LCD monitors often exhibit blurring when displaying dynamic images, a problem that bothers many users. So, why do LCD monitors display blurry dynamic images? Is there any way to improve this? This article will provide a detailed analysis.
Of the four advantages of OLED mentioned above, we focus particularly on the fourth feature because currently, no desktop LCD monitor on the market can completely solve the problem of dynamic blurring. Dynamic blurring on LCD screens typically refers to the blurring of edge contours during image transitions. There are two main reasons for this: one is the response time of the liquid crystal and phosphor residue, and the other is the TFT driving mechanism, such as the Hold-type image control.
Hold time is the main cause of motion blur. The so-called "hold mode" display mode displays a frame of image for a certain period of time. In a television screen, this hold time is equivalent to a vertical cycle (16.7 milliseconds). Generally speaking, it's well known that the response time of an LCD screen is crucial for displaying motion images. For an LCD TV, the frame transition time is approximately 16.7ms. Therefore, whether the response time of an LCD TV can be shorter than 16.7ms is very important for the performance of motion images. However, there is another situation: even if the LCD response time is 0ms (which is unlikely and difficult), the blur will not disappear. This is because LCD screens use the "hold mode" to display images. According to some experimental reports, animations displayed on the screen using the "hold" mode will sway left and right on the retina. This swaying accumulates over time, making the motion image appear blurry. Similar to improving the response time of LCDs, it is necessary to develop display methods that shorten the "hold" time. Based on the above, the blurring of dynamic images on an LCD screen cannot be represented by the traditionally used measurement of liquid crystal response time (LCD response time), which is the time it takes for images to change from white to black and vice versa.
Improving Blurring of Dynamic Images Caused by Hold Time
In an ideal controllable LCD panel with a 0ms response time (100% hold time), the MPRT is 16.7ms (at a frequency of 60Hz). With a hold time of 50%, the MPRT is approximately 8.3ms; with a hold time of 25%, the MPRT is 4.2ms. For typical LCDs, the MPRT is below 8ms; for commercially available LCDs with high image quality requirements, the MPRT can be estimated to be below 4ms. As described above, MPRT comprises two main factors: liquid crystal response time and hold time. Therefore, to achieve optimal image display quality, a liquid crystal response time lower than the values mentioned above is desirable. Methods to improve liquid crystal response time include high-speed dynamic modes such as OCB, IPS, and VA, as well as over-drive technology. Currently, LCD TVs prioritizing image quality have incorporated these methods into their production. There are two methods to improve the blurriness of dynamic images caused by hold time. One is to turn off the backlight source in accordance with the frame rate, and the other is to use motion compensation technology for a faster display. The first method is implemented by using backlight flicker and the insertion of black signals. Of these two technologies, motion compensation technology is the most noteworthy. The intermittent display method, such as backlight turning off and black signal insertion, can improve the blurriness of dynamic images and is relatively simple to implement. However, it is prone to flickering in large-screen, high-brightness situations. In contrast, the motion compensation faster display method can improve the blurriness of dynamic images without increasing flickering, but because it requires large-scale signal processing circuitry, it remains difficult to implement.
Japanese companies announce improved picture quality by shortening hold time
In the past two years, many companies have announced technologies and products related to improving picture quality by shortening hold time. For example, a Japanese company has produced a 32-inch WXGA LCD TV using motion compensation high-speed display technology. The method utilizes motion compensation technology to increase the image signal and driving frequency from the standard 60Hz to 90Hz, reducing the hold time by approximately 70%, and further reducing it by another 70% using a scanning backlight off-hook method, for a total reduction of 50%. This improves dynamic image blurring without increasing screen flicker. Because the backlight off is performed at 90Hz, the human eye is less likely to perceive screen flicker. Additionally, other companies also employ motion compensation technology to increase the image frequency to 120Hz to improve dynamic image quality.
