Microscope

• Microscope

  • is an instrument used to see objects that are too small for the naked eye.
• Properties of a Microscope

  A good good microscope should have at least three properties:

  1. Good resolution
  2. Good contrast
  3. Good magnification
• Good resolution

  Resolution power refers to the ability to produce separate images of closely placed objects to distinguish two separate entitles.
• Unaided eye - 0.2 mm (200um)

  Light microscope - 0.2 um

  Electron microscope - 0.5 nm
• Immersion Oil - has a higher refractive index than air, and the use of oil enhances the resolution power of a microscope
• Good contrast

  • Contrast is improved by staining the specimen.
  • When the stain bind to the cells, the contrast is increase
  • Ex. Wright's stain, Lugol's iodine, Giemsa stain, Papanicolaou
• Good magnification

  Lens/Objectives

  Ocular Lens - 10x

  Scanning objectives - 4x

  Low power objective (LPO) - 10x

  High power objective (HPO) - 40x

  Oil Immersion objective (010) - 100x
• Total magnification of a field is the product of the magnification of objective al lens.

  • Total Magnification = Ocular lens magnification X objective magnification
• TYPES OF MICROSCOPE

  The following are the types of microscopes

  • Bright field microscope
  • Dark field microscope
  • Phase contrast microscope
  • Fluorescence microscope
  • Electron microscope
• Bright field Microscope

  • Light microscope forms a dark image against a brighter background, hence the name bright field.
• Structure:

  3 divided groups

  1. Mechanical part
  2. Magnifying part
  3. Illuminating part
• Bright field Microscope

  Principle:

  • The ray emitted from the light source pass through the iris diaphragm and fall on the specimen.
  • The rays passing through the specimen is gathered by the objective and a magnified image is formed.
  • The image is further magnified by the ocular lens to produce the final magnified virtual image.
• Mechanical Part

  • Head - This is also known as the body. It carries the optical parts in the upper part of the microscope.
• Mechanical Part

  • Base - It holds the various part of microscope, such as the light source, the fine and coarse adjustment knobs. It acts as microscopes support.
• Mechanical Part

  • Arm- This is the part connecting the base and to the head and the eyepiece tube to the base of the microscope. It gives support to the head of the microscope, and it is also used when carrying the microscope it holds the microscope, and it connects the ocular lens to the objective lens.
• Mechanical Part

  • Mechanical stage - The arm bears a stage with stage clips to hold the slides and the stage control knobs to move the slide during viewing.
  • It has an aperture at the center that permit light to reach the object from the bottom.
• Magnifying Part

  • Ocular Lens - the arm contains an eye piece that bears an ocular lens of 10x magnification power.
  • A microscope with two eyepiece is called binocular microscope.
• Magnifying Part

  • Objective lens - the arm also contains the revolving nose piece that bears three to five objective lenses of different magnifying power.
• Illuminating Part

  • Condenser - it is mounted beneath the stage which focuses a cone light on the slide.
• Illuminating Part

  • Iris diaphragm - It control the light pass through the condenser.
• Illuminating Part

  • Light source - it may be a mirror or an electric bulb.
• Illuminating Part

  • Fine and coarse adjustment knob - They sharpen the image.