Color Sensors and Mark Sensors: Working Principles — Atonm Share

Color sensors are widely used in industrial automation. For example, in packaging lines they help determine which product goes into which color package, when to cut candy wrapper film, and how to ensure product windows on boxes face correctly.

There are two basic types of optical color recognition sensors:

(1) Mark sensors

These use incandescent or single-color LED light sources.

Atonm CL3 mark sensors include an integrated RGB light source, are easy to set up and are suitable for common color-detection tasks — offering high cost performance and the ability to detect many colors.

(2) RGB (red, green, blue) color sensors

These measure the reflected ratios of the three primaries to identify an object between different colors. Many are packaged with optics and fiber and housed in metal or polycarbonate enclosures.

Atonm CL2 series color sensors are user-friendly with one-touch setup, delay options and 8-channel outputs. They can store up to 8 different colors, recognize thousands of color variations, and accurately distinguish subtle color differences using brightness, color, or brightness+color methods.

How do color sensors work?

Color sensors detect color changes and help production lines reliably distinguish parts by color. The challenge is often differentiating similar or highly reflective colors, such as certain automotive paints. Proper color matching is essential for parts like trims or mirrors.

Sensors are typically taught a reference color sample; the operator programs the sensor to match that sample and may adjust high/low thresholds through trial and error to define acceptable tolerances.

Modern optical and software advances make sensors more sensitive, able to ignore gloss and distinguish subtle tones. Typical color sensors use a high-intensity white LED; reflected light is analyzed into red, green and blue (RGB) components and intensity. That information verifies correct parts and controls color-critical manufacturing steps.

Sensors with multiple channels can be programmed to recognize multiple colors and provide discrete alarm outputs per channel — sufficient for sorting or pass/fail checks. Next-generation sensors also provide separate RGB outputs for richer control and process intelligence.

In practice, raw RGB outputs are often analog signals. Analog is efficient for communication compared with three separate high-rate digital channels. Some sensors provide digitized raw readings or data-logging modes for trend analysis and deeper diagnosis.