Microscopy: An Introduction

Microscopy Overview

• Microscopes visualize minute objects in science laboratories, providing magnified contrasting images.
• Microscopes use lenses for magnification.
• Lens power varies.
• Types include light, dark-field, phase contrast, electron, and fluorescent microscopes.

History

• Zacharias Janssen, a Dutch spectacle maker, created one of the earliest compound microscopes around 1600, using two lenses.
• "Microscope" comes from the Greek words "mikrós" (small) and "skópéō" (look at).

Structural Parts

• Microscopes have three structural parts: the head, arm, and base.

Head

• The cylindrical metallic head holds the eyepiece lens and connects to the nose piece.
• The head is also called a body tube or eyepiece tube.
• It connects the eyepiece lens to the objective lens.

Arm

• The arm connects the base to the head and eyepiece tube.
• The arm supports the head.
• The arm is a carrying handle.

Base

• The base is the lowermost part, supporting the entire microscope structure.
• The base provides stability.
• Illuminators, light switches, and electrical wiring are installed in the base.

Optical Parts

• Optical parts are used to view, magnify, and produce an image from a specimen on a slide.

Eyepiece

• The eyepiece (ocular lens) is closest to the viewer's eye.
• It is located at the top of the microscope.
• You look at the specimen through the eyepiece.

Eyepiece Tube

• The eyepiece tube is the eyepiece holder for monocular or binocular eyepieces, positioning it above the objective lens.
• Binocular microscope eyepiece tubes are flexible and rotatable.
• Monocular microscope eyepiece tubes are not flexible.

Diopter Adjustment

• The diopter adjustment knob changes the focus on one eyepiece in binocular microscopes.
• The diopter adjustment corrects vision differences between the viewer's eyes.

Nose Piece

• The nose piece is a movable circular structure that houses all the objective lenses.
• The nose piece is also called the revolving turret.
• The nose piece connects to the body tube above the stage.
• Rotating it clockwise or counterclockwise adjusts magnification.
• Changes in magnification occur by changing objectives.

Objective Lenses

• Objective lenses are closest to the specimen and fitted on the nosepiece.
• Standard microscopes have 3–4 objectives with magnifying powers such as 4X, 10X, 40X, and 100X.
• Objective lenses first receive transmitted light from the specimen, magnifying the image.
• Objective lenses are color-coded and different sizes.

Adjustment Knobs

• Adjustment knobs focus the microscope on the specimen.

Fine Adjustment Knob

• Fine adjustment knobs allow for careful focusing by moving the stage up or down very slowly.
• Fine adjustment knobs sharpen the image.
• They are used at high power.

Coarse Adjustment Knob

• Coarse adjustment knobs are for focusing the image under low power magnification.
• The larger knob rapidly moves the stage up or down.
• The stage is raised or lowered with a coarse adjustment knob.

Stage

• The stage is the section on which the specimen is placed for viewing, and has clips to hold slides.
• Common stages are mechanical with slide controls via knobs, rather than moving manually.

Stage Control Knobs

• Stage control knobs move the stage mechanically.
• One knob moves it left and right; the other moves it forward and backward.
• Stage control knobs allow users to move the slide in the field of vision.

Aperture

• An aperture is a hole in the microscope stage.
• The aperture transmits light from the source, which reaches the stage.

Microscopic Illuminator

• The illuminator is a light source within the microscope.
• Some compound microscopes use a mirror to reflect light.
• Other optical microscopes use low-voltage electric bulbs as a constant light source.
• Intensity and wavelength requirements determine bulb types.

Condenser

• Condensers are lenses focusing light from the illuminator onto the specimen.
• Condensers are found under the stage next to the diaphragm.
• Condensers ensure clear, sharp images, particularly at high magnification (400X and above).
• Higher magnification condensers provide clearer images.

Diaphragm

• The diaphragm is the iris, found under the stage, controlling light reaching the specimen.
• The diaphragm is an adjustable apparatus.
• The diaphragm controls light intensity and beam size onto the specimen.

Light Switch

• The light switch is an electrical control device.
• The light switch turns the illuminator on and off.

Brightness Adjustment

• The brightness adjustment system controls voltage to the light bulb.
• The brightness controls light bulb intensity.

Importance of Microscopes

• Microscopes are crucial in scientific research and daily life.
• Microscopes enable studies of microorganisms, cells, and tiny structures.
• Microscopes advance medicine, biology, and technology.
• Healthcare, forensics, and industries utilize microscopes.
• Healthcare, forensics, and industries use microscopes for disease diagnosis, quality control, and scientific discoveries.