In a method and a device for
light propagation time measurement, in particular for cameras, a
light signal clocked by a
clock controller (11) is transmitted from at least one
transmitter (12) into a light path (14) via a retroreflective object (O) to a
receiver (13) for detecting the alteration of the
first light signal on account of the approach, presence and / or distance of the object (O). At the
receiver, the received
signal is determined from the light path on account of the
first light signal and, in order to determine the
propagation time, is cyclically compared in a
comparator (15) with a second signal which is clocked by the
clock controller (11) and which is produced without the light path (14), in order to generate a comparison value at the output of the
comparator (15), which value is used for regulating the amplitude values of the transmitted signal and / or of the second signal such that the received signal and the second signal at least at the input of the
comparator are substantially identical in magnitude. In parallel, the
clock change signal (TW)—occurring during the clock change and corresponding to the
light propagation time—between received signal from the light path (14) and second signal, given the magnitude of received signal from the light path (14) and second signal corrected to substantially identical magnitude at the input of the comparator (15), is detected cyclically. A difference value (S16) is determined by comparison of the clock change signals (TW) between received signal and second signal according to their amplitude in a further comparator (16). The difference value (S16) is altered by means of a phase shifter (17) for altering the phase
delay of the phase of received signal and second signal until the difference value (S16) becomes minimal, preferably zero. The
delay of the phase shifter that occurred given a minimal difference value is used for determining the
light propagation time. A method for light
propagation time measurement which can also operate with more favourable components and lower-frequency amplifiers is created as a result.