LED Projection Knowledge

With the increasing popularity of projection equipment, LED projectors and new projectors are gaining more and more market share in daily life. Here we will briefly introduce some conceptual knowledge about projectors.

LED Projector Introduction

LED (Light Emitting Diode) is also known as light emitting diode. This technology has been used in the display and lighting fields for a long time. Its main body is a piece of electroluminescent semiconductor material. When a forward voltage is applied to its two ends, the current will flow from the LED anode to the cathode, and the semiconductor crystal will emit light of different colors from ultraviolet to infrared. The stronger the current, the stronger the light. The principle of LED light emission is different from that of traditional UHE and UHP bulbs. It does not generate a lot of heat during the light emission process, so the life span can reach more than 10,000 hours.

With the increasing popularity of projection equipment, LED projectors and new projectors are gaining more and more market share in daily life. Here we will briefly introduce some conceptual knowledge about projectors.

LED projector resolution

The resolution of an LED projector is expressed by multiplying the number of horizontal pixels by the number of vertical pixels in the picture. The resolution of an LED projector does not refer to the resolution of the signal that the LED projector can receive, but to the physical resolution of their core light engine (LED chip, LCD panel, LCOS panel, etc.). Although projectors can usually receive signals of multiple resolutions, when the signal resolution is higher than the physical resolution of the projector, the picture details will be significantly lost. Common resolutions and representation methods are as follows:

SVGA: 800x600 Common resolution for economical projectors

XGA: 1024x768 resolution used by mainstream business and education projectors

SXGA+: 1400x1050, a resolution used by high-end projectors for high-end professional applications such as graphics.

480p: 852x480 resolution used by low-end home projectors

720p: 1280x720 or 1280x768 resolution used by mid-range home projectors

1080p: 1920x1080 or 1920x1200 resolution used by high-end home projectors

LED light source

As we all know, LED projector bulbs are relatively expensive consumables. They have a certain service life. When used for a long time, the bulbs will age. Replacing the bulbs is an issue that projector users must consider. This is also a major disadvantage of projectors compared to LCD TVs.

Over the years, major projection manufacturers have been committed to developing bulbs with longer service life. The emergence of LED projection technology has opened up a new situation for the development of projectors. Compared with traditional projectors, the biggest advantage of LED projectors using LED light sources is that they do not need to replace bulbs frequently. The life of the bulb is 10,000-20,000 hours or even longer, and users do not need to worry about the problem of projector bulb loss.

LED (Light Emitting Diode) is also known as light emitting diode. This technology has been used in the display and lighting fields for a long time. Its main body is a piece of electroluminescent semiconductor material. When a forward voltage is applied to its two ends, the current will flow from the LED anode to the cathode, and the semiconductor crystal will emit light of different colors from ultraviolet to infrared. The stronger the current, the stronger the light.

The principle of LED lighting is different from that of traditional UHE and UHP bulbs. It does not generate a lot of heat during the lighting process, so the life span can reach more than 10,000 hours. Since LED is a cold light source, it does not generate a lot of heat like metal halide lamps during operation, and reduces the complex optical path structure required by the original light source, which can reduce the requirements for the projector's cooling system and make the volume much smaller than before. From a small perspective, LED projectors are generally kept below 1 kg, and some are even only about 0.5 kg. This weight is easy to carry and move. And the noise is much smaller.

LED projector performance

Short Throw

Short-throw projection, as the name implies, is an LED projector with a shorter focal length lens. What are the benefits of short-throw projection? The biggest advantage of short-throw LED projectors is that they require a shorter projection distance to achieve the same size of the screen. This type of LED projector no longer requires a larger space scene to project the screen, so it is widely welcomed by users in small and medium-sized enterprises and the education market. For home users, short-throw LED projectors are equally important, especially for some home users with smaller living rooms.

Since short-throw LED projectors use wide-angle or fisheye lenses, the manufacturing process and cost of their lenses are often higher than those of ordinary lenses. The high cost factor is the main reason that is not conducive to the popularization of short-throw projectors.

brightness

The brightness of an LED projector refers to the light output of the LED projector, which is expressed in luminous flux (the energy radiated by the light source to the surrounding space per unit time that makes the human eye feel it), and the unit is lumen. For a projector, the higher the lumen number, the stronger the brightness.

However, since the bulbs of LED projectors are relatively expensive and their power is limited, and blindly increasing the power will cause problems with the heat dissipation of the LED projector, it costs a lot to increase the brightness of the LED projector.

Uniformity

This is a concept related to brightness, which is the ratio of the middle brightness of the projected image to the surrounding brightness. The middle is generally defined as 100%. The brightness of the image projected on the screen by the LED projector is not completely uniform. Some places will have higher brightness and some places will have lower brightness. Of course, the more uniform the brightness distribution of the projector, the better.

Contrast

The ratio of black to white in the image projected by the LED projector is the gradient from black to white. The larger the ratio, the more gradients from black to white, and the richer the color performance.

Projection screen size

Refers to the diagonal size of the projected image. To project the required size, the LED projector needs to be installed at a corresponding distance from the projection screen. Currently, mainstream LED projectors can easily project large screen images of more than 100 inches, and some high-brightness engineering projectors can also project images of more than 200 inches.

Projection distance

Refers to the horizontal distance between the LED projector lens and the screen.

LED rear projection projector

Some users will install the LED projector on the back of the projection screen for projection, which can avoid collision, obstruction and other problems in front projection. However, the projection screen needs to be back-transparent. It is best to set up a dark room separately for the projector, so as to obtain better projection effects.

Horizontal scanning frequency (line frequency)

Also called line frequency, the horizontal scanning frequency of LED projectors has a range. If the horizontal scanning frequency of the input signal from the image source such as a computer exceeds this range, the LED projector will not be able to project, usually displaying "NOSIGNAL". If your computer display configuration is high, it is recommended that you do not buy a low-end projector with a poor horizontal scanning frequency, otherwise it will not be able to project the ideal image effect, or even be unusable.

Vertical scan frequency (refresh rate)

Also called frame rate or refresh rate of displayed images. If the vertical scan frequency of the input signal from the computer exceeds this range, the projector will not be able to project. Within the range, when the vertical scan frequency of the computer is set to a high value, the projection effect is good.

Video input and output interface of LED projector

The video input interface of the LED projector refers to the interface for connecting the computer display signal, so that the computer video signal is transmitted to the LED projector through the input interface and then the computer image is projected. Some LED projectors also have a video output interface, through which other display devices such as monitors and LCD TVs can be connected. If the projector does not have this interface, you can use a VGA splitter to connect to a monitor.