Preprocessing - detailed cropping

Hello,

I'm trying to recognize the machine readable part of a passport. (see the last line in this picture: http://s.hswstatic.com/gif/passport-11.jpg )

I'm using Tesseract on Android (tess-two) and take the picture with a 5 Mpix mobile camera. Unfortunately, the accuracy is not satisfyingly high. What I have tried to improve recognition was cropping the picture and retraining Tesseract for the font used in a passport (ocr-b). Both raises accuracy but still not to an acceptable level.
Here is a typical cropped picture I hand to Tesseract to perform ocr:

The binarized picture created by Tess for the actual recognition looks like this:

This is what Tesseract recognizes:

  09 1 M 1 907 1 8  F8 F857<4 < W<B<O <UME
  QVWBBENO W JMGHJ <RBP6W9BQR ED


I figured that the thin line at the bottom is extremely distracting to Tesseract. If I cut off the line manually and perform ocr, results are perfectly fine and all characters are recognized.
My question is, how can I find and get rid of that line automatically if it is in the cropped picture? This has to be done on an Android phone.

Any help will be appreciated!
Mirko