Two-photon microscope

Related:
Infinity-corrected optics, Femtosecond lasers, Galvoscanners

Concepts

Simplified optics

Beam size on objective

Correctly filling the back aperture of the objective is important.

• Under-filling the objective implies z resolution is lost because the point spread function is not as sharp as it could be.
• Over-filling the objective implies power is lost as the laser beam is cut of.

Computing the beam diameter after the lens assembly is therefore necessary.

$$S_o=S_i.\frac{f_t}{f_s}$$

where,
$S_o$ is the beam size at the objective
$S_i$ is the beam size at the galvo mirror/scan lens
$f_s$ is the focal length of the scan lens
$f_t$ is the focal length of the tube lens

Derivation: (depends on Magnification)

Scan area

The scan area depends directly on the angle of the galvo mirror in the following manner.

$$S_o=tan\theta .f_s.\frac{f_o}{f_t}$$

where,
$S_o$ (or sometime $\frac{a}{2}$) is half the scan area length/width.
$f_s$ is the focal length of the scan lens
$f_t$ is the focal length of the tube lens
$f_o$ is the focal length of the objective lens

Derivation: (depends on Magnification)

MIMMS microscope - simplified

Practical know-how

Setting up the optic table

Newport S-2000 optic table + stabilizer setup: https://www.youtube.com/watch?v=fDdYE1Lb0GM

More on the inner workings of S-2000 (good to give an intuitive idea): https://www.youtube.com/watch?v=0q8cZ-bBzjo