Automatic document feeder

An automatic document feeder for feeding a sheet article, said automatic document feeder comprising:

• a transfer channel;
• a pick-up module for feeding said sheet article into said transfer channel;
• and
• a thickness detecting module for detecting said sheet article that is fed into said transfer channel, wherein said thickness detecting module is disposed within a module housing, said thickness detecting module comprising:
• a detecting member disposed in said transfer channel to be in contact with said sheet article, wherein when said sheet article is transported across said detecting member, said sheet article is sustained against said detecting member, so that said detecting member is moved from a first position to a second position, wherein said detecting member comprises:
• a rolling structure in contact with said sheet article for facilitating feeding said sheet article when said sheet article is transported across said rolling structure;
• and
• a linking rod connected to said rolling structure and a swinging arm, wherein when said sheet article is sustained against said rolling structure and said rolling structure is moved from said first position to said second position, said linking rod and said rolling structure are synchronously moved and said swinging arm is swung from a third position to a fourth position in response to movement of said linking rod, so that a