Patent Application
20210025999
The present invention relates to the field of the optoelectronic systems comprising a system for the emission and/or reception of optical beams and in particular to the optoelectronic systems emitting one or more laser beams. The invention further relates to optoelectronic systems the emitted laser beam or beams of which are spatially shaped via complex optomechanical devices. The optoelectronic systems concerned are in particular LIDAR systems.
The present invention relates to a device for measuring parameters of optical beams emitted by an optoelectronic device and an associated method. The invention further makes it possible to prepare a diagnosis of the optoelectronic system, in particular based on spatial characteristics of the optical beams measured with a metrological property, in order to calibrate the optoelectronic system, for example at the exit from the production line. By way of example, the measurements taken make it possible to determine, among others, an angular deviation between the spatial position of the axis of propagation of the beam measured by the measurement device and the spatial position of the axis of propagation of the theoretical beam.
Measurement methods are known in the state of the art for the calibration of LIDAR devices. These measurement methods are carried out by users outdoors and are operator-dependent. In order to reduce the dependency of the measurement on the operator who carries it out, a hard target handled by an operator is positioned at a long distance from the LIDAR. Despite the long distances, typically greater than one hundred metres, operator influence on the measurement still persists. In addition, the handling of the hard targets by the operators, combined with the long distances separating the LIDAR from the targets, renders the time for implementing the method significantly long. Another problem inherent in the known methods of the state of the art arises from the fact that, taking account of the long distances travelled by the beams outdoors, the atmospheric conditions lead to a significant variability of the measurements and may even prevent them.
An aim of the invention is in particular to propose a method and a device making it possible to overcome the aforementioned drawbacks at least partially.
A further aim is to propose a method and a device making it possible to carry out such measurements indoors.
To this end, according to a first aspect of the invention, a method is proposed for measuring parameters of an optical beam emitted by an optoelectronic system, said method comprising:
By “parameters of the optical beam” is meant any characteristic of the beam, such as, among others, a vector parameter, a spatial parameter, a temporal parameter, a frequency parameter, a geometric parameter, a physical parameter, for example an intensity, a phase parameter.
The optoelectronic system can be a LIDAR. The term LIDAR, known to a person skilled in the art, is an acronym of “LIght Detection and Ranging”.
The movement system can be a movement system with automatic control, such as, among others, a robotic arm or hexapod or any inclined platform.
The robotic arm can be articulated.
The movement system with automatic control can be industrial.
The attachment zone can be a surface of the movement system, positioning and inclination of which are controlled.
The optical sensor coincides with a focal plane of the optical device.
By “expected emission axis of the optical beam” is meant the theoretical emission axis along which said optical beam should be emitted.
By “positioning” an object is meant the combination of a position in space and an orientation of said object.
The alignment axis of the attachment zone extends from the attachment zone and the movement system is arranged to position the attachment zone in space and to orient said alignment axis of the attachment zone.
Calculation of the position of the attachment zone can make it possible, among others, to obtain a set of data pairs, each data pair comprising a position and an orientation of the attachment zone.
Advantageously, the positioning of the attachment zone is carried out at a distance less than four metres, preferably less than two metres, more preferably less than one metre from the optoelectronic system. Advantageously, the positioning of the attachment zone is carried out at a distance comprised between five and thirty centimetres from the optoelectronic system.
The method can comprise determining, by a processing unit, based on the measured parameter or parameters:
A vector representative of the optical beam can for example be defined by a starting position in space of the optical beam, which can for example be integrated with the exit point of the optoelectronic system, and a direction defined in a frame of reference.
The method can comprise:
The optical device is chosen as a function of the measured parameter.
The camera is equipped with an objective chosen in an advantageous manner.
The camera is equipped with an objective that can be chosen as a function of the measured parameter.
The precession movement of the optical axis of the camera about the expected emission axis is caused by a misalignment of the optical axis of the camera with the alignment axis of the attachment zone.
The misalignment of the optical axis of the camera with respect to the alignment axis of the attachment zone means that after a rotation of the attachment zone with respect to the axis, the at least one second position of the optical beam on the sensor will be different from the first position of the optical beam on the sensor.
The misalignment of the optical axis of the camera with respect to the alignment axis of the attachment zone means that a position of the optical beam on the optical sensor is a position of a fictitious optical focal spot.
Acquiring at least one second position of the optical beam on the optical sensor makes it possible to determine the angular deviation based on the two positions of the optical beam on the sensor, the direction of rotation of the attachment zone and the angle of rotation carried out during the rotation step.
When the step of acquiring the at least one second position of the optical beam on the sensor is carried out subsequent to the at least one step of rotation and the rotation of the attachment zone with respect to the alignment axis of the attachment zone is greater or lesser by more than one degree with respect to an angle of 180°, the step of acquiring the at least one second position comprises at least:
When the method comprises acquiring at least one second position of the optical beam on the optical sensor, the method can comprise determining:
Determining the position of the real optical focal spot makes it possible to overcome any misalignment of the optical device with respect to the alignment axis of the attachment zone.
When the step of acquiring at least one second position is carried out subsequent to the at least one step of rotation and the rotation of the attachment zone with respect to the alignment axis of the attachment zone is substantially equal to an angle of 180°, the step of acquiring at least one second position can comprise acquiring one second position only.
When the step of acquiring at least one second position comprises acquiring only one second position, the method can comprise determining:
A maximum angular deviation between the expected emission axis of the optical beam and a real emission axis of the optical beam is less than ±15° so that the emitted beam is focused by the camera on the optical sensor.
The maximum angular deviation is less than ±10°, preferably ±5°.
Advantageously, the angular deviation is less than ±2°.
The method can comprise at least one iteration of the steps of:
In other words, for the first iteration, the attachment zone is positioned:
In other words, for each iteration, the attachment zone is positioned:
The method can comprise a calculation of one or more differences, called control differences, between:
In the event that a value for the control difference, or a value for one of the control differences, or values for control differences, is(are) greater than the metrological accuracy of the movement system, this indicates:
The method can comprise:
Adjustment of the inclination of the optoelectronic system can be carried out prior to the implementation of the method according to the invention.
The optoelectronic system can be mounted on a support that is adjustable with respect to a horizontal plane.
The adjustable support can be arranged to adjust the inclination of the optoelectronic system with respect to the horizontal plane.
The inclinometer can be placed in the optoelectronic system.
According to the invention, the optoelectronic system can emit several optical beams, the method being applied successively to each of said optical beams.
The optical beams can be emitted by one and the same optical source.
The optical beams emitted by the optoelectronic system can be spatially distinct.
The optical beams emitted by one and the same optical source can be oriented successively in different directions over time.
The optical beams emitted by the optoelectronic system can be spatially arranged with respect to one another.
The optical beams emitted by the optoelectronic system can be spatially arranged with respect to the optoelectronic system.
When the optoelectronic system emits several optical beams, the method can comprise determining, by the processing unit, a difference between an expected angle between two optical beams and a real angle between two optical beams.
According to the first aspect of the invention:
According to a second aspect of the invention, a device is proposed for measuring parameters of an optical beam emitted by a LIDAR, said measurement device comprising:
According to the invention, the measurement device is characterized in that it also comprises:
When the LIDAR emits several optical beams, the measured parameter or parameters of an optical beam can be common to all the optical beams.
When the LIDAR emits several optical beams, a parameter of an optical beam can be different:
The attachment zone can be a surface of the movement system, positioning and inclination of which are controlled by said movement system.
Advantageously, the attachment zone can be moved along six axes.
A maximum pitch of a displacement of the attachment zone by the movement system is 1 mm, preferably 0.5 mm.
Advantageously, the pitch of displacement is 0.1 mm.
A maximum pitch of a rotation of the attachment zone by the movement system is 0.05°, preferably 0.025°.
Advantageously, the pitch of displacement is 0.01°.
The device can comprise a processing unit configured and/or programmed to calculate an expected emission axis of the optical beam, based on characteristic data of the LIDAR.
The processing unit can be configured and/or programmed to calculate a position of the attachment zone for which the alignment axis of the attachment zone is aligned with the expected emission axis of the optical beam.
The position of the attachment zone calculated by the processing unit can be defined, among others, by a set of data pairs, each data pair comprising a position and an orientation of the attachment zone.
The movement system with automatic control can be a robotic arm or hexapod or any inclined platform and the attachment zone suitable for being moved is a surface of the movement system, said surface being arranged to be rotated about the alignment axis of the attachment zone.
The movement system with automatic control can be an industrial device.
The robotic arm can be a hexapod. By “hexapod” is meant a device suitable for being moved via six elements.
The attachment zone can be a zone situated at an extremity of the robotic arm.
The alignment axis of the attachment zone can extend from the attachment zone in a predefined direction.
The alignment axis of the attachment zone can extend from the extremity of the robotic arm in a predefined direction.
The support can be mainly comprised in one plane and is arranged to adjust, among others, the angle formed between a horizontal plane and the plane in which the support is comprised.
Advantageously, the support is arranged to adjust an inclination of the support with respect to a horizontal plane.
Advantageously, the support is arranged to adjust an azimuthal orientation of the support.
Adjustment of the inclination of the support can be carried out based on an inclination value measured by an inclinometer of the LIDAR.
The optical device can be arranged in order to measure, among others:
The optical device can be, among others:
The measurement device can comprise several optical devices.
The measurement device can comprise:
When the measurement device comprises several optical devices, each optical device can be linked to a different movement system, the measurement device comprising the set of movement systems.
When the measurement device comprises several optical devices, a single one of the optical devices at a time can be associated with the attachment zone, the optical devices being successively interchanged thereon in an automated manner and/or manually.
When the measurement device comprises several optical devices, the set of optical devices can be linked concomitantly to the attachment zone of the movement device.
When the set of optical devices is linked concomitantly to the attachment zone of the movement device, only one of the optical devices can be positioned so that the expected emission axis of the optical beam is focused on the optical sensor of said optical device.
When the set of optical devices are linked concomitantly to the attachment zone of the movement device, the set of optical devices can be arranged so that the expected emission axis of the optical beam is focused successively on each of the optical sensors of the optical devices.
When the set of optical devices is linked concomitantly to the attachment zone of the movement device, the set of optical devices can be arranged to be moved so that the expected emission axis of the optical beam is focused successively on each of the optical sensors of the optical devices.
According to the invention:
Advantageously, the optical sensor of the camera is a CCD sensor.
The optical sensor of the camera can be a CMOS sensor.
Advantageously, the optical sensor of the camera has a minimum number of pixels of 1 megapixel.
More preferably, the number of pixels is 1.2 megapixels.
Advantageously, the optical sensor of the camera has a minimum pixel size of 10×10 μm, preferably 5×5 μm.
More preferably, the pixel size is 3.75×3.75 μm. The precession movement of the optical axis of the camera about the expected emission axis is caused by a misalignment of the optical axis of the camera with the alignment axis of the attachment zone.
The misalignment of the optical axis of the camera with the alignment axis of the attachment zone is less than an angle of ±2°.
When the processing unit is configured and/or programmed to determine the angular deviation between the expected emission axis of the optical beam and the real emission axis of said optical beam, the processing unit can be configured and/or programmed to determine:
When the processing unit is configured and/or programmed to determine the angular deviation between the expected emission axis of the optical beam and the real emission axis of said optical beam, based on only two positions on the optical sensor of the camera, the processing unit can be configured and/or programmed to determine:
When the processing unit is configured and/or programmed to determine the angular deviation between the expected emission axis of the optical beam and the real emission axis of said optical beam, the processing unit can be configured and/or programmed to apply the step of determining an angular deviation to a set of beams emitted by the LIDAR.
When the LIDAR emits several optical beams, the measured parameter or parameters of an optical beam can be common to all the optical beams.
When the LIDAR emits several optical beams, a parameter of an optical beam can be different:
The optical beams emitted by the LIDAR can be spatially distinct.
The optical beams emitted by the LIDAR can be spatially arranged with respect to one another.
The optical beams emitted by the LIDAR can be spatially arranged with respect to the optoelectronic system.
According to a third aspect of the invention, there is proposed a use of the measurement device according to the second aspect of the invention, in which the optical device is a camera and in which the processing unit is configured and/or programmed to determine a difference between:
According to a fourth aspect of the invention, there is proposed a use of the measurement device according to the second aspect of the invention, in which the optical device is a camera and in which the processing unit is configured and/or programmed to calibrate an inclinometer of a LIDAR based on a difference between:
Other advantages and characteristics of the invention will become apparent on reading the detailed description of implementations and embodiments that are in no way limitative, and from the following attached drawings:
As the embodiments described hereinafter are in no way limitative, variants of the invention can in particular be considered comprising only a selection of the characteristics described, in isolation from the other characteristics described (even if this selection is isolated within a sentence comprising these other characteristics), if this selection of characteristics is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art. This selection comprises at least one, preferably functional, characteristic without structural details, or with only a part of the structural details if this part alone is sufficient to confer a technical advantage or to differentiate the invention with respect to the state of the prior art.
An embodiment of the measurement device 1, 2, 3, 4 and of the measuring method is described with reference to
The measurement device comprises an optical table 3 on which is mounted a support 4 on which the LIDAR 5 is attached. A camera 1 is attached on an attachment zone (not shown) situated at the end of a robotized arm 2. The end of the robotized arm 2 has six degrees of freedom conferred by the different articulations (not referenced) of the robotized arm 2. The camera 1 can be positioned with an accuracy of ±0.5 mm, and the camera 1 can be rotated about an alignment axis 21 of the attachment zone, with an accuracy of ±0.05°. The alignment axis 21 corresponds to the direction extending from the extremity of the robotized arm 2 in which the robotized arm 2 orients the attachment zone.
The support 4 and the robotized arm 2 are attached on the optical table 3 at defined positions. The support 4 is mounted on the optical table 3 relatively to the robotized arm 2, so that the camera 1 can be positioned by the robotized arm 2 at a distance comprised between 5 and 100 cm from the LIDAR 5, and oriented by the robotized arm 2 so as to cover a hemisphere the centre of the base of which is situated at the centre of the optical emission zone of the LIDAR 5.
The camera comprises a CCD sensor 12, the sensor of which comprises 1.2 megapixels and the pixel size of which is 3.75×3.75 μm.
The camera is equipped with an objective 13 the focal distance of which is 50 mm and aperture F/2, therefore 25 mm.
The robotized arm 2 has an angular repeatability of ±0.02° and positioning accuracy of 0.1 mm.
The support comprises an adjustment device 41 of the attitude and azimuth of a stage 42 on which the LIDAR 5 is attached. The adjustment device 41 is attached on the optical table 3. The adjustment device 41 modifies the attitude and azimuth of the stage 42 via two adjustment screws 43, 44. The azimuth is adjusted accurately using a laser alignment system. The attitude is adjusted via data measured by an inclinometer of the LIDAR 5.
A processing unit (not shown) is configured to control the robotized arm 2 and the camera 1. The attachment zone is placed at a position calculated, and oriented in a direction calculated, by the processing unit, so that the alignment axis 21 of the attachment zone coincides with the expected emission axis 61 of one of the beams 7, called first beam, emitted by the LIDAR 5. The position and the direction are calculated based on data relating to the directions of emission of the beams 7 emitted by the LIDAR 5, supplied by the manufacturer.
In the absence of the angular deviation α between the position of the expected emission axis 61 and the position of the real emission axis 62, and in the absence of the angular deviation β between the optical axis 9 of the camera 1 and the alignment axis 21, all the axes 9, 21, 61 and 62 must coincide and the real emission axis 62 must be focused by the objective 13 of the camera 1 at a position 11 on the CCD sensor 12 of the camera 1, the position 11 corresponding to the theoretical optical centre of the camera 1.
In practice, when the camera 1 is mounted on the attachment zone of the end of the robotized arm 2, there is still a non-zero angle β between the optical axis 9 of the camera 1 and the alignment axis 21 of the attachment zone of the robotized arm 2. Thus, in the absence of the angular deviation α between the position of the expected emission axis 61 and the position of the real emission axis 62, but in the presence of an angular deviation between the optical axis 9 of the camera 1 and the alignment axis 21, the real emission axis 62 is focused by the objective 13 of the camera 1 at a position 14 on the CCD sensor 12 of the camera 1, the position 14 corresponding to an optical centre 14 of the camera 1.
In practice, all of the parameters characterizing the optical beams 7 emitted by the LIDAR 5 must be known with accuracy. To this end, the LIDAR 5 is calibrated when leaving the factory. Furthermore, as these parameters are susceptible to drift over time, it is therefore necessary to measure them regularly during the life of the LIDAR. In particular, one of the parameters among the most sensitive and most complex to measure is the spatial position of the emission axes 6 of the optical beams 7 emitted by the LIDAR 5. As the distances of use of the LIDARs are several hundred metres, an angular deviation α of several tens of degrees between the position of the expected emission axis 61 and the position of the real emission axis 62 can result in deviations of the positions of the emitted beams 7 of several metres at the target. In practice, this angular deviation α must be determined in order to calibrate the error resulting from incorrect positioning of the inclinometer on the LIDAR 5. This angular deviation α must also be determined in order to adjust an optomechanical system of the LIDAR 5 during the manufacture of the LIDAR 5.
Thus, in the presence of an angular deviation α between the position of the expected emission axis 61 and the position of the real emission axis 62 and in the presence of an angular deviation β between the optical axis 9 of the camera 1 and the alignment axis 21, the real emission axis 62 is focused by the objective 13 of the camera 1 at a position 15 on the CCD sensor 12 of the camera 1, the position 15 corresponding to the position of a real optical centre 15 of the camera 1.
In a first variant of the embodiment, after the robotized arm 2 has positioned the camera 1 by aligning the alignment axis 21 with the expected emission axis 61, the processing unit acquires a first position 8 of the first beam on the CCD sensor 12 of the camera 1. This first position 8 is defined by the coordinates (ε1x, ε1y) thereof on the CCD sensor 12.
After acquiring the first position 8, the robotized arm 2 turns the camera 1 with respect to the alignment axis 21 through an angle of 180°. The processing unit acquires a second position 10 of the first beam on the CCD sensor 12 of the camera 1. This second position 10 is defined by the coordinates (ε2x, ε2y) thereof on the CCD sensor 12.
In a second variant of the embodiment, after acquiring the first position 8 of the first beam on the CCD sensor 12 of the camera 1, the robotized arm 2 can operate a continuous rotation of the camera 1 about the alignment axis 21 and the processing unit can continuously acquire a set of positions 16 of the first beam on the CCD sensor 12 of the camera 1. In this case, the set of positions 16 describes a circle 16 comprising the first 8 and second 10 positions.
The processing unit then calculates the position of the real optical centre 15. According to the first variant, the position of the real optical centre 15 is determined by the processing unit by calculating the coordinates of the centre of the segment linking the first position 8 to the second 10. According to the second variant, the position of the real optical centre 15 is determined by the processing unit by calculating the coordinates of the centre of the circle 16.
The processing unit then calculates the position of the real emission axis 62 by calculating the coordinates of the axis linking the optical centre 17 of the camera to the real optical focal spot 15.
Determining the real optical focal spot by rotation of the camera 1 about the alignment axis 21 makes it possible to avoid alignment errors, regardless of the accuracy of the optical sensor used. This determination, combined with the use of a robotized arm 2, confers on the measurement an industrial, repeatable character.
In order to measure minimum angular deviations β, the methods of the state of the art envisage positioning the target at significant distances from the LIDAR 5 so as to result in deviations in the positions of the emitted beams 7 that are sufficiently great to be measured by a physical target moved manually. The method according to the invention makes it possible to measure these minimum angular deviations β by positioning the camera 1 in immediate proximity to the LIDAR 5.
The manual measurement methods known to a person skilled in the art call for two operators during a period of 4 to 6 hours. The device associated with the method according to the invention makes it possible to carry out measurements indoors in a few minutes and does not require any operator during implementation of the method. The device achieves accurate, repeatable measurements that are not operator-dependent and do not depend on any external factor.
The device according to the invention makes it possible to determine an angular deviation to within an accuracy of 0.05°.
After having determined the real emission axis 62 of the first beam, the method is applied to each of the beams 7 emitted by the LIDAR 5. The real positions of the emission axes of each of the beams 7 emitted by the LIDAR 5 are then known.
The processing unit determines the angular differences of the beams 7 emitted by the LIDAR between one another.
Based on the angular differences and the defined geometry according to which the beams 7 were spatially shaped, the processing unit determines an angular deviation between:
The inclinometer is calibrated based on the angular deviation determined.
Of course, the invention is not limited to the examples that have just been described, and numerous modifications may be made to these examples without exceeding the scope of the invention.
In addition, the different characteristics, forms, variants and embodiments of the invention may be combined together in various combinations to the extent that they are not incompatible or mutually exclusive.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1755636 | Jun 2017 | FR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2018/066609 | 6/21/2018 | WO | 00 |
