Phase Contrast microscopes create images, without staining, by using refraction and interference caused by structures in a specimen. Structures that refract light appear dark against a bright background of unrefracted light. Structures that differ in refractive indexes will vary in levels of darkness.

Microscopy relies mostly on refraction, which is the change in direction of a light ray because it crosses into a new material.

Perception in Microscopy 

Light waves can interfere in two manners: in phase or out of phase. In phase light waves add their amplitudes (heights), whereas out of phase waves cancel each other out. 

Wave Interference 

-Brightfield Microscopes  
-Darkfield Microscopes  
-Phase Contrast Microscopes  
-Differential Interference Contrast Microscopes (DIC)    
-Fluorescence Microscopes  
-Confocal Microscopes  
-Two-Photon Microscopes  
-Electron Microscopy  
-Scanning Probe Microscopy

Types of Microscopes 

https://openstax.org/details/books/microbiology/

Microbiology covers the scope and sequence requirements for a single-semester microbiology course for non-majors. The book presents the core concepts of microbiology with a focus on applications for careers in allied health. The pedagogical features of the text make the material interesting and accessible while maintaining the career-application focus and scientific rigor inherent in the subject matter. Microbiology’s art program enhances students’ understanding of concepts through clear and effective illustrations, diagrams, and photographs.

Microbiology is produced through a collaborative publishing agreement between OpenStax and the American Society for Microbiology Press. The book aligns with the curriculum guidelines of the American Society for Microbiology.

OpenStax Microbiology Textbook

Phase Contrast Microscopes

After passing through either the specimen or an empty space, the light waves are recombined, and the specimen's alter the interference patterns formed. This produces high-contrast, 3-D images of living microorganisms. 

Differential Interference Contrast Microscopes (DIC)

Most commonly used microscope. Produces visuals of specimen as a dark image on a light background produced by an illuminator and focused by a condenser lens. The eye pieces can be either monocular or binocular. 

Brightfield Microscopes

Darkfield Microscopes are very similar to bright field microscopes except with the addition of an opaque light stop. It produces light images on a dark background, which is good for viewing specimens without staining. 

Darkfield Microscope

Produces 2-D images by scanning the z plane with a laser, which can be processed by computers to develop complex 3-D images, making this microscope especially useful in viewing biofilms and other compact specimens. 

Confocal Microscopes

Use of chromophores called fluorochromes to produce an image of a specimen in bright colors against a dark background.

Fluorescence Microscopes

Uses a scanning technique, fluorochromes, and long-wavelength light (such as infrared). Used to visualize specimens like biofilms and other specimens similar to confocal microscopes, but produces higher resolution.

Two-Photon Microscopes

Both scanning tunneling microscopes (STM) and atomic force microscopes (AFM) utilize an electric probe passed over the specimen to map out an image of the surface of it. 

Scanning Probe Microscopy 

Electrons can behave like a wave to produce higher resolution images than visible light due to their small wavelengths of 0.005nm. Can only be used on non-living specimens due to the preparation prior to viewing. 

Learn Before

Related