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Selecting the best microscope objective

04-09-2019

One of the most important steps to purchasing a microscope that will provide the accurate imaging needed is selecting the right objective. There are hundreds of varieties of objectives on the market, which can make it tough to know where to start when it comes to selecting the best microscope objective for a specific application.

As an industry leader with over 100 years of expertise in the field, Nikon Metrology is here to help. No matter which industry, or type of microscope, there are a few questions to ask in order to get started and on the right path to proper microscope objective selection:

 

 

What is an objective?

Microscope objectives are one of 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. Objectives are also instrumental in determining the magnification of a particular specimen and the resolution under which fine specimen detail can be observed in the microscope.

 

How to select the right objective

To select the proper objective for an application, a few key questions need answering. These questions include, "How much working distance is needed?", and "How much magnification is required?". These aren't the only questions to ask, especially when working in a field that requires complex microscopy solutions, but it is a good place to start.

 


 

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How much working distance is needed?

Working distance is the amount of free space there is between the physical objective lenses and the in-focus object or specimen. Does the sample have relatively large Z height variance, or does it have small or negligible Z variations? For industrial applications when looking into a machined area such as slot, or drilled hole, an objective with a long working distance is required. Since it’s not possible to get the area of interest on the sample in close proximity to the microscope, an objective that can still provide a quality image, even as it's looking at the sample from farther away is needed. In applications where it is possible to examine the sample more directly, the objective won't need such a long working distance.


What is the finest detail that needs to be seen?

This question refers primarily to the Numerical Aperture (NA). Objectives with a higher NA typically have higher magnification, which allows you to see finer details of a sample with better resolution. For example, a microscope used in in semiconductor wafer applications will require a high NA. The components are exceptionally small, and the operator needs to see each component in great detail to determine the quality of each part. A microscope used for quality control in the machining industry will likely not need such a high NA, because the components are larger as well as the feature sizes. It should be noted that numerical aperture decreases as working distance increases.

 

What is the size of the object?

The objective lens is the first and most influential component of the microscope to magnify the image, Other components will contribute to the magnification. Nikon has objective lenses from 150x down to 1x, with field of view ranging approximately from 0.1 mm (0.0004) to 25mm (1”). As magnification increases, numerical aperture (NA) increases and working distance decreases.

Work with a Nikon microscope representative for the best selection. With answers to these questions in hand, it's best to speak with an expert who can help to determine the best options for each individual application. There are a number of microscope objectives to select from with many options for any given application. The best way to ensure that the very best objective is selected for each industry, application, or unique facility, is to speak to an expert.

It’s always important to request a demonstration before making a final decision. Nikon Metrology’s microscopy team works to best fit the objectives to each client's needs, in this way the highest performance is ensured from the objectives selected. This way, the client is able to see for certain that the objective chosen offers the quality imaging required before making an investment.

 


 

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