Lensless dual-color fluorescence imaging device using hybrid filter

Lensless dual-color fluorescence imaging device using hybrid filter


Kulmala, N., Sasagawa, K., Treepetchkul, T., Takehara, H., Haruta, M., Tashiro, H., & Ohta, J. (2022). Lensless dual-color fluorescence imaging device using hybrid filter. Japanese Journal of Applied Physics, 61. https://doi.org/10.35848/1347-4065/ac3ef2


  • Lensless imaging
  • Dual-color fluorescence imaging
  • Hybrid filter
  • Fiber optic plate (FOP)
  • Excitation light rejection
  • Autofluorescence
  • Image processing
  • Fluorescence microbeads


Kulmala et al. (2022) investigated a lensless dual-color fluorescence imaging device that uses a hybrid filter to observe green and red fluorescence components.


This article, published in 2022 in the Japanese Journal of Applied Physics, details the development of a lensless imaging device capable of dual-color fluorescence observation. The authors, Kulmala et al., constructed a hybrid filter by combining interference filters, absorption filters, and a fiber optic plate (FOP). This hybrid filter effectively rejects excitation light in both the blue and yellow wavelengths while transmitting green and red fluorescence.

Key Findings:

  • The hybrid filter demonstrated superior performance when the longpass interference filter was placed on top of the FOP and the notch interference filter on the bottom, effectively minimizing a decrease in excitation rejection performance.
  • The configuration of the absorption filters also proved critical, with the yellow (VY1108) and blue (FDG-007) filters positioned below the FOP for optimal absorption of excitation light.
  • Tests using green and red fluorescent beads showcased the device's ability to distinguish between the two colors, particularly when aided by image processing techniques to separate the green and red channels.


  • Scattering of light through the FOP can reduce the overall performance of the interference filter.
  • The color image sensor's sensitivity to red was higher than green, leading to potential artifacts, even with image processing.
  • The study acknowledges the inherent limitation of reduced spatial resolution in contact imaging devices, particularly noticeable in fluorescence observation due to isotropic fluorescence emission.

Future Directions:

  • The authors suggest exploring alternative filter configurations, such as placing both interference filters on a single side of the FOP, to potentially enhance filter performance.
  • Further refinement of the color image sensor, particularly by reducing red sensitivity, is proposed to improve fluorescence separation accuracy.
  • Investigating image processing methods, such as deconvolution and sparse sampling techniques, combined with optical system improvements like incident angle limitation or phase masks, is recommended to enhance spatial resolution.

Origin: https://iopscience.iop.org/article/10.35848/1347-4065/ac3ef2/pdf


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