Miniaturised optical sensors for industrial applications

When addressing optical sensors for use in e.g. industry, compactness, robustness and performance are essentials. Adhering to these demands, we have developed a suit of compact optical sensors for the specific purposes of measuring angular velocity and linear translations of rigid objects. The technology is based on compact and low-cost laser sources such as Vertical Cavity Surface Emitting Lasers (VCSELs). The methods characterise the object motion by speckle translation in the near field (imaging) or far field (optical Fourier transform) by optical spatial filtering velocimetry. The volume of the two optical solutions is less than 1 cm3, including the application specific integrated circuit (ASIC), which processes the data and interfaces a PC/Laptop directly via a USB driver. The sensors are designed for working distances of 2 and 12 mm for near field and far field, respectively. We will consider the requirements for the optical designs in order to optimize the two sensor concepts for their respective purpose. For the angular velocity sensor the phase curvature of the illuminating beam is important in order to avoid parasitic contributions from any linear (transverse, in-plane) translations. The linear translation sensor is based on an imaging system. Therefore, the optical solution requires some kind of a beam-combining device because the VCSEL and the photodetectors being located in separate areas on the ASIC. We will present these two optical sensor designs and measurements for evaluation of their performance.