JP2633854B2 - Infrared cutoff detector - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared cutoff detector for detecting a cutoff of an infrared beam and issuing a burglar alarm or the like.

(Prior art) Conventionally, in this type of infrared cutoff detector, a light receiver is arranged at a predetermined distance from a projector that emits an infrared beam, and the infrared beam is cut off by the passage of a person or the like. Is detected by a light receiver, and a theft alarm or the like is performed.

Infrared light emitting elements provided in the projector, such as infrared LEDs (infrared light emitting diodes), are intermittently illuminated to reduce power consumption and increase the durability of the elements. Up to 50
Intermittent light emission is performed at a light emission repetition frequency of about 0 Hz.

(Problems to be Solved by the Invention) However, in the emission of an infrared beam by such conventional intermittent light emission, the light emission drive current that can flow once into the infrared LED is based on the off duty ratio of the intermittent light emission cycle. As a result, there is a problem in that the warning distance determined by the effective reach of the infrared beam is restricted, and that the beam is greatly affected by fog or the like.

Therefore, in the conventional apparatus, for example, as shown in FIG. 6, two light-emitting portions 2a and 2b are provided in the light projector 1 and two light-receiving portions 4a and 4b are similarly provided in the light receiver 3 as well. The double beam method of emitting the beams 5a and 5b is adopted, and the spread of the two infrared beams 5a and 5b from the projector 1 causes the light receiving sections 4a and 4b of the light receiver 2 to receive a combined beam of the two infrared beams 5a and 5b. In this way, the infrared beam is apparently intensified.

However, in such a double beam system, there is a problem that the device becomes large, the structure is complicated, and the cost increases.

(Means for Solving the Problems) The present invention has been made in view of such conventional problems, and increases a light-emitting current that can be supplied to an infrared light emitting diode even in a one-beam system, thereby increasing a caution distance. It is an object of the present invention to provide an infrared cutoff detector capable of reducing beam attenuation due to an increase in light and fog.

In order to achieve this object, in the present invention, a light emitter and a light receiver are arranged opposite to each other at a predetermined distance, and an infrared beam having a predetermined light emission pulse width is intermittently emitted from the light emitter at every predetermined period T. In an infrared cutoff detector that emits light toward a light receiver and detects the cutoff of the infrared beam with the light receiver, the light projector is provided with N infrared light emitting diodes, and each of the N infrared light emitting diodes is provided. A driving current flowing in each of the infrared light emitting diodes, while controlling the light emission repeatedly in a cycle (N × T) obtained by multiplying the predetermined cycle T by N without changing the predetermined light emission pulse width and by shifting the predetermined cycle T. and the light emission control means for increasing the acceptable amount of light emission is set to high drive current I ₂ from the driving current I ₁ when light emission drive a single infrared light emitting diode in said constant period T And wherein the digit.

(Operation) In the infrared cutoff detector of the present invention having such a configuration, a plurality of infrared light emitting diodes are sequentially arranged in a predetermined light emission cycle, for example, every light emission cycle (T) determined by a light emission repetition frequency of 500 Hz. Since the number of infrared light emitting diodes is (N) because of light emission driving, the light emitting cycle per infrared light emitting diode is expanded to (T × N), and the element ON time in the light emitting cycle does not change. As the off-duty ratio per infrared light emitting diode can be increased approximately N times, the current that can be passed through the infrared light emitting diode by intermittent light emission drive can be increased as the off duty is large, so that the light emitting current can be reduced. Can increase the intensity of the infrared beam by increasing the emission current,
If the guard distance is the same as the increase in the guard distance, beam attenuation due to fog or the like can be reduced.

(Embodiment) FIG. 1 is a circuit block diagram showing an embodiment of a light projector in an infrared cutoff detector of the present invention.

In FIG. 1, reference numeral 10 denotes a rectifier circuit, for example, a commercial AC
Receiving the voltage dropped to the predetermined voltage by dropping 100V, rectified,
Generates a predetermined DC voltage. Reference numeral 12 denotes a constant voltage circuit, which stabilizes the DC voltage from the rectifier circuit 10 and supplies a constant voltage as a power source to each circuit unit of the projector.

Reference numeral 14 denotes an oscillation circuit. The oscillation circuit 14 oscillates at a repetition frequency of, for example, 500 Hz, and oscillates an oscillation pulse a having a period T including an on-time Ton and an off-time Toff shown in FIG.

The oscillation pulse a from the oscillation circuit 14 is given to the control circuits 16 and 18. The control circuits 16 and 18 are provided corresponding to the two light emitting circuits 20 and 22. Each of the light emitting circuits 20 and 22 incorporates an infrared LED as an infrared light emitting diode.

FIG. 2 shows an example of a circuit configuration of the light emitting circuits 20 and 22 of FIG. 1. The light emitting circuit 20 is provided with an infrared LED 24, and the light emitting circuit 22 is provided with an infrared LED 26. Infrared LED 24,2
6 are intermittently driven to emit light under the switching control of the transistors 28 and 30, respectively. Control signals d and e for the bases of the transistors 28 and 30 are supplied from the control circuits 16 and 18 in FIG. When the power is applied to the infrared LEDs 24 and 26 through the resistors R1 and R2 when the 30 is turned on, the infrared LEDs 24 and 26 emit light.

Referring again to FIG. 1, the control circuits 16 and 18
In synchronization with the oscillation pulse from 4, control signals d and e obtained by dividing the oscillation pulse by 1/2 with gate signals having a 180 ° phase difference are alternately output to the light emitting circuits 20 and 22.

That is, as shown in FIG. 3, the control circuit 16 produces a gate signal b obtained by dividing the oscillation pulse a by half, while the control circuit 18 produces a gate signal c having a 180 ° phase difference from the gate signal b. The control circuit 16 generates a control signal d by taking the logical product of the gate signal b and the oscillation pulse a and outputs the control signal d to the light emitting circuit 20, and the control circuit 18 calculates the logical product of the oscillation pulse a and the gate signal c. Thus, the control signal e is generated and output to the light emitting circuit 22.

Next, the operation of the embodiment shown in FIG. 1 will be described. Oscillation circuit 14
For example, if an oscillation pulse a having a light emission repetition frequency of 500 Hz is oscillated, the oscillation pulse a
The control circuit 16 is provided with the gate signal b or the gate signal c shown in FIG.
Outputs a control signal d to the light-emitting circuit 20 to drive the infrared LED 24 provided in the light-emitting circuit 20 to emit light, while the control circuit 18 outputs a control signal e having a phase T of a period T with respect to the control signal d. 22 to drive the infrared LED 26 to emit light. As described above, the infrared light from the infrared LEDs 24 and 26 provided in the light emitting circuits 20 and 22 that are sequentially driven to emit light by the control signals d and e of the control circuits 16 and 18 is that the infrared LEDs 24 and 26 are arranged in close proximity. As a result, the infrared beams are sequentially emitted as infrared beams at the same position. When viewed from the light receiver, the infrared beam is intermittently emitted from the light emitter at a light emission repetition frequency of 500 Hz.

Looking at the emission drive of the infrared LEDs 24 and 26, the control circuit
The light emission cycle of the infrared LEDs 24 and 26 is twice as long as the cycle T of the oscillation pulse a in the sequential light emission by 16, 18 and the light emission time Ton of the infrared LEDs 24 and 26 is the same. With 2T, the off duty Doff given by Doff = Toff / (Ton + Toff) is approximately doubled if Ton is sufficiently short.

As a result, as shown in the timing chart of FIG.
Since the off-duty of the LED 24 is approximately doubled, the emission current I01 can be increased to I2 as shown in the figure with respect to the emission current I1 at the time of off-duty emission drive at 500 Hz indicated by the broken line. Can enhance the infrared beam. This point is the infrared ray LE that obtains the light emission pulse L2.
The same applies to the emission current I02 of D26.

As a result, apparently the same state as when the infrared LED was driven by the emission current I2 flowing due to the increase in off duty at the emission repetition frequency of 500 Hz, the emission current of the infrared LED was increased without changing the emission repetition frequency of 500 Hz and fired It is possible to increase the infrared beam to be emitted, to increase the caution distance, and to increase the infrared beam to reduce beam attenuation when fog or the like is generated, thereby preventing malfunction.

FIG. 5 is a circuit block diagram showing another embodiment of the present invention. In this embodiment, the light emission drive control is switched by detecting the state of an external environment such as fog which causes beam attenuation. It is characterized by the following. The power supply line is omitted in the embodiment of FIG.

In FIG. 5, reference numeral 32 denotes an environment detection circuit, which detects a fog or a rainfall generated in, for example, a caution area and generates a detection output. The detection output of the environment detection circuit 32 is a current control circuit 34
And the oscillation synchronizing circuit 36.

In the embodiment shown in FIG. 5, the light emitting circuits 20 and 22
Oscillation circuits 38 and 40 are provided for each of the above, the oscillation frequency of the oscillation circuits 38 and 40 is controlled by the oscillation synchronization circuit 36, and the oscillation outputs from the oscillation circuits 38 and 40 enable the light emission circuits 20 and 22 The emission current flowing to the infrared LED is controlled by the current control circuit 34
Controlled by.

When the oscillation synchronization circuit 36 is in the steady monitoring state where the detection output of the environment detection circuit 32 cannot be obtained, for example, the oscillation circuits 38 and 40
Synchronous oscillation is performed at 00 Hz, and the current control circuit 34 limits the emission current flowing to the infrared LEDs of the emission circuits 20 and 22 to a specified current.

On the other hand, when the detection output of the environment detection circuit 32 is obtained, the oscillation synchronization circuit 36 reduces the oscillation frequency of the oscillation circuits 38 and 40 by half to 250 Hz.
Switching to oscillation and the oscillation phase is 500 Hz
The phase is controlled so as to have a phase difference by an amount. At the same time, the current control circuit 34 receiving the detection output of the environment detection circuit 32
The light emission current flowing through 20, 20 and 22 is increased to a predetermined current value higher than the light emission current in the steady monitoring state.

For this reason, in an environmental condition where the infrared beam is expected to be attenuated due to fog or rain, the infrared LEDs of the light emitting circuits 20 and 22 are alternately driven to emit light at a repetition frequency of 250 Hz. Since the off-duty is approximately twice as large as the steady-state monitoring state, a light-emitting current larger than the light-emitting current in the steady-state monitoring state can flow under current control by the current control circuit 34. The beam is strengthened to prevent beam attenuation due to fog or rain.

In the embodiment of FIG. 5, the oscillation circuits 38, 40 are oscillated at 500 Hz in the steady monitoring state. In the steady monitoring state, only one of the oscillation circuits 38, 40 is used. Oscillation drive may be performed.

Also, in the embodiment of FIG. 1, the parts of the control circuits 16 and 18 are used as oscillation circuits as in the embodiment of FIG.
May be used as an oscillation synchronous circuit so that the two light emitting circuits 20 and 22 are driven to emit light intermittently and sequentially.

Further, in the above embodiment, the case where two infrared LEDs are provided in the projector is taken as an example.
The number of EDs is not limited to this. If three or more infrared LEDs are provided as needed and light emission is driven intermittently, the off duty per infrared LED is further increased to further increase the emission current. be able to.

Furthermore, in the above embodiment, the infrared LEDs as independent light emitting elements are arranged close to each other, but one in which two light emitting elements are integrated into one infrared LED is used. Then, the present invention can be easily realized without changing the conventional optical system.

On the other hand, in the above embodiment, the one-beam system is taken as an example. However, in the double-beam system shown in FIG.
The present invention may be applied by providing an LED.

(Effects of the Invention) As described above, according to the present invention, a light emitter and a light receiver are opposed to each other with a predetermined distance therebetween, and a predetermined light emission pulse width is intermittently interposed every predetermined period T from the light emitter. In the infrared cutoff detector that emits the infrared beam toward the light receiver and detects the cutoff of the infrared beam with the light receiver, the light emitter is provided with N infrared light emitting diodes,
Each of the N infrared light-emitting diodes is sequentially and repeatedly controlled to emit light at a period (N × T) obtained by multiplying the predetermined period T by N without changing the predetermined light emission pulse width and by shifting the predetermined period T. The drive current flowing through each of the infrared light emitting diodes is set to a drive current I ₂ higher than the drive current I ₁ allowed when a single infrared light emitting diode is driven to emit light at the constant period T, thereby increasing the amount of emitted light. The light emitting control means for causing the infrared light emitting diode 1
The off-duty ratio per unit can be increased according to the number of elements.
The current flowing through the infrared light emitting diode can be increased by one light emission drive, and the infrared light beam can be strengthened by the increase of the light emission current, thereby increasing the caution distance and reducing the beam attenuation due to fog, rain, and the like.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, FIG. 2 is a circuit diagram of the light emitting circuit of FIG. 1, FIG. 3 is an operation timing chart of FIG. 1, and FIG. FIG. 5 is a timing chart showing light emission pulses and light emission currents, FIG. 5 is a block diagram showing another embodiment of the present invention, and FIG. 6 is an explanatory diagram showing a conventional double beam system. 10: Rectifier circuit 12: Constant voltage circuit 14, 38, 40: Oscillator circuit 16, 18: Control circuit 20, 22: Light emitting circuit 24, 26: Infrared LED (infrared light emitting diode) 28, 30: Transistor 32: Environmental detection circuit 34: Current control circuit 36: Transmission synchronization circuit

Claims (1)

(57) [Claims] 1. A light emitter and a light receiver are arranged opposite to each other at a predetermined distance, and an infrared beam having a predetermined light emission pulse width is intermittently emitted from the light emitter toward the light receiver every predetermined fixed period T; In the infrared cutoff detector for detecting the cutoff of the infrared beam by the light receiver, the light projector is provided with N infrared light emitting diodes.
Each of the plurality of infrared light emitting diodes is sequentially and repeatedly controlled to emit light at a period (N × T) obtained by multiplying the predetermined period T by N without changing the predetermined light emission pulse width and by shifting the predetermined period T, and A driving current I ₁ allowed when a single infrared light emitting diode is driven to emit light at the constant period T is a driving current flowing through each infrared light emitting diode.
Infrared blocking detector, characterized in that a light emission control means for increasing the amount of emitted light is set to a higher drive current I _2.