lcd backlighting for hdtv
According to display search, the LCD display market in 2007 (
The price of TV is estimated to be $27. 4 billion.
In the second quarter of 2008, LCD TV shipments increased by 52% year-on-year to nearly 7 units.
5 million units (79.
8% of total sales of HDTV).
The LCD screen on the LCD hd TV is a selective filter.
It does not shine itself, but selectively filters the light passing through the display from the back.
Most high-definition TVs include a piece of glowing plastic or come with fluorescent lights to provide backlight.
Both technologies are difficult to control.
Many consumers pay attention to screen resolution when choosing high definition (HDTV)system.
Is this a hd TV with 720 p, 1020i or 1020 p?
However, when an expert group, SMPTE (
Association of Film and Television Engineers)
Recently, the importance of screen resolution ranked fourth.
To an important extent, SMPTE ranks contrast, color saturation, color temperature, and grayscale before the screen resolution.
The Imaging Science Foundation has come to a similar conclusion.
Backlight is a key component of increasing contrast and grayscale.
The LCD system allows the backlight level to be adjusted and it is best to perform this function automatically, which is important.
This will increase the contrast of the picture.
In addition, reducing the backlight level will also reduce power consumption and extend the life of the lamp, as the power used and the life of the lamp are directly related to the backlight level.
If the current is 7 mA, the lamp with a 6 mA-hour life span of 50,000 may only have a life span of 30,000 hours, only 1 mA higher (
Example: sharp electronic LCD Display).
Another important factor in choosing a backlight is to consider \"blur \".
When there is fast motion in programming, such as motion, there will be blur.
Pixels respond to lag when the picture changes quickly.
Effective backlight engineering can significantly reduce this by stroking the backlight so that a single pixel does not take longer than it takes.
Examples of this technology include Philips \"Aptura\" and Samsung \"LED Motion Plus \".
The backlight is located on the back of the LCD panel and on both sides to create the panel lighting.
To make the light more uniform, there is an optical diffuser between the lamp and the rear of the optical filter module.
Most LCD systems that use side lights use cold cathode fluorescent lamps (CCF)lamps.
This technology provides very bright white light.
The lifetime of the lamp is usually between 10,000 and 20,000 hours (6-
12 years, 5 hours a day).
The most important drawback is that the intensity of the light cannot change locally and the side light does not lookuniform.
Some lamps contain mercury.
This is an ecological disadvantage.
The main drawback is that most of the backlight is achieved with a piece of glowing plastic.
These panels can be aged (
Although improvements in this area have reduced the problem).
The backlight of the luminous panel produces light using a colored luminous material.
Displays using this technology can be thin and light, and provide a uniform distribution of light.
Main disadvantages: the LED backlight uses a LED matrix that can be controlled separately to provide very good control.
In this configuration, a large number of LEDs are mounted evenly behind the display.
The improvement of Led brightness makes them more practical in backlight.
NEC pioneered the technology on their display, the 80wg.
Other companies such as Samsung have recently introduced versions of the technology.
This should keep prices down.
The price of Samsung model is less than 1/3 of the price of NEC similar display).
The system adopts local dimming technology, and the dynamic contrast can reach 1,000,000: 1.
Actual black level (
\"Holy Grail\" of LCD \")
It can be achieved by turning off the Pixel\'s light source.
This eliminates the typical gray-black images of many LCD HD TVs.
The led group can be controlled locally to produce more light and increase the brightness if necessary.
The problem with conventional white LEDs is that their spectra are not ideal for photographic reproduction because they are basically blue LEDs with yellow fluorescent substances on top.
Their color spectrum has two peaks, one in blue and the other in yellow.
White LEDs based on a set of red, green and blue LEDs are ideal for LCD RGB color filters that can produce the most saturated colors.
Sony\'s \"Triluminos\" LED backlight system is an example of this technology.
Sometimes these HD TVs have a row of LEDs on the top and bottom of the display.
This improves brightness and color reproduction, making the entire display almost completely uniform.
LED backlight is more effective than other technologies.
As the LED backlight wastes less energy and generates less heat, this must be managed by air conditioning.
LED backlight provides a long working life of more than 50,000 hours (
Use for more than 25 years, 5 hours a day).
LED backlight systems may not perform well in a typical retail environment.
Usually, the screen is reflected in order to achieve a high contrast, and then the bright showroom may not make the technology even.
In a more typical less
The problem should not be so noticeable.
Electrical engineering is simpler than LED backlight.
Cold cathode fluorescent lamp (CCF)
High AC voltage required (1,500 VAC)
The operating voltage is 700 VAC or higher at startup.
When the lamp is new, it may need less voltage to start up, but the voltage requirement usually increases as the age increases, which makes the designer\'s problem complicated.
The luminous panel requires a voltage of about 100 VAC @ 400Hz.
Power Inverter (Generating VAC)
DC power supply is required for both CCF and optical panels.
This is a huge expense in terms of the cost, size and weight of the system.
The best inverter for this application allows the output voltage to automatically increase with the aging of the lamp, thus prolonging the service life of the lamp.
The LCD system with LED backlight uses a low voltage DC, usually 12 or 24 VDC.
This creates a smaller, simpler, and more reliable system.
The LED backlight system must be cooled well, otherwise its performance may be affected.
The Led generates less heat than the CCF light, but the heat is very concentrated.
Working at high temperatures can reduce the life of the LED and change its spectrum while reducing the output brightness.
The new OLEDA technology you will hear in the future is organic LED (OLED).
This technology has a completely different backlight technology, which does not require backlight technology.
Because of this, they have much less power.
Since there is no backlight, the OLED system has a larger viewing angle than the LED system.
The OLED display is much thinner than the LCD display.
OLED responds faster than a normal LCD screen.
The average response time of the LCD is 8 to 12 Ms compared to 0 is normal.
The response time of OLED is 01 Ms.
Sony launched an 11-inch hd TV at the Consumer Electronics Show in Vegas.
The new 11 \"Sony TV is called\" XEL-1\".
This is very thin (1/10\")
The current price is $2500.
On November, Samsung presented a 31-inch oled hd TV with a resolution of 1080P at an exhibition in Asia.
Panasonic, Toshiba, LG (Panasonic)
Other companies are investing hundreds of millions of dollars to develop this potentially promising technology.
Toshiba plans to sell a 30-inch OLED display in 2009.
Samsung announced that it will sell large-screen oled hd TVs in 2010.
OLED displays have been used for a while in devices with relatively small panels such as digital cameras, mobile phones, etc. , because they are very energy efficient, which is very important in portable devices.
In theory, OLED displays are less expensive to make than LCD or plasma displays, meaning they shouldn\'t be that expensive.
Keep in mind that the first large LCD and plasma display is much more expensive when it comes out for the first time.
SummaryLCD HD TVs and displays with LED array backlight are now the preferred method, as they show better image quality while saving power consumption.
The ability to control the light output locally is the key to achieving high contrast.