Effect of photon counting shot noise on total internal reflection microscopy

Area of Science:

• Colloid and Surface Science
• Microscopy Techniques
• Statistical Physics

Background:

• Total Internal Reflection Microscopy (TIRM) quantifies particle-substrate distances via scattered light intensity.
• Evanescent wave illumination is key to TIRM's distance measurements.
• Potential profiles (φ(z)) are derived from separation distance distributions.

Purpose of the Study:

• To investigate the impact of photon counting statistics on TIRM's spatial resolution.
• To model and evaluate the blurring effect on potential profiles.
• To establish the role of integration time (τ) in TIRM measurements.

Main Methods:

• Development of a theoretical model for photon counting statistics.
• Brownian dynamics simulations to assess potential profile effects.
• Experimental validation of simulation results.

Main Results:

• Photon counting statistics fundamentally limit TIRM's spatial resolution.
• Sharp features in potential gradients (∂φ/∂z) are significantly blurred.
• A trade-off exists between photon counting distribution width and instantaneous position capture.

Conclusions:

• Photon counting statistics are a critical factor affecting TIRM accuracy.
• Understanding this limitation is essential for precise colloidal potential measurements.
• Optimizing integration time (τ) is crucial for balancing measurement fidelity.