DE102007007311B4 - Scanning unit for a position measuring device for the detection of optical measuring graduations and corresponding position measuring device - Google Patents

Abstract

Scanning unit (1) for the detection of optical measuring standards (100, 200) which have an optical position coding (110, 120, 210, 220), with - a light transmitter (50) which at least partially illuminates the measuring standard (100, 200), - a scanning receiver (10) which has light-sensitive receiver fields (11, 12), with - a scanning diaphragm (20) which has diaphragm openings (21, 22), the receiver fields (11, 12) and / or the diaphragm openings (21, 22) of the scanning diaphragm (20) according to the position coding (110, 120, 210, 220) of the material measure (100, 200) are formed, with - a microlens array (30) which has at least one microlens (31, 33) for imaging the through the position coding (110, 120, 210, 220) of modulated light on the receiver fields (11, 12) of the scanning receiver (10) carries, and with - an aperture diaphragm array (40) which is arranged between the microlens array and the scanning receiver and which each have one Aperture diaphragm opening (41 ) in the optical axis (32) of each microlens (31, 33) of the microlens array, characterized in that ...

Description

Field of the invention

The invention relates to a scanning unit for a position measuring device for the detection of optical measuring standards and a corresponding position measuring device according to the preamble of the independent claims.

Such a position measuring device comprises a measuring standard provided with an optically readable position coding, a light source for emitting light in the direction of the measuring standard and a scanning unit consisting of a scanning receiver with photosensitive structured surfaces for receiving the light modulated by the scale and a lens arrangement which is arranged on the surface of the Abtastempfängers and consists of one or more microlenses and which image the illuminated by the light source portion of the measuring scale on the structured receiver surfaces of the Abtastempfängers.

The position measuring device can be used for the detection of reflective or transmissive scales that are operated in accordance with incident or transmitted light method. In the former case, the light emitter and receiver are on the same side of the scale, the light reflected on the scale and modulated by the position code is subsequently detected by the scanning receiver. At transmissive scales, the light emitter and receiver are located on opposite sides of the scale and the light emitted by the light emitter and passing through the at least partially transparent scale is modulated by the scanning receiver.

The measuring graduation can be configured, for example, for angle measurement as a code disk with circularly arranged codes or for length measurement as a ruler with linearly arranged position codes. The position coding may comprise incremental and / or absolutely coded tracks.

State of the art

State-of-the-art optical position measuring devices use code surfaces as position coding in the form of amplitude objects of differing degrees of transmission or reflection, in the case of an incremental code track in the form of an amplitude grating, the measuring period corresponding to the grating period. In a projective scan of transmissive scales, the code areas are illuminated with substantially parallel light and detected on the opposite side by a scan receiver. Due to illumination with non-ideal parallel collimated light and diffraction at the code fields, the scan receiver must be as close as possible be arranged to scale, which is why only very small distance tolerances of less than 50 microns are allowed. If the distance is too small, the scale collides with the scanning receiver resulting in the destruction of the position measuring device. As the distance increases, the contrast and the interpolability and thus the resolution of the position signals decrease; Finally, if the distance is too large, position signals will no longer be generated.

A prior art scanning receiver is an integrated circuit (iC) which is typically based on CMOS semiconductor processes and which has individual photosensitive receiver arrays which respectively generate position dependent signals. For incremental measuring graduations, these are generally at least four fields, which are each offset by a quarter of a measuring period in the measuring direction to each other and correspondingly generate position-shifted signals phase-shifted by 90 degrees. Eventually, additional receiver fields are provided which scan a corresponding coded reference track and generate a reference or zero signal. The receiver fields on the scanning receiver are each provided either as individual according to the coding of the material measure structured photosensitive surfaces on the surface of the receiver chip, which are evaluated together, as a so-called "phased array", or contiguous surfaces are used, wherein the latter case, a scanning aperture is positioned on the surface of the receiver chip. The scanning diaphragm consists of a glass plate with a chromium layer applied on one side and lithographically structured in accordance with the position coding of the scale, which has transparent openings above the photosensitive scanning surfaces of the scanning receiver. In order to minimize the distances between the openings of the scanning diaphragm for measuring scale, the chromium layer is located on the side of the scanning diaphragm facing towards the material measure.

The scale or the material measure carries the position information in the form of binary codes. Incremental codes are alternating light and dark fields, which are formed like a line, wherein the line width to achieve high resolutions in the measuring direction is significantly narrower than transverse to the measuring direction. For absolute encodings it is necessary to detect several single- or multi-track codes simultaneously. Known absolute encodings are, for example, pseudo-random codes, binary codes, binary coded decimals (BCD), gray codes or vernier Codes. Furthermore, it is known to provide combinations of incremental and absolute codes on a material measure.

From the DE 100 25 410 A1 or the DE 103 03 038 A1 For example, diffractive measuring graduations are known which have a binary position coding in the form of alternately unstructured code surfaces or of code surfaces provided by means of diffractive phase gratings, in which case the lattice constant of the phase lattice is smaller than the measuring period by at least one order of magnitude. For detection, the material measure is imaged by means of a lens on the optical receiver. In particular, in the detection of absolute material measures in which a large area must be detected, lenses of large diameter and thus also comparatively large distances between the scale and the lens or between the lens and the optical receiver. Furthermore, the lens must be adjusted relative to the optical receiver.

From the EP 0 470 420 A1 an optoelectronic scanning device is known in which a code carrier is illuminated by means of a light source and detected by an optoelectronic sensor. For this purpose, an optics in the form of a plurality of juxtaposed gradient index lenses (GRIN lenses) or microlens plates is arranged between the optically scannable code track on the code carrier and the optoelectronic sensor, which images the code track on the photosensitive sensor surface of the optoelectronic sensor.

When using one or more microlens plates arranged one behind the other, the problem of crosstalk exists; H. There are overlapping object fields, which means that the light which passes through a lens of the first lens array, passes into a laterally disposed lens of the second microlens array or in an adjacent receiver field of the scan-receiver. In contrast, with GRIN lenses, the comparatively long overall length and the individual production oppose a compact, simple and inexpensive construction. In addition, the different microlens plates have to be adjusted to each other and the Abtastempfänger consuming.

From the EP 1 447 648 A1 An incremental encoder is known which images a scale grid by means of a lens on an index grid arranged in front of a light receiver. In the image-side focal plane of the lens is an aperture diaphragm.

The DE 102 17 726 A1 shows an optical position measuring device with a periodically arranged lens array, which images a periodic grating structure of a scale in a periodic grating, wherein the images of different lenses have no phase jumps to each other. In particular, a radial lens array is disclosed for imaging a radial lattice structure.

Disclosure of the invention

It is the object of the invention to provide a scanning unit and a corresponding position-measuring device which has a lens array which is equally universally applicable for rotary and linear measuring graduations with different incremental measurement periods and which can be mounted easily and reliably and, in particular, the distance between the microlens array and the scanning chip Reliably ensures the assembly.

This object is achieved by a scanning unit and a corresponding position measuring device according to the independent claims.

Preferred embodiments of the invention as well as other advantageous features of the invention are indicated in the dependent claims.

According to the invention, a lens plate is used as the imaging system, which has at least one refractive or diffractive microlens and is referred to below as microlens array for the sake of simplicity. This is mounted on the receiver chip above the possibly existing scanning diaphragm. The microlens array lies in a plane parallel to the material measure or to the surface of the Abtastempfängers. The microlenses image the positional coding of the measuring scale on the surface of the scanning aperture openings or on the surface of the photosensitive receiver fields of the scanning receiver. The receiver fields are each largely in the optical axis of the respective microlenses. The focal plane of the lenses is preferably in the planar rear side of the lens array. Between the microlens array and the scanning diaphragm or the surface of the scanning receiver is an arrangement of aperture stops, which in the following will be referred to as an aperture diaphragm array for the sake of simplicity. This aperture diaphragm array is realized in the form of a thin opaque layer and assigns each of the microlenses of the microlens array exactly one telecentric aperture diaphragm in the image-side focal point. The aperture stops are transparent openings within the opaque layer. As a result, each lens forms part of the material measure without crosstalk at least on a part of a receiver field. For example, it may be provided that the images of a plurality of microlenses fall on a single receiver field or that the image of each microlens of the microlens array exactly to a receiver field of the scan-receiver or to a defined number of multiple receiver fields passes.

Preferably, at least one collimator lens for collimating the light emitted by the light emitter is integrated laterally over the scanning receiver protruding into the microlens array for the purpose of illuminating reflective measuring graduations.

By using a microlens array, the object field and the image field are split, whereby very small distances between the lens array and the material measure on the one hand and the lens array and the Abtastempfänger on the other hand can be achieved. Furthermore, this arrangement has previously unattainable large distance tolerances between the scale and the Abtastempfänger.

Because of the small diameter of the microlenses, they can have a comparatively short focal length. Due to the small focal length of the individual microlenses then results in a small working distance, which in addition to the intensity of the light in particular increases the contrast, which in turn a better interpolability of the generated by the photosensitive photoelectric receiver fields of the Abtastempfängers position signals is achieved.

The focal length f of the microlenses is preferably between 0.5 mm and 2 mm, the lens diameter D is preferably about 0.3 mm to 2 mm. The f-number k = f / D of the lenses without consideration of the aperture diaphragm is approximately between k = 0.5 for aspheric lenses and k = 4, the numerical aperture A _{Obj of} the lenses is approximately A _Obj ≈ for a 1: 1 imaging D / 4f = 1 / 4k and is therefore preferably less than 0.5.

Due to largely parallel light as well as the aperture diaphragm (telecentric aperture) positioned laterally for each individual microlens, laterally incident light is masked out, so that in particular no overlapping of the image fields of the individual lenses of the microlens array occurs on the different scanning fields of the scanning diaphragm or the scanning chip. In the prior art further measures are required to avoid overlapping of the individual image fields, such as opaque elements for separating the beam paths of the individual microlenses, which, however, makes a separation of the lenses necessary. The advantage of the scanning unit according to the invention, however, with a single aperture diaphragm array, which is formed in the image-side focal plane of the microlenses as a continuous component, as well as with a single contiguous microlens array to avoid overlapping of the image fields of the individual lenses reliably or to a sufficiently small area restrict, without the need for additional resources.

• 1) Absorption der seitlich aus der Maßverkörperung austretenden Beugungsordnungen bei der Abtastung diffraktiv codierter Maßverkörperungen
• 2) größere Schärfentiefe und somit eine erhöhte Axialtoleranz zwischen dem Maßstab und der Abtasteinheit,
• 3) weitgehende Unabhängigkeit des Abbildungsmaßstabes von kleinen Abstands-Änderungen zwischen der Maßverkörperung und dem Mikrolinsenarray und daher weitgehende Konstanz des Abbildungsmaßstabes der Einzellinsen
• 4) enges Gesichtsfeld („field of view”) der Einzellinsen und daher keine Überlappung der Bilder unterschiedlicher, insbesondere benachbarter Mikrolinsen.

The advantages of the telecentric apertures in the common rear focal plane of the microlenses are in detail:

• 1) Absorption of diffraction orders emerging laterally from the measuring standard during the scanning of diffractively coded measuring graduations
• 2) greater depth of field and thus increased axial tolerance between the scale and the scanning unit,
• 3) extensive independence of the imaging scale of small distance changes between the material measure and the microlens array and therefore far-reaching consistency of the magnification of the individual lenses
• 4) narrow field of view of the individual lenses and therefore no overlapping of the images of different, in particular adjacent microlenses.

In addition, such a scanning receiver can in particular be used equally for measuring scales which have reflective or transmissive amplitude or phase gratings as coding. For scanning diffractive measuring graduations, the diameter of the aperture diaphragms is determined, in particular, by the fact that the diffraction orders that are not to be detected and emerge laterally from the material measure are masked out.

For different applications, such as for scanning length or angle encoders, which have incremental or absolute encodings with different resolutions, only different scan aperture must be available, while the scanning surfaces of the scan-receiver can remain unchanged. The arrangement of the microlenses on the microlens array is therefore only to be adapted to the geometry and the arrangement of the scanning surfaces of the scanning receiver and is therefore also universally applicable for different codes.

Preferably, the lens array consists of a glass or plastic substrate and has on its scale side facing the convex curved lens surfaces which are integrally connected to the substrate, and which are arranged in a plane parallel to the surface of the Abtastempfängers level next to each other. The sample receiver facing side of the lens array is preferably flat. This results in plano-convex microlenses whose lens profile can be spherical or preferably also aspherical.

In addition to a microlens array with plano-convex microlenses, the use of biconvex or convex-concave lenses is conceivable. In addition to plano-convex lenses, microlens arrays with bi-aspheric, symmetrical biconvex microlenses are particularly preferably used for 1: 1 imaging due to the better imaging line, which have the same radii of curvature on the front and rear sides.

Furthermore, it is in principle possible to provide refractive microlenses on the type of Fresnel lenses. The advantage here is in particular the small lens height and the simple production by embossing techniques in plastics or glass. Since the illumination takes place with largely monochromatic light, the diffraction that occurs disadvantageously with diffractive lenses does not have a serious effect.

Preferably, the lens surfaces are arranged on the surface of the substrate in a regular rectangular or hexagonal grid. Particularly preferred are microlens arrays with gapless directly adjacent Linsenfächen, d. H. used with a fill factor of 100%. Furthermore, in principle, irregular, non-periodic arrangements are possible. The diameter as well as the lens curvature and thus also the focal length are identical for all individual lenses. It should be noted that the lens "array" may also be degenerate in that it may comprise only a single lens or a single row or column of lenses; the same applies to the aperture diaphragm array.

Different methods can be used to produce the microlens array. It is possible to manufacture the microlens arrays by means of embossing, injection molding or injection-compression molding techniques made of plastic. In this case, either entire wafers can be structured in each case, with the microlens arrays subsequently being singulated or the individual microlens arrays being produced separately.

Furthermore, glass embossing techniques, such as lens sizing, particularly in low glass transition temperature glass types, are known which impress a negative mold directly into glass. In particular, these embossing techniques are capable of producing lens molds extending into each other or directly adjacent one another. In particular, it is possible to produce aspherically shaped lenses. It is also possible with this technique to emboss glass wafers and then to separate the individual microlens arrays.

Another known method, which is used for example by the company SÜSS MicroOptics SA in Neuchatel in Switzerland, uses photolithography with reflow of the developed paint and subsequent reactive ion etching (RIE) in glass wafers. This wafer is then singulated into individual lens arrays or used to make a stamper for a replication technique, such as UV or hot stamping. The lenses produced by the reflow process have a minimum distance of a few micrometers.

The scanning diaphragms and the aperture diaphragms are preferably produced in the form of glass wafers by means of photolithographic structuring of a largely light-impermeable layer which consists, for example, of chromium, aluminum or titanium or titanium compounds and is vapor-deposited or sputtered, for example by means of a resist lift-off method.

In order to produce the scanning unit, either the scanning aperture, the aperture diaphragm array and then the microlens array are positioned on the surface of the scanning receiver one after the other, or the scanning aperture and the microlens array with the aperture diaphragm array arranged therebetween are initially positioned relative to one another and this component is then placed on the surface of the scanning aperture. Receiver arranged. Furthermore, in the latter case, it is possible to position the already separated scanning apertures and microlens arrays relative to one another, or to position the respective wafers which carry the microlenses and the aperture diaphragms or the scanning apertures initially to one another, to bond them and then to apply them by means of a wafer saw seperate.

Furthermore, it is possible to position the wafers of the microlens arrays, the diaphragms and the Abtastempfänger-chips to each other, to bond and then to separate.

The arrangement and the diameter of the microlenses are adapted to the geometry and arrangement of the scanning fields of the scanning receiver. The lens diameter and the focal length of the individual lenses are preferably less than 2 mm. The focal length or the radius of curvature of the microlenses is preferably determined such that, depending on the thickness of the scanning diaphragm plate, the aperture diaphragm and the microlens array and depending on the corresponding refractive indices and the magnification of the distance of the microlenses to the scanning aperture or to the surface of the Receiver surfaces of the scanning receiver corresponds exactly to the image size. Alternatively, the magnification is determined from the lens focal length, refractive indices, and distances, and the scan aperture is adjusted accordingly.

The distances of the microlenses to the scale on the one hand and to the surface of the scanning chip or scanning aperture openings on the other hand are determined by the imaging equation and determine the magnification. When a magnification of 1: 1 is selected, the distance from the object-side major plane of the lenses to the scale surface is also twice the focal length as the distance from the image-side major plane of the lenses to the surface of the scan receiver or apertures of the scan aperture, respectively extended by the factor of the respective refractive indices. Without limitation, by varying the distances, however, magnifying or decreasing real (ie, non-virtual) mappings are also possible, ie mappings on a scale greater or less than one. A reduced image has the advantage that the image contrast is increased.

An array of aperture diaphragms is preferably located in the focal plane of the microlenses, wherein a diaphragm is arranged in the optical axis of each individual lens. Thus, there is an object-side telecentric beam path. As a result, with a slight change in distance between the material measure and the lens array, the image scale remains virtually unchanged, whereby comparatively large distance tolerances between the material measure and the scanning unit are permitted. If largely parallel light is used for illumination, then only a small amount of light is hidden by the telecentric aperture diaphragms.

The aperture diaphragm array is realized by an at least largely opaque layer, which is applied to a carrier substrate and removed only at the locations of the apertures. The apertures are preferably round. The diaphragm plate or the diaphragm support consists of a transparent substrate, such as glass or plastic. For this purpose, a photosensitive lacquer layer is first applied to the substrate surface, for example by spinning, which is exposed through a structured mask and developed, so that the lacquer layer is partially removed. Subsequently, the opaque layer is applied and finally the remaining lacquer layer is removed so that the transparent substrate surface remains uncoated at these points. The opaque layer is made of aluminum or (black) chromium, but preferably titanium or titanium compounds to reduce back reflections, and is preferably applied to a glass surface by vapor deposition, CVD, PVD or sputtering and patterned by photolithography. The surface of an aluminum layer is light Absorbent diaphragm layer can also be black anodized to avoid back reflections of the light. These deposited or sputtered layers typically have a thickness of only about 20 nm to 150 nm. Without limitation, however, other opaque metallic, dielectric or plastic layers can be used. Any existing field stop, which may be provided on the microlens array on the object side, can be applied by means of a corresponding technique.

The aperture diaphragm array may be a separate component. Preferably, however, this aperture array is disposed on already used components, such as the lens array or the scanning aperture. This eliminates a separate component with a corresponding adjustment effort. However, in principle it is also possible to use, for example, a thin metal foil with corresponding openings as an aperture diaphragm array or scanning diaphragm array.

In a first embodiment, the object side of the lens array preferably has the aperture array, wherein an aperture stop is arranged in each case in the optical axis of each individual lens. The thickness of the lens array is dimensioned such that the focal plane of the individual lenses lies in the flat bottom of the lens array. This results in a telecentric optical system, whereby a slight change in the distance between the scale and the lens array does not significantly alter the imaging scale, so that the overall measuring system is comparatively distance tolerable with respect to the distance between the material measure and the scanning receiver. The distance tolerance depends on the measurement period as well as on the parallelism of the illuminating light and is approximately 1 mm for a measuring period length of 100 micrometers, approximately corresponding to 1024 increments on a code disc diameter of 40 mm.

In contrast, projective optical measuring methods without the use of imaging lenses according to the prior art have significantly smaller distance tolerances of about 50 micrometers and less, depending on the width of the measurement grid to be scanned.

Alternatively, when using a scanning diaphragm, the aperture diaphragm array can also be arranged on the side of the scanning diaphragm plate which faces away from the scanning chip. The scanning chip facing side of the aperture plate thereby carries the Abtastblenden, while the opposite side has the aperture diaphragm array. The glass plate thus has on both sides structured partially opaque layers, usually photolithographically structured chromium or titanium layers. In principle, other metallization layers, such as aluminum or dielectric layers come into consideration. The scanning diaphragm has openings corresponding to the coding of the Measuring scale, whereby the magnification and an inversion due to the single-stage mapping are taken into account. The image inversion generated by the individual microlenses provides for a partial inversion of the codes as well as a change in the curvature of the code track in the case of angular code slices.

Further, it is possible to integrate the scanning aperture directly on the surface of the scanning receiver chip, such as through an aluminum layer, which is applied to the chip surface in an additional manufacturing process step.

In this case, a sample receiver with a "phased array", i. H. is used with corresponding to the material scale coded receiver fields and thus no scanning aperture is necessary, either a separate aperture diaphragm plate is used, on which the microlens array is mounted and the aperture apertures facing the microlens array, or it is the aperture diaphragm array on the back of the microlens array and provided a separate transparent glass plate is arranged as a spacer between the microlens array and the Abtastempfänger. Due to the thickness of this glass plate, the distance between the microlens array and the Abtastempfänger is set and it is omitted in the latter case, a separate adjustment of the aperture diaphragm array relative to the microlens array.

The microlens array, the aperture diaphragm array and the possibly required scanning diaphragm are preferably mounted directly on the surface of the scanning receiver chip, quasi as "lens on reticle on chip" or "lens on lass on chip" and then fixed laterally by means of opaque potting compound. Furthermore, it is possible to glue together the surfaces of the individual components, consisting of microlens array and the individual diaphragm plates, in particular cemented with optical adhesive in order to avoid air pockets.

The focal length of the lenses is preferably determined as a function of the thickness and the refractive indices of the microlens arrays, preferably the glass or plastic plates, the scanning diaphragm and the aperture diaphragm array arranged therebetween, so that when the individual components are superimposed on the surface of the scanning receiver the image width is quasi is set exactly by itself, so that in the axial direction parallel to the optical axis of the imaging beam path no distance calibration is required.

Another constructive possibility is to adapt the scanning aperture openings next to the material measure to the imaging scale, which results from the lens focal length and the image size, ie the distance of the microlens array of scanning receiver and the respective refractive indices of the microlens array and the aperture plate. The resulting distance between the measuring scale and the microlens array (the object width) is adjusted accordingly.

Since the glass thicknesses of the microlens array and the scanning aperture are not arbitrarily variable and the image plane must lie in the surface of the scanning apertures or the photosensitive surfaces of the scanning receiver, it may be necessary to increase the focal plane by up to about 10-20% of the focal length to provide about 100-200 microns at most above or below the aperture apertures, d. H. the aperture stops are slightly off-focus.

In the event that diffractive material measures are used which exploit the optical interference and diffraction of the light, then, in addition to the diffraction orders to be detected, other main or secondary orders occur which are not detected. The aperture diaphragm array ensures the dimensioning at the same time the suppression of these not to be detected main or secondary orders.

In order to prevent scattered light from reaching the photosensitive surfaces of the scanning receiver, in addition the object-side region of the lens array between the microlenses can be provided with an opaque layer as the field stop. With a suitable arrangement and focal length of the microlenses, however, this field stop can also be omitted. In particular, when the microlens array has a fill factor of 100%.

The light emitted by the light source is preferably parallelized by means of a converging lens (condenser lens) and thus illuminates the scale. However, it is also possible in principle to operate an optical position-measuring device with divergent light.

As a light source according to the prior art light emitting diodes (LEDs) are used, which emit in the (near) infrared (near IR) spectrum. However, it is also possible to use LEDs which emit in the red spectrum or in the visible spectrum. The half-width is typically about 20-50 nm. Furthermore, the use of semiconductor lasers as a source of illumination is also conceivable. For cost reasons, due to the shorter life, especially at high temperatures and the disadvantageous high spatial and temporal coherence, lasers have as a light source However, in the case of amplitude grid scales, the illumination beam path is collinear with the imaging beam path, and in the case of diffractive codings it can be used, for example, in accordance with FIG DE 103 03 038 A1 be arranged at an angle to this. This angle preferably corresponds to the angle of the first diffraction order of the light diffracted at the diffractive encoding. Thus, in both cases, the illumination beam path merges into the imaging beam path. Subordinate orders are hidden by aperture diaphragms with a corresponding arrangement and a sufficiently small diameter.

Since a single-stage optical image is provided, the inversion of the image must be taken into account. On the one hand, the direction of rotation is apparently opposite, on the other hand, the inversion of the code track curvature in the case of angle encoders must be considered. For this purpose, the apertures on the scanning or the receiver surfaces in the case of a Abtastempfängers with applied to the chip surface "phased arrays" are adjusted accordingly.

In the case of absolute codings, it is advisable to image each code field by means of a separate microlens. Otherwise, in the case of imaging multiple code fields with one lens, the inversion of the code fields mapped by the individual lenses onto the scanning receiver must be taken into account accordingly.

Particularly advantageous is the use of the scanning unit according to the invention in conjunction with a vernier-coded material measure approximately according to the DE 103 32 413 B3 since each code track is incremental and one obtains an absolute position information by taking into account the phase positions of the different code tracks.

embodiments

Further features and advantages of the invention will become apparent in the following description of exemplary embodiments.

Show it:

1 a first embodiment of the invention in a schematic representation,

2 a plan view of the scanning unit according to the 1 .

3 a lateral section through the microlens array according to the first embodiment,

4 a section of a lateral section through a microlens array according to a second embodiment,

5 a lateral section through a section of the position measuring device according to the invention according to the second embodiment,

6 a perspective exploded view of a part of the position measuring device according to the second embodiment,

7a and b show the top view and the lateral overall view of the microlens array according to the second embodiment,

8th shows the divergence of the illuminating light,

9 shows schematically the divergence of the light emerging from the material measure and the imaging beam path,

10 FIG. 12 shows a detail of the plan view of the microlens array with underlying scanning aperture openings and scanning receiver areas according to the second exemplary embodiment, FIG.

11 shows a further embodiment of a scanning unit according to the invention,

the 12a -C show schematically the image inversion in the image of rotary dimensional standards,

13 shows schematically the consideration of the inversion of the coding due to the single-stage mapping,

the 14a and b show the illumination arrangement of transmissive and reflective diffractive measuring graduations,

the 15 represents a preferred arrangement of the microlenses for scanning incrementally coded measuring graduations,

the 16 shows the image field overlap of adjacent microlenses,

the 17 represents a scanning receiver for a reflective measuring standard,

the 18 shows the corresponding microlens array according to the 17 .

the 19 and 20 show sections of the illumination beam path for illuminating a reflective measuring standard,

the 21 shows a scanning receiver with integrated into the microlens array and obliquely arranged collimator lenses,

the 22 shows a scanning receiver with integrated transmitter diode,

the 23 shows a further embodiment of a microlens array with scanning aperture openings arranged underneath,

the 24 shows the course of a light beam incident obliquely into a microlens,

the 25 shows a microlens array with a lens fill factor of 100%,

the 26 and 27 show the illumination of a diffractive material measure in the transmissive case ( 26 ) as well as in the reflective case ( 27 ) and

the 28 shows the image of an incremental coding by adjacent microlenses,

the 29 shows two microlenses with scanning aperture openings arranged behind,

the 30 shows schematically the arrangement of two adjacent scanning apertures,

the 31 shows the hexagonal arrangement of the microlenses and

the 32 shows a preferred arrangement of measuring scale and microlens array.

In the 1 is schematically illustrated a first embodiment of a position-measuring device according to the invention. The scanning receiver 10 in the form of a semiconductor chip, which has been produced approximately in a CMOS process, is on a substrate 17 arranged, which may be about a circuit board or a housing. Bond wires 15 Contact the chip surface with traces (not shown in the drawing) on the substrate 17 ,

Directly on the chip surface is a scanning aperture 20 arranged, the apertures on the side facing the chip above the photosensitive surfaces of the Abtastempfängers 10 are positioned. The scanning aperture 20 consists of glass or plastic and has a refractive index n ₂ at the illumination wavelength λ.

On top of the scan aperture 20 (on the object side) is an aperture diaphragm array 40 arranged, which in turn a microlens array 30 is arranged, such that preferably in the focal plane of the microlenses 31 of the microlens array 30 circular aperture apertures 41 are provided. It lies in the optical axis 32 behind every single microlens 31 exactly one aperture aperture 41 , The aperture panel array 40 is preferably on top of the scan aperture array 20 or on the plane underside of the microlens array 30 arranged. Alternatively, this can be provided a separate component. The microlenses 31 of the microlens array 30 are as plano-convex lens surfaces on the measuring scale 100 facing side of the microlens array 30 arranged and form part of the code tracks of the material measure 100 on the surface of the scanning receiver 10 from. Optionally, on the side of the microlens array 30 , which of the material measure 100 facing, the planar area outside the openings of the microlenses 31 with an opaque layer 38 be designed as a field stop.

Preferably, the stack is on the surface of the scanning receiver 10 consisting of the microlens array 30 , the scanning aperture 20 and the interposed. aperture diaphragm 40 , laterally with an opaque potting compound 16 potted, which also the bonding wires 15 includes.

The measuring standard 100 carries a positional coding which is on the surface of the scanning receiver 10 is shown. The coding can be the scanning unit 1 be facing or away. In the case that the material measure 100 is formed transmissive, the coded side of the measuring scale is preferably the scanning unit 1 facing.

For a 1: 1 scale image, the distance is between the scale 100 and the microlens array 30 twice the focal length f of the microlenses 31 , The thickness d of the microlens array 30 is dimensioned such that the focal plane approximately in the planar back of the microlens array 30 lies.

For a 1: 1 scale image, the scan aperture is shown 20 a thickness f '= n ₂ f, where f is the focal length of the microlenses 31 of the microlens array 30 and n ₂ denotes the refractive index of the scanning diaphragm.

The 2 shows a plan view of the scanning unit 1 according to the 1 , For better visibility, the photosensitive receiver fields covered by the aperture diaphragm and the scanning diaphragm and therefore not visible are visible 11 and 12 shown on the surface of the scanning receiver 10 are arranged side by side with a certain distance from each other. There are 6 microlenses 31 arranged in a regular rectangular 2 × 3 grid next to each other, which partially adjoin one another. The spaces between the microlenses, ie the remaining plane object-side surface of the microlens array 30 can with an opaque layer 38 be provided as a field stop. In the optical axis of each microlens 31 there is an aperture diaphragm 41 through which the light is directed to the receiver fields below 11 . 12 the scan receiver is mapped. The picture of each microlens falls 31 each on exactly two separate recipient fields 11 . 12 of the sample receiver 10 ,

In the 3 is the microlens array 30 shown again in the lateral section. There are three juxtaposed microlenses 31 recognizable, which in each case of the material measure 100 bundle outgoing, largely parallel light. The thickness d of the microlens array 30 in that respect correlates to the focal length f of the individual lenses, in that the focal point of each individual lens in the image-side rear side of the microlens array 30 lies. On this back of the microlens array is an array of aperture stops 40 arranged in the form of an opaque layer, which aperture apertures 41 in the focal points of the respective microlenses 31 having.

Beside material measures, which have non-diffractive codings, which modulate the amplitude of the incident light, are approximately from the DE 103 03 038 Measurement standards are known, which have binary code fields which are unstructured or which are provided with diffractive optical elements, such as with line gratings. In this case, for example, only the minus first diffraction order is detected, for which the material measure is illuminated with obliquely parallel incident light, wherein the illumination angle corresponds to the angle α _{-1 of} the first diffraction order. Then the minus first diffraction order to be detected leaves the material measure largely vertically, while the zeroth diffraction order leaves the material measure obliquely by the angle α _-1 (measured to the surface normal). In particular, the zeroth diffraction order must not be detected here, since this occurs both in the structured and the unstructured code fields.

The light which is incident obliquely parallel and a sufficiently large angle α to the optical axis 32 is in the focal plane outside the aperture apertures 41 collimated at a distance x to the optical axis and thus hidden. In addition, make sure that the distance x to the optical axis is not a multiple of the lens diameter D and thus through an aperture opening of another microlens 31 transmitted. Let n _{1 be} the refractive index of the microlens array, then the distance x becomes: x = dtan (β) with n ₁ sin (β) = sin (α) according to the Snellius law of refraction. This means that in particular must apply:
A / 2 <x = dtan (β), which results for plano-convex lenses with d = fn ₁ from the inequality:
A / 2f <sin (α _-1 ), where sin (α _-1 ) = n ₁ sin (β) and A is the diameter of the aperture stops.

For the diffraction angle α _{-1 of} the minus first order, the relationship applies: sin (α _-1 ) = λ / Λ, where λ is the wavelength of the illuminating light and Λ the lattice constant of the diffraction grating. For λ = 740 nm and Λ = 1.25 μm, for example, a diffraction angle of α _-1 = 36.3 ° is obtained. This results in a thickness d of the microlens array 30 of d = 1.5 mm and a refractive index of n ₁ = 1.4524 (for quartz glass, SiO ₂ ) a distance x = 0.67 mm. With a lens diameter D of, for example, D = 0.42 mm, this means that the light of the zeroth diffraction order is masked out as long as the following applies to the aperture stop A: A <2 min {x, | D-x |, | 2D-x |, ...} = 2min {nD - x |, n∈N∪ {0}}, ie about A = 0.3 mm, since the light must not fall through the apertures of adjacent microlenses.

wobei R der Krümmungsradius der Mikrolinse 31 ist. Weiter gilt für die Entfernung der objektseitigen Hauptebene H zur bildseitigen Hauptebene H' der Zusammenhang:

Für einen Brechungsindex n₁ = 1,5 erhält man somit beispielsweise; HH' = d/3. Die rückseitige (bildseitige) Brennweite (BFL, back focal length) ist nun gegeben durch: BFL = f – d + HH' = R/(n₁ – 1) – d/n₁. Die rückseitige Brennweite ist also genau dann gleich Null, wenn gilt: d(n₁ – 1) = Rn₁, was bedeutet, dass d = fn₁ bzw. dass HH' = R.The 4 shows a further embodiment of the invention. Shown is a single lens 31 a microlens array 30 , which plano-convex microlenses 31 has, which are spaced apart. The microlens array has a refractive index n ₁ , then applies to the image-side focal length f of the plano-convex microlenses:

where R is the radius of curvature of the microlens 31 is. Further, for the distance of the object-side main plane H to the image-side main plane H ', the following applies:

For a refractive index n ₁ = 1.5, one thus obtains, for example; HH '= d / 3. The back focal length (BFL) is now given by: BFL = f - d + HH '= R / (n ₁ - 1) - d / n ₁ . The back focal length is therefore equal to zero if and only if: d (n ₁ - 1) = Rn ₁ , which means that d = fn ₁ or that HH '= R.

For example, if d = 1.5 mm, then the condition with a refractive index of n ₁ = 1.4524 for the focal length f of the microlenses follows: f = 1.033 mm, from which a radius of curvature R of the microlenses of R = 0.467 mm is calculated.

For the lens height s ("lense sag"), the following relationship applies according to Pythagoras: R = s / 2 + D ² / (8s). With a lens height of s = 50 μm and a lens diameter of D = 0.42 mm, for example, a radius of curvature of the lens of R = 0.466 mm results.

On the scanning receiver 10 facing side of the microlens array 30 ie, on the image side, is the aperture diaphragm array 40 in the form of an opaque layer with apertures 41 applied. For a reproduction on a scale of 1: 1, the thickness of the scanning aperture must then be f '= fn ₂ . If, for example, the same type of glass is used for the scanning diaphragm, the thickness f 'of the scanning diaphragm is identical to the thickness d of the microlens array at a magnification of 1: 1.

If a glass type with a different refractive index is used for the scanning diaphragm, the scanning diaphragm must have a different thickness so that the image plane lies in the surface of the scanning receiver or the scanning diaphragm apertures. Since glass plates are not available in any thicknesses, it may be necessary to increase the aperture turbulence array by up to about 10-20% of the focal length in a plane offset parallel to the focal plane of the microlenses 31 to arrange. A shielding of obliquely incident light and a separation of the imaging beam paths of different microlenses 31 are thus still guaranteed. Preferably, microlenses are used with the shortest possible focal length of 2 mm or less in order to achieve with appropriate design in addition to a small structure of the scanning unit in particular even small distances to the material measure. In addition to the resulting compact design of the position measuring device, there is the further advantage that the light, which is the material measure 100 leaves, does not diverges greatly and in addition to a high light intensity in particular sets a high contrast of the light imaged on the Abtastempfänger, resulting in highly interpolatable position signals.

In the 5 is a side section of the position measuring device according to the invention shown according to the second embodiment and shows the imaging beam path starting from the means of bright fields 120 and darkfields 110 coded surface of the material measure 100 , That parallel to the optical axis 32 a microlens 31 running light is through the microlens 31 focused in the image-side focal plane, in which the aperture diaphragm array 40 is arranged, passes through the aperture 41 and gets to the back of the scan aperture 20 displayed. There are in correspondence to the coding of the material measure 100 Apertures (not shown in the drawing) through which the light is applied to the photosensitive receiver fields of the scanning receiver 10 arrives. Due to the divergence of the transmitter light as well as due to diffraction of the light at the code areas, this is the material measure 100 leaving light beams on a divergence angle 2δ. The apertures of the aperture diaphragm array are preferably so large that substantially all the light, which is the material measure 100 with the divergence angle 2δ in the optical axis 32 a microlens 31 leaves, the associated aperture diaphragm goes through non-shadowed. This means that in this case for the diameter A of the aperture stops 41 which are positioned in the focal planes of the microlenses, the following relationship applies: tan (δ) ≤ A / 2f ,

In the 6 is schematically an exploded view of a material measure 100 with brightfields ( 120 ) and darkfields ( 110 ), a microlens array 30 with image-attached aperture diaphragm array 40 and a scan aperture 20 with image apertures arranged on the image side 21 shown. The apertures of the scanning aperture are arranged in groups, with a number of apertures above each of a photosensitive scanning surface of the Abtastempfängers 10 is positioned. Here, by way of example, 6 × 2 groups of scanning surfaces with corresponding scanning diaphragm groups are shown, so that in each case two microlenses 31 that of the material measure 100 emits outgoing light on a respective Abtastblendengruppe. The scanning aperture 21 are preferably not round, but sinusoidally limited for sampling incremental position encodings to generate sinusoidal position signals.

The microlens array 30 and the scan aperture array 20 lie after mounting the scanning unit 1 directly on each other and on the scanning receiver 10 on and are exploded here to view the aperture panel 40 with his apertures 41 release. The apertures 41 in each case lie in the optical axis of each individual lens of the microlens array 30 ,

In the 7a is the top view of the microlens array 30 which exemplifies a rectangular grid (array) of 4 × 6 microlenses 31 having. In the 7b is a side view of the same microlens array 30 illustrated by drawings. On the image-side back of the microlens array 30 is the aperture panel array 40 arranged behind each individual lens 31 of the microlens array 30 an aperture aperture 41 is provided. On the object side of the microlens array, a field stop 38 be provided, which extends over the entire plan area, in which There are no lens openings. Particular preference is given to using microlens arrays with a filling factor of 100%, as in US Pat 25 is shown.

The 8th shows a schematic view of the illumination beam path. It is the light transmitter 50 emitted light through the condenser lens 55 largely collimated in parallel, ie the light emitter 50 is centered on the optical axis in the rear focal plane of the condenser lens 55 arranged. Thus, the light source is displayed at infinity. As a light emitter, an LED (light emitting diode) is preferably used. The light-emitting semiconductor chip has an edge length k. With the focal length F of the condenser lens 55 Thus, half the opening angle δ _{0 of} the emitted light results in: tan (δ ₀ ) = k / 2F , In the case where the lens aperture corresponds to the illumination aperture, tan (δ ₀ ) = A / 2f , so that results: k / F = A / f

With an edge length k = 0.1 mm of the light-emitting semiconductor and a focal length F = 4 mm of the condenser lens, for example, a half opening angle of the illuminating light beam of δ ₀ = 0.72 °. Since the material measure is not a self-radiator, but is illuminated by the light source, the illumination aperture A _{Bel of} the light source for the resolution and for the determination of the aperture A _{Obj of} the microlenses must be taken into account. The distance of object structures at the resolution limit is then:

In the 9 the imaging beam path for a picture of the coding of the scale on a scale of 1: 1 is shown. In this case, the material measure may be embodied as reflective or transmissive. The material measure 100 leaving light beam has an opening angle 2δ and is by means of the microlens 31 through the opening 41 the aperture stop on the surface of the scanning diaphragm 20 or the Abtastempfängers 10 displayed.

The diameter A of the opening of the aperture diaphragm 41 is to be dimensioned at most so large that in dimensional standards with diffractive diffraction gratings no light of the non-detectable diffraction orders through the aperture apertures 41 passes, while the light beam of the light to be detected largely without blanking through the aperture opening 41 through to the scanning receiver 10 arrives. Will the aperture 41 too far closed, the intensity of the light falling on the scanning receiver decreases sharply. Is strongly divergent light used for lighting, such as when no condenser lens between the light emitter 50 and the material measure 100 is provided, so a wide aperture aperture leads to a smaller distance tolerance between the material measure 100 and the scanning unit 1 , Furthermore, by the telecentric arrangement of the aperture stop 40 in the image-side focal plane of the microlenses 31 achieved that the magnification of a slight change in distance or a slight inclination between the material measure 100 and the microlenses 31 only very slightly changes. Overall, due to the image as well as the bundle limitation by the aperture diaphragms, the result is at least the factor 10 increased distance tolerance between the material measure and the scanning unit in comparison to position measuring devices with projectively detected material measures according to the prior art.

The 10 shows a plan view of a section of the scanning unit according to the invention according to the second embodiment. For the sake of clarity, the aperture diaphragms, the scanning diaphragms and any field diaphragm that may be present are shown transparently in order to identify the components underneath. Shown are two photosensitive receiver fields 11 . 12 of the sample receiver 10 with scanning aperture arranged above it 20 , which sinusoidal limited apertures 21 . 22 for detecting an incremental code track having a measurement period p. The individual apertures, which lie behind the same microlens and a receiver field 11 respectively. 12 are assigned at a assumed magnification of the microlenses of 1: 1 each offset by a length p to each other in the measuring direction. The maximum width of the apertures in the measuring direction is p / 2. For a general magnification M, the apertures behind the same lens therefore have an offset of Mp in the direction of measurement and always a maximum width of Mp / 2. In contrast, have the apertures 21 . 22 different recipient fields 11 . 12 , which are arranged perpendicular to the measuring direction, an offset c in the measuring direction by a quarter measuring period (as shown in the drawing, in the general case according to Mp / 4), a half or a three-quarter measuring period to each other, respectively by 90 °, 180 ° and 270 Phase-shifted, sinusoidal position signals to generate. As we will see later, an additional shift or an offset is added for adjacent scanning aperture openings, which are arranged behind different microlenses (cf. 23 and 28 ).

For each scanning field are two microlenses 31 provided, which is the light modulated by the material measure in the plane of the Abtastblenden openings 21 . 22 maps. Because the structured Side of the scan diaphragm, which carries the apertures, preferably to the surface of the Abtastempfängers 10 An image in the plane of the aperture is almost synonymous with an image in the plane of the photosensitive receiver fields 11 . 12 , If the scanning diaphragm with the aperture side of the scanning receiver mounted pioneering, so another separate component would be necessary, which ensures the necessary distance from the aperture diaphragm array; Furthermore, the height of the scanning unit would thereby unnecessarily increased.

The microlenses 31 are arranged in a regular rectangular grid with an offset of b in the measuring direction and an offset of a transverse to the measuring direction, ie the optical axes of adjacent microlenses have a distance of b in the measuring direction and a distance a transverse to the measuring direction. Preferably, these distances are at the position of the receiver fields 11 . 12 adapted to the surface of the Abtastempfängers. Preferably, a = b. However, other possible, such as irregular or hexagonal arrangements of microlenses are possible. A hexagonal arrangement of microlenses shows the 31 , The openings of the scanning apertures are at the arrangement of the microlenses 31 customized.

Through the dotted holes shown 41 The aperture diaphragm, which is located between the microlens array and the scanning diaphragm, can be found in the 10 individual apertures recognize what can be useful for the assembly. In particular, mounting marks may be arranged on the surface of the scanning diaphragm or of the scanning receiver, which simplify the mounting of the microlens array above the scanning diaphragm.

In addition to the successive assembly of scanning diaphragm and microlens array on the surface of the scanning chip above the photosensitive receiver fields, it is also possible to first position corresponding corresponding wafers, which carry the microlens arrays and the Abtastblenden, each other to bonding, and then to separate. In this case, the unit consisting of microlens array and scan aperture array is only to be aligned relative to the receiver fields of the scan receiver. Furthermore, it is possible to align the corresponding microlens, scanning and scanning receiver chip wafers to each other, to bond and then to separate.

The different, superimposed glass or plastic plates, which carry the microlens array and the scanning diaphragm can be cemented or glued together and then with the Abtastempfänger and then laterally potted with an advantageously opaque potting compound. It is also possible that, in particular, the bonding wires of the scanning chip lie within this casting compound.

In the 11 a further advantageous embodiment of the invention is shown in a side sectional view. At the top is a microlens array 30 with symmetrical biconvex microlenses 33 positioned. The radius of curvature of the object-side surface 33 ' the microlens 33 is preferably identical to the radius of curvature of the image side surface 33 '' the lens 33 , As a result, optimum image quality is achieved in connection with preferably aspherical curvatures of the surfaces of the microlenses. However, in principle, the use of lenses with different radii of curvature, especially of convex-concave lens shapes is possible.

The resolution of the individual lenses is proportional to the quotient of the focal length and the lens diameter and is therefore sufficient even with small focal length due to the small lens diameter.

The microlens array has lateral webs 35 on, which are designed in one piece with the microlens array and the positioning of the microlens array 30 on the underlying glass plate 45 In particular, simplify when the microlens array only a single row or a single column of juxtaposed microlenses 33 or only a single microlens. These bridges 35 however, may also be absent in two-dimensional lens arrays.

Due to the biconvex lens design here is the focus is not in the back of the lens array 30 , Therefore, an additional glass plate 45 necessary, whose thickness is such that the focus of the microlenses preferably on the image side of the glass plate 45 lie. Between the bottom of the glass plate 45 and the top of the scan aperture 20 is the aperture panel array 40 arranged, whose openings 41 in the optical axis 32 each of the microlenses 33 lie. Preferably, the aperture diaphragm array 40 on the back of the glass plate 45 or the front of the scan aperture 20 arranged. Particularly advantageous is the arrangement on the front of the scanning diaphragm 20 , as in this case, an additional positioning of scanning aperture 20 to the glass plate 45 each other during assembly of the scanning unit 1 eliminated.

The scanning aperture 20 indicates on its underside, ie to the surface of the Abtastempfängers 10 facing, apertures 21 on, through which the light leaving the material measure by means of the microlenses 33 of the microlens array 30 on the photosensitive surfaces of the Abtastempfängers 10 is shown. The scanning receiver 10 is on a circuit board 17 or mounted in a housing and by means of bonding wires 15 with interconnects (not shown in the drawing) electrically conductively connected. The individual components on the surface of the scanning receiver, ie the microlens array 30 , the glass plate 45 as well as the scanning aperture 20 are cemented or glued together and alternatively or additionally potted laterally by a preferably opaque potting compound and thus arrested. This will be the bonding wires 15 preferably also enclosed by the potting compound.

The 12a Fig. 5c schematically show the image inversion and, consequently, the necessary adjustments of the scanning aperture in the case of a curved code track of a code wheel for an angle measuring device. The curvature of the code track is dashed and exaggerated. Due to the inversion by the single-stage optical lens system, not only the direction of movement of the material measure rotates, but also the curvature of the code track, which is indicated by the solid line in the 12a C is shown. This curvature inversion has to be taken into account in the design of the scan aperture (s) of the scan receiver in the case of the use of "phased arrays" on the chip surface.

In the 13 is a section of a position coding of a material measure 100 represented, consisting of the code sequence C ₁ to C ₄ . This code sequence can be arranged in a single-track position coding parallel to the measuring direction or in a multi-track encoding transversely to the measuring direction. Each two codes are using a microlens 31 on the Abtastempfänger 10 displayed. It inverts for each of the microlenses 31 the order of the codes, which must be taken into account in particular in an absolute position coding by a subsequent signal processing.

In the 14a and 14b are transmissive and reflective measuring standards 200 shown which code fields 220 have, which are structured with diffractive phase grating structures approximately in the form of line grids and code fields 210 that are unstructured. The illuminating light is incident by the angle α _-1 measured to the surface normal, which corresponds to the diffraction angle of the first diffraction order, so that the transmitted or the reflected light of the minus first diffraction order the material measure 200 leaves vertically. If the zeroth diffraction order is not detected, the code fields become 210 as dark fields and the diffractive code fields 220 as hell fields delektiert. This assumes that the aperture A _{Obj of} the microlens is smaller than sin (2α _-1 ), where sin (α ₁ ) = λ / Λ. Since the microlenses of the microlens array have a small focal length and, in particular, a large area is scanned for the scanning of absolutely coded material measures, it may not be possible for light of the zeroth diffraction order to reach at least part of the microlenses.

Therefore, the light of the zeroth diffraction order is masked out by the aperture stops, ie the necessary reduction of the lens aperture is achieved by the aperture stops, which have a sufficiently small opening diameter. The maximum diameter A of the aperture diaphragms is thus determined in the detection of diffractive material measurements by the diffraction angle α _{-1 of} the zeroth diffraction order.

However, in order to detect the light leaving the scale with a sufficient intensity and to obtain a sufficient resolution, the diameter of the aperture stops should also not be too small. Preferably, the diffraction angle α _{-1 is} greater than half the opening angle of the material measure 200 largely perpendicular light leaving the minus first diffraction order. This is achieved by a sufficiently parallel illumination and by a sufficiently small lattice constant Λ. Typical lattice constants lie in a range of Λ = 1 μm to about two micrometers, in particular between 1.2 and 1.5 μm.

In the detection of diffractive measuring standards 200 In addition to the opening angle 2δ ₀ or the aperture A _{Bel of} the illumination optics nor the expansion of the dimensional standard 200 leaving light due to the diffraction be considered. For this purpose, the illuminating light falls at an angle of incidence α _-1 on the material measure 200 , where α _-1 corresponds to the angle of the first diffraction order, then: sin (α _-1 ) = λ / Λ Then follows with m = -1 and an angle of incidence (α _-1 + δ ₀ ) for the diffraction angle δ _{-1 of} the minus first diffraction order: sin (δ _-1 ) = sin (α _-1 + δ ₀ ) - sin (α _-1 ) ≤ sin (δ ₀ ).

The diffraction maximum of the detected minus first diffraction order also becomes narrower the more line grids are used per code area. With a lattice constant Λ and a number N of grid lines per code field 220 for the angle δ ₁ between the first diffraction order and the first secondary minimum, the relationship: sin (δ ₁ ) = λ / NΛ where λ is the wavelength of the light used for illumination.

For example, for a wavelength λ = 850 nm, for N = 35 grid lines per code field and for a grid constant Λ = 1250 nm, a comparatively small aperture angle of δ ₁ = 1.1 ° is obtained.

Overall, the relationship: δ = δ _-1 + δ ₁ ≈δ ₀ + δ ₁ results in a comparatively small bundle expansion of the light, which is the material measure 200 at the diffractive code fields 220 largely perpendicular leaves and from the Abtastempfänger 10 Will be received. It results for the from the material measure 200 thus leaving a total illumination aperture of: A _Bel = sin (2δ) with sin (δ) ≈ sin (δ ₀ ) + sin (δ ₁ ) ≈ k / 2F + λ / NΛ for small angles δ ₀ , δ ₁ .

The aperture apertures are now adjusted to such an extent that the lens aperture A _{Obj is} preferably larger than the illumination aperture A _Bel , but the zeroth order with the diffraction angle α _-1 is hidden, which means that A _Bel <A _Obj <sin ( _FIG . 2α _-1 ) or that applies: k / 2F + λ / NΛ ≈ sin (δ) <sin (u) <sin (α _-1 ) = λ / Λ where u is half the opening angle of the microlenses, then in particular: tan (u) = A / 2f

For a sufficiently large number N of diffraction gratings per code field 220 this condition can be fulfilled with sufficiently parallel collimated light. From the condition A / 2f <sin (α _-1 ) for the diameter of the individual aperture apertures follows in particular the right side of the above inequality.

Furthermore, it must be ensured by a suitable geometry that the zeroth diffraction order does not pass through adjacent aperture apertures on the scanning receiver. This is ensured by a suitable choice of the focal length f of the microlenses and the diameter of the aperture apertures.

bei einem erlaubten Unschärfekreis-Durchmesser U für kleine Öffnungswinkel 2δ. Dabei bezeichne N die Anzahl der Gitterlinien pro Codefeld 220.For a large distance tolerance between the material measure 200 and the scanning unit 1 a small illumination or lens aperture is an advantage. The distance tolerance T between the material measure 200 and the scanning unit is then 1: 1 in a magnification picture

with a permitted circle of confusion diameter U for small opening angles 2δ. N denotes the number of grid lines per code field 220 ,

This results in a significantly higher distance tolerance between the material measure compared to the sand of the technology 200 and the sampling receiver 10 at the same time sufficiently large resolution and at the same time suppression of zeroth diffraction order for a sufficiently small lattice constant Λ of the diffraction grating, with which the diffractive code fields 220 are provided. Furthermore, the height of the diffraction grating can be selected such that the zeroth diffraction order is largely suppressed, which has the advantage that the intensity of the detected minus first diffraction order increases. This can be done in reflective measuring graduations, for example by a step height of the diffraction grating of a quarter wavelength or generally an odd multiple of λ / 4 in air. If the illuminating light passes through a medium with refractive index n, for example the measuring standard itself, if it is transparent and the grid is arranged and mirrored on the reverse side, the step height in reflective measuring graduations is preferably an odd-numbered multiple of λ / (4n) in order to eliminate the zeroth diffraction order effect. For an illumination wavelength of λ = 740 nm and a refractive index of n = 1.5 of the material of measurement, in the latter case the smallest grating height for which an extinction of the zeroth diffraction order occurs is calculated to be λ / (4n) = 123 nm ,

For a high incremental number of lines, which are provided in particular on code discs of small diameter, the code fields are correspondingly narrower. To even small code fields 220 provided with a sufficient number N of grid lines, preferably comparatively small lattice constants of about 2 microns and less are used for this purpose. If, for example, a lattice constant of 1.25 micrometers is used and the wavelength λ of the illuminating light is 880 nm, then the diffraction angle of the minus first diffraction order is α _-1 = 44.7 °.

Other devices, as in the DE 100 25 410 described, illuminate a material measure having diffractive coded and unstructured surfaces, with substantially parallel to the optical axis of light, the diffractive surfaces cause an extinction of the zeroth diffraction order. In this case, preferably only the light of the zeroth diffraction order is detected and the light of the plus first or minus first and higher diffraction orders is hidden by the aperture stops.

aufweisen, so bilden beide Linsen 31, 33 die Hell- und Dunkelfelder im Überlappungsbereich jeweils aufeinander ab, falls ein Übersprechen überhaupt auftritt. Dabei ist M der Abbildungsmaßstab der Mikrolinsen und m eine natürliche Zahl, Für M = 1:1 ergibt sich beispielsweise ein entsprechender Abstand benachbarter Mikrolinsen zu b = m p/2. Im Allgemeinen weisen die von unterschiedlichen Linsen abgebildeten Codefelder jedoch einen Phasenversatz zueinander auf, der durch die Abtastblenden-Öffnungen korrigiert werden muss. Dieser allgemeine Fall wird in der 28 dargestellt und weiter unten beschrieben.The 15 schematically shows the scanning of an incrementally coded material measure 100 with measurement period p, which alternately arranged bright fields 120 and dark fields 110 having the same width. In the case that the optical axes 32 neighboring microlenses 31 . 33 a distance from

have, so form both lenses 31 . 33 the light and dark fields overlap each other in the overlap area if crosstalk occurs at all. In this case, M is the magnification of the microlenses and m is a natural number. For M = 1: 1, for example, there is a corresponding distance of adjacent microlenses to b = mp / 2. In general, however, the code fields mapped by different lenses have a phase offset with respect to each other that must be corrected by the scan aperture openings. This general case is in the 28 shown and described below.

To preclude crosstalk across the measuring direction, adjacent code tracks on the material measure are preferably provided with a sufficient distance.

In the 16 is the overlap area of adjacent microlenses 31 . 33 shown. A crosstalk on the Abtastempfänger can now be excluded by different measures: The microlenses have a corresponding distance from each other, so that no overlap of the image fields of adjacent microlenses occurs or the Abtastblenden or the photosensitive receiver surfaces of the Abtastempfängers only in the overlap-free image field area of the microlenses intended.

Let 2δ be the minimum of the opening angle of the light, which is the material measure 100 leaves, or from the opening angle of the lens, which is bounded by the aperture stop and g the object width, then the height B of half the image field is: B = M ( D / 2 + gtan (δ)). If adjacent microlenses have a distance b from one another, with b ≥ D, then the scanning aperture openings or the photosensitive receiver surfaces are preferably limited to an image field region whose half height B 'applies: B' = min {b -B, B} , With a reduction (M <1), an overlap area can be completely avoided if: 2B <b.

If the opening angle is 2δ = 3.6 ° and the focal length of the microlenses f = 1 mm, then, for a magnification of M = 1: 1, for example, a lateral expansion of half the field of view results B-D / 2 = 63 micrometers. If the microlenses were directly adjacent to each other, the overlap area would be 63 microns. In this area, no Abtastblenden- openings should be provided.

If the distance b of the adjacent microlenses is, for example, b = B + D / 2 = D + 63 μm, then the scannable half image field region B '= D / 2, d. H. the scannable field corresponds to the total lens diameter D.

In the 17 is a scanning unit for scanning a reflective measuring scale 200 shown. The measuring standard 200 has unstructured areas 210 as well as microstructured areas 220 on. The microstructuring can be given, for example, by line grids with lines perpendicular to the plane of the drawing. The light is incident at an angle α, which preferably corresponds to the diffraction angle of the first diffraction order. Accordingly, the light becomes the minus first diffraction order on the microstructured code regions 220 perpendicular in the direction of the Abtastempfängers 10 bent. This light, as previously described, is detected by the scanning receiver, passing through the microlenses 31 of the microlens array 30 is focused and through the apertures of the aperture diaphragm array 40 as well as through the scanning aperture 20 through to the photosensitive receiver surfaces of the scanning receiver 10 arrives.

The microlens array 30 which is above the scanning aperture 20 on the scanning receiver 10 is positioned, projects laterally over the Abtastempfänger 10 out and above the mounted on the board light emitter 50 one in the microlens array 30 integrated collimator lens 55 for collimation of the transmitter light. The light transmitter 50 is arranged laterally and the curvature of the collimator lens 55 is formed such that the light through the collimator lens 55 is aligned laterally at an angle α parallel.

Shown are two on both sides of the Abtastempfängers 10 arranged light emitter 50 , such as LEDs, for illuminating the material measure 200 , However, it is also possible to have only a single light transmitter 50 to provide for lighting and correspondingly a single collimator lens 55 into the microlens array 30 to integrate. The collimator lens 55 can be designed to be reactive or diffractive in the form of a Fresnel lens. Furthermore, it is possible to use both sides of the collimator lenses 55 executed curved, so in particular the light transmitter 50 pointing side. Preferably, the collimator lenses 55 aspherically curved.

The underside of the microlens array 30 points above the scanning aperture 20 an aperture blind 40 on. The opaque layer of this aperture is used in the area outside the Abtastempfängers 10 as a field stop to laterally emitted light of the light transmitter 50 hide. This field stop is above the light emitter 50 openings 44 on, whose shape to the field to be illuminated on the material measure 200 can be adjusted, for example by a rectangular field aperture 44 ,

The potting compound 16 encloses the sample receiver 10 together with the bonding wires 15 and the scan aperture, and ends at the Bottom of the scan aperture array 30 , As a result, a lateral irradiation of light on the photosensitive receiver surfaces of the Abtastempfängers 10 avoided. The microlens array 30 is preferably on the surface of the scanning aperture 20 bonded. The light emitter 50 are preferably by a transparent potting compound (not shown in the drawing) together with the bonding bonding wires 15 shed.

In the 18 is the microlens array 30 shown in a supervisory view. There are in a central area above the Abtastempfängers 10 four microlenses 31 for mapping the coding of the material measure 200 on the scanner surface and laterally each a collimator lens 55 into the microlens array 30 formed, which serve to collimate the light, which by the below the microlens array 30 arranged light emitter 50 is emitted.

The 19 and 20 each show a section of the board 17 which the light emitter 50 carries as well as those section of the microlens array 30 which is the collimator lens 55 for collimation of the front emitted transmitter light. On the underside of the microlens array 30 is a field stop with an opening 44 arranged, wherein the field stop is preferably part of the aperture diaphragm array. Preferably, the surface of the light emitter lies 50 in the back focal plane of the collimator lens 55 , ie at the height of the rear focal point F '', but by a lateral distance L to the optical axis 52 the collimator lens 55 The angle α measured relative to the perpendicular is tan (α) = L / F, where F is the (rear) focal length of the collimator lens 55 is.

Because the light of the light transmitter 50 only one side of the optical axis 52 located part of the collimator lens 55 illuminated, is merely a section of the collimator lens 55 into the microlens array 30 molded and the transmitter 50 is just on the circuit board 17 assembled.

However, it is possible, as in the 20 represented the transmitter 50 obliquely on a support 51 on the circuit board 17 to mount, wherein the mounting angle γ is preferably between zero and α, ie 0 0 ≤ γ ≤ α In this case, the collimator lens 55 completely or substantially completely into the microlens array 30 be formed. The field aperture 44 is asymmetrical to the optical axis 52 the collimator lens 55 on the bottom of the microlens array 30 arranged.

The 21 shows further embodiments of a Abtastempfägers 10 for the detection of a reflective measuring standard 200 , Here are the collimator lenses 55 to collimate the light of the transmitter 50 for the purpose of illuminating the material measure 200 obliquely into the microlens array 30 molded, with the optical axis 52 the collimator lenses 55 preferably by the angle α relative to the optical axis 32 the lenses 31 of the microlens array 30 are offset by the light on the material measure 200 should fall. This embodiment is particularly suitable for a microlens array made of plastic 30 ,

The transmitters 50 can plan on a circuit board 17 be mounted or preferably inclined by the angle α on a suitable support 51 be arranged. The light transmitter 50 facing side of the collimator lens 55 may be plan or preferably also concave.

In addition to using multiple light emitters 50 and collimator lenses 55 , it is also possible to provide only a light emitter and a single collimator lens. Furthermore, on one side of the sample receiver 10 one or more light emitter or Kollimatorlinsen be arranged.

Like the light transmitter LED, the scanning receiver chip can be housed as an SMD or ball-grid-array (BGA) component or arranged as a chip-on-board (COB) on a carrier, for example a printed circuit board. Furthermore, the LED can be enveloped by a transparent potting compound, wherein a bonding wire for contacting can also be embedded in the potting compound.

Furthermore, the light emitter and the scanning receiver can be mounted, for example, as a multi-chip module, for example, on thin film or on a printed circuit board and, for example, also housed in a common housing. Furthermore, it is conceivable to connect the light transmitter and the scanning receiver by means of flip-chip technology with each other and / or with a printed circuit board.

It is also possible to integrate an LED as a light transmitter and the scanning receiver in a single chip, as in the 22 is shown. For this purpose the scanning aperture covers 20 Preferably, the LED and has in this area a field aperture 24 on to the emission of light in the direction of the collimator lens 55 to allow an irradiation of the light on the receiver fields 11 . 12 of the Abtastempfägers 10 However, due to reflections to avoid. The top of the scan aperture 20 or the bottom of the microlens array 30 points above the receiver surfaces or below the imaging microlenses 31 the aperture panel array 40 on which is between the surface of the transmitter 50 and the collimator lens 55 when another field stop with an aperture 44 acts. To reflect at the bottom of the aperture array 40 To avoid this is preferably formed light-absorbing or antireflective. However, it is also possible not to arrange the scanning diaphragm over the light emitter and fed its an opaque wall between the transmitter area 50 and the recipient areas 11 . 12 of the scanning chip 10 provided. The microlens array 30 has the collimator lens in the illumination beam path 55 and in the imaging beam path, the microlenses 31 on.

der durch benachbarte Mikrolinsen abgebildeten Codeteilung. Diese Phasenverschiebung φ₀ ist im allgemeinen ungleich Null.In the 28 is the general situation of two adjacent microlenses in the direction of measurement 31 . 33 shown. The lens pitch, ie the distance of the optical axes 32 the adjacent lenses are in the measuring direction the length b. The measuring standard 100 alternately brightfields 120 and dark fields 110 with an incremental measuring period division p. These can, as already mentioned, be designed in different ways, in particular by means of an amplitude grating (chrome on glass) or a phase grating (diffraction grating) or a combination of the two. Looking at the marginal rays on the scanning receiver 10 or the plane of the scanning apertures, the following equation results: p ₀ = b (1 + 1 / M ) - np, where n is a natural number including zero and where 0 ≤ p ₀ ≤ p. This results in a phase shift of:

the code division represented by adjacent microlenses. This phase shift φ ₀ is generally not equal to zero.

This phase shift must be taken into account for the arrangement of the Abtastblenden openings in front of or on the receiver fields of the Abtastempfängers and is dependent on the lens pitch b in the measuring direction, the magnification M and the measuring period p of the material measure. Although there are discrete values for the lens pitch b for which this phase shift is zero as a function of the magnification M and the measurement period p, the measurement period p in the radial direction is not constant in the case of rotary measuring graduations (code disks) due to the radial widening of the code fields an adjustment of the Abtastblenden openings in this case is necessary. Since, in any case, a scanning diaphragm adapted to the respective measuring standard is necessary, different scanning graduations and uniform lens arrays are used according to the invention for different measuring graduations, wherein only the geometry of the lens arrays and the receiver surfaces of the scanning receiver are to be matched to one another.

The 23 shows a microlens array ( 30 ), consisting of a Cartesian arrangement of 4 × 6 microlenses ( 31 . 33 ) which detect 3 incremental code tracks. This is a linear 3-fold vernier encoding according to the DE 103 32 413 B3 , By means of three incremental codings with different measuring periods, the position can be determined absolutely on the basis of the determination of the phase offset of the different tracks relative to one another.

The microlenses ( 31 . 33 ) are shown schematically. Of course, microlenses with a lens filling factor of 100% can also be used. Behind each microlens three Abtastblendenöffnungen are arranged in each case. Each two microlenses adjacent in the measuring direction (indicated by a double arrow) lie in front of a common receiver field. Due to the lens pitch b in the measuring direction, adjacent scanning aperture openings, which lie behind different, adjacent microlenses of the same receiver field, have a phase shift of φ ₀ = 2π b / p (1 + 1 / M ) modulo 2π (cf. 28 ), resulting in a shift by a length Mp ₀ .

In addition to this phase shift, there is a phase shift of n π / 2 for adjacent microlenses ( 31 . 33 ), which are arranged in front of different receiver fields for generating mutually phase-shifted, sinusoidal position signals, with integer n. Thus, the overall phase shift of the adjacent aperture openings results for the general case: φ = 2π b / p (1+ 1 / M ) + n π / 2 ,

The above phase shift results for linear measuring graduations in a displacement of adjacent scanning aperture ( 21 . 22 ) behind mutually adjacent, different microlenses ( 31 . 33 ) are arranged to be one length: F = Mp φ / 2π = b (M + 1) + n Mp / 4 parallel to the measuring direction. The scanning aperture openings ( 21 ) behind the same microlens ( 31 ) and are arranged in front of the same scanning receiver field, in each case an offset of Mp to each other and a maximum width in the measuring direction of Mp / 2.

In the 29 are in the case of a rotary material measure two adjacent microlenses ( 31 . 33 ), which have a pitch b in the direction of measurement, as well as scanning apertures (FIG. 21 . 22 ).

In the 30 are two adjacent scan aperture openings ( 21 . 22 ) shown schematically. Each of the scanning apertures has a perpendicular to the measuring direction extending center axis, which defines a straight line passing through the two end points P ₁ and P ₂ and P ' ₁ and P' _{2 of} the scanning diaphragm.

For rotary material measures, the incremental period p is dependent on the radius r of the code track by means of: p = 2πr / I, where I is the number of code increments per revolution. This results in a shift dependent on the radius r of the code track: E (r) = b (M + 1) + nπ Mr / 2I parallel to the measuring direction.

The displacement of adjacent scanning aperture ( 21 . 22 ) behind adjacent microlenses ( 31 . 33 ) is now obtained as follows for rotary material measures: runs perpendicular to the measuring direction arranged center axis of a first scanning aperture ( 21 ) behind a first microlens ( 31 ) Is disposed through the straight line that is given a Codespur- through the end points P _1, P _2, wherein the first end point P ₁ has a code track radius r ₁ (ie distance from the center of the code disk), and the second end point P ₂ Radius r ₂ , so runs perpendicular to the measuring direction extending central axis of the adjacent scanning aperture ( 22 ), behind a second, to the first microlens ( 31 ) adjacent microlens ( 33 ), to a good approximation by a straight line which is defined by the points P ' ₁ and P' ₂ , the following relationship applies: | P ₁ - P ' ₁ | = E (r ₂ ) and accordingly | P ₂ - P ' ₂ | = E (r ₁ ) (note the indexing!).

Similarly, for scanning aperture openings ( 21 . 22 ) behind the same microlens ( 31 ): | P ₁ - P ' ₁ | = 2πM / l r ₂ or | P ₁ - P ' ₁ | = 2πM / l r ₁ .

In the 24 is a single microlens ( 31 ) with radius of curvature R and focal length f and light bundles that pass through the center of the lens. These accumulate in the respective focal points. It can be seen that the obliquely incident light at a comparatively large angle α is collimated at a focal point which lies clearly in front of the actual focal plane. Furthermore, the obliquely incident light which impinges in the region of the optical axis of the lens (not shown in the drawing) is focused even more strongly, whereby a coma arises as a monochromatic spherical aberration.

Since the light of the zeroth diffraction order or the light which falls on unstructured surfaces of the material measure, obliquely by the angle α with sin (α) = λ / Λ on the microlenses ( 31 . 33 ) and to be blanked out, the aperture diaphragm array is preferably arranged in a plane perpendicular to the optical axis, which lies between the focal point of the obliquely incident light of the zeroth diffraction order and the focal point of parallel to the optical axis incident light of minus first diffraction order. The latter defines the classic focal plane. Therefore, the aperture diaphragm is preferably at most spaced apart from the focal plane by the distance f (1-cos α) in the direction of the material measure ( 100 . 200 ) arranged.

In the 25 is a sectional view of a microlens array ( 30 ). The microlenses ( 31 . 33 ) are arranged Cartesian. If b is the lens pitch in the direction of measurement and a is the lens pitch perpendicular to it, then preferably √ a² + b² ≤ 2R, where R is the radius of curvature of the microlenses, that is, a fill factor of 100% is achieved. The curved lens surfaces go directly into each other. With a = b this yields: a ≤ √ 2R ,

Preferably, the zeroth diffraction order light does not fall in front of the scanning receiver (FIG. 10 ) arranged microlenses ( 31 . 33 ). This is in the 26 for the transmissive case and in the 27 shown for the reflective case. That on the measuring standard ( 200 ) falling light is transmitted through a field stop aperture or through an aperture edge ( 39 ) so limited that the microlens array ( 30 ) are completely illuminated opposite code structures, the light of zeroth and the minus second diffraction order but not in the microlens array ( 30 ). The corresponding geometric condition is: gtan (α)> v, where g is the object width, α is the diffraction angle of the first diffraction order, and v is the lateral extent of the microlens array (FIG. 30 ) is in the plane on which the code line grid of the material measure ( 200 ) are vertical.

The microstructured side of the transmissive or reflective measuring standard ( 200 ) can, as in the 26 represented to the microlens array ( 30 ) or, as in the 27 shown away from him for the reflective case. Preferably, the coded side of the reflective measuring graduation ( 200 ) from the scanning receiver ( 10 ) path. Here, the coded side is provided with a reflective layer, for example with a metallization, which consists of aluminum, gold or nickel and which is vapor-deposited or sputtered. The material measure is not limited to diffractive codings, but may rather have codings in the form of amplitude or phase gratings. The advantages of a reflective arrangement are in detail:
The overall length of the measuring system is smaller because the distance between the measuring scale and the Abtastempfänger is smaller, since the thickness of the code disk is part of the object's width.

The microstructured side of the code disk, which carries the position coding, is coated with a reflective medium, preferably a metal, such as gold, aluminum or nickel. This coating can be applied by means of sputtering, vapor deposition or electroplating. Therefore, this side of the code disk is protected from external influences, such as soiling or condensation with water vapor.

There is a defocussing of dirt or water vapor, which is located on the surface of the code disc indicative of the scanning receiver; in particular when the distance between the surface of the code disc facing the scanning receiver and the scanning receiver is less than or equal to a focal length f of the microlenses.

In the 32 is a material measure ( 100 ) showing position coding ( 110 . 120 ) has on the Abtastempfänger (not shown in the drawing) or the microlens array opposite side. The microlens ( 31 ) facing side of the material measure ( 100 ) is unstructured and wise preferably a distance of less than or equal to the focal length f of the microlens ( 31 ) on this. Then any dirt particles or scratches that may be present on the side of the material measure facing the scanning receiver ( 100 ) are defocused.

LIST OF REFERENCE NUMBERS

LIST OF REFERENCE NUMBERS

1

scanning

10

scanning receiver

11, 12

recipient fields

15

Bond wires

16

potting compound

17

substratum

20

scan diaphragm

21, 22

Abtastblenden openings

23

light-impermeable layer

24

Field aperture

30

Microlens array

31, 33

microlens

33 ', 33' '

Surface of the microlens 33

32

optical axis of a microlens

35

web

38, 39

field diaphragm

40

aperture diaphragm

41

Aperture diaphragm opening

44

Field diaphragm opening

45

glass plate

50

light source

51

carrier

52

optical axis of the converging lens

55

Condenser lens (condenser lens, collimator lens)

100, 200

Measuring standard

110, 210

darkfield

120, 220

brightfield

R

Radius of the microlens

f

Focal length of the microlens

f '

distance

H

Object-side main plane of the lens

H'

pictorial main plane of the lens

D

Lens diameter

n ₁

Refractive index of the microlens

n ₂

Refractive index of the scanning diaphragm

d

Thickness of the microlens array

s

lens height

A

Diameter of the aperture stops

a, b

Lenticular grid (Cartesian), lens pitch

α

Direction of the incident light

α _-1

Angle of minimum diffraction order

β

Refraction angle of the incident light

2δ ₀

Opening angle of the incident light beam

2δ ₁

Opening angle of the light of the minus first diffraction order

2δ

Total opening angle of the light leaving the scale

2u

Opening angle of the lens aperture

k

Edge length of the LED chip

F

Focal length of the collimator lens

x

lateral deflection of the zeroth diffraction order light in the image side focal plane of the microlens

c

offset

p

incremental measurement period

C ₁ , ..., C ₄

position codes

^A Bel

Lighting aperture

^A obj

Aperture of the microlens

N

Number of grid lines per code field 220

U

Blur circle diameter

T

distance tolerance

M

magnification

B

View area

G

Object distance

k

f-number

L, L ₁ , L ₂

lateral distance

F ', F' '

Focal points of the condenser lens

e

distance

v

Width of the lens array

I

Number of increments Radius of the rotary code track

P ₁ , P ₂ , P ' ₁ , P' ₂

Endpoints of the scan aperture

Claims (41)

Scanning unit ( 1 ) for the detection of optical measuring standards ( 100 . 200 ) containing an optical position coding ( 110 . 120 . 210 . 220 ), having - a light emitter ( 50 ), the material measure ( 100 . 200 ) at least partially illuminated, - a Abtastempfänger ( 10 ), the photosensitive receiver fields ( 11 . 12 ), with - a scanning diaphragm ( 20 ), the apertures ( 21 . 22 ), the recipient fields ( 11 . 12 ) and / or the apertures ( 21 . 22 ) of the scanning diaphragm ( 20 ) according to the position coding ( 110 . 120 . 210 . 220 ) of the material measure ( 100 . 200 ) are formed with - a microlens array ( 30 ), which has at least one microlens ( 31 . 33 ) for mapping the by the position coding ( 110 . 120 . 210 . 220 ) modulated light on the receiver fields ( 11 . 12 ) of the sample receiver ( 10 ), and with - an aperture diaphragm array ( 40 ), which is arranged between the microlens array and the scanning receiver and which each have an aperture diaphragm opening ( 41 ) in the optical axis ( 32 ) of each microlens ( 31 . 33 ) of the microlens array, characterized in that the apertures ( 21 . 22 ) of the scanning diaphragm ( 20 ) above the photosensitive receiver fields ( 11 . 12 ) of the sample receiver ( 10 ) or on the sampling receiver ( 10 ) facing side of the scan diaphragm ( 20 ) are arranged such that the aperture diaphragm array ( 40 ) on the image side of the lens plate or on the object side of the scanning diaphragm ( 20 ) and that on the scanning receiver ( 10 ) above the photosensitive receiver fields ( 11 . 12 ) the scanning aperture ( 20 ) as well as the microlens array ( 30 ) are positioned in the given order. Scanning unit according to the preceding claim, characterized in that all the microlenses ( 31 . 33 ) have the same focal length (f). Scanning unit according to the preceding claim, characterized in that the aperture apertures ( 41 ) lie on the image side in a plane which is the image-side focal plane of the microlens array ( 30 ) has a distance of at most f / 5. Scanning unit according to the preceding claim, characterized in that the aperture diaphragm array ( 40 ) in the image-side focal plane of the microlens array ( 30 ) is arranged so that in each case an aperture diaphragm opening ( 41 ) in the image-side focal point of each microlens ( 31 . 33 ) of the microlens array ( 30 ) is located. Scanning unit according to one of the preceding claims, characterized in that the openings ( 41 ) of the aperture diaphragm array ( 40 ) at most by the length f (1 - cos (α _-1 )) of the image-side focal plane of the microlenses ( 31 . 33 ) in the direction of the material measure ( 200 ) are arranged at a distance, wherein the material measure ( 100 . 200 ) has diffractive optical elements and (α _-1 ) correspond to the angle of the first diffraction order. Scanning unit according to one of the preceding claims, characterized in that the microlens array ( 30 ) of several lenses ( 31 . 33 ) consists. Scanning unit according to one of the preceding claims, characterized in that the image side of the microlens array ( 30 ), the aperture diaphragm array ( 40 ) and the scan aperture ( 20 ) are largely flat. Scanning unit according to one of the preceding claims, characterized in that the scanning diaphragm ( 20 ) and the microlens array ( 30 ) each consist of glass or plastic. Scanning unit according to one of the preceding claims, characterized in that the microlens array ( 30 ), the aperture diaphragm array ( 40 ) and the scan aperture ( 20 ) above the receiver surfaces ( 11 . 12 ) of the sample receiver ( 10 ) cemented or glued and / or laterally with a potting compound ( 16 ) are shed. Scanning unit according to one of the preceding claims, characterized in that the focal length (f) of the microlenses ( 31 . 33 ) in Dependence on the image scale (M) and the respective thickness and the refractive indices (n ₁ , n ₂ ) of the microlens array ( 30 ), the aperture diaphragm array ( 40 ) and the scan aperture ( 20 ) is determined such that the image plane in the surface of the receiver fields ( 11 . 12 ) of the sample receiver ( 10 ) or the apertures ( 21 . 22 ) of the scanning diaphragm ( 20 ) lies. Scanning unit according to one of the preceding claims, characterized in that on the object-side surface of the microlens array ( 30 ) outside the openings of the microlenses ( 31 . 33 ) an opaque field stop ( 38 ) is arranged. Scanning unit according to one of the preceding claims, characterized in that the microlenses ( 31 . 33 ) of the microlens array ( 30 ) relative to the receiver surfaces ( 11 . 12 ) of the sample receiver ( 10 ) are arranged such that the image of each Einzellinse ( 31 . 33 ) to a separate subarea of a receiver field ( 11 . 12 ) or falls on a separate number of recipient fields. Scanning unit according to one of the preceding claims, characterized in that in the overlapping region of the image fields of the microlenses ( 31 . 33 ), if available, no apertures ( 21 . 22 ) are located. Scanning unit according to one of the preceding claims, characterized in that the apertures ( 21 . 22 ) of the scanning diaphragm ( 20 ) are arranged such that they are largely centered in the field of view of the microlenses ( 31 . 33 ) lie. Scanning unit according to one of the preceding claims, characterized in that the microlenses ( 31 . 33 ) of the microlens array ( 30 ) are refractive. Scanning unit according to one of the preceding claims, characterized in that the microlenses ( 31 ) plano-convex with planner image side are formed and that the focal plane of the microlenses ( 31 ) in the image side of the microlens array ( 30 ) lies. Scanning unit according to one of the preceding claims 1 to 15, characterized in that the microlenses ( 33 ) are symmetrical biconvex. Scanning unit according to the preceding claim, characterized in that on the image side of the microlens array ( 30 ) another glass plate ( 45 ) and that the aperture diaphragm array ( 40 ) on the image side of the glass plate ( 45 ) or the object side of the scanning diaphragm ( 20 ) is arranged. Scanning unit according to one of the preceding claims, characterized in that the microlenses ( 31 . 33 ) have aspherical curvatures. Scanning unit according to one of the preceding claims, characterized in that the aperture diaphragm array ( 40 ) in one piece from a thin and outside the apertures ( 41 ) opaque layer exists. Scanning unit according to the preceding claim or claim 11, characterized in that the opaque layer is vapor-deposited or sputtered. Scanning unit according to one of the preceding claims, characterized in that the material measure ( 200 ), Code fields ( 220 ), which have diffractive optical elements, and further code fields ( 210 ), which are unstructured. Scanning unit according to the preceding claim, characterized in that the light which leaves the material measure at an angle (α _-1 ), which corresponds to the diffraction angle of a first diffraction order, through the aperture diaphragms ( 41 ) of the aperture diaphragm array ( 40 ) disappears. Scanning unit according to the preceding claim, characterized in that for the diameter (A) of the individual aperture diaphragms ( 41 ) of the aperture diaphragm array ( 40 ) the relation holds: A <2f λ / Λ with focal length (f) of the microlenses ( 31 . 33 ), Wavelength (λ) of the light transmitter ( 50 ) and lattice constant (Λ) of the diffraction grating. Scanning unit according to one of the preceding claims, characterized in that the light of the light transmitter ( 50 ), which is the material measure ( 100 . 200 ), is largely parallel collimated. Scanning unit according to one of the preceding claims, characterized in that the light transmitter ( 50 ) and sampling receiver ( 10 ) on the same side of the material measure ( 100 . 200 ) are arranged and that at least one lens ( 55 ) for collimating the light of the light transmitter ( 50 ) into the microlens array ( 30 ), wherein that part of the microlens array ( 30 ), the collimator lens ( 55 ), laterally beside the receiver fields ( 11 . 12 ) of the sample receiver ( 10 ) is positioned laterally over the Abtastempfänger ( 10 protrudes). Scanning unit according to one of the preceding claims, characterized in that the material measure ( 100 . 200 ) is reflective. Scanning unit according to one of the preceding claims 26 to 27, characterized in that on the underside of the microlens array ( 30 ) a field stop is arranged below each collimator lens ( 55 ) an opening ( 44 ) having. Scanning unit according to the preceding claim, characterized in that the field stop is part of the aperture diaphragm array ( 40 ). Scanning unit according to one of the preceding claims 26 to 29, characterized in that the light emitter ( 50 ) in the rear focal plane of the collimator lens ( 55 ) is positioned. Scanning unit according to claim 22 and the preceding claim, characterized in that the light emitter ( 50 ) by a lateral distance L from the optical axis 52 the collimator lens ( 55 ), where tan (α _-1 ) = L / F with focal length F of the collimator lens (FIG. 55 ). Scanning unit according to claim 22 and one of the preceding claims 26 to 31, characterized in that the light emitter ( 50 ) in the optical axis ( 52 ) of the collimator lens ( 55 ) and that the optical axis ( 52 ) of the collimator lens at an angle α _-1 with respect to the optical axis of the microlenses ( 31 ) of the microlens array ( 30 ) is tilted. Scanning unit according to one of the preceding claims 26 to 32, characterized in that the light transmitter ( 50 ) is mounted obliquely at an angle γ. Scanning unit according to claims 22 and 33, characterized in that the relation 0 ≤ γ ≤ α ₁ holds. Scanning unit according to one of the preceding claims 26 to 34, characterized in that the light transmitter ( 50 ) and the sampling receiver ( 10 ) are arranged in a single housing. Scanning unit according to one of the preceding claims 26 to 35, characterized in that the light transmitter ( 50 ) and the sampling receiver ( 10 ) are integrated in a chip. Scanning unit according to claim 22, characterized in that the material measure ( 200 ) Has code line grid and that for the lateral extent v of the microlens array ( 30 ) in that plane on which the code line grids of the material measure ( 200 ) are perpendicular, the following applies: v <gtan (α _-1 ), where g is the object width and α _{-1 is} the diffraction angle of the first diffraction order. Scanning unit according to one of the preceding claims, characterized in that the side of the material measure ( 100 . 200 ), which the position coding ( 110 . 120 . 210 . 220 ), from the Abtastempfänger ( 10 ) and that the distance between the to the Abtastempfänger ( 10 ) indicative surface of the material measure ( 100 . 200 ) and the microlens array ( 30 ) less than or equal to the focal length f of the microlenses ( 31 . 33 ). Scanning unit ( 1 ) for the detection of rotary optical measuring standards ( 100 . 200 ) containing an optical position coding ( 110 . 120 . 210 . 220 ) having at least one incremental coding with a number of (I) increments and having - a light emitter ( 50 ), the material measure ( 100 . 200 ) at least partially illuminated, - a Abtastempfänger ( 10 ), the photosensitive receiver fields ( 11 . 12 ), with - a scanning diaphragm ( 20 ), which have a plurality of apertures ( 21 . 22 ) according to the position coding ( 110 . 120 . 210 . 220 ) of the material measure ( 100 . 200 ), and with - a microlens array ( 30 ) containing at least two microlenses ( 31 . 33 ), which are arranged linear, rectangular or hexagonal and whose optical axes in the measuring direction have a distance b not equal to zero to each other and wherein the scanning diaphragm ( 20 ) between the microlens array ( 30 ) and the sampling receiver ( 10 ) is arranged and by the position coding ( 110 . 120 . 210 . 220 ) modulated light through the microlenses to the plane of the apertures ( 21 . 22 ) of the scanning diaphragm ( 20 ) is imaged with a magnification M, characterized in that for adjacent scanning apertures ( 21 . 22 ) behind different, adjacent microlenses ( 31 . 33 ), | P ₁ - P ' ₁ | = E (r ₂ ) and | P ₂ - P ' ₂ | = E (r ₁ ), with E (r _i ) = b (M + 1) + nπ M / 2I r _i for i = 1, 2 and with integer n, wherein the central axis of a first scanning aperture (60) running perpendicular to the measuring direction 21 ) Has end points P ₁ and P ₂ , wherein the first end point P _{1 has} a code track radius r ₁ and the second end point P _{2 has} a code track radius r ₂ and wherein the center axis of the adjacent scanning aperture (C) perpendicular to the measuring direction 22 ) passes through a straight line which is defined by the points P ' ₁ and P' ₂ . Scanning unit according to the preceding claim 39, characterized in that n is integer divisible by 4, if the adjacent microlenses lie in front of the same scanning surface. Position measuring device for scanning an optically coded material measure ( 100 . 200 ), which has at least one optically scannable code track and with a scanning unit ( 1 ) for scanning the measuring standard ( 100 . 200 ) according to one of the preceding claims.

Images