RAY-RT Triangulation Technology

Reflective photo eye systems are designed to generate an alarm signal when an object or person interrupts a beam of light travelling between the light source/photo eye unit and a reflector mounted on the opposite side of the door or gate. Unfortunately, if an object has a highly reflective surface (for example, the metallic paint used on many vehicles) it could provide an alternative return path for the light beam. If this happens, conventional reflective photo eye systems could fail to recognize an obstacle in the path of the moving door.

VITECTOR has invented a method of determining the distance between the photo eye and a reflective object. This enables a RAY-RT unit to distinguish between a clear path (when the light is reflected from the “official” reflector unit) and the situation where the light has been reflected from a shiny obstacle located somewhere between the photo eye and the reflector.

The RAY-RT photo eye contains two photocells and an arrangement of lenses and apertures that allow the unit to detect small variations in the angle of incidence of the light returned from the reflector. As shown in Figure 1, the angle of light reflected from an object will change depending on its distance from the light source/photo eye unit. If the angle of the reflected light detected by the system is within certain pre-set limits, indicating that the source of the reflection is relatively close, the system will recognize the source of the reflection as an obstacle and trigger an alarm. In this way, the RAY-RT is able to detect objects in the path of the door, regardless of their reflective properties.

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