In this study, we developed a femtosecond pulse laser-based micro LED transfer process and optical system technology that precisely transfers micro LED chips with a size of several tens of micrometers. In order to realize the high-speed and precision transfer process of the micro LED chip, the femtosecond pulse laser was applied as a light source for the transfer process. In addition, dynamic release layer was applied to transfer micro LED chips at high speed without direct damages by laser. we analyzed the tendency of chip transfer process by adjusting the parameters for laser irradiation properties and material properties.
We have developed an absolute distance measurement system for the three-dimensional (3D) coordinate measurement. The final project goal is to develop a multilateration based coordinate measuring system for precise 3D positioning. This coordinate measuring system consists of an absolute distance measuring system and four laser tracking stations. Accurate positioning become possible by determining coordinates using only four distance values instead of angular measurements that cause major errors in the coordinate measurement. In each station, distance is measured by the absolute distance measurement system. There are several advantages to using absolute distance measurement instead of an incremental-type laser interferometer for 3D positioning. If the beam is accidentally broken, incremental-type devices must measure again from the beginning. However, in the absolute distance measurement, the distance of an object can be measured continuously without such a problem. The other is to improve coordinate measurement precision by reducing the number of variables in the multilateration algorithm. In order to measure high precision 3D position in a large area, we have developed a femtosecond laser based absolute distance measurement system. Two-femtosecond lasers and optical cross-correlation technique are applied to improve precision in the distance measurement. This method enables several micrometer-level distance measurement at distances of a few tens of meters.
In this study, we develop a 3D coordinate measurement system based on a multilateration technique and an absolute distance metrology for a mobile machine platform. Since the multilateration only uses distance values without angle measurements, it is possible to make 3D coordinate measurements with high accuracy in a large area. In addition, absolute distance is suitable for industrial application because of enabling real-time continuous measurement after the obstruction. The system is composed of four laser tracking stations and a four channel absolute distance meter which is a fs pulse laser based high accuracy absolute distance measurement. In order to measure 3D coordinate of targets, each tracker measures a distance value with real time tracking, and multilateration algorithm is applied to derive 3D coordinate values using the measured distance values. This paper introduces the multiple absolute distances based 3D coordinate measurement system and discusses in detail.
Fiber ultrafast pulses such as mode-locked and noise-like pulses have useful optical characteristics for high precision metrology applications. In this study, we develop an ytterbium doped fiber laser with all normal dispersion which can selectively generate two pulse modes, mode-locked and noise-like pulses, by a turn-key system including polarization control and selective detection parts. The spectral and temporal characteristics of two pulses generated from the single oscillator are analyzed and compared with each other through optical spectrum, RF spectrum and autocorrelation. Furthermore, spectral coherence characteristics are verified through interference signals generated by balanced and unbalanced arm interferometers.
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