An auto-focusing reflection-type lens-less digital holographic microscope

Abstract

This paper introduces an auto-focusing reflection-type lens-less digital holography microscopic system, which has the characteristics of wide field of view, high precision and miniaturization. It can quickly and accurately carry out three-dimensional (3D) reconstruction and quantitative measurement of small devices with reflective surfaces. The system uses 632.8nm laser illumination. After coherent imaging, the hologram is collected by a board-level camera, and digital holography technology is used for phase recovery and 3D reconstruction. At the same time, the compact design of the system and the use of the board-level camera have reduced the overall size to only: 68mmx43mmx38mm. Its auto-focusing function has better focus accuracy and recovery quality than traditional manual adjustment. In addition, we experimented with a miniaturized chip which is micrometers in size, reconstructed its 3D shape, and gave the effect of auto-focusing experiment.