A low cost high resolution scanning aperture fluorescent microscope

Fluorescent microscopy is one of the most widely used tools in the life-sciences. The ability to tag molecules of interest and then localise their positions within two or even three dimensions provides a great deal of information about the underlying chemical and biological processes. However, many microscope are high cost, with expensive imaging optics and lasers illumination systems. We report on the development of the a novel low cost microscope designed for fluorescent imaging of tagged markers within live cells. The microscope is designed using low cost components and aims to give diffraction limited imaging. One of the major costs in a microscope its the optics, especially the objective lens that must provide a flat diffraction limited image. There have been a number of low cost microscopes developed in recent years that completely remove the objective and either directly cast a shadow of the object directly onto the CCD sensor or uses some diffractive process. However, these tend to be bright-field illumination microscopes. Lensless fluorescent microscopes are more difficult since a bandpass filter must be incorporated into the system. The physical size of the filter means the object will be too far away from the CCD sensor to achieve a good image. To overcome this we place a one to one imaging lens within the optical path, which then allows room for the filter. Since one to one lenses are symmetric, the aberrations tend balance out meaning they can provide good image quality with a simple low cost design. However, to achieve sub-micron resolution we introduce a pinhole array into the system which, by scanning can be shown to provide super-resolution images. The excitation illumination is provided by a high powered LED and the system imaged onto a standard CCD camera.