sensory information processing (2)
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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 - PowerPoint PPT PresentationTRANSCRIPT
Sensory Information Processing (2)
Introduction of image sensors
Topics
Outline of image sensorsHistory 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)
Rangefinder camera (1958, 2000)
finder
Double image
base
line
SLR(1959)
What you see is what you get!
Focusing screen(ground glass)
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? 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 degDistortion : under 0.008%
Broadcasting / video
1884 mechanical scan TV 1897 Braun tube 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
歴史
NHK
I/O of image(side talk)
1843 : prototype of facsimileBoth transmitter / receiver have synchronized pendulum with needle for readout / recording
Imaging tube
Braun tube
Projectors and cameraslens
CCD
lensLCD panel
Light source
Condenser lens
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 photographYou are already satisfied by the
number of pixels, but not for image For the geometric measurement, the
lens is the key for precisenessMost lens has the distortion around 1-
2%
Camera
CCD driver / Signal processing
DigitalCapture
CCD
lens
What is principal parameter of the lens?What is aberration?
What is the image degradation by lenses?How to select the lenses?
How the image is recorded electrically?What is the artifact of CCD?
How to select the CCD?
Camera
How to drive the CCD?How the color value is recovered?
How the Synchronize and Sampling is performed?
CCD driver / Signal processing
DigitalCapture
CCD
lens
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 imageCon : image is too dark (to slow)
What is the lens?
Collect enough light on the image sensor For measurement, image should be similar
to the pinhole camera as possibleNo distortion, sharp picture
It is impossible by simple single lensNo defocus (trade-off with the speed)
lens Image sensor / film
Ideal lens
The image is similar to the subject Geometric condition
• No distortion• No image unsharpness
Photometric condition• The lightness is uniform
h
aberration
Components of imaging optics
Lens systemMostly 3~10 elements>20 elements for zoom lens
Aperturedeal the trade-off between light and defocus
Nikkor
Example of the lens
Combination of varied type and shape of the lenses
Why we need many elements?
For correcting monochromatic aberrationThin lens with high index glassThick lens with low index glass
For correcting chromatic aberration
There are some differencesfor aberration even if the focal length is same
White lightF spectrum
(blue)
d spectrum(green)
C spectrum
(red)
Longitudinal chromatic aberration of single lens