US 4,807,152 A · Metrological apparatus

Abstract

Metrological apparatus, particularly for measuring form, has a turntable 4 and a transducer 14 and associated stylus 12 mounted so that the tip 12a of the stylus is displaceable radially and vertically relative to the turntable 4. The problem of obtaining both high resolution and large range of operation is solved by using a transducer/stylus 12,14 having a resolution of 12 nanometers and a range of only 0.4 mm and mounting the transducer 14 on an arm 10 which is driven radially and/or vertically by a computer 30 in response to the output from the transducer 14 to cause the stylus 12 to follow the workpiece surface. High resolution data defining the rotary position of the turntable 4 and the radial and vertical position of the transducer 14 is provided by a photodetector/optical grating arrangement 23, 21, 31; 27, 19, 43 and associated interpolators 42, 44, 46. A novel computer architecture comprising a host 22, master 30 and slaves 33, 35, 37 provides an efficient system for controlling the apparatus and gathering data. Efficient gathering of data is further assisted by the provision of means to cause the stylus 12 to traverse the surface of the workpiece at a constant speed, particularly as a function of the radial position of the transducer.

Claims38

Dependent claims

Metrological apparatus comprising rotatable member means for receiving a workpiece;

first drive means for rotating said member means, sensor means for sensing the surface of a workpiece on the rotatable member means during rotation thereof, means for supporting said sensor for movement relative to said member means, second drive means for effecting said movement of said sensor means and digital computer means for receiving signals derived from said sensor, controlling relative movement between said workpiece and said sensor in response to said signals such that said sensor means follows curvature in said workpiece surface and said sensor traverses said workpiece surface at a speed which is substantially constant, and providing metrological data in dependence both on said signals and on said movement of said sensor.

Metrological apparatus comprising:

a first support and means for supporting a workpiece on said first support;
a second support;
means for mounting said first and second supports for relative rotation about an axis of rotation through said first support;
a third support carried by said second support and movable relative to said second support;
further drive means for effecting movement of said third support relative to said second support;
a transducer;
a stylus carried by said transducer for actuation thereof, said stylus having a tip, said tip being disposed substantially on a radius relative to said axis of rotation, said moement of said third support means relative to said second support means providing movement of said tip in directions parallel to and radially of said axis of rotation;
rotary means for mounting said transducer on said third support for arcuate movement relative thereto between a first operative position in which said stylus extends substantially parallel to said axis of rotation and a second operative position in which said stylus extends substantially transverse to said axis of rotation, said arcuate movement being substantially centered at said stylus tip so that said tip is in substantially the same position for each of the operative positions of said transducer for a given position of said third support;
and
computer means for controlling said drive means to cause said apparatus to perform a metrological operation in which said stylus tip traverses a portion of a workpiece surface.

7 more elements

Dependencies are inferred from the claim text.

Metrological apparatus

Life of this patent

Metrological apparatus

Life of this patent

Abstract

Claims38