Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Patent
1989-07-26
1991-10-22
Eisenzopf, Reinhard J.
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
455112, 455216, 359184, H04B 1010
Patent
active
050603094
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an infrared type detecting device which emits infrared pulse light modulated to have periodicity and which produces a detection output when the infrared rays are obstructed, and particularly to an infrared type detecting device which uses double-modulated infrared pulse light, adapted to make it possible to change the modulating frequency.
BACKGROUND ART
A conventional modulated infrared type detecting device has its modulating frequency fixed from the outset and registers a frequency band received by a light receiver with a single modulating frequency fixed in pulse light emitted from a light projector. However, if there is any noise (disturbance light) which can be detected by the light receiver, there is the possibility of its irregular amplitude causing it to pass through a filter or tuning circuit subsequent to the light receiver to produce a light reception output (indicating that there is no intruder), even if such noise has no frequency which is the same as or similar to the modulating frequency for the infrared rays. Thus, to solve this problem, an infrared type warning device using double-modulated infrared pulse light as disclosed in Japanese Laid-Open Patent Publication No. 21132/1984 uses an emitter (light projector) of the type which modulates the amplitude of a high frequency signal by means of a low frequency signal, while employing in a receiving circuit a phase locked loop (hereinafter referred to as PLL) which follows the frequency and phase of an input signal, with the intention of providing a highly sensitive receiving device. That is, on the light receiving side of this apparatus, pulse light emitted from the light projector is highly sensitively received by a tuned amplifier and PLL, but it has been impossible to switch modulating and demodulating frequencies for high and low frequencies set in a warning device to other values.
DISCLOSURE OF INVENTION
When it is desired to monitor a vast field site by a plurality of infrared type detecting devices, in some cases two or more sets will be continuously arranged on a straight line. In other cases, infrared rays are set at two or more heights so as to effect monitoring by infrared rays arranged in two or more rows, and if detecting devices fixed in frequency to a single value are used, signal interference will take place between their respective light projectors and receivers, leading to malfunction. It will be readily seen that this often takes places in the case of the multi-row type with parallel monitoring lines. Even when two or more sets of light projectors and light receivers are continuously arranged with their respective monitor range defined by substantially straight lines or polygonal lines in very obtuse angles, the light from the endmost light projector reaches not only the light receiver corresponding thereto but also other remote light receivers; thus, even if infrared pulse light from the light projectors mated with such remote light receivers are cut off, the presence of the arrival light result in a so-called miswarning, i.e., failing to produce an intruder detection signal. To avoid these problems, it has been necessary to specially change the frequency for each monitor range. Particularly in the case of a detecting device using double-modulated infrared pulse light, both the light projector and the light receiver require frequency adjustment to be made at two or more places, making both manufacture and inspection complicated.
To solve these problems, the present invention provides a detecting device using double-modulated infrared pulse light and capable of high sensitivity reception, wherein switching between high and low frequencies for the light projector and light receiver is made possible, such switching between high and low frequencies being made possible by simply operating switch sections, one for each of the members, the light projector and light receiver. That is, the light projector is provided with an 1/N- frequency dividing circuit for dividing the ba
REFERENCES:
patent: 3668562 (1972-06-01), Fritkin
patent: 3798547 (1974-03-01), Reudink
patent: 3805192 (1974-04-01), Ocnaschek
patent: 4949396 (1990-08-01), Chung
Eisenzopf Reinhard J.
Pascal L.
Takenaka Engineering Co. Ltd.
LandOfFree
Infrared detector does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Infrared detector, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Infrared detector will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-116149