JPS60120216A - Photoelectric type displacement detecting device - Google Patents

Abstract

PURPOSE:To set absolute original points quickly and automatically, by comparing the number of slits between a plurality of reference marks, which are arranged on a length measuring slit line, with a preset value, and detecting the positions of the marks based on the coincidence signal and the detected mark signal immediately after the coincidence signal. CONSTITUTION:A plurality of reference marks 22A... are arranged on a main scale 10 in parallel with a length measuring slit line 12. The parts of the line 12 between the marks 22A... are sequentially made to be length measuring slits 12A.... A slit counting means 26, which reads the slit number, is operated by a mark detecting means 24 provided on an index scale. The slit number, which is read by the means 26, is compared with the preset slit number, which is determined by a reference-mark setting device 28, by a length-measuring slit-number confirming means 30. The positions of the detected marks 22A... are made to be length measuring original points on conditions of the coincidence signal from the means 30 and the detected mark signal from the means 24 immediately after the coincidence signal.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rechargeable displacement detection device, and in particular, 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 movable relative to the main scale parallel to the slit row direction; The present invention relates to an improvement of 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 repetition of overlapping of each slit during movement.

The photoelectric displacement detection device described above is used in many fields because it can detect displacement non-contact and with high precision. Even if the detection signal is processed into, for example, a digital signal and displayed digitally, the physical absolute origin is unknown from this signal alone, and therefore other means for identifying the absolute origin are required.

Conventional methods have been used to identify the absolute origin in such photoelectric displacement detection devices.

First, when the main scale and index scale are at arbitrary relative positions, there is a method of forcibly setting the displayed value of a digital display including a 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 μ-.

Furthermore, if the power is cut off during measurement, it is necessary to perform the zero clearing operation again, and there is also the problem that even if the zero clearing operation is performed again, it is difficult to set the zero point to match the previous origin. Ta.

Next, a reference mark is provided on the main scale in parallel with the length measurement slit row separately from the sub length slit row, and a corresponding mark to detect the reference mark is provided on the index scale side with the length measurement gate slit row. There is a method in which the reference mark is separately provided, the reference mark is detected using the corresponding 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 arranged along the length measurement slit, and during actual measurement, one of these multiple reference marks is used for the index scale. The absolute origin must be set by overlapping the corresponding marks and reading the reference marks.Therefore, it is necessary to identify one reference mark from multiple reference marks, so it is easy and quick to set the absolute origin. There is a problem in that the origin cannot be set.

In addition, as another means, as described in Japanese Patent Publication No. 5B-406845, a large number of reference marks are provided on the main scale in parallel with the length measurement slit row, 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 mark as the absolute origin.

However, even in this method, the reference mark selection switch is fixed at the position corresponding to the reference mark, or
Alternatively, it is necessary to determine which of a plurality of corresponding mark selection switches should be used, and there is a problem that the absolute origin cannot be set automatically and quickly.

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

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide a rechargeable 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 l1ffi and length of the device or increasing the cost.

The present invention comprises a main scale having a length measurement slit row with a constant pitch, and a length measurement gate slit row with the same pitch as the sub-length slit row of the main scale, and is arranged parallel to the slit row direction with respect to the main scale. A movably arranged index scale receives light transmitted or reflected through these main scales and index scales, and is formed by repeating overlapping of slits in each slit row when the main scale and index scale move relative to each other. and a length measurement photoelectric converter that generates a length measurement signal based on the number of repetitions of brightness and darkness of the light. a plurality of reference marks arranged at pitches, a mark detection means provided on the index scale for detecting the reference marks, and the length measurement slit at the position of each of these reference marks;
When the length measuring slit group is set, a slit counting means is activated by the detection signal of the mark detection means and counts the number of slits in the length measuring slit group between the reference mark and the next reference mark, and this slit counting means The measured slit number confirmation means compares the counted number of slits with the number of slits preset by the reference mark selection setting device, checks whether the two slit numbers match, and outputs a signal. The above object is achieved by comprising a matching signal and an origin setting means that sets the detected reference mark position as the length measurement origin on the condition that the matching signal is input from the mark detecting means and is a direct replica mark detection signal. It is something to do.

Further, the present invention achieves the above object by configuring the slit counting 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 counting means from an auxiliary counter provided separately from a sub-length counter that counts the length measurement signal output from the length measurement photoelectric converter. It is something.

Further, the present invention achieves the above object by sequentially increasing the number of slits in the length measurement slit row of each reference mark garden 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 the sub-length slit row between each of the reference marks the same in the length measurement slit groups located symmetrically in the direction of both ends with the approximate center position of the main scale as the center. It is something.

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

A main scale 10 having a length measurement slit row 12 with a constant pitch, and a sub-length slit row 1 of this main scale 10.
An index scale 16 is provided with a length measurement gate slit row 14 having the same pitch as 2, and is arranged to be movable relative to the main scale 10 in parallel to the slit row direction.
The light transmitted or reflected by the main scale 10 and the index scale 16 is received, and when the main scale 10 and the index scale 16 move relative to each other, the repetition of brightness and darkness of the light is formed by the repetition of overlapping of each slit. A photoelectric displacement detection device comprising: a length measurement photoelectric* converter 18 that generates a length measurement signal from a number;
A plurality of reference marks 2 are arranged on the main scale 10 at unequal pitches in parallel with the sub-length slit row 12.
2A, 228122C, . . . , a mark detection means 24 provided on the index scale 16 and detecting the reference mark 22, and a mark detection means 24 which is operated by the detection signal of this mark detection means 24 and detects each of the reference marks 22A, 222B, 2.
When the length measurement slit array 12 between 2C, . . . is sequentially closed, the length measurement slit group 12A1 or Slit counting means 26 consisting of a counter that reads the number of slits in 12B or 12C1...
Then, the number of slits read by this slit counting means 26 is compared with the number of slits set in advance by the reference mark setting device 28, it is confirmed whether or not the two numbers of slits match, and the signal is output. Detection is performed under the conditions of a sub-length slit number confirmation means 30 consisting of a comparator, a match signal from this length measurement slit number confirmation means 30, and a mark detection signal immediately after the input of the match signal from the mark detection means 24. and an origin setting means 32 which sets the reference mark 22 position determined as the length measurement origin.

The reference mark 22 is a slit with a random pattern, and the mark detection means 24 is configured to detect the reference mark 2.
A reference gate slit 34 consisting of a random pattern of slits corresponding to 2, and this reference gate slit 3
4 and a photoelectric converter 36 that detects the overlap between the reference mark 22 and the reference mark 22.

The length measurement gate slit row 14 is composed of a pair of first and second length measurement gate slit rows 14A and 14B, which are formed with a half-pitch phase shift from each other.

These first and second sub-length gate slit rows 14A11
4B is main scale 1 of index scale 16
are spaced apart in the direction of relative movement with respect to 0, and
The pitch of the slits in one of the length measurement gate slit rows is shifted by half a pitch in the other sub-length slit row.

Further, the length measurement photoelectric converter 18 includes first and second length measurement photoelectric converters 18A118B corresponding to the first and second length measurement gate slit rows 14A and 14B.

Here, the length measurement slits of the sub-length slit array 12 in the main scale 10 have a bright part and a dark part each having a width of 4 .mu.m, and one pitch is 8 .mu.m.

Further, the number of sub-length slits in the sub-length slit row is 12A,
For example, the number of slits 12B, 12C1...
In the figure, the leftmost sub length slit group 12A has a pitch of 12,500 (equivalent to 10 cm), and the next length measurement slit group 12B has a pitch of 12,500 (equivalent to 10 cm).
3000 pitches (equivalent to 10 marks + 4n),...
The main scale 10 is formed so that the number of pitches, ie, the number of slits, increases sequentially from the left end to the right end.

The slit number selection and setting device 28 is adapted to select any sub-major slit group according to the pitch number corresponding to the sub-major slit group between each of the reference marks.

The symbol @38 in FIG. 2 indicates a signal processing section, which converts the analog input signal from the first length measurement photoelectric converter 18A into a digital pulse signal, and converts the analog input signal from the first length measurement photoelectric converter 18A into a digital pulse signal. and the first and second
It is determined whether the index scale 16 is moving to the right or to the left in the figure based on the phase difference between the input signals from the length measuring photoelectric converters 18A and 18B, and the slit counting means 26 is set to be plus or minus depending on the direction. It outputs a negative signal.

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 counting 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, when the fifth reference mark 22E from the left end ToX is set as the absolute origin, the length measurement slit group 12
Slit number selection setting device 2 for the number of slits or pitch number of D
Set by 8.

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

When the index scale 16 is moved rightward in FIG. 1 relative to the main scale 10 in this V position, the mark detection means 24 provided on the index scale 16 detects the reference mark 22B, and The reference mark 22C, furthermore, the reference mark 22D1 and the reference mark 22E 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 counting means 26 counts the number of digital pulse signals output from the signal processing section 38 and outputs this to the sub-length slit number checking means 30.

This sub-length slit number confirmation means 30 compares the setting value from the slit number selection and setting device 28 with the output signal from the slit counting means 26, and determines the number of pulses from the signal processing section 3B, that is, the slit number selection and setting device 28 in advance. The origin setting means 32 compares the number of slits in the set slit group 12D and outputs a signal indicating whether they match or do not match to the origin setting means 32 (step 103). Depending on whether the signal is correct or not, if the signal is negative, a signal is output to clear the slit counting means 26 to clear the slit counting means 26 to zero (step 104). Note that the slit counting means 26 can of course be cleared to zero manually. can.

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

If the match signal is positive, that is, the length measurement gate slit row 14
When A and 14B pass through the length measurement slit group 12D, the position of the reference mark 22E is set as the absolute origin, and an origin setting completion signal is output to the length measurement slit number confirmation means 30, and furthermore, to the slit counting means 26. A counter clear signal is output (step 105). From this point on, the slit counting means 26 is switched to length measurement mode (step 1
06) It becomes the state at the time of 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 mark 22 at another position is to be used as the absolute origin, select the corresponding length measurement slit group using the slit number selection and setting device 28 and read it by the sub-length slit number confirmation means 32 in the same manner as described above. By doing so, the reference mark 22 adjacent to the length measurement slit group can be set as the absolute origin.

Here, if the slit number selection and setting device 28 is configured to be able to sequentially change and select the absolute origin according to a predetermined program, it is possible to
By linking with the device, it is possible to automatically change the absolute origin in sequence according to the order of machining and perform optimal measurements.

Furthermore, 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 and 12B.

For 12C1..., the pitch number is 5 sequentially from the 12A side.
Although the number of pitches is increased by 00 pitches, the number of pitches may be increased or decreased randomly, and the number of pitches to be increased may be a minimum of 100 pitches.

That is, the sub length slit row 12 in the length measurement slit row 12
If the width of the bright part and the dark part of the sub-length slit in the length measurement gate slit array 14 are each set to 4μ-, for example, as described above, and the analog signal obtained from the length measurement photoelectric converter 18 is divided into eight, the signal processing 8IX38 One pulse of the pulse signal derived from is 1 μ-, and this displacement measuring device has a resolution of 1 μm, so even if the difference between the length measurement slit groups is one pitch of the sub-length slits, this can be easily detected. Can be distinguished.

In the above embodiment, the length measurement slit group is specified by the slit number selection and setting device 28 according to the number of pulses corresponding to the length measurement slit group.
Other specifying means, for example, may be specified as the absolute length from the end of the main scale 10.Also, as mentioned above, when the absolute origin is changed sequentially in an NC machine tool, etc. As shown by the two-dot chain line in FIG. 2, the number of length measurement slits 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 determining the reference mark 22, the absolute origin may be specified using the length measurement slit group on the right side or the length measurement 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 sub-length slit group is arranged so as to increase sequentially from the left side to the right side in the figure, but this is also possible even if the number of slits is sequentially decreased. Well, also, for example, the main skate, -
The length measurement slit groups at symmetrical positions in the left-right direction from the center of the lens 10 may have the same number of slits.

Furthermore, the length measurement slit group may be arranged so that the number of slits is increased or decreased in a sequential manner.

Further, the reference mark 22 has a random pattern in which slits are randomly formed, but the present invention is not limited to this. For example, the reference mark 22 may be a mark completely different from the slit. There may be. 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 measurement slit number confirmation means 30 compares the number of pulses specified by the slit number selection and setting device 28 with the number of pulses input from the slit counting means 26, and determines that the two match. However, if the matching signal is to be output only when both pulse numbers exactly match, it may be difficult to operate accurately in terms of time. It is preferable to set a certain tolerance range above and below the set value, and 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 measurement slit group must be made larger than the above-mentioned allowable range.

Further, in the above embodiment, a counter used during length measurement work is used as the slit counting means 26, but the present invention is not limited to this, and as shown in FIG. An auxiliary counter may be provided separately from the length counter 42, and this may be used as the slit counting 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 switched between the main counter 42 and the signal processing section 38. 42 side and the slit counting means 26 side.

In this embodiment, the slit counting means 26 may have a coarser resolution than the main counter 42 used for the sub-length, so the structure is simple.

However, as shown in FIG. 2, when the main counter is used as the slit counting 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 the drawing]

Fig. 1 is an exploded plan view showing the main parts of a rechargeable 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...Sub-major slit row, 12A, 1281120112D. 12E112F...Measuring slit group, 14.14A,
14B... Length measurement gate slit row, 16... Index scale, 18.18A, 18B... Length measurement photoelectric converter, 22.2
2A, 228, 220, 22D. 22E, 22F...Reference mark, 24...Mark detection means, 26...Slit counting means, 28...Slit number selection setting device, 30...Sub-length slit number confirmation means, 32...Origin Setting means, 34... Reference gate slit, 36... Photoelectric converter. Agent Keisuke Matsuyama (and 1 other person)

Claims (5)

[Claims] (1) A main scale equipped with a sub-length slit row with a constant pitch, and a length measurement gate slit row with the same pitch as the length measurement slit row of this main scale, which moves relative to the main scale in parallel to the slit row direction. The index scale is arranged such that the main scale and the index scale receive light transmitted or reflected, and when the main scale and index scale move relative to each other, the slits are formed by overlapping the slits in each slit row. and a length measuring photoelectric converter that generates a sub-length signal from the number of repetitions of brightness and darkness of the light. When the plurality of reference marks arranged, the mark detecting means provided on the index scale for detecting the reference marks, and the sub-long slits between the respective reference mark positions are defined as a -long slit group, the above-mentioned slit counting means that is activated by the detection signal of the mark detection means and counts the number of slits in the length measurement slit group between the reference mark and the next reference mark; A sub-length slit number confirmation means that compares the number of slits set in advance with the number of slits set by the selection setting device to confirm whether or not the two slit numbers match and outputs the signal, and a matching signal from the sub-length slit number confirmation means. and an origin setting means that sets the detected reference mark position as a length measurement origin on the condition that a mark detection signal is received immediately after the input of the matching signal from the mark detection means. (2) The photoelectric displacement detection device according to claim 1, wherein the slit counting means includes a length measurement counter that counts the length measurement signal output from the length measurement photoelectric converter. (3) The slit counting means comprises an auxiliary counter provided separately from a length measurement counter that counts the length measurement signal output from the sub-length photoelectric converter. photoelectric displacement detection device. (4) The number of slits in the sub-length slit row between each reference mark is sequentially increased from one end side to the other end side of the main scale, according to any one of claims 1 to 3. photoelectric displacement detection device. (5) The number of slits in the length measurement slit row between each of the reference marks is the same between the reference marks located symmetrically 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 item 6.