JPH10176927A - Inclination sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify an optical structure, decrease a size and reduce a cost by projecting light from a light emitting element to a liquid face of a container as a parallel beam and also focusing an image of light reflected on the liquid face on a light receiving face of a light receiving element. SOLUTION: Light from a light emitting element 2 is made into parallel beam by a collimator lens 2 and, through a translucent plate-like member 3 and translucent liquid 4, is regularly reflected on a liquid face 4a being a border face between the liquid 4 in a container 7 and an air layer. The reflected light conversely propagates and makes an image on a light receiving element 6 through the liquid 4, the plate-like member 3 and the lens 2. When the inclination sensor inclines by inclination of a face 9c to be measured, the liquid face 4a keeps horizontal, while as an incident angle and a reflection angle of light with respect to the liquid face 4a vary, a position of the image formed on a light receiving face 6a of the light receiving element varies. By calculating an output signal from the light receiving element 6 at the image formation position, a light point coordinate on the light receiving face 6a can be obtained, and inclination data (direction and angle of inclination) of the face 9c to be measured can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inclination sensor for detecting the inclination of an inclined surface, and more particularly to an inclination sensor for measuring instruments and the like, which is suitable for use in cases where the sensor needs to be reduced in size and increased in accuracy. The present invention relates to an inclination sensor for detecting inclination of an inclined surface in two orthogonal directions.

[0002]

2. Description of the Related Art Among tilt sensors for detecting tilt in all directions, a sensor utilizing surface reflection of a liquid is known as a relatively small sensor capable of measuring with high accuracy.
In such an inclination sensor, a viscous liquid is used, and silicon oil is generally used because it does not change with time.

FIG. 2 shows a schematic configuration of a conventional tilt sensor. Conventional tilt sensors are, as shown in FIG.
When light enters from the bottom surface 30 of the container 50 in which the transparent liquid 40 is sealed, the light is incident at a critical angle or more (about 45 °) and reflected so as to be totally reflected on the liquid surface. That is, light from the light source 10 passes through the collimator lens 20 and enters the parallel flat glass plate 30. At this time, the 45 ° prism 70 is connected to the parallel flat glass plate 3 so that the incident light to the parallel flat glass plate 30 does not exceed the critical angle.
By bonding to zero, the incident light enters the transparent liquid without being totally reflected. The light passing through the transparent liquid 40 and reflected on the liquid surface passes through the imaging lens 80 to form an image on the two-dimensional light receiving sensor 60.

When the surface 90 on which such a sensor is installed is tilted, the container 50 is tilted and the level of the liquid 40 is also reduced.
Since the image forming position of the light reflected from the liquid surface on the light receiving sensor 60 changes with inclination to 0, the inclination of the surface on which the sensor is installed is detected. The light that has passed through the collimator lens 20 becomes substantially parallel light. If this is not parallel light,
This is to prevent the image formation position from being changed not only by the tilt of the liquid surface but also by the vertical fluctuation of the liquid surface.

[0005]

In the case of the conventional configuration as shown in FIG. 2, the collimator lens 20, the 45 ° prism 7
0, the imaging lens 80 is required, and further, the distance between the light source 10 and the light receiving sensor 60 is required due to the arrangement. Therefore, in order to increase the size of the sensor or to avoid it, it is necessary to insert an optical reflecting means (mirror, prism) in the optical path. As a result, there is a problem that the optical configuration becomes complicated, the cost is increased, and the device is also increased in size. SUMMARY OF THE INVENTION An object of the present invention is to solve the problems of the related art and to provide a small-sized and low-cost tilt sensor having a simple optical configuration.

[0006]

SUMMARY OF THE INVENTION The tilt sensor according to the present invention comprises:
In order to solve the above-mentioned problems, a container having a plate-shaped member through which light is transmitted and containing liquid therein, a light-emitting element, a light-receiving element, and the plate-shaped member as parallel rays of light from the light-emitting element. And a lens that projects light onto the liquid surface of the container via the light source and forms an image of the light reflected by the liquid surface on a light receiving surface of the light receiving element.

According to this structure, light from the light receiving element is incident on the lens, and light reflected on the liquid surface is again incident on the lens and travels toward the light receiving element. Since the 45 ° prism 70 and the imaging lens 80 of the related art shown in the drawing are not required, the optical configuration can be simplified.

With such an optical configuration, the angle of incidence of light on the liquid surface is smaller than that of the conventional sensor shown in FIG. 2, and light is incident on the liquid surface in a direction substantially perpendicular to the liquid surface. In this case, it is preferable that the container or the plate member is inclined with respect to the optical axis of the lens. When the container or the plate-like member is not tilted, light from the light-emitting element passing through the lens is partially reflected on the surface of the translucent plate-like member of the container and the ceiling portion of the container, and the reflected light May be incident on the light receiving element via the lens. However, by inclining the container or the plate-like member with respect to the optical axis of the lens, this problem does not occur, and high precision can be achieved. The inclination angle θ can be defined by the angle between the surface of the plate member of the container through which light from the light emitting element passes and the normal to the optical axis of the lens.

Further, the lens is arranged so that the optical axis of the lens is perpendicular to the liquid surface, and the light emitting element and the light receiving element are arranged at symmetrical positions with respect to the optical axis of the lens. It is characterized by the following. With this configuration, the light emitting element / light receiving element, the collimator lens,
The liquid container and the liquid container can be arranged substantially in a straight line, and can be made compact.

Further, the container or the plate-shaped member is inclined so that light other than light reflected from the liquid surface does not enter the light receiving element. Further, the inclination angle of the container or the plate-like member with respect to the optical axis of the lens is a focal length of the lens, a refractive index of the plate-like member, a refractive index of the liquid,
And the size of the light receiving element.

By detecting the two-dimensional light spot position on the light receiving surface of the light receiving element, the inclination angle of the inclined surface in two orthogonal directions can be detected.

[0012]

FIG. 1 is a side sectional view of a tilt sensor showing a configuration of an embodiment according to the present invention. This tilt sensor can measure tilt amounts in two orthogonal directions. FIG.
The tilt sensor shown in FIG. 1 includes a container 7 in which a viscous liquid 4 such as silicone oil that transmits light is accommodated, and a storage unit 8 that stores the light emitting element 1, the light receiving element 6, and the collimator lens 2 and supports them. And a mounting portion 9 for mounting, supporting and fixing the container 7 and the storage portion 8. The inclination sensor is provided with mounting screws 9a and 9b at both ends of the mounting portion 9, and a measuring surface 9c of a measuring machine or a device such as a lathe for measuring the inclination.
Installed near. The liquid 4 is preferably silicone oil in terms of stability and the like, but any other liquid may be used as long as it is a light-transmitting liquid. For example, alcohol and water may be used.

The container 7 includes a plate-like member 3 made of a light-transmitting material such as glass and having both surfaces parallel to each other, and a ceiling 5 parallel to the plate-like member 3 and is in a closed state. FIG.
In this example, the transparent plate member 3 constitutes the bottom of the container 7. The container 7 is attached to the attachment 9 at a predetermined angle with respect to the optical axis x of the lens 2. In FIG. 1, the bottom surface 3 of the parallel plate-shaped member 3 of the container 7 is shown.
This inclination angle is represented by an angle θ formed between a and the normal y of the optical axis x of the lens 2 (parallel to the liquid surface 4a).

The collimator lens 2 is disposed so that its optical axis x is perpendicular to a liquid surface 4a that is horizontal with respect to the direction of gravity. The light-emitting element 1 and the light-receiving element 6 Are disposed at substantially symmetric positions about the optical axis x of the collimator lens 2. Light from the light emitting element 1 travels in the direction m in the figure, passes through the collimator lens 2, and is reflected by the liquid surface 4 a of the liquid 4 in the container 7, and the reflected light travels through the collimator lens 2 in the direction n in the figure. Proceeds to the light receiving element 6
Is configured to be incident on the light receiving surface 6a.

The light emitting element 1 is a light emitting diode (LE)
D), a semiconductor laser or the like. The light receiving element 6 is, for example, a quadrant silicon photodiode or a CC.
It can be composed of a device that can detect a two-dimensional light spot position such as a D area sensor. For example, if the light receiving element 6 is formed of an area sensor, the output data from the light receiving element 6 at this time is calculated to determine the light spot coordinates, whereby inclination data in two orthogonal directions can be obtained. When measuring the tilt angle in one direction, a two-division silicon photodiode or a line sensor that detects a one-dimensional light spot position can be used as a light receiving element.

In the optical system arranged as described above, the light emitted from the light emitting element 1 passes through the collimator lens 2 and becomes almost parallel light, and this light is converted into a parallel flat translucent plate member 3 made of glass or the like. After passing through the liquid 4 and the light, the light is specularly reflected on a liquid surface 4a which is a boundary surface between the liquid 4 and the air layer in the container 7, and the reflected light goes backward, and the liquid 4, the plate member 3, and the collimator An image is formed on the light receiving element 6 via the lens 2.

When the tilt sensor described above is tilted as a whole due to the tilt of the measuring surface 9c, the liquid surface 4a is kept horizontal with respect to the direction of gravity, while the incident angle of light of the translucent liquid 4 with respect to the liquid surface 4a changes. And the reflection angle of the light reflected on the liquid surface 4a is 2
Since the magnification changes twice, the image forming position on the light receiving surface 6a of the light receiving element 6 changes. By calculating an output signal from the light receiving element 6 at this image forming position, light point coordinates representing the image forming position on the light receiving surface 6a are obtained. Since the imaging position on the light receiving surface 6a changes depending on the inclination angle and the inclination direction of the measurement surface 9c on which the inclination sensor is installed, the relationship between the coordinates of the imaging position and the inclination direction / inclination angle is obtained in advance. ,
The inclination data (inclination direction and inclination angle) in the two orthogonal directions on the measurement surface 9c can be obtained.

In the case of such an optical system, part of the light is specularly reflected at the liquid surface 4a of the liquid 4 as described above, and part of the light is transmitted through the liquid surface 4a. Although the light amount of specular reflection on the liquid surface 4a is smaller than the transmitted light amount, this light amount loss is not a problem due to the improvement in the performance of various light receiving sensors. However, the light caused by the regular reflection in the p direction shown in FIG. 1 on the surface 3a of the translucent plate member 3 on the way, and the diagram occurring on the inner surface 5a of the ceiling 5 of the container 7 after passing through the liquid surface 4a. If the light due to regular reflection in the r direction indicated by the broken line 1 also goes to the light receiving element 6 at the same time, an unrelated light spot forms an image on the light receiving surface 6a of the light receiving element 6. Therefore, as described above, the container 7 is inclined by a certain angle θ with respect to the normal y of the optical axis x of the lens 2, so that the surface 3 a of the light-transmitting plate-shaped member 3 has regular reflection in the p direction. Light or inner surface 5a of ceiling 5 of container 7
In this case, light due to regular reflection in the r-direction, which is caused by the above, is not directed to the light receiving element 6. Thereby, since the extraneous light does not form an image on the light receiving surface 6a of the light receiving element 6, accurate tilt detection can be performed.

The reflection angles of the specularly reflected light in the p direction and the specularly reflected light in the r direction are determined by the focal length of the lens 2, the refractive index of the plate member 3, and the refractive index of the liquid 4. The inclination angle θ is determined by considering the focal length of the lens 2, the refractive index of the plate member 3, and the refractive index of the liquid 4, and further considering the diameter d of the light receiving surface 6a of the light receiving element 6, It can be determined not to receive such unnecessary reflected light.

As described above, in the tilt sensor shown in FIG. 1, the optical axis x of the collimator lens 2 is arranged in a direction perpendicular to the liquid surface 4a, instead of utilizing the total reflection as in the prior art shown in FIG. Then, the light emitting element 1 was arranged eccentrically from the optical axis x, and the light receiving element 6 was arranged at a position optically symmetric with respect to this position. Thus, the light-emitting element 1, the light-receiving element 6, the collimator lens 2, and the liquid-tight container 7 can be arranged substantially in a straight line, and can be made compact. Also, the collimator lens 2
2 can be used for both the purpose of directing the light from the light emitting element 1 to the liquid surface 4a and the purpose of directing the reflected light from the liquid surface 4a to the light receiving element 6;
Since the prism 70 can be omitted, the cost can be greatly reduced.

The present invention is not limited to the embodiment shown in FIG. 1, and various modifications can be made within the technical idea of the present invention. For example, a configuration in which the tilt sensor shown in FIG. 1 is upside down may be adopted.

Further, the inner surface 5a of the ceiling 5 of the container 7 shown in FIG. 1 can be formed as an anti-reflection surface. For example,
By forming an antireflection film, for example, an antireflection coating film on the surface 5a, reflection on the surface 5a can be preferably reduced.

[0023]

According to the present invention, a tilt sensor having an optical configuration simpler than the conventional one can be constructed. According to the configuration in which the container or the plate-like member is inclined, unnecessary light can be prevented from entering the light receiving element, and accurate inclination detection can be performed. Therefore, it is possible to provide a small-sized, low-cost, high-precision tilt sensor having a simple optical configuration.

[Brief description of the drawings]

FIG. 1 is a side sectional view showing a configuration of a tilt sensor according to an embodiment of the present invention.

FIG. 2 is a side sectional view showing a tilt sensor using total reflection of a liquid surface according to the related art.

[Explanation of symbols]

 Reference Signs List 1 light emitting element 2 collimator lens 3 translucent plate member 3a surface of plate member 3 liquid 4a liquid surface 5 ceiling 6 light receiving element 6a light receiving surface 7 container x optical axis of lens 2 y normal to optical axis x θ Angle between normal y and surface 3 a of plate-shaped member 3

Claims (6)

[Claims] 1. A container having a plate-like member through which light is transmitted and containing a liquid therein, a light-emitting element, a light-receiving element, and the container through the plate-like member as a parallel beam of light from the light-emitting element. A lens that projects light onto the liquid surface and forms an image of the light reflected on the liquid surface on a light receiving surface of the light receiving element. 2. The apparatus according to claim 1, wherein the container or the plate-like member is inclined with respect to an optical axis of the lens.
The tilt sensor according to any one of the preceding claims. 3. The lens is disposed such that an optical axis of the lens is perpendicular to the liquid surface, and the light emitting element and the light receiving element are disposed at symmetric positions with respect to the optical axis of the lens. The tilt sensor according to claim 1 or 2, wherein 4. The inclination according to claim 1, wherein the container or the plate member is inclined so that light other than light reflected from the liquid surface does not enter the light receiving element. Sensor. 5. The inclination angle of the container or the plate-like member with respect to the optical axis of the lens depends on the focal length of the lens, the refractive index of the plate-like member, the refractive index of the liquid, and the size of the light-receiving element. 5. The tilt sensor according to claim 2, wherein the tilt sensor is determined. 6. The light receiving element according to claim 1, wherein the light receiving element detects a two-dimensional light spot position on the light receiving surface.
The tilt sensor according to 2, 3, 4 or 5.