Printer Friendly

Chapter 6: microscopy review.

General Discussion

This module is intended as a guide to familiarize the trainee with the operating theory and care of microscopes used in the laboratory. Emphasis is placed on proper illumination, calibration and preliminary observations made with stereomicroscopes and polarized light microscopes (PLM), which are the instruments typically used first in any fibrous evidence examinations.


Upon satisfactory completion of this training module, the trainee will have developed and demonstrated theoretical knowledge and/or practical skills to:

1. understand microscope optics;

2. properly operate and maintain each microscope and its accessories including adjustments, cleaning and diagnosing problems;

3. establish proper microscope illumination including adjustment for Kohler illumination;

4. calibrate the ocular micrometer, and acquire proper measurements utilizing ocular and stage micrometers; and

5. select appropriate microscopes and accessories for the observational task required.

Training Steps and Check Lists

1. Reading Assignments: Complete Chapter 6 reading assignments listed in Appendix I.

2. Basic Skills

3. Practical Exercises: Complete these exercises located in Appendix II.

6-1 Familiarization with the Stereomicroscope

6-2 Familiarization with the Compound Light Microscope

Part 1 Kohler Illumination

Part 2 Basic Micrometry and Calibrating an Ocular Micrometer

6-3 Familiarization with the Polarized Light Microscope

Part 1 Refractive Index by Becke Line Observations

Part 2 Observation of Extinction Positions and Interference Colors in Crossed Polars

Competency Evaluation

The trainee shall be evaluated by quizzes on theoretical knowledge and basic practical skills as specified in the module objectives. The quizzes should include practical skills questions such as measuring fiber dimensions of length and diameter.

Practical Examination A: Trace Evidence Detection, Collection and Preservation

The trainee should be given simulated case materials to screen for trace evidence. This competency test is to be general in nature and should not cover fiber examination analytical techniques. The trainee should have the skills to perform generalized trace evidence searches and collections upon satisfactory completion of the practical examination.

Basic Skills in Microscopy:                        D     P    C

1. operating, adjusting and cleaning a microscope

2. centering stages and objectives

3. setting up Kohler illumination

4. measuring with ocular and stage micrometers

5. observing relative refractive index by Becke line

6. distinguishing isotropic and anisotropic substances

7. determining extinction positions

8. observing interference colors

9. taking photomicrographs
COPYRIGHT 2005 Federal Bureau of Investigation at
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2005 Gale, Cengage Learning. All rights reserved.

Article Details
Printer friendly Cite/link Email Feedback
Publication:Forensic Science Communications
Geographic Code:1USA
Date:Apr 1, 2005
Previous Article:Chapter 5: casework familiarization/search and recovery.
Next Article:Chapter 7: fiber examinations/preliminary observations.

Terms of use | Privacy policy | Copyright © 2020 Farlex, Inc. | Feedback | For webmasters