JP6937568B2 - Laser rangefinder - Google Patents

Description

The present invention relates to a light wave rangefinder that includes a light receiving optical system that receives measurement light reflected by a measurement object and an emission optical system that irradiates the measurement object with measurement light to measure a distance to a target.

The above-mentioned light wave range finder irradiates the object to be measured with measured light in a modulated predetermined wavelength region, receives the reflected light from the object to be measured, and measures from the phase difference between the internal reference light and the received measurement light. Measure the distance to an object.

FIG. 6 is a cross-sectional view showing the configuration of a conventional laser rangefinder. The light wave rangefinder 400 includes an objective lens 410, a prism 420 having two reflecting surfaces, a light source 430, an emission optical system 440, a reflecting mirror 450, a dichroic mirror 460, a collimation optical system 470, and light receiving. It includes an element 480.

The objective lens 410 is composed of three lenses arranged on the optical axis Oa. The prism 420 is arranged on the optical axis Oa behind the objective lens 410, and has two parallel reflecting surfaces forming an angle of 45 degrees with respect to the optical axis Oa, that is, an ejection reflecting surface that reflects the measurement light in the emitting direction. It includes a 421 and a light receiving reflecting surface 422 that reflects the incident measurement light toward the light receiving element 480.

The light source 430 generates light in a predetermined wavelength region. The injection optical system 440 is arranged on an optical axis Ob parallel to the optical axis Oa, and includes a collimeter 441 that makes the light from the light source 430 parallel light, an optical chopper 442 that intermittently blocks the measurement light, and a throttle member 443. To be equipped with. The reflector 450 is arranged on the optical axis Ob at an angle of 45 degrees, changes the direction of the measurement light from the emission optical system 440 by 90 degrees, and faces the ejection reflection surface 421 of the prism 420 along the optical axis Oct. Reflects the measurement light. The measurement light reflected by the ejection reflecting surface 421 is emitted to the object to be measured through the objective lens 410.

The reflected light from the object to be measured passes through the objective lens 410 and reaches the dichroic mirror 460. The dichroic mirror 460 reflects the measurement light in a predetermined wavelength band from the incident light, transmits the other light, and emits it to the collimation optical system 470. The measurement light reflected by the dichroic mirror 460 is reflected by the light receiving reflecting surface 422 of the prism 420 and is incident on the light receiving element 480.

In such a light wave rangefinder, the diaphragm member narrows the light from the light source and is selected according to the light distribution characteristics of the light emitted from the light source. That is, it is selected and installed so that the light from the light source is emitted most efficiently.

Japanese Unexamined Patent Publication No. 2014-149171

In this type of light wave rangefinder, a retrospective prism is placed on the object to be measured and the prism is irradiated with the measurement light for precise measurement, and a non-measurement is performed by directly irradiating the object to be measured with the measurement light. Measurement can be performed in prism mode. Then, in the prism mode, the diaphragm member 443 is used, and in the non-prism mode, the measurement is performed without using the diaphragm member 443. In the non-prism mode, the diaphragm member 443 is moved so as to be removed from the optical axis Ob, and the object to be measured is irradiated with the measurement light having a large luminous flux to perform the measurement.

Therefore, the diaphragm member 443 can rotate the arm member holding the diaphragm member around the axis to arrange the diaphragm member 443 on the optical axis Ob, and the diaphragm member 443 can be removed from the optical axis Ob. .. The opening shape of the diaphragm provided in the diaphragm member 443 is a slit shape formed in the horizontal direction as described above, and the width dimension is, for example, about 0.7 mm. The width dimension of this slit is determined by the balance between the measurement accuracy and the reach of the measurement light, and is generally about the same regardless of the type of device. Conventionally, the diaphragm member 443 is irradiated with the luminous flux from the light source 430 via the collimator 441.

However, the conventional light wave range finder has a problem that the position adjustment of the diaphragm member 443 is complicated. That is, it is necessary to adjust the position of the diaphragm member so that it is accurately arranged on the optical axis Ob so that the light flux from the light source is correctly irradiated in the state of being used in the prism mode at the time of manufacturing. Further, when the light wave rangefinder 400 is used for a long period of time, the arrangement position of the aperture member 443 may shift, and in this case as well, the position of the aperture member 443 must be adjusted.

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a light wave range finder capable of accurately measuring a distance without adjusting the position of a diaphragm member during manufacturing or aged use. do.

In order to solve the above problems, the invention according to claim 1 is a light wave distance meter that measures a distance to an object to be measured by comparing reflected light and internal reference light, and emits a light flux having a predetermined spread. A light source that emits light along an axis, a narrowing member that can be arranged on the optical axis, has a slit opening that extends in the horizontal direction perpendicular to the optical axis, and narrows the spread width of the light flux from the light source. The arm member holding the throttle member and the throttle member are arranged on the optical axis so as to be able to move in and out of the optical axis by rotating the arm member, and are arranged between the light source and the throttle member to obtain the luminous flux. Includes the slit opening and a light flux expanding means that sandwiches the slit opening up and down and emits light into a region having a height dimension that is 15 times or more the height dimension of the slit opening, and is set by the light wave distance meter. The light wave distance meter is characterized in that the amount of light of the light source is set so that the reflected light from the object to be measured at the measured distance becomes equal to or more than a reference value capable of measuring the distance.

The invention according to claim 2 is characterized in that, in the light wave rangefinder according to claim 1, the diaphragm member includes an adjusting member for adjusting the slit opening in the vertical direction.

The invention according to claim 3 is characterized in that, in the light wave rangefinder according to claim 1, the slit opening is fixed in a state in which the slit opening cannot be adjusted in the vertical direction when the diaphragm member is used. do.

The invention according to claim 4 is the light wave rangefinder according to any one of claims 1 to 3, wherein the luminous flux expanding means is a collimating lens.

According to the light wave range finder according to the present invention, distance measurement can be performed accurately without adjusting the position of the diaphragm member during manufacturing or aged use.

That is, according to the light wave distance meter according to claim 1, the luminous flux from the light source is expanded by the luminous flux expanding means, and the height dimension is 15 times or more the height dimension of the slit opening at the position of the aperture member. At the same time as being emitted into the region, the reflected light from the object to be measured at the measurement distance becomes equal to or more than the reference value at which the distance can be measured, and the tolerance for the position change of the slit opening with respect to the optical axis becomes large. Therefore, even if the diaphragm member is mounted on the mounting base without adjusting the position at the time of manufacturing, the mounting position of the slit opening can be kept within the reference. In addition, the change in the position of the diaphragm member due to aging is within the standard. Therefore, it is possible to accurately measure the distance without adjusting the position of the diaphragm member during manufacturing or aged use.

Further, according to the light wave range finder according to claim 2, since the diaphragm member includes an adjusting member for adjusting the slit opening in the vertical direction, the position of the diaphragm member is adjusted when the diaphragm member moves significantly. be able to.

Further, according to the light wave range finder according to claim 3, since the slit opening is fixed in a state where the slit opening cannot be adjusted in the vertical direction when the diaphragm member is used, the mechanism for adjusting the position can be omitted.

According to the light wave range finder according to claim 4, the luminous flux expanding means can be realized by a simple optical element called a collimating lens.

It is a front view which shows the light wave range finder which concerns on embodiment of this invention. It is sectional drawing which shows the same light wave range finder. The optical system of the light wave rangefinder is shown, (a) is a schematic diagram showing a state of measurement light emission, and (b) is a schematic diagram showing a state of internal reference light emission. It is a perspective view of the light wave range finder which shows the structure of the internal mechanism of the light wave range finder. It is a perspective view which shows the arrangement state of the diaphragm member of the light wave range finder. It is sectional drawing which shows the structure of the conventional light wave range finder.

A light wave rangefinder according to a mode for carrying out the present invention will be described.

FIG. 1 is a front view showing a light wave rangefinder according to an embodiment of the present invention. As shown in FIG. 1, in the light wave rangefinder 100 according to the first embodiment, a pedestal 102 is provided on a base portion 101 attached to a tripod (not shown), and the pedestal 102 includes a telescope unit including an optical system. 103 is supported. The base portion 101 has a leveling screw 104, and can be leveled so that the base 102 is horizontal. The gantry 102 is rotatable about the vertical axis, and the telescope unit 103 is rotatable about the horizontal axis. Further, the gantry 102 is provided with an operation input unit 107 having a display unit 106, and the display unit 106 displays a measured value of a distance to a measurement object or the like.

Next, the optical system of the light wave rangefinder 100 will be described. FIG. 2 is a cross-sectional view showing the same light wave rangefinder, FIG. 3 shows the optical system of the same light wave rangefinder, (a) is a schematic view showing a state of measurement light emission, and (b) is an internal reference light emission. It is a schematic diagram which shows the state of.

In the light wave rangefinder 100, a lens barrel 120 and a base portion 130 are formed in the housing 110. Further, as shown in FIG. 2, the light wave distance meter 100 includes an objective lens system 210 which is a light receiving optical system, an injection optical system 220 which emits measurement light to irradiate a measurement object, and an objective lens as an optical system 200. It includes an injection reflection optical system 240 that guides the measurement light from the system 210 to the optical fiber 260. Further, the optical system 200 includes a light receiving and reflecting optical system 250 and a collimation optical system 270. The optical fiber 260 guides the measurement light to the optical sensor 261 (see FIG. 3). The collimation optical system 270 is used to make the image of the object to be measured from the objective lens system 210 visible, and to determine or correct the direction of the laser rangefinder 100.

The base portion 130 is made of a blank material from an alloy mold and has not been post-processed. The dimensional accuracy is, for example, 0.3 mm. Therefore, by forming a mounting portion for each member of the optical system on the base portion 130, the base portion 130 can be arranged in each direction with an accuracy of ± 0.15 mm without adjusting each member.

The objective lens system 210 is arranged in the lens barrel 120, includes a first optical axis O1 directed to the prism 280, which is the object to be measured, and collects light from the object to be measured. The objective lens system 210 includes three lenses, and various aberrations are corrected to provide positive power as a whole. The emission optical system 220 is arranged on the base portion 130, includes a second optical axis O2 parallel to the first optical axis O1, and emits light from the light source 230 as measurement light which is parallel light. The light source 230 is, for example, a laser diode that generates infrared rays.

The emission optical system 220 includes a collimating lens 221 as a means for expanding the luminous flux, a chopper 226 equipped with a trapezoidal prism 225 that intermittently blocks the emission light and extracts the emission light as internal reference light acquired from the light source, and a microcomputer. It is provided with a circular 222 that is controlled by such means to adjust the amount of external luminous flux, a density filter 310 that adjusts the amount of internal reference light by manually setting a rotation position, and a throttle member 224. The density filter 310 is a disk-shaped member having a density gradient on its circumference. Further, the circular 222 is a disk-shaped member provided with a density filter having a density gradient on the circumference for adjusting the amount of light emitted from the measured light, and is rotationally driven by the circular drive motor 223.

The collimating lens 221 makes the luminous flux from the light source 230 a parallel luminous flux having a predetermined spreading dimension. The spread width of the light flux emitted from the collimating lens 221 is set to, for example, 15 mm as the diameter d of the diaphragm member 224. The diameter d of the luminous flux is at least 15 times the height dimension h of the slit opening 224a of the diaphragm member 224, which will be described later. FIG. 4 shows the region Lf of the luminous flux irradiated to the diaphragm member 224. In the present embodiment, the height dimension h of the slit opening 224a is 0.7 mm, and the light flux from the light source 230 of the collimating lens 221 is 20 times the height dimension h. As a result, the allowable amount of the arrangement position accuracy of the slit opening 224a of the diaphragm member 224 is increased. Further, the diaphragm member 224 can be removed from the second optical axis O2 by the diaphragm drive motor 323. Details will be described later.

Further, the chopper 226 is rotationally driven by the chopper drive motor 227, and is driven so as to appear and disappear on the front side of the collimating lens 221 on the second optical axis O2 at a predetermined timing. Here, the chopper 226 is formed with a plate portion 226a that covers the collimating lens 221. Further, the trapezoidal prism 225 includes two reflecting surfaces 225a and 225b as shown in FIG. 3B, and guides the internal reference light to the optical sensor 261.

When the measurement light is emitted, as shown in FIG. 3A, the chopper 226 deviates from the emission port of the collimating lens 221 and the light from the light source 230 is directed toward the reflector 241 while being intermittently blocked by the circular 222. , Is ejected. In FIG. 3A, the optical axis of the internal reference light is indicated by a chain double-dashed line, and the optical path of the measurement light is indicated by a solid line with an arrow. 3 (a) In the state shown, no internal reference light is generated.

At the time of emitting the internal reference light, as shown in FIG. 3B, the chopper 226 is in a state where the reflecting surface 225a of the trapezoidal prism 225 is arranged at the ejection port of the collimating lens 221. In this state, the light from the light source 230 passes through the collimating lens 221 and is reflected by the reflecting surfaces 225a and 225b of the trapezoidal prism 225 and emitted toward the density filter 310. The internal reference light whose density is adjusted by the density filter 310 is incident on the optical fiber 263. At this time, since the aperture of the collimating lens 221 is completely covered by the plate portion 226a, no light is incident on the objective lens system 210 side. The optical fiber 263 merges with the optical fiber 260, and the internal reference light from the optical fiber 263 and the measurement light from the optical fiber 260 are detected by the same optical sensor 261. In FIG. 3B, the optical path of the internal reference light is indicated by a solid line with an arrow, and the optical axis of the measurement light is indicated by a dashed line. In the state shown in 3 (b), no measurement light is generated.

The emission reflection optical system 240 includes a reflecting mirror 241 having a reflecting surface obliquely formed on the second optical axis O2, and a light transmitting reflecting prism which is a second reflecting means arranged on the incident side (outside) of the objective lens system 210. 242 and the like. The light transmitting / reflecting prism 242 includes a reflecting surface 242a inclined on the first optical axis O1. In this example, a cover glass 281 which is a parallel flat glass is arranged on the outside of the objective lens system 210, and the light transmitting / reflecting prism 242 is arranged so as to be adhered to the inside of the cover glass 281.

The light-receiving reflection optical system 250 is composed of a dichroic mirror 251 and a light-receiving reflection prism 252 which is a light-receiving / reflecting member that reflects light from the dichroic mirror 251 in a perpendicular direction. The dichroic mirror 251 is arranged in the lens barrel 120 and reflects the measurement light, which is the light in a predetermined wavelength band, among the light incident from the objective lens system 210 along the first optical axis O1. Light in other bands is transmitted and incident on the collimation optical system 270 arranged in the lens barrel 120. The operator of the laser rangefinder 100 can perform collimation using the collimation optical system 270. The light receiving / reflecting prism 252 has a reflecting surface 252a formed at an angle of 45 degrees on the first optical axis O1 and reflects the light from the dichroic mirror 251 toward the optical fiber 260.

In such a light wave rangefinder 100, the distance to the prism 280, which is the object to be measured, is determined based on the measurement light from the prism 280, which is the object to be measured, detected by the optical sensor 261 and the internal reference light from the optical fiber 263. Calculate.

Next, the configuration of the diaphragm member 224 will be described. FIG. 5 is a perspective view of the light wave range finder showing the configuration of the diaphragm member of the light wave range finder. The diaphragm member 224 is made of a light-shielding thin plate, and a slit opening 224a extending in the horizontal direction orthogonal to the second optical axis O2 is provided on one of the optical axes. The height dimension h of the slit opening 224a is 0.7 mm. This dimension is determined by the balance between the measurement accuracy and the reach of the measurement light, and is generally about the same regardless of the type of device. Since the slit opening 224a is formed in the horizontal direction, the luminous flux incident from the light source 230 through the collimating lens 221 is extended by a predetermined dimension in the vertical direction due to diffraction. Therefore, the measurement light emitted from the light wave rangefinder 100 irradiates a range in which the vertical direction is larger than the horizontal direction.

FIG. 5 is a perspective view showing an arrangement state of the diaphragm members of the laser rangefinder. The diaphragm member 224 is attached to the tip of the arm member 321. The arm member 321 can swing around the rotation shaft 322, and the rotation shaft 322 is swing-driven by the diaphragm drive motor 323 (arrow a in FIG. 5). When the aperture drive motor 323 is driven and the aperture member 224 is arranged on the second optical axis O2, it can be used in the prism mode using the prism 280, and when the aperture member 224 is moved upward and removed from the second optical axis O2, it is non-existent. Used in prism mode. In the prism mode, precise measurement can be performed, the prism 280 is arranged on the object to be measured, and the measurement is performed. In the non-prism mode, the object to be measured is directly irradiated with the measurement light to perform the measurement.

Further, on the base portion 130, a diaphragm position adjusting screw 324, which is an adjusting member that comes into contact with the arm member 321 and sets the position of the diaphragm member 224 mounting side end of the arm member 321 in the vertical direction so as to be adjustable, is arranged. There is. By rotating the aperture position adjusting screw 324, the tip of the arm member 321 in the prism mode slightly moves up and down (arrow b in FIG. 5), and the position of the slit opening 224a in the vertical direction can be finely adjusted.

In the light wave distance meter 100 according to the present embodiment, it is basically unnecessary to adjust the position of the aperture member 224, but by finely adjusting the position of the aperture member 224, the state of the light wave distance meter 100 can be improved. can. In the present embodiment, when the aperture position adjusting screw 324 is not adjusted, the luminous flux is arranged in the center of the slit opening 224a within a permissible error. Instead of using the position adjusting screw 324, a positioning member can be formed on the base portion 130 so that the arm member 321 comes into contact with the positioning member, and the position adjustment of the diaphragm member 224 can be omitted. Even with this structure, the slit opening 224a of the diaphragm member 224 can be arranged with sufficient accuracy simply by arranging the diaphragm member 224 on the base portion 130. Therefore, the position adjustment can be omitted at the time of assembly, and the structure is resistant to aging due to the absence of the position adjustment portion.

Further, in the light wave rangefinder 100 according to the present embodiment, as shown in FIG. 4, in the density filter 310, a density gradient film 311 having a density gradient formed and a protective film 312 having a constant density, for example, a transparent film 312 are superposed on each other. , The fixing screw 313 is arranged in the density filter mounting portion 131 of the base portion 130 arranged in the telescope portion 103. The density gradient film 311 and the protective film 312 are made of a synthetic resin film. Then, even if the protective film 312 rotates, the density gradient film 311 is attached without joining so that it does not rotate along with the protective film 312.

Hereinafter, the height dimension h of the slit opening 224a of the diaphragm member 224 and the diameter d of the light beam emitted from the collimating lens 221 to the diaphragm member 224 will be described in detail. In the light wave rangefinder 400 shown as a conventional example in FIG. 6, the height dimension of the slit opening of the diaphragm member 443 was 0.7 mm. In this light wave rangefinder 400, the center of the incident light flux was adjusted to be within ± 0.2 mm with respect to the center of the slit opening. However, in order to determine this adjustment position, the position of the position adjustment screw 324 is about half the position from the rotation shaft 322 to the center of the slit opening 224a, so that the allowable range for adjustment is ± 0.1 mm.

With such an allowable amount, when an M2 screw is used as the position adjusting screw 324, the pitch of the screw is 0.4 mm, so that the adjustment amount is equivalent to 1/4 rotation. This accuracy is difficult when the base portion 130 is made of a metal mold. Of course, if the blank material created by the mold is cut later, the accuracy will be improved, but the cost will increase.

In the present embodiment, when the diameter of the light flux to the diaphragm member 224 is 14 mm (twice the conventional value), the light flux density is halved, but the allowable positioning value in the diameter direction of the light flux is doubled. Therefore, at the position of the position adjusting screw 324, the permissible value is doubled, that is, ± 0.2 mm. With such a value, the tolerance accuracy can be obtained even if the base portion 130 is used with a blank material from a metal mold without post-processing. In the current hardware processing, it is possible to sufficiently manufacture within a tolerance of about 0.3 mm in width. Therefore, if the diameter of the light flux is increased to 1.5 times that of the conventional case, it is not necessary to adjust the position with the diaphragm member 224 attached to the base portion 130.

Next, the intensity of the light source will be described. Here, the influence on the measured reach when the diameter d of the luminous flux is doubled as compared with the conventional case will be considered.

<Calculation conditions>
Emission power (objective output) P0:
5mW (output after LD output passes through the optical system)
Emission wide-angle θ:
14'(7'on one side) ≒ 0.233333 °
Light receiving objective diameter φ:
50 mm (effective diameter of light receiving objective of rangefinder body)
Atmospheric attenuation coefficient β:
0.127 (dimensionless) / Visibility 20km equivalent / Wavelength 690nm Regulation reach L:
2000m (Product specifications / Visibility 20km)
Light reception sensitivity (minimum operating light intensity) η0:
1nW (light intensity at objective input of the machine body)

<Reach distance calculation formula>
Now, the amount of light calculated by the following formula is the amount of light returned to the machine, so
If that value (received light amount) is "η",
η = P0 × (φ / 2L tan θ) 2 × EXP (-2βL / 1000)… (1)
(Because the coefficient 2 before the reach distance L in the above equation is twice the measurement distance because the actual path through which the luminous flux passes is a round trip of the measurement distance).

Here, the calculated value η is η0 ≦ η… (2)
If the above conditions are met, the distance will reach the specified distance, and the machine arrival specifications will be met. The first half of Eq. (1) is the part that calculates the area ratio between the received image diameter of the return light and the effective light receiving diameter of the actual machine when going back and forth over the measurement distance, and the exponential part in the latter half is the atmospheric attenuation. This is the calculated term. Since the unit of distance used in atmospheric attenuation calculation is "km", L is internally set to 1/1000. The "atmospheric attenuation coefficient β" differs depending on the emission wavelength, but the formula for β is omitted here. However, β tends to become smaller as the wavelength becomes longer. (Not easily affected by the atmosphere)

Try to calculate based on the conditions and formula.
η = 5 × 10-3 × (50 × 10-3 / (2 × 2000 × tan (0.233333)) 2 × EXP (-2 × 0.127 × 2))
= 5 × 10-3 × 9.421 × 10-6 × 0.60167 = 28.3416 × 10-9 [W]… (3)

The value of (3) was calculated from the calculated value.
Since this value is about 28 [nW], it is the minimum amount of moving light under the above "calculation conditions", "1".
It can be seen that the value is about 28 times larger than [nW] ”.

Therefore, in view of this result, even if the diameter of the light beam to the diaphragm member 224 is doubled and the amount of light passing through the slit opening is reduced to 1/4 in the light wave rangefinder 100 according to the present embodiment.
28 [nW] × 1/4 = 7 [nW]… (4)
Therefore, the amount of light is expected to be about 7 times the minimum operating amount of light "1 [nW]", which meets the standard value for distance measurement. Therefore, it can be seen that the reach specifications of the machine are sufficiently satisfied.

As described above, according to the light wave rangefinder 100 according to the embodiment, since the tolerance of the position change of the slit opening with respect to the optical axis is large, the diaphragm member is attached to the mounting base without adjusting the position at the time of manufacturing. Even so, the mounting position of the slit opening can be kept within the standard, and the position change of the diaphragm member due to aging is within the standard, and the distance is measured without adjusting the position of the diaphragm member during manufacturing or aging. Can be done accurately.

100: Light wave rangefinder 110: Housing 120: Lens barrel 130: Base 131: Density filter mounting 200: Optical system 210: Objective lens system 220: Injection optical system 224: Aperture member 224a: Aperture opening 230: Light source 240: Emission Reflection Optical System 241: Reflector 310: Density Filter

Claims (4)

Compare reflected light with internal reference light
A light wave rangefinder that measures the distance to the object to be measured.
A light source that emits a luminous flux of a predetermined spread along the optical axis and a light source that can be arranged on the optical axis.
A diaphragm member having a slit opening extending in the horizontal direction orthogonal to the optical axis and narrowing the spread width of the luminous flux from the light source.
The arm member holding the diaphragm member and the diaphragm member are arranged on the optical axis so as to be able to move in and out of the optical axis by rotating the arm member.
A luminous flux arranged between the light source and the diaphragm member, the luminous flux is sandwiched between the slit opening and the slit opening up and down, and is emitted into a region having a height dimension of 15 times or more the height dimension of the slit opening. Expansion means and
Including
A light wave range finder characterized in that the amount of light of the light source is set so that the reflected light from the object to be measured at the measurement distance set by the light wave range finder is equal to or more than a reference value capable of measuring the distance. The light wave rangefinder according to claim 1, wherein the diaphragm member includes an adjusting member that adjusts the slit opening in the vertical direction. The light wave rangefinder according to claim 1, wherein the aperture member is fixed so that the slit opening cannot be adjusted in the vertical direction when the aperture member is used. The light wave rangefinder according to any one of claims 1 to 3, wherein the luminous flux expanding means is a collimating lens.

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