Patent ID: 8921762

Claim:
A detection device comprising: an imaging unit detachably attached to an image forming apparatus and configured to form an image of an incident beam on an image detection unit; an emission unit detachably attached to the imaging unit and comprising: a first guided portion that moves to be guided through a first guiding portion of the imaging unit and guiding an attachment-detachment operation of the first guided portion; a first positioned portion correspondingly positioned with a first positioning portion of the imaging unit when the emission unit is mounted to the imaging unit; and an emission member configured to emit a beam toward a direction of a transportation path at which a medium is transported such that a beam reflected from the medium is incident to the imaging unit; and a setting unit detachably attached to the emission unit, accommodated in a drawing unit of the image forming apparatus, and comprising: a second positioned portion correspondingly positioned with a second positioning portion provided at the emission unit when the drawing unit is pressure-inserted into the image forming apparatus; and a reference roll configured to set a position on the medium at which the beam is reflected wherein the imaging unit comprises: a second guided portion that is guided through a second guiding portion of the image forming apparatus and configured to guide an attachment-detachment operation of the second guided portion; and a third positioned portion that is positioned in a third positioning portion of the image forming apparatus when the imaging unit is mounted to the image forming apparatus, and wherein the second guided portion comprises a second slider and the second guiding portion comprises a second rail.