Problems With Page Glare...

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rdmac949
Posts: 10
Joined: 01 Mar 2013, 18:28
E-book readers owned: Android Tablet
Number of books owned: 100
Country: U.S.

Problems With Page Glare...

Post by rdmac949 »

I have some books/magazines where the pages are glossy. This is causing glare on the page from my light source. I think I might have a solution but I don't know. I was going to move the light source from being straight down to one that is off to the side but I haven't tried this yet. Does anyone have experience with this that has a solution? The glare shows up on the far edges of each side of the page not on the glass. Is there a known solution for this problem?
duerig
Posts: 388
Joined: 01 Jun 2014, 17:04
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Country: United States of America

Re: Problems With Page Glare...

Post by duerig »

I think that there are two potential solutions.

One is to change the angle of the lighting unit. Daniel has a video where he moves the light around a scanner build and you can see the effects of different positions: https://www.youtube.com/watch?v=yCvY_GWuWLM

The other is to diffuse the light. Move the light source away from the page (distance diffuses light), get dimmer bulbs but more of them, get a more diffuse light source (floodlight), or interpose frosted glass or something like that.
rdmac949
Posts: 10
Joined: 01 Mar 2013, 18:28
E-book readers owned: Android Tablet
Number of books owned: 100
Country: U.S.

Re: Problems With Page Glare...

Post by rdmac949 »

Cool that's what I was thinking. I just didn't want to waste my time trying it out just to have it not work especially if other people have had similar problems and had solutions.
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daniel_reetz
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Re: Problems With Page Glare...

Post by daniel_reetz »

Third option, if your scanner looks like one of the ones made on this site, just lift the light up higher.
dpc
Posts: 379
Joined: 01 Apr 2011, 18:05
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Location: Issaquah, WA

Re: Problems With Page Glare...

Post by dpc »

You need to do one of two things (or ideally a calculated combination of both):

1. Move the light source up higher away from the center 'v' of the platen.
2. Reduce the camera's viewing angle (i.e. move the camera away from the face of the platen and zoom in tight to the page).

Using a diffuser doesn't eliminate the reflection. It will change a tighter hotspot into something more broad but you'll still be able to see the light source from the camera lens due to a planar reflection on the platen surface. In order to get the light source out of your images the only solution is to move the camera, light source, or platen.

I've done the math and can tell you exactly how far your light source and camera needs to be from the platen to prevent a reflection showing up in the captured image, based on platen angle, page size, and light width. Interestingly enough, if you want to minimize both the camera distance from the platen and the distance of the light above the platen, the optimal platen angle is 102.663 degrees (Dan's choice of 100 deg. from his empirical tests is pretty darn close!).

I've got an Excel spreadsheet around here somewhere with results of a rather involved formula that I was able generate (and simply significantly with Mathematica - yay!) for various platen angles. You input the page size, platen angle, and light width and it spits out the minimum camera and light source distances that are guaranteed to not cause a light reflection to appear in your images. I was in the process of writing an article explaining all of this ("Book Scanner Design - A Mathematical Approach") and then went and got married, and well, you know what happens to projects after such an event occurs. My book scanner is now a cobweb magnet in my unfinished basement but I now have some colorful pillows on my sofa and have discovered a love for homemade meatloaf!

Scan on,
-d
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