My DIY CIH (Prism Lens & BOC Screen)

Hello, This is my DIY CIH upgrade solution for my 10 years projector & screen.

Here is my previous projector (Sony VPH-1001QM) and screen (200 cm in width). My room's width is about 330 cm (pls. ignore other messy stuff in my room )






Some screen shots...






Even though the picture is suffered from unfocused (especially blue color) But it is ok to me for viewing standard def. movies. But when i decided to go for HiDef movies. This projector and screen can't get my desired output. So i decided to upgraded them.

And due to the budget, i chooses to go for Optoma HD20 + DIY Anamorphic lens and DIY scope BOC screen. The project is almost complete. Here's current picture of my DIY lens and screen.

I purchased Optoma HD20 from ebay for the lowest price i can get (include shipping to my country).







I chose prism lens from surplusshed.com (http://www.surplusshed.com/pages/item/l9113d.html). They shipped to me with a little chipped on the one of prisms which i so worried that it might effect the picture output. But with information from guys on this board and actual testing. It didn't has any effect





This is my DIY lens enclosure making step. The enclosure is made from wood. Painted flat white to go along with hd20 color. Flat black paint inside to reduce reflection.






This is the first DIY lens hanger made from aluminium. It is later replaced by made to order metal hanger due to loosely lens holding, clumsy sliding and most important, bad looking -_-'

This is some very first screen shots after hanging projector to the ceiling..

This is another reason for new projector and lens hanger, unbalance hanging point when the lens installed. I need to use strings to pull projector from titling down.




Test pattern.




CA on left and right side.





Movie shots..

When i have projected image on the wall. I can measure and choose the screen size. I decided to make 290 x 120 cm. size screen. i came across these web boards

http://lumenlab.com/forums/lofiversi...hp/t22528.html

http://archive2.avsforum.com/avs-vb/...1&page=3&pp=30

which describes the alternate way to stretch the fabric to screen frame instead of using wooden frame and staples. I decided to use this approach for my DIY screen

I use made to order 20 x 20 mm. square steel bar. which match the size of binding clips i use.



I selected gray color blackout cloth fabric because my room is not 100% light control. So i can get acceptable image when there's some light in the room (white color fabric give too wash out picture)








Clipping step..






Install..





When projecting movie on the screen. There's some reflection on the side of binding clips which i think it can be eliminated by put screen border/masking. But i still fine with it so i leave it that way.

When my big bro (who implemented this projector room 10 years ago) saw my DIY lens hanger. He said i should better design the new hanger. And when my lil bro saw it, he said the same

By (unsaid) it's bad looking together with bad functionality lens hanger i've made. I decided to redesign the the projector and lens hanger

With my big bro's initialized new hanger design. I ended up with this..





After send this design to the shop, i got this 2 weeks later..




Get painted.




Install.. The messy colored strings used as safety wire.








Well, i think this new hanger looks much better than the first one and working much better too (but cause more money -_-') i'm happy with it, anyway

Well, that's all of this project until now. After spending some time with this system. I have some notes about my DIY lens performance here.

- Geometry Distortion

By not using curved screen and using near max zoom of the projector. I got image distortion on all 4 sides of the screen, especially on the left side of the screen . I decided to zoomed in and loose some area of the picture. And by image adjustment that try to make the center screen's proportional most correct. I got horizontal stretched image on the left and right side of the screen.



- Chromatic Aberration (CA)

This is full screen of test grid.



Here's CA on the left, center and right side.



Even though in the image show kind of serious CA on the left side but in real life i can tell it's not that serious. The grid is about 2.5 cm in width. It hardly see the CA from viewing distant.

- Reflection (Ghost image)

Ghost image is the reflection which we could see in some overexposed scene (very bright object/text on very dark background -: ending credits). I got very less reflection/ghosting. It's very hard to see on my DIY Lens so i can't get the picture of it

- Brightness and color saturation

I can notice both of them slightly decrease when using lens comparing with lens removed.

- Picture sharpness

Due to CA previously mentioned. It also decrease image sharpness. I'd like to say that it make the picture more soft, not blur. Here's sample picture

Grid pattern without lens comparing to grid pattern on the center of screen when using lens in CA section above.



Sample movie image, Without lens.


With lens.


The sample above is cartoon image which have sharp drawing. In normal movie the difference is less noticeable.

- Focus Shift

I got slightly difference focus when using and not using lens. So i have to adjust image focus on the projector every time i put lens in and out for best picture quality. That's little annoying. Luckily i didn't remove lens so often

- Horizontal Screen Position Shift

When using Lens, the image position will shift to the left side a little. At first i think this my fault alignment. But i just later read Aussie Bob's Omni-CIH Calculator sheet and found that it seems to be normal issue. It's hard to notice this glitch so i leave it that way.

That's all i can tell about my lens performance for now. Even though it looks like so many artifact and disadvantage using lens. But most of them are aware so i didn't worry about them much. So far i'm very happy with it's price/performance and enjoy using it very much

Thx ilsiu

The protective plastic skip the fan exhaust area. So it should be ok to leave it that way.


Thx adude

These are a huge set of screen shots i'd like to share. Even though they can't tell anything

My main player.




2.35/2.40:1 Movie















16:9 Movie









4:3 Standard definition drama

Hello John, thx for coming by
1. Regarding the two rods that the prism box slides on, are they stainless steel ?

- Yes, they are 6mm dia hardened ss rod.

2. The blocks the rods slide through, what material do you use & do you have to oil the rods for the blocks to slide smoothy ?

- The block is aluminium with 6mm slide bearing inside. With some oil, it slide smoothly

And that's all about my DIY CIH project stuff I'd like to share. I don't have any plan for other improve or upgrade my system in the near future. Just spent good time with it

I'd like to thanks you guys on this DIY Constant Height section for very good information about DIY CIH which made me finish this project.

And thank you to my girlfriend for helping me through this project right from the start. She saved me a lot of budget and brought the best solution we can get that i can't have it by myself. And her friend, Robar who's very kind that used his valuable time testing my projector to verify its functionality before sending it to me.

If anyone has question about my diy project. Pls feel free to ask