Analysis of Four Major Performance Indicators of LED Display

Maximum Brightness

No clear characteristic requirements are given for the important performance of "maximum brightness". Because the environment of the LED display is very different, the illumination (which is person calls the ambient brightness) is different. Therefore, for most complex products, as long as the corresponding test method is specified in the standard, the supplier provides a performance data  (Product Information) list is better than the specific performance requirements given in the standard. These are in line with international standards, but this also result in unrealistic comparisons in bidding, and users do not understand this, resulting in the “maximum brightness” required in many bids is often much higher than the actual needs. Therefore, it is recommended that in order to guide users to correctly understand the "maximum brightness" performance of the LED display, it is necessary for the industry to give a guide: in some occasions, under the different illumination environment, what is the brightness of the LED display can meet the requirements.

Primary Color Dominant Wavelength Error

Changing the primary color wavelength error index from the "primary color wavelength error" to the "primary color dominant wavelength error" is a indicative of reflecting what  is the character of LED display. The dominant wavelength of color is equivalent to the hue of the color observed by the human eye. It is a psychological quantity and an attribute that distinguishes colors from each other. And the performance requirements stipulated by this industry standard, users can not understand from literally that it is an indicator reflecting the color uniformity of LED display. So, is it to guide the user to understand the term first, and then understand this indicator? Or understand the LED display from the customer's point of view first, and then give the user the easy-to-understand performance characteristics?

One of the principles of product standard setting is the “performance principle”: If possible, the requirements should be expressed by performance characteristics, should not be expressed by design and description of the characteristics, this method leaves the greatest room for technological development”. The "primary color dominant wavelength error " is such a design requirement,and replace of "color uniformity", there is no LED that defines the wavelength. For the user, as long as you ensure that the color of the LED display is uniform, and you do not to consider what technical means you use to achieve, to leave as much room for technology development, this is greatly beneficial to the development of the industry.

Duty Ratio

Just like the "performance principle" mentioned above, "if possible, the requirements should be expressed by performance characteristics, should not be expressed by design and description of the characteristics, this method leaves the greatest room for technological development." We believe that "duty ratio" is purely a design technology requirement and should not be used as a performance indicator for LED display product standards. Everyone knows that none of a user who cares about the drive duty ratio of the LED display, they care the effect of the LED display is not the realization of our technology. Why should we create such technical barriers and limit the technological development of the industry?

Refresh Rate

From the point of view of measurement methods, it seems to ignore the problems that users really care about. It also does not take into account the driver ICs, drive circuits and methods used by various manufacturers, which makes the test difficult.For example, the full color screen bidding of Suizhou Stadium, in the expert's sample test, the test of this indicator brings many problems. We can directly test the flashing frequency of the display's light source with an instrument similar to the “light-sensing frequency meter” to reflect this indicator. We have done this test using an oscilloscope to measure the LED drive current waveform of any color to determine the "refresh rate", measured 200Hz in the white field; in the low gray level such as 3 gray scale, the measured frequency is up to more than ten kHz, and measured with PR-650 spectrometer. Whether in the white field, or in the gray level of 200, 100, 50, the measured light source flashing frequency is 200 Hz.