What is the difference between an OLED screen and an LCD screen in an Apple mobile phone

calisontech

Nov 14, 2021

OLED screen and LCD screen are two different screens currently used in iPhones. The main difference between the two stems from the difference in the way they emit light.

The LCD screen relies on the backlight to emit light. It is necessary to install red, green, and blue filters in front of the white backlight, separated by a liquid crystal layer, and then add a polarizer and a glass substrate. The overall thickness is about 0.6-0.8 mm. between;

The OLED screen uses organic compounds. When the current passes through, the sub-pixels can emit red, green, and blue light by themselves. There is no need to add additional backlights and filters, and no liquid crystal layer. Only one polarizing layer is needed. The thickness can be made. To 0.3 mm.

Color display

The OLED screen can control the color at the pixel level, so the color accuracy is almost perfect, and it is almost indistinguishable by the naked eye; because 100% black can be expressed by extinguishing the pixels, theoretically the OLED screen has almost infinite contrast; In the latest iPhone 11 Pro series, the screen brightness can reach 800 nits, ensuring that the screen content can be clearly displayed even in the midday sun.

Because the color brightness of LCD screen can only be adjusted by the backlight panel, and the liquid crystal deflection cannot achieve 100% shading, there are some errors in the color expression of each pixel, so the accuracy and contrast are slightly lower.

Dynamic display

OLED has a faster switching speed than LCD (the time it takes for each pixel to completely change the color), the best LCD display can completely switch the color within a few milliseconds (one thousandth of a second), and the best OLED display The screen can completely switch colors in just a few microseconds (one millionth of a second). When playing games or playing dynamic video content, the chance of blurring or tailing is even smaller.

Energy saving

When the pixels are not expressed (such as black), OLED can directly cut off the power supply of the corresponding pixels, effectively saving power. The LCD screen can only save energy by lowering the overall brightness of the screen, and the energy saving efficiency is relatively low.

Strobe

The problem of stroboscopic is mainly the difference between the two screen dimming methods.

If you need to reduce the brightness of the LCD screen, you only need to directly adjust the brightness of the backlight board, so you can easily achieve global DC dimming (DC dimming, which refers to controlling the display brightness by adjusting the screen voltage or current, that is, changing the power. ).

Since the OLED screen does not have a backlight, when changing the display brightness, if the power is directly adjusted, problems such as uneven color and inaccurate color rendering will occur at low brightness. In this case, many manufacturers have begun to apply PWM dimming on OLED screens.

PWM dimming can control the screen to flash alternately at a certain frequency without changing the power, and use the visual residual effect of the human eye to achieve a continuous display effect. To put it simply, PWM dimming is to continuously alternate between on, off, on and off. The slower the flicker frequency, the lower the brightness actually felt. This also causes the problem of stroboscopic flicker in PWM dimming.

A study by the International Institute of Electrical and Electronics Engineers (IEEE) shows that the flicker that has a low impact on human health should be above 1250Hz; if it does not affect human health, it should be at least 3000Hz.

At present, the LCD screen's stroboscopic frequency is above 1000HZ, and the OLED screen mobile phone using PWM dimming technology has a stroboscopic rate between 200Hz~250Hz. As the screen brightness decreases, the stroboscopic rate will also decrease. Therefore, in the case of low-brightness display, OLED is more likely to cause eye fatigue than LCD.

The stroboscopic performance of iPhone XS Max at 1/50, 1/500, and 1/1000 shutters respectively

Burn screen

Since OLED needs each pixel to emit light by itself, the light-emitting life of pixels of different colors is also different due to different materials. If a certain area displays a high light source for a long time, then the pixels in that area will age faster than the surrounding pixels, just as the light will break down after a long period of use. These pixels will also age faster, causing burn-in in the area.

The burn-in problem is an unavoidable problem for OLED screens. Apple has added an anti-burn screen mechanism since iOS11. Media tests have shown that the iPhone X will burn the screen after 510 hours of continuous display of a picture at the highest brightness. The "dark mode" added in iOS 13 is not only to extend the battery life of the phone, but also part of the reason is to avoid burning the screen.

For LCD screens, the risk of "screen burn" is negligible.

how to choose

If you spend a long time watching the screen (such as reading or playing games), or if you pay more attention to cost performance, a mobile phone with an LCD screen is a more suitable choice.

If you want the screen of your mobile phone to have the best and most perfect performance, and have relatively high requirements for the feel and battery life of the mobile phone, the OLED screen is still the top screen in the mobile phone field. In the same product series, mobile phones with OLED screens generally have a thinner body and a narrower screen frame.