An exposure device includes a first light emitting element substrate including a plurality of first light emitting elements arranged at an arrangement interval T in a longitudinal direction, and a second light emitting element substrate including a part in the longitudinal direction that overlaps with a part of the first light receiving element substrate so as to form an overlapping region. The first and second light emitting element substrates are shifted from each other in a direction perpendicular to the longitudinal direction. The second light emitting element substrate includes a plurality of second light emitting elements arranged in the longitudinal direction. The second light emitting elements are arranged at the arrangement interval T at least outside the overlapping region. When an interval between two of the second light emitting elements of the second light emitting element substrate disposed in the overlapping region is expressed as a specified interval TS, the specified interval TS and the arrangement interval T satisfy:

T≦TS≦2T.

An example scanner device includes a sealed enclosure including a scan window to allow light to enter the sealed enclosure, and an optical assembly including a light source and an image sensor. The light source is to emit light through the scan window onto a medium to be scanned. The image sensor is to capture light reflected by the medium through the scan window. The optical assembly is rotatably positioned within the sealed enclosure. An actuator is disposed within the sealed enclosure to rotate the optical assembly to aim the optical assembly at different locations on the scan window.

An example scanner device includes a sealed enclosure including a scan window to allow light to enter the sealed enclosure, and an optical assembly including a light source and an image sensor. The light source is to emit light through the scan window onto a medium to be scanned. The image sensor is to capture light reflected by the medium through the scan window. The optical assembly is rotatably positioned within the sealed enclosure. An actuator is disposed within the sealed enclosure to rotate the optical assembly to aim the optical assembly at different locations on the scan window.

An exposure device includes a first light emitting element substrate including a plurality of first light emitting elements arranged at an arrangement interval T in a longitudinal direction, and a second light emitting element substrate including a part in the longitudinal direction that overlaps with a part of the first light receiving element substrate so as to form an overlapping region. The first and second light emitting element substrates are shifted from each other in a direction perpendicular to the longitudinal direction. The second light emitting element substrate includes a plurality of second light emitting elements arranged in the longitudinal direction. The second light emitting elements are arranged at the arrangement interval T at least outside the overlapping region. When an interval between two of the second light emitting elements of the second light emitting element substrate disposed in the overlapping region is expressed as a specified interval TS, the specified interval TS and the arrangement interval T satisfy:
TTS2T.