Microscopy

• Microscope


  An instrument which provides an enlarged image of minute objects such as sub cellular structures that are generally not visible to the naked eye

  
• Microscopy


  The science of investigating small objects and structures using a microscope

  
• Microscopy


  1. Produce a magnified image of the specimen

  2. Separate the details in the image

  3. Render the details visible to the human eye or camera

  
• The word "microscope" is formed of two Greek words: "micros"- small and 'skipein'-to look
• The complexity of microscopes has increased from simple lens to complex scanning electron microscope since its invention
• Zoocharia Jansen used second lens that enlarged imaged formed by first lens by 50-100X

  1590
• The Arab Alhazan described the use and characteristics of glass lenses

  11th century
• Eye glasses were invented

  Late 1200s
• Telescope was invented, with Galileo improving upon it with his own models

  1608
• Microscope was invented possibly by Hans and Zacharias Jansen

  Around 1600

  
• The first known image of a microscope is a drawing by Isaac Beeckman

  1631

  
• Robert Hooke published the book "MICROGRAPHIA" with the first big microscope (with 200X maximum magnification)

  1665

  
• Anton van Leeuwenhoek provided improved microscope and was first to observe unicellular animal

  1673

  
• Ernst Ruska invented electron microscope which can magnify as much as million times

  1931

  
• Types of microscopes

  • Light Microscope
  • Electron Microscope

  
• Light Microscope

  • Uses light source for illumination of specimen
  • Commonly used light sources include sunlight, UV light, laser light, LEDs

  
• Types of Light Microscopes

  • Simple dissecting microscope
  • Compound microscope
  • Stereomicroscopes
  • Bright field microscope
  • Dark field microscope
  • Phase contrast microscope
  • Fluorescence microscope

  
• Simple Microscope

  Consists of a biconvex lens that can be moved up and down, with the object placed on a platform and light focused by a concave mirror

  
• Compound Microscope

  Has 2 sets of lenses - an objective lens of short aperture and focal length, and an eyepiece lens of larger aperture and focal length

  
• Stereo-Microscope

  Allows for binocular (two eyes) viewing of larger specimens, produces a three dimensional (3-D) visualization, used for dissections and close work

  
• Interference Microscope

  Used for quantitative studies of macromolecules and cell components
• Inverted Microscope

  Has the light source and condenser set up high above the stage and pointing down, with the objectives and objective turret located beneath the stage pointing up

  
• Electron Microscope

  Uses electrons instead of light, can magnify up to a million times but cannot view living cells

  
• Parts of a simple microscope

  • Mechanical parts
  • Optical parts

  
• Optical parts of a simple microscope

  • Mirror
  • Lens
  • Eyepiece
  • Diopter adjustment
  • Body tube
  • Arm
  • Coarse adjustment
  • Fine adjustment

  
• How a microscope works

  1. Light from the illuminator passes through the aperture, through the slide, and through the objective lens, where the image of the specimen is magnified

  2. The magnified image continues up through the body tube to the eyepiece, which further magnifies the image the viewer sees

  
• Magnification

  The total magnification is the ocular (eyepiece) magnification multiplied by the objective magnification
• Light microscopes use lenses to bend and focus light rays to produce enlarged images of small objects

  
• Workings of a Light Microscope

  1. The specimen is mounted on a slide and positioned in the specimen stage

  2. A beam of light is focused on the specimen by the condenser

  3. The objective lens picks up the light transmitted by the specimen and produces the first magnified image

  4. The eyepiece lens further magnifies the image

  
• Applications of Light Microscope

  • Study of preserved minute specimens
  • Study of activities inside cells
  • Identifying macromolecules of cells
  • Medical diagnosis
  • Histopathological studies

  
• Workings of Light Microscope (LM)

  1. Specimen mounted on slide and positioned in specimen stage

  2. Beam of light focused on specimen by condenser

  3. Objective lens picks up light transmitted by specimen and produce first magnified image

  4. Eyepiece lens further magnifies the image

  
• Light Microscope (LM)

  • Used to study preserved minute specimen
  • Used to study activities inside the cell
  • Used in identifying macromolecules of cell
  • Used in Medical diagnosis
  • Used in histopathological studies

  
• Workings of Compound Microscope

  1. Light transmitted and focused by mirror and condenser

  2. Focused light illuminates the object or specimen

  3. Refracted light collected by objective where primary image is formed

  4. Eyepiece further magnifies the primary image

  
• Magnification


  Total magnification is objective lens magnification power multiplied by ocular lens magnification power
• Resolution

  Ability to distinguish that two objects are separate and not one, determined by wavelength of light entering objective lens
• Oil Immersion


  1. Immersion oil placed between glass and objective lens

  2. Enhances resolution by preventing light rays from dispersing and changing wavelength
• Applications of Light Microscope (LM)

  • Observation of morphology of microorganisms
  • Detection of cell structures
  • Observation of intracellular structures
  • Observation of motility
  • Measurement of size
  • Observation of blood smears
• Bright-Field Microscopy

  • Forms dark image against bright background
  • Resolving power limited by wavelength of illuminating beam
  • Resolution determined by physical parameters like wavelength and light generating power

  
• How image is formed in Bright-Field Microscope

  1. Light from illuminated specimen focused by objective lens creating enlarged image

  2. Ocular lens further modifies the primary image

  3. Total magnification is objective magnification multiplied by eyepiece magnification

  
• Advantages of Bright-Field Microscope

  • Commonly used to view live and immobile specimens
  • Staining required for transparent or colorless specimens