JPH045504A - A and b phase signals generating circuit - Google Patents

Abstract

PURPOSE:To obtain a B signal which is simple in length of each cycle showing integral unit length by generating the B phase signal which is 90 deg. out of phase with an A phase signal by exclusively ORing the A phase signal exclusively with a C signal which is a half in one-cycle length. CONSTITUTION:An up/down counter 50 inputs an up or down pulse outputted by a pulse shaping and direction deciding circuit and outputs a signal which increases or decrease in one-cycle length stepwise every time the up or down pulse is inputted. A BCD counter 60 outputs the A phase signal which shows desired unit length whose one-cycle length is >=4 times as large as the step quantity according to the counted value of the counter 50. The decision circuit 70 generates the C signal which shows length whose one-cycle length is a half as large as that of the A phase signal. An EX-OR circuit 80 ORs the A phase signal exclusively with the C signal to output the B signals which is 90 deg. out of phase with the A phase signal.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an A/B phase signal generation circuit, and is particularly applied to a laser interferometer that measures the amount of movement of an object to be measured. The present invention relates to an A/B phase signal generation circuit that generates an A phase signal and a B phase signal that have different phases depending on the amount of movement of an object to be measured.

[Conventional technology]

Conventionally, laser interferometers have been used as detection means to detect the amount of movement of movable tables in machine tools.
FIG. 4 is a block diagram showing the servo system of the machine tool.

In the same figure, the laser interferometer 10 includes, for example, H, -N
, a gas laser is used as a Rade light source 12, and this laser light source 1
2, a laser beam with a wavelength λ (=0.6329912 μm) is projected onto the beam splitter 14.

One laser beam separated by the boom splitter 14 is reflected by a fixed mirror 16, and the other laser beam is reflected by a movable mirror 18 disposed on a movable table 20, and these reflected beams are transmitted via the beam splitter 14. The light is input to the lever 19.

When the movable mirror 18 moves, due to the principle of interference, the amount of movement λ/
Interference fringes that repeat brightness and darkness every 2 are generated, and the
9 receives this interference pattern, converts it into an electrical signal corresponding to brightness, and outputs it to the encoder 22. Note that the receiver 19 is composed of a plurality of photodetectors whose light receiving positions differ by λ/8.

The encoder 22 receives an electric signal inputted from the receiver 19 and outputs an signal A having the same period as the electric signal and having a phase different by 90 degrees depending on the moving direction of the movable table 20.
A phase signal and a B-phase signal are generated (see FIGS. 5(A) and 5(B)) and outputted to the pulse shaping/direction determining circuit 24.

The pulse shaping/direction determining circuit 24 determines the moving direction of the movable table 20 based on the phase shift of the input A/B phase signals, and uses one up pulse or down pulse for one period as a feedback pulse to calculate a deviation counter. 26
Output to.

A forward pulse train command or a reverse pulse train command for controlling the moving position of the movable table 20 is applied from a command circuit 28 to other inputs of the deviation counter 26. Find the difference with the feedback pulse.

The count value of this deviation counter 26 is
A zero movement command is applied to the actuator 34 via the D/A converter 30 and the drive circuit 32, thereby causing the movable table 20 to move.

[Problem to be solved by the invention]

By the way, in a generally widely used optical system in which a corner cue prism is used as the movable mirror 18, the A/B phase signal output from the encoder 22 has a length per period of λ/ as shown in FIG. 2 (=0.3164956μm)
Therefore, the length of each feedback pulse applied to the deviation counter 26 is also 0.316.
It becomes 4956 μm.

Therefore, when using a laser interferometer as a detection means for detecting the amount of movement of a movable table of a machine tool, etc., the amount of movement per command pulse can be expressed as a simple integer (for example, 1 μm, 2 μm, 10 μm, etc.). can't do it,
There is a problem in that when a movement command for a movable table or the like is given numerically to the NC controller side, it becomes complicated and difficult to use.

The present invention was made in view of the above circumstances, and uses a laser interferometer to input up-down pulses corresponding to the wavelength of a laser light source, and the length of one cycle indicates a desired unit length of a simple integer. An object of the present invention is to provide an A/B phase signal generation circuit capable of generating an A phase signal and a B phase signal.

[Means to solve problems]

In order to achieve the above object, the present invention inputs an up pulse or a down pulse, which is a pulse outputted from a laser interferometer for each period of brightness and darkness of interference fringes, and which is outputted according to the moving direction of the object to be measured. and an increase/decrease counter that increases or decreases by a step amount indicating the length of the preceding arrangement period each time the up pulse or down pulse is input; means for creating an A-phase signal indicating a desired unit length that is twice or more; a means for creating a signal; inputting the A phase signal and the C signal;
It is characterized by comprising a logic circuit that creates a B-phase signal that is 90° out of phase with the phase signal.

[Effect]

According to the present invention, the increase/decrease counter counts the step amount indicating the length of the interference fringe per cycle each time an up pulse or a down pulse outputted from the laser interferometer for each cycle of brightness and darkness of the interference fringe is input. Count up or count down. Based on the count value of the increase/decrease counter, an A-phase signal indicating a desired unit length whose length per cycle is at least four times the step amount is created based on the change in the count value. Similarly, a C signal whose length per cycle is half the length of the A-phase signal is created. Then, by calculating the exclusive OR of the previous E A-phase signal and the C signal, a B-phase signal having a phase shift of 90° from the A-phase signal is created.

The A-phase signal and B-phase signal created in this way have a simple integer unit length per period, and when the increase/decrease counter counts up or down, The phase is 90 depending on the moving direction of
The signal will be advanced by 90 degrees or delayed by 90 degrees.

〔Example〕

Preferred embodiments of the A/B phase signal generation circuit according to the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an A/B phase signal generation circuit according to the present invention.

As shown in the figure, this A/B phase signal generation circuit includes an increase/decrease counter 50 and a binary coded decimal (BDC) counter 60.
,..., the discrimination circuit 70, and the
It is composed of an OR (EX-OR) circuit 80.

The increase/decrease counter 50 inputs the up pulse or down pulse indicating the length λ/2 (-0,3164956 μm) per pulse output from the pulse shaping/direction discrimination circuit 24 in FIG. 3164956 every time you input a down pulse
It is configured as an up/down counter that increases and decreases in steps of .

This increase/decrease counter 50 is, for example, 1 as shown in FIG.
It can be configured by connecting BCD counters 52, 54, . . . for each digit in 0-base in series.

In addition, in Figure 3, CI; Carry information input terminal B1. Carry information input terminal C○; Carry information input terminal 301 carry information input terminal CL: Count value clear terminal shows.

Each digit of the counter has step value input terminals DA, DB, D% DO into which the step value of that digit is input.
Each time an up pulse or down pulse is input, the step value is counted up or down by that step value. Incidentally, the step value of the counter 52 in the least significant digit is 6.
The step value of the counter 54 in the second lower digit is 5.

These digit counters count up by "step value + 1" when inputting an amplifier pulse when CI is "1", and count down by "step value + 1" when inputting a down pulse when BI is "1'". In cases other than the above, the count is up or down by the "step value" depending on the up pulse or down pulse.

Then, when the count value becomes 10 or more with the next up pulse, "1" is output to C○, and when the count value becomes smaller than 0 with the next down pulse, "1" is output to BO. Output.

The BCD counters 60, . . . are constructed by connecting commercially available BCD counters in series. In FIG. 1, only the least significant digit (10° μm) of the counter 60 is shown. This BCD counter 60 counts up or down by one in response to an output signal from the carry information output terminal C○ or the carry down information output terminal B○ of the most significant digit (10-'μm) of the increase/decrease counter 50. . The output signal from the least significant bit output terminal Q of the BCD counter 60 is output as an A-phase signal and is added to one input of the EX-OR circuit 80.

The determination circuit 70 inputs the 4-bit BCD output of the most significant digit of the increase/decrease counter 50 and determines whether the value of the BCD output is 5 or more. '' is applied to the other input of the EX-OR circuit 80.

Here, the A-phase signal output from the terminal QA of the BCD counter 60 has a width of 1 μm as shown in FIG. 2(B).
It is a signal with a pitch of 2 μm that repeats “1” and “0” every time, and the C signal output from the discrimination circuit 70 is shown in FIG.
As shown in A), it is a 1 μm pitch signal that repeats “1” and “0” every 05 μm.

The EX-OR circuit 80 performs an exclusive OR on the A-phase signal and the C signal, and generates a B-phase signal with a pitch of 2 μm and whose phase is shifted by 90 degrees with respect to the A-phase signal, as shown in FIG. 2(C). Output.

Note that the C signal shown in FIG. 2(A) shows a signal waveform when the increase/decrease counter 50 counts up. When 50 counts down, the C signal has a signal waveform that is 180 degrees out of phase with the signal waveform shown in Figure 2 (A), and in this case, the B phase signal is 90 degrees ahead of the A phase signal. It turns out.

In this embodiment, the A-phase signal and the B-phase signal are created with a pitch of 2 μm, but the pitch is not limited to this, for example, the pitch is 10 μm.
A-phase signals and B-phase signals with appropriate pitches can be created. However, one cycle of the C signal is required to be more than twice the step amount, so the A phase signal and the B
The length of one cycle of the phase signal needs to be four times or more the amount of steps.

In addition, when creating A-phase signals and B-phase signals with a pitch of 10 μm, the A-phase signal is created depending on whether the count value of the 1 μm digit counter is 5 or more, and the 1 μm digit and 01 μm
From the count value of the m-digit counter, create a C signal with a period half of the period of the A phase signal above, and combine the 200 signal and the A
The B-phase signal can be created by taking the exclusive OR of the phase signals.

In addition to this embodiment, the increment/decrement counter can also be used for gate arrays, AS
'The entire circuit may be designed and constructed from the beginning using a large-scale LSI such as an IC.

〔Effect of the invention〕

As explained above, according to the A/B phase signal generation circuit according to the present invention, A phase signals and B phase signals of a desired pitch are generated in real time from up pulses or down pulses generated in relation to the detection output of a laser interferometer. can occur,
Especially when using a laser interferometer as a means for detecting the amount of movement of a movable table of a machine tool, etc.
By using the B-phase signal generation circuit, feedback pulses of a desired pitch can be obtained, and there is an advantage that the feeding of the movable table, etc. can be controlled at a pitch independent of the wavelength of the laser beam.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the A/B phase signal generation circuit according to the present invention, and FIGS. 2(A) to (C) are diagrams of FIG. Signal waveform diagrams at each part, Figure 3 is a block diagram showing an example of the configuration of the increase/decrease counter in Figure 1, Figure 4 is a block diagram showing the servo system of a machine tool using a laser interferometer, Figure 5 (Δ) and (B
) are waveform diagrams of the A-phase signal and B-phase signal output from the encoder of FIG. 4, respectively. 10... Laser interferometer, 5o... Increase/decrease counter,
60... BCD counter, 7o... Discrimination circuit, 80
...EX-OR circuit. m5 figure

Claims (1)

[Claims] Input an up pulse or a down pulse that is output from a laser interferometer for each period of brightness and darkness of interference fringes, and that is output according to the moving direction of the object to be measured, and the up pulse or an increase/decrease counter that increases or decreases by a step amount indicating the length of one cycle each time a down pulse is input; means for creating an A-phase signal indicating a unit length; and means for creating a C-signal whose one cycle length is half the length of the A-phase signal based on the count value of the increase/decrease counter. An A/B phase signal generation circuit comprising: a logic circuit that receives the A phase signal and the C signal and creates a B phase signal that is 90 degrees out of phase with the A phase signal.