Introduction

The Series Polarizing Microscope with Halogen Lamp uses reflected and transmitted light to observe birefringent materials such as rocks and polymers. The halogen lamp is used as a light source, and a pair of polarizing filters produce polarized light. The polarizer is placed before the specimen, and the analyzer (a second polarizer) is fixed perpendicularly to the first polarizer.

Apparatus

The microscope is equipped with an eyepiece, eyepiece tube, blue and frosted filters, polarizer, and collector. It supports both binocular and trinocular heads that can be inclined at 30°. It comes with 4 achromatic objective lenses with different magnifications. In addition, it has a quadruple nosepiece sliding polarizing analyzer, 120 mm rotatable, and double layer mechanical stage with 75mm×35mm moving range which helps not only in moving the stage in a vertical direction but also along the horizontal axes. The coaxial coarse and fine focus system includes a minimum division of fine focusing up to 2 microns. An Abbe condenser is used to focus the light onto the specimen. Furthermore, a 6V 20W halogen lamp and a polarizer are used to illuminate the sample.

Principle

A pair of polarizers are used to produce the polarized plane light. The light coming from the halogen lamp passes through the first polarizer placed before the sample. Then it goes through the second polarizer known as an analyzer placed perpendicularly to it. The analyzer combines the different rays emerging from the specimen and produces the final images. 

Protocol

1. Connect the microscope to a power supply and turn it on.
2. Turn the turret until you obtain the desired objective.
3. Place the specimen on the stage and make sure your sample is well-protected by covering it with a coverslip.
4. Secure your slide with metal clips.
5. Slowly use the coarse adjustment knob while looking through the lens to bring your specimen into focus. Make sure that the slide doesn’t contact the camera’s lens at all.
6. Maximize the light output by adjusting the condenser.
7. Use the diaphragm beneath the stage to adjust the light.

Applications

The Series Polarizing Microscope with Halogen Lamp is used from basic imaging of pharmacological ingredients to morphology and optical crystallography. Böhme, Morales-Rivas, Diederichs, & Kerscher (2018) used a polarized microscope to study coarse structures having intrinsic optical anisotropic properties.

The series polarizing microscope is used in the processes of the homogenization of sugars, salt, flour, and developing photographic powders. It is also used in chemical preparations, precipitates, and the detection of adulterants and contaminants. Moreover, the polarizing microscope has just entered the dyes industry, where its usage is being considered for partly managing the manufacturing processes of intermediates and end products.

One of the most impressive uses of this microscope is the depiction of mineral development textures, alteration, and other internal textures that are not detectable by conventional analytical methods. With these findings, scientists can re-create the geological processes that led to mineral creation and subsequent modification in miniature.

Other uses of the microscope include studying unstained mammalian birefringent cochlear sections, which was conducted by researchers Kalwani et al. (2013). 

Precautions

1. Remove smudges from the lens using lens paper. Avoid using a cloth to apply pressure to the lenses since they are very delicate.
2. Keep your eyepiece clean by wiping it down with an alcohol-based wipe before you begin.
3. Glass slides should be handled with care. 
4. Turn off the microscope when it is not in use, it will extend its life.
5. Whenever you move the microscope, be sure you do it with two hands, one holding the base and the other the microscope’s arm.
6. Lower the nosepiece, switch off the light source, and lower the objective lenses before the string microscope. 
7. Keep the area surrounding your microscope clean and plan for preventive maintenance. 

Strengths and Limitations

Strengths

A plethora of aspects of the various birefringent materials may be studied using the Series polarizing microscope with halogen lamp, such as refractive indices, isotropic/birefringent characteristics, extinction, dichroic/polychroism opaqueness, and reflected light hues. Polarized light microscopy is a valuable technique for generating contrast in birefringent specimens and determining the characteristics of crystallographic axes in diverse materials. 

Limitations

Proper alignment of optical parts demands a skilled person. Another limitation of this microscope is that it can only be used to study anisotropic materials.

Summary

1. The Series Polarizing Microscope with Halogen Lamp uses reflected and transmitted light to observe birefringent materials such as rocks and polymers.
2. This microscope is equipped with an eyepiece, eyepiece tube, 4 objective lenses, nosepiece, polarizers, blue and frosted filters, Abbe condenser, Coaxial coarse/fine focus system, and collector
3. A pair of polarizers are used to produce the polarized plane light.
4. The microscope can be used in various applications from basic imaging of pharmacological ingredients to morphology and optical crystallography.
5. A plethora of aspects of various birefringent materials may be studied using the microscope, such as refractive indices, isotropic/birefringent characteristics, extinction, dichroic/polychroism opaqueness, and reflected light hues.
6. The microscope can only be used to study anisotropic materials.

References

1. Böhme, L., Morales-Rivas, L., Diederichs, S., & Kerscher, E. (2018). Crystal c-axis mapping of hcp metals by conventional reflected polarized light microscopy: Application to untextured and textured cp-Titanium. Materials Characterization, 145, 573–581. https://doi.org/10.1016/j.matchar.2018.09.024
2. Kalwani, N. M., Ong, C. A., Lysaght, A. C., Haward, S. J., McKinley, G. H., & Stankovic, K. M. (2013). Quantitative polarized light microscopy of unstained mammalian cochlear sections. Journal of Biomedical Optics, 18(2), 026021. https://doi.org/10.1117/1.jbo.18.2.026021‌