Konfokale

Konfokale, in optics and microscopy, describes systems in which illumination and detection are focused at the same focal point to achieve optical sectioning. In practice, a confocal microscope uses a focused light beam to excite a small spot in the specimen and a pinhole in the detection path to reject out-of-focus light, producing sharp images of thin optical sections.

The core principle is that only light originating from the focal plane passes through the pinhole and reaches the detector, while light from above or below the plane is largely blocked. By scanning the focused spot across the sample and collecting signals point by point, a two-dimensional image is built. By acquiring images at successive focal depths, a 3D reconstruction of the specimen can be formed.

Typical components include a laser or other coherent light source, a high numerical aperture objective, a scanning mechanism (for point-scanning systems), a conjugate pinhole (often set to about 1 Airy unit), and a sensitive detector such as a photomultiplier tube. Computers control scanning, collect data, and render images. Variants of confocal systems include spinning-disk confocal microscopes, which use a disk with many pinholes to achieve higher acquisition speeds with parallel detection.

Performance characteristics depend on wavelength, objective NA, and pinhole size. Lateral resolution in visible light with high-NA objectives is typically around 200–300 nanometers, while axial (z) resolution is roughly 500–700 nanometers, better than widefield for optical sectioning but influenced by imaging conditions.

Applications span biology, medicine, and materials science, especially where thick specimens, live-cell imaging, or precise 3D reconstructions are needed. Limitations include reduced signal due to the pinhole, slower imaging for point-scanning configurations, and higher instrument cost and complexity.