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Technique

Technique

Outdoor Touch screen

What’s different?

Using the IR(Infra Red) Touch Screens in an outdoor environment requires the specific technologies to reduce sunlight interference.
A worthy touch screen should not be affected by weather factors such as snow, heavy rain, strong winds and humidity. Also, it should eliminate sunlight interference and protect against water or dust as it is more suitable for the outdoor environments and more convenient for the use with IR Touch screens.

What are our state of art technologies applied to the outdoor environments?

To eliminate sunlight interference in outdoor environments, we have used the innovative optical filter technologies. These state of the art filter technologies will eliminate sunlight interferences and provide multi-touch operations in the outdoor environment.

The three filters we used follow :
  • 1. Anti-Solar Filter is the polarized filter removing the direct sunlight, which is incoming to the IR sensor plane of the touch panel. This anti-solar filter provides an excellent uniformity.
  • 2. Sun-Block Filter removes any reflected and refracted light which is inside the bezel of touch module frame. It also helps to get over reflection and refraction phenomenon from the touch glass.
  • 3. Front IR Filter removes lower wavelength of sunlight and improves the transmissivity of IR LED’s wavelength

Overall, these technologies maximize the efficiency of the IR Touch Screens.

How to secure the required Signal to Noise ratio(S/N) in outdoor IR touch environments

To secure the required S/N ratio in the outdoor environment is one of the most important technologies.

The stronger the sunlight interference, the worse the S/N ratio becomes.The failure rate of the Touch function will increase if the S/N ratio of the Touch module deteriorates.

Thus, the technologies applied to IRON provide a stable touch function in the outdoor environment by ensuring S/N ratio.

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As mentioned above, there are two main causes making noises. One is the interference from the sunlight and the other is from the circuit of the PCBA Board. In other words, it is important to have the S / N required for IR sensor technologies, and engineers should consider reducing these overall noise intensities in outdoor environments.

The PCB circuit should be also designed to reduce noise, and the impedance of the IR signal as well as the low noise power-line design should also be considered.Based on the above-mentioned basis, IRON was designed by securing the required S/N ratio for multi-touch operation in the outdoor environment. At the same time, special filters applied to IRON, optimized flame and PCB design contributed to ensuring a satisfactory S/N ratio.

＊Required S/N: Minimum Signal to Noise ratio to perform a Multi-Touch Functions
To reduce total noise intensity

Major noise factor is sunlight interference noise and PCBA board circuits noise, especially sunlight noise is the biggest and powerful.

Most important thing to stable operation of touch screen in outdoor environment, securing the required signal to noise ratio(S/N) is.

It is also important to block sunlight, but it is also important to apply algorithms to ensure stable operation of the circuit.

Higher Protection level with creative design of frame

IRON is satisfied with IP65(standard) and IP66(option) protection level without touch glass.

Aluminum extruded one-body frame structure of touch module makes it have price competitiveness and increase yield rate.

The design of the waterproof structure using protection rubber is our creative design, which makes it possible to meet the protection level such as IP65/IP66.

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A. Extruded one-body Frame structure

Extruded one-body type can minimize the number of frame connection.

By minimizing connection, water and dust can be prevented effectively.

B. Rubber Protection

By inserting the rubber between IR filters mounted in the frame, the waterproof capability is maximized.

It is made of materials that can operate in outdoor climate change environments.

Operation free regardless any environment.
Regardless of the location of the Sun, Sunlight is the most powerful interference source.

Various directional interference of sunlight is the biggest obstacles to use in the outdoor environment.Outdoor touch modules should be ready to protect in any directional and simultaneous interference environment.

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As changing the position of the sun, IR touch frame may be affected simultaneously from various sunlight inteference such as reflectied, refracted and directly incident light. Outdoor IR touch system may installed in front of store or nearby building, on the road and etc.IR touch system, in order to be used in outdoor environment stably, must endure from all simultaneous interference of any direction, any kind of light.

How to verify the performance of outdoor IR touch?
Conditions to be considered when testing.

Place the Touch Module to be tested where various interferences are caused by sunlight such as direct, reflected and refracted sunlight. Angles with the face of the Touch Module relative to the sunlight are gradually changed horizontally or vertically. To measure the exact sunlight interference, direct light from sunlight, reflection or refraction in the surrounding environment must be considered.

At last, you can test the combined Glass and Touch Module together.

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Things to consider during testing

The Touch Durability Test for interference from sunlight must simultaneously measure all the light generated interference from the IR sensor surface and consider the Multi-Touch function in such an interference environment.

Procedure of the test (Touch Durability in Sunlight Interference)

Unfortunately, there is no standard to demonstrate and measure performance for outdoor touch products to date. However, we have established guidelines for the testing methods and verification procedures based on our existing know-how founded on common sense.

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How to Measure Minimum Facing Angle(MFA) and Power of Sun Light

When the IR sensors in the IR arrayed planes are directed to the Sun, the Incident Angle can be thought of as the Minimum Facing Angle(MFA) when the IR sensors in the IR arrayed planes are directed to the Sun

When the IR sensors in the IR arrayed planes are directed to the Sun, the Incident Angle can be thought of as the Minimum Facing Angle(MFA) when the IR sensors in the IR arrayed planes are directed to the Sun

  • 1.Place the touch module on the test stand. Test stand should be made with rigid material to stand wind.
  • 2.Adjust the tilt angle with manipulating the tilting controller of the test stand. If single or multi touch function become disabled, stop adjusting and maintain operable state. This incident angle that IR sensors in the IR arrayed plane can directly look up the sun is referred to as the maximum facing angle.
  • 3. Measure the maximum facing angle with the sun using an solar angle measuring instrument.(SAMI) The solar angle measuring instrument can be provided separately, and which measures the incident angle of sun automatically. At this point, measure the solar incident power come into IR sensor plane using solar power meter.
  • 4. After finding the angle of the maximum incident angle, turn the direction of the touch module from side to side to verify normal operation of the multi-touch function.
    * The Operational condition may be changed according to number of multi-touch function and buyer’s demand.
    This measurement procedure is suitable for reliability test of outdoor IR touch frame.

This method for testing is very reasonable for the reliability test of the outdoor IR Touch module.