What is the basic structure and principle of LCD touch screen?

Infrared touch display structure:

The infrared touch display is easy to install, just add the light point pitch frame on the display.Infrared emitting tubes and receiving tubes are arranged on the four sides of the light spot from the frame, forming an infrared net on the surface of the screen.

Principle of action:

When a user touches a certain point on the screen with a finger, the two infrared rays passing through the position will be blocked, and the computer can instantly calculate the position of the touched point. Any touch object can change the infrared rays on the contact to realize touch screen operation.

Advantages and disadvantages:

The infrared touch display is cheap, easy to install, and can better sense light touch and fast touch. Not subject to current, voltage and static electricity interference, suitable for harsh environmental conditions.

However, since the infrared touch display mainly relies on infrared sensing action, it has poor resistance to light interference and is not waterproof. It is afraid of dirt and any small foreign objects will cause errors.

Capacitive touch display structure:

The structure of the capacitive touch display is mainly to plate a transparent thin-film conductor layer on the glass screen, and then add a protective glass to the conductor layer. The double glass design can completely protect the conductor layer and the sensor. In addition, long and narrow electrodes are plated on all four sides of the additional touch screen to form a low-voltage AC electric field in the conductive body.

Principle of action:

When the user touches the screen, due to the electric field of the human body, a coupling capacitor is formed between the finger and the conductor layer. The current from the four-side electrode will flow to the contact, and its strength is proportional to the distance between the finger and the electrode. The controller is located behind the touch screen. The ratio and strength of the current will be calculated, and the position of the touch point will be accurately calculated.

 Advantages and disadvantages:

The double glass of the capacitive touch display can not only protect the conductors and sensors, but also effectively prevent external environmental factors from affecting the touch screen, such as dirt, dust or oil stains on the screen. The capacitive touch display can still accurately calculate the touch position.

The capacitive touch display has serious light reflection, and the four-layer composite touch screen of the capacitive technology has uneven light transmittance for each wavelength, and there is a problem of color distortion. In principle, the capacitive touch display uses the human body as an electrode of a capacitive element. When a conductor is close to the ITO working surface, a capacitor of sufficient capacitance will be coupled, and the flowing current will cause malfunction.