Shadow Optical Sensor of Linear Dimensions and Displacements Based on a Charge-Coupled Photodetector

The article is devoted to the development of a shadow optical sensor of linear dimensions and displacements based on a charge-coupled photodetector, which has an extended frequency range and increased accuracy in controlling linear dimensions and displacements. The article discusses methods for non-contact measurement of the amplitude and frequency of oscillations of an object operating under conditions of alternating loads, as well as the features of the shadow projection method. To evaluate the capabilities of this sensor, its prototype was made from ready-made elements. To filter the background illumination, the useful signal is extracted from the difference between two sequentially read frames: with the transmitter on and off. After finding the difference between two successively received frames from the sensor with the transmitter on and off, the controller determines the largest shadow of the object by the threshold value of the useful signal and, tracking the positions of the extreme points of the shadow, determines the linear dimensions and frequency of the object’s vibration. The oscillation frequency of the object is determined using the fast Fourier transform. The block diagram and visual model of the prototype are given. The laser module DSP6505-0818 is used as an emitter in the sensor. The photodetector is implemented on a ready-made CCD module of the TSL1401 type. The computing module is made on the STM 32f103c8t6 type microcontroller. The linear zone of the sensor is 8 mm, the maximum operating frequency is 4.5 kHz.