Measurement device with multiplexed position signals

A method for determining a 3D position of a contact portion of a stylus based on position signals received from a scanning probe that the stylus is attached to, the method comprising:

• determining that the scanning probe has been positioned so that the contact portion of the attached stylus has come into contact with a workpiece that is being measured, wherein the scanning probe comprises:
• a stylus suspension portion, comprising:
• a stylus coupling portion that is configured to be rigidly coupled to the stylus;
• and
• a stylus motion mechanism that is configured to enable axial motion of the stylus coupling portion along an axial direction, and rotary motion of the stylus coupling portion about a rotation center;
• and
• a stylus position detection portion, comprising:
• a light source configuration comprising a controllable rotary detection light source that is configured to provide a rotary detection beam and a controllable axial detection light source that is configured to provide an axial detection beam;
• a multiple-spot position detector portion;
• multiplexing signal processing and control circuitry;
• a rotary position detection configuration, comprising:
• a rotary position detection beam path configured to receive the rotary detection beam from the controllable rotary detection light source;
• and
• a rotary detection deflector that is located along the rotary position detection beam path and that is coupled to the stylus suspension portion and that is configured to output a variable-deflection rotary detection light beam to the multiple-spot position detector portion;
• and
• an axial position detection configuration, comprising:
• an axial position detection beam path configured to receive the axial detection beam from the controllable axial detection light source;
• and
• an axial detection deflector that is located along the axial detection beam path and that is coupled to the stylus suspension portion and that is configured to output a variable-deflection axial detection light beam to the multiple-spot position detector portion, wherein the axial detection deflector is configured to move in the axial direction in response to the axial motion, wherein the axial detection deflector is also configured to move in at least one direction transverse to the axial direction in response to the rotary motion;
• wherein:
• the multiple-spot position detector portion is configured to receive the variable-deflection rotary detection light beam and in response thereto to output X and Y position signals indicative of a rotation of the stylus coupling portion about the rotation center, and is also configured to receive the variable-deflection axial detection light beam and in response thereto to output a Z position signal indicative of a position of the stylus coupling portion about the axial direction;
• the multiplexing signal processing and control circuitry is configured to multiplex the variable-deflection rotary detection light beam and the variable-deflection axial detection light beam onto the multiple-spot position detector portion, and to provide demultiplexing to separate the X and Y position signals from the Z position signal;
• and
• the stylus position detection portion is configured such that the Z position signal is substantially insensitive to motion of the axial detection deflector in the at least one direction that is transverse to the axial direction;
• and
• receiving the X, Y and Z position signals from the multiplexing signal processing and control circuitry;
• and
• processing the X, Y and Z position signals to determine a 3D position of the contact portion of the stylus.

A system for determining a 3D position of a contact portion of a stylus based on position signals received from a scanning probe that the stylus is coupled to, the system comprising:

• a receiving portion for receiving X and Y position signals and a Z position signal from the scanning probe, wherein the scanning probe comprises:
• a stylus suspension portion, comprising:
• a stylus coupling portion that is configured to be rigidly coupled to the stylus;
• and
• a stylus motion mechanism that is configured to enable axial motion of the stylus coupling portion along an axial direction, and rotary motion of the stylus coupling portion about a rotation center;
• and
• a stylus position detection portion, comprising:
• a light source configuration comprising a controllable rotary detection light source that is configured to provide a rotary detection beam and a controllable axial detection light source that is configured to provide an axial detection beam;
• a multiple-spot position detector portion;
• multiplexing signal processing and control circuitry;
• a rotary position detection configuration, comprising:
• a rotary position detection beam path configured to receive the rotary detection beam from the controllable rotary detection light source;
• and
• a rotary detection deflector that is located along the rotary detection beam path and that is coupled to the stylus suspension portion and that is configured to output a variable-deflection rotary detection light beam to the multiple-spot position detector portion;
• and
• an axial position detection configuration, comprising:
• an axial detection beam path configured to receive the axial detection beam from the axial detection light source;
• and
• an axial detection deflector that is located along the axial detection beam path and that is coupled to the stylus suspension portion and that is configured to output a variable-deflection axial detection light beam to the multiple-spot position detector portion, wherein the axial detection deflector is configured to move in the axial direction in response to the axial motion, wherein the axial detection deflector is also configured to move in at least one direction transverse to the axial direction in response to the rotary motion;
• wherein:
• the multiple-spot position detector portion is configured to receive the variable-deflection rotary detection light beam and in response thereto to output the X and Y position signals indicative of the rotation of the stylus coupling portion about the rotation center, and is also configured to receive the variable-deflection axial detection light beam and in response thereto to output the Z position signal indicative of the position of the stylus coupling portion about the axial direction;
• the multiplexing signal processing and control circuitry is configured to multiplex the variable-deflection rotary detection light beam and the variable-deflection axial detection light beam onto the multiple-spot position detector portion, and to provide demultiplexing to separate the X and Y position signals from the Z position signal;
• and
• the stylus position detection portion is configured such that the Z position signal is substantially insensitive to motion of the axial detection deflector in the at least one direction that is transverse to the axial direction;
• and
• a processing portion for processing the X, Y and Z position signals to determine a 3D position of the contact portion of the stylus.