Thickness measurement of optical data carriers

The data is initially transferred to a master when CDs, DVDs, HD-DVDs or Blu-ray discs are produced. Depending on the number of copies required, different dies made from nickel are produced from the master by galvanization. For faultless production, these dies must have a thickness of 297µm ±3µm. During galvanising, this dimension is checked several times to ensure compliance. The company ISEDD GmbH from Bielefeld has developed a measuring device for this, which enables fast, accurate inspection of the dies. Capacitive sensors from Micro-Epsilon are used for measuring the thickness. One sensor is positioned above the die, another below the die, which is moved between the sensors during measurements. The die can also be rotated in order to measure thickness profile or for several measuring points.