Near-infrared Sensor

Quick detection of objects by reflection/ transmission of light

Sensors which can catch near-infrared rays, electromagnetic waves close to visible light
They are used in a wide variety of fields such as automatic door sensors and security sensors.

Principle of near-infrared sensor

They detect objects by emitting near-infrared rays and identifying the rate of change caused by the reflection or transmission of light.
Near-infrared rays are called optical sensors and have properties to respond quickly and detect stationary objects with their precise detection range.
Optex carries mainly two types of product lines.

1. Near-infrared reflection detection type: mainly applied to automatic door sensors.

Near-infrared rays (light) are transmitted from the light-emitting elements mounted on the sensors and this light is projected on the floor through the optical system (lens).
This projection range is configured as a 3D detection area, and if any human/ object intrudes in this area, the volume of the reflection of light changes.
Such changes are converted into detection signals

2. Near-infrared transmission detection type: mainly applied to security sensors and automatic door sensors.

Near-infrared rays are projected to the light-receiving elements on the opposite side through the optical system (lens) on the sensors, and the detection area is configured.
If any human /object intrudes into the area between the light-emitting and light-receiving modules facing each other, the volume of infrared rays changes, and this change is converted into detection signals.

The highly reliable technology of Optex provides the secure detection of targeted objects.

Sensors may be affected by the following indoor/outdoor factors.

  • Intrusion of objects other than humans which have a certain reflection rate
  • Natural phenomena such as sunlight, rain, snow, fog, etc., which affect the reflection rate.
  • Interference from other similar devices or sensors which function with the same mechanism principle.

Considering those factors, Optex takes measures to eliminate such obstructive factors to sensors in order to ensure precise detection.

1. in the case of the near-infrared reflection detection type (for the use of automatic doors)

  • Optex's unique micro-computing control provides safe, secured and comfortable passage

Automatic doors are required to have excellent quick activation and safety with a stable detection system unaffected by factors to cause malfunction.
Optex has realized intelligent sensing with its original micro-computing technology 'N-Pro', incorporating functions to meet individual requirements.

1) Measures taken to deal with malfunction factors arising due to changes in natural environment.

Sensors can malfunction due to environmental changes such as rain or snow, or electromagnetic noise. But Optex sensors are capable of controlling a number of information, including changes in the natural environment or ambient temperature, by its original micro-computing system.
Effects are categorized into those from the natural environment and those from human intrusions in the detection area.

2) Measures to improve safety

Optex has improved the safety of automatic doors with a 'Stationary object detection function' where doors do not shut when a person stands still within the detection area, and with a synchro-doorway function' where standing on the door rail is detected.

2. In the case of the near-infrared transmission detection type 【for security use】

  • Measures to be taken to deal with natural phenomena by 'sensitivity margin' and 'distance margin'.

When sensors are used outdoors, it should be assumed that false motion detection alerts are activated as the sensitivity of sensors decreases due to light attenuation caused by rain, fog or stains.
Optex has developed products with a sufficient sensitivity margin and distant margin, maximizing data of field tests and data on their use and installation conditions around the world.

*Relation between Sensitivity and Distance

For example, if the detection distance is doubled, the sensor-coverage area will be quadrupled. Then sensitivity per area will decease to one fourth without correction.
On the other hand, if sensitivity is randomly increased, factors to leading to false motion detection alerts will also increase. Therefore, it is necessary that designing takes this tradeoff relationship into consideration. 

  • Implementation of various measures based on foreseeing/anticipating/ the installation environment

It is required that sensors have diverse functions taking the installation environment into consideration, and reflecting concepts of a sufficient sensitivity and distant margin.
For example, while excessively strong light emission will cause a malfunction of sensors, stains on a lens may also attenuate the intensity of light emission.
In Optex products, the sensitivity of sensors is controlled by the 'Automatic Transmitting Power Control (ATPC Function) '. If multiple sensors are installed in proximity, the timing of the emitting beam is automatically adjusted by the 'TDM Communication Function' in order to avoid interference between the devices.
Performance stability is maintained
Optex, incorporating diverse technology, provides solutions according to the customer's use.
Optex combines various technology such as introducing highly-density patterning to detection areas, flexibility in responding to changes of weather or environment with temperature compensation circuits, etc.