Communications: directive radio wave systems and devices (e.g. – Presence detection only
Reexamination Certificate
2002-05-21
2003-03-18
Sotomayor, John B. (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Presence detection only
C342S028000, C342S107000, C340S552000
Reexamination Certificate
active
06535159
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an immersion object detection method for irradiating an electric wave such as a millimeter wave within e.g., a detection area to detect a reflected wave therefrom, thereby detecting existence of the immersion object within the detection area, and an immersion object detection system using such a method.
2. Description of the Background Art
Conventionally, with respect to crime prevention sensors for detecting a human body and the like, various types of sensors such as an infrared sensor, an ultrasonic sensor, an electric wave sensor and the like have been proposed. Among the above-mentioned sensors, the electric wave sensor, which is considerably less susceptible to natural environmental variation factors such as rain, snow and wind even when used outdoors, makes it possible to detect a human body within the detection area with high precision.
With respect to the electric wave sensor that includes various types, an electric wave sensor having the following construction has been disclosed. The electric wave sensor first irradiates an electric wave, in which the frequency has been modulated, to a detection area. Then, it receives a reflected wave of the irradiated electric wave and generates a beat wave by mixing the reflected wave with the original electric wave. This beat wave is spectrum-analyzed to examine the frequency at which a peak exists and the intensity thereof, thereby detecting a human body and the distance therefrom.
Thus, the electric wave sensor is free from the influences of external disturbances due the natural environmental environment factors, and also detects the position of the detected human body, so that this provides excellent performances as a crime prevention sensor.
On the other hand, with respect to the infrared sensor, etc., a regression reflecting type photoelectric sensor for detecting an immersion of an object by using a regression reflecting method. With respect to the regression reflecting method, in the case of an infrared sensor, a reflection plate, etc. is previously placed within a detection area, and an infrared ray is irradiated to this reflection plate, so that by detecting a reflected light from the reflection plate, any immersion of an object such as a human body into the detection area is detected.
As described above, the electric wave sensor detects a human body by examining the frequency at which a peak exists and the intensity thereof in a beat wave that has been spectrum-analyzed. Here, in general, a human body has a low reflectance to an electric wave. Moreover, it has been known that the intensity of the reflected wave decreases in inversely proportional to the distance raised to the fourth power. More specifically, in the case that a human body to be detected is far away from the sensor main body, the intensity of the reflected wave from the human body decreases considerably.
On the other hand, the beat wave obtained by mixing the reflected wave to be received with the original transmission wave contains noise components. These noise components result from a thermal noise in a circuit for generating a transmission wave and in a receiving circuit, a noise caused by a mixer for mixing a reflected wave and a transmission wave and a noise contained in a transmission wave as it own.
Therefore, the wave sensor has a problem that the intensity of the reflected wave from the human body positioned far away from the sensor main body come to reduce to the same level as the intensity of the above-mentioned noise components or a level weaker than the intensity thereof, thereby failing to detect the human body.
On the other hand, the above-mentioned regression reflecting type sensor has a problem that it can detect immersion of any object between the sensor and the reflection plate while it fails to detect how far the immersion object is away from the sensor main body and to identify the immersion object.
SUMMARY OF THE INVENTION
The present invention has been devised to solve the above-mentioned problems, and an objective thereof is to provide an immersion object detection method capable of detecting an immersion object within a detection target area irrespective of its short distance/long distance and of specifying the position thereof, and an immersion object detecting system using such a method.
In order to solve the above-mentioned problems, according to a first aspect of the present invention, an immersion object detection method includes the steps of irradiating a wave to a detection target area; detecting a reflected wave from the detection target area by reflected wave detection means; and determining that an immersion object exists within the detection target area in a case that the reflected wave cannot be detected from at least one reflection member among a plurality of reflection members placed within the detection target area, and simultaneously specifying a position of the immersion object in accordance with a position of the reflection member which cannot detect.
In accordance with the above-mentioned method, first, the wave irradiated to the detection target area is reflected in the detection target area, and the reflected wave is detected by the reflected wave detection means. Moreover, a plurality of reflection members are placed within the detection target area. Then, in the above-mentioned method, if there is any reflection member which cannot detect by the reflected wave detection means, a detecting operation of the immersion object and a specifying operation of the position thereof are carried out.
Here, if the reflection members are made of a material having high reflectance to the wave, it is possible to detect the reflected wave from a wider range as compared with a case in which, e.g., the reflected wave from the immersion object itself are detected. Moreover, in accordance with the position of the reflection member which cannot detect, the position of the immersion object is specified so that it becomes possible to provide the detection target area as a wider area, and also to specify the position of the immersion object.
Moreover, depending on the kind of the wave and the performance of the reflected wave detection means, in some cases, it is not possible to specify the position of the immersion object based on only the directly reflected wave from the immersion object. However, the application of the above-mentioned method makes it possible to specify the position of the immersion object even in such a case.
Furthermore, according to the first aspect, the immersion object detection method is characterized in that the plurality of reflection members are placed such that distances from the reflected wave detection means to each of the reflection members are different, respectively, and the position of the immersion object is specified as any position between a reflection member having the furthest distance from the reflected wave detection means among the reflection members which can detect the reflected wave and a reflection member having the nearest distance from the reflected wave detection means among the reflection members which cannot detect the reflected wave.
In the above-mentioned method, the plurality of reflection members are placed such that the distances from the reflected wave detection means to the respective reflection members are different, respectively. In the case an immersion object exists within the detection target area in this state, the reflected wave from the reflection member placed in a position closer to the reflected wave detection means than the immersion object are detected, while the reflected wave from the reflection member placed in a position farther from the reflected wave detection means than the immersion object are not detected because they are shielded by the immersion object. By utilizing this fact, the above-mentioned method specifies the position of the immersion object. Therefore, it becomes possible to accurately specify the position of the immersion object by using a comparatively s
Kawamoto Ryuji
Nishiguchi Tadao
Shimamoto Hiroshi
Dickstein , Shapiro, Morin & Oshinsky, LLP
Omron Corporation
Sotomayor John B.
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