Raindrop detection device, raindrop detection method, and raindrop detection program

Abstract

This raindrop detection device (20) comprises a housing unit (21), an opening part (21a), a light source unit (22a), a light reception unit (22b), a voltage depression unit (26g), and a microcomputer (25). The light reception unit (22b) is disposed in a position facing the light source unit (22a) in the housing unit (21), receives light emitted from the light source unit (22a), and converts the intensity of the received light to a voltage value. Upon the voltage value obtained through the conversion in the light reception unit (22b) exceeding a predetermined threshold value, the voltage depression unit (26g) drops the voltage value to less than or equal to a predetermined voltage value. The microcomputer (25) (raindrop detection unit (25a)) detects raindrops that have passed between the light source unit (22a) and the light reception unit (22b) in accordance with a change in the voltage value obtained through the conversion in the light reception unit (22b), and detects raindrops using the voltage value dropped in the voltage depression unit (26g) when the voltage value exceeds the predetermined threshold value.

Description

Raindrop detection device, raindrop detection method, and raindrop detection program

[0001] The present invention relates to a raindrop detection device, a raindrop detection method, and a raindrop detection program that detect raindrops and calculate the amount of rainfall.

[0002] In recent years, rain sensors that are installed outdoors and measure rainfall by detecting raindrops have been used. For example, Patent Document 1 discloses a rain sensor that includes a light-emitting unit, a light-receiving unit, and a calculation unit, and that counts the number of times the rain sensor signal exceeds a threshold value during wiper wiping control as the amount of rainfall for a certain period of time, and switches the wiper between intermittent and continuous operation depending on the count value.

[0003] JP 2018-159580 A

[0004] However, the conventional rain sensor described above has the following problems. Specifically, the rain sensor disclosed in the publication described above only determines the amount of rainfall as a count value over a certain period of time, making it difficult to obtain more accurate information about the amount of rainfall and to control the wiper operation in response to changes in the amount of rainfall. In particular, when the light-receiving unit receives natural light such as sunlight or artificial light such as vehicle headlights, the amplitude indicating the change in voltage when raindrops are detected may be reduced due to the influence of external light other than the light emitted from the light-emitting unit, making it difficult to detect the amount of rainfall with high accuracy.

[0005] An object of the present invention is to provide a raindrop detection device, a raindrop detection method, and a raindrop detection program that are capable of suppressing the influence of ambient light and detecting raindrops with high accuracy.

[0006] (Means for Solving the Problem) A raindrop detection device according to a first aspect of the present invention includes a housing, an opening, a light source, a light receiving unit, a voltage conversion unit, a voltage drop unit, and a raindrop detection unit. The housing has a cylindrical outer circumferential surface and a ceiling surface. The opening is formed on the ceiling surface of the housing. The light source is provided in the housing and emits light toward raindrops passing through the opening. The light receiving unit is disposed in a position facing the light source in the housing and receives the light emitted from the light source. The voltage conversion unit converts the amount of light received by the light receiving unit into a voltage value. The voltage drop unit reduces the voltage value when the voltage value converted by the voltage conversion unit exceeds a predetermined threshold. The raindrop detection unit detects raindrops passing between the light source and the light receiving unit in accordance with changes in the voltage value converted by the voltage conversion unit, and detects raindrops using the voltage value reduced by the voltage drop unit when the voltage value exceeds the predetermined threshold.

[0007] In this case, for example, to prevent ambient light such as natural light or artificial light (car headlights, flashlights, etc.) from entering the opening of the housing through which raindrops pass, changing the amount of light received by the light-receiving unit and reducing the accuracy of raindrop detection, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage value is reduced to detect raindrops. Here, the light source unit is, for example, an LED (Light Emitting Diode), and irradiates light in a predetermined direction toward the light-receiving unit, which is arranged facing the light-receiving unit at a predetermined distance.

[0008] The light receiving unit is, for example, a photodiode that receives light emitted from the light source unit and outputs it as a voltage value. Raindrop detection includes, for example, detecting the diameter of raindrops, the volume of each raindrop, the amount of rainfall per unit time, and the speed of raindrops. Ambient light that reduces raindrop detection accuracy includes, for example, natural light such as sunlight, and artificial light such as automobile headlights, flashlights, and outdoor lamps.

[0009] The voltage drop unit is, for example, an electrical circuit including a transistor that drops the voltage when a high voltage exceeding a predetermined voltage value is applied. By discharging voltage exceeding a predetermined threshold, the voltage value sent to the raindrop detection unit is lowered. Even if the amount of light received by the light receiving unit fluctuates significantly due to the influence of ambient light, if the voltage value converted from the amount of received light exceeds a predetermined threshold, raindrops can be detected by lowering the voltage increase due to the ambient light to a range that does not affect raindrop detection. As a result, the influence of ambient light can be suppressed, enabling highly accurate raindrop detection.

[0010] A raindrop detection device according to a second aspect of the present invention is the raindrop detection device according to the first aspect of the present invention, wherein the voltage drop unit increases the voltage value that is reduced as the voltage value exceeds the threshold. As a result, for example, in an electric circuit (voltage drop unit) including a transistor, the voltage value that is reduced increases as the voltage value exceeds the threshold, thereby increasing the voltage value that is reduced and minimizing the impact on raindrop detection accuracy.

[0011] The raindrop detection device according to a third aspect of the present invention is the raindrop detection device according to the first or second aspect of the present invention, further including an abnormality determination unit that determines an abnormality has occurred if the voltage value in the voltage drop unit does not drop below the predetermined voltage value when the voltage value exceeds a predetermined threshold. As a result, if the voltage value does not drop below the predetermined value even after the voltage drop unit performs a process to drop the voltage value above the predetermined threshold, it is assumed that strong light, such as artificial light, has been detected by the light receiving unit, and it can be determined that an abnormality has occurred. As a result, the abnormality determination result can be reported to a server connected to the raindrop detection device, or a light indicating an abnormality can be turned on in the raindrop detection device.

[0012] The raindrop detection device according to a fourth aspect of the present invention is the raindrop detection device according to the first or second aspect of the present invention, further comprising a first disturbance factor processing unit that cuts out changes in light intensity due to disturbance factors corresponding to the second frequency band, out of a first frequency band corresponding to changes in light intensity due to raindrop detection and a second frequency band corresponding to changes in light intensity due to disturbance factors. This separates the fall speed of raindrops in different frequency bands from changes in light intensity due to disturbance factors, and performs processing to cut out changes in light intensity due to changes in light intensity due to disturbance factors. This allows for highly accurate detection of raindrops by detecting only changes in light intensity due to raindrop detection.

[0013] A fifth aspect of the present invention is a raindrop detection device according to the fourth aspect of the present invention, further comprising a second disturbance factor processing unit that performs processing to cut out any remaining changes in light quantity due to disturbance factors that were cut out by lowering the voltage value in the voltage drop unit. This allows for more accurate raindrop detection by cutting out unnecessary changes in light quantity in the voltage drop unit and then further cutting out any remaining changes in light quantity due to disturbance factors.

[0014] A raindrop detection device according to a sixth aspect of the present invention is the raindrop detection device according to the first or second aspect of the present invention, further comprising a shielding structure that blocks sunlight entering through the opening from entering the light receiving unit. This allows for, for example, taking into consideration the angle and time of day at which natural light, such as sunlight, enters the opening, and employs a shielding structure that makes it difficult for light other than light from the light source to enter the light receiving unit by adjusting the position of the light receiving unit, the depth of the opening, etc., so that natural light is not detected by the light receiving unit. This eliminates the effects of ambient light other than the above-mentioned natural light, enabling highly accurate raindrop detection.

[0015] A seventh aspect of the present invention provides a raindrop detection method for a raindrop detection device including a housing having a cylindrical outer circumferential surface and a ceiling surface, an opening formed in the ceiling surface of the housing, a light source provided in the housing for irradiating light toward raindrops passing through the opening, and a light receiving unit disposed opposite the light source in the housing for receiving the light irradiated from the light source and converting the amount of received light into a voltage value. The raindrop detection method includes a voltage drop step and a raindrop detection step. In the voltage drop step, the voltage value is lowered when the voltage value converted by the light receiving unit exceeds a predetermined threshold. In the raindrop detection step, raindrops passing between the light source and the light receiving unit are detected in accordance with changes in the voltage value converted by the light receiving unit, and when the voltage value exceeds the predetermined threshold, raindrops are detected using the voltage value lowered in the voltage drop step.

[0016] In this case, for example, to prevent ambient light such as natural light or artificial light (car headlights, flashlights, etc.) from entering the opening of the housing through which raindrops pass, changing the amount of light received by the light-receiving unit and reducing the accuracy of raindrop detection, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage value is reduced to detect raindrops. Here, the light source unit is, for example, an LED (Light Emitting Diode), and irradiates light in a predetermined direction toward the light-receiving unit, which is arranged facing the light-receiving unit at a predetermined distance.

[0017] The light receiving unit is, for example, a photodiode that receives light emitted from the light source unit and outputs it as a voltage value. Raindrop detection includes, for example, detecting the diameter of raindrops, the volume of each raindrop, the amount of rainfall per unit time, and the speed of raindrops. Ambient light that reduces raindrop detection accuracy includes, for example, natural light such as sunlight, and artificial light such as automobile headlights, flashlights, and outdoor lamps.

[0018] In the voltage drop step, for example, an electrical circuit including a transistor that drops the voltage when a high voltage exceeding a predetermined voltage value is applied is used to lower the voltage value sent to the raindrop detection unit by discharging the voltage that exceeds a predetermined threshold. As a result, even if the amount of light received by the light receiving unit fluctuates significantly due to the influence of ambient light, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage increase due to the ambient light can be reduced to a range that does not affect raindrop detection, and raindrop detection can be performed. As a result, the influence of ambient light can be suppressed, allowing for highly accurate raindrop detection.

[0019] A raindrop detection program according to an eighth aspect of the present invention is a raindrop detection program that causes a computer to execute a raindrop detection method for a raindrop detection device including a housing having a cylindrical outer circumferential surface and a ceiling surface, an opening formed in the ceiling surface of the housing, a light source unit provided in the housing that irradiates light toward raindrops passing through the opening, and a light receiving unit disposed opposite the light source unit in the housing that receives the light irradiated from the light source unit and converts the amount of received light into a voltage value. The raindrop detection program includes a voltage drop step and a raindrop detection step. In the voltage drop step, the voltage value is reduced when the voltage value converted by the light receiving unit exceeds a predetermined threshold. In the raindrop detection step, raindrops passing between the light source unit and the light receiving unit are detected in accordance with changes in the voltage value converted by the light receiving unit, and when the voltage value exceeds the predetermined threshold, raindrops are detected using the voltage value reduced in the voltage drop step.

[0020] In this case, for example, to prevent ambient light such as natural light or artificial light (car headlights, flashlights, etc.) from entering the opening of the housing through which raindrops pass, changing the amount of light received by the light-receiving unit and reducing the accuracy of raindrop detection, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage value is reduced to detect raindrops. Here, the light source unit is, for example, an LED (Light Emitting Diode), and irradiates light in a predetermined direction toward the light-receiving unit, which is arranged facing the light-receiving unit at a predetermined distance.

[0021] The light receiving unit is, for example, a photodiode that receives light emitted from the light source unit and outputs it as a voltage value. Raindrop detection includes, for example, detecting the diameter of raindrops, the volume of each raindrop, the amount of rainfall per unit time, and the speed of raindrops. Ambient light that reduces raindrop detection accuracy includes, for example, natural light such as sunlight, and artificial light such as automobile headlights, flashlights, and outdoor lamps.

[0022] In the voltage drop step, for example, an electrical circuit including a transistor that drops the voltage when a high voltage exceeding a predetermined voltage value is applied is used to release the voltage that exceeds a predetermined threshold, thereby lowering the voltage value sent to the raindrop detection unit. As a result, even if the amount of light received by the light receiving unit fluctuates significantly due to the influence of ambient light, if the voltage value converted from the amount of received light exceeds a predetermined threshold, the voltage increase due to the ambient light can be reduced to a range that does not affect raindrop detection, and raindrop detection can be performed.

[0023] As a result, the influence of ambient light can be suppressed and raindrops can be detected with high accuracy.

[0024] EFFECT OF THE INVENTION The raindrop detection device according to the present invention can suppress the influence of ambient light and detect raindrops with high accuracy.

[0025] 1 is an overall perspective view showing the configuration of a raindrop detection device according to an embodiment of the present invention. A side view of the raindrop detection device of FIG. 1. A top view of the raindrop detection device of FIG. 1. A cross-sectional view showing the configuration of the raindrop detection device at the cross-sectional view of line A-A in FIG. 3. (a) is a perspective view showing a board on which the main components of the raindrop detection device of FIG. 4 are arranged. (b) is a top view thereof. A control block diagram of the raindrop detection device of FIG. 4. A diagram showing functional blocks generated inside the microcomputer of FIG. 6. A graph showing the relationship between elapsed time and changes in voltage indicating raindrops detected in the raindrop detection device of FIG. 6. A flowchart showing the basic flow of processing of a raindrop detection method using the raindrop detection device of this embodiment.

[0026] A raindrop detection device according to one embodiment of the present invention will be described below with reference to FIGS. 1 to 9. In this embodiment, unnecessary detailed description may be omitted. For example, detailed description of well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Furthermore, the applicant provides the accompanying drawings and the following description to enable those skilled in the art to fully understand the present invention, and does not intend for them to limit the subject matter described in the claims.

[0027] (1) Configuration of the Raindrop Detection Device 20 As shown in FIGS. 1 to 3 , the raindrop detection device 20 according to this embodiment detects raindrops that pass through a predetermined opening 21 a provided on the top surface of the housing 21, and calculates the amount of rainfall by detecting the size of the detected raindrops and the amount per unit time.

[0028] As shown in Fig. 4, the raindrop detection device 20 includes a housing 21, a light source 22a and a light receiving unit 22b provided inside the housing 21, legs 23, a base 24, and a microcomputer 25. As shown in Fig. 4, the housing 21 is a substantially cylindrical member and includes an opening 21a, an inner wall surface 21b, a ceiling surface 21c, and an outer peripheral surface 21d.

[0029] The opening 21a is provided at approximately the center of the ceiling surface 21c and is formed to penetrate the interior of the housing 21. The inner wall surface 21b forms the inner wall of the housing 21 at the penetration portion formed by the opening 21a. The light source unit 22a and the light receiving unit 22b are arranged at positions facing each other on the inner wall surface 21b.

[0030] The ceiling surface 21c is a substantially disk-shaped portion that forms the ceiling portion of the substantially cylindrical housing 21, and an opening 21a is provided in its central portion. The outer peripheral surface 21d is a surface that forms the outer peripheral portion of the substantially cylindrical housing 21, and a predetermined gap is provided between the lower end of the outer peripheral surface 21d and the base 24. As shown in FIG. 4, the light source unit 22a and the light receiving unit 22b are arranged in opposing positions on the inner wall surface 21b of the opening 21a. As shown in FIGS. 5(a) and 5(b), the light source unit 22a and the light receiving unit 22b are arranged in opposing positions on the substantially circular substrate 22c so as to sandwich the raindrop detection area A1.

[0031] The light source unit 22a is, for example, an LED (Light Emitting Diode), and as shown in Figures 5(a) and 5(b), irradiates infrared light toward the light receiving unit 22b via a lens 22d that collimates the light. The light receiving unit 22b is, for example, a photodiode, and as shown in Figures 5(a) and 5(b), is disposed in a position facing the light source unit 22a, receives light condensed via a lens 22e that condenses the light radiated from the light source unit 22a, converts the light condensed via a lens 22e, and outputs a voltage value corresponding to the amount of received light.

[0032] Light is emitted from the light source 22a to a raindrop detection area A1 (see FIG. 4) formed between the light source 22a and the light receiving unit 22b. Raindrops block a portion of the light detected by the light receiving unit 22b, reducing the amount of light received by the light receiving unit 22b, thereby detecting the presence or absence of raindrops. In the raindrop detection device 20 of this embodiment, as shown in FIG. 4, the light source 22a and the light receiving unit 22b are each positioned recessed from the opening 21a. That is, the light source 22a and the light receiving unit 22b are not positioned near the inner wall surface 21b that forms the opening 21a, but are positioned away from the inner wall surface 21b (shielding structure). Furthermore, the opening 21a is set to a sufficient height to prevent sunlight with a shallow angle of incidence, such as from the morning sun or the evening sun, from entering the light receiving unit 22b (shielding structure).

[0033] As a result, for example, by taking into consideration the angle at which sunlight enters the opening 21 a, it is possible to prevent sunlight from being received by the light receiving portion 22 b. As shown in Figures 5(a) and 5(b), the substrate 22 c is a substantially circular member with an opening formed in its center, and the light source portion 22 a, the light receiving portion 22 b, and the lenses 22 d and 22 e are arranged on the upper surface of the substrate 22 c.

[0034] An opening formed in the center of the substrate 22c corresponds to the raindrop detection area A1 and the opening 21a formed in the housing 21. The lens 22d is disposed above the light source 22a, such as an LED, with its multiple fan-shaped portions facing the light receiving unit 22b. The lens 22d reflects the infrared light emitted from the light source 22a at 90 degrees to collimate it and emits it toward the light receiving unit 22b.

[0035] The lens 22e is disposed above the light receiving unit 22b such as a photodiode, with its multiple fan-shaped portions facing the light source unit 22a. The lens 22e collects the infrared light emitted from the light source unit 22a, reflects it at an angle of 90 degrees, and directs it to the light receiving unit 22b disposed directly below. The multiple legs 23 are provided on the upper surface of the base 24.

[0036] The base 24 is a substantially disk-shaped member that supports the housing 21 of the raindrop detection device 20 via a plurality of legs 23 erected on its upper surface 24a. The microcomputer 25 is connected to the light source 22a and the light receiving unit 22b, and detects raindrops that pass between the light source 22a and the light receiving unit 22b in response to changes in the amount of light received by the light receiving unit 22b.

[0037] More specifically, in addition to the light source unit 22a and the light receiving unit 22b, the raindrop detection device 20 includes, as shown in FIG. 6, a microcomputer 25, a DC (direct current) cut unit 26a, an amplifier unit 26b, an AC (alternating current) / DC (direct current) light quantity conversion unit 26c, an amplifier unit 26d, an AC (alternating current) environmental component cancellation unit (first disturbance factor processing unit) 26e, an AC modulation drive unit 26f, a voltage drop unit 26g, an abnormality determination unit 26h, an ambient light cut unit (second disturbance factor processing unit) 26i, and a memory (storage unit) 27.

[0038] 6, the microcomputer 25 is connected to a memory 27 and reads various programs and data stored in the memory 27 to control the various components of the raindrop detection device 20 and to implement a correction method for the raindrop detection device 20, which will be described later. Here, infrared light emitted from the light source unit 22a is received by the light receiving unit 22b and converted into a voltage value. Then, the DC cut unit 26a removes DC environmental components such as ambient light from the detection result detected by the light receiving unit 22b.

[0039] The detection result, from which the DC environmental component has been removed, is amplified by amplifier 26b, converted to a DC component by AC / DC light intensity converter 26c, and the amplified signal by amplifier 26d is input to microcomputer 25. In the raindrop detection device 20 of this embodiment, infrared light emitted from light source 22a is received by light receiver 22b, converted into a voltage value, and then sent to voltage drop unit 26g.

[0040] The voltage drop unit 26g is an electrical circuit including a transistor that drops the voltage when a voltage equal to or greater than a predetermined voltage is applied. When the voltage converted from the amount of light received by the light receiving unit 22b exceeds a predetermined threshold, the voltage drop unit 26g determines that the increase in the amount of received light is due to the reception of artificial light such as an automobile headlight or a flashlight, and drops the voltage to a range that does not affect raindrop detection.

[0041] The magnitude of the voltage dropped by the voltage drop unit 26g is determined by whether a current flows through the base (input) of the transistor and turns the transistor ON. For example, when the ambient light is strong, the base current increases, and when the current exceeds a certain value, the transistor turns ON and a photocurrent due to the ambient light flows to GND. Specifically, when the voltage drop unit 26g receives a voltage value exceeding a predetermined voltage value from the light receiving unit 22b, the voltage drop unit 26g reduces the voltage value by a larger amount as the voltage value exceeds the threshold.

[0042] This allows the above-described shielding structure (the arrangement of the light-receiving unit 22b) to prevent an increase in the amount of received light due to natural light such as sunlight to be detected, and the voltage value can be reduced to reduce a significant increase in the amount of received light at the light-receiving unit 22b due to the influence of ambient light other than natural light. Therefore, even when light from an artificial light or the like is incident on the light-receiving unit 22b through the opening 21a, the increased amount of received light can be cut off, and only the change in the amount of received light due to raindrop detection can be extracted and used for subsequent raindrop detection processing.

[0043] The DC cut unit 26a transmits the detection result data (ADRAW) from the light receiving unit 22b before removing the disturbance light component to the microcomputer 25 via the abnormality determination unit 26h. The abnormality determination unit 26h receives an electrical signal from which the DC environmental component has been removed from the voltage value reduced by the voltage drop unit 26g, and determines that an abnormality has occurred if the reduced voltage value does not decrease to a predetermined voltage value or less that does not affect raindrop detection.

[0044] As a result, if the voltage value does not drop below the predetermined threshold even after the voltage drop unit 26g has performed a process to drop the voltage value above the predetermined threshold, it is assumed that the light receiving unit has detected strong artificial light, such as a light, and it can be determined that an abnormality has occurred. As a result, the abnormality determination result can be notified to a server connected to the raindrop detection device 20, or a light indicating an abnormality can be turned on in the raindrop detection device 20.

[0045] The microcomputer 25 receives the detection results (excluding detection results determined to be abnormal) from the light receiving unit 22b, controls the AC / DC light intensity converter 26c to perform AC / DC conversion processing by PWM (Pulse Width Modulation) control, and controls the AC modulation driver 26f to switch the light intensity of the light source unit 22a. Furthermore, a signal indicating the light intensity level converted into an AC component by the AC / DC light intensity converter 26c is sent to an AC environmental component canceller 26e, which removes the AC voltage component that drives the light source unit 22a, such as an LED, and sends the signal to the AC modulation driver 26f, where it is used to adjust the output of the light source unit 22a.

[0046] Furthermore, the AC environmental component cancellation unit (first disturbance factor processing unit) 26e, which receives a signal indicating the light quantity level from the AC / DC light quantity conversion unit 26c, selects a first frequency band corresponding to changes in light quantity due to the detection of raindrops and a second frequency band corresponding to changes in light quantity due to disturbance factors. The first frequency band corresponding to the falling speed of raindrops is, for example, approximately 500 to 3000 Hz, and the second frequency band corresponding to changes in light quantity due to disturbance factors is, for example, several Hz to 100 Hz.

[0047] This allows the raindrop detection to be performed with high accuracy by cutting out changes in light intensity that are presumed to be caused by disturbances according to the frequency band, thereby detecting only changes in light intensity due to raindrop detection. In addition, the disturbance light cutter (second disturbance factor processor) 26i, which receives a DC signal indicating the light intensity level from the AC / DC light intensity converter 26c, performs processing to cut out changes in light intensity that were not completely cut out by lowering the voltage value in the voltage drop unit 26g, among the changes in light intensity due to disturbances.

[0048] That is, the voltage input to the ambient light cutter 26i is the "raindrop voltage component + ambient light component." The low-pass filter extracts only the ambient light component (close to DC), and by taking the difference between the "raindrop voltage component + ambient light component" and the "ambient light component," the ambient light cutter 26i can extract only the raindrop voltage component. This allows the voltage drop unit 26g to cut unnecessary changes in light intensity, and then further cut changes in light intensity due to disturbance factors that could not be completely cut, thereby enabling more accurate raindrop detection.

[0049] The microcomputer 25 loads various programs stored in the memory 27 and generates the functional blocks shown in Fig. 7. That is, as shown in Fig. 7, the microcomputer 25 has a raindrop detection unit 25a, a diameter calculation unit 25b, and a rainfall calculation unit 25c. The raindrop detection unit 25a detects raindrops that pass between the light source unit 22a and the light receiving unit 22b (raindrop detection area A1) in accordance with changes in the amount of light received by the light receiving unit 22b.

[0050] More specifically, when raindrops pass through the raindrop detection area A1, part of the infrared light emitted from the light source unit 22a is blocked, causing a change in the light detection result at the light receiving unit 22b. As shown in Fig. 8, the raindrop detection unit 25a regards the change in voltage value (peak value) obtained by amplifying the detection result at the light receiving unit 22b as a raindrop candidate, and if the peak value of the voltage corresponding to each raindrop candidate exceeds a predetermined threshold, the raindrop candidate is detected as a raindrop.

[0051] The detection result shown in FIG. 8 illustrates an example in which three raindrop candidates were detected within the measurement time, and all of the raindrop candidates had peak values ​​exceeding the threshold, resulting in their detection as raindrops. The difference between the three peak values ​​in the graph shown in FIG. 8 primarily manifests as differences in the diameter, transmittance, and other characteristics of the detected raindrops. The diameter calculation unit 25b calculates the diameter of the raindrops detected by the raindrop detection unit 25a. Specifically, the diameter calculation unit 25b calculates the diameter of the voltage value having a peak value corresponding to the raindrop detected by the raindrop detection unit 25a using a table or the like showing the relationship between the voltage value and the diameter.

[0052] Assuming that the transmittance of raindrops is approximately constant, the larger the diameter of the raindrop, the greater the amount of infrared light irradiated from the light source unit 22a that is blocked, resulting in a larger diameter of the raindrop. The rainfall calculation unit 25c calculates the amount of rainfall per unit time using the diameter of the raindrop calculated by the diameter calculation unit 25b. Specifically, the rainfall calculation unit 25c calculates the volume V (= 4 / 3 × π × r) of each raindrop from the diameter R of the raindrop that has passed through the raindrop detection area A1. ３ ) and integrate the volume of raindrops detected per unit time to calculate the amount of rainfall. Note that π is the ratio of the circumference of a circle to its diameter, and r is the radius (= diameter R / 2).

[0053] <Raindrop Detection Method> In the raindrop detection method of this embodiment, the raindrop detection device 20 detects raindrops (rainfall sensing) according to the flowchart shown in Fig. 9. That is, in step S11, the microcomputer 25 repeatedly determines, using a timer, whether a sampling interval has elapsed, and proceeds to step S12 each time the interval has elapsed.

[0054] Next, in step S12, the microcomputer 25 acquires data (AD values ​​(converted into A / D converted light-receiving voltage values)) indicating the measurement results of the light-receiving unit 22b. Next, in step S13, the voltage drop unit 26g determines whether the voltage value changed in the light-receiving unit 22b is greater than a predetermined threshold value. If it is greater than the threshold value, the process proceeds to step S14; if it is equal to or less than the threshold value, the process skips steps S14 and S15 and proceeds to step S16.

[0055] Next, in step S14, since it was determined in step S13 that the voltage value converted by the light-receiving unit 22b was greater than the predetermined threshold, the voltage drop unit 26g performs a process of lowering the voltage value received from the light-receiving unit 22b in order to cut off the increase in the amount of received light caused by disturbances. Next, in step S15, the abnormality determination unit 26h determines whether the voltage value lowered by the voltage drop unit 26g has dropped to a predetermined voltage value. If the voltage value has dropped to the predetermined voltage value, the process proceeds to step S15; if the voltage value has not dropped to the predetermined voltage value, the process proceeds to step S20, where the abnormality determination unit 26h determines that an abnormal amount of light that cannot be reduced by the process in the voltage drop unit 26g has been detected, determines that an abnormality has occurred, and ends the process.

[0056] Next, in step S16, since it is determined in steps S13 and S15 that the voltage value is equal to or lower than the predetermined threshold value or has dropped to the predetermined voltage value, the diameter calculation unit 25b calculates the diameter of the raindrop based on the voltage value. Next, in step S17, the rainfall calculation unit 25c calculates the volume of the raindrop from the diameter of the raindrop calculated in step S16.

[0057] Next, in step S18, the microcomputer 25 determines whether the predetermined number of raindrops has been stored, and if it is determined that the predetermined number of raindrops has been stored, the measurement ends, whereas if it is determined that the predetermined number of raindrops has not been stored, the process from step S11 onward is repeated. Next, in step S19, the rainfall calculation unit 25c calculates the rainfall amount per unit time using the raindrop volume calculated in step S17, and the process ends.

[0058] As a result, if the amount of light received by the light-receiving unit 22b increases significantly due to the influence of ambient light, and the voltage value converted from the amount of received light by the light-receiving unit 22b exceeds a predetermined threshold, the voltage corresponding to the increase in the amount of received light due to the disturbance factor is reduced to a range that does not affect raindrop detection, and raindrops can be detected by detecting only the change in the amount of received light due to the detection of raindrops. As a result, the influence of ambient light can be suppressed and raindrops can be detected with high accuracy.

[0059] <Major Features> The raindrop detection device 20 of this embodiment includes a housing 21, an opening 21a, a light source 22a, a light receiving unit 22b, a voltage drop unit 26g, and a microcomputer 25 (raindrop detection unit 25a). The housing 21 has a cylindrical outer circumferential surface and a ceiling surface. The opening 21a is formed on the ceiling surface of the housing 21. The light source 22a is provided in the housing 21 and emits light toward raindrops passing through the opening 21a. The light receiving unit 22b is positioned opposite the light source 22a in the housing 21. It receives light emitted from the light source 22a and converts the amount of received light into a voltage value. The voltage drop unit 26g reduces the voltage value when the voltage value converted by the light receiving unit 22b exceeds a predetermined threshold. The microcomputer 25 (raindrop detection unit 25a) detects raindrops that have passed between the light source unit 22a and the light receiving unit 22b in accordance with changes in the voltage value converted by the light receiving unit 22b, and when the voltage value exceeds a predetermined threshold, detects raindrops using the voltage value reduced by the voltage drop unit 26g.

[0060] As a result, even if the amount of light received by the light-receiving unit 22b fluctuates significantly due to the influence of external light (e.g., weak artificial light), when the voltage value converted from the amount of received light exceeds a predetermined threshold, raindrops can be detected by reducing the voltage equivalent to the increase in the amount of received light caused by the external disturbance to a range that does not affect raindrop detection. As a result, the influence of external light can be suppressed and raindrops can be detected with high accuracy.

[0061] In addition, in the raindrop detection device 20 of this embodiment, as shown in FIG. 4, the height (depth) of the opening 21a is sufficiently ensured, and the light source unit 22a and the light receiving unit 22b are each positioned recessed from the opening 21a to prevent natural light such as sunlight from being received by the light receiving unit 22b (shielding structure). This, for example, takes into account the angle at which sunlight enters the opening 21a, and prevents strong sunlight from entering through the opening 21a and being received by the light receiving unit 22b. As a result, the above-mentioned shielding structure eliminates the effects of natural light such as strong sunlight, and then performs a voltage drop process to suppress an abnormal increase in the amount of received light by the voltage drop unit 26g, thereby reducing the effects of artificial light being received by the light receiving unit 22b or performing an abnormality determination process.

[0062] [Other Embodiments] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the invention.

[0063] (A) In the above embodiment, the present invention has been described as an example of a raindrop detection device and a raindrop detection method. However, the present invention is not limited to this. For example, the present invention may be realized as a raindrop detection program that causes a computer to execute the above-described raindrop detection method.

[0064] The raindrop detection program is stored in a memory (storage unit) installed in the raindrop detection device, and the CPU loads the raindrop detection program stored in the memory and causes the hardware to execute each step. More specifically, the CPU loads the raindrop detection program and executes each of the above-described steps to achieve the same effect as described above. The present invention may also be realized as a recording medium storing the raindrop detection program.

[0065] (B) In the above embodiment, an example was described in which, when a significant increase in the amount of received light is detected, the voltage drop unit 26g reduces the voltage value to cut off the amount of received light caused by disturbance factors, and the AC environmental component cancellation unit 26e and the disturbance light cut unit 26i perform processing to further cut off the increase in the amount of received light caused by disturbance factors. However, the present invention is not limited to this.

[0066] For example, the voltage drop unit 26g may be configured to reduce the voltage value and only cut off the amount of received light caused by disturbance factors. In other words, it is not necessary to further reduce the amount of received light caused by disturbance factors downstream of the voltage drop unit 26g. Alternatively, the voltage drop unit 26g may be configured to reduce the voltage value and only perform one of the AC environmental component cancellation unit 26e and the disturbance light cut unit 26i.

[0067] (C) In the above embodiment, an example was described in which it was determined that an abnormality had occurred when the voltage value reduced by the voltage drop unit 26g had not decreased to a predetermined voltage value. However, the present invention is not limited to this. For example, the voltage drop unit may be configured to not have a function for determining an abnormality as long as it is capable of sufficiently reducing the voltage to be dropped.

[0068] (D) In ​​the above embodiment, an example was described in which a shielding structure was employed in which the light receiving unit 22b was positioned away from the opening 21a (recessed from the inner wall surface 21b) to prevent natural light such as sunlight from entering the opening 21a and causing an abnormal amount of received light to be detected by the light receiving unit 22b. However, the present invention is not limited to this. For example, a configuration in which a shielding member is positioned near the light receiving unit to prevent natural light such as sunlight from being received by the light receiving unit may be used. Alternatively, a shielding structure in which the size of the opening is reduced to suppress the effect of sunlight and the like on the light receiving unit may be used.

[0069] <Note> The raindrop detection device according to the first invention comprises: a housing having a cylindrical outer peripheral surface and a ceiling surface; an opening formed in the ceiling surface of the housing; a light source provided in the housing and irradiating light toward raindrops passing through the opening; a light receiving unit disposed opposite the light source unit in the housing and receiving the light irradiated from the light source unit and converting the amount of received light into a voltage value; a voltage drop unit that reduces the voltage value when the voltage value converted in the light receiving unit exceeds a predetermined threshold; and a raindrop detection unit that detects raindrops that have passed between the light source unit and the light receiving unit in accordance with a change in the voltage value converted in the light receiving unit, and detects raindrops using the voltage value reduced in the voltage drop unit when the voltage value exceeds a predetermined threshold.

[0070] A second aspect of the present invention is the raindrop detection device of the first aspect, wherein the voltage drop unit increases the voltage drop as the voltage value exceeds the threshold. A third aspect of the present invention is the raindrop detection device of the first or second aspect, further comprising an abnormality determination unit that determines that an abnormality has occurred if the voltage drop unit does not decrease the voltage value to a predetermined voltage value or less when the voltage value exceeds a predetermined threshold.

[0071] A raindrop detection device according to a fourth aspect of the present invention is the raindrop detection device according to any one of the first to third aspects of the present invention, further including a first disturbance factor processing unit that cuts off changes in the amount of light due to disturbance factors corresponding to a first frequency band corresponding to changes in the amount of light due to the detection of raindrops and a second frequency band corresponding to changes in the amount of light due to disturbance factors.

[0072] A fifth aspect of the present invention is the raindrop detection device of the fourth aspect, further comprising a second disturbance factor processing unit that performs processing to cut out any changes in light quantity due to the disturbance factors that were not completely cut out by lowering the voltage value in the voltage drop unit.A sixth aspect of the present invention is the raindrop detection device of any one of the first to fifth aspects, further comprising a shielding structure that blocks sunlight entering through the opening from entering the light receiving unit.

[0073] The raindrop detection device of the present invention has the effect of suppressing the influence of external light and enabling highly accurate detection of raindrops, and is therefore widely applicable to sensors that measure rainfall, weather sensors that include such sensors, and the like.

[0074] 20 Raindrop detection device 21 Housing 21a Opening 21b Inner wall surface 21c Ceiling surface 21d Outer surface 22a Light source unit 22b Light receiving unit 22c Board 22d, 22e Lens 23 Leg 24 Base 24a Top surface 25 Microcomputer 25a Raindrop detection unit 25b Diameter calculation unit 25c Rainfall calculation unit 26a DC cut unit 26b Amplification unit 26c AC / DC light quantity conversion unit 26d Amplification unit 26e AC environmental component cancellation unit (first disturbance factor processing unit) 26f AC modulation drive unit 26g Voltage drop unit 26h Abnormality determination unit 26i Disturbance light cut unit (second disturbance factor processing unit) 27 Memory (storage unit) A1 Raindrop detection area

Claims

a light source provided in the housing and irradiating light toward raindrops passing through the opening; a light receiving unit disposed opposite the light source in the housing and receiving the light irradiated from the light source and converting the amount of received light into a voltage value; a voltage drop unit that reduces the voltage value converted by the light receiving unit when the voltage value exceeds a predetermined threshold; and a raindrop detection unit that detects raindrops passing between the light source and the light receiving unit in accordance with changes in the voltage value converted by the light receiving unit, and detects raindrops using the voltage value reduced by the voltage drop unit when the voltage value exceeds a predetermined threshold.

2. The raindrop detection device according to claim 1, wherein the voltage drop unit increases the voltage value that is reduced as the voltage value exceeds the threshold value.

3. The raindrop detection device according to claim 1 or 2, further comprising an abnormality determination unit that determines that an abnormality has occurred if the voltage value in the voltage drop unit does not drop to a predetermined voltage value or less when the voltage value exceeds a predetermined threshold.

4. The raindrop detection device according to claim 1 or 2, further comprising a first disturbance factor processing unit that cuts out changes in light intensity due to disturbance factors corresponding to the second frequency band, out of a first frequency band corresponding to changes in light intensity due to the detection of raindrops and a second frequency band corresponding to changes in light intensity due to disturbance factors.

5. The raindrop detection device according to claim 4, further comprising a second disturbance factor processing unit that performs processing to cut out any changes in light quantity caused by the disturbance factors that were not completely cut out by lowering the voltage value in the voltage drop unit.

6. The raindrop detection device according to claim 1 or 2, further comprising a shielding structure that blocks sunlight entering through the opening from reaching the light receiving section.

7. A raindrop detection method for a raindrop detection device comprising: a housing having a cylindrical outer peripheral surface and a ceiling surface; an opening formed in the ceiling surface of the housing; a light source provided in the housing and irradiating light toward raindrops passing through the opening; and a light receiving unit disposed opposite the light source in the housing and receiving the light irradiated from the light source and converting the amount of received light into a voltage value, the raindrop detection method comprising: a voltage drop step of lowering the voltage value until it becomes equal to or less than the predetermined voltage value when the voltage value converted in the light receiving unit exceeds a predetermined threshold; and a raindrop detection step of detecting raindrops that have passed between the light source and the light receiving unit in accordance with changes in the voltage value converted in the light receiving unit, and detecting raindrops using the voltage value lowered in the voltage drop step when the voltage value exceeds the predetermined threshold.

8. A raindrop detection program for a raindrop detection device comprising: a housing having a cylindrical outer peripheral surface and a ceiling surface; an opening formed in the ceiling surface of the housing; a light source provided in the housing and irradiating light toward raindrops passing through the opening; and a light receiving unit disposed opposite the light source in the housing and receiving the light irradiated from the light source and converting the amount of received light into a voltage value, the raindrop detection program comprising: a voltage drop step of lowering the voltage value to a predetermined voltage value or less when the voltage value converted in the light receiving unit exceeds a predetermined threshold; and a raindrop detection step of detecting raindrops that have passed between the light source and the light receiving unit in accordance with changes in the voltage value converted in the light receiving unit, and detecting raindrops using the voltage value lowered in the voltage drop step when the voltage value exceeds the predetermined threshold.

Images