Papers by Keyword: Optical Testing

Abstract: An optical engine system have been designed which can realize the goal of spark ignition and homogeneous charge compression ignition. This system consists of an optical engine and an electric control system. We have measured temperature in cylinder and molar coefficient of the main material (CO2, O2, N2, H2O, fuel) which has a resolution of nanosecond level and millimeter level. To realize the visualization in cylinder, extended pistons, extended cylinder liner and extended cylinder body have been designed and all of them have optical window. To realize the path of laser, a ring gasket of the laser window has been added between the original cylinder head and the extended cylinder body. An optical engine electronic control system based on SCM 80C196 has been designed to make the optical engine work in different testing strategies. The experimental results show the optical engine work well under the control of electric control system and we can detect optical Raman spectroscopy in the optical engine.

Abstract: Recently most of modern absolute measurement rotation the flats or spheres in the interferometer. We review traditional absolute testing of flats methods and emphasize the method of reconstruction of rotational shear. The rotation of the lens can lead to some errors such as angle rotation error, center excursion error and other coordinate system motion error. 36 Zernike polynomials are used to generate 3 flats and Matlab are used to simulate the arithmetic. There have some phase problems on FFT arithmetic in Matlab which can cause some errors. Results are shown about how these errors influence the accuracy. The analysis results can also be used in other interferometer systems which have the motion of the coordinate system.

Abstract: The deformations of the 600mm aperture interferometer mirrors induced by gravity and supporting forces must be controlled strictly to ensure the accuracy of the large aperture interferometer to achieve 63nm. The mirror deformations induced by two types of forces and four axial distribution positions are analyzed respectively by finite element method. And the deformed interference wavefront are simulated by synthesizing deformations of reference flat and test flat mirrors. The maximum deformed interference wavefront formed by the cosine wave force at the middle of the mirrors and the minimum formed by the square wave force at the periphery of the mirrors. The peak to valley value varies 30nm and root mean square value varies 2.8nm between them. The measurement accuracy of large aperture interferometers can be improved by adjusting the force distributions and supporting positions of the mirrors according to the analysis.

Abstract: Recent developments in next generation disc technology, cameras in mobile phones, zoom-lenses for small digital cameras and camcorders, digital SLRs, and television cameras have amplified the demand for affordable optical systems with outstanding image quality, a combination that can only be achieved using aspheric surfaces. The metrology of aspheric surfaces is a classical problem, but solutions so far have not fulfilled all demands for system cost, TACT (Total Average Cycle Time), minimized tooling, measurement uncertainty, spatial resolution, robustness in a production environment and many more. Zygo Corp. presents here a new method [1,2] for measurement of rotationally symmetrical aspheric surfaces using a new commercial system, which has the potential to fulfill these industry requirements. During measurement, the surface is scanned along its symmetry axis in a Fizeau cavity with a spherical reference surface. The coordinates x,y,z at the (moving) zone of normal incidence are derived from simultaneous phase-measurements at the apex and zone. Phase-shifting Fizeau interferometry and displacement interferometry are combined in the new commercial system to realize this new method. Aspheric departure from a best-fitsphere approaching 800 microns can be measured, and absolute measurement is possible with an absolutely calibrated transmission sphere. A custom parabolic artifact is measured with conventional null Fizeau interferometry and by the new commercial system. Data is reported for each technique along with a difference map achieved by fiducialized data subtract where 32.0 nm peak-to-valley (PV) and 3.6 nm R.M.S. are achieved.

Abstract: Freeform optics fabrication has become one of the hottest topics in optics industry in recent years. Although it still remains a challenge, many have tried different ways of manufacturing it. Some have achieved degrees of success. By means of a Nanotech 350-FG five axis diamond turning machine, we too have successfully produced some prototype freeform optics and lens arrays with Slow Tool Servo and Milling method. The produced freeform optics are mainly for automobile LED headlamps and the lens arrays are for LED illumination. In order to produce the freeform optics, we developed our own DT Slow Tool Servo program which is capable of generating a DT program for diamond turning a universal/general 3D freeform surface. Slow Tool Servo technique and Diamond Milling technique were mainly employed to produce these freeform surfaces. The manufacturing process and machining parameter details will be given in the paper. The two main methods we used will be compared and discussed as well. In measuring the freeform surface, a 3D white light interferometer was used to scan and obtain the surface coordinates. The software made by ourselves enabled us to compare the measure results of the work piece with that of the design drawings. The deviation of our finished forms is within 5 um from that of the nominal. The surface quality Rq is about 10 nm. Measuring equipment and methodology will also be discussed in the paper.