JP5881397B2 - Snow, hail, rain discrimination method and discrimination device - Google Patents

Description

  The present invention relates to a determination method and a determination apparatus for determining whether a fallen object falling in the air is snow, hail, or rain.

  In order to prevent road freezing and avalanche countermeasures, techniques for observing meteorological conditions have been developed since observation of meteorological conditions is important. For example, Patent Document 1 discloses a method for determining rain, snow, or fog.

  Patent Document 1 uses infrared light for discrimination of weather conditions, and is reflected from a light emitter that projects infrared light of a single wavelength into the air and falling objects such as snow and rain in the air. And a light receiver for receiving the backscattered light. Then, an average value, a deviation value, and a variation coefficient using these as a function are calculated based on the amount of light received by the light receiver, and rain, snow, and fog are discriminated based on the variation coefficient value. Since the average value in the amount of received light is snow, fog> rain, and the deviation value is rain, snow> mist, the discrimination is made by making the variation coefficient as a function of rain> snow> mist. .

  In addition to Patent Document 1, in recent years, a snowfall sensor that combines an optical sensor, a rain sensor, and a temperature sensor has been used for weather observation. That is, using near-infrared light having a single wavelength of 875 nm, the optical sensor data, rain sensor data, and temperature sensor data in the forward scattered light of this near infrared light are processed to discriminate between snow and hail. Is to do.

JP-A-4-175687

  When snowfall occurs in snowy areas such as mountainous areas, the snow covered surface layer becomes heavy, causing avalanches. For this reason, it is important to determine whether the weather condition is snow or hail from the viewpoint of preventing snow mountain distress.

However, in Patent Document 1, even if snow, rain, and fog can be discriminated, hail cannot be discriminated.霙 is a meteorological phenomenon in which rain and snow are mixed, and because of the limit region of rain and snow, single wavelength infrared light is used. This is because the discrimination is difficult to understand.
The same applies to a snowfall sensor in which an optical sensor, a rain sensor, and a temperature sensor are combined, and the use of single-wavelength near-infrared light makes it ambiguous to distinguish between snow and hail. In addition, since this snowfall sensor is combined with various sensors, there are many components, and the operation and control are troublesome, and the processing of the obtained data is troublesome.

  The present invention has been made in view of such conventional problems, and provides a determination method capable of clearly determining not only snow and rain, but also snow and rain. An object of the present invention is to provide a discriminating apparatus which can be discriminated with a simple configuration and can be easily operated, controlled and processed.

The method for discriminating snow, hail, and rain according to the present invention is directed to near-infrared light in a wavelength region with a large amount of absorption by water and near-infrared light in a wavelength region with a small amount of absorption by water directed at falling objects in the air. A projecting stage for projecting light, a light receiving stage for receiving near-infrared light in the respective wavelength regions from the falling objects in the air, and the received near-infrared light with respect to the intensity of the projected near-infrared light. the variation value of the intensity measured for each of the respective wavelength ranges, with snow, sleet, and determining step of determining either rain a value based on the measured variable value is compared with a predetermined reference value, the light receiving The step is characterized in that the near-infrared light projected in the projecting step receives the transmitted light that has passed through the fallen object in the air .

In this case, the determination step sets a predetermined threshold for the variation value of the near-infrared light intensity for each wavelength region, sets the variation value equal to or greater than the threshold value as an effective value for each wavelength region, and sets both wavelengths. It is preferable to obtain a discriminant value by comparing the effective values of the area and compare the discriminant value with the predetermined reference value to discriminate between snow, hail and rain.
The near-infrared light in the wavelength range where the amount of absorption by water is large is in the wavelength range of 1400 nm to 1500 nm, and the near-infrared light in the wavelength range where the amount of absorption by water is small is in the wavelength range of 900 nm to 1350 nm. Is preferred.

According to the snow, hail, and rain discriminating apparatus of the present invention, after projecting near-infrared light in a wavelength region having a large amount of absorption by water toward a fallout in the air, the near-infrared light is dropped in the air. A first optical path portion that receives light from the first light path, and after projecting near-infrared light in a wavelength region with a small amount of absorption by water toward the falling object in the air, the first infrared light is received from the falling object in the air. The variation value of the intensity of the received near infrared light with respect to the intensity of the two optical path portions and the projected near infrared light is measured for each of the first optical path portion and the second optical path portion, and based on the measured variation value A discriminating means for discriminating one of snow, hail, and rain by comparing the value with a predetermined reference value, and the first optical path section and the second optical path section transmit transmitted light that has passed through the fallout in the air. It is characterized by receiving light .

In this case, the discriminating means sets an effective value when the variation value of the intensity of the near infrared light is equal to or greater than a predetermined threshold, and an effective value on the first optical path side and an effective value on the second optical path side. It is preferable to obtain a discriminant value by the comparison operation and compare the discriminant value with the predetermined reference value to discriminate between snow, hail and rain.
The first optical path unit includes a first light emitter that emits near-infrared light in a wavelength range of 1400 nm to 1500 nm, and the second optical path unit emits infrared light in a wavelength range of 900 nm to 1350 nm. It is preferable to provide two light emitters.

According to the method for discriminating snow, hail, and rain according to the present invention, near-infrared light in two wavelength regions, a wavelength region with a large amount of water absorption and a wavelength region with a small amount of water absorption, is used. Project near-infrared light toward a falling object in the air, receive transmitted light that has passed through the falling object in the air, and compare the intensity when projected and the intensity when received from the falling object for each wavelength range Therefore, snow, hail and rain can be clearly identified.

According to the snow, hail, and rain discriminating device of the present invention, each of near-infrared light in two wavelength regions, a wavelength region with a large amount of water absorption and a wavelength region with a small amount of water absorption, is used as a fallout in the air. In order to compare the intensity at the time of light projection and the intensity at the time of light reception in each of the optical path parts, the first optical path part and the second optical path part for receiving the transmitted light that has been projected toward and transmitted through the fallen object in the air , Snow, hail, and rain can be clearly identified. In addition, since the optical path unit and the discriminating means for discriminating snow, hail, and rain based on the intensity from the optical path unit, the configuration can be simplified, and the operation, control, and processing can be simplified. Become.

It is a figure which shows the near-infrared spectrum of water. It is a block diagram which shows the discrimination | determination apparatus of one Embodiment of this invention. It is sectional drawing which shows the 1st optical path part of one Embodiment. (A) is a graph which shows the effective value of rain in wavelength 945nm, (B) is a graph which shows the effective value of rain in wavelength 1450nm. (A) is a graph which shows the effective value of snow in wavelength 945nm, (B) is a graph which shows the effective value of snow in wavelength 1450nm. (A) is a graph showing the effective value of wrinkles at a wavelength of 945 nm, and (B) is a graph showing the effective values of wrinkles at a wavelength of 1450 nm. It is a top view which shows the optical system in the discrimination device of a reference example .

  According to the present invention, snow, hail, and rain are discriminated by projecting near-infrared light of two wavelength ranges having different wavelengths toward a falling object in the air and transmitting the near-infrared light of each wavelength region in the air. The weather conditions of snow, hail, and rain are discriminated by comparing the intensity of the near infrared light received from the falling object and the intensity of the received near infrared light for each wavelength range. The present invention utilizes the fact that the amount of absorption of near infrared light by water varies depending on the wavelength range of near infrared light.

  Figure 1 shows the near-infrared absorption spectrum of water. As shown in FIG. 1, water has a large absorbance in the wavelength region of 1400 nm to 1500 nm and a large amount of absorption of near infrared light in this wavelength region, while the absorbance of near infrared light in the wavelength region of 900 nm to 1350 nm is small. The absorption amount of near-infrared light in this wavelength region is small. Among the fallouts falling from the sky, rain is water and snow is crystals, so rain has a large amount of absorption of near-infrared light in the wavelength range of 1400 nm to 1500 nm, and near red in the wavelength range of 900 nm to 1350 nm. While the amount of absorption of outside light is small and the variation in the amount of absorption in these two wavelength regions is large, snow reflects near infrared light regardless of the difference in wavelength, so near red in the two wavelength regions. The amount of external light absorbed does not vary as much as the left. The kite is a meteorological phenomenon in which rain and snow are mixed, so it shows characteristics between rain and snow in the two wavelength regions. Therefore, based on the above qualitative characteristics, it is possible to determine whether the fallout in the air is snow, hail or rain.

In the present invention, as an aspect of receiving two near infrared lights projected toward a falling object in the air, the transmitted light that has passed through the falling object in the air is received . Hereinafter, the transmitted light is received. A form is demonstrated.

  FIG. 2 shows a discriminating apparatus 1 applied to an embodiment that receives transmitted light. The discriminating apparatus 1 projects first infrared light in a wavelength region with a large amount of absorption by water toward the falling object 2 in the air, and then receives the transmitted light transmitted through the falling object 2 in the air. A second optical path unit 4 that receives near-infrared light in a wavelength range in which the amount of absorption by water is small toward the falling object 2 in the air and then receives transmitted light that has passed through the falling object 2 in the air; And a discriminating means 5 for discriminating that the falling object 2 is any one of snow, hail and rain. In the following description, the wavelength region where the amount of water absorption is large is 1450 nm, and the wavelength region where the amount of water absorption is small is 945 nm. These two wavelength regions can be changed as appropriate within the above-mentioned ranges. is there.

  The first optical path unit 3 includes a first light emitter 31 that emits near-infrared light having a wavelength of 1450 nm, and the second optical path unit 4 includes a second light emitter 41 that emits near-infrared light having a wavelength of 945 nm. The light emitters 31 and 41 use LEDs. As the first light emitter 31 having a wavelength of 1450 nm, for example, an LED having a trade name “L23888-01” (manufactured by Hamamatsu Photonics Co., Ltd.) can be used. As the second light emitter 41 of 945 nm, for example, an LED having a trade name “L10660-01” (manufactured by Hamamatsu Photonics Co., Ltd.) can be used.

  The first light emitter 31 and the second light emitter 41 are connected to the LED blinking circuit 8 to emit light. The LED blinking circuit 8 is driven by being connected to a power source 6 and an oscillator 7. The LED blinking circuit 8 receives the signal from the oscillator 7 and causes the first light emitter 31 and the second light emitter 41 to emit light simultaneously. The oscillator 7 outputs a signal to the LED blinking circuit 8 and simultaneously outputs the synchronization signal to the lock-in amplifiers 11 and 12 as a reference signal.

  The first optical path unit 3 and the second optical path unit 4 include light receivers 32 and 42 that are provided with the fallen object 2 interposed therebetween and that face the first light emitter 31 and the second light emitter 41, respectively. The light receivers 32 and 42 receive the transmitted light that is projected toward the falling object 2 and transmitted through the falling object 2 by the light emission of the corresponding light emitters 31 and 41. As the light receivers 32 and 42, those capable of receiving near-infrared light in a wavelength range of a range used for determining a falling object are selected. For this reason, photodiodes capable of receiving near-infrared light in the range of 900 nm to 1500 nm are used for the light receivers 32 and 42. As the light receivers 32 and 42, for example, an InGaAs photodiode made of a trade name “G8370-81” (manufactured by Hamamatsu Photonics Co., Ltd.) can be used. Such InGaAs photodiodes have wavelength sensitivity characteristics that receive near-infrared light in the wavelength range of about 900 nm to 1700 nm at 25 ° C.

  The first optical path unit 3 includes a plano-convex lens 33 and a polarizing plate 34 on the emission side of the first light emitter 31, and a polarizing plate 35 and a plano-convex lens 36 on the incident side of the light receiver 32. The same applies to the second optical path section 4, which includes a plano-convex lens 43 and a polarizing plate 44 on the emission side of the second light emitter 41, and a polarizing plate 45 and a plano-convex lens 46 on the incident side of the light receiver 42. The plano-convex lenses 33 and 43 on the emission side use near-infrared light emitted from the light emitters 31 and 41 as parallel beams, and the polarizing plates 34 and 44 following the plano-convex lenses 33 and 43 use near-infrared light as linearly polarized light. . The incident-side polarizing plates 35 and 45 are arranged so that the direction of the threat is the same as that of the outgoing-side polarizing plates 34 and 44, thereby blocking ambient light. As a result, the transmitted light that has passed through the falling object 2 passes through the plano-convex lenses 36 and 46 and is collected and incident on the light receivers 32 and 42 to be received.

  FIG. 3 shows a specific structure in the first optical path portion 3. A support pipe 37 and a support pipe 38 that are optical paths of near-infrared light are opposed to each other with the fallen object 2 interposed therebetween. The support pipes 37 and 38 are separated by a distance D, and the space between the separated support pipes 37 and 38 is a measurement space for the fallen object 2. A first light emitter 31, a plano-convex lens 33 and a polarizing plate 34 are arranged in the support pipe 37, and a polarizing plate 35, a plano-convex lens 36 and a light receiver 32 are arranged in the support pipe 38. The support pipes 37 and 38 are formed in a cylindrical shape from a synthetic resin such as polypropylene or polyethylene. In FIG. 3, L is the optical path length between the first light emitter 31 and the light receiver 32. The optical path length L can be set to 500 mm, for example, and the distance D to be a measurement space can be set to 300 mm, for example. As the plano-convex lens 33, for example, a trade name “SLSQ-30-50P” (manufactured by Sigma Koki Co., Ltd.), and as the polarizing plate 34, for example, a trade name “NT48-” having a pass wavelength of 900 nm to 2000 nm. 889 "(manufactured by Edmond Co.) is used. The structure of the first optical path unit 3 shown in FIG. 3 is the same as that of the second optical path unit 4.

  The discriminating means 5 includes lock-in amplifiers 11 and 12 corresponding to the two wavelength ranges, and a discriminating unit 9 to which the lock-in amplifiers 11 and 12 are connected.

  The lock-in amplifier 11 of the determination unit 5 is connected to the light receiver 32 of the first optical path unit 3, and the lock-in amplifier 12 is connected to the light receiver 42 of the second optical path unit 4. Upon receiving near-infrared light having respective wavelengths (1450 nm and 945 nm), the light receivers 32 and 42 made of photodiodes convert the optical signals into electric signals, and then send them to the lock-in amplifiers 11 and 12 as measurement signals. Output. Since the lock-in amplifiers 11 and 12 receive the synchronization signal of the signal output to the LED blinking circuit 8 as a reference signal, the lock-in amplifiers 11 and 12 are directed from the light emitters 31 and 41 to the fallen object 2. The intensity of the near-infrared light projected in this way (synchronized with the reference signal) and the intensity of the transmitted light (measurement signal) of the falling object 2 received by each of the light receivers 32 and 42 are input for each wavelength. Each of the lock-in amplifiers 11 and 12 measures the lock-in output corresponding to the fluctuation of the intensity (measurement signal) of the near-infrared light on the light receiving side with respect to the intensity of the near-infrared light on the light emitting side (synchronized with the reference signal). To do. When the fallen object 2 is not falling, the lock-in output is constant because the intensity of near-infrared light does not change between light projection and reception, whereas when the fallen object 2 is falling, the transmitted light is not transmitted. Since the strength decreases, the lock-in output fluctuates. A / D converters 13 and 14 are connected to the lock-in amplifiers 11 and 12, and after the fluctuation value of the lock-in output for each wavelength is A / D-converted, the lock-in amplifiers 11 and 12 are connected to the discrimination unit 9 composed of a personal computer or the like. Is output.

  The determination unit 9 determines whether the fallout object 2 is snow, hail, or rain based on the input fluctuation value of the lock-in output. As a discrimination method, a threshold value is measured for each fluctuation value of the lock-in output from the lock-in amplifiers 11 and 12, and a fluctuation value equal to or larger than the threshold value is set as an effective value at each wavelength (1450 nm, 945 nm). A method can be employed in which the effective value is compared and calculated as a discriminant value, and the discriminant value is compared with a reference value to discriminate between snow, hail, and rain.

  The threshold value in the above method is set to a value that can distinguish whether or not the fluctuation value of the lock-in output fluctuates clearly, and the number of data of the fluctuation value of the input lock-in output It is set as appropriate according to the distribution state of the fluctuation value and others. The effective value comparison calculation at each wavelength in the above method is performed by, for example, calculating the ratio between the effective value at the wavelength of 1450 nm and the effective value at 945 nm. For example, the effective value at the wavelength of 1450 nm is divided by the effective value at 945 nm. To perform a comparison operation. A discriminant value is obtained by comparing the effective values of the two wavelengths, and the fallen object 2 is discriminated by comparing the discriminant value with a reference value. The reference value is set empirically by observing the actual weather conditions of snow, hail, and rain, and the reference value is appropriately changed according to the region, time, temperature, etc. where the weather observation is performed.

  Next, the determination of the falling object 2 according to this embodiment will be specifically described.

  The discrimination device 1 shown in FIG. 2 is installed outdoors. At the time of installation, the optical length L is set to 500 mm, the distance D between the support pipes 37 and 38 is set to 300 mm, and the fallen object 2 is set to fall between the support pipes 37 and 38. After this installation, the discriminator 1 is driven with respect to actual rainy, snowy, or hail weather conditions. The discriminating apparatus 1 drives a predetermined time (for example, 10 minutes) to obtain a fluctuation value of 10000 points of lock-in output, and performs data processing on the fluctuation value of this lock-in output. In the data processing, the maximum fluctuation value among the fluctuation values of the 10,000 lock-in outputs is set to “1”, and fluctuation values of other lock-in outputs are proportionally calculated and normalized. Thereby, the graphs of FIGS. 4 to 6 are obtained. The graphs of FIGS. 4 to 6 show the fluctuation value of the lock-in output at each point at 10,000 points. The threshold is set to 0.2 from the graphs of FIGS. The fluctuation value of the lock-in output when the threshold value is 0.2 or more becomes an effective value, and the number of effective values is measured.

  FIG. 4 is a measurement graph when the weather condition is rain. FIG. 4A shows data with a wavelength of 945 nm, and FIG. 4B shows data with a wavelength of 1450 nm. In the case of rain, there are three effective values for near infrared light with a wavelength of 945 nm, whereas there are 422 effective values for near infrared light with a wavelength of 1450 nm. This is because the transmitted light transmitted through the fallout 2 is weakened by the infrared light having a wavelength of 1450 nm being absorbed by the raindrops.

  FIG. 5 is a measurement graph when the weather condition is snow, (A) is data with a wavelength of 945 nm, and (B) is data with a wavelength of 1450 nm. As shown in FIGS. 5A and 5B, the near-infrared light with a wavelength of 945 nm has 107 effective values, and the near-infrared light with a wavelength of 1450 nm has 222 effective values. Many effective values of near-infrared light are generated. This is due to near-infrared light reflection on the snow surface and inside. The shape of the snow is irregular, and since it contains air, it is easily reflected inside and on the surface of the snow, and near infrared light is reflected regardless of the difference in wavelength. Due to this reflection, the transmitted light is weakened and many effective values are generated.

  FIGS. 6A and 6B are measurement graphs when the weather condition is dredging. FIG. 6A shows data with a wavelength of 945 nm, and FIG. 6B shows data with a wavelength of 1450 nm. As shown in FIG. 6A, there are six effective values for near-infrared light having a wavelength of 945 nm, and slightly more effective values are generated than in the case of rain. As shown in FIG. 6B, there are 84 effective values for near-infrared light having a wavelength of 1450 nm, and there are more effective values than for near-infrared light having a wavelength of 945 nm. Since the kite is a meteorological phenomenon in which snow and rain are mixed, near infrared light having a wavelength of 1450 nm transmitted through the kite is absorbed, and the effective value increases. The effective values of the wavelength 945 nm and the wavelength 1450 nm in such a kite are intermediate values between snow and rain.

  Table 1 qualitatively shows the number of effective values from the graphs of FIGS. In Table 1, “◯” indicates that there are many effective values, “Δ” indicates that there are some effective values, and “×” indicates that there are almost no effective values.

  Table 2 quantitatively summarizes the graphs of FIGS. In this case, about 6000 points of snow data and about 4000 points of hail data are obtained, so the number of effective snow values is multiplied by 1.7 and the number of hail effective values is multiplied by 2.5. Therefore, it is standardized to 10,000 points.

  With the effective values in Table 2 above, the measured value varies depending on the amount of snow, rain, and hailfall, so the effective value of the two wavelengths in each weather condition is proportionally calculated to calculate the discriminant value. The proportional calculation is performed by dividing the effective values of the two wavelengths, and is calculated by the discrimination value = (the number of effective values at the wavelength of 1450 nm) / (the number of effective values at the wavelength of 945 nm). Table 3 shows the result of proportional calculation.

  As shown in Table 3, there is a two-digit difference between rain and snow discriminant values. In the case of hail, the discriminant value is somewhat larger than the snow discriminant value. This is due to meteorological phenomena where snow and rain are mixed. The reference values are set as follows for the discriminant values shown in Table 3. The reference value is set so as to classify the weather conditions of rain, hail, and snow. In this embodiment, the reference value in the case of rain is 100 or more, and the reference value of hail is in the range of about 6-20. The snow reference value is set in the range of 2 to 3, and the reference value is compared with the discrimination value. This makes it possible to clearly determine whether the fallout 2 is snow, hail, or rain.

  In this embodiment, the optical path length L is set to 500 mm. However, the optical path length L can be increased to 1000 mm or the like. As a result, the amount of fallout passing through the optical path between the light emitters 31 and 41 and the light receivers 32 and 42 increases, so that the distinction between snow and hail can be further clarified. In the present invention, the threshold value and reference value for the variation value can be changed as appropriate.

  According to such an embodiment, the near-infrared light in the two wavelength regions of 1450 nm and 945 nm is used to project the falling object 2 in the air, and the intensity of the projected near-infrared light and the falling object 2 are transmitted. Since the intensity of the near-infrared light is compared for each of the two wavelength ranges, snow, hail and rain can be clearly determined.

  Further, according to the discriminating device of this embodiment, two optical path portions that project and receive near-infrared light in the two wavelength regions of 1450 nm and 945 nm on the fallout object 2 and the intensity from these optical path portions. Since it is comprised by the discrimination | determination means which discriminate | determines snow, hail, and rain based on it, it is a simple structure and operation, control, and a process become easy.

FIG. 7 shows a discrimination device in a reference example . FIG. 7 shows an optical system in the discriminating apparatus, and the same members as those in FIG. The optical system of this reference example receives reflected light reflected from the falling object 2 in the air.

  As shown in FIG. 7, the optical system includes a first optical path unit 3 and a second optical path unit 4. The first optical path unit 3 projects near-infrared light (for example, wavelength 1450 nm) in a wavelength region having a large amount of absorption by water toward the falling object 2 in the air, and then reflects the reflected light reflected from the falling object 2 in the air. Receive light. For this reason, the first optical path unit 3 includes a first light emitter 31 that emits near-infrared light in a wavelength range in which the amount of absorption by water is large, and a plano-convex lens 33 and a polarizing plate that are disposed on the emission side of the first light emitter 31. 34 forms a light projecting side, and a light receiving side is formed by a light receiving device 32 that receives near-infrared light reflected by the falling object 2, and a polarizing plate 35 and a plano-convex lens 36 arranged on the incident side of the light receiving device 32. ing. The second optical path unit 4 projects near-infrared light (for example, wavelength 945 nm) in a wavelength region with a small amount of absorption by water toward the falling object 2 in the air, and then receives reflected light reflected from the falling object 2 in the air. To do. The second optical path unit 4 has the same arrangement structure as the first optical path unit 3, and emits near-infrared light in a wavelength region in which the amount of absorption by water is small and emission from the first light emitter 41. A light projection side is formed by the plano-convex lens 43 and the polarizing plate 44 arranged on the side, and a light receiving device 42 that receives near-infrared light reflected by the falling object 2 and a polarizing plate arranged on the incident side of the light receiving device 42. The light receiving side is formed by 45 and the plano-convex lens 46.

  In the 1st optical path part 3 and the 2nd optical path part 4, it arrange | positions in the position where the optical path of the light reception side orthogonally crossed with respect to the optical path of the light projection side. Therefore, after passing through the fallen object 2, the near infrared light traveling straight along the light path on the light projecting side does not reach the light receiving side, but is projected from the light projecting side and is reflected from the light falling object 2 to the light receiving side. Only infrared light is received on the light receiving side.

  In the reflection at the falling object 2, when near-infrared light having two wavelengths hits snow, both near-infrared light having both wavelengths are reflected by the snow surface and refracted to the light receiving side. Therefore, in the case of snow, near-infrared light is reflected regardless of the difference in wavelength, so that there is little variation in the amount of absorption of near-infrared light having two wavelengths. In the case of rain, near infrared light reflected on the outer surface and near infrared light reflected on the inner surface after entering the rain are generated. Near-infrared light reflected on the outer surface of the rain is reflected to the light receiving side without being absorbed, but near-infrared light reflected on the inner surface of the rain is absorbed inside the rain. For this reason, in the case of rain, there is a large difference in the amount of absorption between near infrared light in a wavelength region where the amount of absorption by water is large and near infrared light where the amount of absorption by water is small. The kite is a meteorological phenomenon in which rain and snow are mixed, so it shows characteristics between rain and snow with near-infrared light in two wavelength ranges. Accordingly, even in the case of reflected light from the falling object 2 in the air, it is possible to clearly determine whether snow, hail, or rain is the same as the above-described transmitted light.

Claims (6)

A projecting stage for projecting near-infrared light in a wavelength region with a large amount of absorption by water and near-infrared light in a wavelength region with a small amount of absorption by water toward a falling object in the air,
A light receiving step for receiving near-infrared light in the respective wavelength ranges from the falling objects in the air;
A variation value of the intensity of the received near infrared light with respect to the intensity of the projected near infrared light is measured for each wavelength region, and a value based on the measured variation value is compared with a predetermined reference value. And a discrimination stage for discriminating between snow, hail and rain ,
In the light receiving step, the near infrared light projected in the light projecting step receives the transmitted light transmitted through the falling object in the air . In the determination step, a predetermined threshold value is set for the fluctuation value of the near-infrared light intensity for each wavelength region, and a variation value equal to or greater than the threshold value is set as an effective value for each wavelength region. 2. The snow, hail, and rain of claim 1, wherein a discriminant value is obtained by a value comparison operation, and the discriminant value is compared with the predetermined reference value to discriminate between snow, hail, and rain. How to determine. The near-infrared light in a wavelength range where the amount of absorption by water is large is a wavelength range of 1400 nm to 1500 nm, and the near-infrared light in a wavelength range where the amount of absorption by water is small is a wavelength range of 900 nm to 1350 nm. The snow, hail, and rain discrimination method according to claim 1. A first optical path portion that receives near infrared light in a wavelength region having a large amount of absorption by water toward a falling object in the air, and then receives the near infrared light from the falling object in the air;
  A second optical path portion that receives near infrared light in a wavelength region with a small amount of absorption by water toward a falling object in the air, and then receives the near infrared light from the falling object in the air;
  A variation value of the intensity of the received near infrared light with respect to the intensity of the projected near infrared light is measured for each of the first optical path portion and the second optical path portion, and a value based on the measured variation value is set as a predetermined reference. And a discriminating means for discriminating between snow, hail and rain in comparison with the value,
  The first optical path section and the second optical path section receive transmitted light that has passed through the fallen object in the air, and a snow, hail, and rain discrimination device. The determination means sets an effective value when the fluctuation value of the intensity of near infrared light is equal to or greater than a predetermined threshold, and compares the effective value on the first optical path side and the effective value on the second optical path side 5. The apparatus for discriminating snow, hail and rain according to claim 4, wherein a discriminant value is obtained by comparing the discriminant value with the predetermined reference value to discriminate between snow, hail and rain. The first optical path unit includes a first light emitter that emits near infrared light in a wavelength range of 1400 nm to 1500 nm, and the second optical path unit emits infrared light in a wavelength range of 900 nm to 1350 nm. The apparatus for discriminating snow, hail and rain according to claim 4, further comprising a vessel.

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