SPECIFICATIONS
USER’S MANUAL
SWEEP
V1.0
5
Copyright ©2014-2017 Scanse LLC - www.scanse.io
Sweep uses 905nm laser light, which passes through several kinds of clear glass and plastic very well. Based on our
testing, clear Polycarbonate plastic is one of the best choices, as it can be molded to fit the profile of the
application’s enclosure, is very inexpensive, and in most
cases, is m
ore than 95% translucent to Sweep’s light
beam. Factors that can affect the performance of a window are:
•
Thickness of the window. Thicker windows will block more light, as well as bend the light more if the beam is
not hitting the window normal to the surface.
•
Scratches and dust. The presence of scratches and dust on the window will scatter the laser light, and may
reflect some of the light back into the sensor’s detector, causing measurement errors.
•
Surface coatings. There are a variety of coatings that can help with the performance of windows. One is an
anti-reflective (AR) coating, which can help reduce the amount of laser light that is reflected as it passes
through the window
’
s surface.
Sweep employs a time of flight ranging method. This technique involves transmitting a packet of micro pulses of
light in a unique pattern. When this light bounces off an object and returns to the receiving detector, a correlation
algorithm is used to identify the unique light pattern from ambient noise.
Each light packet is different from the
last, which allows multiple Sweep sensors to operate adjacent to each other without interference
.
The light packets that Sweep uses can vary in length, which can affect accuracy of range measurements, as well as
the maximum range and update rate. Under normal operation, Sweep limits the maximum time per measurement
to a value determined by the sample rate set using the
LR
command (see LR packet structure description). If not
enough light is returned from the environment, the measurement fails, and a 1 is returned as the range value. On
the other hand, if a lot of light is returned from the environment, the correlation algorithm can reach its maximum
accuracy early, and can return a range value more quickly. This is what makes the update rate of Sweep variable.
The value of setting a slower sample rate using the
LR
command, is that more light will be gathered from a target,
and the range measurements will be more accurate. The exact accuracy is determined by many factors, including
the target surface characteristics and ambient noise, so we cannot give an exact number for relative accuracy
between the different
LR
settings.
Sweep uses an optical encoder to measure the angle of the rotating sensor head. The angle that is recorded for a
range data point is the angle the sensor is at when the measurement is completed. The beginning of the scan, and
zero degrees is located where the status LED projects out of the base of the sensor, as indicated in Figure 7.
Sweep can be used for a variety of applications, including robot guidance/obstacle avoidance, 3D scanning,
surveying, people tracking and many more.
You can download the Sweep visualizer at
www.scanse.io/downloads
The purpose of the Scanse visualizer is to provide a way to quickly evaluate Sweep’s performance in your
application/environment. For some applications, like surveying, our visualizer can be used to take quick
measurements between range data points within a scan. It
contains a programming tool for updating Sweep’s
firmware.
A full tutorial for using the visualizer can be found in software support section at
support.scanse.io.
