Confocal Microscope Parts – Labeled Light Path Diagram

All 11 parts on the diagram

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Laser to specimen 7

Laser It makes the light that is sent to the specimen.
Objective lens It brings the laser beam to a point in the specimen. The returning light passes back up through it.
Dichroic mirror (dichromatic mirror) It reflects the laser beam and lets the emitted light pass.
Scanning mirrors They sweep the laser beam across the specimen, point by point.
Specimen The thing being imaged. It is usually labeled with fluorescent dyes.
Focal plane The one thin level of the specimen that is in focus.
Laser beam The light sent in. It makes one point of the specimen glow.

Specimen to detector 4

Pinhole A small hole that blocks out-of-focus light. Only light from the focal plane gets through it.
Photomultiplier tube (detector) It turns the light that passes the pinhole into an electrical signal.
Emitted light (fluorescence) Light given off by the lit point of the specimen. It travels back through the objective.
Out-of-focus light Light from above or below the focal plane. The pinhole plate stops it.

How this list was compiled: Every name checked on 2026-10-02 and kept only where at least two of these use it. (1) Wikipedia, Confocal microscopy, https://en.wikipedia.org/wiki/Confocal_microscopy : the pinhole in front of the detector that blocks out-of-focus light, point illumination by a laser, the focal plane, the specimen, the oscillating mirrors that scan the beam, the objective lens, the photomultiplier tube that turns the light signal into an electrical one. (2) A review article, Confocal Microscopy: Principles and Modern Practices, Current Protocols in Cytometry, 2020, read in the US National Library of Medicine's archive, https://pmc.ncbi.nlm.nih.gov/articles/PMC6961134/ (the text and the caption of its figure 1, Components of a confocal microscope): laser source, dichromatic mirror, objective lens, sample, scanning mirrors, excitation beam, emitted fluorescence, pinhole, out-of-focus light, photomultipliers, focal plane. (3) A microscope maker's primer, Introductory Confocal Concepts, https://www.microscopyu.com/techniques/confocal/introductory-confocal-concepts : laser, photomultiplier tube, scanning mirrors, pinhole aperture at the detector, dichromatic mirror, objective lens, specimen, plane of focus. The other name of the dichromatic mirror, dichroic mirror, is from a second review article in the same archive, Fluorescence Microscopy, Cold Spring Harbor Protocols, 2014, https://pmc.ncbi.nlm.nih.gov/articles/PMC4711767/ (the caption of its figure 4, Basic elements of a laser scanning confocal microscope: the laser light goes to the scan mirrors by way of a dichroic mirror, and the returning fluorescence passes through it), and from Wikipedia, Fluorescence microscope, and the Florida State University page Anatomy of the Fluorescence Microscope, https://micro.magnet.fsu.edu/primer/techniques/fluorescence/anatomy/fluoromicroanatomy.html . Labels, hints, detail lines and position notes were written for this site. Licence: own work

The drawing: Drawn for this site on 2026-10-02 from plain geometry; nothing traced. Licence: own work

How it works

The confocal microscope parts are named here on one light path: the laser, the dichroic mirror, the scanning mirrors, the objective lens, the pinhole and the photomultiplier tube. Tap a part to read what it does.

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From the laser to the specimen

The dichroic mirror turns the laser beam toward the scanning mirrors, and the objective lens brings it to one point on the focal plane. The scanning mirrors sweep that point across the specimen.

Specimen to detector

The lit point gives off light, which goes back through the objective lens and straight through the dichroic mirror. Light from the focal plane passes the pinhole and reaches the photomultiplier tube. Out-of-focus light lands on the plate beside the hole. A computer builds the picture point by point.

The laser beam and the emitted light share one path below the dichroic mirror, so the thin band is drawn inside the wide one.

Questions and answers

What are the parts of a confocal microscope?

A laser for the light, a dichroic mirror, scanning mirrors that move the beam, an objective lens, a pinhole in front of the detector, and a detector, most often a photomultiplier tube. A computer builds the image from the detector's signal.

What are the confocal microscope parts and functions?

The laser lights one point. The scanning mirrors sweep that point over the specimen. The objective lens focuses the beam and collects the light given off. The pinhole blocks out-of-focus light. The photomultiplier tube turns the remaining light into an electrical signal.

What does the pinhole do in a confocal microscope?

It lets through light that comes from the focal plane and blocks most light from above and below it. That is why a confocal image shows one thin level of a thick specimen sharply.

Why is it called a confocal microscope?

The lit point in the specimen and the pinhole in front of the detector share one focus. Light from that point comes to a point again exactly at the pinhole, and confocal means having the same focus.

What do the scanning mirrors do?

Only one point of the specimen is lit at a time, so the beam has to be moved to build an image. The mirrors swing to sweep the beam across the specimen in a pattern of parallel lines.