JPS6326877B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a snow measuring device, and particularly to a photoelectric snow measuring device.

As a means of measuring the depth of snow, there is a snow measuring device that projects a beam of light from a projector onto the snow surface, receives and evaluates the reflected light with a photodetector, and measures the depth of snow. be.

An example of the optical configuration of this photoelectric snow measuring device will be briefly described below.

As shown in FIG. 1, a light emitter 1 and a light receiver 2 are set so that their optical axes 1A and 2A intersect with each other at a predetermined angle. The light beam 3 projected by the projector 1 forms light spots 5, 5A, 5B on the snow surface 4, 4A, 4B to be measured. At this time, light spot images 8, 8A, 8B are formed by the light reflected from the light spots 5, 5A, 5B on the snow surface onto the light receiving surface of the photodetector 7 by the light receiving lens 6 of the light receiver 2. Measured snow surface 4 is 4
When the light spot changes from A to 4B, the position of the light spot image 8 formed on the light receiving surface of the photodetector 7 also changes from 8A to 8B. That is, as shown in FIG. 2, when the snow surface 4 to be measured is at the level 4A, a light spot image 8A is formed on the light receiving surface 7A of the photodetector 7, and the snow surface 5 to be measured is at the level 5B. When the light spot has cooled, a light spot image 8B is formed at a position different from that described above.

As the photodetector 7 of the snow surface measuring device with such an optical configuration, for example, a split type detector or a position detector is used.

In the split type detector, the light receiving surface 7A is divided into two parts, and when a light spot image is formed on the light receiving surface 7A, the amount of light received by the light spot image formed on each of the divided light receiving surfaces 7A is divided into two parts. The output signal current is proportional to It changes. In addition, the position detector has an undivided light-receiving surface 7A, and the light-receiving surface 7A is formed of a uniform and highly sensitive semiconductor light-receiving element over the entire surface, and electrodes for transmitting output signals are attached to both ends of the light-receiving surface 7A. The photocurrent generated in the semiconductor light receiving element by the light spot images 8, 8A, 8B moving linearly on the light receiving surface 7A is transferred to the electrodes at both ends and the imaging position of the light spot images 8, 8A, 8B. The output signal current is divided according to the distance between the electrodes and output signal currents to the respective electrodes at both ends.

The light receiving surface 7A of the photodetector 7 is detected from the two output signal currents obtained from the split type detector or position detector.
The image forming position of the light spot images 8, 8A, 8B formed on the snow surface is determined, and conventional methods for signal processing include measurement based on changes in reflectance on the snow surface 4, 4A, 4B to be measured. For the purpose of removing errors, obtain the sum signal and difference signal of the above two output signal currents,
These ratios are calculated to obtain imaging position information.
Conventionally, a divider is generally used to find the ratio of the above two signals, but in order to construct the divider, two signals are usually used to convert the sum signal and the difference signal into logarithmic signals, respectively. A conversion circuit, a subtraction circuit that subtracts a difference signal from the sum signal converted into a logarithmic signal, and a conversion circuit that converts the output signal of the subtraction circuit into an antilogarithmic signal are required, and the circuit configuration is complicated and expensive. In addition, since the circuit configuration is multistage, there is a drawback that the drift is large and the measurement error is large.

In addition, as described above, the measured snow surfaces 4, 4A, 4
Although the change in the reflectance of B is temporarily removed by signal processing, if the reflectance of the snow surfaces 4, 4A, and 4B decreases extremely (for example, when dust accumulates on the snow surface, etc.) (This phenomenon occurs.) The amount of reflected light incident on the photodetector 7 becomes extremely small, and the value of the output signal current output from the photodetector 7 falls below the signal processing range, resulting in an increase in snow depth. Measurement becomes impossible.

The first object of the present invention is to eliminate the need for the above-mentioned complicated processing, so the circuit configuration is simple, there is little error due to drist, and the amount of reflection of the beam-like rays on the snow surface changes. To obtain a snow measuring device that does not become unable to measure even when the snow is covered.

Furthermore, it is generally known that the reflectance of the snow surface differs depending on the condition of the snow surface (for example, whether it is covered in snow or melting snow), and therefore the reflectance itself is measured. If possible, it would be very convenient to know the condition of the snow surface.

A second object of the present invention is to make it possible to measure the reflectance of the snow surface to be measured at the same time as measuring the depth of snow, and to perform the measurement using a simple circuit configuration.

In addition, not only the reflected light from the light spots 5, 5A, and 5B that contributes to measurement, but also light unrelated to measurement, such as sunlight and ambient illumination light, enters the light receiving surface 7A of the photodetector 7. . In order to distinguish and extract the reflected light from the light spots 5, 5A, and 5B from these many types of incident light, light modulated into projection light (beam-shaped light beam) 3 from the projector 1 is generally used.

By the way, when measuring snowfall using light, especially during snowfall, backlight etc. are reflected by flying snow particles.
This reflected light may become a signal equivalent to the modulated light (measurement light). This phenomenon significantly deteriorates the signal-to-noise ratio (S/N ratio) of the measuring device and becomes a major cause of measurement errors.

A third object of the present invention is to improve the modulation method of the projected light 3 from the projector 1, and to achieve a signal-to-noise ratio (S/
The purpose of the present invention is to obtain a snow measuring device with a better snow accumulation ratio (N ratio).

For the above purpose, in the present invention, an operational amplifier is used in place of the divider, and the sum signal of the two output signal currents from the photodetector is input to the operational amplifier, and comparison processing with a reference value is performed. The result of comparison processing, that is, the luminance of the light emitting element of the projector is controlled by the output of the operational amplifier, and the amount of reflected light (light spot image) that enters the photodetector, that is, the above-mentioned sum signal, is kept constant. The imaging position of the light spot image is detected based on the difference signal between the output signals from the photodetector at this time, and the driving current of the light emitting element subjected to the above brightness control is used to detect the imaging position of the light spot image. Then, the reflectance of the snow surface to be measured is determined, and the modulation (luminance modulation) of the drive current of the light emitting element is performed based on pulses with a random period to improve the S/N ratio. I made it.

Embodiments of the present invention will be described below with reference to FIGS. 3 to 7.

Fig. 3 is a block diagram of an embodiment of the present invention, and Fig. 4 is a circuit diagram of a reflectance detection circuit that obtains measurement information of the reflectance when the reflectance of the snow surface to be measured is measured in this embodiment. 5 is a block diagram showing the details of the oscillator for modulating the projected light beam, FIG. 6 is a diagram for explaining the relationship between the output signal of the photodetector and the imaging position of the light spot image, and FIG. 7 FIG. 2 is a diagram illustrating the relationship between snow depth and the imaging position of a light spot image.

In Figures 3 to 7, 10 is the snow surface to be measured (hereinafter referred to as the snow surface), 11 is a light source (light emitting element) in the floodlight (indicated by "1" in Figure 1), 13
is the driving current of the light source 11, 12 is the beam-shaped light beam projected by the light source 11, and 13 is the beam-shaped light beam 1.
2 is the reflected light obtained by reflecting on the snow surface 10, and 14 is the light spot image formed on the surface by the reflected light 13 (indicated by "8A" or "8B" in FIG. 2). A photodetector for detecting the position (indicated by "7" in FIG. 1), I1 and I2 are photodetectors 14
Two output signal currents, 15 and 1, are output from
6 is a converter that converts the output signal currents I1 and I2 into voltage signals, respectively; 17 is a converter 15, 16;
18 is an adder that performs addition processing on the output signals of converters 15 and 16 and outputs a sum signal; 19 and 20 respectively perform subtraction processing on the output signals of converters 15 and 16 and output a sum signal; 21 is an oscillator for modulating the light source 11; 21A is the oscillation output signal of the oscillator 21; 22 and 23 are the difference signal and the sum signal, respectively (the difference signal and the sum signal are the oscillation output signal of the oscillator 21); The synchronous detectors 24 and 25 detect the signal (modulated by the output signal) in synchronization with the output signal of the oscillator 21. 26 is a comparison amplifier composed of an operational amplifier that compares the value of the output signal of the low-pass filter 25 with a reference value; 27 is a reference voltage source that serves as a reference value for comparison in the comparison amplifier 26;
8 is a light source driver that controls the brightness of the drive current I3 of the light source 11 with the output signal of the comparison amplifier 26 and modulates the luminance of the drive current I3 with the oscillation output signal of the oscillator 21; 29 is a voltage proportional to the drive current I3; Resistors 30, 31, and 32 for obtaining a signal all constitute an integrator for integrating the voltage signal obtained by the resistor 29, and each is an operational amplifier, a resistor, and a capacitor, and V0 is a photodetector 14. position detection information of the light spot image formed on the spot;
V1 is reflectance detection information of the snow surface 10, 33, 34, and 35 all constitute the oscillator 21,
33 is a rectangular wave oscillation circuit, 34 is an n-bit shift register, 34A is the output of the shift register 34,
35 is an exclusive OR circuit.

Output signal currents I1 and I2 of the photodetector 14
When the photodetector 14 is the split type detector, corresponds to the current output from each of the two divided light receiving surfaces, and when the photodetector 14 is the position detector, the current is output from the electrodes at both ends. Corresponds to photocurrent.

The light source 11 receives a driving current I3 from the light source driver 28.
However, since the driving current I3 is modulated by the oscillation output signal 21A of the oscillator 21, the light source 11 projects, for example, a brightness-modulated beam 12 onto the snow surface 10. The photodetector 14 captures the reflected light 13 of the beam 12 on the snow surface 10, and outputs output signal currents I1 and I2 according to the position of the light spot image formed on its light receiving surface. These output signal currents I1 and I2 are applied to the converter 1
5 and 16 into voltage signals proportional to their respective values, the signals are input to a subtracter 17 and an adder 18, respectively, and the difference and sum are calculated.

The difference signal and sum signal of the output signal currents I1 and I2 obtained by the subtracter 17 and the adder 18 are amplified by amplifiers 19 and 20, respectively, and the oscillation output of the oscillator 21 is output by the synchronous detectors 22 and 23. signal 2
Detected in synchronization with 1A, and further low-pass filter 2
4 and 25, it is converted into a DC signal. In this way, the output signal currents I1, I2 of the photodetector 14
A DC signal corresponding to the difference signal and the sum signal (hereinafter, the former is referred to as the "difference DC signal", and the latter is referred to as the "sum DC signal")
That's what it means. ) is obtained.

The sum DC signal is compared with the voltage (reference voltage) of the reference voltage source 27 by the comparator amplifier 26, and when the sum DC signal is larger than the reference voltage, it corresponds to the difference between the sum DC signal and the reference voltage. the light source driver 2 so that the amount of light emitted by the light source 11 is reduced.
8 to control the drive current I3 of the light source 11, and conversely, when the sum of the DC signals is smaller than the reference voltage, the amount of light emitted from the light source 11 is similarly controlled to increase by the same value. By controlling in this way, the reflected light 13 that enters the photodetector 14
The light intensity (the projected beam-like light beam is brightness modulated, so the light intensity here means the integrated value (average value) of the incident light intensity) is controlled so that it is always a constant value, and this The snow depth can be measured by measuring the DC signal value of the difference between the two times. That is, the DC signal of the difference becomes the imaging position detection information V0 of the optical spot image. This imaging position detection information V0 is input to an arithmetic processor (not shown), and the snow depth is calculated as described below.

Here, the relationship between the image forming position detection information V0 of the light spot image and the light spot image forming position of the photodetector 14, and the relationship between the image forming position and the snow depth are shown in FIGS. 6 and 7. explain.

For example, when the above-mentioned position detector is used as the photodetector 14, as shown in FIG.
can be expressed by an equivalent circuit in which a current source is connected to the imaging position of the light spot image 5 on the light-receiving surface, which can be represented by the resistance value between the electrodes at both ends.

The center of the photodetector 14 is set as a reference point "0", the light receiving surface is set from "-S" to "S" on both sides of the reference point, and the imaging position of the light spot image 5 is set at "x" (- S≦x≦S), and if the current value generated by the current source is "I", the output signal currents "I1" and "I" flowing out from the electrodes at both ends are
The following relationship holds between the current "I" and the current "I" generated by the current source.

I1+I2=I...(1) I1=S-x/2SI...(2) I2=S+x/2SI...(3) As described above, the amount of light incident on the photodetector 14 is controlled to be constant. From each of the above relational expressions (1) to (3)
The current "I" at is constant.

In addition, position detection information “V0” of the light spot image 5
Since is a voltage signal proportional to the difference signal between the output signal currents "I1" and "I2", the following relationship holds: V0=A(I1-I2); (A is a constant) (4).

From the relationships (1) to (4) above, the imaging position "x" of the optical spot image 5 can be expressed as x=-S/AIV0 (5).

As mentioned above, since the current “I” is constant, the imaging position “x” is determined by the position detection information “V”.
It can be understood as a value proportional to 0".

Next, with reference to FIG. 7, the relationship between the imaging position "x" of the light spot image 5 and the snow depth (this will be referred to as "y") will be described.

As shown in FIG. 7, the optical axis 1A of the light projector 1 and the optical axis 2A of the light receiver 2 intersect at a set angle α.
Further, the light receiving surface of the photodetector 14 and the optical axis 2A of the light receiver 2 are perpendicular to each other.

The intersection point of the snow surface 10 and the optical axis 1A (beam-shaped ray 12) of the floodlight 1 is A, and the optical axes 1A and 2A of both of the above are
B is the intersection of the reflected light 13 and the optical axis 2A of the light receiver 2. (This intersection C is the optical point of the light receiving lens of the light receiver 2 (indicated by "6" in Fig. 2). ), the intersection of a perpendicular drawn from the intersection A to the optical axis 2A of the light receiver 2 and the optical axis 2A is D, the height from the ground surface 9 to the intersection B is "k", and the photodetector 14
The distance between the light-receiving surface and the intersection C is "m", the intersection B,
If the distance between C is "n", then the intersections A, C and D
Since the triangle formed by the center 0 of the photodetector 14, the imaging position "x", and the intersection C have a similar relationship, the snow depth "y" is y=nx/xcosα+msinα+k... ...(6)

In the relationship (6) above, angle α, distances k, m, n
are known constants set in advance, and therefore, the snow depth "y" is determined based on the position detection information "V0" of the light spot image 5 obtained in FIG. It can be determined from the imaging position x of the image 5.

Further, in the present invention, by detecting the average value of the drive current I3 supplied to the light source 11, the snow surface 10
can detect changes in reflectance. This is because in the embodiment of the present invention shown in FIG. 3, the amount of reflected light 13 incident on the photodetector 14 is always kept constant, so when the reflectance of the snow surface 10 changes, the light source This is because the drive current I3 of No. 11 is controlled to increase or decrease in accordance with the change in reflectance.

FIG. 4 shows an example of a reflectance detection circuit for the snow surface 10, and this detection circuit is constructed by inserting an integrating circuit into the current path of the light source 11.

As described above, the light source driver 28 controls the brightness of the light source 11 so that the light beam 12 from the light source 11 is reflected by the snow surface 10 and the amount of reflected light 13 that enters the photodetector 14 is kept constant. do. Therefore, the drive current I3 supplied to the light source 11 changes in inverse proportion to the change in reflectance of the snow surface 10. Therefore, the fourth
As shown in the figure, by inserting a resistor 29 in series with the light source 11 in the current path supplied to the light source 11, a voltage signal that is inversely proportional to the reflectance of the snow surface 10 appears at both ends of the resistor 29. . The reflectance detection information of the snow surface 10 is obtained from this voltage signal, but since the driving current I3 of the light source 11 is modulated as described above, it is composed of a resistor 31, a capacitor 32, and an operational amplifier 30. When converted into a DC signal by an integrating circuit, the value of the DC signal becomes a value proportional to the average value of the drive current I3, and this value becomes a signal inversely proportional to the reflectance of the snow surface 10, and becomes the reflectance detection information V1. Become.

Furthermore, since the output signal of the comparison amplifier 26 and the drive current I3 are in a proportional relationship, the reflectance detection information V1 can also be obtained by integrating the output signal of the comparison amplifier 26. Although the output signal of the comparison amplifier 26 is a DC signal, the level of this DC signal changes due to circuit noise, noise caused by changes in the environment at the measurement site, etc., so even in this case, It is necessary to integrate the output signal.

Reflectance detection information V1 obtained as above
is input to the arithmetic processor (not shown), and the reflectance of the snow surface 10 is calculated.

Furthermore, regarding the oscillator 21, in the past, an oscillator that generates a single-period rectangular pulse was generally used, and the modulation of the measurement light (projection beam) was simple brightness modulation, but in the embodiment of the present invention, By using an oscillator that generates random pulses, the measurement light is randomly modulated in brightness, thereby improving the S/N ratio.

That is, in the embodiment of the present invention, a random pulse generating circuit as shown in FIG. 5 is used as the oscillator 21. In this random pulse generation circuit, a rectangular wave pulse outputted from a single-period rectangular wave oscillation circuit 33 is input to the clock input terminal of an n-bit shift register 34, and the shift register 34
Some of the parallel outputs 34A of the exclusive OR circuit 3
5, exclusive OR is performed between them as appropriate, and the result (output of exclusive OR circuit 35) is input to the input terminal of the shift register 34. With this configuration, the output terminal of the shift register 34 receives a non-repetitive pulse signal having an arbitrary period and pulse width from the oscillation period of the rectangular wave oscillation circuit 33 to a period (2 ⁿ -1) times the oscillation period. This becomes the oscillation output signal 21A of the oscillator 21.

Making the oscillation output signal 21A a random pattern in this way widens the frequency band of the oscillation output signal 21A, and when the brightness modulation of the measurement light is performed based on such a random pulse with a wide frequency band, Based on the teachings of spread spectrum theory, S/ in position detection processing of optical spot images can be improved.
The N ratio can be improved.

As described in detail above, according to the present invention, by controlling the amount of light incident on the photodetector to be always constant, it is possible to accurately measure the snow depth with an inexpensive circuit configuration. By using the spread spectrum method for the brightness modulation method of the light source,
Since the S/N ratio in the position detection process of the optical spot image is improved, it is possible to measure snow depth with high resolution even when it is snowing, as well as when there is no snowfall.
Further, the present invention has the advantage that the reflectance of the snow surface can be measured extremely easily, and the present invention has extremely significant effects.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the measurement principle of a photoelectric snow measuring device, FIG. 2 is a diagram showing the internal configuration of the light receiver in FIG. 1, and FIG. 3 is a diagram showing the configuration of a snow measuring device according to an embodiment of the present invention. FIG. 4 is a circuit diagram showing the configuration of the snow surface reflectance measurement circuit according to the embodiment of the present invention, and FIG. 5 is a block diagram showing the configuration of the oscillation circuit used in the embodiment of the present invention. , FIG. 6 is an explanatory diagram of the relationship between the output signal of the photodetector and the optical spot image forming position, and FIG. 7 is an explanatory diagram of the relationship between the optical spot image forming position and the snow depth. . 1... Emitter, 2... Light receiver, 4A, 4B, 1
0...Snow surface to be measured, 7, 14...Photodetector, 11
...Light source, 12...Projection light, 13...Reflected light, 1
7... Subtractor, 18... Adder, 21... Modulation oscillator, 22, 23... Synchronous detector, 26... Comparison amplifier, 27... Reference voltage source, 28... Light source driver, 29 ... Resistor for reflectance detection, 30 ... Operational amplifier for integrator, 31 ... Resistor for integrator, 32 ...
...Integrator capacitor, 33...Square wave oscillation circuit, 34...n-bit shift register, 35
...Exclusive OR circuit, I1, I2...Output signal current of photodetector, I3...Driving current of light source, V0
...Position detection information, V1...Reflectance detection information, α
...The setting angle between the emitter and receiver.

Claims (1)

[Scope of Claims] 1. Snow measurement in which the depth of snow is measured by projecting a beam-like light beam onto the snow surface to be measured and receiving and evaluating the reflected light of the beam-like light beam from the snow surface. In the device, (A) a light source that projects a beam-like light beam onto the snow surface to be measured; (B) a light source that receives reflected light from the snow surface of the beam-like light beam projected from the light source; (C) an adder that calculates the sum of the two output signals of the photodetector and outputs a sum signal; (D) the photodetector that outputs a sum signal by calculating the sum of the two output signals of the photodetector; a subtracter that calculates the difference between the two output signals of the device and outputs a difference signal; (E) a comparator that compares the sum signal with a reference value and sends out an output signal according to the comparison value; (G) an oscillator that generates a pulse train signal with a random pattern; (H) a light source driver that randomly modulates the brightness of the beam from the light source using a pulse train signal from the subtractor; (H) an arithmetic processor that calculates the snow depth based on the difference signal output from the subtracter; Snow measuring device. 2. A snow cover in which a beam-shaped light beam is projected onto the snow surface to be measured, and the reflected light of the beam-shaped light beam from the snow surface is received and evaluated to measure the depth of the snow cover and the reflectance of the snow surface. In the measurement device, (A) a light source that projects a beam-shaped light beam onto the snow surface to be measured; (B) a light-receiving surface that receives reflected light from the snow surface of the beam-shaped light beam projected from the light source; (C) an adder that calculates the sum of the two output signals of the photodetector and outputs a sum signal; (D) an adder that outputs a sum signal by calculating the sum of the two output signals of the photodetector; a subtracter that calculates the difference between the two output signals of the detector and outputs a difference signal; (E) a comparator that compares the above sum signal with a reference value and sends out an output signal according to the comparison value; ) an oscillator that generates a pulse train signal with a random pattern; a light source driver that randomly modulates the brightness of the light beam from the light source using a pulse train signal from an oscillator; (H) a detection circuit that detects the value of the output signal of the comparator or the value of the light source drive output of the light source driver; (I) Arithmetic processing for calculating the snow depth based on the difference signal output from the subtracter and calculating the reflectance of the measured snow surface based on the detection signal output from the detection circuit. A snow measuring device consisting of a device and a.