JPH10243475A - Optical communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain near distance communication and power saving by optimizing a transmission output of a slave set side by allowing a slave set side to receive a reference signal with a prescribed output from a master set through optical communication, to detect the signal strength and to adjust a transmission signal output to be sent to the master set depending on the strength thereby optimizing the transmission output of the slave set side. SOLUTION: A reception signal strength detection circuit provided to a slave set includes a photo diode 6 that receives a reference signal sent from a light emitting diode 3 of a master set and converts the reference signal into an electric signal, an amplifier 7 such as an operational amplifier to amplify the signal, and a signal detection means such as an analog detection circuit, an RSSI circuit and an AM detection circuit placed to the post-stage. The reference signal from the master set is outputted at a constant output, and the slave set detects the strength of the signal from the master set so as to grasp a spatial state such as a distance or the like between the master set and the slave set. The slave set adjusts the strength of transmission of data to the master set to a degree that the master set sufficiently detects the transmission data of the slave set based on the strength of the reference signal received by the slave set and transmits the data from a light emitting diode 9 so as to allow the slave set to reduce the transmission output within the maximum distance thereby reducing the power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an optical communication system, and more particularly to an optical cordless remote controller.

[0002]

2. Description of the Related Art For remote control of home electric appliances, optical communication based on transmission and reception of an optical signal by a photodiode or a phototransistor is mainly used. For example, O of the parent machine such as TV
N-OFF and channel switching are performed by an optical signal (burst wave) transmitted from the controller (child device).
When the burst wave corresponding to the command is transmitted from the light emitting diode of the slave unit, it is received by the photodiode on the master unit side,
The IC at the subsequent stage counts the length of the burst wave and executes an instruction determined by the length.

[0003] In such a conventional cordless remote controller, as schematically shown in Fig. 6, the master unit is generally an installation device, and the slave unit is a small device suitable for carrying. In the communication method, as shown in FIG. 7, the slave unit transmits unidirectional data to the master unit, and the master unit always detects a signal in a reception waiting state and extracts data. In addition, in order to satisfy the maximum communication distance with the master unit, the slave unit always transmits at a maximum constant output during data transmission.

[0004]

However, the environment in which the cordless remote control is used is not constant in communication distance but varies greatly from a few cm to a maximum communication distance of about 10 m. Generally, the output of the slave unit and the receiving circuit of the master unit are designed in accordance with the usage condition of the maximum distance. Since the output of the slave unit at the time of transmission is always constant and the maximum output, the received signal strength of the signal sent from the slave unit at the master unit is too high for use within the maximum communication distance, and the Since the required transmission power is larger than the required transmission power, there is a case where a waste of power which is regarded as important in a portable device as a portable device occurs. In addition, during a short distance, the received signal strength is too large, the receiving circuit of the master unit is saturated, and normal reception cannot be performed due to occurrence of distortion or the like.

An object of the present invention is to provide an optical communication system capable of suppressing power consumption by optimizing the transmission output of a slave unit and capable of communicating at a very short distance as compared with the related art.

[0006]

In order to achieve the above object, an optical communication system according to the first aspect of the present invention transmits a reference signal having a constant output from a master unit, and the slave unit transmits the reference signal. And the signal strength of the reference signal is detected, and the transmission signal output from the slave unit is adjusted based on the signal strength and transmitted to the master unit.

According to a second aspect of the present invention, in the optical communication system, the reference signal of the master unit is an intermittent constant output signal, and when the strength of the received reference signal is lower than a threshold value, the slave unit transmits at least the reference signal. The signal strength is detected again over one or more cycles of the intermittent operation of the master unit.

According to a third aspect of the present invention, in the optical communication system according to the first or second aspect, when the signal strength of the reference signal received by the slave is lower than a threshold value, The transmission is not performed.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a basic configuration of the present invention. FIG. 1 shows an example of a configuration and FIG. 2 shows a communication flowchart.

First, an optical reference signal having a constant output is sent from the master unit. The reference signal is a transmission output circuit including an oscillator 1 having a specific frequency built in the master unit, an amplifier 2 such as an operational amplifier for amplifying the signal, and a light emitting diode 3 for converting and transmitting the amplified electric signal to an optical signal. Made with The master unit amplifies the photodiode 4 for receiving the transmission signal from the slave unit and the received transmission signal,
An amplifier 5 to be sent to a subsequent circuit is also included.

On the other hand, the slave unit comprises a reception signal strength detection circuit for detecting the signal strength of the reference signal of the master unit, and a transmission output circuit for adjusting the transmission signal strength according to the detected signal strength and transmitting the signal. The received signal strength detection circuit receives a reference signal sent from the light emitting diode 3 of the master unit and converts the reference signal into an electric signal, an amplifier 7 such as an operational amplifier for amplifying the signal, and a log detection circuit and RS
Signal detection means (not shown) such as SI circuit and AM detection circuit
The transmission output circuit includes signal generation means (not shown) for generating a burst wave or the like corresponding to a key input or the like, and output adjustment means such as a CPU for adjusting the strength of the transmission signal output according to the detected signal strength. (Not shown), and an amplifier 8 such as an operational amplifier for amplifying a transmission signal from the signal generating means in conjunction with the above.
And receive the signal output from it and convert it to an optical signal,
Includes a light emitting diode 9 that transmits to the parent device.

When it is necessary to transmit a signal to the slave (for example, when switching channels in a television), the slave first receives a reference signal from the master and detects its strength. The reference signal of the master unit is output at a constant output, and the reception intensity of the reference signal of the master unit in the slave unit is attenuated almost in proportion to the increase in the distance between the slave units due to light diffusion, as shown in FIG. . Therefore, by detecting the signal strength of the master unit, the spatial state such as the distance between the master unit and the slave unit can be grasped.

Next, the slave unit adjusts the transmission data of the slave unit to the extent that the master unit can sufficiently detect the transmission data based on the strength of the received reference signal, and transmits the adjusted data. For example, the slave unit has in advance a table of the output signal strength of the slave unit with respect to the signal strength from the master unit, and the table shows that the transmission signal strength is strong if the reception signal strength is low as shown by the solid line in FIG. If the intensity is high, the transmission signal intensity is set low. On the line shown in FIG. 4, it is set so that the minimum transmission signal strength that is accurately received by the master unit is secured.

Thus, if the signal strength of the master unit is weak, the slave unit increases the transmission signal strength so that it reaches the master unit accurately,
Further, if the signal strength of the master unit is strong, the transmission signal strength can be reduced within a range that can be accurately reached. Therefore,
Conventionally, as shown by the dashed line in FIG. 4, regardless of the strength of the received signal, that is, regardless of the distance between the slaves, the slave always transmits at the maximum output so as to satisfy the maximum communication distance. According to the invention, when the distance between the slave units is short, the transmission output of the slave unit can be reduced.

The adjustment of the transmission signal strength of the slave unit with respect to the reception signal strength from the master unit may be performed by calculation by the CPU, setting data in a memory in advance, or setting by an analog circuit. good. Also, in these CPUs and the like, a threshold value is set in advance with a level at which the signal strength of the slave unit is not sufficient for the master unit even at the maximum output,
In this case, if the transmission from the slave unit is canceled, the wasteful power of the slave unit can be further reduced.

FIG. 5 is a diagram showing an application example of the present invention.
9 is a flowchart illustrating a case where the parent machine performs an intermittent operation. At this time, the master unit is caused to transmit an optical reference signal having a constant output by an intermittent operation. On the other hand, the slave unit is set so as to continue to detect the received signal strength for a time including at least one intermittent operation cycle of the master unit. For this reason, the power consumed in transmitting the reference signal in the master unit is reduced, and the slave unit does not detect the reference signal only while no signal is transmitted from the master unit, and operates in the same manner as described above. be able to.

When the signal strength received from the base unit from the base unit is equal to or higher than the set threshold value, the same process as in FIG. 2 is followed. The configuration may be such that the detection of the time and the master device signal strength is continued. In any case, if the signal detection level is lower than the threshold value even after the set time has passed, it is desirable that the maximum output of the slave unit cannot be reached, and data transmission is not performed. In addition, in order to make a distinction from a failure, if the slave unit has a display device such as a liquid crystal display, it should be displayed that transmission is impossible.

[0018]

As described above, according to the present invention, there is an advantage that it can be used up to a very short distance, and there is also an advantage that the transmission power of the slave unit can be reduced within the maximum distance. Further, when the master unit is far away, it is possible to set so that no signal is sent from the slave unit, so that the power consumption of the slave unit can be further reduced.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one configuration example of the present invention.

FIG. 2 is a diagram showing an example of a communication flowchart according to the present invention.

FIG. 3 is a diagram illustrating a relationship between a received signal strength and a distance between the child device and the parent device in the child device.

FIG. 4 is a diagram illustrating an example of a relationship between a reception signal strength and a transmission output in a slave unit.

FIG. 5 is a flowchart showing an example in which the master unit of the present invention outputs a reference signal in an intermittent operation.

FIG. 6 is a schematic diagram of a conventional example.

FIG. 7 is an example of a conventional communication flowchart.

[Explanation of symbols]

 1: Oscillator 2, 5, 7, 8: Amplifier 3, 9: Light emitting diode 4, 6: Photodiode

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/06 // H04B 7/26 102

Claims (3)

[Claims] In an optical communication system between a parent device and a child device using light, a reference signal having a constant output is emitted and transmitted from the parent device, and the child device receives the reference signal and receives the reference signal. An optical communication system, comprising: detecting a signal strength of a slave device, adjusting a transmission signal output from the slave device based on the signal strength, and transmitting the adjusted signal to the master device. 2. The reference signal of the master unit is an intermittent constant output signal, and the slave unit has at least one cycle of the intermittent operation of the master unit when the signal strength of the received reference signal is lower than a threshold value. The optical communication system according to claim 1, wherein the signal intensity is detected again over the above. 3. The optical communication system according to claim 1, wherein the slave does not perform transmission from the slave when the reception strength of the reference signal is lower than a threshold.