Guide beam direction setting apparatus

Abstract: A guide beam direction setting apparatus of the present invention has a guide beam generator (12) having a guide-beam emission optical system (14) for emitting a guide beam (P), an indicator-beam emission optical system (15) for emitting an indicator beam (K), and detection units (23) for detecting the indicator beam. The indicator beam (K) is a beam which has a flat spatial spread in the emission direction of the guide beam. The detection units (23) are disposed so that they correspond to the collimation direction (L) of a collimation direction unit (11) and that they are spaced from the indicator-beam emission optical system (15), and the emission direction of the guide beam (P) is aligned with the collimation direction (L) by detecting the indicator beam (K) with the detection units (23).

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a guide beam direction setting apparatus which aligns the direction of emission of the guide beam emitted from a guide beam generator with the direction of collimation of a survey to prescribe the emission direction of the guide beam, and more particularly to a guide beam direction setting apparatus capable of application to a tunnel digging operation. 2. Description of Related Art There is a method of tunnel construction which lays pipes, such as Hume concrete pipes and metallic steel pipes, at a position of fixed depth from the ground. As this construction method, there is known an open cut method according to which piping grooves are dug at a position of fixed depth from the ground and pipes are laid. There is also known a dig propulsion method according to which piping tunnels are dug at a place of fixed depth from the ground and pipes are connected in sequence by press fitting. In these construction methods a survey is made in order to determine the direction in which the pipes are laid. Fig. 1 schematically illustrates a conventional guide beam direction setting apparatus for determining the direction in which the pipe is laid. In the figure, reference numeral 1 denotes a vertical pit, reference numeral 2 a surveying machine, such as a theodolite, installed on the ground surface GL, and reference numeral 3 a surveying machine installed at a place of fixed depth from the ground. The surveying machine 2 is employed as a collimation direction means. A hanging frame 4 is installed on the ground surface GL as a plumb-bob device. The hanging frame 4 hangs two weights 6 thereon with two suspension wires 5. The two suspension wires 5 are tensioned by the weights 6 so that they become parallel with each other. The weight 6 is immersed into liquid 7, such as oil having a high viscosity, in order to prevent the oscillation of the suspension wire 5, such as lateral and vertical swings. An operator determines a direction of collimation L in accordance with a pipe laying plan and operates the hanging frame 4 so that the two suspension wires 5 are superimposed and seen as a signal wire. In this way, an imaginary plane including the collimation direction L is formed. For example, a theodolite or a level is employed as the surveying machine 3. The surveying machine 3 adjusts collimation so that the suspension wires 5 are seen as being superimposed. In this way, the collimation direction L as viewed on the ground is aligned with the collimation direction as viewed underground. This collimation direction is assumed to be a digging direction. Also, if there is provided a guide beam generator which emits a guide beam in a direction aligning with the collimation direction of the surveying machine 3, the digging direction can be prescribed based on the direction of emission of the guide beam. If the digging operation of the tunnel 8 is performed based on the collimation directioin of this surveying machine 3 (or the guide beam), pipe laying can be performed according to plans. However, the conventional direction setting apparatus, where the collimation direction of the surveying machine 3 (or the emission direction of the guide beam) and the collimation direction L are aligned with each other by making use of a plumb-bob device, is on an elaborate scale. In addition, the operation of aligning the collimation direction (or the emission direction of the guide beam) with the collimation direction L takes time. Furthermore, in this conventional direction setting apparatus, the size of the vertical pit 1 is restricted from recent road circumstances and therefore the base length (i.e., interval between two suspension wires 5) cannot be freely enlarged. Therefore, if the copying of the survey is made from the ground surface GL to the pit 1 and from the pit 1 to the tunnel 8, cumulative error will become significant. US-A-4 175 861 describes a system for the alignment of a laser beam generator instrument and a remotely located sighting instrument which comprises a projection device mounted on one of said instruments including a laser generator for generating a laser beam and a fixed optical member mounted in the path of the laser beam which projects a fan-shaped beam on the longitudinal axis of the other instrument, a receiving device having a pair of windows fitted with ground glass screens spaced along the longitudinal axis of the receiving device which form an image of axially displaced portions of said fan-shaped beam on the ground glass screens, a system of optical elements which deflect the fan-shaped beam images from each of the screens at angles which are precisely equal, and an eyepiece positioned for the simultaneous observation of the beam images formed on the screens through the optical elements. The optical system includes a five-sided prism and a 90° prism, the axes of which are normal to the principal axes of the instruments and reflect the fan-shaped beam images received on the screens via reflectors by 90°, so that relative angular movement of the principal axis of the instruments causes the fan-shaped beam images appearing on the screens to move in opposite directions as viewed in the eyepiece. SUMMARY OF THE INVENTION The present invention has been made in view of the aforementioned problems. Accordingly, it is an objective of the present invention to provide a guide beam direction setting apparatus which is capable of easily and quickly aligning the emission direction of a guide beam with the collimation direction of a survey and with high accuracy. This object according to the invention is solved with a guide beam direction setting apparatus including the features of claim 1. Preferred embodiment of this apparatus are defined in the subclaims. A guide beam direction setting apparatus according to the present invention comprises: a main body; a guide beam generator provided in said main body and having a guide-beam emission optical system for emitting a guide beam; an indicator-beam emission optical system, provided in said main body, for emitting a linear indicator beam having a flat spatial spread linearly extending in the emission direction of said guide beam; collimation direction means; a pair of retroreflection plates disposed symmetrically with respect to a collimation direction of said collimation direction means and spaced from said main body, the retroreflection plates being adapted for reflecting said linear indicator beam toward said indicator-beam emission optical system; detection means, provided in said main body for detecting said linear indicator beam reflected toward said indicator-beam emission optical system by said pair of retroreflection plates; and rotation control means, provided in said main body, being suitable for swinging said linear indicator beam in the direction of said both retroreflection plates, and for rotating and controlling said indicator-beam emission optical system so that the emission direction of said guide beam is aligned with said collimation direction, based on a detected output of said detection means. According to a preferred embodiment two pairs of retroreflection plates are provided, and the retroreflection plates are disposed at symmetrical positions with respect to an optical axis of the indicator-beam emission optical system. According to a further preferred embodiment, the linear indicator beam is circularly polarized light; one of the two pairs of retroreflection plates are provided with a quarter-wave plate, the detection means is provided with a polarizing beam splitter for separating the reflected linear indicator beam into a linear indicator beam reflected by the pair of retroreflection plates having said quarter-wave plate and a linear indicator beam reflected by the pair of retroreflection plates having no quarter-wave plate; the detection means is provided with a pair of light receiving elements for receiving reflected indicator beams separated by the polarizing bream splitter, and the rotation control means rotates and controls said indicator-beam emission optical system, based on detected outputs of the pair of light receiving elements. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be described in further detail with reference to the accompanying drawings wherein: Fig. 1 is a diagram used to explain a conventional guide beam direction setting apparatus for setting a direction in which pipes are laid; Fig. 2 is a schematic view showing another guide beam direction setting apparatus; a pipe laser apparatus being installed in a vertical pit and a surveying machine being set above the pipe laser apparatus to perform a tunnel digging operation for laying pipes; Fig. 3 is a schematic view showing the guide beam direction setting apparatus of Fig.2 and the optical relationship between the guide beam generator and the surveying machine; Fig. 4 is a partially enlarged view used to explain the operation of the cylindrical lens shown in Fig. 3; Fig. 5 is a diagram showing the positional relationship between an optical indicator-beam emission system and detection means and also showing how the emission direction of a guide beam and a collimation direction are aligned in the apparatus of Fig.2; Fig. 6 is a diagram showing an alternative of the optical indicator-beam emission system shown in Fig. 5; Fig. 7 is a diagram showing an alternative of the detection means shown in Fig. 6; Fig. 8(a) is a diagram showing an alternative of the cylindrical lens shown in Fig. 4, two cylindrical lenses being spaced in the emission direction of the guide beam and a parallel plane portion being formed between the two cylindrical lenses; Fig. 8(b) is a diagram showing another alternative of the cylindrical lens shown in Fig. 4, two pairs of cylindrical lenses being spaced in the emission direction of the guide beam and a parallel plane portion being formed between the two pairs of cylindrical lenses; Fig. 9 is a diagram showing an alternative of the optical indicator-beam emission system shown in Fig. 4; Fig. 10 is a front sectional view showing the detailed construction of the guide beam generator in the apparatus of Fig.2; Fig. 11 is a side sectional view showing the detailed construction of the guide beam generator in the apparatus of Fig. 2; Fig. 12(a) is schematic view showing a further guide beam direction setting apparatus and the optical relationship between the guide beam generator and the surveying machine; Fig. 12(b) is a plan view of the diaphragm plate shown in Fig. 12(a); Fig. 12(c) illustrates the diffracted pattern of a laser beam diffracted by the slit shown in Fig. 12(b); Fig. 13 is a partially enlarged view used to explain the operation of the cylindrical lens shown in Fig. 12; Fig. 14 is a schematic diagram showing the positional relationship between the optical indicator-beam emission system and the detection means and also showing how the emission direction of the guide beam and the collimation direction are aligned; Fig. 15(a) is a schematic view showing a guide beam direction setting apparatus according to a first embodiment of the present invention and also showing how a linear indicator beam is reflected; Fig. 15(b) is a schematic view showing the plane positional relationship of the reflecting system of Fig. 15 (a) to the cylindrical lens and the case where the collimation direction L and the direction in which the linear indicator beam K extends have been aligned; Fig. 15(c) is a schematic view showing the plane positional relationship of the reflecting system of Fig. 15(a) to the cylindrical lens and the case where the collimation direction L and the direction in which the linear indicator beam K extends have not been aligned; Fig. 16(a) is a schematic view showing a guide beam direction setting apparatus according to a second embodiment of the present invention and the state where retroreflection plates have been disposed; Fig. 16(b) is a schematic view showing the guide beam direction setting apparatus according to the second embodiment and the relationship between the optical indicator-beam emission system and the retroreflection plates; Fig. 16(c) is a diagram used to explain the detected output of a light receiving element shown in Fig. 17; Fig. 17 is a schematic diagram showing the relationship between the optical indicator-beam emission system, the detection means, and the rotation control means shown in Fig. 16(b); Fig. 18(a) is a schematic view showing a guide beam direction setting apparatus according to a third embodiment of the present invention and the state where retroreflection plates have been disposed; Fig. 18(b) is a schematic view showing the guide beam direction setting apparatus according to the third embodiment and the relationship between the optical indicator-beam emission system and the retroreflection plates; Fig. 18(c) is a diagram used to explain the detected output of a light receiving element shown in Fig. 19; Fig. 19 is a schematic diagram showing the relationship between the optical indicator-beam emission system, the detection means, and the rotation control means shown in Fig. 18(b); and Fig. 20 is a diagram showing an alternative of the state where the retroreflection plates have been disposed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Figs. 2 and 3, there is shown a guide beam direction setting apparatus for better explaining the invention. In Fig. 2, reference numeral 10 is a vertical pit, 11 a surveying machine, such as a theodolite, installed on the ground surface GL, and 12 a guide beam generator. A pipe laser is used as the guide beam generator 12. The vertical pit 10 is covered, for example, with an iron plate (not shown). The surveying machine 11 is placed on the iron plate (not shown). The guide beam generator 12 is installed just under the surveying machine 11. The iron plate has, for example, a hole formed just under the surveying machine 11. The surveying machine 11 is employed as collimation direction means of determining a direction of collimation L. In Figs. 2 and 3, reference numeral 13 denotes a collimating telescope. The guide beam generator 12, as shown in Fig. 3, has an optical guide-beam emission system 14 for emitting a laser beam P as a guide beam and an optical indicator-beam emission system 15 for emitting an indicator beam K. The indicator beam K has a flat spatial spread in the direction of emission of the guide beam P. The optical guide-beam emission system 14 is roughly constituted by a laser beam source 16 and a collimator lens 17. The collimator lens 17 collimates the laser beam emitted from the laser beam source 16. The optical indicator-beam emission system 15 is roughly constituted by a laser beam source 18, a collimator lens 19, and a cylindrical lens 20. The optical indicator-beam emission system 15 emits a laser beam P' in the vertical direction thereof. The emitted laser beam P' is collimated by the collimator lens 19 and then is guided to the cylindrical lens 20. The cylindrical lens 20 converts the collimated laser beam P' to an indicator beam K, which has a flat spatial spread in the emission direction of the guide beam P. Thus, the cylindrical lens 20 has a power of spatially enlarging the indicator beam K in the emission direction of the guide beam P. The indicator beam K used herein is taken to be a laser beam L0 (see Fig. 4) which is seen as linearly extending in the emission direction of the guide beam P when viewed from the installation side of the surveying machine 11. The indicator beam K also spreads in the form of a fan on a vertical plane. A parallel plane portion 21, as shown on an enlarged scale in Fig. 4, is formed on the central top portion of the cylindrical lens 20. Part of the indicator beam K is transmitted through this parallel plane portion 21 and then is formed into a spot beam S. The spot beam S fulfills a role of prescribing an optical axis center (i.e., the center of a sphere). The spot beam S is recognized by a spherical center telescope 22 of the surveying machine 11. Note that the spherical center telescope 22 has the center of rotation of the surveying machine 11 as its optical axis. Therefore, the center of rotation of the surveying machine 11 is aligned with the optical axis of the optical indicator-beam emission system 15. The surveying machine 11 is provided integrally with a pair of spaced diffusing plates 23. The pair of diffusing plates 23, as shown in Fig. 5, are provided with triangular reference scales 24, respectively. By connecting the vertexes of this pair of reference scales 24, line Q is defined. The direction of this line Q is parallel with the collimation direction L. The pair of diffusing plates 23 fulfill a role as detection means, which detects the indicator beam K (linear laser beam L0) and prescribes the direction of emission of the guide beam P. Note that if the diffusing plate 23 is provided in front of the spherical center telescope 22 so that the spot beam S can be indirectly collimated, recognition of the spot beam S will become even easier. The indicator beam K (linear laser beam L0) is projected on the diffusing plates 23. An operator rotates the guide beam generator 12 so that the indicator beam K (linear laser beam L0) is aligned with the reference scales 24, while viewing the indicator beam K (linear laser beam L0) projected on the diffusing plates 23. This operation can align the emission direction of the guide beam P and the collimation direction L with each other. If the spacing between the pair of diffusing plates 23 is enlarged, the base length will then be correspondingly enlarged. With this operation, alignment accuracy between the emission direction of the guide beam P and collimation direction L can be enhanced. However, if the spacing between the pair of diffusing plates 23 is enlarged, the spacing between detection means will be correspondingly enlarged. Hence, as shown in Fig. 6, reflecting mirrors 25 and 26 are provided so that the indicator beam K is focused just under the surveying machine 11. If the detection means are constructed in this way, the alignment accuracy between the emission direction of the guide beam P and the collimation direction L can be enhanced without increasing the size of the detection means. In this embodiment, the operator directly views the diffusing plates 23 to align the emission direction of the guide beam P and the collimation direction L with each other. However, as shown in Fig. 7, the positions at which the indicator beam K is received may be detected by employing a pair of light receiving elements 27, such as line sensors, area sensors, and CCDs, instead of employing the diffusing plates 23. In the case the beam received positions are displayed on a screen, based on the outputs of the light receiving elements 27. Then, the offset from the reference scale 24 on the screen is corrected while viewing the screen, and the emission direction of the guide beam P and the collimation direction L are aligned with each other. Also, based on the outputs of the light receiving elements 27, the guide beam generator 12 may be remotely controlled so that the emission direction of the guide beam P and the collimation direction L are automatically aligned with each other. The cylindrical lens 20, in addition to the shape shown in Fig. 4, may be formed into shapes shown in Figs. 8(a) and 8(b). Fig. 8(a) illustrates an example where two cylindrical lenses 20 are spaced in the emission direction of the guide beam P, and Fig. 8(b) illustrates an example where two pairs of cylindrical lenses 20 are spaced in the emission direction of the guide beam P. In either case a parallel plane portion 21 is formed in the central portion between the cylindrical lenses 20 for forming the spot beam S. When the cylindrical lens 20 with the shape shown in Fig. 4 is employed, the indicator beam K on the right side will be blocked if the left half portion of the cylindrical lens 20 (indicated by reference character q') has a stain on it. For this reason, the symmetry of the indicator beam K with respect to the spot beam S is degraded. If the symmetry of the indicator beam K with respect to the spot beam S is degraded, superimposition between the collimation direction L and the guide beam P will become difficult. However, if the cylindrical lenses 20 with the shapes shown in Figs. 8(a) and 8(b) are employed, the symmetry of the indicator beam K with respect to the spot beam S is maintained by one cylindrical lens 20 even when another cylindrical lens 20 has a stain at a position of q'. Therefore, superimposition between the collimation direction L and the guide beam P can be performed without difficulty. In addition, as shown Fig. 9, a mask 29 with a slit 28 may be provided before or after the cylindrical lens 20 in order to define the spot beam S of the indicator beam K and the spread portion of the indicator beam K. In this way, the confirmation of the spot beam S becomes even easier. In this embodiment the cylindrical lens 20 has been employed for forming the linear indicator beam K which has a flat spatial spread in the emission direction of the guide beam P. However, an optical diffraction member may be employed instead of the cylindrical lens 20. Also, in the case where the laser source 18 comprises a semiconductor laser, the laser beam has a large spreading angle in the direction perpendicular to a parallel direction with the junction thereof, so the direction where the spreading angle is large is caused to correspond to the emission direction of the guide beam P. If done in this way, the constitution of the optical indicator-beam emission system 15 can be simplified in comparison with a laser having a circular laser beam, such as a He-Ne laser. In addition, in the case where a three-point light emitting type (multi-point light emitting type) is employed as a semiconductor laser, the array direction of the light emitting points is caused to correspond to the emission direction of the guide beam P. Thus, the indicator beam K with a spatial spread in the emission direction of the guide beam P can be easily formed. Figs. 10 and 11 show the detailed construction of a pipe laser apparatus that is used as the guide beam generator 12. In these figures, reference numeral 30 denotes a box-shaped outer frame structure. The outer frame structure 30 has a U-shaped hanging frame 31 (also called the main body of the optical system) fixed thereto. The U-shaped hanging frame 31 has a pair of opposed spherical seats 32 formed in the inner opposite sides thereof, and the seats 32 have horizontal axis centers, respectively. Spherical-axis portions 34 are formed on the opposite surfaces of a rectangular body 33 which forms part of the optical guide-beam emission system 14, and they are fitted in the spherical seats 32. Thus, the rectangular body 33 is rotatable in three-axis directions. The spherical-axis portion 34 has at its front a spherical shape which engages the spherical seat 32. The proximal portion of the spherical-axis portion 34 is cylindrical in shape. An oscillating frame structure 35 is mounted on the cylindrical portion of the spherical-axis portion 34 of the rectangular body 33 so that it is freely rotatable. The spherical-axis portions 34 are provided with horizontal pins 36 and 37 protruding in the opposite directions, respectively. The outer frame structure 30 is provided with a horizontal rotation drive unit 38 on the side of the pin 36 and a twisting unit 39 on the side of the pin 37. From the rear end face of the rectangular body 30 a pin 40 is protruded. The outer frame structure 30 is provided with an elevating unit 41 which elevates the rectangular body 33 through this pin 40. The horizontal rotation drive unit 38 has a gear box 42, a guide shaft 43, a screw shaft 44, a slider 45, and a motor 46 for horizontal adjustment. The gear box 42 is fixed to the U-shaped hanging frame 31. The guide shaft 43 horizontally protrudes from the gear box 42. The screw shaft 44 extends in parallel with the guide shaft 43. The slider 45 meshes with the screw shaft 44 and also is inserted on the guide shaft 43 so that it is freely slidable. The motor 46 rotates the screw shaft 44 through the bear box 42. An engagement pin 47 is stood up in the slider 45 and engages the pin 36 of the rectangular body 33 so that it is freely slidable. The pin 36 of the rectangular body 33 is urged by a spring (not shown) so that it always abuts the engagement pin 47. If the motor 46 is driven to rotate, the screw shaft 44 will then be rotated. The rotation of the screw shaft 44 causes the slider 45 to move horizontally. The horizontal displacement of this slider 45 is transmitted to the pin 36 of the rectangular body 33 through the engagement pin 47, so the rectangular body 33 (optical guide-beam emission system 14) is horizontally rotated integrally with the oscillating frame structure 35. The twisting drive unit 39 has a gear box 48, a guide shaft 49, a screw shaft (not shown), a slider 50, and a twisting motor 51. The gear box 48 is fixed to the U-shaped hanging frame 31 on the opposite side of the aforementioned horizontal rotation drive unit 38. The guide shaft 49 extends vertically downward from the under surface of the gear box 48. The aforementioned screw shaft (not shown) extends in parallel with the guide shaft 49. The screw shaft meshes with the slider 50, and the guide shaft 49 is fitted into the slider 50 so that the slider 50 can freely slide. The motor 51 drives the screw shaft to rotate. An engagement pin 52 is stood up in the slider 50 and engages the pin 37 of the rectangular body 33 so that it is freely slidable. The pin 37 of the rectangular body 33 is urged downward by a spring 53 so that it always abuts the engagement pin 52. If the motor 51 is driven to rotate, the screw shaft will then be rotated. The rotation of the screw shaft causes the slider 50 to move vertically. The vertical displacement of this slider 50 is transmitted to the pin 37 of the rectangular body 33 through the engagement pin 52, so the rectangular body 33 (optical guide-beam emission system 14) is twisted and rotated integrally with the oscillating frame structure 35. The elevation drive unit 41 has a gear box 55, a guide shaft 56, a screw shaft (not shown), a slider 57, and a motor 58 for elevation. The gear box 55 is fixed to the outer frame structure 30 through a bracket 54. The guide shaft 56 vertically protrudes from the gear box 55. The screw shaft (not shown) extends in parallel with the guide shaft 56. The screw shaft (not shown) meshes with the slider 57, and the guide shaft 56 is fitted into the slider 57 so that the slider 57 can freely slide. The motor 58 drives the screw shaft to rotate. An engagement pin 59 is stood up in the slider 57 and engages the pin 40 of the rectangular body 33 so that it is freely slidable. The pin 40 of the rectangular body 33 is urged downward by a spring 60 so that it always abuts the engagement pin 59. If the motor 58 is driven to rotate, the screw shaft will then be rotated. The rotation of the screw shaft causes the slider 57 to move vertically. The vertical displacement of this slider 57 is transmitted to the pin 40 of the rectangular body 33 through the engagement pin 59, so the rectangular body 33 (optical guide-beam emission system 14) is elevated integrally with the oscillating frame structure 35. An angle setting unit 62 is provided on the side surface of the rectangular body 33. A pin 61 is provided near the rear end of the oscillating frame structure 35 and extends in parallel with the pin 36. The angle setting unit 62 relatively rotates the rectangular body 33 (optical guide-beam emission system 14) with respect to the oscillating frame structure 35 through the pin 61 and sets the horizontal angle of the optical guide-beam emission system 14. That is, the angle setting unit 62 has a gear box 63, a guide shaft 64, a screw shaft 65, a slider 66, and a motor 67 for setting angle. The gear box 63 is fixed to the side surface of the rectangular body 33. The guide shaft 64 vertically protrudes from the gear box 63. The screw shaft 65 extends in parallel with the guide shaft 64. The screw shaft 65 meshes with the slider 66, and the guide shaft 64 is fitted into the slider 66 so that the slider 66 can freely slide. The motor 67 rotates the screw shaft 65 through the gear box 63. An engagement pin 68 is stood up in the slider 66 and engages the pin 61 of the oscillating frame structure 35 so that it is freely slidable. The pin 61 of the oscillating frame structure 35 is urged downward by a spring 68a so that it always abuts the engagement pin 68. If the motor 67 is driven, the slider 66 will then be vertically moved. The vertical displacement of the slider 66 is transmitted to the pin 61 of the oscillating frame structure 35 through the engagement pin 68, so the oscillating frame structure 35 is elevated with respect to the rectangular body 33. This embodiment is freely movable in the three-axis directions by employing the spherical seats. However, a gimbal structure may be used excluding the twisting operation. Usually, the rotation in the twisting direction is manually performed when the guide beam generator 12 is installed. The procedure of setting the inclination of the guide laser beam P by this pipe laser apparatus will be described. The apparatus is roughly installed in parallel and operated. Then, the angle setting unit 62 and the elevating unit 41 perform an adjustment operation so that an incline sensor 76, described later, and the guide beam P become horizontal. This causes the pipe laser apparatus to be set horizontally, that is, to a reference position. Based on this horizontal reference position, the oscillating frame structure 35 is inclined in a direction opposite to a set angle by the angle setting unit 62. Therefore, the angle setting unit 62 is caused to reach an inclined state. Next, if the rectangular body 33 is inclined integrally with the angle setting unit 62 by the elevating unit 41 so that the incline sensor 76 becomes horizontal, the guide beam P will be inclined at the set angle. However, this setting method, even in the case where the angle detection range of the incline sensor 76 is narrow, can directly incline an incline sensor if its angle of detection is wide. The optical indicator-beam emission system 15 in this embodiment comprises a light source unit 69 and the cylindrical lens 20. The light source unit 69 is provided in the lower portion of the oscillating frame structure 35. The light source unit 69 is roughly constituted by a laser beam source 70, a reflecting mirror 71, a beam splitter 72, and a collimator lens 19. The laser beam source 70 is provided in one of the mutually opposed wall surfaces of the oscillating frame structure 35. The reflecting mirror 71 is provided on the other wall surface so as to be opposed to the laser beam source 70. The beam splitter 72 is provided between the laser beam source 70 and the reflecting mirror 71. The collimator lens 19 is disposed between the beam splitter 72 and the laser beam source 70. The beam splitter 72 has a role of splitting the laser beam emitted from the laser beam source 70 into upper and lower beams in the vertical direction. When the beam is emitted only upward, a reflecting mirror may be employed instead of the beam splitter 72. Note that holes 73, 74, and 75 are respectively formed in the upper and lower portions of the oscillating frame structure 35, the U-shaped hanging frame 31, and the outer frame structure 30 for allowing the laser beam P' (linear indicator beam K) emitted in the vertical direction to pass vertically. In addition, the incline sensor 76 for detecting the inclination of the emission direction of the guide beam P and an incline sensor 76' extending in the direction crossing the incline sensor 76 are provided on the upper surface of the oscillating frame structure 35. Furthermore, the front surface of the outer frame structure 30 is formed with a hole 77 through which the guide beam P passes. The lower portion of the outer frame structure 30 is provided with support legs 78. With this arrangement, the outer frame structure 30 can be roughly adjusted in the horizontal direction. However, when the guide beam generator 12 is mounted on a stand shown in Fig. 2, the support legs 78 are not always needed. As previously described, this embodiment has been constructed so that the optical indicator-beam emission system 15 is provided in the guide beam generator 12 and that the diffusing plates 23 are provided in the surveying machine 11. However, the diffusing plates 23 may also be provided in the guide beam generator 12, and the optical indicator-beam emission system 15 may be provided in the surveying machine 11. In this case the indicator beam K has a flat spatial spread in the collimation direction L. In other words, the indicator beam K is seen as linearly extending in the collimation direction L when viewed from the side of the guide beam generator 12. In the case where the laser beam source 18 is constituted by a semiconductor laser, the direction where the spreading angle is large corresponds to the collimation direction L. In the case where the laser beam source is of a multi-point light emitting type, the array direction of light emitting points corresponds to the collimation direction L. The diffusing plates 23, on the other hand, are installed in correspondence with the emission direction of the guide beam P. Furthermore, this embodiment has been described with reference to the digging operation of the tunnel 8. However, this is merely an example. For example, this guide beam direction setting apparatus can be employed for detecting the bending or torsion of a building construction or a large-sized metal cutting machine tool. That is, the guide beam direction setting apparatus is also applicable to the detection and alignment of the pillars and walls of a building construction and the assembly, fabrication, and installation of large-sized machines. According to the aforementioned embodiment, the emission direction of the guide beam P and the collimation direction L of a survey can be easily and quickly aligned with each other, and cumulative error can be reduced. Moreover, miniaturization is possible. Referring to Figs. 12 through 14, there is shown a guide beam direction setting apparatus. For an optical indicator-beam emission system 15, a diaphragm plate SP is provided between a collimator lens 19 and a cylindrical lens 20, as shown in Fig. 12(a). The diaphragm plate SP, as shown in Fig. 12(b), has a slit SL which extends in the direction where the linear indicator beam K extends. This slit SL fulfills a role of diffracting the laser beam P' . The diffracted pattern is shown in Fig. 12(c). The laser beam P' is diffracted by the slit SL and then is guided to the cylindrical lens 20. The operation of the cylindrical lens 20 is the same as previously described. The laser beam P' becomes a clear linear laser beam L0 where the luminance brightness is high by the diffraction effect of the slit SL and which extends in the direction in which the slit SL extends, as shown in Figs. 13 and 14. In Fig. 12(c), reference character CE denotes the intensity distribution of the peak portion of the laser beam P' whose luminance brightness is high. Note that the slit SL is not limited to a rectangular shape. In this embodiment the cylindrical lens 20 is convex in shape. However, the cylindrical lens may be concave in shape. In the case where the cylindrical lens is convex in shape, the laser beam P' is converged and forms a focal point. However, in the case of a concave lens, the laser beam P' linearly enlarges without forming a focal point. Also, this embodiment is constructed so that the diaphragm plate SP is provided between the collimator lens 19 and the cylindrical lens 20. However, the diaphragm plate SP may be provided in front of the cylindrical lens 20. Note that in the case where the guide beam generator 12 is provided in a pipe laser apparatus, the diaphragm plate SP is provided on the back surface of the cylindrical lens 20. In Fig. 11 the diaphragm plate SP is shown by a broken line. According to this embodiment, the line width of the linear indicator beam can be made narrow and clear by a diffraction phenomenon, and consequently, the accuracy of the alignment of the emission direction of the guide beam P with the collimation direction L can be enhanced. First Embodiment of the Invention Referring to Figs. 15(a) through 15(c), there is shown a guide beam direction setting apparatus constructed in accordance with a first embodiment of the present invention. Fig. 15(a) illustrates a construction where a pair of reflecting mirrors 100A and 100B are provided in detection means. These reflecting mirrors 100A and 100b reflect the linear indicator beam K two times, thereby constituting a reflecting system which spatially inverts the extending direction of the linear indicator beam K with respect to the collimation direction L. In the case where the collimation direction L and the extending direction of the linear indicator beam K are aligned with each other, the direction of the linear indicator beam K1, which is first reflected by the reflecting mirror 100A and then is reflected by the reflecting mirror 100B and which reaches the diffusing plate 23, and the direction of the linear indicator beam K2, which is first reflected by the reflecting mirror 100B and then is reflected by the reflecting mirror 100A and which reaches the diffusing plate 23, are aligned with each other, as shown in Fig. 15(b). However, as shown in Fig. 15(c), when the linear indicator beam K is shifted from the collimation direction L by an angle of , the linear indicator beam K1 is reflected by the reflecting mirror 100A and then is reflected by the reflecting mirror 100B. When this occurs, the extending direction of the linear indicator beam K1 is spatially inverted with respect to the collimation direction L. Reference character K1' denotes the spatially inverted linear indicator beam. The same may be said of the case where the linear indicator beam K2 is reflected by the reflecting mirror 100B and then is reflected by the reflecting mirror 100A. Therefore, the linear indicator beams K1' and K2', spatially inverted with respect to the collimation direction by two reflections, reach the diffusing plate 23, together with the linear indicator beams K1 and K2. From the angle formed by the linear indicator beam K1 (K1') and the linear indicator beam K2 (K2'), the extending direction of the linear indicator beam K with respect to the collimation direction L can be recognized with double accuracy. That is, according to this embodiment, the linearly extending direction of the linear indicator beam is spatially inverted with respect to the collimation direction L. Therefore, by confirming both the direction of the linear indicator beam before mirror-image inversion and the direction of the linear indicator beam after mirror-image inversion, the direction of the linear indicator beam to the collimation direction can be judged with double accuracy. Second Embodiment of the Invention Referring to Figs. 16 and 17, there is shown a guide beam direction setting apparatus constructed in accordance with a second embodiment of the present invention. As shown in Fig. 16(b), the surveying machine 11 is provided with a pair of retroreflection plates 101A and 101B which are symmetrical with respect to the collimation direction L. Two pairs of the retroreflection plates 101A and 101B are provided at symmetrical positions with respect to the optical axis 01 of an optical indicator-beam emission system 15. However, one pair of retroreflection plates 101A and 101B are masked, and in this embodiment, they are not used. The optical indicator-beam emission system 15 has a holed mirror HM between a collimate lens 19 and a cylindrical lens 20. Reference character H0 denotes the holed portion of the mirror HM. A laser beam P' passes through the holed portion H0 and is guided to the cylindrical lens 20. Therefore, the laser beam P' is assumed to be a linear indicator beam K and guided to the retroreflection plates 101A and 101B. The structure of the retroreflection plates 101A and 101B is known, for example, in Japan Laid-Open Patent Publication No. HEI 7-83656. The linear indicator beam K is reflected by the retroreflection plates 101A and 101B and becomes a reflected beam K'. This reflected beam K' returns in the same direction as the incident direction upon the retroreflection plates 101A and 101B and then reaches the optical indicator-beam emission system 15. The reflected beam K' is reflected by the reflecting surface of the holed mirror HM and then goes to a collective lens 102. The reflected beam K' is collected to a light receiving element 103 by the collective lens 102. The output of the light receiving element 103 is input to rotation control means 104. The rotation control means 104 has a role of rotating and controlling the motor 46 shown in Fig. 11. If the motor 46 is rotated in both directions at constant speed, the linear indicator beam K will be swung, for example, in a range of angle , as shown in Fig. 16(a). During the time the linear indicator beam K is swung at this angle , the beam K is reflected by the retroreflection plates 101A and 101B. The reflected beam K' is received by the light receiving element 103. The detected outputs q1 and q2 of the light receiving element 103 are shown in Fig. 16(c). Times t1 and t2 are obtained by the reciprocal vibration of this linear beam K1. Time tm is obtained by averaging the times t1 and t2. In the case where the optical axis 01 of the optical indicator-beam emission system 15 is aligned with the collimation direction L, the linear indicator beam K can be automatically aligned with the collimation direction L if the time for driving the motor 46 is set based on the average time tm. That is, the guide beam P can be aligned with the collimation direction L. In the case of the motor 46 with an encoder, the guide beam P can be aligned with the collimation direction L by converting the pulse signal of the encoder to angle. Third embodiment Referring to Figs. 18 and 19, there is shown a guide beam direction setting apparatus constructed in accordance with a third embodiment of the present invention. In this embodiment two pairs of retroreflection plates 101A and 101B are used. For an optical indicator-beam emission system 15 of this embodiment, a quarter-wave plate 105 is provided between a cylindrical lens 20 and a holed mirror HM, and converts linearly polarized light to circularly polarized light or circularly polarized light to linearly polarized light. One of the two pairs of retroreflection plates 101A and 101B is provided with a quarter-wave plate 106 for converting the polarization direction of the circularly polarized laser beam P' in the opposite direction, as shown in Figs. 18(a) and 18(b). The linearly polarized laser beam P' passes through the holed portion H0 of the holed mirror HM and is guided to the quarter-wave plate 105. The laser beam P' is converted, for example, to circularly polarized light with clockwise rotation, or right-circularly polarized light by the quarter-wave plate 105. Then, the right-circularly polarized light is converted to a linear indicator beam K by the cylindrical lens 20. This linear indicator beam K is guided to the pair of retroreflection plates 101A and 101B having the quarter-wave plate 106 and to the pair of retroreflection plates 101A and 101B having no quarter-wave plate. For the linear indicator beam K reflected by the pair of retroreflection plates 101A and 101B having the quarter-wave plate 106, the direction of polarization is rotated counterclockwise (opposite direction) with respect to the light traveling direction when the linear indicator beam K passes through the quarter-wave plate. The direction of polarization of the linear indicator beam K, reflected by the pair of retroreflection plates 101A and 101B having no quarter-wave plate 106, remains the same (clockwise) with respect to the light traveling direction. The reflected beam of right-circularly polarized light and the reflected beam of left-circularly polarized light return back to the optical indicator-beam emission system 15. The reflected beam of left-circularly polarized light and the reflected beam of right-circularly polarized light pass through the quarter-wave plate 105 and are converted to linearly polarized light. Thus, both reflected beams K' become linearly polarized light beams which cross each other. The reflected beams K' of linearly polarized light, which cross each other, return to the holed mirror HM. Then, both reflected beams of light, K', lead to a polarizing beam splitter 107 which constitutes part of the detection means. This polarizing beam splitter 107 splits the reflected beams K' of linearly polarized light which cross each other. One reflected beam K' passes through the polarizing beam splitter 107 and is guided to a collective lens 102A, while the other reflected beam K' is reflected toward a collective lens 102B by the polarizing beam splitter 107. Both reflected beams K', collected by the collective lenses 102A and 102B, are received by light receiving elements 103A and 103B, respectively. The detected outputs of the light receiving elements 103A and 103B are input to rotation control means 104. The detected outputs q1 and q2 of the light receiving element 103A and the detected outputs q1' and q2' of the light receiving element 103B are shown in Fig. 18(c). The times t1, t2, t1', and t2' are obtained by the reciprocal vibration of the linear beam K1. The time tm is obtained by averaging the times t1 and t2. Also, the time tm' is obtained by averaging the times t1' and t2'. Based on the average of the times tm and tm', the time for driving the motor 46 is set. If done in this way, the linear indicator beam K can be automatically aligned with the collimation direction L, as in the second embodiment. Therefore, the guide beam P is aligned with the collimation direction L. In this third embodiment, the guide beam P is aligned with the collimation direction L, based on the detected outputs of two pairs of retroreflection plates. Therefore, as compared with the second embodiment, the alignment accuracy can be further enhanced. In the case of the motor 46 with an encoder, the driving time can be obtained by using angles instead of the aforementioned times. As shown in Fig. 20, two retroreflection surfaces 101' in the form of a circular arc plate may be provided symmetrically with respect to the optical axis 01, and quarter-wave plates 106' may be provided on one side of each surface 101' with respect to the collimation direction L, respectively. If done in this way, the detected output, based on the reflected beam K' of the linear indicator beam K from the place where the quarter-wave plate has been provided, and the detected output, based on the reflected beam K' of the linear indicator beam K from the place where the quarter-wave plate has not been provided, will become identical when the linear indicator beam K is just superimposed on the collimation direction L, as shown by reference character KL in Fig. 20. Therefore, by detecting the difference between both detected outputs, the collimation direction L can be detected independent of time and angle (for the detailed construction, see Japan Laid-Open Patent Publication No. HEI 7-83656). Note that if the rotation control means 104 is controlled by a remote controller (not shown), remote control will become easy. According to the second and third embodiments, the detection means receives the linear indicator beam reflected by the retroreflection plates, and the rotation control means automatically controls the optical indicator-beam emission system so that the emission direction of the guide beam is aligned with the collimation direction, based on the detected output of the detection means. Therefore, the collimation direction and the emission direction of the guide laser beam can be automatically aligned.

Claims: A guide beam direction setting apparatus comprising: a main body (31); a guide beam generator (12) provided in said main body (31) and having a guide-beam emission optical system (14) for emitting a guide beam (P) ; an indicator-beam emission optical system (15), provided in said main body (31), for emitting a linear indicator beam (K) having a flat spatial spread linearly extending in the emission direction of said guide beam (P); collimation direction means (11); detection means (103), and rotation control means (104), provided in said main body (31), for rotating and controlling said indicator-beam emission optical system (15) so that the emission direction of said guide beam (P) is aligned with a collimation direction (L), based on a detected output of said detection means (103) characterized by a pair of retroreflection plates (101A, IOIB) disposed symmetrically with respect to said collimation direction (L) of said collimation direction means (11) and spaced from said main body (31), the retroreflection plates (101A, 101B) being adapted for reflecting said linear indicator beam (K) toward said indicator-beam emission optical system (15); wherein said detection means (103) are provided in said main body (31) for detecting said linear indicator beam (K) reflected toward said indicator-beam emission optical system (15) by said pair of retroreflection plates (101A, 101B); and said rotation control means (104) is also suitable for swinging said linear indicator beam (K) in the direction of said both retroreflection plates (101A, 101B). The guide beam direction setting apparatus as set forth in claim 1, characterized in that two pairs of retroreflection plates (101A,101B) are provided, and said retroreflection plates are disposed at symmetrical positions with respect to an optical axis of said indicator-beam emission optical system (15). The guide beam direction setting apparatus as set forth in claim 2, characterized in that said linear indicator beam (K) is circularly polarized light; one of said two pairs of retroreflection plates (101A,101B) are provided with a quarter-wave plate (106) said detection means (103) is provided with a polarizing beam splitter (107) for separating said reflected linear indicator beam (K') into a linear indicator beam reflected by the pair of retroreflection plates (101A,101B) having said quarter-wave plate (106) and a linear indicator beam (K) reflected by the pair of retroreflection plates (101A, 101B) having no quarter-wave plate; said detection means (103) is provided with a pair of light receiving elements (103A, 103B) for receiving reflected indicator beams (K') separated by said polarizing beam splitter (107); and said rotation control means (104) rotates and controls said indicator-beam emission optical system (15), based on detected outputs of said pair of light receiving elements (103A,103B).

Inventors: HAYASHI KUNIHIRO, OHTOMO FUMIO, YOSHINO KENICHIRO, HAYASHI, KUNIHIRO, OHTOMO, FUMIO, YOSHINO, KENICHIRO
Applicants: TOPCON CORP, KABUSHIKI KAISHA TOPCON
Application year: 1997
Main classification: G01C15
IPC codes: E21D9, G01C15