It’s comparatively straightforward to know how optical microscopes work at low magnifications: one lens magnifies a picture, the following magnifies the already-magnified picture, and so forth till it reaches the attention or sensor. At excessive magnifications, nevertheless, that mannequin begins to fail when the characteristic dimension of the specimen nears the optical system’s diffraction restrict. In a latest video, [xoreaxeax] constructed a easy microscope, then designed one other microscope to beat the diffraction restrict with out lenses or mirrors (the video is in German, however with automated English subtitles).
The primary a part of the video goes over how lenses work and the way they are often mixed to amplify photos. The primary microscope was made out of digital camera lenses, and will resolve onion cells. The shorter the focal size of the target lens, the stronger the magnification is, and a spherical lens provides the shortest focal size. [xoreaxeax] due to this fact made one by melting a little bit of soda-lime glass with a torch. The image it gave was vague, however extremely magnified.
Apart from the dodgy lens high quality given by melting a shard of glass, at such excessive magnification a number of the indistinctness was brought on by the specimen performing as a diffraction grating and directing some mild away from the target lens. [xoreaxeax] visualized this by taking a collection of images of a laser shining by way of a pinhole at totally different focal lengths, thus getting cross sections of the sunshine discipline emanating from the pinhole. When repeating the process with a piece of onion pores and skin, it grew to become obvious that diffraction was strongly scattering the sunshine, which meant that some mild was being diffracted out of the lens’s discipline of view, inflicting element to be misplaced.
To get better the misplaced particulars, [xoreaxeax] eradicated the lenses and easily captured the interference sample produced by passing mild by way of the pattern, then wrote a ptychography algorithm to reconstruct the unique construction from the interference sample. This required many photos of the topic beneath totally different lighting situations, which a rotating illumination stage supplied. The algorithm was finally capable of get better a kind of picture of the onion cells, however it was lower than distinct. The truth that the lens-free setup was capable of produce any picture in any respect is nonetheless spectacular.
To see one other strategy to ptychography, try [Ben Krasnow’s] strategy to rising microscope decision. With an electron microscope, ptychography may even picture particular person atoms.
