"time of flight sensors: how do i choose them and how do i integrate them?," a...
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Copyright © 2017 Basler AG 1
Mark Hebbel, Head of New Business Development
May 2017
ToF Sensors: How Do I Choose Them
and How Do I Integrate Them?
Copyright © 2017 Basler AG 2
Basler AG
Industrial
and
network
cameras
Area scan
and
line scan
cameras
CCD
and
CMOS
sensors
USB 3.0, GigE
Fast Ethernet,
FireWire,
Camera Link,
BCON
Interfaces
www.baslerweb.com
Basler is the largest unit volume
producer of digital cameras for
industrial applications in the world.
Copyright © 2017 Basler AG 3
• What is ToF? (for beginners)
• When you integrate the sensor
• Remember the speed of light
• Synchronisation, lighting, shutter
• Which sensors are available?
• Let other people do the hard work: the ToF module
• Multiple module systems – things to remember
Agenda
Copyright © 2017 Basler AG 5
• ... to analyze volume, shape or 3D position of objects
• ... to detect parts and defects that are low-contrast but have a detectable
height difference
• ... to read imprinted code or text when contrast information is missing
Why 3D?
2D vision
doesn’t...
3D vision shows
height differences.
Copyright © 2017 Basler AG 6
ToF Use Cases
Robot belt picking Box content verification Robot assembly
• Find the optimal
gripping position
• Verify presence and
position
• Verify position and
presence
• Measure co-planarity
Copyright © 2017 Basler AG 7
ToF Use Cases
Food portioning Robot bin picking Obstacle recognition
• Give the total volume
• Find optimal cutting
positions
• Unload bins with
randomly oriented parts
• Find the best gripping
coordinates of the most
suitable part to pick
• Make 3D image of the
surroundings
• Bypass obstacles
Copyright © 2017 Basler AG 8
ToF Advantages and Disadvantages
• Large field of view
• Low processing power
• Fast integration and ease of use
• No contrast requirements
• One component only
• No moving parts
• Compact
• High Speed
• Strong ambient light (e.g. Sunlight)
• Multipath and scattered light
• Depth accuracy: 1 cm
(Compared to other
3D techniques)
Copyright © 2017 Basler AG 9
• Send out modulated waves of light
ToF Principles
I’m not going to talk about single pixel ToF (or 3 or 12 pixels). This is a vision summit.
Copyright © 2017 Basler AG 11
• Influences the accuracy of the measurement and the kind of sensor and
electronics to be used
What Kind of Wave or Light Signal?
Copyright © 2017 Basler AG 12
• Advantage
• Works with old LED technology
• Disadvantages
• Sensitive to daylight, small opening angle
• Requires a special pixel design resulting in larger pixels
ToF with Sine Waves
Copyright © 2017 Basler AG 13
• Advantage
• More accuracy and
• With the right LED optics a large opening angle
• Smaller pixels
• Disadvantage
• Needs use of modern “expensive” LED technology (laser,
VCSEL diodes)
ToF with Square Wave
Copyright © 2017 Basler AG 15
• Three types of sensor architecture
• Electronic fast shutters
• Electronics causes large pixel sizes. No amplification
• Demodulation devices
• Popular at the moment
• SPAD (single-photon-avalanched-diodes) based
• At the moment very low resolutions
Possible Sensor Architectures
Copyright © 2017 Basler AG 16
• High Sensitivity
• Low noise
• High dynamic range
• High fill factor
• High QE in the IR
• High demodulation contrast
• High modulation frequency
• Low modulation power
Requirements for a Demodulation ToF Sensor
Common to all image sensors
Specific for ToF sensors
Copyright © 2017 Basler AG 17
Available Raw Sensors
Frame Rate Power
Pmd/Infineon IRS1125C 352x288 Bare die 45 fps 300 mW
Panasonic MN34092BL 640x480 Packaged 30 fps -
TI OPT8241 320x240 COG (78) Up to 150 fps ?
Melexis MLX75023 320x240 BGA package 600 fps “raw” 400 mW
Samsung 5K32A 320x240 ? ? ?
Espros EPC660 320x240 Packaged 65 fps 0.75 W
All numbers are from the datasheets (where available) and not tested.
Copyright © 2017 Basler AG 18
• ToF sensors are available in the range from $100 to $500
• Volumes of 10 k/year
• Maximum range? “up to 9 m” or “up to 240 m” depending on system
design
Soft Specifications
Copyright © 2017 Basler AG 19
• Light is fast, very fast. (3x10^8 m/s or 1 m in 3.33x10^-9 s)
• Electrical signal is 95.1% of that
• Temperature stability (Cu 16.6 x10^-6 m/(m K) )
• 10K is 0.02% change of length
• PCB track length is important
• Lighting trigger
• Calibration is important
Integrating Electronics@Speed of Light
Copyright © 2017 Basler AG 20
• Sheet of white paper
• 0.1 mm accurate positioning
• 22°C room temperature
• 20 minutes sensor + electronics warm-up time
• No ambient light
• 40x40 pixels in the center of the range map
• 25 images
Calibrating the Sensor
Copyright © 2017 Basler AG 27
• Processors are out, SoMs are in
• Let the others do the
• Light integration
• And calibration
• Get a ready integrated sensor and light in a module
ToF Modules
Copyright © 2017 Basler AG 30
• Interfering IR light signals from your own system
• Don’t point cameras at themselves
• Synchronise the cameras somehow (for instance PTP)
Watch Out With Multiple Modules
Copyright © 2017 Basler AG 32
• What to expect in the future
• Smaller pixels and higher resolution
• More combined 2D and 3D imaging
• Reduced power consumption for mobile applications
Trends in Sensor Development
Copyright © 2017 Basler AG 33
• ToF has a high speed advantage and with combined sensors (normal +
depth) provides more info with one device
• ToF is “tricky” when a lot of ambient light is about or several ToF modules
are used in the same space
• Building a ToF camera is complex due to the calibration involved
• ToF technology is improving rapidly and expect big progress especially in
resolution and power consumption in the future
Summary
Copyright © 2017 Basler AG 35
Resource
Stereo Vision Structured Light Laser
Scanner
Time of Flight
Range Medium Medium Short High
XY-Resolution Medium Medium Depends High
Depth Accuracy Medium Medium to high High Medium
Software Complexity High Medium High Low
Real Time Capability Low Medium Low High
Low Light Weak Good Good Good
Outdoor Good Weak Medium Currently Weak
Compactness Medium Medium Weak Good
Material Cost Medium Medium to High High Medium to low
Copyright © 2017 Basler AG 36
• White Paper – Time-of-Flight Cameras
(http://www.baslerweb.com/en/products/cameras/3d-cameras/time-of-
flight-camera/white-paper-time-of-flight-cameras)
Resource
Copyright © 2017 Basler AG 37
• Sensors (datasheets as of 22.02.2017)
• EPC https://www.espros.com/index.php/portfolio_item/epc660/
• TI http://www.ti.com/product/OPT8241
• Pmd/infineon http://www.infineon.com/dgdl/Infineon-
REAL3+Image+Sensor+Family-PB-v01_00-
EN.PDF?fileId=5546d462518ffd850151a0afc2302a58
• Melexis https://www.melexis.com/en/product/MLX75023/Automotive-
QVGA-Time-of-Flight-Sensor
Resource
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