JPH09257952A - Dew condensation and raindrop detection sensor and detection method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable detection of raindrop and dew condensation with one sensor by providing a light guiding plate formed in a band-like shape capable of detecting dew condensation on the inner surface of window pane, a light emitting element for raindrop serving also as that for dew condensation, a semi-reflection member blanching light from the element, and a mirror reflecting light after being branched. SOLUTION: An optical axis emitted in a light guiding plate 3 from a light emmitting element for raindrop and dew condensation reaches a half mirror 7 where part thereof is incident to a window pane 2 while the rest is reflected thereagainst and incident to the plate 3. The light made incident to the pane 2 is reflected against the outer surface thereof and a mirror 8, then converged by a light conversion lens 9 and is incident to a light receiving element 6 for raindrop. According to the deposition level of raindrop, the light receiving quantity of the element 6 varies. The incident light to be plate 3 is reflected against the inner surface of the plate 3 and the mirror 8 and advances, therafter it is collected by a focusing lent 9 and made incident to a light receivin element for dew condensation 5. When dew condensation on the inner surface of the palte 3 occurs, the quantity of light to the element 5 varies according to the deposition level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dew condensation and raindrop detection sensor for detecting raindrops adhering to an outer surface of a window glass of a vehicle or the like and a dewdrop detection method and a method for detecting the same.

[0002]

2. Description of the Related Art Various types of raindrop detection sensors and their detection methods have been known. For example, the one disclosed in JP-A-59-44641 is known. That is, FIG. 4 is a vertical cross-sectional view showing an example of a conventional raindrop detection sensor.

As shown in FIG. 4, the raindrop detecting sensor 51 is made of a translucent material fixed to a part of the inner surface of the wind glass 2 corresponding to the sliding area of the wiper blade mounted on the outer surface of the wind glass 2. A support 53 and a raindrop light emitting element 34 supported on one end of the support 53;
A raindrop light-receiving element 6 supported at the other end is provided. In addition, lead wires 58a and 58b are drawn out from the raindrop light emitting element 34 and the raindrop light receiving element 6, respectively, and are connected to an external connector 59. A condenser lens is provided at the tip of the raindrop light emitting element 34 and the raindrop light receiving element 6.

As shown in FIG. 4, both ends of the support body 53 are convex portions 53a and 53b, and the raindrop light-emitting element 34 and the raindrop light-receiving element 6 are held by the support portion 53, and the central thin-walled portion 53c is provided. It is held at an appropriate interval. The outside of the support body 53 is protected by the protector 57. Further, as the translucent material of the support body 53, a material having a refractive index substantially the same as that of the window glass 2 for light, such as acrylic resin, polycarbonate, or glass, is selected.

Further, a mirror 8 made of aluminum is provided on the lower surface of the central thin portion 53c with the windshield 2.
It is attached by a stamping method or the like so as to be in close contact with the inner surface 2b of the. The support body 53 is adhered to the inner surface 2b of the window glass 2 with an appropriate transparent adhesive having the same refractive index.

In the raindrop detection sensor 51 having the above structure, the raindrop light emitting element 34 at one end of the support 53 is provided.
When the light is emitted from the light source, the light is made to be an optical axis by the condenser lens 9 and is obliquely projected from the support body 53 to the inner surface 2b of the window glass 2. However, the materials of the support body 53 and the wind glass 2 have the same refractive index. Since it is selected, the optical axis goes straight on and reaches the outer surface 2a of the window glass 2. The optical axis is reflected by the outer surface 2a, and when it reaches the inner surface 2b, it is reflected by the mirror 8, reaches the outer surface 2a, and is reflected again.
Eventually, when the mirror 8 is cut off, the optical axis is again made incident on the inside of the support body 53, and is captured by the condenser lens 9 of the raindrop light-receiving element 6 to detect the amount of light received.

However, when the optical axis reaches and is reflected from the inside of the windshield 2 to the outer surface 2a, total reflection occurs when only air is present on the outer surface 2a, but when moisture such as raindrops adheres, the reflectance is increased. Changes. Therefore, if raindrops adhere to the outer surface 2a of the windshield 2, the amount of light received by the raindrop light-receiving element 6 decreases, so if this signal is converted into a control signal at the end of the connector 59, automatic control of the wiper blade will be performed. You can In addition, the light emitting element 34 for raindrops
Since the light receiving element 6 for raindrops is fixedly provided at both ends of the support body 53, troublesome work such as optical axis alignment is performed in the manufacturing stage, and in the assembling stage, the light guide plate 3 is simply attached. Just attach it to the windshield 2. Therefore, not only the work efficiency is improved, but also the reliability can be improved.

[0008]

However, in the conventional raindrop detection sensor 51, the windshield 2 is used.
Although the raindrops attached to the outer surface 2a can be detected, the dew condensation attached to the inner surface 2b cannot be detected. The defroster is manually turned on after visually confirming that the dew condensation on the inner surface 2b of the windshield has occurred. There is a problem in terms of safety because the driver will drive with unclear visibility until the cloudiness due to condensation is removed. Further, if a dew condensation detecting sensor is provided separately, there is a problem that the cost increases.

The present invention has been made in view of the above problems, and provides a highly safe and inexpensive dew condensation and rain drop detection sensor capable of detecting both rain drops and dew condensation with a single detection sensor. That is.

[0010]

The above object is a dew condensation and raindrop detection sensor according to claim 1, wherein a part of the inner surface of the wind glass corresponding to the sliding area of the wiper blade mounted on the outer surface of the wind glass is provided. Raindrop detection including a fixed light guide plate made of a translucent material, a raindrop light emitting element supported at one end of the light guide plate, and a raindrop light receiving element supported at the other end In the sensor, the light guide plate is in the form of a strip plate capable of detecting condensation attached to the inner surface of the wind glass, and the light emitting element for raindrops is a combined use light emitting element for condensation and raindrops. A semi-reflective member provided between the window glass and the light guide plate for branching, and provided between the window glass and the light guide plate for reflecting the branched light, respectively. Solution by a dew condensation and raindrop detection sensor, characterized in that a mirror and a dew condensation light receiving element provided separately from the raindrop light receiving element that receives light emitted after reflection inside the light guide plate are provided. can do.

According to the dew condensation and raindrop detection sensor having the above structure, not only raindrops attached to the outer surface of the windshield but also dewdrops attached to the inner surface of the light guide plate can be detected. Therefore, one dewdrop and raindrop detection sensor can be used. It can be applied not only to the blade but also to the automatic control of the defroster. Therefore, not only the application can be expanded at low cost, but also the safety can be improved.

Further, the above-mentioned problem is the dew condensation and raindrop detection sensor according to claim 2, wherein the spectral member for branching the light from the dual-purpose light emitting element before entering the window glass and the light guide plate. And a beam splitter for further branching one of the branched lights, and a first light receiving element and a second light receiving element provided for respectively receiving the light branched by the beam splitter. This can be solved by the dew condensation and raindrop detection sensor according to claim 1.

According to the dew condensation and raindrop detection sensor having the above-mentioned configuration, the control signals to the wiper blade and the defroster are not simply the light receiving amounts incident on the raindrop light receiving element and the dew condensation light receiving element, but first and second, respectively. Since the light is emitted based on the comparison value with the amount of light received by the light receiving element, even if the light amount of the dual-purpose light emitting element is reduced due to deterioration, the light is not emitted due to a malfunction and the reliability can be further improved.

Further, the above-mentioned problem is a dew condensation and raindrop detection sensor according to a third aspect of the present invention, wherein a light-transmitting member fixed to a part of the inner surface of the windshield corresponding to a sliding region of a wiper blade mounted on the outer surface of the windshield. Raindrop detection sensor comprising a light guide plate made of a conductive material, a raindrop light emitting element supported at one end of the light guide plate, and a raindrop light receiving element supported at the other end of the light guide plate. The light-receiving element is a dual-purpose light-receiving element capable of detecting dew condensation adhering to the inner surface of the window glass, and the light emitted from the window glass and the light-guide plate is incident on the dual-purpose light-receiving element, so that the other of the light-guide plates. A reflector provided at one end of the light guide plate, and the raindrop emission device provided at one end of the light guide plate separately for shifting the incident time of light to the window glass and the light guide plate. The element can be solved by condensation and rain detection sensor, characterized in that the separate condensation light emitting element is provided.

In the dew condensation and raindrop detection sensor having the above-described structure, the light emitting element for raindrops and the light emitting element for dew condensation emit light at different intervals at different time zones. Therefore, the dual-purpose light receiving element can detect the amount of light as incident light for raindrops or as incident light for dew condensation for each time period. Therefore, the light-receiving element is integrated as a dual-purpose light-receiving element, and the half mirror is not required, so that the cost can be reduced.

Further, the above-mentioned problem is the method for detecting dew condensation and raindrops according to claim 4, wherein a light transmitting member fixed to a part of the inner surface of the wind glass corresponding to the sliding region of the wiper blade mounted on the outer surface of the wind glass. In a detection method of receiving light emitted from a raindrop light emitting element supported at one end of a light guide plate made of a conductive material by a raindrop light receiving element supported at the other end of the light guide plate, the light guide plate is Condensation that adheres to the inner surface of the windshield can be detected, and the light emitting element for raindrops is a combined light emitting element for both condensation and raindrops, and the light from the combined light emitting element is branched by a semi-reflecting member, and the light after branching Is reflected by a mirror, and the light emitted after the reflection is received by a dew condensation light-receiving element in addition to the raindrop light-receiving element, and the light from the dual-purpose light-emitting element is received by the windshield. Before being made incident on the light guide plate and in the light guide plate, one of the branched lights is further branched by a beam splitter, and the light branched by the beam splitter is a first light receiving element and a second light receiving element. This can be solved by a method of detecting dew condensation and raindrops, which is characterized by receiving light by means of light.

Further, the above-mentioned problem is a method for detecting dew condensation and raindrops according to claim 5, wherein the light receiving results from the first and second light receiving elements are compared from the light receiving element for raindrops and the light receiving element for dew condensation by a comparison circuit. It can be solved by the method of detecting dew condensation and raindrops according to claim 4, which is outputted as a control signal necessary for automatic control of the wiper blade and the defroster, as compared with the light reception result.
According to the dew condensation and raindrop detection method having the above-described configuration, the control signal to the wiper blade and the defroster is not merely the amount of light received by the raindrop light receiving element and the dew condensation light receiving element, but of the first and second light receiving elements, respectively. Since the light is output based on the comparison value with the amount of received light, even if the light amount of the dual-use light emitting element is reduced due to deterioration, it is not output due to malfunction, and the reliability can be further improved.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a dew condensation and raindrop detection sensor and a detection method thereof according to the present invention will be described below with reference to FIGS.
It will be described in detail based on. 1 is a vertical cross-sectional explanatory view showing a first embodiment of a condensation and raindrop detection sensor of the present invention, and FIG. 2 is a vertical cross-sectional explanatory view showing a second embodiment of a condensation and raindrop detection sensor of the present invention. FIG. 3 is an explanatory longitudinal sectional view showing a third embodiment of the dew condensation and raindrop detection sensor of the present invention.

As shown in FIG. 1, a dew condensation and raindrop detection sensor 1 according to a first embodiment of the present invention corresponds to a wiper blade sliding area mounted on an outer surface of a windshield 2 such as a front windshield of a vehicle. The central main portion fixedly provided on a part of the inner surface of the wind glass 2 is a strip-shaped light guide plate 3 for detecting dew condensation made of a translucent material, and is supported by one end of the light guide plate 3. The combined light emitting element 4 for dew condensation and raindrops, and the light receiving element 5 for dew condensation supported on the other end.
And a light receiving element 6 for raindrops, a half mirror 7 which is a semi-reflective member provided between the window glass 2 and the light guide plate 4 for branching light from the dual-purpose light emitting element 4, and the branched light. The mirror 8 is provided between the window glass 2 and the light guide plate 3 for reflection by aluminum vapor deposition or the like. A condenser lens 9 is provided at the front ends of the light receiving element 5 for condensation and the light receiving element 6 for raindrops. Further, the dual-purpose light emitting element 4 is protected by the protector 10, and the dew condensation light receiving element 5 and the raindrop light receiving element 6 are protected by the protector 11.

In the dew condensation and raindrop detection sensor 1 having the above-described structure, first, when the optical axis emitted from the dual-purpose light emitting element 4 into the light guide plate 3 strikes the half mirror 7 obliquely, a part of the optical axis remains in the windshield 2. The other portion is reflected by the half mirror 7 and is transmitted into the light guide plate 3. Then, the light transmitted through the windshield 2 travels in a zigzag manner while being reflected by the outer surface of the windshield 2 and the mirror 8, and then collected and incident on the light receiving element 6 for raindrops by the condenser lens 9. At this time, if raindrops adhere to the outer surface of the windshield 2, the amount of light reflected by the raindrop light-receiving element 6 changes because the amount of reflection decreases depending on the degree of adhesion. Therefore, if this change in the amount of received light is transmitted by the control circuit as a control signal necessary for automatic control, the wiper blade can be automatically controlled.

Similarly, the light reflected in the light guide plate 3 travels in a zigzag manner while being reflected by the inner surface of the light guide plate 3 and the mirror 8, and then is collected by the condenser lens 9 and incident on the light receiving element 5 for condensation. To be done. At this time, if dew condensation adheres to the inner surface of the light guide plate 3, the amount of light reflected by the dew condensation light receiving element 5 changes because the amount of reflection decreases depending on the degree of adhesion. Therefore, if the change in the amount of received light is output by the control circuit as a control signal required for automatic control, the defroster can be automatically controlled.

As described above, according to the dew condensation and raindrop detection sensor 1 of the present embodiment, not only raindrops adhering to the outer surface of the window glass 2 but also dew condensation adhering to the inner surface of the light guide plate 3 can be detected. Therefore, one dew condensation and raindrop detection sensor 1 can be applied to not only the wiper blade but also the automatic defroster control. Therefore, not only the application can be expanded at low cost, but also the safety can be improved. Although the light receiving element 5 for dew condensation detects dew condensation attached to the inner surface of the light guide plate 3, it may be considered that dew condensation on the inner surface of the wind glass is detected if the material of the light guide plate is selected. Also, the combined light emitting element 4 and the raindrop light receiving element 6
Since the light-receiving element 5 for condensation and the light-receiving element 5 for condensation are fixedly provided at both ends of the light-guide plate 3, troublesome work such as alignment of the optical axis is performed in a factory or the like in which it is manufactured. It suffices to attach 3 to the windshield 2, which not only improves work efficiency but also improves reliability.

Further, when the light source is close to white light, if a prism is used as a semi-reflective member instead of the half mirror 7, the light is split into long wavelength and short wavelength. Either one of the branched lights having different wavelengths is fed to the window glass 2,
By guiding the other to the light guide plate 3 and changing the light receiving element 6 for raindrops and the light receiving element 5 for dew condensation to light receiving elements adapted to the respective wavelengths, the same function as that of the dew condensation and raindrop detection sensor 1 described above can be provided. .

The dew condensation and raindrop detection sensor 21 of the second embodiment of the present invention is different from that of the first embodiment in that the light emitted from the dual-purpose light emitting element 4 is emitted by the half mirror 7. V-shaped mirror 2 which is a spectral member before branching
The light is split by 2 and one light is incident on the half mirror 7, while the other light is further split by the beam splitter 23. This branched light is to be detected by the first and second light receiving elements 24 and 25. Therefore, the same reference numerals are given to the components having the same configuration, and the description of the configuration and the action is omitted.

Next, a method of detecting the dew condensation and raindrop detection sensor 21 will be described. In FIG. 2, the comparison circuit 26 compares the amount of light received by the dew condensation light receiving element 5 with the amount of light received by the second light receiving element, and the comparison value is used as the comparison value.
The signal is amplified in 7 and output as a control signal to automatically control the defroster. Similarly, although not shown, the incident amount received by the raindrop light receiving element 6 and the incident amount received by the first light receiving element are compared by another comparison circuit, and this comparison value is amplified by another amplification circuit. Is transmitted as a control signal to automatically control the wiper blade.

As described above, according to the dew condensation and raindrop detection sensor 21 of the present embodiment, the control signals to the wiper blade and the defroster are simply incident on the raindrop light receiving element 6 and the dew condensation light receiving element 5. The output is based not on the amount of light but on the comparison value with the amount of light received by each of the first and second light receiving elements 25 and 26. Therefore, even if the amount of light of the dual-purpose light emitting element 4 is reduced due to deterioration, it is not output due to a malfunction. Therefore, the reliability can be further improved.

Next, a third embodiment of the dew condensation and raindrop detection sensor of the present invention will be described with reference to FIG. The dew condensation and raindrop detection sensor 31 in the present embodiment is different from the first embodiment in that the light-receiving element 5 for dew condensation and the light-receiving element 6 for raindrop are combined into one and the light-receiving element 3 is also used.
2 is provided, so that the light emitted from the window glass 2 and the light guide plate 33 are both incident on the dual-purpose light receiving element 32, the reflector 37 is provided at the other end of the light guide plate 33.
Is provided. Therefore, the half mirror 7
The light emitting element 4 which is also used as
The light emitting element 34 for raindrops and the light emitting element 3 for dew condensation on one end
5 are provided. Therefore, detailed description is omitted by assigning the same reference numerals to the components having the same configuration.

As described above, according to the dew condensation and raindrop detection sensor 31 of the present embodiment, the raindrop light emitting element 34 and the dewdropping light emitting element 35 emit light at different intervals at regular intervals. Has become. Therefore, the dual-purpose light receiving element 32
Can detect the amount of light as incident light for raindrops or as incident light for dew condensation for each time zone. Therefore, in the dew condensation and raindrop detection sensor 31, since the light receiving element is integrated as the combined light receiving element 32 and the half mirror is not necessary, the cost can be reduced.

The present invention is not limited to the above-described embodiments, but can be implemented in other modes by making appropriate changes. For example, the V-shaped mirror 22 and the beam splitter 23 in the second embodiment.
Can be supported by replacing it with a half mirror.

[0030]

As described above, according to the dew condensation and raindrop detection sensor of the first aspect of the present invention, the light guide plate is in the form of a strip plate capable of detecting the dew condensation attached to the inner surface of the windshield, and the light emission for raindrops. The element is a dual-purpose light emitting element for both dew condensation and raindrops, and a semi-reflective member provided between the window glass and the light guide plate for branching the light from the dual-purpose light emitting element, and for reflecting the light after branching, respectively. In addition, a mirror provided between the windshield and the light guide plate, and a light receiving element for dew condensation provided separately from the raindrop light receiving element for receiving the light emitted after reflection inside the light guide plate are provided. Therefore, it is possible to detect not only the raindrops adhering to the outer surface of the windshield but also the dewdrops adhering to the inner surface of the light guide plate. Therefore, one dewdrop and raindrop detection sensor can be applied to not only the wiper blade but also the automatic defroster control. be able to. Therefore, not only the application can be expanded at low cost, but also the safety can be significantly improved.

Further, according to the dew condensation and raindrop detection sensor of the second aspect, a light splitting member for branching the light from the dual-use light emitting element before entering the window glass and the light guide plate, and the branched light. And a first light receiving element and a second light receiving element provided to receive the light split by the beam splitter, respectively. Therefore, the control signals to the wiper blade and the defroster are output based on the comparison values with the light receiving amounts of the first and second light receiving elements, not simply the light receiving amounts incident on the raindrop light receiving element and the condensation light receiving element. Therefore, even if the light amount of the dual-use light emitting element 4 is reduced due to deterioration, it is not output due to a malfunction, and the reliability can be further improved.

Further, according to the dew condensation and raindrop detection sensor of the third aspect, the raindrop light receiving element is a dual-purpose light receiving element capable of detecting dew condensation adhering to the inner surface of the wind glass, and is emitted from the wind glass and the light guide plate. A reflector provided at the other end of the light guide plate for allowing light to enter the dual-purpose light receiving element, and one end of the light guide plate separately for shifting the incident time of light to the window glass and the light guide plate. In addition to the raindrop light emitting element provided in the above, a dew condensation light emitting element is provided. Therefore, the light-emitting element for raindrops and the light-emitting element for dew condensation are emitted at different intervals in different time zones, and the dual-purpose light-receiving element serves as incident light for raindrops or incident light for dew condensation for each time zone. As a result, the amount of light can be detected. Therefore, the light-receiving element is integrated as a dual-purpose light-receiving element, and the half mirror is not required, so that the cost can be reduced.

Further, according to the method of detecting dew condensation and raindrops according to claims 4 and 5, the light guide plate can detect dew condensation adhering to the inner surface of the windshield, and the light-emitting element for raindrops is a dual-purpose light-emitting element for both condensation and raindrops. That is, the light from the combined light emitting element is branched by the semi-reflecting member, the branched light is reflected by the mirror, and the light emitted after reflection is received by the light receiving element for dew condensation separately from the light receiving element for the raindrop, The light from the dual-purpose light emitting element is split by the spectral member before being made incident on the window glass and the light guide plate, one of the split lights is further split by the beam splitter, and the first split light is received by the beam splitter. Light is received by the element and the second light receiving element. Also, the first
・ The light receiving result from the second light receiving element is compared with the light receiving results from the raindrop light receiving element and the dew condensation light receiving element by the comparison circuit, and is output as a control signal necessary for automatic control of the wiper blade and the defroster.

Therefore, the control signals to the wiper blade and the defroster are not the received light amounts incident on the raindrop light receiving element and the dew condensation light receiving element, but the comparison values with the light receiving amounts of the first and second light receiving elements, respectively. Since the light is output based on this, even if the light amount of the dual-use light emitting element is reduced due to deterioration, it is not output due to a malfunction, and the reliability can be further improved.

[Brief description of drawings]

FIG. 1 is an explanatory longitudinal sectional view showing a first embodiment of a dew condensation and raindrop detection sensor of the present invention.

FIG. 2 is an explanatory longitudinal sectional view showing a second embodiment of the dew condensation and raindrop detection sensor of the present invention.

FIG. 3 is a vertical cross-sectional explanatory view showing a third embodiment of the dew condensation and raindrop detection sensor of the present invention.

FIG. 4 is a vertical sectional view showing an example of a conventional raindrop detection sensor.

[Explanation of symbols]

 1, 21, 31 Condensation and raindrop detection sensor 2 Wind glass 3 Light guide plate 4 Combined light emitting element 5 Condensation light receiving element 6 Raindrop light receiving element 7 Half mirror (semi-reflective member) 8 Mirror 22 V-shaped mirror (spectral member) 23 Beam Splitter 24 First light receiving element 25 Second light receiving element 26 Comparison circuit 32 Combined light receiving element 33 Light guide plate 34 Raindrop light emitting element 35 Condensation light emitting element 37 Reflector

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI Technical display area G01W 1/11 G01V 9/04 P

Claims (5)

[Claims] 1. A light guide plate made of a translucent material fixed to a part of the inner surface of the wind glass corresponding to a wiper blade sliding area attached to the outer surface of the wind glass, and one end portion of the light guide plate. A raindrop detection sensor comprising a supported light emitting element for raindrops and a light receiving element for raindrops supported at the other end, wherein the light guide plate is a strip plate shape capable of detecting condensation attached to the inner surface of the windshield. The light emitting element for raindrops is a combined light emitting element for dew condensation and raindrops, and a semi-reflective member provided between the window glass and the light guide plate for branching light from the combined light emitting element. A mirror provided between the window glass and the light guide plate for reflecting the branched light, and the raindrop for receiving the light emitted after the reflection inside the light guide plate. Condensation and rain detection sensor, characterized in that the condensation-receiving element and the optical device is provided separately are provided. 2. A light-splitting member for splitting the light from the dual-purpose light emitting element before entering the window glass and the light guide plate, and a beam splitter for further splitting one of the split lights. The dew condensation and raindrop detection sensor according to claim 1, further comprising: a first light receiving element and a second light receiving element provided for respectively receiving the lights branched by the beam splitter. 3. A light guide plate made of a translucent material fixed to a part of the inner surface of the wind glass corresponding to a wiper blade sliding area attached to the outer surface of the wind glass, and one end of the light guide plate. In a raindrop detection sensor including a supported raindrop light-emitting element and a raindrop light-receiving element supported at the other end, the raindrop light-receiving element can also detect dew condensation adhering to the inner surface of the windshield. A combined light-receiving element, a reflector provided at the other end of the light-guide plate so that light emitted from the window glass and the light-guide plate is incident on the combined light-receiving element, the window glass and the light-guide plate. A light-emitting element for dew condensation is provided separately from the light-emitting element for raindrops provided separately at one end of the light guide plate in order to shift the incident time of light to the light guide plate. And the raindrop detection sensor. 4. A raindrop supported on one end of a light guide plate made of a translucent material fixed to a part of the inner surface of the wind glass corresponding to a wiper blade sliding area attached to the outer surface of the wind glass. In a detection method of receiving light emitted from a light emitting element by a raindrop light receiving element supported at the other end of the light guide plate, the light guide plate can detect dew condensation attached to the inner surface of the windshield, The light-emitting element is a dual-purpose light emitting element for both condensation and raindrops, the light from the dual-purpose light emitting element is branched by a semi-reflecting member, the branched light is reflected by a mirror, and the light emitted after the reflection is received by the raindrop. A light-receiving element for dew condensation is also used to receive light separately from the element, and the light from the dual-purpose light-emitting element is split by a spectroscopic member before entering into the window glass and the light guide plate. , One of the branched optical additional branches by the beam splitter, condensation and rain detection method is characterized in that to receive the light branched by the beam splitter by the first and second light-receiving elements. 5. A comparison circuit compares the light reception results from the first and second light receiving elements with the light reception results from the raindrop light receiving element and the condensation light receiving element, and is required for automatic control of the wiper blade and the defroster. 5. The dew condensation and raindrop detection method according to claim 4, wherein the dew condensation and raindrop detection is performed as a control signal.