JPS61204515A - Correcting device for error of inclination sensor - Google Patents

Abstract

PURPOSE:To correct an error in measurement due to variation in the refracting index of the 1st liquid and to take an accurate measurement by providing the 2nd medium in an optical path of reflected light and setting a specific relation between its refractive index and the rate of variation in refracting index or thickness. CONSTITUTION:The 2nd medium 8 having thickness D is arranged in the optical path of the reflected light from the horizontal surface 3 of the 1st liquid 2. Then, an equation holds, where K is the ratio of variation in the refractive index between the medium 8 and liquid 2, (t) is the thickness of the air part between an image forming lens 6 and a photodetector 7, and N is the refractive index of the medium 8. Consequently, even if the liquid 2 varies in refracting index with temperature, etc., the error is corrected by the medium 8, so a slanting surface is measured accurately.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) This invention relates to an error correction device for a tilt sensor, and more particularly, to an error correction device for a tilt sensor, and more particularly, to a tilt sensor that uses a change in the refractive index of a liquid in a tilt sensor that utilizes the angle of change of reflected light from a horizontal surface of the liquid. The present invention relates to an optical mechanism for correcting inclination angle detection errors caused by tilt angle detection.

(Prior Art) Conventionally, a tilt sensor has been put into practical use that detects the tilt of a tilted needle body that holds a liquid and holds a container by utilizing the phenomenon that a liquid always forms a horizontal surface due to the action of gravity. This is because the path of the reflected light from the horizontal surface of the liquid in the container fixed to the inclinometer body deviates depending on the inclination of the inclinometer body, so by photoelectrically detecting this declination angle, This is what we are trying to find. At this time, the polarization angle of the reflected light changes according to the change in the refractive index of the liquid in the container, so
In the above-mentioned tilt angle measurement, measurement errors due to minute fluctuations in the refractive index of the liquid due to changes in temperature cannot be avoided.

To explain this in more detail, in the conventional tilt sensor system as shown in FIG. The light is emitted when the inclinometer body is θ as shown in the figure.
When the light is tilted, the angle of the incident light on the container 1 does not change, so it deflects by 20 degrees as indicated by the dashed arrow, and then when it passes through the liquid 2 and is emitted into the air, it is refracted and photographed by δ. However, for convenience's sake, before the angle θ tilts, the liquid 2
It is assumed that the light indicated by the solid arrow coming out from is not refracted,
This is a condition that does not necessarily require firing. Now, since there is a relationship of sin δ=nXsin2# at this time, this is used to detect δ and obtain the inclination angle θ. Therefore, if n changes due to a change in temperature or the like, a corresponding measurement error will occur.

(Problems to be Solved by the Invention) The present invention provides an error correction device for improving measurement accuracy by correcting measurement errors caused by changes in the refractive index of liquid in the conventional tilt sensor as described above. The purpose is to

(Means for solving the problem) In FIG. 1, the reflected light from the horizontal surface 3 of the first liquid 2 passes through the second medium 8 having a thickness D after passing through the first liquid 2. This second medium 8 is provided so as to satisfy the following relational expression.

Here, k is the ratio of the rate of change of the refractive index of the second medium 8 and the first numerical body 2, t is the thickness of the air portion between the imaging lens 6 and the light receiving detection #7, 1 = 1++11° D: Thickness of the second medium 8; N: Refractive index of the second medium 8.

(Function) The refractive index n of the first liquid 2 changes by dn, and the first liquid 2
Even if an error is introduced into the reflected light emitted from the detector 7, if the second medium is set and arranged so as to satisfy the above relational expression, this error will be compensated for and there will be no error at all in the reflected light that reaches the photodetector 7. is not introduced.

(Example) Next, the present invention will be described in detail with reference to FIGS. 1 and 2.

As shown in FIG. 1, a container 1, a light source 4, a collimating lens 5, and an imaging lens 6 are connected to the inclinometer main body (not shown).
, the light receiving detector 7 is fixed in the arrangement shown in the figure, and the container 1 is
In order to obtain parallel reflected light from the horizontal surface 3 of the liquid 2 contained in the liquid 2, the light source 4 and the collimating lens 5 are positioned on the side of the incident light beam to the surface 3, and the imaging lens 6 is positioned on the side of the reflected light.
and the light receiving detector 7 are positioned so that the image of the light source 4 is formed on the light receiving detector 7. In this way, a tilt sensor is constructed that detects the tilt angle by utilizing the displacement of the reflected light on the light receiving detector 7.

In the present invention, after the reflected light passes through the liquid 2, it passes through a second medium IX8 having a uniform thickness, such as silicone oil, to prevent measurement errors due to changes in refractive index with the first liquid. Correct. For this purpose, the refractive index and rate of change in the refractive index of the medium 8, or its thickness are set as described below.

FIG. 2 schematically shows the optical path of the tilt sensor shown in FIG. 1, and the present invention will be described in detail as follows using FIG. 1 and FIG. 2.

n, N are the refractive indices of the first liquid 2 and the second medium 8, 1=1
．． +1. is the thickness of the air portion, D is the thickness of the second medium 8,
0 is the inclination of the inclinometer body, that is, the inclination angle to be detected, a
and r are the deflection angle of the light beam emitted from the first liquid 2 and the second medium fJi! as shown in the figure. , 8, the position of the image of the light source obtained on the detector 7, that is, the displacement of the reflected light, can be expressed as follows, based on the case where θ=0.

h=h, +h snow −1−−−−−−−−−−−−−−−
-+1) However, hI=ttanδ hl=Dtanr, where sinδ=nsin2θ, N sinr=
Since there is a relationship n x sin 2θ, equation (1) becomes as follows.

If θ is small, h−t2no(t+ −) −−−−−−−□
f3). Therefore, the change in refractive index dn and the change in h due to dN, that is, the detection error dh, are as follows.

D2 n OD dh=20(t+)dn---dN-(41N
Therefore, in order to eliminate the error dh, it is sufficient that dh=o holds, so if k is the ratio of the rate of change of the refractive index of the liquid and the medium, from equation (4), if good. That is, the refractive index N and the rate of change of the refractive index d of the second medium are set so that equation (5) holds true.
The above objective can be achieved by selecting N/N or by setting the thickness D so as to satisfy D=NX t/(k-1).

(Effects of the Invention) As is clear from the above explanation, when the present invention is used, when measuring the tilt angle by detecting the deflection angle of a light beam that passes through a liquid and is reflected on its horizontal surface,
By simply adding a simple optical mechanism, it is possible to compensate for measurement errors caused by fluctuations in the refractive index of the liquid based on temperature changes, etc., making it possible to provide a sensor with a high tilt angle of 8 degrees.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of the main part of an embodiment of a tilt sensor equipped with an error correction device according to the present invention, FIG. 2 is a schematic diagram showing the optical path of the tilt sensor of FIG. 1, and FIG. 3 is a conventional FIG. 2 is a schematic diagram illustrating a tilt sensor of this type. 1-container, 2-first liquid, 3-horizontal surface of first liquid, 4-light source, 5-collimating lens, 6-imaging lens,
7-Photodetector, 8-M2 medium

Claims (2)

[Claims] (1) In a tilt sensor that detects a tilt angle based on the polarization angle of reflected light from a horizontal surface of a first liquid, the reflected light passes through a second medium having a uniform thickness after passing through the first liquid. The refractive index of the second medium, the rate of change in the refractive index, or the thickness thereof are set so as to correct a detection error due to a change in the refractive index of the first liquid. Error correction device for tilt sensor. (2) An error correction device for a tilt sensor according to claim 1, wherein the second medium is set to satisfy the following relational expression. k=(t+D/N)/(D/N) where, k: ratio of change rate of refractive index of the second medium and first liquid, t: air portion between the imaging lens and the light receiving detector thickness, D: thickness of the second medium, N: refractive index of the second medium.