Lighting Schemes The Heart and Soul of Imaging Quantitative Microscopy & Image Analysis Workshop.

Lighting Schemes

The Heart and Soul of Imaging

Quantitative Microscopy & Image Analysis Workshop

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Copyright: B. Pourdeyhimi - 2000

Image Representation

Analog

I ntrinsic

Sym bolic

Sem antic

I m age R epresentation

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Illumination Image Plane

Scene Image Formation Image Plane

X

Y

Camera

Image Formation and Geometry

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g x y z t( , , , , )


Energy emitted g (and/or reflected or transmitted) by the scene is

wherex, y, z = Geometric

coordinatel = Wavelengtht = Time

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f x y t T g x y z t( , , , ) ( , , , , )


The captured energy f is mapped onto image plane (also known as focal plane) according to the following relationship

Note key role of illumination in the g function

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g x y z t( , , , , ) f x y t( , , , )


Mapping is linear but not reversible

Mapping is characterized by Mapping geometry Ability to resolve small details Spectral “windows”

Image Formation

Not Reversible

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Imperfections of Imaging Systems

Image of infinitely small point is always a finite-size "blob". This is caused by Fundamental diffraction limit of imaging system Atmospheric turbulence Scatter

The finite size of blobs limits Image resolution Ability to discriminate points that are very close

to one another

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Camera

Radiance

Specimen

Raised feature

Annular dark card

Conical source

Directional Frontlighting

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On-axis Illumination

Camera

Collimated light

Object under inspection

Half silvered mirror

(Beam Splitter)

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45o45o 45o45o

Ring Light


Camera

Light Input

Ring Light

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Cavity

Ring Light Minimizes Shadows

Ring Light

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Shadow Formation - Light Size

Large ShadowNo Shadow

Light

Object

Light

Object

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Shadow Formation - Light Position

Large Shadow

Object

Light

Object

Light

Small Shadow

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Directed Darkfield Frontlighting


Camera

Directed Light

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Directed Brightfield Frontlighting


Camera

Directed Light

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Diffuse Lighting


Directed Light

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Diffuse Lighting - Hemispherical Enclosure

Lamp

Diffusing coating


Camera

Reflector/Baffle

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Diffuse Lighting Using a Box Enclosure

Shiny object

Baffles

Flood lampScattered light

Diffusing surface

Camera

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Camera

Object

Diffuser

Light

Backlighting

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Collimated Backlighting

Camera

Pinhole

Lens Lens

Object

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Condenser Lens

Lens

Object

Camera

Lighting Schemes The Heart and Soul of Imaging Quantitative Microscopy & Image Analysis Workshop.

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