In recent yearstouch screenThe development of technology has played a significant role in its selection as the human-machine interaction interface for HMI systems. This type of device has been questioned in various aspects. However, nowadays their performance changes have made them frequently replace the use of mice and keyboards. From durable and exquisite, widely used types to the development of various innovative technologies, touch screen technology is constantly advancing and developing.
Progress, refinement, and improvement
The main touch technologies work mainly through the intervention of mechanical fields (resistive), electric fields (capacitive), acoustic waves (surface acoustic waves, SAW), and infrared (IR) light. Just a month ago, 3M Touch Systems launched a new technology. Dispersion signal technology recognizes touch information through the vibration of the substrate glass caused by touch. The developers of this technology position it as a breakthrough in the field of touch screens. It is said that this acquired technology has high transparency, performance, supports stylus and signature recognition, and has full glass durability.
Sensors located in various corners of the screen can measure the energy of vibrations, and this type of touch screen works using these sensors. Through advanced digital signal processing, it applies dispersion adjustment algorithms to analyze signals and provide contact coordinates. This method helps eliminate problems caused by screen contamination and surface scratches, and has higher palm contact inhibition ability. For example, when the operator's palm or other object is placed on the screen surface, touch information can also be displayed. Even if someone leans against the screen surface or places a tablet on it, fingers, gloved hands, or touch needles can still trigger the signal. Touching causes vibration, which emits bending waves that propagate through the substrate glass from the contact point to the edge of the screen, ignoring other stationary information.
According to Doug Kuller, a project manager at 3M Touch Systems, at the Society for Information Display (SID) 2004 international seminar and exhibition in May, this technological advancement can change the prospects of the touch screen industry and will become a development platform for 3M Touch Systems products that will soon be launched in large quantities. It also reflects the effectiveness of joint research and development between 3M and NXT, a British company engaged in sound and speech technology.
Another achievement before this technological advancement was the digital ink technology launched by Touch International last year, which combines many characteristics of capacitive and resistive screens. Lightweight, suitable in shape, non fragile, and wear-resistant, this material accepts input from touch needles, fingers, and gloved hands, but does not respond to accidental contact with the operator's hands or palms. It is particularly suitable for small-sized devices such as PDAs and other handheld devices.
Resistive touch screen - still irreplaceable
Despite the promising new technologies recently introduced, traditional products seem to still dominate the market in recent years. Although the choice of product depends on its application scenario, resistive touch screens are still the most common choice for people. In contrast, it is not expensive and easy to produce, making it convenient to assemble into a display. The improvement work has overcome many previously pointed out deficiencies in properties and transparency, making it a flexible and economical solution applicable in most situations. The emergence of four wire, five wire, and seven wire eight wire touch screens has made product performance more reliable, while improving product optical characteristics and durability. Ai Zelasko, responsible for the development of display technology business at Avnet Applied Computing Solutions, pointed out that "in use, due to the need for the light emitted by the TFT (thin film transistor) behind the screen to pass through multiple layers of materials, its brightness will be reduced, which has led to the development of different types of thin film technologies for touch screens, resulting in better screen transparency. Spending funds on screens rather than TFTs may result in better optical effects with less cost. At present, the improvement of TFT performance also contributes to the improvement of optical effects. The standard TFT nowadays is 400 nits. In the case of transmission leakage of 2% or 3%, the light efficiency has almost no effect like the old model display with only 250 nits. (Nite is a unit of measurement for brightness; 1 nite is equivalent to one square meter of candlelight.)
All touch screen technologies, whether resistive, capacitive, surface acoustic wave, infrared, or dispersive signal, have their own advantages and disadvantages. Joe Kirby, Vice President of Technical Development at Dolch Computer Company, sees it this way: "Actually, there are no bad touch screen technologies, it's just that some technologies are not suitable for the right applications. For example, resistive and traditional capacitive screens are generally not used in fragile or harsh environments and are usually more suitable for indoor use rather than outdoor use. Technologically improved infrared touch screens are very durable and do not lose records. However, mechanical limitations make them unsuitable for small-sized devices such as PDAs. In any case, before making a decision, you need to determine how to use this thing, where to use it, and why to use it. If cost is the dominant factor and the device operates in a relatively good environment, then resistive touch screens are usually a reasonable choice. ”
Ann Ke from Wonderware also agrees with this viewpoint. Their company launched a touch screen computer combined with Intouch HMI software last autumn, thus entering the touch screen market. She said, "We have tried to standardize resistive touch screens. We believe it represents most of our market demand, and of course, it may not solve all problems, but it is indeed suitable for most applications
Product Selection
Although not as widely used as resistive touch screens, capacitive touch screens are also a popular option. These types of devices have fast response times, higher resolution even in slightly larger sizes, and are more durable (scratch resistant), making them popular as touch screens for gaming consoles. A related technology, near-field imaging (projected capacitive), improves the performance of capacitive touch screens and limits the drift phenomenon that may occur in them and resistive touch screens.
Advanced technologies such as surface acoustic waves (SAW) and infrared light (IR) (along with enhanced IR) are also effective in special situations. SAW has high accuracy and can be used for outdoor operations and glove wearing operations without being affected by temperature and humidity fluctuations. However, the transmission of sound waves can be hindered by dirt, resulting in input errors. Therefore, SWA touch screens are mostly used in clean rooms. He is reliable but also expensive, making it slightly difficult to assemble into a monitor. Durable industrial applications often use IR based on the principle of light blocking,. Suitable for indoor and outdoor work, it can be scraped with reinforced anti glare glass or packaged differently according to different environments.