JP2655276B2 - Tilt angle detector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tilt angle detector for electrically detecting a tilt angle of an object to be measured with respect to a horizontal or gravity direction.

(Prior Art) As a conventional tilt angle detector, a bubble tube in which a gas and a transparent liquid are sealed in a transparent container having an upper inner surface formed into a spherical concave surface, and a bubble tube directed upward or downward toward the bubble tube A light transmitting unit for irradiating light, a light receiving element for converting light transmitted through the bubble tube into an electric signal (for detecting a position of a quadrant of a circle), and a calculating unit for calculating an inclination angle based on the electric signal The light from the light transmitting unit that has passed through the bubble tube is received by the light receiving element, and the bubble shadow b formed on the light receiving element a relatively moves on the light receiving element a according to the inclination angle as shown in FIG. It is known that a change in the light amount distribution caused by changing the position is regarded as an electrical change by the light receiving element a, and the change is calculated by an arithmetic unit to measure the tilt angle photoelectrically.

(Problems to be Solved by the Invention) However, according to the above-described conventional tilt angle detector, a change in bubble diameter due to a change in temperature, a change in light emission intensity of a light transmitting unit, a change in photoelectric conversion sensitivity of a light receiving element, and the like. In addition, there is an inevitable disadvantage that a large error enters the measurement result.

In addition, since the bubble shadow is circular, sensitivity is reduced when the inclination angle is increased, which limits the measurement range to be narrowed, and requires correction or the like to obtain a correct inclination angle. There was an inconvenience to do.

The reason why the sensitivity is reduced when the inclination angle increases is described below. The output of the light receiving element is proportional to the amount of light incident on the element, and the amount of light is proportional to the irradiation area.
In order to detect the inclination in the direction, the area difference M between the two irradiation portions of the light receiving element divided on the Y axis may be obtained. This area difference M is However, R: the radius of curvature of the bubble tube, θ _X : the inclination angle in the direction, r: the radius of the bubble shadow The inclination detection sensitivity G is proportional to the amount of the area difference M differentiated by the inclination angle θ _X. This is illustrated in FIG. That is, θ _X
When = 0, G = 4Rr, which is the maximum value, G decreases as the inclination increases, and G = 0 when θ _X = r / R.

A change in the sensitivity means that an error occurs in the measured value unless the sensitivity is corrected. In a state such as G = 0, the output does not change even if a gradient is applied. It becomes impossible to do.

 The above can be applied to the inclination in the Y direction.

(Means for Solving the Problems) An object of the present invention is to eliminate the above-mentioned inconvenience, and it is an object of the present invention to provide an air bubble formed by enclosing a gas and a transparent liquid in a transparent container having an upper inner surface formed into a spherical concave surface. A tube, a light transmitting unit that irradiates light from above or below toward the bubble tube, a light receiving element that converts light transmitted through the bubble tube into an electric signal, and a calculation unit that calculates an inclination angle based on the electric signal Wherein the light receiving element comprises a light receiving portion for position detection within the movable range of the bubble shadow and a light receiving portion for reference outside the movable range, and the light receiving portion for position detection comprises a pair of rectangular light receiving portions. The pieces are arranged so that their center lines in the longitudinal direction along the tilt detection direction coincide with each other, and the width of each rectangular light receiving piece is equal and smaller than the diameter of the bubble shadow.

(Operation) According to the present invention, the light from the light transmitting unit transmitted through the bubble tube is irradiated on the light receiving unit for detecting the position of the light receiving element so as to form a bubble shadow. At the same time, the light is irradiated onto the reference light receiving unit. The position-detecting light-receiving unit detects and outputs the change in the light amount distribution caused by the relative change in the position of the bubble shadow according to the tilt angle as an electrical change. Changes such as conversion sensitivity are output as electrical changes. Outputs from the respective light receiving units, which are proportional to the irradiation area, the irradiation intensity, and the like, are input to a calculation unit, where they are calculated to obtain the inclination angle.
When this is done, the light emission intensity of the light transmitting section,
Even if the photoelectric conversion sensitivity fluctuates, this fluctuation is reliably captured by the reference light-receiving unit and compensated by the calculation unit, as well as errors due to changes in bubble diameter and sensitivity reduction when the tilt angle becomes large. Since the compensation is performed by the calculation unit, there is no room for a large error in the measurement result, and the inclination angle can be accurately measured.

(Example) Next, an example of the present invention will be described with reference to the drawings.

1 to 3, reference numeral 1 denotes a bubble tube. The bubble tube 1 is formed by enclosing a transparent liquid 5 with bubbles 4 in a transparent container 3 having an upper inner surface formed into a spherical concave surface 2. .

A light transmitting unit 6 is provided below the bubble tube 1, and the light transmitting unit 6 includes a light source 7 such as a light emitting diode and a lens 8 for irradiating the light from the light source 7 to the lower portion of the bubble tube 1 in parallel. Consisting of

Above the bubble tube 1, a light receiving element 9 is disposed, which converts light transmitted through the bubble tube into an electric signal and detects a two-dimensional tilt angle, that is, a tilt angle in the XY direction. , A position detecting light receiving unit 11 provided within the movable range of the bubble shadow 10 and a reference light receiving unit 12 provided outside the movable range.

The position detecting light receiving unit 11 is configured by connecting a pair of rectangular light receiving pieces 13 and 14 to X.
And the other pair of rectangular light receiving pieces 15 and 16 are arranged so that the longitudinal center lines along the Y direction coincide with each other. .

Each rectangular light receiving piece 13, 14, 15, 16 had the same dimensions, and their width was smaller than the diameter of the bubble shadow 10.

Reference numeral 17 denotes a calculation unit which receives an electric signal from the position detecting light receiving unit 11 and an electric signal from the reference light receiving unit 12 and calculates an inclination angle.

At this time, the light from the light source 7 that has passed through the bubble tube 1 is transmitted to the four rectangular light receiving pieces 13, 14, 15, and 1 serving as the position detecting light receiving unit 11.
At the same time, the light is irradiated so as to form the bubble shadow 10 on the reference light receiving unit 12. The electrical output from both light receiving units 11 and 12 in proportion to the irradiation area, irradiation intensity, etc.
The outputs from the position detecting light-receiving unit 11 are different from each other in the X direction, that is, between the rectangular light receiving pieces 13 and 14, and between the outputs in the Y direction, that is, between the rectangular light receiving pieces 15 and 16. The value of the difference is divided by the value of the output of the reference light receiving unit 12. The result of the division is a value proportional to only the position of the bubble shadow 10, that is, a value proportional to the inclination, irrespective of error factors of fluctuations such as the diameter of the bubble shadow 10 and the irradiation intensity. In this case, a correct inclination angle can be obtained by performing an inverse operation based on the divided result.

The detection of the tilt in the X direction can be considered as follows.

That is, the bubble shadow 10 shown in FIG.
Is formed, the output from each of the rectangular light receiving pieces 13, 14, 15, 16 of the position detecting light receiving unit 11 is an area S ₁₃ , which is irradiated with light from the light source 7 passing through the bubble tube 1. S ₁₄ , S ₁₅ , S ₁₆
Is output in proportion to. The irradiation areas S ₁₃ and S ₁₄ are obtained by the following equations.

Here, the width and length of the rectangular light receiving pieces 13 and 14 are D and L, the radius of the bubble shadow 10 is r, and the radius of curvature of the upper inner surface of the bubble tube 1 is R and XY.
The inclination components of the directions are θ _X and θ _Y. The rectangular light receiving pieces 13,1
When the centers of 4,15,16 and bubble shadow 10 are coincident,
That is, a state in which the center 0 'of the bubble shadow 10 and the origin 0 of the XY axis coincide is regarded as horizontal.

Emission intensity of light transmitting unit 6 and light receiving units 11 and 12 per unit area
Assuming that a coefficient taking into account the photoelectric conversion efficiency and the like of K is K, the outputs V ₁₃ , V ₁₄ , and V ₁₂ of the light receiving pieces 13, ₁₄ , and ₁₂ are V ₁₃ =
KS ₁₃ , V ₁₄ = KS ₁₄ , V ₁₂ = KS ₁₂ , and the following value T _X is obtained. As a result, T _X becomes a value proportional to the inclination angle θ _X ,
From this equation (1) Is obtained, and the inclination angle θ _X in the X direction is obtained.

That is, the output V _{13 of} the light receiving piece 13, the light receiving piece 14, and the light receiving section 12,
When the value of T _X is obtained from V ₁₄ and V ₁₂ , as shown in equation (1), the value of T _X takes into account the radius r of the bubble shadow 10 affected by temperature, the photoelectric conversion efficiency, and the like. Since the coefficient K is not included, if θ _X is calculated by the equation (2), the correct X independent of the temperature, the light emission intensity of the light transmitting unit 6 and the photoelectric conversion sensitivity is obtained.
The inclination angle of the direction can be determined.

Obviously, the inclination angle in the Y direction can be obtained in a similar manner.

Turning now seeking sensitivity to tilt angle, is _{G = dT X / dθ X =} 2DR / S 12 = constant from equation (1). That is, the sensitivity is constant over the entire measurement range, as shown by the dashed line in FIG. Therefore, correction for obtaining a correct tilt angle becomes unnecessary, and the measurement range is widened.

 The above can be applied to the inclination in the Y direction.

It should be noted that the order of the subtraction and the division for obtaining T _X does not matter whichever, and the method may be either analog or digital.

Further, it is possible to a K a constant by applying a control to a constant value of V _12, it is also possible to eliminate the division.

Further, it is obvious that the reference light receiving unit 12 may have any shape, any number, and any position as long as the irradiation intensity and the photoelectric conversion sensitivity can be detected.

FIG. 4 shows another embodiment of the present invention. In this case, the position detecting light-receiving unit 11 is one of the above-described embodiments in the X direction.
A pair of light-receiving pieces 13 and 14 are provided, and a pair of light-receiving pieces 18 and 19 serving as a reference light-receiving section 12 are provided on both outer sides thereof. In this embodiment, an accurate tilt angle in the X direction can be obtained in exactly the same manner as in the above embodiment.

If the shapes of the position detecting light-receiving unit 11 and the reference light-receiving unit 12 are made particularly in the two embodiments described above, the calculation formula of the inclination angle θ is simplified, the linearity is improved, and the measurement range is widened. .

(Effect of the Invention) As described above, according to the present invention, the light receiving element for converting the light transmitted through the bubble tube into an electric signal is provided within the movable range of the bubble shadow and the position detecting light receiving unit is provided for reference outside the movable range. The position detecting light-receiving section is provided with a pair of rectangular light-receiving pieces such that the center lines in the longitudinal direction along the tilt detection direction coincide with each other, and the width of each rectangular light-receiving piece is equal, The diameter of the bubble shadow is made smaller than the diameter of the bubble shadow, so the electrical output from both light receiving units is processed by the calculation unit to change the bubble diameter due to temperature, etc., and the photoelectric characteristics of the sending / receiving unit. Measurement errors due to changes in
There is an effect that the detection accuracy can be maintained even under conditions where there is a change in temperature, a change in light emission intensity of the light transmitting unit, and a change in photoelectric conversion sensitivity of the light receiving unit. Further, since the sensitivity is constant over the entire measurement range irrespective of the tilt angle, there is an effect that the measurement range is not restricted and correction for obtaining a correct tilt angle is not required.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an embodiment of the present invention, FIG. 2 is a two-dimensional array diagram of the light receiving element, FIG. 3 is a positional relationship between the light receiving element and a bubble shadow, and FIG. FIG. 5 is a diagram showing a positional relationship between a light receiving element and a bubble shadow according to another embodiment of the invention, FIG. 5 is a diagram showing a positional relationship between a light receiving element and a bubble shadow according to a conventional example, and FIG. FIG. DESCRIPTION OF SYMBOLS 1 ... Bubble tube 2 ... Concave surface 3 ... Transparent container 4 ... Bubble 5 ... Transparent liquid 6 ... Light transmitting part 9 ... Light receiving element 10 ... Bubble shadow 11 ... Position detecting light receiving part 12 ... Reference light receiving parts 13, 14, 15, 16 ... Light receiving pieces of position detecting light receiving parts 17 ... Calculation parts 18, 19 ... Light receiving parts of reference light receiving parts

Claims (1)

(57) [Claims] 1. A bubble tube in which a gas and a transparent liquid are sealed in a transparent container having an upper inner surface formed into a spherical concave surface, and a light transmitting unit for irradiating light from above or below toward the bubble tube. A light-receiving element that converts light transmitted through the bubble tube into an electric signal,
A tilt angle detector including a calculating unit that calculates a tilt angle based on the electric signal, wherein the light receiving element includes a position detecting light receiving unit within a movable range of the bubble shadow and a reference light receiving unit outside the movable range. The position detecting light receiving unit is provided with a pair of rectangular light receiving pieces arranged such that their center lines in the longitudinal direction along the tilt detection direction coincide with each other. The width of each rectangular light receiving piece is equal and smaller than the diameter of the bubble shadow. An inclination angle detector characterized by comprising: