Patent ID: 7327493

Claim:
An image reading system which can read a film original and performs at least two scanning operations including prescanning and actual scanning, comprising: a photoelectric conversion unit adapted to read light having transmitted through the film original and converting the transmitted light into an electrical signal; an adjustment unit adapted to adjust level of the electrical signal output from said photoelectric conversion means; an A/D conversion unit adapted to convert the electrical signal whose level is adjusted by said adjustment unit into digital data; a table conversion processing unit adapted to perform table conversion processing for the digital data by using a look-up table; and a control unit adapted to determine an exposure state of the film original from prescanned image data which has undergone table conversion processing by said table conversion processing unit and is linear with respect to an output from said A/D conversion unit, setting an adjustment state of said adjustment unit in actual scanning in accordance with the exposure state, performing digital calculation for the prescanned image data, and generating display image data which reflects a setting of the adjustment state, wherein said table conversion processing unit performs table conversion processing using a linear look-up table which provides a linear output with respect to digital data A/D-converted by said A/D conversion unit, wherein said control unit performs table conversion processing using a look-up table corresponding to a type of the film original for the linear prescanned image data, wherein said control unit creates a display image generation look-up table for generating display image data from prescanned image data having undergone table conversion processing using the look-up table corresponding to the type of the film original, and generates a display image on the basis of the created look-up table, and wherein said control unit creates an actual scanning look-up table by synthesizing the linear look-up table, the look-up table corresponding to the type of the film original, and the display image generation look-up table, and causes said table conversion processing means to perform table conversion processing for actually scanned data by using the created actual scanning look-up table.