Image scanner having contact-type image sensor movable under automatic document feeder

An image scanner comprising:

• a first contact glass on which a first original document is placed, said first contact glass having a first bottom surface opposite to a surface on which said first original document is placed;
• an automatic document feeder having a second contact glass through which a second original document fed through the inside of the automatic document feeder is scanned, said automatic document feeder having a second bottom surface opposite to a side on which said second original document is fed, wherein said first bottom surface of said first contact glass and said second bottom surface of said second contact glass lie in the same plane;
• an image sensor scanning said first original document while moving under said first contact glass, said image sensor scanning said second original document by moving to a fixed position directly under said second contact glass;
• spacer means, provided on said image sensor, maintaining a distance between said image sensor and said first contact glass to be constant by contacting said first bottom surface of said first contact glass when said image sensor is scanning said first original document, said spacer means maintaining a distance between said image sensor and said second contact glass to be constant by contacting said second bottom surface of said second contact glass when said image sensor is scanning said second original document;
• pressing means for pressing said image sensor via said spacer means against said first bottom surface of said first contact glass when said image sensor is scanning said first original document, and for pressing said image sensor via said spacer means against said second bottom surface of said second contact glass when said image sensor is scanning said second original document;
• and
• separating means for separating said spacer means from said first bottom surface of said first contact glass when said image sensor is moved from a position under said first contact glass to said fixed position under said second contact glass, and for separating said spacer means from said second bottom surface of said second contact glass when said image sensor is moved from said fixed position under said second contact glass to a position under said first contact glass.