WO2011113666A2

WO2011113666A2 - Scanning unit for an optical position measuring device

Info

Publication number: WO2011113666A2
Application number: PCT/EP2011/052604
Authority: WO
Inventors: Reiner Burgschat; Mario Himmel
Original assignee: Dr. Johannes Heidenhain Gmbh
Priority date: 2010-03-16
Filing date: 2011-02-22
Publication date: 2011-09-22
Also published as: WO2011113666A3; DE102010002902A1

Abstract

The invention relates to a scanning unit for an optical position measuring device. Said unit comprises at least one light source and a detector assembly having at least one incremental signal detector region and a reference signal detector region. The incremental signal detector region is designed as a structured detector assembly which comprises a plurality of groups of individual detector elements. The in-phase detector elements of multiple groups are electrically interconnected in order to generate incremental partial signals. The reference signal detector region comprises a plurality of identically designed detector elements. Individual detector elements are electrically interconnected in order to generate reference signals. A transparent insulating layer is arranged above the detector elements of the incremental signal detector region and/or of the reference signal detector region. Said layer has at least one contacting opening above each of a plurality of predetermined detector elements, via which opening the corresponding detector elements can be electrically connected to each other.

Description

Scanning unit for an optical position-measuring device

The present invention relates to a scanning unit for an optical position measuring device.

Known incremental optical position-measuring devices often comprise not only incremental graduations on the side of the sampled material measure, but also one or more reference markings or reference mark structures, via which reference signals can be generated. The reference signals are used to produce the absolute reference to one or more defined relative positions of the two mutually movable elements whose relative movement is to be detected by means of the optical position measuring device. Depending on the configuration of the respective reference marking, the scanning unit must be designed accordingly on the scanning side.

The object of the present invention is to provide a scanning unit for an optical position-measuring device that is adaptable and easy to manufacture with very little effort on a wide variety of scanning configurations. Furthermore, it is desirable to have sufficient insensitivity to contamination on the material measure scanned thereby. This object is achieved by a scanning unit for an optical position-measuring device with the features of claim 1.

Advantageous embodiments of the scanning unit according to the invention for an optical position-measuring device result from the measures listed in the claims dependent on claim 1.

The scanning unit according to the invention for an optical position-measuring device comprises at least one light source and a detector arrangement with at least one incremental signal detector area and one reference ence signal detector area. The incremental signal detector area is designed as a structured detector arrangement, which comprises a plurality of groups of individual detector elements. The in-phase detector elements of several groups are electrically interconnected to generate incremental partial signals. The reference signal detector area comprises a plurality of identically formed detector elements. Individual ones of the detector elements are electrically interconnected to generate reference signals. Arranged above the detector elements of the incremental signal detector region and / or the reference signal detector region is a transparent insulating layer which has at least one contact opening above a plurality of predetermined detector elements, via which the corresponding detector elements can be electrically connected to each other. Preferably, the detector arrangement comprises two incremental signals Detector areas between which the reference signal detector area is arranged.

In one possible embodiment, these are within the reference signal detector range

- Several first groups of adjacent detector elements electrically connected to each other and

- several second groups of adjacent detector elements electrically connected to each other, which are different from the first group and - the number of detector elements in each first group and each second group is identical.

Advantageously, further detector elements which are not assigned to the first or second groups are electrically connected to one another and the number of further detector elements corresponds to the sum of the number of detector elements in the first and second groups.

It is possible for at least two light sources to be arranged laterally adjacent to different sides of the detector arrangement. Furthermore, the detector arrangement and the at least one light source can be arranged on top of a transparent carrier substrate, the photosensitive side of the detector arrangement and the light-emitting side of the light source being oriented in the direction of the top side of the carrier substrate. On the underside of the carrier substrate, an opaque and anti-reflective coating with window areas in front of the light source and the detector array is arranged.

In such a variant, a diaphragm with a light-permeable gap can be arranged on the carrier substrate in front of the light-emitting side of the light source.

Furthermore, it is possible to form a protective cap on the carrier substrate above the detector arrangement and the at least one light source.

In this case, the protective cap may comprise a cover element designed as a printed circuit board, on which one or more signal processing modules are arranged. An optical position measuring device comprises, in addition to the scanning unit according to the invention, a material measure with an incremental graduation and one or more reference markings.

As an advantage of the scanning unit according to the invention, it should be mentioned that the configuration of the contact openings in the insulating layer above the detector elements of the reference signal detector area and / or the incremental signal detector area provides a simple configuration possibility for flexibly adapting the respective detector areas to different sampled structures on the sides of the material measure adapt. Only by changes to a single mask, namely that for the insulating layer, can a wide variety of configurations of the reference signal detector area and / or of the incremental signal detector area be realized. The scanning unit according to the invention can in this case be used both in linear and in rotary optical position-measuring devices; as well as incident and transmitted light systems are thus feasible.

Further advantages and details of the present invention will become apparent from the following description of embodiments with reference to the accompanying figures. It shows

Figure 1 is a plan view of a part of the scanning unit according to the invention; FIGS. 2a-2c each show a variant of an optical position-measuring device with different embodiments of the scanning unit according to the invention; Figure 3 is a schematic representation of an optical

Position measuring device with a further embodiment of the scanning unit according to the invention; 4a and 4b are plan views of a portion of the sampled material measure and the reference signal detector area used for this purpose of a further embodiment of the scanning unit according to the invention.

FIG. 1 shows a plan view of a part of the detection plane of an exemplary embodiment of a scanning unit designed according to the invention for an optical position-measuring device. Shown in the figure is a detector arrangement 1 for generating incremental and reference signals. level signals comprising two incremental signal detector areas 10, 20 and a reference signal detector area 30 arranged therebetween. On the various detector areas 10, 20, 30, the coming of a - not shown - dimensional standard coming forth beam after they have acted there an incremental graduation and one or more reference marks.

In the case of the relative movement of scanning unit and material measure along a measuring direction x, incremental incremental signals which are phase-shifted by 90 ° result from the incremental-signal detector regions 10, 20, which can be further processed by downstream electronics in a known manner. By scanning one or more reference markings on the side of the material measure, a reference signal can be generated with the aid of the reference signal detector region at the corresponding known positions, to which the subsequently generated incremental signals are related.

In the present example, the two incremental signal detector regions 10, 20 are each designed identically as a structured detector arrangement. These include a plurality of groups of identical optoelectronic detector elements which are in the form of elongated rectangles. The longitudinal axis of the detector elements extends in the indicated y-direction. In one possible embodiment, four such detector elements with a width of the rectangular narrow side in the x direction of 5μηι and intervening gaps of 5μηι are arranged approximately within a range of 40μηι along the x-direction.

In-phase detector elements of a plurality of groups are electrically interconnected in the incremental signal detector regions 10, 20 to produce four incremental sub-signals with particular phase shifts; Typically, four incremental sub-signals are generated with the phase relationships 0 °, 90 °, 180 ° and 270 °. The electrical contacting of the interconnected detector elements takes place in a metallization plane of the scanning unit. From the usual way interconnection of the four incremental sub-signals, the two periodic incremental signals are obtained with a phase shift of 90 °. In the case of a scanned measuring graduation with an incremental graduation periodicity of 20 μm, a so-called single-field scanning can be realized with the scanning beam path light source - transmission grating - incremental graduation - structured detector arrangement via incremental signal detector regions 10, 20 formed in this way. This is characterized by the fact that the four incremental sub-signals can all be obtained from a single graduation period of the sampled incremental graduation. This results in particular in a uniform influencing of all four incremental partial signals in the case of local contamination of the incremental graduation. Eventual errors in signal processing can thus be minimized.

As a particular advantage of the use of two incremental signal detector areas 10, 20 in the present exemplary embodiment of the scanning unit according to the invention, it must be stated that reliable generation of incremental signals can thereby be ensured even with larger soiling. Although the amplitude of the resultant incremental signals is significantly reduced in the case of a complete embodiment of one of the two incremental signal detector regions 10, 20, it is possible to compensate this amplitude drop by means of known correction methods and to provide incremental signals with a constant amplitude on the output side.

As an alternative to this variant, however, provision can also be made for designing only an incremental signal detector region and a reference signal detector region in the scanning unit according to the invention.

The reference signal detector area centrally arranged in the present example in the detector arrangement 1 of the scanning unit according to the invention 20 of the detector assembly 1 also comprises a plurality of identically constructed detector elements in the form of elongated rectangles, the longitudinal axis of each extends in the y-direction, ie perpendicular to the measuring direction x. The detector elements in the reference signal detector area 20 are also arranged along the measuring direction x with a certain periodicity. In a possible embodiment, approximately detector elements are provided with a width of the rectangular narrow side of 32μηι, which are arranged in a periodic grid of 40μηι along the measuring direction x.

At least above the detector elements of the reference signal detector area 20, an insulating layer transparent to the radiation used is arranged in the detector arrangement. The insulating layer has contacting openings above those detector elements which are to be electrically connected to each other via the metallization level. Due to the contacting openings in the insulating layer, it is possible in a particularly simple manner to flexibly interconnect the various detector elements of the reference signal detector area 20. Only by changing a single lithography mask can a wide variety of variants of reference signal detector regions 20 be formed.

The reference signal detector region 20 can be configured in this way, in particular in such a way that differently formed reference markings on the material measure can be scanned. Thus, it is possible to scan reference marks, which consist only of individual graduation marks or graduation ranges or else so-called coded reference marks, which comprise a large number of graduation marks in a specific geometrical arrangement, etc.

Analogously, the electrical contacting of the detector elements in the incremental signal detector areas can also be undertaken. In this way, for example, the detector configuration can be different graduation periods of the scanned incremental graduation.

With the aid of the scanning unit according to the invention, it is also possible to realize a wide variety of scanning and / or setup configurations for optical position-measuring devices. In FIGS. 2a-2c, three different such sample configurations are shown schematically. The corresponding position-measuring devices each comprise a material measure as well as the scanning unit movable along the measuring direction x. In the examples illustrated, the material measure is in each case designed as a linear measuring standard which extends along the measuring direction x and is scanned in the incident light via the scanning unit according to the invention. In FIGS. 2a-2c, the measuring direction x is oriented perpendicular to the plane of the drawing.

The measuring scale and the scanning unit are e.g. connected to each other along the measuring direction x movable machine parts whose relative position is to be determined. The position-dependent incremental and reference signals generated via the position-measuring device are further processed by a downstream sequential electronic unit which controls the positioning of the movable machine parts via it. In the embodiment of the position-measuring device illustrated in FIG. 2a, a material measure 40 is provided which comprises two adjacently arranged tracks with an incremental graduation 42.1 and one or more reference markings 42.2; the two tracks extend along the measuring direction x.

The arranged on a scale carrier 41 incremental 42.1 is formed in the present example as a reflection division. This consists of periodically arranged in the measuring direction x division regions of different reflectivity. In the parallel next to it lane are formed one or more reference marks 42.2, for example, each consisting of a single low-reflective division region, while the area surrounding this partition region of this track is designed to be highly reflective.

The inventively embodied scanning unit 50 of this optical position-measuring device comprises a transparent carrier substrate 53, on the upper side of which two light sources 51 .1, 51 .2 as well as a so-called opto-chip 52 are arranged. One of the two light sources 51 .1 is used here for illuminating or scanning the incremental graduation 42. 1 on the measuring graduation 40; the other light source 51. 2 for scanning the reference marking 42. 2. Opto-chip 52 includes i.a. on the carrier substrate 53 side facing a detector assembly 1, as described with reference to Figure 1. Furthermore, the opto-chip 52 comprises electronic components (not shown) for further processing of the position-dependent signals generated via the detector arrangement 1.

In the further embodiment of an optical position-measuring device shown in FIG. 2b, only a single track with an incremental graduation 142 is arranged on a scale carrier 141 on the side of the scanned measuring graduation 140. The reference mark is integrated in the incremental graduation 142. This can e.g. by omitting a plurality of adjacent division regions of the incremental division 142 e rfo l g e n, u m d ergesta l t ei ne detectable Aperiodizität in the incremental graduation 142 form. Of course, a plurality of reference marks can be formed in the incremental pitch 142 in this way.

On the side of the scanning unit 150 according to the invention, in contrast to the previously explained embodiment of FIG. 2a, only a single light source 151 is arranged on the upper side of the carrier substrate 153, which serves to scan or illuminate the incremental graduation 142 with the reference marking integrated therein. As in the previous example, an opto-chip 152 is further arranged on the upper side of the carrier substrate 153, which in turn comprises a detector arrangement 1 according to FIG. 1 as well as further electronic components for signal processing. Because of the provided integrated image and the reference matrix, the incremental graduation 142 differs in particular from the design of the reference signal detector range from the first example. It is now necessary to electrically interconnect other detector elements of the reference signal detector area. However, this can be done as explained above without much effort through corresponding openings in the insulating layer. For the scanning of reference marks integrated in the incremental graduation 142 and the design of the reference signal detector region required for this purpose, reference is made to the following explanations regarding FIG.

Finally, FIG. 2c shows a further variant of an optical position-measuring device with the complete construction of a further embodiment of the scanning unit 250 according to the invention. The scanning concept provided in this example basically corresponds to that of FIG. 2a. That is, on the side of the measuring scale 240, two parallel tracks with an incremental pitch 242.1 and one or more reference markings 242.2 are provided. In the scanning unit 250, two light sources 251 .1, 252,2 are placed on the carrier substrate 253, which illuminate the respective tracks on the scale 240. Analogous to the above example, furthermore, the opto-chip 252 with the detector arrangement 1 is arranged on the upper side of the carrier substrate 253.

On the upper side of the carrier substrate 253 are further - not shown - conductor track structures arranged, via which the opto-chip 252 and the light sources 251 .1, 251 .2 are electrically contacted. Furthermore, so-called transmission grating structures are arranged in front of the two light sources 251 .1, 251 .2 for reference signal and incremental signal generation on the upper side of the carrier substrate 253. In this case, the transmission grating may be formed, for example, as a diaphragm with a translucent gap, the width of the gap being matched to the structure of the material measure 340 scanned therewith. On the underside of the carrier substrate 253, an antireflecting and opaque coating is further arranged, which has light-permeable window areas in front of the light sources 251 .1, 251 .2 and the various detector areas.

In addition, a protective cap, which consists of the lateral carrier elements 254.1, 254.2 and the cover element 255, is additionally arranged on the carrier substrate 253. The various elements of the protective cap surround or encapsulate the opto-chip 252 on the carrier substrate 253 and serve i.a. for additional protection of the Opto-Chip 252 against mechanical damage. The cover member 255 is preferably formed as a printed circuit board with corresponding conductor tracks. On the side facing the opto chip 252, a further signal processing module 256 is also arranged, via which the further processing of the signals of the opto chip 252 takes place; Of course, several more signal processing blocks can be provided on the circuit board here. With regard to this structure, reference is also made to EP 1 1 14 662 B1 of the Applicant.

On the basis of the figure 3, the scanning is integrated into the reference mark integrated in the incremental graduation with the aid of the scanning unit according to the invention. In addition to the material measure 340 with the reference mark 343 integrated in the incremental graduation 342, only that part of the scanning unit 350 that is needed to generate the reference signal is shown in this figure.

In the scanning unit 350, a single light source 351 is provided for generating the various position-dependent signals, which is formed for example as an LED. The light-emitting side of the light source is oriented in the direction of the carrier substrate 353, wherein a width matched to the periodicity of the incremental graduation 342 is formed on the carrier substrate 353 in front of the light source 351. As already indicated above, the reference mark 343 integrated into the incremental graduation 342 is formed at the location of the respective reference position along the measuring path in the present example by omitting certain non-reflecting partial regions from the periodic incremental graduation 342. According to FIG. 3, approximately three non-reflective subregions shown in dark are omitted. The resulting aperiodic structure acts as a detectable reference mark 343. Of course, significantly more subregions of the incremental graduation 342 can also be omitted to form the reference mark 343 integrated in the incremental graduation 342. Likewise, it is of course possible to omit reflective subregions of the same at least partially reflecting the subregions of the incremental graduation 342 and thus to form an aperiodic structure, which can then be used as a reference mark.

To scan this aperiodic structure or reference mark 343, it is necessary to electrically connect certain detector elements of this detector region 330 to one another on the scanning unit 350 or in the reference signal detector region 330 arranged there. In the present example, these are the detector elements 330.1, 330.2, 330.3, which detect a Gaussian signal maximum with respect to the radiation reflected by the material measure 340 when the reference mark 343 is moved over, which is illuminated by the light source 351. Incidentally, the width of the Gaussian reference signal generated in this way can be adjusted by selecting the width of the transmission gap in front of the light source 351. Depending on the configuration of the reference marking 343 on the material measure 340, this can of course also be other detector elements in the reference signal detector region 330. In any case, the electrical contacting of the required detector elements takes place via a metallization plane, which is connected to the respective detector elements via contacting openings. Preferably, a compensation signal is connected in difference to the signals from the detector elements 330.1, 330.2, 330.3, which are thus electrically contacted with one another, for equal-level compensation. A further concrete embodiment of the scanning unit according to the invention is finally explained with reference to FIGS. 4a and 4b. FIG. 4 a shows a plan view of a part of an incremental graduation 442 which is formed integrally in the one reference mark. The dark portions of the incremental graduation 442 are non-reflective, while the bright portions are reflective. The reference mark 443 integrated in the incremental graduation 442 is formed in the present example by omitting in each case a non-reflective subregion from the periodic arrangement of reflective and non-reflecting subregions at six locations.

FIG. 4b shows a partial view of the reference signal detector region 430, which is suitable for scanning the reference marking from FIG. 4a. Tuned to the location of the six omitted non-reflective portions, a first group of interconnected triplets of detector elements 430.1a-430.6a are electrically connected to produce a first fractional reference signal thereabove when the scanning unit passes over the reference mark 443. Furthermore, a second group of triplets of interconnected detector elements 430.1 b - 430.6b is electrically conductively connected to each other in order to generate a second sub-reference signal, which has a certain phase shift relative to the first sub-reference signal. Analogously to the first group of detector elements 430.1a-430.6a, of course, the selection of the position of the second group of detector elements in the reference signal detector area 430 also takes place as a function of the aperiodic structure of the reference mark 443. The embodiment of the aperiodic structure of the reference marking 443 is preferably carried out in such a way that when passing the same by means of the scanning unit only one of the interconnected triplets of detector elements of a group detects a signal. Only at a single position do all six groups of three of a group detect a signal and thus generate the reference signal. In this way, insensitivity of the scan is guaranteed against any contamination of the material measure. The remaining detector elements in the reference signal detector region 430 are also all electrically connected to one another and thus provide a compensation signal that can be used for the DC compensation of the sub-incremental signals. With regard to the signal evaluation, it has proven advantageous if the sum of the number of detector elements from the first and second groups is selected to be identical to the number of remaining interconnected detector elements from which the compensation signal is derived.

The sub-reference signals of the first and second groups are connected in sum and difference to each other, converted into rectangular signals and generated via a logical UN D link, a further processable reference signal. With regard to such a generation of a reference signal, reference is made to EP 1 050 742 B1 of the Applicant.

Instead of integrating a reference mark 343 in the incremental graduation, as shown in FIG. 4a, an aperiodic structure with an identically formed reference mark could also be arranged in a parallel track adjacent to the incremental graduation, as in FIG. 2a. This could then also be scanned with a reference signal detector range, as shown in Figure 4b.

In addition to the variants discussed so far, there are, of course, in the context of the present invention still further possible embodiments.

Claims

claims

1 . Scanning unit for an optical position measuring device with

at least one light source (51, 1, 51, 2, 151, 251, 1, 251, 2, 351),

- A detector arrangement (1) with at least one incremental signal detector area (10, 20) and a reference signal detector area (30, 430), wherein

- The incremental signal detector region (10, 20) is designed as a structured detector array, which comprises a plurality of groups of individual detector elements and the in-phase detector elements of several groups are electrically interconnected to produce incremental partial signals and

- The reference signal detector area (30; 430) comprises a plurality of identically formed detector elements and individual ones of the detector elements for generating reference signals are electrically interconnected, and

a transparent insulating layer is arranged above the detector elements of the incremental signal detector region (10, 20) and / or the reference signal detector region (30; 430) and has at least one contact opening above a plurality of predetermined detector elements via which the corresponding detector elements can be electrically connected to one another are.

2. Scanning unit according to claim 1, wherein the detector arrangement (1) comprises two incremental signal detector areas (10, 20), between which the reference signal detector area (30; 430) is arranged.

A scanning unit according to claim 1 or 2, wherein within the reference signal detecting area (30; 430)

- Several first groups of adjacent detector elements are electrically connected to each other and - Several second groups of adjacent detector elements are electrically connected to each other, which are different from the first group and

- the number of detector elements in each first group and each second group is identical.

Scanning unit according to claim 3, wherein further detector elements which are not assigned to the first or second groups are electrically connected to one another and the number of further detector elements corresponds to the sum of the number of detector elements in the first and second group.

Scanning unit according to at least one of the preceding claims, wherein at least two light sources (51 .1, 51 .2; 251 .1, 251 .2) are arranged laterally adjacent to different sides of the detector arrangement (1).

Scanning unit according to at least one of the preceding claims, wherein

- The detector assembly (1) and the at least one light source (51.1, 51 .2; 151; 251 .1, 251.2; 351) on the upper side of a transparent support substrate (53; 1 53; 253; 353) are arranged and the photosensitive side the detector arrangement and the light-emitting side of the light source (51 .1, 51 .2; 151; 251 .1, 251 .2; 351) are oriented in the direction of the upper side of the carrier substrate (53; 153; 253;

an opaque and antireflective coating on the underside of the carrier substrate (53; 153; 253; 353) with window areas in front of the light source (51 .1, 51 .2; 151; 251 .1,251,2; 351) and the detector arrangement (FIG. 1) is arranged.

A scanning unit according to claim 6, wherein in front of the light-emitting side of the light source (51 .1, 51 .2; 151; 251 .1, 251 .2) a diaphragm with a transparent gap on the carrier substrate (53; 153; 253; 353) is arranged.

8. Scanning unit according to claim 6, wherein on the carrier substrate (253) above the detector arrangement (1) and the at least one light source (251.1, 251 .2), a protective cap is formed.

9. Scanning unit according to claim 8, wherein the protective cap comprises a cover element (255) designed as a printed circuit board, on which one or more signal processing modules (256) are arranged.

10. Optical position-measuring device with a scanning unit according to at least one of the preceding claims and a material measure (40; 140; 240; 340) with an incremental graduation (42.1; 142; 242.1; 342) and one or more reference markings (42.2; 242.2; 343).