From Diffuse to Through-Beam: Understanding Photoelectric Sensor Types

Photoelectric sensors have been in use for more than 50 years. You’ll find them in everyday devices like garage door openers and in highly automated manufacturing environments that produce everything from the food we eat to the cars we drive.

Selecting the correct photoelectric sensor ensures machines perform accurately and reliably. Over time, these sensors have evolved into various types, each suited for different tasks and environments.

So, how do you choose the right one for your industrial needs? Here’s a quick overview of the main types and when to use them.

Diffuse sensors

These general-purpose sensors are great for basic object detection where simplicity and cost-efficiency are priorities.

• Detects contrast differences based on surface, color, and material

• Operates in light-on or dark-on mode, depending on the target

• Offers economical installation with easy mounting and alignment

• Provides shorter sensing ranges compared to retroreflective and through-beam types

• Uses IR (Infrared) light for improved detection in harsh environments

• Uses laser light for higher precision detection

• Requires only one electrical device for mounting

Diffuse sensor with background suppression

Designed for more complex detection tasks, these sensors provide reliable performance even when background conditions vary.

• Detects objects regardless of surface, color, or material

• Detects dark objects against very similar or light backgrounds (and vice versa)

• Maintains a consistent sensing range across varying reflectivity

• Eliminates the need for reflectors or separate receivers

• Serves as a good option to through-beam or retroreflective sensors

• Offers red or laser red options ideal for detecting small parts

Retroreflective sensors

Ideal for longer-range applications, these sensors use a reflector to detect objects with high accuracy and repeatability.

• Simplifies alignment, generous mounting tolerances

• Uses large reflectors to support longer sensing ranges

• Detects reliably across a variety of surfaces, colors, and materials

• Uses polarized filters to detect shiny or reflective objects

• Requires one electrical device and one reflector for operation

• Provides repeatable detection by passing light through the object twice

Through-beam sensors

These sensors offer the most reliable detection method, using a separate transmitter and receiver for high precision over long distances.

• Enables precise measurements with excellent reproducibility

• Provides the most reliable detection, especially on conveyors

• Resists contamination and performs well in harsh environments

• Supports long sensing ranges

• Includes separate transmitter and receiver units

Fork sensors

With a fixed optical axis and compact design, fork sensors provide fast, accurate object detection in tight or demanding spaces.

• Offers red light, infrared, or laser options

• Features a robust metal housing for rugged use

• Simplifies alignment to the target object

• Delivers high optical resolution and reproducibility

• Provides various fork widths with standardized mounting holes

• Aligns the transmitter and receiver mechanically and optically for higher reliability

The next time you select a photoelectric sensor for your manufacturing process, use these features to help choose the type that will deliver the best performance for your application.