Light microscopy

This article examine the microscope.

Resolution

$R=1.22*{gamma \over {NA_{obj}+NA_{cond}}}$ .^[1]
Where:

$R$ = resolving distance; smaller better.
$NA_{obj}$ = numerical aperture of the objective; typically 0.25 - 1.4, >1.0 is oil immersion, it is usu. inscribed on the lens itself.
$NA_{cond}$ = numerical aperture of the condenser.
$gamma$ = wave length of light.

It follows from the above equation that, closure of the condenser diaphragm results in a loss of resolution, i.e. R is larger.^[1]

Stated differently:^[2]

Opening the condenser --> increases resolution & brightness -- but -- decreases depth of field (DOF) & contrast.
Closing the condenser --> increases DOF & contrast -- but -- decreases resolution & brightness.

NA = numerical aperture.

General formula for NA:^[3]
$NA=n*sin(theta)$ .

Where:

N = f/D.

Where:

At infinity:
$N=1/(2*NA_{i})$ .
$f/D=1/(2*NA_{i})$ .
$2*NA_{i}=D/f$ .

If one substitutes the above into the equation at the top:
$R=1.22*{gamma \over (D/2*f)}$ .

Notes:

Condenser -- large flattened lens beneath the specimen.
- Iris diaphragm.
  - Condenser diaphragm --> incr. contrast for resolution ---- large dia. good resol. bad contrast?
    - Field aperature diaphragm --> optical illumination.