Optical filters are added to white on blue LCDs to give them their characteristic appearance. For example, a character positive LCD with a backlight will have black lettering on a background that is the color of the backlight, and a character negative LCD will have a black background with the letters being of the same color as the backlight. LCDs can either be normally on (positive) or off (negative), depending on the polarizer arrangement. They use the same basic technology, except that arbitrary images are made from a matrix of small pixels, while other displays have larger elements. For instance: preset words, digits, and seven-segment displays, as in a digital clock, are all good examples of devices with these displays. LCDs are available to display arbitrary images (as in a general-purpose computer display) or fixed images with low information content, which can be displayed or hidden. Liquid crystals do not emit light directly but instead use a backlight or reflector to produce images in color or monochrome. (In a backlit LCD, this layer is replaced or complemented with a light source.)Ī liquid-crystal display ( LCD) is a flat-panel display or other electronically modulated optical device that uses the light-modulating properties of liquid crystals combined with polarizers. Reflective surface to send light back to viewer.Polarizing filter film with a horizontal axis to block/pass light.Glass substrate with common electrode film (ITO) with horizontal ridges to line up with the horizontal filter.Vertical ridges etched on the surface are smooth. The shapes of these electrodes will determine the shapes that will appear when the LCD is switched ON. Polarizing filter film with a vertical axis to polarize light as it enters.Note that keystoning can also be compensated for by tilting the screen slightly.Leave yourself some wiggle room just in case, though, and as mentioned above, test the setup before making things permanent.
So if some tilt will be necessary, it's best to mount your projector towards the long end of the throw range, given the available zoom. All else being equal, the greater the throw, the less keystone distortion for a rise in image height.Rather, just simply mark the spot on the wall/screen where you want the image top to be, turn the projector on, and tilt it until it lines up. This is FYI only, you will not need to measure this angle, and would be pressed to do so accurately anyway. The calculator gives the needed tilt angle in degrees.net" with "projector calculator" in the subject line. Comments, corrections, and suggestions are welcome and should be sent to "smspam comcast.The calculator asks for the desired distance to raise top of image, but if you instead want to lower the image, simply input a negative number.This is generally true, but there may be projectors that work differently. The calculator assumes that the zoom scales the image while keeping the offset constant.Also, set up the projector and screen in a temporary fashion to check image size and placement BEFORE you start hammering, drilling, and sawing. Double check all measurements and calculations yourself before spending any money on a projector or screen. Most people find image spill over onto the border to be less distracting than having parts of the screen unlit. The dimensions of the resulting zoomed images are shown at the bottom. Most likely you can compensate for one or more of these by using a small amount of zoom. Note that the resulting image will be smaller than nominal in all three dimensions (top width, bottom width, and height). Hit "calculate" to see the amount of tilt from horizontal necessary to raise the image, and the resulting image distortion.It actually doesn't matter which units you use as long as you're consistent. Also, enter the amount by which you wish to raise the image. These numbers can be determined from projector calculators such as this web-based one at projector central or this Mitsubishi-specific one (requires installation). In the input section, enter the lens drop, image drop, image height, and throw distance as shown in the diagram, assuming no tilt.These can be important considerations, particularly for rooms with low ceilings and high offset projectors. It also determines the resulting keystone image distortion. This Javascript calculator determines the amount of tilt or pitch needed to raise a projected image a given height. Tilt and Keystone Distortion Calculator for Front Projection Home Theater Tilt and Keystone Distortion Calculator for Projectors
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