How Our Engineers Design Light Guides to Control LCD Backlight Brightness
Controlling light is crucial to harness the full potential and power of an LCD backlight. Ashlyn Fridrich, a Global Lighting Technologies Project Engineer, shares the four most important aspects of controlling backlight brightness with LCD lighting. Ashlyn asserts that, “It all comes down to power, LED efficiency, LCD transmissivity, and light guide efficiency. We commonly apply these four aspects to applications like TVs, automotives, consumer electronics, and instrumentation devices.”
Devices and applications with LCDs stand to gain a competitive edge due to their thin and lightweight design, ideal for portable devices like laptops and smartphones. Information can be easily updated and changed on the display which provides infinite variability for users, according to Ashlyn. Additionally, LCDs deliver clearer images thanks to their high resolutions, and their versatility in shapes and sizes enhances suitability for a variety of applications.
To get the best result and tap into these benefits, it’s important to optimize the lighting and display for the intended application. Read on for more insights from Ashlyn about each of the four LCD backlight controlling factors and how they make an impact. Another member of our team also sheds light on the difference between a backlight vs. a front light display.
1. Power
Perhaps the most obvious element is the actual amount of power supplied; this is simplest way to increase or decrease the brightness of an LCD backlight. Increasing the power to the LEDs within a customer’s allowable forward current range increases the brightness of the lights, while decreasing power decreases brightness in the same fashion.
Ashlyn says, “The power source of an application is dependent on the customer’s need. For example, portable devices are battery-powered whereas home and automotive devices tend to be plugged into a power source.” As custom light guide manufacturers, we can craft solutions for many types of power sources.
“More power equals more brightness, but the brightness will only increase to what the LEDs can handle at their maximum rating,” Ashlyn concludes.
The brightness of an application is determined by the power source but also by the type of LEDs used, the light guide, and any external components that are needed, such as optical films and masks. The overall brightness of the application is typically viewed from the standpoint of the final assembly with all components assembled together.
2. LED Efficiency
Even if a power source remains at a consistent strength, the efficiency of the LEDs and the system as a whole impact how bright the LCD backlight will be. By using superior components and technology with maximum efficiency, more brightness can be squeezed out of the same power source. Factors that may impact LED efficiency include the quality of the die, the chemical makeup of the LEDs, and even the color temperature of the LEDs. Here’s how:
- The better quality of the die, the fewer imperfections there are, resulting in higher LED efficiencies. This also results in less variation from part to part and tighter tolerances.
- The chemical makeup of the LED results in differences in color as well as performance.
- The wavelength of light and efficiency can vary between LEDs. As a result, some wavelengths (colors) emitted are higher in efficiency than others. This is why a blue-white light is brighter than a yellowish-white light.
Ashlyn further explains how high-efficiency LED light guides illuminate LCD backlights. “For backlit LCD applications,” she says, “the light guide is placed behind the LCD. The light guide is lit up with LEDs and they shine through the LCD to illuminate the medium. For front lit LCD applications, it’s simply the opposite and the light guide is placed in front of the LCD instead.”
3. LCD Transmissivity
Different types of LCDs offer varying degrees of transmissivity, which refers to the degree that a medium allows visible light to pass through it. LCDs may allow less than one percent of light to be transmitted from the backlight to the user, whereas others can result in almost no loss. Therefore, choosing the correct LCD for your application is critical.
According to Ashlyn, there are three main groups of LCDs:
- TN (twisted nematic) – used in PC gaming applications for quicker response times and refresh rates
- IPS (in-plane switching) – used in monitors and display screens with professional use in mind
- VA (vertical alignment) – used in applications that require viewing from multiple angles, such as digital signage or TVs
Some customers wonder if LCD backlights are necessary. Ashlyn reminds them that, “all LCD applications require a backlight because LCDs do not emit light on their own. Each pixel on the LCD acts as a small window with a color filter. The window opens and closes, but what the end user sees is the light from the backlight travelling through the pixel when it’s opened.”
Regardless of the degree of transmissivity, our team uses our knowledge of light guides, pattern application, and optical films to extract the most amount of light through an LCD. Plus, you can depend on expert support when it’s time to select the best LCD for your application.
4. Light Guide Efficiency
Not to be overlooked in an LCD backlight is the light guide. The quality and efficiency of the light guide has a dramatic impact on the final brightness of the LCD backlight. This is because the light guide directs light from the LED to the LCD, and much can be lost along the way. Light guides with high efficiency levels, including those with optical lens-based light extraction patterns, can increase efficiency by twenty to thirty percent.
According to Ashlyn, two major characteristics define an efficient light guide:
- Properly coupled with its LEDs. If the LEDs are taller than the thickness of the light guide, excess light will be lost into space; however, if the light guide is the correct all the light will be projected through the lightguide.
- Contain an optical pattern that helps to extract the most light with the least amount of power. If the optical pattern is optimized on the light guide, then fewer LEDs and less power consumption will be needed to achieve the target brightness in the application.
Project Engineers like Ashlyn offer the insight and expertise that streamline the light guide design process. The result is an efficient light guide that aligns with your requirements and goals.
Control and Harness the Power of LCD Backlight Brightness
By considering these four key factors – power, LED efficiency, LCD transmissivity, and light guide efficiency – LCD backlight projects are made more streamlined. Besides controlling backlight brightness, our team works to maximize your device or application’s useful life with an efficient, money-saving system.
For more information on a full range of LED and LCD lighting products and technologies, contact us here. In addition to offering LCD backlight products, Global Lighting Technologies is a worldwide leader for developing a full range of efficient, innovative, and customized lighting solutions.