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How Do Different Modes of Photoelectric Switch Sensors Work? A Comprehensive Explanation!

How Do Different Modes of Photoelectric Switch Sensors Work? A Comprehensive Explanation!

2025/2/17

What is a Photoelectric Sensor?

A photoelectric sensor is a type of switch that detects changes in light (such as intensity, reflection, or obstruction) and converts these changes into electrical signals. Its operation is based on detecting the presence or variation of light to control the system.

The main feature of photoelectric sensors is their "non-contact" operation. They do not require direct contact with the object being detected; instead, they use light emission and reception to detect the presence, position, or changes of objects. This characteristic makes photoelectric sensors widely used in various industrial applications, especially in automated production lines, object detection, and safety protection systems.

The core formula for a photoelectric sensor is: 

Detection ability = f (light intensity, object reflectivity, environmental interference, detection distance).

How Do Different Modes of Photoelectric Switch Sensors Work?

Photoelectric sensors mainly have three common working types: Diffuse Reflective, Specular Reflective, and Through-Beam. Each type has different working principles and application scenarios, catering to various industrial needs.

Photoelectric Sensors Diffuse Reflective Type


1️⃣ Working Principle: The emitter and receiver are integrated into the same probe and rely on diffuse reflection (Lambertian reflection) from the object's surface. After the light is scattered by the object, a portion returns to the receiver, triggering the signal.

2️⃣ Applicable Scenarios:
▪️Object Characteristics: Suitable for non-transparent and rough-surfaced objects (e.g., cardboard, wooden pallets, dark plastics).
▪️Limitations: Prone to misjudgment with highly reflective objects (mirrors/metal), and for black light-absorbing objects (e.g., rubber), detection distance may need to be reduced.
▪️Industrial Cases:
Packaging Lines: Detects the position of cardboard boxes (distance ≤ 1m, installation angle avoids reflective interference).
Robotic Grabbing: Recognizes pallet positions (adjust sensitivity for compatibility with different colors).
▪️Environmental Requirements: Avoid direct sunlight (choose models with anti-light interference, e.g., modulated frequency >5kHz).
Photoelectric Sensors Diffuse Reflective Type
Diffuse Reflective Sensors

Photoelectric Sensors Specular Reflective Type


1️⃣ Working Principle: The emitter and receiver are on the same side, relying on a reflector (prismatic reflector) to return the light along the same path. When an object blocks the light path, it triggers the signal.

2️⃣ Applicable Scenarios:
▪️Object Characteristics: Can detect transparent/semitransparent objects (e.g., glass bottles, PET films), relying on the stability of the reflector.
▪️High Precision Detection: Resolution can reach ±0.1mm (e.g., detecting film tension).
▪️Industrial Cases:
Pharmaceutical Industry: Detects the presence of ampoules (reflectors need to be corrosion-resistant, e.g., 316L stainless steel).
Printing Machines: Detects transparent film breakage (requires polarized filters to eliminate mirror-like interference).
▪️Environmental Requirements: Long-distance detection (up to 50m) requires a laser light source, and dust environments require periodic cleaning of the reflector.
Photoelectric Sensors Specular Reflective Type
Specular Reflective Sensors

Photoelectric Sensors Through-Beam Type


1️⃣ Working Principle: The emitter and receiver are separated and directly detect light path obstruction. It has the strongest anti-interference capability, as the receiver only recognizes the specific frequency light signal from the emitter.

2️⃣ Applicable Scenarios:
▪️Object Characteristics: Suitable for objects of any material (including transparent/highly reflective), with detection reliability >99.9%.
▪️Micro Object Detection: Fiber-optic through-beam types can detect objects as small as 0.1mm in diameter (e.g., electronic component pins).
▪️Industrial Cases:
Automotive Welding Lines: Detects car bodies passing through (high-temperature models, -25°C~80°C).
Logistics Sorting: High-speed parcel counting (response time <1ms, IP67 protection).
▪️Environmental Requirements: Long distances (up to hundreds of meters) require synchronized signal transmission, and vibration environments require mechanical reinforcement of installation.
Photoelectric Sensors Through-Beam Type
Sensors Through-Beam Sensors

How to Choose a Photoelectric Sensor?

1️⃣ Object Detection:
• Transparent/Reflective → Through-Beam or Specular Reflective Type (with polarized filters).
• Black/Light-Absorbing → Diffuse Reflective Type (reduce detection distance or choose a laser light source).

2️⃣ Detection Distance:
• ≤ 0.3m → Diffuse Reflective Type (economical choice).
• 0.3–10m → Specular Reflective Type (requires reflector maintenance).
• 10m → Through-Beam Type (laser light source + synchronized signal).

3️⃣ Environmental Interference:
• Dust/Oil → Through-Beam Type (IP69K protection) or Specular Reflective Type (regular cleaning).
• Strong Ambient Light → Modulated light + narrow-band filtering (e.g., 940nm infrared to resist sunlight interference).

4️⃣ Response Speed:
• High-Speed Production Lines (>1kHz) → Through-Beam Type (fiber-optic type can reach 100kHz).
Industry
Recommended Type
Typical Case
Technical Key Points
Food Packaging
Diffuse + Specular Reflective
Detecting food boxes covered with transparent film
Compensate for film reflection interference
Semiconductor Manufacturing
Through-Beam (Fiber-optic)
Wafer transport positioning
0.01mm repeatable precision, clean environment
Steel Metallurgy 
Through-Beam (High-temperature type)
Continuous casting billet position detection
High-temperature resistant (>150°C), anti-electromagnetic interference
Warehousing & Logistics
Specular Reflective (Long Distance)
AGV navigation using reflective boards
10–30m detection, multi-reflector encoding

Engineering Details Often Overlooked

1️⃣ Installation Angle: Diffuse Reflective type should avoid the mirror reflection angle of the object (e.g., metal surfaces should be installed at a 15° angle).
2️⃣ Background Suppression: Advanced diffuse reflective sensors can be programmed to detect objects within specific distances (suppress background interference).
3️⃣ Safety Redundancy: For safety gate applications, Through-Beam types must comply with the EN/IEC 61496-1 standard (dual-channel redundancy).

Photoelectric Sensors

Photoelectric Sensors GM12 Series
GM12 Series
Type
Model
Detection range
Diffuse Reflective
GM12-10
20-100 mm
GM12-20
20-200 mm
GM12-30
20-300 mm
Through-Beam
GM12-200
2000 mm
GM12-500
5000 mm
GM18 Series
Type
Model
Detection range
 Diffuse Reflective
GM18-30
30-300 mm
GM18-50
50-500 mm
GM18-100
80-1000 mm
Specular Reflective
GM18-500
5000 mm
GM18-1500
15000 mm
Through-Beam
GM18-200
2000 mm
GM18-300
3000 mm
Photoelectric Sensors GM18 Series
Photoelectric Sensors Ultra-thin Micro GP13 Series
Ultra-thin Micro GP13 Series
Type
Model
Detection range
 Diffuse Reflective
GP13-03N-ZAA
2~30 mm (White paper)
GP13-03P-ZAA
2~30 mm (White paper)
Through-Beam 
(Front detection)
GP13-D30N-ZBA
300 mm
GP13-D30P-ZBA
300 mm
GP13-D50N-ZBA
500 mm
GP13-D50N-ZBA
500 mm
Through-Beam 
(Side detection)
GP13-L30N-ZBA
300 mm
GP13-L30P-ZBA
300 mm
GP13-L50N-ZBA
500 mm
GP13-L50P-ZBA
500 mm
Ultra-small Laser Sensor GFS Series
Type
Model
Detection range
Diffuse Reflective
GFS-51N-ZAA
2-50 mm
GFS-51P-ZAA
2-50 mm
Through-Beam
GFS-51N-ZBA
2000 mm
GFS-51P-ZBA
2000 mm
Photoelectric Sensors Ultra-small Laser Sensor GFS Series
Photoelectric Sensors Universal Square GF43 Series
Universal Square GF43 Series
Type
Model
Detection range
 Diffuse Reflective
GF43-15N-ZAA
30-150 mm (adjustable)
GF43-15P-ZAA
30-150 mm (adjustable)
Specular Reflective
GF43-02N-ZCA
2 M
GF43-02P-ZCA
2 M
Through-Beam
GF43-10N-ZBA
10 M
GF43-10P-ZBA
10M
Bar-shaped Light Emission GF21 Series
Type
Model
Detection range
Through-Beam
GF21-150N-ZBA
150 cm
GF21-150P-ZBA
150 cm
Photoelectric Sensors Bar-shaped Light Emission GF21 Series

Photoelectric Sensor with Background Suppression Function

What is the Background Suppression Function of a Photoelectric Sensor?


The Background Suppression (BGS) function is a detection technology based on the principle of triangulation. It works by limiting the sensor's effective detection range, making it respond only to objects within the set distance while ignoring background objects. This function is primarily used in diffuse reflective photoelectric sensors but is also applicable to other types, such as specular reflective sensors. Its core feature is the ability to effectively distinguish between target objects and background interference, making it especially suitable for detecting low-reflectivity objects or in complex background environments.
Photoelectric Sensor With Background Suppression Function GB43 Series
With Background Suppression Function GB43 Series
Type
Model
Detection range
Diffuse Reflective
GB43-100N-ZAA
30-1500 mm (Maximum detection distance)
60-1000 mm(Stable detection distance)
GB43-100P-ZAA
Photoelectric Sensor With Background Suppression Function GB43 Series
With Background Suppression Function GB43 Series
Type
Model
Detection range
 Diffuse Reflective
GB43-10N-ZAA
30-100mm (adjustable)
GB43-10P-ZAA
30-100mm (adjustable)
GB43-30N-ZAA
30-300mm (adjustable)
GB43-30P-ZAA
30-300mm (adjustable)
GFL43-30N-ZAA
30-300mm (adjustable)
GFL43-30P-ZAA
30-300mm (adjustable)
Photoelectric Sensor Small Size GSB Series with Background Suppression Function
Small Size GSB Series with Background Suppression Function
Type
Model
Detection range
Diffuse Reflective
GSB-12N
2 - 150 mm(Maximum detection distance)
3 - 120 mm(Stable detection distance)
GSB-12P

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