Recently, Sony released its latest “hover touch” screen technology, attracting a lot of attention. Many people are looking forward to it, while others believe it is more of a gimmick than practical. In fact, since the emergence of touch screens, the pursuit of new display technologies has never ceased. From early resistive screens to today’s capacitive screens, various mobile manufacturers continue to develop their own screen technologies, with each innovation bringing significant changes to display performance. So what are these technologies all about? Today, I will explain them one by one, hoping to help everyone.
Hover Screen Technology
Working Principle of Hover Touch Technology
What is the working principle of hover touch technology? Erik Hellman, a research engineer and co-inventor at Sony Mobile, elaborated on the hover touch technology:
Like many smartphones, the Xperia sola uses capacitive touch sensing to record user inputs on the screen. The events that occur when touching the phone’s screen are called touch events. Capacitive touch works by covering the phone with an X-Y electrode grid, utilizing the voltage above. When a finger approaches the electrode, the capacitance changes and can be measured. By comparing the measurements from all electrodes, the position of the finger can be accurately located.
There are two types of capacitive sensors on the touch screen: mutual capacitance and self-capacitance. Mutual capacitance is used to achieve multi-touch detection. Self-capacitance can generate a stronger signal than mutual capacitance, detecting fingers further away, but cannot perform multi-touch detection due to an effect known as “ghosting”.
The circle represents the touch point, and the red X indicates the ghosting position.
Mutual Capacitance for Multi-Touch
With mutual capacitance, each intersection of the lines in the above image forms a parallel plate capacitor. This means that each intersection is a capacitor, ensuring that measurements can be precise for each finger, enabling multi-touch. However, because the area of the intersection between two lines is very small, the sensor’s electric field is also very small. The sensor is so small that the signal strength is very low, making it unable to sense very weak signals. Therefore, when a user’s finger hovers over the screen, the mutual capacitance sensor cannot detect the signal.
Self-Capacitance and Ghosting Effect
In the self-capacitance case, each X or Y line in the above image is a capacitive sensor. Clearly, self-capacitance sensors are larger than mutual capacitance ones. Larger sensors can create powerful signals, allowing devices to detect fingers up to 20mm above the screen. When a finger hovers over the screen, the nearest sensor line will be activated (X1, Y0). If two fingers are detected, four lines will be activated, leading to the ghosting effect. As shown in the above image, when two fingers are detected, four possible touch points (X1, Y0), (X1, Y2), (X3, Y0), and (X3, Y2) will appear, and the correct combination is ambiguous, preventing multi-touch.
Combining Self-Capacitance and Mutual Capacitance for Hover Touch
Hover touch is achieved by running both self-capacitance and mutual capacitance simultaneously on a capacitive touch screen. Mutual capacitance is used for normal touch sensing, including multi-touch, while self-capacitance is used to detect fingers hovering above. Since hover touch technology relies on self-capacitance, it is not possible to achieve hovering multi-touch. In other words, when performing a hover operation, the screen does not support multi-touch. Multi-touch can only be realized in contact situations.
This technology was developed in collaboration with Cypress Technologies. By utilizing existing capacitive touch sensors, the threshold for touch input can be lowered, distinguishing between hover touch and contact touch. All Android applications can operate normally. However, only applications that explicitly respond to hover touch events will react, meaning that the implementation of hover touch technology requires support from internal application programs.
Hover Touch Screen
Regarding the possibilities for developers and the initial implementation of hover touch, in the Xperia sola, this feature can only be realized in the built-in browser. The built-in browser can trigger “hover events” that have never appeared on previous phones. This use case was previously only activated when using a standard mouse on a PC. All existing websites that can respond to hover events can be operated using hover touch technology on the Xperia sola.
Standard HTML5 hover events have already been implemented in the native Android browser on Xperia phones. This means that web developers can now utilize hover touch technology through standard HTML5 hover events. However, we are preparing more interesting things for developers. In the upcoming Xperia sola Android 4.0 ICS upgrade, third-party developers can utilize this technology in their own applications, as Google has introduced a new open-source API in ICS for handling hover events.
Applications of Hover Touch Technology in the Future
Through the above explanation, we understand the working principle of hover touch technology. So what is the use of this technology? Let’s explore a bit.
As we all know, capacitive touch screens have a significant drawback: during winter, we must take off our gloves to operate the phone, which is very inconvenient. If hover touch technology matures, we could use the touch screen without taking off thick gloves, greatly enhancing user convenience.
In gaming, we can also fully utilize this technology to provide a better user experience. For instance, when playing racing games, we can control the throttle and brake intensity based on the depth of finger pressure, which is quite exciting, but this requires the “hover touch” precision to be sufficiently high.
Of course, the potential of this technology is far from limited to this. How far this technology can develop depends on how software developers utilize it. We can imagine that if this technology is applied to the iOS system, it would certainly become another revolutionary innovation, leading to a plethora of high-quality applications and games. But can Android fully utilize and develop this technology? We shall see.
WhiteMagic Technology
The WhiteMagic technology may not be particularly familiar to everyone; it is the screen technology used in Sony Mobile’s new device, the Xperia P, released at MWC 2012. As we know, ordinary LCDs use the RGB three primary color pixel arrangement, while WhiteMagic technology creatively adds a white sub-pixel to this basis, using an RGBW (Red, Green, Blue, White) pixel arrangement to increase screen brightness. This means that each pixel point of the WhiteMagic screen consists of four sub-pixels, as shown in the following image.
Sub-pixel arrangement of the WhiteMagic screen
The purpose of WhiteMagic technology is to improve screen brightness so that the content displayed on the screen can be clearly seen even in bright outdoor light. Depending on different usage scenarios, the WhiteMagic screen can automatically switch between two brightness modes:
Outdoor mode: In bright outdoor light, the transparency of the white sub-pixel increases, allowing the WhiteMagic screen to achieve about double the brightness under the same backlight brightness, making it easy to see the screen even in bright sunlight.
Indoor mode: In low light environments indoors, to achieve the same brightness as ordinary panels, only 50% of the original backlight brightness is needed, leading to only 50% of the original power consumption (which also means longer standby time). Therefore, the WhiteMagic screen is also one of the most power-efficient screens on the market. As shown in the following image.
If you have used Nokia N9 or Lumia series phones, you must have been attracted by their pure black backgrounds, refreshing display effects, and anti-glare capabilities in bright outdoor light. This is because the screens of Nokia phones utilize ClearBlack display (CBD) technology, which enhances the display effect outdoors. So what is CBD technology?
CBD technology incorporates a polarizing layer into the display structure, which helps solve glare problems without increasing screen brightness, while maintaining image quality and deepening black colors as much as possible. In addition, CBD display phones can create amazing color contrast, allowing your applications, videos, and images to display clearly and realistically on the screen, while ensuring that battery life is not significantly affected.
CBD Technology Display Principle
First, let’s discuss the structure of touch screens to better explain how CBD displays work. The touch screen of your phone is essentially like a multilayer pancake made of different components. The position of the “polarizing film” layer is fundamental to achieving the excellent visual effects of CBD displays. The polarizing film is a circular layer that effectively eliminates excess reflections. Reducing reflections helps improve visual contrast, thus displaying vivid colors and purer blacks.
In CBD display phones, the polarizing film is located between the window and the touch sensor. The goal of this layer is to stack optical performance with air gap solutions. By placing the polarizing film between the touch sensor and the display, engineers can effectively block reflections from the capacitive sensor grid. To help you imagine, try tilting a traditional touch screen phone under direct sunlight… Did you see the grid formed by small dots? That is the capacitive sensor grid.
Furthermore, by placing the polarizing film in that position, light is dispersed, reflections are minimized, resulting in a clearer screen, and the contrast between all icons and colors is very distinct. To understand the difference between CBD display phones and ordinary phones, please refer to the image on this page. The left side is a phone with a CBD display, and the right side is one without; it is clear that the glare and reflection phenomena are particularly severe on the latter.
Comparison between ordinary screens and WhiteMagic screens
As seen in the above image, the maximum brightness of the WhiteMagic screen can reach 935cd/m2 without increasing backlight brightness, while the indoor mode brightness can be maintained at around 530cd/m2, with backlight brightness only being 50% of that of ordinary screens, saving battery consumption.
In addition to CBD technology, Nokia N9 and Lumia series phones also feature a special screen technology called curved vacuum screens. The screen surface is covered with a beautiful curved Corning glass and uses a seamless design, making the screen surface appear as if it is贴在玻璃表面， creating a strong three-dimensional effect, as if the screen content is floating above the device. The screen is vacuum processed, so there is no need to worry about dust entering the screen.
Retina Display Technology
When it comes to Retina technology, everyone is probably familiar with it; yes, it is the screen display technology widely used in some Apple devices. First applied to the screen of the iPhone 4, this technology brought extremely clear display effects to the iPhone 4.
The iPhone 4 uses a Retina display
The Retina display is a liquid crystal screen with an ultra-high pixel density, compressing a resolution of 960×640 into a 3.5-inch display. This means that the pixel density of this screen reaches 326 pixels per inch. Users familiar with real resolution will know that the resolution of a typical computer screen is 72 pixels per inch. The resolution of the iPhone 4 is more than four times that of a computer, even exceeding the range that the human eye can distinguish. Therefore, the display is very delicate. Text in e-books, web pages, and emails appears clear at any size, and images and videos look stunning from any angle.
The display effect of the iPhone 4 is extremely delicate
It is well-known that the delicacy of a phone screen is directly related to its size and resolution, and there is a professional term for measuring screen delicacy—PPI. The higher the PPI value, the more delicate the screen. The iPhone 4 achieved an astonishing 326 PPI (326 pixels per inch), exceeding the range recognizable by the human eye.
The Retina display uses in-plane switching (IPS) technology to achieve a wider viewing angle than standard liquid crystal displays. This means you can hold the iPhone in almost any way and still achieve vibrant image effects. It is very suitable for sharing photos with friends or controlling the iPhone while playing driving and flying games. Moreover, the contrast presented by the Retina display is four times that of previous displays, with lighter colors being brighter and darker colors being more stable, making everything more appealing.
Conclusion:
Today, I introduced various screen technologies from major mobile manufacturers, and I believe everyone has gained some understanding of smartphone display and control technologies. In the future, when purchasing a phone, do not blindly pursue screen resolution and materials; in fact, various special screen technologies are also crucial factors affecting display performance and user experience.
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