CN114114674B - A beam stabilization device based on inertia-free feedback correction - Google Patents

Abstract

The invention discloses a light beam stabilizing device based on inertial feedback correction. The invention realizes the position and angle control of the light beam by using the light beam deflector, completely eliminates the mechanical movement in the control execution component and eliminates the interference of environmental noise. And the advantage of high response frequency (can reach more than 1 MHz) of the acousto-optic deflector is utilized to realize rapid and high-precision beam angle drift correction. The stable light beam obtained by the method and the device can be widely used for super-resolution microscopic imaging systems and high-precision laser direct-writing photoetching systems.

Description

A beam stabilization device based on inertia-free feedback correction

technical field

The invention belongs to the field of ultra-precision optical imaging and writing, and in particular relates to a beam stabilization device based on inertialess feedback correction.

Background technique

With the continuous expansion of the application field of laser equipment and the continuous improvement of requirements, the performance indicators of the light source system are also continuously strengthened. However, due to factors such as its own principle, structure and external environment, the laser itself is difficult to avoid the problem of beam drift. In addition to the drift when the light source itself generates the beam, the devices in the subsequent optical path will also affect the stability of the beam transmission due to its own structural characteristics and environmental changes, such as the mechanical structural parts are strained by temperature and external force, the airflow in the system cavity Density changes, electromagnetic interference, etc. will cause the beam to deviate from the ideal conduction path, and the final light spot will be affected by the superposition of the above factors, resulting in translation in position and deflection in angle. Usually, the precision optical system is placed in a closed and controlled constant temperature and humidity environment. The vibration isolation platform is used for passive shock absorption and is equipped with an air filter system, which can avoid the influence of the environment on the stability of the optical path in the system to a certain extent. However, as the precision requirements of precision optical systems continue to increase, the cost of high-standard environmental control systems is also difficult to control. The residual beam drift after control by passive means such as environmental control cannot be ignored. The beam drift of the optical system needs to be introduced more effectively. means to be controlled.

Usually, the drift of the beam can be equivalent to the offset of the position and the angle. The beam has a translation parallel to the ideal axis in position, and forms an angle with the ideal axis in angle. The beam drift phenomenon in the optical system can be regarded as a random real-time process. Using the beam stabilization device, the active control method of monitoring feedback can be used to correct the beam pointing in real time, and the beam drift that cannot be controlled by passive means can be eliminated to the greatest extent. The system meets the predetermined accuracy requirements.

At present, beam stabilization devices have been widely used in many fields such as laser communication, optical measurement, laser processing, etc. Its basic components include actuators, controllers, and beam monitoring parts. The control algorithm optimization has achieved good stable control performance. However, with the continuous improvement of the performance indicators of precision optical systems, the current beam stabilization devices still have certain shortcomings, which are mainly reflected in the beam stabilization performance limitation caused by the performance of the actuator itself. The actuators in the current beam stabilization devices are mainly mechanical devices. For the driven fast mirror, the driving device is usually a voice coil motor driver or a piezoelectric ceramic driver, both of which have a certain inertia in structure and the mirror itself, which leads to a long response time during execution and a limited control frequency.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a beam stabilization device based on inertia-free feedback correction in view of the deficiencies of the prior art.

The present invention realizes through the following technical solutions:

A beam stabilization device based on inertialess feedback correction, comprising two pairs of beam deflectors, a first beam splitting prism, a second beam splitting prism, a first lens, a second lens, a first photoelectric sensor, a second photoelectric sensor and a control wherein, each pair of beam deflectors includes a vertically placed X-axis beam deflector and a Y-axis beam deflector, which are used to angularly deflect the beam along the X and Y directions of the incident beam, respectively. The incident beam is split by the first beam splitting prism into an outgoing beam and a first reflected beam, and the first reflected beam is split into a first monitoring beam and a second monitoring beam after being split by the second beam splitting prism; the first monitoring beam passes through The first lens reaches the first photoelectric sensor, and the second monitoring beam passes through the second lens to reach the second photoelectric sensor; the incident beam reaches the incident position of the second pair of beam deflectors and the first photoelectric sensor. The detection surface of the sensor is in an object-image relationship with respect to the first lens; the detection surface of the second photoelectric sensor is placed at the focal surface of the second lens. The first photoelectric sensor and the second photoelectric sensor monitor the position and angle of the beam independently and send them to the controller. The controller controls the two pairs of beam deflectors to deflect and correct the optical path of the incident beam according to the monitoring information.

Further, in the two pairs of beam deflectors, the two X-axis beam deflectors are placed in parallel and opposite to each other, and the two Y-axis beam deflectors are placed in parallel and opposite directions.

Further, the beam deflector is an acousto-optic deflector or an electro-optic deflector.

Further, when the controller controls the two pairs of beam deflectors to deflect and correct the optical path of the incident beam according to the monitoring information, the incident position of the incident beam reaching the second pair of beam deflectors remains unchanged after passing through the first pair of beam deflectors.

Further, the first photoelectric sensor and the second photoelectric sensor are position detectors or four-quadrant detectors.

Further, it also includes a second reflection mirror for adjusting the direction of the first monitoring beam or the second monitoring beam to be parallel to the optical path of the incident beam.

Further, it also includes a third lens; the third lens and the second lens form a lens group.

Further, the first beam splitting prism has a high transmittance and reflectance ratio, transmits most of the energy of the main beam and exits the rear end of the beam stabilization device, and reflects a small part of the remaining energy into the monitoring optical path. The second dichroic prism has the same transmittance and reflection ratio, and divides the first reflected light beam into a first monitoring light beam and a second monitoring light beam.

The beneficial effects of the present invention are as follows: the present invention provides a beam stabilization device based on angle-free inertial feedback correction, which utilizes a beam deflector without inertial feedback to simultaneously correct the beam angle and position. Compared with the traditional beam stabilization device, the All mechanical actuators are used, the beam drift correction accuracy of the system is improved, and the correction period can be greatly reduced by virtue of the high control frequency of the beam deflector to achieve rapid correction of the beam angle and position.

Description of drawings

1 is a schematic diagram of a beam stabilization device based on angle-free inertial feedback correction of the present invention;

Fig. 2 is the detection of position drift of the present invention and the real-time correction optical path design diagram;

Fig. 3 is the detection and real-time correction optical path design diagram of the angle drift of the present invention;

Fig. 4 is the principle diagram of utilizing beam deflector to correct optical path position in the present invention;

FIG. 5 is a schematic diagram of the optical path angle correction using a beam deflector in the present invention.

In the figure, 1-X-axis first beam deflector, 2-Y-axis first beam deflector, 3-X-axis second beam deflector, 4-Y-axis second beam deflector, 5-first beam splitter prism, 6-Second beam splitting prism, 7-First lens, 8-Second lens, 9-Second mirror, 10-Third lens, 11-First photoelectric sensor, 12-Second photoelectric sensor, 13- controller.

Detailed ways

The present invention will be further described below through examples and accompanying drawings, but the protection scope of the present invention should not be limited by this.

The present invention provides a beam stabilization device based on inertialess feedback correction, comprising two pairs of beam deflectors, a first beam splitting prism 5 , a second beam splitting prism 6 , a first lens 7 , a second lens 8 , and a first photoelectric sensor 11 , the second photoelectric sensor 12 and the controller 13, etc.; wherein, each pair of beam deflectors includes a vertically placed X-axis beam deflector and a Y-axis beam deflector, which are respectively used to angle the beam along the X and Y directions of the incident beam. Deflection, the incident beam deflected by the two pairs of beam deflectors is split into an outgoing beam and a first reflected beam through the first beam splitting prism 5, and the first reflected beam is split into a second beam after being split by the second beam splitting prism 6. a monitoring beam and a second monitoring beam; the first monitoring beam passes through the first lens 7 to reach the first photoelectric sensor 11 , and the second monitoring beam passes through the second lens 8 to reach the second photoelectric sensor 12 ; The incident position of the incident beam reaching the second pair of beam deflectors and the detection surface of the first photoelectric sensor 11 with respect to the first lens 7 are in an object-image relationship; the detection surface of the second photoelectric sensor 12 is placed on the second lens 8 focal plane. The first photoelectric sensor 11 and the second photoelectric sensor 12 monitor the position and angle of the beam independently and send them to the controller 13. The controller 13 controls the two pairs of beam deflectors to deflect and correct the optical path of the incident beam according to the monitoring information.

As a preferred solution, as shown in FIG. 1, the two pairs of beam deflectors include an X-axis first beam deflector 1, a Y-axis first beam deflector 2 and a second pair of beam deflectors that form the first pair of beam deflectors The X-axis second beam deflector 3, the Y-axis second beam deflector 4, wherein the X-axis first beam deflector 1 and the X-axis second beam deflector 3 are placed in parallel and opposite, and the Y-axis first beam deflector 2 and the Y-axis second beam deflector 4 are placed in parallel and opposite to each other for performing two angular deflections of the beam along the X and Y directions of the incident beam, so as to realize the position and angle control of the X-axis and the Y-axis.

Further, a second reflection mirror 9 is also included for adjusting the direction of the first monitoring beam or the second monitoring beam to be parallel to the optical path of the incident beam, so as to reduce the volume of the device.

Further, a third lens 10 is also included; the third lens 10 and the second lens 8 form a lens group that can be equivalent to a telephoto lens, which is convenient for shortening the optical path and finding the focus during debugging. Figure 1 shows a specific device structure diagram of a preferred solution. The method for real-time stabilization of an incident beam of the present invention is further described below in conjunction with the device shown in Figure 1, and the details are as follows:

An incident beam with a wavelength of 532nm, after entering the beam stabilization device, is transmitted through two pairs of vertically placed beam deflectors (X-axis first beam deflector 1, Y-axis first beam deflector 2, X-axis second beam deflector 3, Y-axis second beam deflector 4), an acousto-optic deflector model 4090-7 from Gooch & Housego, UK can be selected, its scanning angle is about 44mrad, and the Bragg angle is 1.76°. Arbitrary deflection is achieved within a certain range near the Bragg angle of the beam deflector, and the angle deflection is performed on a fixed plane according to the orientation of the beam deflector. In the present invention, the beam can be deflected twice in the X and Y directions.

The beams emitted from the two pairs of beam deflectors are emitted after passing through the first beam splitting prism 5. The beam splitting prism has a transmittance reflection ratio of 9:1, so 90% of the energy of the main beam is transmitted through the rear end of the beam stabilization device, and the remaining 10 % energy is reflected into the monitoring optical path. After the reflected beam is split by the second beam splitting prism 6 with a transmittance and reflectance ratio of 1:1, it is equally divided into a first monitoring beam and a second monitoring beam, and the first monitoring beam is projected to the first photoelectric sensor 11 after passing through the first lens 7 On the detection surface, the photoelectric sensor processes the signal and sends the position information to the controller 13, and the system obtains the beam position and angle deflection by detecting the real-time displacement of the focus. Fig. 2 is the detection and real-time correction optical path design diagram of position drift, wherein d ₀ =30mm is the distance from the incident point of the second pair of beam deflectors to the center of the first beam splitting prism 5, and d ₁ =40mm is the center of the first beam splitting prism 5 to the first beam splitting prism 5. The distance from the center of the dichroic prism 6, d ₂ =30mm is the distance from the center of the second dichroic prism 6 to the center of the first lens 7, d ₃ =100mm is the distance from the center of the first lens 7 to the detection surface of the first photoelectric sensor 11, The focal length of the first lens 7 is f ₁ =50mm, and the above distance values satisfy the following relational formula (1):

（1）

(1)

According to the above relationship, the incident position of the incident beam reaching the second pair of beam deflectors and the detection surface of the first photoelectric sensor 11 with respect to the first lens 7 are in an object-image relationship. When adjusting the angle of the incident beam, the controller calculates and selects the respective deflection angle, so that the beam still passes through the center of the first beam splitting prism 5 after changing the angle. Due to the above object-image relationship, the spot position at the object point remains unchanged. The position of the light spot on the detector 11 is also unchanged; when the two pairs of beam deflectors are performing position correction, the position of the light spot on the first photoelectric sensor 11 will change accordingly due to the existence of the object-image relationship. Therefore, the first photoelectric sensor 11 can realize independent monitoring of the position of the light beam without being disturbed by the angle correction.

The second monitoring beam passes through the second lens 8 , the first reflecting mirror 9 and the third lens 10 and then enters the detection surface of the second photoelectric sensor 12 . The system obtains the angle deflection by detecting the real-time displacement of the focus. Fig. 3 is the detection and real-time correction optical path design diagram of angle drift, wherein d ₄ =60mm is the distance from the second lens 8 to the center of the first reflecting mirror 9, and d ₅ =28mm is the center of the first reflecting mirror 9 to the third lens 10 distance, d ₆ is the distance from the third lens 10 to the detection surface of the second photoelectric sensor 12, the second lens 8 selects the lens of Solebo model LBF254-100-A, the focal length f ₂ =100mm, the third lens 10 Select the lens of Soleimbo model LD2060, the focal length f ₃ =-15mm, the equivalent focal length F of the combined lens group can be calculated according to the relationship (2):

（2）

(2)

The distance d ₆ from the third lens 10 to the detection surface of the second photoelectric sensor 12 can be calculated according to the relational formula (3):

（3）

(3)

According to the above conversion results, the detection surface of the second photoelectric sensor 12 is placed at the focal surface of the lens group formed by the second lens 8 and the third lens 10. At this time, when the light beam only changes in position, the spot position at the focal surface When the beam angle changes, the spot at the focal plane will move accordingly, and the change in the beam angle can be obtained by calculation. Therefore, the second photoelectric sensor 12 can realize the independent monitoring of the beam angle without being disturbed by the position correction.

The position and angle of the beam are independently monitored by two photoelectric sensors, and the information is transmitted to the controller 13. The controller calculates the angular position information, calculates the correction amount, and feeds back the driving signal to the beam deflector, so as to realize the control of the position and angle of the beam. Correction in real time. Specifically, the controller 13 precisely controls the deflection angles of the beams in the X direction and the Y direction by controlling the frequencies of the four beam deflectors. Placement on the same plane means adjusting the front and rear beam deflectors of the same axis (the first beam deflector 1 on the X axis and the second beam deflector 3 on the X axis are placed on the same plane, and the first beam deflector 2 on the Y axis and the second beam deflector on the Y axis are placed on the same plane. The two beam deflectors 4) are placed on the same plane) through the cooperation of their respective angle settings, the position and angle of the beam on the plane can be controlled. Figure 4 is a schematic diagram of the position control of the light beam realized by the cooperation of the two beam deflectors placed on the same plane. is the beam deflector B; when the incident beam is shifted from the L1 position to the L2 position, the beam exit angle and position need to be corrected to the exit angle and position of the L1 optical path. During this process, the incident angle of beam deflector A remains unchanged. Increasing the input frequency of beam deflector A increases its exit angle, and restores the incident point of the beam at beam deflector B to the incident intersection of the L1 optical path and beam deflector B. , at this time, the incident angle of the beam deflector B increases, that is, the input frequency of the beam deflector B needs to be reduced, and the output angle of the beam deflector B needs to be reduced to restore it to the original size. the exit angle and position. Figure 5 is a schematic diagram of the front and rear beam deflectors placed on the same plane to achieve the angle control of the beam, in which the beam deflectors are placed in opposite directions (that is, the deflection directions are opposite), when the incident beam is deflected from the L1 angle to the L2 angle. When the beam exit angle and position need to be corrected to the exit angle and position of the L1 optical path. During this process, the incident angle of the beam deflector A becomes larger. Since the distance between the beam deflectors A and B is usually smaller than the distance between the beam deflection starting point and the beam deflector A, it is necessary to increase the input frequency of the beam deflector A to increase its frequency. The exit angle is to restore the incident point of the beam at the beam deflector B to the incident intersection of the L1 optical path and the beam deflector B. At this time, the incident angle of the beam deflector B increases, and the input frequency of the beam deflector B is adjusted to reduce its output. The angle of the outgoing light is corrected back to the outgoing angle of the L1 optical path. At this time, when the light beam is incident from the L2 angle, the outgoing angle and position of the L1 optical path are still maintained. The above angle and position correction directions are vice versa. In the present invention, the X-axis first beam deflector 1 and the X-axis second beam deflector 3 cooperate to realize the position and angle correction of the beam in the X direction, and the Y-axis first beam deflector 2 and the Y-axis second beam deflector 4 The position and angle correction in the Y-direction of the beam can be realized by cooperation.

Obviously, the above-mentioned embodiments are only examples for clear description, and are not intended to limit the implementation manner. For those of ordinary skill in the art, changes or modifications in other different forms can also be made on the basis of the above description. All implementations need not and cannot be exhaustive here. However, the obvious changes or changes derived from this are still within the protection scope of the present invention.

Claims (8)

1. A light beam stabilizing device based on inertial feedback correction is characterized by comprising two pairs of light beam deflectors, a first beam splitter prism (5), a second beam splitter prism (6), a first lens (7), a second lens (8), a first photoelectric sensor (11), a second photoelectric sensor (12) and a controller (13); each pair of beam deflectors comprises an X-axis beam deflector and a Y-axis beam deflector which are vertically arranged and are respectively used for carrying out angle deflection on beams along the X direction and the Y direction of an incident beam, the incident beam deflected by the two pairs of beam deflectors is split into an emergent beam and a first reflected beam through the first beam splitter prism (5), and the first reflected beam is split into a first monitoring beam and a second monitoring beam through the second beam splitter prism (6); the first monitoring light beam reaches the first photoelectric sensor (11) after passing through the first lens (7), and the second monitoring light beam reaches the second photoelectric sensor (12) after passing through the second lens (8); the incident position of the incident beam reaching the second pair of beam deflectors and the detection surface of the first photoelectric sensor (11) are in an object-image relationship with respect to the first lens (7); the detection surface of the second photoelectric sensor (12) is placed at the focal surface of the second lens (8);

the first photoelectric sensor (11) and the second photoelectric sensor (12) respectively and independently monitor the position and the angle of the light beam and send the light beam to the controller (13), and the controller (13) controls the two pairs of light beam deflectors to deflect and correct the light path of the incident light beam according to monitoring information.

2. The apparatus of claim 1, wherein the two pairs of beam deflectors are arranged with the two X-axis beam deflectors in parallel and the two Y-axis beam deflectors in opposite directions.

3. The device of claim 1, wherein the beam deflector is an acousto-optic deflector or an electro-optic deflector.

4. The optical beam stabilizing apparatus based on non-inertial feedback correction as claimed in claim 1, wherein the controller (13) controls the two pairs of beam deflectors to deflect and correct the optical path of the incident beam according to the monitoring information, and keeps the incident position of the incident beam reaching the second pair of beam deflectors unchanged after the incident beam passes through the first pair of beam deflectors.

5. The optical beam stabilizing device based on no inertial feedback correction according to claim 1, wherein the first photo-sensor (11) and the second photo-sensor (12) are position detectors or four-quadrant detectors.

6. The beam stabilizer based on no inertial feedback correction of claim 1, further comprising a second mirror (9) for adjusting the direction of the first monitor beam or the second monitor beam to be parallel to the optical path of the incident beam.

7. The optical beam stabilizing device based on the inertial feedback correction of claim 1, further comprising a third lens (10); the third lens (10) and the second lens (8) form a lens group.

8. The device of claim 1, wherein the transmittance-reflectance of the first beam splitter prism is greater than 0.5, and the transmittance-reflectance of the second beam splitter prism is equal.

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