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hardware:objectives [2020/07/28 12:03]
Jon Daniels [4f spacing] |
hardware:objectives [2022/10/07 11:25]
Jon Daniels [Magnification] |
| ==== Magnification ==== | ==== Magnification ==== |
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| Like all infinity microscopes, the magnification is given by the ratio of the effective focal lengths of tube lens and objective. Field of view is just camera sensor size divided by magnification. The sensor size is readily available. The most typical sCMOS cameras have 6.5um square dexels and the sensor comprises an array of 2048x2048 dexels ("dexel" is the more precise term for detection pixel). Other sensor sizes are being used; watch out for 11um square dexels which usually require increasing magnification in order to sample sufficiently for diffraction-limited resolution. | Like all infinity microscopes, the magnification is given by the ratio of the effective focal lengths of tube lens and objective. The captured fField of view is just camera sensor size divided by magnification. The sensor size is readily available. The most common sCMOS cameras have 6.5um square pixels and 2048x2048 pixels, but there are a wide variety of cameras. Some cameras have 11um pixels which usually require increasing magnification in order to sample sufficiently for diffraction-limited resolution. |
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| By default ASI uses 200 mm focal length tube lenses (Nikon glass) but a offers a [[http://asiimaging.com/docs/mim_ramm_vts#mim_tube_lenses_and_assemblies|variety of tube lenses]] so the magnification can easily be chosen otherwise. Typical reasons to adjust the magnification include to adequately sample on the camera (for sensors with larger pixels or using low-mag high-NA objectives) or to increase the field of view by intentionally spatially undersampling ((the main concern in this situation becomes vignetting, see http://asiimaging.com/docs/mim_ramm_vts#infinity_space_limitations)). | By default ASI uses 200 mm focal length tube lenses (Nikon glass) but a offers a [[http://asiimaging.com/docs/mim_ramm_vts#mim_tube_lenses_and_assemblies|variety of tube lenses]] so the magnification can easily be chosen. Typical reasons to adjust the magnification include to adequately sample on the camera (for sensors with larger pixels or using low-mag high-NA objectives) or to increase the field of view. When decreasing magnification, beware of the objective's intrinsic field of view (usually specified by field number, of vignetting (see http://asiimaging.com/docs/mim_ramm_vts#infinity_space_limitations), and ensure that the spatial sampling on the camera is sufficient (see https://asiimaging.com/docs/infinity_microscope_basics#spatial_sampling). |
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| Note that using Olympus objectives with Nikon tube lens will result in 1.11x increase in magnification. The [[http://asiimaging.com/docs/cleared_tissue_objective#magnification|effective focal length of the cleared tissue objective]] depends on the media refractive index. | Note that using Olympus objectives with Nikon tube lens will result in 1.11x increase in magnification. The [[http://asiimaging.com/docs/cleared_tissue_objective#magnification|effective focal length of the cleared tissue objective]] depends on the media refractive index. |
