Apparatus for monitoring a process chamber

The process chamber monitoring apparatus. The process chamber, the monitoring device is arranged in correspondence with the ends of the viewport process chamber including a view port formed in the chamber body (view port),, having a first thickness toward the center of the process chamber, pin holes (pin hole) is formed in the cover portion, and the view is inserted is placed into the port, and including a sensing via the pinhole monitor the inside of the process chamber, the sensing area of ​​the sensing portion is determined in accordance with said first thickness value, the cover portion do.