Fluorescence biosensing system and biodetection method

A biodetection method, comprising:

• providing a fluorescence biosensing system comprising a sensing device and a light emitting device, wherein the sensing device comprises a first upper sub-polarizer aligned with a first lower sub-polarizer and a second upper sub-polarizer aligned with a second lower sub-polarizer;
• disposing a sample at a reaction area of the sensing device;
• emitting an excitation light to the first upper sub-polarizer and the second upper sub-polarizer by the light emitting device to obtain a polarized excitation light;
• refracting the polarized excitation light toward the reaction area,
• wherein a portion of the polarized excitation light passing through the first upper sub-polarizer reaches the second lower sub-polarizer;
• reflecting the portion of the polarized excitation light out of the sensing device by the second lower sub-polarizer;
• and
• detecting an emission light from the sample by the sensing device.