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Sensory Information
Processing (2)
Introduction of image sensors
Topics

Outline of image sensors

History of image sensors
• Cameras and photography
• Broadcasting, movie and video
• Electronic / digital imaging

Components of image sensors
• Optics, imaging device, signal line, capture

Approximation of image sensor
• Geometry of the camera
History of photography
１８３９ daguerreotype (silver plate)
 １９００ roll film
 １９３５ color film
 １９３２ 35mm film still camera(Leica)
 １９３０-５０ rangefinder cameras
 １９５０-６０ SLR (Single lens reflex) camera
 １９６０-７０ auto exposure
 １９７７ autofocus
 １９９５ digital camera (casio QV-10)
..mainly not for image quality improvement,
but just for convenience

Rangefinder camera（1940-1960)
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Rangefinder camera (1958, 2000)
SLR(1959)

Focusing screen
(ground glass)
What you see is what you get!
Electronic / Digital imaging
Difference between film and digital
camear is only at imaging device
 Ex. Digital SLR / film SLR

What matters for image
quality?

For convenience



cost
Small / light
Do up-to-date cameras
have high performance
in image quality?



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
8bit quantization
Number of Pixels
Cheap, small lens
Imaging sensor vs.
film
Compression (JPEG)
Lens for aerial survey : Aviogon
(1952, design by L. Bertele)
Field of view : 96 deg
Distortion : under 0.008%
Broadcasting / video
NHK
１８８４ mechanical scan TV
 １８９７ Braun tube
歴史
 １９２５ Invent of TV broadcast
 １９３０ Invent of imaging tube
 １９５１ Development of VTR
 １９５３ NHK started TV broadcast
 １９６０ Color TV broadcast in Japan
 １９８５ CCD Video camera for consumer
 ２０１１ Analog broadcast discontinue

I/O of image(side talk)
Braun tube
1843 : prototype of facsimile
Both transmitter / receiver have
synchronized pendulum with needle
for readout / recording
Imaging tube
Projectors and cameras
CCD
lens
LCD panel
Condenser lens
lens
Light source
Very similar construction
What is the key for image
quality?
Camera is generally just a box
 There is no much variation for CCD or
film  Lens is the key for photograph


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You are already satisfied by the
number of pixels, but not for image
For the geometric measurement, the
lens is the key for preciseness

Most lens has the distortion around 12%
Camera
How the image is recorded electrically?
What is the artifact of CCD?
How to select the CCD?
CCD
CCD driver /
Signal processing
Digital
Capture
lens
What is principal parameter of the lens?
What is aberration?
What is the image degradation by lenses?
How to select the lenses?
Camera
How the Synchronize and
Sampling is performed?
CCD
CCD driver /
Signal processing
Digital
Capture
lens
How to drive the CCD?
How the color value is recovered?
What is the ideal image
sensor?

Similar image should be captured for the plane
perpendicular to the optical axis

No distortion

No defocus (blurring)
Pinhole camera

Image is formed through small “pinhole”
Pro : There is rigid Geometric relationship
between the subject and image
 Con : image is too dark (to slow)

What is the lens?
lens
Image sensor / film
Collect enough light on the image sensor
 For measurement, image should be similar
to the pinhole camera as possible

No distortion, sharp picture
 It is impossible by simple single lens
 No defocus (trade-off with the speed)

Ideal lens
h

The image is similar to the subject

Geometric condition
• No distortion
• No image unsharpness

Photometric condition
• The lightness is uniform
aberration
Components of imaging
optics

Lens system
Mostly ３～１０ elements
 >20 elements for zoom lens
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Aperture
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Nikkor
deal the trade-off between light and defocus
Example of the lens
Combination of varied type and shape of the lenses
Why we need many elements?

For correcting monochromatic aberration
Thin lens with high index glass
 Thick lens with low index glass


There are some differences
for aberration even if
the focal length is same
For correcting chromatic aberration
White light
Longitudinal chromatic
aberration of single lens
C spectrum(red)
d spectrum(green)
F spectrum(blue)