TFT LCD screen refresh rate

The refresh rate of a display screen refers to the number of times the screen refreshes its image per second, measured in Hertz (Hz). For example, a refresh rate of 60Hz means the screen can refresh its image 60 times per second. The higher the refresh rate, the better the image stability, the smoother the animation, and the faster the response time. TFT displays typically have refresh rates between 60Hz and 240Hz.

Screen refresh rate refers toelectron beamThe refresh rate is the number of times an image is scanned on a screen. A higher refresh rate results in a more stable and natural-looking image, with less strain on the eyes. Conversely, a lower refresh rate leads to more flickering and jitter, causing faster eye fatigue. Generally, a refresh rate of 80Hz or higher can completely eliminate flickering and jitter, reducing eye strain. The refresh rate is a hardware characteristic of a monitor, defining its ability to update displayed content per unit of time, and is closely related to the frame rate (FPS) output by the graphics card.

A 60Hz refresh rate is sufficient for most everyday uses, including web browsing, watching movies, and general office tasks. However, gamers or professional designers may need higher refresh rates for a smoother gaming experience or more accurate image display. Options with refresh rates of 120Hz and above, such as 120Hz, 144Hz, or 240Hz, are designed specifically for these needs.

You can think of a monitor's refresh rate simply as its ability to rapidly display "a series of static images." The image we see is actually composed of a series of static images displayed per second. These images switch rapidly, creating the "dynamic" image we perceive.

1. The essence of a picture is static. :
   • Each time a monitor refreshes, it actually draws a static "image" on the screen.
   • When the refresh rate is high, these images are updated faster, and the human eye perceives the image as smoother and more continuous.
2. Similar to a book-turning animation :
   • Imagine you're holding a small animation book. By quickly flipping through the pages, the static images "come to life." The monitor's refresh rate is like the speed at which you turn the pages.
     • If you scroll slowly (e.g., at 30Hz), you'll feel the animation stutter.
     • If you flip fast (e.g., at 120Hz), the animation will look very smooth.
3. "Dynamic" is an illusion caused by visual persistence. :
   • The human eye and brain perceive images through the "persistence of vision" effect. When one image disappears and the next image quickly appears, the brain connects these static images and mistakenly perceives them as a continuous "dynamic" scene.

Relationship between refresh rate and dynamic images

1. 60Hz = 60 frames per second :
   • This means the display updates 60 still images per second.
   • In normal scenarios (such as office work or watching videos), 60Hz is enough to make the picture feel smooth.
2. High refresh rate makes the motion smoother :
   • When the refresh rate increases (such as 120Hz, 240Hz), the monitor can display more "static images", and the changes in the picture are more subtle.
   • For fast-moving content (such as gaming or VR), a high refresh rate allows you to see more details and reduces ghosting or blurring.
3. Ghosting and tearing at low refresh rates :
   • If the refresh rate is too low (such as 30Hz), static images will switch slowly, resulting in a lack of continuity and causing "stuttering" or "ghosting".
   • If the generated image speed (FPS) and refresh rate are not synchronized, screen tearing may occur.

1. Raster Scanning:
   • Traditional monitors (such as CRT monitors) refresh the image line by line, that is, starting from the top left corner of the screen, the image is drawn line by line from top to bottom.
   • Although LCD and OLED displays do not require line-by-line scanning, they still logically retain a similar refresh concept.
2. Fixed refresh cycle:
   • Taking 60Hz as an example: 60 refreshes per second means that the time taken for each refresh is 1 second / 60 = 16.67 milliseconds.
   • Within those 16.67 milliseconds, the graphics card needs to prepare one frame of image data for the monitor to display.
3. Screen update and refresh:
   • The monitor updates the displayed content according to the refresh rate, but if the graphics card's frame rate is not enough to match the refresh rate (such as 30 FPS for a 60Hz monitor), it may cause the image to be displayed repeatedly or tearing.

1. Refresh Rate vs. Frame Rate

• refresh rate (Refresh Rate):
  • Display hardware characteristics refer to the maximum number of images that a screen can display per second.
• Frame rate (Frame Rate, FPS):
  • The speed at which a graphics card renders images refers to the number of frames generated per second.
• Ideally, the frame rate and refresh rate should be matched (e.g., 60 FPS to 60Hz) for the smoothest visuals. If the refresh rate is much higher than the frame rate, it will cause stuttering; if the refresh rate is lower than the frame rate, it may waste the graphics card's performance.

2. The impact of refresh rate on image quality

• High refresh rate (such as 120Hz or 144Hz)  :
  • The dynamic visuals are smoother, making them suitable for fast-moving scenes such as games or sports videos.
  • Reduce motion blur and ghosting.
• Low refresh rate (e.g., 60Hz)  :
  • There is no obvious difference in static images, but blurry or torn images may appear in dynamic scenes.

3. The Perceived Limits of Refresh Rate

• The human eye has limited sensitivity to refresh rate:
  • 60HzSuitable for general use, such as office work or video viewing.
  • 120Hz or higherMore suitable for gaming and professional scenarios, and more sensitive to rapidly changing visuals.