Microscope objective lenses can be classified in several ways, including:
- By magnification
- By microscopy technique
- By lens shape
- By aberration correction
But most commonly, when talking about types of objective lenses we are referring to the different magnifications and purposes of the four most common types of microscope objective lenses on compound light microscopes.
Those four are:
- The scanning lens (4x)
- The low power lens (10x)
- The high power lens (40x)
- The oil immersion lens (100x).
Below I outline all the types of objective lenses based on the four above means of classification. First, I’ll start with the types of lenses based on magnification.
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The four most common types of Microscope Objective Lenses
The below lenses are the four most common magnification levels for objective lenses. You can get lenses with other magnification levels also.
Scanning Objective Lens (4x)
The scanning objective lens usually has 4x magnification and can be identified by a red strip band around the perimeter of the lens.
The scanning objective is designed for getting your bearings right before moving onto the low power lens. Its name, the ‘scanning’ lens, derives from the fact you are zoomed-out enough that you can scan around your specimen at this magnification level to prepare to move on to higher magnifications.
Using this objective, aim to:
- Achieve focus using the coarse focus knob.
- Center the specimen using your fingers or the mechanical stage.
A 4x magnification lens will usually achieve between 40x and 80x total magnification (with a 10x and 20x eyepiece respectively). This is the same sort of magnification that you’d get with a stereo microscope, and can provide close-up magnification of visible specimens such as feathers and leaves.
Low Power Lens (10x)
The low power objective lens usually has 10x or 20x magnification. You can identify it by a yellow strip around the lens housing.
This objective can be very useful for viewing prepared specimens on slides. It will achieve somewhere around 100x to 200x magnification for a 10x or 20x eyepiece respectively. This sort of magnification is great for viewing small specimens like:
- Fly legs
- Onion skin
- Brine shrimp
- Hair
- Skin
To use this lens, first start with the red striped scanning lens to achieve focus and center the specimen. Then rotate the objective turret clockwise to the yellow striped low power lens. Next, adjust the focus with the coarse focus knob to refine your focus and the mechanical stage to re-center your specimen.
High Power Lens (40x)
The high power lens is identifiable by a blue strip around the lens housing. Most compound light microscopes are sold with a 40x magnification high power lens, although this is not always the case. You may get a 32x or 60x magnification high power lens, for example.
The high power lens is used for looking at smaller specimens like bacteria and cells that are invisible to the naked eye. It’s commonly used for looking at:
- Mould
- Cells
- Germs
- Tardigrades
A 40x lens will achieve magnification of 400x when combined with a 10x eyepiece or 800x magnification with a 20x eyepiece. It is also very commonly used with 25x eyepieces to reach 100x magnification.
Oil Immersion Lens (100x)
Not all beginner level microscopes will have an oil immersion lens, and they’re not really necessary for most hobby microscopy experiments.
You can identify a 100x lens because it will have a white or off-white cream colored stripe around the lens housing.
These lenses are called ‘oil immersion lenses’ because you usually need to use them with oil in order to view your specimen. At higher magnifications achieved with a 100x lens, there will often be too much distortion in the final image. To address distortion at high magnification levels, you can use oil immersion.
Oil immersion is achieved by placing a drop of oil above your specimen, then rotating the 100x lens over the oil so the gap between the specimen and the lens is covered by oil rather than air. The light waves moving through the oil will experience less distortion than if they move through air.
Total Magnification of a Compound Light Microscope
To identify the total magnification that you will achieve on a microscope, you need to multiply the magnification of the objective lens with the magnification of your eyepiece. Most microscopes come with 10x, 20x, or 25x eyepieces.
Here are the common total magnifications you can achieve with common light microscope settings:
10x Eyepiece | 20x Eyepiece | 25x Eyepiece | |
4x Scanning Lens | 40x | 80x | 100x |
10x Low Power Lens | 100x | 200x | 250x |
40x High Power Lens | 400x | 800x | 1000x |
100x Oil Immersion Lens | 800x | 2000x | 2500x |
Specialty Objective Lenses for Advanced Microscopy Methods
There are some specialty objective lenses that you can also purchase for a microscope to conduct advanced microscopy methods. Four common specialty lenses are listed below.
1. Phase Contrast Objectives
Phase contrast is an advanced microscopy method designed to increase contrast for translucent specimens in order to make them more visible. A phase contrast objective has a dark ring around the lens to manipulate phase variations in light rays and convert them to amplitude variations. In simple terms, it manipulates light rays to deliver strong image contrast when looking through the eyepiece.
To conduct phase contrast methods, you need both a phase contrast objective and a specialized substage condenser.
2. Differential Interference Contrast (DIC) Objectives
Differential interference contrast (DIC) objectives are designed specifically to increase contrast of translucent specimens during brightfield microscopy. With a DIC objective, the need to use staining techniques is minimized as contrast can be achieved without staining.
A DIC objective is rarely found on a compound light microscope bought for hobby or school use.
3. Long Working Distance (LWD) Objectives
Long Working Distance objectives are designed to view specimens when the objective is a longer distance away from the specimen than usual. This is often required when a specimen is embedded in thick slides or below thick glass plates.
You can get other long working distance objectives such as LWD (Long Working Distance), ULWD (Ultra-Long Working Distance), and ELWD (Extra-Long Working Distance).
4. Reflected Darkfield Objectives
A reflected dark field objective is designed specifically for darkfield microscopy techniques. These techniques create a black background with high contrast to help to see specimens that are hard to see due to their translucency.
For a reflected darkfield objective, it is a lens structure also designed specifically for viewing specimens that are not placed within a covered slide.
You can tell you have a reflected darkfield objective because it will have demarcations such as Neo, BF/DF, or BD written on the objective. See here for more information on Reflected Darkfield Objectives.
Types of Objectives with Aberration Correction
1. Achromatic Lenses
Most microscope objectives are achromatic, to the extent that if there are no markings stating that they are not achromatic, you can assume that they are. In otherwise, this is the standard lens type. An achromatic objective normalizes red and blue light so they meet at the one focal point, while also correcting green light for spherical aberrations.
2. Apochromatic Lenses
These lenses are adjusted for blue, green, red and also deep blue. They are more expensive than chromatic lenses but also produce better high color images for the eye. They’re usually also spherically corrected for blue color aberrations.
3. Plan
Plan objective lenses are designed to correct for spherical aberrations to produce a crisp flat image. Plan corrections can be combined with other lens types, so you can have plan-achromatic, plan-apochromatic, etc. You can also have semi-pan objectives.
4. Infinity Corrected Lenses
Infinity corrected lenses allow for a theoretically infinite distance between the front and back of the objective. DIN standard objectives have a 160mm distance between the objective’s focal plane and back of the lens, and these lenses are often calibrated to perfectly align for that 160mm distance. By contrast, infinity correction projects a parallel light beam to the back of the objective. This is hard to explain, but easy to understand if you look at the diagram on this page.
Oil vs Dry Objectives
1. Dry Objectives
By default, compound light microscopes have dry objectives, meaning the space between the specimen and the objective is simply filed with air. Any objective with magnification under 100X you can assume is a dry objective unless otherwise marked.
2. Oil Immersion Objectives
100X objectives and above are often designed to allow for oil immersion. These are called ‘oil’ or ‘wet’ objectives. You can place oil in the space between the specimen and the objective so the light waves passing through that space pass through oil rather than air. This decreases distortion and leads to a higher quality image.
Oil immersion is often necessary at higher magnifications because of the physical limits of magnification. At super high magnifications, the light moving through air distorts too much to create a quality image. Oil immersion can minimize this issue.
Standards for Microscope Objective Lenses
1. DIN Standard
DIN is the international standard for objectives which regulates several elements of the objective, including the thread size. In practice, a microscope that accepts DIN standard objectives is incredibly versatile because you can buy replacement objectives without too much hassle. You just need to buy an objective that complies with DIN standards.
2. Color Bands
The color bands of objectives are more or less universal. They are:
- Red: 4x magnification
- Yellow: 10x magnification
- Blue: 40x magnification
- White: 100x magnification
There are other colors for less common objectives. See: objective lens color codes.
3. Numerical Aperture
You will find that the numerical aperture (NA) of the objective is usually demarcated on many objective lenses. Ensure you NA of the objective and that of the condenser are compatible for best quality image.
Conclusion
As you can see, there are many different types of objective lenses on microscopes. This list is by no means exhaustive, but does outline the common objective types that you will find on a regular compound light microscope in a school or home setting.
In reality, 90% of all beginner to intermediate experiments can be conducted with the four objectives you get out of the box – these are: the scanning objective, low power objective, high power objective and oil immersion objective.
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Chris Ramsay
Hi, I’m Chris and I run things around here! I share all my microscopy experiments, microscope information and tricks, how to guides, and microscope reviews in the articles on this site. Browse around to see what you like (I recommend the experiment ideas section) or connect with me on any of the social platforms listed below.
FAQs
What are the 3 types of objectives lenses? ›
Many microscopes will be equipped with a scanning objective (4x), a low power objective (10x), a high power objective (40x), and perhaps even an oil immersion objective lens.
What are the types of objective lenses? ›Objective lenses come in various magnification powers, with the most common being 4x, 10x, 40x, and 100x, also known as scanning, low power, high power, and (typically) oil immersion objectives, respectively.
What are the 3 different lenses on a microscope? ›Compound microscopes use three lenses are used to accomplish the viewing, the eyepiece lens, condenser lens and objective lens.
How many objective lenses are there? ›Objective Lenses: Usually you will find 3 or 4 objective lenses on a microscope. They almost always consist of 4x, 10x, 40x and 100x powers. When coupled with a 10x (most common) eyepiece lens, total magnification is 40x (4x times 10x), 100x , 400x and 1000x.
What are the 4 microscope objectives? ›Magnification: Your microscope has 4 objective lenses: Scanning (4x), Low (10x), High (40x), and Oil Immersion (100x).
How many objective lenses are on a microscope? ›How many objective lenses are on a microscope? Usually, you will find three or four objective lenses on a microscope, typically consisting of 4x, 10x, 40x, or 100x powers.
What are objective lenses explain? ›: a lens or system of lenses in a microscope, telescope, etc., that forms an image of an object.
What are objective lenses used for? ›Objective lenses are the lenses that directly observe the object the microscope user is examining. In stationary microscopes, the objective lens then focuses reflected light from the object up a tube toward the ocular lens, which is the lens the user looks through.
What are the lenses called on a microscope? ›The compound microscope has two systems of lenses for greater magnification, 1) the ocular, or eyepiece lens that one looks into and 2) the objective lens, or the lens closest to the object. Before purchasing or using a microscope, it is important to know the functions of each part.
What is the 4x objective lens called? ›Scanning Objective Lens (4x)
Its name, the 'scanning' lens, derives from the fact you are zoomed-out enough that you can scan around your specimen at this magnification level to prepare to move on to higher magnifications. Using this objective, aim to: Achieve focus using the coarse focus knob.
Which objective lens used first? ›
When using a light microscope it's important to start with the low power objective lens as the field of view will be wider, increasing the number of cells you are able to see. This makes it easier to find what you're looking for.
How many lenses are there? ›The two main types of lenses are: Convex Lens (Converging) Concave Lens (Diverging)
How many objective lenses are there in a compound? ›Objective lens- There is usually 3 or 4 objective lens in the microscope that has different powers. Also, they can magnify objects to a good resolution.
Which objective lens is the shortest? ›Types of Objective Lenses
A scanning objective lens that magnifies 4x is the shortest objective and is useful for getting a general overview of a slide.
While the modern microscope has many parts, the most important pieces are its lenses. It is through the microscope's lenses that the image of an object can be magnified and observed in detail.
What are microscope lenses made of? ›Lenses are made of optical glass, a special kind of glass which is much purer and more uniform than ordinary glass. The most important raw material in optical glass is silicon dioxide, which must be more than 99.9% pure.
What are the three objectives in a compound light microscope? ›Standard objectives include 4x, 10x, 40x and 100x although different power objectives are available.
Is objective lens concave or convex? ›The objective lens is a convex lens of short focal length (i.e., high power) with typical magnification from 5× to 100×. The eyepiece, also referred to as the ocular, is a convex lens of longer focal length.
What is objective lens and eyepiece lens? ›The objective lens or mirror collects light and brings it to focus creating an image. The eyepiece is placed near the focal point of the objective to magnify this image. The amount of magnification depends on the focal length of the eyepiece.
Where are the objective lenses attached? ›The revolving nosepiece is the inclined, circular metal plate to which the objective lenses, usually four, are attached. The objective lenses usually provide 4x, 10x, 40x and 100x magnification.
Which of the following lenses is the best choice for the objective of a microscope? ›
Solution : A microscope should have an objective of very small focal length and small aperture and an eyepiece of comparatively larger focal length and larger aperture. So lens `L_3` is to be used as objective and `L_1` as eyepiece.
Which type of lens is used in simple microscope? ›The convex lens used in a simple microscope produces a magnification of 5. The image is formed at the least distance of distinct vision.
Why does a microscope have two lenses? ›Why Do Compound Microscopes Use Two Lenses? The advantage of using two convex lenses when viewing a specimen is that the objective and ocular lenses work together to enlarge an image more than a single lens could.
What is the 40x lens also known as? ›OMAX 40X (Spring) Achromatic Objective Lens for Compound Microscopes.
What is a 10X lens also known as? ›Low Power Objective (10X): This next shortest objective is probably the most useful lens for viewing slides.
What is the difference between 4x 10X and 40x on a microscope? ›For example, optical (light) microscopes are usually equipped with four objectives: 4x and 10x are low power objectives; 40x and 100õ are powerful ones. The total magnification (received with 10x eyepiece) of less than 400x characterizes the microscope as a low-powered model; more than 400x as a powerful one.
What is objective lens magnification? ›Objectives typically have magnifying powers that range from 1:1 (1X) to 100:1 (100X), with the most common powers being 4X (or 5X), 10X, 20X, 40X (or 50X), and 100X.
What is a spring objective lens? ›Re: What İs Spring Objective
The objective is mounted below a spring inside a shroud or barrel and can move up and down inside the barrel, up with any physical pressure and down with spring pressure.
Microscope objectives are perhaps the most important components of an optical microscope because they are responsible for primary image formation and play a central role in determining the quality of images that the microscope is capable of producing.
WHAT IS lens short answer? ›A lens is a piece of transparent glass which concentrates or disperses light rays when passes through them by refraction. Due to the magnifying property, lenses are used in telescopes and other magnifying devices.
What are the 2 types of lenses? ›
Lenses may be divided broadly into two main types: convex and concave. Lenses that are thicker at their centers than at their edges are convex, while those that are thicker around their edges are concave. A light beam passing through a convex lens is focused by the lens on a point on the other side of the lens.
WHAT IS lens form? ›The relationship between the front and back surface curves of a lens is referred to as the lens form (or lens profile). A lens with a given focal power can be produced by many different lens forms, as long as the sum of the front and back surface powers remains constant—or at least nearly so (neglecting thickness).
What are 2 lenses in a compound microscope? ›There are two types of lenses that are used in the compound microscope: The objective lens is placed close to the object that needs to be examined. The eyepiece allows the image to be viewed. The eyepiece is also known as the ocular lens.
How many lenses are there in simple microscope? ›The simple microscope consists of a single lens traditionally called a loupe. The most familiar present-day example is a reading or magnifying glass. Present-day higher-magnification lenses are often made with two glass elements that produce a colour-corrected image.
How many lenses are used in light microscope? ›Devised with a system of combination of lenses, a light microscope consists of 2 optical elements, particularly the target lens and therefore the ocular lens. Usually, three or four objective lenses are used on a magnifier. They nearly always contain 4x, 10x, 40x, and 100x powers.
What is the 40x objective lens called? ›High Power Objective (40x): This objective (sometimes called the "high-dry" objective) is useful for observing fine detail such as the striations in skeletal muscle, the arrangement of Haversian systems in compact bone, types of nerve cells in the retina, etc.
What is objective lense? ›Definition of objective lens
technical. : a lens or system of lenses in a microscope, telescope, etc., that forms an image of an object.
Standard objectives include 4x, 10x, 40x and 100x although different power objectives are available.
What is the 4x objective lens called? ›Scanning Objective Lens (4x)
Its name, the 'scanning' lens, derives from the fact you are zoomed-out enough that you can scan around your specimen at this magnification level to prepare to move on to higher magnifications. Using this objective, aim to: Achieve focus using the coarse focus knob.
For example, optical (light) microscopes are usually equipped with four objectives: 4x and 10x are low power objectives; 40x and 100õ are powerful ones. The total magnification (received with 10x eyepiece) of less than 400x characterizes the microscope as a low-powered model; more than 400x as a powerful one.
What color bands are used on the 4x 10X 40X and 100X objectives respectively? ›
Red band for a 4x scanning objective lens, Yellow band for a 10x low power objective lens, Blue band is for a 40x high power objective lens, and. White band for a 100x oil immersion lens.
What color is the 4x objective lens? ›Color the 4X objective black. The second objective is the low-power objective (F), which is almost always made to produce a magnification of 10 times (10X). Color the low-power objective purple.
Which objective lens used first? ›When using a light microscope it's important to start with the low power objective lens as the field of view will be wider, increasing the number of cells you are able to see. This makes it easier to find what you're looking for.
Which lens is used in microscope? ›Microscopes use convex lenses in order to focus light.
What is objective lens magnification? ›Objectives typically have magnifying powers that range from 1:1 (1X) to 100:1 (100X), with the most common powers being 4X (or 5X), 10X, 20X, 40X (or 50X), and 100X.
What is the use of objective lens in microscope? ›The objective, located closest to the object, relays a real image of the object to the eyepiece. This part of the microscope is needed to produce the base magnification. The eyepiece, located closest to the eye or sensor, projects and magnifies this real image and yields a virtual image of the object.
How do you read an objective lens? ›Microscope objective lenses will often have four numbers engraved on the barrel in a 2x2 array. The upper left number is the magnification factor of the objective. For example, 4x, 10x, 40x, and 100x. The upper right number is the numerical aperture of the objective.
Where are objective lenses located? ›The objective lens of a microscope is the one at the bottom near the sample. At its simplest, it is a very high-powered magnifying glass, with very short focal length. This is brought very close to the specimen being examined so that the light from the specimen comes to a focus inside the microscope tube.
What is 40X magnification? ›A 40x objective makes things appear 40 times larger than they actually are. Comparing objective magnification is relative—a 40x objective makes things twice as big as a 20x objective while a 60x objective makes them six times larger than a 10x objective. The eyepiece in a typical desktop microscope is 10x.
What is 10X on a microscope? ›We all know that 10X means that the objective lens has an effective magnification of ten times life size and when combined in the compound with a 10X ocular lens will give a final magnification of 100X (10 X 10).
How do you use a 40X microscope? ›
Begin by turning your microscope on and adjusting the light intensity to about five or six then