A method of assembling a turbine engine includes defining a first chamber and defining a second chamber. The turbocharger comprises a compressor and a turbine which has a turbine housing and a wastegate device with a regulating flap. The optical film of the current invention is advantageous because the prism structure and the opposite surface of the optical film are prevented from damage due to external impact, vibration and friction, and the attachment of impurities due to frictional static charges is prevented. The first end is disposed so that there is a gap between the first end and an edge of the device area.