Device and method for isolating a trigger signal of a LiDAR sensor and test system
A device and to a method for isolating a trigger signal for a test system of a LiDAR sensor, having an optical element, which is arranged in a signal pat of the trigger signal before a converging lens or a trigger detector and which is designed to allow the trigger signal to pass and to at least partially absorb a back reflection, in particular reflected off a surface, of the trigger signal that has passed through the optical element. A test system for a LiDAR sensor is also provided.
1 . A device for isolating a trigger signal for a test system of a LIDAR sensor, the device comprising:
a trigger detector;
a converging lens connectable to the trigger detector via an optical transmission medium, the converging lens or the trigger detector being configured to receive a trigger signal or a laser pulse, generated by a LIDAR sensor; and
an optical element arranged in a signal path of the trigger signal before the converging lens or the trigger detector and which is designed to allow the trigger signal to pass and to at least partially absorb a back reflection of the trigger signal that has passed through the optical element and which is reflected off a surface of the trigger detector.
2 . The device according to claim 1 , wherein the optical element is formed by an optical isolator, and
wherein the optical isolator has a Faraday rotator disposed between a first polarizer and a second polarizer.
3 . The device according to claim 2 , wherein an optical axis of the first polarizer has an orientation that coincides with a plane of polarization of the trigger signal, wherein the Faraday rotator is designed to rotate the polarization of the trigger signal by 45° in a predefined direction of rotation, and wherein an optical axis of the second polarizer is oriented by 45° in the predefined rotational direction with respect to the first polarizer.
4 . The device according to claim 3 , wherein the Faraday rotator is designed to rotate the polarization of the back reflection of the trigger signal, passed through optical isolator by 45° in the predefined direction of rotation so that the back reflection passed through the Faraday rotator is oriented orthogonally to the optical axis of the first polarizer.
5 . The device according to claim 1 , wherein the optical element is formed by a delay element, which is designed to circularly polarize the particularly linearly polarized trigger signal generated by the LiDAR sensor.
6 . The device according to claim 5 , wherein a polarizer is arranged in the signal path of the trigger signal before the delay element.
7 . The device according to claim 1 , wherein the optical power of the back reflection of the trigger signal passed through the optical element, after passing through the optical element twice, is below a detection threshold of a receiver of the LIDAR sensor.
8 . The device according to claim 7 , wherein the optical element is designed to attenuate an optical power of the trigger signal by 50-70%, in the first pass through the optical element, and to provide a total attenuation of the trigger signal and the back reflection, again passing through the optical element, by more than 99%.
9 . The device according to claim 1 , wherein the optical element and the converging lens or the trigger detector are arranged in a covering cap, attachable to a transmitter unit of the LiDAR sensor or on a carrier device arranged in the signal path of the trigger signal.
10 . The device according to claim 9 , wherein the trigger detector has a predefined number of photosensitive diodes, which are configured to transmit the received trigger signal as an electrical signal to a signal generator.
11 . The device according to claim 9 , wherein the optical element is arranged at least in the region of an opening angle of the transmitter unit of the LiDAR sensor.
12 . A test system for a LIDAR sensor, the test system comprising:
a LIDAR sensor generating a trigger signal;
a device to isolate the trigger signal according to claim 1 ; and
a signal generator,
wherein the trigger detector is configured, in response to receiving the trigger signal from the LiDAR sensor under test, to control the signal generator, to generate a simulated back reflection of the trigger signal, and to transmit the simulated back reflection to a receiver of the LiDAR sensor using a predefined number of photosensitive diodes.
13 . The test system according to claim 12 , wherein the LiDAR sensor is formed by a flash LiDAR or a mechanical rotating scanning LiDAR.
14 . A method for isolating a trigger signal for a test system of a LIDAR sensor, the method comprising:
receiving a trigger signal generated by a LiDAR sensor through a converging lens connected to a trigger detector via an optical transmission medium or through a trigger detector;
passing the trigger signal through an optical element arranged in a signal path of the trigger signal before the converging lens or the trigger detector; and
at least partially absorbing a back reflection, which has passed through the optical element and is reflected off a surface of the trigger detector.
15 . The device according to claim 1 , wherein the optical isolator is a Faraday isolator.
16 . The device according to claim 1 , wherein the delay element is a λ/4 waveplate.
17 . The device according to claim 5 , wherein the polarizer is a linear polarizer.
18 . The device according to claim 7 , wherein the optical element is designed to attenuate the optical power of the trigger signal by 65%.
19 . The device according to claim 7 , wherein the optical element is designed to provide a total attenuation of the trigger signal and the back reflection, again passing through the optical element, by 99.9%.
20 . The method according to claim 14 , wherein the trigger signal is a laser pulse.