JP2000147122A - Light-wave distance meter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make reliably and accurately measurable distance by a planar-type galvano mirror as a light path changeover means. SOLUTION: When a light path is changed by a galvano mirror 3 so that light deflected by the planar-type galvano mirror 3 enters an optical fiber 5, the light passes only through a reference light path to a beam splitter 11, and a reference pulse beam enters a photo detector 13. On the other hand, when the light path is changed so that the light deflected by the planar-type galvano mirror 3 enters optical fiber 6, the light passes merely through a range-finding optical path. A distance-measuring means 14 obtains distance to an object to be measured according to the reception time deference between a reference pulse light signal and a reception pulse light signal passing through the range- finding light path. The galvano mirror 3 is used as a light path changeover means, thus eliminating a malfunction of a light path changeover shutter, extremely speedily changing the light path, quickly finding range for a number of times, and hence outputting the average value as a range-finding value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lightwave distance measuring apparatus, and more particularly to a lightwave distance measuring apparatus having a novel configuration in which a part of the optical system is constituted by small and lightweight optical elements.

[0002]

2. Description of the Related Art A lightwave distance measuring device transmits a laser beam, receives the laser beam reflected by a measuring object and returns, and
The distance is measured based on the phase and delay time of the received laser light. FIG. 6 is a block diagram showing a conventional lightwave distance measuring apparatus for measuring a distance based on the delay time of the received laser light. In FIG. 6, pulse laser light generated by a laser diode 101 as a light source is applied to a relay lens 10.
At 2, the beam becomes a parallel beam and enters the beam splitter 103. The beam splitter 103 splits the pulse laser light into transmitted light and reflected light.

[0003] The transmitted light transmitted through the beam splitter 103 passes through the position of an optical path switching shutter 104, is condensed by a relay lens 105, is incident on an optical fiber 106, passes therethrough, and becomes a parallel beam by a relay lens 109. The light is attenuated to a predetermined amount by a light attenuating filter 110, condensed by a relay lens 112 via a beam splitter 111, and is received as a reference pulse light by a light receiving element 113.
Incident on. The light receiving element 113 outputs a signal corresponding to the amount of incident reference pulse light to the distance measuring unit 114.

The optical path from the beam splitter 103 to the beam splitter 111 via the optical fiber 106 is a reference optical path. Then, when the optical path switching shutter 104 is switched to open the reference optical path side (at this time, the distance measuring optical path side described later is closed), the reference pulse light passing through this reference optical path enters the light receiving element 113. The transmittance of the light amount attenuation filter 110 is adjusted at the time of assembly so that the amount of light incident on the light receiving element 113 from the reference optical path is attenuated to a predetermined value.

On the other hand, the reflected light reflected by the beam splitter 103 passes through the position of the optical path switching shutter 104, is condensed by the relay lens 115, and is condensed by the optical fiber 11.
6 and passes through it to form a beam splitter 119.
The light is reflected by a mirror-coated surface 120 near the optical axis, reflected by a dichroic mirror 121, and transmitted from the objective lens 123 to a measurement object (not shown) as transmission pulse light.

The pulse light returned from the object to be measured is received by the objective lens 123 and becomes a received pulse light. The received pulse light is reflected by the dichroic mirror 121, passes through a portion of the surface 120 of the beam splitter 119 other than the mirror, and passes through the optical fiber 124 and the relay lens 12.
5. The light enters the beam splitter 111 via the light amount adjustment filter 126. Then, the beam splitter 111
Is reflected by the lens 112 and is collected by the light receiving element 1.
13 is incident.

The path from the beam splitter 103 to the objective lens 123 is a transmission optical path of a distance measuring optical path, and the path from the objective lens 123 to the light receiving element 113 via the beam splitter 111 is a receiving optical path of the distance measuring optical path. is there.
The light receiving element 113 outputs to the distance measuring means 114 a signal corresponding to the amount of incident pulse light received. The reception pulse light enters the light receiving element 113 when the optical path switching shutter 104 is switched to open the distance measurement optical path side. Then, the distance measuring means 114 obtains a distance to the measurement object from a time difference between the signal based on the reference pulse light and the signal based on the received pulse light.

More specifically, a plurality of reference optical paths and a plurality of distance measuring optical paths, for example,
The signals from the 000 pulsed lights are obtained, and the distance to the object to be measured is determined based on the difference between the time averages of the respective signals. By taking the average value of a plurality of times, the influence of disturbance such as the fluctuation of the air in the distance measuring optical path is reduced, and the difference between the value of the reference optical path and the value of the distance measuring optical path is used for the lightwave distance measuring apparatus. Errors due to internal temperature changes are eliminated.

Prior to the distance measurement, an object to be measured is measured by an eyepiece lens 127 and a reticle 12 by a measurer.
8. Observed through a collimating optical system including an erecting prism 129, a focusing lens 122, and an objective lens 123, the focusing lens 122 is adjusted in the X direction and focused.
The reticle 128 and the end face of the optical fiber 124 are located at optically equivalent positions.

Further, the amount of the received pulse light incident on the light receiving element 113 via the receiving optical path side of the distance measuring optical path is determined by the amount of the reference pulse light incident on the light receiving element 113 via the reference optical path in order to secure the accuracy of distance measurement. The light amount is adjusted by the light amount adjustment filter 126 so as to be at the same level as the light amount. Light intensity adjustment filter 1
Reference numeral 26 denotes a circular filter whose optical density continuously changes in the circumferential direction. The circular filter 26 is rotated by a motor 130 having a rotation axis fixed at the center of the light amount adjustment filter 126 to adjust the transmittance of the received pulse light.

[0011]

However, since the conventional apparatus uses a motor to operate the optical path switching shutter, a malfunction of the optical path switching shutter due to a failure of the motor easily occurs, and the reliability is reduced. There was a problem of lowering. Furthermore, since a plurality of values of the reference optical path and the value of the distance measuring optical path are sequentially obtained, a time lag occurs between the acquisition of the value of the reference optical path and the value of the distance measuring optical path in a short time, and particularly high measurement values are obtained. If you need distance accuracy,
If the distance measurement is performed while the lightwave distance measuring device is in a thermal transient state, there is a problem that an error is likely to occur.

It is an object of the present invention to solve this problem and to provide a light-wave distance measuring device which has high reliability and can measure a distance with high accuracy.

[0013]

According to the present invention, there is provided an optical path switching means for switching light from a light source to one of a distance measuring optical path and a reference optical path; A light transmission / reception system that transmits reflected light from the measurement object and sends the reflected light from the measurement object to the reception light path of the distance measurement light path, and light from the distance measurement light path or the reference light path. Light receiving means for receiving light and converting it to an electric signal, and distance measuring means for obtaining a distance to a measurement object from a relationship between light from the distance measuring optical path and light from the reference optical path received by the light receiving means. In the optical distance measuring apparatus, the optical path switching means is constituted by any of a planar galvanomirror, an acousto-optic device, and a tuning fork in which a light source is fixed to one long portion.

In the lightwave distance measuring device, the distance measuring means determines a distance to an object to be measured from a relationship between light from the distance measuring light path received by the light receiving means and light from the reference light path. The distance processing is performed a plurality of times, and an average value of the distances to the plurality of measured objects is calculated.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. However, the technical scope of the present invention is not limited to the embodiment. FIG. 1 is a diagram showing a configuration of a lightwave distance measuring apparatus according to a first embodiment of the present invention. In FIG. 1, a pulse laser beam generated by a laser diode 1 as a light source is converted into a parallel beam by a relay lens 2 and is incident on a planar galvano mirror 3 as an optical path switching unit. Light incident on the planar galvano mirror 3 is reflected, deflected, and condensed by the relay lens 4.

The planar type galvanometer mirror 3 is either in a first state in which the deflected and condensed light is incident on the end face 7 of the optical fiber 5 or in a second state in which the light is incident on the end face 8 of the optical fiber 6. Then, the optical path is switched to the optical fiber 5 or 6. Details of the planar galvanomirror 3 and details of the optical path switching by the planar galvanomirror 3 will be described later.

The light incident on the optical fiber 5 from the end face 7 passes through it, becomes a parallel beam by the relay lens 9, attenuates to a predetermined amount of light by the light amount attenuation filter 10, and passes through the beam splitter 11 to the relay lens. The light is condensed at 12, and enters the light receiving element 13 as reference pulse light. The light receiving element 13 outputs a signal corresponding to the amount of incident reference pulse light to the distance measuring means 14.

The optical path from the planar type galvanometer mirror 3 to the beam splitter 11 via the optical fiber 5 is a reference optical path. When the planar galvanomirror 3 switches the optical path so that the light deflected by the planar galvanomirror 3 enters the optical fiber 5, the light passes only through the reference optical path (at this time, a distance measuring optical path side described later). Does not pass through), the reference pulse light passing through this reference optical path enters the light receiving element 13. The transmittance of the light amount attenuation filter 10 is adjusted during assembly so that the amount of light incident on the light receiving element 13 from the reference optical path is attenuated to a predetermined value.

On the other hand, the light that has entered the optical fiber 6 from the end face 8 passes through it, is reflected by the mirror-coated surface 20 near the optical axis of the beam splitter 19, is reflected by the dichroic mirror 21, and is reflected by the objective. The light is transmitted from the lens 23 to a measurement object (not shown) as transmission pulse light. The pulse light reflected back from the measurement object is received by the objective lens 23 and becomes a received pulse light.
The received pulse light is reflected by the dichroic mirror 21, passes through a portion of the surface 20 of the beam splitter 19 other than the mirror, and passes through the optical fiber 24 and the relay lens 2.
5. The light enters the beam splitter 11 via the light amount adjustment filter 26. Then, the light reflected by the beam splitter 11 is condensed by the lens 12 and enters the light receiving element 13.

The optical path from the planar type galvanometer mirror 3 to the objective lens 23 is a transmission optical path of a distance measuring optical path, and the optical path from the objective lens 23 via the beam splitter 11 to the light receiving element 13 is a distance measuring optical path. Is the receiving optical path. The light receiving element 13 outputs to the distance measuring means 14 a signal corresponding to the amount of the incident reception pulse light. When the planar galvanomirror 3 switches the optical path so that the received pulsed light enters the light receiving element 13 and the light deflected by the planar galvanomirror 3 enters the optical fiber 6, only the distance measuring optical path is used. Light passes (at this time, light does not pass on the reference optical path side).

The distance measuring means 14 calculates the distance to the object from the time difference between the signal based on the reference pulse light and the signal based on the received pulse light. Prior to the distance measurement, the object to be measured is observed by a measurer through a collimating optical system including an eyepiece 27, a reticle 28, an erect prism 29, a focusing lens 22, and an objective lens 23. 22 is adjusted in the X direction and focused. The reticle 28 and the end face of the optical fiber 24 on the side of the beam splitter 19 are located at optically equivalent positions.

Further, the amount of the received pulse light that enters the light receiving element 13 via the receiving optical path side of the distance measuring optical path is determined by the amount of the reference pulse light that enters the light receiving element 13 via the reference optical path in order to ensure the accuracy of distance measurement. The light amount is adjusted by the light amount adjustment filter 26 so as to be at the same level as the light amount. The light amount adjustment filter 26 is a circular filter whose optical density continuously changes in the circumferential direction. The light amount adjustment filter 26 is rotated by a motor 30 having a rotation axis fixed at the center of the light amount adjustment filter 26 to reduce the transmittance of the received pulse light. adjust.

The distance measuring means 14 is constituted by arithmetic means such as a CPU. The arithmetic means is also used as a control means, and outputs a control command to a driver for controlling the state of the planar galvanomirror 3 and a driver for a motor 30 for rotating the light quantity adjusting filter 26, thereby outputting the planar galvanomirror 3 and the light quantity adjusting filter 26. Is a predetermined state or position.

Here, a planar type galvano mirror will be described. Planar type galvanometer mirrors are disclosed in
It is a known optical element described in -175005. FIG. 2 is a plan view of the planar galvanometer mirror 3. The planar galvanomirror is a silicon substrate 5
1, a flat movable plate 54, and a torsion bar 55 that pivotally supports the movable plate 54 on the silicon substrate 51, and these are integrally formed. A planar coil 56 that generates a magnetic field when energized is provided at a peripheral portion of an upper surface of the movable plate 54, and a total reflection mirror 57 is provided at a central portion of the upper surface surrounded by the planar coil 56. Reference numeral 58 denotes an electrode for energizing the planar coil 56. Further, a glass substrate 52 is provided on both left and right ends of the upper surface of the silicon substrate 51, and a glass substrate 53 is provided on the entire lower surface.
A permanent magnet (not shown) for applying a magnetic field to the planar coil 56 is fixed at a predetermined position of No. 3.

The principle of operation is that a magnetic field generated when an electric current is applied to the plane coil 56 acts on a magnetic field formed across the plane coil 56 by the permanent magnet (not shown) to generate a Lorentz force. The movable plate 54 rotates around the torsion bar 55 as a rotation axis. Total reflection mirror 57
Is a first state when the plane coil 56 is not energized, or a second state when the plane coil 56 is energized and rotated by a predetermined angle from the first state. The energization and non-energization of the planar coil 56 are controlled by a command signal from a calculation means as the control means.

Next, the operation of the planar galvanomirror 3 as an optical path switching means will be described with reference to FIGS. 3 (a) and 3 (b). FIG. 3A shows a state in which the planar coil 56 is in the first state in which the current is not supplied, and the light deflected by the planar galvanomirror 3 is condensed by the relay lens 4 and is incident on the end face 7 of the optical fiber 5. I have. FIG. 3B shows that the plane coil 56 is in the second state of energization, and the deflected light is condensed by the relay lens 4 and is incident on the end face 8 of the optical fiber 6. That is, the planar galvanomirror 3 switches the light from the relay lens 2 to either the reference optical path or the distance measuring optical path. Note that the movable plate 54 rotates in the θ1 direction in the figure.

In the lightwave distance measuring apparatus of the first embodiment, the planar type galvanometer mirror 3 is used instead of the conventional motor for switching between the reference optical path and the distance measuring optical path. Defects are eliminated and reliability is improved. Further, since a semiconductor element manufacturing process is used for manufacturing a planar galvanomirror, the productivity is high and the manufacturing cost of the device is reduced.

The switching between the reference optical path and the distance measuring optical path by the planar galvanomirror 3 can be performed at a much higher speed than a conventional motor-driven shutter. Therefore, the arithmetic means as the control means makes the switching between the reference optical path and the distance measuring optical path continuously performed a plurality of times, and combines the light from the plural sets of reference optical paths and the light from the distance measuring optical path that are temporally adjacent to each other. From the relationship, a plurality of distances to the object to be measured are obtained, and an average value of the plurality of obtained distances is obtained as a distance measurement value. Each of the light from the temporally adjacent reference light path and the light from the distance measuring light path is an average of the light emitted by the laser diode 1 for a plurality of successive light emission operations, for example, ten light emission operations, each time the light path is switched. For example, a value for calculating the average of 100 average values obtained by switching the optical path 100 times may be used.

The adjustment of the amount of incident light from the light receiving optical path to the light receiving element 13 by the light amount adjusting filter 26 also requires the same high speed as in the optical path switching, but instead of the light amount adjusting filter 26 driven by the motor, It can be realized by using an element whose transmittance is changed by an electric signal, for example, a liquid crystal element, or an optical branching element that variably controls a refractive index of an optical waveguide formed on a substrate by an electric signal to change a light branching ratio. .

Since the time lag between the light from the reference optical path and the light from the distance measuring optical path combined to determine the distance to the object to be measured is extremely small, the thermal change inside the lightwave distance measuring apparatus during that time is also small. . As a result, distance measurement with higher accuracy becomes possible. Further, even if the lightwave distance measuring device is in a thermal transient state, its influence can be minimized. FIG.
FIG. 8 is a diagram illustrating an optical path switching portion inside a lightwave distance measuring apparatus according to a second embodiment of the present invention. The lightwave distance measuring device according to the second embodiment is a modification of the lightwave distance measuring device according to the first embodiment. The lightwave distance measuring device according to the first embodiment is shown in FIG. Only the optical path switching means is different.
In FIG. 4, the same components as those of the lightwave distance measuring apparatus according to the first embodiment are denoted by the same reference numerals, and the description is simplified or omitted.

In the lightwave distance measuring apparatus according to the second embodiment,
An acousto-optic device 31 was used as the optical path switching means instead of the planar galvano mirror 3 of the first embodiment. In the lightwave distance measuring apparatus according to the present embodiment, the pulse laser light generated by the laser diode 1 as the light source is converted into a parallel beam by the relay lens 2 and enters the acousto-optic element 31. The acousto-optic element is a known optical element and is used as an optical deflector.

In FIG. 4, an electric signal is applied from an oscillator 32 to a transducer 33 so that an ultrasonic wave propagates in the acousto-optic element 31. Then, a refractive index modulation type grating is formed in the acousto-optic element 31, and the incident light is diffracted. Assuming that the angle of this diffraction is θ2, the oscillator 3
2 is diffracted in the direction of θ2 = fλ / v with respect to the driving frequency f of the electric signal from the light source 2. Here, v is the speed of sound propagating in the acousto-optic element.

The driving frequency f of the electric signal from the transmitter 32
Can be changed by a command signal from the arithmetic means as the control means. That is, the driving frequency f
, The diffraction angle θ2 can be changed, the incidence of light on the optical fiber 5 or the optical fiber 6 can be switched, and the reference optical path and the distance measuring optical path can be switched.

As described above, the other configuration is the same as that of the first embodiment, and the distance measuring operation is the same as that of the lightwave distance measuring apparatus of the first embodiment, and therefore the description is omitted. Second
In the lightwave distance measuring apparatus of this embodiment, the conventional optical path switching shutter driven by a motor is replaced with an acousto-optic element, so that the operation failure of the optical path switching shutter due to the failure of the motor is eliminated, and the reliability is improved.

The acousto-optic device 31 of the present embodiment can also switch between the reference optical path and the distance measuring optical path at a high speed, so that the distance measurement with high accuracy can be performed in the same manner as in the first embodiment. The effects of thermal transients can be minimized. FIG. 5 is a diagram showing an optical path switching portion of a lightwave distance measuring apparatus according to a third embodiment of the present invention. The lightwave distance measuring device of the third embodiment is a modification of the lightwave distance measuring device of the first embodiment, and is different from the lightwave distance measuring device of the first embodiment only in the portion shown in FIG. Are different. In FIG. 5, the same components as those of the lightwave distance measuring apparatus according to the first embodiment are denoted by the same reference numerals, and the description is simplified or omitted.

In the lightwave distance measuring apparatus according to the third embodiment,
As the optical path switching means, a tuning fork 38 on which the light source 1 is fixed is used instead of the planar galvano mirror 3 of the first embodiment. In the lightwave distance measuring device according to the third embodiment, a laser diode 1 as a light source is attached to the tip of one long portion of a U-shaped tuning fork 38. The laser diode 1 is caused to vibrate in a direction perpendicular to the optical axis (Y direction in the drawing) by the vibration of the tuning fork 38. At the side of the tip of the other long portion of the tuning fork 38, the tuning fork 3
A solenoid 40 for oscillating 8 is provided. A signal is given to the solenoid 40 from the tuning fork vibration control circuit 41, and the solenoid 40 is controlled so that the amplitude of the vibration of the tuning fork 38 becomes constant.

The pulse laser light generated by the laser diode 1 is condensed by a lens 39. Due to the vibration of the tuning fork 38, the position of the focal point on the optical fiber side (left side of the lens 39 in FIG. 5) by the lens 39 changes, and the optical fiber 5
Alternatively, the incidence of light on the optical fiber 6 is periodically switched, so that the reference optical path and the distance measuring optical path can be switched.
The other configuration is the same as that of the first embodiment, and the distance measuring operation is the same as that of the lightwave distance measuring apparatus of the first embodiment, so that the description will be omitted.

In the lightwave distance measuring apparatus according to the third embodiment, the conventional optical path switching shutter driven by the motor is replaced by the tuning fork 38 in which the light source 1 is fixed. Operation failure is eliminated, and the reliability is improved. The tuning fork 38 to which the light source 1 of the present embodiment is fixed can also switch between the reference optical path and the distance measuring optical path at a high speed, so that measurement can be performed with high accuracy in the same manner as in the first embodiment. The effects of distance and thermal transients can be minimized.

In the first to third embodiments, the description has been given of the lightwave distance measuring device for measuring the distance by time delay. However, the lightwave distance measuring device of the present invention is the lightwave distance measuring device for performing the distance measurement by phase. Applicable to devices. In the first to third embodiments, a laser diode is used as the light source 1, but a light emitting diode may be used.

[Brief description of the drawings]

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

FIG. 2 is a plan view of a planar galvano mirror of the lightwave distance measuring apparatus of FIG. 1;

FIG. 3 is a diagram showing an optical path switching portion of the lightwave distance measuring device in FIG. 1;

FIG. 4 is a diagram showing an optical path switching portion of a lightwave distance measuring apparatus according to a second embodiment of the present invention.

FIG. 5 is a diagram showing an optical path switching portion of a lightwave distance measuring apparatus according to a third embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional lightwave distance measuring device.

[Explanation of symbols]

1, 101 laser diode 3 planar mirror mirror 5, 6, 24, 106, 116, 124 optical fiber 7, 8 end face of optical fiber 13, 36, 43, 113 Light receiving element 14, 114 Distance measuring means 23, 123 Objective lens 31 Acousto-optic element 32 Oscillator 33 Transducer 38 Tuning fork 39 Lens 40 Solenoid 41: Tuning fork vibration control circuit 54: Movable plate 55: Torsion bar 56: Flat coil

Claims (4)

[Claims] An optical path switching means for switching light from a light source to one of a distance measuring optical path and a reference optical path; and transmitting light from a transmission optical path of the distance measuring optical path to the object to be measured and the object to be measured. A transmission / reception optical system that receives reflected light from the optical path and sends it to a receiving optical path of the distance measuring optical path; light receiving means for receiving light from the distance measuring optical path or light from the reference optical path and converting the light into an electric signal; A light-wave distance measuring device having a distance measuring means for obtaining a distance to an object to be measured from a relationship between light from the distance measuring light path received by the light receiving means and light from the reference light path, wherein the light path switching means is a planar type. An electro-optical distance measuring device comprising a galvanomirror. 2. An optical path switching means for switching light from a light source to one of a distance measuring optical path and a reference optical path; and transmitting light from a transmitting optical path of the distance measuring optical path to the object to be measured and the object to be measured. A transmission / reception optical system that receives reflected light from the optical path and sends it to a receiving optical path of the distance measuring optical path; a light receiving unit that receives light from the distance measuring optical path or light from the reference optical path and converts the light into an electric signal; A distance measuring means for obtaining a distance to a measurement object from a relationship between light from the distance measuring light path and light from the reference light path received by the means, wherein the optical path switching means is an acousto-optical element A lightwave distance measuring device comprising: 3. A light source; an optical path switching means for switching light from the light source to one of a distance measuring optical path and a reference optical path; and transmitting light from a transmitting optical path of the distance measuring optical path to an object to be measured, A transmission / reception optical system that receives reflected light from the object to be measured and sends the reflected light to a reception optical path of the distance measurement optical path; and a light receiving unit that receives light from the distance measurement optical path or light from the reference optical path and converts the light into an electric signal. A light-wave distance measuring device, comprising: a distance measuring unit that obtains a distance to an object to be measured from a relationship between light from the distance measuring optical path received by the light receiving unit and light from the reference optical path; Is a tuning fork, and the light source is fixed to one long side of the tuning fork. 4. The lightwave distance measuring device according to claim 1, wherein said distance measuring means is configured to detect a difference between light from said distance measuring optical path received by said light receiving means and light from said reference optical path. A lightwave distance measuring apparatus, wherein distance measurement processing for obtaining a distance to a measurement target from a relationship is performed a plurality of times, and an average value of the calculated distances to the plurality of measurement targets is obtained.