Tests look for defects, search for morphological features of the platter, or are a power spectrum test, where a region of the disk is examined and the resulting data is split up into various wavelength of interest, from 0.5 microns to 5,000 microns covering the roughness-to-waviness band. The Model 42000 inspects a disk in an environment much like that of a hard drive. Being non-contact, the LDV, which operates to 1/100th of an angstrom, can conduct several tests on the same platter throughout the manufacturing process (substrate, polish, plate, wash, and coat) without risk of a surface impact. The THôT tester takes approximately 65 seconds, while a selected area test takes as little as 10 to 20 seconds. The test can be done on conventional platters or the recently introduced perpendicular magnetic recording (PMR) technology.
The Model 42000 comes in two models (both use the Galil controller). The engineering model is manually operated and attaches to a standard computer. A disk is manually loaded onto the spindle and the test is performed with specific criteria the user can then inspect the flaw(s) visually via the microscope. The full-production model, where the test is set up with pass-fail criteria, searches for all morphological characteristics and wavelengths of the disk.