1. What is the Diffraction Limited Spot Size?

The diffraction limited spot size represents the smallest possible focused spot diameter achievable by an optical system due to the wave nature of light. It's determined by the Airy disk formula and represents the fundamental resolution limit of optical systems.

2. How Does the Calculator Work?

The calculator uses the Airy disk formula:

Where:

• \( SS \) — Spot size (meters)
• \( \lambda \) — Wavelength of light (meters)
• \( NA \) — Numerical aperture (dimensionless)

Explanation: The formula calculates the diameter of the Airy disk, which is the diffraction pattern produced when light passes through a circular aperture. The factor 1.22 comes from the first zero of the Bessel function describing the pattern.

3. Importance of Spot Size Calculation

Details: Calculating the diffraction limited spot size is crucial for optical system design, microscopy resolution assessment, laser focusing applications, and understanding the fundamental limits of optical resolution in imaging systems.

4. Using the Calculator

Tips: Enter wavelength in meters and numerical aperture as a dimensionless value. Both values must be positive numbers. For typical optical wavelengths, use values like 500e-9 m (500 nm) for visible light.

5. Frequently Asked Questions (FAQ)

Q1: What is the significance of the 1.22 factor?
A: The factor 1.22 comes from the first zero of the first-order Bessel function, which defines the radius where the intensity first falls to zero in the Airy pattern.

Q2: How does numerical aperture affect spot size?
A: Higher numerical aperture results in smaller spot size, meaning better resolution. This is why high-NA objectives are used in microscopy for superior resolution.

Q3: What wavelengths are typically used?
A: Common wavelengths include 405 nm (violet), 488 nm (blue), 532 nm (green), and 633 nm (red) for various laser and optical applications.

Q4: Can spot size be smaller than this calculation?
A: This represents the diffraction limit for conventional optics. Techniques like super-resolution microscopy can achieve smaller effective spot sizes through specialized methods.

Q5: How does this relate to microscope resolution?
A: The spot size calculation determines the minimum resolvable distance between two points, defining the resolution limit of optical microscopes and other imaging systems.