Research On Contact Lenses Projection Measurement Technology

With the improvement of civil living conditions, the requirement on contact lenses is fast increasing, people wearing contact lenses put with the safety and comfort of a higher demand. Contact lenses have been classified as medical equipment in many countries, which requires researching on measurement methods and techniques of contact lenses'important parameter, and a strict quality testing for contact lens production, processing and marketing process.With the deep understanding the principles and methods of present contact lenses measurement instruments, an instrument of using optical projection and Charge Coupled Device (CCD) sensor to measure the curvature and optical center thickness of contact lens is designed. When the instrument is under operation, the contact lens is projected to the projection screen and the linear CCD. Video signal of the contact lens outputs from the CCD. During the signal gain and processing stage, electrical control system considers AT89C52 SCM as the central part. The output video signal of CCD is binary in order to make the measuring edge firstly. Then the signal is sent to the single chip. After Counting and calculating, the curvature and optical center thickness of contact lens are worked out and sent to a LED screen. In accordance with the contact lens sample request for constant temperature, a constant-temperature control device is embedded in the instrument structure. In order to eliminate systematic errors, a benchmark case is used to ensure the measurement accuracy. The software system splits into modules including the main program, the temperature control program, the measuring program, the parameter calculation program, LED display program, and standard storing program. Each is relative to necessary functions.Experiment shows that the instrument's precision is superior to±0.1 mm in lenses curvature and±0.01mm in optical center thickness, meet national standards.There are six chapters in this thesis. The first chapter concluded the background of this technology, and gave the summary of this paper and put forwards the design. The second chapter showed the measuring principle, the whole system design and the major mechanical structure design. The third chapter detailed description of the hardware design scheme and gave a lot of system circuit. The fourth chapter was about system software design. The fifth chapter analyzed the instrument error and the methods for the elimination of errors. The sixth chapter was the sum-up of the whole-length in which the next work is showed.