CN115639664A - Laser uniform illumination system and light guide pipe - Google Patents

Abstract

The laser uniform illumination system and the light guide pipe provided by the embodiment of the application adopt the light guide pipe with the isosceles trapezoid cross section, the light guide pipe at least comprises one sub light guide pipe with the isosceles trapezoid cross section, all the sub light guide pipes are sequentially overlapped together from top to bottom, the top edge of the sub light guide pipe cross section positioned at the top is the top edge of the light guide pipe cross section, and the bottom edge of the sub light guide pipe cross section positioned at the bottom is the bottom edge of the light guide pipe cross section; between any two adjacent sub-light pipes, the bottom side of the cross section of the sub-light pipe positioned above is attached to the top side of the cross section of the sub-light pipe positioned below, and the lengths of the sub-light pipes are consistent. The application provides a laser uniform lighting system sets up the cross section of light pipe into isosceles trapezoid, utilizes imaging lens's imaging principle, and the height ratio of the light intensity is close to one on the control surveyed sample surface, improves the homogeneity of light intensity distribution.

Description

Laser uniform lighting system, light pipe

technical field

The present application relates to the technical field of laser illumination and imaging, in particular to a laser uniform illumination system and a light pipe.

Background technique

A high-throughput optical fluorescence biochemical application system usually includes a detection module, a large-area sample to be tested, and a laser illumination system. The detection module can be a high-resolution optical microscope, and the area of the sample to be tested can be greater than 10mmx10mm. High power laser light source. After the laser light source is transmitted through the light guide tube and imaging lens, it is irradiated on the surface of the measured sample, and the height ratio of the light intensity distribution formed on the surface of the measured sample (that is, the ratio of the highest light intensity/lowest light intensity, HLR) is closer to First, the better the optical imaging quality, the more conducive to microscope observation.

Since the optical system of the microscope is usually along the normal direction of the area where the surface of the measured sample is located, when the laser is incident through the light guide, it must be obliquely incident on the measured sample in a direction deviated from the normal. Sometimes in order to avoid being blocked by the objective lens, it will be A relatively large angle of oblique incidence leads to an oblique light intensity distribution on the surface of the tested sample. As the area of the tested sample increases, the ratio of light intensity distribution on the surface of the tested sample will become more and more high.

If the high-low ratio of light intensity distribution on the surface of the tested sample is high, it means that the light intensity distribution is uneven, which makes the difference in the laser energy received by the tested sample will be very large, which will affect the consistency of the optical signal generated by the subsequent tested sample. Not conducive to the detection of the microscope.

Contents of the invention

In order to solve the technical problem of uneven light intensity distribution formed on the surface of the sample to be tested because the surface of the sample to be tested is not perpendicular to the optical path, the application discloses a uniform laser illumination system and a light guide through the following embodiments.

The first aspect of the present application discloses a uniform laser illumination system, including: a laser, a light guide, an imaging lens, and a sample to be measured; the surface of the sample to be tested;

The cross-section of the light pipe is an isosceles trapezoid, the distance between the bottom edge of the cross-section of the light pipe and the optical axis is a first height value, and the distance between the top edge of the cross-section of the light pipe and the optical axis is The distance between the second height value, the height of the cross-section of the light pipe is the sum of the first height value and the second height value, and the optical axis is the center of the imaging lens and the measured sample A straight line formed by connecting the centers of the irradiated areas on the surface;

The light pipe includes at least one sub-light pipe, and the cross-section of the sub-light pipe is an isosceles trapezoid;

If the light pipe includes more than two sub-light pipes, all the sub-light pipes are stacked up and down in sequence, and the top edge of the cross-section of the sub-light pipe at the top is the cross-section of the light pipe. The top edge of the section, the bottom edge of the sub-light pipe cross-section located at the bottom is the bottom edge of the light pipe cross-section;

Between any two adjacent sub-light pipes, the bottom edge of the cross-section of the upper sub-light pipe is in contact with the top edge of the cross-section of the lower sub-light pipe, and the lengths are consistent.

Optionally, the length of the bottom side of the cross-section of the light guide is the ratio of the width of the irradiated area on the surface of the measured sample to the first vertical axis magnification; the first vertical axis magnification is the distal distance value The ratio between the light guide distance value, the far end distance value is the farthest distance value between the imaging lens and the irradiated area on the surface of the measured sample, and the light guide distance value is the imaging lens The distance value from the light-emitting end face of the light guide;

The length of the top edge of the cross-section of the light guide is the ratio of the width of the irradiated area on the surface of the measured sample to the second vertical axis magnification; the second vertical axis magnification is the ratio of the proximal distance value to the guide The ratio between the light distance values, the near-end distance value is the shortest distance value between the imaging lens and the irradiated area on the surface of the measured sample.

所述第二高度值为

其中，B为所述被测样品表面的长度，α为所述被测样品表面的中心法线与所述光轴之间的夹角，β₁为所述第一垂轴放大率，β₂为所述第二垂轴放大率。Optionally, the first height value is

The second height value is

Wherein, B is the length of the measured sample surface, α is the angle between the center normal of the measured sample surface and the optical axis, β ₁ is the first vertical axis magnification, β ₂ is the magnification of the second vertical axis.

Optionally, the angle between the center normal of the surface of the measured sample and the optical axis is between (30°, 90°).

Optionally, the light-emitting end surface of the light guide is an inclined plane, and the lower edge of the light-emitting end surface protrudes more than the upper edge;

The angle between the light exit end surface of the light guide and the longitudinal vertical plane depends on the object-image relationship of the imaging lens, the focal length of the imaging lens, the first height value, the second height value, the The far distance value is set with the near distance value.

Optionally, the light guide distance value includes a near light guide distance value and a far light guide distance value; the near light guide distance value is the distance between the lower edge of the light exit end surface of the light guide pipe and the imaging lens value, the value of the remote light guide distance is the distance value between the edge of the light exit end face of the light guide and the imaging lens.

Optionally, the first vertical axis magnification is the ratio between the distance value at the far end and the distance value near the light guide;

The second vertical axis magnification is a ratio between the proximal distance value and the far light guide distance value.

Optionally, if the light pipe includes N sub-light pipes, the height of the cross-section of each sub-light pipe is:

Among them, h ₁ , h ₂ , ..., h _N-1 and h _N are the heights of the N sub-light pipes from bottom to top, b is the height of the cross-section of the light pipe, and a ₁ represents the height of the light guide The bottom edge of the tube cross-section, a ₂ represents the top edge of the light guide cross-section.

The second aspect of the present application discloses a light guide pipe, which is the light guide pipe in the laser uniform illumination system described in the first aspect of the present application.

Optionally, anti-reflection coatings are provided on both the light incident end surface and the light exit end surface of the light guide pipe.

The laser uniform illumination system and the light guide provided in the embodiment of the present application adopt a light guide with an isosceles trapezoidal cross section, and the light guide includes at least one sub-light guide with an isosceles trapezoidal cross section, because the measured The imaging of the sample surface is an inverted image, so the top edge of the light guide will be imaged under the surface of the sample under test, and the bottom edge of the light guide will be imaged above the surface of the sample under test. According to the tilted orientation, if the lower side of the measured sample surface is closer to the imaging lens, the image distance is shorter, and the magnification is smaller, the top side of the light guide is longer than the bottom side, so that the light imaged to the lower side of the tested sample surface Higher intensity; if the upper edge of the measured sample surface is closer to the imaging lens, the image distance is short, and the magnification is small, the bottom edge of the light guide is longer than the top edge, so that the light intensity imaged to the upper edge of the measured sample surface higher. Combining the imaging principle of the imaging lens and the size setting of the isosceles trapezoidal cross-section of the light guide, this application can effectively improve the uniformity of light intensity distribution on the surface of the tested sample, and control the ratio of light intensity on the surface of the tested sample to be close to In one, improve the uniformity of light intensity distribution.

Description of drawings

Fig. 1 is a schematic diagram of the measured sample surface perpendicular to the projection light path in the laser illumination system;

Fig. 2 is the schematic diagram that the measured sample surface is not perpendicular to the projection light path in the laser illumination system;

Fig. 3 is a schematic structural diagram of a light guide pipe in the uniform laser illumination system disclosed in the embodiment of the present application;

Fig. 4 is a schematic diagram of the image projection optical path of the laser uniform illumination system disclosed in the embodiment of the present application;

Fig. 5 is a schematic diagram of the magnification effect of the light guide tube and the imaging lens in the image projection optical path of the laser uniform illumination system disclosed in the embodiment of the present application;

Fig. 6 is a schematic structural diagram of a light guide composed of a plurality of sub-light guides in the uniform laser illumination system disclosed in the embodiment of the present application;

Fig. 7 is a schematic diagram of the structure of the image projection optical path of the laser uniform illumination system disclosed in the embodiment of the present application, where the light-emitting end surface of the light guide is an inclined plane;

Fig. 8 is a schematic structural diagram of two sub-light guides forming a light guide in the uniform laser illumination system disclosed in the embodiment of the present application;

FIG. 9 is a schematic structural view of three sub-light guides forming a light guide in the uniform laser illumination system disclosed in the embodiment of the present application.

Detailed ways

In order to facilitate the implementation of the technical solution of the application, some concepts involved in the application are firstly described below.

In the existing standard image projection optical path, the laser light emitted by the laser 101 is guided by the light guide 102 and the imaging lens 103 to form an optical path 105 and projected onto the surface of the measured sample 104 . 1, the surface of the sample 104 to be tested is perpendicular to the optical path 105. In this case, the cross section of the light guide 102 can actually be a square with a side length of 1 mm, and the length of the light guide 102 can actually be 50 mm. Since the light pipe with a square light cross-section itself has a homogenizing effect, the height ratio of the light intensity distribution of the image projected on the surface of the sample 104 to be tested is close to one. In this application, the high to low ratio (high to low ratio, HLR) refers to the ratio between the highest light intensity and the lowest light intensity of the irradiated area on the surface of the sample to be tested.

It should be noted that, in this application, the optical path is also referred to as the optical axis, which is a straight line formed by connecting the center of the imaging lens and the center of the irradiated area on the surface of the sample to be measured.

When the surface of the tested sample 104 is no longer perpendicular to the optical path 105, but inclined at an angle α, as shown in Figure 2, the image projected on the tested sample surface will be distorted and deformed, forming an inclined light intensity distribution The height ratio of the light intensity distribution will be greater than 1, and with the increase of the value of α or the increase of the surface area of the measured sample, the value of the height ratio of the light intensity distribution will also become larger and larger.

In order to solve the technical problem of uneven light intensity distribution formed on the surface of the sample to be tested because the surface of the sample to be tested is not perpendicular to the optical path, the application discloses a uniform laser illumination system and a light guide through the following embodiments.

The first embodiment of the present application discloses a uniform laser illumination system, the composition of which is basically the same as that shown in Figure 2, including: a laser 101, a light guide 102, an imaging lens 103, and a sample to be tested 104; The laser light emitted by the laser 101 passes through the light pipe 102 and the imaging lens 103 in sequence, and irradiates the surface of the sample 104 to be measured.

Compared with the traditional laser lighting system, the uniform laser lighting system provided in this embodiment is mainly different in the structure of the light guide pipe. Referring to Fig. 3, the cross-section of the light pipe in this embodiment is isosceles trapezoidal, the size of the light pipe is set according to various parameters in the lighting system, different application scenarios require different lighting areas, therefore, the The size of the required light pipe is also different, depending on the requirements and the magnification ratio of the projection light path. In order to correct the distortion of the irradiated area on the surface of the tested sample, the size and height of the upper and lower sides of the cross-section of the light guide are determined according to the simulation results, which will be described in detail below.

It should be noted that, in the existing general definition, the two parallel sides of an isosceles trapezoid are called the bases of the trapezoid, the longer base is called the lower base, and the shorter base is called the upper base. It is not applicable in this application, because the description of the cross-sectional size of the light pipe in this application will have limitations in orientation and length. If the longer bottom is called the lower bottom one-sidedly, it will lead to confusion. In order to To prevent ambiguity, in this application, once the position of the light guide in the lighting system is defined, the upper side is called the top side and the lower side is called the bottom side for the cross-section of the light guide. In combination with Figure 3, the side where ① is located is the top side, and the side where ② is located is the bottom side.

The light guide includes two ports, namely the laser input port and the laser output port. In this embodiment, the end face corresponding to the laser input end is called the light input end face, and the end face corresponding to the laser output end is called the light output end face. Referring to FIG. 4 , the distance between the light emitting end surface of the light pipe 102 and the center of the imaging lens 103 is L. The distance between the center of the imaging lens 103 and the center of the irradiated area on the surface of the sample to be tested is L', where L' is much larger than L.

The surface of the sample to be tested is a rectangular surface with dimensions A*B, width A, and length B. In some implementations, the surface of the sample to be tested may be a square surface, ie A=B. The irradiated area on the surface of the sample to be tested can refer to the projected rectangular area shown on the far right in Figure 4, with a size of A*C, a width of A, and a length of C. Based on the projection principle, C=B*cos(α ).

In practical applications, the imaging lens 103 is a positive lens with a focal length of F', and the imaging lens can be a single lens or a combination of multiple lenses. The sizes of L', L and F' are all set by technicians according to actual needs.

Fig. 5 is a schematic diagram of the position between the light guide, imaging lens and the sample to be tested in this embodiment. The lenses are enlarged renderings. The isosceles trapezoid between the light guide 102 and the imaging lens 103 is not a physical component, but a cross section of the light guide 102 .

In Fig. 5, the length of the bottom edge of the cross-section of the light pipe is a ₁ , the length of the top edge is a ₂ , and the distance between the bottom edge of the cross-section of the light pipe and the optical axis is a first height value b ₁ , the light guide The distance between the top edge of the cross-section of the tube and the optical axis is a second height value b ₂ , and the height of the cross-section of the light pipe is the sum of the first height value b ₁ and the second height value b ₂ , the optical axis is a straight line formed by connecting the center of the imaging lens and the center of the irradiated area on the surface of the measured sample.

There are many ways to couple the laser. The key point of the coupling is to focus the laser spot to the end face of the complete light pipe, and the incident angle should satisfy the total reflection inside the light pipe. For example, semiconductor laser diodes are collimated and focused coupled into light guides. For fiber output lasers, if the end face of the fiber can be contained by the end face of the light guide, and the divergence angle of the laser output from the fiber is appropriate (satisfies the total reflection inside the light guide), it can be directly connected to the light guide. The method of coupling the laser to the light guide is similar to the method of coupling into the optical fiber. There should be many papers or patent introductions, and the coupling method will not be discussed here.

Referring to FIG. 3 and FIG. 6 , the light guide includes at least one sub-light guide, and the cross-section of the sub-light guide is an isosceles trapezoid. If the light pipe includes more than two sub-light pipes, all the sub-light pipes are stacked up and down in sequence, and the top edge of the cross-section of the sub-light pipe at the top is the cross-section of the light pipe. The top edge of the section, the bottom edge of the sub-light pipe cross-section located at the bottom is the bottom edge of the light pipe cross-section.

Between any two adjacent sub-light pipes, the bottom edge of the cross-section of the upper sub-light pipe is in contact with the top edge of the cross-section of the lower sub-light pipe, and the lengths are consistent.

The left side of Fig. 6 shows the structure diagram of the light guide tube composed of two sub-light guide tubes, and the right side shows the structure diagram of the light guide tube composed of three sub-light guide tubes. When the light pipe includes more than two sub-light pipes, all the sub-light pipes are stacked up and down in sequence to form the whole light pipe, and the sum of the heights of all the sub-light pipes is equal to the height of the whole light pipe.

The laser uniform illumination system provided in the first embodiment of the present application adopts a light pipe with an isosceles trapezoidal cross section, and the light pipe includes at least one sub-light pipe with an isosceles trapezoidal cross section, because the surface of the sample to be measured The imaging of the light guide is an inverted image, so the top edge of the light guide will be imaged under the surface of the sample to be tested, and the bottom edge of the light guide will be imaged above the surface of the sample under test. According to the tilted orientation, if the lower side of the measured sample surface is closer to the imaging lens, the image distance is shorter, and the magnification is smaller, the top side of the light guide is longer than the bottom side, so that the light imaged to the lower side of the tested sample surface Higher intensity; if the upper edge of the measured sample surface is closer to the imaging lens, the image distance is short, and the magnification is small, the bottom edge of the light guide is longer than the top edge, so that the light intensity imaged to the upper edge of the measured sample surface higher. Combining the imaging principle of the imaging lens and the size setting of the isosceles trapezoidal cross-section of the light guide, this application can effectively improve the uniformity of light intensity distribution on the surface of the tested sample, and control the ratio of light intensity on the surface of the tested sample to be close to In one, improve the uniformity of light intensity distribution.

In conjunction with Fig. 7, since the surface of the sample to be tested is in an inclined state, there are different horizontal distances between the centerline of the imaging lens and the irradiated area of the surface of the sample to be tested. In this embodiment, when defining the size of the cross-section of the light pipe, The farthest horizontal distance and the shortest horizontal distance are mainly used, that is, L ₁ ' and L ₂ ' in the figure, where L ₁ ' is called the far-end distance value, and the far-end distance value is the distance between the imaging lens and the The farthest distance value between the irradiated areas on the surface of the measured sample, L ₂ ' is called the near-end distance value, and the near-end distance value is the distance between the imaging lens and the irradiated area on the surface of the tested sample closest distance value. According to Fig. 7, L, L ₁ ' and L ₂ ' satisfy the following geometric relationship:

In one implementation manner, the length a1 _of the bottom edge of the cross-section of the light guide is the ratio of the width A of the irradiated area on the surface of the sample to be measured to the _first vertical axis magnification β1. The _first vertical axis magnification β1 is the ratio between the far end distance value and the light guide distance value, and the light guide distance value is the distance value between the imaging lens and the light exit end surface of the light guide pipe.

The top edge length a2 of the cross-section of the light guide is the ratio of the width A of the irradiated area on the surface of the tested sample to the _second vertical axis magnification β2; the _second vertical axis magnification β2 is the ratio of the near _- end distance value to The ratio between the light guide distance values.

所述第二高度值为

其中，B为所述被测样品表面的长度，α为所述被测样品表面的中心法线与所述光轴之间的夹角，β₁为所述第一垂轴放大率，β₂为所述第二垂轴放大率。Further, the first height value is

The second height value is

Wherein, B is the length of the measured sample surface, α is the angle between the center normal of the measured sample surface and the optical axis, β ₁ is the first vertical axis magnification, β ₂ is the magnification of the second vertical axis.

In one implementation, referring to FIG. 5 , the light-emitting end surface of the light guide 102 is set as a vertical plane, and the uniform light effect of the trapezoidal light guide can be used to improve the energy uniformity of the irradiated area and reduce the surface area of the sample to be tested. The height ratio of light intensity distribution.

In another implementation manner, referring to FIG. 7 , the light-emitting end surface of the light guide pipe 102 is set as a slope, and the lower edge of the light-emitting end surface protrudes more than the upper edge. In this case, there is an included angle ф between the light exit end surface of the light guide and the longitudinal vertical plane, and the size of the included angle ф depends on the object-image relationship of the imaging lens, the focal length of the imaging lens, and the second A height value, the second height value, the far distance value and the near distance value are set.

In conjunction with FIG. 7 , the light guide distance value is set to include a near light guide distance value L ₁ and a far light guide distance value L ₂ ; the near light guide distance value L ₁ is the distance between the lower edge and _The distance value between the imaging lenses, the distance value L2 of the far light guide is the distance value between the edge of the light exit end surface of the light guide and the imaging lens.

The first vertical axis magnification β ₁ is a ratio between the far-end distance value L ₁ ′ and the near-light guide distance value L ₁ .

The second vertical axis magnification β ₂ is a ratio between the near-end distance value L ₂ ′ and the far-guide light distance value L ₂ .

Specifically, in combination with Figure 7, the imaging lens is regarded as a thin lens, and according to the relationship between the object and the image, it can be obtained:

The first vertical axis magnification β ₁ and the second vertical axis magnification β ₂ can be obtained by the following formula:

Through the conversion of the formula, we can get:

In this embodiment, if L ₁ ≈L ₂ , then the error caused by the difference between L ₁ and L ₂ can be ignored in the light guide. In this case, the light exit end surface of the light guide is a vertical plane.

Of course, if accurate calculation is required, the values of L ₁ and L ₂ can also be obtained according to the object-image relationship formula:

Then, calculate the angular size of ф according to the following formula:

Based on the above formula, ф is calculated, and the light-emitting end face of the light guide can be set as an inclined plane.

Referring to FIG. 7 , the angle α between the center normal of the surface of the tested sample and the optical axis is between (30°, 90°).

In practical applications, if α=90°, then the incident direction of the laser light is parallel to the surface of the tested sample, and the projected image cannot be imaged on the surface of the tested sample. If α < 30°, the pattern is distorted and the uniformity is low, and it is not worthwhile to adjust the uniformity in terms of cost. However, if the cost is not considered, in the uniform laser illumination system provided in this embodiment, the value range of α may be (0°, 90°).

Theoretically, after the light pipe is imaged onto the inclined surface of the tested sample, the highest value and the lowest value of the light intensity distribution correspond to the a ₂ side and a ₁ side of the light pipe respectively. Because the projection is an inverted image, a ₂ is projected to the lower edge of the tested sample surface, and a ₁ is projected to the upper edge of the tested sample surface.

通过合理设置导光管横截面的尺寸，便可以控制HLR接近于一，提高对被测样品表面光强分布的均匀度。Assuming that the light energy distribution on the end surface of the light pipe is absolutely uniform, that is, the energy density P is equal at the edge of a ₁ and a ₂ of the light pipe, that is, P(a ₁ )=P(a ₂ ), at this time HLR=P _max /P _min =P(a ₂ )*a ₂ /P(a ₁ )*a ₁ =a ₂ /a ₁ . In the formula, P _max and P _min are the highest light intensity and the lowest light intensity of the light guide in the imaging area on the surface of the sample under test, respectively. The HLR of a single light pipe is

By reasonably setting the size of the cross-section of the light pipe, the HLR can be controlled to be close to one, and the uniformity of the light intensity distribution on the surface of the tested sample can be improved.

可以得知a₁，a₂反比于两个垂轴放大率，也就是说照明区域的的B值越长，倾斜角α越大，会导致a₂/a₁(HLR)的值越高。According to the formula

It can be known that a ₁ and a ₂ are inversely proportional to the magnification of the two vertical axes, that is to say, the longer the B value of the illuminated area, the larger the inclination angle α, which will lead to a higher value of a ₂ /a ₁ (HLR).

When the light pipe only includes one sub-light pipe, for example, the length of the top side of the cross-section of the light pipe can be set to 1.8 mm, the length of the bottom side can be set to 1.5 mm, and the height can be set to 0.9 mm. It can be calculated that HLR=1.2, thus, the height ratio of the light intensity distribution on the surface of the tested sample is already close to one, and the uniformity of the light intensity distribution on the surface of the tested sample is improved.

When the light guide includes two sub-light guides, refer to FIG. 8, divide the light guide into two sub-light guides according to the direction b of the total height of the light guide, which are respectively sub-light guide 1 and sub-light guide 2 .

The sub-light pipe 1 and the sub-light pipe 2 will form respective imaging spots, and each sub-light pipe has its own HLR, denoted by HLR ₁ and HLR ₂ respectively. When the extreme values of the respective energy distributions of the two sub-light pipes are the same, that is, P _1max =P _2max , P _1min =P _2min , the HLR of the overall light pipe is minimum, and at this time HLR=HLR ₁ =HLR ₂ . In the formula, P _1max and P _1min , P _2max and P _2min are respectively the highest light intensity and the lowest light intensity of sub-light guide 1 and sub-light guide 2 in the irradiated area on the surface of the sample to be tested.

Assume that the light energy distribution on the end surface of the sub-light pipe 1 is absolutely uniform, and the energy density is P ₁ , and the light energy distribution on the end surface of the sub-light pipe 2 is absolutely uniform, and the energy density is P ₂ . It is assumed that the length of the top side of the sub-light pipe 1 (ie, the bottom side of the sub-light pipe 2 ) is x, and a ₁ <x<a ₂ . It can be concluded that:

From HLR ₁ =HLR ₂ , P _1max =P _2max , we can get:

优化为

被测样品表面光强分布的均匀度将得到更显著的提高。At this time the HLR value is determined by the single light pipe's

optimized for

The uniformity of light intensity distribution on the surface of the tested sample will be more significantly improved.

可以计算出子导光管1的高度h₁和子导光管2的高度h₂：according to

The height h _{1 of sub-light pipe 1} and the height h ₂ of sub-light pipe 2 can be calculated:

In this way, the end face structures of the two light pipes can be determined, and then the proportional relationship between the input energy of the two light pipes can be obtained. Let the input energy of sub-light pipe 1 and sub-light pipe 2 be W ₁ and W ₂ respectively, The end face areas are S ₁ and S ₂ respectively, which can be calculated as:

式中

In the formula

Exemplarily, the length of the top side of the cross-section of the sub-light pipe 2 can be set as 1.8 mm, the length of the bottom side can be set as 1.643 mm, and the height can be set as 0.47 mm. The length of the top side of the cross-section of the sub-light pipe 1 can be set to 1.643 mm, the length of the bottom side can be set to 1.5 mm, and the height can be set to 0.43 mm.

When the light guide includes three sub-light guides, refer to FIG. 9, divide the light guide into three sub-light guides according to the direction b of the total height of the light guide, which are respectively sub-light guide 1 and sub-light guide 2 and sub-light pipe 3.

Sub-light pipe 1 , sub-light pipe 2 and sub-light pipe 3 will form respective imaging spots, and each sub-light pipe has its own HLR, denoted by HLR ₁ , HLR ₂ , and HLR ₃ respectively. When the extreme values of the respective energy distributions of the three sub-light guides are the same, that is, P _1max =P _2max =P _3max , P _1min =P _2min =P _3min , the overall HLR is the minimum, and at this time HLR=HLR ₁ = HLR2 _{= HLR3} . In the formula, P _1max and P _1min , P _2max and P _2min , P _3max and P _3min are the highest values of sub-light pipe 1, sub-light pipe 2, and sub-light pipe 3 in the irradiated area on the surface of the sample to be tested, respectively. Light intensity and minimum light intensity.

Assuming that the light energy distribution on the end face of sub-light pipe 1 is absolutely uniform, and the energy density is P ₁ , the light energy distribution on the end face of sub-light pipe 2 is absolutely uniform, and the energy density is P ₂ , the light energy distribution on the end face of sub-light pipe 3 is absolutely Uniform, the energy density is P ₃ . Let the length of the top side of the sub-light pipe ₁ (i.e. the bottom side of the sub-light pipe 2) be x1, the length of the top side of the sub-light pipe 2 (i.e. the bottom side of the sub-light pipe 3) be _x2 , and a ₁ < x ₁ < x ₂ < a ₂ . It can be concluded that:

From HLR ₁ ＝HLR ₂ ＝HLR ₃ , P _1max ＝P _2max ＝P _3max can get:

优化为

由此可知，HLR最终结果将更接近于一。At this point the HLR value is determined by the two light guides

optimized for

It can be seen that the final result of HLR will be closer to one.

可以计算出导光管1的高度h₁、导光管2的高度h₂、导光管3的高度h₃：according to

The height h ₁ of light pipe 1, the height h ₂ of light pipe 2, and the height h ₃ of light pipe 3 can be calculated:

In this way, the end face structures of the three sub-light pipes are determined, and then the proportional relationship of the input energy of the three sub-light pipes can be obtained. The input energies of the sub-light pipe 1, the sub-light pipe 2 and the sub-light pipe 3 are respectively W ₁ , W ₂ , W ₃ , the end face areas are S ₁ , S ₂ , S ₃ respectively, and can be calculated as follows:

式中

In the formula

Exemplarily, the length of the top side of the cross-section of the sub-light pipe 3 can be set to 1.8 mm, the length of the bottom side can be set to 1.694 mm, and the height can be set to 0.318 mm. The length of the top side of the cross-section of the sub-light pipe 2 can be set to 1.694 mm, the length of the bottom side can be set to 1.594 mm, and the height can be set to 0.3 mm. The length of the top side of the cross-section of the sub-light pipe 1 can be set to 1.594 mm, the length of the bottom side can be set to 1.5 mm, and the height can be set to 0.282 mm.

The more sub-light pipes the light pipe contains, that is, the more the overall light pipe is divided, the more uniform the light intensity distribution in the imaging area will be. The number of divisions can be determined according to actual needs. The above calculation results are obtained under the assumption that the light energy distribution on the end surface of the light pipe is absolutely uniform. In fact, although the homogenization properties of the light pipe itself can optimize the uniformity of light intensity distribution on the end face of the light pipe, the uniformity of energy distribution on the end face will still be affected by factors such as the nature of the actual incident light spot and the length of the light pipe. No discussion. Therefore, in practical application, it is necessary to adjust the energy ratio of the coupled laser light of each light guide according to the actual light intensity distribution on the end surface of the light guide.

基于上文论述的内容，每个所述子导光管横截面的高度为：If the light pipe includes N sub-light pipes, the HLR will be optimized as

Based on the content discussed above, the height of each sub-light pipe cross-section is:

Among them, h ₁ , h ₂ , ..., h _N-1 and h _N are the heights of the N sub-light pipes from bottom to top, b is the height of the cross-section of the light pipe, and a ₁ represents the height of the light guide The bottom edge of the tube cross-section, a ₂ represents the top edge of the light guide cross-section.

The relationship between the light pipe and the laser is optical coupling, which can be realized by some optical coupling devices, and there are many coupling methods. The laser with the right power ratio is achieved by adjusting the output power of the laser.

If the laser power coupled into the light pipe is the same, the output laser power is also the same (assuming that the internal laser loss of each light pipe is the same), the larger the cross-sectional size of the light pipe, the lower the output laser power density.

The number of sub-light pipes can be determined according to the uniformity requirement of the irradiated area. The higher the uniformity requirement, the more sub-light pipes are required. The details can be obtained from simulation calculations. When the demand for the number of sub-light pipes increases, if each sub-light pipe is coupled with a laser diode, the number of required lasers also increases accordingly. Of course, when optimizing the uniformity, the output power of the laser should be adjusted to further adjust the proportional relationship of the output power of each sub-light guide. While maintaining this power ratio relationship, the output power of each sub-light pipe is increased or decreased, which changes the brightness of the entire illuminated area.

The second embodiment of the present application provides a light guide pipe. The light guide pipe is the light guide pipe in the laser uniform illumination system described in the first embodiment of the present application. Please refer to the first embodiment for details.

The choice of light pipe material depends on the laser used, and the material is required to have high transmission and low absorption for the laser used. In some implementations, the light pipe is made of a light transmissive material, such as BK7 glass, fused silica glass, or the like.

Both the light-incident end surface and the light-exit end surface of the light guide pipe are provided with an anti-reflection film. However, in some cases, if the illumination intensity is much higher than the actual application requirements, it is not necessary to coat the AR coating.

Whether the side of the light guide is coated or not depends on whether the incident laser meets the total reflection angle. If the total reflection angle is satisfied, no coating is required, otherwise, high reflection coating is required.

For the light pipe disclosed in this embodiment, because the imaging of the surface of the measured sample is an inverted image, the top edge of the light pipe will be imaged to the lower edge of the measured sample surface, and the bottom edge of the light pipe will be imaged to the surface of the measured sample. top of the sample surface. According to the tilted orientation, if the lower side of the measured sample surface is closer to the imaging lens, the image distance is shorter, and the magnification is smaller, the top side of the light guide is longer than the bottom side, so that the light imaged to the lower side of the tested sample surface Higher intensity; if the upper edge of the measured sample surface is closer to the imaging lens, the image distance is short, and the magnification is small, the bottom edge of the light guide is longer than the top edge, so that the light intensity imaged to the upper edge of the measured sample surface higher. Combining the imaging principle of the imaging lens and the size setting of the isosceles trapezoidal cross-section of the light guide, this application can effectively improve the uniformity of light intensity distribution on the surface of the tested sample, and control the ratio of light intensity on the surface of the tested sample to be close to In one, improve the uniformity of light intensity distribution.

The similar parts between the embodiments provided in the present application can be referred to each other, and the specific implementations provided above are only a few examples under the general concept of the present application, and do not constitute a limitation of the protection scope of the present application. For those skilled in the art, any other implementations expanded based on the proposal of the present application without creative work shall fall within the scope of protection of the present application.

Claims (10)

1. A laser uniform illumination system, is characterized in that, comprises: laser device, light guide tube, imaging lens and measured sample; The laser light that described laser device sends passes through described light guide tube and described imaging lens successively, irradiates to all The surface of the sample to be tested; The cross-section of the light pipe is an isosceles trapezoid, the distance between the bottom edge of the cross-section of the light pipe and the optical axis is a first height value, and the distance between the top edge of the cross-section of the light pipe and the optical axis is The distance between the second height value, the height of the cross-section of the light pipe is the sum of the first height value and the second height value, and the optical axis is the center of the imaging lens and the measured sample A straight line formed by connecting the centers of the irradiated areas on the surface; The light pipe includes at least one sub-light pipe, and the cross-section of the sub-light pipe is an isosceles trapezoid; If the light pipe includes more than two sub-light pipes, all the sub-light pipes are stacked up and down in sequence, and the top edge of the cross-section of the sub-light pipe at the top is the cross-section of the light pipe. The top edge of the section, the bottom edge of the sub-light pipe cross-section located at the bottom is the bottom edge of the light pipe cross-section; Between any two adjacent sub-light pipes, the bottom edge of the cross-section of the upper sub-light pipe is in contact with the top edge of the cross-section of the lower sub-light pipe, and the lengths are consistent. 2. The laser uniform illumination system according to claim 1, wherein the length of the base of the light guide cross section is the ratio of the width of the irradiated area on the surface of the measured sample to the first vertical axis magnification The first vertical axis magnification is the ratio between the far-end distance value and the light guide distance value, and the far-end distance value is the farthest between the imaging lens and the irradiated area on the surface of the measured sample a distance value, the light guide distance value is the distance value between the imaging lens and the light exit end surface of the light guide pipe; The length of the top edge of the cross-section of the light guide is the ratio of the width of the irradiated area on the surface of the measured sample to the second vertical axis magnification; the second vertical axis magnification is the ratio of the proximal distance value to the guide The ratio between the light distance values, the near-end distance value is the shortest distance value between the imaging lens and the irradiated area on the surface of the measured sample. 3. The laser uniform illumination system according to claim 2, wherein the first height value is

The second height value is

Wherein, B is the length of the measured sample surface, α is the angle between the center normal of the measured sample surface and the optical axis, β ₁ is the first vertical axis magnification, β ₂ is the magnification of the second vertical axis. 4. The laser uniform illumination system according to claim 3, wherein the angle between the center normal of the surface of the measured sample and the optical axis is between (30°, 90°). 5. The laser uniform illumination system according to claim 2, wherein the light-emitting end surface of the light guide pipe is an inclined plane, and the lower edge of the light-emitting end surface is more prominent than the upper edge; The angle between the light exit end surface of the light guide and the longitudinal vertical plane depends on the object-image relationship of the imaging lens, the focal length of the imaging lens, the first height value, the second height value, the The far distance value is set with the near distance value. 6. The laser uniform lighting system according to claim 5, wherein the light guide distance value includes a near light guide distance value and a far light guide distance value; the near light guide distance value is the light guide distance value of the light guide pipe The distance value between the lower edge of the light exit end surface of the light pipe and the imaging lens, and the far light guide distance value is the distance value between the edge of the light exit end surface of the light pipe and the imaging lens. 7. The laser uniform illumination system according to claim 6, wherein the first vertical axis magnification is the ratio between the far end distance value and the near light guide distance value; The second vertical axis magnification is a ratio between the proximal distance value and the far light guide distance value. 8. The laser uniform illumination system according to claim 1 or 2, wherein if the light guide comprises N sub-light guides, the height of each sub-light guide cross-section is:

Among them, h ₁ , h ₂ , ..., h _N-1 and h _N are the heights of the N sub-light pipes from bottom to top, b is the height of the cross-section of the light pipe, and a ₁ represents the height of the light guide The bottom edge of the tube cross-section, a ₂ represents the top edge of the light guide cross-section. 9. A light guide, characterized in that the light guide is the light guide in the laser uniform illumination system according to any one of claims 1-8. 10 . The light pipe according to claim 9 , wherein anti-reflection coatings are provided on both the light incident end surface and the light exit end surface of the light guide pipe. 11 .

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