Camera Technology Basics Overview Basics of Camera Technology Saugaato Ray [email protected] Director &...
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Transcript of Camera Technology Basics Overview Basics of Camera Technology Saugaato Ray [email protected] Director &...
Camera Technology
Basics Overview
Basics of Camera Technology
Saugaato [email protected]
Director & CEOSATMAC INFOSYS LTD.
Camera Technology ConceptsImage acquisition, processing, encoding
– Lenses
– Raster scanning
– CCD technology
– Image processing
– Video signals
Output
Image
AcquisitionProcess Encoding
Light
LensLens
Optical Optical BlockBlock
ImagerImager
GainGainGammaGamma
Color BalanceColor BalanceWhite ClipWhite Clip
Enhancement Enhancement
Analog / Digital OutputAnalog / Digital Output
Format Format ConversionConversion
& Digitization
Image Acquisition
• Lenses
• Optical block
• Imager
Lenses
•Zoom/Focus Control
–Fixed – e.g.- SNC-P1.
–Manual => Vari-focal- eg- CS-50P, DF-40P.
–Auto Zoom and Focus –eg - SNC-RZ30P.
Imager
• Sensor– CCD / CMOS
• Scanning– Interlaced / progressive
CCD vs. CMOS
CCD CMOS
Advantage
* High sensitivity
* High Quality
* Low power consumption
* High speed read-out
* Smear-less
* Easiness of consolidating chip
* Low Cost
Disadvantage
* Smear
* External pulse for the drive
* Larger in size.
* More power consumption.
* Noisy
* Low Image Quality.
* Low Sensitivity.
CCD Imagers
• CCD’s (Charge Coupled Devices) made their first commercial appearance in a camera in 1981. It uses solid-state technology
• There are three types of CCD imagers viz IT (Interline Transfer), FIT (Frame Interline Transfer) & FT (Frame Transfer)
• FIT sensors are the most expensive to produce & are primarily used in high end broadcast cameras. Now Sony has IT CCD with technology which give better results as FIT.
Miniaturization and SensitivityU
nit
cell
area
[um
]2
Pixels
1/4TypeDiagonal 4.5mm
1/2TypeDiagonal 11mm
1/3TypeDiagonal 6mm
Larger the size of CCD, more is the Sensitivity.
The size of an imager greatly determines the overall potential quality of an image.
The larger the area of any given type of CCD, the better the image quality.
Imager SizeImager Size
The imager size is the
diameter of the circle
Scanning
odd lines
Field one
even lines
Field two
Frame
All linesInterlaced Scanning --- odd lines and even lines scanned separately
PAL Scanning
25 frames per second2 fields per frame
50 fields per second
625 lines per frame312.5 lines per field
Processing technology
• Exposure
• White Balance
• Gamma Correction
• Day / Night
• DynaView
Exposure
Exposure is affected by• Mechanical Iris• Electronic shutter
– CCD Iris [auto shutter function]
• Electronic gain
Dark Bright
AGC
Incoming
Iris
or
gain
leve
l
Mechanical IrisElectronic shutter
Electronic Shutter
Time
Exp
osur
e In
tens
ity
Shutter
Slow <<< >>> Fast
Exposure time
Electronic Gain
Gain-up Output signal level
6 dB 2 times
9 dB 3 times
12 dB 4 times
18 dB 8 times
24 dB 16 times
As the Gain increases, the S/N ratio decreases !!
~ Sample picture ~
24dB gain up0dB (no gain up)
AGC (Automatic Gain Control)
• Circuitry that automatically adjusts the electronic amplification of the video signal to compensate for varying levels of scene illumination.
White Balance
Levels BalancedLevels UnbalancedCombination of R, G & B gives White, properly balanced RGB levels
gives perfect white.
Picture Sample
Before After
Properly BalancedWhite Level ..
Gamma Correction
Light Directed onto Camera Imager
Light Directed onto Camera Imager
Display System Gamma
Display System Gamma
Camera GammaCamera Gamma
CRT Brightness
CRT Brightness
Day/Night Mode
B/W mode Color mode
<--- Automatic ---><----- Manual ----->
Remove IR Cut Filter
Sensitivity Improvement technology
• IR light has high content of heat. During daylight it hampers image of ccd.• IR filter comes in place during Daylight, cutting off IR spectrum.• At night it is automatically removed to improve sensitivity of CCD.
DynaView
DynaView = One picture at One picture at Normal Shutter picture + high speed shutter picture
Normal Shutter speed: 1/60 or 1/50
High speed: 1/500 ~ approx 1/8000
Camera show a high light picture with about x8~10 brightness.
Technology Definition Minimum Illumination
• A measure of the least illumination that will produce an image at the highest Gain of the camera with the lens aperture set to full open.– Minimum Illumination specifications will be affected
by the lens used.
– Because the highest Gain is used, the image quality is affected by lower S/N Ratio.
Technology Definition Resolution
• A measure of the ability to image picture detail.– Vertical Resolution is limited to the number of scan lines
that make up the image. This theoretical limit for a PAL Video signal is 483 lines.(525 Lines - 42 lines of the Vertical Interval)
– Horizontal Resolution is the number of alternating black and white lines which can be imaged across 75% of the width of the picture. (Assuming PAL Video with a 4:3 Aspect Ratio)
– Horizontal resolution increases with size of the CCD and with the number of CCD sensors used in the camera.
What is the difference
• Sensitivity
• Image Quality
• Why Larger Imager is good
• About Lens
• PAL / NTSC
Sensitivity
• Sensitivity Depends on– Imaging cell size– Day / Night function– Super HAD, Exwave HAD technology– With or Without Color filter– Signal gain-up
Sensitivity
• Sensitivity Depends on– Imaging cell size
The bigger imager cell size become,
The Higher sensitivity goes.
Sensitivity
• Sensitivity Depends on– Imaging cell size
The bigger imager size become,
The Higher sensitivity goes.
Here is a question….
Sensitivity• Sensitivity Depends on
– Imaging cell size
The bigger imager size become,
The Higher sensitivity goes.
Q. Which has higher sensitivity
A. 1/3 inch 30k Pixels
B. 1/3 inch 60k Pixels
Sensitivity
• Sensitivity Depends on– Imaging cell size
The bigger imager size become,
The Higher sensitivity goes.
Q. Which has higher sensitivity
A. 1/3 inch 30k Pixels
B. 1/3 inch 60k Pixels
Sensitivity
• Sensitivity Depends on– Day / Night function
Normal Color Imager has IR filter
Sensitivity
• Sensitivity Depends on– Day / Night function
Normal Color Imager has IR filter
Without IR filter,
Tone of color will collapse
Imager will be easily affected by heat.
( IR is a heat ray )
Sensitivity• Sensitivity Depends on
– Day / Night function
Day / Night function cuts off the IR filter
in the night time
We can see image in very dark circumstances
(Notice : In Night mode, Image goes to B/W)
Sensitivity
• Sensitivity Depends on– Super HAD, Exwave HAD technology
One of Imager structure technology
Sensitivity
• Sensitivity Depends on– Super HAD, Exwave HAD technology
( Imager structure )
• Super HAD
• Exwave HAD
• Super Exwave
Sensitivity
• Sensitivity Depends on– Super HAD, Exwave HAD technology
( Imager structure )
• Super HAD– Higher Efficiency Micro lens Array before imager
– Good on both Day mode and Night mode
• Exwave HAD
• Super Exwave
Sensitivity
• Sensitivity Depends on– Super HAD, Exwave HAD technology
( Imager structure )
• Super HAD– Higher Efficiency Micro lens Array before imager
– Good on both Day mode and Night mode
• Exwave HAD– Higher Sensitivity to Infrared
– Good on night mode
• Super Exwave
Sensitivity• Sensitivity Depends on
– Super HAD, Exwave HAD technology( Imager structure )
• Super HAD– Higher Efficiency Micro lens Array before imager
– Good on both Day mode and Night mode
• Exwave HAD– Higher Sensitivity to Infrared
– Good with Day / Night function
• Super Exwave– Much higher sensitivity to Infrared
– Better with Day / Night function
Comparison of Hyper HAD CCD and Super HAD CCD Sensor Structure
On-chip Micro lens of Conventional CCD On-chip Micro lens of Super HAD CCD
Hyper HAD CCD Sensor Structure Super HAD CCD Sensor Structure
Exwave HAD
Wave Length [nm]
Rel
ativ
e R
espo
nse
The past CCD vs. Exwave HAD Spectral Sensitivity
The past CCD Exwave HAD
Super Exwave
Exwave HAD vs. Super Exwave
Exwave HAD Super Exwave
Exwave HAD vs. Super Exwave
< Exwave HAD> 0.7lx
< Super Exwave>0.55lx
illumination
High
Low
Sensitivity
• Sensitivity Depends on– With or Without Color Filter
Color Imager = B / W Imager + Color Filter
Sensitivity
• Sensitivity Depends on– With or Without Color Filter
Color Imager = B / W Imager + Color Filter
Color Imager is just like B/W with Sunglasses
Sensitivity
• Sensitivity Depends on– With or Without Color Filter
Color Imager = B / W Imager + Color Filter
Color Imager is just like B/W with Sunglasses
The reason why color imager has lower sensitivity
Sensitivity
• Sensitivity Depends on– Signal gain-up
Sensitivity
• Sensitivity Depends on– Signal gain-up
• Some camera has more gain-up capacity.
Sensitivity
• Sensitivity Depends on– Signal gain-up
• Some camera has more gain-up capacity.
( Gain-up is amplification of signal from imager )
Sensitivity
• Sensitivity Depends on– Signal gain
• Some camera has more gain-up capacity.
( Gain-up is amplification of signal from imager )
• Even though Image may be noisy,we can get image in darker situation.
Sensitivity
• Sensitivity Depends on– Imaging cell size– Day / Night function– Imager structure– With or Without Color filter– DSP gain up
Image quality
• Image quality Depends on– Imaging cell number– With or Without DynaView Technology– With or Without Variable Gamma Curve
Image quality
• Image quality Depends on– Imaging cell number
Image quality
• Image quality Depends on– Imaging cell number
The more imaging cell become,
the higher image resolution goes.
Image quality
• Image quality Depends on– Imaging cell number
The more imaging cell become,
the higher image resolution goes.
(Notice : Higher resolution Imager have less
sensitivity.)
Image quality
• Image quality Depends on– With or Without DynaView Technology
Image quality
• Image quality Depends on– With or Without DynaView Technology
prevents dark area from going to absolute black,
While preventing bright area from going to absolute white.
Image quality
• Image quality Depends on– With or Without DynaView Technology
prevents dark area from going to absolute black,
While preventing bright area from going to absolute white.
By taking picture twice in one frame period.
Image quality
• Image quality Depends on– With or Without DynaView Technology
prevents dark area from going to absolute black,
While preventing bright area from going to absolute white.
By taking picture twice in one frame period.
1st. At slower shutter speed for dark area to be bright.
Image quality
• Image quality Depends on– With or Without DynaView Technology
prevents dark area from going to absolute black,
While preventing bright area from going to absolute white.
By taking picture twice in one frame period.
1st. At slower shutter speed for dark area to be bright.
2nd.At faster shutter speed for bright area to be dark.
Image quality
• Image quality Depends on– With or Without Variable Gamma Curve
Image quality
• Image quality Depends on– With or Without Variable Gamma Curve
• Enhancing Vividness of Image
Image quality
• Image quality Depends on– With or Without Variable Gamma Curve
• Enhancing Vividness of Image
– Taking brightest pixel of image to absolute white
– Taking darkest pixel of image to absolute black
Image quality
• Image quality Depends on– With or Without Variable Gamma Curve
• Enhancing Vividness of Image
– Taking brightest pixel of image to absolute white
– Taking darkest pixel of image to absolute black
– Taking reddest pixel of image to absolute red
– Enhancing solidity of object.
Why Larger Imager is good
• To achieve higher sensitivity,
The imaging cell must be larger.
• To achieve higher resolution
More imaging cell is needed.
Why Larger Imager is good
• To achieve higher sensitivity,
The imaging cell must be larger.
• To achieve higher resolution
More imaging cell is needed.
• What would you do,
if you want both sensitivity and resolution?
Why Larger Imager is good
• To achieve higher sensitivity, the imaging cell must be larger.
• To achieve higher resolution, more imaging cell is needed.
• What would you do,
if you want both sensitivity and resolution?
• Larger imager can achieve both of these.
Why Larger Imager is good
• To achieve higher sensitivity, the imaging cell must be larger.
• To achieve higher resolution, more imaging cell is needed.
• What would you do, if you want both sensitivity and resolution?
• Larger imager can achieve both of these.
• This is why larger imager is good.
Why Larger Imager is good
• To achieve higher sensitivity, the imaging cell must be larger.
• To achieve higher resolution, more imaging cell is needed.
• What would you do, if you want both sensitivity and resolution?
• Larger imager can achieve both sensitivity and resolution,
even though Larger imager is more expensive.
Why Larger Imager is good
• To achieve higher sensitivity, the imaging cell must be larger.
• To achieve higher resolution, more imaging cell is needed.
• What would you do, if you want both sensitivity and resolution?
• Lager imager can achieve both sensitivity and resolution,
even though Lager imager is more expensive.
1/3 > 1/4 > 1/6
About Lens
• Brightness
• Image Angle
• Iris Servo
About Lens
• Brightness
The smaller F value goes….
About Lens
• Brightness
The smaller F value goes….
the brighter
the lens become.
About Lens
• Brightness
The smaller F value goes….
the brighter
the bigger
the lens become.
About Lens
• Brightness
The smaller F value goes….
the brighter
the bigger
the more expensive
the lens become.
About Lens
• Image Angle
The smaller f value goes….
About Lens
• Image Angle
The smaller f value goes….
the wider
image angle become.
About Lens
• Image Angle
The smaller f value goes….
the wider
image angle become.
Wide Angle Lens..
About Lens
• Image Angle
The larger the f value goes….
About Lens
• Image Angle
The larger the f value goes….
the narrower
image angle become.
About Lens
• Image Angle
The larger the f value goes….
the narrower
image angle become.
Tele-Photo Lens..
About Lens• Image Angle
Vari-focal Lens can Change Image angle
like zoom lens.
About Lens
• Image Angle
Vari-focal Lens can Change Image angle
like zoom lens.
( With Vari-focal Lens,
Image will go out of focus, after changing Image Angle,
while image don’t go out of focus with ordinary zoom lens.
Vari-focal Lens is cheaper than ordinary zoom lenses)
End.