JP4876659B2 - Optical scanning module and encoder - Google Patents

Description

  The present invention relates to an optical scanning module and an encoder, and more particularly to an optical scanning module that scans illumination light from a light source, and an encoder that uses the optical scanning module.

  Conventionally, a relatively large number of optical encoders have been used to control the position of a moving body. There are various types of optical encoders. In recent years, a scale in which a periodic pattern is formed along the moving direction of the moving body, and illumination light for illuminating the scale in the moving direction of the moving body. A probe that vibrates along, a detector that reflects off the scale and detects reflected light including vibration information of the illumination light and position information of the scale, and a detection signal detected from the detector, and illumination There has been proposed an encoder (also referred to as a scan-type encoder) that obtains scale position information based on a drive signal for vibrating light (see, for example, Patent Document 1). The scan type encoder as disclosed in Patent Document 1 has a large S / N ratio of the output signal, and can detect the position of the scale with high accuracy.

  However, in this scan type encoder, it is necessary to oscillate illumination light for illuminating the scale along the moving direction of the moving body and scan a periodic pattern within a necessary range. For this reason, for example, when the probe is reciprocated with a predetermined stroke in the vibration direction, a large space is required for driving the probe in order to sufficiently secure the stroke, and the probe drive mechanism is enlarged. There was a tendency to.

  On the other hand, as a method of scanning the illumination light for illuminating the scale along the moving direction of the moving body, for example, a tuning fork crystal resonator is used, and the illumination light incident on the scale using the vibration of the tuning fork crystal resonator is used. It is conceivable to modulate the emission angle. However, in this case, the modulation of the emission angle of the illumination light by the tuning fork type crystal resonator has a drawback that it is easily affected by disturbance.

US Pat. No. 6,639,686

The present invention has been made under the above circumstances. From a first viewpoint, the present invention is an optical scanning module that scans illumination light, and includes a reflection surface on which the illumination light is incident, and has a predetermined period. reflecting optical member and configured to reflect the illumination light by the reflection surface while reciprocating in a direction intersecting with the reflecting surface; enters the illumination light reflected by the reflecting optical member, the reciprocating movement of the reflecting optical member And a changing member that changes an emission angle of the illumination light in a measurement direction corresponding to the intersecting direction .

According to this, illumination light is reflected by the reflective surface of a reflective optical member, and injects into a change member. At this time, since the reflecting optical member reciprocates in a direction intersecting the reflecting surface at a predetermined cycle, the illumination light reflected by the reflecting surface of the reflecting optical member enters the changing member while reciprocating. To do. Illumination light incident on the changing member is changed in its emission angle in the measurement direction corresponding to the intersecting direction by the changing member in accordance with the reciprocating movement of the reflecting optical member (reflecting surface). As a result, the illumination light emitted from the changing member is scanned within a predetermined angle range. That is, the reciprocating movement of the illumination light reflected by the reflecting surface of the reflecting optical member is converted into scanning in the angular direction by the changing member, and as a result, a large scanning angle and consequently a scanning width can be obtained. Accordingly, the stroke of the reflecting optical member in the measurement direction can be reduced, and for example, a small vibrator or the like can be adopted as the reflecting optical member, and errors due to reciprocation can be reduced and highly accurate position detection can be performed. It becomes possible.

According to a second aspect of the present invention, there is provided an optical scanning module that scans illumination light emitted from an illumination light source, the container to which the illumination light source is connected, the container being accommodated in the container, and the illumination light being measured in a measuring direction. Means for reflecting the illumination light while vibrating, and an optical element on which the illumination light reflected by the means is incident and angle-modulates the illumination light in the measurement direction according to the vibration of the illumination light. It is the 2nd optical scanning module provided .

According to this, since the configuration includes the optical element and the means for reflecting the illumination light while vibrating the illumination light, it is possible to reduce the vibration of the illumination light in the measurement direction, and to reduce errors due to the vibration. Therefore, highly accurate position detection becomes possible. Further, means for reflecting the illumination light while vibrating the illumination light in the measurement direction is accommodated in the container. Thereby, for example, adhesion of foreign matter such as fine particles to the means is suppressed, and the possibility of being affected by disturbance such as scattering of illumination light by the foreign matter is effectively suppressed. Further, since the frequency of change of the illumination light is suppressed at the same time, it is possible to, based on the vibration periods scanning illumination light with high precision (or angle modulation).

The first of the present invention, with any of the second optical scanning module, along with the first, the illumination light scanned by one of the second optical scanning module is irradiated, the diffraction of the measurement direction a periodic direction An encoder comprising: a scale on which a grating is formed; and a light receiving element that receives the illumination light and outputs an output signal .

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. FIG. 1 schematically shows a configuration of an encoder 100 according to an embodiment. The encoder 100 is a diffraction interference type encoder, and is a linear encoder that detects the displacement of a moving body (not shown) that moves in the directions of arrows B and B ′ (X-axis direction) in FIG. 1.

  As shown in FIG. 1, the encoder 100 includes a light source unit 10, an optical fiber 12, an optical scanning module 20, an index diffractive optical element (index scale) 13, mirrors 14A and 14B, a moving diffractive optical element (moving scale) 15, And a light receiving element 16.

  The light source unit 10 includes a light source that oscillates, for example, coherent light, for example, laser light having a wavelength λ (= 850 nm). The illumination light IL emitted from the light source unit 10 is guided into the optical scanning module 20 by an optical fiber 12 having one end connected to the light source unit 10.

  The optical scanning module 20 includes a casing 22, a scanning vibrator (hereinafter abbreviated as "vibrator") 21, a lens 24, and the like.

  The casing 22 is a hollow, substantially rectangular parallelepiped shape made of a metal such as aluminum or stainless steel, and is an airtight container filled with an inert gas which is a rare gas such as nitrogen gas or helium or a mixed gas thereof. . A round hole 22c is formed in the side wall of the casing 22 on the -X side, and a connector 12a provided at the other end of the optical fiber 12 is inserted into the round hole 22c via a sealing material (not shown). Yes. The other end (exit end) of the optical fiber 12 is inserted into the connector 12a, and the illumination light IL is emitted from the exit end in the + X direction.

  The vibrator 21 is disposed at a position within the casing 22 and at a predetermined distance on the + X side of the connector 12a, perpendicular to the XZ plane and inclined by 45 ° with respect to the YZ plane and the XY plane. The vibrator 21 is made of, for example, a rectangular plate crystal, and is connected to an oscillation circuit (not shown) and a power source. The vibrator 21 is periodically vibrated at a predetermined frequency and a predetermined amplitude in the thickness direction as indicated by arrows A and A ′ by applying a voltage from the power source to the oscillation circuit. (Reciprocating drive). Thereby, the illumination light IL incident on the vibrator 21 is reflected in the −Z direction by the surface (reflection surface) 21a of the vibrator 21 and is vibrated (scanned) in the X-axis direction with a predetermined amplitude.

  The lens 24 is fitted into an opening 22b formed in the bottom wall of the casing 22 directly below the vibrator 21 via a sealing material (not shown). The lens 24 has a convex refraction having a convex incident surface (aspherical surface) on which the illumination light IL reflected by the vibrator 21 is incident and a planar exit surface on which the incident illumination light IL is emitted. An optical element (aspheric lens). The lens 24 illuminates the illumination light IL periodically oscillated (reciprocatingly driven) with a predetermined amplitude in the X-axis direction according to the incident position on the lens 24, in other words, according to the reciprocating movement of the vibrator 21. Refract and change the exit angle. As a result, as indicated by an arrow C in the figure, the illumination light IL is angle-modulated within a predetermined angular velocity range and scanned along the surface of the index scale 13 in the X-axis direction.

  The index scale 13 is formed of a rectangular plate-like glass member that is disposed below the optical scanning module 20 in parallel with the XY plane and whose longitudinal direction is the X-axis direction. On the upper surface of the index scale 13, a diffraction grating (transmission type phase grating) having a predetermined pitch p with the periodic direction as the X-axis direction is formed. The index scale 13 generates a plurality of diffracted lights based on the incident illumination light IL. FIG. 1 shows ± first-order diffracted light generated from the diffracted light at the central portion of the index scale 13 in the X-axis direction. The diffracted light emitted to the + X side indicated by the solid line is the + 1st order diffracted light, and the diffracted light emitted to the −X side indicated by the dotted line is the −1st order diffracted light. The exit angles of these diffracted lights are determined by the diffraction grating pitch p of the index scale 13 and the laser light wavelength λ.

  The mirrors 14A and 14B are disposed below the index scale 13 so that the reflecting surfaces thereof face each other and are substantially parallel to the YZ plane. The + 1st order diffracted light generated at the index scale 13 is reflected by the mirror 14A and then enters the moving scale 15. On the other hand, the −1st order diffracted light generated by the index scale 13 is incident on the moving scale 15 after being reflected by the mirror 14B. In the present embodiment, ± 1st-order diffracted light emitted from the same position of the index scale 13 intersects at the same position on the moving scale 15 after being reflected by the mirrors 14A and 14B (that is, ± 1 separated by the index scale 13). The positional relationship among the index scale 13, the mirrors 14A and 14B, and the arrangement surface of the moving scale 15 is set so that the next diffracted light enters the same position of the moving scale 15.

  The moving scale 15 is attached to a moving body (not shown), and moves with the moving body along the X-axis direction as indicated by arrows B and B 'in the drawing. The moving scale 15 is made of a rectangular plate-shaped glass member having a longitudinal direction arranged in parallel to the XY plane below the mirrors 14A and 14B and having an X-axis direction as a longitudinal direction. On the surface of the moving scale 15, a diffraction grating (transmission type phase grating) whose periodic direction is the X-axis direction is formed. The pitch of this diffraction grating is the same as the pitch of the index grating of the index scale 13, and the pitch p is not more than 50 μm, for example, about 8 μm.

  When the diffracted light of ± 1st order diffracted light emitted from the index scale 13 enters the moving scale 15, it is diffracted again by the diffraction action of the diffraction grating formed on the moving scale 15. The outgoing angle of the diffracted light generated by the moving scale 15 is determined by the incident angle of the ± first-order diffracted light incident on the moving scale 15, the pitch p of the diffraction grating of the moving scale 15, and the wavelength λ of the laser light.

  From the moving scale 15, the −1st order diffracted light of the + 1st order diffracted light from the index scale 13 and the + 1st order diffracted light of the −1st order diffracted light from the index scale 13 are both emitted vertically downward (−Z direction). The diffracted lights enter the light receiving element 16 in a state where they interfere with each other. The light receiving element 16 outputs an electric signal indicating the interference intensity of the interference light.

  The output signal from the light receiving element 16 in this case is a signal based on the illumination light IL that is vibrated by the vibrator 21 and further angle-modulated by the lens 24. Therefore, the position information of the moving scale 15 can be calculated by processing the signal from the light receiving element 16 using the Bessel series expansion with respect to time.

  As described above, according to the optical scanning module 20 according to the present embodiment, the illumination light IL emitted from the light source unit 10 is reflected by the surface (reflection surface) 21a of the vibrator 21 through the optical fiber 12, The light enters the lens 24. At this time, the vibrator 21 vibrates (reciprocates) at a predetermined cycle in the thickness direction (directions indicated by arrows A and A ′), and thus is reflected by the surface (reflection surface) 21a. The illumination light IL enters the lens 24 while reciprocating. The illumination light IL incident on the lens 24 is refracted by the lens 24 according to the incident position (according to the reciprocating movement of the vibrator 21), so that the emission angle is changed. As a result, the illumination light IL emitted from the lens 24 is scanned within a predetermined angle range. That is, the reciprocating movement of the illumination light IL reflected by the reflecting surface 21a of the vibrator 21 is converted into scanning in the angular direction by the lens 24. As a result, a large scanning angle and eventually a scanning width (X on the index scale 13) are converted. (Scanning width in the axial direction) can be obtained. Therefore, in the present embodiment, the vibration width (stroke) of the vibrator 21 can be reduced, and a small vibrator can be employed as the vibrator 21. This downsizing increases the resonance frequency of the vibrator 21 itself, and can improve the frequency during reciprocating drive (during vibration).

  In addition, by reducing the vibration width of the vibrator 21, it is possible to reduce an error when the illumination light IL is vibrated by the vibrator 21 and to reduce the size of the optical scanning module 20.

  Further, according to the optical scanning module 20 according to the present embodiment, the illumination light IL emitted from the light source unit 10 enters the vibrator 21 accommodated in the casing 22 through the optical fiber 12 connected to the light source unit 10. Then, it is reflected by the vibrator 21 and scanned. In this case, the casing 22 is constituted by a lens 24 through which a part of the illumination light IL scanned by the vibrator 21 is transmitted, and the inside is filled with an inert gas. Therefore, the illumination light IL incident on the vibrator 21 existing in the inert gas inside the casing 22 or the illumination light IL reflected by the vibrator 21 is scattered by foreign matters such as minute particles, or the atmosphere. The possibility of being affected by disturbances, such as the effects of temperature fluctuations, is effectively suppressed. Further, the influence on the disturbance received by the vibrator 21, for example, the change in the vibration frequency of the vibrator 21 due to the change in the relative humidity of the atmosphere or the adhesion of foreign matter is also suppressed. Therefore, it is possible to scan the illumination light IL with high accuracy based on the vibration period of the vibrator 21 and to perform angle modulation via the lens 24. In addition, since a part of the casing 22 that houses the vibrator 21 is configured by the lens 24 through which the illumination light IL is transmitted, the number of components can be reduced.

  In addition, the encoder 100 according to the present embodiment is a small-sized encoder that can reduce the error when vibrating the illumination light IL and reduce the frequency during reciprocating drive (during vibration) by reducing the vibration width. While the vibrator 21 is used, the drift of the vibration center of the illumination light IL is effectively suppressed, and the illumination light IL is scanned with high accuracy based on the vibration cycle of the vibrator 21, and the angle is modulated via the lens 24. An optical scanning module 20 is provided. Therefore, according to the encoder 100, by scanning the illumination light IL on the index scale 13 by the optical scanning module 20, it becomes possible to scan the illumination light IL with high accuracy, and as a result, the position of the moving scale 15 is accurately set. It becomes possible to ask.

  In the above embodiment, the vibrator 21 made of a quartz crystal having a rectangular plate shape is used to scan the illumination light IL. However, the present invention is not limited to this, and a reflective optical element such as a mirror or a prism is used. The element may be reciprocated in a direction intersecting the reflecting surface, for example, in the thickness direction, using a driving element such as a piezoelectric element or other driving mechanism. In short, it is only necessary that the illumination light incident on the changing member (the lens 24 in the above embodiment) can be vibrated with a predetermined stroke in the X-axis direction. In this sense, the reciprocating movement (vibration) of the vibrator 21 and the reciprocating movement of the reflective optical element are not limited to the directions of the arrows A and A ′ described above, and may be any direction that intersects the reflecting surface.

  Moreover, although the said embodiment demonstrated the case where the lens 24 served as a part of casing 22 of the optical scanning module 20, it is not restricted to this, For example, the 1st modification shown by FIG. 2 (A) is shown. Like the optical scanning module 20 ′, the index scale 13 may be mounted in an opening formed on the bottom surface of the casing 22 ′. Further, in the case of the optical scanning module of FIG. 2A, instead of the vibrator 21, a vibrator 21 ′ that rotates around a point O in the figure as indicated by arrows D and D ′ is used. ing. The vibrator 21 ′ can be composed of, for example, a tuning fork type crystal vibrator. Further, the inside of the casing 22 ′ in FIG. 2A is filled with the inert gas as described above.

  When the optical scanning module 20 ′ of FIG. 2A is used in place of the optical scanning module 20 of the first embodiment, the optical scanning module 20 ′ of FIG. 14B, the moving scale 15 and the light receiving element 16 may be combined to form an encoder. By doing in this way, similarly to the above embodiment, the illumination light IL incident on the vibrator 21 ′ existing in the inert gas inside the casing 22 ′ or the illumination light IL reflected by the vibrator 21 ′ is obtained. For example, the possibility of being affected by disturbances such as being scattered by foreign matters such as fine particles or being affected by temperature fluctuations of the atmosphere is effectively suppressed. In addition, the influence on the disturbance that the scanning vibrator receives, for example, the change in the vibration frequency of the vibrator due to the change in the relative humidity of the atmosphere or the adhesion of foreign matter is suppressed at the same time. Accordingly, the illumination light IL can be angularly modulated with high accuracy based on the vibration period of the vibrator 21 '. In addition, since a part of the casing 22 ′ is configured by an index scale through which the illumination light IL is transmitted, the number of parts can be further reduced as compared with the above embodiment.

  Alternatively, an optical member 13 ′ having an index grating formed on the plane of a plano-convex lens is formed on the bottom surface of the casing 22 ″, for example, as in the optical scanning module 20 ″ of the second modification shown in FIG. 2B. It may be installed without any gap in the opening. In the case of the optical scanning module 20 ″ of FIG. 2B, the vibrator 21 ′ is used instead of the vibrator 21. Further, the inside of the casing 22 ″ of FIG. As described above, it is filled with an inert gas.

  When the optical scanning module of FIG. 2B is used instead of the optical scanning module 20 of the first embodiment, the optical scanning module 20 ″ of FIG. 2B and the mirrors 14A, 14B, What is necessary is just to comprise an encoder combining the moving scale 15 and the light receiving element 16. By doing in this way, the effect equivalent to the above-mentioned 1st modification can be acquired.

  In the above-described embodiment and each modified example, the illumination light IL emitted from the light source unit 10 is guided to the inside of the casing (airtight container) using the optical fiber 12, but the present invention is not limited to this. A small light source such as may be provided inside the casing. In this case, the light source becomes a part of the optical scanning module.

  In the above-described embodiment, the case where the vibrator 21 or 21 ′ is housed in an airtight container has been described. However, the influence of disturbance on the vibrator can be ignored, or the influence can be removed by another means. In such a case, an airtight container is not necessarily provided. Even in such a case, by using a combination of a reflecting optical member that reciprocates in the direction intersecting the reflecting surface like the above-described vibrator 21 and a changing member such as the lens 24, the reflecting surface of the reflecting optical member can be used. The reciprocating movement of the reflected illumination light is converted into angular scanning by the changing member, and as a result, a large scanning angle and thus a scanning width can be obtained.

  In the above embodiment, the grating pitches of the diffraction gratings included in the index scale 13 and the moving scale 15 are the same. However, the present invention is not limited to this, and the pitches of both gratings may be different from each other.

  In the above-described embodiment, the case where the moving scale 15 moves has been described. However, the present invention is not limited to this, and the present invention is also suitable when the moving scale is fixed and a part other than the moving scale 15 such as an optical system moves. Applicable to. Of course, the configuration of the diffractive interference transmission optical encoder is not limited to the configuration of the above embodiment. For example, instead of the above-described mirrors 14A and 14B, the −1st order diffracted light of the + 1st order diffracted light from the index scale 13 and the + 1st order diffracted light of the −1st order diffracted light from the index scale 13 are the same on the moving scale 15. A diffractive optical element that enters the light source may be used.

  In the above embodiment, the case where the present invention is applied to a diffractive interference transmission type optical encoder has been described. However, the present invention is not limited to this, and the present invention is not limited to a so-called optical pickup system, a so-called shadow picture system, and the like. Even an encoder of this type can be suitably applied when scanning illumination light on a scale. Further, the present invention can be applied not only to a transmissive optical encoder but also to a reflective optical encoder.

  In the above embodiment, a convex aspherical lens is used as the lens 24. However, the present invention is not limited to this, and the present invention is also suitable when a planoconvex lens, a biconvex lens, a planoconcave lens, a biconcave lens, a meniscus lens, or the like is used. It is.

  Moreover, although the said embodiment demonstrated the case where the inside of the casing 22 was filled with the inert gas, not only this but the inside of the casing 22 may be a vacuum state.

  As described above, the optical scanning module of the present invention is suitable for scanning illumination light, and the encoder of the present invention is suitable for detecting displacement or position information of a moving body.

It is a figure which shows schematic structure of the encoder which concerns on one Embodiment of this invention. FIG. 2A is a diagram for explaining the optical scanning device according to the first modification, and FIG. 2B is a diagram for explaining the optical scanning device according to the second modification.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Light source unit, 12 ... Optical fiber, 13 ... Index scale, 15 ... Moving scale, 20 ... Optical scanning module, 21 ... Vibrator, 21a ... Reflecting surface, 22 ... Casing, 24 ... Lens, 100 ... Encoder, IL ... Illumination light.

Claims (14)

An optical scanning module that scans illumination light,
A reflective optical member having a reflective surface on which the illumination light is incident, and reflecting the illumination light on the reflective surface while reciprocating in a direction intersecting the reflective surface at a predetermined period ;
A change member that enters the illumination light reflected by the reflection optical member and changes an emission angle of the illumination light in a measurement direction corresponding to the intersecting direction according to the reciprocation of the reflection optical member ; Optical scanning module provided.   The optical scanning module according to claim 1, wherein the reflective optical member is a scanning vibrator.   The optical scanning module according to claim 1, wherein the reflective optical member is a reflective optical element that is reciprocally driven by a drive source.   The changing member has an incident surface on which the illumination light is incident and an exit surface on which the incident illumination light is emitted, and either the incident surface or the exit surface is formed in a convex shape or a concave shape. The optical scanning module according to claim 1, further comprising an optical element.   The optical scanning module according to claim 4, wherein the optical element is a refractive optical element.   The at least reflective optical member of the reflective optical member and the changing member is disposed in an airtight container whose inside is maintained in a vacuum state or a state filled with an inert gas. The optical scanning module as described in any one of 1-5.   The optical scanning module according to claim 6, wherein the changing member constitutes a part of the hermetic container.   8. The optical scanning module according to claim 6, wherein an illumination light source that emits the illumination light is integrally connected to the airtight container. An optical scanning module that scans illumination light emitted from an illumination light source,
A container to which the illumination light source is connected;
Means for reflecting the illumination light contained in the container and vibrating the illumination light in a measurement direction;
An optical scanning module comprising: an optical element on which the illumination light reflected by the means is incident and angle-modulates the illumination light in the measurement direction according to vibration of the illumination light. The said optical element refracts the said illumination light so that the scanning angle of the said illumination light may be enlarged according to the incident position of the said illumination light changed by the vibration of the said illumination light. Optical scanning module. 11. The container according to claim 9, wherein a part of the container is constituted by the optical element through which the illumination light is transmitted, and the inside is filled with a vacuum state or an inert gas. 2. An optical scanning module according to 1. Before Symbol Light optical element includes an optical scanning module according to any one of claims 9 to 11, characterized in that a refractive optical element. Before Symbol Light optical element includes an optical scanning module according to any one of claims 9 to 11, characterized in that an optical element in which the diffraction grating on one surface thereof are formed. The optical scanning module according to any one of claims 1 to 13 ,
Together with the illumination light scanned is irradiated by the optical scanning module, and the scale in which the diffraction grating is formed to the measurement direction a periodic direction,
A light receiving element that receives the illumination light and outputs an output signal .

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