In the spectrum, the wavelength from 0.76-400™ is called infrared, which is invisible light. All substances above absolute zero (-273. 15SC) can produce infrared rays, which are called heat rays in modern physics. Infrared detection technology is a detection method that uses the same wavelength of infrared emitting tube and infrared receiving tube (infrared pair tube for short). As long as there is an object blocking the connection between the infrared pair tubes, the received signal will drop sharply, so infrared can be used to detect objects The barrier is widely used in anti-theft systems, automatic sensing systems, counters and other systems.
If infrared is used for short distances, the degree of blocking can be detected according to the attenuation of the received signal. This is the so-called analog method. The analog method uses a dense array of receiving tubes at the receiving end, which can also be used for contrast imaging; to prevent interference, infrared detection is also The pulse method can be used, that is, the infrared transmitter tube emits a fixed frequency signal, and the receiver only detects this frequency, and the pulse method has a very strong anti-interference ability.
If the pulse mode modulates the signal at the working frequency, it can also be used for digital communication. This is infrared communication. The remote control of household appliances, infrared communication of computers, and even the fastest optical fiber communication today are all due to this. Infrared communication has no effect on the human body. Because of the short transmission distance and no space pollution, it is popular nowadays.
Infrared detection technology used in touch screen technology mainly has 3 technical difficulties:
1) Ambient light factors. The infrared receiving tube has a working range between the minimum sensitivity and the maximum illuminance, but the touch screen product cannot limit the use range.
2) Quick detection. Infrared touch screens generally have at least 64 sets of infrared pairs in size, that is, at least one infrared detection is required within 0.4ms.
3) Surrounding reflection, refraction, interference. The infrared transmitting tube has a transmitting angle, and the receiving tube has a larger receiving angle. If the surrounding reflection is to a certain degree, it will cause the finger to be unable to block the signal wherever it is.
To solve these problems, the biggest advantage of choosing the analog mode is that the resolution of the touch screen can be improved, but the anti-interference ability is not as good as the pulse mode. Although the pulse mode has strong anti-interference ability, there is a pulse mode that requires a response time on the receiver side. However, touch screens require extremely fast speeds, so there must be technological breakthroughs in adaptive circuits, microcontroller software, mold design, and light-transmitting material selection.
