APPARATUS FOR EMITTING AND RECEIVING LIGHT SIGNALS, MORE PARTICULARLY INFRARED SIGNALS

Abstract: There serves to emit light signals, more particularly infrared signals, and to receive such signals, an apparatus in which a light emitting arrangement (15) and a light receiv­ ing arrangement (20) are arranged in or behind a plate (32) which is translucent or transparent to said light signals or infrared signals. At least one surface of the plate (32) has such a finish between the light emitting arrangement (15) and the light receiving arrangement (20) that light rays are impeded or prevented from being passed on within the plate (32).

Description: The invention relates to an apparatus for emitting and receiving light signals as pointed out in the precharacterising portion of claim 1. Such an apparatus is known, for example, from GB-A-2 079 088. It is customary to use infrared remote control equipment in connection with the remote control of equipment pertaining to entertainment electronics, more particularly television receivers and video recorders. This infrared remote control equipment emits infrared signals for the purpose of adjusting the various functions of the equipment in response to corresponding operation of the keys. Furthermore, it is already known to transmit the audio signals of a television receiver by means of an infrared transmission system and to make them audible over headphones. The infrared transmission system in that case comprises an infrared transmitter which is connected to an audio signal output of the television receiver in question. The headphones are connected with an infrared receiver which allows the respective infrared signals transmitted from the infrared transmitter to be received and to be converted into signals which are audible over the headphones. It has become apparent that when operating an infrared remote control system and an infrared audio signal transmission system of the aforesaid kind, problems can arise owing to the fact that infrared signals emitted from the infrared remote control system are received by the infrared receiver of the infrared audio signal transmission system. Accordingly, the underlying object of the invention is to develop, with comparatively little expense in terms of construction, an apparatus for emitting and receiving light signals, more particularly infrared signals, so that substantially interference-free transmission of light signals, more particularly infrared signals, is ensured both in the direction of transmission and in the direction of reception. The above-mentioned object is achieved according to the invention by an apparatus of the kind specified in the introduction by the characterising features of claim 1. The invention has the advantage that in total comparatively little constructional expense is sufficient in order to ensure substantially interference-free operation when transmitting light signals in both directions. Namely, according to the invention, a single plate, which is both simple to produce and easy to install and which, additionally, gives the whole apparatus a better appearance from the point of view of shape, is sufficient. With regard to interference-free operation it is to be noted that an increased impedance to cross-interference between the two light signal paths is achieved by the invention. Preferably, said surface of the plate is roughened. This gives the advantage that the surface in question can be produced particularly easily. Said surface of the plate advantageously has a ribbing cross-wise with respect to the possible direction of propagation of the light from the light emitting arrangement to the light receiving arrangement. This results in particularly effective protection against interference of the light receiving arrangement by the light emitted from the light emitting arrangement. The previously mentioned ribbing is advantageously produced in a saw-tooth form. The light path from the light emitting arrangement to the light receiving arrangement within the plate is thereby interrupted in a particularly effective manner. Said surface of the plate preferably has at least one area of reduced thickness extending over the plate in question cross-wise in respect of the possible direction of propagation of the light from the light emitting arrangement towards the light receiving arrangement. This measure, which, if necessary, can be taken in addition to the previously mentioned measures, represents effective protection against rays which otherwise pass through without hindrance in the longitudinal direction of the plate in question. Said plate preferably has a black coating on at least one of its surfaces. This has the advantage that the surface in question is protected from penetration by interfering rays. Finally, it is advantageous if said plate has a lens portion at the area of the light receiving arrangement. The effectiveness of the light receiving arrangement can be improved thereby in a particularly simple manner. The invention is explained in greater detail in the following, by way of example, with the aid of drawings. Figure 1 represents perspectively a system for transmitting light signals. Figure 2 diagrammatically shows in a block circuit the principle construction of a device or an apparatus appertaining to the system according to Figure 1. Figure 3 shows a perspective exploded view of the basic construction of the apparatus for transmitting and receiving light signals appertaining to the system according to Figure 1. Figure 4 shows an enlarged sectional view along the intersection line IV-IV of a front plate of the apparatus represented in Figure 3. Figure 5 shows a perspective view of the front plate developed according to the invention for the apparatus shown in Figure 3. Figure 6 shows an enlarged cutaway portion of the front plate shown in Figure 5 along the intersection line VI-VI therein. Figure 1 represents a system serving to transmit light signals and more particularly infrared signals, to which system a remote control apparatus 1 and a television receiver 2 belong. Headphones 3, which are to reproduce audio signals which originate from the television receiver 2, are connected to the remote control apparatus 1. The television receiver has a signal receiving arrangement 4 for receiving the light signals emitted from the apparatus 1 and a light signal emitting arrangement 5 which emits light signals corresponding to the audio signals. The apparatus 1 comprises, according to Figure 1, a housing 24 which consists of an upper housing portion 25 and of a lower housing portion 26. A front plate 28, in or behind which a light emitting arrangement and a light receiving arrangement are located, is shown at the front of the housing 24 in Figure 1. The light emissions are effected by operation of the keys 251. In Figure 2 a block circuit diagram shows the essential construction of the system represented in Figure 1. The remote control apparatus 1 is shown in greater detail in the lower portion of Figure 2 and the essential construction of the television receiver 2 is shown in the upper portion of Figure 2. The television receiver 2 comprises a television receiving section 6 which is connected to the light receiving arrangement 4 and to the light emitting arrangement 5. The light emitting arrangement 5 has two FM modulators 7, 8 which serve, for example, to modulate the audio signals corresponding to the right-hand and left-hand sound channels and the carrier frequencies of which are chosen so that they are different from each other, such as 525 kHz and 875 kHz. The outputs of the two FM modulators 7, 8 are connected to a mixer 9 which mixes the modulated signals and which passes its output signals to an amplifier 10 which feeds a light emitting diode 11. This light emitting diode 11 is an infrared light emitting diode in the present case. The light signal receiving arrangement 4 of the television receiver 2 has a photodiode 12 which is particularly responsive to infrared rays. The output of photo-diode 12 is connected to an amplifier 13 to which a decoder 14 is in turn connected. This decoder 14 serves to supply control signals with the aid of which the television receiving circuit 6 is controlled with regard, for example, to channel control, volume and mains switching. On the output side the television receiving circuit produces a video signal for a picture tube 27 and audio signals for the left-hand and right-hand sound channels. The circuit arrangement of the remote control apparatus 1 represented in the lower portion of Figure 2 comprises a light emitting arrangement emitting, in the present case, infrared signals and a light receiving arrangement receiving infrared signals. An infrared light emitting diode 15 which is connected to the output of an amplifier 16, the input of which is connected to the output of a modulator 17, belongs to the light emitting arrangement. One input of this modulator 17 is connected to the output of a pulse code generator 18 and a further input of the modulator 17 is connected to the output of an oscillator 19 which supplies a carrier signal for the modulator 17, the carrier signal being modulated therein by the signals or pulses emitted by the pulse code generator 18. The pulse code generator 18 has its input connected to the keys 251. To the light receiving arrangement of the remote control apparatus 1 there belongs a photodiode 20, the output of which is connected to the input of an amplifier 21, the output of which is in turn connected to the inputs of two FM demodulators 22, 23 which demodulate the signals supplied to them to provide audio signals at the output for the right-hand and left-hand sound channels, that is, signals which correspond to those signals which have been supplied to the FM modulators 7 or 8. Front plate 28, which is translucent to the light emitted from the light emitting diode 15 and to the light to be received by the photodiode 20, belongs, additionally, as shown in Figure 2, to the remote control apparatus 1. In the present case the plate 28 in question is translucent to infrared light. In front of the photodiode 20 the plate 28 has a lens portion 29 which focuses the infrared light arriving at this area onto the photodiode 20. The remote control apparatus according to Figure 1 is illustrated in Figure 3 in a perspective exploded view showing its essential elements. Merely the lower portion of the housing 26 and the previously mentioned front plate 28 are shown in greater detail. An adjusting device 30 and a printed circuit board 31 are located in the lower portion of the housing 26. The adjusting device 30, in the present case, should be a volume adjusting device with the aid of which the level of the output signals to be supplied to the headphones 3, according to Figure 1, can be adjusted. The printed circuit card can comprise the circuit portions mentioned in Figure 2 with regard to the remote control apparatus 1. Furthermore, a battery compartment for accommodating supply batteries can be contained in the lower portion of the housing 26. As regards the front plate 28, Figure 3 shows that this plate has the lens portion 29, behind which the photodiode 20 is located, in its left-hand area. The light emitting diode 15 is located at a distance from the photodiode 20, likewise behind the plate 28. A sectional view of the front plate 28 shown in Fig.3 taken along the intersection line IV-IV marked is shown in Figure 4 in a cutaway portion. Furthermore, Figure 4 shows the light emitting diode 15 and also the photodiode 20 which is mounted at the back of the plate 28 at the location at which, on the front of the plate, the lens portion 29 is provided. The photodiode 20, in the present case, is screened in a light-proof manner by means of a screening arrangement 201 at the back of the plate 28. It can be seen from Figure 4 that the light emitting diode 15 does not solely send out light rays such that they pass through the plate 28. On the contrary, the light emitting diode 15 also emits light rays which can propagate in the plate 28, this being indicated by a zigzag line in the plate. These light rays can reach the photodiode 20 practically without hindrance in the case of the construction shown in Figure 4 and give rise thereby to interference. Figure 5 shows a front plate for a remote control apparatus 1 constructed according to the invention. This front plate is referenced 32 in Figure 5. Between its light emitting area 34, for the light emitting diode 15, and its light receiving area, for the photodiode 20, with the lens portion 33 being located on the exterior of the latter area, said front plate 32 has a surface area 35 which has such a surface finish that light rays are impeded or prevented from being further passed on from the light emitting area 34 towards the photodiode 20 within the plate 32. The surface area 35 is, as can be seen in Figure 5, a roughened surface area which is formed in this case by a saw-tooth shaped ribbing. In the present case, this surface area is coated in addition with a black coloured layer 37 which allows the infrared rays to be absorbed. Furthermore, the plate 32 has an area of reduced thickness extending over the whole height of said plate, in the form of a groove 39 in or adjacent the light of infrared light receiving area in which the photodiode 20 is located. Two projections 40 stand out from the back of the plate 32, as can be seen in Figure 5, on both sides of this area of attenuation 39. These projections 40 merely serve, in the present case, to secure the upper portion of the housing. The portions 38 shown in Figure 5 also merely serve for securing purposes. Figure 6 shows an enlarged cutaway portion of the plate shown in Figure 5 taken along the intersection line VI-VI. The position of the roughened surface area 35 at the back of the plate 32 can be seen clearly from Figure 6. It can be seen that the rough surface 36 gives rise to random reflection of the rays emitted from the light emitting diode 15 into the plate 32. This reflection is effective in such a way that practically none of the rays emitted from the light emitting diode 15 reach the photodiode 20. The photodiode 20 is, on the contrary, merely able to receive rays which are supplied to it through the lens portion 33. With regard to the roughened surface area 35, it may also be noted in Figure 6 that this area is coated with a black layer 37. Also, from Figure 6 it can be seen that the thinned area or area of reduced thickness 39 extends into the plate 32, ie. in the present case, away from the roughened surface 36. The area of reduced thickness in question ensures, as already indicated above, that no straight path is present for light passing through from the light emitting diode 15 to the photodiode 20 within the plate 32, that is, specifically on that side on which the photodiode 20 is mounted on the plate 32. The photodiode 20 is also screened here in a light-proof manner by means of a screening portion 201. Although the light emitting diode 15 and the photodiode 20 are shown as being positioned behind the plate 32, they can, of course, be mounted in recesses in the plate 32, if this is of sufficient thickness at the areas where the diodes are to be positioned. In all, there is thus available a plate 32 which can be produced in a particularly simple manner and which can be installed easily and through which a high impedance to cross-interference between the two light transmission channels is achieved.

Claims: Apparatus having a light emitting arrangement (15) for emitting light signals, more especially infrared signals, to at least one device (2) receiving such signals, and having a light receiving arrangement (20) for picking up corresponding light signals emitted by said at least one device (2) characterized in that the light emitting arrangement (15) and the light receiving arrangement (20) being accommodated spaced apart from each other in or behind a plate (32), which is transparent or translucent to the light emitted from the light emitting arrangement (15) and to the light to be received by the light receiving arrangement (20), characterized in that at least one surface of the plate (32) has a surface finish located in its area (35) between the light emitting arrangement (15) and the light receiving arrangement (20),which surface impedes light rays from being passed on from the light emitting arrangement (15) to the light receiving arrangement (20) within said plate (32). Apparatus according to claim 1, characterized in that said surface (35) of the plate (32) is roughened. Apparatus according to claim 1 or 2, characterized in that said surface (35) of the plate (32) has a ribbing (36) cross-wise with respect to the possible direction of propagation of the light from the light emitting arrangement (15) towards the light receiving arrangement (20). Apparatus according to claim 3, characterized in that the ribbing (36) is produced in a saw-tooth form. Apparatus according to one of claims 1 to 4, characterized in that said surface of the plate (32) has at least one area of reduced thickness (39) extending over the plate (32) cross-wise in respect of the possible direction of propagation of the light from the light emitting arrangement (15) towards the light receiving arrangement (20). Apparatus according to one of claims 1 to 5, characterized in that the plate (32) has a black coating (37) on at least one of its surfaces. Apparatus according to one of claims 1 to 6, characterized in that the plate (32) has a lens portion (33) in the area for the light receiving arrangement (20).

Inventors: FUJIOKA, YOSHIHISA, YAMAMOTO, KOICHI
Applicants: SONY CORPORATION
Application year: 1984
Main classification: G01J1
IPC codes: H04B10, G02B6, H04N5