Image reading apparatus

An image reading apparatus in which an integral scanning optical unit is moved in a sub-scan direction to read imagewise information of an original, said apparatus comprising:

• an integral scanning optical unit in which a light source device configured to illuminate an original placed on an original table, a plurality of mirrors configured to reflect a light beam from the original illuminated by said light source device and an imaging optical system configured to image the light beam reflected by said plurality of mirrors, upon a reading device, are integrally accommodated;
• wherein at least one of said plurality of mirrors is so configured that the light beam is incident thereon twice or more,
• wherein, in a sub-scan section, reflection surfaces of said plurality of mirrors are disposed in a space at an original-reading-position side of a light entrance surface of said imaging optical system,
• wherein the reflection surface of a mirror disposed at a position optically closest to the light entrance surface of said imaging optical system is placed at a position furthermost from said original table with respect to a direction of a normal thereto, as compared with the reflection surfaces of the remaining mirrors;
• and
• wherein, when in the sub-scan section a distance to the original table from a center of the reflection surface of the mirror disposed furthermost from the original table in the direction of a normal thereto is denoted by a and a largest distance between centers of the reflection surfaces of said plurality of mirrors in the sub-scan direction is denoted by b, conditions
• 0.65<a/b <1.0 and
• a <30.0 mm
• are satisfied.

An image reading apparatus in which an integral scanning optical unit is moved in a sub-scan direction to read imagewise information of an original, said apparatus comprising:

• an integral scanning optical unit in which a light source device configured to illuminate an original placed on an original table, a plurality of mirrors configured to reflect a light beam from the original illuminated by said light source device and an imaging optical system configured to image the light beam reflected by said plurality of mirrors, upon a reading device, are integrally accommodated;
• wherein at least one of said plurality of mirrors is so configured that the light beam is incident thereon twice or more,
• wherein, in a sub-scan section, reflection surfaces of said plurality of mirrors are disposed in a space at an original-reading-position side of a light entrance surface of said imaging optical system,
• wherein the reflection surface of a mirror disposed at a position optically closest to the light entrance surface of said imaging optical system is placed at a position furthermost from said original table with respect to a direction of a normal thereto, as compared with the reflection surfaces of the remaining mirrors;
• and
• wherein, when in the sub-scan section a distance to the original table from a center of the reflection surface of the mirror disposed furthermost from the original table in the direction of a normal thereto is denoted by a and a distance to the original table from a barrel which holds said imaging optical system is denoted by c, conditions
• 0.5<c/a <0.7 and
• a <30.0 mm
• are satisfied.