The primary object presented in this contribution is the miniaturization of a displacement sensor system with the potential for high accuracy measurements and for cost-effective production in polymers. The measurement of linear displacements can be performed by different methods e.g. magnetoresistive, potentiometric, electromagnetic or inductive encoder systems. For movements in the millimeter range and above the most precise systems are based on optical methods.
The displacement measurement of our sensor system uses the intensity modulation of two amplitude gratings, moving relative to each other and illuminated by a LED. To increase the system resolution and the signal quality the grating/detector combination is divided into four areas which are phase shifted to each other. The grating period is 25 μm with a geometrical accuracy below 1 μm. The amplitude gratings have been processed on a glass substrate lithographically. Applying electro-discharge machining a miniaturised optical bench for the passive alignment of the optical and the opto-electronic components has been realised.
The sensor has an overall size of 6x4x3 mm3 and is designed for the future replication in one single polymer part. In combination with an electronic interpolation the sensor will be capable for a sub-micrometer accuracy.