[docs]def fiber_distance_capillary(gel_thickness=2e-6, glass_thickness=40e-6,
channel_width=40e-6, gel_index=1.449,
glass_index=1.474, medium_index=1.335):
"""Effective distance between the two optical fibers
When the optical stretcher is combined with a microfluidic
channel (closed setup), then the effective distance between
the two optical fibers (with the the stretched object at the
channel center) is defined by the refractive indices of
the optical components: index matching gel between fiber and
channel wall, microfluidic glass channel wall, and medium
inside the channel.
Parameters
----------
gel_thickness: float
Thickness of index matching gel (distance between fiber
and glass wall) [m]
glass_thickness: float
Thickness of glass wall [m]
channel_width: float
Width of the microfluidic channed [m]
gel_index: float
Refractive index of index matching gel
glass_index: float
Refractive index of channel glass wall
medium_index: float
Refractive index of index medium inside channel
Returns
-------
eff_dist: float
Effective distance between the fibers
Notes
-----
The effective distance is computed relative to the medium,
i.e. if `gel_index` == `glass_index` == `medium_index`, then
`eff_dist` = 2*`gel_dist` + 2*`glass_dist` + `channel_width`.
"""
eff_dist = 2 * medium_index / gel_index * gel_thickness \
+ 2 * medium_index / glass_index * glass_thickness \
+ channel_width
return eff_dist