Image forming system, sheet processing device, and control method of sheet processing device

A sheet processing device, comprising:

• a stapler configured to staple a sheet;
• a process tray positioned on an upper surface of the sheet to be stapled;
• a first sensor disposed on an upper side of the process tray, and configured to output a first signal corresponding to a first distance to an object disposed at a first position of a sheet placement region of an upper surface of the process tray, or a first thickness of the object disposed at the first position;
• and
• a second sensor disposed on the upper side of the process tray, and configured to output a second signal corresponding to a second distance to the object disposed at a second position on a downstream side in a sheet discharge direction from the first position of the sheet placement region of the upper surface of the process tray, or a second thickness of the object disposed at the second position, wherein
• the first signal and the second signal are transmitted to an image forming device, and an operation is performed by the sheet processing device on the basis of a content received from the image forming device.

A control method of a sheet processing device, the method comprising:

• detecting a first distance to an object disposed at a first position of a sheet placement region of an upper surface of a process tray where a sheet to be stapled is placed, or a first thickness of the object disposed at the first position;
• detecting a second distance to the object disposed at a second position on a downstream side in a sheet discharge direction from the first position of the sheet placement region of the upper surface of the process tray, or a second thickness of the object disposed at the second position;
• and
• controlling stapling the sheet on the basis of the detecting results of the first distance or the first thickness and the second distance or the second thickness.