Microsoft SENSECAM V2.3B User Manual

Company confidential proprietary information. Do not distribute.
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1. Introduction
1.1. Overview of v2 SenseCam
SenseCam is a small digital camera that is designed to take photographs automatically
without user intervention. Unlike a regular digital camera or a cameraphone, it does not
have a view finder or a display that can be used to frame photos. Instead, it is fitted with a
wide-angle (fish-eye) lens that maximises its field-of-view. This in turn means that nearly
everything in front of the camera is captured. In addition to the camera functionality, a
number of different sensors are built into the v2 SenseCam. These include a light intensity
and colour sensor, a passive infrared (body heat) detector, a temperature sensor and a tri-
axis accelerometer. These sensors are monitored by the camera‟s microcontroller, and
changes in sensor readings can be used to automatically trigger the camera shutter. For
example, a significant change in light level, or the detection of body heat in front of the
camera can be used as triggers. Additionally, an internal timer may be used to trigger the
shutter, for example causing an image to be captured automatically every 30 seconds. The
maximum possible rate is an average of around one photo every 5 seconds, i.e. 12 photos
per minute. SenseCam also has a manual trigger button that lets the wearer take pictures in
the more traditional fashion, albeit without the use of a viewfinder.
The VGA resolution images are stored as compressed .JPG files on an internal flash
memory card (currently 1Gbyte cards are fitted). The typical image size (around 30k bytes)
allows for over 30 thousand images to be stored in the camera. In addition to image data, the
memory card is used to store a log file, which records the sensor data each time the sensors
are read (every few seconds). The log file also records the reason for taking each photograph
(e.g. manual shutter press, timed capture or significant change in sensor readings). The log
file is in a comma-separated value format suitable for importing directly into Microsoft
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Excel and many other data manipulation tools. The SenseCam has a built-in real time clock
that ensures the timestamps of all files on the storage card are accurate. Timestamp
information is also recorded in the log file along with each entry.
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Note that Excel 2003 has a 32k row limit which can be exceeded by large sensor files.
SenseCam v2.3 User Guide
© 2009 Microsoft Corporation, all rights reserved.
C 2.3
ENSE AM V
Steve Hodges
James Srinivasan
Alex Butler
Matthew Lee
Gavin Smyth
James Scott
Alban Rrustemi
Microsoft Research Cambridge
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10/03/2009