JP2012134724A - Optical space transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform emission of an optical signal for transmitting information and emission of an optical signal for adjusting an optical axis with the same light emitting element.SOLUTION: A beacon generating circuit 23 generates a beacon signal having a frequency band different from that of a transmission signal. A superimposing circuit 24 superimposes an input signal and the beacon signal to make a superimposed signal voltage. A light emitting unit 26 transmits a superimposed optical signal by flashing of a light emitting element 27. A light receiving unit 42 has four light receiving elements 43 for receiving the superimposed optical signal. A low-pass filter 46 separates four beacon signals from four superimposed signal voltages. A level detecting circuit 47 detects the levels of the four beacon signals. A direction detecting circuit 48 detects a difference between a light emitting axis direction and a light receiving axis direction from these levels. A direction adjusting unit 49 adjusts the light receiving axis direction by moving a lens 41 and the light receiving unit 42. A bypass filter 50 separates the input signal from the converted superimposed signal voltage. An output unit 55 outputs the transmission signal.

Description

  The present invention relates to an optical space transmission device that spatially transmits information using optical communication such as infrared communication and visible light communication.

  Conventionally, in an optical space transmission device or an optical space transmission system that spatially transmits information using optical communication, a pilot light for guide or the like is irradiated from the transmission device on the transmission side, and the transmission device on the reception side has the amount of received light. There is a technology for automatically controlling the direction of light reception based on this. According to this technique, even if a large-diameter lens is used to increase the light receiving sensitivity, the light receiving unit whose directivity is narrowed by using the lens can be automatically opposed to the transmitting side. Therefore, it is possible to perform highly sensitive reception without the need for direction alignment.

  For example, in the optical space transmission device of Patent Document 1, the light emitting unit has a light emitting element for direction adjustment separately from the light emitting element that emits an optical signal that transmits information, and the light receiving unit has four light receiving elements. is doing. This device receives infrared light from the light-emitting elements for direction adjustment with four light-receiving elements, and controls the direction of the light-receiving parts so that the amounts of light received by the respective light-receiving elements coincide with each other. Automatically facing in the direction of.

  Conventionally, there is a technique for simultaneously transmitting a plurality of signals from a transmission device on the transmission side to a transmission device on the reception side using a plurality of lights having different wavelengths. This technique uses the characteristic that optical signals having different wavelengths do not interfere with each other and can be separated.

  For example, the apparatus of Patent Document 2 has a plurality of light sources that emit optical signals having different wavelengths, and the transmission apparatus multiplexes (multiplexes) the light from these light sources into one beam for transmission. On the receiving side, the multiplexed beam is received by a plurality of light receiving elements, and optical signals having different wavelengths are extracted from the respective light receiving elements.

JP 05-183515 A No. 2006/082893

  The optical space transmission device described in Patent Document 1 includes a light-emitting element and a light-receiving element for optical signals that transmit information, and a light-emitting element and a light-receiving element for beacon signals for optical axis adjustment. Providing two types of light-emitting elements and light-receiving elements in this way has a problem of complicating circuits and control. In addition, the wavelength division multiplexing optical space transmitter described in Patent Document 2 wavelength-multiplexes a plurality of optical signals that transmit information, and can multiplex the multiplexed optical signals on the same optical axis. However, this apparatus does not consider adjusting the optical axes of the transmission side and the reception side.

  The present invention has been proposed in order to solve the above-mentioned problems of the prior art, and is a beacon for transmitting / receiving wavelength-division multiplexed optical signals for transmitting information and adjusting the optical axes of light emitting elements and light receiving elements. It is an object of the present invention to provide an optical space transmission system capable of transmitting and receiving signals with the same light emitting element and light receiving element.

The optical space transmission apparatus of the present invention has the following characteristics.
(1) The optical space transmission device includes a first device having at least an optical signal transmission unit and a second device having at least a reception unit.
(2) The transmission unit generates a beacon signal in a frequency band different from the transmission signal input from the input unit, and a superimposition circuit that superimposes the transmission signal and the beacon signal to generate a superimposed signal voltage And a light emitting unit having a light emitting element that emits an optical signal based on the superimposed signal voltage.
(3) The receiving unit includes a light receiving unit having three or more light receiving elements that receive the optical signal, a light receiving circuit that converts each optical signal received by the three or more light receiving elements into a superimposed signal voltage, and And a filter for separating the superimposed signal voltages into beacon signals.
(4) The reception unit detects a reception level of each light receiving element from each separated beacon signal, and a direction detection circuit detects the input direction of the optical signal from each detected reception level And a direction adjusting unit that adjusts the optical axis direction so that the light receiving unit faces the direction facing the transmitting unit.
(5) The receiving unit includes a filter that selectively separates a transmission signal from the superimposed signal voltage, and a limiting amplifier circuit that converts the selectively separated transmission signal into a binary signal.

In the present invention, the following configurations can be employed as appropriate.
(6) In the receiving unit, the filter includes an adding circuit that separates the superimposed signal voltages from the light receiving elements into transmission signals, and adds the separated transmission signals. The limiting amplification circuit converts the transmission signal into a binary output signal.
(7) The transmission unit includes a parallel conversion circuit that converts an input transmission signal into three or more parallel signals, and a code conversion circuit that converts the three or more parallel signals into codes having a low low frequency spectrum respectively. And the light emitting unit emits light as an optical signal obtained by wavelength multiplexing the superimposed signal voltage corresponding to the three or more parallel signals using different wavelengths.
(8) The receiving unit includes an optical filter unit disposed on a front surface of the light receiving unit, and a serial conversion circuit that converts the signal into a serial signal and outputs a transmission signal, and the optical filter unit is wavelength-multiplexed. Each light receiving element receives the received optical signal in accordance with the wavelength, and the serial conversion circuit converts a parallel signal corresponding to each optical signal received by each light receiving element into a transmission signal.

  According to the present invention, the light emitting element for transmitting an optical signal and the light emitting element for adjusting an optical axis are the same, and these optical signals are superimposed and transmitted to transmit information. It is possible to share the light receiving element and the light receiving element for receiving the beacon signal, and it is possible to provide an optical space transmission device that is simple in configuration and excellent in reliability.

It is a block diagram which shows the structure of the optical space transmission system of 1st Embodiment. It is a block diagram which shows the structure of the transmission part of 1st Embodiment, and a receiving part. It is a graph which shows the frequency band of a transmission signal and a beacon signal. It is a perspective view which shows a lens and a light-receiving part. It is a block diagram which shows the structure of the transmission part of 2nd Embodiment, and a receiving part. It is a perspective view which shows an example of the light emission part of 2nd Embodiment. It is a perspective view which shows the lens of 2nd Embodiment, an optical filter part, and a light-receiving part. It is a block diagram which shows the structure of the transmission part of other embodiment, and a receiving part.

  Embodiments of the present invention will be described below. In each embodiment, the description of the same contents is omitted.

[First Embodiment]
The optical space transmission system according to the first embodiment will be described with reference to FIGS.

(Constitution)
As shown in FIG. 1, the optical space transmission system of the first embodiment includes two optical space transmission devices 10, and these optical space transmission devices 10 mutually communicate with each other by an LED (Light Emitting Diode) or the like. Send and receive information using. The optical space transmission device 10 receives a transmission signal of a 100BASE-FX signal that is a standard for transmission through an optical fiber from a network or the like, converts the transmission signal into an optical signal, and transmits the optical signal by optical communication. A receiver 40 that receives an optical signal transmitted by communication, converts the optical signal into a transmission signal, and outputs the signal to a network or the like.

  FIG. 2 shows the configuration of the first transmitter 20 and the second receiver 40 in the two optical space transmission apparatuses 10 that transmit and receive each other. The two optical space transmission apparatuses 10 receive the optical signal transmitted from the first transmission unit 20 when the second reception unit 40 receives the optical signal transmitted from the second transmission unit 20. May be received by the first receiving unit 40. Since these two cases are functionally the same, they will be described with reference to FIG. 2 for convenience.

  The configuration of the transmission unit 20 will be described below. The output of the input unit 21 that receives the transmission signal and the output of the beacon generation circuit 23 that generates a beacon signal having a bandwidth different from that of the input transmission signal are connected to the superposition circuit 24.

  The superimposing circuit 24 receives the input transmission signal from the input unit 21 and the beacon signal generated by the beacon generating circuit 23, and the superimposing circuit 24 superimposes them and outputs them to the driving circuit 25 as a superimposed signal voltage. . The drive circuit 25 is connected to the light emitting element 27 and blinks the light emitting element 27 as a superimposed light signal. The light emitting unit 26 includes a light emitting element 27 such as an LED that emits an optical signal.

  The configuration of the receiving unit 40 will be described below. The lens 41 focuses the superimposed optical signal received from the light emitting unit 26 of the other optical space transmission device 10. The focused spot light is applied to the light receiving unit 42. The light receiving unit 42 includes four light receiving elements 43 such as photodiodes. The light receiving circuit 44 converts the current value output from the four light receiving elements 43 into a superimposed signal voltage and outputs it to the distributor 45. The distributor 45 distributes the four superimposed signal voltages from the light receiving circuit 44 to the low-pass filter 46 and the high-pass filter 50.

  The low-pass filter 46 separates a low frequency signal, that is, four beacon signals from the four superimposed signal voltages distributed, and outputs the separated signals to the level detection circuit 47. The level detection circuit 47 detects each level corresponding to the amount of light received by the light receiving unit 42 from these four beacon signals, and outputs the result to the direction detection circuit 48.

  Based on the light receiving levels of the four light receiving elements detected by the level detecting circuit 47, the direction detecting circuit 48 and the light receiving direction of the lens 41 and the light receiving unit 42 (hereinafter referred to as the light receiving axis direction) and the light emitting unit of the device facing each other. The angle difference from the direction 26 (hereinafter referred to as the light emission axis direction) is detected, and the result is output to the direction adjustment unit 49.

  The direction adjustment unit 49 adjusts the light receiving axis direction with an actuator using a motor or the like based on the detection result of the direction detection circuit 48. By this adjustment, the light receiving axis direction and the light emitting axis direction are made to coincide. For example, the direction adjusting unit 49 tilts the entire light receiving unit 42 with the actuator so that the light receiving levels of the four light receiving elements detected by the direction detecting circuit 48 are equal.

  A high-pass filter 50 that separates a high-frequency signal, that is, four transmission signals, from the four superimposed signal voltages distributed by the distributor 45 is connected to an adder circuit 52. An adder circuit 52 that adds the four transmission signals is connected to a limiting amplifier circuit 51. This limiting amplifier circuit 51 converts the added transmission signal into a binary digital signal and outputs the binary digital signal to the output unit 55. The output unit 55 transmits this transmission signal.

(Function)
The operation of the optical space transmission system of the first embodiment will be described. A transmission signal of 100BASE-FX standard is received by the input unit 21.

  Next, the beacon signal generated by the beacon generation circuit 23 and the transmission signal received by the input unit 21 are superimposed by the superimposition circuit 24 to become a superimposed signal voltage. The beacon signal is, for example, a 10 kHz sine wave, and is a signal used for adjustment of the reception axis direction of the reception unit 40. As shown in FIG. 3, the transmission signal and the beacon signal have different frequency bands. Since the frequency bands are thus different, these signals can be separated by the low-pass filter 46 and the high-pass filter 50.

  The drive circuit 25 receives the superimposed signal voltage superimposed by the superimposing circuit 24, controls the current flowing through the light emitting element 27 based on the input superimposed signal voltage, and causes the light emitting element 27 to blink. The light emitting unit 26 transmits a superimposed optical signal corresponding to the blinking as optical communication. The superimposed light signal transmitted from the light emitting unit 26 is irradiated and focused on the lens 41 of the other optical space transmission device 10 and is irradiated as spot light to each of the light receiving unit 42, that is, the four light receiving elements 43.

  FIG. 4 is a perspective view showing the relationship among the light emitting element 27, the lens 41, and the light receiving unit 42. As shown in FIG. 4A, the light receiving unit 42 is divided into four by four light receiving elements 43. When an optical signal is applied to the four light receiving elements 43, a current converted from the energy of the light is generated and input to the light receiving circuit 44. The light receiving circuit 44 converts these into four superimposed signal voltages which are digital signals. Next, these four superimposed signal voltages are distributed by the distributor 45 so as to be input to the low-pass filter 46 and the high-pass filter 50. The four superimposed signal voltages distributed by the distributor 45 are separated by the low-pass filter 46 into four beacon signals that are low-frequency signals and pass through. These four beacon signals are input to the level detection circuit 47, and the respective levels corresponding to the amount of light received by the light receiving unit 42 are detected.

  FIG. 4A shows that an optical signal from the light emitting element 27 is irradiated as spot light to the four light receiving elements 43 via the lens 41. The spot light is irradiated with an equal amount of light to the four light receiving elements. This is because the optical axis of the optical signal from the light emitting element 27 matches the optical axis of the lens 41.

  FIG. 4B shows a case where the light emitting element 27 is positioned above the light receiving unit 42. In this case, as shown in the figure, the spot light is not evenly applied to the four light receiving elements 43. For example, the amount of light applied to the upper two light receiving elements 43 is small, while the amount of light applied to the lower two light receiving elements 43 is large.

  The level detection circuit 47 detects the level of the amount of light received by each of the four light receiving elements 43 and supplies it to the direction detection circuit 48. The direction detection circuit 48 detects the amount of deviation between the light receiving axis direction and the light emitting axis direction based on the detected levels.

  Next, the lens axis direction is adjusted by the direction adjusting unit 49 based on the detection result of the direction detection circuit 48. That is, the lens axis direction is adjusted so as to coincide with the direction of the light emitting unit 26. In this adjustment, the directions of the light emitting axis and the light receiving axis are made to coincide with each other by inclining the light receiving surface so that the light is uniformly applied to the four light receiving elements 43 arranged symmetrically on the same plane. Specifically, the entire light receiving surface is tilted by the actuator so that the four light receiving levels from the level detection circuit 47 are equal.

  FIG. 4C shows a state in which the direction adjusting unit 49 moves in the light receiving axis direction and adjusts the directions of the lens 41 and the light receiving unit 42. That is, the light receiving axis direction as shown in FIG. 4B is moved in the direction coincident with the light receiving axis direction as shown in FIG. It is in a state.

  On the other hand, the four superimposed signal voltages distributed by the distributor 45 and input to the high-pass filter 50 are separated by the high-pass filter 50 into transmission signals that are high-frequency signals. The high pass filter 50 outputs the four separated transmission signals to the adder circuit 52. The adder circuit 52 adds the four transmission signals. That is, the four transmission signals based on the optical signals divided into four by the four light receiving elements 43 of the light receiving unit 42 are added, and the four divided signals are added. The transmission signal added by the adder circuit 52 is output to the limiting amplifier circuit. The limiting amplifier circuit 51 converts this transmission signal into a binary digital signal. The binary digital signal is input to the output unit 55, and the output unit 55 transmits the binary digital signal to a device having an Ethernet port such as a PC.

(effect)
The optical space transmission system according to the first embodiment has the following effects.
(1) The light emitting unit 26 can superimpose a transmission signal for transmitting information and a beacon signal for adjusting the optical axis, and transmit both with a single optical signal. Therefore, a plurality of light emitting elements are not required, and a single light emitting element 27 can transmit a transmission signal and a beacon signal in a superimposed manner, thereby simplifying the configuration of the light emitting unit.
(2) The optical space transmission device 10 of the first embodiment can receive the optical signal on which the light receiving unit 42 is superimposed, and does not require a light receiving unit dedicated to the beacon signal, so the configuration of the light receiving unit 42 is simple. Can be

(3) Since the frequency bands of the transmission signal and the beacon signal are greatly different, the receiving unit 40 that receives the signal in which both are superimposed is divided into two different signals superimposed by the low-pass filter 46 and the high-pass filter 50. Can be easily separated.
(4) Since the superimposed signal voltages received by the four light receiving elements are added by the adder circuit, the received signal has high intensity and little deterioration of the transmission signal.

[Second Embodiment]
The optical space transmission system according to the second embodiment will be described with reference to FIGS. Note that the basic configuration of the optical space transmission device 10 of the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

(Constitution)
As illustrated in FIG. 5, the transmission unit 20 and the reception unit 40 of the second embodiment add a parallel conversion circuit 28, a serial conversion circuit 53, and an optical filter unit 54 to the transmission unit 20 and the reception unit 40 of the first embodiment. This is the configuration. These configurations will be described below.

  The input unit 21 receives a 100BASE-T signal from an Ethernet device such as a PC, the output of the input unit 21 is input to a parallel conversion circuit 28, and the parallel conversion circuit 28 receives four transmission signals as serial signals. Is converted into a parallel signal. The parallel signal may be a signal based on the MII interface specification. The output side of the parallel conversion circuit 28 is connected to the code conversion circuit 29. The code conversion circuit 29 performs code conversion on each of the four parallel signals input from the parallel conversion circuit 28. That is, the code conversion circuit 29 performs scrambling and 4B5B processing on the input 25 Mbps × 4 parallel signal to obtain a 31.25 Mbps × 4 parallel signal.

  A superimposing circuit 24 is connected to the output side of the code conversion circuit 29. That is, the output side of the code conversion circuit 29 and the output side of the beacon generation circuit 23 are connected to the superimposing circuit 24. The superimposing circuit 24 superimposes the four parallel signals and the beacon signal having a frequency of 10 kHz to generate four superimposed signal voltages. Since the 31.25 Mbps parallel signal to be superimposed is a signal that does not include a low frequency spectrum by scrambling and 4B5B processing, it is superimposed in a state where it can be separated from the beacon signal upon reception. A light emitting unit 26 is connected to the output side of the superimposing circuit 24 through a driving circuit 25. The light emitting unit 26 includes light emitting elements 27R, 27G, 27B, and 27Y that are LEDs that emit optical signals. For example, 27R emits red light, 27G emits green light, 27B emits blue light, and 27Y emits yellow light. The light emitting elements 27R to 27Y emit optical signals having different wavelengths. In the present embodiment, the drive circuit 25 causes each of the light emitting elements 27R to 27Y to blink independently based on four superimposed signal voltages, and emits light as a superimposed optical signal wavelength-multiplexed with four different wavelengths.

  FIG. 6 is a perspective view showing an example of the light emitting unit 26 of the present embodiment. As shown in this figure, the light emitting section 26 is formed in a stem shape, and the light emitting elements 27R to 27Y are attached to the plane of the tip of the stem at equal intervals. Since the light emitting unit 26 is formed in this way, signals from the light emitting elements 27R to 27Y are emitted in a parallel state.

  On the other hand, the receiving unit 40 includes a lens 41 as in the first embodiment. An optical filter unit 54 is provided on the output side of the lens 41. The optical filter unit 54 has four types of optical filters 54R, 54G, 54B, and 54Y. The optical filters 54R to 54Y are optical elements that transmit only light in a specific wavelength range with respect to incident light and do not transmit other light. The optical signals from the light emitting elements 27R, 27G, 27B, and 27Y are transmitted only from the optical filters 54R, 54G, 54B, and 54Y, respectively, so that four wavelengths are separated.

  Also in the present embodiment, the light receiving unit 42 includes four light receiving elements 43R, 43G, 43B, and 43Y on the output side of the lens 41. The optical filter 54R is attached to the surface of the light receiving element 43R on the lens 41 side. Similarly, the optical filter 54G is attached to the light receiving element 43G, the optical filter 54B is attached to the light receiving element 43B, and the optical filter 54Y is attached to the light receiving element 43Y.

  FIG. 7 is a perspective view showing the lens 41, the optical filter unit 54, and the light receiving unit 42. As shown in the figure, the light receiving unit 42 is divided into four by light receiving elements 43R to 43Y. Each of the optical filters 54R to 54Y is attached to correspond to these four divided areas.

  The light receiving circuit 44 converts the current value, which is the output of the light receiving elements 43R to 43Y, into four superimposed signal voltages. The distributor 45 distributes the four superimposed signal voltages from the light receiving circuit 44 so as to be input to the low-pass filter 46 and the high-pass filter 50. The low-pass filter 46 passes only low-frequency signals, that is, four beacon signals at the four superimposed signal voltages. The subsequent processing is the same as in the first embodiment.

  On the other hand, the high-pass filter 50 passes only high-frequency signals, that is, four 31.25 Mbps parallel signals, at the four superimposed signal voltages. The limiting amplifier circuit 51 converts these four parallel signals into binary signals, then 5B4B conversion and descrambling, and converts them into four parallel signals of 25 Mbps. The serial conversion circuit 53 Two parallel signals are converted into serial signals reconstructed into 100BASE-T signals, input to the output unit 55, and output from the output unit 55 as transmission signals.

(Function)
The operation of the optical space transmission system of the second embodiment will be described. A 100BASE-T standard transmission signal input to the input unit 21 is input from the input unit 21 to the parallel conversion circuit 28. The parallel conversion circuit 28 converts the transmission signal from a serial signal to a parallel signal. In this conversion, for example, an input 100 Mbps serial signal is converted into a 25 Mbps × 4 parallel signal. With this conversion, a transmission rate of 100 Mbps is transmitted at four transmission rates of 25 Mbps. The parallel signal converted to 25 Mbps × 4 is input to the code conversion circuit 29 and subjected to coding processing such as scramble processing and 4B5B processing for reducing the low frequency spectrum, and 31.25 Mbps × 4 parallel signal. It becomes.

  Next, the beacon signal generated by the beacon generation circuit 23 and the four parallel signals subjected to scramble processing and the like are superimposed by the superimposition circuit 24 to become four superimposed signal voltages. Next, the drive circuit 25 blinks each of the light emitting elements 27R, 27G, 27B, and 27Y based on the four superimposed signal voltages, and emits light as four superimposed optical signals. An optical signal has a characteristic that it does not interfere with other optical signals having different wavelengths, and these optical signals can transmit information as wavelength division multiplexing communication. The light emitting element 27R is red and has a wavelength of 620 to 750 nm, the light emitting element 27G is green and has a wavelength of 495 to 570 nm, the light emitting element 27B is blue and has a wavelength of 450 to 495 nm, and the light emitting element 27Y is yellow and has a wavelength of 570 to 570. 590 nm.

  The four superimposed optical signals transmitted from the light emitting unit 26 of the transmitting unit 20 are irradiated and focused on the lens 41 provided in the light receiving unit 42 of the receiving unit 40, and are used as spot light as the optical filters 54R to 54R. The light receiving elements 43R to 43Y are irradiated through 54Y. When an optical signal is applied to the light receiving elements 43R to 43Y, a current converted from the energy of the light is generated and input to the light receiving circuit 44. The light receiving circuit 44 converts these into four superimposed signal voltages. Next, each of these four superimposed signal voltages is distributed by the distributor 45 so as to be input to the low-pass filter 46 and the high-pass filter 50.

  One of the four superimposed signal voltages distributed by the distributor 45 is separated by the low-pass filter 46 into four beacon signals that are low-frequency signals. These four beacon signals are input to the level detection circuit 47, and the respective levels corresponding to the amount of light received by the light receiving unit 42 are detected. The operation of the direction detection circuit 48 and the direction adjustment unit 49 is the same as that of the first embodiment described above, and is based on the difference in inclination between the light emitting axis direction and the X axis and Y axis of the light receiving surface of the light receiving unit 42. The lens axis direction is adjusted.

  The other of the four superimposed signal voltages distributed by the distributor 45 is separated into four parallel signals that are high-frequency signals by the high-pass filter 50. At this time, based on the beacon signal, the direction of the lens axis is adjusted by the direction adjusting unit 49 and coincides with the direction of the light emitting unit 26, and the levels of these four parallel signals are substantially the same. ing.

  The four parallel signals that have passed through are converted into binary signals by the limiting amplifier circuit 51, and then subjected to 4 descrambling processing and 5B4B processing to become 25 Mbps × 4 signals as transmission signals. These four parallel signals are converted by the serial conversion circuit 53 into a serial signal reconstructed into a 100BASE-T signal.

(effect)
The optical space transmission system of the second embodiment has the following effects in addition to the effects common to the first embodiment.
(1) The optical communication from the transmission unit 20 to the reception unit 40 by serial-parallel conversion has a transmission rate of ¼, so that it can cope with high-speed transmission signals. That is, when a high-speed transmission signal is transmitted to the optical space transmission device 10 and the transmission signal is transmitted to another optical space transmission device by optical communication, a reliable optical signal can be obtained by reducing the transmission speed of this optical communication. Can communicate.
(2) It is possible to send and receive optical signals in which four types of transmission signals and one beacon signal are superimposed on one optical signal with a simple configuration in which multiplexed optical signals are simply separated by an optical filter unit. Therefore, a large amount of transmission signals can be transmitted and received with a simple configuration.

[Other Embodiments]
The present invention is not limited to the above embodiment, and includes other embodiments as described below.

(1) Although the first embodiment includes the adder circuit 52, the adder circuit 52 may be omitted. By not including the adder circuit 52, the configuration of the optical space transmission device 10 can be simplified. Hereinafter, the light receiving circuit 44, the distributor 45, the low-pass filter 46, and the high-pass filter 50 used in the optical space transmission device 10 having this configuration will be described with reference to FIG.

  The light receiving circuit 44 converts the current values that are the outputs of the four light receiving elements 43 into four superimposed signal voltages, and outputs them to the distributor and the low-pass filter 46. The distributor 45 receives one of the four superimposed signal voltages from the light receiving circuit 44 and distributes it to the low-pass filter 46 and the high-pass filter 50. The low pass filter 46, to which one superimposed signal voltage from the distributor 45 and three superimposed signal voltages from the light receiving circuit 44 are input, separates a low frequency signal, that is, four beacon signals. On the other hand, the high-pass filter 50 separates a high-frequency signal, that is, a transmission signal from one superimposed signal voltage distributed by the distributor 45, and outputs it to the limiting amplifier circuit 51.

(2) The transmission signals of the first and second embodiments are 100BASE-FX and 100BASE-T, but are not limited thereto. For example, the transmission signal may be an analog signal or a digital signal other than the LAN.
(3) Although the direction adjustment unit 49 of the first and second embodiments uses an actuator as a moving means in the light receiving axis direction, the present invention is not limited to this. For example, the light receiving axis direction may be moved manually. . In this case, the direction of tilting from the detection result of the direction detection circuit 48 may be indicated by an arrow or the like using display means such as a liquid crystal display.
(4) The light receiving unit 42 of the first and second embodiments is configured by four light receiving elements, but is not limited thereto, and may be configured by three or five or more light receiving elements. In the adjustment by the direction adjusting unit 49, the optical axis is determined by at least three light receiving elements. In this case, in the second embodiment, the parallel number converted by the parallel conversion circuit 28 and the number of light emitting elements of the light emitting unit 26 are combined with the number of light receiving elements of the light receiving unit 42.

DESCRIPTION OF SYMBOLS 10 ... Optical space transmission apparatus 20 ... Transmission part 21 ... Input part 23 ... Beacon generation circuit 24 ... Superimposition circuit 25 ... Drive circuit 26 ... Light emission part 27, 27R, 27G, 27B, 27Y ... Light emission element 28 ... Parallel conversion circuit 29 ... Code conversion circuit 40... Receiving unit 41... Lens 42. Light receiving unit 43, 43 R, 43 G, 43 B, 43 Y... Light receiving element 44. Direction adjustment unit 50 ... high-pass filter 51 ... limiting amplifier circuit 52 ... addition circuit 53 ... serial conversion circuit 54 ... optical filter units 54R, 54G, 54B, 54Y ... optical filter 55 ... output unit

Claims (3)

An optical space transmission device that performs communication between devices having at least an optical signal transmitter in one device and at least a receiver in the other device,
The transmitter is
A beacon generating circuit that generates a beacon signal in a frequency band different from the input transmission signal, a superimposing circuit that superimposes the transmission signal and the beacon signal to form a superimposed signal voltage, and an optical signal based on the superimposed signal voltage A light emitting unit having a light emitting element that emits light,
The receiver is
A light receiving unit having three or more light receiving elements that receive the optical signal, a light receiving circuit that converts each optical signal received by each of the three or more light receiving elements into each superimposed signal voltage, and each superimposed signal voltage for each beacon. A filter that separates signals, a level detection circuit that detects a reception level of each light receiving element from each of the separated beacon signals, and a direction detection circuit that detects an input direction of the optical signal from each detected reception level; A direction adjusting unit that adjusts the optical axis direction of the light receiving unit so that the light receiving unit faces the transmitting unit, a filter that separates one of the superimposed signal voltages into a transmission signal, and the separated transmission signal An output unit for outputting,
An optical space transmission device. The receiver is
The filter has an addition circuit that separates the superimposed signal voltage from each of the light receiving elements into transmission signals, and adds the separated transmission signals,
The optical space transmission apparatus according to claim 1, wherein the output unit outputs the added transmission signal. The transmitter is
A parallel conversion circuit that converts an input transmission signal into three or more parallel signals;
A code conversion circuit for encoding the three or more parallel signals;
The light emitting unit emits a superimposed signal voltage corresponding to the three or more parallel signals as an optical signal wavelength-multiplexed using different wavelengths,
The receiver is
An optical filter unit disposed in front of the light receiving unit, and a serial conversion circuit that converts a parallel signal into a serial signal and outputs a transmission signal,
The optical filter unit causes the light receiving elements to receive the wavelength-multiplexed optical signal according to the wavelength,
The serial conversion circuit converts a parallel signal corresponding to each optical signal received by each light receiving element into a transmission signal;
The optical space transmission device according to claim 1.

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