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cheap 5x macro objective using lens scavenged from flatbed scanner

Posted by Dominik Schläfli  
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Dominik Schläfli August 04, 2011 09:51PM
The objective in a CCD based flatbed scanner can be used to create an ultra low cost 5x macro lens. I disassembled a defective Canoscan 4200f, and mounted the lens on a fixed length tube. On an APS-C sized sensor, the field of view is approximately 4 mm. Objective diameter is 18 mm, working distance is ca 25 mm. The image quality is surprisingly good: The first file below is a 1000x1000 crop straight from the camera (original image 3072*2048). the field of view is about 1.3, and it shows the readout electronics of the scanner detector line. the chip is ca 0.5 mm wide. Each of the 4 long parallel traces is about 2.5 um wide. The second file is the full frame scaled down to 50%. There is no visible vignetting, chromatic or geometric aberration at the edges.
open | download - scan_1mm3.jpg (224.3 KB)
open | download - scan_4mm.jpg (292.7 KB)
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Dominik Schläfli August 05, 2011 11:24PM
Did some tests with stacking. The image was scaled to 50 % and slightly sharpened. The lens lets plenty of stray light enter the tube, and the black paper lining isn't dark enough for really high contrast.

The second file is a 1 mm wide crop from an ipod touch 4g display.
open | download - gaudefroyite.jpg (508.1 KB)
open | download - ipod4g.jpg (259.2 KB)
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Uwe Kolitsch August 06, 2011 01:57PM
Encouragingly sharp photos!
Do you have a photo of your setup?
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Dominik Schläfli August 08, 2011 08:22PM
The idea was to make a quick and dirty test, with the lens operating under the same conditions as in the scanner, with a distance of 200 mm from the lens to the paper (or the DSLR CCD in our case). Hot melt glue, an aerosol can, black paper and a sacrificed body cap were used. The z-stacking was done with an old microscope stage.
open | download - top_view.jpg (47.7 KB)
open | download - lens.jpg (30.2 KB)
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Dominik Schläfli August 08, 2011 09:28PM
How does the scanner lens compare to an olympus szx 12 stereo microscope ? The images all show the same 0.55 mm wide detail from an integrated circuit, just cropped from the camera output file.
The first one shows a side by side comparison at 5x. The scanner lens looks just a tad sharper, but it could also be due to the difference in lighting.
The second one shows the result when taken with the scope at 18x.
My next tests will be with the scanner lens at higher magnifications, to see if the resolution at 5x is limited by the lens or the CCD.
open | download - sbs5x.jpg (86.1 KB)
open | download - chip_scope18x_550um.jpg (155.7 KB)
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Dominik Schläfli August 13, 2011 10:42PM
I changed the tube, increasing the length to reach 7x, where the objective still performs well, and adding better black absorbers to improve contrast.
This variscite came out nicely.
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Amir C. Akhavan August 14, 2011 12:27AM
indeed, not bad
:)
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