Scientists use confocal microscopes to obtain 2-D and 3-D images of samples. The microscopes are effective at eliminating background light, allowing them to see clean images with high resolution.
Background
The confocal microscope generates images based on the principle of fluorescence. When high-intensity light, such as a laser, shines on the sample, it emits a different colored light back. A photomultiplier tube detects the emitted light and sends it to a computer for analysis. Fluorescence can cause the entire sample to emit light, creating a background haze in the image.
Design
The clarity of images in a confocal microscope comes from a concept known as conjugate focal points, where its name is derived. The microscope has a set of lens through which light from the sample passes through. Images can be formed from different points, but only those coming from the focal point of the lens can be seen clearly. A screen with a pinhole is placed at the focal point of the objective lens, or conjugate point, effectively blocking out background light. This allows the viewer to focus only on light coming from the focal point.
Creating Images
Confocal microscopes can focus only on one point of the sample at any time. The microscope has to scan a series of points to generate an image. By scanning different points in multiple planes, the computer can reconstruct a 3-D image of the sample.
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