Abstract: A measuring apparatus and a measuring method capable of measuring a surface of an object includes a movable body having a mounting portion on which the object is mounted, and first and second surfaces not coplanar with each other, a first scale portion provided to press the first surface and to measure a first scale position along a first scale axis parallel to a normal direction of the first surface, a second scale portion provided to press the second surface and to measure a second scale position along a second scale axis parallel to a normal direction of the second surface, a first probe having a reference point of position measurement set on a probe axis parallel to the second direction and at an intersection of the first scale axis and the second scale axis, and a second probe measuring a position along the probe axis.

Abstract: A method for accurately producing the drilled hole in a wall of a component fabricated by investment casting process, such as for use in a blade or steam turbine includes the following steps. The 3D data of actual component is obtained from the measurements or from the numerical simulation. The actual model and the ideal model are aligned and compared, a series of cutting planes are given to establish a series of 2D cross-sections of the actual and ideal models after registration. Each cross-section is dispersed into discrete points, the distance between each corresponding points are calculated and formed into 2D displacement. The accurate parametric model consisting of the depth, hole center, and the nominal vector is obtained on the basis of considering the deviations in geometrical and positional values. The drilled hole is then produced according to the corrected parametric drilled-hole geometrical and positional value.

Abstract: A method for shape classification of an object is provided. Shape categories are provided which specify a plane and points therein relative to the object, and also specify at least one limit coordinate for each such point, the limit coordinate defining a boundary in a direction normal to the plane for the shape of the object considered in order for the object to be classified into a respective shape category. The shape categories can be provided by a user, making the method very flexible. The shape categories can in particular be derived from a set of samples of objects representing a shape category to be defined. For classification, the position of a surface of the object is measured at each of the points defined in the shape category, and the result is compared with the corresponding limit coordinate.

Abstract: This invention concerns improvements in the inspection, assessment and re-working of manufactured components such as nozzle guide vanes (NGVs) and blades, in particular by improving the comparison of the component with nominal data. Dimensional data of a physical component is obtained and used to create a virtual digitized model of the component which is aligned with a nominal CAD model of the component in a virtual space. The correspondence is assessed and used to adjust weightings of different regions of the digitized model to improve the alignment. This process is repeated within the digital space until either conformance is reached or it is determined that this is not possible.

Abstract: The present disclosure is directed to an improved system and method for repairing a bend in a turbine blade of a turbine of a gas turbine engine. The system includes an articulating guide configured to fit into an access port of the turbine. The articulating guide includes a proximal end and a distal end. The system also includes a repair tool configured at the distal end of the articulating guide. Further, the repair tool is configured to fit over the turbine blade. Thus, the repair tool is configured to bend the turbine blade to an unbent position while the turbine blade is secured within the turbine.

Abstract: A computer-assisted inspection system provides computer architectures and software controlled algorithms to automatically provide vehicle inspections and repair recommendations including estimated repair time and cost of depression type damage such as dents. Features provided by a handheld wireless touchscreen based inspection device include flat car part picking, auto grading including seller grading, and automatic calculation of body and bumper dent repair parameters and directions.

Abstract: An apparatus of checking dimensions of an object includes a checking platform. The checking platform has a checking slot extending from one side and arriving at another side thereof. The checking slot is defined by a first side wall, a second side wall and a bottom wall, wherein the first side wall has a front section connecting to a rear section. The second side wall has a middle section connecting to a front section and a rear section, wherein the distance between the front section of the first side wall and the front section of the second side wall is greater than that between the rear section of the first side wall and the rear section of the second side wall, and is smaller than that from a connecting location to the middle section of the second side wall.

Abstract: A method and apparatus for inspecting a surface of an object. Data from measuring the surface of the object is obtained to form surface data for the object. A range of frequencies for features on the object is selected based on a range of distances between adjacent peaks for the features. The features are formed by a tool moving along a number of paths. Desired surface data for the features is obtained from the surface data using the range of frequencies selected. A determination is made as to whether the desired surface data for the features meets a policy specifying a desired surface for the object. In response to an absence of a determination that the desired surface data for the features meets the policy, the object is reworked.

Abstract: A system for generating surface data defining a position and location of an object is described. The system includes a non-contact measuring device for measuring the location of one or more points on a surface of an object with respect to the measuring device, an optical imaging device for capturing image information, and a processor. The processor is programmed to use the captured image information to determine location and orientation data for both the measuring device and the optical imaging device with respect to a fixed point in space, receive location measurement data from the measuring device, and combine the location and orientation data with the location measurement data to generate surface data for the object.

Abstract: A test kit for unevenly worn sheave grooves, a tool for regrooving sheave grooves that are found to be unevenly worn, and a method for testing for and maintaining the sheave grooves utilizing the test kit and tool. The test kit includes magnetic standards which adhere to a sheave beneath the portion of the sheave touched by the ropes, facilitating testing without having to unrope the sheave. Unevenly worn sheave grooves are visually ascertained by holding a straightedge adjacent to the magnetic standards. The regrooving tool includes a shank that can be received by a stand set up next to the sheave, a body attached to the shank, and an interchangeable cutting insert received by the body that is inserted in the sheave groove. When the sheave is rotated, the sheave groove is ground by the cutting insert, with each groove being ground sequentially until all grooves are again uniform.

Abstract: A test kit for unevenly worn sheave grooves, a tool for regrooving sheave grooves that are found to be unevenly worn, and a method for testing for and maintaining the sheave grooves utilizing the test kit and tool. The test kit includes magnetic standards which adhere to a sheave beneath the portion of the sheave touched by the ropes, facilitating testing without having to unrope the sheave. Unevenly worn sheave grooves are visually ascertained by holding a straightedge adjacent to the magnetic standards. The regrooving tool includes a shank that can be received by a stand set up next to the sheave, a body attached to the shank, and an interchangeable cutting insert received by the body that is inserted in the sheave groove. When the sheave is rotated, the sheave groove is ground by the cutting insert, with each groove being ground sequentially until all grooves are again uniform.

Abstract: An apparatus of checking dimensions of an object includes a checking platform. The checking platform has a checking slot extending from one side and arriving at another side thereof. The checking slot is defined by a first side wall, a second side wall and a bottom wall, wherein the first side wall has a front section connecting to a rear section. The second side wall has a middle section connecting to a front section and a rear section, wherein the distance between the front section of the first side wall and the front section of the second side wall is greater than that between the rear section of the first side wall and the rear section of the second side wall, and is smaller than that from a connecting location to the middle section of the second side wall.

Abstract: A railway car coupler head contour gauge includes a cylindrical portion configured to be rotatably coupled to a coupler head. The railway car coupler head contour gauge also includes a pulling lug gauging portion, and a contoured gauging surface that is configured to align with a contour face of a top pulling lug of the coupler head during gauging. The coupler head contour gauge may also include a convex portion configured to align with a buffing shoulder of the coupler head.

Abstract: A method for measuring the profile of a component in the region of an edge of the component comprises the following steps: determining the position of an edge point of the component; defining a center line for the component in the region of the edge; and measuring at least one dimension of the component with reference to the center line.

Abstract: A lapping or polishing machine includes a material having a first finishing surface to process a surface of a work item, a measuring tool to measure a contour of the first finishing surface, and a conditioning tool having a second finishing surface to process the first finishing surface to reduce a difference between the measured contour and a desired contour of the first finishing surface.

Abstract: The present invention relates to an “S” shaped detection test piece for comprehensively detecting the precision of the numerical control milling machine and the detection method thereof. The detection test piece consists of an “S” shaped equal thickness edge strip (1) and a rectangular base (2), respectively forming two “S” shaped curves in two different planes and the projections of which in the base plane (3) cross each other and have open and close angle (?) states formed at the intersection.

Abstract: A railway car coupler head contour gauge includes a cylindrical portion configured to be rotatably coupled to a coupler head. The railway car coupler head contour gauge also includes a pulling lug gauging portion, and a contoured gauging surface that is configured to align with a contour face of a top pulling lug of the coupler head during gauging. The coupler head contour gauge may also include a convex portion configured to align with a buffing shoulder of the coupler head.

Abstract: A railway car coupler head contour gauge includes a cylindrical portion configured to be rotatably coupled to a coupler head. A gauging blade is coupled to the cylindrical portion. The gauging blade includes a gauging contour that is configured to align with a contour face of a top pulling lug of the coupler head after operational use of the coupler head.

Abstract: A measuring device, includes a guiding rail, a sliding unit levitatedly slidably engaged with the guiding rail, and a measuring unit fixed to the sliding unit and comprising at least one dial gauge mounted thereto.

Abstract: A railway car coupler head contour gauge includes a cylindrical portion configured to be rotatably coupled to a coupler head. A gauging blade is coupled to the cylindrical portion. The gauging blade includes a gauging contour that is configured to align with a contour face of a top pulling lug of the coupler head after operational use of the coupler head.

Abstract: A method for measuring the profile of a component in the region of an edge of the component comprises the following steps: determining the position of an edge point of the component; defining a centre line for the component in the region of the edge; and measuring at least one dimension of the component with reference to the centre line.

Abstract: An exemplary contour measuring device (100) includes a pair of guide rails (13), a movable fixture (14), a first probe (15), a second probe (16), and an error correcting unit (17). The movable fixture is movably disposed on the guide rails. The first probe is configured for measuring an object along a contour measuring direction and obtaining a first measured contour value from the object to be measured. The second probe is configured for measuring a standard object whose contour is known along the contour measuring direction and obtaining a second measured contour value from the standard object. The error correcting unit is configured for compensating the first measured contour value according to the second measured contour value.

Abstract: A system for measuring the height of a wind deflector mounted to the roof of a vehicle. A longitudinal base has a first end, an opposing second end, a generally planar top surface and a generally planar bottom surface. An adjustable stop is proximate the first end of the base and extends away from the bottom surface. A level indicator is affixed to the top surface of the base. An arm is spaced apart from the top surface of the base, and a displacement indicator is affixed to the arm. The displacement indicator displays information relating to the height of the wind deflector above the roof when the second end of the base contacts the wind deflector proximate the roof, the level indicator indicates that the base is on a level plane, and the displacement indicator is in contact with a top edge of the wind deflector.

Abstract: A tool for indicating the flushness between a vehicle body roof panel and a sunroof panel that is adjustably mounted within a sunroof opening of the vehicle body roof panel. The tool will signal a vehicle assembly operator in the event that the sunroof panel needs to be vertically adjusted up or down. The tool includes a housing that sits on the roof panel. A lever is pivotally mounted on the housing and has a feeler extending from the housing to contact with the sunroof panel so that the pivotal position of the lever relative the housing is determined by the degree of flushness or lack of flushness between the two panels. An indicator is associated with the lever to indicate to the vehicle assembly operator whether or not the sunroof panel needs vertical adjustment relative to the roof panel to obtain an acceptable degree of flushness.

Abstract: A method an apparatus for measuring the depths of many fine holes formed in the surface of a sample by etching. Positional information on a plurality of hole patterns is acquired by scanning, with a stylus, the surface of the sample in which the hole patterns are formed by etching. The depths of the plurality of hole patterns are measured by scanning, with the stylus, bottom faces of the plurality of hole patterns and the surface of the sample in the respective vicinities of the hole patterns on the basis of the positional information that has been acquired. Information on distribution of the depths of the plurality of hole patterns is displayed on a screen on the basis of information on the measured depths of the plurality of hole patterns and the positional information on each of the hole patterns.

Abstract: A metrology system includes a laser, a position sensitive detector array, a first collimator, a second collimator, and a mirror. The position sensitive detector array and the first collimator are positioned at a reference point. The second collimator and the mirror are positioned at a point target at a distance from the reference point. A laser beam is alternately provided to the first collimator and the second collimator by optical fiber. The position sensitive detector array measures position data from a first laser crosshair generated by the first collimator and from a second laser crosshair generated by the second collimator. By alternating the activation of the first collimator and the second collimator it is possible to measure 5 degrees-of-freedom for the point target. A metrology system processing unit provides analog data processing. The metrology system that is suitable for, but not limited to, facilitating active compensation of large spacecraft structures.

Abstract: An apparatus for measuring the dimensions of an articulated connector for reconditioning while it is still mounted to the end structure of a rail car is disclosed. The connector is measured to find areas and amounts of wear on portions of the connector. The measurements are taken relative to a reference portion of the connector. A pivot gauge apparatus can be used to determine if a male casting meets industry standards. The pivot gauge includes a fixable base for interaction with the casting and a pivotably mounted arm with measurement portions.

Abstract: A method for confirming the dimensions of an articulated connector while it is still mounted to the end structure of a rail car is disclosed. The connector is measured by use of a gauge secured to a reference point on portions of the connector. Another portion of the gauge is aligned with a non-reference point to determine if the dimensions fall within industry standards.

Abstract: A measurement block 10 which moves longitudinally on a road surface includes disk-shaped first, second, and third rollers 11, 12, and 13 having the same outer diameter with a predetermined spacing set therebetween, a first coupling rod 14 which is mounted on rotary shafts of the first and second rollers in a revolving manner, a second coupling rod 15 which has the same length as the first coupling rod and which is mounted on rotary shafts of the second and third rollers in a revolving manner, a distance measurement device 16 which is mounted on the rotary shaft of the first or second roller, and a rotary encoder 18 which is mounted on the second coupling rod to detect an angle between the first and second coupling rods. Each time the measurement block moves by a length between the first and second coupling rods, the angle between the first and second coupling rods is detected by the angle detection means to thereby create a longitudinal profile based on the detected value.

Abstract: A conformance gauge is used as an inspection tool to check that component features lie within tolerance limits. When the component has been designed using CAD tools the CAD data file defining external surfaces of the component is used as the basis to create a second CAD data file defining the surfaces of the inspection to conform to the corresponding surfaces of the component. Viewing apertures or slots are then defined in the data file to the tolerance limits of features to be checked. The second CAD data file is then provided to a rapid prototyping system, eg a stereolithography machine to produce the final inspection gauge.

Abstract: A method of preparing a surface on a die coater to improve the uniformity of the coating layer on the substrate. A surface of the die block is machined. The die block is then positioned on a measuring surface in a free state so that the machined surface being measured is substantially vertical. The vertical orientation of the die block substantially removes the effect of gravity on any residual stress during measuring. The steps of machining, positioning, and measuring the die block are repeated until the desired total indicated run-out is achieved. The positioning step may also include interposing at least two point supports between the die block and the measuring surface. In another embodiment, the die blocks are positioned in a reference state or a production state for measuring.

Abstract: A method of characterizing the shape of a probe element for a scanning probe microscope including using two test pattern surfaces of known configuration, the first surface having a pointed wedge-shaped tip and the second surface having an hour-glass type cross-section, wherein the surfaces are scanned to generate scan lines having curved transition zones that are geometrically matched in order to generate a probe characteristic representation curve, wherein the probe characteristic representation curve is a graphic representation of the shape of the tip of the probe.

Abstract: A conformance gauge is used as an inspection tool to check that component features lie within tolerance limits. When the component has been designed using CAD tools the CAD data file defining external surfaces of the component is used as the basis to create a second CAD data file defining the surfaces of the inspection to conform to the corresponding surfaces of the component. Viewing apertures or slots are then defined in the data file to the tolerance limits of features to be checked. The second CAD data file is then provided to a rapid prototyping system, eg a stereolithography machine to produce the final inspection gauge.

Abstract: A technique for measuring distortion in a structure of interest, such as a spacecraft antenna reflector (18), and optionally compensating for the distortion. A first set of targets (22) on the structure (18) is scanned by an attitude transfer system (24) to measure the angular location and range of each target relative to a reference point on another structure (12) having a frame of reference. The orientation of the structure of interest is them determined from the measured locations of the targets. A second set of targets (60 or 82) on the structure of interest is scanned by a figure sensing module (26) located at a reference point on the structure itself. From measured angular locations and ranges of the second set of targets, any shape distortion in the structure of interest can be determined, and distortion may be corrected with the use of actuators (98).

Abstract: There is provided a reference gage that has first and second reference planes parallel to one another and perpendicular to a rotational axis of the reference gage, and a distance between the reference planes is already known as a reference distance. To calibrate the measuring head, the measuring direction of the measuring head is set parallel to the rotational axis of the measuring head or the table on which the reference gage is placed, and a reference value of the reference distance on the reference gage is entered. Then, the reference distance is measured by the measuring head to acquire measured data, and a measured value of the reference distance is calculated from the measured data. The measuring head is calibrated so that the measured value accords with the reference value. The time required for calibrating the measuring head is thus reduced.

Abstract: Method and device for accurately measuring a longitudinal contour of a measuring object, wherein use is made of clamping members for retaining a measuring object to be measured; a scanning arm which is pivotable about an axis transverse to a longitudinal center line of the clamped measuring object and whose free end comprises one scanning needle, the scanning arm being mounted on a driving device which, in operation, can move the scanning arm in one linear direction of movement parallel to the longitudinal center line of the measuring object, and means being provided for detecting the angular displacement of the scanning arm and the position of the scanning arm in said one linear direction of movement; and a processor for processing information regarding the angular displacement and the position of the scanning arm, wherein a contour measurement is made in such a manner that the scanning needle moves along a contour flank in downward direction only, i.e. in the direction of the bottom of a profile groove.

Abstract: A dimensional weighing apparatus is disclosed which has a weighing scale for determining the actual weight of a carton, and a conveyor means along which cartons are moved after being weighed to pass the cartons through a measuring station at which the length, width and height of the cartons are measured. A first measuring means measures both the height and length as the cartons move through the measuring station by means of a member that rides up the leading vertical face of the cartons to measure the height and then across the top surface thereof to measure the length. A second measuring means measures the width of the cartons as they move through the measuring station by means of carton contact members mounted along the side surfaces of the carton and move in and out of contact with the carton.

Abstract: A mechanism (10) for scanning the contour of a tri-dimensional body (R) including control circuitry (120) for processing and storing the pattern data obtained. The contour pattern is measured by using contour follower members (92x) that rapidly slide between the two arms (108,108') of a scan rotor assembly (100) that is driven by a reference step motor (102). Coaxially aligned phase disks (82x) are slidably mounted over outer slots (112x, 112x') on the outer periphery of the arms and a linkage mechanism (94x) is pivotally mounted on one end to a predetermined point (91x) in the phase disk and the other end (93x) to the contour follower member. The phase disks are slowed down by frictional force applied to the phase disks are this slowing down force is overcome by the contour follower once it comes in contact with the reference body.

Abstract: A device for measuring the gap between the opposed facing surfaces of two adjacent parts, and simultaneously measuring the contour between outwardly facing surfaces of the parts. A gap measuring element is mounted to be movable along a first path relative to a first reference member carried by the main body. The first reference member is selectively engagable with one of the parts. The gap measuring element is insertable into the gap for engagement with the other of the parts. The gap measuring element is coupled to a transducer for generating a signal representative of the relative position of the gap measuring element along its path. The signal is proportional to the gap between the opposed facing surfaces of the parts. Additionally, a contour measuring element is mounted to be movable along a second path relative to a second reference member carried by the main body. The second reference member is selectively engagable with the outwardly facing surface one of the first and second parts.

Abstract: A device for measuring the gap between the opposed facing surfaces of two adjacent parts, and simultaneously measuring the contour between outwardly facing surfaces of the parts. The device is preferably hand-held, and has a main body with a gap measuring element supported relative to the main body. The gap measuring element is mounted to be moveable along a first path relative to a first reference member carried by the main body. The first reference member is selectively engagable with one of the parts. The gap measuring element is insertable into the gap for engagement with the other of the parts. The gap measuring element is coupled to a transducer for generating a signal representative of the relative position of the gap measuring element along its path. The signal is proportional to the gap between the opposed facing surfaces of the parts. A contour measuring element is also supported relative to the main body.

Abstract: The present invention discloses a system and method for determining airfoil characteristics from coordinate measuring machine probe center data. A coordinate measuring machine measures external coordinates along an airfoil and sends the coordinates to a computer. The computer sorts and orders the coordinates into a plurality of probe center points along a plurality of sections along the airfoil. The probe center points are triangulated to detect and eliminate errant points. Then the probe center points are correlated to a nominal part of the airfoil stored in the memory of the computer until a specified plane of interest is obtained. A discrete inset operation is performed on the correlated data for the plane of interest until a maximum thickness is obtained. The inset points are then joined to form an airfoil meanline, which is used to determine characteristics such as leading edge thickness, trailing edge thickness, and chord length.

Abstract: A camshaft checking apparatus, in particular for checking the parameters of the profiles of cams, comprising a support structure and a motor means for positioning and axially rotating the shaft, linear transducers for determining radial dimensions of cams in the course of the rotation, a measuring head for cooperating with a reference portion of the camshaft and locating an angular shaft reference position, a rotary transducer for defining said angular position and angular measuring positions, and a control unit for receiving and processing signals arriving from the linear transducers, measuring head and the rotary transducer.

Abstract: An electronic bubble level display is provided for determining surface normality when coupled with three sensors (18, 20, 22) sensing distance to the surface. The signals from the sensors are provided to an electronic processor (34) for computing the surface angularity and translating the angularity to specific positions on an LED dot matrix display chip (38).

Abstract: A panel testing apparatus for measuring the curvature of an inner surface, the thickness of an edge portion, and the thickness of a center portion of the panel comprises a lifting device for accepting and transporting the panel to a testing position, and a panel supporting device for maintaining the panel in a predetermined position during testing. The apparatus comprises a panel inner curvature measuring device, edge thickness measuring device, and a center thickness measuring device, each of which using one or more linear variable differential transformers for the purpose of providing panel measurement data.

Abstract: A system and method for contact measurement of dimensional parameters of a container in which rollers coupled to LVDT sensors are placed in contact with a container as the container is rotated about its central axis so that the sensors develop analog signals that vary as a function of variations in geometry of the container. The sensor output signals are fed through multiple input channels to an a/d convertor/multiplexer, which is controlled by a central microcontroller for selecting in turn among the plurality of sensor signals. Within the microcontroller, each sensor signal is compared to a threshold indicative of maximum acceptable deviation of the corresponding dimensional parameter, and the container under test is rejected if the parameter exceeds such threshold. The microcontroller includes facility for real-time display of measured parameters in English or metric units at the selection of an operator, and for communication of measurement data to a remote computer.

Abstract: In a copy control device wherein a model (6) and a workpiece moved relatively with a tracer head (4) and a tool in an X-Y plane, measured distance values to the surface of the model, which are detected by first and second non-contact detectors (5a, 5b) obliquely mounted on the tracer head (4) rotatable about a Z axis are periodically sampled to obtain the coordinate values of measured points on the surface of the model, a normal vector (Nn) on the surface of the model is calculated from three coordinate values out of four measured points (P1n-1, P1n, P2n-1, P2n) successively obtained by the both detectors, and the tracer head is rotated so as to move along a projection (N1n) of the normal vector (Nn) on the X-Y plane, so that measuring axes of the detectors are controlled to be approximately vertical to the surface of the model.

Abstract: A measurement tool adapted for measuring surfaces of a known desired curvature and specifically grooves, holes, chips, gouges, chafing and/or out of round areas therein. The measurement device is constructed with an attachment member having a curvature matching the "set up" curvature of the part to be measured. The measuring member or probe, is sharpened to permit it to extend through an aperture formed in the attachment member for facilitating its initial setting relative to the attachment member and the surface to be measured. Any movement of the probe during measurement is then a manifestation of a deviation from the original "set up" curvature.

Abstract: A system for generating a solid model of the sidewall of the container. A mandrel selectively holds the container in first and second locations. In the first location, a non-contact measurement apparatus utilizing a digital camera produces digital information for generating a three dimensional sidewall surface profile of the container based upon shadow edge detection. In the second position, a contact measurement apparatus produces information for generating a three dimensional sidewall thickness map of the container. A computer collects the information from the contact and non-contact measurement apparatuses and produces an overall solid model of the sidewall of the container based upon sidewall surface profile and sidewall thickness. The computer generates can tilt, diameter, can ovality, and can squarity information.

Abstract: An apparatus for determining the profile of a cylindrical workpiece whose radius varies with axial position. The apparatus is equipped with a spindle head and a pair of detectors. The spindle head supports and rotates the workpiece. The detectors are mounted on opposite sides of the axis of rotation of the workpiece and detect the position of the outer surface of the workpiece. When the workpiece is being rotated, the spindle head is moved parallel to the axis of the spindle. As a result, the detectors cross the outer surface of the workpiece. Also, the detectors are moved radially along an ideal profile of the workpiece in synchronism with the movement of the head. A control unit calculates the average of first and second output signals from the detectors, respectively, and produces the average as the profile error. In another embodiment, only one detector is used. The control unit measures the profile while the detector is positioned on one side of the axis of the spindle.

Abstract: An apparatus containing four linear gauges (I, II, III and IV) allows simultaneous measurement of the main parameters of a lens blank, namely the vertex radius (or asphericity), the centre thickness, and the front surface sag. A first head member (6) presents contacts (12) which contact the front conicoid surface of a lens blank (101) on a first circle. A measuring head (8) presents contacts (13) on a second circle. Gauges (I and II) measure relative displacements between the contacts (12 and 13) and the end of pointer (3), from which the asphericity or vertex radius can be calculated. Gauges (III and IV) are coupled respectively to the rear and front surfaces of the lens blank (101). The perimeter (106) of the lens blank (101) is aligned with a reference plane (R). The displacements of the gauges (III and IV) can be used to calculate the centre thickness and front surface sag of the lens.