JPH063117A - Optical rain gage - Google Patents

Abstract

PURPOSE:To obtain an optical rain gage which can measure the radius of a rain drop and the amount of rainfall with high precision in a short time. CONSTITUTION:When distances of luminescent spots formed by a reflected light and a transmitted refracted light from a rain drop 1, from the center of the rain drop on a photosensor 6, are denoted by r1 and r2, angles of incidence of the reflected light and the transmitted refracted light on the rain drop 1 by theta1 and theta2, the magnification of an imaging optical system 5 by (m) and the radius of the rain drop 1 by R, an arithmetic device 8 determines R by an equation R=(r1+r2)/m.(sintheta1+sintheta2). When a distance between the object- side principal point of the imaging optical system 5 and the rain drop 1 is denoted by H, an angle formed by the optical axis of images of first luminescent spots in a pair and by a reference line by delta1 and an angle formed by the optical axis of images of second luminescent spots in a pair and by the reference line by delta2, the amount DELTAH of deviation of the rain drop 1 from a focal surface is computed from dimensions of these delta1 and delta2 and a corrective value R' of R is determined by an equation R'=RX(H+DELTAH)/H.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light rain gauge for measuring the size of raindrops in nature and the amount of rainfall.

[0002]

2. Description of the Related Art Conventionally, among rain gauges that measure the amount of rain falling from the atmosphere to the ground,
As a rain gauge that can measure its diameter and can determine the raindrop diameter distribution, for example, a light rain gauge that calculates back the average precipitation amount on the light propagation path and the particle size distribution using scintillation of light generated by raindrops Known (Nobuhiko Murayama, “Meteorological Observations in the Future”, p44, Tokyodo Publishing (1
983))). With this light rain gauge, He- of several mW
The falling velocity of the scintillation pattern generated by raindrops by blocking the Ne laser beam is obtained by the same method as that of the optical anemometer.

In the above-described light rain gauge, it is possible to back-calculate the average precipitation amount and the particle size distribution on the propagation path from the relationship between the size of the raindrops near the ground and the final velocity. Further, it is possible to similarly obtain the raindrop diameter from the change in light intensity due to the raindrop.

However, in general, when the raindrop diameter is obtained by the change in light intensity, the measurement is performed with an analog amount, so that highly accurate detection cannot be performed. Further, in the raindrop measurement over a long period, the stability of the entire system ( There is a drawback that an expensive system is required because it is required to reduce the fluctuation of the gain of the amplifier or the like.

As a raindrop measuring device for solving the above-mentioned drawbacks, Japanese Patent Application No. 1-134544, Japanese Patent Application No. 1-139218 and Japanese Patent Application No. 2-22663.
There is a raindrop measuring device described in the specification of No. 8. In these raindrop measuring devices, when a raindrop is irradiated with light, the distance between two bright points of reflected light scattered by the raindrop and refracted light passing through the raindrop is detected and geometrical-optical calculation is performed. We are looking for raindrop size.

The above-mentioned raindrop measuring device will be described in detail with reference to FIG. This raindrop measuring device utilizes the fact that reflected light 3 and transmitted refracted light 4 obtained by irradiating each raindrop 1 with a parallel light beam 2 are emitted from each raindrop 1. Here, if the distances of the reflected light 3 and the transmitted refracted light 4 obtained from each raindrop 1 from the center of the raindrop 1 are R ₁ and R ₂ , respectively, the distance between both bright points is (R ₁ + R ₂ ). Become.

On the other hand, since the positions of both bright spots are uniquely determined by the refractive index of the raindrop 1 and the incident angle of the incident light with respect to the raindrop 1, the diameter of the raindrop 1 can be obtained from the distance (R ₁ + R ₂ ). Actually, the reflected light 3 and the transmitted refracted light 4 from the raindrop 1 are imaged on the one-dimensional optical sensor 6 by the imaging optical system 5.

Reflected light 3 and transmitted refracted light 4 on the optical sensor 6
The distances r ₁ and r ₂ of the bright spots from the raindrop center are obtained from the incident angles θ ₁ and θ ₂ of the reflected light 3 and the transmitted refracted light 4 and the magnification m of the imaging optical system 5, respectively. The radius R of is calculated by the following equation 1.

[0009]

[Equation 1]

Since (r ₁ + r ₂ ) is obtained from the signal from the optical sensor 6, the radius R of the raindrop 1 when it is regarded as a true sphere can be obtained from the equation 1. If the radius Ri of each raindrop 1 is obtained, the total volume V of raindrops is V = (4
It can be obtained as / 3) · πΣ (Ri) ³ .

In the above-mentioned detection method, unlike the above-described light rain gauge, the distance between bright spots is obtained. In other words, since an analog quantity such as scattered light quantity or light intensity change is not used, highly accurate detection is possible.

[0012]

However, in the above-described optical rain gauge, since the radius R of the raindrop depends on the magnification m of the optical image forming system as shown in the equation 1, the raindrop does not correspond to the optical image forming system. When out of focus, the size of the imaged raindrop may change. In order to avoid this and to enable highly accurate measurement, a raindrop drop hole for guiding raindrops may be provided near the focal plane of the engineering imaging system. In addition, when the raindrop drop hole is provided, raindrops other than the hole portion will be received, so the number of raindrops to be measured will eventually decrease, and it will take a long time for highly accurate measurement. There are cases.

An object of the present invention is to provide a light rain gauge capable of highly accurately measuring the diameter of a raindrop and the amount of rainfall in a short time.

[0014]

According to the present invention, illuminating means for irradiating falling raindrops with parallel rays having a beam width larger than the diameter of the raindrops, and scattering by the raindrops receiving the rays. The first pair of bright spots of the two pairs of bright spots formed by the reflected light and the transmitted refracted light that passes through the raindrops are imaged at the first position by the first optical system, and the two pairs of bright spots are formed. Of the second pair of bright spots of the image forming optical system at the second position by the second optical system at the second position, an optical sensor for receiving an image from the image forming optical system, and the optical sensor. And a calculation means for calculating the radius and the rainfall amount of the raindrop based on the detection signal from the raindrop on the optical sensor of the bright spot formed by the reflected light and the transmitted refracted light. the distance from the center and r _1, r _2, and for the raindrops of the reflected light and transmitted refracted light ₁ elevation angle theta, and theta _2, the magnification of the imaging optical system and m, the radius of the raindrop when the R, R
= (R ₁ + r ₂ ) / m · (sin θ ₁ + sin θ ₂ ), R is obtained, the distance between the object-side principal point of the imaging optical system and the raindrop is set to H, and the first pair of bright If the angle between the optical axis of the point image and the reference line is δ ₁ and the angle between the optical axis of the second pair of bright spot images and the reference line is δ ₂ , then these δ ₁ The amount of deviation ΔH from the raindrop drop position and the focal plane is calculated according to the magnitude of δ ₂ , and the correction value R ′ of R is R ′ =
It is calculated by the formula R × (H + ΔH) / H, and R ′
A light rain gauge is obtained which is characterized in that the amount of rainfall is calculated by calculating the volume of raindrops.

[0015]

Embodiments of the present invention will now be described with reference to the drawings.

As shown in FIG. 1, the light source 7 irradiates the raindrop 1 with parallel rays 2 having a beam width larger than the diameter of the raindrop 1. The scattered light from the raindrop 1 is scattered in all directions. Of these, the optical axis A of the imaging optical system 5
Along the optical axis B and those along the optical axis B are imaged at different positions on the one-dimensional photosensor 6 to generate two bright spot pairs (four bright spots in total). The one-dimensional optical sensor 6 converts the intensity of scattered light from the imaging optical system 5 into an electric signal and sends it to the arithmetic unit 8. The computing device 8 uses the calculation method described later to determine the raindrop 1
The diameter and distribution, volume, and rainfall per unit time are calculated and displayed on the display device 9.

The image forming optical system 5 for connecting two or more optical axes together can be constructed in various ways. The imaging optical system 5 shown in FIG. 2 is an optical system having optical axes A and B using the two surfaces of the prism 5a.

Raindrops 1 can be obtained by using two or more optical axes.
The image of the upper bright spot will be generated corresponding to each optical axis. At this time, the values of the angles δ ₁ and δ ₂ between the optical axes A and B and the reference line can be obtained from the one-dimensional bright spot position of the optical sensor 6. Then, a method of concretely calculating the falling position of the raindrop and the amount of deviation thereof when the raindrop 1 deviates from the focal plane depending on the magnitudes of δ ₁ and δ ₂ will be described with reference to FIG.

Consider a case where the raindrop 1 on the focal plane O is deviated to P and Q. When the raindrop 1 approaches the optical sensor 6 side from the focal plane O (point P), the image of O moves from position A to A ′ and from position B to B ′. Conversely, when moving away (point Q), the O image moves from position A to A ″ and from position B to B ″.

Generally, the diameter of the raindrop 1 is 1/100 or less with respect to the distance H between the object-side principal point of the imaging optical system 5 (which may be considered to be the lens center in a thin lens) and the object-side focus. In many cases, even if the center of two bright spots is assumed as the center of the raindrop 1, the error is extremely small. So position A,
A ′ and A ″ are values obtained by calculating the centers of the two bright spots from the raindrop 1. If necessary, the centers can be accurately calculated from R ₁ and R ₂ shown in FIG.

Using the magnification m of the imaging optical system, OO '=
AA ′ / m and OO ″ = AA ″ / m. Also OP
Is given by the following equation 2.

[0022]

[Equation 2]

OQ is given by the following equation 3.

[0024]

[Equation 3]

The approximations in the equations 2 and 3 may be adopted for simplification of calculation, but δ ₁ ′ and δ ₂ ″ may be used as they are. This method is generally used as triangulation. It is also used in rangefinders.

Although the above description has been made for the case where the raindrop 1 is on the optical axis of the one-dimensional optical sensor 6, even when the raindrop 1 deviates from the optical axis, the raindrop is based on the values of δ ₁ and δ _2. It is obvious that the drop position of 1 can be calculated and the amount of deviation from the focal plane can be obtained.

Here, if the deviation from the focal plane is ΔH and the distance between the object-side principal point of the imaging optical system 5 (think of it as the lens center in a thin lens) and the raindrop 1 is H, the raindrop 1 The size changes by (H × ΔH) / H. That is, the image is large when the raindrop 1 approaches the one-dimensional optical sensor 6 side from the focal plane (ΔH = −OP), and the opposite direction (ΔH = O).
It looks small in Q).

Therefore, R obtained by the equation (1) is (H +
By correcting by multiplying by ΔH) / H, the correction value R ′
[R ′ = R × (H + ΔH) / H] can be obtained. By calculating the volume of the raindrop 1 using this correction value R, it is possible to calculate an accurate rainfall amount.

All of the above calculations are performed by the arithmetic unit 8. In the above description, it was described that the bright spot position does not change depending on the viewing angle, but since δ ₁ and δ ₂ are smaller than θ (that is, R is smaller than H), the above is approximately correct. It is understood that the calculation is performed.

The image forming optical system 5 may be composed of a prism having three optical axes A, B and C as shown in FIG.

Further, the image forming optical system 5 may be constituted by a combination of reflecting mirrors having two optical axes A and B as shown in FIG. In an optical system that combines a reflecting mirror, when compared to an optical system that is configured with a prism, the dispersion due to the wavelength of light is similar to that of a prism (so-called spectral distribution by a prism).
Therefore, there is an advantage that a clear image can be obtained without using monochromatic light such as He-Ne laser as the parallel light beam 2.

FIG. 8 shows measurement data with and without correction of ΔH in the case of H = 370 using an optical system in which a reflecting mirror is combined. Here, a ball lens having a diameter of 3 mm and made of an optical glass material (BK-7) was used for measurement with a standard size. According to the invention,
It has been shown that the measurement can be performed with extremely high accuracy.

[0033]

According to the present invention, the diameter of raindrops and the amount of rainfall can be measured with high accuracy in a short time.

[Brief description of drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is a front view showing an optical system according to an embodiment of the present invention.

FIG. 3 is a diagram for explaining an optical system of the present invention.

FIG. 4 is a diagram for explaining a part of an optical system of the present invention.

FIG. 5 is a diagram showing an image formation state by the optical system in the present invention.

FIG. 6 is a front view showing another embodiment of the optical system according to the present invention.

FIG. 7 is a front view showing still another embodiment of the optical system according to the present invention.

FIG. 8 is a diagram for explaining measurement values obtained by the light rain gauge of the present invention and a conventional light rain gauge.

[Explanation of symbols]

 1 raindrop 3 reflected light 4 transmitted refracted light 5 imaging optical system 6 optical sensor 7 light source 8 arithmetic unit

Claims (1)

[Claims] 1. A beer larger than a diameter of a raindrop is included in a falling raindrop.
First pair at two bright spots formed by illumination means for irradiating parallel light rays having a beam width, reflected light scattered by raindrops that have received the light rays, and transmitted refracted light transmitted through the raindrops. Image of the luminescent spot of the second optical system at the first position with the first optical system, and the second pair of bright points of the two luminescent spots of the second optical system at the second position. And an optical sensor that receives an image from the imaging optical system, and an arithmetic unit that calculates the radius and the amount of rainfall of the raindrop based on a detection signal from the optical sensor. The calculation means sets the distances of the bright spots formed by the reflected light and the transmitted refracted light from the center of the raindrop on the photosensor to r ₁ and r _2, and determines the incident angles of the reflected light and the transmitted refracted light with respect to the raindrop. theta _1, and theta _2, the magnification of the imaging optical system and m, the radius of the raindrop when the R, _{= (R 1 + r 2)} / m ·
R is calculated by the equation (sin θ ₁ + sin θ ₂ ),
The distance between the object-side principal point of the imaging optical system and the raindrop is H,
The angle between the optical axis of the image of the first pair of bright spots and the reference line is δ
_1, and the angle between the optical axis and the reference line of the image of the bright spot of the second pair when the [delta] _2, from falling position and the focal plane of the raindrops by these [delta] ₁ and [delta] ₂ of the large and small The amount of deviation ΔH is calculated, the correction value R ′ of R is calculated by the formula R ′ = R × (H + ΔH) / H, and the volume of raindrops is calculated using this R ′ to calculate the amount of rainfall. A light rain gauge.