JPH07118679B2 - Automatic collimation type optical receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic collimation type optical receiver, and more particularly to an automatic collimation type optical device including a collimation servo device for collimating an optical axis of an objective lens and a partner station. It is the most suitable one using a data communication device and an automatic collimation type distance measuring device (lightwave distance meter).

[Outline of Invention]

An inductance circuit is connected to the current supply side of a 4-quadrant light receiving element that receives the servo light for automatic collimation, and an optical data signal having a modulation frequency higher than that of the servo light is output from the light receiving element and separated from the servo signal to form an inductance circuit. It is an automatic collimation type optical receiving device that is designed to be taken out from.

[Conventional technology]

In civil engineering, harbor construction, coastal construction, etc., there is a demand for a system that measures the position or distance of a moving body such as a bulltozer, dredger, or work platform from a fixed position.

Conventionally, a light-wave distance system is provided at one of the fixed position and the moving body, and a reflector (corner cube prism, etc.) is provided at the other side to make the optical axes coincide with each other, and the moving body such as the platform is swayed. There is known a system capable of performing position measurement without trouble even when it is moved (for example, Japanese Utility Model Publication No. 59-8221).

A known automatic collimation type optical wave range finder has an optical axis for collimation servo parallel to the range finder and collimates the collimation servo light from the measurement point into four divided light receiving elements (the light receiving surface is divided into horizontal and vertical four quadrants). It is equipped with a servo system that receives the divided photo diodes, etc.), feeds back the output to horizontal and vertical swing motors, and connects the servo light to the origin of the light receiving element.

Since the distance measurement data by the range finder is used on the side of the sill, the range finder is usually placed on the side of the stool and the reflector is placed on the land side.

When a corner cube prism is used as a reflector, the emitted light path and the reflected light path between the rangefinder and the reflector do not change at all even if the optical axis of the prism changes by about 30 °. Therefore, if the corner cube prism is placed on the stool side and the rangefinder is placed on land, stable distance measurement can be performed without being affected by the pitching or rolling of the ship. However, in this case, the distance measurement data on the land side must be transmitted to the sill side.

Further, it is necessary to transmit measurement data, weather condition correction data such as temperature, atmospheric pressure, etc. from the sill side to land or vice versa.
Further, when the work device such as the platform is unmanned, the command data for the position control and work control calculated based on the position measurement value must be transmitted to the unmanned device.

As described above, a data transmission system is indispensable in an advanced marine work system, but for this reason, it is very expensive to provide a communication path and a transmitting / receiving device exclusively. Therefore, it is possible to use the optical path for collimation servo as an optical data communication path.

[Problems to be solved by the invention]

When the objective lens is shared by the servo light and the data light, it is necessary to divide the optical axis reaching each light receiving portion by using a semi-transparent mirror or the like, and the long distance performance deteriorates due to insertion loss. For this reason, it is conceivable to separate the data signal from the output of the 4-quadrant light receiving element for servo by a filter or the like. However, when the incident light and the optical axis of the objective lens are deviated from each other, such as before the start of the collimation servo, no light may be incident on one of the four quadrants of the light receiving element or the output may be substantially zero.
Therefore, even in such a state, in order to secure the optical data reception path, it is necessary to extract the optical data signal from the signal obtained by adding the outputs of all four quadrants.

However, the reception circuit (narrowband amplifier, level detector, etc.) of the 4-quadrant light receiving element for the servo signal modulated at about 5 KHz has a poor phase characteristic for an optical data signal of about 5 MHz, and has a 4-quadrant output. The addition easily causes a data error. In order to sufficiently improve the phase characteristics of the narrow band amplifier and the level detector, a very expensive circuit is required. The present invention has been made in consideration of this problem.
Without being affected by the phase characteristics of the quadrant servo signal receiving circuit,
It is an object of the present invention to obtain a collimation servo signal and an optical data signal separately.

[Means for solving problems]

The automatic collimation type optical receiving device of the present invention includes a light receiving element which is arranged on the optical axis of the objective lens and derives the output of four quadrants representing either the up, down, left or right direction of the image forming point of the incident collimation servo light. Prepare

Based on the output of the light receiving element, the collimation servo device for directing the optical axis of the objective lens to the partner station is operated.

An inductance circuit having low impedance with respect to the modulation frequency of the collimation servo light is connected to the current supply terminal of the light receiving element.

The data signal corresponding to the transmission data light having a modulation frequency higher than the modulation frequency of the collimation servo light is obtained from the receiving circuit connected to the inductance circuit.

[Action]

The sum of four quadrant servo signals flows through the current supply terminal of the light receiving element. Therefore, even if one of the four quadrant outputs becomes zero depending on the position of the servo optical axis, the sum current of the four quadrant outputs continues to flow as long as light is incident. Therefore, even if the collimation servo system is disturbed, the optical data reception path is secured.

Since the inductance circuit has a low impedance with respect to the modulation frequency of the collimated servo light, the photoelectric conversion characteristic of the servo light does not change even if the inductance circuit is inserted into the power feed line of the light receiving element. On the other hand, the impedance of the inductance circuit becomes large with respect to the modulation frequency of the data light, and the voltage drop thereof allows the data signal to be separated from the servo signal and taken out.

〔Example〕

FIG. 1 is an overall block diagram of an optical range finder system for marine operations showing an embodiment of the present invention, and FIGS. 2 and 3 are front views of range finder devices of a land station and a siding station. Each station has a base 1
An automatic collimation device 2 provided above is provided, and a parallel optical axis is formed with each collimation device 2, and a lightwave range finder 3 is provided at the land station, and a reflector 4 is provided at the base station. The optical distance meter 3 includes an objective lens 5 (transmission / reception lens), and the reflector 4 includes a corner cube prism 6.

The collimation device 2 includes a horizontal arm 7 rotatable in a horizontal plane and a vertical arm 8 rotatable in a vertical plane, and is driven by an X-axis gear motor 9 and a Y-axis gear motor 10, respectively. A light transmitting / receiving unit 11 including a light transmitting lens 12 and a light receiving lens 13 is mounted on the vertical arm 8. A light emitting element 14 such as an LED is arranged at the focal point of the light transmitting lens 12, and the light receiving lens 13
A light receiving element 15 such as a photodiode is arranged at the focal point of. In addition, the light transmitting / receiving unit 11 of the land station and the base station have exactly the same optical system.

The light receiving lens 13 has a relatively large diameter, and a plurality of light transmitting lenses 12 are annularly arranged along a concentric circle around the light receiving lens 13.
Therefore, weak transmitted light from a very distant place can be condensed with high sensitivity by the large-diameter light receiving lens 13. Further, by transmitting light from a large number of small-diameter light transmitting lenses 12, the amount of light transmitted can be easily increased. Therefore, it is possible to transmit and receive light over a considerable distance with a relatively compact optical system.

The light transmitting lenses 12 are divided into a group for servo and a group for data transmission. In FIG. 1, the sine wave output (5 kHz) of the oscillator 18 is supplied via the drive circuit 19 to the light emitting elements 14 arranged at the respective focal points of the servo light transmitting lens 12. As a result, the AM-modulated collimating servo light enters the light-receiving lens 13 of the collimation optical system on the side of the ship through the light-sending lens 12, and forms an image on the light-receiving element 15 arranged at the focal point.

On the other hand, from the light emitting element 14 in the light transmitting / receiving unit 11 on the stool side, collimated servo light similarly AM-modulated is emitted toward the land station through the light transmitting lens 12, and passes through the light receiving lens 13 of the land station. The light is received by the light receiving element 15.

The collimating servo light sent from the light transmitting / receiving unit 11 of the land station to the base station is reflected by the reflector 4 of the base station and returns to the light receiving system of the time station to become an interference signal of the servo system. To prevent this, change the AM modulation frequency of the collimation servo light of the
It is set to 3 kHz, which is different from the AM modulation frequency of 5 kHz for land stations. The terrestrial station servo system selects the frequency of the received servo signal as described later, responds only to the servo light (3 kHz) from the base station, and eliminates the interference due to the return light (5 kHz) of the own station.

The light receiving element 15 may be, for example, a two-dimensional (XY plane) semiconductor position detecting element that detects the position of the light spot from the origin. This device has a structure in which four electrodes (two pairs of X and Y) are provided on the four sides of a photodiode having a rectangular light receiving surface, and the charge generated at the position where the light spot hits reaches each electrode as a photocurrent. The voltage is divided by the resistance layer of the light-receiving surface in inverse proportion to the distance of and is taken out from each electrode.

In FIG. 1, the output of each electrode of the light receiving element 15 is frequency-selected (tuned to 3 kHz) by a tuning circuit 20 including a tuning transformer 20a and a tuning capacitor 20b, passes through amplifiers 21a-d, and is detected by detectors 22a-d. Synchronous detection is performed and converted into a DC level signal having a level value corresponding to the light receiving position. The detection outputs of the four stations are converted into digital values by the A / D converter 23 as position detection signals for up and down (U, D) and left and right (L, R), and then stored in the system controller 24 via the bus 24. Incorporated into the microprocessor.

In the microprocessor, the XY coordinate position of the light receiving spot on the light receiving surface of the light receiving element 15 is calculated from the position detection data of U, D, L and R. System controller 25
Derives drive pulses to the motor drive circuits 26X, 26Y for each axis based on this coordinate position data, and the X-axis,
The Y-axis gear motors 9 and 10 are driven, respectively. Light receiving element 15
The servo loop from the motor 9 to the motors 9 and 10 operates so that the light receiving spot of the light receiving element 15 is located at the origin of the XY coordinates of the light receiving surface. When the servo is effective, the collimation optical system optical axes of the land station and the base station coincide with each other. As a result, the optical axis of the optical distance meter 3 of the land station is correctly directed to the reflector 4 of the base station, and measurement refusal is possible.

Since a similar collimation servo system is provided in the base station, the two opposing stations collimate each other.

Means for finely adjusting the direction of the optical axis of the collimation device 2 of each station is provided. In Fig. 1, this fine adjustment means is a joystick.
However, a fine adjustment knob may be provided in the gear system of each of the X-Y axis motors 9 and 10. The voltage output corresponding to the operation of the joystick 27 in the X and Y directions is sent to the system controller 25 via the A / D converter 28, and the controller 25
A fine adjustment drive pulse is derived from the motor drive circuits 26X and 26Y to finely move the motors 9 and 10. Therefore, for example, the operator operates the joystick 27 while looking through the collimation telescope of the optical distance meter 3 to collimate the partner station. When the start button of the servo is pressed when the collimation is completed, the collimation servo described above is started, and thereafter, automatic collimation that follows the fluctuation and movement of the platform is performed.

The deviation of the optical axis and the like detected by the light receiving element are displayed by the display 29 connected to the bus 24 of the system controller 25. The display 29 is, for example, a CRT, and the spot 29a in the XY coordinate display shows the deviation from the origin of the X axis (horizontal direction) and the Y axis (vertical direction). CRT bar display 2
9b shows the total light receiving level (light receiving intensity) of the light receiving element 15.

When the circuit section 30 of the optical distance meter 3 is operated in the collimation state, the transmitting / receiving unit 31 placed at the focus position of the objective lens 5 transmits the distance measuring light of about 15 MHz (AM) and the reflected light from the measuring point. Is received. The phase difference between the transmitted light and the received light is measured by the circuit unit 31, and the inter-station distance is calculated based on the measured phase difference. The distance data is transferred to the system controller 25 via the interface 32 and the bus 24, and further sent to the base station via the modem 33.

The light-transmitting optical path and the light-receiving optical path for automatic collimation between the land station and the base station are also used as bidirectional optical communication paths. That is, the output from the transmission terminal S of the modem 33 is introduced into the FM modulator 34 and the carrier of 5.5 MHz is FM-modulated with the transmission data. The FM output is the light emitting element 1 for transmission via the drive circuit 35.
Given to 4 '. The transmission data light from the light emitting element 14 'is sent to the base station through the light transmitting lens 12.

On the other hand, the base station is provided with a similar modem 33, transmitting light emitting element 14 ', etc., and transmits the transmission data light on the servo light receiving optical path of the land station. At this time, for the same reason as the collimation servo system described above, the FM carrier of the transmitted light from the base station is changed.
5MHz, carrier frequency of data transmitted from land station
Different from 5.5MHz. This eliminates the self-crosstalk on the side of the land station due to the existence of the reflected optical path of the rangefinder 3. The transmission data from the base station is physical condition correction data for distance measurement such as atmospheric pressure and temperature.

The data light sent from the base station is received by the light receiving element 15 together with the servo light through the light receiving lens 13. The data signal is separated from the servo signal and taken out from the anode of the planar photodiode forming the light receiving element 15. A current is supplied to the anode A of the planar photodiode from the power supply line provided with the decoupling capacitor 36 through the primary winding 37a of the transformer 37. When the inductance of the primary winding 37a is set to about 1 μH, the impedance is 0.03Ω or less for the servo signal of 5 KHz, and the insertion loss can be ignored. Therefore, the decoupling capacitor 36
Therefore, the direct current that is not modulated by the servo frequency can be supplied to the anode A of the light receiving element 15.

On the other hand, for an FM data signal of 5MHz, the impedance of the primary winding 37a is about 30Ω, and the insertion loss is 2Ω.
It can be taken out from the next winding 37b. The extracted data signal is led to the FM demodulator 40 via the amplifier 39. As mentioned above, in order to eliminate the self-crosstalk of the transmission data signal of 5.5MHz, the tuning capacitor 3 is attached to the secondary winding 37b of the transformer 37.
8 are combined and tuned to the received data signal of 5 MHz.

When the servo system malfunctions or the servo starts,
Servo light may be significantly deviated from the optical axis on the light receiving element 15 in the four quadrants, and one to three of the four quadrant outputs may become substantially zero. Even in such a case, the data signal can be obtained from the transformer 37 connected to the anode of the light receiving element 15 without any trouble.

FIG. 4A shows a four-quadrant photodiode 43 that can be used as the light receiving element 15 of FIG. The photodiode 43 has elements 43a to 43d that are vertically divided into four parts, left and right, and a light reception signal corresponding to the shift of the image forming point of the servo light can be obtained from each element. Also in the case of this photodiode 43, if the image formation point is largely deviated from the origin, one output of the four quadrants may remain and the other outputs may become zero.

Therefore, as shown in FIG. 4B, four elements 43a-4
The 3d cathode is connected in common, the primary winding 37a of the transformer 37 is inserted into the power supply line connected to the cathode, and the optical data signal is obtained from the secondary winding 37b via the amplifier 29.
The servo signal is taken out through a tuning circuit including a tuning transformer 20a and a tuning capacitor 20b inserted between the anodes of the elements 43a to 45d and the ground.

FIG. 5 shows a modification of the light receiving circuit portion of FIG. In this example, a current is supplied to the anode A of the light receiving element 15 through the inductance element 44. This inductance element 44
Is about 300 for an optical data signal of 5MHz at 10μH.
It becomes an impedance of Ω. Therefore, if a high input impedance amplifier such as FET 46 is connected to the anode A via the coupling capacitor 45, the data signal can be extracted.

On the other hand, the inductance element 44 has a low impedance of about 0.3Ω for a 5 KHz servo signal. Therefore, as in FIG. 1, the servo signal is sent from each cathode to the tuning circuit 20,
It can be obtained via the amplifiers 21a to 21d.

FIG. 6 shows a reference embodiment, in which a servo signal is taken out from each of the four quadrant electrodes of the planar photodiode type light emitting element 15 through the tuning circuit 20 and the amplifiers 21a to 21d, and the output line of one electrode is output. Insert the primary winding 47a of the transformer 47 into
An optical data signal is obtained from one end of the secondary winding 47b through an amplifier 48. Since the primary impedance of the transformer 47 is set sufficiently low with respect to the servo signal frequency, the servo signal and the data signal can be separated and taken out from the output of the light receiving element 15 even in this configuration.

Assuming that the distance from the origin of the light receiving element 15 to the opposing electrodes 15a and 15b is L (distance between the electrodes 2L) and the distance from the origin to the image forming point of the incident light is x, the cathode current from each electrode 15a and 15b. Is I _a + I _b = I _o (I _o is photocurrent). Therefore, when the position x of the image forming point is largely deviated to the side of the voltage 15b, x≈L, and the output current from the electrode 15a becomes zero. Therefore, in the configuration shown in FIG. 6, a data signal may not be obtained.

〔The invention's effect〕

As described above, the present invention connects the current supply terminal of the collimation servo light-receiving element 15 to the inductance circuit showing a high impedance for the received signal of the transmission data light having a high modulation frequency, and extracts the data signal. Therefore, even if the position of the image forming point on the light receiving surface is deviated to any of the four image output, it is possible to obtain the data signal without any trouble based on the combined current of the four quadrants flowing in the inductance circuit. it can. Further, since the inductance circuit exhibits a low impedance with respect to the modulation frequency of the collimated servo light, it does not hinder the current supplied to the light receiving element, and therefore the light receiving sensitivity for the servo light does not decrease. Therefore, it is possible to configure a simple automatic collimation type optical receiver in which one objective lens and one light receiving element are shared by the collimation servo optical system and the optical data optical system.

[Brief description of drawings]

FIG. 1 is an overall block diagram of an optical range finder system for marine operations showing one embodiment of the present invention, and FIGS. 2 and 3 are front views of range finder devices of a land station and a ship station, respectively. FIG. 4A is a diagram of a light receiving surface of a 4-quadrant photodiode used as a light receiving element, FIG. 4B is a circuit diagram of a light receiving circuit, and FIG.
FIG. 6 is a circuit diagram of a light receiving circuit when a quadrant planar photodiode is used, and FIG. 6 is a circuit diagram showing a reference example of the light receiving circuit. In the reference numerals used in the drawings, 2 ... Automatic collimation device 3 ... Optical distance meter 4 ... Reflector 5 ... Objective lens 6 ... Corner cube prism 7 ... Horizontal arm 8 ... Vertical arm 9 …… X-axis gear motor 10 …… Y-axis gear motor 11 …… Transmitting and receiving unit 12 …… Sending lens 13 …… Receiving lens 14 …… Light emitting element 15 …… Light receiving element 18 …… Oscillator 33 …… Modem 34 …… FM modulator 37 …… Transformer 40 …… FM demodulator 43 …… Photodiode 44 …… Inductance element.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norio Numazawa 315-1 Miwamachi, Machida-shi, Tokyo Inside Optec Co., Ltd. (72) Inventor Koichi Hayashi 315-1 Miwamachi, Machida-shi, Tokyo Inside Optec Co., Ltd. ( 72) Inventor Misao Machida 315-1 Miwamachi, Machida-shi, Tokyo Within Optec Co., Ltd. (72) Inventor Keiyo Kusumoto 315-1 Miwamachi, Machida-shi, Tokyo Within Intec Co. (72) Inventor Harumichi Sekikawa 315-1 Miwamachi, Machida, Tokyo (56) References JP-A-58-48540 (JP, A) JP-A-63-35030 (JP, A)

Claims (1)

[Claims] 1. A light-receiving element which is arranged on the optical axis of an objective lens and which derives outputs of four quadrants that represent shifts of image points of incident collimating servo light in vertical and horizontal directions, and an output of the light-receiving element. A collimation servo device for collimating the optical axis of the objective lens to the other station based on the above, and an inductance circuit connected to the current supply terminal of the light receiving element and exhibiting low impedance with respect to the modulation frequency of the collimation servo light. And a receiving circuit connected to the inductance circuit to obtain a data signal corresponding to transmission data light having a modulation frequency higher than the modulation frequency of the collimation servo light.