Sheet type discrimination device, sheet type discrimination method, and sheet type discrimination program

A sheet type discrimination device comprising:

• a first light source unit that irradiates a sheet with light having a first wavelength and light having a second wavelength;
• a detection unit that detects light from the sheet and acquires a detection value based on the light;
• and
• a control unit that derives a determination result of a type of the sheet by using the detection value, wherein
• the first light source unit and the detection unit are located on a same side with respect to the sheet,
• the detection value includes:
• a first detection value based on light from the sheet when the sheet is irradiated with light having the first wavelength;
• and a second detection value based on light from the sheet when the sheet is irradiated with light having the second wavelength, and
• the control unit
• discriminates first-type recycled paper by first processing using the first detection value, and
• discriminates second-type recycled paper different from the first-type recycled paper by second processing using the second detection value.