JPH01236834A - Automatic searching device in optical space transmitter - Google Patents

Abstract

PURPOSE:To surely attain optical axis alignment and a focus adjusting by enlarging a beam irradiation pattern at the light receiving side of an optical beam initially, facilitating the grasping of a mutual position, stopping the optical beam gradually, minimizing a beam irradiation pattern and executing a light axis position adjustment. CONSTITUTION:Since a beam irradiation pattern is expanded at respective light receiving surfaces in an initial condition, light receiving parts 16A and 16B of transmitting receiving devices A and B at an opponent side are respectively brought into the expanded beam irradiation pattern. Thus, when opponent side light receiving parts 16A and 16B are respectively put into the beam irradiation diameter, the beam irradiation pattern is gradually minimized by a control means and a projecting beam azimuth is gradually controlled. Thus, the optical axis alignment between the transmitting and receiving devices A and B of two points is accomplished, and simultaneously, focus adjustment is executed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an automatic search device that enables communication with phase JL in an optical space transmission device.

[Summary of the invention]

This invention expands the beam J, irradiation i, and By gradually and normally controlling the azimuth angle of the emitted beam based on the information, the beam diameter can be adjusted so that mutual communication is possible, and the positional relationship between the light beam and the light receiving part can be automatically adjusted. It has been made possible.

[Conventional technology]

When performing bidirectional optical space transmission between two points, it is necessary to align the optical axes and adjust the focus so that the light beams are irradiated onto the light receiving surface.

Conventionally, this has been done manually using a telescope or the like.

By the way, the light beam used in the optical space transmission device is narrowed very sharply at the light receiving surface in order to transmit and receive main signal information with a good S/N ratio. For this reason, it was very difficult to manually adjust the beam exit azimuth between the two points.

Therefore, a technique as shown in FIG. 8 was proposed as a method for automatically searching for this optical axis position.

In other words, as shown in FIG. 8, the automatic search mechanism considers transmitters (1) and (21) located at two locations, each of which does not know the exact direction of the other device.
1 is the emission side of the light beam, and the other side, for example, the transmitter/receiver (2) is considered as the light receiving side.
) Consider a two-dimensional plane (X-Y plane) including the light-receiving surface.

Then, a light beam is transmitted from the transmitter/receiver (1) on the emission side onto this two-dimensional plane, #1 in FIG. #2. #3...
Scan like this.

This is also performed with the transmitter/receiver (2) on the emitting side and the transmitter/receiver +1) on the light receiving side.

Through this, the mutual positions are known, and then optical axis adjustment and focus control are performed.

[Problem to be solved by the invention] However, in the technique shown in FIG.
When they simultaneously discover each other's positions,
Although it is possible to mutually exchange information that the other party has been captured, in other cases, it is inconvenient that the receiving side cannot notify the emitting side by optical space transmission that the receiving side has captured the beam on the emitting side. There is.

Since it is very difficult to simultaneously capture the other side, the automatic search mechanism shown in FIG. 8 is not practical.

The object of the present invention is to provide an automatic search device that does not have these drawbacks.

[Means to solve the problem]

In the automatic search device for a bidirectional optical space transmission device between two points, which is provided with transmitters and receivers according to the present invention, radiation angle control means for controlling the size of the beam irradiation pattern on the light receiving surface is provided on the light beam emission side. , on the light receiving side, detecting a deviation in the positional relationship between the received light beam and the light receiving section 6;
means for transmitting servo information based on this deviation to the output side; azimuth control means for controlling the output direction of the output light beam on the output side based on the received servo information; and radiation angle control means on the output side for receiving the light. While controlling the size of the beam irradiation pattern on the surface to be gradually reduced, information on the deviation formed on the light receiving side is received based on the reduced light beam, and based on this information on the deviation, the direction control means and control means for gradually and appropriately changing the emission direction of the light beam.

[Effect]

In the initial state, the beam irradiation pattern on each light-receiving surface is expanded, so it is easy to bring the light-receiving parts of the respective transmitters and receivers into the expanded beam irradiation pattern.

In this way, when the respective partner light receiving parts enter the beam irradiation diameter, the control means gradually decreases the rebeam irradiation pattern (while gradually controlling the output beam azimuth. As a result, Focus adjustment is performed at the same time as the optical axis positions between the two transmitters and receivers are aligned.

〔Example〕

FIG. 1 is a block diagram of an example of an optical space transmission device equipped with an automatic search device according to the present invention.

In the figure, A and B are handsets, respectively, and these handsets A,
The handsets A and B are placed at two visible points, and two-way communication is performed between these handsets A and B via an optical space transmission line (3) set as described below.

Here, since the transmitters/receivers 5A and 5B have exactly the same structure, only the structure of the transmitter/receiver A will be described, assuming that the same parts are given the same numbers with the suffixes ¥A and B.

<IOA> removes the optical system and connects the optical beam transmitter (IIA)
, lens thread (12Δ), and beam splitter (13A)
), lens systems (14A) and (15A), and light receiving section (
16A).

Lens systems (128), (14A) and (15A) consist of small bodies or compound lenses.

The light beam transmitter (11Δ) generates a laser beam, and the output laser beam is transmitted to the laser drive circuit (25A).
) is modulated by the signal to be transmitted. In this case, the signal to be transmitted consists of main signal information to be transmitted and a servo signal consisting of information on optical axis deviation and focus deviation.

As described later, the main signal information is, for example, 100M
The drive signal occupies a band of Hz±10M1lz, and the servo 1d'4 is, for example, 450 to 470kl.
Depending on the type of deviation, an FM transduction signal with a different carrier frequency is generated. However, the servo signals are F with a shallow modulation depth of about ±1 kllz, respectively.
M transformation signal is sent.

FIG. 2 shows the frequency spectrum of No. 14 to be transmitted.

The light beam from the light beam transmitter (IIA) is emitted from this optical system (10^) via the lens system (12/l) - beam splitter (13A) - lens system (14A). The light beam incident on the optical system (10A) passes through the lens thread (14A) to the beam splitter (10A).
3A), is reflected, and enters the light receiving section (16A) via the lens thread (15A).

In this case, the optical beam transmitter (IIA') is
As shown in , it is possible to move r+J in the optical axis direction (Z-axis direction), and the position of the optical beam transmitter (IIA) in the Z-axis direction can be changed according to the drive signal from the Z-axis direction drive circuit (21). . When the position of the light beam transmitter (IIA) in the Z-axis direction changes, the distance between the light beam transmitter (IIA) and the lens system (12A) changes, thereby changing the diameter of the light beam emitted from the optical system (IOA). , that is, the radiation angle changes, and the size of the beam irradiation pattern on the light receiving surface on the light receiving side changes.

In addition, in this case, the entire optical system (Cl0A) can be positioned vertically, horizontally and horizontally with one fixed point as the center, and the optical axis direction can be adjusted according to the drive signal from the azimuth drive circuit (22). The optical axis position of the optical system (<l0A), that is, the azimuth angle of the output beam is changed.

In this example, the light receiving section (16A) is 4 as shown in FIG.
A main light receiving section consisting of 4+Ild photodiodes P1 to P4, and four sub photodiodes P5 to 1)8 provided around the 4+Ild photodiodes P1 to P4 in the upper, lower, left and right positions in this example.

These four photodiodes of this light receiving unit (IOA)
The outputs of P1 to P4 and the outputs of the surrounding sub-photodiodes are supplied to a servo information generation circuit (23A), in which information on optical axis deviation is generated mainly based on the outputs of the surrounding sub-photodiodes. . Information on this optical axis shift can also be generated using the light receiving outputs of the photodiodes PL.about.P4 of the main light receiving section. Further, information on defocus is generated based on the outputs of the photodiodes P1 to P4 of the main light receiving section. In this example, the optical axis misalignment information is divided into vertical misalignment information and horizontal misalignment information, and each is FM modulated. For example, for information on vertical deviation, the carrier frequency is 450kHz,
When the size of the deviation is maximum, carrier) is larger than the number of subliquids.
450kHz±
It is made to occupy 41 areas of 1 kllz.

Similarly, the 1N signal of the shift in the left and right direction is a signal in the band of 460 kllz±1 kllz with the carrier frequency being 460 kHz. Furthermore, the information on defocus is 470k.
The signal has a band of Hz±l kllz.

And this servo information generation circuit (1・from 23^>
' Servo information consisting of M-modulated shift information is supplied to the adder circuit (24A).

The adder circuit (24A) is supplied with a variable m signal of the main signal for transmission. In this case, the main signal is subjected to FM modulation or *keying such as 4-phase PSK.

In this case, the modulation carrier frequency of the main signal is, for example, 100
M)1z, and its bandwidth is, for example, about 100M41z±2°MIIZ.

Then, the output signal of this adder circuit (24A) is sent to the light beam transmitter (II) via the laser drive circuit (25^).
A ) is supplied to the laser generating section of the adder circuit (24A
) generates a modulated laser beam according to the output signal of the

In this way, since the main signal and servo information have different transmission bands, it is easy to separate them from the received light output.

That is, the light receiving output from the light receiving section (16A) (including the output from not only the main light receiving section but also the sub photodiode) is passed through the amplifier (26^) to the band pass filter (27A).
, ) from which a modulated signal of the main signal is obtained,
This is supplied to the main signal demodulator.

The light receiving output from the amplifier (26A) is also supplied to a bandpass filter circuit (28A). This circuit (2
8A) is equipped with 3 (161) band-pass filters of the pass band corresponding to the above-mentioned three shift information bands, and each shift information (FM modulated) is taken out to form the control A3. In this control signal forming circuit (20A), the information on each shift is FM modulated, and a Z-axis direction drive signal and an azimuth drive signal are formed according to the demodulated output. The signals are respectively supplied to a Z-axis direction drive circuit (21A) and an azimuth angle drive circuit (22A), and optical axis adjustment and focus adjustment are performed.

In this case, the control No. 18 forming means (20^) is provided with a microcomputer, and the transmitter/receiver A is installed at the second point.

Due to the initial condition of installing B or for some other reason, transmitter A
, H is so shifted that even the sub-photodiode cannot receive light, the optical axes and focus are adjusted as follows.

FIG. 4 is a flowchart of the axis alignment and focus alignment. Below, we will explain about the handset A side.

That is, first, initial settings are made. Each of the transceivers A and B is equipped with an optical observation means, and at the time of initial setting, the operator adjusts the position so that the emitted light beam from the other party enters the receiving section. At this time, before this person adjusts their position,
The distance between handsets A and B is entered by this person. Then, the control signal and signal forming circuit (20A) controls the position of the light beam transmitter (IIA) in the Z-axis direction according to the distance, and the diameter of the emitted beam is adjusted to the field of view that can be adjusted by a human using the observation means on the light receiving side. The size of the beam irradiation pattern is set to cover the area. The size of this beam irradiation pattern is considerably wider and larger than the irradiation pattern of a focused light beam during stable optical space communication, so a person can capture the light beam from the other party with observation means. is relatively easy.

In this way, in the 51i2I, when the light beams from the other side are captured with the light beams spread out as shown by the solid line, the search is started. Then, the light receiving section (16A) receives the light beam that is expanded at this time. This received light beam necessarily includes the servo information transmission number 1 because the light beam is also irradiated onto the light receiving section of the other party. However, at this time, the received light beam is spread out, so the power density of the light is low. However, the servo information transmission signal (450~470kllz±1k
llz) is the main No. 16 transmission signal (100MIlz±2
The bandwidth is sufficiently narrower than that of 0MI+2). Revenge tll
The noise power entering the iI unit is proportional to the bandwidth. Therefore, the servo information has a frequency of 1 kHz/20M compared to the raw signal.
It is possible to respond to signal levels as low as Hz = 5 x 1O-5 = -43dll. This corresponds to -21.5 dB in terms of optical power density, and it is possible to demodulate servo information even if the diameter of the light beam irradiation pattern is increased by about 10 times when using current. It goes without saying that if the transmission band of servo information can be made narrower than ever before, the light beam can be further expanded.

As described above, servo information can also be obtained from a spread light beam. However, since the light beam has spread, the transmitter/receiver B on the other end outputs 40 indicating that there is no deviation in the optical axis, and this is sent as servo information. However, since the focus is not adjusted at all, the focus error information is sent as servo information.

In the control signal forming circuit (2 (IA)), these servo information +
It receives the signal U, outputs a signal to control the Z-axis direction, and directs the output light beam from the optical beam transmitter 11fB (IIA) to the fifth
Narrow down as shown by the dashed line in the diagram. This light beam is changed by the servo information μ generated at this time by the servo information generation circuit (23^).

When the beams of light intersect in this way, the other party's transmitter/receiver B recognizes that the relative positional relationship between the light beam and its own device has changed. 1 will be given. If it becomes like the broken line in Fig. 5, it can be detected by the sub-photodiode Ps+Pb of the light receiving part (16B) of the transceiver B that the °C optical axis is shifted upward, and from the transceiver B, Information on the deviation is sent as servo information to the transceiver. In the transmitter/receiver, upon receiving this servo information *U, the control signal forming circuit (20A) sends a signal for changing the emission azimuth to the azimuth angle drive circuit (22).
A ), thereby changing the output azimuth of the light beam to ) to match the transmitter B.

lJj! 44 When the azimuth angle is changed, information indicating that the optical axis has not deviated is sent again as information on the optical axis deviation, so the control signal forming circuit (20A) again sends a signal to change the Z-axis direction to the Z-axis direction drive circuit ( 2LA), thereby focusing the light beam. Then, handset B again
Then, it is detected that an optical axis deviation has occurred, and information on the deviation is sent from the transceiver B, so the transceiver A receives this and adjusts the emission azimuth.

Thereafter, the information reception and output azimuth angle control of light beam narrowing and optical axis deviation is repeated until information U is sent from the handset B as defocus information indicating that there is no defocus, that is, the position is in focus.

The above operations are carried out at the same time on handsets A and B, and as a result, as shown in Fig. 6, both handsets , B are connected by a light beam. Therefore, bidirectional communication with a good S/N ratio of the main signal is possible.

FIG. 7 is a block diagram of an example of an optical axis deviation information generating circuit.

The figure shows an example of a circuit that generates information on optical axis deviation in the vertical direction. The light receiving output of sub-photodiodes P5 and P6 is
1) and (32), respectively, to bandpass filters (33) and (34). These band bus filters (33) and (34) are for obtaining only band components of servo information.

The output signals of the bandpass filters (33) and (34) are supplied to level detection circuits (35) and (36), where the received light is output and the bell is detected, and the detection ratio Norgebel is sent to the subtraction circuit (37). They are supplied to each other and their height (also holds positive and negative signs) is determined. The output of this difference is information indicating how much the optical axis of the output beam of the other party is shifted in the vertical direction.

Then, the output of this difference is supplied to the FM modulation circuit (38), where it is FM modulated and made into a signal with a band of 450k)lz±lkllz, which is then sent to the laser driver (39) (
(corresponding to the drive circuit (25A) or (25B)) to drive the laser light source (40).

The optical axis deviation in the left and right direction is determined by the photodiode Pv and photodiode P instead of the photodiode P5 in FIG.
It is generated and transmitted in the same way by substituting photodiode P8 for ε.

The sub-photodiodes P-5 to P8 are optically connected to lens threads (15A ) (1511), and if an optical axis misalignment occurs during main signal transmission, information on the misalignment is transmitted to the light beam output side and the optical axis illumination is performed. be. And the sub photodiode P
When the optical axis deviates to the extent that the light beam does not enter any of the points 5 to P, the above-mentioned search operation is performed.

Additionally, defocus information can be generated from the outputs of the four photodiodes P1-P4 using techniques used, for example, in conventional compact disc players and laser disc devices.

In the above example, the position changing means in the Z-axis direction controls the movement of the light beam transmitter (IIA) or (IIB) in the Z-axis direction, but the beam irradiation pattern on the receiving side of the light beam is To change the size, use a lens system (12
A) (12B) and optical beam transmitter (IIA)
(IIB), the movement of the lens systems (12A) and (12B) in the Z-axis direction may be controlled.

(Effects of the Invention) As described above, according to the present invention, when optically aligning the transmitters and receivers of the light beam placed at two points, initially the light beam receiving side is By making the beam irradiation pattern large to make it easier to capture each other's positions, and gradually narrowing down the light beam and adjusting the optical axis position while making the beam irradiation pattern smaller, the optical axis can be reliably aligned. In this case, unlike when searching for a partner device by searching a two-dimensional plane in the past, unless the partner device is mutually discovered at the same time,
The inconvenience of not being able to align the optical axis or focus does not occur at all.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an example of an optical space transmission device equipped with an automatic search device according to the present invention, FIG. 2 is a frequency spectrum diagram of the transmission signal, and FIG. 3 is a diagram showing the configuration of an example of the light receiving section. FIG. 4 is a flowchart for explaining the search operation, FIGS. 5 and 6 are diagrams for explaining the search operation, and FIG. 1 is an example of optical axis shift +U generating means. The I-/R diagram and the FF18 diagram are diagrams for explaining a conventional automatic search device. (IIA) (IIB) is a light beam transmitter, (168) (16B) is a light receiver, (20A) (20B)
(218) (21B) is a Z-axis (optical axis) direction drive circuit, (22A) (22B)
is the output beam azimuth drive circuit, (23A)
(231!) is a servo information generation circuit.

Claims (1)

[Scope of Claims] A bidirectional optical space transmission device between two points, which includes transmitters and receivers, comprising: radiation angle control means for controlling the size of a beam irradiation pattern on a light receiving surface on a light beam output side; On the side, a means for detecting a deviation in the positional relationship between the received light beam and the light receiving part and sending servo information based on this deviation to the emitting side; an azimuth control means for controlling an emission direction; and on the emission side, the radiation angle control means gradually reduces the size of a beam irradiation pattern on the light receiving surface, and forms a light beam on the light receiving side based on the reduced light beam. an automatic search device for an optical space transmission device, comprising means for receiving servo information and gradually and appropriately changing the emission direction of a light beam by the direction control means based on the servo information.