GB2443877A

GB2443877A - A Laser Beam apparatus for a measuring system

Info

Publication number: GB2443877A
Application number: GB0622771A
Authority: GB
Inventors: Mark Nigel Baldock
Original assignee: Individual
Current assignee: Individual
Priority date: 2006-11-15
Filing date: 2006-11-15
Publication date: 2008-05-21
Anticipated expiration: 2026-11-15
Also published as: GB2443877B; GB0622771D0

Abstract

Apparatus (101, 501) for providing a laser beam between selected positions comprising a laser (202, 502) for generating a laser beam, and directing means (209, 521) for adjusting in two dimensions the direction of the laser beam. The apparatus also has a light sensor (208, 508) configured to receive reflected laser light and for producing electrical signals in response to the amount of received light, and a control circuit (204, 504). The control circuit is configured to control the directing means such that the laser beam is scanned horizontally and vertically, while monitoring the electrical signals generated by the light sensor to determine the direction of the target. The control circuit controls the directing means such that the laser beam is manoeuvred to the direction of the target, and maintains the laser beam in that direction. Also disclosed is a laser measuring method, for use in construction work.

Description

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Apparatus For Providing A Laser Beam

Technical Field

The present invention relates to apparatus for providing a laser beam between selected positions, and a method of making measurements from a straight line.

Brief Summary of the Invention

According to a first aspect of the present invention, there is provided apparatus for providing a laser beam between selected positions comprising a laser for generating a laser beam; directing means for adjusting in two dimensions the direction of the laser beam; a light sensor configured to receive reflected laser light and for producing electrical signals in response to the amount of received light; and a control circuit configured to control said directing means such that said laser beam is scanned horizontally and vertically, while monitoring said electrical signals generated by said light sensor to determine the direction of said target, and then control said directing means such that said laser beam is manoeuvred to the direction of said target, and maintain said laser beam in said direction.

According to a second aspect of the present invention, there is : *.. provided a method of making measurements from a straight line, said * *.* method comprising the steps of: locating a laser at a first position; locating * *** a target at a second position; directing a laser beam from said laser to said :m: 25 target; intercepting said laser beam to produce a laser spot; and measuring a distance from said laser spot. * S

Brief Description of the Several Views of the Drawings *SSSS.

* 1 Figure 1 shows apparatus for providing a laser beam between two selected positions; Figure 2 shows schematically the laser generating unit 101; Figure 3 shows the laser generating unit 101 and reflecting device 103 in use; Figure 4 shows an illustration the subsequent use of the laser beam 305; and Figure 5 shows an alternative laser generating unit 501.

Description of the Best Mode for Carrying out the Invention Figure 1 Apparatus for providing a laser beam between two selected positions is shown in Figure 1. The apparatus comprises a laser generating unit 101 which contains a diode laser arranged to generate a laser beam, and a housing having a window 102 for allowing a laser beam from the laser to pass through.

The unit 101 is used in co-operation with a reflecting device 103 which comprises a target 104, in the form of a reflector, and a stand 105. The stand has a pair of legs 106 with feet 107, and a support surface 108 to which the reflector 104 is attached. The support surface and legs are configured such that when the feet are placed on a horizontal surface the reflector is held in a substantially vertical plane.

The reflector 104 in the present example is formed of glass and is ::::. effectively an array of corner cubes. However, in other embodiments, other *.. retroreflectors such as a cat's eye reflector, or an area coated with glass bead composite material, as is known in the art, are used.

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Figure2 * * The laser generating unit 101 is shown schematically in Figure 2. For ease of explanation, only components that are central to an explanation of ****S.

* the function of the unit are shown, and other components such as a battery power supply have been omitted.

Within the housing 201, the unit 101 has a diode laser 202 with a collimating lens 203. The unit also comprises a control circuit 204 including a microprocessor 206 and associated memory 205. The memory comprises read only memory which stores instructions performed by the microprocessor during operation, and may also comprise random access memory used for the storage of data generated during operation. Alternatively, the random access memory may be contained within the microprocessor.

The control circuit 204 has an output connected to a laser power supply 207 so that it controls the operation of the laser 202.

The unit 101 also contains a photoelectric device 208 capable of generating an electrical signal indicative of the amount of light it receives. The output of the photoelectric device 208 is connected to an input of the microprocessor 206 so that the microprocessor is able to monitor the light level illuminating the photoelectric device.

The unit 101 also comprises laser beam directing apparatus 209. The directing apparatus 209 comprises a first mirror 210, and a second mirror 211 and means to rotate the mirrors as required, under the control of the microprocessor 206.

The first mirror 210 has the shape of a regular decagonal prism (i.e. a ten sided prism) having a plane reflecting surface on each of its ten sides, and is configured to rotate about its axis so that the ten sides pass before the : ., beam emerging from the laser. The axis of the first mirror is generally * ** arranged to be substantially vertical, and therefore the rotation of the mirror *..* causes the beam to be reflected at varying horizontal angles.

:: 25 The second mirror is a flat mirror that is configured to receive the beam reflected by the first mirror and to rotate about a horizontal axis to : * deflect the beam at varying vertical angles. ***.

In the present example, the laser 202 emits red light, but other * embodiments in which lasers emit other visible wavelengths are envisaged.

In the present example, the photoelectric device is placed close to the path of the laser beam, and consequently a portion of laser light reflected back to the unit 101 is received by the photoelectric device. In an alternative embodiment, a beam splitter is placed between the second mirror 211 and the window 102 such that laser light reflected back to the unit 101 is reflected by the beam splitter into an appropriately positioned photoelectric device.

Figure 3 The laser generating unit 101 and reflecting device 103 are shown in use in Figure 2. The reflecting device 103 is placed at a first predetermined position and the unit 101 is placed at a second predetermined position such that its window 102 approximately faces the reflecting device 103.

The unit 101 has a number of manually operated controls including an on-off switch 301, a sequence-start switch 302 and laser-off switch 303.

Once positioned, the unit is switched on, using switch 301, and the sequence-start switch 302 is depressed.

Under the control of the control circuit 204, the laser power supply 207 provides power to the laser 202 such that it emits a continuous beam of light: Also, under the control of the control circuit 204, the laser beam directing apparatus 209 adjusts the orientation of the second mirror 211 such that the laser beam is reflected at its maximum vertical angle, and starts the first mirror rotating so that the beam is deflected repeatedly from left to right. The * *. second mirror is then made to rotate relatively slowly so that the laser beam * * . * *** sweeps through a series of closely-spaced, almost horizontal, parallel lines 304.

While the laser beam is scanning, the photoelectric device 208 provides a signal back to the microprocessor indicative of the amount of light it receives. * a * a *

The photoelectric device 208 is illuminated by background light, such * as normal daylight, and also reflected laser light. The laser beam is generally reflected away from the unit 101, absorbed, diffused, etc. and so the laser light makes little contribution to the resulting signal from the photoelectric device. However, when the laser strikes the reflector 104, a relatively large portion of the incident beam is reflected back towards the unit 101, resulting in a measurable increase in the signal. Depending upon the distance of the laser from the reflector 104, the laser beam may hit the reflector on several horizontal sweeps. The microprocessor 206 stores each of the positions of the mirrors over which peaks in the signal occur.

Once the second mirror has reached its lowest vertical angle, and the scan is completed, the microprocessor determines the position of the second mirror that gave a peak in the signal indicating that the reflector 104 ha been hit. If the reflector 104 was hit on several horizontal sweeps, then the middle one of the corresponding second mirror positions is calculated. The second mirror is then rotated back to this position.

The first mirror is then rotated until the signal from the photoelectric device 208 indicates that the laser beam is hitting the target reflector 104. If the microprocessor determines that the beam is hitting the reflector over a small range of angles of the mirror 210, the middle of these angles is determined as relating to the centre of the reflector. The first mirror position is then adjusted so that the beam strikes the centre of the reflector 104 as indicated by dotted line 305. The unit then continues to emit a laser beam towards the reflector 104.

Figure 4 * *** The subsequent use of the laser beam 305 is illustrated in Figure 4.

By putting an object 401 in the path of the laser beam 305, a laser spot 402 is produced on that object. The distance between another object and the laser spot can then be measured. Thus for example, if a measuring rule 401 * is used to intercept the laser beam 305 a laser spot 402 appears on the rule and the distance to an object located at the end 403 of the rule 401 may be * measured.

An example of the use of the unit 101 and reflecting device 103 is when laying kerbs. In this case where a series of kerb stones is to be laid in a straight line, then a first and last kerb stone in the line may be positioned, and the unit 101 placed on the first stone and the reflecting device 103 placed on the last stone. The unit 101 is then used, as described above, to generate a laser beam between the unit 101 and the reflecting device 103. The remaining kerb stones in the series may then be accurately positioned by making measurements from the laser beam as described A second example of the use of the unit 101 and reflecting device 103 is during the excavation of an area of land, such as a car park. The unit is positioned at one side of the area to be excavated, for example on a kerb stone, and the reflecting device at the other side, for example on a kerb stone. The unit is then used, as described above, to generate a laser beam between the unit 101 and the reflecting device 103. Measurements are then made from the laser beam down to the ground surface, and it is thus determined how much material is to be removed from the ground. Material may then be removed, for example by a mechanical digger, without moving the unit and reflecting device.

Once sufficient material has been excavated, the unit 101 and reflecting device 103 may then be used for measurements when material such as stones, tarmac etc. is laid on the ground.

It should be noted that, in each of these examples, the positioning of the unit 101 and reflecting device 103 and subsequent measurements from : ., the laser beam may be done by just a single person; the person having only very limited training.

It should also be understood that the above described measurement method could be performed with a unit that has a manually adjustable laser.

Thus, the laser may be incident upon mirrors that have manually adjustable : * * screw threaded mountings that allow a person to accurately adjust the laser * direction towards the reflecting device. Once the laser is directed towards the S.....

reflector 104 measurements from the laser beam may then be made as described above.

The advantage of this alternative method is that it uses relatively simple, and less costly apparatus. However, the positioning of the laser beam is relatively time consuming when compared to the automated seeking method of the unit 101.

It may also be noted that the unit 101 and reflector 103 are useable on ground that is not level, as the unit 101 is capable of finding the reflecting device whether it is at a level above or below the unit.

Figure 5 An alternative laser generating unit 501 to unit 101 is shown in Figure 5. Like unit 101, the unit 501 has a housing 511 having a window 512 through which a laser 502 is able to emit a laser beam. The laser is operated by a laser power supply 507 under the control of a control circuit 504 comprising a microprocessor 506 and memory 505. The microprocessor 506 receives signals from a photoelectric device 508 in a similar manner to device 208.

Unlike unit 101, unit 501 has actuators 521 configured to alter the orientation of the laser itself, in two mutually perpendicular dimensions.

In operation, the unit 501 functions in a similar manner to unit 101, but scanning of the laser beam is performed by manoeuvring the laser 502 itself.

In a further alternative embodiment, an actuator is used to rotate the * ** laser in the vertical direction only, and the laser beam is arranged to reflect of ::::: a rotating mirror, similar to mirror 210 of unit 101, which deflects the beam in the horizontal direction.

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Claims

Claims 1. Apparatus for providing a laser beam between selected

positions comprising: a laser for generating a laser beam; directing means for adjusting in two dimensions the direction of the laser beam; a light sensor configured to receive reflected laser light and for producing electrical signals in response to the amount of received light; and a control circuit configured to control said directing means such that said laser beam is scanned horizontally and vertically, while monitoring said electrical signals generated by said light sensor to determine the direction of said target, and then control said directing means such that said laser beam is manoeuvred to the direction of said target, and maintain said laser beam in said direction.
2. Apparatus according to claim 1, wherein said directing means comprises a reflective element configured to reflect said laser beam, and a means for rotating said reflective element to scan said laser beam.
3. Apparatus according to claim 1 or claim 2, wherein directing means comprises a means for rotating said laser to scan said laser beam.
4. Apparatus according to claim 1 or claim 2, wherein said directing means comprises a first reflective element and a second reflective : * element each configured to reflect said laser beam, and a means for 0SS rotating said first reflective element in a first direction and for rotating said * second reflective element in a second direction to scan said laser beam.
5. Apparatus according to any of claims I to 4, wherein said target comprises a reflecting device.
6. Apparatus according to claim 5, wherein said reflecting device comprises a retroreflector.
7. Apparatus according to any of claims 1 to 6, wherein said laser beam is manoeuvred to a direction in which the electrical signals indicated largest amount of received light.
8. Apparatus according to any of claims 1 to 7, wherein said apparatus further comprises a beam splitter configured such that the laser beam generated by said laser is directed along a first path toward said beam splitter and light reflected back from said target to said beam splitter is reflected by said beam splitter along a second different path to said light sensor.
9. A method of making measurements from a straight line, said method comprising the steps of: locating a laser at a first position; locating a target at a second position; : ** directing a laser beam from said laser to said target; intercepting said laser beam to produce a laser spot; and measuring a distance from said laser spot.

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10. A method of making measurements according to claim 9, * wherein said target is a retroreflector and said method comprises the step ***.

of scanning said laser beam in a horizontal and vertical direction, and **.. I detecting amounts of reflected laser light.
11. A method of making measurements according to claim 9, wherein said measurement comprises measuring vertically between a ground surface and said laser spot.
12. A method of making measurements according to claim 9, wherein said measurement comprises measuring between said laser spot and a kerb stone.
13. A method of making measurements substantially as herein described with reference to the accompanying Figures.
14. Apparatus for providing a laser beam between selected positions substantially as herein described with reference to the accompanying Figures. b 1$ *. S * .5* I... *

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