Canon LIDE 20 Scanner Disassembly

Tips on taking a Canon Canoscan LIDE 20 apart. ( In most of these pictures I have already taken the scanner apart at least once.)

PAGE_STATUS: Draft.
Should break this into parts.

I’m hoping to make a tolerable large format digital camera back for an 8×10″ field camera by modifying a Canon LIDE scanner.

The LIDE scanners are:

• very common
• supported by open-source drivers
• very cheap on the used market
• are connected by a single usb cable for both power and data
• easily powered by a netbook
• lightweight
• a long-lived series with steady incremental improvements
• lessons learned on one series apply almost directly to most others

Overview

Image by awrose via Flickr

The general idea is to strip out the optics and slap the scanner on the back of a field camera.

The sensor is a linear array with a lenslet strip positioned directly in front of it. This strip will be removed, leaving the sensor at the bottom of a deep, dark channel with a narrow field of view in the scanning direction.  As the sensor moves across the image plane, the incident rays will be occluded by the channel for a large portion of the scan.  So the channel must be widened.  This might be tricky as the sensor is glued to the structure, cannot tolerate any flexure, and should not be touched by debris.

The light source normally use to illuminate the object being scanned will need to be removed, disabled, or at least covered.

The LIDE’ scanners use the glass platen itself as support for the sensor housing.  I would like to remove the glass but there must be something to support the sensor housing.  Maybe a large rectangle can be cut out of the glass..   or two strips cut out for the guides.

The last bit of hardware is to mount the scanner onto the camera.  I’ll get everything else settled before worrying about this to much.

Software.
Even the Canon drivers will continue to work until you yank out the light source.  Once it’s out the driver may just return a scanner failure notice, or lamp failure, or calibration failure.  Afterward you’ll need to use something like SANE‘s free , open source drivers (assuming you’re using Linux).  In the end you’ll either need to some basic programming using something like the underlying bits of SANE or you can buy a copy of VueScan.  VueScan is available not only for Linux but even for more obscure systems like Mac or even Windows.  And yes, it’s worth it.

The part I haven’t started at all yet is building the image chain for this beast.  Shouldn’t be too hard.

Imaging Expectations

It’s gonna be noisy.  Anything in the scene that moves will be distorted (linear array).  B&W only.  No idea where the sensor cuts off…  ~360nm to ??~1100nm??… maybe 900.. dunno.   Unsure if integration time varies with scanning settings or if it’s just fixed.  Scan times for older models ~1min, newer models ~8sec.   Output image: TIF up to 19000×26000 pixels, at ?10bit.   Unsure about bitdepth..  Canon claims 16b, but I’ll call BS on that.  It’ll depend on the noise. Wouldn’t be surprised if it was only 6 or 7 bit in the end.

Begin disassembly

Here’s the scanner, minus the cover. The cover is easy to remove by simply flexing the hinge a bit.    -v2  Well, on the LIDE 25 it took a lot more pressure than the LIDE 20.

Remove platen retainers

A plastic retainer runs down each long side of the platen. They stop the platen from sliding forward which would free it. There are no screws. The plastic strips are held in place with tape along most of their length.

Begin at the front of the scanner and pry up the ‘ovals’.

You can see coming at the sides of the ovals is a good place to work. (I initially started at the very end.)

Pull gently while slipping something underneath to separate the tape from the plastic. As I’m planning on removing the platen permanently, scratches were not a concern.

One strip off, one to go.
With both retaining strips gone, the platen will slide back with moderate pressure. Once back, the platen can be removed entirely.

Sensor and platform details

Move the platform toward the middle of the scanner. I did this by pulling the cable mid-scan. Ugly, but I haven’t had any problems.  Notice the ‘rod’ and the ‘string’.

WARNING: There are two, free-floating plastic glides on the top of the platform. Collect these now.

Drive string

The ‘string’ is freed by unlocking the endpiece where the spring sits. On the bottom of the scanner (be sure not to turn the scanner over), next to the platform lock, you’ll see a small, round hole. Insert say a small screw driver and push gently to allow this ‘string lock’ to be freed. While pushing the screw driver, slide the string lock free.
You can carefully flip the platform over to see how the string runs through the gears. Separate the string from the platform. Be sure not to kink the string.

Sensor package removal

WARNING: There is a small spring underneath the sensor package. It will come free as you remove the package.

The sensor package pivots on a hinge on the platform. It can be worked free with very little pressure as it slides to unlock when slightly elevated.

Sensor detail

Here you can see the light guide and the lenslet strip. In this picture the light guide is just above the screwdriver tip and the lenslet strip is one of the black horizontal pieces.  There’s a better shot of the lenslet placement a few pics below.

Here is the LED used to illuminate objects during scans. It seemed to be just butted against the light guide without adhesive.

Light guide removal

This is easier than I had expected. I gave each of the attachment points a gentle prying. Not enough to really see any movement. Then started prying at the end opposite the LED, switching to just pulling with my fingers as soon as I could get a hold.

Lenslet removal

Like the light guide, the lenslet strip is easy to pry out.  The strip will be discarded, the only real concern is with possible damaging the sensor directly below while removing the strip.

WARNING: There is nothing protecting the sensor but this lenslet strip.
A note on cleaning the sensor… Don’t worry about a bit of dust getting on the linear array. But do make sure that your tools and particles of plastic created while working keep clear of the sensor. If you wish to clean the sensor use air. A small squeeze bulb is perfect. Do NOT use those old cans of compressed “air” from back in the film camera days. They contain chemicals that can contaminate the senor’s silicon.
Ha!  That turned out to be a non-issue.  The sensor is embedded within some form of clear plastic or something similar.  (pics and description coming soon)

 

 

LIDE 25

 

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• VueScan 9 Versatile Scanner Software: Better than Ever, Charles W. Moore, Miscellaneous Ramblings (lowendmac.com)