Microscope

• Microscope


  High precision optical instrument designed to produce magnified visual or photographic images of objects too small to be seen with the naked human eye

  
• Microscopy


  • To get a magnified image, in which structures may be resolved which could not be resolved with the help of an unaided eye

  
• Magnification


  The ratio of the size of an object seen under microscope to the actual size observed with unaided eye
• Total magnification


  Calculated by multiplying the magnifying power of the objective lens by that of eye piece
• Resolving power


  The ability to differentiate two close points as separate
• The resolving power of human eye is 0.25 mm
• The light microscope can separate dots that are 0.25µm apart

  
• The electron microscope can separate dots that are 0.5nm apart

  
• Imaging Techniques


  • Optical Microscopy
  • Confocal Microscopy
  • Transmission Electron Microscopy (TEM)
  • Scanning Electron Microscopy (SEM)
  • Atomic Force & Scanning Tunneling Microscopies (AFM/STM)

  
• Imaging Techniques


  1. Light Rays

  2. Coherent Light Source (Laser)

  3. Electrons

  4. Molecular Mechanical Probes
• F.H Janssen & Z.Janssen constructed the first simple compound light microscope -10x to 30x


  1590

  
• Robert Hooke developed a first laboratory compound microscope

  1665

  
• Anton Von Leeuwenhoek developed a first simple microscope with a magnification of 200x – 300x


  1672

  
• Anton was the first to see and describe bacteria, yeast, plants, and life in a drop of water- He is called as Father of microscopy
• The term microscope was coined by Faber


  1623

  
• The first electron beam microscopes were developed which were a breakthrough in technology as they increased the magnification from about 1000x or so up to 250,000x or more


  Early 1930's

  
• Light Microscopes


  A type of microscope that uses visible light and magnifying lens(es) to enlarge specimen

  
• Types of Light Microscopes

  • Monocular (one ocular lens)
  • Binocular (two ocular lenses)

  
• Types of Light Microscopes

  • Simple Optical Microscopes
  • Compound Optical Microscopes

  
• Simple Optical Microscope

  A microscope that uses a single lens for the magnification of the sample

  
• Compound Optical Microscope

  A microscope that has more than one lens, with a combination of lenses and two optical parts known as an objective lens and an eyepiece or ocular lens

  
• Stereo Microscope/Dissecting microscope

  A special type of light microscope that enables the viewer to see the sample in 3-dimensions, with a magnification power ranging from 10x to 80x, primarily used to inspect large specimens

  
• Types of Light Microscopes (technique)

  • Bright field Light Microscope
  • Phase Contrast Light Microscope
  • Dark-Field Light Microscope
  • Fluorescence Light Microscope

  
• Contrasting techniques

  • Brightfield
  • Darkfield
  • Phase contrast
  • DIC
• Electron Microscope

  A microscope that uses a beam of accelerated electrons as a source of illumination, with a high resolution of images and able to magnify objects in nanometres

  
• Ernst Ruska (1906-1988), a German engineer and academic professor, built the first Electron Microscope in 1931

  
• Types of Electron Microscope

  • Transmission Electron Microscope (TEM)
  • Scanning Electron Microscope (SEM)

  
• Parts of a Compound Light Microscope

  • Ocular Lens or Eye piece
  • Diopter Adjustment
  • Body tube (Head)
  • Arm
  • Coarse adjustment
  • Fine adjustment
  • Nosepiece
  • Specimen or slide
  • Stage
  • Stage clips
  • Stage height adjustment (Stage Control)
  • Aperture
  • On/off switch
  • Illumination
  • Diaphragm
  • Condenser
  • Base

  
• Ocular Lens or Eye piece

  The eyepiece consists of a series of lenses mounted in a tube (barrel) at the upper end of the microscope, with a basic function to look at the focused, magnified image projected by the objective lens and magnify that image a second time before your eye looks at the image of the specimen