Data-stitching algorithm based on elasticity.

Data-stitching algorithms are widely used to combine multiple sequential data or extend the working area of measurement systems. However, stitched data by the least squares method have inconsistency at the intersections due to their measurement errors, mainly drift error. We propose a new stitching algorithm, to the best of our knowledge, that considers sequential data as an elastic body. We examine the algorithm with several types of sequential data and confirm mitigating of error of drift.

Point-diffraction interferometer wavefront sensor with birefringent crystal.

A key technique in direct imaging of extrasolar planets with ground-based telescopes is extreme adaptive optics. It requires a wavefront sensor capable of achieving high accuracy with a small number of photons. Imada et al. [Appl. Opt.54, 7870 (2015)APOPAI0003-693510.1364/AO.54.007870] proposed a type of wavefront sensor that employs a point-diffraction interferometer (PDI). This type of sensor has problems concerning a low photon-usage efficiency and manufacturing feasibility. In addition, they did not give sufficient study on the optimum pinhole size. Here, we propose a novel PDI, with which these problems are overcome, and study the optimum pinhole size for it. The sensor is incorporated with birefringent crystal as the key component to achieve high efficiency and is feasible to manufacture realistically. We run numerical simulations to optimize the pinhole size, where the photon noise is evaluated.

Interferometric testing for off-axis aspherical mirrors with computer-generated holograms.

The interferometers with computer generated holograms (CGHs) have been used to measure off-axis aspherical mirrors. However, the conventional CGH interferometer could not produce a high lateral resolution because of the blur and the distortion of the interferogram of the test mirror caused by the nonzero order diffraction of the CGH. We further develop the application of CGHs concerning interferometers in order to improve the lateral resolution of the interferogram. In particular, we change the application of the CGH in such a way that the returned test beam passes through the CGH with zeroth order diffraction and demonstrates the performance of the CGH interferometer when used for the measurement of the primary mirror of the Okayama Astrophysical Observatory 3.8 m telescope project. As a result, our CGH interferometer produces a good interferogram with high resolution of 2.8 mm for the off-axis aspherical mirror with a size of 1.2 m. With improved usage of the CGH, we successfully demonstrated a high lateral resolution interferometer.