From Event: SPIE Commercial + Scientific Sensing and Imaging, 2017
A flat-field aberration corrected concave blaze grating for 400-1100nm is designed and fabricated. The concave grating, which has a free-form profile with blaze grating pitch and variable line spacing, is fabricated using five-axis CNC machine with nanometer machining precision. An optical system is setup to measure the focused spot size, spectral resolution and diffraction efficiency to evaluate the performance of aberration-corrected concave grating. The blaze grating reaches a diffraction efficiency of 70%. The focused vertical spot size is 50µm, which indicates a 50µm spatial resolution at the image plane. The focused horizontal spot size is 300µm, which converts to a spectral resolution of 6nm. The design methodology can be applied to an Offner type hyperspectral imager with a free-form convex grating and variable line spacing to achieve high efficiency and high spatial and high spectral resolving power.
Cheng-Hao Ko, Bang-Ji Wang, Jih-Run Tsai, Yueh-Hsun Wu, Sheng-Yu Tsai, Shin-Fa Lin, and Chiu-Der Hsiao, "Design and verification of an aberration-corrected free-form concave blaze grating with variable line spacing for hyperspectral imaging (Conference Presentation)," Proc. SPIE 10213, Hyperspectral Imaging Sensors: Innovative Applications and Sensor Standards 2017, 1021307 (Presented at SPIE Commercial + Scientific Sensing and Imaging: April 12, 2017; Published: 9 June 2017); https://doi.org/10.1117/12.2261647.5460497461001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon