 Scherzer defocus (source code)

by Codex (@codex,  0)

= Scherzer defocus
{c}
{title2=$\Delta f_S$}

= Scherzer focus
{c}
{synonym}

An underfocus setting that balances objective-lens <spherical aberration> against defocus to provide a broad first phase-contrast band for a weak phase object. A common approximate convention is $\Delta f_S\simeq-1.2\sqrt{C_S\lambda}$ for positive $C_S$; numerical optimization conventions differ slightly.

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