Differences

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--- multi-immersion_objectives [2025/09/19 15:42] – [Location of Back Focal Plane] added 57-12-5 jon
+++ multi-immersion_objectives [2026/10/07 14:18] (current) – [Known Safe Media] jon
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 All of these objective lenses have been designed with large working distance.  A unique feature is that the working distance is exactly the same for all media.
-For most objective lenses, the WD depends on the medium's RI due to refraction at the objective/media surface.  Realizing this was going to be a practical issue we specifically designed both objectives to have uniform WD for all RI.  The optical implementation of this feature is straightforward: the first element of the objective is concave with radius of curvature centered on the focal plane.  Thus to first order there is no refraction at that surface and hence the WD is constant for all RI.  For the same reason, there is no intrinsic spherical aberration as the medium RI changes, unlike objective lenses with a flat first surface.
+For most objective lenses, the WD depends on the medium's RI due to refraction at the objective/media surface.  Realizing this was going to be a practical issue we specifically designed all of these objectives to have uniform WD for all RI.  The optical implementation of this feature is straightforward: the first element of the objective is concave with radius of curvature centered on the focal plane.  Thus to first order there is no refraction at that surface and hence the WD is constant for all RI.  For the same reason, there is no intrinsic spherical aberration as the medium RI changes, unlike objective lenses with a flat first surface.
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 Per optical simulations for the 54-10-12 objective lens, the location of the back focal plane referenced to flange is approximately 31.07 mm - 38.80 mm * RI + 9.42 mm * RI^2 (negative inside flange).  Specifically, this is ~4  mm inside the flange for water, ~5.4 mm inside the flange for FocusClear, and ~6.5 mm inside the flange for ethyl cinnamate (RI 1.56).
-Per optical simulations for the 54-12-8 objective lens, the location of the back focal plane referenced to flange is approximately -11.75 mm - 22.90 mm * RI + 5.87 mm * RI^2 (negative inside flange).  Specifically, this is ~31.8  mm inside the flange for water, ~32.5 mm inside the flange for FocusClear, and ~33.2 mm inside the flange for ethyl cinnamate (RI 1.56). The difference in back focal plane position between the two objectives depends on RI, but is to a good approximation the location is 27 mm deeper inside the objective for the 54-12-8 as measured from the flange, or 5 mm closer to the sample.
+Per optical simulations for the 54-12-8 objective lens, the location of the back focal plane referenced to flange is approximately -11.75 mm - 22.90 mm * RI + 5.87 mm * RI^2 (negative inside flange).  Specifically, this is ~31.8  mm inside the flange for water, ~32.5 mm inside the flange for FocusClear, and ~33.2 mm inside the flange for ethyl cinnamate (RI 1.56). The difference in back focal plane position between the 54-10-12 and 54-12-8 depends on RI, but is to a good approximation the location is 5 mm closer to the sample for the 54-12-8.
 Per optical simulations for the 57-12-5 objective lens, the location of the back focal plane referenced to flange is ~44.0 mm inside the flange for water and ~44.9 mm inside the flange for the design medium which is RC1.52.
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 The objectives have minimal spherical aberration in the NIR spectrum to allow for multi-photon excitation, though they are corrected chromatically only in the visible.  Internal anti-reflective coatings are optimized for visible, but it is possible to make a batch with coatings optimized for NIR (e.g. 800-1600 nm); contact ASI if you are interested in this possibility.
-Chromatic aberrations are rooted in dispersion, which describes how the exact RI changes with wavelength (commonly reported as the Abbe number).  For a specific medium the dispersion can be corrected, but since these objectives are designed to work in many media it cannot be perfectly corrected for all of them.  Chromatic correction could have been improved with a correction collar; this was deemed to add too much complexity for the corresponding benefit.  Hence, during the design we could only optimize the chromatic correction for one media, but it turns out that both TDE and CLARITY/Focus Clear are very well corrected for.  The middle dotted line on the plot below shows the approximate "perfect" correction line.  Chromatic aberrations can be categorized as lateral color, meaning different wavelengths have slightly different magnification, and axial color, meaning that the focus point is shifted slightly. These chromatic effects scale with the distance from the "perfect" correction line in the plot.  The lateral color for water, a rather extreme case as seen from the plot, amounts to ~0.3% change in magnification between 480 nm light and 640nm light for the 54-10-12.  We expect that the lateral color can be corrected in post-processing if needed. The axial color remains within the diffraction limit for all media simulated.
+Chromatic aberrations are rooted in dispersion, which describes how the exact RI changes with wavelength (commonly reported as the Abbe number).  For a specific medium the dispersion can be corrected, but since these objectives are designed to work in many media it cannot be perfectly corrected for all of them.  Chromatic correction could have been improved with a correction collar; this was deemed to add too much complexity for the corresponding benefit.  Hence, during the design we can only optimize the chromatic correction for one media, but TDE and CLARITY/Focus Clear are very well corrected for simultaneously. The middle dotted line on the plot below shows the approximate correction line used for 54-10-12 and 54-12-8, whereas the bottom line going through methyl salicylate was chosen for the 57-12-19 (i.e. emphasizing organic solvents).
+Chromatic aberrations can be categorized as lateral color, meaning different wavelengths have slightly different magnification, and axial color, meaning that the focus point is shifted slightly. These chromatic effects scale with the distance from the "perfect" correction line in the plot.  In the 54-10-12, the lateral color for water, (a rather extreme case as seen from the plot). amounts to ~0.3% change in magnification between 480 nm light and 640nm light.  We expect that the lateral color can be corrected in post-processing if needed. The axial color generally remains within the diffraction limit for all media for all the objectives but should be simulated if this is important.
 {{:documentation:abbenumber_vs_ri.png?300|}}
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   * water with salt, sugars, and/or other non-aggressive solutes including routine-use biological buffers
-  * FocusClear (CLARITY)
+  * FocusClear (CLARITY protocol)
   * glycerol
   * CUBIC-1, CUBIC-2, CUBIC-R1, CUBIC-R2
@@ Line 213: / Line 215: @@
   * TDE (2,2-thiodiethanol)
   * ECi (ethyl cinnamate)
-  * benzyl benzoate and BB-PEG (PEGASOS)
+  * PEGASOS (benzyl benzoate and BB-PEG)
-  * BABB
+  * BABB (benzyl alcohol and benzyl benzoate)
   * DBE (dibenzyl ether)
   * 100% ethanol
+  * DMSO (dimethyl sulfoxide)
+  * formamide
   * other proprietary organic media

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