Displacement detector

The present invention relates to a displacement detection device. For example, the present invention relates to a laser interference type displacement detection device.

Conventionally, a laser interference type displacement detection device is known. As shown in FIG. 11, the conventional laser interference type displacement detection device 100 includes a main scale 110 and a detection head unit 120. The main scale 110 has a reflective diffraction grating 111 along the longitudinal direction, which is the length measurement direction. The detection head unit 120 includes a light emitting / receiving unit 130 and an optical device unit unit 600. The light emitting / receiving unit 130 includes a light source 131 that emits laser light and a light receiving means 134 that receives the interference light of the light reflected by the main scale 110. The optical device unit unit 600 includes a beam splitter 601 that demultiplexes the light from the light source 131, a first mirror 602 that reflects one of the light demultiplexed by the beam splitter 601 toward the main scale 110, and a beam splitter 601. The second mirror 603 and the third mirror 604 that reflect the other light demultiplexed by the main scale 110 toward the main scale 110, and the fourth mirror that reflects one reflected diffracted light from the main scale 110 toward the half mirror 607. It includes a 605 and a fifth mirror 606 that reflects the other reflected diffracted light from the main scale 110 toward the half mirror 607.

In such a configuration, the light emitted from the light source 131 is split by the beam splitter 601 and then diffracted by the main scale 110. The light diffracted by the main scale 110 interferes with the half mirror 607, and the interference light is received by the light receiving means 134. Then, when the main scale 110 is displaced, the brightness of the interference light changes, and the amount of displacement of the main scale 110 is detected from the state of this change in brightness. Further, the direction of displacement of the main scale 110 is detected by demultiplexing the light and interfering with the two luminous flux diffracted from the main scale 110.

Here, the demultiplexing and reflection of light can be performed by using a diffraction grating, and a diffraction grating is also arranged instead of a beam splitter or a mirror (for example, Patent Document 1).

<patcit num="1"><text>Japanese Unexamined Patent Publication No. 2002-372407</text></patcit>

<p> In order to split the light from the light source 131 and reflect and diffract the split light on the main scale 110 to obtain the interference of the diffracted light, many optical components such as the beam splitter 601 and the mirrors 602 to 606 are used. Must be used. In addition, it takes a lot of time and effort to adjust many mirrors 602 to 606 and align the optical axes. When many optical components are provided, the device becomes large and the optical path becomes long. Where the interference state of laser light changes even with fluctuations in air density, the detection accuracy may be reduced if the optical path is long.</p><p> Here, a diffraction grating can be used instead of a beam splitter or a mirror. For example, in order to increase the number of reflections on the main scale and improve the detection resolution, the diffracted light from the main scale is directed toward the main scale. Need to recurse. Then, since a reflection mirror is provided, improving the detection resolution and reducing the number of parts to shorten the optical path have become incompatible at the same time.</p><p> An object of the present invention is to provide a displacement detection device capable of improving the detection resolution and the environmental resistance.</p>

<p> The displacement detection device according to claim 1 includes a main scale having a diffraction grating, and a detection head unit that is provided so as to be movable relative to the main scale and detects a relative displacement amount with respect to the main scale. The detection head unit includes a light emitting and receiving unit having a light source that emits coherent light and a light receiving element that receives light diffracted by the main scale, and at least two different orders that diffract the light from the light source. A demultiplexing diffraction grating that demultiplexes the diffracted light of the above, a deflection diffraction grating that diffracts the light diffracted by the demultiplexing diffraction grating and deflects the light to be spot-projected on the main scale, and the main scale. The diffraction grating for re-irradiation, which re-irradiates the main scale by reflecting and diffracting the diffracted light from the spot projection position of the above, and the diffracted light re-irradiated and diffracted on the main scale are superposed. It is characterized in that it is provided with a wave combining means for interfering with each other.</p><p> In such a configuration, coherent light (eg, laser light) is emitted from the light source. This light is demultiplexed by being diffracted by a demultiplexing diffraction grating, and is demultiplexed into, for example, two luminous fluxes. These demultiplexed lights are deflected by being diffracted by the deflection diffraction grating. The light deflected by the deflection diffraction grating is applied to the main scale diffraction grating and diffracted by the main scale. The light diffracted on the main scale is reflected and diffracted by the re-irradiation diffraction grating and re-irradiated on the main scale. The re-irradiated light is diffracted again on the main scale, and then the diffracted light is combined by a wave combining means to be used as interference light. This interference light is received by the light receiving element. Then, the relative displacement amount between the main scale and the detection head portion is detected from the signal output from the light receiving element based on the change in the interference light.</p><p> According to such a configuration, the light emitted from the deflection diffraction grating to the main scale is reflected by the re-irradiation diffraction grating and recursed to the main scale. Then, it will be diffracted twice by the main scale. Then, the luminous flux received by the light receiving element has four-fold phase information as compared with the luminous flux diffracted only once on the main scale. As a result, the amount of movement of the main scale is detected with four times the resolution by the interference sine wave signal output from the light receiving element. Furthermore, when the light is demultiplexed in the direction along the relative movement direction between the main scale and the detection head due to the demultiplexing by the diffraction grating for demultiplexing, the diffracted light from the main scale depends on the traveling direction of the main scale. It shows opposite phase changes. Then, information on the traveling direction of the main scale can be obtained from the signal received by the light receiving element.</p><p> Multiple optical devices with beam splitter and mirror functions are required to divide one luminous flux into two luminous fluxes and re-irradiate the light toward the main scale. If these functions are realized by a diffraction grating, The number of optical devices can be reduced, and component costs and assembly costs can be reduced. Further, since the number of optical devices may be small, the optical path adjustment is easy, and the detection error due to the optical path adjustment error can be reduced to improve the detection accuracy. Further, since the number of constituent elements can be reduced by using the diffraction grating, the overall configuration can be made compact. Then, the total optical path length can be shortened. For example, laser light can be used as a displacement detection device having excellent environmental resistance by shortening the optical path length, where interference waves fluctuate even when the air density changes.</p><p> Here, the demultiplexing diffraction grating, the deflection diffraction grating, the re-irradiation diffraction grating, and the main scale diffraction grating are configured to diffract the diffracted light of a specific order particularly strongly when the light is diffracted. Is preferable. For example, the demultiplexing diffraction grating is preferably configured to diffract the light from the light source and divide it into two luminous fluxes. In such a configuration, a specific interference order may be strengthened from the equation of the diffraction condition. For example, when the diffraction grating is composed of reliefs of surface irregularities, the lattice height of the diffraction grating is set to the wavelength of light. On the other hand, it may be 1/n (n is a positive integer), it may be a blazed diffraction grating, or when the diffraction grating is composed of periodic optical density, the period of density is set to a predetermined length. It should be.</p><p> The displacement detection device according to claim 2 is the displacement detection device according to claim 1, wherein the detection head portion is arranged between the light emitting and receiving portion and the deflection diffraction grating, and is a transmission type diffraction grating. The first diffraction scale is provided, and the light from the light source is demultiplexed by the first diffraction scale to form the demultiplexing diffraction grating, and the diffracted light from the main scale is the same. The wave combining means is configured by being combined on the first diffraction scale.</p><p> According to such a configuration, one luminous flux is divided into two luminous fluxes, and only one diffraction grating is required to combine the two luminous fluxes, so that the number of components is reduced and the overall configuration is made compact. can do. Then, since the entire optical path length can be shortened, the displacement detection device having excellent environmental resistance can be obtained. Further, since the component cost and the assembly cost can be reduced by reducing the number of components, the detection accuracy can be improved while being inexpensive.</p><p> The displacement detection device according to claim 3 is the displacement detection device according to claim 1 or 2, wherein the detection head portion receives light from the demultiplexing diffraction grating from one side and the other. A transmission type second diffraction grating that transmits and diffracts light from the surface side toward the main scale is provided, and the deflection diffraction grating is provided with a diffraction grating provided on the one surface side of the second diffraction scale. The re-irradiation diffraction grating is provided with a reflecting means that is covered from one surface side of the second diffraction grating on a part of the diffraction grating and reflects light incident from the other surface side of the second diffraction scale. It is characterized in that it is composed of.</p><p> According to such a configuration, when the light is incident from the other surface side of the second diffraction scale and reflected by the reflecting means, the light is reflected by the reflecting means by the action of the diffraction grating provided on the one surface side of the second diffraction scale. It is diffracted when it is done. Since the re-irradiation diffraction grating is configured by providing a reflecting means on the second diffraction scale, the re-irradiation diffraction grating can be easily formed, and the re-irradiation diffraction grating can be integrated with the second diffraction scale. Therefore, the number of parts can be reduced. Further, although it is costly to form the diffraction grating separately, a highly accurate reflection type diffraction grating can be obtained by a simple method of providing a reflection means on the second diffraction scale.</p><p> Here, the diffraction grating for re-irradiation may be provided on the other surface side of the second diffraction scale. That is, the deflection diffraction grating is provided with a transmission type second diffraction grating in which light from the demultiplexing diffraction grating is incident from one surface side and light is transmitted and diffracted from the other surface side toward the main scale. A diffraction grating provided on one surface side of the second diffraction scale is provided, and the re-irradiation diffraction grating is covered with a part of the diffraction grating from the other surface side of the diffraction scale. It may be configured to include a reflecting means for reflecting light incident from the other surface side of the diffraction scale. However, in this case, it is necessary to engrave the uneven relief forming the diffraction grating on the surface of the reflecting means.</p><p> It should be noted that the re-irradiation diffraction grating may not be provided on the second diffraction scale together with the deflection diffraction grating, or the reflection type diffraction grating may be independently arranged as the re-irradiation diffraction grating. Is.</p><p> The displacement detecting device according to claim 4 is the displacement detecting device according to claim 1, wherein the main scale has a reflection type diffraction grating, and the detection head portion includes the light emitting light receiving portion and the main scale. A diffraction scale having a transmission type diffraction grating on both the front and back surfaces is provided between the two, and the light from the light source is demultiplexed by the diffraction grating provided on the light emitting / receiving portion side of the diffraction scale. The demultiplexing diffraction grating is configured by the above, and the combining means is configured by combining the diffracted light from the main scale, and the deflection diffraction grating is the main scale of the diffraction scale. It is composed of a diffraction grating provided on the side, and the re-irradiation diffraction grating is covered with a part of the diffraction scale on the main scale side to direct the reflected diffracted light from the main scale toward the main scale. It is characterized in that it is provided with a reflection type diffraction grating that reflects and diffracts.</p><p> According to such a configuration, the diffraction grating for demultiplexing, the wave combining means, the diffraction grating for deflection, and the diffraction grating for re-irradiation are integrally configured on one diffraction scale, so that the number of parts is extremely reduced. can do. Therefore, it is possible to reduce the parts cost and the assembly cost. Then, the optical path adjustment at the time of assembly can be made very easy. Further, the optical path can be shortened as much as possible by reducing the number of parts as much as possible. Therefore, the displacement detection device having excellent environmental resistance can be obtained.</p><p> The displacement detection device according to claim 5 is the displacement detection device according to any one of claims 1 to 4, wherein the main scale has a reflection type diffraction grating, and the re-irradiation diffraction grating is It is characterized in that the reflected diffracted light from the main scale is reflected and diffracted twice or more with the main scale and re-irradiated.</p><p> In such a configuration, if the number of times the light is re-irradiated to the main scale by the re-irradiation diffraction grating is increased, the luminous flux received by the light receiving element is several times as large as the luminous flux reflected once by the main scale. It will have phase information. As a result, the resolution for detecting the relative movement amount of the main scale can be improved.</p><p> As a configuration in which the reflected diffracted light from the main scale is reflected and diffracted twice or more with the main scale and re-irradiated, for example, the reflected light from the main scale is reflected a plurality of times by the re-irradiation diffraction grating. As an example, the diffraction grating for re-irradiation is configured to be wide and the reflecting surface is enlarged.</p><p> The displacement detecting device according to claim 6 is the displacement detecting device according to any one of claims 1 to 5, wherein the detection head portion includes the light emitting and receiving unit, the demultiplexing diffraction grating, and the above. The deflection diffraction grating and the re-irradiation diffraction grating are provided in a state where their respective longitudinal directions are aligned with the longitudinal direction of the main scale, and are arranged between the deflection diffraction grating and the main scale. The light refracting means for refracting the light deflected by the deflection diffraction grating toward the center line along the longitudinal direction of the main scale is provided.</p><p> According to such a configuration, the light can be refracted toward the center line of the main scale by the light refracting means. For example, even when the light incident on the light refracting means from the light source is substantially perpendicular to the main scale, the light emitted from the light refracting means is refracted and irradiated on the main scale. Then, since the diffracted light from the main scale has an angle with respect to the incident light on the main scale, the diffracted light from the main scale can be incident on the diffraction grating for re-irradiation by a path different from the incident light. Further, the diffracted light from the main scale can be incident on the light receiving element. If the light emission direction from the light source can be made close to vertical, for example, the width of the demultiplexing diffraction grating and the deflection diffraction grating in the end direction can be shortened to about the beam diameter of the laser. The length in the lateral direction can be shortened. By shortening the lateral direction, the device becomes compact and the optical path becomes short, and as a result, the displacement detection device having excellent environmental resistance can be obtained.</p><p> Here, examples of the light refracting means include a prism and a lens that refract light.</p><p> The displacement detecting device according to claim 7 is the displacement detecting device according to any one of claims 1 to 6, wherein the detection head portion emits light combined by the combining means to the side of the light source. The light emitting and receiving unit includes a reflecting member that reflects the light to, and the light emitting and receiving unit includes the light source and the light receiving element on the same side with respect to the reflecting surface of the reflecting member.</p><p> In such a configuration, if the light combined by the wave combining means is reflected by the reflecting surface of the reflecting member toward the same side as the light source and the reflected light is received by the light receiving element, the light receiving element will receive the light. It will be placed on the same side as the light source. Then, since the electrical components such as the light source and the light receiving element can be arranged close to each other on the same side, the electrical wiring can be organized and the wiring can be simplified. Here, the reflective surface of the reflective member may be parallel to the surface perpendicular to the length measurement direction of the main scale, or may be parallel to the surface including the length measurement direction and perpendicular to the main scale. It is preferable that the light source and the light receiving element are arranged on the same side, and further, the light source and the light receiving element are arranged together in one place.</p>

Hereinafter, embodiments of the present invention will be illustrated and described with reference to reference numerals attached to each element in the drawing. (First Embodiment) The first embodiment according to the displacement detection device of the present invention will be described. FIG. 1 shows a perspective view of the internal structure of the displacement detection device 100. Figure 2 shows the optical path along with the basic configuration of the displacement detection device. The displacement detection device 100 includes a main scale 110 and a detection head unit 120. The main scale 110 is provided so as to be slidable along the longitudinal direction, which is the length measurement direction. A reflection type diffraction grating 111 is provided along the longitudinal direction on the surface of the main scale 110 facing the detection head portion 120. The detection head unit 120 irradiates light toward the main scale 110 and receives the reflected light from the main scale 110. Then, the relative movement amount between the main scale 110 and the detection head unit 120 is detected based on the phase information of the reflected light.

The detection head unit 120 includes a light emitting / receiving unit 130, an optical device unit unit 140, and a frame body 150. The light emitting / receiving unit 130 emits light toward the main scale 110 through the optical device unit unit 140, and receives the light reflected from the main scale 110 and passed through the optical device unit unit 140. The light emitting / receiving unit 130 includes a light source 131, light receiving elements 132A and 132B, and retardation plates 133A and 133B. The light source 131 is a laser light source that emits interfering laser light. The laser emission direction from the light source 131 will be described later with reference to FIGS. 2, 3 and 4. The light receiving elements 132A and 132B are elements that output an interference sine wave signal by receiving the reflected light from the main scale 110 and performing photoelectric conversion. Two light receiving elements, a light receiving element 132A and a light receiving element 132B, are provided, and two light fluxes of the light flux reflected toward the light emitting and receiving unit 130 are received. The retardation plates 133A and 133B are arranged in front of the light receiving element 132A and the light receiving element 132B, respectively, and give a phase difference of 90 ° to each other with respect to the light flux incident on the light receiving element 132A and the light receiving element 132B, respectively.

The optical device unit unit 140 is arranged between the light emitting / receiving unit 130 and the main scale 110 to demultiplex, combine, or reflect light. The position of the optical device unit unit 140 is fixed with respect to the light emitting / receiving unit 130, and the optical device unit unit 140 moves relative to the main scale 110 integrally with the light emitting / receiving unit 130. The optical device unit unit 140 includes a first diffraction scale 141 and a second diffraction scale 143. The first diffraction scale 141 is arranged between the light emitting / receiving unit 130 and the main scale 110 on the light emitting / receiving unit 130 side in parallel with the main scale 110. The first diffraction scale 141 is formed of a transparent member such as glass in a flat rectangular shape, and is a transmission type first diffraction grating (diffraction grating for demultiplexing, combining means) in the same direction as the diffraction grating 111 of the main scale 110. Has 142. The first diffraction grating 142 is a phase grating in which grooves are formed at a predetermined pitch on the surface of the first diffraction scale on the light emitting / receiving unit 130 side. Further, the first diffraction grating 142 is formed at a lattice height that diffracts light of a predetermined interference order particularly strongly.

The second diffraction scale 143 is arranged between the light emitting / receiving unit 130 and the main scale 110 on the main scale 110 side in parallel with the main scale 110. The second diffraction scale 143 is formed of a transparent member such as glass, and a diffraction grating having a predetermined pitch is engraved on the surface of the light emitting / receiving unit 130 side in the same direction as the diffraction grating 111 of the main scale 110. This diffraction grating is formed at a lattice height that diffracts light of a predetermined interference order particularly strongly. Further, on the surface of the second diffraction scale 143 on the light emitting / receiving portion 130 side, a metal film (reflecting means) 146 is vapor-deposited along the longitudinal direction at a substantially central portion in the lateral direction. The metal film 146 is provided with a width such that the lateral direction of the second diffraction scale 143 is divided into three equal parts. Then, on the second diffraction scale 143, a transmission type second diffraction grating (diffraction grating for deflection) 144 is configured in both side regions of the metal film 146. Further, the metal film 146 constitutes a reflection type third diffraction grating (re-irradiation diffraction grating) 145 when the second diffraction scale 143 is viewed from the main scale 110 side.

The light emitting / receiving unit 130 and the optical device unit unit 140 are surrounded by a frame body 150 and integrated as a detection head unit 120.

Next, with reference to FIGS. 2, 3 and 4, the optical path from the light emitted from the light source 131 to being reflected by the main scale 110 and incident on the light receiving elements 132A and 132B will be described. FIG. 2 shows the basic configuration of the displacement detection device 100 in a perspective view and shows the optical path three-dimensionally. FIG. 3 shows the optical path in the front view of the displacement detection device 100 viewed from the vertical direction in the length measurement direction. FIG. 4 shows an optical path in a side view of the displacement detection device 100 as viewed from the length measurement direction.

First, the laser beam L is emitted from the light source 131 toward the optical device unit unit 140. At this time, as shown in FIG. 3, when viewed from the direction perpendicular to the length measurement direction of the main scale 110, the emission direction of the laser beam L is inclined with respect to the vertical plane along the lateral direction of the main scale 110. are doing. Further, as shown in FIG. 4, when viewed from the length measurement direction of the main scale 110, the emission direction of the laser beam L is also inclined with respect to the vertical plane along the longitudinal direction of the main scale 110. Then, as shown in FIG. 2 or 4, the laser beam L irradiates a point P on the first diffraction scale 141 on the end side of the center in the lateral direction.

The light emitted from the light source 131 enters the first diffraction scale 141 and is emitted as diffracted light by the first diffraction grating 142. At this time, a plurality of diffracted lights are generated by the first diffraction grating 142, but since the zero-order diffracted light L0 and the minus first-order diffracted light L1 are used for detection, only the zero-order diffracted light L0 and the minus first-order diffracted light L1 are used in the drawing. Is shown. In this way, the laser beam L is beam-split (demultiplexed) into the zero-order diffracted light L0 and the minus first-order diffracted light L1 by the first diffraction grating 142. In the following description, the zero-order diffracted light is referred to as transmitted light, and the minus first-order diffracted light is referred to as first-order diffracted light.

The primary diffracted light L1 and the transmitted light L0 diffracted by the first diffraction grating 142 enter the second diffraction grating 144 of the second diffraction scale 143 and are emitted as diffracted light. Of the diffracted light, only the first diffracted light is used for detection, and the first diffraction light L2 is emitted from the second diffraction grating 143 corresponding to the first diffraction light L1 of the first diffraction grating 142, and the transmitted light of the first diffraction grating 142 is emitted. The first-order diffracted light L3 is emitted from the second diffraction grating 144 corresponding to L0. In this way, the first-order diffracted light L1 and the transmitted light L0 are deflected by the second diffraction grating 144 so as to be spot-projected to one point on the main scale 110.

The first-order diffracted light L2 and the first-order diffracted light L3 from the second diffraction grating 144 are applied to the main scale 110. At this time, the first-order refracted light L2 and the first-order diffracted light L3 are applied to one point P1 on the main scale 110. The primary diffracted light L2 and the primary diffracted light L3 are reflected and diffracted at the same time by the reflective diffraction grating of the main scale 110, and the diffracted light L4 is used as the reflected diffracted light from the one point P1 to the primary diffracted light L2 and the primary diffracted light L3. Diffracted light L5 is emitted. Here, the diffracted light reflected on the same side as the incident direction of the primary diffracted light L2 from the second diffraction grating 144 is defined as the diffracted light L4, and the same side as the incident direction of the first diffracted light L3 from the second diffraction grating 144. Let the diffracted light reflected by the grating be the diffracted light L5.

The diffracted light L4 and the diffracted light L5 reflected by the main scale 110 are incident on the third diffraction grating 145 of the second diffraction scale 143. The diffracted light L4 and the diffracted light L5 from the main scale 110 are reflected and diffracted at the same time by the reflection type third diffraction grating 145. Then, the diffracted light L4 and the diffracted light L5 from the main scale 110 are reflected again toward the main scale 110 as the diffracted light L6 and the diffracted light L7 by the third diffraction grating 145. At this time, the diffracted light L6 and the diffracted light L7 by the third diffraction grating 145 are re-irradiated to substantially one point P2 of the main scale 110.

The diffracted light L6 and the diffracted light L7 from the third diffraction grating 145 are reflected and diffracted at the same time by the diffraction grating at one point P2 of the main scale 110, and are diffracted as the diffracted light L8 and the diffracted light L9. It is incident on the diffraction grating 144. Here, the diffracted light reflected from the third diffraction grating 145 on the same side as the incident direction of the diffracted light L6 is defined as the diffracted light L8, and the diffracted light L7 reflected from the third diffraction grating 145 is reflected on the same side as the incident direction. Let the diffracted light received be the diffracted light L9.

The diffracted light L8 and the diffracted light L9 from the main scale 110 are diffracted by the second diffraction grating 144, the primary diffracted light L10 is emitted corresponding to the diffracted light L8, and the primary diffracted light L11 corresponds to the diffracted light L9. Be ejected. Thus, the second diffraction grating 144 deflects the diffracted light L8 and the diffracted light L9 toward one point on the first diffraction scale 141.

The first-order diffracted light L10 and the first-order diffracted light L11 from the second diffraction grating 144 are applied to one point P3 of the first diffraction grating 142. Then, the primary diffracted lights L10 and L11 from the second diffraction grating 144 are combined by the first diffraction grating 142 and emitted as interference light. Here, the diffracted light L12 is diffracted or transmitted to the same side where the primary diffracted light L10 from the second diffraction grating 144 is incident, and the primary diffracted light L11 from the second diffraction grating 144 is incident. The diffracted light that is diffracted or transmitted to the same side as the above is referred to as the diffracted light L13. The diffracted light L12 and the diffracted light L13 are received by the light receiving elements 132A and 132B in a state where the retardation plates 133A and 133B have a phase difference of 90 degrees, respectively.

When the main scale 110 is slid and moved while the light receiving elements 132A and 132B receive the light flux taking such an optical path, the diffraction grating 111 of the main scale 110 is moved. Then, the phase of the diffracted light is changed, and as a result, the interference sine wave signal output from the light receiving element is changed. Then, the sine wave signals from the light receiving elements 132A and 132B are processed by a signal processing unit (not shown), and for example, the sine wave signals from the light receiving elements 132A and 132B are differentially amplified and then synthesized as a Lissajous figure. The relative movement amount of the main scale 110 is detected from the state of movement of the Lissajous figure.

According to the first embodiment having such a configuration, the following effects can be obtained. (1) The light transmitted through the second diffraction grating 144 and radiated to the main scale 110 is reflected by the third diffraction grating 145 and recursed to the main scale 110. That is, it is reflected and diffracted twice by the main scale 110. Then, the luminous flux received by the light receiving elements 132A and 132B has phase information that is four times larger than the luminous flux that is reflected and diffracted once by the main scale 110. As a result, the amount of movement of the main scale 110 can be detected with four times the resolution by the interference sine wave signals output from the light receiving elements 132A and 132B.

(2) Since the primary diffracted light L1 and the transmitted light L0 demultiplexed by the first diffraction grating 142 show opposite phase changes depending on the traveling direction of the main scale 110, the main light is received by the light receiving elements 132A and 132B. Information on the traveling direction of the scale 110 can be obtained.

(3) Multiple optical devices with beam splitter and mirror functions are required to divide one luminous flux into two luminous fluxes and to recurse the light toward the main scale 110. These functions are combined with the first diffraction scale. It can be done by two optical devices, 141 and the second diffraction scale 143. Therefore, the number of optical devices may be small, and the component cost and the assembly cost can be reduced. Further, since the number of optical devices may be small, the optical path adjustment is easy, and the detection error due to the optical path adjustment error can be reduced to improve the detection accuracy.

(4) In addition to the main scale 110, only the first diffraction scale 141 and the second diffraction scale 143 are required as the optical device, and the overall configuration can be made compact because there are few components. Then, the total optical path length can be shortened. For example, in the case of laser light, where the interference wave fluctuates even when the air density changes, the displacement detection device 100 having excellent environmental resistance can be obtained by shortening the optical path length.

(5) The third diffraction grating 145 is configured by depositing a metal film on the second diffraction scale 143. Therefore, the third diffraction grating 145 can be easily formed, and the number of parts can be reduced by integrating the third diffraction grating 145 with the second diffraction scale 143. Furthermore, although it is difficult to precisely form irregularities that form a phase grating by processing a metal plate, a simple method of depositing a metal film on the phase grating of the second diffraction grating 144 is a highly accurate reflection type diffraction. You can get a grating.

(6) If the metal film 204 constituting the third diffraction grating 145 is exposed on the outer surface, corrosion or peeling may occur, but it is protected by the second diffraction scale 143 and the first diffraction scale 141. Not exposed to the outside. Therefore, the durability can be improved by protecting the metal film 204. Even if the surface of the metal film 204 is corroded or the like, it is the surface of the second diffraction grating 144 viewed from the main scale 110 side that functions as a phase grating, so that the surface of the metal film 204 Corrosion does not affect the optical performance.

(Second Embodiment) Next, the second embodiment according to the displacement detection device of the present invention will be described. The basic configuration of the second embodiment is the same as that of the first embodiment, but the second embodiment is characterized in that the optical device unit unit is configured by one diffraction scale. FIG. 5 shows a view of the second embodiment as viewed from between the optical device unit unit and the main scale 110. In FIG. 5, the optical device unit 200 is composed of one diffraction scale 201. The diffraction scale 201 is arranged parallel to the main scale 110 between the light emitting and receiving unit 130 and the main scale 110. The diffraction scale 201 is made of a transparent member such as glass and is formed in a flat rectangular parallelepiped shape. A first diffraction grating 142 is provided on one surface of the diffraction scale 201 on the light emitting / receiving unit 130 side. Further, in the diffraction scale 201, a second diffraction grating 202 is provided on one surface on the main scale 110 side. Further, a metal film 204 is vapor-deposited along the longitudinal direction at a substantially central portion in the lateral direction on one surface of the main scale side 110 of the diffraction scale 201. Here, the metal film 204 has irregularities on the surface similar to the irregularities of the second diffraction grating 202, and the metal film 204 constitutes the reflection type third diffraction grating 203.

In the second embodiment having such a configuration, the light emitted from the light source 131 is received by the light receiving elements 132A and 132B through the same path as in the first embodiment, and the relative movement amount of the main scale 110 is reduced. Detected. According to such a second embodiment, the following effects can be obtained in addition to the effects (1) and (2) of the first embodiment. (7) Since the optical device unit 200 is composed of one diffraction scale 201, the number of parts can be reduced to the utmost. Therefore, it is possible to reduce the parts cost and the assembly cost. Then, the optical path adjustment at the time of assembly can be made very easy. (8) The optical path can be shortened as much as possible by reducing the number of parts as much as possible. Further, since the optical device unit 200 is composed of one diffraction scale 201, almost all of the optical paths are inside the device, and the stroke of traveling in the air can be reduced. Therefore, the displacement detection device 100 having excellent environmental resistance can be obtained.

Although the metal film 204 may be exposed from the detection head portion 120 by being provided on the main scale 110 side of the diffraction scale 201, a transparent protective film may be provided on the metal film 204, or the main scale 110 may be provided. A housing may be provided to shield between the detection head portion 120 and the detection head portion 120 from the outside.

(Third Embodiment) Next, the third embodiment according to the displacement detection device of the present invention will be described with reference to FIG. The basic configuration of the third embodiment is the same as that of the first embodiment, but in the third embodiment, the first diffraction scale 141 and the second diffraction scale 143 are brought close to each other in the optical device unit unit 140. It has characteristics. Here, since it is necessary to diffract the light by the second diffraction grating 144, the refractive index between the second diffraction grating 144 and the first diffraction scale 141 is different from that of the first and second diffraction scales 141 and 143. Different media such as air need to be present. Alternatively, when the first diffraction scale 141 and the second diffraction scale 143 are made of materials having different refractive indexes, the first diffraction scale 141 and the second diffraction grating 144 may come into contact with each other. The first diffraction scale 141 and the metal film 146 may be in contact with each other.

According to such a configuration, in addition to the effects (1) to (6) of the above-described embodiment, the following effects can be obtained. (9) By bringing the first diffraction scale 141 and the second diffraction scale 143 close to each other, the overall configuration can be made compact. Then, the total optical path length can be shortened. In addition, almost all of the optical paths are inside the device, and the number of strokes in the air can be reduced. As a result, the displacement detection device 100 having excellent environmental resistance can be obtained.

(Fourth Embodiment) Next, the fourth embodiment according to the displacement detection device of the present invention will be described with reference to FIG. 7. The basic configuration of the fourth embodiment is the same as that of the first embodiment, but the fourth embodiment is characterized in that the width of the metal vapor deposition film is widened. For example, the metal film 146 may be deposited on two-thirds of the region of the second diffraction scale 143 in the lateral direction (perpendicular to the length measurement direction).

In such a configuration, the light emitted from the light source 131 is demultiplexed and deflected by the optical device unit unit 140, and is applied to the main scale 110 as diffracted light L14. The diffracted light L14 is reflected and diffracted by the main scale 110, and is incident on the third diffraction grating 145 as the diffracted light L15. The diffracted light L15 is reflected and diffracted by the third diffraction grating 145 and incident on the main scale 110. Then, the light is reflected and diffracted a plurality of times between the main scale 110 and the third diffraction grating 145, and then passes from the main scale 110 through the second diffraction grating 144 and the first diffraction grating 142 at the light receiving elements 132A and 132B. Received light.

According to the fourth embodiment having such a configuration, the following effects can be obtained in addition to the effects (1) to (6) of the above-described embodiments. (10) By widening the metal vapor deposition film 146, the number of times light is recurred to the main scale 110 can be increased. Then, the luminous flux received by the light receiving elements 132A and 132B has several times the phase information as compared with the luminous flux reflected and diffracted once by the main scale 110. As a result, the resolution for detecting the relative movement amount of the main scale 110 can be improved. Then, by a simple method of widening the metal vapor deposition film 146, the number of reflections on the third diffraction grating 145 can be increased to dramatically improve the detection resolution.

The width of the metal vapor deposition film 146 is not particularly limited, and may be formed wide as long as the region of the second diffraction grating 144 is left on the second diffraction scale 143.

(Fifth Embodiment) Next, the fifth embodiment according to the displacement detection device of the present invention will be described with reference to FIG. The basic configuration of the fifth embodiment is the same as that of the first embodiment, but the fifth embodiment is characterized in that the third diffraction scale 301 is provided in the optical device unit unit 140. The optical device unit unit 140 includes a first diffraction scale 141, a second diffraction scale 143, and a third diffraction scale 301. The first diffraction scale 141 is similar to the configuration described in the first embodiment, and includes a first diffraction grating 142. The second diffraction scale 143 includes the second diffraction grating 144 as described in the first embodiment, but the metal vapor deposition film is not vapor-deposited. The third diffraction scale 301 is arranged between the second diffraction scale 143 and the main scale 110 substantially parallel to the main scale 110. The third diffraction scale 301 has a flat rectangular parallelepiped shape narrower than the first diffraction scale 141 and the second diffraction scale 143, and has a phase lattice formed on one surface on the second diffraction scale 143 side and a metal film 303. Is vapor-deposited. A reflective third diffraction grating 302 is formed by depositing a metal film 303 on this phase grating.

In the fifth embodiment having such a configuration, the light emitted from the light source 131 is received by the light receiving elements 132A and 132B through the same path as in the first embodiment, and the relative movement amount of the main scale 110 is detected. Will be done.

According to such a fifth embodiment, in addition to the effects (1) and (2) of the above-described embodiment, the following effects can be obtained. (11) The third diffraction grating 302 is brought close to the main scale 110 by providing the third diffraction scale 301 separately from the second diffraction scale 143 and arranging the third diffraction scale 301 on the main scale 110 side. Can be done. Then, the optical path can be shortened as a whole. For example, laser light can be used as a displacement detection device having excellent environmental resistance by shortening the optical path length, where interference waves fluctuate even when the air density changes.

(Sixth Embodiment) The sixth embodiment according to the displacement detection device of the present invention will be described with reference to FIG. The basic configuration of the sixth embodiment is the same as that of the first embodiment, but in the lateral direction perpendicular to the length measurement direction, the incident light from the second or third diffraction grating is more than the incident angle. It is characterized in that it is provided with a prism (light refraction means) that emits emitted light toward the main scale with a large refraction angle. In FIG. 9, the optical device unit 400 includes a prism 401 in addition to the first diffraction scale 141 and the second diffraction scale 143. The prism 401 is provided on the surface of the second diffraction scale 143 on the main scale 110 side. The prism 401 has a shape having a thickness substantially near the center and becoming thinner linearly toward the end in the lateral direction perpendicular to the length measurement direction.

When the light L2 emitted from the light source 131 and diffracted by the second diffraction grating 144 is incident on the prism 401, the emitted light L14 is emitted from the prism 401 toward the main scale 110. At this time, the refraction angle of the emitted light L14 emitted from the prism 401 becomes larger than the incident angle of the incident light L2. Similarly, the light L15 diffracted and reflected by the third diffraction grating 145 also has a large refraction angle when it is emitted from the prism 401 as the emitted light L16. On the other hand, when the light L17 and L18 diffracted and reflected by the main scale 110 are incident on the prism, the refraction angle of the emitted light L19 and L20 emitted from the prism 401 becomes small.

According to the sixth embodiment having such a configuration, the following effects can be obtained in addition to the effects of the above-described embodiment. (12) Since the main scale 110 can be irradiated with light by making the refraction angle larger than the incident angle by the prism 401, the emission angle when emitting light from the light source 131 toward the first diffraction scale 141 is directed more vertically. be able to. Then, the length of the displacement detection device 100 in the lateral direction can be shortened.

Here, if the light from the light source 131 is emitted vertically without the prism 401 being provided, the reflected light is vertically reflected from the main scale 110, so that the incident light from the light source 131 and the reflected light from the main scale 110 are reflected. Will overlap. Then, the reflected light from the main scale 110 cannot be incident on the third diffraction grating 145, and it becomes difficult for the light receiving elements 132A and 132B to receive the reflected light from the main scale 110. In the sixth embodiment, since the prism 401 is provided, the refraction angle of the light emitted from the prism 401 is increased to increase the angle of incidence on the main scale 110 even if the light emission direction from the light source 131 is close to vertical. can do. Then, the reflected light from the main scale 110 can be incident on the third diffraction grating 145 by a path different from the light from the light source 131, and the reflected light from the main scale 110 can be transmitted to the light receiving elements 132A and 132B. It can be incident. Since the emission direction of the light from the light source 131 can be made close to vertical, for example, the width of the second diffraction grating 144 can be shortened to about the beam diameter of the laser, and the length in the lateral direction of the displacement detection device 100 can be shortened. Can be shortened. Then, by shortening the lateral direction, the device becomes compact and the optical path becomes short, and as a result, the displacement detection device 100 having excellent environmental resistance can be obtained.

(7th Embodiment) The 7th embodiment according to the displacement detection device of the present invention will be described with reference to FIG. The basic configuration of the seventh embodiment is the same as that of the first embodiment, but in the seventh embodiment, the light source 131 is arranged to emit the light reflected from the main scale 110 and diffracted by the first diffraction scale 141. It is characterized in that it is provided with a reflective member 501 that reflects to the side. In FIG. 10, the light emitting / receiving unit 500 includes a light source 131, light receiving elements 132A and 132B, and a reflecting member 501 in addition to the retardation plates 133A and 133B. The reflective member 501 has a reflective surface 502 provided perpendicular to the lattice surface of the first diffraction grating 142 of the first diffraction scale 141 along the lateral direction. The reflecting surface 502 faces the light emitting direction of the light source 131. Both the light receiving elements 132A and 132B are arranged on the light source 131 side, and one of the light receiving elements (132A) directly receives the diffracted light from the first diffraction grating 142, while the other light receiving element (132B) receives the diffracted light directly. After being diffracted by the first diffraction grating 142, the light reflected by the reflecting surface 502 is received.

In such a configuration, when the light is reflected from the main scale 110 and diffracted by the first diffraction grating 142, the light diffracted toward the light source 131 and the light diffracted in the direction opposite to the light source 131. (See Fig. 2 of the first embodiment). The light diffracted toward the light source 131 is received by the light receiving element 132A as it is, and the light diffracted in the direction opposite to the light source 131 is reflected by the reflecting surface 502 and then received by the light receiving element 132B.

According to the seventh embodiment having such a configuration, the following effects can be obtained in addition to the effects (1) to (6) of the above-described embodiments. (13) Since the reflecting member 501 is provided, the light is reflected toward the light source 131 side. Then, the light source 131 and the two light receiving elements 132A and 132B are arranged on the same side, and the optical components for light emission and light reception can be combined into one region. In particular, since the positions of the light receiving elements 132A and 132B can be set to the same side, the connection wiring to the processing means for processing the signals output from the light receiving elements 132A and 132B can be shortened.

The present invention is not limited to the above embodiment, and modifications, improvements, and the like within the range in which the object of the present invention can be achieved are included in the present invention. For example, although the main scale 110 has been described as having a reflective diffraction grating 111, the diffraction grating of the main scale 110 may be a transmission type. In this case, the third diffraction grating (diffraction grating for re-irradiation) is arranged on the side opposite to the light emitting / receiving unit 130 with the main scale 110 in between.

It goes without saying that not only when the main scale 110 moves with respect to the detection head unit 120, but also when the main scale 110 is fixed and the detection head unit 120 may move. The lattice shape of the diffraction grating may be rectangular wavy, sine wavy, triangular wavy, or the like, and is not particularly limited. Further, the diffraction grating is not limited to a diffraction grating having an uneven relief on the surface, and may be a phase grating in which the refractive index inside the medium changes periodically.

It was explained that the 0th-order diffractive light and the negative 1st-order diffractive light are used among the light demultiplexed by the 1st diffraction grating (diffraction grating for demultiplexing, combiner means) 142, but the light from the light source 131 is coherent light. If there is, the interference light can be detected regardless of the order of the diffracted light, so the order of the interference light is not limited.

As an example, the present invention is used for an optical encoder using a diffraction grating.

<figref num="1">It is a perspective view which saw through the internal structure of 1st Embodiment which concerns on the displacement detection apparatus of this invention.</figref><figref num="2">In the first embodiment, the basic configuration of the displacement detection device is shown in a perspective view and the optical path is shown.</figref><figref num="3">In the first embodiment, the optical path is shown in a front view of the displacement detection device viewed from a direction perpendicular to the length measurement direction.</figref><figref num="4">In the first embodiment, the optical path is shown in a side view of the displacement detection device viewed from the length measurement direction.</figref><figref num="5">It is a figure which shows the 2nd Embodiment which concerns on the displacement detection apparatus of this invention.</figref><figref num="6">It is a figure which shows the optical device unit part in 3rd Embodiment which concerns on the displacement detection apparatus of this invention.</figref><figref num="7">It is a figure which showed the optical path in the side view seen from the length measuring direction in 4th Embodiment which concerns on the displacement detection apparatus of this invention.</figref><figref num="8">It is a perspective view of the 5th Embodiment which concerns on the displacement detection apparatus of this invention.</figref><figref num="9">It is a side view seen from the length measuring direction in the 6th Embodiment which concerns on the displacement detection apparatus of this invention.</figref><figref num="10">In the seventh embodiment of the displacement detection device of the present invention, the optical path is shown in a front view seen from a direction perpendicular to the length measurement direction.</figref><figref num="11">It is a figure which shows the structure of the conventional displacement detection apparatus.</figref>

Code description

100 ... displacement detector, 110 ... main scale, 111 ... diffraction grating, 120 ... detection head, 130 ... light emitting / receiving part, 131 ... light source, 132A ... light receiving element , 132B ... light receiving element, 133A ... retardation plate, 133A ... retardation plate, 134 ... light receiving means, 140 ... optical device unit, 141 ... first diffraction scale, 142 ... 1st diffraction grating (diffraction grating for demultiplexing, combiner means), 143 ... 2nd diffraction scale, 144 ... 2nd diffraction grating (diffraction grating for deflection), 145 ... 3rd diffraction Grating (diffraction grating for re-irradiation), 146 ... metal film (reflection means), 150 ... frame, 200 ... optical device unit, 201 ... diffraction scale, 202 ... second diffraction Grating, 203 ... 3rd Diffraction Grating, 204 ... Metal Film, 301 ... 3rd Diffraction Scale, 302 ... 3rd Diffraction Grating, 303 ... Metal Film, 400 ... Optical Device Unit Unit, 401 ... prism (light refraction means), 500 ... light emitting / receiving part, 501 ... reflecting member, 502 ... reflecting surface, 600 ... optical device unit part, 601 ... beam splitter , 602 ... 1st mirror, 603 ... 2nd mirror, 604 ... 3rd mirror, 605 ... 4th mirror, 606 ... 5th mirror, 607 ... half mirror,