The laboratory measurement and evaluation of the performance of an apo-achromatic collimator is presented in this work. This customized collimator was optimized to utilize a high-resolution spectrograph located at the Thai National Telescope (TNT). The Center for Optics and Photonics (COP) under the National Astronomical Research Institute of Thailand (NARIT) aims to evaluate and control the performance of the achromatic triplet collimator with a Fizeau interferometer to ensure that the correspondence with optical and optomechanical tolerances. The parameters controlled include the Root- Mean-Square (RMS) and Peak-To-Valley (PTV) wavefront errors and the Modulation Transfer Function (MTF). The achromatic triplet consists of three lenses optimized for spectroscopy in the visible range at 0.1 numerical aperture (NA). Its effective focal length is 150 mm, and the lens clear aperture is 0.15 NA at 50 mm. These three customized lenses were assembled into a build-in-house opto-mechanical aluminum housing. The collimator is measured by the infinite conjugate lens test to describe wavefront errors and the MTF. The result suggests the performance of the assembled achromatic triplet collimator conforms with Zemax optical design below 0.1 NA. The RMS and PTV wavefront errors and MTF measured with the interferometer appear comparable to the Zemax optical design of the collimator within this range. Therefore, we conclude that our in-house manufacturing, assembly, and control are acceptable for astronomy applications.
The EXOplanet high resolution SPECtrograph (EXOhSPEC) instrument is an echelle spectrograph dedicated to the detection of exoplanets by using the radial velocity method using 2m class telescopes. This spectrograph is specified to provide spectra with a spectral resolution R < 70, 000 over the spectral range from 400 to 700 nm and to reach a shortterm radial velocity precision of 3 m/s. To achieve this the separation between two adjacent spectral orders is specified to be greater than 30 pixels and to enable a wide range of targets the throughput of the instrument is specified to be higher than 4%. We present the results of the optimization of the spectrograph collimator performed and initial tests of its optical performance. First, we consider the spectrograph design and we estimate its theoretical performance. We show that the theoretical image quality is close to the diffraction limit. Second, we describe the method used to perform the tolerancing analyzes using ZEMAX software to estimate the optical performance of the instrument after manufacturing, assembly and alignment. We present the results of the performance budget and we show that the estimated image quality performance of EXOhSPEC are in line with the specifications. Third, we present the results of the stray light analysis and we show that the minimum ratio between the scientific signal and the stray light halo signal is higher than 1,000. Finally, we provide a status on the progress of the EXOhSPEC project and we show the first results obtained with a preliminary version of the prototype.
In this research, the mapping of the path length difference that involves the specimen is proposed for improving qualitative phase imaging (QPI) techniques. Phase-quality images are developed using the principle of phase- shift in digital holography and then this system has been applied to investigate biological cells and tissues. In our setup a microscopic digital holographic interferometer with polarizers and a quarter wave plate has been designed for detecting cells specimen. The resulting image contains information of the thickness in any area and the refractive index of the specimen. Moreover, a quadrature – phase shifting holography (QPSH) technique is purposed. Experimental results are shown improving QPI. Merits and limitations of this method are also described.
Applying of a phase-shifting digital holography combined with compressive sensing to inspect the soldering quality of
surface mount technology (SMT) which is a method for producing electronic circuits. In SMT, the components are
mounted and connected with each other directly onto the surface of printed circuit boards (PCBs). By reconstructing the
multidimensional images from a few samples of SMT, the results are solved by an optimization problem. In this paper,
two problems have been concerned. The first one is to examine the devices and the soldering quality of connections
between them, which are in micro-scaled. The second is to observe the effect of heat treatment of soldering material and
devices on the surface mount board.
In this paper we propose a modern technique to evaluate the shape changes of solder paste by using double-view in-line digital holography. We observed the transformation of three different kinds of solder paste composition: pure solder paste, solder paste mixed with 0.02%, 0.05%, 0.10% graphene (GPN) and 0.02%, 0.05%, 0.10% graphene oxide (GPNO), respectively. The shape of the solder pastes was investigated at different melt temperatures (i.e. 200°C, 250°C, and 300°C) for 30 seconds using a collimated beam propagating through the solder paste, then being double reflected on a mirror and second incident on another sides of the solder paste. The double images bearing beams were recorded with a CCD sensor simultaneously. The single recorded digital hologram from double view technique was reconstructed using digital holography. The results show that the double-view technique provides reliably data. Moreover, it would be developed for observing more than two images by single holography writing in the future.
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