Abstract: An apparatus monitors positions on an external object having at least one beacon (1(i), i=1, 2, . . . , I) attached to it. The apparatus has an image sensor (11), a lens system (13) and a processing unit (9). The lens system (13) receives at least one light beam (5(i)) transmitted from the at least one beacon (1(i)) and transfer the at least one light beam (5(i)) to the image sensor (11). The image sensor (11) forms image data. The processing unit (9) identifies the at least one beacon (1(i)) within the image data based on the at least one light beam (5(i)), determines current location data of the at least one beacon (1(i)) based on the image data, compares the current location data with former location data of the one or more beacons (1(i)) as stored in a memory (15) and determines whether the object has moved relative to a fixed reference frame based on the comparison.

Abstract: A camera monitors positions on an external object having a beacon (1(i), i=1, 2, . . . , I; 130; 430) attached to it. The apparatus has at least one image sensor (120; 321, 322; 420; 520), an imaging optical element (101) for projecting light on the image sensor (120), and a processing unit (9). The imaging optical element (101) may be non-refractive and receives a light beam (5(i); 131) transmitted from the beacon (1(i); 130; 430) and transfers the light beam (5(i); 131) to the image sensor (120; 321, 322; 420; 520). The image sensor (120; 321, 322; 420; 520) forms image data based on the received light beam (5(i); 131) and background light. The processing unit (9) processes the image data such that it filters image data components relating to the background light and renders image data components relating to the light beam.

Abstract: A sensor circuit (10), including a silicon photomultiplier, SiPM, sensor (20), a voltage source (32), a current-to-voltage converter (24), and a limiting bias circuit (34). The SiPM sensor (20) has avalanche photodiode, APD, elements (30) connected in parallel between a cathode (K) and an anode (A). The voltage source (32) is configured to apply a reversed bias voltage (Vb) across the SiPM sensor, so that each APD element operates in reverse-biased Geiger mode, and the APD elements operate in integration mode. The bias circuit (34) is connected between the voltage source (32) and the anode, and is configured to limit currents through the APD elements, and to present an AC load impedance for an alternating current within a predetermined operating frequency range (fo) generated by the APD elements at the anode (A) as well as a DC load impedance, such that said AC load impedance is lower than said DC load impedance.

Abstract: An apparatus monitors positions on an external object having at least one beacon (1(i), i=1, 2, . . . , I) attached to it. The apparatus has an image sensor (11), a lens system (13) and a processing unit (9). The lens system (13) receives at least one light beam (5(i)) transmitted from the at least one beacon (1(i)) and transfer the at least one light beam (5(i)) to the image sensor (11). The image sensor (11) forms image data. The processing unit (9) identifies the at least one beacon (1(i)) within the image data based on the at least one light beam (5(i)), determines current location data of the at least one beacon (1(i)) based on the image data, compares the current location data with former location data of the one or more beacons (1(i)) as stored in a memory (15) and determines whether the object has moved relative to a fixed reference frame based on the comparison.