Beyond the partial light intensity imager: eliminating Moiré patterns
A partial light intensity imager (PLII) was proposed in our previous research for enhancing the dynamic range to 2.2x105 lx in strong light. Moiré patterns may occur, however, since the PLII employs both a liquid crystal display (LCD) and a charge-coupled device (CCD) camera as its key devices, which can be regarded as two gratings. This research calculates the fringe widths and spectra for both the LCD and the CCD, and analyzes the relationship between the fringe width and the applied voltage on each pixel of the LCD. According to the theoretical results, we find that changing the rotational angle of the liquid crystal (LC) molecule by regulating the applied voltage is an effective method to eliminate the Moiré patterns in the PLII. Based on this principle, an experiment has been designed, and the Moiré patterns fringe width is alleviated from 20 pixels to10 pixels distance before and after, and the results verify the correctness of the theoretical analysis.