Moderators: Dave Moll, Andrew Davie, Steve Anderson
Dave Moll wrote:May I just say what an excellent animation showing how the light is deflected as it hits the sides of the rotating hexagonal mirror. Presumably there is a second mirror handling deflection in the other orientation - one rotating at one-sixth line speed and the other at the appropriate fraction of frame speed.
Harry Dalek wrote:I can't get my head around if it matters it should work visa versa ?
gary wrote:Harry Dalek wrote:I can't get my head around if it matters it should work visa versa ?
Not unless I am completely misunderstanding your arrangement.
You have a beam of light right?
Gary i tried to draw what i am seeing The lens projects the full image from the lens on to the frame mirror which rocks the polygon the line mirror only sees a strip of light that is reflected to it and depending on the angle of the frame image so it sees changes with that angle ,the polygon reflects the strip of light to the light box with a light sensor.
Because the strip of light from the polygon is so thick i only want the light sensor to see a tiny part of that polygon thick line and i also only want the light sensor to see a point of light from that line.the beam of light hits the *thin* line scanner and is reflected on a *wide* frame scanner which is perpendicular to the line scanner right?
Well it would if the light sensor was a light reflecting from the polygon to frame mirror and out the lens in a FFS it would work that way i would need a thin mask line for the light ...thats why i was thinking of a laser much easier to do a quick FFS projector to see how the rocking mirror gos ...i sort of think it needs to run twice the frame speed to work correctly as of the fly back takes up half the time me thinks ; ).
I have never read in nbtv that a rocking frame mirror or sensor on a rod has this problem and it had me interested ....i know with my laser monitor change the speed slower you see more lines slowing it down you still see a picture but it is compressed due the larger number on lines the effect has me wondering does or will it look or work at all the same on a camera idea or work at all.The frame scanner is positioned in such a way that the line scan starts at one side of the mirror and ends at the other side such that the beam is always on the frame scanner mirror right?
Yes the frame mirror just rocks so the light line angle of the image will be scan up or down the image depending on how much the frame mirror can rock .If you go the other way the beam is frame scanned perpendicularly across the *thin* line scanner so most of the time it is missing the line scanner unless the frame scanner angle is very tiny and your video seems to imply that it is not.
Gary i am making up for the thickness and size of the mirrors polygon and frame mirror by the size of light the light sensor sees i have gone with an examples i have seen in drawings in the newsletters most of the time you never see the results but take their word for it ,so i will try that and see if it works for me .
I still have 2 other ideas in case the pin hole camera light box on a direct light camera causes me grief ,i will try a vertical mask thin line instead of the light dot and would rather a dvd lens in place of the pin hole idea if that works.
Also increasing light levels i see in a past drawing i posted the main lens ma not be needed well a film pin hole camera doesn't either .I may be completely misreading your set up, but it is late for this old codger, so I am off to be, and will look again tomorrow, just confirm those things please.
Have a look at m drawing i know i am dreadful at drawing but think it sort of make it out , i know i am also bad at optics but i enjoy things that are a bit harder reason i like controlling rotating things .PS As nice as your animation is it is only showing the line scanner - presumably it is a laser printer scanner and the frame scanning is done by the movement of the paper past the line scan.
gary wrote:Harry, that last diagram you drew seems almost perfect - the only thing missing is the lens that focuses the image onto the plate that has the pin hole in it. If the polygon was wide enough you would see the whole image but as it is not you will just see a bar of it I suppose - but if it is in focus I can't see why it would matter.
The only thing is whether the relationship between the polygon and the rocking mirror is such that the whole image traverses the pin hole, but once you get a lens in there it should be easy to see that and make adjustments as necessary.
Also make sure that the light is projected onto the sensitive surface of the photocell and not on or across the "divides".
Suggestion: replace the photocell with a bright white led - that should throw a point of light up on the wall (or whatever) and trace out a raster - then post up a well lit white sheet of paper with some large letters on it (NBTV ), replace the led with the photocell and make sure a bar of the paper image is thrown on pin hole plate and adjust lens for perfect focus if necessary.
Oh but the lens at the front of the system is not necessary I don't think.
gary wrote:Harry, I base my recommendations for the lenses on what is normally used for a Weiller style mirror drum, after all your arrangement is really the same but with the line and frame scanning separated out. The only thing I am not confident about is the effect of the separation between the line and frame scanners - this is definitely one of those projects where for me it would be a suck it and see procedure...
See Newsletter Volume 3/4
Users browsing this forum: No registered users and 37 guests