Patent ID: 6951186

Claim:
An apparatus comprising: a recoverable and reusable unit performing a function independent of determining the degree of deterioration of said recoverable and reusable unit, which is recoverable and reusable after use of said unit and said apparatus in an environment, depending on the degree of deterioration of said unit due to the environment in which said apparatus is used, wherein said recoverable and reusable unit is an optical member; and deterioration indicator means for determining the degree of deterioration of said recoverable and reusable unit before said unit is reconditioned for reuse by permitting a determination of the degree of deterioration thereof, said deterioration indicator means being disposed inside said apparatus, the deterioration-resisting power of said deterioration indicator means that deteriorates over time due to the environment in which said apparatus is used being less than or equal to the deterioration-resisting power of said recoverable and reusable unit, said deterioration indicator means being arranged so as not to participate in any functions of said apparatus during use of said apparatus, and said deterioration indicator means having a property which is a measure of the deterioration of said deterioration indicator means due to the temperature and/or humidity of the environment in which said apparatus is used.