| 主权项 |
1. A vein locating device, for locating a vein on a patient, the vein locating device comprising:
a housing; an objective lens; a condenser lens disposed within the housing, the condenser lens being aligned with the objective lens along a common axis; an infrared light source for emitting infrared light from the vein locating device onto an area of skin of the patient; and a sensor circuit including a first photosensor, a second photosensor, a comparator, and a marking light; wherein the first photosensor is positioned to sense infrared light backscattered from a central portion of the area of skin and the second photosensor is positioned to sense infrared light backscattered from a peripheral portion of the area of skin, the first photosensor generating a signal that is proportional to an intensity of infrared light sensed and the second photosensor generating a signal that is proportional to an intensity of infrared light sensed, the comparator generating a signal when the signal generated by the first photosensor differs from the signal generated by the second photosensor, and the signal generated by the comparator causing the marking light to mark the central portion of the area of skin with visible light to indicate a location of a vein. |
