JP2020051782A - Optical angle sensor - Google Patents

Abstract

To provide an optical angle sensor by which a change in the phase of diffracted light due to environmental conditions can be prevented and an amount of change in the angle due to the rotation of a measurement target can be detected with high accuracy while circumventing the limitation due to the coherency of the light source.SOLUTION: The optical angle sensor 1 includes a light source 2, a transmissive diffraction grating 3, first reflection means 4a, second reflection means 4b, and light receiving means 5. The transmissive diffraction grating 3 includes a first diffraction grating section 6 configured to split light into the first light and the second light, a second diffraction grating section 7 configured to diffract the first light and the second light, a third diffraction grating section 8 configured to diffract the first light and the second light via the first reflection means 4a and the second reflection means 4b, and a fourth diffraction grating section 9 configured to combine the first light and the second light. The light receiving means 5 receives the combined light of the first light and the second light, which are split by the first diffraction grating section 6, diffracted by the second diffraction grating section 7, reflected by the first reflection means 4a or the second reflection means 4b, diffracted by the third diffraction grating section 8, and combined in the fourth diffraction grating section 9.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an optical angle sensor.

2. Description of the Related Art Conventionally, an optical angle sensor including a light source that emits light, a light receiving unit that receives light from the light source, and a calculation unit that calculates an amount of change in angle due to rotation of a measurement target is known.
For example, a two-dimensional angle sensor described in Patent Literature 1 includes a light source for projecting a light beam on a detection target, a lens provided in an optical path of light reflected from the detection target by the light beam, and a lens near a focal point of the lens. A detection element (light receiving means) using a photodiode provided. The two-dimensional angle sensor detects the angle of the detection target by calculating the photocurrent detected by the detection element.

  Specifically, the two-dimensional angle sensor detects the inclination of the detection target from the shape of the light projected on the detection element and the magnitude of the amount of the light. When the shape of the light projected onto the detection element and the magnitude of the light amount are changed by a lens or the like, the change may affect the detection result as noise. The two-dimensional angle sensor has a problem that it is necessary to provide a high-quality and expensive optical component such as a lens in order to suppress noise due to a change in the shape of the light and the magnitude of the light amount of the light, which is costly. .

  To solve such a problem, for example, Patent Literature 2 uses a laser interferometer. A laser interferometer measures the amount of change in the angle due to the rotation of a measurement object using the interference of a laser beam. A laser light source (light source) that emits a laser beam and a laser beam that is emitted from the laser light source A first optical fiber that transmits the laser beam, a first lens that makes the laser beam from the first optical fiber parallel, and a laser beam that is made parallel by the first lens, and after splitting through two corner cubes, A polarization beam splitter for detecting a rotation angle that combines split laser beams, a polarization plate that polarizes the laser beam emitted from the polarization beam splitter for detecting a rotation angle, and a second optical fiber that transmits the laser beam through the polarization plate A second lens for converging the laser beam on the end face of the light receiving element, and a light receiving signal processing unit (light receiving means) for converting the laser beam via the second optical fiber into an electric signal Preliminary comprises a computing means), a.

  The laser light source is a He-Ne laser that irradiates a laser beam with good coherence (coherence) of the electric signal detected by the light reception signal processing unit. Then, the laser beam irradiated to the light receiving signal processing unit via the rotation angle detecting polarization beam splitter causes interference on the irradiation surface to which the laser beam is irradiated in the light receiving signal processing unit. The laser interferometer measures the change in the angle due to the rotation of the measurement target by converting the change in the intensity of the interference light caused by the change in the optical path length due to the rotation into an electrical signal in the received light signal processing unit and calculating it. can do.

  Specifically, when two corner cubes provided in the laser interferometer rotate, the difference in optical path length between the two laser beams split by the rotation angle detecting polarization beam splitter changes, and the intensity of the interference light, Specifically, a change in the brightness of the interference light is observed. At this time, the change in the difference in optical path length is twice the length obtained by multiplying the arrangement distance of the two corner cubes by the rotation angle. The laser interferometer can measure the rotation angles of the two corner cubes by detecting the amount of change in brightness of the interference light. Therefore, the laser interferometer detects the rotation angle from the change in brightness of the interference light regardless of the shape of the light and the magnitude of the light amount of the light, so that the laser interferometer does not need to include a high-quality and expensive optical component such as a lens. , The rotation angle of the object to be measured can be detected.

JP 2003-156319 A JP-A-11-237207

However, the laser interferometer described in Patent Document 2 has the following problem.
For example, two laser beams split by the rotation angle detection polarization beam splitter are rotated from the laser beam splitting point in the rotation angle detection polarization beam splitter via corner cubes corresponding to the respective laser beams. The optical path lengths up to the combining point of the laser beams in the polarization beam splitter for use differ from each other.

  Specifically, assuming that the optical path length of one of the divided laser beams is L, the optical path length of the other divided laser beam is twice as long as the optical path length L of the one laser beam. . The laser light source provided in the laser interferometer is a He-Ne laser, and its coherent length is several meters. Therefore, even if the optical path lengths of the two laser beams are significantly different from each other, interference occurs.

However, when a semiconductor laser having a very short coherent length of several cm is used as a light source, if the optical path lengths of the two divided laser beams differ from each other by about twice, the irradiation surface in the light receiving signal processing unit No interference occurs. Therefore, when a semiconductor laser is used as a light source, a laser interferometer uses two laser beams by using an optical component such as a diffraction grating for diffracting light from the light source in order to avoid limitations due to its coherence. Need to be substantially equal to each other.
In addition, even when the laser interferometer uses a semiconductor laser as a light source and the optical path lengths of the two laser beams are substantially the same, even if the optical components expand or expand due to environmental changes such as temperature. May shrink. As a result, the position at which the laser beam from the semiconductor laser is split into two laser beams may move from the original position.

FIG. 12 is a schematic view showing a conventional optical angle sensor.
The optical angle sensor 100 shown in FIG. 12 includes, for example, a light source 2, a transmission diffraction grating 300, a first reflecting unit 400a and a second reflecting unit 400b such as a prism, and a light receiving unit 500. The optical angle sensor 100 is configured such that the optical path lengths of two laser beams from the light source 2 are substantially the same.

  When heat is applied due to, for example, an environmental change, the transmission diffraction grating 300 moves from the position of the transmission diffraction grating 300a indicated by the broken line to the position of the transmission diffraction grating 300b indicated by the solid line in the direction of the arrow in the drawing due to thermal expansion. Sometimes. When the transmission diffraction grating 300 moves from the position of the transmission diffraction grating 300a indicated by the broken line to the position of the transmission diffraction grating 300b indicated by the solid line, the phase of the diffracted light transmitted through the transmission diffraction grating 300b changes, and Even if is not rotated, the object to be measured may be detected as rotated.

  Specifically, when the phase change caused by a plurality of diffracted lights diffracted by the transmission diffraction grating 300 is φ, the diffraction order is n, and the transmission diffraction grating indicated by a solid line is located from the position of the transmission diffraction grating 300a indicated by a broken line. The amount of movement of the transmission diffraction grating 300 to the position 300b is represented by Δx, and the period of a plurality of gratings of the transmission diffraction grating 300 is represented by p, and can be expressed by Expression (1).

  φ = n × Δx ÷ p (1)

For example, as shown in FIG. 12, the light emitted from the light source 2 becomes a plurality of diffracted lights by the transmission type diffraction grating 300. At this time, of the plurality of diffracted lights, the light used for detection is ± 1st-order diffracted light. In FIG. 12, the optical path of the light that generates the interference light in the light receiving unit 500 is indicated by an arrow.
Then, the + 1st-order diffracted light is reflected by the first reflection means 400a toward the transmission type diffraction grating 300, diffracted again in the + 1st-order direction by the transmission type diffraction grating 300, and received as a + 2nd-order diffraction light. The means 500 is irradiated. The -1st-order diffracted light is reflected by the second reflection means 400b toward the transmission diffraction grating 300, and is again diffracted in the -1st direction by the transmission diffraction grating 300, and the diffraction order is -2nd order. The light is applied to the light receiving means 500 as light. In FIG. 12, in order to clarify the diffraction order of the diffracted light, the diffraction order is indicated only by a numeral near the arrow indicating the light.

If the transmission type diffraction grating 300 does not move from the position of the transmission type diffraction grating 300a indicated by the broken line, the movement amount Δx becomes 0, and the phase change φ generated by the diffracted light becomes 0. That is, even if the diffraction order n of the diffracted light applied to the light receiving means 500 is ± 2nd order, the diffracted light does not have a phase change φ because it is canceled by the moving amount Δx.
However, when the transmission diffraction grating 300 moves from the position of the transmission diffraction grating 300a indicated by the broken line to the position of the transmission diffraction grating 300b indicated by the solid line by the movement amount Δx, the phase change φ caused by the diffracted light becomes ± 2Δx / p. For this reason, when the diffracted light whose phase has been changed due to the movement of the transmission type diffraction grating 300 is irradiated on the light receiving unit, the optical angle sensor 100 assumes that the measurement target is rotated even if the measurement target is not rotated. May be detected.

  Therefore, when the laser interferometer described in Patent Document 2 uses a diffraction grating to split or combine light, for example, a phase change occurs in the diffracted light due to movement of the diffraction grating due to an environmental change, and the measurement object rotates. Even if it is not performed, there is a problem that interference having an angular displacement occurs and an error may occur in the detection result.

  An object of the present invention is to prevent a phase change of diffracted light due to an environmental change while avoiding a limitation due to a coherency of a light source, and to accurately detect a change in an angle due to rotation of a measurement target. It is to provide an angle sensor.

  An optical angle sensor according to the present invention includes a light source that irradiates light, a transmission diffraction grating having a plurality of gratings that diffract light from the light source, and light transmitted through the transmission diffraction grating directed toward the transmission diffraction grating. A first reflecting means for reflecting light, a second reflecting means for reflecting light, which is different from light reflected by the first reflecting means via the transmission type diffraction grating, toward the transmission type diffraction grating, and a transmission type diffraction grating. Light receiving means for receiving light, and arithmetic means for calculating the light received by the light receiving means as a signal of the change in angle in the measurement object that rotates around a predetermined axis as a rotation axis, the transmission diffraction grating, A first diffraction grating section for splitting light from the light source into a first light and a second light, a second diffraction grating section for diffracting the first light and the second light split by the first diffraction grating section, The first light passing through the first reflecting means and the second light passing through the second reflecting means are circulated. A third diffraction grating section, and a fourth diffraction grating section that combines the first light and the second light via the third diffraction grating section to generate a combined light, and wherein the first reflection means includes a second diffraction grating. The first light diffracted through the grating portion is reflected in a direction parallel to and opposite to the direction in which the first light is incident, and the second reflection means reflects the second light diffracted through the second diffraction grating portion. The light is reflected in a direction parallel to and in a direction opposite to the direction in which the second light is incident, and the first reflection means and the second reflection means emit light from the light source in the first diffraction grating portion within the measurement range of the measurement target. The optical path length of the first light from the division point to the fourth diffraction grating unit via the first reflection unit, and the division point of the light from the light source in the first diffraction grating unit via the second reflection unit The optical path length of the second light until it reaches the fourth diffraction grating portion has an angle that is the same length. Divided by the diffraction grating, diffracted by the second diffraction grating, reflected by the first reflection means or the second reflection means, diffracted by the third diffraction grating, and synthesized by the fourth diffraction grating. The combined light of the first light and the second light thus received is received, and the calculating means calculates an amount of change in the angle due to the rotation of the measurement target from a signal based on the combined light received by the light receiving means.

  According to such an aspect of the invention, in the optical angle sensor, the first reflecting means and the second reflecting means move the first reflecting means from the light dividing point in the first diffraction grating within the measurement range of the measurement object. The optical path length of the first light until reaching the fourth diffraction grating through the second diffraction means from the splitting point of the light in the first diffraction grating to the fourth diffraction via the second reflecting means. Since the optical path length of the light has the same angle, the difference between the optical path length of the first light and the optical path length of the second light, which changes due to the rotation of the object to be measured, is kept within several cm. Can be. That is, the optical angle sensor can cause interference on the light receiving surface of the light receiving unit even when, for example, a semiconductor laser having a very short coherent length is used as the light source.

The optical angle sensor includes a second diffraction grating unit that diffracts the first light and the second light, and a second diffraction grating that diffracts the first light via the first reflecting unit and the second light via the second reflecting unit. By including the three diffraction grating portions, the first light and the second light can be diffracted a plurality of times. Accordingly, the optical angle sensor can cancel the diffraction orders of the first light and the second light and set the diffraction order n in Expression (1) to 0. Therefore, the transmission type diffraction sensor expands or contracts due to an environmental change. Even if the position of the grating has shifted from the original position, it is possible to suppress the generation of interference light having an angular displacement due to a phase change of the diffracted light.
Therefore, the optical angle sensor can prevent the phase change of the diffracted light due to the environmental change while avoiding the limitation due to the coherence of the light source, and can detect the amount of change in the angle due to the rotation of the measurement target with high accuracy. .

  At this time, the optical angle sensor has one transmission type diffraction grating, and one transmission type diffraction grating has a first diffraction grating portion, a second diffraction grating portion, a third diffraction grating portion, and a fourth diffraction grating portion. A grating portion is provided, and the first light and the second light split by the first diffraction grating portion are reflected toward one transmission diffraction grating and diffracted by the third diffraction grating portion. A mirror for reflecting the one light and the second light toward one transmission diffraction grating; the light receiving means is divided by the first diffraction grating, reflected by the mirror, and reflected by the second diffraction grating; The first light and the second light reflected by the first or second reflecting means, diffracted by the third diffraction grating, reflected by the mirror, and combined by the fourth diffraction grating. The arithmetic means receives the combined light of the light, and the arithmetic means calculates the amount of change in the angle due to the rotation of the object to be measured from a signal based on the synthetic light received by the light receiving means. It is preferable.

  According to such a configuration, the optical angle sensor has one transmission-type diffraction grating, and one transmission-type diffraction grating includes the first diffraction grating unit, the second diffraction grating unit, and the third diffraction grating. By providing the part and the fourth diffraction grating part together, the number of parts can be reduced. Therefore, the optical angle sensor can reduce costs.

Here, when a plurality of transmission type diffraction gratings are used in the optical angle sensor, it is necessary to dispose a plurality of transmission type diffraction gratings at a predetermined distance in order to diffract light from a light source. As a result, the size of the optical angle sensor may be increased.
However, the first light and the second light split by the first diffraction grating portion are reflected toward one transmission diffraction grating, and the first light and the second light diffracted by the third diffraction grating portion are reflected. Since a mirror that reflects light toward one transmission diffraction grating is provided, the size of the optical angle sensor can be suppressed.

  Alternatively, the optical angle sensor has a plurality of transmission type diffraction gratings, and the plurality of transmission type diffraction gratings include a first transmission type diffraction grating provided with a first diffraction grating portion and a fourth diffraction grating portion; A second transmission type diffraction grating provided with two diffraction grating portions and a third diffraction grating portion, wherein the light receiving means is divided by the first diffraction grating portion of the first transmission type diffraction grating, and the second transmission type diffraction grating is provided. Diffracted by the second diffraction grating portion of the diffraction grating, reflected by the first reflection means or the second reflection means, diffracted by the third diffraction grating portion of the second transmission diffraction grating, and converted to the first transmission diffraction grating. Receiving the combined light of the first light and the second light combined by the fourth diffraction grating section, and calculating the change in the angle due to the rotation of the measuring object from the signal based on the combined light received by the light receiving means. Is preferably calculated.

  According to such a configuration, the optical angle sensor has a plurality of transmission-type diffraction gratings, and the plurality of transmission-type diffraction gratings includes a first transmission grating in which the first diffraction grating unit and the fourth diffraction grating unit are provided. A first diffraction grating unit, a fourth diffraction grating unit, and a second diffraction grating unit, comprising: a first diffraction grating unit; and a second transmission type diffraction grating provided with a second diffraction grating unit and a third diffraction grating unit. And the third diffraction grating portion can be freely designed. Therefore, the optical angle sensor can improve the degree of freedom in design.

Here, when one transmission diffraction grating is used for the optical angle sensor, it is necessary to use a mirror having a size corresponding to one transmission diffraction grating. If one transmission diffraction grating is long, the mirror is also long, and the optical angle sensor may become large in the long direction.
However, the optical angle sensor includes the first transmission type diffraction grating and the second transmission type diffraction grating, and does not need to include the mirror. Therefore, compared with the case where one transmission type diffraction grating is used, It is possible to suppress an increase in the size in the longitudinal direction while reducing the number of parts.

  At this time, one of the first reflecting means or the second reflecting means is fixedly provided, and the other of the first reflecting means or the second reflecting means is attached to the object to be measured, and is synchronized with the rotation of the object to be measured. It is preferable that the rotation is performed.

Here, when the first reflection means and the second reflection means are attached to the object to be measured, the rotation of the object to be measured becomes slow due to the weight of the first reflection means and the second reflection means, which affects the measurement result. There is.
However, according to such a configuration, one of the first reflection means and the second reflection means is fixedly provided in the optical angle sensor, and the other of the first reflection means or the second reflection means is provided as a measurement object. , The weight of the object to be measured is lighter than when the first reflection means and the second reflection means are attached to the object to be measured. Therefore, the optical angle sensor can suppress the influence of the weight on the measurement result and detect the amount of change in the angle due to the rotation of the measurement target with high accuracy.

  Alternatively, it is preferable that the first reflection means and the second reflection means are attached to the object to be measured, and rotate in synchronization with the rotation of the object to be measured.

  According to such a configuration, the first reflection unit and the second reflection unit are attached to the measurement target that rotates with the predetermined rotation axis, and rotate in synchronization with the rotation of the measurement target. , The first reflecting means and the second reflecting means rotate simultaneously by the same angle. That is, the total amount of change in the angle due to the rotation of the first reflecting means and the second reflecting means is compared with the case where one of the first reflecting means or the second reflecting means is fixed and the other is attached to the object to be measured. Double. Thereby, the intensity of the combined light combined by the fourth diffraction grating portion is doubled as compared with the case where one of the first reflection means or the second reflection means is fixed and the other is attached to the object to be measured. . For this reason, the sensitivity of the light receiving means is doubled. Therefore, as compared with a case where one of the first reflecting means or the second reflecting means is fixed and the other is attached to the object to be measured, the optical angle sensor is capable of rotating the object to be measured with high precision from a signal with high sensitivity. The change amount of the angle can be detected.

  At this time, the first reflection means and the second reflection means are respectively line-oriented with respect to the rotation axis of the first reflection means or the second reflection means and the axis parallel to the optical axis of the light from the light source. Preferably, they are arranged at symmetrical positions.

  According to such a configuration, the first reflection unit and the second reflection unit in the optical angle sensor are configured so that the rotation axis of the first reflection unit or the second reflection unit and the axis parallel to the optical axis of the light from the light source. And are arranged at positions that are line-symmetric with respect to the respective axes. For this reason, as compared with the case where the first reflection unit and the second reflection unit are arranged at positions that are asymmetric, the first reflection unit and the second reflection unit can be disposed within the measurement range of the measurement target by the first diffraction grating unit. And the optical path length of the first light from the splitting point of the light from the light source from the light source to the fourth diffraction grating portion via the first reflecting means, and the second from the splitting point of the light from the light source in the first diffraction grating portion. It is possible to easily design the optical path length of the second light to reach the fourth diffraction grating portion via the reflection means so as to have the same angle.

  At this time, the first diffraction grating portion has a division surface on which light from the light source is irradiated, and the fourth diffraction grating portion is orthogonal to the rotation axis of the first reflection unit or the second reflection unit on the division surface. Having a plurality of gratings arranged side by side in the orthogonal direction, the light receiving means includes a plurality of light receiving elements arranged side by side in the orthogonal direction, and receives a plurality of diffracted lights through the plurality of gratings, It is preferable that the calculating means calculates the amount of change in the angle due to the rotation of the measurement target from a plurality of signals based on the plurality of diffracted lights received by the plurality of light receiving elements.

  According to such a configuration, the fourth diffraction grating section has a plurality of gratings arranged in parallel along a direction orthogonal to the rotation axis of the first reflecting means or the second reflecting means on the division surface, The light receiving means includes a plurality of light receiving elements arranged side by side in the orthogonal direction, and receives a plurality of diffracted lights via a plurality of gratings. The plurality of diffracted lights generate interference fringes on the light receiving surface of the light receiving unit along a direction parallel to the rotation axis of the first reflecting unit or the second reflecting unit. For this reason, the plurality of light receiving elements of the light receiving means can detect, for example, a four-phase signal from the interference fringes. The calculating means can calculate, for example, the rotation direction of the measurement target and the amount of change in the angle due to the rotation from the four-phase signal. Therefore, the optical angle sensor detects the amount of change in the angle due to the rotation of the measurement target from the interference fringes with higher accuracy than when calculating the amount of change in the angle due to the rotation of the measurement object from the interference light. Can be.

  Alternatively, the fourth diffraction grating portion is provided in parallel along a direction orthogonal to a rotation axis of the first reflection means or the second reflection means on the division surface, and has a predetermined inclination with respect to an optical axis of light from the light source. It has a plurality of inclined gratings arranged at an angle, and the light receiving means includes a plurality of light receiving elements arranged in parallel along a direction parallel to the rotation axis of the first reflecting means or the second reflecting means. Receiving the plurality of diffracted light beams through the plurality of inclined gratings, and calculating means for calculating the amount of change in the angle due to the rotation of the measurement target from the plurality of signals based on the plurality of diffracted lights received by the light receiving means. preferable.

  According to such a configuration, the fourth diffraction grating section has a plurality of inclined gratings arranged at a predetermined inclination angle with respect to the optical axis of the light from the light source, and A plurality of diffracted lights are received through a plurality of gratings having tilt angles. The plurality of diffracted lights generate interference fringes on a light receiving surface of the light receiving unit along a direction orthogonal to a rotation axis of the first reflecting unit or the second reflecting unit. For this reason, the plurality of light receiving elements of the light receiving means can detect, for example, a four-phase signal from the interference fringes. The calculating means can calculate, for example, the rotation direction of the measurement target and the amount of change in the angle due to the rotation from the four-phase signal. Therefore, the optical angle sensor detects the amount of change in the angle due to the rotation of the measurement target from the interference fringes with higher accuracy than when calculating the amount of change in the angle due to the rotation of the measurement object from the interference light. Can be.

  In this case, the fourth diffraction grating unit includes a plurality of combining units having different phases, the light receiving unit includes a plurality of light receiving units corresponding to the plurality of combining units, and the calculating unit includes a plurality of light receiving units. It is preferable to calculate the direction of rotation of the measurement target and the amount of change in the angle due to the rotation of the measurement target from a plurality of signals having different phases based on the received light.

  According to such a configuration, since the optical angle sensor can generate a plurality of combined lights by the plurality of combining units, when the optical angle sensor includes four combining units and four light receiving units, for example, the optical angle sensor detects a four-phase signal. can do. Therefore, the optical angle sensor can detect an angular displacement by rotating the measurement target with high accuracy using a plurality of signals such as a four-phase signal.

  Alternatively, the optical angle sensor includes a first quarter-wave plate disposed on an optical path of the first light passing through the first reflecting unit or the second light passing through the second reflecting unit, and includes a fourth diffraction grating unit. Beam splitter for splitting the combined light by the first and second split beams into a first split beam and a second split beam, and a second beam splitter disposed on the optical path of the first split beam and the second split beam split by the split beam splitter. A 波長 wavelength plate, a third 波長 wavelength plate disposed on the optical path of the second split light via the second ４ wavelength plate, and a third 板 wavelength plate via the second 波長 wavelength plate. A first split light polarization beam splitter that splits one split light into a first polarized light and a second polarized light, and splits the second split light through a third quarter-wave plate into a third polarized light and a fourth polarized light A second split light polarization beam splitter, a first light receiving unit that receives light having a phase of 0 degree from the first polarized light, A second light receiving unit for receiving light having a phase of 180 degrees, a third light receiving unit for receiving light having a phase of 90 degrees from the third polarized light, and a fourth light receiving unit for receiving light having a phase of 270 degrees from the fourth polarized light It is preferable to provide:

  According to such a configuration, the optical angle sensor includes the first quarter-wave plate disposed on the optical path of the first light via the first reflecting unit or the second light via the second reflecting unit. A light receiving unit, as the plurality of light receiving units, a first light receiving unit that receives light having a phase of 0 degree from the first polarized light; a second light receiving unit that receives light having a phase of 180 degrees from the second polarized light; Since a third light receiving unit that receives light having a phase of 90 degrees from the three polarized lights and a fourth light receiving unit that receives light having a phase of 270 degrees from the fourth polarized light are provided, for example, a four-phase signal is detected from the combined light. can do. Therefore, the optical angle sensor can detect the displacement of the angle due to the rotation of the measurement target with high accuracy using, for example, a four-phase signal, which can be obtained from a plurality of diffracted lights.

  Alternatively, the optical angle sensor includes a quarter-wave plate disposed on an optical path of the first light passing through the first reflecting unit or the second light passing through the second reflecting unit, and the combined light by the fourth diffraction grating unit. A fifth diffraction grating portion having an irradiation surface on which a plurality of gratings each having a plurality of diffracted lights are arranged side by side, and a fifth diffraction grating portion arranged in a direction orthogonal to the direction in which the plurality of gratings are arranged side by side and the irradiation surface. A sixth diffraction grating portion having a plurality of gratings provided, the plurality of diffraction light beams by the fifth diffraction grating portion being further converted into a plurality of diffraction light beams, and a sixth diffraction grating portion disposed on an optical path of the plurality of diffraction light beams by the sixth diffraction grating portion. And a plurality of polarizers for converting the plurality of diffracted lights into a plurality of polarized lights having different phases, respectively, wherein the light receiving unit includes a plurality of light receiving units corresponding to each of the plurality of polarizers, and the arithmetic unit includes a plurality of Multiple signals with different phases based on the light received by the light receiving unit It is preferable to calculate the angle of variation depending on the direction and the measured rotation of al measurement target turning.

  According to such a configuration, the optical angle sensor includes the 波長 wavelength plate disposed on the optical path of the first light passing through the first reflecting unit or the second light passing through the second reflecting unit. In order to include a plurality of polarizers corresponding to the plurality of diffraction gratings diffracted by the diffraction grating and the second diffraction grating, and a plurality of light receiving units corresponding to the plurality of polarizers, respectively, the split beam splitter described above, Compared with the case where the split light polarization beam splitter and the second split light polarization beam splitter are provided, for example, a four-phase signal can be obtained from a plurality of diffraction gratings without using these optical components. Therefore, the optical angle sensor can achieve space saving and cost reduction while achieving higher accuracy as compared with the above-described optical angle sensor.

FIG. 1 is a schematic diagram illustrating an optical angle sensor according to a first embodiment. Block diagram showing the optical angle sensor FIG. 4 is a schematic diagram showing rotation of a reflection unit in the optical angle sensor. Schematic showing an optical angle sensor according to a second embodiment. Schematic showing an optical angle sensor according to a third embodiment. The schematic diagram which shows the transmission type diffraction grating and the light receiving means in the optical angle sensor which concerns on 4th Embodiment. Schematic diagram showing a transmission type diffraction grating and light receiving means in an optical angle sensor according to a fifth embodiment. Schematic diagram showing a transmission type diffraction grating and light receiving means in an optical angle sensor according to a sixth embodiment. Schematic showing an optical angle sensor according to a seventh embodiment. Schematic showing an optical angle sensor according to an eighth embodiment. Schematic diagram showing an optical angle sensor according to a modified example Schematic diagram showing a conventional optical angle sensor

[First Embodiment]
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a schematic diagram showing an optical angle sensor according to the first embodiment.
As shown in FIG. 1, the optical angle sensor 1 includes a light source 2 for irradiating light, a transmission diffraction grating 3 having a plurality of gratings 60, 70, 80, and 90 for diffracting light from the light source 2, and a transmission type diffraction grating 3. Reflection means 4a for reflecting light passing through the transmission type diffraction grating 3 toward the transmission type diffraction grating 3, and transmitting light different from light reflected by the first reflection means 4a via the transmission type diffraction grating 3. It includes a second reflecting means 4b for reflecting light toward the diffraction grating 3, and a light receiving means 5 for receiving light passing through the transmission type diffraction grating 3.
The optical angle sensor 1 is provided inside a measuring device that measures a rotating measurement object (not shown). In the first embodiment, the measurement target rotates around the X axis. In the following description, the X axis may be described as the rotation axis of the measurement target.

The light source 2 irradiates light having a certain width toward the transmission diffraction grating 3. The light source 2 is, for example, a semiconductor laser. The light source 2 is not limited to a semiconductor laser, and may be any light source having a coherent length of several cm.
The transmission type diffraction grating 3 is formed in a long shape with translucent glass, and has a plurality of gratings 60, 70, 80, 90 arranged at a predetermined pitch. The transmissive diffraction grating 3 is not limited to glass, and may be formed of any translucent member.
Light from the light source 2 via the plurality of gratings 60, 70, 80, 90 of the transmission diffraction grating 3 becomes a plurality of diffracted lights.

Here, the plurality of diffracted lights include a diffracted light traveling in the same direction as the optical axis of the light emitted from the light source 2, a diffracted light traveling on both sides of the optical axis at a predetermined diffraction angle, and a diffracted light traveling on both sides of the optical axis. Diffracted light traveling at a diffraction angle larger than a predetermined diffraction angle.
Assuming that the diffracted light traveling in the same direction as the optical axis is the 0th-order diffracted light, the diffracted light is ordered as ± 1st-order diffracted light and ± 2nd-order diffracted light in the direction in which the diffraction angle increases with respect to the 0th-order diffracted light. be able to.
The light receiving means 5 detects a signal mainly from interference light generated by ± first-order diffracted light.
In the following description and drawings, the optical path of the light that generates the interference light in the light receiving unit 5 is indicated by an arrow.

The transmission diffraction grating 3 is configured to split the light from the light source 2 into a first light and a second light, and to convert the first light and the second light split by the first diffraction grating 6. A second diffraction grating section 7 for diffracting the light, a third diffraction grating section 8 for diffracting the first light via the first reflecting section 4a and the second light via the second reflecting section 4b, and a third diffraction section 8 And a fourth diffraction grating unit 9 that combines the first light and the second light via the first light and the second light into a combined light. The first diffraction grating portion 6, the second diffraction grating portion 7, the third diffraction grating portion 8, and the fourth diffraction grating portion 9 are provided in one transmission diffraction grating 3.
Further, the optical angle sensor 1 reflects the first light and the second light split by the first diffraction grating section 6 toward one transmission diffraction grating 3, and causes the third diffraction grating section 8 to reflect the first light and the second light. And a mirror that reflects the diffracted first light and second light toward one transmission diffraction grating.

The first reflecting means 4a is a prism having two orthogonal reflecting surfaces, and converts the first light diffracted through the second diffraction grating portion 7 into a direction parallel to and opposite to the direction in which the first light is incident. Reflect in the direction. Specifically, the first reflection unit 4 a emits the first light incident through the second diffraction grating unit 7 of the transmission diffraction grating 3 toward the third diffraction grating unit 8 of the transmission diffraction grating 3. .
The second reflecting means 4b is a prism having two orthogonal reflecting surfaces, and converts the second light diffracted through the second diffraction grating portion 7 into a direction parallel to and opposite to the direction in which the second light is incident. Reflect in the direction. Specifically, the second reflection unit 4b emits the second light incident through the second diffraction grating unit 7 of the transmission diffraction grating 3 toward the third diffraction grating unit 8 of the transmission diffraction grating 3. .

  The first reflection means 4a and the second reflection means 4b are attached to the measurement object that rotates around the X axis that is the rotation axis, and rotate in synchronization with the rotation of the measurement object. In addition, the first reflection unit 4a and the second reflection unit 4b are respectively axes of a rotation axis of the first reflection unit 4a or the second reflection unit 4b and an axis parallel to the optical axis of light from the light source 2. Are disposed at positions that are symmetrical with respect to. That is, the first reflecting means 4a and the second reflecting means 4b are arranged at positions symmetrical with respect to a plane formed by the X axis and the Z axis which is an axis parallel to the optical axis of the light from the light source 2. ing.

  At this time, it is preferable that the rotation axes of the first reflection means 4a and the second reflection means 4b coincide with the rotation axis of the measurement target. As a result, the first light and the second light that are applied to the light receiving unit 5 via the first reflecting unit 4a and the second reflecting unit 4b are transmitted even if the first reflecting unit 4a and the second reflecting unit 4b rotate. Irradiation is performed on the same position of the light receiving unit 5 without any deviation of the irradiation position.

  The first diffraction grating section 6 has a division surface 61 on which light from the light source 2 is irradiated. The first diffraction grating section 6 includes a plurality of gratings 60 arranged in parallel along the Y direction, which is a direction orthogonal to the X axis that is the rotation axis of the first reflecting means 4a or the second reflecting means 4b, on the division surface 61. Having. Similarly, the second diffraction grating portion 7, the third diffraction grating portion 8, and the fourth diffraction grating portion 9 are orthogonal to the X axis, which is the rotation axis of the first reflecting means 4a or the second reflecting means 4b, on the division surface 61. It has a plurality of grids 70, 80, 90 arranged side by side along the Y direction which is the direction.

  The second diffraction grating unit 7 diffracts the first light split by the first diffraction grating unit 6, and diffracts the second light split by the first diffraction grating unit 6. A second diffraction grating portion 7b. The second diffraction grating section 7 diffracts into diffracted light having the opposite sign that is paired with each diffraction order of the plurality of lights split by the first diffraction grating section 6. Specifically, when the first light is the + 1st-order diffracted light, the second diffraction grating portion 7a diffracts the light so as to be the -1st-order diffracted light. When the second light is a -1st-order diffracted light, the second diffraction grating portion 7b diffracts the light so as to be a + 1st-order diffracted light. In the following description and drawings, in order to clarify the diffraction order of the diffracted light such as the first light and the second light, the diffraction order may be described only by numerals near the arrow indicating the light. .

  The third diffraction grating unit 8 further includes a third diffraction grating unit 8a that further diffracts the first light diffracted by the second diffraction grating unit 7a, and a second light diffracted by the second diffraction grating unit 7b. And a third diffraction grating portion 8b that diffracts the light. Specifically, the third diffraction grating portion 8a further diffracts the first light, which has been converted into the -1st-order diffracted light by the second diffraction grating portion 7a, in the -1st-order direction. The third diffraction grating portion 8b further diffracts the second light, which has been converted into the + 1st-order diffracted light by the second diffraction grating portion 7b, in the + 1st-order direction.

  The fourth diffraction grating unit 9 includes a first light and a second light that are transmitted through the second diffraction grating unit 7, the first reflection unit 4a, the second reflection unit 4b, the third diffraction grating unit 8, and the mirror 10. The light receiving means 5 is irradiated with the combined light obtained by diffracting the two lights. Specifically, the fourth diffraction grating section 9 diffracts the first light, which has been further diffracted in the -1 order direction by the third diffraction grating section 8a, in the +1 order direction. In addition, the fourth diffraction grating section 9 further diffracts the second light diffracted in the +1 order direction into the −1 order direction by the diffraction of the third diffraction grating section 8b. The fourth diffraction grating section 9 irradiates the diffracted first light and second light as combined light toward the light receiving means 5.

The first light and the second light are diffracted a plurality of times by the second diffraction grating unit 7 and the third diffraction grating unit 8, so that even if the position of the transmission diffraction grating 3 fluctuates due to thermal expansion or the like. The effects are negated. Therefore, there is no effect on the interference light.
Specifically, the diffraction order is n, the amount of movement of the transmission diffraction grating 3 from its original position is Δx, and the period of the plurality of gratings 60, 70, 80, 90 of the transmission diffraction grating 3 is p. When the phase change caused by the first light and the second light, which are the diffracted lights, is φ, it can be expressed by Expression (1).

  φ = n × Δx ÷ p (1)

  According to Equation (1), for example, the first light diffracted as the + 1st-order diffracted light by the first diffraction grating unit 6 is converted into the second diffraction grating unit 7a, the third diffraction grating unit 8a, and the fourth diffraction grating unit 9. , The diffraction order is diffracted into the opposite diffraction order of the opposite sign, and the diffraction order n becomes zero. The second light diffracted by the first diffraction grating portion 6 as the -1st-order diffracted light passes through the second diffraction grating portion 7b, the third diffraction grating portion 8b, and the fourth diffraction grating portion 9. As a result, the diffraction order is diffracted into the opposite diffraction order of the opposite sign, so that the diffraction order n becomes 0 similarly to the first light.

  Thus, the first light and the second light pass through the second diffraction grating portion 7, the third diffraction grating portion 8, and the fourth diffraction grating portion 9 and are diffracted with opposite signs whose diffraction orders are paired. In order to cancel out the effects of the orders, the value of φ, which is the phase change caused by the diffracted light as the first light and the second light, also becomes 0. Therefore, even if the transmission type diffraction grating 3 moves by the movement amount Δx in the Y direction from the original position, the influence of the movement of the transmission type diffraction grating 3 does not occur.

The light receiving unit 5 receives the combined light combined by the fourth diffraction grating unit 9 as a signal of a change in the angle of the measurement object that rotates around the X axis that is the predetermined axis as the rotation axis. As the light receiving means 5, a PDA (Photo Diode Array) is used. The PDA is a light receiver having the property that the interference light applied to the light receiving surface can be measured at one time. The light receiving means 5 is not limited to a PDA, but may be an arbitrary light receiver such as a PSD (Position Sensitive Detector) or a CCD (Charge-Coupled Device).
In the optical angle sensor 1, the light source 2, the transmission type diffraction grating 3, the first reflecting means 4a, the second reflecting means 4b, the mirror 10, and the light receiving means 5 are arranged so as to have the same height. Have been.

FIG. 2 is a block diagram showing the optical angle sensor.
As shown in FIG. 2, the optical angle sensor 1 further includes a calculating means 20 for calculating the light received by the light receiving means 5 as a signal of a change in the angle of the measurement object that rotates about a predetermined axis as a rotation axis. .
The first reflection means 4a and the second reflection means 4b rotate synchronously with the rotation of the measurement target. Accordingly, the optical path lengths of the first light and the second light also change. The calculating means 20 calculates the rotation of the object to be measured from a signal based on the interference light generated from the combined light composed of the first light and the second light, which is changed by the rotation of the first reflection means 4a and the second reflection means 4b. Calculate the angle change.

FIG. 3 is a schematic diagram showing the rotation of the reflection means in the optical angle sensor.
Specifically, FIG. 3A is a diagram illustrating a state before the measurement target rotates in the optical angle sensor 1, and FIGS. 3B and 3C illustrate the measurement target in the optical angle sensor 1. FIG. 4 is a view showing a state in which is turned in a predetermined direction.
Hereinafter, the optical path of light in the optical angle sensor 1 will be described with reference to FIGS.

  In the optical angle sensor 1, the first light split by the first diffraction grating unit 6 is transmitted from the splitting point P1 of the first diffraction grating unit 6 to the mirror 10 as shown in FIGS. And is reflected toward the second diffraction grating portion 7a. At this time, if the first light is the + 1st-order diffracted light, it is diffracted in the -1st-order diffraction direction by the second diffraction grating portion 7a. The first light having passed through the second diffraction grating portion 7a enters the first reflection means 4a, and is emitted by the first reflection means 4a toward the third diffraction grating portion 8a. At this time, the first light is further diffracted in the -1st-order diffraction direction by the third diffraction grating portion 8a and enters the fourth diffraction grating portion 9. The first light having passed through the third diffraction grating portion 8a is reflected toward the fourth diffraction grating portion 9 via the mirror 10. The first light incident on the fourth diffraction grating section 9 is diffracted in the + 1st-order diffraction direction and is irradiated on the light receiving means 5. Therefore, the first light (+ 1st-order diffracted light) incident on the light receiving means 5 is diffracted in the -1st-order diffraction direction via the second diffraction grating portion 7a, and is diffracted in the -1st-order diffraction direction via the third diffraction grating portion 8a. , And diffracted in the + 1st-order diffraction direction via the fourth diffraction grating section 9, so that the diffraction order n becomes 0 in total.

  The second light split by the first diffraction grating section 6 is reflected by the mirror 10 from the split point P1 in the first diffraction grating section 6 toward the second diffraction grating section 7b. At this time, if the first light is the -1st-order diffracted light, it is diffracted in the + 1st-order diffraction direction by the second diffraction grating portion 7b. The second light having passed through the second diffraction grating portion 7b enters the second reflection means 4b and is emitted by the second reflection means 4b toward the third diffraction grating portion 8b. At this time, the second light is further diffracted in the + 1st-order diffraction direction by the third diffraction grating portion 8b and enters the fourth diffraction grating portion 9. The second light having passed through the third diffraction grating portion 8b is reflected toward the fourth diffraction grating portion 9 via the mirror 10. The second light incident on the fourth diffraction grating section 9 is diffracted in the -1st-order diffraction direction and is irradiated on the light receiving means 5. Therefore, the second light (-1st-order diffracted light) incident on the light receiving means 5 is diffracted in the + 1st-order diffraction direction via the second diffraction grating section 7a, and is diffracted in the + 1st-order diffraction direction via the third diffraction grating section 8a. Since the light is diffracted and diffracted in the -1st-order diffraction direction via the fourth diffraction grating section 9, the diffraction order n becomes 0 in total.

  The light receiving unit 5 is divided by the first diffraction grating unit 6, reflected by the mirror 10, diffracted by the second diffraction grating units 7a and 7b, and reflected by the first reflection unit 4a or the second reflection unit 4b. Then, the light is diffracted by the third diffraction grating portions 8a and 8b, reflected by the mirror 10, and receives the combined light of the first light and the second light combined by the fourth diffraction grating portion 9. Then, the calculating means 20 calculates the amount of change in the angle due to the rotation of the measurement target from the signal based on the combined light received by the light receiving means 5.

  In the optical angle sensor 1, the first reflection unit 4 a and the second reflection unit 4 b are configured to perform first reflection from the division point P 1 of the light from the light source 2 in the first diffraction grating unit 6 within the measurement range of the measurement target. The optical path length of the first light before reaching the fourth diffraction grating section 9 via the means 4a and the splitting point P1 of the light from the light source 2 in the first diffraction grating section 6 through the second reflection means 4b. The optical path length of the second light before reaching the four diffraction grating portions 9 has an angle that makes the same length.

Specifically, as shown in FIG. 3A, a case where the first reflecting means 4a and the second reflecting means 4b are arranged symmetrically with respect to an axis parallel to the optical axis of the light from the light source 2. , The first light and the second light have the same optical path length. At this time, the light receiving unit 5 can receive the interference light having the highest sensitivity of the change in the brightness to the change in the difference in the optical path length between the first light and the second light.
Then, as shown in FIG. 3B, when the measurement target rotates in the θ direction, the first reflection unit 4a and the second reflection unit 4b rotate in the θ direction with the rotation of the measurement target. . Further, as shown in FIG. 3C, when the measurement target rotates in the −θ direction, the first reflection unit 4a and the second reflection unit 4b rotate in the −θ direction with the rotation of the measurement target. Move. At this time, the interference light applied to the light receiving means 5 changes the optical path length of each of the first light and the second light according to the rotation direction of the first reflection means 4a and the second reflection means 4b. It changes from the interference light generated in the case of (A). The calculating means 20 calculates the amount of change in the angle of how much the measurement target has rotated from the original position from the signal based on the change in the interference light.

According to the first embodiment, the following operations and effects can be obtained.
(1) In the optical angle sensor 1, the first reflection unit 4a and the second reflection unit 4b move the first reflection unit 4a from the light splitting point P1 in the first diffraction grating unit 6 within the measurement range of the measurement target. And the optical path length of the first light until it reaches the fourth diffraction grating section 9 via the second diffraction means 4b from the light splitting point P1 of the first diffraction grating section 6 via the second reflection means 4b. Since the optical path length of the second light before the measurement has the same angle as the angle, the difference between the optical path length of the first light and the optical path length of the second light, which changes due to the rotation of the object to be measured, is counted. cm. That is, the optical angle sensor 1 can cause interference on the light receiving surface of the light receiving unit 5 even when a semiconductor laser having a very short coherent length is used as the light source 2.

(2) The optical angle sensor 1 includes a second diffraction grating unit 7 that diffracts the first light and the second light, and a second light that passes through the first reflection unit 4a and the second light that passes through the second reflection unit 4b. By providing the third diffraction grating unit 8 for diffracting light, the first light and the second light can be diffracted a plurality of times. Accordingly, the optical angle sensor 1 can cancel the diffraction orders of the first light and the second light and set the diffraction order n in Expression (1) to 0. Even if the position of the diffraction grating has moved from the original position, it is possible to suppress the generation of interference light having an angular displacement due to a phase change of the diffracted light.
Therefore, the optical angle sensor 1 prevents the phase change of the diffracted light due to the environmental change while avoiding the limitation due to the coherence of the light source 2, and detects the angle change due to the rotation of the measurement target with high accuracy. Can be.

(3) The optical angle sensor 1 has one transmission type diffraction grating 3, and one transmission type diffraction grating 3 includes a first diffraction grating section 6, a second diffraction grating section 7, and a third diffraction grating. By providing the part 8 and the fourth diffraction grating part 9 together, the number of parts can be reduced. Therefore, the optical angle sensor 1 can achieve cost reduction.
(4) The optical angle sensor 1 reflects the first light and the second light split by the first diffraction grating section 6 toward one transmission diffraction grating 3 and the third diffraction grating section 8. Since a mirror is provided for reflecting the first light and the second light diffracted by the device toward one transmission diffraction grating 3, the optical angle sensor 1 can be prevented from being enlarged.

(5) The first reflection means 4a and the second reflection means 4b are attached to the measurement object that rotates about a predetermined rotation axis, and rotate in synchronization with the rotation of the measurement object. The reflection means 4a and the second reflection means 4b rotate simultaneously by the same angle. As a result, the intensity of the combined light combined by the fourth diffraction grating unit 9 is 2 compared to a case where one of the first reflection unit 4a and the second reflection unit 4b is fixed and the other is attached to the measurement target. Double. For this reason, the sensitivity of the light receiving means 5 is doubled. Therefore, the optical angle sensor 1 is capable of detecting the object to be measured with high sensitivity from the signal with high sensitivity as compared with the case where one of the first reflecting means 4a or the second reflecting means 4b is fixed and the other is attached to the object to be measured. The amount of change in the angle due to the rotation can be detected.

(6) The first reflection means 4a and the second reflection means 4b in the optical angle sensor 1 are parallel to the rotation axis of the first reflection means 4a or the second reflection means 4b and the optical axis of the light from the light source 2. It is arranged at a position that is line-symmetric with respect to each axis. For this reason, compared with the case where the first reflection unit 4a and the second reflection unit 4b are arranged at positions that are asymmetric, the first reflection unit 4a and the second reflection unit 4b are located within the measurement range of the measurement target. The optical path length of the first light from the division point P1 of the light from the light source 2 in the first diffraction grating section 6 to the fourth diffraction grating section 9 via the first reflection means 4a, and the first diffraction grating section 6 The optical path length of the second light from the division point P1 of the light from the light source 2 to the fourth diffraction grating section 9 via the second reflecting means 4b is easily designed to have the same angle. can do.

[Second embodiment]
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. In the following description, the parts already described are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 4 is a schematic diagram showing an optical angle sensor according to the second embodiment.
In the first embodiment, the first diffraction grating portion 6, the second diffraction grating portion 7, the third diffraction grating portion 8, and the fourth diffraction grating portion 9 are provided in one transmission diffraction grating 3. I was
In the second embodiment, as shown in FIG. 4, the optical angle sensor 1A has a plurality of transmission type diffraction gratings 3A, and the plurality of transmission type diffraction gratings 3A have a first diffraction grating portion 6A and a fourth diffraction grating. The first transmission grating 3Aa having a grating portion 9A and a second transmission diffraction grating 3Ab having a second diffraction grating portion 7A and a third diffraction grating portion 8A. Different from the embodiment.

In the first embodiment, the optical angle sensor 1 reflects the first light and the second light split by the first diffraction grating unit 6 toward one transmission diffraction grating 3, There was provided a mirror 10 for reflecting the first light and the second light diffracted by the third diffraction grating section 8 toward one transmission diffraction grating 3.
In the second embodiment, the optical angle sensor 1A does not include the mirror 10, and the light receiving unit 5 is divided by the first diffraction grating unit 6A of the first transmission diffraction grating 3Aa, and the second transmission diffraction grating 3Ab. The light is diffracted by the second diffraction grating section 7A, reflected by the first reflection means 4a or the second reflection means 4b, diffracted by the third diffraction grating section 8A of the second transmission diffraction grating 3Ab, and converted to the first transmission type. The combined light of the first light and the second light combined by the fourth diffraction grating section 9A of the diffraction grating 3Aa is received, and the calculating means 20 (see FIG. 2) outputs a signal based on the combined light received by the light receiving means 5. The second embodiment differs from the first embodiment in that the amount of change in the angle due to the rotation of the measurement target is calculated from the above.
Hereinafter, an optical path of light in the optical angle sensor 1A will be described with reference to FIG.

  As shown in FIG. 4, the first light split by the first diffraction grating portion 6A of the first transmission diffraction grating 3Aa is transmitted from the split point P1 of the first diffraction grating portion 6A to the second transmission diffraction grating 3Ab. The light is emitted toward the second diffraction grating portion 7Aa. At this time, if the first light is the + 1st-order diffracted light, it is diffracted in the -1st-order diffraction direction by the second diffraction grating portion 7Aa. The first light having passed through the second diffraction grating portion 7Aa enters the first reflection means 4a, and is emitted by the first reflection means 4a toward the third diffraction grating portion 8Aa of the second transmission type diffraction grating 3Ab. . At this time, the first light is further diffracted in the -1st-order diffraction direction by the third diffraction grating portion 8Aa and enters the fourth diffraction grating portion 9A of the first transmission type diffraction grating 3Aa. The first light that has entered the fourth diffraction grating portion 9A via the third diffraction grating portion 8Aa is diffracted in the + 1st-order diffraction direction and is irradiated on the light receiving means 5. Accordingly, the first light (+ 1st-order diffracted light) incident on the light receiving means 5 is diffracted in the -1st-order diffraction direction via the second diffraction grating portion 7Aa, and is diffracted in the -1st-order diffraction direction via the third diffraction grating portion 8Aa. , And diffracted in the + 1st-order diffraction direction via the fourth diffraction grating portion 9A, so that the diffraction order n becomes 0 in total.

  The second light split by the first diffraction grating portion 6A of the first transmission diffraction grating 3Aa is transmitted from the division point P1 in the first diffraction grating portion 6A to the second diffraction grating portion 7Ab of the second transmission diffraction grating 3Ab. It is emitted toward. At this time, if the second light is the -1st-order diffracted light, it is diffracted in the + 1st-order diffraction direction by the second diffraction grating portion 7Ab. The second light having passed through the second diffraction grating portion 7Ab enters the second reflection means 4b, and is emitted by the second reflection means 4b toward the third diffraction grating portion 8Ab of the second transmission type diffraction grating 3Ab. . At this time, the second light is further diffracted in the + 1st-order diffraction direction by the third diffraction grating portion 8Ab and enters the fourth diffraction grating portion 9A of the first transmission diffraction grating 3Aa. The second light incident on the fourth diffraction grating portion 9A via the third diffraction grating portion 8Ab is diffracted in the -1st-order diffraction direction and is irradiated on the light receiving means 5. Accordingly, the second light (-1st-order diffracted light) incident on the light receiving means 5 is diffracted in the + 1st-order diffraction direction via the second diffraction grating portion 7Ab, and is diffracted in the + 1st-order diffraction direction via the third diffraction grating portion 8Ab. Since the light is diffracted and diffracted in the -1st-order diffraction direction via the fourth diffraction grating portion 9A, the diffraction order n becomes 0 in total.

  Also in the optical angle sensor 1A, the first reflection unit 4a and the second reflection unit 4b are connected to the first reflection unit from the division point P1 of the light from the light source 2 in the first diffraction grating unit 6A within the measurement range of the measurement target. The optical path length of the first light before reaching the fourth diffraction grating section 9A via the first diffraction grating section 4a and the fourth point via the second reflection means 4b from the division point P1 of the light from the light source 2 in the first diffraction grating section 6A. The optical path length of the second light before reaching the diffraction grating portion 9A has an angle that is the same.

In the second embodiment, the same operations and effects as (1), (2), (5), and (6) in the first embodiment can be obtained, and the following operations and effects can be obtained. Can play.
(7) The optical angle sensor 1A has a plurality of transmission type diffraction gratings 3A, and the plurality of transmission type diffraction gratings 3A have a first transmission type in which a first diffraction grating portion 6A and a fourth diffraction grating portion 9A are provided side by side. A first diffraction grating portion 6A and a fourth diffraction grating portion 9A to provide a second diffraction grating portion 3Aa and a second transmission type diffraction grating 3Ab provided with a second diffraction grating portion 7A and a third diffraction grating portion 8A. , The second diffraction grating portion 7A and the third diffraction grating portion 8A can be freely designed. Therefore, the optical angle sensor 1A can improve the degree of freedom in design.
(8) The optical angle sensor 1A includes a first transmission type diffraction grating 3Aa and a second transmission type diffraction grating 3Ab, and does not include the mirror 10 in the first embodiment. Compared to the case where the lattice 3 is used, it is possible to reduce the number of components and suppress an increase in size in the long direction.

[Third embodiment]
Hereinafter, a third embodiment of the present invention will be described with reference to FIG. In the following description, the parts already described are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 5 is a schematic diagram showing an optical angle sensor according to the third embodiment.
In the first embodiment, the first reflection unit 4a and the second reflection unit 4b are attached to the object to be measured, and are rotated in synchronization with the rotation of the object to be measured.
In the third embodiment, as shown in FIG. 5, the first reflecting means 4Ba of the optical angle sensor 1B is attached to the object to be measured, and the second reflecting means 4Bb is fixedly provided in the optical angle sensor 1B. The first reflecting means 4Ba differs from the first embodiment in that it rotates in synchronization with the rotation of the measurement object.

Further, in the first embodiment, the first reflecting means 4a and the second reflecting means 4b are arranged so that the first reflecting means 4a or the X-axis, which is the rotation axis of the second reflecting means 4b, and the light from the light source 2 The axis was parallel to the axis, and the axis was arranged at a position symmetrical with respect to each axis. As a result, the first reflection means 4a and the second reflection means 4b are simultaneously rotated, and even if the arrangement is rotated, they are arranged at positions that are line-symmetric.
The third embodiment is different from the first embodiment in that the first reflecting means 4Ba and the second reflecting means 4Bb are arranged so as to be asymmetrical by rotating.

  The first reflection means 4Ba and the second reflection means 4Bb are arranged so as to be asymmetric. However, also in the optical angle sensor 1B, the first reflection means 4Ba can be used for the first diffraction in the measurement range of the measurement object. The optical path length of the first light from the division point P1 of the light from the light source 2 in the grating section 6 to the fourth diffraction grating section 9 via the first reflecting means 4Ba, and the light source 2 in the first diffraction grating section 6 And the optical path length of the second light from the splitting point P1 of the light from the light source to the fourth diffraction grating section 9 via the second reflecting means 4Bb has an angle that makes the same length. Also in the third embodiment, the calculating means 20 (see FIG. 2) calculates the signal based on the interference light generated from the combined light composed of the first light and the second light, which is changed by the rotation of the first reflecting means 4Ba. The amount of change in the angle due to the rotation of the measurement target is calculated.

In the third embodiment, the same operations and effects as (1) to (4) in the first embodiment can be obtained, and the following operations and effects can be obtained.
(9) The second reflecting means 4Bb is fixedly provided in the optical angle sensor 1B, and the first reflecting means 4Ba is attached to the object to be measured. Therefore, the first reflecting means 4a and the second reflecting means 4b are provided. The weight of the object to be measured is lighter than that in the first embodiment in which is attached to the object to be measured. Therefore, the optical angle sensor 1B can suppress the influence of the weight on the measurement result and detect the amount of change in the angle due to the rotation of the measurement target with high accuracy.

[Fourth embodiment]
Hereinafter, a fourth embodiment of the present invention will be described with reference to FIG. In the following description, the parts already described are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 6 is a schematic diagram showing a transmission type diffraction grating and a light receiving unit in the optical angle sensor according to the fourth embodiment.
In the first embodiment, the calculating unit 20 detects the amount of change in the angle due to the rotation of the measurement target based on the interference light received by the light receiving unit 5.
In the fourth embodiment, as shown in FIG. 6, the fourth diffraction grating section 9C in the optical angle sensor 1C is configured to rotate the first reflection unit 4a or the second reflection unit 4b on the division surface 61 (see FIG. 1). It has a plurality of gratings 90C arranged side by side along an orthogonal direction orthogonal to the axis, and the light receiving means 5C includes a plurality of light receiving elements 51C to 54C arranged side by side along the orthogonal direction. The arithmetic means 20 receives the plurality of diffracted lights transmitted through the light receiving element 51C to calculate the change amount of the angle due to the rotation of the measurement target from the plurality of signals based on the plurality of diffracted lights received by the plurality of light receiving elements 51C to 54C. This is different from the first embodiment.
In FIG. 6, for convenience of explanation, the light source 2, the first reflection means 4a, the second reflection means 4b, the first diffraction grating section 6 and the second diffraction grating on the transmission type diffraction grating 3 in FIG. The part 7, the third diffraction grating part 8, and the mirror 10 are omitted.

  The traveling direction of the first light passing through the plurality of gratings 90C is diffracted toward the −Y direction, and the traveling direction of the second light passing through the plurality of inclined gratings 90C is diffracted toward the + Y direction. Here, when the first light is, for example, the + 1st-order diffracted light and the second light is, for example, the -1st-order diffracted light, the light of another diffraction order (for example, ± 2nd-order diffracted light) is the first light and the second light. Are diffracted in different separating directions, and are not irradiated on the light receiving means 5C. Then, the first light (+ 1st-order diffracted light) and the second light (-1st-order diffracted light) are provided on the light receiving surface of the light receiving means 5C (the plurality of light receiving elements 51C to 54C) by the first reflecting means 4a or the second reflecting means. An interference fringe is generated along the X direction which is a direction parallel to the rotation axis of 4b.

It is preferable that the optical angle sensor 1C uses a four-phase signal (a plurality of sine wave signals) having a phase difference in order to specify the rotation direction of the measurement target. Therefore, the plurality of light receiving elements 51C to 54C are designed to be able to acquire a four-phase signal in accordance with the period of the interference fringes.
For example, when the plurality of gratings 60 of the first diffraction grating unit 6 (see FIG. 1) are designed to have a period of 1 μm, the plurality of gratings 90C of the fourth diffraction grating unit 9C have a period of 1.005 μm. It is designed to be slightly shifted with respect to the period of the plurality of gratings 60 of the first diffraction grating portion. The plurality of light receiving elements 51C to 54C are designed to have the same period as the plurality of gratings 90C of the fourth diffraction grating section 9C at 1.005 μm.

Specifically, the plurality of light receiving elements 51C to 54C include a first light receiving element 51C, a second light receiving element 52C, a third light receiving element 53C, and a fourth light receiving element 54C.
The first light receiving element 51C receives light having a phase of 0 degree from interference fringes generated on the light receiving surface via the plurality of inclined gratings 90C. The second light receiving element 52C receives light having a phase of 90 degrees from the interference fringes generated on the light receiving surface via the plurality of inclined gratings 90C. The third light receiving element 53C receives light having a phase of 180 degrees from the interference fringes generated on the light receiving surface via the plurality of inclined gratings 90C. The fourth light receiving element 54C receives light having a phase of 180 degrees from the interference fringes generated on the light receiving surface via the plurality of inclined gratings 90C.

  The plurality of light receiving elements 51C to 54C are repeatedly arranged in the order of the first light receiving element 51C, the second light receiving element 52C, the third light receiving element 53C, and the fourth light receiving element 54C along the Y direction orthogonal to the X axis. ing. The optical angle sensor 1C detects a four-phase signal from the signals received by the plurality of light receiving elements 51C to 54C, and the arithmetic unit 20 (see FIG. 2) determines the rotation direction of the measurement target and the rotation of the measurement target. It is possible to calculate the amount of change in angle due to movement.

In the fourth embodiment, the same operations and effects as (1) to (6) in the first embodiment can be obtained, and the following operations and effects can be obtained.
(10) The fourth diffraction grating section 9C has a plurality of gratings 90C, and the light receiving means 5C includes a plurality of light receiving elements 51C to 54C and receives a plurality of diffracted lights passing through the plurality of gratings 90C. The plurality of diffracted lights generate interference fringes on the light receiving surface of the light receiving unit 5C along a direction parallel to the rotation axis of the first reflecting unit 4a or the second reflecting unit 4b, and the plurality of light receiving elements 51C to 54C. Can detect four-phase signals from interference fringes. The calculating means 20 can calculate the rotation direction of the object to be measured and the amount of change in the angle due to the rotation from the four-phase signal. Therefore, the optical angle sensor 1C detects the amount of change in the angle due to the rotation of the object to be measured from the interference fringe with higher accuracy than when calculating the amount of change in the angle due to the rotation of the object to be measured from the interference light. be able to.

[Fifth Embodiment]
Hereinafter, a fifth embodiment of the present invention will be described with reference to FIG. In the following description, the parts already described are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 7 is a schematic diagram showing a transmission type diffraction grating and light receiving means in the optical angle sensor according to the fifth embodiment.
In the first embodiment, the fourth diffraction grating section 9 is arranged along the Y direction which is a direction orthogonal to the X axis which is the rotation axis of the first reflecting means 4a or the second reflecting means 4b on the division surface 61. A plurality of gratings 90 are provided, and the calculating means 20 detects the amount of change in the angle due to the rotation of the measurement target based on the interference light received by the light receiving means 5.
In the fifth embodiment, as shown in FIG. 7, the fourth diffraction grating section 9D of the optical angle sensor 1D is configured to rotate the first reflecting means 4a or the second reflecting means 4b on the division surface 61 (see FIG. 1). The light receiving unit 5D includes a plurality of inclined gratings 90D that are arranged side by side along an orthogonal direction orthogonal to the axis and are arranged with a predetermined inclination angle θ with respect to the optical axis of the light from the light source 2. A plurality of light receiving elements 51D to 54D are juxtaposed along a direction parallel to the rotation axis of the first reflecting means 4a or the second reflecting means 4b, and receive a plurality of diffracted lights via a plurality of inclined gratings 90D. The calculating means 20 (see FIG. 2) differs from the first embodiment in that the calculating means 20 calculates the amount of change in the angle due to the rotation of the measuring object from a plurality of signals based on the plurality of diffracted lights received by the light receiving means 5D. .
In FIG. 7, for convenience of explanation, the light source 2, the first reflecting means 4a, the second reflecting means 4b, the first diffraction grating section 6 on the transmission type diffraction grating 3, and the second diffraction grating in FIG. The part 7, the third diffraction grating part 8, and the mirror 10 are omitted.

The traveling direction of the first light passing through the plurality of inclined gratings 90D is diffracted toward the + X direction, and the traveling direction of the second light passing through the plurality of inclined gratings 90D is diffracted toward the -X direction. Here, when the first light is, for example, the + 1st-order diffracted light and the second light is, for example, the -1st-order diffracted light, the light of another diffraction order (for example, ± 2nd-order diffracted light) is the first light and the second light. Are diffracted in different separating directions, and are not irradiated on the light receiving means 5D. The first light (+ 1st-order diffracted light) and the second light (-1st-order diffracted light) are provided on the light receiving surface of the light receiving means 5D (the plurality of light receiving elements 51D to 54D) by the first reflecting means 4a or the second reflecting means. An interference fringe is generated along a Y direction which is a direction orthogonal to the rotation axis of 4b.
The optical angle sensor 1D preferably uses a four-phase signal (a plurality of sinusoidal signals) having a phase difference in order to specify the rotation direction of the measurement target. Therefore, the plurality of light receiving elements 51D to 54D are designed so as to be able to acquire a four-phase signal in accordance with the period of the interference fringe generated on the light receiving surfaces of the plurality of light receiving elements 51D to 54D.

  Specifically, the plurality of light receiving elements 51D to 54D include a first light receiving element 51D, a second light receiving element 52D, a third light receiving element 53D, and a fourth light receiving element 54D. The first light receiving element 51D receives light having a phase of 0 degree from the interference fringes generated on the light receiving surface via the plurality of inclined gratings 90D. The second light receiving element 52D receives light having a phase of 90 degrees from interference fringes generated on the light receiving surface via the plurality of tilt gratings 90D. The third light receiving element 53D receives light having a phase of 180 degrees from the interference fringes generated on the light receiving surface via the plurality of inclined gratings 90D. The fourth light receiving element 54D receives light having a phase of 180 degrees from the interference fringes generated on the light receiving surface via the plurality of inclined gratings 90D. The plurality of light receiving elements 51D to 54D are repeatedly arranged in the order of the first light receiving element 51D, the second light receiving element 52D, the third light receiving element 53D, and the fourth light receiving element 54D along a direction parallel to the X axis. I have. The optical angle sensor 1D detects a four-phase signal from the signals received by the plurality of light receiving elements 51D to 54D, and the arithmetic unit 20 (see FIG. 2) determines the rotation direction of the measurement target and the rotation of the measurement target. It is possible to calculate the amount of change in angle due to movement.

In the fifth embodiment, the same operations and effects as (1) to (6) in the first embodiment can be obtained, and the following operations and effects can be obtained.
(11) The fourth diffraction grating section 9D has a plurality of inclined gratings 90D, and the light receiving means 5D receives a plurality of diffracted lights via the plurality of inclined gratings 90D. The interference fringes are generated on the light receiving surface along the direction perpendicular to the rotation axis of the first reflecting means 4a or the second reflecting means 4b. Therefore, the plurality of light receiving elements 51D to 54D of the light receiving unit 5D can detect a four-phase signal from the interference fringes. The calculation means 20 can calculate the rotation direction of the measurement target and the amount of change in the angle due to the rotation from the four-phase signal. Therefore, the optical angle sensor 1D detects the change in the angle due to the rotation of the measurement target from the interference fringe with higher accuracy than when calculating the change in the angle due to the rotation of the measurement target from the interference light. be able to.

[Sixth embodiment]
Hereinafter, a sixth embodiment of the present invention will be described with reference to FIG. In the following description, the parts already described are denoted by the same reference numerals, and description thereof will be omitted.

  FIG. 8 is a schematic diagram showing a transmission type diffraction grating and a light receiving unit in the optical angle sensor according to the sixth embodiment. Specifically, FIG. 8A is a schematic diagram showing the arrangement of the fourth diffraction grating section 9E and the light receiving means 5E in the optical angle sensor 1E, and FIG. 8B is a schematic view showing the fourth diffraction grating section 9E. It is a figure which shows the specific phase difference of the some grating | lattice 90E which the several combination part 91E-94E which has has.

In the first embodiment, the fourth diffraction grating section 9 includes a plurality of fourth diffraction grating portions 9 arranged in parallel along the direction orthogonal to the X axis that is the rotation axis of the first reflecting means 4a or the second reflecting means 4b on the dividing surface 61. Was provided.
In the sixth embodiment, as shown in FIG. 8A, the fourth diffraction grating section 9E in the optical angle sensor 1E includes a plurality of combining sections 91E to 94E having different phases, respectively. And a plurality of light receiving units 51E to 54E respectively corresponding to the synthesizing units 91E to 94E. The arithmetic unit 20 (see FIG. 2) includes a plurality of light receiving units 51E to 54E having different phases based on the light received by the plurality of light receiving units 51E to 54E. It differs from the first embodiment in that the direction of rotation of the measurement target and the amount of change in angle due to the rotation of the measurement target are calculated from the signal.
In FIG. 8A, for convenience of explanation, the light source 2, the first reflecting means 4a, the second reflecting means 4b, the first diffraction grating portion 6 on the transmission type diffraction grating 3, and the second The two diffraction grating portions 7, the third diffraction grating portion 8, and the mirror 10 are omitted.

The fourth diffraction grating section 9E includes a first combining section 91E, a second combining section 92E, a third combining section 93E, and a fourth combining section 94E as a plurality of combining sections 91E to 94E.
The first synthesis unit 91E has a plurality of gratings 90E arranged at a phase of 0 degrees. The second synthesis unit 92E has a plurality of gratings 90E whose phases are arranged at 90 degrees. The third synthesis unit 93E has a plurality of gratings 90E whose phases are arranged at 180 degrees. The fourth synthesis unit 94E has a plurality of gratings 90E whose phases are arranged at 270 degrees.

The light receiving unit 5E includes a first light receiving unit 51E, a second light receiving unit 52E, a third light receiving unit 53E, and a fourth light receiving unit 54E as the plurality of light receiving units 51E to 54E.
The first light receiving unit 51E receives light having a phase of 0 degree via the first combining unit 91E. The second light receiving unit 52E receives light having a phase of 90 degrees through the second combining unit 92E. The third light receiving unit 53E receives light having a phase of 180 degrees via the third combining unit 93E. The fourth light receiving unit 54E receives light having a phase of 270 degrees via the fourth combining unit 94E.

  The first light and the second light passing through the mirror 10 that reflects the light from the third diffraction grating unit 8 in the first embodiment and the third diffraction grating unit 8A in the second embodiment overlap each other to form a plurality of combined light beams. Irradiation is performed on the entire portions 91E to 94E (the fourth diffraction grating portion 9E). The light applied to the entirety of the plurality of combining units 91E to 94E is simultaneously applied to each of the plurality of light receiving units 51E to 54E as interference light of each phase. The plurality of light receiving units 51E to 54E detect four-phase signals as the corresponding phase signals from the irradiated interference light. The calculation means 20 can calculate the rotation direction of the measurement target and the amount of change in the angle due to the rotation from the four-phase signal. Therefore, the optical angle sensor 1E can detect the amount of change in the angle due to the rotation of the measurement target with higher accuracy than when the optical angle sensor 1E does not include the plurality of combining units 91E to 94E and the plurality of light receiving units 51E to 54E. Can be.

  As shown in FIG. 8 (B), the plurality of combining units 91E to 94E of the fourth diffraction grating unit 9E form a plurality of combining units when the period of the plurality of gratings 90E is q, the integer is m, and the offset is k. The first combining unit 91E and the second combining unit 92E, and the third combining unit 93E and the fourth combining unit 94E are arranged in a relationship such as Expression (2).

  k1 = m × q + q ÷ 8 (2)

  Specifically, the second synthesizing unit 92E is arranged offset from the first synthesizing unit 91E by the value of k1 obtained by Expression (2). The third combining unit 93E is arranged offset from the first combining unit 91E in the Y direction by the value of k2 obtained by q の 4. The fourth synthesizing unit 94E is arranged to be offset from the third synthesizing unit 93E by the value of k1 obtained by Expression (2). Therefore, the plurality of light receiving units 51E to 54E can receive interference light beams having different phases from the plurality of combining units 91E to 94E.

In the sixth embodiment, the same operations and effects as (1) to (6) in the first embodiment can be obtained, and the following operations and effects can be obtained.
(12) Since the optical angle sensor 1E includes four combining units 91E to 94E and four light receiving units 51E to 54E, it can detect a four-phase signal. Therefore, the optical angle sensor 1E can detect the angular displacement due to the rotation of the measurement target with high accuracy using a plurality of signals such as a four-phase signal.

[Seventh embodiment]
Hereinafter, a seventh embodiment of the present invention will be described with reference to FIG. In the following description, the parts already described are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 9 is a schematic diagram illustrating an optical angle sensor according to the seventh embodiment.
In the first embodiment, the fourth diffraction grating section 9 includes a plurality of fourth diffraction grating portions 9 arranged in parallel along the direction orthogonal to the X axis that is the rotation axis of the first reflecting means 4a or the second reflecting means 4b on the dividing surface 61. The light receiving means 5 has received light passing through the plurality of gratings 90.
In the seventh embodiment, the optical angle sensor 1F includes a first quarter-wave plate 45a disposed on the optical path of the first light via the first reflecting means 4a or the second light via the second reflecting means 4b. And a split beam splitter 30F that splits the combined light from the fourth diffraction grating unit into a first split light 11F and a second split light 21F; a first split light 11F split by the split beam splitter 30F; A second quarter-wave plate 45b disposed on the optical path with the split light 21F, and a third quarter wave disposed on the optical path of the second split light 21F via the second quarter-wave plate 45b. A 分割 wavelength plate 45c, a first split light polarization beam splitter 31F that splits the first split light 11F via the second 波長 wavelength plate 45b into a first polarization 12F and a second polarization 13F, and a third Second split light 21 via the quarter-wave plate 45c of And a second split light polarization beam splitter 32F that splits the light into a third polarized light 22F and a fourth polarized light 23F. The light receiving unit 5F has a plurality of light receiving units 51F to 54F, and the plurality of light receiving units 51F to 54F A first light receiving portion 51F that receives light having a phase of 0 degree from the first polarized light 12F, a second light receiving portion 52F that receives light having a phase of 180 degrees from the second polarized light 13F, and a phase that is received from the third polarized light 22F. The third embodiment is different from the first embodiment in that a third light receiving unit 53F that receives 90-degree light and a fourth light-receiving unit 54F that receives light having a phase of 270 degrees from the fourth polarized light 23F are provided.

The optical angle sensor 1F includes the first quarter-wave plate 45a, detects a four-phase signal from the combined light from the fourth diffraction grating unit 9 in the first embodiment, and measures the object based on the four-phase signal. Angular displacement due to the rotation of the camera can be detected.
The optical angle sensor 1F further includes a reflecting portion 10a that reflects the combined light from the fourth diffraction grating portion 9 toward the light receiving unit 5F. The reflection unit 10a is a mirror. The reflecting section 10a only needs to reflect the combined light toward the light receiving unit 5F, and may be a beam splitter, a half mirror, or the like.

  The split beam splitter 30F is a non-polarizing beam splitter. The beam splitter 30F, which is a non-polarized beam splitter, does not split the combined light emitted from the fourth diffraction grating unit 9 into S-polarized light and P-polarized light, but splits unpolarized light on average, The combined light passing through the fourth diffraction grating section 9 is split into a first split light 11F and a second split light 21F.

The first split light polarization beam splitter 31F and the second split light polarization beam splitter 32F are polarization beam splitters.
The polarization beam splitter is a plate-type optical component that separates light into two polarization components, S-polarized light that is S-randomly polarized light and P-polarized light that is P-randomly polarized light.
The first split light polarization beam splitter 31F splits the first split light 11F from the split beam splitter 30F, reflects the first polarized light 12F, and transmits the second polarized light 13F. The second split light polarization beam splitter 32F splits the second split light 21F from the split beam splitter 30F, reflects the third polarized light 22F, and transmits the fourth polarized light 23F.
In the seventh embodiment, the first polarized light 12F and the third polarized light 22F will be described as S polarized light, and the second polarized light 13F and the fourth polarized light 23F will be described as P polarized light.

  The first split light 11F becomes light having a phase shifted by 90 degrees with respect to the first split light 11F through the second quarter-wave plate 45b, and is irradiated to the first split light polarization beam splitter 31F. The first split light 11F applied to the first split light polarization beam splitter 31F is split into a first polarized light 12F that is S-polarized light and a second polarized light 13F that is P-polarized light. The first light receiving unit 51F receives the first polarized light 12F and receives the interference light having the phase of 0 degree, and the second light receiving unit 52F receives the second polarized light 13F and has the 180 degree phase. The interference light is received.

  The second split light 21F is a light that is 180 degrees out of phase with the second split light 21F by passing through the second quarter-wave plate 45b and the third quarter-wave plate 45c, and the second split light polarization. The light is irradiated to the beam splitter 32F. The second split light 21F applied to the second split light polarization beam splitter 32F is polarized and split into a third polarized light 22F that is S-polarized light and a fourth polarized light 23F that is P-polarized light. The third light receiving unit 53F receives the third polarized light 22F and receives the interference light having a phase of 90 degrees, and the fourth light receiving unit 54F receives the fourth polarized light 23F and has a phase of 270 degrees. The interference light is received. Thereby, the calculating means 20 (see FIG. 2) can acquire the four-phase signals from the plurality of light receiving units 51F to 54F. The calculating means 20 calculates and detects the direction of rotation of the measurement target and the amount of change in the angle due to the rotation of the measurement target by calculating the four-phase signal.

Also in the seventh embodiment, the same operations and effects as (1) to (6) in the first embodiment can be obtained, and the following operations and effects can be obtained.
(13) The optical angle sensor 1F includes a first quarter-wave plate 45a disposed on the optical path of the first light via the first reflecting means 4a or the second light via the second reflecting means 4b, The light receiving unit 5F includes, as a plurality of light receiving units 51F to 54F, a first light receiving unit 51F that receives light having a phase of 0 degree from the first polarized light 12F and a second light receiving unit that receives light having a phase of 180 degrees from the second polarized light 13F. A second light receiving unit 52F, a third light receiving unit 53F that receives light having a phase of 90 degrees from the third polarized light 22F, and a fourth light receiving unit 54F that receives light that has a phase of 270 degrees from the fourth polarized light 23F. Therefore, a four-phase signal can be detected from the combined light. Therefore, the optical angle sensor 1F can detect the angular displacement due to the rotation of the measurement target with high accuracy using the four-phase signal that can be obtained from the plurality of diffracted lights.

[Eighth Embodiment]
Hereinafter, an eighth embodiment of the present invention will be described with reference to FIG. In the following description, the parts already described are denoted by the same reference numerals, and description thereof will be omitted.

FIG. 10 is a schematic diagram showing an optical angle sensor according to the eighth embodiment.
In the seventh embodiment, the optical angle sensor 1F includes a split beam splitter 30F, a first wave plate 45a, a second quarter wave plate 45b, and a third quarter wave plate 45c. The first split light polarization beam splitter 31F, the second split light polarization beam splitter 32F, and the plurality of light receiving units 51F to 54F were provided.

  In the eighth embodiment, as shown in FIG. 10, the optical angle sensor 1G is arranged on the optical path of the first light via the first reflecting means 4a or the second light via the second reflecting means 4b. A fifth diffraction grating portion 31G having an irradiation surface 30G provided with a four-wavelength plate 45a, and having a plurality of gratings 311G arranged in parallel with the fourth diffraction grating portion 9 to make a plurality of diffracted light beams synthesized by the fourth diffraction grating portion 9; It has a plurality of gratings 322G arranged side by side in a direction orthogonal to the direction in which the plurality of gratings 311G of 31G are arranged side by side on the irradiation surface 30G, and further converts a plurality of diffraction lights by the fifth diffraction grating portion 31G into a plurality of diffraction lights. And a plurality of polarizers 46a to 46d arranged on the optical path of a plurality of diffracted lights by the sixth diffraction grating section 32G and converting the plurality of diffracted lights into a plurality of polarized lights having different phases. And light receiving means G includes a plurality of light receiving units 51G to 54G corresponding to the plurality of polarizers 46a to 46d, respectively, and the arithmetic unit 20 (see FIG. 2) controls the phase based on the light received by the plurality of light receiving units 51G to 54G. The third embodiment is different from the seventh embodiment in that the direction of rotation of the measurement target and the amount of change in the angle due to the rotation of the measurement target are calculated from a plurality of different signals.

The optical angle sensor 1G further includes a reflecting portion 10a that reflects the combined light from the fourth diffraction grating portion 9 toward the light receiving unit 5G. The reflection unit 10a is a mirror. The reflecting section 10a only needs to reflect the combined light toward the light receiving means 5G, and may be a beam splitter, a half mirror, or the like.
The plurality of polarizers 46a to 46d are polarizing lenses and include a first polarizer 46a, a second polarizer 46b, a third polarizer 46c, and a fourth polarizer 46d. The plurality of polarizers 46a to 46d need only be able to polarize the incident light, and may use any type of polarizer.

The light receiving unit 5G is provided to face the plurality of polarizers 46a to 46d. The light receiving unit 5G includes a first light receiving unit 51G, a second light receiving unit 52G, a third light receiving unit 53G, and a fourth light receiving unit 54G as the plurality of light receiving units 51G to 54G. The plurality of light receiving units 51G to 54G are provided on the same surface.
The plurality of lights split by the fifth diffraction grating unit 31G and the sixth diffraction grating unit 32G become polarized lights having different phases when transmitted through the plurality of polarizers 46a to 46d.
The first light receiving unit 51G receives light having a phase of 0 degree via the first polarizer 46a. The second light receiving unit 52G receives light having a phase of 90 degrees via the second polarizer 46b. The third light receiving unit 53G receives light having a phase of 180 degrees via the third polarizer 46c. The fourth light receiving unit 54G receives light having a phase of 270 degrees via the fourth polarizer 46d.

Thereby, the calculating means 20 can acquire four-phase signals from the plurality of light receiving units 51G to 54G. The calculating means 20 calculates and detects the direction of rotation of the measurement target and the amount of change in the angle due to the rotation of the measurement target by calculating the four-phase signal.
In addition, since the plurality of light receiving units 51G to 54G are provided on the same surface facing the plurality of polarizers 46a to 46d, they can be modularized. For this reason, the optical angle sensor 1G does not need to include the plurality of light receiving units 51G to 54G for each position to be irradiated with light as in the seventh embodiment, so that cost reduction and space saving are achieved. be able to.

In the eighth embodiment as well, the same operations and effects as (1) to (6) in the first embodiment can be obtained, and the following operations and effects can be obtained.
(14) The optical angle sensor 1G includes a plurality of polarizers 46a to 46d corresponding to a plurality of diffraction gratings diffracted by the fifth diffraction grating unit 31G and the sixth diffraction grating unit 32G, and a plurality of polarizers 46a to 46d. In order to provide the plurality of light receiving units 51G to 54G corresponding to each of the above, the split beam splitter 30F of the seventh embodiment, the first split light polarization beam splitter 31F, and the second split light polarization beam splitter 32F are provided. Compared with the case, a four-phase signal can be obtained without using these optical components. Therefore, compared with the optical angle sensor 1F, the optical angle sensor 1G can achieve space saving and cost reduction while achieving higher accuracy.
(15) The light receiving unit 5G is provided on the same surface facing the plurality of polarizers 46a to 46d, and includes the plurality of light receiving units 51G to 54G corresponding to the plurality of polarizers 46a to 46d, respectively. By making the plurality of light receiving units 51G to 54G modular, downsizing can be achieved.

[Modification of Embodiment]
It should be noted that the present invention is not limited to the above embodiments, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.
For example, in each of the above-described embodiments, the optical angle sensors 1 and 1A to 1G are provided in the measuring device. However, the optical angle sensors 1 and 1G may be provided in other devices instead of the measuring device. Is not particularly limited.

  In each of the above embodiments, the first reflecting means 4a and the second reflecting means 4b are prisms. However, instead of prisms, three flat plates having a property of reflecting light are combined at right angles to each other, and the apex of the cube is formed. It may be a shaped corner cube. In short, the first reflecting means reflects the first light diffracted through the second diffraction grating portion in a direction parallel to and in a direction opposite to the direction in which the first light has entered, and the second reflecting means serves as the second reflecting means. Any structure may be used as long as the second light diffracted through the diffraction grating portion can be reflected in a direction parallel to the direction in which the second light is incident and in the opposite direction.

FIG. 11 is a schematic diagram illustrating an optical angle sensor according to a modification.
In the above embodiments, the light source 2, the transmission type diffraction gratings 3, 3A, the first reflecting means 4a, 4Ba, the second reflecting means 4b, 4Bb, and the light receiving means 5, 5C to 5G are optically angled. In the sensors 1, 1A to 1G, they were arranged so as to have the same height. In the optical angle sensor 1H in this modification, as shown in FIG. 11, a light source 2H irradiates light toward the transmission diffraction grating 3 from above (upward on the paper), and a light receiving unit 5H includes a first reflecting unit. The light reflected by the mirror 4a and the second reflecting means 4b and further reflected by the mirror 10 is received from below (downward in the drawing), and the light source 2H and the light receiving means 5H are not arranged at the same height. This is different from the above embodiments. That is, the light receiving unit is split by the first diffraction grating unit, reflects the first reflection unit and the second reflection unit, and is a combined light of the first light and the second light combined by the fourth diffraction grating unit. And any height may be used. The light source and the light receiving unit may be arranged so as to be shifted from each other in the X direction when viewed from the Y direction, for example.

In each of the above embodiments, the first diffraction grating portions 6 and 6A and the fourth diffraction grating portions 9, 9A and 9C to 9E are provided in a single transmission diffraction grating 3 (first transmission diffraction grating 3Aa). However, the first diffraction grating portion and the fourth diffraction grating portion need not be provided in one transmission diffraction grating, and may be provided as individual transmission diffraction gratings.
In the first embodiment, the first reflection unit 4a and the second reflection unit 4b are arranged so that the X axis, which is the rotation axis of the first reflection unit 4a or the second reflection unit 4b, and the optical axis of the light from the light source 2 Although the first and second reflection units are arranged at positions that are line-symmetric with respect to the respective axes, the third reflection unit and the second reflection unit do not have to be arranged with line symmetry. As in the form, they may be arranged asymmetrically.

  In the first embodiment, the first reflection unit 4a and the second reflection unit 4b are connected to the measurement object that rotates around the rotation axis, and rotate in synchronization with the rotation of the measurement object. However, as in the third embodiment, only the first reflecting means 4Ba may be connected and attached to the measurement target. Further, in the third embodiment, only the first reflecting means 4Ba is attached to the object to be measured, but only the second reflecting means 4Bb, not the first reflecting means 4Ba, may be attached to the object to be measured. In short, at least one of the first reflection means and the second reflection means may be connected to the object to be measured and rotate in synchronization with the rotation of the object to be measured.

In each of the above embodiments, the fourth diffraction grating portions 9, 9A, 9C to 9E are transmission diffraction gratings, but may be, for example, beam splitters. That is, the fourth diffraction grating portion may be any type as long as the first light and the second light can be combined.
In the fourth embodiment, the plurality of gratings 60 of the first diffraction grating unit 6 are designed to have a period of 1 μm, and the plurality of gratings 90C of the fourth diffraction grating unit 9C and the plurality of light receiving elements 51C to 54C are one. Although it was designed to have a period of 0.005 μm, the plurality of gratings of the first diffraction grating unit, the plurality of gratings of the first diffraction grating unit, and the plurality of light receiving units have interference fringes on the light receiving surface of the light receiving unit. Any design is possible as long as it is formed and the amount of change in the angle due to the rotation of the measurement object can be acquired from the interference fringes.

  In the seventh embodiment and the eighth embodiment, the optical angle sensors 1F and 1G include the reflection unit 10a that reflects the combined light from the fourth diffraction grating unit 9 toward the light receiving units 5F and 5G. However, the optical angle sensor does not have to include the reflection unit. When the optical angle sensor is not provided with the reflection unit, the optical angle sensor detects the amount of change in the angle due to the rotation of the measurement target by arranging the light receiving unit at a position where the combined light from the fourth diffraction grating unit is irradiated. be able to.

  As described above, the present invention can be suitably used for an optical angle sensor.

1, 1A to 1H Optical angle sensor 2, 2H Light source 3, 3A Transmission diffraction grating 4a, 4Ba First reflecting means 4b, 4Bb Second reflecting means 5, 5C to 5H Light receiving means 6, 6A First diffraction grating section 7 , 7A Second diffraction grating unit 8, 8A Third diffraction grating unit 9, 9A, 9C to 9E Fourth diffraction grating unit 10 Mirror 10a Reflecting unit 20 Calculation unit 61 Division plane P1 Division point

Claims (11)

A light source for emitting light,
A transmission diffraction grating having a plurality of gratings for diffracting light from the light source,
First reflecting means for reflecting light passing through the transmission type diffraction grating toward the transmission type diffraction grating;
Second reflecting means for reflecting light, which is different from light reflected by the first reflecting means via the transmission diffraction grating, toward the transmission diffraction grating,
Light receiving means for receiving light through the transmission type diffraction grating,
Calculating means for calculating the light received by the light receiving means as a signal of a change in the angle of the object to be measured which rotates about a predetermined axis as a rotation axis,
The transmission diffraction grating,
A first diffraction grating section for dividing light from the light source into first light and second light;
A second diffraction grating unit that diffracts the first light and the second light split by the first diffraction grating unit;
A third diffraction grating unit that diffracts the first light via the first reflecting unit and the second light via the second reflecting unit;
A fourth diffraction grating unit that combines the first light and the second light via the third diffraction grating unit to generate combined light,
The first reflecting means reflects the first light diffracted through the second diffraction grating portion in a direction parallel to and in a direction opposite to the direction in which the first light is incident;
The second reflection means reflects the second light diffracted through the second diffraction grating portion in a direction parallel to and in a direction opposite to the direction in which the second light has entered,
The first reflection unit and the second reflection unit may be configured to perform the fourth diffraction via the first reflection unit from a division point of the light from the light source in the first diffraction grating unit within a measurement range of the measurement target. The optical path length of the first light until reaching the grating portion, and the length of the light from the splitting point of the light from the light source in the first diffraction grating portion to the fourth diffraction grating portion via the second reflecting means Has an angle such that the optical path length of the second light is the same as the optical path length;
The light receiving unit is divided by the first diffraction grating unit, diffracted by the second diffraction grating unit, reflected by the first reflection unit or the second reflection unit, and transmitted to the third diffraction grating unit. Receiving the combined light of the first light and the second light that has been diffracted and combined by the fourth diffraction grating section,
The optical angle sensor according to claim 1, wherein the calculating means calculates an amount of change in the angle due to the rotation of the object to be measured from the signal based on the combined light received by the light receiving means. The optical angle sensor according to claim 1,
Having one transmission diffraction grating,
The one transmission diffraction grating includes the first diffraction grating portion, the second diffraction grating portion, the third diffraction grating portion, and the fourth diffraction grating portion, and
The first light and the second light split by the first diffraction grating portion are reflected toward the one transmission diffraction grating, and the first light and the second light diffracted by the third diffraction grating portion are reflected. A mirror for reflecting the two lights toward the one transmission diffraction grating;
The light receiving unit is divided by the first diffraction grating unit, reflected by the mirror, diffracted by the second diffraction grating unit, reflected by the first reflection unit or the second reflection unit, Receiving a combined light of the first light and the second light that is diffracted by the third diffraction grating, reflected by the mirror, and combined by the fourth diffraction grating;
The optical angle sensor according to claim 1, wherein the calculating means calculates an amount of change in the angle due to the rotation of the object to be measured from the signal based on the combined light received by the light receiving means. The optical angle sensor according to claim 1,
Having a plurality of the transmission type diffraction gratings,
The plurality of transmission diffraction gratings,
A first transmission type diffraction grating provided with the first diffraction grating portion and the fourth diffraction grating portion,
A second transmission type diffraction grating provided with the second diffraction grating portion and the third diffraction grating portion,
The light receiving unit is divided by the first diffraction grating unit of the first transmission diffraction grating, is diffracted by the second diffraction grating unit of the second transmission diffraction grating, and is divided by the first reflection unit or the first reflection grating. The first light reflected by the second reflection means, diffracted by the third diffraction grating portion of the second transmission type diffraction grating, and combined by the fourth diffraction grating portion of the first transmission type diffraction grating. And a combined light of the second light,
The optical angle sensor according to claim 1, wherein the calculating means calculates an amount of change in the angle due to the rotation of the object to be measured from the signal based on the combined light received by the light receiving means. The optical angle sensor according to any one of claims 1 to 3,
One of the first reflecting means or the second reflecting means is fixedly provided,
An optical angle sensor, wherein the other of the first reflecting means and the second reflecting means is attached to the object to be measured, and rotates in synchronization with rotation of the object to be measured. The optical angle sensor according to any one of claims 1 to 3,
The optical angle sensor according to claim 1, wherein the first reflection unit and the second reflection unit are attached to the object to be measured, and rotate in synchronization with rotation of the object to be measured. The optical angle sensor according to any one of claims 1 to 5,
The first reflecting means and the second reflecting means are respectively arranged with respect to a rotation axis of the first reflecting means or the second reflecting means and an axis parallel to an optical axis of light from the light source. An optical angle sensor, wherein the optical angle sensor is arranged at a position which is line-symmetrical. The optical angle sensor according to any one of claims 1 to 6,
The first diffraction grating portion has a division surface on which light from the light source is irradiated,
The fourth diffraction grating portion includes a plurality of gratings arranged in a line along an orthogonal direction orthogonal to a rotation axis of the first reflecting means or the second reflecting means on the division surface,
The light receiving unit includes a plurality of light receiving elements arranged in parallel along the orthogonal direction, and receives a plurality of diffracted lights through the plurality of gratings,
The optical angle sensor, wherein the calculating means calculates an amount of change in angle due to rotation of the measurement target from a plurality of signals based on the plurality of diffracted lights received by the plurality of light receiving elements. The optical angle sensor according to any one of claims 1 to 6,
The first diffraction grating portion has a division surface on which light from the light source is irradiated,
The fourth diffraction grating portion is arranged in parallel along a direction orthogonal to a rotation axis of the first reflection means or the second reflection means on the division surface, and is arranged with respect to an optical axis of light from the light source. Having a plurality of inclined gratings arranged with a predetermined inclination angle,
The light receiving means includes a plurality of light receiving elements arranged side by side along a direction parallel to a rotation axis of the first reflecting means or the second reflecting means, and a plurality of diffracted lights passing through the plurality of inclined gratings. Receiving light,
The optical angle sensor according to claim 1, wherein the calculating means calculates a change in angle due to rotation of the measurement target from a plurality of signals based on the plurality of diffracted lights received by the light receiving means. The optical angle sensor according to any one of claims 1 to 8,
The fourth diffraction grating section includes a plurality of combining sections each having a different phase,
The light receiving unit includes a plurality of light receiving units corresponding to each of the plurality of combining units,
The calculation means calculates a direction of rotation of the measurement target and a change amount of an angle due to the rotation of the measurement target from a plurality of signals having different phases based on the light received by the plurality of light receiving units. Optical angle sensor. The optical angle sensor according to any one of claims 1 to 8,
A first quarter-wave plate disposed on an optical path of the first light passing through the first reflecting means or the second light passing through the second reflecting means,
A split beam splitter that splits the combined light by the fourth diffraction grating unit into a first split light and a second split light;
A second quarter-wave plate disposed on an optical path of the first split light and the second split light split by the split beam splitter;
A third quarter-wave plate disposed on the optical path of the second split light via the second quarter-wave plate;
A first split light polarization beam splitter that splits the first split light through the second quarter-wave plate into a first polarized light and a second polarized light;
A second split light polarization beam splitter that splits the second split light through the third quarter-wave plate into a third polarized light and a fourth polarized light;
A first light receiving unit for receiving light having a phase of 0 degree from the first polarized light, a second light receiving unit for receiving light having a phase of 180 degrees from the second polarized light, and a light receiving unit having a phase of 90 degrees from the third polarized light; An optical angle sensor comprising: a third light receiving unit that receives light; and a fourth light receiving unit that receives light having a phase of 270 degrees from the fourth polarized light. The optical angle sensor according to any one of claims 1 to 8,
A quarter-wave plate disposed on the optical path of the first light via the first reflecting means or the second light via the second reflecting means,
A fifth diffraction grating portion having an irradiation surface on which a plurality of gratings each of which makes the combined light by the fourth diffraction grating portion a plurality of diffracted lights are arranged in parallel;
The fifth diffraction grating section has a plurality of gratings arranged side by side in a direction orthogonal to the direction in which the plurality of gratings are arranged side by side on the irradiation surface, and further includes a plurality of diffracted lights by the fifth diffraction grating section. A sixth diffraction grating section for a plurality of diffracted lights,
A plurality of polarizers arranged on an optical path of the plurality of diffracted lights by the sixth diffraction grating unit, and a plurality of polarizers for converting the plurality of diffracted lights into a plurality of polarized lights having different phases.
The light receiving unit includes a plurality of light receiving units corresponding to each of the plurality of polarizers,
The calculation means calculates a direction of rotation of the measurement target and a change amount of an angle due to the rotation of the measurement target from a plurality of signals having different phases based on the light received by the plurality of light receiving units. Optical angle sensor.

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