JPH0797763B2 - Relay method in space propagating optical communication - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relay method for performing communication by spatial light propagation using light as a carrier, and more particularly to a relay method optimal for indoor space propagation optical communication. is there.

2. Description of the Related Art In recent years, a spatial propagation optical communication system has been developed in which information data is spatially transmitted and received using light as a carrier wave, and in particular, it is the same as various terminal devices such as facsimiles, printers, cash registers, etc. as slave stations installed indoors. A system for performing communication with a device as a master station arranged in a room, for example, a host computer, by spatial light propagation is being put to practical use.

Conventionally, in such an indoor space propagation optical communication system, as shown in FIG.
The repeater 2 is attached, and transmission / reception is performed between the terminals 3a to 3c in the room and the repeater 2 by spatially propagating light. On the other hand, between the repeater 2 and the master station 4 such as a host computer, It has been customary to connect with a wire 5 such as an optical fiber or an ordinary electric wire cable, and perform transmission / reception by non-space transmission through the wire 5. However, in order to actually apply such a system, wiring work for connecting the repeater 2 and the master station 4 with the wire 5 is required, and when the master station 4 is moved, the wiring must be changed again. There is the inconvenience of having to do construction.

Therefore, recently, as shown in FIG. 8, not only between the terminals 3a to 3c and the repeater 2, but also between the repeater 2 and the master station 4 such as a host computer, an optical signal generated by the spatial propagation light is used. Transmission and reception systems are being developed. According to such a system, no wiring work is required, and the master station can be arbitrarily moved according to indoor conditions and rearrangement.

By the way, the repeater used in the system as shown in FIG. 8 is basically designed to be able to receive an optical signal from any location in the room and to transmit an optical signal to any location in the room. In addition, it is desirable that both the receiving side (light receiving side) and the transmitting side (light emitting side) be omnidirectional. However, a light emitting element used for this kind of communication, such as a light emitting diode, has a strong directivity and is normally effective only in an angle range of about 15 to 20 °, so that transmission (light emission) is performed nondirectionally. In order to achieve this, it is necessary to cover the interior area of the room with a large number of light emitting elements of at least 40 to 50.
When a large number of light emitting elements are used in this way, there arises a problem that the current consumption of the repeater as a whole becomes extremely large even if the current consumption per light emitting element is small.

In the system shown in FIG. 8, when the receiving side (light receiving side) and the transmitting side (light emitting side) are both omnidirectional,
In addition to the spatially propagating light from the original terminal equipment entering the light receiving element of the repeater, the spatially propagating light emitted from the light emitting element of the repeater itself may enter due to multiple reflections and irregular reflections in the room. In such a case, the received signal due to the original propagating light may be disturbed by the signal due to reflection, and accurate signal relay may not be performed. Such jamming is similar to multipath jamming in wireless communication and is therefore also referred to hereinbelow as multipath jamming.

Regarding the former one of the above-mentioned two kinds of problems, that is, the problem of current consumption due to the use of a large number of light emitting elements, one solution has already been proposed in JP-A-59-133744. In this proposed repeater, multiple units that receive and emit light only within a certain range are prepared, and those units can be attached to and removed from the repeater mounting holder in all directions. As a result, the number of light emitting elements and light receiving elements actually used is reduced by mounting the unit only in that direction according to the arrangement direction of the terminal device or the master station, and the current consumption is reduced.

Problems to be Solved by the Invention In the above-mentioned proposed repeater, although the problem of current consumption can be solved to some extent, multipath interference is still unsolved. That is, even with the proposed repeater, it was inevitable that the optical signal emitted from the light emitting element of the repeater would enter the light receiving element of the same repeater due to multiple reflection and irregular reflection.

In addition, although the proposed repeater has the effect of reducing the current consumption, the current consumption may increase in some cases. That is, when the number of terminals is large and the terminals are arranged apart from each other, the number of units to be attached to the repeater also increases, and in that case, the current consumption must increase to some extent. I didn't get it.

In addition, in the repeater proposed above, the unit must be attached and detached according to the arrangement of the terminal and the master station, and there is a problem that the labor for that is complicated.

The present invention has been made in view of the above circumstances, and in a relay method in space propagating optical communication, particularly in a relay method of a method in which transmission and reception between a repeater and another device are all performed by optical signals by space propagating light, Basically, it is omnidirectional, and the current consumption can be made extremely small. At the same time, the reliability of data transmission can be improved by preventing interference such as multipath interference, and other troublesome work etc. The purpose of the present invention is to provide a relay method that eliminates the need.

MEANS FOR SOLVING THE PROBLEMS The present invention is directed to receiving a light signal of spatially propagating light transmitted from a device by a light receiving element of a repeater, amplifying the signal in the repeater, and spatially propagating the light signal of the repeater by a light emitting element. In the relay method of space propagation optical communication for transmitting to another device as an optical signal by light, the repeater is configured to include an inclined outer peripheral surface portion that is inclined with respect to the central axis line around a vertical axis line, The inclined outer peripheral surface portion is divided into a plurality of regions in the circumferential direction, and a light receiving element and a light emitting element are arranged in each region, and the light receiving elements in all the regions can receive light at the initial stage of signal relay. When it is confirmed that the light signal is received by the light receiving element in any of the areas, the light receiving elements in the areas other than the area where the reception is confirmed are controlled to be in the unreceivable state, Reliable reception Only the light receiving element in the recognized area is set to the receivable state, and then the light emitting element is scanned so as to be set to the transmittable state for each area. Moreover, in the scanning process of the light emitting element, the light emitting element in the transmittable state is changed. When the area is in the area of the light receiving element for which the reception is confirmed and the area adjacent thereto, the light receiving element is once controlled to the unreceivable state, and the area of the light emitting element in the transmittable state is the light receiving for which the reception is confirmed. It is characterized in that when it is separated from the area of the element, the unreceivable state of the light-receiving element confirmed to be received is released.

Function In the relay method of the present invention, the relay is installed, for example, on the ceiling in the room. The spatially propagating light, which is an optical signal transmitted from a device such as a terminal, is incident on a region (or a region adjacent to the device) facing the direction of the device in the isolated region of the inclined outer peripheral surface of the repeater. In the initial stage when the relay is started, the light receiving elements are set to be in the receivable state in all areas. That is, the light receiving elements in all areas are simultaneously set in the receivable state, or the scanning control is performed so that the light receiving elements in each area are sequentially set in the receivable state in an arbitrary area order within a certain period. When the optical signal from the device is incident on the light receiving element in any area, the optical signal is converted into an electric signal by the light receiving element in that area and is taken into the repeater. In this way, when the signal is captured and the reception of the optical signal in any area is confirmed, the light receiving elements in the areas other than the area where the reception of the optical signal is confirmed are in the unreceivable state. . That is, only the light-receiving element in the area where the reception of the optical signal is confirmed remains in the receivable state (hereinafter, that area is referred to as the selectively receivable area).

Then, the light emitting elements are sequentially scanned in each area so as to be in a transmittable state, and the relayed signals are sequentially transmitted from the light emitting elements in each area as optical signals by spatial propagation light. That is, the data signal received by the light receiving element in the selective receivable area and converted into an electric signal is demodulated, modulated or interpolated, or amplified or waveform shaped in the repeater according to the signal modulation method. After that, the light-emitting elements in each region are sequentially transmitted as optical signals by spatially propagating light.

Here, in the process in which the light emitting element in the transmittable state is scanned for each area and the optical signal is transmitted, the selective receivable area itself is fixed, but the area in the transmittable state is When in the selectively receivable area and the area adjacent thereto, the light emitting elements in the selectively receivable area are controlled to be in the unreceivable state. That is, when the area in the transmittable state comes close to the selective receivable area by scanning, the receiving element in the selective receivable area is controlled to be in the unreceivable state once, and the area in the transmittable state is When the light receiving element is separated from the selective receivable area, the non-receivable state of the light receiving element in the selective receivable area is released again, and the light receiving element returns to the receivable state. Therefore, the selective receivable area actually receives the optical signal only while the transmittable area is apart from the position-fixed selective receivable area. This means that the light receiving elements in the area to which the light emitting element to which the optical signal is currently being transmitted from the repeater and the area in the vicinity thereof are always in the unreceivable state,
The optical signal emitted from the light emitting element is less likely to be incident on the light receiving element which is in a receivable state due to multiple reflections and irregular reflections in the room, and therefore, the possibility that signal transmission accuracy is deteriorated due to multipath interference is significantly reduced. .

Even if the receiving device such as the host computer is located in any direction with respect to the repeater, the light emitting elements in each area are sequentially scanned as described above, so that the light emitting elements in any area are The transmitted optical signal is always received by the light receiving section of the receiving side device.

Further, as is clear from the above description, the light emitting elements are not set to be in the transmittable state at the same time, but are scanned so as to be sequentially set in the transmittable state in each area. Therefore, the light emitting elements operating simultaneously at a certain time. Are only a small part of all the light emitting elements, and therefore the current consumption is much smaller than that in the case of driving all the light emitting elements at the same time.

Example An example of the relay method of the present invention will be described below with reference to FIGS.

FIG. 1 and FIG. 2 show an example of the appearance of the repeater 2. In this example, the inclined outer peripheral surface portion 6 inclined by a predetermined angle θ with respect to the vertical central axis 0 of the repeater 2 has a circumference. It is divided into _eight regions P _{1 to} P ₈ at equal intervals in the direction. In each of the regions P _{1 to} P ₈ , three light emitting diodes (hereinafter referred to as “LED”) 7a, 7b and 7c as light emitting elements and one photodiode (hereinafter referred to as “PD”) as a light receiving element are provided.
8 are provided. Here, the three LEs in each area P _{1 to} P ₈
D7a to 7c are attached so that the angles are slightly different from each other.

PDs, LEs belonging to the respective regions P _{1 to} P ₈ when relaying an optical signal by spatially propagating light using such a repeater 2
An example of the operating state of D is shown in FIGS. 3 (A) to (H). In FIGS. 3 (A) to (H), a white area surrounded by a solid line indicates an area in which the LED is in a transmittable state, and hereinafter, the area in which the LED is in a transmittable state, that is, in a light-emissible state, emits light. It is called a surface. Also, FIG. 3 (A)-
The cross-hatched area in (H) indicates the area in which the PD is in the receivable state. In the following, the PD is in the receivable state, that is, the area in which the optical signal can be received and the signal can be received. It is called a surface.

In the initial stage of the start of relaying, as shown in FIG. 3 (A), control is performed so that all the areas P _{1 to} P ₈ become the light receiving surface. It should be noted that in this state, the light emitting element in any area is not in the transmittable state. That is, none of the regions serves as a light emitting surface.

As described above, while all the regions P _{1 to} P ₈ are the light receiving surface, an optical signal from the device is incident on one of the regions, for example, the region P ₅ , and the optical signal is transmitted on the region P _5. Is confirmed to have been received, as shown in FIG. 3 (B), reception in the areas P _{1 to} P ₄ and P _{6 to} P ₈ excluding the area P ₅ is stopped,
Only the area P ₅ where reception is confirmed is the light receiving surface. That is, the area P ₅ becomes the selective receivable area described above.
Only the light receiving elements in the P ₅ is a state that can perform the reception of the optical signal from the device.

Subsequently, as shown in FIG. 3 (C), one of the regions, for example, the region P ₁ becomes the light emitting surface, and subsequently, the light emitting surface is
Move each area in the circumferential direction as shown in FIGS. 3 (C) to (H), and then P ₁ → P ₂ → P ₃ → P ₄ → P ₅ → P ₆ → P ₇ → P ₈ in that order Become light emitting surfaces in sequence. In the process in which the light emitting surface scans each area in this manner, the light emitting surface is separated from the selectively receivable area P ₅ , that is, for example, the light emitting surface is P ₇
→ P ₈ → P ₁ → P ₂ → P ₃
Selective receivable area as shown in FIGS. 3 (C) to (D)
P ₅ actually maintains the receiving state, but when the area that is the light emitting surface approaches the selective receivable area P ₅ , the selective receivable area P ₅ is controlled to be in the unreceivable state. It That is, for example, as shown in FIG. 3 (E), when the area P ₄ adjacent to the selectively receivable area P ₅ is the light emitting surface, the selectively receivable area P ₅ is in the unreceivable state (not the light receiving surface). Become. The reception impossible state of selective coverage areas P ₅ is then Figure 3 period in which the selective coverage area P ₅ as shown in (F) has a light emitting surface, and Figure 3 followed by ( As shown in G), the area P ₆ next to the selectively receivable area P ₅ is maintained until the period when it is the light emitting surface. Then, as shown in FIG. 3 (H), the selective receivable area is reached when the area P ₇ distant from the selective receivable area P ₅ becomes the light emitting surface.
The unreceivable state of P ₅ is released and its selective receivable area
P ₅ becomes the light receiving surface again, that is, the receivable state. Thereafter, the same process is repeated while the light emitting surface sequentially moves in each region. Therefore, in the example shown in the figure, while the light emitting surface makes a round in the entire region, reception is performed in 5/8 of that period, and reception is not performed in the remaining 3/8 period.

In the example of FIG. 3, all areas P ₁ to
Although P ₈ is used as the light-receiving surface at the same time, it is not always necessary to use the light-receiving surface at the same time, and P _{1 to} P ₈ may be controlled so as to become the light-receiving surface in an arbitrary region order. Further, in the example of FIG. 3, the area that is simultaneously the light emitting surface at a certain time is one area, but in some cases, a plurality of adjacent areas may be the light emitting surface at the same time. Regarding an example of the case where two regions are the light emitting surface at the same time, the situation after the light receiving surface is fixed to the region P ₅ , for example, is shown in FIG. 4 (A) according to FIGS. 3 (C) to (H).
~ (F). In this case also controlled so that its selective reception area P ₅ when at least one of the two light emitting surface adjacent to the selective coverage area P ₅ becomes impossible receiver, select any of the two light emitting surface unreceivable state of selective coverage areas P ₅ is released upon leaving the specific coverage area P _5.

FIG. 5 is a block diagram showing an example of the circuit configuration of the repeater used in the method of the present invention.

In FIG. 5, the eight receiving circuit units 9 _{1 to} 9 ₈ correspond to the PDs of the areas P _{1 to} P ₈ , respectively, and from these receiving circuit units 9 _{1 to} 9 ₈ , When an optical signal from the device, for example, an optical signal obtained by CMI-modulating the information data to be transmitted is incident on the PD corresponding to each unit,
A data signal obtained by converting the optical signal into an electric signal and a reception detection signal indicating that the optical signal is incident are output. The reception detection signal is the reception unit discrimination circuit 10
And received by any one of the receiving circuit units 9 _{1 to} 9 ₈ , in other words, in which of the areas P _{1 to} P ₈ the optical signal is incident, the result is given to the system controller 11. . On the other hand, the data signal output from _one of the receiving circuit units 9 _{1 to} 9 ₈ is transmitted to the switch circuit 12
It is sent to the demodulator 13 via a _{1-12 8.} Switch circuit 12 ₁ to 1
2 _8, to directly turned on and off controlled by the switch control circuit 14, also the switch control circuit 14 that is indicated whether the one of the switching circuits 12 ₁ to 12 ₈ ON or OFF by the information from the system controller 11 It The demodulator 13 not only demodulates a CMI-modulated data signal, but also performs signal interpolation and error correction, and its operation is controlled by a signal from the system controller 11. The demodulation output signal of the demodulator 13 is input to the modulator 15 and is CMI-modulated again.
The modulated signal is given to the transmission circuit units 16 _{1 to} 16 ₈ . These transmission circuit units 16 _{1 to} 16 ₈ respectively cause the LEDs 7a to 7c of the respective regions P _{1 to} P ₈ to emit light in accordance with the data signal from the modulator 15, and transmit the optical signal as spatial propagation light. And these transmitter circuit units 16 ₁
To 16 _8, only unit specified by the control signal from the transmission unit control circuit 17 can transmit state (light emission state)
Is controlled so that

In the circuit arrangement of FIG. 5 as described above, first, in the initial state of the relay start, all of the reception circuit unit 91 _to 93 of the ₈ output system path of the switch circuit 12 ₁ to 12 ₈ is not turned on, All the receiving circuit units 9 _{1 to} 9 ₈ are ready to receive signals. This state is the state in which all areas P _{1 to} P ₈ are ready to be received as described above.
It corresponds to FIG. In this state, the transmission circuit units 16 _{1 to} 16 ₈ are all controlled by the transmission unit control circuit 17 to be in the transmission disabled state.

Region is the state described above, for example, if it is incident optical signal in a region P _5, is output received detection signal from the reception circuit unit 9 ₅ corresponding to the region P _5, the receiving unit discriminating circuit 10
Detects the reception in the area P ₅ and sends the information to the system controller 11. As a result, the system controller 11 turns on only the switch circuit 12 ₅ corresponding to the area P ₅ among all the switch circuits 12 _{1 to} 12 ₈ and turns off the other switch circuits 12 _{1 to} 12 ₄ and 12 _{6 to} 12 _8. The switch control circuit 14 is controlled so that Therefore, only the output data signal of the receiving circuit unit 9 ₅ corresponding to the area P ₅ is demodulated.
Will be entered in 13. This state corresponds to the state shown in FIG. 3B in which only the area P ₅ as described above is the selectively receivable area.

Then, as each of the transmission circuit unit 16 ₁ to 16 ₈ are sequentially transmittable state, the transmission by the information from the system controller 11 unit control circuit 17 each transmission circuit unit 16 ₁ to 1
6 ₈ scan control. Thereby, the receiving circuit unit
The signal after demodulation and modulation of the signal received by 9 ₅ (the signal that has undergone signal interpolation and error correction) is the LED of each transmission circuit unit 16 _{1 to} 16 ₈ , that is, the LEDs of each area P _{1 to} P ₈ in order. Sent.

In the process of sequential signals from the LED of each transmission circuit unit 16 ₁ to 16 ₈ as described above is transmitted, the switch circuit 12 ₅ of the output system path of the reception circuit unit 9 _5, corresponding to the receiving circuit unit 9 ₅ The switch control circuit 14 controls the switch control circuit 14 so that the information (selective receivable area) P ₅ and the transmission circuit units in the area in the vicinity thereof are in the off state during the transmission possible state. That According to the example of FIG. 3 (C) ~ (H), the switch circuit 12 ₅ is a period during which any of the units of the transmission circuit unit 16 ₁ to 16 _3, 16 _7, 16 ₈ is in transmit state is kept in the oN state, the reception signal by the reception circuit unit 9 ₅ region P ₅ is is taken, whereas the switch circuit 12 ₅ is a period during which any of the units of the transmission circuit unit 16 _{4-16 6} is in the transmittable state There are controlled to the oFF state, the uptake of the signal received by the reception circuit unit 9 ₅ region P ₅ is temporarily interrupted.

As described above, according to the circuit configuration of FIG. 5, the optical signal can be received and transmitted, that is, the optical signal can be relayed by the method as shown in FIG.

In the above description with reference to FIG. 5, the case where the number of areas that are simultaneously in the transmission enabled state is 1, that is, the number of areas that are the light emitting surfaces is 1 at the same time has been described.
System controller with the same circuit configuration shown in FIG.
By setting in 11, it is possible to arbitrarily change the number of regions to be the light emitting surface at the same time. Therefore, the system shown in FIG. 4 can also be realized by the circuit configuration of FIG.

Also, the scanning speed for transmission can be arbitrarily changed by the setting in the system controller 11, but in general, one signal (a 1-bit signal) from the area at an arbitrary position to the entire area is scanned. ) Is transmitted reliably, it is desirable to scan at a frequency equal to or higher than the frequency obtained by multiplying the frequency of the original signal bit by a multiple of the number of divided areas, for example, 2-3 times. That is, in the case of being divided into eight areas as described above, one signal is transmitted by scanning all eight areas, so at least eight areas are included in one bit of the original signal. Are required to be scanned, and moreover, a scanning frequency of several times or more is required in order to increase the certainty and reliability of data transmission, and in the end, the number of area divisions is 2 to 2 with respect to the original bit frequency. A scanning frequency of about 3 times or more is required.

Although the inclined outer peripheral surface portion 6 of the repeater 2 is divided into _eight areas P _{1 to} P ₈ in the examples of FIGS. 1 to 4, the number of area divisions is not limited to eight. Of course, for example, as shown in FIG. 6, it may be divided into ₁₆ regions P _{1 to} P ₁₆ . Also in this case, the number of regions which simultaneously become the light emitting surface is not limited to one, but can be about 2 to 4.

Further, as shown in FIG. 6, when the number of area divisions is large, that is, when the range of one area is narrow, the selective receivable area is fixed in order to prevent the occurrence of multipath interference more reliably. The period during which the reception state of the selectively receivable area is interrupted during the transmission scanning of each area is a total of five areas of the selectively receivable area and two areas on both sides thereof, or more. It is desirable to set the period in which the number of areas is in the transmittable state.

In addition, in the above example, in the process of scanning the area in the transmittable state, the scanning is performed so that the areas adjacent to each other are sequentially set in the transmittable state, but it is possible to scan while skipping some areas. good. For example, as shown in FIG. 2, when the number of area divisions is eight, scanning may be performed while skipping two areas. In this case, P _{1 in} Fig. 2
If the area is scanned in the clockwise direction, the area ready for transmission will be scanned in the order of P ₁ → P ₄ → P ₇ → P ₂ → P ₅ → P ₈ → P ₃ → P ₆ → P _1. Will be. Even in this process, when the transmittable area approaches the receivable area, the area is controlled to be in the unreceivable state.

Also, in the example of FIGS. 1 and 2, three LEDs 7a are provided in one area.
7c are provided, the number of LEDs arranged in one area can be arbitrarily determined as needed. Furthermore, the first
In the example of FIG. 2 and FIG. 2, each region P _{1 in} which the inclined outer peripheral surface portion 6 is divided
Although have to P ₈ to the respective inclined planes, in some cases it may be a curved surface may be a part of a spherical surface continuous in its entirety when the inclination outer peripheral surface 6. When the inclined outer peripheral surface portion 6 is formed as a part of a continuous spherical surface as described above, each of the areas P _{1 to} P ₈ divided in the circumferential direction is also a part of the same spherical surface. Will not appear.

EFFECTS OF THE INVENTION As is clear from the above description, according to the relay method of the present invention, the optical signal by the spatially propagating light transmitted from the device is received by the light receiving element of the relay, and is amplified in the relay. When transmitting to another device as an optical signal by spatially propagating light by the light emitting element of the repeater, regardless of the position of the transmitting side device and the receiving side device, reception and transmission are basically omnidirectional. Although it can be performed, the number of light emitting elements that are in the transmitting state (light emitting state) at the same time is significantly smaller than the total number of light emitting elements, so that the power consumption is extremely low and the light emitting element of the repeater The optical signal transmitted from the receiver is less likely to be received by the light receiving element of the same repeater due to multiple reflections or irregular reflections in the room, and therefore the signal due to the reflection interferes with the original received signal. Very unlikely to be affected. Therefore, according to the relay method of the present invention, it is possible to perform omnidirectional relay of the all-space optical propagation method that does not use wires at low running cost and high signal transmission accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing an example of the appearance of a repeater used in a relay method of the present invention, FIG. 2 is a bottom view of the repeater of FIG. 1, and FIG. 1 and 2 are schematic views showing an example of the scanning condition of the repeater, and FIG. 4 is a schematic diagram showing another example of the scanning condition of the repeater shown in FIGS. 1 and 2. FIG. 5 is a block diagram showing an electric circuit configuration of a repeater used in the relay method of the present invention, and FIG. 6 is a bottom view showing another example of the repeater used in the relay method of the present invention. FIG. 8 is an explanatory diagram showing an example of a conventional relay method, and FIG. 8 is an explanatory diagram showing a conventional relay method which is the premise of the present invention. 2 ...... repeater, 6 ...... inclined outer peripheral surface, P ₁ to P ₈ ...... region,
7a, 7b, 7c ... Light emitting diodes (LE
D), 8 ... Photodiode (P
D).

Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H04B 10/17 10/22

Claims (1)

[Claims] 1. A light receiving element of a repeater receives an optical signal of spatially propagating light transmitted from a device, amplifies this in a repeater, and a light emitting element of the repeater converts the optical signal into another optical signal of spatially propagating light. In a relay method of space propagating optical communication for transmitting to a device, the repeater is configured to include an inclined outer peripheral surface portion that is inclined with respect to a central axis thereof around a vertical axis, and the inclined outer peripheral surface portion is a peripheral portion. The light receiving element and the light emitting element are arranged in each of the areas, and the light receiving elements in all the areas are set to be ready to receive light at the initial stage of signal relay. When it is confirmed that the optical signal is received by the light receiving element in that area, the light receiving elements in the areas other than the area where the reception is confirmed are controlled to be in the unreceivable state, and Light receiving element only Is set to a receivable state, and then the light emitting element is scanned so as to be in a transmittable state for each area, and in the scanning process of the light emitting element, the reception is confirmed in the area of the light emitting element in the transmittable state. When in the area of the light receiving element and the area adjacent thereto, the light receiving element is once controlled to the unreceivable state, and when the area of the light emitting element in the transmittable state is separated from the area of the light receiving element whose reception is confirmed, A relay method in space propagating optical communication, characterized in that the reception-disabled state of the light-receiving element confirmed to be received is released.