Introduction to the screen material of mainstream smartphone and analysis of LCD flash screen phenomenon

Tn
TN (Twisted nematic) is a twisted-to-column panel, which belongs to the active matrix liquid crystal display. Since TFT is an active matrix LCD allows the arrangement of liquid crystal to have memory, will not be restored immediately after the current. At the same time, TFT in the back of the LCD set special light tube, can be active on the screen of individual pixels to control, while its output gray class number is less, liquid crystal molecular deflection speed, response time is easy to improve.

The TN type is almost the prototype of all current LCD screen technology improvements.

Advantages: Good brightness, high contrast, strong layering, mature process, low price
Cons: Poor viewing angle, low color gamut, lower power consumption, and relatively poor touch sensitivity
Representative: Motorola ME860 (Atrix 4G)

ASV
Sharp's ASV (Advance Super View) is not a panel type, but a technique for improving image quality, improving the response speed and viewing angle of the TN display. ASV technology is mainly by reducing the spacing between the particles on the LCD panel, increasing the liquid crystal grain glazing, and the overall adjustment of the liquid crystal particles arrangement to reduce the reflection of the LCD TV, increase brightness, angle of view and contrast. This gives us a clear, translucent screen display effect.
Advantages: Fast response, high contrast and brightness, wide viewing angle, fine display effect
Cons: Color richness in general

Representative: Meizu M9, cool Pie N930

Slcd

SLCD is an abbreviation for the English splice Liquid crystal display, which is a special LCD screen for splicing. SLCD is a high-grade derivative of LCD, using the world's advanced industrial-grade LCD panel. SLCD is a complete splicing display unit which can be used as a monitor and can be spliced into a large screen. According to different needs, the realization of single-screen split display, single alone display, any combination display, full screen splicing, vertical screen display, image frame can be optional compensation or coverage, Full HD signal real-time processing.

Advantages: Large viewing angle, high degree of reduction, mature process
Cons: Brightness, color general
Rep: HTC Incredible S

Ips
IPS (In-plane switching) is a kind of reality technology that the liquid crystal molecule rotates in the plane to realize the brightness control.

IPs hard screen has a clear and ultra-stable dynamic display effect, depending on its innovative horizontal conversion molecular arrangement, change the VA soft screen vertical molecular arrangement, thus has a more robust and stable liquid crystal structure. So that the display is not subjected to squeezing distortion.

Apple iphone 4 is based on the IPs screen, of course, it is also added on the basis of Retina screen display technology, a pixel is split into four pixels to display, pixel density increased 4 times times, to 326ppi, and 300ppi is the resolution that people can see, 326ppi is to let you look at the screen when you have the feeling of paper products. It also gets its name "Retina display".
Advantages: 1, dynamic picture, no residual image, 2, the dynamic picture, the response speed is even, 3, the dynamic picture, color no offset.
Cons: Color gamut and brightness general
Rep: IPhone

AMOLED
OLED display technology is different from the traditional LCD display, no backlight, a very thin organic material coating and glass substrate, when the current passing, these organic materials will glow. And the OLED display screen can be made lighter and thinner, with a larger viewing angle, and can significantly conserve power consumption.
AMOLED, known as the active Matrix Organic light emitting Diode, is a reality technology developed in the OLED reality technology. Show the image contrast and brightness are very high, a wide range of views, because of the characteristics of self-illumination so the brightness is very uniform, so in the power-saving commendable, but at the same time the shortcomings are obviously the technology is not mature, good product rate is not high.
Advantages: Power saving, bright color, high brightness, high contrast, fast response speed, large viewing angle, volume "Light" "thin"
Disadvantages: Color particles strong, color reduction in general, good product rate bottom, high cost
Representative: Nokia N8, Lenovo Le phone,i9000

Super AMOLED

Super AMOLED is an evolutionary version of AMOLED, also known as the "Super Screen", on the basis of which the latter mainly improves the color reduction aspect and the visual angle aspect, and uses the new laminated design, makes it more thin and sensitive than the AMOLED.
Advantages: Power saving, bright color, high brightness, high contrast, large viewing angle, and faster response and thinner
Disadvantages: Strong color particles, color reduction in general, low yield, high cost
Representative: Galaxy Nexus, I9100, I9300, GN868

Super AMOLED Plus

Super AMOLED Plus is the third evolutionary version of AMOLED, referred to as the SAP screen, is also one of the top screen materials, it changes the Super AMOLED arrangement is the normal way of the RGB matrix arrangement, and added the dnie+ image processing engine, It solves the common problems of AMOLED particles, makes the image more clear and meticulous, and also improves the color saturation and contrast. The most representative is the I9100 in the world.
Advantages: Power saving, bright color, high brightness, high contrast, large viewing angle, fast response speed, thin and delicate color
Disadvantage: Color is too bright, sometimes feel distorted, low yield, the current Samsung exclusive use.
Representative: Galaxy S II

Although different screens have the advantages and disadvantages of technical parameters, in fact, in the eyes of the human eye, daily use does not feel too big gap. The main need to combine personal preferences and cost-effective to weigh the selection.

Color Brilliance Super Amoled>amoled~ips>slcd>tn

Color Fullness Super Amoled~ips>amoled>slcd>tn

Contrast Super amoled>amoled> Ips~slcd>tn

Visual Angle Super Amoled>ips>slcd~amoled>tn

Show Fineness Super Amoled~ips>amoled>slcd>tn

The sun shows sharpness Super Amoled>amoled>ips>slcd>tn

Color Reduction Ips>super AMOLED>AMOLED~SLCD>TN

Color Softness Ips~slcd>super amoled>amoled>tn

Save Power Super Amoled~amoled>slcd>ips~tn

Ips~slcd>super Amoled>amoled>tn of Visual comfort

First, Flicker
Flicker commonly known as the rise of the pattern, is that we encounter more than a splash screen. Ideally, the central value of the vcom is consistent with the central value of the vpixel and the difference between VPIXELH and Vpixell is the same as the difference between Vcomh and VCOML, in which case there is no flicker phenomenon. The flicker phenomenon occurs when the center or difference of the two voltages is biased. For flicker, if the use of line inversion, then the phenomenon is as follows: Take a display module up and down, there are a lot of horizontal stripes, and stop shaking after the transverse stripes to reduce or disappear, the most obvious under the gray scale. If you are using frame inversion, the phenomenon is that the whole picture has a light and dark splash screen. For flicker, the improvement is to adjust the voltage vcom of the common electrode.

By adjusting the values of the vcom and VCOMH in conjunction, the first attempt to adjust the direction can make the flicker lighter, finally determining the best effect on a particular value. However, since the adjustment of the value of vcom and Vcomh is a jump rather than a continuous change, so sometimes you can only adjust the flicker to a very non-obvious state and can not be completely resolved, if the customer is not satisfied with the words may try to adjust the gamma or change to frame inversion mode, Because the human eye can not be distinguished by a splash screen greater than 100Hz, a slight flicker in this mode cannot be distinguished.

For fixed ic,vcom and VCOMH values are not determined unchanged, with the panel is different, customer supply VDD voltage difference, gamma value changes, will have an impact on vpixel, resulting in flicker generation, You will need to readjust the values of vcom and VCOMH to eliminate flicker.

Second, the refresh frequency setting is not correct caused by the splash screen

For this type of splash screen, the display is not stable when you play an animation or quickly switch pictures, there may be one or two horizontal stripes and the position is not fixed. This is related to two frequency, one is from the CPU to send data to ram inside the frequency, the other is the module internal refresh frequency. You can match the refresh rate to the CPU write speed by adjusting the registers. It also allows the customer to match the two by changing the write speed of the CPU.

Third, the scanning direction is inconsistent causes the splash screen

This splash screen phenomenon and the above mentioned frequency does not match the phenomenon of flashing screen is very similar, this phenomenon is not often appear, but because of the contact is not much, may sometimes appear bad when not in this direction to consider, how to adjust the frequency phenomenon or always exist, It's time to check if the CPU's update direction is consistent with the module's refresh direction when sending data to RAM.

Four, the IC refresh frequency and the backlight PWM signal frequency mismatch causes the splash screen

This situation is more than now on the CSTN module, in the semi-bright state is relatively easy to produce, because the PWM signal is to deceive people's eyes by letting the backlight switch between the light and dark states, the feeling is that the backlight is dark down, the condition is that the frequency is fast enough, if this frequency and IC refresh frequency does not match, Two frequencies may be caused by interference with each other to make the picture similar to the phenomenon of water ripple. This phenomenon more than now Sitronix IC, their home IC in order to do the power is relatively small, will generally be the default crystal oscillator frequency is set relatively low, so in the semi-illuminated state often appear this phenomenon. Improvement measures: Change the crystal frequency and refresh frequency look at the effect, because the crystal oscillator after the cycle becomes smaller, the likelihood of matching will be greater, so the general direction of debugging is to change the IC's refresh frequency, in addition to allow customers to adjust the PWM signal to match debugging.

Introduction to the screen material of mainstream smartphone and analysis of LCD flash screen phenomenon