Design Laser Vibrometer for Respiratory Frequency Detection

Abstract

The process of measuring breathing patterns is considered very important in medical diagnosis allowing the detection of many diseases. In literature, many methods used to monitor the respiratory process have been studied. Some of these methods need the usage of certain tools to be in contact while others do not require any contact with patient body. The later are divided into optical and non-optical methods.

In this work, Helium Neon (He -Ne) laser with a wavelength of 632.8nm was chosen as an optical tool for measuring the frequencies of moving object. We popose a model that simulates the movement of chest wall during the resporatory process. The proposed model is composed of a striped paper placed on a platform that is connected to the Arduino circuit. The displacement and frequency of the vibrating body could be changed by programming the Arduino circuit so that the vibrant body movement simulates all breathing movements corresponding to young and old people in all proper cases in addition to some pathological ones. The principle of measuring is as follows: the laser is illuminating the striped paper and the reflected radiation is picked up by reflection Probe that is connected to an Optical Spectrum Analyzer which in its turn is connected to the computer and the results are presented via Spectra Suit. The studied signal represents the change of the intensity of the reflected laser versus time. Because the captured signal contains information about the vibrant body movement frequency, the reflected signal is taken and analyzed with Matlab to obtain its spectral (frequency) components. A good agreement is obtained between applied and measured frequencies of the vibrating striped paper.