1. CChinahina OOutsourcingutsourcing
Visual Inspection IntroductionVisual Inspection Introduction

2. OutlineOutline
• IntroductionIntroduction
• Basic principlesBasic principles
• Manual Vision InspectionManual Vision Inspection
– Human VisionHuman Vision
– Common Inspection applicationsCommon Inspection applications
– EquipmentEquipment
• Automated or Machine VisionAutomated or Machine Vision
InspectionInspection
– Machine VisionMachine Vision
– Common Inspection ApplicationsCommon Inspection Applications
– EquipmentEquipment
• Advantages and LimitationsAdvantages and Limitations

3. IntroductionIntroduction
• Visual inspection is commonly defined as “theVisual inspection is commonly defined as “the
examination of a material, component, or product forexamination of a material, component, or product for
conditions of nonconformance using light and the eyes,conditions of nonconformance using light and the eyes,
alone or in conjunction with various aids.alone or in conjunction with various aids.
• Visual inspection often also involves, shaking, listening,Visual inspection often also involves, shaking, listening,
feeling, and sometimes even smelling the componentfeeling, and sometimes even smelling the component
being inspected.being inspected.
• Visual inspection consists of at least two majorVisual inspection consists of at least two major
processes.processes.
– The first is a search process.The first is a search process.
– The second is a process of combining relevant knowledge,The second is a process of combining relevant knowledge,
sensory input, and pertinent logical processes to provide ansensory input, and pertinent logical processes to provide an
identification that some anomaly or pattern represents a flawidentification that some anomaly or pattern represents a flaw
that poses a risk to the performance of the part.that poses a risk to the performance of the part.
• Visual inspection is commonly employed to support otherVisual inspection is commonly employed to support other
NDT methods.NDT methods.
• Digital detectors and computer technology have made itDigital detectors and computer technology have made it
possible to automate some visual inspections. This ispossible to automate some visual inspections. This is
known as “machine vision inspection.”known as “machine vision inspection.”

4. IntroductionIntroduction
• Visual inspection is the most basic and mostVisual inspection is the most basic and most
commonly employed NDT method.commonly employed NDT method.
• It is applicable to a wide variety of material typesIt is applicable to a wide variety of material types
and product forms.and product forms.
• Several characteristics about the part beingSeveral characteristics about the part being
examined may be determined, which includeexamined may be determined, which include
dimensional conformance, the presence ofdimensional conformance, the presence of
discontinuities, general fit and wear, and simplediscontinuities, general fit and wear, and simple
cosmetic compliance.cosmetic compliance.
• It can be performed by direct or indirect methodsIt can be performed by direct or indirect methods
during various stages of manufacturing or afterduring various stages of manufacturing or after
the component has been placed in-service.the component has been placed in-service.

5. • The quality of an inspection are affectedThe quality of an inspection are affected
primarily by four factors.primarily by four factors.
– The quality of the detector (eye or camera).The quality of the detector (eye or camera).
– The lighting conditions.The lighting conditions.
– The capability to process the visual data.The capability to process the visual data.
– The level of training and attention to detail.The level of training and attention to detail.
IntroductionIntroduction

6. IntroductionIntroduction ––
Manual Versus AutomatedManual Versus Automated
InspectionInspection
• The majority of visualThe majority of visual
inspections are completedinspections are completed
by an inspector, butby an inspector, but
machine vision is becomingmachine vision is becoming
more common.more common.
• The primary advantage of anThe primary advantage of an
inspector is their ability to quickly adapt to ainspector is their ability to quickly adapt to a
variety of lighting and other non-typical conditions,variety of lighting and other non-typical conditions,
and their ability to use other senses.and their ability to use other senses.
• The primary advantage of a machine visionThe primary advantage of a machine vision
inspection system is their ability to make veryinspection system is their ability to make very
consistent and rapid inspections of specific detailsconsistent and rapid inspections of specific details
of a component.of a component.
• Machine vision is primarily used in productionMachine vision is primarily used in production
applications where a large number of componentsapplications where a large number of components
require inspection and the inspection conditionsrequire inspection and the inspection conditions

7. BasicBasic Principles –Principles –
The Human EyeThe Human Eye
• Light enters the eyeLight enters the eye
through the pupil and anthrough the pupil and an
image is projected on theimage is projected on the
retina.retina.
• Muscles move the eyeballMuscles move the eyeball
in the orbits and allow youin the orbits and allow you
to focus the image on theto focus the image on the
central retina or fovea.central retina or fovea.

8. • Rods are sensitive to blue-green light and are used for visionRods are sensitive to blue-green light and are used for vision
under dark or dim conditions.under dark or dim conditions.
• Cones operate only in relatively bright light, but they provide usCones operate only in relatively bright light, but they provide us
with our sharpest images and enable us to see colors. There arewith our sharpest images and enable us to see colors. There are
three types of conesthree types of cones
– L-cones are red absorbing cones or those that absorb best at theL-cones are red absorbing cones or those that absorb best at the
relatively long wavelengths peaking at 565 nmrelatively long wavelengths peaking at 565 nm
– M-cones are green absorbing cones with a peak absorption at 535M-cones are green absorbing cones with a peak absorption at 535
nmnm
• S-cones are blue absorbing cones with a peak absorption at 440S-cones are blue absorbing cones with a peak absorption at 440
nm.nm.
Basic Principles –Basic Principles –
The Human EyeThe Human Eye
The retina is a mosaic of two basic types of photoreceptors, rods and cones.

9. • Cones provide us with our sharpestCones provide us with our sharpest
images because most of the 3 millionimages because most of the 3 million
cones in each retina are confined tocones in each retina are confined to
a small region just opposite the lensa small region just opposite the lens
called the fovea. The maximumcalled the fovea. The maximum
concentration is about 180,000concentration is about 180,000
cones per square mm.cones per square mm.
• Our sharpest and most colorfulOur sharpest and most colorful
images are produced in the fovea.images are produced in the fovea.
• Outside of this region our vision isOutside of this region our vision is
relatively poor but, since we canrelatively poor but, since we can
quickly redirect our eyes we tend notquickly redirect our eyes we tend not
to be aware of our poor peripheralto be aware of our poor peripheral
vision.vision.
Basic Principles – Visual AcuityBasic Principles – Visual Acuity

10. •Normal visual acuity or 20/20 vision is defined as the ability toNormal visual acuity or 20/20 vision is defined as the ability to
resolve a spatial pattern separated by a visual angle of one minuteresolve a spatial pattern separated by a visual angle of one minute
or 1/60 of a degree of arc.or 1/60 of a degree of arc.
•One degree of a scene is projected on about 290 micrometers of theOne degree of a scene is projected on about 290 micrometers of the
retina.retina.
•In 290 micrometers there are 123 cones and in 1/60 of a degreeIn 290 micrometers there are 123 cones and in 1/60 of a degree
there 2 cones which is the number required to resolve an object.there 2 cones which is the number required to resolve an object.
•The size of an object that can be seen at a given distance can beThe size of an object that can be seen at a given distance can be
calculated using the following formula: X = (d tancalculated using the following formula: X = (d tan /2)2/2)2
b
2

’
d d’
n
b’
c
’
~425 by 425 cones
180,000
Cones
1 mm
1 mm
X
X/2
Basic Principles – Visual AcuityBasic Principles – Visual Acuity
When visually inspecting an object for a defect, a comfortable viewing distance “d” might
be around 12 inches. At 12 inches, the normal visual acuity of the human eye is 0.0035
inch. (It must be noted that this value is for the situation where there is good lighting and high contrast
between the objects being viewed.)
There is a
limit to what
the unaided
eye can see.

11. Basic Principles –Basic Principles –
Contrast SensitivityContrast Sensitivity
• Contrast sensitivity is a measure of how faded or
washed out an object can be before it becomes
indistinguishable from a uniform field
• It has been experimentally determined that the
minimum discernible difference in gray scale level
that the eye can detect is about 2% of full brightness
• Contrast sensitivity varies with
– the size or spatial frequency
of a feature
– The lighting conditions
– Whether the object is lighter
or darker than the background
The graph to the right plots the
visibility of a spot as a function of the
above variables

12. In this image:In this image:
– The luminance of pixels is variedThe luminance of pixels is varied
sinusoidally in the horizontalsinusoidally in the horizontal
direction. The spatial frequencydirection. The spatial frequency
increases exponentially fromincreases exponentially from
left to right.left to right.
– The contrast also variesThe contrast also varies
logarithmically from 100% at thelogarithmically from 100% at the
bottom to about 0.5% at the top.bottom to about 0.5% at the top.
– The luminance of peaks andThe luminance of peaks and
troughs remains constant alongtroughs remains constant along
a given horizontal path through the image.a given horizontal path through the image.
It should be noted, however, that
larger objects are not always
easier to see than smaller objects
as contrast is reduced.
Campbell, F. W. and Robson, J. G. (1968) Application of Fourier analysis to
the visibility of gratings. Journal of Physiology (London) Image Courtesy
of Izumi Ohzawa, Ph.D. University of California School of Optometry
Basic Principles –Basic Principles –
Contrast SensitivityContrast Sensitivity
If object visibility was dictated solely by image contrast, the alternating
bright and dark bars should appear to have equal height everywhere in the
image. However, the bars seem to be taller in the middle of the image.

13. • Under normal lighting conditions the
cones are operating and the eye has
good visual acuity and is most
sensitive to greenish yellow color,
which has a wavelength around 555
nanometers (photopic curve).
• When the light levels drop to near total
darkness, the response of the eye
changes significantly as shown by the
scotopic response curve on the left.
• At this level of light, the rods are most
active and the human eye is more
sensitive to any amount of light that is
present, but is less sensitive to the
range of color.
• At this very low light level, sensitivity
to blue, violet, and ultraviolet is
increased, but sensitivity to yellow and
red is reduced.
Basic Principles – Light LevelsBasic Principles – Light Levels

14. • Effective visual inspection requiresEffective visual inspection requires
adequate lighting.adequate lighting.
• The type of inspection will dictate theThe type of inspection will dictate the
lighting requirements. Inspection oflighting requirements. Inspection of
components with fine detail and low contrastcomponents with fine detail and low contrast
will require greater illumination thanwill require greater illumination than
components with large details and highcomponents with large details and high
contrast.contrast.
• Light intensity may be measured with aLight intensity may be measured with a
suitable light meter. The unit of measuresuitable light meter. The unit of measure
for white light is foot-candles (fc) =(for white light is foot-candles (fc) =( 10.76410.764
luxlux ))
– A foot-candle is equal to the amount of directA foot-candle is equal to the amount of direct
light thrown by one standard candle at alight thrown by one standard candle at a
distance of 1 foot. Min Inspection Lighting 46distance of 1 foot. Min Inspection Lighting 46
fc= 500 lux.fc= 500 lux.
• Inspection of components with fine detailInspection of components with fine detail
and low contrast may require 100 foot-and low contrast may require 100 foot-
candles or more. (1076 Lux min)candles or more. (1076 Lux min)
• Specification requirements for lightingSpecification requirements for lighting
should be reviewed prior to performing anshould be reviewed prior to performing an
Basic Principles –Basic Principles –
Light Intensity MeasurementLight Intensity Measurement

15. Basic Principles –Basic Principles –
Light DirectionalityLight Directionality
• The directionality of the
light is a very important
consideration.
• For some applications,
flat, even lighting
works well.
• For other applications,
directional lighting is
better because it
produces shadows that
are larger than the
actual flaw and easier
to detect.

16. Is the book facing towards
or away from you?
Basic Principles – Perspective
The eye/brain need visual clues
to determine perspective.

17. Are the horizontal lines parallel or
do they slope?
How many black dots do you see?
Sometime the eye/mind has trouble correctly processing
visual information.
Basic Principles –Basic Principles –
Optical IllusionsOptical Illusions

18. • When evaluations are made byWhen evaluations are made by
an inspector, eye examinationsan inspector, eye examinations
must be done at regularmust be done at regular
intervals to assure accuracyintervals to assure accuracy
and sensitivity. Theseand sensitivity. These
examinations may consistexaminations may consist
of the following:of the following:
• Near Vision (Jaeger)Near Vision (Jaeger)
• Far Vision (Snellen)Far Vision (Snellen)
• Color DifferentiationColor Differentiation
• When using machine vision,When using machine vision,
different but similardifferent but similar
Basic Principles – VisionBasic Principles – Vision

19. • For best results the inspector orFor best results the inspector or
machine vision operator must have:machine vision operator must have:
– A basic knowledge of materialA basic knowledge of material
processing, forming, machining andprocessing, forming, machining and
joining processes.joining processes.
– A general understanding of designA general understanding of design
features, application and servicefeatures, application and service
requirements.requirements.
– Specific instructions on what to look forSpecific instructions on what to look for
and specific accept/reject criteria.and specific accept/reject criteria.
Basic PrinciplesBasic Principles

20. InspectionInspection ApplicationsApplications
• Detection of surface anomalies such asDetection of surface anomalies such as
scratches, excess surface roughness, andscratches, excess surface roughness, and
areas void of paint or plating.areas void of paint or plating.
• Crack, porosity, corrosion or other flawCrack, porosity, corrosion or other flaw
detection.detection.
• Dimensional conformance.Dimensional conformance.
• Precision measurements.Precision measurements.
• Foreign object detection.Foreign object detection.
• Component location.Component location.
Applications for visual inspection and many and range
from looking a product over for obvious defect to
performing detailed inspections. Some of the common
applications include:

21. • Visual inspection ofVisual inspection of
manufacturedmanufactured
materials andmaterials and
components is a costcomponents is a cost
effective means ofeffective means of
identifying flaws.identifying flaws.
• Visual inspection of aVisual inspection of a
casting reveals acasting reveals a
crack between acrack between a
threaded opening andthreaded opening and
a pressed fit.a pressed fit.
• The aluminum sandThe aluminum sand
casting has hot tearscasting has hot tears
and shrinkage at theand shrinkage at the
transition zones.transition zones.
Inspection Applications –Inspection Applications –
Flaw DetectionFlaw Detection

22. • In this example, visualIn this example, visual
inspection of a fireinspection of a fire
escape reveals a failureescape reveals a failure
in a handrail tube.in a handrail tube.
• The failure is in theThe failure is in the
tube seam and is likelytube seam and is likely
the result of icethe result of ice
expansion.expansion.
Inspection Applications –Inspection Applications –
Flaw DetectionFlaw Detection
In-service inspections of
existing components and
structures is commonly
accomplished visually.

23. Normal inspectionNormal inspection
practices for highwaypractices for highway
bridges rely almostbridges rely almost
entirely on visualentirely on visual
inspection to evaluate theinspection to evaluate the
condition of the bridges.condition of the bridges.
Inspection Applications –Inspection Applications –
Flaw DetectionFlaw Detection

24. Over 80 percent of all aircraft
inspections are performed
visually.
Inspection Applications –Inspection Applications –
Flaw DetectionFlaw Detection

25. • Weld quality requirementsWeld quality requirements
are commonly determinedare commonly determined
through visual inspection.through visual inspection.
• Many standards haveMany standards have
established acceptanceestablished acceptance
criteria for welds.criteria for welds.
Slag rolled into toe of weld
Transverse weld crack
Inspection Applications –Inspection Applications –
Flaw DetectionFlaw Detection

26. DimensionalDimensional ConformanceConformance
• Visual inspection is commonly employedVisual inspection is commonly employed
for general dimensional conformance,for general dimensional conformance,
assembly fit, and alignment betweenassembly fit, and alignment between
components.components.
• Common applications include determining:Common applications include determining:
– Weld size and tolerance.Weld size and tolerance.
– Component dimensions.Component dimensions.
– Material alignment and allowable distortion.Material alignment and allowable distortion.

27. DimensionalDimensional ConformanceConformance
Welds are commonly inspected for dimensional tolerance.Welds are commonly inspected for dimensional tolerance.
• There are several types of gages used to inspect weldingThere are several types of gages used to inspect welding
fit up and finished weldments.fit up and finished weldments.
• These gages are intended for general inspection whereThese gages are intended for general inspection where
close tolerances are not required.close tolerances are not required.
• The gage used is determined by the application.The gage used is determined by the application.
Fillet gauge set
Palmgren gauge
VWAC gauge
Cambridge gauge

28. Dimensional ConformanceDimensional Conformance
Visual inspection is commonly used to determine weld sizeVisual inspection is commonly used to determine weld size
and tolerances according to standards and engineeringand tolerances according to standards and engineering
specifications.specifications.
Throat measurement
using a Palmgren
gauge.
Leg size determination
with fillet gauge.
Convexity measurement
with VWAC gauge.

29. Undercut in a weld is readily seen visually. In manyUndercut in a weld is readily seen visually. In many
cases its depth must be measured to determine if itcases its depth must be measured to determine if it
exceeds code requirements.exceeds code requirements.
Measurement of undercut
depth with VWAC gage.
Dimensional ConformanceDimensional Conformance

30. Dimensional ConformanceDimensional Conformance
Component finish dimensions are checked withComponent finish dimensions are checked with
the use of measurement devices, such asthe use of measurement devices, such as
transferring gages and precision measurementtransferring gages and precision measurement
gages.gages.
The finished depth of a
machined mold is determined
with a depth micrometer.
Small hole gage used in
determining hole diameter.

31. Dimensional ConformanceDimensional Conformance
Alignment/DistortionAlignment/Distortion
• Visual inspection frequently involvesVisual inspection frequently involves
checking materials and components forchecking materials and components for
fit and alignment.fit and alignment.
• Many standards establish allowableMany standards establish allowable
tolerances for fit and distortion.tolerances for fit and distortion.
• Structural fabrication requiresStructural fabrication requires
dimensional inspection of finisheddimensional inspection of finished
components prior to shipment to thecomponents prior to shipment to the
field site.field site.
• Basic tools are used for the inspection.Basic tools are used for the inspection.
An inspector will set up string lines atAn inspector will set up string lines at
known distances and plum them usingknown distances and plum them using
a tape measure. Measurements area tape measure. Measurements are
then taken at various locations andthen taken at various locations and
compared to code requirements.compared to code requirements.
In this image a
fabricated girder is
being inspected for
distortion, sweep
and web flatness.

32. EquipmentEquipment
• Visual inspection equipment includes a varietyVisual inspection equipment includes a variety
of different tools. These may range from basicof different tools. These may range from basic
rulers, tape measures and spring type calipersrulers, tape measures and spring type calipers
to rigid or flexible borescopes and remoteto rigid or flexible borescopes and remote
crawlers with cameras.crawlers with cameras.
• Many tools have been designed for specificMany tools have been designed for specific
applications such as the various weld gauges.applications such as the various weld gauges.
• Some of the specialized tools such as crawlersSome of the specialized tools such as crawlers
have been designed to satisfy the inspectionhave been designed to satisfy the inspection
needs in applications where conventionalneeds in applications where conventional
techniques are not feasible.techniques are not feasible.

33. Equipment – BasicEquipment – Basic
MeasurementsMeasurements
• One of the most commonOne of the most common
tools used in visualtools used in visual
inspection is the rule orinspection is the rule or
scale.scale.
• Used to measure linearUsed to measure linear
dimensions, when properlydimensions, when properly
used will measure withinused will measure within
0.015” or 1/64” and smaller.0.015” or 1/64” and smaller.
• Rules are made in a varietyRules are made in a variety
lengths, widths, andlengths, widths, and
thicknesses.thicknesses.
• They are graduated inThey are graduated in
common fractions, decimalcommon fractions, decimal
units, and metric units, orunits, and metric units, or
combinations of both.combinations of both.
• The specific type of rule isThe specific type of rule is
typically chosen relative totypically chosen relative to
the application.the application.

34. • Sliding calipers are aSliding calipers are a
precision refinement ofprecision refinement of
the common rule, whichthe common rule, which
results in greaterresults in greater
accuracy ofaccuracy of
measurements.measurements.
• They may incorporateThey may incorporate
either a dial indicator oreither a dial indicator or
digital readout.digital readout.
• Sliding-type calipers areSliding-type calipers are
commonly used to checkcommonly used to check
dimensional tolerances ofdimensional tolerances of
machined components,machined components,
wear on components, andwear on components, and
fit between components.fit between components.
Equipment –Equipment –
Precision MeasurementsPrecision Measurements

35. Equipment –Equipment –
Precision MeasurementsPrecision Measurements
• Micrometers are preciseMicrometers are precise
measurement instrumentsmeasurement instruments
used to make accurateused to make accurate
direct readings in contactdirect readings in contact
measurements.measurements.
• Micrometers are designedMicrometers are designed
for inside, outside, andfor inside, outside, and
depth measurements, anddepth measurements, and
are available in a wideare available in a wide
variety of shapes andvariety of shapes and
sizes.sizes.
• Micrometers may be eitherMicrometers may be either
thousandth inch (.001”) orthousandth inch (.001”) or
ten thousandth inchten thousandth inch
(.0001”) measurement(.0001”) measurement
capable.capable.

36. • Micrometers operate onMicrometers operate on
the principle that athe principle that a
precision made screwprecision made screw
with a pitch of fortywith a pitch of forty
threads per inch willthreads per inch will
advance one fortieth of anadvance one fortieth of an
inch (.025”) with eachinch (.025”) with each
complete turn.complete turn.
• On a one inchOn a one inch
micrometer, the sleeve ismicrometer, the sleeve is
marked longitudinally withmarked longitudinally with
forty lines to the inchforty lines to the inch
which corresponds to thewhich corresponds to the
number of threads on thenumber of threads on the
spindle.spindle.
EquipmentEquipment ––
PrecisionPrecision MeasurementsMeasurements

37. • The reading line on theThe reading line on the
sleeve is divided into fortysleeve is divided into forty
equal parts by verticalequal parts by vertical
lines, each designateslines, each designates
1/401/40thth
” or .025” and every” or .025” and every
fourth line denotesfourth line denotes
hundreds of thousandthshundreds of thousandths
and is numbered 1 – 0.and is numbered 1 – 0.
• The beveled edge of theThe beveled edge of the
thimble is divided intothimble is divided into
twenty five equal partstwenty five equal parts
with each representing .with each representing .
001”, with every line001”, with every line
numbered from 0 -24.numbered from 0 -24.
Equipment –Equipment –
Precision MeasurementsPrecision Measurements

38. Example:Example:
– One major division on theOne major division on the
sleeve is visible, representingsleeve is visible, representing
one tenth of an inch.one tenth of an inch.
– Two minor divisions areTwo minor divisions are
visible, which each representvisible, which each represent
an additional 25 thousandths.an additional 25 thousandths.
– Line 15 on the thimbleLine 15 on the thimble
coincides with the readingcoincides with the reading
line on the sleeve indicatingline on the sleeve indicating
that fifteen one thousandthsthat fifteen one thousandths
of an inch should be added toof an inch should be added to
the measurement.the measurement.
– By adding all three values,By adding all three values,
the micrometer reading isthe micrometer reading is
obtained.obtained.
Equipment –Equipment –
Precision MeasurementsPrecision Measurements
0.100”
(2 X 0.025) 0.050”
(15 X .001) 0.015”
0.165”

39. Reading the ten thousandths micrometer.Reading the ten thousandths micrometer.
• The ten thousandths micrometer incorporates a vernier scale.The ten thousandths micrometer incorporates a vernier scale.
• The vernier consists of ten divisions the sleeve, whichThe vernier consists of ten divisions the sleeve, which
occupies the same space as nine divisions on the beveledoccupies the same space as nine divisions on the beveled
edge of the thimble.edge of the thimble.
• The difference between one of the ten spaces on the sleeveThe difference between one of the ten spaces on the sleeve
and one of the nine spaces on the thimble is 1/10and one of the nine spaces on the thimble is 1/10 thth
of aof a
division or 0.0001”.division or 0.0001”.
Equipment –Equipment –
Precision MeasurementsPrecision Measurements
Example:
− The second major divisions (line 2) on the
sleeve is visible (2 x 0.100” = 0.200”)
− Three minor divisions after line 2 are visible
(3 X 0.025” = 0.075”)
− The beveled edge of the thimble is between
0 and 1 (0 x 0.001 = 0)
− The vernier scale has the sixth line on the
sleeve perfectly lined up with one of the
marks on the thimble ( 6 x 0.0001 = 0.0006”)
− The micrometer reading is: 0.2756”
0.200”
0.075”
0.000”
0.0006”
0.2756”

40. Equipment – TransferringEquipment – Transferring
GaugesGauges
• Transfer instruments areTransfer instruments are
used to takeused to take
measurements which aremeasurements which are
transferred to directtransferred to direct
measurement devices.measurement devices.
• They consist of calipers,They consist of calipers,
dividers, telescopingdividers, telescoping
gages and small holegages and small hole
gages.gages.

41. Equipment – TransferringEquipment – Transferring
GaugesGauges
• Spring type calipers areSpring type calipers are
available for contactavailable for contact
measurements of inside andmeasurements of inside and
outside dimensions.outside dimensions.
• They are useful for measuringThey are useful for measuring
distances between and overdistances between and over
surfaces.surfaces.
• They are commonly used toThey are commonly used to
transfer dimensions or sizestransfer dimensions or sizes
between the work piece andbetween the work piece and
standard measuring devices,standard measuring devices,
such as graduated rules.such as graduated rules.
• The size of a linear or roundedThe size of a linear or rounded
indication of a discontinuity mayindication of a discontinuity may
be measured with dividers.be measured with dividers.

42. Equipment – TransferringEquipment – Transferring
GaugesGauges
• Small hole gages are a type of transfer instrument used toSmall hole gages are a type of transfer instrument used to
measure small holes or slots.measure small holes or slots.
• They are generally supplied in sets with a range of 1/8” -They are generally supplied in sets with a range of 1/8” -
1/2”.1/2”.
• The actual measurement is determined by transferring aThe actual measurement is determined by transferring a
properly adjusted gage to a micrometer.properly adjusted gage to a micrometer.

43. Equipment – TransferringEquipment – Transferring
GaugesGauges
• Telescoping gages makeTelescoping gages make
inside measurements suchinside measurements such
as hole diameter and slotas hole diameter and slot
width.width.
• They are designed to beThey are designed to be
measured by a micrometermeasured by a micrometer
after being set to the holeafter being set to the hole
or slot size.or slot size.
• To make accurateTo make accurate
measurements it ismeasurements it is
important to make sure theimportant to make sure the
telescoping gage istelescoping gage is
aligned properly in thealigned properly in the
measuring faces of themeasuring faces of the
micrometer.micrometer.

44. Equipment – Screw Pitch GageEquipment – Screw Pitch Gage
• The screw pitch gage is aThe screw pitch gage is a
basic visual aid forbasic visual aid for
checking the number ofchecking the number of
threads per inch and roughthreads per inch and rough
inaccuracies of threads.inaccuracies of threads.
• The gage consists of aThe gage consists of a
steel case with a numbersteel case with a number
of folding leaves at eachof folding leaves at each
end.end.
• Each leaf is number andEach leaf is number and
contains teethcontains teeth
corresponding to a specificcorresponding to a specific
thread pitchthread pitch ..

45. Direct and RemoteDirect and Remote
Visual InspectionVisual Inspection
• Many codes refer to direct visual examination asMany codes refer to direct visual examination as
a visual inspection which requires that access toa visual inspection which requires that access to
the area is sufficient to place the eye within 24the area is sufficient to place the eye within 24
inches of the surface to be examined and at aninches of the surface to be examined and at an
angle of not less than 30angle of not less than 30 º to that surface.º to that surface.
• If these requirements cannot be met, thenIf these requirements cannot be met, then
remote visual inspection may be used.remote visual inspection may be used.
• Remote visual inspection may be accomplishedRemote visual inspection may be accomplished
with the use of a number of optical aids such as,with the use of a number of optical aids such as,
mirrors, magnifiers, and rigid or flexiblemirrors, magnifiers, and rigid or flexible
borescopes.borescopes.

46. Optical AidsOptical Aids
• Mirrors are valuable aids inMirrors are valuable aids in
visual inspection, they allowvisual inspection, they allow
the inspection of threaded andthe inspection of threaded and
bored holes, inside surfaces ofbored holes, inside surfaces of
pipes and fittings, as well aspipes and fittings, as well as
many others.many others.
• Magnifiers assist the visualMagnifiers assist the visual
inspector by enlarging the sizeinspector by enlarging the size
of the object being examined.of the object being examined.
• Comparators are a magnifierComparators are a magnifier
with a measuring capability.with a measuring capability.
The comparator hasThe comparator has
interchangeable reticles whichinterchangeable reticles which
provide measurements forprovide measurements for
threads, angles, linearthreads, angles, linear
measurement, diameters andmeasurement, diameters and

47. Optical AidsOptical Aids
• Borescopes are visual aids used for the inspection ofBorescopes are visual aids used for the inspection of
internal surface areas.internal surface areas.
• They are designed for remote viewing in difficult toThey are designed for remote viewing in difficult to
reach areas such as jet engines, cylinders, tanks, andreach areas such as jet engines, cylinders, tanks, and
various enclosed chambers.various enclosed chambers.
• Borescopes are available in many different diametersBorescopes are available in many different diameters
and lengths, and are classified as rigid or flexible.and lengths, and are classified as rigid or flexible.

48. Visual Inspection With A Borescope
Clean Surface Corrosion Damage

49. Optical AidsOptical Aids
• Advances in technology has allowed videoAdvances in technology has allowed video
equipment to be adapted to portable and roboticequipment to be adapted to portable and robotic
devices.devices.
• Portable video probes allow inspectors toPortable video probes allow inspectors to
remotely perform examinations in closedremotely perform examinations in closed
chambers which are inaccessible by conventionchambers which are inaccessible by convention
inspection means.inspection means.
• Robotics have been developed whereby camerasRobotics have been developed whereby cameras
can be affixed to crawlers and submersibles.can be affixed to crawlers and submersibles.
– Retrieval tools can be affixed to robotics to removeRetrieval tools can be affixed to robotics to remove
foreign objects.foreign objects.
• Conventional recording techniques mayConventional recording techniques may
be employed for image capture andbe employed for image capture and
storage with many of the remote videostorage with many of the remote video
inspection methods.inspection methods.

50. Machine Vision InspectionMachine Vision Inspection

51. • Machine vision technology uses an imagingMachine vision technology uses an imaging
system and a computer to analyze an image andsystem and a computer to analyze an image and
to make decisions based on that analysis.to make decisions based on that analysis.
• In inspection applications, the machine visionIn inspection applications, the machine vision
optics and imaging system enable the processoroptics and imaging system enable the processor
to "see" objects precisely and thus maketo "see" objects precisely and thus make
decisions about which component meet a specificdecisions about which component meet a specific
inspection criteria.inspection criteria.
• Machine vision can eliminate human factor errorMachine vision can eliminate human factor error
that might result from doing difficult, tedious, orthat might result from doing difficult, tedious, or
boring tasks. It also allows process equipment toboring tasks. It also allows process equipment to
be utilized 24 hours a day.be utilized 24 hours a day.
Machine Vision – BasicMachine Vision – Basic
PrinciplesPrinciples

52. The following process steps are common to allThe following process steps are common to all
machine vision applications:machine vision applications:
• Image acquisitionImage acquisition : An optical system gathers an image, which is: An optical system gathers an image, which is
then converted to a digital format and stored into computer memory.then converted to a digital format and stored into computer memory.
• Image processingImage processing : A computer processor uses various: A computer processor uses various
algorithms to enhance elements of the image that are of specificalgorithms to enhance elements of the image that are of specific
importance to the process.importance to the process.
• Feature extractionFeature extraction : The processor identifies and quantifies: The processor identifies and quantifies
critical features in the image (e.g., the position of holes on a printedcritical features in the image (e.g., the position of holes on a printed
circuit board, the number of pins in a connector, the orientation of acircuit board, the number of pins in a connector, the orientation of a
component on a conveyor) and sends the data to a control program.component on a conveyor) and sends the data to a control program.
• Decision and controlDecision and control : The processor's control program makes: The processor's control program makes
decisions based upon the data. Are the holes within specification?decisions based upon the data. Are the holes within specification?
Is a pin missing?Is a pin missing?
Machine Vision – Basic Principles

53. Machine Vision - Applications
As mentioned previously, machine vision is primarily used in
production applications where a large number of components
require inspection and the inspection conditions can be closely
controlled. Uses include:
• Assembly verification (caps, fasteners,
electronic board components, etc.)
• Surface inspection (dents, scratches,
porosity.
and other undesirable features)
• Verification of colors, gradients, patterns
in fabrics and labels.
• Confirmation of proper labeling for
medications, foods and other products.
• Inspection of coating coverage.
• Feature measurements.
Assembly Verification
Spark Gap Measurement

54. Key System ElementsKey System Elements
• A variety of components areA variety of components are
included in a machine visionincluded in a machine vision
system, which depend on thesystem, which depend on the
environment, the application,environment, the application,
and the budget. However, theand the budget. However, the
following components arefollowing components are
common to all vision systems :common to all vision systems :
– Front-end opticsFront-end optics : this includes the lighting, the lens, and the: this includes the lighting, the lens, and the
camera.camera.
– Frame grabberFrame grabber : this is a computer processor board that: this is a computer processor board that
accepts the video input from the camera, digitizes it, and storesaccepts the video input from the camera, digitizes it, and stores
it for analysis.it for analysis.
– ProcessorProcessor : A computer processor is required to control the: A computer processor is required to control the
vision application.vision application.
– Control SoftwareControl Software : Computer software is used for controlling: Computer software is used for controlling
and executing vision tasks.and executing vision tasks.
Machine Vision - Equipment

55. Advantages of Visual InspectionAdvantages of Visual Inspection
• Readily used on almost all materials.Readily used on almost all materials.
• Simple to perform.Simple to perform.
• Low in cost, (application dependent).Low in cost, (application dependent).
• Relatively quick.Relatively quick.
• Results may be permanently recorded.Results may be permanently recorded.
• Can be automated.Can be automated.

56. Limitations of Visual InspectionLimitations of Visual Inspection
• Direct inspections are limited to surfaces only.Direct inspections are limited to surfaces only.
• Indirect inspections require greater inspectorIndirect inspections require greater inspector
knowledge and training.knowledge and training.
• Inspector dependent, knowledge of materialsInspector dependent, knowledge of materials
and processing, eye sight.and processing, eye sight.
• Standards (workmanship) may be difficult toStandards (workmanship) may be difficult to
obtain.obtain.

57. Glossary of TermsGlossary of Terms
• Borescope: A visual inspection aid used for the inspection ofBorescope: A visual inspection aid used for the inspection of
internal surfaces. Borescopes are rigid and flexible.internal surfaces. Borescopes are rigid and flexible.
• Corrosion: The deterioration of a metal by chemical or electro-Corrosion: The deterioration of a metal by chemical or electro-
chemical reaction with its environment.chemical reaction with its environment.
• Defect: A discontinuity which interferes with the usefulness of aDefect: A discontinuity which interferes with the usefulness of a
part. A fault in any material or part which is detrimental to itspart. A fault in any material or part which is detrimental to its
serviceability.serviceability.

58. Glossary of Terms, Cont.Glossary of Terms, Cont.
• Direct Visual Inspection: Visual inspection conducted where the eyeDirect Visual Inspection: Visual inspection conducted where the eye
can be place within 24” of the area to be inspected at an angle ofcan be place within 24” of the area to be inspected at an angle of
not less than 30not less than 30˚.˚.
• Discontinuity: An interruption in the normal physical structure orDiscontinuity: An interruption in the normal physical structure or
configuration of a part.configuration of a part.
• Foot Candle: The amount of direct light thrown by one standardFoot Candle: The amount of direct light thrown by one standard
candle on a surface one foot away. 1 Foot-candle = 10.764 Lux.candle on a surface one foot away. 1 Foot-candle = 10.764 Lux.

59. Glossary of Terms, Cont.Glossary of Terms, Cont.
• Inherent Discontinuity: Discontinuities which are ordinarily normal toInherent Discontinuity: Discontinuities which are ordinarily normal to
the material at the time it originally solidifies from the molten state.the material at the time it originally solidifies from the molten state.
They consist of porosity, inclusions, and pipe.They consist of porosity, inclusions, and pipe.
• Magnifier: An optical glass which enlarges the real size of an objectMagnifier: An optical glass which enlarges the real size of an object
being inspectedbeing inspected
• Micrometer: A precise measuring instrument used to take accurateMicrometer: A precise measuring instrument used to take accurate
readings in contact measurement.readings in contact measurement.

60. Glossary of Terms, Cont.Glossary of Terms, Cont.
• Pocket Comparator: A magnifier with measuring capability throughPocket Comparator: A magnifier with measuring capability through
a system of interchangeable reticles.a system of interchangeable reticles.
• Power of Magnification: The amount that the real size of an objectPower of Magnification: The amount that the real size of an object
is enlarged. The power if designated by “X”.is enlarged. The power if designated by “X”.
• Remote Visual Inspection: Inspection conducted where the eyeRemote Visual Inspection: Inspection conducted where the eye
cannot be placed within 24” of the area to be inspected, or at ancannot be placed within 24” of the area to be inspected, or at an
angle less than 30angle less than 30˚.˚.

61. Glossary of Terms, Cont.Glossary of Terms, Cont.
• Reticle: A series of lines, dots, cross hairs, or wires in the focus ofReticle: A series of lines, dots, cross hairs, or wires in the focus of
the eyepiece of and optical instrument.the eyepiece of and optical instrument.
• Rule or Scale: A measuring device used to make linearRule or Scale: A measuring device used to make linear
measurements.measurements.
• Screw Pitch Gages: A visual aid used to check the number ofScrew Pitch Gages: A visual aid used to check the number of
threads per inch and rough inaccuracies in threads.threads per inch and rough inaccuracies in threads.

62. Glossary of Terms, Cont.Glossary of Terms, Cont.
• Secondary Processing: Metal removal processes, heat treatmentSecondary Processing: Metal removal processes, heat treatment
and plating processes used to produce and article of the desiredand plating processes used to produce and article of the desired
shape and finish from the formed material.shape and finish from the formed material.
• Service Discontinuity: Discontinuities induced in components afterService Discontinuity: Discontinuities induced in components after
they have been placed in service.they have been placed in service.
• Transfer Instruments: A group of instruments used to takeTransfer Instruments: A group of instruments used to take
measurements which are transferred to precise direct measuringmeasurements which are transferred to precise direct measuring
devices. They consist of calipers, dividers, telescoping gages, anddevices. They consist of calipers, dividers, telescoping gages, and
small hole gages.small hole gages.

63. Glossary of Terms, Cont.Glossary of Terms, Cont.
• Vernier Scale: A device for indicating a fraction of a whole divisionVernier Scale: A device for indicating a fraction of a whole division
of a scale readingof a scale reading
• Visual Scale: The ability to see. The keenness of perception.Visual Scale: The ability to see. The keenness of perception.
• Wear: Wear is deterioration due to use. Wear will cause aWear: Wear is deterioration due to use. Wear will cause a
reduction in cross section and strength.reduction in cross section and strength.
• Weld Inspection Gages: A group of measuring devices used toWeld Inspection Gages: A group of measuring devices used to
inspect welding fit up and finished weldments.inspect welding fit up and finished weldments.

64. Questions?Questions?
• Thank you for your time.Thank you for your time.