JP2018091764A - Light wave range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a range measurement to be correctly conducted even if a position adjustment of a diaphragm member is not made when manufactured or used over a long period.SOLUTION: The present invention relates to a light wave range finder 100 that compares reflection light with internal reference light to measure a distance to a measured object, and includes: a light source 230 that emits a prescribed broadening beam of light along an optical axis; a diaphragm member 224 that is equipped with a slit opening 224a arrangeable on the optical axis, orthogonal to the optical axis and extending in a horizontal direction, and narrows a width of the broadening beam of light from the light source; and a collimate lens 221 that is arranged between the light source and the diaphragm member, and emits the beam of light to the slit opening and, across the slit opening up and down, an area Lf with a height dimension 20 times a height dimension h of the slit opening. An amount of light of the light source is set so that reflection light from a measured object in a measurement distance set by the light wave range finder is equal to or greater than a reference value enabling a distance measurement.SELECTED DRAWING: Figure 4

Description

  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-mentioned optical rangefinder irradiates the object to be measured with modulated measurement light in a predetermined wavelength region, receives 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 the object.

  FIG. 5 is a cross-sectional view showing the configuration of a conventional optical distance meter. The light wave 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 unit. 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 that form an angle of 45 degrees with respect to the optical axis Oa, that is, the reflecting surface for emission that reflects in the direction in which the measurement light is emitted. 421 and a light receiving reflection surface 422 that reflects incident measurement light toward the light receiving element 480.

  The light source 430 generates light in a predetermined wavelength region. The emission optical system 440 is disposed on an optical axis Ob parallel to the optical axis Oa, and collimator 441 that converts light from the light source 430 into parallel light, an optical chopper 442 that intermittently blocks measurement light, and a diaphragm 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 measuring light from the emission optical system 440 by 90 degrees, and is directed toward the reflecting surface 421 for emission of the prism 420 along the optical axis Oc. Reflects the measurement light. The measurement light reflected by the emission reflecting surface 421 is emitted to the measurement object through the objective lens 410.

  The reflected light from the measurement object reaches the dichroic mirror 460 through the objective lens 410. The dichroic mirror 460 reflects measurement light in a predetermined wavelength band from incident light, transmits other light, and emits it to the collimating 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 a lightwave distance meter, the diaphragm member is used to squeeze 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 light from the light source is emitted most efficiently.

JP 2014-149171 A

  In this type of optical distance meter, in order to perform precise measurement, a recursive prism is placed on the object to be measured and a prism mode is used to irradiate the prism with measuring light, and non-measurement is performed by directly irradiating the object to be measured with measuring light. Measurements can be made in prism mode. In the prism mode, measurement is performed without using the diaphragm member 443 in the non-prism mode. In the non-prism mode, the diaphragm member 443 is moved away from the optical axis Ob, and measurement is performed by irradiating the object to be measured with measurement light with a large luminous flux.

  For this reason, the diaphragm member 443 can displace the diaphragm member 443 from the optical axis Ob by rotating the arm member holding the diaphragm member about the axis to dispose the diaphragm member 443 on 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 the width dimension is, 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 apparatus. Conventionally, the diaphragm 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. In other words, the diaphragm member needs to be adjusted in position so that the diaphragm member is accurately arranged on the optical axis Ob so that the light beam from the light source is correctly irradiated in a state where the diaphragm member is used in the prism mode. In addition, when the optical distance meter 400 is used for a long period of time, the arrangement position of the diaphragm member 443 may be shifted. In this case, the position of the diaphragm member 443 must be adjusted.

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

  In order to solve the above-mentioned problem, the invention according to claim 1 is an optical distance meter that measures the distance to the object to be measured by comparing the reflected light and the internal reference light, and emits a light beam having a predetermined spread. A light source that emits along an axis, a diaphragm member that can be disposed on the optical axis, includes a slit opening that extends in a horizontal direction perpendicular to the optical axis, and narrows the spread width of the luminous flux from the light source; The light beam is disposed between the light source and the diaphragm member, and the light beam exits the slit opening and the region having a height dimension of 15 times or more of the height dimension of the slit opening. The light quantity of the light source is set so that the reflected light from the object to be measured at a measurement distance set by the light wave distance meter is equal to or greater than a reference value capable of distance measurement. It is a light wave distance meter characterized by.

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

  The invention according to claim 3 is the lightwave distance meter according to claim 1, wherein the diaphragm member is fixed in a state in which the slit opening cannot be adjusted in the vertical direction when the diaphragm member is used. To do.

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

  According to the lightwave distance meter according to the present invention, it is possible to accurately measure the distance without adjusting the position of the diaphragm member at the time of manufacture or use over time.

  That is, according to the optical distance meter of claim 1, the light beam from the light source is expanded by the light beam expanding means, and has a height of 15 times or more the height of the slit opening at the position of the diaphragm member. The reflected light from the object to be measured at a measurement distance becomes equal to or greater than a reference value capable of measuring the distance, and the tolerance of the position change with respect to the optical axis of the slit opening increases. For this reason, even if the diaphragm member is attached to the attachment base without adjusting the position at the time of manufacture, the attachment position of the slit opening can be kept within the reference. Further, the position change of the diaphragm member due to the secular change falls within the standard. Therefore, it is possible to accurately measure the distance without adjusting the position of the diaphragm member at the time of manufacture or use over time.

  Further, according to the lightwave distance meter according to claim 2, the diaphragm member includes an adjustment member that adjusts the slit opening in the vertical direction, so that the position of the diaphragm member is adjusted when the diaphragm member moves largely. be able to.

  According to the lightwave distance meter of the third aspect, the diaphragm member is fixed in a state where the slit opening cannot be adjusted in the vertical direction when the diaphragm member is used, so that a mechanism for position adjustment can be omitted.

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

It is a front view which shows the light wave distance meter which concerns on embodiment of this invention. It is sectional drawing which shows the optical wave distance meter. FIGS. 2A and 2B show an optical system of the optical wave distance meter, where FIG. 2A is a schematic diagram showing a state of measurement light emission, and FIG. 2B is a schematic diagram showing a state of internal reference light emission. It is a perspective view of the light wave distance meter which shows the structure of the internal mechanism of the same light wave distance meter. It is a perspective view which shows the arrangement | positioning state of the aperture member of the same optical distance meter. It is sectional drawing which shows the structure of the conventional lightwave distance meter.

  An optical distance meter according to an embodiment for carrying out the present invention will be described.

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

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

  In the optical distance meter 100, a lens barrel 120 and a base portion 130 are formed in a housing 110. As shown in FIG. 2, the optical distance meter 100 includes, as an optical system 200, an objective lens system 210 that is a light receiving optical system, an emission optical system 220 that emits measurement light and irradiates a measurement object, and an objective lens. And an exit reflection optical system 240 that guides 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 lightwave 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 mold and is not post-processed. The dimensional accuracy is, for example, 0.3 mm. For this reason, the base part 130 can be arranged with an accuracy of ± 0.15 mm in each direction without adjusting each member by forming a mounting portion for each member of the optical system.

  The objective lens system 210 is disposed in the lens barrel 120 and includes a first optical axis O1 directed to the prism 280 that 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 a positive power as a whole. The emission optical system 220 is disposed on the base unit 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 that is parallel light. The light source 230 is, for example, a laser diode that generates infrared rays.

  The emission optical system 220 includes a collimator lens 221 that is a light beam expanding means, a chopper 226 that includes a trapezoidal prism 225 that intermittently blocks the emitted light and extracts the emitted light as internal reference light acquired from a light source, and a microcomputer And a diaphragm 222 that adjusts the amount of internal reference light by manually setting the rotational position, and a diaphragm member 224. The density filter 310 is a disk-shaped member having a density gradient on the circumference. The circular 222 is a disk-like member that is provided with a density filter having a density gradient on the circumference for adjusting the measurement light emission light amount and is rotationally driven by a circular drive motor 223.

  The collimating lens 221 turns the light beam from the light source 230 into a parallel light beam having a predetermined spreading dimension. The spread width of the light beam 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 a slit opening 224a of a diaphragm member 224 described later. FIG. 4 shows a region Lf of the light beam irradiated on the diaphragm member 224. In this embodiment, the height dimension h of the slit opening 224a is 0.7 mm, and the collimating lens 221 sets the luminous flux from the light source 230 to 20 times the height dimension h. Thereby, the tolerance of the arrangement position accuracy of the slit opening 224a of the aperture member 224 increases. 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 a chopper drive motor 227, and is driven so as to appear at 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 226 a that covers the collimating lens 221. 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 is detached from the exit of the collimator lens 221, and the light from the light source 230 is directed to the reflecting mirror 241 while being interrupted intermittently by the circular 222. Injected. In FIG. 3A, the optical axis of the internal reference light is indicated by a one-dot chain 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 reflecting surface 225 a of the trapezoidal prism 225 is disposed at the exit of the collimator lens 221. In this state, light from the light source 230 passes through the collimating lens 221, is reflected by the reflecting 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 collimating lens 221 is completely covered with 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 an alternate long and short dash line. In the state shown in FIG. 3B, no measurement light is generated.

  The exit reflecting 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 as second reflecting means 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 plane parallel glass, is disposed outside the objective lens system 210, and the light transmitting / reflecting prism 242 is disposed on the inside of the cover glass 281.

  The light receiving / reflecting optical system 250 includes a dichroic mirror 251 and a light receiving / reflecting 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 disposed in the lens barrel 120 and reflects measurement light, which is light in a predetermined wavelength band, among 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 disposed in the lens barrel 120. An operator of the optical distance meter 100 can collimate 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 an optical wave distance meter 100, the distance to the prism 280, which is a measurement object, is measured 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 diaphragm member 224 will be described. FIG. 5 is a perspective view of the light wave distance meter showing the configuration of the diaphragm member of the light wave distance meter. The aperture member 224 is formed of a light-shielding thin plate, and a slit opening 224a extending in the horizontal direction perpendicular to the second optical axis O2 is formed on one of the optical axes. 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 apparatus. 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 due to diffraction. For this reason, the measurement light emitted from the lightwave distance meter 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 member of the optical wave distance meter. The aperture member 224 is attached to the tip of the arm member 321. The arm member 321 can swing around a rotation shaft 322, and the rotation shaft 322 is driven to swing by an aperture drive motor 323 (arrow a in FIG. 5). When the diaphragm drive motor 323 is driven and the diaphragm 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 diaphragm member 224 is moved upward and removed from the second optical axis O2, it is non-movable. Used in prism mode. In the prism mode, precise measurement can be performed, and measurement is performed by arranging the prism 280 on the object to be measured. In the non-prism mode, measurement is performed by directly irradiating the object to be measured with measurement light.

  In addition, the base portion 130 is provided with an aperture position adjusting screw 324 that is an adjustment member that comes into contact with the arm member 321 so as to adjust the vertical position of the end portion of the arm member 321 on the aperture member 224 mounting side. Yes. 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 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 diaphragm member 224 is basically unnecessary, but by performing fine position adjustment of the diaphragm member 224, the state of the lightwave distance meter 100 is improved. it can. In the present embodiment, when the aperture position adjusting screw 324 is not adjusted, the light beam is arranged within the allowable error at the center of the slit opening 224a. In addition, without using this position adjustment screw 324, a positioning member can be formed in the base part 130, and the position adjustment of the aperture member 224 can be omitted so that the arm member 321 contacts the positioning member. Also with this structure, the slit opening 224a of the diaphragm member 224 can be disposed with sufficient accuracy simply by disposing the diaphragm member 224 on the base portion 130. For this reason, the position adjustment can be omitted at the time of assembly, and the structure is strong against aging because there is no position adjustment portion.

  In the lightwave distance meter 100 according to this embodiment, as shown in FIG. 4, the density filter 310 includes a density gradient film 311 having a density gradient and a protective film 312 having a constant density, for example, transparent. The fixing screw 313 is arranged on the density filter attaching part 131 of the base part 130 arranged on the telescope part 103. The density gradient film 311 and the protective film 312 are made of a synthetic resin film. And 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 diaphragm member 224 and the diameter d of the light beam emitted from the collimator lens 221 to the diaphragm member 224 will be described in detail. In the optical wave distance meter 400 shown in FIG. 6 as a conventional example, the height of the slit opening of the diaphragm member 443 is 0.7 mm. In the optical wave 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 this adjustment position, since the position of the position adjustment screw 324 is a half position from the rotation shaft 322 to the center of the slit opening 224a, 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 screw pitch is 0.4 mm, and thus the adjustment amount is 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 with the metal mold is cut later, the accuracy will increase, but the cost will increase.

  In the present embodiment, if the diameter of the light beam to the diaphragm member 224 is 14 mm (twice that of the prior art), the light beam density is 1/4, but the positioning allowable value in the diameter direction of the light beam is doubled. For this reason, at the position of the position adjusting screw 324, the allowable value is doubled, that is, ± 0.2 mm. If it is such a value, even if it uses the base part 130 with the blank material from a metal mold | die, without performing a post-process, it will become tolerance accuracy. In the present hardware processing, manufacturing within a tolerance of about 0.3 mm in width is sufficiently possible. Therefore, if the diameter of the light beam is 1.5 times that of the prior art, there is no need 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 measurement reach distance when the diameter d of the light beam is doubled as compared with the conventional case will be considered.

<Calculation conditions>
Light emission power (objective output) P ₀ : 5mW (output after LD output passes through optical system)
Light emitting wide angle θ: 14 '(7' on one side) ≒ 0.233333 °
Receiving objective diameter: 50mm (Effective diameter for receiving light on the distance meter)
Atmospheric attenuation coefficient β: 0.127 (dimensionless) / Visibility 20km equivalent / 690nm wavelength reach L: 2000m (Product specification / Visibility 20km)
Photosensitivity (minimum operating light intensity) η ₀ : 1nW (light intensity at machine object input)

<Reach distance formula>
Now the amount of light calculated by the following formula returns to the machine,
If the value (received light intensity) is “η”,
η = P ₀ × (φ / 2Ltanθ) ² × EXP (-2βL / 1000) (1)
(Before the reach distance L in the above equation, the coefficient 2 is twice the measurement distance because the path through which the actual light beam passes is a round trip of the measurement distance).

Here, the calculated value η is η ₀ ≦ η (2)
If the conditions are met, the specified distance will be reached, and the machine arrival specifications will be satisfied. The first half of equation (1) is the part that calculates the area ratio between the received light image diameter of the return light and the effective light receiving diameter of the actual machine when the measurement distance is reciprocated. This is the calculated term. The unit of distance used in the atmospheric attenuation calculation is “km”, so 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. (Not easily affected by the atmosphere)

Try to calculate based on 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 can be seen that the value is about 28 times larger than “1 [nW]”, which is the minimum moving light amount under the “calculation conditions”.

Therefore, in view of this result, in the lightwave distance meter 100 according to the present embodiment, even if the diameter of the light flux to the diaphragm member 224 is doubled and the amount of light passing through the slit opening becomes ¼,
28 [nW] × 1/4 = 7 [nW] (4)
Therefore, the light intensity is expected to be about 7 times the minimum operating light intensity of “1 [nW]” and meets the standard value for distance measurement. For this reason, it turns out that the range specification of a machine is fully satisfied.

  As described above, according to the lightwave distance meter 100 according to the embodiment, since the tolerance of the position change with respect to the optical axis of the slit opening is large, the diaphragm member is attached to the attachment base without adjusting the position at the time of manufacture. In addition, the mounting position of the slit opening can be kept within the standard, and the position change of the diaphragm member due to secular change is within the standard, and distance measurement is possible without adjusting the position of the diaphragm member during manufacturing or aging Can be done accurately.

100: light wave distance meter 110: housing 120: lens barrel 130: base part 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: Emitting reflection optical system 241: Reflecting mirror 310: Density filter

Claims (4)

A light wave rangefinder that measures the distance to an object to be measured by comparing reflected light and internal reference light,
A light source that emits a light beam having a predetermined spread along the optical axis;
A diaphragm member that can be arranged on the optical axis, includes a slit opening that extends in a horizontal direction perpendicular to the optical axis, and narrows a spread width of the light flux from the light source;
The light beam is disposed between the light source and the diaphragm member, and the light beam exits the slit opening and the region having a height dimension of 15 times or more of the height dimension of the slit opening. Spreading means;
Including
The light amount of the light source was set so that the reflected light from the object to be measured at the measurement distance set by the light wave distance meter was equal to or greater than a reference value capable of distance measurement.
Lightwave distance meter characterized by that.   The light wave distance meter according to claim 1, wherein the diaphragm member includes an adjustment member that adjusts the slit opening in a vertical direction.   2. The optical wave rangefinder according to claim 1, wherein the diaphragm member is fixed in a state in which the slit opening cannot be adjusted in the vertical direction when the diaphragm member is used. The light wave distance meter according to any one of claims 1 to 3, wherein the light beam expanding means is a collimating lens.