With the development and application of LED display (LED display) technology, the requirement for whether to display digital content in various applications is increasing. Taking the LED display of commercial advertisement as an example, the business owner has been giving the most of the short-term advertising time of about 30 seconds, giving more information to the consumers, and successfully attracting his attention, which has always been the most troublesome for business owners. Using the consumer's mobile phone, combined with Quick Response Code (QR Code, hereinafter referred to as QR code), undoubtedly provides a very good consumer experience, but this application has further improved the LED display The technical threshold.
Market trend of QR code
After the 1970s, the emergence of point-of-sales (POS) and barcode (Figure 1) solved the problem that traditional retailers did not have a good tool to count the sales and inventory of goods. Barcode has become popular, but new problems have followed. The problem is that Barcode has a limited capacity, and Barcode itself can represent up to 20 words in English. The demand for "Code itself if it can contain more information" is increasing.
In 1994, DENSO WAVE INCORPORATED disclosed the QR code. The name of the QR code is derived from the Quick Response Code (QR Code, hereinafter referred to as the QR code), also known as the 2D Barcode. The QR code can hold a large capacity of about 7000 English digits. Chinese character processing can be performed, and the reading speed is 10 times faster than other encodings.
In 2002, mobile phones with two-dimensional code reading function began to go on the market. This kind of graphics containing many information attracted people. It is very convenient to visit mobile websites through reading, or get various offers, so the QR code quickly Popular in society. According to independent research firm Forrester Research, Inc., on average, 15% of consumers in the US, UK, France, and Germany are already using mobile phones to scan QR codes (Figure 2) [2], and the ratio continues increase.
LED display basic working principle
The LED display is a display composed of modules. The resolution of the length, width and size can be adjusted as required. However, the input source is fixed resolution. Generally, it is scaled by multimedia playback software, which makes the original image easy. The ratio changes.
The basic working principle of the LED display is line scanning, which illuminates the first line one after the other, and the second line, etc., from top to bottom, completely presents one frame of image, which is called static scanning. Considering the cost of the chip and the demand for the brightness of the light, the line scan is divided into 1~32 lines of scanning, but has the disadvantages of poor display effect and large brightness loss. The poor display performance includes a reduction in the refresh rate of the LED display (Figure 3).
Application limit of QR code on LED display
The QR code can guarantee the reading when the display of the QR code is clear and conforms to the standard. This can be via the LCD screen (E-mail), Internet (Website), etc. (Liquid Crystal Display, LCD) ) There will be no problems when displayed. When applied in magazine printing, product packaging boxes, business cards, etc., the QR code provides dirty correction and damage, and provides error correction function, which can correct up to about 30% to ensure reliable setting. Read.
However, as the basic operation principle of the above-mentioned LED display line scanning, when the two-dimensional code is applied to the LED display screen, the following error conditions are likely to occur and cannot be read.
1. Position detection patterns
The QR code can be quickly read from any direction of 360°. The mystery lies in the three positioning patterns in the QR code. It can be explained that the QR code is not affected by the background pattern, and the reading is fast and stable. However, when the LED display performance is not good enough to achieve a high refresh rate (indoor LED display: refresh rate >500Hz / outdoor LED display: refresh rate >1000Hz), the three positioning patterns cannot be fully presented, so it cannot be effectively positioned. (Figure 4).
2. QR code whose modules are distorted
When the LED display is not effective, high gray scale (>14bit) cannot be realized, and when the screenless processor is reduced or enlarged, it is easy to cause the deformation of each code module, although the appearance is the same as the ordinary two-dimensional. The code is the same, but it's actually hard to read, and sometimes it can't be read. (Figure 5)
Two-dimensional code application LED display example - "traditional switch type"
LED display screens can be divided into "traditional switch type" and "Scrambled PWM type" depending on the driver chip. Take the accumulation technology chip as an example. The "traditional switch type" driver chip includes JIX5020, MBI5024, etc. "Traditional switch type The driver chip selects three performances of "refresh rate", "grayscale" and "brightness of LED". For general application, in order to obtain high LED brightness, "high LED brightness mode" will be selected. Even the refresh rate and grayscale performance deteriorate (indoor LED display: brush rate frequency <500Hz / outdoor LED display: refresh rate <1000Hz). When the QR code is applied to the "High LED Light Brightness Mode", scanning with a mobile phone may result in an inability to scan correctly.
"Traditional Switch Type" Driver Chip - Low Grayscale, High Refresh (High Refresh Rate Mode)
The "traditional switch type" driver chip includes JIX5020, MBI5024, etc. The "traditional switch type" driver chip is practical, and the control system can select "high refresh rate mode". Take the 1:16 scan LED display as an example. The LED driver chip of the "traditional switch type" technology broadcasts a two-dimensional code picture (as shown in Figure 6, the original image on the lower left).
Most of the current two-dimensional codes have been designed with the background image. However, when using the "traditional switch type" driver chip to select the "two-dimensional code image" played in the "high refresh rate mode", the use of the mobile phone is in progress due to insufficient gray scale. When scanning,
1. The three positioning patterns and codes in the two-dimensional code are confused with the background color, so that the two-dimensional code cannot be significantly reduced.
2. Due to insufficient representation of the color scale, the effect of the shooting and the background image appear serious color patches, which greatly reduces the advertising effect.
Editor: Liu Hai
We are the China leading Agents and suppliers of Medical Epidemic Preventive Materials, such as Medical protective face mask, Medical surgical face mask, Medical Epidemic Preventive Suit, Medical Infrared Thermometer, N95 Medical mask , KN95 protective face mask, Medical Isolation gown , etc.
We are specialized manufacturers from China, Surgical mask, Epidemic Preventive Suit and Infrared Thermometer, Medical Materials suppliers/factory, wholesale high-quality products of medical Epidemic Preventive materials R & D and manufacturing, we have the perfect after-sales service and technical support. Look forward to your cooperation!
Medical And Epidemic Preventive Materials
Medical protective mask, Medical surgical mask, Medical Epidemic Preventive Suit, Medical Infrared Thermometer, N95 Medical mask, KN95 protective face mask, Medical Isolation gown
Shenzhen Daceen Technology Co., Ltd. , https://www.daceen-sz.com