What does LED display refresh rate and gray level mean? As follow optokingdom Engineer will explain for everyone.
With the development of indoor LED display and application more and more, both in the command center, the monitoring center and the studio, you can see the LED display is widely used. However, the overall performance of the LED display system, the display is able to meet the needs of the users? Whether these LED display images can accord with human visual viewing? These LED display can withstand different camera angles of different camera shutter test? This is the LED display needs to face the need to consider the problem, I would some factors affecting LED display (including the refresh and gray level etc.) make a analysis.
LED display refresh rate (visual refresh rate)
“Visual refresh rate” refers to the rate of screen updates, usually in Hertz (Hz) as a unit, in general, the visual refresh rate of more than 3000Hz, for high-performance LED display. The higher the visual refresh frequency, the more stable the screen display, the smaller the sense of visual flicker. LED display low “visual refresh rate”, in addition to its influence on camera, photography, horizontal horizontal stripes, but also has a similar lighting and flashing tens of thousands of pieces of image, the human eye watch may therefore produce discomfort, and even cause damage to the eyes.
Although the human eye, the visual refresh rate of more than 60Hz has been felt is a continuous picture, but the higher the visual refresh frequency, the more stable the image display, the more difficult to feel the human eye fatigue. Now in the high quality video, in order to get a more detailed picture, such as wonderful playback or close-up photography process, have to take more than 1000Hz per second camera. At this time, LED display for will be captured, under the high-speed shutter can still show footage (no black scan line) or continuous tone, is a great challenge.
Gray level of LED display screen
“Gray level” refers to a variety of colors in between the dark and the light, the color changes with different class, generally in the 14 bit gray scale (bit), which has at least more than 16384 kinds of color class, is a high-performance LED display screen. If the gray series deficiencies, lack of hierarchy or color will occur is gradient color gradation is not very smooth, but can not fully show the color film. LED display screen effect greatly reduced. Some of the low efficiency of the LED display screen in the 1/500s shutter, you can check out the obvious color distribution, if we increase the shutter speed, such as 1/1000s or 1/2000s, the situation will be more obvious.
What is the impact of the LED screen refresh rate and gray level?
We know that LED screen several core components, such as LED switching power supply, LED drive chip, LED lamp, the refresh frequency and gray level LED display, LED driver chip directly determines the LED screen frequency, gray level refresh in visual performance. In the current LED driver chip, the high technology “ScrambledPWM (S-PWM) technology, S-PWM technology is to improve the traditional pulse width modulation (PWM) technology, which will be an image conductiontime dispersed into a number of shorter turn-on time to increase the overall visual update rate. Further, a new generation of LED driver chip built-in S-PWM technology, can be originally each frame (frame) counting time (LED ON, LED OFF grain grain) way, broken down into several average counts, and each scattered parts, can not maintain the original scattered before the ratio of On/Off. As shown below.
S-PWM technology provides a different counting mode, so the image refresh rate can be raised to a maximum of 64 times. If replaced by S-PWM to improve the image refresh frequency of the operation, just use a low order clock (such as 5MHz) can be easily refresh the visual refresh rate 64 times, and can reach more than 4800Hz. Compared to the general video refresh rate of at least 10 times higher than the capacity, but also to avoid the occurrence of high frequency electromagnetic interference (EMIissue), over-voltage surge (Overshoot) and under voltage surge (Undershoot) problem.
S-PWM driver chip LED display, with a digital camera high-speed shutter to take photos, there will still be no horizontal black scan line and color distribution (as shown below). Its visual refresh frequency, the performance of gray level, far beyond the use of traditional switching type driver chip LED display.
High quality LED driver chip, built in S-PWM technology, making the refresh rate of up to 3840Hz, gray level up to 16bit, in the case of high-speed shutter camera, after the emergence of the level of black scan lines and color distribution