In one aspect, there is disclosed a high temperature composite insulation assembly for a fuel cell that includes a core portion having inner and outer surfaces. A light given out from each lens in the light-incident-side fly’s eye lens becomes two light fluxes via respective polarizing beam splitters and the two light fluxes pass through two lenses in the light-exit-side fly’s eye lens. The locking mechanism prevents movement of the inner plunger rod relative to the outer plunger rod while both the inner and outer plunger rods are depressed, until the outer plunger rod has been depressed a first predetermined distance. A silicon nitride film which is a lower layer is formed using NH3 as a nitrogen source gas by a CVD method and contains a larger number of N\u2014H bonds than the upper layer. This information from the beginning and end of a given frame is differenced and to this is added the amount of charge indicated by the number of times the counter overflowed during the integration period.