AU628301B2 - Position meter using laser beam - Google Patents

Description

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PCT

N: W 4.U4E M 0 F 4 G01S 5/16 (11) I sPS S WO 89/03049 Al (43) g aB 1989 4 6 8(06.04.89) (21) tSB S- POT/JP88/01008 (74) ftEIA (22) Dl~JIB 1988-9308 (30. 09. 88) f± X~IE, i (YONEHARA, Maasaaki et al.) (31) fa -g -~jA62-244386 ?105 fios j 5t1 6- RW~BA Tokyo, (,JP) 41M863-3625 (81) (32) aB 1987-9830B (30. 09, 87) AU, DE, SU, US.

19884-1A119 (11. 01. 88) ,lafSj fWi~ lF (33) Hi&k JP (71) 1 B§ A, *L io}§s a K 3-c) 6 2 8 -e 1 (KABUSHIKI KAISHA KOMATSU SEISAKUSHO)C JP/JP) 7107 ,EZ.-Ti -3S64 Tokyo, (JP) (72) Re am; 1.U.J.P. 1 JUN 198 s,:/t5BiiA ;Km tC s) (ONO, Toyoichi )JP/JP) ?254 tJil9Al-m 3 TE6 8 8 5 Kanagawa, (JP)

AUSTRALIAN

(TANABE, Kenj i )CJP/JP) ?254 fJII-YWWE7 B 1 8t Kanagawa, (JP) 18 APR 1989 i li- (ASAYAMA, Yosh io)CJP/JP] T253 fJI;:; b-Mi ~S9~ i 9 0- 10 Kanagawa, (JP) PATENT OFFICE (54)Title: POSITION METER USING LASER BEAM ael<7)-sr v-f -96%HIs- fflittilRs (57) Abstract The present invention provides a position meter which can be used by installing only one laser receiver and can reliably measure the position of a point to be measured even if there is a great difference in level between the position of installation of a laser projector and that of the laser receiver on rugged outdoor construction sites. The position meter of the invention includes laser projectors (10, 13) disposed at two specified points spaced apart from each other, one laser receiver (16) disposed at the point of measurement, reference direction finders (11, 14) and reference direction signal transmitters (12, 15) disposed on the side of the laser projectors and a reference direction receiver (17) and an operational unit (18) disposed on the side of the laser receiver. Furthermore, the laser projector of the invention includes projection angle changing means for changing the elevation angle or depression angle of the laser beam while the laser receiver includes position correction means for correcting the laser beam reception height on the basis of the output from the projection angle changing means.

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SPECIFICATION

POSITION MEASURING-APPARATUS MAKING USE OF LASER BEAMS Technical Field of the Invention The present invention relates to a position measuring apparatus making use of laser beams, and more particularly to an apparatus suitable for position measurement on a land surface having great uneveness such as an-outdoor construction work field or the like.

Background Technique of the Invention Heretofore, as apparatus for measuring a position of a point to be measured by the triangulation based on a geometrical relation between two fixed points (reference points) and the point to be measured, those disclosed in the gazettes of Laid-Open Japanese Patent Applications Nos. 62-273408 and 62-273409 (both filed by the same and No. 62-50616 applicant as the applicant of this application) (Applicant: KASHIMA KENSETSU respectively, are known.

In the measuring apparatus according to these known techniques, laser lighthouses serving as laser beam projectors are respectively installed at the two fixed points, while at the point to be measured or on a moving body such as a working vehicle or the like which is used as an object to be measured is provided a laser beam

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*1 2 receiver. And laser beams are respectively projected in a horizontal plane while being rotated, respectively, from the above-mentioned two laser lighthouses, and when these projected laser beams are received by the aforementioned laser beam receiver, an angle (rotational angle) formed between the straight line connecting the two fixed points and a straight light extending from one fixed point up to the point to be measured and another angle (rotational angle) formed between the straight line connecting the two fixed points and another straight line extending from the other fixed point up to the point to be measured, are calculated by an arithmetic unit, and from the calculated both angles and the distance between the two fixed points, the position of the point to be measured is calculated in a two-dimensional manner (as x- and i-coordinates) through the triangulation process.

In the case of such measuring apparatus, in order to calculate the angle formed between the straight line connecting the two fixed points and the straight line extending from one or the other fixed point to the point to be measured, the respective projection time differences from the time when the respective laser beams projected from the respective lighthouses installed at one and the 11.25 other, two fixed points were projected along the L i *rr 3 straight line connecting the two fixed points up to the time the points irradiate the point to be measured, must be measured. To that end, at the point to be measured, two beam receivers consisting of a first beam receiver opposed to the laser lighthouse installed at one fixed point and a second beam receiver opposed to the laser lighthouse installed at the other fixed point, are necessary.

Accordingly, the laser beam receivers become large-sized and heavy in weight, and so the installing position is limited or it was inconvenient for moving the point to be o measured.

In addition, since a laser beam is projected from a laser lighthouse in the horizontal directions, to take into "consideration a level difference between the installed position of the beam projector and the point to be measured, on the beam receiver, a vertical length of a beam receiver surface is made adjustable. However, in an environment where a level difference of the land surface is remarkably large such as an outdoor construction work "0 field, or the like field where unevenness is great, often a projected laser beam would miss the beam receiving surface of the beam receiver, and there occurs the case where position measurement of a point to be measured becomes impossible.

In the event that the position measurement has thus become impossible, even if it should be temporary, the work Smaking use of a moving body such as a working bc\14\5345.res 92 6 -4vehicle or the like would be compelled to interrupt, and also, in order to measure the above-mentioned unmeasurable point, it would be forced to take a countermeasure through another method, resulting in loss in labor and time, and thus economy in work would be greatly deteriorated.

It is to be noted that as a method for resolving such problems, a method of designing a vertical length of the beam receiver long has been also investigated. However, this method has not become to be employed and practiced, because of the fact that in the case where the beam receiver is installed on a moving body, there is a fear that stability of the moving body in question may be degraded and also rise of an installation cost would be brought about.

Summary of the Invention The present invention has been worked out in view of the above-mentioned circumstance, and a first object of the invention is to provide a position measuring apparatus making use of laser beams, in which a laser beam receiver installed at a point to be measured is only one.

Another object of the present invention is to provide a position measuring apparatus making use of laser beams, which can reliably achieve position measurement of a point to be measured even in an environment i where level differences between installation positions of laser beam projectors at two laser lighthouses and a beam receiving surface of a laser beam receiver installed at the point to be measured are remarkably large, such as an outdoor construction work field where unevenness is great.

Still another object of the present invention is to provide a position measuring apparatus making use of laser beams, wherein three-dimensional position measurement of a point to be measured is made possible by providing means for correcting a beam receiving height in a laser beam receiver installed at the point to be measured.

In order to achieve the aforementioned first object, according to a first aspect of the present invention, there is provided a position measuring apparatus making use of laser beams, wherein first and second laser beam projection means installed at two fixed points separated from each other for projecting laser beams while rotating about rotary axes consisting of vertical axes at the respective installation points, and laser beam receiver means disposed at the point to be measured for receiving the laser beams respectively projected in a rotary manner from the aforementioned first and second laser beam projector means are provided, and the position of the aforementioned point to be measured is measured by triangulation based on the output of the above-mentioned -6laser beam receiver means, characterized in that the apparatus further comprises reference direction detectors and reference direction signal transmitter means respectively provided on the side of each of the abovementioned laser beam projector means, and reference direction signal receiver means and arithmetic means provided on the side of the aforementioned laser beam receiver means, and the apparatus is constructed in such manner that the receiving direction of the laser beam is detected by the aforementioned arithmetic means to discriminate a laser beam projected from which laser beam projector means is the received laser beam, and also a time difference from the above-mentioned each reference direction detector up to the aforementioned point to be measured during rotation of the beam is calculated.

In order to achieve the above-mentioned second object, according to a second aspect of the present invention, there is provided a position measuring apparatus making use of laser beams, characterized in that each of the frist and second laser beam projector means in the abovementioned first aspect includes beam projecting angle changing means which can change an angle of elevation or an angle of depression of the laser beams projected from these projector means.

2 In order to achieve the above-mentioned third object, -7 according to a third aspect of the present invention, there is provided a position measuring apparatus making use of laser beams, characterized in that each of the first and second laser beam projector means in the above-mentioned first aspect includes beam projecting angle changing means which can change an angle of elevation or an angle of depression of the laser beams projected from these projector means, and moreover the above-mentioned laser beam reciever means includes beam receiving level correction means for connecting the beam receiving level detected by the above-mentioned laser beam receiver means on the basis of the output from the aforementioned beam projecting angle changing means, whereby a three-dimensional position of the abovementioned point to be measured can be measured.

The above-mentioned and other objects, aspects and advantages of the present invention will become apparent for those skilled in the art from the following description disclosing preferred embodiments conformable to a principle of the present invention as practical examples, and from explanation in conjunction with the accompanying drawings.

Brief Description of the Drawings Fig. 1 is a schematic front view showing a general construction of a first preferred embodiment of the present 8 invention; Fig. 2 is a schematic plan view of the first preferred embodiment shown in Fig. i, Figs. 3 and 4 are schematic perspective views of a laser lighthouse having a laser beam projector, and a laser beam receiver, respectively; Fig. 5 is a block diagram of arithmetic means used in the first preferred embodiment; Figs. 6A and 6B are diagrams for explaining direction discriminating operations for projected laser means; Fig. 7 is a schematic front view showing modifications of respective ones of two laser lighthouses to be used in the first preferred embodiment; Fig. 8 is a schematic perspective view showing a state of arrangement of devices in a second preferred embodiment of the second preferred embodiment of the present invention; Fig. 9 is a perspective view conceptionally showing a construction of a mirror drive section available in the second preferred embodiment illustrated in Fig. 8; Fig. 10 is a diagram for explaining a principle of position measurement employed in the second preferred embodiment; Fig. 11 shows respective time charts of laser beam receiving signals output from respective reference Z C c,0L 9direction detectors at two fixed points and laser beam receiving signals output from a beam receiver at a point to be measured; Figs. 12A to 12E are illustrations of modes of variation of a point to be measured in the second preferred embodiment; Fig. 13 is a block diagram conceptionally showing a construction of an arithmetic unit available in the second prefer-ed embodiment; and Fig. 14 is a flow chart showing a procedure of processing in the arithmetic unit shown in Fig. 13.

Detailed Description of the Preferred Embodiments In the following, preferred embodiments of the present invention will be described in detail in connection with the accompanying drawings.

At first, a first preferred embodiment of the present invention will be explained with reference to Figs. 1 to 7.

As shown in Fig. 2, a triangle ABC including a point to be measured C is two-dimensionally formed by first and second fixed points (reference points) A and B horizontally separated by a predetermined distance L and the point to be measured C, and the respective vertexes A and B of this triangle ABC serve as first and second reference 25 points.

L 10 At the first reference point A are provided a first laser lighthouse 10 for projecting a rotary laser beam, a reference direction detector 11 and reference direction signal transmitter means 12, at the second reference point B a provided a second laser lighthouse 13 for projecting a rotary laser beam rotating in the opposite direction to the first laser lighthouse 10, a reference direction detector 14 and reference direction signal transmitter means 15, and at the point to be measured C are provided a laser beam receiver 16, reference direction signal receiver means 17 and an arithmetic means 18.

The above-mentioned first and second laser lighthouses 10 and 13 are, as shown in Figs. 1 and 3, such that laser beam projectors 10c and 13c having rotary laser beam projecting sections 10b and 13b are disposed on respective tripods 10a and 13a, while the laser beam receiver 16 is, as shown in Figs. I and 4, such that photo-sensitive elements 16b are disposed in multiple as aligned in the vertical direction on respective surfaces of a polygonal post having a pentagonal or higher order polygonal cross-section and also received beam processing means 16c is provided, and these members are positioned within a same horizontal A+ plane.

reterence adirection detectors and reference direction signal transmitter means respectively provided on the side of each of said laser beam projector means, and /2r :f /2 i "|t U 11 The above-mentioned respective reference direction detectors 11 and 14 are mounted respectively on the laser beam projectors 10c and 13c as opposed to the laser beam projecting section 10b and 13b, these detectors consist of laser beam receivers which send signals respectively to the reference direction signal transmitter means 12 and 15 when they have received laser beams, and the reference direction siganl transmitter means 12 and 15 are adapted to output reference direction signals. In other words, the reference direction signal transmitter means 12 and 15 operate as transmitters.

The above-mentioned reference direction signal receiver means 17 operates as a receiver, which outputs a signal to the arithmetic means 18 when it has received the transmitted reference direction signal.

The above-described arithmetic means 18 is provided with means 20 for discriminating laser lighthouses on the basis of received signals at the laser beam receiver 16, means 21 for detecting reference direction timing on the basis of received signals of the reference direction signal receiver means 17, first and second angle calculator means 22 and 23 for calculating the rotational angles of the first and second laser lighthouses, that is, first and second angles a and 8 on the basis of these

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low 12 received signals, coordinate calculator means 25 for calculating X- and Y-coordinates of the point C to be measured on the basis of these angles and a reference distance L given by reference distance input means 24, display means 26 for displaying the position of the point C to be measured, and height calculator means 27 for calculating a height of the laser beam.

The above-described laser lighthouse discriminator means 20 senses the moving direction of the laser beam on the basis of the sequence of reception of a laser beam in the horizontal direction by the photo-sensitive elements 16b of the laser beam receiver 16, and thereby the first and second lighthouses 10 and 13 rotating in the opposite directions to each other can be discriminated.

For instance, when a laser beam is recieved sequentially from a first photo-sensitive element 16b 1 towards a second photo-sensitive element 16b 2 as shown in Fig. 6A, the laser beam is judged to be a laser beam projected from the first laser lighthouse 10, while when a laser beam is received sequentially from a third photosensitive element 16b 3 towards a second photo-sensitive element 16b 2 as shown in Fig. 6B, the laser beam is judged to be a laser beam projected from the second laser lighthouse 13.

The above-described first and second angle calculator

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er (Ib) 0isposeu at inr ^0IH 0 ILIa crU7 ll w1, IW l I. uIIV. 41 Lr-wI-J:fl i-n -VJ ui- ters (12, 15) disposed on the side of the laser projectors and a reference direction receiver (17) and an operational unit (18) disposed on the side of the laser receiver. Furthermore, the laser projector of the invention includes projection angle changing means for changing the elevation angle or depression angle of the laser beam while the laser receiver includes position correction means for correcting the laser beam reception height on the basis of the output from the projection angle changing means.

13 means 22 and 23 calculate angles on the basis of a time difference from the time when a timing signal from the reference direction timing detector means 21 was input up to the time when the laser beam receiver 16 receives a laser beam.

The coordinate calculator means 25 and the display means 26 are identical those in the prior art.

In addition, as shown in Fig. 7, the laser beam projectors 10c and 13c of the first and second laser lighthouses 10 and 13 could be mounted to the tripods 10a and 13a via screw rods 10d and 13d so as to be vertically movable with a leveling photo-sensitive element 13e mounted to the laser beam projector 13c of the second laser lighthouses 13, also an actuator 13f for rotating the screw rod 13d being provided, so that when the first and second laser lighthouses 10 and 13 are installed, the laser beam projector may be moved vertically by driving the actuator 13f until the leveling photo-sensitive element 13e reveives the laser beam projected from the first laser lighthouse If the above-described provision is made, since the laser beam of the first laser lighthouse 10 and the laser beam of the second laser lighthouse can be held at the same level, there is no need to carry out level adjustment through manual operations, and the work can be done easily.

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i y\ EG 7)A~l :U7 IT IJ RO )I-7.=7 BJ JP B* SD 7X-S BR t3D KP 0. z:t0A.rR1F SE CF :P 7 uP77 T: KR 42;W SN f lJ CH A4 Z LK A n3Z/ t TD 31t-t CM :b Lu TG DE MC us control could be performed by making use of a CPU or the like in such manner that if the leveling photosensitive element 13e has received a laser beam after a drive switch of the actuator 13f was turned ON, the actuator may be stopped.

Next, description will be made on a second preferred embodiment of the present invention with reference to Figs. 8 to 14 0 FIt is to be noted that the above-mentioned operation c ontrol could be positierformed by making use apparatus a C ording the like in such manner that if the leveling phototo a seond preferment 13e has reeived a laser beam after antion.

La5 drive switch of the actuator 13f was turned ON this figure actuator maare respectively installed at preset two fixed points A and B in an outdoor co wi be made on a secold; and preferred laser bembodiment of the present inventionons are preset so asrence to Figs. 8 to 14.

Fig. 8 is a schematic view showing a mode of arrangement of a position measuring apparatus according hto a seond preferred embodiment of the present invention.

ThLaser beam projectors 10 and 13 shown in those projectingfigure are respetively installed g rotat preset two fixed points A with a fixed period, and they rotate respectivelyin andthese laser beam projecting positions synchronized with each other.

In the illustrated embodiment, it is assumed that thevel.

both laser beam projectors 10 and 13 re those projecting laser beams while being rotated over the whole direction with a fixed period, and they rotate respectively in i the same direction and as synchronized with each other.

In the illustrated embodiment, it is assumed that the both laser beam projectors 10 and 13 rotate in the anticlockwise direction as viewed from the above as L A ,indicated by arrows in the same figure.

L i ~L 15 In the reference directions of the laser beams rotationally projected from the above-mentioned projectors 10 and 13, that is, in the direction indicated by a dash-dot line in the same figure, are respectively disposed reference direction detectors 11 and 14.

The reference direction detectors 11 and 14 are connected to a transmitter-receiver 30, and this transmitter-receiver 30 transmits reception signals of the laser beams received by these reference direction detectors 11 and 14 and an output signal of a controller 18a to another transmitter-receiver 31 as will be described later and also receives data transmitted from that transmitter-receiver 31.

The controller 18a is connected to the abovementioned trnasmitter-receiver 30, and controls mirror drive sections 32 and 33 as will be described later on Ii: the basis of the output signal of the aforementioned transmitter-receiver On the other hand, at the location C which is a point to be measured, is disposed a laser beam receiver 16 having a beam receiving section of predetermined vertical length H. This laser beam receiver 16 is composed of a plurality of photo-sensitive elements 16b... disposed at predetermined intervals along the 4 1 16 vertical direction.

The transmitter-receiver 31 is connected to an arithmetic unit 18b, and operates to receive data transmitted from the above-mentioned transmitter-receiver 30 and also to transmit data obtained from the abovedescribed arithmetic unit 18b to the aforementioned transmitter-receiver Here, description will be made on a principle of position measurement (triangulation) employed in the present invention.

Fig. 10 is a basic diagram showing geometrical relations between two fixed points A and B and a point to be measured C.

In the same figure, if a distance between the two fixed point A and B is denoted by L, an angle formed between an x-axis and a sector AC is denoted by a' and an angle formed between the x-axis and a sector BC is denoted by ab' then x- and X-coordinates of the point to be measured C are represented by the following equations sin ab cos ea

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sin(ab Oa) (1) sin a bsin a sin (ab a) /<r>-irxb a bc\14\5345.res 92 6 17 In this position measuring method, upon seeking for the above-mentioned angles aa and ab it is effected by detecting the rotational angles after the laser beams rotationally projected from the above-described laser beam projectors 10 and 13, have reached the aforementioned reference direction, until they are received by the aforementioned laser beam receiver 16, with respect to the respective ones of the laser beam projectors 10 and 13 at the two fixed points A and B.

More particularly, as shown in Fig. 11, the repetition periods of the laser beams projected from the laser beam projectors 10 and 13 at the two fixed points A and B are denoted respectively by Ta and Tb (Fig. 11, and here Ta Tb is assumed). If the periods after the laser beams projected from the laser beam projectors 10 and 13 at the two fixed points A and B have reached the reference direction (the direction of the x-axis) until they are received by the laser beam receiver 16 at the point C are denoted respectively by ta and tb (Fig. 11 and with respect to the points A and B, then the above-described rotational angles a a and ab are represented by the following equations ta t b -a T T "b 7 2 /LUtA>X a b -18- Hence, by substituting these angles a and ab and the distance L between the two laser beam projectors and 13 into the above-described equations a two-dimensional position of the aforementioned point to be measured C can be measured.

By the way, in this case it is an essentially necessary condition for achieving the subject position mesurement that the laser beams rotationally projected from the above-mentioned two laser beam projectors 10 and 13 should be surely received at the aforementioned laser beam receiver 16.

Fig. 12A illustrates the case where laser beams are projected in the horinzontal directions from the laser beam projectors 10 and 13 installed at the two fixed points A and B and the laser beams are received by the laser beam receiver 16 installed at the point to be measured C, that is at the same level as the aforementioned points A and B, and the various dimensions in the vertical direction of the laser beam receiver 16 are preset in such manner that when the levels of the two fixed points A and B and the level of the point to be measured C 1 are equal to each other, the laser beam may be received at the center of the laser beam receiving section of the laser beam receiver 16.

In addition, Figs. 12B and 12C respectively I I r 3 '141 it _I 19 illustrate the cases where the laser beam receiver 16 has been moved to points to be measured C 2 and C 3 whose level differences from the point C 1 fall within a range

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of and installed there, and in these cases also, at the illustrated points, reception of laser beams at the laser beam receiving section of the laser beam receiver 16 is possible.

However, when the laser beam receiver 16 is moved to and installed at a point to be measured C 4 or C 5 whose level difference from the point C 1 exceeds as shown in Figs. 12D and 12E, the above-mentioned rotationally projected laser beam would not be received at the laser beam receiving section of the laser beam receiver 16.

Therefore, in this second preferred embodiment, means for changing angles of elevation or angles of depression of the laser beams projected rotationally from the aforementioned laser beam projectors 10 and 13 are provided so that laser beam reception can be achieved even in such cases.

More particularly, angles of elevation or angles of depression of the laser beams are changed by mirror drive sections 32 and 33 provided in the respective laser beam projectors 10 and 13 shown in Fig. D.

The mirror drive section 32 or 33 has a construction QL4A 5 1 comprising a mirror 36 and 37 disposed on an optical axis

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20 of a laser beam source 34 or 35, a motor 38 or 39 for rotating this mirror 36 and 37 about a horizontal axis via speed reduction gears, a pulse encoder 40 or 41 for outputting pulses of the number corresponding to an amount of rotation of the motor 38 or 39, a counter 42 or 43 for counting the output pulses of the encoder or 41, and a driver 44 or 45 for driving the motor 38 or 39.

It is to be noted that the above-described mirrors 36 and 37 rotate about the rotary axes of the laser beam projectors 10 and 13 as synchronized therewith as indicated by an arrow G in the same figure, and they rotationally project laser beams through laser beam projecting ports 10a and 13a towards the laser beam receiving section of the laser beam receiver 16.

Here, description will be made on the operations of the above-described mirror drive sections 32 and 33.

The inclination angles of the mirrors 36 and 37 are set, in the initial condition, at the reference angles such that optical axes D of the laser beams projected from the laser beam projecting parts 10a and 13a towards the laser beam receiver 16 may be directed in the parallel directions with respect to the installed surface of the laser beam projectors 10 and 13.

On the other hand, if commands from the controller i 21 18a are applied to the drivers 44 and 45, the inclination angles of the mirrors 36 and 37 are changed by the motors 38 and 39 from the above-mentioned reference angle by a predetermined angle. Thereby, an optical axis E or F changed from the above-mentioned optical axis D by +a or -a either in the direction of an angle of elevation or in the direction of an angle of depression, can be obtained.

In the case where the optical axis has changed in the above-described manner, even in the cases shown in Figs. 12D and 12E, as shown by dash lines in these respective figures the laser beams projected from the laser beam projectors 10 and 13 becomes to be receivable at the laser beam receiving section of the laser beam receiver.16, and so, position measurement becomes possible.

It is to be noted that angle change amounts from the reference angle with respect to the mirrors 36 and 37, that is, optical axis variation angles of the laser beams are measured by the counters 42 and 43, and they are fed back to the controller 18a.

Fig. 13 is a block diagram conceptionally showing a construction of an arithmetic unit 18b provided on the side of the laser beam receiver 16. In addition, Fig. 14 shows a processing procedure in the arithmetic 22 unit 18b.

In the following, the second preferred embodiment will be explained in more detail with reference to these figures.

In the case of carrying out position measurement by making use of laser beams, in preparation for the position measurement, measurements of installation errors of the respective laser beam projectors 10 and 13 are effected, and the data obtained by the measurements are used for correcting measurement data obtained in the position measurement as will be described in the following, but further explanation thereof will be omitted because the correction calculation is not driectly relevant to the present application.

When the above-mentioned preparation for position measurement has been finished, an operator moves the laser beam receiver 16 to the respective points to be measured and instals it there.

Upon such movement and installation, if necessary, an operator performs angle adjustment of the mirrors 36 and 37 so that laser beams can be received at the laser beam receiver 16.

In other words, the inclination angles of the abovementioned mirrors 36 and 37 are, in the initial condition at the time point of commencing position measurement, I 23 preset at such angles that laser beams can be projected in the horizontal direction as shown in Fig. 12A.

Accordingly, starting from this condition, when the laser beam receiver 16 is moved to and installed at the point C 2 or C 3 shown in Figs. 12B and 12C, since the laser beam can be received at the laser beam receiver 16, angle adjustment of the aforementioned mirrors 36 and 37 is not effected.

However, when the laser beam receiver 16 is moved to and installed at the point to be measured C 4 or C 5 as shown in Figs. 12D and 12E, mirror angle change command data for changing the inclination angles of the mirrors 36 and 37 by a predetermined angle so that laser beam reception can be effected at the same laser beam receiver 16, are input to a mirror angle changing command input section 20a (Step 101).

The above-described mirror angle change comands are transmitted via the transmitter-receiver 31 to the transmitter-receiver 30. It is to be noted that the angle change command signal transmitted from the transmitter-receiver 31 to the transmitter receiver is added with a signal for discriminating to which mirror the commands are directed.

At the transmitter-receiver 30, the angle change command signal transmitted from the transmitter- 1' -24receiver 31 is received, and the controller 18a controls the inclination angles of the respective mirrors 36 and 37 or the basis of these received data.

In this case, in the controller 18a, feed-back control for the above-mentioned inclination angles on the basis of the feedback signals fed from the counters 42 and 43 is effected. Soon when the inclination angles of the respective mirrors 36 and 37 have reached predetermined angles corresponding to the abovementioned angle change command data which are the target values, the outputs from the counters 42 and 43, that is, the angle chagne amounts from the reference angles with respect to the mirrors 36 and 37, are transmitted via the controller 18a form the transmitter-receiver to the transmitter-receiver 31. These angle change amounts are input from the aforementioned transmitterreceiver 31 to the coordinate calculator section It is to be noted that after the above-described laser beam projection angle changing operation, an 20 operator confirms whether or not reception of alaser beam is effected in the laser beam receiver 16, and when it has been known that reception of a laser beam is not effected, by reinputting mirror angle change command data having a changed angle, the above-described processing is executed repeatedly. Whereas, when it has 25 been known that reception of a laser beam has been effected, the processing is transferred to the next step 103 (Step 102).

If the inclination angles of the mirrors 36 and 37 are definitely determined in the above-described manner, the laser beams projected from the laser beam projectors 10 and 13 are received by the respective reference direction detectors 11 and 14, and the reception signals of the laser beams received by these reference direction detectors 11 and 14 are transmitted via the transmitter-receiver 30 to the transmitterreceiver 31.

In the transmitter receiver 31, when the laser beam reception signal transmitted from the transmitterreceiver 30 has been received, a laser beam reception signal of the laser beam projector 10 is output to a time measuring section 21 a while the laser beam reception signal of the laser beam projector 13 is output to a time measuring section 21b (Step 103).

On the other hand, the laser beam projectors and 13 are further rotated, and when the laser beams projected from these laser beam projectors 10 and 13 have been received at the laser beam receiving section of the laser beam receiver 16, these laser beam reception signals are respectively input to a level 26 calculator section 27 and the above-mentioned time difference measuring sections 21a and 21b as signals representing a laser beam receiving level and laser beam reception time. It is to be noted that the signal representing the laser beam receiving level is input to the level calculator section 27 as a signal indicating by what photo-sensitive element among the respective photo-sensitive elements 16b the laser beam has been received.

Here, explanation will be made on the method for discriminating from which laser beam projector the abovedescribed laser beam reception signal was projected.

As described previously, the laser beam projectors and 13 are rotated nearly as synchronized with each other. Furthermore, as shown in Fig. 10, in this triangulation, arrangement is made so as to fulfil Sa 900 and ab 90'. Accordingly, the relation between the respective times ta and tb elapsed from the amount when the laser beams reached the reference direction until they are received by the laser beam receiving section of the laser beam receiver 16 would become ta tb', and on the basis of such sequence of laser beam reception, one can discriminate from which laser beam projector the laser beam has been received (Step 104).

In

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27 In the time different measuring sections 21a and 21b, the above-described times ta and tb with respect to the laser beam projectors 10 and 13 can be respectively detected on the basis of the laser beam reception signal output from the transmitter-receiver 31 and indicating the reference direction and the laser beam reception signals output from the laser beam receiving section of the laser beam receiver 16 (See Fig. 11: Step 105).

By substituting these times t a and t b into the above-described equations the respective rotational angles a a and ab of the laser beam projectors 10 and 13 can be calculated respectively by the angle calculator sections 22 and 23 (Step 106).

Furthermore, by substituting these calculated rotational angles a a and ab and the distance L between the respective laser beam projectors 10 and 13 into the aforementioned equations a two-dimensional position of the laser beam 16, that is, a position C y) of the point to be measured can be calculated in the coordinate calculator section 25 (Step 107).

On the other hand, in the level calculator section 27, a temporary level position Z 1 in the vertical 1.1 direction of the point to be measured C is calculated on the basis of the output of the laser beam receiving r 28 section of the laser beam receiver 16.

In other words, this temporary level position Z 1 denotes the level position of the point to be measured C in the stage of not taking into consideration the inclinations of the mirrors 36 and 37, and in this case since the installed point A of the laser beam projector (or the installed point B of the laser beam projector 13) is used as the origin in the vertical direction and since provision is made such that when the level positions of the installed point A and the point to be measured C are equal to each other (See Fig. 12A) the laser beam may be received at the center of the laser beam receiving section of the laser beam receiver 16, the above-mentioned temporary level height position Z 1 is represented as a displacement from the center of the laser beam receiving section of the laser beam receiver 16.

For instance, when the laser beam receiving bH position is deviated by H downwards from the center of the laser receiving section of the laser beam receiver 16 as shown in Fig. 12B, the temporary level position becomes Z In addition, at the point to be measured 1 2'

C

4 shown in Fig. 12D also, since laser beam reception is effected by the same photo-sensitive element as the photo-sensitive element 16b, the temporary level i 29 position becomes likewise Z= More particularly, in the case shown in Fig. 12B and in the case shown in Fig. 12D, as to a photosensitive element 16b of the laser beam receiving section in the laser beam receiver 16, since laser beam reception is effected by the identical photo-sensitive element, the temporary level positions Z 1 become identical, but in the case of Fig. 12D since the inclinations of the mirrors 36 and 37 are chagned, the temporary level position Z 1 in this case does not represent a true level position. The thus obtained temporary level position Z 1 is input to the coordinate calculator section 25 (Step 108).

Next, in the coordinate calculator section 25, on the basis of the above-mentioned angle change amount output from the above-described transmitter-receiver 31, it is judged whether the inclination angles of the abovedescribed mirrors 36 and 37 have changed from the reference angle or not (Step 109).

In the where the result of judgement in the abovedescribed step 109 is No, that is, in the case where the inclination angles of the mirrors 36 and 37 are the reference angles, the processing that the temporary level position Z 1 calculated in the above-described S step 108 is used as a coordinate position Z in the 30 vertical direction of the point to be measured, is executed (Step 110).

In this case, the above described coordinate position Z is stored jointly with the two-dimensional coordinate values x and y of the point to be measured which were calculated in the above Step 107, and they are also displayed in the display section 26 (Step 111).

On the other hand, in the case where the result of judgement is YES, that is, in the case where the inclination angles of the mirrors 36 and 37 have been tilted and changed from the reference angle, on the basis of this angle change amount as well as the twodimensional position x, y of the point to be measured and the two-dimentional positions A (xA, yA and B (xB, YB of the two fixed points A and B which were calculated in the aforementioned .Step 107, a processing for correcting the above-described temporary level position Z 1 is executed.

More particularly, assuming that the inclination angles of the mirrors 36 and 37 have been changed and the directions of the optical axes of the laser beams have chagned from the horizontal direction by and -a in the direction of the angle of elevation and in the direction of the angle of depression, then in order to seek for the coordinate position Z of the point to be 31 measured, it is necessary to add (or subtract) a correction value Z 2 accompanying with the abovementioned change of the optical axis to or from the aforementioned temporary level position Z 1 In order to seek for the above-mentioned correction value Z 2 a distance XAC between the points A and C and a distance BC between the points B and C are respectively calculated on the basis of the following equations from the two-dimensional positions A (XA, YA) and B (x B, B) of the two fixed points A and B and the twodimensional position C (xC, yc) of the point to be measured C: 9 AC V(xA XC)2 y A YC) 2 (3) 9 BC /(xB XC)2 (yB YC 2 And the amount of change of the direction of an angle of elevation or the direction of an angle of depression of the corresponding optical axes +a or -a is calculated from the angle change amounts of the abovedescribed mirrors 36 and 37, and by substituting this amount of change and the aforementioned distance ,AC or £BC into the following equation the abovementioned correction value Z 2 can be calculated (Step 112): 32 Z k tan a (where kAC or kBC).

If the correction value Z 2 is calculated in the above-described manner, then a processing for calculating the coordinate position Z according to the following equation can be executed: Z Z I z 2 In this connection, since the temporary level position Z 1 of the point to be measured C 4 shown in Fig. 12D is Z 1 H/2 similarly to the temporary level position Z 1 in Fig. 12B as described previously, and since the correction value Z 2 becomes kAC tan a (or YBC tan a) from the above-described equation a true coordinate position of the point to be measured

C

4 becomes Z H/2 £AC tan a (or H/2 £BC tan a) (Step 113).

When the coordinate position Z has been calculated in this way, the coordinate position Z is stored jointly with the two-dimensional coordinates x, y of the point to be measured which were calculated in the aforementioned Step 107, and also they are displayed in the displaying section 26 (Step 111).

As explained above, according to the second preferred embodiment, the optical axis of the laser beam is made to change in the direction of an angle of 33 elevation or in the direction of an angle of depression, and so, laser beam reception at the laser beam receiver can be effected reliably.

In addition to the above embodiment, as a modification of the second preferred embodiment, a true vertical position coordinate of the point to be measured can be sought for by correcting the laser beam receiving level position of the laser beam receiver on the basis of the amount of change of this optical axis. Thereby, three-dimensional position measurement for the point to be measured, becomes possible.

It is to be noted that while angle change commands for the minor drive sections 36 and 37 are given by operator's manual data input in the second preferred embodiment, it should not be limited thereto.

More particularly, it is naturally possible to automate the angle change control for the mirrors by providing in the arithmetic unit 18b, means for judging whether or not laser beam reception has been effected in the laser beam receiving section of the laser beam receiver 16, and angle change command generator means for generating angle change commands for appropriately changing inclination angles of the mirrors 36 and 37 when it has been judged by the judging means that laser beam reception has not been jV .,U3

U

34 effected.

Still further, while the angle change commands for the mirror drive sections 32 and 33 are given by wireless communication making use of two transmitterreceivers in the second preferred embodiment, it is not limited thereto, but naturally the invention can be practiced by wired communication. Also, the commands in this case should not be limited to commands relying upon remote control from the point to be measured, but modification could be made such that commands may be given directly to the controller 18a at the installation points of the laser beam projectors.

In addition, while explanation was made supposing the case where the respective points in the work field are measured spot by spot in the second preferred embodiment, modification could be made such that a laser beam receiver is loaded on a moving body and the position of that moving body may be measured. Of course, as position measurement of a moving body, it is not limited to vehicles but it is applicable to position measurement of every moving body such as position measurement of ships in harbors or the like.

Also, while reference direction signals respectively obtained from two laser beam projectors are transmitted or received by means of a single transmitter-receiver 35 in the second preferred embodiment, it is a matter of course that modification could be made in such manner that the above-described reference direction signals may be transmitted or received by separate transmitterreceivers.

Furthermore, while the directions of rotation of the two laser beam projectors are chosen to be the same direction in the second preferred embodiment, of course they could be rotated in the opposite directions to each other like the above-described first preferred embodiment.

Moreover, while the laser beams projected from two laser beam projectors are received by a common laser beam receiving section of the laser beam receiver 16 in the second preferred embodiment, in order to individually receive the laser beams projected respectively from two projectors, laser beam receiving sections having different heights from each other could be provided.

Also, while the reference direction detector 11 and 14 for discriminatively receiving laser beams projected from two laser beam projectors are provided respectively in the respective reference directions of the two laser beam projectors in the second preferred gLIA embodiment, it is not always necessary to provide these 4 36 reference direction detectors 11 and 14, but the respective laser beam projectors could be rotated synchronously at a constant speed, and position measurement could be done on the basis of only reception timing at the point to be measured of the laser beams projected from the respective laser beam projectors.

In essence, so long as it is an apparatus for carrying out triangulation by making use of laser beams, the construction of it per se is arbitrary.

It is to be noted that while examples of carrying out triangulation by projecting laser beams were disclosed in these preferred embodiments, of course, it is not limited to laser beams but so long as there are light beams having excellent straight traveling property, it is also naturally possible to practice the invention by making use of such light beams.

In addition, while the directions of optical axes of laser beams are changed by changing the angles of the mirrors 36 and 37 in the second preferred embodiment, the invention is not limited thereto, but the abovementioned directions of optical axes could be changed by tilting the laser beam projectors themselves.

In essence, so long as the directions of optical axes of laser beams can be changed, the method is i:; I i I Ar 37 arbitrary.

Furthermore, in order to detect the laser beam receiving position in the vertical direction, a position sensor (PSD) could be employed in the laser beam receiving section of the laser beam receiver 16.

1

Claims (10)

1. A position measuring apparatus making use of laser beams, wherein first and second laser beam projector means installed at two fixed points separated from each other for projecting laser beams while rotating about rotary axes consisting of vertical axes at the respective installation points, and laser beam receiver means disposed at the point to be measured for receiving the laser beams respectively projected in a rotary manner from said first and second laser beam projector means are provided, and the .of said point to be measured is measured by triangulation based on the output of said laser beam receiver means; characterized in that said apparatus further comprises reference direction detectors and reference direction signal transmitter means respectively provided on the side of each of said laser beam projector means, and reference direction signal receiver means and arithmetic means provided on the side of said laser beam receiver means, and the apparatus is constructed in such manner that the receiving direction of the laser beam is detected by said arithmetic means to discriminate a laser beam projected from which laser beam projector means is the received laser beam, and also a time 4,U 39 difference from each said reference direction detector up to said point to be measured during rotation of the beam is calculated.

2. A position measuring apparatus making use of laser beams as claimed in Claim 1, characterized in that each of said first and second laser beam projector means includes beam projecting angle changing means which can change an angle of elevation or an angle of depre- ssion of the laser beams projected from these laser beam projector means.

3. A position measuring apparatus making use of laser beams as claimed in Claim 1, characterized in that each of said first and second laser beam projector means includes beam projecting angle changing means which can change an angle of elevation or an angle of depression of the laser be, rojected from these laser beam projector means, and mcreover said laser beam receiver means includes beam receiving level correction means for correcting the beam receiving level detected by said laser beam receiver means on the basis of the output from said beam projecting angle changing means, whereby a three-dimensional position of said point to be measured can be measured.

4. A position measuring apparatus making use of laser beams as claimed in Claim 1, characterized in that each L.A1 0UChJLL. L1L LtC(;tI 40 of said first and second laser beam projector means includes means for moving the respective laser beam projectors in the vertical direction in order to adjust a laser beam projecting level.

A position measuring apparatus making use of laser beams as claimed in Claim 1, characterized in that said laser beam receiver means includes a laser beam receiver having a pentagonal or higher order polygonal shape with respect to its horizontal cross-section.

6. A position measuring apparatus making use of laser beams as claimed in Claim 1, characterized in that said arithmetic means includes means for discriminating the laser beam projector means, one set of two angle detectors, timing detector means, means for detecting the levels of the laser beams, reference distance input means, coordinate calculator means and display means.

7. A position measuring apparatus making use of laser beams as claimed in either one of Claims 2 and 3, characterized in that said laser beam projecting angle changing means includes one mirror rotating synchro- nously with rotation of said laser beam projector means on an optical axis of a laser beam source and disposed so as to be arbitrarily tilted up and down about a horizontal axis, and mirror drive means for giving e ii tilt-up and tilt-down operations to said mirror.

8. A position measuring apparatus making use of laser beams as claimed in Claim 4, characterized in that one of the vertical moving means of said laser beam projectors is provided with a photo-sensitive element for levelling use and one actuator for driving said vertical moving means by the output from said levelling use photo-sensitive element.

9. A position measuring apparatus making use of laser beams as claimed in Claim 7, characterized in that said mirror drive means includes one motor, one pulse encoder for outputting pulses of the number corresponding to an amount of rotation of said motor, one counter for counting the output pulses of said encoder, driver means for driving said motor, and one controller for controlling said driver means in accordance with the output of said counter.

10. A position measuring apparatus making use of laser beams substantially as hereinbefore described with reference to the accompanying drawings. DATED this June 25, 1992 CARTER SMITH BEADLE Fellows Institute of Patent Attorneys of Australia Patent Attorneys for the Applicant: KABUSHIKI KAISHA KOMATSU SEISAKUSHO 4\5345.res 92 6 42 Abstract A position measuring apparatus making use of laser beams, which aims at that it is necessitated only to instal one laser beam receiver and that position measurement of a point to be measured can be achieved reliably even in an outdoor construction work field having violent unevenness where a level difference between a installed position of a laser beam projector and a installed position of alaser beam receiver is remarkably large. This position measuring apparatus is provided with laser beam projectors (10, 13) installed respectively at two fixed points separated from each other, one laser beam receiver (16) installed at the point to be measured, reference direction detectors (11, 14) and reference direction signal transmitters (12, 15) provided on the side of the laser beam projectors, and a reference direction signal receiver (17) and an arithmetic unit (18) provided on the side of the laser beam receiver. Furthermore, the laser beam projector is provided with a laser beam projecting angle changing device for changing an angle of elevation on an angle of depression of the projected laser beam, and on the other hand, the laser beam receiver is provided with a received laser beam level position jI 43 connecting device for correcting the received laser beam level position on the basis of the output from the laser beam projecting angle changing device.