Touch screens are everywhere today. For this reason, Jackson Hsieh, Technical Sales Department manager at Super-Union Optical (SUO), introduced the basic principles of projective capacitive touch panels, 3G imaging formats and shutter-type 3D TV technology, and explained the market situation for these different technologies, during the recent Digitimes Technical Forum (DTF).
In a speech titled "Projective capacitive panels and 3D panels: Principles and market overview, Hsieh explained that touch screen technologies used by smartphones, mobile Internet devices (MID), tablet computers, notebooks and all-in-one PCs can be differentiated as shown in the table at the end of the article.
Each type of touch technology has its own characteristics, but as the market moves towards multi-touch functionality, resistive and electromagnetic technologies are beginning to decline. The projective capacitive technologies that are currently regarded as the focal point for development in the industry can be subdivided into glass type and film type panels according the type of substrate material they use.
Principles of projective capacitive touch technology
Projective capacitive touch screens use two layers of grids of rhomboidal glass or film sensors, with one layer responsible for X-axis detection and the other for Y-axis detection. Each rhomboidal sensor has a capacitive pair, between which there is mutual capacitance; an electrostatic field is generated on the surface of each sensor and projected to the outer side of the screen through the non-capacitive material of the glass or plastic film, with the user directly touching the glass, rather than the surface of the sensor itself. The control IC periodically checks the status of each indium tin oxide (ITO) electrode on the X and Y axes of the panel, first providing a pulse voltage to a particular drive port, and then reading a corresponding voltage from the corresponding sensor port. This information is then converted into digital values, which are provided to the control IC for data analysis, and the results of this analysis express whether a finger has touched the panel.
3D market overview and technical trends
Citing figures from market research organizations, Hsieh explained that shipments of 3D TVs, 3D Blu-ray players and 3G games consoles will all break through the 200 million mark in 2015. The ensuing demand for liquid crystal shutter (LCS) 3D glasses means that shipments of such devices may reach 210 million units, increasing the value of the market to JPY4.250 billion (US$50.6 million).
Key manufacturers of current 3D technology include Dolby, NHK Media, Nvidia, RealD, Sensio, TDVision, XpanD and THX. Other than its technology's lack of compatibility with existing 2D MPEG/DVB video/broadcasting standards, RealD in particular is more than a match for the industry giant Dolby in areas such as marketing, CE market position and CE 3G deployment.
In terms of H.264 definitions, the 3D video formats currently on the market include the frame sequential format used for Blu-ray 3D, the side-by-side left/right eye system used by BSkyB, and the over-under left/right eye technology adopted by CableLabs/DirectTV. As RealD's patents for side-by-side technology expire in August 2011, Hsieh believes that this will be the right moment for Taiwan-based manufacturers to move into the sector.
| Comparison of 3D display technologies | |||||
| Type | Subtype | Viewing angle | Resolution | Brightness | Hardware requirements |
| 3D glasses | Shutter glasses | 2 | Unchanged | <50% | 120Hz display, shutter glasses, single synchronization device |
| Polarized 3D glasses (monitor) | 2 | 1/2 | 50% | Micro phase retarder display polarized glasses | |
| Polarized 3D glasses (projector screen) | 2 | Unchanged | 50% | Two projectors, special screen, polarized glasses | |
| Colored glasses | 2 | 1/2 | Loss of color fidelity | Colored glasses | |
| Naked-eye 3D | Grating spectroscopy | 2-N | 1/N | 1/N | Grating |
| Lenticular lens spectroscopy | 2-N | 1/N | >1/N | Lenticular lens | |
Source: Super-Union Optical (SUO)
3D displays can be divided into 3D glasses-based and naked eye 3D technologies. The latter technology is still very much in its infancy, and displays using 3D glasses are currently still the norm, with shutter 3D glasses being the mainstream choice. Current mainstream 3D TV designs all use video frequency time division display technologies, in which the left and right eye images are displayed one after the other, while shuttered glasses alternately open and close over the right and left LCDs, allowing both eyes to see different full HD images, which the brain then reassembles into a 3D scene.
| Common problems with shutter-type 3D TV displays | |
| Number | Problem |
| 1. | Crosstalk. Scanning backlight or black frame insertion methods can be used to increase panel driving frequency and improve LCD shutter response rates, in order to reduce crosstalk. |
| 2. | Light degradation problems with glasses. This requires increasing the efficiency of light emission in panels and improving light emission control. |
| 3. | Insufficiently vibrant color. This can be improved by the addition of primary colors via yellow light, as in Sharp's Quattron four color (RGBY) LCD technology. |
| 4. | Flicker issues with glasses. This must be dealt with by reducing interference and improving LCD response times. |
| 5. | Lack of software. 2D to 3D image conversion technology can be used to broadcast existing 2D content as lifelike 3D content. |
Source: Super-Union Optical (SUO)
| Good active 3D shutter glasses require attention in the following areas: | |
| Number | Area |
| 1. | Contrast levels, reaction times, transmittance and field of view for the lenses of the shutter glasses. |
| 2 | There must be absolutely no issues of ghosting, pseudo stereo, dropped frames or inability to operate. |
| 3 | Insufficiently vibrant color. This can be improved by the addition of primary colors via yellow light, as in Sharp's Quattron four color (RGBY) LCD technology. |
| 4. | Design of the glasses must be comfortable and ergonomic. |
Source: Jackson Hsieh, Technical Sales Department manager at Super-Union Optical (SUO)
Last but not least, Hsieh gave a brief introduction to SUO. The firm is located in Tainan Science Park, where it strives to provide industry-leading products in areas including 2.8-inch to 19-inch projective capacitive touch panels, 3D LCS glasses and polarizer lens products.
Jackson Hsieh, Technical Sales Department manager at Super-Union Optical (SUO)
Photo: Staff reporter, Digitimes
| Comparison of touch panel technologies | |||||
| Technology | Resistive | Capacitive | Surface acoustic wave (SAW) | Infrared | Electromagnetic sensor |
| Sensor method | Voltage detection | Senses changes in capacitance caused by static electricity in the human body | Detects acoustic waves | Blocked optical signal | Electromagnetic sensor |
| Price | Cheap | Quite expensive | Expensive | Very expensive | Expensive |
| Durability | Good | Excellent | Good | Average | Excellent |
| Accuracy | Good | Good | Good | Good | Good |
| Transmittance | 85-90% | More than 90% | More than 92% | 100% | More than 90% |
| Touch media | Finger/stylus | Finger (gloves cannot be worn) | Finger/stylus | Finger/stylus | Dedicated electromagnetic stylus |
| Panel characteristics | Vulnerable to scratching and flame, fairly low transmittance | Resistant to scratching, stains, water, static electricity and dust, fast reaction time, multitouch recognition | Resistant to scratching and flame | Resistant to scratching and flame, very reliable, not very resistant to water or stains | High sensitivity, large volume, difficult to assemble |
| Sizes (inches) | 1-20 | 3-19 | 9-42 | Unlimited | 3-29 |
Source: Super-Union Optical (SUO)
