Robot Vision SS 2005 Matthias R¼ther 1 ROBOT VISION Lesson 5: Camera Hardware and Technology Matthias R¼ther

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Matthias Rüther
Kawada Industries Inc. has introduced the HRP-2P for Robodex 2002.  This humanoid appears to be very impressive. It is 154 cm (60") tall, weighs 58kg (127 lbs) and has 30 DOF. Here is a news release . Notice the LACK of a battery pack.  Here is a new story about HRP2 . 
Robot Vision SS 2005 Matthias Rüther
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Optik: kenngrößen, Bauarten
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provides color information, light intensity, like human eye
Near infrared (~700nm to 5m)
Similar properties as visible light, NO heat information; black sky, plants are white, used for vegetation inspection, remote sensing, to detect reflective markers
http://www.echeng.com/photo/infrared/tutorial/
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surface inspection (detecting cracks, fluid leaks etc.)
flame inspection (alcohol flames are barely visible to human eye)
Forensics (finger print, blood, etc.)
http://www.echeng.com/photo/infrared/tutorial/
http://www.engineeringtalk.com/news/jai/jai106.html
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Accumulate in each pixel signal charge proportional to local illumination intensity => spatial sampling function
Properties
Responsivity: amount of output signal per unit of input optical energy
Dynamic range: ratio of saturation level to signal threshold
Uniformity: consistency of response
Speed: frame rate / readout time
Windowing: can subwindows of the chip be sampled?
Antiblooming
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Properties:
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Composite Video: de facto standard for consumer products, combines color, brightness and synchronisation data to one „composite“ signal.
S-Video: Y/C or Component Video; splits video data in two channels: luminance (Y) and chrominance (C). Provides less granularity and sharper image. C = U/V for PAL and C = I/Q for NTSC
RGB: standard for computer monitors. Four signals (red, green, blue, sync)
Large distances possible (~20m). Higher frequencies degrade with length (low pass) and noise adds to the signal.
http://www.datapro.net/videodoc.html#Page01
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NTSC: National Television Standards Comitee; North/Central America, Mexico, Canada, Japan.
PAL: Phase Alteration Line; UK, Western Europe, Middle East, Parts of Africa and South America
SECAM: Systeme Electronic Pour Coleur Avec Memoire, similar to PAL, chrominance is FM modulated; France, Russia, parts of Africa, Eastern Europe
Format
Country
Mode
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Standardized
Not a High Volume Product -> expensive
Max 10m cable, no power provided
Physical Layer: Low Voltage Differential Signaling (LVDS); high-speed, low-power general purpose interface standard; known as ANSI/TIA/EIA-644, approved in March 1996.
350 mV nominal signal swing
Theoretical 1.923 Gbps
28bit I/O, serialized 7:1 and transferred
Up to 2.38 Gbps
http://217.33.241.242/download/Coreco%20Imaging/GENERAL/Application%20Notes/cameralink-specification.pdf
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Consists of both hardware and software specification
Completely digital--no conversion to analog
Data rates of 100, 200, or 400 Mb per second (800Mbps by 1394b)
Flexible--supports daisy-chain and branching cable configurations
Inexpensive
Max 4.5m cable length
Power provided by bus
Invented by Apple in mid 90‘s as LAN bus (100Mbps)
Development hampered by license fees in 1998 ($1 per port)
Since 1999 owned by 1394LA ($0.25 per unit)
Firewire remains trademark of apple.
Robot Vision SS 2005 Matthias Rüther
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Plug and Play
Provides Power
IEEE1394 is faster (10-70%), due to protocol architecture!
http://www.cwol.com/firewire/firewire-vs-usb.htm
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Up to 90% humidity
Common Sensor dimensions:
Mounting usually by ¼“ screws
Lens mount standards: C-mount and CS-mount; 1“ thread; differing by flange focal distance
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… or how to calculate the focal length.
Lenses (or lens systems, a „compound“ lens) are used to project light rays on an image sensor.
If all rays originating from a distinct point of light intersect in one point on the image plane, a sharp image of this point is acquired.
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Magnification = size of image / size of object
E.g. size of object = 5cm; size of image = 5mm -> magnification = 0.1
Depends on working distance (lens – object distance) -> impractical for standard lenses
Focal length = working distance * size of image / (size of object + size of image)
E.g. to capture a 1000m wide object from 500m on a CCD chip measuring 4.8x6.4mm, you need 3.2mm of focal length
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Lens Iris
The Iris limits the amount of light getting through the lens.
-> the image appears darker (avoids overexposure in bright scenes)
-> less lens area is used -> fewer lens errors are incorporated
-> sharpness is increased
Sharpness: theoretically impossible to focus 3D object, but:
Blurred points of some size appear sharp to human eye (e.g. on 35mm film, 1/30mm spots appear sharp)
-> „Depth of field“
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F = focal length
e.g.: a 10mm wide object is imaged on a 1/3“ Megapixel CCD from a distance of 100mm, the blurred spot size is max. 5μm
-> best f is 26.5mm, choose 25mm standard lens
-> DOF=0.08mm at full aperture
-> DOF= 0.24mm at aperture = 4
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Adjustable/fixed focus
Adjustable/fixed Iris
Macro lenses
Near field imaging (wd ~75mm-90mm, dof ±0.06mm… ±5mm, magnification 0.14…8)
Telecentric lenses
Parallel projection, moving object towards lens does not change the image
Robot Vision SS 2005 Matthias Rüther
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Lighting
Illumination is the most critical part in a machine vision system.
Small illumination changes may severely affect performance of vision algorithms.
If possible, adjust lighting conditions and keep them fixed!
Properties:
Intensity
Spectrum
Direction
Hazards:
Robot Vision SS 2005 Matthias Rüther
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Fiber optic light guidance to avoid heating
High power consumption (150W lamp)
Heavy DC power source necessary to avoid flicker
Lamp life: 200-10000hrs
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Possible to generate all primary colors
Bright White LED‘s possible (up to 5W per piece) -> Cooling
Life time: 100000+ hrs
Small/light housing
Fast strobe (time limited by driver circuit, down to 1μs pulses)
Packed in LED arrays
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