We propose a scheme based on the photorefractive effect to manipulate polychromatic spectra. A sinusoidal phase grating can be obtained by exposing photorefractive material to light, and it is used to diffract monochromatic or polychromatic light. The resultant diffracted spatial intensity distribution for monochromatic light is mapped to spectrum distribution for polychromatic light via the spatial–spectral correspondence relationship for mono-polychromatic light diffraction. Theoretical analyses and numerical examples show that for different detection angles, the diffracted spectrum exhibits different features, and that specific spectral line selection or line filter effects can be achieved. We also discuss the possibility of applying this spectral scheme to detect temperature or the grating’s period changes.
This paper proposes a capsule endoscope (CE), based on color multiplexing, to simultaneously record front and side images. Only one lens associated with an X-cube prism is employed to catch the front and side view profiles in the CE. Three color filters and polarizers are placed on three sides of an X-cube prism. When objects locate at one of the X-cube's three sides, front and side view profiles of different colors will be caught through the proposed lens and recorded at the color image sensor. The proposed color multiplexing CE (CMCE) is designed with a field of view of up to 210 deg and a 180 lp/mm resolution under f-number 2.8 and overall length 13.323 mm. A ray-tracing simulation in the CMCE with the color multiplexing mechanism verifies that the CMCE not only records the front and side view profiles at the same time, but also has great image quality at a small size.
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