Single side reading	Read the front side of the OMR form
Dual Side Reading	Read both sides of the OMR form

: Each sensor can recognize Marks and Timing Marks directly.
Every marks need to print on the same position of reading sensors.

Type of sensor	Wave length	Mark Implements	Dropout color	Readable color
Infrared sensor(IR)	940nm	Pencil	Colors other than readable color	Black, Blue, Pigments
Visible sensor (VR)	660 nm	Pencil + Pen	Red , Orange , Pink	Black, Blue

Read pencil marks only
Infrared light can not see by naked eye.

Infrared sensor(Pencil read sensor)

• 
  Image : Infrared light can not see by naked eye.
• 
  Image : Dropout mark frames

Red lights onto mark frames

• Example: Red , Orange, and Pink are dropout by visible red light
  
  
• Blue line can not drop out by the visible red light