阅读说明：本技术 能调节光斑直径的光学系统、方法及激光成像装置 (Optical system and method capable of adjusting diameter of light spot and laser imaging device ) 是由 陈乃奇 张向非 于 2021-09-10 设计创作，主要内容包括：本发明公开了能调节光斑直径的光学系统,光学系统包括：在光轴上依次设置的环形光生成模块,成像透镜以及聚焦平面；环形光生成模块发出中空环形光束,在成像透镜上形成环形光,环形光经成像透镜透射后,在聚焦平面上形成衍射图案；定义发光光源的波长为λ,成像透镜的焦距为f,成像透镜的外直径为a,环形光的内直径为b,b=k×a,k∈(0,1),为可以变化的系数值,发光光源在聚焦平面上得到的衍射图案圆心的圆形亮斑的半径的值为：,n为随k增大而减小的第二变量值。本发明还公开了利用光学系统调节光斑直径的方法及包括该光学系统的激光成像装置。本发明能够调小光斑直径,提高成像分辨率,且能降低成像透镜的制造工艺难度。(The invention discloses an optical system capable of adjusting the diameter of a light spot, which comprises: the annular light generation module, the imaging lens and the focusing plane are sequentially arranged on the optical axis; the annular light generation module emits a hollow annular light beam to form annular light on the imaging lens, and the annular light is transmitted by the imaging lens to form a diffraction pattern on the focusing plane; defining the wavelength of a luminous source as lambda, the focal length of an imaging lens as f, the outer diameter of the imaging lens as a, the inner diameter of annular light as b, b = k × a, k ∈ (0,1), and the radius of a circular bright spot at the center of a diffraction pattern obtained by the luminous source on a focusing plane is variable The values of (A) are: and n is a second variable value that decreases as k increases. The invention also discloses a method for adjusting the diameter of the light spot by using the optical systemAnd a laser imaging apparatus including the optical system. The invention can reduce the diameter of the light spot, improve the imaging resolution and reduce the manufacturing process difficulty of the imaging lens.)

1. Can adjust optical system of facula diameter, its characterized in that: the optical system includes: the annular light generation module, the imaging lens and the focusing plane are sequentially arranged on the optical axis; the annular light generation module emits a hollow annular light beam to form annular light on the imaging lens, and the annular light is transmitted by the imaging lens to form a diffraction pattern on the focusing plane;

wherein the wavelength of the hollow annular light beam is λ, the focal length of the imaging lens is f, the outer diameter of the imaging lens is a, the inner diameter of the annular light beam is b, b = ka, k belongs to (0,1), the value of b is adjustable, k is a first variable value which is increased along with the increase of b, the radius of a circular bright spot at the center of the diffraction pattern is larger, and n is a second variable value which is decreased along with the increase of k; the portion within the diameter b on the imaging lens is a spherical lens region, and the portion between the diameter b and the diameter a of the imaging lens is an aspherical lens region.

2. The optical system of claim 1, wherein: the annular light generation module is an annular light emitting module which emits the hollow annular light beam; the size of the annular light emitting area of the annular light emitting module can be adjusted, so that the b value can be adjusted.

3. The optical system of claim 1, wherein the annular light generating module is composed of a point light source and a circular light blocking sheet disposed between the point light source and the imaging lens, and the conical light beam emitted from the point light source is blocked by the circular light blocking sheet to form the annular light on the imaging lens;

the circular light blocking sheet can move back and forth on the optical axis and/or the outer diameter of the circular light blocking sheet can be adjusted, so that the b value can be adjusted.

4. The optical system according to any one of claims 1 to 3, wherein: k =0.25, n = 0.58.

5. The optical system according to any one of claims 1 to 3, wherein: k =0.5 and n = 0.51.

6. The optical system according to any one of claims 1 to 3, wherein: k =0.75, n = 0.42.

7. A method of adjusting a spot diameter using the optical system according to any one of claims 1 to 3, characterized in that: the method comprises the following steps:

step 1: an annular light generation module, an imaging lens and a focusing plane are sequentially arranged on an optical axis;

step 2: a hollow annular light beam emitted by the annular light generation module forms a diffraction pattern on the focusing plane after being transmitted by the imaging lens;

and step 3: according to the formulaAnd reducing n to reduce the radius r of the circular bright spot positioned at the center of the diffraction pattern.

8. The method of claim 7, wherein: when the annular light generation module is an annular light emitting module, the annular light emitting module emits the hollow annular light beam, and the value b is increased by enlarging the annular light emitting area of the annular light emitting module, so that k is increased, n is decreased, and the radius r is decreased.

9. The method of claim 7, wherein: when the annular light generation module is composed of a point light source and a circular light blocking sheet arranged on a light path between the point light source and the imaging lens, the value b is increased by moving the circular light blocking sheet towards the imaging lens and/or increasing the outer diameter of the circular light blocking sheet, so that k is increased, n is decreased, and the radius r is decreased.

10. A laser imaging apparatus, characterized in that: the laser imaging apparatus comprising the optical system according to any one of claims 1 to 3.

Technical Field

The invention belongs to the field of optics, and particularly relates to an optical system and method capable of adjusting the diameter of a light spot and a laser imaging device.

Background

Referring to fig. 1, light emitted from a light source 10 is collimated by a collimating lens 20, then emitted to a focusing lens 30 in parallel, focused by the focusing lens 30, and then converged on an imaging surface 40 to form a light spot with a diameter of h. In order to reduce the value of the spot diameter, i.e., to make the value of the spot diameter h smaller, it is a common practice in the prior art to insert an annular diaphragm 50 having an adjustable inner diameter d on the optical path between the collimator lens 20 and the focusing lens 30. The size of the spot diameter h is changed by adjusting the size of the inner diameter d of the annular diaphragm sheet 50. However, in fact, the spot diameter h can be adjusted only large, not small, no matter how large the inner diameter d of the annular diaphragm 50 is. This greatly restricts the development of industries such as PCB (printed circuit board), laser lithography, and lithography machines. For the field of PCB boards, the smaller the diameter of a light spot is, the smaller the focusing area on the PCB is, the more things can be printed on the PCB board by laser, and the higher the printing precision is; for the photoetching machine, the smaller the light spot is, the higher the photoetching precision is.

Disclosure of Invention

The invention provides an optical system capable of adjusting the diameter of a light spot, and aims to solve the problem that the diameter of the light spot cannot be adjusted to be small so that the resolution of an image cannot be improved.

The scheme of the invention is as follows:

an optical system capable of adjusting a spot diameter, comprising: the annular light generation module, the imaging lens and the focusing plane are sequentially arranged on the optical axis; the annular light generation module emits a hollow annular light beam to form annular light on the imaging lens, and the annular light is transmitted by the imaging lens to form a diffraction pattern on the focusing plane;

the wavelength of the hollow annular light beam is f, the focal length of the imaging lens is f, the outer diameter of the imaging lens is a, the inner diameter of the annular light is b, b = k × a, k ∈ (0,1), the value of b is adjustable, k is a first variable value which is increased along with the increase of b, and the inner radius of the bright ring at the innermost side of the concentric bright band is equal to the inner radius of the bright ring at the innermost side of the concentric bright bandN is a second variable value which decreases as k increases; the portion within the diameter b on the imaging lens is a spherical lens region, and the portion between the diameter b and the diameter a of the imaging lens is an aspherical lens region.

Furthermore, the annular light generation module is an annular light emitting module which emits a hollow annular light beam; the size of the annular light emitting area of the annular light emitting module can be adjusted, so that the b value can be adjusted.

Furthermore, the annular light generation module consists of a point light source and a circular light blocking sheet arranged between the point light source and the imaging lens, and after a conical light beam emitted by the point light source is blocked by the circular light blocking sheet, annular light is formed on the imaging lens; the circular light blocking sheet can move back and forth on the optical axis and/or the outer diameter of the circular light blocking sheet can be adjusted, so that the b value can be adjusted.

Further, k =0.25, n = 0.58.

Further, k =0.5, n = 0.51.

Further, k =0.75, n = 0.42.

The invention also discloses a method for adjusting the diameter of the light spot by using the optical system, which comprises the following steps:

step 1: an annular light generation module, an imaging lens and a focusing plane are sequentially arranged on an optical axis;

step 2: a hollow annular light beam emitted by the annular light generation module is transmitted by the imaging lens, and then a diffraction pattern is formed on a focusing plane;

and step 3: according to the formulaAnd reducing n to reduce the radius r of the circular bright spot at the center of the diffraction pattern.

Further, when the annular light generation module is an annular light emitting module, the annular light emitting module emits a hollow annular light beam, and the value b is increased by enlarging an annular light emitting area of the annular light emitting module, so that k is increased, and n is decreased to decrease r.

Further, when the annular light generation module is a point light source and a circular light blocking sheet is arranged on a light path between the point light source and the imaging lens, the value of b is increased by moving the circular light blocking sheet towards the imaging lens and/or increasing the outer diameter of the circular light blocking sheet, so that k is increased, n is decreased, and r is decreased.

The invention also discloses a laser imaging device which comprises the optical system capable of reducing the diameter of the light spot.

The optical system capable of reducing the diameter of the light spot disclosed by the invention has the following beneficial technical effects:

1. the annular light generation module, the imaging lens and the focusing plane are sequentially arranged on the optical axis, so that the annular light generation module emits a hollow annular light beam, the hollow annular light beam forms annular light on the imaging lens, and the annular light is transmitted through the imaging lens to form a diffraction pattern on the focusing plane. By increasing the inner diameter b of the ring light, and thus k, since n decreases with increasing k, according to the formulaSince the outer diameter a of the imaging lens cannot be adjusted without limitation, the wavelength λ of the hollow annular beam and the focal length of the imaging lens are set to be largeUnder the condition of constant value, the radius r of the round bright spot positioned at the center of the diffraction pattern can be reduced by reducing the value of n so as to realize the purposes of reducing the diameter of the light spot and improving the imaging resolution. That is to say, by increasing the inner diameter b of the annular light, the purposes of reducing the diameter of the light spot and improving the imaging resolution ratio are achieved. To increase the inner diameter b of the annular light, the following technical means can be adopted: (1) when the annular light generation module is an annular light emitting module, the inner diameter of the hollow annular light beam is increased, and the inner diameter b of the annular light formed by the hollow annular light beam incident on the imaging lens is increased; (2) when the annular light generation module is a point light source and a circular light blocking sheet arranged on a light path between the point light source and the imaging lens, the purpose of increasing b can be achieved by increasing the diameter c of the circular light blocking sheet or/and increasing the distance L from the circular light blocking sheet to the imaging lens.

2. The technical proposal can reduce the radius of the round bright spot at the center of the diffraction pattern circleAnd further, the resolution of the image is improved, the diameter of an imaging light spot is reduced, and the focusing precision is improved. The technology is applied to the field of laser plate making, and the image printing precision of the laser plate making is greatly improved; the PCB printing precision can be improved by applying the PCB printing technology in the PCB industry, so that more precise circuits can be printed on the same PCB, and the utilization rate of the PCB is improved. For other industries, such as laser surgery, as the spot size becomes smaller, it can be used for more demanding minimally invasive surgery. For example, in the laser welding and cutting industry, the welding seam becomes thinner due to the fact that the light spot becomes smaller, and the laser welding and cutting method is suitable for welding of precise instruments. Of course, these applications are merely exemplary and not limiting herein;

3. when the imaging lens is manufactured, only the part between the diameter b and the diameter a of the imaging lens is required to be designed into the aspheric lens, the inner side of the diameter b of the imaging lens is not penetrated by light beams, the imaging lens is not required to be designed into the aspheric lens, and only the spherical lens is required to be designed, so that the process manufacturing difficulty of the imaging lens is greatly reduced, the cost is reduced, and the optical path difference of a light path is reduced.

The method for adjusting the diameter of the light spot by using the optical system disclosed by the invention has the following beneficial effects:

according to the formulaWhen the outer diameter a of the imaging lens is not changed, the value of b is increased to increase the value of k, and the value of n is decreased with the increase of k according to the formulaThe radius r of the circular light spot positioned at the center of the diffraction pattern can be reduced, so that the image resolution of the circular light spot is improved.

The laser imaging equipment disclosed by the invention has the advantages that the optical system capable of adjusting the diameter of the light spot is contained, so that the diameter of the light spot can be reduced, and the resolution of the image is improved.

Drawings

FIG. 1 is a schematic diagram of an optical path structure of a light-emitting source for imaging in an optical path;

FIG. 2 is a prior art optical path diagram of an annular diaphragm 50 inserted into the optical path to reduce the diameter h of the light spot;

FIG. 3 is a schematic diagram of the optical path structure of the present invention;

FIG. 4 is a diagram illustrating an embodiment of an optical path structure according to the present invention;

FIG. 5 is a diagram of another embodiment of the optical path structure of the present invention;

FIG. 6 is a schematic diagram of the interval between diameter b and diameter a of the imaging lens 60 of FIG. 3;

FIG. 7 is a schematic diagram of a diffraction pattern of light formed on the focal plane 40 by the annular light generating module 11 of FIG. 3;

FIG. 8 is a photograph of a circle of bright spots at the center of a diffraction pattern obtained by adjusting the apparatus;

FIG. 9 is a schematic view of a hollow annular beam;

fig. 10 is a schematic diagram of a ring-shaped light-emitting source composed of a plurality of light-emitting units 80.

The names and serial numbers corresponding to the components in the figure are respectively: the light source device comprises a light emitting source 10, an annular light generating module 11, an annular light emitting module 12, a point light source 13, a circular light blocking sheet 14, a collimating mirror 20, a focusing lens 30, a focusing plane 40, an annular diaphragm sheet 50, an imaging lens 60, a circular bright spot 70 positioned at the center of a diffraction pattern, and a light emitting unit 80.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious 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 given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, fig. 1 is a schematic diagram of an optical path structure of a light-emitting source for imaging in an optical path, including: the light source 10, the collimator lens 20, the focusing lens 30 and the focusing plane 40 are arranged in sequence on the light path. The light emitted from the light source 10 is collimated by the collimating mirror 20 and then emitted in parallel, and is focused on the focusing plane 40 by the focusing lens 30 to form a light spot with a diameter h. For many industries, such as the laser lithography industry, medical equipment, PCB board industry, and lithography machine field, it is desirable that the smaller the spot diameter the better, and the smaller the spot diameter h, the higher the imaging resolution and the higher the imaging accuracy. Referring to fig. 2, in order to reduce the spot diameter h, currently, a measure is taken to insert an annular diaphragm 50 with an adjustable inner diameter d between the collimator lens 20 and the focusing lens 30. It is desirable to reduce the spot diameter h by adjusting the size of the inner diameter d of the annular diaphragm 50. However, in fact, no matter how large the inner diameter d of the annular diaphragm 50 is, the spot diameter h can only be adjusted to be large, but cannot be adjusted to be small, and the intended purpose of people cannot be achieved.

Referring to fig. 3, the present invention discloses an optical system capable of adjusting a spot diameter, including an annular light generating module 11, an imaging lens 60, and a focusing plane 40, which are sequentially disposed on a light path. The plurality of light rays 50 emitted by the annular light generating module 11 form a hollow annular light beam. The hollow annular light beam forms annular light on the imaging lens 60, and the annular light is transmitted through the imaging lens 60 to form a diffraction pattern on the focusing plane 40, and the schematic diagram of the diffraction pattern is shown in fig. 7. Defining the wavelength of the hollow annular light beam as f, the focal length of the imaging lens 60 as f, the outer diameter of the imaging lens 60 as a, the inner diameter of the annular light as b, b = k × a, b ∈ (0,1), and k is a first variable value that increases as b increases. Radius of the circular bright spot 70 at the center of the diffraction patternAnd n is a second variable value that decreases as k increases. Referring to fig. 6, a portion within diameter b on the imaging lens 60 is a spherical lens region, and a portion between diameter b and diameter a of the imaging lens 60 is an aspherical lens region. According to the formulaIt will be appreciated that to reduce r, the inner radius r can be reduced by reducing n when λ, a, f are constant. Since k increases, n decreases and k is the ratio of b to a. Thus, when b is increased, r decreases. Instant messengerThe purpose of reducing the radius r can be achieved by increasing b, and the diameter of an imaging light spot can be reduced. The diameter of the imaging spot is generally referred to as the diameter 2r of the circular bright spot 70 at the center of the diffraction pattern shown in fig. 7. The imaging light spot diameter can be adjusted to be small, so that the image resolution is greatly improved.

The hollow ring beam as referred to in the present application, see fig. 9, fig. 9 is a schematic view of a hollow ring beam, wherein within the cone between diameter a and diameter b, several luminescent beams are spread, whereas within the black area within diameter b, no luminescent beam is present.

Example 1

Referring to fig. 4, fig. 4 is a diagram of an embodiment of a schematic diagram of an optical path structure of the present invention, that is, the annular light generating module is an annular light emitting module 12, and the annular light emitting module 12 emits a hollow annular light beam. As one example, the ring light-emitting module 12 may be a ring light-emitting source composed of a plurality of light-emitting units 80 as shown in fig. 10, and the ring light-emitting source emits a hollow ring light beam. The hollow annular beam is incident on the imaging lens 60 to form annular light. It can be understood that, in this embodiment, the size of the annular light emitting area of the annular light emitting module can be adjusted, so that the value b can be adjusted, and the purpose that r can be adjusted to be small is achieved.

Example 2

In this embodiment, the annular light generating module is composed of the point light source 13 in fig. 5 and the circular light blocking sheet 14 disposed between the point light source 13 and the imaging lens 60, and it can be understood that the conical light beam emitted by the point light source 13 is blocked by the circular light blocking sheet 14 to form annular light on the imaging lens 60. Due to the existence of the circular light blocking sheet 14, the peripheral part of the conical light beam emitted by the point light source 13 can be incident to the imaging lens 60, and after the conical light beam is transmitted and focused by the imaging lens 60, the conical light beam is focused and imaged on the focusing plane 40. The central part of the conical beam emitted from the point light source 13 cannot pass through the imaging lens 60 and is focused on the focusing plane 40 because it is blocked by the circular light-blocking sheet 14. After being blocked by the circular light-blocking sheet 14, the conical light beam emitted from the point light source 13 forms a diffraction pattern of light on the focusing plane 40 as shown in fig. 7. Fig. 7 is a schematic diagram of the diffraction pattern of light, and a physical diagram of the circular bright spot 70 located at the center of the diffraction pattern in fig. 7 is shown in fig. 8, and it can be seen from fig. 8 that the diameter of the obtained circular bright spot is reduced to 0.48 μm by using the device. Namely, the circular focusing light spot can be adjusted to be 0.48 microns by the device. In the light-emitting energy distribution, the energy distributed on the circular bright spots 70 is the largest and accounts for about 86% of the energy emitted by the point light source 13, and the energy gradually decreases outwards along with the continuous expansion of the outer diameter of the concentric circles. In the laser direct imaging field, energy on the circular bright spot 70 is used, and therefore, the smaller the radius r of the circular bright spot 70 is, the higher the imaging accuracy is.

In this embodiment, the circular light-blocking sheet 14 can move back and forth on the optical axis, and the size of the outer diameter c of the circular light-blocking sheet 14 can be adjusted. The purpose of b adjustment can be achieved by moving the circular light-blocking sheet 14 back and forth on the optical axis and/or adjusting the outer diameter c of the circular light-blocking sheet 14. Specifically, referring to fig. 5, according to the foregoing description, in order to achieve the purpose of decreasing r, it is necessary to increase the value of b, and it can be understood that the purpose of increasing the value of b can be achieved by increasing the distance L between the circular light-blocking sheet 14 and the imaging lens 60, that is, by moving the circular light-blocking sheet 14 toward the light-emitting source 10, and/or by increasing the diameter of the circular light-blocking sheet 14.

The adjusting of the spot diameter according to the present invention mainly means reducing the radius r of the circular bright spot 70 located at the center of the diffraction pattern as shown in fig. 7.

For the laser plate making industry, the medical equipment field, the PCB industry and the photoetching machine field, the smaller r is better, and the higher the imaging precision is.

How the value of r is calculated is described below.

Referring to FIGS. 3 and 7, the wavelength of the hollow annular beam is defined asThe focal length of the imaging lens 60 is f, the outer diameter of the imaging lens is a, and the inner diameter of the hollow ring-shaped light beam forming the ring-shaped light on the imaging lens 60 is b, it is understood that the value of b does not exceed a. Define b = k × a, a ∈ (0,1), k is followed byb is increased by a first variable value, and the radius of the circular bright spot at the center of the diffraction pattern obtained by the light source 10 on the focusing plane 40 is:. n is a second variable value that decreases as k increases.

The derivation process of (1) is as follows:

the circular ring diffraction satisfies the equation:

;

order toWherein t is a constant, and wherein,

；

to obtain。

Table 1 exemplarily lists that k takes different values, and the corresponding value of n.

Table 1: correspondence table of n and k

As can be seen from the above table, n decreases as k becomes larger. Therefore, to reduce r, according to the formulaThis can be achieved by: since n is a second variable value which becomes smaller as k becomes larger, the value of k needs to be increased to decrease the value of n,i.e. the ratio of b to a needs to be increased. Therefore, if the value a is constant, the object of reducing the circular bright spot diameter 2r can be achieved by increasing the value b.

Referring to fig. 3 and 7, since only the annular portion between the diameter b and the diameter a on the imaging lens 60 is effectively used, that is, only the annular portion between the diameter b and the diameter a is used for the hollow annular light beam to transmit therethrough. Therefore, when the imaging lens 60 is manufactured, only the annular part between the diameter b and the diameter a needs to be designed into an aspheric lens, and the part within the diameter b needs to be designed into a spherical lens, and because the difficulty of the process for manufacturing the spherical lens is smaller than that of the process for manufacturing the aspheric lens, the imaging lens 60 only needs to design the annular part between the diameter b and the diameter a into the aspheric lens, so that the manufacturing difficulty of the imaging lens 60 is greatly reduced, and the optical path difference of the imaging lens 60 is reduced.

The invention also discloses a method for adjusting the diameter of the light spot by using the optical system, which comprises the following steps:

step 1: an annular light generation module, an imaging lens and a focusing plane are sequentially arranged on an optical axis;

step 2: a hollow annular light beam emitted by the annular light generation module is transmitted by the imaging lens, and then a diffraction pattern is formed on a focusing plane;

and step 3: according to the formulaAnd reducing n to reduce the radius r of the circular bright spot at the center of the diffraction pattern.

Further, when the annular light generation module is an annular light emitting module, the annular light emitting module emits the hollow annular light beam, and the value b is increased by enlarging an annular light emitting area of the annular light emitting module, so that k is increased, n is decreased, and the radius r of the circular bright spot at the center of the diffraction pattern is decreased.

Further, when the annular light generation module is composed of a point light source and a circular light blocking sheet disposed on a light path between the point light source and the imaging lens, the value of b is increased by moving the circular light blocking sheet toward the imaging lens and/or increasing the outer diameter of the circular light blocking sheet, so that k is increased, and n is decreased to decrease r.

In steps 1-3, the order of placement of the optical elements is shown in FIG. 3. After the optical elements are placed, the optical elements are positioned to obtain bright bands of concentric circles with alternate bright and dark colors on the focusing plane according to the method shown in step 2. The purpose of decreasing r is then achieved by increasing the value of b according to the formula provided in step 3.

The method has the beneficial effects that: according to the formulaWhen the increase of the outer diameter a of the imaging lens is not considered, the value b is increased, finally n is reduced, the radius r of the circular bright spot positioned at the center of the diffraction pattern can be reduced, and therefore the resolution of laser imaging is improved.

In this application, though according to formulaThe purpose of decreasing r can be achieved by increasing a, but this method is not generally employed because the outer diameter a of the imaging lens cannot be increased without limit. The present application therefore achieves the object of improving the resolution of an image by reducing r mainly by reducing n, i.e. by increasing the value of b.

The present invention also discloses a laser imaging apparatus (not shown) including the aforementioned optical system capable of reducing the spot diameter. Because the laser imaging device comprises the optical system, the laser imaging device can improve the imaging precision of the laser imaging device, namely improve the image resolution.

Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments or portions thereof without departing from the spirit and scope of the invention.