Is a temporal and / or
spatial coincidence of events or interactions of objects.
To conclude from the
coincidence of two or more events to a causal (causal) connection logically
represents a fallacy which is called cum hoc ergo propter hoc (lat.).
Nonetheless, the term language is sometimes used to indicate a suspected causal
connection of coincident events.
Table of Contents
• 1Sinneswahrnehmung
• 2Organisation
• 3Strahlungsmessungen
o 3.1Experimentalphysik
o 3.2Positronen emission
tomography
• 4Farbfernsehtechnik
• See also
• 6Weblinks
Sensory perception
In physiological
perception, two signals are perceived as one (and are called coincident) when
their temporal difference is less than a time-dependent period. When viewed,
this period is 20-30 ms. When listening, stimuli that are more than 3-4 ms
apart can be separated. The order of succession, on the other hand, can only be
determined in each sense organ if the stimuli are at least 30-40 ms apart.
organization
In organizational
science, coincidence is a criterion for fulfilling an order or service. In this
case, the determination of coincidence takes place in a plurality of contiguous
steps:
• The identity of the
objects or persons concerned is determined.
• The identities are
compared with the known specifications.
• The time of the
coincidence is determined.
• The location of the
meeting is documented.
These findings can be
carried out automatically with the help of appropriate tools. If there is no
connection in place, time, or if the identities deviate from the specifications,
or if such a connection is not recognized, there is no coincidence and the
order is not fulfilled or the service is not performed. This applies, for
example, to health care or logistics.
radiation measurements
experimental Physics
In the case of physical
measurements, coincidence means the "simultaneous" occurrence of the
signals from two (or more) particle or radiation detectors (more precisely,
their time difference is below a predetermined resolution time). If one only
accepts those signals which satisfy such a coincidence condition, then the
events of a particular, interesting type can be separated from the
"background" of events which are not more interesting but possibly
much more frequent. With this method, Bothe and Geiger first demonstrated the
Compton effect (detailed representation: see coincidence measurement).
The coincidence events
sought are referred to as true coincidences, in contrast to eventual
coincidences. In the case of a true coincidence, a single physical process is
the cause of both detector signals, in the case of a random two different and
independent processes. Therefore, the two detector signals of the true
coincidence are temporally correlated, i.e., at a certain time interval from
each other; At other intervals, only coincident coincidences are found. This is
used to distinguish the two coincident types, so that the separately measured
background can be subtracted from coincident coincidences by the measurement
result.
In some cases, the events of interest are identified by
coincidence, rather than by coincidence. The condition for the registration is
then, for example, that a signal in detector 1 is not accompanied by a signal
in detector 2.
Positron emission
tomography
Positron emission
tomography (PET), a medical imaging technique, also uses coincidences to
suppress unwanted detection events, but also to accurately determine the
location of the radiation source. With a large number of detectors operating at
the same time, the spatial distribution of a radioactive substance in the
examination volume is measured by determining which detectors respond as often
to coincidence.
Color television
technology
In (analog) color
television technology, coincidence refers to the temporal coincidence of the
signal edges in the luminance signal and in the color difference signals.
Because of the smaller
bandwidth in the color difference signal channels, the edges are less steep and
are delayed more. The luminance signal is delayed so far that the flanks
recognizable in the modulated color difference signal coincide with those of
the luminance signal in the transmitted signal. On the receiver side, the
matching of the signal edges in the luminance signal and in the color
difference signals is achieved by a delay compensation of the order of 1000 ns.
The spatial
correspondence of the three color channels is referred to as convergence, in
particular in the case of picture tubes.
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