DE2615676A1 - DIGITAL DISPLAY MEASURING DEVICE, IN PARTICULAR DISTANCE MEASURING DEVICE - Google Patents

Description

British Patent Application No. 14846/75 April 8, 1976 Filed: April 10th, 1975 9853-76 Dr.v.B / S

James Neill Holdings limited Napier Street, Sheffield . S11 8HB, England

Digital display measuring device, in particular distance measuring device

The present invention relates to a digitally indicating measuring device according to the preamble of claim 1. The measuring device According to the invention, for example, for determining a dimension of an object or for determining a distance which moving an object.

Distance or distance measuring devices in which the number of interference or Moirl fringes is counted walk past a given point and are generated by two grids that move in relation to each other, are known, see e.g. the overview in the publication "G-ratings in Metrology", which is published in the journal "Journal of Physics E; Scientific Instruments », Volume 5, No. 3, March 1972, pages 193-198.

The known measuring devices that work with interference patterns are both bulky and expensive. These disadvantages result to some extent from the difficulties that make making and copying more accurate and prepare high-resolution grids. The problems

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in the manufacture of an accurate grid which can be used as a template for the production of grids for measuring devices are discussed in the above mentioned publication. These difficulties are, among other things, the reason for being at the known measuring devices of the type of interest here used line grids with a period of 10 m and that generally required resolution of 1 or 2 yum to be achieved by an analog electronic division process seeks.

The present invention is based on the object of avoiding the above-described indurations.

One aspect of the invention relates to an improved method for making a mother grid. Another aspect of the invention relates to the provision of a measuring device which is small enough to be able to be held in the hand, that is self-sufficient and that without connection to any additional ones Devices or separate power sources operated can be. However, the invention is not limited to hand-held measuring devices, but can also be used with other measuring devices, e.g. implement table measuring devices or measuring devices in machine tools and the like.

The present invention, in addition to being useful in the manufacture of better mother grids, has a number of features which help reduce the size and cost of the device so that, as stated, handheld meters can be constructed which are independent of the grid and other power sources.

Another feature of the invention is a relatively simple electrical circuit arrangement for counting the strip of an interference figure.

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In a preferred embodiment of the invention a circuit arrangement is used in which per fringe cycle only four pulses need to be generated, and these pulses are obtained from the signals transmitted by two or more detectors originate which are constructed in a known manner, e.g. as described in G-B-PS 760 321 is.

To achieve a resolution of 1, the grids, which are used to generate the interference or moire fringes, a period down to 4 / µm.

Yet another feature of the invention which allows a particularly large difference (signal-to-noise ratio) to be achieved between the modulated signal output from the detectors and the unmodulated background noise is that a support arrangement is provided which keeps the two grids movable with respect to one another as close as possible to arrange them together. This is especially true for gratings with periods as small as ^ xao. necessary. In a preferred embodiment of the invention, the distance between the grids is not greater than 12 μm, but the device can also be operated with a distance of up to 20 μm between the grids.

In a specific embodiment of the invention, which will be explained in more detail below, finds the invention is applied to a handheld micrometer, and the embodiment yet to be described has compared to the known, working with a micrometer screw the gate part that the measurements much faster than with the latter can be carried out. One reason for this is that the relative position of the spindle or the button of the Measuring device according to the invention is instantly displayed digitally with respect to a system and that the button is immediately can be brought into the required position,

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while with the known screw micrometers up to 20 It takes seconds to turn the screw spindle all the way back.

Another feature of the invention, which is also referred to in the description of the exemplary embodiment is, consists in the use of a system that the button with a substantially constant force against the stop or the system presses so that the objects to be measured located between the system and the button are always the same Force is exerted.

Another feature of the invention is that a damping system is provided which controls the speed controls with which the spindle or the button slides, and thus the frequency of the pulse signal that a pulse counting circuit is fed.

In the following, exemplary embodiments of the invention will now be explained in more detail with reference to the drawing; show it:

Iig. 1A is a partially sectioned plan view of a Handheld micrometer according to an embodiment of the invention;

Pig. 1B shows a longitudinal section in a plane B-B of Pig.1A; Pig. 1C shows a cross section in a plane A-A of Pig.1B;

Pig. 2A is a side view of a glass measuring block assembly for a meter according to the invention;

Pig. 2B is an end view of the arrangement according to Pig. 2A;

Pig. 20 is an exploded perspective view of the arrangement according to Pig. 2A and B;

Pig. 5 shows a longitudinal section of a coupling unit for a meter according to the invention;

Pig. 4A and 4B are end and plan views, respectively, of a glass measuring block assembly including a radiation source and a Radiation receivers are assigned;

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Pig. 5 is a block diagram of a circuit arrangement for a meter according to the invention;

Pig. Figure 6A is a longitudinal section of a grille and damper assembly;

Pig. Fig. 6B shows a cross section in a plane A-A of Fig. 6A;

Pig. 7A is a schematic view of the arrangement according to Pig. βλ and βΒ and a mask system;

Pig. Figure 7B is a view in the direction of arrow B in Figure 7A;

Pig. 70 a view in a plane A-A of the Pig. 7A, seen in the direction of the arrows and

Pig. 8 is a graphical representation of a method for Production of a grid suitable as a template (mother grid).

In Pig. 1A, 1B and 10 is one micrometer or one Micrometer has the same effect as a measuring device that can be comfortably held in the hand. It contains a measuring pin 1, which is mounted displaceably with respect to an anvil 2 attached to a bracket 3. The anvil 2 and the one opposite it The end of the measuring pin 1 forms jaws for contact with a measuring object, similar to a conventional micrometer (»Micrometers»).

The measuring device furthermore contains a main frame 4 with a bearing holder 5 comprising the measuring pin 1. One leg of the bracket 3 includes the bearing holder 5 and is fastened to the main frame 4 by means of an adhesive and a pin or wedge 6. The bearing holder 5 carries a Lg & er 7, which forms a LagerfHache for the measuring pin 1. A second bearing surface 8 for the measuring pin 1 is located in the main frame 4. The measuring pin 1 is connected to a displaceable button 10 via a first part of a lever 9. The mentioned first part of the lever 9 extends through a

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Slot 11 in a housing 12 is a second part of the lever 9. It connects the measuring pin 1 with a damping device. The measuring pin 1 is connected by means of a retaining pin 15 one end of a coil spring 14 stressed in bending ("flexator" spring) connected, the other end by means of a mounting step 16 is attached to the main frame 4. Several such springs can be provided. The coil spring 14 is in principle a tension spring, but here, as can be seen from FIG. 1B, bending is stressed. In this way, between the mounting pins 15 and 16 generates a substantially constant force which presses the measuring pin 1 against the anvil 2. This power is also then still present when the measuring pin 1 is in contact with the anvil 2. Of course, other devices can also be used to press the plunger against the anvil 2.

The damping device 13 contains a piston 17 in a cylinder or body 18, which is connected to the lever 9 is. The piston 17 is via a flexible rod 19 coupled to an end cap 20. The end cap 20 is fastened to the main frame 4 by means of a screw 21. The damping device 13 also includes a sealed bellows 22 which is filled with a viscous fluid.

When the body 18 moves relative to the piston 17, which slides in it, a braking force occurs between the piston 17 and the body 18 due to the presence of one of the viscous fluid which limits the speed at which the measuring pin in the bearings 7 and 8 able to gis iten. The measuring pin 1 moves towards the anvil 2 under the influence of the helical spring which is subjected to bending stress and whose state is anjiälis2? Nd zero. To open the biscuit jaws, the measuring pin, which is slidably supported in bearings 7 and 8, is withdrawn along the housing 12 by the operator using the button 10, which is coupled to the measuring pin via the first part of the lever 9.

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As shown in Figures 2A, 2B and 20, the meter includes a glass block 23 which has an optical gate 24 on one surface. The surface 25 is adjacent to a surface 26 of a second glass block 27 which is attached to the main frame 4. A second optical grating 28 is located on the surface 26. The block 23 is displaceable along the block 27 and, for this purpose, is coupled to the measuring pin 1 by means of a coupling device 29. The displaceable glass block 23 has a beveled surface over which it is pressed by a leaf spring 31 (I ¹ Ig. 1C) against the glass block 27, which is used as a base or reference, and a base glass block 30. The leaf spring 31 is held on a lever 32 by two pins (not shown). In this way, intimate contact between the glass block 23 and the glass blocks 27 and 30 is maintained. The lever 32 transmits the reaction force of the leaf spring 31 via a ball arrangement 33 to a strip 34, which consists of a material of low friction and is attached to an extension of the main frame 4. The lever 32 is connected to the plunger so that it can rotate freely about the plunger with a minimum of orthogonal movement. This is achieved, as can best be seen from FIG. 3, by a bearing member 35 which extends through a hole in the lever 32, is connected to the end of the measuring pin 1 and forms one end of the coupling device 29.

The one in Pig. 3, the coupling device 29 shown in detail contains a pin 36 with a conical part at one end, which is inserted into a conical seat 37 in a component 38 which, as shown, with the sliding glass block 23 is connected. The other end of the pin 36 which is also conical is seated in a conical one Seat 39 in the bearing link 35. The conical seats 37 and 39 have larger vertex angles than the corresponding conical ones End portions of the pin 36. The components 35 and 38 are through

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a helical spring 40 under tension flexibly with one another gekqpelt, which holds the pin 36 in the seats 37 and 39. The coupling device 29 is, as can be seen, like this designed that it forces the sliding glass block 23, the movement of the measuring pin 1 along its longitudinal axis directly to follow, while on the other hand a certain linear movement and rotational movement of the glass block 23in allows other directions, so that wear and manufacturing tolerances are compensated. The coupling device 29 is therefore a type of cardanic coupling with five 3-row degrees of rotation.

Next, with reference to FIG. 2A, Figures 2B and 20 explain the construction and arrangement of the glass blocks in more detail 23, 27 and 30 are received. It should be emphasized in this connection that instead of the one described above Embodiment also used transparent glass blocks, of course, other combinations of mechanical stable transparent materials or transparent and reflective materials can be used.

The material chosen for blocks 23, 27 and 30 is machined and / or polished to produce smooth, rectangular surfaces. The gratings 24 and 28 are line gratings and are applied to the surfaces 25 and 26 by conventional photomechanical processes using optically opaque thin layers. The period of the gratings, that is to say the distance which a line and a space occupy, is preferably 4 μm. You can of course also use other values for the period. During the production of the grids 24 and 28, the surfaces 25 and 26 of the blocks 23 and 27 are coated with a chrome layer in a vacuum. A photoresist layer is then applied to the chrome layers and exposed to ultraviolet light by means of a mother grid. The parts of the photoresist exposed to the ultraviolet Ii at are in a developer

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more easily soluble than the unexposed parts, so that the unneeded areas of the ear layers after development of the photoresist layers are exposed. The exposed areas of the chrome layers are then etched away, and you thereby receives an image of the original parent grid. Processes of this kind are also found in the manufacture of printed matter Circuits usage.

A mother lattice can be obtained by the following with reference to J ¹ Ig. 8 explained method can be produced. The lines of the gratings 24 and 28 are formed on the surfaces 16 and 26 in such a way that they run essentially perpendicular to the longitudinal edges of the surfaces 25 and 26. When assembling the blocks, it is important that the base block 30 is accurately attached to the reference block and that its surface 41 and the surface 26 of the reference block 27 are both as flat as possible. It is also important that the sliding block 23 fits snugly into the angle between the base block 30 and the reference block 27 when the glass blocks 23, 27 and 30 are assembled. The easiest way to do this is to ensure that the surface 42 of the sliding block 23 and the surface 43 of the base block 30 which is adjacent to it are perpendicular to the surface 25 of the sliding block 23 which the grid 24 supports . The surface 25 of the displaceable block 23 is of course flat.

It is not necessary that the grids 24 and 28 to reach to the longitudinal edges of the blocks 23 and 27, and to create low-friction G-guide surfaces and to reduce the wear and tear of the grids during operation ensure a certain distance between the grids, the surfaces are 25 and 26 of blocks 23 and 27 are provided with spacer rails or strips 44 and 45 extending along the edges of the Blöke run away. The spacer strips 44 and 45 have expediently a thickness between 1 and 10 µm. In the preferred embodiment, the spacer strips are

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4 um thick. On the surfaces 42 and 43 of the blocks 23 and 30 are thin spacer layers 46 and 47, which form low-friction sliding surfaces. In the particular embodiment described, the spacer strips exist 44 and 45 and the spacer layers 46 and 47 made of spray-applied polytetrafluoroethylene. Other solid lubricants can also be used, e.g. molybdenum disulfide, tungsten diselenide or graphite. These materials can be applied either by spraying or by vacuum deposition.

To improve the adhesion of the sprayed-on spacer strips 44 and 45 and the spacer layers 46 and 47, it is expedient to use the relevant surface areas roughening the glass blocks locally, e.g. by etching or sandblasting, before the lubricant is applied.

Other methods of spacing and lubricating the blocks can also be used. For example, an oil film can be used between the surfaces 25 and 26, which is used for lubrication, and the distance between the blocks can be ensured by means of metallic spacer strips that are vapor-deposited in a vacuum. Again Another possibility is to hold the block 23 between two oil films of approximately the same thickness, which through block 27 and an additional similar block on the other side of block 23 may be included.

Around blocks 23, 27 and 30 into a single unit assemble, they are placed in a device holding them in the intended orientation. The angle between the grids 24 and 28 is by Eippsii the base block 30 is set in such a way that interference or moiré fringes of the desired Period. In the preferred embodiment, a fringe period of about 12 mm is used. With help

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the capillary forces or in some other way then becomes a without Adhesive that cures with air or can be cured by UY radiation between the surface 26 of the reference block 27 and introduced the surface 41 of the base block 30, which is in contact with part of the surface 26, and the The glue is set so that the two blocks are fixed at the correct angle to each other. Of course you can other adhesives and other methods of joining the blocks can also be used.

In the loose. 4A and 4B is the arrangement of the glass blocks 23, 27 and 30 and the radiation source and radiation receiver assigned to them are shown in more detail. The radiation source contains a lamp 48 which generates a beam of radiation which is passed through a lens 49, the sliding block 23, the gratings 24 and 28, the reference block 37 and a lens array 50 on an array with photosensitive devices 51 and 52 throws. The photosensitive devices 51 and 52 are perpendicular to the direction of the stripe pattern spaced, which arises when the radiation from the lamp 48 passes through the grids 24 and 28 o The photosensitive Devices 51 and 52 perceive movements of the striped pattern that occur during a longitudinal relative movement of the blocks 23 and 27 and thus the grid 24 and arise in relation to one another. In the case of the special one described Embodiment of the invention, the photosensitive devices 51 and 52 consist of silicon phototransistors, and their distance is equal to a quarter of a quarter Period of the stripe pattern, so that the photosensitive devices 51 and 52 with a shift of the grids and 28 provide output signals with respect to one another that are approximately sinusoidal and have a phase difference of approximately Have 90 °. In the particular embodiment described, the lamp 48 is an infrared light emitting one Semiconductor diode, and the radiation beam from the lamp 48 is deflected by mirrors 53 and 54 to the width of the Device to be able to reduce without changing the beam path.

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Of course, you can also use other radiation sources and use other radiation sensors. To monitor the Output radiation from lamp 48 is another photosensitive one Device 55 is provided, which in the present example also consists of a phototransistor and provides a signal that is used to adjust a circuit arrangement and compensate for changes in voltage from the Power source or aging effects of the lamp is used.

Like Pig. 5 shows, the output signals of the phototransistors 51 and 52 are each fed to an amplifier 56 and 57, the output signals of which are made square in the course of amplification in downstream stages 58 and 59, respectively. The output signals of the amplifiers or stages 58 and 59 are kept symmetrical about a voltage value which is set in accordance with the changes in a direct current output signal from the photosensitive device 55 serving as a reference. Ideally, the outputs of amplifiers 58 and 59 are square waves with a 90 ° phase shift with respect to one another. The output signals of the amplifiers 58 and 59 are both fed to a detector circuit 60, which supplies an output pulse for each amplitude transition of the two square waves, and to a phase detector 61. The detector circuit 60 provides a pulse for every quarter of a cycle of the stripe pattern. In the described preferred embodiment with a grid period of 4 VM , this corresponds to a measuring pin displacement of 1 yum. I ¹ Ur a lattice with a period of 8 µm would be the displacement 2 µm. The output pulses from the detector circuit 60 and the output signal from the phase detector 61 are fed to an up-down counter 62. The phase detector 61 determines the direction of movement of the striped pattern from the input signals fed to it and accordingly sets the counter 62 to count up or down. The output signal of the counter 62 is fed to a digital display device 63 on which the

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Position of the end of the measuring pin 1 in relation to the anvil 2 can be read exactly.

The housing contains a power source 64, which is conveniently contains rechargeable batteries, furthermore electrical circuit elements 65, a switch 66, the Controls the supply of power to the circuit arrangements, and the digital display device 63.

When using the measuring device, the electrical circuit arrangements are energized and the counter 62 is set to zero upon actuation of switch 66. The plunger 1 is then withdrawn from the anvil 2 by the Button 10 along slot 11 in housing 12 with your thumb is withdrawn against the force exerted by the coil spring 14, whose I-spring constant is essentially zero or is constant, and the damping device 13 is applied.

An object to be measured is then inserted between the anvil 2 and the measuring pin 1 and. the button 10 is released, so that the measuring pin 1 under the influence of the spring can tilt back in the direction of the anvil 2 until it hits the object to be measured, which is in contact with the anvil 2. The coil spring 14 then exerts a closing force which, as the Spring constant essentially has the value zero, is essentially constant over the entire working range of the measuring device. The return speed of the measuring pin 1 is controlled by the damping device 13. The position of the measuring pin 1, as a result of the query described above, of which the grids 23 and 27 penetrate during its movement Radiation from lamp 48 generated interference pattern continuously displayed by the display device 63 through the phototransistors 51 and 52; the counter 62 counts forward when the plunger is moved in one direction and backward when the plunger is moved in the other

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Direction is shifted. The display device can be read when the object to be measured is located between the anvil 2 and the measuring pin 1; On the other hand, the display device can also be set to zero by actuating the switch 66 when the measuring pin 1 is in contact with the measuring object, then removing the measuring object and counting down the counter until the closed position of the measuring pin 1 is reached, whereupon a negative display of the size is displayed of the object can be read. There is therefore the possibility of measuring, even if the display device cannot be easily read in situ.

Another embodiment of the present measuring device, in which oil or another fluid to keep the distance between the Grid and its damping is used, is particularly suitable for circular or cylinder section grid arrangements.

A specific guide format with a circular segment arrangement is described below with reference to Pig. 6A to 70 explained. The measuring device according to this exemplary embodiment contains a rod 67 made of transparent material, such as glass, which can be displaced with little play in a tube 68 made of transparent material. When the arrangement is mounted in a measuring device, the rod 67 is connected at one end 69 via an articulated coupling (not shown), e.g. the coupling device 29 according to lig.1B, to a measuring pin of the measuring device, while the tube 68 is attached to the main frame of the measuring device . The space between the rod 67 and the tube 68 and a bellows unit 70 sealing this arrangement are filled with a transparent, viscous damping fluid. The viscous damping fluid acts as a damping means when the rod 67 is displaced in the tube 68 when the measuring pin of the measuring device is displaced. Grids 71 and 72, respectively, are applied to the outside of the rod 67 and the inside of the tube 68.

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When applying the grid, which can be done in the manner described above, the angle between the two grids adjusted so that a striped pattern of the desired period results between the grids after assembly. The grid 72 can also be applied externally to tube 68, but this is less desirable.

As FIG. 6a shows, there are also a lamp 73 and a Lens 74 is provided which collimates the light from the bulb and through one side of the tube 68 and the two grids and 72 throws. The transparent rod 67 is dimensioned so that it acts as a lens and the light that by means of the Grids 71 and 72 generated interference fringe patterns modulated light focused on a detector arrangement 75. the Detector arrangement 75 contains two phototransistors 76 and 77 shown schematically in FIG. 7B.

In order to receive quadrature signals from the phototransistors 76 and 77, i.e. signals shifted by 90 ° in phase, it is appropriate to use a mask 78 as shown in FIG. The rod 67 acts as a cylinder lens, and the mask 78 is required to remove the portion of the stripe pattern weed out which is to be focused on the respective phototransistor. The mask 78 accordingly an opening 79 »which limits the light which is focused on the phototransistor 76, and an opening 80 which limits the light to be focused on the other phototransistor 77.

It will now be explained with reference to FIG. 8 how a mother grid can be produced. Thereby find techniques as they are known from the production of integrated circuits and semiconductor circuits, in a modified form Use. With regard to the known techniques, see pages 193 to 205 of the book "Dividing, Ruling and Mask-Making" by D.F. Horn, Adam Hilger Verlag, London, 1974, referenced.

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The first step in the process, represented by block 81 in FIG. 8, is to make a Original template or template. For example, a plastic laminate can be used for this, which is available under the designation "Rubylith master" is available in stores and has a translucent base white material and a removable cover made of ruby-colored material. The original template is represents a small section of a grid 100 times the size of the grid required. In the plastic laminate is carried out with a program-controlled, coordinate-controlled ten submachine, also known as the coordinateograph, cut a pattern. The original template contains a 33cm long and 4 cm wide sheet or film made of the plastic laminate. In the plastic laminate are along its width one hundred lines, each extending in the longitudinal direction of the plate, with spaces of 400 aub each incised.

A photographic recording of high accuracy is then made from the original template, scaled down by a factor of 10 Scale produced, which is symbolized by the block 82. The negative thus obtained becomes ordinary referred to as a reticle.

The reticle is then, as symbolized by the block 83, in a known, step-by-step operation A multiplication camera is used, for example, as described in pages 200 to 205 of the aforementioned book by D.F. Horn described is, and with a further reduction by a factor of 10 to part of a final motherboard copied, which may be a photographic plate or a chromium plate coated with photoresist. the The relative position of the reticle and the final mother plate in the camera are then changed so that a factor 10 reduced image of the reticle at a very precisely defined distance from the first image on the mother plate

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is produced. This step-by-step copying of the reticle onto the final mother plate is long repeatedly until a photographic image of a grid of the required length is produced on the final mother board has been. The image is then developed, as represented by block 84, and the completed mother grid can then be used to produce line grids with opaque lines and clear spaces Glass blocks and the like can be used as explained with reference to Figs. 2A, 2B and 2C.

The exemplary embodiments described can be modified in the most varied of ways. For example you can move the displaceable measuring pin 1 in the bearings 7 and 8 by turning an associated button or wheel, without the plunger turning itself.

You can also apply to other than the described surfaces of the glass block 23 », e.g. on the beveled surface, a Apply a layer of lubricant.

Furthermore, the spacer strips 44 and 45 on surfaces 25 and 26 of blocks 23 and 27 by a continuous strip on one of these surfaces and a series of separate lubricant areas, e.g., speckled Areas to be replaced on the other face. The lubricant or slippery material on the one hand the surfaces need not be the same as the material on the other surface with which it interacts.

In order to ensure good adhesion of the lubricant to surfaces 25 and 26, the lubricant is preferred in particle form, e.g. applied by spraying or deposition in a vacuum and not by gluing a preformed body on the surface in question.

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Claims (9)

Claims 1 / digitally displaying measuring device with a first component, which is displaceable with respect to a second component, further comprising a first diffraction grating which is connected to the first component coupled and movable with this and a second diffraction grating which is a fixed position with respect to of the second component and is arranged with respect to the first diffraction grating that with the help of electromagnetic Radiation that successively penetrates the two diffraction gratings, an interference fringe pattern can be generated is; further comprising a source of electromagnetic radiation and a radiation detector arrangement so related to the grid are arranged so that the radiation from the radiation source falls through the grid and the radiation detector arrangement responds to the resulting interference fringe pattern and output pulses according to the changes of the interference fringe pattern and a pulse counter connected to the output of the detector arrangement, characterized in that a digital display device is connected to the output of the pulse counter (62) (63) is connected that a device (44, 45) is provided to keep the grids (24, 28) at a predetermined distance from one another, and that a device (13) for controlling the speed of the first displaceable component (1) is provided. 2. Heßgerät according to claim 1, gekenn ze lehn et by an elastic device (14), which on the first, displaceable component (1) exerts a substantially constant force which the first component (1) in Direction on the second component (2) pushes. 609843/1 100 3. Measuring device according to claim 1 or 2, characterized in that the grids (24, 28) are held at a distance from one another by a solid lubricant (44, 45). 4. Measuring device according to claim 1 or 2, characterized in that the grids (71, 72) through a liquid lubricant are kept at a distance from each other. 5. Measuring device according to one of the preceding claims, characterized in that the first, displaceable component (1) is coupled to the first grid (24, 71) via a type of universal joint (29). 6. Measuring device according to one of the preceding claims, characterized in that the Grids (24, 28) are flat. 7. Measuring device according to one of the preceding claims, characterized in that the device to control the speed of movement of the first, displaceable component (1) a coupled with this Contains arrangement with a piston (17) and a cylinder (18). 8. A method for producing a master grid, in particular for a measuring device according to claim 1, characterized in that that a representation of a small part of a grid made on an enlarged scale will; that this representation is photographically reduced to a first plate; that from the picture on the first plate produced a further reduced image on a second plate (83) by photographic reduction will; that from the picture on the first plate then 6 0 9843/1100 Once again reduced images are generated on such places on the second plate that a regular A grid pattern of the appropriate length is created, and the second plate is then developed into a mother grid. 9. A method for manufacturing a measuring device according to any one of claims 1 to 7, characterized in that it is chn e t that a photoresist layer with an image of one after the mother grid produced by the method according to claim 8 is exposed; that the exposed material is developed, around a metal layer under the PhoioLackschicht to uncover, and that the uncovered areas of the metal layer are removed by etching. B 0 9 8 4 3/1 1 0 0 Blank page