In this Letter, we present a highly compact and low-cost holographic microscope which is especially suitable for observing transparent samples with certain specific supports such as microchannels. This microscope employs only an inexpensive laser diode, a dual precision round aperture, and a digital light sensor. The total cost of the system except for the digital sensor is less than 400 US dollars, and a hand-held system can be made based on our setup. Besides the simple, cheap, and compact setup, this system can capture the off-axis interference pattern of two spherical waves and reconstruct the quantitative phase profile along with the amplitude image of the observed sample with the twin image eliminated in real time. Experimental results show that the resolution of our system is better than 2 μm, and the 3D structure of blood cells can be retrieved.
