Ostoskori Tuotteita: 0 | Hinta: 0.00€ | Koriin »


22.05.2012 | KeepLoop optical compatibility with mobile phones

KeepLoop microscope has been designed to work with most mobile devices that have a camera. Most of the small lenses that you find from miniature cameras of mobile phones, tablets or laptops have quite similar properties. Due to the strict size restrictions (mainly height) they all have focal lengths in the approximate range of 2 mm – 5 mm and the pupil sizes are between 0.5 mm and 2 mm. This similarity has made it possible for us to develop the universal extreme-macro-lens, which is the heart of KeepLoop device. The lens has been designed is such a way that there is lots of tolerance on the distance between the lens and camera pupil. This makes it possible to take pictures with cameras that are fairly deep inside the master device (e.g. Nokia N82) and with cameras that are positioned close to the back surface of the device (e.g. Samsung Galaxy S II). Optically the KeepLoop microscope is designed to work with all miniature cameras and the main challenge is how to attach the lens to the back of differently shaped devices.

As the master device cameras are not all the same, the features that determine the exact optical performance characteristics also vary. In order to test the compatibility of our microscope with different mobile phones, we conducted a trial where we used KeepLoop with eleven camera phones. The ultimate resolution test was to image a grating made for calibrating microscopes (Thorlabs' R1L3S2P 1 mm Stage Micrometer). The grating had a 1 mm scale divided into 100 line-pairs, which means that the widths of the single lines, and the spacing between the lines, was only 5 µm. The results showed that all of the 8MP cameras were able to resolve even the single lines, but there were clear differences on how reliable the imaging was. One example of images taken with Samsung Galaxy S II, Nokia N7 and iPhone 4S is shown below.

Some of the 5MP phones (e.g. Huawei U8800) were almost able to reproduce the grating image, but generally the sharpness was not as good and around 10 µm resolution can be expected with these devices. This is no surprise when the pixel mapping from the object to the image is taken into account. With the 8MP cameras, one image pixel corresponds to circa 2.5 µm feature size on the object, whereas with the 3MP - 5MP cameras one pixel is closer to 3 µm - 4 µm feature size. This difference means that when two 8MP camera pixels are put side-to-side they can be fitted inside those 5 µm grating lines, but with the 3MP - 5MP sensors this is not possible. The 8MP cameras are actually imaging the grating lines at the theoretical resolution limit (Nyquist frequency) of the image sensor. This also means that the signal processing made to the raw image is of high quality and the processing may actually explain the most of the resolution differences between cameras with the same pixel count.


‹ Takaisin
© 2012-2023 KeepLoop Oy - Toimitusehdot | Takaisin etusivulle