JPS61150852A - Car theft preventive system - Google Patents

Abstract

PURPOSE:To prevent a car theft by detecting the theft with infrared rays intercepted by broken window glass or a burglar intruding in a car. CONSTITUTION:Infrared rays emitted from an illuminant 3 are reflected by a window glass 2 and reflectors 5, 6 in a car. When an optical path is not intercepted, the infrared rays enter into a light receiver 4. When it is found by a comparing circuit 14 that the amplitude is less than a threshold value, a timer circuit 15 is activated, and drives an alarm 16 for a certain time.

Description

DETAILED DESCRIPTION OF THE INVENTION (7) Technical Field The present invention relates to an automobile theft prevention system. When a car is stopped and the driver is not inside, a theft incident may occur. Conventional cars had only door locks as a device to prevent theft.

There are thefts where people break windows and take things from inside cars. They also steal equipment from outside the vehicle. Furthermore,
Often, entire cars are stolen.

(B) Prior Art Locking the door alone cannot completely prevent theft. If the window is open, they can reach in, unlock the door, open the door, and steal whatever is inside.

Even if the window glass is closed, you can open the door by breaking the glass. If you open the door and go inside, you can not only steal what's inside, but you can also steal the car itself.

Also, some people have the talent of unlocking doors by some means.

Once the driver leaves the vehicle, there is no device to monitor the vehicle, so it is not possible to effectively prevent third parties from intruding and stealing the vehicle.

(Europe) Configuration The automobile anti-theft system of the present invention uses infrared rays to detect whether there is a person inside the automobile or whether the window glass has been broken.

It consists of an emitter that emits infrared rays, a suitable reflector, and a receiver that detects infrared rays, creating an infrared optical path inside the car where the infrared rays are multiple reflected and transmitted from the emitter to the receiver. Form it. Car window glass is also used as a reflector.

If the window glass is broken or someone enters the car, the infrared rays will be blocked.

As a result, the amount of infrared light entering the receiver decreases, and the signal level of the detector decreases. This allows theft to be detected.

Since this is a situation in which theft is expected to occur, in order to prevent this, for example, the alarm 6 is issued to intimidate the thief. Since it is intended to warn the owner of the occurrence of a theft incident, it must be able to emit a sufficiently loud sound. Sound may be output along with simple sound. Infrared light is invisible to the naked eye, so even if a warning device like this is activated, you won't be able to tell.

Therefore, a person intending to commit theft cannot detect the existence of the security device in advance. Even after the sound is generated,
There is no way to turn this device off.

Since infrared rays are hot rays, DC disturbance components increase especially in summer. Is this the same level as the signal component?
Rather, the level of the disturbance component is higher. It must be possible to distinguish between disturbance components and signal components.

Therefore, the light emitter emits pulsed light with a constant repetition frequency F. The intensity of the infrared light emitter itself may be modulated, or if this is difficult, the light from the light emitter may be externally modulated by rotating a rotating disk with a large number of circular holes in its periphery.

For the light receiver, a detector must be used that is fast enough to respond to frequency F. In the receiver, the DC level is lowered and only the signal light is extracted from the AC components through a suitable filter.

FIG. 1 is a plan view illustrating the general structure of an automobile anti-theft system.

An infrared emitter 3 and a receiver 4 are installed in the car 1.
Put on. The infrared rays emitted from the emitter 3 are multiple reflected by the reflecting mirrors 5, 6, . . . and the window glass 2 and enter the receiver 4. When providing this optical path inside the automobile 1, sufficient care must be taken to ensure that the reflected light enters the next reflecting mirror.

In this example, the light is reflected three times on the optical path from the light emitter to the light receiver, but it may be reflected three times.

This system is deactivated when the car is in motion, but is not activated when the driver enters the vehicle.

The system is activated when the driver exits the vehicle and locks the door with the key.

The receiver detects the intensity of the incident infrared light, but first drops the direct current component and passes it through a filter that selects only the frequency F to determine the level of the signal intensity-modulated at the frequency F.

This level changes over a long period of time due to fogging of the reflecting mirror, dirt on the glass, and aging of the light emitting device.

However, in the short time it takes for the driver to exit the vehicle, lock the key, and then return to the vehicle,
It is thought that this will not change.

Suppose that window glass 2 is broken. Since it is no longer reflected here, the signal light does not reach the light receiver 4. The same thing would happen if someone broke into the car.

Therefore, the light receiver 4 compares the amplitude component of the signal of frequency F with a predetermined threshold value, and when the signal amplitude becomes smaller, it determines this as a sign of theft and issues an alarm.

Once an alarm is issued, a timer circuit or the like is used to continue issuing the alarm for a certain period of time.

Even if there is no obstacle on the optical path, the alarm is not stopped immediately. When the presence of an obstacle repeatedly appears on the optical path, an alarm is generated for a certain period of time each time, and when the obstacle remains on the optical path, an alarm is sounded intermittently.

Such devices are unlocked when the driver opens the door lock again with the key.

FIG. 2 shows an example of the circuit configuration.

The light emitter 3 is a semiconductor element that emits infrared rays and can be internally modulated. In this case, the output of the light emitter drive circuit 11 is controlled by the puff ref oscillator 10 which oscillates at the frequency F. The light emitter 3 repeats blinking at a frequency F.

As already mentioned, the infrared light emitted from the light emitter 3 is transmitted to the window glass 2.2 or the pre-installed reflector 5.6 inside the car.
reflected by. After being subjected to multiple reflections, the infrared light enters the light receiver 4 when the optical path is not blocked by anything.

The photoreceiver 4 is an infrared detector, which must have a fast response that can follow changes in the frequency F.

The infrared light is converted into current or voltage by the photoreceiver 4. There is also a lot of direct current. However, only the frequency F component is extracted by the filter 13.
1. The amplitude of this component is compared with a predetermined threshold value in the comparator circuit 14.

This amplitude is typically above a threshold. However, if something exists in the optical path and blocks the light, this amplitude becomes less than the threshold value.

Since the comparison circuit 14 determines that the amplitude has become below the threshold, the timer circuit 15 is activated at this time.

The timer circuit 15 drives the alarm 16 for a certain period of time. This intimidates intruders and alerts neighbors and car owners to the possibility of theft.

The timer circuit 15 may be a mechanical timer or may be a simple circuit combining a resistor and a capacitor. A timer circuit with a sufficiently long time constant can be constructed using a timer IC, a resistor, and a capacitor. of course,
An accurate timer may be constructed using an oscillator circuit and a counter.

In this example, the intensity of the light emitter 30 is oscillated at a constant frequency F. However, more complex modulation circuits may be used.

In this case, instead of the filter 13, a corresponding demodulation circuit is provided downstream of the light receiver 4.

If the response of the light emitter 3 is slow and the negative force field is sufficiently quickly internally modulated, a disk with a large number of slits in the periphery may be rotated.

In short, in order to distinguish between the signal light emitted from the light emitter 3 and the disturbance DC light, it is sufficient to provide some kind of modulation and demodulation device. Even though it is called signal light, it is not necessary to transmit a complicated signal, but only the presence or absence of signal light needs to be determined, so simple modulation and demodulation may be used. The simplest method is to modulate the intensity at a constant frequency.

The modulation method may be either internal modulation or external modulation.

In what has been described above, the emission spectrum of infrared rays is arbitrary, and the infrared rays are distinguished from DC disturbance light by varying the intensity.

When an infrared laser or the like is used as a light emitter, the emission wavelength is single, so an optical filter that passes only this wavelength can be placed in front of the receiver to detect only the signal light. Of course, infrared light that exists in the outside world has a component of this wavelength, but it is small compared to signal light. In this way, direct current light and signal light can be distinguished.

FIG. 3 shows such a configuration.

The infrared laser 3' no longer needs to be modulated;
The wavelength of the infrared light after multiple reflection is selected by an optical filter 13'. The output is detected after entering the photoreceiver 4, but the demodulator is no longer necessary and the comparator circuit 1
4, the signal is compared with a threshold value.

B) Effect: If the window glass of a car is broken or something breaks into the car, the device of the present invention will issue an alarm, making it possible to prevent theft accidents. can.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the interior of a vehicle for explaining the general configuration of the anti-theft system of the present invention. FIG. 2 is a schematic circuit diagram of the theft prevention system of the present invention. FIG. 3 is a schematic circuit configuration diagram showing another example. 1...Car 2...Window glass 3...Emitter 4...Receiver 5.6...Reflector 10...・Pulse oscillator 11... Light emitter drive circuit 13... Filter 14... Comparison circuit 15... Timer circuit 16... Alarm invention Kazu Hirano Husband Hisakazu Ishigaki

Claims (2)

[Claims] (1) A light emitter 3 that emits infrared light, a modulation device that internally or externally modulates the light emitter 3 and outputs infrared light at a constant frequency F or adds other modulation to produce modulated light, and a light emitter Reflecting mirrors 5, 6, etc. are provided to multiple-reflect the infrared light emitted from the infrared light from the vehicle window glasses 2, 2, etc. A light receiver 4, a demodulator that demodulates the output of the light receiver 4 and extracts a signal component, a comparison circuit 14 that compares the magnitude of the signal component with a predetermined threshold value, and a comparator circuit 14 that compares the magnitude of the signal component with a predetermined threshold value. An anti-theft system for an automobile, which is comprised of a timer circuit 15 that is turned on for a certain period of time, and an alarm 16 that is driven by the timer circuit 15, and functions after the door of the automobile is key-locked until the key is released. . (2) An infrared laser 3' and reflecting mirrors 5, 6 provided to multiple-reflect the infrared light emitted from the infrared laser 3' together with the car window glasses 2, 2, . . . ,..., an optical filter 13' is provided in the multiple reflection path of the infrared light and selects the light of the emission wavelength of the infrared laser, and the infrared signal light transmitted through the optical filter 13' is A light receiver 4 that detects the intensity, a comparison circuit 14 that compares the signal output of the light receiver 4 with a predetermined threshold, and a timer circuit 15 that turns on for a certain period of time when the signal output becomes lower than the threshold. An anti-theft system for an automobile, characterized in that the anti-theft system for an automobile is comprised of an alarm 16 which is activated by an alarm 16, and functions after the door of the automobile is locked until the key lock is released.