GB2426574A

GB2426574A - A laser micrometer which has two feeler pins that should be abutted against the surface of the object that is to be measured

Info

Publication number: GB2426574A
Application number: GB0508893A
Authority: GB
Inventors: Jonathan Valente
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-04-29
Filing date: 2005-04-29
Publication date: 2006-11-29
Anticipated expiration: 2025-04-29
Also published as: GB2426574B; GB0508893D0

Abstract

A micrometer 3 which comprises: two contact surfaces 10, 11 such as contact surfaces of respective pins/ feeler pins, adapted to be abutted against an object. The contact surfaces are disposed a known distance 2C apart. The micrometer is arranged to measure a distance between a location on a surface of the object and a point whose location relative to the contact surfaces is known. The micrometer can output information from which the distance of the location on the surface of the object from a vector connecting points at which the two contact points 10, 11 abut the surface is determined. A wave emitter and receiver such as a laser head (1, fig. 2) may be located between the two contact surfaces 10, 11 to emit waves to a location on the surface of the object, and receive the reflected waves from that location. The wave may be a light wave, or a sound wave. A processor, which may be part of the receiver/emitter, may control the emitter. The processor may be a computer that calculates the dimension of the object from the output of the receiver. The object may have a circular cross-section or a cross-section in a shape of an arc whose diameter is to be determined.

Description

"LASER MICROMETER" Description of Invention THE PRESENT INVENTION relates to laser micrometers. There are a number of methods which may be used to determine the diameter of a circular object, and when an accurate measurement required a conventional micrometer is often used. Conventional micrometers are manufactured in a range of sizes, the largest of which can generally be used to measure the diameter of a circular object of up to approximately one metre. A conventional micrometer typically comprises a "C" shaped section. At one end of the "C" section is a fixed pin, while at the opposing end of the "C" section there is a pin with a threaded portion which may pass through a correspondingly threaded hole in the "C" section. By rotating the threaded pin it is, therefore, possible to vary the distance between the two pins.If the amount by which the threaded pin advances when rotated through a fraction of a full rotation is known, then the distance between the two pins can be determined very accurately by noting the number of whole and fractional rotations made by the threaded pin when adjusting the pins from a position where they contact each other (and hence are separated by zero distance). An object whose diameter is to be determined, may be placed between the two pins of the micrometer and the threaded pin adjusted so that each pin contacts a diametrically opposing section of the object. The amount by which the threaded section is rotated during this time is measured and hence the distance between the two pins is accurately determined. When using a micrometer of this type, the larger the diameter of the object to be measured, the larger the maximum distance by which the two pins must be able to be separated, and hence the larger the "C" shaped section of the micrometer must be. Although it is possible to measure diameters of around 1 metre with such device, a micrometer of this size is expensive and difficult to handle. Another conventional device for providing accurate measurements is the laser micrometer. This device works in a similar manner to the conventional micrometer, however lasers (rather than pins) are used to make the appropriate measurements. A laser micrometer typically consists of a "C" section with a fixed surface at a first end and a laser emitter/receiver at a second end (opposing the first end). An object may be placed against the fixed surface and a beam from the laser emitter/receiver is reflected from a surface of the object. By measuring the time taken for the beam to travel to the surface of the object and then return to the laser emitter/receiver, the distance between the laser emitter/receiver and the surface of the object may be calculated and hence the diameter of the object may be determined.Alternatively, a laser micrometer may comprise a "C" shaped section having laser emitter/receivers at both the first and second ends. The reflections of each laser from the sides of an object placed between the two lasers are used to determine the distance of each side of the object from each end of the "C" shaped section. Using these distances it is then possible to determine a dimension of the object. Although a laser micrometer may be used to determine a diameter of an object more accurately, the distance between the two ends of the device must still be larger than the dimension of the object which is to be measured. A further alternative device currently used to measure the diameter of an object is a co-ordinate measuring machine (CMM). A CMM consists of a flat rectangular bed usually constructed of a hard material, for example granite. A track runs along an edge of the bed, and a carriage is provided which may run on the track. The carriage supports an elongate support arm which extends in a direction perpendicular to the track parallel to, and some distance above. An elongate probe arm is supported by a second track on the support arm and may move along a length of the support arm. The probe arm may also move in a direction perpendicular to the support arm (so that an end of the probe arm can be raised or lowered relative to the bed). A probe is attached to an end of the probe arm nearest to the bed.The probe can, therefore, be moved to a plurality of locations on or above the bed and utilised to measure one or more dimensions of an object secured to the bed. CMMs of this type are extremely large, expensive, heavy and difficult to move. Another alternative to determining diameter of circular objects is a precision measuring tape. A precision measuring tape is largely similar to a standard measuring tape however the markings on the tape are positioned to a greater degree of accuracy. The measuring tape may be wound around the outer circumference of a circular object to determine the circumferential length of that object. From this length it is then possible to determine the diameter of the object being measured. Although such a device is cheap, it is still not particularly accurate. Inaccuracies in measurements using this device become particularly acute to when measuring large objects, where the measuring tape may not always stay parallel to the plane of a circular cross-section being measured. Even a small discrepancy in the measured circumferential value may result in a large error when calculating the diameter of the object. It is object of the present invention to seek to ameliorate the problems associated with measuring devices for determining the diameter of a relatively large circular object. Accordingly one aspect of the present invention provides a micrometer comprising : two contact surfaces, adapted to be abutted against an object, the contact surfaces being disposed a known distance apart; an emitter positioned to emit a measurement wave towards the object; and a receiver which is positioned to receive the measurement wave reflected from a location of a surface of the object and operable to output information from which the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined. Advantageously, the one or both of the emitter and receiver are located substantially between the two contact surfaces. Preferably, the emitter and receiver are adjacent one another. Conveniently, the emitter and receiver are secured to one another. Advantageously, the emitter and receiver are combined to form a transceiver unit. Conveniently, one or more of the emitter and receiver are held in a cradle. Preferably, one or more of the two contact surfaces, the emitter and the receiver are secured to a support arrangement. Advantageously, the measurement wave is a light wave. Conveniently, the measurement wave is a laser. Preferably, the measurement wave is a sound wave. Advantageously, the contact surfaces abut a different surface from that from which the measurement wave is reflected. Conveniently, the contact surfaces abut or the same surface as that from which the measurement wave is reflected. Preferably, the contact surfaces are surfaces of respective pins. Advantageously, a processing arrangement operable to control the emitter is provided. Conveniently, the processing arrangement is attached to or forms part of one or more of the receiver, the emitter, and the contact surfaces. Preferably, the processing arrangement is a computer. Advantageously, a calculation arrangement to calculate a dimension of the object from information output by the receiver is provided. Conveniently, the calculation arrangement is attached to or forms part of one or more of the receiver, the emitter, and the contact surfaces. Preferably, the calculation arrangement is a computer. Another aspect of the present invention provides a method of using a using a micrometer comprising the steps of: abutting two contact surfaces of the micrometer against an object, the contact surfaces being disposed a known distance apart; emitting a measurement wave from an emitter; reflecting the measurement wave off a location on a surface of the object; receiving at a receiver the reflected measurement wave; outputting from the receiver information from which the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined. Advantageously, a method further comprises the step of determining the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object. Preferably, a method further comprises the step of calculating a dimension of the object utilising the known distance between the two contact surfaces and the distance of the location on the surface of the object from the vector. Conveniently, the object has at least one circular cross section and the method further comprises the step of determining a diameter of the cross section. Preferably, the object has at least one cross section in the shape of an arc of a circle and the method further comprises the step of determining a diameter of the circle. Advantageously, a method further comprises the step of locating one or both of the emitter and receiver substantially between the two contact surfaces. Preferably, a method further comprises the step of placing the emitter and receiver adjacent one another. Conveniently, a method further comprises the step of securing the emitter and receiver to one another. Preferably, a method further comprises the step of combining the emitter and receiver to form a transceiver unit. Advantageously, a method further comprises the step of holding one or more of the emitter and receiver in a cradle. Preferably, a method further comprises the step of securing one or more of the two contact surfaces, the emitter and the receiver to a support arrangement. Conveniently, a method further comprises the step of providing light as the measurement wave. Advantageously, the step of providing light as the measurement wave comprises the step of providing a laser as the measurement wave. Preferably, a method further comprises the step of providing a sound wave as the measurement wave. Conveniently, the abutting step further comprising the step of abutting the contact surfaces with a different surface from that from which the measurement wave from the emitter is reflected. Advantageously, the abutting step further comprises the step of abutting the contact surfaces with the same surface as that from which the measurement wave from the emitter is reflected. Preferably, a method further comprises the step of providing respective pins as the contact surfaces. Conveniently, a method further comprises the step of providing a processing arrangement operable to control the emitter. Preferably, a method further comprises the step of attaching the processing arrangement to, or providing the processing arrangement as part of, one or more of the receiver, the emitter, and the contact surfaces. Advantageously, the step of providing a processing arrangement comprises the step of providing a computer. Preferably, a method further comprises the step of providing a calculation arrangement operable to calculate a dimension of the object from information output by the receiver. Conveniently, a method further comprises the step of attaching the calculation arrangement to, or providing the calculation arrangement as part of, one or more of the receiver, the emitter, and the contact surfaces. Advantageously, the step of providing a calculation arrangement comprises the step of providing a computer. Another aspect of the present invention provides a micrometer comprising: two contact surfaces, adapted to be abutted against an object, the contact surfaces being disposed a known distance apart; and a measuring arrangement operable to measure a distance between a location on a surface of the object and a point whose location relative to the contact surfaces is known, and to output information from which the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined. Advantageously, the measuring arrangement comprises a measuring member which is operable to advance towards and contact the location on the surface of the object. Another aspect of the present invention provides a method of using a using a micrometer comprising the steps of: abutting two contact surfaces of the micrometer against an object, the contact surfaces being disposed a known distance apart; measuring a distance using a measuring arrangement between a location on a surface of the object and a point whose location relative to the contact surfaces is known; and outputting from the measuring arrangement information from which the distance of a location on a surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined. Advantageously, the step of measuring using a measuring arrangement comprises the step of extending a measuring member towards the surface of the object. Preferably, a method further comprises the step of determining the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object. Preferably, a method further comprises the step of calculating a dimension of the object utilising the known distance between the two contact surfaces and the distance of the location on the surface of the object from the vector. According to another aspect of the present invention provides a method of calibrating a micrometer comprising the steps of: abutting two contact surfaces of the micrometer against a calibration surface, the contact surfaces being disposed a known distance apart; and determining a distance from a measuring arrangement to a measurement point on the calibration surface or on an object placed in contact with the calibration surface whose location relative to the contact surfaces is known. Another aspect of the present invention provides a method according to Claim 49, further comprising the steps of: estimating a likely distance that is to be measured by the measuring arrangement in normal use of the micrometer; selecting an object having an appropriate size so that, when the object is placed on the calibration surface the distance from the measuring arrangement to a surface of the object is approximately the distance to be measured; and placing the object on the calibration surface so that the surface of the object provides the measurement point. Preferably, a method further comprises the step of setting the distance from the measuring arrangement to the known location as a notional origin or zero distance. In order that the present invention may be more readily understood, embodiments thereof will be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a perspective view at a first angle of a laser micrometer embodying the present invention. Figure 2 shows a perspective view at a second angle of a laser micrometer embodying the present invention. Figure 3 shows a plan view of a first support member. Figure 4 shows a plan view of a second support member. Figure 5 shows a perspective view of a pin holding member. Figure 6 shows two perspective views of a pin. Figure 7 shows a perspective view of a slide. Figure 8 shows two perspective views of a cradle. Figure 9 shows two perspective views of a handle securing member and handle. Figure 10 shows a laser micrometer embodying the present invention in use.Figure 11 shows a diagram depicting how measurements made by a laser micrometer embodying the present invention may be used in a calculation. In figure 1 a laser micrometer embodying the present invention is shown. This laser micrometer comprises first and second support members, 2a and 2b, defining a chassis 3 (described in more detail below). The first support member 2a comprises a sheet of stiff material, (for example aluminium) which is formed in an elongate arc shape. The first support member 2a has first and second pair of pin holding member connection holes 12a, 13a, which are disposed at respective first and second ends of the first support member 2a. In each of the pairs of pin holding member connection holes 12a, 13a, one of connection holes is located towards a front edge 14a of the first support member 2a, which is concave in shape, and the other connection hole in each pair of pin holding member connection holes 12a,13a is located towards a back surface 15a of the first supporting member 2a, which is convex in shape. Preferably, there is a distance of approximately 34mm between the two holes in each pair of pin holding member connection holes 12a,13a.All of the pin holding member connection holes run through the thickness of the first support member 2a. The first support member 2a also has a first and second pair of pin holding member support holes 69,70, which are disposed at respective first and second ends of the first support member 2a. In each of the pairs of pin holding member support holes 69, 70, the two holes are position between the pin holding member connection holes 12, 13. First and second pairs of handle connection holes 16a, 17a are also provided in the first support member 2a. The first and second pairs of handle connection holes 16a, 17a are located towards the respective first and second ends of the first support member 2a, but closer to the centre thereof than the pin holding member connection holes 12a, 13a. In each pair 16a,17a of handle connection holes, one hole is located towards the back surface 15a of the first support member 2a and the other handle connection hole is located towards the front surface 14a of the first support member 2a. Preferably, there is a distance of approximately 33mm between the two handle connection holes in each pair 16a, 17a of handle connection holes.In a similar way to the two pairs of pin holding member connection holes 12a,13a the two pairs of handle connection holes 16a,17a run through the thickness of the first support member 2a. Each pair of the handle connection holes 16a,17a is located generally adjacent to one of the pairs of pin holding member connection holes 12a,13a. All the pin supporting member connection holes 12a,13a and handle connection holes 16a,17a are generally circular in shape and preferably have a diameter of 6mm. Four circular lightening holes 18a, 19a, 20a, 21 a are also located in the first support member 2a, and pass through the thickness thereof. These holes are arranged in first and second pairs, such that one hole 18a, 20a in each pair is larger than the other hole 19a,21 a in that pair. The pairs of lightening holes 18a,19a,20a,21 a are respectively located between a centre of the first support member 2a and one of the first and second ends thereof, but are generally closer to the ends of the first support member 2a than to the centre. The larger hole 18a,20a in each pair of holes is located closer to the centre of the first support member 2a than the smaller hole in each pair 19a,21a.All the four lightening holes 18a,19a,20a,21a are located closer to the centre of the first support member 2a than the pin supporting member connection holes 12a,13a and the handle connection holes 16a,17a. In addition, all the four lightening holes 18a,19a,20a,21a in the first support member 2a are located such that a central point of each hole 18a,19a,20a,21a is equidistant from the concave 14a and convex 15a surfaces of the first support member 2a. These four holes 18a,19a,20a,21a are provided to reduce the overall weight of the first supporting member 2a, (and hence the quantity of material needed to manufacture this component) but are not of a size which would hinder the beneficial qualities of the material used in the construction of the first support member 2a. In an exemplary embodiment of the present invention the four lightening holes 18a,19a,20a,21a are such that the larger hole 18a,20a in each pair has a diameter of 36mm and the smaller hole 19a,21a has a diameter of 34mm. The first support member 2a has a width, at a central axis thereof, of 76.4mm. The arc of the first support member 2a is such that the central axis, which is perpendicular to an axis which runs the length of the first support member 2a and is always equidistant from the convex 15a and concave 16a surfaces of the first support member 2a, has an angle of 30[deg] between itself and first 22a and second 23 end surfaces of the first support member 2a. The larger of the four holes 18,20 are 110.74mm from the central axis, and the smaller of the four holes 19,21 are preferably 157.29mm from the central axis.Each pair of pin holding member connection holes 12a,13a are approximately 232.32mm from the central axis and each pair of handle connection holes 16a,17a are approximately 193.25mm from the central axis. The second support member 2b is of generally identical shape and dimensions to the first support member 2a, and has corresponding pin holding member connection holes 12b,13b, handle connection holes 16b,17b and lightening holes 18b,19b,20b,21b. In addition, the second support member 2b has three slide connection holes 24,25,26 which are aligned near a central axis of the second support member 2b, which is identical to the central axis of the first support member 2a. The three slide connection holes 24,25,26 are, however, displaced from the central axis of the second support member 2b in a direction towards a second end 23b of the second support member 2b. In an exemplary embodiment of the present invention the slide connection holes 24,25,26 are all approximately 20.8mm from the central axis.A first slide connection hole 24 is located towards a convex back surface 15a of the second support member 2b, a second slide connection hole 26 is located towards a concave surface 14a front of the second support member 2b, and a third slide connection hole 25 is located between the first 24 and second 26 slide connection holes. The three slide connection holes 24,25,26 run through thickness of the second support member 2b in a similar way to the other holes. Two pairs of slide securing holes 27,28,29,30 also run through the thickness of the second support member 2b. A first pair of slide securing holes 27,28 is located towards a first end 22b of the second support member 2b, such that they are nearer to the first end 22a of the second support member 2b than the slide connection holes 24,25,26 are. A second pair of slide securing holes 29,30 are located towards the second end 23b of the second support member 2b, and are nearer to the second end 23b than the three slide connection holes 24,25,26 are. In each pair of slide securing holes 27,28 & 29,30, one hole is aligned with the first slide connection hole 24b and the other hole is aligned with the second slide connection hole 26b. Two pin holding members 8,9 are also provided. Each pin holding member 8,9 has a base portion 41 with a generally rectangular cross-section. A pair of connection holes 44 is provided in each of two opposing side surfaces of the base portion 41 of each pin holding member 8,9, and these connection holes are appropriately arranged so that they may be used to attach the pin holding members 8,9 to the pin holding member connection holes 12,13 of the first and second support members 2a, 2b. A support pillar 42, which is generally cylindrical in shape, extends from a first major surface of the base portion 41 of each pin holding member 8,9. The height of the support pillar 42 is approximately equal to the depth of the base portion 41. The support pillar 42 supports a pin connection portion 43, which is substantially oblong in shape and has two cylindrical bores 46, 47 passing therethrough. Two of the surfaces of the oblong shape of the pin connection portion 43 are parallel with the major surfaces of the base portion 41, and the cylindrical bores 46,47 passing through the pin connection portion 43 run substantially parallel to the sides of the base portion 41 which have connection holes 44 provided therein. In an exemplary embodiment of the present invention, the depth of each pin holding member base portion 41 is 16mm, and the width thereof is 60mm. The height of each base portion 41 is 50mm, and the connection holes 44 have diameters of 6mm. Each connection hole is equidistant from a central axis of the base portion 41, and the connection holes 44 are 34mm apart. Pins 10,11 are passed through the cylindrical bores 46, 47in the pin connection portion 43. Each of these pins 10,11 terminates at one end thereof in a circular pin head 48 having diameter larger than that of the cylindrical bore 46, 47. A shaft 49 extends from the centre of one side of the circular pin head 48 of each pin 10,11. A first section 50 of each shaft is generally equal in length to the cylindrical bores 46, 47 in the pin connection portion 43. The diameter of the first section 50 of the shaft 49 is approximately equal to or slightly greater than the diameter of the cylindrical bore 46, 47. A second portion 51 of the shaft 49 extends from (and is coaxial with) the first portion 51 of the shaft 49, and has a diameter slightly less than the diameter of the cylindrical bores 46, 47 of the pin connection portion 43. In order to insert the pins 10,11 into the cylindrical bores 46,47, the pins 10,11 are cooled to a low temperature, such that each of the pins 10, 11 contract and the diameter of the first section 50 of the shaft 49 of each pin 10, 11 is less than that of the cylindrical bores 46, 47. Each of the pins 10,11 are then inserted fully into the respective cylindrical bore 46, 47, so that the head 48 of each of the pins 10, 11 is flush with a surface of the pin connection portion 43. The pins 10,11 are then allowed to return to room temperature so that the diameter of the first section 50 of the shafts 49 increases to become equal to the diameter of the cylindrical bores 46, 47. Thus, it would be appreciated that each of the pins 10,11 is held securely in place by function between the relevant cylindrical bore 46, 47 and first portion 50 of the shaft 49 of each pin 10,11. The end of each pin 10,11 furthest from the head thereof is machined to terminate in a straight edge 52 which is substantially perpendicular to the length of the pin 10,11. This straight edge 52 provides a contact surface. The machining is achieved by forming a first flat inclined surface 53, oriented at around 30[deg] to the longitudinal axis of the pin 10,11, and the second flat inclined surface 54 oriented at an angle of around 60[deg] of the longitudinal axis of the pin. Preferably, the machining of the pins 10,11 takes place after the laser micrometer has been assembled. This allows for the precise machining of the first 53 and second 54 flat inclined surfaces (and hence the straight edge) to be adjusted to take into account manufacturing tolerances in the construction of the laser micrometer. It will be understood that this allows a length of each pin 10, 11 to be set in accordance with the dimensions of a specific micrometer. There are a number of known techniques for machining the first 53 and second 54 flat inclined surfaces of each pin 10, 11, for example, spark erosion. It will be understood that the straight edge 52 of each pin 10, 11, is, in fact, a small rounded surface between the first 53 and second 54 flat inclined surfaces. As will be understood from the description of the use of a micrometer embodying the present invention, the rounded surface of the straight edge 52 of each pin 10,11 will result in any object which is abutted against the rounded surface contacting a slightly different part of the rounded surface depending on the orientation of the object and its dimensions. In order to overcome any errors created by this issue it is envisaged that the rounded surface of the straight edge 52 of each pin 10,11 may be machined to have a known radius (e.g. 1 mm) which may accordingly be accounted for in any subsequent calculations. The two pin holding members 8,9 are connected to the pin holding member connection holds 12,13 in the first and second support members 2a, 2b by passing bolts through these holes, and it will be appreciated that, when the pin holding members 8,9 are connected to the first and second support members 2a, 2b these components form a sturdy, hollow chassis 3. To reduce any relevant movement between the two pin holding members 8,9 and the first and second support members 2a, 2b metal dowels (not shown) are inserted through each of the pin holding member support holes 69, 70 in the first and second support members 2a, 2b.These metal dowels extend through corresponding holes 45 in each of the pin holding members 8,9. Two handle securing members 6,7 are also provided, each of which comprises a substantially rectangular body having a width generally equal to the width of each pin holding member base portion, and has connection holes 55 on two opposing connection surfaces of the body, corresponding to the handle connection holes 16, 17 in the first and second supporting members 2a,2b. The handle securing members 6,7 are attached to the first 2a and second 2b support members by passing bolts through these connection holes 16,17,55, so that the handle securing members extend between the first and second support members 2a,2b. A groove 56 with a generally rectangular cross-section is cut in one side surface (a surface which extends between the two connection surfaces of the handle securing member) of the handle securing member 6,7. A corresponding rectangular tongue 57 on a handle 4,5 may be inserted into the groove 56 in each handle supporting member 6,7, and held in place by an interference fit. Alternatively, co-operating retaining arrangements such as an indentation and a corresponding detent (not shown) are provided in the groove and on the tongue to retain the tongue in the groove. Each handle 4,5 comprises an elongate portion which extends away from the tongue section, and a semi-circular portion which extends from the elongate portion and is joined at the ends thereof by a gripping member 58 to form a handle by which a user may hold or carry the micrometer.Preferably, the gripping member 58 has a rubber sheath over at least a portion thereof to help the user to handle the micrometer more easily. A slide 31, shown in figure 7, comprises a generally flat rectangular main body having connection holes 33 formed therethrough which correspond to the respective slide connection 24,25,26 and securing holes 27,28,29,30 in the second supporting member 2b. The holes 33a in the slide 31 which correspond to the slide connection holes 24,25,26 are aligned so as to be equidistant from first 35 and second 36 opposing edges of the slide 31, all the holes being 33 aligned along an axis parallel with the first 35 and second 36 edges. A slide portion 37 extends along an entire length of a first major surface 34 of the slide 31 parallel with the first 35 and second 36 edges, and is generally in the form of a raised strip. The slide portion 37 has a width which is less than the width of the slide main body, and is aligned so as to be equidistant from the first 35 and second 36 edges thereof. The slide portion 37 comprises two side engaging surfaces 38,39 which extend away from the first major surface 34 of the slide 31 and at an angle with respect to the first major surface 34, so that the slide portion 37 becomes wider as it protrudes away from the first major surface 34 (i.e. in a "dovetail"). The two engaging 38,39 surfaces are connected by a top engaging surface 40 which is parallel with the first major surface 34 of the slide 31.The slide is attached to an inner side of the second support member 2b, by passing securing bolts through the appropriate connection holes. In an exemplary embodiment of the present invention the first and second edges of the slide are 113mm apart, the length of the slide is 70mm, the width of the slide portion is at a minimum point 30.33mm, and the two engaging surfaces are each set at an angle of 60[deg] with respect to the first surface of the slide. A cradle 32 comprises a main body with a generally rectangular cross-section. A first face of the cradle body has groove 60 running thereacross in a shape corresponding to the slide portion 37 of the slide 31. The groove 60 runs through a length of the main body of the cradle 32 and is generally equidistant from opposing first 61 and second 62 side surfaces of the main body. A second face 63 of the main body is generally flat and on an opposite side of the main body of the cradle 32 to the first face 59 thereof. Two guide portions 64, 65 protrude away from the second face along first opposing edges 67, 68 (which correspond to edges between the second face and the two side surfaces 61, 62) thereof, such that the two guide portions 64, 65 are parallel with the groove 60.Therefore, the cradle 32 has a generally 'U' shaped crosssection, with the groove 60 being formed in a base part of the 'U'. Two holes 66 extend through the second face 63 to a bottom surface of the groove 60 in the first face 59 of the main body of the cradle 32. These holes 66 are located closer to the first edge 67 of the second face 63 then to the second edge 68 thereof, and are positioned close to third and fourth edges of the cradle main body, between which the length of the main body of the cradle 32 is defined. In an exemplary embodiment of the present invention the cradle 32 has a length of 76.2mm, while the groove 60 has a width of 40mm at its widest point and a depth of 8mm. The internal surfaces of the groove are set at 60[deg] to the first face and the bottom surface of the groove is parallel to the first end surface 59 of the main body of the cradle 32. The holes 66 in the main body of the cradle 32 are generally round in shape and 4mm in diameter, 32.5mm from the closer of the first edges, and 61 mm away from each other. The guide portions 64, 65each have a width of 4mm and a height of 18mm above the face of the main body. A generally oblong laser head 1 is provided, and is of a size and shape such that it may be slid into the main body of the cradle 32 and be received and held in place between the two guide portions. The laser head 1 has a laser generator operable to emit a laser beam and, receive and detect incoming reflections of the emitted laser beam. The laser head 1 preferably has at least one output, and may also comprise one or more inputs. It will be appreciated that the laser head 1 will need to be powered and that this may be achieved by the use of a mains supply or one or more batteries. It will be understood that the pin holding members 8,9 and handle securing members 6,7 may be secured to both the first and second support members 2a,2b by the use of bolts. The pin holding members 8,9 when secured in this way, are oriented to direct the pins 10,11 in a direction away from the concave inner 14 surfaces of the support members 2a,2b. The handle securing members 6,7 on the other hand, are oriented to present the grooves (for connection to the handles 4,5) in substantially the opposite direction (i.e. towards the convex surfaces 15 of the support members 2a,2b). The slide 31 may be secured to the second support member 2b, and the laser head 1 secured to the cradle 32. The laser head 1 is secured to the cradle 32 by passing a bolt through holes in the laser head 1 which correspond directly with the holes in the cradle 66 (when the laser head 1 is positioned between the two guide portions of the cradle 32). When a bolt is passed through one of the holes in the laser head 1 which corresponds with the holes 66 in the cradle 32 (which are threaded), the bolt is of a length such that it may also extend through the cradle 32 from the second face 63 to the bottom surface of the groove 60 in the first face 59 in the main body of the cradle 32.The cradle 32 and laser head 1 can, in this arrangement, be slid onto the slide 31 and secured in position by rotating the bolt such that it passes through the cradle 32 (as described above) and presses against the top engaging surface 40 of the slide portion 37. In this arrangement, the two side engaging surfaces 38, 39 of the slide portion 37 abut corresponding side surfaces in the groove 60 of the cradle 32. Thus, the position of the slide and cradle with respect to each other may be varied and the slide secured at multiple positions the length of the slide 31. The micrometer is now ready for use. Figure 2 shows the micrometer in use. The micrometer is placed against an object to be measured, which has a cross-section that is circular or arcuate. The pins 10,11 are placed against an outer circumferential edge of the object to be measured. The laser head 1 emits a laser towards the outer circumferential surface of the object, and the beam is reflected back towards the receiver of the laser head 1. Information about the emitted and reflected beams (e.g. the time taken for the signal to travel from the laser head to the surface and reform) can then be used to determine the distance of the laser head 1 from the outer circumferential edge of the circular object. The distance between the sets of pins 10,11 is known and may be called a chord. The length of this chord may be divided into two, so that one half thereof forms a first side of a triangle, as shown in Figure 3. The distance of the object from the laser head 1 can be used to determine the depth of the chord within the object and this forms another side of the triangle (perpendicular to the first), also see Figure 3. From this information and using Pythagoras' theorem it is possible to determine the radius of the circle. The following mathematical formula may be applied:

and therefore, this calculation may be carried out by a computer (not shown) which may be specifically created for this purpose or a general purpose computer programmed to carry out this calculation. It is envisaged that such computer may comprise a hand held or a "desk top" device, which may be connected to the laser head 1 by a wired or wireless connection to receive data therefrom. The computer may further be operable to trigger the emission of the laser beam from the laser head 1, by sending a control signal to the laser head 1 via the connection or via a second connection to an output of the laser head 1. Further methods may be used to calculate the depth of the chord within the object, for instance interferometry, which can provide a very accurate measurement of the distance of a mirror element above the object's surface. Although the description above discloses only an object of circular or arcuate form, it will be understood that in an alternative embodiment of the present invention a dimension of an object which is not circular or arcuate may be determined. For example, by adjusting the formula given above it may be possible to determine a width of a hexagon. In this example each of the sets of pins 10,11, and hence the sets of contact surfaces, are abutted against different surfaces (ie a first and second surface) of the object and the beam is reflected off a third surface (which is different from the first and second surfaces) of the object which is between the first and second surfaces of the object. The width of the object may then be determined by utilising a similar method to that described above in relation to circular or arcuate objects. It will be understood that accurate calibration of this device is essential to the overall accuracy of the micrometer. Calibration of a micrometer embodying the present invention will be carried out utilising slip gauges which are manufactured to have a known length. The micrometer is placed such that the pins 10,11 abut a flat bed surface. An estimation is made of a dimension of an object to be measured and a look-up table utilised to determine a likely distance between a surface of the object and a vector connecting the points at which the pins 10,11 would abut the object if the micrometer was placed such that the contact surfaces abut against the surface of the object. A slip gauge is then selected such that a length thereof is equal to or approximately equal to the aforementioned distance (as defined in the look-up table).This slip gauge is then placed upon the flat surface such that the length extends towards the laser head 1 of the micrometer. The laser head 1 of the micrometer has a known operating range (for example 25mm 1 mm). Therefore, the position of the cradle 32 holding the laser head 1 may be adjusted relative to the slide 31 such that an end surface of the slip gauge is within range of the laser head 1. The cradle 32 and laser head 1 are then secured to the slide 31 as described above. Following this, the laser head is "zeroed" such that the distance between the laser head and slip gauge end surface represents a notional origin or zero distance. This "zeroing" may be carried out by utilising a ZERO button (not shown) which may be built into the laser head 1 or the computer. It will be understood that when the micrometer is used to measure the dimension of an object following calibration, information output by the laser head 1, may be used to calculate the distance of a surface of the object being measured from the laser head as a displacement from the "zeroed" position. Therefore, since the range of the laser is known, the distance of the laser head from the surface of the object in question can be determined. It will be understood that the one or more outputs from the laser head 1 may simply be output to a digital display which shows distance information output by the laser head 1. Alternatively, the data may be output to an associated computer which may be portable (or hand-held), or of a "desktop" type (or non-portable) Preferably, this distance information is output in "real time". Ideally, the components of the device embodying the present invention described above are constructed out of aluminium and the cradle, slide and pins are constructed from steel. Preferably, the laser head 1 further comprises a multi colour light emitting diode which will illuminate when power is applied to the laser head 1. It will be appreciated that although a laser is specifically described above, there are a number of measurement devices and techniques operable output information from which a distance of a location on a surface of an object from a vector connecting points at which the two contact surfaces abut the object can be determined, which may be substituted for the laser and associated parts described above. Such devices form further embodiments of the present invention. In another embodiment of the present invention the substitute measuring device (as mentioned above) could be a mechanical measuring member, such as a threaded rod. Such a measuring member would advance from the micrometer described above until the member contacts the surface of the object, for example, a scale along a surface of the measuring member may be used to determine the distance which it has advanced before it contacts a surface of the object to be measured. It will be understood that such a method is comparable to the method utilising a laser described previously. It will also be understood that calibration of such a device could take a similar form to the calibration of the laser device previously described. In particular, the micrometer could be arranged in a similar fashion (i.e. with the pins 10,11 abut a flat bed surface and an estimation may be made of a dimension of an object to be measured and a slip gauge selected appropriately). The slip gauge may then be placed on the flat bed surface and the measuring member advanced towards the slip gauge. When the measuring member contacts a surface of the slip gauge a reading may be taken from the scale of the measuring member and this used as the "zeroed" position. Alternatively, other calibration techniques which are known to a skilled person may be utilised. Ideally, the laser (or substitute device) is positioned between the two contact surfaces. This is not however essential and alternative arrangements are conceivable alternative arrangements. When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or components. The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

1. A micrometer comprising : two contact surfaces, adapted to be abutted against an object, the contact surfaces being disposed a known distance apart; an emitter positioned to emit a measurement wave towards the object; and a receiver which is positioned to receive the measurement wave reflected from a location of a surface of the object and operable to output information from which the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined.

2. A micrometer according to Claim 1, wherein the one or both of the emitter and receiver are located substantially between the two contact surfaces.

3. A micrometer according to any preceding claim, wherein the emitter and receiver are adjacent one another.

4. A micrometer according to any preceding claim, wherein the emitter and receiver are secured to one another.

5. A micrometer according to any preceding claim, wherein the emitter and receiver are combined to form a transceiver unit.

6. A micrometer according to any preceding claim, wherein one or more of the emitter and receiver are held in a cradle.

7. A micrometer according to any preceding claim, wherein one or more of the two contact surfaces, the emitter and the receiver are secured to a support arrangement.

8. A micrometer according to any preceding claim, wherein the measurement wave is a light wave.

9. A micrometer according to Claim 8, wherein the measurement wave is a laser.

10. A micrometer according to any preceding claim, wherein the measurement wave is a sound wave.

11. A micrometer according to any preceding claim, wherein the contact surfaces abut a different surface from that from which the measurement wave is reflected.

12. A micrometer according to any preceding claim, wherein the contact surfaces abut or the same surface as that from which the measurement wave is reflected.

13. A micrometer according to any preceding claim, wherein the contact surfaces are surfaces of respective pins.

14. A micrometer according to any preceding claim, further comprising a processing arrangement operable to control the emitter.

15. A micrometer according to Claim 14, wherein the processing arrangement is attached to or forms part of one or more of the receiver, the emitter, and the contact surfaces.

16. A micrometer according to Claims 14 or 15, wherein the processing arrangement is a computer.

17. A micrometer according to any preceding claim, further comprising a calculation arrangement to calculate a dimension of the object from information output by the receiver.

18. A micrometer according to Claim 17, wherein the calculation arrangement is attached to or forms part of one or more of the receiver, the emitter, and the contact surfaces.

19. A micrometer according to Claim 17 or 18, wherein the calculation arrangement is a computer.

20. A method of using a using a micrometer comprising the steps of: abutting two contact surfaces of the micrometer against an object, the contact surfaces being disposed a known distance apart; emitting a measurement wave from an emitter; reflecting the measurement wave off a location on a surface of the object; receiving at a receiver the reflected measurement wave; outputting from the receiver information from which the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined.

21. A method according to Claim 20, further comprising the step of determining the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object.

22. A method according to Claim 24, further comprising the step of calculating a dimension of the object utilising the known distance between the two contact surfaces and the distance of the location on the surface of the object from the vector.

23. A method according to any one of Claims 20 to 22, wherein the object has at least one circular cross section and the method further comprises the step of determining a diameter of the cross section.

24. A method according to any one of Claims 20 to 23, wherein the object has at least one cross section in the shape of an arc of a circle and the method further comprises the step of determining a diameter of the circle.

25. A method according to any one of Claims 20 to 24, further comprising the step of locating one or both of the emitter and receiver substantially between the two contact surfaces.

26. A method according to any one of Claims 20 to 25, further comprising the step of placing the emitter and receiver adjacent one another.

27. A method according to any one of Claims 20 to 26, further comprising the step of securing the emitter and receiver to one another.

28. A method according to any one of Claims 20 to 25, further comprising the step of combining the emitter and receiver to form a transceiver unit.

29. A method according to any one of Claims 20 to 28, further comprising the step of holding one or more of the emitter and receiver in a cradle.

30. A method according to any one of Claims 20 to 29, further comprising the step of securing one or more of the two contact surfaces, the emitter and the receiver to a support arrangement.

31. A method according to any one of Claims 20 to 30, further comprising the step of providing light as the measurement wave.

32. A method according to Claim 31, wherein the step of providing light as the measurement wave comprises the step of providing a laser as the measurement wave.

33. A method according to any one of Claims 20 to 30, further comprising the step of providing a sound wave as the measurement wave.

34. A method according to any one of Claims 20 to 33, wherein the abutting step further comprising the step of abutting the contact surfaces with a different surface from that from which the measurement wave from the emitter is reflected.

35. A method according to any one of Claims 20 to 33, wherein the abutting step further comprises the step of abutting the contact surfaces with the same surface as that from which the measurement wave from the emitter is reflected.

36. A method according to any one of Claims 20 to 35, further comprising the step of providing respective pins as the contact surfaces.

37. A method according to any one of Claims 20 to 36, further comprising the step of providing a processing arrangement operable to control the emitter.

38. A method according to Claim 37, further comprising the step of attaching the processing arrangement to, or providing the processing arrangement as part of, one or more of the receiver, the emitter, and the contact surfaces.

39. A method according to Claim 37 or 38, wherein the step of providing a processing arrangement comprises the step of providing a computer.

40. A method according to any one of Claims 20 to 39, further comprising the step of providing a calculation arrangement operable to calculate a dimension of the object from information output by the receiver.

41. A method according to Claim 40, further comprising the step of attaching the calculation arrangement to, or providing the calculation arrangement as part of, one or more of the receiver, the emitter, and the contact surfaces.

42. A method according to Claim 40 or 41, wherein the step of providing a calculation arrangement comprises the step of providing a computer.

43. A micrometer comprising: two contact surfaces, adapted to be abutted against an object, the contact surfaces being disposed a known distance apart; and a measuring arrangement operable to measure a distance between a location on a surface of the object and a point whose location relative to the contact surfaces is known, and to output information from which the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined.

44. A micrometer according to Claim 43, wherein the measuring arrangement comprises a measuring member which is operable to advance towards and contact the location on the surface of the object.

45. A method of using a using a micrometer comprising the steps of: abutting two contact surfaces of the micrometer against an object, the contact surfaces being disposed a known distance apart; measuring a distance using a measuring arrangement between a location on a surface of the object and a point whose location relative to the contact surfaces is known; and outputting from the measuring arrangement information from which the distance of a location on a surface of the object from a vector connecting points at which the two contact surfaces abut the object can be determined.

46. A method according to Claim 45, wherein the step of measuring using a measuring arrangement comprises the step of extending a measuring member towards the surface of the object.

47. A method according to Claim 45 or 46, further comprising the step of determining the distance of the location on the surface of the object from a vector connecting points at which the two contact surfaces abut the object.

48. A method according to Claim 47, further comprising the step of calculating a dimension of the object utilising the known distance between the two contact surfaces and the distance of the location on the surface of the object from the vector.

49. A method of calibrating a micrometer comprising the steps of: abutting two contact surfaces of the micrometer against a calibration surface, the contact surfaces being disposed a known distance apart; and determining a distance from a measuring arrangement to a measurement point on the calibration surface or on an object placed in contact with the calibration surface whose location relative to the contact surfaces is known.

50. A method according to Claim 49, further comprising the steps of: estimating a likely distance that is to be measured by the measuring arrangement in normal use of the micrometer; selecting an object having an appropriate size so that, when the object is placed on the calibration surface the distance from the measuring arrangement to a surface of the object is approximately the distance to be measured; and placing the object on the calibration surface so that the surface of the object provides the measurement point.

51. A method according to Claim 49 or 50, further comprising the step of setting the distance from the measuring arrangement to the known location as a notional origin or zero distance.

52. A micrometer as hereinbefore described with reference to and as shown in the accompanying drawings.

53. A method of using a micrometer as hereinbefore described with reference to and as shown in the accompanying drawings.

54. Any novel feature or combination of features described herein.