Optical: The beam from a light source is focused onto a sample and either the transmitted or scattered light is collected by an objective lens and the image is magnified onto a camera or to the observers eye. The resolution can be down-to about 200 nm, and the microscopes can be fairly cheap, small and easy to use.
Transmission Electron Microscope (TEM): The beam from an electron source iluminates a sample and transmitted and scattered electrons are collected by an objective lens and the image is magnified onto a camera or on a flu screen. The resolution can be down-to about 0.05nm.
Scanning Tunnel Microscope (STM): Electrons from a very bright electron source are focused onto a very sample that has a voltage applied to it. When the tip-sample distance becomes so small that the electron clouds of the tip and sample touch, electrons can much more easily tunnel between the two and this gives rise to a tip-sample current (often a few pA at a 1V bias voltage). This current can be used to maintain a fixed tip-sample distance when the tip is scanned over the sample, and this can give images of conducting surfaces with atomic resolution.
Scanning Near-field Optical Microcsope (SNOM): As electrons can tunnel between electrical conductors, photons can tunnel between optical guiding structures. The SNOM used a narrow light guide to measure how the optical electromagnetic field changes as the guide is moved across the sample. Light can be sent from below the sample and then scattered into the scanning light guide above it. The resolution can be much smaller than the wavelength of light.
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Overview of the different types of microscopes: *Optical: The beam from a light source is focused onto a sample and either the transmitted or scattered light is collected by an objective lens and the image is magnified onto a camera or to the observers ey
Overview of the different types of microscopes: *Optical: The beam from a light source is focused onto a sample and either the transmitted or scattered light is collected by an objective lens and the image is magnified onto a camera or to the observers ey