GB2080646A

GB2080646A - Information recording system

Info

Publication number: GB2080646A
Application number: GB8122428A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1980-07-24
Filing date: 1981-07-21
Publication date: 1982-02-03
Also published as: FR2487552A1; DE3028055A1; DE3028055C2; FR2487552B1; GB2080646B

Abstract

In Figure 2, the position of a reading head 13 relative to an information track 10 is obtained using counting (at 19) of sections of the track, each section being a light zone and a dark zone. Absolute-position groups of bits (starting and ending with sync signals) are recorded on the track also, one bit per section, the bit value being given by whether the light or the dark zone is the longer, these bits being received in a shift register 23. The proportions of the zones could be selectively 1:4, 1:2 or 1:1. A separate track can be used for the bits. <IMAGE>

Description

SPECIFICATION Information recording system This invention relates to a recording system for information which is stored in a binary coded form in at least one information track, comprising at least one reading head which produces path dependent or angle dependent impulses by means of a reading device when a relative displacement occurs between the reading head and the track in the longitudinal direction of the track, and to which an interpretation device is connected.

The known recording systems of this type used for digital position measurement determine the position either by incremental measurement or by absolute measurement. The expenditure required for in cremental measurement is low since a single track is sufficient and with the provision of only two reading devices it is possible to recognise the direction of movement as well as the movement itself. One serious disadvantage, however, is that before the energy supply is switched on, after a current failure or other breakdown, the reading head must be moved into a known, accurateiy defined position since it is only from this position that the measure ments can be carried out. Furthermore, if the head is not first moved into such a known position it is not possible to check while the device is in operation whether a position is correctly recorded.Although the recording systems which carry out absolute measurement are free from these disadvantages, they generally require a relatively large number of tracks and a substantially greater number of reading devices. They are therefore expensive and in many cases there is not sufficient space available for the installation or such an elaborate system. Another disadvantage is that a dual code generally cannot be used since it produces errors whenever a signal change would be necessary in several tracks simul taneously but cannot be achieved simultaneously owing to unavoidable inaccuracies. It is therefore necessary to operate with a one-step code but this requires a code conversion circuit to provide a steady sequence of position members.

It is an object of the present invention to provide a recording system of the type mentioned above which is simple in construction like the known systems carrying out incremental measurements but is capable of carrying out absolute position mea surements. This problem is solved by a system having the features of claim 1.

Since the additional information enables one or more absolute positions to be characterised, it is possible to carry out an absolute position measure ment with the system according to the invention even when only one track is available. Since the reading head need only have one additional reading device for this purpose, the additional expenditure required is minimal. Even when this additional device the expenditure is still slight compared with that required for the known systems used for absolute measurements, where two or more tracks and a correspondingly larger number of reading devices are provided, since the subject of this application provides the same output with a sub stantiallysmaller number of tracks and reading devices.

It is to be regarded as a special advantage that the additional information can be used not only to solve the problem of absolute position measurement but also for other purposes. For example, in a store with high shelves, it is easy to ascertain not only the correct passage but also the particular shelf-level.

Possible applications of the system according to the invention include, for example, its use in angle coders, rotation measuring instruments, code rulers and positioning devices for lifts, floor conveyors, shelf installations and the like.

It is advantageous if the additional information is stored in the track in the form of at least one binary coded word and the interpretation device links the impulses transmitted from the additional reading device to the path dependent or angle dependent impulses and composes the binary coded word from them because the expenditure required for the system is in that case particularly low compared with its performance. This also applies if the additional information represents at least one absolute position value.

In a preferred embodiment, each absolute position value is stored in the track in the form of a serially readable sequence of marks and the beginning and end of the sequence are each characterised by a synchronous signal. To recognise an absolute position value, the reading head and the track need then only be moved towards each other until the synchronous signal or one of the synchronous signals is recognised. The associated absolute value is then read and interpreted during the following relative movement.

Although it would be possible in principle to select any length of step for the path dependent or angle dependent impulses, these impulses preferably form a sequence of equal step lengths because equal distances are then available for the counting steps or position steps which are to be measured.

In a preferred embodiment, the absolute position values, which form a series of values increasing or decreasing by equal steps, are stored in a sequence of sections of equal lengths in a first track. Each of the sections of equal length of a second track associated with the sections of equal length of the first track is sub-divided into that number of equal steps, or an integral fraction or integral multiple of this number, by which two successive position values differ from each other. The special advantage of this embodiment is that with only two tracks it is possible to store a very large number of absolute position values, in other words a very high power of resolution is obtained even with very long path lengths.

The recording system according to the invention is also much more versatile than the known systems since the track in which the additional information is stored can be spatially separated from the track in which a counting information is stored.

The interpretation device is capable of particularly high performance if it is equipped with a micro processer, The invention will now be described by way of examples with reference to the drawings, in which Figure 7 is a schematic representation of a first exemplary embodiment with corresponding block circuit diagram, Figure 2 is a schematic representation of a second exemplary embodiment with block circuit diagram, Figure 3 is a signal chain of the example of Figure 2, Figure 4 is a schematic representation of a third exemplary embodiment, Figure 5 is a schematic representation of a fourth exemplary embodiment and the corresponding block circuit diagram, Figure 6 is a schematic representation of a fifth exemplary embodiment, Figure 7 is the block circuit diagram of the example shown in Figure 6, Figure 8 is a block circuit diagram of a modification of the example of Figure 6, and Figure 9 is the block circuit diagram of a modification of the example of Figure 8.

The exemplary embodiment shown in Figure 1 has a single track 10 comprising sections of equal length immediately following one upon the other, each of which has a light permeable light zone 11 and a light impermeabie dark zone 12. The sections need not necessarily all have the same lengths but this arrangement is advantageous since it provides the same magnitude for all the counting or positioning steps to be measured. As may be seen from Figure 1, light zones 11 and dark zones 12 alternate in the longitudinal direction of the track 10. The lengths of the light zones and the dark zones within each section of the track 10 may vary. This enables an information in addition to the counting or positioning steps to be stored in the track.In the example given, the additional information is stored in track 10 in a dual coded form, i.e. each section contains a binary information in the form of a "1" or a "0", depending on whether its light zone 11 is longer or shorter than its dark zone 12. If the light zone of a given section is longer than its dark zone 12, this section stores the signal "1". Conversely, subdivision of a section into a longer dark zone 12 and a shorter light zone 11 corresponds to the signal "0". It would, of course, be possible to use not only the condition that one zone of each section of the track is greater or smaller than the other zone for storing an information but also to use the proportions of the two zones, which could, for example, be 1:4 or 1:2 or 1:1, depending on the information.

The information stored in track 10 is interpreted by means of a reading head 13 which is capable of displacement relative to the track 10 in the longitudinal direction of the track. For example, the reading head 13 may be displaced along the track 10 in one or the other direction. The reading head 13 contains three reading devices which, since track 10 is an optically scanned track in the example given, consist each of a light transmitter 14, 15 or 16, respectively, and a corresponding light receiver 14', 15' or 16'. The track 10 is situated between the transmitters and receivers so that the signal state of the receivers changes when the light barrier formed between transmitter and receiver is interrupted or released by a dark zone.In the example given, the light receivers produce the signal-"1 " when a light zone 11 is situated between them and the associated senders.

1~he two reading devices with senders 14 and 15 which are arranged relatively close together in the direction of movement of the reading head 13 produce the counting impulses which are used to determine the counting or positioning steps and to recognise the direction of movement. The third reading device, which is formed by the light transmitter 16 and light receiver 16', serves to read the additional information fed into the track. It may thus be used to determine whether the light zone 11 in the particular section scanned at the moment is longer than the corresponding dark zone 12 so that the signal "1 " is stored or whether the dark zone 12 is the longer zone and hence "0" is stored as additional signal.The distance of the reading device 16, 16' from the reading device 14, 14' in the direction of movement of the reading head is therefore equal to approximately half the length of one section of the track 10.

Connected to the output of the light receiver 14' are two monostable circuit elements 17 and 18 which give off an impulse at their output Q when there is a signal change from 0 to 1 or from 1 to Oat their input D. Output signals from the circuit element 17 cause a counter 19 connected to the two circuit elements to count forwards while output signals from the circuit element 18 cause the counter to count backwards. When the light receiver 15' produces the signal "0", no signal appears at the output Cl of the circuit elements even when a signal is applied to the input since the cancelling input of the two circuit elements 17 and 18 is connected to the output of the light receiver 15'.

One input D of a flank controlled memory 20 is connected to the light receiver 16'. The other input C of this memory is connected to the output of a gate 21 which has both its inputs connected to the outputs of the circuit elements 17 and 18. The memory 20 thus stores the instantaneous information of the light receiver 16' at the moment when a forward or backward counting process is taking place. The criterion for take-over of information of the light receiver 16' is thus a signal change at light receiver 14' with simultaneous signal "1" of light receiver 15'. A memory 22 having both its inputs connected to the output of circuit element 17 or 18 memorises whether the information stored in memory 20 was obtained during a forward movement or backward movement of the reading head 13. If one assumes, for example, that the reading device 14, 14' is still just within the region of a dark zone 12, as shown in Figure 1,then a movement of the reading head 13 to the right as viewed in Figure 1 is accompanied by the production of a forward counting impulse by the light receiver 14' when the transition to the following light zone 11 occurs. At the same time, the instantaneous signal "1 " of the light receiver 16' is stored in the memory 20. If the reading head 13 is moved still further to the right, no counting impulses occurs at the transition of the reading device 14,14' to the next following dark zone 12 since in this case the reading device 15, 15' is already situated in this dark zone and therefore suppresses the release of an impulse both from the output of element 17 and from the output of element 18.It is only when the reading device 14, 14' reaches the next light zone 11 at the beginning of the following section of track 10 that a forward counting impulse is again produced, and the signal "1" is stored in memory 20 because in this section of the track 10 the light zone 11 is again longer than the dark zone 12. In the two following sections of track 10, the dark zone 12 is longer than the light zone 11 in this particular example. Consequently, when the reading head 13 enters these sections, the memory 20 each time stores the signal "0". From the sequence of signals stored in the memory 20 it is possible, for example, to deduce the absolute position of the reading head 13.

The example illustrated in Figure 2 differs from that of Figure 1 only in that instead of the memory 20 there is provided a forward-backward sliding register 23 which may be followed, as indicated in Figure 2, by a gate 23' and a memory 24. Similar parts have therefore been indicated by the same reference numerals as in Figure 1 and parts which are similar in construction may be explained with reference to the description of Figure 1.

By using the sliding register 23, a coded information is available after a certain number of counting impulses, in other words impulses which have activated the counter 19. In the example given, this coded information may be stored and read out in a parallel form. If, as is advisable, a portion of the storage places of the sliding register, for example, the first two places, are reserved for storing a code signal or synchronous signal for characterising the beginning of a coherent signal sequence, i.e. of a word, then the presence of the code information or synchronous information can be recognised by means of the gate 23' connected in series with the code signal outputs of the sliding register 23.When this information has been recognised, the gate 23' produces a take-over signal for the memory 24, whereby the remaining information in the sliding register 23 is taken over in the correct position in the memory 24, where it is then available at any time for interpretation. Figure 3 shows an example of a coherent signal sequence or signal chain which begins with one code signal and ends with the next following code signal. In this example, the code signal consists of two successive "1 " signals followed by two "0" signals. The following signals are in each case separated by a 0 signal to ensure that there will never be two successive "1" signals except in the codeor synchronous information. All according to how track 10 is coded, the signal situated between the "0" signals may be either an "1" signal or an "0" signal, as indicated by the broken lines.

The length of the signal chain is determined by the information which must be stored within a chain, for example by the magnitude of the absolute position value associated with that section of the track which correponds to the signal chain.

The example illustrated in Figure 4 indicates that a track 110 which, like track 10 of the examples shown in Figures 1 to 3, contains information additional to the counting or positioning step information, and has the same form as track 10, may be associated with a reading head 113 which contains more than one reading device for reading the additional information. Figure 4 shows the reading head 113 with two reading devices 116,116' and 124,124'. Three different signal states can therefore be transmitted to the following interpretation device with each counting step, namely the signal "0" at the outputs of both light receivers 116' and 124', the signal "1' at the outputs of both light receivers, and the signal "O" at either light receiver and signal "1" at the other light receiver.This additional, third signal state not provided in the examples of Figures 1 to 3 may be used to form a code signal or synchronous signal to characterise the beginning or end of a signal chain.

Figure 5 represents an example having two parallel track 210 and 210'. The capacity for information storage can be increased to a much greater extent by means of one or more additional tracks than is possible in the known systems carrying out absolute position measurement, and the additional expenditure for providing one or more additional tracks is far less than in these known systems if information is transmitted serially from the individual tracks. The reading head 213 which is capable of displacement relatively to the two tracks 210 and 210' in the longitudinal direction of the tracks contains at least one, preferably more than one reading device for the track 210 in which the additional information is stored, each such reading device consisting of a light transmitter 216 and a light receiver 216'.The track 210' is a counting track consisting of light zones 211 alternating with dark zones 212 of equal length.

These zones may also be shorter than illustrated in Figure 5; this is particularly advantageous if the two tracks are provided on spatially separated bodies which are displaceable relatively to each other and exact alignment with each other cannot always be ensured. In order that forward-backward recognition may also be possible, this track 210' has two reading devices associated with it, each consisting of a light transmitter 214 or 215 and a light receiver 214' or 215'. The arrangement of these reading devices is the same as in the example of Figure 1. In this example, the feature for evaluating the signals of track 210 need not necessarily be a take-over criterion as in the examples previously described but may consist of the covering of a specified number of steps of track 210'. Track 210 is subdivided into definite sections of equal size, the length of each section corresponding to a specified number of counting steps of track 210'.

Two flank controlled monostable circuit elements 217 and 218 are connected to the output of one light receiver 216' of the reading head 213. The output of element 218 is connected to the O-setting input of a cou nter 219 which countsthecounting impulses produced by means of the two reading devices each consisting of a lighttransmitter214Or215and a light receiver 214' or 215', as already explained in the description of the examples of Figures 1 to 4. The output of the circuit element 217 is connected with the clock input of a sliding register 225 whose input is connected to the output of the counter 219.The signal "1" is inserted in the sliding register 225 whenever the light zone 211 of track 210 is greater than half the number of counting steps which the track 210' contains over a length equal to one of the sections of equal length of the track 210. If the light zone 211 of the track 210 is equal to or smaller than half the counting steps, the signal "0" is inserted in the sliding register 225. This arrangement could, of course, be extended in the sense that other step numbers could also be used for evaluation, for example 1/4 or 3/4 of the number of counting steps associated with a section of track 210. It would, of course, equally well be possible to treat the signals differently during the forward and the backward movement of the reading head 213.A comparison of the length of the lightzones or dark zones of the track 210 with the counting steps of the track 210', for example, is particularly advantageous when the two tracks are provided on parts which are displaceable relatively to each other, e.g. a shelf and a stacking conveyor, and one track is not precisely correlated with the other track, for example, owing to slippage of the wheels of the conveyor as it moves along the shelf. Since the counter 219 is reset to zero at the beginning of each following zone, any errors due to inaccuracies of the tracks or of the correlation of one track with another are not summsted. If the two tracks 210 and 210' are mounted on spatially separated bodies, the reading head is also divided.

Another exemplary embodiment with two parallel tracks 310,310' is illustrated in Figures 6 and 7. Of these two tracks, which are designed to be optimally scanned as in the previous examples described and therefore consist of light zones and dark zones, it is the coding track 310 which contains the additional information. The clock or timing track 310' has light zones 211 and dark zones 312 of equal length alternating with each other. A reading head 313 contains a reading device for the coding track 310, consisting of a light transmitter 316 and a light receiver 316', and two reading devices for the scanning track 310', each consisting of a light transmitter 313 or 315 and a light receiver 314' or 315'.These reading devices are arranged in the same manner as the reading devices for the count ing or positioning steps of the embodiments described above and are also able to recognise the direction of counting.

In a multiflank counting such as may be carried out with the clock track 310' it is possible to select a certain flank as reference point four producing a code signal or synchronous mark to characterise the beginning of a coherent signal chain of the coding track 310. If, for example, on a dark/light flank in the forward direction or a lightidark flank in the reverse direction, which the light receiver 314' recognises, the light receiver 316' at the same time recognises a specific piece of information in the coding track 310, then this event may be used to mark the beginning or end of a following signal chain.In that case, either anotherflank or the covering of a specific number of counting steps in relation to the appearance of the beginning or end mark, in other words of the synchronous signal, may be used as criterion for the takeoverofthe individual elements of this signal chain.

In the example according to Figures 6 and 7, the timing or clock track is designed to produce a 4-flank counting. Each section of the coding track 310, which is equal in length to eight zones of the clock track, each of which zones forms a signal chain, is to be subdivided into sixteen successive bit positions each of which is associated with a flank of the clock track.

With the exception of the first bit position, which is associated with the first flank of the associated signal chain and is required for the synchronous signal, and of the fifth, ninth and thirteenth bit.

position, which must be left free because within each signal chain a flank corresponding to the first flank is recognised four times, a certain valency may be associated with the other twelve bit positions. In the example given here, these valencies are 24 to 215 although different valencies could, of course, be chosen or the information could be stored in some other form.

In the example given, the first signal chain shown on the left contains an "1" in those bit positions which are associated with the valencies 29 or 210.

This signal chain and hende the section of the coding track 310 which contains this signal chain therefore has the absolute position value 29 + 210 = 1536. The middle signal chain contains "1" in those bit positions which have the valencies 24, 29 and 210. The absolute position value 1552 is therefore associated with the corresponding section of the coding track 310. The section of coding track 310 shown on the right in Figure 6 accordingly has the absolute position value 1568. Each chain thus differs from the next chain in its absolute position value by the value 16.Since, as the reading head 313 moves over the section associated with a signal chain, that is to say from the beginning of a signal chain to the beginning of the next signal chain, it covers sixteen steps fixed by the clock track, these steps may be added to or substracted from the position value of the signal chain, depending on the direction of the movement, so that each step is also defined by an absolute value or, in other terms, the power of resolution extends right down to individual steps.

As indicated in Figure 7, the output signals of the light receivers 314' and 315' are transmitted to a flank interpretation circuit 330 which delivers a forward or backward counting impulse, depending on the direction of movement of the reading head 316, at its two outputs Al and A2 with each step, i.e.

at each flank, in the manner known for 4-flank counting, but at its outputs A3 and A4 it delivers an impulse only when a flank having the number 1 is recognised, in the manner known for 1-flank counting. The counting impulses at the outputs Al and A2 drive a forward-backward counter 319 as well as introducing the signals delivered by the light receiver 316' associated with the coding track 310 into 9 forward-backward sliding register 331. Since there is only one synchronous information and no valency position of the signal chain in flank No. 1, a sliding operation of the sliding register 331 is prevented by means of a gate 332 which has both its inputs connected with the outputs A3 and A4 of the flank interpretation circuit 330. The output of gate 332 is connected for this purpose to the blocking input of the sliding register.If recognition of the flank number is accompanied by recognition of a synchronous signal in the coding track 310, the counter 319 is set to its starting position by way of a gate 333 in the event of a forward movement and to its end position by way of a gate 334 in the event of backward counting. One input of the two gates is connected to the signal line coming from the light receiver 316' while the other input is connected to the output A3 or the output A4 of the flank interpretation circuit 330, as shown in Figure 7. The output of the gate 333 is connected to that input of the counter 319 through which all the outputs can be set to "O".

The output of the gate 334 is accordingly connected to that setting input of the counter 319 through which all outputs can be set at "1". Two bistable memory elements 335 and 336 are set or set back by the falling flanks of the signals of these gates with which they are connected in series so that in cooperation with gates 337 and 338 which are connected to the output of gate 333 and of the memory element 335 or the output of gate 334 and of the memory element 336, an impulse appears at the output of a gate 339 only when a synchronous signal has been travelled over in the forward direction and the preceding synchronous signal was also recognized during a forward movement, or if a synchronous signal was travelled over in the reverse direction and the preceding synchronous signal was also recognised during a reverse movement.The two inputs of the gate 339 are for this purpose connected to the output of the gate 337 and the gate 338. This ensures that when the synchronous signals occur, a complete, self-contained signal chain is present in the sliding register 331.

Connected in series with the twelve digit sliding register 331 whose twelve outputs are associated with the valencies 24to 215 is the twelve digit input of a memory 340 which is activated by an impulse at the output of the gate 339 by way of its control input E3 for rising flanks to take over the contents of the sliding register 331.

On recognition of a synchronous signal, however, the reading head 313 is already in a position which is associated not with what has just been read but with the next following signal chain. The twelve digit output of the memory 340 is therefore connected in series with an addition/subtraction circuit 341 which executes an increase by one valency when there is an "1" signal at its addition operation input and a decrease by one valency, i.e. in the present case by 24, when there is an "1" signal at its subtractionoperation input. The first mentioned operation input is therefore connected to the output of gate 333 and the other is connected to the output of gate 334.

When there is no signal at the operation inputs of the addition/subtration circuit 341, the information available at the twelve bit input is directly passed through to the output. Immediately after an addition in the case of forward counting or subtraction in the case of backward counting, the arithmetical value is taken over from the addition/subtraction circuit 341 into the memory 340 when a synchronous signal is recognised by way of the gate 342. The output of circuit 341 is therefore connected to a second twelve digit input E2 of memory 340. The gate 342 is connected to the control input E4 for decaying flanks of the memory 340. The two inputs of gate 342 are connected to the signal lead from the light receiver 316' and to the output of gate 332.

The value transmitted to the memory 340 by way of the addition/subtraction circuit 341 combines with the value of the counter 319 to form the sixteen bit position value which is an absolute position. This position value is rechecked after every sixteen steps in the manner previously described and is automatically corrected in the event of any faults. The apparatus therefore need not be moved back to the mechanical zero position after it has been switched off or after a current failure. It need only be moved back by the short distance in which the value of a signal chain can be reconstructed by the interpretation circuit illustrated in Figure 7. In a suitable constructed circuit this can be achieved after only 16 steps.In a circuit as shown in Figure 7, interpretation is begun at the synchronous signal for the sake of simplicity so that recognition is in this case possible after at the mostthirtytwo steps. However, the reading head 313 may be arranged to be movable on its carrier so that when the current is switched on it may be displaced relatively to its carrier so that when the system is taken into operation or after current failure the absolute position value can be ddtermined without the part which is to be positioned having first to be displaced.

As illustrated in Figure 8, a counter 343 having its twelve digit input EO connected to the twelve outputs of the sliding register 331 may be provided instead of memory 340 and the addition/subtraction circuit 341 connected with it in series. This counter 343 is charged with the signal chain in the sliding register 331 when a signal with rising flank appears at the output of the gate 339 since the output of gate 339 is connected with a control input of the counter.

Furthermore, an input for "forward counting" of the counter 343 is connected with an output of the counter 319 at which a signal appears when transfer is necessary. In addition, an input for "backward counting" of the counter 343 is connected with an output of counter 319 at which a "borrower" signal occurs. Since, as already mentioned above, when a synchronous signal is recognised the reading head 313 is already in a position no longer corresponding to the position which has just been read but already associated with the next following signal chain, the counter 319 is so designed that also the operation of setting it or setting it back releases at its transfer output or at its borrower output an impulse which increases or reduces the value of the signal chain loaded into the counter 343. The counted value of counter 343 together with the value of counter 319 therefore forms an absolute sixteen bit position value.

As regards the formation of the other parts of the circuit shown in Figure 8, reference may be had to the cdmments on Figure 7, since the two circuits are in this respect similar.

Since a recording system such as that shown in Figures 6 to 8 continues to operate correctly by incremental counting by way of the clock track 310' in the event of failure of an information chain, as also in the other examples described, additional informations may be transmitted or introduced instead of absolute position values. An example of this is shown in Figure 9. Since the circuit in this figure is similar to that of Figures 7 and 8, similar parts are indicated by the same reference numerals as in Figures 7 and 8. To avoid repetition, reference may be had to the description of corresponding parts of the circuit given with reference to Figures 7 and 8.

In the exemplary embodiment shown in Figure 9, it was assumed that a fifteen bit information is sufficient to represent the absolute position values.

The bit thereby released is used to detect whether the information is a position information oran additional information. When this bit of highest valency is not set into the code and the signal at the corresponding output of the sliding register 331 is therefore an "0" signal, the charging command for the counter 343 connected in series with the sliding register 331 is transmitted to the charging input of counter 343 from the gate 339 by way of a gate 344.

The interpretation circuit then operates as in the example illustrated in FigureS. If, on the other hand, the highest valency bit is set, the charging command from gate 339 is only passed on by a gate 345, and the additional information now in the sliding register 331 is taken over by a memory 346. The counter 343 then continues to operate correctly in a purely incremental manner by the impulses coming from the counter 319.

As shown in Figure 9, each of the gates 344,345 has one of its inputs connected to the output of the gate 339 while its other input is connected to the output for the highest valency bit of the sliding register 331. The inputs of the additional memory 346 are connected to the eleven outputs of the sliding register 331 to which counter 343 is also connected.

The reading of information during continuous counting as absolute position values or as other information both in the forward and in the backward direction is, of course, not limited to embodiments which have the form of tracks shown in Figure 6.

A spiral or helical arrangement of tracks may be used for measuring angles or movements of rotation. If the signals of a track are constantly repeated, as is the case with a clock track, such a track may be circuiar outside the spiral.

The tracks described may easily be produced by means of photo-sensitive carrier materials. The carrier material cut to the correct size and shape is moved pasta light transmitter, and this movement may be mechanically connected with a conventional position recorder. A computer which has been fed with the mathematical course of the tracks then switches the light transmitter on or off as required in accordance with this formula and the position values obtained. Copies may easily be produced from the exposed and developed original.

Claims

1. Recording system for information stores in a binary coded form in at least one information track, comprising at least one reading head which produces path dependent or angle dependent signals by means of a reading device when relative displacement occurs between the reading head and the track in the longitudinal direction of the track, which reading, head is connected to an interpretation device, wherein the track or, where there are two or more tracks, at least one of the tracks, contains additional information, and the reading head has at least one additional reading device which receives additional information during reception ofthe path dependent or angle dependent signals.

2. Recording system according to claim 1, wherein the additional information is stored in the track in the form of at least one binary coded word and that the interpretation device links pulses from the additional reading device with path dependent or angle dependent pulses and uses them to compose the binary coded word.

3. Recording system according to claim 1 or claim 2, wherein the additional information represents at least one absolute position value.

4. Recording system according to claim 3, wherein each absolute position value is stored in the track in the form of a serially readable sequence of marks, the beginning and end of which is characterised in each case by a synchronous signal.

15. Recording system according tq any preceding claim wherein the path dependent or angle dependent signals or pulses form a sequence with equal step lengths.

6. Recording system according to claim 4 or claim 5, wherein the absolute position values, which form a series of values increasing or decreasing by steps of equal magnitude, are stored in immediately successive sections of equal length of a first track, each of the sections of equal length of a second track associated with each of the sections of equal length of the first track being subdivided into that number of equal steps or that integral fraction or integral multiple of this number by which two successive position values differ.

7. Recording system according to any preceding claim wherein the track which stores the additional information is spatially separated from a track which delivers a counting information.

8. Recording system according to any preceding claim wherein the interpretation device contains a microprocessor.

9. Recording system constructed and arranged substantially as herein described and shown in the drawings.