RT - Journal Article T1 - In-depth optical trapping by tuning correction collar of dry objective lens JF - opsi YR - 2017 JO - opsi VO - 23 IS - 0 UR - http://opsi.ir/article-1-1276-en.html SP - 445 EP - 448 K1 - Spherical aberration K1 - Optical tweezers K1 - Correction collar value of dry objective lens K1 - Optimal depth AB - Optimized optical tweezersre indispensable tools for micromanipulation for biological tissues. Using electromagnetic theory the spatial intensity profile at the afocus of a dry objective lens and its trapping stiffness are calculated. Presence of mediums with different refractive indices after the objective introduces significant amounts of spherical aberrations, which degrades the strength of the trap. Here we have shown, that tuning the correction collar of the objective on a value larger than the thickness of the coverslip can compensate for this aberration, which in turn maximizes the trapping stiffness. This tuning possibility allows for trapping at desired depth of the sample under investigation with optical tweezers LA eng UL http://opsi.ir/article-1-1276-en.html M3 ER -