Display Technology
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Evolving display technology: mini and micro LED displays
Mini LED and Micro LED are two display technologies that are becoming more widely used in an increasingly diverse range of display and product applications. Mike Fowle, business development manager at Review Display Systems, provides an overview of current TFT LCD and OLED technology and investigates the features and benefits of the newly emerging mini LED and micro LED display technologies
TFT LCD - stable and established The ubiquitous TFT (thin film transistor) LCD has been a mainstay for design and development engineers for over three decades and has been extensively used in a broad range of industries and applications. During this time significant enhancements have included wide viewing angle technologies including IPS (in- plane switching) and MVA (multi-domain vertical alignment), and high brightness, long-life white LED backlights. TFT technology remains essentially much the same as when the TFT display was first developed and introduced, but now with highly refined manufacturing techniques and high yield rates.
OLED - exceptional optical performance
Much acknowledged OLED (organic light emitting diode) display technology has seen significant investment and commercial success in high volume OEM markets such as flat screen televisions and mobile phones but remains seldom seen in medium-size (5” to 17”) display applications. OLED display technology provides excellent optical performance in terms of deeper, darker black levels, highly saturated, vivid colour reproduction, enhanced contrast ratios and fast response times. OLED technology, materials and derivative development continue apace but OLED displays remain complex and costly to manufacture.
Micro LED - emerging potential A more recent, emerging display technology development is micro LED (light emitting diode) which is considered by some industry analysts to be a potential long term successor to TFT and OLED display technology. Micro LED is a direct drive, emissive (no backlight is needed) display technology, constructed with an array
24 February 2023
of microscopic (from 50µm to 2µm) LEDs forming the individual pixels. Micro LEDs enable higher image quality in direct emission displays because each pixel is constructed of three subpixels - each composed of a red, green, and blue micro LED. Manufacturing costs are reduced due to the simple physical structure of micro LED technology, while resolutions and sizes of micro LED displays can be scaled with relative ease.
Micro LED also addresses an ongoing technical issue of OLED technology: image retention or screen burn-in. Due to the inherently different material properties of micro LED and OLED, individual micro LED pixels have no risk of retaining static images and operate without any significant degradation. Brightness levels up to 5,000 nits can be achieved with micro LED displays,
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which is approximately five times the peak luminance of current OLED displays. Micro LED technology is already being deployed in a scalable tile format to build displays of any size and resolution. Applications include smart watches, handheld tablets and video wall displays.
Mini LED - enhanced backlight performance
Mini LED is a backlight technology that can enable enhanced optical performance with an increase in the number of dimming zones and improved backlight control on next generation TFT displays. Mini LEDs are smaller than the average LED, with diodes measuring in the range of 200µm, or about a fifth of the size of a standard LED. The smaller size means that more LEDs can be packaged together in the same area,
allowing a full array backlight to boast thousands of LEDs, offering many discrete dimming zones.
Local dimming and control Local dimming is a feature of LED backlit displays that enables a backlight to be dimmed in selected regions of the active display area. Even with thousands of individual die, mini and micro LED backlights have unique, individual die control. Controlling each dimming region individually enables improved optical performance by enhancing the contrast ratio and producing darker black image elements.
Existing micro LED displays typically offer in the region of 4000 dimming zones, mini LED provides 400 dimming zones, compared with a standard TFT display
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