Image reading optical system and image reading device

An image reading optical system, comprising:

• a sensor including an array of reading elements that read incident light;
• a plurality of imaging mirrors that reflect light traveling from a readable object to the sensor;
• a plate member that is disposed at an angle with respect to a travel direction of light traveling from a first one of the imaging mirrors to a subsequent one of the imaging mirrors to cross the light,
• wherein at least part of the plate member is disposed along light incident on the first one of the imaging mirrors;
• a first diaphragm that regulates light traveling from the first one of the imaging mirrors to the subsequent one of the imaging mirrors in a specific direction;
• and
• a second diaphragm that regulates, in a direction crossing the specific direction, the light traveling from the first one of the imaging mirrors to the subsequent one of the imaging mirrors with a projection projecting from the plate member.

An image reading optical system, comprising:

• a sensor including a plurality of reading elements arranged in a first direction;
• a plurality of imaging mirrors that reflect light traveling from a readable object to the sensor;
• a first diaphragm that has a light receiving surface that receives part of light traveling from a first one of the imaging mirrors to a subsequent one of the imaging mirrors, the first diaphragm regulating the light in the first direction;
• and
• a second diaphragm that regulates the light traveling from the first one of the imaging mirrors to the subsequent one of the imaging mirrors in a second direction crossing the first direction, the second diaphragm including a first light shielding portion and a second light shielding portion disposed at different positions in a travel direction of the light to block part of the light, at least one of the first and second light shielding portions deviating from a plane passing the light receiving surface.