JP6215572B2 - Displacement measuring device - Google Patents

Description

  The present invention relates to a displacement measuring apparatus and a displacement measuring method using optical interference.

  For example, Patent Document 1 discloses a displacement measuring device using optical interference. This displacement measuring device includes a laser light source, a collimator lens, a first diffraction grating, a second diffraction grating, and an optical sensor in this order from the light source side. The optical sensor diffracted light (for example, 1st order) diffracted by the first diffraction grating and diffracted light (for example, 1st order) generated by diffracting the 0th order light traveling straight through the first diffraction grating with the second diffracted light. Next, the interference light is detected. This displacement measuring device measures a change in the distance between the first and second diffraction gratings, that is, a displacement to be measured based on a change in the amount of light due to the brightness of the interference light detected by the optical sensor (for example, patent document). 1 specification paragraphs [0020], [0023], [0027], see FIGS.

  The photoelectric encoder described in Patent Document 2 includes two diffraction gratings and a moving grating. Six light beams (21a, 21b, 22a, 22b, 23a, 23b) generated by being diffracted by two diffraction gratings are incident on the moving grating, and light beams in three different directions are emitted from the moving grating 5. Are received by three light receiving elements, respectively. Based on the output signals of these light receiving elements, the encoder processing circuit calculates the phase information of the interference light intensity, so that the displacement of the moving grating in the x and z directions and the displacement of the pitch angle that is the inclination around the y axis are reduced. Information is obtained (see, for example, paragraphs [0008] to [0014] in FIG. 1 of Patent Document 2).

International Publication No. 2011/043354 Pamphlet JP 2005-326232 A

  In the photoelectric encoder of Patent Document 2, since the linear displacement and the angular displacement around the axis are measured as described above, the number of optical components is increased and it is difficult to reduce the size.

  An object of the present invention is to provide a displacement measuring apparatus and a displacement measuring method capable of measuring at least an angular displacement around a predetermined axis without using a large number of optical components.

In order to achieve the above object, a displacement measuring apparatus according to the present invention includes a light source, a diffraction grating pair, a plurality of light receiving regions, and an arithmetic means.
The diffraction grating pair is disposed along the path of the light beam from the light source, is relatively movable, and generates diffracted light.
The plurality of light receiving regions can detect interference light of a set of diffracted light along the path of n-order diffracted light (n is an integer other than 0) generated from any one of the diffraction grating pairs. .
The arithmetic means calculates an angular displacement of a relative rotation of the diffraction grating pair based on signals obtained from the plurality of light receiving regions.

  The displacement measuring apparatus mainly includes an opposing diffraction grating pair and a plurality of light receiving regions capable of detecting interference light, thereby calculating the relative angular displacement of the diffraction grating pair by the arithmetic processing of the arithmetic means. be able to. That is, the angular displacement can be measured with a small number of optical components, and the apparatus can be miniaturized.

  The diffraction grating pair may have a plurality of grating lines, and the plurality of light receiving regions may be arranged in a first direction that is an arrangement direction of the plurality of grating lines. Further, the calculation means may calculate the angular displacement around an axis along a second direction that is a direction of the lattice line. The amount of the interference light received by each light receiving region changes according to the angular displacement of the diffraction grating pair around the axis along the second direction. Therefore, the calculation means can calculate the angular displacement around the axis along the second direction.

  In order for the calculation means to calculate the angular displacement, if the entire plurality of light receiving areas are set as the detection area, the interference fringes of the interference light detected in the detection area are determined based on the width of the detection area in the first direction. The condition that the width in the direction 1 is narrow is necessary.

  The calculation means may calculate the angular displacement about an axis along the second direction based on calculation values of signals obtained in two light receiving areas as the plurality of light receiving areas.

  The displacement measuring device may further include a plurality of light receiving regions configured to be further arranged in the second direction. Further, the calculation means is the direction of the optical axis of the diffraction grating pair based on signals obtained from the plurality of light receiving regions in the first direction and the plurality of light receiving regions in the second direction, respectively. The angular displacement around the axis along the third direction may be calculated. The predetermined calculation value based on the amount of the interference light received by these light receiving regions changes according to the angular displacement of the diffraction grating pair around the axis along the third direction. Therefore, the calculation means can calculate the angular displacement around the axis along the third direction.

  For example, the plurality of light receiving regions may be four light receiving regions arranged in a matrix. The calculation means is configured to calculate a signal obtained in each of the two light receiving areas located on the first diagonal line among the four light receiving areas, and a second diagonal line intersecting the first diagonal line. The angular displacement around the axis along the third direction may be calculated by calculating a value based on the calculated values of the signals respectively obtained in the two light receiving regions located at the position.

  The plurality of light receiving regions include a first light receiving region group arranged on a path side of + n order diffracted light (n is a natural number of 1 or more), and -n order diffracted light (n is 1 or more). It may be configured as a second light receiving region group disposed on the path of (natural number). By using the first and second light receiving region groups, it is possible to increase the detection sensitivity of the change in the interference light according to the angular displacement of the diffraction grating pair. Alternatively, the calculation means detects an angular displacement around an axis along a predetermined direction based on the signal obtained from the first light receiving region group, and based on the signal obtained from the second light receiving region group, Can also detect angular displacements about axes in different directions.

  The diffraction grating pair may have a plurality of grating lines. The first light receiving region group includes a first light receiving region and a second light receiving region arranged in a first direction that is an arrangement direction of the plurality of lattice lines, and the second light receiving region group includes: And a third light receiving region and a fourth light receiving region arranged in the first direction. The third light receiving region is located on the same side as the first light receiving region in the first direction with the optical axis of the diffraction grating pair as a center, and the fourth light receiving region is the first light receiving region. It may be located on the same side as the second light receiving region in the direction of 1. Further, the calculation means is based on the calculated values of the signals obtained in the first and third light receiving areas and the calculated values of the signals obtained in the second and fourth light receiving areas, respectively. By calculating the value, the angular displacement around the axis along the second direction that is the direction of the lattice line may be calculated.

In the displacement measuring method according to the present invention, light from the light source is incident on a pair of relatively movable diffraction gratings arranged along a path of light from the light source, so that diffracted light is emitted from the diffraction grating pair. Including generating.
Interference light of a set of diffracted light along the path of n-order diffracted light (n is an integer other than 0) generated from any one of the diffraction grating pairs is detected by the plurality of light receiving regions.
Based on the signals obtained in the plurality of light receiving regions, the angular displacement of the relative rotation of the diffraction grating pair is calculated.

  As described above, according to the present invention, it is possible to measure an angular displacement around at least a predetermined axis without using a large number of optical components.

FIG. 1 is a diagram schematically showing a configuration of a basic optical system of a displacement measuring apparatus according to the first embodiment of the present invention. FIG. 2 is a perspective view of the displacement measuring device shown in FIG. FIG. 3 is a diagram schematically showing a light receiving region of the PD shown in FIG. FIG. 4 shows an interference pattern of each diffracted light emitted from the diffraction grating pair. 5A to 5C show the change in the interference pattern for each tilt angle around the y-axis between the diffraction grating pair. FIG. 6 is a perspective view showing the configuration of the displacement measuring apparatus according to the second embodiment. FIG. 7 shows a detection region of the PD 41 shown in FIG. FIG. 8 is an actually measured graph showing the relationship between the tilt angle between the diffraction grating pair around the y-axis and the calculated value. FIG. 9 is a diagram showing the generation of a tilt angle around the z-axis between diffraction gratings in order to explain the third embodiment of the present invention. 10A to 10E show changes in the interference pattern for each tilt angle around the z-axis of the diffraction grating pair 20. FIG. 11 is an actual measurement graph showing the relationship between the calculated tilt and the tilt angle about the relative z-axis between the diffraction grating pair. FIG. 12 is a perspective view showing a configuration of a displacement measuring apparatus according to the fourth embodiment of the present invention. FIG. 13 shows an interference pattern when the relative tilt angle about the y-axis between the diffraction grating pairs is generated and the amounts of light received by the two PDs in the fourth embodiment. FIG. 14 is a perspective view showing a configuration of a displacement measuring apparatus according to the fifth embodiment of the present invention. FIG. 15 is a graph schematically showing the relationship between the relative displacement in the z direction between the diffraction grating pairs and the signal detected by the PD in the eighth embodiment of the present invention. FIG. 16 is a cross-sectional view showing the optical system shown in FIGS. 2 and 6 and a housing for housing the optical system.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1. First Embodiment (1) Basic Configuration of Displacement Measuring Device FIGS. 1 and 2 are diagrams schematically showing a basic optical system configuration of a displacement measuring device according to a first embodiment of the present invention. .

  The displacement measuring apparatus 100 includes a light source 12, a collimator lens 14, a diffraction grating pair 20, and a PD (Photo Detector) 31 as an optical sensor.

  The light source 12 is an LD (Laser Diode) or an LED (Light Emitting Diode), and is driven by a driver (not shown).

  The collimator lens 14 turns the light emitted from the light source 12 into parallel light 15. At least the light source 12 and the collimator lens 14 constitute an optical system that generates parallel light.

  Light from the light source 12 and the collimator lens 14 enters the diffraction grating pair 20 and emits diffracted light. The diffraction grating pair 20 includes a first diffraction grating 21 and a second diffraction grating 22. The first diffraction grating 21 and the second diffraction grating 22 are arranged so as to face each other along the paths of the light beams from the light source 12 and the collimator lens 14, here along the optical axes of the light source 12 and the collimator lens 14. As described later, it is relatively movable in a predetermined direction.

  The first diffraction grating 21 advances the incident parallel light 15 by dividing it into a straight-ahead light 30 that is zero-order light and an n-order diffracted light (n is an integer other than 0) 23. In the present specification, when the positive / negative sign of “n” is not indicated, n can be an integer other than 0, and attention is paid to one of positive and negative n.

  The -n-order diffracted light (n is a natural number of 1 or more) is diffracted light that is line-symmetric with + n-order diffracted light (n is a natural number of 1 or more) about the axis along the z direction. In the present embodiment, first-order diffracted light is used as the diffracted light 23.

  The second diffraction grating 22 further divides the straight traveling light 30 emitted from the first diffraction grating 21 and incident on the second diffraction grating 22 into a straight traveling light 30 (0th order light) and an nth order diffracted light 25. To proceed. In the present embodiment, the first-order diffracted light traveling along the path of the first-order diffracted light 23 is used as the diffracted light 25.

  The second diffraction grating 22 also generates zero-order light that travels the first-order diffracted light 23 emitted from the first diffraction grating 21 in the same direction. Here, for convenience of explanation, the first-order diffracted light 23 of the first diffraction grating 21 and the zero-order light of the second diffraction grating 22 along the path thereof are collectively expressed as the first-order diffracted light 23. Further, after passing through the first diffraction grating 21 and the second diffraction grating 22, the 0th order light traveling in the same direction as the parallel light 15 is collectively expressed as a straight traveling light 30.

  In summary, the configurations of the diffracted beams 23 and 25 are as follows.

Diffraction light 23: 1st-order diffracted light of diffraction grating 21 and 0th-order light of diffraction grating 22 Diffraction light 25: 0th-order light of diffraction grating 21 and 1st-order diffracted light of diffraction grating 22

  Among the diffracted lights generated by the first diffraction grating 21 and the second diffraction grating 22, the interference light 27 of at least one set of diffracted lights along the path of the first-order diffracted light 23 by the first diffraction grating 21 is It is generated from the diffraction grating pair 20. For example, the first-order diffracted light 23 from the first diffraction grating 21 interferes with the first-order diffracted light 25 generated when the straight light 30 enters the second diffraction grating 22 to generate interference light 27.

  In the present embodiment, the 0th-order light and the 1st-order diffracted light are used. However, the displacement may be measured using other predetermined orders of diffracted light. In practice, there are many diffracted lights other than those shown in FIG. 1, but the illustration is omitted to facilitate the following description.

  The first diffraction grating 21 and the second diffraction grating 22 have substantially the same shape and the same size. For example, the diffraction grating 21 (and 22) has a plurality of grating lines 21a (and 22a) which are grooves along the y direction orthogonal to the z direction in FIG. The pitch P of the grating lines 21a of the first diffraction grating 21 and the pitch P of the grating lines 22a of the second diffraction grating 21 are formed substantially the same. As an example of the lattice lines 21a and 22a, the pitch P is 3.3 μm and the groove depth is 473 μm. Of course, it is not restricted to these values.

  The displacement measuring apparatus 100 according to the present embodiment calculates the angular displacement Δθ of the relative rotation of the first diffraction grating 21 and the second diffraction grating 22 around the y axis that is an axis along the grating lines 21a and 22a. Measured. That is, the tilt angle Δθ around the y-axis between the first diffraction grating 21 and the second diffraction grating 22 is to be measured.

  In this specification, two axes orthogonal to the z direction are defined as x and y axes. As described above, the direction along the grating lines 21a and 22a of each diffraction grating is the y direction (second direction), and the arrangement direction of the grating lines 21a and 22a is the x direction (first direction). The PD 31 is disposed at a position where the interference light 27 can be detected. Specifically, as shown in FIG. 2, the PD 31 is arranged so as to be shifted in the x direction from the z axis that is the optical axis of the diffraction grating pair 20.

  FIG. 3 is a diagram schematically showing a light receiving region of the PD 31. The PD 31 has a plurality of light receiving areas. Specifically, the PD 31 has light receiving areas A and B configured by dividing a detection area, which is an entire area of the light receiving surface, into two. The light receiving areas A and B configured by dividing the detection area of one PD 31 in this way are arranged along the arrangement direction of the grating lines 21a and 22a of the diffraction grating pair 20, that is, along the x direction. And the diffraction grating pair 20 are relatively arranged.

  The arithmetic circuit 40 functioning as an arithmetic means calculates a tilt angle Δθ by performing predetermined arithmetic processing based on a signal obtained by the PD 31. The arithmetic circuit 40 mainly includes hardware such as an MPU (Micro Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The arithmetic circuit 40 may include a PLD (Programmable Logic Device) such as an FPGA (Field Programmable Gate Array) in addition to or instead of the MPU, or a DSP (Digital Signal Processor), ASIC (Application Specific Integrated Circuit) or the like may be provided. The arithmetic circuit 40 may be configured by a plurality of physically separated chip packages or elements.

(2) Principle of Detection of Tilt Angle Around Y-axis of Diffraction Grating Pair FIG. 4 shows an interference pattern of each diffracted light emitted from the diffraction grating pair 20. In the figure, the interference pattern is divided into five substantially circular regions, which are arranged along the x direction. That is, FIG. 4 conceptually shows the state of the amount of light (or brightness) detected by these PDs in a state where five PDs are arranged along the x direction. Among these five PDs, the central PD mainly receives light including the straight light 30.

  Two PDs located on the right side of both sides of the central PD are PDs 31 that mainly receive light (typically diffracted light 23 and 25) traveling along the path of the first-order diffracted light.

5A to 5C show changes in the interference pattern for each tilt angle Δθ around the y-axis between the first diffraction grating 21 and the second diffraction grating 22. As the tilt angle Δθ changes, the amount of light detected by the PD 31 also changes. In particular, as the tilt angle Δθ increases, the inventors of the present invention have the lightness of the light received in the detection region of the PD 31 (that is, mainly the interference light 27) with the center line m in the x direction of the detection region as a boundary. I found that the difference between the two becomes larger. Therefore, if the signals (for example, voltage signal levels) obtained in the light receiving areas A and B are S _A and S _B , the difference value S _A −S _B between the signals obtained in the light receiving areas A and _B is calculated. Thus, it was found that the tilt angle Δθ can be detected.

The arithmetic circuit 40 can output the tilt angle Δθ by storing in advance data based on a look-up table indicating the relationship between the calculated difference value S _A −S _B and the tilt angle Δθ. Further, the arithmetic circuit 40 can determine the relative rotation direction between the diffraction grating pair 20 based on the difference in the sign of the calculated difference value S _A −S _B.

  As described above, the displacement measuring apparatus 100 according to the present embodiment includes the diffraction grating pair 20 and the PD 31 having the plurality of light receiving regions A and B, and thus the diffraction grating pair is obtained by the arithmetic processing of the arithmetic circuit 40. An angular displacement of 20 relative rotations can be calculated. That is, the angular displacement can be measured with a small number of optical components, and the apparatus can be miniaturized.

2. Second Embodiment Next, a displacement measuring apparatus according to a second embodiment of the present invention will be described. In the following description, the same members, functions, etc. included in the displacement measuring apparatus 100 according to the first embodiment will be simplified or omitted, and different points will be mainly described.

  FIG. 6 is a perspective view showing the configuration of the displacement measuring apparatus according to the second embodiment. The displacement measuring apparatus 200 includes a PD 41 having a light receiving area different from the light receiving area of the PD 31 of the displacement measuring apparatus 100.

  FIG. 7 shows the detection area of the PD 41. The PD 41 has not only a plurality of light receiving areas arranged in the x direction but also a plurality of light receiving areas arranged in the y direction. That is, the detection area is divided into four light receiving areas A, B, C, and D, for example, in a matrix.

  The PD 41 receives the interference light 27 (see FIG. 1) along the path of the first-order diffracted light, for example, similarly to the PD 31 in the first embodiment. The arithmetic circuit 40 (see FIG. 1) calculates based on signals obtained in the four light receiving regions of the PD 41, and relative to the diffraction grating pair 20 around the y-axis for the same purpose as in the first embodiment. An angular displacement Δθ of a typical rotation is calculated.

The signal levels obtained in the light receiving areas A, B, C and D are S _A , S _B , S _C and S _D , respectively. The arithmetic circuit 40 calculates the following calculated value S ₁ .

S ₁ = (S _A + S _B ) − (S _C + S _D )

The calculated value obtained by this calculation formula is equivalent to the difference value S _A −S _{B of the} signals obtained in the light receiving areas A and B in the PD 31 according to the first embodiment.

FIG. 8 is an actual measurement graph showing the relationship between the relative tilt angle Δθ (deg) between the diffraction grating pair 20 and the calculated value S ₁ . The calculated value on the vertical axis is normalized. In this experiment, the pitch P between the grating lines of the diffraction grating pair 20 was 3.3 μm, and the size of the light detection area of the PD 41 was 1 mm square.

Under such conditions, when the tilt angle Δθ is 0.98 ° or less, the width in the x direction of the interference fringes to become equal to or larger than the width of the x-direction of a detection region of the PD 41, the arithmetic values S ₁ was 0 . When the tilt angle Δθ exceeds 0.98 °, the calculated value S ₁ becomes larger than 0, and the tilt angle Δθ can be calculated.

In the case where the pitch P between the grating lines of the diffraction grating pair 20 is 3.3 μm, if the size of the detection region of the PD 41 exceeds 1 mm square, even if the tilt angle Δθ is 0.98 ° or less, the principle Specifically, the tilt angle Δθ can be detected. Although not shown in the experimental data of FIG. 8, the arithmetic circuit 40 can calculate the arithmetic value S ₁ even when the tilt angle Δθ is larger than 1.5 °.

The arithmetic circuit 40 calculates (S _A + S _B ) − (S _C + S _D ) by storing in advance data indicating the relationship between the tilt angle Δθ and the calculation value S ₁ as described above. The tilt angle Δθ corresponding to the calculated value can be obtained. In addition, the arithmetic circuit 40 can determine the tilt direction of the tilt angle Δθ based on the difference in the sign of the calculated value.

3. Third Embodiment The configuration of a displacement measuring apparatus according to a third embodiment of the present invention is the same as that of the displacement measuring apparatus 200 including the PD 41 having the four-divided light receiving areas A to D. The difference between the two is the direction of relative rotation of the diffraction grating pair 20 to be detected and the calculation method by the calculation circuit 40 for detection.

  As shown in FIG. 9, the arithmetic circuit according to the present embodiment calculates a tilt angle Δφ that is an angular displacement about the z axis that is the optical axis direction (third direction) between the two diffraction gratings 21 and 22. To do.

  10A to 10E show changes in the interference pattern for each tilt angle Δφ around the z-axis of the two diffraction gratings 21 and 22. As described above, when the tilt angle Δφ occurs, the interference fringes appear to twist in the rotation direction. In this case, in FIG. 10, focusing on the light receiving areas A to D of the PD 41, the larger the tilt angle Δφ, the smaller the amount of light obtained in the light receiving areas A and D may be less than the amount of light obtained in the light receiving areas B and C. all right.

That is, the calculated value of the signal obtained in the two light receiving areas A and D located on the first diagonal line and the two light receiving areas C and D located on the second diagonal line intersecting the first diagonal line are obtained. The tilt angle Δφ can be obtained from the calculated value S ₂ based on the calculated value of the received signal. For example, the calculated value S ₂ is obtained by the following equation.

S ₂ = (S _A + S _D ) − (S _B + S _C )

FIG. 11 is an actual measurement graph showing the relationship between the relative tilt angle Δφ (deg) between the diffraction grating pair 20 and the calculated value S ₂ . The calculated value on the vertical axis is normalized. Again, the pitch P between the grating lines of the diffraction grating pair 20 was 3.3 μm, and the size of the detection region of the PD 41 was 1 mm square.

Under such conditions, when the tilt angle Δφ is 0.147 ° or less, the width of the interference fringes in the x direction is equal to or greater than the width of the detection region of the PD 41 in the x direction. In this case, the calculated value S ₂ is 0. Met. Therefore, when the tilt angle Δφ exceeds 0.147 °, the calculated value S ₂ becomes larger than 0, and the tilt angle Δθ can be calculated.

In the case where the pitch P between the grating lines of the diffraction grating pair 20 is 3.3 μm, if the size of the detection region of the PD 41 exceeds 1 mm square, even if the tilt angle Δθ is 0.147 ° or less, the principle Specifically, the tilt angle Δθ can be detected. Although not shown in the experimental data of FIG. 11, the arithmetic circuit 40 can calculate the arithmetic value S ₂ even when the tilt angle Δθ is larger than 0.3 °.

4). Fourth Embodiment FIG. 12 is a perspective view showing a configuration of a displacement measuring apparatus according to a fourth embodiment of the present invention. In this displacement measuring apparatus 300, the first PD 41 (first optical sensor) and the second PD 42 (second optical sensor) are located symmetrically on the x axis with the z axis that is the optical axis of the diffraction grating pair 20 as the center. An optical sensor) is arranged. That is, the first PD 41 detects, for example, interference light along the path of + n-order diffracted light (for example, + 1st-order diffracted light) by the first diffraction grating 21, and the second PD 42 is, for example, by the first diffraction grating 21 − Interference light along the path of nth order diffracted light (for example, −1st order diffracted light) is detected.

  As described above, the PD 41 has light receiving areas A to D (first light receiving area group) divided into four parts (see FIG. 7). Similarly, the PD 42 has light receiving areas E, F, G, and H (second light receiving area group) divided into four in a matrix. The light receiving region A + B (first light receiving region) and the light receiving region E + F (third light receiving region) are on the same side in the detection region in the x direction, with the z axis being the optical axis of the diffraction grating pair 20 as the center. To position. Further, the light receiving region C + D (second light receiving region) and the light receiving region G + H (fourth light receiving region) are located on the same side in the detection region in the x direction with the z axis as the center.

FIG. 13 shows an interference pattern when the tilt angle Δθ, which is a relative rotational angular displacement between the diffraction grating pair 20, and the amounts of light received by the PDs 41 and 42, respectively. Signals obtained in the light receiving areas E, F, G, and H are denoted as S _E , S _F , S _G , and _SH , respectively. As can be understood from the lightness distribution shown in FIG. 13, the arithmetic circuit 40 obtains the following arithmetic value S ₃ .

S ₃ = (S _A + S _B + S _E + S _F ) − (S _C + S _D + S _G + S _H )

  That is, the arithmetic circuit 40 obtains a difference value between arithmetic values obtained by adding the light receiving areas located on the same side in the x direction with the z axis as the center. Since the output value obtained in this way is larger than the output value obtained only by the PD 41 as in the second embodiment, the detection sensitivity can be increased as a result, and the tilt can be performed with high accuracy. The angle Δθ can be obtained.

5. Fifth Embodiment FIG. 14 is a perspective view showing a configuration of a displacement measuring device according to a fifth embodiment of the present invention. The displacement measuring apparatus 400 includes a first PD 31 (first optical sensor) having light receiving areas A and B (first light receiving area group) divided into two in the x direction, and in the same way in the x direction. And a second PD (second optical sensor) 32 having light receiving areas E and F (second light receiving area group) divided into two. The PDs 31 and 32 are arranged at symmetrical positions in the x direction around the z axis. As a result, the arithmetic circuit 40 can calculate the calculated value S ₄ by the following equation and obtain the tilt angle Δθ.

S ₄ = (S _A + S _E ) − (S _B + S _F )

  Also by the displacement measuring apparatus according to the present embodiment, the same effect as that of the displacement measuring apparatus according to the fourth embodiment can be obtained.

6). Sixth Embodiment A displacement measuring apparatus according to a sixth embodiment has the configuration of the displacement measuring apparatus 200 shown in FIG. 6, for example, and the tilt between the diffraction grating pair 20 around both the y and z axes is relative. The angles Δθ and Δφ are detected.

For example, the arithmetic circuit 40 acquires signals from the respective light receiving areas A to D of the PD 41. Then, the arithmetic circuit 40 calculates the tilt angle Δθ around the y-axis based on the calculated value S ₁ = (S _A + S _B ) − (S _C + S _D ), as in the second embodiment, and around the z-axis. The tilt angle Δφ is calculated based on the calculated value S ₂ = (S _A + S _D ) − (S _B + S _C ) as in the third embodiment.

  The arithmetic circuit 40 only needs to have a software switch for selecting one of the tilt angles Δθ and Δφ as a measurement target. For example, the displacement measuring device can select and output a measurement target by switching a switch based on a user's operation or automatically switching a switch according to a predetermined algorithm.

  In the case of this embodiment, it is desirable that the displacement measuring device includes a mechanism that allows the diffraction grating pair 20 to rotate individually for each axis around both the y and z axes.

Here, the photoelectric encoder described in Patent Document 2 measures displacement in two orthogonal axes and angular displacement around one axis, that is, a total of three displacements. For this reason, this photoelectric encoder applies the principle of laser Doppler shift and calculates phase information using three diffraction gratings and three light receiving elements, so the processing circuit needs to perform complicated calculations. is there. On the other hand, the displacement measuring apparatus according to this embodiment includes two diffraction gratings and one optical sensor. When this displacement measuring apparatus measures the displacements of both Δθ and Δφ in this way, it is one less than the measurement target of the photoelectric encoder of Patent Document 2, but has one diffraction grating and one optical sensor compared to the photoelectric encoder. It can be reduced one by one. Therefore, it is possible to reduce the size of the apparatus.

7). Seventh Embodiment A displacement measuring apparatus according to a seventh embodiment has the configuration of the displacement measuring apparatus 300 shown in FIG. 12, for example, and the tilt between the diffraction grating pair 20 around both the y and z axes is relative. The angles Δθ and Δφ are detected.

For example, the arithmetic circuit 40 acquires signals from the light receiving areas A to D of the PD 41 and from the light receiving areas E to H of the PD 42, respectively. Then, the arithmetic circuit 40 calculates the tilt angle Δθ around the y-axis based on the calculated value S ₁ = (S _A + S _B ) − (S _C + S _D ) as in the second embodiment. On the other hand, the arithmetic circuit 40 calculates the tilt angle Δφ around the z-axis based on the calculated value S ₅ = (S _E + S _H ) − (S _F + S _G ) as in the third embodiment.

  In the case of this embodiment, it is desirable that the displacement measuring device includes a mechanism that allows the diffraction grating pair 20 to rotate individually for each axis around both the y and z axes.

Displacement measurement equipment according to the present embodiment is provided with two diffraction gratings and two light sensors. When this measurement apparatus measures the displacements of both Δθ and Δφ in this way, it is one less than the measurement target of the photoelectric encoder disclosed in Patent Document 2, but the number of diffraction gratings is reduced by one compared to the photoelectric encoder. Two sensors can be reduced. Therefore, it is possible to reduce the size of the apparatus.

8). Eighth Embodiment A displacement measurement device according to an eighth embodiment of the present invention includes, for example, the configuration of any one of the displacement measurement devices according to the first to seventh embodiments, and a tilt angle. At least one of Δθ and Δφ is detected, and the displacement Δz on the straight line in the z direction between the diffraction grating pair 20 is detected.

  Referring to FIG. 1, for example, when the second diffraction grating 22 is displaced in the z direction with respect to the first diffraction grating 21, a difference in path (optical path) between the diffracted lights 23 and 25 occurs. Therefore, interference fringes are generated by the interference light 27 between the diffracted light 23 by the first diffraction grating 21 and the diffracted light 25 by the second diffraction grating 22. The PD 31 detects a change in the amount of interference fringes.

  FIG. 15 is a graph schematically showing the relationship between Δz and a signal (voltage signal) detected by the PD 31. In this manner, the detection signal of the PD 31 draws a sine curve according to the repeated bright and dark interference fringes. This sine curve corresponds to the displacement in the z direction to be measured. The arithmetic circuit 40 can obtain a signal intensity corresponding to a displacement in a predetermined range in the z direction by using, for example, a substantially linear region corresponding to a half wavelength among the light amount change of the sine curve of the interference fringes.

  In the case of the present embodiment, it is desirable that the displacement measuring device includes a mechanism that allows the diffraction grating pair 20 to individually rotate around the y-axis and move in the z-axis direction.

9. Housing for Supporting Optical Components of Displacement Measuring Device FIG. 16 is a cross-sectional view showing an embodiment of the optical system shown in FIGS. 2 and 6 and a housing 50 for housing the optical system.

  The housing 50 has a hole 55 in which the optical path is disposed. The hole 55 includes a first hole 55a from the light source 12 to the diffraction grating pair 20 and a second hole 55b from the diffraction grating pair 20 to the PD 31. The second hole 55b is formed at an angle that allows the interference light 27 along the path of the n-th order, here, the first-order diffracted light to pass.

  An axis along the longitudinal direction of the first hole 55a coincides with the z-axis. Mounting boards 51 and 52 are mounted on both ends of the housing 50 in the z-axis direction, respectively. The light source 12 is mounted on the mounting substrate 51, and the PD 31 is mounted on the substrate of the mounting substrate 52.

  The housing 50 includes a light source side member 50a, a sensor side member 50b, and a spring portion 50c provided therebetween. The spring portion 50c is formed by providing two cutouts 53 on each of two opposing side surfaces of the casing 50 and providing a slit 54 therein. The diffraction grating pair 20 is held by the housing 50 so as to sandwich the slit 54. By the spring part 50c, the casing 50 can be expanded and contracted in the direction along the z axis, and can be deformed around the y and z axes, so that the first diffraction grating 21 and the second diffraction grating 22 can be moved relative to each other. Thus, displacement measurement of Δz, Δθ, and Δφ can be performed.

  In such a structure of the spring portion 50c, the rigidity of the spring portion 50c around the z-axis is higher than that around the y-axis, so that the detectable angular range around the z-axis can be detected around the y-axis. Narrower than the angle range.

  As described above, the light source side member 50a and the sensor side member 50b are connected by the spring portion 50c. Therefore, the set of the second diffraction grating 21 and the PD 31 can move integrally with the set of the light source 12, the collimator lens 14 and the first diffraction grating 21. Thereby, the PD 31 can accurately detect the interference light according to the displacement along the direction along the z axis, around the y axis, or around the z axis.

  As a material of the housing 50, metal or resin is used. In the case of a metal, for example, stainless steel, aluminum and the like can be mentioned. The light source side member 50a and the sensor side member 50b may be formed of a first material, and the spring portion 50c may be formed of a second material having a Young's modulus lower than that of the first material. In this case, the first material is a metal and the second material is a resin. Of course, different types of metals may be used as the first and second materials, or different types of resins may be used.

  As a modified example of the case 50, for example, a case having a hole portion arranged in line symmetry with the second hole portion 55b around the optical axis of the diffraction grating pair 20 is shown in FIG. It can be realized as a housing that supports the system.

10. Other Embodiments The present invention is not limited to the above-described embodiments, and various other embodiments can be realized.

  The arithmetic circuit 40 according to each of the above embodiments adds or subtracts signals obtained in each light receiving area. However, multiplication may be performed instead of the addition, or division may be performed instead of the subtraction. Alternatively, the tilt angles Δθ and Δφ may be calculated according to another predetermined arithmetic expression.

  The PD according to each of the above embodiments is, for example, a sensor having a light receiving region divided into two or four. However, the PD detection area may be divided into, for example, three or more in the x direction, may be divided into three or more in the y direction, or may be divided into three or more in both the x and y directions. May be. Then, the relationship between the tilt angle Δθ and / or Δφ and the value obtained from the signal obtained by the one or more PDs by a predetermined arithmetic expression is converted into data, and the arithmetic circuit 40 stores the data in advance. .

  It is also possible to detect both Δθ and Δφ by combining the PD 31 shown in FIG. 2 and the PD 42 shown in FIG.

  In the above embodiment, the light emitted from the light source 12 is incident on the collimator lens 14, and the collimator lens 14 generates the parallel light 15. However, the parallel light 15 does not necessarily have to be formed. For example, diffused light or convergent light having a predetermined light orientation angle is generated by a light source or an optical system including the light source, and the diffused light or convergent light is diffracted. It may be incident on the grating pair 20. The optical axis of the diffraction grating pair 20 is typically configured to match the optical axis of the light source or optical system, but they may be configured not to match.

  The detection region including the plurality of light receiving regions of the PD used in each of the above embodiments is rectangular, but may be a circle, an ellipse, or the like, and is configured to be divided into equal areas to form a plurality of light receiving regions. Any shape can be used.

  In each of the above embodiments, for example, a plurality of light receiving areas are provided by dividing a detection area of one PD. However, a plurality of PDs may be provided so that one PD corresponds to one light receiving region.

  It is also possible to combine at least two feature portions among the feature portions of each embodiment described above.

DESCRIPTION OF SYMBOLS 12 ... Light source 20 ... Diffraction grating pair 21a, 22a ... Grating line 23, 25 ... Diffraction light 27 ... Interference light 30 ... Straight light 31 ... PD
40 ... arithmetic circuit 41 ... first PD
42 ... Second PD
100, 200, 300, 400 ... displacement measuring device

Claims (8)

A light source;
Each having a plurality of grating lines, arranged along the path of a light beam from the light source, and capable of relative movement, each generating a diffracted light; and
A plurality of light receiving regions arranged in a first direction which is an arrangement direction of the plurality of grating lines, wherein n-order diffracted light (n is other than 0) generated from any one of the diffraction grating pairs An optical sensor having two light receiving areas capable of detecting interference light of a set of diffracted light along a path of an integer) ,
Based on the signals respectively obtained in the two light receiving regions, the angular displacement of the relative rotation of the diffraction grating pair, and the angular displacement around the axis along the second direction that is the direction of the grating line , Calculating means for calculating ,
The said calculating means is a displacement measuring device which calculates the said angular displacement around the axis | shaft along a said 2nd direction based on the calculated value of the signal each obtained in the said 2 light reception area | region . The displacement measuring apparatus according to claim 1,
The calculation means calculates the angular displacement about the axis along the second direction by calculating a difference value between signals obtained in the two light receiving regions or a value obtained by dividing the signals. the displacement measuring device for. A light source;
Each having a plurality of grating lines, arranged along the path of a light beam from the light source, and capable of relative movement, each generating a diffracted light; and
A plurality of light receiving regions arranged in a matrix by being arranged in a first direction that is an arrangement direction of the plurality of grating lines and a second direction that is a direction of the grating lines, the diffraction grating An optical sensor having four light receiving regions capable of detecting interference light of a set of diffracted light along the path of nth order diffracted light (n is an integer other than 0) generated from any one diffraction grating of the pair;
Based on the signals respectively obtained in the four light receiving regions, the angular displacement of the relative rotation of the diffraction grating pair, around an axis along the third direction that is the direction of the optical axis of the diffraction grating pair comprising a calculating means for calculating the angular displacement,
The computing means is located on the second diagonal line intersecting the computed value of the signal obtained in each of the two light receiving areas located on the first diagonal line of the four light receiving areas and the first diagonal line. A displacement measuring device that calculates the angular displacement about an axis along the third direction by calculating a value based on a calculated value of a signal obtained in each of the two light receiving regions .   The displacement measuring apparatus according to claim 3,
  The calculation means is obtained by adding or multiplying signals obtained in the two light receiving areas located on the first diagonal line and in the two light receiving areas located on the second diagonal line, respectively. An angular displacement about an axis along the third direction is calculated by calculating a difference value from the addition value or multiplication value of the signal.
  Displacement measuring device.   The displacement measuring apparatus according to claim 3,
  The calculation means is obtained by adding or multiplying signals obtained in the two light receiving areas located on the first diagonal line and in the two light receiving areas located on the second diagonal line, respectively. An angular displacement about an axis along the third direction is calculated by calculating a value obtained by dividing the signal addition value or multiplication value.
  Displacement measuring device. A light source;
Each having a plurality of grating lines, arranged along the path of a light beam from the light source, and capable of relative movement, each generating a diffracted light; and
A set along the path of the nth-order diffracted light (n is an integer other than 0) generated from any one of the diffraction grating pairs arranged in a first direction which is an arrangement direction of the plurality of grating lines. A plurality of light receiving regions capable of detecting interference light of diffracted light of
Based on the signals obtained in the plurality of light receiving regions, the angular displacement of the relative rotation of the diffraction grating pair, and the angular displacement around the axis along the second direction, which is the direction of the grating line. Calculating means for calculating ,
The plurality of light receiving regions include a first light receiving region group arranged on a path side of + n order diffracted light (n is a natural number of 1 or more), and -n order diffracted light (n is 1 or more). It is configured as a second light receiving region group arranged on the course side of (natural number),
The first light receiving region group includes a first light sensor divided into a first light receiving region and a second light receiving region arranged in the first direction,
The second light receiving region group includes a second light sensor divided into a third light receiving region and a fourth light receiving region arranged in the first direction,
The third light receiving region is located on the same side as the first light receiving region in the first direction around the optical axis of the diffraction grating pair, and the fourth light receiving region is the first light receiving region. Located on the same side as the second light receiving region in the direction,
The computing means computes the computation values of the signals obtained in the first light receiving area and the third light receiving area, and the signals obtained in the second light receiving area and the fourth light receiving area, respectively. A displacement measuring device that calculates the angular displacement around an axis along the second direction by calculating a value based on the value .   The displacement measuring device according to claim 6,
  The calculation means is obtained by adding or multiplying signals obtained in the first light receiving region and the third light receiving region, respectively, and in the second light receiving region and the fourth light receiving region, respectively. The angular displacement about the axis along the second direction is calculated by calculating a difference value from the addition value or multiplication value of the signal.
  Displacement measuring device.   The displacement measuring device according to claim 6,
  The calculation means is obtained by adding or multiplying signals obtained in the first light receiving region and the third light receiving region, respectively, and in the second light receiving region and the fourth light receiving region, respectively. The angular displacement about the axis along the second direction is calculated by calculating a value obtained by dividing the addition value or the multiplication value of the signal.
  Displacement measuring device.