Image Sensing Device

An image sensing device disposed on a transmission path of an illumination beam and a plurality of scan lines are performing exposure on a scan document by the illumination beam, and sequentially sensing the scan lines to correspondingly output a plurality of analog signals, comprises:

• N red light sensing units;
• N green light sensing units;
• N blue light sensing units, wherein N≧2;
• and
• a control circuit used for accumulating an exposure capacity Qi generated by the ith red light sensing unit, the ith green light sensing unit, and the ith blue light sensing unit in an exposure time Ti and an exposure capacity Qi+1 generated by the (i+1)th red light sensing unit, the (i+1)th green light sensing unit, and the (i+1)th blue light sensing unit in the next exposure time Ti+1 until accumulating an exposure capacity QN generated in the TNth exposure time, wherein i is an positive integer ranging from 1 to N,
• wherein, the exposure capacities Qi to QN are sequentially stored in a register and outputted from the control circuit, so that an image of each scan line can be sequentially transferred to an analog signal with the sum of the exposure capacities Qi to QN.