Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
1998-12-09
2001-04-10
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S2140AG, C250S2140AG
Reexamination Certificate
active
06215116
ABSTRACT:
The present invention relates to a proximity detecting device for detecting the presence of an object in a target area and comprising an emitter, a circuitry for supplying electrical pulses of a predetermined energy level to said emitter so as to emit detection pulses towards said target area, a receiver arranged for receiving the detection pulses and converting them into electrical signals, an amplifier for amplifying said electrical signals, and a control circuitry for determining on the basis of the amplified electrical signals whether the object is present in said target area or not.
Such a device is used in particular for detecting the presence of a human or a human body part and may be used to activate all kinds of different systems such as for example alarm systems, automatic door opening systems, counting devices, automatic bathroom fittings such as hand dryers, faucet devices, urinals, toilets, showers, soap dispensers, towel dispensers, wash fountains, etc. U.S. Pat. No.4,682,628 discloses for example a faucet device which is provided with an automatic active infrared detection system. Instead of infrared detection pulses, it is also possible to use other light pulses or for example ultrasonic pulses.
A drawback of the existing active infrared detection systems is that they are unable to detect small variations in the amplitude of the received detection pulses, and are thus unable to apply a movement criterion for detecting the presence or the continuing presence of the object. In practice they are only designed for detecting the simple presence of the object. This means that, for example in the case of a faucet device, the sensor, i.e. the emitter and the receiver, may not be directed into the sink or wash basin if one wants to avoid delicate and time consuming adjustments when installing them. Moreover, even when the sensor has been accurately adjusted, a stationary object such as for example a stack of dishes may cause false actuations, i.e. may keep the faucet open resulting in an important waste of water. When one would consider applying a movement criterion to the existing infrared detection systems to avoid such situations, this would not result in a practical solution to the above described problem due to the fact that variations in amplitude of the received detection pulses would only be detectable within a very restricted detection field. Indeed, the power received by the receiver is inversely proportional with the squared distance between the emitter and the receiver, when they are disposed opposite to one another, and even with the fourth power of the distance between the object and the emitter/receiver when the emitter and receiver are disposed next to one another and the emitted pulses are reflected by the object to the receiver. Consequently, when the emitted detection pulses are of a sufficient energy level to enable an accurate detection at a certain distance, the same energy level would be much too high to detect variations at a somewhat shorter distance. In other words, at this shorter distance the detection device would be blinded.
An object of the present invention is now to provide a proximity detecting device which enables to detection of changes in amplitude or energy level of the received detection pulses accurately over a sufficiently large distance range.
To this end, the proximity detecting device is characterized according to the invention in that it further comprises means for determining the amplitude of the amplified electrical signals and means for increasing the energy level of said electrical pulses when the amplitude of the amplified electrical signals is below a first threshold value and for decreasing the energy level of said electrical pulses when the amplitude of the amplified electrical signals is above a second threshold value, which is greater than or equal to said first threshold value.
In this way, the energy level of the emitted detection pulses is always automatically adjusted to the distance of the object which is to be detected and to other parameters such as the color, gloss, etc. thereof which also determine the amplitude of the pulses received by the receiver. Consequently, an accurate measurement of the amplitude of the received detection pulses is always possible, at least when the object is within the detection field, and no separation adjustment is required when installing the device, especially not when the target area is delimited in front of the emitter by a surface reflecting the emitted detection pulses towards the receiver. In this latter case, the energy level of the emitted detection pulses is immediately automatically adjusted, in the absence of any other object, on the basis of the pulses reflected by such surface. This surface is usually more reflective than for example the hands of a user so that, in the absence of a user, the energy level of the emitted detection pulses is automatically lowered resulting in a saving of energy.
In an advantageous embodiment of the device according to the invention, the amplifier provides a voltage gain which decreases as the amplitude of the amplified electrical signal increases and vice versa which increases as the amplitude of the amplified electrical signal decreases.
By providing such a non-linear amplification of the received signals, the amplitude thereof, or more particularly changes in the amplitude thereof, are correctly detectable over larger distance variations for a particular energy level of the emitted detection pulses. Consequently, less adjustments are to be applied to this energy level or, in other words, the energy level of the emitted detection pulses can be adjusted with larger steps.
REFERENCES:
patent: 4314207 (1982-02-01), Pinternagel
patent: 4682628 (1987-07-01), Hill
patent: 5142134 (1992-08-01), Kunkel
patent: 5225669 (1993-07-01), Hasch et al.
patent: 43 12 186 (1994-10-01), None
patent: 0463440 (1992-01-01), None
patent: 0813075 (1997-12-01), None
European Search Report dated Mar. 1, 1999 pertaining to application No. 97-203984.6 (4 pages).
European Search Report dated May 26, 1998 pertaining to application No. 97-203984.6 (3 pages).
Cahill Sutton & Thomas P.L.C.
Inter Company Computer Engineering Design Services in het kort C
Lee John R.
Pyo Kevin
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