A variable focus imaging lens assembly for an imaging system of an imaging-based bar code reader for imaging and decoding a target bar code. The OELD includes an anode, a cathode, an emissive layer, a hole source and an electron source. The ion gun is also cheaper to manufacture since it does not require a separate power supply. The enclosure is configured with multiple bores, each bore being sized and located to receive a respective coolant-carrying tube of the tubes extending from the cold plates. The device may also be used to treat hypertension, and to function as a blood pressure regulator.