The Compound Microscope - Helmut Hund GmbH

Outline 

• History of Microscopy 

• The Magnifying Glass 

• The Compound Microscope 

• Brightfield: Köhler Illumination 

we bring technologies together. optics – electronics – precision mechanics © Helmut Hund GmbH, 2008

Microscopy 

µικροσ µικροσ (mikros): small 

σκοπειν σκοπειν (skopein): to observe 


History of Microscopy 

• Well…: 

< 10000 BC 



• Zacharias Janssen (1580 – 1638): 

First Compound Microscope (1595) 



• Cornelis Jacobszoon Drebbel (1572 – 1633): 

1605: Experiments with lenses, 

magnifications 

• Robert Hooke (1635 - 1703): 

First two-lens light microscope, 

book “Micrographia”, 1655 



• Antoni van Leeuwenhoek (1632 – 1723): 

High-quality lenses, 

270-fold magnification, 

staining of specimens 



• Étienne-Louis Malus (1755 – 1812): 

Examined refraction of light and 

polarization 

• George Gabriel Stokes (1819 - 1903): 

Discovered light fluorescence, 

examined absorption of light 



• Ernst Abbe (1840 – 1905): 

1866: Cooperation with Carl Zeiss, 

1870: Formula for optical resolving power, 

1889: Carl Zeiss foundation 

∆x 

= 

NA 

Objective 

NA 

λ 

+ 

Condenser 



• Paul Ehrlich (1854 – 1915): 

Developed staining techniques 

for immunology further 

• Hans Christian Gram (1853 - 1938): 

Gram staining of bacteria 



• August Köhler (1866 – 1948): 

1893: PhD degree at University of Gießen, 

1894: Köhler illumination, 

1900: Started at Carl Zeiss 



• Frits Zernike (1888 – 1966): 

1930: Invents phase-contrast microscopy, 

1941: Industrialization (German Wehrmacht), 

1953: Nobel Prize for Physics 



• Marvin Minsky (1927 – ): 

1955: Confocal Laser Scanning Microscope, 

1956: Coined term “Artificial Intelligence” 



• Stefan W. Hell (1962 – ): 

2000: First published the STED microscope, 

2002: MPI Biophys. Chemistry, Göttingen 

2006: German Future Award 

Leica TCS STED 


The Magnifying Glass 

mm 

M 

f 

250 

= 

M ≤ 3 


The Compound Microscope 

Sketch! Microscope optics 

according to DIN: Distance 

mounting face objective – 

mounting face eyepiece 

= 160 mm 

(mechanical tube length) 



• Total magnification: 

M tot = M obj x M eyepiece 

• Example: 

Objective 100x, eyepiece 10x: 

M tot = 1000x 



Numerical aperture (NA) of an objective 

NA = n · sinα 



Numerical aperture (NA) of an objective: 

• “Useful magnification”: 

M useful 

M Museful, max = 1250 

= (500 … 1000) x NA 

• Resolving power (Abbe): 

∆x 

= 

NA 

Objective 

NA 

λ 

+ 

Condenser 



Magnification > Useful Magnif.? 

→ “Empty” Magnification 



Objective markings (DIN 58878) 



Objective markings (DIN 58878) 

Infinity-corrected optics: 

Parallel rays behind 

objectives. 

Required: 

Tube lens to form the 

real intermediate image. 



Objectives: Optical corrections 

• Achromats/Apochromats: 

Correction of chromatic aberrations 



Objectives: Optical corrections 

• (Semi) planachromats: “flat” images 

Feld: 

18 mm 

80 % Feld: 

15 mm 

60 % Feld: 

11 mm 



Illumination: Components 

Condenser 

Collector 



Illumination: Beam path 

The collector images the lamp filament onto the 

aperture diaphragm. 




Aperture diaphragm in condenser back focus: Rays from 

aperture diaphragm form parallel rays behind condenser. 




Distance condenser – specimen: field diaphragm gives 

sharp image in image plane. 


Alignment for Köhler Illumination 

Image of Field Diaphragm 

not 

centered 

not 

centered centered opened 



Köhler Illumination: Effect 



Köhler Illumination: Components 

• Field diaphragm 

• Height-adjustable condenser 

• Aperture diaphragm 

“Essential Requirements” in IVDD!!! 



Aperture (Condenser) Diaphragm 

• Important for Köhler illumination 

• When closed: contrast ↑, resolution ↓ 

aperture diaphragm 



Aperture (Condenser) Diaphragm 

• When closed: contrast ↑, resolution ↓

The Compound Microscope - Helmut Hund GmbH

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