JPH0619479B2 - Rain, snow and fog identification method and device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a rain, snow and fog discrimination method and apparatus for discriminating whether a scattering reflector existing in the atmosphere is rain, snow or fog. In particular, the present invention relates to means for eliminating the influence of stains on the light emitting / receiving surface.

[Prior Art] In general, observation of meteorological conditions is an observation project that is highly demanded by society and industry, and its automation is an important technology in a year that makes it possible to perform such important observations quickly and inexpensively. is there.

The meteorological phenomenon to be observed includes, for example, rainfall, snowfall, fog, and the like. For detection of rain, snow, and fog, for example,
This can be realized by utilizing the scattering phenomenon of light rays by the water droplets or the like that compose them.

That is, when light rays such as infrared rays are projected into the atmosphere, the light rays are scattered and reflected by rain, snow, fog and the like. Focusing on the amount of light rays scattered in one arbitrary direction among the scattered light rays (specifically, the amount of light received by the light receiving element), the amount of light received differs depending on the type of the scattering reflector. Therefore, observing the amount of received light (hereinafter referred to as backscattered light),
It is possible to identify whether it is currently raining, snowing, or foggy.

[Problems to be Solved by the Invention] However, in the technique for evaluating the amount of received backscattered light, it becomes difficult or impossible to identify when the light emitting / receiving surface is contaminated. That is, the contamination of the light projecting / receiving surface attenuates the amount of backscattered light received, which becomes an obstacle in identifying whether it is rain, snow, or fog.

In order to avoid such an unidentifiable state, an automatic correction circuit having a function of detecting the degree of contamination of the light emitting / receiving surface and controlling the amount of light emission according to the degree of contamination is required. Therefore, the conventional device has a complicated configuration.

The present invention has been made to solve such a problem, and even in the case where the light emitting / receiving surface is contaminated without requiring a redundant circuit configuration such as an automatic correction circuit. The purpose is to make it possible to suitably identify rain, snow, and fog.

[Means for Solving the Problems] In order to achieve such an object, the applicant of the present application provides a rain, snow and fog identifying method and device having the following configurations.

First, the rain, snow and fog identification method of the present invention is a method of projecting light rays into the atmosphere and observing the amount of backscattered light received by a scattering reflector in time series to obtain an average value μ of the amount of received light for a predetermined period.
And the deviation value σ, and the variation coefficient K as σ / μ,
The variation coefficient K is characterized by identifying whether the scattering reflector existing in the atmosphere is rain, snow, or fog.

Next, the rain, snow and fog discriminating apparatus of the present invention includes a timing clock generation circuit for generating a timing clock,
A light projecting unit that projects a light beam forward according to a timing clock, a light receiving unit that receives backscattered light from a scattering reflector existing in the atmosphere, and an average of the amount of backscattered light received for a predetermined number of times of light reception. A calculation unit for obtaining the value μ and the deviation value σ, and the variation coefficient K as σ / μ;
A comparison unit that compares the predetermined identification reference value set corresponding to each of snow and fog with rain, snow, or fog to determine whether the scattering reflector present in the atmosphere is rain, snow, or fog. Characterize.

[Operation] In the present invention, backscattered light is observed in time series.

That is, light projection and reception of light rays are executed at a predetermined timing,
When the received light amount Vi at the time point i is obtained, the average value μ and the deviation value σ of the received light amount Vi for the period of i = 1 to n (n: integer) are obtained using this received light amount Vi.

The average value μ is an average value of the received light amount Vi, and is a value that is proportional to the particle density and scattering cross-sectional area of the scattering reflector and inversely proportional to the square of the distance.

The deviation value σ (variation) takes a larger value as the temporal change of the received light amount Vi is larger. Therefore, the deviation value σ becomes very small in the case of a scattering reflector whose time change is very gentle like fog. In comparison between rain and snow, rain has a greater temporal change than snow, and the deviation value σ is large.

The average value μ and the deviation value σ can be expressed by the following equations according to a well-known calculation law.

Next, in the present invention, the variation coefficient K is calculated. The variation coefficient K is calculated by the following equation.

K = σ / μ The variation coefficient K is an index showing whether the scattering reflector is rain, snow or fog. That is, the average value μ and the deviation value σ
The following magnitude relationship holds for the mean value μ: snow, fog> rain deviation value σ: rain, snow> fog Therefore, the following magnitude relationship holds for the variation coefficient K.

Mutation coefficient K: rain>snow> fog (3) In the present invention, this fact is utilized to identify whether the scattering reflector existing in the atmosphere is rain, snow or fog.

When identification is performed by such a method, even if the amount of received light is attenuated due to stains on the light emitting / receiving surface or the like, good identification can be performed without being affected by this attenuation. For example, if the average value at the time of damping is μ _att and the deviation value is σ _att , then the effects of damping are proportionally included in both.

When this is verified by a mathematical formula, it becomes as follows. First, letting Vi be the amount of light received when no attenuation has occurred,
The received light amount V _att i at the time of attenuation can be expressed as V _att i = αVi. However, α is the attenuation rate. The attenuation rate α can be regarded as constant during the period of executing the light reception n times, and therefore the average value μ _att can be expressed as follows.

However, μ is an average value when there is no attenuation. Similarly, the deviation value σ _att is Becomes However, σ is a deviation value when there is no attenuation.
In summary, μ _att = α μ σ _att = ασ (4)

When the variation coefficient K _att at this time is obtained based on the equation (4), K _att = σ _att / μ _att = ασ / α μ = σ / μ = K (5), and the variation coefficient K when there is no attenuation is obtained. Match.

As described above, the present invention does not employ a redundant circuit configuration, and rain, snow,
The fog is accurately identified.

Next, in the apparatus according to claim (2), the time-series observation in the method according to claim (1) is simply executed according to the timing clock, and it is discriminated whether it is rain, snow, or fog. Is realized by comparison with predetermined identification reference values set corresponding to rain, snow, and fog, respectively.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of a rain, snow and fog discriminating apparatus according to an embodiment of the present invention.

The device 10 shown in this figure has a transmitting circuit 12 and a receiving circuit 14, an infrared light emitting element 16, an infrared light receiving element 18, and two optical lenses 20 as means for projecting and receiving infrared rays.
In addition, two transparent protective plates 22 are provided.

The transmission circuit 12 generates a pulse train having the same repetition period according to the timing clock. The timing clock is generated in the timing clock generation circuit 24. When the timing clock is supplied to the transmission circuit 12 at a constant cycle, the transmission circuit 12 generates a pulse train at a constant cycle. The pulse train generated in the transmission circuit 12 is applied to the infrared light emitting element 16 as a transmission signal.

The infrared light emitting element 16 generates infrared light by applying a transmission signal. The emitted pulsed infrared rays are projected forward through the optical lens 20 and the transparent protective plate 22. The optical lens 20 and the transparent protective plate 22 are arranged one by one on both sides of the light projecting and receiving, the optical lens 20 determines the range relating to the light projecting and receiving, and the light projecting protective plate 22 sets the internal configuration of the device 10 to the outside Protect from the like.

The projected light beam is scattered and reflected by the scattering reflector 100 existing in the area shown by vertical hatching in the figure. This region is a region where the infrared light emitting element 16 projects light and reflected light can be received by the infrared light receiving element 18, that is, a visual field.

The backscattered light of the light reflected by the scattering reflector 100 is received by the infrared light receiving element 18 via the transparent protective plate 22 and the optical lens 20. The infrared light receiving element 18 supplies its output to the receiving circuit 14.

The receiving circuit 14 outputs a signal indicating the amount of light received by the infrared light receiving element 18 to the computing unit 26. In this embodiment, the calculation unit 26 is configured as a configuration for performing a discrimination calculation of rain, snow, and fog.
And a comparison unit 28 are provided.

The calculation unit 26 receives the signal from the reception circuit 14 and calculates the average value and the deviation value of the received light amount. This calculation is executed according to the above-mentioned equations (1) and (2). The variation coefficient obtained as a result of the calculation is input to the comparison unit 28. The comparison unit 28 compares a predetermined identification reference value with this variation coefficient to identify whether the scattering reflector 100 is rain, snow, or fog.

In this identification, an identification reference value is set for each type of scattering reflector 100. Normally, the relationship as expressed by the above-mentioned expression (3) is established, and therefore in this embodiment as well, the identification reference value is set in consideration of this relationship.

For example, in the case of fog, since the density is high and the temporal change in the amount of received light is small, the variation coefficient is almost zero. Further, in the case of snow, the particle density is smaller and the moving speed is faster than in the fog, so that the temporal change is large. Comparing rain and snow, rain has a greater temporal change than snow. Therefore, the relationship as described above is established.

Therefore, according to the above-mentioned principle, in the present embodiment, it is possible to eliminate the influence of the contamination of the light emitting / receiving surface. This is because the effect of the attenuation is canceled by the division of the average value and the deviation value by the equation (5).

[Effects of the Invention] As described above, according to the present invention, rain, snow, and fog are discriminated based on the variation coefficient K which is the ratio of the average value μ and the deviation value σ of the amount of received light. The effect of attenuation due to stains on the light receiving surface is eliminated, and more accurate identification can be performed. Further, for this reason, it is not necessary to employ a redundant device configuration, and it is possible to realize a simple, compact and inexpensive device.

According to claim (2), such a device can be easily realized by generating and comparing timing clocks.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a rain, snow and fog discriminating apparatus according to an embodiment of the present invention. 10: Rain, snow and fog identification device 12 ... Transmission circuit 14 ... Reception circuit 16 ... Infrared light emitting element 18 ... Infrared light receiving element 20 ... Optical lens 22 ... Transparent protective plate 24 ... Timing clock generation Circuit 26 …… Calculator 28 …… Comparison 100 100 …… Scattering reflector (rain, snow, fog)

Claims (2)

[Claims] 1. An average value μ and a deviation value σ of the amount of received light for a predetermined period by observing the amount of backscattered light received by a scattering reflector by projecting a light beam into the atmosphere.
The variation coefficient K is determined as σ / μ, and the value of the variation coefficient K identifies whether the scattering reflector existing in the atmosphere is rain, snow, or fog. And fog identification method. 2. A timing clock generation circuit for generating a timing clock, a light projecting means for projecting a light beam forward according to the timing clock, and a light receiving device for receiving backscattered light from a scattering reflector existing in the atmosphere. Means, and the average value μ of the amount of backscattered light received for a predetermined number of times of light reception
And the deviation value σ is calculated, and the variation coefficient K is calculated as σ / μ, and the variation coefficient K is compared with predetermined identification reference values set corresponding to rain, snow, and fog, respectively, and present in the atmosphere. A rain, snow, and fog identifying device, comprising: a comparing unit that identifies whether the scattering reflector is rain, snow, or fog.