JPH07264133A - Optical transmitter - Google Patents

Abstract

PURPOSE:To select a light emitting element having the best directivity for a receiver side among plural light emitting elements located at a sender side. CONSTITUTION:An input signal is modulated by a modulation circuit 1 and converted into an optical signal by light emitting elements 31-34 and it is transmitted and demodulated by a receiver side. A light emission control means 12 stimulates sequentially the light emitting elements 31-34 at the sender side and a light emitting element selection means 13 at the receiver side detects a light receiving level of each light emitting element and selects a light emitting element with the best directivity for the receiver side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for spatially transmitting an AV signal by infrared rays.

[0002]

2. Description of the Related Art Recently, an attempt has been made to perform signal transmission between AV devices without a cord. As the method, it is originally preferable to use radio waves, but optical transmission by infrared rays is exclusively used in accordance with the regulations of the Radio Law. Figure 2
Is a typical configuration diagram of optical transmission, 1 is a modulation circuit, 2 is a light emitting element drive circuit, and 3 is a light emitting element which converts an electric signal into an optical signal. Further, 4 is a light receiving element that receives the optical signal output from the light emitting element 3 and converts it into an electrical signal (photocurrent), 5 is a filter circuit that extracts only the modulated signal, and 6 is demodulation that demodulates the modulated signal into the original signal. Circuit.

[0003]

In the optical transmission device configured as described above, unlike the transmission by radio waves, the problem of directivity of light is parasitically present. For this reason, attempts have been made to provide a plurality of light emitting elements 3 and radiate the light emitting elements at different angles. However, since a plurality of light emitting elements are used, current consumption becomes unnecessarily large. It was In order to solve this problem, Japanese Patent Laid-Open No. 4-243331 discloses that a plurality of transmitters are provided with respective light receiving elements, and the power of infrared rays emitted from the receivers toward the transmitters is detected to obtain the most directivity. A method has been proposed in which a light-emitting element is driven by selecting a transmitting section with good performance, but this method requires as many light-receiving elements as the number of light-emitting elements, resulting in a large-scale device and cost problems. .

The present invention has been made in order to solve the above-mentioned problems, and has a simple structure, a light emitting element having the best directivity is selected and driven from a plurality of light emitting elements, and unnecessary power is consumed. It is an object to obtain an optical transmission device that consumes less energy.

[0005]

In order to achieve the above object, an optical transmission device of the present invention comprises at least two or more light emitting elements for converting an electric signal into an optical signal, and a drive circuit for driving the light emitting element. A light emitting control means for sequentially emitting the light emitting elements one by one, a light receiving element for receiving an optical signal output from the two or more light emitting elements and converting the light signal into an electric signal, and the light emitting element sequentially operated by the light emission control means. Light emitting element selecting means for detecting the optical signal level input to the light receiving element of each light emitting element by emitting light and selecting the light emitting element having the maximum signal level, and the output of the light emitting element selecting means is fed back to the transmitting side. And a switching means for switching.

[0006]

The light emission control means causes the plurality of light emitting elements to sequentially emit light to detect the level at the receiving side, so that the light emitting element selecting means selects the light emitting element having the best light receiving level, and the information thereof. By sending back to the transmitting side, by driving only the light emitting element with the best directivity, there is no need to drive extra light emitting elements, that is, without increasing the power consumption, The same transmission quality can be obtained.

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an optical transmission device according to an embodiment of the present invention. The description will be made assuming that the signal to be transmitted is a video signal.
In FIG. 1, 1 is a modulation circuit for modulating a video signal as an input signal, 21 to 24 are light emitting element drive circuits for driving the light emitting elements 31 to 34, and 31 to 34 are light emitting elements for converting electric signals into optical signals. So, they are facing different directions so that they can cover as much space as possible. Reference numeral 11 switches the light emitting element driving circuits 21 to 24 based on a signal from a light emitting element selecting means 13 described later,
A switching circuit for driving one of them, 12 is a light emission control means for sequentially emitting light from the light emitting elements 31 to 34 through the light emitting element drive circuits 21 to 24 during a period such as a blanking period of a video signal that does not affect the image, 4 is light emitting elements 31 to 34
A light-receiving element for receiving the optical signal emitted from the light-receiving element and converting it into an electric signal, 5 is a filter circuit for extracting only the video modulation signal from the signal output from the light-receiving element 4, and 6 is the original video signal for the modulation signal. A demodulation circuit for demodulating, 51 is a filter circuit for extracting the frequency of the optical signal that causes the light emission elements 31 to 34 to sequentially emit light by the light emission control means 12, and 13 is each when light emission elements 31 to 34 are sequentially emitted by the light emission control means 12. Of the light emitting elements 31 to 34, the light receiving element level received by the light receiving element 4 is detected, and the light emitting element selecting means for selecting the light emitting element having the highest light receiving signal level, and 14 is the light emitting element selecting means 13. A light emitting element for converting an output signal into an optical signal, and a light receiving element 15 for converting an optical signal from the light emitting element 14 into an electric signal.

Next, the operation of the optical transmission device configured as described above will be described. First, when the video signal is in the blanking period, the light emission control means 12 operates to operate the light emitting element drive circuits 21 to 24, and the light emitting elements 31 to 34.
Light sequentially one by one. The light emitting element selecting means 13 receives this signal via the light receiving element 4 and receives the light emitting elements 31 to 34.
The light power levels from the light emitting elements are detected one by one, and the light emitting element having the highest level among the optical signals from the plurality of light emitting elements is selected. This selection signal is transmitted to the switching circuit 11 via the light emitting element 14 and the light receiving element 15. Switching circuit 1
In No. 1, the light emitting element drive circuit that maximizes the signal level input to the light emitting element selecting means 13 is operated based on the information from the light emitting element selecting means 13.

When the blanking period ends, the video modulation signal output from the modulation circuit 1 is output as an optical signal from the light emitting element selected as described above via the switching circuit 11. Further, when the signal from the light emitting element selecting means 13 is returned to the transmitting section, the light receiving level of the light receiving element 15 may be decreased due to the directivity of the light emitting element 14, but the light emitting element selecting means 13 outputs the signal. Since the amount of information of the signal to be transmitted is extremely small, digital transmission may be used. Therefore, even if the power of the optical signal input to the light receiving element 15 is very small, the information can be transmitted relatively easily. Further, although the description has been made here assuming that the signal to be transmitted is a video signal, the present invention is not limited to being a video signal in particular, and the signal frequency at the time of sequential light emission of the light emitting elements 31 to 34 by the light emission control means 12 is set as the transmission signal. If separated from the frequency band, only the light emission signals of the light emitting elements 31 to 34 by the light emission control means 12 are sequentially input to the light emitting element selection means 13 by the filter circuit 51, so that the light emission elements can be selected even during signal transmission. . Although the number of light emitting elements is four here, it goes without saying that the number is not limited to four.

[0011]

As described above, according to the optical transmission device of the present invention, since only the light emitting element having the best directivity is driven, the light emitting element which is not directly related to the transmission quality consumes extra power. In addition, by providing only one light receiving element for receiving the feedback signal from the receiving section in the transmitting section, the light emitting element having the best directivity can be selected, and a great effect such as realization with a simple configuration can be achieved. is there.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an optical transmission device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a conventional optical transmission device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Modulation circuit 4,15 Light receiving element 5,51 Filter circuit 6 Demodulation circuit 11 Switching circuit 12 Light emission control means 13 Light emitting element selection means 21-24 Light emitting element drive circuit 14,31-34 Light emitting element

Claims (1)

[Claims] 1. At least two or more light emitting elements for converting an electric signal into an optical signal, an issuing element drive circuit for driving the light emitting element, a light emission control means for causing the light emitting elements to sequentially emit light one by one, A light receiving element that receives an optical signal output from two or more light emitting elements and converts it into an electrical signal, a filter circuit that extracts a specific frequency from the output of the light receiving element, and detects an optical signal level input to the light receiving element. 2 above
A light emitting element selecting means for selecting a light emitting element having a maximum signal level among two or more light emitting elements, and an output of the light emitting element selecting means is fed back to a transmitting side to emit only the light emitting element having the maximum signal level. An optical transmission device comprising: switching means for switching.