JP2018091764A5 - - Google Patents

Description

Lightwave rangefinder

  The present invention relates to a lightwave distance meter 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, and measures a distance to a target.

  The above-described lightwave distance meter irradiates the measured light in the predetermined wavelength region to the measured object, receives the reflected light from the measured object, and measures from the phase difference between the internal reference light and the received measured light. Measure the distance to the object.

  FIG. 5 is a sectional view showing a configuration of a conventional lightwave distance meter. The lightwave distance meter 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 collimating optical system 470, and a light receiving device. And an element 480.

  The objective lens 410 is composed of three lenses arranged on the optical axis Oa. The prism 420 is disposed 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 emitting reflecting surface that reflects in the direction in which the measuring light is emitted. 421, and a light receiving reflection surface 422 that reflects the incident measurement light toward the light receiving element 480.

  The light source 430 generates light in a predetermined wavelength range. The emission optical system 440 is disposed on the optical axis Ob parallel to the optical axis Oa, and collimates 441 to collimate the light from the light source 430, optical chopper 442 for intermittently blocking the measurement light, and aperture member 443. Is provided. The reflecting mirror 450 is disposed at an angle of 45 degrees with respect to the optical axis Ob, changes the direction of the measurement light from the emission optical system 440 by 90 degrees, and faces the emission reflecting surface 421 of the prism 420 along the optical axis Oc. Reflects measurement light. The measurement light reflected by the emission reflection surface 421 is emitted to the measurement object via the objective lens 410.

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

  In such an electro-optical distance meter, the aperture member stops 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.

JP 2014-149171 A

  In this type of optical distance meter, a prism mode in which a recursive prism is arranged on the object to be measured for precise measurement and a measuring light is irradiated on the prism, and a non-linear mode in which the object is directly irradiated with the measuring light to perform measurement. Measurement can be performed in the prism mode. In the prism mode, the stop member 443 is used, and in the non-prism mode, the measurement is performed without using the stop member 443. In the non-prism mode, the diaphragm member 443 is moved so as to be out of the optical axis Ob, and measurement is performed by irradiating the measurement object with a large luminous flux to the measured object.

  For this reason, the diaphragm member 443 can rotate the arm member holding the diaphragm member about the axis to dispose the diaphragm member 443 on the optical axis Ob and remove the diaphragm member 443 from the optical axis Ob. . As described above, the aperture shape of the aperture provided in the aperture member 443 is a slit shape formed in the horizontal direction, and has a width dimension of, for example, about 0.7 mm. The width dimension of the slit is determined by the balance between the measurement accuracy and the reach of the measurement light, and is generally the same regardless of the type of the device. Conventionally, the aperture member 443 is irradiated with a light beam from a light source 430 via a collimator 441.

  However, the conventional optical distance meter 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 aperture member such that the aperture member is accurately positioned on the optical axis Ob so that the light beam from the light source is correctly irradiated in a state of being used in the prism mode during manufacturing. Further, if the optical distance meter 400 has been used for a long period of time, the position of the stop member 443 may be shifted, and in this case, the position of the stop member 443 must be adjusted.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a lightwave distance meter that can accurately perform distance measurement without performing position adjustment of a diaphragm member during manufacturing or use over time. I do.

In order to solve the above problem, an invention according to claim 1 is a lightwave distance meter that measures a distance to a measured object by comparing reflected light and internal reference light, and emits a light beam having a predetermined spread. A light source that emits along an axis, and a stop member that can be arranged on the optical axis, includes a slit opening that extends in a horizontal direction orthogonal to the optical axis, and narrows the spread width of the light flux from the light source; The light flux is disposed between the light source and the aperture member, and the light flux is sandwiched between the slit opening and the slit vertically, and is emitted to a region having a height of 1.5 times or more the height of the slit opening. Light beam expanding means, and the light amount of the light source is set such that the reflected light from the object under measurement at the measurement distance set by the lightwave distance meter is equal to or greater than a reference value capable of distance measurement , A lightwave distance meter characterized in that:

  According to a second aspect of the present invention, in the optical distance meter according to the first aspect, the aperture member includes an adjusting member that adjusts the slit opening in a vertical direction.

  According to a third aspect of the present invention, in the lightwave distance meter according to the first aspect, the aperture member is fixed so that the slit opening cannot be adjusted vertically when the aperture member is used. I do.

  According to a fourth aspect of the present invention, in the lightwave distance meter according to any one of the first to third aspects, the light beam expanding means is a collimating lens.

  ADVANTAGE OF THE INVENTION According to the lightwave distance meter which concerns on this invention, distance measurement can be performed correctly, without adjusting the position of a diaphragm member at the time of manufacture or use over time.

That is, according to the lightwave distance meter according to claim 1, the light beam from the light source is expanded by the light beam expanding means, and at the position of the diaphragm member, the height is at least 1.5 times the height of the slit opening. The reflected light from the object to be measured at the measurement distance becomes greater than or equal to a reference value at which the distance can be measured at the same time as being emitted to the dimension area, and the tolerance of the positional change of the slit opening with respect to the optical axis increases. For this reason, 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. Further, a change in the position of the aperture member due to aging is within the standard. Therefore, it is possible to accurately measure the distance without adjusting the position of the aperture member at the time of manufacture or during long-term use.

  According to the optical distance meter according to the second aspect of the present invention, since the aperture member is provided with the adjustment member that adjusts the slit opening in the vertical direction, the position of the aperture member is adjusted when the aperture member moves significantly. be able to.

  According to the third aspect of the present invention, the aperture member is fixed in a state in which the slit opening cannot be adjusted vertically when the aperture member is used, so that a mechanism for adjusting the position can be omitted.

  According to the optical distance meter according to the fourth aspect, the light beam expanding means can be realized by a simple optical element called a collimator lens.

FIG. 1 is a front view showing an optical distance meter according to an embodiment of the present invention. It is sectional drawing which shows the same light wave range finder. 3A and 3B illustrate an optical system of the lightwave distance meter, in which FIG. 4A is a schematic diagram illustrating a state of emission of measurement light, and FIG. 4B is a schematic diagram illustrating a state of emission of an internal reference light. 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 | positioning state of the aperture member of the same light wave distance meter. It is sectional drawing which shows the structure of the conventional lightwave distance meter.

  An optical distance meter according to an embodiment of the present invention will be described.

  FIG. 1 is a front view showing a lightwave distance meter according to an embodiment of the present invention. As shown in FIG. 1, a light range finder 100 according to the first embodiment has a base 102 provided on a base 101 attached to a tripod (not shown), and the base 102 includes a telescope unit including an optical system. 103 is supported. The base 101 has a leveling screw 104 and can be leveled so that the gantry 102 is horizontal. The gantry 102 is rotatable about a vertical axis, and the telescope unit 103 is rotatable about a horizontal axis. 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 and the like.

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

  The optical distance meter 100 has a housing 110 in which a lens barrel 120 and a base 130 are formed. As shown in FIG. 2, the optical distance meter 100 includes, as an optical system 200, an objective lens system 210 as a light receiving optical system, an emission optical system 220 for emitting measurement light and irradiating the measurement object, and an objective lens. And an exit reflection optical system 240 for guiding the measurement light from the system 210 to the optical fiber 260. The optical system 200 includes a light receiving / reflecting optical system 250 and a collimating optical system 270. The optical fiber 260 guides the measurement light to the optical sensor 261 (see FIG. 3). The collimating optical system 270 is used to determine and correct the direction of the optical distance meter 100 so that the object image from the objective lens system 210 can be viewed.

  The base portion 130 is made of a blank material from an alloy product type, and is not subjected to post-processing. The dimensional accuracy is, for example, 0.3 mm. For this reason, by forming a mounting portion for each member of the optical system on the base portion 130, the members can be arranged in each direction with an accuracy of ± 0.15 mm without adjusting each member.

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

  The emission optical system 220 includes a collimator lens 221 that is a light beam expanding unit, a chopper 226 including a trapezoidal prism 225 that intermittently blocks emission light and takes out emission light as internal reference light acquired from a light source, and a microcomputer. A circular filter 222 that controls the amount of external light flux under the control of the like, a density filter 310 that adjusts the amount of internal reference light by manually setting a rotational position, and an aperture member 224. The density filter 310 is a disk-shaped member having a density gradient on the 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 emitted measurement light, and driven to rotate by a circular drive motor 223.

The collimator lens 221 converts the light beam from the light source 230 into a parallel light beam having a predetermined spread dimension. The spread width of the light beam emitted from the collimator lens 221 is, for example, 15 mm as the diameter d of the stop member 224. The diameter d of the light beam is at least 1.5 times the height h of the slit opening 224a of the aperture member 224 described later. FIG. 4 shows a region Lf of a light beam irradiated on the diaphragm member 224. In the present embodiment, the height h of the slit opening 224a is 0.7 mm, and the collimator lens 221 sets the light flux from the light source 230 to 20 times the height h. As a result, the permissible amount of the arrangement position accuracy of the slit opening 224a of the diaphragm member 224 increases. Further, the aperture member 224 can be removed from the second optical axis O2 by the aperture drive motor 323. Details will be described later.

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

  At the time of emission of the measurement light, as shown in FIG. 3A, the chopper 226 separates from the exit of the collimator lens 221, and the light from the light source 230 is directed toward the reflection mirror 241 while being intermittently blocked by the circular 222. Be injected. In FIG. 3A, the optical axis of the internal reference light is indicated by a dashed line, and the optical path of the measurement light is indicated by a solid line with an arrow. In the state shown in FIG. 3A, the internal reference light is not generated.

  When the internal reference light is emitted, as shown in FIG. 3B, the chopper 226 is in a state where the reflection surface 225 a of the trapezoidal prism 225 is arranged at the exit of the collimator lens 221. In this state, the light from the light source 230 passes through the collimator lens 221, is reflected by the reflection surfaces 225 a and 225 b of the trapezoidal prism 225, and is emitted toward the density filter 310. The internal reference light whose density has been adjusted by the density filter 310 enters the optical fiber 263. At this time, since the opening of the collimator lens 221 is completely covered by the plate portion 226a, no light enters the objective lens system 210 side. The optical fiber 263 joins 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 chain line. In the state shown in FIG. 3 (b), no measurement light is generated.

  The exit reflection optical system 240 includes a reflection mirror 241 having a reflection surface formed obliquely on the second optical axis O2, and a light transmission reflection prism that is a second reflection unit disposed on the incident side (outside) of the objective lens system 210. 242. 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 plane glass is arranged outside the objective lens system 210, and the light transmission / reflection prism 242 is adhered and arranged inside the cover glass 281.

  The light receiving / reflecting optical system 250 includes a dichroic mirror 251 and a light receiving / reflecting prism 252 that is a light receiving / reflecting member that reflects light from the dichroic mirror 251 in a right angle direction. The dichroic mirror 251 is disposed in the lens barrel 120, and reflects the measurement light, which is light in a predetermined wavelength band, of the light incident from the objective lens system 210 along the first optical axis O1. Light in other bands is transmitted and enters the collimating optical system 270 arranged in the lens barrel 120. The operator of the optical distance meter 100 can collimate using the collimating optical system 270. The light receiving / reflecting prism 252 has a reflecting surface 252a formed at an angle of 45 degrees with the first optical axis O1, and reflects light from the dichroic mirror 251 toward the optical fiber 260.

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

  Next, the configuration of the aperture member 224 will be described. FIG. 5 is a perspective view of the lightwave distance meter showing the configuration of the aperture member of the lightwave distance meter. The aperture member 224 is formed of a light-shielding thin plate, and has a slit opening 224a extending in a horizontal direction orthogonal to the second optical axis O2 at one optical axis. The height 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 the same regardless of the type of the device. Since the slit opening 224a is formed in the horizontal direction, the light beam incident from the light source 230 via the collimating lens 221 extends by a predetermined dimension in the vertical direction by diffraction. For this reason, the measurement light emitted from the electro-optical distance meter 100 irradiates a range where the vertical direction is larger than the horizontal direction.

  FIG. 5 is a perspective view showing an arrangement state of a stop member of the lightwave distance meter. The aperture member 224 is attached to the tip of the arm member 321. The arm member 321 is swingable about a rotation shaft 322, and the rotation shaft 322 is driven to swing by a diaphragm drive motor 323 (arrow a in FIG. 5). When the diaphragm driving motor 323 is driven to dispose the diaphragm member 224 on the second optical axis O2, the diaphragm member 224 can be used in a prism mode using the prism 280. When the diaphragm member 224 is moved upward and disengaged from the second optical axis O2, a non- Used in prism mode. In the prism mode, precision measurement can be performed, and the measurement is performed by arranging the prism 280 on the object to be measured. In the non-prism mode, the measurement is performed by directly irradiating the object with the measurement light.

  Also, on the base portion 130, a diaphragm position adjusting screw 324, which is an adjusting member for setting the vertical position of the end of the arm member 321 on the side of the diaphragm member 224 in contact with the arm member 321, is arranged. I have. By rotating the stop position adjusting screw 324, the tip of the arm member 321 in the prism mode is finely moved up and down (arrow b in FIG. 5), and the vertical position of the slit opening 224a can be finely adjusted.

  In the lightwave distance meter 100 according to the present embodiment, the position adjustment of the stop member 224 is basically unnecessary, but by performing the fine adjustment of the position of the stop member 224, the state of the lightwave distance meter 100 can be improved. it can. In the present embodiment, the light beam is arranged within the tolerance within the center of the slit opening 224a when the stop position adjusting screw 324 is not adjusted. Note that a positioning member can be formed on the base portion 130 without using the position adjusting screw 324, and the position adjustment of the diaphragm member 224 can be omitted such that the arm member 321 contacts the positioning member. Also with this structure, the slit opening 224a of the diaphragm member 224 can be arranged with sufficient accuracy only by disposing the diaphragm member 224 on the base portion 130. For this reason, the position adjustment can be omitted at the time of assembling, and the structure has no position adjusting portion and is resistant to secular change.

  Further, in the optical distance meter 100 according to the present embodiment, as shown in FIG. 4, the density filter 310 is formed by stacking a density gradient film 311 having a density gradient and a protective film 312 having a constant density, for example, a transparent protective film 312. The fixing screw 313 is disposed on the density filter mounting portion 131 of the base 130 disposed on the telescope 103. The concentration 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 with the protective film 312.

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

  With such an allowance, when an M2 screw is used as the position adjusting screw 324, the pitch of the screw is 0.4 mm, which is an adjustment amount for １ ／ rotation. This accuracy is difficult when the base part 130 is formed by a metal mold. Of course, if the blank material created by the die is later cut or the like, the accuracy is improved but the cost is increased.

  In the present embodiment, if the diameter of the light beam to the stop member 224 is 14 mm (twice the conventional value), the light beam density becomes 1/4, but the positioning allowance in the diameter direction of the light beam becomes twice. Therefore, the allowable value at the position of the position adjusting screw 324 is also doubled, that is, ± 0.2 mm. With such a value, even if the base portion 130 is used with a blank material from a metal mold without performing post-processing, tolerance accuracy is obtained. In addition, in the current metalworking, manufacturing within a tolerance of about 0.3 mm in width is sufficiently possible. Therefore, if the diameter of the light beam is set to be 1.5 times as large as that in the related art, it is not necessary to perform the position adjustment with the stop member 224 attached to the base portion 130.

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

<Calculation conditions>
Emission power (objective output) P ₀ : 5 mW (output after LD output has passed through the optical system)
Emission wide angle θ: 14 '(7' on one side) ≒ 0.233333 °
Light receiving objective diameter φ: 50mm (effective diameter of light receiving objective of the rangefinder body)
Atmospheric attenuation coefficient β: 0.127 (Dimensionless) / Visibility 20km / Range reachable at 690nm L: 2000m (Product specification / Visibility 20km)
Light receiving sensitivity (minimum operating light intensity) η ₀ : 1nW (light intensity at the time of objective input of the machine body)

<Area formula>
Now the light amount calculated by the following formula is the light amount that returns to the machine,
If the value (received light amount) is “η”,
η = P ₀ × (φ / 2Ltanθ) ² × EXP (-2βL / 1000)… (1)
(Before the reaching distance L in the above equation, the coefficient 2 is twice as large as the measured distance since the actual light beam travels back and forth over the measured distance).

Here, the calculated value η is η ₀ ≦ η (2)
If the condition of (1) is satisfied, it will reach the specified distance, and will meet the machine reach specification. The first half of the equation (1) is a part for calculating the area ratio between the light receiving image diameter of the return light and the effective light receiving diameter of the actual device when going back and forth over the measurement distance. This is the calculated term. Since the unit of the distance used in the atmospheric attenuation calculation is "km", L is set to 1/1000 internally. The “atmospheric attenuation coefficient β” varies depending on the emission wavelength, but the calculation formula of β is omitted here. However, β tends to decrease as the wavelength increases. (Less 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)

From the calculated values, the value of (3) was calculated.
Since this value is about 28 [nW], it is understood that the value is about 28 times larger than “1 [nW]”, which is the minimum moving light amount under the “calculation conditions”.

Therefore, in consideration of this result, in the lightwave distance meter 100 according to the present embodiment, 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 becomes ４,
28 [nW] × 1/4 = 7 [nW]… (4)
Thus, a light amount approximately seven times the minimum operation light amount of "1 [nW]" can be expected, and the reference value for distance measurement can be satisfied. For this reason, it is understood that the machine reaches the reaching distance specification sufficiently.

  As described above, according to the lightwave distance meter 100 according to the embodiment, since the positional change of the slit opening with respect to the optical axis is large, the diaphragm member is mounted on the mounting base without adjusting the position during manufacturing. In addition to being able to fit the slit aperture installation position within the standard, changes in the position of the diaphragm member due to aging can be kept within the standard, and distance measurement can be performed without adjusting the position of the diaphragm member during manufacturing or use over time. Can be performed accurately.

100: light wave distance meter 110: housing 120: lens barrel 130: base 131: density filter mounting part 200: optical system 210: objective lens system 220: emission optical system 224: diaphragm member 224a: diaphragm aperture 230: light source 240: Emission reflecting optical system 241: Reflecting mirror 310: Density filter

Claims (4)

A lightwave distance meter that measures the distance to the object by comparing the reflected light with the internal reference light,
A light source that emits a light beam having a predetermined spread along the optical axis, and can be arranged on the optical axis;
An aperture member that extends in a horizontal direction perpendicular to the optical axis, and is provided between the light source and the aperture member; Light beam expanding means for vertically sandwiching the slit opening and emitting light to a region having a height dimension of 1.5 times or more the height dimension of the slit opening;
Including
The light wave distance meter, wherein the light amount of the light source is set such that the reflected light from the object at the measurement distance set by the light wave distance meter is equal to or more than a reference value capable of distance measurement .   The optical distance meter according to claim 1, wherein the aperture member includes an adjusting member that adjusts the slit opening in a vertical direction.   2. The optical distance meter according to claim 1, wherein the aperture member is fixed such that the slit opening cannot be adjusted vertically when the aperture member is used. 3. The lightwave distance meter according to any one of claims 1 to 3, wherein the light beam expanding means is a collimator lens.