Single Grating Reflective Digital Holography With Double Field of View

Abstract

Since 1960s, digital holography (DH) has been developed significantly as an exquisite optical sensing technique with its computational interpretation. Recent advances in the image sensor and the coherent light source have suggested the possibility of using DH in portable form that can be utilized in industrial fields. Field of view (FOV) should be sufficiently wide and the system be simple for successful landing of DH on the industrial market. To embody the possibility, in this paper, we present a method for implementing off-axis reflective DH using a single diffraction grating. Beam splitter and mirror in the conventional off-axis DH are replaced with a single diffraction grating. This replacement enables the implementation of simple interferometer while maintaining the performance of the holography. In addition, we apply the multiplexed illumination method to enhance space-bandwidth product of off-axis hologram. Using the wavelength dependence of the diffraction grating, the FOV can be doubled without additional optical element. We demonstrate the proposed method by three holographic imaging experiments with two laser diodes. The prototype provides lateral resolution of 19.69 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m with the FOV of 6.85 mm × 8.72 mm. The FOV is 1.9 times wider than the image sensor area of 6.85 mm × 4.59 mm. Overall size of the prototype is 12 cm × 17 cm × 5 cm, showing the suitability of implementation to the various industrial fields.