JP2006047079A - Distance-measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provive a distance-measuring instrument of a simple photoreception optical system, and to precisely find the range in the measurement of both the far distance and the near distance. <P>SOLUTION: This distance-measuring instrument, for projecting a range finding light to a measured object, and for receiving a reflected range finding light from the measured object to measure the distance, is provided with a light source part 15 for emitting the range-finding light; a light projection optical system 16 for projecting the range-finding light from the light source, and the light-receiving optical system 18 having one portion used in common with the light projection optical system, and for receiving the reflected range-finding light from the measured object made incident and converged, and the photoreception optical system has the center part made incident and converged with the reflected range-finding light; and a perforated mask 53 for limiting transmitted luminous energy, in response to a shift of a light-converging position from the center part. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a lightwave distance measuring device that projects distance measuring light onto a measurement object, receives reflected distance measuring light from the measurement object, and measures the distance to the measurement object. The present invention relates to a non-prism type distance measuring apparatus that is a natural object and does not use a prism such as a corner cube.

  In the conventional optical wave distance measuring device, as shown in Patent Document 1, a retroreflective prism is used as a measurement object, and distance measuring light is projected onto the retroreflective prism and the distance measuring light reflected by the retroreflective prism is used. Receives light and measures distance.

  An outline of the distance measuring apparatus will be described with reference to FIG.

  In the figure, reference numeral 1 denotes a light emitting element. A distance measuring light 2 irradiated from the light emitting element 1 is deflected by a mirror 3 in the direction of a light projecting optical axis 4 and is converted into a parallel light beam through an objective lens 5. The reflected distance measuring light 7 projected toward the cube 6 and reflected by the corner cube 6 is condensed on the light receiving element 11 through the objective lens 5, the condenser lens 8 and the mirror 9. In FIG. 5, reference numeral 12 denotes a collimating optical system.

  In the distance measuring apparatus using the retroreflective prism, the reflected distance measuring light is in a substantially parallel state regardless of the distance to the measurement object, and the reflected distance measuring light incident on the distance measuring apparatus is condensed. The positions are substantially the same, and it is possible to reliably receive the reflected distance measuring light with little influence of disturbance light without considering the light receiving state of the light receiving element 11.

  However, manpower is required to install the measurement object, which is a two-person operation and a complicated operation.

  Also, in recent years, due to the accuracy and sensitivity of the light receiving device, and the advancement of measurement methods, it is possible to receive distance measuring light directly reflected by natural objects such as building walls without using retroreflective prisms for measurement objects. Non-prism type distance measuring devices that perform distance measurement using a wide range of devices are widely used.

  In the non-prism type distance measuring device, since the object to be measured is a natural object, there is no need to install a prism as the object to be measured, so that one person can work and the workability is greatly improved. .

  In the non-prism method, the measurement object is a natural object, and diffuse reflected light from the surface of the natural object is detected. In the case of a long distance of several hundreds of meters, the diffusely reflected light incident on the optical system is a substantially parallel light beam. Therefore, the optical system of the light receiving unit is set to collect the parallel light beam. In short distance measurement of several meters, diffused light is also guided to the light receiving unit. When the outgoing light beam and the reflected light beam are coaxial optical systems, the parallel light beam portion at the center is blocked by the reflecting mirror and condensed into a donut shape excluding the light receiving center. In order to guide the diffused light collected in a donut shape to the light receiving unit, for example, a reflection mirror for short distance is provided.

  Similarly, it collects in a donut shape even at a short distance of around 10 m. However, since it is not easy to make a reflection mirror or the like correspond to a certain short distance in order to guide the diffused light to the light receiving portion, the light receiving portion receives this light. It is set to a size that can be done.

  Although the received light beam from a long distance is condensed at the center of the light receiving portion, the light receiving portion is set to a size that can cope with a certain short distance, so that ambient light is received from the periphery. Since the amount of light received from a long distance is weak, it is buried in disturbance light, and the reflected distance measuring light from the measurement object cannot be detected, resulting in a problem that the distance measuring distance is shortened.

JP-A-4-319687

  In view of such a situation, the present invention provides a simple light receiving optical system with a non-prism method, and enables highly accurate distance measurement in both long distance measurement and short distance measurement.

  The present invention provides a light source unit that emits distance measuring light in a distance measuring device that measures distance by projecting distance measuring light onto the object to be measured and receiving reflected distance measuring light from the object to be measured. A light projecting optical system for projecting distance measuring light from the light source unit, and a light receiving optical system for receiving reflected distance measuring light from the measurement object incident and condensed in common with the light projecting optical system The light receiving optical system is a distance measuring device having a central portion where reflected distance measuring light is incident and collected, and a perforated mask that restricts the amount of light that is transmitted according to a deviation of the condensed position from the central portion. In addition, the perforated mask relates to a distance measuring device having a central opening provided around the optical axis of the light receiving optical system and a peripheral opening provided radially with respect to the central opening, The light receiving optical system has a light receiving fiber for guiding reflected distance measuring light to the light receiving element, and the perforated mask is the light receiving light. Relates to a distance measuring device provided on the incident surface of Aiba, further also said central opening reflected distance measuring light is related to the distance measuring device is a shape that transmits light beams in the case of incident parallel state.

  According to the present invention, in the distance measuring device that projects the distance measuring light onto the measurement object, receives the reflected distance measurement light from the measurement object, and measures the distance, the light source unit that emits the distance measurement light A light projecting optical system that projects the distance measuring light from the light source unit, and a light receiving optical system that receives a part of the light projecting optical system and receives reflected distance measuring light from the measurement object that is incident and collected An optical system, and the light receiving optical system has a central portion where the reflected distance measuring light is incident and collected, and a perforated mask that restricts the amount of light that is transmitted according to the deviation of the condensed position from the central portion. From far distance measurement to short distance measurement, it is possible to receive reflected distance measuring light while restricting the incoming of disturbance light, and it is possible to carry out highly accurate distance measurement from long distance measurement to short distance measurement with a simple configuration.

  According to the invention, the perforated mask has a central opening provided around the optical axis of the light receiving optical system and a peripheral opening provided radially with respect to the central opening. When reflected distance measuring light is incident in a parallel state in long-distance measurement, the amount of light is less limited, and the amount of light necessary for distance measurement is obtained and disturbance light is limited. In addition, reflected distance measuring light is parallel in near-field measurement. When the light is incident in a state other than the above, it is possible to receive the peripheral portion of the light beam, and to exhibit excellent effects such as short distance measurement.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 shows the outline of a distance measuring apparatus according to the present invention, in which 15 is a light source unit, 16 is a light projecting optical system, 17 is an internal reference optical system, 18 is a light receiving optical system, and 19 is an eyepiece optical system. The system (telescope) is shown. The distance measuring device can be used for both a prism measuring method using a prism and a non-prism measuring method using no prism.

  First, the light source unit 15 will be described.

  The laser light source 21 emits infrared distance measuring light of, for example, 780 nm. A first collimating lens 22 and an optical path switching unit 24 are disposed on the optical axis 20 of the laser light source 21.

  The optical path switching means 24 can select a first optical path 25 and a second optical path 26, and the first optical path 25 and the second optical path 26 coincide with the light projecting optical axis 27 by the optical path switching means 24. It is like.

  In the optical path switching means 24, for example, when the rhombus prism 28 is rotatably supported and the first optical path 25 is selected, the distance measuring light from the laser light source 21 is incident on the rhombus prism 28, The light is reflected twice by the rhombus prism 28 and coincides with the light projecting optical axis 27 in a state parallel to the optical axis 20.

  The second optical path 26 coincides with the extension of the optical axis 20. The second optical path 26 includes a second collimating lens 29, an optical fiber 31, and a third collimating lens 32 at the exit end of the optical fiber 31. Provided, and the optical axis of the third collimating lens 32 coincides with the light projecting optical axis 27.

  In a state where the optical path switching means 24 selects the first optical path 25, the center line of the rhombus prism 28 coincides with the first optical path 25, and both end faces of the rhombus prism 28 are respectively in the optical axis. 20. Located on the light projecting optical axis 27. Ranging light emitted from the laser light source 21 is reflected twice by both end faces of the optical path switching unit 24 and emitted onto the light projecting optical axis 27.

  In the state where the optical path switching unit 24 selects the second optical path 26, the rhomboid prism 28 is off the optical axis 20. Ranging light emitted from the laser light source 21 is collected by the second collimating lens 29, enters the optical fiber 31 from the incident end of the optical fiber 31, and is measured from the optical fiber 31. The light is collimated by the third collimating lens 32 and emitted onto the light projecting optical axis 27.

  The projection optical system 16 will be described.

  A beam splitter 35, a concave lens 36, a first optical path deflecting member 37, a second optical path deflecting member 38, and an objective lens 39 are disposed on the light projecting optical axis 27, and the light is projected between the beam splitter 35 and the concave lens 36. A light amount adjusting means 41 is provided.

  The projected light amount adjusting means 41 includes a light amount adjusting plate 43 that is rotated by a light amount adjusting motor 42 having a positioning function such as a stepping motor, and the transmitted light amount continuously changes in the circumferential direction. It is provided so as to block the light projecting optical axis 27.

  The concave lens 36 is disposed so that the focal position of the concave lens 36 and the focal position of the objective lens 39 coincide with each other, and constitutes a beam expander together with the objective lens 39, and is guided to the concave lens 36. The parallel light beam can be enlarged and projected. For this reason, the influence by optical members, such as the said beam splitter 35 and the said light quantity adjustment board 43, can be suppressed to the minimum. Further, the light projecting efficiency is improved as compared with the structure in which the laser light source 21 is disposed at the focal position of the objective lens 39.

  The beam splitter 35 transmits distance measuring light (infrared light) from the laser light source 21 substantially entirely and reflects a part thereof. The first optical path deflecting member 37 and the second optical path deflecting member 38 are mirrors that totally reflect the distance measuring light.

  The internal reference optical system 17 will be described.

  The internal reference optical system 17 is provided between the light source unit 15 and the light receiving optical system 18 described later. The internal reference optical system 17 has an internal reference optical axis 44 that matches the reflected optical axis of the beam splitter 35. On the internal reference optical axis 44, a condenser lens 45, a density filter 46, and a dichroic prism 47 are disposed.

  A chopper means 48 is provided between the light projecting optical axis 27 and the internal reference optical axis 44. The chopper means 48 includes a chopper plate 49 that blocks the light projecting optical axis 27 and the internal reference optical axis 44, and a chopper motor 51 that can rotate and position the chopper plate 49. The internal reference optical axis 44 is in a passing state when the chopper plate 49 is blocking the light projecting optical axis 27, and the projection is performed when the chopper plate 49 is blocking the internal reference optical axis 44. The optical optical axis 27 is in a passing state.

  Thus, by rotating the chopper plate 49, the distance measuring light from the light source unit 15 is applied to the light projecting optical axis 27, or the internal reference optical axis 44 is used as internal reference light. Irradiated or alternatively selected.

  The density filter 46 adjusts the light intensity of the internal reference light so that the reflected distance measuring light from the measurement object and the internal reference light have substantially the same light intensity.

  The light receiving optical system 18 will be described.

  The light receiving optical system 18 includes a light receiving optical axis 52 that matches the extension of the internal reference optical axis 44. The light receiving optical axis 52 includes the dichroic prism 47, mask 53, light receiving fiber 54, and fourth collimating lens 55. An interference filter 56, a condensing lens 57, and a light receiving element 58 are provided. As the light receiving element 58, for example, an avalanche photodiode (APD) is used, and the interference filter 56 has a characteristic of transmitting the oscillation wavelength band of the laser light source 21. When the light receiving element 58 receives the reflected distance measuring light, the received light signal is sent to the calculating unit 65, and the calculating unit 65 calculates the distance to the measurement object based on the received light signal.

  The objective lens 39 collects the light beam on the incident surface of the light receiving fiber 54 when a parallel light beam is incident. That is, the laser beam projected from the light source unit 15 in the long distance measurement is reflected by the measurement object, and the light source image is formed on the incident surface of the reflected distance measuring light of the light receiving fiber 54 by the objective lens 39. It has become. The diameter of the incident surface of the light receiving fiber 54 is equal to or greater than the diameter of the reflected distance measuring light beam at the position of the incident surface that can be used for short distance measurement.

  As shown in FIG. 3, the mask 53 has an outer diameter sufficiently larger than the incident surface of the light receiving fiber 54, and is continuous with the central opening centered on the light receiving optical axis 52, and the central opening. Peripheral openings are provided radially. A light beam passage hole 81 is formed as a central opening, and a slit hole 82 extending outward from the light beam passage hole 81 is formed on the diameter of the light passage hole 81 as a peripheral opening. . The diameter D of the light beam passage hole 81 is set to be the same as or slightly larger than the diameter of the light beam at the position of the mask 53 when the parallel light beam is collected on the incident surface of the light receiving fiber 54.

  The eyepiece optical system 19 will be described.

  The eyepiece optical system 19 has an eyepiece optical axis 60 that matches the optical axis extension of the objective lens 39 that passes through the dichroic prism 47. A viewing lens provided on the eyepiece optical axis 60 with a focusing lens 61 movably provided along the eyepiece optical axis 60, an erecting prism 62 for converting the image into an erect image, and a collimation line such as a cross. A quasi-plate 63 and an eyepiece lens 64 are provided.

  The operation will be described below with reference to FIG. In FIG. 4, reference numeral 75 denotes an object to be measured, and a solid line indicates a condensed state of reflected distance measuring light in a long distance measurement, and a two-dot chain line indicates a condensed state of reflected distance measured light in a short distance measurement. Show.

  First, when performing non-prism distance measurement using a wall surface of a building, which is a natural object, as the measurement object 75, non-prism measurement is selected by an operation unit (not shown) of the distance measurement device. When the non-prism measurement is selected, the rhombus prism 28 is positioned so as to block the second optical path 26 and the light projecting optical axis 27.

  The eyepiece optical system 19 collimates the measurement object 75 to determine a measurement point.

  The distance measuring light emitted from the laser light source 21 is deflected to the first optical path 25 by the rhomboid prism 28, passes through the beam splitter 35, and is transmitted to the measurement object 75 by the light projecting optical system 16. Lighted.

  The beam diameter and divergence angle of the ranging light to be projected depend on the size of the light source. In the case of a semiconductor laser (LD), the light source of the laser light source 21 has a diameter of about 3 μm and is irradiated with distance measuring light with little spread.

  Ranging light is projected from the light projecting optical system 16 onto the measuring object 75, and the reflected ranging light reflected by the measuring object 75 is diffused because the reflecting surface is generally not a mirror surface or a mirror surface. It will be a thing.

  Further, as described above, when the measurement object 75 is at a long distance, for example, in the distance measurement of about several hundred meters, the reflected distance measuring light incident on the distance measuring device is only the parallel light portion of the diffused light beam. The light is condensed on the incident surface of the light receiving fiber 54 by the objective lens 39. The diameter D of the light beam passage hole 81 is set to be the same as or slightly larger than the diameter of the light beam under the condition that the reflected distance measuring light is collected on the incident surface of the light receiving fiber 54. The distance light enters the incident surface of the light receiving fiber 54, but disturbance light having an angle with respect to the light projecting optical axis is blocked by the light beam passage hole 81. Although disturbance light may enter through the slit hole 82, the amount of light incident from the slit hole 82 is small relative to the amount of light passing through the light beam passage hole 81 and does not affect distance measurement. .

  Next, when measuring a short distance with a non-prism, for example, in a distance measurement up to about 10 m, the reflected distance measuring light incident on the distance measuring device is not a parallel light but an angled light beam and is not condensed. To reach the incident surface of the light receiving fiber 54. That is, the focusing position of the reflected distance measuring light by the objective lens 39 is behind the incident surface of the light receiving fiber 54. Accordingly, the diameter of the reflected distance measuring light beam at the position of the mask 53 is larger than that of the light beam passage hole 81.

  Since the central portion of the reflected distance measuring light is blocked by the second optical path deflecting member 38, the reflected distance measuring light is a light beam lacking the central portion, and is therefore reflected through the light beam passage hole 81. The distance measuring light does not enter the light receiving fiber 54 or a state in which a sufficient amount of light does not enter occurs. The slit hole 82 allows a part of the periphery of the reflected distance measuring light to enter the incident surface of the light receiving fiber 54.

Since the light quantity is inversely proportional to the square of the distance, a large quantity of light reaches the distance measuring device in short distance measurement. For example, when the object to be measured is 500 m and 10 m, the light quantity of (500/10) ² = 2500 times is obtained in the short distance measurement with respect to the long distance measurement. Therefore, even if the amount of incident light is limited by the slit hole 82, a sufficient amount of light for distance measurement can be obtained.

  Thus, in the long distance measurement, the incident of the disturbance light is suppressed and the reflected distance measuring light can be guided to the light receiving fiber 54, and the highly accurate measurement is possible. In the short distance measurement, the reflected distance measuring light is received by the light receiving light. A sufficient amount of light can be obtained without focusing on the incident surface of the fiber 54, and measurement is possible.

  When the reflected distance measuring light is incident on the light receiving fiber 54 and the reflected distance measuring light is guided to the fourth collimating lens 55 by the light receiving fiber 54, the fourth collimating lens 55 makes a parallel light beam. The disturbance light is cut by the interference filter 56, and is collected on the light receiving element 58 by the condenser lens 57. The light receiving element 58 receives distance measuring light having a large S / N ratio.

  The light amount adjustment motor 42 rotates the light amount adjustment plate 43 according to the distance measurement, adjusts the intensity of the distance measuring light emitted by the light amount adjustment plate 43, and the light reception regardless of the distance to the measurement object. The intensity of the reflected distance measuring light received by the element 58 is made constant. The chopper means 48 switches whether the distance measuring light is projected onto the object to be measured or is incident on the light receiving optical system 18 as the internal reference light. The density filter 46 reflects the internal reference light and the reflected light. The light intensity of the internal reference light is adjusted so that the light intensity with the distance measuring light is substantially the same.

  The light receiving element 58 transmits light reception signals of the reflected distance measuring light and the internal reference light to the calculation unit 65, and the calculation unit 65 calculates the distance to the measurement object using the light reception signal from the light receiving element 58. As described above, since the disturbance light except the wavelength band of the reflected distance measuring light is removed by the interference filter 56, the reflected distance measuring light received by the light receiving element 58 has a large S / N ratio and high accuracy. Is possible.

  When performing prism distance measurement, prism measurement is selected by an operation unit (not shown) of the distance measuring device. In the prism measurement, in order to measure the prism in the distance measuring range, a light beam having a larger divergence angle than the non-prism measurement is emitted.

  When prism measurement is selected, the rhombus prism 28 is positioned in a state of being off the optical axis 20.

  Ranging light emitted from the laser light source 21 is collected and incident on the incident surface of the optical fiber 31 by the second collimating lens 29. The exit end face of the optical fiber 31 is located on the light projecting optical axis 27, and the distance measuring light emitted from the optical fiber 31 is collected by the third collimating lens 32 and then the beam splitter 35. And is projected onto a measurement object (a retroreflective prism such as a corner cube) by the light projecting optical system 16.

    The distance measuring light reflected from the measurement object enters from the objective lens 39 through the light projecting optical axis 27. The light is condensed by the objective lens 39. The reflected distance measuring light transmitted through the objective lens 39 is incident on the dichroic prism 47. The reflected distance measuring light reflected by the dichroic prism 47 enters the light receiving fiber 54. Reflected distance-measuring light is guided to the fourth collimating lens 55 by the light receiving fiber 54, collimated by the fourth collimating lens 55, disturbance light is cut by the interference filter 56, and collected by the condenser lens 57. The light is received by the light receiving element 58.

  Even in the distance measurement by prism measurement, the interference light is cut by the interference filter 56, so that the S / N ratio is improved. The fourth collimating lens 55 makes the reflected distance measuring light incident on the interference filter 56 in a vertically incident state so that the reflected distance measuring light is not reduced in light quantity by the interference filter 56. This is the same as the non-prism measurement.

  An example of the optical path switching means 24 will be described with reference to FIG.

  The rhombus prism 28 is held by a prism holder 66, and a rotation shaft 67 protrudes from the prism holder 66, and the rhombus prism 28 is rotatably supported via the rotation shaft 67. The rotary shaft 67 is connected to an actuator (not shown) such as a motor (not shown) and a solenoid, and the rhombus prism 28 is inserted into the second optical path 26 and the light projecting optical axis 27 by the actuator. It is designed to rotate at the required angle so that it can be removed.

  In addition, although the said slit hole 82 was arrange | positioned on one diameter, you may arrange | position radially on several diameters. The slit hole 82 and the light beam passage hole 81 may not be continuous. Alternatively, instead of the slit hole 82, a plurality of small holes may be formed, and light beams around the reflected distance measuring light may be incident on the light receiving fiber 54 through the small holes. Further, the shape of the slit hole 82 may be wider or narrower as it goes outward from the center. Furthermore, the mask 53 may be provided directly on the incident surface of the light receiving fiber 54. The reflected distance measuring light is guided to the light receiving element 58 through the light receiving fiber 54. However, the light receiving fiber 54 is omitted and the reflected distance measuring light is directly incident on the light receiving element 58. It may be a light receiving surface.

It is a schematic block diagram which shows embodiment of this invention. It is principal part explanatory drawing of the optical path switching means used by this embodiment, (A) is a top view, (B) is a front view, (C) is a side view. It is a front view of the mask used in this embodiment. It is explanatory drawing which shows the condensing state of the reflected ranging light in this embodiment. It is explanatory drawing which shows the optical system of the conventional distance measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 15 Light source part 16 Light projection optical system 17 Internal reference optical system 18 Light reception optical system 19 Eyepiece optical system 21 Laser light source 24 Optical path switching means 27 Light projection optical axis 38 2nd optical path deflection member 39 Objective lens 41 Light projection light quantity adjustment means 53 Mask 54 Light-receiving fiber 58 Light-receiving element

Claims (4)

  In a distance measuring device that projects distance measuring light onto a measurement object, receives reflected distance measuring light from the measurement object, and measures the distance, a light source unit that emits distance measuring light, and a light source unit A light projecting optical system for projecting a distance measuring light, and a light receiving optical system for receiving a reflected distance measuring light from a measurement object incident and condensed in common with the light projecting optical system. The light receiving optical system includes a central portion where reflected distance measuring light is incident and collected, and a perforated mask that restricts the amount of light to be transmitted according to a deviation of the condensed position from the central portion. .   The distance measuring device according to claim 1, wherein the perforated mask has a central opening provided around the optical axis of the light receiving optical system and a peripheral opening provided radially with respect to the central opening.   The distance measuring device according to claim 1, wherein the light receiving optical system includes a light receiving fiber that guides reflected distance measuring light to a light receiving element, and the perforated mask is provided on an incident surface of the light receiving fiber.   The distance measuring device according to claim 2, wherein the central opening has a shape that transmits a luminous flux when reflected distance measuring light is incident in a parallel state.

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