JPH11205234A - Space light receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To align optical axes in a short time with loose accuracy in the range finding by retrieval of opposite devices in the case of installation of the receivers. SOLUTION: A deviation width from a transmission beam optical axis is set to be O-R1 in the case of an intensity P1 of a transmission beam that provides a light receiving amount of a limit of detection in optical axis deviation in a conventional embodiment. The receiver can detect the optical axis deviation up to a point R2 at which an intensity P2 of a transmission beam is about 10% of the intensity P1, and then the permissible deviation width is 0 to R2 so as to widen the width more than the conventional embodiment. Thus, the optical axes of the receivers are aligned with a looser accuracy than that of the conventional embodiment quickly by using the receivers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spatial light receiving apparatus provided with an optical axis shift correction function for controlling the direction of a light receiving optical axis of the apparatus with respect to a light receiving beam while receiving the light beam in the atmosphere. .

[0002]

2. Description of the Related Art Conventionally, there has been disclosed a spatial optical communication apparatus having an optical axis deviation correcting means for projecting and receiving light in the atmosphere.
This is disclosed in Japanese Patent No. 716, in which two similar communication devices are installed facing each other across a space to perform bidirectional communication.

FIG. 19 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 fixed on an optical axis adjusting table 1 provided on a gantry. The own apparatus and the other apparatus assembled so that the optical axis O1 of the communication optical system 2 and the optical axis O2 of the collimating telescope 3 as the observation optical system are arranged opposite to each other at a predetermined distance. .

[0004] The spatial optical communication apparatus includes a transmitting light La and a receiving light Lb.
The optical axis direction variable unit 4 is disposed 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 unit 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. Figure 20
As shown in the figure, an elliptical mirror portion E2 that reflects most of the incident light is provided at the center of the transparent parallel plate E1.

Further, in the reflection direction of the light receiving light branching element 7,
A lens group 10 having positive power, a four-divided sensor 11 are arranged, and a lens group 12 having positive power, and a laser beam which becomes linearly polarized in a direction perpendicular to the plane of the drawing are arranged in the incident direction of the polarizing beam splitter 6. A laser diode 13 is disposed as a light emitting element of a signal generating unit that emits light.
The output of the quadrant sensor 11 is connected to the signal processing unit 14,
The output of the signal processing unit 14 is connected to the optical axis direction variable unit 4 via the optical axis direction control unit 15.

As the polarization beam splitter 6, for example, an optical element is used in which a dielectric multilayer thin film that reflects most of S-polarized light and passes most of P-polarized light is deposited on the bonding surface. In order to perform the most efficient light projection and light reception using this polarization beam splitter 6, the transmission light La
It is sufficient that the received light Lb becomes P-polarized light when is S-polarized light. In order to perform the most efficient light-emitting and light-receiving operations by arranging the receiving devices having the same structure to face each other, The optical system 2 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 S is located at the center of the four-divided sensor 11, the transmission light La irradiates the partner device with a receivable intensity distribution and receives the light Lb from the partner device.
In order to ensure that the light receiving element 9 does not deviate from the effective light receiving area of the signal detecting light receiving element 9, the center of the signal detecting light receiving element 9 and the light receiving element of the four-divided sensor 11 should Laser diode 13 when viewed from
It is necessary to make adjustments so as to coincide with the light emission point of.

The light beam emitted from the laser diode 13 becomes almost parallel light by the lens group 12, is reflected on the boundary surface of the polarizing beam splitter 6, is further reflected by the optical axis direction variable mirror 5, and is transmitted as transmission light La by itself. The light is emitted from the other device (not shown). On the other hand, the light projected from the partner device enters the optical device in the optical axis direction variable unit 4 as the received light Lb, is reflected by the optical axis direction variable mirror 5, passes through the polarization beam splitter 6, and passes through the polarization beam splitter 6 to receive light. 7
A light beam of about 90% of the total received light amount passes through the light receiving light splitting element 7 and is condensed by the lens group 8 on the signal detecting light receiving element 9. Further, a light beam of about 10% of the remaining amount of received light is reflected by the received light branching element 7 and condensed by the lens group 10 on the four-divided sensor 11.

The positional deviation information of the light receiving beam spot S on the light receiving surface of the four-divided sensor 11 is sent to an optical axis direction control unit 15 as an optical axis deviation correction signal via a signal processing unit 14 to control the optical axis direction. 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 section rotates, and the optical axis direction variable mirror 5 is moved as shown in FIG.
As shown in FIG.

FIGS. 22 and 23 show the movement of the light receiving beam spot S on the light receiving surface of the four-divided sensor 11 at this time, and the rotation of the variable mirror 5 about the axis F causes the light receiving beam spot S to move. The light receiving surface moves up and down as shown by the arrow in FIG. 22, and the rotation around the variable mirror 5 axis G causes the light receiving beam spot S to move in the upper right 45 ° direction of the light receiving surface as shown by the arrow in FIG. Moving. As described above, the operation of moving the light receiving beam spot S in two different directions is repeated, and the center of the light receiving beam spot S is located at the position where the cross-shaped separator T at the center of the light receiving section effective area U of the four-divided sensor 11 intersects. Control to reach.

By performing such optical axis misalignment correction control in two-way optical communication devices facing each other across a space, the central portion of the spread of both transmission beams is located at the beam inlet of the facing device. It can always be maintained in the same state. In this conventional spatial optical communication apparatus, when the optical axis alignment is performed by installing the apparatuses opposing each other, the collimating telescope 3 is looked into, and the laser light Lb from the opposing apparatus or the strobe light Ls for position confirmation from the opposing apparatus is used. Using the attitude adjustment mechanism of the optical axis adjustment table 1 in which the communication optical system 2 and the collimating telescope 3 are integrated, so that is located at the center of the crossing cross line in the collimating telescope 3, The tilt adjustment is performed in two perpendicular directions.

[0012]

(1) However, in the above-described conventional two-way spatial optical communication system, when the optical axes are aligned when the devices are opposed to each other, 10% of the total amount of light received by the devices is incident. Only available, and the beam that can be used for optical axis alignment and the communication beam have the same beam diameter,
If the search for the opposing device by the collimating telescope 3 or the like is not performed sufficiently carefully, accurate positioning cannot be performed.

(2) Further, since the distribution of the amount of received light branched to the two light receiving elements is constant, there is a problem that it is not possible to set the distribution of the amount of received light efficiently according to a change in environmental conditions.

An object of the present invention is to solve the above-mentioned problem (1) and to provide a spatial light receiving device capable of performing optical axis alignment in a short time with a low accuracy in aiming work by searching for an opposing device when installing the device. Is to do.

Another object of the present invention is to solve the above-mentioned problem (2) and to set an efficient distribution of the amount of branched received light to the two received light detectors according to a change in environment during communication. An object of the present invention is to provide a spatial light receiving device capable of communicating accurately under various environmental conditions.

[0016]

According to the present invention, there is provided a spatial light receiving apparatus comprising: a first light receiving optical system and a main signal detecting unit; and a second light receiving optical system. Optical axis deviation detecting means comprising a system and a light receiving beam spot position detecting part; receiving light branching means for branching received light to the first and second light receiving optical systems; Spatial light having an optical axis direction changing means for changing a shared light receiving optical axis direction, and an optical axis direction control means for sending a control signal to the optical axis direction changing means based on an optical axis deviation signal from the optical axis deviation detecting means. In the receiving device, the optical axis deviation detecting means receives the light projected from the opposing device, and detects the optical axis of the received light and the second position based on the positional deviation information of the light receiving beam spot on the light receiving surface from the reference position. Form an optical axis deviation signal of the optical axis of the light receiving optical system A signal processing unit, the received optical branching means comprising the branched light amount changing unit for changing the branch received light amount that leads to the first and second light receiving optical system.

[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, in which a branched light reception amount variable unit 21 is provided obliquely with respect to incident light, behind an optical axis direction variable unit 20 for deflecting the optical axis direction of the receiving optical system. Are located. Dividing light amount variable section 2
As shown in FIG. 2, the first receiving light branch surface 21a has a region H1 that transmits most of the incident light and a region H2 that transmits approximately 10% of the incident light and reflects approximately 90% of the incident light. The method of switching the amount of received light is performed by parallelly moving the variable amount 21 of branched received light along the receiving light branch surface 21a and inserting the region H1 or the region H2 into the optical path.

In the transmission direction of the variable branched light receiving amount unit 21, an optical axis shift detecting unit including a lens group 22 having a positive power and a four-divided light receiving element 23 is arranged. In the direction, a lens group 24 having positive power and a light-receiving element 25 for signal detection are arranged. The output of the quadrant light receiving element 23 is output to the signal processing unit 26,
The optical axis direction control unit 27 and the optical axis direction variable unit 20 are sequentially connected.

In the receiving apparatus having the above-described configuration, the transmission beam L from the transmitting apparatus on the opposite side, which is disposed at a predetermined distance from the transmitting apparatus on the opposite side, is used.
When the transmission beam L is received, the transmission beam L is
0, after the region H1 of the reception light branch surface 21a is inserted into the optical path in the branch light reception amount variable unit 21,
Most of the incident light passes through the lens group 22 and is divided into four light receiving elements 2
Focus on 3. On the other hand, when the region H2 of the receiving light splitting surface 21a is inserted in the optical path, about 10% of the incident light is condensed on the four-divided light receiving element 23, and about 90% of the signal is detected via the lens group 24. To the light receiving element 25 for use.

FIG. 3 shows an intensity distribution curve C1 of the transmission beam L in the vertical section when the optical axis of the transmission beam L from the transmission device intersects with the vertical section including the receiving point as a reference point O. ing. The two shaded areas D1 correspond to the incident light taken into the light-receiving element 25 for signal detection in terms of the amount of received light.
An area D2 sandwiched between the two hatched portions D1 corresponds to the incident light taken into the four-divided light receiving element 23 in terms of the amount of received light.

Conventionally, when the optical axis is aligned at the time of the opposing installation, the optical axis deviation of the transmission beam L has a width O to R1 at the receiving point.
After the optical axis is adjusted by the collimating telescope so as to be within the range, the optical axis direction control operation is started.

However, in the optical axis alignment at the time of opposing installation by the apparatus of the present embodiment, the first variable
Is set in the optical path, all the incident light captured in the area D3 can be received by the four-divided light receiving element 23. Then, the positional deviation information of the light receiving beam spot is converted into an optical axis deviation correcting signal by the signal processing unit 26 and sent to the optical axis direction control unit 27, and the optical axis direction variable unit 20 controls the light receiving optical axis. .

In the case of the intensity P1 of the transmission beam L which is the light receiving amount at the detection limit of the optical axis deviation in the conventional example, if the deviation width from the optical axis of the transmission beam is O to R1, in this embodiment, about 10% of the intensity P1 Since the optical axis deviation can be detected up to the point R2 at which the intensity P2 of the transmission beam L is obtained, the allowable deviation width becomes O to R2, which can be made wider than the conventional example. Therefore, by using the receiving apparatus of the present embodiment, the optical axis of the receiving apparatus can be more quickly adjusted with less accuracy than the conventional example. On the other hand, with respect to the optical axis alignment of the opposing transmitting apparatus, the optical axis alignment with the receiving apparatus of the present embodiment is performed by a collimating telescope having highly accurate optical axis alignment as in the conventional example.

In this way, after the optical axis alignment of both the transmitting and receiving devices is completed, the branched light receiving amount varying unit 2 of the receiving device
In 1, communication is enabled by setting the second area H2 in FIG. 2 to be in the optical path.

Light-receiving element 2 for signal detection in a receiver
Since the effective light receiving area 5 is generally small, the optical axis direction correction method as in the present embodiment is used so that the light receiving spot S does not deviate from the effective light receiving area even when the apparatus is vibrated. On the other hand, for the opposing transmitting device, the divergence angle of the projection beam is set so that the transmission beam L does not deviate from the receiving device even if the device vibrates.

FIG. 4 shows a branch light receiving amount variable section 2 according to the first embodiment.
FIG. 6 is a front view of a modification of the first embodiment, in which a region H1 that transmits most of incident light and about 10% of incident light are used instead of a rectangular parallel plane member;
A fan-shaped parallel plate member having an area H2 that transmits about 90% and reflects about 90% is used. The fan-shaped pivot I is rotated in the direction of the arrow around the axis of rotation, and one of the two regions H1 and H2 is inserted into the optical path.

FIG. 5 shows another modification, in which the second area H2 of the variable section 21 shown in FIG. 2 is divided into a central light beam area H3 that transmits about 10% of the incident light flux and an incident light flux H2. The region H4 reflects about 90%.

In the above embodiment, the receiving light branch surface 2
When switching between the first area H1 and the second area H2 in FIG. 1a, the transmitted light of the branched light receiving amount variable section 21 is divided into four parts in consideration of the setting error of the angle of the receiving light branch surface 21a with respect to the light receiving optical axis. The branched light reception amount varying unit 21 is arranged so that the light is guided on the light receiving surface of the light receiving element 23 within a small displacement range. Therefore, when the switching is performed with high accuracy without an angle setting error caused by the switching between the first and second regions H1 and H2, the optical axis shift detecting unit after the lens group 22 and the lens group 24 and after in FIG. The light receiving amount branching surface 2 having a configuration in which the present signal detecting unit is replaced, and in which the transmittance and the reflectance of each of the regions H1 and H2 are reversed.
The same effect as that of the first embodiment can be obtained by using the branch light reception amount varying unit 21 having 1a.

FIG. 6 shows another modified example of the branching light receiving amount variable section 21. The second area of the receiving light branching surface 21a shown in FIG.
A hollow parallel flat plate H6 having a hollow portion H5 as an area H3 of the H2 is used as a branching light receiving amount variable portion 21 and is translated or rotated within the light receiving amount branching surface 21a, so that the hollow parallel flat plate 2 is formed.
1b may enter and exit the optical path.

Further, as shown in FIG.
a, the hollow parallel flat plate 21b enters and exits the optical path by rotating about a rotation axis Z outside the incident light beam, and the branched light reception amount variable unit 21 having the light reception amount branch surface 21a in FIG. The same effect can be obtained.

FIG. 8 is a front view of a receiving light splitting surface according to a second embodiment, in which a receiving light variable portion 21 having a light receiving splitting surface 21a including four regions M1 to M4 is disposed in a receiving apparatus. Each area M1 to M4 can enter and exit. The first area M1 passes most of the incident light, as does the area H1 in FIG.
The second to fourth regions M2 to M4 have central portions N1 to N3 that almost pass the incident light beam, and the other oblique line segments almost reflect the light beam. The passing area N2 of the third area M3 is the second area M2
Is smaller than the passing area N1, and the passing area N3 of the fourth area M4 is even smaller. In this area M4, most of the incident light is reflected.

The switching between the first area M1 and the third area M3 is used at the time of optical axis alignment when the apparatus is installed facing the same as in the first embodiment. The second to fourth regions M2 to M4 rotate around the center K of the disc-shaped light receiving / branching surface as a rotation axis in accordance with an environmental change during communication, and select and set any one of the regions M2 to M4. Has been.

For example, FIG. 9 shows that the optical axis of the transmission beam L from the transmitting device intersects the vertical section including the receiving point when the transparency of the transmission space between the opposing devices at the time of communication is improved as compared to when the communication starts. The intensity distribution of the transmission beam L in the vertical section when the point is set as the reference point O is shown. The transmission beam L at the start of communication shows an intensity distribution as shown by a curve C2, and the receiving device when the third region M3 in FIG. The hatched area D3 indicates the area where the light is incident on the light-receiving element 26 for signal detection of the present invention, and the dotted area D4 sandwiched between the two shaded areas D3 indicates the area where the light is incident on the four-divided light-receiving element 24. I have.

Assuming that the transparency of the transmission space has been improved after a predetermined time has elapsed and the intensity distribution of the transmission beam L has become as shown by the curve C3, the second area M2 is located on the optical path in the branching light receiving amount variable section 21 of the receiving apparatus. , The incident light amount to the four-divided light receiving element 24 is increased to increase the amount as indicated by the dotted line D5, and the incident light amount to the present signal detecting light receiving element 26 is reduced to reduce the shaded part. Set to be D6. And
At this time, by reducing the level of the optical axis direction control signal transmitted from the transmitting device, a higher quality main signal can be obtained.

In order to more effectively exert the function of the present embodiment, a light receiving intensity detecting circuit for detecting the intensity of the received light received by the four-division light receiving element 24 is provided. The above-described operation may be performed after confirming the alarm lamp that is turned on when the operation is continued for a predetermined time or more.

Next, FIG. 10 shows, for example, the case where the transparency of the transmission space between the opposing devices at the time of communication is lower than that at the time of communication, and the shaking of both opposing devices is small. FIG. 4 shows a graph of an intensity distribution. Similarly to FIG. 9, the curve C2 is the intensity distribution curve of the transmission beam L at the start of communication, the two hatched parts D5 are the area where the incident light enters the signal detection light-receiving element 26, and the dotted line between the hatched parts D5. The portion D6 is a region where the incident light enters the four-divided light receiving element 24.

Assuming that after a predetermined time has elapsed from the start of communication, the transparency of the transmission space has decreased and the intensity distribution of the transmission beam L has become as shown by a curve C4. If the vibration of the receiving device is small, the optical axis of the receiving device When the direction control is controlled so as to be maintained in the final state, and the fourth area M4 is switched so that the fourth area M4 enters the optical path by the branch light receiving amount variable section 21, the area where the incident light is introduced into the light detecting element 26 for signal detection is hatched. As shown in the section D7, it is possible to compensate for a decrease in the amount of light received by the signal detection light-receiving element 26. At this time, the signal level for controlling the optical axis direction on the transmitting side is instructed to be reduced by using the remote communication means, thereby suppressing an adverse effect on the signal due to signal multiplexing, thereby improving the S / N of the signal. be able to.

In order to more effectively exert the function of the present embodiment, the receiving apparatus is provided with a light receiving intensity detecting circuit for detecting the received light intensity of the four-divided light receiving element 24 and vibration detecting means such as a vibration sensor. After confirming the alarm lamp that is lit when the light receiving state of light intensity below a certain level continues for a certain period of time or when the vibration state below a certain level continues for a certain period of time, both states are checked using the remote communication means. It is good to contact and perform the same operation as above.

FIGS. 11 and 12 show the configuration of the third embodiment, in which a receiving light branch surface is provided behind the optical axis direction variable unit 20 instead of the branch light receiving amount variable unit 21 of the first embodiment. A liquid crystal layer 30 is disposed obliquely in the optical path at the position 21a, and a glass block 31 is disposed on the incident light side and the reflected light side, which is a plane substantially perpendicular to the light rays, and utilizes the optical anisotropy of the liquid crystal. The optical path is switched over. Other configurations are shown in FIG.
The same reference numerals denote the same members.

As shown in FIG. 13, the glass block 31 has a liquid crystal layer 30 having an elliptical hollow hole 30a interposed therebetween. Transparent electrodes 32 are formed on the front and back of the liquid crystal layer 30 by vapor deposition or the like. A lead wire is welded to the lead wire contact portion 33a of the transparent electrode 32, and the power supply 33 and the branch light receiving amount switch 34 are connected by the lead wire.

As shown in FIG. 11, the received light transmission beam L
Is a P-polarized light Lp having a plane of polarization within a plane parallel to the plane of the drawing, when the switch 34 is turned on, almost all of the incident light is transmitted to the four-divided light receiving element 23. Next, as shown in FIG. 12, when the switch 34 is turned off, most of the light incident on the liquid crystal layer 30 is reflected, and only the light flux at the center reaches the four-division light receiving element 23. The reflected light from is guided to the signal detection light receiving element 25. In this way, by turning on / off the branch light receiving amount switch 34, the same effect as in the first embodiment having the light receiving amount branch surface 21a shown in FIG. 5 can be obtained.

Further, as shown in FIG.
1a is formed of a transparent electrode 32a of a central elliptical portion and a transparent electrode 32b of the other peripheral portion, and is provided with a lead wire contact portion 33a connected to the first switch and a lead wire contact portion 33b connected to the second switch. Is provided, and by changing the on / off combination of the first switch and the second switch, the light receiving branch surface 21 shown in FIG.
The same effect as in the second embodiment having a can be obtained. A correspondence table of the switching area of the light receiving branch surface 21a which is equivalent to the second embodiment by the combination of the ON and OFF of the two switches is shown below.

First switch Second switch Switching area ON ON First area M1 OFF ON Second area M2 ON OFF Third area M3 OFF OFF Fourth area M4

In the second and third embodiments, the optimum amount of branched light received by the two receiving light receiving elements 24 and 26 can be set in accordance with a change in the environment during communication. It is possible to perform higher quality communication under an environmental condition.

FIGS. 15 and 16 show the configuration of the fourth embodiment, in which the incident light of the P-polarized light Lp having a polarization plane in a plane parallel to the plane of the paper is almost transmitted, and the polarization direction of the P-polarized light Lp is changed. A polarization beam splitter 40 having a polarization splitting surface 40a that almost reflects the incident light of the orthogonal S-polarized light Ls, and a half-wave plate 41 for changing the polarization direction of the incident light are arranged on the reception light incident side. I have.

As in the case of the second region H2 of the light receiving / branching surface 21a shown in FIG. 5, the center of the polarization splitting surface 40a is a hollow portion that transmits all polarized light components. When the 波長 wavelength plate 41 rotates the optical axis Y clockwise by an angle θ as shown in FIG. 17, the deflection direction Z of the incident light is shifted rightward by an angle 2θ from the vertical direction immediately after exiting the 波長 wavelength plate 41. It has the property of rotating.

In FIG. 15, the angle θ of the half-wave plate 41 is 0 degree or 90 degrees, and almost all the incident light of the P-polarized light Lp passes through the polarizing beam splitter 40 and enters the four-divided light receiving element 23. Received. On the other hand, in FIG.
The angle θ of the two-wavelength plate 41 becomes 45 degrees, the transmitted light becomes S-polarized light Ls, and the polarization splitting surface 4 of the polarization beam splitter 40 becomes
Only the light that has passed through the hollow portion 0a reaches the quadrant light receiving element 23, and the other light flux is reflected by the polarization separation surface 40a and received by the main signal light receiving element 25.

FIG. 18 shows the rotation angle θ of the optical axis Y of the half-wave plate 41 and the amount of light received by the two receiving light receiving elements 24 and 26. The amount of light received by the four-divided light receiving element 23 of the optical axis deviation detecting unit is represented by a curve C5, and the amount of light received by the light receiving element 25 of the present signal detecting unit is represented by a curve C6. Accordingly, the first, second, and second embodiments of the first embodiment having the light reception amount branch surface 21a shown in FIG. The same effect as in the case where the third regions M1, M2, and M3 are used can be obtained.

It should be noted that a Faraday rotator can be used instead of the half-wave plate as the polarization direction rotating means.
Further, when the received light is not linearly polarized light but circularly polarized light, 1 /
By arranging a quarter-wave plate on the receiving light incident side of the two-wave plate 41 and converting circularly polarized light into linearly polarized light, the same effect as in the present embodiment can be obtained.

[0050]

As described above, in the spatial light receiving apparatus according to the present invention, the amount of branched light received to be guided to the signal detecting means and the optical axis deviation detecting means is changed, so that the spatial light receiving apparatus can be installed at the time of installation. In the optical axis alignment, since the parallelism between the optical axis of the communication optical system and the aiming optical axis for searching for the opposing device can be loosened from the required accuracy, the optical axis alignment can be performed in a shorter time, and the entire device can be aligned. Manufacturing costs can be reduced.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a front view of a receiving light branch surface.

FIG. 3 is a graph showing a light receiving state.

FIG. 4 is a front view of another reception light branch surface.

FIG. 5 is a front view of still another receiving light branching surface.

FIG. 6 is a perspective view of a branch light reception amount variable unit according to a modification.

FIG. 7 is a perspective view of a branch light reception amount variable unit according to another modification.

FIG. 8 is a front view of a receiving light branch surface of the second embodiment.

FIG. 9 is a graph showing a light receiving state.

FIG. 10 is a graph showing a light receiving state.

FIG. 11 is a configuration diagram of a third embodiment.

FIG. 12 is a configuration diagram when a changeover switch is off.

FIG. 13 is a perspective view of a receiving light branch surface.

FIG. 14 is a perspective view of another reception light branch surface.

FIG. 15 is a configuration diagram of a fourth embodiment.

FIG. 16 is a configuration diagram when a half-wave plate rotates.

FIG. 17 is an explanatory diagram of properties of a half-wave plate.

FIG. 18 is a graph showing a change in the amount of branched received light.

FIG. 19 is a configuration diagram of a conventional example.

FIG. 20 is a front view of a receiving light branch surface.

FIG. 21 is a perspective view of an optical axis direction variable mirror.

FIG. 22 is a front view of a quadrant sensor.

FIG. 23 is a front view of the quadrant sensor.

[Explanation of symbols]

 REFERENCE SIGNS LIST 20 optical axis direction variable section 21 branched light receiving amount variable section 21 a receiving light branch surface 21 b hollow parallel plate 23 quadrant light receiving element 25 light receiving element for signal detection 26 signal processing section 27 optical axis direction control section 30 liquid crystal layer 31 glass block 32 Transparent electrode 34 Branch light receiving amount selection switch 40 Polarization beam splitter 40a Polarization separation surface 41 1/2 wavelength plate

Claims (10)

[Claims] A first signal detecting means comprising a first light receiving optical system and a main signal detecting unit; an optical axis deviation detecting means comprising a second light receiving optical system and a light receiving beam spot position detecting unit; Receiving light splitting means for splitting received light into a second light receiving optical system, optical axis direction changing means for changing a shared light receiving optical axis direction of the first and second light receiving optical systems, and optical axis shift detecting means An optical axis direction control means for transmitting a control signal to the optical axis direction variable means based on an optical axis deviation signal from the optical axis deviation detecting means, wherein the optical axis deviation detecting means receives light projected from the opposing device. A signal processing unit that forms an optical axis shift signal of an optical axis of the received light and an optical axis of the second light receiving optical system based on positional shift information from a reference position of the light receiving beam spot on the light receiving surface; Receiving light branching means, the first and second light receiving optical systems; A spatial light receiving device provided with a branch light receiving amount variable section for changing a branch light receiving amount leading to the light. 2. The optical system according to claim 1, wherein when the optical axis is aligned at the time of installation of the apparatus, the amount of light received by the second light receiving optical system is larger than that of the first light receiving optical system. 2. The spatial light receiving device according to claim 1, wherein the amount of light received by the first light receiving optical system is set to be larger than that of the second light receiving optical system. 3. 3. The spatial light receiving device according to claim 1, wherein the branch light receiving amount variable section changes a branch light receiving amount to the light receiving optical system when the light receiving amount changes during communication. 4. The spatial light receiving device according to claim 3, further comprising: a received light intensity detecting means for detecting a received light intensity; and a vibration detecting means for detecting a vibration state of the device. 5. The spatial light receiving device according to claim 1, wherein the branch light receiving amount variable section changes a transmittance and a reflectance on a receiving light branch surface to the first and second light receiving optical systems. apparatus. 6. The spatial light receiving device according to claim 1, wherein the branch light receiving amount variable section changes a transmission area and a reflection area on a receiving light branch surface to the first and second light receiving optical systems. apparatus. 7. The branch light receiving amount variable section includes a plurality of regions having different light receiving amount distributions to the first and second light receiving optical systems, and region switching means for switching each of these regions.
7. The spatial light receiving apparatus according to claim 5, wherein the amount of light received by the first and second light receiving optical systems is changed. 8. The spatial light receiving device according to claim 7, wherein the area switching means switches the respective areas by parallel or rotational movement of the light receiving amount branch surface within the plane. 9. The branch light receiving amount variable section changes the amount of light received by the first and second light receiving optical systems by moving the receiving light branch surface in and out of the optical path. 6. The spatial light receiving device according to 5. 10. The spatial light receiving device according to claim 6, wherein the reception light branch surface is formed of a liquid crystal layer, and the transmission area and the reflection area are changed by switching a voltage applied to the liquid crystal layer.