Levels are fundamental metrological tools for machine leveling and angle measurements. Current levels are all based on the pendulum principle and bubble vial principle. The former is precise but complicated, while the latter is not precise enough. This paper presents a novel, simple and precise optoelectronic level. It is based on the principle of light refraction in the transparent and viscous fluid. The fluid surface is always in leveling condition regardless whether the ground is level or not. Measuring the refraction angle with precise dual-axis autocollimator can directly reflect the inclined angle of the level. A leakage prevention design is also proposed to allow the level to be placed in any pose. Calibrated by an angular interferometer, the error of the dual-axis optoelectronic level is better than ±0.7 arcsec in the measuring range of ±100 arcsec, and better than ±0.4 arcsec for the range of ±30 arcsec, for both axes. Without the need of a pendulum mechanism, this is a simpler design for precision level.
DVD player is regarded as a mature and low-cost commercial product for multimedia and computer data storage. Fundamentally the pickup head is a key part of the DVD player and it uses focused laser beam to read the data on the DVD disk tracks whose width is approximately 0.74μm. This research focused on the control aspect applied to a DVD pickup head for the development of an auto-focusing laser probe. Practically, the laser pickup head has the S-curve linearity property with the measuring range of about 7μm [3]. To extend the measurement range, the feedback control of VCM in the focusing direction is needed. This study used Genetic Algorithms (GAs) to search for appropriate PID gains for VCM control. In MATLAB simulation, the GAs tuning scheme could produce the optimised gains within less than 0.02 sec. Moreover, the experimental results demonstrated that the VCM auto-focusing measurement range could be extended to 1350μm.
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