Device and method for measuring an object
The invention relates to a device and to a method for measuring an object that moves in a direction of movement along a movement axis, wherein the device has a first sensor arrangement having a first SMI sensor and a second SMI sensor, wherein the SMI sensors irradiate measurement light beams in opposite directions along a movement axis. A control and evaluation unit is configured to receive first and second measured signals, to determine a speed of the object along the movement axis from at least one of the measured signals, to detect a first characteristic change of the second measured signal, a first characteristic change of the first measured signal, and a second characteristic change of the first measured signal, and to determine an object length of the object along the movement axis.
1. A device for measuring an object that moves in a direction of movement along a movement axis, the device comprising
a first sensor arrangement having
a first self-mixing interference sensor (SMI sensor) for transmitting first measurement light beams along a first measurement axis, for receiving first measurement light beams reflected back from a first working zone of the first SMI sensor, and for generating a first measured signal from the first measurement light beams reflected back, wherein the first SMI sensor is oriented in such a way that the transmitted first measurement light beams run at least in part in the direction of movement of the object,
a second SMI sensor for transmitting second measurement light beams along a second measurement axis, for receiving second measurement light beams reflected back from a second working zone of the second SMI sensor, and for generating a second measured signal from the second measurement light beams reflected back, wherein the second SMI sensor is oriented in such a way that the transmitted second measurement light beams run at least in part against the direction of movement of the object,
wherein the first working zone has an end remote from the first SMI sensor and the second working zone has an end remote from the second SMI sensor 18 . 2 , and the ends define a measurement distance having a measurement distance length in parallel with the movement axis;
a control and evaluation unit for receiving the first measured signal and the second measured signal and for determining a speed of the object along the movement axis from at least one of the measured signals,
wherein the control and evaluation unit is configured
to detect a first characteristic change of the second measured signal at a first time;
to detect a first characteristic change of the first measured signal at a second time;
to detect a second characteristic change of the first measured signal at a third time; And
to determine an object length of the object along the movement axis while using the first time, the third time, the speed, and the measurement distance length.
2. The device in accordance with claim 1 , wherein the control and evaluation unit is configured to store the speed over the time.
3. The device in accordance with claim 2 , wherein the control and evaluation unit is configured to determine a length value at a variable speed by temporal integration of the variable speeds between the first time and the third time and to determine the length of the object along the movement axis from the length value and the measurement distance length.
4. The device in accordance with claim 3 , wherein the measurement distance length is positive when the end of the first working zone remote from the first SMI sensor is arranged upstream of the end of the second working zone remote from the second SMI sensor in the direction of movement, is negative when the end of the first working zone remote from the first sensor is arranged downstream of the end of the second working zone remote from the second SMI sensor in the direction of movement, and the control and evaluation unit is configured to determine the length of the object by addition of the length value and the measurement distance length.
5. The device in accordance with claim 1 , wherein the control and evaluation unit is configured to determine a length value at a constant speed of the object from a time difference between the third time and the first time and the constant speed and to determine the length of the object along the movement axis from the length value and the measurement distance length.
6. The device in accordance with claim 5 , wherein the measurement distance length is positive when the end of the first working zone remote from the first SMI sensor is arranged upstream of the end of the second working zone remote from the second SMI sensor in the direction of movement, is negative when the end of the first working zone remote from the first sensor is arranged downstream of the end of the second working zone remote from the second SMI sensor in the direction of movement, and the control and evaluation unit is configured to determine the length of the object by addition of the length value and the measurement distance length.
7. The device in accordance with claim 1 , wherein the first measurement axis has a first angle with respect to a plane perpendicular to the movement axis and the second measurement axis has a second angle with respect to the plane perpendicular to the movement axis, with the angles having different signs and with the amounts of the angles being the same.
8. The device in accordance with claim 1 , wherein the first measurement axis and the second measurement axis lie in a common measurement plane.
9. The device in accordance with claim 8 , wherein the movement axis of the object lies in the common measurement plane.
10. The device in accordance with claim 1 , wherein the first measurement axis and the second measurement axis lie in parallel measurement planes.
11. The device in accordance with claim 10 , wherein the movement axis of the object lies between the parallel measurement planes.
12. The device in accordance with claim 1 , wherein the object is moved by a transport medium, with the transport medium being disposed in at least one working zone of the SMI sensors.
13. The device in accordance with claim 1 , wherein the object is moved by a transport medium, with the transport medium being disposed outside the working zones of the SMI sensors.
14. The device in accordance with claim 1 , wherein the control and evaluation unit is configured to determine the speed along the movement axis while using the first and second measured signals.
15. The device in accordance with claim 1 , wherein the device has a second sensor arrangement having a third SMI sensor and a fourth SMI sensor, with the measurement axes of the third and fourth SMI sensors being aligned in parallel with the measurement axes of the first and second SMI sensors of the first sensor arrangement.
16. A method of measuring an object that moves in a direction of movement along a movement axis, the method comprising the steps of:
transmitting first measurement light beams by a first self-mixing interference sensor (SMI sensor) of a first sensor arrangement along a first measurement axis, wherein the first SMI sensor is oriented in such a way that the transmitted first measurement light beams extend at least in part in the direction of movement of the object;
receiving first measurement light beams reflected from a first working zone of the first SMI sensor;
generating a first measured signal from the reflected first measurement light beams;
transmitting second measurement light beams by a second self-mixing interference sensor of the first sensor arrangement along a second measurement axis, wherein the second SMI sensor is oriented in such a way that the transmitted second measurement light beams extend at least in part against the direction of movement of the object;
receiving second measurement light beams reflected from a second working zone of the second SMI sensor;
generating a second measured signal from the reflected second measurement light beams;
wherein the first working zone has an end remote from the first SMI sensor and the second working zone has an end remote from the second SMI sensor and the ends define a measurement distance having a measurement distance length in parallel with the movement axis;
receiving the first measured signal and the second measured signal by a control and evaluation unit; and
determining a speed along the movement axis from at least one of the measured signals,
detecting a first characteristic change of the second measured signal at a first time;
detecting a first characteristic change of the first measured signal at a second time;
detecting a second characteristic change of the first measured signal at a third time; and
determining a length of the object along the movement axis while using the first time, the third time, the speed, and the measurement distance length.