JP2004053333A - Encoder device - Google Patents

Abstract

To reduce the thickness of an encoder device that detects a change in the relative position of two opposing objects by light.
An encoder device is provided on one object and has a reflection section (10) having a row of reflection surfaces (11), and an illumination is provided on the other object and illuminates the reflection section to detect reflected light. It comprises a detection unit (20). The illumination detection unit includes a light emitting element (21), a light receiving element (22), a plate-shaped light guide element (30), and a light shielding unit (40) having a row of light shielding surfaces (41). The light guide element is arranged to face the reflecting portion, and the groove provided on the surface (32) while totally reflecting light from the light emitting element provided from the end face (33) on the two surfaces and traveling inside the light guide element. The light is emitted from the surface (31) on the side of the reflecting section, with the direction changed according to the row of (35). The light receiving element is opposed to the reflecting part with the light guiding element therebetween, and detects light from the reflecting part transmitted through the light guiding element.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an encoder device that detects a change in the relative position of two objects using light.
[0002]
[Prior art]
Many devices including a portion that performs a linear motion or a rotary motion include an encoder device that detects a change in the relative position of two objects using light. FIG. 14 shows the configuration of a conventional encoder device. This encoder device includes a reflecting section 70 having a row of reflecting surfaces 71 having a constant pitch, and an illumination detecting section 80 for illuminating the reflecting section 70 and detecting reflected light. The reflection unit 70 is provided on one of the objects such that the direction of the row of the reflection surfaces 71 matches the direction of the change in the relative position (indicated by the arrow A), and the illumination detection unit 80 faces the reflection unit 70. Is provided on the other object.
[0003]
The illumination detection unit 80 includes a light-emitting element 81 that emits illumination light, a light-receiving element 82 that receives reflected light from the reflection unit 70 to detect the amount of received light, and a light-shielding unit 90 that has a row of light-shielding surfaces 91 with a constant pitch. Become. In general, a light-emitting diode is used as the light-emitting element 81 and a photodiode is used as the light-receiving element 82 in order to reduce the size of the device. The light emitting element 81 and the light receiving element 82 are housed in a housing 85 having an opening, and the light shielding unit 90 is attached to the opening of the housing 85. The housing 85 is arranged such that the light shielding unit 90 is parallel to the reflection unit 70 and is close to the reflection unit 70. The size of the reflection surface 71 of the reflection unit 70 and the light-shielding surface 91 of the light-shielding unit 90 in the column direction are both approximately の of the column pitch.
[0004]
The light emitted by the light emitting element 81 passes through a gap between the two light shielding surfaces 91 of the light shielding unit 90 and enters the reflection unit 70. If the reflecting surface 71 is located at the incident site, the light is reflected, and if the gap between the two reflecting surfaces 71 is located at the incident site, the light is absorbed or transmitted. The light reflected by the reflection surface 71 is incident on the light receiving element 82 through the same gap of the light shielding unit 90 as when traveling toward the reflection unit 70. Due to the change in the relative position in the direction of the arrow A, the reflecting surface 71 and the gap between the two reflecting surfaces 71 are alternately located at the incident portion of the reflecting portion 70, whereby the amount of light received by the light receiving element 82 is periodically changed. Changes to It can be seen that the relative position between the two objects has changed due to the change in the amount of received light, and the amount of change in the relative position can be determined from the period of the change in the amount of received light and the pitch of the reflecting surface 71.
[0005]
The pitch of the rows of the reflection surface 71 and the light-shielding surface 91 is about a fraction of the size of the light receiving element 82 in the direction of the change in the relative position. The light emitted from the light emitting element 81 is divergent light. Therefore, the light from the light emitting element 81 passes through the plurality of gaps of the light shielding unit 90 and is incident on the plurality of reflecting surfaces 71 of the reflecting unit 70, and the light receiving element 82 receives the light from the plurality of reflecting surfaces 71. By setting the pitch of the row of the reflection surface 71 and the light shielding surface 91 and the size of the light receiving element 82 in such a relationship, the change width of the amount of light received by the light receiving element 82 is increased and the change in the relative position can be easily detected. And increasing the detection accuracy (resolution) of the relative position by reducing the period of the change in the amount of received light.
[0006]
[Problems to be solved by the invention]
In the encoder device described above, the light emitting element 81 and the light receiving element 82 are arranged side by side, and the light from the light emitting element 81 is obliquely incident on the reflecting section 70. Since the light incident on the reflection surface 71 is reflected at the same reflection angle as the incident angle, not only the light reflected from the reflection surface 71 that passes through the gap of the light shielding unit 90 but also enters the light shielding surface 91. Some are obstructed. If the amount of light blocked by the light-shielding surface 91 is large, the change width of the amount of light received by the light receiving element 82 becomes small, and this makes it difficult to detect the change.
[0007]
In order to avoid this, it is necessary to increase the distance D from the light emitting element 81 and the light receiving element 82 to the light shielding unit 90 and reduce the angle of incidence of light on the reflecting unit 70 and the angle of reflection of light from the reflecting unit 70. Therefore, there is a limit in reducing the thickness of the illumination detection unit 80. For this reason, the conventional configuration cannot meet the demand for miniaturization and thinning.
[0008]
Further, since the reflected light from the reflecting surface 71 is a divergent light, it spreads beyond the gap between the light shielding portions 90 on the plane on which the light receiving element 82 is provided, but from the reflecting surface 71 opposed to both ends of the light receiving element 82. The spread of the reflected light slows down the change in the amount of received light, making it difficult to detect the change in the amount of received light. Since the spread of the reflected light from the reflecting surface 71 is approximately proportional to the distance D, the resolution of the relative position to be detected is limited in the conventional encoder device in which the distance D is large.
[0009]
The present invention has been made in view of such a problem, and an object of the present invention is to provide a thin encoder device, particularly, an encoder device that is thin but can detect a relative position with high resolution.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, there is provided an encoder device for detecting a change in a relative position between a first object and a second object facing each other. A reflecting section having a plurality of reflecting surfaces arranged in a row at a constant pitch in a detection direction; and an illumination detecting section provided on the second object and illuminating the reflecting section to detect light reflected from the reflecting section. In the above, the illumination detection unit has a deflecting structure on one surface, and while the reflected light is totally reflected on the two surfaces and travels through the inside, the direction is changed by the deflecting structure and emitted from one surface. A light guide element, a light emitting element that emits light to be given to the light guide element, and a light receiving element that detects the amount of light received by receiving the light, the surface of the light guide element that emits light faces the reflective portion, and emits light. The element gives light to the light guide element from its end face, There a configuration facing to the reflecting portion and between the light guide element.
[0011]
This encoder device has a plate-shaped light guide element in the illumination detection unit in addition to the light-emitting element and the light-receiving element. The light guide element faces the reflection unit, and the light-receiving element is a reflection unit via the light guide element. Oppose. The light emitted from the light emitting element enters the light guide element from the end face, is redirected by the deflecting structure, is emitted from the surface on the reflection part side, and becomes illumination light for illuminating the reflection part. The light receiving element detects light reflected by the reflection surface of the reflection section and transmitted through the light guide element. The light guide element is thin, and the light guide element and the light receiving element can be brought close to each other, thus providing a thin encoder device.
[0012]
The deflecting structure of the light guide element may be a simple reflection surface or a diffraction grating. If the deflecting structure is a diffraction grating, the unevenness is approximately the size of the wavelength of light and does not affect the thickness of the light guide element, so that it is extremely easy to make the light guide element thin. The deflecting structure can be provided on the surface on the reflection portion side, or can be provided on the surface on the opposite side. The diffraction grating may be set to transmit diffracted light when provided on the surface on the reflection portion side, and may be set to reflect diffracted light when provided on the opposite surface.
[0013]
Regarding the direction in which the change in the relative position is detected, the pitch of the rows of the reflecting surfaces of the reflecting portions is equal to or less than half the size of the light receiving element, the light guide element has a plurality of deflection structures, and the deflection structure of the light guide element is It is preferable to form a row at substantially the same pitch as the reflection surface of the reflection section in the direction in which the change in the relative position is detected. In this way, light from a plurality of reflecting surfaces of the reflecting portion is incident on the light receiving element, the width of change in the amount of received light increases, and the cycle of the change in the amount of received light is not the size of the light receiving element but the reflecting surface. It is determined by the pitch of the row, and becomes smaller. Therefore, it is possible to reliably detect a change in the relative position and at a high resolution. Moreover, since the light guide element is thin, the spread of light from the reflecting surface on the plane where the light receiving element is located is small, and a high resolution determined by the pitch of the rows of the reflecting surface can be easily realized.
[0014]
Here, the light detection unit is a light-shielding unit having a plurality of light-shielding surfaces arranged in a row at the same pitch as the reflection surface of the reflection unit in the direction of detecting the relative position, in the direction of detecting the relative position of the light guide element. It may be included. The optical path from the reflecting section to the light guide element can be regulated, and even when the degree of divergence of light emitted from the light emitting element is large, the change in the amount of light incident on the light receiving element becomes clear, and the relative position can be reliably determined. Can be detected.
[0015]
Further, the illumination detection unit includes two light receiving elements, the light guide element has a discontinuous portion where the pitch of the deflection structure is discontinuous, and the two light receiving elements sandwich the discontinuous portion of the light guide element. You may make it oppose a reflection part with one and the other of two parts interposed. In this way, a phase difference can be caused in the change in the amount of light detected by the two light receiving elements, and the direction of the change in the relative position can be known from the phase difference.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows the configuration of the encoder device 1 according to the first embodiment. The encoder device 1 includes a reflection unit 10 provided on a first object and an illumination detection unit 20 provided on a second object. Either the first object or the second object may move, or both may move.
[0017]
The reflecting section 10 has a plurality of reflecting surfaces 11 arranged in a row at a constant pitch. The reflection surface 11 is made of a material having high reflectance, for example, aluminum, and is provided on the surface of a thin substrate 12 that absorbs or transmits light. Each reflecting surface 11 has a strip shape long in the direction perpendicular to the rows of the reflecting surfaces 11, and the width thereof is set to approximately の of the pitch of the rows of the reflecting surfaces 11.
[0018]
The reflection unit 10 is attached to the first object such that the direction of the row of the reflection surfaces 11 coincides with the direction in which the relative position between the first object and the second object changes (indicated by an arrow A). When the relative position between the first object and the second object changes along a straight line, the row of the reflecting surfaces 11 is linear, and the relative position is along the circumference as when one object rotates. When it changes, the rows of the reflecting surfaces 11 are circular. Note that the reflection surface 11 may be provided directly on the surface of the first object, and the substrate 12 may be omitted.
[0019]
The illumination detector 20 illuminates the reflector 10 and detects reflected light. The illumination detection unit 20 includes a light emitting element 21, a light receiving element 22, a light guiding element 30, and a light shielding unit 40. The light emitting element 21 emits light for illuminating the reflecting unit 10, and the light receiving element 22 receives the reflected light from the reflecting unit 10 and detects the amount of received light. In order to reduce the size and weight of the encoder device 1, a light emitting diode is used as the light emitting element 21 and a photodiode is used as the light receiving element 22.
[0020]
The light guide element 30 has a plate shape and is made of a transparent optical material such as glass. One surface 31 of the light guide element 30 is a plane, and the other surface 32 is a plane parallel to the surface 31 when viewed macroscopically. However, a plurality of grooves 35 are formed on the front surface 32 so as to form a row at the same pitch as the row of the reflection surfaces 11 of the reflection section 10.
[0021]
The light guide element 30 has two end faces 33 and 34 perpendicular to the direction of the row of the grooves 35, and the light emitting element 21 is arranged to face one end face 33. The light emitted by the light emitting element 21 passes through the end face 33 and enters the inside of the light guide element 30, is totally reflected by the two surfaces 31 and 32, and travels toward the other end face 34. While traveling inside the light guide element 30, some of the light enters the grooves 35 in the surface 32.
[0022]
The groove 35 functions as a deflection structure that changes the direction of light. The groove 35 is shown in FIG. The groove 35 has a surface 35a on the end surface 33 side and a surface 35b on the end surface 34 side, and the surface 35b has a sawtooth shape substantially perpendicular to the entire surface 32. The angle Φ formed by the surface 35a on the end surface 33 side with respect to the entire surface 32 is set in a range of 35 ° to 55 °. The surface 35a reflects the incident light in a direction almost perpendicular to the entire surface 32. The light emitted from the light emitting element 21 is a diverging light, and the incident angle of the light to the two surfaces 31, 32 of the light guide element 30 and the surface 35a of the groove 35 has a spread, but the angle Φ is set as described above. Thus, the central ray of the light reflected by the surface 35a becomes substantially perpendicular to the surfaces 31 and 32. The light reflected on the surface 35 a of the groove 35 transmits through the surface 31.
[0023]
With such a configuration, the light guide element 30 emits light from the light emitting element 21 partly from the surface 31 while traveling inside. The light guide element 30 may have a thickness of about twice the depth of the groove 35, and can be manufactured to a thickness of about 1 mm or less.
[0024]
The light-shielding portion 40 is composed of a plurality of light-shielding surfaces 41 arranged in rows at the same pitch as the reflection surface 11 of the reflection portion 10. The light shielding surface 41 is provided on the surface 31 of the light guide element 30. The width of the light shielding surface 41 is approximately 略 of the pitch of the row of the light shielding surface 41. The light shielding portion 40 is provided such that the surface 35 a of the groove 35 of the light guide element 30 faces the center of the gap between the light shielding surfaces 41. Instead of providing the light-shielding surface 41 directly on the surface 31 of the light guide element 30, the light-shielding part 40 may be provided on the surface of a transparent substrate.
[0025]
The light guide element 30 is arranged such that the surface 31 on which the light shielding unit 40 is provided faces the reflection unit 10. The light receiving element 22 is disposed so as to face the reflection unit 10 with the light guide element 30 interposed therebetween. The reflection part 10, the light receiving element 22, the light guide element 30, and the light shielding part 40 are all parallel.
[0026]
The light emitted by the light emitting element 21 is reflected by the surface 35 a of the groove 35 while traveling inside the light guide element 30, and exits almost vertically through a portion of the surface 31 between the light shielding surfaces 41, The illumination light illuminates the reflection unit 10. This light is incident on the reflecting section 40 almost perpendicularly. If the reflecting surface 11 is located at the incident site, the light is reflected, and if the gap between the reflecting surfaces 11 is located at the incident site, the light is absorbed or transmitted. The light reflected by the reflection surface 11 is incident on the light guide element 30 almost vertically through the same gap of the light shielding section 40 as it travels to the reflection section 10, passes through the light guide element 30, and reaches the light receiving element 22. Incident.
[0027]
Due to a change in the relative position of the first object and the second object in the direction of arrow A, the reflection surface 11 and the gap between the two reflection surfaces 11 are alternately located at the incident portion of the reflection unit 10, whereby the light receiving element The light reception amount detected by the light source 22 periodically changes. It can be seen that the relative position between the two objects has changed due to the change in the amount of received light, and the amount of change in the relative position can be determined from the period of the change in the amount of received light and the pitch of the reflecting surface 11.
[0028]
Since the light is substantially perpendicularly incident on the reflecting portion 10 and is reflected substantially vertically, few of the light reflected by the reflecting portion 10 are blocked by the light shielding surface 41 of the light shielding portion 40. In addition, the pitch of the rows of the reflecting surface 11 of the reflecting portion 10, the groove 35 of the light guide element 30, and the light shielding surface 41 of the light shielding portion 40 is several times the size of the light receiving element 22 in the direction of the relative position change. That is, light from a plurality of reflection surfaces 11 is incident on the light receiving element 22. Therefore, the change width of the amount of received light detected by the light receiving element 22 is large, and it is easy to detect a change in the relative position. Further, the cycle of the change in the amount of received light detected is small, and the detection accuracy (resolution) of the relative position is small. Is also expensive. Further, since the light guide element 30 is thin, the spread of light from the reflecting surface 11 on the plane where the light receiving element 22 is located is very slightly suppressed, and a high resolution determined by the pitch of the rows of the reflecting surface 11 is reliably realized. You.
[0029]
The light-shielding surface 41 of the light-shielding portion 40 may be made of a material having a light-shielding property, such as aluminum, chromium, and chromium oxide. However, when the pitch of the rows of the reflecting surface 11, the groove 35, and the light shielding surface 41 is particularly small in order to particularly increase the resolution, if the reflectance of the light shielding surface 41 is high, light from the surface 35a of the groove 35 is There is a possibility that the light is incident on the light-shielding surface 41 and reflected, and the light reflected by the light-shielding surface 41 is incident on the light receiving element 22 to reduce the change width of the detected light reception amount. In consideration of this point, it is desirable that the light shielding surface 41 be made of a material having a low reflectance (high absorption). For example, chromium is suitable.
[0030]
As described above, since the light guide element 30 is thin and the light receiving element 22 is only slightly separated from the surface 32 of the light guide element 30, the illumination detector 20 is thin as a whole. Therefore, the separation distance between the first object and the second object necessary for detecting the relative position may be small, and the encoder device 1 is suitable for equipment that requires miniaturization.
[0031]
Although not shown, the illumination detection unit 20 has a thin casing having an opening, the light emitting element 21 and the light receiving element 22 are housed in the casing, and the light guide element 30 is attached to the opening of the casing. . The illumination detection unit 20 includes a power supply circuit that supplies power to the light emitting element 21 and the light receiving element 22, and a signal processing circuit that amplifies an output signal of the light receiving element 22 and detects a change in signal intensity. These circuits are attached to the housing, and the illumination detection unit 20 is a single unit as a whole.
[0032]
FIG. 3 shows the illumination detector 20 of the encoder device 2 according to the second embodiment. In the encoder device 2, the surface 32 of the light guide element 30 is changed so that the surface 35b of the groove 35 is eliminated, and the surface 35a is inclined between the surfaces 35a. The surface 32 is a repetition of a prism-shaped convex portion composed of two surfaces 35a and 35c, and is macroscopically parallel to the surface 31. It is the same as the encoder device 1 that the surface 35 a changes the direction of the light traveling inside the light guide element 30 and uses the illumination light to be emitted substantially perpendicularly from the surface 31.
[0033]
FIG. 4 shows the illumination detection unit 20 of the encoder device 3 according to the third embodiment. In the encoder device 3 of the present embodiment, the surface 32 of the light guide element 30 is further changed so that the inclination of the surface 35c is reduced, and a part of the surface 35b of the groove 35 is left. Although the angle of incidence of light on the surface 35a, which largely changes the direction of light, is relatively small, and light transmitted through the surface 35a occurs, in the first embodiment and the present embodiment, light transmitted through the surface 35a is guided from the surface 35b. The light can be re-entered into the optical element 30, and the light use efficiency is high.
[0034]
The traveling direction of the re-entered light can be adjusted by the inclination angle of the surface 35b. Here, in order to compensate for the fact that light traveling inside the light guide element 30 approaches parallel to the surfaces 31 and 32 every time the light is totally reflected by the inclined surface 35c, The surface 35b is slightly inclined. Therefore, the groove 35 is V-shaped.
[0035]
FIG. 5 shows the configuration of the encoder device 4 according to the fourth embodiment. In the first to third embodiments, the surface 35a that simply reflects light is used as a deflection structure. However, in the encoder device 4 of the present embodiment, a plurality of diffraction gratings 37 are formed on the surface 32, and this is Used as a deflection structure. The diffraction grating 37 is of a reflection type that diffracts incident light while reflecting it. The diffraction grating 37 is formed so as to form a line at the same pitch as the reflection surface 11 of the reflection unit 10 and the light-shielding surface 41 of the light-shielding unit 40, but may have a slightly different pitch.
[0036]
The setting of the diffraction grating 37 will be described with reference to FIG. As shown in FIG. 6, the pitch of the unevenness of the diffraction grating 37 is Λ, the wavelength of light is λ, the incident angle of light on the diffraction grating 37 is θ1, the diffraction angle of light by the diffraction grating 37 is θ2, the light guide element 30 is formed. Equation 1 holds when the refractive index of is expressed by n.
sin (θ1) + sin (θ2) = λ / (Λ · n) Equation 1
[0037]
Here, for example, λ = 0.55 μm, θ1 = 80 °, θ2 = 0 °, and n = 1.5. In this setting, from Equation 1, the pitch of the irregularities is Λ = 0.37 μm. This is a size that can be easily manufactured by photolithography using a stepper as an exposure system.
[0038]
The difference in height of the unevenness of the diffraction grating 37 is about the wavelength of light or less, and is negligible compared to the thickness of the light guide element 30 required to have a certain mechanical strength. Therefore, in the present embodiment using the diffraction grating 37 as the deflection structure, it is possible to make the light guide element 30 thinner than in each of the above embodiments using the inclined surface 35a as the deflection structure.
[0039]
FIG. 7 shows the configuration of an encoder device 5 according to the fifth embodiment. The encoder device 5 of the present embodiment is a modified example of the encoder device 1 of the first embodiment, in which a plurality of grooves 36 are formed on the surface 31 of the light guide element 30 on the reflection section 10 side, and the light shielding section 40 is formed. It is omitted. The grooves 36 are formed so as to form a row at the same pitch as the row of the reflection surfaces 11 of the reflection section 10.
[0040]
The groove 36 is shown in FIG. The groove 36 has a surface 36a on the end surface 33 side and a surface 36b on the end surface 34 side, and the surface 36a has a sawtooth shape substantially perpendicular to the entire surface 31. The angle Φ formed by the surface 36b on the side of the end surface 34 with respect to the entire surface 31 is set in the range of 35 ° to 55 °, similarly to the surface 35a of the first embodiment. The surface 36a transmits the incident light, and the surface 36b reflects the light transmitted through the surface 36a in a direction almost perpendicular to the entire surface 31. Although the angle of incidence of light on the surface 36b has a spread, the central ray of the light reflected by the surface 36b becomes substantially perpendicular to the surface 31 by setting the angle Φ as described above.
[0041]
FIG. 9 shows the configuration of an encoder device 6 according to the sixth embodiment. In the encoder device 6 of the present embodiment, a diffraction grating 38 is formed on the surface 31 of the light guide element 30 and has a deflection structure. As in the encoder device 5 according to the fifth embodiment, the light shielding unit 40 is omitted. The diffraction grating 38 is of a transmission type that diffracts while transmitting incident light. The diffraction gratings 38 are formed so as to form a line at the same pitch as the reflection surface 11 of the reflection section 10, but may have a slightly different pitch.
[0042]
The setting of the diffraction grating 38 will be described with reference to FIG. As shown in FIG. 10, the pitch of the unevenness of the diffraction grating 38 is Λ, the wavelength of light is λ, the incident angle of light on the diffraction grating 38 is θ1, the diffraction angle of light by the diffraction grating 38 is θ2, Equation 2 holds when the refractive index of n is represented by n.
n · sin (θ1) + sin (θ2) = λ / Λ Equation 2
[0043]
Here, for example, λ = 0.55 μm, θ1 = 80 °, θ2 = 0 °, and n = 1.5. In this setting, from Equation 2, the pitch of the concavities and convexities is Λ = 0.37 μm, and it can be easily manufactured by photolithography using a stepper as the exposure system.
[0044]
The omission of the light-shielding portion 40 as in the fifth and sixth embodiments may be employed in a configuration in which a deflection structure is provided on the surface 32 of the light guide element 30 as in the first to fourth embodiments. it can. However, when a light emitting element 21 having a relatively large degree of divergence of emitted light is used, it is preferable to provide a light shielding unit 40 in order to suppress the spread of light on a plane where the light receiving element 22 is located. .
[0045]
FIG. 11 shows an illumination detector 20 of the encoder device 7 according to the seventh embodiment. The encoder device 7 according to the present embodiment includes a reflecting section 50 facing the end face 34 of the light guide element 30. The light guide element 30 has a groove 35 on the surface 32 as in the encoder device 1 of the first embodiment. Some of the light from the light emitting element 21 that enters from the end face 33 and travels inside the light guide element 30 does not exit midway and reaches the end face 34. It can be used for illuminating the reflector 10 without losing any light.
[0046]
The two surfaces 35a and 35b of the groove 35 are both set at an angle of 35 ° to 55 ° with respect to the surface 32. The surface 35a reflects the direct light from the light emitting element 21 and the surface 35b reflects the light. The light reflected by the portion 50 is reflected to generate illumination light that exits substantially perpendicularly from the surface 31. The reflecting section 50 may be provided separately from the light guide element 30, or may be provided directly on the end face 34 of the light guide element 30.
[0047]
FIG. 12 shows the configuration of an encoder device 8 according to the eighth embodiment. The encoder device 8 of the present embodiment includes two light receiving elements 22. The light guide element 30 has grooves 35 on the surface 32 as a deflecting structure as in the encoder device 1 of the first embodiment, but the rows of the grooves 35 have portions B with discontinuous pitch. The pitch of the portion B is set to be larger than the pitch of the other portions by 1/4. The light shielding portion 40 also has a portion where the pitch of the row of the light shielding surface 41 is discontinuous corresponding to the row of the grooves 35. There is no discontinuous portion in the row of the reflecting surfaces 11 of the reflecting section 10.
[0048]
One of the two light receiving elements 22 is located closer to the end face 33 than the part B where the pitch of the row of the groove 35 and the light shielding surface 41 is discontinuous, and the other is located closer to the end face 34 than the part B. As shown in FIG. 13, the amounts of light received by the two light receiving elements 22 change in the same cycle τ according to the change in the relative position between the first object and the second object. / 4) A phase difference of τ occurs. Further, the sign of the phase difference changes depending on whether the relative position changes in one direction or the opposite direction. Therefore, the direction of change in the relative position between the first object and the second object can be known from the phase difference appearing in the output signals of the two light receiving elements 22.
[0049]
Note that, here, the pitch difference from the other portion of the discontinuous portion B in the row of the groove 35 and the light shielding surface 41 is set to 1/4, but may be set to any value other than an integral multiple of 1/2. Good.
[0050]
In each of the above embodiments, the pitch of the row of the reflecting surfaces 11 of the reflecting unit 10 is set to a fraction of the size of the light receiving element 22 in order to detect a change in the relative position with high resolution. When the resolution is not required, the pitch of the row of the reflection surfaces 11 of the reflection unit 10 can be made substantially equal to the size of the light receiving element 22. In that case, the light shielding unit 40 is unnecessary. Further, at least one deflection structure of the light guide element 30 is sufficient, but it is desirable to provide a plurality of deflection structures in order to increase the amount of light received by the light receiving element.
[0051]
As a material of the light guide element 30, a resin can be used in addition to glass. If a resin is used, it can be produced by injection molding or compression molding, and the production efficiency is improved. The material may be selected in consideration of optical properties such as transparency and refractive index. For example, polymethyl methacrylate (PMMA), a copolymer of methyl methacrylate and another methacrylate or acrylate, polycarbonate (PC), Cycloolefin polymers are suitable.
[0052]
In particular, the cycloolefin polymer has a specific gravity of 1.0, which is smaller than other resins (for example, PMMA of 1.2), and a refractive index of 1.53, which is larger than other resins (for example, PMMA has a refractive index of 1.49), and hence a high light confinement effect, which is preferable in terms of weight reduction and thickness reduction. In addition, since it has high fluidity before solidification, it is suitable for injection molding, and has low hygroscopicity and is hardly deformed even under high humidity conditions, so that it is suitable for thin light guide elements.
[0053]
【The invention's effect】
An encoder device for detecting a change in a relative position between a first object and a second object facing each other, the plurality of encoder devices being provided on the first object and forming a line at a constant pitch in a direction for detecting a change in the relative position. And a lighting unit provided on the second object and illuminating the reflecting unit to detect reflected light from the reflecting unit. As in the present invention, the lighting detecting unit includes A plate-shaped light guide element having a deflecting structure on one surface, while reflecting the given light on the two surfaces and traveling inside, while changing the direction by the deflecting structure and emitting from the one surface, The light-emitting element includes a light-emitting element that emits light to be given to the light-guiding element, and a light-receiving element that receives the light and detects the amount of received light. Light is given from the end face, and the light receiving element interposes the light guide element When a configuration facing the morphism portion, a thin light guiding element is close to the reflective portion, it is possible to close the light-receiving element to the light guide element, a thin encoder device.
[0054]
If the deflection structure of the light guide element is a diffraction grating, it becomes very easy to make the light guide element thin.
[0055]
Regarding the direction in which the change in the relative position is detected, the pitch of the rows of the reflecting surfaces of the reflecting portions is equal to or less than half the size of the light receiving element, the light guide element has a plurality of deflection structures, and the deflection structure of the light guide element is If rows are formed at substantially the same pitch as the reflecting surface of the reflecting portion in the direction in which the change in the relative position is detected, light from the plurality of reflecting surfaces of the reflecting portion is incident on the light receiving element, and the variation width of the received light amount is changed. Becomes larger, and the cycle of the change in the amount of received light is determined not by the size of the light receiving element but by the pitch of the rows of the reflecting surfaces, and becomes smaller. Therefore, a change in the relative position can be reliably detected with high resolution. In addition, since the light guide element is thin, the spread of light from the reflecting surface on the plane where the light receiving element is located becomes small, and high resolution determined by the pitch of the array of reflecting surfaces can be easily realized.
[0056]
Further, the illumination detection unit includes a light-shielding unit having a plurality of light-shielding surfaces arranged in a row at the same pitch as the reflection surface of the reflection unit, in a direction to detect the relative position, in the direction of detecting the relative position of the light guide element. By doing so, it is possible to regulate the optical path from the reflecting portion to the light guide element, even when the degree of divergence of light emitted from the light emitting element is large, the change in the amount of light incident on the light receiving element becomes clear, A change in the relative position can be reliably detected.
[0057]
The illumination detection unit includes two light receiving elements, the light guiding element has a discontinuous portion where the pitch of the deflection structure is discontinuous, and the two light receiving elements sandwich the discontinuous portion of the light guiding element. When one part and the other part are interposed and opposed to the reflection part, a phase difference can be generated in the change in the amount of light detected by the two light receiving elements, and not only the speed of the relative position change but also , It is also possible to know the direction of the change in the relative position.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view of an encoder device according to a first embodiment.
FIG. 2 is a schematic cross-sectional view of a groove provided in a light guide element of the encoder device according to the first embodiment.
FIG. 3 is a schematic cross-sectional view of an illumination detection unit of an encoder device according to a second embodiment.
FIG. 4 is a schematic cross-sectional view of an illumination detector of an encoder device according to a third embodiment.
FIG. 5 is a schematic sectional view of an encoder device according to a fourth embodiment.
FIG. 6 is a schematic sectional view of a diffraction grating provided in a light guide element of an encoder device according to a fourth embodiment.
FIG. 7 is a schematic sectional view of an encoder device according to a fifth embodiment.
FIG. 8 is a schematic cross-sectional view of a groove provided in a light guide element of an encoder device according to a fifth embodiment.
FIG. 9 is a schematic sectional view of an encoder device according to a sixth embodiment.
FIG. 10 is a schematic sectional view of a diffraction grating provided in a light guide element of an encoder device according to a sixth embodiment.
FIG. 11 is a schematic sectional view of an illumination detector of an encoder device according to a seventh embodiment.
FIG. 12 is a schematic sectional view of an encoder device according to an eighth embodiment.
FIG. 13 is a diagram illustrating a relationship between a change in a relative position and the amount of light received by two light receiving elements in the encoder device according to the eighth embodiment.
FIG. 14 is a schematic sectional view of a conventional encoder device.
[Explanation of symbols]
1-8 Encoder device
10 Reflector
11 Reflective surface
20 Illumination detector
21 Light-emitting element
22 Light receiving element
30 Light guide element
31, 32 Light guide element surface
33, 34 Light guide element end face
35, 36 groove
35a, 35b, 36a, 36b Groove surface
37, 38 Diffraction grating
40 Shading part
41 Shading surface
50 Reflector

Claims (5)

An encoder device for detecting a change in a relative position between a first object and a second object facing each other, comprising: a plurality of encoder devices provided on the first object and arranged in a line at a constant pitch in a direction for detecting a change in the relative position. And a lighting detection unit provided on the second object and illuminating the reflection unit to detect light reflected from the reflection unit.
The illumination detector has a deflecting structure on one surface, and a plate-like guide that changes the direction by the deflecting structure and emits the light from one surface while totally reflecting the given light on the two surfaces and traveling inside. An optical element, a light emitting element that emits light to be given to the light guide element, and a light receiving element that receives light and detects the amount of light received,
The surface of the light guide element from which light is emitted faces the reflector, the light emitting element gives light to the light guide element from its end face, and the light receiving element faces the reflector with the light guide element in between. Encoder device. The encoder device according to claim 1, wherein the deflection structure of the light guide element is a diffraction grating. Regarding the direction in which the change in the relative position is detected, the pitch of the rows of the reflecting surfaces of the reflecting portions is equal to or less than half the size of the light receiving element,
The light guide element has a plurality of deflection structures,
3. The encoder device according to claim 1, wherein the deflection structure of the light guide element forms a line at substantially the same pitch as the reflection surface of the reflection portion in a direction in which a change in the relative position is detected. The illumination detection unit includes a light-shielding unit having a plurality of light-shielding surfaces arranged in a row at the same pitch as the reflection surface of the reflection unit in a direction in which the relative position is detected in the direction in which the light guide element emits light. The encoder device according to claim 3, wherein: The illumination detection unit includes two light receiving elements,
The light guide element has a discontinuous portion where the pitch of the deflecting structure is discontinuous, and the two light receiving elements have a reflecting portion between one and the other of the two portions sandwiching the discontinuous portion of the light guide element. The encoder device according to claim 3, wherein the encoder device is opposed to.

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