CN112828481B

CN112828481B - Method and system for processing and reading two-dimensional code in transparent material

Info

Publication number: CN112828481B
Application number: CN202011635542.8A
Authority: CN
Inventors: 王雪辉; 曹思洋; 陈航; 王建刚
Original assignee: Wuhan Huagong Laser Engineering Co Ltd
Current assignee: Wuhan Huagong Laser Engineering Co Ltd
Priority date: 2020-12-31
Filing date: 2020-12-31
Publication date: 2022-05-03
Anticipated expiration: 2040-12-31
Also published as: CN112828481A; WO2022141808A1

Abstract

The invention discloses a method for processing and reading a two-dimensional code in a transparent material, wherein a shielding layer is arranged on one surface of the transparent material, and the method comprises the following steps: focusing an ultrafast laser pulse to a preset position in a transparent material, controlling the laser pulse to process point by point from a starting point according to a processing track at a set repetition frequency and power, and jumping to the next point after each point is processed for a set time length until all points in the whole two-dimensional code area are processed, thereby completing a single processing period; the two-dimensional code area is irradiated downwards from the oblique upper side through the illumination light source, the mirror reflection or the diffuse reflection of the shielding layer at the bottom of the transparent material to light is utilized, a target image is obtained through the CCD visual system, and the two-dimensional code is read through the contrast differentiation. The invention also discloses a system for processing and reading the two-dimensional code in the transparent material. The invention can prepare the two-dimensional code in the transparent material with a single side being shielded and realize accurate reading, and is beneficial to the engineering application of the two-dimensional code assigning and reading.

Description

Method and system for processing and reading two-dimensional code in transparent material

Technical Field

The invention belongs to the technical field of ultrafast laser transparent material inner carving, and particularly relates to a method and a system for processing and reading a two-dimensional code in a transparent material.

Background

Two-dimensional codes are a coding mode which is developed abnormally and rapidly in recent years, can express more information and data types compared with traditional bar codes, and have the advantages of wide coding range, strong fault-tolerant capability, high decoding reliability and the like, so that the two-dimensional codes are widely applied to modern production life. Particularly, with the rapid development of the internet, the two-dimensional code is fully applied as an online and offline link, and great convenience is brought to the life of people.

At present, most of two-dimensional code assigning technologies adopt ink-jet printing, but the two-dimensional code generated by the method has limited storage time, can be influenced by the environment to cause the failure of the two-dimensional code, and is not beneficial to long-time storage. In recent years, as laser marking technology has matured, marking areas have the advantages of being permanent and non-erasable, and the marking areas are free of environmental pollution, a method for realizing code assignment by laser marking is becoming popular in the market. However, the two-dimensional code obtained by the method has the defects of large size, poor hiding performance and low anti-counterfeiting degree.

Due to the ultrahigh peak power of the ultrafast laser, the ultrafast laser can generate nonlinear interaction with the transparent material at a focus, and has the characteristic of selective processing, so that the ultrafast laser can act inside the transparent material, and a formed modified area has good hiding property. And because the ultrafast laser acts on the multiphoton threshold effect of the transparent medium and the Gaussian characteristic of the laser beam, the processed structure size can break through the diffraction limit, thereby being capable of carrying out high-precision engraving and realizing the two-dimensional code assigning effect of micro size. The Chinese patent application publication No. CN110626086A discloses a method for engraving a micro two-dimensional code in a glass laser in 2019, 12 and 31, and the obtained two-dimensional code can obtain a complete and clear pattern through the amplification of a microscope. However, the method does not provide a complete two-dimensional code reading mode, and the method aims at the condition that the upper surface and the lower surface of the transparent glass are not shielded, but in practical application, the bottom surfaces of a lot of transparent materials needing to be endowed with codes are shielded, so that the development of a whole set of code-endowing code reading technology close to practical engineering application is necessary.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention provides a method and a system for processing and reading a two-dimensional code in a transparent material, wherein the method can be used for preparing the two-dimensional code in the transparent material with a single-side shielding and realizing accurate reading, and is favorable for the engineering application of the two-dimensional code assigning and reading.

According to an aspect of the present specification, there is provided a method of processing and reading a two-dimensional code inside a transparent material having a shielding layer on one side thereof, the method including:

processing the two-dimension code: focusing an ultrafast laser pulse to a preset position in a transparent material, controlling the laser pulse to process point by point from a starting point according to a processing track at a set repetition frequency and power, and jumping to the next point after each point is processed for a set time length until all points in the whole two-dimensional code area are processed, thereby completing a single processing period;

reading the two-dimensional code: the two-dimensional code area is irradiated downwards from the oblique upper side through the illumination light source, the mirror reflection or the diffuse reflection of the shielding layer at the bottom of the transparent material to light is utilized, a target image is obtained through the CCD visual system, and the two-dimensional code is read through the contrast differentiation.

Specifically, the ultrafast laser is a picosecond or femtosecond laser.

Specifically, a shielding layer is present on one side of the transparent material, and the shielding layer may be made of ink, plastic, metal, or the like, which is not limited in this respect, as the case may be.

Further, after a single processing period is completed, the laser pulse can be controlled to jump to the starting point again, and multiple times of processing can be realized according to the previous set cycle. The number of machining may be one or more, and the present invention is not limited thereto, as the case may be.

As a further technical solution, the method for processing the two-dimensional code further includes: the preset position is 0.1-1mm below the surface of the transparent material; the set repetition frequency range is 310-2000 kHz; the set power range is 0.2-1.9W; the set time period ranges from 0.02 to 0.5 ms.

As a further technical solution, the method for reading a two-dimensional code further includes: for the condition that the shielding layer is arranged at the bottom of the transparent material and the surface of the shielding layer is smooth, an illumination light source is adopted to enter from the upper side to the lower side, reflected light of the shielding layer at the bottom enters a CCD (charge coupled device) vision system arranged right above through refraction of the two-dimensional code area, and the two-dimensional code is read through contrast differentiation.

As a further technical solution, the method for reading a two-dimensional code further includes: for the situation that the shielding layer is arranged at the bottom of the transparent material and the surface of the shielding layer is rough, the area is irradiated from the oblique upper side of the two-dimensional code area by adopting an illumination light source, a shadow area is formed on the shielding layer at the bottom when light passes through the two-dimensional code area, a CCD (charge coupled device) vision system is arranged above the shadow area to scan the shadow part, and the two-dimensional code is read by distinguishing the contrast. The reason for this is: the shielding layer with the rough surface can only generate diffuse reflection to light, and insufficient light enters a CCD (charge coupled device) vision system through the two-dimensional code area, so that the contrast of the acquired image is extremely low, and reading cannot be realized.

Under the condition that the surface of the shielding layer is smooth, the code reading mode is that the code points are light-transmitting, and no light enters the CCD in other areas, so that the background of the collected image is black, the code points are bright points, and the larger contrast is easily obtained. Under the condition that the surface of the shielding layer is rough, the code reading mode is that the CCD collects light which penetrates through the code points and light which does not penetrate through the code points, and if a certain contrast is obtained, the absorption rate of the laser action area to the light and the absorption rate of the laser non-action area need to have a certain difference, otherwise, the problem that the contrast of the collected image is low and the collected image cannot be read exists.

The laser is focused in the transparent material, energy is deposited at a focus due to a nonlinear effect, and the material at the focus gradually increases in temperature along with the increase of the deposited energy, so that the phenomena of modification, melting, ablation and the like occur. Due to the hiding and aesthetic requirements, no ablation spots and no distinct melting zones of the laser can occur within the transparent material, so that the interaction of the laser with the transparent material can only stay in the modification stage. The modified region undergoes changes in physical parameters such as refractive index and absorption due to the action of laser light, and thus, when the region is irradiated with light, the intensity of light transmitted through the laser-affected region and the peripheral region differs. In order to increase the difference as much as possible and improve the readability of the two-dimensional code, it is necessary to deposit as much laser energy as possible without creating a significant laser active area, and to achieve a greater degree of modification.

Because ultrafast laser acts on the material and can produce plasma, plasma can form shielding effect to follow-up laser to cause the phenomenon that the laser action zone develops to the laser source direction from focus department, simultaneously because heat accumulation and thermal diffusion, the laser action zone widens gradually, when the peak power density of laser drops to be not enough to the ionization material and produces plasma, the action zone of laser can fall back to focus department again, has finally produced the drop-shaped structure of falling water that the width is wide from top to bottom. The stronger the nonlinear effect, the higher the concentration of the generated plasma, the faster the speed of the laser action point developing towards the laser source, and a tail will be formed at the lower end of the laser action area, which is not favorable for the laser to be fully deposited in the material. Therefore, the laser with low single pulse energy is required to act on the transparent material, and due to the reduction of peak power, the nonlinear interaction between the laser and the transparent material can be effectively weakened, so that the phenomenon that the laser action point rises too fast is avoided, energy can be fully deposited in the material, and a laser action area with a high light absorption coefficient is obtained. In addition, the high repetition frequency and the multiple processing can further enhance the deposition of laser energy on the basis of not increasing the nonlinear effect, are beneficial to increasing the light absorption rate of a laser action area, and promote the effective reading of the two-dimensional code.

According to an aspect of the present specification, there is provided a system for processing and reading a two-dimensional code inside a transparent material having a shielding layer on one side thereof, the system including a processing device and a reading device; the processing device comprises an ultrafast laser, a beam expanding collimating lens, a light guide lens, a focusing lens, a sample stage and an industrial personal computer, wherein a laser beam emitted by the ultrafast laser is incident on the focusing lens through the beam expanding collimating lens and the light guide lens and then focused inside a transparent material on the sample stage by the focusing lens, and the industrial personal computer is respectively connected with the ultrafast laser and the sample stage and controls the ultrafast laser and the sample stage to work; the reading device comprises an illumination light source and a CCD visual system.

As a further technical scheme, the repetition frequency range of the ultrafast laser is 310-2000kHz, the power range is 0.2-1.9W, and the single-point action time range is 0.02-0.5 ms.

As a further technical scheme, for the condition that the bottom of the transparent material is provided with a shielding layer and the surface of the shielding layer is smooth, the illumination light source enters from the oblique upper side to the lower side, reflected light of the shielding layer at the bottom enters a CCD visual system arranged right above through refraction of the two-dimensional code area, and the CCD visual system acquires a target image and reads the two-dimensional code through contrast differentiation.

As a further technical scheme, for the condition that the bottom of the transparent material is provided with a shielding layer and the surface of the shielding layer is rough, the illumination light source irradiates the area from the oblique upper side of the two-dimensional code area, a shadow area is formed on the shielding layer at the bottom by light passing through the two-dimensional code area, a CCD vision system is arranged above the shadow area to scan the shadow part, and the CCD vision system acquires a target image and realizes the reading of the two-dimensional code through the contrast differentiation.

Compared with the prior art, the invention has the beneficial effects that:

(1) according to the invention, by controlling the parameters of the ultrafast laser, the laser only generates a modification effect on the material, and an obvious laser action area can not be generated, so that the two-dimensional code obtained by code-assigning processing has certain hiding property.

(2) The code reading technology provided by the invention is of a reflective type aiming at the transparent material with the shielding layer on one side, and the code reading is realized by utilizing the mirror reflection or diffuse reflection effect of the shielding layer on light, so that the code reading technology is closer to the practical engineering application compared with the existing transmission type code reading technology.

Drawings

Fig. 1 is a schematic view of a processing apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic diagram of laser active regions obtained by different processing methods according to an embodiment of the present invention.

Fig. 3 is a schematic diagram of a two-dimensional code region according to an embodiment of the invention.

Fig. 4 is a schematic view of a two-dimensional code reading apparatus under the condition that the surface of the shielding layer is smooth according to an embodiment of the invention.

Fig. 5 is a schematic view of a two-dimensional code reading device under the condition that the surface of the shielding layer is rough according to an embodiment of the invention.

In the figure: 1. an ultrafast laser; 2. a beam expanding collimating lens; 3. a light guide mirror; 4. a focusing mirror; 5. a sample; 6. a sample stage; 7. an industrial personal computer; 8. a two-dimensional code area; 9. code points; 10. a shielding layer; 11. an illumination light source; 12. a shadow region; 13. a CCD vision system.

Detailed Description

The technical solutions of the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings, and it is to be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.

In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, "above" or "below" a first feature means that the first and second features are in direct contact, or that the first and second features are not in direct contact but are in contact with each other via another feature therebetween. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. "beneath," "under" and "beneath" a first feature includes the first feature being directly beneath and obliquely beneath the second feature, or simply indicating that the first feature is at a lesser elevation than the second feature.

The invention provides a method for processing and reading a two-dimensional code in a transparent material, which is realized by adopting a system comprising a processing device and a reading device and comprises the following specific implementation steps:

firstly, as shown in fig. 1, a sample 5 is placed on a sample stage 6, a laser beam emitted by an ultrafast laser 1 passes through a beam expander 2 and a light guide lens 3 and is finally focused inside the sample 5 by a focusing lens 4, and an industrial personal computer 7 controls the ultrafast laser 1 and the sample stage 6 through electric signals so as to enable the ultrafast laser and the sample stage 6 to work cooperatively.

In order to ensure that the laser does not form a significant active region in the transparent material and to ensure that the laser deposits enough energy in the material to make the region have a large absorption rate of light, the laser should modify the material with low power. If the single pulse energy is too large, the nonlinear effect of the laser and the material is strong, a large amount of plasma is generated in a short time and rapidly develops along the optical axis to the light source, and therefore a tail region is formed at the lower part of the laser action region (fig. 2(a)), which is not favorable for the deposition of laser energy. Under the condition, the laser repetition frequency is increased, on one hand, the single pulse energy is reduced, the nonlinear effect is weakened, on the other hand, the pulse number in unit time is increased, and the heat accumulation is increased. The tail-like region of the lasing region gradually shortens to disappear, the upper droplet-like structure also gradually transitions to an elliptical shape and increases in width (fig. 2(b) - (c)), and the aspect ratio of the entire lasing region gradually decreases, indicating that the energy of the laser deposition gradually increases. Preferably, the laser power should be in the range of 0.2-1.9W and the laser repetition frequency should be in the range of 310-2000 kHz.

The laser is focused on a certain point in the transparent material to interact with the point to generate a code point 9 of the two-dimensional code, and preferably, the duration of the single-point action of the laser is within the range of 0.02-0.5ms in order to ensure that the laser does not generate an obvious action trace in the material. After the processing is finished, the laser jumps to the next point along the preset path to continue the processing until the complete two-dimensional code area 8 is realized, as shown in fig. 3, and a processing cycle is completed. According to actual requirements, the laser can jump back to the starting point again for multiple times of processing, which is not limited in the present invention, as the case may be.

Two cases are distinguished when reading two-dimensional codes:

in the first case, as shown in fig. 4, the bottom masking layer 10 of the sample 5 has a smooth surface and is specular. The illumination light source 11 is used for incidence from the upper side to the lower side, reflected light passes through the two-dimensional code area 8 and is finally collected by the CCD visual system 13 right above, and accurate reading of the two-dimensional code can be achieved through contrast analysis.

In the second case, as shown in fig. 5, the bottom surface masking layer 10 of the sample 5 is rough and diffusely reflective. The two-dimensional code area 8 is irradiated from the oblique upper side by the illumination light source 11, a shadow area 12 is generated on the bottom shielding layer 10, the CCD vision system 13 is adopted to collect and analyze the contrast of the shadow area 12, and finally the two-dimensional code is accurately read.

Example 1

The embodiment adopts ultraviolet picosecond laser to code the glass with the bottom coated with the smooth ink layer, the power is 0.2W, the repetition frequency is 1MHz, the laser action time is 0.06ms, and the processing times are 1 time. The length of the laser action area is 24.25 μm, the width of the laser action area is 5.45 μm, and the length-width ratio is 4.45. Under the irradiation of the reflected light of the side light source, clear images can be obtained through a CCD vision system, and accurate reading is achieved.

Example 2

The embodiment adopts ultraviolet picosecond laser to code glass with a rough ink layer coated on the bottom, the power is 0.6W, the repetition frequency is 1MHz, the laser action time is 0.1ms, and the processing times are 3 times. The length of the laser action area is 54.84 μm, the width of the laser action area is 10.33 μm, and the aspect ratio is 5.309. A side light source is adopted to irradiate the two-dimensional code area, and a clear image can be obtained by acquiring and analyzing a shadow area through a CCD (charge coupled device) vision system, so that accurate reading is obtained.

Example 3

In the embodiment, ultraviolet picosecond laser is adopted to code glass with the bottom coated with a rough plastic layer, the power is 0.65W, the repetition frequency is 1MHz, the laser action time is 0.1ms, and the processing times are 2 times. The length of the laser action region is 45.38 μm, the width of the laser action region is 10.19 μm, and the aspect ratio is 4.453. A side light source is adopted to irradiate the two-dimensional code area, and a clear image can be obtained by acquiring and analyzing a shadow area through a CCD (charge coupled device) vision system, so that accurate reading is obtained.

In the description herein, references to the description of the terms "one embodiment," "certain embodiments," "an illustrative embodiment," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for processing and reading a two-dimensional code inside a transparent material, wherein one side of the transparent material is provided with a shielding layer, the method comprising:

reading the two-dimensional code: irradiating a two-dimensional code area from the upper oblique direction to the lower direction through an illumination light source, utilizing the mirror reflection or diffuse reflection of a shielding layer at the bottom of a transparent material to light, acquiring a target image through a CCD (charge coupled device) vision system, and realizing the reading of the two-dimensional code through the contrast differentiation;

for the condition that the shielding layer is arranged at the bottom of the transparent material and the surface of the shielding layer is smooth, an illumination light source is adopted to enter from the upper side to the lower side, reflected light of the shielding layer at the bottom enters a CCD (charge coupled device) vision system arranged right above through refraction of the two-dimensional code area, and the two-dimensional code is read through contrast differentiation;

for the situation that the shielding layer is arranged at the bottom of the transparent material and the surface of the shielding layer is rough, the area is irradiated from the oblique upper side of the two-dimensional code area by adopting an illumination light source, a shadow area is formed on the shielding layer at the bottom when light passes through the two-dimensional code area, a CCD (charge coupled device) vision system is arranged above the shadow area to scan the shadow part, and the two-dimensional code is read by distinguishing the contrast.

2. The method of processing and reading a two-dimensional code inside a transparent material according to claim 1, wherein the method of processing a two-dimensional code further comprises: the preset position is 0.1-1mm below the surface of the transparent material; the set repetition frequency range is 310-2000 kHz; the set power range is 0.2-1.9W; the set time period ranges from 0.02 to 0.5 ms.

3. The method of claim 1, wherein the number of times of processing is one or more.

4. A system for processing and reading a two-dimensional code in a transparent material is characterized in that one side of the transparent material is provided with a shielding layer, and the system comprises a processing device and a reading device; the processing device comprises an ultrafast laser, a beam expanding collimating lens, a light guide lens, a focusing lens, a sample stage and an industrial personal computer, wherein a laser beam emitted by the ultrafast laser is incident on the focusing lens through the beam expanding collimating lens and the light guide lens and then focused inside a transparent material on the sample stage by the focusing lens, and the industrial personal computer is respectively connected with the ultrafast laser and the sample stage and controls the ultrafast laser and the sample stage to work; the reading device comprises an illumination light source and a CCD visual system; for the condition that the shielding layer is arranged at the bottom of the transparent material and the surface of the shielding layer is smooth, the illumination light source enters from the oblique upper side to the lower side, reflected light of the shielding layer at the bottom enters a CCD visual system arranged right above through refraction of the two-dimensional code area, and the CCD visual system acquires a target image and reads the two-dimensional code through contrast differentiation; for the condition that the bottom of the transparent material is provided with the shielding layer and the surface of the shielding layer is rough, the illumination light source irradiates the area from the oblique upper side of the two-dimensional code area, light passes through the two-dimensional code area to form a shadow area on the shielding layer at the bottom, a CCD vision system is arranged above the shadow area to scan the shadow part, and the CCD vision system acquires a target image and reads the two-dimensional code through contrast differentiation.

5. The system as claimed in claim 4, wherein the ultrafast laser has a repetition frequency of 310-2000kHz, a power range of 0.2-1.9W, and a single point action time of 0.02-0.5 ms.