JP2001174291A - Optical encoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical encoder, having a reference point detection function and absolute position detection function and capable of exactly detecting the displacement of a scale in the x-direction, without being affected by the gap change between the scale and a head. SOLUTION: A first photodetector 3 has a plurality of photodetecting areas formed at intervals of approximately np11(z11+z21)/z11, where z11 is the optical distance along the main axis of the first light beam from the light beam emitting surface of the interferable light source 1 to the plane where the first scale pattern 21 is formed in the direction of space period of diffraction interference pattern formed on the photodetection surface, z21 is the optical distance from the surface where the first scale pattern is formed to the first photodetector along the main axis of the first light beam, p11 is the space period of the first scale pattern, and (n) is a natural number. The second light beam is received with the second photodetector 3', after reflecting or diffracting and transmitting with the second scale pattern 22.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an optical encoder, and more particularly, to an optical encoder applicable as an optical displacement sensor for detecting a displacement of a precision mechanism.

[0002]

2. Description of the Related Art As a prior art relating to a configuration of an optical encoder applicable as an optical displacement sensor, first, a first conventional example by the present inventor (Japanese Patent Application No. 11-6411).
Will be described.

FIGS. 9 (a) and 9 (b) show the configuration of an optical encoder according to this conventional example (Japanese Patent Application No. 11-6411).

[0004] That is, this optical encoder is shown in FIG.
(A) and (b), a laser beam emitted from a semiconductor laser 1 (or a surface emitting laser 10), which is a coherent light source, is radiated to a transmission type diffraction grating scale 2 and is generated by this. The specific part of the diffraction interference pattern is configured to be detected by either the photodetector 3 or the photodetector 33.

In the following, the coherent light source is also simply referred to as a light source.

In the case where the semiconductor laser 1 as a coherent light source and the photodetector 3 are arranged on the same side with respect to the scale 2, as shown in FIG.
The main axis 5 of the light beam emitted from the surface emitting laser 10 (or the surface emitting laser 10) is inclined at an angle φ with respect to the perpendicular to the scale surface.

Next, the operation of the optical encoder which can be applied as the optical displacement sensor configured as described above will be described.

[0008] As shown in FIG. 9A, each configuration parameter is defined as follows.

Z1: the length measured on the principal axis of the light beam from the light source to the surface on which the diffraction grating is formed on the scale; z2: the light receiving surface of the photodetector from the surface on which the diffraction grating is formed on the scale Length measured on the principal axis of the light beam, p1: pitch of the diffraction grating on the scale, p2: pitch of the diffraction interference pattern on the light receiving surface of the photodetector, θx: pitch of the diffraction grating on the scale The divergence angle of the light beam of the light source with respect to the direction, θy: the divergence angle of the light beam of the light source in a direction perpendicular to the above θx, where the divergence angle of the light beam is に 対 し て of the direction in which the light beam intensity peaks. The angle between a pair of boundary lines 6 is shown.

[0010] The "pitch of the diffraction grating on the scale" means a spatial period of a pattern formed on the scale and having modulated optical characteristics.

[0011] The "pitch of the diffraction interference pattern on the light receiving surface of the photodetector" means a spatial period of the intensity distribution of the diffraction interference pattern generated on the light receiving surface.

According to the theory of light diffraction, when z1 and z2 have a specific relation satisfying the relation shown in the following equation (1), an intensity pattern similar to the diffraction grating pattern of the scale is generated by the photodetector. Generated on the light receiving surface.

(1 / z1) + (1 / z2) = λ / k (p1) ² (1) where λ is the wavelength of the light beam emitted from the light source, and k is an integer.

At this time, the pitch p2 of the diffraction interference pattern on the light receiving surface can be expressed by the following equation (2) using other constituent parameters.

P2 = p1 (z1 + z2) / z1 (2) When the scale 2 is displaced in the pitch direction of the diffraction grating with respect to the light source 1, the intensity distribution of the diffraction interference pattern is scaled while maintaining the same spatial period. 2 in the direction of displacement.

Therefore, if the spatial period p20 of the light receiving area 4 of the photodetector 3 is set to the same value as p2, a periodic intensity signal is obtained from the photodetector 3 every time the scale moves by p1 in the pitch direction. Therefore, the displacement amount of the scale 2 in the pitch direction can be detected.

Here, as shown in FIGS. 9A and 9B, the light source 1 and the photodetector 3 are arranged on the same side of the scale 2 so that z1 = z2. Even if the spatial gap between the scale 2 and the light source 1 changes, the pitch of the diffraction interference pattern on the light receiving surface does not change from the equation (2).

Further, in practical use, the light receiving elements of the photodetector having a spatial period P20 are shifted at intervals of P20 / 4,
Four groups of light receiving elements arranged alternately are formed, and outputs from the light receiving elements of these groups are respectively denoted by Va, Vb, Va ', V
b ', and Va-Va' and Vb-Vb 'are used as so-called A-phase (sine wave) and B-phase (cosine wave) outputs of the encoder.

In Japanese Patent Application No. 11-6411, V
Since the intensity of the laser beam can be monitored by calculating the arithmetic sum of each output of a, Vb, Va ', and Vb', the feedback is performed so that the intensity change of the laser beam due to environmental change or aging change is constant. Or the A-phase (or B-phase) output signal and Va, Vb, V
It is possible to correct to some extent the effect of changes in the intensity of the laser beam due to environmental changes or changes over time by performing appropriate calculations with the signals of the arithmetic sums of the outputs a 'and Vb'. It is.

Next, a second conventional example (Japanese Patent Application No. 11-6411) by the present inventor will be described as a second conventional technique.

FIGS. 10A and 10B show the configuration of an optical encoder according to the second conventional example (Japanese Patent Application No. 11-6411).

In this optical encoder, as shown in FIGS. 10A and 10B, the main axis 5 of the laser beam emitted from the semiconductor laser 1 (or the surface emitting laser 10), which is a coherent light source, is on the scale surface. The direction of inclination with respect to the vertical line is different.

That is, in the second conventional example, FIG.
As shown in (b), the main beam axis 5 of the optical beam and the pitch direction of the scale are maintained perpendicular to each other.
In the conventional example, as shown in FIG. 9B, the main axis 5 of the light beam and the pattern direction of the scale are held perpendicular to each other.

In the first conventional example, z1 and z2 are (1) due to an initial arrangement error at the time of assembling an optical encoder applicable as an optical displacement sensor and mechanical fluctuation due to displacement of a scale. Let us consider a case where the relation deviates from the relational expression expressed by the expression.

As an example, consider the case where the photodetector uses a photodetector 3 arranged on the same side of the scale as the light source.

For example, the light source and the light receiving surface are fixed,
As shown in FIG. 9A, when each of them and the scale are shifted from the position of the scale 2 to the position of the scale 22 by Δz, that is, when the gap between the sensor head and the scale fluctuates, FIG. In the light intensity distribution of (a), the curve 13 changes as shown by the curve 14.

That is, not only is the diffraction interference pattern on the light receiving surface slightly disturbed, but also the output of the encoder changes because the position of the diffraction interference pattern on the light receiving surface moves in the x direction.

Therefore, in the first conventional example, an error occurs even when an attempt is made to measure the displacement of the scale in the x direction due to the influence of the gap variation between the scale and the head.

On the other hand, in the second conventional example, the inclination direction of the light beam is different, and the main axis 5 of the light beam and the pitch direction (the x direction in the figure) of the scale are held perpendicular to each other. As shown in the light intensity distribution diagram of FIG. 7A, even if the gap between the sensor head and the scale fluctuates, the light intensity distribution changes from the curve 13 to the curve 14.

In this case, the diffraction interference pattern on the light receiving surface is only slightly disturbed, and the position of the diffraction interference pattern on the light receiving surface does not move in the x direction.

Therefore, in the second conventional example, the displacement of the scale in the x direction can be accurately detected with little influence from the fluctuation of the gap between the scale and the head.

[0032]

By irradiating a plurality of tracks each having a different scale pattern with a laser beam, a reference point detecting function and an absolute position detecting function can be realized. In the encoders of the first and second conventional examples, no method has been proposed for providing a plurality of scale patterns and adding a reference point detecting function or an absolute position detecting function.

In order to provide these functions while avoiding the problem of the influence of the gap between the scale and the head in the conventional example, a special configuration is required as described in the solution according to the present invention.

Here, a configuration in which a plurality of tracks having different scale patterns are irradiated with a laser beam will be abbreviated to a “multi-beam & track configuration”.

The simplest form of extending the above-described conventional configuration to a multi-beam & track configuration is as shown in FIG. 11A and FIG. 11B.

FIG. 11A shows a case where one of the multi-tracks is formed into a single pattern for detecting a reference position.

FIG. 11B shows a case where one of the multi-tracks is a diffraction pattern formed at a different pitch from the pattern of the other track, and the minimum of both pitches is obtained by the principle of the vernier encoder. Absolute value measurement can be performed in a common multiple scale movement range.

However, in these configurations, as described above, even if an attempt is made to measure the displacement of the scale in the x direction, the diffraction interference pattern moves in the x direction on the light receiving surface due to the influence of the gap between the scale and the head. , The problem that an error occurs in the displacement measurement in the x direction is inevitable.

The second problem of the conventional example is that it is necessary to arrange the laser light emitting surface of the light source, the scale surface, and the light receiving surface of the photodetector at an angle, so that it can be applied as an optical displacement sensor. This makes it difficult to assemble the optical encoder.

In the actual manufacturing process, die bonding of the semiconductor laser 1 (or the surface emitting laser 10) to the inclined substrate surface under a microscope and wire bonding of wiring to the inclined semiconductor laser electrode are required under a microscope. .

In these assembling steps, a jig for correcting the inclination is required. Further, in order to observe the inclined part with a microscope, it is necessary to raise and lower the focal point of the microscope. And the assembly cost is high.

The third problem of the conventional example is that, in practical use, the calculated sum of each of the outputs Va, Vb, Va 'and Vb' used as a monitor for detecting the intensity of laser light slightly changes when the scale moves. However, fluctuations occur due to scale movement during feedback and correction of the light source output.

Although the exact reason is unknown, it is considered that the interference pattern on the light receiving surface slightly deviates from the theoretical shape.

The problems to be solved in the present invention are summarized as follows.

1) To provide an encoder having a reference point detecting function and an absolute position detecting function and capable of accurately detecting the displacement of the scale in the x direction without being substantially affected by the gap fluctuation between the scale and the head.

2) By a mounting mode that does not use an inclined substrate,
Reduce assembly costs.

3) To provide a configuration and means capable of stabilizing the encoder signal output even when the surrounding environment changes.

The present invention has been made in view of the above circumstances, and has a reference point detecting function and an absolute position detecting function. It has a structure and means that can accurately detect the displacement of the encoder and reduce the assembly cost and stabilize the encoder signal output even when the surrounding environment changes by the mounting form that does not use the inclined substrate. It is an object of the present invention to provide an optical encoder applicable as an optical displacement sensor.

[0049]

According to the present invention, in order to solve the above-mentioned problems, (1) a coherent light source and a first light beam for reflecting, diffracting, and transmitting a light beam from the coherent light source.
The scale pattern and the second scale pattern are formed and movably supported scale, provided between the coherent light source and the scale, a plurality of light beams emitted from the coherent light source A beam splitting optical element for splitting the beam into a beam; and first and second photodetectors for detecting the light beam split by the beam splitting optical element, wherein the first photodetector includes the beam splitter. The first light beam split by the optical element is reflected, diffracted, or transmitted by the first scale pattern so that the light beam of the coherent light source is directed in the spatial periodic direction of the diffraction interference pattern formed on the light receiving surface. The optical distance along the main axis of the first light beam from the exit surface to the surface on which the first scale pattern is formed is z11, and the first scale pattern is formed. When the optical distance along the main axis of the first light beam from the surface to the first photodetector along the main axis is z21, the spatial period of the first scale pattern is p11, and n is a natural number, approximately np11 (Z11 + z21) / z
Having a plurality of light receiving areas formed at intervals of 11,
A second light beam of the plurality of light beams split by the beam splitting optical element is reflected, diffracted, or transmitted by the second scale pattern and received by the second photodetector. Is provided.

(Corresponding Embodiments of the Invention) Embodiments of the present invention correspond to the first to seventh embodiments.

Here, the "coherent light source" has been described centering on the vertical cavity surface emitting laser 10 in these embodiments, but the general semiconductor laser 1 and other coherent light beams are used. It includes a light source that can emit light.

The "optical distance" means a distance measured with reference to the wavelength of the light beam.

For example, when the refractive index is constant in the area where the distance is measured, it indicates the geometrically measured distance, but when the refractive index is different, it is refracted along the path to be measured to the geometric distance. This means that the contribution of the change in the light wavelength due to the rate distribution is considered.

The term "scale pattern of a predetermined period for generating a diffraction interference pattern" means a diffraction grating on which a periodic modulation pattern of optical characteristics such as amplitude or phase is formed, and generates a diffraction interference pattern on a light receiving surface. All types of diffraction gratings such as reflective diffraction gratings and transmission diffraction gratings.

Further, the photodetector is substantially np11 (z11 + z21) / z1 in the spatial period direction of the diffraction interference pattern.
"Having a plurality of light-receiving areas formed at intervals of 1 and receiving a predetermined portion of the diffraction interference pattern" means "np1 substantially in the pitch direction of the diffraction interference pattern on the light-receiving surface.
This means a light receiving element group configured to add and output the outputs of a plurality of light receiving areas formed at an interval of 1 (z11 + z21) / z11, and also when a plurality of light receiving element groups are formed. included.

It should be noted that the value of n that determines the interval between the light receiving areas does not necessarily need to be constant over the entire area.

Numerical conditions np11 in "a plurality of light receiving areas formed at intervals of np11 (z11 + z21) / z11 in the pitch direction of the diffraction interference pattern"
Regarding (z11 + z21) / z11, the sensor functions as a sensor even if it deviates slightly from this. Therefore, in implementing the present invention, the numerical condition np11 (z11 + z21) / z
Even a deviation of about ± 30% from 11 is considered to be included in the scope of the present invention.

(Effects) The light beam emitted from the coherent light source is split into a plurality of light beams by a beam splitting optical element, of which the first light beam is applied to the first scale pattern and has a spatial period p2. = P11 (z11 + z2
1) A diffraction interference pattern having / z11 is generated on the light receiving surface of the first photodetector.

Hereinafter, the case where n = 1 will be described for simplicity.

The light-receiving area of the first photodetector is p21 = np2 = np11 (z11 + z2) in the pitch direction of the diffraction grating.
1) Since they are formed at an interval of / z11, each of these light receiving areas detects only the same specific phase portion of the diffraction interference pattern on the light receiving surface.

When the scale is displaced by x1 in the pitch direction of the diffraction grating, the diffraction interference pattern shows
Since the displacement is made by x2 = x1 (z11 + z21) / z11 in the same direction, the scale becomes p1 in the pitch direction of the diffraction grating.
For each displacement of one, an output signal varying with periodic intensity is obtained from the first photodetector.

On the other hand, the second light beam split by the beam splitting optical element is applied to the second scale pattern, and receives the light beam reflected, diffracted, or transmitted by the second scale pattern. The light detector detects the intensity.

By combining the first and second scale patterns as shown in Supplementary Notes 2, 3, and 4 described below, the function of monitoring the light output of the coherent light source, the function of detecting the absolute position,
A reference position (or origin) detection function can be realized.

Further, two or more of these additional functions can be simultaneously realized by increasing the number of beam branches and the number of photodetectors according to the number of scale patterns.

Further, since the coherent light source, the scale surface, and the light receiving surface can all be arranged in parallel, a mounting form that does not use an inclined substrate is possible, and the assembly cost can be greatly reduced.

According to the present invention, in order to solve the above-mentioned problems, (2) a first light beam bending element provided between the scale and the first photodetector; And a second photodetector provided between
And the first and second light beams transmitted or reflected and diffracted through the first and second scale patterns respectively form the first and second light beam bending elements. The optical encoder according to (1), wherein the optical encoder passes through and is respectively received by the first and second photodetectors.

(Corresponding Embodiment of the Invention) Embodiments relating to the present invention correspond to the fourth to sixth embodiments.

In this configuration, the first and second light beam bending elements may be integrated with or separate from the beam splitting optical element, respectively.

(Functions and Effects) In this section, the functions and effects similar to those of the invention (1) will be omitted.

The first and second light beams split by the first beam splitting optical element are the first and second light beams, respectively.
After irradiating the first and second light beam bending elements 71 and 72, the optical axis is bent again, and each is guided to the first and second photodetectors. I will

If the angles at which the first beam splitting optical element and the first and second light beam bending elements bend the optical axis are set to be the same, the main axes of the first and second light beams are scaled. It is symmetrical with respect to a perpendicular drawn from a point where the plane intersects.

As described in the description of the conventional example, if the light source and the photodetector are arranged on the same side with respect to the scale 2 and z11 = z21 and z21 = z22, the scale 2 and the light source Equation (2) shows that the pitch of the diffraction interference pattern on the light receiving surface does not change even if the spatial gap changes.

Therefore, according to the structure of the present invention, the optical distance from the light source to the scale surface measured on the main axis of the first and second light beams and the distance from the scale to the light receiving element can be determined with a very simple design. There is an advantage that the optical distance to reach can be the same.

When the height of the light receiving surface and the virtual point light source of the light source are different, an optical element for correcting the height may be inserted into the optical path of the optical axis.

According to the present invention, in order to solve the above-mentioned problems, (3) a coherent light source, a first scale pattern and a second scale pattern for reflecting, diffracting, and transmitting a light beam from the coherent light source are provided. A scale formed movably supported with a scale pattern formed thereon, and a beam splitter provided between the coherent light source and the scale, for splitting a light beam emitted from the coherent light source into a plurality of beams. An optical element, and first and second photodetectors for detecting a light beam split by the beam splitting optical element, wherein the first photodetector is split by the beam splitting optical element The light beam of the coherent light source is directed in the spatial period direction of the diffraction interference pattern formed on the light receiving surface by the first light beam being reflected, diffracted, or transmitted by the first scale pattern. The optical distance along the main axis of the first light beam from the beam exit surface to the surface on which the first scale pattern is formed is z11, and the first light from the surface on which the first scale pattern is formed is the first light beam. When the optical distance along the main axis of the first light beam to the detector is z21, the spatial period of the first scale pattern is p11, and n is a natural number, the interval is approximately np11 (z11 + z21) / z11. Has a plurality of light receiving areas formed in, the second light beam of the plurality of light beams branched by the beam branching optical element, without irradiating the scale pattern,
An optical encoder is provided, wherein the optical encoder is received by the second photodetector.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the seventh embodiment.

(Operation and Effect) In this section, the same operation and effect as (1) or (2) will be omitted.

The second light beam among the light beams split by the beam splitting optical element 7 is directly detected by the second photodetector without being irradiated on the scale.

Therefore, the function of monitoring the intensity of the light output of the coherent light source can be realized.

Therefore, even if the surrounding environment of the optical encoder applicable as the optical displacement sensor changes, the second
By feeding back the output of the light intensity detecting means comprising the photodetector to the driving means of the laser light source, it is possible to stabilize the light output, thereby realizing stable sensing against such a state change. It becomes possible.

As compared with the forms of Supplementary Notes 2 and 6, which will be described later, a scale with a uniform reflectance or transmittance is not required, so that the scale cost is reduced and the scale of the scale is reduced when stabilizing the light output. There is an advantage that it does not need to be affected by defects and dust adhesion.

[0082]

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

(First Embodiment) FIG. 1 and FIG.
1 shows a configuration of an optical displacement sensor applied as an optical encoder according to a first embodiment of the present invention.

Here, FIG. 1 (a) and FIG. 2 (a)
FIG. 3 is a plan view of the scale 2 in the first embodiment as viewed in the −z direction.

FIG. 1B shows the yz of this embodiment.
It is sectional drawing in a plane.

FIG. 2B is a diagram showing the embodiment of FIG.
FIG. 3A is a cross-sectional view in the xz plane with respect to the a1-a1 ′ cross section in FIG.

FIG. 2C is a cross-sectional view in the xz plane with respect to the cross section a2-a2 'in FIG. 2A.

The first embodiment of the present invention and its modifications are configured as follows.

As shown in FIG. 1B, the laser beam emitted from the surface emitting laser 10 as a coherent light source is
The light is split into at least two light beams by a diffraction grating 7 used as a beam splitting optical element.

In FIG. 1B, the main axis of the first light beam immediately after branching is indicated by a solid line 5, and the main axis of the second light beam immediately after branching is indicated by a solid line 5 '.

The first and second light beams are irradiated on the first and second scale patterns 21 and 22 on the scale 2, respectively, and the main axes 15 and 1 of the light beams are respectively irradiated.
It is folded back along the line indicated by 5 'and is received by the first photodetectors 3 and 3' (hereinafter, this case is referred to as a reflection type configuration) or the main axis 25 of the light beam and The light passes through the scale 2 along 25 'and is received by the second photodetectors 33 and 33' (hereinafter, this case is referred to as a transmission type configuration).

Here, in the reflection type configuration according to the present embodiment, the first scale pattern 21 is a pattern in which the reflectance in the x direction periodically changes at p11, and the second scale pattern 21 The pattern 22 has a uniform reflectance pattern.

In the transmission type configuration, the first scale pattern 21 is a pattern in which the transmittance in the x direction periodically changes at p11, and the second scale pattern 22 has a uniform transmittance. A rate pattern is formed.

Then, as shown in FIG. 1B, the photodetector 3 is adhered to the case 11.
The surface emitting laser 10 is attached to the surface of the laser light source.

A transparent cover 61 for sealing an optical displacement sensor applied as an optical encoder according to the first embodiment and fixing a diffraction grating is arranged on the upper surface of a case 11.

Further, as shown in FIG. 2B, the first photodetector 3 or 33 has a light receiving area group having a rectangular light receiving area having a period of p21.

Here, the period p21 is substantially equal to np11 (z1
1 + z21) / z11.

However, in this embodiment, n = 1.

A solid line 6 indicates a boundary of the spread of the light beam.

Next, the operation of the modified example of the first embodiment of the present invention will be described.

The interference pattern generated by the first light beam generates a diffraction interference pattern having a period of p21 in the x direction on the light receiving surface of the first photodetector 3 or 33.

Normally, this light receiving area group is shown in FIG.
As shown in the figure, four groups are formed so as to be staggered at an interval of p21 / 4.
A-phase, B-phase, A- phase, B
A phase signal is output.

That is, when the scale 2 moves by p11 in the x direction, the phase becomes 1/4 from the A phase, the B phase, the A phase, and the B phase.
Different periodic outputs are obtained for each period.

On the other hand, since the second scale pattern has a uniform optical pattern, the output of the second photodetector 3 'or 33' is proportional to the output of the light beam.

If the output of the light beam fluctuates due to environmental changes, changes over time, etc., the second photodetector 3 'or 3
The output of 3 'is fed back to the driving device of the coherent light sources 1 and 10 to suppress the output fluctuation, or the encoder output signal is corrected by using the output of the second photodetector 3' or 33 '. By doing so, stable displacement sensing can always be realized.

The optical distances of the principal axes of the light beams from the light sources 1 and 10 to the scale 2 and the principal axes 15 and 15 ′ of the light beams from the scale 2 to the first photodetector 3 or 33.
It is desirable to set the thickness t of the diffraction grating 7 in order to optimally adjust the optical distance (or 25, 25 ') (hereinafter, this is referred to as optical distance adjustment).

Incidentally, each configuration of the first embodiment of the present invention can of course be variously modified and changed.

As the coherent light source, an example of the surface emitting laser 10 has been described, but a normal edge emitting semiconductor laser or another coherent light source may be used.

Although the optical beam splitting optical element has been described as an example of the diffraction grating 7, another optical element such as a prism or a half mirror may be used.

The above-mentioned optical distance adjustment is not limited to the case where the thickness is adjusted by the thickness of the diffraction grating, but an optical medium having a different refractive index is inserted on the optical axis, or the height of the light source and the photodetector is adjusted. May be attached.

(Second Embodiment) FIG. 3 shows a configuration of an optical displacement sensor applied as an optical encoder according to a second embodiment of the present invention.

The cross-sectional structure in the yz plane in the present embodiment is the same as that in FIG. 1B, and the behavior of the main axis of the light beam from the coherent light source 1 to the first photodetector 3 is a ray-optical behavior. Are the same as in the first embodiment.

Further, the first beam passes through the scale 2 and
The mode and operation of reaching the first photodetector 3 and obtaining an encoder signal from the photodetector 3 are the same as those of the first embodiment.

Therefore, in the present embodiment, only the differences due to the difference between the second scale pattern and the first embodiment will be described.

FIG. 3A is a plan view of the scale 2 in the first embodiment as viewed in the −z direction.

FIG. 3B is a sectional view in the xz plane with respect to the section taken along line a1-a1 'in FIG. 3A.

FIG. 3C is a cross-sectional view in the xz plane with respect to the cross section a2-a2 'in FIG. 3A.

[0118] The second embodiment of the present invention is configured as follows.

Pitch p1 of second scale pattern 22
2 is formed so as to be different from the pitch p11 of the first scale pattern 21.

Correspondingly, as shown in FIG. 3C, the sectional structure in the xz plane with respect to the a2-a2 'section is
The light receiving area is formed in a strip shape, and this pitch becomes p22 corresponding to the pitch of the second scale pattern, and the shift of the light receiving area group becomes p22 / 4.

Here, the pitch p22 of the light receiving area group is
It is approximately p12 (z12 + z22) / z12.

Next, the operation of the second embodiment of the present invention will be described.

The second light beam is received by the second photodetector 3 'by the same function as the first light beam forms a diffraction interference pattern on the light receiving surface of the first photodetector 3. A diffraction interference pattern is formed on the surface, and scale 2 is set to p1 in the x direction.
For every two movements, a periodic output signal is obtained from the second photodetector 3 '.

Accordingly, the intensity of the output from the first photodetector 3 and the output from the second photodetector 3 'varies with the period of the displacements p11 and p12 of the scale 2 in the pitch direction. Based on the principle of the near encoder, p11 and p1
An absolute position detection function can be added in the scale movement range of the least common multiple of two.

It is to be noted that each configuration of the second embodiment of the present invention can of course be variously modified and changed.

For example, the number of branches of the light beam may be two or more, and a scale pattern and a photodetector corresponding to each of them may be formed.

(Third Embodiment) FIG. 4 shows a configuration of an optical displacement sensor applied as an optical encoder according to a third embodiment of the present invention.

The cross-sectional structure in the yz plane in the present embodiment is the same as that in FIG. 1B, and the behavior of the main axis of the light beam from the coherent light source 1 to the photodetector 3 is the same as that of the light beam. This is the same as the first embodiment.

Also, the first beam passes through the scale 2 and
The mode and operation of reaching the first photodetector 3 and obtaining an encoder signal from the photodetector 3 are the same as those of the first embodiment.

Accordingly, in the present embodiment, only the differences due to the difference between the second scale pattern 22 and the first embodiment will be described.

FIG. 4A is a plan view of the scale 2 in the first embodiment as viewed in the −z direction.

FIG. 4B is a sectional view in the xz plane with respect to the section taken along line a1-a1 'in FIG.

FIG. 4C is a cross-sectional view in the xz plane with respect to the cross section a2-a2 'in FIG. 4A.

The third embodiment of the present invention is configured as follows.

The second scale pattern 22 is formed of an optical pattern having a period pz of a specific reference position.

Correspondingly, as shown in FIG. 4C, the cross-sectional structure in the xz plane with respect to the a2-a2 'cross section is the same as that of the first embodiment.

Next, the operation of the third embodiment of the present invention will be described.

When the second light beam is irradiated where the reflectance or transmittance of the second scale pattern 22 changes, the output from the second photodetector 3 'changes.
If a portion where the reflectance or transmittance of the second scale pattern 22 changes is formed at a desired position in advance,
A reference position detection function can be added.

Incidentally, each configuration of the third embodiment of the present invention can of course be variously modified and changed.

As the second scale pattern 22, only one single pattern may be formed, or the second scale pattern 22 may be formed at reference position intervals according to the application.

The number of branches of the light beam may be two or more, and a scale pattern and a photodetector corresponding to each of them may be formed.

(Fourth, Fifth, Sixth Embodiments) FIG.
Shows the configuration of an optical displacement sensor applied as an optical encoder according to the fourth, fifth, and sixth embodiments of the present invention.

That is, with respect to a plan view of the scale 2 viewed in the −z direction, diagrams corresponding to the fourth, fifth, and sixth embodiments are shown in FIGS. 5A and 5B, respectively. , (C)
Is shown in

The sectional structure in the yz plane is the fourth, fifth,
The same applies to the sixth embodiment, and is shown in FIG.

On the other hand, as for sectional views in the xz plane, figures corresponding to the fourth, fifth and sixth embodiments are respectively shown in FIGS. 2B and 2C and FIG. ) And (c), and those shown in FIGS. 4 (b) and (c).

The fourth, fifth, and sixth embodiments of the present invention are configured as follows.

In the fourth, fifth, and sixth embodiments, the first scale pattern 21 and the second scale pattern 22, the first photodetector 3 or 33, and the second light The detectors 3 'or 33' are respectively
This is the same as the first, second, and third embodiments.

In FIG. 5D, a light beam emitted from a surface emitting laser 10 as a coherent light source is split into at least two beams by a diffraction grating 7 used as a first beam splitting optical element. .

In FIG. 5D, the main axis of the first light beam immediately after the branch is indicated by a solid line 5, and the main axis of the second light beam immediately after the branch is indicated by a solid line 5 '.

The first and second light beams are respectively applied to the first and second scale patterns 21 and 2 on the scale 2.
2 and folded back along the lines indicated by the main axes 15 and 15 'of the light beam, each of which is a diffraction grating 71, 72 used as a first and second light beam bending element.
The optical axis is bent, and the light is received by the first photodetectors 3 and 3 '(hereinafter, this case is referred to as a reflection type configuration).
Or transmitted through the scale 2 along the principal axes 25 and 25 'of the light beam, each having its optical axis bent by a diffraction grating 77 used as first and second light beam bending elements, and Are received by the photodetectors 33 and 33 '(hereinafter, this case is referred to as a transmission type configuration).

Next, the operation of the fourth, fifth, and sixth embodiments of the present invention will be described.

The operation of the fourth, fifth, and sixth embodiments is as follows.
This is the same as the first, second, and third embodiments, respectively, except that the light beam is bent by the diffraction grating 77 used as the first and second light beam bending elements.

Here, if the bitches pg of the diffraction gratings 7 and 77 used as the first beam splitting optical element and the first and second light beam bending elements are all the same, the light beam immediately after being emitted from the light source 1 is obtained. Main shaft and photodetector 3
The main axes of the light beams incident on the light beams become parallel.

In this case, in FIG. 5D, the lines b1-b1 'and b2-b2' perpendicular to the scale surface from the point where the first and second light beams intersect with the scale 2 Since the main axis of the light beam from the light source 1 to the scale 2 and the main axis of each light beam from the scale 2 to the photodetector 3 and the like are symmetrical, z11 = z21, z21 = z
There is an advantage that the calculation of 22 becomes easy.

This means that z11 = z21, z11 = z21, no matter how the bending angle of the optical axis by the beam splitting optical element is set.
Since the design such that z21 = z22 can be easily realized, in the fourth, fifth, and sixth embodiments, the size of the sensor, the gap between the scales, the pitch of the scale, and the like can be freely set. There is an advantage that it can be designed with a certain degree.

It is to be noted that the respective configurations of the fourth, fifth, and sixth embodiments of the present invention can of course be variously modified and changed.

As shown in FIG. 5D, when there is a problem that the height of the light receiving surface differs from the virtual point light source position of the light source, the optical distance is adjusted as described above. Alternatively, the optical distance adjusting means 50 may be inserted on the optical axis of the light beam.

The first beam splitting optical element and the first and second light beam bending elements may be formed integrally or separately.

(Seventh Embodiment) FIG. 6 shows a configuration of an optical displacement sensor applied as an optical encoder according to a seventh embodiment of the present invention.

In the seventh embodiment, the behavior of the main axis of the light beam from the coherent light source 10 to the first photodetector 3 is the same as that of the first embodiment in terms of ray optics.

Therefore, only the differences between the seventh embodiment and the first embodiment will be described below.

FIG. 6A is a plan view of the scale 2 according to the seventh embodiment viewed in the −z direction. FIG. 6B is a cross-sectional view in the zy plane. (C) is a sectional view in the xz plane.

The seventh embodiment of the present invention is configured as follows.

As shown in FIG. 6A, the scale pattern 21 is formed so as to have a pitch p0 in the x direction.

Correspondingly, as shown in FIG. 6C, a sectional structure in the xz plane with respect to the c1-c1 'section is formed, and the light receiving area is formed in a strip shape.
P12 corresponding to the pitch of this pitch scale pattern
And the shift of the light receiving area group on the first photodetector 3 is p12 / 4.

Here, the pitch p12 of the light receiving area group is
It is approximately np0 (z11 + z21) / z11.

On the other hand, although not shown, the cross-sectional structure in the xz plane with respect to the c2-c2 'cross section is the second photodetector 3'.
The light receiving area is formed as a single area, and the light beam emitted from the light source 10 is configured to be directly incident on the light receiving area on the second photodetector 3 'by the light beam branching means. I have.

Next, the operation of the seventh embodiment of the present invention will be described.

A light beam emitted from the coherent light source 10 is
After the optical axis is bent by the diffraction grating 7 as the beam branching unit in the same manner as in the above-described fourth, fifth, and sixth embodiments, the light passes through the scale 2 and again passes through the diffraction grating and the beam branching unit. Then, the light reaches the first photodetector 3.

The mode and operation of obtaining an encoder signal from the first photodetector 3 are the same as those of the fourth, fifth and sixth embodiments described above.

In this embodiment, the coherent light source 10
Is reflected, transmitted, or diffracted by the diffraction grating 7 which is a beam splitting means, and directly enters the second photodetectors 3 ', 33' without passing through a scale pattern to detect the intensity. Is done.

The outputs from the second photodetectors 3 ', 33' are outputs proportional to the output of the light beam.

In the case where the output of the light beam fluctuates due to environmental changes, changes over time, etc., the second photodetectors 3 ', 33'
Is output to the driving device of the coherent light source 10 to suppress the output fluctuation, or the encoder output signal is corrected by the output of the second photodetectors 3 'and 33' to always provide stable displacement sensing. Is feasible.

In the present embodiment, since the intensity of the light beam can be detected without using the uniform reflectance and transmittance patterns of the scale 2, the detection error due to the intensity fluctuation of the light beam can be suppressed.

As a result, there is an advantage that the scale 2 can be stably realized irrespective of defects, dust and dirt.

Incidentally, each configuration of the seventh embodiment of the present invention can of course be variously modified and changed in accordance with the above-described first to sixth embodiments.

(Eighth Embodiment) FIG. 7 is a perspective view showing a configuration of an optical displacement sensor applied as an optical encoder according to an eighth embodiment of the present invention.

The eighth embodiment of the present invention is configured as follows.

Scale 2 has two scale patterns 2
1 and 22, the first scale pattern 21 is formed so as to have a pitch p11 in the x direction, and the second scale pattern 22 is formed as a single pattern having an appropriate width for reference position detection. Have been.

As shown in FIG. 7, the surface emitting laser 10 used as the light coherent light source is formed so that two light beams are emitted from different coordinate positions in the x direction and the y direction.

The first light beam irradiates the first scale pattern 21, whereby a diffraction interference pattern is formed on the light receiving surface of the first photodetector 3.

The second light beam is applied to the second scale pattern 22, and the reflected light is detected by the second photodetector 3 '.

The surface emitting laser light source 10 includes the principal axis 5 of the light beam emitted from the surface emitting laser light source 10, and is in an in-plane perpendicular to the spatial period direction of the scale 2 and the first scale pattern 21. It is arranged to incline only at.

Next, the operation of the eighth embodiment of the present invention will be described.

The first light beam emitted from the beam emission window 101 of the surface emitting laser 10 is the first scale pattern 2
1, the diffraction interference pattern is formed on the light receiving surface of the first photodetector 3 and the encoder signal is obtained from the first photodetector 3. The operation is the same as that of the embodiment.

The beam emission window 1 of the surface emitting laser 10
02, the second light beam passes through the second scale pattern 22, and the reflected light is obtained from the second detector 3 '. The operations of the third and sixth embodiments are the same as those of the third and sixth embodiments. Is the same.

In this embodiment, the surface emitting laser 10 is used as the coherent light source, and the first and second light sources can emit light beams from any position.
Are appropriately applied to the first scale pattern 21 and the second scale pattern 22, and the corresponding first light detector 3 and second light detector 3 ', respectively. Therefore, there is an advantage that the degree of freedom in sensor design is wider than in the first to seventh embodiments.

In addition, it is not necessary to assemble the light beam branching means at an appropriate position, which is effective for reducing the cost of assembly.

Further, there is an advantage that a signal output with a good S / N can be obtained without losing the amount of light due to the light beam branching means.

It is to be noted that each configuration of the eighth embodiment of the present invention can of course be variously modified and changed.

As shown in FIG. 8, the light receiving areas of the second scale pattern 22 and the second photodetector 3 'are formed periodically, and the vernier type is formed as in the second or fifth embodiment. It is also possible to realize the absolute value detection of the displacement by the encoder.

Alternatively, a light beam, a scale pattern,
By increasing the number of sets of photodetectors, an absolute encoder other than the vernier type can be realized.

When it is necessary to adjust the position of the light source and the scale or the optical distance between the scale and the photodetector, the optical distance adjusting means 50 is used to adjust the optical distance as described above. It may be inserted on the optical axis of the light beam.

In this embodiment, a surface emitting laser is used as a light source capable of outputting a plurality of light beams. However, any light source capable of outputting a plurality of coherent beams can be used. Not something.

In the present specification described in the above embodiments, in addition to claims 1 to 3 described in the claims, the inventions shown below as supplementary notes 1 to 9 are described. include.

(Supplementary Note 1) In the optical encoder according to claim 1, the beam splitting optical element includes a main axis of the light beam immediately after the light beam is emitted from the coherent light source, and a pitch direction of the first scale pattern. An optical encoder characterized by being arranged so that a main axis of a light beam is branched in a plurality of directions only in a plane perpendicular to the optical axis.

(Corresponding Embodiments of the Invention) Embodiments according to the present invention correspond to the first to seventh embodiments.

(Operation and Effect) In this section, the same operation and effect as those of the first aspect will be omitted.

The beam splitting optical element includes the main axis of the light beam immediately after emitted from the coherent light source, and
10A is arranged so that the main axis of the light beam is branched in a plurality of directions only in a plane perpendicular to the pitch direction of the scale pattern of FIG. According to the principle described in, the diffraction interference pattern on the light receiving surface does not move in the scale pitch direction.

Therefore, there is an advantage that a position detection error hardly occurs even if the spatial gap between the scale and the light source fluctuates.
The addition of a function of monitoring the intensity of the light output of the coherent light source, a function of detecting an absolute position, a function of detecting a reference position pattern, and the like are compatible.

(Supplementary Note 2) The optical encoder according to claim 1, wherein the second scale pattern has a uniform reflectance, transmittance, or diffraction efficiency.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the first embodiment.

(Function and Effect) In this section, the same function and effect as those of the first aspect will be omitted.

The second beam split by the beam splitting optical element
A second scale pattern having a light beam-like reflectance, transmittance or diffraction efficiency.

The reflection by the second scale pattern,
Since the intensity of the transmitted or diffracted light beam is detected by the second photodetector, the function of monitoring the intensity of the light output of the coherent light source can be realized.

Therefore, even if the surrounding environment of the sensor changes,
By feeding back the output of the light intensity detecting means comprising the second photodetector to the driving means of the laser light source,
Since the light output can be stabilized, stable sensing can be realized with respect to such a state change.

(Supplementary Note 3) In the optical encoder according to Claim 1, the second scale pattern has a predetermined period p12 different from the first scale pattern, and the second scale pattern is located on the second side from the light beam emission surface of the coherent light source. The optical distance measured along the main axis of the second light beam reaching the surface on which the scale pattern is formed is z12, and the second scale pattern formed along the main axis of the second light beam is formed. Assuming that the optical distance from the surface to the light receiving surface of the second photodetector is z22, the second photodetector is substantially np12 (z12 + z2) in the spatial period direction of the diffraction interference pattern.
2) An optical encoder having a plurality of light receiving areas formed at an interval of / z12 and configured to receive a predetermined portion of the diffraction interference pattern.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the second embodiment.

It is to be noted that a configuration in which the number of tracks of the scale pattern is increased to increase the number of branches of the corresponding light beam and the number of photodetectors is also included.

(Function and Effect) In this section, the same function and effect as those of the first aspect will be omitted.

The second beam split by the beam splitting optical element
Is irradiated on a second scale pattern having a predetermined period p12 different from the first scale pattern, and receives a diffraction interference pattern having a spatial period p2 = p12 (z11 + z21) / z11 on a second photodetector. Generate on the surface.

For this reason, since the second photodetector is formed with a group of light receiving niria having a spatial period p22 = np2 in the X direction, the scale from the second photodetector is shifted in the pitch direction of the scale pattern ( A periodic signal intensity is output each time the movement is made by p12 in the x direction).

Accordingly, the outputs from the first and second photodetectors are the displacement amounts p11, p11 in the scale pitch direction, respectively.
Since the intensity changes in the cycle of p12, an absolute position detection function can be added in the scale movement range of the least common multiple of p11 and p12 based on the principle of the Vernier encoder.

(Supplementary Note 4) The optical encoder according to claim 1, wherein the second scale pattern is a single or a plurality of scale patterns formed at a predetermined reference position.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the third embodiment.

(Function and Effect) In this section, the same function and effect as those of the first aspect will be omitted.

The second light beam split by the beam splitting optical element 7 irradiates a single scale pattern or a second scale pattern formed at a predetermined reference position.

The intensity of the light beam reflected or transmitted by the second scale pattern is detected by a second photodetector.

The output of the second photodetector changes only when the second light beam is applied to the reference position of the second scale pattern. Can be added.

(Supplementary note 5) The optical encoder according to claim 2, wherein the first beam splitting optical element and the first
And the second light beam bending element includes the main axis of the light beam immediately after being emitted from the coherent light source, and bends the main axis of the light beam only in a plane perpendicular to the pitch direction of the first scale pattern. An optical encoder characterized by being arranged as follows.

(Corresponding Embodiments of the Invention) Embodiments of the present invention correspond to the fourth to sixth embodiments.

(Function and Effect) In this section, the same function and effect as those of the second aspect will be omitted.

The first beam splitting optical element and the first and second light beam bending elements include the main axis of the light beam immediately after being emitted from the coherent light source, and extend in the pitch direction of the first scale pattern. Since the main axis of the light beam is arranged to bend in a plurality of directions only in a vertical plane, even if the spatial gap between the scale and the light source fluctuates, the light receiving surface can be obtained according to the principle described with reference to FIG. The diffraction interference pattern above does not move in the scale pitch direction.

Accordingly, there is an advantage that a position detection error hardly occurs even if the spatial gap between the scale and the light source fluctuates, an intensity monitoring function of an optical output of the coherent light source, an absolute position detection function, and a detection function based on a reference position pattern. Etc. can be compatible.

(Supplementary note 6) The optical encoder according to claim 2, wherein the second scale pattern has a uniform reflectance, transmittance, or diffraction efficiency.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the fourth embodiment.

(Function and Effect) In this section, the same function and effect as those of the second aspect will be omitted.

The second light beam split by the beam splitting optical element 7 is applied to a second scale pattern having a uniform reflectance, transmittance or diffraction efficiency, and then irradiated to the first scale.
, And the optical axis is bent again and guided to the second photodetector.

The light beam reflected or transmitted by the second scale pattern and further bent by the second light beam bending element is subjected to intensity detection by the second photodetector. Can be realized.

Therefore, even if the surrounding environment of the sensor changes,
By feeding back the output of the light intensity detecting means comprising the second photodetector to the driving means of the laser light source,
Since the light output can be stabilized, stable sensing can be realized with respect to such a state change.

(Supplementary note 7) The optical encoder according to claim 2, wherein the second scale pattern has a predetermined period p12 different from the first scale pattern, and the second scale pattern is arranged on the light beam emitting surface of the coherent light source. The optical distance measured along the main axis of the second light beam to the surface on which the second scale pattern is formed is z12, and the second scale pattern measured along the main axis of the second light beam is Assuming that an optical distance from the formed surface to the light receiving surface of the second photodetector is z22, the second photodetector converts the diffraction interference pattern generated from the second scale pattern into a first interference pattern. And a photodetector that receives light through a light beam bending element that is the same as or separate from the beam splitting optical element, and substantially np12 (z1) in the spatial period direction of the diffraction interference pattern.
An optical encoder comprising a plurality of light receiving areas formed at an interval of (2 + z22) / z12 so as to receive a predetermined portion of the diffraction interference pattern.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the fifth embodiment.

It should be noted that a configuration in which the number of branches of the light beam and the number of photodetectors are increased in accordance with the number of tracks of the scale pattern is also included.

(Function and Effect) In this section, the same function and effect as those of the second aspect will be omitted.

The second light beam split by the beam splitting optical element 7 irradiates a second scale pattern having a predetermined period p12 different from the first scale pattern,
It is bent by the second light beam bending element, and the spatial period p2 = p
A diffraction interference pattern having 12 (z11 + z21) / z11 is generated on the light receiving surface on the second photodetector.

Therefore, the second photodetector outputs a periodic signal intensity every time the scale moves by p12 in the pitch direction of the scale pattern.

Accordingly, the outputs from the first and second photodetectors are respectively the displacement amounts p11, p11 in the scale pitch direction.
Since the intensity changes in the cycle of p12, an absolute position detection function can be added in the scale movement range of the least common multiple of p11 and p12 based on the principle of the Vernier encoder.

(Supplementary note 8) The optical encoder according to claim 2, wherein the second scale pattern is one or more scale patterns formed at a predetermined reference position.

(Corresponding Embodiment of the Invention) The embodiment relating to the present invention corresponds to the sixth embodiment.

(Operation and Effect) In this section, the same operation and effect as those of the second aspect are omitted.

The second light beam split by the beam splitting optical element 7 is applied to a second scale pattern formed of a single or a plurality of scale patterns formed at a predetermined reference position.

The light beam reflected or transmitted by the second scale pattern has its optical axis bent by a second light beam bending element, and then its intensity is detected by a second photodetector.

The output of the second photodetector changes only when the second light beam is applied to the reference position of the second scale pattern. Can be added.

(Supplementary Note 9) A coherent light source capable of emitting a plurality of light beams, and a first light beam displaced to cross the light beam emitted from the coherent light source and emitted from the coherent light source A scale formed with a first scale pattern of a predetermined period for generating a diffraction interference pattern, and a first photodetector for receiving the diffraction interference pattern, wherein a light beam emission surface of the coherent light source First
The optical distance measured along the main axis of the first light beam reaching the surface on which the scale pattern of
The optical distance from the surface on which the first scale pattern is formed to the light receiving surface of the first photodetector, measured along the main axis of the light beam, is z21, and the spatial period of the first scale pattern Where p11 and n are natural numbers, the first photodetector has a plurality of light receiving areas formed at intervals of approximately np11 (z11 + z21) / z11 in the spatial period direction of the diffraction interference pattern, and An optical encoder configured to receive a predetermined portion of the interference pattern, wherein the coherent light source and the photodetector are disposed at substantially the same optical distance from the scale, and on the same side, The main axis of the light beam emitted from the light source includes the main axis of the light beam emitted from the coherent light source, and only in a plane perpendicular to the spatial period direction of the first scale pattern. , A second light beam of the plurality of light beams is applied to the second scale pattern formed integrally with the scale, and the second light beam Is the second
An optical encoder having a second photodetector for receiving a light beam reflected, diffracted, or transmitted by the scale pattern of (1).

(Corresponding Embodiments of the Invention) Embodiments relating to the present invention correspond to the eighth and ninth embodiments.

(Function and Effect) The first light emitted from the coherent light source
Are applied to the first scale pattern, respectively, and the spatial period p2 = p11 (z11 + z21) / z1
A diffraction interference pattern having 1 is generated on the light receiving surface on the first photodetector.

When the scale is displaced by p11 in the pitch direction of the diffraction grating in the same manner as in claim 1, x2 = p11 (z11 + z21) / in the same direction on the light receiving surface.
Since the scale is displaced by z11, every time the scale is displaced by p11 in the pitch direction of the diffraction grating, an output signal that changes with a periodic intensity is obtained from the first photodetector.

On the other hand, the second light beam is applied to the second scale pattern, and the intensity is detected by the second photodetector which receives the light beam reflected, diffracted and transmitted by the second scale pattern. .

By setting the first and second scale patterns appropriately, the coherent light source can be detected by detecting the intensity of the reflected or transmitted light from a fixed reflection or transmittance scale, as in the case of appendixes 2 to 4. Light output intensity monitoring function,
Absolute position detection function using vernier encoder pattern,
It is possible to realize an origin detection function and the like based on the reference position pattern.

Further, two or more of these additional functions can be realized simultaneously by increasing the number of beam branches and the number of photodetectors according to the number of scale patterns.

Although the coherent light source, the scale surface, and the light receiving surface cannot all be arranged in parallel, there is an advantage that the beam splitting optical element and its assembly are not required.

[0252]

Therefore, as described above, according to the present invention, a reference point detecting function and an absolute position detecting function are provided.
The displacement of the scale in the x-direction can be accurately detected with little effect from the gap fluctuation between the scale and the head, and the mounting form that does not use the inclined substrate reduces the assembly cost and changes the surrounding environment. Thus, it is possible to provide an optical encoder applicable as an optical displacement sensor having a configuration and means capable of stabilizing an encoder signal output.

[Brief description of the drawings]

FIG. 1 shows a configuration of an optical displacement sensor applied as an optical encoder according to a first embodiment of the present invention.

FIG. 2 shows an optical displacement sensor applied as an optical encoder according to a first embodiment of the present invention, in which a scale (a), an a-a ′ cross section (b) thereof, and a scale b are shown.
-B 'section (c) is shown.

FIG. 3 shows a configuration of an optical displacement sensor applied as an optical encoder according to a second embodiment of the present invention.

FIG. 4 shows a configuration of an optical displacement sensor applied as an optical encoder according to a third embodiment of the present invention.

FIG. 5 shows a configuration of an optical displacement sensor applied as an optical encoder according to fourth, fifth, and sixth embodiments of the present invention.

FIG. 6 shows a configuration of an optical displacement sensor applied as an optical encoder according to a seventh embodiment of the present invention.

FIG. 7 shows a configuration of an optical displacement sensor applied as an optical encoder according to an eighth embodiment of the present invention.

FIG. 8 shows a configuration of an optical displacement sensor applied as a modification of the optical encoder according to the eighth embodiment of the present invention.

FIG. 9 shows a configuration diagram of an optical encoder according to a first conventional example.

FIG. 10 shows a configuration diagram of an optical encoder according to a second conventional example.

FIG. 11 shows the simplest possible form when the configuration of the conventional example shown in FIGS. 9 and 10 is extended to a multi-beam & track configuration.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Coherent light source, 2 ... Scale, 3 33 ... 1st light detector, 3 ', 33' ... 2nd light detector, 5 ... Main axis of 1st light beam, 5 '... 2nd Main axis of light beam 15, 15 ': Main axis of light beam 10, Surface emitting laser 7, Diffraction grating used as beam splitting optical element 71, 72 ... Diffraction grating used as light beam bending element, 11 ... case, 21 ... first scale pattern, 22 ... second scale pattern, 25, 25 '... main axis of light beam, 50 ... optical distance adjusting means, 61 ... transparent cover, 101, 102 ... beam emission window.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Iwao Komazaki 2-43-2, Hatagaya, Shibuya-ku, Tokyo F-term in Olympus Optical Co., Ltd. 2F103 BA32 BA37 CA02 CA04 CA08 DA01 DA12 EA02 EA15 EB02 EB15 EB16 EB22

Claims (3)

[Claims] A scale formed with a first scale pattern and a second scale pattern for reflecting or diffracting and transmitting a light beam from the coherent light source, the scale being movably supported; A beam splitting optical element provided between the coherent light source and the scale, for splitting a light beam emitted from the coherent light source into a plurality of beams; and detecting a light beam split by the beam splitting optical element. And a first light detector, wherein the first light detector reflects or diffracts the first light beam split by the beam splitting optical element with the first scale pattern, A surface on which the first scale pattern is formed from a light beam emission surface of the coherent light source in a spatial periodic direction of the diffraction interference pattern formed on the light receiving surface by transmission; A first optical distance along the optical beam of the main shaft at z11, first from the first surface of the scale pattern is formed to the first photodetector
When the optical distance along the main axis of the light beam is z21, the spatial period of the first scale pattern is p11, and n is a natural number, a plurality of intervals formed at an interval of approximately np11 (z11 + z21) / z11 A second light beam having a light receiving area, among the plurality of light beams split by the beam splitting optical element, being reflected, diffracted, or transmitted by the second scale pattern and transmitted by the second photodetector; An optical encoder characterized by receiving light. 2. A first light beam bending element provided between the scale and the first photodetector, and a second light beam bending element provided between the scale and the second photodetector. And the first and second light beams transmitted or reflected and diffracted through the first and second scale patterns respectively correspond to the first and second light beam bending elements. Through each,
The optical encoder according to claim 1, wherein the light is received by the first and second photodetectors. 3. A coherent light source; and a scale movably supported by forming a first scale pattern and a second scale pattern that reflect or diffract and transmit a light beam from the coherent light source; A beam splitting optical element provided between the coherent light source and the scale, for splitting a light beam emitted from the coherent light source into a plurality of beams; and detecting a light beam split by the beam splitting optical element. And a first light detector, wherein the first light detector reflects or diffracts the first light beam split by the beam splitting optical element with the first scale pattern, A surface on which the first scale pattern is formed from a light beam emission surface of the coherent light source in a spatial periodic direction of the diffraction interference pattern formed on the light receiving surface by transmission; A first optical distance along the optical beam of the main shaft at z11, first from the first surface of the scale pattern is formed to the first photodetector
When the optical distance of the light beam along the main axis is z21, the spatial period of the first scale pattern is p11, and n is a natural number, a plurality of light beams are formed at intervals of approximately np11 (z11 + z21) / z11. A light receiving area, wherein a second light beam of the plurality of light beams split by the beam splitting optical element is received by the second photodetector without being irradiated on a scale pattern. Optical encoder.