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Colour Inspection on AOI

Introduction

The AOI machine has the capability of performing colour inspection. The

following gives an overview of how colour inspection is implemented and how

it can be used to inspect Devices that would otherwise be difficult to handle

using only grey-scale information.

Theory of Operation

The AOI machine utilises a colour Image to capture image colour information.

Inside the software colour information is converted into Hue and Saturation

values. Hue is a measure of colour. It is a scalar quantity that ranges from 0 to

360, with pure blue at 0, pure green at 120 and pure red at 240. Saturation is

a measure of the purity of colour; the extent to which it differs from grey of the

same brightness. Images with low colour content have low saturation values.

Brightly coloured images have high saturation values. All shades of grey,

including black and white, have a saturation value of zero, which means they

have no colour content.

During the training process the hue value of the region of interest (ROI) is

calculated and stored as reference. During inspection the calculated hue

value is compared with the reference hue to determine pass-fail status.

Device Colour Inspection

Colour inspection is an optional Device of the Device inspection. When

enabled, colour inspection verifies the shade of colour of a Device in addition

to the grey-scale template matching that we are already doing. Specifically, a

10 x 10 pixel area at the centre of the template is used to extract colour

information for verification.

The size and position of area to extract colour information from is fixed. Colour

inspection is turned on for capacitors by default during CAD import. Editing

the Scanspection.INI file [CADImport] section can change this default.

[CADImport]

DefPosChk=1

DefPosTol=1000

AxInvAngleOffset=0

DefColourOn=C

Device colour inspection can be enabled or disabled from Device menu on a

Device-by-Device basis. It can also be enabled or disabled globally from the

Functions Options page.

Usage Note

Some small capacitors or resistors have no labels and are very difficult to

distinguish from the background under grey-scale. Using colour inspection

capability, we can detect presence and wrong Device. Train template like you

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AOpen AOI-702U Especificaciones Pagina 110