Imaging method and biosensor for detecting spectrum shift

An imaging method for detecting spectrum shift, comprising:

• receiving a first light beam by a first photodiode and a second photodiode to simultaneously obtain a first image signal with a first image intensity from the first photodiode and a second image signal with a second image intensity from the second photodiode,
• wherein the first image signal corresponds to the first light beam filtered by a first filter, the second image signal corresponds to the first light beam filtered by a first double-layered filter comprising a second filter overlapped on a third filter, and the third filter has a wavelength range same as a wavelength range of the first filter,
• wherein a difference between a peak wavelength of the first image signal and a center wavelength of the first filter is within ±5 nm,
• wherein a difference between the peak wavelength of the first image signal and a cut-on/cut-off wavelength of the second filter is within ±5 nm;
• receiving a second light beam by the first photodiode and the second photodiode to simultaneously obtain a third image signal with a third image intensity from the first photodiode and a fourth image signal with a fourth image intensity from the second photodiode,
• wherein the third image signal corresponds to the second light beam filtered by the first filter, the fourth image signal corresponds to the second light beam filtered by the first double-layered filter;
• and
• determining a spectrum shift from the first light beam to the second light beam by comparing the first image intensity and the second image intensity to the third image intensity and the fourth image intensity.