TFT RGB LCD construction and

Question

I am trying to understand the construction of an RGB TFT LCD that has brightness control in it.

I could not understand how does the TFT color LCD pixels glow? Does each of the pixel has its own light that it emits just like an LED or is it that there is a backlight bulb behind the TFT LCD screen and that bulb gives out the light that is passed through the transparent pixels while blocked by the opaque pixels?

If this is the case then how does the colors come on the TFT LCD? Are the colors due to the backlight bulb or the colors are in each of the individual pixels?

Edit: For example this LCD: https://www.alibaba.com/product-detail/High-brightness-1000cd-m2-5-inch_60312509314.html

Is there a single backlight bulb behind its screen?

In that particular panel, there are 20 LEDs used for the backlight. — Dave Tweed, Sep 20 '19 at 14:19
We can't say for sure, but it's the only thing that makes sense. — Dave Tweed, Sep 21 '19 at 14:07

score 3 · Accepted Answer · edited Sep 20 '19 at 14:17

An LCD doesn't emit light. It either has a reflector behind it, or a separate light source (backlight). The backlight may be controllable on any scale from a monolithic whole to a pixel.

The LCD selectively blocks light. In a color LCD, each pixel will have 3 segments which correspond to red, blue, and green filters. Color is achieved by blocking these filters to varying degrees with the corresponding element of the LCD matrix.

score 3 · Answer 2 · answered Sep 20 '19 at 14:21

https://en.m.wikipedia.org/wiki/LED-backlit_LCD

LCD transmissive displays are either diffused edge-lit or back lit. The edge lit are spot LEDs on 1 or 2 sides constrained into the edge of the glass by U metal brackets with diffusion plastic layers between glass and crystal layer to spread the backlight evenly.

For large LCD screens they use large diffused arrays of true white LED light. They still use fresnel and diffusion layers of plastic to focus and diffuse the backlight. You control the intensity to exceed your ambient light by some amount for clarity but should not be excessive to cause eye-strain.

Some TV’s have Zone brightness control to match the image content and enhance contrast since TV signals are bandwidth limited to 8 bits.

TFT RGB LCD construction and

2 Answers2