| dc.description.abstract | Abstract
To design some low cost, practical electro-optical systems with CMOS image sensor, light sources and centroid method is the goal of this dissertation. The centroid method has been applied to many large field applications, including target or star tracking, industrial applications, infrared image tracking, et al. However, Laser triangulation and target tracking are normally used in conjunction with position sensing detectors (PSDs) or with charge coupled devices (CCDs), where the centroid position is found through intensity profile fitting to a similar Gaussian shaped light spot. In this dissertation, a CMOS image sensor is adopted to function as a one-dimensional array position sensing detector (in active range finder and pulse measurement system) or two-dimensional array position detector (in passive range finder and tilt sensor).
First, the presented range finders with a CMOS image sensor and different light sources are based on simple triangulation method. By adjusting the exposure time (ET) of the CMOS image sensor, the image processing and triangulation range finder can be integrated in one system. Hence the fields of applications are very versatile, ranging from industrial automation to traffic, aiming system and blind guidance as well.
Second, a low cost prototype of a laser range finder using a CMOS image sensor is developed for the automotive field. The system presented here is also based on triangulation. The gravity of the infrared laser spot on CMOS image sensor is converted into pixel coordinates proportional to the distance to be measured. The system is operated in two modes: continuous wave (CW) and pulsed mode. The comparison of these two modes also has been conducted and presented. From the experimental results, it was found that the distance could be estimated with accuracy better than 1.1% within the range of 5 to 45 meters.
Third, a low cost, compact electro-optical (EO) leveler using a CMOS image sensor is developed for the purpose of tilt angle measurement. The two lenses optical system is designed to find the tilt information of the total system. ZEMAX was used to design and predict the performance of this optical system. One lens was designed to be bowl shaped and can hold a liquid. The gravity of the light spot on the CMOS image sensor is converted into pixel coordinates proportional to the tilt angle to be measured. The experimental results verified the simulation results. The reading tilt angle can be estimated with a resolution at better than 4.2 sec of arc.
Final, a non-invasive, non-contact measurement of pulse waveforms by applying optical triangulation technology on skin surface vibration is developed. The arterial pulsation information can be obtained with this measurement system. An algorithm to evaluate the pulsing activities from center of laser spot intensity on a certain wrist point has been conducted by Fast Fourier Transform (FFT). The amplitude and frequency of vibration of skin can be known by this measurement system. | en_US |