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Browse Prior Art Database

CRT Screen Byte Optical Information Interface

IP.com Disclosure Number: IPCOM000099696D
Original Publication Date: 1990-Feb-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 131K

Publishing Venue


Related People

Kugel, LE: AUTHOR [+4]


This article describes a quick, versatile method and hardware embodiment for data transfer from a cathode ray tube (CRT) screen.

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

CRT Screen Byte Optical Information Interface

       This article describes a quick, versatile method and
hardware embodiment for data transfer from a cathode ray tube (CRT)

      Light-emitting diode (LED) to photodiode interfaces have been
used to provide isolation of manufacturing tools. In this article, a
CRT is substituted for many LEDs.  The suction assembly disclosed
herein includes a small suction cup containing a small scanner. Two
or three suction assemblies are attached to CRT screens at particular
locations to scan for information presented in a small section of the
screen, the location of which is programmable.  Protruding from each
suction assembly is a wire which conveys the information to another
device.  The CRT displays a three-by-three fixed size dot pattern on
the order of .25 x .25 inch per dot.  The matrix would be .75 inch
square.  Each pattern of dots codes for a byte of information (8
bits) plus a synchronization bit.  The sync bit indicates the other 8
bits are ready to read and that a pattern is valid. For example:
      **O  The "O" represents the sync bit.

      The dot pattern could change with each screen refresh which
would be on the order of 60 Hz for a TV set.  This allows a
transfer rate of 60 bytes a second.  Multiple suction assemblies can
be used for multiple bytes.  Character-only displays can utilize this
basic idea by displaying a character such as a "*".  Nine wires leave
the suction assembly (IR links could replace the wires).

      A matrix of photodiodes is used.  Alignment is accomplished by
providing two alignment marks or patterns which accompany the dot
pattern.  In addition a few test patterns are generated for a final
alignment check.  A simple alignment check consists of going through
all 9 single-bit patterns, or requiring that all 256 patterns are
checked.  This also checks for intensity.

      The suction assembly contains the photodiodes and is
lightweight.  It can be made with injection molding.  An interface
box consists of simple logic which prepares the bytes in a computer
memory format for storage or use.  The box itself can store the
patterns.  The donor CRT screen need have no special interfaces.  It
merely needs to be able to project simple dot patterns.  A TV screen
could be used. It is electrically isolated.  The user cannot damage
the donor.  Electro-magnetic compatibility (EMC) problems associated
with standard electrical connections are avoided. This would work in
harsh environments, including under water, since everything is
sealed.  Both units can be sealed to be immune from EMI.  Ground
loops are avoided.  It is also radiation hardened (low sensitivity to
gamma rays, alpha particles).  It is easily incorporated into a
user's application.  Only a small portion of the screen used and the
position of the dono...