JP2002054952A - Automatic adjustment device and automatic adjustment method for lissajous signal in linear scale - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically adjust the Lissajous signal of a linear scale. SOLUTION: The signal level (peak value) of the phase A is measured and converted into a digital signal. A voltage value obtained by cutting the peak value of the digital signal voltage of the phase A undergone the analog-digital conversion by half is provided as a common level COM1. A controlling microcomputer 44 calculates the level difference between a common level COM of a reference value and the common level COM1 of the phase-A signal, and corrects an offset portion to set the common level COM and the common level COM1 in common. Then, the controlling microcomputer 44 measures the amplitude of the phase-A signal, and calculates its difference from the amplitude of the reference value, operates the variable resistor EVR1 of a gain adjuster 41 to correct it, and thus sets the amplitude of the reference value and that of a signal L1 in common.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for automatically adjusting a Lissajous signal on an optical linear scale suitable for measuring a relative movement amount during machining of a machine tool or the like.

[0002]

2. Description of the Related Art Accurate measurement of the relative movement of a tool with respect to a workpiece in a machine tool or the like is an essential requirement for precision machining, and various measuring devices have been commercialized. Have been. As one of them, an optical scale using moire fringes obtained by superposing two optical gratings has been conventionally known. As shown in FIG. 6, the optical scale has a main scale 101 in which a grid (notched line) is provided on one surface of a transparent glass scale 100 such that light transmitting portions and non-light transmitting portions are arranged at a predetermined pitch.
And an index scale 103 having a grid (notched line) on one surface of a transparent glass scale 102 such that light-transmitting portions and non-light-transmitting portions are arranged at a predetermined pitch, as shown in FIG. In addition, the index scale 103 is opposed to the main scale 101 at a small interval,
As shown in FIG. 7A, the grid of the index scale 103 is arranged so as to be tilted by a small angle with respect to the grid of the main scale 101.

In such an arrangement, moire fringes shown in FIG. 8 occur. The interval between the moire fringes is W, and the interval W
Every time a dark or bright part occurs. The dark portion or the bright portion moves from the top to the bottom or from the bottom to the top in accordance with the direction in which the index scale 103 relatively moves left and right with respect to the main scale 101.
03, the pitch of the lattice is P, and the mutual inclination angle is θ [ra
d], the interval W between the moire fringes is expressed as follows: W = P / θ The moire fringe spacing W is optically the grating spacing P
Is enlarged to 1 / θ times. For this reason, when the grating moves by one pitch P, the moire fringes are displaced by W, and by optically reading the moving distance of W, the amount of movement within the pitch P can be accurately measured. Become.

Therefore, as shown in FIG. 8, a photoelectric conversion element 110 for optically detecting a change in moire fringes is provided on an index scale, and a light source is provided on the opposite side of the main scale. The change in the current flowing through the photoelectric conversion element 110 is read while the scale 103 is relatively moved. That is, when the index scale 103 is in the state A with respect to the main scale 101, the photoelectric conversion element 110
The amount of light irradiated to the photoelectric conversion element 110
Current flowing in becomes the maximum value I _1. Next, when the photoelectric conversion element 110 moves relatively to the state B, the amount of light applied to the photoelectric conversion element 110 slightly decreases, and the current becomes I ₂ . Is irradiated with the least amount of light, and its current also becomes the smallest I ₃ . Then, when the photoelectric conversion element 110 further moves to the state D, the amount of light applied to the photoelectric conversion element 110 slightly increases, and the current becomes I
_2, and when moving to a state of E, again becomes the most amount of high position, the current is a maximum value I _1. As described above, the current flowing through the photoelectric conversion element 110 changes sinusoidally in accordance with the movement of the scale, and when one cycle of the change has elapsed, the main scale 1 is shifted by the lattice interval P.
01 and the index scale 103 have relatively moved.

[0005] The optical scale thus configured is
The light emitted from the light source 105 passes through the glass main scale 101 and further passes through the glass index scale 103, and is received by the photoelectric conversion element 110 as moiré fringes. In FIG. 8, only one photoelectric conversion element 110 is shown, but two photoelectric conversion elements are connected to each other by two signals having a phase difference of 90 ° from each other (the two signals having the 90 ° A signal obtained by inverting the A-phase signal and the B-phase signal by 180 °
The phase signal and the B-phase signal are also output simultaneously. The use of the inverted signal is to ensure the reliability of the signal and the high-speed followability. ) Is output, the moving direction and the moving distance of the scale can be measured from these two signals.

The optical scale constructed as described above is mounted on an NC machine tool and measures the relative movement between the workpiece and the tool. In general, when performing numerical control, the optical scale from the origin is used. Since this is programmed as a movement amount, this relative movement amount needs to be measured as a movement amount from the origin. Therefore, as shown in FIG. 7A, an origin position 109 (Z) is provided in advance on the normal main scale in advance, and when the index scale passes through the origin position, FIG.
Is detected.

When assembling a scale, a small current from a photoelectric conversion element (photocell) 110 is applied to a current-voltage converter (IV converter) 120 by a control circuit as shown in FIG. And the A and A signals are added with the same polarity by the differential amplifier 130, and the amplified signal is sent to the gain / offset adjuster 140.
Gain adjuster 14 composed of a variable volume or the like
1. The gain is adjusted and the offset is adjusted by the offset adjuster 142, and an appropriate signal level, for example, 2V
A Lissajous waveform 150 of _PP is obtained.

[0008] Assuming that the Lissajous signal L1 obtained from the signal obtained from the photoelectric conversion element is in a state shown by a dotted line as shown in FIG. 10, for example, an ideal Lissajous signal L0 (shown by a solid line) And the actually obtained signal L1 indicated by the dotted line has a different common level,
It is offset and the amplitude is smaller. Conventionally, the adjustment of the scale signal has been performed manually using a mechanical volume (VR) so that the operator visually adjusts it to a specified value (ideal signal L0) while looking at the oscilloscope.

[0009]

This adjustment is performed by an operator operating an adjustment volume (VR) of the gain adjuster 141 and the offset adjuster 142 while checking an oscilloscope (not shown). ing. In the adjustment by this method, since the adjustment is performed using a mechanical volume, it is difficult to perform detailed operations, the adjustment level may be different for each operator, it takes time, and the man-hour is considerably increased. . Further, depending on the place where the scale is installed, it may be difficult to connect the terminals of the oscilloscope, and it may be difficult to set the adjusting device. Therefore, it is required that this adjustment be performed automatically so that an appropriate signal level can be obtained.

[0010]

According to a first aspect of the present invention, there is provided a Lissajous signal forming section for optically detecting the amount of movement of a scale and outputting it as a voltage, and converting the signal formed by the Lissajous signal forming section into a signal. It has an adjustment unit to adjust and output,
The adjuster controls a gain adjuster including an electronic volume control, an offset adjuster, an input terminal for analog-to-digital conversion of an analog signal formed by the Lissajous signal forming unit, and the two adjusters. A control microcomputer having a control terminal for adjusting a gain and an offset amount in order to adjust the signal to a set value stored in advance, and a storage unit for storing the set value of the adjusted signal. An automatic adjustment device for a Lissajous signal in a linear scale, comprising:

According to a second aspect of the present invention, a step of slightly moving a linear scale to be adjusted, a step of optically detecting an amount of movement of the scale, and outputting a Lissajous signal as a voltage value, To a digital signal, a step of calculating a center voltage value of a maximum voltage and a minimum voltage of the converted digital signal, and a step of calculating the center voltage value and a reference center voltage value set as a reference value. Calculating the difference as an offset amount, correcting the signal with an electronic volume of an offset adjuster based on the calculated offset amount, measuring an amplitude of the signal obtained by the correction, Calculating a difference from a reference amplitude set as a value; and Correcting the signal with a formula volume, the method for automatically adjusting a Lissajous signal in a linear scale, wherein the invention according to claim 3 slightly shifts a linear scale to be adjusted, Optically detecting the amount of movement of the scale, outputting a Lissajous signal as a voltage value, converting the Lissajous signal to a digital signal, measuring the amplitude of the converted digital signal, and setting a reference value Calculating a difference from a reference amplitude set as; correcting the signal by an electronic volume of a gain adjuster; and calculating a maximum voltage of the signal obtained by the correction. And calculating a center voltage value of the minimum voltage, and the center voltage value is set as a reference value. Calculating a difference from the reference center voltage value as an offset amount, and correcting the signal by an electronic volume of an offset adjuster based on the calculated offset amount. This is a method for automatically adjusting a Lissajous signal on a scale.

[0012]

FIG. 1 shows an example of an embodiment of the present invention.
It will be described based on. FIG. 1 is a block diagram of a signal output device provided with a Lissajous signal automatic adjustment circuit according to the present invention.

The automatic Lissajous signal adjustment apparatus of the present invention comprises a photoelectric conversion element 10, a current-voltage converter (IV converter) 20, a differential amplifier 30, a gain adjuster 41, an offset adjuster 42, and an amplifier 43. And a gain / offset adjuster 40 comprising a control microcomputer 44 and the like, and converts the amount of movement of the scale output from the photoelectric conversion element 10 to output a weak current as a Lissajous signal.
0 is obtained.

An A-phase signal composed of a small current from a photoelectric conversion element (photocell) 10 and an A-phase signal are converted into a voltage by a current-voltage converter (IV converter) 20, and a differential amplifier 30 The A-phase signal and the A-phase signal are added so as to have the same polarity. The signal output from the differential amplifier 30 is
The signal is sent to the gain / offset adjuster 40, and the gain and offset are adjusted by the gain adjuster 41 and the offset adjuster 42.

The gain / offset adjuster 40 comprises the gain adjuster 41, the offset adjuster 42, the amplifier 43, and the control microcomputer 44 as described above.
The gain adjuster 41 and the offset adjuster 42 are EVR
In the embodiment of the present embodiment, an electronic volume having a resolution of, for example, 10 bits is used. A control microcomputer 44 is provided to control the gain adjuster 41 and the offset adjuster 42. The control microcomputer 44 has a configuration corresponding to a resolution of 10 bits, and A / D converts a signal obtained from the output of the amplifier 43. An input terminal t1 for A / D conversion for taking in the data, a control terminal t2 for supplying a control signal to the gain adjuster 41, and a control terminal t3 for supplying a control signal to the offset adjuster 42 are provided. I have. The EEPROM 45
This is not necessary if VR1 and EVR2 are data holding types. However, if the electronic volume cannot hold data, the control data is stored in the EEPROM 45.

In FIG. 2, when the adjuster slightly moves the scale manually or automatically by a motor or the like, a signal including a weak current is output from the photoelectric conversion element 10. A Lissajous signal L1 (waveform is shown by a dotted line) obtained from this signal is a common level voltage (normally a common level) of an ideal Lissajous signal (a waveform is shown by a solid line) as a reference signal. The voltage COM is set to 2 V.) and the common level is different and offset.
Further, the amplitude is also reduced. In the example of FIG. 2, the signal L1
Are 1.95 V, the maximum voltage V _{PH is} 2.45 V, and the minimum voltage V _{PL is} 1.45 V.

The flow of the automatic Lissajous signal adjustment process according to the present invention will be described below. a. A switch or the like is used to enter an automatic adjustment mode, in which the scale is slightly moved automatically or manually to output a weak current commensurate with the amount of movement from the photoelectric conversion element. When entering the automatic adjustment mode, the control microcomputer 44 becomes functional,
The terminal of the microcomputer 44 waits for an input. It should be noted that the automatic adjustment is generally performed at the time of assembling the scale, but may be set so as to be automatically performed at the time of restart or at regular intervals, or may be performed manually at any time. May be set.

B. The signal level (peak value) of the A phase (the following processing is the same for the B phase, so the description of the B phase is omitted) is measured. The analog signal having the measured value is input to the A / D conversion input terminal t1 of the microcomputer 44 and is converted into a digital signal.
The signals of the A phase or the B phase are obtained by inverting one signal such as the A phase and the A phase and adding them to obtain the respective signals. The A-phase, A-phase and B-phase, B-phase signals are
Each of the photoelectric conversion elements is specified and provided to obtain a separate signal.

C. The A-phase signal output as an analog value is subjected to A / D conversion, and a voltage value obtained by halving the peak value of the voltage of the A-phase digital signal to a common level COM1.
And

D. The control microcomputer 44 is an EEPROM
The common level COM and the common level C of the A-phase signal which are ideal values set as the reference values stored in the A.45 signal
The level difference from OM1 is calculated, and the difference is output as control data for the offset. Then, the electronic volume EVR2 of the offset adjuster 42 is operated to correct the difference, and the common level COM and the common level COM1 are matched. Note that the EEPROM 45
Is unnecessary when the gain / offset adjuster 40 is of the holding type, and the value stored in the gain / offset adjuster 40 is used as the adjustment reference value.

E. When the offset correction is performed and the common level COM and the common level COM1 become common, the processing enters the gain adjustment processing. The control microcomputer 44 measures the amplitude of L1 of the obtained signal, calculates a difference from an ideal amplitude serving as a reference value stored in the EEPROM 45, and performs control for correcting the difference. Send data. Then, the electronic volume control EVR1 of the gain adjuster 41 is operated to make the amplitude of the reference value and the amplitude of the signal L1 coincide. Although the adjustment of the Lissajous signal has been described such that the gain adjustment is performed after performing the offset adjustment, the offset adjustment may be performed after performing the gain adjustment.

F. The adjustment mode ends. The adjusted Lissajous signal is transmitted to an internal circuit (not shown). However, if the gain / offset adjuster 40 is not a data holding type, the set value is stored in the EEPROM 45.

A specific example of the adjustment of the Lissajous signal will be described in detail below. Obtained by the photoelectric conversion element, the amplifier 4
The signal L1 output from 3 is shown in FIG.
The control microcomputer 44 has a resolution of 10 bits.
It is assumed that a built-in / D converter can sample a maximum value of 4 V of an analog signal. Also, the common level COM of the signal as the reference value is 2V.

As described above, analog data of 10 bits
When converted to digital data, it has a resolution of 1023, and when converted to digital data,
3.9 mV per A / D conversion value bit (4 ÷ 1024)
= 0.0039), which is the value shown on the right axis in FIG. That is, 2 V of the reference common level COM is 5
11 to the digital level COM1 of the signal L1.
1.95 volts is 498 (1023 x 1.95 ÷
4) The amplitude value of 0.5 V is 128 (1023 × 0.5 ÷).
4), the maximum voltage value V _PH is 626 (= 498 + 12)
8), the minimum voltage value V _PL is 370 (= 498−12)
8).

FIG. 3 shows the offset adjustment of the Lissajous signal.
The voltage is divided into a resistance value of 100 kΩ as shown in FIG. 3, and the voltage is divided by an offset adjuster 42 using a 10 kΩ variable resistor. The 10 kΩ variable resistor is processed by a control signal of a control microcomputer 44. In this case, the range that can be controlled by the variable resistor 10 kΩ is 2 V ± 0.095 V. When this portion is adjusted by the EVR 2 having a resolution of 10 bits, the weight of 1 bit is as follows. 0.095 × 2 ÷ 1024 = 0.18 mV With a change of 1 bit, 0.18 mV is offset-corrected.

The digital value of the common level COM1 of the signal L1 is 498 [= (V _PH + V _PL ) ÷ 2 = (626 + 3)
70) ÷ 2], the offset value is 13 (= 5
11-498), which is 281 (= 13 × 3.9 ÷ 0.18) in terms of the offset amount of the volume EVR2.
= 281.66), and it is sufficient to shift upward by 281 minutes.

The gain adjustment of the Lissajous signal is controlled by a control microcomputer 44 by a gain adjuster 41 having a 10 kΩ feedback resistor connected to an amplifier 43 as shown in FIG. The reference signal is L
“0” is shown in FIG. 5B and has an amplitude width of 2 V _PP , and its digital value is 512. On the other hand, it is assumed that the amplitude of the signal L1 obtained by the photoelectric conversion element is 1 V _PP .

Since the volume EVR1 of the gain adjuster 41 has a resolution of 10 bits at 10 kΩ,
The resistance value per it is 9.76 Ω (= 10 kΩ ÷ 10
24). Since the gain adjustment starts with a gain of 1, the initial value of the volume EVR1 is 102 (=
1 kΩ ÷ 9.76Ω).

The gain calculation process is performed in the following procedure under the control of the control microcomputer. a. The digital value of the amplitude is calculated based on the maximum voltage V _PH and the minimum voltage V _PL of the signal L1. That is, V _PH −V _PL = 626
-370 = 256 b. The reference amplitude is 2V _PP and this digital value is 5
Since it is 12, the magnification with the digital value of the signal L1 is 2 (= 512 ÷ 256). c. By multiplying the reference value 1 kΩ of the volume EVR1 by the magnification determined by b, 204 (= 102 × 2) is obtained, and this value becomes a gain adjustment value for setting the output to 2 V _PP .

In the case of gain adjustment, the adjustment value is held in the adjuster 41. When the gain adjuster 41 is not of the data holding type, the set value may be stored in the EEPROM 45. Further, if necessary, after the gain adjustment, the offset adjustment is repeated again to obtain a more accurate Lissajous signal output.

[0031]

As is clear from the above description, the present invention automatically adjusts the level of the Lissajous signal simply by moving the scale, so that it is possible to reduce the number of steps and suppress the variation in adjustment. It is possible to adjust the Lissajous signal without being affected by the installation environment of the scale.

[Brief description of the drawings]

FIG. 1 is a block diagram of an adjusting device according to the present invention.

FIG. 2 is a diagram showing an example of a Lissajous signal before adjustment.

FIG. 3 is a circuit diagram of an offset adjuster.

FIG. 4 is a circuit diagram of a gain adjuster.

FIG. 5 is a diagram showing an example of a Lissajous signal before gain adjustment.

FIG. 6 is a perspective view of an optical scale and a cross-sectional view of the optical scale.

FIG. 7 is an explanatory diagram showing a grid for detecting an origin position and a detection waveform thereof.

FIG. 8 is a diagram showing the movement of moiré fringes.

FIG. 9 is a block diagram of a conventional Lissajous signal adjustment device.

FIG. 10 is a diagram showing an example of a reference Lissajous signal and a Lissajous signal before adjustment.

[Explanation of symbols]

10 photoelectric conversion element, 20 current-voltage converter (IV
Converter), 30 differential amplifier, 41 gain adjuster, 4
2 Offset adjuster, 43 Amplifier, 44, 50 Output of Lissajous signal.

────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission Date] August 15, 2000 (2008.1.
5)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0005

[Correction method] Change

[Correction contents]

[0005] The optical scale thus configured is
The light emitted from the light source 105 passes through the glass main scale 101 and further passes through the glass index scale 103, and is received by the photoelectric conversion element 110 as moiré fringes. In FIG. 8, only one photoelectric conversion element 110 is shown, but two photoelectric conversion elements are connected to each other by two signals having a phase difference of 90 ° from each other (the two signals having the 90 ° signals and .A phase signal and B phase signal of the B phase signal and inverted 180 ° -
The A-phase signal and the -B-phase signal are also output simultaneously. The use of the inverted signal is to ensure the reliability of the signal and the high-speed followability. ) Is output, the moving direction and the moving distance of the scale can be measured from these two signals.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction contents]

When assembling a scale, a small current from a photoelectric conversion element (photocell) 110 is applied to a current-voltage converter (IV converter) 120 by a control circuit as shown in FIG. And the A and -A signals are added by the differential amplifier 130 with the same polarity, and the amplified signal is sent to the gain / offset adjuster 140, where the gain adjuster 1 composed of a variable volume or the like is used.
41, gain adjustment and offset adjustment are performed by the offset adjuster 142, and a proper signal level, for example, 2V
A Lissajous waveform 150 of _PP is obtained.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction contents]

An A-phase signal composed of a small current from a photoelectric conversion element (photocell) 10 and an A-phase signal are converted into a voltage by a current-voltage converter (IV converter) 20, and the differential amplifier 30 Thus, the A-phase signal and the −A-phase signal are added so as to have the same polarity. The signal output from the differential amplifier 30 is sent to a gain / offset adjuster 40, and the gain is adjusted by a gain adjuster 41 and an offset adjuster 42.
Offset adjustment is performed.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction contents]

B. The signal level (peak value) of the A phase (the following processing is the same for the B phase, so the description of the B phase is omitted) is measured. The analog signal having the measured value is input to the A / D conversion input terminal t1 of the microcomputer 44 and is converted into a digital signal.
The signals of the A phase or the B phase are obtained by inverting one signal such as the A phase and the -A phase , and adding them to obtain the respective signals. Incidentally, A-phase, -A phase and B-phase, -B phase signal <br/> items, the photoelectric conversion element is provided to be identified respectively, are obtained as a separate signal.

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 6]

[Document name to be amended] Drawing

[Correction target item name] Fig. 9

[Correction method] Change

[Correction contents]

FIG. 9

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2F069 AA02 BB01 DD16 EE22 FF01 FF03 GG07 GG63 HH14 MM11 NN01 NN08 NN09 2F103 BA00 BA35 CA01 CA05 DA12 EB01 EB11 EB33 ED00 ED02 ED06 ED11 ED27 FA12 FA16 FA17

Claims (3)

[Claims] 1. A scale movement amount is optically detected, and
A Lissajous signal forming unit that outputs a voltage, and an adjusting unit that adjusts and outputs the signal formed by the Lissajous signal forming unit, wherein the adjusting unit includes a gain adjuster including an electronic volume and an offset adjuster An input terminal for analog-to-digital conversion of an analog signal formed by the Lissajous signal forming unit, a gain and a gain for controlling the two adjusters and adjusting the signal to a preset value stored in advance. A device for automatically adjusting a Lissajous signal in a linear scale, comprising: a control microcomputer having a control terminal for adjusting an offset amount; and a storage unit for storing a set value of the adjusted signal. 2. A step of slightly moving a linear scale to be adjusted; a step of optically detecting an amount of movement of the scale and outputting a Lissajous signal as a voltage value; and converting the Lissajous signal to a digital signal. Calculating a center voltage value of a maximum voltage and a minimum voltage of the converted digital signal; anda difference between the center voltage value and a reference center voltage value set as a reference value is set as an offset amount. Calculating, and correcting the signal with an electronic volume of an offset adjuster based on the calculated offset amount, measuring an amplitude of the signal obtained by the correction, and setting the reference value. Calculating a difference from the reference amplitude, and calculating the difference between the calculated amplitude and an electronic volume of a gain adjuster. Steps and automatic adjustment method of Lissajous signal in linear scale, characterized in that it consists of correcting the signal by. 3. A step of slightly moving a linear scale to be adjusted; a step of optically detecting a movement amount of the scale and outputting a Lissajous signal as a voltage value; and converting the Lissajous signal into a digital signal. Measuring the amplitude of the converted digital signal, and calculating the difference from the reference amplitude set as a reference value, the electronic volume of the gain adjuster the difference of the calculated amplitude Correcting the signal according to, and calculating a center voltage value of a maximum voltage and a minimum voltage of the signal obtained by the correction, the center voltage value, and a reference center voltage value set as a reference value. Calculating the difference between the two as an offset amount; and an electronic volume of an offset adjuster based on the calculated offset amount. Steps and automatic adjustment method of Lissajous signal in linear scale, characterized in that it consists of correcting the signal by.