How Do Microscope Lenses Work?

Types of Microscope Lenses

Microscope lenses come in different types that vary based on the magnification’s power. Here are the types of microscope objective lenses.

Low Magnification Lenses

Low magnification objective lens typically ranges from 2x to 20x. Using a 10x or 20x eyepiece will magnify objects by 100x or 200x. This lens lets you view tiny specimens such as skin, hair, and fly legs. Furthermore, it has a yellow band that encircles the housing of the lens.

Utilizing this microscope objective lens is pretty simple. Firstly, you need to adjust the scanning lens to properly focus and center the specimen. Afterward, you need to turn the objective turret clockwise to face the low magnification lens. Lastly, re-center your specimen after you’ve fine-tuned the focus with the coarse focus knob.

Scanning Objective Lenses

This lens, in conjunction with the eyepiece lens, will provide the smallest magnification possible. For example, a microscope with a 10x eyepiece lens and a 4x objective lens will have a magnification factor of 40x. The magnification you get from this lens is similar to what you would from a stereo microscope, allowing you to study specimens like leaves and feathers. Also, the lens has a red band that encircles the housing of the lens. Scanning object lenses have low power and are typically used to scan a specimen before using higher magnifications.

Oil Immersion Lenses

Most basic microscopes do not come with an oil immersion lens, and this is because most leisure microscopy experiments do not require them. These lenses can reach up to 200x or more magnification with a 10x eyepiece lens and a 200x objective lens. You can find this lens by a white or cream-colored band around the lens.

Due to the difference between the glass slide and the refractive indices of air, a specific oil is required to help fill the space. Without this oil, the objective lens won’t function correctly. Hence, you won’t get the appropriate magnification and resolution, leaving you with too much distortion.

High Magnification Lenses

You can identify a high magnification lens by the blue band around the housing of the lens. Typically, compound microscopes come with a 40x lens. However, there are cases when this is not true. For example, you might buy a microscope with a high magnification lens of 60x or more.

This type of lens is usually used for smaller specimens, such as cells and bacteria, which cannot be seen with just the human eye. This includes molds, tardigrades, germs, and others.

How Do Microscope Lenses Work?

An optical microscope comes with lenses that change how rays of light travel through them. When light bounces off an object under a microscope and goes through the lens, it deflects toward the eye. This makes the item seem bigger than it is.

The simplest types of microscopes are magnifying glasses with a single convex lens (meaning both sides are curved outward). This kind of lens usually makes items look 5–10 times bigger by changing how the light gets into the human eye. Compound microscopes are used in schools, homes, and professional labs. They have at least two lenses that work together to magnify an image.

There is one lens above the object, called the objective lens. Also, there’s another one close to your eye (eyepiece). In some cases, each type of lens consists of various lenses. Compound microscopes can typically magnify by 10x, 20x, 40x, or 100x. However, you can find professional ones that can reach up to 200x magnification or more. There are also modern microscopes like the electron microscope for those who want higher magnification.

Specialized Lenses for Advanced Microscopy Techniques

You can purchase certain specialized microscope objectives when you want to perform advanced microscopy experiments. Here are some of the most common lenses to buy.

Long Working Distance (LWD) Objectives

Long-working distance objectives are made so you can see specimens even when they are farther away than usual. This is usually needed when a sample is stuck in a thick slide or is under a thick glass plate. 

Differential Interference Contrast (DIC) Objectives

The use of differential interference contrast (DIC) lenses in brightfield microscopy helps to visualize transparent samples better. By providing contrast without the need for staining, DIC objectives reduce the amount of staining performed. In most cases, a DIC lens will not be present on a compound microscope for school or home use.

Phase Contrast Objectives

Phase contrast microscopy makes translucent specimens easier to see by making the difference between the background and the foreground stronger. In a phase contrast objective, a black ring around the lens is used to control and translate changes in the phase of light rays into changes in their amplitude. In addition, the way the light rays are bent and focused gives the image seen through the eyepiece a lot of contrast.

Reflected Darkfield Objectives

A reflected darkfield objective works for darkfield microscopy. This technique produces a dark background with a strong contrast to aid in the visibility of translucent specimens. This object is designed to observe samples not dropped inside a covered slide. Reflected darkfield objectives typically have signs like BD, Neo, or BF/DF to help you identify them.

Conclusion

Microscope objective lenses work by changing how light goes through them. Essentially, when light shines on an object underneath a microscope, this light travels through the lens and bends toward your eyes, which makes the object bigger than it is. Remember that magnification power varies based on the type of lens and microscope, with magnification reaching 1000x and above. You can also find specialized objective lenses for advanced experiments.

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