Compound Microscope and Its Forensic Applications

The term “compound” in compound microscopes refers to the microscope having more than one lens.
Devised with a system of combination of lenses, a compound microscope consists of two optical parts, namely the objective lens and the ocular lens.
A compound microscope is of great use in pathology labs so as to identify diseases.
Various crime cases are detected and solved by drawing out human cells and examining them under the microscope in forensic laboratories.
The presence or absence of minerals and the presence of metals can be identified using compound microscopes.
Students in schools and colleges are benefited by the use of a microscope for conducting their academic experiments.
It helps to see and understand the microbial world of bacteria and viruses, which is otherwise invisible to the naked eye.
Plant cells are examined and the microorganisms thriving on it can be ascertained with the help of a compound microscope. Thereby, a compound microscope has proved to be crucial to biologists.

1. COMPOUND MICROSCOPE AND ITS FORENSIC APPLICATIONS PARTH CHAUHAN M.Sc FORENSIC SCIENCE SESSION 2020 - 22 LNJN NICFS, DELHI

2. HISTORY Galileo Galilei (1609) Zacharias Janssen and Hans Janssen (1590) Robert Hooke (1670)

3. Working of Compound Microscope: A compound microscope works on the principle that when a tiny object to be magnified is placed just beyond the focus of its objective lens, a virtual, inverted and highly magnified image of the object is formed at the least distance of distinct vision from the eye held close to the eye piece.

4. Parts & Its Functions:

5. Mechanical Support System Stage Turret Base Base – Supports microscope Arm – supports the tube and connect it to the base. Turret – holding and rotation of objective lenses. Stage Mechanical stage – move back and forth the slide. Arm Body tube

6. Optical System Eye-piece Objective Eye-piece – 10x - upper eye lens Objective - 4x – scanning objective 10x – low power objective 40x – high power objective 100x – oil immersion objective

7. Illumination System Illuminator Condenser Diaphragm Illuminator – low voltage halogen bulbs as light source. Condenser - collect the light form the illuminator and focus onto the specimen Diaphragm – regulate amount of light passing through the central aperture.

8. Adjustment system Fine adjustment Coarse adjustment Coarse adjustment – raises / lowers stage to bring the image into focus Fine adjustment – bring image into sharp focus. Other components such as: Power switch, Stage stop, condenser adjustment Rheostat control knob

9. Specimen Slide Preparation

10. Standard Operating Procedure (SOP) :

11. Drawbacks and Limitations: It is tedious to stain the specimen before visualizing under the compound microscope. Use of coverslip may damage the specimen. Use of oil immersion may distort the image. Magnification capacity and resolution power is limited upto a certain limit.

12. Forensic Applications: Confirmatory examination of blood using compound microscope . Fig 1 : Takayama test (40x objective) Microscopic examination in field of Bank notes and security documents. Fig 2 : “RBI500” on Mahatma Gandhi’s portrait of 500 Rupee note Various crime cases are detected and solved by drawing out human cells and examining them under the microscope in forensic laboratories.

13. Fig 4: ‘Bharat’ Devanagari scripted in Hindi language printed on security thread of 2000 Rupee note Fig 5: ‘RBI’ Roman alphabet – English language printed on left collar of Mahatma Gandhi’s portrait of 2000 Rupee note Fig 6: ‘RBI 50’ Roman alphabet – English language and west Arabic scripted numbers printed on right collar of Mahatma Gandhi’s portrait of 50 Rupee note.

14. Fig 7: “KOTAKMAHINDRABANK” printed on the amount box of cheque of Kotak Mahindra Bank. Fig 8: “CANARABANK” printed on the amount box of cheque of Canara Bank.

15. Reference : P.R. DeForest , ‘‘Foundations of Forensic Microscopy’’, in Forensic Science Handbook , ed. R. Saferstein , Prentice - Hall Inc., Englewood Cliffs, NJ, Vol. 1, 1982 . https :// microbenotes.com/compound-microscope-principle-instrumentation-and applications /#:~:text=the%20stage%20opening ., Applications,the%20microscope%20in%20forensic%20laboratories . https://www.microscope.com/education-center/how-to-guides/mount-slides / https://www.ruf.rice.edu/~bioslabs/methods/microscopy/oilimm.html#:~:text=Attempting%20to%20use%20immersion%20oil,oil%20immersion%20lens%20into%20place.

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