JPH0531100B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for instantly and accurately measuring visibility at airports, ports, expressways, etc.

<Conventional technology and its problems> The conventional visual distance measurement method calculates the attenuation coefficient σ of light traveling through fog using the theory of monodisperse aerosol gas (consisting of fine particles with the same particle size).
A method of calculating the viewing distance V using Koschmieder's formula V = 3/σ or 3.9/σ, or a method of photoelectrically converting the light coming from the visible object using a photocell and outputting an analog voltage, and calculating only the light scattered by aerosol. There is a method of finding the attenuation coefficient σ and calculating the viewing distance V using the Koschmieder equation.

However, although these methods are successful in precisely measuring the particle size distribution in the process of calculating the extinction coefficient σ, which is the overall effect of polydisperse aerosol gas (consisting of fine particles of various particle sizes), they have many problems. There is a problem in that it is very difficult to mathematically analyze the reaction of the dispersion model to light, and when calculating the viewing distance V, it is difficult to calculate the distance V when the object is simply viewed at infinity without directly measuring the light coming from the background. Because it is replaced by the amount of light, if there is a relatively nearby forest or mountain in the background of the object, the viewing distance V
There was a problem that a large error occurred.

<Means for Solving the Problems> The present invention attempts to solve the above-mentioned problems, and its gist is to provide a subject having a light-emitting section, an approximate blackbody section, and an illuminance meter, and an object for observation. Using a solid-state camera, the light emission of the light emitting part of the object to be viewed is set to 0, and the brightness per unit area of the approximate blackbody part is measured as y ₁ and the brightness per unit area of the background light as y ₂ . Light is emitted from the light emitting part of the object, and the brightness per unit area of the light emitting part at that _time is measured, and the brightness per unit area of the external light A(0) is measured using the above illuminance meter.
This method calculates the visibility of each object from these y ₁ , y ₂ , y ₃ and A(0).

<Embodiments and Operations> The method of the present invention will be described in detail below with reference to the drawings showing an apparatus for carrying out the method.

FIG. 1 is an explanatory diagram showing an example of an apparatus used in the method of the present invention, in which a subject 1 and an observation solid-state camera 2 are disposed facing each other with a certain distance between them. As shown in FIG.
The solid-state camera 2 is equipped with a light-shielding tube 6 having a built-in telephoto lens as shown in FIG.
and is connected to a microcomputer type control device 7.

The internal structure of the object to be viewed 1 is shown in FIG. 4, and as shown in FIG. The solid-state camera 2 sends the image captured on its light-receiving surface to the microcomputer control device 7, and therefore, the image of the object to be viewed is the same as the image stored in the main memory of the microcomputer control device 7. You can understand it.

Now, when light is incident on a gas containing floating particles (aerosol gas), the light is scattered and absorbed, and the intensity of the incident light gradually attenuates. When the incident light is a parallel ray, this relationship is given by I=Ioe ^- 〓, and this equation is called Bouguer's (or Lambert-Beer's) law. Here, Io is the initial intensity of the incident light, I is the intensity at the point where the light has traveled the distance, and σ is the attenuation coefficient of the fine particles.

When Bouguer's law is applied to the observation of any object on the ground, for the light emitted from the object...B ₁ () = B ₁ (0)
e ^- 〓 For the light coming from the background of the object...B ₂ () = B ₂
(0) e ^- 〓 Against scattered light from the sun, night lights, etc....B ₃
()=B ₃ (∞) (1-e ^- 〓) Therefore, the contrast C(0) at the position of the object (=0) is C(0)=B ₁ (0)-B ₂ ( 0)/B ₂ (0)=B ₁ (0)/
B ₂ (0)-1 Contrast C() at a distance from the object
is C()=
{B ₁ () + B ₃ ()} − {B ₂ () + B ₃ ()} /B ₂
()+B ₃ () However, B ₁ (0) and B ₂ (0) are B ₁ () and B ₂ respectively
() at =0, and B ₃ (∞)
is the limit value of B ₃ () at = infinity.
B ₃ () is obtained by integrating a differential equation such that dB/d=−σB+Ba, and B ₃ (∞)=Ba/σ.
Ba is the amount of sunlight mixed in per unit length, and σB is the amount of reduction due to scattering per unit length.

This method handles it approximately, but if you want to make more precise measurements, B ₃ (∞) of B ₃ (∞) = Ba / σ can be changed depending on the angle of sunlight. Let me point out something different.

In the method of the present invention, the light-receiving element or camera filter in the solid-state camera 2 has a standard luminous efficiency characteristic that is the spectral characteristic of the human eye, and the light-emitting part 3 of the subject
The next measurement is performed by making it possible to blink freely by a command from the microcomputer type control device 7. That is, the measurement is performed with the light emission of the object's light emitting section set to 0 (light source dimmed). As a result, the approximate blackbody part (Fig. 2 4)
The brightness per unit area of the surface y ₁ and the brightness per unit area of the background light (Fig. 5, 6) y ₂ are obtained.

y ₁ = B ₁ ( ₀ ) + B ₃ ( ₀ ) = 0 + B ₃ ( ₀ ) = B ₃ ( ₀ ) y ₂ = B ₂ ( ₀ ) + B ₃ ( ₀ ) = B ₂ ( ₀ ) + y ₁ ∴y ₂ − y ₁ =B ₂ ( ₀ ) Equation (1) Here, since the distance ₀ between the solid-state camera and the object to be viewed is constant and known, the following equation is obtained from Equation (1).

y ₁ = B ₃ ( ₀ ) = B ₃ (∞) (1-e ^- 〓 ⁰ ) y ₂ - y ₁ = B ₂ ( ₀ ) = B ₂ (0) e ^- 〓 ⁰ Formula (2) However, Formula ( In 2), the attenuation coefficient σ, the solar equiscattered light limit value B ₃ (∞), and the background light initial value B ₂ (0) remain unknown.

Next, light is emitted from the light emitting section of the object and measurement is performed.

Let the observed value of the object light be y ₃ and the initial value of the light source be known.
If B' ₁ (0), then the following equation is obtained.

y ₃ = B′ ₁ ( ₀ ) + B ₃ ( ₀ ) = B′ ₁ ( ₀ ) + y ₁ (Note) y ₁ is obtained from equation (1) ∴y ₃ −y ₁ = B′ ₁ ( ₀ ) =B' ₁ (0)e ^- 〓 ⁰ (Note) B' ₁ (0)≠B ₁ (0) ∴σ=1/ ₀ ogeB' ₁ (0)/y ₃ −y ₁ Equation (3) Above During the observation of y ₃ , the light flux is diffused due to aerosol, but this diffusion is removed by an image processing program to observe y ₃ .

Substituting the aerosol attenuation coefficient σ obtained in this way into equation (2), B ₃ (∞) = y ₁ / (1-e ^- 〓 ⁰ ) B ₂ (0) = (y ₂ - y ₁ )/e ^- 〓 ⁰ η Formula (4) The limit value B ₃ (∞) of scattered light from the sun, etc. and the initial value B ₂ (0) of background light are determined.

Now, the intrinsic brightness of an object B ₁ (0) is determined by the brightness A (0) in the current environment of the place where the object is placed and at the current time, and the reflectance (albedo) of the object for light. It is multiplied by η. That is, B ₁ (0) = ηA (0) Equation (5) However, if the object also emits light from itself, assuming the emitted light intensity is D (0), B' ₁ (0) = η' A(0)+D(0) Equation (6) η' is the reflectance to external light during self-emission. (There are times when it can be approximated as η'0.) Although η is unique to the object, it takes a different value depending on the color of the light hitting the object, so when storing it in a computer, It is important to memorize each color.

In the method of the present invention, the external light intensity A(0) is determined by the illumination meter 5
It was actually measured by Equation (5) or Equation (6) (however, η′0)
B ₁ (0) or B′ ₁ (0) can be calculated by

Equation (3) gives the aerosol extinction coefficient σ, Equation (4) gives the limit value B ₃ (∞) of the amount of light that enters the observation optical axis due to scattering of light from the sun and night lighting, and the initial value of the background light. B ₂
(0) is obtained, and the intrinsic brightness B ₁ (0) of the object is determined by observation using an illuminance meter. Furthermore, the radiation intensity D(0) of the self-luminous object can be substituted into the formula in several different ways by switching the radiation intensity of the light emitting part of the object. Thus, the contrast C() is C()=B ₁ ()+B ₃ ()/B ₂ ()+B ₃ ()
-1 formula (7) However, B ₁ ()=B ₁ (0)e ^- 〓=ηA(0)e ^- 〓or B'
₁
(0)e ^- 〓+η′A(0) B ₂ ()=B ₂ (0)e ^- 〓 B ₃ ()=B ₃ (∞) (1−e ^- 〓), at any distance from the object. The contrast C() can be calculated.

Moreover, this C() is different from C() under the actual measurement environment for individual objects with various reflectances η.
It is possible to calculate the value of C() for a self-luminous body by setting B ₁ ()=B′ ₁ (0)×e ⁻ 〓. (B′ ₁ (0) is the emitted light intensity of the self-luminous body) <Effects of the invention> According to the method of the present invention described above, the intensity of sunlight during the day or the intensity of illumination at night is high. Even in such cases, it is possible to accurately determine the visibility of each unique object without being affected by those lights.

That is, in the conventional method, it is assumed that B ₂ (0) = B ₃ (∞), and C () = C (0).
e ^- 〓 was obtained. This is a well-known formula called Koschmieder's formula. In the above, if we substitute B ₂ (0) = B ₃ (∞) into the formula we created, we get C
It has been confirmed that ()=C(0)e ^- 〓 can be obtained. However, when the background of the object is filled with the distant sky, it is OK to set B ₂ (0) = B ₃ (∞), but when the background of the object is filled with relatively nearby forests, mountains, etc. The main source of light is the scattered light from sunlight and night lighting that hits those forests and mountains, so when the intensity of sunlight and night lighting is high, B ₂ (0) =
We must not assume that B ₃ (∞). In this sense, the method of the present invention, which basically separates B ₂ (0) and B ₃ (∞), is superior to the conventional method in that it is a device that correctly understands the formula derivation conditions specified by Mr. Koschmioeder. This is a new method that is completely different from the previous method, and conventionally there was a large measurement error (difference between the actual visibility value measured by a person and the actual value measured by the device) during the daytime or at night in a brightly lit place.

Furthermore, in the conventional method, in Koschmioeder's formula C()=C(0)e ^- 〓, C()/C(0)
Visibility is defined as = e ^- 〓 is 0.02 or 0.05 = e ^- 〓, which is based on actual experience that the larger the intrinsic contrast C(0) at = 0, the easier it is to distinguish the object from a distance. This is a contrary definition, and in the method of the present invention, C(0) and σ are determined from actual measurements and calculations, and C() itself is calculated, which makes the conventionally relative definition of visibility absolute. be praised. This realizes an innovative system that calculates the visibility of each object by replacing objects with different reflectances one after another and simulating experiments in a real measurement environment through calculations. This fact could not be derived from the conventional definition of relative visibility.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of the measuring device used in the method of the present invention, FIG. 2 is a view taken along the line A-A in FIG. 1, and FIG. 3 is a view taken along the line B-B in FIG. FIG. 4 is an explanatory diagram of the internal structure of the object to be viewed, and FIG. 5 is an explanatory diagram of the image captured by the solid-state camera. In the figure, 1...object, 2...solid camera, 3...
...Light emitting part, 4...Approximate black body part, 5...Luminance meter, 6
... Light-shielding tube, 7... Microcomputer type control device.

Claims (1)

[Claims] 1. Using a viewing object equipped with a light emitting section, an approximate blackbody section, and an illuminance meter, and a solid-state camera for observation, the light emission of the viewing object's light emitting section is set to 0, and the brightness per unit area of the approximate blackbody section is determined. y ₁ and the brightness per unit area of the background light y ₂ , then emit light from the light emitting part of the object and measure the brightness per unit area of the light emitting part y ₃ at that time, and A method in which the brightness A(0) of external light per unit area is determined using the illuminance meter, and the visibility of each object is calculated from these y ₁ , y ₂ , y ₃ and A(0).