DIY Video Projector - Page 15

tim0 · 17th October 2001, 02:26 PM

Hi Faidzir,

cool thing the 50 Hz flash, but doesn't it create unbearable flicker?
For me, one of the great things about LCDs and projectors is that they don't flicker.
I guess you'd have to push up the frequency to 100 Hz to eliminate visible flicker. OTOH- i dunno. Maybe the "afterglow" time of the flashbulb is long.
What's your experience?

Unfortunately i had no luck getting a service manual for my projector. Hence i don't know about the lamp voltage, start/stop behavior etc. I will not mess with it until the lamp is broken.

I will stay tuned here, and the LEDs are definitely still an option... it would be GREAT to have a silent projector that can be ON always - no big electricity or lamp bills.

Vince, did you try how the light output is without the fresnel lenses? Does the LCD itself eat so much light?

later
Timo

vdi_nenna · 17th October 2001, 02:58 PM

The frensel lenses magnify the light somewhat. The LCD does eat up much of the light. Yet, with the LCD pixels off, there still is light passing through. Good example of black contrast.

The way I see it, the LEDs can be used. We'll probably need more of them and a better condenser system for them.

A method to guide the light would help. Avoiding light scattering into the box. e.g., light leaving the LCD should not mix with the source light. I see it as the equivalent of having ambient light in a room where there is a projected image on a screen. The projected light has to be extremely powerful to compete w/ the ambient light.

Then, there is the issue of the projection lenses. If you look at what dwalls32 wrote, there is definate issues wi the lense system we both are using.

I've seen projectors that are large, but to bulid on that's 4ft long is too much. by using the correct focal length lenses, we should be able to remedy this. The question is how? This needs to be researched some.

What I'd like to know is where are all the people who design/engineer these projectors? Don't they DIY? Is it such a guarded secret?

Timo, can you take a reading of the lamp while it's running?

tim0 · 17th October 2001, 03:32 PM

Hi Vince,

i can't take a reading of the lamp while it's running, it sits in a closed box assembly that can only be pulled out as a whole. I hope you understand that i won't pull it before the lamp is gone anyways.
If (i hope!) we can go the LED route, i'll have to make an external power supply anyways and just have to figure out how to trick the protection circuit in case it shuts off the LCD when there is no lamp in the socket...
My projector has three 1.3" panels. It is a bit dusty (red spots), so when i clean it i can try to take some pictures of the internals.

Here's what's printed on the lens:
f=46.5 ~ 74.4 mm
1:3.0 ~ 1:3.8
LCD Projector Power Zoom Lens

BTW; there is a slew of older projectors out there which use 6" LCD panels. While searching for a used unit i was offered a Sayett projector with halogen light and 6" LCD for 280 $. Didn't jump on it because of poor 100:1 contrast (present one has 200:1 and 300ANSI and that's allright).

Timo

vdi_nenna · 17th October 2001, 04:39 PM

Here's some help-

http://perso.club-internet.fr/legault/focal.html

Focal reducer is what interests me the most right now.

dwalls32 · 18th October 2001, 05:26 AM

I have been playing with the parts I have so far...I tried a somewhat compacted overhead layout...I am waiting on another projector lens and more LED's, but I posted a graphic on my webpage that shows the general layout I have been playing with. Maybe the new project lens I ordered will work better than the spare smaller one I have been using...(of course the LED's on the panel aren't arranged like that)

[Edited by dwalls32 on 10-18-2001 at 12:42 AM]

vdi_nenna · 18th October 2001, 01:29 PM

That's interesting because the mirror effectively doubles the distance from the LCD to the projector lens.

Your setup looks compact too, which leave room for the control.

Nice ideas there!

dwalls32 · 18th October 2001, 02:00 PM

I was hoping for a compact design...still, I'm having problems with my projection lens not collecting enough of the image. What it does collect is sharp, but I ordered an overhead projector, and I'm hoping that lens does a better job...

vdi_nenna · 18th October 2001, 02:26 PM

That's the same problem I had. It didn't collect enough of the image. The solution was to use a plano-convex lens after the LCD. Convex side facing the the LCD.

My spacing was all off, so I couldn't get it to project to the screen w/ the plano-convex lense.

from SurplusShed.com

GLASS ASPHERIC CONDENSER LENS
Item No.: L1314
72.5mm diameter with a focal length of 44.46mm. Double convex with a standard spherical curve on one side and an aspherical curve on the other. Center thickness is 27.1mm. Probably designed for use in a high efficiency projector system. Aspherics offer superior aberration correction for light concentration that would normally require several spherical elements.

[Edited by vdi_nenna on 10-18-2001 at 09:31 AM]

dwalls32 · 18th October 2001, 04:31 PM

Yeah..I bought that lens after reading the earlier posts. Same thing, didn't work for me either. I ordered an old overhead projector and it should be in soon...hopefully I can use the optics from that to do some good...I like the reducer Vince was looking at...

eac74 · 18th October 2001, 05:40 PM

Hi ive just found this forum and read through it.

I used a 2.2" screen from a casio pocket television in an old kodak slide projector.With the kodak projector you can move the lenses about as they are all just mounted in slides. Works well with video from a distance but its a bit pixelated for a computer.

What i wanted to ask was i was told that you can get glass that dissipates heat better than normal glass. Has anyone heard of this.

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17th October 2001, 02:26 PM	#141
tim0 diyAudio Member Join Date: Apr 2001 Location: Germany	Hi Faidzir, cool thing the 50 Hz flash, but doesn't it create unbearable flicker? For me, one of the great things about LCDs and projectors is that they don't flicker. I guess you'd have to push up the frequency to 100 Hz to eliminate visible flicker. OTOH- i dunno. Maybe the "afterglow" time of the flashbulb is long. What's your experience? Unfortunately i had no luck getting a service manual for my projector. Hence i don't know about the lamp voltage, start/stop behavior etc. I will not mess with it until the lamp is broken. I will stay tuned here, and the LEDs are definitely still an option... it would be GREAT to have a silent projector that can be ON always - no big electricity or lamp bills. Vince, did you try how the light output is without the fresnel lenses? Does the LCD itself eat so much light? later Timo

17th October 2001, 02:58 PM	#142
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	The frensel lenses magnify the light somewhat. The LCD does eat up much of the light. Yet, with the LCD pixels off, there still is light passing through. Good example of black contrast. The way I see it, the LEDs can be used. We'll probably need more of them and a better condenser system for them. A method to guide the light would help. Avoiding light scattering into the box. e.g., light leaving the LCD should not mix with the source light. I see it as the equivalent of having ambient light in a room where there is a projected image on a screen. The projected light has to be extremely powerful to compete w/ the ambient light. Then, there is the issue of the projection lenses. If you look at what dwalls32 wrote, there is definate issues wi the lense system we both are using. I've seen projectors that are large, but to bulid on that's 4ft long is too much. by using the correct focal length lenses, we should be able to remedy this. The question is how? This needs to be researched some. What I'd like to know is where are all the people who design/engineer these projectors? Don't they DIY? Is it such a guarded secret? Timo, can you take a reading of the lamp while it's running?

17th October 2001, 03:32 PM	#143
tim0 diyAudio Member Join Date: Apr 2001 Location: Germany	Hi Vince, i can't take a reading of the lamp while it's running, it sits in a closed box assembly that can only be pulled out as a whole. I hope you understand that i won't pull it before the lamp is gone anyways. If (i hope!) we can go the LED route, i'll have to make an external power supply anyways and just have to figure out how to trick the protection circuit in case it shuts off the LCD when there is no lamp in the socket... My projector has three 1.3" panels. It is a bit dusty (red spots), so when i clean it i can try to take some pictures of the internals. Here's what's printed on the lens: f=46.5 ~ 74.4 mm 1:3.0 ~ 1:3.8 LCD Projector Power Zoom Lens BTW; there is a slew of older projectors out there which use 6" LCD panels. While searching for a used unit i was offered a Sayett projector with halogen light and 6" LCD for 280 $. Didn't jump on it because of poor 100:1 contrast (present one has 200:1 and 300ANSI and that's allright). Timo

17th October 2001, 04:39 PM	#144
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	Here's some help- http://perso.club-internet.fr/legault/focal.html Focal reducer is what interests me the most right now.

18th October 2001, 05:26 AM	#145
dwalls32 diyAudio Member Join Date: Oct 2001	I have been playing with the parts I have so far...I tried a somewhat compacted overhead layout...I am waiting on another projector lens and more LED's, but I posted a graphic on my webpage that shows the general layout I have been playing with. Maybe the new project lens I ordered will work better than the spare smaller one I have been using...(of course the LED's on the panel aren't arranged like that) [Edited by dwalls32 on 10-18-2001 at 12:42 AM]

18th October 2001, 01:29 PM	#146
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	That's interesting because the mirror effectively doubles the distance from the LCD to the projector lens. Your setup looks compact too, which leave room for the control. Nice ideas there!

18th October 2001, 02:00 PM	#147
dwalls32 diyAudio Member Join Date: Oct 2001	I was hoping for a compact design...still, I'm having problems with my projection lens not collecting enough of the image. What it does collect is sharp, but I ordered an overhead projector, and I'm hoping that lens does a better job...

18th October 2001, 02:26 PM	#148
vdi_nenna diyAudio Member Join Date: Oct 2000 Location: PA, USA	That's the same problem I had. It didn't collect enough of the image. The solution was to use a plano-convex lens after the LCD. Convex side facing the the LCD. My spacing was all off, so I couldn't get it to project to the screen w/ the plano-convex lense. from SurplusShed.com GLASS ASPHERIC CONDENSER LENS Item No.: L1314 72.5mm diameter with a focal length of 44.46mm. Double convex with a standard spherical curve on one side and an aspherical curve on the other. Center thickness is 27.1mm. Probably designed for use in a high efficiency projector system. Aspherics offer superior aberration correction for light concentration that would normally require several spherical elements. [Edited by vdi_nenna on 10-18-2001 at 09:31 AM]

18th October 2001, 04:31 PM	#149
dwalls32 diyAudio Member Join Date: Oct 2001	Yeah..I bought that lens after reading the earlier posts. Same thing, didn't work for me either. I ordered an old overhead projector and it should be in soon...hopefully I can use the optics from that to do some good...I like the reducer Vince was looking at...

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18th October 2001, 05:40 PM	#150
eac74 diyAudio Member Join Date: Oct 2001 Location: Fort William, Scotland	Hi ive just found this forum and read through it. I used a 2.2" screen from a casio pocket television in an old kodak slide projector.With the kodak projector you can move the lenses about as they are all just mounted in slides. Works well with video from a distance but its a bit pixelated for a computer. What i wanted to ask was i was told that you can get glass that dissipates heat better than normal glass. Has anyone heard of this.