Compact, low-cost Blu-Ray pickup-based digital holographic microscope

The concept of point-of-care testing is an active area of research. The trend nowadays is to develop cost-effective yet efficient units that can be used at home by nonprofessionals. Digital holography is an optical technique of great interest as it provides quantitative phase images from a single recorded image. However, the available setups either employ the inline lensless configuration (which involve an iterative phase recovery process) or the complex, bulky and expensive classical Mach-Zehnder configuration. Self-referencing digital holographic systems are ideal as only few components are needed. Blu-Ray pickup heads contain a high quality objective lens and a laser diode which have been used in the past in optical microscopy. However, it has been rarely uses in digital holography. In this paper, we present a low-cost selfreferencing digital holography microscope in a transmission configuration using a BluRay pickup coupled with a Raspberry-Pi computer, making the whole setup very compact. A low-cost 2D motorized translation stage is developed using the mechanical components found in the Blu-Ray drive. A Graphical User Interface (GUI) written in Python allows the user to control the hardware components and to reconstruct the holograms from which continuous phase images are extracted. The interferometer is successfully tested on microspheres and red blood cells after estimating the magnification of the microscope using a USAF target.