Optics: measuring and testing – Of light reflection
Reexamination Certificate
2000-12-26
2003-07-08
Rosenberger, Richard A. (Department: 2877)
Optics: measuring and testing
Of light reflection
C318S483000, C250S573000
Reexamination Certificate
active
06590662
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an object sensor and an object sensing method for sensing an object such as a water drop that exists on a sensing surface of a product. Especially, it is related to a rain sensor and a rain sensing method applied to vehicles, and a windshield wiper controller and a windshield wiper control method using the object sensor.
2. Description of the Related Art
Conventionally, many types of rain sensors for vehicles are developed. For example, a rain sensor employing an optical method as follows is known. A light emitted from a photo emission element (light emission element) is reflected on a sensing surface and the reflected light is received by a photo detector, and then a rain drop is sensed. That is, the reflection condition varies if an object such as a water drop exists on the sensing surface, and the amount of the detected light by the photo detector will decrease. A conventional rain sensor senses a rain drop by detecting this variation.
The above mentioned varying detection, normally, a method for comparison with the reference value (threshold method) had been used (i.e. JP 10-186059 A).
In practical use of such a conventional rain sensor, the rain sensor will be used in various conditions, so that a means for preventing malfunction is necessary. In order to achieve this object, the conventional rain sensor uses plural reference values which are set according to the operation modes (JP 10-186059 A), or replaces and switches reference values one by one (JP 2-68248 A).
As mentioned above, with the conventional rain sensor, the logic for rain drop detection is complicated, and consequently, a high-speed processing for of rain drop detection becomes difficult. In addition, in either of the above mentioned conventional methods, the rain drop is detected by the comparison with the reference value based on judging the status on the sensing surface. Therefore, the prevention of the malfunction is difficult because of the influence of the light from the outside or the influence of the status of the sensing surface, e.g. where dirt is present.
Moreover, the photo emission element and the photo detector have a disadvantage that the element characteristic will vary when the temperature varies. Especially, the photo emission element such as LED has a characteristic that the output will decrease when the temperature rises. By this characteristic, such element has a problem that an appropriate detection cannot be processed unless data correction by monitoring and feeding back the output is processed.
For example, in JP 57-118952 A, a windshield wiper controller is disclosed. This apparatus employs a method in which a light emitted from a photo emission element and reflected on the surface of a windshield glass is received by a photo detector, then the amount of the rain drop is judged according to the received light signal level, and the windshield wiper is driven.
In more detail, the received light signal is detected, then the detected signal is provided to the differential circuit and pulse signals corresponding to the envelope of the received light signal are picked out, and these pulse signals are counted.
In this JP 57-118952 A, the detailed method of how to pick out the pulse signals is not clearly disclosed. However, judging from FIG.
3
(
c
) of the publication, the system will pick out a pulse signal when detecting the intersection of the envelope and the threshold.
In short, in the technology disclosed in the JP 57-118952 A, a rain drop impacting the surface of the windshield may be detected and counted and the detection for impact of a rain drop is processed by comparison the envelope with the threshold.
SUMMARY OF THE INVENTION
Therefore, with the foregoing in mind, the object of the present invention is not to judge the status of the sensing surface by comparison of the signal from the sensing surface with the reference value. The present invention provides an object sensor and a object sensing method that can detect the dynamic impact of a rain drop and does not require the complex judgment logic and also provides a windshield wiper controller using the object sensor.
Moreover, the object of the present invention is to provide an object sensor and a object sensing method that can detect a rain drop appropriately even though the signal level fluctuates and provide a windshield wiper controller using the object sensor.
In order to solve the above-mentioned problems, the first object sensor sensing the status of a sensing surface by detecting a light with a photo detector, which light has been emitted by a photo emission element and reflected on the sensing surface, comprises: a means for generating a time lag signal from the output signal of the photo detector; a means for calculating a differential signal between the output signal of the photo detector and the time lag signal; and a means for judging the status of the sensing surface by detecting the generation of the differential signal.
According to the above mentioned configuration, the status of the sensing surface can be detected by evaluating the variation over time of the signal level, not evaluating the signal level itself of the photo detector.
In order to solve the above-mentioned problems, the second object sensor sensing the status of a sensing surface by detecting a light with a photo detector, which light has been emitted by a photo emission element and reflected on the sensing surface, comprises: a means for canceling noise in a signal outputted from a photo detector; a means for generating a time lag signal from the noise-cancelled signal; a means for calculating a differential signal between the noise-cancelled signal and the time lag signal; and a means for judging the status of the sensing surface by detecting the generation of the differential signal.
According to the above configuration, the status of the sensing surface can be detected by evaluating the differential signal between the variation over time of the signal from the noise canceling processing and the variation over time of the first order time lag signal generated from the noise-cancelled signal, not by evaluating the signal level itself of the photo detector, so that the small fluctuation such as noise can be eliminated and only the significant varying of the signal level can be detected based on the status on the sensing surface.
In order to solve the above-mentioned problems, the third object sensor sensing the status of a sensing surface by detecting a light with a photo detector, which light has been emitted by a photo emission element and reflected on the sensing surface, comprises: a means for generating a first order time lag signal from the output signal of the photo detector; a means for generating a second order time lag signal from the first order time lag signal; a means for calculating a differential signal between the first order time lag signal and the second order time lag signal; and a means for judging the status of the sensing surface by detecting the generation of the differential signal.
According to the above configuration, the status of the sensing surface can be detected by evaluating the differential signal between the first order time lag signal and the second order time lag signal, not by evaluating the signal level itself of the photo detector. Because of evaluating the differential signal between the first order time lag signal and the second order time lag signal, the small fluctuation such as noise can be eliminated and only the significant varying of the signal level can be detected based on the status on the sensing surface.
It is preferable that in the above mentioned first, second or third object sensor, said means for canceling the noise and/or said means for generating a time lag signal are/is an analog circuit for generating the time lag signal.
It is preferable that the object sensor further comprises an A/D conversion means for converting an analog signal to a digital signal by sampling the analog signal of the photo
Kokuryo Kazuto
Nagao Shinji
Barth Vincent P
Merchant & Gould P.C.
Nippon Sheet Glass Co. Ltd.
Rosenberger Richard A.
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