JPH0360041B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a photoelectric displacement detection device, and more particularly to a main scale equipped with a length measurement slit row with a constant pitch, and a length measurement gate slit row with the same pitch as the length measurement slit row of the main scale. , an index scale arranged to be relatively movable parallel to the slit row direction with respect to the main scale, and receives light transmitted or reflected by the main scale and the index scale, and the main scale and the index scale During the relative movement of
The present invention relates to an improvement in a photoelectric displacement detection device comprising a length measurement photoelectric converter that generates a length measurement signal from the number of repetitions of brightness and darkness of the light formed by repeated overlapping of each slit.

The photoelectric displacement detection device described above is used in many fields because it can detect displacement non-contact and with high precision, but because the detection signal draws a function curve that repeats increases and decreases in the length measurement direction, For example, even if the detection signal is processed into a digital signal and displayed digitally, the physical absolute origin is unknown from this signal alone, and therefore other means to identify the absolute origin are required. Ta.

Conventionally, the following methods have been used to identify the absolute origin in such a photoelectric displacement detection device.

First, when the main scale and index scale are at arbitrary relative positions, there is a method of forcibly setting the displayed value of the digital display including the counter to zero using other detection means, such as a dial gauge. .

Although this method is simple, it may be difficult to determine the absolute origin with an accuracy of μm.

In addition, if the power is cut off during measurement, it is necessary to perform the zero clearing operation again, and furthermore, even when the zero clearing operation is performed again, it is difficult to set the zero point to match the previous origin. It was hot.

Next, a reference mark is provided on the main scale in parallel with the length measurement slit row, separate from the length measurement slit row, and a corresponding mark to detect the reference mark is provided on the index scale side in the length measurement gate slit row. There is a method in which the reference mark is provided separately from the reference mark, the corresponding mark is used to detect the reference mark, and the position thereof is set as the absolute origin.

According to this method, the absolute origin can be accurately obtained, but a large number of reference marks are placed along the measurement slit, and during actual measurement, the index scale is placed on one of these multiple reference marks. It is necessary to overlap the corresponding marks of , read the reference marks, and set the absolute origin. Therefore, it is necessary to identify one reference mark from multiple reference marks, which makes it easy and quick. The problem is that it is not possible to set an absolute origin.

In addition, as another means, as described in Japanese Patent Publication No. 58-406845, a large number of reference marks are provided on the main scale in parallel with the length measurement slit array, and a movable reference mark is provided along the main scale. A mark selection switch is provided, and this reference mark selection switch is fixed in advance at a position corresponding to a desired reference mark, and when the corresponding mark on the index scale side detects the reference mark and the reference mark selection switch is activated at the same time, the reference mark selection switch is activated. There is a way to set the reference mark as the absolute origin.

However, even with this method, it is necessary to determine which reference mark selection switch should be fixed at a position corresponding to which reference mark, or which of multiple corresponding mark selection switches should be used. Another problem is that the absolute origin cannot be set quickly.

Further, when the reference mark selection switch is provided as described above, there are problems in that not only the displacement detection device itself becomes long and large, but also the cost increases.

The present invention has been made in view of the above-mentioned conventional problems, and it is an object of the present invention to provide a photoelectric displacement detection device that can easily, quickly, and automatically set an absolute origin.

Another object of the present invention is to provide a photoelectric displacement detection device that can reliably set and detect the absolute origin without increasing the weight and length of the device or increasing the cost.

The present invention is provided with a main scale having a length measuring slit row with a constant pitch, and a length measuring gate slit row with the same pitch as the length measuring slit row of the main scale, and which is arranged relative to the main scale in parallel to the slit row direction. A movably arranged index scale and light transmitted or reflected by the main scale and index scale are received, and when the main scale and index scale move relative to each other, the slits in each slit row are repeatedly overlapped. and a length measurement photoelectric converter that generates a length measurement signal from the number of repetitions of brightness and darkness of the light formed by the length measurement gate slit in the middle of the length measurement slit row. The length is shorter than the length of the length measurement gate slit row, and the length is within a range where fluctuations in the amount of light received by the length measurement photoelectric converter do not affect measurement accuracy, and the distance is longer than the length measurement gate slit row. , a plurality of reference position detection units each having a length measurement slit missing are provided, whereby the length measurement slit row is divided into a plurality of length measurement slit groups each having a different number of slits, and the length measurement slit row is divided into a plurality of length measurement slit groups each having a different number of slits. A reference mark formed on the position detection section, a mark detection means provided on the index scale for detecting the reference mark, and a detection signal of the mark detection means are activated to detect the number of slits in the length measurement slit group. Compare the slit group reading means to be read and the number of slits read by the slit group reading means with the number of slits preset by the slit group selection setting device to check whether or not the two numbers of slits match. The detection is performed under the conditions of a length measuring slit group confirmation means that outputs the signal, a matching signal from the length measuring slit group checking means, and a mark detection signal immediately after the input of the matching signal from the mark detection means. The above object is achieved by including an origin setting means that sets the reference mark position as the origin of length measurement.

Further, the present invention achieves the above object by configuring the mark detection means to include a detection mark having a shape corresponding to the reference mark, and a photoelectric converter that detects the overlap of this detection mark with the reference mark. It is something.

Further, the present invention achieves the above object by making the reference mark a slit with a random pattern, and making the detection mark in the mark detection means a reference gate slit consisting of a slit with a random pattern corresponding to the reference mark. It is something to do.

Further, the present invention achieves the above object by forming the reference mark by providing non-slit portions on at least both sides of the length measuring slit row.

Further, the present invention achieves the above object by constructing the slit group reading means from a length measurement counter that counts length measurement signals output from the length measurement photoelectric converter.

Further, the present invention achieves the above object by configuring the slit group reading means from an auxiliary counter provided separately from a length measurement counter that counts length measurement signals output from the length measurement photoelectric converter. It is something to be achieved.

Further, the present invention achieves the above object by sequentially increasing the number of slits in each length measuring slit group from one end of the main scale to the other end.

Further, the present invention achieves the above object by making the number of slits in each length measuring slit group the same in the length measuring slit groups located symmetrically in the direction of both ends with the approximate center position of the main scale as the center. .

Embodiments of the present invention will be described below with reference to the drawings.

A main scale 10 is provided with a length measuring slit row 12 having a constant pitch, and a length measuring gate slit row 14 having the same pitch as the length measuring slit row 12 of this main scale 10, parallel to the slit row direction with respect to the main scale 10. The main scale 10 and the index scale 16 are arranged so as to be movable relative to each other.
A measuring device that receives light transmitted or reflected by the main scale 10 and the index scale 16, and generates a length measurement signal from the number of repetitions of brightness and darkness of the light formed by repeating overlapping of each slit when the main scale 10 and the index scale 16 move relative to each other. In the photoelectric displacement detection device comprising a long photoelectric converter 18, the length measuring slit array 1
2, the length is shorter than the length of the length measurement gate slit array 14, and has a length within a range where fluctuations in the amount of light received by the length measurement photoelectric converter 18 do not affect measurement accuracy; Measuring gate slit row 1
A plurality of reference position detection units 20 each having a length measurement slit missing are provided at intervals longer than 4, and the length measurement slit row 12 has a plurality of length measurement slit groups 12A, 12B, each having a different number of slits. 12C,
12D, . . . and the reference marks 22A, which are formed on the reference position detection section 20.
22B, 22C, . . . , a mark detection means 24 provided on the index scale 16 and detecting the reference mark 22, and this mark detection means 2.
The length measuring slit group 1 is activated by the detection signal of 4.
Slit group reading means 26 consisting of a length measuring counter that reads the number of slits 2A, 12B, 12C, ...
Then, the number of slits read by the slit group reading means 26 is compared with the number of slits set in advance by the slit group selection setting device 28, and it is confirmed whether or not the two numbers of slits match. Measuring slit group confirmation means 30 consisting of an output comparator
The position of the detected reference mark 22 is determined as the length measurement origin under the conditions of the matching signal from the length measurement slit group confirmation means 30 and the mark detection signal immediately after the input of the matching signal from the mark detection means 24. An origin setting means 32 is provided.

The reference mark 22 is a slit in a random pattern, and the mark detection means 24 includes a reference gate slit 34 consisting of a slit in a random pattern corresponding to the reference mark 22, and a reference gate slit 34 and the reference mark 22. A photoelectric converter 36 that detects the overlap of
It is composed of.

Further, the length measuring gate slit array 14 includes a pair of first,
and second length measurement gate slit rows 14A, 14B
It consists of

These first and second length measurement gate slit rows 1
4A and 14B are arranged apart from each other in the direction of relative movement of the index scale 16 with respect to the main scale 10, and the pitch of the slits in one length-measuring gate slit row is shifted by half a pitch from the other length-measuring gate slit row. has been done.

Further, the length measurement photoelectric converter 18 includes first and second length measurement photoelectric converters 18A, corresponding to the first and second length measurement gate slit rows 14A, 14B.
It is composed of 18B.

The length of the reference position detecting section 20 formed by missing the length measuring slit is, for example, approximately one pitch of slits when the number of slits in the length measuring gate slit rows 14A, 14B is 200 pitches. There is.

Here, the length measuring slits of the length measuring slit array 12 in the main scale 10 have a width of 4 μm in a bright portion and a width in a dark portion, and therefore, one pitch is 8 μm.

Further, the number of slits in the length measuring slit groups 12A, 12B, 12C, ... in the length measuring slit row is, for example, the number of slits in the length measuring slit group 12 at the left end in FIG.
A is determined to be 12,500 pitches (equivalent to 10cm), and the next measuring slit group 12B is determined to be 13,000 pitches (equivalent to 10cm + 4mm), etc., and the number of pitches, that is, the number of slits is increased sequentially from the left end to the right end of the main scale 10. and form it.

The slit group selection and setting device 28 is adapted to select any length-measuring slit group according to the pitch number corresponding to each length-measuring slit group.

Reference numeral 38 in FIG. 2 indicates a signal processing section, and the signal processing section 38 is connected to the first length measurement photoelectric converter 18.
The analog input signal from A is converted into a digital pulse signal and outputted to the slit group reading means 26. Then, it is determined whether the index scale 16 is moving rightward or leftward in the figure, and a plus or minus signal is output to the slit group reading means 26 depending on the direction.

Further, reference numeral 40 in the figure indicates a display section, which displays or records measured dimensions in accordance with the output from the slit group reading means 26, that is, the number of pulse counts.

Next, the operation of the above embodiment will be explained with reference to FIG.

First, in FIG. 1, the fifth and sixth length-measuring slit groups 12 from the left end of the length-measuring slit row 12
When the reference position detecting section 20 between the length measuring slits 12E and 12F is set as the absolute origin, the number of slits or the number of pitches of the length measuring slit group 12E is set by the slit group selection setting device 28.

As shown in FIG. 3, the length measurement slit group confirmation means 30 reads the setting value set by the slit group selection and setting device 28, ie, the signal for identifying the slit group, in step 101.

In this state, when the index scale 16 is moved relative to the main scale 10 in the right direction in FIG. Reference position detection unit 20 between 12C
Next, the reference mark 22B provided between the length measuring slit groups 12C and 12D is
C, as well as the reference mark 22D between the length measurement slit groups 12D and 12E, and the length measurement slit groups 12E and 1.
The reference marks 22E between 2F are sequentially scanned.

In this case, when the reference gate slit 34 in the mark detection means 24 matches the reference mark 22, a reference gate signal is outputted to the origin setting means 32 in accordance with the output of the photoelectric converter 36 (see step 102).

On the other hand, the slit group reading means 26 counts the number of digital pulse signals output from the signal processing section 38 and outputs this to the length measurement slit group confirmation means 30.

This length measurement slit group confirmation means 30 compares the setting value from the slit group selection setting device 28 with the output signal from the slit group reading means 26, and determines the number of pulses from the signal processing section 38, that is, the slit group selection setting device 28 in advance. The number of slits in the slit group 12E set by 28 is compared with the number of slits in the slit group 12E, and a signal indicating whether the two match or do not match is outputted to the origin setting means 32 (step 28).
103).

The origin setting means 32 outputs a signal for clearing the slit group reading means 26 depending on whether the matching signal from the length measurement slit group confirmation means 30 is correct or not, and clears the slit group reading means 26 to zero. (Step 104). Note that the slit group reading means 26
Of course, you can also clear it to zero manually.

After being cleared, the slit group reading means 26 counts the pulse signals from the signal processing section 38 again.

When the coincidence signal is positive, that is, when the length measurement gate slit rows 14A and 14B pass through the length measurement slit group 12E, the position of the reference mark 22 is set as the absolute origin, and the length measurement slit group confirmation means 3
0, and outputs a counter clear signal to the slit group reading means 26 (step 105). From this point on, the slit group reading means 26 is switched to length measurement mode (step 106).
This is the state during normal measurement.

Therefore, the distance from the set absolute origin will be displayed or recorded on the display unit 40 after switching to this measurement mode.

If the reference position detection section 20 at another position is used as the absolute origin, select the corresponding length measurement slit group using the slit group selection setting device 28 and check the length measurement slit group in the same manner as described above. By having the means 32 read it, the reference position detecting section 20 adjacent to the length measuring slit group can be set as the absolute origin.

In the above embodiment, when the length measurement gate slit rows 14A and 14B move relative to the length measurement slit row 12, in the portion where the slit is missing, that is, in the reference position detection section 20, the slits pass through or pass through these slit rows. The amount of reflected light is increased or decreased depending on the width of the reference position detection section 20, but as described above, the width of the reference position detection section 20 is very short compared to the length measurement gate slit rows 14A and 14B. Since the variation in the amount of light received by the length measurement photoelectric converter 18 is 1/200, and the length is within a range that does not affect measurement accuracy, there is no problem.

Furthermore, if the slit group selection setting device 28 is configured to be able to sequentially change and select the absolute origin according to a predetermined program, machining can be easily performed by linking it to a control device such as an NC machine tool. Change the absolute origin one by one according to the order,
Optimal measurements can be taken automatically.

Further, the absolute origin can be quickly and easily changed depending on the shape and size of the material to be machined.

Here, the length measuring slit groups 12A, 12B,
For 12C,..., the pitch number is sequentially from the 12A side.
Although the number of pitches is increased by 500 pitches, the number of pitches may be increased or decreased randomly, and the number of pitches to be increased may be at least 1 pitch.

That is, the widths of the bright and dark parts of the length measuring slits in the length measuring slit row 12 and the length measuring gate slit row 14 are each set to 4 μm, for example, as described above, and the length measuring photoelectric converter 1 is
If the analog signal obtained from 8 is divided into 8, one pulse of the pulse signal derived from the signal processing section 38 will be 1 μm, and this displacement measuring device will be 1 μm.
Since it has a resolution of m, even if the difference between the length measurement slit groups is one pitch of length measurement slits, it can be determined.

In addition, as described above, when the reference position detection unit 20 in which no length-measuring slit is provided between each length-measuring slit group is arranged, when forming the length-measuring slit row 12, the length-measuring slits are placed closely together. This is convenient in terms of production since there is no need to sequentially arrange them.

In the above embodiment, the length measurement slit group is specified by the slit group selection and setting device 28 using the number of pulses corresponding to the slit group. It may be specified as the absolute length from the end of the scale 10, and in cases where the absolute origin is changed sequentially in NC machine tools as mentioned above, the length may be specified as the absolute length from the end of the scale 10. so that
The length measurement slit group may be specified using a control signal from a control device 29 of the machine tool or the like.

Further, in the case of the above embodiment, the case where the index scale 16 moves relative to the main scale 10 from the left direction to the right direction in FIG. As a means for specifying, the absolute origin may be specified using the length measuring slit group on the right side or the length measuring slit groups on both sides in the drawing of the reference mark 22.

Further, in the above embodiment, as described above, the number of slits in the length measuring slit group is arranged so as to increase sequentially from the left side to the right side in the figure, but this is arranged so that the number of slits in the length measuring slit group increases sequentially from the left side to the right side in the figure. Good too,
Further, for example, length measurement slit groups at symmetrical positions in the left-right direction from the center of the main scale 10 may have the same number of slits.

Furthermore, the length-measuring slit group may be arranged so that the number of slits is increased or decreased in sequence.

Further, the reference mark 22 has a random pattern formed by randomly forming slits, but the present invention is not limited to this. For example, the reference mark 22 may be a mark completely different from the slits. It's okay to be hot. Furthermore, the reference mark 22 may be formed by providing non-slit portions on both sides of the same slit as the length measurement slit row. In these cases, the reference gate slit 34 is naturally used as a detection mark of a pattern corresponding to the reference mark 22.

In the above embodiment, the length measuring slit group confirmation means 30 uses the number of pulses designated by the slit group selection setting device 28 and the slit group reading means 2.
It is designed to compare the number of pulses input from 6 and output a matching signal when the two match, but if the matching signal is output only when both numbers of pulses exactly match, Since accurate operation may be difficult in terms of time, it is recommended to set a certain tolerance range above and below the set value and set it to output a matching signal when both pulse numbers match within this tolerance range. . However, in this case, the difference in the number of slits between each length-measuring slit group must be made larger than the above-mentioned allowable range.

Further, in the above embodiment, a counter used during the length measurement operation is used as the length measurement slit group reading means 26, but the present invention is not limited to this, and as shown in FIG. Alternatively, an auxiliary counter may be provided separately from the length measurement counter 42, and this may be used as the length measurement slit group reading means 26.

In this case, a switching device 44 is provided between the main counter 42 and the signal processing section 38, and this switching device 44 is switched by the origin setting means 32 when setting the origin, so that the output signal from the signal processing section 38 is changed. Main counter 42 side and length measurement slit group reading means 2
6 side so that it is output.

In this embodiment, length measurement slit group reading means 2
The counter 6 may have a coarser resolution than the main counter 42 used for length measurement, so the structure is simple.

However, as shown in FIG. 2, when the main counter is used as the length measurement slit group reading means 26, there is an advantage that the configuration is simpler.

Further, even in a photoelectric displacement detection device in which a plurality of counters are arranged in series, each origin can be easily set.

Since the present invention is configured as described above, the absolute origin can be easily and reliably set automatically with a simple configuration and without increasing the size, weight, or significant cost of the device. It has the excellent effect of being able to

[Brief explanation of drawings]

Fig. 1 is an exploded plan view showing the main parts of a photoelectric displacement detection device according to the present invention, Fig. 2 is a block diagram including a partial cross-sectional view showing the same embodiment, and Fig. 3 shows the operation of the same embodiment. FIG. 4 is a block diagram illustrating another embodiment of the present invention. 10... Main scale, 12... Measuring slit row, 12A, 12B, 12C, 12D, 12
E, 12F, 12G...Measuring slit group, 14,
14A, 14B... Length measurement gate slit row, 16
...Index scale, 18, 18A, 18
B... Length measurement photoelectric converter, 20... Reference position detection unit, 22A, 22B, 22C, 22D, 22E,
22F... Reference mark, 24... Mark detection means, 26... Slit group reading means, 28... Slit group selection setting device, 30... Length measurement slit group confirmation means, 32... Origin setting means, 34... Reference gate slit, 36...photoelectric converter.

Claims (1)

[Scope of Claims] 1. A main scale equipped with a length measurement slit row with a constant pitch, and a length measurement gate slit row with the same pitch as the length measurement slit row of the main scale,
An index scale is arranged to be movable relative to the main scale parallel to the slit row direction, and the main scale and the index scale receive light transmitted or reflected from the main scale and the index scale. a length measurement photoelectric converter that generates a length measurement signal from the number of repetitions of brightness and darkness of the light formed by repetition of overlapping slits in each slit row during relative movement;
In the photoelectric displacement detection device, there is provided a length-measuring gate slit in the middle of the length-measuring slit row, which is shorter than the length of the length-measuring gate slit row, so that fluctuations in the amount of light received by the length-measuring photoelectric converter improve the measurement accuracy. A plurality of reference position detecting sections having length measurement slits omitted are provided with a length in a range that does not affect the length measurement gate slits and at intervals longer than the length measurement gate slits, so that the length measurement slit row is a reference mark that is divided into a plurality of length measurement slit groups with different numbers of slits, and is formed on the reference position detection section; and a mark that is provided on the index scale and detects the reference mark. a detecting means, a slit group reading means which is activated by the detection signal of the mark detecting means and reads the number of slits in the length measuring slit group, and a slit group selection setting device which reads the number of slits read by the slit group reading means. A measuring slit group confirmation means that compares the number of slits with a preset number to confirm whether or not the numbers of slits match and outputs the signal, and a matching signal from the length measuring slit group confirmation means and the above-mentioned A photoelectric displacement detection device comprising: origin setting means that sets the detected reference mark position as a length measurement origin on condition of a mark detection signal immediately after input of the matching signal from the mark detection means. 2. The photoelectric type according to claim 1, wherein the mark detection means comprises a detection mark having a shape corresponding to the reference mark, and a photoelectric converter that detects the overlap of this detection mark with the reference mark. Displacement detection device. 3. Claim 2, wherein the reference mark is a slit in a random pattern, and the detection mark of the mark detection means is a reference gate slit consisting of a slit in a random pattern corresponding to the reference mark. The photoelectric displacement detection device described. 4. The photoelectric displacement detection device according to claim 2, wherein the reference mark is formed by providing non-slit portions on at least both sides of the length measurement slit row. 5. The method according to any one of claims 1 to 4, wherein the slit group reading means comprises a length measurement counter that counts length measurement signals output from the length measurement photoelectric converter. Photoelectric displacement detection device. 6. Claims 1 to 6, wherein the slit group reading means comprises an auxiliary counter provided separately from a length measurement counter that counts length measurement signals output from the length measurement photoelectric converter. The photoelectric displacement detection device according to any one of item 4. 7. The photoelectric displacement detection according to any one of claims 1 to 6, wherein the number of slits in each of the length measurement slit groups is sequentially increased from one end side to the other end side of the main scale. Device. 8. The number of slits in each length-measuring slit group is the same in the length-measuring slit groups at symmetrical positions in the direction of both ends with the approximate center position of the main scale as the center. The photoelectric displacement detection device according to any one of the above.