What Is a Color Recognition Sensor and How to Choose One?

What we commonly call a Color Sensor usually refers to the following two types of color sensors:

1. A color mark sensor used to detect and compare surface grayscale of objects.

These sensors work by detecting differences in reflectance between colors to identify and compare surface grayscale variations of the target object—similar to a black-and-white camera.

2. A color sensor that recognizes and compares the surface color values (RGB) of objects. These sensors typically use RGB (red, green, blue) LED light sources and calculate the ratio of R, G, B wavelengths in the reflected light to determine whether the detected color matches the set value—similar to a color camera.

You can see that RGB color sensors can cover many functions of grayscale-based color mark sensors, but whether to choose an RGB sensor depends on your specific needs.

If you need high response speed and high switching frequency, and the mark to be detected is simple—e.g., a repeated printed pattern on a high-speed production line with fixed mark positions—a standard color mark sensor will suffice.

If you need to detect non-repetitive, non-fixed printed patterns or objects with multiple colors, choose an RGB color sensor. By measuring RGB values precisely and calibrating reference colors, an RGB sensor can provide accurate comparison results. Note that RGB sensors typically transmit more information and therefore respond more slowly than grayscale-based mark sensors.

Effect of mounting distance

Because mark sensors detect grayscale differences while RGB sensors detect RGB values, if the target object is outside the sensor's effective detection range, sensitivity will decrease significantly or detection may fail. Ensure the target stays within the sensor's calibrated detection range to avoid interference from ambient lighting.

For example, if the sensor's effective detection distance is 18–28 mm, the target must be within that range.

Impact of similar colors

Mark sensors usually set output thresholds between the mark color and the background color, but cannot always exclude interference from similar colors. In such cases, either modify the product marking or detection path, or use an RGB color recognition sensor to avoid interference from similar hues.

Effect of surface flatness

Test actual samples with the sensor to determine potential effects. Surface irregularities (bumps or folds) can significantly affect reflected light and grayscale detection. For such surfaces, choosing an RGB color sensor is often better.