All Research Areas

Active illumination microscopy

Active illumination microscopy (AIM) is a method of redistributing dynamic range in a scanning microscope using real-time feedback to control illumination power on a sub-pixel time scale. The principle of the feedback is to maintain a fixed detection power, thereby transferring high measurement resolution to weak signals while virtually eliminating the possibility of image saturation. As a result, this technique enhances both the weak-signal relative sensitivity and the dynamic range of a laser scanning optical microscope. We have demonstrated a fully integrated instrument that performs both feedback and image reconstruction. The image is reconstructed on a logarithmic scale to accommodate the dynamic range benefits of AIM in a single output channel. While AIM is applicable to any type of scanning microscope, we have applied it specifically to two-photon microscopy.


Publications Related to this Research Area

Practical implementation of log-scale active illumination microscopy

K. K. Chu, D. Lim and J. Mertz,

Biomedical Optics Express

Active illumination microscopy (AIM) is a method of redistributing dynamic range in a scanning microscope using real-time feedback to control illumination power on a sub-pixel time scale. We describe and demonstrate a fully integrated instrument that performs both feedback and image reconstruction. The image is reconstructed on a logarithmic scale to accommodate the dynamic range benefits of AIM in a single output channel. A theoretical and computational analysis of the influence of noise on active illumination feedback is presented, along with imaging examples illustrating the benefits of AIM. While AIM is applicable to any type of scanning microscope, we apply it here specifically to two-photon microscopy.

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Enhanced weak-signal sensitivity in two-photon microscopy by adaptive illumination

K. K. Chu, D. Lim and J. Mertz,

Optics Letters

We describe a technique to enhance both the weak-signal relative sensitivity and the dynamic range of a laser scanning optical microscope. The technique is based on maintaining a fixed detection power by fast feedback control of the illumination power, thereby transferring high measurement resolution to weak signals while virtually eliminating the possibility of image saturation. We analyze and demonstrate the benefits of adaptive illumination in two-photon fluorescence microscopy.

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AIM principle

In a conventional scanning microscope, the illumination power is fixed. In an AI microscope, the illumination power is varied to keep the detection power fixed.

TPEF stack of GFP-labeled cleared mouse brain without (left) and with (right) AI

Intensities are displayed in log scale to highlight weak structures and noise. Stacks were acquired with identical exposure times. Total energy delivered to sample was slightly less with AI.