25. Device according to one of the preceding claims, characterized in that for the production of a structured sensor region partially the aluminum layer, the uppermost doped layer and preferably at least a portion of the intrinsic layer is etched away. 26. Device according to one of the preceding claims, characterized in that for the production of a structured sensor region partially the aluminum layer, the uppermost doped layer and preferably at least a part of the intrinsic layer is etched away. 27. Device according to one of the preceding Ansprächen, characterized in that for the production of a structured sensor region partially the aluminum layer, the uppermost doped layer and preferably at least a portion of the intrinsic layer is etched away. 28. Device according to one of the preceding claims, characterized in that the physical scale comprises two tracks with optical elements, wherein a first track of the generation of an incremental signal and the second track of the determination of a position number or an index signal is used. 29. Device according to one of the preceding claims, characterized in that the light source, preferably an LED, is arranged behind the substrate. 30. Device according to one of the preceding claims, characterized in that the light source is arranged substantially in the same plane as the light receiver. 31. Device according to one of the preceding claims, characterized in that the light source, preferably an OLED, which is formed directly on the substrate between the light receivers. 32. Device according to one of the preceding claims, characterized in that the light source is embedded in a metallic layer, so that stray light can be prevented. 33. Device according to one of the preceding claims, characterized in that an air gap in the light path between the light source and the substrate is present. 34. Device according to one of the preceding claims, characterized in that the evaluation circuit is arranged on the other side of the carrier plate in the form of an integrated circuit for processing the light receiver signals in the flip-chip method, wherein the light receivers are electrically connected to the integrated circuit. 35. Device according to one of the preceding claims, characterized in that the carrier plate consists of ceramic. 36. A method of making a sensor head for a position measuring device, comprising the steps of: a depositing a plurality of groups of light receivers onto a transparent substrate in a thin-film process, which groups of light receivers each serve to produce a single sensor head, b each providing a diaphragm for a group of light receivers, c applying contact points, preferably in the form of solder balls, so-called bumps, to the light receivers, d providing a carrier plate with conductor tracks or contact points, which coincide with the contact points of the light receiver, and e bonding the glass substrate and the support plate using an electrically conductive adhesive. 37. The method according to claim 36, characterized in that an electrically non-conductive layer is previously applied to the carrier plate, which has recesses which coincide with the contact points of the light receiver, and that the recesses are at least partially filled with the electrically conductive adhesive. 38. The method of claim 36 or 37, characterized in that on the back of the carrier plate an evaluation circuit is applied. 39. The method according to any one of claims 36 to 38, characterized in that a part of the existing spaces between glass substrate and carrier plate are filled with an underfill. 40. Position measuring device, in particular encoder, comprising - a support, a sensor head arranged on the support with a light source and a light receiver element, a measuring element which can be moved relative to the sensor head and has optical elements which can be mounted on a moving part of a device, for example a motor, and interact with the sensor head for the determination of an absolute position value, characterized that the sensor head is movably arranged on the support, and means are provided for displacing the sensor head relative to the support by a certain amount. 41. Position measuring device according to claim 40, characterized in that the displacement means for moving the sensor head are formed by a motor, which is in operative connection with the sensor head. 42. Position measuring device according to claim 40 or 41 or, characterized in that the dimensional standard is a code disk. 43. Position measuring device according to one of claims 40 to 42 and 2 to 42 or, characterized 44. A method for determining the absolute position of a movable part in the rest position by means of a position measuring device, which allows the determination of the absolute position of the part by means of a relative to a sensor head movable scale embodiment, which is coupled to the movable part, characterized in that to determine the absolute position of the movable part in the rest position of the sensor head is moved relative to the moving part.