Decoherence illumination system and method for obtaining illumination light by decoherence

Abstract

The present application relates to the technical field of optical detection, and especially relates to a decoherence illumination system and a method for obtaining illumination light through decoherence, the decoherence illumination system comprising: a light source, the light source being used for emitting initial illumination light; a decoherence element, the decoherence element being located in a transmission light path of the initial illumination light, the decoherence element comprising N independent control units; a microlens array assembly, the microlens array assembly being located on a side of the decoherence element away from the light source, the microlens array assembly comprising N sub-apertures arranged in an array, the sub-apertures corresponding to the control units one by one; wherein the N control units of the decoherence element are sequentially turned on, and a time interval from when a previous control unit is turned off to when a next control unit is turned on is greater than a coherence time of the initial illumination light, so that the initial illumination light incident to different sub-apertures is decohered. The present application is at least beneficial to solve the problem of sub-aperture light interference when the microlens array assembly is used as a homogenization element under the condition that a narrowband laser is used as a light source.

Description

Technical Field

[0001] This invention belongs to the field of optical detection technology, and particularly relates to an anticoherence illumination system and a method for obtaining illumination light through anticoherence. Background Technology

[0002] In semiconductor testing, a homogenizing rod is often used to form a uniform illumination spot. However, the homogenization effect of the homogenizing rod is affected by the length of the homogenizing rod, the cross-sectional area of ​​the homogenizing rod, and the aperture angle of the incident spot. To improve the homogenization effect of the homogenizing rod, it is necessary to increase the length of the homogenizing rod, decrease the cross-sectional area of ​​the homogenizing rod, or increase the aperture angle of the incident spot. However, due to the constraints of processing conditions, space occupation, and the overall illumination optical path, it is often difficult to achieve the required state for the above three parameters. That is, it is difficult to obtain a large number of reflections in a small space and under the condition that the aperture is matched with the subsequent imaging system.

[0003] Related technologies use microlens arrays for light homogenization. This method can reduce the overall system size and obtain a more uniform homogenized light spot while matching the aperture angle of the subsequent imaging system. However, the light sources used in semiconductor detection are mostly narrowband lasers. The emitted light from narrowband lasers has high coherence. When using microlens arrays for light homogenization, the sub-aperture beams will eventually overlap at the illumination surface, producing high-contrast interference fringes. Therefore, the use of microlens arrays to achieve light homogenization is limited when using narrowband lasers as illumination sources. Summary of the Invention

[0004] In view of this, the present invention aims to provide an anticoherent illumination system and a method for obtaining illumination light through anticoherence, which at least helps to solve the problem of interference of sub-aperture light when using a microlens array as a homogenizing element under the condition of using a narrowband laser as an illumination source.

[0005] To achieve the above objectives, the technical solution created by this invention is implemented as follows: This invention provides an anticoherence illumination system, comprising: a light source for emitting initial illumination light; an anticoherence element located in the transmission optical path of the initial illumination light, the anticoherence element including N independent control units; and a microlens array assembly located on the side of the anticoherence element away from the light source, the microlens array assembly including N sub-apertures arranged in an array, each sub-aperture corresponding to a control unit; wherein the N control units of the anticoherence element are sequentially turned on, and the time interval between the turning off of one control unit and the turning on of the next control unit is greater than the coherence time of the initial illumination light, so that the initial illumination light incident on different sub-apertures is anticoherent.

[0006] Furthermore, the initial illumination light is a narrow-bandwidth laser.

[0007] Furthermore, the wavelength bandwidth of the initial illumination light is in the range of 0.1 picometer to 0.001 picometer.

[0008] Furthermore, each control unit includes at least one reflector.

[0009] Furthermore, the decoherence element is a digital micromirror device.

[0010] Furthermore, the decoherence lighting system also includes a rotating diffuser, which is located in the transmission optical path of the initial illumination light between the light source and the decoherence element.

[0011] Furthermore, the decoherent illumination system also includes a beam expander, which is located in the transmission optical path of the initial illumination light between the rotating scatterer and the decoherent element.

[0012] Furthermore, the microlens array assembly includes a first microlens array and a second microlens array arranged sequentially along the beam transmission direction.

[0013] Furthermore, the decoherent illumination system also includes a focusing lens group, which is located in the illumination light transmission path on the side of the second microlens array away from the first microlens array.

[0014] Furthermore, the focal length of the first microlens array is f1, the focal length of the second microlens array is f2, the size of the sub-aperture is a×b, the focal length of the focusing lens group is f3, and the size of the illumination light spot is A×B, where A=a×f3 / f1 and B=b×f3 / f1.

[0015] Furthermore, the anticoherence illumination system also includes a focusing mechanism used to adjust the focal length of the focusing lens group.

[0016] Furthermore, the coherence time of the initial illumination light is , , This represents the frequency bandwidth of the initial illumination light.

[0017] Furthermore, ,in, Represents the speed of light. The wavelength bandwidth representing the initial illumination light. The wavelength represents the center wavelength of the initial illumination light.

[0018] Another aspect of the present invention provides a method for obtaining illumination light by decoherence, comprising: initial illumination light emitted by a light source is incident on a decoherence element and then on a microlens array assembly; wherein N control units controlling the decoherence element are sequentially turned on, such that the time interval between the previous control unit being turned off and the next control unit being turned on is greater than the coherence time of the initial illumination light, so as to decoherence of the initial illumination light incident on different sub-apertures of the microlens array assembly.

[0019] Compared with the prior art, the present invention can achieve the following beneficial effects: The decoherence illumination system and the method for obtaining illumination light by decoherence provided by the present invention set a decoherence element in front of the microlens array assembly. The control unit of the decoherence element corresponds one-to-one with the sub-aperture of the microlens array assembly. During the formation of illumination light, the N control units of the decoherence element are turned on sequentially, and the time interval between the closing of the previous control unit and the turning on of the next control unit is greater than the coherence time of the initial illumination light, so that the initial illumination light incident on different sub-apertures is decoherent, thereby making the initial illumination light form a decoherent uniform illumination light after passing through the microlens array assembly. This solves the problem of interference caused by the superposition of light of different sub-apertures of the microlens array assembly when using a narrow bandwidth laser as a light source. It is beneficial to improve the uniformity of the generated illumination spot. Moreover, the decoherence illumination system has a simple structure, small size, and does not require complex coding modulation. Attached Figure Description

[0020] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 An equivalent schematic diagram of the anticoherence lighting system described in the embodiments of the present invention; Figure 2 A schematic diagram of the structure of the anticoherence lighting system described in the embodiment of the present invention; Figure 3 A schematic diagram showing the correspondence between the sub-apertures and the reflectors of the microlens array assembly described in the embodiments of the present invention; Figure 4 This is a schematic diagram illustrating the conduction sequence of the control unit of the decoherence element described in an embodiment of the present invention.

[0021] Explanation of reference numerals in the attached figures: 1. Light source; 4. Decoherence element; 103. Control unit; 11. Microlens array assembly; 101. Sub-aperture; 102. Mirror; 100. Incident light spot; 2. Rotating scatterer; 8. Illumination surface; 3. Beam expander assembly; 31. Focusing lens; 32. Collimating lens; 5. First microlens array; 6. Second microlens array; 7. Focusing lens group. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and do not constitute a limitation thereof.

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] The invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0026] refer to Figures 1 to 4 This invention provides an anticoherence illumination system, comprising: a light source 1 for emitting initial illumination light; an anticoherence element 4 located in the transmission optical path of the initial illumination light, the anticoherence element 4 including N independent control units 103; and a microlens array assembly 11 located on the side of the anticoherence element 4 away from the light source 1, the microlens array assembly 11 including N sub-apertures 101 arranged in an array, each sub-aperture 101 corresponding to a control unit 103; wherein the N control units 103 of the anticoherence element 4 are sequentially turned on, and the time interval between the turning off of one control unit 103 and the turning on of the next control unit 103 is greater than the coherence time of the initial illumination light, so that the initial illumination light incident on different sub-apertures 101 is anticoherent.

[0027] In some cases, N can be an integer greater than 3.

[0028] It should be noted that the previous control unit 103 is adjacent to the next control unit 103, and the N control units 103 of the decoherence element 4 can be turned on sequentially according to their arrangement. In some examples, N=4, see reference. Figure 4 The four control units 103 can be turned on sequentially in the order of upper left, upper right, lower right, and lower left.

[0029] Furthermore, the initial illumination light is a narrow-bandwidth laser. Light source 1 can be a narrow-bandwidth continuous laser.

[0030] Furthermore, the wavelength bandwidth of the initial illumination light is in the range of 0.1 picometer to 0.001 picometer.

[0031] Furthermore, each control unit 103 includes at least one reflector 102.

[0032] Furthermore, the decoherence element 4 is a digital micromirror device (DMM). A DMM is a high-speed spatial light modulator. A typical DMM includes multiple mirrors 102 arranged in an array. Each mirror 102 can be independently and electrically flipped, controlling the on / off state of its corresponding optical path. In this invention, the multiple mirrors 102 of the DMM are divided into N control units 103 according to the distribution of the sub-apertures 101. Each control unit 103 may include one mirror 102 or multiple mirrors 102. The mirrors 102 corresponding to each control unit 103 are synchronously switched on and off to achieve the on / off state of the corresponding control unit 103.

[0033] Generally, the size of the reflector 102 is smaller than the size of the sub-aperture 101 of the microlens array assembly 11. Therefore, multiple reflectors 102 can be used to form a control unit 103. In some examples, refer to Figure 3 A control unit 103 may include four reflectors 102, that is, one sub-aperture corresponds to four reflectors 102. Figure 3 In the diagram, the dashed circle represents the incident light spot 100 of the incident microlens array assembly, and the 2×2 sub-aperture on the right is a magnified view of a portion of the whole formed by all the sub-apertures on the left.

[0034] Since the image captured by the camera in actual use is the intensity integral of the incident light over a certain period of time, the initial illumination light is modulated by the decoherence element 4 so that the light incident on each sub-aperture 101 of the subsequent microlens array assembly 11 is incoherent light. Therefore, when the light spots of each sub-aperture 101 at the subsequent illumination surface 8 are superimposed, no interference will occur, so that the illumination light spot finally formed at the illumination surface 8 has no interference fringes.

[0035] Furthermore, the coherence time of the initial illumination light is , , This represents the frequency bandwidth of the initial illumination light.

[0036] Furthermore, ,in, Represents the speed of light. The wavelength bandwidth representing the initial illumination light. The wavelength represents the center wavelength of the initial illumination light.

[0037] Furthermore, the decoherence illumination system also includes a rotating diffuser 2, which is located in the transmission optical path of the initial illumination light between the light source 1 and the decoherence element 4. The rotating diffuser 2 is used to eliminate speckle noise. In some examples, the rotating diffuser 2 is a rotating diffuser sheet.

[0038] Furthermore, the decoherence illumination system also includes a beam expander 3, which is located in the transmission optical path of the initial illumination light between the rotating scatterer 2 and the decoherence element 4. The beam expander 3 is used to enlarge the size of the initial illumination light so that the initial illumination light incident on the decoherence element 4 can cover each control unit 103 of the decoherence element 4. In some examples, the beam expander 3 may include a focusing lens 31 and a collimating lens 32 arranged sequentially along the transmission optical path of the beam.

[0039] Furthermore, the microlens array assembly 11 includes a first microlens array 5 and a second microlens array 6 arranged sequentially along the beam transmission direction.

[0040] In some embodiments, the first microlens array 5 includes N first microlenses arranged in an array along a direction perpendicular to the optical axis, and the second microlens array 6 includes N second microlenses arranged in an array along a direction perpendicular to the optical axis. The first microlenses and the second microlenses correspond one-to-one, and the corresponding first microlenses and the second microlenses constitute a sub-aperture 101.

[0041] Furthermore, the decoherent illumination system also includes a focusing lens group 7, which is located in the illumination light transmission path on the side of the second microlens array 6 away from the first microlens array 5. That is, the light passing through the microlens array assembly 11 is focused onto the illumination surface 8 by the focusing lens group 7, thereby forming an illumination spot. In some examples, the focusing lens group 7 may include multiple lenses arranged along the transmission path of the light beam.

[0042] Furthermore, the focal length of the first microlens array 5 is f1, the focal length of the second microlens array 6 is f2, the size of the sub-aperture 101 is a×b, the focal length of the focusing lens group 7 is f3, and the size of the illumination light spot is A×B, where A=a×f3 / f1 and B=b×f3 / f1. Additionally, d1=f1, where d1 is the distance between the first microlens array 5 and the second microlens array 6.

[0043] In other words, the size of the illumination spot ultimately formed at the illumination surface 8 is determined by the ratio of the focal length of the microlens array assembly 11 to the focal length of the focusing lens group 7, and the shape of the illumination spot is determined by the shape of the sub-aperture 101 of the microlens array assembly 11. By changing the focal length of the focusing lens group 7, the size of the final illumination spot can be changed, thus completing the continuous adjustment of the spot size.

[0044] In some examples, f1=f2=20mm, the size of each sub-aperture 101 is 0.5mm×0.5mm, the distance between the first microlens array 5 and the second microlens array 6 is 20mm, the distance between the second microlens array 6 and the focusing lens group 7 is 20mm, and the focal length of the focusing lens group 7 can be adjusted within the range of 67mm~200mm. When the focal length of the focusing lens group 7 is 67mm, the simulated spot size of the emitted light from the focusing lens group 7 is 1.68mm×1.68mm. When the focal length of the focusing lens group 7 is 100mm, the simulated spot size of the emitted light from the focusing lens group 7 is 2.5mm×2.5mm. When the focal length of the focusing lens group 7 is 200mm, the simulated spot size of the emitted light from the focusing lens group 7 is 5mm×5mm.

[0045] Furthermore, the decoherence illumination system also includes a focusing structure for adjusting the focal length of the focusing lens group 7. Specifically, the focusing structure adjusts the focal length of the focusing lens group 7 by adjusting the spacing between the lenses in the focusing lens group 7.

[0046] Another aspect of this invention provides a method for obtaining illumination light through decoherence. This method is based on the aforementioned decoherence illumination system. The parts that are the same as or corresponding to those described above can be referred to the aforementioned embodiments, and will not be repeated here.

[0047] The method for obtaining illumination light by decoherence includes: initial illumination light emitted by light source 1 is incident on decoherence element 4 and then on microlens array assembly 11; wherein, N control units 103 controlling decoherence element 4 are turned on sequentially, such that the time interval between the previous control unit 103 being turned off and the next control unit 103 being turned on is greater than the coherence time of the initial illumination light, so that the initial illumination light incident on different sub-apertures 101 of microlens array assembly 11 is decoherent.

[0048] The decoherence illumination system and the method for obtaining illumination light through decoherence provided by the present invention use a decoherence element 4 to modulate the coherence of light from each sub-aperture 101 of the microlens array assembly 11 to achieve decoherence and thus obtain uniform illumination light. Compared with the traditional light homogenizing rod, the decoherence illumination system provided by the present invention is compact, has no strict requirements on the size of the incident light emitted by the light source 1, and has a better light homogenization effect. The control units 103 of the decoherence element 4 cooperate with each sub-aperture 101 of the microlens array assembly 11, solving the problem of interference caused by the superposition of sub-apertures 101 when using a narrowband laser as the light source 1 and the microlens array assembly 11 for light homogenization.

[0049] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention disclosure can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0050] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A coherent lighting system, characterized in that, include: A light source, which is used to emit initial illumination light; The decoherence element is located in the transmission optical path of the initial illumination light, and the decoherence element includes N independent control units; A microlens array assembly is located on the side of the decoherence element away from the light source. The microlens array assembly includes N sub-apertures arranged in an array, and each sub-aperture corresponds one-to-one with a control unit. In this process, the N control units of the decoherence element are turned on sequentially, and the time interval between the turn-off of the previous control unit and the turn-on of the next control unit is greater than the coherence time of the initial illumination light, so as to decoherence of the initial illumination light incident on different sub-apertures.

2. The decoherence lighting system according to claim 1, characterized in that, The initial illumination light is a narrow-bandwidth laser.

3. The decoherence lighting system according to claim 2, characterized in that, The wavelength bandwidth of the initial illumination light is in the range of 0.1 picometer to 0.001 picometer.

4. The anticoherence lighting system according to claim 1, characterized in that, Each control unit includes at least one reflector.

5. The anticoherence lighting system according to claim 1, characterized in that, The decoherence element is a digital micromirror device.

6. The decoherence lighting system according to claim 4, characterized in that, The decoherence illumination system further includes a rotating diffuser located in the transmission optical path of the initial illumination light between the light source and the decoherence element.

7. The anticoherence lighting system according to claim 6, characterized in that, The decoherent illumination system further includes a beam expander, which is located in the transmission optical path of the initial illumination light between the rotating scatterer and the decoherent element.

8. The decoherence lighting system according to claim 1, characterized in that, The microlens array assembly includes a first microlens array and a second microlens array arranged sequentially along the beam transmission direction.

9. The decoherence lighting system according to claim 8, characterized in that, The decoherent illumination system further includes a focusing lens group, which is located in the illumination light transmission path on the side of the second microlens array away from the first microlens array.

10. The decoherence lighting system according to claim 9, characterized in that, The focal length of the first microlens array is f1, the focal length of the second microlens array is f2, the size of the sub-aperture is a×b, the focal length of the focusing lens group is f3, and the size of the illumination light spot is A×B, where A=a×f3 / f1 and B=b×f3 / f1.

11. The decoherent lighting system according to claim 9, characterized in that, The anticoherence illumination system also includes a focusing structure for adjusting the focal length of the focusing lens group.

12. The decoherence lighting system according to claim 1, characterized in that, The coherence time of the initial illumination light is , , This represents the frequency bandwidth of the initial illumination light.

13. The decoherence lighting system according to claim 12, characterized in that, ， in, Represents the speed of light. The wavelength bandwidth representing the initial illumination light. The wavelength represents the center wavelength of the initial illumination light.

14. A method for obtaining illumination light by decoherence, characterized in that, include: The initial illumination light emitted by the light source is incident on the decoherence element, and then on the microlens array assembly; In this process, N control units controlling the decoherence element are turned on sequentially, such that the time interval between the turn-off of one control unit and the turn-on of the next control unit is greater than the coherence time of the initial illumination light, so that the initial illumination light incident on the microlens array assembly at different sub-apertures is decoherent.

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