JPH06152537A - Automatic light beam tracking device - Google Patents

Abstract

PURPOSE:To suppress the deterioration in the responsiveness or normal deviation characteristic of a control system due to the change of a transmitting distance, and to improve the stability of the control system. CONSTITUTION:A tracking mirror 11 arranged in a light beam adjusting mechanism 24 is provided on the optical path of a received light L, and a four-division photoelectric detector 13 is provided through an optical system 12 in the reflecting direction of the tracking mirror 11. The output of the four-division photoelectric detector 13 is connected to a control part 23, and the output of the control part 23 is connected to the light beam adjusting mechanism 24. In a tracking state, a direct current signal from a command signal generator 18 in the control part 23 is added to a tracking error angle, an the tracking mirror 11 is changed by only a micro-angle. Then, the changing amount of the gain of the four-division photoelectric detector 13 corresponding to the changing amount is detected, the gain for canceling the changing amount is calculated by a calibration arithmetic part 16, and the gain of a compensating element 27 is changed to the calculated value. Thus, an open loop gain can be always held to be the optimal value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light beam automatic tracking device in an optical signal receiving device for performing communication and measurement by a light beam.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram of a conventional light beam automatic tracking device, in which a received light L is incident on a tracking mirror 2 in a light beam adjusting mechanism 1 and a four-division photoelectric detector via an optical system 3. The deviation of the optical axis of the received light L is detected by 4. The shift signal is processed by the control unit 5, and the command signal is input to the light beam drive adjusting mechanism 1. The light beam drive adjusting mechanism 1 follows the tracking mirror 2 according to this command signal.
To align the optical axes. The spot size of the received light incident on the four-division photoelectric detector 4 is sufficiently large to cover the measurement range of the tracking error angle. Further, in order to easily cover the deviation of the optical axis, the received light L from the communication partner or the measurement point has a divergence angle.

[0003]

However, the relationship between the amount of movement of the spot position on the four-division photoelectric detector 4, that is, the tracking error angle, and the normalized output signal of the tracking error angle detecting section in the control section 5 is as follows. , As shown in FIG. 4, it changes depending on the spot size of the received light incident on the four-division photoelectric detector 4. Therefore, when the spot size on the four-division photoelectric detector 4 changes due to the change in transmission distance, the open loop gain of the feedback control system changes in the above-described conventional example, and the automatic tracking control characteristic deteriorates.

That is, as the transmission distance becomes shorter, the spot size becomes larger and the open loop gain of the feedback control system becomes smaller, so that the speed response and steady deviation characteristic of the control system deteriorate. On the contrary, as the transmission distance becomes longer, the spot size becomes smaller and the open loop gain of the feedback control system becomes larger, so that the stability of the control system deteriorates.

Further, as shown in FIG. 4, the range in which the output signal is not saturated with respect to the movement amount of the spot center on the four-division photoelectric detector 4 also changes with the change of the spot size. That is, as the spot size becomes smaller, the range in which the output signal does not saturate becomes narrower, and there is a problem that tracking error easily occurs.

An object of the present invention is to provide an optical beam automatic tracking device in which the stability of the control system is improved by suppressing the deterioration of the quick response and the steady deviation characteristic of the control system caused by the change of the transmission distance.

[0007]

A first light beam automatic tracking device for achieving the above object includes a light beam angle adjuster for adjusting received light and a signal corresponding to an incident angle of the received light. A four-division photoelectric detector for outputting, an optical system for condensing the received light on the four-division photoelectric detector, a signal from the four-division photoelectric detector, and a command signal to the light beam angle adjuster. In a light beam automatic tracking device including a control unit that outputs a signal, the tracking mirror is changed by a small angle in the tracking state, the control unit detects a gain change of the four-division photoelectric detector, and
It is characterized in that the gain change of the divided photoelectric detector is corrected.

Further, the second light beam automatic tracking device comprises a light beam angle adjuster for adjusting the angle of the received light, a four-division photoelectric detector for outputting a signal corresponding to the incident angle of the received light, Light composed of an optical system for condensing the received light on a four-division photoelectric detector and a control unit for processing a signal from the four-division photoelectric detector and outputting a command signal to the light beam angle adjuster. In the automatic beam tracking device, an actuator that changes the distance between the four-division photoelectric detector and the optical system is provided, the tracking mirror is changed by a small angle in the tracking state, and the control unit is incident on the four-division photoelectric detector. The actuator is controlled so that the spot size of the received light is constant.

[0009]

The first light beam automatic tracking device having the above-mentioned configuration changes the tracking mirror by a small angle in the tracking state, detects the change amount of the gain of the four-division photoelectric detector with respect to the change amount, and changes the gain. The gain that cancels the amount is calculated in the control unit, and the gain of the compensation element is changed to that value to correct the amount of change in the gain of the four-division photoelectric detector.

The second light beam automatic tracking device changes the tracking mirror by a small angle in the tracking state to detect the amount of change in the gain of the four-division photoelectric detector, and from this result, determines the size of the spot size. The distance between the condenser lens and the 4-division photoelectric detector is estimated by using the actuator, and the spot size of the received light formed on the 4-division photoelectric detector is always maintained at an optimum value.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail with reference to the embodiments shown in FIGS. FIG. 1 is a block diagram of the first embodiment. A tracking mirror 11 is provided in the incident direction of the received light L, and a four-division photoelectric detector 13 is provided in the reflection direction of the tracking mirror 11 via an optical system 12. It is provided. The output of the four-division photoelectric detector 13 is the tracking error detector 14
The output of the tracking error detector 14 is connected to the adder 15 and the calibration calculator 16.

The output of the adder 15 is connected to the compensating element 17, the output of the calibration calculator 16 is connected to the compensating element 17 and the command signal generator 18, and the output of the command signal generator 18 is the adder 15. And a terminal 19a of the switch 19. Further, the output of the compensating element 17 is connected to the terminal 19b of the switch 19, and the switch 19 is connected to the mirror driving control circuit 20. The output of the mirror drive control circuit 20 is connected to the tracking mirror 11 via an actuator 21. The angle of the tracking mirror 11 is detected by the mirror angle detector 22, and the output of the mirror angle detector 22 is connected to the mirror drive control circuit 20.

Then, the tracking error detector 14 and the adder 1
5, the calibration calculation unit 16, the compensation element 17, the command signal generator 18, and the switch 19 constitute a control unit 23, and a mirror driving control circuit 20, an actuator 21,
The mirror angle detector 22 constitutes a light beam adjusting mechanism 24.

To correct the change in the control system open loop gain due to the change in spot size, first connect the switch 19 to the terminal 19b and set the gain of the compensating element 17 to a low value so that the feedback control system does not oscillate. After that, the received light L is tracked. At this time, the received light L is deflected by the tracking mirror 11, detected by the four-division photoelectric detector 13 via the optical system 12, and converted into an electric signal. Further, this electric signal is input to the tracking error detection unit 14 and the tracking error angle is estimated. This tracking error angle is input to the mirror drive control circuit 20 via the adder 15, the compensation element 17, and the switch 19, and the mirror drive control circuit 20 outputs the tracking error angle and the output of the mirror angle detector 22 to the tracking mirror. 11 is compared, and the tracking mirror 11 is driven from the actuator 21 by feedback control so that the tracking error angle is eliminated.

Next, the command signal generator 18 outputs a direct current signal, and the direct current signal is added to the feedback signal from the tracking error detector 14 in the adder 15 so that the center of the spot is the four-division photoelectric detector 13. The received light L is tracked by feedback control so that the light is incident on a position that is changed by a small amount from the center. Tracking mirror 1 at this time
The angle A of 1 and the output signal a of the tracking error detection unit 14 are input to a memory unit (not shown).

Further, the command signal generator 18 inverts the polarity of the DC signal to be output, and the spot is incident on the position where the center of the spot is changed from the center of the four-division photoelectric detector 13 by a minute amount in the opposite direction to the above case. After doing so, let it track. Similarly, the angle B of the tracking mirror 11 and the output signal b of the tracking error detection unit 14 at this time are input to the memory unit.

Here, if K is a coefficient for converting the angle change amount of the tracking mirror into the angle amount of the reception beam, |
a−b | / (K · | A−B |) represents the sum of the gains of the optical system 12, the four-division photoelectric detector 13, and the tracking error detection unit 14 in the transmission distance between the used devices.
This value is compared with the sum of the reference gains calculated in advance from the optimum open loop gain, the difference is canceled out, and the gain of the compensating element 17 is adjusted so that the open loop gain becomes the optimum value. Calculate with 16.

In use, the DC signal from the command signal generator 18 is changed to 0, and the gain of the correction element 17 is changed to the value calculated by the above-mentioned calibration calculator 16 to perform automatic tracking. In this way, even if the transmission distance changes and the sum of the gains of the four-division photoelectric detector 13 and the tracking error detector 14 changes, the open loop gain of the control system can be maintained at an optimum value.

In FIG. 1, the tracking system for the received light is shown only for one axis, but in reality the angles of the two axes can be controlled so that two-dimensional control can be performed.

FIG. 2 is a block diagram of the second embodiment.
The same reference numerals as in FIG. The output of the calibration calculator 16 is connected to the actuator 31 that drives the optical system 12.

First, as in the first embodiment, | ab |
The value of / (K · | AB |) is calculated. This value represents the sum of the gains of the optical system 12, the four-division photoelectric detector 13, and the tracking error detection unit 14 in the spot size, and this value and the reference gain calculated in advance from the optimum spot size. Are compared, and the optical system 12 is driven using the actuator 31 so that they are equalized by feedback control.

In use, the DC signal of the command signal generator 18 is set to 0, and the spot is tracked so that the center of the spot is incident on the center of the four-division photoelectric detector 13. In this way, even if the transmission distance changes and the spot size on the four-division photoelectric detector 13 changes, the spot size can be automatically adjusted to the optimum value.

Although the optical system 12 is moved to change the defocus amount in the second embodiment, the optical system 1
The same effect can be obtained by moving the 4-division photoelectric detector 13 instead of 2.

[0024]

As described above, in the light beam automatic tracking device according to the first invention, the distance from the communication partner or the measuring point to the light beam automatic tracking device is changed by calculating the compensation element gain by the control unit. Even in such a case, since the open loop gain of the control system can be maintained at an optimum value, it is possible to prevent deterioration of the automatic tracking control characteristic and always perform optimal automatic tracking of the light beam.

In the light beam automatic tracking device according to the second aspect of the invention, the distance from the communication partner or the measuring point to the light beam automatic tracking device is changed by adjusting the distance between the four-division photoelectric detector and the optical system. Even in such a case, the spot size of the received light incident on the four-division photoelectric detector can be maintained at the optimum value, so that the deterioration of the automatic tracking control characteristic is prevented and the automatic light beam automatic tracking is always performed. be able to.

[Brief description of drawings]

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

FIG. 2 is a configuration diagram of a second embodiment.

FIG. 3 is a block diagram of a conventional example.

FIG. 4 is a graph showing a relationship between a tracking error angle and an output signal of a tracking error angle detector.

[Explanation of symbols]

 11 tracking mirror 12 optical system 13 four-division photoelectric detector 14 tracking error detector 15 adder 16 calibration calculator 17 compensation element 18 command signal generator 19 switch 20 mirror drive control circuit 21 actuator 22 mirror angle detector 23 control Part 24 Light beam adjusting mechanism 31 Actuator

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location G05D 3/00 M 9179-3H

Claims (2)

[Claims] 1. A light beam angle adjuster for adjusting received light, and a signal 4 for outputting a signal corresponding to an incident angle of the received light.
A divided photoelectric detector, an optical system for condensing the received light on the four-divided photoelectric detector, a signal from the four-divided photoelectric detector is processed, and a command signal is output to the light beam angle adjuster. In a light beam automatic tracking device including a control unit, a tracking mirror is changed by a small angle in a tracking state, the control unit detects a gain change of the 4-division photoelectric detector, and the 4-division photoelectric detection is performed by a compensation element. Optical beam automatic tracking device characterized by compensating for gain changes in the device. 2. A light beam angle adjuster for adjusting an angle of received light, a four-division photoelectric detector for outputting a signal corresponding to an incident angle of the received light, and the received light on the four-division photoelectric detector. In the light beam automatic tracking device comprising an optical system for condensing the light beam and a control unit for processing a signal from the four-division photoelectric detector and outputting a command signal to the light beam angle adjuster, An actuator that changes the distance between the detector and the optical system is provided, the tracking mirror is changed by a small angle in the tracking state, and the control unit makes the spot size of the received light incident on the four-division photoelectric detector constant. An optical beam automatic tracking device which controls the actuator as described above.