Optimal design of a touch trigger probe

A tungsten stylus with a ruby ball tip was screwed into a floating plate, which was supported by four leaf springs. The displacement of the tip caused by the contact force in 3D could be transferred into the tilt or vertical displacement of a plane mirror mounted on the floating plate. A quadrant photo detector (QPD) based two dimensional angle sensor was used to detect the tilt or the vertical displacement of the plane mirror. The structural parameters of the probe are optimized for equal sensitivity and equal stiffness in a displacement range of ±5 μm, and a restricted horizontal size of less than 40 mm. Simulation results indicated that the stiffness was less than 0.6 mN/μm and equal in 3D. Experimental results indicated that the probe could be used to achieve a resolution of 1 nm.