Optical microscope

The optical microscope, also called a light microscope, is a tool that uses visible light and lenses to make small objects look bigger. It is the oldest type of microscope, invented in the 1600s. Optical microscopes help scientists and students see very tiny things that are too small for the naked eye.

Objects are placed on a stage and can be looked at through one or two eyepieces on the microscope. Different objective lenses can be chosen to make the object look bigger or smaller. Some microscopes, like the stereo microscope, can make objects look three-dimensional. A camera can also be used to take a picture of what is seen, called a micrograph.

Lighting is important for seeing objects clearly. Clear objects can be lit from below, while solid objects can be lit from the front (bright field) or the side (dark field). Special lighting, such as polarised light, helps study certain materials. Phase-contrast imaging can make very small details easier to see by highlighting differences in how light passes through the object. Optical microscopes can usually see objects as small as around 200 nanometers, but they cannot see smaller than this because of the diffraction limit of visible light. For even bigger magnification, scientists use other kinds of microscopes such as scanning electron microscopy, transmission electron microscopy, and scanning probe microscopy.

Types

There are two main types of optical microscopes: simple microscopes and compound microscopes. A simple microscope uses the optical power of one lens or a group of lenses to make things bigger, like a magnifying glass. A compound microscope uses many lenses to make things look much bigger. It is the most common type used in modern research.

Compound microscopes can have different lenses that you can change for different sizes. They can also use special lighting, like phase contrast. There are other types of microscopes for special jobs, like stereo microscopes that show samples in three dimensions. There are also digital microscopes that connect to a computer so you can see images on a screen.

Main article: Digital microscope

History

See also: History of optics and Timeline of microscope technology

The first simple microscopes were single lenses used to make objects look bigger. People used these lenses as early as the 13th century, when eyeglasses were common. The compound microscope, with more than one lens, appeared in Europe around 1620. No one knows for sure who invented it first.

Antonie van Leeuwenhoek made small, simple microscopes in the 1600s. These let him see very tiny objects clearly. It took many years for compound microscopes to work as well as his simple ones. In the 1850s, John Leonard Riddell made the first microscope that you could look at with both eyes.

Today, microscopes use special lighting. In 1893, August Köhler created a lighting method that makes images clearer. Later, Frits Zernike invented phase contrast lighting in 1953. This helped scientists see live cells clearly without staining them. Fluorescence microscopy, which uses special light to highlight parts of cells, is now very important for studying biology.

Components

All modern optical microscopes have the same basic parts that help them show tiny objects up close.

The main parts of an optical microscope include the eyepiece, which is the lens you look through, and the objective lenses, which are close to the sample and gather light. There are also focus knobs to move the stage up and down, a stage to hold the sample, and a light source to shine light on the sample. Other parts like the condenser help focus the light properly. These parts work together to make small objects look bigger so we can see them clearly.

Operation

Main article: Microscopy

Optical microscopes use light to show tiny details that we cannot see with our eyes alone. They shine light on objects in different ways to make small parts more clear. Some ways include using special light that shows hidden patterns or using dark lighting to make certain parts stand out.

Modern microscopes can do more than just show pictures. They can help scientists study how some materials glow under special light, look closely at surfaces, and even measure tiny colors and patterns in a sample. These extra tools need special parts added to the basic microscope.

Applications

Optical microscopy is used in many important areas, such as microelectronics, nanophysics, biotechnology, and mineralogy. It helps scientists study very small objects and materials.

It is also used in medical diagnosis, especially in histopathology for looking at tissues, and in smear tests for examining cells. In factories, binocular microscopes are popular because they help reduce eye strain during long use. Some microscopes are made to look at objects from far away, which is useful when the object might be dangerous or behind a window. Measuring microscopes help scientists make precise measurements, and small portable microscopes are useful when a full lab microscope is not available.

Limitations

Optical microscopes cannot show very tiny details very clearly. When you look at something very small, it can look like a fuzzy circle with rings around it, called an Airy disk. How well a microscope can show two close points as separate depends on the type of light used and how good the lenses are. There is a limit to how small things can look clearly, called the diffraction limit.

Scientists have found ways to see even smaller details than this limit. Special methods help improve how clearly things look. In 2014, three scientists won a big award for making microscopes that could see extremely tiny parts, even single molecules. These advances let us study things at a level that was once thought impossible.

Alternatives

Scientists have made special tools to see even smaller things than regular light microscopes. These tools use different kinds of waves. Some of these tools are the atomic force microscope, scanning electron microscope, scanning ion-conductance microscopy, scanning tunneling microscope, transmission electron microscopy, and X-ray microscope.

These microscopes can see very tiny details because they use waves that are shorter than visible light. But they often need special conditions, like vacuums, so it’s hard to look at living things. They also can’t show colors, but they help scientists study very small parts of materials.