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Digital holography
Published in Tomoyoshi Shimobaba, Tomoyoshi Ito, Computer Holography, 2019
Tomoyoshi Shimobaba, Tomoyoshi Ito
Figure 4.10 shows an example of off-axis digital holography. In an inline hologram, object light, direct light, and reference light completely overlap, and the image quality significantly deteriorates. In order to avoid the superimposition of these unnecessary lights, it is possible to use the off-axis optical system. By tilting the mirror on the reference light arm, the reference light can be obliquely incident and an off-axis hologram can be recorded by an image sensor.
Design of a compact off-axis two-mirror freeform infrared imager with a wide field of view
Published in Journal of Modern Optics, 2019
Jingfei Ye, Jun Yu, Zhenzhen Song, Shixin Pei, Qun Yuan, Zhishan Gao, Yu He
For the pupil diameter () of an infrared imager, a larger pupil will increase the incident light flux. However, if the pupil diameter is too large, the size of the first viewing mirror will be larger across the full field of view. Moreover, the conflicts of edges between the viewing mirror and focusing mirror could be encountered. In this design, the pupil diameter is set as 12 mm in order to achieve a large field of view and maintain a relatively small physical size for the off-axis reflective freeform infrared imager. The optical specifications of our freeform infrared imager are listed in Table 1. It should be noted that, for an extremely compact and off-axis optical system, the correspondence of image height and field of view based on Gaussian optics can be released. There is little difference from a coaxial optical system. In fact, we make a compromise between the field of view, sensor size, and focal length in practical optical engineering. In our design, we deliberately do not limit the image size for the compact off-axis freeform infrared imager. We concentrate on how to obtain a high-performance and compact infrared imager with a large pupil diameter and a fast focal ratio over a wide field of view.