Automated inspections using image processing techniques can

be valuable for preventing the outflow of defective products.

Visual inspection is vital for assuring the function and

performance of products by eliminating flaws and defects such

as stains, dents, dirt, and burrs. The following guide features

innovative techniques for appearance inspection using a vision

system. The examples are actual achievements of Keyence's

state-of-art CV3000 Series. This guide will introduce several

techniques users may consider when implementing

appearance inspection with a vision system.

ADVANCED TECHNIQUES

G U I D E F O R I M P L E M E N T I N G V I S I O N S Y S T E M S

VisualInspectionTechniques

Examples of difficult Inspections and Solution Techniques

Highlighting mark indicating the presence of a fluorescent agent.

Technique for reducing GLARE on A glossY surfacecase 4

4

case 1

Solution Technique

Black-light

Solution Technique

Stripe illumination

Solution Technique

Color shading

Filter

Stain tool

Grouping processing

Solution Technique

Polarizing filter

• The following technique reduces specular-reflective light on a transparent film surface using a polarizing filter.

Without polarizing filter

With polarizing filter

Color camera image

Color camera image

Specular-reflective light is reflected by the film surface.

Camera

Object

Transparent film

Illumination

The i l luminat ion is separated into the light reflected on the film surface and the light reflected on the object surface, making it difficult to see the object.

• Principle of a polarizing filter

The specular-reflective light on the film surface is reduced.

Camera

With polarizing filter

Object

Transparent film

Illumination

If polarizing filters are installed on the front of the lens and the source of illumination, the light that passes through the filters and is specularly reflected on the film is blocked by the filter on the front of the lens. This prevents the light from entering the camera and allows users to capture an image where the influence of diffuse reflection is reduced.

Illumination

Polarizingfilter A

Polarizingfilter B

GlassTransparent filter, etc.

Object

Camera

1

23

4

5

Polarizing filter for illumination

Polarizing filter for lens

Light ① emitted from the illuminator is polarized with Polarization filter A and becomes Light ②. Part of Light ② is specularly reflected by the glass surface, becoming specular reflection ③. The rest of Light ② is reflected by the target surface, becoming Light ④. Light ④ is diffused when it passes through the glass surface. Light ④ also passes through Polarization filter B, becoming Light ⑤ and entering the camera. Light ③, which is luster, is intercepted by Polarization filter B and eliminated.

Detecting a subtle dent on a glossy surface.case 2

Reducing glare on a glossy surface.case 4Detecting low contrast foreign material.case 3

Principle

© KEYENCE CORPORATION, 2007 CV-Inspection3-KA-C-E　0038-1 600240 Printed in Japan

KA2-0017

Specifications are subject to change without notice.

CALL TOLL FREE

TO CONTACT YOUR LOCAL OFFICE

1 - 8 8 8 - 5 3 9 - 3 6 2 3

Corporate Office 50 Tice Blvd., Woodcliff Lake, NJ 07677 Phone:201-930-0100 Fax:201-930-0099 E-mail:keyence@keyence.com

Fax : 201-930-0099www.keyence.com

KEYENCE CORPORATION OF AMERICA

1

2

If black-light (ultraviolet light) is irradiated on a substance containing a fluorescent agent, the substance will shine due to the fluorescent reaction. Using this property allows for detection of substances that are usually invisible to the human eye.

White illumination (color image)

Raw Image Processed image

Stripe-shaped surface illumination

Almost invisible in white illumination.

Black-light (color image) Black-light

Blue fluorescence is generated by black-light.

Detecting a substance containing a fluorescent agent.

Major applications involving a black-light

• Presence/absence inspection of flux on a PCB• Presence/absence inspection of adhesive on sanitary goods• Oil leak inspection for car parts

Place the stripe illumination and camera so that specular reflection occurs as shown in the figure to the left. If there is a dent on the object, it is detected by the stripe distortion as shown in the image above.

A monochrome camera could not detect the two foreign substances because there is not a sufficient difference in contrast or color.

Striped illumination

Camera

Object

• The following example illustrates the detection of foreign substances where there is almost no difference in color and contrast of the background and the detected substances.

Only these two foreign substances need to be detected.

Color shade processing screen Shrink filter and contrast conversion processing screen

Processing screen Stain toolPost-grouping stability screen

Foreign substance extraction via color shade processingStep 1 Detection with increased

brightness and filteringStep 2

Detection with the stain inspection tool

Detection of only large defects by grouping Step 3 Step 4

When a color camera is used for processing

Technique for detecting LOW CONTRAST FORIEGN MATERIALcase 3

Illumination with a striped pattern is reflected onto an object. If the object surface has a dent, the stripe is distorted. This distortion can be easily detected using the CV-3000's powerful stain tool.

Detecting a dent by reflecting striped illumination on an object.

Technique for improving contrast of a substance containing a fluorescent agentcase 1

Technique for detecting a subtle dentcase 2

Raw image

Color camera image

Gray image

Undetectable

Monochrome binary image

Undetectable

Detected image

Blue cross marks indicate the detected targets

3

2

If black-light (ultraviolet light) is irradiated on a substance containing a fluorescent agent, the substance will shine due to the fluorescent reaction. Using this property allows for detection of substances that are usually invisible to the human eye.

White illumination (color image)

Raw Image Processed image

Stripe-shaped surface illumination

Almost invisible in white illumination.

Black-light (color image) Black-light

Blue fluorescence is generated by black-light.

Detecting a substance containing a fluorescent agent.

Major applications involving a black-light

• Presence/absence inspection of flux on a PCB• Presence/absence inspection of adhesive on sanitary goods• Oil leak inspection for car parts

Place the stripe illumination and camera so that specular reflection occurs as shown in the figure to the left. If there is a dent on the object, it is detected by the stripe distortion as shown in the image above.

A monochrome camera could not detect the two foreign substances because there is not a sufficient difference in contrast or color.

Striped illumination

Camera

Object

• The following example illustrates the detection of foreign substances where there is almost no difference in color and contrast of the background and the detected substances.

Only these two foreign substances need to be detected.

Color shade processing screen Shrink filter and contrast conversion processing screen

Processing screen Stain toolPost-grouping stability screen

Foreign substance extraction via color shade processingStep 1 Detection with increased

brightness and filteringStep 2

Detection with the stain inspection tool

Detection of only large defects by grouping Step 3 Step 4

When a color camera is used for processing

Technique for detecting LOW CONTRAST FORIEGN MATERIALcase 3

Illumination with a striped pattern is reflected onto an object. If the object surface has a dent, the stripe is distorted. This distortion can be easily detected using the CV-3000's powerful stain tool.

Detecting a dent by reflecting striped illumination on an object.

Technique for improving contrast of a substance containing a fluorescent agentcase 1

Technique for detecting a subtle dentcase 2

Raw image

Color camera image

Gray image

Undetectable

Monochrome binary image

Undetectable

Detected image

Blue cross marks indicate the detected targets

3

Automated inspections using image processing techniques can

be valuable for preventing the outflow of defective products.

Visual inspection is vital for assuring the function and

performance of products by eliminating flaws and defects such

as stains, dents, dirt, and burrs. The following guide features

innovative techniques for appearance inspection using a vision

system. The examples are actual achievements of Keyence's

state-of-art CV3000 Series. This guide will introduce several

techniques users may consider when implementing

appearance inspection with a vision system.

ADVANCED TECHNIQUES

G U I D E F O R I M P L E M E N T I N G V I S I O N S Y S T E M S

VisualInspectionTechniques

Examples of difficult Inspections and Solution Techniques

Highlighting mark indicating the presence of a fluorescent agent.

Technique for reducing GLARE on A glossY surfacecase 4

4

case 1

Solution Technique

Black-light

Solution Technique

Stripe illumination

Solution Technique

Color shading

Filter

Stain tool

Grouping processing

Solution Technique

Polarizing filter

• The following technique reduces specular-reflective light on a transparent film surface using a polarizing filter.

Without polarizing filter

With polarizing filter

Color camera image

Color camera image

Specular-reflective light is reflected by the film surface.

Camera

Object

Transparent film

Illumination

The i l luminat ion is separated into the light reflected on the film surface and the light reflected on the object surface, making it difficult to see the object.

• Principle of a polarizing filter

The specular-reflective light on the film surface is reduced.

Camera

With polarizing filter

Object

Transparent film

Illumination

If polarizing filters are installed on the front of the lens and the source of illumination, the light that passes through the filters and is specularly reflected on the film is blocked by the filter on the front of the lens. This prevents the light from entering the camera and allows users to capture an image where the influence of diffuse reflection is reduced.

Illumination

Polarizingfilter A

Polarizingfilter B

GlassTransparent filter, etc.

Object

Camera

1

23

4

5

Polarizing filter for illumination

Polarizing filter for lens

Light ① emitted from the illuminator is polarized with Polarization filter A and becomes Light ②. Part of Light ② is specularly reflected by the glass surface, becoming specular reflection ③. The rest of Light ② is reflected by the target surface, becoming Light ④. Light ④ is diffused when it passes through the glass surface. Light ④ also passes through Polarization filter B, becoming Light ⑤ and entering the camera. Light ③, which is luster, is intercepted by Polarization filter B and eliminated.

Detecting a subtle dent on a glossy surface.case 2

Reducing glare on a glossy surface.case 4Detecting low contrast foreign material.case 3

Principle

© KEYENCE CORPORATION, 2007 CV-Inspection3-KA-C-E　0038-1 600240 Printed in Japan

KA2-0017

Specifications are subject to change without notice.

CALL TOLL FREE

TO CONTACT YOUR LOCAL OFFICE

1 - 8 8 8 - 5 3 9 - 3 6 2 3

Corporate Office 50 Tice Blvd., Woodcliff Lake, NJ 07677 Phone:201-930-0100 Fax:201-930-0099 E-mail:keyence@keyence.com

Fax : 201-930-0099www.keyence.com

KEYENCE CORPORATION OF AMERICA

1