Understanding Crosstalk in Display Technology: Causes and Control
What is Crosstalk in Display Technology
Passive matrix LCDs do not suffer from crosstalk issues due to their low resolution and control methods. However, as TFT display technology advances, with increasing resolutions and aperture ratios (for higher transmittance), and narrower electronic circuitry, crosstalk and other tft display defects becomes a concern.
On a black background, displaying white squares or displaying black squares on a white background makes it easy to observe this cross-interference phenomenon. Depending on the phenomenon, crosstalk can be categorized into horizontal and vertical crosstalk.
Causes of Crosstalk
Crosstalk refers to the unnecessary interaction between adjacent pixels on a display. When sub-pixels are voltage-driven to change their state (e.g., turning on or off, rotating liquid crystal molecules to different angles), the presence of parasitic capacitance between data signal lines and common electrodes, as well as between data signal lines and pixel electrodes, affects the existing states of other sub-pixels.
At point A, the pixel is outside the display window, and the voltage applied to the signal line at point A remains unchanged. However, at point B, due to the presence of parasitic capacitance, the voltage on the signal line changes during the window scanning period, leading to a change in the pixel’s potential. This is the cause of horizontal crosstalk, and the cause of vertical crosstalk is the same.
Effects of Crosstalk
- Motion Blur: Rapid transitions can lead to blurring and trailing effects on moving objects, affecting the display’s ability to accurately represent fast motion.
- Contrast Reduction: Crosstalk reduces the brightness differences between adjacent pixels or adjacent frames, which undoubtedly impacts contrast and sharpness.
- Image Quality Reduction: Crosstalk results in unclear boundaries, causing images to extend into neighboring areas due to horizontal or vertical crosstalk, thereby reducing image quality.
Methods for Detecting Crosstalk
Detecting crosstalk in display technology requires specialized equipment and testing patterns. The testing parameters are as follows: viewing distance from the screen is 30-50 cm, viewing angle is ±45°, and brightness ranges from 300 to 800 LUX. Using CA310 or CA410, test the brightness at positions A, B, C, and D. If the brightness difference exceeds 2%, it indicates the presence of undesirable crosstalk.
Products require 100% visual inspection, and displays that may potentially exhibit defects undergo 100% instrument testing to ensure effective defect interception. Harmony Optoelectronics has stringent requirements for TFT display product quality. Our products undergo at least 5 rounds of inspections before shipping, and they are accompanied by shipment reports.