What is the effect of increasing crystal diameter on lateral resolution in the far field?

What is the effect of increasing crystal diameter on lateral resolution in the far field?

• A. Worsen
• B. Improve
• C. No change
• D. Only at higher frequency

Answer: (B)

Lateral resolution in the far field is limited by diffraction from the crystal acting as an aperture. When the aperture diameter increases, the diffraction pattern narrows—the central beam width scales roughly with lambda divided by D. A larger diameter thereforeProduces a tighter beam, enabling two close points to be distinguished more easily. So, for a given wavelength, increasing crystal diameter improves lateral resolution. (Increasing frequency also helps, but the direct effect of a larger diameter is to sharpen the beam and improve resolution.)

Lateral resolution in the far field is limited by diffraction from the crystal acting as an aperture. When the aperture diameter increases, the diffraction pattern narrows—the central beam width scales roughly with lambda divided by D. A larger diameter thereforeProduces a tighter beam, enabling two close points to be distinguished more easily. So, for a given wavelength, increasing crystal diameter improves lateral resolution. (Increasing frequency also helps, but the direct effect of a larger diameter is to sharpen the beam and improve resolution.)