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Browse Prior Art Database

Improved Charge Coupled Device for Barcode Applications

IP.com Disclosure Number: IPCOM000106174D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 6 page(s) / 147K

Publishing Venue

IBM

Related People

Kangas, PD: AUTHOR [+4]

Abstract

Disclosed is a Charge Coupled Device (CCD) with improved light gathering power via a change in F value of the primary lens. It also demonstrates the effective use of a control at the entry window.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Improved Charge Coupled Device for Barcode Applications

      Disclosed is a Charge Coupled Device (CCD) with improved light
gathering power via a change in F value of the primary lens.  It also
demonstrates the effective use of a control at the entry window.

      The device disclosed herein while depicted as CCD technology,
is not limited to that technology and will function with any device
emulating a film plane.

      In Fig. 1 the major components are shown of the subject device
and the optical positioning and paths.  Item 1 is the CCD unit which
will serve as the film plane that captures the barcode pattern to be
detected and processed for eventual application to a system unit.

      Item 2 is the primary lens and is used to focus the image seen
in the single surface mirror 3 on the CCD or film plane.  The focal
length is such as to accomplish this.  The angle of the mirror 3 is
such that its field of view encompasses optical bandpass filter 4 and
target area 5.  A bandpass filter was selected so as to view only the
frequency of the light sources 6 and 7.

      The light emitted by the sources passes through lenses 8 and 9
which are silvered on one side and shaped so as to provide a line of
light in the area of the target.  Our objective in the system is to
view only the target area and the light generated by our sources
while minimizing the effect and the quantity of ambient light.

      Fig. 2 provides a more detailed view of the optics utilized in
the subject device.  In this illustration the CCD surface 1 is
separated from the lens 2 by a distance of (a).  The value of (a) is
set at 36mm.  Also, the mirror 3 is placed a distance (b) from the
lens 2.  This figure is also set at 36mm.  The lens diameter (c) has
been set at a value of 25mm which yields a light gathering value of F
1.44 or approximately 3 times the value found in many like devices.

      The next device, the bandpass filter 4 is optically transparent
to the mirror and serves to greatly reduce all frequencies other than
the single frequency generated by the two light sources in the
subject device.  This bandpass filter plays an important part in the
reduction of ambient light effects on the operation of the device.

      The last components in the illustration is the target 5 which
is one of the many vertical elements contained in a typical barcode
symbol.  In the illustration only a single barcode element is shown
for ease of illustration and simplicity.  In practice, the length of
the ba...