Geometrical instruments – Gauge – Movable contact probe – per se
Patent
1994-05-19
1997-08-26
Will, Thomas B.
Geometrical instruments
Gauge
Movable contact probe, per se
33559, 33556, G01B 5016
Patent
active
056599692
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to probes, such as are used with coordinate measuring, machine tools, robot and similar machines.
BACKGROUND OF THE INVENTION
In co-ordinate measuring machines, an object is measured by relative motion of a probe and an object in a controlled manner, usually from a datum, until a "touch" on the object is indicated by the probe or the probe is displaced by an indicated amount. The co-ordinates of the touch position are recorded or the probe indication combined with the machine indication. By repeated such actions the dimensions of the object can be determined. Appropriate actions are carried out with probes in machine tools, robot and similar machines.
UK Patent Application 8815984.3, published as GB-A-2220748, describes a touch probe for taking two dimensional measurements which can be mounted on a suitable kinematic mounting, to be movable to make measurements in the third dimension. However, the mounting is expensive and bulky.
The use of a cone of light emitted from a fibre optic and reflected by a plane mirror to an array of receiver fibre optics has been proposed (EP A 0429378--CNRS/CEMAGREF) for force measurement by the determination of the direction and amplitude of small lateral displacements of the mirror when the mirror is mounted to be responsive to an applied force, e.g. in an anemometer, by fluid flow or in a "joy-stick". In this arrangement only a part of the divergent cone of light is incident on the deflected mirror and the greater the defection the less light is so-incident. Furthermore the reflected light continues to diverge so that some of the already-reduced light misses the fibre receiver array while that reaching the array is of reduced intensity, due to the continued divergence.
Another form of three-dimensional probe for displacement indication is based on three small grating scales but this also is bulky, complex and expensive.
SUMMARY OF THE INVENTION
It is an object of this invention to provide a probe which overcomes such shortcomings and provides measurements in all three dimensions,
According to the invention, there is provided a probe for a position determining apparatus and the like including a sensing space, a stylus supported for position determining movement and extending, means to emit into the space sensing radiation into the space and means to collect the sensing radiation from the space. The stylus in supported within the space means to deflect emitted sensing radiation upon movement of the deflecting means with position determining movement of the stylus. The stylus is supported for three-dimensional position determining movement, the deflection means concentrating the sensing radiation and the collection means being sensitive to a variation of intensity distribution of collected deflected radiation with the three-dimensional movement of the stylus, the stylus being free of mechanical connection for determining the position.
The sensing radiation may be one of light and like radiation, including visible light, infra-red light, ultra-violet light and other electromagnetic radiation.
The collection means for light radiation may include a fibre optic having an array of optical fibre elements. The collection means may include optoelectronic means responsive to deflected light intensity variation to produce a deflection-related signal and a signal processing arrangement to derive therefrom the movement of the deflection means and thereby determine the stylus movement in three dimensions. The optoelectronic means may be responsive to deflected light collected by the individual optical fibre elements.
The emission means for light radiation may be at least one optical fibre. The emission fibre may be one of the collection of fibre optic elements.
The deflection means may be one if a reflective and a refractive device for concentrating the deflected sensing radiation. When the radiation is light, the deflection means may be one of a lens, a mirror and a prism.
The probe can be arranged for analogue and/or touch operation.
REFERENCES:
patent: 4158768 (1979-06-01), Lavelli
patent: 4694184 (1987-09-01), Pryor
patent: 4942671 (1990-07-01), Enderle et al.
patent: 4972597 (1990-11-01), Kadosaki et al.
patent: 5103572 (1992-04-01), Ricklefs
patent: 5222304 (1993-06-01), Butler
Born, Max and Wolf, Emil, "Electromagnetic Theory of Propagation, Interference and Diffraction of Light," Principles of Optics, Sep. 22, 1975, pp. 434-449.
Butler Clive
Yang Qingping
British Technology Group Limited
Will Thomas B.
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