Channel: itfreetraining

Category: Education

Description: In this video from ITFreeTraining, I will look at projectors. Projectors are found in most meeting rooms. A projector’s basic purpose is to project an image onto a flat screen or a wall for viewing. Download the PDF handout: itfreetraining.com/handouts/ap/2a20.pdf CRT Projector 0:11 The first generation of projectors used CRT. Essentially these projectors contained three very bright CRTs that projected the image outwards. These units were very big, heavy and nowadays obsolete. There were some advantages to them like having good response times, a good display of black and a descent resolution, although newer technology can do a lot better. CRT projectors were often seen mounted to a ceiling. These required some setup to get them to work correctly, so once installed, it was not a simple matter to move them somewhere else. Their size and difficulty to move is probably the main reason they are no longer sold today. Liquid Crystal Display (LCD) 0:54 The next advancement in projectors was Liquid Crystal Displays or LCD. These significantly reduced the size of the projector. It also meant you could move it around quite easily. If you have watched our videos on monitors, you will understand the process is similar to how an LCD screen works. The process is essentially that the projector has a very bright backlight. This is significantly brighter than what you would have in an LCD screen. This is to be expected because the projector must project light a much greater distance then an LCD monitor would have to. In order to control what light is seen, the light travels through an LCD panel which blocks or allows light to pass through. So far, we have light, but we don’t have any color. In order to get color, a color wheel is added. The color wheel spins and changes the color of the light as it goes through. Different LCD projectors will have different colors on their color wheel and different amounts of color allocated to different parts of the wheel. Don’t be surprised if you find the color wheel is not red, green and blue. Once the light goes through the color wheel it will be projected to a surface, for example a screen or even a white wall, where you will be able to see an image. This are the basics of how an LCD projector works. Similar to an LCD screen but with the addition of a color wheel to change the light to a different color rather than a filter. Like an LCD screen, projectors have a native resolution that they should run at. If you run the projector at a lower resolution, the image will be scaled and won’t look as good, so when possible run the projector at its native resolution. The problem with this approach is that the LCD panel will need to be timed with the color wheel. Essentially the LCD panel will need to change fast enough to match the speed of the color wheel. This makes it difficult to reproduce certain colors. For example, a bright blue will be almost all blue with very little red and green. The LCD panel must essentially max out and then go to the opposite extreme to match the spinning wheel. So, you can imagine, this has an effect on color reproduction. In order to improve color reproduction, there is a different method that is used that divides the light into red, green and blue to give a better result. 3LCD 3:21 To divide the light into three different colors, a technology called 3LCD is used. 3LCD works like this: as before, you have a light source. The light shines through a series of dichroic mirrors. A dichroic mirror will reflect one wavelength in one direction while allowing the other wavelengths to pass through. Description to long for YouTube, please see the following link for the rest of the description itfreetraining.com/ap/2a20 References “The Official CompTIA A+ Core Study Guide (Exam 220-1001)” Chapter 2 Position 839 - 1076 “CompTIA A+ Certification exam guide. Tenth edition” Pages 750 – 753 “CRT projector” en.wikipedia.org/wiki/CRT_projector “Picture: CRT projectors” commons.wikimedia.org/wiki/File:Kalht_01.jpg “Picture: Cat” unsplash.com/photos/VvTVkc_p-eg “Digital Light Processing” en.wikipedia.org/wiki/Digital_Light_Processing “Picture: cat” unsplash.com/photos/dCrjY-Bt6Kg “Picture: DLP picture” en.wikipedia.org/wiki/File:Digital_micromirror2.svg “Picture: Small cat” pixabay.com/photos/kitty-cat-kitten-pet-animal-cute-551554 “Throw (projector)” en.wikipedia.org/wiki/Throw_(projector) Credits Trainer: Austin Mason ITFreeTraining.com Voice Talent: HP Lewis hplewis.com Quality Assurance: Brett Batson pbb-proofreading.uk