Image reading apparatus and image forming apparatus having a rectangular mirror and a casing for the mirror and an image sensor, wherein opposite ends of the mirror are bonded to the casing with adhesives that differ from each other in hardness

An image forming apparatus comprising:

• a light source configured to illuminate an original;
• a mirror configured to reflect light reflected by the original, said mirror being a rectangular plate member which has a reflecting surface reflecting light, a back surface positioned in a back side of said reflecting surface, a first side surface positioned in one end of said mirror in a longitudinal direction, a second side surface positioned in the other end portion of said mirror in the longitudinal direction, a first chamfered portion formed on an edge portion of said back side in said first side surface and a second chamfered portion formed on an edge portion of said back side in said second side surface;
• an image sensor configured to read the light reflected by said mirror;
• a casing configured to hold said mirror and said image sensor, said casing having a first wall portion opposing said first side surface of said mirror in the lengthwise direction and a second wall portion opposing said second side surface of said mirror in the lengthwise direction,
• wherein said first side surface and said first chamfered portion are bonded to said first wall portion with a first adhesive and said second side surface and said second chamfered portion are bonded to said second wall portion with a second adhesive which has a hardness less than that of said first adhesive;
• and
• an image former configured to form an image on a sheet on the basis of image information read by said image sensor.