The present disclosure discloses methods, systems and scanners for scanning document with varying light intensity. The method includes receiving a bound document positioned on an upper surface of a platen, for scanning, wherein the bound document, when opened for scanning, includes a flat region and a curved region. A distance between the bound document positioned on the platen and a contact image sensor (CIS) is continuously monitored and measured, to detect the curved region. Upon detection, a control command is generated to vary the intensity of the light to be emitted from a light source. Then, light with varying intensity is emitted for illuminating the curved region of the bound document. Thereafter, the light reflected from the bound document is received for capturing an image of the bound document. Finally, a digital version of the bound document is generated without any dark strip or without any distortion.