RU1795706C - Photoelectric position converter - Google Patents

Abstract

FIELD: measurement technology. SUBSTANCE: photoelectric position converter has optically coupled radiation source 1, lens 2, roller 3 with code scale, line multielement photodetector 4 and signal processing unit 5. Enhanced authenticity and reliability of measurements is achieved by manufacture of code scale of roller in the form of optically clear marks applied with spacing smaller than half of input aperture of photodetector and by combination of optically clear and opaque sections between marks carrying information of location of marks. Invention makes it possible to conduct measurements of large distances and to lower technical requirements for precision of manufacture of code scales. EFFECT: simplified design, enhanced authenticity and reliability of measurements. 3 dwg

Description

 The invention relates to measuring equipment, in particular to position measuring transducers, and can be used in measuring systems of numerically controlled machines, in coordinate measuring machines, and large-sized product monitoring tools.

 Known photoelectric position transducer (FEPP), containing movable and fixed elements-measures on which raster paths and masks are applied in the form of a picture from a set of slots, as well as an additional mask in the form of a picture on one of the measures, is identical to the picture of the first mask, to another measure a negative pattern is applied to the first mask, which allows one to determine the position of the moving element of the measure relative to the stationary one only at zero points.

 The closest to the proposed technical essence and the achieved result is FEPP, which we adopted as a prototype, based on a ruler with a code scale.

 The photoelectric position transmitter comprises an optically coupled radiation source, a lens, a photodetector, a code scale, and a signal processing unit from a photodetector. To convert linear displacement, the entire field of the code scale is divided into linear tracks, each of which carries its own weight value about the displacement value.

 When reading information from the code scale, the reading elements are arranged in a straight line perpendicular to the linear code tracks. When moving the scale, reading elements fix codes of zeros and ones under them.

 Reading information from the code scale can lead to big errors, since with a binary code scale two adjacent numbers can differ in the values of all their bits.

 The minimum discreteness of linear displacement measurements according to the prototype is determined by the linear dimensions of its least significant bit of the code scale of the line.

 An increase in the range of measurements of linear displacements entails an increase in the number of code bits applied to the line.

 Both a decrease in the discreteness of linear measurements and an increase in the range of linear measurements cause both significant technological difficulties in manufacturing a ruler with a code scale and difficulties in acquiring information.

 A disadvantage of the known FEPP is the high complexity of manufacturing a ruler with a code scale for measuring large distances and the difficulty of acquiring reliable information from it.

 The purpose of the invention is the simplification, reliability and reliability of FEPP.

 This goal is achieved by the fact that the FEPP, containing an optically coupled radiation source, a lens, a ruler with a code scale, a photodetector and a signal processing unit, the code scale of the line is made in the form of optically transparent marks located on the ruler with a pitch of less than half the input aperture of the photodetector, and combinations of optically transparent and opaque sections between brands, the optical density of which is different from the optical density of the brands, and the photodetector is made in the form of a linear multie a photosensitive array element (LFE) connected to a signal processing unit consisting of a video signal shaper, a reference voltage source, four keys, two comparators, a single pulse shaper, three frequency dividers, four triggers, two pulse counters, a shift register and an OR element, in wherein the first output of the video shaper is connected to the first inputs of the first and second comparators, the second inputs of which are connected to the outputs of the reference voltage source, the output of the first comparator connected to the first input of the single pulse shaper, the output of the second comparator is connected to the first input of the shift register, the second output of the video shaper is connected to the first inputs of the first, second, third and fourth triggers, the first input of the first pulse counter and the second input of the shaper, the third output of the shaper the video signal is connected to the first inputs of the first, second, third and fourth keys, the output of the fourth key is connected to the first input of the second pulse counter, the output the first key is connected to the first input of the first frequency divider, the output of the single pulse shaper is connected to the first inputs of the OR element, the second and third frequency dividers, the second inputs of the second trigger, the first frequency divider and the shift register, the output of which is connected to the second input of the second pulse counter, the output the third frequency divider is connected to the second inputs of the first, third and fourth triggers and the third inputs of the second pulse counter, the output of the first frequency divider is connected to the third inputs and the second and third triggers, the outputs of the second and third triggers are connected by the second inputs of the first and third keys, respectively, the output of the third key is connected to the second input of the frequency divider, the output of which is connected to the second input of the third frequency divider and the third input of the shift register, the output of the OR element is connected with the third input of the first trigger, the output of which is connected to the second input of the second key, the output of the second key is connected to the second input of the first pulse counter, the output of which is connected to the third input the second trigger and the second input of the OR element, the output of the fourth trigger is connected to the second input of the fourth key.

 The simplification of the proposed FEPP follows from the following.

 The resolution of the prototype ruler is determined by the geometric dimensions of the least significant bit of the ruler with a code scale, subsequent application of the digits increases the FEPP measurement range and all the digits of the ruler are measuring and, therefore, require the same accuracy of their deposition and relative position. The placement capacity of the proposed FEPP is determined by the geometric size of the cell of the photodetector and the accuracy of the step marks. The brand location code is not directly measuring and does not affect the accuracy of measurements. The accuracy of applying the code is determined only by the ability to remove information about it. Therefore, a decrease in accuracy simplifies the manufacture of a code line, guides for movement, an indicator head including a radiation source, a lens, and a photodetector. The minimum geometric size of the transparent and opaque parts located between the grades is determined by the size of the gap between the grades, the input aperture of the LFE and the number of digits of the brand location code, which reflects the integer number of steps of the marks located before the beginning of the LFE.

 Measurement on a portion of the code line of less than one step is performed with discreteness of the geometric value of the LFE cell.

 Improving the reliability and reliability of the FEPP is ensured by simplifying its adjustment and adjustment, the interchangeability of rulers and indicator heads, the stability of the FEPP parameters and the preservation of measurement accuracy when the moving parts are worn, this characterizes the reliability and durability of the work.

 In FIG. 1 shows a functional diagram of a photoelectric position transmitter; figure 2 one of the fixed positions of the linear multi-element photodetector relative to the line and the signals on the elements of the signal processing unit; figure 3 mechanism for the implementation of the marks and the code of their location on the line.

 The photoelectric position transmitter (Fig. 1) contains optical conjugated to each other a radiation source 1, a lens 2, an immovable, in the present embodiment, ruler 3 with a code scale made in the form of optically transparent grades located in increments of less than half the input aperture of the photodetector 4 and a combination of optically transparent and opaque sections between grades whose optical density is different from the optical density of grades and a photodetector made in the form of multi-element photosensitivity a linear array, for example, a charge-coupled linear device (CCD) connected to a signal processing unit 5 with a video signal shaper 6 included in it, the first output of which is connected to the first inputs of the first 7 and second 8 comparators, the second inputs of the comparators 7 and 8 are connected to the outputs of the reference voltage source 9, the output of the comparator 7 is connected to the first input of the single pulse shaper 10, the output of the comparator 8 is connected to the first input of the shift register 11, the second output of the video signal shaper 6 is connected to the first inputs and the first 12, second 13, third 14 and fourth 15 triggers, the first input of the first counter 16 pulses and the second input of the shaper 10 single pulses, the third output of the shaper 6 video signal connected to the first inputs of the first 17, second 18, third 19 and fourth 20 keys, the output of the fourth key 20 is connected to the first input of the second counter 21 pulses, the output of the first key 17 is connected to the first input of the first frequency divider 22, the output of the shaper 10 of single pulses is connected to the first input of the OR element and the second inputs of the second three 13, the first frequency divider 22 and the first inputs of the second 24 and third 25 frequency dividers, the output of the third frequency divider 25 is connected to the second inputs of the first 12, third 14 and fourth 15 triggers, the third input of the second pulse counter 21, the output of the shift register 11 is connected to the second input of the second counter 21 pulses, the output of the first frequency divider 22 is connected to the third inputs of the second 13 and third 14 triggers, the outputs of the second 13 and third 14 triggers are connected to the second inputs of the first 17 and third 19 keys, output d of the third key 19 is connected to the second input of the second frequency divider 24, the output of which is connected to the second input of the third frequency divider 25 and the third input of the shift register 11, the output of the OR element 23 is connected to the third input of the first trigger 12, the output of which is connected to the second input of the second key 18, the output of the second key 18 is connected to the second input of the first pulse counter 16, the output of which is connected to the second input of the OR element 23 and the third input of the fourth trigger 15, the output of which is connected to the second input of the fourth key 20.

 FEPP works as follows.

 When the indicator head, elements 1, 2, 4, is moved relative to the fixed code line 3 on the photosensitive cells of the LFE, for example, a charge-coupled device (CCD), charges are formed in accordance with optically transparent brands and optically transparent and opaque sections between the brands that carry information about the location of the marks and the relationship of the CCD and the code line (figure 2). Stamps, stamp location codes and the video signal from them are shown conditionally for consideration of the principle of FEPP operation.

 CCD charges are converted by the shaper 6 into a video signal (Fig. 2, a), reflecting optically transparent marks, having a large voltage amplitude with respect to the signals of optically transparent sections between the marks.

From the first output of the shaper 6, the video signal is supplied to the inputs of the first 7 and second 8 comparators to their other inputs from a voltage source 9; reference voltages of different sizes U ₀₁ , U ₀₂ are supplied, which allow one to select signals from brands and from location codes of brands by voltage amplitude.

 As a result of selection at the output of comparator 8, pulse sequences from a complete video signal are formed (Fig. 2, g).

 At the output of the comparator 7, signals from the marks of the line are formed (Fig. 2, d).

From the second output of the video signal shaper 6, a single pulse (Fig. 2, b) corresponding, for example, to an enable shutter signal (U _sp ) for a CCD (K 1200 CL 1), sets the initial state of a single pulse shaper 10, the first trigger 12 (Fig. 2 , k) controlling the second key 18, second 13, third 14 and fourth 15 triggers and writes to the first counter 16 pulses the number N installed on its inputs (short circuit to the "case" and + U _IP , D-inputs of the counters ) not shown in FIG.

 The recorded N number corresponds to the number of discreteness that fit into the geometric step size of marks I.

The second inputs of the first 17, second 18, third 19 and fourth 20 keys are supplied with clock pulses (TI) from the third output of the video signal shaper 6 corresponding to the signal of the third phase (U _fz ) of the CCD (K 1200 CL1) (Fig. 2, c).

For the relative positioning of the ruler with the code scale 3 and the multi-element photodetector (CCD) 40 shown in figure 2, the step I is equal to
II _x + I _meas. Where I _{x is the} distance equal to the offset of the beginning of the CCD from the beginning of the line or from the beginning of the mark;
I _edited distance measured from the beginning of the CCD prior to the first mark.

The number N is equal to the sum of two numbers
NN _x + N _meas . where N _{x is the} number of discrepancies falling within the distance I _x ;
N _meas. the number of discontinuities within the measured distance I _rev .

 The beginning of line 3 and the beginning of the first cell of LFE 4 should be combined. The initial polling pulse of the CCD (figure 2, b), the output of the first trigger 12 is set to a single state (figure 2, l), which places the passage of the TI through the second key 18 to the subtracting input of the reverse counter 16 pulses (figure 2, m).

 Upon the arrival of the first pulse from the first comparator 7 (Fig. 2, e), the single-pulse generator 10 is triggered and generates a short-range pulse (Fig. 2, g) at the output, which, having passed the OR element 23, resets the first trigger 12, prohibiting the passage of the input of the first counter 16 pulses through the second key 18.

 The pulse from the output of the shaper 10 of single pulses is reset to zero state the first 22, second 24, third 25 frequency dividers and shift register 11 and is set to a single state second trigger 13 (Fig. 2, p), allowing the passage of TI through the first key 17 to the input the first frequency divider 22. The eighth pulse from the output of the first frequency divider 22 (FIG. 2, c) discards the second trigger 13 (FIG. 2, p) and sets the third trigger 14 (FIG. 2, t) into a single state, allowing its output level to pass the TI through the third a key 19 to the input of the second frequency divider 24.

 At the output of the second frequency divider 24, a pulse sequence is generated with dividing the input TI by 16 (Fig.2, e), which is fed to the shift register 11, its other input receives a pulse sequence from the output of the second comparator 8 (Fig.2, g).

 The pulses at the output of the second frequency divider 24 (FIG. 2, f) are shorter in duration than the pulses at the output of the second comparator 8 (FIG. 2, n) and are aligned in time, approximately with their middle.

 The number of pulses at the output of the second frequency divider 24 (Fig.2, e) corresponds to the number of bits of the binary-decimal code location marks. For our case, there are 24 such discharges.

Information from the output of the second comparator 8 (Fig.2, d) using the output pulses from the second frequency divider 24 is entered into the shift register 11. The pulse sequence from the output of the second frequency divider 24 (Fig.2, e) is fed to the input of the third frequency divider 25 with the division ratio 24 (Fig. 2, i), the 24th pulse at the output of the third frequency divider 25, the information from the output of the shift register 11 in the parallel code is entered into the second counter 21 pulses by D inputs. The same trigger resets the third trigger 14 (FIG. 2, t) and sets the first trigger 12 (FIG. 2, l) and the fourth trigger 15 (FIG. 2, n) into a single state. As a result, the second key 18 will pass the TI (Fig. 2, m) to the input of the first reverse counter 16 pulses and through the fourth key 20 will pass the TI (Fig. 2, p) to the input of the second counter 21. The number of received TI at the inputs of the counters is N _x discreteness and the last impulse N _x discreteness from the output of the reverse first counter 16 (“Loan” signal) (Fig. 2, k) the first 12 and fourth 15 of the trigger are reset, prohibiting the passage of the TI through the second 18 and fourth 20 keys to the inputs of the first 16 second 21 TI pulse counters.

In the counter 25 pulses, information about the brand location code previously entered in the parallel code from the shift register 11 has already been entered and N _x pulses (discretencies) corresponding to the distance I _x will be received from it and its counting input from the output of the fourth key. In this way, complete information about the location of the measuring head is concentrated in the second counter 21 pulses.

 The step of making marks of less than half of the input aperture of the LFE is necessary to remove information about the location of the mark at any position of the measuring head.

 The use of a linear multielement photosensitive CCD type K 1200 TsL1 line at FEPP with an output aperture of 15 μm and a cell resolution of 15 μm allows you to choose the pitch of the grades.

 I 6 mm (0.4 input CCD aperture).

 The selected stamp pitch corresponds to 400 CCD cells. Mark and 24 bits of code comprise 25 sectors at one step.

 Each sector corresponds to 400/2516 CCD cells.

 The width of one sector is 16 cells. x 15 μm 0.24 mm.

 The execution mechanism of the marks and the code of their location on the line is shown in Fig.3.

For position 1 of the CCD in the FEPP, the distance I _x1 is measured.

For position 2 of the CCD FEPP, the distance I _x2 is measured and one step of the ruler marks is summed with it, the code of which is placed after the second mark.

For position 3 of the CCD in the FEPP, the distance I _x3 is measured and two steps of the ruler marks are summed with it, the code of which is placed after the third mark.

 The third and fourth step of the marks of the line is shown in more detail with the indication of the sizes, low and high digits of the binary-decimal code.

 Brand location codes are located to the right of the brand for the specified line.

Location code 1st brand 000000
2nd mark 000006
3rd grade 000012
4th mark 000018
5th mark 000024
6th grade 000030, etc.

The location of the code to the right of the brand provides the measurement of the distance I _x II _ism and the removal of information about the location of the brand (code).

If two integer steps and I _x 0 fall into the CCD aperture, then the mark location code is determined by the first step. When changing the pitch of the marks on the ruler, their location code will also change.

 The signal processing unit can be implemented on the following elements. In the shaper 6 video signals are generated signals (pulsed and constant) for the operation of the CCD (K 1200 TsL1).

The pulsed signals of the first U _f1 , second U _f2 , third U _f3 , photo shutter U _sf , permitting shutter U _sp , reset shutter U _s R and video signal amplification can be implemented according to known schemes.

 Comparators 7, 8 can be performed on MS K 554 CA3.

 Shaper 10 single pulses (FOI) can be performed on the RS-4 trigger and circuit I. Initially, the FOI on the R-input is reset (initial state). The pulse from the first comparator 7 is fed to the S-input of the RS-flip-flop and to the input of the circuit I. To the other input of the circuit And the resolving potential is supplied from the inverse output of the RS-flip-flop. When the RS flip-flop overturns at the S-input at the inverse output, a prohibiting level is formed for the And element and a single pulse is formed at the output of a short duration. For subsequent pulses to the S-input, pulse formation does not occur.

The last formation of a single pulse is possible after the reset of the RS-trigger, i.e. signal supply (Fig. 2, b). Name works on the principle of "latch". As keys 17, 18, 19, 20 it is possible to use elements 2I-NOT MS 155 LA3. As triggers 12, 13, 14, 15, it is possible to use D-triggers K 155 TM 2 using the inputs R, S, C and connecting the D-inputs to the busbars "housing" and "+ U _etc. ". As frequency dividers 22, 24, 25, it is possible to use MS binary reversible counters MSC 155IE7. Previously, the number 8 is divided into a frequency divider 22 by 8 (counter K 155 IE 7), and then an additional calculation of up to 16 is performed and the transfer signal "P" is used at the output.

 As a frequency divider 25 to 24, you can use, for example, two series-connected counters K 155 IE7 with preliminary recording of the number on the D-inputs "B" of the low order and "4" and "8" of the high order and counting up to 24 with the output signal transfer "R".

 As counters 16, 21 you can use reversible counters K 155 IE6.

 As the shift register 11, you can use the MS shift registers K 155 IR13.

 As an element OR 23, you can use MSC 155 LI1. It is possible to perform FEPP on other series and types of MS. In the manufacture of FEPP for specific MS series, it is necessary to take into account the polarity of the pulses and voltage levels supplied to the inputs and, if necessary, include inverters in these circuits.

 Constructive simplification of FEPP and its code line, reduction of high precision requirements for applying optical transparent and opaque sections of the stamp location code, reduction of high accuracy requirements for manufacturing movable parts of the code line and indicator parts of the code line and indicator head allows manufacturing of rulers for measuring long distances, while increasing reliability and reliability of the conversion.

Claims (1)

 A PHOTOELECTRIC POSITION CONVERTER containing optically coupled radiation source, lens, code scale, photodetector and signal processing unit, characterized in that, in order to simplify the reliability and reliability of the conversion, the line code scale is made in the form of a ruler with optically transparent marks located on a line with a step of less than half the input aperture of the photodetector, and code groups located between the brands and consisting of optically transparent and opaque sections, the optical density of the transparent sections of which is different from the optical density of the grades, the photodetector is made in the form of a multi-element photosensitive array connected to a signal processing unit made in the form of a video signal shaper, a voltage reference source, four keys, two comparators, a single pulse shaper, three dividers frequency, four triggers, two pulse counters, a shift register and an OR element, in which the first output of the video signal conditioner is connected to the first inputs of the first and second comparators, the second inputs of which are connected to the outputs of the reference voltage source, the output of the first comparator is connected to the first input of the single pulse shaper, the output of the second comparator is connected to the first input of the shift register, the second output of the video shaper is connected to the first inputs of the first, second, the third and fourth triggers, the first input of the first pulse counter and the second input of the single pulse shaper, the third output of the video shaper is connected with the first inputs of the first, second, third and fourth keys, the fourth key output is connected to the first input of the second pulse counter, the first key output is connected to the first input of the first frequency divider, the output of the single pulse shaper is connected to the first inputs of the OR element, second and third frequency dividers , the second inputs of the second trigger, the first frequency divider and the shift register, the output of which is connected to the second input of the second pulse counter, the output of the third frequency divider is connected to the second inputs the first, third and fourth triggers and the third input of the second pulse counter, the output of the first frequency divider is connected to the third inputs of the second and third triggers, the outputs of the second and third triggers are connected to the second inputs of the first and third keys, respectively, the output of the third key is connected to the second input of the second divider frequency, the output of which is connected to the second input of the third frequency divider and the third input of the shift register, the output of the OR element is connected to the third input of the first trigger, the output of which is Inonii to a second input of the second switch, the second switch output is connected to a second input of the first pulse counter whose output is connected to a third input of the fourth flip-flop and the second input of the OR gate, the fourth flip-flop output coupled to a second input of the fourth key.

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