JP4693213B2 - Apparatus and method for adjusting peak level of origin signal in linear scale - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus and method for adjusting a peak level of an origin signal in an optical linear scale suitable for measuring a relative movement amount during machining of a machine tool or the like.
[0002]
[Prior art]
In a machine tool or the like, accurately measuring the relative movement of a tool with respect to a workpiece is an indispensable requirement for performing precision machining, and various measuring apparatuses for this purpose have been commercialized.
As one of them, an optical scale using moire fringes obtained by superposing two optical gratings is conventionally known. As shown in FIG. 2, the optical scale includes a main scale 101 provided with a grid (scribing line) on one surface of a transparent glass scale 100 so that translucent portions and non-translucent portions are arranged at a predetermined pitch, and transparent 4 is provided with an index scale 103 provided with a lattice (scribing line) so that a light transmitting portion and a non-light transmitting portion are arranged at a predetermined pitch on one surface of the glass scale 102, as shown in FIG. The index scale 103 is opposed to the main scale 101 with a minute interval, and the grating of the index scale 103 is arranged so as to be inclined at a minute angle with respect to the grating of the main scale 101 as shown in FIG. .
[0003]
When arranged in this manner, moire fringes shown in FIG. 5 are generated. The interval between the moire fringes is W, and a dark portion or a bright portion is generated for each interval W. This dark portion or bright portion moves from top to bottom or from bottom to top in accordance with the direction in which the index scale 103 moves relatively to the left and right relative to the main scale 101. Is P and the mutual inclination angle is θ [rad].
W = P / θ
It is indicated.
The interval W of the moire fringes is an interval obtained by optically expanding the lattice interval P to 1 / θ times. For this reason, when the grating moves by one pitch P, the moire fringes are displaced by W, so that the movement amount in the pitch P can be accurately measured by optically reading the movement distance of W. Become.
[0004]
Therefore, as shown in FIG. 5, a photoelectric conversion element 110 for optically detecting a change in moire fringes is provided on the index scale, and a light source is provided on the opposite side of the main scale, so that the index scale 103 is attached to the main scale 101. The change of the current flowing through the photoelectric conversion element 110 is read while relatively moving.
That is, when the index scale 103 is in a state of A to the main scale 101, the amount of light irradiated to the photoelectric conversion element 110 is largest, the current flowing to the photoelectric conversion element 110 becomes the maximum value I _1. Next, when the light source moves relative to the B state, the amount of light applied to the photoelectric conversion element 110 slightly decreases, and its current becomes I ₂ . Is irradiated with the least amount of light, and its current is the smallest I ₃ . Further, when the light is further moved to the D state, the amount of light applied to the photoelectric conversion element 110 is slightly increased, and the current becomes I ₂ . The current has a maximum value I1.
As described above, the current flowing through the photoelectric conversion element 110 changes in a sine wave shape according to the movement of the scale, and when the change passes for one period, the main scale 101 and the index scale 103 are relatively moved by the lattice interval P. It has moved.
[0005]
In the optical scale configured in this manner, 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 then is received as moire fringes by the photoelectric conversion element 110. Is done.
Although only one photoelectric conversion element 110 is shown in FIG. 5, two photoelectric conversion elements are provided so that an A-phase signal and a B-phase signal having a phase difference of 90 ° are output from each other. The moving direction and moving distance of the scale can be measured from these two signals.
[0006]
By the way, the optical scale configured in this way is mounted on an NC machine tool and measures the relative movement amount of the workpiece and the tool. In general, when the numerical control is performed, the movement amount from the origin is used. Since it is programmed, this relative movement must be measured as the movement from the origin. Therefore, as shown in FIG. 4A, the origin position 109 (Z) is provided in advance in the normal main scale, and the origin as shown in FIG. 4B is detected when the index scale passes through this origin position. .
[0007]
That is, as shown in FIG. 4B, since a signal that changes within one pitch P of the main scale 101 is detected as the origin detection signal even at the position of the origin Z, the waveform of the origin detection signal Sz For example, when the peak point is clipped at a predetermined level TH to form the origin pulse signal Pz as shown in FIG. 5B, the rising point of the origin pulse signal Pz can be set as the origin Z of the main scale.
A signal represented by a one-dot chain line in the figure indicates a case where the relative speed of the scale is faster than the reference, and a dotted line indicates a deviation of the origin position caused by a difference in the moving direction of the scale.
[0008]
At the time of assembling the scale, the Z-phase signal, which is the origin signal, is adjusted using a mechanical volume so that the operator has an appropriate level. An example is shown in FIG. Since the origin signal Sz is output only as a signal at a certain level, adjustment is performed to offset the signal. The above-mentioned level TH is also called a common level, and the peak level is determined depending on how much signal width is required at that level.
[0009]
FIG. 6A is a block diagram showing an outline of the origin adjustment device, which is a Z-phase signal signal line, a DC component DC signal line of the photoelectric conversion element itself, and an adjusted origin signal (Z Phase signal) output line, amplifiers 11 and 12, volume VR13, and adder 14 for adding the outputs of the Z-phase signal and volume VR13.
As shown in FIG. 6B, the origin adjustment is performed by adding the level of the DC component DC of the photoelectric conversion element to the signal from the Z-phase signal line as an offset amount. The peak level is adjusted manually by the operator.
[0010]
[Problems to be solved by the invention]
In this adjustment, the operator operates the adjustment volume VR13 while checking an oscilloscope (not shown). Using this mechanical volume to make adjustments relying solely on the operator's vision, the origin signal is displayed only momentarily, making fine operation difficult and the adjustment level also being adjusted by the operator. There may be different cases, which takes time and takes a lot of man-hours. Furthermore, the environment where the scale is installed may be a place where it is difficult even to connect the terminal of the oscilloscope, and it may be difficult even to prepare an environment for adjustment.
Therefore, it is required to perform this adjustment automatically so as to obtain an appropriate signal level.
[0011]
[Means for Solving the Problems]
The invention of claim 1 is a step of causing the index scale to pass through an origin position provided in advance in the main scale and outputting an origin signal.
Analog / digital conversion of the origin signal to obtain a digital signal; sampling the digital signal to obtain a peak voltage;
Calculating a correction amount by comparing the peak voltage with a reference peak voltage set as an adjustment reference value;
The step of operating the electronic volume to correct the peak voltage by adding a DC voltage of the photoelectric conversion element itself to an adder by operating an electronic volume to match the reference peak voltage;
This is a method for adjusting the peak level of the origin signal in a linear scale having
[0012]
The invention of claim 2 is an apparatus for adjusting the peak level of an origin signal in a linear scale that optically reads the relative movement amount by a photoelectric conversion element by moving the index scale relative to the main scale. And
The photoelectric conversion element that outputs an origin signal;
An electronic volume that adjusts the voltage of the DC component of the photoelectric conversion element itself and gives it to the adder;
An adder for adding the voltage of the DC component from the electronic volume to the origin signal;
A control microcomputer for controlling the electronic volume so that the peak voltage of the origin signal matches the reference peak voltage;
Is a device for adjusting the peak level of the origin signal in a linear scale having
[0013]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a block diagram of an embodiment of an apparatus for adjusting the peak level of an origin signal according to the present invention, and members having the same functions as those of the conventional example shown in FIG. .
[0014]
FIG. 1A is a block diagram of a circuit of an apparatus for adjusting the peak level of an origin signal in a linear scale according to the present invention, in which a Z-phase signal signal line, a DC component DC included in a photoelectric conversion element itself. Signal line, adjusted origin signal (Z-phase signal) output line, amplifiers 11 and 12, electronic volume 15 denoted as EVR, voltage value of Z-phase signal and voltage value output by electronic volume 15 Is constituted by an adder 14, a control microcomputer 16, and an EEPROM 17.
[0015]
The control microcomputer 16 has an A / D conversion input terminal t1 for A / D converting and taking in the Z-phase signal output from the amplifier 11, and a control terminal t2 for supplying a control signal to the electronic volume 15. Is provided.
The EEPROM 17 is not necessary if the electronic volume EVR 15 is a data holding type, but if it is a type of electronic volume that cannot hold data, control data is stored in the EEPROM 17.
[0016]
A method for adjusting the peak level of the origin signal is shown below.
(A) The electronic volume 15 is adjusted to move the volume position to the vicinity of the center. (To prevent the Z-phase signal from being saturated.)
(B) The index scale is slowly moved manually or automatically, and the origin position (FIG. 4 (a) 109) provided in advance on the main scale is passed. At this time, since a Z-phase signal (origin signal) composed of a weak current is output from the photoelectric conversion element 110, the Z-phase signal is fetched from the A / D conversion input terminal t1 of the control microcomputer 16. The control microcomputer 16 samples the A / D converted Z-phase signal to obtain a peak voltage (shown as S-PEAK in FIG. 1B).
[0017]
(C) The control microcomputer 16 compares the obtained peak voltage S-PEAK with the reference peak voltage R-PEAK set as the adjustment reference value, and the peak voltage S-PEAK and the reference peak voltage R- The correction amount of the peak voltage R-PEAK is calculated so that PEAK matches. If the electronic volume EVR15 is not a holding type, the value stored in the electronic volume EVR15 is used as the adjustment reference value.
[0018]
(D) Next, the control microcomputer 16 adds the correction amount of the peak voltage S-PEAK calculated by comparison with the reference peak voltage R-PEAK by operating the electronic volume EVR15 via the control terminal t2. The controller 14 is controlled to add the correction amount, and the peak voltage S-PEAK is made to coincide with the common level COM (reference peak voltage R-PEAK). As described above, the common level COM determines the peak level so as to obtain the necessary signal width at the level TH shown in FIG. 4B.
[0019]
(E) End of adjustment. When the electronic volume 15 is not a data holding type, an adjustment value is stored in the EEPROM 17.
[0020]
Automatic adjustment is generally performed when the scale is assembled, but it may be set to be executed automatically at restart or at regular intervals, or set to be executed manually at any time. You may do it.
[0021]
【The invention's effect】
In the present invention, the peak level can be automatically adjusted simply by passing the origin of the main scale through the index scale, so that man-hours can be reduced, variation in adjustment can be suppressed, and the scale installation environment can be affected. It is possible to adjust the peak level of the origin signal.
[Brief description of the drawings]
FIG. 1 shows an optical scale origin adjustment device of the present invention, where (a) is a block diagram of its circuit, and (b) is a waveform diagram of an origin signal (Z-phase signal) and its adjustment signal.
FIG. 2 is a perspective view of an optical scale.
FIG. 3 is a cross-sectional view of an optical scale.
FIG. 4 is an explanatory diagram showing a lattice for detecting an origin position and a detected waveform thereof;
FIG. 5 is a diagram showing movement of moire fringes.
6A and 6B show a conventional optical scale origin adjustment device, where FIG. 6A is a block diagram of the circuit, and FIG. 6B is a waveform diagram of an origin signal (Z-phase signal) and its adjustment signal.
[Explanation of symbols]
11, 12 Amplifier, 14 Adder, 15 Electronic volume, 16 Control microcomputer 16, 17 EEPROM

Claims (2)

A step of outputting an origin signal by passing the index scale through a preset origin position in the main scale;
Analog / digital conversion of the origin signal to obtain a digital signal; sampling the digital signal to obtain a peak voltage;
Calculating a correction amount by comparing the peak voltage with a reference peak voltage set as an adjustment reference value;
The step of operating the electronic volume to correct the peak voltage by adding a DC voltage of the photoelectric conversion element itself to an adder by operating an electronic volume to match the reference peak voltage;
Method for adjusting peak level of origin signal in linear scale having An apparatus for adjusting a peak level of an origin signal in a linear scale that optically reads the relative movement amount by a photoelectric conversion element by moving an index scale relative to a main scale ,
The photoelectric conversion element that outputs an origin signal;
An electronic volume that adjusts the voltage of the DC component of the photoelectric conversion element itself and gives it to the adder;
An adder for adding the voltage of the DC component from the electronic volume to the origin signal;
A control microcomputer for controlling the electronic volume so that the peak voltage of the origin signal matches the reference peak voltage;
A device for adjusting the peak level of the origin signal in a linear scale having

Images