CRT (Cathode Ray Tube)

The CRT (Cathode Ray Tube), is the vital component in most computer monitors and televisions. It is responsible for the images that we see in monitors and television sets.

How a CRT Works

The main component of a CRT is the picture tube. The tube is wide at the front and narrows at the rear end. The shape at the rear end can be compared to a bottle neck. The rear end consists of a negative charged filament, which is known as cathode. The filament is enclosed in a vacuum and is the most crucial component in the CRT.

On receiving electricity, the filament heats up and emits electrons. These electrons are channeled into the vacuum. Positively charged anodes, which are already present in the vacuum, attract these negatively charged electrons. The anodes channel the negatively charged particles into three narrow beams. During this time, the acceleration rate of the particles also increases. The increase in acceleration rate is to create the maximum effect when the particles strike the phosphor coated screen of the monitor or television set.

Monitors are made of phosphors which release red, green and blue light. The property of phosphor that it glows when exposed to radiation is put to use here. Phosphor absorbs ultraviolet light and emits visible light of fluorescent color. The monitors are arranged with stripes of phosphors that emit red, green and blue. The negatively charges electrons are in the form of three beams which strike the phosphors to create the desired colors. Monitor with more phosphor stripes per inch create higher quality pictures.

A magnetic field is created inside the picture tube to direct the negatively charged beams. Copper steering coils are used to create the magnetic field. The electrons move vertically and horizontally inside a magnetic field.

When the voltage is varied, the number of electrons emitted also varies. The negative beam is controlled to produce the desired effect by varying the voltage to copper steering coils. The image that appears on the monitor is painted and repainted several times in a second. This is done by the controlled emission of negatively charged beams at a very high rate. The emission of electrons is required even when the image is still as phosphors only glows for a short period of time.

CRT Flickering

The rate at which the phosphorous is made to glow is known as the refresh rate. Monitors of lower resolution have a high refresh rate, as it takes only a small amount of time to glow the phosphors again. CRT flickering occurs when the refresh rates drops below 60 Hz. As the resolution of the monitor increases, the refresh rates drops but most high resolution monitor has refresh rate above 60 Hz.

Dot Pitch

The sharpness of a picture is determined by the dot pitch. A lower dot pitch is considered ideal for CRT monitors. Most CRT monitors have a dot pitch somewhere around 0.28.

CRT Resolution

CRT's use several lines of phosphorous colored dots to create a picture. These dots are sometimes referred as pixels. But in true technical terms these dots are different from the modern day pixels. The display becomes more clear when there are more colored lines per inch. The number of colored line per inch is directly proportional to the resolution. A 1024×768 resolution monitor is clearer than a 800×600 resolution monitor due to this. As the resolution increases, the lines per inch become denser. The resolution factor is much less significant when it comes to documents which contain only text. For better quality graphics, a high resolution is a must.

What are the different sizes of CRT monitor?

CRT monitors for computers vary from 15 to 21 inches across, as measured diagonally. Larger size monitors are produced for specific purposes. The viewing screen of a CRT monitor will always be 2.5 inch shorter than the original size. This is because when measuring the size, the asing of the picture tube is also included.

CRT Alternatives

Plasma, LCD, and DLP displays are viable competitors to CRT technology. These techologies are often chosen over CRT when monitor depth or weight are important considerations.

CRT continues to be the most economical and dependable display technology. The gaming industry prefers CRT due to its high refresh rates. Aside from cost, the greatest advantage CRT has over other technologies is that the color display is consistent from any angle.