1. Bright field microscopy

1.1 Microscope setup
Make sure the microscope is well-maintained and functional. After turning on the light source (transmitted light), set the intensity to the right amount.

1.2 Specimen preparation
Prepare a thin section of the specimen, which is usually covered with a coverslip and mounted on a glass slide. If necessary, stain the specimen to improve contrast.

1.3 Objective selection
Select a brightfield objective lens based on the needs of your sample. Magnification (e.g., 10x, 40x) and numerical aperture (NA) are labels applied to objective lenses.

1.4 Sample placement
Stage clips should be used to hold the prepared slide in place on the microscope stage.

1.5 Kohler illumination
To achieve Köhler illumination, adjust the condenser so that the specimen is evenly and brightly illuminated.

1.6 Focus adjustment
To focus the specimen, adjust the coarse and fine focus settings.

1.7 Observation and imaging
Examine the specimen by looking through the eyepiece. For the best contrast, adjust the objective and condenser apertures. If desired, use a camera that is attached to the microscope to take pictures.

2. Dark Field Imaging

2.1 Microscope setup
Use a darkfield condenser with an opaque disc so that the specimen can only receive scattered or oblique light instead of direct light.

2.2 Sample preparation
Cut a thin section of the specimen as for brightfield microscopy.

2.3 Objective selection
Select a darkfield objective lens that is appropriate for the specimen. The darkfield condenser and darkfield objectives are intended to function together.

2.4 Sample placement
Stage clips should be used to hold the prepared slide in place on the microscope stage.

2.5 Condenser adjustment
Place the darkfield condenser correctly or insert it into the condenser turret. Make sure the condenser is adjusted so that the specimen only receives scattered light.

2.6 Focus adjustment
To focus the specimen, adjust the coarse and fine focus settings. The contrast produced by scattered light is essential to darkfield microscopy.

2.7 Observation and imaging
View the specimen under darkfield illumination through the eyepiece. For the best contrast, adjust the condenser and objective apertures. If desired, use a camera that is attached to the microscope to take pictures.

2.8 Changing specimens
Readjust the condenser and focus on each new specimen when you switch them out.

3. DIC microscopy

3.1 Sample Preparation

• Polish the sample: Metallurgical samples must be polished to a mirror finish using abrasive papers and diamond pastes to ensure a smooth surface.

• Etch the sample (if needed): Use a suitable chemical etchant to reveal grain boundaries, phases, or other microstructural features. Thermal etching can also be done.

• Clean the sample: Remove any residue using ethanol or distilled water and dry with air or tissue.

3.2 Set Up the Microscope

• Turn on the DIC microscope: Power up the light source and microscope system.

• Choose the correct objective lens: Select a suitable magnification (e.g., 10×, 20×, or 50×) based on the feature size to be observed.

• Ensure DIC optics are in place: This includes the polarizer, Wollaston prisms (or Nomarski prisms), analyzer, and appropriate DIC slider for the objective in use.

3.3 Place the Sample

• Mount the sample on the microscope stage using a sample holder or metal clip.

• Adjust the stage to bring the region of interest under the objective lens.

3.4 Focus and Align

• Use coarse and fine focus knobs to focus on the sample surface.

• Align the DIC prisms: Ensure proper alignment of the polarizer and analyzer to generate the interference contrast.

• Adjust shear direction: Rotate the DIC slider to optimize contrast depending on the feature orientation

3.5 Optimize Image Contrast

• Adjust prism offset (bias): This step controls the degree of shadowing and contrast—critical for highlighting subtle surface features.

• Modify light intensity: Too much or too little light can affect image quality; adjust the illumination for best visual contrast.

3.6 Observe and Document

• Observe the microstructure: Look for features like grains, inclusions, cracks, or surface roughness.

• Capture images: Use the microscope camera/software to take high-quality images for documentation or analysis.

4. Polarized Light Microscopy

4.1 Sample Preparation

• Polish the sample: Use SiC abrasive papers followed by fine diamond paste or alumina slurry.

• Etch the sample: Etching can help reveal grain boundaries or phase differences, but sometimes PLM can work on unetched samples, especially if you're analyzing birefringent phases or textures.

• Clean the surface: Use alcohol or acetone, then dry thoroughly.

4.2 Microscope Setup

• Use a polarizing optical microscope: It must be equipped with:

• A polarizer (below the sample) to generate plane-polarized light.

• An analyzer (above the sample) to detect changes in light polarization.

• Insert both polarizer and analyzer: The two are usually oriented perpendicular to each other (cross-polarized).

4.3 Place and Focus the Sample

• Mount the polished sample on the microscope stage.

• Focus the microscope on the surface using coarse and fine knobs.

• Use suitable magnification (e.g., 10×, 20×, or 50× objectives) depending on feature size.

4.4 Observe Under Crossed Polarized Light

• Rotate the stage: Slowly rotate the sample stage to see how light interacts with different grains or phases. Anisotropic grains will change brightness and color as the stage rotates.

• Identify features:

• Grain orientation differences: Grain contrast appears due to birefringence.

• Phase identification: Some phases may show unique colors or extinction angles.

• Stress patterns: Internal stresses can be detected in transparent or semi-transparent materials.

5. General tips:

5.1 Light intensity
Adapt the light intensity to the specimen's needs and the setup of the microscope.

5.2 Aperture control
Try varying the objective and condenser apertures to get the best contrast.

5.3 Image documentation
If a camera is available, use it to take pictures for documentation and analysis.