3d shapes - detection and or measurement
|Detection or imaging of
three-dimensional (3d) objects requires a number of views be made to establish
three dimensions of a target. |
Capacitive and electric field sensing techniques use a sensor array
comprising multiple electrodes to obtain data for image mapping. The greater
the density of data collected the greater the resolution of the resulting image
Radar and Sonar based imaging achieves 2 and 3 dimensional views by multiple
views, using the same transducer rather than a sensor array, with each view
taken by the transducer separated by a different viewing angle.
A characteristic of capacitive and electric field image mapping techniques
is non-invasive mapping. Capacitive and electric field sensor arrays can
project fields over an air gap which penetrate materials to map objects beneath
the surface. This non-invasive mapping is also possible with "ground radar"
when close proximity to the surface is achieved.
Radar image mapping is better suited to long-range operation through air and
Sonar image mapping best suited to long-range operation through water.
Ultrasound image mapping, using low frequency sound waves at a low range,
can map embedded objects but requires an acoustic coupling with the surface to
achieve this. Gel is used for example to gain an acoustic coupling between an
ultrasound probe and a pregnant mothers stomach so that ultrasound systems can
create an image of a baby while in its mother's womb.
When capacitive and electric fields are used for image mapping, multiple
sense electrodes are typically built into a sensor array where very low
parasitic capacitance of each electrode and circuit is required to minimise
Processing electronics deal with the multiple inputs from the sensor array
to produce an image map of the target which may be intended for human or
automatic (machine) evaluation.
If destined for human evaluation the system collates and presents the data
to a screen. Various modes can be used but humans will use their own reasoning
to decide what an object is and therefore what action might be
If destined for automatic machine evaluation, the sensing and control system
must be programmed to interpret the data gathered.
This may take the form of identifying if certain shapes are present,
determining specific characteristics and making particular measurements
Examples include the measurement of human feet, or detection of land mines
under the soil.
In the case of measuring feet: specific features of the human foot must be
measured which will correspond to a shoe size.
In the case of landmines: matching 3d shapes found to known mines in a
stored database will allow identification of which landmine has been