DE102006011540A1 - Scanning unit for detection of optical measure embodiments, has aperture diaphragm array arranged in picture-sided focal plane of micro lens array, and aperture opening is located in picture-lateral focal point of each micro lens of array - Google Patents

Abstract

The unit (1) has a light transmitter, a scanning receiver, an optical auxiliary scanning diaphragm (20) and micro lens array (30).The optical measure embodiments (100) have an optical position coding. An aperture diaphragm array (40) is arranged in the picture-sided focal plane of the micro lens array, such that an aperture diaphragm opening (41) is located in the picture-lateral focal point of each micro lens (31) of the micro lens array. The scanning diaphragm, the aperture diaphragm array and the micro lens array are positioned on each other in the given series directly on the surface of the scanning receiver (10) above the photo-sensitive receiver field. An independent claim is also included for the position measuring unit for the scanning of optically coded measure embodiments.

Description

Field of the invention

The 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 the independent one Claims.

A Such position measuring device comprises one with an optical readable position coding provided material measure, a light source for Emission of light in the direction of the measuring standard and a scanning unit, consisting of a scanning receiver with photosensitive structured areas for receiving the the scale modulated light and from a lens array on the surface of the scanning receiver is arranged and consists of one or more microlenses and which on the illuminated by the light source area of the material measure the structured receiver surfaces of the scanning receiver depict.

The Position measuring device can be used for detection of reflective or even transmissive scales, which correspond in the incident light or transmitted light method can be operated. In the former case the light transmitter and receiver are on the same side of the scale, that on the scale reflected and modulated by the position code light is then from the Scanning receiver detected. At transmissive scales, light emitters and receivers are on across from lying sides of the scale arranged and emitted by the light emitter and by the at least partially transparent scale passing and modulated light is detected by the scanning receiver.

The Measuring standard can be arranged as a code disc with circular about angle measurement Codings or for length measurement designed as a ruler with linearly arranged position coding be. The position coding can be incremental and / or absolute have encoded tracks.

was standing of the technique

optical position Encoders According to the prior art use code surfaces in position coding as Shape of different strong transmissive or reflective Amplitude objects, in the case of an incremental code track in the form of a Amplitude grating, wherein the measurement period corresponds to the grating period. At a projective sampling of transmissive scales the code areas illuminated with largely parallel light and on the opposite Page through a scanning receiver detected. Due to the illumination with not ideal-parallel collimated Light and the diffraction at the code fields must be the scanning receiver so as close as possible on the scale be arranged, which is why only very small clearance tolerances less than 50 microns are allowed. Is the distance too low, the scale collides with the scanning receiver what the destruction the position measuring device has the consequence. With increasing The contrast and the interpolability of the position signals are distanced and thus the position accuracy; the distance is eventually too big, so will be no position signals generated anymore.

One scanning receiver In the prior art, an integrated circuit (integrated circuit, iC), which is usually based on CMOS processes and the individual photosensitive receiver fields which respectively generate position-dependent signals. For incremental material measures These are usually at least four fields, each one by one Quarter measuring period arranged offset in the measuring direction to each other are and correspondingly offset by 90 degrees position-dependent signals produce. Eventually, additional receiver fields are provided, the scan a corresponding coded reference track and enter a reference or generate zero signal. The receiver fields on the scan receiver are each structured either as a single according to the coding of the material measure photosensitive surfaces on the surface of the receiver chip provided, which are evaluated together, as a so-called "phased array ", or it are contiguous areas used in the latter case, on the surface of the receiver chip a scanning aperture is positioned. The scan diaphragm consists of a glass plate with a one-sided and applied accordingly the position coding of the scale lithographically structured chromium layer, which transparent openings has above the photosensitive scanning surfaces of the scanning receiver. Around the distances the openings the scanning aperture for the material measure to minimize, the chromium layer is preferably on the to the material measure towards the side of the scanning diaphragm.

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 large 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, BCD codes (binary coded decimals), 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. This results in particular in detection of absolute material measures in which a large area must be detected, large diameter lenses 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, optics in the form of a plurality of juxtaposed Gradientindex 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.

at Use of one or more successively arranged microlens plates exists the problem of crosstalk, i.e. there are overlapping ones Object fields, which means that the light passing through a lens of the first lens array falls, in a laterally arranged lens of the second microlens array or in an adjacent recipient field of the scan receiver arrives. In contrast, For GRIN lenses, the comparatively large overall length and the individual production a compact and simple design. In addition, the different microlens plates to each other and the Abtastempfänger consuming to be adjusted.

epiphany the invention

It The object of the invention is a scanning unit or a corresponding Specify position measuring device, which can be mounted very easily and reliably is and above in addition, the problem of crosstalk eliminated.

These The object is achieved by a Scanning unit and a corresponding position measuring device solved according to the independent claims.

preferred Embodiments of the invention and other advantageous features of the invention are in the dependent claims specified.

According to the invention is a Lens plate used as imaging system, which at least one refractive or diffractive microlens and in the following for the sake of simplicity, is called a microlens array. This will be on the receiver chip mounted above the optional scanning aperture. The microlens array lies in one to the material measure or to the surface of the sample receiver parallel plane. The microlenses form the position coding the material measure the surface the scanning aperture openings or on the surface the photosensitive receiver fields of the sample receiver from. Here are the recipient fields each largely in the optical axis of the respective microlenses. The focal plane of the lenses is preferably in the flat rear side of the lens array. Between the microlens array and the scanning aperture or the surface of the Scanning receiver There is an array of aperture stops, which in the following for the sake of simplicity, is called an aperture diaphragm array. This aperture diaphragm array is realized in the form of a thin opaque layer and each of the microlenses of the microlens array has exactly one telecentric aperture in the image-side focal point too. The Aperture apertures are transparent openings within the opaque Layer. As a result, each lens forms part of the material measure without a crosstalk at least to a part of a recipient field from. It can for example be provided be that the images of multiple microlenses on a single receiver field fall or that the image of each microlens of the microlens array exactly to a recipient field the sample receiver or reaches a defined number of multiple recipient fields.

Preferably is at least one collimator lens for collimation of the light emitter emitted light on the material measure laterally over the scanning receiver protruding integrated into the microlens array.

By the use of a microlens array is the object field and the Split image field, resulting in very small distances between the lens array and the material measure on the one hand, and the lens array and the scanning receiver on the other be achieved. Furthermore, this arrangement has so far unattainable size Distance tolerances between the scale and the receiver.

by virtue of the small focal length of the individual microlenses results small working distance, which in addition to the intensity of light in particular also the contrast increases, which in turn allows better interpolation of the light-sensitive photoelectric receiver fields of the sample receiver generated 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 0.4 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 aspherical lenses and k = 4, the numerical aperture A _{Obj of} the lenses is approximately A _Obj ≈ D / 4f for a 1: 1 imaging = 1 / 4k and is therefore preferably less than 0.5.

by virtue of of largely parallel light as well as behind each one Microlens positioned telecentric screen becomes laterally incident light hidden, so that in particular no overlapping of the image fields of Single lenses of the microlens array on the different scanning fields the scanning or the sampling chip occurs. In the prior art are to avoid overlap the individual image fields require further action, such as opaque elements for separating the beam paths of the individual microlenses, which, however, makes a separation of the lenses necessary. The advantage the scanning unit according to the invention however, with only a single aperture array, that in the image-side focal plane of the microlenses as coherent Component is formed, as well as with a single contiguous Microlens array an overlap the image fields of the individual lenses reliably avoid or on to restrict a sufficiently small area without further aids to need.

• 1) Absorption 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.

Furthermore such a scanning receiver can especially equally for measuring standards which are used as coding reflective or transmissive Amplitude or Have phase grating. For scanning diffractive measuring standards the diameter of the aperture stops is determined in particular by that not to be detected, laterally from the material measure emerging diffraction orders are hidden.

For different Use cases, for example for the scanning of length or angle encoders, which incremental or absolute encodings with different resolutions have to have only different scanning apertures are available, while the scanning surfaces of the scan receiver unchanged can stay. The arrangement of the microlenses on the microlens array is therefore only to the geometry and the arrangement of the sensing surfaces of Scanning receiver and is therefore also for different codes usable.

Preferably the lens array consists of a glass or plastic substrate and indicates at its the graduation facing side convex curved lens surfaces on, which are integrally connected to the substrate, and in one to the surface of the sample receiver parallel plane are arranged side by side. Which the Abtastempfänger facing Side of the lens array is preferably flat. This results in plano-convex microlenses, their lens profile spherical or preferably aspherical can be.

Next a microlens array with plano-convex microlenses is also the Use of biconvex or convex-concave lenses conceivable. Next plano-convex lenses are due to the better imaging line for 1: 1 Illustrations particularly preferred micro-lens arrays with bi-aspheric, symmetrical biconvex microlenses used which front and back the same radii of curvature exhibit.

Farther is possible in principle, To provide refractive microlenses after the type of Fresnel lenses. The advantage here is especially in the small lens height and the simple production by embossing techniques in plastics or glass. Because the lighting is largely monochromatic Light occurs, which adversely affects diffractive lenses Diffraction not serious.

Preferably, the lens surfaces are arranged on the surface of the substrate in a regular rectangular or hexagonal grid. However, in principle, irregular, non-periodic arrangements are possible. The through knife and the curvature and thus the focal length are identical for all individual lenses. It should be understood 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, as well as the aperture diaphragm array.

to Production of the microlens array can be different methods be used. It is possible, the microlens arrays by means of embossing and plastic injection molding techniques. It can either Whole wafers are structured in each case, with the microlens arrays subsequently separated or the individual microlens arrays are manufactured separately. Furthermore, glass embossing techniques, such as the pressing of lenses in glass types with lower Glass transition temperature known, imprint a negative mold directly into glass. These embossing techniques in particular are able to run into each other or directly produce adjacent lens molds. In particular it is possible aspherical produce shaped lenses. Even with this technique it is possible to use glass wafers to shape and then singulate the individual microlens arrays.

One Another known method, such as the company SUSS MicroOptics SA is used in Neuchatel in Switzerland, using photolithography Reflow of the developed paint and subsequent reactive ion etching (reactive ion etching, RIE) in glass wafers. This wafer is then transformed into individual Lens arrays singulated or stampered for a replication technique, such as UV or hot stamping used. The lenses produced by the reflow process have one Minimum distance of a few micrometers.

The Scanning diaphragms are in the form of glass wafers by means of photolithographic Structuring a largely opaque layer, for example, chromium, aluminum or titanium or titanium compounds exists and is vapor-deposited or sputtered.

to Manufacture of the scanning unit, either one after the other, the scanning aperture, the aperture diaphragm array and then the microlens array the surface the scanning receiver is positioned, or it will be first the scanning aperture and the microlens array with interposed Aperture aperture array positioned to each other and this assembly subsequently on the surface of the scan receiver arranged. Furthermore, it is possible in the latter case, the already isolated Position scanning apertures as well as microlens arrays to each other, or the respective wafers, which the microlenses and the aperture stops or carry the scanning apertures, first to position each other, to bond and then for example by means of a wafer saw to separate.

The Arrangement and the diameter of the microlenses are to the geometry and arrangement of the scanning fields of the Abtastempfängers adapted. The lens diameter and the focal length of the individual lenses are preferably smaller than 2 mm. The focal length or the radius of curvature of the microlenses is preferably set such that, depending on the thickness of the Scanning plate, the aperture diaphragm and the microlens array as well dependent on from 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 Scan receiver exactly the image width corresponds.

The distances the microlenses to the scale on the one hand and to the surface the Abtastchips or the Abtastblendenöffnungen other hand determined by the mapping equation and determine the magnification. Preferably becomes a picture scale chosen from 1: 1. In this case is the distance from the object-side main plane of the lenses to the scale surface as well the double focal length, such as the distance from the image-side main plane the lenses to the surface of the sample receiver or the openings the scan aperture, however, each by the factor of the respective Refractive indices extended. Without restriction are by varying the distances but also magnifying or decreasing real (i.e., non-virtual) mappings possible, i. Illustrations in scale bigger or less than one.

In the focal plane of the microlenses is an array of aperture stops, wherein in the optical axis of each individual lens arranged a diaphragm is. Thus, there is an object-side telecentric beam path. This leaves at a slight change in distance between the material measure and the lens array, the magnification almost unchanged, thereby comparatively large Distance tolerances between the material measure and the scanning unit permissible are. If largely parallel light is used for illumination, so is illuminated by the telecentric Aperturblenden only little light.

The aperture diaphragm array is realized by a largely opaque layer, which is removed only at the locations of the apertures. The apertures are preferably round. The opaque layer is made of aluminum or chromium, but preferably of titanium or titanium compounds, to reduce back reflections, and is preferably applied to a glass surface by means of vapor deposition or sputtering and structured by photolithography. In addition, the surface of an aluminum layer as a light-absorbing diaphragm layer may be black anodized in order 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 aperture array may be a separate component. Preferably However, this aperture array is on already used components, such as the lens array or the scanning aperture. Consequently deleted a separate component with a corresponding adjustment effort.

in the In the first case, the object side of the lens array preferably has the Aperture array, wherein in the optical axis each Einzellinse in each case an aperture diaphragm is arranged. 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 gives you a telecentric optical system, resulting in a slight change in distance between the scale and the lens array does not substantially alter the magnification, so that the total measuring system comparatively distance tolerable in terms of on the distance between the material measure and the sampling receiver is. The distance tolerance depends from the measuring period as well as from the parallelism of the illuminating light off and is approx. 1 mm for a measuring period length of 100 microns, about 1024 increments on one Code disc diameter of 40 mm.

In contrast, show Projective optical measuring methods without the use of imaging lenses according to the state The technology significantly lower distance tolerances of about 50 microns and less, depending on the width of the measurement grid to be scanned.

alternative may also use the aperture diaphragm array when using a scan aperture on the scanning chip side facing away from the Abtastblendenplatte be arranged. The scanning chip side facing the aperture plate contributes the scanning apertures while the opposite lying side has the aperture diaphragm array. The glass plate points thus partially structured partially opaque layers on, usually photolithographically structured chromium or Titanium layers. In principle, other metallization layers, such as aluminum or dielectric layers. The Sensing aperture has openings according to the coding of the material measure, the magnification and a Inversion due to the single-step figure to consider are. The image inversion generated by the individual microlenses takes care of a partial reversal of the codes as well as a change in the curvature of the Code track for angular code discs.

In in the case of a scanning receiver with a "phased Array ", i.e. with according to the material measure coded receiver fields is used and thus no scan aperture is necessary, either uses a separate aperture plate on which the microlens array is mounted and their aperture apertures the microlens array or it will be the aperture panel on the back the microlens array provided and a separate transparent Glass plate as a spacer between the microlens array and the sampling receiver arranged. Due to the thickness of this glass plate is the distance between set the microlens array and the Abtastempfänger 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 directly on the surface of the receiver chip, quasi as "lense mounted on reticle on chip and subsequently laterally by means of opaque Fixing compound fixed. Furthermore, it is possible to use the surfaces of individual components, consisting of microlens array and the individual Glue aperture plates together, especially with optical To cement glue to avoid air bubbles.

Preferably The focal length of the lenses will vary depending on the thickness as well the refractive indices of preferably formed as glass plates Microlens arrays, the scanning and arranged in between Aperture array defined so that when superimposing the individual Components on the surface the scan receiver the Image size quasi adjusted by itself, so that in axial Direction parallel to the optical axis of the imaging beam path None Distance calibration is required more.

Since the glass thicknesses of the microlens array and scan aperture are not freely variable and the image plane must lie in the surface of the scan aperture or photosensitive areas of the scan receiver, it may be necessary to increase the focal plane by up to about 10% of the focal length to provide about a maximum of 100-200 microns above or below the aperture apertures, ie Aperture apertures are slightly off focus.

In the trap that diffractive dimensional standards used, which is the optical interference and diffraction of the Take advantage of light, so occur in addition to the diffraction orders to be detected other major or minor orders that are not detected. The aperture diaphragm ensures if correctly dimensioned at the same time the suppression of these not to be detected major or minor orders.

Around to avoid stray light on the photosensitive surfaces of the Scan-receiver arrives, can additionally the object-side region of the lens array between the microlenses with an opaque Layer be provided as a field stop. With a suitable arrangement and Focal length of the microlenses, this field stop can also be omitted.

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

When Light source according to the state of Technology light emitting diodes (LEDs) are used, which in the (near) infrared (near IR) emit spectrum. However, the use is also possible from 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 conceivable. For cost reasons, due to the shorter life, especially at high temperatures and the disadvantageously high spatial and temporal coherence have laser as a light source in the scale-bound position measurement but so far not enforced.

While in the case of amplitude grid scales, the illumination beam path is collinear with the imaging beam path, 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 stops with a corresponding arrangement and a corresponding diameter.

There a single-stage optical image is provided must the inversion of the figure will be taken into account. On the one hand the direction of rotation is apparently opposite, on the other hand must the inversion of the code track curvature in the Trap of angle encoders considered become. For this purpose, the apertures on the scanning diaphragm or the receiver surfaces in Case of a scanning receiver with "phased arrays "accordingly customized.

in the In the case of absolute encodings, it is recommended that each code field imaged by means of a separate microlens. Otherwise must in the Case of mapping multiple code fields with a lens the Inverting the code fields through the individual lenses the sampling receiver 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 made clear.

It demonstrate:

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 7b show the top view and the overall side 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 receiver surfaces according to the second exemplary embodiment, FIG.

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

the 12a - 12c show schematically the image inversion in the image of rotative material measures,

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

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

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.

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 in the focal plane of the microlenses 31 of the microlens array 30 preferably 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 provided 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 aperture diaphragm array therebetween 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 recognition The photosensitivity fields covered by the aperture diaphragm and the scanning diaphragm and therefore not visible are photosensitive receiver fields 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.

Light which 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 = d tan (β) with n ₁ sin (β) = sin (α) according to Snell's law.

Beside material measures, which have non-diffractive codings, which modulate the amplitude of the incident light, are approximately from the DE 103 03 038 Maßver bodies known which have binary code fields that are unstructured or 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. This means that in particular: A / 2 <x = d tan (β), which is the case for plano-convex lenses with d = fn ₁ from the inequality: A / 2f <sin (α _-1 ), where sin (α _-1 ) = n ₁ sin (β).

For the diffraction angle α _-1 of the connection minus first-order applies: sin (α ₁₎ = λ / Λ, where λ is the wavelength of the illuminating light and Λ the grating 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 diaphragm aperture A: A <2 min {x, | D-x |, | 2D-x |, ...} = 2 min {| nD - x |, n ∈ N ∪ {0}}, ie about A = 0.3 mm, since the light must not fall through the aperture 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) = R n₁, was bedeutet, dass d = f n₁ 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) = R n 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, resulting in a radius of curvature R of the Microlenses of R = 0.467 mm calculated.

According to Pythagoras, the following relationship applies for the lens height s ("lense sag"): 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.

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 aperture, then the thickness f 'of the scanning aperture is identical to the thickness d of the microlens array.

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. Because glass plates are not available in any thicknesses, it may be necessary to increase the aperture diaphragm array by up to about 10% 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 the various 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 running light is through the microlens 31 focused in the 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 For scanning incremental position encodings, they are preferably not round but sinusoidal in order to generate sinusoidal position signals.

The microlens array 30 and the scan aperture array 20 lie after mounting the scanning unit 1 directly on top of each other 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 are provided, which extends over the entire plan area, in which there are no lens openings.

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. The light transmitter is an LED (light emitting diode). The light-emitting semiconductor chip has an edge length k. With the focal length F of the condenser lens 55 Thus, half the aperture angle δ _{0 of} the emitted light is: tan (δ ₀ ) = k / 2F. In the case that the lens aperture corresponds to the illumination aperture, tan (δ ₀ ) = A / 2f, giving 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, the 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, results due to the figure and the bundle limitation by the aperture apertures increased by at least a factor of 10 distance tolerance between the material measure and the scanning unit.

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 on the scanning 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, the one receiver field 11 respectively. 12 are assigned, therefore, at a assumed magnification of the microlenses of 1: 1 also each have a distance p to each other in the measuring direction. In contrast, have the apertures 21 . 22 different recipient fields 11 . 12 an offset c in the direction of measurement by a quarter of a measuring period (as shown in the drawing), a half or a three-quarter measuring period to each other to generate in accordance with 90 °, 180 ° and 270 ° phase-shifted, sinusoidal position signals. 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. Since the structured side of the scanning aperture, 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 distances b in the measuring direction and distances a across the measuring direction. Preferably, these distances are at the position of the receiver fields 11 . 12 adapted to the surface of the Abtastempfängers. However, it is also possible other arrangements, such as irregular arrangements, but in particular arrangements adapted to the openings of the scanning aperture microlenses 31 ,

Through the dotted holes shown 41 The aperture diaphragm, which is located between the microlens array and the scanning diaphragm, you can see individual apertures, which can be useful for mounting. 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.

Next the sequential assembly of scanning diaphragm and microlens array on the surface of the scanning chip above the photosensitive receiver fields it is also possible corresponding wafers, which the microlens arrays and the Abtastblenden wear, first to position each other, to bond and then to seperate. In this case, the unit consisting of microlens array and scan aperture array only relative to the receiver fields of the sample receiver align.

The different on top of each other lying glass plates, which the microlens array and the scanning diaphragm wear, can cemented or glued and then laterally with an advantageously to be potted opaque potting compound. It is also possible that within this potting compound in particular also the bonding wires of the Scanning chips are.

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 identical to the radius of curvature of the surface arranged on the image side 33 '' the lens 33 , As a result, optimum image quality is achieved in connection with preferably aspherical curvatures of the surfaces of the microlenses.

The Resolution of the Single lenses is proportional to the quotient of the focal length and the lens diameter and is therefore synonymous with small focal length due to the small lens diameter sufficient.

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 is aperture 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 - 12c 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 exaggerated by dashed lines. 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 - 12c is shown. This curvature inversion must be taken into account in the design of the scan aperture (s) of the scan receiver when using phased arrays.

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 about one-lane Position coding to be arranged parallel to the measuring direction or in a multi-track encoding transversely to the direction of measurement. 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 detected as bright fields. 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 measuring graduations, it is unavoidable that light of the zeroth diffraction order reaches at least a 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 order of diffraction 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, 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 adapted to the 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: k / 2F + λ / NΛ≈Sin (δ) <sin (u) <sin (α _-1 ) = λ / Λ, where u is half the aperture 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, the right-hand side in particular follows 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 achieved by a suitable choice of the focal length f of the microlenses and the diameter of the aperture apertures secured.

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 prior art 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 as 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. For example, if a lattice constant of 1.25 microns is used and the wavelength λ of the illuminating light is 880 nm, 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.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. Where M is the magnification of the microlenses and m is a natural number. For M = 1: 1, for example, a corresponding distance of neighboring microlenses to b = mp / 2 results.

Around a crosstalk to exclude across the measuring direction, adjacent code tracks on the measuring standard 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 to each other, so that no overlapping of the image fields of adjacent microlenses occurs or the scanning 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 From the aperture angle of the lens bounded by the aperture stop and g the object width, the height B of the half frame is: B = M (D / 2 + g tan (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 Micrometers.

Is the distance b of the adjacent microlenses, for example b = B + D / 2 = D + 63 microns, so is the scannable half frame area B '= D / 2, i. the scannable image field corresponds to the entire 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 panel array 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 to collimate the light emitted by the transmitter. 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 moved laterally to achieve an obliquely parallel light beam to illuminate the material measure. The angle α measured to the solder 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 is only 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 Preferably, the mounting angle γ is preferably between zero and α, ie 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 Abtastempfängers 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.

Of the Scanning receiver chip Like the light transmitter LED, it can be used as an SMD or ball-grid-array (BGA) device housed or as a chip-on-board (COB) on a carrier, such as a printed circuit board be arranged. Furthermore, the LED of a transparent Encapsulated casting compound be, wherein a bonding wire for contacting also in the potting compound can be embedded.

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

It is also possible to integrate an LED as a light transmitter and the scanning receiver in a chip, as in 22 is shown. For this purpose, the scanning diaphragm preferably also covers the LED and has a field diaphragm opening in this area 24 on to the emission of light in the direction of the collimator lens 55 to allow direct irradiation of the light on the receiver fields 11 . 12 of the sample receiver 10 however 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 as 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 receiver 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.

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

field stop

40

aperture diaphragm

41

Aperture diaphragm opening

44

Field diaphragm opening

45

glass plate

50

light source

51

carrier

52

optical Axis of the condenser lens

55

converging lens (Condenser lens, collimator lens)

100 200

Measuring standard

110 210

darkfield

120 220

brightfield

R

radius the microlens

f

focal length the microlens

f '

distance

H

object-side Main plane of the lens

H'

image-side Main plane of the lens

D

Lens diameter

n ₁

refractive index the microlens

n ₂

refractive index the scanning aperture

d

thickness of the microlens array

s

lens height

A

diameter the aperture stops

a, b

lenticular (Cartesian)

α

direction of the incoming light

α _-1

angle the minus first diffraction order

β

angle of refraction of the incoming light

2δ ₀

opening angle of the incoming light beam

2δ ₁

opening angle the light of the minus first diffraction order

2δ

Total opening angle of the scale leaving light

2u

opening angle the lens aperture

k

Edge length of the LED chips

F

focal length the collimator lens

x

lateral Distraction of the light of the zeroth diffraction order 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 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' '

foci the condenser lens

Claims (35)

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 - an optional additional scanning diaphragm ( 20 ), 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, and with - a microlens array ( 30 ), which has at least one microlens ( 31 . 33 ) and in one to the material measure ( 100 . 200 ) parallel plane between the material measure ( 100 . 200 ) and the sampling receiver ( 10 ) is arranged to image the by the position coding ( 110 . 120 . 210 . 220 ) modulated light on the receiver fields ( 11 . 12 ) of the sample receiver ( 10 ), characterized in that an aperture diaphragm array ( 40 ) in the image-side focal plane of the microlens array ( 30 ) is arranged such 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 ) and that directly on the surface of the Abtastempfängers ( 10 ) above the photosensitive receiver fields ( 11 . 12 ) the scanning aperture ( 20 ), the aperture diaphragm array ( 40 ) as well as the microlens array ( 30 ) are positioned in the given order. Scanning unit according to the preceding claim, characterized in that the apertures ( 21 . 22 ) of the scanning diaphragm ( 20 ) on the sampling receiver ( 10 ) facing side of the scanning diaphragm are arranged. 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 planar and are positioned directly on each other. Scanning unit according to one of the preceding claims, characterized in that the scanning diaphragm ( 20 ) and the microlens array ( 30 ) each consist of one-piece glass or plastic platelets. 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 ) as a function of the magnification (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 recipient fields ( 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 the preceding claim, characterized in that the aperture diaphragm array ( 40 ) on the image side of the microlens array ( 30 ) or on the object side of the scan aperture ( 20 ) is arranged. Scanning unit according to one of the preceding claims 1 to 12, 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 in one piece from a thin and outside the apertures ( 41 ) opaque layer exists. Scanning unit according to the preceding claim or Claim 7, characterized in that the opaque layer evaporated or sputtered. Scanning unit according to one of the preceding claims with a material measure ( 200 ), which code fields ( 220 ), which have diffractive structures, and further code fields ( 210 ), which are unstructured, 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 23 to 24, 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 23 to 26, characterized in that the light emitter ( 50 ) in the rear focal plane of the collimator lens ( 55 ) is positioned. Scanning unit according to claim 20 and the preceding claim, characterized in that the light transmitter ( 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 20 and one of the preceding claims 23 to 28, 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 23 to 29, characterized in that the light transmitter ( 50 ) is mounted obliquely at an angle γ. Scanning unit according to claims 20 and 30, characterized in that the relation 0 ≤ γ ≤ α _-1 . Scanning unit according to one of the preceding claims 23 to 31, 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 23 to 32, characterized in that the light transmitter ( 50 ) and the sampling receiver ( 10 ) are integrated in one chip. 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 material measure ( 100 . 200 ) according to one of the preceding claims. Position measuring device according to the preceding claim, characterized in that the material measure ( 100 . 200 ) has at least one incrementally coded track with a measuring period (p) and that the distance of the microlenses ( 31 . 33 ) of the microlens array ( 30 ) in the measuring direction a natural multiple of

is.