Laser uniform illumination system, light guide tube

Abstract

The laser uniform illumination system and the light guide pipe provided by the embodiments of the present application adopt the light guide pipe with the isosceles trapezoidal cross section, and the light guide pipe at least comprises one sub light guide pipe with the isosceles trapezoidal cross section, all the sub light guide pipes are stacked together in sequence from top to bottom, the top edge of the cross section of the uppermost sub light guide pipe is the top edge of the cross section of the light guide pipe, and the bottom edge of the cross section of the lowermost sub light guide pipe is the bottom edge of the cross section of the light guide pipe; between any two adjacent sub light guide pipes, the bottom edge of the cross section of the upper sub light guide pipe is in close contact with the top edge of the cross section of the lower sub light guide pipe, and the lengths are consistent. The laser uniform illumination system provided by the present application sets the cross section of the light guide pipe as the isosceles trapezoid, utilizes the imaging principle of the imaging lens, controls the height ratio of the light intensity on the surface of the measured sample to be close to one, and improves the uniformity of the light intensity distribution.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of laser illumination imaging technology, and particularly relates to a laser uniform illumination system and a light guide pipe. BACKGROUND

[0002] A high-throughput optical fluorescence biochemical application system usually comprises a detection module, a large-area measured sample and a laser illumination system. The detection module can be a high-resolution optical microscope, the area of the measured sample can be greater than 10mmx10mm, and the laser illumination system usually adopts a high-power laser light source. After the laser light source is transmitted through the light guide pipe and the imaging lens, it is irradiated onto the surface of the measured sample. The higher the high-low ratio (i.e. the ratio of the highest light intensity to the lowest light intensity, HLR) of the light intensity distribution formed on the surface of the measured sample is, the better the optical imaging quality is, and the more conducive to the observation of the microscope.

[0003] 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 light is incident through the light guide pipe, it must be obliquely incident on the measured sample deviating from the normal direction. Sometimes, in order to avoid being blocked by the objective lens, it is obliquely incident at a relatively large angle, which results in the formation of an inclined light intensity distribution on the surface of the measured sample. With the increase of the area of the measured sample, the high-low ratio of the light intensity distribution on the surface of the measured sample will be higher and higher.

[0004] If the high-low ratio of the light intensity distribution on the surface of the measured sample is high, it means that the light intensity distribution is uneven, which makes the difference of the laser energy received by the measured sample very large, affects the consistency of the light signal generated by the measured sample subsequently, and is not conducive to the detection of the microscope. SUMMARY

[0005] In order to solve the technical problem that the light intensity distribution formed on the surface of the measured sample is uneven due to the fact that the surface of the measured sample is not perpendicular to the optical path, the present application discloses a laser uniform illumination system and a light guide pipe through the following embodiments.

[0006] The first aspect of the present application discloses a laser uniform illumination system, comprising: a laser, a light guide pipe, an imaging lens and a measured sample; the laser light emitted by the laser passes through the light guide pipe and the imaging lens in sequence, and irradiates onto the surface of the measured sample;

[0007] The cross section of the light guide pipe is isosceles trapezoidal. The bottom edge of the cross section of the light guide pipe is apart from the optical axis by a first height value, the top edge of the cross section of the light guide pipe is apart from the optical axis by a second height value, the height of the cross section of the light guide pipe is the sum of the first height value and the second height value, and the optical axis is a straight line connecting the center of the imaging lens and the center of the irradiated area of the surface of the measured sample.

[0008] The light guide tube comprises at least one sub light guide tube, and the cross section of the sub light guide tube is isosceles trapezoidal;

[0009] If the light guide tube comprises more than two sub light guide tubes, all the sub light guide tubes are stacked one above another, the top edge of the cross section of the uppermost sub light guide tube is the top edge of the cross section of the light guide tube, and the bottom edge of the cross section of the lowermost sub light guide tube is the bottom edge of the cross section of the light guide tube.

[0010] The bottom edge of the cross section of the upper sub light guide tube and the top edge of the cross section of the lower sub light guide tube between any two adjacent sub light guide tubes are consistent in length.

[0011] Optionally, the length of the bottom edge of the cross section of the light guide tube is the ratio of the width of the irradiated region of the surface of the measured sample to the first vertical magnification, the first vertical magnification is the ratio of the far-end distance value to the light guide distance value, the far-end distance value is the farthest distance value between the imaging lens and the irradiated region of the surface of the measured sample, and the light guide distance value is the distance value between the imaging lens and the light exit end surface of the light guide tube.

[0012] The length of the top edge of the cross section of the light guide tube is the ratio of the width of the irradiated region of the surface of the measured sample to the second vertical magnification, and the second vertical magnification is the ratio of the near-end distance value to the light guide distance value, and the near-end distance value is the closest distance value between the imaging lens and the irradiated region of the surface of the measured sample.

[0013] Optionally, the first height value is The second height value is Wherein, B is the length of the surface of the measured sample, a is the included angle between the central normal line of the surface of the measured sample and the optical axis, β1 is the first vertical magnification, and β2 is the second vertical magnification.

[0014] Optionally, the included angle between the central normal line of the surface of the measured sample and the optical axis is between 30° and 90°.

[0015] Optionally, the light exit end surface of the light guide tube is an inclined plane, and the lower edge of the light exit end surface protrudes more than the upper edge.

[0016] The included angle between the light exit end surface of the light guide tube and the longitudinal vertical plane is determined according to the object-image relationship of the imaging lens, the focal length of the imaging lens, the first height value, the second height value, the far-end distance value and the near-end distance value.

[0017] Optionally, the light guiding distance value includes a near light guiding distance value and a far light guiding distance value; the near light guiding distance value is the distance between the lower edge of the light emitting end face of the light guide tube and the imaging lens, and the far light guiding distance value is the distance between the upper edge of the light emitting end face of the light guide tube and the imaging lens.

[0018] Optionally, the first vertical magnification is the ratio between the far-end distance value and the near-end light guide distance value;

[0019] The second vertical magnification is the ratio between the near-end distance value and the far-end light guide distance value.

[0020] Optionally, if the light guide tube includes N sub-light guide tubes, then the height of the cross-section of each sub-light guide tube is:

[0021]

[0022] Among them, h1, h2, ..., h N-1 and h N The heights of the N sub-light guides from bottom to top are as follows: b is the height of the cross-section of the light guide, a1 represents the bottom edge of the cross-section of the light guide, and a2 represents the top edge of the cross-section of the light guide.

[0023] The second aspect of this application discloses a light guide tube, which is the light guide tube in the laser uniform illumination system described in the first aspect of this application.

[0024] Optionally, both the light-incident end face and the light-exit end face of the light guide tube are provided with anti-reflection films.

[0025] The laser uniform illumination system and light guide provided in this application embodiment employ 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 image of the sample surface being tested is inverted, the top edge of the light guide will be imaged onto the bottom edge of the sample surface, and the bottom edge of the light guide will be imaged onto the top edge of the sample surface. Depending on the tilt orientation, if the bottom edge of the sample surface is closer to the imaging lens, resulting in a shorter image distance and lower magnification, the top edge of the light guide should be longer than the bottom edge, thus increasing the light intensity imaged onto the bottom edge of the sample surface. Conversely, if the top edge of the sample surface is closer to the imaging lens, resulting in a shorter image distance and lower magnification, the bottom edge of the light guide should be longer than the top edge, thus increasing the light intensity imaged onto the top edge of the sample surface. By combining the imaging principle of the imaging lens with the size setting of the isosceles trapezoidal cross section of the light guide tube, this application can effectively improve the uniformity of light intensity distribution on the surface of the sample being tested, control the ratio of high to low light intensity on the surface of the sample being tested to be close to one, and improve the uniformity of light intensity distribution. Attached Figure Description

[0026] Figure 1This is a schematic diagram of the sample surface being perpendicular to the projected light path in a laser illumination system.

[0027] Figure 2 This is a schematic diagram showing that the surface of the sample under test in a laser illumination system is not perpendicular to the projected light path.

[0028] Figure 3 This is a schematic diagram of the structure of the light guide tube in the laser uniform illumination system disclosed in the embodiments of this application;

[0029] Figure 4 This is a schematic diagram of the image projection optical path of the laser uniform illumination system disclosed in the embodiments of this application;

[0030] Figure 5 This is a schematic diagram of the magnification effect of the light guide tube and imaging lens in the image projection optical path of the laser uniform illumination system disclosed in the embodiments of this application.

[0031] Figure 6 This is a schematic diagram of the structure of a light guide tube composed of multiple sub-light guide tubes in the laser uniform illumination system disclosed in the embodiments of this application;

[0032] Figure 7 This is a schematic diagram of the structure of the light guide tube with an inclined plane at the light-emitting end face in the image projection optical path of the laser uniform illumination system disclosed in the embodiments of this application;

[0033] Figure 8 This is a schematic diagram of the structure of a light guide tube composed of two sub-light guide tubes in the laser uniform illumination system disclosed in the embodiments of this application;

[0034] Figure 9 This is a schematic diagram of the structure of a light guide tube composed of three sub-light guide tubes in the laser uniform illumination system disclosed in the embodiments of this application. Detailed Implementation

[0035] To facilitate the explanation of the technical solution of this application, some concepts involved in this application will be explained first below.

[0036] In existing standard image projection optical paths, the laser emitted by laser 101 is guided through light guide tube 102 and imaging lens 103 to form optical path 105, which is then projected onto the surface of the sample 104 under test. See [link to relevant documentation] Figure 1 In this case, the surface of the sample 104 being tested is perpendicular to the light path 105. 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 square cross-section of the light guide itself has a uniform light distribution effect, the image projected onto the surface of the sample 104 has a high-to-low ratio of light intensity close to one. In this application, the high-to-low ratio (HLR) refers to the ratio between the highest and lowest light intensities in the irradiated area on the surface of the sample.

[0037] It should be noted that in the present application, the optical path is also referred to as the optical axis, which is a straight line connecting the center of the imaging lens and the center of the irradiated area on the surface of the measured sample.

[0038] When the surface of the measured sample 104 is no longer perpendicular to the optical path 105, but is inclined at an angle a, as shown in Figure 2 , the image projected on the surface of the measured sample will be distorted, forming an inclined light intensity distribution, so that the high-low ratio of the light intensity distribution will be greater than 1, and as the value of a increases or the area of the surface of the measured sample increases, the value of the high-low ratio of the light intensity distribution will also increase.

[0039] In order to solve the technical problem that the light intensity distribution formed on the surface of the measured sample is uneven due to the surface of the measured sample being not perpendicular to the optical path, the present application discloses a laser uniform illumination system and a light guide pipe through the following embodiments.

[0040] The first embodiment of the present application discloses a laser uniform illumination system, the structure of which is basically the same as that shown in Figure 2 , and includes a laser 101, a light guide pipe 102, an imaging lens 103, and a measured sample 104; the laser emitted by the laser 101 passes through the light guide pipe 102 and the imaging lens 103 in turn, and irradiates the surface of the measured sample 104.

[0041] The laser uniform illumination system provided by the present embodiment, compared with the traditional laser illumination system, the most important difference lies in the structure of the light guide pipe. Referring to Figure 3 , the cross section of the light guide pipe in the present embodiment is isosceles trapezoidal, and the size of the light guide pipe is set according to various parameters in the illumination system. Different application scenarios require different illumination areas, so the size of the required light guide pipe is also different, which is determined according to the requirements and the magnification of the projection light path. In order to correct the distortion of the irradiated area on the surface of the measured sample, the size of the upper and lower sides and the height of the cross section of the light guide pipe are determined according to the simulation results, which will be described in detail below.

[0042] It should be noted that in the existing general definition, the two parallel sides of the isosceles trapezoid are called the base sides of the trapezoid, and the longer one is called the lower base and the shorter one is called the upper base, which is not applicable in the present application. Because the description of the cross-sectional size of the light guide pipe in the present application will have limitations in orientation and length, if the longer base side is simply called the lower base, it will lead to ambiguity. In order to prevent ambiguity, once the position of the light guide pipe in the illumination system is defined, the side located on the top is called the top side and the side located on the bottom is called the bottom side. In combination with Figure 3 , ① the side is the top side, and ② the side is the bottom side.

[0043] The light guide pipe includes two ports, a laser incident port and a laser emission port, in this embodiment, the end face corresponding to the laser incident port is referred to as the light incident end face, and the end face corresponding to the laser emission port is referred to as the light emission end face. Referring to Figure 4 , the distance between the light emission end face of the light guide 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 region of the surface of the measured sample is L', where L' is much greater than L.

[0044] The surface of the measured sample is a rectangular surface with dimensions A*B, the width is A, and the length is B. In some implementations, the surface of the measured sample can be a square surface, that is, A=B. The irradiated region of the surface of the measured sample can be seen in Figure 4 , the rightmost projected rectangular region shown in the figure has dimensions A*C, the width is A, and the length is C. Based on the projection principle, C=B*cos(α).

[0045] In practical applications, the imaging lens 103 is a positive lens with a focal length F'. The imaging lens can be a single lens or a combination of multiple lenses. The sizes of L', L, and F' are set by the technician according to the actual needs.

[0046] Figure 5 This is a schematic diagram of the positions of the light guide pipe, imaging lens, and measured sample in this embodiment. It should be noted that in order to clearly show the positional relationship between the light guide pipe and the imaging lens, the light guide pipe and the imaging lens in the dashed box are enlarged views. The isosceles trapezoid between the light guide pipe 102 and the imaging lens 103 is not a physical component, but a cross-section of the light guide pipe 102.

[0047] Figure 5 In the figure, the length of the bottom edge of the cross-section of the light guide pipe is a1, the length of the top edge is a2, the distance between the bottom edge of the cross-section of the light guide pipe and the optical axis is a first height value b1, the distance between the top edge of the cross-section of the light guide pipe and the optical axis is a second height value b2, the height of the cross-section of the light guide pipe is the sum of the first height value b1 and the second height value b2, and the optical axis is a straight line connecting the center of the imaging lens and the center of the irradiated region of the surface of the measured sample.

[0048] There are many ways to couple the laser, the key point of coupling is to focus the laser spot to the end face of the complete light pipe, and the incident angle meets the total reflection inside the light pipe. For example, the semiconductor laser diode is coupled into the light pipe after collimation and focusing. For fiber output laser, if the end face of the fiber can be contained by the end face of the light pipe, and the laser divergence angle of the fiber output is appropriate (satisfying the total reflection inside the light pipe), the light pipe can be directly connected with the light pipe. The method of coupling laser into the light pipe is similar to the method of coupling into the fiber, and there are many papers or patents introducing the coupling method, which will not be discussed here.

[0049] In combination Figure 3 And Figure 6 The light pipe includes at least one sub-light pipe, and the cross section of the sub-light pipe is isosceles trapezoidal. If the light pipe includes more than two sub-light pipes, all the sub-light pipes are stacked one above another, the top edge of the cross section of the uppermost sub-light pipe is the top edge of the cross section of the light pipe, and the bottom edge of the cross section of the lowermost sub-light pipe is the bottom edge of the cross section of the light pipe.

[0050] Between any two adjacent sub-light pipes, the bottom edge of the cross section of the upper sub-light pipe is in line with the top edge of the cross section of the lower sub-light pipe, and the lengths are consistent.

[0051] Figure 6 The left side shows a light pipe structure diagram composed of two sub-light pipes, and the right side shows a light pipe structure diagram composed of three sub-light pipes. When the light pipe includes more than two sub-light pipes, all the sub-light pipes are stacked one above another to form the entire light pipe, and the sum of the heights of all the sub-light pipes is equal to the height of the entire light pipe.

[0052] The laser uniform illumination system provided by the first embodiment of the application adopts the light pipe with the isosceles trapezoidal cross section, and the light pipe includes at least one sub-light pipe with the isosceles trapezoidal cross section. Because the imaging of the surface of the measured sample is inverted, the top edge of the light pipe will be imaged to the lower edge of the surface of the measured sample, and the bottom edge of the light pipe will be imaged to the upper edge of the surface of the measured sample. According to the inclined direction, if the lower edge of the surface of the measured sample is closer to the imaging lens, the image distance is short, and the magnification is small, the top edge of the light pipe is longer than the bottom edge, so that the light intensity imaged to the lower edge of the surface of the measured sample is higher; if the upper edge of the surface of the measured sample is closer to the imaging lens, the image distance is short, and the magnification is small, the bottom edge of the light pipe is longer than the top edge, so that the light intensity imaged to the upper edge of the surface of the measured sample is higher. In combination with the imaging principle of the imaging lens and the size setting of the isosceles trapezoidal cross section of the light pipe, the application can effectively improve the uniformity of the light intensity distribution on the surface of the measured sample, control the height-to-low ratio of the light intensity on the surface of the measured sample to be close to one, and improve the uniformity of the light intensity distribution.

[0053] Combining Figure 7 Since the surface of the measured sample is in an inclined state, there is a different horizontal distance between the central line of the imaging lens and the irradiated area of the surface of the measured sample. In the embodiment, when the size of the cross section of the light guide pipe is defined, the farthest horizontal distance and the nearest horizontal distance, i.e. L1' and L2' in the figure, are mainly used. L1' is referred to as a far-end distance value, which is the farthest distance value between the imaging lens and the irradiated area of the surface of the measured sample. L2' is referred to as a near-end distance value, which is the nearest distance value between the imaging lens and the irradiated area of the surface of the measured sample. According to the geometry relationship of L, L1' and L2', the following relationship is satisfied: Figure 7

[0054] In an implementation, the bottom edge length a1 of the cross section of the light guide pipe is the ratio of the width A of the irradiated area of the surface of the measured sample to the first vertical magnification β1. The first vertical magnification β1 is the ratio between the far-end distance value and the light guide distance value, which is the distance value between the imaging lens and the light exit end surface of the light guide pipe.

[0055] The top edge length a2 of the cross section of the light guide pipe is the ratio of the width A of the irradiated area of the surface of the measured sample to the second vertical magnification β2. The second vertical magnification β2 is the ratio between the near-end distance value and the light guide distance value.

[0056] Further, the first height value is The second height value is Wherein, B is the length of the surface of the measured sample, α is the included angle between the central normal of the surface of the measured sample and the optical axis, β1 is the first vertical magnification, and β2 is the second vertical magnification.

[0057] In an implementation, referring to Figure 5 The light exit end surface of the light guide pipe 102 is arranged as a vertical plane. The light uniformity of the irradiated area can be improved and the high-low ratio of the light intensity distribution of the surface of the measured sample can be reduced by using the light uniformity of the trapezoidal light guide pipe.

[0058] In another implementation, referring to Figure 7 The light exit end surface of the light guide pipe 102 is arranged as an inclined plane, and the lower edge of the light exit 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 pipe and the longitudinal vertical plane, which is determined according to the object-image relationship of the imaging lens, the focal length of the imaging lens, the first height value, the second height value, the far-end distance value and the near-end distance value.

[0059] Combining Figure 7 ​The light guide distance value includes a near light guide distance value L1 and a far light guide distance value L2; the near light guide distance value L1 is a distance value between a lower edge of an out-light end surface of the light guide pipe and the imaging lens, and the far light guide distance value L2 is a distance value between an upper edge of the out-light end surface of the light guide pipe and the imaging lens.

[0060] The first vertical axis magnification β1 is a ratio between the far end distance value L1' and the near light guide distance value L1.

[0061] The second vertical axis magnification β2 is a ratio between the near end distance value L2' and the far light guide distance value L2.

[0062] Specifically, in combination with Figure 7 The imaging lens is regarded as a thin lens, and according to an object-image relationship, the following can be obtained:

[0063]

[0064] The first vertical axis magnification β1 and the second vertical axis magnification β2 can be obtained by the following formula:

[0065]

[0066] Through conversion of the formula, the following can be obtained:

[0067]

[0068] In the embodiment, if L1≈L2, the light guide pipe can ignore the error caused by L1 and L2 being different, and in this case, the out-light end surface of the light guide pipe is a vertical plane.

[0069] Of course, if accurate calculation is required, the values of L1 and L2 can also be obtained according to the object-image relationship formula:

[0070]

[0071] Then, the angle size of ф is calculated according to the following formula:

[0072]

[0073] Based on the above formula, the out-light end surface of the light guide pipe can be set to be an inclined plane after ф is calculated.

[0074] Referring to Figure 7 The size of the included angle α between the central normal of the surface of the measured sample and the optical axis is between (30°, 90°).

[0075] In practical applications, if α = 90°, the incident direction of the laser is parallel to the surface of the sample being tested, and the projected image cannot be imaged onto the sample surface. If α < 30°, the degree of pattern distortion and uniformity deterioration is relatively low, and from a cost perspective, it is not worthwhile to perform uniform adjustment. However, if cost is not a concern, the value of α in the laser uniform illumination system provided in this embodiment can be in the range of (0°, 90°).

[0076] Theoretically, after the light guide image is projected onto the tilted surface of the sample, the highest and lowest values ​​of the light intensity distribution correspond to sides a2 and a1 of the light guide, respectively. Because the projection is an inverted image, a2 is projected onto the lower edge of the sample surface, and a1 is projected onto the upper edge of the sample surface.

[0077] Assuming the light energy distribution at the end face of the light guide is absolutely uniform, that is, the energy density P is equal at the edges a1 and a2 of the light guide, i.e., P(a1) = P(a2), then HLR = P max / P min =P(a2)*a2 / P(a1)*a1=a2 / a1. Where P... max and P min These represent the highest and lowest light intensities of the light guide in the imaging region on the sample surface, respectively. The HLR of a single light guide is... By properly setting the dimensions of the light guide tube's cross-section, the HLR can be controlled to be close to one, thereby improving the uniformity of the light intensity distribution on the surface of the sample being tested.

[0078] According to the formula It can be seen that a1 and a2 are inversely proportional to the magnification of the two vertical axes. That is to say, the longer the B value of the illumination area and the larger the tilt angle α, the higher the value of a2 / a1 (HLR) will be.

[0079] When the light guide tube consists of only one sub-light guide tube, for example, the top side length of the cross-section of the light guide tube can be set to 1.8 mm, the bottom side length can be set to 1.5 mm, and the height can be set to 0.9 mm. Calculation shows that HLR = 1.2. In this way, the ratio of the height of the light intensity distribution on the surface of the sample is close to one, and the uniformity of the light intensity distribution on the surface of the sample is improved.

[0080] When the light guide tube includes two sub-light guide tubes, see [link to relevant documentation]. Figure 8 The light guide tube is divided into two sub-light guide tubes along the total height b of the light guide tube, namely sub-light guide tube 1 and sub-light guide tube 2.

[0081] Sub-light guides 1 and 2 will form their own imaging spots, and each sub-light guide has its own HLR, denoted as HLR1 and HLR2 respectively. When the extreme values ​​of the energy distributions of these two sub-light guides are the same, i.e., P... 1max =P2max , P 1min = P 2min , the HLR of the overall light guide tube is minimized, and at this time HLR = HLR1 = HLR2. In the formula, P 1max and P 1min , P 2max and P 2min are respectively the highest light intensity and the lowest light intensity in the irradiated area of the surface of the sample under test for the sub-light guide tube 1 and the sub-light guide tube 2.

[0082] Assume that the light energy distribution on the end face of the sub-light guide tube 1 is absolutely uniform, and the energy density is P1, and the light energy distribution on the end face of the sub-light guide tube 2 is absolutely uniform, and the energy density is P2. Let the length of the top side of the sub-light guide tube 1 (i.e., the bottom side of the sub-light guide tube 2) be x, and a1 < x < a2. It can be obtained that:

[0083]

[0084] From HLR1 = HLR2, P 1max = P 2max , it can be obtained that: [[ID=(28]]

[0085]

[0086] At this time, the HLR value is optimized from that of a single light guide tube to The uniformity of the light intensity distribution on the surface of the sample under test will be significantly improved.

[0087] According to The height h1 of the sub-light guide tube 1 and the height h2 of the sub-light guide tube 2 can be calculated:

[0088]

[0089] In this way, the end face structures of the two light guide tubes are determined, and then the input energy ratio relationship of the two light guide tubes can be obtained. Let the input energies of the sub-light guide tube 1 and the sub-light guide tube 2 be W1 and W2 respectively, and the end face areas be S1 and S2 respectively, and it can be calculated that:

[0090] In the formula

[0091] Exemplarily, the top side length of the cross-section of the sub-light guide tube 2 can be set to 1.8 mm, the bottom side length can be set to 1.643 mm, and the height can be set to 0.47 mm. The top side length of the cross-section of the sub-light guide tube 1 can be set to 1.643 mm, the bottom side length can be set to 1.5 mm, and the height can be set to 0.43 mm.

[0092] When the light guide tube includes three sub-light guide tubes, see Figure 9, along the total height b direction of the light guide tube, the light guide tube is divided into 3 sub-light guide tubes, namely sub-light guide tube 1, sub-light guide tube 2, and sub-light guide tube 3.

[0093] Sub-light guide tube 1, sub-light guide tube 2, and sub-light guide tube 3 will form their respective imaging light spots, and each sub-light guide tube has its own HLR, which are represented by HLR1, HLR2, and HLR3 respectively. When the extreme values of the respective energy distributions of these three sub-light guide tubes are the same, that is, P 1max = P 2max = P 3max , P 1min = P 2min = P 3min , the overall HLR is the smallest, and at this time HLR = HLR1 = HLR2 = HLR3. In the formula, P 1max and P 1min , P 2max and P 2min , P 3max and P 3min are the highest light intensity and the lowest light intensity in the irradiated area of the surface of the measured sample for sub-light guide tube 1, sub-light guide tube 2, and sub-light guide tube 3 respectively.

[0094] Assume that the light energy distribution on the end face of sub-light guide tube 1 is absolutely uniform, and the energy density is P1, the light energy distribution on the end face of sub-light guide tube 2 is absolutely uniform, and the energy density is P2, and the light energy distribution on the end face of sub-light guide tube 3 is absolutely uniform, and the energy density is P3. Let the length of the top side of sub-light guide tube 1 (i.e., the bottom side of sub-light guide tube 2) be x1, the length of the top side of sub-light guide tube 2 (i.e., the bottom side of sub-light guide tube 3) be x2, and a1 < x1 < x2 < a2. It can be obtained that:

[0095]

[0096] From HLR1 = HLR2 = HLR3, P 1max = P 2max = P 3max it can be obtained that:

[0097]

[0098] At this time, the HLR value is optimized from that of two light guide tubes to It can be seen from this that the final result of HLR will be closer to one.

[0099] According to the height h1 of light guide tube 1, the height h2 of light guide tube 2, and the height h3 of light guide tube 3 can be calculated:

[0100]

[0101] In this way, the end-face structures of the three sub-light guides are determined, and the input energy ratio of the three sub-light guides can be derived. Let the input energies of sub-light guide 1, sub-light guide 2, and sub-light guide 3 be W1, W2, and W3, respectively, and the end-face areas be S1, S2, and S3, respectively. Then, the following can be calculated:

[0102] In the formula

[0103] For example, the top edge length of the cross-section of sub-light guide tube 3 can be set to 1.8 mm, the bottom edge length can be set to 1.694 mm, and the height can be set to 0.318 mm. The top edge length of the cross-section of sub-light guide tube 2 can be set to 1.694 mm, the bottom edge length can be set to 1.594 mm, and the height can be set to 0.3 mm. The top edge length of the cross-section of sub-light guide tube 1 can be set to 1.594 mm, the bottom edge length can be set to 1.5 mm, and the height can be set to 0.282 mm.

[0104] The more sub-light guides a light guide contains, i.e., the more segments the overall light guide is divided into, the more uniform the light intensity distribution in the imaging area. The number of segments can be determined according to actual needs. The above calculation results are derived under the assumption of absolutely uniform light energy distribution at the end face of the light guide. In reality, although the homogenizing properties of the light guide itself can optimize the uniformity of light intensity distribution at the end face, the uniformity of end face energy distribution is still affected by factors such as the nature of the actual incident light spot and the length of the light guide, which will not be discussed in this application. Therefore, in practical applications, the energy ratio of the coupled laser in each light guide should be adjusted according to the actual light intensity distribution at the end face of the light guide.

[0105] If the light guide tube includes N sub-light guide tubes, then HLR will be optimized as follows: Based on the above discussion, the height of the cross-section of each sub-light guide tube is:

[0106]

[0107] Among them, h1, h2, ..., h N-1 and h N The heights of the N sub-light guides from bottom to top are as follows: b is the height of the cross-section of the light guide, a1 represents the bottom edge of the cross-section of the light guide, and a2 represents the top edge of the cross-section of the light guide.

[0108] The relationship between the light guide tube and the laser is optical coupling, which can be achieved through various optical coupling devices and can take many forms. Obtaining a laser with the appropriate power ratio is achieved by adjusting the output power of the laser.

[0109] If the laser power coupled into the light guide tube is the same, the output laser power will also be the same (assuming that the laser loss inside each light guide tube is the same). The larger the cross-sectional size of the light guide tube, the lower the output laser power density.

[0110] The number of sub-light guides can be determined based on the uniformity requirements of the irradiated area; the higher the uniformity requirement, the more sub-light guides are needed. This can be determined through simulation calculations. When the required number of sub-light guides increases, if each sub-light guide is coupled with a laser diode, the number of lasers required must also increase accordingly. Of course, optimizing uniformity involves adjusting the laser's output power, thereby adjusting the output power ratio of each sub-light guide. While maintaining this power ratio, increasing or decreasing the output power of each sub-light guide changes the brightness of the entire irradiated area.

[0111] The second embodiment of this application provides a light guide tube, which is the light guide tube in the laser uniform illumination system described in the first embodiment of this application. For details, please refer to the first embodiment.

[0112] The choice of light guide material depends on the laser used; the material must have high transmittance and low absorption for the laser. In some implementations, the light guide is made of light transmission materials, such as BK7 glass or fused silica glass.

[0113] Both the light-incident and light-exit ends of the light guide tube are coated with anti-reflection films. However, in some cases, if the illumination intensity is much higher than the actual application requirements, the anti-reflection film may not be necessary.

[0114] Whether the sides of the light guide tube are coated depends on whether the incident laser meets the total internal reflection angle. If the total internal reflection angle is met, no coating is needed; otherwise, a high-reflectivity coating is required.

[0115] The light guide disclosed in this embodiment images the sample surface invertedly. Therefore, the top edge of the light guide images the lower edge of the sample surface, and the bottom edge images the upper edge. Depending on the tilt, if the lower edge of the sample surface is closer to the imaging lens, resulting in a shorter image distance and lower magnification, the top edge of the light guide is longer than the bottom edge, resulting in higher light intensity imaged onto the lower edge of the sample surface. Conversely, if the upper edge of the sample surface is closer to the imaging lens, resulting in a shorter image distance and lower magnification, the bottom edge of the light guide is longer than the top edge, resulting in higher light intensity imaged onto the upper edge of the sample surface. By combining the imaging principle of the imaging lens with the isosceles trapezoidal cross-section of the light guide, this application effectively improves the uniformity of light intensity distribution on the sample surface, controls the ratio of high to low light intensity on the sample surface to be close to one, and enhances the uniformity of light intensity distribution.

[0116] Similar parts between the embodiments provided in this application can be referred to mutually. The specific implementation methods provided above are only a few examples under the overall concept of this application and do not constitute a limitation on the scope of protection of this application. For those skilled in the art, any other implementation methods extended from the solution of this application without creative effort shall fall within the scope of protection of this application.

Claims

1. A laser uniform illumination system, characterized in that, include: A laser, a light guide tube, an imaging lens, and a sample under test; the laser emitted by the laser passes sequentially through the light guide tube and the imaging lens and illuminates the surface of the sample under test. The cross-section of the light guide tube is an isosceles trapezoid. The distance between the bottom edge of the cross-section of the light guide tube and the optical axis is a first height value. The distance between the top edge of the cross-section of the light guide tube and the optical axis is a second height value. The height of the cross-section of the light guide tube is the sum of the first height value and the second height value. 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 sample under test. The light guide tube includes at least one sub-light guide tube, and the cross-section of the sub-light guide tube is an isosceles trapezoid. Alternatively, the light guide tube may include two or more sub-light guide tubes, all of which are stacked on top of each other in sequence, with the top edge of the cross-section of the uppermost sub-light guide tube being the top edge of the cross-section of the light guide tube, and the bottom edge of the cross-section of the lowermost sub-light guide tube being the bottom edge of the cross-section of the light guide tube. Between any two adjacent sub-light guide tubes, the bottom edge of the cross-section of the upper sub-light guide tube and the top edge of the cross-section of the lower sub-light guide tube are in contact and have the same length; The length of the bottom edge of the cross-section of the light guide tube is the ratio of the width of the irradiated area on the surface of the 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, the far-end distance value is the farthest distance between the imaging lens and the irradiated area on the surface of the sample, and the light guide distance value is the distance between the imaging lens and the light-emitting end face of the light guide tube. The length of the top edge of the cross-section of the light guide tube is the ratio of the width of the irradiated area on the surface of the sample to the second vertical axis magnification; the second vertical axis magnification is the ratio between the near-end distance value and the light guide distance value, and the near-end distance value is the closest distance between the imaging lens and the irradiated area on the surface of the sample. The light-emitting end face of the light guide tube is a slanted plane, and the lower edge of the light-emitting end face protrudes more than the upper edge. The angle between the light-emitting end face of the light guide tube and the longitudinal vertical plane is set according to the object-image relationship of the imaging lens, the focal length of the imaging lens, the first height value, the second height value, the far end distance value, and the near end distance value.

2. The laser uniform illumination system according to claim 1, characterized in that, The first height value is The second height value is Wherein, B is the length of the surface of the sample under test, α is the angle between the center normal of the surface of the sample under test and the optical axis, β1 is the first vertical magnification, and β2 is the second vertical magnification.

3. The laser uniform illumination system according to claim 2, characterized in that, The angle between the central normal of the surface of the sample being tested and the optical axis is between (30° and 90°).

4. The laser uniform illumination system according to claim 1, characterized in that, The light guiding distance value includes a near light guiding distance value and a far light guiding distance value; the near light guiding distance value is the distance between the lower edge of the light-emitting end face of the light guide tube and the imaging lens, and the far light guiding distance value is the distance between the upper edge of the light-emitting end face of the light guide tube and the imaging lens.

5. The laser uniform illumination system according to claim 4, characterized in that, The first vertical axis magnification is the ratio between the far-end distance value and the near-end light guide distance value; The second vertical magnification is the ratio between the near-end distance value and the far-end light guide distance value.

6. The laser uniform illumination system according to claim 1, characterized in that, If the light guide tube comprises N sub-light guide tubes, then the height of the cross-section of each sub-light guide tube is: Where h1, h2, ..., h N-1 and h N The heights of the N sub-light guides from bottom to top are as follows: b is the height of the cross-section of the light guide, a1 represents the bottom edge of the cross-section of the light guide, and a2 represents the top edge of the cross-section of the light guide.

7. A light guide tube, characterized in that, The light guide tube is the light guide tube in the laser uniform illumination system according to any one of claims 1-6.

8. The light guide tube according to claim 7, characterized in that, Both the light-incident and light-exit ends of the light guide tube are provided with anti-reflection films.

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