Starting my design, questions and sanity check...

[82spider]

I have found a lot of good information here but some of the details are escaping me. If someone can take a minute to help me clarify a few point about the optics I'd really appreciate it. These questions will refer to the picture attached (blue lines are light)

I believe these calculations are correct:
100" image / 7" LCD = 14.3 magnification
12' throw distance = 240mm lens fl
Hence a 257mm LCD to lens distance???

- Since the LCD to lens distance is greater than the fl, does that suggest the second image in my drawing?

- That 257mm is tothe optical center of the lens, not the front glass correct?

- I have seen two fresnels before the LCD and one before/one after. Do both setups temporarily make the light parrellel then aim it back to the lens? is there an advantage one way or the other?

- Does C = Front Fresnel FL - Lens FL ?

- Is the light source treated as a point source? Does that mean A + B = Front Fresnel FL?

- What is the condensor about and how does it's placement effect the brightness/light distribution?

- Do people use a relector on the light?

It is a lot of questions, I know, but I have had trouble finding answers to them here so far. I appreciate your help!!

 

[mastertech]

have a look at this threadhttp://www.diyaudio.com/forums/showthread.php?s=&threadid=52500&perpage=10&pagenumber=1

 

[82spider]

Yeah, I have read that. It talks (mostly) about the lens side of the LCD and many of my questions regard the light side. I believe I have it correct but I'd like to to sure 🙂 I want to gather parts together in the next couple weeks and needs someone to make sure I'm on the ball. Thanks for your help

 

[Rox]

I believe these calculations are correct:
100" image / 7" LCD = 14.3 magnification
12' throw distance = 240mm lens fl
Hence a 257mm LCD to lens distance???

YES YOUR MATH ARE CORRECT.

- Since the LCD to lens distance is greater than the fl, does that suggest the second image in my drawing?

NO, THE FIRST IMAGE IS OK

- That 257mm is tothe optical center of the lens, not the front glass correct?

YES, IT IS THE OPTICAL CENTER OF THE LENS DISTANCE (LETS SAY AT THE MIDLE OF THE LENS)

- I have seen two fresnels before the LCD and one before/one after. Do both setups temporarily make the light parrellel then aim it back to the lens? is there an advantage one way or the other?

kEYSTONE POSIBILITY AND MORE LIGHT EFFICENCY (REAALY NOT TO MUCH)

- Does C = Front Fresnel FL - Lens FL ?

NO, YOU NEED TO DO A PERFECT LIGHT CONE FROM THE LCD TO THE TRIPLET SURFACE, WORK OUT THE FRESNELL FOCAL FOR THAT SETUP.

- Is the light source treated as a point source? Does that mean A + B = Front Fresnel FL?

CANT SEE YOUR IMAGE RIGHT NOW BUT GUESS A=LIGHT-CONDENSER DISTANCE AND B=CONDENSER-REAR FRESNELL DISTANCE. THEN, A+B IS NOT REAR FRESENLL DISTANCE SINCE THE CONDENSER LENS WILL VIRTUALLY FARTHER THE LIGHT POSITION. WORK IT OUT WITH THE THING LENS EQUATION AS YOU DID PREVIOUSLY WITH THE PROYECTION LENS (IS THE SAME EQUATION BUT OTHER SETUP).

- What is the condensor about and how does it's placement effect the brightness/light distribution?

NEED TO WORK OUT FOR YOUR CONDENSOR SPECS... THE TRICK IS THAT THE VIRTUAL LIGHT POINT NEEDS TO BE AT REAR FRESSNELL FOCAL POINT (REALLY IT WILL BE SOMETHING CLOSER DEPENDS ON CONDENSOR POWER)

- Do people use a relector on the light?

YES, THE MOST COMON IS THE ESPHERICAL REFELCTOR, WILL GIVE YOU 2x BRIGHTESS (UTOPIC)

It is a lot of questions, I know, but I have had trouble finding answers to them here so far. I appreciate your help!!

Sorry i couldn´t quote it step by step, my coments are in blocks.

good luck