JPH0712936A - Range finder using light wave - Google Patents

Abstract

PURPOSE:To provide a range finder which uses light waves and can perform highly accurate measurement by canceling distance measuring bias errors caused by temperature variation, etc. CONSTITUTION:A range finder using light waves is constituted of a signal generator 2 which outputs modulated signals of a fixed frequency, optical transmitter 3 which outputs linearly polarized light, polarization controller 5 which switches the polarizing direction of incident light to P- or S-polarized light, polarization beam splitter 6 which transmits the light from the controller 5 when the light is P-polarized light and reflects the light in the direction perpendicular to the incident direction when the light is S-polarized light, corner-cube reflector 7 installed to a measuring point, another corner-cube reflector 8 which is set in the range finder and forms an internal calibrating optical path, optical receiver 10 which converts the light condensed through a condenser lens 9 into electric signals, and phase difference measuring instrument 11 which measures the phase difference between the output signals of the signal generator 2 and optical receiver 10.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical distance measuring device,
In particular, the present invention relates to an optical distance measuring device that measures a distance from the phase difference between a transmission signal and a reception signal.

[0002]

2. Description of the Related Art A conventional lightwave distance measuring apparatus of this type is a light output from an optical transmitter 3 with a modulated signal of a constant frequency output from a signal generator 2 in the lightwave distance measuring apparatus 1 as shown in FIG. Is intensity-modulated, and the intensity-modulated light is converted into a required beam width by the light projecting lens 4, and then sent to the corner cube reflector 7 placed at the measurement point through the beam splitter 12.

The reflected light from the corner cube reflector 7 returns to the light wave distance measuring device 1, and a part of the light is reflected by the beam splitter 12, and then the optical receiver 10 is received by the condenser lens 9.
Is focused on. In the optical receiver 10, the optical signal is converted into an electric signal having the same frequency as the signal output by the signal generator 2 and sent to the phase difference measuring device 11.

The phase difference measuring device 11 measures the phase difference between the output signal from the signal generator 2 and the output signal from the optical receiver 10, and uses the phase difference measuring device 1 and the corner cube reflector 7 to determine the phase difference. Seeking the distance between.

[0005]

In this conventional lightwave distance measuring apparatus, the signal delay time caused by the temperature change in the optical transmitter 3, the optical receiver 10 and the phase difference measuring device 11 causes
There is a drawback in that a distance measurement bias error occurs and accurate measurement cannot be performed.

Further, in order to perform accurate measurement, it is necessary to calibrate at a known distance in advance and then perform the measurement. Therefore, there are problems that the measurement is complicated and real-time measurement cannot be performed. It was

An object of the present invention is to provide an optical wave distance measuring device which solves the above drawbacks and problems.

[0008]

An optical wave distance measuring apparatus according to the present invention includes an optical transmitter that outputs linearly polarized light, and the polarization direction of light emitted from this optical transmitter is either P-polarized light or S-polarized light. A polarization controller for switching, a polarization beam splitter for transmitting P-polarized light and reflecting for S-polarized light in a direction perpendicular to the incident direction, and a corner cube reflector forming an internal calibration optical path are provided.

Further, in the optical distance measuring device of the present invention, after guiding the light emitted from the optical transmitter by the optical fiber, any one of the two optical fibers forming a part of the two optical paths by the optical bypass switch. One of the two optical paths is used as an internal calibration optical path in which the optical path length is accurately calibrated.

[0010]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention. The lightwave distance measuring apparatus 1 of the present embodiment converts a signal generator 2 that outputs a modulated signal of a constant frequency, an optical transmitter 3 that outputs linearly polarized light, and an output light of the optical transmitter 3 into a required beam width. The projection lens 4, the polarization controller 5 for switching the polarization direction of the incident light to either P or S polarization, and the light exiting the polarization controller 5 is transmitted when it is P polarization and is transmitted when it is S polarization. A polarization beam splitter 6 that reflects in the direction orthogonal to the incident direction, a corner cube reflector 8 that is placed inside the optical distance measuring device to form an internal calibration optical path, and the light condensed by the condenser lens 9 is converted into an electric signal. It is composed of an optical receiver 10 and a phase difference measuring device 11 for measuring the phase difference between the output signal of the signal generator 2 and the output signal of the optical receiver 10.

A corner cube reflector 7 is installed at the measuring point.

Next, the operation of this embodiment will be described.

Light emitted from the optical transmitter 3 is in a linearly polarized state, and is intensity-modulated by a signal of a constant frequency output from the signal generator 2. The intensity-modulated light is converted into a required beam width by the light projecting lens 4 and then enters the polarization controller 5.

The polarization controller 5 arbitrarily switches the polarization direction of the incident beam to either P-polarized light or S-polarized light and sends it to the polarization beam splitter 6.

In the polarization beam splitter 6, the incident light is P
In the case of polarized light, it is transmitted, and in the case of S polarized light, it is reflected in the direction perpendicular to the incident direction.

At the time of distance measurement, P-polarized light is selected as the light emitted from the polarization controller 5, passes through the polarization beam splitter 6, and is emitted toward the corner cube reflector 7 placed at the measurement point.

The light reflected by the corner cube reflector 7 becomes non-linearly polarized light and returns to the light wave distance measuring device 1. After being partially reflected by the polarization beam splitter 6 at a right angle to the incident direction, a condenser lens is provided. It is focused on the optical receiver 10 by 9.

The optical receiver 10 converts the intensity-modulated light into an electric signal having the same frequency as that of the intensity-modulated light and outputs the electric signal to the phase difference measuring device 11.

The phase difference measuring device 11 receives the signal output from the signal generator 2 and the signal output from the optical receiver 10,
The phase difference between the two signals is measured to obtain the distance between the lightwave distance measuring device 1 and the corner cube reflector 7.

Next, at the time of calibration, the output light of the polarization controller 5 is selected as S-polarized light, reflected by the polarization beam splitter 6 in the direction perpendicular to the incident direction, and placed on the internal calibration optical path. Go to 8.

The light reflected by the corner cube reflector 8 becomes non-linearly polarized light, returns to the polarization beam splitter 6, and a part of the light is transmitted. Converted to a signal.

In the phase difference measuring device 11, the phase difference between the output signal of the signal generator 2 and the output signal of the optical receiver 10 is measured, and then the optical path length of the internal calibration optical path is obtained.

Now, the measured value of the distance from the lightwave distance measuring device 1 to the corner cube reflector 7 is R _m , the true value of the distance is R _o , the optical path length inside the lightwave distance measuring device at the time of distance measurement is R _i ,
The measurement error caused by the temperature change of the signal delay time in the optical transmitter 3, the optical receiver 10, and the phase difference measuring device 11 is ΔR.
Then, the true value R _{o of the} distance is given by R _o = R _m −R _i −ΔR.

On the other hand, if the measured value of the optical path length at the time of internal calibration is L _m and the true value is L _o , ΔR is given by ΔR = L _m −L _o , and the true value R _{o of the} distance is R _o = R _m −R _i − (L _m −L _o ), the distance measurement error ΔR caused by the temperature change of the signal delay time should be canceled by using the internal calibration optical path whose optical path length is accurately calibrated. You can

As described above, the present embodiment has an optical transmitter that outputs linearly polarized light, and a polarization controller that switches the polarization direction of light emitted from the optical transmitter to either P-polarized light or S-polarized light. A polarization beam splitter and a corner cube reflector that forms an internal calibration optical path are used, and by switching the polarization direction of the light by a polarization controller, the light is switched to the internal calibration optical path side. High accuracy because the calibration of the error of the distance measurement value due to the temperature change of the signal delay time in the electric circuit such as the phase difference measuring device can be performed in real time by using the internal calibration optical path whose optical path length is accurately determined in advance. It becomes possible to measure.

FIG. 2 is a block diagram showing another embodiment of the present invention. The lightwave distance measuring apparatus 1 according to the present embodiment includes a signal generator 2
The optical transmitter 3 that emits light modulated by a signal of a constant frequency that is output from the optical transmitter 3 and the emitted light of the optical transmitter 3 that is guided by the optical fiber 13 or the optical fiber 14 that forms a part of the measurement optical path. An optical bypass switch 16 for switching and connecting to either one of the optical fibers 15 forming a part of the internal calibration optical path, and light projecting lenses 4 and 17 for converting the light emitted from the optical fibers 14 and 15 into a required beam width. , A beam splitter 12 for splitting the light into two, and an optical receiver 10 for converting the light condensed by the condenser lens 9 into an electric signal.
And a phase difference measuring device 11 for measuring the phase difference between the output signal of the signal generator 2 and the output signal of the optical receiver 10.

A corner cube reflector 7 is installed at the measuring point.

Next, the operation of this embodiment will be described.

The emitted light of the optical transmitter 3 whose intensity is modulated by the signal of the constant frequency output from the signal generator 2 is guided to the optical fiber 13 and enters the optical bypass switch 16. In the optical bypass switch 16, the port A or the port B is arbitrarily selected and connected to either the optical fiber 14 forming a part of the measurement optical path or the optical fiber 15 forming a part of the internal calibration optical path. .

When measuring the distance, first, the port A is selected, the light passing through the optical fiber 14 is converted into a required beam width by the light projecting lens 4, and the beam splitter 12 is used.
The light transmitted through is transmitted to the corner cube reflector 7 installed at the measurement point. The light reflected by the corner cube reflector 7 returns to the lightwave distance measuring apparatus 1, the light reflected by the beam splitter 12 is condensed by the condenser lens 9, and enters the optical receiver 10.

The optical receiver 10 converts the modulated light into an electric signal having the same frequency as that of the modulated light and outputs the electric signal to the phase difference measuring device 11.

The phase difference measuring device 11 receives the signal output from the signal generator 2 and the signal output from the optical receiver 10,
The distance between the lightwave distance measuring device 1 and the corner cube reflector 7 is measured from the phase difference between the two signals.

Next, the port B of the optical bypass switch 16 is selected for calibration of the distance measurement value, and the light passing through the internal calibration optical fiber 15 is converted into a required beam width by the light projecting lens 17. After passing through the beam splitter 12 and condensed by the condenser lens 9, it enters the optical receiver 10 and is converted into an electric signal.

The output signal of the optical receiver 10 is the phase difference measuring device 1
1, the phase comparison with the output signal from the signal generator 2 is performed, and the optical path length of the internal calibration optical path is measured from the phase difference.

As in the embodiment of FIG. 1, the measured value of the distance from the lightwave distance measuring device 1 to the corner cube reflector 7 is R _m , the true value of the distance is R _o , and the measurement optical path length inside the lightwave distance measuring device is Assuming that the distance measurement error caused by the temperature fluctuation of the signal delay time in R ′, the optical transmitter 3, the optical receiver 10 and the phase difference measuring device 11 is ΔR, the true value of the distance R _o is R _o = R _m −R It is given by'-ΔR. On the other hand, assuming that the measured value of the optical path length of the internal calibration optical path is L _m and the true value is L _o , ΔR is given by ΔR = L _m −L _o , and thus the true value R _{o of the} distance is R _o = R _m -R '- can be calculated by (L _m -L _o), ranging error ΔR resulting from the temperature variation of the signal delay time can be canceled using the internal calibration optical path optical path length is precisely calibrated .

As described above, in the present embodiment, the optical bypass switch is switched at an arbitrary time, so that the signal delay time in an electric circuit such as an optical transmitter, an optical receiver and a phase difference measuring device is caused by a temperature change. Since the error in the distance measurement value can be calibrated in real time by using the internal calibration optical path whose optical path length is accurately determined in advance, highly accurate measurement is possible. In addition, the use of the optical fiber and the optical bypass switch has an effect that the degree of freedom of the device configuration is improved.

[0038]

As described above, according to the lightwave distance measuring apparatus of the present invention, the distance measuring bias error due to temperature fluctuation or the like is canceled, and highly accurate measurement is provided.

[Brief description of drawings]

FIG. 1 is a block diagram showing a lightwave distance measuring apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a lightwave distance measuring apparatus according to another embodiment of the present invention.

FIG. 3 is a block diagram showing an example of a conventional optical path distance measuring device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Optical distance measuring device 2 Signal generator 3 Optical transmitter 4,17 Projection lens 5 Polarization controller 6 Polarization beam splitter 7, 8 Corner cube reflector 9 Condensing lens 10 Optical receiver 11 Phase difference measuring device 12 Beam splitter 13 , 14, 15 Optical fiber 16 Optical bypass switch

Claims (4)

[Claims] 1. An optical transmitter that outputs linearly polarized light, a polarization controller that switches the polarization direction of outgoing light of the optical transmitter to either the P direction or the S direction, a polarization beam splitter, and internal calibration. A lightwave distance measuring device having a corner cube reflector forming an optical path, wherein the light is switched to an internal calibration optical path side by switching the polarization direction of the light by the polarization controller. 2. A signal generator that outputs a modulated signal of a constant frequency, an optical transmitter that outputs linearly polarized light, a light projecting lens that converts the light emitted from the optical transmitter into a required beam width, and a light projecting lens. A polarization controller that switches the polarization direction of the outgoing light to either P or S polarization, and the light that exits the polarization controller is transmitted in the case of P polarization and reflected in the direction perpendicular to the incident direction in the case of S polarization. A polarizing beam splitter, a corner cube reflector that forms an internal calibration optical path, a condenser lens that collects the light from the polarizing beam splitter, and an optical receiver that converts the light condensed by the condenser lens into an electrical signal. And a phase difference measuring device that measures a phase difference between the output signal of the signal generator and the output signal of the optical receiver. 3. The light emitted from the optical transmitter is guided by an optical fiber and then selectively switched to one of two optical fibers forming a part of two optical paths by an optical bypass switch. An optical distance measuring device having a structure for connection and using one of two optical paths as an internal calibration optical path whose optical path length is accurately calibrated. 4. An optical transmitter for emitting light modulated by a signal of a constant frequency output from a signal generator, and emitted light of the optical transmitter guided by a first optical fiber,
An optical bypass switch for switching and connecting to either the second optical fiber forming part of the measurement optical path or the third optical fiber forming part of the internal calibration optical path, the second optical fiber and the third optical fiber. Two lenses that convert the light emitted from the optical fiber to the required beam width, a beam splitter that splits the light into two, a condenser lens that collects the light from the beam splitter, and a light that is condensed by the condenser lens. An optical wave distance measuring device comprising: an optical receiver for converting the signal into an electric signal; and a phase difference measuring device for measuring a phase difference between the output signal of the signal generator and the output signal of the optical receiver.