Touch screen monitor - video projector

In first year, we had approached CRT monitors and the flat-faced monitors. These technologies are largely widespread. To perfect our knowledge, let us see the two other types "screening": the touch monitor and the video projector.

15.2. Touch screen monitor.

The touch monitors directly make it possible to order Windows while pressing on the monitor with the finger or pens special. This technique is not very precise for normal programs, but are used rather easily with professional programs conceived for stores, HORECA, hospitals applications, or in certain industries.

Approximately, these monitors are identical to normal monitors (CRT or flat). An additional connection connects on the serial port or USB following the models, replacing the mouse.

The tactile paving stone is cut according to lines and columns. The lines and the columns are separate. When a point is pressed, the line and the column where one supports come into contact making short-circuit. The controller determines the place according to the line and the column.

For example, if we support on the intersection of lines 1 and columns 3, the flow of these 2 only lines is cut. This determines the exact position where the finger is posed. On the first touch monitors, one even directly posed a grid on the front face of the cathode ray tube.

Since, several types of touch monitors are developed. Each one has its advantages and its defects.

15.2.1. Resistive touch monitor

The touch monitors answer the pressure of a finger or a pen. They generally include/understand a base out of glass or acrylic resin which is traversed by a grid containing of the resistive and conductive layers. The interior layer is separated by invisible points. These monitors are generally the least expensive. Nevertheless, their clearness is less compared to a normal monitor. They are nevertheless very solid, including under chemical conditions or liquids.

15.2.2. Infra-red touch monitor

These touch monitors are traversed not by electric cables, but by infra-red raies (invisible with the naked eye). Instead of integrating the tactile part on the monitor, the grid is placed in front of the monitor. A diode and an electric eye (which provides a power in the presence of light) are installed at each ends of lines or columns. While supporting on a given place, one thus breaks luminous flow.

Like this type of monitor does not include moving parts, they are particularly solid also. Nevertheless, their use is limited in certain parts where the luminosity is too large, as vis-a-vis with a window, under certain angles.

15.2.3. Acoustic technology of surface. (Surface Acoustic Wave, SAW)

It is technology more currently advances some. They function in the same way as the infra-red monitors. Two sound frequencies are generated, one coming from the left, one of the top of the monitor, moving through all the monitor. The signals rebound continuously on the edges until the moment when they reach the side opposite of the emission. When a finger touches the monitor, the sound wave is absorbed, and is returned more slowly towards the opposite probe. The delay makes it possible to determine co-ordinates X and y of the point of impact. With the difference of 2 other technologies, part Z can also be given. This makes it possible for example to determine if the person supports more or less extremely.

As the front face of the monitor is out of glass (idem that for a normal monitor), they can also be wet. Clearness is particularly high for this type of monitors.

15.2.4. Capacitive.

The capacitive tactile paving stones consist of a surface out of glass traversed by a grid of capacitive load. With the difference of the resistive monitors, the fingers cannot be used on this type of monitors. You must obligatorily use a conductive special pen. While supporting on a given place, one creates a capacitive connection which modifies the frequency of an oscillating circuit following the place of the impact. This frequency (or rather the difference) is used to determine the place.

These monitors are solid with an excellent clearness. They are usable in practically all the environments.

15.2.5. Comparison

	Resistive	Infra-red	Surface Acoustic Wave	Capacitive
resolution of touched	High	High	means	High
clearness	Means	good	good	good
Operation	finger or pen	finger or pen	Finger or broad pen	special pen
Durability	Can be damaged by pointed objects	very high	do not resist water, likely of moulds	very high

15.3. Video projector

The videos projectors make it possible to post the videos sources coming from various sources on a distant monitor of the projector: computers but also TV, video tape recorder... In the case of the TV, several standards are represented according to the country. Standard NTSC is used in the United States in general on the American continent. France uses the standard SECAM while the majority of the other European countries use the system STAKE.

The video projectors are characterized by their luminosity expressed in Lumens. For small rooms and a restricted number listeners, 600 lumens is sufficient. On the other hand, for rooms of 600 semi-enlightened people, 2000 Lumens is a minimum. The luminosity also determines the maximum distance between the support of projection (monitor) and the projector.

The resolution of a projector is in conformity with the definitions of the graphics accelerators. The resolution of posting is thus determined by the resolution selected about the PC and the maximum resolution of the projector. This intervenes only for "data-processing" postings, the definition of a DVD being lower than that of VGA.

The videos projectors generally integrate several connectors of entry, as well data-processing as video. Certain projectors allow the use of a laser mouse which replace the mouse directly on the projection monitor.

High speakers are sometimes added in the case. They are insufficient for normal presentations.

Certain projectors make it possible to reverse the image. This makes it possible to hang the projector with the ceiling with back.

One finds in the market of the TV-Hifi of monitors LCD (or even monitor plasma) of the same type as the monitors. This technology was already seen in first.

15.3.1. Technology LCD (Liquid Crytal Display)

Video-projectors LCD are most current and most transportable since their weight often turns to the turn of 3 kg. Of a compact weight, their luminosity is sufficient for the majorities of the presentations and the home cinema. Other side of the coin, the lamp is relatively expensive and fragile (2000 hours typical lifespan, of 1500 to 4000 hours). The pencil of light generated by the lamp crosses a panel made up of a multitude of points (liquid crystals). The orientation of each crystal is determined by an electric field. According to the orientation, the light will be more or less important on the monitor according to three basic colors'. The maximum resolution is determined by the number of these crystals.

Tri-LCD technology is a derivative. The videos-projectors using this technology uses 1 not friends 3 panels luminous. The quality of the image is appreciably improved with higher resolutions.

In the 2 cases, the precision of the image is degraded with the distance. This explains why each projector has a maximum size of posting. A manual adjustment nevertheless is envisaged on the objective.

15.3.2. The projectors videos Tritube.

This technology made famous for Belgian firm BARCO uses a similar technique with that of the TV. Although most luminous with true contrasts (the black is indeed black), this technology is used little out of data-processing projectors. This technology allows the largest postings (up to 10 meters length) with one lifespan old lamps 10.000 hours. Contrary to other technologies, the lamp opera hat not but wears. The disadvantages are nevertheless numerous: delicate adjustment (practically a technician with each change of place of the projector requires), obstruction important, fixed objective (not of zoom)

As these projectors allow a projection only in the darkness, these projectors are reserved for true the cinema, especially considering their price.

15.3.3. Projectors DMD (DIGITAL Micro mirror Device) or DLP (DIGITAL Processing Light)

Invented by Texas Instrument, technology DLP rests on a matrix of mirrors called DMD. It east is similar with that of the LCD, except that the crystals liquid are replaced by small mirrors controlled by transistors. The mirrors rotate on their axis to determine which light is projected along an axis from + 10 °

A DMD chip makes approximately 2 cm 2 and contains between 500.000 and 1.300.000 microphone-mirrors.

The luminosity is higher than that of the LCD with a rate of excellent contrast (though lower than that of the tri-tube).

This technology is integrated so much in home cinema than in data-processing video projection and will replace technology LCD in the long term. Nevertheless, as for projectors LCD, the lifespan of the lamp (and its price) makes it not easily usable for an intensive use.

The light is projected by the lamp on an optics of correction. It crosses then a chromatic wheel (separation of the colors) which is again corrected by an optics of control. System DMD controlled by the chart with processor DLP then will transmit (or not) towards the monitor via a lens of projection.

The chromatic wheel with some side effects on the image in particular a small effect of flutter.

Course: Color Parameters

Resolutions, colors...

Video Card

Course: Operation, type, bus, ...

Training: CRT and TFT

Technologies of the standard monitors

Normalizes	*Horizontal resolution vertical resolution**
VGA	640 * 480
SVGA	800 * 600
XVGA	1024 * 768
SXGA	1280 * 1024
HDTV	1920 * 1080
HDTV more	1920 * 1200
QXGA	2048 * 1536

15. Touch screen monitor and Video multi-media projector

15.1. Introduction.