JP2009294154A - Inclination sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inclination sensor for accurately detecting the slope of an attached member. <P>SOLUTION: Light emitted by a laser diode 110 is converted into circularly polarized light via a collimator lens 120 and a first λ/4 plate 130. Of the circularly polarized light, P-polarized light passes through a reflective surface 141 and is applied as reference light to an imaging element 190 while S-polarized light is reflected as measurement light by the reflective surface 141. The measurement light is converted into S-polarized light by a second λ/4 plate 150, a mirror surface 161, a third λ/4 plate 170, and a fixed mirror 180, and enters the imaging element 190. A weight body 162 with the mirror surface 161 formed thereon is rockable relative to a polarizing beam splitter 140. Therefore, the optical path of light incident on the mirror surface 161 and that of reflected light are not identical when this inclination sensor 100 is inclined. That is, interference fringes are formed by the reference light and the measurement light on an imaging surface 191. An inclination angle calculation part 192 measures an inclination angle θ of the inclination sensor 100 by measuring the number and direction of the interference fringes. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a tilt sensor that detects the tilt of an attached member.

2. Description of the Related Art Conventionally, a tilt sensor including a swingable electrode and a fixed electrode is known. When the tilt sensor tilts, the swingable electrode swings according to the tilt, and the distance from the fixed electrode changes. Since the amount of charge accumulated between the electrodes changes due to the change in the interval, an inclination sensor that detects the inclination by detecting the change in the amount of charge is known.
JP 2003-329444 A

  However, when the tilt sensor is miniaturized in accordance with the demand for miniaturization of the device, the amount of charge that can be accumulated between the electrodes decreases. As a result, the amount of change in charge caused by the oscillation of the electrode is also reduced, so that the S / N ratio of the signal output from the tilt sensor is lowered according to the amount of change in charge.

  An object of this invention is to obtain the inclination sensor which can detect the inclination of the attached member correctly.

  A tilt sensor according to a first invention of the present application includes a first polarizing plate that converts incident light into first light having a first polarization direction and second light having a second polarization direction; An optical splitter that receives the second light, transmits the first light, and changes the traveling direction of the second light; a mirror that reflects the second light; and an elastic body that swayably supports the mirror An interference fringe measurement that receives the first light transmitted through the optical splitter and the second light reflected by the mirror and observes the interference fringes formed by the first light and the second light. And a section.

  It is preferable that the light emitting device further includes a light emitting device, and the light emitting device projects light onto the first lens.

  It is desirable to further include a first lens that converts incident light into parallel light and irradiates the first polarizing plate, and the first polarizing plate preferably converts the parallel light incident from the first lens.

  You may further provide the inclination angle calculation part which detects the inclination of an inclination sensor using the interference fringe which the interference fringe measurement part observed.

  It is preferable to further include a second polarizing plate that converts the polarization state of the light incident on the inclined mirror and the light reflected by the inclined mirror.

  It is preferable to further include a fixed mirror that reflects the light reflected by the inclined mirror, and a third polarizing plate that converts the polarization state of the light incident on the fixed mirror and the light reflected by the fixed mirror.

  As described above, according to the present invention, an inclination sensor capable of accurately detecting the inclination of an attached member is obtained.

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

  First, the configuration of the tilt sensor 100 will be described.

  The tilt sensor 100 includes a laser diode 110 that is a light emitting element that emits laser light, a collimator lens 120 that is a first lens that converts diffused light into parallel light, and first to third polarizing plates. To third λ / 4 plates 130, 150 and 170, an inclined mirror 160 whose reflection angle changes due to its own weight, a fixed mirror 180 which does not change its reflection angle, and an image sensor 190 such as a CCD that forms an interference fringe measurement unit. The optical beam splitter mainly divides incident light, that is, a polarization beam splitter 140.

  The inclined mirror 160 includes a rectangular tube-shaped frame body 164, a weight body 162 that is a rectangular parallelepiped having a constant weight, and an elastic body 163 that is provided inside the frame body 164 and connects the frame body 164 and the weight body 162. It consists of. The weight body 162 has a constant weight, one side forms a mirror surface 161, and is provided inside the frame body 164. The elastic body 163 connects the side surface perpendicular to the mirror surface 161 in the weight body 162 and the inner side surface of the frame body 164. The inclined mirror 160 is integrally formed of silicon.

  The polarization beam splitter 140 is a rectangular parallelepiped and has a reflection surface 141 that is a plane passing through the two sides. P-polarized light is transmitted through the reflecting surface 141, and S-polarized light is reflected.

  The first to third λ / 4 plates 130, 150, and 170 are attached to three surfaces of the surface of the polarization beam splitter 140 that does not intersect with the reflecting surface 141, that is, the surface facing the reflecting surface 141. The imaging element 190 is attached to the remaining one surface so that the imaging surface 191 faces the other surface.

  The collimator lens 120 is attached to the back surface of the surface of the first λ / 4 plate 130 attached to the polarization beam splitter 140 so that the optical axis thereof is perpendicular to the surface of the polarization beam splitter 140.

  The laser diode 110 is attached to the back surface of the surface attached to the first λ / 4 plate 130 in the collimator lens 120.

  A frame body 164 of the tilting mirror 160 is attached to the back surface of the surface attached to the polarization beam splitter 140 in the second λ / 4 plate 150. That is, the weight body 162 and the mirror surface 161 are swingable with respect to the polarization beam splitter 140. When the elastic body 163 is not distorted, the inclined mirror 160 is attached to the second λ / 4 plate 150 so that the mirror surface 161 is horizontal to the surface of the polarization beam splitter 140.

  A fixed mirror 180 is attached to the back surface of the third λ / 4 plate 170 attached to the polarization beam splitter 140. That is, the laser diode 110, the collimator lens 120, the first to third λ / 4 plates 130, 150, 170, the fixed mirror 180, and the image sensor 190 are fixed to the polarization beam splitter 140.

  The imaging element 190 transmits an image formed on the imaging surface 191 to the tilt angle calculation unit 192. The tilt angle calculation unit 192 calculates the tilt angle of the tilt sensor 100 using the image transmitted from the image sensor 190.

  By providing the laser diode 110, the collimator lens 120, the first to third λ / 4 plates 170 130, 150, 170, the tilt mirror 160, the fixed mirror 180, and the image sensor 190 directly on the polarization beam splitter 140, the tilt sensor 100. Can be miniaturized.

  Further, by using a surface emitting laser diode as the laser diode 110, the inclination sensor 100 can be further reduced in size.

  Next, the function and operation of the tilt sensor 100 will be described.

  The light emitted from the laser diode 110 enters the collimator lens 120. This light is linearly polarized light. The collimator lens 120 converts incident light into parallel light.

  The parallel light is incident on the first λ / 4 plate 130. The first λ / 4 plate 130 converts parallel light that is linearly polarized light into circularly polarized light. The phases of P-polarized light and S-polarized light in this circularly polarized light are shifted by 90 degrees. Circularly polarized light enters the polarization beam splitter 140. Of the circularly polarized light, the P-polarized light is transmitted through the reflecting surface 141 and is emitted from the surface where the imaging element 190 is removed in the polarizing beam splitter 140. This light is called reference light and is shown by a solid line in FIG.

  Of the circularly polarized light incident on the polarizing beam splitter 140, S-polarized light is reflected by the reflecting surface 141. This light is called measurement light, and is indicated by a broken line in FIG. The measurement light is emitted from the surface on which the second λ / 4 plate 150 is attached in the polarization beam splitter 140 and passes through the second λ / 4 plate 150. Then, it is reflected by the mirror surface 161 and passes through the second λ / 4 plate 150 again. By passing through the second λ / 4 plate 150 twice, the measurement light is converted from S-polarized light to P-polarized light.

  The reference light that has become P-polarized light passes through the reflecting surface 141 and enters the third λ / 4 plate 170. The reference light that has passed through the third λ / 4 plate 170 is reflected by the fixed mirror 180 and passes through the third λ / 4 plate 170 again. By passing the third λ / 4 plate 170 twice, the measurement light is converted from P-polarized light to S-polarized light. The measurement light that has become S-polarized light is reflected again by the reflecting surface 141. Then, the light enters the image sensor 190.

  Since the weight body 162 having the mirror surface 161 is connected to the frame body 164 via the elastic body 163, the weight body 162 can swing with respect to the polarization beam splitter 140. When the tilt sensor 100 is not tilted with respect to gravity, the mirror surface 161 is parallel to the surface of the polarization beam splitter 140 to which the tilt mirror 160 is attached (see FIG. 1). For this reason, the traveling directions of the reference light and the measurement light incident on the imaging surface 191 are parallel, and no interference occurs between the reference light and the measurement light (see FIG. 4).

  On the other hand, when the tilt sensor 100 is tilted with respect to gravity, the mirror surface 161 is not parallel to the surface of the polarizing beam splitter 140 to which the tilt mirror 160 is attached. Therefore, the light paths of the light incident on the mirror surface 161 and the reflected light are not the same, and the traveling directions of the reference light and the measurement light incident on the imaging surface 191 are not parallel (see FIG. 2). For this reason, a phase difference occurs between the reference light and the measurement light on the imaging surface 191, and interference occurs between the reference light and the measurement light. Due to this interference, interference fringes are formed on the imaging surface 191 (see FIGS. 5 to 7).

  Next, the principle of calculating the tilt angle from the number and direction of interference fringes will be described.

  FIG. 3 is a view of the mirror surface 161 as viewed from the polarization beam splitter 140 side. In accordance with the right-handed system, the Y-axis is placed on the mirror surface 161 toward the laser diode 110, the Z-axis is directed perpendicularly to the mirror surface 161 toward the polarization beam splitter 140, and the X-axis is placed from the front toward the back in FIG. . Gravity acts in the negative Y-axis direction.

  FIG. 5 shows interference fringes appearing on the imaging surface 191 when the weight body 162 is inclined with respect to gravity by θx ° around the X axis. At this time, the interference fringes are parallel to the X axis. When the weight body 162 is tilted counterclockwise about the X axis, the number of interference fringes increases from the Z axis negative direction toward the positive direction as the tilt angle θx ° increases. When the weight body 162 is tilted clockwise about the X axis, the interference fringes move from the positive direction of the Z axis toward the negative direction as the tilt angle θx ° increases. By observing this moving direction, it is possible to detect in which direction the weight 162 is inclined around the X axis. Further, the value of θx ° can be detected by examining the number of interference fringes.

  FIG. 6 shows interference fringes appearing on the imaging surface 191 when the weight body 162 is inclined with respect to gravity by θy ° around the Y axis. At this time, the interference fringes are parallel to the Z axis. When the weight body 162 is tilted counterclockwise about the Y axis, the number of interference fringes increases from the negative X axis direction toward the positive direction as the tilt angle θy ° increases. When the weight body 162 is tilted clockwise around the Y axis, the interference fringes move from the X axis positive direction toward the negative direction as the tilt angle θy ° increases. By observing this moving direction, it is possible to detect in which direction the weight 162 is inclined around the Y axis. Further, the value of θy ° can be detected by examining the number of interference fringes.

  FIG. 7 shows interference fringes that appear on the imaging surface 191 when the weight 162 is inclined with respect to gravity by θα ° around an axis that forms α ° with the X axis. At this time, the interference fringes extend in the direction of α ° with respect to the X axis. The tilt direction and tilt angle θα ° of the weight body 162 can be detected in the same manner as when the weight body 162 tilts around the X axis or the Y axis.

  According to the present embodiment, since the signal output from the tilt sensor 100 is a signal output from the image sensor 190, the S / N ratio is higher than that of a conventional tilt sensor that outputs charges accumulated between electrodes. A signal can be obtained.

  In addition, since the present embodiment uses light interference, it is possible to measure a minute inclination angle by adjusting the elasticity of the elastic body 163.

  The inclined mirror 160 does not have to be made of silicon, and may not be formed integrally.

It is the figure which showed notionally the cross section of the inclination sensor. It is the figure which showed notionally the cross section when an inclination sensor inclines. It is the figure which looked at the mirror surface from the polarization beam splitter side. It is the figure which looked at the image pick-up surface from the polarization beam splitter when the inclination sensor is not inclined. It is the figure which looked at the image pick-up surface from the polarization beam splitter when the inclination sensor inclines. It is the figure which looked at the image pick-up surface from the polarization beam splitter when the inclination sensor inclines. It is the figure which looked at the image pick-up surface from the polarization beam splitter when the inclination sensor inclines.

Explanation of symbols

Reference Signs List 100 tilt sensor 110 laser diode 120 collimator lens 130 first λ / 4 plate 140 polarization beam splitter 150 second λ / 4 plate 160 tilt mirror 170 third λ / 4 plate 180 fixed mirror 190 imaging device

Claims (6)

A first polarizing plate that converts incident light into first light having a first polarization direction and second light having a second polarization direction;
An optical splitter that receives the first light and the second light, transmits the first light, and changes a traveling direction of the second light;
An inclined mirror having a mirror that reflects the second light and an elastic body that swingably supports the mirror;
Interference fringe measurement for receiving the first light transmitted through the light splitter and the second light reflected by the mirror and observing interference fringes formed by the first light and the second light. And a tilt sensor.   The tilt sensor according to claim 1, further comprising a light emitting element, wherein the light emitting element projects light onto the first lens. A first lens that converts incident light into parallel light and irradiates the first polarizing plate;
The tilt sensor according to claim 1, wherein the first polarizing plate converts parallel light incident from the first lens.   The inclination sensor according to claim 1, further comprising an inclination angle calculation unit that detects an inclination of the inclination sensor using the interference fringe observed by the interference fringe measurement unit.   The tilt sensor according to claim 1, further comprising a second polarizing plate that converts a polarization state of light incident on the tilt mirror and light reflected by the tilt mirror. A fixed mirror that reflects the light reflected by the tilt mirror;
The tilt sensor according to claim 1, further comprising a third polarizing plate that converts a polarization state of light incident on the fixed mirror and light reflected by the fixed mirror.