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hardware:objectives [2019/12/20 23:25]
Jon Daniels [Mechanical Angle] |
hardware:objectives [2020/01/24 18:41]
Jon Daniels [Mechanical Angle] |
| ==== Mechanical Angle ==== | ==== Mechanical Angle ==== |
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| For traditional SPIM with two orthogonal objectives, the objectives have to be able to co-focus before they mechanically bump ((for low-NA illumination you can sometimes extend the working distance a bit of the illumination objective by introducing diverging rays into its back aperture, but this is only a small net win)). There are details about the tip profiles to consider, but the most important/fundamental factor in whether or not two objectives can be co-focused orthogonally is only indirectly related to the working distance. Rather the condition is simply whether the sum of their mechanical half-angles is less than 90°. For any objective, the mechanical angle must be at least as big as the optical angle, i.e. it must be at least big enough to capture the cone of rays corresponding to its numerical aperture (NA). The mechanical angle is computed as arctan(dia/2/WD) where dia is the diameter of the first surface (assuming the rest of the objective lens fall inside the line from the focal plane to this first surface as is usually the case). The optical (half) angle is computed as arcsin(NA/RI) where RI is the medium refractive index. Some objective lenses have mechanical angles only barely larger than the lower bound optical angle, but others are much less efficient in a mechanical/bulkiness sense. | For traditional light sheet microscopy with two orthogonal objective lenses, the objectives have to be able to co-focus before they mechanically bump ((For low-NA illumination you can sometimes extend the working distance a bit of the illumination objective by introducing diverging rays into its back aperture, but this is usually only a small win.)). Regardless of working distance, the most important/fundamental factor in whether or not two objectives can be co-focused orthogonally is simply whether the sum of their mechanical half-angles is less than 90° ((However if the working distance of one is very long then perhaps they can co-focus with only use of the optical angle.)). For any objective lens, the mechanical angle must be at least as big as the optical angle, i.e. it must be at least big enough to capture the cone of rays corresponding to its numerical aperture (NA). The mechanical angle is computed as arctan(dia/2/WD) where dia is the diameter of the first surface (assuming the rest of the objective lens fall inside the line from the focal plane to this first surface as is usually the case). The optical (half) angle is computed as arcsin(NA/RI) where RI is the medium refractive index. Some objective lenses have mechanical angles only barely larger than the lower bound optical angle, but others are much less efficient in a mechanical/bulkiness sense. |
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| A detailed overview and helpful table of many objective lenses can be found in Supplementary Note 6 in the Power/Huisken review paper ([[https://media.nature.com/original/nature-assets/nmeth/journal/v14/n4/extref/nmeth.4224-S1.pdf|link to supplemental]]). | A detailed overview and helpful table of many (more) objective lenses can be found in Supplementary Note 6 in the Power/Huisken review paper ([[https://media.nature.com/original/nature-assets/nmeth/journal/v14/n4/extref/nmeth.4224-S1.pdf|link to supplemental]]). |
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| Here are a few objectives that have been used with iSPIM/diSPIM-types systems. Notice that all are used as dipping lenses, even the few that have correction collars. | Here are a few objectives that have been used with iSPIM/diSPIM-type systems. Notice that all are used as dipping lenses, even the few that have correction collars. |
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| ^ Objective ^ Optical angle (NA) ^ Mechanical angle ^ Comments ^ | ^ Objective ^ Optical angle (NA) ^ Mechanical angle ^ Comments ^ |
| | Nikon 40x/0.8 W | 37° | 42.5° | common high-resolution diSPIM | | | Nikon 40x/0.8 W | 37° | 42.5° | common high-resolution diSPIM | |
| | Nikon 10x/0.3 W | 13° | 36° | common low-resolution diSPIM | | | Nikon 10x/0.3 W | 13° | 36° | common low-resolution diSPIM | |
| | | Nikon 16x/0.8 W | 37° | 45° | does it actually fit with pair? (if you try it please speak up) | |
| | Olympus 20x/0.5 W | 22° | 45° | fits better than expected (WD is probably a bit more than spec) | | | Olympus 20x/0.5 W | 22° | 45° | fits better than expected (WD is probably a bit more than spec) | |
| | Olympus 20x/1.0 W | 49° | 52° | | | | Olympus 20x/1.0 W | 49° | 52° | | |
| | Nikon 25x/1.1 W | 56° | 58° | usual lattice detection | | | Nikon 25x/1.1 W | 56° | 58° | usual lattice detection | |
| | | Olympus 60x/1.0 W | 49° | 53° | sometimes oSPIM detection | |
| | Olympus 60x/1.1 W | 56° | 57° | usual oSPIM detection, potential lattice detection | | | Olympus 60x/1.1 W | 56° | 57° | usual oSPIM detection, potential lattice detection | |
| | SO 54-10-7 29x/0.66 W | 30° | 30° | usual lattice illumination | | | SO 54-10-7 29x/0.66 W | 30° | 30° | traditional lattice illumination | |
| | | TL20X-MPL 20x/0.6 W | 27° | ~30° | new (2020) cost-effective lattice illumination | |
| | Nikon 20x/1.0 glyc | 43° | ~54° | cleared tissue confocal used in light sheet (RI 1.44 - 1.50) | | | Nikon 20x/1.0 glyc | 43° | ~54° | cleared tissue confocal used in light sheet (RI 1.44 - 1.50) | |
| | Olympus 25x/1.0 glyc | 43° | 56° | cleared tissue confocal used in light sheet (RI 1.41 - 1.52) | | | Olympus 25x/1.0 glyc | 43° | 56° | cleared tissue confocal used in light sheet (RI 1.41 - 1.52) | |
