JPH0735856A - Optical range finder - Google Patents

Abstract

PURPOSE:To facilitate assemblage of a light emitting means, on objective lens, a light receiving element, etc., while reducing the size thereof. CONSTITUTION:Means 3 for projecting a laser beam 22 to a target 25 and an objective lens 6 for condensing the laser beam 23 reflected on the target 25 are aligned with a first axis 20. A light receiving element 8 is disposed on a second axis and receives the returning laser beam 23 reflected on a plane mirror 7. In this regard, a separator 5 is disposed on the first axis 20 in order to guide the projected laser beam 22 only to the outside. When an infrared laser beam is projected, means for projecting an aiming beam is disposed while being aligned with the first axis 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical distance meter for measuring the distance to a target using a semiconductor or gas laser, LED (light emitting diode), SLD (super luminescent diode) or the like.

[0002]

2. Description of the Related Art An optical distance meter for measuring the distance to a target by the phase difference of modulated light is disclosed in US Pat. No. 3,619,058.
JP-A-47-32852, JP-A-55-1190
82, JP-A-57-3063, and JP-A-60-212.
No. 380 to 211382 and Japanese Patent Application No. 2-305571. These optical distance meters form a calibration optical path of a predetermined length inside, and calibrate the external measurement value up to the target object with the measurement value by this calibration optical path to improve the measurement accuracy.

Conventionally, in most light wave rangefinders, a light emitting unit for projecting modulated light onto a target object and a light receiving unit for receiving modulated light reflected from the target object are laterally juxtaposed to each other for the convenience of providing a calibration optical path. The optical axes of the light emitting and light receiving units are separated so that they intersect at the target. In another optical distance meter, the light emitting and receiving units are arranged in front and back so as to share an optical axis or are arranged to face each other by using a plurality of beam splitters, prisms or objective lenses.

[0004]

A conventional light-wave rangefinder having separate light-emitting and light-receiving optical axes is disclosed in, for example, JP-A-47-32.
As shown in No. 852, miniaturization is difficult. That is, the light-receiving unit needs a large-aperture objective lens that takes up space, while a small-aperture objective lens is sufficient for the light-emitting unit, but since a calibration optical path is formed in front of the light-receiving and light-emitting elements, The distance from the unit must be separated by the radius of the large-aperture objective lens. Therefore, this type of optical distance meter requires a larger-diameter objective lens as the light-receiving sensitivity is increased, and it becomes larger and more difficult to carry.

Further, in a light-wave distance meter that shares an optical axis, as shown in, for example, US Pat. No. 3,619,058, the light reflected on the inner surface of a beam splitter or an objective lens is erroneously recognized as externally reflected light by a target object. May be

The present invention solves the above-mentioned problems, can miniaturize the optical distance meter to the extent that it can be easily carried, and can eliminate the influence of the disturbance light reflected by the beam splitter or the objective lens to perform a quick distance measurement. An object is to provide a lightwave rangefinder.

[0007]

SUMMARY OF THE INVENTION An optical distance meter according to the present invention comprises a light emitting means for projecting outward light onto a target object along a first axis, and a front side of the light emitting means for aligning with the first axis. And the objective lens for collecting the backward light reflected by the target object, and the objective lens arranged in alignment with the first axis between the objective lens and the light emitting means, A plane mirror that reflects the backward light along the second axis, a light-receiving element that is disposed on the second axis and receives the backward light from the plane mirror, and the first mirror between the plane mirror and the objective lens. And a separator that is aligned with the first axis and guides the outward light.

Another optical distance meter according to the present invention is, instead of the above-mentioned objective lens and plane mirror, aligned with the first axis line to collect the return path light reflected by the target object and to have the second axis line. It has a concave mirror that reflects along. A separator that is aligned with the first axis and allows the outward light to pass therethrough passes through the concave mirror.

When the outgoing light is infrared light, visible light projection means for aiming visible light onto the target object along the first axis is further arranged. Therefore, the infrared light and the visible light are a beam splitter arranged on the front side of the light emitting means, for example, a cold mirror that transmits the infrared outward light and reflects visible light, or reflects the infrared outward light and is visible. Combined by a cold filter that transmits light.

It is preferable that the separating body is a cylindrical member which is arranged so as to penetrate through the plane mirror and further penetrate through the objective lens and whose outer peripheral surface is coated with a light absorbing material. The light emitting means is a semiconductor laser that emits laser light, a light emitting diode or a super luminescent diode.

The beam splitter, for example, the cold mirror or the cold filter is arranged so as to split a part of the outgoing light into calibration light, and is arranged between the plane mirror or the concave mirror and the outgoing light and the calibration light. A shutter means for switching between light and light at a predetermined time ratio is arranged.

In this shutter means, a substantially C-shaped elongated hole is formed at the passing position of the forward light and a rotatable disc having an opening formed at the passing position of the calibration light, or the shutter is driven by an electric signal. It includes a liquid crystal shutter that switches the forward light and the calibration light at a predetermined time ratio.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a lightwave distance meter according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment of a lightwave rangefinder 1 according to the present invention.
In the embodiment, the case 2 and the shutter plate 9 are partially cross-sectioned. In this lightwave distance meter 1, the forward laser beam 22 modulated by the light emitting means 3 at, for example, 150 kHz or 15 MHz is projected onto the target 25 along the first axis 20. The light emitting means 3 is arranged in alignment with the first axis line on the front side of the semiconductor laser 31 which emits a coherent laser beam of 640 nm wavelength, and makes the laser beam a parallel beam of about 3 mmφ. And a collimating lens 32.

On the other hand, the return laser beam 23 reflected by the target 25 is condensed by the objective lens 6 aligned with the first axis 20, and the condensed return laser beam 23 is collected by the plane mirror 7.
Is reflected along the second axis 21 at
The light receiving element 8 arranged above receives light. Further, between the plane mirror 7 and the light receiving element 8, a circular ND filter holding plate 33 for adjusting the light quantity of the returning laser beam is arranged.

A center of the holding plate 33 is axially supported by the case 2, and a plurality of circular holes are formed around the holding plate 33 at equal intervals. Except for one hole, an ND filter having a density of, for example, 2 times or 4 times is sequentially attached to each hole. Therefore, grooves are formed in the peripheral portion of the holding plate 33 so as to correspond to the holes. On the other hand, one end of a leaf spring is fixed to the case 2, and the leaf spring is arranged so that the protrusion near the other end enters one of the grooves. In this holding plate 33, when the peripheral groove is engaged with the other end of the leaf spring and the angular position of the holding plate 33 is temporarily fixed, the return path laser light reflected by the plane mirror 7 passes through the filter hole. Arranged to do so.

In addition, the holding plate 33 has knurls formed in its peripheral portion, and a part of the peripheral portion projects from the case 2,
It can be rotated with your finger. Alternatively, the holding plate 33 may be angularly driven by a motor (not shown) that is rotatably supported by the output shaft of the reduction mechanism (not shown) and that transmits rotation to the reduction mechanism. In this case, a button for starting the motor, a micro switch that operates when the leaf spring enters the groove, and a control circuit that controls the electric power of the motor are provided.

According to the present invention, the case 2 is provided with the separator 5 for preventing the outward laser beam 22 from being diffusely reflected by the back surface of the objective lens 6 and leaking to the light receiving element 8. This separator 5 is a metal cylindrical member that is aligned with the first axis and guides the outward laser light 22 only to the outside, a high-refractive-index glass cylinder, or a glass cylinder in which metal is vapor-deposited on the cylindrical surface. Contains. Of course, the objective lens 6 has an antireflection film 1
It may be applied or vapor-deposited in layers or multiple layers.

In the first embodiment, the separating body 5 is arranged so as to penetrate the objective lens 6 and the plane mirror 7, respectively. The separating body 5 may penetrate only the plane mirror 7, and the leading annular surface may contact the objective lens 6. Further, the separating body 5 may be arranged such that the leading annular surface and the trailing elliptic annular surface are in contact with the objective lens 6 and the plane mirror, that is, the beam splitter 7, respectively.

Further, a beam splitter (dichroic mirror) 4 forming a calibration optical path of a predetermined length for calibrating the measured value up to the target 25 is arranged between the light emitting means 3 and the rear part of the separating body 5. The beam splitter 4 splits the calibration laser light 24 from the outgoing laser light 22 and causes the light receiving element 8 to receive the calibration laser light 24 via the first and second reflecting mirrors 13 and 14.

Further, a circular shutter plate 9 is arranged between the beam splitter 4 and the separating body 5 and is rotated by a motor 12 in a clockwise direction at a constant angular velocity. The shutter plate 9 has a forward laser beam 22 and a calibration laser beam 2 on it.
The C-shaped long hole and the bracket-shaped sector hole for setting the passage time of No. 4 at a predetermined ratio are coaxially formed, respectively, and the passing time of the forward path and the calibration laser light is measured by an electric circuit (not shown). The index (not shown) to be sent to () is formed in the peripheral portion. This index is detected by, for example, a rice-hole-shaped round hole or a bonded magnet, and a photocoupler or magnetic Hall element.

FIG. 1 shows a state in which the modulated outward laser beam 22 passes through the slot 10 and hits the target 25, and the modulated backward laser beam 23 from the target 25 is received by the light receiving element 8. On the other hand, the modulated calibration laser light 24 is blocked by the shutter plate 9. In this state, the phase difference between the output modulated wave supplied to the light emitting means 3 and the input modulated wave obtained from the light receiving element 8 is measured, for example, 10 times, and the total value of these is averaged and finally converted into a distance. is doing.

In the calibration state, the calibration laser beam 24 passes through the sector hole 11 and reaches the light receiving element 8, and the phase difference between the input and output modulated waves is measured once, so that the measurement error due to the temperature or the atmospheric pressure is eliminated. I am compensating. Further, in order to perform the distance measurement with high accuracy, an external distance measurement time of 10 cycles and a calibration time of 1 cycle are allocated every time the shutter plate 9 makes one rotation. Therefore, the arc angle of the C-shaped long hole for distance measurement provided in the shutter plate 9 is assigned 10: 1 with respect to that of the calibration sector hole. The second reflecting mirror 14 may be omitted and the reflected light from the first reflecting mirror 13 may be directly incident on the light receiving element 8.

2 and 3 are front views of the shutter plate 9 used in the optical distance meter of the first embodiment. In this shutter plate 9, a C-shaped elongated hole 10 is formed at a passing position A of the outward laser beam 22, that is, a radius a, and a sector hole 11 is formed at a passing position B of the calibration laser beam 24, that is, a radius b. . The long hole 10 and the sector hole 11 are used for the shutter plate 9
It is formed by a milling machine such that it is sandwiched between two circles that are coaxially arranged around the rotation axis O, and the arc angles are approximately 300 degrees and 30 degrees.

Further, in the long hole 10 and the sector hole 11, the relative angle between the starting points around the rotation axis O is the first axis, that is, the passing position A of the forward laser light 22 in the plane including the shutter plate 9. , Output shaft of motor 12 and calibration laser light 24
The angle is determined to be the same as the angle AOB according to the passing position B of. The shutter plate 9 rotates clockwise at a constant angular velocity and, as shown in FIG. 2, passes the forward laser beam 22 in the range from the position shown by the solid line to the position shown by the phantom line of the elongated hole 10. Then, the calibration laser beam 24 is cut off during that time.

As shown in FIG. 3, the shutter plate 9 allows the calibration laser beam 24 to pass in the range from the position shown by the solid line to the position shown by the phantom line of the sector hole 11,
Meanwhile, the outward laser beam 22 is blocked.

In the conventional optical distance meter, the shutter plate is intermittently rotated in the clockwise or counterclockwise direction, but in the present invention, the shutter plate 9 is rotated in one direction so that the forward laser beam 22 and the calibration laser beam are rotated. 24 and a predetermined time ratio (for example, 10: 1)
Since it is switched by, the accuracy of the external measurement value can be increased and the calibration measurement value can be quickly calibrated.

FIG. 4 is a partial sectional view showing a second embodiment of the lightwave distance meter 1. In the second embodiment, the first and second prisms 15 and 17 are used as means for splitting the outward laser beam 22, and the first and second prisms 15 and 17 are used.
17 are provided with first and second liquid crystal shutters 16 and 18, respectively, and the first and second liquid crystal shutters 16 and 1 are provided by an electric signal.
8 is switched alternately. Therefore, the ratio between the measurement by the forward laser beam 22 and the measurement by the calibration laser beam 24 and the measurement time can be arbitrarily adjusted by the electric signal.
Moreover, since there are no mechanical parts such as a motor and a shutter plate, it is possible to reduce the weight of the optical distance meter 1 without impairing reliability.

In FIG. 4, the light emitting means 3, the objective lens 6, the light receiving element 8 and the like, which have the same structure as in the first embodiment, are designated by the same reference numerals as those in the first embodiment, and the description thereof is omitted. Omit it.

FIG. 5 is a partial cross-sectional view showing a third embodiment of the lightwave distance meter 1. In the third embodiment, the returning laser beam 23 is condensed and reflected by the light receiving element 8 by one concave mirror 19. Therefore, according to the third embodiment, an expensive and relatively heavy objective lens can be omitted, and weight reduction and cost reduction can be achieved.

In the third embodiment, the shutter plate 9 similar to that in the first embodiment is used as the shutter means, but the shutter means in which the prism and the liquid crystal shutter of the second embodiment are combined is used. It can also be applied. Also,
In FIG. 5, the light emitting means 3, the objective lens 6, the light receiving element 8 and the like, which have exactly the same configuration as the first embodiment, are the same as the first embodiment.
The same reference numerals as those in the embodiment of FIG.

In the light wave rangefinders of the first to third embodiments, the light emitting means 3 is a semiconductor laser of visible light.
Unique optical pumping etc. appear in this semiconductor laser,
This causes measurement drift. That is, the distance value changes with the passage of time. Although this drift can be ignored in the normal measurement field, it cannot be ignored in the high-precision measurement field, and products with higher accuracy are required.

FIG. 6 is a partial cross-sectional view showing a fourth embodiment of the lightwave distance meter 1. In the fourth embodiment, an LED (light emitting diode), particularly a recently developed ultra-high brightness SLD (super luminescent diode) is used as the light emitting means 3 for distance measurement. The SLD has a more stable luminous intensity than the semiconductor laser, has the advantages of both the semiconductor laser and the LED, and can produce parallel light of about 3 mmφ, like the semiconductor laser.

However, this SLD emits infrared rays having a wavelength of 850 nm, and unfortunately, no product having a visible light wavelength has been developed yet. Therefore, a normal visible light semiconductor laser is required for aiming the target. That is, the outward light from the light emitting means 3 having the SLD and the collimating lens is emitted through the cold mirror 4. The cold mirror 4 has a catalog transmission loss of about 20% at a wavelength of 850 nm, but the actual transmission loss is about 10 to 15%.

A semiconductor laser 40 for emitting visible light for aiming is arranged above the cold mirror 4.
The reflected sighting visible light is aligned with the first axis. Therefore, this aiming visible light is 10 at the cold mirror 4.
It reflects nearly 0% and illuminates the target at the same time as the outward light. The illuminated target is displayed on a telescopic sighting meter built into the lightwave rangefinder.

Instead of the cold mirror which transmits infrared rays, a cold filter which reflects infrared rays can be used. In this case, the semiconductor laser that projects the sighting visible light is arranged on the first axis, and the SLD is arranged above the cold filter with the reflected axis aligned with the first axis. The calibration light uses a small amount of infrared light that passes through the cold filter. The light of the visible light semiconductor laser is reflected by the cold filter and leaks into the calibration optical path and enters the light receiving element, but since it is not modulated, it does not affect the calibration measurement value.

This cold filter is manufactured as an A type having spectral characteristics reverse to those of a cold mirror and having an average visible light transmittance of 85% or more, and a B type having a heat ray absorbing glass substrate. Since the cold filter is almost colorless and does not absorb infrared rays, it does not heat up so much and therefore is less likely to be damaged. The coating consists of a very hard, heat-resistant multilayer film with no absorption.

The optical rangefinder of the present invention has been described above by exemplifying the first to fourth examples. The essential point of the configuration of the optical rangefinder according to the present invention is that the modulated forward laser light is the inner surface of the objective lens. This is to use a separator that prevents the light from being reflected by and leaked to the light receiving element. Although the separator is illustrated as a tubular or cylindrical shape, for example, an optical fiber having a high transmittance core and a high refractive index clad having a diameter of 3 mm, a binding fiber obtained by bundling optical fibers having a thin hair, or a solid glass is used. It may be a cylinder. Further, by providing a light absorbing means (for example, a black film) on the circumferential surface of this separator, it is possible to prevent diffuse reflection of the return path laser light.

A circuit for measuring the distance to the target using laser light and a circuit configuration for calibrating the measured value of the distance to the target using the measured value of the calibration laser light are well known in the art. Since the same circuit configuration as that of the optical distance meter can be applied, the description of the circuit configuration will be omitted.

[0040]

As described above, in the optical distance meter according to the present invention, the backward light reflected from the target object along the same axis as the forward light is condensed by the coaxial objective lens and the plane mirror, and another axial line is collected. By arranging a separating body that reflects only the outward light by reflecting the light in the direction and receiving it by the light receiving element, and between the objective lens and the plane mirror, the outward light is reflected by the objective lens and leaks to the light receiving element. Therefore, the forward light can be reliably collimated and projected onto the target object.

Further, an infrared LED which usually has a large light emission output
Alternatively, since the SLD is used, it is possible to measure a distance to a place aimed by visible light longer than usual, for example, twice or more or with high accuracy, and it is possible to achieve weight reduction and cost reduction at the same time.

In the optical distance meter according to claim 4 or 5, the separator penetrates the plane mirror and further penetrates the objective lens, so that the degree of leakage of the outward light inside the device is extremely reduced. At the same time, the alignment with the plane mirror or the objective lens can be carried out very easily, and the assembly can be carried out very easily.

In the optical distance meter according to the tenth aspect of the present invention, the shutter means sets a predetermined time ratio, for example, the number of times of forward light measurement to 1
Since 0 and that of the calibration light are switched alternately at a ratio of 1, the distance to the target can be measured quickly and accurately.

The shutter plate is rotated at a constant speed, for example, in the clockwise direction by a circular shutter plate having a substantially C-shaped elongated hole formed in the outgoing light passage portion and an opening formed in the calibration light passage portion. , The distance between the forward light and the calibration light is quickly measured in synchronization with this rotation.

Since the liquid crystal shutter means switches the forward light and the calibration light at a predetermined time ratio by an electric signal,
The influence of mechanical vibration is eliminated, and the weight of the optical distance meter can be reduced.

Further, since the concave mirror collects the backward light and reflects it on the light receiving element, an expensive and relatively heavy objective lens can be omitted, and the weight and cost can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic partial sectional view showing a first embodiment of a lightwave distance meter according to the present invention.

FIG. 2 is a plan view showing a rotation range of a shutter plate of the optical distance meter shown in FIG. 1 during measurement.

FIG. 3 is a plan view showing a rotation range of a shutter plate of the optical distance meter shown in FIG. 1 during calibration.

FIG. 4 is a schematic partial cross-sectional view showing a second embodiment of the optical distance meter according to the present invention.

FIG. 5 is a schematic partial cross-sectional view showing a third embodiment of the optical distance meter according to the present invention.

FIG. 6 is a schematic partial sectional view showing a fourth embodiment of the optical distance meter according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lightwave distance meter 3 Light emitting means 5 Separator 6 Objective lens 7 Plane mirror 8 Light receiving element 19 Concave mirror

Claims (17)

[Claims] 1. A light emitting means for projecting outward light onto a target object along a first axis, and a front side of the light emitting means aligned with the first axis and arranged to be reflected by the target object. An objective lens that collects the backward light, and an intermediate lens between the objective lens and the light-emitting means that is aligned with the first axis and reflects the collected backward light along the second axis. A plane mirror, a light receiving element that is arranged on the second axis and receives the backward light from the plane mirror, and is arranged between the plane mirror and the objective lens in alignment with the first axis, A light wave range finder comprising: a separating body that guides the outward light. 2. The outward light is infrared light, and a cold mirror which is arranged in front of the light emitting means and transmits the infrared outward light and reflects visible light, and the visible light reflected by the cold mirror The lightwave rangefinder according to claim 1, further comprising visible light projection means for aiming the object at the target along the first axis. 3. The outward light is infrared light, and a cold filter is provided in front of the light emitting means to reflect the infrared outward light and transmit visible light, and the visible light transmitted through the cold filter. The lightwave rangefinder according to claim 1, further comprising visible light projection means for aiming the object at the target along the first axis. 4. The optical distance meter according to claim 2, wherein the separating body is arranged so as to penetrate the plane mirror. 5. The optical distance meter according to claim 4, wherein the separation body is arranged so as to penetrate the objective lens as well. 6. The optical distance meter according to claim 2 or 3, wherein the separating body is a cylindrical member having an outer peripheral surface coated with a light absorbing material. 7. The lightwave rangefinder according to claim 1, wherein the light emitting means is a laser that emits laser light. 8. The lightwave rangefinder according to claim 2, wherein the light emitting means is a light emitting diode. 9. The optical distance meter according to claim 2, wherein the light emitting means is a super luminescent diode. 10. A beam splitter for dividing a part of the outward light into calibration light is arranged between the light emitting means and the plane mirror, and the forward light and the calibration light are arranged between the beam splitter and the plane mirror. The lightwave rangefinder according to claim 1, further comprising shutter means for switching between and at a predetermined time ratio. 11. The cold mirror is arranged so as to divide a part of the infrared outward light into calibration light, and a predetermined time ratio between the outward light and the calibration light is provided between the cold mirror and the plane mirror. The optical distance meter according to claim 2, further comprising a shutter means for switching by. 12. The cold filter is arranged so as to divide a part of the infrared outgoing light into calibration light, and the cold light and the calibration light are placed at a predetermined time ratio between the cold filter and the plane mirror. The lightwave rangefinder according to claim 3, wherein shutter means for switching by means of is arranged. 13. The shutter means includes a rotatable disc having a substantially C-shaped elongated hole formed at a position where the outward light passes and an opening formed at a position where the calibration light passes.
The lightwave rangefinder according to any one of 1 to 12. 14. The lightwave distance meter according to claim 10, wherein the shutter means includes a liquid crystal shutter that switches the forward light and the calibration light at a predetermined time ratio by an electric signal. 15. A light emitting means for projecting outward light onto a target object along a first axis, and a return light which is aligned with the first axis and is reflected by the target object and a second light. A concave mirror that reflects along an axis, a light-receiving element that is disposed on the second axis and that receives the reflected backward light, a penetrating through the concave mirror and aligned with the first axis, A light-wave rangefinder having a separating body that guides outward light. 16. The outward light is infrared light, and a cold mirror which is disposed in front of the light emitting means and transmits the infrared outward light and reflects visible light, and the visible light reflected by the cold mirror 16. The lightwave rangefinder according to claim 15, further comprising visible light projection means for aiming the object on the target along the first axis. 17. The outward light is infrared light, and a cold filter is provided in front of the light emitting means to reflect the infrared outward light and transmit visible light, and the visible light transmitted through the cold filter. 16. The lightwave rangefinder according to claim 15, further comprising visible light projection means for aiming the object on the target along the first axis.