Reflection-type high-precision high-power laser optical axis calibration method

Abstract

The invention relates to a reflective high-precision high-power laser optical axis calibration method, which comprises the following steps of: coarse alignment: enabling a reflecting light plate and an emergent light plate to be visible on a black paint plate; adjusting the posture of the reflector, and moving the reflection light spot; calculating a light spot center position by an image, and establishing an angle and position function relationship; the deviation angle is inversely calculated through the position difference, and the reflector is strictly perpendicular to the optical axis. According to the reflective high-precision high-power laser optical axis calibration method, on the premise that an oversized and overweight laser is not moved, other elements are moved, calibration of the laser optical axis is completed under the condition that the requirement for the spatial distance is not large, vibration can be reduced, and devices can be protected.

Description

Technical Field

[0001] The present invention relates to the technical field of laser optical axis calibration, and particularly to a method for calibrating the optical axis of a high-power laser with high precision by reflection. Background Art

[0002] Lasers with an optical power exceeding 500 mW are called "Class 4 lasers", and their direct and scattered light can cause damage to the eyes and skin, posing certain risks. However, at the same time, high-power lasers are also essential tools for scientific research, industry, and national defense applications, and the calibration of parameters such as wavelength, pulse width, and quality is also required in the industry.

[0003] In fields such as optical imaging, a high-power laser and the assembled optical components need to be aligned along the optical axis to function. Due to the high precision requirements, large volume, and heavy weight of the supporting optical components, when the laser is turned on, manually using brackets, rulers, and diaphragms to find a way to align the optical axis takes a long time and is inefficient. Moreover, judging by experience is both dangerous and difficult to ensure accuracy. Therefore, a method for calibrating the optical axis of a high-power laser that does not require human eye observation, is fast and efficient, is needed, so that the laser is shipped with a reference for optical axis calibration. When the laser is turned off, the optical components can still be quickly and safely aligned with the optical axis of the laser.

[0004] The technical solution disclosed in the Chinese patent document with the publication number 109238251A, the publication date of January 18, 2019, and the title "Self-calibrating long-distance laser calibration axis and its calibration method" is as follows: relying on a dividing plate to rotate a laser emitter, observing the spot trajectory as a circle or an ellipse on a distal blackboard, and adjusting the angle of the laser emitter through two mutually perpendicular adjusting screws to make the spot return to the center of the trajectory, which needs to be repeated about 20 times until only one point remains on the spot trajectory to complete the calibration. This method is a one-way laser optical axis calibration, requiring a large space distance (more than 5 m). Due to the objective divergence angle of the laser, there is an upper limit on the accuracy of observing the trajectory with the naked eye (greater than 0.05 degrees), and for high-power, high-precision, super-large, and super-heavy lasers, rotation cannot be achieved through this solution, resulting in operational limitations. Summary of the Invention

[0005] The present invention aims to solve the technical problem in the prior art that there is no fast and safe method for calibrating the optical axis of a high-power laser, and provides a method for calibrating the optical axis of a high-power laser with high precision by reflection.

[0006] To solve the above technical problems, the technical solution of the present invention is specifically as follows:

[0007] A reflective, high-precision, high-power laser optical axis calibration method is disclosed. The applicable system includes: a high-power laser, a black paint plate, a photographing tool, a reflector, and a parallel mechanism, which are sequentially arranged along the optical path. The high-power laser is placed on a base, the photographing tool is close to the optical path, and the reflector is connected to the parallel mechanism.

[0008] The black painted board is used to show incident and reflected light spots;

[0009] The shooting tool is used to record the positions of the outgoing light spot and the reflected light spot in the image plane coordinate system;

[0010] The reflector is used to achieve strict perpendicularity to the laser optical axis through posture;

[0011] The parallel mechanism is used to output the angle to achieve the posture adjustment of the reflector;

[0012] The high-power laser optical axis calibration method comprises the following steps:

[0013] Step 1: Coarse alignment, the reflected light plate and the output light plate are both visible on the black paint plate;

[0014] Step 2: Adjust the reflector posture and move the reflected light spot;

[0015] Step 3: Calculate the center position of the light spot from the image and establish the functional relationship between angle and position;

[0016] Step 4: Back-calculate the deviation angle through the position difference to ensure that the reflector and the optical axis are strictly perpendicular.

[0017] In the above technical solution, step 1 is specifically as follows:

[0018] Place the high-power laser on the base;

[0019] Under the premise of known distance and spot size, place and fix the black paint board;

[0020] A hole with the same size as the exiting light spot is opened in the black paint plate;

[0021] The position of the reflector is roughly adjusted to ensure that the reflected light spot on the black paint plate is clearly visible with diffraction rings.

[0022] In the above technical solution, step 2 is specifically as follows:

[0023] Relying on the precise control of the reflector, the parallel mechanism outputs angles multiple times in the Oy and Ox directions, allowing the reflector to adjust its angle multiple times along the perpendicular angles, leaving a vertical movement trajectory and movement distance on the black paint plate.

[0024] In the above technical solution, step 3 is specifically as follows:

[0025] Relying on the image processing results of the shooting tool, the center of the elliptical spot on the image is obtained, the moving distance is obtained, and the functional relationship between the moving distance and the output angle is obtained according to the conversion between the spatial coordinate system and the image plane coordinate system.

[0026] In the above technical solution, step 4 is specifically as follows:

[0027] Adjust the reflector posture to ensure that it is strictly perpendicular to the laser optical axis;

[0028] The optical axis is guided to the prism attached to the high-power laser by using a photoelectric theodolite, and the posture of the spacer is adjusted to complete the alignment.

[0029] The present invention has the following beneficial effects:

[0030] The reflective high-precision high-power laser optical axis calibration method of the present invention can move other components without moving the ultra-large and ultra-heavy laser itself, and complete the calibration of the laser optical axis when the spatial distance requirement is not large, thereby reducing vibration and protecting the device.

[0031] The reflective high-precision high-power laser optical axis calibration method of the present invention uses a reflective optical path and photogrammetry, with a sensitivity at the pixel level; it can achieve a calibration accuracy of about seconds when using an ordinary camera or a mobile phone to take pictures. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] Figure 1 The diagram is a structural diagram of a system applicable to the reflective high-precision high-power laser optical axis calibration method of the present invention.

[0034] Figure 2 The figure is a schematic diagram of the steps of the reflective high-precision high-power laser optical axis calibration method of the present invention.

[0035] The reference numerals in the figures indicate:

[0036] 1- High-power laser; 2- Black paint board; 3- Shooting tool; 4- Reflector; 5- Parallel mechanism. DETAILED DESCRIPTION

[0037] The present invention will be described in detail below with reference to the accompanying drawings.

[0038] The reflective high-precision high-power laser optical axis calibration method of the present invention is as follows: Figure 1 As shown, the applicable system includes: a high-power laser 1, a black paint plate 2, a shooting tool 3, a reflector 4 and a parallel mechanism 5 arranged in sequence in the direction of the optical path.

[0039] Wherein: The high-power laser 1 is placed on the base without need of movement; the black paint board 2 is placed on the fixing frame and kept stationary; the photographing tool 3 is close to the optical path without blocking the photographing; the reflecting mirror 4 is connected to the parallel mechanism 5 through a fixing bracket.

[0040] The method for calibrating the optical axis of the high-power laser with high reflectivity and high precision according to the present invention depends on the precise adjustment of the reflecting mirror 4. As Figure 1 shown, the black paint board 2 is used to display the outgoing light spot and the reflected light spot; the photographing tool 3 records the positions of the two light spots in the image plane coordinate system; the parallel mechanism 5 can accurately output the angle γ to realize the attitude adjustment of the reflecting mirror 4. Under the conversion calculation between the space coordinate system and the image plane coordinate system, the functional relationship between the moving distance d of the light spot and the attitude adjustment angle γ of the reflecting mirror 4 is obtained and the deviation angle Δγ is inversely calculated, and the attitude of the reflecting mirror 4 is adjusted to be strictly perpendicular to the laser optical axis. The optical axis is guided to the prism attached to the high-power laser 1 through an optoelectronic theodolite, and the attitude of the shim is adjusted to complete the alignment.

[0041] As Figure 2 shown, the method for calibrating the optical axis of the high-power laser with high reflectivity and high precision according to the present invention includes the following steps:

[0042] Step 1: Coarse alignment, both the reflected light board and the outgoing light board are visible on the black paint board 2;

[0043] Specifically: Place the high-power laser 1 on the base without need of movement. On the premise of known distance and light spot size, place and fix the black paint board 2. The black paint board 2 is provided with a hole having the same size as the outgoing light spot. Due to the objective diffraction effect, the outgoing light spot is clearly visible. The position of the reflecting mirror 4 is coarsely aligned to make the reflected light spot on the black paint board 2 clearly visible with a diffraction ring. The photographing tool 3 is close to the optical path without blocking the photographing; the reflecting mirror 4 is connected to the parallel mechanism 5 through a fixing bracket.

[0044] Step 2: Adjust the attitude of the reflecting mirror 4 to move the reflected light spot;

[0045] Specifically: Depending on the precise adjustment of the reflecting mirror 4, the parallel mechanism 5 outputs the angles γ1 / γ2 in the Oy / Ox directions for multiple times, so that the reflecting mirror 4 adjusts the angles γ1 / γ2 for multiple times along the perpendicular angles, leaving a perpendicular movement track and a movement distance d on the black paint board 2. It can be known from geometric analysis that the movement distances d caused by the angle γ1 or the angle γ2 are perpendicular to each other.

[0046] Step 3: Calculate the center position of the light spot in the image, and establish the functional relationship between the angle and the position;

[0047] Specifically: relying on the image processing result of the photographing tool 3, due to the existence of the diffraction effect, there are two overexposed spots and diffraction rings in the image. According to the edge algorithm and the fuzzy entropy algorithm, the center of the elliptical spot is obtained, and the moving distance d is obtained. According to the conversion between the space coordinate system and the image plane coordinate system, the functional relationship between the moving distance d and the output angle γ is obtained.

[0048] Step 4: Back-calculate the deviation angle through the position difference to make the reflector 4 strictly perpendicular to the optical axis.

[0049] The deviation angle Δγ is back-calculated. Specifically: adjust the attitude of the reflector 4 to be strictly perpendicular to the laser optical axis. Since the photographing tool 3 uses photogrammetry for measurement, the sensitivity of about one second can be basically achieved during the measurement process. Relying on the image processing result and the accurate output of the parallel mechanism 5, the calibration result can meet the vertical accuracy of the reflector 4 and the laser optical axis at the second-level accuracy. Guide the optical axis to the prism attached to the high-power laser 1 through an optoelectronic theodolite, and adjust the attitude of the shim to complete the alignment. This enables the high-power laser 1 to come with an optical axis calibration reference when leaving the factory. When the high-power laser 1 is shut down, the optical components can still be quickly and safely aligned with the laser optical axis. The shim is located on one side of the high-power laser 1 and is used to correct the pointing of the laser optical axis. The optical axis calibration is completed by grinding and researching the pitch and azimuth angles of the shim.

[0050] In the reflective high-precision optical axis calibration method of the high-power laser of the present invention, the optical axis calibration method relies on the image processing result of the photographing tool 3 and the stable output angle γ of the parallel mechanism 5, and ensures that all devices remain relatively stationary during the measurement process. The photographing tool 3 does not block the optical path and faces the black paint board 2 directly, and stably shoots the result according to the output angle of the parallel mechanism 5, and remains relatively stationary. The parallel mechanism 5 outputs the angle γ multiple times in the Oy / Ox direction, so that the reflector 4 adjusts the angle multiple times along mutually perpendicular angles, leaving a perpendicular moving track on the black paint board 2. The photographing tool 3 extracts the spot moving distance d according to the edge algorithm and the fuzzy entropy algorithm of the overexposed spot image, and obtains the functional relationship between the distance d and the angle γ.

[0051] The reflective high-precision optical axis calibration method of the high-power laser of the present invention can move other components without moving the ultra-large and overweight laser itself, and complete the calibration of the laser optical axis when the space distance requirement is not large, which can reduce vibration and protect the devices.

[0052] The reflective high-precision optical axis calibration method of the high-power laser of the present invention uses a reflective optical path and photogrammetry, and the sensitivity is at the pixel level; it can achieve a calibration accuracy of about one second when using an ordinary camera or a mobile phone to take pictures.

[0053] Obviously, the above embodiments are merely examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. And the obvious changes or modifications derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for calibrating the optical axis of a high-power laser with high precision by reflection, characterized in that, The applicable system includes, in the optical path direction, successively arranged: a high-power laser (1), a black paint board (2), a photographing tool (3), a reflecting mirror (4), and a parallel mechanism (5); where: the high-power laser (1) is placed on a base, the photographing tool (3) is close to the optical path, and the reflecting mirror (4) is connected to the parallel mechanism (5); The black paint board (2) is used to display the outgoing light spot and the reflected light spot; The photographing tool (3) is used to record the positions of the outgoing light spot and the reflected light spot respectively in the image plane coordinate system; The reflecting mirror (4) is used to achieve strict perpendicularity with the laser optical axis through its attitude; The parallel mechanism (5) is used to output an angle to achieve the attitude adjustment of the reflecting mirror (4); The method for calibrating the optical axis of the high-power laser includes the following steps: Step 1: Coarse alignment, both the reflected light board and the outgoing light board are visible on the black paint board (2); Step 2: Adjust the attitude of the reflecting mirror (4) to move the reflected light spot; Step 3: Calculate the center position of the light spot in the image, and establish the functional relationship between the angle and the position; Step 4: Inversely calculate the deviation angle through the position difference to achieve strict perpendicularity between the reflecting mirror (4) and the optical axis.

2. The method for calibrating the optical axis of a high-power laser with high precision by reflection according to claim 1, characterized in that Specifically, Step 1 is as follows: Place the high-power laser (1) on the base; Place and fix the black paint board (2) on the premise of known distance and light spot size; Open a hole on the black paint board (2) with the same size as the outgoing light spot; Coarsely align the position of the reflecting mirror (4) to make the reflected light spot on the black paint board (2) clearly visible with diffraction rings.

3. The method for calibrating the optical axis of a high-power laser with high precision according to claim 1, characterized in that, Specifically, Step 2 is as follows: Relying on the precise control of the reflecting mirror (4), the parallel mechanism (5) outputs angles multiple times in the Oy and Ox directions, so that the reflecting mirror (4) adjusts the angle multiple times along mutually perpendicular angles, leaving perpendicular movement trajectories and movement distances on the black paint board (2).

4. The method for calibrating the optical axis of a high-power laser with high precision and reflection type according to claim 1, wherein, Specifically, Step 3 is as follows: Relying on the image processing result of the photographing tool (3), obtain the center of the elliptical light spot on the image, obtain the movement distance, and obtain the functional relationship between the movement distance and the output angle according to the conversion between the space coordinate system and the image plane coordinate system.

5. The method for calibrating the optical axis of a high-power laser with high precision and reflection type according to claim 1, characterized in that, Specifically, Step 4 is as follows: Adjust the attitude of the reflecting mirror (4) to achieve strict perpendicularity with the laser optical axis; Guide the optical axis to the prism attached to the high-power laser (1) through an optoelectronic theodolite, and adjust the attitude of the shim to complete the alignment.

Images