The objective lens is one of the most important parts of a microscope, since it determines its basic performance and function. Yet, these precision pieces of optical equipment are often not well understood.

Here, we break down the anatomy of an objective lens into easy-to-understand terms and discuss the common parts that make up an objective.

4 Core Components of a Microscope Objective Lens

While objective designs vary based on factors like their intended purpose, microscopy method, aberration correction, and manufacturer, all microscope objectives share some similar characteristics. Here are four common components to know:

1. Barrel: The physical outer housing of the objective body. It is made of brass with a typical parfocal distance of 45 mm.
2. Screw threads: Threads are used to mount the objective to the microscope nosepiece. They are typically sized to the Royal Microscopical Society (RMS) standards for compatibility with various microscope systems.
3. Lenses: A microscope objective may contain a single lens, which is typically made of glass, or a complex internal lens system made up of many lens elements. This system may include several types of lenses, including:
   • Meniscus and hemispherical lenses: A meniscus lens contains two spherical curved surfaces, convex on one side and concave on the other. When combined with a hemispherical lens, they work together to capture light rays and improve the numerical aperture.
   • Lens triplets and doublets: Put simply, a lens triplet is a compound lens that consists of three individual lenses. A lens doublet is two simple lenses paired together.
   • Single lens element: A single lens on its own.
   • Lens spacers: These are spacers that sit between the lenses.
   • Internal lens housing: As the name implies, this structure houses the internal lens system.
   • Objective rear aperture: A hole or opening where light enters the objective.
4. Inscribed specifications: The objective barrel’s surface is inscribed with specifications, such as the numerical aperture (NA) and magnification. The immersion medium and magnification are also color coded on the outer barrel. This label helps you quickly identify the objective’s capabilities at a glance and determine whether it’s suited to your application. To learn more about common objective specifications, read this resource next.

In addition to these core components, some objectives include a spring-loaded retractable assembly to protect the front lens elements and specimen from collision damage.

Keep in mind, objectives with more optical corrections for aberrations and flatness typically contain many lenses. For instance, sophisticated plan-apochromatic objectives have about 15 lens elements—while common achromatic objectives contain significantly fewer lenses.

The Potential of Modern and Advanced Objective Lens Designs

Knowledge is power when it comes to objective lenses. Many objective designs require you to make a tradeoff in one area of performance when you improve another. However, advances in objective technology enable our latest optical designs to overcome this common limitation.

For instance, Olympus X Line objectives are packed with many ultra-thin convex and concave lenses to offer exceptional flatness, aberration correction, and numerical aperture in one lens system. The result? Bright, high-quality images throughout the field of view.

To discover the right objective for your application, use our objective finder or reach out with any questions.

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