JPH03287015A - Reflection type optical displacement detector - Google Patents

Abstract

PURPOSE:To obtain a reference point detection signal with high accuracy by providing a fixed optical grating for reference point detection on the surface of a main scale on the opposite side from an optical grating for displacement detection. CONSTITUTION:The fixed optical grating 7 for reference point detection is provided on the grating formation surface 9B of the grating formation surface 9 of the main scale 4 on the opposite side from the formation surface 9A for the fixed optical grating 3 for displacement detection. The light beam emitted by a light emission source 5 is reflected by a reflecting surface 16, passed through the grating 7, and then made incident directly on a movable optical grating 8 for reference point detection to detect a reference point signal having a sharp waveform as the main scale 4 and an index scale 2 move relatively. The reference point detection signal with high accuracy can, therefore, be obtained. Further, the grating 7 may be formed on a transparent plate 20 independent of the main body 4 and adhered to the surface 9B.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a fixed optical grating for displacement detection attached to one side of a detection target that is displaced relative to each other, and a fixed optical grating attached to the other side of the detection target. The present invention relates to an improvement in a reflective optical displacement detector that detects the amount of relative movement between objects to be detected from a displacement detection optical signal generated when a displacement detection optical grating is moved relative to the object to be detected.

[Prior Art] Generally, in a displacement detector that measures the length of an object,
When measuring the amount of relative movement of an object, a main scale on which an optical grating is formed and a detector including an index scale are fixed to the object to be measured, and the amount of relative movement between the main scale and the detector is optically read. Optical displacement detectors are known.

This optical displacement detector is widely used as a positioning device for machine tools, optical instruments, precision measuring instruments, etc.

Typically, such optical displacement detectors.

Transmissive or reflective optical displacement detector force IJ)
It is being

Among these, in the transmission type displacement detector, a light emitting source and a light receiving element are arranged facing each other with a fixed optical grating for displacement detection and a movable optical grating in between.

On the other hand, a single-reflection type displacement detector has an index scale 2 equipped with a movable optical grating 1 for displacement detection and a main scale equipped with a fixed optical grating 3 for displacement detection, as shown in FIG. 4, the light emitting source 5 and the light receiving element 6 consisting of a photodiode are arranged on one side (index scale 2 side), so compared to a transmission type optical displacement detector, it is smaller and cheaper. Cost reduction can be achieved.

In FIG. 7, reference numeral 7 indicates a fixed optical grating for detecting a reference point provided on the main scale 4, and reference numeral 8 indicates a movable optical grating for detecting a reference point provided on the index scale 2, both of which have the same random pattern. It is said that

FIG. 9 shows the grating forming surface 9 of the main scale 4. 9th
In the figure, it is shown that the fixed optical grating 7 for detecting a reference point has a random pattern, whereas the fixed optical grating 3 for detecting displacement has a pattern with a constant grating interval.

In the reflective optical displacement detector shown in FIG.
After passing through the displacement detection movable optical grating l, the light is received by the displacement detection signal light receiving element 6A of the light receiving elements 6, where it is converted into an electrical signal and sent to the preamplifier IO.
The signal is input to the signal processing circuit 11 via A. Figure 10 (A
) shows the waveform of the displacement detection signal detected by the light receiving element 6A. Here, P indicates the lattice spacing.

Further, the light emitted from the light emitting source 5 is reflected by the fixed optical grating 7 for reference point detection, passes through the movable optical grating 8 for detection, and is received by the light receiving element 6B for the reference point detection signal of the light receiving element 6. Here it is converted into an electrical signal. Figure 10 (B
) shows the waveform of the reference point detection signal detected by the reference point detection signal light receiving element 6B. The reference point detection signal 14 occurs when the random pattern of optical gratings 7 and 8 are superimposed.

Note that the distance between the fixed optical grating 3 for displacement detection and the fixed optical grating 1 for displacement detection needs to be determined to a predetermined value depending on the resolution of the reflective optical displacement detector. Therefore, the grating forming surface 9 on which the fixed optical grating 3 for displacement detection is formed is provided on the grating forming surface 9B on the side closer to the grating forming surface 13 of the index scale 2, and on the grating forming surface 9A on the far side. There are cases.

[Problem to be solved by the invention] However, in the past, the fixed optical grating 3 for displacement detection was
In the case of a configuration in which the first grating forming surface 9A is located instead of the grating forming surface 9B, as shown in FIG. It was provided on surface 9B. The reason for this is that after the fixed optical grating 3 for displacement detection is formed on the second grating forming surface 9B by a photoetching process, a new alignment is performed, and then the fixed optical grating 3 for detecting the reference point is formed on the first grating forming surface 9A. This is because adopting the photoetching step No. 7 results in high costs and is not easy in terms of manufacturing technology.

As a result of placing the fixed optical grating 7 for reference point detection on the grating forming surface 9A, the distance between the movable optical grating 8 for reference point detection and the fixed optical grating 7 for reference point detection is the same as that of the substrate 15 of the main scale 4.
They were unnecessarily separated by the thickness of the Therefore, the 10th
As shown in FIG.
As shown in 4B, the waveform becomes dull and there is a problem that a highly accurate reference point detection signal 14 cannot be obtained.

In addition, due to these problems, it was necessary to stop providing an optical grating 7.8 for detecting a reference point from the beginning and to use it only as a pure incremental displacement detector without detecting a reference point. .

Also, when providing the optical grating 7.8 for reference point detection, this is mainly due to manufacturing process reasons, but the 8th
As shown in the figure, the fixed optical grating 7 for detecting the reference point is arranged at a constant interval L (for example, 50 mm) in the longitudinal direction of the index scale 4.
mm). Therefore, especially in long displacement detectors, there may be multiple fixed optical gratings 3 for reference point detection even though they are unnecessary, and if they get in the way, the gratings should be removed even if they are baked in. A process was necessary.

In addition, in connection with this, even in cases where reference signals are required at multiple positions, such as when setting displacement strokes in machine tools, etc., the fixing for reference point detection can be done in accordance with the displacement stroke to be set. There was a problem in that the interval between the optical gratings 3 could not be set.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to attach the fixed optical grating 3 for displacement detection to the first position of the grating forming surface 9 of the main scale where the fixed optical grating 3 for displacement detection is located.
It is an object of the present invention to provide a reflective optical displacement detector that can be easily installed on a second grating forming surface 9B opposite to the grating forming surface 9A.

[Means for Solving the Problems] Therefore, the present invention provides a main scale that is attached to one side of an object to be detected that is displaced relative to each other, and a main scale that is attached to the other side of the object to be detected and that is disposed along the main scale. an index scale that is movable back and forth; a movable optical grating for displacement detection and a movable optical grating for reference point detection formed on the grating-forming surface of the index scale; and a fixed position for displacement detection formed on the grating-forming surface of the main scale. It has an optical grating and a fixed optical grating for detecting a reference point, and a light emitting source and a light receiving element arranged on the index scale, and a light beam emitted from the light emitting source is reflected by the fixed optical grating for detecting displacement. , in a reflective optical displacement detector that detects relative displacement between objects to be detected by a displacement detection signal detected by the light receiving element after passing through the movable optical grating for displacement detection, the fixed reference point detection; The optical grating is
A second grating forming surface of the main scale opposite to the first grating forming surface on which the displacement detection fixed optical grating is located.
The first grating forming surface includes a reflecting surface that reflects the light beam emitted from the light emitting source and directs it toward the reference point detection fixed optical grating and the reference point detection movable optical grating. The above-mentioned problem is solved.

Further, the present invention is characterized in that the fixed optical grating for reference point detection is formed on a transparent plate separate from the main scale, and the transparent plate is adhered to the second grating forming surface of the main scale. shall be.

[Function] The fixed optical grating 3 for displacement detection is provided on the second grating forming surface 9B of the grating forming surface 9 of the main scale, which is opposite to the first grating forming surface 9A on which the fixed optical grating 3 for displacement detection is located. With the configuration of the present invention, the light beam emitted from the light emitting source 5 is
It is reflected by the reflecting surface 16 on the grating forming surface, passes through the fixed optical grating 8 for detecting a reference point, and immediately enters the movable optical grating 8 for detecting a reference point nearby, and the light is reflected between the main scale 4 and the index scale 2. A reference point signal with a sharp waveform is detected as the relative movement occurs.

The fixed optical grating 7 for detecting a reference point is manufactured separately from the main scale 4, and then aligned with the fixed optical grating 3 for displacement detection on the first grating forming surface of the main scale 4. At the same time, it is adhered to the second grating forming surface of the main scale 4.

[Embodiments] Preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a sectional view showing a first embodiment of a reflective optical displacement detector according to the present invention.

This first embodiment has a main scale 4 attached to one side of a detection target (not shown) that is displaced relative to each other, and a main scale 4 attached to the other side of the detection target and extending along the main scale 4. an index scale 2 capable of reciprocating, and a grating forming surface 13 of the index scale 2;
A movable optical grating 1 for displacement detection and a movable optical grating 8 for detecting a reference point are formed on the grating forming surface 9 of the main scale 4, and a fixed optical grating 3 for displacement detection and a fixed optical grating for detecting a reference point are formed on the grating forming surface 9 of the main scale 4. and a light emitting source 5 and a light receiving element 6 arranged on the index scale 2,
A light beam emitted from the light emitting source 5 is reflected by the fixed optical grating 3 for displacement detection, and after passing through the movable optical grating 1 for displacement detection, a signal 1 for displacement detection is detected by the light receiving element 6.
7, in which the fixed optical grating 7 for detecting a reference point is the fixed optical grating 7 for detecting displacement of the grating forming surface 9 of the main scale 4. 3 is located on the second grating forming surface 9B opposite to the first grating forming surface 9A, and the second grating forming surface 9B reflects the light rays irradiated from the light emission #5 and performs the reference inspection. A reflective surface 16 is provided that faces the output fixed optical grating 7 and the reference point detection movable optical grating 8.

The light receiving element 6 includes a displacement detection light receiving element 6A that receives a displacement detection signal and a reference point detection signal light receiving element 6B. Although not shown, there are a plurality of displacement detection light receiving elements 6A, and these detect a sine wave and a cosine wave, each having a waveform similar to that shown in FIG. 10(A) but with a phase shift of 90 degrees, It is used to determine the direction of relative movement.

The outputs of the displacement detection light receiving element 6A and the reference point detection signal light receiving element 6B are each amplified by a preamplifier 10A10B, then subjected to signal processing by a signal processing circuit 11, and the results are displayed on a display means 12. Since the configurations of the signal processing circuit 11 and the display means 12 are well known, their explanation will be omitted.

In this embodiment, the fixed optical grating 7 for detecting the reference point is
It is located in the second grating formation i9B on the side closer to the grating forming surface 13 of index 2. On the other hand, the fixed optical grating for displacement detection is located on the first grating forming surface 9B due to the requirement regarding resolution that it should be at a predetermined distance from the movable optical grating 1 for displacement detection.

The reflective surface 16 is made by evenly depositing chromium on the second grating forming surface 9A.

FIG. 2 is a perspective view of the main scale 4, and FIG. 3 is a sectional view of the main scale taken along line 1--1 in FIG.

The fixed optical grating 7 for detecting the reference point is a thin grating glass plate 20, which is a transparent plate separate from the main scale 4, and has chromium deposited on one surface thereof, and is shown in FIGS. 1 to 3. The other surface of the lattice glass thin plate 20 is bonded to the second lattice forming surface of the main scale 4 with an adhesive 19. The adhesive 19 is a transparent adhesive, and is thinly applied to the other surface of the lattice glass thin plate 20.

Note that it is not necessary to apply a thin layer over the other surface of the thin lattice glass plate 20, and the peripheral side of the thin lattice glass plate 20 may be adhered to the second lattice forming surface 9B. In this case, the adhesive 19 does not need to be transparent.

The other straight end of the thin grating glass plate 20 is bonded in such a way that the fixed optical grating 7 for detecting a reference point is aligned in the same direction as the grating arrangement direction of the fixed optical grating 3 for detecting displacement.

Next, the operation of this embodiment will be explained. A portion of the light emitted from the light emitting source 5 irradiates the fixed optical grating 3 for displacement detection and is reflected, and then passes through the movable optical grating 1 for displacement detection and is detected by the light receiving element 6A for displacement detection. . Further, the other part of the light beam from the light emitting source 5 is reflected by the reflecting surface 16 provided on the grating forming surface 9A, and is reflected by the fixed optical grating 7 for reference point detection.
After passing through the reference point detection movable optical grating 8, the light is detected by the reference point detection light receiving element 6B.

Since the fixed optical grating 7 for reference point detection and the movable optical grating 8 for reference point detection are arranged close to each other, the light rays diffracted by the fixed optical grating 7 for reference point detection are scattered in brightness and darkness. The incidence of light entering the optical grating 8 is reduced. That is,
For example, when considering a case where the fixed optical grating 7 for detection and the movable optical grating 8 for detecting a reference point overlap, it is necessary to take into account that light rays are diffracted in various directions by the fixed optical grating 7 for detecting a reference point. do not have. And fixed optical grating 7 for reference point detection.
When combined with the movable optical grating 8 for detecting a reference point, the degree of functioning as one optical grating rather than two optical gratings is enhanced. As a result, the waveform of the reference point detection signal 14 detected by the reference point detection light receiving element 6B becomes sharp.

Further, the fixed optical grating 7 for reference point detection is chromium-deposited on one surface of a thin grating glass plate 20 that is separate from the main scale 4 . With the fixed optical grating 7 for reference point detection on the thin grating glass plate 20 aligned in the same direction as the grating arrangement direction of the fixed optical grating 3 for displacement detection,
The other side of the lattice glass thin plate 20 is attached to the main scale 4.
It is adhered to the second lattice forming surface with an adhesive 19.

Next, the effects of this embodiment will be described.

As described above, since the waveform of the reference point detection signal 14 detected by the reference point detection light receiving element 6B becomes sharp, a highly accurate reference point detection signal can be obtained. As a result, even if the displacement detection optical grating 3 is located on the side 9A far from the grating forming surface 13 of the index scale 2 due to the resolution to be set, the reflective optical displacement detector has a highly accurate reference point detection signal. can be provided.

In addition, the fixed optical grating 7 for reference point detection is attached to the main scale 4.
The fixed optical grating 7 for detecting the reference point can be easily provided by forming it on one surface of a thin grating glass plate 20 that is separate from the grating glass plate 20 and then bonding the thin grating glass plate 20 to the grating forming surface 9B. In addition, as shown in FIG. 4, a plurality of fixed optical gratings 7 for detecting reference points are deposited with chromium on one surface of the thin grating glass plate 20 at arbitrary intervals, and are adhered to the grating forming surface 9B. A plurality of fixed optical gratings for detecting reference points can be easily provided at intervals of . the result,
When a reference signal is required at multiple positions, such as when setting a displacement stroke in a machine tool, etc., the interval of the fixed optical grating 3 for detecting the reference point is set in accordance with the set displacement stroke. can be easily done.

Next, another embodiment according to the present invention will be described using FIG. 5. In this embodiment, the length of the displacement detection movable optical grating 1 in the direction perpendicular to the grating arrangement direction is longer than that in the embodiment shown in FIG. Other points are the same as the embodiment shown in FIG.

Also in this embodiment, the fixed optical grating 7 for detecting the reference point is
In this case, the light emitting source 5 is one in which chromium is deposited on one side of a grid glass thin plate 20 that is separate from the main scale 4.
A part of the light beam emitted from the displacement detection movable optical grating 1 passes through the displacement detection fixed optical grating 3, and after being reflected by the displacement detection fixed optical grating 3, the light beam passes through the displacement detection variable optical grating 1. It is detected by the displacement detection light receiving element 6A.

By adopting such a configuration, the present applicant is able to
3-24128 etc., the reflective optical displacement detector is configured using so-called three optical gratings, and the fixed optical grating 3 for displacement detection and the fixed optical grating 7 for reference point detection are mutually connected to each other on the main scale. 4 can be provided in opposite configurations. As a result, it is possible to provide a reflective optical displacement detector configured using so-called three optical gratings that can output a highly accurate reference point detection signal.

Although the present invention has been described above with reference to preferred embodiments, the present invention is not limited to these embodiments, and various improvements and design changes can be made without departing from the gist of the present invention. Of course.

For example, in the case where the fixed optical grating 7 for displacement detection is first etched into a grating glass plate 20 separate from the main scale 4 because it is judged that it is not advantageous in the manufacturing process, the fixed optical grating 7 for displacement detection is etched directly. It goes without saying that the case where it is formed on the second grating forming surface 9B also belongs to the present invention.

Further, the degree of coherence of the light from the light emitting source 5 does not matter.

Therefore, it goes without saying that the light emitting source 5 may be a so-called LED or a laser diode.

Furthermore, the plurality of fixed optical gratings for detecting reference points shown in FIG.
A plurality of grating glass plates 20 each having a single fixed optical grating 7 for detecting a reference point may be provided at required positions.

Further, the reflective surface 16 is not limited to the case where chromium is vapor-deposited on the second grating forming surface 9B, but may also be a grating similar to the fixed optical grating 5 for displacement detection, or the fixed optical grating 3 for displacement detection itself. It doesn't really matter if there is. In any case, it is sufficient that the intensity distribution of the light beam reflected by the reflecting surface 16 is uniform on average in the fixed optical grating 20 for detecting the reference point.

Further, the thicknesses of the main scale 4, the grating glass thin plate 20, the reflective surface 16, etc. shown in FIG. 5 are shown schematically, and therefore the illustrated size relationships are not essential.

[Effects of the Invention] As described above, the present invention provides a fixed optical grating for displacement detection on the first grating forming surface of the main scale where the fixed optical grating for displacement detection is located, and the second optical grating on the opposite side from the grating forming surface. Since it is configured to be provided on the grating forming surface, it is possible to provide a reflective optical displacement detector having a highly accurate reference point detection signal.

In addition, the fixed optical grating for reference point detection is the main scale 4.
Since it is formed on a separate transparent plate 20 and the transparent plate 20 is adhered to the second grating forming surface of the main scale, the fixed optical grating for detecting the reference point can be easily provided at any position.

[Brief explanation of drawings]

FIG. 1 is a sectional view of one embodiment of the present invention, and FIG. 2 is a perspective view of the main scale in FIG. 1. FIG. 3 is a sectional view of the main scale shown in FIG. 2. FIG. 4 is a perspective view of the main scale showing a case where there are a plurality of fixed optical gratings for detecting reference points. FIG. 5 is a sectional view of a second embodiment of the present invention. FIG. 6 is a plan view showing the optical grating surface of the index scale. FIG. 7 is a sectional view of a conventional reflective optical displacement detector. FIG. 8 is a plan view showing an optical grating surface of a conventional main scale having a plurality of fixed optical gratings for detecting reference points. FIG. 9 is a plan view showing the optical grating surface of a conventional main scale. FIG. 10 is a diagram showing the waveforms of the displacement detection signal and the reference point detection signal. 2 ・ 3 ・ 4 ・ 5 ・ 7 ・ 8 ・ 9 ・ AB 16 ・ 20 ・ Index scale Fixed optical grating for displacement detection Main scale Fixed optical grating for light source reference point detection Movable optical grating for reference point detection 1 lattice forming surface 2nd lattice forming surface Opposite oblique lattice glass thin plate

Claims (2)

[Claims] (1) A main scale attached to one side of an object to be detected that is displaced relative to each other, an index scale that is attached to the other side of the object to be detected and movable back and forth along the main scale, and the index scale. a movable optical grating for displacement detection and a movable optical grating for reference point detection formed on the grating forming surface of the main scale; a fixed optical grating for displacement detection and a fixed optical grating for detecting the reference point formed on the grating forming surface of the main scale; , a light emitting source and a light receiving element arranged on the index scale, the light beam emitted from the light emitting source is reflected by the fixed optical grating for displacement detection, and passes through the movable optical grating for displacement detection. In a reflective optical displacement detector that detects relative displacement between objects to be detected using a displacement detection signal detected by the light receiving element, the fixed optical grating for reference point detection is arranged on the grating forming surface of the main scale. The second grating forming surface is located on the opposite side of the first grating forming surface on which the fixed optical grating for displacement detection is located, and the first grating forming surface is provided with a second grating forming surface that reflects the light beam emitted from the light emitting source. 1. A reflective optical displacement detector, characterized in that there is a reflective surface facing the fixed optical grating for detecting a reference point and the movable optical grating for detecting a reference point. (2) The fixed optical grating for reference point detection is formed on a transparent plate separate from the main scale, and the transparent plate is adhered to the second grating forming surface of the main scale. The reflective optical displacement detector according to item (1).