1. An optical sheet optimization method comprising the steps of: extracting a statistic sample using transmissivity, haze data and luminance data of an optical diffusion sheet corresponding to the transmissivity and the haze data; making a regression model for the extracted statistic sample; calculating a regression coefficient to minimize an error term (residual) of the regression model and deriving a regression expression using the calculated regression coefficient; and predicting a luminance of the optical diffusion sheet due to changes of the transmissivity and the haze data using the derived regression expression.