阅读说明：本技术 一种测量激光损伤三维结构的装置及方法 (Device and method for measuring laser damage three-dimensional structure ) 是由 刘诚 齐乃杰 王绶玙 孔艳 蒋志龙 于 2019-06-03 设计创作，主要内容包括：本发明公开了一种测量激光损伤三维结构的装置及方法,属于相移数字全息领域。本发明根据相移算法引入相应的相移量,并用CCD成像设备记录相应的全息图。本发明相较于其他方法结构简单,易于操作,既降低了该激光损伤检测的成本,也实现了对三维损伤的快速、无损测量,给损伤修复带来了便利。(The invention discloses a device and a method for measuring a laser damage three-dimensional structure, and belongs to the field of phase shift digital holography. The invention introduces corresponding phase shift amount according to a phase shift algorithm, and uses CCD imaging equipment to record corresponding hologram. Compared with other methods, the method has a simple structure, is easy to operate, reduces the cost of laser damage detection, realizes quick and nondestructive measurement of three-dimensional damage, and brings convenience to damage repair.)

1. A device for measuring laser three-dimensional damage is characterized by comprising a super-radiation light-emitting diode light source, a focusing lens, a collimating lens, an attenuation sheet, a polarizer, a beam splitting prism, a quarter-wave plate, a reflector, an imaging lens, an analyzer and imaging equipment; the superradiation light-emitting diode light source is provided with a focusing lens and a collimating lens along the beam direction, and then is sequentially provided with an attenuation sheet, a polarizer and a beam splitter prism; a quarter wave plate and a reflector are sequentially arranged along the direction of the reflected light beam separated by the beam splitter prism; the analyzer, the imaging lens and the imaging device are sequentially arranged in the direction of a reflected light beam of the reflector; the device also comprises piezoelectric ceramics and an electric control translation stage, wherein the electric control translation stage is connected with a computer.

2. A device according to claim 1, wherein the polariser is oriented perpendicular to the analyser.

3. The device of claim 1 or 2, wherein the optional focal length of the imaging lens is in a range of 5-12 cm, and the distance from the imaging lens to the target surface of the imaging device is in a range of 11.25-48 cm.

4. The apparatus according to any of claims 1 to 3, wherein the minimum pixel unit of the imaging device is less than or equal to 8.7 μm and the resolution is greater than or equal to (700 x 700).

5. A method for detecting laser three-dimensional damage, which is characterized in that the device of any one of claims 1 to 4 is used for detection.

6. The method according to claim 5, characterized in that the method places the sample to be measured at a position 6-16 cm away from the imaging lens, and gradually adjusts the distance between the sample and the beam splitter prism by controlling the electrically controlled translation stage and the piezoelectric ceramic; and the adjustment is to push the electric control translation stage to the direction of the beam splitting prism, and the information collected by the imaging equipment is recorded every time the electric control translation stage is pushed one step.

7. The method according to claim 6, wherein the step of collecting information in the method is specifically:

(1) keeping object beam and reference beam, adjusting piezoelectric ceramic to record four phase shift diagrams respectively, and marking intensity as I₁、I₂、I₃、I₄；

(2) Only the object beam is reserved to record the diffraction light spot of a sample to be measured, and the intensity is marked as

(3) Recording a reference light spot by only retaining the reference beam, intensity index

(4) And (5) controlling the electric control translation stage to move, and repeating the processes (1) to (3) until the acquisition is finished.

8. The method according to claim 6 or 7, characterized in that the acquired information is used to calculate the phase distribution of the sample to be measured at the target surface of the imaging device according to a four-step dephasing method.

9. The method of claim 8, wherein the phase distribution of the sample to be measured at the target surface of the imaging device is calculated according to a four-step phase shifting method by the following specific calculation process:

(a) after the phase shifter is applied with voltage, four-step phase shifting is introduced to obtain the following light intensity diagram:

in the formulaIs the distribution of the phase difference between the wave surface of the measured object and the reference wave surface (i.e. the distribution of the phase difference between the wave surface of the measured object and the reference wave surface

(b) To obtain the information of the damage, taking the difference between every two of the 4 light intensity maps after deformation, namely I'₄-I'₂、I'₁-I'₃：

(c) To l'₁、I'₂Taking the square and then summing to obtain:

(d) after the reference light is eliminated, the related damage intensity information can be obtained:

(e) is prepared from'₁、I'₂By dividing, the phase difference can be obtained

(f) for the obtained phase differenceThe tangent function of (a) is inverse tangent to obtain the phase differenceThe value of (c):

(g) and (3) repeating the processes of (a) to (f) on the data of different depths, and stacking and superposing the phase information in a slice mode, so that a three-dimensional distribution of the laser damage at the position is obtained.

10. Use of the device according to any one of claims 1 to 4 or the method according to any one of claims 5 to 9 for repairing or processing laser damage to an optical element.

Technical Field

The invention relates to a device and a method for measuring a laser damage three-dimensional structure, belonging to the field of phase shift digital holography.

Background

With the continuous development of laser technology, the laser power becomes higher and higher, and high-power laser devices such as an ignition device in the united states, laser mega-joules in france, and magical light III in china are the most typical representatives. In these practical applications, the energy intensity of the transmitted light often reaches the maximum optical damage threshold of the optical element, and each optical element may generate defects due to processes in the manufacturing process, impurities in the glass material, the use environment or the excitation condition, the defects are easy to generate small-scale focusing under the irradiation of strong laser to cause damage to the element surface and the film layer, and once the fine damage of the element surface occurs, a vicious circle is formed in the subsequent use process to quickly cause the rejection of the whole element. Laser quenching is an effective method for repairing fine damage, but before repairing, the specific area and morphology of the damaged element need to be known, otherwise, the damaged element cannot be repaired efficiently and secondary damage may be caused.

To solve this problem, many laboratories have developed techniques for characterizing optical damage by detecting the areas of laser damage that occur to optical elements after they have been irradiated with laser light. Destructive measurement techniques such as polishing taper (taper method), sphere (ball and socket method), acid etching, etc., or nondestructive testing techniques such as total internal reflection microscope (ITIRM), white light interferometry, X-ray scattering, etc. However, these methods have more or less disadvantages, such as the need for destructive sampling analysis or borehole analysis, which cannot be done without destructive inspection; or the detection equipment is complex, expensive and inconvenient to operate, the detection is not time-consuming and labor-consuming, the spatial resolution is low, the depth information of the damage cannot be detected, and the like.

Disclosure of Invention

Aiming at the defects in the prior art, the invention provides the device and the method for measuring the laser damage three-dimensional structure based on the phase-shift digital holographic technology, which can realize the accurate measurement of the sub-surface three-dimensional distribution of the laser damage area and have important significance for researching the repair, processing and improvement process of the laser damage of the optical element.

The invention provides a device for measuring laser three-dimensional damage measurement, which comprises a super-radiation light-emitting diode light source, a focusing and collimating lens, an attenuation sheet, a polarizer, a beam splitter prism, a quarter-wave plate, a reflector, an imaging lens, an analyzer and an imaging device; the superradiation light-emitting diode light source is provided with a focusing lens and a collimating lens along the beam direction, and then is sequentially provided with an attenuation sheet, a polarizer and a beam splitter prism; a quarter wave plate and a reflector are sequentially arranged along the direction of the reflected light beam separated by the beam splitter prism; the analyzer, the imaging lens and the imaging device are sequentially arranged in the direction of a reflected light beam of the reflector; the device also comprises piezoelectric ceramics and an electric control translation stage, wherein the electric control translation stage is connected with a computer.

In one embodiment of the invention, the polarizer and analyzer are oriented perpendicular.

In one embodiment of the invention, the distance between the imaging lens and the target surface of the imaging device is 11.25-48 cm, for example, 28.5cm can be selected.

In one embodiment of the invention, the focal length of the imaging lens is 8 cm.

In one embodiment of the present invention, the minimum pixel unit of the imaging device is 7.4 microns with a resolution of 2048 x 2048.

The second purpose of the invention is to provide a method for detecting laser three-dimensional damage by using the device.

In one embodiment of the invention, in order to obtain a clear image with 2.1 times magnification, the method includes placing a sample to be measured at a position 13.5 cm away from an imaging lens, controlling an electrically controlled translation stage and piezoelectric ceramics, gradually adjusting the distance between the sample and a beam splitter prism, recording information acquired by an imaging device every step, and calculating the phase distribution of the sample to be measured at a target surface of the imaging device according to a four-step phase shifting method.

In an embodiment of the present invention, the step of acquiring information in the method specifically includes:

(1) keeping object beam and reference beam, adjusting piezoelectric ceramic to record four phase shift diagrams respectively, and marking intensity as I₁、I₂、I₃、I₄；

(2) Only the object beam is reserved to record the diffraction light spot of a sample to be measured, and the intensity is marked as

(3) Recording a reference light spot by only retaining the reference beam, intensity index

(4) And (5) controlling the electric control translation stage to move, and repeating the processes (1) to (3) until the acquisition is finished.

In one embodiment of the present invention, the specific calculation process for calculating the phase distribution of the sample to be measured at the target surface of the imaging device according to the four-step phase shifting method is as follows:

(a) after the phase shifter is applied with voltage, four-step phase shifting is introduced to obtain the following light intensity diagram:

in the formulaIs the distribution of the phase difference between the wave surface of the measured object and the reference wave surface (i.e. the distribution of the phase difference between the wave surface of the measured object and the reference wave surface)；

(b) To obtain the information of the damage, taking the difference between every two of the 4 light intensity maps after deformation, namely I'₄-I'₂、I'₁-I'₃：

(c) To l'₁、I'₂Taking the square and then summing to obtain:

(d) after the reference light is eliminated, the related damage intensity information can be obtained:

(e) is prepared from'₁、I'₂By dividing, the phase can be obtainedPotential difference

The tangent function of (c):

(f) for the obtained phase difference

The tangent function of (a) is inverse tangent to obtain the phase difference

The value of (c):

(g) and (3) repeating the processes of (a) to (f) on the data of different depths, and stacking and superposing the phase information in a slice mode, so that a three-dimensional distribution of the laser damage at the position is obtained.

Has the advantages that: the invention provides a method and a device for measuring a laser damage three-dimensional structure based on a phase-shift digital holographic technology aiming at the defects of the prior art means of laser damage detection. In the field of holographic imaging, phase-shifted digital holography has a higher imaging speed than that of conventional holography, and the phase of the reference light is controlled by a phase-shifting device, so that a corresponding amount of phase shift can be introduced according to the phase-shifting algorithm used, and an imaging device (usually a charge coupled device, i.e., a CCD) is used to record a corresponding hologram. Compared with other methods, the method has simple structure and easy operation, reduces the cost of laser damage detection, realizes the rapid and nondestructive measurement of three-dimensional damage, and brings convenience to damage repair; on the other hand, the device can also reach the measurement accuracy of axial 10 microns, and the collection and the recovery of whole data can be realized in 10 seconds simultaneously, make whole device more high-efficient, have increased the practicality of the device.

Drawings

FIG. 1 is a schematic diagram of an apparatus for implementing laser three-dimensional damage measurement based on phase shift digital holography; wherein, 1, super-radiation LED light source; 2, a focusing lens; 3, a collimating lens; 4, an attenuation sheet; 5, a polarizer; 6, a quarter wave plate; 7, a reflector; 8, an imaging lens; 9, an analyzer; 10, an imaging device; and 11, a beam splitter prism.

Fig. 2 shows laser damage points measured by using the device of the present invention.

FIG. 3 is a single layer simulation of the detection method; (a) the method comprises the following steps The upper left is a set single-layer original damage intensity graph, and (b) is a set single-layer original damage phase graph; (c) a graph of the recovered lesion intensity; (d) to a recovered phase map; (e) and (f) comparing the intensity and phase results of the same location initially and after recovery.

FIG. 4 is a three-dimensional optical slice of laser damage point recovery detected using the apparatus of the present invention, each slice being 10 microns apart along the direction of laser incidence.

Detailed Description