How to check if the LCD screen is qualified

- Jul 16, 2018-

    types of lcd--第二张图.jpg


LCD liquid crystal display, each dot (Dot) contains 3 pixels of R, G, B. Pixel English: pixel, px

    The bright spot is the short circuit of the pixel tube. When the other pixel tubes are off, the shorted pixel tube is bright.

    Dark point: dark point is the pixel tube is no longer shining

    White point: otherwise, it is a black point

    Color cast: twisted, water ripples spread, and the boundaries are unclear.

    A micro-bright spot, a dark spot defect, that is, a blemish luminescence causes a defect of less than half a point.

    White spot: The foreign object or dirt inside the LCD screen causes the vertical observation to be slightly dark, and it is white spotted at a certain angle of incidence (up and down 30°, left and right 45°).

    Visual inspection:

    No panel deformation, LCD and the host can be tightly engaged, the shaft is not too loose or too tight, the switch LCD should be no abnormal sound.

    The surface of the LCD display should be free from corrosion and chipping. The coating should be uniform and free of condensation, peeling, cracking and abrasion.

    Electrical performance check requirements:

    The LCD display test program appears as follows: full red, all green, all blue, all white, all gray, all black.

    LCD inspection angle range: up and down 30 °, left and right 45 °

    Eye and LCD display distance 30cm

    Start inspection after 5 seconds of visual inspection

    Record, please draw a sketch of the defect, in order to facilitate the re-judgment

    Electrical performance check items:

    No abnormal display, no backlight, no flicker, etc., no bright lines, dark lines.

    Contrast (only for LCD quality evaluation machine): Contrast display is accurate to 3%, LCD four corner contrast is less than 5% compared with the center part, no dark display, no brightness adjustment.

    Shadow: In each monochrome picture, the color should be normal, no color cast; uniform, no obvious shadow.

    White spot: White spots or stains that cause white spots, foreign matter size specifications: round, diameter ≤ 0.5mm; number ≤ 2

    Water ripple: LCD is turned on to 90o, black screen state, normal keyboard stroke, there should be no water ripple; LCD quality evaluation, increase test items: use a single finger to dial the LCD left and right upper corners, or tap (for control tapping Strength, it is recommended to use the middle finger finger to hit the upper shell of the TouchPad on both sides of the host, the water ripple phenomenon disappears within 3 seconds acceptable.

    The boundary is clear and there are no abnormalities such as blurring and diffusion.

    Uneven LCD brightness: white color due to uneven installation or deformation of the LCD surface. When each color (red, blue, green, black, gray, white) appears, it is counted as unqualified, and the rest is operated according to the normal machine; if it appears under each screen, it is a non-conforming product.

    LCD afterimage: When the backlight is turned off and the STR/STD is off, the image remains or diffuses, shrinks, or frames the moving image caused by the screen still staying on the screen. Residence time ≤ 10 seconds.

    Ghost: Diffusion, shrink, or framed motion on the screen when powering on, switching between screens, and STR/STD wake up. Residence time ≤ 3 seconds.

    Bright and dark spot defects: Check the dark spots on the all-white screen, check the highlights on the all-black screen, and check for defects such as scratches and dents. Defects are defined as major drawbacks if the indicators in the table below are not met.

    A LCD with a resolution greater than or equal to 1024X768 is slightly brighter, and a dark dot is less than half a point. A defect equal to or greater than half of the defect is equivalent to a defect.