mathias said:
hi mathias,
meanwhile it is even possible for diy-pj s to do keystone correction.
Duffy in the german diy forum posted a solution for that: i didn't try it it yet but it sounds logical and he also posted results and pics which showed that it works.
i posted the link
the site is in german, but i think the pictures speak for itself
http://web102.sun-15.de/forum/phpBB2/viewtopic.php?t=2361
keystone correction discussed in this forum:
http://www.diyaudio.com/forums/showthread.php?s=&threadid=20731&highlight=
you can also tilt LCD for keystone correction, so light will hit groves of second fresnel in 90 degree angle and reduce the light loss.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=20731&highlight=
you can also tilt LCD for keystone correction, so light will hit groves of second fresnel in 90 degree angle and reduce the light loss.
I know it´s possible to do keystone correction in diy-pj, I read that a half year ago, but didn´t mean keystonecorrection. Keystonecorrection is done by tilting the pj up or down, but this is the not the case with commercialprojectors, they are NOT tilted to get the result in the picture above.
Mathias that idea is done with an offset lens, it can also be done with a mirror, no one has botherd with it cos its not somthing thats realy useful, the only use for that is maybe a roof mounted projector and kept strait so it can help keep a height from a persons head. Also on a table if you like your projector flat, but with that being said to get an image higher on the wall a projector doesnt need to be tilted very high to get a high image on the wall (unless u like watching stuff on the ceiling lol). So in regards to this type of offset image shifting no one realy bothers with it cos there is realy no use for it. keystone is the more usable option and what people are realy botherd about. I can garentee u that the later projectors dont have this as its an option thats not feasably used by any end user.
Trev
Trev
Mathias how manny projectors have u had? ive had 5, not one of them has this system, maybe only on your model it works the way it does, but on others most dont utilise this feature anymore, this is a feature mathias that is not encorported in ALL projectors anymore, simply to cut costs on somthing that is not practical to a HOME user. In my last post change option to feature because this is a feature weather u like it or not and its somthing u PAY FOR.
Trev
I don´t know if we are talking about the same thing, I look like a questionmark right now ?
This features has been on all projectors I have seen, without it, you have to keystone 45 degrees if it´s mounted in the roof. And in a classroom the picture should be 10 cm from the floor without this features and nobody could see the bottom of the picture because of the benchs.
This features has been on all projectors I have seen, without it, you have to keystone 45 degrees if it´s mounted in the roof. And in a classroom the picture should be 10 cm from the floor without this features and nobody could see the bottom of the picture because of the benchs.
LOL how high is the roof? 30ft? maybe the projectors u have seen with this are in short throw projectors, there is no way u tilt a projector 45deg and the keystone is what u use to correct it, tell me somthing, if this thing your talking about is so good and can project through benches while on the floor lol then why do they have keystone on a projector? i know the answer but do u?
Trev
yea that would be something, funny anyway.I found a good link to the famous X1-projectors everybody is talking about, that explane the offset that all commercialprojectors allmost have.
http://www.infocus.com/service/x1/faq-installation.asp?site_lang=1&site_region=1&cat=offset
Using image off set u can loose resolution, its ok if a 16:9 image on a 4:3 lcd but if its a 4:3 ratio lcd and u want to offset a 4:3 image then u will loose reso, the 7inch lilliput has the feature already so im lucky
The only way u will not loose reso is if the lcd is not using all of its area at one given time, this would mean that a 4:3 ratio lcd is not actually 4:3, it would be higher and wider then its active reso states, which means the lcd is not fully using its total active area at any 1 given time and the only area u are using is the reso of the projector.
An easier way of saying this is that the image on the lcd is actually smaller then the total active area of the lcd's capabilites.
Trev
The only way u will not loose reso is if the lcd is not using all of its area at one given time, this would mean that a 4:3 ratio lcd is not actually 4:3, it would be higher and wider then its active reso states, which means the lcd is not fully using its total active area at any 1 given time and the only area u are using is the reso of the projector.
An easier way of saying this is that the image on the lcd is actually smaller then the total active area of the lcd's capabilites.
Trev
Trev, please read the X1 link, the offset has nothing to do with the resolution, they use the optics for the offset.
"An image offset of 100% means that all of the image is above the lens plane, with the bottom right at the lens plane" this is the offset I mean and all commercialprojector have this. DIY-projectors have 50% offset.
"An image offset of 100% means that all of the image is above the lens plane, with the bottom right at the lens plane" this is the offset I mean and all commercialprojector have this. DIY-projectors have 50% offset.
It doesnt say anything about using optics to do this, and i was refering to diy projectors loosing reso. This cant be automatic, the projector has to be told in some way where the image is to go, ie a button or a switch to move somthing, either a lens, mirror or the image. As i stated in a last post that its either the lcd image shifted, a lens being offset, or done by a mirror.
Trev
To explain easy the difference how the picture is projected in a Commercialprojector and in a DIY-projector is like this:
The commercial is projecting the whole picture over the objectlens height. DIY-projectors is projecting the half picture over and the the other half under the objectlens height.
This kind of default offset is done in commercialprojectors with optics like lenses or mirrors, and I hope someone can think out how this work, because I promise you, that you want that in your diy-projector.
The commercial is projecting the whole picture over the objectlens height. DIY-projectors is projecting the half picture over and the the other half under the objectlens height.
This kind of default offset is done in commercialprojectors with optics like lenses or mirrors, and I hope someone can think out how this work, because I promise you, that you want that in your diy-projector.
I have posted a solution of the diy-offset problem in this link, it´s maybe what you mean Trev.
http://www.diyaudio.com/forums/showthread.php?s=&threadid=20731
http://www.diyaudio.com/forums/showthread.php?s=&threadid=20731
Nope not at all, the frensel lens is cut offset, the mirror has to be also cut offset to compensate the shift, i fooled around with this in small amounts on mine, not on purpose but because the lcd is not centerd in its frame, thats how i know this, also in an infocus i had it utilised a similar system where the light engine and the frensel wer both offset, but we can actually make it so the light is still strait and only the image is offset. its not as hard as u think to acheive this.
Trev
Trev
Re: Update
Mathias,
Seems like a great idea. Have you had any success on changing the bulb? I searched on the net (UHP bulb replacement), but I get the 400$ lamp UHP replacement results. Would you have a link or any ideas on search terms on where to get that small lamp, or a specialty store that may carry them?
Found this old thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=10894
Though it isn't exactly the same as what you mentionned...
mathias said:
Mathias,
Seems like a great idea. Have you had any success on changing the bulb? I searched on the net (UHP bulb replacement), but I get the 400$ lamp UHP replacement results. Would you have a link or any ideas on search terms on where to get that small lamp, or a specialty store that may carry them?
Found this old thread
http://www.diyaudio.com/forums/showthread.php?s=&threadid=10894
Though it isn't exactly the same as what you mentionned...
This is the information I know today: A UHP-lamp is a Ultra High pressure mercury arc-lamp manufactured by Philips, UHM is the same type of lamp but manufactured by Matsushita and the P-VIP is also the same but from Osram. This type of lamps are not the same as a xenon short arc bulb that I sad before, UHP lamps use mercury gas instead of xenon and they have higher voltage but lower current than xenon lamps. UHP-lamps have a arc length of 1mm against 9mm of a cdm-t lamp. Most new UHP-lamps are driven on DC-voltage and use a DC-voltage ballast, HQI-lamps can not run on DC-voltage, so don´t try to connect a HQI-lamp to the built in ballast.
The lampmodule reflector can be of parabolic or eliptical type, most common is the parabolic, I have that in my projector.
The company Ushio is in 99% of the case the supplier to these UHP-lamps.
http://www.ushio.com
The problem is as usually that most companies don´t sell this type of bulb to end-users, so if anyone can find a company that sells this type of bulbs, please let me know. If you want to make money, start a company that sells this UHP-lamps cheap and I promise you that you will be rich !
If we can´t find a supplier of this lamps, the cdm-t bulb will be a cheap choice, but needs some optics to work and a ballast.
More and more people are interesting in this because the price on a UHP-lampmodule is a bad joke.
Anyway I haven´t got time with this now, but I will do more research before the summer.
The lampmodule reflector can be of parabolic or eliptical type, most common is the parabolic, I have that in my projector.
The company Ushio is in 99% of the case the supplier to these UHP-lamps.
http://www.ushio.com
The problem is as usually that most companies don´t sell this type of bulb to end-users, so if anyone can find a company that sells this type of bulbs, please let me know. If you want to make money, start a company that sells this UHP-lamps cheap and I promise you that you will be rich !
If we can´t find a supplier of this lamps, the cdm-t bulb will be a cheap choice, but needs some optics to work and a ballast.
More and more people are interesting in this because the price on a UHP-lampmodule is a bad joke.
Anyway I haven´t got time with this now, but I will do more research before the summer.
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