A KDP-type crystal cone growth region imaging identification method and system

Abstract

The present invention discloses an imaging identification method and system for determining the cone growth region of a KDP crystal, relating to the technical field of KDP crystal quality inspection. The method comprises the steps of obtaining a KDP crystal to be tested and inspecting the crystal; establishing an imaging identification system, and using the imaging identification system to image the KDP crystal to obtain a scattered light image of the KDP crystal. The KDP crystal to be tested is placed in the imaging identification system, and scattered laser light is incident obliquely on the surface of the KDP crystal to be tested, causing the crystal to move horizontally. The scattered light image is captured in real time by a CCD camera matrix; and the crystal growth region at all measurement areas of the KDP crystal to be tested is determined using the scattered light image. The present invention can quickly and effectively use the scattered light image to directly determine the cone growth region of the KDP crystal, resulting in a simpler identification method and more accurate identification results.

Description

Technical Field

[0001] The present invention relates to the technical field of KDP crystal quality detection, and in particular to an imaging discrimination method and system for a cone growth region of a KDP crystal. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] Potassium dihydrogen phosphate (KH2PO4, KDP) and its deuterated form (KD X H (2-X) PO4, referred to as DKDP), ammonium dihydrogen phosphate (NH4H2PO4, referred to as ADP) and its deuterated compound (N(D X H 1-X )4(D Y H 1-Y )2PO4, abbreviated as DADP) and other crystal materials are collectively referred to as KDP-type crystal materials. Tetragonal KDP-type crystals have many advantages, such as a wide light transmission band, strong resistance to laser damage, high nonlinear conversion efficiency, the ability to grow into large-sized single crystals and easy processing. They are widely used in high-tech fields such as laser frequency conversion and electro-optical Q-switching. In recent years, inertial confinement fusion (ICF) projects have attracted widespread attention. Large-sized KDP-type crystals are the only nonlinear optical crystal materials that can be used for electro-optical switching and frequency conversion in ICF projects. With the continuous improvement of transmitted laser energy in ICF projects, improving crystal quality and resistance to laser damage has also become one of the research focuses.

[0004] KDP crystals are mainly prepared by two methods: the traditional growth method and the seeded crystal rapid growth method. KDP crystals grown by the traditional growth method grow along the

[001] direction through the (101) cone surface at a growth rate of 0.5-1 mm / day. The growth cycle is long, and the grown crystals have a large seed recovery zone. This region is a polycrystalline region and cannot be actually utilized. Therefore, this growth method has a long cycle, high risk, high cost, and low crystal utilization. The seeded crystal rapid growth technology developed in recent years can allow crystals to grow simultaneously along the

[100] and

[001] directions at a growth rate of 10-20 mm / day. This greatly shortens the crystal growth cycle, reduces costs, and minimizes the crystal recovery zone, greatly improving crystal utilization. Therefore, the KDP crystal rapid growth method has great application prospects.

[0005] The point seed crystal rapid growth method uses point seed crystals to rapidly grow simultaneously along the

[001] and

[100] directions in a highly supersaturated solution. The resulting crystals contain a columnar region where the columnar surface grows and a cone region where the cone surface grows. Therefore, there is a cone-column interface where the cone and column regions meet inside the crystal. The quality of this part of the crystal is poor and cannot meet the requirements. Due to the charge of the columnar surface, the columnar crystal is more likely to adsorb impurity ions in the solution, resulting in a larger linear absorption coefficient, and the resulting components are difficult to meet engineering requirements. Therefore, the large quality difference between the cone and column growth areas of KDP-type crystals grown by the rapid growth method is the biggest disadvantage of the rapid growth process, which restricts the application of crystals in engineering. Certain measures need to be taken to distinguish the cone-column region and improve the utilization rate of the crystal.

[0006] The Chinese invention patent, entitled "Method and Device for Identifying and Measuring the Growth Region of Conical Columns in KDP-Type Crystals," published on March 2, 2021, with publication number CN112432898A, uses the varying transmittances of different crystal regions as a criterion. However, this method places high demands on crystal quality, and the criteria for determination cannot be standardized under different conditions. The determination of the cone-column junction is ambiguous, making it difficult to perform in practice. Furthermore, the laser wavelength used is deep ultraviolet, requiring specialized personnel. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the purpose of the present invention is to provide an imaging judgment method and system for the cone column growth area of ​​KDP crystals, which can quickly and effectively use scattered images to directly judge the cone column growth area of ​​KDP crystals. The judgment method is simpler and the judgment result is more accurate.

[0008] In order to achieve the above object, the present invention is implemented through the following technical solutions:

[0009] A first aspect of the present invention provides an imaging identification method for a KDP-type crystal cone growth region, comprising the following steps:

[0010] Obtaining a KDP crystal to be tested and inspecting the KDP crystal to be tested;

[0011] An imaging discrimination system is constructed and used to image the KDP crystal to be tested, thereby obtaining a scattered light image of the KDP crystal. The KDP crystal to be tested is placed in the imaging discrimination system, and scattered laser light is incident obliquely on the surface of the KDP crystal to be tested. The crystal is moved in the horizontal direction, and the scattered light image is captured in real time by a CCD camera matrix.

[0012] The crystal growth area at all measurement areas of the KDP crystal to be tested is determined by the scattered light image.

[0013] Furthermore, the KDP-type crystal to be tested is a fast-growing type II cut KDP crystal.

[0014] Furthermore, KDP crystals include potassium dihydrogen phosphate and its isotope compound deuterated potassium dihydrogen phosphate crystals, ammonium dihydrogen phosphate and its isotope compound deuterated ammonium dihydrogen phosphate crystals.

[0015] Furthermore, the inspection standards for the KDP crystals to be tested are:

[0016] The KDP crystals to be tested have been cut, oriented, and polished, and have no obvious processing defects on the surface, and no obvious growth defects inside the crystals.

[0017] Furthermore, the specific steps of using the imaging discrimination system to image the KDP crystal to be tested are as follows:

[0018] The KDP crystal to be tested is placed on a displacement platform, and the scattered laser is incident obliquely on the surface of the KDP crystal to be tested;

[0019] The CCD camera matrix lens is focused on the surface of the KDP crystal to be tested;

[0020] The scattered light is captured by the CCD camera matrix and the image is read by the software in the computer.

[0021] Furthermore, the laser light source emits continuous laser, and the laser energy fluctuation is ≤1%, wherein the continuous laser wavelength is 380nm-780nm.

[0022] Furthermore, the angle between the laser and the surface of the KDP crystal to be measured is 30°-60°, the laser spot is shaped into a line by the lens, and the linear laser coincides with the edge of the crystal.

[0023] Furthermore, the focusing field length of the CCD camera matrix lens is shorter than the length of the linear laser.

[0024] Furthermore, the specific steps of determining the crystal growth area at all measurement areas of the KDP crystal to be measured by using the scattered light image are as follows:

[0025] There are two areas of different brightness in the scattered light image, and there is a clear dividing line between the two areas. The area with higher brightness is the area with more obvious scattered light, which is the cylindrical growth area of ​​the KDP crystal to be tested; the area with darker brightness has less obvious scattered light, which belongs to the conical growth area of ​​the KDP crystal to be tested; the dividing line located in the middle of the crystal belongs to the cone-column junction of the KDP crystal to be tested.

[0026] The second aspect of the present invention provides an imaging discrimination system for the imaging discrimination method of the KDP crystal cone growth area described in the first aspect, comprising a laser light source, a lens, a displacement platform, a CCD camera and a computer. The displacement platform is used to place the KDP crystal to be tested. The laser beam generated by the laser light source becomes a linear light source through the lens and is obliquely incident on the surface of the displacement platform. The CCD camera matrix lens is above the displacement platform and is used to capture reflected light. The CCD camera matrix lens is focused on the surface of the KDP crystal to be tested, and the transmitted light is scattered by the KDP crystal to be tested and then captured by the CCD camera matrix lens. The CCD camera is connected to the computer, and the computer controls the displacement platform to move the KDP crystal to be tested in the horizontal direction to obtain an image in real time.

[0027] One or more of the above technical solutions have the following beneficial effects:

[0028] The present invention discloses an imaging method and system for identifying the cone growth region of a KDP crystal. The method involves surface treating a KDP crystal, placing the KDP crystal in a scattered light path system, and collecting scattered images using a CCD camera array. This method can easily and efficiently acquire images of the cone growth region distribution of rapidly growing KDP crystals. Compared to the complex structures of existing techniques, the identification system of the present invention is simple and easy to implement, capable of direct imaging. The cone growth region of the KDP crystal is identified based on the imaging results, resulting in a highly automated system that eliminates the need for manual judgment, reduces the technical requirements of the experimenter, and provides more accurate results.

[0029] Advantages of additional aspects of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0031] Figure 1 1 is a structural diagram of an imaging discrimination system in Embodiment 1 of the present invention;

[0032] Figure 2 This is a diagram showing the imaging effect of a scattered light image in Example 1 of the present invention;

[0033] Among them, 1. Laser light source, 2. Lens, 3. Displacement platform, 4. CCD camera, 5. Computer. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0035] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or their combinations;

[0036] Example 1:

[0037] A first embodiment of the present invention provides an imaging method for identifying the growth region of a KDP-type crystal cone. This method performs a scattering scan of a KDP-type crystal under test within the visible light range, and directly identifies the fast-growing KDP-type crystal cone growth region based on the scanned image. The method specifically includes the following steps:

[0038] Step 1: Obtain the KDP crystal to be tested and inspect it.

[0039] In one specific embodiment, the KDP crystal to be tested is a fast-grown Type II cut KDP crystal with a crystal size of 30 mm × 30 mm × 10 mm. The inspection criteria for the KDP crystal to be tested in this embodiment are: the KDP crystal to be tested has undergone the processing steps of cutting, orientation, and polishing, and has no obvious surface defects such as scratches, and no obvious growth defects within the crystal.

[0040] KDP crystals include potassium dihydrogen phosphate and its isotope compound deuterated potassium dihydrogen phosphate crystals, ammonium dihydrogen phosphate and its isotope compound deuterated ammonium dihydrogen phosphate crystals.

[0041] Step 2: Build an imaging and discrimination system and use it to image the KDP crystal to obtain a scattered light image of the KDP crystal. The KDP crystal to be tested is placed in the imaging and discrimination system. The scattered laser is incident obliquely on the surface of the KDP crystal to be tested. The crystal is moved horizontally, and the CCD camera matrix captures the scattered light image in real time.

[0042] Step 2.1: Build an imaging discrimination system.

[0043] In a specific embodiment, Figure 1As shown, the imaging discrimination system of the imaging discrimination method includes a laser light source 1, a lens 2, a displacement platform 3, a CCD camera 4 and a computer 5. The displacement platform 3 is used to place the KDP crystal to be tested. The laser beam generated by the laser light source 1 becomes a linear light source through the lens and is obliquely incident on the surface of the displacement platform 3. The CCD camera matrix lens is above the displacement platform and is used to capture reflected light; the CCD camera matrix lens is focused on the surface of the KDP crystal to be tested, and the transmitted light is scattered by the KDP crystal to be tested and then captured by the CCD camera matrix lens; the CCD camera 4 is connected to the computer 5, and the computer 5 controls the displacement platform 3 to move the KDP crystal to be tested in the horizontal direction to obtain an image in real time.

[0044] Step 2.2: Place the KDP crystal to be tested on the displacement platform, and allow the scattered laser to be incident obliquely on the surface of the KDP crystal to be tested.

[0045] In a specific embodiment, the angle between the laser light source 1 and the plane of the displacement platform 3 is 45°, and the CCD camera matrix lens is placed perpendicular to the displacement platform 3, so that the 45° reflected light enters the lens.

[0046] The laser light source 1 is a visible light laser light source, which emits continuous laser light, and the laser energy fluctuation is ≤1%, wherein the continuous laser wavelength is 380nm-780nm. Preferably, the continuous laser wavelength in this embodiment is 532nm. This solution has strong applicability, and any wavelength within the visible light range (380nm-780nm) can be used. This embodiment selects a 532nm wavelength laser with relatively mature manufacturing technology, and the laser cost is low and safer. The 532nm visible light band continuous light emitted by the laser light source 1 is obliquely incident on the surface of the displacement platform after passing through the lens 2, and the laser energy fluctuation is <1%. The angle between the laser and the surface of the KDP crystal to be measured is 30°-60°. Preferably, this embodiment uses a laser with an angle of 45° between the laser and the surface of the KDP crystal to be measured. The laser spot is shaped into a linear shape by the lens, and the linear laser coincides with the edge of the crystal. The coincidence of the linear laser and the edge of the crystal can ensure the integrity of the image and make it easier to achieve positioning. In this embodiment, the lens 2 is a Powell prism with a focal length of 10 cm, and the movement accuracy of the two-dimensional displacement platform in the X and Y directions is 100 μm.

[0047] Step 2.3: The CCD camera matrix lens is focused on the surface of the KDP crystal to be tested.

[0048] In a specific embodiment, the CCD camera matrix lens is placed perpendicular to the displacement platform 3, and the CCD camera matrix lens is focused on the surface of the KDP crystal to be measured; the scattered light is captured by the CCD camera matrix, and the focusing field length of the CCD camera matrix lens is less than the linear laser length.

[0049] Step 2.4: The scattered light is captured by the CCD camera matrix and the image is read by the software in the computer 5.

[0050] Step 2.5: Move the KDP crystal to be tested horizontally at a constant speed, with an amplitude slightly smaller than the CCD camera's field of view. In this embodiment, the movement distance is 0.8 field lengths, allowing for 10% edge overlap, which ensures a more accurate demarcation line. The CCD camera matrix then captures the scattered light image in real time, which can be used to determine the KDP crystal's growth region.

[0051] In a specific embodiment, in a constructed imaging discrimination system, the device is kept at a fixed angle and the KDP crystal to be measured is moved in a plane. Specifically, the crystal to be measured is moved in the X direction or Y direction perpendicular to the plane of the incident light, so that the measuring light and the CCD camera matrix continuously scan the surface of the KDP crystal to be measured. The above process is repeated to measure the scattering image of the corresponding position of the crystal, and the KDP crystal scattering image is spliced ​​by a computer based on the coordinates of the corresponding measurement points moved in the X and Y directions.

[0052] This embodiment starts from the edge of the crystal and moves in the X direction in sequence, each time moving 0.8 CCD field lengths. After the same line of movement is completed, it returns to the origin position, moves in the Y direction by 0.8 CCD field lengths, and continues to move in the X direction. Repeat this step to obtain all images, and use computer software to splice the obtained images. The edge overlap is 10%, and a complete image can be obtained. Figure 2 As shown in the figure, the crystal growth area of ​​all measurement areas of the KDP crystal to be measured can be determined through the image.

[0053] Step 3: Determine the crystal growth area at all measurement areas of the KDP crystal to be tested by using the scattered light image.

[0054] In a specific embodiment, Figure 2 As shown, there are two areas of different brightness in the scattered light image, and there is an obvious dividing line between the two areas. The area with higher brightness is the area with more obvious scattered light, which is the cylindrical growth area of ​​the KDP crystal to be tested; the area with darker brightness has less obvious scattered light, which belongs to the conical growth area of ​​the KDP crystal to be tested; the dividing line located in the middle of the crystal belongs to the cone-column junction of the KDP crystal to be tested.

[0055] Example 2:

[0056] Embodiment 2 of the present invention provides an imaging discrimination system for the imaging discrimination method of the cone growth region of the KDP crystal described in embodiment 1, comprising a laser light source, a lens, a displacement platform, a CCD camera, and a computer. The displacement platform is used to place the KDP crystal to be tested. The laser beam generated by the laser light source is transformed into a linear light source by the lens and is obliquely incident on the surface of the displacement platform. The angle between the laser light source and the plane of the displacement platform is 45°. The CCD camera matrix lens is above the displacement platform and is used to capture reflected light. Specifically, the CCD camera matrix lens is placed perpendicular to the displacement platform so that the 45° reflected light enters the lens. The CCD camera matrix lens is focused on the surface of the KDP crystal to be tested. After the transmitted light is scattered by the KDP crystal to be tested, it is captured by the CCD camera matrix lens. The CCD camera is connected to the computer, and the computer controls the displacement platform to move the KDP crystal to be tested in the horizontal direction to acquire images in real time.

[0057] The laser light source selected in this embodiment emits continuous laser light with a laser energy fluctuation of ≤1%. The continuous laser wavelength is 380nm-780nm, preferably 532nm. The lens is a Powell prism with a focal length of 10cm. The two-dimensional displacement platform has an X and Y movement accuracy of 100μm. The crystal is a fast-grown Type II cut KDP crystal with a crystal size of 30mm×30mm×10mm. It has been cut, oriented, and polished to ensure that there are no obvious surface defects such as scratches, and no obvious growth defects within the crystal.

[0058] The steps involved in the above embodiment 2 correspond to those in the method embodiment 1. For the specific implementation method, please refer to the relevant description part of the embodiment 1.

[0059] Although the above describes the specific embodiments of the present invention in conjunction with the accompanying drawings, it is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art on the basis of the technical solution of the present invention without any creative work are still within the scope of protection of the present invention.

Claims

1. A method for imaging and distinguishing the growth region of a KDP-type crystal cone, characterized in that: The following steps are involved: Obtaining a KDP crystal to be tested and inspecting the KDP crystal to be tested; An imaging discrimination system is constructed and used to image the KDP crystal to be tested, thereby obtaining a scattered light image of the KDP crystal. The KDP crystal to be tested is placed in the imaging discrimination system, and scattered laser light is incident obliquely on the surface of the KDP crystal to be tested. The crystal is moved in the horizontal direction, and the scattered light image is captured in real time by a CCD camera matrix. The crystal growth area of ​​all measurement areas of the KDP crystal to be tested is determined by using the scattered light image. The specific steps are as follows: There are two areas of different brightness in the scattered light image, and there is a clear dividing line between the two areas. The area with higher brightness is the area with more obvious scattered light, which is the cylindrical growth area of ​​the KDP crystal to be tested; the area with darker brightness has less obvious scattered light, which belongs to the conical growth area of ​​the KDP crystal to be tested; the dividing line located in the middle of the crystal belongs to the cone-column junction of the KDP crystal to be tested.

2. The imaging identification method of the KDP-type crystal cone growth region according to claim 1, characterized in that: The KDP crystal to be tested is a fast-growing type II cut KDP crystal.

3. The imaging identification method of the KDP-type crystal cone growth region according to claim 1, characterized in that: KDP crystals include potassium dihydrogen phosphate and its isotope compound deuterated potassium dihydrogen phosphate crystals, ammonium dihydrogen phosphate and its isotope compound deuterated ammonium dihydrogen phosphate crystals.

4. The imaging identification method of the KDP-type crystal cone growth region according to claim 1, characterized in that: The inspection standards for the KDP crystals to be tested are: The KDP crystals to be tested have been cut, oriented, and polished, and have no obvious processing defects on the surface, and no obvious growth defects inside the crystals.

5. The imaging identification method of the KDP-type crystal cone growth region according to claim 1, characterized in that: The specific steps of using the imaging discrimination system to image the KDP crystal to be tested are as follows: The KDP crystal to be tested is placed on a displacement platform, and the scattered laser is incident obliquely on the surface of the KDP crystal to be tested; The CCD camera matrix lens is focused on the surface of the KDP crystal to be tested; The scattered light is captured by the CCD camera matrix and the image is read by the software in the computer.

6. The imaging identification method of the KDP-type crystal cone growth region according to claim 5, characterized in that: The laser light source emits continuous laser, and the laser energy fluctuation is ≤1%, wherein the continuous laser wavelength is 380nm-780nm.

7. The imaging identification method of the KDP-type crystal cone growth region according to claim 6, characterized in that: The angle between the laser and the surface of the KDP crystal to be measured is 30°-60°, the laser spot is shaped into a line by the lens, and the linear laser coincides with the edge of the crystal.

8. The imaging identification method of the KDP crystal cone growth region according to claim 7, characterized in that: The focusing field length of the CCD camera matrix lens is smaller than the length of the linear laser.

9. An imaging discrimination system for the imaging discrimination method of the KDP crystal cone growth region according to any one of claims 1 to 8, comprising a laser light source, a lens, a displacement platform, a CCD camera and a computer, wherein the displacement platform is used to place the KDP crystal to be tested, the laser beam generated by the laser light source becomes a linear light source through the lens and is obliquely incident on the surface of the displacement platform, the CCD camera matrix lens is above the displacement platform and is used to capture reflected light; the CCD camera matrix lens is focused on the surface of the KDP crystal to be tested, and the transmitted light is scattered by the KDP crystal to be tested and then captured by the CCD camera matrix lens; the CCD camera is connected to the computer, and the computer controls the displacement platform to move the KDP crystal to be tested in the horizontal direction to acquire an image in real time.

Images