JP2000310545A - Displacement measuring apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a real-time property in an absolute displacement measuring apparatus. SOLUTION: An ABS sensor 1 outputs signals which indicate the coarse position and the fine position of a moving element with reference to a fixed element. The signals are processed respectively by a demodulation circuit 2 and a demodulation circuit 3. The signal which indicates the coarse position is processed by an ABS data computing part 4, and high-order-digit data DH for absolute-position data is generated. The signal which indicates the fine position is introduced to a PLL counting-pulse generation part 7 via a selector 5. In the PLL counting-pulse generation part 7, a pulse signal PULSE which corresponds to the phase difference between a dense-scale phase signal CMP which is input and a reference signal CNT which is generated at the inside, and the phase of the reference signal CNT is controlled in such a way that the reference signal CNT at the inside follows the phase signal CMP, A counter 8 counts the phase signal PULSE so as to generate low-order-digit data indicating the fine position. The data DH and the data DL are synthesized by a microcomputer 9, and the absolute position data is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an absolute type displacement measuring device for obtaining absolute displacement information according to a displacement amount of an object to be measured. The present invention relates to a displacement measuring device suitable for applications requiring high-speed sampling.

[0002]

2. Description of the Related Art As small measuring instruments such as digital calipers, digital micrometers, and height gauges for displaying measured values on a liquid crystal display device or the like, those using a capacitance type displacement sensor are known. Capacitive displacement sensors are
The displacement amount is detected by extracting a signal of a periodic capacitance change generated between the electrode patterns with the movement of a movable element such as a slider that moves relatively to a fixed element such as a main scale.

[0003] There are two types of such displacement sensors, an incremental (INC) type and an absolute (ABS) type, depending on the form of the output signal. INC type is
The displacement is measured by continuously measuring the periodic signal generated by the movement of the slider from the reference position. In contrast, the ABS type is disclosed, for example, in Japanese Patent Application No. 2-1324.
No. 34, Japanese Patent Application No. 2-169454, and the like, demodulate periodic signals obtained from a plurality of types of scales having different densities such as a coarse scale, an intermediate scale, and a fine scale. By obtaining phase information corresponding to the absolute position and synthesizing them, it is possible to detect the absolute displacement amount (position) of the movable element.

[0004]

The ABS type measuring system has a great advantage that even when the power supply is temporarily cut off, the home position can be returned by turning on the power again. When applied to an application that requires real-time properties for length calculation, there is a problem that the operating frequency must be increased and current consumption increases. In addition, the INC type length measuring system has an advantage that the measured data can be obtained at a high speed with a small amount of processing, but there is a problem that the origin is lost due to a power cut or the like.

On the other hand, the present applicant has proposed a capacitance type A
An ABS encoder has been proposed in which a BS type displacement measuring device is combined with a photoelectric INC type displacement measuring device so that absolute position data can be output even while the scale is moving (Japanese Patent Laid-Open No. 5-71938). JP-A-8-23360
No. 2, etc.). This is provided with storage means preset by absolute position data measured in a stationary state at power-on or the like, and a predetermined lower digit of the position data held in the storage means can be obtained from the photoelectric displacement converter. This is updated by the INC signal. In other words, the photoelectric INC signal obtained in real time with the scale movement is incorporated as a part of the ABS data.

However, combining an electrostatic capacitance type ABS type displacement detector and a photoelectric type INC type displacement detector results in an increase in the volume and power consumption of the apparatus, so that low power consumption is assumed. It cannot be applied to small measuring instruments that

Accordingly, the present applicant has a counting means for presetting the absolute position data obtained by processing the output signal of the capacitance type ABS sensor, and also processes the output signal of the ABS sensor for scale movement. There has also been proposed a capacitance type displacement measuring device which can output an absolute position data in real time by obtaining a follow-up increment signal and thereby updating the absolute position data of the counting means (Japanese Unexamined Patent Application Publication No. 9-1997). 21603). In this method, a phase difference between a phase signal generated from a fine-scale output signal and a reference signal is obtained, for example, at each rising edge of each reference signal, and an amount corresponding to a difference between a previous phase difference and a current phase difference is obtained. It is updated by the increment or decrement operation of the counting means. Thereby, absolute position information can be obtained in real time.

It is an object of the present invention to provide a displacement measuring apparatus based on the above-mentioned conventional ABS system, which further improves real-time performance and has low current consumption and low cost.

[0009]

A displacement measuring apparatus according to the present invention outputs at least a signal indicating a coarse position and a signal indicating a fine position, which are output signals indicating absolute position information of a movable element with respect to a fixed element. An absolute displacement sensor, a first demodulating means for demodulating a signal indicating the coarse position among output signals of the absolute displacement sensor to generate a first phase signal indicating a coarse position, and the absolute displacement sensor A second demodulation means for demodulating the signal indicating the fine position in the output signal of the sensor to generate a second phase signal indicating the fine position; and a first phase signal from the first demodulation means. An absolute data calculating means for processing to generate a higher-order digit part of the absolute position data; a count pulse corresponding to a phase difference between a second phase signal from the second demodulation means and a reference signal; Signal and And it generates an output, a phase locked-counting pulse generating means for controlling so as to synchronize the phase of said reference signal to said second phase signal, the phase synchronization and
Counting means for counting the counting pulses output from the counting pulse generating means based on the signal indicating the counting direction to generate a lower digit part of the absolute position data; and an upper digit part generated by the absolute data calculating means. And a combining operation means for combining the lower digit part generated by the counting means with the absolute position data to generate the absolute position data.

According to the present invention, when the lower digit part of the absolute position data is generated based on the signal indicating the fine position among the output signals of the absolute displacement sensor, the second phase signal indicating the fine position and the reference signal are used. A counting pulse corresponding to the phase difference with the signal and a counting direction thereof are generated, and based on this, a lower digit portion is generated by an increment operation. This eliminates the need for complicated calculations for synthesizing the ABS data, and makes it possible to update the measured value every time a count pulse is output, so that peak detection and the like during scanning measurement can be performed.

In this case, if the period of the reference signal is constant, the phase between the second phase signal and the reference signal is greatly shifted depending on the moving speed of the movable element with respect to the fixed element, and the phase difference is correctly detected. However, if the reference signal is made to follow the second phase signal, the second
The phase difference between the phase signal and the reference signal does not become too large, and only the deviation of the phase difference from the previous phase difference comparison can be always detected. This allows
It can follow the high-speed movement of the scale.

The phase synchronization / counting pulse generating means includes:
For example, a phase comparison circuit that detects the phase difference between the second phase signal and the reference signal, a frequency division circuit that divides the reference clock signal to generate the reference signal, and absorbs the phase difference detected by the phase comparison circuit And a frequency division switching circuit for controlling the frequency division ratio of the frequency division circuit.

A reference phase signal output means for outputting a reference phase signal for providing a reference phase for detecting an absolute phase of an output signal of the absolute displacement sensor; and one of the reference phase signal and the second phase signal Selecting means for outputting the reference phase signal to the phase synchronization / counting pulse generation means, wherein the phase synchronization / counting pulse generation means controls the reference signal to be synchronized with the reference phase signal when the reference phase signal is input. This is convenient for verifying the absolute position.

That is, the displacement measuring apparatus of the present invention is provided with an absolute position verification mode. In this absolute position verification mode, a reference phase signal is introduced into the phase synchronization / counting pulse generating means, and the reference signal and the reference phase signal are used. After synchronization, the counting means is cleared, and the second phase signal is introduced to the phase synchronization / counting pulse generation means to obtain absolute position data. Thus, the absolute position can be verified very easily in the process of phase synchronization. This absolute position verification mode
For example, the transition may be made when the power is turned on or when the moving speed of the movable element with respect to the fixed element exceeds a predetermined measurable speed.

Further, the displacement measuring device of the present invention may be provided with a count measuring mode. In the count measurement mode, the combining operation means stores the combined absolute position data as start data, clears the counting means, and thereafter adds the count value of the counting means to the start data to obtain the absolute position data. Calculate the data. By providing such a counting and measuring mode, it is not necessary to perform the combining process of the upper digits, so that extremely high-speed processing can be performed, and the real-time measurement can be further improved. It is conceivable that the counting and measuring mode is shifted when the user operates a mode switch or the like, or when the moving speed of the movable element with respect to the fixed element exceeds a predetermined speed.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a configuration of an ABS / INC combined length measuring system according to an embodiment of the present invention. In this system, A
A capacitance sensor is used as the BS sensor 1. A
As will be described in detail later, the BS sensor 1 has a main scale and a slider, each of which has a predetermined pattern of electrodes formed and arranged relative to each other, and performs capacitive coupling of the main scale and the slider determined according to their relative positions. It outputs an output signal including three types of absolute position information of the reflected coarse scale, medium scale, and fine scale.

Among the output signals of the ABS sensor 1, the output signals of the coarse scale and the middle scale corresponding to the upper digit part of the absolute position data are input to the demodulation circuit 2, and the output signal of the fine scale is input to the demodulation circuit 3. You. The demodulation circuits 2 and 3 perform processing such as sampling, mixing, low-pass filtering, and binarization processing on these output signals, and output a phase signal CMP. Phase signals CMP Coa., CMP Med. For coarse scale and middle scale output from demodulation circuit 2
Is supplied to the ABS data calculation section 4, where the upper digit ABS data is generated. On the other hand, the phase signal CMP Fin. For fine scale output from the demodulation circuit 3 is supplied as one input of the selector 5. The other input of the selector 5 is supplied with a reference phase signal CPO output from a reference counter / sensor drive circuit 6 for generating a drive signal Sd of the ABS sensor 1. Selector 5
Selects these inputs and outputs PL as the phase signal CMP.
L, which is supplied to the counting pulse generator 7. The PLL / counting pulse generator 7 generates a counting pulse signal PULSE and an up / down signal U / P according to the phase difference between the input phase signal CMP and the internally generated reference signal CNT, The phase synchronization control for synchronizing the reference signal CNT with the phase signal CMP is executed. Incremental U
The / D counter 8 counts the pulse signal PULSE in the direction indicated by the up / down signal U / D supplied from the PLL / counting pulse generator 7. The data DH from the ABS data calculation unit 4 and the data DL from the counter 8 are supplied to the microcomputer 9, where the two data are combined to obtain the absolute value data. The obtained absolute value data is displayed on the display unit 10.

FIG. 2 is a diagram showing a schematic configuration of the ABS sensor 1 used in this embodiment. This ABS sensor 1
Is composed of a main scale 22 serving as a fixed element and a slider 21 serving as a movable element slidable in the x direction in FIG. The transmission electrodes 23 are arranged on the slider 21 at a predetermined pitch Pt0. The transmitting electrodes 23 are arranged on the main scale 22 with the receiving electrodes 24a, 24a arranged at a pitch Pr.
4b. These receiving electrodes 24a,
24b are connected one-to-one to the transmission electrodes of the pitches Pt1 and Pt2 adjacent in the arrangement direction. The transmission electrodes 25a and 25b are capacitively coupled to detection electrodes 26a and 16b and 27a and 27b provided on the slider 21, respectively.

The transmitting electrodes are commonly connected every seven electrodes to form a plurality of electrode groups, each group consisting of eight electrodes. These electrode groups have eight-phase periodic signals a,
, h are supplied as drive signals Sd. These drive signals Sd are specifically signals chopped by high-frequency pulses, and are supplied from the above-described reference counter / sensor drive circuit 6. The drive signal S
The eight-phase periodic signal d is controlled by the reference counter / sensor drive circuit 6 so that the phase relationship is different between the case where the coarse scale and the medium scale are measured and the case where the fine scale is measured.

The pitch Wt of the electric field pattern generated when the drive signal Sd is supplied to the transmission electrode 23 is eight times the pitch Pt0 of the transmission electrode 23, and the pitch Wt is
N times the pitch Pr of the receiving electrodes 24a and 24b (for example, 3
Times). The receiving electrodes 24a and 24b are provided with triangular or sinusoidal electrodes so as to mesh with each other. The phase of the signal received by each of the receiving electrodes 24a and 24b is determined according to the capacitive coupling area between the transmitting electrode 23 and the receiving electrodes 24a and 24b.
And the position of the main scale 22.

The receiving electrodes 24a and 24b and the transmitting electrode 25
If the pitches a and 25b are formed at the same pitch, the detection electrodes 26a, 26b, 27a and 27b simply detect a periodic signal that is repeated every time the position in the x direction of the main scale 22 changes by the pitch Pr. become. In this embodiment, the transmission electrodes 25a and 25b are connected to the reception electrodes 24a and 24a in order to measure the absolute positions of three levels of coarse, medium and fine.
24b, and the reference position x0
Deviations D1 (x), D, which are functions of distance x in the measurement direction from
2 (x).

The deviations D1 (x) and D2 (x) are given, and the detection electrodes 26a and 26b and 27a and 27b are provided.
Are the pitches Wr1 (= 3Pt1) and Wr2 (= 3Pt2), respectively.
The waveform pattern of the detection electrodes 26a, 2
6b and the detection electrodes 27a, 27b,
(X), the receiving electrode 24 in a large cycle corresponding to D2 (x).
Output signals B1, B2 and C1, C2 on which small periods determined by the pitches a, 24b are superimposed are obtained. By taking the difference between the output signals C1 and C2, the output signal Oc including the coarse-scale absolute position information determined by the deviation D1 (x)
Is obtained, and by taking the difference between the output signals B1 and B2,
An output signal Om including the middle-scale absolute position information determined by the deviation D2 (x) is obtained. The output signals C1,
By taking the difference between the sum of C2 and the sum of output signals B1 and B2, an output signal Of including absolute position information of a fine scale determined by the receiving electrode pitch is obtained.

The output signals Oc and Om are demodulated by the demodulation circuit 2 and the output signal Of is demodulated by the demodulation circuit 3, whereby the phase signal CMP Coa. , CMP Med., CMP Fin. FIG. 3 is a waveform diagram showing the relationship between these phase signals CMP and reference phase signal CPO. The absolute position of each scale can be obtained as the phase of each phase signal CMP with reference to the reference phase signal CPO. Specifically, the absolute position is continuously calculated from the rising edge of the reference phase signal CPO to the next rising edge. Phase information obtained by counting up is obtained by sampling at the rising edge of the phase signal CMP. The absolute positions of the obtained scales are weighted and combined as shown in FIG. 4 to obtain the absolute position data.

In the present invention, the position information DH of the coarse scale and the middle scale is synthesized by the ABS data calculation unit 4, while the position information DL of the fine scale is obtained by the counter 8. The position information DL on the fine scale is calculated as follows. FIGS. 5 and 6 are waveform diagrams of each section for explaining the operation of the PLL / count pulse generating section 7. P
The LL / counting pulse generator 7 receives the input phase signal CM.
A pulse signal PULSE corresponding to the phase difference between P and the internally generated reference signal CNT is generated and supplied to the counter 8. In the example of FIG. 5, the phase of the phase signal CMP is
It shows the case where it is proceeding with respect to NT, and in this case,
The up / down signal U / D becomes H (up) level. The example of FIG. 6 shows a case where the phase of the phase signal CMP is delayed with respect to the reference signal CNT. In this case, the up / down signal U / D is at the L (down) level. As is clear from both figures, the reference signal CNT
After detecting a phase difference with the phase signal CMP, the phase is controlled to eliminate the phase difference. Therefore, when the required amount of the pulse signal PULSE for counting the absolute position is output, control is performed so that the phases of the phase signal CMP and the reference signal CNT are aligned.

The PLL / counting pulse generator 7 functioning as described above can be configured, for example, as shown in FIG. The PLL / counting pulse generator 7 includes an edge differentiating circuit 100, a phase comparing circuit 110, a frequency dividing switching circuit 120, and a frequency dividing circuit 130. The edge differentiating circuit 100 detects a falling edge of the input phase signal CMP. In the edge differentiating circuit 100, a falling edge of the phase signal CMP is detected by a flip-flop (hereinafter, referred to as “FF”) 101 at a rising edge of the clock signal CK. Then, from the output change of the FF 101, the FF 102 and the NOR gate 103 generate and output a differential pulse P1 having a pulse width of one cycle of the clock signal CK.

In the phase comparison circuit 110, a counter pulse corresponding to the phase difference between the falling edge of the phase signal CMP indicated by the differentiated pulse P1 and the rising edge of the reference signal CNT output from the frequency dividing circuit 130 Signal PUL
SE and up / down to instruct up / down of counter
And a down signal U / P. That is, the differential pulse P1
Is converted into a falling pulse for one pulse width of the clock signal CK (inverted clock signal by the inverter 104) by the NAND gate 111, and the EX-NOR gate 112 compares the phase with the reference signal CNT. EX-N
The output of the OR gate 112 is divided by the FF 113.
When the falling of the phase signal CMP precedes the rising of the reference signal CNT, the output of the FF 113
It falls at the falling edge of the NAND gate 111 and rises at the rising edge of the reference signal CNT. When the rise of the reference signal precedes the fall of the phase signal CMP, the output of the FF 113 falls at the rise of the reference signal CNT, and the NAND gate 1
It rises at the rise of 11. The output of FF113 is NO
The clock signal C is output by the R gate 114 and the FF 115
After phase matching with K, the pulse gate signal PG
The clock signal CK supplied to the other input of the OR gate 105
Is gated for a time corresponding to the phase difference between the phase signal CMP and the reference signal CNT. Thereby, the pulse signal PULS
E is obtained.

On the other hand, the differential pulse P1 is
The timing of the trailing edge is delayed by the half gate of the clock signal CK by the R gate 117. The FFs 118 and 119 detect the timing relationship between the timing of the differentiated pulse and the phase of the pulse gate signal PG, and output an up / down signal U / P. The U / P signal is a phase signal C
When the phase of the MP is advanced with respect to the reference signal CNT, the level becomes “H”, and when the phase of the MP is delayed, the level becomes “L”.

In the frequency division switching circuit 120, a pair of FFs 12
1, 122 are input to four inverted output multiplexers (hereinafter, referred to as “MPX”) 123, 124, 12
5, 126, and two inverters 127, 128 to switch the reference clock RC introduced into the frequency divider 130.
Determine the frequency of K. The MPXs 123 and 124 are switched by the switching signal SELa (= U / D).
X125 and X126 are switched by a switching signal SELb (= PG). In this embodiment, the MPX1
By switching between 23 and 126, the following three operation modes are realized.

[0029]

[Table 1]

In the stop mode, the pulse gate signal PG
And when the up / down signal U / D is both L, that is, while the phase signal CMP is delayed with respect to the reference signal CNT and the count pulse PULSE is output to correct the delay. Mode. In the stop mode, since the MPXs 123 and 125 select the input A, the FF 121 → the inverter 127 → the MPX 123 →
A feedback loop of MPX125 → FF121 is formed, and when the / Q output of FF121 is H, the feedback input to the D terminal becomes L, and the output does not change even when the clock signal is input. Therefore, the frequency dividing circuit 1
The dividing operation of 30 is interrupted.

In the normal mode, the pulse gate signal PG
Is H, that is, when the phase signal CMP and the reference signal CNT are completely synchronized, or when the counter 7 is not performing the counting operation. In the normal mode, since the MPXs 125 and 126 select the input B, the FF121 → the inverter 127 → MPX126 → F
A feedback loop of F122 → MPX125 → FF121 is formed. In this case, the FFs 121 and 122
Alternately inverts its output at the rising edge of the clock signal CK, so that the reference clock RCK is a signal obtained by dividing the frequency of the clock signal CK by 4. Accordingly, the cycle of the reference signal CNT, which is the final stage output from the 1/16 frequency divider 130 formed by cascading the four FFs 131, 132, 133, and 134, is 64 times the cycle of the clock signal CK. Become.

In the 1/2 mode, when the pulse gate signal PG is L and the up / down signal U / D is H, that is, the phase signal CMP is advanced with respect to the reference signal CNT.
This mode is executed while the count pulse PULSE is being output to correct the advance. In the 1/2 mode, the MPX 123 selects the input B and the MPX 125 selects the input A, so that FF121 → MPX123 → M
A feedback loop of PX125 → FF121 is formed. In this case, since this feedback loop functions as a frequency dividing circuit that divides the clock signal CK by 分, the cycle of the reference signal CNT which is the final output from the frequency dividing circuit 130 is equal to the cycle of the clock signal CK. It becomes 32 times. In the モ ー ド mode, the cycle of the reference signal CNT is の of the cycle of the normal mode, so that the phase of the reference signal CNT quickly follows that of the phase signal CMP.

By the above operation, the generation of the pulse signal PULSE according to the phase difference between the phase signal CMP and the reference signal CNT and the synchronization of the phase signal CMP and the reference signal CNT are performed.

FIG. 8 is a state transition diagram showing a measuring operation mode using the ABS / INC combined length measuring system.
First, when the operation of the system is started, the counter 8
Is executed (S1). This processing mode is an absolute position verification mode. Specifically, the input of the reference phase signal CPO of the selector 5 is activated,
The reference phase signal CPO is introduced as a phase signal CMP into the PLL / counting pulse generator 7. Thereby, the reference signal C
Since NT synchronizes with the reference phase signal CPO, the value of the counter 8 is cleared when the synchronization is established. Subsequently, the fine-scale phase signal CMP Fin. By switching the input side to active, the pulse signal PULSE corresponding to the phase difference between the phase signal CMP and the reference signal CNT.
Is output, and the count value of the counter 8 indicates the correct absolute position.

When the ABS processing of the counter 8 is completed,
Next, the mode shifts to the normal mode (S2). In this mode, the output data DH of the ABS data operation unit 4 and the count value DL of the counter 8 are combined, and if necessary, an offset value is added thereto to obtain absolute position data. To display. Note that, for example, when a preset operation is performed, the offset value is obtained by subtracting the current value of the combined data from the preset value (S3).

When a peak detection instruction (PEAK ON) is input in the normal mode, the following processing is executed. This peak detection is a measurement mode in which the surface of the measurement target 31 is traced by the measurement probe 32 to measure the highest position or the lowest position, as shown in FIG.
Measurement requires real-time performance. In this case, first, the microcomputer 9 stores a value obtained by adding the offset value to the combined data as start data, and clears the counter 8 (S5). Then, the scanning mode is entered (S6).
This mode is a counting (incremental) measurement mode, in which the absolute position data is calculated by adding the counter value sequentially updated by the counting operation of the counter 8 and the stored start data (S6). In this case, the data used for calculating the absolute position is the counter value and the stored start value, and the data DH from the ABS data calculation unit 4 is not used, so that extremely high-speed measurement is possible. In the peak detection, the magnitude of absolute position data sequentially obtained is compared to detect a peak value, which is displayed. When the peak detection is completed (PEAK OFF), the counter value is changed to ABS by the same processing as in step S1, and the process returns to the normal mode (S7).

In the scanning detection mode, the moving speed of the slider 21 with respect to the main scale 22 is monitored.
When the moving speed exceeds the unmeasurable overspeed, a process may be performed to execute the ABS process as in steps S1 and S7 and then return to the incremental mode. It is also conceivable to automatically switch to the incremental mode as in steps S5 and S6 when the moving speed exceeds a predetermined speed.

In this apparatus, since the amount of processing in the incremental mode (count measurement mode) is small, sufficient speed can be obtained even if the operating frequency is lowered, and the current consumption can be greatly reduced. Further, by lowering the operating frequency, it is possible to use a low-speed and inexpensive 4-bit microcomputer or the like, so that the cost can be reduced accordingly. In the incremental mode, even when overspeed occurs, the absolute value can be returned to the correct value in the absolute position verification mode (S7).
It is possible to transition to the measurement without deteriorating the merit of the ABS system.

[0039]

As described above, according to the present invention,
An extremely high-speed measurement update in the counting and measurement mode is possible, which makes it possible to follow a high-speed movement of the scale and further improves the real-time property, so that peak detection and the like during scanning measurement can be achieved.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an ABS / INC combined length measuring system according to an embodiment of the present invention.

FIG. 2 is a diagram showing details of an ABS sensor in the system.

FIG. 3 shows a phase signal C of each scale in the system.
FIG. 4 is a waveform chart showing a relationship between MP and a reference phase signal CPO.

FIG. 4 is a diagram for explaining a concept of a synthesis process of each scale in the same system.

FIG. 5 is a waveform diagram of each part of a PLL / counting pulse generator in the same system.

FIG. 6 is a waveform diagram of each part of a PLL / counting pulse generator in the same system.

FIG. 7 is a block diagram of a PLL / counting pulse generator in the same system.

FIG. 8 is a state transition diagram at the time of measurement in the same system.

FIG. 9 is a diagram for explaining a scanning measurement mode in the system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... ABS sensor, 2, 3 ... Demodulation circuit, 4 ... ABS data calculation part, 5 ... Selector, 6 ... Reference counter / sensor drive circuit, 7 ... PLL / count pulse generation part, 8 ... Incremental U / D counter, 9 ... microcomputer, 10 ... display unit.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F063 AA11 CA12 CA15 DA01 DA04 DB03 DC08 DD02 DD06 HA05 2F069 AA03 AA06 AA31 DD04 GG06 GG12 HH12 HH21 JJ06 JJ13 MM38 NN08 NN09 2F077 AA30 AA33 HHTTTT46TT

Claims (7)

[Claims] 1. An absolute displacement sensor for outputting at least a signal indicating a coarse position and a signal indicating a fine position, which is an output signal indicating absolute position information of a movable element with respect to a fixed element. First demodulation means for demodulating the signal indicating the coarse position in the output signal to generate a first phase signal indicating the coarse position; and outputting the signal indicating the fine position in the output signal of the absolute displacement sensor. Second demodulation means for demodulating to generate a second phase signal indicating the fine position, and processing the first phase signal from the first demodulation means to generate an upper digit part of the absolute position data An absolute data calculating means, for generating and outputting a counting pulse corresponding to the phase difference between the second phase signal from the second demodulating means and the reference signal and a signal indicating the counting direction; To A phase synchronizing / counting pulse generating means for controlling so as to synchronize with the second phase signal; counting the count pulses output from the phase synchronizing / counting pulse generating means based on the signal indicating the counting direction; A counting means for generating a lower digit part of the absolute position data; a synthesizing means for synthesizing an upper digit part generated by the absolute data calculating means and a lower digit part generated by the counting means to generate the absolute position data A displacement measuring device comprising: a calculating means. 2. The phase synchronization / counting pulse generation means, wherein: a phase comparison circuit for detecting a phase difference between the second phase signal and a reference signal; and a frequency division of a reference clock signal to generate the reference signal. 2. The displacement according to claim 1, further comprising: a frequency dividing circuit; and a frequency dividing switching circuit that controls a frequency dividing ratio of the frequency dividing circuit to absorb a phase difference detected by the phase comparing circuit. measuring device. 3. A reference phase signal output means for outputting a reference phase signal for providing a reference phase for detecting an absolute phase of an output signal of the absolute displacement sensor; and the reference phase signal and the second phase. Selecting means for outputting any one of the signals to the phase synchronization / counting pulse generation means, wherein the phase synchronization / counting pulse generation means uses the reference signal as the reference 3. The displacement measuring device according to claim 1, wherein the displacement measuring device is controlled to synchronize with a phase signal. 4. An absolute position verification mode, wherein in the absolute position verification mode, the reference phase signal is introduced into the phase synchronization / counting pulse generation means to synchronize the reference signal with the reference phase signal. 4. The displacement measuring apparatus according to claim 3, wherein said counting means is cleared, and said second phase signal is introduced into said phase synchronization / counting pulse generating means to obtain absolute position data. 5. A counting / measuring mode, wherein in the counting / measuring mode, the synthesizing operation means stores the synthesized absolute position data as start data, clears the counting means, and thereafter sets the counting means. The displacement measuring device according to any one of claims 1 to 4, wherein the absolute position data is calculated by adding the count value of the above and the start data.
Counting means and said 6. The displacement measuring apparatus according to claim 5, wherein when the moving speed of the movable element with respect to the fixed element exceeds a predetermined speed, the mode shifts to the counting and measuring mode. 7. The displacement measuring device according to claim 4, wherein when the moving speed of the movable element with respect to the fixed element exceeds a predetermined measurable speed, the mode shifts to the absolute position verification mode.