Text of Robot Vision SS 2005 Matthias R¼ther 1 ROBOT VISION Lesson 5: Camera Hardware and Technology...
PowerPoint-Präsentation* 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 * Optik: kenngrößen, Bauarten * 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/ * 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 * 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 Robot Vision SS 2005 Matthias Rüther * Robot Vision SS 2005 Matthias Rüther * * * * * Properties: * 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 * 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 * * 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 * * 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 * Plug and Play Provides Power IEEE1394 is faster (10-70%), due to protocol architecture! http://www.cwol.com/firewire/firewire-vs-usb.htm * 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 4333.psd 4334.psd * … 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. 4335.psd * 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 4337.psd * 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“ 4343.psd * 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 4344.psd * 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 * 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 * Fiber optic light guidance to avoid heating High power consumption (150W lamp) Heavy DC power source necessary to avoid flicker Lamp life: 200-10000hrs * 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 * * *
