# Presentation: 197230

## Care and Use of the Bright Field Microscope

**Malaria parasite **

***Mycobacterium tuberculosis ***

## Importance of the Microscope

- Important for hematology, microbiology, TB, and malaria testing
- Compound microscope used in bacteriology, biology, and medicine to examine minute objects such as bacteria, other unicellular organisms, and plant and animal cells and tissue
- Advances in fluorochrome stains and monoclonal antibody techniques caused growth in use of fluorescence microscopy in both biomedical analysis and cell biology

## Basic Components of the Microscopeand their functions...

- Power switch

- Light intensity control

- Condenser

- Stage

- Objectives

- Eyepiece lens

- Stage motion control knobs

- Course and fine adjustments knobs

- Field diaphragm ring

- Aperture diaphragm

## Care and Maintenance of the Microscope

- Good preventive maintenance and care includes:
- Regular cleaning of oculars and objectives
- Avoid damaging oculars and other optics with eye make-up or other debris
- Careful handling to avoid abrupt motions
- Protect from direct sunlight, high temperature, humidity, dust and vibration
- Use appropriate materials to clean the lenses
- Cover when not in use with vinyl or plastic dust cover

## Cleaning the Microscope

- Routine Cleaning Supplies:
- Commercial lens tissue for optics
- Caution:  Do not use paper towels or other rough paper products
- Cotton swabs with wooden shaft (optics)
- 70% isopropyl alcohol
- Dilute methanol is satisfactory
- Mild detergent and soft cloth for stage and base of microscope

## Cleaning Oculars and Objectives

- Unplug the microscope
**Wash hands**
- Remove dust from optical glass surfaces
- Carefully remove eyepieces, objectives, condenser, and filters–one at a time
- Excessive rubbing can cause damage to iridescent coating on lens
- Clean and replace as completed
**Do Not** take eyepiece or objectives apart

## Unplug microscope and allow bulb to cool
Carefully place microscope on its side
Open bulb house; use tissue to remove bulb
Use tissue (to avoid fingerprints) to pick up new bulb 
Insert new bulb and close bulb house

- Carefully place microscope on its side
- Open bulb house; use tissue to remove bulb
- Use tissue (to avoid fingerprints) to pick up new bulb
- Insert new bulb and close bulb house

**Replacing Microscope Bulb**

## Plug in microscope and turn on illuminator.  Rotate nosepiece to lock 10X objective in place
Place smear on stage and center it under the 10X objective
Open the field diaphragm all the way and close condenser diaphragm all the way
Move up (rack up) stage to its highest position
Adjust the oculars for interpupillary distance so that only one circle of light is seen
Rack up condenser as high as possible

- Place smear on stage and center it under the 10X objective
- Open the field diaphragm all the way and close condenser diaphragm all the way
- Move up (rack up) stage to its highest position
- Adjust the oculars for interpupillary distance so that only one circle of light is seen
- Rack up condenser as high as possible

**Setting the Koehler Illumination**

## Setting the Koehler Illumination (continued)

- Close field diaphragm until diameter of illuminated image is smaller than the field of view
- Lower condenser with positioning knob until you have a sharp, focused image of the edges of the field diaphragm
- Adjust condenser using centering screws so that the circle of light is centered in field
- Open field diaphragm until illuminated image is just larger than the field of view.  If more light is needed, use the transformer.
- Koehler illumination is now set.  It is important not to move the condenser up or down or change the field diaphragm.

**Setting the Koehler Illumination ****(continued)**

## Operation of the Microscope – Examining Smears

- Put smear on stage and center it under the 10X objective
- Adjust intensity of the light to a comfortable level with the transformer
- Open condenser diaphragm about 70% to achieve a good balance of resolution and contrast
- Adjust oculars for interpupillary distance so that when looking with both eyes only one circle of light is seen

## Examining Smears (continued)

- Adjust sharpness of image by moving adjustment ring on adjustable ocular
- Once 10X focus is achieved, rotate nosepiece so that the 40X objective is in place
- Readjust the intensity of light to a comfortable level using the transformer
- Use the fine adjustment knob to focus up and down through the different planes of the field

## Microscope Problems – Troubleshooting 1 

**Problem**:  Black Field
**Possible Causes:**
- Microscope not plugged in
- Power not available at outlet
- Illuminator not turned on
- Bulb burned out
- Objective not clicked into place
- Condenser too low with diaphragms closed

## Microscope Problems – Troubleshooting 2 

**Problem**:  Field only partially illuminated
- Possible Causes:
- Objective not clicked into position
- Condenser not centered correctly
- Condenser too low
- Field diaphragms closed too much

## Microscope Problems – Troubleshooting 3 

-                   objective
- Possible Causes:
- Wrong objective in place
- Objective not screwed into place
- Not in correct plane of focus

**Microscope Problems – Troubleshooting 3 **

## Microscope Problems – Troubleshooting 4 

**Problem**:  Difficulty focusing with 40X
-                   objective
- Possible Causes:
- Not in correct plane of focus
- Not initially focused at 10X

## Microscope Problems – Troubleshooting 5 

**Problem**:  Blurry image at 10X or 40X
- Possible Causes:
- Dirty objective
- Dirty slide
- Dirty coverslip
**Problem**:  Ground glass appearance
- Possible Causes:
- Condenser too high

## Credits

**Thanks to STD/HIV Prevention Training Center of New England**
**in Collaboration with**
**State Laboratory Institute**
**and**
**National Laboratory Training Network, CDC**