JP7063743B2 - Encoder - Google Patents

Description

The present invention relates to an encoder.

Currently, there is an optical encoder as one of the devices for measuring the amount of movement. The optical encoder has a scale and a detection head that moves along the scale. The scale is provided with, for example, an absolute pattern for detecting the origin position and an incremental pattern for detecting the relative movement amount between the scale and the detection head. The optical encoder determines the origin position by the origin signal which is the detection result of the absolute pattern on the scale. Then, the positional relationship between the scale and the detection head can be detected by considering the movement amount obtained from the detection result of the incremental pattern with the origin position as a reference.

Generally, the incremental pattern is configured as a diffraction grating in which a plurality of lattice patterns are arranged in the measurement direction. The diffraction grating is irradiated with light, and the light intensity of the interference fringes generated by the interference between the +1st-order diffracted light diffracted by the diffraction grating and the -1st-order diffracted light is detected. In such an optical encoder, since the interference fringes due to the +1st order diffracted light and the -1st order diffracted light are detected with high accuracy, it is necessary to suppress the influence of the diffracted light of another order such as the 0th order diffracted light on the interference fringes. ..

For example, an encoder in which an optical block is arranged between a light source and a scale to remove 0th-order diffracted light has been proposed (Patent Document 1). In this encoder, an index grid is inserted between the light source and the scale, and the light from the light source is irradiated. A shield that shields the 0th-order diffracted light is inserted between the index grid and the scale. This shield is arranged at a position that shields the 0th-order diffracted light and does not shield the + 1st-order diffracted light and the -1st-order diffracted light. Therefore, the +1st-order diffracted light and the -1st-order diffracted light reach the scale, but the 0th-order diffracted light does not reach the scale. As a result, the light that reaches the detection unit from the scale is only the +1st-order diffracted light and the -1st-order diffracted light, and the influence of the 0th-order diffracted light can be avoided.

Further, another example of an encoder using an index grid has been proposed (Patent Document 2). This encoder irradiates the scale with light from a light source and detects the transmitted diffracted light. An index lattice is inserted between the scale and the detection unit, and the diffraction grating is formed only at the position where the + 1st-order diffracted light and the -1st-order diffracted light are incident among the diffracted light from the scale, and other diffracted light including the 0th-order diffracted light is formed. Diffracted light is blocked. The +1st-order diffracted light and the -1st-order diffracted light incident on the index grating are diffracted by the diffraction grating, and interference fringes are generated on the detection unit. As a result, the light that reaches the detection unit from the scale is only the +1st-order diffracted light and the -1st-order diffracted light, and the influence of the 0th-order diffracted light can be avoided.

Further, an encoder that removes 0th-order diffracted light by using a spatial filter has been proposed (Non-Patent Document 1). In this encoder, the scale is irradiated with laser light, and the generated diffracted light is parallelized by a collimator lens. Then, the 0th-order diffracted light is generated by using a spatial filter provided with a slit only at a position where only the + 1st-order diffracted light and the -1st-order diffracted light pass among the parallelized next-order diffractors emitted from the collimator lens. Blocks other diffracted light, including. After that, by converging the +1st-order diffracted light and the -1st-order diffracted light on the detection unit with the converging lens, interference fringes can be generated on the detection unit.

In addition, as a countermeasure against the 0th-order diffracted light, a structure that prevents the generation of the 0th-order diffracted light by optimizing the structure of a fine diffraction grating has been proposed (Patent Document 3).

Japanese Patent No. 2619566 Japanese Patent No. 4856844 Japanese Unexamined Patent Publication No. 8-219812

Kazuhiro Hane, 2 others, "Optical Encoder Using Metal Surface Diffraction Grating", Journal of Precision Engineering, Vol. 64, No. 10, 1998

However, the above encoder has the problems described below. In Patent Documents 1 and 2 and Non-Patent Document 1, it is necessary to add optical elements such as an index grid, a lens, and a spatial filter in order to eliminate the influence of the 0th-order diffracted light. Therefore, the size of the encoder becomes large and the structure becomes complicated.

Further, in these examples, the +1st order diffracted light and the -1st order diffracted light and the other diffracted light are separated by utilizing the difference in the diffraction angle. However, if the order of the diffracted light is to be separated accurately, the separation distance of the diffracted light of each order cannot be increased unless the distance between the optical elements is increased, so that the encoder becomes larger.

In Patent Document 3, since only a diffraction grating with an optimized structure can be used, the optical design of the entire encoder is restricted.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an encoder capable of removing the influence of unnecessary diffracted light and improving the position detection accuracy.

The encoder according to the first aspect of the present invention is
A scale with an incremental pattern and
A detection head that is movable in the measurement direction relative to the scale, detects diffracted light diffracted by the incremental pattern of light radiated to the scale, and outputs a detection result.
A signal processing unit that calculates a relative displacement between the scale and the detection head according to the detection result of the detection head is provided.
The detection head is
A light source that irradiates the scale with light,
A detection unit having a light receiving unit in which a plurality of light receiving elements for outputting a detection signal of the diffracted light from the scale are periodically arranged in the measurement direction at a predetermined period.
An optical element that guides the diffracted light to the detection unit is provided.
The plurality of light receiving elements are arranged in an even number in the measurement direction.
The predetermined period is an odd multiple of the basic period, which is the period of the interference fringes generated on the light receiving portion by the +1st order diffracted light and the -1st order diffracted light among the diffracted light.
The width of the light receiving element in the measurement direction is a value that is not an integral multiple of the basic period.

The encoder according to the second aspect of the present invention is the above-mentioned encoder.
The + 1st-order diffracted light, the -1st-order diffracted light, and the 0th-order diffracted light from the scale are incident on the detection unit.

The encoder according to the third aspect of the present invention is the above-mentioned encoder.
The light receiving unit has a plurality of detection regions arranged in the measurement direction.
Each of the detection units has an even number of the light receiving elements arranged in the measurement direction.
Of the plurality of light receiving regions, two light receiving regions adjacent to each other are arranged so as to be offset by 1/4 of the basic period so as to be far from each other in the measurement direction.

The encoder according to the fourth aspect of the present invention is the above-mentioned encoder.
In the detection unit, the first and second light receiving regions are arranged in this order in the measurement direction.
The detection unit outputs the detection signal from the first light receiving region to the signal processing unit as an A phase signal, and outputs the detection signal from the second light receiving region to the signal processing unit as a B phase signal. , The thing.

The encoder according to the fifth aspect of the present invention is the above-mentioned encoder.
In the detection unit, the first to fourth light receiving regions are arranged in this order in the measurement direction.
The detection unit is a differential A phase which is a differential signal between an A phase signal which is a detection signal from the first light receiving region and an A-phase signal which is a detection signal from the third light receiving region. A signal and a differential B-phase signal which is a differential signal between a B-phase signal which is a detection signal from the second light-receiving region and a B-phase signal which is a detection signal from the fourth light-receiving region. , Is output to the signal processing unit.

The encoder according to the sixth aspect of the present invention is the above-mentioned encoder.
The light receiving unit has a plurality of detection regions arranged in the measurement direction.
Each of the detection units has an even number of the light receiving elements arranged in the measurement direction.
Of the plurality of light receiving regions, two light receiving regions adjacent to each other are arranged so as to be offset by 1/3 of the basic period so as to be far from each other in the measurement direction.

The encoder according to the seventh aspect of the present invention is the above-mentioned encoder.
In the detection unit, the first to third light receiving regions are arranged in this order in the measurement direction.
The detection unit includes an A phase signal which is a detection signal from the first light receiving region, a B phase signal which is a detection signal from the second light receiving region, and a C which is a detection signal from the third light receiving region. A differential A-phase signal and a differential B-phase signal, which are generated by synthesizing a phase signal and whose phases are different from each other by 90 °, are output to the signal processing unit.

The encoder according to the eighth aspect of the present invention is the above-mentioned encoder.
The optical element collects +1st-order diffracted light and -1st-order diffracted light on the detection unit 5 to form the interference fringes.

The encoder according to the ninth aspect of the present invention is the above-mentioned encoder.
The optical element is either a diffraction grating or a lens.

The encoder according to the tenth aspect of the present invention is the above-mentioned encoder.
The optical element is composed of two mirrors.
One mirror reflects the +1st order diffracted light toward the detection unit.
The other mirror reflects the -1st order diffracted light toward the detection unit.

The encoder according to the eleventh aspect of the present invention is the above-mentioned encoder.
k is an integer greater than or equal to 2 and
The basic period is P,
The k detection regions arranged in the directions intersecting the measurement directions form a detection row.
The detection regions are shifted from each other in the measurement direction at a pitch of P / k.

The encoder according to the twelfth aspect of the present invention is the above-mentioned encoder.
n is an integer of 1 or more,
The k detection rows are periodically arranged at a pitch of nP + P / k in the measurement direction.

According to the present invention, it is possible to provide an encoder capable of removing the influence of unnecessary diffracted light and improving the position detection accuracy.

The above and other objects, features, and advantages of the present invention will be more fully understood from the following detailed description and accompanying drawings. The accompanying drawings are shown for illustration purposes only and are not intended to limit the invention.

It is a perspective view which shows the schematic structure of the optical encoder 100 which concerns on Embodiment 1. FIG. It is a perspective view which shows the structure of the optical encoder 100 which concerns on Embodiment 1. FIG. It is a figure which shows the interference fringe generated on the detection part by the +1st order diffracted light and the -1st order diffracted light. It is a figure which shows the interference fringe generated on the detection part by the +1st order diffracted light, the -1st order diffracted light and the 0th order diffracted light. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on Example 1. FIG. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on Example 2. FIG. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on Example 3. FIG. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on Example 4. FIG. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on Example 5. FIG. It is a figure which shows the relationship between the interference fringe which concerns on the comparative example 1 and a light receiving element. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on the comparative example 2. FIG. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on the comparative example 3. FIG. It is a figure which shows the relationship between the interference fringe and the light receiving element which concerns on Comparative Example 4. FIG. It is a figure which shows typically the structure of the light receiving part which concerns on Embodiment 2. FIG. It is a figure which shows typically the other structure of the light receiving part which concerns on Embodiment 2. FIG. It is a figure which shows typically the other structure of the light receiving part which concerns on Embodiment 2. FIG. It is a perspective view which shows the structure of the optical encoder which concerns on Embodiment 3. FIG. It is a figure which shows an example of the optical element which concerns on Embodiment 3. FIG. It is a figure which shows the other example of the optical element which concerns on Embodiment 3. FIG. It is a figure which shows the other example of the optical element which concerns on Embodiment 3. FIG. It is a perspective view which shows the structure of the optical encoder which concerns on Embodiment 4. FIG. It is a top view which shows the structure of the optical encoder which concerns on Embodiment 4. FIG. It is a side view which shows the structure when the optical encoder 400 which concerns on Embodiment 4 is seen along the X-axis direction. It is a side view which shows the structure when the optical encoder 400 which concerns on Embodiment 4 is seen along the Y-axis direction. It is a figure which shows typically the structure of the light receiving part LRU1 which concerns on Embodiment 5. It is a figure which shows typically the structure of the other light receiving part LRU2 which concerns on Embodiment 5. It is a figure which shows typically the structure of the light receiving part LRU3 which concerns on Embodiment 6. It is a figure which shows typically the structure of the other light receiving part LRU4 which concerns on Embodiment 6.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In each drawing, the same elements are designated by the same reference numerals, and duplicate explanations are omitted as necessary.

Embodiment 1
The optical encoder according to the first embodiment of the present invention will be described. FIG. 1 is a perspective view showing a schematic configuration of the optical encoder 100 according to the first embodiment. Here, a case where the optical encoder 100 is configured as a transmission encoder will be described. As shown in FIG. 1, the optical encoder 100 includes a scale 1, a detection head 2, and a signal processing unit 3. The scale 1 and the detection head 2 are configured to be relatively movable along the measurement direction (X-axis direction in FIG. 1) which is the longitudinal direction of the scale 1. The scale 1 is provided with a pattern used for position detection, and interference light is generated by irradiating the pattern with light. The detection head 2 detects a change in the measurement direction of the interference light, and outputs a detection signal DET, which is an electric signal indicating the detection result, to the signal processing unit 3. The signal processing unit 3 can calculate the positional relationship between the scale 1 and the detection head 2 by processing the received detection signal DET.

In the following, the direction perpendicular to the length measurement direction (X-axis direction in FIG. 1) and indicating the width of the scale 1 is defined as the Y-axis. That is, the main surface of the scale 1 is an XY plane. Further, the direction perpendicular to the main surface (XY plane) of the scale 1, that is, the direction perpendicular to the X-axis and the Y-axis is defined as the Z-axis. Further, in the perspective view referred to below, the direction from the lower left front of the paper to the upper right is the positive direction of the X-axis. The direction from the lower right front to the upper left back of the paper is the positive direction of the Y axis. The direction from the lower side to the upper side of the paper surface is the positive direction of the Z axis.

The optical encoder 100 will be described in more detail. FIG. 2 is a perspective view showing the configuration of the optical encoder 100 according to the first embodiment. As shown in FIG. 2, the detection head 2 has a light source 4 and a detection unit 5. As described above, the scale 1 and the detection head 2 are configured to be relatively movable in the measurement direction (X-axis direction in FIG. 2).

The light source 4 is a light source that outputs parallel light 4A. The light source 4 has, for example, a light source element and a collimator. The light output by the light source is collimated by a collimator to become parallel light 4A. Examples of the light source element include LED (Light Emitting Diode), semiconductor laser, SLED (Self-Scanning Light Emitting Device), OLED (Organic light-emitting diode), and the like. Can be used. Further, as the collimator, various collimating means such as a lens optical system can be used.

The scale 1 is a plate-shaped member having a plane perpendicular to the Z axis (XY plane) in FIG. 2 as a main plane and a longitudinal direction in the X axis direction. The scale 1 is arranged at a position where the parallel light 4A from the light source 4 is vertically incident on the main surface (XY plane). In FIG. 2, the scale 1 is arranged on the negative direction side of the Z axis with respect to the light source 4.

The origin pattern 6 and the incremental pattern 7 are formed on the plate-shaped member constituting the scale 1.

In the origin pattern 6, typically, one lattice-shaped light transmitting portion 6A having the Y axis of FIG. 2 as the longitudinal direction is formed. However, the pattern of the origin pattern 6 is not limited to this example, and other patterns such as those composed of a plurality of grid patterns may be applied as appropriate.

In the incremental pattern 7, a plurality of grid-like light transmitting portions having the Y axis as the longitudinal direction in FIG. 2 are arranged side by side in the X axis direction. That is, in the incremental pattern 7, the light transmitting portions 7A and the impermeable portions 7B are arranged alternately in the X-axis direction and repeatedly at the pitch g.

The scale 1 is preferably made of glass. In this case, for example, the impermeable portion is formed by the metal film deposited on the glass, and the region where the metal film does not exist becomes the light transmitting portion. However, any material that can form a lattice-shaped light transmitting portion that transmits light and a non-transmitting portion that does not transmit light can be used as a material that constitutes scale 1.

The detection unit 5 is configured to be able to detect the light that has passed through the scale 1. The detection unit 5 has a light receiving unit 8 and a light receiving unit 9. The light receiving unit 8 and the light receiving unit 9 are arranged side by side in the Y-axis direction. The detection unit 5 outputs the signals output by the light receiving units 8 and 9 as the detection signal DET.

The light receiving unit 8 is configured to be able to detect the light transmitted through the origin pattern 6, and outputs the detection result to the signal processing unit 3. In this example, a light receiving element 10 is arranged in order to detect the light transmitted through the light transmitting portion 6A of the origin pattern 6. As a result, the light receiving unit 8 outputs the electric signal obtained by photoelectric conversion of the light passing through the light transmitting unit 6A of the origin pattern 6 to the signal processing unit 3.

The light receiving unit 9 is configured to be able to detect the light that has passed through the incremental pattern 7, and outputs the detection result to the signal processing unit 3. For example, the light receiving unit 9 outputs an electric signal obtained by photoelectric conversion of the light passing through the incremental pattern 7 to the signal processing unit 3. The light receiving unit 9 is configured as a light receiving element array in which an even number of light receiving elements 11 (for example, photodiodes) are arranged at a pitch suitable for detecting interference fringes due to light diffracted by the incremental pattern 7.

Further, the light receiving unit 9 may be configured such that a diffraction grating provided with an even number of light transmitting units is arranged on a photodiode having a large light receiving area. In this case, each of the portions provided with the light transmitting portion substantially functions as the above-mentioned light receiving element.

Next, the interference fringes generated on the light receiving unit 9 will be described. The light transmitted through the incremental pattern 7 is diffracted, and interference fringes due to the diffracted light are generated on the light receiving portion 9. Here, first, the interference fringes 20 generated on the light receiving portion 9 by the +1st order diffracted light and the -1st order diffracted light will be described. FIG. 3 is a diagram showing the interference fringes 20 generated on the light receiving portion 9 by the +1st order diffracted light and the -1st order diffracted light. As shown in FIG. 3, an interference fringe 20 having a period P is generated on the light receiving portion 9 by the +1st order diffracted light and the -1st order diffracted light. Hereinafter, the period of the interference fringes 20 generated on the light receiving portion 9 by the +1st order diffracted light and the -1st order diffracted light is referred to as a basic period P.

However, the light receiving unit 9 is also incident with the +1st order diffracted light transmitted through the incremental pattern 7 and the diffracted light of a degree other than the -1st order diffracted light. Of these, since the 0th-order diffracted light has a high light intensity, the interference fringes generated on the light receiving portion 9 are affected by the 0th-order diffracted light.

FIG. 4 is a diagram showing the interference fringes 30 generated on the light receiving portion 9 by the +1st order diffracted light, the -1st order diffracted light, and the 0th order diffracted light. As shown in FIG. 4, in the interference fringes 30 generated on the light receiving portion 9 by the + 1st-order diffracted light, the -1st-order diffracted light, and the 0th-order diffracted light, high peaks 31 and low peaks 32 appear alternately. Since the high peak 31 and the low peak 32 are separated from each other by the basic period P, the interference fringe 30 has a waveform in which the high peak 31 and the low peak 32 repeatedly appear in the period 2P which is twice the basic period P. Have. Therefore, if the light intensity of the interference fringes 30 is simply photoelectrically converted, the output signal OUT indicating the conversion result also has a waveform in which high peaks and low peaks repeatedly appear at a period of 2P, which is twice the basic period P. ..

On the other hand, in the optical encoder 100, the influence of unnecessary interference terms such as the above-mentioned 0th-order diffracted light is suppressed by conforming the configuration and arrangement of the light receiving element of the light receiving unit 9 to the following design conditions. Hereinafter, the configuration and arrangement of the light receiving element 11 of the light receiving unit 9 in the present embodiment will be described in detail. In the light receiving unit 9, a plurality of light receiving elements 11 are arranged in the X direction so as to satisfy the following design conditions 1 to 3.

[Design condition 1]
In the present embodiment, the light receiving elements 11 of the light receiving unit 9 are arranged so that the number of arrangements in the X direction is an even number. Hereinafter, this condition is referred to as design condition 1.

[Design condition 2]
Further, in the present embodiment, the light receiving element 11 of the light receiving unit 9 is arranged so that the arrangement period in the X direction is an odd multiple of the basic period P of the interference fringes. Hereinafter, this condition is referred to as design condition 2.

[Design condition 3]
Further, in the present embodiment, each light receiving element 11 is configured so that the width W in the X direction is not an integral multiple of the basic period P of the interference fringes. Hereinafter, this condition is referred to as design condition 3.

By satisfying the above design conditions 1 to 3, the light receiving unit 9 eliminates the influence of the periodicity twice the basic period P brought about by the 0th-order diffracted light on the interference fringes 30, and fluctuates in the basic period P. The output signal can be obtained. Hereinafter, the mechanism will be described with reference to examples.
[Example 1]
FIG. 5 shows the relationship between the interference fringes and the light receiving element according to the first embodiment. In Example 1, the number of light-receiving elements arranged was 10, the arrangement cycle of the light-receiving elements was 1 times the basic period P of the interference fringes, and the width W of the light-receiving elements was 0.5 times the basic period P of the interference fringes. In this example, the light receiving elements 11A and the light receiving elements 11B are arranged alternately.

As shown in FIG. 5, focusing on the light receiving element 11A, the light receiving elements 11A are arranged in a period 2P that is twice the basic period P. Focusing on the light receiving element 11B, the light receiving elements 11B are arranged in a period 2P that is twice the basic period P. That is, the light receiving element 11A detects the light intensity in the phase θ of the interference fringes that fluctuate in the period 2P twice the basic period P, and the light receiving element 11B detects the light intensity in the period 2P twice the basic period P. Detects the light intensity in phase (θ + 2π).

Let n be 1/2 of the number of array of light receiving elements, and let I (θ) be the intensity of light detected by each of the light receiving elements 11A and 11B in the phase θ. The phase θ is defined with respect to the basic period P, and the interference fringes move by the basic period P every time the phase changes by 2π. Further, as described above, since the interference fringe 30 has a period twice the basic period P, the light intensity I (θ) detected by each of the light receiving elements 11A and 11B in the phase θ has the same value for each phase 4π. Will be. That is, I (θ) ≠ I (θ + 2π) and I (θ) = I (θ + 4π). This relationship also holds in the following Examples and Comparative Examples. Assuming that the intensity of the light detected by the light receiving unit 9 is _ITOTAL under the conditions described below, the following equation [1] is established.

I _TOTAL = nI (θ) + nI (θ + 2π) [1]

As shown in the equation [2], the equation [1] takes the same value for each phase 2π, so that the peak of the same intensity appears in the _ITOTAL with the basic period P as the period.

I _TOTAL = nI (θ + 2π) + nI (θ + 2π + 2π)
= NI (θ + 2π) + nI (θ)
= NI (θ) + nI (θ + 2π) [2]

As a result, it can be understood that an output signal OUT that increases or decreases in the basic period P can be obtained.

[Example 2]
FIG. 6 shows the relationship between the interference fringes and the light receiving element according to the second embodiment. In Example 2, the number of light-receiving elements arranged was 4, the arrangement cycle of the light-receiving elements was 3 times the basic period P of the interference fringes, and the width W of the light-receiving elements was 0.5 times the basic period P of the interference fringes. In this example, the light receiving elements 11A and the light receiving elements 11B are arranged alternately.

As shown in FIG. 6, focusing on the light receiving element 11A, the light receiving elements 11A are arranged in a period 6P which is 6 times the basic period P. Focusing on the light receiving element 11B, the light receiving elements 11B are arranged in a period 6P which is 6 times the basic period P. That is, the light receiving element 11A detects the light intensity in the phase θ of the interference fringes that fluctuate in the period 2P twice the basic period P, and the light receiving element 11B detects the light intensity in the period 2P twice the basic period P. The light intensity in phase (θ + 6π) is detected.

Assuming that 1/2 of the number of light receiving elements arranged is n, the light intensity detected by each of the light receiving elements 11A and 11B in the phase θ is I (θ), and the light intensity detected by the light receiving unit 9 is _ITOTAL , the following is assumed. Equation [3] holds.

I _TOTAL = nI (θ) + nI (θ + 6π)
= NI (θ) + nI (θ + 2π + 4π)
= NI (θ) + nI (θ + 2π) [3]

That is, the equation [3] is the same as the equation [1] of the first embodiment. Therefore, as in Example 1, in _ITOTAL , peaks of the same intensity appear with the basic period P as the period. As a result, it can be understood that an output signal OUT that increases or decreases in the basic period P can be obtained.

[Example 3]
FIG. 7 shows the relationship between the interference fringes and the light receiving element according to the third embodiment. In Example 3, the number of light-receiving elements arranged was 4, the arrangement cycle of the light-receiving elements was 3 times the basic period P of the interference fringes, and the width W of the light-receiving elements was 1.5 times the basic period P of the interference fringes. In this example, the light receiving elements 11A and the light receiving elements 11B are arranged alternately.

In this configuration, although the width of the light receiving element is different from that of Examples 1 and 2, the light receiving element 11A detects the same waveform, the light receiving element 11B also detects the same waveform, and the number of light receiving elements 11A and the light receiving light are received. The number of elements 11B is the same. Therefore, the equations [1] and [2] are established as in the first embodiment. As a result, the output signal OUT that increases or decreases in the basic period P is obtained as in the second embodiment.

[Example 4]
FIG. 8 shows the relationship between the interference fringes and the light receiving element according to the fourth embodiment. In Example 4, the number of light-receiving elements arranged was 2, the arrangement cycle of the light-receiving elements was 5 times the basic period P of the interference fringes, and the width W of the light-receiving elements was 1.5 times the basic period P of the interference fringes. In this example, the light receiving elements 11A and the light receiving elements 11B are arranged alternately.

In this configuration, although the number and width of the light receiving elements are different from those in the third embodiment, the light receiving elements 11A and the light receiving elements 11B are separated by five times the basic period P, and as a result, the above equation [1] and the above equation [1] and [2] holds. As a result, the output signal OUT that increases or decreases in the basic period P is obtained as in the third embodiment.

[Example 5]
Example 5 is a modification of Example 2, and shows an example in which a four-phase signal can be obtained. FIG. 9 shows the relationship between the interference fringes and the light receiving element according to the fifth embodiment. In the fifth embodiment, the number of light receiving elements arranged in each phase is an even number, the arrangement cycle of the light receiving elements of each phase is three times the basic period P of the interference fringes, and the width W of the light receiving elements of each phase is the basic period of the interference fringes. It was set to 0.5 times P. Further, in this example, the light receiving elements pertaining to the A phase, the B phase, the A-phase and the B-phase are indicated by using the reference numerals A, B, A- and B-, respectively.

As shown in FIG. 9, the light receiving elements 12 to 15 related to the A phase, the B phase, the A-phase, and the B-phase are arranged in the same manner as the light receiving elements 11 (light receiving elements 11A and 11B) according to the second embodiment, respectively. Has been done. In other words, although the arrangement period of the light receiving elements adjacent to each other is 0.75 times the basic period P, the configuration is such that a four-phase signal is obtained. It becomes the same as in Example 2. That is, according to the fifth embodiment, as in the second embodiment, an output signal OUT that increases or decreases in the basic period P can be obtained without being affected by unnecessary interference light.

Further, in order to make a comparison with the examples, a comparative example in the case where any one of the above design conditions 1 to 3 is not satisfied will be examined.
[Comparative Example 1]
FIG. 10 shows the relationship between the interference fringes and the light receiving element according to Comparative Example 1. In Comparative Example 1, the number of light-receiving elements arranged was 3, the arrangement cycle of the light-receiving elements was 3 times the basic period P of the interference fringes, and the width W of the light-receiving elements was 0.5 times the basic period P of the interference fringes. In this example, the light receiving elements 11A and the light receiving elements 11B are arranged alternately. That is, Comparative Example 1 does not satisfy the above-mentioned design condition 1.

The quotient when the number of light receiving elements is divided by 2 is m, the light intensity detected by each of the light receiving elements 11A and 11B in the phase θ is I (θ), and the light intensity detected by the light receiving unit 9 is _ITOTAL . Then, the following equation [4] holds.

I _TOTAL = (m + 1) I (θ) + mI (θ + 2π) [4]

In the equation [4], when the phase fluctuates by 2π, that is, the basic period P, the following equation [5] is obtained.

I _TOTAL = (m + 1) I (θ + 2π) + mI (θ + 2π + 2π)
= (M + 1) I (θ + 2π) + mI (θ) [5]

As described above, since the interference fringes fluctuate in a period 2P that is twice the basic period P, the light intensities of the interference fringes at positions separated by the basic period P are not equal. Therefore, the value of _ITOTAL differs between the equation [3] and the equation [4].

In the equation [4], when the phase fluctuates by 4π, that is, twice the basic period P, the following equation [6] is obtained.

I _TOTAL = (m + 1) I (θ + 4π) + mI (θ + 2π + 4π)
= (M + 1) I (θ) + mI (θ + 2π) [6]

Therefore, the equation [5] is the same as the equation [3]. That is, in I _TOTAL , peaks of the same intensity appear with a cycle of twice the basic cycle P. As a result, the output signal OUT becomes a signal having a waveform in which peaks of different intensities are mixed, which fluctuates with a cycle of twice the basic period P as in the case of the interference fringe 30, and the accuracy of position detection is lowered.

[Comparative Example 2]
FIG. 11 shows the relationship between the interference fringes and the light receiving element according to Comparative Example 2. In Comparative Example 2, the number of light-receiving elements arranged was 4, the arrangement cycle of the light-receiving elements was twice the basic period P of the interference fringes, and the width W of the light-receiving elements was 0.5 times the basic period P of the interference fringes. In this example, the light receiving elements 11A and the light receiving elements 11B are arranged alternately. That is, Comparative Example 2 does not satisfy the above-mentioned design condition 2.

As shown in FIG. 11, focusing on the light receiving element 11A, the light receiving elements 11A are arranged in a period 4P which is four times the basic period P. Focusing on the light receiving element 11B, the light receiving elements 11B are arranged in a period 4P which is four times the basic period P.

Assuming that 1/2 of the number of light receiving elements arranged is n, the light intensity detected by each of the light receiving elements 11A and 11B is I (θ), and the light intensity detected by the light receiving unit 9 is _ITOTAL , the following equation [ 7] holds.

I _TOTAL = nI (θ) + nI (θ + 4π)
= 2nI (θ) [7]

That is, as shown in the equation [6], since _ITOTAL directly reflects the light intensity of the interference fringes in the phase θ, it fluctuates with a period of 2P, which is twice the basic period, like the interference fringes. As a result, the output signal OUT becomes a signal having a waveform in which peaks of different intensities are mixed, which fluctuates with a cycle of twice the basic period P as in the case of the interference fringe 30, and the accuracy of position detection is lowered.

[Comparative Example 3]
FIG. 12 shows the relationship between the interference fringes and the light receiving element according to Comparative Example 3. In Comparative Example 3, the number of light-receiving elements arranged was 4, the arrangement cycle of the light-receiving elements was set to 3 times the basic period P of the interference fringes, and the width W of the light-receiving elements was set to 1 times the basic period P of the interference fringes. In this example, the light receiving elements 11A and the light receiving elements 11B are arranged alternately. That is, Comparative Example 3 does not satisfy the above-mentioned design condition 3.

In this example, similarly to the second embodiment, the waveforms of the interference fringes detected by the light receiving element 11A are the same, and the waveforms of the interference fringes detected by the light receiving element 11B are the same. However, since the width W of the light receiving element coincides with the basic cycle P, the output signal OUT from the light receiving unit 9 is smoothed, and the cycle of the output signal OUT becomes twice the basic cycle P. .. That is, the cycle of the output signal OUT becomes larger than the basic cycle P, and the accuracy of the position detection is lowered by that amount.

In this example, the case where the width W of the light receiving element is once the basic period P has been described, but the same holds true even when the width W of the light receiving element is an odd multiple of the basic period P.

[Comparative Example 4]
FIG. 13 shows the relationship between the interference fringes and the light receiving element according to Comparative Example 4. In Comparative Example 4, the number of light receiving elements arranged was 4, the arrangement cycle of the light receiving elements was 3 times the basic period P, and the width W of the light receiving elements was 2 times the basic period P. That is, Comparative Example 4 does not satisfy the above-mentioned design condition 3.

In this example, similarly to the second embodiment, the waveforms of the interference fringes detected by the light receiving element 11A are the same, and the waveforms of the interference fringes detected by the light receiving element 11B are the same. However, since the width W of the light receiving element is twice the basic period P and coincides with the period of the interference fringes 30, the intensity of the light detected by the light receiving unit 9 becomes constant. As a result, the output signal OUT becomes a signal having no periodicity, and position detection cannot be performed.

In this example, the case where the width W of the light receiving element is twice the basic period P has been described, but the same holds true even when the width W of the light receiving element is an even multiple of the basic period P.

In the above, the 0th-order diffracted light having the greatest influence among the unnecessary diffracted light has been focused on, but the present embodiment can suppress the influence of the unnecessary diffracted light of another order. Hereinafter, the mechanism thereof will be described for suppressing the influence of the + second-order diffracted light and the second-order diffracted light.

Here, the complex amplitude of the + second-order diffracted light is u _{+ 2} , the complex amplitude of the + 1st _- order diffracted light is u ₊₁ and the complex amplitude of the 0th-order diffracted light is u ₀ . When the complex amplitude is expressed as u _-2 , the interference fringes generated on the light receiving unit 9 can be expressed as the sum I of the multiplication of these five complex amplitudes and the five complex amplitudes and the conjugate complex amplitudes. Here, the conjugate to the complex amplitude of the diffracted light of each order is represented by displaying a line at the top.

The period of the interference fringes indicated by each term in the above equation can be calculated from the traveling directions of the two diffracted lights. Since it is the basic period P of the interference fringes due to the +1st order diffracted light and the -1st order diffracted light, the period of the interference fringes of each term is as shown in the following table.

The interference fringes caused by the 0th-order diffracted light and the + 1st-order diffracted light and the interference fringes caused by the 0th-order diffracted light and the -1st-order diffracted light have a period twice the basic period P as described above. It is possible to eliminate the effect.

Since the interference fringes due to the + 1st-order diffracted light and the + 2nd-order diffracted light and the interference fringes due to the -1st-order diffracted light and the -2nd-order diffracted light have twice the basic period P, the interference fringes of these interference fringes are configured by this configuration. It is possible to eliminate the effect.

The interference fringes of the -1st-order diffracted light and the + 2nd-order diffracted light and the interference fringes of the + 1st-order diffracted light and the -2nd-order diffracted light have a period of 2/3 times the basic period P. In this case, as a result, the influence of unnecessary interference light is eliminated by the arrangement of the light receiving elements 11A and 11B.

Therefore, according to this configuration, it is possible to remove a part of the influence of the interference fringes due to the + second-order diffracted light and the second-order diffracted light, that is, the influence of the interference fringes having a period twice and two-thirds of the basic period. Is.

On the other hand, the interference fringes due to the second-order diffracted light and the + second-order diffracted light have a period 1/2 times the basic period P, but the influence of the interference fringes remains without being removed. However, since the light intensities of the second-order diffracted light and the + second-order diffracted light are significantly smaller than the light intensities of the 0th-order diffracted light, the -1st-order diffracted light, and the + 1st-order diffracted light, the influence thereof is relatively minor. Therefore, as described above, by removing the influence caused by the unnecessary diffracted light of other order, the position detection accuracy is sufficiently improved without removing the influence of the interference fringes caused by the second-order diffracted light and the + second-order diffracted light. Can be made to.

Further, in the above, it has been explained that the interference component having a period of 2/3 times and 2 times the basic period can be removed, but considering the case where diffracted light of a third order or higher order is mixed, n is set to 0 or more. When it is an integer, it can be generalized as being able to remove an interference component having a period of 2 / (2 × n + 1) times the basic period P among all the generated interference fringes. That is, it can be understood that according to this configuration, among the unnecessary interference components generated by the mixing of higher-order diffracted light larger than the first order, the components having a predetermined period can be removed.

As described above, according to this configuration, it is possible to suppress or prevent the influence of unnecessary diffracted light without adding an optical element or the like for removing unnecessary diffracted light. Therefore, since the physical dimensions of the encoder do not increase, it is advantageous in reducing the size of the encoder.

Embodiment 2
The optical encoder according to the second embodiment of the present invention will be described. In this embodiment, a modified example of the light receiving unit 9 will be described. FIG. 14 is a diagram schematically showing the configuration of the light receiving portion according to the second embodiment. In the light receiving unit 40, two detection regions 41 and 42 are arranged in the X direction. The detection areas 41 and 42 are also referred to as first and second light receiving units, respectively.

The detection regions 41 and 42 have the same configuration as the light receiving unit 9 according to the first embodiment, respectively. However, the light receiving element of the detection area 42 is arranged so as to be offset in the X direction by 1/4 of the basic period P with respect to the light receiving element of the detection area 41. That is, the detection regions 41 and 42 are arranged so as to be offset in the X direction by 1/4 of the basic period P so as to move away in the X direction. In this case, the distance between the light receiving elements at the shortest distance in the connecting portion of the detection regions 41 and 42 is 1.25C.

According to this configuration, the detection area 41 can output an A-phase signal (0 °), and the detection area 42 can output a B-phase signal (90 °). By generating the phase difference signal in this way, more accurate position detection can be realized.

Further, another configuration example of the light receiving unit will be described. FIG. 15 is a diagram schematically showing another configuration of the light receiving portion according to the second embodiment. In the light receiving unit 50, the four detection regions 51 to 54 are arranged in this order in the X direction. Each of the detection regions 51 to 54 has the same configuration as the light receiving unit 9 according to the first embodiment. The detection regions 51 to 54 are also referred to as first to fourth light receiving units, respectively.

The light receiving element of the detection area 52 is arranged so as to be offset in the X direction by 1/4 of the basic period P with respect to the light receiving element of the detection area 51. The light receiving element of the detection area 53 is arranged so as to be offset in the X direction by 1/4 of the basic period P with respect to the light receiving element of the detection area 52. The light receiving element of the detection area 54 is arranged so as to be offset in the X direction by 1/4 of the basic period P with respect to the light receiving element of the detection area 53. That is, the detection regions 51 to 54 are arranged so as to be offset in the X direction by 1/4 of the basic period P so that the two adjacent light receiving portions are separated in the X direction. In this case, the distance between the light receiving elements at the shortest distance in the connecting portion of the two adjacent light receiving portions is 1.25C.

According to this configuration, the detection area 51 is an A-phase signal (0 °), the detection area 52 is a B-phase signal (90 °), the detection area 53 is an A-phase signal (180 °), and the detection area 54 is a B-phase. A signal (270 °) can be output. As a result, a differential A-phase signal is generated from the A-phase signal (0 °) and the A-phase signal (180 °), and the differential B-phase is generated from the B-phase signal (90 °) and the B-phase signal (270 °). It can generate a signal. By generating the phase difference signal in this way, more accurate position detection can be realized.

Further, another configuration example of the light receiving unit will be described. FIG. 16 is a diagram schematically showing another configuration of the light receiving portion according to the second embodiment. In the light receiving unit 60, the three detection regions 61 to 63 are arranged in this order in the X direction. Each of the detection regions 61 to 63 has the same configuration as the light receiving unit 9 according to the first embodiment. The detection areas 61 to 63 are also referred to as first to third light receiving units, respectively.

The light receiving element of the detection area 62 is arranged so as to be offset in the X direction by 1/3 of the basic period P with respect to the light receiving element of the detection area 61. The light receiving element of the detection area 63 is arranged so as to be offset in the X direction by 1/3 of the basic period P with respect to the light receiving element of the detection area 62. That is, the detection regions 61 to 64 are arranged so as to be offset in the X direction by 1/3 of the basic period P so that the two adjacent light receiving portions are separated in the X direction. In this case, the distance between the light receiving elements at the shortest distance in the connecting portion of the two adjacent light receiving portions is 4 / 3C.

According to this configuration, the detection area 61 can output an A-phase signal (0 °), the detection area 62 can output a B-phase signal (120 °), and the detection area 63 can output a C-phase signal (240 °). As a result, more accurate position detection can be realized by synthesizing the three-phase signals to generate the differential A-phase signal (0 °) and the differential B-phase signal (90 °).

Embodiment 3
Next, the optical encoder according to the third embodiment will be described. FIG. 17 is a perspective view showing the configuration of the optical encoder 300 according to the third embodiment. Here, the optical encoder 300 is configured as a transmissive encoder.

As shown in FIG. 17, the optical encoder 300 has a configuration in which an optical element 70 is added to the optical encoder 100 according to the first embodiment. The optical element 70 is configured so that diffracted light including at least +1st-order diffracted light, -1st-order diffracted light, and 0th-order diffracted light is incident, and the incident diffracted light is guided to the light receiving unit 9 of the detection unit 5. In other words, the optical element 70 is configured to collect the incident diffracted light on the detection unit 5 so that the + 1st-order diffracted light and the -1st-order diffracted light form an interference fringe 20 on the light receiving unit 9. Ru. In FIG. 17, as an example, the optical element 70 is represented as a diffraction grating. In the optical element 70, the light transmitting portions 70A extending in the Y direction are periodically arranged in the X direction on the flat plate member 70B having a main surface parallel to the XY plane. However, it goes without saying that various optical elements capable of condensing diffracted light on the light receiving unit 9 may be used as the optical element 70.

FIG. 18 shows an example of the optical element according to the third embodiment. As shown in FIG. 18, a diffraction grating 71 is provided as an optical element. The diffraction grating 71 has the same configuration as the optical element 70 configured as a diffraction grating. The diffraction grating 71 further diffracts the + 1st-order diffracted light L _{+ 1} and the _-1st -order diffracted light L-1 toward the detection unit 5 to form the interference fringes 20. Various diffraction gratings including an amplitude grating and a phase grating may be used as the diffraction grating 71.

FIG. 19 shows another example of the optical element according to the third embodiment. As shown in FIG. 19, the lens 72 is provided as an optical element. The lens 72 collects the +1st-order diffracted light L _{+ 1} and the -1st-order diffracted light L _-1 on the detection unit 5 to form the interference fringes 20. Various lenses such as an aspherical lens may be used as the lens 72. The lens 72 is only an example of an optical element, and the optical system may have two or more lenses as long as the + 1st-order diffracted light L _{+ 1} and the -1st-order diffracted light L _-1 can be focused on the detection unit 5. .. For example, a bilateral telecentric lens system (double lens, 4f design) or a double bilateral telecentric lens system may be used.

FIG. 20 shows another example of the optical element according to the third embodiment. As shown in FIG. 20, mirrors 73 and 74 are provided as optical elements. It is desirable that the mirrors 73 and 74 are arranged symmetrically so as to face each other with respect to the optical axis of the optical encoder 300. Here, the optical axis of the optical encoder 300 is an axis parallel to the Z axis that passes through the center of the light source and the center of the detection unit 5. The mirror 73 reflects the +1st-order diffracted light L ₊ 1 incident from the scale 1 toward the detection unit 5. The mirror 74 reflects the _-1st- order diffracted light L-1 incident from the scale 1 toward the detection unit 5. As a result, the reflected diffracted light can form an interference fringe 20 on the detection unit 5. The arrangement of mirrors is not limited to this arrangement. If the diffracted light can be suitably guided to the detection unit 5, another arrangement may be used.

In the example shown in FIGS. 18 to 20, the 0th-order diffracted light L0 also reaches the detection unit 5 via the optical element. However, it goes without saying that the influence of the 0th-order diffracted light L0 can be suppressed or eliminated based on the principle described in the above-described embodiment. Therefore, as described above, shading for error suppression is not an essential function, and a simpler design becomes possible.

As described above, according to the present configuration, it is possible to suppress or prevent the influence of unnecessary diffracted light without adding an optical element or the like for removing unnecessary diffracted light, as in the above-described embodiment.

Embodiment 4
Next, the optical encoder according to the fourth embodiment will be described. FIG. 21 is a perspective view showing the configuration of the optical encoder 400 according to the fourth embodiment. FIG. 22 is a top view showing the configuration of the optical encoder 400 according to the fourth embodiment. FIG. 23 is a side view showing a configuration when the optical encoder 400 according to the fourth embodiment is viewed along the X-axis direction. FIG. 24 is a side view showing a configuration when the optical encoder 400 according to the fourth embodiment is viewed along the Y-axis direction.

Compared with the optical encoder 300, in the optical encoder 400, the scale 1 and the optical element 70 are replaced with the scale 90 and the optical element 80, respectively, and the arrangement of each component is changed.

In the present embodiment, the optical encoder 400 is configured as a reflection type encoder. The light source 4 and the detection unit 5 are arranged on the side of one surface (upper surface of FIG. 21) of the optical element 80. The scale 90 is arranged on the side of the other surface (lower surface of FIG. 21) of the optical element 80.

In FIGS. 21 to 24, the parallel light 4A, the laser light 4D, the + 1st-order diffracted light L ₊₁ and the _-1st -order diffracted light L-1 are represented by three lines in order to show the light path. The three lines in FIGS. 21, 22 and 24 are represented so as to be separated in the X-axis direction. The three lines in FIG. 23 are represented so as to be separated in the Y-axis direction. When viewed along the X-axis direction, the + 1st-order diffracted light L _{+ 1} and the -1st-order diffracted light L _-1 overlap. Therefore, in FIG. 23, for simplification, only the +1st order diffracted light L _{+ 1} is displayed.

In the present embodiment, the parallel light 4A output from the light source 4 is incident on the scale 90. In this embodiment, the light source 4 has a semiconductor laser 4B and a collimating lens 4C. The semiconductor laser 4B outputs the laser beam 4D to the collimating lens 4C. In FIG. 21, the semiconductor laser 4B is represented as a CAN package in which a semiconductor laser diode that outputs a laser beam 4D is mounted inside. The wavelength of the laser beam 4D may be, for example, 660 nm. The collimating lens 4C collimates the laser beam 4D and outputs the parallel light 4A to the scale 90.

Since the optical encoder 400 is configured as a reflection type encoder, the light source 4 is arranged so that the parallel light 4A is incident on the scale 90 from a direction in which the parallel light 4A is inclined with respect to the surface of the scale 90. In the example of FIGS. 21 to 24, the parallel light 4A is incident on the scale 90 from a direction inclined by a predetermined angle in the YY plane with respect to the surface of the scale 90. However, the incident direction of the parallel light 4A in FIGS. 21 to 24 is only an example, and may be another direction. Therefore, since the paths of the +1st-order diffracted light L ₊₁ and the _-1st -order diffracted light L-1 do not overlap with the parallel light 4A, the detection unit 5 can suitably receive the diffracted light without interfering with the light source 4. can.

The scale 90 is configured as a reflective grid. The pitch _Ps of the incremental pattern of the scale 90 may be, for example, 2 μm. The parallel light 4A incident on the scale 90 is diffracted and reflected by the scale 90.

The optical element 80 is configured so that diffracted light including at least +1st-order diffracted light, -1st-order diffracted light, and 0th-order diffracted light is incident, and the incident diffracted light is guided to the light receiving unit 9 of the detection unit 5. In other words, the optical element 80 is configured to collect the incident diffracted light on the detection unit 5 so that the + 1st-order diffracted light and the -1st-order diffracted light form the interference fringes 20 on the detection unit 5. Ru.

The configuration of the optical element 80 will be described. The optical element 80 is configured as a transmissive grid. The optical element 80 is composed of a periodic pattern 81 and a transparent substrate 82. The transparent substrate 82 is a plate-shaped member made of a transparent material such as glass or synthetic quartz and having a main surface parallel to the XY plane. For the sake of simplicity, the transparent substrate 82 is omitted in FIG. 22.

The distance D1 in the Z-axis direction between the upper surface of the scale 90 and the lower surface of the transparent substrate 82 may be, for example, 2.5 mm. The thickness T1 of the transparent substrate 82 in the Z-axis direction may be, for example, 2.286 mm (0.09 inch). The distance D2 in the Z-axis direction between the upper surface of the scale 90 and the light receiving surface of the detection unit 5 may be, for example, 13.28 mm.

The periodic pattern 81 is formed on the upper surface of the transparent substrate 82 on the side of the light source 4 and the detection unit 5. The periodic pattern 81 may be configured as a phase grid. In this case, the periodic pattern 81 is composed of grooves extending in the Y-axis direction and periodically arranged in the X-axis direction. Periodic grooves may be formed by general photolithography and etching (eg, reactive ion etching: dry etching such as RIE (Reactive Ion Etching)).
The pitch Pi of the periodic groove may be, for example, 4/3 μm ( _1.333 ... μm).

ピッチＰ_ｓが２μｍ、ピッチＰ_ｉが４／３μｍ（１．３３３．．．μｍ）の場合、ピッチＰ_ｆは２μｍとなる。 The pitch P _f of the interference fringes 20 can be defined by the following equation.

When the pitch P _s is 2 μm and the pitch P _i is 4/3 μm (1.333 ... μm), the pitch P _f is 2 μm.

As described above, according to the present configuration, it is possible to suppress or prevent the influence of unnecessary diffracted light without adding an optical element or the like for removing unnecessary diffracted light, as in the above-described embodiment.

The optical element 80 is not limited to the diffraction grating. Various optical elements such as a lens and a mirror described in the third embodiment may be used as the optical element 80.

Embodiment 5
In this embodiment, a modified example of the light receiving unit 9 according to the above-described embodiment will be described. FIG. 25 schematically shows the configuration of the light receiving unit LRU1 according to the fifth embodiment. The light receiving unit LRU1 has a plurality of detection rows DS arranged in the Y direction. In this example, for simplification, the light receiving unit LRU1 having two detection rows DS arranged in the Y direction will be described. In FIG. 25, DS 11 shows one of the two detection columns DS and DS 12 shows the other of the two detection columns DS. Needless to say, in the light receiving unit LRU1, three or more detection rows may be arranged in the Y direction.

Each of the detection columns DS has a plurality of light receiving regions. In this embodiment, a four-phase structure provided with four detection regions DA11 to DA14 will be described. The detection regions DA11 to DA14 are configured to give A-phase, B-phase, A-phase, and B-phase signals, respectively. Needless to say, each of the detection columns DS may be provided with two (two-phase structure), three (three-phase structure), or five or more detection regions.

Each of the detection regions DA11 to DA14 has the same configuration as the detection region of the light receiving unit 9 according to the first embodiment. While the detection regions DA11 to DA14 are arranged in the Y direction, they are each shifted in the X direction by 1/4 (P / 4) of the basic period P in order to give a four-phase signal.

Specifically, the light receiving element 11 in the detection area DA12 is shifted in the X direction by P / 4 with respect to the light receiving element 11 in the detection area DA11. The light receiving element 11 of the detection area DA13 is shifted in the X direction by P / 4 with respect to the light receiving element 11 of the detection area DA12. The light receiving element 11 of the detection area DA14 is shifted in the X direction by P / 4 with respect to the light receiving element 11 of the detection area DA13.

The light receiving elements 11 of the detection region DA11 are connected to each other in order to synthesize an output signal, and the combined signal is output as an A phase signal. The light receiving elements 11 of the detection region DA12 are connected to each other in order to synthesize an output signal, and the combined signal is output as a B phase signal. The light receiving elements 11 of the detection region DA13 are connected to each other in order to synthesize an output signal, and the combined signal is output as an A-phase signal. The light receiving elements 11 of the detection region DA14 are connected to each other in order to synthesize an output signal, and the combined signal is output as a B-phase signal.

The in-phase signals output from the detection columns DS11 and DS12 are combined, and the combined signal is output to the signal processing unit 3. Specifically, the A-phase signals output from the detection columns DS11 and DS12 are combined, and the combined A-phase signal is output to the signal processing unit 3. The B-phase signals output from the detection columns DS11 and DS12 are combined, and the combined B-phase signal is output to the signal processing unit 3. The A-phase signals output from the detection columns DS11 and DS12 are combined, and the combined A-phase signals are output to the signal processing unit 3. The B-phase signals output from the detection columns DS11 and DS12 are combined, and the combined B-phase signals are output to the signal processing unit 3.

According to this configuration, the detection regions DA11 to DA14 output an A-phase signal (0 °), a B-phase signal (90 °), an A-phase signal (180 °), and a B-phase signal (270 °), respectively. can do. Therefore, as in the second embodiment, it is possible to generate a phase difference signal and perform more precise position detection.

Further, since the detection regions are arranged in the Y direction intersecting the measurement direction (X direction), even if there is a detection region that is contaminated or has a defect, other uncontaminated or defect-free detection regions are present. The detection area can compensate for the effects of contamination or defects. Therefore, the accuracy of the output signal of the light receiving unit can be suitably maintained.

Next, another configuration of the light receiving unit will be described. FIG. 26 schematically shows the configuration of another light receiving unit LRU2 according to the fifth embodiment. In this example, the light receiving unit LRU2 has a three-phase structure.

The light receiving unit LRU2 has a configuration in which the detection columns DS11 and DS12 of the light receiving unit LRU1 are replaced with the detection columns DS21 and DS22, respectively.

Each of the detection columns DS21 and DS22 has three detection regions DA21 to DA23. The detection regions DA21 to DA23 are configured to give A-phase, B-phase, and C-phase signals, respectively.

Each of the detection regions DA21 to DA23 has the same configuration as each of the light receiving regions DA11 to DA14 except for the arrangement pitch of the light receiving elements 11. While the detection regions DA21 to DA23 are arranged in the Y direction, they are each shifted in the X direction by 1/3 (P / 3) of the basic period P in order to give a three-phase signal.

The light receiving element 11 in the detection area DA22 is shifted in the X direction by P / 3 with respect to the light receiving element 11 in the detection area DA21. The light receiving element 11 of the detection area DA23 is shifted in the X direction by P / 3 with respect to the light receiving element 11 of the detection area DA22.

The light receiving elements 11 of the detection region DA21 are connected to each other in order to synthesize an output signal, and the combined signal is output as an A phase signal. The light receiving elements 11 of the detection region DA22 are connected to each other in order to synthesize an output signal, and the combined signal is output as a B phase signal. The light receiving elements 11 of the detection region DA23 are connected to each other in order to synthesize an output signal, and the combined signal is output as a C phase signal.

The in-phase signals output from the detection columns DS21 and DS22 are combined, and the combined signal is output to the signal processing unit 3. Specifically, the A-phase signals output from the detection columns DS21 and DS22 are combined, and the combined A-phase signal is output to the signal processing unit 3. The B-phase signals output from the detection columns DS21 and DS22 are combined, and the combined B-phase signal is output to the signal processing unit 3. The C-phase signals output from the detection columns DS21 and DS22 are combined, and the combined C-phase signal is output to the signal processing unit 3.

According to this configuration, the detection regions DA21 to DA23 can output an A-phase signal (0 °), a B-phase signal (120 °), and a C-phase signal (240 °), respectively. Therefore, similarly to the light receiving unit LRU1, it is possible to generate a phase difference signal and perform more precise position detection.

Further, similarly to the light receiving unit LRU1, the accuracy of the output signal of the light receiving unit can be suitably maintained.

By modifying the light receiving unit described in the present embodiment, it is possible to realize a light receiving unit corresponding to a polyphase signal. Specifically, it is possible to realize a light receiving unit that can handle k-phase signals. Here, k is an integer of 2 or more. In this case, in one detection row, k detection regions in which the light receiving elements are arranged in the measurement direction (X direction) may be arranged in the direction (Y direction) intersecting the measurement direction (X direction) with a period P. , K detection regions may be shifted from each other in the measurement direction by pitch P / k.

Embodiment 6
In this embodiment, a modified example of the light receiving portions LRU1 and LRU2 according to the fifth embodiment will be described.

FIG. 27 schematically shows the configuration of the light receiving unit LRU3 according to the sixth embodiment. The light receiving unit LRU3 is a modification of the light receiving unit LRU1. The light receiving unit LRU3 is configured to have a four-phase structure.

In the light receiving unit LRU3, the four detection rows DS11 are arranged at a pitch of nP + P / 4 in the X direction, and the four detection rows DS12 are arranged at a pitch of nP + P / 4 in the X direction. Here, n is an integer of 1 or more. In this example, DS11_1 to DS11_4 each show four detection columns DS11 arranged from left to right along the X direction of the paper in the figure. DS12_1 to DS12_1 show four detection columns DS12 arranged from left to right along the X direction of the paper in the figure, respectively.

The detection row DS11_1 outputs A-phase, B-phase, A-phase, and B-phase signals in the same manner as the detection row DS11 of the light receiving unit LRU1.

In this configuration, since the two adjacent detection regions are substantially shifted in the X direction by nP + P / 4, the phase corresponding to one light receiving element of the two adjacent detection regions is the phase corresponding to the two adjacent detection regions. There is a substantial 90 ° shift with respect to the phase corresponding to the other light receiving element of.

Therefore, the detection regions DA11 of the detection columns DS11_1 to DS11_4 output signals of A phase, B phase, A-phase, and B-phase, respectively. The detection regions DA12 of the detection columns DS11_1 to DS11_4 output B-phase, A-phase, B-phase, and A-phase signals, respectively. The detection regions DA13 of the detection columns DS11_1 to DS11_1 output signals of A-phase, B-phase, A-phase, and B-phase, respectively. The detection regions DA14 of the detection columns DS11_1 to DS11_4 output B-phase, A-phase, B-phase, and A-phase signals, respectively. The in-phase signals output from the detection columns DS11_1 to DS11_4 are combined, and the combined signals are output to the signal processing unit 3.

Since the principle of the detection columns DS11_1 to DS11_1 can be applied to the detection columns DS12_1 to DS12_1, the description of the detection columns DS12_1 to DS12_1 will be omitted.

According to this configuration, since the detection region is also arranged in the measurement direction (X direction) as compared with the light receiving unit LRU1, even if there is a detection region contaminated or has a defect, other uncontaminated or defective detection regions are present. Other detection regions without defects can compensate for contamination or unwanted effects of defects in the X direction. Therefore, the influence of contamination or defects can be further suppressed. Therefore, the accuracy of the output signal of the light receiving unit can be suitably maintained.

By deforming the light receiving unit LRU3, it is possible to realize a further improved configuration. In this configuration, the detection columns DS11_1 to DS11_4 form a set that gives a four-phase signal, and the detection columns DS12_1 to DS12_1 also form a set that gives a phase signal. Therefore, by arranging two or more sets having such four detection rows in the measurement direction (X direction), it is possible to further suppress the unnecessary influence of contamination or defects in the X direction.

Next, another configuration of the light receiving unit will be described. FIG. 28 schematically shows the configuration of another light receiving unit LRU4 according to the sixth embodiment. The light receiving unit LRU4 is a modified example of the light receiving unit LRU2 having a three-phase structure.

In the light receiving unit LRU4, the three detection rows DS21 are arranged at a pitch of nP + P / 3 in the X direction, and the three detection rows DS22 are arranged at a pitch of nP + P / 3 in the X direction. In this example, DS21_1 to DS21_3 show three detection columns DS21 arranged from left to right along the X direction of the paper in the figure, respectively. DS22_1 to DS22_3 show three detection columns DS22 arranged from left to right along the X direction of the paper in the figure, respectively.

The detection row DS21_1 outputs A-phase, B-phase, and C-phase signals in the same manner as the detection row DS21 of the light receiving unit LRU2.

In this configuration, since the two adjacent detection regions are substantially shifted in the X direction by nP + P / 3, the phase corresponding to one light receiving element of the two adjacent detection regions is the phase corresponding to the two adjacent detection regions. There is a substantial 120 ° shift with respect to the phase corresponding to the other light receiving element of.

Therefore, the detection regions DA21 of the detection columns DS21_1 to DS21_3 output the signals of the A phase, the B phase, and the C phase, respectively. The detection regions DA22 of the detection columns DS21_1 to DS21_3 output B-phase, C-phase, and A-phase signals, respectively. The detection regions DA23 of the detection columns DS21_1 to DS21_3 output C-phase, A-phase, and B-phase signals, respectively. The in-phase signals output from the detection columns DS21_1 to DS21_3 are combined, and the combined signals are output to the signal processing unit 3.

Since the principle of the detection columns DS21_1 to DS21_3 can be applied to the detection columns DS22_1 to DS22___, the description of the detection columns DS22_1 to DS22_3 will be omitted.

According to this configuration, since the detection region is also arranged in the measurement direction (X direction) as compared with the light receiving unit LRU2, even if there is a detection region contaminated or has a defect, other uncontaminated or defective detection regions are present. Other detection regions without defects can compensate for contamination or unwanted effects of defects in the X direction. Therefore, the influence of contamination or defects can be further suppressed. Therefore, the accuracy of the output signal of the light receiving unit can be suitably maintained.

By deforming the light receiving unit LRU4, it is possible to realize a further improved configuration. In this configuration, the detection columns DS21_1 to DS21_3 form a set that gives a three-phase signal, and the detection columns DS22_1 to DS22_3 also form a set that gives a three-phase signal. Therefore, by arranging two or more sets having such three detection rows in the measurement direction (X direction), it is possible to further suppress the unnecessary influence of contamination or defects in the measurement direction (X direction).

By modifying the light receiving unit described in the present embodiment, it is possible to realize a light receiving unit corresponding to a polyphase signal. Specifically, it is possible to realize a light receiving unit that can handle k-phase signals. Here, k is an integer of 2 or more. In this case, in one detection row, k detection regions in which the light receiving elements are arranged in the measurement direction (X direction) may be arranged in the direction (Y direction) intersecting the measurement direction (X direction) with a period P. , K detection regions may be shifted from each other in the measurement direction by pitch P / k.

Further, k detection regions are arranged in the same row in the measurement direction (X direction) at a pitch of nP + P / k. In this case, the j-th detection region arranged in the X direction can output a signal having a phase of 2π (j-1) / k + θ _int . However, j is an integer (2 ≦ j ≦ k) of 2 or more and k or less, and θ _int is the initial phase in the first (j = 1) detection region.

Other Embodiments The present invention is not limited to the above embodiments, and can be appropriately modified without departing from the spirit. In the above-described embodiment, the optical encoder 100 has been described as a transmissive encoder, but this is merely an example. That is, of course, the optical encoder 100 may be configured as a reflection type encoder.

Further, in the above-mentioned encoder, an index grid for selecting the order of the diffracted light to be propagated may be arranged between the light source and the scale and / or between the scale and the detection unit. Further, an optical element such as a diffraction grating or a lens that forms an image of the diffracted light from the scale may be arranged between the scale and the detection unit.

In the above-described embodiment, a configuration for generating an A-phase signal (0 °), a B-phase signal (90 °), an A- signal (180 °), and a B- signal (270 °) has been described. The order of the phases can be changed and may be shifted such as 1/4, 1/2, −1 / 2 and -1/4. For example, there may be A phase, A-phase, B phase and B-phase shifted by 1/2, -1/4, 1/2 and -1/4.

A configuration may be configured in which the light receiving elements have at least three different phases of the basic period of the interference fringes and are shifted by the amount corresponding to each of the at least three phases. Elements corresponding to at least three phases may be grouped into one or more groups for each phase.

The detection regions corresponding to three or more phases do not need to be arranged in the X direction in a predetermined order. The detection regions may be arranged in a predetermined order in the Y direction in the same range as in the X direction. The detection regions corresponding to three or more phases may be two-dimensionally arranged in the X direction and the Y direction.

In the above-mentioned encoder, the distance between the scale and the detection unit is not particularly limited. However, when an optical element such as a diffraction grating or a lens that forms an image of diffracted light from the scale is not arranged between the scale and the detection unit, the distance between the scale and the detection unit is preferably an interference fringe on the detection unit. It is desirable to set the distance to occur.

1, 90 scale 2 Detection head 3 Signal processing unit 4 Light source 4A Parallel light 5 Detection unit 6 Origin pattern 6A, 7A Light transmission unit 7 Incremental pattern 8, 9, LRU1 to LRU4 Light receiving unit 10, 11, 11A, 11B Light receiving element 20 , 30 Interference fringe 7A Light transmitting part 7B Non-transmitting part 31, 32 Peak 40, 50, 60 Light receiving part 41, 42, 51 to 54, 61 to 63 Detection area 70, 80 Optical element 70A Light transmitting part 70B Flat plate member 71 Diffraction Lattice 72 Lens 73, 74 Mirror 100, 300, 400 Optical Encoder C Basic Period DET Detection Signal OUT Output Signal 81 Periodic Pattern 82 Transparent Substrate

Claims (5)

A scale with an incremental pattern and
A detection head that is movable in the measurement direction relative to the scale, detects diffracted light diffracted by the incremental pattern of light radiated to the scale, and outputs a detection result.
A signal processing unit that calculates a relative displacement between the scale and the detection head according to the detection result of the detection head is provided.
The detection head is
A light source that irradiates the scale with light,
A detection unit having a light receiving unit in which a plurality of light receiving elements for outputting a detection signal of the diffracted light from the scale are periodically arranged in the measurement direction at a predetermined period.
An optical element that guides the diffracted light to the detection unit is provided.
The plurality of light receiving elements are arranged in an even number in the measurement direction.
The predetermined period is an odd multiple of the basic period, which is the period of the interference fringes generated on the light receiving portion by the +1st order diffracted light and the -1st order diffracted light among the diffracted light.
The width of the light receiving element in the measurement direction is a value that is not an integral multiple of the basic period .
The +1st-order diffracted light, the -1st-order diffracted light, and the 0th-order diffracted light from the scale are incident on the detection unit.
k is an integer greater than or equal to 2 and
The basic period is P,
The k detection regions arranged in the directions intersecting the measurement directions form a detection row.
The detection regions are shifted from each other in the measurement direction at a pitch of P / k.
Encoder. n is an integer of 1 or more,
The k detection rows are periodically arranged at a pitch of nP + P / k in the measurement direction.
The encoder according to claim 1 . The optical element collects the +1st-order diffracted light and the -1st-order diffracted light on the detection unit to form the interference fringes.
The encoder according to claim 1 or 2 . The optical element is either a diffraction grating or a lens.
The encoder according to claim 3 . The optical element is composed of two mirrors.
One mirror reflects the +1st order diffracted light toward the detection unit.
The other mirror reflects the -1st order diffracted light toward the detection unit.
The encoder according to claim 3 .

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