JPS58204339A - Water drop detector - Google Patents

Abstract

PURPOSE:To detect the water drop stuck over a wide region with good sensitivity, by disposing a light source which irradiates light to glass from the inside surface side thereof, and an image splitting lens and a photodetector so as to receive the reflected light from the water drop stuck on the outside of the glass. CONSTITUTION:A water drop detector consists of a light emitting part 4, a photodetection part 5, an image splitting lens 14, and an optical filter 15, the latter three of which are arranged on the same optical axis and are installed in a dashboard 12. The lens 14 is a condenser lens of the prism having the bisected or trisected condensing faces, by which the detection region is expanded two or three times. The reflected light from the water drop stuck on the glass differs in the direction from the reflected light from the glass and the level of the incident light to the part 5 increases when the water drops sticks on the glass. The sticking of the water drop is thus detected and a wiper 11 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a water droplet detection device that is effective in detecting water droplets adhering to the windshield of an automobile and automatically controlling wipers.

Conventionally, this type of water droplet detection device uses a method in which two conductors 1.2 are formed into a comb shape or a thinly wound shape and are pasted within the area wiped by a wiper on the outer surface of the windshield, as shown in Figure 1a), or There is a method in which a light emitting section 4 is arranged on the outer surface of the windshield 3 and the transmitted light is received by a light receiving section 5 on the inner surface. +al method uses conductor 1. 2
This method takes advantage of the fact that the resistance value between the wires changes, but even if the wiper wipes away the previous water droplets, they remain without being completely removed. The disadvantage is that the value does not change (poor responsiveness). In addition, since the wiper moves in sliding contact with the conductor 1.2, there is a drawback of poor durability.

On the other hand, the method of Yama) utilizes the fact that when light hits the water droplet 6, the amount of light incident on the photodetector 5 decreases;
There are problems with the placement of the light receiving sections 4 and 5, and since one of them is mounted outside the vehicle, maintenance is difficult and there are also problems with durability.

The present invention aims to realize a water drop detection device free from the above-mentioned drawbacks by detecting reflected light using the concave surface of water droplets, and particularly aims to enlarge the detection field of view using an image splitting lens.

The present invention provides a water droplet detection device that optically detects water droplets adhering to the outer surface of a glass glass from the inner surface thereof. It is characterized by comprising an image splitting lens arranged therein and a photodetector that photoelectrically converts the reflected light collected by the lens, which will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, which is applied to automatic wiper control. In the same figure, IO is the engine hood, 11 is the wiper blade, 12 is the dash board,
Reference numeral 13 indicates a nozzle, and a water drop detection device is installed inside the dash board 12 so as not to obstruct the driver's visibility. The water droplet detection device of this example includes a light emitting section 4, a light receiving section 5, and an image splitting lens 1.
4 and an optical filter 15, the latter three of which are arranged on the same optical axis. The image splitting lens 14 is a condensing lens whose light-converging surface is a two-split prism as shown in FIG. The type lens 14 has two detection areas 1
The sum of 7A and 17B is magnified twice as much as a convex lens of the same diameter (three times as much for lens 14').

These detection areas 17A and 17B are set within the wiping range of the wiper. In this example, in order to reduce the influence of sunlight and other external light, an optical filter 15 is provided in front of the image splitting lens 14 to block wavelengths other than those emitted by the light emitting section 4. In order to make the difference clear, it is preferable to apply pulse modulation to the output light of the light emitting section 4. The light emitting portions 4 may be provided at two or more locations as shown in the figure, or may be provided on the optical axis 16.

The water droplets 6 adhering to the detection areas 17A and 17B act as a kind of concave mirror due to their outer shape. There are two types of reflected light from the direction of the glass 3: specular reflected light that directly reflects the luminous flux from the light emitting section 4, and reflected light from the water droplets. The latter water droplet reflected light is once focused near the glass surface (at a position of f=R/2, where R is the radius of curvature of the water droplet) and then diffused, so the direction is different from that of the specularly reflected light. When these reflected lights are observed on the optical axis 16 through the image splitting lens 14, the level of light incident on the light receiving section 5 increases when water droplets are attached.

You can use this or use IPA control as shown in Figures 4 and 5.
This will be explained with reference to the figures. The light emitting unit 4 includes a light source 20 such as a light emitting diode, and a drive circuit 2 that pulse-modulates the output light a.
Consists of 1. The other configuration is the light receiving section 5, and the input stage is the photodetector 2.
2 (an optical filter 15 and a lens 14 are interposed between them). The photodetector 22 consists of a plurality of photodetecting element arrays, and the output thereof is taken out in time series by a multiplexer 23. The frequency division of clock generator 24 and its output 118!25 determines the selection order of multiplexer 23. The output of the multiplexer 23 is amplified by an amplifier 26,
Furthermore, only the signal light component is extracted by a bandpass filter 27. The bias component shown in Fig. 5 (mountain) is the detection area 17.
This is a case where no water droplet 6 is attached to A or 17B,
When the water droplets are attached, the level of the signal light component increases significantly.

The signal number is the element number of the photodetector array ■, ■, ■,...
...They are arranged in chronological order. Detector 2
8 performs envelope detection of the signal. Then, the signal C that has passed through the /% pass filter 29 is connected to the rate level TH.
The light is input to the comparator 30 of I to obtain an output d corresponding to the water droplet reflected light. Each of the judgment signals d indicates adhesion of water droplets, but the signal d is passed through the integrator 31 in order to reduce malfunctions and facilitate sensitivity adjustment. and the integral output e
When exceeds the comparison threshold TH2 of the comparator 32, a water droplet detection signal f is generated (sensitivity adjustment is performed by TR2). Although the pulse width TR of this signal f changes depending on the state of water droplet adhesion, the wiper drive circuit 33 is triggered at its rising edge to generate the wiper drive signal g for a certain period of time Tw. As a result, when the wiper motor 34 operates, the signal f
Since the water droplets that were the cause of the occurrence are removed, the wiper operation is in a standby state until the next water droplet adheres. Figure 5 (f
) is the interval at which the wiper operates intermittently, and this period changes depending on the state of adhesion of water droplets (how it rains, etc.).

The water droplet detection device of the present invention described above is of the reflected light detection type, so it is easy to wear and durable.

Furthermore, since the condensing lens is an image splitting lens, the detection area is expanded compared to the case where the condensing lens is a convex lens, and there is an advantage that the detection sensitivity of actual immersion adhesion is improved.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional water droplet detection device, FIGS. 2 and 3 are block diagrams showing an embodiment of the present invention, and FIGS. 4 and 5 are block diagrams showing wiper control signal processing. These are signal waveform diagrams for each part. In the figure, 3 is a window glass, 4 is a light emitting part, 5 is a light receiving part, 6 is a water droplet, and 14 is an image splitting lens. Applicant Fujitsu Ten Ltd. Representative Patent Attorney Minoru Aoyagi Figure 1 fal (b) (a
) (b) Figure 4

Claims (1)

[Claims] A water droplet detection device that optically detects water droplets adhering to the outer surface of glass from its inner surface includes a light source that illuminates a portion of the glass from the inner surface, and an image arranged to receive reflected light from the water droplets. A water droplet detection device comprising a split lens and a photodetector that photoelectrically converts reflected light collected by the lens.