JPH09181340A - Correcting device for optical axis shift - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce an correction error of optical axis shift which is generated by an uneven intensity distribution, even if there is an uneven intensity distribution in a light-receiving beam, and moreover, make it possible to conduct a stable space optical communication even if fluctuations in the extent of microns are generated in the atmosphere. SOLUTION: When the optical axis shift of the light-receiving optical axis of its own device from a light-receiving beam LB is detected on the basis of information on the positional shift of the beam LB from a reference position, and an optical axis shift correcting signal is sent to a variable part 20 in the optical axis direction on the basis of information on the optical axis shift to control the direction of the light- receiving optical axis of the own device, a plurality of diffracted lights are generated from the one beam LB by a diffraction grating of a hologram 21 provided in a light- receiving optical system and a plurality of diffracted light spots are formed on the light-receiving surface of a light-receiving beam spot position detection light-receiving element 22. Even in the case where an intensity distribution on an entrance pupil, which is the beam take-in port of the own device, is uneven, a correction of the optical axis shift is made by contriving so as to bring the center of the light intensity of a light-receiving beam spot closer to the center of a luminous flux.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical axis deviation compensating device for controlling a direction of a light receiving optical axis of its own device with respect to a light receiving beam while receiving a light beam in the atmosphere.

[0002]

2. Description of the Related Art Conventionally, a spatial optical transmission device as shown in FIG. 32, for example, is disclosed in Japanese Unexamined Patent Publication No. 5-133716 as a device for projecting and receiving light in the atmosphere provided with an optical axis deviation correcting means. Therefore, two similar devices are installed facing each other across a space to perform bidirectional communication.

That is, the laser light emitted from the laser diode 1 and linearly polarized in the direction perpendicular to the paper surface is made into a substantially parallel light flux by the lens group 2 having a positive power, reflected by the boundary surface of the polarization beam splitter 3, and further. It is reflected by the variable mirror 4a of the movable portion 4 in the optical axis direction, and is emitted as the transmitted light LA from the device A to the device B (not shown).

The received light LB from the device B enters the device A,
It is reflected by the variable mirror 4a, passes through the polarization beam splitter 3, and reaches the light receiving / branching element 5. At this time, the received light
About 90% of LB is transmitted through the light-receiving / branching element 5 and is focused on the signal-receiving light-receiving element 7 by the lens group 6 having a positive power, and the remaining about 10% is reflected by the light-receiving / branching element 5. ,
The position detection light receiving element 9 receives the light by the lens group 8 having a positive power.

As the polarization beam splitter 3, an optical element in which a multi-layered thin film is vapor-deposited on its bonding surface is used, and this multi-layered thin film reflects about 99% of S-polarized light and P
It is designed to transmit polarized light. In order to perform the most efficient projection / reception using this polarization beam splitter 3, it is only necessary to establish a relationship such that the reception light LB becomes P polarization when the transmission light LA is S polarization. In order to face the transmitter and receiver of the
The transmission / reception common optical axis O1 is arranged so as to be inclined rearward in the plane of the drawing and to have an inclination of 45 degrees in the vertical direction.

Further, in order to perform large capacity communication capable of wide band and high speed response, a small element having an effective light receiving area of 1 mm or less such as an avalanche photodiode is used as the light receiving element 7 for detecting the present signal. There is. Furthermore, when the center of the light receiving beam spot SP is located at the center of the position detecting light receiving element 9, the transmitted light LA can irradiate the partner device B with an intensity distribution that can be received, and the received light from the partner can be received. Since it is necessary to prevent the LB from falling out of the effective light receiving area of the main signal detecting light receiving element 7, the main signal detecting light receiving element 7 and the position detecting light receiving element 9 are
The positional deviation is adjusted with an accuracy of μm with respect to the optical axis of the transmitted light.

The positional deviation information of the light receiving beam spot SP on the light receiving surface of the position detecting light receiving element 9 is sent to the optical axis direction control section 11 as an optical axis deviation correction signal via the signal processing section 10, and the optical axis is controlled. The direction control unit 11 sends a mirror drive signal to the drive unit of the optical axis direction changing unit 4. Based on this signal, the motor of the drive unit rotates, and the variable mirror 4a rotates about the axis A1 and the axis A2 as shown in FIG.

At this time, the light receiving beam spot SP on the light receiving surface of the position detecting light receiving element 9 is moved in the vertical direction of the light receiving surface of FIG. 34 by the rotation of the variable mirror 4a around the axis A1 as shown by an arrow a2. Then, by the rotation of the variable mirror 4a around the axis A2, the variable mirror 4a is moved in the upper right 45 ° direction or the upper left 45 ° direction on the light receiving surface of FIG. 35 as shown by the arrow a2. in this way,
By repeating the operation of moving the light receiving beam spot SP in two different directions, control is performed so that the center of the light receiving beam spot SP is located at the center of the light receiving surface of the position detecting light receiving element 9.

The above control is continuously performed during communication so that the two-way optical communication device facing each other across the space receives the light beam from the other device B at the center of the position detecting light receiving element 9. By mutually performing the optical axis deviation correction, it is possible to adjust so that the central part of the intensity distribution of both transmission beams always coincides with the beam inlet of the partner device B.

As the position detecting light receiving element 9, FIG.
Although a four-division sensor divided into four elements 12 as shown in FIG. 35 is generally used, when such a light receiving element 9 is used for position detection, separation between the respective division elements 12 is performed. In order to prevent the light receiving beam spot SP from falling into the insensitive area of the band 13 and losing its output, or to prevent the output from changing rapidly when it crosses the separation band 13, the light receiving beam spot SP should have an appropriate area. Is desirable.
For this reason, generally, the light receiving surface position of the four-divided sensor is set at a position defocused from the condensing point.

[0011]

However, in the above-mentioned conventional spatial light transmission apparatus for transmitting and receiving light in the atmosphere, the phenomenon that the transmission beam fluctuates due to the vibration of the installation location of the apparatus or the fluctuation of the atmosphere is affected. receive. The atmospheric fluctuations are roughly classified into two types: macroscopic fluctuations that cause fluctuations in the entire transmission beam, and micro fluctuations that cause differences in the intensity distribution within the transmission beam. The fluctuation is dealt with by providing an optical axis deviation correction function in which the transmission beam diameter at the transmission point is widened to some extent.

On the other hand, FIG. 36 shows a modeled explanatory view of microscopic fluctuations of the atmosphere. In the transmission path between two devices for communication, the atmospheres having different pressures and temperatures are mixed, so that the refraction The rate has a non-uniform distribution that varies with time. As a result, a strong intensity portion W1 and a weak intensity portion W2 are generated in the divergence W of the transmission beam, and the intensity of the light beam at a certain point in space changes with time, resulting in a weak intensity portion. W2 is observed to oscillate randomly in the divergence W of the transmission beam, which is called atmospheric microfluctuation.

In the conventional bidirectional spatial light transmission device having the optical axis deviation correction function, the light receiving surface of the position detecting light receiving element 9 is set at a position defocused from the converging point. In the state where there are micro fluctuations in the atmosphere, the received light beam spot SP on the light receiving surface does not have a uniform intensity distribution, but the light intensity distribution at the beam intake port M of the device corresponding to the entrance pupil as shown in FIG. Will be projected as is.

Therefore, as shown in FIG. 38, in the light receiving beam spot PS having the diameter T, a weakly shaded portion P1 and another strong portion P2 are generated, and a light intensity center different from the light beam center BC is generated. The PC is determined to be the optical axis, and this positional shift amount S
A deviation in the direction of the optical axis occurs by an angle corresponding to the above, and as a result, there is a problem that the other party's device B causes a deviation of the light beam and communication is disabled.

An object of the present invention is to solve the above problems,
Even if the received light beam has a non-uniform intensity distribution, an optical axis shift correction device that reduces the optical axis shift correction error caused by this and can perform stable communication even if microscopic fluctuations of the atmosphere occur. To provide.

[0016]

An optical axis deviation correcting device according to the present invention for achieving the above object is a light receiving optical system, a light receiving beam spot position detecting section, and position deviation information from a light receiving beam spot reference position. Based on the optical axis deviation information detected by the optical axis deviation detecting means, the optical axis direction varying means and the optical axis deviation detecting means for detecting the optical axis deviation of the light receiving optical axis of the own device with respect to the received light. An optical axis deviation correction device having an optical axis direction control means for transmitting an optical axis deviation correction signal to the optical axis direction varying means to control the direction of the light receiving optical axis of the device itself, wherein a diffraction element is provided in the light receiving optical system. A plurality of diffracted light beams are provided to generate a plurality of diffracted light beams to form a plurality of diffracted light spots on the light receiving surface of the received light beam spot position detection unit.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail based on embodiments with reference to FIGS. FIG. 1 is a block diagram of a spatial light receiving device having an optical axis shift correction function of the first embodiment, in which an optical axis direction changing unit 20 for deflecting the optical axis direction of the received light LB is used.
Behind is a hologram 21 using a photographic plate having a high-resolution photosensitive material fixed on the surface of transparent glass, and a light receiving beam spot position detecting section including a position detecting light receiving element 22 and a signal processing section 23 is further provided. The output of the position detection light receiving element 22 is connected to the optical axis direction changing unit 20 via the signal processing unit 23 and the optical axis direction control unit 24.

As the optical axis direction variable section 20, a single mirror as shown in FIG. 33, which is controlled by two-axis rotation, or an optical axis direction variable section 20, which has respective rotary axes B1 and B2 as shown in FIG. One of the mirrors 25a and 25b is controlled by one axis rotation, or two transparent glasses 26a and 26b having respective rotation axes C1 and C2 as shown in FIG. It is possible to use, for example, a variable apex angle prism with a variable apex angle control which is hermetically sealed.

In the optical axis shift correcting device, the received light LB including the pilot signal for controlling the optical axis direction emitted from the partner device is received on the light receiving surface of the position detecting light receiving element 22, and the light at this time is received. The positional deviation information from the reference position of the beam is sent to the signal processing section 23, converted into an optical axis deviation signal and sent to the optical axis direction control section 24. Based on this optical axis shift signal, the optical axis direction control unit 24 operates the optical axis direction changing unit 20 to perform control to match the received light optical axis of the own device with the received light LB.

Next, as shown in FIG. 4, the photographic plate of the hologram 21 of the light receiving optical system is irradiated with the parallel light having the same wavelength as the received light LB as the reference light LR from diagonally below. at the same time,
The point object light LM generated by branching from the same light source as the reference light LR is emitted from the front of the photographic plate, and the point object light LM shifts adjacent moving sections by an equal distance d in a plane parallel to the photographic plate. Multiple exposure.

The received light is reflected on the hologram surface 21a from the direction opposite to the reference light LR direction of the hologram 21 thus created.
When the hologram 21 is arranged so that the LB is incident on it, as shown in FIG.
Although the 0th-order light LO is transmitted as it is, the position of the point object light LM at the time of manufacturing the hologram 21 is changed to the diffracted light paraxial image plane G1.
Diffracted light LD is generated.

When the light receiving surface G2 of the position detecting light receiving element 22 is placed at a position defocused from the paraxial image plane G1 of the diffracted light by a distance x, the light receiving effective portion 22 is divided into four as shown in FIG.
On the position-detecting light receiving element 22 composed of a and the separation band 22b between them, diffracted light spots DS of diameter δ are arranged so as to overlap each other at the spot center interval d, and the maximum spread of all diffracted light spots DS is obtained. A light receiving beam spot having a spot diameter of the interval T is formed at the position of the light receiving surface G2. Here, assuming that the distance from the hologram surface 21a to the paraxial image plane G1 of the diffracted light is L and the effective diameter of the incident light ray on the hologram surface 21a is D, the following equation is established. δ / x = D / L (1)

Next, as shown in FIG. 7, the received beam spot position detection error caused by the microfluctuation of the atmosphere is strong in the central one horizontal row diffracted light spot DS and the weak portion P1 only in the horizontal direction. If there is a difference in the part P2, the position detection error is the light intensity center PC of the total diffracted light spot DS.
Can be considered as the difference S between the light beam center BC.

FIG. 7 shows a diffracted light spot DS at a position defocused by a distance x from the paraxial image plane G1 of diffracted light.
Only one horizontal row in the center is shown, and the diameter δ
The diffracted light spots DS are arranged so as to overlap each other at the spot center interval d. Assuming that the number of spots arranged in a horizontal row in the center of the diffracted light spot DS is N, the light receiving beam spot diameter T is expressed by the following equation. T = (N-1) d + δ (2)

The difference S between the light beam center BC and the light intensity center PC caused by the non-uniform intensity distribution of each diffracted light spot DS is as shown in FIG. It does not exceed 1/2.

Further, one diffracted light spot diameter δ is 10 μm.
When it is reduced to about m, some of the diffracted light spots DS fall into the insensitive area of the separation band 22b of the four-division sensor as shown in FIG. 8, and the diffracted light spots DS are separated during the optical axis deviation correction control. When it crosses the position, the position shift detection output changes abruptly, which is not preferable for control. In order to obtain such a received light beam spot, assuming that the distance L from the hologram surface 21a to the paraxial image plane G1 of the diffracted light is 100 mm and the incident light effective diameter D of the hologram surface 21a is 20 mm,
According to (1), the light receiving surface G2 of the position detecting light receiving element 22 is placed at the defocus position x where x = δ · L / D = 50 μm.

Further, since the number N of spots of the diffracted light spots DS arranged in a horizontal line in the center is 5, when the receiving beam spot diameter T is selected to be 400 μm, d = (T-δ) is obtained from the equation (2).
/(N-1)=97.5 μm spot center interval, that is, the moving interval d of the point object light LM when the hologram 21 is manufactured.
Thus, a plurality of diffracted light spots DS form a received light beam spot. At this time, the difference S between the light beam center BC and the light intensity center PC due to the non-uniformity of the intensity distribution in each diffracted light spot DS does not exceed δ / 2 = 5 μm as shown in FIG. .

Next, the overlapped portions of the adjacent diffracted light spots DS increase, and the received light beam spot position detection error increases. As shown in FIG. In the case of a double received light beam spot, the received light beam spot diameter T is selected to be 400 μm which is the same as the above, the distance L from the hologram surface 21a to the paraxial image plane G1 of the diffracted light is 100 mm, and the effective incident light diameter of the hologram surface 21a is 100 mm. If D is 20 mm, formula (1)
Therefore, the light receiving surface G2 of the position detecting light receiving element 22 is placed at the defocus position x where x = δ · L / D = 1 mm.

Further, since the number N of spots arranged in a horizontal line in the center of the diffracted light spot DS is 5, d = (T
−δ) / (N−1) = 50 μm spot center interval d
Thus, a plurality of diffracted light spots DS form a received light beam spot. At this time, the difference S between the light beam center BC and the light intensity center PC due to the non-uniformity of the intensity distribution in each diffracted light spot DS does not exceed δ / 2 = 100 μm as shown in FIG. .

When light is received by the optical axis deviation correcting means of the conventional example, the received light beam spot position detection error caused by the non-uniform intensity distribution in the received light beam spot is as shown in FIG. Diameter T = 4
Considering at 00 μm, the maximum value of the shift amount S between the light beam center BC and the light intensity center PC may be close to T / 2 = 200 μm, but in this embodiment, the received beam spot position detection error is the maximum. Even in such a case, the error can be reduced to 1/2 or less as compared with the case of the conventional optical axis deviation correcting means.

Therefore, when the width of the separation band 22b between the elements of the surface-divided sensor used as the position detecting light receiving element 22 is t and the light receiving beam spot diameter is T, the diffracted light spot diameter δ is t ≦ δ ≦ When T / 2 (3), the diffractive element acts effectively, and a PSD (Position Sensit
When a non-divided sensor such as an ive device) is used, the diffractive element effectively works when δ ≦ T / 2 (4).

Such a hologram 21 is an amplitude modulation hologram in which interference fringes are recorded on a silver salt photosensitive material or the like and developed and then blackened silver particles are used. By changing to a fringe of a change in the refractive index or a change in the thickness due to, for example, a phase modulation hologram, absorption loss of light can be suppressed and higher diffraction efficiency can be obtained.

The hologram 21 is a transmissive hologram 21 in which diffracted light is emitted to the side opposite to the received light LB with the hologram surface 21a as a boundary. As shown in FIG. 12, the reference light LR is emitted from the opposite direction. By doing so, it is possible to create the reflection hologram 31 in which the received light LB and the diffracted light exist on the same side with respect to the hologram surface 31a.
The same effect as described above can be obtained.

FIG. 13 is a block diagram of a spatial light transmission device having an optical deviation correction function of the second embodiment, which is behind an optical axis direction variable section 20 capable of simultaneously deflecting a light projecting optical axis and a light receiving optical axis. Is provided with a light projecting / receiving branching element 34, and a light projecting section composed of a lens group 35 having a positive power and a light emitting element 36 is arranged in the reflecting direction of the light projecting / receiving branching element 34. In the transmission direction of 34, a plurality of transmissive portions 37a are two-dimensionally arrayed on a surface mainly for reflection through a plurality of aperture members 37, and a lens group 38 having a positive power and a position detection light-receiving element are received. A light-receiving beam spot position detection unit including an element 22 and a signal processing unit 23 is arranged. Others are the same as those in FIG. 1, and the same reference numerals represent the same members.

As shown in FIG. 14, the plural aperture member 37 is composed of a square transmissive portion 37a having a side length of a and a reflective portion 37b in the other portion, and the plural transmissive portions 37a have a pitch P = 3a. They are arranged periodically in the vertical and horizontal directions. The reflective portion 37b of the multi-opening member 37 can be formed by performing vacuum deposition, photosensitization, or the like on a dielectric thin film or a metal thin film that reflects the received light LB.
May be a light blocking portion that absorbs or blocks the received light LB.

In order to prevent the twice-reflected light of the multiple aperture member 37 from entering the light receiving effective portion 22a of the position detecting light receiving element 22, the surface having the plurality of transmitting portions 37a or the opposite surface with respect to the incident optical axis. It is arranged to tilt a little. Instead of newly providing the plurality of opening members 37 as in the present embodiment, a plurality of transmitting portions 37a may be directly processed on the emission surface of the received light LB of the light projecting / receiving branch element 34.

The laser light emitted from the light emitting element 36 becomes a substantially parallel light flux by the lens group 35 having a positive power, and is reflected by the boundary surface of the light projecting / branching element 34. Is emitted as transmission light LA to.
On the other hand, the received optical LB containing the pilot signal from the other device
Is incident on the optical axis direction variable portion 20, passes through the light projecting / receiving light splitting element 34 to reach the plurality of aperture members 37, and the light flux passing through the transmitting portion 37a is received by the lens group 38 having positive power. It is focused on 22 and received as a beam spot. Then, this received light beam spot is passed through the signal processing unit 23 as an optical axis deviation correction signal to be the optical axis direction control unit 2.
4, the optical axis direction variable unit 20 is driven and the optical axis shift is corrected.

In the intensity distribution of the diffraction image by the multiple aperture member 37, local maxima appear periodically as shown in FIG. 15, and the curve SC connecting the maxima is represented by the square of the sinc function as shown in FIG. It has the same shape as the intensity distribution of the diffraction image of one square aperture. Therefore, this diffraction image is the 0th order light D0, the 1st order diffracted light D
Almost all of the total imaging energy is occupied by the first and second-order diffracted lights D2.

In FIG. 17, the arrangement in FIG. 13 is reversed left and right, and a plurality of aperture members 37 and a lens group 38 having a positive power are provided.
It is the figure which extracted only, the focal length of the lens group 38 which has positive power is set to f, and the front focus position H1 of the lens group 38 which has positive power in the distance f behind the multiple aperture member 37.
Is positioned, there is a diffracted light paraxial image plane G1 at a position of a distance f behind the rear focal position H2 of the lens group 38 having a positive power.

Therefore, when the light receiving surface G2 of the position detecting light receiving element 22 is placed at a position defocused from the paraxial image plane G1 of the diffracted light by a distance x, a diffracted light spot DS having a diameter δ is spotted as shown in FIG. The maximum diffracted light spot DS has a maximum spot diameter T
A light receiving beam spot is formed at the position of the light receiving surface G2.

Assuming that the focal length of the lens group 38 having a positive power is f and the effective diameter of the incident light beam is D, the following equation is established. δ / x = D / f (5)

If the diffraction angle of the first-order diffracted light is θ,
The following equation holds. d = f · tan θ (6)

Further, when the wavelength of the incident light beam is λ, the pitch P of the openings of the multiple opening member 37 is expressed by the following equation. P = λ / sin θ (7)

Here, when the diffraction angle θ is small, tan θ≈
Since it is sin θ, the following relational expression holds. P≈f · λ / d (8)

When a surface-divided sensor is used as the position detection light receiving element 22, the lower limit of the diffracted light spot diameter δ is when one diffracted light spot diameter δ is about 10 μm. If the focal length f of the lens group 38 having positive power is 100 mm and the effective diameter D of incident light is 20 mm,
According to (5), the light receiving surface G2 of the position detecting light receiving element 22 is placed at the defocus position x where x = δ · f / D = 50 μm.

Since the number N of spots of the diffracted light spot DS lined up in one horizontal line in the center is 5, when the light receiving beam spot diameter T is selected to be 400 μm, d = (T−δ) is obtained from the equation (2).
A plurality of diffracted light spots DS are lined up at a spot center interval d of (N-1) = 97.5 μm.

Here, the wavelength λ of the received light LB is 0.83 μm.
Then, from the formula (8), the pitch P of the transmissive portions 37a of the multiple aperture member 37 shown in FIG. 14 is 851 μm, and therefore the length a of one side of the square transmissive portion 37a may be 284 μm. At this time, the difference S between the light beam center BC and the light intensity center PC due to the non-uniformity of the intensity distribution in each diffracted light spot DS is
As in the first embodiment, δ / 2 = 5 μm is not exceeded.

Next, even if the overlapped portions of the adjacent diffracted light spots DS increase and the received light beam spot position detection error increases, the error is larger than the error caused by the conventional optical axis deviation correction means. The upper limit of the diffracted light spot diameter δ at which
Similar to the first embodiment, this is a case where the light receiving beam spot diameter T is twice the diffracted light spot diameter δ.

The conditions are the same as those described above, the receiving light beam spot diameter T is 400 μm, and the lens group 3 having a positive power is used.
The focal length f of 8 is 100 mm, and the effective diameter D of the incident light is 2
Assuming 0 mm, x = δ · f / D = 1 mm from the formula (5).
The light receiving surface G2 of the position detecting light receiving element 22 is placed at the defocus position x.

Further, since the number N of spots arranged in a horizontal line in the center of the diffracted light spot DS is 5, d = (T
−δ) / (N−1) = 50 μm spot center interval d
Thus, a plurality of diffracted light spots DS form a received light beam spot.

Here, the wavelength λ of the received light LB is 0.83 μm.
Then, from the formula (8), the pitch P of the square transmissive portions 37a of the multi-opening member 37 shown in FIG. 14 is 1.66 mm. Therefore, the length a of one side of the square transmissive portion 37a is 553 μm.
What should I do? At this time, the difference S between the light beam center BC and the light intensity center PC due to the non-uniformity of the intensity distribution in each diffracted light spot DS does not exceed δ / 2 = 100 μm as in the first embodiment. .

In this way, if the diffractive element of this embodiment is used under the condition that there are microscopic fluctuations in the atmosphere as shown in FIG. 35, the position detecting light receiving element 22 is used as in the first embodiment. (3) when using a surface-division sensor as
When the non-divided sensor is used, the diffracted light spot diameter δ that satisfies the expression (4) is effectively used.

The above description is for the lens group 3 having a positive power.
8 shows the case where there is no aberration, but the lens generally has aberration, and FIG. 19 shows the peripheral light flux LS and the central light flux LC when the lens group 39 having spherical aberration is used. FIG.
As shown in FIG. 21, the intensity distribution of the diffraction image of the multiple aperture member 37 in which a large number of square transmissive portions 37a ′ with P = 2b, in which the aperture pitch is P, one side length of the aperture is b, is shown in FIG.
As shown in, the curve becomes a series of maximum values that appear periodically. This is the intensity distribution of the diffraction image by one aperture si
It has the same shape as the distribution curve SC represented by the square of the nc function, and the diffracted image occupies most of the total imaging energy by the 0th-order light D0 and the 1st-order diffracted light D2.

FIG. 22 shows a front view of the multi-aperture member 37. The first zone 37c of the multi-aperture member 37 corresponds to the 0th-order light transmitting position of the peripheral light flux LS of FIG.
The second zone 37d of No. 7 corresponds to the 0th-order light transmitting position of the central light flux LC in FIG. First zone 3 of multi-opening member 37
7c is provided with a plurality of transmissive portions 37a in which the length of one side of the apertures is a and the pitch of the apertures is P = 3a, similar to the aperture arrangement shown in FIG. Three
7d is provided with a plurality of transmissive portions 37a 'in which the length of one side of the opening is b = 3 / 2a and the pitch of the openings is P = 2b, similar to the opening shown in FIG.

Such an optical axis shift detecting means is arranged in a positional relationship of the focal length f between the front focus H1 of the lens group 39 having spherical aberration and the surface where the aperture is widened, as in FIG. . As shown in FIG. 23, the diffracted light spot diameter δ1 by the peripheral light flux LS is 10 μm or more, and as shown in FIG.
The light-receiving surface G2 of the position-detecting light-receiving element 22 is set at a position of / 2 or less. Thus, as shown in FIG. 25, the diffracted light spot DS by the central light flux LC and the diffracted light spot DC by the peripheral light flux LS are the spot diameters at which the diffractive element of the present embodiment effectively acts and the received light beam spot diameters. It will exist in T.

FIG. 26 is a block diagram of a spatial light transmission device having an optical axis deviation correcting function of the third embodiment, which is a reflection of the second embodiment using the transmitted light from the plural aperture members 37. This is an example in which a plurality of aperture members 41 utilizing light is used, and the same reference numerals as those in FIG. 13 represent the same members. The square transmissive portion 41a becomes a reflection portion 37b which is the reverse of the embodiment shown in FIGS. 14 and 20, and the reflection portion 41b of this embodiment is shown in FIG.
22 and the transparent portion 37a of the embodiment shown in FIG. Also,
Since the multi-opening member 41 is inclined by 45 degrees with respect to the optical axis, in order to obtain the same diffraction effect as that of the embodiment of FIG. 13, the arrangement pitch P of the reflecting portions 41b is a lateral length as shown in FIG. The length should be 2 ^1/2 times the length.

In the above embodiment, the diffracted light spot DS is formed by extending the cross line of the separation band 22b of the 4-division sensor used as the position detecting light receiving element 22 in the direction of 45 degrees with respect to the vertical direction. Is the separator 22b
It is possible to avoid the occurrence of a position detection error due to a drop in position.
Further, when the direction in which the cross line of the separation band 22b of the four-division sensor extends is aligned with the vertical direction and the horizontal direction, the openings in FIGS. 14 and 20 are diamond-shaped rotated by 45 degrees as shown in FIG. The opening 41 b ′ may be used, and if it is a rhombic opening having a diagonal length of 2 ^1/2 a, it becomes an opening equivalent to the opening shown in FIG. 27.

Also in the present embodiment, even when the device shakes or micro-fluctuations of the atmosphere occur, the transmission light LA can be accurately projected in the direction of the partner device B (not shown), so that it is stable. Can communicate.

29 to 31 are block diagrams of a spatial light receiving device having an optical axis deviation correcting function of the fourth embodiment, and FIG.
9 is equipped with the optical axis shift compensating device of FIG. 1, and the light receiving element 42 for detecting this signal is provided on the transmission side of the received light LB of the equivalent type hologram 21.
And a receiving device having the present signal detecting means composed of a lens group 43 having a positive power.

FIG. 30 is equipped with the optical axis shift compensating device of FIG. 12, and on the transmission side of the reception light LB of the reflection type hologram 31, a light receiving element 42 for detecting this signal and a lens group 43 having a positive power.
It is a receiving device having the present signal detecting means.

FIG. 31 is provided with the optical axis deviation compensating device of FIG. 26, and comprises a light receiving element 42 for detecting this signal and a lens group 43 having a positive power on the transmission side of the received light LB of the multiple aperture member 41. It is a receiving device having the present signal detecting means. The same applies to the configuration in which the transmissive portion 41a and the reflective portion 41b of the multi-aperture member 41 are reversed, and the main signal detection portion side including the lens group 43 and the received light beam spot position detection portion side including the lens group 38 are interchanged. The effect of can be obtained.

The operation principle of the optical axis deviation compensating device of these four embodiments is the same as that of the above-mentioned embodiments, that is, the diffracted light from the diffractive element is guided to the received beam position detecting section and the non-diffracted light from the diffractive element is guided. Since it is configured to lead to this signal detection unit,
The entire light beam of the received light LB can be effectively used, and therefore, a receiving device can be obtained which has a high light beam utilization efficiency and a stable reception power level.

In the above description, the surface division type sensor is mainly used as the position detecting light receiving element 22.
Even when using a non-split sensor such as the one described above, if the received beam spot on the light receiving surface cannot always maintain a focused state, a diffractive element is used to determine the direction of the optical axis generated by microscopic fluctuations in the atmosphere. The control error can be reduced.

[0064]

As described above, the optical axis deviation compensating device according to the present invention receives the light beam received by the device itself against the light receiving beam including the pilot signal even if the device shakes or the microscopic fluctuation of the atmosphere occurs. The optical axes can be matched, and the reception power level can be stabilized by providing this signal detection unit on the non-diffracted light side of the optical axis shift correction device.
Furthermore, by providing a light projection unit in the optical axis deviation correction device and making the optical axis of the received beam spot position detection unit coincide with the optical axis of the light projection unit, the light is accurately projected to the other device and the transmission state is stabilized. Can be made.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a spatial light receiving device using a transmission hologram according to a first embodiment.

FIG. 2 is a perspective view of an optical axis direction control unit.

FIG. 3 is a sectional view of an optical axis direction control unit.

FIG. 4 is an explanatory diagram of a hologram creating method.

FIG. 5 is an explanatory diagram of diffraction development of a hologram.

FIG. 6 is a front view of a received light beam spot formed by a diffraction element.

FIG. 7 is an explanatory diagram of a received beam spot position detection error.

FIG. 8 is a front view of a light receiving beam spot formed by a diffraction element.

FIG. 9 is an explanatory diagram of a received beam spot position detection error.

FIG. 10 is a front view of a light receiving beam spot formed by a diffraction element.

FIG. 11 is an explanatory diagram of a received beam spot position detection error.

FIG. 12 is a configuration diagram of a spatial light receiving device using a reflection hologram.

FIG. 13 is a configuration diagram of a spatial light transmission device according to a second embodiment.

FIG. 14 is a front view of a plurality of openings of the diffraction element.

FIG. 15 is a graph showing an intensity distribution of diffracted light by a diffractive element.

FIG. 16 is a graph showing an intensity distribution of light diffracted by the diffractive element.

FIG. 17 is an explanatory diagram of diffractive development using a diffractive element.

FIG. 18 is a front view of a light receiving beam spot formed by a diffraction element.

FIG. 19 is an explanatory diagram of an optical path of a lens group having spherical aberration.

FIG. 20 is a front view of a plurality of openings of the diffraction element.

FIG. 21 is a graph showing an intensity distribution of diffracted light by a diffraction element.

FIG. 22 is a front view of the diffraction element.

FIG. 23 is an illustration of diffractive development with a diffractive element.

FIG. 24 is an illustration of diffractive development with a diffractive element.

FIG. 25 is a front view of a light receiving beam spot formed by a diffraction element.

FIG. 26 is a configuration diagram of a spatial light transmission device according to a third embodiment.

FIG. 27 is a front view of a plurality of openings of the diffraction element.

FIG. 28 is a front view of a plurality of openings of the diffraction element.

FIG. 29 is a configuration diagram of a spatial light receiving device according to a fourth embodiment.

FIG. 30 is a configuration diagram of a spatial light receiving device.

FIG. 31 is a configuration diagram of a spatial light receiving device.

FIG. 32 is a block diagram of a conventional spatial light transmission device.

FIG. 33 is a perspective view of an optical axis direction control unit.

FIG. 34 is a front view of a position detecting light receiving element.

FIG. 35 is a front view of a position detection light receiving element.

FIG. 36 is an explanatory diagram of micro fluctuations in the atmosphere.

FIG. 37 is a front view of a position detecting light receiving element.

FIG. 38 is an explanatory diagram of a received beam spot position detection error.

[Explanation of symbols]

 20 Optical axis direction variable section 21, 31 Hologram 22 Position detection light receiving element 23 Signal processing section 24 Optical axis direction control section 33 Light emitting and receiving branching element 36 Light emitting element 37, 41 Multiple aperture member 39 Lens group 42 Main signal detecting light receiving element

Claims (8)

[Claims] 1. A light-receiving optical system, a light-receiving beam spot position detection unit, and an optical axis shift for detecting an optical axis shift of a light-receiving optical axis of its own device with respect to received light based on position shift information from a light-receiving beam spot reference position. A detecting means, an optical axis direction changing means, and an optical axis deviation correction signal to the optical axis direction changing means based on the optical axis deviation information detected by the optical axis deviation detecting means, and the light receiving optical axis of the device itself. In the optical axis shift correction device having an optical axis direction control means for controlling the direction of the received light beam, a diffractive element is provided in the light receiving optical system to generate a plurality of diffracted light beams from one received light beam to detect the received light beam spot position. A plurality of diffracted light spots are formed on the light receiving surface of the optical section, which is an optical axis deviation correcting device. 2. The optical axis shift correction according to claim 1, wherein the diffractive element is a hologram that forms a plurality of diffracted light spots on the light receiving surface of the received light beam spot position detection unit when a received light beam is incident. apparatus. 3. The diffractive element has an opening in which a plurality of transmissive portions are two-dimensionally arranged periodically on a surface mainly reflecting or blocking light, and the transmitted light transmitted through the opening is the received beam. The optical axis shift correction device according to claim 1, which is guided to a spot position detection unit. 4. The diffractive element has a light-shielding portion in which a plurality of reflecting portions are two-dimensionally arranged periodically on a surface mainly for transmission,
The optical axis deviation correction device according to claim 1, wherein the reflected light reflected by the light shielding portion is guided to the received light beam spot position detection portion. 5. The optical axis deviation correcting device according to claim 1, wherein a condition of δ ≦ T / 2 is satisfied, where T is a received light beam spot diameter of the received light and δ is a diffracted light spot diameter. 6. The light receiving beam spot position detection unit uses a surface-divided sensor as a light receiving element for position detection. The light receiving beam spot diameter is T, the diffracted light spot diameter is δ, and the distance between the divided elements of the surface divided sensor. Let t be the separation band width of
The optical axis deviation correction device according to claim 1, wherein a condition of ≦ δ ≦ T / 2 is satisfied. 7. A light projecting means comprising a light projecting optical system and a signal generating section, and a light projecting / receiving light branching means, so that the light projecting optical axis and the light receiving optical axis coincide with each other in the optical axis direction varying means. The optical axis deviation correction device according to claim 1, 8. A main signal detecting means comprising the light receiving optical system and a main signal detecting section, wherein the optical axis of the light receiving beam spot position detecting optical system in the optical axis direction varying means and the main signal detecting optical system. 2. The optical axis shift correction according to claim 1, wherein the optical axis of the diffractive element is guided to the received beam spot position detection unit, and the non-diffracted light is guided to the main signal detection unit. apparatus.