High precision alignment between the fiber core in the focal plane and the image of the target star is of great significance for the observation of multi-target telescopes. In this work, we propose and demonstrate a Special-shaped Micro-lens Aimer for Real-time Targeting, namely SMART, combining a special-shaped microlens and a fiber bundle to realize online alignment and improve the coupling efficiency of fibers. The platform in the center of the microlens transmits the starlight to the science fiber of the fiber bundle without changes in focal ratio. Six side micro-lenses couple leakage light to six feedback fibers and return misalignment signals. The structural parameters of SMART are well designed. Fresnel diffraction theory is applied to build a model for simulating the performance of SMART. In the SMART measurement, a pinhole with a diameter of 200 μm is used to imitate the effect of atmospheric turbulence during astronomical observations. Experimental results indicate that when the image spot is offset relative to the science fiber, the misaligned direction and displacement distance are identified by the signal of feedback fibers in SMART with a resolution of 0.02 mm and a detection range of 0.08 mm to 0.26 mm.
The small-field radiotherapy is a developing technique because it can reduce the damage to normal tissues. However measurement of the dose distributions of small radiation fields in radiotherapy is a challenge. In this work, we designed and produced an optic fiber X-ray sensor array with high spatial resolution. The sensing array includes 7 sensing probes connecting to an 8-channel optical switch and a photon counting detector (PCD). To verify the practicality of the system, these sensors were measured under a 10×10 cm2 field of a medical linear accelerator. For the small-field application, the dose distribution of radiotherapy fields 1×1 cm2 and 0.8×0.8 cm2 were measured. The distribution of these small radiotherapy fields were given based on the experimental results.
A fiber IFU with 8064 fibers is designed and manufactured for the Fiber Arrayed Solar Optical Telescope. 8064 fibers are divided to two 2D arrays for different polarization states and 12 pseudo fiber slits for 12 spectrometers. There are many relative techniques have been developed during this process. The hexagon microlens array fits the 100% filling factor. The quartz micropores plate guarantee the positioning accuracy among different temperatures. The 18m fiber cables with special designs transfer the signal with low focal ratio degradation. The quartz V-grooves are used to control the positions of the fibers to form those pseudo slits. Besides, a six-dimensional alignment system and a fast alignment and detection system are built to align the microlens array with micropores and measure the focal ratio, transmission efficiency and alignment accuracy of the IFU, respectively.
It is well-known that the surface roughness of materials plays an important role in the operation and performance of technological systems. The roughness influences key parameters, such as friction and wear, and is directly connected to the functionality and durability of the respective system. Tactile methods are widely used for the measurement of surface roughness, but a destructive measurement procedure and the lack of feasibility of online monitoring are crucial drawbacks. In the last decades, several non-contact, usually optical systems for surface roughness measurements have been developed, e.g., white light interferometry, light scatter analysis, or speckle correlation. These techniques are in turn often unable to assign the roughness to a certain surface area or involve inappropriate adjustment procedures. One promising and straightforward optical measurement method is the surface roughness measurement by analyzing the fringe visibility of an interferometric fringe pattern. In our work, we employed a spatial light modulator in the interferometric setup to vary the fringe visibility and provide a stable and reliable measurement system. In previous research, either the averaged fringe visibility or the fringe visibility along a defined observation profile were analyzed. In this article, the analysis of the fringe visibility is extended to generate a complete roughness map of the measurement target. Thus, surface defects or areas of different roughness can be easily located.
The inspection of technical surfaces is often performed by two-wavelength electronic speckle-pattern interferometry (ESPI) combined with a phase-shifting procedure. As in conventional specular interferometry, the characteristic fringe spacing in the generated interferogram is defined by the applied wavelengths and the sensitivity is therefore constant in one fringe pattern. Subsequently, this technique is limited to surface structures with similar phase gradients and low structural density. To measure more complex structures, a high-resolution generated reference wavefront (HRGW) is adapted to the measurement object for local sensitivity adaption. The feasibility of this principle is directly linked to the functionality of the used spatial light modulator (SLM). A key factor of a proper phase-control is the structural setup of the SLM. In this article, the general influence of the microstructure of SLMs in adaptive ESPI is evaluated.
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