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Browse Prior Art Database

Ultrasonic Motion Sensor for Display Monitor Power Saving

IP.com Disclosure Number: IPCOM000113558D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 2 page(s) / 86K

Publishing Venue

IBM

Related People

Chen, JC: AUTHOR [+3]

Abstract

An improved method of controlling the power-down state of a display monitor is disclosed, the improvement being the use of a pulsed ultrasonic motion sensor instead of a keyboard activity monitor. This provides better human factors, and can be used in situations for which a keyboard monitor is inapplicable.

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

Ultrasonic Motion Sensor for Display Monitor Power Saving

      An improved method of controlling the power-down state of a
display monitor is disclosed, the improvement being the use of a
pulsed ultrasonic motion sensor instead of a keyboard activity
monitor.  This provides better human factors, and can be used in
situations for which a keyboard monitor is inapplicable.

      Computer display power-down can save electrical power and
extend the life of the display.  The major difficulty is in reliably
determining when it is appropriate to power it up or down.  A common
method is to monitor the keyboard for activity.  Power is reduced in
stages after predetermined periods of inactivity, and restored when a
keystroke is detected.  Unfortunately, the display will then shut
down whenever its operator becomes engaged in a lengthy phone
conversation or similar activity.  This is visually distracting and
in some cases may interfere with the task.  There are other
situations for which an activity monitor is simply inapplicable, for
example a display used for public information or public access.

      The solution is to control power down with a motion sensor
which can detect an active viewer near the display.  Such a sensor
must be compact and inexpensive.  Further, it must be capable of
reliably detecting the small, slow movements of a seated person close
to the display, while rejecting the much larger movements of people
walking past at a distance.  Detectors used in intrusion alarms, or
to open doors, turn on lights, etc. are generally not satisfactory in
this regard.

      A pulsed, phase sensitive ultrasonic motion sensor is disclosed
which is more suitable.  Variations between successive echoes are
used to detect motion.  Echoes from distant people or objects, which
arrive at a later time, are rejected by timing.  A block diagram of
the ultrasonic device is shown in the figure.  The key to good
performance at reasonable cost is the 1-chip microcontroller M with
built-in Analog-to-Digital (A/D) convertor.  The controller
periodically applies a group of voltage pulses W1 to amplifier A1
which drive...