Disk-mount device for automatic successive testing of computer-drive disk blanks by interferometry

Abstract

A substantially vertical sample stage for interferometric testing of computer-drive disks is positioned along an inclined trackway. The stage includes three pressure tips that provide a fixed, aligned plane against which the back surface of the disk being tested is positioned in optical alignment with the reference surface of the instrument. The degree of protrusion of two of the pressure tips can be adjusted to set the proper tip/tilt of the disk. Each disk being tested is allowed to roll down the trackway by gravity to a rubber stop in front of the stage. The trackway is also tilted slightly to cause the disk to roll on edge and lean against the sidewall of the trackway. After the disk is stopped in front of the stage, a retractable finger engages the forward edge of the disk and produces a slight backward motion to release the disk from the rubber stop and align it with the stage. An air-stream burst is then applied to the back surface of the disk to create a suction that attracts the disk to the three pressure tips while supported by two edge points in contact with the retractable finger and the inclined trackway. Interferometric testing is carried out and, finally, the finger is retracted and the disk allowed to roll down the inclined trackway away from the stage while another disk is rolled into position for testing.