Using colour to enhance the contrast between label print and the label media

Different light colours can enhance the contrast between label print and the label media itself. The greater the contrast the easier it is for Perceptor IoT - as with any machine vision system - to detect, inspect and verify the areas of interest specified.

The Perceptor IoT inspection camera uses red (630nm) illumination to comply with ISO 15415/15416 code verification. Red light is often used in machine vision as it minimizes ambient reflections and glare. But red light is also readily absorbed by materials including label media and so, depending on the colour of the label/label content, the contrast will vary.

The Perceptor IoT camera can be supplied with blue, green or red LEDs. However, it is important to note that the user cannot verify barcodes to ISO15415 or ISO15416 when using blue or green LEDs. 

Red label/content: using red light on a red label or with red content means the red label or content will not absorb any light. The light will be reflected and the Perceptor IoT sensor will receive all the light back and the resulting image will be white.

Any black content absorbs the red light so that will appear as black because no light is returned to the sensor.

White content or label media won't absorb the light and so it will reflect and appear as white in the image.

Green label/content: using red light on a green label/green content means the light will be absorbed and the resulting image will be dark, making it impossible to distinguish between the black printed information and the background label media.

Blue label/content: as with the green label, using red light on a blue label/content means the light will be absorbed and the resulting image will be dark, making it impossible to distinguish between the black printed information and the background label media.

Green and blue media are very unresponsive to red light and so will also produce very dark images.

Images produced: Perceptor IoT always returns a mono image with different grayscale values according to the colour of the media and the content.

A custom image sensor can be provided if a project or production line requires it - an InfraRed, Green and Blue light solution can be implemented with your Perceptor IoT hardware kit. Please contact us to discuss.

InfraRed light: beyond the visible spectrum, it is used as it is beneficial for applications that require imaging where there would otherwise be very little contrast between media, content and background.

Image: The opposite colours to a colour on the wheel will absorb the light and give a dark image. For example, blue and green through to yellow will absorb light when using red wavelength light thereby making the image very dark.