Vein display instrument, also known as a vein viewer or vein finder, is a medical device that uses near-infrared light to locate blood vessels beneath the skin. It works by projecting a real-time image of the patient's veins onto the skin's surface, allowing healthcare professionals to easily identify and access veins for procedures like intravenous injections, blood sampling, and other vascular access. The device utilizes the different light absorption and scattering properties of venous hemoglobin and surrounding tissues to create a clear visual map of the veins, improving success rates, reducing patient discomfort, and increasing efficiency for medical staff.