JP2009139692A - Laser beam scanner and optical antenna device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser beam scanner allowing quick spiral scanning over a wide range, and to provide an optical antenna. <P>SOLUTION: The laser beam scanner includes: a first wedge prism 1 and a second wedge prism 2; a first rotation-driving means and a second rotation-driving means for rotating the first wedge prism 1 and the second wedge prism 2, respectively; and a rotation speed control means for controlling the first rotation-driving means and the second rotation-driving means to rotate the first wedge prism 1 and the second wedge prism 2 at different rotation speeds, respectively. The first wedge prism 1 and the second wedge prism 2 are arranged to transmit a laser beam, and respective rotation directions thereof are equal with respect to an advancing direction of the laser beam. With such an arrangement, the scanner allows the laser beam scanning of drawing a desired spiral locus on an optional face in a space. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention, for example, emits a laser beam that has been signal-modulated by one apparatus into space, receives the laser beam by the other apparatus, and performs signal demodulation to perform laser beam scanning used for optical space communication. The present invention relates to a device and an optical antenna device.

  In optical communication between artificial satellites using laser light (optical inter-satellite communication), the direction of the partner satellite is optically determined in order to reach a converging transmission laser beam to a partner satellite at a very long distance. A means to detect is needed. When the laser beam emitted from the partner satellite is received, the problem can be solved by mounting a sensor for detecting the direction of arrival of the laser beam. However, if this is not the case, another means for optically detecting the direction of the counterpart satellite is further required.

  As a means for optically detecting the direction of the other satellite, the angle of the transmitted laser beam is changed with time, and the other satellite is scanned over the range of possible angles. There is a laser beam scanning device that makes it possible for a partner satellite to always receive a transmission laser beam of its own satellite without knowing the exact direction of the satellite (see, for example, Non-Patent Document 1).

  The laser beam scanning device described in Non-Patent Document 1 changes the reflection angle by controlling the inclination of a plane mirror in order to bend the angle of the laser beam, and also has a spiral shape called spiral scan. A scanning pattern is performed.

  In the spiral scan, the angular range (two-dimensional vector) that allows for the space where the partner satellite can exist can be limited to approximately the inside of the circular boundary by orbit calculation. Further, the existence probability of the partner satellite is distributed with the center of the circular boundary as a peak. Therefore, if the scanning of the laser beam is started from the center of the circular boundary, the purpose can be achieved in a short time in a short time, and such a spiral scan is considered good.

  Therefore, since the conventional laser beam scanning apparatus is configured as described above, the transmission laser beam of the own satellite can reach the partner satellite without knowing the exact direction of the partner satellite.

"Beaconless satellite laser acquisition-modeling and feasibility", Military Communications Conference, 2004. MILCOM 2004. IEEE Vol. 1, P41-47 Date: 31 Oct. -3 Nov. 2004

However, the prior art has the following problems.
First, in order to shorten the scanning time per time, it is necessary to increase the angular velocity of the plane mirror tilt for bending the angle of the laser beam. However, increasing the angular velocity has a limit that depends on the inertia weight of the drive mechanism and the mirror. Therefore, there is a problem that there is a limit to shortening the scanning time per time.

  Second, the plane mirror is placed on the small aperture side of the telescope that converts the laser beam diameter in order to reduce the inertia weight of the mirror. On the other hand, the tilt angle range needs to be larger by the magnification of the telescope. is there. As an example, in order to scan a range of radius 0.2 deg using a 10 × telescope, a tilt angle range of 1 deg is required, and there is a problem that it is difficult to achieve high speed performance.

  The present invention has been made to solve the above-described problems, and an object thereof is to obtain a laser beam scanning apparatus and an optical antenna apparatus capable of spiral scanning over a wide range at high speed.

  The laser beam scanning apparatus according to the present invention bends the laser beam propagating in the space and changes the bending angle with time so as to draw a desired spiral trajectory on an arbitrary surface in the space. A laser beam scanning device for scanning a beam, wherein a first wedge prism and a second wedge prism, a first wedge driving prism and a second wedge prism are respectively rotated by a first rotation driving means and a second wedge prism. A rotation drive means, and a rotation speed control means for controlling the first rotation drive means and the second rotation drive means so that the first wedge prism and the second wedge prism rotate at different rotation speeds; The first wedge prism and the second wedge prism are arranged to transmit the laser beam and Those equal each rotational direction with respect to the traveling direction of the Zabimu.

  The optical antenna apparatus according to the present invention is an optical antenna apparatus that transmits a laser signal to a space, to which the laser beam scanning apparatus according to the present invention is applied.

  According to the present invention, by rotating two wedge prisms in the same rotation direction at different rotation speeds, by scanning a laser beam so as to draw a desired spiral trajectory on an arbitrary surface in space, A laser beam scanning device and an optical antenna device capable of spiral scanning over a wide range at high speed can be obtained.

  Hereinafter, preferred embodiments of a laser beam scanning device and an optical antenna device of the present invention will be described with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram of a laser beam scanning apparatus according to Embodiment 1 of the present invention. The laser beam scanning apparatus of FIG. 1 includes wedge prisms 1 and 2 having the same apex angle, rotary bearings 3 and 4 of the wedge prisms 1 and 2, spur gears 5 a and 5 b rotating with the wedge prisms 1 and 2, spur gear 5 a, 5b includes pinion gears 6a and 6b for transmitting a driving force to each of them, and an electric motor 7 connected to the rotation shafts of the pinion gears 6a and 6b. From the laser beam scanning device having such a configuration, a deflected laser beam 8 (that is, a laser beam 8 having a deflection angle 9) is output.

  Next, the operation of the laser beam scanning apparatus according to the first embodiment will be described. The speed reduction ratio determined by the number of teeth of the pinion gear 6a and the spur gear 5a is different from the speed reduction ratio determined by the number of teeth of the pinion gear 6b and the spur gear 5b. Therefore, when the electric motor 7 is driven at a constant speed, the wedge prism 1 and the wedge prism 2 rotate in the same rotational direction but at different rotational speeds.

  When the laser beam is transmitted through the wedge prisms 1 and 2, the traveling direction is deflected by refraction. Further, due to the rotational movement described above, the deflection direction changes with time, and spatial scanning can be performed.

  In such a configuration, the spur gears 5a and 5b, the pinion gears 6a and 6b, and the electric motor 7 correspond to the rotation driving means. Further, by configuring the reduction ratio determined by the number of teeth of the pinion gear 6a and the spur gear 5a to be different from the reduction ratio determined by the number of teeth of the pinion gear 6b and the spur gear 5b, the rotational speed control means is realized. Yes.

  Next, the point that the spatial scanning pattern by the rotational movement of the wedge prisms 1 and 2 is a spiral scan will be described. FIG. 2 is an explanatory diagram of parameters representing the deflection angle by laser beam scanning in the first embodiment of the present invention. 2 shows the laser beam scanning apparatus 10 shown in FIG. 1 and a virtual plane 11 for visually representing a scanning pattern.

  Here, the scalar component θ1 and the azimuth angle θ2 of the deflection angle by laser beam scanning are defined as shown in FIG. These parameters can be expressed as a vector sum of deflection angles by the wedge prisms 1 and 2.

  FIG. 3 is an explanatory diagram showing the relationship of the vector sum of deflection angles in the first embodiment of the present invention. In FIG. 3, the deflection angle vector is represented by a straight arrow, the length of the arrow is represented by a scalar component, and the azimuth is represented by an angle formed with a horizontal line.

  In FIG. 3, three deflection angle vectors 20a, 20b, and 22 are shown. The deflection angle vector 20 a is a deflection angle vector by the wedge prism 1. Further, the deflection angle vector 20 b is a deflection angle vector by the wedge prism 2. Further, the deflection angle vector 22 is a deflection angle vector by the laser beam scanning device 10 expressed by a combination of the deflection angle vector 20a and the deflection angle vector 20b.

  Further, in FIG. 3, two trajectories 21 and 23 are shown. The locus 21 is a locus drawn by the deflection angle vector 22 when the wedge prism 1 is fixed and the wedge prism 2 is rotated. The locus 23 is a locus drawn by the deflection angle vector 22 when the wedge prisms 1 and 2 are rotated while the angle Δφ formed by the deflection angle vectors 20a and 20b is fixed.

  As is clear from FIG. 3, when Δφ is changed, the scalar component (θ1 in FIG. 2) of the deflection angle vector 22 can be changed steplessly from 0 to an arbitrary value. Further, when the wedge prisms 1 and 2 are rotated in the same direction while keeping Δφ constant, the deflection angle vector 22 becomes a circular scanning pattern as indicated by the locus 23.

  As already described, since the wedge prisms 1 and 2 are rotationally driven via gear trains having different reduction ratios, Δφ changes with time. Accordingly, when the rotational drive is started from the state where the deflection angle vector 22 is the 0 vector, that is, the state where Δφ is 180 degrees, the azimuth angle θ2 increases and the scalar component θ1 of the deflection angle vector 22 also increases with time. Go. As a result, spiral scan can be realized.

  Further, it can be seen that when the scalar component θ1 of the deflection angle vector 22 reaches the maximum value, that is, when the time when Δφ becomes 0, it automatically switches from the outside to the inward spiral scan. Therefore, even if the rotation direction of the electric motor 7 is always constant, the spiral scan can be continuously performed. By designing the above-described reduction ratio and rotation speed so as to have appropriate values, the laser beam can be scanned so as to draw a desired spiral trajectory.

  As described above, according to the first embodiment, the following two effects can be obtained by using the laser beam scanning apparatus having the above-described configuration. As a first point, in the conventional method in which the plane mirror is tilted, the angle of the mirror has to be reciprocated. On the other hand, the laser beam scanning apparatus according to the first embodiment only needs to rotate the electric motor in a certain direction, and can realize high-speed and stable scanning at low cost.

As a second point, in order to expand the scanning range, in the conventional method in which the plane mirror is tilted, it is necessary to increase the driving amount of the mirror angle. On the other hand, the laser beam scanning apparatus according to the first embodiment uses a wedge prism with a high refractive index or a wedge prism with a large apex angle, and only changes the reduction ratio of the gear train as necessary. The scanning range can be expanded. Therefore, various scanning ranges can be realized at low cost.
A mechanical element (reduction gear) having a similar function may be used as an alternative to the spur gears 5a and 5b and the pinion gears 6a and 6b. For example, a bevel gear or a worm gear may be used, or a mechanism such as a CVT (transmission device not using a gear) of an automobile may be used.

Embodiment 2. FIG.
In the first embodiment, two wedge prisms having the same apex angle are required. However, the vertex angle of commonly available wedge prisms includes manufacturing tolerances and cannot be used depending on the required accuracy. Therefore, in the second embodiment, a configuration that obtains an effect equivalent to that of the first embodiment using the wedge prism having the manufacturing tolerance will be described.

  In the configuration of the laser beam scanning apparatus according to the second embodiment, instead of the wedge prism 2, only two wedge prisms are used while being fixed together in the same holder, and the configuration diagram is omitted.

  FIG. 4 is an explanatory diagram of the deflection angle vector of the laser beam scanning apparatus according to the second embodiment. In FIG. 4, the same numerals and symbols as those in FIG. 3 have the same meaning and description thereof is omitted. In the second embodiment, instead of obtaining the deflection angle vector 20b by the wedge prism 2, the deflection angle vector 20b is obtained by combining the deflection angle vector 20b1 by one of the two wedge prisms and the deflection angle vector 20b2 by the other. It has gained.

  Here, the deflection angle vectors 20b1 and 20b2 are clearly different from the deflection angle vector 20a. However, the deflection angle vector 20b, which is a combined vector of the deflection angle vectors 20b1 and 20b2, can be made equal to the deflection angle vector 20a by appropriately setting the angles formed by the respective deflection angle vectors 20b1 and 20b2 (FIG. 4). Therefore, by using these two wedge prisms as a substitute for the wedge prism 2, an operation equivalent to that of the laser beam scanning apparatus according to the first embodiment is possible.

  As described above, according to the second embodiment, the following two effects are obtained by using the laser beam scanning apparatus having the above-described configuration. As a first point, an effect equivalent to that of the laser beam scanning apparatus according to the first embodiment can be obtained. Further, as the second point, since a wedge prism having a large tolerance can be used, the cost can be reduced as compared with the laser beam scanning apparatus according to the first embodiment.

  In the second embodiment described above, the case where two wedge prisms are collectively fixed to the same holder instead of the wedge prism 2 has been described. However, the present invention is not limited to such a configuration. A similar effect can be obtained by having a third wedge prism that rotates at a rotational speed equal to one of the two wedge prisms 1 and 2 that rotate at different speeds.

Embodiment 3 FIG.
In the first embodiment, the configuration of the rotation driving means in which one common electric motor 7 is connected to the rotation shafts of the pinion gears 6a and 6b has been described. On the other hand, in the third embodiment, a configuration of a rotation driving unit in which individual motors are connected to the rotation shafts of the pinion gears 6a and 6b will be described.

  FIG. 5 is a configuration diagram of the laser beam scanning apparatus according to the third embodiment of the present invention. In FIG. 5, the numerals and symbols equivalent to those in FIG. Compared to the configuration shown in FIG. 1, the configuration shown in FIG. 5 includes stepping motors 30 a and 30 b, stepping motor drivers 31 a and 31 b, and a sequence control device 32 instead of the electric motor 7.

  The stepping motor drivers 31a and 31b are drivers that give drive pulses to the stepping motors 30a and 30b, respectively. The sequence control device 32 is a controller that gives control commands to the stepping motor drivers 31a and 31b.

  In such a configuration, the spur gears 5a and 5b, the pinion gears 6a and 6b, and the stepping motors 30a and 30b correspond to the rotation driving means. Further, the stepping motor drivers 31a and 31b and the sequence control device 32 correspond to the rotation speed control means.

  Next, the operation will be described. The pinion gears 6a and 6b are driven by stepping motors 30a and 30b, respectively. Therefore, the wedge prisms 1 and 2 can be rotated at an arbitrary rotational speed. The sequence control device 32 gives a control command for rotating the wedge prisms 1 and 2 according to a predetermined program to the respective stepping motor drivers 31a and 31b.

  In other words, the sequence control device 32 stores a drive pulse time change pattern for driving the stepping motors 30a and 30b in advance in a storage unit (not shown) so as to obtain a desired spiral trajectory. A drive pulse is output as a control command for the stepping motor drivers 31a and 31b based on the pulse time change pattern.

  As described above, according to the third embodiment, the use of the laser beam scanning apparatus having the above-described configuration has the following three effects. As a first point, an effect equivalent to that of the laser beam scanning apparatus according to the first embodiment can be obtained.

  As a second point, the angular velocity of the deflection angle scalar quantity θ1 and the angular velocity of the azimuth angle θ2 can be arbitrarily controlled independently. Therefore, it is possible to control the spiral pitch of the spiral scan scanning pattern so as to be evenly spaced. Furthermore, as a third point, it is possible to control the radiation divergence in the spiral scan angle range to be uniform.

Embodiment 4 FIG.
In the third embodiment, the configuration in which individual stepping motors are connected to the rotation shafts of the pinion gears 6a and 6b has been described. On the other hand, in the fourth embodiment, a configuration in which individual DC servo motors are connected to the rotation shafts of the pinion gears 6a and 6b will be described.

  FIG. 6 is a configuration diagram of a laser beam scanning apparatus according to the fourth embodiment of the present invention. In FIG. 6, the numerals and symbols equivalent to those in FIGS. 1 and 5 indicate the same parts and the description thereof is omitted. In the configuration shown in FIG. 5, stepping motors 30 a and 30 b, stepping motor drivers 31 a and 31 b, and a sequence control device 32 are provided instead of the electric motor 7. On the other hand, in the configuration of FIG. 6, instead of the electric motor 7, DC servo motors 40 a and 40 b, servo motor drivers 41 a and 41 b, a feedback control device 42, and rotary encoders 43 a and 43 b are provided.

  The servo motor drivers 41a and 41b are drivers that supply driving power to the servo motors 40a and 40b. The rotary encoders 43a and 43b include a scale that rotates together with the wedge prism 1.2 and a scale reading sensor, and reads the rotation amount. Further, the feedback control device 42 is a controller that calculates numerical values read by the rotary encoders 43a and 43b and gives control command values to the servo motor drivers 41a and 41b.

  In such a configuration, the spur gears 5a and 5b, the pinion gears 6a and 6b, and the servo motors 40a and 40b correspond to the rotation driving means. The servo motor drivers 41a and 41b, the feedback control device 42, and the rotary encoders 43a and 43b correspond to the rotation speed control means.

  Next, the operation will be described. Based on the outputs of the rotary encoders 43a and 43b, the feedback control device 42 calculates the rotational speed of the wedge prisms 1 and 2 and the current value of the relative azimuth angle Δφ as feedback amounts. Further, in the feedback control device 42, as a target value for obtaining a desired spiral scanning pattern, the rotational speed and rotational acceleration of the wedge prisms 1 and 2 with respect to the value of Δφ with the passage of time are functions or numerical values in a numerical table. The format is stored in advance in a storage unit (not shown).

  The feedback control device 42 performs feedback control based on the feedback amount and the target value, and gives a control command to the servo motor drivers 41a and 41b. Thereby, a desired spiral scanning pattern can be obtained.

  In other words, the feedback control device 42 stores in advance a target rotational speed time change pattern for driving the servo motors 40a and 40b so as to obtain a desired spiral locus in a storage unit (not shown), Using the output values of the rotary encoders 43a and 43b corresponding to the relative angle detector as feedback data, a control command is given to the respective servo motor drivers 41a and 41b to perform feedback control.

  As described above, according to the fourth embodiment, the following two effects are obtained by using the laser beam scanning device having the above-described configuration. As a first point, an effect equivalent to that of the laser beam scanning apparatus according to the third embodiment can be obtained. The second point is that feedback control of the speed and acceleration of the servo motor enables a smoother and more accurate scanning pattern to be drawn compared to the stepping motor sequence control described in the third embodiment. It becomes.

Embodiment 5 FIG.
In the fifth embodiment, a case where the laser beam scanning device described in the first to fourth embodiments is applied to an optical antenna device will be described. FIG. 7 is a configuration diagram of an optical antenna device according to Embodiment 5 of the present invention. The optical antenna device shown in the fifth embodiment is applied to communication between optical satellites.

  The optical antenna device of FIG. 7 includes any of the laser beam scanning devices 10 described in the first to fourth embodiments. As other components, the optical antenna apparatus of FIG. 7 includes a laser beam transmitting unit 50, a laser beam receiving unit 51, a first beam splitter 52, a second beam splitter 53, an FPM 54 which is a chip tilt drive mirror, A telescope 55, a CPM 56 that is a two-axis gimbal drive mirror, a lens 57, and a two-dimensional detector 58 that is a CCD device are provided.

  Next, the operation will be described. The transmitted laser beam emitted from the laser beam transmitting means 50 is emitted outside the casing through the laser beam scanning device 10, the beam splitter 52, the FPM 54, the telescope 55, and the CPM 56. The CPM 56 bends the transmission beam in the direction in which the other satellite is highly likely to exist by orbit calculation by an electronic computer (not shown).

  The laser beam scanning apparatus 10 performs spiral scanning in order to make the transmitted laser beam reach the partner satellite. On the other hand, when the partner satellite is performing spiral scanning with the same system, the laser beam scanning device 10 stops spiral scanning.

  Assume that the CPM 56 receives the transmission laser beam of the partner satellite (hereinafter, the received laser beam is referred to as a reception laser beam). In this case, the received laser beam reaches the two-dimensional detector 58 through the CPM 56, the telescope 55, the FPM 54, the first beam splitter 52, the second beam splitter 53, and the lens 57.

  Based on the condensing position of the two-dimensional detector 58, an angle shift of the laser beam incident on the laser beam receiving means 51 is calculated by an electronic computer (not shown), and the angle of the FPM 54 is corrected based on the calculation result.

  Furthermore, the deflection angle of the laser beam scanning device 10 is controlled by a computer (not shown) so as to calculate the optical difference between the transmitted and received laser beams and correct the optical difference. As described above, the transmission beam can reach the partner satellite.

  As described above, according to the fifth embodiment, the use of the optical antenna device having the above-described configuration has the following two effects. As a first point, by using the laser beam scanning apparatus 10 of the system shown in the previous embodiment 4, high-speed spiral scanning becomes possible. Therefore, it is possible to make the transmission beam reach the partner satellite in a short time. Further, as a second point, the optical line difference correction is performed by the laser beam scanning device, so that the size and cost of the device can be reduced.

It is a block diagram of the laser beam scanning apparatus in Embodiment 1 of this invention. It is explanatory drawing of the parameter showing the deflection angle by the laser beam scanning in Embodiment 1 of this invention. It is explanatory drawing which shows the relationship of the vector sum of the deflection angle in Embodiment 1 of this invention. It is explanatory drawing of the deflection angle vector of the laser beam scanning apparatus in this Embodiment 2. FIG. It is a block diagram of the laser beam scanning apparatus in Embodiment 3 of this invention. It is a block diagram of the laser beam scanning apparatus in Embodiment 4 of this invention. It is a block diagram of the optical antenna apparatus in Embodiment 5 of this invention.

Explanation of symbols

  1, 2 wedge prism, 5a, 5b spur gear, 6a, 6b pinion gear, 7 electric motor, 10 laser beam scanning device, 11 virtual plane, 20a, 20b, 20b1, 20b2, 22 deflection angle vector, 21, 23 locus, 30a, 30b Stepping motor, 31a, 31b Stepping motor driver, 32 Sequence control device, 40a, 40b Servo motor, 41a, 41b Servo motor driver, 42 Feedback control device, 43a, 43b Rotary encoder, 50 Laser beam transmission means, 51 Laser Beam receiving means, 52 first beam splitter, 53 second beam splitter, 54 FPM, 55 telescope, 56 CPM, 57 lens, 58 two-dimensional detector.

Claims (6)

A laser beam scanning device that scans the laser beam so as to draw a desired spiral trajectory on an arbitrary surface in the space by bending the laser beam propagating in the space and changing the bending angle with time. There,
A first wedge prism and a second wedge prism;
A first rotation driving means and a second rotation driving means for rotating the first wedge prism and the second wedge prism, respectively;
A rotation speed control means for controlling the first rotation drive means and the second rotation drive means so that the first wedge prism and the second wedge prism rotate at different rotation speeds;
The first wedge prism and the second wedge prism are arranged so as to transmit the laser beam, and the respective rotation directions with respect to the traveling direction of the laser beam are equal to each other. . The laser beam scanning apparatus according to claim 1, wherein
The first rotation driving means and the second rotation driving means are driven by one electric motor and rotation of the electric motor to the respective rotary motions of the first wedge prism and the second wedge prism. A first spur gear and a second spur gear for transmission;
The rotation speed control means is configured by making a reduction ratio by the first spur gear different from a reduction ratio by the second spur gear. The laser beam scanning apparatus according to claim 1, wherein
A third wedge prism that rotates at a rotational speed equal to one of the first wedge prism and the second wedge prism that rotate at different rotational speeds;
The first wedge prism, the second wedge prism, and the third wedge prism are arranged so as to transmit the laser beam, and have the same rotation direction with respect to the traveling direction of the laser beam. A laser beam scanning device characterized by the above. The laser beam scanning apparatus according to claim 1, wherein
Each of the first rotation driving means and the second rotation driving means is constituted by a stepping motor,
The rotational speed control means has a storage unit for storing in advance a drive pulse time change pattern for driving the stepping motor so as to obtain the desired spiral trajectory, and based on the drive pulse time change pattern A laser beam scanning device that outputs a driving pulse to the stepping motor. The laser beam scanning apparatus according to claim 1, wherein
A first relative angle detector and a second relative angle detector for outputting a relative angle of each of the first wedge prism and the second wedge prism with respect to a predetermined reference;
The first rotation driving means and the second rotation driving means are each constituted by a servo motor,
The rotation speed control means includes a storage unit that stores in advance a target rotation speed time change pattern for driving the servo motor so as to obtain the desired spiral trajectory, and the first relative angle detector And a feedback control of the rotational speed of each servo motor using each relative angle output from the second relative angle detector as feedback data. In an optical antenna device that transmits a laser signal to space,
6. An optical antenna device to which the laser beam scanning device according to claim 1 is applied.

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