Scorpion Vision Software

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(No Transcript)
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How to start

• How to specify the task
• How to get a good image

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How to specify the inspection task

• Expectations
• How to specify the requirements
• Control and absolute measurements
• High yield and/or zero faults

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Too high expectations?

• Focus on key issues the basis for the
  investment
• Dont include all nice to have inspections in
  the beginning
• It is easy to make a system so complex that it
  never will work according to your expectations
• Keep it simple
• Implement nice to have issues over time and
  after acceptance of the initial system

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How to set the requirements

• A vision system perform measurements
• Dimensions, form, area, angles
• Requirements must be a figure or a set of figures
  with tolerances
• Define the measurement procedures

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Tolerance and Accuracy

• Tolerances
• The specified max and min limits for the
  measurement
• Used as inspection criteria (Pass, Fault)
• Accuracy
• The uncertainty of the measurement performed by
  the inspection system

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Control or Absolute Measurements

• Absolute measurements
• The result is absolute correct within the
  measurement accuracy
• Must be verified by alternative methods
• Require complex calibration
• Measurement accuracy1/10 of tolerance
• Time consuming

• Control
• Relative measurements (compare with one or a set
  of master objects)
• Standard deviation (Repeatability) within
  measurement accuracy
• Measurement accuracy1/3 1/5 of tolerances
• Most vision systems and the subject for this
  lecture

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The ideal inspection system
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The real life
At Customers
Site
Operation
Operation
Finished
Products
No. 1
No. N
Station
Station
No. 1
No. N
Y ppm
X(1) ppm
X(N) ppm
Defect Parts
Defect Parts
Defect Parts



Z(1) ppm
Z(N) ppm

A(1) ppm
OK Parts
OK Parts
A(1) ppm
Parts due to
Parts due to
Inspection
Inspection
Failed
Failed
Inspection Conditions Defect, OK
, Inspection Failed
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Yield problems

• Yield often drop due to
• Larger variation in the products than expected
• Varying contrast due uncontrolled light
• Production working close to the limits

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How to get a good image

• Camera sufficient resolution and quality
• Lens according to distance to and size of
  object
• Light sufficient contrast to see the details
• External light protection secure constant light
  and contrast

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The optical system

• Camera
• TechnologyDigital using CCD chips
• Lens
• Adapted to the individual applications
• Camera types
• Area
• Line scan(high speedapplications)

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Impact of the lens

• Gives the FOW with a given distance between
  object and camera
• Lens distortion and perspective

Camera
Lens
Distance
Grid used forminimiselens distortionand
perspective
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Very high precision gauging

• With a normal lens perspective and shadows may
  cause it impossible to measure with required
  accuracy
• With a Tele centric lens this problem is
  minimised
• High cost lens, must be bigger than the object

Camera
Tele centricLens
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Field of View (FOW)
Pixels in Y direction
Piksels in X direction
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Grey scale pictures
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Pixel resolution

• VGA Camera
• 640 x 480 pixels
• FOV 5mm x 5mm
• Resolution ca. 0,01mm
• FOV 50mm x 50 mm
• Resolution ca. 0,1mm
• FOV 500mm x 500mm
• Resolution ca. 1 mm

• XGA Res. Camera
• 1024 x 768 pixels
• FOW 5mm x 5mm
• Resolution ca. 0,005mm
• FOW 50mm x 50 mm
• Resolution ca. 0,05mm
• FOW 500mm x 500mm
• Resolution ca. 0,5 mm

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How to select camera

• Pixel resolution
• Requirement are set by the size of object and
  measurement tolerances
• In many situation we can measure in the sub
  pixel range
• Quality
• Normally means the ability to separate greyscale
  values between individual pixels

Measure distance between two linesin stead of
two points
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To big object

• Select a camera with higher resolution
• Use two cameras calibrated together
• Use an array of camerasor
• Use Robot Vision
• The robot moves the object in different positions

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Multi camera example
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Camera in perspective

• Advanced four point calibration for correction of
  perspective

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The purpose of lighting

• To illuminate the object and highlight contrasts
  of details
• To secure constant light environment, 24 hour a
  day, 360 days a year

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Moving object during inspection

• Shutter time must be adjusted to match speed and
  resolution requirements
• In the example a shutter time of max 0,1 ms is
  required
• Shorter shutter time require more light intensity

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Front light
Camera
Light source
Light source

• Direct light
• Experiment with number of lamps and light angle
• Diffuse light
• Must be used when reflections is a problem
• Gives no shadow

Lightangle
Camera
Light source
Light source
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Special front light

• Ring light
• For circular object
• Cloudy day
• On Axis
• To avoid shadows in holes
• Fibre optics
• For small objects and very light intensive
  applications

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Back light

• Create a silhouette of the object
• Ideal for inspecting holes, edges, measuring
  areas
• May be difficult to implement in a production line

Camera
Light source
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Protection from external light

• External light is not suitable as illumination
  for optical inspection system
• All system should be protected against sunlight
  and external light

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Final comments

• The key to get a good image is the combination of
  camera(s) and light
• Spend time to find the best solution
• The final solution is often different from your
  starting point
• Sometimes an optical inspections can not be done
  according to your initial requirements
• Revise requirements
• Or better find it out early than after weeks of
  efforts after system implementation