An automatic adjustment system for the optical head of a magnetooptical disk drive

The authors developed a fully automatic adjustment system for mass production of the optical head for magnetooptical disk drives. The optical head is composed of small-sized (millimeter-scale) optical components, such as the laser diode, the collimator lens, the object lens, various prisms, and various detectors. In the assembly of the head, the positioning and fixation must be executed with an accuracy on the micrometer order, and the adjustment process is indispensable. Adjustment is a process where the object is iteratively measured and manipulated, and is finally fixed so that the specified performance is realized. A lens, for example, is moved, the shape of the convergence beam is observed, and the lens is then moved and fixed so that the beam takes the specified shape. Such an adjustment requires a considerable amount of time by an experienced worker, and has been one of the bottlenecks in the mass production of optical heads. The adjustment process for the optical head consists of adjustment of the optical axis of the laser diode, adjustment of the beam shape, and adjustment of the servo signal. The authors devised a series of adjustment algorithms composed of measurement, recognition, calculation of manipulation, execution of manipulation, verification, and fixation. They then developed the necessary techniques and installations that realize the algorithms. The key in the adjustment of the optical head is to process the measured value, to recognize the shape of the beam and the waveform, and to determine the manipulation, rather than simply using the measured value itself. Using the developed automatic adjustment system, the adjustment process, which requires approximately 9 minutes for an experienced worker, can be completed in about 6 minutes. © 1999 Scripta Technica, Syst Comp Jpn, 30(10): 1–12, 1999