GB2191600A - Apparatus for measuring distances - Google Patents

Abstract

The apparatus comprises a source for directing a beam of light towards a surface (9) whose distance is to be measured, a sight or sights for observing a selected part of the surface, means for directing the beam of light to impinge on the part and an arrangement for indicating the inclination of the beam with respect to the line of view. A particular embodiment comprises a housing (2), a laser source (1) located within the housing, together with mirrors (4,5) for directing light from the source to a selected part which is also observed through a telescopic sight (8) mounted upon the housing. Means may also be provided for effecting movement of the beam in a second plane different from that in which beam movement takes place for measuring purposes. Alternatively, the telescopic sight may be capable of angular movement. <IMAGE>

Description

SPECIFICATION Improvements in or relating to apparatus for measuring distances This invention relates to apparatus for measuring distances.

GB Patent Application No 86.05508 describes apparatus that uses laser beams to measure the distance of an object from a reference point and it is an object of the present invention to provide a modified form of that apparatus that is of simpler construction whilst providing the same facilities.

According to the present invention apparatus for measuring distances comprises a source of light, a sight or sights for observing a selected part ofthe object or surface, means for directing the beam of lightto impinge on the selected part and an arrange mentfor measuring the attitude of the beam with respectto the line of view along the sight or sights to the selected part.

Preferably, the sight is a telescopic sight fitted with a suitable graticule.

The light source may be a laser source which may be a continuous laserorone pulsed at afrequency high enough to create the visual impression of continuous wave operation.

The lasersource may bea rubylaserora gas laser, for example a helium-neon laser, or helium cadmium laser.

In one embodiment of the invention, the beam of light may be capable of pivotal movement in a plane differentfrom that in which movementtakes place for distance measurements, for example a plane at right angles.

Alternatively, the line of sight along the sight or sights may be pivotable, means being provided for indicating and/or measuring the extent of pivotal movement.

Byway of example only, embodiments of the invention will now be described in greater detail with reference to the accompanying drawings of which: Figure lisa schematic layout of a first embodiment iliustrating its method of operation, and Figures2 and 3 are explanatory drawings.

Basically, the invention provides a source of light, asightorsightsforobservingaselected part of an object or surface,whose distance from a reference point is to be measured and means for directing the beam of lightto impinge on the selected part and an arrangement for measuring the attitude ofthe beam with respecttothelineofviewalongthesightor sights to the selected part.

The sight may be a telescopic sight with a suitable graticule, for example, a cross or circle. Such a sight enables a userto observe more accurately the posi tion of impingement on the objectorsurface ofthe light beam.

Figure 1 shows schematically a particular arrangement using a laser source indicated by block 1 located within a housing 2. Also iocated within the housing 2 and positioned in the path ofthe beam 3 of coherent Iightfrom the laser source isa deflector 4 Light from deflector4 impinges on a second deflector 5 that is mounted for movement about an axis 6 which directs the beam 3 outwardly from the housing 2 via a slot7 in an end wall ofthehousing.

Mounted upon the upper (as seen in Figure 1) of the housing 2 is a telescopic sight 8 through which the user is able to observe an object or surface 9 whose distance from the observer is to be measured.

The sight 8 has a graticule comprising cross wires 10, Figure2Oracircle11,Figure3.

Mounted externally on the housing 2 is a control, operation of which buy a user, rotates the reflector 5 about the axis 6. The control may be a knob directly mounted upon a shaft lying along the pivotal axis 6 or it may comprise a slow motion drive that enables the userto rotate the shaft very accurately.

Means are also included for measuring and indicating the extent of pivotal movement of the reflector 5.

The degree of accuracy required for the indication depends upon the range of distanceforwhich the apparatus is designed. For example, for distances up to several hundreds of feet (or say 100 metres) indi- cation to an accuracy of 1 ' of arc is needed.

Preferably, however, reflector 5 is fitted with a shaft encoder that electronically scans a scale movable with the reflector. The output of the encoder may befed to a visual display of alpha-numericform via means for converting the output into units of length, iefeed and/or metres.

The means may comprise a micro-processor having storage facilities and programmed to enable a userto store measured distances and to perform calculations involving those distances. The microprocessor may have an output portfortransferring stored data to a computer and/or to a printer for providing a print-out of the data.

To measure distances, the laser source 1 is energised and the telescopic sight directed towards and focused on a part of the object or surface whose distance from the user isto be measured. The reflector 5 is then pivoted to direct the beam 3 on to the object or surface. The angular position of the deflector is then adjusted until the area 12 of light resulting from the impingement of the beam 3 is accurately centred on the cross wires 10 of the telescopic sight or the circle is as shown in Figures 2 and 3 respectively.

The distance of the object or surface from the observer is then derived from the equation X = Ytan A where Xis the distance, Ythe distance between the line of sight through the telescopic lens and the centre of reflector5, and A is the angle of inclination of the reflector 5.

Angle A may be observed directly if the shaft isfitted with a protractor scale or alternatively the distance may be observed directly on the display.

Another embodiment of the apparatus allows a user to measure distances and the angle between selected points. Beam 3 from reflector 5 can also be swung in a second plane at right angles to the plane in which the reflector is pivoted when measuring distances as described above.

To measure the angle between selected points, the user first directs the housing and to cause the beam 3 to impinge on a first of the points, the reflector is then pivoted to produce movement of the beam in the second plane and to cause the beam to impinge on the second point. The degree of rotational movement of the reflector is equal to the angular relationship ofthetwo points and may be indicated on a protractor scale or on the display referred to above if signals representing the movement are fed to the microprocessor.

Movement of the beam 3 to measure distances and angles may be produced in otherwaysthan those described above. Suitable refractors may be used for example.

The housing 2 may be a hand-held unit and may be capable of tripod mounting for accurate observations. The hand-held unit may be contoured to provide a hand grip and it may have a carrying strap or straps which may also be used to support the unit when in use. A part of the housing may be rotatabie relatively to the remainder ofthe housing to produce the movementofthe beam necessaryforangular measurements.

It will be appreciated that the use of coherent light produces very sharply defined areas of light upon the object orsurface and thus contributes to the accuracy ofthe apparatus. Furthermore, the use of opticallyvisible light enables the apparatus to be used underconditions of little or no natural light,forex- ample, it is particularly suitable for use in mines where lighting is poor or non-existent.

For very short distances, a light source of conventional, ie non-coherent light may be used with collimating means to produce a narrow, substantially non-divergent beam of light.

Itwill also beappreciatedthatangularmeasure- ments may be effected using the beam 3 and rotation of the reflector 5 as described above for distance measurement. By aligning the beam 3 first on a selected area and then rotating the reflector to align the beam on a second selected area, the angular relationship between the two areas can be measured. If necessary,thehousing2 mayhavetobere- orientated to allow the requisite angular movement of the beam.

Claims (7)

1. Apparatus for measuring distancescompris- ing a sourcefor directing a beam of light towards a surface whose distance from an observation point is to be measured, a sight or sights for observing a selected part ofthe surface, means for directing the beam of lightto impinge on the selected part, and an arrangementfor indicating the inclination ofthe beam with respect to the line of view along the sight or sights.

2. Apparatus as claimed in claim 1 in which the sight is a telescopic sight.

3. Apparatusasclaimed in claim 1 or 2 in which further means are provided for imparting angular movement to the beam of light in a plane different from that in which movement ofthe beam takes place for distance measurement and for indicating the extent of such angular movement.

4. Apparatus as claimed in claim 1 or2inwhich the sight or sights is or are angularly movable, means being provided for indicating the extent of the angular movement.

5. Apparatus as claimed in any one ofthe preceding claims in which the source is a source of coherent light.

6. Apparatus as claimed in any one of the preceding claims in which the arrangement is such thatthe indication isthat of distance from the observation pointto the selected part.

7. Apparatus for measuring distance substantially as herein described with reference to and as illustrated in the accompanying drawings.