The original document does not come in contact with the sheet-through exposure glass, which prevents adhesive dirt (ball pen ink) on the document from adhering to the sheet-through exposure glass.

ADF cross-section diagram, non-contact scanning

[A]: Sheet

[B]: Sheet-through exposure glass

[C]: Read position

[D]: Document

  • Contact scanning
    As the document comes in contact with the sheet-through exposure glass this is useful for dealing with adhesion of free dirt particles (paper scraps, etc.). (Self-cleaning mechanism using paper)
    On the other hand, sticky dirt adhering to the document sticks to the sheet-through exposure glass and may give rise to the appearance of black lines.
    ADF cross-section diagram, contact scanning

    [A]: Sheet-through exposure glass
    [B]: Read position
    [C]: Document
    If black lines due to free dirt particles appear within a short time, such as when users have documents with large amounts of paper scraps, you can change from the non-contact scanning system to the contact scanning system with the procedure in Troubleshooting - Vertical Streaks on Copies due to Scanning Problems.

  • Reference (reading position correction)
    By changing SP4-020-001 (Dust Check Dust Detect:On/Off), when dirt is detected at the reading position, the reading position may be changed to avoid the dirt.
    (If it cannot be avoided, an alert is displayed on the operation panel advising the user to perform target glass cleaning).
    Image diagram

    [A]: Read position
    [B]: Sheet-through exposure glass
    [C]: Dirt

    • Dirt is detected when a document passes through, so the alert will not disappear until the reading of the next document begins, even after the sheet-through exposure glass cleaning is performed.
    • If dirt is detected not on the sheet-through exposure glass but on the background guide plate, the alert will not disappear even if the glass is wiped.
    • The time required for the first copy is slightly (almost imperceptibly) longer.
    • The detection threshold value can be changed using SP4-020-002 (Dust Check Dust Detect:Lvl). (The larger the value is, the smaller the dirt particles that can be detected become.)
    • It is prohibited to change the setting of SP4-020-003 (Dust Check Lvl Dust Reject:Lvl).