FocalCalc is a small app developed by a member at Lumenlab which acually calculates the distances between all components and helps one design the projector accordingly. Will have to arrange a digicam - The result is much better than these pics seem to show. Some pics are from the earlier stage of building so look messy Further tweaking will improve the output. Still have to put some finishing touches final wiring and painting and have to ceiling mount it. Amazing results. Well worth the effort.
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FocalCalc is a small app developed by a member at Lumenlab which acually calculates the distances between all components and helps one design the projector accordingly. Will have to arrange a digicam - The result is much better than these pics seem to show.
Some pics are from the earlier stage of building so look messy Further tweaking will improve the output. Still have to put some finishing touches final wiring and painting and have to ceiling mount it. Amazing results.
Well worth the effort. The build process is what i enjoyed the most. A great learning experience and very rewarding results on the whole. Update: Typed on a Pi. Component descriptions.
The Lcd: The Lcd is the primary component around which the actual projector is built. It is what forms the image on the screen. The lcd needs to be as small as possible with the maximum possible resolution. Smaller lcds make the enclosure smaller and small size helps us get better corner to corner brightness and focus. The most nerve wracking part of the build is stripping the lcd to its panel and carefully handling the FFC ribbon cable that connects the glass panel to the controller board.
Utmost care has to be taken while handling this as one wrong pull and the lcd is history. Higher contrast ratio lcds are also preferable. WS 15 inchers are not recommended as the sides may fall out of the fov of the projection triplet making sides dim and out of focus.
The best option would be to use a car lcd. Its a 15 inch lg b. Dismantled it in a matter of minutes. Didnt remove the lcd panel until the last moment. This results in a brighter crisper output. The process is risky. The film has to be soaked for 10 to 12 hours using paper towels and distilled water then pulled out. I dont intend to remove it now as im quite satisfied with the results for now. The lamp: Our project needs a very bright point light source which provides max lumens and minimum heat emission.
Metal halide lamps are perfect for this application as they provide max lumens light output vs heat generated. They also generate a high colour temprature k-kelvin and a high CRI colour rendering index output similar to white daylight.
Mh lamps use a ballast 5 kgs. Very heavy to step up mains voltage which is applied across a glass arc filled with gases.
This excites them resulting in light radiation. I bought mine from a local electricals shop. Available everywhere. I got a w Lamp radium brand - chinese and a matching ballast priya make - w with warranty along with the bulb holder mogul base. Total amount paid : Better brightness and colour.
Also, a reflector needs to be used in collabaration with the lamp to use tne unutilized light from the back of the lamp. I have used 2 v 4 inch fans. One for the lamp and one for the lcd. Iv cut a slit below the lcd which allows cool air to pass around the lcd and exit through the fan at the top. Also wood is used so Fresnel lenses: A fresnel lens is a flat acrylic plastic lens used in ohp projectors. Have you seen a page magnifier?
It is a fresnel. I wont go deep and describe its working here. We have used 2 fresnels on our build. The first one is a mm focal length which is used as a collector. It is placed between the lcd and lamp. It collects light from the lamp and focusses it through the lcd. The second fresnel the Collimitor is a mm fl lens placed between the lcd and the projection lens.
It focuses the light coming from the lcd to the projection lens. Each material flint,quartz,pyrex etc has its own unique optical properties refractive indexes etc. Only one fl is available here so we have to design our projector using this mm fl triplet. Sourced from lensel optics pune. Total cost of 3 lenses shipped to mumbai Rs. Building the box: Mdf is the preferred material for building the enclosure.
I had wood lying around so used it. Mdf is easier to work with and is cheaper too a sheet 8ft x 4ft. How it works: The following diagram shows the placement of components in our system. The first fresnel is placed close to the lcd panel 10 to 15 mm and focusses light from the lamp arc to all sections of the panel.
Fresnels have a property that they require a point light source to operate effectively. That is the reason why mh lamps are used for this purpose. Other light sources like cfls do not have a point source and are hence useless for this task. The lamp arc is placed at the focal length position of the fresnel ie mm.
This focussed light passes through the lcd and to the second fresnel at around 10 to 15 mm from the Lcd between the Lcd and the Projection Triplet. The reason for using such a bright light is that lcd pass only 15 to 20 percent of the light that hits on one side of the panel. The lamps we are using are extremely bright. The second fresnel focusses this lcd image to the triplet which then focusses it on the screen.
Accurate component placement is vital for a crisp projection. Hence, i used focalcalc for determining distances between various components. Excellent tool. It also calculates the final output size of the projection. Some tips: 1. Before starting the build, decide where to mount it. My projector is 2ft x 1ft x 1ft quite large and projects inches at 8 ft distance.
Component availability is limited and so anyone building one will most probably use the same components. Keystoning is also an important issue i forgot. Keystoning is used to get a level image if the projector is mounted at an angle to the screen. If at an angle the image will be trapezoidal without adjustment. The front fresnel has to be kept parallel to the screen in order to get proper projection.
Around 15 degrees of keystoning is achievable. No more. One can also use nvkeystone which is a part of the nvidia driver app. Good for movies but crappy text. Get all components before starting. Plan the build accordingly. I started early and made the box a bit small.
Had to extend it to accomodate the fresnels later. Use the w Osram lamp. I got a w one but image was not bright enough. Got it replaced. There is a watt one also available. Much better Colour Temprature and brightness.
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Nishakar Learn how your comment data is processed. To ignite a Metal Halide bulb, some interesting voltages are needed. Unsurprisingly, p output from the TiVo produced the most pleasing results. I built one of these back in from the lumenlab plans and it is projetor running!