Terahertz frequency metrology and sensitivity issues in photomixer spectrometer

A developer roller contact device that provides a more reliable and longer lasting electrical connection between a bias voltage source and a developer roller of a toner cartridge assembly used in printers, copiers and facsimile machines. In the first embodiment, an improved contact device has been developed that has a conductive cylindrical member with a rim on one end. The cylindrical member is sized to fit snugly within the developer roller to contact the inner wall of the roller. The rim abuts against the end of the developer roller to hold the contact device in position. A contact surface provided inside the cylindrical member presses against the electrical contact mounted on the cartridge assembly. A second embodiment of the contact device is for a different type of cartridge assembly. The cylindrical member is divided into a large diameter portion for snugly fitting within the developer roller and a small diameter portion for fitting within an alignment piece on the cartridge assembly. A coil spring is held under tight pressure or compression between the end of the small diameter portion and the electrical contact mounted on the cartridge assembly. The coil spring completes the electrical connection between the contact device and the bias voltage source.