This standard specifies the Measuring method of the darkroom contrast ratio and the bright room contrast ratio of the Optical inspection functional film for the display screen of flat panel display devices, and the calculation method of the darkroom contrast ratio improvement rate and the bright room contrast ratio improvement rate after the flat panel display device is assembled with the Optical inspection functional film. The scope of application includes the measurement of the darkroom contrast ratio of the Optical inspection functional film and the bright room contrast ratio. The document cites several normative reference documents, including GB/T 18910.11-2012, GB/T 20871.2-2007, GB/T 2 2181.1 - 2008, etc., to ensure the implementation and compliance of the standard. The contrast ratio is given by Equation (1).