JPS6273824A - Photodetection system for optical telephone set - Google Patents

Abstract

PURPOSE:To attain talking with prescribed talking quality or over even under a disturbing light disabled for talking conventionally by providing at lest two photodetecting elements and selecting the other photodetecting element when a disturbing light is given to one photodetecting element. CONSTITUTION:When direct sunlight is made incident from a front face and a photodetection signal is given to a photodetecting element 1, the photodetection signal is subjected to suppression. Thus, in the output of an amplifier 3, an output waveform 13b subject to disturbing light is decreased apparently less than an output waveform 13a not receiving the disturbing light. Thus, when the photodetecting element 1 causes suppression, a comparator output of a comparator circuit 5 is '0' and a photodetector selection circuit 6 selects a photodetecting element 2. Conversely, a sunlight is received from the rear face of an automobile, the photodetecting element 1 is selected in opposition to the case that the sun ray is received from the front face. Thus, a photodetecting output having a prescribed amplitude or over is obtained from a photodetecting element not subject to a disturbing light even under the disturbing light impossible for talking conventionally.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a light receiving system for a so-called optical telephone that uses light as a transmission means.

[Conventional technology]

Conventionally, this type of optical telephone has one light-receiving element in the node set, and is configured to be able to receive all of the light from the desired beam to make a call.

[Problem that the invention seeks to solve]

However, since such conventional optical telephones have only one light-receiving element, the output signal of the light-receiving element is likely to be suppressed when receiving light from a source other than the desired light source. This
In order to deal with this, frequency modulation methods have been adopted, but when the interfering light becomes strong, such as sunlight, it is severely suppressed, causing a drop in call quality and even making it impossible to make calls.

The present invention has been devised in view of these points, and its purpose is to provide a light receiving system for an optical telephone that allows calls to be made at a certain level of call quality or higher without being affected by interfering light such as sunlight. It is in.

[Failure to solve the problem]

The light receiving system of the optical T1 talker according to the present invention is such that the handset has at least two light receiving elements and an amplifier connected to each of the light receiving elements, a comparison circuit for comparing the outputs of the respective amplifiers, and a comparison circuit for comparing the outputs of the respective amplifiers. Features [Function] The present invention is characterized in that it is configured with a light receiving element selection circuit that selects each of the light receiving elements according to the output.In the present invention, at least two light receiving elements are provided;
By selecting the other light-receiving element when one light-receiving element receives interference light, it becomes possible to communicate with a certain level of communication quality or higher even under interference light, which was previously impossible.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the light receiving system of the optical telephone according to the present invention, in which two light receiving elements are used. In Fig. 1, reference numerals 1 and 2 indicate respective light receiving elements disposed in the handset, which will be described later, 3 and 4 are amplifiers that amplify the signal voltages generated in these light receiving elements 1 and 2, and 5 is an amplification device. When the signal output of one light-receiving element 1 is larger than the other light-receiving element 2, the logic level "1" is set as the output, and when the signal output of the light-receiving element 2 is larger, the logic level is set as the output. A signal voltage comparator circuit outputs "0", and 6 is "0" among the outputs of this comparator circuit 5.
This is a light-receiving element selection circuit that selects light-receiving element 1 when "l" is input, and light-receiving element 2 when "0" is input. think.

As shown in FIG. 2, light sources 8 and 9 are placed at the rearview mirror 7 in front of the driver's seat and at the back of the rear seat.

The light receiving elements 1.2 of the handset 10 are attached to the left and right sides of the receiver 11 as shown in FIG.

2. In Fig. 3, 12 indicates a transmitter. However, if you use it in the front seat at night or during the daytime when direct sunlight does not shine into the interior of the car, it will receive light from the light source 8 of the rearview mirror 7, and if you use it in the rear seat, it will receive light from the light source 8 of the rear view mirror 7. The light receiving elements 1 and 2 are selected by receiving light from a light source 9.

By the way, at times when the sun is low, such as in the morning or evening, direct sunlight can easily enter the interior of the car, so the light source 8 of the rearview mirror 7 is received by the light receiving element 1, and the light source 9 of the rear seat is received by the light receiving element 2, and the amplifier 3, The output waveform of No. 4 is shown in FIG.

Here, FIG. 4(,) shows the output waveform 13 of the amplifier 3, and FIG. 4(b) shows the output waveform 14 of the amplifier 4. Now, when direct sunlight enters the front surface and the light reception signals are combined on the light receiving element 1, the light reception signals are suppressed.

Therefore, as shown in FIG. 5, the output waveform 13m of the amplifier 3 when not receiving interference light is smaller than the output waveform 13b when receiving interference light. Therefore, when the light-receiving element 1 causes suppression, the comparison output of the comparison circuit 5 becomes "0", and the light-receiving element selection circuit 6 selects the light-receiving element 2.
Select. Conversely, when sunlight is received from the back of the car, the light receiving element 1 is
Select. As a result, a light receiving output of a certain amplitude or more can be obtained from the light receiving element which conventionally cannot communicate and does not receive the interfering light even under the interference light.

In addition, although two light receiving elements were used in the above-mentioned embodiment, the present invention is not limited to this, and two or more light receiving elements may be used.

〔Effect of the invention〕

As explained above, the present invention provides at least two light-receiving elements, and when one light-receiving element receives interference light, the remaining light-receiving element is selected. Even if a telephone call cannot be made due to reception, a received light output with a certain amplitude or higher can be obtained, so that a telephone call can be made with a certain call quality or above, which has a great practical effect.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram showing an embodiment of the light receiving system of the optical telephone according to the present invention, FIG. Fig. 4 is a diagram showing the output waveform of each amplifier in Fig. 1;
The figure is a diagram showing changes in the output of one amplifier for explaining the operation of the above embodiment. 1.2...φ light receiving element, 3,4...Input amplifier, 5.
... Comparison circuit, 6... Light receiving element selection circuit. Patent questioner NEC Corporation

Claims (1)

[Claims] In an optical telephone that uses light as a transmission means, the handset has at least two light-receiving elements and an amplifier connected to each of the light-receiving elements, and a comparison circuit that compares the outputs of the respective amplifiers, and the output of the comparison circuit. A light-receiving element selection circuit is provided for selecting each of the light-receiving elements according to the interference light, so that when any of the light-receiving elements receives interfering light, the selection circuit selects the light-receiving element that does not receive the interfering light. The light receiving method of optical telephones is characterized by: