Position detector

A position detector comprising:

• first and second members mounted for relative movement along a measuring path;
• said first member comprising a magnetic field generator for generating a magnetic field;
• said second member comprising first and second conductors which are inductively coupled to said magnetic field generator, the magnetic coupling between said first conductor and said magnetic field generator varying with a first spatial frequency and the magnetic coupling between said second conductor and said magnetic field generator varying with a second different spatial frequency, as a result of which, in response to a magnetic field generated by said magnetic field generator, a first signal is generated in a first receive circuit which first signal varies in dependent upon the relative position and orientation of the first conductor and the magnetic field generator and a second different signal is generated in a second receive circuit which second signal varies in dependence upon the relative position and orientation of the second conductor and the magnetic field generator;
• and
• means for processing said first and second signals to determine the relative position and orientation of the two moveable members in dependence upon said first and second spatial frequencies.

A position detector comprising:

• first and second members mounted for relative movement in a measuring plane;
• said first member comprising a magnetic field generator for generating a magnetic field;
• said second member comprising first and second groups of circuits for sensing the relative position and orientation of the first and second members in two different directions in said plane;
• and
• means for determining the relative orientation of the first and second members in said plane using the relative orientations in said first and second directions;
• characterised in that each group of windings comprises first and second conductors which are inductively coupled to said magnetic field generator, the first conductor extending in a geometrically varying manner having a first characteristic dimension along the corresponding direction and the second conductor extending in a geometrically varying manner having a second different characteristic dimension along said corresponding direction.

A position detector comprising:

• first and second members mounted for relative movement along a measuring path;
• said first member comprising a magnetic field generator for generating a magnetic field;
• said second member comprising first and second circuits each comprising a conductor which is inductively coupled to said magnetic field generator, the conductor of said first circuit extending in a geometrically varying manner having a first characteristic dimension along the measuring path and the conductor of said second circuit extending in a geometrically varying manner having a second different characteristic dimension along the measuring path, as a result of which, in response to a magnetic field generated by said magnetic field generator, a first signal is generated in said first circuit and a second different signal is generated in said second circuit, the first and second signals both varying in dependence upon the relative position and orientation of the two moveable members;
• and
• means for processing said first and second signals to determine said relative position and orientation a relationship between the respective characteristic dimension of the geometrical variation of said two conductors.

A position detector comprising:

• first and second members mounted for relative movement along a measuring path;
• said first member comprising a magnetic field generator for generating a magnetic field;
• said second member comprising first and second periodic windings which extend along the measuring path and which are inductively coupled to said magnetic field generator, the period of said first winding being different to the period of said second winding, as a result of which, in response to a magnetic field generated by said magnetic field generator, a first signal is generated in said first circuit and a second different signal is generated in said second circuit, the first and second signals both varying in a substantially sinusoidal manner in dependence upon the relative position and orientation of the two moveable members;
• means for processing said first and second signals to provide a first value which depends upon said relative position and orientation and a second different value which depends upon said relative position and orientation;
• and
• means for combining said first and second values to determine said relative position and orientation in dependence upon a relationship between the two periods of said windings.

An X-Y digitising system comprising:

• first and second members mounted for relative movement in the X-Y direction;
• said first member comprising a first magnetic field generator for generating a magnetic field substantially in a first direction and a second magnetic field generator for generating a magnetic field substantially in a second direction different from said first direction;
• said second member comprising two sets of periodic windings, each set comprising first and second periodic windings, which extend along the measuring path and which are inductively coupled to said first and second magnetic field generators, the period of said first winding being different to the period of said second winding, as a result of which, in response to a magnetic field generated by each of said magnetic field generators, a first signal is generated in said first circuit and a second different signal is generated in said second circuit, the first and second signals both varying in dependence upon the relative position and orientation of the two moveable members;
• means for processing said first and second signals from each of said magnetic field generators to provide a first value which depends upon said relative position and orientation and a second different value which depends upon said relative position and orientation;
• and
• means for combining said first and second values to determine said relative X-Y position and to determine said relative orientation in dependence upon a relationship between the two periods of said windings.

A position detector comprising first and second members mounted for relative movement along a measuring path;

• said first member comprising a plurality of conductors each extending in a geometrically varying manner having a different characteristic dimension along the measuring path;
• said second member comprising means for interacting with said conductors, such that in response to an input driving signal applied to one of said conductors, there is induced in the other said conductors an output signal, said interacting means and said geometrically varying conductors being arranged so that said output signal varies as a function of the relative position between said first and second members along said path;
• and
• means for processing said signal to derive said relative position.

A method of detecting the relative position and orientation between first and second members mounted for relative movement along a measuring path, the method comprising the steps of:

• providing a magnetic field generator for generating a magnetic field on said first member;
• providing first and second conductors which are inductively coupled to said magnetic field generator or said second member, the first conductor extending in a geometrically varying manner having a first characteristic dimension along the measuring path and the second conductor extending in a geometrically varying manner having a second different characteristic dimension along the measuring path, as a result of which, in response to a magnetic field generated by said magnetic field generator, a first signal is generated in a first receive circuit which first signal varies in dependence upon the relative position and orientation of the first conductor and the magnetic field generator and a second different signal is generated in a second receive circuit which second signal varies in dependence upon the relative position and orientation of the second conductor and the magnetic field generator;
• generating a magnetic field using said magnetic field generator;
• receiving the first and second signals from said receive circuits;
• and
• processing said first and second signals to determine the relative position and orientation of the two movable members using a relationship between the respective characteristic dimension of the geometrical variation of said two conductors.

A position detector comprising:

• first and second members mounted for relative movement;
• said first member comprising a magnetic field generator for generating a magnetic field;
• said second member comprising first and second groups of circuits for sensing the relative position and tilt of the first and second members in two different directions;
• wherein each group of circuits comprises at least two windings which are inductively coupled to said magnetic field generator and wherein the magnetic coupling between the at least two windings varies with different spatial frequencies;
• and
• means for determining the relative rotation between the first and second members using the sensed tilt in the first and second directions.