Product image
Systems by Application

Color Inspection

The human eye sees a color in accordance to how the different wavelengths are recognized and interpreted by the brain.

This differs from human to human, and that’s why colors very often are discussed among people, and where two people can have a completely different perception of what color a painting or a dress seems to have.

In machine vision we are struggling with some of the same problems - how to decide what color a color has? It is very hard to measure the correct color. It depends on how you do it.

There are many things that have influence on the color ‘seen’ by a camera, and the challenge to present the ‘same’ color to an operator, that has his perception of that specific color. We need a setup independent of the human perception, that can be calibrated and work precisely independent of time.

A color is a reflection of a specific spectrum of wavelengths that is not absorbed by the material the lights hits. The light is of importance, the materiel the light travels along or through and the disturbance from filters, lenses etc.

To try to define a color, you need to have a specific light source and a normed color table to calibrate your system against. There are different suppliers of these standard color tables. The normed color tables are sensitive to sunlight, and therefore has to be stored in darkness – to be sure, the color will give the same result, next time the calibration is done. To match the measured color against the standard color space you need to do several calibrations.

The cameras are mostly the same, but the light sources are very different, that’s why you need to calibrate every time, you are changing your light source. There are other disturbances like the lens and the coating on the lens. These can be calibrated with some effort, but is necessary for a precise measurement.

JLI has deep knowledge about colors, light and the different aspects of how to measure the color correct. JLI has developed a special series of calibrations tools that gives us a very precise color detection. These tools have helped international customers to have full control of their colored products, at any time in the production line – from supplier to end product.