A dual path programmable array microscope (PAM): simultaneous acquisition of conjugate and non-conjugate images

Area of Science:

• Microscopy and Imaging Technologies
• Optical Physics
• Biophotonics

Background:

• Programmable array microscopes (PAMs) use spatial light modulators (SLMs) for patterned illumination and detection.
• Existing PAMs and Nipkow-disk microscopes collect conjugate images (Ic), but dual-signal systems offer potential advantages.
• Confocal laser scanning microscopy (CLSM) is a benchmark for optical sectioning but can be time-consuming.

Purpose of the Study:

• To characterize a novel dual-signal PAM capable of simultaneously collecting conjugate (Ic) and non-conjugate (Inc) images.
• To evaluate the imaging speed, noise characteristics, and optical sectioning capabilities of the dual-signal PAM.
• To investigate the impact of illumination patterns and unit cell dimensions on axial response and image quality.

Main Methods:

• Simultaneous acquisition of Ic and Inc images using a modified PAM with an SLM in the primary image plane.
• Measurement of axial responses under various conditions, including different illumination patterns and unit cell sizes.
• Simulation of point spread functions (PSFs) and optical transfer functions (OTFs) for both Ic and Inc images.
• Comparative analysis of optical sectioning achieved through different subtraction methods (Inc subtraction vs. widefield subtraction).

Main Results:

• The dual-signal PAM demonstrates significantly more time-efficient excitation and better emission light utilization compared to CLSM.
• Axial response sharpening was observed with decreasing unit cell size, similar to other microscopes collecting Ic images.
• Optical sectioning capabilities were comparable for specific scan patterns and processed pseudorandom sequence (PRS) scans.
• Non-conjugate subtraction provided superior optical sectioning with lower noise levels compared to scaled widefield subtraction.
• Simulations showed that non-conjugate imaging (Inc) avoids the 'missing cone' problem, enabling high-quality deconvolution.

Conclusions:

• The dual-signal PAM offers superior performance in terms of speed and noise characteristics over single-sided instruments.
• The novel Inc image provides valuable information, enabling high-quality deconvolution without the missing cone artifact.
• This advanced microscopy technique is adaptable to diverse data analysis strategies and shows promise for improved biological imaging.