JP3192359B2 - Space optical communication equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises an observation means for aligning an optical axis, and emits a light beam using a space as a medium.
The present invention relates to a spatial light communication device that receives light.

[0002]

2. Description of the Related Art Conventionally, as an apparatus for projecting and receiving light in the atmosphere, which comprises an observation means and an optical axis deviation correcting means, Japanese Patent Laid-Open Publication No.
2. Description of the Related Art A spatial optical communication device disclosed in JP-A-133716 is known, in which two similar communication devices are installed facing each other across a space to perform bidirectional communication.

FIG. 8 shows a configuration diagram of a conventional spatial optical communication apparatus. A communication optical system 2 for transmitting and receiving communication light and a collimating telescope 3 are placed on an optical axis adjustment table 1 provided on a gantry. Fixed,
The optical axis O1 of the communication optical system 2 and the optical axis O2 of the collimating telescope 3, which is an observation optical system, are assembled in parallel.

[0004] The spatial optical communication apparatus includes a transmission light LA and a reception light LB.
The optical axis direction variable section 4 is provided at a position where the optical axis O1 is transmitted and received, and the optical axis direction variable mirror 5 is inclined in the optical axis direction variable section 4 at approximately 45 degrees with respect to the optical axis O1. In the reflection direction of the optical axis direction variable mirror 5, a polarizing beam splitter 6, a light receiving light splitting element 7, a lens group 8 having a positive power, and a signal detecting light receiving element 9 are sequentially arranged. A lens group 10 having a positive power and a four-divided sensor 11 are arranged in the reflection direction, and a lens group 12 having a positive power and a light receiving element of a signal generation unit are arranged in the incident direction of the polarization beam splitter 6. A laser diode 13 that emits a laser beam that becomes linearly polarized light in a direction perpendicular to the paper surface is arranged.

[0005] The output of the four-divided sensor 11 is supplied to a signal processing unit 14.
And the output of the signal processing unit 14 is the optical axis direction control unit 1
5 is connected to the optical axis direction variable unit 4.

As the polarizing beam splitter 6, for example, S
An optical element is used in which a dielectric multilayer thin film that reflects most of the polarized light and transmits most of the P-polarized light is deposited on the bonding surface. In order to use the polarizing beam splitter 6 to perform the most efficient light projection / reception, the transmission light
The relationship may be such that the received light Lb becomes P-polarized light when La is S-polarized light. In order to perform the most efficient light-emitting and light-receiving operations by arranging transmitting / receiving devices having the same structure in opposition, communication The optical system 2 for use may be inclined at 45 degrees to the vertical direction toward the rear of the paper.

In the case of performing large-capacity communication capable of achieving a wide band and high-speed response, a small element having an effective light receiving area of 1 mm or less in diameter, such as an avalanche photodiode, is used as the light detecting element 9 for signal detection. There are many. Further, when the center of the light receiving beam spot P is located at the center of the four-divided sensor 11, the transmission light La irradiates the partner device B within the receivable intensity distribution, and the reception light Lb from the partner device B In order to ensure that the effective light receiving area of the signal detecting light receiving element 9 does not deviate from the effective light receiving area, the center of the signal detecting light receiving element 9 and the light receiving element of the four-divided sensor 11 are viewed from the front of the apparatus during the assembly stage of the device. Sometimes it is necessary to make adjustments so as to coincide with the emission point of the laser diode 13.

The light emitted from the laser diode 13 is
The light is converted into a substantially parallel light beam by the lens group 12, reflected at the boundary surface of the polarization beam splitter 6, further reflected by the optical axis direction variable mirror 5, and projected from the apparatus A to the apparatus B (not shown) as the transmission light La.

The light projected from the device B enters the device A as received light Lb, is reflected by the mirror 5, passes through the polarization beam splitter 6, and reaches the received light splitting element 7. Here, about 90% of the total amount of received light passes through the received light branching element 7 and is condensed by the lens group 8 on the present signal detecting light receiving element 9. The remaining 10% of the total amount of received light is reflected by the received light splitting element 7,
Received.

The positional deviation information of the light receiving beam spot P on the light receiving surface of the four-divided sensor 11 is sent to the optical axis direction control unit 15 as an optical axis deviation correction signal via a signal processing unit 14, and the optical axis direction control is performed. The mirror driving signal is sent from the unit 15 to the driving unit of the optical axis direction variable unit 4. Based on this signal, the motor of the drive unit rotates, and the optical axis direction variable mirror 5 rotates around the axes E and F as shown in FIG.

FIGS. 10 and 11 show the movement of the light receiving beam spot P on the light receiving surface of the four-divided sensor 11 at this time, and the rotation of the variable mirror 5 around the axis E moves the light receiving beam spot P. The light receiving surface is moved up and down as shown by the arrow in FIG. 10, and the rotation of the variable mirror 5 about the axis F is performed by moving the light receiving beam spot P in the direction of 45 degrees to the upper right of the light receiving surface as shown by the arrow in FIG. Move to Thus, two different
The operation of moving the light receiving beam spot P in the direction is repeated so that the center of the light receiving beam spot P is
Is controlled so as to be located at a point where the cross-shaped separating body T at the center of the light receiving section effective area S intersects.

The above-described optical axis misalignment correction control is performed by operating the two-way optical communication devices facing each other with a space therebetween so that the center of the spread of both transmission beams is opposite to that of the device. It can be maintained in a state that always matches the entrance.

As described above, when the conventional spatial optical communication device is installed to face and aligns the optical axis, the collimated telescope 3 is viewed and the laser beam Lb from the facing device or the position from the facing device is confirmed. Communication optical system 2 and collimating telescope 3 so that the strobe light Ls for communication is located at the point where the crosshairs cross in the telescope.
Using the attitude adjustment mechanism of the optical axis adjustment table 1 that integrates the two, the horizontal and vertical tilt adjustments are performed.

[0014]

However, in the conventional spatial optical communication apparatus described above, in communication for correcting the optical axis shift, the optical signals of the two devices installed opposite each other are corrected each time the optical axis shift is corrected. It is necessary to perform axis alignment, and the optical axis direction variable mirror 5 is accurately returned to the initial position so that the optical axis O1 of the communication optical system 2 and the optical axis O2 of the observation optical system 3 become parallel. There must be. However, at this time, the return position tends to fluctuate due to a use environment such as a temperature change, and even after the initial setting, the parallelism between the optical axis O1 of the communication optical system and the optical axis O2 of the observation optical system 3 is reduced. This causes a problem that the optical axis cannot be aligned at the time of opposing installation.

An object of the present invention is to solve the above-mentioned problems,
An object of the present invention is to provide a spatial optical communication device that can surely perform optical axis alignment at the time of facing installation with good reproducibility.

[0016]

A spatial optical communication apparatus according to the present invention for achieving the above object has a light projecting means comprising a light projecting optical system and a signal generating unit and / or a first light receiving optical system. A light receiving means comprising a signal detecting unit, a second light receiving optical system, and a light receiving beam spot position detecting unit for receiving the light projected from the opposing device and detecting a positional deviation obtained from a reference position of the light receiving beam spot on the light receiving surface. Optical axis deviation detecting means for detecting an optical axis deviation between the optical axis of the received light and the optical axis of the second light receiving optical system based on the information, and optical axis deviation information detected by the optical axis deviation detecting means Optical axis direction control means for sending an optical axis deviation correction signal to the optical axis direction variable section based on the optical axis direction control means for controlling the direction of the projecting optical axis and / or the receiving optical axis of the own apparatus, and observation means for searching for the opposing apparatus. Wherein the optical axis direction variable section includes the light projecting optical system and And / or by arranging the optical axis of the first light receiving optical system, the optical axis of the second light receiving optical system, and the optical axis of the optical system of the observation means in parallel to each other, It is characterized in that the direction can be changed while maintaining the parallelism.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 shows a configuration diagram of the first embodiment, which is a light projecting device including light projecting means, optical axis deviation detecting means, optical axis direction control means, and observation means. Behind the optical axis direction variable unit 20, a light projecting means, an optical axis shift detecting means, and an observing means are arranged in parallel, and an optical system of a projecting optical axis O3, a light receiving optical axis O4 on the optical axis shift detecting side and an observing means. Are arranged so as to be parallel to the optical axis O5, and all the optical axis directions can be changed simultaneously while maintaining the parallelism.

The light projecting means comprises, as light emitting elements, a signal generating section 21 including a linearly polarized laser diode and a light projecting optical system of a lens group 22 having a positive power. And a light receiving optical system of a lens group 24 having a positive power.
5. The output of the light-receiving beam spot position detection unit 23 is connected to the optical axis direction variable unit 20 via the signal processing unit 26 and the optical axis direction control unit 27.

The optical axis direction changing section 20 has a structure as shown in FIG.
A single mirror 5 that is controlled to rotate in the axial direction;
A mirror composed of two mirrors 28 and 29, each of which is controlled to rotate by one axis in a direction in which two rotation axes G and H are orthogonal to each other as shown in FIG. 2, or two transparent parallel plates as shown in FIG. 3
A liquid variable apex prism 3 in which a transparent liquid 32 is sealed between a bellows-like film 33 and an apex angle is variably controlled between 0 and 31.
4 are used.

When the liquid variable apex angle prism 34 shown in FIG. 3 is used, the reflected light of the own transmission light La returns from the transparent parallel plate 30 or 31, which may cause an optical axis direction control error. Therefore, as shown in FIG.
1 is arranged at an angle equal to or more than the maximum apex angle θ from a state perpendicular to the projection optical axis O3 so that the projection light is not perpendicular to the transparent parallel plates 30 and 31.

In order to align the optical axis of the transmitting device having such a configuration with the opposing device of the communication partner, first, the collimating telescope 25 is used.
, The background light Lh is captured, and the optical axis direction variable unit 20 is driven to search for the opposing device. Next, the optical axis is aligned with the strobe light Ls from the opposing device to check the light receiving level, and then the optical axis direction control operation is performed in the same manner as in the conventional example, so that the communication is possible.

The control of the optical axis direction control unit 27 acts on the drive unit of the optical axis direction variable unit 20 due to the fluctuation of the apparatus caused by the wind or the vibration of the installation place during the communication. It is set to the initial position just before the alignment. At this time, even if there is an initial position return error, the optical axes of all optical systems
Since the parallelism of O3, O4, and O5 is not lost, the optical axis alignment can be performed each time with the same accuracy as the first time without using a means for improving the initial position return accuracy.

As the observation means, not the collimating telescope 25,
When using a CCD camera with a zoom lens, search for the opposing device at the wide-angle zoom position, align the optical axis with the strobe light Ls or the received light Lb at the telephoto zoom position, and then adjust the optical axis direction. What is necessary is just to perform a control operation.
In addition, a non-split sensor such as a PSD (Position Sensitive Device) may be used instead of the 4-split sensor as the light-receiving element for position detection, and a light-emitting diode is used as the light-emitting element instead of a linearly polarized laser diode. You may. Further, a spatial optical communication apparatus for receiving is constructed by using a conventional signal receiving means including a conventional signal detecting light receiving element 9 and a lens group 8 having a positive power instead of the light projecting means. You can also.

FIG. 5 shows the configuration of the second embodiment, and FIG.
The present invention is a spatial optical communication device in which bidirectional communication is performed by adding a main signal receiving means for receiving the main signal. 1 denote the same members. Optical axis direction variable section 20
Behind the lens, the light projecting means, the optical axis deviation detecting means and the present signal detecting means are arranged in parallel, and on the light receiving optical axis O6 of the present signal detecting means, a lens group 36 having a positive power is provided. The light receiving optical system and the main signal detection unit 35 are arranged.
Further, the first and second 2
An optical path turning portion 38 composed of a plurality of mirrors 37a and 37b is arranged, and the collimating telescope 2 is set in the reflection direction of the first mirror 37a.
5 are arranged. The optical path turning section 38 includes a first mirror 37a disposed in front of the collimating telescope 25 at an inclination of 45 degrees with respect to the optical axis O5 of the observation optical system, and the optical axis direction changing section 30.
The second mirror 37b disposed on the side at an inclination of 45 degrees with respect to the optical axes O3, O4, O5 of the communication optical system.

If a plurality of optical systems are arranged in parallel as in this embodiment, it is inevitable that the optical axis direction variable section 20 becomes large. However, in consideration of the power consumption and the responsiveness of the optical axis direction control, it is necessary to reduce the size of the optical axis direction variable unit 20 to a necessary minimum. Therefore, the optical path turning section 38 is disposed between the observation optical system and the optical axis direction variable section 20 so as to extend toward the communication optical system. Further, as the optical path turning portion 38, a prism 39 having a parallelogram side surface in which two mirror portions are integrated as shown in FIG. 6 can be used.

When two such two-way optical communication devices are installed facing each other to perform optical axis alignment, the same operation as in the first embodiment is performed on each other to enable two-way communication. Optical axis alignment can be performed with the same accuracy as the first time.

FIG. 7 is a block diagram of the third embodiment. An optical axis direction variable section 40 is provided at a position facing a partner apparatus for transmitting and receiving a light beam. The optical axis direction variable mirror 41 is 4
It is inclined at 5 degrees. In the reflection direction of the optical axis direction variable mirror 41, a beam expander 42, which comprises a lens having a positive power and a lens having a negative power, expands the projected light and reduces the received light, A projecting / receiving light splitting member 43 that reflects one of them and transmits the other, a partial reflecting mirror 44, a lens group 45 having positive power, and a main signal detecting unit 46 are sequentially arranged.

In the incident direction of the projecting / receiving light branching member 43,
A lens group 47 having a positive power, a signal generating unit 48 using a laser diode as a light emitting element are arranged, and a lens group 49 having a positive power and a four-divided sensor 50 are arranged in the reflection direction of the partial reflection mirror 44. Are arranged. The output of the quadrant sensor 50 is output to the signal processing unit 5.
1. It is connected to the optical axis direction variable unit 40 via the optical axis direction control unit 52.

An optical path turning section 53 is provided near the outer periphery of the beam expander 42 between the beam expander 42 and the optical axis direction variable mirror 41, and an observation is made on the optical axis O8 in the reflection direction of the optical path turning section 53. The collimating telescope 55 of the optical system is arranged, and the mirror 55 inside the optical path turning section 53 is arranged at an inclination of 45 degrees with respect to the optical axis O8 of the observation optical system.

When a laser diode is used as the light emitting element of the signal generator 48, the emission illuminance may be increased by increasing the emission aperture of the transmission light, depending on the emission wavelength and emission output, from the viewpoint of safety for the human body such as eyes. Must be suppressed to a predetermined level or less, and at the time of long-distance communication, a larger amount of incident aperture of the received light is required because the amount of received light per unit area is reduced due to attenuation of the light amount in the transmission space. As described above, when the diameter of the incident and the outgoing light beams is increased, the size of the optical axis direction variable mirror 41 tends to increase. However, considering the power consumption and the control response in the optical axis direction, the optical axis direction variable mirror 41 has a minimum size. It must be kept to a minimum size.

Therefore, in the present embodiment, the light projecting / receiving light branching section 43 which reflects one of the projected light and the received light and transmits the other is used. The axis and the light receiving optical axis are made to coincide with each other, and the optical path turning portion 53 is arranged on the outer peripheral portion between the beam expander 42 and the optical axis direction variable mirror 41, so that the optical axis O7 of the communication optical system and the observation optical system The optical axis O8 is set to be parallel.

The optical path turning section 53 receives light on the optical axis deviation detecting side.
Without blocking Lc, the transmission light La is brought close to the center of the communication light beam so as not to block the effective light beam having a peak intensity ratio of 13.5% or more, for example, and guides the background light Lh to the observation optical system side. Like that.

Further, in this embodiment, the partial reflection mirror 44 is used as the received light branching means, the central light beam Lc of the received light is guided to the optical axis deviation detecting unit 50, and the received light peripheral light beam Lb is transmitted to the main signal detecting unit. It leads to 46. Further, the reflecting surface of the mirror 55 of the optical path turning portion 53 may be formed by depositing a metal film. However, if the reflecting surface is formed by depositing a dielectric thin film, the amount of blocking of the received light Lb can be reduced. be able to.

In the case where two such bidirectional optical communication devices are arranged to communicate with each other, light-emitting elements having different emission wavelength bands are used, and light transmission / reception in which spectral transmittance or spectral reflectance characteristics are reversed. It is preferable to separate the projected / received light by the light branching unit 43, and when linearly polarized laser diodes having the same emission wavelength band are used as light emitting elements, the polarization beam splitter 6 having the same spectral characteristics as the conventional example is used.
The optical system of FIG. 7 may be inclined at 45 degrees to the vertical direction at the rear of the page.

In the present embodiment, similarly to the first embodiment, the optical axis direction variable section 40 controls the optical axis O8 of the observation optical system.
Is arranged so as to be parallel to the optical axis O7 of the communication optical system, so that the size of the optical axis direction variable section 40 is minimized, and the optical axis alignment with the opposing device with which communication is performed is always the first time. It can be performed with similar accuracy.

[0036]

As described above, in the spatial optical communication apparatus according to the present invention, the optical axis direction variable section is arranged so that the optical axis of the observation optical system is parallel to the optical axis of the communication optical system. Thereby, even if an initial position return error of the optical axis direction variable unit occurs, the optical axis alignment at the time of the opposing installation with the communication partner device can always be performed with the same accuracy as the first time,
Communication with good reproducibility can be performed by performing reliable optical axis alignment.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a light projecting device of a first embodiment.

FIG. 2 is a perspective view of an optical axis direction variable mirror.

FIG. 3 is a side view of a liquid variable apex angle prism.

FIG. 4 is an explanatory diagram of an arrangement of a liquid variable apex angle prism.

FIG. 5 is a configuration diagram of a two-way communication device according to a second embodiment.

FIG. 6 is a side view of the optical axis direction variable prism.

FIG. 7 is a configuration diagram of a two-way communication device according to a third embodiment.

FIG. 8 is a configuration diagram of a conventional example.

FIG. 9 is a perspective view of an optical axis direction variable mirror.

FIG. 10 is a front view of a quadrant sensor.

FIG. 11 is a front view of a four-divided sensor.

[Explanation of symbols]

 20, 40 Optical axis direction variable section 21, 48 Signal generation section 23, 50 Received beam spot position detection section 25, 55 Collimated telescope 26, 51 Signal processing section 27, 52 Optical axis direction control section 35, 46 Main signal detection section 38, 53 Optical path turning section 41 Optical axis direction variable mirror 42 Beam expander 43 Projecting / receiving light branching section 44 Partial reflection mirror

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) G02B 26/08 H04B 10/10 H04B 10/105 H04B 10/22 G03B 5/00

Claims (6)

(57) [Claims] 1. A light projecting means comprising a light projecting optical system and a signal generating section and / or a light receiving means comprising a first light receiving optical system and a main signal detecting section; a second light receiving optical system and a light receiving beam spot position detection. And an optical axis of the received light and an optical axis of the second light-receiving optical system based on positional deviation information obtained from the reference position of the light-receiving beam spot on the light-receiving surface by receiving the light projected from the opposing device. Optical axis deviation detecting means for detecting the optical axis deviation of the optical axis deviation detecting means for transmitting an optical axis deviation correcting signal to the optical axis direction variable section based on the optical axis deviation information detected by the optical axis deviation detecting means; An optical axis direction control unit that controls a direction of an optical axis and / or a received optical axis; and an observation unit that searches for the opposing device. The optical axis of the first light receiving optical system, the optical axis of the second light receiving optical system, A spatial optical communication apparatus characterized in that by arranging the optical axes of the optical systems of the observation means in parallel with each other, it is possible to change the optical axis directions of all these optical systems while maintaining parallelism. 2. The optical axis direction changing section has two mirrors each having one rotation axis, and these two rotation axes are arranged at a predetermined interval, and the two rotation axes are orthogonal to each other. The spatial optical communication device according to claim 1, wherein the optical axis direction is controlled by rotating the mirror around each rotation axis. 3. The optical axis direction variable sections are orthogonal to each other.
The spatial optical communication device according to claim 1, wherein one mirror having one rotation axis is rotated around the two rotation axes by the optical axis direction control means to control the optical axis direction. 4. The spatial optical communication device according to claim 1, wherein the optical axis direction variable section controls an optical axis direction by changing an angle formed by two transparent members sealing a transparent liquid therebetween. 5. The spatial optical communication device according to claim 1, further comprising an optical path turning unit for guiding background light to the observation optical system between the observation optical system and the optical axis direction variable unit. 6. A light-projecting / receiving light branching means for reflecting one of light-emitting light and light-receiving light and transmitting the other light, and the light-projecting optical axis and the light-receiving optical axis coincide in the optical axis direction variable section. 6. The spatial optical communication according to claim 5, wherein the optical axes of the observation optical systems are arranged in parallel with the two optical axes so that the optical axis directions of all the optical systems can be changed simultaneously while maintaining the parallelism. apparatus.