Through a glass, brightly

4 min read

By combining touchscreen functionality with mirrored glass, a multitude of new applications are possible

Touchscreen functionality not only simplifies and improves human-machine interaction, but it has also enabled designers to improve the appearance of highly featured products for applications ranging from white goods and information kiosks to gaming equipment, home automation and industrial control. Touch technologies that are compatible with new types of optically coated mirrored glass now enable new types of products, such as hidden control panels, decorative appliances and smart mirrors, presenting a variety of intelligent functions in so called 'magic mirrors'. Better image for tvs Consumer electronic brands have already begun using mirrored glass in products, such as tvs that can appear as a mirror when not in use. Product families, such as Philips' Miravision wall mounted lcd tv, act as a mirror when powered down and have encouraged tv designers to move forward from traditional, box like enclosure styles to create a more attractive, eye catching item. Mirror tvs can transition between tv and mirror modes by using an optically coated glass front panel. Using the same principle as a two way mirror, the coating allows the glass to appear transparent, when in front of an illuminated background, or as a mirror when the background is dark. When the lcd tv is turned on, the glass appears transparent due to the transmissive properties of the mirrored coatings and the high brightness of the display. With the display turned off, when the tv is powered down or in standby mode, the dark background causes the glass to operate in the highly reflective and mirrored mode. Adding value through touch This change in appearance, depending on whether the stronger light source is in front of the glass or behind, opens opportunities for many types of imaginative and unusual products offering new and interesting effects. Adding touchscreen capability using a technology such as projected capacitive sensing – which does not interfere with the precise reflective and transmissive properties achieved through the coating process – extends these opportunities even further. A Projected Capacitive Technology (PCT) touch sensor typically comprises an array of micro fine conductive tracks, which are positioned closely to form an XY grid. This grid then generates a capacitive sensing field in front of the sensor (see figure 1). The sensing array is encapsulated within a composite construction, the outer layer of which may be ordinary glass or polycarbonate, eliminating direct contact with the user. When the user's finger approaches the front surface of the sensor, a measurable change in capacitance is produced at the corresponding position in the array. A controller ic, usually connected to the array via a flexible flat tail fused to the glass, calculates the XY coordinates of the touch and feeds the information back to the controlling computer. A PCT sensor can be made using almost all types of glass and can be designed to detect touch through overlays approaching 20mm in thickness. Unlike most other touch technologies, the PCT sensor can be completely sealed, allowing enclosures to reach very high standards of protection (such as IP67 or NEMA 4x) from the ingress of liquid, dust or other contaminants. Depending upon application, PCT touch sensors may be enhanced with antireflective or antiglare coatings, or equipped with filters to enable privacy viewing or to improve readability in sunlight. These non conductive treatments do not impair the sensing performance of the projected capacitive panel. Particular mirror coatings also have low levels of conductance and can, therefore, also be used with a PCT sensor to integrate the properties of a mirror and a touch sensor into a single 'magic mirror' screen. Zytronic has successfully supplied prototype sensors to customers that enable the display to perform as a normal touchscreen when illuminated, but which revert to mirrored panel when powered down or in stand by mode. It is possible to wake the display from stand by in a number of ways, including touching the mirror or using a separate projected capacitive button. Display as mirror Product designers can use this combination in numerous contexts. When building the control panel for a home automation system, for example, it is desirable to locate the panel in an easily accessible position. However, when not in use, the dark panel may be unsightly and intrusive. A more attractive display, such as one that transforms into a mirror when not in use, can overcome this potential barrier and encourage more homeowners to take advantage of the utility and convenience of home automation. Similar benefits can be achieved for point of presence equipment, such as signage or kiosks. In these ecologically aware times, it is desirable to turn power hungry displays off when not in use. A touchscreen that becomes a mirror when powered down may enable designers to reduce power consumption of the system while, at the same time, presenting a more aesthetically pleasing appearance than a conventional display. The success of the Apple iPhone has intensified demand for pure glass fronted, bezel free product designs in other markets where styling is a prime concern and this approach is being seen increasingly in domestic appliances such as ovens and refrigerators. In such applications, a practical touch technology is required that allows the designer creative liberty, but which gives engineers and users the assurances of durability and reliability. Mirror as display Among other concepts, some recent product demonstrations have presented interactive mirrors for use in bathrooms or dressing areas, offering busy homeowners or hotel guests to use a variety of features including web access. Touchscreen functionality enables actions such as click, scroll and drag to select hyperlinks, browse pages, or drag a window to a new location in the mirror for convenience. Via the touchscreen, the user can choose to display a webcam image in the mirror to help with personal grooming. For this type of application, the ability to seal the assembly to prevent potential damage from water or steam is critical. Other applications for the touch enabled smart mirror include advanced retail equipment. A full length smart mirror in a fitting room or at the point of sale, for example, can provide enhanced facilities to help customers ensure correct fit, view alternative colours or to call up matching clothes or accessories. Touching the mirror to activate an attached digital camera can provide the customer with a series of alternative views to help with the buying decision. Looking forward Now that the characteristics of a mirror can be combined with the features of a touchscreen display, product designers are already taking advantage of opportunities to improve appearance or disguise electronic displays, and to create new types of products. In the future, the addition of other growing technologies such as voice or face recognition, home wireless networking or GPS, could deliver even more imaginative and unforeseen applications for touch sensitive mirrors.