JPH11168435A - Spatial optical transmission equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide spatial optical transmission equipment with which high quality data transmission is enabled by preventing the generation of a disturbance component for making present flood into return light and making it incident to a present photodetector. SOLUTION: Concerning the spatial optical transmission equipment provided with a flood chamber 3 arranged with a flood element 6, light reception chamber 4 arranged with a photodetector 7, transmission circuit connected to the floor element 6 and reception circuit connected to the photodetector 7, this equipment is further provided with a photodetector 11 for self-emission cancel arranged for photodetecting only one part of light flooding from the flood element 6, self-emission cancel circuit 26 for inverting a photodetecting signal outputted from the photodetector 11, attenuating its level and outputting an inverted signal at the same level as the outputted photodetecting signal when the photodetector of the reception circuit receives only the return light of flood light from the flood element 6, and adder 30 for adding the signal outputted from the self-emission cancel circuit 26 to the reception circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial light transmission device for transmitting data by light radiated into space,
The present invention relates to a spatial light transmission device suitable for performing data transmission between two distant points by a full-duplex bidirectional method.

[0002]

2. Description of the Related Art A spatial light transmission device for transmitting data between two distant points by light radiated into a space does not require a cable laying, so that an automatic guided vehicle in a factory, a crane device, a three-dimensional warehouse, etc. It is becoming popular as a device for transmitting data between moving objects or between a fixed object and a moving object.

[0003]

In this type of spatial light transmission device, when both wish to transmit and receive data simultaneously, a full-duplex bidirectional communication system is adopted. Since the light receiver and the light transmitter are operated at the same time, the influence of the return light has a considerable effect on the communication quality.

In particular, in the case of the baseband system in which data is transmitted without performing modulation, the infrared light emitted from the light emitter of one device easily returns directly to the light receiver, and the light emission and light reception can be completely separated. Otherwise, a problem that data from the other party cannot be satisfactorily received tends to occur.

On the other hand, in the case of a broadband system in which a carrier is modulated by a data signal and transmitted by a modulation system such as FSK or ASK, the carrier frequency used on the light emitting side and the light receiving side are selected differently, and the received signal is banded. Since processing is performed through a pass filter, full-duplex bidirectional communication can be performed if conditions are met.

However, when the transmission distance is long, for example, several hundreds of meters, the light intensity of the light projection becomes very high. Therefore, the return light directly returning from the light projector to the light receiver side of the unit adversely affects the data transmission. There is. For example, in the case of long-distance transmission, as shown in FIG. 7, a convex lens 32 for condensing is arranged in front of the light projector 30 and the light receiver 31, and a space including the light projector 30 and the convex lens 32, and the light receiver 31 and the convex lens 32. Is surrounded by a partition wall or the like, and a structure in which the light emitting chamber and the light receiving chamber are separated from each other is adopted.

However, there is a case where a single near-infrared transmission filter (an acrylic plate that transmits only near-infrared light) 33 is disposed on the front surface in terms of design or configuration. In such a case, FIG. As shown, near infrared rays emitted from the projector 30 travel in a plane direction in the near infrared transmission filter 33 and enter the own light receiving chamber through the lens. Then, the returned light is received by its own light receiver 31 and becomes a disturbance component, which may hinder normal data transmission.

In particular, in the case of long-distance transmission, the projector emits strong light and the receiver receives weak light received over a long distance. Even if the return light is generated, it becomes a disturbance component, and there is a problem that normal data transmission cannot be performed.

On the other hand, in the case of short-distance transmission, as shown in FIG.
A light emitter 36 is arranged in a light emitting room partitioned by a partition 35, and a light receiver 37 is installed in a light receiving room next to the light emitting room, and a light condensing lens is not used. A near-infrared transmission filter 38 is arranged, and a few meters with a relatively wide directional angle.
May be transmitted over short distances. Also in this case, the light projected from the light projector 36 is transmitted in the planar direction through the near-infrared transmission filter 38 or passes through the gap of the partition wall 35 and enters the own light receiving chamber, and the returned light is There is a problem that light is received by the light receiver 37 and becomes a disturbance component, so that normal data transmission cannot be performed.

The present invention has been made in view of the above points, and prevents high-quality data transmission by preventing the occurrence of a disturbance component in which its own light becomes return light and invades its own light receiving element. It is an object of the present invention to provide a spatial light transmission device capable of performing the above operation.

[0011]

In order to achieve the above object, a spatial light transmission device according to the present invention comprises: a light emitting chamber in which a light emitting element is provided; a light receiving chamber in which a light receiving element is provided; In a spatial light transmission device that includes a transmitting circuit connected to an optical element and a receiving circuit connected to the light receiving element and transmits data by light emitted to the space, light emitted from the light emitting element And a light-receiving element for canceling self-emission arranged so as to receive only a part of the light-receiving element, inverting the light-receiving signal output from the light-receiving element, attenuating the level, and causing the light-receiving element of the receiving circuit to emit the light. A self-light-emission cancel circuit that outputs a signal at the same level as the light-receiving signal to be output and an inverted signal when only the return light of the light emitted from the optical element is received, and receiving the signal output from the self-light-emission cancel circuit. And an adder to be added to the circuit. Characterized in that was.

[0012]

According to the spatial light transmission apparatus having the above-described structure, when the light leaking from the light emitting chamber enters the light receiving element of itself and is received as return light, the light emission canceling circuit removes the receiving circuit. When the light receiving element receives only the return light of the light emitted from the light emitting element, a signal having the same level as the light receiving signal to be output and inverted is output, and the signal is added to the receiving circuit via the adder. . For this reason, even when the light leaking from the light emitting chamber enters the own light receiving element as return light and is received, the signal of the disturbance component due to the return light disappears from the receiving circuit, and the oppositely installed counterpart. Only the transmission signal from the spatial light transmission device is output from the receiving circuit, and the received transmission data can be obtained favorably.

Therefore, in a transmission device in which a spatial light transmission over a long distance or a light guide portion such as a filter is arranged on the front surface, high-quality data transmission can be performed even when adverse effects of return light are likely to occur. .

The light-receiving element for canceling self-emission is
If it is arranged in the adjacent room adjacent to the light emitting room and the light receiving room via the partition and receives light emitted from the light emitting room through the window provided in the partition, it can receive only its own light emitted. it can.

A light-transmitting plate is disposed in front of the light-emitting chamber and the light-receiving chamber, and the emitted light propagates in the light-transmitting plate in a plane direction, so that return light is transmitted to its own light-receiving element. Easy to invade. However, at the location corresponding to the partition inside the translucent plate,
If a groove having a substantially semicircular cross section is formed and the tip of the partition is fitted and arranged in the groove, propagation of light in a plane direction in the light transmitting plate can be suppressed, and return light can be reduced.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. 1 is a front view of the spatial light transmission device, FIG. 2 is a right side view thereof, and FIG. 3 is a sectional view thereof. This device is a short-distance spatial light transmission device that does not use a condensing lens. In a thin case 1, a light projecting unit and a light receiving unit are arranged, and a transmitting circuit, a receiving circuit, It has a built-in cancellation circuit and the like. As shown in FIG. 2, an attachment base 15 is attached to the case 1 via a pivot 16.

An opening is formed in the upper front part of the case 1,
A near-infrared transmission filter 2 that transmits only near-infrared rays is attached to the opening as a light-transmitting plate so as to close the opening. Inside, a light-emitting chamber 3 and a light-receiving chamber 4 are formed by being partitioned by a partition wall 5, and a plurality of light-emitting elements 6 formed of light-emitting diodes or the like that emit near-infrared rays are arranged in the light-emitting chamber 3. The light receiving chamber 4 is provided with a light receiving element 7 such as a photodiode for receiving a near infrared ray and outputting a signal. The light emitting element 6 and the light receiving element 7 are mounted on a substrate 8 together with circuit elements.

As shown in FIG. 4, the partition 5 has a substantially T shape in plan view.
It is formed in the following shape, and partitions the light emitting chamber 3 and the light receiving chamber 4
The lower adjacent room 9 is partitioned. Next door room 9 and floodlight room 3
A window 10 is formed in the partition wall 5 therebetween, and a light-receiving element 11 for canceling self-emission is disposed in the adjacent room 9 so as to face the window 10. The light receiving element 11 is provided on a second
The self-light emission cancel circuit, which is described later, is mounted on the substrate 12. The light receiving element 11 for canceling self-emission has a structure for receiving only the light emitted from the light emitting element 6.

The periphery of the light-emitting room 3, the light-receiving room 4, and the adjacent room 9 separated by the partition wall 5 is surrounded by the side of the case 1,
The front surfaces of the light emitting chamber 3 and the light receiving chamber 4 are closed by attaching the near infrared transmitting filter 2 described above. Near infrared transmission filter 2
At the location corresponding to the inner partition wall 5, as shown in FIG.
A groove 2a having a semicircular cross section is formed along the partition wall 5, and a tip end of the partition wall 5 is fitted into and closely adhered to the groove 2a having a semicircular cross section in an assembled state. By forming the groove 2a having a semicircular cross-section inside the near-infrared ray transmitting filter 2 between the light projecting chamber 3 and the light receiving chamber 4, the near-infrared ray traveling in the plane direction is effectively attenuated by the groove 2a. Thus, the transmission of near-infrared rays from the light-emitting chamber 3 to the light-receiving chamber 4 can be effectively prevented.

FIG. 5 is a block diagram showing a configuration of an electric circuit of the spatial light transmission device. This device includes a broadband type transmitting circuit and a receiving circuit, and further has a self-erasing device that removes a near infrared ray emitted from its own light emitting element 6 into its own light receiving element 7 and becomes a disturbance component. The light emission cancel circuit 26 is provided.

The transmitting circuit includes a modulating unit 21 for frequency-modulating a carrier of a predetermined frequency in accordance with the transmitting signal, for example, a light emitting driving unit 22 for driving the light emitting element 6 based on the modulated signal sent from the modulating unit 21; Consists of The receiving circuit includes a light receiving amplifier 2 for amplifying a light receiving signal output from the light receiving element 7.
3. an adder 30 that adds the amplified received light signal and a self-emission inversion signal from the self-emission cancellation circuit 26;
And a demodulation unit 25 for demodulating a signal output from the amplifier 24 and extracting a received data signal.

The self light emission cancel circuit 26 is provided in the adjacent room 9.
A light receiving amplifier 27 that receives and receives and amplifies a light receiving signal of the light receiving element 11 that receives light emitted from the light emitting element 6 of the light emitting element 6 disposed therein;
An inverting circuit 28 for inputting, inverting, and outputting the light receiving signal output from the light receiving amplifier 27, and a variable attenuator 2 for attenuating and outputting the level of the inverted signal output from the inverting circuit 28
9.

The output side of the variable attenuator 29 is connected to one input side of the adder 30 of the receiving circuit. The signal attenuation rate of the variable attenuator 29 is such that the level of the inverted signal output therefrom is The setting is made so as to match the level of the light receiving signal output from the light receiving amplifier 23 of the light receiving element 7.

That is, FIG. 6 is a waveform diagram of each part of the circuit when its own transmitting circuit and receiving circuit are operated when data signals are not transmitted from the other party, that is, when there is no light emission from the other party. FIG. 6A shows the waveform of the output signal of the light receiving amplifier 23, and this waveform corresponds to a portion where the own light has entered the light receiving element 7 as return light.

On the other hand, b is the waveform of the signal output from the light receiving amplifier 27 of the self light emission cancel circuit 26 and corresponds to the light emission of the light emitting element 6 received through the window 10 by the light receiving element 11 arranged in the adjacent room 9. It is the part that did. Then, the waveform of the signal b is inverted through the inverting circuit 28 and c
And the waveform of the signal c is a variable attenuator 29
, A signal d having the same level as the signal a on the light receiving circuit side is obtained, and the signal d and the signal a are added by the adder 30.

Next, the mode of use of the spatial light transmission device will be described. This device is used, for example, when performing data transmission between two computer terminal devices, and one device is connected to one terminal. The other device is connected to the data output terminal of the device, and the other device is connected to the other terminal device.
The two spatial light transmission devices are installed facing each other such that the optical axes on the light projecting side and the light receiving side are aligned with the optical axes on the opposite side.

In a pair of spatial light transmission apparatuses for performing full-duplex two-way communication, data input to each apparatus is transmitted as a transmission signal to a modulation unit 21 of a transmission circuit, and a carrier having a predetermined frequency is converted by the transmission signal. For example, a frequency-modulated and modulated transmission signal is sent to the light emission drive unit 22. The light emitting drive unit 22 drives the light emitting element 6 based on the signal, and emits near infrared light on which the transmission signal is superimposed from the light emitting element 6, and the near infrared light is transmitted from the light emitting chamber 3 to the near infrared light transmitting filter 2. And is released toward the other device.

On the other hand, near-infrared rays radiated in the same manner as above from the other party's apparatus toward the spatial light transmission apparatus enter the light receiving chamber 4 through the near-infrared transmitting filter 2 and are received by the light receiving element 7. . The light receiving signal output from the light receiving element 7 is amplified by the light receiving amplifier 23 and sent to the adder 30.

At the same time, the light-receiving element 11 for canceling self-light emission arranged in the adjacent room 9 outputs a light-receiving signal corresponding to the near-infrared light of the light-emitting element 6 received through the window 10, and the light-receiving signal passed through the light-receiving amplifier 27 is The received light signal is inverted by the next inverting circuit 28 and attenuated at a predetermined attenuation rate in the next variable attenuator 29, and the inverted and attenuated light receiving signal is input to the adder 30 of the receiving circuit.

When there is near-infrared rays, that is, return light, leaking from the light projecting chamber 3 into the light receiving chamber 4, the signal output from the self-light emission cancel circuit 26 is a signal inverted at the same level as the light receiving signal corresponding to the return light. Therefore, the disturbance component corresponding to the return light is eliminated at the output side of the adder 30 in the receiving circuit, and only the signal transmitted from the device on the other end is amplified by the amplifier 24.
And is amplified. Then, the amplified signal is demodulated in the demodulator 25, and the received data can be extracted from the demodulator 25.

As described above, even when the light leaking from the light projecting chamber 3 or the light traveling in the plane direction through the near infrared transmitting filter 2 enters the light receiving chamber 4 as return light and is received by the light receiving element 7. The signal of the disturbance component due to the return light disappears from the receiving circuit, and only the transmission signal from the opposing spatial optical transmission device installed oppositely is output from the receiving circuit. Therefore, the received transmission data can be satisfactorily taken out, and high-quality data transmission can be performed.

The spatial light transmission device of the present invention is not limited to the above embodiment, but can be implemented in the following modes.

In the above-mentioned broadband optical transmission,
In addition to frequency modulation, amplitude modulation, phase modulation, or the like can be used, and a baseband system that does not perform modulation can be used.

In the above embodiment, the apparatus for short-distance transmission without using a condenser lens has been described. However, the present invention can be applied to an apparatus for long-distance transmission using a condenser lens.

As the transmission light, light having a wavelength other than near-infrared light can be used.

Although a near-infrared transmission filter is used as the light-transmitting plate, a transparent or colored light-transmitting plate having no wavelength selectivity and having a normal light-transmitting property can also be used.

[Brief description of the drawings]

FIG. 1 is a front view of a spatial light transmission device according to an embodiment of the present invention.

FIG. 2 is a right side view of the device.

FIG. 3 is a sectional view taken along the line III-III of FIG. 1;

FIG. 4 is a schematic perspective view showing the vicinity of a light emitting chamber 3 and a light receiving chamber 4 inside the apparatus.

FIG. 5 is a configuration block diagram of an electric circuit of the spatial light transmission device.

FIG. 6 is a waveform diagram of each part of the circuit when the transmitting / receiving circuit is operated when there is no light emission from the other party.

FIG. 7 is a sectional view of a conventional spatial light transmission device.

FIG. 8 is a sectional view of a conventional spatial light transmission device.

[Explanation of symbols]

 3-light-emitting room 4-light-receiving room 5-partition wall 6-light-emitting device 7-light-receiving device 9-adjacent room 10-window 11-light-receiving device 26-self light emission cancel circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04B 10/18 10/28 10/26 10/14 10/04 10/06

Claims (3)

[Claims] A light emitting chamber in which a light emitting element is arranged, a light receiving chamber in which a light receiving element is arranged, a transmitting circuit connected to the light emitting element, and a receiving circuit connected to the light receiving element. In a spatial light transmission device for transmitting data by light radiated into space, a light-emitting element for canceling self-light emission arranged to receive only a part of the light emitted from the light-emitting element Inverting the light receiving signal output from the light receiving element,
A self-luminous canceling circuit that attenuates the level and outputs a signal at the same level as the received light signal to be output and an inverted signal when the light receiving element of the receiving circuit receives only the return light of the light emitted from the light emitting element. An adder for adding a signal output from the self-light emission canceling circuit to the receiving circuit. 2. The light-receiving element for canceling self-emission,
The spatial light according to claim 1, wherein the spatial light is disposed in an adjacent room adjacent to the light-emitting room and the light-receiving room via a partition, and receives only light emitted from the light-emitting room through a window provided in the partition. Transmission equipment. 3. A light-transmitting plate is provided in front of the light-transmitting chamber and the light-receiving chamber, and at a position inside the light-transmitting plate corresponding to the partition,
3. The spatial light transmission device according to claim 2, wherein a groove having a substantially semicircular cross section is formed, and the tip of the partition wall is fitted and arranged in the groove.