Today it is almost impossible to find a person who still uses a CRT monitor or an old picture tube television. This technique was quickly and successfully replaced by LCD models, which are based on liquid crystals. But matrices are no less important. What are liquid crystals and matrices? You will learn all this from our article.
Background
The world first learned about liquid crystals in 1888, when the famous botanist Friedrich Reinitzer discovered the existence of strange substances in plants. He was amazed that some substances, which initially had a crystalline structure, completely change their properties when heated.
So, at a temperature of 178 degrees Celsius, this substance first became cloudy, and then completely turned into a liquid. But the discoveries did not end there. It turned out that a strange liquid in the electromagnetic respect manifests itself as a crystal. It was then that the term "liquid crystal" appeared.
LCD Matrix Operation
This is the basis of the matrix. What is a matrix? This is an ambiguous term. One of its meanings is a laptop display, an LCD monitor, or a modern TV screen. Now we will find out what the principle of their work is based on.
And it is based on the usual polarization of light. If you remember the school physics course, then it just tells that some substances are capable of transmitting light of only one spectrum. That is why two polarizers at an angle of 90 degrees may not transmit light at all. In the case when a device is located between them that can turn the light, we will be able to adjust the brightness of the glow and other parameters. In general, this is the simplest matrix.
Simplified Matrix Design
A regular LCD will always consist of several permanent parts:
- Backlight lamps.
- Reflectors that ensure uniformity of the aforementioned backlight.
- Polarizers.
- Glass substrate on which conductive contacts are applied.
- A number of notorious liquid crystals.
- Another polarizer and substrate.
Each pixel of such a matrix is formed from red, green and blue dots, a combination of which allows you to get any of the available colors. If you turn on everything at the same time, the result is white. By the way, what is matrix resolution? This is the number of pixels on it (1280x1024, for example).
What are the matrices?
If simplified, then they are passive (simple) and active. Passive - the simplest, in them the pixels are triggered sequentially, from line to line. Accordingly, when trying to establish the production of displays with a large diagonal, it turned out that it was necessary to increase the length of the conductors disproportionately. As a result, not only did the cost increase significantly, but the voltage also increased, which led to a sharp increase in the number of interference. And therefore passive matrices can only be used in the manufacture of low-cost monitors with a small diagonal.
The active types of monitors, TFT, allow you to control each (!) Of millions of pixels individually. The fact is that each pixel is controlled by a separate transistor. To prevent the cell from losing its charge prematurely, a separate capacitor is added to it. Of course, due to such a scheme, it was possible to repeatedly reduce the response time of each pixel.
Mathematical justification
In mathematics, a matrix is an object written in the form of a table whose elements are at the intersection of its rows and columns. It should be noted that matrices are generally widely used in computers. The same display can be interpreted as a matrix. Since each pixel has certain coordinates. Thus, any image that is formed on the display of a laptop is a matrix, the cells of which contain the colors of each pixel.
Each value occupies exactly 1 byte of memory. Little? Alas, even in this case, only a FullHD frame (1920 × 1080) will occupy a couple of MB. And how much space will it take for a movie to last 90 minutes? That is why the image is compressed. The determinant is of great importance.
By the way, what is a matrix determinant? It is a polynomial combining elements of a square matrix in such a way that its value is preserved during transposition and linear combinations of rows or columns. In this case, a matrix is understood as a mathematical expression describing the arrangement of pixels in which their colors are encoded. It is called square because the number of rows and columns in it is the same.
Why is this so important? The fact is that when coding, the Haar transform is used. In fact, the Haar transformation is the rotation of points in such a way that they can be conveniently and compactly encoded. The result is an orthogonal matrix, for decoding which the determinant is just used.
Now we will consider the main types of the matrix (what the matrix itself is, we have already found out).
TN + film
One of the cheapest and most common display models today. It has a relatively fast response time, but rather poor color rendering. The problem is that the crystals in this matrix are arranged so that the viewing angles are insignificant. To combat this phenomenon, a special film has been developed that allows you to slightly expand the viewing angles.
The crystals in this matrix are lined up in a column, thereby resembling a soldier in a parade. The crystals are twisted into a spiral, thanks to which they ideally tightly cling to each other. So that the layers fit well on the substrates, special notches are made on the surface of the latter.
Each crystal has an electrode that regulates the voltage on it. If there is no voltage, then the crystals rotate 90 degrees, as a result of which light freely passes through them. It turns out the usual white pixel of the matrix. What is red or green? How is he doing?
As soon as voltage is applied, the spiral is compressed, and the compression ratio directly depends on the current strength. If the value is maximum, then the crystals generally stop transmitting light, resulting in a black background. To get the gray color and its shades, the position of the crystals in the spiral is adjusted so that a certain amount of light they let through.
By the way, by default, all colors are always activated in these matrices, as a result of which the pixel is white. That is why it is so easy to identify a burnt pixel, which always appears as a bright dot on the monitor. Given that color matrices of this type of matrix are always problems, it is very difficult to achieve a black display as well.
To at least somehow correct the situation, the engineers placed the crystals at an angle of 210 °, as a result of which the color rendering quality and response time increased. But in this case, there were some overlays: in contrast to the classic TN-matrices, there was a problem with shades of white, the colors were blurry. This is how DSTN technology came about. Its essence is that the display is divided into two halves, each of which is controlled separately. Display quality has improved dramatically, but the weight and cost of monitors has grown.
This is what the matrix is in a TN + film type laptop.
S-IPS
Hitachi, having suffered a lot from the drawbacks of the previous technology, decided not to try to improve it anymore, but simply invent something radically new. Moreover, Gunter Baur in 1971 found out that crystals can not be arranged in the form of twisted columns, but laid parallel to each other on a glass substrate. Of course, in this case, the transmitting electrodes are also attached there.
If there is no voltage on the first polarizing filter , the light freely passes through it, but is delayed on the second substrate, the plane of polarization of which is always located at an angle of 90 degrees with respect to the first. Due to this, not only the monitor’s response speed sharply increases, but also the black color - really black, and not a variation of the dark gray hue. In addition, wide viewing angles are a great advantage.
Technology disadvantages
Alas, turning crystals that are parallel to each other takes a lot more time. And therefore, the response time on older models reached a truly cyclopean value, 35-25 ms! Sometimes it was possible to observe even a loop from the cursor, and it was better for users to forget about dynamic scenes in toys and films.
Since the electrodes are located on the same substrate, much more electricity is required to turn the crystals in the desired direction. Therefore, all monitors based on IPS-matrices rarely receive the Energy Star for efficiency. Of course, to illuminate the substrate, it is also required to use more powerful lamps, but this does not improve the situation with increased energy consumption.
The manufacturability of such matrices is high, and therefore, until recently, they were very, very expensive. In short, with all the advantages and disadvantages, such monitors are great for designers: they have excellent color rendering quality, and in some cases you can sacrifice response time.
This is what an IPS matrix is.
MVA / PVA
Since both types of matrices described above have drawbacks that are virtually impossible to eliminate, Fujitsu has developed a new technology. In fact, MVA / PVA is a revised version of IPS. The main difference is the electrodes. They are located on the second substrate in the form of peculiar triangles. This solution allows crystals to respond faster to voltage changes, and color reproduction becomes much better.
Cameras
And what is the matrix in the camera? In this case, the so-called conductor crystal, which is also known as the charge-coupled device (CCD). The more cells there are in the camera’s matrix, the better. When the shutter of the camera opens, a stream of electrons passes through the matrix: the more there are, the stronger the current. Accordingly, in the dark parts of the current is not formed. Matrix sections that are sensitive to certain colors, as a result, form a complete image.
By the way, what is the size of the matrix when it comes to computers or laptops? Everything is simple - this is the name of the screen diagonal.