DE1159174B - Device for measuring the mutual position of two objects - Google Patents

Description

Device for measuring the mutual position of two objects The invention relates to a device for measuring the position of an object relative to one other object by scanning two each connected to one and the other object, scales that can be scanned using the light point method, namely one coarse and one Fine scale. The features of the coarse scale form reference lines for the finely divided, with its features, an auxiliary scale covering approximately a full part of the coarse scale. The generated by simultaneous scanning of the scales while swiping over the scales Pulses are fed to an electrical counting device.

Such a device can be used in various devices, in which precise adjustment of a sliding movement or an angular movement executing element is desired. So z. B. with a jig drilling machine, used for extremely precise machining, straight movements of the table can be carried out with high precision. These movements are normal controlled by hand, or manual control with mechanical assistance is used, whereby scales with fine graduations and optical magnification are used for Achieving the required level of accuracy.

There are purely mechanical slide calipers of various types for Measure or display lengths or distances known, their scale divisions can be obtained by markings or structural elements. In one Mechanically operating device, any play easily causes errors. It is also known to measure length by counting electrical impulses, in such a way that one scale is moved past another scale and off the coincidence or the non-coincidence or from the transition to the coincidence of the a measured value is derived from both scales.

There are also devices for fine reading with graduations provided devices became known, which consists of a sawtooth-shaped sections Have main scale in which the tooth flank forming a reference line is perpendicular stands to the measuring direction and the other tooth flank runs obliquely to the measuring direction.

As far as the known devices use a fixed light source, with which scales moving against each other are scanned, exists in principle the disadvantage that with slow movements of the scales only with great difficulty or with special Effort flawless impulses can be derived for the control of the following Stages, e.g. B. amplifier or control stages are suitable. Even with constantly changing different movements of the scales, different impulses are to be expected, for their perfect processing must still be taken care of, so that the accuracy requirements to be met.

It is also known to measure a precision rule by means of two deflecting glasses to deflect different oscillation amplitudes and each deflection glass a scale of different Assignment to classification. However, the two scales are on a single one Carrier provided, and the display of the position shift is stroboscopic, by the photocells arranged behind the scales for the synchronous control of Flashlight lamps are used to illuminate movable pointers via fixed scales will. The effort for this known device, which is only used to display positional deviations is set up is substantial.

The invention eliminates the known, from a coarse and a Fine-scale existing and photoelectrically scanned devices adhering Disadvantages in that the coarse scale can be moved relative to the auxiliary scale and that the pulse sequence generated when the auxiliary scale is simultaneously scanned is continuous is and with the resulting from the coarse scale and as an interrupted pulse train Occurring impulses with a corresponding formation of the coarse graduation by a corresponding Associating device cooperate in such a way that each time at the first coincidence of pulses from the two rows after scanning a coarse scale feature Impulse for the resetting of the continuous one originating from the auxiliary scale Pulse train receiving counter is delivered.

The counting device with its coincidence circuit is a rough one Measurement and with each reading of the coarse scale a constant under all circumstances Fine measurement of the greatest accuracy guaranteed in a very simple manner.

Vibrating light sources have become known for microscope reading. However, this is a different task and it is also missing known device a counting device with a coincidence circuit, which only an advantageous device for accurately measuring and determining the mutual Position of two objects, since the measured values are used as control variables or d "1. to eliminate the unwanted deviations in the simplest possible way be asked.

The main scale division (rough scale) can either be known per se Cut in an opaque building element or in some other way be formed or in the form of opaque markings on a clear one Scale should be attached.

The light pattern is preferably made by optically reducing a precisely executed larger scale plate, like a grid, obtained through direct incident light or is illuminated by reflection and with opaque or light-absorbing interpolation graduations.

When the light from the light source hits all the divisions of the plate is directed at the same time, the pattern can be scanned by means of a movable mask thereby generating a scanning light beam. The mask can consist of a Hollow cylinders are made with a helical slot, which is fixed with a Cooperates screen, which is provided in the longitudinal direction with a gap. Even the light can be obtained in the form of a fine beam, which the pattern the plate scans. This light can be through opto-mechanical means or with Using the electron beam of a cathode ray tube can be obtained, as in a light spot scanning device.

In the device according to the invention, the longitudinal profile or the Width of the main scale division of little importance if only sentences more appropriate Pages are designed or marked in the same way, with sufficient Accuracy in order to be able to serve as reference lines for the interpolation system. this facilitates the construction of an exact main scale. Such a scale can be a with An incised rod or flat plate with an attached to one side Be sawtooth profile, with tooth edges running perpendicular to the scale being the exact ones Represent reference surfaces while the sloping edges have any profile that can be easily manufactured and not be exactly uniform needs.

The invention is based on specific embodiments on the basis of a Illustrated embodiment illustrated in the drawings. Here is a sawtooth Rod present, which is attached to the movable table of a jig drill or another Tool is arranged and part of the device for measuring the distance forms for the purpose of maintaining a very precise and possibly automatic setting.

Figures 1 and 2 illustrate the light pattern and pulse train which correspond to two different counts. The impulses are accurate for the sake of clarity shown below the elements of the pattern. It should be noted, however, that the pattern as Function of length is plotted while the pulse trains are on a time scale are applied.

Fig. 3 is a diagram showing the positions for various Figure 4 illustrates counts and Figure 4 is a block diagram of the apparatus.

On the table of the tool in the longitudinal direction of the table is one horizontal main scale arranged in a sawtooth shape. The vertical counting edges serve as graduations and lie with the required final accuracy at mutual intervals of 2.5 mm. If the accuracy is insufficient, the Errors in the positions of the vertical edges are measured, and a correction is made in the measuring system appropriate.

To the mutual distances of 2.5 mm in hundredths or thousandths To subdivide parts of it, the procedure is as follows: A sample plate or transparent interpolation scale, which can have a length of 10 to 25 cm evenly divided by invisible markings, in such a way that the light in a hundred or a thousand evenly spaced points can pass through. This scale is scanned by a light spot that is as small or smaller than the openings is in the scale. The light spot preferably sweeps the scale more evenly or almost constant speed, always in same direction. The scanning is done many times per second. A lens higher optical quality and with a numerical aperture appropriate for the required Resolution is sufficient, produces a reduced image of the scanned scale on the sawtooth-shaped main scale. The reduction is such that the images the hundred or thousand openings exactly between two consecutive verticals Edges of the main scale are falling.

The light falling along the sawtooth-shaped edge of the main scale is picked up by a photocell, which interrupted one off as a result of the scanning Pulse series supplies existing output voltage. In Fig. 1, for the sake of clarity an interpolation of ten instead of a hundred or a thousand is shown Number of pulses between the edge Vn, i.e. H. the last vertical edge V the Scale, and the last pulse of the scan a measure for the subdivision of the distance of 2.5 mm. This number increases as the main dial moves to the left. In at a given moment one encounters the inclined edge S, and the desired one Part of the pulse train is interrupted. To continue counting in the right way The interpolation scale is also activated directly by means of a second photocell observed whose output voltage consists of a continuous series of pulses. The two pulse series occurring are shown in Fig. 2 for the case that the inclined edge S is encountered during the count.

We meet the last vertical edge V at D, and the count would have to be continued to E in order to achieve a count of 8 in this case. Apparently count D would have to start where the first coincidence between pulses of the two rows occurs. The last coincidence occurs at F, and that at G non-coincidences may not end the count. This is going through made relatively simple upstream connections possible. However, the case requires according to Fig. 1 a different treatment.

As soon as scanning begins, there will be a collapse at H and counting will begin with the devices in place. The non-coincidence at K does not end this process, and the next coincidence D the counting can therefore continue. In this case, which occurs for several possible positions on the main scale, the whole row is counted regardless of the position. By means of a further device, however, it can be achieved that a coincidence D preceded by a non-coincidence K resets the counter, the entire counting from H to D being canceled. Successive coincidences F, G let the counter work undisturbed. At the end of each scan, the devices are completely reset. If a scan begins with a non-coincidence, this is recorded and the devices are prepared for the first coincidence when the count begins. The count continues even if there is a non-coincidence of the pulses, but in this case the devices are prepared for another coincidence if this should follow. The case of non-coincidence-coincidence-non-coincidence-coincidence (anticoincidence-coincidence-anticoincidence-coincidence = AC-C-AC-C) can occur with scans longer than the distance between two coarse-scale markings. The first coincidence C, preceded by a non-coincidence AC, causes a reset pulse to be applied to the counter. The counter continues to run until the second coincidence C, under the influence of which a reset pulse is again fed to the counter, so that the count made up to that point is cleared. At this second coincidence C the counting starts again. The end of the scan cycle then provides the result of the count from the last vertical edge V to the last pulse, as required.

The succession of cases that occurs when the main scale Moved to the left (scanning to the right) is shown in Fig. 3 for an interpolation 1 : 10 shown with thirteen pulses.

When the scan length is shorter than the distance between the intercept point with the inclined edge S and the second next vertical edge V, then they are four cases shown are the only ones that are possible. They all contain the sequence "Non-coincidence A - Coincidence C" followed by A or nothing. The succession C guarantees a correct count. This is followed by another sequence AC or nothing. This causes the state in which the auxiliary devices be left behind at the end of the scan. However, there the sequence in each case contains at least three changes from AC to C or vice versa, the position of the circles at the beginning of the next count is unimportant because it is a sequence AC-C in any case from the correct vertical edge V before the start of the count occurs. A reset at the end of each scan is not necessary, provided that that the scanning length is sufficiently long.

Fig. 4 schematically shows a block diagram of the devices used in this embodiment. Photoelectric multipliers are used to observe the optical image of the interpolation scale. The pulse shaping stages 101 and 102 produce pulses with an amplitude of approximately 100 volts. These pulses are reversed in the reversing stages 103 and 104 so that transmission of light results in a pulse of positive sign. The pulses are fed to coincidence device 105, which may include a single tube controlled by two grids. Coincidence results in a negative pulse which is fed to flip-flop 107, which has two stable operating positions (bistable pair). An amplified negative pulse is available at an anode for resetting; the occurrence of the first collapse is recorded by the operational location of the device 107.

In the delay stage 108 and the pulse width controller 112 , the pulses P 2 of the continuous pulse train are delayed by a time equal to a quarter of the pulse width, and their width is reduced to half the original. In this way it is achieved that an undesired non-coincidence is not recorded if a pulse of the interrupted series P 1 would occur somewhat out of phase with a P2 pulse. If they do not coincide, a negative signal is fed to the other tube of the bistable multivibrator 107 by means of the device 066, so that the non-coincidence is recorded as a new position of the bistable multivibrator. The second anode of the bistable flip-flop 107 results in a positive rectangular pulse train which coincides with the interruption of the series of P 1 pulses. The trailing edge of this pulse train is used to reset the counter.

The counter 110 is fed by the continuous pulse series P2 and forwards the counts to a comparison device 109 , in which the counts are compared with a required rated number which is determined by the input part. Differences, which can be positive or negative, result in signals that are passed on to an inductor if manual adjustment of the tool is used or to a servomechanism if the adjustments are made automatically.

The design described is for square or trapezoidal ones Main scale divisions, as indicated at S1 or S2 (Fig. 1), or other forms the scale division can be used; the accuracy and uniformity of the widths or the profiles are of little importance if only the reference margins V are accurate are designed and at the correct mutual distances. Execution can also be done with little change on an arcuate or circular sawtooth scale Used when angular movements have to be carried out or controlled, z. B. in devices for aiming guns.

In a modified embodiment, which is shown schematically in FIGS 6, the scanning device generates two light spots, which in the case of a horizontal scale are held vertically one above the other when scanning. A Light spot carries out an uninterrupted scan of the sawtooth scale. The other Light spot is used to generate pulses and is associated with its movement Intervals masked by a pattern plate or mask T 1 (Fig. 6) so that a Interpolation between vertical edges V of the scale is possible. When generating of a reduced image of the scanning pattern, however, only the light spot is used for scanning of the sawtooth used, while the pulse generating light spot opposite the reduced lens system is shielded and scanned by a separate photocell will. This photocell therefore gives a series of pulses during the scan continues uninterrupted. The scanning spot for the sawtooth is only provided by the sawtooth scale interrupted, and the output voltage of the associated photocell is in the upper Part of Fig. 5 indicated. When the light spot behind the vertical edge V to the When it appears, the cell current suddenly increases, so that the output voltage decreases, Q; this change is different from the one going in the positive direction Change R that occurs when the spot disappears behind the sloping edge S. The edge Q, which changes in the negative sense, is used as a signal that the Starts counting the pulses that occur in the output circuit of the photocell. the The number counted at the end of the scan gives the required interpolation. the Both light spots can if desired by means of a vertical line of light be obtained, which strokes over a horizontal pattern or a mask, such as shown in FIG. 6. The mask has a continuous slit T2 for the light spot the sawtooth scan and a series of openings for the one that generates the pulses Light spot; the latter is opposed to the optical by a screen or reflector T3 Shielded reduction system.

A device that acts in the manner as shown in FIGS. 5 and 6 is explained in detail below with reference to FIGS. 7 to 10. This device can be used on the horizontally movable table of a tool Find. In this device, the main scale or coarse scale is an organ with a with screw-threaded element, one or both of its threaded sides as Reference surface are formed and in which the thread profile along a longitudinal surface is exposed. The scale organ has coarse graduations of 2.5 mm, while the interpolation scale, for example, has a hundred tick marks, so that one Measurement up to 0.025 mm is possible.

In Fig. 7, there is a solid light source with a linear filament 1 and a condenser lens 2 a perpendicular parallel light beam in which a Scanning element in the form of a mirror 3 at 45 ° with a vertical cylindrical lens 4 goes back and forth. The scanning element is supported by a carriage, not shown, which is moved back and forth by appropriate means, the movement in the horizontal Direction is perpendicular to the plane of the drawing. The mirror therefore moves in the bundle back and forth and throws a constant portion of the bundle onto lens 4. The latter has the shape of a ground and polished glass rod with a length of 25 mm and a thickness of 12.5 mm. It is arranged and generated with its axis perpendicular a vertical line image of the filament at a distance of about 4 mm from the Surface. The width of the line is reduced using one of the following to be described lens system about 0.005 mm.

The optical system is arranged on a base plate 8. The interpolation scale plate 5, which will be described later, is arranged in the vicinity of the scanning element above a horizontal, right-angled opening at the end of a light-tight housing 9. A horizontal partition plate T3 divides the dial plate 5 and the housing 9 into an upper and a lower part in the same way. A mirror 10 reflects light from the upper part of the scale 5 in the direction of a photomultiplier 12. The housing 9 with its contents, the scanning element and the light source are arranged on a carriage, so that the length of the system and also the optical reduction factor, the z . B. 40. 1 can be set. A second light-tight housing 14 is rigidly arranged on the base plate 8 and connected to the housing 9 by a telescopic tube-like connection 15. The housing 14 contains a microscope 17 with a 16 mm objective and an adjusting element. The threaded coarse scale 18 is arranged with its measuring surface 19 opposite the microscope objective, while a photomultiplier cell 22 is attached to the other side.

To a significant loss of resolution and an overload The photocell must be avoided when light falls at a small angle reflection on the lower surface of the partition plate T3 is avoided; because otherwise a second, irregular image of the light line would be visible in the microscope objective. A mirror can also be used to double the length of the light beam, how it is perceived by the lens. Reflections through the walls of the housing 9 and 14 must be avoided.

As shown in Fig. 8, the dial plate 5 includes an upper one Part s' with opaque markings and a lower, bright part 5 ". The Interpolation scale of the plate part 5 'is created, for. B. by photographic reduction a large drawing in white and black or by direct engraving. In the Fig. 8 is a complex view, the lower half of which is represented by the Microscope objective and the upper half of which would be seen through the photocell 12. That enlarged The back projected image of the rough scale division V is added for explanation. The helical plate of the scale element used has a sawtooth-shaped one axial cross-section, so that a sawtooth profile is created on the measuring surface 19 (Fig. 7), which has sloping sides S and vertical reference edges V.

The line of light generated by the scanning beam is at 23 as consisting of two parts consisting shown, which are separated from the wall T3. The use of a stroke of light offers significant advantages over circular or square light spots, which are generated with the device according to FIG. 6. Apart from the achievable higher Triggering power and the larger amount of incident light results in a further difference between the voltage changes on the photocell 22 and the corresponding changes R and Q according to Fig. 5. Marking the light line by an inclined edge S takes place gradually, so that a gradual decrease in current in of the cell and a corresponding voltage increase R 1 (in Fig. 8) occurs which easily from the rapid change Q1 (as a result of the appearance of the bundle behind an edge V) can be distinguished without paying attention to the difference in polarity needs. This property allows the electro-optical system to operate during the Carriage return can remain effective without the need for switching, which is not would only complicate the device, but would also cause voltage changes, which cannot be directly distinguished from the desired change Q 1.

The waveform produced by the returning beam can therefore be represented as a continuation of the waveform Q 1, R 1 of Figure 8 and includes opposite changes R2, Q2. When the line of light appears behind a vertical edge V, the sharply sloping wave Q 1 arises in the photocell 22, while the covering by an inclined edge S results in the slowly increasing wave R 1. Covering with a vertical edge V during the return movement results in the steeply rising edge Q2, while the appearance of the bundle behind an inclined edge S results in the slowly decreasing line R 2. The waveform obtained from this by differentiation is shown in Fig. 10 and contains two sharp pulses of large amplitude, but opposite signs, as well as two pulses of much lower amplitude (e.g. the tenth part of the former) and longer duration. One of the sharp impulses corresponding to Q 1 can be clearly distinguished from the other three signals and is used as a control impulse. This pulse opens a gate through which the remaining pulses generated by the interpolation scale are fed to the counter. The number of these pulses is a measure of the distance from the edge V (FIG. 8) to the right end 6 of the interpolation scale and therefore results in the necessary partial shift of the main scale.

The interpolation scale on plate 5 has more than a hundred graduation marks, z. B. one hundred and ten, so that certain tolerances at the limits of the scanning path are permitted. The scanning must start in the middle part of section 7 and end in the middle part of section 11 (Fig. 8). In this way it is achieved that 1. a scale length is scanned with at least one hundred and ten graduation marks, Il. the light line 23 of the interpolation scale at the end of the forward scan disappears, since it passes edge 6, and 11I. the light line 23 never on the bright part 5 "of the scale plate is covered, except for the shape of the coarse scale.

From II it follows that a signal at the end of the effective or forward scan occurs. This signal, as will be explained in more detail below, is necessary for differentiation the return scan from the forward scan. The property I enables one gradual transition from one sawtooth edge to the next, while III one enables clear differentiation of the reference margins.

FIG. 9 shows a block diagram of the device for selecting and counting the pulses originating from the photomultiplier 12 (FIG. 7) and for carrying out the corresponding interpolation measurement, and FIG. 10 shows various waveforms obtained with the device according to FIG. The device contains the following elements: a) a manually operated input unit 26 with control switches 27 and 28 for entering the settings in quarters and fortieth parts of a millimeter of the desired table position, and each switch has an operating button, and further specified buttons 29 are used for coarse setting of the table to the nearest quarter of a millimeter, b) a detector 30 for generating a pulse 63 (Figures 9 and 10) which closes the gate 32 at the end of each forward scan, c) a device 31 for differentiating the waveform Q 1, R 1, R 2, Q 2 (Figs. 8 and 10) and to receive the pulse 62 which opens the gate 32, d) a gate 32 which is operated by pulses 62 and 63 such that only the effective part 66 of each of the Photocell 12 derived pulse series is allowed to pass, e) a counter 34 for counting the portion of each pulse series passing through the gate 32, the initial position of the counter being set by the switches 27 and 28 t, to which it is connected by the line 33, f) a register 36 to which the successive counts of the counter 34 are forwarded in parallel via the transmission relay 35, g) a transmission pulse generator 37 which generates a transmission pulse 64 (Fig. 9 and 10), which is derived from the pulse 63 and closes all Realis 35 for a controllable transmission time at the same time, h) a device 39 for generating a recovery pulse 65 (FIGS. 9 and 10), which after a caused by the delay device 38 Time delay is derived from the pulse 64, the recovery pulse 65 is used to reset the counter via the switch of the manually operated input unit, i) a device 40 through which the size and direction of the error of the table position are derived from the register, j) a measuring instrument 41 for display. d; .s position error. in terms of amount and direction (left or right of the zero position).

Each operating cycle of the device comprises the following phases: a) The The passed pulse train representing a measurement is received by the counter 34 and subtracted from the number that was previously set by switches 27, 28 of the input unit was discontinued.

b) The transmission relays 35 are under the action of the devices 30, 37 momentarily closed so that c) the difference, d, h. the bug in the Counter is held to the register 36 and from there to the measuring instrument 41 is passed on.

d) The transmission relays are again under the control of the devices 30 and 37 open. e) The device 38 initiates a delay, to enable phase d); this delay equals mechanical inertia the relay off.

f) The counter 34 is controlled by the device 39 via the switches 27, 28 is reset so that it can receive and count the next series of pulses.

Phases a) and b) occur during the forward scan and the Phases c) and f) during the unused return. How the system works is described in more detail below.

The four buttons or dials on the hand-operated input unit 26 are set to indicate the desired position of the machine. A series of pulses is available for each scan, the number of which equals the total number so many fortieths of a millimeter is in the part of 2.4 mm to which is set became. The input unit is z. B. set to 60.155. In; the assumption that the table is set by other means within the appropriate scale division of 2.5 mm the two scales in question are in this case on 6 (fortieth of a second) and 2 (four hundredths) set by the buttons on switches 27 and 28. If the Saw scale and therefore also the table happens to be in a position in which each sample delivers 78 pulses, this means that the partial shift the scale is 0.195 mm. The. both numbers 155 and 195 need to be compared and size and signs of their difference are displayed to the operator so that they can move the table of the machine (and therefore also the sawtooth scale) until there are just sixty-two pulses in each row. When this situation is reached is, the measuring instrument 41 is at zero, and the table has a position that of the The setting of the input unit.

The counter 34 contains two decades, each made up of four bistable pairs exist and are connected in series so that the counter only count to one hundred can. The fact that the counter can only count to a hundred is used to a gradual transfer from one edge of the scale of the sawtooth to the other to achieve, whereby it is not necessary, very: exact limits for the scanning length and determine the location, which, as noted, may change if turn scanned more than one hundred tick marks.

The counter 34 is set up in such a way that when receiving consecutive Pulses the count is increased by one for each pulse. For example, it is assumed that the counter shows the number 156 and gives it a series of hundred pulses, will lead. The counter then runs through the following "cycle: 56, 55, 54, 53 ... 3, 2, 1, 0, 99, 98, 97, 96 ... 59, 58, 57, 56.

The last number of the cycle is equal to the first, so that a series of hundred pulses is indistinguishable from a series of zero pulses in terms of result. Assuming again that the count is indicating 56 after twenty-four pulses have been applied, the counter will cycle through: 56, 55, 54, 53 ... 35, 34, 33. 32.

It then stands at 32, which is the difference between 56 and 24. In all cases the input unit for choosing the location (in this case 56) is used, from which the decreasing count is based; in this way it arises the obtained subtraction of the pulse train from the initial setting.

If the required table position (and therefore the manual adjustment of the Input unit) is increased in value, the edge V (Fig. 8) is moved to the left. With a setting between 80 and 90 (fortieth of a millimeter) the next vertical edge to the right (V, Fig. 8) hit by the scan, and a second opening pulse 63 for the gate is generated during the forward scan. This has no effect since the gate 32 is already open. At one setting of 100 or 0 fortieths, one hundred pulses are added to the interpolation scale with each scan 5 'received. From this setting to a setting from 10 to 20 is the The number of pulses received is the same as the manual setting plus 100, and this number appears at the meter.

At a certain moment, the left edge V is no longer hit by the scan, and only one pulse is generated to open the gate, namely that of the right edge V. The pulse count can then be: 113, 114, 115, 116, 117, 118 ... due to the fact that the edges V and V 'are exactly a hundred pulses apart. There is therefore no interruption when the count of one edge V is passed to the other.

The transfer of the setting of the input unit to the counter takes place in parallel in the following way: At the moment in which .the counter must be adjusted to the input reading, a single reset pulse generated. It is activated simultaneously via switches 27, 28 and separate lines in one of the conductors 33 of each of the four stages of the two parts constituting the counter The decade counter is supplied, and each conductor 33 contains eight lines for this purpose. Each switch is an eight-bank ten-way switch, and the wiring of the banks and Paths is such that the corresponding bistable pairs are returned to the correct location to display the number given by the setting of the switches. It it is possible that when resetting, a flashover between the steps in the counter and takes place from the counter part of the "fortieth". The reset pulse 65 is long enough to cover any. transition situation occurring as a result of this phenomenon to surpass in duration, and the meter will take the desired position, when the reset pulse ends. As soon as the reset pulse ends, the counter is ready to carry out a further subtraction in the manner described.

The pulsed output of the photocell 12 is at the end of the forward scan, when the line of light passes the edge 6, interrupted, this edge being the second The reference edge, which interacts with the actual working edge V, is used. This interruption is indicated by rectification in unit 50, and a signal results 3, which is unique and indicates that the forward scan has ended. This Signal is to lock the gate 32 and to operate the generator 37 for the Impulse transmission used. The thus obtained. transmitted pulse 64 is used to close of the transmission relay 35 and for the parallel transmission of the difference number from the counter on the register. The delay device 38 enables the transmission relay to open, and the reset pulse generator 39 provides the delayed reset pulse 65, which is used for the purpose already described. As a result of the unused Backlash, therefore, becomes time for the transfer and reset functions available.

If the number of pulses in a row that is allowed to pass is greater than the number set in the counter, the result is the complement of the difference compared to 100. Errors from 50 to 99 are regarded as negative errors and those from 0 to 49 as positive errors. The contents of the register 36 are checked for the size and meaning of the error by means of the device 40, which generates a direct voltage of associated amplitude and polarity. This DC voltage is fed to the measuring instrument 41, the zero point of which is in the middle of the scale and which gives an indication of the direction in which the table of the machine must be moved in order to compensate for the error.

To use the correct margin V, it must be within 0.0125 mm from its end position. The coarse adjustment system must have this accuracy, as was also assumed in the above description. If so desired A test system can be provided for the coarse adjustment to check for electrical Paths the real position of the table with a desired coarse setting (e.g. in centimeters or in millimeters), which is effected by means of the buttons 29 will. Such a system can give a display on a separate instrument; the device can also be such that the device 9 of the instrument 41 input signals are suppressed and the display of the instrument on the right or left until the table is 0.125 mm from the desired end position is performed. In this position the control opens automatically the signal taken from the device 40 for the fine adjustment, so that the Operator receives a completely clear display.

The transmission relays can be electromagnetic relays or gate circuits be with diodes. Furthermore, the accuracy of the system can range from 0.25 to 0.025 mm are increased by the fact that on the interpolation scale 5 'a division in Thousandths is attached and the input unit 26 with another switch Scale is added, including at the same time a third part in the counter 34 must be attached for counting desired parts of a millimeter.

Although the table can be operated by an operator using the display of the Instrument 41 can be set by hand, these displays can also be used for Control of a servo system that automatically adjusts the table can be used. In the former case, the device is preferably such that the amplitude of the Error due to the distance between the pointer and the center of the scale except for one certain maximum amplitude is conditioned, over which increasing error displays with constant or almost constant amplitude.

Claims (4)

PATENT CLAIMS: 1. Device for measuring the position of an object in relation to another object by scanning two scales, each connected to one and the other object, scannable by the light point method, of which the features of the coarse scale reference lines for the finely divided, with their features about one Form an auxiliary scale covering the full partial area of the coarse scale, in which the pulses generated by simultaneous scanning of the scales when the scales are scanned are fed to an electrical counting device, characterized in that the coarse scale (V, S) is opposite the auxiliary scale (T 1; Fig. 6 ) is displaceable and that the pulse sequence generated when the auxiliary scale is scanned at the same time is a continuous one and interacts with the pulses originating from the coarse scale and occurring as an interrupted pulse sequence with a corresponding formation of the coarse graduation by a corresponding allocation device in such a way that in each case at the first Z If pulses from the two rows coincide after a coarse scale feature has been scanned, a pulse for resetting the counter (110) receiving the continuous pulse sequence originating from the auxiliary scale is emitted. 2. Device according to claim 1, characterized in that the coarse scale is well-known saw-toothed portions is made to where the a reference lens-forming tooth flanks (V) are perpendicular or nearly perpendicular to the measuring direction, while the other flank ken (S) inclined to the Direction of measurement run. 3. Device according to claim 2, characterized in that scanned by means of a light beam which performs a movement parallel to its edge on the scale. 4. Device according to claims 1 and 3, characterized in that a mask with two on top of each other arranged parts (T1, T2) is provided, one of which is provided with marks through which an uninterrupted series of electrical impulses can be delivered and forms the auxiliary scale, while the other part is entirely transparent and both the completely translucent and the one containing the individual features Part are arranged parallel to each other so that both parts are assigned to the sawtooth scale can be.