A portable vein projector, including an LED light source, a CMOS image sensor, a semi-transparent and semi-reflecting mirror, a micro-projector, and an image processing unit. The LED light source operates to project near-infrared light on the skin surface area. The near-infrared light is reflected by the skin surface, and part of reflected light penetrates through the semi-transparent and semi-reflecting mirror, enters into the CMOS image sensor to form an image in the CMOS image sensor. The image is transmitted from the CMOS image sensor to the image processing unit where the image is processed, and the image is transmitted to the micro-projector. The micro-projector outputs visible light. The visible light is reflected by the semi-transparent and semi-reflecting mirror and is imaged on the skin surface area to yield a vein image.
