All about projector

What is Projector

Types of Projector

Advantages & Disadvantages

What are lumens

What is projector throw distance?

What is Projector Screen?

Rear or Front projection?

By – Roshan Mendonca

A projector is an optical device that projects an image (or moving images) onto a

surface, commonly a projection screen. The most common type of projector used today

is called a video projector. Video projectors are digital replacements for earlier types of

projectors such as slide projectors and overhead projectors.

Most projectors create an image by shining a light through a small transparent lens, but

some newer types of projectors can project the image directly, by using lasers. A virtual

retinal display, or retinal projector is a projector that projects an image directly on the

retina instead of using an external projection screen.


There Are Three Type of Projectors they are

1. DLP

2. LCD

3. CRT

DLP Projection :-

DLP technology is based on an optical semiconductor called a DMD chip (Digital

Micro mirror Device), which was invented in 1987 by Texas Instruments. The way it works

is that a DMD chip is made up of millions of tiny mirrors, that can rotate at a 10 degrees

angle (12 degrees on better models).

On the DMD chips, shade is usually extra using a shade controls. This can be a controls

in which rotates rounded something by 150x for each second to 250x and even more.

A lot of the more affordable products will be made up of your several message shade

controls. This will be Red/Green/Blue and generally a clear message



Advantages OF DLP Projector:-

Filter-free design, Sealed projection system. No problems related to failed air-

filter. Higher contrast, Less pixelation , Lighter and smaller

DISADVANTAGE OF DLP Projector:-

Rainbow effect, Color wheels can produce rainbow effect. Rainbow effect

(sometimes referred to as color separation artifacts) are momentary flashes of

banded color that look like rainbows. They occur at random, and they only last for an

instant. This problem tend to appear only in slower color wheel projectors.. Also,

rainbow artifacts problem never appears in 3-DLP chip projectors thanks to it’s 3

single DLP chips technology


LCD Projection :-An LCD projector is a type of video projector for displaying video, images or computer

data on a screen or other flat surface. It is a modern equivalent of the slide projector or

overhead projector. To display images, LCD (liquid-crystal display) projectors typically

send light from a metal-halide lamp through a prism or series of dichroic filters that

separates light to three polysilicon panels – one each for the red, green and blue

components of the video signal. As polarized light passes through the panels

(combination of polarizer, LCD panel and analyzer), individual pixels can be opened to

allow light to pass or closed to block the light. The combination of open and closed

pixels can produce a wide range of colors and shades in the projected image.


ADVANTAGE OF LCD Projectors:-

Higher contrast ratio in specific projector models. Sharper image in specific projector

models

DISADVANTAGE OF LCD Projectors:-

Low contrast ratio, the design of equipment, equipping them with high quality optics.

High-weight, Dust blobs Impurities in panels. LCD structure projector should be

cleaned every 300 hours of use. Color decay, Limited lifetime Screen-door effect, it is

when the lines between pixels become visible (and as a result separate pixels

become visible), and this effect becomes distracting.

Dust issues. Due to dust accumulation contrast ratio might be reduced up to 50%

over time. Dead pixels. You might heard about it while talking about LCD monitors.

The same issue comes to LCD projectors. This happen when one pixel becomes permanently off or on. If it is only a single pixel - you might even not notice it.


CRT Projection :-CRT- “Cathode Ray Tube “

This is the largest and most experienced player. Many of you have probably seen this

kind of projector at a bar or in an auditorium at a school. CRT utilizes three tubes,

sometimes called "guns." The three colors combine or converge to make your image.

CRTs do not have a fixed number of pixels, making them versatile machines capable of

clear images from higher or lower resolution sources. CRTs also require periodic

'calibration' by a trained professional, which can mean additional expense for the end

user down the road. These projectors are generally used in fixed installations because

of their size. CRTs are typically not as bright as the other technologies, but the refined

picture quality of a properly calibrated CRT is tough to beat. Its worth noting that to

replace the Guns, it costs quite a bit of money.


What are Lumens?

Lumens are a unit of measurement of the total brightness that comes from a light source, in this case, a projector.

One may also see the term ANSI Lumens. ANSI is an acronym for the American National Standards Institute. In

general, the more lumens a projector has, the brighter the image on the screen.

Why do Lumens Matter?

Lumens are extremely important when choosing a projector if the user wants a bright, sharp image to be displayed.

Usually, the brighter the image, the sharper the contrast will be. Lumens are extremely important due to the fact

that projectors with lower Lumens require ambient lighting to be low. In addition, less lumens generally means that

the projector will need to be closer to the screen. These two factors have obvious consequences for many

conference rooms, classrooms, lecture halls, and home theater set ups.

Projector Lamps are the Lumens Source:-

The part of the projector that produces light is the lamp, which has a bulb. There are a variety of bulb types

including UHP, UHE, halogen, and metal halide. The bulb is extremely important to the image’s brightness.

Almost all business and home theater projectors rely on lamps that use mercury. We’ll call them UHP lamps, but they

are mercury vapor lamps. They are basically a cousin of the mercury vapor lamps used in street lights. When you

read about the lamps in projectors, though, you’ll see them called UHP (ultra high pressure), or any of a half dozen

plus acronyms. UHP, UHM, NSH, UHE, etc, are the same thing, in almost all cases.

There is a second type of lamp in use, on very high end, and extremely bright projectors, and these work differently.

They are Zenon lamps. Overall, they have a better color range than the UHP type lamps, and use zenon, not

mercury. These Zenon lamps tend to be significantly more expensive, and have a shorter life than most UHP lamps.

They typically have a lamp life of 500 to 1500 hours compared to UHP lamps good for 1500 to 5000 hours.


What is projector throw distance?

A projector’s throw distance is the distance between the projector and the image on the screen (i.e., the

distance that the image is “thrown”).

Calculating throw distance:-

Throw distance is calculated by measuring the distance from the projector’s lens to the projection screen that the

image is being cast onto.

What is a projector throw ratio?

The throw ratio of a projector is the result of dividing the distance between the projector’s lens and the projection

screen by the width of the image being projected, or more simply: Screen width x Throw ratio = Throw distance

For example, if you know that you want to use a projection screen that is ten feet wide and you know that your

projector’s throw ratio is 1.8:1 (which means 1.8 ft of throw distance per foot of screen width) then you should

place your projector 18 feet away from the projection screen since 10 multiplied by 1.8 equals 18.


A projection screen is an installation consisting of a surface and a support structure used

for displaying a projected image for the view of an audience. Projection screens may

be permanently installed, as in a movie theater; painted on the wall; or semi-permanent

or mobile,[citation needed] as in a conference room or other non-dedicated viewing

space such as an outdoor movie screening (open air cinema).

Different markets exist for screens targeted for use with digital projectors, movie

projectors screen, overhead projectors and slide projectors, although the basic idea for

each of them is very much the same: front projection screens work on diffusely

reflecting the light projected on to them, whereas back projection screens work by

diffusely transmitting the light through them.


Big screen images - rear or front projection?

Optical front projection and rear projection screens provide many of the same benefits. Both screen types offer

enhanced contrast and brightness compared to conventional non-optical projection screens. When this is said,

there are major differences. Generally speaking, optical rear projection screens generate the best image, but

they also require more space. Optical front projection screens are extremely space-effective, but also less

resistant to ambient light than rear projection screens.

Benefits of front projection screens:- Easy to install

No dedicated projection room required

Space-effective design

Cost-effective solution

Enhanced mobility of screen and projector

Benefits of rear projection screens:- Enhanced contrast and image brightness

Suitable for high brightness applications

No shadows from the presenter/viewers cast onto the screen

Projection equipment is hidden behind the screen

Noise-free operation


Thank You


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All about projector