SINGLE PASS CLEAVING OF ULTRAFAST LASER MODIFIED C-SHAPED GLASS EDGES

We report on single-pass laser cleaving of transparent materials with C-shaped edges that exhibit 45-deg tangential angles to the surface. A holographic 3D beam splitter distributes several foci along the desired edge contours, including C-shaped edges. Single-pass, full thickness laser modifications are achieved requiring single-side access to the workpiece only without inclining the optical head. After having induced laser modifications with feed rates in the order of 100 mm/s actual separation is performed using a selective etching strategy.

4D Measurements and Analysis of Heat Release Rate in a Model Gas Turbine Combustor

Time-resolved volumetric measurements (4D measurements) were performed to study the heat release rate characteristics in a model gas turbine combustor at 10 kHz. For this purpose, a high-speed camera combined with an image intensifier and a set of customized fiber probes were employed to continuously capture the CH* chemiluminescence signals from nine different viewing angles. Based on the measurements, the computed tomography program was performed to reconstruct the shot-to-shot 3D distributions of the CH* signals. Specific focuses have been made to demonstrate the capabilities of the current tomographic technique in applications of a realistic combustor, in which the full optical access was usually not available for every viewing angle. The results showed that the 3D reconstruction can successfully retrieval the flame edge contours rather than the signal intensity. The flame surface area was then calculated based on the reconstructed flame edge contours and used to infer the heat release rate. The fluctuation of global/local flame surface area indicated that there existed distinct difference between the global instability and local instabilities at various locations in the non-symmetric combustor. The global instability appears to be an integration of those local instabilities.

A micro optical probe for edge contour evaluation of diamond cutting tools

This paper presents a micro optical probe, which is employed to evaluate edge contours of single point diamond tools with a size in a range of several millimetres. The micro optical probe consists of a laser source with a wavelength of 405 nm, an objective lens with a numerical aperture of 0.25, a photodiode for measurement, and a compensating optical system including another photodiode for compensation of laser intensity. A collimated laser beam, which is divided by a beam splitter in the compensating optical system, is focused by the objective lens so that the focused spot can be used as the micro optical probe. The micro optical probe traces over an edge contour of an objective tool while the signals of both the two photodiodes are monitored. The output of the photodiode for measurement is compensated by using that of the photodiode for laser intensity compensation to eliminate the influence of the laser instability. The signal of the photodiode for measurement is used to define the deviation of edge contour within the diameter of the micro optical probe. To verify the feasibility of the developed optical probe, the optical system was mounted on a diamond turning machine, and some experiments were carried out. Two types of edge contours of the diamond tools having a straight cutting edge and a round cutting edge were measured on the machine.