GB2080653A

GB2080653A - Optical communication systems

Info

Publication number: GB2080653A
Application number: GB8120256A
Authority: GB
Original assignee: BERMACO Srl
Current assignee: BERMACO Srl
Priority date: 1980-07-03
Filing date: 1981-07-01
Publication date: 1982-02-03
Also published as: FR2486278A1; IT8005177A0; ES8203531A1; DE3123758A1; BE889433A; ES503616A0

Abstract

A pair of infra-red photocells (1,2) comprising an emitting photocell (1), energised by impulses from an impulse generator (4), producing very short duration impulses, and a receiving photocell (2) for receiving these impulses and converting these into a square wave suitable for energising a relay, by means of an amplifier (7), monostable multivibrator (8) and an amplifier (9). <IMAGE>

Description

SPECIFICATION A pair of photocells for infra-red rays This invention relates to a pair of infra-red ray photocells for the activation of any static or electromagnetic relay generally for use as a power control.

In the field of photoelectric devices, photocells of the so-called modulated light type, which generally use a laser diode projector almost always (but not necessarily) generating infra-red rays, are already known. Modulation of the light is necessary in order to prevent exterior light from interfering with their operation.

Embodiments of the known type are characterised in that they use continuous modulated impulse emissions of relatively low power.

At the present time it is necessary to use complex, bulky and expensive equipment with a high power consumption in order to produce a light impulse projector of appreciable power.

The object of this invention on the other hand is to produce a pair of photocells which operate with the projection of light impulses of very short duration but of considerable power (flash effect), although the actual energy consumption is of the order of magnitude of the known photocells mentioned above.

According to the present invention there is provided in combination, pair of infra-red ray photocells, comprising an emitting photocell for the projection, under pulsed conditions, of very short duration light impulses which are spaced in time and are of high power, and a receiving photocell constructed and arranged to render the said system of impulses equivalent to a conventional continuous system of impulses with conversion of the time interval between two consecutive light impulses into energising time and to recognise the code of the said projected impulses.

The present invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a block diagram of a photocell pair; and Figures 2 and-S show, respectively, the impulses from the emitting photocell and the square wave output signal from the receiving photocell.

In the drawings, the emitting photocell is indicated generally, by the reference numeral 1 and the receiving photocell is indicated generally the reference numeral 2.

The emitting photocell 1 includes an infra-red ray projector 3, or laser diode, energised by a series of impulses from an impulse generator 4 powered from supply 5.

The impulse generator 4 is designed to produce very short duration impulses, which are widely spaced in time and are of considerable power. A graph of the impulses emitted is shown, for example, in Figure 2 of the drawings, from which the duration and spacing of the impulses with respect to time can be seen.

More specifically, if for example under conventional operating conditions the frequency of the impulses is n, the impulse generator 4 emits lin impulses in the same length of time. As a result, in the case in question the time interval between two successive impulses will be n - lin while the duration of each impulse will at the most be equal to the duration of each of then impulses of conventional operation.

It is however understood that the frequency of the impulses emitted by projector 3, if not in fact 1/n, may be any fraction of the frequency specified for a modulated light photocell of conventional type.

As far as the power of the projector impulses is concerned, if for example a SIEMENS LD 242 diode is used, the power in conventional operation would be 1.6 V x 200 mA = 0.32 Watt, while, with the system of impulses described herein, it is possible to achieve a power of 4.5 V x 4A = 18 Watt with all the consequent and otherwise unobtainable advantages.

For its part the receiving photocell 2 is designed to convert the abovementioned system of impulses (which is unsuitable for energising a relay) into a conventional continuous system. For this purpose the receiving photocell includes a sensor 6, which is capable of receiving the light impulses from projector 3 and of energising a monostable multivibrator 8 via an amplifier 7. The latter can only be energised by a very short period impulse which makes it possible to both recognise the code of the projected light and also transform the whole into a square wave signal of the type shown in Figure 3. In practice, the said monostable multivibrator 8 is designed to convert the "interval time" between two successive signals in the impulse system into "energising time".In any case, after suitable amplification by means of amplifier 9 and integration, the square wave output signal from the monostable multivibrator is capable of energising a relay for use, as appropriate, as a power control, as if the projected light were continuous or modulated in the conventional way.

It is nevertheless understood that the quantities and arrangements illustrated above are provided purely by way of example, it being obvious that the pair of photocells may be arranged in different ways so long as light impulses are emitted from the projector under pulsed (flash) conditions and a monostable multivibrator is used in the receiver with the abovementioned function of rendering the said system of impulses equivalent to the conventional modulated or continuous system.

1. In combination, a pair of infra-red ray photocells, comprising an emitting photocell for the projection, under pulsed conditions, of very short duration light impulses which are spaced in time and are of high power, and a receiving photocell constructed and arranged to render the said system of impulses equivalent to a conventional continuous system of impulses with conversion of the time interval between two consecutive light impulses into energising time and to recognise the code of the said projected impulses.

2. A pair of photocells according to claim 1, in

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION A pair of photocells for infra-red rays This invention relates to a pair of infra-red ray photocells for the activation of any static or electromagnetic relay generally for use as a power control. In the field of photoelectric devices, photocells of the so-called modulated light type, which generally use a laser diode projector almost always (but not necessarily) generating infra-red rays, are already known. Modulation of the light is necessary in order to prevent exterior light from interfering with their operation. Embodiments of the known type are characterised in that they use continuous modulated impulse emissions of relatively low power. At the present time it is necessary to use complex, bulky and expensive equipment with a high power consumption in order to produce a light impulse projector of appreciable power. The object of this invention on the other hand is to produce a pair of photocells which operate with the projection of light impulses of very short duration but of considerable power (flash effect), although the actual energy consumption is of the order of magnitude of the known photocells mentioned above. According to the present invention there is provided in combination, pair of infra-red ray photocells, comprising an emitting photocell for the projection, under pulsed conditions, of very short duration light impulses which are spaced in time and are of high power, and a receiving photocell constructed and arranged to render the said system of impulses equivalent to a conventional continuous system of impulses with conversion of the time interval between two consecutive light impulses into energising time and to recognise the code of the said projected impulses. The present invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a block diagram of a photocell pair; and Figures 2 and-S show, respectively, the impulses from the emitting photocell and the square wave output signal from the receiving photocell. In the drawings, the emitting photocell is indicated generally, by the reference numeral 1 and the receiving photocell is indicated generally the reference numeral 2. The emitting photocell 1 includes an infra-red ray projector 3, or laser diode, energised by a series of impulses from an impulse generator 4 powered from supply 5. The impulse generator 4 is designed to produce very short duration impulses, which are widely spaced in time and are of considerable power. A graph of the impulses emitted is shown, for example, in Figure 2 of the drawings, from which the duration and spacing of the impulses with respect to time can be seen. More specifically, if for example under conventional operating conditions the frequency of the impulses is n, the impulse generator 4 emits lin impulses in the same length of time. As a result, in the case in question the time interval between two successive impulses will be n - lin while the duration of each impulse will at the most be equal to the duration of each of then impulses of conventional operation. It is however understood that the frequency of the impulses emitted by projector 3, if not in fact 1/n, may be any fraction of the frequency specified for a modulated light photocell of conventional type. As far as the power of the projector impulses is concerned, if for example a SIEMENS LD 242 diode is used, the power in conventional operation would be 1.6 V x 200 mA = 0.32 Watt, while, with the system of impulses described herein, it is possible to achieve a power of 4.5 V x 4A = 18 Watt with all the consequent and otherwise unobtainable advantages. For its part the receiving photocell 2 is designed to convert the abovementioned system of impulses (which is unsuitable for energising a relay) into a conventional continuous system. For this purpose the receiving photocell includes a sensor 6, which is capable of receiving the light impulses from projector 3 and of energising a monostable multivibrator 8 via an amplifier 7. The latter can only be energised by a very short period impulse which makes it possible to both recognise the code of the projected light and also transform the whole into a square wave signal of the type shown in Figure 3. In practice, the said monostable multivibrator 8 is designed to convert the "interval time" between two successive signals in the impulse system into "energising time".In any case, after suitable amplification by means of amplifier 9 and integration, the square wave output signal from the monostable multivibrator is capable of energising a relay for use, as appropriate, as a power control, as if the projected light were continuous or modulated in the conventional way. It is nevertheless understood that the quantities and arrangements illustrated above are provided purely by way of example, it being obvious that the pair of photocells may be arranged in different ways so long as light impulses are emitted from the projector under pulsed (flash) conditions and a monostable multivibrator is used in the receiver with the abovementioned function of rendering the said system of impulses equivalent to the conventional modulated or continuous system. CLAIMS

2. A pair of photocells according to claim 1, in which the said emitting photocell includes a light impulse generatorforwhich there is a high ratio between impulse emission time and interval time, and in which the said receiving photocell includes a monostable multivibrator which can be activated by the said pulses of very short duration and is capable of recognising the code of the projected light and of transforming the said impulses into a square wave signal capable of energising a relay or other power unit.

3. In combination, a pair of infra-red ray photocells substantially as herein described with reference to and as illustrated in the accompanying drawings.