Necessary Experience When Using Microscopes

This article shares 9 tips for using a microscope to help you improve your microscopy skills. Some of these points might be things you’ve learned but forgotten over time, or if you’re new to microscopy, they will guide you in using the microscope better.

1. Clean the microscope thoroughly before use.

• You can’t get a clear field of view if your microscope is dirty, the light is dim, the objective lens is moldy, or the eyepiece is cloudy. Before you start using the microscope, take some time to clean it. Use a dry, clean gauze to wipe the objective lens and eyepiece. If there is mold, use xylene to clean it. Check the light source or clean the mirror (if you are still using a mirror for illumination, which is rare nowadays).

2. Prepare good specimens.

• No matter how good your microscope is, you can’t view anything clearly if your specimen is poor. For wet mount preparations, remember to cover the specimen with a cover slip. For viewing under the 100x objective lens, ensure that the specimen is dry and thin. Make sure to use the correct side of the slide for the 100x objective. Many users mistakenly view the wrong side; the side with the specimen should be the one facing the objective. If you see a field of view under the 10x objective but can’t see it under 100x, you might be looking at the wrong side.

3. Use good quality immersion oil.

• Immersion oil is crucial when using the 100x objective. It increases the refractive index of the medium. Without it, you can’t achieve a clear view. However, if the immersion oil is of poor quality, your view will be blurry or unclear. The oil should be transparent, viscous, and within its expiration date. Some places use yellow-colored oil, which is of poor quality and can damage the objective lens. Based on my experience, Merck immersion oil is a good choice. Remember to check the expiration date. Expired oil becomes thin, and the image will gradually become blurred, possibly even lifting the specimen off the slide.

4. Proper lighting.

• Lighting is the most crucial aspect of microscopy. To get a clear field of view, you need to choose the appropriate light intensity. Each objective lens requires a different level of light. Maximum light intensity isn’t always the best. Before viewing, determine which objective you will use and adjust the light accordingly. For the 10x objective, set the light to the lowest level by lowering the condenser and closing the diaphragm to 10x, with the light intensity at 1-2. For the 40x objective, set the light to medium by raising the condenser, opening the diaphragm to 40x, and setting the light to 4-5. After focusing, you can adjust the light intensity as needed. For the 100x objective, the light should always be at maximum, with the condenser and diaphragm fully open, and the light intensity at maximum.

5. Using the 10x objective.

• The 10x objective, combined with a 10x eyepiece, magnifies the specimen 100 times. This objective is used for fresh preparations of parasites in feces, preliminary evaluation of blood smears, and bone marrow samples. To focus: Place the specimen on the stage, rotate to the 10x objective, and adjust the light accordingly. Looking at the stage, raise it to the maximum height using the coarse focus knob. Look through the eyepiece and slowly lower the stage with the coarse focus knob until the field of view appears, then use the fine focus knob to sharpen the image. This should take no more than 10 seconds. My students usually take 8-9 seconds to achieve a clear view.

6. Using the 40x objective.

• This is the hardest objective to focus with, in my opinion. Proper lighting is crucial. There are two ways to achieve focus: directly with the 40x objective or through the 10x objective. Based on my experience, using the 10x objective first is much easier. Focus with the 10x objective as described above. Once focused, increase the light intensity, rotate to the 40x objective, and use the fine focus knob to sharpen the image. Remember, if you achieve focus with the 10x objective, you should be able to see the field of view when switching to the 40x objective with minimal adjustment. Never use the coarse focus knob at this stage as it might break the slide.

7. Using the 100x objective.

• The 100x objective is actually quite easy to use. There are two ways to achieve focus: through the 10x objective or directly with the 100x objective. I recommend using the direct method for quicker results. Place a drop of immersion oil on the slide where you want to view, place the slide on the stage, set the light to maximum, and rotate to the 100x objective. Looking at the slide, use the coarse focus knob to raise the stage until it touches the objective lens, then raise it slightly more so the objective lens slightly compresses (be careful not to break the slide). Look through the eyepiece and slowly lower the stage with the coarse focus knob until the field of view appears, then use the fine focus knob to sharpen the image. This should take no more than 15 seconds.

8. Observing the field of view.

• When observing the field of view to evaluate the specimen, depending on the type of specimen, you may need to scan the entire slide or just a part of it. However, you must move the slide in a zigzag pattern from left to right and from top to bottom until you have scanned the necessary area.

9. Use both eyes for viewing.

• This is the most common mistake among technicians. Many often use only one eye. A lot of people ask me how to use both eyes and what the advantages are. Microscopes are typically binocular, meaning they are designed for both eyes. Have you ever felt eye strain while using a microscope? If so, it’s likely because you were using one eye. Using both eyes makes viewing much more comfortable, the field of view clearer, and reduces eye strain. To use both eyes, start with the eyepieces spread apart, then gradually bring them closer. Initially, you’ll see two separate circles, which will gradually overlap into one. Ensure that you see only one circle with each eye by alternately closing each eye. If you still see one circle, you’ve got it. When done correctly, it feels like looking down a well, with a clear depth of field. It might take some time for your eyes to adjust, but practice makes perfect.

These are 9 tips for using an optical microscope. I hope this article will be useful for those who are working with microscopes. If you have any questions or comments, please feel free to respond here. Thank you for your attention.

DUC DUONG TECHNOLOGY SCIENCE  COMPANY LTD

Address: 1014/67 Tan Ky Tan Quy, Binh Hung Hoa, Binh Tan, HCM

Tel: (028) 3762 8042 - 3762 8043 - 3750 8514 - 3750 8793

Fax: 028 3762 8043

Email: ducduong@ducduongco.com

Website: www.ducduongco.com