Registers – Coded record sensors – Particular sensor structure
Patent
1990-12-11
1993-04-06
LaRoche, Eugene R.
Registers
Coded record sensors
Particular sensor structure
235437, 235462, 382 12, 382 46, 382 47, G06K 903
Patent
active
052005984
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a reader for optically encoded data and in particular to a reader for data encoded using the SOFTSTRIP format.
Using the SOFTSTRIP format data is encoded on a carrier such as a strip of paper or card as rows of dibits, each dibit comprising a rectangular region which is divided in two with one half black and the other half white. A white-black combination is used to code for one binary value and a black-white combination used for the other binary value. A series of such rows are printed one after the other along the length of the data strip. A headed having a predefined format is printed at the start of the strip. Each row of dibits is bounded by alignment dibits which form respectively a checker-board and rack alignment patterns extending longitudinally down the edge of the strip.
To recover data from such a data strip an optical reader is required which translates the variation in light intensity from the dibits into an electrical signal and then decodes the signal appropriately to recover the data.
U.S. Pat. No. 4,692,603 discloses one example of an optical reader for data strips. The reader includes a guide which receives and aligns a substrate bearing the data strip. The data strip is fed past a scanning head bearing a number of lenses. The lenses scan across the row of dibits to focus light from successive dibits onto a photodetector. If the data strip is tilted with respect to the reader then dibits from different rows may be read in a single scan, causing corruption of the data. To avoid this, this prior art system includes a number of mechanisms to eliminate tilt. On start-up the scanner first moves along the header section of the strip in one direction and then reverses moving back up the strip, while scanning all the time. Logic circuitry is provided to determine from the output of the scanner during this alignment procedure the angle of tilt of the strip. A tilt adjustment motor is then activated to move the strip relative to the reader to correct the tilt. The start-up procedure is then repeated until the strip is satisfactorily aligned.
SUMMARY OF THE INVENTION
According to the present invention, an optical reader for reading high density dibit encoded data from a data strip comprising an optical detector and a decoder connected to the optical detector and arranged to decode the output from the optical detector is characterised in that the optical detector includes a row of photo sensitive elements arranged to extend transversely across a row of debits and to form an image of the row of bidits and in that decoder buffer means arranged to store the image, and image transform means arranged to detect a skew angle of the reader relative to the strip and to transform the image stored in the buffer means to compensate for the distortion of the image in accordance with the skew angle.
The present invention provides an optical reader with many advantages over the prior art systems. By using a detector capable of imaging an entire row of dibits at a time it removes the need to physically scan the row. As a result the reader of the present invention is markedly more simple both mechanically and optically with consequent savings in cost and advantages in terms of reliability. A further important advantage of the present invention is that means are provided to correct for any distortion in the image resulting from tilting of the data strip. It is therefore not necessary with the reader of the present invention to provide a guide to hold the strip in a predetermined orientation with respect to the reader nor to provide a tilt adjustment mechanism to shift the strip with respect to the reader.
The relative insensitivity of the reader of the present invention to the alignment of the strip makes it particularly suitable for use as a hand-held device.
Preferably the optical detector comprises a CCD array.
Preferably the image transform means include a one-dimensional image resampling sequencer arranged to receive image data from the buffer means and to apply to the image d
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LaRoche Eugene R.
Nguyen Tan
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