GB1560127A - Optical remote control - Google Patents

Description

(54) OPTICAL REMOTE CONTROL (71) We, SIEMENS AKTIENGESELLSCHAFT, a German Company, of Berlin and Munich, Federal Republic of Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to optical remote control systems, wherein an optical (e.g. infra-red) signal containing the control information is transmitted in the form of a pulse code from a transmitter to a receiver in a device which is to be controlled, and is particularly but not exclusively, concerned with remote control for television receivers.

It is known to carry out remote control of televisions by ultrasonic- or infrared transmission. The individual functions of the television which are to be operated, for example the selection of the television programmes, the volume control, the picture brightness or the picture contrast are assigned a specific command in a specific code. At the transmitter end there is arranged a matrix in which columns and rows can be selectively connected to one another in order to select a specific command which is converted into the code in the transmitter. At the receiver end the command is decoded and subsequently fed to stores via which either the programmes or similar parameters such as volume, picture brightness or picture contrast are controlled in accordance with the command.

The aforementioned analogue values such as volume, picture brightness or picture contrast can be varied in stepped fashion, if a command with which such an analogue value is varied by one stage is in each case transmitted and received.

In previously employed codes, such as for example a frequency or frequency coding in each case assigned to a command, in which different frequencies are assigned to binary values and are sequentially transmitted, satisfactory resistance to interference could be achieved only by means of multiple analysis.

The aim of the present invention is to pro vide a system in which the outlay required to achieve the requisite resistance to interfer ence can be reduced.

In accordance with one aspect of the pres ent invention there is provided an optical remote-control system comprising: a trans mitter comprising a light-emitting device and control means for modulating the light out put thereof with a command signal in the form of coded pulses in response to instruc tions from an operator, the control means being arranged, in operation, to encode the pulses by phase modulation; and a receiver comprising a light-sensitive device and con- trol means including means for decoding phase-modulated pulses.

The invention also extends to the transmit ter and to the receiver of this system.

In another aspect, the invention provides an optical remote control method in which an optical signal containing the control informa tion is transmitted, as command signals in the form of coded pulses, from a transmitter to a receiver in a device to be controlled and in which the pulses are encoded by phase mod ulation.

Phase modulation, or biphase coding pos sesses considerable advantages for async hronous signal sampling at the receiving end and in particular for infrared transmission.

At the receiving end, at the latest following the duration of one bit, a synchronisation signal obtained from the flanks of the pulses of the code is available for sampling. This results in high oscillator tolerances for the overall system. This results in high oscillator tolerances for the overall system.

Furthermore there are simple facilities for checking the biphase code as each bit must consist of a 0-1 or a 1-0-sequence.

Finally a high degree of resistance to inter ference can be achieved without multiple analysis.

An exemplary embodiment of the invention will now be described with reference to the drawings, in which: Fig 1. illustrates a command in the form of a biphase code; and Fig 2. is a schematic block circuit diagram of a receiver. In accordance with Fig. 1, a biphase code is composed of a sequence of pulses exhibiting different widths and different intervals from one another, which in particular are modulated onto a carrier of e.g. 30 Khz. This pulse sequence is interrogated at time intervals to of equal length in respect of its rising and falling flanks (indicated by arrows), whereby a binary value is produced which in the present case amounts to seven bits - 20 to 26. The represented command can, for example, be a volume command for a television.

If desired this command can be periodically transmitted with a predetermined cycle time T to a receiver in the device to be controlled, producing a quasi-continuous change of a corresponding, controlled analogue value.

The arrangement can also be contrived to be such that the corresponding command is periodically transmitted producing a successive, stepped switch-over of the corresponding analogue value.

Here the cycle time can be selected to be such that in the control device, analogue values such as volume, picture brightness and picture contrast can be continuously passed through from the physiological standpoint.

It has proved particularly expedient to select the cycle time to be such that it is possible to pass through the entire range of an analogue value, such as the volume in approximately 5 to 10 sec.

In Fig. 2 is schematically illustrated, as a block circuit diagram, a receiver suitable for use in a television set, in which the received command sequence is firstly demodulated in a demodulator 1, i.e. freed of the carrier, and then decoded in a decoder 2. This decoder 2 is followed by an error recognition stage 3 which checks whether the received signal is actually a genuine command code and not for example a fault picked up from other light sources, for example an optical sound transmission system. For this purpose, it is provided in particular that the decoding of the pulse code in the receiver of the device to be controlled commences with a predetermined delay relative to the end of the code. In this case the analysis of the pulse code occurs with a specific delay t1 at the end of a command.Only when no further information arrives during this interval tl (see Fig. 1), is the decoded information which has arrived before this interval of time further processed.

Following the error recognition stage 3, the decoded command is fed into a programming store 4 and an analogue store 5, via which either a programme switch-over or a change of analogue values such as volume L, picture brightness H or picture contrast K is effected.

WHAT WE CLAIM IS: 1. An optical remote-control system comprising: a transmitter comprising a light-emitting device and control means for modulating the light output thereof with a command signal in the form of coded pulses in response to instructions from an operator, the control means being arranged, in operation, to encode the pulses by phase modulation; and a receiver comprising a lightsensitive device and control means including means for decoding phase-modulated pulses.

2. A system according to claim 1 in which the control means of the transmitter is arranged to modulate the light with a carrier which is itself modulated with the pulses and in which the control means of the receiver includes a demodulator for obtaining the pulses from the modulated carrier.

3. A system according to claim 1 or 2 in which the light-emitting and receiving devices utilize radiation, in the infra-red region.

4. A system according to claim 1, 2 or 3 in which, for the control of an analogue quantity, the transmitter is operable to repeatedly transmit a respective command and the control means of the receiver is arranged to control the rate of adjustment of the analogue quantity in accordance with the cycle time of the received command.

5. A system according to claim 4 in which the cycle time is selected to be such that the entire range of the desired analogue quantity can be passed through in approximately 5 to 10 sec.

6. A system as claimed in any one of the preceding claims in which the control means of the receiver is arranged to store the received code and to wait a predetermined length of time after reception thereof before decoding of the received code.

7. An optical remote control system sub stantially as hereinbefore described with reference to the accompanying drawings.

8. The transmitter of any one of the pre

Claims (1)

1. ceding claims.

   9. The receiver of any one of the preceding claims.

   10. A television receiver including a receiver according to claim 9 for control thereof.

   11. An optical remote control method in which an optical signal containing the control.

   information is transmitted, as command signals in the form of coded pulses, from a transmitter to a receiver in a device to be controlled and in which the pulses are encoded by phase modulation.

   12. A method according to claim 11 in which, for the control of an analogue quantity, the desired command is repeatedly transmitted from the transmitter with a predetermined cycle time and the receiver controls the rate of adjustment of the analogue quantity in accordance with the cycle time of the received command.

   13. A method according to claim 11 or 12, wherein the cycle time is variable.

   14. A method according to claim 11, 12 or 13, in which the cycle time is selected to be such that the entire range of the desired analogue quantity can be passed through in approximately 5 to 10 sec.

   15. A method according to any one of claims 1 to 4, in which decoding of the pulse code in the receiver of the device to be controlled takes place only after a predetermined delay relative to reception of the end of the code.

   16. An optical remote control method substantially as hereinbefore described with reference to the accompanying drawings.