google patents launched today. you can search for any patent.

I like this site:
http://www.patentlysilly.com/

totally useless for searching for patents, but good for a laugh

check this one out:
http://www.google.com/patents?vid=USPAT550...le+lamp#PPP2,M1
dual lamp system
off for more searching pleasure

My curiosity got the better of me. I just ran a very quick test using BEF and a collimated light source. This does show allot of promise.

DJ

it looks like from the diagram that you would need custom fresnels made to deal with the angled light. the rings are shaped different on the different fresnels. thats a really cool find though

EDIT- i looked at this some more and realize ther is just one weird fresnel. can you get a fresnel like that with strait ridges?

nice find..!!

heres a pdf link

http://www.freepatentsonline.com/5504544.pdf

DAZZ

The prismatic film the patent refers to ..is it close in specs to the BEF ?

I believe it is the same thing I think they even termed it as BEF (I only briefly read it though). Even if it isn’t BEF, BEF does do the same thing. I looked at using BEF some time back but I didn’t really think it through hard enough, I was probably concentrating on other things. Then when I looked at the patent it seemed so simple (sort of). For my quick test I used a 100mm collimated spot light and a piece of BEF all hand held so I didn’t take any angle measurements. When the light was entering the BEF from an angle of about 45°-60° the beam was bent to exit the BEF perpendicular to it (0°). What is surprising is the acceptable incidence angle is larger than I thought it would be. What I mean is that with an incidence angle of 45° the light exited at 0° and when the incidence angle was 60° the exiting light was still at 0°. In other words it is very tolerant, a good thing for us. I also noticed it doesn’t appear to eat allot of light, I would compare it to placing a sheet of plastic in the light path (no lux readings just by eye). I’ll draw you up a quick pic to show you one possible way of using it.

So I’ve gone and gotten myself all exited about something again but I can’t follow it though, going on a holiday for a week in lees than 8 hours.

DJ

edit:
The angle is close to 60°

This is just a concept, the angles could be larger. There are other ways to use BEF as well this is just the first one that I though about.

DJ

Something to get you thinking while I’m gone.

oooo TWO into one
Click to view attachment

And a shot with the lamps misaligned
Click to view attachment
DJ

that is freakin neat. an idea with great potential to actually combine two light sources.

DAZZZ when you get excited....I get excited !!

Damn but ur now on hols !!! arrghhhh


When you get back if you have already gone....where did you get your BEF piece from..are you sure it's BEF not DBEF or some other suchlike..?

If we had 2x para reflectors that cover the panel maybe we wouldnt need the fresnels.or perhaps the light variation would still be seen..in any case the 2x fresnel idea is looking more than good.
Cant wait till you get back and start testing/measuring etc.



CHeers oh and Merry Xmas !

Haven’t gone yet, I can’t sleep now. It is plain BEF, DBEF is a reflective polarizer I think. I removed it from an old 12” laptop. There were actually two BEFs, One enhanced vertically and the other horizontally. I’ve looked at my set up a bit more and it does waste a little more light than I first thought as reflection. But if set up correctly some of the reflection could be recycled. Because both lamp/reflector/fresnel are a mirror of each other the reflected light should pass back though to be recycled. It doesn’t seem to be a great loss.

Merry xmas
DJ

Doh .
I just took a lux measurement.
No BEF single lamp=1445
With BEF single lamp=659
With BEF dual lamps=1193

At least I can sleep now.

DJ

Edit:
We could still probably look at fresnel prisms.

Sleep well DAZZ..

bugger..another one crossed off the list

well, I spent the evenong trying to read that patent, and I think the key to its efficiencey id the prism angle....he specifically does some calcs and shows that the prism angle should be 60 degrees, with the fresnels shooting at it at a similar angel there is very little loss, however the only BEF I can find on the net is the 3M kind we were using for marks recycling light engine and 3M only make s90 degree BEF....although admittedlyI'm only fairly positive that the angle the patent mentions and the prism angle in the 3M literature is the same heres somthing I copied form the patent that speaks to this:
----------------------------------------------------------------------------------------------------------------------------
1) The incident light 16a and 16b must be collimated so that light rays from each lamp enter the entire prismatic film 9 at the same entrance angle .theta.;

2) The preferred vertex angle .alpha. of the linear prismatic beam-combining film 9 is 60.degree. plus or minus 2.degree.; and

3) The preferred entrance angle .theta. of the collimated light entering the linear beam combining film is 60.degree. plus or minus 3.5.degree..

If the prism vertex angle .alpha. is greater than 62.degree., less than 90% of each reflecting facet is utilized. For example, for an acrylic plastic prismatic film with a refractive index n=1.492, a vertex angle .alpha. of 62.degree., and an entrance angle .theta. of 63.5.degree., only about 90% of each reflecting facet is utilized. Excessive underfilling of the reflecting facets causes the collimated exit beams 17a and 17b produced by each adjacent microprism to be spatially separated, and dark banding begins to appear on the illuminated projection screen.

On the other hand, when the prism vertex angle .alpha. is less than 58.degree., less than 90% of the incident light rays 16a and 16b exit perpendicular to the film. For example, for an acrylic plastic prismatic film with a refractive index n=1.492, a vertex angle .alpha. of 58.degree., and an entrance angle .theta. of 56.5.degree., about 10% of the incident rays miss each reflecting facet. The light missing the reflecting facet exits the film in an uncollimated and uncontrolled direction, and does not contribute to the illumination on the projection screen.

Table 1 below illustrates the fraction of beam filling of each facet (BFF) for various vertex angles .alpha. of the film 9. Values of BFF less than unity represent underfilling of the reflecting facet, while values of BFF greater than unity represent overspilling of the reflecting facet. As explained above, more than 10% of the incident light is spatially separated or wasted at vertex angles .theta. above 62.degree. or below 58.degree., upon exiting the film 9.
TABLE 1
______________________________________
.alpha. .theta.
BFF
______________________________________
50 42.3 1.55
58 56.5 1.11
59 58.3 1.05
60 60.0 1.0
61 61.7 0.947
62 63.5 0.895
.
70 77.7 0.446
______________________________________

I should mention that paladin suggested this very setup a couple of weeks ago in my plog....we got some pretty smart people here now id someone could find some 60 degree BEF.....

What’s the point in sleeping now, I’ll be getting up in two hours.

Try googling lenticular lenses or fresnel prisms. I’ve seen them quite often on sites that deal with fresnels. RPTVs use them or use to use them. I’m not sure on their angles though.

DJ

Info different fresnels


http://www.display-optics.com/pdf/OpticalM...urfacesrev4.pdf

thanks dazz and cc, I'll check that stuff out, the really nice part about this "bride of frankenfresnel" approach is that it blends the 2 lamps outputs and eliminated the center line issue

This an RPTV Screen patent utilizing fresnel's and fresnel prisms...some interesting info if you are bored.

http://www.freepatentsonline.com/4512631.pdf

ref the original patent prismatic film

BFF = Beam Filling of each Facet

I wonder where the inventor got this film ?