What Is an IR Touch Screen?

Infrared Touch Screen Technology consists of infrared emitting and receiving sensing elements mounted on the outer frame of the touch screen. On the screen surface, an infrared detection network is formed. Any touching object can change the infrared on the contact to achieve touch screen operation . The implementation principle of infrared touch screen is similar to surface acoustic wave touch, it uses infrared transmitting and receiving sensing elements. These elements form an infrared detection network on the screen surface. Touch-controlled objects (such as fingers) can change the infrared of the contact point, which is then converted into the coordinate position of the touch to achieve the response of the operation. On an infrared touch screen, a circuit board device arranged on four sides of the screen includes an infrared transmitting tube and an infrared receiving tube, correspondingly forming a horizontally and vertically crossed infrared matrix.

Infrared technology touch screen

Infrared Touch Screen Technology

Ambient light factor. The infrared receiver has a working range between the minimum sensitivity and the maximum illuminance, but touch screen products cannot limit the range of use. From dark cabaret rooms to outdoor use under high intensity sunlight on Hainan Island. As a product, it must adapt.

Quick detection, the infrared touch screen generally has at least 64 sets of infrared pairs, which means that at least 0.4 milliseconds to complete an infrared detection.

The surrounding reflection, refraction, and interference. The infrared transmitting tube has an emission angle, and the receiving tube has a wide range of receiving angles. If the surrounding reflection reaches a certain level, you will find that your finger cannot block the signal anywhere.

To solve these problems, the biggest advantage of choosing the analog method is that it can analyze and improve the resolution of the touch screen, but the anti-interference ability is not as good as the pulse method. Although the pulse method is selected, although the anti-interference ability is strong, the pulse method requires a response process at the receiver. The problem of time, but the touch screen requires extremely fast speed, so it is necessary to have technological breakthroughs in several aspects such as adaptive circuits, microcontroller software, mold design, selection of light-transmitting materials.

The infrared touch screen works with multiple pairs of infrared transmitting and receiving tubes. The performance and life of the infrared pair are reliable. Any object that blocks light can be used as a touch object. However, the infrared touch screen uses nearly 100 pairs of sensors and shares peripheral circuits. This requires that not only the performance of the sensor is good, but also that the "light-resistance characteristics" and "junction capacitance" of nearly 100 pairs of infrared diodes are consistent. In actual application, if any pair fails, it can be found during the power-on self-test and ignored afterwards. It is replaced by neighboring infrared rays. Since each pair of infrared rays only "supervises" a narrow band of about 6mm, and The thickness of a finger is usually around 15mm, which is imperceptible to the user. But if the production process does not carry out aging test on the infrared emitting tube, there is no good quality management system, and nearly 100 pairs of sensors will soon not be a one-to-two pair "behind the scene" problem, and the overall life will be difficult to guarantee. Therefore, users who purchase infrared screens should know whether the manufacturers have strict quality inspection methods or whether they have passed ISO9000 certification.

The infrared screen relies on the infrared matrix. The x and y coordinates of multiple points on the matrix can be combined into a square multiple of touch points. See the figure below. The two points A, B and two points C and D are for the infrared screen. The same effect ca nt be distinguished. The processing method is that the common treatment of multi-touch by infrared screens on the market, whether continuous or not, is either not judged or judged as the upper left corner, that is, whether it is A, B or C, D Both were judged as point C. The infrared screen that is really technically good should be the midpoint of multi-touch determination with continuous coordinates, that is, the touch of a large object (such as a thick finger) is judged, and discontinuous multi-touch is not judged, so it is said Excellent technology is that this algorithm has stricter product quality requirements and does not allow a variety of fault conditions.

The capacitive touch screen itself is actually a set of precise leakage sensors, which ca nt be touched by a gloved hand. Due to the use of the capacitive method, there is a drift phenomenon. The capacitive touch screen in the next section has a detailed introduction.

Ultrasonic touch screens include surface acoustic wave touch screens and bulk acoustic wave touch screens. They both use electro-acoustic piezoelectric transducers as sensors. The piezoelectric crystals used by the receiving sensor and the transmitting sensor are not a model. The difference is that the transmitting transducer has high power and the receiving transducer is more sensitive. The piezoelectric transducer has a long life and stable operation, and normal operation can guarantee no problems for 10 years. After the touch screen is installed, the transducer is hidden, but care must be taken during transportation and installation. The exposed transducer crystal cannot be squeezed. The surface acoustic wave touch screen has two pairs of sensors, X and Y axes. The surface acoustic wave on the screen is used to detect finger touch. It can be said that the working surface is a layer of invisible and unbreakable acoustic energy. It is not afraid of violent use. Inquiries are currently the most popular touch screen products on the market. ^[1]

For a long time, the touch screen market is in a colorful situation. Touch screens using different technologies are adapted to different application environments. Infrared touch technology is just one of them, with its own advantages and disadvantages. People in the industry are very fond of the advantages of infrared touch technology, and their deficiencies are very clear, and they have made unremitting efforts to improve. So far, infrared touch technology has entered the fifth generation. Judging from some of its characteristics, it is very likely to stand out from various touch technologies and become a tide in the touch screen market.

The early infrared touch screen appeared in 1992 with a resolution of only 32 × 32. The first-generation infrared touch technology has low resolution, is susceptible to environmental interference and malfunctions, and requires use in a certain shading environment. Because of these limitations, infrared touch screens once faded from the market.

The second-generation infrared touch screen was launched in 1994 with a resolution of 64 × 64, which improves the anti-light interference performance and can adapt to most indoor environments. The third-generation infrared touch screen was launched in 1997 with a resolution of 320 × 240 and can be used outdoors in direct sunlight. The main contribution of the fourth-generation infrared touch screen is to improve the resolution to 800 × 600. In 1998 roll out. Judging from the development of infrared touch screens, the main progress has been made along the two aspects of increasing resolution and adapting to strong light interference environments, but basically it has not overcome the problems of short product life and easy drift of device characteristics.

The recently introduced fifth-generation infrared touch technology not only improves the resolution to 1000 × 720, but also improves the anti-light interference performance to the direct sunlight environment. It is also more important in terms of product life and maintenance-free performance. leap. The fifth generation of infrared touch adopts the guiding idea of redundant distribution of probability function devices, and the working life is more than 7 years in the working environment. This means that when the supporting display reaches the end of its life, the touch screen itself is still working normally.

The improvement in performance indicators of the fifth generation infrared touch screen is enough to push the application of touch screen to a new level. It can be used in some cases. For example, in the past, when the touch screen tracked the movement of a finger, a lot of broken pens appeared, which could not be used for Chinese character recognition. The fifth-generation touch screen can meet the requirements of accuracy, smoothness and tracking speed when tracking the movement of fingers. The user's writing can be converted into an image track very smoothly, fully supporting handwriting recognition input.

The sixth generation touch screen is adapted

In fact, it is already possible to use a single device such as the fifth-generation touch screen as a complete human-machine interface platform instead of a mouse, writing pad, or even a keyboard.

From the perspective of the application, the touch screen should not only be designed as a simple device that converts the touch position into coordinate information, but also should be designed as a complete human-machine interface system. The fifth-generation infrared touch screen is based on such standards, and through the built-in processor and perfect driver software, the product concept is improved.

Therefore, the new infrared touch technology will have a very significant impact on domestic and foreign markets.

First, the fifth-generation infrared touch screen is very likely to stand out and break the world of sonic screens, resistive screens, capacitive screens, and infrared screens. The most likely situation is that infrared screens occupy more than 80% of the mainstream market, resistive screens and capacitive screens are locked in application areas below 4 inches, and sonic screens will be gradually eliminated.

Second, the fifth-generation infrared touch screen is expected to break the situation of foreign manufacturers occupying the domestic market for a long time, and clear the US and Japanese touch screen products from the Chinese market with better quality and lower prices. However, some manufacturers in Taiwan Province of China will

1 Resistive touch screen

-Not afraid of water and dirt

-Has a small size cost advantage, suitable for industrial control products, personal portable products

-Afraid of scratches, low light transmittance, low temperature

2 surface acoustic wave touch screen

-New easy to use, suitable for short-term products

-Fear of water and ash, need maintenance

-The launch transducer is fragile and there is a repair rate

3 capacitive touch screen

-Drift, easy to partially fail

-The human body becomes part of the circuit, wearing gloves does not work

-High environmental requirements for humidity, temperature, grounding, etc.

4 Infrared touch screen

-Poor stability

-External or built-in, does not affect the appearance of the display, can adapt to large screens

-May be disturbed by light

-Good anti-riot performance

-Touch any object

-Completely enclosed and maintenance-free, adapted to harsh environments

-Completely maintenance-free after installation

The infrared sensing touch screen is suitable for a variety of occasions where the object is unknown in the open air. The sensing medium of the infrared touch screen is any object that can block light, such as fingers, pens, sticks, and so on. ^[1]