FR3127354A1 - AUTOMATIC CONTINUOUS ALIGNMENT SYSTEM OF A PULSE LASER SPOT - Google Patents

Abstract

SYSTEM FOR AUTOMATIC CONTINUOUS ALIGNMENT OF A PULSE LASER SPOT The invention relates to a system which makes it possible to automatically detect the position of a pulse laser spot (1.1) by a camera (5) which detects the wavelength of the laser, and to continuously align the laser spot with respect to the camera (5) which detects the laser by means of a device for directing the laser. Figure to be published with abstract: Figure 1

Description

AUTOMATIC CONTINUOUS ALIGNMENT SYSTEM OF A PULSE LASER SPOT

A system provides real-time continuous alignment of a pulsed laser signal in the infrared wavelength during the designation period.

In particular, the invention relates to a system which makes it possible to automatically detect the position of a pulsed laser signal by means of a camera which is capable of detecting the wavelength of the laser, and to continuously align the laser designation according to the detected position relative to the camera using a device to align the laser.

Systems including both a laser designator and a camera can be used for laser designation of a target that is being monitored by a camera. One of the key parameters determining designation performance in these usage scenarios is the quality of alignment of the laser signal with the cameras in the same system. It is possible to align the camera and laser unit in a point alignment process at the factory or in the field. However, mechanical and opto-mechanical effects, such as thermal stress, static or dynamic loads, pressure difference, etc., can impact the performance of point laser alignment in the field.

In the current state of the art, IRCL (short wavelength infrared) or similar infrared cameras are used to display the infrared pulsed or non-pulsed laser mark. However, there is no system to measure misalignment by capturing the pulsed laser mark in the image.

When searching the current state of the art, applications US20190215459, CN207752146, CN104780306 and US8400619 were found.

Application numbered US20190215459 relates to a laser distance measurement system comprising a laser designed to illuminate a target with a laser mark having a specific wavelength. The application mentions that the laser mark is digitally aligned in the field of view of the imaging device having an optical center. Although the application mentions the centering of the laser mark in the image, it does not include any explanation as to the change in the direction of propagation of the beams emitted by the laser.

The application numbered CN207752146 relates to the automatic adjustment of the coaxial cavity laser propagation path. The application does not describe continuous alignment of a laser system, but rather a one-time alignment process. However, the application does not include a system that calculates the misalignment of the laser mark for each laser pulse and performs continuous alignment. In the present invention, the laser is aligned in real time with each shot in the field, but in CN207752146 the alignment is done once and fixed with an adhesive.

The application numbered CN104780306 concerns a laser night vision device and a method for aligning light signals at different distances from the center of the field of vision. Although the application mentions the centering of the laser mark in the image, it does not mention changing the direction of propagation of the beams emitted by the laser and the use of image processing techniques for the alignment.

Application numbered US8400619 relates to target tracking and beam steering systems and methods. In particular, the application relates to systems and methods for automatically tracking a target by processing a series of video images obtained from the area in which the target is located and automatically guiding the transmission path of the laser beam emitted by the laser range finder so that the laser beam falls on the target being tracked. In the application, the laser is assumed to be well aligned and the position of the laser is guided on moving objects using a motorized system. However, the process of receiving laser position feedback and directing the laser based on that feedback is not performed.

Therefore, due to the drawbacks described above and the insufficiency of the existing solutions on the subject, it has become necessary to make an improvement in the technical field concerned.

The invention aims to provide continuous alignment of the pulsed laser designation in the infrared wavelength in real time during the designation time. With the invention, instead of printing, on the image, the laser spot detected by the infrared camera, this laser spot is maintained dynamically on the viewfinder without shifting the viewfinder.

The object of the invention is to align the position of a pulsed laser spot to be automatically detected by a camera which detects the wavelength of the laser, and to align the laser spot with respect to the camera which detects the laser by using a device which directs the laser according to the detected position.

The invention aims to measure the misalignment by capturing the pulsed laser signal in the image. Thus, alignment shifts that occur over time can be dynamically corrected.

The aim of the invention is to eliminate the need to position aiming marks differently on different cameras and viewpoints, since it actively directs the pulsed laser output, unlike the process of shifting the sight according to the laser spot.

The invention aims to dynamically correct the position of the laser spot and to provide a live display of position information on the output image.

The present invention therefore relates to a system for automatically detecting the position of a pulsed laser spot by a camera which is capable of detecting the wavelength of the laser, and for continuously aligning the laser spot with respect to the camera. laser detection device depending on the detected position, characterized in that it comprises:

- a laser source, which is configured to generate the laser spot,

- a laser direction unit which, by means of mechanical/optical elements contained therein, is configured to angularly change the direction of the laser spot to form an aligned laser spot,

- at least one laser receiver, which is configured to capture first and second laser spots reflected from the target,

- an image processing unit, which is configured to process images captured by the camera to determine the presence and position of the second reflected laser spot in the image,

- a control unit, which is configured to determine the direction in which the laser spot should be directed so as to align the second reflected laser spot detected by the image processing unit with the laser spot, and to transmit data on this direction to the laser steering unit.

According to a particular feature of the invention, the laser steering unit is configured to align a laser spot of different wavelengths.

According to a particular feature of the invention, the laser steering unit is configured to mechanically align the laser source, the camera and an optical interface.

According to a particular characteristic of the invention, the camera is configured to detect a laser spot created by the laser spot aligned on the target.

According to a particular characteristic of the invention, the system comprises an optical interface configured to form an image, on the camera, of the laser signal information transported by the second reflected laser spot.

According to a particular feature of the invention, the control unit is configured to provide a necessary connection for the alignment process between the laser steering unit and the image processing unit once the laser spot is captured by the camera and its position is determined by means of the image processing unit.

According to a particular characteristic of the invention, the system comprises an image output unit configured to transfer images produced by the camera out of the system.

The detailed description given below with reference to the appended drawings makes it possible to better understand the structural and characteristic properties and all the advantages of the invention; for this reason, the evaluation must be made taking into consideration these drawings and this detailed description. In these drawings:

is a representative view of the system of the invention.

Description of reference signs

1.Laser source

1.1. laser spot

2. Laser steering unit

2.1. Aligned laser spot

2.2. Propagation medium

2.3. laser spot

3. Target

3.1. First reflected laser spot (reflected laser spot-1)

3.2. Second reflected laser spot (reflected laser spot-2)

4. Laser receiver

4.1. Optical

5. Camera

5.1. Optical interface

6. Control unit

6.1. Laser shot signal

6.2. First trigger signal (trigger signal-1)

6.3. Timing signal

6.4. Second trigger signal (trigger signal-2)

6.5. Location determination signal

6.6. alignment signal

7. Image processing unit

8. Image output unit

8.1. Image signal

In this detailed description, the preferred embodiments of the invention are described solely for the purpose of better understanding the subject matter and without any limiting effect.

The automatic laser alignment system of the invention illustrated in the generally comprises a laser source 1 which generates a pulsed laser spot, a laser steering unit 2 which guides the direction of the pulsed laser spot using optical and mechanical components, a laser receiver 4 which measures the distance laser, a camera 5 which detects light at the wavelength of the pulsed laser, a control unit 6, an image processing unit 7 and an image output unit 8. With the system in question, the laser designation initiated automatically by the user or by a different machine interface is detected by the camera 5 and the laser spot is continuously aligned with the camera.

The automatic laser alignment system includes:

- a laser source 1 designed to generate the laser spot 1.1,

- a laser directing unit 2 comprising mechanical/optical elements for directing the laser spot 1.1,

- at least one 4 laser receiver designed to capture the laser-1,2 3.1, 3.2 spot reflected from target 3,

- a camera 5 designed to image the target 3 and the reflected laser spot-2 (second reflected laser spot) 3.2,

- an image processing unit 7 designed to detect the presence and position of the reflected laser spot-2 3.2 in the image by processing images captured by the camera 5,

- a control unit 6 designed to determine the direction in which the laser spot 1.1 must be directed so as to align the position of the reflected laser spot-2 3.2 detected by the image processing unit 7 with the image acquisition and to transmit data on this direction to the laser direction unit 2.

Laser source 1 generates laser spot 1.1, which is intended for continuous alignment. Said laser spot 1.1 can be guided by the laser steering unit 2 and aligned to the center or any desired point with respect to the center of the laser detection camera 5. The laser spot 1.1 generated by the laser source 1 can present as a continuous or intermittent pulsed laser mark. Said laser spot 1.1 can be in the infrared, visible or ultraviolet band. The 1.1 laser spot can be in the 1064nm or 1540-1570nm band. The laser source 1 can generate the laser spot 1.1 at more than one wavelength. In this case, the laser steering unit 2 can be used to align laser signals of different wavelengths. The laser spot 1.1 can have any divergence value.

The laser direction unit 2 angularly changes the direction of the laser spot 1.1 generated by the laser source 1. The laser direction unit 2 changes the direction of the laser spot 1.1 as it enters into an aligned laser spot 2.1. The laser steering unit 2 is controlled by the control unit 6 for steering operation. Preferably, the change of direction can be carried out by optical, mechanical, opto-mechanical interfaces. The laser steering unit 2 can mechanically align the laser source 1, the camera 5 and the optical interface 5.1. Further, the camera 5, the image processing unit 7 and the image output unit 8 can be aligned by digital conversion operations. The laser direction unit 2 can use one or more prisms to change the direction of the laser spot 1.1. The beam steering operation to be performed by the laser steering unit 2 can be handled by the control unit 6 using digital or similar machine interface instructions, or the mechanical and opto-mechanical units performing the beam direction on the laser steering unit 2 can be directly controlled by the control unit 6. After the laser steering unit 2 receives the direction instruction from the control unit 6, the alignment information produced by the image processing unit 7 is monitored until the instruction is executed and the aligned laser spot 2.1 reaches the desired exit angle. Moreover, while the laser directing unit 2 aligns the position of the spot, the phase of the alignment can be controlled by the control unit 6 in real time.

The aligned laser spot 2.1 is the laser spot 1.1 generated by the laser source 1 and aligned by the laser steering unit 2. The aligned laser spot 2.1 reaches the target 3 by crossing the determined propagation medium 2.2 (atmosphere). The aligned laser spot 2.1 can have any divergence value.

The propagation medium 2.2 is the medium through which the aligned laser beam 2.1 travels to the target 3 while the reflected laser spot 2.3 travels to the optics 4.1 and the optical interface 5.1. The propagation medium 2.2 has a disturbing effect on the aligned laser spot 2.1, the reflected laser spot-1 (first reflected laser spot) 3.1 and the reflected laser spot-2 (second reflected laser spot) 3.2.

The laser spot 2.3 is the mark left by the aligned laser spot 2.1 on the target 3 and detected by the camera 5. The size of the laser spot 2.3 increases proportionally to the divergence value of the aligned laser spot 2.1, but its luminosity decreases proportional to the square of the divergence value. The brightness of the laser spot 2.3 decreases with the distance between the laser steering unit 2 and the target 3 due to the distortion effect from the propagation medium 2.2.

Target 3 is where aligned laser spot 2.1 creates laser spot 2.3. The luminosity of the laser spot 2.3 varies according to the response of the target 3 and of the propagation medium 2.2 to the wavelength.

The reflected laser spot-1 3.1 is the part of the reflection coming from the laser spot 2.3 which reaches the optics 4.1.

The reflected laser-2 spot 3.2 is the part of the reflection coming from the laser spot 2.3 which reaches the optical interface 5.1. The amount of energy carried by the reflected laser spot-23.2 is a key performance criterion for the operation of the automatic laser alignment system of the invention. The amount of energy transported by the reflected laser spot-2 3.2 is related to the amount of energy of the aligned laser spot-2 2.1, its divergence value, the distance traveled in the propagation medium 2.2, its transmittance in the propagation medium 2.2, target reflectivity 3 for aligned-2 laser spot 2.1, optical interface size 5.1, f# value (f-number, also called aperture number), transmittance for laser spot reflected-2 3.2, the filtering power of the optical interface 5.1 for the wavelength range outside the propagation medium 2.2.

The laser receiver 4 uses the link between the laser pulse coming from the laser source 1 and the laser reflection coming from the laser receiver 4 to determine the distance between the system of the invention and the laser receiver 4.

Optics 4.1 focuses the reflected laser spot-1 3.1 that comes from the laser beam 2.3 onto the laser receiver 4.

Camera 5 is a system that converts laser signal information, which is reflected from laser spot 2.3 and reaches optical interface 5.1 as reflected laser spot-2 3.2, into an image. The laser detection camera 5 is equipped to detect the wavelength of the laser spot 1.1 produced by the laser source 1. If the laser spot 1.1 is in the infrared band or in the range of 1064 nm or 1540-1570 nm, an IRCL 5 camera can be used. The starting point of the integration time and the integration time interval of the camera 5 are controlled by the control unit 6 separately for each laser pulse. It is important that the integration time of the camera 5 be as short as possible to detect the pulsed laser signal without missing it so as to eliminate the background image and improve the signal-to-ratio value. -noise (SNR). For this reason, the integration time of the camera 5 can be limited to the entire time of flight of the pulsed laser shot, or the arrival time of the reflected laser spot-2 3.2 can be estimated based on the target range information obtained from the laser receiver 4 during previous shots, and this estimate can be used to shift or shorten the integration time. By predicting the arrival time of the reflected laser spot-2 3.2, one can achieve a shorter integration time and increase the dominance of the laser signal in the whole scene.

The synchronization between the control unit 6 and the camera 5 can be such that the integration time of each pulse can be shifted. Camera 5 can operate at any frames per second (fps) value. Camera 5 can operate with a fixed or variable integration time. Camera 5 can be used such that the normal scene image is taken between the image frames to be generated for laser pulse detection.

The optical interface 5.1 captures the laser signal information carried by the reflected laser spot-2 3.2 to form an image on the camera 5. The optical interface 5.1 may include one or more lenses and may include one or more filters. The filter on the 5.1 optical interface can pass or block the reflected laser spot-2 3.2 wavelength range or other wavelength ranges at certain rates. The filter on the 5.1 optical interface can be located directly in front of the light detection sensor on the reflected laser spot-2 3.2, between the lenses in the optical component, or in front of the optical components. The filter in the 5.1 optical interface can be moved by any electrical mechanism, by a hand-operated lever or by an electrical command, or it can be fixed. The viewing angle is provided by the 5 camera and the 5.1 optical interface. One or more polarizing filters, preferably fixed or rotating, can be used in the 5.1 optical interface. Said polarizing filter can be rotated manually, by means of a motorized system or by other means, or its polarization can be controlled by means of an electric signal.

The control unit 6 provides logic and control operations as well as synchronization between functional units. Camera 5 provides synchronization between laser source 1 and camera 5 so that the image of camera 5 can be detected in the scene where the laser is present. Once the laser spot 2.3 is captured by the camera 5 and its position is determined by the image processing unit 7, it provides the necessary link between the laser directing unit 2 and the processing unit frame 7 for the alignment process.

The laser firing signal 6.1 is the signal sent to the laser source 1. Preferably, it can be sent through the control unit 6. The delay between the laser firing signal 6.1 and the trigger signal- 1 (first trigger signal) 6.2 can be fixed, variable, or a function of the signal from the laser receiver 4. The laser firing signal 6.1 can be a serial, parallel, or discrete signal for each pulse, or it can be a a single instruction that triggers the pulse with a certain frequency.

Trigger-1 signal 6.2 is the signal generated to trigger the camera 5 integration time using the laser shot. This signal can be generated by the laser source 1 or by another unit or another receiver which detects that the laser source 1 is about to fire or has fired. It can occur before, during or after the generation of the 1.1 laser spot. The trigger-1 signal 6.2 can be a discrete signal indicating the laser pulse, or a serial or parallel digital signal which provides the laser pulse information at another timing. Trigger-1 signal 6.2 carries delay information from laser receiver 4.

Timing signal 6.3 is the signal from camera 5 indicating when the laser signal should be received such that the laser signal falls within the integration time. This signal can be generated by the laser source 1 or the control unit 6, or by another unit or another receiver which detects that the laser source 1 is about to fire or has fired. Timing of timing signal 6.3 is offset based on laser delay information obtained using laser receiver 4 during previous laser firings. The delay signal 6.3 can be generated as soon as the trigger-1 signal 6.2 is received or with a certain delay. Timing signal 6.3 and trigger-1 signal 6.2 can be the same signal in hardware. Timing signal 6.3 can be a fixed duration signal or it can contain the camera integration time 5. Trigger-1 signal 6.2 can be a discrete signal indicating the laser pulse or a serial or parallel digital signal which provides the laser pulse information according to another timing. If it is necessary to take more than one image frame to find the laser spot, the timing signal 6.3 may be triggered more than once or the camera 5 may be triggered to take more than one image.

The trigger-2 signal (second trigger signal) 6.4 is the signal used for the image processing unit 7 to operate simultaneously with the camera. The trigger-2 signal 6.4 informs the image processing unit 7 of the presence of a laser signal in the next image frame and triggers the image processing unit 7 to execute logic operations of way to find the laser signal. The trigger-2 signal 6.4 can be generated by the control unit 6 or the laser source 1. The trigger-2 signal 6.4 can be generated as soon as the trigger-1 signal 6.2 is received or with a certain delay. The trigger-2 6.4 signal can be the same signal as the trigger-1 6.2 signal in hardware. If more than one image frame needs to be taken to find laser spot 1.1, trigger-2 signal 6.4 may operate more than once or trigger camera 5 and image processing unit 7 to take more than a picture.

The location determination signal 6.5 comprises the position information of the laser spot 2.3 coming from the image processing unit 7 with respect to the camera 5. The position information can be given with reference to the line of sight , in the center or at any other point of the camera 5. The position determination signal 6.5 can be a digital signal representing the whole of the image frame or part of the image, or it can be a signal giving position information only.

Alignment signal 6.6 is the signal emitted from position determination signal 6.5 to laser receiver 4, which aligns laser spot 1.1 with the laser alignment requirement. From the alignment signal 6.6, the angular correction of the aligned laser spot 2.1 according to the received information is provided and the laser spot 2.3 is brought into the desired alignment with respect to the camera 5. If necessary, a discrete signal or serial or parallel digital may be transmitted from the laser steering unit 2 to the control unit 6 indicating that the alignment command has been executed or is in progress. The aforementioned discrete signal can wait for the triggering of the trigger-2 signal 6.4 or the delay signal 6.3. The alignment signal 6.6 can be generated as soon as the position determination signal 6.5 is received or with a certain delay or filtering. Alignment signal 6.6 may be the same signal as position determination signal 6.5 in hardware.

The image processing unit 7, when triggered by the trigger-2 signal 6.4, searches for the presence and position of the laser spot 1.1 in the image coming from the camera 5 and transmits the position information to control unit 6 for alignment of laser steering unit 2. Image processing unit 7 uses one or more images from camera 5 to find incoming laser spot 1.1. The image processing unit 7 can also use the whole image coming from the camera 5, or the central part or another part of the image to find the laser spot 1.1. The image processing unit 7 performs digital operations such as panning, zooming in or out, subtracting from another image, adding, multiplying, cropping, sharpening, an optimization, a convolution of different filters with the image, the passage of different filters through a window, a filtering of the results, etc. for the image from camera 5. Image processing unit 7 may have its own hardware, or it may operate in the same hardware as laser source 1, laser steering unit 2, camera 5, the image processing unit 7 and the image output unit 8. Furthermore, the system of the invention can operate in different hardware inside or outside the system. The image processing unit 7 can print a pattern or other symbology on the incoming image and, when necessary, it can shift the pattern printed on the image according to the information produced by the position determination signal 6.5.

The image output unit 8 is the unit where the images produced by the camera 5 or other receivers are transferred out of the system. The image output unit 8 may be a unit operating on the same hardware as the image processing unit 7. The image output unit 8 may combine the image of the camera 5 coming from the image processing unit 7 with a different image.

The image signal 8.1 constitutes the image information coming from the image output unit 8 and sent outside the system of the invention. The output image may be carried by a digital, analog, serial, parallel or any other signal, or it may be transferred outside the system by a monitor, digital or any other process, memory recording , wired or wireless data link, wireless communication, fiber optic communication, radio signal, projection, printer, scanner, monocular, binocular or other equipment or process.

The system of the invention may preferably include a camera system which detects one or more different wavelengths, and laser pointing or designating units which emit a pulsed or continuous laser at one or more different wavelengths. of different waves. The automatic laser alignment system can be part of a larger system or used as a floor-mounted system or on a mobile platform. However, it can also be a handheld system, guided by a gimbal or pan-tilt, or controlled by a line-of-sight mirror.

Claims (7)

System for automatically detecting the position of a pulsed laser spot (1.1) by a camera (5) which is able to detect the wavelength of the laser, and for continuously aligning the laser spot (1.1) with respect to the laser detection camera (5) depending on the detected position, characterized in that it comprises:
- a laser source (1), which is configured to generate the laser spot (1.1),
- a laser direction unit (2) which, by means of mechanical/optical elements contained therein, is configured to angularly change the direction of the laser spot (1.1) to form an aligned laser spot (2.1),
- at least one laser receiver (4), which is configured to capture first and second reflected laser spots (3.1, 3.2) from the target (3),
- an image processing unit (7), which is configured to process images captured by the camera (5) to determine the presence and position of the second reflected laser spot (3.2) in the image,
- a control unit (6), which is configured to determine the direction in which the laser spot (1.1) should be directed in order to align the second reflected laser spot (3.2) detected by the image processing unit ( 7) with the laser spot (1.1), and to transmit data on this direction to the laser direction unit (2). System according to claim 1, characterized in that the laser directing unit (2) is configured to align a laser spot (1.1) of different wavelengths. System according to claim 1, characterized in that the laser steering unit (2) is configured to mechanically align the laser source (1), the camera (5) and an optical interface (5.1). System according to Claim 1, characterized in that the camera (5) is configured to detect a laser spot (2.3) created by the aligned laser spot (2.1) on the target (3). System according to Claim 1, characterized in that it comprises an optical interface (5.1) configured to form an image, on the camera (5), of the laser signal information transported by the second reflected laser spot (3.2). System according to claim 1, characterized in that the control unit (6) is configured to provide a necessary connection for the alignment process between the laser steering unit (2) and the processing unit. image (7) once the laser spot (2.3) is captured by the camera (5) and its position is determined by means of the image processing unit (7). System according to claim 1, characterized in that it comprises an image output unit (8) configured to transfer images produced by the camera (5) out of the system.