Tijdreekssamenhang

Tijdreekssamenhang is a Dutch term that translates to “temporal coherence” in English. In wave physics it describes the correlation between two points along a wave propagating through time. When a wave field possesses high tijdreekssamenhang, its properties at one time instant are strongly related to the properties at a nearby instant, implying the wave is predictable and exhibits a narrow spectral bandwidth. Conversely, low tijdreekssamenhang indicates significant variation between successive time instants, leading to a broad spectrum and less predictable behavior.

The temporal coherence length, often denoted by \(l_c\), is the distance a wave travels during a coherence time, \( \tau_c \). It is inversely proportional to the spectral width \(\Delta \nu\) of the source: \( l_c = c / \Delta \nu \), where \(c\) is the propagation speed. This relationship shows that a source with a very narrow frequency spread—such as a laser—exhibits long temporal coherence, whereas thermal light from a lamp has short coherence because of its broad spectrum.

In optics, tijdreekssamenhang is essential for interference phenomena. The visibility of interference fringes in a Michelson interferometer decreases when the optical path difference exceeds the coherence length. This effect is exploited in coherence tomography, a biomedical imaging technique that uses low-coherence light to attain fine depth resolution.

Beyond optics, the concept is applied in radar, acoustics, and quantum mechanics. In radar, the coherence time of a transmitted chirp determines range resolution. In acoustic signal processing, time‑domain cross‑correlation functions assess the similarity of signals, often referred to as temporal correlation or coherence. In quantum physics, the temporal coherence of an electron beam influences the visibility of interference in double‑slit experiments.

Scientific measurement of tijdreekssamenhang typically involves interferometric setups or spectral analysis. The coherence time can also be inferred from the FWHM of the power spectral density via the Wiener–Khinchin theorem. Understanding temporal coherence is therefore vital for designing systems that rely on precise wave manipulation and for interpreting observational data across many domains.