ADVANCED LINK PHOTONICS
A Leading Rugged Display Innovator
Innovative and Patented
LCD Integration Technologies
Air-gap integration, IR cut coating,
thin CS glass70
WE INNOVATE in
DISPLAY INTEGRATION
Founder of Advanced Link Photonics Dr. Raymond Wang has extensive education and R&D experience in the field of optics. Based on his background and vision, he leads and organizes our team to innovate and focus on display integration technologies for outdoor applications. As a result, our company excels in rugged display integration for aerospace, military, defense, and industrial applications.
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By collaborating with you, our engineering team has learned, developed, and implemented many technologies in various aspects of display head assembling. Through years of facing customers' toughest challenges, we understand the phrase "the problems are in the details," and have demonstrated that Advanced Link Photonics excels in facing the challenges and implementing the right solutions in a timely manner. Here, we are listing some examples of our innovative technologies which have been implemented and contribute to the reliable rugged sunlight readable DHAs solutions, including night vision, rugged touch panel, EMi, and heater, that you are using now in your systems.
Whether you need a partner for the complete development of a sub-system or to supplement your engineering team, we invite you to connect to innovate and tackle your toughest challenges together in your display needs.
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Low Reflection Air-Gap Bonding for Sunlight Readable Feature
Thin film transistor liquid crystal displays (TFT LCDs) became popular over CRT displays in the 1990s ~ early 2000s after multiple breakthroughs brought in by various research parties in the field. The light weight and convenience of TFT LCDs opened the market for outdoor applications. However, the surface reflectivity of a regular LCD is ~4%. Assuming the sunlight reaching the LCD surface is ~30,000 nits, the reflected luminance off the surface from the incident sunlight may reach 1,200 nits. This reflected luminance makes the use of a regular LCD very difficult in outdoor applications.
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To make LCD sunlight readable under strong sunlight of outdoor displays is the main challenge to display integrators in this market segment. Increasing the brightness of backlight and applying anti-reflection treatment on LCD surfaces are two traditional approaches to reach some level of sunlight readability. However, these upgrades fall short when a display assembly contains various functional parts in the stack, such as mirror-like resistive touch panels, EMI windows, and heaters. Hence, many reflective surfaces are introduced in the DHA stack and the total reflectivity may be easily more than 20%, which makes the screen unreadable under strong incident sunlight. Advanced Link Photonics proudly innovated and introduced several patented technologies to the outdoor display market to tackle this problem.
One such innovative idea is to convert a regular transmissive LCD into a transflective-type LCD (TrioLCD™) passively and reflect the incident sunlight as part of effective luminance for the viewer. This integration greatly improves the contrast ratio of display under strong ambient light and make the LCD screen sunlight readable.
Another innovative idea is to control the polarization of light out of LCD to achieve total reflection control, for which ALP was awarded a series of patents. When integrating the highly reflective functional parts, such as a resistive touch panel, EMI window, and heater in a DHA design, it is very challenging to achieve contrast ratio of CR > 4:1 under the strong incident sunlight and obtain the desirable sunlight readability. Controlling the polarization of the light path effectively eliminates the undesirable reflectance introduced by many layers of integrated functional parts in the stack of DHA and achieves satisfactory sunlight readability.
The red curve is the measured surface reflectance from a resistive touch panel integrated TrioLCD (RT-TrioLCD™) which is the least among the different configurations compared.
The same screen of a TrioLCD was overlaid with a regular resistive touch panel and with a treated resistive touch panel based on our integration approach without optical bonding, in other words, an air-gap integration. All three areas have comparable readabilities indoors. However, the readabilities under the sunlight are very different. It is worth pointing out that integration of resistive touch panels using an air-gap integration gives a superior optical performance under the sun in contrast with the traditional integration of polarized resistive touch panels, in which the area is not sunlight readable.
Our patent also describes how our integration will help the viewing of a LCD, configured with a polarized surface, and be more convenient to viewers wearing polarized sunglasses, which are commonly used to block the strong sunlight randomly reflected off objects. When a viewer wears polarized sunglasses for the off-axis polarization between the sunglasses and the outgoing LCD luminance, there are invisible zones around LCD to a viewer. This may be avoided by applying our integration as shown in the figure to the right. A display with invisible dark zones may be converted to a display (or DHA) with no dark zones using our integration approach.
. Display with dark zones
. Display with no dark zones
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Chem. Strengthened 0.2 and 0.3 mm Glass: Rugged Touch Panel
Comparison of commercially available AR film vs our AR coating on polarizer revealed our AR coating sustains the UV exposure better.
Though our polarizer has a harder surface for a film-to-glass (FG) resistive touch panel, a plastic surface is just not enough to meet the demanding environments in the field, and a resistive touch panel with more scratch resistance surface is required, which leads to the development of GG and GFG resistive touch panels. ALP further advanced the GFG with a self-developed chemically strengthened 0.2 mm or 0.3 mm glass surface, which is scratch and impact resistant. Our chemically strengthened 0.3 mm glass sheet was tested against Gorilla glass and a few other chemically strengthened glass sheets in our ball drop testing system (2 oz steel ball from a 100cm drop). Only Gorilla glass and our 0.3 mm chemically strengthened glass survived the test. In addition, we may further strengthen ITO glass to help survive military impact tests, such as ball-drop and boot-kick tests providing highly rugged touch panel for demanding display usages.
The impact resistance of an ALP rugged touch panel (made from strengthened 1.1 mm ITO glass and overlaid with chemically strengthened 0.3 mm) and a regular glass surface touch screen (made from commercially strengthened 1.1 mm ITO glass and overlaid with a regular 0.3 mm glass) was compared by using the ball-drop test. The test results are displayed in the photo to the right; the touch panel on the right has the regular 0.3 mm glass surface, and the touch panel on the left has ALP's rugged touch panel with 0.3 mm CS glass surface. Results indicate that the rugged touch panel survived almost all 5 points drop from 100 cm except point 1 with a small dent on 0.3 mm surface glass from a 90 cm drop. On the other hand, the regular glass surface touch panel has breakage on both surface glass and ITO glass on all the points at heights from 20 ~ 60 cm.
The assembly may be further strengthened with a proper backing glass sheet laminated to the back of the touch panel. The further strengthened assembly becomes highly impact resistant and may survive a boot kick test.
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NVIS Filter for Night Vision Compatible Display
ALP developed coating processes that would produce different classes of IR-cut off filters, NVIS filters, suitable for night vision compatible applications. We can also make filters with customized IR cut-off specifications. These filters are designed for color display with LED backlight and has a transmission more than 90 %. The filter may satisfy the NVIS radiance requirements of MIL-STD-3009 with a minimum impact on color saturation and display luminance. With our coating technology the IR cut-off window is narrow, usually < 20 nm, and highly effective. A typical IR-cut filter curve is given in the figure. We offer not only the NVIS compatible filters for display integrator, but also offer various semi-complete NVIS compatible LCD integration parts. Please call us for details.
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ALP has recently integrated miniLED local dimming brightness enhancement technology into our DHA design. We also have successfuly developed a process to integrate our NVIS technology to a miniLED local dimming backlight system.
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NVIS Parameter Measurements
Display Color T(%) u’ v’ NVIS Radiance
Color white 90 0.17 0.47 1.4E-9
Color max 92 - - 1.4E-9
Local Dimming mini-LED: Brightness Enhancement > 5,000 nits
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mini-LED Zoning
Illumination and brightness of LCD are key factors in displaying a great picture. One of the biggest advancements in LCD illumination is the mini-LED introduced in 2021. The extra-tiny light-emitting diodes make the idea of zoning backlighting possible. Zoning mini-LED backlighting may seem like a relatively small change, but the technology offers real improvements to LCD. Along with color and contrast, brightness makes a huge difference in how well an LCD can display an image. Zoning of the tiny mini-LED makes local dimming of mini-LED backlight possible, in which the LEDs are turned on in accordance with RGB scales of an image. Application of this technology enhances brightness while reducing power consumption. It may provide up to 10,000 nits of brightness depending on the design of the dimming zones. Each mini-LED backlight board may be divided into zones by 8 increments. A board may be divided up to (1~8)x(1~8) zones. The number of mini-LED in each zone determines the final brightness outcome and local dimming effect. To light up a larger LCD, up to 4 mini-LED boards may be connected in a serial format. We have developed dual mode NVIS compatible backlighting. In addition, the local dimming also prevents the LEDs from being lit the whole time, which reduces the heat generation and prolongs the lifespan. The contrast ratio is enhanced indefinitely, considering that theoretically, a black color screen will have no luminance coming from mini-LEDs!
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High Efficient EMI Shilding
Development of iMesh was brought forth by solving a problem for a customer, who received a polarized touch panel integrated with an etched micro-mesh causing significant optical interference. It was obvious that the integration was not done right.
To resolve the interference problem, ALP developed a unique micro-mesh EMI shield integration technology, which not only meets military standards (i.e., higher than 50dB at frequencies 1 - 1,000MHz), but also offers superior optical performance over etched mesh, as shown in the comparative photo above.
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ALP's iMesh™ is a naked non-woven micro-mesh, substrate-free blackened nickel (or blackened copper) with almost no reflection and contains no extra substrate. The wiring of iMesh precisely intersects at a 90 degree angle that is not achievable by other processes, such as etched micro-mesh.
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The advantage of integrating a substrate-free micro-mesh is that it may be incorporated into any position in a DHA without causing unwanted optical interference.
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Speed Warming Heater
Speed of a heater warming up is also essential in field applications. ALP's partner developed high temperature soldering processes for heater wire, which allows heater wire to be soldered on to bus bars to withstand our outgoing pulling tests. The heater is usually terminated on opposite sides with silver or copper bus bars. A contact wire is securely soldered on the bus bar and ready for power supply.
The properties and heating efficiency of ALP's LCD heater bonded 10.4" touch screen was measured and given as an example. Test unit was positioned in the enviromental chamber and the chamber temperature was maintained at -40°C during the test. Thermal probe was positioned at the center of touch panel and temperature readings were taken every 30 seconds.
It was thought to have efficient heating a heater must be optically bonded to the LCD glass. We ran a quick test using two 10.4" DHAs. The heater in one of the units was integrated with optical bonding and the heater in the other unit was integrated with tape bonding to the back of LCD glass. Both units were placed in the environmental chamber and the temperature was brought to and kept at -40°C for the test. The venting in chamber was kept on during the test and the thermal sensor was positioned on the top surface of the unit. Our test results indicated that the warming up speed between the bonding configuration and the non-bonding configuration has no significant differences.
The non-bonding unit might have been more efficient for the heat might not have been consumed by the bonding gel.
