A new scanner design using plastic tubing

Built a scanner? Started to build a scanner? Record your progress here. Doesn't need to be a whole scanner - triggers and other parts are fine. Commercial scanners are fine too.

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davidlandin
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Re: A new scanner design using plastic tubing

Post by davidlandin »

elwi wrote:
the alignment of the cameras on the camera support arms is really giving me hard times. I get a lot of keystone in every possible position. I have tried and tested every possible position but I think there is no perfect one. The platen hanger position interferes with the camera support arm position but I need both at those positions exactly where they are since the platen hangers are perfect for the platen balancing and the camera support arms so that the cameras point at the center of the book.

Therefore I am thinking about buying two goose-necks and applying them on the sides of the base frame similar to the goose-neck used in this thread http://www.diybookscanner.org/forum/vie ... ?f=1&t=698,

I have illustrated how to:
FFXBJKHHX6AQKKB.MEDIUM.jpg
You do need to spend quite a bit of time getting the cameras adjusted to get the minimum keystone effect. It would certainly be worth trying the goose-neck camera supports. I think you just need patience and to spend some time getting the camera position right - or as right as you can.

I think you will certainly need to use post-processing to correct any remaining keystone effects. Can Ii recommend that you have a look at YASW. This is a free keystone correction and picture trimming package. I've made a YouTube video showing how to use it, and you can look at it here
http://youtu.be/__a9urAtQD4

David Landin
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davidlandin
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Re: A new scanner design using plastic tubing

Post by davidlandin »

Henck wrote: To avoid reflections from the frame tubes or camera holders - why not wrap a black cloth around the tubes and fasten it with black cable clips? Maybe the use of handlebar tape may be helpful.
This is a good idea Henry, and I also like dpc's idea of using Hockey Tape. I'm not a sports person, so I never heard about hockey tape. But I checked it out on eBay, and it is matt and non-reflective, and also self-adhesive and cheap. So it looks like great stuff! Thanks dpc!
Henck wrote: My question:

the pdf building instruction uses two models of the scanner, is this right? In the plan there is shown a back section in the base structure. Is this part added to prevent tipping?
Yes you are right Henry - I've made three of these scanners now and they have all been slightly different, as I have improved the design or made necessary changes.

The back section is shown of the latest model on this photo
Back section added
Back section added
Snap_2014.09.13_16h39m33s_005.png (303.11 KiB) Viewed 9799 times
I felt that sometimes the structure was tipping backwards, and so this extra extra section at the back (marked with the arrow) prevents tipping.

David Landin
cday
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Re: A new scanner design using plastic tubing

Post by cday »

davidlandin wrote:The light is a 20 watt LED light used for outdoor flood lighting.
Could you report on the evenness of the light from the LED floodlight you are using?

When a page can ultimately be converted to black and white –- containing only black text and line drawings -- good results can usually be obtained even when the lighting is fairly uneven.

When a page must remain as grayscale or colour -- halftone drawings and photographs -- even lighting is important to allow optimal enhancement of the resulting images, and uneven lighting can seriously limit the results that can be obtained.
The light is ... very bright ...
You say the lamp is very bright, but the low cost 'point and shoot' cameras being widely used reportedly need a lot of light to produce good results. When photographing a white page are you obtaining a near-white background?
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davidlandin
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Re: A new scanner design using plastic tubing

Post by davidlandin »

cday wrote: Could you report on the evenness of the light from the LED floodlight you are using?
Yes the light does seem very even across the page when illuminated by one of these LED floodlights.
cday wrote: When a page can ultimately be converted to black and white –- containing only black text and line drawings -- good results can usually be obtained even when the lighting is fairly uneven. When a page must remain as gray-scale or colour -- halftone drawings and photographs -- even lighting is important to allow optimal enhancement of the resulting images, and uneven lighting can seriously limit the results that can be obtained.

You say the lamp is very bright, but the low cost 'point and shoot' cameras being widely used reportedly need a lot of light to produce good results. When photographing a white page are you obtaining a near-white background?
My scanner is currently in the hands of a friend who lives 150 miles away. But I will ask him to take images of a coloured page, a white page with text, a photograph and a half tone drawing.

I'll post them on this site when I get the examples from him.

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elwi
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Re: A new scanner design using plastic tubing

Post by elwi »

Dear David,

Thanks for the explanations and photos on how to attach the light. I now have a 20 Watt LED and attaching it like you showed me. The goosenecks also arrived, I am thrilled If I can reduce keystone! The software you showed looks good.

Thanks again for your help

Elwi
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Re: A new scanner design using plastic tubing

Post by buckeye43210 »

David,

I've been thinking about your design and have a suggestion for the light and camera supports. Instead of drilling holes into the enlarged tee sections and securing them with bolts, why not cut lateral slits into the sides of the tee sections and securing them using hose clamps? The following isn't an exact example of what I'm thinking about, but I think you can get the gist...

Image

You would probably only need to cut two or four slits into the tee section for this to work.
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davidlandin
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Re: A new scanner design using plastic tubing

Post by davidlandin »

Hi Buckeye

This looks a nice solution. and it would take less time than all the drilling I was doing. The slits would have to be fairly wide to allow the T to "crunch down" and make a firm grip on to the tube. But I think this is a fine idea, and would result in a really tight grip. This is important because the cameras and the lights can be reasonably heavy, and can have a tendency to rotate the T around the tube, which you don't want to happen.

Thanks. Good modification!
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Re: A new scanner design using plastic tubing

Post by davidlandin »

I'm currently looking at a platen with a 110 degree angle rather than 90 degrees. I've seen wider angles on a commercial machine which made me consider trying this out. The 90 degree platens are easier to make, since they are a right angle, and there are lots of easy to find onbects which are right andle in shape. But I've now developed a simple way of making platens with different sized angles. My friend will be trying out the prototype in a few days, and we will see how it goes.

The plus with the wider angle may be that the camera can see further into the gutter. This is important with books where the print goes right into the gutter - less important if you have a wide inner margin.

The downside may be that the wide angle doesn't press so firmly into the gutter. So it may be a case of swings and roundabouts - one advantage and one disadvantage. Anyway I will see how it works and if successful I'll provide more details of the way the 110 degree platen was made.

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Re: A new scanner design using plastic tubing

Post by dpc »

Some thoughts on a wider platen angle...

The advantage of a wider platen angle is that you won't see a reflection of the adjacent platen (and adjacent page's image) on the page you're photographing and allows you to get the camera closer to the page. The disadvantage is that the closer the camera is to the page, the wider the field of view and the higher you'll need to place your light so that it won't be seen reflected off the platen back into the camera (glare). You'll also lose light intensity by moving it farther away from the page.

When designing a scanner you typically want to make the structure as compact as possible while selecting camera and light positions and a platen angle that prevent the aforementioned reflection artifacts. I've done the math and it turns out that the ideal platen angle is 102.67 degrees between the two platen halves. Using this angle will allow you to minimize the camera distance from the platen surface and minimize the light distance above the platen 'v'. If you increase the platen angle you'll have to raise the light. If you decrease the angle you'll have to increase the camera distance.

I'm afraid I don't understand the benefit of a wider platen angle to be able to see more information closer to the gutter of the book. The reason you can't get into the gutter is from page curvature. A smaller platen angle (i.e. 90 deg.) will be better at eliminating this curvature and allow you to see more of the content in this area.
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davidlandin
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Re: A new scanner design using plastic tubing

Post by davidlandin »

One of the problems I have is that some of my books have an extremely narrow margin between the print and the gutter. We are talking here about maybe 0.5cm wide on either side of the gutter. So I am going to try a wider angle. I've seen commercial scanners that press the book open flat - 180 degrees, and you can definitely see the full page then. Also having seen a commercial scanner with a 110 degree opening I wonder if this is a good compromise between 90 and 180 degrees. I may be that I will need to press these hyper narrow margin books up against a horizontal flat platen and use a single overhead camera.

We'll see what happens when my friend tries out the new platen and 110 degree book supports on the old scanner.

I take your point about the knock-on effects of having to move the lighting higher. We will just have to give it a try and see what happens.

David Landin
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