Application of Machine Vision Technology in LCD Screen Automated Inspection

The liquid crystal display, or LCD for short, is an important product of modern society, and is the carrier of display and communication in computer televisions, smart home appliances, mobile communication equipment, and automotive instruments and industrial equipment. The testing of LCD screens and the functional testing of the display part previously relied on the eyes of workers. On the one hand, as the cost of labor continues to rise, the cost of testing is becoming more and more overwhelming. On the other hand, the accuracy and speed of manual testing methods cannot Meet the requirements of production efficiency. In recent years, machine vision technology has been introduced into the detection and application of LCD screens, and has played a good role in promoting the development of the industry. As a member of the machine vision industry, Wei Shi Imaging has developed mature application cases for industrial cameras, telecentric lenses and smart vision products in the LCD production and inspection industry. This article we will use this as a basis to introduce LCD automated inspection applications. Key technologies and selection methods.

LCD screen detection

Before selecting a solution for LCD screen detection, we must first understand the standards for LCD screen detection. Possible types of LCD screens are:

1. Bright point: Because bubbles or impurities enter the sub-pixel, the light directly passes through the color filter to display the color. At this time, the RGB color point will appear in the case of a black screen. These points will always be white as long as they are turned on , Also called "grey point". For the bright spot detection scheme, the LCD screen is set to a completely black background image, and then the entire image is collected, and the contrast analysis can be found.

2. Dark point: In the case of a white screen, a non-simple RGB color point appears, also called a "black point". No matter what color the screen displays, the dark point is black and does not emit light. The detection scheme for dark spots is to set the LCD bottle to a full white background image, and then collect the entire image, which can be found by contrast analysis.

3. Color points: Red, green and blue dots are always displayed. The screens are set to different solid colors such as all black, all red, all blue, all green, and all white. At this time, the entire image is collected, and abnormal pixels can be found by contrast analysis.

LCD screen detection

For the number of dead pixels of the above types, the standardization organization has strict regulations. As a provider of automatic detection equipment, iJUNCO develops hardware and software equipment to identify every dead pixel on the screen and make accurate judgments. To achieve this, we need to choose the right industrial camera, industrial lens, and image processing software.

According to the experience of iJUNCO in providing solutions for many LCD screen manufacturers, when detecting screens smaller than 50 inches, at least one 2900W CCD area scan camera is generally required, that is, Vision image MV-E2900 camera, supporting high resolution Rate industrial lens or telecentric lens to obtain the screen image, and then use image processing software to determine. The figure below shows the same screen when using a 30-200-500-2900W industrial camera to shoot detailed pictures. It can be clearly seen that the use of a high-resolution industrial camera will greatly help the detection results.

LCD screen detection