The light curtain in the turnstile gate is a safety detection device based on infrared or laser technology, mainly used to detect obstacles (such as human bodies, luggage, etc.) in the passenger passage area, prevent tailgating, forced entry or illegal detention, and ensure safe and orderly passage.

The basic components of a light curtain: transmitter and receiver

• The light curtain consists of a set of infrared emitters and receivers, usually installed on both sides of the gate channel (such as the inside or top of the gate). The transmitting end emits multiple infrared rays at a fixed frequency, and the receiving end synchronously receives these rays, forming a dense "beams barrier".
• Beam layout: The light curtain covers the entire passage area through multiple sets of parallel arranged infrared beams. Common layouts include vertical light curtains (detecting obstacles within a height range) and horizontal light curtains (detecting leg or luggage areas).

The working principle of the application of light curtains on turnstiles

• Normal passage detection
  Continuous scanning: The light curtain emits infrared rays at high frequencies, and the receiving end monitors in real-time whether the signal of each beam of light is obstructed. When passengers pass through normally, their bodies will block some of the beams. The system determines whether it is a legal passage based on the number and duration of the blocked beams.
• Preventing tailgating and intrusion
  Multi beams collaborative detection: The light curtain accurately identifies trailing behavior by overlapping multiple beams.
  Tailgating detection: If the previous person passes through and the light curtain detects subsequent obstruction (such as the second person passing closely), it immediately triggers an alarm and locks the gate.
• Reverse intrusion: If a passenger attempts to forcefully enter in reverse, the light curtain detects an abnormal direction of movement and the linkage gate mechanical arm blocks the abnormal passage.

Example of application scenarios for  turnstile gate light curtains

• Single person normal passage: After the passenger swipes their card, the light curtain detects that there is a single person blocking, and the gate opens; After passengers pass through, the light curtain returns to an unobstructed state and the gate closes.
• Tailgating detection: When the first person passes, the light curtain detects obstruction; If the second person does not swipe their card and follows closely behind, and the light curtain detects continuous obstruction, the system will determine it as trailing and the gate will be urgently closed.
• Luggage towing: When passengers carry large luggage, the light curtain determines legal passage through obstruction mode (such as the obstruction area concentrated at the bottom) to avoid misjudgment.

LSED series turnstile gate light curtain   https://www.gteksensor.com/Productdetails/240.html

• Min spacing：20mm
• Max detection distance：8m
• Min height：160mm
• Slim shape：Section size：20*20mm
• Integrated shell with high waterproof performance
• Multiple sets use together without crosstalk
• Cascading function