Contrast

Definition

Contrast in wave optics refers to the degree of difference in intensity between two points in an image. High contrast enhances the visibility of details by making light and dark areas more distinct.

5 Must Know Facts For Your Next Test

1. Contrast is crucial for differentiating structures in microscopy, especially when using techniques that exploit wave characteristics of light.
2. The contrast can be manipulated through various optical methods, including phase contrast and differential interference contrast microscopy.
3. Higher numerical aperture (NA) lenses typically provide better contrast by collecting more diffracted light.
4. Staining samples can artificially enhance contrast by increasing the intensity differences between structures.
5. Interference patterns produced by coherent light sources, such as lasers, can greatly affect the contrast observed in microscopic images.

Review Questions

• How does increasing the numerical aperture (NA) of a lens affect image contrast?
• What are two optical methods used to enhance contrast in microscopy?
• Why is staining often used to improve contrast in microscopic samples?

Related terms

Numerical Aperture (NA): A dimensionless number characterizing the range of angles over which a system can accept or emit light. Higher NA values result in better resolution and contrast.

Phase Contrast Microscopy: A technique that converts phase shifts in light passing through a transparent specimen to brightness changes in the image, enhancing low-contrast structures.

Differential Interference Contrast (DIC): An optical microscopy technique that uses interference patterns to enhance the edge contrasts of specimens without staining.