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02.04.2012 | KeepLoop magnification and resolution

KeepLoop lens can’t be directly compared to a standard microscope lens. The main reason for this is the fact that it is only one part of a whole optical system, which is formed when our device is placed on top of the master device camera optics. Properties like focal length, f#, FOV (field of view) and optical power of the whole system are determined by the combination or our lens and the master device objective.

Optical magnification of the KeepLoop extreme-macro-lens in combination with the device camera objective has the approximate ratio of 1:2. This means that if the camera sensor has pixel size of e.g. 1.4 µm, the area that one single pixel sees on the imaged object is roughly double in size, 2.8µm. Aberrations in the whole optical system blur the image, so the actual resolution is much less than what would be expected from the theoretical optical magnification value alone. It is also not possible to reliably resolve features that fill only one pixel, as there is the possibility that the feature falls directly between two pixels and they both show the same information. Theoretically, two side-by-side pixels can be seen as adequate, but 3 - 5 pixels are needed for reliable outcome. In practice, the KeepLoop lens can resolve object features that are below 10 µm (0.01 mm) in size. The final resolution is determined by the pixel size and optical properties of the camera objective. Current high-end mobile cameras have smaller pixels (still above 1 µm) as well as better optics and the resolution with the microscope can be as good as ~6 µm.

As KeepLoop is used only for digital imaging, the magnification of our microscope is mainly determined by the display device. When the digital image recorded with the CMOS sensor is displayed on a larger screen, the final magnification is determined purely as the ratio between the imaged area on the object and the visible area on the screen. The extreme-macro-lens typically makes a good image over an area, which is between 2 – 4 mm wide and 1.5 – 3 mm high. Example: If an object area of 3 mm x 4 mm is imaged with the mobile microscope and the image is displayed with a 10” tablet, the magnification of the image is around 50x. But if the same image is displayed with a full HD projector showing a 100” image, the magnification can be as high as 500x. As the digital image is displayed on a big screen, the eye sees also the enlarged matrix of pixels. This means that the significant factor is not the magnification, but the quality of the optics and mainly resolution of the lens system.

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